Dyestuff sector is one of the core chemical industries in India. There are two types of colorants dyes and pigments. Dyes are soluble substances used to pass color to the substrate and find applications primarily in textiles and leather. Pigments are coloring materials, which are water insoluble. Key end-user industries of pigments include wood-coloring, stone, textiles, paints & coatings, food and metals. Pigment are usually manufactured as dry colorants and grounded into fine powder. The dyes market, meanwhile, largely depends upon the fortunes of its principal end-user, textiles, which account for about 70 percent of the total demand. Their importance has grown in almost every area of an economic activity.
In the colorants market, Asia-Pacific accounts for the largest share. This region is one of the key markets for dyes and pigments production. In the Asia-Pacific, India and China are the important countries contributing towards the growth of colorants market. Rising consumer spending will drive increased demand for colorants in textiles. Increases in value demand will reflect the growing importance of expensive, higher value dyes and pigments that meet increasingly stringent performance standards. Growing demand for high-quality value-added pigments is one of the key factors expected to result in a spurt in growth.
This book describes the various formulae, manufacturing processes and photographs of plant & machinery with supplier’s contact details. The major contents of the book are metal pigments, black pigments, inorganic colour pigments, organic colour pigments, extender pigments, white pigments, photocatalytic activity of titanium dioxide pigment, azo pigments, bisazo pyridine pigments, high grade organic pigments, high temperature stable inorganic pigments, anti corrosive pigments, metals and metal ions in pigmentary systems, control of organic pigment dispersion properties, pigments for plastics, rubber & cosmetics, pigments for printing inks, vat dyes, reactive dyes, disperse dyes, direct dyes and sulphur dyes etc.
It will be a standard reference book for professionals, entrepreneurs, those studying and researching in this important area and others interested in the field of textile dyes & pigments.
Modern Technology of Textile Dyes & Pigments (2nd Revised Edition)
Author: Dr. H. Panda
Published: 2016
Format: paperback
ISBN: 9789381039717
Code: NI67
Pages: 512
$ 44.95
1675
Publisher: NIIR PROJECT CONSULTANCY SERVICES
Usually ships within 5 days
Contents
1. Metal Pigments
Aluminium Powder and Paste
Zinc Powder Pigments
Lead Powder and Paste
2. Black Pigments
Carbon Black
3. Inorganic Colour Pigments
Colour in Pigments
Crystal Form and Shape
Hiding Power and Opacity
Tinting Strength
General Characteristics
Manufacture of Colour Pigments
4. Organic Colour Pigments
Toners and Lakes
General Characteristics
Colour in Organic Materials
Manufacture of Organic Pigments
Spot Tests for Colour Pigments
Commercial Pigments
Lightfastness in Tints
5. Extender Pigments
Type of Extenders
6. White Pigments
General Comparison of White Pigments
White lead Pigments
7. Photocatalytic Activity of Titanium Dioxide Pigment
Experimental
Pigment Samples
Florida Exposure Series
Statistical Procedures
Results & Discussion
Acrylic Paints
Alkyd Paints
Summary
8. Use of Flocculation Gradient in Determining the Efficiency of Titanium Dioxide Utilisation in Paint
States of dispersion
Flocculation
Assessment of degree of flocculation
Conclusion
9. Titanium Dioxide Pigments in Water-reducible and Water soluble vehicles
Procedure of the evaluation
Preliminary tests
Results of the investigation
Optical properties of TiO2 pigments
Conclusions
10. Azo Pigments
Red Pigments
Permanent Reds
The Pyrazolone Red
Yellow Pigments
Manufacture of azo pigments
Coupling Component
Coupling preparation
Diazotization
Preparation of Coupling component
11. Bisazo Pyridone Pigments
Experimental
12. Novel Gold Colours and Effects with Environmentally Safe-to-use Mica Pigments
New Golden Pearl Lustre Pigment
Gold Colours and Effects
Other Colours Shades
13. Fluorescent Pigments
Pigment Manufacture
Photostability of Fluorescent Pigments
Fluorescent Application
Phosphorescent Luminous Pigments
Properties and Characteristics
Pearl Luster Pigments
14. High Grade Organic Pigments
Azo Condensation
Vat Pigments and Related Compounds
Thioindigo Pigments
Immersion Processes
Perylene-Perinone pigments
Toning White Enamels
Phthalocyanine
15. Phthalocyanines
Methods for formation of pigments from crude
Acid pasting
Concentration of the sulfuric acid
Amounts of the sulfuric acid
Production of b-form pigment by salt grinding
Manufacture of metal free phthalocyanine
Phthalocyanine complexes from metals other than copper
Flocculation, flotation and flooding
Flotation
Application of phthalocyanine pigments
Phthalocyanine dyes of Textile materials
Phthalocyanine reactive dyes
16 High Temperature Stable Inorganic Pigments
17. New Metal Complex Pigments
Experimental
Metal complex formation
Results and Discussion
18. Latest Developments in Organic Pigments for Automotive Finishes
Violet
Advantages of using Mica Pearl
19. Preparation of Iron Oxide Pigment from Industrial Waste
Preparation of the pigment
20. Anti Corrosive Pigments
Electrochemical theory of Corrosion
Anticorrosive Pigments
Anti corrosive properties of Zinc Dust
Zinc Dust Pigmented coating
Corrosion mechanism
Corrosion mechanism
Good Inter coat Adhesion
Mechanism of Corrosion
Corrosion Control
Preparation of Anti corrosive Pigment Strontium Chromate
Synthetic Lamellar Iron Oxide: a New Pigment for
Anti-corrosive Primers
The need for an improved barrier pigment
Comparisons with traditional iron oxides
Summary and general conclusions
21. An Overview of Aluminium Pigment Technologies
Colour and Sparkle
Distinctness of Image—DOI
Tint strength
Particle size distribution
22. Metals and Metal Ions in Pigmentary Systems
23 Control of Organic Pigment Dispersion Properties
Experimental
Results and Discussion
24 Advances in the Science and Technology of Pigments
Arylamide Azo Yellows
Azo Red Pigments
Heterocyclic Pigments
Metal Complex Pigments
Surfaces treatment
Environmentally safe chemistry
Novelty and profitability pressures
25 Pigments for Plastics, Rubber and Cosmetics
Selection of pigment
Colouring Techniques
Colouring Thermoplastics
Polyethylene
Vulcan Fast and Vulcan Pigments
26. Pigments for Printing Inks
Fastness to Light
Organic pigment for printing ink should offer
27. Vat Dyes
Indigoid Dyes
Indigo
Thioindigoid Dyes
Anthraquinone Vat Dyes
Chemical Constitution of Quinone Vat Dyes
The Reduction of Quinone Vat Dyes
Vat Dye Dispersions
Reducing Vat Dyes with Hydros
Scheme 1
Scheme 2
Manufacture of Common Vat Dyes
CI Vat Brown 1 CAS 2475-33-4
CI Vat Yellow 2 CAS No. 129-09-9
CI Vat Yellow 4 CAS No. 128-66-5
CI Vat Orange 1 CAS No. 1324-11-4
CI Vat Orange 15 CAS No. 128-70-1 6
CI Vat Blue 20 CAS No. 116-71-2
CI Vat Green 1 CAS No. 128-58-5
Waste Streams of Vat Dye Manufacture
28. Reactive Dyes
Nucleophilic Substitution Systems
Trichloropyrimidine Dyes
The Chloropyridazine Systems
Quinoxaline Derivatives
Chloroacetyl and Bromoacetyl Derivatives
Vinylsulphone Dyes
Acrylamide Dyes
Evidence for Chemical Combination Cellulose
Properties of Reactive Dyes
Types of Reactive Dyes
Reactive Dye Structure
Properties
29. Disperse Dyes
Azo Dyes
Anthraquinone Disperse Dyes
Miscellaneous Disperse Dyes
Methine or Styryl Dyes
Coumarm Dyes
Formazine Dyes
Chemical Constitutions of Disperse Dyes
Disperse Dye Dispersions
Fastness Properties of Disperse Dyes
Manufacturing Process
30. Direct Dyes
Chemical Constitution of Direct Dyes
Major Types of Direct Dyes
Cationic Direct Dyes
Anionic Direct Dyes
Classification According to Dyeing Behaviour
Class A
Class B
Class C
31. Sulphur Dyes
Introduction
Properties of Sulphur Dyes
Sulphurised Vat Dyes
Ready-reduced and Solubilised Sulphur Dyes
32. Photographs of Plant & Machinery with Supplier’s Contact Details
Sample Chapters
Metal Pigments
Certainly there is no resemblance or connection between metal
pigments and metallic stearates. It was merely a matter of convenience
to group these two short subjects together in one chapter.
The principal metal pigments are those made from aluminium,
zinc and mixtures of copper and zinc which range from 100% copper
to about 70% copper and 30% zinc. Pigments from the copper-zinc
alloys are known as “bronze powders.” Metal lead pigments are
available and metal silver pigments have specialized uses such as
conductive coatings for printed circuits. Similarly, nickel and stainless
steel pigments find use where a combination of metallic appearance
and alkali resistance is required.
The metal industry produces fine particle size metals in both
powder and flake forms which are used in a variety of industries. The
paint industry uses chiefly the flake form of aluminium and bronze
and zinc in the powder form. Since metal, even as very thin foil, is
completely opaque to visible and ultraviolet light, it could be anticipated
that metal pigments would have exceptionally good hiding power.
However, they have relatively low tinting strength and for some finishes
they are coloured with various amounts of colour pigments.
Finely divided metals react with moisture, and hydrogen gas is
one of the products. If this reaction occurs in tightly closed containers
it may develop sufficient pressure to bulge or rupture the container.
Therefore, every effort must be made to store metal pigments under dry
conditions and to use paint vehicles which are as nearly anhydrous
as possible. In many cases two containers are used to ship metallic
paints. One container has the metal pigment and the other contains
the remainder of the paint. Shortly before application the metal pigment
is mixed into contents of the second container.
Metal pigments fulfill several important functions in coatings.
Bronze powders are widely used for decorative coatings. Aluminium
pigments also are used for decorative purposes; in addition, they impart
heat reflective properties, reduced permeability to moisture, and good
durability to coatings. Zinc dust contributes corrosion- inhibitive
properties in primers for iron and steel and excellent adhesion in primers
for galvanized iron. The many applications for metal pigments and
metallic stearates are discussed in later chapters. This chapter outlines
the types, method of manufacture, and general properties of the principal
metal pigments and metallic stearates available at present.
The lubricant is added to prevent the aluminium particles from
being mechanically welded together under impact and also to develop
a bright metallic lustre on the flakes. Usually, the lubricant is stearic
acid but other fats and oils may be used, such as tallow and olive and
rapeseed oils. It is believed that chemical reaction occurs between
stearic acid and aluminium during the milling operation to form a
strongly adhering coating of aluminium stearate on the finished flake.
This coating makes possible the leafing action of the flakes in a paint
film with the resulting brilliant metallic finish. The coating is quite
stable under conditions of normal use, but it may be loosened or
removed at temperatures above 180oF, also by certain solvents, and by
chemical reaction with materials such as lead driers and free acids in
vehicles. Further discussion of conditions for proper leafing is given
later under physical and chemical properties.
The liquid medium for wet milling usually is mineral spirits, but
liquids such as solvent naphtha or certain plasticisers are used for
specific applications. The mill is run until test shows the required
degree of fineness has been attained; then the paste is washed from the
mill with mineral spirits. The batch is filtered and adjusted to the
specified solid content either by drying or by addition of liquid medium.
The solid content of commercial aluminium pastes usually is 65%, but
special grades may be as high as 73.5%. Flake aluminium powders are
produces by complete drying of the paste through evaporation of the
mineral spirits under vacuum. The foregoing process produces the
leafing type of aluminium pigments. These may be treated to convert
them into the non-leafing type, or a special lubricant may be used
which produces the non-leafing type directly.
An indirect indication of the particle size is obtained from the
water-covering test. A weighed amount of powder is dusted on to the
surface of a rectangular pan of water as uniformly as possible between
two movable baffles. The layer of powder then is manipulated by means
of the baffles to produce as extensive an area as possible and still
maintain a continuous layer. The area of this layer is measured, and
the results are expressed as square centimenters covered per gram of
powder. The coverage ranges from about 8000-10,000 sq cm/gm for
the coarse grades, 14,000-18,000 sq cm/gm for the lining grades, and
25,000-30,000 sq cm/gm for the extra fine lining grades.
Leafing grades may be distinguished from the non-leafing grades
by mixing a small amount of paste or powder with mineral spirits of
xylene. The leafing grades produce the familiar metallic surface on the
liquid, whereas the non-leafing graders yield a gray suspension. This
test does not give satisfactory results with liquids having surface tension
values of less than 25. For example, VM&P naphtha does not permit
satisfactory leafing because of its low surface tension values. The extent
of leafing of aluminium pigments is measured by the spatula immersion
test. A polished spatula of standard dimensions is dipped in a specific
mixture of pigment and coumarone resin solution, withdrawn rapidly,
and allowed to drain in a cylinder for three minutes. The coating then
is examined for extent of leafing over the total depth of immersion. The
ratio of the depth of the fully leafed portion to the total depth is
calculated and expressed as percent leafing. This test may be used to
determine possible loss of leafing of an aluminium paint on aging.
Handling and Storage. Aluminium pastes and powders should
be stored in closed containers at normal temperatures. Open containers
permit loss of volatile liquid from pastes with consequent drying and
uncertainty of composition. Free access of pigments to air and moisture
should be avoided. Long exposure to air produces oxidation of the
metal with a consequent loss of adhesion of the stearate layer and
reduction of leafing property. Moisture reacts chemically with finely
divided aluminium with a resulting production of hydrogen gas and
loss of leafing property. The use of paste eliminate the dust hazard
connected with the powder type. In addition, paste has a higher
apparent density, therefore it occupies less space and mixes with paint
vehicles more easily than powder.
Black Pigments
Charred bones and soot from smoky fires were used as black
colouring materials by pre-historic man. Modern man also uses bone
black and soot as black pigments for paints and printing inks, but he
has wide range of types and grades of black pigments for specific
applications. In addition to the blacks composed chiefly of carbon, he
used certain inorganic blacks in which good filling properties are more
important than depth of colour. The general types of black pigments
are listed in Table 1 together with their raw materials and approximate
range of composition.
Bone black is obtained by pulverizing carbonized bones. It has
good blackness and also low oil absorption and good filling properties.
Vegetable black is obtained by carbonizing wood and other plant
products. At present it finds-only limited use in coatings, and it is
being replaced by blacks having more uniform composition varies with
source and type of raw material, and they may be replaced with greater
uniformity with mixtures of extender pigments and carbon black.
Mineral black is used in coatings such as freight car paints and metal
primers and surfacers. The natural and synthetic black oxides of iron
are described. They are used where good filling properties are more
imortant than blackness of colour. Antimony sulfide is used almost
excliusively in camouflage paints, since it reflects the same as green
foliage when photographed with infrared film. Black toners are organic
compounds used in conjunction with carbon black to increase the
blackness of specialty finishes. An apprarent increase in blackness of
finishes made with certain standard carbon blacks may be obtained by
addition of up to 25% of in iron blue. The type of iron blue generally
used is the toning blue.
In addition to the black pigments listed in Table 1 the paint
industry uses a variety of bituminous materials such as pitches,
asphalts, and gilsonite in black and dark coloured coatings.
Furnace Black. The furnace process not only give higher yields of
carbon, but also the plant occupies much less space and is free from
the smoke nuisance associated with burner houses. Also, the furnace
process may be adjusted to use either gas or oil as the raw material.
Continued improvements since the furnace process was inaugurated
have produced smaller size particles with better blackness, but it
remains to be seen whether this trend can be continued to produce
colour equal to the better grades of channel black.
In the furnace process the same operations of partial combustion
to produce the necessary temperature and thermal decomposition of
the remainder take place, but a single large flame replaces the large
number of small flames of the channel process. Gas and air are admitted
separately to a firebrick-lined furnace which operates at a temperature
of about 2400oF. Through controlled air supply and the particular
design of the inlet ports, a large portion of the gas is decomposed
instead of being burned completely. The hot gases from the furnace,
carrying the black in suspension, are cooled by water sprays. Then the
products pass through an electrostatic field which agglomerates the
carbon particles so that they may be collected in cyclone collectors,
and the exhaust gases are vented to the atmosphere. From the collectors
the black may be bagged or routed through pelletizing equipment. The
variables in the furnace process are:
Thermal Black. Thermal black represents only a small percentage
of carbon black production. Two general types are produced; one is
based on natural gas as the raw material and the other on acetylene.
The black from natural gas has the largest particle size and greyest
colour of the carbon blacks, and the black from acetylene is intermediate
in size and colour between furnace and channel black. Thermal black
is produced by thermal decomposition without simultaneous
combustion.
In the natural gas process the thermal decomposition takes place
in an insulated chamber containing a network of firebrick. First, the
chamber is heated to 1800-2500oF direct combustion of an air-gas
mixture. Then the combustion is stopped, and a charge of “make-gas”
is passed through the heated chamber. The resulting carbon and spent
gases are cooled by water sprays, and the carbon collected in bag
filters. This process gives a high yield of carbon, but the particle size is
large and the colour is quite grey. Somewhat smaller particle size may
be obtained by diluting the make-gas with spent flue gases.
The carbon content of bone black is about 20% that of carbon
black. Since the hiding power and tinting strength depend on the carbon
content, it will be apparent that bone black is much weaker than carbon
black in these respects. However, bone black is much lower in oil
absorption, therefore a greater percentage can be incorporated in a
formulation without developing excessive consistency. This feature is
desirable in the production of low-sheen black finishes or when good
filling properties are required, such as in leather finishing. Its particle
size, relatively large, is expressed as percent retained on a 325-mesh
screen. When used with other colours it shows less tendency to float
than carbon black because of the larger particle size. Bone black is
fairly easy to disperse in coating vehicles and is wetted by water much
easier than regular carbon black. For this reason it finds use in tinting
calcimine, casein and latex paints, and water base inks. Generally,
bone black is considered too abrasive for lithographic inks, but is used
in artists colours and many standard coatings.
Vegetable Black. Vine black was produced originally from stems
and twigs of grape and hop vines and from organic wastes of the wine
industry. It is the most important member of the family of “vegetable”
blacks which are produced from many kinds of cellulosic materials
obtained from plants and trees. Vegetable blacks are made by dry
distillation and carbonization of the vegetable material in the absence
of air. They range from 30-70% in carbon content, the remainder being
a mixture of calcium and potassium carbonates. As may be expected,
vegetable blacks show an alkaline reaction. They are somewhat low in
colour value and in oil absorption. At present they find very limited
application in coatings and have been replaced to a great extent by
mixtures of furnace black and black iron oxides.
Mineral blacks are coarse pigments with low oil absorption and
good filling properties. They may be used in coatings such as freight
car paints and sanding surfacers. In view of the availability at low
cost of carefully classified extended pigments described, and of the
newer furnace blacks, it would appear that combinations of these
materials could be made by paint manufacturers to meet the
requirements of mineral blacks with possible improvement in
performance.
Antimony Trisulfide. Antimony sulfide occurs in nature as the
grayblack mineral known as stibnite. It may be pulverized to the
required particle size and used as a pigment in camouflage paints.
When such paints are photographed with infrared film, the antimony
sulfide gives the same reflection characteristics as green foliage.
Antimony sulfide may be made by reaction between antimony
and sulfur or by precipitation from solution of antimony trichloride
with hydrogen sulfide. The natural products range from 64-66% Sb2S3,
and the technical grade of precipitated material contains about 94%
Sb2S3. Owing to its low colour value, its use in paints is limited almost
entirely to the camouflags type.
Extender Pigments
Introduction
Extender pigments are much lower in price than prime pigments
and are used in paints primarily to reduce cost. However, by careful
selection of the partiuclar type of extender for specific paints, it is often
possible to improve certain properties of the paint or the dry coating.
Proper choice of extender may improve properties such as consistency,
leveling, and pigment settling in the paint. Certain extenders reinforce
the structure of the dry coating mechanically, while others increase its
resistance to the transmission of moisture.
Flat finish and semi-gloss paints are produced by using pigment
concentrations high enough to prevent the formation of a layer of clear
oil or resin in the surface of the coating which would give it gloss.
When pigment particles are in the surface they diffuse the light and
prevent specular or glossy reflection. In paints with high pigment
concentration sufficient hiding may be obtained by replacing some of
the opaque pigment with extender pigment. Since extenders are lower
in price than opaque pigments, a reduction in material cost will result.
The refractive indexes of extender pigments range from 1.55 to
1.65, and since these values are only slightly different from those for
oils and resins, extenders generally do not contribute to the hiding
power of paints. In special cases, such as their use in wood fillers and
flat varnishes, lack of opacity is desirable to prevent a “muddy” effect
in clear furniture finishes. Certain chemically prepared extenders such
as Micro-Cel pigments have refractive indexes in the range of those for
oils and resins, but in combination with while opaque pigments they
contribute slightly to hiding power. The reson for this phenomenon is
not clearly understood at characteristics, and the effect of these factors
on the scattering of light in the coating. Detailed knowledge of the
various types and grades of extenders will enable the paint formulator
to produce paints having maximum properties at minimum costs.
Type of Extenders
Extender pigment are obtained from two general sources: (1) by
pulverization of certain rocks and sedimentary deposits; (2) by chemical
precipitation. The two types are referred to as natural and precipitated
extenders respectively. The natural deposits such as limestone, quartz,
and clay are found in various parts of the country, and the pigments
usually are processed at the deposits. The markets are supplied from
local deposits whenever possible, because the low price of extender
pigments will not permit high freight charges. There may be
considerable variation in composition and properties of natural
deposits with corresponding differences in extender pigments obtained
from them. Therefore paint manufacturers having plants in eastern,
central, and western states may have to adjust their formulations
containing extenders to accommodate variations in extenders supplied
to the different plants.
Extender pigments also may be used to advantage to increase the
consistency of paints. Some extenders that have much higher oil
absorption values than white pigments may be employed to increase
the consistency of white paints without raising the cost. The oil
absorption of a particular pigment is directly proportional to its
available surface; therefore the grade having finer particle size usually
has higher oill absorption. Since oil absorption also is affected by the
nature of the pigment surface, the oil absorption values vary among
the different type of extender pigments because their different surface
characteristics as discussed before.
Extender pigments are marketed as white powders, but because
of their low refractive indexes they do not contribute whiteness or high
reflectance to oleoresinous paints. However, some grades of natural
extenders contain traces of metallic oxides, such as iron oxide, which
cause slight discolouration or reduction in reflectance of white paints.
Such grades should not be used for flat or semi-gloss white finishes
but would be entirely satisfactory for coloured finishes or in metal
primers and surfacers.
Extender pigments may vary considerably in characteristics such
as reactivity with components of paint vehicles, sensitivity to and
solubility in water, and in the pH of water slurries. Their reactivity is
due in part to variations in origin and methods of processing, but
some of the reactivity is inherent in the particular extenders. For
example, barytes is very inert chemically and not sensitive to moisture
adsorption, whereas calcium carbonate is more readily affected by acidic
conditions. Calcium sulfate may adsorb sufficient moisture in humid
weather to change the consistency characteristics of a paint. The pH
and specific resistance of water slurries of extenders are important if
these pigments are to be used in water-dispersed paints; they should
be checked carefully. Some extenders have sufficient solubility in water
to liberate enough cations to affect the stability of latex or other types
of emulsion paints.
Calcium Carbonate Extenders. Calcium carbonate extender
pigments are very widely used and are frequently referred to as whiting.
They are available as both natural and precipitated types and in a
wide range of particle size. The very coarse grades are preferred for
putty and glazing compounds, the intermediate sizes for oleoresinous
flat and semi-gloss finishes and caulking compounds, and ultrafine
precipitated grades are available for gloss finished and printing inks.
Natural whiting is obtained from two main sources: limestone
and chalk. Limestone is widely distributed throughout the world and
is found in most of the states of the United States. Limestone and the
related rocks, marble and calcite, are crystalline and were formed in
the earth’s crust by reactions between calcium salts and water
containing carbon dioxide. When magnesium salts were present, a
mixture of magnesium and calcium carbonates were precipitated which
is known as dolomite limestone. Chalk is an oolitic variety of calcium
carbonate and was formed by deposition of shells and marine animals.
Natural whitings are made by quarrying the rock, crushing and
grinding it, and then classifying the powdered material for particle
size requirement. The grinding process may be either dry or wet. In dry
grinding the screened crushed rock is powdered with a hammer or
roller mill and classfied for particle size by the air-flatation process. A
stream of compressed air passes through the mill and carries out the
particles which are small enough to “float” on it; the larger particles
drop back into the mill. The rate of air flow is a factor in the particle
size obtained in the product.
High Temperature Stable Inorganic Pigments
The pottery industry has, for several thousand years, been using
high temperature stable inorganic pigments, which do not fade or
discolour even at the high temperatures (between 400o and 1400oC)
required for the maturing of enamels and glazes. Moreover, there are
many examples of beautiful colour and decoration work from as early
as the Shang dynasty in China (1500 B.C.), which have come down to
our period without much change in the shade or brightness of the
colours. While it is true, that the glaze substrate in which these pigments
are embodied, provides substantial protection from contact with air,
water, chemicals and other destructive elements, it is nevertheless also
true that the light-fastness of these pigments must be something fantastic
for them to have remained unchanged for periods of 3000 years and
more.
While the tinting power of many inorganic colours tends to the
rather less than that of organic pigments, inorganic pigments tend to
have greater opacity, hiding power, bleed resistance, and of course
light-fastness. They are more resistant to heat, and, being mostly ionic
bonded, are usually less reactive with the organic vehicles, which are
usually covalent bonded.
High temperature stable inorganic pigments can also be used for
normal temperature applications such as the pigmentation of rubbers,
plastics, paints, cements, etc. Almost any colour and shade, including
those shown in IS:5-1978 and many more not shown in the I.S. charts,
are obtainable with high temperature stable pigments.
High temperature stable pigments are mostly exides, sulphides
or silicates of various metals
Shades of red, yellow, pink and violet are also obtainable from
compounds of tin, copper and gold. Such compounds are, naturally,
quite expensive, but produce very attractive, long lasting shades. Blues
and violets are produced from compounds of vanadium, titanium,
uranium, copper and cobalt. Cobalt colours are, of course, fairly
expensive, but have excellent light-fastness and binding power. They
come mostly in the spinel crystalline form, which are stable upto
1600oC., and inert to acids and alkalies.
Because of chemical stability, light-fastness, resistance to dilute
acids and alkalies, dispersability and compatibility with other organic
and inorganic pigments, high temperature stable pigments make
excellent colours for.
Preparation of Iron Oxide Pigment from Industrial Waste
Paint is used for decoration, protection of metals and functional
applications. The constituents of a paint are vehicle, pigment, solvent
and additivies. Pigments are mainly used for giving body to the paint,
protection and for specialised functions. These are finely divided solids
of different shades used in the paint to give colour, hiding, consistency,
durability, build, etc. These particles are substantially insoluble in water.
Pigments may be classified as natural and synthetic, depending on
their origin.
Iron oxides are extensively used as inert pigments in the paint
industy. A dye intermediate manufacturing industry in the country
was faced with the problem of accumulation of huge volumes of slude
in their factory during the iron and acid reduction process. Efforts
have been made elsewhere to convert the sludge into useful pigment.
These results of the preliminary studies made in this direction are
reported in this paper.
Preparation of the pigment
The sample supplied by the firm contained total iron as Fe2O3-
90.5% and ferrous iron as FeO 3%. The colour of the product was
black. The sludge was washed first with water to remove the soluble
impurities such as chlorides, etc. This washed product was
subsequently subjected to the treatments as shown in Table 1 and visual
observations were made.
A water wash was given to remove the chloride present in the
sludge. It may be seen from the above table that the sludge heated to
500oC at the end of one hour only showed some slight change in the
colour. The temperature was gradually increased from 150oC and the
colour change was observed at 500oC only. The time of heating also
determined by increasing the duration from 30 minutes onwards and
changes could be seen only at the end of 60 minutes. Further heating
did not show any change. No change could be observed when the
slude was treated with different treatments as indicated in Sl. Nos. 2 to
6. When the chloride-free sludge was treated with 10% iron oxide or
pigment grade synthetic iron oxide, the colour of the sludge changed
to that of the pigment grade red oxide at 500oC itself. But the product
was heated to 700oC and maintained there for three hours for the
transformation to be completed. Thus the waste product was converted
into a pigment grade iron oxide.
The water extract of the waste as well as the treated products
were analysed for pH and chloride. It was found that the pH was
neutral i.e. 6.5-7.0 in all the cases except the sludge which was slightly
acidic (
Add Your Comments
About NIIR PROJECT CONSULTANCY SERVICES |
NIIR PROJECT CONSULTANCY SERVICES (NPCS) is a reliable name in the industrial world for offering integrated technical consultancy services. NPCS is manned by engineers, planners, specialists, financial experts, economic analysts and design specialists with extensive experience in the related industries.
Our various services are: Detailed Project Report, Business Plan for Manufacturing Plant, Start-up Ideas, Business Ideas for Entrepreneurs, Start up Business Opportunities, entrepreneurship projects, Successful Business Plan, Industry Trends, Market Research, Manufacturing Process, Machinery, Raw Materials, project report, Cost and Revenue, Pre-feasibility study for Profitable Manufacturing Business, Project Identification, Project Feasibility and Market Study, Identification of Profitable Industrial Project Opportunities, Business Opportunities, Investment Opportunities for Most Profitable Business in India, Manufacturing Business Ideas, Preparation of Project Profile, Pre-Investment and Pre-Feasibility Study, Market Research Study, Preparation of Techno-Economic Feasibility Report, Identification and Selection of Plant, Process, Equipment, General Guidance, Startup Help, Technical and Commercial Counseling for setting up new industrial project and Most Profitable Small Scale Business.
NPCS also publishes varies process technology, technical, reference, self employment and startup books, directory, business and industry database, bankable detailed project report, market research report on various industries, small scale industry and profit making business. Besides being used by manufacturers, industrialists and entrepreneurs, our publications are also used by professionals including project engineers, information services bureau, consultants and project consultancy firms as one of the input in their research.
Let's Connect
Fill in the form below, &
we'll get back to you within 24 hours.