Manufacture of Thinners & Solvents (Properties, Uses, Production, Formulation with Machinery Details)

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Manufacture of Thinners & Solvents (Properties, Uses, Production, Formulation with Machinery Details)

Author: NPCS Board of Consultants & Engineers
Format: Paperback
ISBN: 9789381039830
Code: NI306
Pages: 232
Price: Rs. 1,575.00   US$ 150.00

Published: 2017
Publisher: NIIR PROJECT CONSULTANCY SERVICES
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Solvents are defined as chemicals compound that are introduced during manufacture of the paint itself and before packaging, in order to maintain all components of the paint in a liquid / viscous state such as we know it. A solvent is usually a liquid but can also be a solid or a gas. Solvents find various applications in chemical, pharmaceutical, oil, and gas industries, including in chemical syntheses and purification processes.
Thinners are defined as chemical compounds that are introduced into the paint prior to application, in order to modify the viscosity and other properties related to the rate of curing that may affect the functionality and aesthetics of the final layer painting.Paint thinner, a solvent used in painting and decorating, for thinning oil-based paint and cleaning brushes. A Thinner may be a single solvent or a combination of solvent types. Often, specific thinners are required by the manufacturer of a coating to prevent damage to coating properties that may occur when an inappropriate thinner is used.
Solvents (for cleaning up or softening) and Thinners (for diluting or extending) are useful not only in painting but in other areas such as Wooden Furniture industry, Automobile industry, Ink industry, Rubber industry.
As the paint industry is a major consumer of Thinners & Solvents, and is expanding at a tremendous speed, it is very obvious that the demand of thinners, too, will increase tremendously. The paints & coatings accounts for the largest share in the aliphatic hydrocarbon Thinners & Solvents market. It is also projected to be the fastest-growing application of the aliphatic hydrocarbon Thinners and Solvents market.
The book contains Properties, Uses, manufacturing of Thinners & Solventsand providing information regarding thinner formulation. It also covers raw material suppliers, photographs of plant & Machinery with supplier’s contact details. Some of the fundamentals of the book are thinner in Paint Industry, Health and Safety Measures of Chemicals, Pollution Control, Waste Disposal of Hazardous Chemicals and Storage, Labelling and Packaging of Chemicals etc.
It will be a standard reference book for professionals and entrepreneurs. Those who are interested in this field can find the complete information from manufacture to final uses of Solvents and Thinners. It will be very helpful to consultants, new entrepreneurs, technocrats, research scholars, libraries and existing units.

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Contents

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1. Solvents
Classification of Solvents
Boiling Points
Rates of Evaporation
Polarity
Industrial Applications
Use
Chemical Composition
  I. Organic Solvents
II. Inorganic Solvents
Chemical Structure
Behavior Toward Magdala Red
2. Application of Solvents
3. Properties of Solvents
Introduction
Molecular Weight
Boiling Point
Freezing Point
Density
Liquid Expansion Coefficient
Surface Tension and Absolute Viscosity
Flash Point and Explosive Limits
Autoignition Temperature
Electrical Conductivity
Immediate Danger to Life and Health
4. Environmental, Health and Safety Regulation
Fire
Explosive Peroxide Formation
Health Effects
Ways Solvents Can Enter Your Body
Absorption
Swallowing
What Are the Warning Signs?
Acute Poisoning
What to Do
Chronic Poisoning After Years of Repeated Exposures, the Typical Later Effects are
What to Do
How Solvents Affect the Skin
What to Do
How Much Exposure is Bad for You?
Environmental Contamination
Duties of Employers and Employees
Material Safety Data
Training
5. Manufacturing Process of Solvent
6. Uses of Solvent in Various Industries
Adhesives and Sealants
Common Use of Adhesive in Various Industry
Sealants
Common Use of Sealants in Various Industry
Aerospace
Acetone
Alcohol
Benzene
Methyl Ethyl Ketone (MEK)
Methylene Chloride
Toluene
Turpentine
Mineral Spirits
Naphtha
Linseed Oil
Asphalt Compounding
Biotechnology
Biotransformation Using Solvent-Tolerant Microorganisms
Solvent-Resistant Microorganisms
Process of Solvent Toxicity for Microorganisms
Choice of Solvent for Enzymatic Reaction in Organic Solvent
Low Water Systems
Classification of Organic Solvents
(1) Water-Miscible Organic Solvents
(2) Water-Immiscible Organic Solvents
(3) Water-Insoluble Organic Solvents
Classification of Solvents Commonly Used for Enzymatic Reactions in Organic Media
Properties of Enzymes Affected by Organic Solvents
Thermal Stability (Half-Life), t1/2
Specificity and Selectivity, Kcat/Km
Coil Coating
Cosmetics and Personal Care Products
Electronic Industry
Cleaning in Electronics Manufacturing
Factors Affecting Cleaning
Dry Cleaning
Drycleaning Solvents
Petroleum Drycleaning Solvents
Dry Cleaning Processes
Solvent Storage Tanks
Detergents
Process of Cleaning
Textile Finishing
Waterproofing
Milling
Antistatic Finishing
Fabricated Metal Products
Machining Operations
Metal Parts Cleaning and Stripping
Solvent Cleaning
Aqueous (Alkaline and Acid) Cleaning and Stripping
Abrasive Cleaning and Stripping
Water Cleaning
Waste Streams
Food Industry
Mechanical Extraction
Solvent Extraction
The Solvent Extraction Process
Flow diagram of Oilseed Extraction Process
Review of Solvents Studied for Extraction Efficiency
Iron Steel Industry
List of Solvents Releases from the Iron and Steel Industry
Uses of Solvent in Ship Industry
Cleaning Operations Using Organic Solvents
Pulp and Paper
Printing Industry
Pharmaceutical Industry
7. Solvent Recycling, Removal and Degradation
Introduction
Process Description and Emissions
General Processes in Solvent Recycling Operations
Solvent Recycling Operations
Solvent Storage
Solvent Handling
Initial Treatment
Typical Fixed-Bed Activated Carbon Solvent Recycling System
Distillation and Purification
Distillation Process for Solvent Recycling
Spills
Equipment Leaks
Emission Estimation Techniques: Acceptable Reliability and Uncertainty
Direct Measurement
Mass Balance
Engineering Calculations
Emission Factors
8. Solvents Market
Industrial Solvent Market
Green Solvent and Bio-Solvents Market
9. Thinners
Introduction
Uses of Thinners
Types of Thinner Used in industries
Types of Thinner Based on the Paint with which it is Mixed
10. Manufacturing Process
Thinner Formulation
11. Formulation of Thinners
Epoxy Thinner
Composition of Ingredients
Handling and Storage
Physical and Chemical Properties
Paint Thinner
Composition of Thinner
Handling and Storage
Precautions to Be Taken in Handling
Precautions to be Taken in Storing
Physical and Chemical Properties
Acrylic Thinner
Composition/Information on Ingredients
Handling and Storage
Physical and Chemical Properties
Varnish Thinner
Composition/Information on Ingredients
Handling and Storage
Handling Precautions
Incompatible Materials
Storage Conditions
Physical and Chemical Properties
12. Thinner in Paint Industry
Odorless Paint Thinner
Requirements of the Thinners
Functions of the Thinners
Properties of Paint Thinner
Solvents Used as Paint Thinners Include
Other Solvents Sometimes Used in the Production of Paint Thinners Include
13. Health and Safety Measures of Chemicals
Health Hazards
Solvents – Thinners
How to Control Health Hazards
Environmental Control
Use Appropriate Personal Protection
Respirators
Eye and Hearing Protection
Protective Clothing
Handling and Storage
Accidental Release Measures
Precautions
Spill or Leak
Do Not Get Water Inside Containers
Fire and Explosion Hazards
Things to Do and Not to do Before Mixing Thinner in Paint
Material Safety Data Sheet
What is a Material Safety Data Sheet (MSDS)?
What is the Purpose of an MSDS?
What information is on the MSDS?
Reactivity Data
Why is an MSDS Hard to Read?
When Would We Use an MSDS?
Hazard Communication Standard
Solvents
14. Pollution Control
Environmental Concerns
Pollution Caused by Thinner
Major Emissions
Impacts on Human Health and Environment
What is Pollution Prevention?
Methods for Reducing the Pollution
15. Waste Disposal of Hazardous Chemicals and Storage
General Requirements for Storage of Chemicals
Prohibited and Restricted Hazardous Chemicals
Exposure Standards
Identifying Hazards
Hazardous Chemicals Generated or Manufactured in the Workplace
Segregate Incompatibles
Segregate Families
Flammable Liquid Storage
Classifications of Flammable and Combustible Liquids
Flammable Liquids
Combustible Liquids
Corrosive Storage
Transporting Chemicals
Hazardous Waste Disposal
General Requirements for Waste Disposal
Standard of Containers
Containers to be Resistant to the Contents
Containers should be in Good Condition
Containers to be Securely Closed
No Mixing of Incompatible Wastes in a Container
Sufficient Air Space in Containers When Storing Liquid Wastes
Disposal of Paint Related Materials
Hazardous Waste Minimization
Process Level Impacts
16. B.I.S. Specifications of Solvents and Thinners
Solvents
Thinner
17. Labelling and Packaging of Chemicals
Introduction
General Requirements of Labelling and Packaging in Accordance with the Chemical Labelling & Packaging (CLP) Regulation
General Labelling Rules
Elements of the CLP Hazard Label
CLP Labelling Requirements Versus Discretion of the Supplier
Classification of Hazardous Substance/Mixtures
Updating the Hazard Label
Labelling of Workplace Chemicals
Hazard Labels for Supply and Transport Outer and Inner Packaging Classified for Supply but not for Transport
Outer and Inner Packaging Classified for Both Transport and Supply
Single Packaging Classified Under Both Supply and Transport
CLP Rules on Packaging of Substances and Mixtures
Child-Resistant Fastening and Tactile Warnings of Danger
Child-Resistant Fastening (CRF)
Tactile Warning of Danger (TWD)
Hazard Pictograms
Shape, Colour and Dimensions
Precedence Rules
Blank Pictograms
Signal Words
Hazard Statements
Precautionary Statements
Codes for Hazard and Precautionary Statements
Code Ranges of Hazard and Precautionary Statements Under CLP
Guidance on Particular Aspects of CLP Hazard Labelling
Further Aspects to Consider for the CLP Hazard Label
Size of the Label and of the Label Elements
Minimum Dimensions of Labels and Pictograms Under CLP
18. Photographs of Machinery with Supplier’s
Contact Details


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Sample Chapters


(Following is an extract of the content from the book)
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 Solvents

Solvents are substances that are liquid under the conditions of application and in which other substances can dissolve, and from which they can be recovered unchanged on removal of the solvent.

From the production of life-saving drugs to them manufacture of household rubber gloves, solvents play a vital role in modern society. However, they share one thing in common—all the world’s production of solvents eventually ends up by being destroyed or dispersed into the biosphere. There is negligible accumulation of solvents in long-term artefacts so the annual production of the solvent industry equates closely to the discharge.

The development of our knowledge of solutions reflects to some extent the development of chemistry itself.

The first solvent used by man was undoubtedly water; however, its first use by man for industrial purposes is shrouded in unrecorded events of prehistoric times. As far back as the time of the Greek philosophers there was speculation about the nature of solution and dissolution. The Greek alchemists considered all chemically active liquids under the name ‘‘Divine water’’.

Solvent contribution to the total is similar in magnitude to all the volatile organic compound (VOC) arising from the fuelling and use of motor vehicles. Since the latter source is being substantially reduced by improvements in cars and in the fuel distribution system, it is not surprising that increased pressure will be brought to bear on solvent users to cut the harm done to the environment by their discharges.

The purpose of solvents is to convert substances into a form suitable for a particular use. The importance of the role of solvents is brought out most clearly by the fact that many substances exhibit their greatest usefulness when in solution. Lacquer solvents, for example, are selected to produce homogeneous combinations and so selected as to impart the most desirable mechanical properties. The physical properties of a fabricated solution can be regulated at will by the proper choice of solvents, thus adapting them to the most varied uses and methods of applications. Some of the more important uses for solvents are in the adhesives, coatings, electronics, ink, pesticide, pharmaceutical, photographic reproduction, and textile industries. Large quantities of solvents are also involved in dry cleaning, metal degreasing, oil refining and recovery, and as fuel additives.

From the molecular-microscopic point of view, solvents break the crystal lattice of solid reactants, dissolve gaseous or liquid reactants, and they may exert a considerable influence over reaction rates and the positions of chemical equilibria. Because of nonspecific and specific intermolecular forces acting between the ions or molecules of dissolved reactants, activated complexes as well as products and solvent molecules (leading to differential solvation of all solutes), the rates, equilibria, and the selectivity of chemical reactions can be strongly influenced by the solvent. Other than the fact that the liquid medium should dissolve the reactants and should be easily separated from the reaction products afterwards, the solvent can have a decisive influence on the outcome (i.e., yield and product distribution) of the chemical reaction under study. Therefore, whenever a chemist wishes to perform a certain chemical reaction, she/he has to take into account not only suitable reaction partners and their concentrations, the proper reaction vessel, the appropriate reaction temperature, and, if necessary, the selection of the right reaction catalyst but also, if the planned reaction is to be successful, the selection of an appropriate solvent or solvent mixture.

Solvents vary in their dissolving power, so that the line of demarcation between solvents, latent solvents and non-solvents is difficult to define. Some of the factors which influence solvency are atmospheric conditions, purity and molecular association. Molecular aggregation is the explanation for increased, attenuated, or decreased solvent power or, more concisely, eccentric solvency. Any substance that will dissolve another is called a solvent. Thus, we have a gaseous solution when a liquid or a solid is dissolved in a gas; a liquid solution when any one of these is dissolved in a liquid, and a solid solution when any one of them is dissolved in a solid.

In industry it is generally understood that solvents are simple or complex, pure or impure compounds or mixtures of compounds (either natural or synthetic) which dissolve many water- insoluble products like fats, waxes, resin, etc., forming homogenous solution ; that such organic solvents dissolve these water –insoluble products in various proportions depending on the solvent power of the solvent, the degree of solubility of the solute, and the temperature; and that the solute can be recovered with its original properties by the removal of the solvent from the solution. It is understood in industry that there is a much more limited number of solvents which do not have the properties given above but which nevertheless are of considerable importance; they are the inorganic solvents like water, liquid ammonia, liquid metals, and inorganic gases.

Classification of Solvents—Solvents have been classified on various arbitrary bases, e.g.:

    1.  Boiling point.

    2.  Evaporation rate.

    3.  Polarity.

    4.  Industrial applications.

    5.  Chemical composition.

    6.  Proton donor and proton acceptor relationships.

    7.  Behavior toward Magdala Red.

Typical classifications are given below:

Boiling Points

    1.  Low-boiling solvents (boiling points below 100ºC.).

    2.  Medium-boiling solvents (boiling points near 125ºC.).

    3.  High-boiling solvents (boiling points between 150 to 200ºC.).

    4.  Plasticizers and softeners (boiling points near 300ºC or above).

Rates of Evaporation

    1.  Fast-evaporating solvents (liquids having evaporation rates at least three times greater than that of butyl acetate). e.g., acetone, ethyl acetate, benzene.

    2.  Medium-evaporating solvents (liquids having evaporation rates greater than 1½ times that of butyl acetate). e.g., ethyl alcohol, toluene, sec.-butyl acetate.

    3.   Slow-evaporating solvents (liquids having evaporating rates greater than that of    Pentasol but slower than that of secondary butyl acetate). e.g.,butyl acetate, amyl alcohol, Cellosolve.

4. Extra-slow-evaporating solvents (liquids evaporating more slowly than Pentasol). e.g., ethyl lactate, diacetone alcohol,butyl Cellosolve.

Polarity

    1.  Polar solvents (solvents containing the hydroxy or ketook groups, associated with strong polarity and high dielectric constants). e.g.,alcohols, acetone.

         Polar solvents dissolve shellac substitutes including phenolic resins of both heat hardening and non-heat hardening types, glyptals and acrolein resins and are of interest to the electrical insulation industry.

    2.  Non-polar solvents (solvents with low dielectric constants). e.g., hydrocarbons, benzene, petroleum hydrocarbons,carbon disulfide.

Non-polar solvents dissolve amberols, oil-soluble phenolic resins, polymerized coumarone resins, etc., and are used primarily in the manufacture of varnishes.

Environmental, Health and Safety Regulation

All solvents should be considered hazardous. How serious     the threat is to health largely depends how much, how often and in what way someone is exposed. Employees in the following industries may be especially at risk: boat building dry cleaning plastics footwear printing painting photographic engineering building chemical manufacture.

 

Most organic solvents are flammable or highly flammable, depending on their volatility. Exceptions are some chlorinated solvents  like dichloromethane and chloroform. Mixtures of solvent vapors and air can explode. Solvent vapors are heavier than air; they will sink to the bottom and can travel large distances nearly undiluted. Solvent vapors can also be found in supposedly empty drums and cans, posing a flash fire hazard; hence empty containers of volatile solvents should be stored open and upside down.

Both diethyl ether and carbon disulfide have exceptionally low autoignition temperatures which increase greatly the fire risk associated with these solvents. The autoignition temperature of carbon disulfide is below 100ºC (212ºF), so objects such as steam pipes, light bulbs, hotplates and recently extinguished bunsen burners are able to ignite its vapours.

Explosive Peroxide Formation

Ethers like diethyl ether and tetrahydrofuran (THF) can form highly explosive organic peroxides upon exposure to oxygen and light, THF is normally more able to form such peroxides than diethyl ether. One of the most susceptible solvents is diisopropyl ether.

The heteroatom (oxygen) stabilizes the formation of a free radical which is formed by the abstraction of a hydrogen atom by another free radical. The carbon centred free radical thus formed is able to react with an oxygen molecule to form a peroxide compound. A range of tests can be used to detect the presence of a peroxide in an ether; one is to use a combination of iron (II) sulfate and potassium thiocyanate. The peroxide is able to oxidize the Fe2+ ion to a Fe3+ ion which then form a deep red coordination complex with the thiocyanate. In extreme cases the peroxides can form crystalline solids within the vessel of the ether.

Unless the desiccant used can destroy the peroxides, they will concentrate during distillation due to their higher boiling point. When sufficient peroxides have formed, they can form a crystalline and shock sensitive solid precipitate. When this solid is formed at the mouth of the bottle, turning the cap may provide sufficient energy for the peroxide to detonate. Peroxide formation is not a significant problem when solvents are used up quickly; they are more of a problem for laboratories which take years to finish a single bottle. Ethers have to be stored in the dark in closed canisters in the presence of stabilizers like butylated hydroxytoluene (BHT) or over sodium hydroxide.

Peroxides may be removed by washing with acidic iron (II) sulfate, filtering through alumina, or distilling from sodium/benzophenone. Alumina does not destroy the peroxides; it merely traps them. The advantage of using sodium/benzophenone is that moisture and oxygen are removed as well.

Health Effects

Ways Solvents Can Enter Your Body

Solvents can be absorbed into the body by three routes. They can be:

•        Inhaled into the lungs.

•        Absorbed through the skin.

•        Swallowed.

Of these three, inhaling a harmful vapour is the most common route. Inhalation once inhaled, the solvent vapours come in direct contact with the blood supply in the lungs and dissolve into the bloodstream. They are then carried by the blood to the body’s organs. Here they may damage the organ’s ability to function.

Absorption

 If solvents are in contact with the skin, they may pass through and enter the bloodstream and be carried directly to the organs. Solvents differ in their ability to penetrate the skin’s protective fats and oils to reach the bloodstream but all will have a direct effect on the skin and can cause problems such as dermatitis.

Swallowing

Swallowing solvent may seem unlikely but avoid smoking, eating or drinking while handling solvents.

What Are the Warning Signs?

The toxic effects of solvents may be noticed immediately, sometime later or both.

Acute Poisoning

The first effects are often similar to drinking too much

alcohol and may lead to poor work or a work accident. Effects will vary with the particular solvent, but will usually include:

•        A light-headed feeling.

•        Slower reaction time.

•        Poorer co-ordination, balance and power of reasoning.

This stage can be followed by:

•        Nausea and dizziness getting more and more severe.

•        Loss of consciousness (referred to as narcosis in some of the Material Safety Data Sheets).

What to Do

•        Remove the person or people away from exposure to the vapour.

•        Check the first aid instructions in this book and on the product label and MSDS to see if there is anything else to do to help.

Recovery from the effects of acute exposure is usually both complete and fairly rapid once the victim is breathing clear air.

Chronic Poisoning After Years of Repeated Exposures, the Typical Later Effects are:

•        Mood changes.

•        Tiredness.

•        Weakness.

•        Persistent dermatitis.

•        Effects on the liver and kidney.

Solvent Recycling, Removal and Degradation

 

Introduction

A solvent is essentially a material used to dissolve or dilute           another substance. There are many examples of solvent uses including degreasing, cleaning and fabric scouring, diluting, reducing, extracting, and inducing reaction in synthesis media. A spent solvent is defined as, “Any material that has been used and as a result of contamination can no longer serve the purpose for which it was produced without processing.” In other words, a spent solvent is a solvent that has been used at least once and cannot be used again for its original purpose without being processed, due to contamination during use. Such a material is considered solid waste and is considered hazardous. The paint and coatings industry accepts this as part of their business, while governments have made it an integral part of their municipal and special waste regulations. That said, solvent recycling does require effort as well as specialized technology.

Process Description and Emissions

Waste solvents are organic dissolving agents that are contaminated with suspended and dissolved solids, organics, water, other solvents, or any other substance not added to the solvent during its manufacture. Recycling is the process of restoring waste solvent to a condition that permits its reuse, either for its original purpose or for other industrial needs.

Not all waste solvents generated by industry are recycled because the costs of reclamation may exceed the value of the recycled solvent, it is not always technically feasible to do so, and the manufacturers of new solvents often prevent their customers from utilising the recycled product

There is a distinct difference between ‘’recovered’’ and ‘’recycled’’ solvent no matter which product you are considering. Solventborne (SB) products that are in high demand for commercial infrastructure projects still dominate the industrial paint industry. While it is true that 90 percent of solvent ‘wastes’ are ‘recovered’ during paint production, the level of recycling for solvents at paint plants is lower depending on several factors: the grade of solvent used, nature of the production and the level of contamination. A majority of industrial paint manufacturers have purchased their own solvent recycling equipment for internal use and can reuse solvents as many times as needed. Industries that produce waste solvents include solvent refining, polymerisation processes, vegetable oil extraction, metallurgical operations, pharmaceutical manufacture, surface coating, and cleaning operations (dry cleaning and solvent degreasing). The amount of solvent recovered from the waste varies from about 40 to 99 percent, depending on the extent and characterisation of the contamination and on the recovery process employed. Companies recovering solvents that do not have internal recycling systems send the solvents to outside companies for transfer, treatment or elimination. A number of solvents can be recycled and even resold by solvent recyclers such as acetone and varsol.

Design parameters and economic factors determine whether solvent reclamation is accomplished as a main process by a private contractor, as an integral part of a main process (such as solvent refining), or as an added process (as in the surface coating and cleaning industries). Most contract solvent reprocessing operations recover halogenated hydrocarbons, such as dichloromethane and trichloroethylene, from degreasing, and/or aliphatic, aromatic, and naphthenic solvents such as those used in paint, ink, and coatings industries. They may also reclaim small quantities of numerous specialty solvents, such as phenols, nitriles, and oils.

Industrial operations may not incorporate all of these steps. For example, initial treatment is necessary only when liquid waste solvents contain dissolved contaminants.

 

Solvent Recycling Operations

For architectural latex plants, the market is largely dominated by waterborne products with less than 5% in volume of sales being solvent borne. For waterborne paint plants, the solvent is water and some recycling occurs with ‘washing waters’ that have been used several times. At the end of their cycle these used waters are then transferred to other chemical companies with expertise in treatment or elimination. Another portion is used in other value-added applications such as cement and asphalt production. The recycled solvent borne mixtures may find other industrial applications in the future, other than solvent purifying to a certain calorific level suitable for the production of cement or asphalt.

Generally the solvents from left over paint stocks have several markets:

     (1)      Export markets with a high demand for alternative uses for solvents.

     (2)      Local markets for commercial and industrial use.

     (3)      Companies specialized in adding value using recycled products to meet specifications for use in functions like cement making facilities.

In contrast with the waterborne paint market, the solventborne paint market opportunities are still extremely limited. It should be noted that 11 percent of the recovered paint quantities (15 percent of the 75 percent recovered paint quantities altogether) comes from the bottom vat residues where recovered paint is mixed and cannot be reused and no value can be extracted from this quantity. The settled matter at the bottom of the recipient containers has to be recovered and eliminated. Aside from the obvious environmental benefits the advantages of solvent recovery and recycling are real.

The process of recovering and recycling solvents can be challenging. If not done properly the recovered solvents will not reach the desired level of decontamination for further use. For proper use these recycling processes require specialized equipment, proper maintenance, periodic cleaning, specialized labour, etc. Nevertheless, the return on investment for manufacturers and other users from a sustainability standpoint can be huge. Solvent recovery and recycling can produce a triple benefit: environmental, economic and social.

Solvent Storage

Solvents are stored before and after recycling in containers ranging from 0.2 m3 to tanks with capacities of 75 m3 or more. Most of these tanks have a fixed-roof design. The two significant types of emissions from fixedroof tanks are breathing and working losses. A breathing loss tank is the expulsion of vapour from a tank through vapour expansion and contraction that result from changes in ambient temperature and barometric pressure. This loss occurs without any liquid level change in the tank. The combined loss from filling and emptying tanks is called the working loss. Evaporation during filling operations results from an increase in the liquid level in the tank. As the liquid level increases, the pressure inside the tank exceeds the relief pressure, and vapours are expelled from the tank. Evaporative emissions during the emptying process occur when air, drawn into the tank during liquid removal, becomes saturated with organic vapour and expands, expelling vapour through the vapour relief valve.

Solvent Handling

Handling includes loading waste solvent into process equipment and filling drums and tanks prior to transport and storage. The filling is most often done through submerged or bottom loading. Emissions of VOCs to air may occur during material loading of solvents due to displacement of organic vapours. VOCs may be emitted from a tank when the vessel is uncovered or when a lid is open. Surface evaporation may occur during solvent recycling operations if containment vessels are exposed to the atmosphere. Surface evaporation emissions are generally fugitive in nature.

Initial Treatment

Waste solvents are initially treated by vapour recovery, or mechanical separation. Vapour recovery include removal of solvent vapours from a gas stream in preparation for further reclaiming operations. In mechanical separation undissolved solid contaminants are removed from liquid solvents. Vapour recovery or collection methods employed include condensation, adsorption, and absorption. Technical feasibility of the method chosen depends on the solvent’s miscibility, vapour composition and concentration, boiling point, reactivity, and solubility, as well as several other factors.

Condensation of solvent vapours is accomplished by water-cooled condensers and refrigeration units. For adequate recovery, a solvent vapour concentration well above 20 mg/m3 is required. To avoid explosive mixtures of a flammable solvent and air in the process gas stream, air is replaced with an inert gas, such as nitrogen. Solvent vapours that escape condensation are recycled through the main process stream or recovered by adsorption or absorption.

Adsorption systems are capable of recovering solvent vapours in concentrations below 4 mg/m3 of air. Solvents with boiling points of 200ºC or more do not desorb effectively with the low-pressure steam commonly used to regenerate the carbon beds. The mixture of steam and solvent vapour passes to a water-cooled condenser. Water-immiscible solvents are simply decanted to separate the solvent, whereas water miscible solvents must be distilled and solvent mixtures must be decanted and distilled. Fluidised bed operations are also in use.

Typical Fixed-Bed Activated Carbon Solvent Recycling System

Absorption of solvent vapours is accomplished by passing the waste gas stream through a liquid in scrubbing towers or spray chambers. Recovery by condensation and adsorption results in a mixture of water and liquid solvent, while absorption recovery results in an oil and solvent mixture.

Initial treatment of liquid waste solvents is accomplished by mechanical separation methods. This includes both removing water by decanting and removing undissolved solids by filtering, draining, settling, and/or centrifuging. A combination of initial treatment methods may be necessary to prepare waste solvents for further processing. Separation of dissolved impurities is accomplished by simple batch, continuous, or steam distillation. Mixed solvents are separated by multiple simple distillation methods, such as batch or continuous rectification.

Manufacturing Process

Thinner is a mixture of aliphatic and/or aromatic   compound. They are used to reduce the viscosity of paint and used for better brush ability or spraying or dipping, used to clean brush or spray gun, used to clean surface before painting, some thinners are used to remove paints - called paint strippers.

 

Manufacturing process of thinner is very simple only a simple blending machine is sufficient for making thinner.

Thinner Formulation

•   25% butyl acetate 

•   5-10% Acetone 

•   1-10% ethyl acetate 

•   1-10% n- Butanol 

•   1-10% anhydrous isopropanol 

•   1-10% xylene 

•   1-10% propylene glycol 

•   10-20% aliphatic petroleum distillate such as Stoddard solvent or other high purity mineral spirits

All the above chemicals are blended properly in a container and packed and supplied in metal and plastic barrels and also available in different containers.

 

Thinner in Paint Industry

In the area of paint we speak indistinctly solvent and thinners, both are chemicals compounds that are added to the paint but with different functions and objectives. A paint thinner is used to thin oil-based paints or clean up after their use. Commercially, solvents labeled “Paint Thinner” are usually mineral spirits having a flash point at about 40°C (104°F),

Thinners are defined as chemical compounds that are introduced into the paint prior to application, in order to modify the viscosity and other properties related to the rate of curing that may affect the functionality and aesthetics of the final layer painting.

In response to the above definitions, both solvents and thinners are chemical compounds with low molecular weight even be the same compound, but the difference is the function for which are designed and at which the moment that they are added. Solvents dissolve the paint before packaging; thinners diluted the paint before applying.

The concept of dissolve and dilute we will understand better with the following example, imagine we have a glass of chocolate into small pieces, if we add hot milk chocolate dissolve transforming from a solid to a liquid state, if you later add more hot milk dilute liquid chocolate decreasing its viscosity, ie we make it fluid. In this example the hot milk acts as both solvent and thinner.

 

In painting, as in the previous example, the chemical compound used as solvent can be the same act as a thinner, but in many cases the thinner is different to the solvent used during its manufacturing process, in the latter case the thinner must be fully compatible with the solvent which incorporates painting.

Odorless Paint Thinner

Odorless paint thinner is a substitute for traditional turpentine and is an excellent alternative to regular paint thinner — the obvious benefit being that odorless paint thinner does not have the same powerful smell as traditional paint thinner

Requirements of the Thinners

•   Must be compatible with the solvents contained in the paint itself.

•   Must be volatile under the conditions that form the paint film, ie once you start the process of drying / curing of paint thinners must evaporate in order to not be part of the dried paint.

Functions of the Thinners

•   Adjust the viscosity of paint depending on the application method and the paint used (roller application, gun spray, paints with high solids contents)

•   Control and regulate the drying time and evaporation (slow thinners in summer and fast thinners in winter) and thus prevent functional and aesthetic problems (boiled, loss of gloss...)

Paint thinner is a solvent used to thin oil-based paints or clean up after their use. Commercially, solvents labeled “Paint Thinner” are usually mineral spirits having a flash point at about 40°C (104°F), the same as some popular brands of charcoal starter.

Solvents Used as Paint Thinners Include

•   Mineral spirits / White spirit 

•   Acetone

•   True turpentine

•   Naphtha

•   Methyl ethyl ketone (MEK)

•   Dimethylformamide 

•   (DMF)

•   2-Butoxyethanol, or any of the other glycol ethers

Other Solvents Sometimes Used in the Production of Paint Thinners Include

•   Ethylbenzene

•   Xylene

•   n-butyl acetate

•       Butan-1-ol

Solvents Used as Paint Thinners Include

•   Mineral spirits / White spirit 

•   Acetone

•   True turpentine

•   Naphtha

•   Methyl ethyl ketone (MEK)

•   Dimethylformamide 

•   (DMF)

•   2-Butoxyethanol, or any of the other glycol ethers

Other Solvents Sometimes Used in the Production of Paint Thinners Include

•   Ethylbenzene

•   Xylene

•   n-butyl acetate

•       Butan-1-ol

Pollution Control

Pollution is the introduction of contaminants into the natural environment that cause adverse change.

 

It was the industrial revolution that gave birth to environmental pollution as we know it today. The pollutants found in the largest quantities at thinner and solvent manufacturing sites include volatile organic compounds. However, other pollutants found include arsenic, cadmium, cyanide, mercury, chromium and lead.

 

With the coming of the Industrial Revolution, humans were able to advance further into the 21st century. Technology developed rapidly, science became advanced and the manufacturing age came into view. With all of these came one more effect, industrial pollution. Earlier, industries were small factories that produced smoke as the main pollutant. However, since the number of factories were limited and worked only a certain number of hours a day, the levels of pollution did not grow significantly. But when these factories became full scale industries and manufacturing units, the issue of industrial pollution started to take on more importance.

VOCs are low molecular weight chemicals made from carbon and hydrogen, and often including oxygen, nitrogen, chlorine and other elements. Because of their low molecular weight, VOCs convert to vapor easily, and VOC vapors are emitted from certain products and processes. There are thousands of VOCs, many of which are familiar compounds in everyday life, such as ethyl alcohol, propane, mineral spirits, and the chemicals in gasoline, kerosene and oil. While many VOCs are relatively non-hazardous (aside from their flammability), there are thousands of VOCs that are toxic, and some can cause eye, nose and throat irritation and headaches, while others are known carcinogens. Some examples of toxic VOCs include benzene, formaldehyde, toluene, vinyl chloride and chloroform. VOCs come from a wide variety of products, most of which are used daily by society. The list includes most fuels, paints, stains and lacquers, cleaning supplies, pesticides, plastics, glues, adhesives and refrigerants. VOCs, including many more uncommon and toxic types, are very commonly used in manufacturing processes as solvents or raw materials in the production of plastics, chemicals, pharmaceuticals, and electronic products.

Environmental Concerns

Businesses may produce many different types of thinner, paint and ink waste in their manufacturing processes or as a result of the services they provide. Some may contain toxic metals at or above regulatory limits. Solvents are generally used during cleanup that may be hazardous wastes as well as air pollutants. Wastes improperly managed can harm human health and the environment.

When discharged, these substances can cause harm to the environment by:

•   Poisoning animals and plants.

•   Smothering small aquatic plants and animals and destroying where they live.

•   Preventing light from entering the water, making it difficult for animals to find food and for plants to get energy from the sun.

     •     Irritating and clogging the gills of fish.

•   Chemicals building up in the bodies of plants and animals, causing long-term health effects or rendering them unfit for human consumption.

Pollution CausEd by Thinner

Chemicals used in manufacturing thinnes such as Benzene, toluene, ethylbenzene, xylenes (as BTEX). The substance BTEX is a group of chemicals, which is quantified by one analytical method. Toluene, ethylbenzene and xylene, which includes three structurally related isomers are colourless liquids, immiscible with water but miscible with organic solvents. They have a characteristic strong odour and are highly flammable. 

Major Emissions

Toluene, ethylbenzene and xylenes can enter the environment during manufacture or use of these substances or products containing them. Due to the high volatility of BTEX compounds, emissions are expected to occur principally to air. 

Impacts on Human Health and Environment

Excessive exposure to toluene may impair hearing and cause health effects on the brain (neurological), and the unborn child; while for ethylbenzene the brain, eye, lung and skin are of principal concern. Excessive exposure to xylene isomers may cause health effects on the brain, digestive system, ear, eye, heart, kidney, liver, lung, skin, nose, reproductive system, throat and the unborn child. The BTEX compounds are categorised as Volatile Organic Compounds (VOCs) that may contribute to the formation of ground-level ozone and photochemical smog, which can cause damage to plants and materials as well as pose human health concerns such as asthma and cancer. BTEX compounds are considered harmful to aquatic organisms. VOCs contaminate air and water, and, in indoor applications, they can linger for hours, exposing painters, janitors and carwash workers to hazardous levels.

What is Pollution Prevention?

Pollution prevention is simply not making the waste (or pollutant) in the first place. It means doing what we can to reduce the amount and toxicity of the pollution we generate. Preventing pollution may be something as simple as using a catch basin to prevent spills, or something as complex as redesigning your operation to increase efficiency and reduce waste. Simple things like choosing non-hazardous solvents when possible can protect the environment and reduce the number of environmental regulations that you are faced with. Pollution prevention means thinking about the environmental impact of your actions and trying to limit that impact.

Pollution prevention techniques include:

•   Modifying equipment or technology.

•   Modifying processes or procedures.

•   Reformulating or redesigning products.

•   Substituting raw materials.

•   Improving housekeeping, maintenance, training, or inventory control.

•   Incorporating demand-side management when designing or renewing projects.

•   Incorporating integrated resource planning into project planning.

Methods for Reducing the Pollution

•   Pollution should be prevented or reduced at the source.

•   Pollution that cannot be prevented should be recycled in an environmentally safe manner.

•   Pollution that cannot be prevented or recycled should be treated in an environmentally safe manner.

•   Disposal or other releases into the environment should be used “only as a last resort” and should be conducted in an environmentally safe manner. Disposal in accordance with local legal provisions. Disposal recommendations apply to the original material and its container and not to any materials which are a waste by-product of the user’s operation. Chemical residues generally count as special waste. The disposal of the latter is regulated through corresponding laws and regulations.

•   Reuse the leftover thinner.

•   Choose the less toxic chemical for formation thinner.

•   Avoid acidic, caustic and hazardous substances.

•   Reuse solvent. Pour the solvent into a glass or metal container and allow the solids to separate out.


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