Textile industry in India is the second largest employment generator after agriculture. It holds significant status in India as it provides one of the fundamental necessities of the people. Textile processing is one of the important industries related with textile manufacturing operations. It is a general term that covers right from singeing to finishing & printing of fabric apart from giving huge value-addition at every stage of processing. A number of new innovations have led to the industrialization of the textile industry. The silk reeling techniques are excellent methods to produce superior grade raw silk which is used by the textile industry to produce exotic fabric. Silk reeling is the final and purely commercial phase of sericulture. It is concerned with unwinding of the silk filaments of the cocoon. The sericulture industry is agro based and flourishing mostly in rural areas. More than 50 per cent of silk is reeled by a villager using country charka which forms the cottage industry. Silk provides much needed work in several developing and labour rich countries. The textile industry is primarily concerned with the production of yarn, and cloth and the subsequent design or manufacture of clothing and their distribution. The raw material may be natural or synthetic using products of the chemical industry.
Some of the fundamentals of the book are chemical modification of textile celluloses, fabric varieties, silk as a textile fibre, silk reeling technology, silk re-reeling technology, fluidized beds to textile processing, high alpha cellulose pulp for viscose rayon, reaction of cellulose with cross linking agents, textiles adhesives, flame retardants for textiles, halogenated flame retardants, antinomy and other organic compounds, surfactants, chemical used in textiles, etc.
This book contains fabric varieties, silk reeling technology, cellulose ethers, crease resistance of cellulose textiles, tone and shade control in textile, textiles adhesives, flame retardants for textiles, chemical used in textiles. This book will be resourceful to upcoming entrepreneur, Seri culturist, existing industries, technical institutions etc.
Chemical Modification of Textile Celluloses
cellulose is a linear polymer containing hundreds of interlinked
through oxygen bridges. It contains both primary alcoholic groups
secondary ones (CHOH), and from the chemical point of view, one would
cellulose to behave like alcoholic compounds. However, when one thinks
cellulose from the point of view of textile end use, he is confronted
number of limitations. Such limitations arise out of the necessity to
practically all the textile properties that cellulose normally
instance, the chemical treatment must not alter the tensile strength,
believed to depend on chain length and intermolecular cohesion;
treatment should not adversely affect the moisture relations of
thirdly the elastic properties which make spinning possible should not
destroyed; and lastly the treatment should affect useful textile
such as dye-ability, handle, drape, lustre and softness.
the ultimate analysis, all the above limitations involve a through
understanding of the physical structure and chemical properties of
cellulose. Fortunately, thanks to the numerous pioneering researches
during the last fifty years or so, a fund of knowledge is now available
makes discussion possible. Modern fibre science has made great strides
result of the impetus received through the synthesis of new chemical
one time it was considered that ‘king cotton’ will have to lose ground
modern synthetic fibres. But it was soon realized that, if starting
materials like coal tar or petroleum chemicals, which have no relation
whatsoever with fibrous properties, one could synthesize such valuable
as nylon or terelyne, one could as well start from cotton, flax, ramie,
and look forward to many and far reaching results. This view has gained
considerable support during the last ten years1-3.
textile materials are linear polymers characterized by the presence of
chain molecules possessing polar side groups, such as OH, NH2, etc.,
residual valencies. The long chains are arranged in a remarkably
fashion and are held together by Van der Waals forces, hydrogen bonds
linkages between acidic and alkaline polar groups of adjacent
textile celluloses, the chain length varies from 300–600 glucose units
(regenerated fibres) to 3,000–7,000 or more glucose units (natural
The cohesive forces between the side chains are due to hydrogen bonding
the hydroxyl groups of adjacent chains. In some places, along the
chains are packed together in a rather rigid and orderly fashion. These
are called ‘crystalline’ regions and are believed to contribute mainly
tensile strength and chemical stability. Further, these molecules are
oriented towards the fibre axis. The degree of such orientation plays
important part in the tensile behaviour of cellulose. In other regions,
packing of molecules is not orderly; these regions known as ‘amorphous’
are believed to be more easily accessible to moisture, dyes and other
chemicals. They may also account for the elasticity and extensibility
following points are worth recapitulating: (i) the chain length and
orientation contribute largely to the strength and other tensile
textile celluloses; (ii) the manner of random packing of molecules in
‘amorphous’ regions of cellulose determines its accessibility to all
chemical agencies. Chemicals having a molecular size greater than the
voids in the amorphous regions cannot enter them and hence cannot bring
easy chemical transformation; (iii) the alcoholic nature of polar
groups in cellulose makes possible reaction between cellulose and
groups, resulting in reactions, such as etherification, esterification,
xanthation, oxidation, etc., and (iv) chemicals having strong hydrogen
properties have an affinity for cellulose and can bring about changes
physical properties of cellulose by altering the nature of packing of
chains (mercerization) or by clinging on to them and then adding to
until the size of the agglomerate becomes so big that a removal, by
of the effect is made difficult.
ideas can be made clear by reference to Figs. 1 and 2, which show the
residue from which cellulose is built, the manner in which molecular
cohere in the fibre and the manner in which they are packed.
are two ways in which the subject can be viewed. Cellulose may be
a linear polymer containing a number of hydroxyl groups which make a
typical chemical modification possible. One might then list together
type reactions under suitable categories, e.g., esterification,
oxidation and xanthation, and consider the different useful properties
resulting from such reactions. Alternatively, cellulose may be
considered as a
fibrous material exhibiting a number of useful or defective textile
and then consider ways and means of chemical modification with a view
rectifying the defective properties. The objective of this paper is to
attention on what has been done or can be done to improve the textile
properties of cellulose by taking recourse to chemical modifications.
of Textile Cellulose
following are a few of the numerous textile properties of cellulose:
drap; resilience and drape; elasticity and strength lustre;
dimensional stability; spinnability; abrasion and flex resistance;
and electrical insulation; quick drying; water repellency; air
resistance to mildew and rot-proofness; absorbency; wash resistance;
relative importance of one or more of these properties, however, varies
country to country, climate to climate and dress habits of different
Moreover, it is ultimately the end use that determines the exact manner
which one or more properties are selected or modified. However, the
can be broadly grouped4 under the following headings:
based on polymer structure—(i) elongation and elastic properties; (ii)
resistance, tear strength and wear life; (iii) wet strength,
stability and wash resistance;
crease-resistance and drape;
and (v) bulk density and warmth.
based on form,
dimensions and surface characteristics of fibre—(i) lustre; (ii)
and clinging resistance (iii) resistance to soiling; and (iv)
based on hydrophilic
or hydrophobic characteristics—(i) Water repellency; (ii) absorbency;
quick drying; (iv) electrical insulation; (v) dye-receptivity; and
based on structure—(i) mildew-and rot-resistance; (ii) resistance to
deterioration by light, heat, chemicals, etc.,
flame resistance; and (iv)
any treatment which changes the molecular packing in cellulose will
significant effect on these two properties. The simplest and the most
example is treatment of cotton yarn under tension with steam, whereby
elongation is considerably reduced; such destretched yarns find
application in the manufacture of improved tyre cords. References to
are too numerous to mention here, but a process developed at the Shri
Research Institute three years ago is worth mentioning. The yarns were
in a mixture of amyl and butyl alcohol for a short time and then
steamed to remove the solvent. Increase in tenacity of the order of
cent was recorded. Unfortunately, the method could not be utilized
due to various considerations.
example of a simple chemical treatment which altered the elastic
cellulose comes from the Southern Regional Laboratory in U.S.A. Bandage
was mercerized in caustic soda washed and dried without tension. Such
has more desirable properties and a much higher elongation (35%) than
material. It fits the various parts of the human body more efficiently
its elastic nature.
third and extremely important chemical method of altering the
elastic properties of cellulose is by reaction involving the use of
Life, Tear Strength and
is being more and more realized that changes in the crystallinity of
can be brought about by chemical means. Segal et al. treated native
aliphatic amines and obtained cottons with varying degrees of
was thus possible to bring down the crystallinity from 90 to as low as
cent. The treated cottons show altered dyeing properties, improved
reactivity, better flex life and improved tear strength. Further
such decrystallized cotton had been handicapped by lack of enough
material for test purposes. It appears, however, that Greathouse et al.
succeeded in trying the process on a pilot plant scale and increasing
developments may be expected in the near future.
Stability, Wash and Crease-Resistance and Drape
these related properties have assumed importance since the introduction
regenerated cellulose fibres, and have been largely improved by cross
and by aminoplast resin modification. Considerable attention is being
towards the treatment of cotton in this way, and the introduction of
resins and nitile lattices along with the conventional
melamine-formaldehyde resins need special mention here, as they seem to
overcome some of properties to a significant extent.
drape is associated with yarn and fabric construction, it would appear
decrystallization and cross linking could improve these properties to a
Density and Warmth
properties do not appear to have received as much attention as they
would perhaps be safe to assume that these two properties are
that warmth can be increased by changes in bulk density. In an
on the thermal properties of textiles, Morris lists a number of
factors that contribute to the thermal characteristics of textiles,
specific heat, bulk density and conductivity. However, there appears to
little work done on the chemical modification of cellulose from this
view. An interesting development for improving the heat retaining
textiles is the use of metallic flakes in the binding polymer sprayed
surface, followed by baking. It is claimed that the fabric retains its
permeability and at the same time, due to cloth shrinkage, the trapped
insulation. In a country like India, attempts to make cotton more warm
prove useful in the long run.
far, chemical methods to enhance lustre have been restricted to the use
mercerization. There have been numerous investigations on caustic
and the latest series of papers by Fourt et al. are worthy of mention.
treatment of cotton with a
strong solution of caustic soda changes the crystal structure of cotton
cellulose from cellulose I to cellulose II (Fig. 3 and Table 1). The
involved in the development of lustre have been summarized by Marsh.
3. Unit cell of cellulose I
have been notable contributions in the resin treatment of textiles with
to obtain permanent lustre. In all such processes, the materials are
with resins, dried and schreinered or calendared, and then cured. The
obtained are made wash resistant.
Does Fabric Mean?
fabric is a cloth material, which has the warp (vertical yarm) and the
filling (horizontal yarn) crossing each other at right angles. Though
fabrics may appear very much similar at one glance, there are various
varieties, which have absolutely different patterns. For example, there
material and vertical knitwear cloth, in which the cloth material is
only by intertwining the warp with the warp on the left and right
There is also horizontal knitwear material in which the cloth is made
thread making its way in zigzag direction horizontally, while forming a
continuously. Another way is to make felt cloth, in which the wool
overlapped flat on each other and while rubbing them under heat, alkali
pressure, they are turned into felt.
Terms Related to
fabric has slightly tightened part at the edge, with a width of 3–5 mm
sides all through its length. This is called as the Selvedge of the
warp used for selvedge is called as selvedge yarn. As against the
other part of the fabric excluding the selvedge is called as Ground.
sides get stretched while fabric manufacturing, dyeing and arranging
they can get easily torn. Therefore, in order to give it additional
the warp slightly thicker than that of the ground is used or the warp
that of the ground is arranged in double and used as one warp.
selvedge part tends to be slightly thicker than the ground part. When
ground is a plain fabric or a figured texture fabric etc., many times
fabric or figured diagonal fabric is used only for the selvedge part.
silk fabrics and woolen fabrics, a special pattern or a yarn of
is used for the selvedge part. This also serves the purpose of
design. Moreover, the woolen fabrics have the trade-mark or
company name woven on the selvedge. This is commonly called as selvedge
width of fabric is decided according to the purpose of its use
custom for each variety. For example, the fabric for the inner lining
of kimono (Japanese style dress material) is said to be of less width.
It is of
about 36 cm and the belt material is about 30 cm in heavy belts. In
belts, the standard width is about 68–69 cm. In the export fabrics,
fabric is about 2–3 times wider than the inner lining material. The
which have double or triple the width of inner lining material, is
double wide fabric, triple wide fabric respectively. These are called
general as wide fabrics. When the fabrics for special use have
width, they are called as narrow fabrics. However, this is just a
classification and there is no clear numerical boundary drawn anywhere.
width of woolen fabrics is usually 154–158 cm (60–62 in) but its ground
mostly of about 76–91 cm (30–36 in) in all varieties of the fabrics.
showing the width, when the
width is to be shown excluding the selvedge, it is called as Within
When the selvedge is included in the shown width, it is called as
weaving a fabric, usually 5–10 reverse parts are taken as one length
weaving is done. But, the length of one roll 91 piece) sent to the
the product is as per the trading custom. The standard length of one
silk or artificial silk fabric is 45.72 m (50 yds), cotton fabric is
45.72 m (30 – 50 yds), the carded woolen fabric is 50 – 55 m, spun
fabric is 40 – 45 m and the hemp fabric is 55 m (60 yds). The cotton
used for internal lining of kimono is about 10.6 m long. The silk
crape etc.) have 11.4 m as 1 reverse. However, each fabric variety
tends to get
a little longer successively.
degree of density of the warp and the weft has a great impact on the
and appearance of the fabric. It is one of the important conditions in
determining the name and usage of the fabric. The degree of this
the number of warps and weft in the fixed section. The method of taking
section depends on the variety of the fabric and on the country. Each
has its own custom but generally, the number of threads between 2.54 cm
or between 1 cm etc. is shown, But, sometimes, the total number of
wefts between a square inch is also shown.
(=0.132 oz) is used as the unit for showing the weight (indirectly, it
means thickness) of the fabric per unit area. The origin of the Momme
unit showing the weight per fixed area of the fabric. The fabric with
[cloth measure 1 Sun (=1.193 in)] width, 22.727 m [60 Shaku (=0.994
and 3.75 gr weight (1 Momme) is said to be of 1 Momme. The fabric of
area and weight 18.75 gr (5 Momme) is said to be of 5 Momme. The Momme
special unit used only in Japan. Today, it is used only for the habutae
and crepe silk in the silk fabrics and not for the other fabrics. The
method of showing the weight per unit area of the fabric is to use gr
per square m for all the fabric varieties. In case of woolen fabrics,
is fixed to be 60–62 in. So, since long it has been the custom to use
expression telling how many ounces it is from the number of ounces per
Mix Spun Fabric, Mix Woven
Fabric and Graded Fabric
fabric is either mixed spun or mixed woven, depending on the variety of
used for warps and wefts. Mixed spun fabric has the mixed spun yarn
used for a
part or whole of the warp and weft. The mixed woven fabric has yarn of
strands (ply) used in a part or whole of the warp and weft. The fabric,
has yarns of different kinds
used for the warp and weft or the fabric, which has yarns of different
fibers combined and woven in stripes partially in the warp and weft is
called as mixed woven fabric. When it is said ‘mixed weaving’, it
that it is a fabric with yarns of different varieties of fibers. If the
is arranged with stripes of thick and thin yarn made from the same
variety, it is called as graded fabric.
Tone, Texture and Flavor
fabric differs in hardness, softness, smoothness and stiffness
which gives a feel that there is something at the core of the fiber)
on the combination of various conditions such as, the physical
the fiber that makes up the fabric, the yarn thickness, the twisting
the pattern of fabric, th density and the finishing method etc. The
one gets after touching the fabric or the feeling that one gets after
its appearance, when it is worn as clothes, is also different in case
fabrics. The condition of these feelings is shown by the words Tone,
and Flavor. These are mainly special terms, which show the complex
The goodness or badness of tone or texture is an important element
judging the value of the fabric. This cannot be measured mechanically
cannot be shown numerically. The person, who handles the fabrics,
fabric and judges the goodness or badness of it form his experience of
is a slang word used in the trading world, when the tone of mainly the
woolen fabrics is to be shown. When one picks up the fabric with a
has a touch of ‘shari’ (rustling).
is also a slang word showing the touch of carded woolen fabrics. This
shows the extent of goodness or badness of the woolen fabrics, which
feel of slipperiness.
the yarn or the fiber gives a feeling of bulkiness, when it is held in
it is called as Bulky. Apart from the elasticity of fiber, this
according to the pattern and finishing method of the yarn or fabric.
the fabrics are worn on the body as clothes or when they are hung down
vertical curtain, the loose part sags down and it shows a curved line.
condition varies according to the variety of fabrics. The main
cause this, are fiber weight, stiffness, flexibility, surface
twists, density of fabric, condition of pattern and finishing. All
different conditions can be generalized under one name as Drape
quality is one of the important properties for deciding the clothes
value in the material for ladies dresses.
the fabrics are woven by using firmly twisted yarn for the weft
both warp and weft) and the twists are reversed in alternate yarns,
one thread twisted clockwise and the next anticlockwise. Thus fine
made to occur on the surface of fabric when the yarn shrinks after
These creases are called as Crape. For example, the creases seen on
or crepe silk.
two fabric sheets are piled on each other and if we look through them
shifting that piled position suitably, we can see inconsistent light
darkness like the film of wood grains. These are shown because the
condition of see-through rays changes due to the piling of tall parts
parts of the warps and wefts floating on the fabric surface. This is
Moire. In order to settle this on the fabric surface, two sheets of
piled up in a position so that they will show the moire and they are
between rollers. While heating, they are given pressure. Due to this,
taller parts on the surface get pressed to a large extent and become
Therefore, the rays are reflected on flat surface according to the
those parts look very white. Further, there is also a method of setting
moire, in which a film resembling the moire is carved on the surface of
roller and the process of pressing is carried out with it on the
surface of the
fabric. On the contrary, when plain dyed fabrics, especially plain
fabrics, are to be given a calendar finishing, the morre film is seen
unnecessarily and it spoils the appearance of the product.
Wash and Wear
the synthetic fibers have very little moisture absorption rate. So,
shirts and dresses made with them are washed, even without starching
they are taken out from water and hung up without wringing, the water
drained naturally. The clothes get dried very fast. They do not get
and so ironing is not required for them. They can be worn immediately.
Wash and Wear (abbreviated as WW) means ‘wearing immediately in the
How to Show the Pattern
mixed status of warps and wefts, which make up the fabric, is called as
pattern. Even if the fabric is woven with the same yarn, its strength,
appearance and tone changes according to the weave (interlacing
pattern of the fabric is shown with the pattern diagram. The design
used to draw the pattern diagram. The section 1. inserted between the
lines in vertical direction, shows1 warp. Similar section in the
direction shows one weft. For example, in Fig. 1, (a) each of 1, 2, 3
the warp and each of i, ii, iii, ... is the weft. The design paper
one bold line drawn after every 8 lines.
the relation of the vertical and horizontal, usually the squares are
is called as design paper of 8¢ 8). However, in the fabrics with
texture, when the fabric having different thickness of warp and weft is
designed, the paper having section lines of the width proportionate to
thickness of the yarn to be used, is taken (For example, the paper
shown in (b)
of Fig. 1. This is called as design paper of 8¢16). In short, if the
proportionate to the thickness of the warp and weft is not used the
the designed pattern and the scale of woven pattern will be different.
from the table, the method of drawing the pattern drawing is to color
in black (or other color). The places, where the warp crosses over the
also colored in black.
relation of the two is as shown in Fig. 2. In it (a) shows the actual
the fabric. When this is seen from the lower side of the diagram, its
cross-section looks like (b) and when it is seen from the right side of
diagram, its cross-section looks like (c). The fabric of such a pattern
shown in pattern drawing, as shown in (d). (The part painted with
lines shows 1 complete pattern.) In this case, it is seen that the warp
weft are taken up and down one by one and the interlacing is done.
sometimes, depending on the pattern, there is also one warp crossing
or more wefts continuously in the pattern drawing. Again, while drawing
pattern drawing, the beginning is usually done from the first hole at
end on left side. For this point, the place where the warp crosses over
weft is taken as the cardinal point. Normally, the direction of warp
is shown with 2–3 circles drawn.
2 Plain weave pattern
Varieties of Patterns
are unlimited varieties of patterns but there are three basic
as Plain weave, Twill weave and Sateen weave. All the other patterns
the variations of these three basic patterns or a combination of them.
three varieties of patterns are called as the 3 basic patterns of
Plain weave: Plain weave is
the simplest of all fabric patterns. The warp and the weft are crossed
each other one by one alternately up and down and they are interlaced.
It is as
shown in Fig. 2. In this pattern, the crossing length of both the warp
is stopped at minimum. So, the texture is tightly close. This pattern
very strong fabric. This pattern is widely used for the fabrics used
such as cambric, yukata material and habutae etc.
Twill weave: Twill weave, as
shown in Fig. 3, has the warp of 1 float over the weft of i and it
the weft of ii, iii. Similarly, it floats over the weft of iv and then
under v and vi. Such floating and sinking is repeated.
position of mixing warp of 2, 3, ... with the weft is only shifted in
one by one and the floating and sinking similar to 1 is repeated.
in twill weave, the point of warp floating is seen in slanting line on
surface of the fabric. This is called as slanting line. The surface on
this line runs from lower left towards upper right is called as the
of the fabric.
twill of Fig. 3 is called as 1/2 Twill and the twill of Fig. 4(a) is
(b) is 2/2 twill and (c) is 1/2 1/1 2/1 twill. Apart from this various
can be made in twill weave. The most commonly used patterns is 1/2 and
the display method of twill pattern, the horizontal line is considered
lowest end weft in the pattern drawing.
warps are counted from left side and the number, which floats over this
is written as numerator. The number sinking below this weft is written
denominator. Thus the status of one cycle of floating and sinking is
number. This is a common method of displaying twill-weave pattern in
the countries. Besides, when it is necessary to show the direction of
slanting line, it is marked with arrows such as 1/3 or 2/2.
twill weaving, if the floating length of warp and weft is longer than
plain weaving, only the pattern of fabric is loosened. Thus, the
fabric is reduced to some extent.
Sateen weave: In this
pattern the structural points, between the warp and the weft, are made
few. These structural points are also dispersed so that will not be
The fabric surface has either only the warps floating on it or only the
floating on it. The fabric with only the warp floating, is called as
sateen and the fabric with the weft floating, is called as Weft sateen.
sateen pattern, the floating yarn covers the structural point and so it
almost not seen. Therefore, the surface is smooth and lustrous.
characteristic feature of sateen is that since the texture is loose, it
to touch. The sateen pattern has varieties also. There are fabrics in
warps and wefts taken at each time and the pattern is completed. Some
have 8 of them at a time and some have 12 at a time. These are
called as 5 ends of shaft sateen (It means weaving the fabric using 5
threads), 8 ends of shaft sateen and 12 ends of shaft sateen.
5 shows the pattern, of 5 shaft sateen with 2 cycles of warps and
wefts. (a) is
the state showing the actual fabric from the black side, (b) is the
cross-sectional state showing this from the lower side, (c) is the
cross-section state showing it from the right side and (d) is its
diagram. Figure 6 shows the structural diagram of two cycles of 8 shaft
and Fig. 7 shows one cycle of 12 shaft sateen. In it (a) is the state
its lower side and (b) is the state seen from its right side. As seen
structural diagrams, the sateen pattern has the floating point of the
only at one place in one cycle (one complete pattern).
structural point is arranged at a fixed distance following the rules.
distance (gap) is called as the skipping point of the satin pattern.
example, in the 5 shaft sateen, the warp 2 floats over 1, 3 over 2, 4
and 5 over 4. From these positions, each one floats on the weft shifted
every two yarns and so the skipping points are 2. Figure 6 and Fig. 7
the skipping points in them are 3 and 5 respectively. So, similar to
of 5 shaft sateen, if the structural point is made at the point, where
are shifted at every 3 or 5 yarns sequentially, a complete pattern can
a basic principle while drawing the structural diagram of sateen, the
which has few points with the warps floating over the wefts, should be
top in the drawing. Accordingly, in case of warp sateen, as shown in
Fig. 7 the
status, seen from the back of the fabric, is drawn. While weaving also,
weaving is done while keeping the backside upwards. The reason for this
that, the number of holes to be painted is less in the structural
drawing. Besides, during the weaving, the number of warps lifted up for
a shed, is less. So the lifting force can also be saved.
to the same reason as in case of sateen weave, while weaving the
figured fabrics, the whole fabric is woven in reversed status.
these cases, when the fabric is in the machine front surface is
backside of the fabric.
Silk Reeling Technology
single filament from the cocoon cannot be used for any purpose as it is
fine (2 to 3 denier). Hence based on the denier of the silk yarn
required to be
produced for any particular end use, a known number of filaments are
and unwound together to form a single compact raw silk yarn. The
the filaments from softened cocoons in a water media, combining the
and winding the same onto a spool or reel is called reeling.
cocoons are brushed to detect the end of the filament after which they
transferred to the reeling basin for unwinding the filaments. New
added or joined to the existing filaments in the group, as and when any
filament breaks or the filament in the cocoon is unwound completely, so
continuous raw silk yarn of a required denier is obtained.
of Silk Reeling
the very beginning, silk from cocoons was spun into yarn; like cotton.
the hand spinning wheel was developed where the reel—a square drum was
by one hand and the other hand was used for twisting and joining the
filaments. The cocoons were boiled in a pan near the equipment.
over this equipment
was another hand reeling machine with a large reel of 75 cms
connected to a handle for rotation. The reeler operated the handle with
hand and simultaneously drew and twisted the filaments with the other
a further development, the reel circumference was reduced and other
such as a distributor, thread guide, ‘V’ shaped brackets for
were developed. The cocoon softening procedure was also changed, with
cooking vessel embedded in a hearth. The number of skiens made was also
increased to two.
the 17th and 18th century, silk reeling machines underwent a lot of
improving the quality and also increasing the production of silk yarn.
reeling machineries were
designed and developed such as the Italian systems, French systems and
Rotellino Galbiste systems of reeling.
these reeling systems, reeling was direct to form hanks so that they
directly used for winding and twisting operations.
machinery included automatic
brushing arrangement, jetteboutte assembly, button to combine the
together and croissure for agglutination of filaments. The large
were enclosed with a built-in heating arrangement for drying the raw
the Italian system of direct reeling, the filaments were twined within
i.e. the tavelletta type of croissure was adopted. The agglutinated
were drawn behind the reeler and wound on to the reels placed about 2
The agglutination of filaments in this method was advantageous as the
end was coiled with itself and was not dependent on the neighbouring
the French system of reeling, the two neighbouring ends twine with each
for agglutination of the filaments. This type of twining is called the
type of croissure.
Italian system of reeling is not found in the silk reeling industry
some silk reeling areas in the Kolar district of Karnataka state in
However the French type of reeling is still in vogue in Karnataka and
as Charaka reeling.
direct reeling of the Italian
type comprised of a reeling table with stand and basins for water on
table. Each basin was about one metre in width and had 10 threading
frame with glass pulleys to facilitate croissure and guide the thread
large reels placed at a distance of about 2 mts. The basins were
water pipe connections, cold water tanks were fitted to each basin,
valves for maintaining a constant level of water in the tank.
following factors play an important role for smooth unwinding of
the cocoon and in improving the quality and quantity of raw silk yarn.
detecting the correct end of the cocoon filament, the softened cocoons
transferred into a metallic tub called reeling basin on the reeling
Luke warm water at a temperature of 33 to 40°C is maintained in the tub
unwinding of the filaments are done in this water media. Temperature
quality of water play an important role.
quality of water used in reeling influences the raw silk production and
quality. Generally the pH of reeling water should be between 6.5 and
water converges the sericin molecules on to the filament surface and
loss of excessive sericin. Due to the convergence of sericin on to the
filament, neatness and cleanness characters of raw silk yarn also
reeling, water in the reeling basin gets turbid and the concentration
water is increased due to sericin dissolving into the water and also
matter getting released from the cocoon and pupal body. High
the reeling water reduces cocoon reelability, thereby affecting the
the yarn. Further more, the raw silk colour becomes dull, as the turbid
adheres on to the silk surface. Hence the concentration of the reeling
has to be low and has to be uniformly maintained in all the basins to
variations in the colour of raw silk yarn from basin to basin
reeling of yellow cocoons. In order to maintain uniform concentration
a definite quantity of water has to be supplied to each basin and
an over flowing facility.
temperature of reeling water is another important factor which has to
considered for producing good quality raw silk. Higher temperature
the sericin dissolution into the reeling bath. This increases the
of the cocoon, cohesion and smoothness of raw silk, but will reduce the
cleanness of the raw silk, as high dissolution of sericin leads to silk
off the cocoon surface in lumps. Large lumps of silk are called slubbs
sluggs which cannot pass through the button hole, get obstructed
thread break or reel stoppage due to the increase in yarn tension which
the reeling efficiency.
the temperature of the bath is low, the reelability is reduced, which
irregular denier of the yarn, reduction in cohesion and increase in
reeling tension which affects the elastic properties of the raw silk
Generally, it is considered that the reeling bath temperature has to be
maintained at 30 to 45°C. For floating system of cocoon reeling, the
temperature is slightly higher at 40 to 45°C and in between 30 to 35°C
sunken system of cocoon reeling.
cocoons have to be reeled in a low temperature bath. Cocoons which have
reelability or cooked in the pan method of boiling have to be reeled in
is the device which facilitates the new cocoon filament to join the
filaments being unwound in the event of filament breaks, so that a
denier raw silk yarn is produced. In the absence of jetteboutte, the
has to filing the new filament on to the group of filaments, which is a
skilfull operation and requires trained personnel with good eye sight
efficient reeling and to maintain the target yarn denier.
jetteboutte which can also be termed as end gathering device consists
inner brass or stainless steel tube and is fixed on to the stainless
plate above the reeling tray with a lock nut. On this tube is a loosely
circular outer casing made of moulded nylon or HDPE and fits over the
the help of nylon bushes. The outer casing has a flange at one end for
accommodating the driving belt for its rotation and the other (bottom
extended into a curved portion like wings or fins as in fig. 1.
end derives its rotation by frictional contact from a moving
endless belt. Generally the speed of the jetteboutte is between 400 to
a filament has to be joined to a group of filaments being reeled, to
continuity and also uniform denier of the raw silk yarn, the new
fed to the revolving fins of the jetteboutte, which pulls up the
the end and draws the filament into the tube such that it joins the
filaments. By this mechanism, filament feeding is made easier even for
unskilled operator. The end feeding efficiency and the uniformity of
silk yarn is improved. Whereas in reeling machines without jettebouttes
cottage basin, etc. the operator has to fling the filament end on to
of filaments, which is a highly skilful job. This flinging of the
may also result in the extra length of the filament end forming a loop
folding up on the raw silk yarn which is considered a bad cast or loop
and is a
cleanness defect of the yarn.
is a circular ceramic device 20 to 25 mm diameter with concave and
surfaces and a hole of definite size in the center. This device is
mounted in a
button holder just above the jetteboutte, such that the filament is
through the hole. The function of the button is to eliminate excess
adhered onto the silk filaments, combine the loose filaments and
of filaments which may arise due to poor quality cocoons or faulty
process, from getting into the raw silk yarn.
size of the button hole is an important factor in reducing the
defects and also the reeling efficiency. Generally the size of the
button is 2
to 3 times more than the average size of the raw silk yarn being
any waste material three times bigger than the average diameter of the
not allowed to pass through. The average diameter of the button hole is
in the Table.
the diameter of the hole is much smaller than its standard size the
reeling tension increases, which leads to yarn breakages or reels
frequently, reducing the efficiency of reeling. If the whole diameter
higher, slubbs pass through the hole causing cleanness defects.
types of button devices such as the ceramic buttons are available which
cheaper but with a short life. Aluminium alloy buttons even though
tamper proof and has a long life. Stainless steel buttons similar to
clearing device are also available. However, the ceramic buttons are
in the industry. The buttons are generally placed with the concave
being upwards in the Indian silk industry. Fixing the button in this
will lead to water particles collecting in the concave portion and
on the filaments. In China the buttons are fixed with the convex
upwards, such that the water particles slide and drop into the reeling
Retaining the size of the hole is important for maintaining the quality
filaments from the buttons are made to pass over plastic pulleys and
with itself or with the neighbouring end. This portion of the filament
coiled is termed as croissure and the pulleys facilitating the coiling
called croissure pulleys.
objective of a croissure is
to bind the filaments drawn from the button by the coils so that the
filaments are bound together under the coils pressure to make a compact
silk yarn. This binding is obtained due to the wet sericin on the
which agglutinate or cement the filaments together.
proper agglutination is not obtained, the filaments get separated
easily by the
slightest abrasion which arises during the fabric manufacturing
loose binding of filaments show poor tensile properties. Hence,
improves the cohesion property of the raw silk yarn.
more, croissure squeezes out the water from the raw silk yarn (water
on to the filaments as they are unwound from the cocoon in the reeling
If the water is not eliminated, the softened sericin on the yarn forms
spots as it dries on the reel. Croissure also brings circular cross
shape of the yarn, by which the lustre of the yarn is increased.
types of croissure are generally adopted in the reeling industry to
desired objective. They are (i) Chambon or the French type of croissure
(ii) Tavelletta or the Italian type of croissure.
type of croissure is not commonly adopted in the silk reeling industry
in some of the conventional reeling devices such as the hand operated
due to a number of disadvantages.
this type of croissure, filaments from two neighbouring ends are coiled
each other and the threads are drawn once again to the respective reels
winding the compact yarn.
passage of yarn during the formation of Chambon croissure is as shown
fig. 3. As the required tension is low in this croissure, the degree of
agglutination of the filaments is low. If any one of the two threads
during reeling, the broken thread joins with the unbroken thread and
to the reel causing double thread in the hank / skien which is a major
Fluidized Beds to Textile Processing
technique of fluidization, though known for the last fifty or so,
industrial interest only recently. It was first introduced in the
industry during World War II. The inherent advantages of this technique
(i) exposure of a large specific surface for the reaction; (ii) high
conductivity of the reaction surface; (iii) excellent control and
temperature; and (iv) high overall heat-transfer co-efficient1. These
advantages have made this technique applicable in many commercial
such as roasting of gold ores, calcination of limestone, manufacture of
black, phthalic anhydride, hydrocarbons and chemical synthesis from
and carbon monoxide, catalytic dehydration and dehydrochlorination,
diffusion of gases, etc.; it is also reported to be applicable to the
of iron ores and manufacture of cement.
late, this technique has attracted the attention of textile
well. For the last three years, the British Rayon Research Association
and the Shri Ram Institute for Industrial Research in India7 have taken
development of this technique for textile processing.
a fluid is caused to flow upward through a bed of suitably sized solid
particles at a velocity sufficiently high to buoy the particles and to
to them a violently turbulent motion, the bed exhibits characteristics
to those normally associated with fluids, such as, mobility and
pressure, and hence this bed is called Fluid Bed or Fluidized Bed; the
technique is known as Fluidization.
effects of different
variables on some of the characteristics of the bed are discussed below:
of fluidizing medium—The relation between velocity of the upward flow
and the pattern of fluidization and also the pressure drop of the
of gases are shown in Fig. 1 & 2.
1a represents a vertical pipe containing a fixed bed of solid discrete
particles supported on a grid, a steam of gas entering below the grid
passing upward through the bed and two pressure taps P1 and P2 located
the middle of the packed height and at a distance of L. Fig. 2 shows
graphically, in the logarithmic scale, the relation between superficial
gas velocity and (P1 – P2)/L.
increasing the velocity of upward flowing gas gradually from zero, the
passes through the voidage in the bed without any movement of the solid
particles; this is represented by curve OA in Fig. 2. On increasing the
velocity of gas, there is a slight expansion of the bed and
particles so that the bed attains the loosest stable configuration
this is represented by curve AB. At point B, (P1 – P2)/L has reached a
equal to the weight of solids per unit tube cross-section between the
and P2. The condition at B is known as dense homogeneous phase or
further increasing the velocity of gas, a part of the gas flows through
denser but expanded bed which constitutes a continuous phase while the
of the gas passes through the bed in the form of bubbles which
discontinuous phase (Fig. 1c). Now the solids are violently agitated;
condition may be termed as turbulent or two-phase fluidization, which
represented by curve BD. At point D the number and size of bubbles
as a result a number of them coalesce and grow to a size equal to that
tube before escaping from the bed and this creates gas pockets pushing
columns or slugs of solid particles up the tube. Every few seconds a
burst through the top of the tube. This is termed as slugging (Fig. 1d).
increasing the velocity still further, a disperse or dilute homogeneous
fluidization results (Fig. 1e) which is represented by the curve HF.
Point F at
which only one particle remains, represents the balancing velocity for
particle or that of the largest particle in any mixture and falls on
OEFG which represents the pressure drop for the flow of gas alone
transfer coefficient—The overall heat transfer coefficient in a
is higher than that in a packed bed and far higher (40-100 times) than
a gas convection system on account of the reasons given below:
heat transfer coefficient in the fluidization bed is not affected by
thermal conductivity of the solid particles constituting the bed (the
conductivity of the bed is about 100 times that of silver). The heat
coefficient increases gradually with increase in the mass rate of gas
the bed starts slugging (corresponding to the point D in Fig. 2). On
increase in mass rate of gas flow, there is a steep fall in the heat
coefficient (sometimes as much as 50%). The effect of mass rate of gas
shown in Fig. 3.
effects of particle diameter and solid concentration or bulk density of
are also shown in Fig. 3. The smaller the particle diameter, the higher
heat transfer coefficient. With increase in solid concentration, the
coefficient gradually increases, reaches a maximum and gradually falls
the heat transfer coefficient in the fluidized bed is considerably
the extent of 50%) by slugging conditions in the bed, it is important
consider the effects of different variables on slugging conditions.
effect of diameter of the solid particles constituting the bed and the
density of the particles to that of the fluidizing medium are shown in
wherein curves DP1 and DP2 represent the bed density versus ratio of
density to fluid density of the bed of particle sizes DP1 and DP2. At
of particle density / fluid density, rs/rf
(corresponding to P), the bed of particle size DP1 will
slugging, while the bed of particle size DP2 will slug between bed
A and A¢, while the bed of particle size DP1, will fluidize with
rs/rf represented by Q between bed voidages B and B¢.
effect of increasing the height/diameter ratio of the bed is similar to
increasing the diameter of particles constituting the bed. The higher
ratio the wider is the range of bed voidage during which slugging
the lower is the heat transfer coefficient.
has been found that the dimensionless group Dp Lf/A or (particle diam.
height)/(cross-sectional area of bed) defines the transition from the
(Type 2) in the ordinary fluidized bed to that (Type 1) in the slugging
the transition value being 0.008. In Fig. 5, Type 1 curve corresponds
> 0.008, where the heat transfer coefficient decreases as the
increases; and Type 2 curve corresponds to Dp Lf/A < 0.008,
where the heat
transfer coefficient increases to a maximum and then falls down with
in bed height. From the relationship Dp Lf/A it is clear that the
ratio of height to cross-section of the bed and greater the particle
the greater is the slugging tendency.
Reaction of Cellulose with Crosslinking Agents
consists of long chains of glucopyranose residues linked through 1 : 4
b-glucosidic bonds. These chains are close packed with some degree of
the so-called crystalline regions, whereas in non-crystalline regions,
glucopyranose residues are present in a more or less disoriented
Along the b-axis, the chains are held together, forming a sort of
micelles, by hydrogen bonds, which are most likely to be formed in the
orderly crystalline regions. Along the c-axis there are only weak Van
forces between the laminae.
certain degree of confusion exists in the use of the terms ‘amorphous’,
‘crystalline’, ‘accessible’ and ‘inaccessible’ regions, and values
these by different authors vary according to the methods used for their
measurement. There is also some confusion in the notations for the
Whereas crystallographers call the fibre axis or the axis along the
the molecular chains as b-axis, physicists and chemists call this the
In spite of all this, cellulose can be described as a three-dimensional
polymer, in which there are strong covalent
bonds along the a-axis, hydrogen bonds along the a-axis, hydrogen bonds
the b-axis and weak Van der Waals forces along the c-axis, and in which
long chains of glucose anhydride units are arranged in different
order and disorder in different portions of the macromolecule. Cotton
viscose both have the same basic structure; they differ, however,
their average degree of polymerization and the amount of amorphous or
accessible region. Thus while cotton has a degree of polymerization
c. 3,000 with 15 to 30 percent accessible region, viscose has a D.P. of
and has 50 to 60 percent of accessible region.
two main weaknesses of cellulosic textiles, namely, poor dimensional
in wet treatments and ease of creasing, can be understood on the basis
structure of cellulose. When cellulose is treated with water or other
solution, they enter into the accessible region and produce
swelling by overcoming the weak hydrogen bonds and Vander Walls forces
the b- and c-axis. It can be easily seen that such a swelling of fibres
yarn would result in longitudinal shrinkage due to constraints placed
fibres by the yarn twist.
cross-sectional swelling of yarn in a fabric results in a shrinkage
length and width.
a tensile stress is increasingly applied to a cellulosic fibre, the
hydrogen bonds between molecular chains are easily broken producing
one chain against another till the fibre ruptures. Thus, in the
behaviour of these fibres, there is, at relatively low strains, a large
plastic flow or time-dependent creep, where the extension produced is
non-recoverable. This poor elastic performance is responsible for the
creasing of cotton and rayon fabrics.
order to reduce water-imbibition and improve crease recovery, attempts
been made to introduce covalent cross bonds between glucose residues on
neighbouring chains of the cellulose molecule. Since the early attempts
Eschalier1 and, a little later, of Cross and Bevan2, to improve the wet
strength of rayon by treatment with formaldehyde and acetic or lactic
followed by drying at 40-50°C., considerable progress has been made,
reagents have been used to cross link cellulose, However, it is only in
years that we have obtained some understanding of the mechanism of
linking reactions, such as that of cellulose with formaldehyde. It
would not be
out of place to review, in some detail, the significant results
and Guyot postulated that methylene bridge, -O-CH2-O-, are formed by
with two glucose residues of cellulose. Wood disagreed with this
suggested that methylene bridges were formed on two hydroxyls of the
glucose residue or, alternatively, that hydroxy-methyl groups,
formed in the hydroxyls of cellulose. According to Schenk, the changes
about by formaldehyde in the properties of cellulose can be explained
formation of cross links between two adjacent cellulose molecular
Dilleniusb also arrived at the same conclusion from a review of earlier
5 is not very likely to occur, since it involves the formation of a
ring. Reactions 1 and 3 involve the formation of hydroxy-methyl groups
any loss of water. Reactions 2 and 4, on the other hand, lead to the
of ethers with removal of one molecule of water and give products which
stable to hydrolysis. In reaction 6 also, there is no loss of water.
combining weight of formaldehyde will be 30 in reaction 1 and multiples
in reaction 3, depending on the value of n. On the other hand, the
weight of formaldehyde in reaction 2 is only 12, whereas in reaction 4,
21, 24 and 25.2 respectively, for n = 2, 3 and 4.
and Gagliardi used
experimental data on material balance, amount of fixed formaldehyde and
combining weight of formaldehyde to study the mode of reaction.
rayon was treated with 20 per cent formaldehyde and different
hydrochloric acid catalyst, approximately equal weight gains were
after curing. However, on boiling with water, there was a loss in
products cured with higher acid concentrations. Similar results were
by using catalysts of widely varying acidities. This suggests that
there is a
substantial change in the nature of the product of
reaction as the acidity of the catalyst increases. It is likely that
alkaline or weakly acid conditions of curing, reactions 1, 3 and 6 take
Under strongly acidic conditions of curing, reactions 2 and 4 are more
combining weight of formaldehyde varies with its concentration in
lower concentrations, the combining weight approaches a value of 12,
corresponding to the formation of simple methylene ethers as in
reaction 2. At
higher concentrations, the combining weight increases and ethers of the
Z-O(CH2O)n-Z are probably formed according to reaction 4. Reduced
eater-imbibition, insolubility in cellulose solvents and increased
stiffness and elastic recovery also point to the formation of cross
and Pacsu used a different approach in the study of the cellulose
reaction. They argued that if some of the hydroxyls of cellulose were
in cross link formation, this should be reflected in the results of
and methanolysis of the methylated product and in such reactions as
oxidation. By reacting acid-treated cotton with formaldehyde in the
phase at 110-150°C. for 1-24 hr., they obtained a fixed formaldehyde
5 percent or more. Methylation of the product gave a methoyl content of
per cent against 43 per cent methoxyl for untreated native cellulose.
molecule of formaldehyde reacts with two, and only two, hydroxyls in
and complete methylation of all residual free hydroxyls was obtained,
theoretical methoxyl content of the product should have been 37.2 per
This was a definite evidence that the reaction occured between
formaldehyde and two cellulose hydroxyl groups, and that the fixed
was covalently bonded to the cellulose molecule.
of methylated formaldehyde-reacted cellulose gave 39.1 per cent of 2,
6-trimethyl glucoside, 31.9 per cent dimethyl methyl glucoside and 29.0
cent monomethyl methyl glucoside. The dimethyl derivative represents
fraction of glucose residues in which one hydroxyl is involved in a
bridge, while the monomethyl derivative represents those glucose
which one hydroxyl is involved in a methylene bridge and the bridge
the methylation of an adjacent hydroxyl. The yield of trimethyl methyl
glucoside agrees well with the assumption that each molecule of
substitutes two, and only two, hydroxyl groups. The complete absence of
3-dimethyl methyl glucoside shows that the primary hydroxyl groups are
involved in methylene bridges. This was further confirmed by the
periodate oxidation; periodic acid consumption was much lower for
treated cellulose than for natural cellulose.
studied the changes in bending, torsion and stretching moduli as the
formaldehyde (both fixed and soluble) in viscose rayon was increased.
observed that all three moduli increased with increase of formaldehyde,
through a maximum at 5-7 per cent formaldehyde content, and then
(Figs. 1 and 2). If one molecule of formaldehyde reacts with two
groups in different glucose units, the maximum amount of formaldehyde
fibre would be;
the reaction is confined to the amorphous parts only, the maximum would
approximately 9.3 × 0.6 = 5.6 per cent. If was concluded that as the
concentration of formaldehyde is increased, an increasing number of
links is formed giving an increase in the moduli upto c. 5 per cent
formaldehyde. When the fixed formaldehyde is 7 per cent, some of the
links are longer, consisting of two or more formaldehyde molecules,
decrease in the moduli. The moduli decreases further as the fixed
increases to c. 9 per cent, when most of the cross links probably
contain on an
average two formaldehyde molecules.
treatment confers dimensional stability, crease-resistance and reduced
to cotton and rayon materials. However, the acid catalysed reaction
cellulose degradation and brittleness. Various alternative methods have
tried to produce cross bonding; some of them are mentioned here.
readily with viscose in the presence of an acid catalyst. The reaction
analogous to that with formaldehyde and the probable cross bonds formed
also forms cross bonds with viscose cellulose. The bonds are, however,
different in that co-ordination complexes, not covalent links, are
energy of this bond is 10–20 kg. cal. as compared to 80–100 kg. cal.
covalent bond. The bond is broken by water and by chemical treatment.
of ethylene urea,
produced by the interaction of ethyleneimine and an isocyanate, are
capable of producing cross bonds. The reaction occurs at comparatively
temperatures (100–120°C.) without a catalyst, according to the
form amide also forms cross bonds with viscose in the presence of an
catalyst. The reaction is as follows:
formamide liberates formaldehyde and forms ether links, its residue
attached to the cellulose at the end of the reaction to give the
a misnomer for cellulose nitrate, is an important commercial product.
It is an
essential ingredient of blasting explosives, and a base for
propellants. It is
also used in the celluloid and lacquer industries.
in 1832 observed the formation of inflammable materials by the action
acid on cotton, starch and wood fibre, and obtained impure products
called xyloidines. Pelouze in 1838 investigated the action of nitric
cotton. The technological importance of the process was recognized in
Shonbein who took out a patent for nitrated cellulose obtained by
cotton with a mixture of nitric and sulphuric acids. The products
him were, however, unstable and there were some serious explosions, the
being the one in Faversham in 1847. This led the governments in several
countries to ban its manufacture and use.
progress was in the direction of preparing a stable product and the
researches of Abel led to the understanding of the cause of
instability, and to
the manufacture of stable nitrocellulose.
three alcoholic groups—two secondary and one primary—present in each
residue of the cellulose chain may react giving three or more compounds
corresponding to the successive nitration of the three hydroxyls. The
product of the reaction should be trinitrate C6H7O5(NO2)3 with a
content of 14.15 per cent, but it is not possible to obtain a stable
with this nitrogen content by the action of sulphuric and nitric acid
By using special techniques, it is possible to obtain a product nearing
theoretical composition. However, in actual practice, a series of
with nitrogen contents varying from 10–13.5 per cent are prepared. The
grades of nitrocellulose usually met with in industry, and their uses
in Table 1.
was first prepared in India at the Cordite Factory, Aruvankadu, which
today the only factory producing it. Till very recently, the only use
nitrocellulose was for defence purposes. During the last three years,
Factory has been supplying nitrocellulose of grade (iii) to
artificial leather, book binding cloth and lacquers, and so far 170
this material has been supplied. It has been estimated that the paint
will require 500 tons of nitrocellulose per annum during the second
period. The gelignite industry, sponsored by the Government of India,
collaboration with Messrs Imperial Chemical Industries, also uses
nitrocellulose. Proposals for the manufacture of raw photographic films
India are also under consideration. Thus the demand for nitrocellulose
raw materials in common use are cotton, in the form of spinners’ waste
linters, and paper. Where cotton is plentiful, linters constituted the
raw material, as they are otherwise wasted and their removal is
for oil recovery from cotton seed and for utilizing the oilcake as
spinners’ waste, available from textile mills, is used as the raw
Aruvankadu. This material is expensive, as it finds other uses and has
good export market. In England, paper in the form or scrolls or sheets,
into small pieces, are used for nitration.
waste is first treated to remove waxes, lignin, hemicellulose, etc., by
with alkali pressure, a process called ‘kiering’. The kiered product is
free of alkali and dried. The process of kiering, washing and drying
has to be
done under properly controlled conditions as otherwise the product
ball up or form knots and the penetration of acids, in the subsequent
displacement process (Fig. 1)
is largely employed for the nitration of the cleaned material. The
consists in dipping the cotton in mixed acid for hr. at the end of
acid is slowly displaced by water.
nitration unit consists of 4 pans, and each pan received a charge of
cotton and 6 cu. ft. of mixed acid. After hr. during which the
ranges between 17° and 21°C., water is slowly let in at the top, while
corresponding quantity of spent acid is drawn off from the bottom. The
acid is revivified by doping with nitric acid and used again. The
float shuts off the flow of acid as soon as the specific gravity falls
and diverts it into waste. The following are the working figures for
manufacture: Acid composition— sulphuric acid, 70; nitric acid, 22; and
per cent. Composition of recovered acid—sulphuric acid, 71.5; nitric
18.5; and water 10 per cent. Yields, 170 per cent.
are certain inherent disadvantages in this method. The mixed acid is
troublesome to handle. On wet days it fumes heavily and in spite of
draught arrangements, handling is difficult. The feeding of dry cotton
has to be carefully controlled. Only small quantities should be fed
and rapidly pushed under the acid with stainless steel forks.
heating occurs with onset of decomposition. The maximum permissible
content of cotton is 2.5 per cent; if this is exceeded pan fires are
occur. Sometimes, in spite of all precautions, fires set in with
accompanied by intense fumes of nitrogen dioxide, which are dangerous.
of the risks involved, the process does not find much favour. As
disadvantages, the process is foolproof and requires comparatively
operational control. Small variations in composition of mixed acid,
variations in temperature and even time of nitration and displacement
accommodated. The quality of the batches is remarkably uniform.
second method, which has found favour in many countries, is the
process (Fig. 2). It consists of a constant volume reservoir, from
mixed acid is measured out into the nitrator. Cellulose is added to the
under stirring. The nitration is carried out for 20–45 min. at the end
which, the contents are emptied into a centrifuge and the acid
wet nitrocellulose is rapidly drowned in a large volume of water and
The advantages of this method are: space required for the plant is
compared to the displacement process ; manual labour is reduced : the
is clean and capable of practically continuous operation by having
units running in cycles: the period of nitration is shorter ; and a
of cellulosic material can be used as raw material. Further, air-dried
cellulose can be used. By altering the temperature of nitration by
calorifiers, any type of nitrocellulose can be produced for commercial
purposes. As against these advantages, the acid composition is to be
maintained, and each manufacturer has to work out the conditions of
best suited for the raw material employed and the final product
in the centrifuge are common; it has been found that if the nitrated
is over centrifuged and has less than a minimum acid content, the
tends to catch fire. Corrosion is a serious problem and maintenance
high. The chief drawback is that the nitrocellulose obtained is more
than that produced by the displacement process and requires more
after-treatment. Further, the proportion of acid to cellulose is high
(sometimes as high as 1: 60, as against 1: 30 in the dis-placement
the recovery of spent acid is poor.
nitrated fibre is boiled in lead-lined vats a number of times, with
water between boils. The initial acidity which is c. 0.10 per cent goes
0.04 per cent. In Aruvankadu (height above sea level, 6,000 ft.)
boils of 8 hr. duration at a pressure of 7 lb. /sq. in., corresponding
temperature at 105°C. are done.
stabilized material is beatered in hollanders, of the type used in
industry, in a faintly alkaline medium. It is subjected to a series of
called potchering, to remove impurities. Finally, as nitrocellulose is
to slow decomposition even at ordinary temperatures of storage, a small
quantity of finely divided precipitated chalk is added to the material
neutralize any acid that may be produced during storage. The material
centrifuged and sold either ‘alcohol-wet’ or ‘water-wet’. For some
uses, diphenylamine (1%) is used as stabilizer.
cellulose retains most of the physical characteristics of the original
material, except that the fibres are hard and brittle.
of Varying Nitration
the wide range of permissible variations in the proportions of nitric
sulphuric acid and water in industrial practice, the selection is
considerations of cost and also of the marked swelling or dissolving
the fibre exhibited by some of the compositions. Using cotton waste as
material and the displacement process for nitration, a mixed acid
sulphuric and nitric acids in the ratio of 1 : 3, gives a
13 per cent nitrogen ; with a mixed acid containing ; sulphuric acid,
nitric acid, 22.5 ; and water 15 per cent, a product containing 12.2
nitrogen is obtained. Further, while the production with the first
soluble in ether- alcohol (2: 1) to the extent of only 10 per cent, the
is completely soluble in the mixed solvent. This difference in
one of the criteria for distinguishing guncotton from other types of
conditions have a significant bearing on the viscosity of the resultant
products, a property of extreme significance in its use for particular
purposes. It has been shown that by substituting anhydrous phosphoric
by using phosphorus pentoxide and nitric acid at 0°C., a very high
nitration is obtained, without significant degradation of cellulose.
method has been employed for estimating the degree of polymerization
molecular size of the original cellulose.
main characteristics of nitrocellulose are its nitrogen content and
The latter depends on the raw material employed and the condition of
The viscosity can be brought down to any limit, either by degrading the
material before nitration or by depolymerizing the nitrated material by
under pressure. The latter is the preferred method, as the preliminary
degradation of raw cellulose results in a friable material difficult to
and entails heavy losses in processing. During pressure boiling, a
amount of acidity develops by hydrolysis and some nitrogen is lost. By
control of pressure and time, any required type of product can be
some cases, as in the case of low-viscosity industrial nitrocellulose,
boiling achieves both stability and degradation.
trade practice, ether-alcohol solubility provides the criterion for the
of nitrocellulose. This solvent is scarcely suitable for viscosity
determination. Acetone can also be used, but it is hygroscopic. The
Chemical Industries use a mixture of 95 per cent acetone and 5 per cent
as solvent. Butyl acetate and ethyl acetate have also been used, but
the purity of the solvent is important in viscosity determinations. In
practice, the solvent in use (Hercules solvent) consists of mixture of
ethyl acetate, 25 parts alcohol and 55 parts toluol by weight, and
determinations are made with a 1 per cent solution for highly viscous
a 12.2 per cent solution for degraded material.
molecular weight of nitrocellulose is determined by osmometric method.
true values obtained by the method are different from those obtained by
Dissolving Pulp for Rayon Industry
pulp, a highly purified form of chemical pulp, is the chief raw
employed in the manufacture of rayon, cellulose acetate, cellophane,
nitrocellulose, methyl cellulose, ethyl cellulose and other cellulose
meet the requirements of industry, which produces 47 tons of rayon per
India at present imports dissolving pulp values at Rs. 1.8 crores per
we are able to utilize indigenous cellulosic raw materials and
dissolving pulp industry in India we will be able to effect a saving in
exchange to the tune of Rs. 6.5 crores per annum.
the manufacture of viscose rayon (Fig. 1 & Table 1 and Fig. 2),
pulp, usually bleached sulphite pulp, is steeped in sodium hydroxide
of 18 per cent strength at 20°C. for 1 hr. to form soda cellulose. The
pulp is then pressed to yield alkali cellulose which contains:
sodium hydroxide, 15; and water 55 per cent. The pressed out alkali is
generally reused after recovery. The pressed alkali cellulose is
23°C. for 1 hr. and aged in the presence of air at a temperature of
c. 30 hr. Ageing is essentially a cellulose depolymerization step and
optimized to yield a product of the desired viscosity for later
aged alkali cellulose is then reacted with carbon disulphide at 28°C for hr. to form sodium
cellulose xanthate. The
xanthated mass is dissolved in dilute caustic solution at 18°C. in the
of hr., to give
containing : cellulose, 7.5 ; sodium hydroxide, 6.4 ; and total
per cent. It is then filtered to remove unreacted cellulose fibres,
impurities and gels, deaerated under vacuum and ripened and 20°C. for
c. 40 hr.
Cellulose xanthate partially de-esterifies during ripening, and many
reactions also occur.
viscose is pumped through spinnerettes into an acid spinning bath to
continuous filament. During spinning, the excess of caustic is
xanthate is de-esterified and regenerated cellulose molecules are
the spinning stretch. The spum yarn in the cake is then washed,
bleached, finished, dried, conditioned and rewound in the form of cones
the selection of dissolving pulp, two major considerations are
: (i) commercial, e.g., price and availability, and (ii) technical
with which the pulp responds to rayon making and the effect of pulp
constituents on the yield and quality of the final product. This paper
mainly with the technical aspects of pulp selection.
pulp is generally prepared from wood and as such, it contains wood
constituents, the proportions of which depend upon the extent of
results of pulp analysis (Table 2) indicate that pulp contains alpha-,
and gamma-cellulose extractibles, ash components and small proportions
has been arbitrarily defined as the fraction which remains insoluble
is treated with 17.5 per cent sodium hydroxide, at 20°C. for 30 min. It
corresponds to cellulose with a degree of polymerization (D.P.)
Viscose rayon has a D.P. range of
350 and the alpha-cellulose value gives a measure of the overall pulp
quality. Pulp consumers are interested in getting a pulp containing
alpha-cellulose. The determination of alpha-cellulose, however,
information on the polymolecularity of long chain molecules and this
necessitates the measurement of D.P.
is the term applied to polyoses, mainly xylans, arabinans, glucosans,
galactans, mannans, etc., which are removable by cold or hot dilute
they are present in relatively small quantities in dissolving pulp,
manufacturers evaluate hemicellulose in terms of Cross and Bevan’s
certain amount of hemicellulose is necessary in paper pulp in order to
high degree of hydration, but for dissolving pulp, except for that
sheet formation and its swelling, hemicellulose is usually an
constituent. Cellulose molecules of less than 200 D.P. are usually
producing a coherent fibre7. It is still uncertain whether the chemical
configuration of hemicellulose influences pulp quality; the degree of
polymerization and its physical state are far more important than
is that fraction which gets precipitated when soluble pulp
obtained by treating pulp with 17.5 per cent sodium hydroxide at 20°C.
min., are neutralized. This fraction includes polyoses with D.P.
10 to 150.
is that fraction which remains in solution when the soluble
obtained by treating pulp with 17.5 per cent sodium hydroxide at 20°C.
min. are neutralized. This fraction includes polyoses with D.P. up to
molecular fractions of cellulose that remain unextracted during
undergo xanthation and appear in the yarn. They do not contribute to
tenacity and they, therefore, act as diluents or fillers. Moreover, the
solubility of cellulose xanthate is influenced by the chain length of
cellulose; the smaller the chain length, the greater the solubility of
xanthate found. Soluble xanthates hinder the effects of spinning
stretch. It is
desirable, therefore, to keep the concentration of low molecular
fractions to a
The effect of chain length distribution on the properties of rayon has
extensively studied. The changes in the D.P. of cellulose during
manufacture are given in Fig. 3. A rayon pulp of good quality should be
uniform as possible with respect to molecular size, and the purpose of
in viscose manufacture is to make the chains uniform with respect to
degradation to a D.P. of c. 500, as brought about by the oxidation of
cellulose, removes the differences in molecular weight distribution in
It appears, therefore, that molecular weight distribution is not an
characteristic of viscose pulps which are subjected to alkaline ageing.
yarn tenacity increases with the increase in D.P. up to 350–400 after
relationship is asymptotic. Published word in this field indicates the
desirability of keeping the D.P. of finished yarn in the range of
reducing power of cellulose is usually expressed in copper number,
represents the copper is Fehling’s solution reduced by 100 g, of
copper number of cotton cellulose ranges from 0.05–0.08; higher copper
indicate degradation. Bleached sulphite wood pulps have a copper
1.5–2.5 and as it provides chiefly a measure of hydrocellulose and
in the pulp and gives no additional information to that given by alkali
solubility and viscosity tests, copper number is seldom determined.
non-cellulosic constituents of pulp have a pronounced effect on
They should be as low as possible without affecting the uniformity of
earths, such as calcium and magnesium, hinder pulp reactivity and
poor viscose filtration. High percentage of silica also has a similar
Calcium is detrimental also because it tends to cause incrustations
rate of alkali cellulose ageing is distinctly influenced by the
certain metals, such as iron, nickel, cobalt, cerium, vanadium,
maganese, which catalyse the ageing process. Nickel has the lowest, and
and manganese the highest catalstic effect.
litle as 0.1 per cent iron in wood pulp reduces the ageing time of
cellulose to one-forth the normal ageing time. Even smaller
iron (0.0018–0.015%) has an appreciable effect on cellulose
The presence of copper in small amounts has no effect.
concentration of lignin, a polymer of phenyl propane groups, should be
as possible in pulp. Its presence interferes with pulp reactivity.
constituents soluble in organic solvents, like ethyl ether, are fats,
acids, resins, waxes and non-volatile hydrocarbons. In small
act as wetting and emulsifying agents and are, therefore, useful.
processibility is usually measured by converting the pulp to xanthate
determining the case with which the xanthate dissolves in caustic as
by the filtration characteristics of viscose. Filtration is influenced
processing conditions adopted for viscose manufacture, filter area,
media and the pressure drop maintained during filtration. The
can be conveniently used to preduct pulp processibility by comparing
of d v/d q vs. 1/v (v = volume of viscose filtered, q = time in min).
for a pressure
drop of 20 lb./sq. in. using the
filter media and viscose processing conditions as that used in
manufacture. A laboratory scale set-up with a filter area of 12 sq.cm.
suffice for the test.
Dissolving pulp should be uniform in quality through out the
also from consignment to consignment. Slight differences in viscosity,
solubility, ash constituents, etc., can have pronounced effect on
conditions. For stable operation, it is essential that tha variations
recommends that the viscosity may be considered uniform if viscose made
ten 60 lb. Samples of successive lots of pulp does not vary by more
than 6 per
cent from the average. Pulp uniformity can also be judged by the
alpha-cellulose content of pulp which should not vary by more than ±1
from the average.
pulp should also show uniformly high solubility as gauged by the
characteristics of viscose made from successive lots.
of pulp sheets:
Steeping is an important processing requirement as far as sheet
concerned. A pulp which does not steep well is likely to cause
difficult in the
subsequent operations of ageing, xanthation, filtration and spinning.
under the best commercial conditions, the geometry of books, that is,
size, spacing, etc., results in a gradient in alkali content from
sheets to the central sheet. To avoid this, the pulp sheet should be
to absorb alkali evenly. The absorption properties of the fibre mass
balanced against the physical design of pulp sheet. With a correct
between absorption rate and rate of caustic rise due to capillary
steeped sheet should neither float nor slump in the press, and it
free from areas of incomplete penetration. The importance of pulp
which affect steeping cannot be over-emphasized, because there are no
ways of adjusting the subsequent processing stages to compensate for
suffered from non-uniform steeping.
effect of different constituents of pulp on the manufacture of rayon
studied by a number of investigators in Europe, U.S.A., Canada and
on their results our own experience in this field, we have arrived at
following specifications for dissolving pulp (Table 3).
it is not possible to get an exact idea of the quality of rayon which
produced from given pulp specification, complete evaluation of pulp by
plant tests is necessary.
Anti-Crease and Anti-Shrink Finishes for Viscous Rayons
rayon, a regenerated cellulose fibre, is significantly different from
natural cellulose fibre, cotton. The former has a low degree of
(D.P., 250–600), compared to cotton (D.P., 3,000 and above); it is
amorphous, the crystallinity being 25-40 per cent as compared to 70-80
cotton. The characters which viscose rayon possesses owing to these
are: (i) greater susceptibility to dimensional changes when washed;
wet strength; and (iii) low tensile strength per unit cross-section
from molecular configuration, the strains introduced during spinning
weaving, and the strain introduced in rayon fabric during the various
dyeing and finishing, have a marked effect on the dimensional behaviour
fabric. The combined effect leads to a shrinkage of 20-25 per cent in
georgettes and a shrinkage of 7-15 per cent in satins, crepes, staple
have been made from time to time to improve the properties of viscose
suitable chemical modification. The earliest attempt by Eschalier is
noteworthy. The process proposed by him involved the use of
formaldehyde in the
presence of acidic catalysts, and it was claimed that shrink resistance
tensile properties of rayon improved as a result of the treatment. The
did not, however, attain commercial success. Interest in the aldehyde
of textiles was revived after the end of the First World War Marsh et
(Tootal Broadhirst & Lea Co.) made a notable contribution when
introduced the urea-formaldehyde anti-crease process. Since then, a
firms in U.S.A., U.K. Germany, Holland, Japan, etc. have made notable
contributions in this field. The main lines of work are:
Treatment with synthetic
resin pre-condensates formed from ureamelamine or their derivatives and
formaldehyde; (ii) treatment with aldehydes alone, such as
glyoxal, etc., and (iii) treatment with other cross bonding agents such
vinyl sulphone, epichlorhydrin, potassium disulphate, ethylamine, etc.
attempts were in the direction of modifying either the properties of
those of cross linking agents in such a manner that there is an
one or more of the following aspects: (i) reduction in brittleness
softer handle; (ii) reduction in chlorine retention resulting in better
bleachability; (iii) improvement in wet tensile and wear values; and
improvement in process details, such as type of catalyst, protective
and temperature or manner of curing.
manufactures c. 500 million yards of rayon cloth. A large part of it is
processed neither for anti-creasing nor for anti-shrinking
is an increasing demand for Indian rayon fabrics, particularly in
south East Asia. Processing of fabrics for anti-creasing and
will improve the quality of products and stimulate foreign demand.
Shri Ram Institute took up
studies on anti-crease and anti-shrink finishes in
1953. Available techniques were first examined, and later,
compound, designated Srifirset, which could be used for improving the
anti-crease and anti-shrink properties of rayon fabrics was discovered.
for the preparation of urea-formaldehyde pre-condensate and for
goods were worked out. The stability of the treating solution was
different temperatures and the ‘know-how’ of the process was developed
object of rendering help to those interested in the process.
process which uses resins and the process which uses formaldehyde
involve three steps: (i) Padding with treating solution, (ii) drying,
curing at high temperature.
were made to simplify the process to eliminate the need for curing. On
analyzing the normal formalizing process, it was found that free water
in the treating solution made high temperature curing imperative. A
evolved in which the free water was bound by the addition of
compounds, such as calcium chloride, magnesium chloride and aluminium
The new process consists in simply treating rayon textiles with a
containing formaldehyde, acid catalyst and a hydrophilic agent, say
chloride, for a certain duration at room temperature, washing and then
No baking is necessary. All forms of textile material, viz., fibres,
fabrics, can be treated, and treated fabrics posses better draping
and crease recovery; they are also shrink-proof.
the process appeared attractive a detailed study was undertaken. The
different variables, such as duration of impregnation and concentration
in the treating bath, were studied. The results are given in Tables 1
increasing the duration of impregnation or the concentration of acid in
treating bath, the shrinkage is reduced and the loss in tensile
increased. The result was confirmed by experiments carried out with
fabric in place of yarn (Table 3). As the loss in tensile strength is
process has no practical utility.
normal urea-formaldehyde process suffers from the following
unstability of treating bath, (ii) many steps, such as padding, drying
curing, involved in the treatment, and (iii) embrittlement of treated
Attempts made to overcome these defects, resulted in the discovery of a
compound, Srifirset (a carbohydrate derivative of urea) and the
a process for utilizing Srifirset with formaldehyde.
development work involved a detailed study of Srifirset: formaldehyde
the bath. Srifirset concentration. pH of the bath. temperature of
duration of drying. The results are summarized in Tables 4–9.
has been observed that when the pH of the treating bath is lowered, the
shrinkage is reduced. The combined Srifirset increases as the
duration of drying increases ; but long exposure at high temperature
yellowing with loss of tensile strength. The higher the temperature of
the lower is the shrinkage. Among the catalysis tried, a mixture of
acid and aluminium sulphate appears to be the best from the point of
dimensional stability and minimum loss in tensile strength ; ammonium
is the best from the point of view of anit-crease properties. It will
from the results set out in Tables 4–9 that the optimum conditions for
treatment are approximately as follows : Srifirset-formaldehyde ratio,
Srifirset conc., 12 per cent for crepes and 8 per cent for georgettes ;
; drying temp., 90–140°C. ; and
of drying, 1–10 min.
Heat Treatment of Resin-Treated Cellulosic Textiles
is common experience in mills that lack of consistent drying of
to non-uniformity of the finished goods. This is particularly so in the
finishing of textiles. Though the technology of resin finishing has
considerably, and the known-how of the process involved is well
the quality of the finished product depends on the experience and
the finisher, in regard to control of conditions, particularly at the
and baking stage.
following are the difficulties that finishers encounter in the
Non-uniform resin distribution due to non-uniform padding, non-uniform
baking and migration of resin ; (ii) excessive losses in the physical
mechanical properties of treated material due to surface deposition of
excessive drying and/or baking, improper pH control and choice of
(iii) poor wash-fastness of treated materials due to surface resin,
baking and poor catalyst action ; (iv) variation in fabric geometry
affects the degree of drying and baking required and the amount of
resin to be
applied ; and (v) satisfactory handle and feel, which are entirely
factors and but which neverthless depend on the factors mentioned above.
moisture content of the material is an important factor to be taken
consideration during the various stages of operation, particularly
baking ; moisture content is responsible for (i) the migration of
obtaining the requisite degree and rate of drying and baking, (iii)
activity and pH control and (iv) physical and chemical modification of
Properties and Moisture Content
is well known that moisture plays an important part in modifying the
and chemical properties of textile materials, particularly cellulosic
materials, which contain a large number of hydrophillic groups.
Increase in the
wet tensile strength of cotton and decrease of the same in rayons may
as outstanding examples.
of water by cellulose is
due to absorption and capillary condensation. It is the rigidly held
through strong hydrogen bonding forces which causes hysteresis
bonds between cellulose OH groups are broken by water and are not
reformed in the same fashion, thus enabling some water to be entrapped
structure of the polymer.
is known that cellulose can contain non-freezable water.
and related phenomena are bound to influence the course of resin
and subsequent physical properties of the treated fibre. For example,
be interesting to see how far the trapped moisture would help to
losses in tensile strength due to stresses produced by the polymerized
embedded in the structure ; the trapped moisture may help to plasticize
rigid structure of cellulose after resin treatment so that the
could still be maintained in a mobile condition to impart strength to
et al. have shown that thermal treatment of cellulosic fibre leads to
modifications depending on the moisture content of fibres. The
affected are swelling and sorption capacity which decrease to the
extent of 50
per cent in cellulose, 30 per cent in silk; the density increases and
results in increased crystallinity up to 4 per cent in cellulose. At
optimum moisture content, the properties are modified to the maximum
initial stages of heat treatment.
increase in temperature the
modifications are more pronounced; after a certain limiting
tendering of fibre starts. This limit depends on the nature of the
fibre but is
between 110 and 130°C.
a wet textile fabric is subjected to heat treatment, drying proceeds at
constant rate till moisture content attains a certain critical value,
the critical moisture content. After this, the rate of drying falls off
is a rapid rise in the temperature of the fabric depending on the
of the source of heat. Therefore, during the period of steady rate of
the temperature of the fabric would be the same as the temperature of
evaporation of water and thus there would be no risk of excessive
being produced on the material before the critical moisture content is
This critical moisture content is a specific property of the fibre, and
moisture (per cent) for various fabrics are the following: Cotton, 25 ;
rayon, 28 ; silk, 27 ; and wool, 39.
Tone and Shade Control in Textiles
is an old industry and development in it for a long time came only
until in fact Perkin synthesized Mauve . . . . It was really the advent
(synthetic) fibres which demonstrated the need for new dyeing
was only when grave difficulties were experienced in dyeing a new fibre
established dyestuffs and techniques, that new techniques were evolved
. . . .
New dyeing processes were, therefore, forthcoming to meet the special
of new fibres, but when once the new processes had been developed,
was extended to natural fibres too and often with beneficial results.”
new dyeing processes envisage continuous operation at elevated
in continuous dyeing—Continuous dyeing of textiles consists of the
steps: (i) Passage of the fabric through the dye solution or dispersion
treatment); (ii) padding to obtain uniform distribution ; and (iii)
treatment to obtain diffusion and fixation or chemical reaction of the
molecules with the fibre substance at localized sites in a short time.
of these steps is a technique by itself requiring efficient control,
is difficult to rectify the mistakes at the subsequent step. Hence it
needless to stress the importance of the factors that are responsible
efficiency of each of these steps in obtaining well-penetrated, uniform
shades without any adverse effect on the tone of dyeing.
treatment—The passage of cloth through the dye solution or dispersion
enable it to absorb enough solution so that thorough wetting takes
the dye solution penetrates the fabric completely.
in the continuous method of dyeing, the following restrictions are
which a compromise must be reached for the process to be economical as
efficient: (i) The time of contact with the dye liquor is of the order
fraction of a second. For example, in the Standfast Molten Metal Unit,
contact time is 0.44 sec, at 30 yd per min. and 0.11 sec. at 120 yd per
(ii) The volume of dye bath must be as small as possible in order that
minimum wastage of dye liquor at the end of the run. (The dye bath of
Standfast Molten Metal Unit is the smallest known in continuous dyeing
operations.) (iii) The concentration of the dye solution should be much
than that normally used. (iv) The affinity of the dyestuffs for the
what is known as tailing effect. (v) The dye bath temperature should be
as possible so that the time required during the heat treatment of
reduced to a minimum. (vi) The rate of feed must match the rate of
the dye solution by the material in order to reach (dynamic)
early as possible. (vii) The feed liquor should not be far different in
concentration from the dye bath solution ; in fact, it would be
the feed liquor is of the same concentration as the dye bath solution
study of these factors with respect to dye bath construction forms an
aspect of the continuous dyeing technique for obtaining uniform shades
minimum tailing effect.
effect arises on account of the affinity of the dye for the fibre,
amount of dye uptake by the fibre is always in excess of that given by
squeeze per cent. As a result of this, the concentration in the fabric
corresponding variation in colour. At the equilibrium stage the excess
of dye taken up by the fabric equals the difference between the added
the dye in the trough, so that the fabric gets a continuous and uniform
The problem of tailing is related to the time required for the padding
to come to an equilibrium, or in other words, the length of cloth which
run before a uniform colour is obtained. Table 1 illustrates this point.
yardage required to ensure consistency of depth (within 5%) can be
by taking into consideration the affinity factor, dye bath capacity and
affinity factor itself is a complex entity depending on a number of
besides the intrinsic character of the dye molecule itself, e.g.
temperature of the dye bath, presence of salt and other compounds in
bath, fabric construction and fibre properties, and padding system.
appears to be no systematic study of each of these aspects
Adequate details of the work done so far are not available. Some
available with respect to the Standfast Molten Metal Unit where the
and agitation in the bath stimulate horizontal as well as vertical
liquor on both sides of the cloth. Recently, the idea of high
turbulence in a
small narrow dye bath through jets has been introduced to overcome the
difficulty of tailing in continuous ribbon dyeing . Bond’s machine
jets of hot dye solution to obtain complete dyeing. The latest
dye bath construction is the application of ultrasonics to obtain
transfer and penetration. This, however, is still of academic interest.
Recently, the authors have applied the techique of fluidized beds of
discrete particles where the dye solution acts as the fluidizing medium
addition to be homogeneity of dye bath liquor and fabric penetration,
obtained satisfactorily by adopting a few of the methods, there are
factors, such as properties of high concentrated dye solutions, dye
capacity, rate of feed affinity and strike of the dye and fabric
which demand attention. All these contribute to the tailing effect,
differential shade obtained in the beginning and at the end. Mann and
have carried out a fundamental study of these factors and suggested
reducing and tailing effect. One of the suggestions pertains to the dye
capacity and the rate of feed. According to them, the trough capacity
as low as possible so that the cloth empties it many times, at least
one and a
half-times, within a short time.
is, therefore, evident that
the control of shade in a continuous dyeing system is a complex problem
requiring considerable skill and knowledge on the part of the dyer. This complication would be
all the more
aggravated when a mixture of dyes is to be applied to the fabrics. In
understand this complex system in which a number of variables are
is necessary to study the affinity factor under various sets of
are normally encountered and evaluate their relationship with other
cloth passes through the liquid first and then through the padding
obtain the requisite squeeze per cent and uniform distribution of the
the length and the width of the fabric. Hence, uniformity of shade
the efficiency of the padding mangle, particularly in a system of
dyeing not involving subsequent leveling off of the dye. It is only
that the padding mangle and the padding system have received attention
fundamental point of view. It has already been pointed out that the
mangle also plays an important part in the tailing effect by
liquor pick-up on which dye feed depends.
treatment—The dye molecules which have been transferred to the
or close to the requisite sites are fixed in situ finally by heat
Methods of heat treatment for the fixation of dye molecules on the
considerably improved since the advent of synthetic fibres, which
require high temperatures. Molten metal, hot oil, steaming chambers,
infra-red heating and, more recently fludized beds (Fig. 2) are some of
methods of heat treatment. These developments have been essentially
meet the special demands of synthetics which are employed, mainly, as
dyes. The dyes have no affinity for the fibre and are supposed to form
solution with the fibre material. In adopting these techniques for
fibres, a number of problems are to be faced, such as stability and
of natural fibres at high temperatures, stability and behaviour of
high temperatures, high rates of diffusion of dyestuffs at high
and moisture versus migration of dyestuff molecules into the fibre
account of the high rates of diffusion at elevated temperatures, the
time of heat treatment is considerably reduced ; for example, for vats
in pad steam
process it is about 15–25 sec. and for directs, 2 to 3 min.; in the
Molten Metal Unit, it is 1.6-7 sec. In the fluidized bed technique
the Shri Ram Institute for Industrial Research, the authors have found
heat treatment for 3 to 8 sec. (even 1 to 3 sec.) is sufficient to
satisfactory dyeing. In all these cases, particularly when the
exceeds 120–130°C., the dyeings suffer from tone change as compared to
dyeing. Tone changes are due to decomposition or structural changes in
molecules, e.g. possible over-reduction in the case of leuco-vat dyes
reduction of directs in the presence of cellulose and alkali. In fact,
present, manufacturers of dyestuffs supply a classified lists of
dyestuffs for the use of dyers ; however, the lists cannot be used to
advantage where conditions are not identical with those recommended by
manufacturers. It appears that the tone can be controlled, to a certain
by properly controlling moisture and by using protective agents, such
hydrogen peroxide, sodium percarbonate, perborate and dichromate. These
however, are not useful above 100°C. ; further they increase the
the material after decomposition. Ammonium salts of mineral acids are
better, but not altogether satisfactory. The addition of monochrom
gives better results than all the protective agents recommended so far.
compositions are becoming increasingly used, for example in the garment
manufacturing trade, for bonding fabrics together. In the garment
trade it is known to bond two fabrics together using a hot melt
composition which is capable of being activated by heat and pressure in
pressing operation. However, in many cases the physical properties of
adhesive composition have to be quite specific in order to retain a
satisfactory adhesive bond throughout the lifetime of a garment.
example, an adhesive composition for use in the garment manufacturing
be required to retain its bond strength when a garment is being washed
soapy water and also when the garment is being dry cleaned in cleaning
such as perchloroethylene, trichloroethylene or alcoholic spirits. In
to the requirement of resistance to dry-cleaning solvents and to
warm soapy water, it is important that adhesives have a relatively wide
softening point range to enable their use effectively in industrial
bonding of fabric sheet, for example, in the known procedures for
spaced dots of adhesive from powered resin adhesive.
process described relates to water-soluble compositions prepared by
the presence of an alkaline reagent, an aliphatic aldehyde containing
than 4 carbon atoms, or a reversible polymer thereof, with an
N-3-oxohydrocarbon-substituted acrylamide having the formula
each R1 is individually hydrogen or a hydrocarbon or substituted
radical, at least one R1 being hydrogen; each of R2 and R3 is hydrogen
hydrocarbon or substituted hydrocarbon radical; and R4 is hydrogen,
a lower alkyl or substituted lower alkyl radical; the reaction being
in a diluent comprising (1) water, or (2) an organic liquid which is a
for the reactants or the product or both, or (3) a mixture of diluents
1 and 2.
preparation of the preferred compositions of this process, from one to
and preferably all five of the R1 radicals in the
acrylamide reagent are hydrogen; R2 and R3 are lower alkyl radicals;
and R4 is
hydrogen or methyl. Suitable N-3-oxohydrocarbon-substituted acrylamides
described in U.S. Patents 3,277,056 and 3,425,942.
are N-(1, 1-dimethyl-3-oxobutyl) acrylamide, referred to as diacetone
acrylamide, and N-(1, 3-diphenyl-1-methyl-3-oxopropyl) acrylamide,
as diacetophenone acrylamide. Because diacetone acrylamide is preferred
most readily available, it will frequently be referred to in this
preparation of the water-soluble compositions of this process is
the following examples. All parts and percentages are by weight unless
1: A solution of 338 parts (2 mols) of diacetone acrylamide in 1,000
water is heated to 50°C and 45 parts of a 3% aqueous solution of
phosphate is added. Dropwise addition of a 37% aqueous solution of
is then begun and is continued for one hour, a total of 650 grams (8
formaldehyde) being added. During the formaldehyde addition, three
portions of trisodium phosphate solution, one of 14 parts and two of 15
are added. Heating is continued for five hours after formaldehyde
complete, and during that time additional increments of trisodium
solution are added, care being taken that the pH of the mixture never
above 10, until a total of 299 parts have been introduced (0.16 mol or
percent based on formaldehyde). The solution is cooled and filtered,
volatile materials are removed by heating under vacuum at 55°C. The
a 61% aqueous solution of the desired water-soluble composition.
2: Following the procedure of Example 1, a similar reaction product is
from diacetone arcylamide and acetaldehyde.
3: Following the
procedure of Example 1, a similar reaction product is prepared from
acrylamide and n-butyraldehyde.
4: A solution of 280 parts (1.66 mols) of diacetone acrylamide in 296
distilled water is heated to 33°C, and 164 parts of paraformaldehyde (5
based on monomeric formaldehyde) is added over 20 minutes. The solution
heated to 47°C and 8.3 parts of a 10% aqueous solution of potassium
is added over 10 minutes. The reaction mixture is stirred and heated to
over about ½ hour, at which time an exothermic reaction begins;
continued and the temperature is kept at about 50°C by passing cooling
through a jacket on the reaction vessel.
the end of the 2-hour stirring period, an additional 8.3 parts of the
hydroxide solution is added, and a final 8.3 parts is added after a
2-hour stirring period (total 0.9 mol percent based on formaldehyde).
mixture is stirred for an additional 2 hours, cooled to 24°C and
product, a 55% aqueous solution of the desired water-soluble
contains 3.04% nitrogen.
5: To a solution of 644
parts (3.81 mols) of diacetone acrylamide in 681 parts of water, at
added, with stirring, 372 parts of paraformaldehyde (11.3 mols based on
monomeric formaldehyde). The mixture is heated to 43°C and 19 parts of
aqueous solution of potassium hydroxide is added. The mixture is
heated, wit stirring, to 48° to 55°C and maintained at this temperature
additional 10 parts of
potassium hydroxide solution is then added and stirring is continued
hours, followed by addition of a third 19 ml portion of potassium
solution (total 0.87 mol percent based on formaldehyde) and stirring
for 2 more
hours. The solution is then cooled to 29°C, 0.044 part of
added and the mixture is filtered. The product, a 53% aqueous solution
desired water-soluble composition, contains 3.04% nitrogen.
6: A mixture of 1,352 parts (8 mols) of diacetone acrylamide, 1,136
methanol and 480 parts of a solution comprising 55% formaldehyde (8.8
formaldehyde), 35% methanol and 10% water is heated to 44°C, and 10
parts of a
10% solution of potassium hydroxide in methanol (0.2 mol percent of
hydroxide based on formaldehyde) is added. The mixture is heated at 44°
for 7 hours, with stirring, and is then stripped of volatile materials
distillation at 48°C/4 torr. The water-soluble product contains 7.08%
7: Following the procedure of Example 6, a water-soluble product
6.16% nitrogen is obtained from 1,014 parts (6 mols of diacetone
1,706 parts of methanol, 491 parts (9.0 mols of formaldehyde) of
formaldehyde-methanol-water solution, and 10 parts of methanolic
hydroxide (0.2 mol percent potassium hydroxide based on formaldehyde).
8: Following the
procedure of Example 6, a water-soluble product containing 6.38%
obtained from 1,014 parts (6 mols) of diacetone acrylamide, 1,767 parts
methanol, 654 parts (12 mols of formaldehyde of
and 10 parts of methanolic potassium hydroxide (0.15 mol percent
hydroxide based on formaldehyde).
9: A mixtre of 291 parts of ethyl acrylate, 16 parts of the product of
4, 596 parts of water and 90 parts of a 21% aqueous solution of a
alkaryl polyether sulfate anionic emulsifier sold under the trade name
X-301 is purged with nitrogen for 45 minutes, after which a solution of
parts of ammonium persulfate in 10 parts of water and a solution of 0.3
sodium formaldehyde sulfoxylate in 15 parts of water are added. The
vessel is cooled as the mixture is stirred and an exothermic reaction
place which causes the temperature to rise the 59°C. After the 10
additional solution of 0.3 part of sodium formaldehyde sulfoxylate in
parts of water is added and the mixture is filtered, yielding the
10: A mixture of 87 grams of diacetone acrylamide, 30 grams of the
Example 6, 180 grams of butyl acrylate, 3 grams of acrylic acid, 418
water and 34 grams of an anionic emulsifier sold under the trade name
is purged with nitrogen. To the mixture is added 5 ml of a 10% aqueous
of sulfuric acid, 1.0 gram of sodium formaldehyde sulfoxylate and 1.5
ammonium persulfate. The mixture is stirred under nitrogen for about 15
and then heated to 72°C, after which 1 ml of t-butyl hydroperoxide is
Heating is continued at about 60° to 65°C for 2 hours. The desired
latex is then filtered through cheese cloth and neutralized with 10%
11: Following the
procedure of Example 10, a tetrapolymer latex is prepared from 30 parts
diacetone acrylamide, 30 parts of the product of Example 8, 120 parts
acrylate, 20 parts of methacrylic acid and 283 parts of water, and is
neutralized with 10% aqueous ammonia solution.
12: Following the procedure of Example 10, a terpolymer latex is
70 parts of the product of Example 7, 110 parts of butyl acrylate, 20
methacrylic acid and 280 parts of water, and is subsequently
28% aqueous ammonia solution.
13: A pressure bottle is charged with 25 parts of styrene, 70 parts of
9.6 parts of the product of Example 5, 200 parts of butadiene, 0.2 part
potassium persulfate, 4 parts of diamyl sodium sulfosuccinate, 0.25
sodium naphthalene sulfonate emulsifier sold under the trade name Tamol
part of cumene hydroperoxide, 0.5 part of t-dodecyl mercaptan and 0.2
sodium formaldehyde sulfoxylate. The bottle is sealed and agitated for
at 50°C; it is then opened and 2 parts of an alkylphenyl
nonionic emulsifier sold under the trade name Triton X-405, 7.8 parts
and 0.2 part of sodium diethyl dithiocarbamate are added. Volatile
are removed by steam stripping, yielding the desired terpolymer latex.
14: Following the procedure of Example 13, a tetrapolymer latex is
from 15 parts of styrene, 70 parts of butadiene, 10 parts of diacetone
acrylamide, 9.6 parts of the product of Example 5 and 200 parts of
15: A reaction flask is charged with 500 parts of water, 36 parts of
36 parts of butyl acrylate, 4 parts of the product of Example 4, 1 part
acrylic acid, 5 parts each of an oxyethylated alkylphenol water soluble
emulsifier solid under the trade name Igepal CO-710 and a similar
emulsifier sold under the trade name Igepal CO-520 and 2.5 parts of
lauryl sulfate. The mixture is purged with nitrogen and stirred as a
of 0.2 part of amonium persulfate in 5 parts of water and a solution of
part of sodium formaldehyde sulfoxylate in 5 parts of water are added.
is continued as the mixture is heated to 68°C, and there are
added (1) a mixture of 410 parts of water, 286 parts of styrene, 286
butyl acrylate, 36 parts of the product of Example 4, 6 parts of
5 parts each of Igepal CO-710 and
CO-520, and 1 part of sodium lauryl sulfate; (2) a solution of 1.4
ammonium persulfate in 50 parts of water; and (3) a solution of 1.4
sodium formaldehyde sulfoxylate in 50 parts of water. The addition
over 1 hour at 68° to 72°C. Stirring is continued at 72° to 80°C as
portions of ammonium persulfate and sodium formaldehyde sulfoxylate are
followed by portions of t-butyl hydroperioxide and sodium formaldehyde
mixture is cooled to room temperature and filtered through cheesecloth,
solution of Igepal CO-710 in 25 parts of water and a solution of Triton
in 7 parts of water are added, and the material is stirred briefly. The
is the desired tetrapolymer latex.
addition polymers of this process, particularly latexes thereof, have a
self-cross-linking properties which make them particularly useful as
Because of these self-crosslinking properties, the polymers may be
acidic (preferably) or alkaline conditions at temperatures from room
temperature to about 200°C to form adherent films with a high
acetone insolubles. Such polymers are especially useful as laminating
and binders for textiles and nonwoven fabrics. It is possible to
adhesive in which the only ingredient present in substantial amounts in
polymer latex of this process, with the optional presence of such
thickeners, antifoam agents, protective colloids, pigments and the like
are known in the art. Particularly useful for this purpose are polymers
containing units derived from an acidic compound such as acrylic acid.
example, the polymer of Example 10, 11 and 12 may be combined with a 5%
hydroxyethylcellulose solution (as a protective colloid) in an amount
provide 4.5 parts of hydroxyethylecellulose per 100 parts of polymer to
composition suitable for use as an adhesive. However, such adhesives
cure only at undesirably high temperatures, frequently above 150°C. The
preferred adhesive compositions additionally contain at least one
selected from the group consisting of alkaline reagents (e.g., sodium
hydroxide, potassium hydroxide) and the aminoplast compositions
described herein. Both of these substances may be present, but it is
satisfactory to use only in an amount of about 0.5 to 10.0 parts per
of the polymer of this process. It is particularly preferred to use
hexamethoxy-methylmelamine. Typical adhesive compositions containing
polymers are listed below.
utility of the adhesive compositions containing the polymers of this
illustrated by a procedure in which the adhesive is applied in a
pattern by pyramidal dots from an engraved roll onto a strip of cotton
resting on a piece of soft rubber. A layer of tricot is placed over the
adhesive and a cylindrical weight is rolled over the laminate to assure
bonding. The laminate is then placed in a forced-air oven, tricot side
150°C for 3 minutes. The cured laminates are found to have excellent
resistance, dry and wet strength and “hand”. Latexes of the addition
contaning units derived from styrene and butadiene (e.g., the products
13 and 14) may be used as glass-to-rubber adhesives.
have found that acceptable bond strength is fabric to fabric bonds and
resistance to washing in warm soapy water and to dry cleaning may be
by use of an adhesive composition comprising a polyamide formed from a
in controlled proportions of at least one lactam, a mixture of
dicarboxylic acids and at least one diamine. The components are
give polymer molecules having a degree of irregularity which interferes
crystallization and contribute to a substantial degree amorphous
characteristics giving a wide melting point range.
addition, the compounds
selected for copolymerization include components having a relatively
number of carbon atoms in chains in repeating units of the copolyamide
molecular chain to impart improved wash resistance to the composition
with components giving improved resistance to attack by drycleaning
Also, by balancing the range of relative proportions and the conditions
polymerization to control the molecular weight and softening point
range of the
resulting copolyamide material having physical properties enabling it
reduced to powdered condition to retain this condition without undue
while at the same time having a relatively wide range of softening or
temperatures particularly avoiding critical temperature control and
handling problems encountered in use of the material for the hot melt
between, for example, layers of fabric.
A series of copolyamides were prepared by the procedure set forth below
reagent mixtures and forming products having the properties listed in
on next page.
procedure used for making the copolyamide involved melting the lactam
dicarboxylic acid components together in a reaction vessel. Thereafter,
was added and the temperature allowed to rise to from 100° to 120°C.
reaction mixture was heated under reflux conditions until salt
completed and at this point the temperature was raised to 200°C to
water. The temperature of 200°C was maintained for 2 hours and then a
was applied to the reaction mixture and heating continued for a further
200°C. At this point, polymerization was complete and the resinous
materials was poured out into a casting tray. The resinous material was
cryogenically ground and screened to form a uniform powder having a
size of from 60 to 210 microns. The copolyamide powders were used to
pieces of fabric and the bonds between the pieces of fabric were tested
Flame Retardants For Textile
Retardants For Textile
associated with the ready combustibility of cellulosic materials were
recognized as early as the 4th century BC, when Aeneas is said to have
recommended treatment of wood with vinegar to impart fire resistance.
annals of Claudius record that wooden storming towers used in the siege
Piraeus in 83 BC were treated with a solution of alum to protect them
technique of imparting flame resistance to textile fabrics is relative
Among the earliest references is an article by Sabattini published in
Recognizing a need to prevent fire, he suggested that clay or gypsum
be added to the paint used for theater scenery to impart some flame
Perhaps the first noteworthy recorded attempt to impart flame
cellulose was made in England in 1735 when Obadiah Wyld was granted a
for a flame-retardant mixture containing alum, ferrous sulfate, and
France in 1821, Gay-Lussac developed a flame-resistant finish by
and jute fabrics with a mixture of ammonium phosphate, ammonium
first successful, launder-resistant, flame-retardant finish for fabric
based on the work of Perkin who precipitated stannic oxide within the
This fabric was flame resistant but afterglow was severe and persistent
to completely consume the fabric.
retardants are mainly used on cottons and rayons. Fabrics made from
silk (qv) and protein-like synthetic polymers are not considered
combustible, for the most part, to warrant the need for flame-retardant
finishes (see Biopolymers; Textiles).
World War II the flammability of textiles of all types has received
increased attentionl, spurred by the Conference on Burns and Flame
Fabric in 1966 and by the 1967 amendment to the Flammable Fabrics Act
Flammability standards were established by the Department of Commerce
enforced by the Federal Trade Commission. This responsibility was taken
the Consumer Product Safety Commission When it was created in 1973.
term used in connection with flame-resistant fabrics are sometimes
Fire resistance and flame resistance are often used in the same context
terms fireproof or flameproof. A textile that is flame resistant or
resistant does not continue to burn or glow once the source of ignition
been removed, although there is some change in the physical and
characteristics. Fireproof or flameproof, on the other hand, refer to
that is totally resistant to fire or flame. No appreciable change in
physical and chemical characteristics. Fireproof or flameproof, on the
hand, refer to material that is totally resistant to fire or flame. No
appreciable change in the physical or chemical properties is noted.
an example of a fireproof material.
organic fibers undergo a glowing action after the flame has been
and flame-resistant fabrics should also be glow resistant. Afterglow
as much damage as the flaming itself since it can completely consume
fabric. The burning (decomposition) temperature of cellulose is about
whereas afterglow temperature is approximately 345° C.
modification of cellulose with fire retardants gives products whose
to laundering and weathering is superior to that of finishes based on
physical deposition of the flame retardant within the fabric, yarn, or
The reactions involved are either esterification or etherification. The
is preferred because ether linkages are more stable to hydrolysis.
flame resistance of a textile fiber is affected by the chemical nature
fiber; ease of combustion; fabric weight and construction; efficiency
flame retardant; environment; and laundering conditions.
can change significantly when treated fabric is exposed to sunlight,
by laundering, even though repeated washing and tumble drying of
samples of the
same specimen did not indicate any significant changes, especially in
durability of the finish. Dry heat alone, followed by laundering or
can also have a deleterious effect.
are classified into natural fibers, e.g. cotton, flax, silk, or wool;
regenerated fibers, e.g. rayon; synthetic fibers, e.g., nylons, vinyls,
polester, acrylics; and inorganic fibers, e.g. glass or asbestos,
Combustibility depends on chemical makeup and whether the fiber is
organic or a mixture of both.
weight and construction of the fabric affect its burning rate and ease
ignition. Lightweight, loose-weave fabrics usually burn faster than
heavier-weight fabrics; therefore, a higher weight add-on of fire
needed to impart adequate flame resistance.
materials are by far the most important class of compounds used to
durable flame resistant to cellulose. They usually contain either
bromine and sometimes both. A combination of urea and phosphoric acid
flame resistance to cotton fabrics at a lower add-on than when the acid
is used alone. Other nitrogenous compounds, such as guanidine, or
could be used instead of urea. Amide and amine nitrogen generally
flame resistance, whereas nitrile nitrogen can detract from the flame
contributed by phosphorus. The most effcient flame-retardant systems
two retardants, one acting in the solid and the other in the vapor
in flame-resistant fabric
escapes from the tar to the vapor phase during pyrolysis in air. It
have little or no effect on the amount of phosphorus remaining in the
Bromine contributes flame resistant almost completely in the vapor
when used in conjection with phosphorus compounds has synergistic
Phosphorus content can be reduced without changing the efficiency of
temperature of the environment influences the burning characteristics
as measured by the oxygen index (OI). This is true for untreated as
flame-retardant fabrics. For example, the OI. value of untreated fabric
when burned at 25°C and 0.14 when burned at 150°C. For flame-retardant
an OI value of 0.35 at 25°c may be reduced to 0.27 when burned at
Sunlight and heat can also destroy some flame retardancy, especially
followed by laundering or autoclaving. The moisture content of fabric
affect flame retardancy.
retardancy of a treated cellulosic fabric is reduced when the retardant
contains acid groups and the treated fabric is soaked or laundered in
containing calcium, magnesium, or alkali metal ions. Phosphate and
carbonate-based detergents affect durability of fire retardants.
detergents can result in a substantial loss of fire resistance because
of fatty acid salts. Phosphorus based flame retardants are adversely
by water hardness and sodium hypochlorite.
such, has no appreciable vapor pressure and does not burn. However, on
to high temperatures it decomposes exothermically into flammable
causing further degradation and decomposition until complete treated
flame-retardant-treated cellulose. Decomposition takes place in two
First, thermal decomposition causes cellulose to decompose
gaseous, liquid, tarry, and solid products. The flammable gases thus
ignite, causing the liquids and tars to volatilize to some extent. This
produces additional volatile fractions which ignite and produce a
which does not burn readily. This process continues until only
material remains. After the flame has subsided, the second stage
residual carbonized residue slowly oxidizes and glowing continues until
carbonaceous char is consumed.
(qv) treated with an effective flame retadant forms, in general, the
decompostion products upon burning as untreated cotton; however, the
tar is greatly reduced with a corresponding increase in the solid char.
Consequently, as decomposition takes place, smaller amounts of the
gases are available from the tar, and greater amounts of nonflammable
from the decomposition of the char fraction.
glow retardant chemicals, such as compounds containing phosphorus,
first reactions to be prevalent. Oxidation of carbon monoxide is not
sufficiently exothermic to maintain afterglow of the char.
flame resistance to cellulose has been explained by the following
theory: As early
as 1821, Gay-Lussac suggested that fire resistance was due to formation
layer of fusible materials which melted and formed a coating thereby
the air necessary for the propagation of a flame. This was based on the
efficiency of some easily fusible salts as flame retardants.
borates, and ammonium salts are good examples of coating materials that
a foam on the fiber by liberation of gases such as carbon dioxide,
theory: The flame
retardant produces noncombustible gases at burning temperature which
flammable gases produced by decomposition of the cellulose to a
below the flaming limit.
theory: Heat input
from a source is dissipated by an endothermic change in the retardant
heat supplied from the source is conducted away from the fibres so
the fabric never reaches temperature of combustion.
theory: Strong acids, bases, metal oxides, and oxidants that tend to
cellulose, especially under the influence of heat, usually impart some
of flame resistance to cellulose. This is also true of the more
retardants, such as phosphoric and sulfuric acid, which are good
agents. When this happens, cellulose on combustion produces mainly
water rather than carbon dioxide and water.
retardants for cotton may possibly act through a dehydration process by
acid or base formation through a carbonium ion or carbanion mechanism.
theory is being further investigated.
theories suggested that flame-retarded cellulose decomposed at high
to l-glucosan which in turn broke down to form other volatile products
were highly flammable. However, if bases are present in the fabric
burning, deydrocellulose is formed by a base-catalyzed dehydration
char formation. Base-catalyzed at an energy level below that required
l-glucosan by propagating structural changes at an energy level below
required to convert the coformers of the glucopyranose ring.
Flame-retardant finishes that are not durable to laundering and
in general, relatively inexpensive and efficient. In some cases,
two or more salts are much more effective than any one of the
For example, an add-on of 60% of borax Na2B4O7×10H2O is required to
fabric from burning. Boric acid, H3BO3, by itself, is ineffective as a
retardant even in the amounts that equal the weight of the fabric.
mixture of seven parts borax and three parts boric acid imparts flame
resistance to a fabric with as little as 6½% add-on.
water-soluble flame retardants are most easily applied by impregnating
fabric with a water solution of the retardant, followed by drying.
of the concentration and regulation of the fabric wet pickup controls
amount of retardant deposited in the fabric. Fabric can be processed on
finishing range consisting of any convenient means of wetting the
the solution, such as a padder or dip tank, followed by a drying on
cans, in an
oven, on a tenter frame, or merely by tumbling in a mechanical dryer.
Water-soluble flame retardants also may be applied by spraying or
dipping fabrics, or as a final rinse in a commercial or home laundry.
water-soluble flame retardants, most widely used for textiles are
Table 1. Less commonly used are sulfamates of urea or other amides and
aliphatic amine phosphates, such as triethanolamine phosphate
phosphamic acid [2817-45-0] (monoimido phosphoric acid), H2PO3NH2, and
salts; and alkylamine bromides, phosphates, and borates.
Semidurable fire retardants are those that resist removal for one to
launderings. Such retardants are adequate for applications such as
upholstery, and mattress ticking. If they are sufficiently resistant to
sunlight or can be easily protected from actinic degradation, they can
applied to outdoor textile products.
codeposits and flame and glow resistance properties to textile fabrics.
However, some insoluble deposits may also degrade the fabrics.
frequently improve glow resistance. They are usually more soluble than
deposit responsible for flame resistance and are more easily removed
are several methods for introducing the insoluble deposits into the
structure. Most generally used is the multiple-bath method, in which
is first impregnated with a water-soluble salt or salts in one bath,
then passed into a second bath which contains the precipitant.
semidurable retardants are used on cotton and are based on a
phosphorus and nitrogen compounds.
studies to produce durable flame retardants for cellulose were based on
treatment with inorganic compounds containing antimony and titanium.
patents were issued based on these types of treatmets, e.g. DuPont’s
process and the Titanox FR process of the Titanium Pigment Corporation.
the Erifon process titanium and antimony oxychlorides were applied from
solution (pH4) to fabric, which was then neutralized by passing through
solution of sodium carbonate, followed by rinsing and drying. Fabrics
finished exhibited good flame resistance but also considerable
fabric characteristics were changed by this treatment. A large amount
fabric was treated by this type of process for the military service.
it has now been replaced by flame retardants based on phosphorus.
basic chemicals used in the Titanox FR process were titanium acetate
and antimony oxychloride. As with the Erifon process, it was difficult
the fabric without dulling its appearance.
fire-resistant fabric was obtained by treating fabric with a suspension
emulsion fire-retardant salts or oxides, eg, antinomy oxide, with a
organic vehicle, such as chlorinated paraffin. Antimony oxide alone is
poor flame retardant. When used, however, in conjunction with a
compound, which can form hydrochloric acid on heating, a very good
retardant is produced.
abbreviation, FWWMR, for
fire, water, weather and mildew resistance has frequently been used to
treatment with a chlorinated organic metal oxide. A plasticizer,
pigments, fillers, stabilizers, or fungicides are usually added.
However, hand, drape, flexibility, and
color of the fabric are more affected by this type of finish than by
flame retardants. Durability of this finish is good and fabric
properly retains its flame resistance after four to five years of
exposure. This type finish is well suited for very heavy fabrics, e.g.
tarpaulins, or awnings, but not for clothing or interior decorating
The metal oxides can be fixed to cotton by use of resins, e.g.
vinylacetate–chloride copolymers (vinylite VYHH) or PVC.
flame retardant has been developed based on an oil–water emulsion
plasticizer (PVC latex) and antimony oxide. High add-ons are necessary
impart adequate flame resistance but the strength of the fabric is
Halogenated Flame Retards
development and extensive use of synthetic polymers in both old and new
of applications has intensified the concern for combustibility.
new polymers are not necessarily more flammable than natural polymers,
more readily used in forms, e.g., foams, electrical applications, etc,
result in an increased fire control problem.
with the development of many synthetic polymer systems during the 1930s
1940s, a significant advance in the science of imparting flame
occurred, i.e., the use of halogenated organic materials to impart
resistance to these new polymer systems.
early plastics applications, the small size of fabricated articles and
relative scarcity of these articles made fire retardancy a secondary
consideration. Advances in plastics technology have led to increasing
large-scale applications, especially in the construction industry.
polymers have fuel values (heats of combustion) comparable to common
wood, oil, alcohol, etc, it is readily understandable that they
the burning process in a typical fire.
halogenated products used as flame-retardants for plastics currently in
mainly compounds containing high (50–85 wt %) levels of either chlorine
bromine, i.e., decabromodiphenyl oxide [1163-19-5], chlorendic acid
tetrabromophthalic anhydride [632-79-1], etc. These materials fall into
distinct types: dditives and reactives. The additives have the
being readily added to a polymer by mechanical means with a minimum of
reformulation being required. The reactives, on the other hand, require
development of essentially new polymer systems.
massive polymer forms are considered, though the materials and concepts
discussed are almost similarly applicable to fibers, fabrics, coatings,
compounds are included under Flame retardants—phosphorus compounds.
discussion of the principles of developing flame-retardant polymer
acknowledge the chaotic situation that exists at present. This
arisen for a variety of reasons: technical, economic, legal, and
semantic problem is the worst in that it is at the root of most of the
problems and is caused by the fact that the term fire or flame
retardant may be
perceived in a variety of ways depending upon the user’s viewpoint. The
as defined above, means simply that some change has been made in
so that it will pass one or more of at least a hundred different
tests. These tests
are normally designed
to minimize, but not eliminate, the fire risk associated with the use
polymer in some specific use or product. As a consequence, a
modification of a
polymer that makes it suitable for one use does not necessarily make it
suitable for others. There is no single fire-retardant chemical or
is applicable to all polymer systems or even to all uses of a single
is, therefore, necessary that early in the development of a
polymer system the question “Why?” is answered before much effort it
answering the question “How?”.
is not unusual to see many compounds proposed as flame-retardant
are clearly unusable in any practical sense, but that allow a polymer
pass a specific flammability test. A polymer system can be easily
that it can be called “flame-retardant” by some “test”. It is
however, to do so and keep a polymer system that is low-cost,
and physiologically acceptable, and also mechanically and esthetically
dissimilar from nonfire-retardant counterparts.
of the most common approaches used to modify the burning properties of
at the present time is by incorporation of halogen into the polymer
either directly or through the use of halogenated additives. The usual
rationale for the use of the halogens as flame retardants is based on
theory that they function in the gas phase as radical traps. It is
agreed that the combustion of gaseous fuels is a high temperature
proceeds via a free radical mechanism.
the radical-trap theory of flame inhibition it is thought that
effectively compete with equations 2–5 for those radical species that
critical for flame propagation, i.e., ·OH and ·O·, thereby slowing the
energy production and resulting in the extinction of the flame.
fluoride does not significantly enter into the flame chemistry, thus
fluorinated compounds are generally considered to be ineffective as
flame-retardant agents. The radical-trap theory of flame inhibition,
attractive in that it can be adapted to any situation, tends to lead to
belief that the simple inclusion of small amounts of halogen into a
system will render the system flame retardant.
recent physical theory of flame suppression by the halogens, although
that the halogens enter into flame chemistry, suggests that this
per se cannot be the primary mechanism by which the halogens function.
it is postulated that the halogens act by altering the physical
i.e., the density and mass heat capacity of the gaseous fuel–oxidant
that flame propagation is effectively prevented. The physical theory is
primarily based on the observations that any gaseous mixture of fuel
halogenated agent generally propagates flame when mixed with air as
long as the
mass fraction of halogen in the mixture is less than ca 0.7, and the
effectiveness of the halogens is directly proportional to their atomic
i.e., F:Cl:Br:I = 1.0:1.9:4.2:6.7. The halogenated agents probably act
same basic mechanisms as the inert gases, i.e., CO2 N2, etc, and their
suppressant effective are additive to those of the inert gases.
is the mass fraction of oxygen in the combustion zone; Hc is the net
combustion of the sample (J/g); r is the stoichiometric mass
Cp is the specific heat of the gases in the combustion zone Ts is the
temperature of the sample (°C), Ta is the ambient temperature (°C); and
the apparent heat of gasification (J/g). The B number contains the
properties of the polymeric materials. Thus the mass burning rate or
intensity can be related to the fundamental properties of the material.
applied to liquid fuels, the Spalding B number in its simplest form can
visualized as the ratio of the heat of combustion and the heat of
(DHc/DHv). Table 1 shows the significance of this ratio applied to
halogen-containing fuels. In Table 1 the flash and fire points are
both in °C, as normally reported, and as the weight of compound present
gas phase over the surface of the liquid at this temperature (mg/L).
introduction of halogen has a lesser effect upon DHv per milligram of
evaporated. The ratio DHc/DHv decreases with added halogen indicating
energy is available from the flame for gasification, and, in order to
flame burning, additional heat from some outside source is required.
DHv is the
amount of heat required to vaporize the weight of fuel (latent heat of
vaporization) present in the gas phase at the appropriate flash and
after the fuels have been raised to these temperature by the outside
Note the large increase in mass that must be vaporized in order to
sustained burning in the case of bromobenzene, at least 100 times the
must be vaporized in the case of benzene itself.
physical theory apparently accounts for the effects seen when
agents are used as flame retardants. In view of the fact that the
content of a typical plastic is generally ca 1–30 wt %, it is obvious
the typical polymer were totally vaporized the gases given off would be
capable of flame propagation.
order to visualize the role of halogen it is necessary to examine the
balance that occurs at the surface of the polymer. Figure 1 shows a
of this balance. Heat received by the polymer surface may arise either
heat flux from the flame (QT) or as an externally applied heat flux
from another source. Heat is lost either as the heat required for
(QG) of the polymer or as heat lost (QL) through radiation, conduction,
convection, dripping, etc. QT and QG are agent dependent, whereas QE is
obviously agent independent, except in char-forming systems. QL may be
dependent if the agent acts by increasing the drip rate of the burning
Halogenated agents affect the heat balance through QT, QG, and QL.
phosphorus may act in the gas phase, it appears to be the most
element affecting QG and QE through char formation.
the burning process involves heating of the substrate to a temperature
enough to drive off flammable vapors. When the rate of vapor evolution
high enough to generate a flammable mixture, the mixture ignites. If
of vapor or gas evolution becomes sufficiently high, the heat produced
combustion process may return enough heat to the substrate so that the
evolution of fuel becomes self-sustaining.
a flame retardant that acts in the vapor phase is added to the system,
the vapor that distills from the polymer does not contribute to the
combustion but results only in a reduction in the mass fractions of the
and fuel in the combustion zone. Hence, there is an increase in the
of material that must be vaporized per unit time in order to keep the
burning. A corresponding increase in the amount of energy must be added
system from an external heat source (QE, Figure 1) in order to vaporize
dripping and char formation interfere with the energy feedback cycle
QE) and consequently cause an increase in the intensity of the external
flux required to balance the energy–fuel cycle.
the flame is actively spreading over the surface of a material, the
composition of the vapor being evolved ahead of the moving flame is not
necessarily the same as the elemental composition of the polymer. The
composition of the vapors may vary considerably between the temperature
which the material first begins to evolve vapors and the temperature at
the rate of evolution supports the flame. With this type of dynamic
condition, changes in the substrate and the structure of the agent are
important than they are under steady-state conditions.
are five fundamental methods used to fire-retard both natural and
polymer systems. They are:
the decomposition temperature of the polymer. This is generally
increasing the cross-linking density of the polymer, as with ladder
the fuel content of the system. This approach generally involves
the polymer backbone, adding halogenated additives, adding inert
fillers, or by
resorting to inorganic systems (increase QG, decrease QT).
polymer flow by selective chain scission. This approach is generally
to thermoplastic polymer systems where interrupting the polymer
results in reduction of the viscosity of the polymer and promotes
selective decomposition pathways. This method is most applicable to
where the introduction of phosphorus compounds generates phosphorus
catalyze the loss of water and the retention of the carbon as char
QG, decrease QT).
means include (1) bonding a nonflammable skin on the polymer, (2)
polymer with an intumescent coating, (3) design of the system, and (4)
of sprinklers (decrease QE).
Antimony oxide, a commonly employed fire retardant adjunct for
halogen-containing polymer systems, is usually employed as a means of
the halogen levels required to obtain a given degree of flame
the polymer system. This reduction is often desirable since the
halogen content for the system may be so high that it affects the
properties of the system. In other cases, the antimony oxide is used
give a more cost-effective system.
been widely studied in attempts to explain the apparent, synergistic
obtained with this combination of elements. No completely satisfactory
is available as yet, but it is generally agreed that the active agents,
antimony trihalides or antimony oxyhalides, act principally in the gas
As with the halogens, it is generally postulated that the antimony
as radical traps.
scale tests show that the optimum halogen (Cl, Br)/antimony atom ratio
systems is 3/1, corresponding to the atom ratio found in the antimony
trihalides, i.e., SbCl3, SbBr3. On the usual weight basis, this
a ratio of ca 0.9/1 for the chlorine–antimony system and ca 2/1 for the
the antimony halides appear to act principally in the gas phase, some
the condensed-phase chemistry cannot be ruled out. Antimony–halogen
flame-retardant compositions usually produce a carbonaceous residue,
polymers such as polypropylene, which produces none in the absence of
retardants. The production of the carbonaceous residue probably results
the antimony trihalides, strong Lewis acid catalysts, which are capable
promoting the dehydrohalogenation of organic halides, and coupling and
rearrangement reactions in organic systems.
Anatomy and other Inorganic Compounds
many polymers, the high concentrations of halogenated organic
to impart flame retardancy, adver-sely affects their physical
practicle, halogen-containing flame retardants are formulated with
compounds that behave synergistically with the halogen. This enables
formulators to use less additivies without diminishing flame
in many instances, flame retardancy is improved when inorganic halogen
synergists are used.
1979 approximately 15,900 metric tons of antimony trioxide [1309–64–4]
(commonly referred to as antimony oxide) was used to impart flame
a variety of plastics. Antimony trioxide is manufactured by oxidizing
antimony sulfide ore and/or antiomony metal in air at 600–800°C(1).
properties for antimony trioxide are listed in Table 1 (see Antiomony
trioxide is a white pigment (qv). Its pigment strength is a function of
average particle size and the particle size distribution. Particle size
controlled during its manufacture to produce either a high tint or a
product. The difference in the particle size and particle size
between high tint and low tint antimony trioxide is illustrated in
Both grades have the same flame inhibiting efficacy but have different
on pigementation and physical properties.
products and trade names
of antimony trioxide are summarized in Table 2.
grades are available at
higher costs. They include White Star S15 from the Harshaw Chemical
ultra-fine antimony oxide from PPG Industries.
Trioxide in Cellulosics: Antimony trioxide can be used as a
flame retardant in cellulosic materials. In these substrates, it reacts
endothermically with the hydroxyl groups and forms a variety of
endothermic reaction absorbs heat needed to propagate the flame. The
formed are difficult to ignite and shield the underlying cellulose from
flame, minimizing pyrolytic and oxidative degradation.
Pentoxide: Antimony pentoxide [1313-60-9] is manufactured by the
antimony trioxide with nitrates or peroxides. For Sb2O5 the wt% of
72.8 and the specific gravity is 3.8.
antimony pentoxide is primarily available as a stable colloid (Nyacol,
as a redispersible powder (Nyacol, Inc.; PPG Industries, Inc.) It is
significantly more expensive than antimony trioxide and is designed
for highly specialized applications. Antimony pentoxide manufacturers
fiber and fabric treatment applications as a potential area for its
redispersible powder form of antimony pentoxide, which is also
plastics, contains 88% antimony pentoxide, and 12% dispersing agents.
be exercised when this product is incorporated into plastic since the
dispersing agents can adversely affect the thermal stability and
Antimonate: Sodium antimonate [15593-75-6], Na2OSb2O5.½H2O, is a
white powder made by the oxidation of antimony trioxide in a basic
few of its properties are shown in Table 2.
pigmenting strength of sodium antimonate is less than antimony
trioxide. It is
recommended for formulations in which deep tone colours are required.
it contains 62 wt % antimony, somewhat higher concentrations are needed
it as effective as antimony trioxide which has 83 wt % antimony.
Metal Antimony Compounds: Recent developments in inorganic flame
synergists have centered on mixed products that contain antimony and
metals which reported give excellent performance at reduced cost.
CPA (M & T Chemical, Inc.) appears to be as effective as
in most flame retardant applications, and has a significantly lower
Although it contains a lower level of antimony compared to antimony
other metals contained in the product significantly boost its flame
Industries has developed a series of antimony–silico complex under the
name Oncor. These products contain up to 50% antimony trioxide. They
opacifying than either high- or low-tint antimony oxide. Generally,
antimony–silico complexes are less effective flame retardants than
trioxide. Therefore, although the cost per kilogram is less than
trioxide, the cost-effectiveness of the antimony–silico complexes can
Mechanisms: Antimony trioxide is used almost exclusively with
halogen compounds. Most of the mechanisms proposed indicate that
trioxide is activated by reaction with halogenes, forming antimony
or antimony oxyhalides. This can be shown simply by the following
trichloride and antimony oxychloride work primarily as flame-phase
retarders. The type of antimony halide formed depends on the
the hydrogen halide and the temperature of the reaction.
this study, a typical aliphatic chlorinated parafirm containing 70 wt %
chlorine (Chlorowax, Diamond Shamrock) weas heated alone at a rate of
A 67% weight loss was noted at 250–360°C (see Fig. 2). The loss is
to 93 wt % of the theoretical stoichiometric quantity of hydrogen
an equal weight of antimony trioxide was added to the chlorinated
the mixture was heated at the same rate, a 76% weight loss at 310–400°C
noted (see Fig. 3). If there were no reaction, the loss would have been
37.5% since only half of the mixture was the chlorinated paraffin, and
trioxide does not volatilize below 656°C. The higher weight loss
some reaction between either the decomposition products of the
paraffin or the chlorinated paraffin itself and antimony trioxide have
place. The gas generated by the reaction has been analyzed and
antimony trichloride. The weight loss is equivalent to 90% of the
quantity of antimony trichloride that can be formed from the mixture.
thermal analysis, it is apparent that antimony trichloride is the
antimony species formed from combination of antimony trioxide and
chlorine com-pounds that generate high concentrations of hydrogen
appears that antimony oxyhalides are the primary antimony compounds
organic halogen compounds, which do not generate hydrogen chloride
upon thermal exposure, and antimony trioxide are heated together.
trihalides are the flame-retarding species whether they are generated
from the starting antimony–halogen mixture or from antimony oxyhalide
They inhibit combustion by altering the manner and type of
products formed by the plastic and by modifying the reactions in the
make them less exothermic. In the condensed phase or molten polymer
beneath the flame, antimony trihalide promotes reactions that form
chars instead of highly volatile reactive gases. The chars act as heat
which deflect the heat of the flame, and slow down the thermal and
decomposition of the polymer. The chars also form a seal around the
preventing potentially flammable gas from escaping and entering the
in the flame, the antimony trihalides decomposes into various antimony
and halogen compounds. The decom-position mechanism has not been
decomposition mechanism has been proposed in which antimony trihalides
antimony tribomide decompose in a stepwise manner and participate
2700 metric tons of borates was used as flame retarders for poly(vinyl
chloride), cellulosics and unsaturated halogenated polyesters in 1979.
borate is by far, the most widely used of this class of compounds.
There is a
variety of zinc borates available that vary in zinc, boron and water
and trade names of
commercially available borate flame retardants are shown in Table 4.
borate is rarely used alone. It acts synergistically with antimony
enabling compounders to extend antimony trioxide in some formulations.
borate is also used with
high levels of aluminium trihydrate in some halogenated unsaturated
Acid-Sodium Borate: Boric acid [10043-53-3] and sodium borate
(borax) are two of the oldest known flame retardants. They are used
to flame-retard cellulosics such as cotton (qv) and paper (qv). Both
are in expensive and fairly effective in these applications. Their use
limited to products for which nondurable flame retardancy is acceptable
both are very water soluble.
Mechanism: Boron compounds function as flame retardants in both the
condensed phases. Flame-phase-active boron compounds are generated from
combination of borates and halogenated organic compounds. These
usually generate boron trihalides, which have been used to reduce the
volatility of air–hexane mixtures.
acid and borax are effective condensed-phase flame retardants in
compounds, especially in cellulosic fibers. When these compounds are
a flame, they melt and form a glasslike coating around the fibers.
exposure causes the coating to dehydrate, generating water which cools
flame and cause it to extinguish. The boron residue also reacts with
hydroxyl groups of the cellulose to generate additional quantities of
form an inorganic char that is difficult to ignite and burn. The char
insulator that slows down the rate of polymer degradation and fuel
compounds that also contain other metals are active in both phases.
zinc borate is not used alone to flame-retard PVC, it does inhibit
in the condensed and flame phases. Upon exposure to the flame, the PVC
generates hydrogen chloride which can react with the zinc borate to
nonvolatile zinc compounds as well as volatile and nonvolatile boron
nonvolatile zinc compounds and boric acid promote char, reducing fuel
formation, and the boron trichloride and water cool and extinguish the
Fluoroborate: Ammonium fluoroborate [13826-83-0], NH4BF4, is another
boron-containing compound that has some utility as a flame retardant.
decompose to yield both halogen and boron functionalities to the
flame-retarding process. Flame-retardant plastic formulations recently
published suggest that ammonium fluoroborate should be used primarily
combination with antimony trioxide. Manufacturers propose that the
reaction describes functionally what takes place when the two products
exposed to flaming conditions.
products formed contribute to extinguishing the flame by the mechanisms
proposed in preceding paragraphs.
producers of ammonium fluoroborate include Allied Chemical Corporation,
Hook, Pa.; Cabot Corporation, Boyertown, Pa.; and Harshaw Chemical
159, 000 metric tons of alumina trihydrate [21645-51-2] (ALTH) was used
flame-retard unsaturated polyesters and foam carpet backing in 1979.
made either from bauxite by the Bayer process or from recovered
the sinter process. Physical properties listed in Table 5 and principal
suppliers in Table 6.
trihydrate is the only aluminium compound of commercial significance as
retardant. It functions as a flame retardant in both the condensed and
aluminium trihydrate is exposed to temperature above 250°C, it forms
evolution of water absorbs heat. The water cools the flame and dilutes
flammable gases and oxidant in the flame. The aluminium residue, an
heat conductor, increases removal of heat from the flame zone.
ALTH is an inexpensive compound, it is a comparatively inefficient
retardant. High add-on level, up to four times as much as the plastic
are needed to impart acceptable flame retardance. It is used alone only
polymers in which large amounts of filler can be tolerated and
(or density) is desired. The major application areas for ALTH are
thermoet polyesters and styrene–butadiene rubber latex rug backing.
trihydrate is also used as a secondary synergist to improve the flame
retardance of polymer systems that already contain antimony trioxide,
borate or some phosphorus flame retardants.
compounds have been used as flame retardants of cellulosics for many
Molybdenum compounds). Recently, they have found some use in other
Molybdenum compounds appear to function as condensed-phase flame
After ignition of PVC formulations containing molybdenum oxide
(MoO3) and antimony oxide, 90% of the molybdenum remained in the ash
10% of the antimony was found.
most of the molybdenum remained in the ash and the formulation did have
flame-retardant properties, molybdenum is probably a condensed-phase
retardant that promotes char. The precise mechanism of action has not
sufficiently defined to warrant further speculations.
hydrophilic moiety in anionic surfactants is a polar group that is
charged in aqueous solutions or dispersions. In commercial products it
either a carboxylate, sulphonate, sulfate or phosphate group. In dilute
alkaline solutions in soft water the solubilizing power of the sodium
the four anionic radicals is approximately equal and strong enough to
the hydrophobic tendency of a 12-carbon saturated hydrocarbon group;
sulfate is actually a somewhat stronger solubilizer than the sulphate.
neutral or acidic media or in the presence of heavy-metal ions, the
solubilizing power of the carboxylate is markedly less than that of the
ionic environment associated with anionic surfactants influences the
of their solutions. Sodium and potassium salts are generally more
water and less soluble in hydrocarbons. Conversely, the calcium, barium
magnesium salts are more compatible with hydrocarbon solvents and less
water. Ammonium and amine salts, e.g., triethanolamine, improve the
compatibility of anionics with water and hydrocarbons and are widely
are usually associated with lower solubilities of anionic surfactants.
offset this effect, the molecular weight of the hydrophobe is lower in
designed for use at high electrolyte affected by total-ionic strength
by the identity of the associated cations. The anionic surfactants can
divided into four groups according to their anionic groups–(1)
(2) Sulfonates, (3) Sulfates and Sulfated Products, (4) Phosphate
and a small volume of aminocarboxylates are the only commercial
products in the
carboxylate class of surfactants. Two types of aminocarboxylate
N-acylsarcosinates and acylated protein hydrolysates, are produced in
quantities as specialities. Both series of products are fatty acyl
of aminocraboxylates. As compared to the corresponding soaps, the
tendency of the amide linkages in these molecules is strong enough to
significantly lessen inactivation of the carboxylate ions by the
magnesium ions that are present in hard water.
many years soap was the only surfactant produced commercially. Inspite
development of many new surfactant types, it may be noted that soap
some desirable properties which are not found in many other
sodium and potassium cocofatty acid soaps are unexcelled as lathering
cleansing agents in bar detergents for personal use in soft to medium
water. The C14 to C18 fatty acid sodium soaps are effective laundry and
industrial detergents in soft to medium hard hot water. Soaps,
salts, are excellent emulsifiers, dispersants and solubilizing agents
wide range of industrial uses. Soaps have an emollient action in
the skin and leave a soft feel on textile fabrics.
N-lauroylsarcosinate and the N-acylsarcosinate derived from coconut
are soap like detergents with good lathering properties. They are
used in dentifrices where it is claimed they also inactivate the
convert glucose to
lactic acid in the
mouth. N-Oleoyl-sarcosinate is used as a textile auxiliary and
N-acylsarcosinates are prepared by the condensation of a fatty acid
with sarcosine (i.e., N-methylglycine obtained from the reaction of
methylamine, formaldehyde, and sodium cyanide) in alkaline aqueous
acyl aminocarboxylates are prepared from protein hydrolysates by
fatty acid chlorides or by direct condensation with fatty acids. The
products are mistures that vary in compostition from acyl derivatives
polypeptides from incompletely hydrolyzed protein to mixtures of
acids derived from completely
hydrolyzed protein. Collagen from leather scraps and low grade-hide
used as a source of protein. Derivatives of the incompletely hydrolyzed
have a great tolerance for hard water but their effectiveness as
most effective structure for an anionic surfactant is a sulfonate of
general formula RSO3Na where R is a biodegradable hydrocarbon group in
molecular weight range. The R group can be alkyl or alkylarylene and
product can be a random mixture of isomers as long as it does not
chain-branching that interferes with biodegradability. The surface
the SO3– group is not oversensitive to variations in the pH or to heavy
ions and the C–S linkage is not susceptible to hydrolysis or oxidation
normal conditions of use.
processes on surfactant raw materials can usually be adjusted to
decrease slightly the degree of substitution of the solublizing group
hydrophobe. The average molecular weight of the hydrophobic bases can
increased or decreased slightly. Minor adjustments in these two
produce significant differences in performance. Sulfonates are usually
in the production process as free acids that can be neutralized to form
metal salts, alkaline earth metal salts,or amine salts; thus
another parameter for modification of properties. Manipulation of these
variables leads to products with a multiplicity of combinations of
from the same raw materials and production equipment.
surfactants of commercial importance in this group are alkylbenzene
petroleum sulfonates, di-alkyl sulfosuccinates, naphthalene sulfonates,
N-acyl-N-alkyltaurates, 2-sulfo ethyl esters of fatty acids and olefin
dodecylbenzene sulfonates rank next to soaps in total usage. The sodium
linear dodecylbenzene sulfonate is commonly referred to as ‘LAS’.
dodecylbenzene sulfonic acid is called LAS acid, and salts other than
are named in an analogous manner, e.g., LAS ammonium salt. commercial
dodecylbenzene sulfonic acid is a light coloured, viscous liquid that
almost entirely as an intermediate for the manufacture of alkalimetal,
earth metal, and amine salts.
comparisons of the performance of alkylbenzene sulfonates to that of
sulfonates, the effect of the benzene ring is often considered as
equivalent to three carbon atoms in an aliphatic chain. Alkylbenzene
acids are strong organic acids and form essentially neutral alkalimetal
that have a good solubility in aqueous solutions at use concentrations
entire pH range. These acids are not sensitive to precipitation by the
hardness of the surface waters, but the alkaline earth metal salts are
water soluble than the alkali metal and amine salts. The calcium salts
sufficiently soluble in hydrocarbons for use in these media. The
sulfonates are one of the most chemically stable types of surfactants.
sulfonic group is not susceptible to acidic or alkaline hydrolysis
conditions of storage or use. The compounds are stable to strong
agents is aqueous solutions at use concentrations and are stable in
formulated products containing oxidizing agents.
surface activity of unformulated, unbuilt dodecylbenzene sulfonates is
sufficiently strong for the salts to be useful for their detersive,
emulsifying, dispersing, and foaming properties, but they are not
surfactants. The widespread usage of LAS stems from other factors which
their low cost reproducible quality, adequate supply, light colour, low
and excellent response to formulation and builders. For example, LAS
are only average foamers but mixtures of LAS with foaming properties.
Similarly, LAS performs well in built heavy-duty cleaning products
wetting, foaming, emulsifying and dispersing properties of the
component are as important as the detergency power. Amine salts of LAS
ABS acids are used in blends with other emulsifiers, particularly the
types, in emulsifiable concentrates of pesticides.
petroleum sulfonates are the only large-volume class of surfactants
used predominantly in non-aqueous systems. They are available as
the refining of certain petroleum fractions. They are usually grouped
broad classes–water soluble types called ‘green soaps’; and oil soluble
called ‘mahogany soaps’ (which may also be soluble in water).
green soaps are of little use. The mahogany soaps are valuable for
properties of solubilization, detergency, dispersion, emulsification,
corrosion inhibition. Their principal use is in lubricating oils for
dispersion, detergency, micellar solubilization of water, and corrosion
inhibition. They are also widely used in other products for corrosion
inhibition and emulsification. Alkylaromatic hydrocarbon sulfonates are
surfactant components in both product types. The green soaps contain a
proportion of disulfonates than the mahogany sulfonates, which are
di (2-ethyl-hexyl) sulfosuccinate is the largest volume product of this
It is now a widely used specialty surfactant. These sulfosuccinates as
salts are available as white, waxy, odourless solids or as concentrated
colourless solutions. The di–C8 esters have the optimum solubility
use in tap water or aqueous solution with low inorganic salt content;
alkyl esters are more effective in saline solutions. Sodium dialkyl
sulfosuccinates are highly surface active but the susceptibility of the
linkage to acidic or alkaline hydrolysis
limits their usefulness. The products have strong wetting,
and solubilization properties. The symmetrical diesters are produced by
esterification of maleic anhydride using conventional technology
addition of sodium bisulfite across the olefin linkage.
series of specialty surfactants make up the widely used but relatively
low-volume group naphthalene sulfonate products, viz., salts of
alkylnaphthalene sulfonates; salts of sulfonated
condensates; salts of naphthalene sulfonates; and salts of
the concentrated dry form,
most of the salts are almost odourless light-grey solids. They are
highly soluble in water. In fact, except for the nonyl derivatives, the
naphthalene soft water. The naphthalene sulfonates are stable to
acidic or alkaline media and are not sensitive to oxidation by strong
agents under use conditions.
naphthalene sulfonates are used in many different applications as
dispersing agents. Several members of the series are effective as
and suspending agents in disperse systems. Some of the products are
their solubilizing properties. Hard water does not adversely affect the
activity of typical members of the series.
taurates are technically interesting as the only class of anionic
with the combination of many advantages. They are stable against
acidic or alkaline media at use concentrations. They show no loss of
performance in hard water. They have soap like biodegradability and
feel on washed fabrics; and they have a molecular structure capable of
either strong wetting or strong detergent configurations. For example,
products RCON(R¢)CH2CH2SO3Na are strong detergents when R = C11 – C17
and R¢ =
CH3 or C2H5, but are strong wetters when R = R¢ = C6 – 9. Relatively
material costs have held usage of the presently available
taurates in the specialty category and have precluded the introduction
additional products with markedly different properties.
N-Oleoyl-N-methyltaurate is marketed as a light-yellow solid at about
cent assay or at lower concentrations in water as a light-coloured
solution or gel. It is principally used in detergent applications
builders. Foaming of the N-methyl derivatives is only moderate and is
readily improved by the usual foam builders; the N-cyclohexyl
low foaming detergents with good wetting power.
production of sodium N-oleoyl-N-methyltaurate involves three chemical
yields average 95 per cent or higher in each step.
Esters of Fatty
products, known commercially as b-sulfoesters, resemble closely in
the fatty acids from which they are derived, but they have the
hard water does not impair their performance. Only the sensitivity of
linkage to hydrolysis has prevented their widespread usage in consumer
detergents. Hydrolysis is not a problem with detergents for personal
the sodium salt of the 2-sulfoethyl ester of lauric acid, or similar
acid mixture, has found acceptance as the foaming and cleansing
synthetic detergent bars. The oleic acid analog is less foaming but is
detergent with specialty uses in neutral or mildly alkaline systems.
esters can be produced commercially from isethionate (obtained by the
of ethylene oxide with a concentrated solution of sodium bisulfite) and
fatty acid or acyl chloride. The reaction between the acyl chloride
which is a
viscous liquid and the powdered, anhydrous sodium isethionate is
carried out in
the absence of water or solvent under vacuum in a heavy duty mixer.
total charge is added to the reactor and brought to temperature, HCL is
evolved, leaving the finally divided, light coloured product as the