The Process Of Manufacturing

Paints(An internship at Akzo Noble)

-By Ananya Kapur

1

CONTENTS INTRODUCTION 3ABOUT PAINTS 4The Components of Paints 4Pigments 5Binders 6Extenders 11Solvents 12Additives 13PAINT DRYING 14ENVIRONMENTAL ISSUES 15PAINT MANUFACTURING PROCESS 16

2

Introduction

About this Project:

As a child watching cars be painted in my fathers show room I always wondered what made them stay

in their place, how the got their pretty colors and their sheen. As I grew into a chemistry student at

Vasant Valley School I felt it interesting to learn about paints, their components and properties. At this

step I contacted Akzo Noble in search of an internship that could give me the knowledge I desired and

was thrilled when they provided me with what they wanted. The contents of this project are my results

regarding the same.

About Akzo Nobel-

Akzo Nobel India Limited (a Dutch Company) is engaged in manufacturing of paints, varnishes,

enamels or lacquers, organic and inorganic chemical compounds. The Company operates through two

segments: Coatings and Others. Coatings segment consists of decorative, automotive and industrial

paints, and related activities. Others segment consists of chemicals and polymers. The Company

manufactures and markets a range of coatings covering decorative paints; performance coatings;

marine coatings; protective coatings; metal coatings; powder

Coatings; specialty coatings; vehicle refinishes, and specialty chemicals. The Company provides

solutions to the industries and sectors, including oil and gas; infrastructure, such as airports and stadia;

power; construction; mining, and minerals. The Company's portfolio includes brands, such as Dulux,

Sikkens, Butanox, Elotex, International and Interpon. It has over six plants, which are located at

Telangana, Karnataka, Madhya Pradesh, Punjab and Maharashtra.

3

About PaintsPaint is used to decorate, protect and prolong the life of natural and synthetic materials, and acts as a

barrier against environmental conditions.

Paints may be broadly classified into Decorative paints, applied on site to decorate and protect

buildings and other objects, and Industrial coatings which are applied in factories to finish

manufactured goods such as cars.

 The constituents of paint

Paints contain:

pigment(s) - prime pigments to impart color and opacity

binder (resin) - a polymer, often referred to as resin, forming a matrix to hold the pigment in

place

extender - larger pigment particles added to improve adhesion, strengthen the film and save

binder

Solvent (sometimes called a thinner) - either an organic solvent or water is used to reduce the

viscosity of the paint for better application.  Water-borne paints are replacing some paints that

use volatile organic compounds such as the hydrocarbons which are harmful to the

atmosphere.

additives - used to modify the properties of the liquid paint or dry film

The binder (resin) and solvent together are sometimes known as the vehicle. The binder may be

dissolved as a solution or carried as a dispersion of microscopically small particles in a liquid.

4

Pigments

Pigments serve three main functions: the optical function of providing color, opacity and gloss; a protective function with regards to the surface underneath the paint and with regards to the binder which can be destroyed by UV; and a reinforcing function for the paint itself in that they help the binder to stick. Pigments are composed of tiny solid particles less than 1μm in diameter, a size that enables them to refract light (light has wavelengths between 0.4μm and 0.7μm).

For the pigment to be effective it has to be evenly dispersed throughout the solvent and in contact with the solvent. Surrounding pigment particles is a layer of moist air and, in some cases, other gases. To bring the pigment into contact with the solvent this layer has to be displaced and this displacement is known as wetting. If a pigment is not properly wetted in a paint it may result in color streakiness in the finished paints, thus solvents and pigments must be chosen that result in a well wetted pigment. Wetting and dispersing agents are used to improve the wetting properties of the resin/solvent system.

A variety of natural and synthetic pigments are used in paints, providing a complete spectrum of colors and a variety of finishes. Pigments are broadly classified as either organic or inorganic. In organic pigments the color is due to light energy absorbed by the delocalized B electrons of a conjugated system. The electrons do not usually absorb all wavelengths of light, so some frequencies are allowed to pass through. It is this unabsorbedlight that we see, so the color of a given pigment is the opposite color of the frequencies absorbed by the molecule. The greater the number of conjugated bonds in a system, the lower the energy of light absorbed, thus a molecule with little or no conjugation will absorb in the UV (and hence appear white), whereas one with more conjugation will absorb in the blue and appear yellow, or in the green and appear red etc. Functional groups that absorb visible light (and hence appear colored) are called 'chromophores', and some of the moreCommon ones are —N=N—, —C=C—, —C=O, —C=S, —C=NH, —N=O, —NO2.

Organic pigments are usually preferable as in general they are:

• brighter• stronger (although this varies greatly between organic pigments)• more transparent (this is not always an advantage)• more stable

In addition they have greater tinting strength (i.e. less pigment is required to get an equally strong color), better gloss development and some absorb UV light, preventing it from damaging the binder. However, inorganic pigments are also widely used as they do not bleed, are heat and light stable and are much cheaper than organic pigments. In addition they are used for some specialist pigments (such as anti-corrosion pigments), and for black and white pigments, as it is not possible to get pure black or white organic pigments. One such white pigment, titanium dioxide, is widely agreed to be the single most important pigment in use today. It is the strongest known pigment in terms of both opacity and tinting power which, coupled with its pure white tint and its fine particle size, means that it can be used as an opacifier to prepare films with a high hiding power and reduced pigment content. This has resulted in paints with much improved elasticity and hence improved durability.

As stated earlier, pigments provide other properties to paints than just color and hiding power. Anti-corrosive pigments are a very important area of study. Steel is probably the metal most often requiring protection against corrosion and the development of pigments to inhibit the corrosion of steel has occupied chemists for many years. The anti-corrosive pigment which has been used for many years in red lead, Pb3O4. In combination with linseed oil, red lead has in the past been the standard anti-corrosive primer for iron and steel. Unfortunately, red lead is toxic and much research has been, and is still being, carried out worldwide to find anti-corrosive

Pigments which are as effective as red lead. Anti-corrosive pigments for iron and steel commonly in use include zinc phosphate, zinc chromate, zinc molybdate and barium metaborate, although

5

alternatives to chromates are being sought as they are toxic and environmentally hazardous. Paints are often formulated with other mineral compoundsBinders in paints

The three most important binders (resins) used in modern paints are:

acrylic polymers (resins)

alkyd polymers (resins)

epoxy polymers (resins)

Acrylic polymers (resins)

The binder in many emulsion paints is based on homo polymers or co-polymers of ethenyl ethanoate

(vinyl acetate) and a propenoate (acrylic) ester.

Ethenyl ethanoate is manufactured by passing a mixture of ethanoic acid vapors, ethene and oxygen

over heated palladium(ll) and copper(ll) chlorides:

Ethenyl ethanoate and an acrylic ester (for example, methyl 2-methylpropenoate) are then co-

polymerized to form a random array, in which these groups link into a linear chain:

Other acrylic esters used as co-monomers with ethenyl ethanoate are ethyl propenoate, butyl

propenoates, or a co-polymer of butyl propenoate and methyl 2-methylpropenoate.

The polymers used in these paints are carried in water (water-borne emulsion paints) which as described above is much better for the environment than paints in which the binders are in organic solvents.

6

Water-borne emulsion paints are used as decorative paints, particularly for the inside and outside of

buildings (including masonry paints and exterior primers).

Emulsion paints are so-called as they are made by a process known as emulsion polymerization, in

which the liquid monomers to be polymerized are first dispersed in water, as an emulsion.  The

polymers produced by this process typically have relative molecular masses of 500 000 - 1 000 000.

As such they are useful only as dispersions since they would be extremely viscous if they were carried

in solution and this would make them

unusable. 

IN this graph- relationship between relative molecular

mass and viscosity for solution and dispersion polymers.

Acrylic resins may also be used in industrial paints, either as water-borne emulsion paints or as solvent-

borne paints.  Solvent-borne industrial paints can have a tough protective finish and are widely used in

industry as topcoats, for example on car bodies.  The paint frequently comes as two components which

are mixed together just before use: the main paint portion typically consists of an acrylic resin

produced by the polymerization of a propenoate ester formed from a polyhydric alcohol (diols and

triols).  The resulting polyester has numerous hydroxyl groups (-OH) pendant from the polymer

backbone.  The hydroxyl groups react with the other compound often consisting of a polymeric

isocyanate such as a trimer of 1,6-diisocyanatohexane (hexamethylene diisocyanate):

 

7

Such a compound is known as a cross linker for it produces, on reaction with the resin, a three-

dimensional structure similar to the polyurethane formed from a polyol and an isocyanate.

When these two components are mixed together, a chemical reaction takes place between the hydroxyl

groups on the polymer (acrylic resin) and the isocyanate groups on the cross linker:

This reaction proceeds relatively slowly at room temperature, allowing enough time for the paint to be

applied, after which the solvent thinner evaporates and the painted item is placed in an oven to

accelerate the chemical reaction.  This greatly increases the molecular mass of the polymer causing it to

become a three-dimensional molecule and form a hard film, resistant to chemicals.

Alkyd polymers (resins)

Decorative gloss paints typically contain alkyd polymers (resins).  A typical resin is that produced from

a polyol such as propane-1,2,3-triol (glycerol) with a dibasic acid such as benzene-1,2-dicarboxylic

(phthalic) anhydride and a drying oil (linseed or soybean oil).  On being heated together, ester

linkages are formed, and water is a by-product. The name alkyd is derived from alcohol and anhydride.

The first step in making the alkyd polymer is the reaction between the triol and the drying oil to

produce a mono glyceride.  For example:

8

The mono glyceride then reacts with the anhydride to form the alkyd polymer (resin):

The alkyd resins, which generally have relative molecular masses in the range of 10 000 - 50 000, are

usually carried in organic solvents (solvent-borne paints).  Turpentine extracted from trees was used in

the past as the solvent, but this has been replaced by solvents from petrochemical feedstock, such as

'white spirit' which is a mixture of aliphatic and alicyclic hydrocarbons. Once the alkyd resin is applied,

the pendant oil drying groups react with oxygen in the air to form a cross-linked, hard thermoset

coating, with a high molecular mass.

Epoxy polymers (resins)

Epoxy resins are often used as the binder in industrial coatings (primers).  They give the paint excellent

adhesion together with high resistance to chemicals (corrosion), and physical resistance necessary, for

example, on ships and chemical storage tanks.

9

The epoxy resins are made from 1-chloro-2,3-epoxypropane (produced from 3-chloropropene) and

substituted phenols, such as bisphenol A:

 

The value of n can be controlled to give a range of resins varying from viscous liquids to solids with

high melting points.  Epoxy resins can be carried in solvents such as aromatic hydrocarbons, alcohols,

ketones and esters (solvent-borne paints) or as dispersions in water (water-borne paints) as true

emulsions.  They are not normally used in topcoats for outdoors because they are susceptible to UV

degradation, but they make excellent interior coatings and exterior primers.

Epoxy resins are also used as adhesives (e.g. Araldite) and electrical insulators.

10

Extenders

These may be described as inert substances, lacking in opacity, which are added to specific pigments

for a variety of reasons. Barytes, asbestine, and whiting are among the substances.

It is true that extenders are almost invariably cheaper than the pigments to which they are added, and

that in consequence their use means a saving of money to the manufacturer. However, they fulfil

certain definite and valuable functions which vary according to the nature of the paint in which they are

incorporated.

In some cases, they supply physical properties which are lacking in the main pigment or pigments.

They may, for example, help to keep the pigment particles better in suspension in the medium, thus

tending to prevent undue sediment. Again, they may possess the property of reducing gloss and can, for

this reason, play a useful part in the preparation of flat paints and enamels.

Extenders are solid components of paint. They are finely ground natural materials, most commonly

earth, and they have no effect on the color of the paint, but they do alter some properties.

They have many varied functions:

Provide easier application of the paint. Provides greater adhesive properties. Provides roughness in the film (i.e. undercoats). Gives body to the paint, increases bulk in the coating. Prevents heavy pigments from settling out. Provides a greater water resistance. Flatten bases. Reduces the cost of paints. Increases the hardness of the paint film.

Common Name Formula Uses

Whiting  CaCO3 Undercoats and flat paints

Talc H2Mg3(SiO3)4 Mg3Si4O10(OH)2 Assists TiO2 dispersion, improves sanding.

Barytes BaSO4 Traffic paints

Kaolin Hydrated aluminum silicate Assists TiO2 dispersion, decreases viscosity

Silica SiO2 Flattening agent, traffic paints

Mica Hydrous aluminum postassium silicates Chemical and solar resistant

11

Solvents

Solvents are one of the three components of paints. They are petroleum-based chemicals which

dissolve the pigment and binding agent for application. Most enamel-based paints use a mild

petroleum-based solvent with an alkyd vehicle, and have a long drying and curing time. There are

following types of Solvents.

Aromatic Hydrocarbon Solvents

Aromatic hydrocarbon solvents have a benzene ring structure. These solvents are produced in the petroleum refining industry from the distillation of petroleum stock and other chemical conversion processes, such as catalytic hydrogenation and alkylation. These solvents impart stronger odors and have higher solvency rates than aliphatic hydrocarbon solvents.

Common aromatic hydrocarbon solvents used in paints and coatings are benzene, toluene, ethyl benzene, mixed xylenes (BTEX) and high flash aromatic naphthas. Additional information can be found under our Petrochemical Industry VOCs guide. Aromatic solvents are also widely used in printing inks, pesticides, insecticides, and agricultural chemicals.

Short-term exposure to these solvents from inhalation can result in irritation to the upper respiratory tract and eyes, also dizziness, fatigue and headaches. Long-term effects may cause disorders in blood (benzene); cardiovascular and kidney effects, unconsciousness, dysfunction of the CNS (xylene). Benzene is classified as a human carcinogen.

Aliphatic Hydrocarbon Solvents

Aliphatic hydrocarbon solvents do not contain a benzene ring. They are mixtures of either saturated, long straight chain (normal-paraffin) or branched chain (iso-paraffin) or cyclic paraffin’s. These solvents are produced by distillation of crude oil by the appropriate boiling point range fraction, and then are treated to improve color and odor.

Short-term exposure to these solvents may cause dizziness, giddiness, nausea and headaches, irritation to skin and eyes, and euphoria sometimes resulting in unconsciousness. Long-term effects include muscular weakness, blurred vision, headache, fatigue, and numbness, damage to lungs and skin, and neurological disorders.

In addition to their use as solvents or diluents in paints and thinners, they are widely used in oil extraction, degreasing, rubber manufacture, and as carriers for aerosols and disinfectants. Gasoline and kerosene are examples of aliphatic hydrocarbon solvents.

Common aliphatic hydrocarbon solvents used in paints and coatings are mineral spirits, hexanes, heptane’s, and VM & P Naphthas.

Oxygenated Solvents (Active Solvents)

Oxygenated solvents are synthetic compounds with oxygen functionality. These solvents are primarily used as active solvents for most synthetic resins due to their strong solvency. They dissolve resins and films; reduce viscosity of paints, varnishes and lacquers for application. The four most widely used in this category are: ketones, esters, glycol ethers, and alcohols.

12

Additives

Although used in very small quantities, additives can have a huge impact on coating performance and application properties. Used in the right order, at the right time, and at the right levels, additives can help improve the appearance and durability of a coating, the flow of paints, the efficiency of the manufacturing process, and even the sustainability of formulations.Formulators can optimize paint processing, appearance, application, and stability through the use of our broad portfolio of additive technologies

Wetting and Dispersing Additives

Flow and leveling additives

Defoamers and dearaters

Rheology modifiers

Catalysts and driers

Depending on the type of paint and intended use, additives may include:

dispersants - to separate and stabilise pigment particles

silicones - to improve weather resistance

thixotropic agents - to give paints a jelly-like consistency that breaks down to a liquid when

stirred or when a brush is dipped into it

driers - to accelerate drying time

anti-settling agents - to prevent pigment settling

bactericides - to preserve water based paints in the can

fungicides and algaecides - to protect exterior paint films against disfigurement from moulds,

& algae

13

Paint drying

As the paint dries, a film is formed which adheres to the surface of the material to which it is being

applied.

Emulsion paints dry by a physical process involving the evaporation of water followed by coalescence

of the polymer droplets and their subsequent integration into a hard polymer matrix that acts as a binder

for the pigment.

On applying gloss paints, the alkyd polymer cross-links by an oxidation reaction with oxygen in the air

once the solvent has largely evaporated. This reaction is accelerated using salts of transition metals (for

example, cobalt and manganese naphthenates). The transition metal ion (with variable oxidation state)

catalyses cross linking of the polymer chains, producing a hard surface film to the paint. ( Paint Curing

Mechanism reaction shown Below)

14

Environmental issues

Lead compounds are no longer used in decorative paints and automotive paints.  The quantity of lead

compounds still being used in specialized industrial paints has been greatly reduced and eventually

alternatives will be found. This also applies to chromates which, although they perform well and in the

past have been extensively used on motor vehicles, are very toxic.

Because volatile hydrocarbons can lead to pollution in the troposphere, coatings with lower organic

solvent content are required.  The routes to achieve this include:

water-based polymers (emulsion paints)

higher solids content polymers (using less solvent)

powder coatings

Water-based gloss paints are now available but the initial gloss of the finish is usually not as high as

organic solvent based paints.  The customer's choice is between a high performance product and a more

environmentally friendly one. Intense research effort continues to improve these paints.

High solids paints (which are solvent-based) are now available but not without compromises in cost

and performance.  The relative molecular masses of the polymer resins are reduced to a maximum of ca

1000 compared to 5000 in conventional paints.  This allows the proportion of the polymer to be

increased from 20-30% to 40%, hence the term high solids. The main problem is the need to maintain a

low viscosity.  As the amount of solids increases so does the viscosity, reaching a point at which the

paint cannot be applied properly. The lower proportion of solvent tends to slow down the drying and

film hardening process, so changes are made to the structure of the polymer - increased branching tends

to reduce viscosity for the

Same molecular mass.  The application of the paint is more difficult. If applied by aerosol, the paint has

to be under pressure.  Sometimes the paint is applied hot. It is difficult to get as good a finish in

appearance using high solids paint.

Powder coatings are used in particular for goods such as bicycles and white goods (refrigerators,

washing machines).  The powder is made up of a resin (often an epoxy resin), pigments, and a catalyst

to promote cross-linking when the powder is heated, and additives.  The powder is sprayed on to the

article using an electrostatic spray gun and is then heat cured to produce a hard coating.  Recently

acrylic powder coatings have been introduced as clear-coats on car bodies.  Although an ideal solution

for many applications, curing is achieved at high temperature in an oven and is therefore not

universally applicable (e.g. painting of wood and plastics).

15

 Paint Manufacturing Process

1. Making the paste

1 Pigment manufacturers send bags of fine grain pigments to paint plants. There, the pigment is premixed with resin (a wetting agent that assists in moistening the pigment), one or more solvents, and additives to form a paste.

2. Dispersing the pigment

2 The paste mixture for most industrial and some consumer paints is now routed into a sand mill, a large cylinder that agitates tiny particles of sand or silica to grind the pigment particles, making them smaller and dispersing them throughout the mixture. The mixture is then filtered to remove the sand particles.

3 Instead of being processed in sand mills, up to 90 percent of the water-based latex paints designed for use by individual homeowners are instead processed in a high-speed dispersion tank. There, the premixed paste is subjected to high-speed agitation by a circular, toothed blade attached to a rotating shaft. This process blends the pigment into the solvent.

3. Thinning the paste

4 Whether created by a sand mill or a dispersion tank, the paste must now be thinned to produce the final product. Transferred to large kettles, it is agitated with the proper amount of solvent for the type of paint desired.

4. Canning the paint

5 The finished paint product is then pumped into the canning room. For the standard 8 pint (3.78 liter) paint can available to consumers, empty cans are first rolled horizontally onto labels, then set upright so that the paint can be pumped into them.

A machine places lids onto the filled cans, and a second machine presses on the lids to seal them. From wire that is fed into it from coils, a bailometer cuts and shapes the handles before hooking them into holes precut in the cans. A certain number of cans (usually four) are then boxed and stacked before being sent to the warehouse.

16