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A GUIDE FOR

THE PAINT MAKER by

Onyenekenwa Cyprian Eneh First Published January 2000 by Computer Edge Publishers for Welfare & Industrial Promotions (WIPRO) International Block D Unit 1, The Eastern Nigeria Industrial Estate, 30 Zik Avenue, Uwani, P.O. Box 9060, Enugu, Tel: 042-251691

ISBN 978-35223-1-0

Second Edition July 2016 by Welfare & Industrial Promotions (WIPRO) International 6 Corridor Layout, Independence Layout, P.O. Box 9060, Enugu, Tel: +234803-338-7472

Copywright © 2016 Onyenekenwa Cyprian Eneh

Conditions for Sale All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the publisher.

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DEDICATION To Most Gracious God Almighty, who creates and gives the increase; To my beloved wife. Amuche, and children: Chimezie, Chinelo, Chinemelum and Chinedum.

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PREFACE AND ACKNOWLEDGEMENTS A man would do nothing, if he waited until he could do it so well that no one could find fault with what he has done - Cardinal Newman. Self-help project is the only sustainable solution to the problems of a developing economy. Good a thing, the successive Nigerian national budgets, rolling plans and United Nations assisted programmes often focus on enterprise development as a major propelling force towards addressing the problem of a poor economy. In developing countries, published materials are not available to the students and entrepreneurs. Africans are particularly poor in handing down their discoveries to others in the present or successive generations who aspire in the same field. This book is a modest presentation of simplified facts on paint making for entrepreneurial success at a low cost. The supports from my family and colleagues are gratefully acknowledged. Onyenekenwa Cyprian Eneh (Ph.D., fcsn, ficcon) July, 2016

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FOREWORD The students and industrialists alike in developing countries lack books on paints making. The few available materials are so specialized or professional in presentation that they are of little help. Yet, paints are a class of products that serves important aesthetic, protective and functional values. This booklet is the much-needed simplified, do-it-yourself paint making. After the Introduction, it presents Colour, Paints Technology, Paint Terminology, Paints Composition/Formulation, Paint Factory Practice, Paint Qualities and Quality Control, and Organization of a Paint Factory. The lecturers and students of Fine/Applied Arts, Textiles, Coating and Paint Chemistry, etc. will find it useful. The entrepreneur aspiring in paint making will find adequate help in it. I conratulate Dr. O.C. Eneh on this great work that has revealed professional practice (hitherto regarded as sacred trade secrets) to students and indusrialists to enable enterprise development and self-elp projects in the dwindling economy of Nigeria. He has also done noble to revise the first edition after 15 years. I recommend the book to every student, entrepreneur, family and institutional libraries. Prof. P.A. Akah (Ph.D., fnas) Professor of Pharmacology and Toxicology University of Nigeria, Nsukka. July 2016

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TABLE OF CONTENTS Publishers page. ... ... ... ... ... Dedication ... ... ... ... ... ... Preface and Acknowledgements ... ... ... Foreword ... ... ... ... ... ... Chapter 1: Introduction ... ... ... ... Chapter 2: Colour ... ... ... ... ... Chapter 3: Outline of Paint Technology ... ... Chapter 4: Terms in Paint Technology ... ... Chapter 5: Paint Types, Composition and Formulation Chapter 6: Paint Factory Practice ... ... ... Chapter 7: Paint Qualities and Quality Control ... Chapter 8: Organization of a Paint Factory ... Index ... ... ... ... ... ... ...

... ... ... ... ... ... ... ... ... ... ... ... ...

Tables, Figures, Plates and Boxes Table 1: Selected paints and their pvc ... ... ... Table 2: Typical formulations of paints ... ... ... Table 3: A typical formulation of exterior latex paint ... Table 4: Formuls for primer ... ... ... ... ... Fig. 1: Dispersion of white light ... ... ... ... Fig. 2: Absorption, reflection and transmission of components of white light by/through an object ... ... ... Fig. 3: Colour wheel ... ... ... ... ... ... Fig 4: Flow chart for paint manufacture using mills ... Fig 5: An outlay of paint factory ... ... ... ... Plate I: Diamond Chart ... ... ... ... ... Plate II: Brushdown sheet ... ... ... ... ... Box 1: Pigments and extenders and their functions ... ... v

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER ONE INTRODUCTION HISTORICAL Paint is a very ancient industry. Noah was asked to use pitch within and without the Ark (Genesis 6:14). The prehistoric inhabitants of the earth recorded their activities in colours on the walls of their caves. The crude paints were probably clays suspended in water. The Egyptians developed a variety of colours by 1500 B.C., and by 1000 B.C., they discovered varnish, using natural resins and beeswax for the film-forming ingredient (resin). Scientific and engineering research, however, revolutionized paint industry in recent years. USES AND ECONOMICS Paints preserve architectural structures from weather attacks. Uncoated wood and metal deteriorate, especially in presence of soot, C, and sulphur dioxide, SO2. Thus, SO2 in the atmosphere reacts with water vapour (both gases, g), to form aqueous (aq) SO2, which reacts further with water to form sulphurous acid, H2SO3, from which SO2 reacts with metals, e.g. copper, Cu2+, as illustrated in chemical expressions below: (SO2) (g) + H2O (SO2) (aq) + H2O SO32- + Cu2+

(SO2) (aq) H2SO3 SO3 - + Cu+

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Onyenekenwa Cyprian Eneh A guide for the paint maker Paints also increase the attractiveness of manufactured products, as well as the aesthetic appeal of dwellings. Thus, paints serve utility and art purpose. In the United States of America, paints annual sales clocked N4 billion (NI.5 trillion) in 1977. There were 1,500 paint companies with over 60,000 employees. In 1971, industrial paints for the first time sold more than architectural paints, indicating a shift in trend. This highlights the importance of paint ventures in a developing economy, such as Nigeria. Surface coating is a wider term which includes paint (relatively opaque solid coatings applied as thin layers, whose films are usually formed by polymerization of poly-unsaturated oil), varnishes (clear coatings), enamels (pigmented varnishes), lacquers (films formed by evaporation only), printing inks, polishes, etc. However, the entry of plastic resins into surface coating industry has made the classification relatively meaningless.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER TWO COLOUR INTRODUCTION Coloured substances have since ages fascinated man. Even the earliest peoples had crude means of adding colours to cloth, ornamental, skin and building. The light is made up of seven major components distinguishable to the human eye. These are red, orange, yellow, green, blue, indigo and violet (ROYGBIV). A mnemonic for the seven components of light is Richard of York gave battle in Vienna. As long as all these components are present, the light appears in its usual white colour (also regarded as colourless). If, on the other hand, any of the components is absent, the mixture of the remaining components will form another colour, other than white, and the substance becomes coloured. The seven components of white light can be viewed through a triangular glass prism. R O

White light

Y G

triangular glass prism

B I

Fig. 1: Dispersion of white light 3

V

Onyenekenwa Cyprian Eneh A guide for the paint maker When the white light falls on a substance, the object may absord, reflect or transmit the light components.

white light

A

T

R Key A Absorbed light components(s) R reflected light component(s) T transmitted light component(s) Fig. 2: Absorption, reflection and transmission of components of white light by/through an object The colour of the object is the appearance of the mixture of the light components it reflects. If the object absorbs none of the light components, i.e. it reflects all seven components, it appears white. Conversely, if the object absorbs all the light components, i.e. it reflects and transmits none of the components, it appears black. But, if it transmits all the components, i.e. it reflects and absorbs none of them, it will be colourless (white). The colour which is reflected (or transmitted) is that which is not absorbed, and is usually described as complimentary to that which is absorbed. The figure below illustrates a colour wheel, with complementary colours arranged diagonally opposite each other. For examples, yellow-red (orange) is the complementary colour of blue; red-violet (purple), of green; and yellow, of blue-violet. A 4

Onyenekenwa Cyprian Eneh Ene A guide for thee paint maker red rose absorbs blue blue-green light; a yellowish-green green pea absorbs violet.

wheel illustrating ten colours of the visible Fig. 3: Colour wheel, spectrum. Colours diagonally opposed are complementary to each other. Red, yellow, and blue are known is the primary colours because they can be mixed to get other colours. COLOUR OF PAINT Actually, the human eye is capable of distinguishing some ten million colours. Of this vast number, many are probably not no reproducible by the commercial building paints, and the noticeable differences in other individual cases may be so slight as to have little ittle practical importance. It is possible to develop a colour system consisting of five components: white, blue, yellow, red, and black – which by intermixing will give a reas reasonably large number of other colours. colours It is necessary that the three coloured components c be as brilliant as 5

Onyenekenwa Cyprian Eneh A guide for the paint maker possible in order to achieve the brighter shades, and for this reason this method is not economical, particularly in cases where the desire final colours are dull shades like browns. Another important drawback is that areas of the colour solid are not well represented with this limited number of primaries. For example, mixtures of blue and red give grayish red-blue shades rather than true violets and purples. Another problem where matching or harmonization with the environment is concerned is metamerism, but this is a problem common to any colour-matching system. A pair of colours may match each other under one source of illumination, but fail to do so under another; e.g. light from artificial sources and that from the sky in daylight. This phenomenon is known as metamerism and is generally caused by a difference in chemical components between the two pigment mixtures. Paint companies offer a line of 10-20 factory-made shades, including white, in a given type of coating such as interior wall paint. If none of these is satisfactory to the purchaser, modifications may be made in several ways. The large paint companies may publish elaborate colour guides illustrating several hundreds of colours that may be made either by such formulae as one gallon of paint plus a specified size tube of tinting concentrate; or simple ratios of paints themselves such as one quart and one gallon, one pint and one pint, etc. These guides may be arranged in such a way that a complementary or harmonious colour can be placed in juxtaposition for viewing, or in families of shades graduated from just off-white to a highly saturated colour. In other words, the latter arrangement is one of constant hue and graduated saturation. 6

Onyenekenwa Cyprian Eneh A guide for the paint maker BIBLIOGRAPHY Cannell, D. (1967). Paint. In Kirk-Othmer. Encylopedia of Chemical Technology. Vol. 14. 2nd ed., John Wiley & Sons Inc., New York. Cyprian Eneh (1986). Colour and Dye, Sunday Satellite p. 10. DePUY and Rinehart (1967). Introduction to Organic Chemistry. John Wiley & Sons Inc., New York. Estok, D.K. (1959). Organic Chemistry, A Short Text. Saunders company. Judd, D.B. and Wyszecki, G. (1963). Colour in Business, Science and Industry. 2ed., John Wiley & Sons Inc., New York.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER THREE OUTLINE OF PAINT TECHNOLOGY PAINT Paint is a mixture composed basically of solid colouring matter (the pigment) and liquid (the vehicle). It is applied as a coating to various types of surfaces, including dwellings, public buildings, factories, bridges, ships, and storage tanks. The purpose of coating may be decorative, as in beautifying of objects and provision of aesthetics; protective, as in preservation against weather, moisture, solar radiation, chemicals, and mechanical damage; or functional, as in communication of an impression. By obliterating the surface over which it is applied paint serves the purpose of its use. It may be a water-based paint (emulsion) or an oil-based paint (gloss). The vehicle consists of the nonvolatile and volatile liquids. The nonvolatile portion is mostly a resinous or resin-forming compound called the binder. The types of resin are oils, alkyds, cellulosics, acrylics, vinyls, phenolics, expoxies, polyurethanes, silicones, amino resins (ureas and melamines), latex form, styrenebutadiene, polyvinyl, and acetates. The volatile portion is used to lower the viscosity of the paint composition to achieve ease of application and good leveling. At times thinner is added to thin down the viscosity. This portion consists of hydrocarbon solvents, water, ketones or esters. The pigments are insoluble powders of very fine particle size. They impart colour and opacity to the paint. Colourants may also be added. Paint also contains extenders which are certain materials that add little to the opacity of, and impart other desirable 8

Onyenekenwa Cyprian Eneh A guide for the paint maker properties to, the paint. Depending on the desired colour of the paint, the pigments, colourants and extender-pigments may be titanium dioxide, calcium carbonate, magnesium silicate, clay, inorganic colours, barium sulphate, mica, zinc oxide, real lead metallics (principally aluminium), carbon blacks, organic colours, and white lead. INTRODUCTION TO PAINT MANUFACTURE The manufacture of paint involves mixing, dispersion, thinning, adjustment and filling. Each of these steps may be accomplished separately or two/more of them can be accomplished together in one piece of equipment. All the pigment is mixed in a tub with the help of rotating blades. The particles are wetted with vehicle, and the flocculated aggregates are eliminated. Many dispersers in use today include steel roller, ball, pebble, sand, high-speed impeller, Moorehouse, Werner-Pfleiderer, and Cowles dispersers. Actually, there is little or no breakdown of pigment particles (as the word grinding, commonly in use in the industry, suggests). Many modern pigments are extremely fine. Some of the extenders, which may be coarse, normally have their particle size reduced before they are introduced into paint. Fractional percentages of dispersing agents may be added, especially for emulsion paints. In practice, complete breakdown of particles and aggregates is hard to achieve and often not essential. The extent of breakdown or degree of dispersion required varies with the type of paint, and there is an acceptable degree of dispersion for each type. The 9

Onyenekenwa Cyprian Eneh A guide for the paint maker degree of dispersion necessary for gloss enamel is much higher than that required for undercoat or primer. After dispersion, the balances of the liquids are added. The formulator dictates the proportions of dry and liquid material for dispersion. Consideration is given to many factors, among which are the rheology of the system, the viscosity of the mix, the reactivity of either pigment or vehicle under dispersing conditions, the exothermic nature of such reactions, and other factors. The amount of liquid used depends on the type of equipment, some (e.g. roller mills) requiring a sticky, heavy paste, while others (e.g. ball and pepple mills) require a thin mix. The pigment-volume concentration, Pigment Volume PVC

= Pigment Volume + Binder Volume

Below a certain pigment concentration each particle in the film of the paint is assumed to be completely surrounded by binder. But above this concentration point there is no longer sufficient binder to encase all the particles. Thus, the film contains voids and becomes porous. This pigment concentration point is called the critical pigment-volume concentration (CPVC), above which many paint properties, such as permeability, tensile strength, flexibility, and gloss, are adversely affected. Too low a PVC tends to produce such defects as blistering, cracking, and checking, whereas a high concentration than the CPVC results in paints likely to exhibit 10

Onyenekenwa Cyprian Eneh A guide for the paint maker premature erosion, excessive moisture transmission, and rusting (in the case of metal surface). The CPVC varies according to the nature of both pigments and vehicles in specific combinations. The following paints have the given PVC: Table 1: Selected paints and their pvc Flat plaints 50-75% Exterior house paints 28-36% Semigloss paints 35-45% Metal primers 25-40% Gloss paints 25-35% Wood primers 35-40% PLANTS/MACHINERY The plants found in an average paint industry may include mixers, fork-lift, sieving machine and canning machine. A mixer is principally made up of a blade, a vessel (containing the materials to be mixed) and the machine which turns the blade. It may make use of electricity and has a device for regulating the speed. Forklift is a machine for lifting and transferring goods, such as gloss, finished products, etc. from one position to another. A sieving machine is made up of wire-mesh for sieving paints. The paint may flow to the mesh through a tube running from the vessel. The canning machine comprises of a vessel into which the paint to be canned flows. The vessel has out-lets from where, when opened with the fast device, the paint flows into the cans. There is also a device which compresses the covered cans to ensure that the can is strongly covered.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

PACKAGES Paints are packaged in metallic or plastic containers of different sizes: l00mI, 250m1, 500ml, I litre, 4 litres, 20 litres, etc. A number of the containers are, in turn, packed in a carton, for ease of displacement and handling. It is important that the cover of the packaged product be air-tight. Anti-skinning agents are necessary for paints packaged in metallic containers. Labels may be printed directly on the container and the carton, or may be printed on papers of appropriate sizes which are pasted as applicable. SAFETY MEASURES The safety requirement in paint industries recognizes that paint sticks to wears and skin and that some of the raw materials for paint making are not good to inhale. Workers, therefore, often wear mask to cover their body including the nostrils. They also wear boots. And, here in Nigeria, the industry needs fireextinguisher system as well as a stand-by generator. BIBLIOGRAPHY Cannell, D. (1967). Paint. In Kirk-Othmer. Enclyclopedia of Chemical Technology, Vol. 14. 2ed. John Wiley & Sons inc., New York. Eneh, O.C. (1981). SIWES Report for B.Sc. lndustrial Chemistry, submitted to the Department of Pure & Industrial Chemistry, University of Nigeria, Nsukka. 12

Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER FOUR TERMS IN PAINT TECHNOLOGY COLOUR Paints are colouring substances. Colour charts are often available in the industry. OPACITY OR HIDING POWER This refers to the ability of the paint to obliterate the surface which it coats. DENSITY This a measure of bubbles contained in a given volume of paint. VISCOSITY This is a measure of flow of the paint. WETTING AGENT OR SURFACTANT The substance used to aid dispersion of pigments as well as promote and stabilize the emulsion in emulsion paints. SEALER This is a coating used when the surface to be painted is highly porous or can exude a material which will damage subsequent coats of paint. Examples of porous surfaces are asbestos and other building boards. The sealers are chosen to satisfy the suction of the surface and seal off any alkali, such as lime. For the surfaces mentioned, sealers based on vinyl emulsion are frequently used.

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Onyenekenwa Cyprian Eneh A guide for the paint maker Timber often contains knots which can exude a resinous substance that will soften and often discolour paint films. To avoid this, the knots are treated with a sealer called knotting which is a solution of shellac in methylated spirit. PRIMER This is the paint intended as the first coat on a substrate. It is often designed to perform as both primer and sealer. It functions to (i) give adequate protection to the substrate and will adhere to substrate or sealer, (ii) provide a surface to which the undercoat will adhere well. Primers are formulated according to the type of substrate to be coated, and a knowledge of the nature and behaviour of the various types of surface is indispensable to the paint formulator. In using primers, the secondary coating should be the type that would not chemically react with the primary coating thus removing it from the substrate. UNDERCOAT, FILLERS AND STOPPERS This is the coating following the primer, and its main purpose is the obliteration and the colouring of the under surface to which it is applied. Compositions known as fillers and stoppers may be regarded as parts of the undercoat. They are heavily pigmented materials serving as means of filling and stopping up pit and dents and similar irregularities of the contour of the surface, so that the surface finally prepared for the receipt of the finishing coat becomes uniform in texture and colour and free from imperfections. 14

Onyenekenwa Cyprian Eneh

A guide for the paint maker

FINISH This is the paint that serves as the final coating on the surface, giving it the colour it bears. It is, however, different from woodfinish, the application of which is rather preceded by sanding, sealer and filler which seal the pore on the wood. VARNISH This is resin either (a) dissolved in or reacted with, drying oil and usually further diluted with volatile solvent, or (b) dissolved in solvent. It is specifically no paint, but serves a protective purpose of paints. It is applied to the underneath of boats. INTERGARD This is a quick-drying catalyzed oil paint widely used in marine works. SPLASH ZONE COMPOUND This is the material mainly used in marine works, especially in ships, where the pressure from the water as well as the contents of the sea water, like salt, and other weather conditions are tense. This normally results in corrosion which ordinary paints cannot prevent completely. It is highly pigmented and thick, thus avoids being lost in the application process (best achieved manually), lasts long and, most importantly, proves excellently adhesive to the substrate. EMULSION OR WATER PAINT This is a water-based paint. The pigment is dispersed in the aqueous phase both polymer and pigment form distinct dispersed phases and should coalesce only in the film when the water evaporates. 15

Onyenekenwa Cyprian Eneh

A guide for the paint maker

LATEX PAINT The term latex denotes a suspension of polymer particles in water. Emulsion paints consist basically of a combination of pigment and latex, hence it is called latex paint. Water paints other than latex include whitewash, casein paint, paint and linseed emulsion paint. WHITEWASH This may be made by mixing unslaked lime with water and allowing it to stand for a few days before use, or starting with calcium hydroxide in the first place. The applied coating converts to calcium carbonate. Certain additives, like glue, have been used for their cheapness. CASEIN PAINT This is usually supplied as a powder to be mixed by the user. Casein is about 10-12% of the composition, together with some lime to convert it to insoluble calcium caseinate after application. The balance is pigments plus preservatives. CEMENT PAINT This is used to a limited extent on masonry. It is supplied as a powder containing Portland cement and white or alkali-resistant coloured pigments. It is mixed with water for application. LINSEED EMULSION PAINT This may be prepared from linseed oil emulsified by a combination of lipophilic and hydrophilic emulsifiers. The emulsified linseed oil is made into paint by formulae similar to those used for latex paints, except that addition of metallic driers is necessary. 16

Onyenekenwa Cyprian Eneh

A guide for the paint maker

GLOSS OR OIL PAINT This is the oil-based paint. It is shiny in appearance. ENAMEL The word enamel strictly means a glass-like substance fused on to metal surfaces. By enamel in the paint industry, however, is generally understood a high gloss. Besides the glossy wall paints which may be called enamels (there is no sharp division), practically all trade sales lines include a large selection of bright strong colours and black for use on comparatively small areas such as lawn furniture, cabinet doors, and similar surfaces. These have a low pigment volume, and are pigmented with such colourant as toluidene red, phthalocyanine blue, hansa yellow, and gas black, titanium dioxide and lampblack for grays. The nonvolatile vehicle is usually alkyd resin, but there are many other varieties that may be, and are, used. Specifications on these products call for a high pigment dispersion to produce the maximum in smoothness and leveling out. EXTERIOR AND INTERIOR PAINTS Exterior paints are used to coat exterior surfaces, while interior paints are used to coat interior surfaces. Both organic solvent and emulsion types are made classes of paint. Considering solvent types only, there are a number of reasons why it is not practicable to use the same material for both exteriors and interiors. For example, linseed oil-based paints yellow severely when not exposed to light and outside weather. The slow drying of 17

Onyenekenwa Cyprian Eneh A guide for the paint maker exterior paints could not be tolerated on inside walls. High-cost, low-opacity pigments, such as lead, are both unnecessary and undesirable. More is expected in the way of appearance in the case or inside paints, especially the high-gloss materials. CRACKING AND ADHESION Cracking is the break on the paint film that extends from the surface to the underlying material. It reflects a loss or lack of adhesion. CHALKING, ABRASION, HARDNESS AND ADHERENCE These refer to the hardness to scratch or otherwise of the dry coating. Chalking is a progressive powdering of the film from the surface inward, caused by continued and destructive oxidation of oil after the original drying of the paint. Very rapid chalking is termed erosion. FINENESS This is a measure of the presence of the unwanted particles or flocculated aggregates of particles in the paint. CHECKING This refers to the slight fine breaks in the surface of a film visible to the eye or a 10-power microscope. FLOODING OR FLOATING This is a defect involving the separation of individual pigment particles, thus giving a non-uniform colour.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

THIXOTROPY This is the property of a liquid or gel to lose viscosity under stress and regain the gel state when the stress is removed. FLOW This is the ability of an applied film to level out evenly and produce a smooth coat. LEVELING Brush marks are left behind immediately after the brushing of paint. These furrows or striations soon disappear due to the leveling of the wet film prior to drying. Acceptable leveling becomes important, since brush marks are considered as signs of weakness (incipient corrosion or cracking). SAGGING If the paint is applied to a vertical surface a downward flow (due to influence of gravitation) takes place. This is variously referred to as running, curtaining, or sagging. A certain tolerable degree of this flow is necessary for satisfactory leveling, but excessive sagging is inexcusable. BLISTERING This is usually the effect of the sun which heats and softens the paint coating and develops vapour pressure under the dried top layer from the volatile matter trapped by too rapid drying and skinning over the top surface of the film. The heat-expanded vapour causes the soft film to blister. The volatile matter in the film may arise from the resinous constituents of the wood carrying the coating, from solvent residues or from moisture. 19

Onyenekenwa Cyprian Eneh

A guide for the paint maker

LIVERING This is the appearance in a paint of semi-solid, jelly-like masses resembling raw liver. It is caused by chemical reactions, which may occur between certain pigments and vehicles. DRYING We can look at the drying of paints in a number of ways. The first is illustrated by the use of a pigment dissolved in a volatile liquid (e.g. Alcohol). When applied to a surface, the liquid soon evaporates and leaves the pigment matter spread over the surface in a thin, even, hard layer, which serves the desired purpose. The second is illustrated by the dissolution of the pigment in oil. The oil does not evaporate, but absorbs oxygen, and due to oxidation and polymerization, the liquid oil is changed into a solid, sufficiently hard and tough to protect the surface underneath. The third is the reaction between separate components of the vehicle. In this case, product may be supplied in two separate containers which are mixed just before use, to prevent solidification of the material in the package. A combination of these can also apply. SKINNING Paints, after sometime, develop some thickening. This is known as skinning.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

FREEZING This is the tendency to solidify or lose fluidity by stored paint. GLOSS This refers to the specular reflectance or the light reflected at the same angle as the angle of incidence. BIBLIOGRAPHY Cannell, D. (1967). Paint. In Kirk-Othmer. Enclyclopedia of Chemical Technology, Vol. 14. 2 ed. John Wiley of Sons Inc. New York. Martens, C.R. (1964). Emulsion and Water-Soluble Paints and Coatings. Reinhold Pu Corp. Patten, C.T. (1964). Paint Flow and Pigment Dispersion. John Wiley & Sons Inc. New York.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER FIVE PAINT TYPES, COMPOSITION AND FORMULATION Aside from the three basic components of paint - pigment, volatile vehicle and non-volatile vehicle - there are numerous other additives used in paint, mostly as an integral part of the formula, but sometimes for corrective purposes. These include metallic driers; pigment-dispersing agents; anti-flooding compounds; antisettling agents, e.g. metallic stearates or lecitin; anti-skinning agents for oxidizing-type paints - these may be considered mild antioxidants while they are in the container, but dissipate by evaporation when the film is applied; gelling agents for non-drip agents; mildewcides and fungicides; viscosity stabilizers; deodorants - these are usually perfumes used in fractional percentages to mask odours during the drying period; ultraviolet absorbers - a typical use is in daylight fluorescent paint to delay fading of the pigment; stabilizers, e.g. materials which absorb Cl or HCl as possible decomposition products from chlorinated resins, or similar applications. The modem paint constituents can be outlined as (Shreve and Brink, 1977: 381): Resins (film formers) Synthetics: alkyds, acrylics, vinyls, cellulosics, rosin esters, epoxies, urea melamines, urethanes, styrenes, phenolics, hydrocarbons, polyesters. Natural: shellac, rosin, etc. 22

Onyenekenwa Cyprian Eneh

A guide for the paint maker

Solvents Ketones, aromatics, aliphatics, alcohols, glycol ethers, glycol ether esters, glvcols. glycol esters, chlorinated products, terpenes, etc. Drying oils and Fatty Acids Linseed oil, soyabean oil, fatty acids, tall oil, castor oil, tung oil, safflower oil, fish/marine oil, coconut oil, oiticica oil. Pigments and Extenders Titanium dioxide, calcium carbonate, magnesium silicate, clay, inorganic colours, barium sulphate, mica, zinc oxide, zinc dust, red lead, metallics (principally aluminum), carbon blacks, organic colours, white lead. Driers Cobalt, manganese, lead and zinc, naphthanates, resinates, linoleates, 2-ethyihexoates, tallates. Plasticizers Octyl, decyl, 2-ethyihexyl and similar esters of phthalic, sebacic, adipic. azel aic, and similar acids.

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Onyenekenwa Cyprian Eneh A guide for the paint maker The Pigments and Extenders are further outlined as: Box1: Pigments and extenders and their functions

Ingredients White: titanium dioxide, zinc oxide, lithopone, zinc suiphide, antimony oxide. Black carbon black, lampblack, graphite, iron black. Blue: ultramarine copper phthalocyanine, iron blues. Red: red lead, iron oxides, cadmium reds, toners or lakes. Metallics: aluminium, zinc dust, bronze powder. Yellow: litharge, ocher, lead or zinc chromate, hansa yellows, ferric yellows, cadmium lithopone. Orange: basic lead chromate, cadmium. Green: chromium oxide, chrome green, hydrated chromium oxide, phthalocyanine green, permansa greens (phthalocyanine blue plus zinc chromate). Brown: burnt sienna, burnt umber, vandyke brown. Metal Protective: red lead, blue lead, zinc.

Function To protect the film reflecting the destructive ultraviolet light, to strengthen the film, and to impart an aesthetic appeal. Extenders or Inerts or fillers China clay, talc, asbestors (short fibres), silica, whiting, metal stearates, gypsum, mica, barite, blanc flexi China clay, orange, molybdenum orange. To reduce the pigment cost and in many cases increase the covering and weathering power of pigments by complementing pigment particle size, thus improving consistency, leveling and settling. Pigments should possess the following properties: opacity and good covering power, wetability by oil, chemical inertness, non-toxicity or low toxicity, reasonable costs.

Source: Sreve and Brink (1977: 382)

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

The pigment, although usually an inorganic substance, may also be a pure, insoluble, organic dye known as a toner, or an organic dye precipitated on an inorganic carrier, such as aluminum hydroxide, barium sulphate, or clay, thus constituting a lake. Extenders reduce the cost and often increase durability of paint. Pigments should be non-toxic or of low toxicity to both the painter and inhabitants. Different pigments possess differing covering power per unit weight. EXTERIOR BUILDING PAINTS Wood is used for the construction of dwellings and other types of structure. The most important type of protective coating for these surfaces is what is commonly known as house paint. This was made up of two ingredients, basic carbonate of lead (white lead) and either raw or boiled linseed oil. With raw linseed oil, the drier was added, whereas the boiled oil contains a small amount of drier in the form of metallic soaps. The raw oil, however, was unsatisfactory in many ways. Usually, the professional painters bought “white lead in oil” which consisted of about 89% basic carbonate of lead and 11% linseed oil by weight This was thinned with a further quantity of oil for application, somewhat more oil being used in the first coat for bare wood than in succeeding coats. Three coats had to be applied to achieve a uniform white appearance, since the opacity of white lead is low because of its low refractive index. White lead is subject to severe discolouration from both sulphide fumes and dirt colouration. Also, it eventually fails by checking, presenting a bad surface for repainting. This type of paint was also quite slow in drying and a 25

Onyenekenwa Cyprian Eneh A guide for the paint maker number of days had to be allowed between coats. Added to this was the uncertainty of the pigment-binder relationship in the actual film applied, as many painting contractors varied the amount of added oil at will. Little wonder straight white lead is virtually obsolete. Mixed pigment, ready-to use house paints have been in use for a good many years. Generally speaking, the pigmentation of exterior wood paints includes white lead (carbonate or sulphate), titanium dioxide, zinc oxide, and extender pigments. White lead is used to promote durability and adherence through the formation of small amounts of lead soaps with the linseed oil. Titanium dioxide contributes whiteness, whiteness retention and opacity. Titanium dioxide is not only more chemically inert but has considerably higher light reflectance than lead, and therefore remains whiter. Since its refractive index is 2.7 for the rutile form and 2.55 for the anatase, as compared with 2.00 for white lead, its opacity or ability to obliterate the surface is much greater. It follows that an excessive amount of titanium is inadvisable, in that the user would be tempted to spread the paint too thin and thereby lose durability. Titanium dioxide also promotes self-cleaning of the film by chalking. But a paint which did not chalk at all would accumulate so much dirt it would become unsightly. The rutile crystal type is much slower chalking than the anatase, therefore it is the practice to use a proportion of each in a standard white house paint. Anatase alone will chalk too rapidly, and rutile alone too slowly. Zinc oxide contributes hardness to the film and is a mild mildewcide. Mildew is frequently a problem in certain geographical or climatic areas. Zinc oxide also helps to control over-rapid chalking. 26

Onyenekenwa Cyprian Eneh

A guide for the paint maker

The term extender is used to denote transparent white to colourless pigments which contribute little to opacity, but because of their comparatively large particle size and random structure, frequently acicular, hold the film together and reduce cracking tendencies. Extender pigments are also used to control the pigment-volume concentration (PVC). A typical material used is talc (magnesium silicate). Others include calcium carbonate, silica, clay, and mica. A variation of the standard-type formula is to use all rutile (nonchalking) titanium dioxide and no anatase. This is to hold chalking to the minimum for trim and tinting purposes. By this means the tendency to form white streaking over adjacent non-white surface is minimized; also, if the paint is slightly tinted to a buff, ivory, green, blue, or other pasted shade, the appearance of premature fading, because of the formation of white titanium dust on the surface, is avoided. The binder in organic solvent house paints is still commonly linseed oil. The liquid portion of earlier ready-mixed products was almost all raw linseed oil, containing only a minor amount of mineral spirits as a carrier for metallic driers. This type of paint was deficient in flow. Consequently, the film thickness was very non-uniform because of brush-marks. This, of course, resulted in uneven erosion. It is now the practice to use a proportion of heat-bodied linseeds oil along with some raw oil. Since this results in appreciably higher viscosities, a larger proportion of volatile thinner is added to the formula for ease of application. The applied film levels out smoothly to uniform 27

Onyenekenwa Cyprian Eneh A guide for the paint maker thickness. The heat-bodied oil also contributes increased moisture resistance to the film. Although formally the same paint was used for both first and succeeding coats, modem practice is to supply a specially formulated primer as the first coat. The priming formulation generally has a higher pigment-volume concentration, a higher content of lead pigment and extender, and in some products, zinc in any form is omitted. The effect of the higher pigment volume in the priming coat is to produce a lower gloss, which helps to provide better mechanical adhesion of the succeeding coat, and it also promotes faster drying. It is contended by some authorities that zinc in a coating, which is in immediate contact with bare wood, increases the tendency to blister where moisturetransmission conditions prevail. A pigment-volume concentration for an exterior house paint primer is usually in the range of 35%, and for a finish coat, 30%. Typical formulations are: Table 2: Typical formulations of paints House Paint Undercoater

Ingredients White lead Rutile titanium dioxide

Ready-Mixed Finish Coat, Exterior

% by wt 32

Ingredients White lead

8

Zinc oxide

Extender pigment Raw linseed Resin

23 12 1 Thinner (including drier)12 Heat-bodied linseed oil 12

Titanium dioxide Extender pigment Raw linseed oil

% by wt 19 16

10 17 23 Heat-bodied linseed oil 7 Thinner (including drier) 8

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Onyenekenwa Cyprian Eneh A guide for the paint maker Exterior wood paints designed for fume resistance are formulated with no lead compounds, the prime pigments being zinc oxide, titanium dioxide, and extenders. These are slightly less durable, but have the advantage of good colour retention in atmosphere polluted with hydrogen sulphide, since zinc oxide and zinc sulphide are both white, and the other pigments present are unaffected. A test method is to expose a painted panel to a saturated atmosphere of hydrogen sulphide for a specified number of hours. LATEX EXTERIOR PAINTS These are synthetic resin emulsion paints suitable for exterior exposure. The advantages of latex paints over oil paints are fast drying, absence of odour, ease of cleanup, and excellent colour retention. Some examples of materials used are dispersion agents for pigments, protective colloids and thickeners (sodium polyacrylates, carboxymethylcellulose, colloidal clays, gum arabic, and others) to thicken the water phase and reduce settling, defoamers, coalescing agent ,freeze thaw additives (glycols, e.g. ethylene glycol), mildewcides and preservatives (mercurial, copper and phenolic compounds), and pH controller (ammonium hydroxide used for adjustment). A typical formulation for an exterior latex paint is given below. Formulation A is mixed and ground on a high-speed stone mill, and then formulation B is added.

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Onyenekenwa Cyprian Eneh A guide for the paint maker Table 3: A typical formulation of exterior latex paint Formulation

lb

gal

Formulation B Ib

Dispersing agent

15

2.0

Acrylic latex

0.2 6.0 7.2 5.0

Preservative Defoamer Water

(40% nonvolatile)

Defoamer 2 Water 50 Titanium dioxide 250 Extender pigments 117 Hydroxyethlcellulose, 2% aq. Solution 50 Ethylene glycol 25

605 9 2 8

gal

68.9 1.0 0.2 1.0

6.0 2.6

Stainless steel or other corrosion-resistant equipment are used for handling emulsion paints. Containers also have to be waterresistant. The latex is added last because of its inability to withstand the shear effects and heat developed in the dispersion operation. Priming new wood with an oil-type undercoater before the application of latex exterior paints is recommended, for greater resistance to moisture. Any good quality exterior paint including oil and latex paint, may be used for masonry, except that the original surface, if not previously painted, generally requires special treatment, Masonry surfaces are likely to contain alkaline compounds. The first coat used on such surfaces is therefore usually an alkaline- resistant resinous type, pigmented or unpigmented, to act as a sealer.

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Onyenekenwa Cyprian Eneh A guide for the paint maker Most exterior paints are white. The principles for the formulation of white exterior paint apply to house paints in light colours. The tinting pigment, which is generally a very small proportion, must be carefully made. The preferred colouring materials are those which have good chemical stability, such as iron oxide reds, browns and yellows, phthalocyanine blue and green, and lampblack. Many precipitated pigments, such as organic reds and ferrocyanide blues, have the drawback of rather rapid fading when diluted with a large proportion of white and exposed to sunlight. Some of these have excellent permanence when used in concentrated form in deep colours, and are used for this purpose in trim paints. The white pigment must be as chalk-resistant as possible, hence the rutile titanium dioxide is used. INTERIOR SURFACES OF BUILDINGS The principal pigments used for interior whites are titanium dioxide, zinc oxide, and various carbonate and siliceous extenders, which are used to control pigment volume and gloss. Most ordinary solvent-type paints for interior use contain some oil and dry by oxidation. Vehicles may be oleoresinous or a combination including some free oil, generally heat-bodied. Oils used in interior compositions include bleached linseed oil, dehydrated castor, soyabean, and to a lesser extent, tung and oiticia. Soyabean-oil fatly acids are widely used in the manufacture of oxidizing alkyd vehicles, these being extensively used for wall paint because of superior resistance to yellowing, economy, and good availability. Many resins, e.g. resin ester, pure and rosin-modified phenolic, maleic epoxy-ester, and others may be used, but the workhorse for wall paints is the soya-phthalic alkyd material. 31

Onyenekenwa Cyprian Eneh A guide for the paint maker One effect of the resin content is to increase hardness and reduce drying time. A high pigment content acts in the same way, hence heavily pigmented flat finishes, as a rule, contain less resin and more oil than glossy ones, in order to maintain toughness and flexibility. High-gloss interior paints contain no relatively coarser extender pigments and are processed to the maximum degree of smoothness. About 5-10% of zinc oxide is frequently used with the titanium to help control yellowing as the film ages. Since zinc oxide is mildly and chemically active, it tends to inhibit the formation of coloured compounds in the vehicle. Titanium dioxide is chemically inert and does not have a retarding effect. A high-gloss paint film ages has a reading of 80-85 in a photometric equipment with the reference standard 95. Semigloss wall paints are formulated with a higher pigment volume, this usually being adjusted to produce readings of 50-70. Since 3-3.5 lb of titanium dioxide in a gallon will give adequate opacity in a white or pale tint, the additional pigment volume is made up by using extender pigments, which are considerably less costly. A common material in both semigloss and flit wall pa is a combination of co-precipitated titanium dioxide and anhydrous calcium sulphate. As supplied, these materials may contain 30% titanium thoxide 70% calcium sulphate, or 50% of each Straight extenders for interior paint magnesium silicates, mica, calcium carbonate, clays and others. C organic-surface-treated bentonite clays may be used in minor percentages to impart thixotropy and reduce settling tendencies. Semigloss paints have good washability 32

Onyenekenwa Cyprian Eneh A guide for the paint maker and strain resistance, and the subdued sheen is considered more pleasing to the eye than a high gloss. Flat oil or alkyd paints have a glossmeter reading of 0-10. The median range of gloss, 10-50, is very difficult to control from the standpoint of film uniformity, and is not much used. Slight variations in the thickness of film applied, or irregularities in the surface, are apt to cause non-uniformities of sheen which are very objectionable. It is probable that very little oil flat is now used for domestic purposes, its place having been taken by latex emulsion. Considerable; quantities of oil flat are still used, however, for industrial purposes, where this type may be preferred over water paint for one reason or another. Wail primer and sealer is used on new masonry and plaster walls, or old ones in porous condition, before the application of a finish coat. It is formulated to have a pigment volume and gloss in the medium range, in order to give a nonporous surface for uniformity of the finish to be applied over them, but still low enough in sheen to give good mechanical adhesion of the top coat. Many interior alkyd or oil paints (organic-solvent-type) are offered today wider the designation of “ordourless.” This property is achieved by using, as the volatile portion, petroleum solvent containing little or no saturated or cyclic components. Mineral spirits, the standard fraction supplied by refineries as a general purpose paint thinner, ordinarily contains a certain amount of these compounds. These increase the solvent power or ability to hold resin in solution, but also increase the odour. Odourless thinners, from which these compounds have been removed, have lower 33

Onyenekenwa Cyprian Eneh A guide for the paint maker solvent power. It follows that the vehicles used in these paints have to be carefully controlled so that they are not too highly polymerized, to avoid precipitation or thickening in the container. The lower odour achieved by such paints is confined to the drying period during evaporation of the solvent, as there is still odour attributable to the oxidation and reaction products of the binder. The, decorative material par excellence in present use is latex paint, which is marketed under various trade names. Its advantages are ease of use by nonprofessional, easy cleaning, low odour, fast drying, and economy (compared to wallpaper). It is used not only ‘for dwellings and institutions, but also for factory installations where operations do not produce chemicals and moisture- laden atmospheres. The three main types of latexes (synthetic resin dispersion) are polymers based on esters of acrylic acid, poly (vinyl acetate), and styrene-butadiene. The general principles applying to exterior latex paints also apply to the interiors. White pigmentation consists mainly of titanium dioxide and extenders, basic compounds such as zinc oxide and lead salts not being suitable. PVA is widely used. Styrenebutadiene is used mostly for interior paints; acrylic ester, like PVA, may be used in either application, but its greatest use is probably in exterior formulae. The most outstanding difference between inside and outside latex paints is in pigment-volume concentration. A typical pigment volume for exterior purposes is 30%, the relatively high 34

Onyenekenwa Cyprian Eneh A guide for the paint maker concentration of binder to provide film integrity against weathering. Pigment volume of an interior formulation is likely to be in the range of 55-70%, but an excessively high pigment content has an adverse effect on stain resistance. To obtain improved washability and adhesion, a small amount of drying oil or alkyd resin is sometimes incorporated, up to 15% of the binder content. To achieve other colours for the paints than white, hansa yellows, chromium oxide, phthalocyanine greens and blues, and various iron oxide and hydroxide pigments may be used. Most extender pigments are suitable except those that have an appreciable degree of water solubility, such as calcium sulphate. Clays are used in water paints because of their thixotropic properties and dry hiding power. The popular interior latex paints on the market have a low to flat sheen. It is possible to formulate semigloss and gloss materials, but there are several difficulties that have not been fully overcome. One is that it is difficult to incorporate sufficient pigment to give opacity and still have some gloss. Another is that the resins used in the flat varieties do not develop much hardness, and the relatively high pigment content is relied on for this property. INDUSTRIAL MAINTENANCE PAINTS Most coating types, including exterior and interior oil, alkyd, and emulsion types, are used for large industrial plants. There are also many others designed for industrial use, excluding those used for products finishing particularly in the field of metal protection. Painting is one of the more important means of combating corrosion. Paint films on steel give a mechanical barrier against 35

Onyenekenwa Cyprian Eneh A guide for the paint maker moisture, and are much less affected by electrolytic action than metal. Practically every paint will protect against rust for a limited time. For durability, corrosion-inhibitive primers are used, the property of inhibition being mostly a function of the pigment. Some pigments inhibit corrosion, some are neutral in this respect, and some tend to stimulate it. The pigments that are effective corrosion inhibitors include a number of metallic chromates and red lead, Pb and to a lesser extent zinc oxide and metallic zinc dust. The number of existing formulae for structural-steel primers is immense. Red lead in a linseed-oil vehicle is well known. A typical ready-mixed red lead- linseed-oil paint is composed of 77% red lead, 15% raw and bodied linseed oils, and 8% thinner and drier. A gallon of this composition contains almost 20 lb of pigment and weighs about 24 lb. Mixed pigment primers for general-purpose structural-steel priming perform as well, or sometimes better than, pure red lead, and do not have the disadvantages of excessive handling weight, slow drying, and high cost. Navy steel-ship maintenance primer is of this type. The formula is as follows:

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Onyenekenwa Cyprian Eneh Table 4: Formuls for primer Ingredient lb/100gal Red lead 380 Zinc yellow 70 Mica 65 Iron oxide red 10 Magnesium silicate 160 Aluminium stearate 6 Nonvolatile vehicle 292 Volatile 348

A guide for the paint maker

The vehicle is oil-alkyd resin. For general-purpose primers contain free raw linseed oil as part of the binder. STRUCTURAL-STEEL PREPARATION There are many types of primer vehicle formulations, ranging from those containing more or less drying oil to oil-free synthetics. The further the vehicle departs from a type containing polar groups (e.g. drying oils), the more stringent is the need for removal of oxide corrosion products which interfere with adhesion. In using some of the advanced type of synthetic formulations, sandblasting is mandatory Specifications for several degrees of blasting are available. Finishing coats over the primers so far discussed are usually of the long- oil alkyd-type, and are supplied in a variety of colours including white. White is a preferred colour for storage tanks subject to evaporation losses, because of its high reflectance of solar radiation. 37

Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHEMICAL RESISTANT COATINGS Epoxy resins may be converted to coatings with good resistance to m acid and alkaline environments, by esterification of the epoxide and hydroxyl groups with dehydrated castor-oil fatty acids. Linseed or soyabean-oil acids may also be used There ate no particular complications in using them; when used on exterior surfaces they chalk more rapidly than alkyd paints. Chlorinated rubber, paints are widely used for conditions of extreme moisture, such as daily decontamination of surfaces by washing and even continuous immersion. These are also used for swimming pools. The resin itself contains about 70% chlorine and needs to be stabilized with additives to inhibit the release of small amounts of hydrochloric acid. As it is brittle in itself, it is usually heavily plasticized. Films of these materials are not heat-resistant above 65.6°C and are affected by contact with vegetable and animal oils. Films dry to recoat in about ½ hr. Spray application is necessary. Solvents have to be the aromatic type, e.g. xylene. Vinyl chloride-vinyl acetate copolymer resin-based coatings are more flexible than chlorinated rubber, and have excellent exterior durability. They are insoluble in hydrocarbons and it is therefore necessary to use oxygenated solvents like ketones and volatile esters in their formulation Adhesion of vinyl resins to the substrate is somewhat of a problem, so far the priming coat a grade containing 1-2% hydroxyl or other polar groups is used to improve this property. Even so, the steel must be sandblasted to remove rust and to provide a slightly roughened surface. Another primer that may be used is based on vinyl butyral resin, which is soluble in ethanol or 2-propanol. 38

Onyenekenwa Cyprian Eneh

A guide for the paint maker

Oil-free epoxy formulations are used for industrial maintenance and have been recently introduced into the retail market for use on certain areas in dwellings. Curing of the epoxy resins to hard, resistant films may be brought about by reacting them with amines, polyamines, or polyamides to produce cross-linking. Polyamides are probably most frequently used. As this reaction would take place in the can, if pre-mixed, the product is furnished in two compartments, one containing the epoxy component, and the other the polyamide. These are mixed just before use, the type and amount of each part being adjusted to give eventual curing and also to provide several hours of potlife (i.e, retention of fluidity) at normal temperatures after mixing. The pigment may be ground in either the dissolved epoxy resin component or the amide solution. Here again it is necessary to use ketone and ester solvents. The fully cured film, however, attains complete insolubility in most solvents, in contrast to straight resin solutions such as chlorinated rubber and vinyl. It also resists decomposition and fusing at temperatures up to 149°C and has a very high degree of chemical resistance. For application on steel, preparation of the surface by blasting is considered best in order to give maximum adhesion. Metal primers for epoxy-ester, chlorinated rubber, vinyl, and epoxy-amide coatings are fonnulated with the same type resin used in the finish coats and contain rust-inhibitive pigments. Other synthetic or natural coatings used for chemical resistance, some of which may be air-dried at one-coat thickness, include the natural asphalt, coal-tar asphalt, polystyrene, styrene-butadiene; methacrylates, silicones, urethane, neoprene, and many more. 39

Onyenekenwa Cyprian Eneh A guide for the paint maker Zinc-rich maintenance coatings consist of a high concentration of metallic zinc dust dispersed in a binder. The formulation principle is that the dried film, in order to give cathodic protection to steel, should contain zinc in such volume that the particles are in electrical contact. This means that 90-95% by weight of the nonvolatile portion is zinc. The binder may be organic-resin types such as are used in conventionally pigmented paints, including, for example, chlorinated rubber, polystyrene, epoxy amide and others, or it may consist of aqueous silicate solution. In the latter case some zinc silicate is formed. Also at the interface there is probably some iron silicate. These paints are extremely durable under conditions of exposure to moisture and brine, and cases of no failure after more than 20 years of such service have been cited. To achieve the conditions of electrochemical contact required, steel surfaces should be blasted before application of these coatings, especially the aqueous silicate type. GALVANIZED STEEL To avoid failure by peeling of zinc-coated steel, an oleoresinous paint containing portland cement as part of the pigment is commonly used for relatively small areas on houses. For large areas in industry zinc dust paint is preferred, which calls for 80% pigment containing 80% zinc dust and 20% zinc oxide, and 20% vehicles containing 90% linseed oil and 10% drier and thinner, by weight. Here the dried film contains about 65% zinc dust as against more than 90% in the inc rich types which are intended for plain steel. A variation of this formula using a phenolic or oil vehicle has been used for coating the interior of potable- water tanks.

40

Onyenekenwa Cyprian Eneh A guide for the paint maker The vinyl butyral-phosphoric acid metal conditioned as discussed above is also satisfactory for zinc-coated steel. This may be followed by either oil, oil-resin vehicle, or synthetic finishes. Latex emulsion, including the vinyl, acrylic, and styrene varieties, has given promising results on zinc. Phosphating the zinc surface, if properly done, provides good adhesion of paints without the necessity of special primers. This is best done at the steel mill, as hand phosphating in the field is not under good control. TRAFFIC PAINTS High pigment volume, the use of fast-drying vehicles such as lowoil-content resin combinations or oil-free synthetic resins, and lowboiling solvents such as petroleum Tractions with distillation ranges from 100 to 150°C are the three factors responsible for the fast-drying characteristics of the road-stripping paints. Resin solutions like platicized chlorinated rubber or styrene-butadiene may be used. Some aromatic hydrocarbon solvent has to be included in these vehicles to maintain solubility. MARINE PAINTS There are two areas of the ship that need special formulations: the bottom and the boot-topping area. The bottom is subject to fouling by the accumulation of the hull which is intermittently immersed and exposed to air, known as the “wind and water line,” and represents an extreme degree of exposure to the elements. Antifouling paints for ship bottoms are formulated with copper and mercury compounds as poisons for marine growth, using binders 41

Onyenekenwa Cyprian Eneh A guide for the paint maker which are not too permanent so that gradual breakdown of the film and release of poison can take place. Tributyltin compounds are used as the toxic material. A typical formulation calls for zinc oxide, ferric oxide, magnesium silicate, cuprous oxide, mercuric oxide, rosin, pine oil, coal tar, and solvent. Because of self-erosion, it is desirable to repaint steel bottoms once a year, or oftener if the operation is in tropical water. SPECIALTIES DAYLIGHT FLUORESCENT COLOURS: These are widely used for safety purposes and attention-attracting devices. The colouring matters are hard resins containing a small percentage of fluorescent dye in solution. This composition is ground to fine particle size to form pigments. The dyes have the property of converting short wave visible radiation into longer wavelengths, the reflected light being concentrated in a rather narrow band in the yellow, orange, or red portion of the spectrum, the resulting colours thus being extremely brilliant. Vehicles may be conventional alkyd, or, as in a type which is used for greater visibility of aircraft, hydrocarbon-soluble acrylic resin. FIRE-RETARDATION PAINTS: These contain compounds which intumesce when the temperature is raised beyond a certain point. Urea and acid phosphate esters, pentaerythriol, and others are types of materials uced. AEROSOL COLOURS: These are alkyd compositions. The two components are paint thinned out to low viscosity so that it will atomize and a gaseous propellant which is liquid under pressure. 42

Onyenekenwa Cyprian Eneh A guide for the paint maker The most usual propellant is dichiorodifluoromethane (CCl2F2) which has a boiling point of -30°C. Other halogenated hydrocarbons may be used as modifiers. The measured amount of paint is filled into the cans, which is then sealed, and the propellant is forced in through the valve under pressure at a low temperature. The fluorinated hydrocarbons have a very low solvent power, so that in order to prevent precipitation of the paint ingredients, strong solvents are used. INSECTICIDAL PAINT: This paint is meant for protection of substrate against insects. It has various colours in both enamel and emulsion. During drying of the insecticidal paint, movement of particles takes place throughout the paint film. These particles are carried to the surface by the normal evaporation of the solvents in the coating and cyrstalize to form the insect repelling layer. BIBLIOGRAPHY Bigos, J. (1955). Good Painting Practice, Vol. 1, and Systems Specifications, Vol. 2, of Steel Structures Painting Manual, Steel Structures Paint Council, Pittsburgh, Pa., 1. Cannel, D. (1965). Titanium, Zinc, and Oil Exterior Paint Fume Resistant, Ready Mixed, White. Cannel, D. (1967). Paint. In Kirk-Othmer. Encyclopedia of Chemical Technology, Vol.14, 2ed, John Wiley & Sons Inc., New York. Heaton, N. (1956). Outlines of Paint Technológy. Charles Griffin & Co. Ltd., London. Mattiello, J. (1941). Protective and Decorative Coatings. John Wiley & Sons Inc. U.S.A. 43

Onyenekenwa Cyprian Eneh A guide for the paint maker Martens, C.R. (1964). Emulsion and Water-soluble Paints and Coatings. Reinhold Pub. Corp., New York Munger, C.G. (1963). Zinc Dust Coatings in the Process Industries, Mater Protect, 2 (3). Singer, E. (1966). Fundamentals of Paint, Varnish and Lacquer Technology. The American Paint Journal Company, U.S.A.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER SIX PAINT OPERATIONS AND WORKSHOP PRACTICE PAINT MANUFACTURE MILLS Function of Paint Mills The basic operation in paint manufacture is the breakdown of pigment aggregates followed by wetting and dispersion of the individual particles. This is accomplished by applying a rubbing force or shear sometimes accompanied by pressure to the mixture of pigment and paint medium. Shearing forces are exerted between the aggregates and the paint mill surfaces and are predominant in the milling of high consistency pastes. General Principles of Paint Mills The old pigment dispersion consists of milling a pigment and modern mixture at high consistency, that is, high pigment content. A preliminary mixing (prenuxing) of the pigment and medium was carried out in a heavy duty horizontal or vertical mixer or possibly in an edge runner mill. The paste was then fed to a triple roll mill for dispersion, after which it was ‘thinned down. Whether further refining was necessary depended on the type of paint being produced. ‘Oil paints giving high build films were not refined further, but simply strained before filling. Modern mills which use the principle of dispersion at high consistency are the high torque disperser and the high speed disperser. Pigment and medium are charged directly into these mills and with some easily dispersible pigments in the high speed 45

Onyenekenwa Cyprian Eneh A guide for the paint maker disperser, further refining is unnecessary. The high speed disperser, however, are generally used in manufacture of emulsion paints where the additives are first added to thicken, followed by addition of the pigments, they binder (polyvinylacrylate, PVA) and finally the solvent (thinner i.e. water). The process of paint manufacture is always batch-wise, that is, the raw-materials being fed into a plant at a known time only to be removed as the final product at a specific time. Types of Mill Pre-mixers: Mixers for pastes - these are often called pug mixers and can be horizontal or vertical. A modern form of the latter is the high torque disperser. High Speed Millers: They are of several designs but the common ones are the Silverson and Greaves types which consist of high speed propeller rotating with a fixed circular cage. The wall of the cage can be a wire-mesh screen or a ring pierced with holes through which the pigment/medium mixtures are expelled at high velocity. l shear is produced and with some pigments these machines can give a high degree of dispersion. Dispersion Mills: Dispersing mill can be divided broadly into two classes: (a) mills which require premixed pastes or slurries and (b) mills into which the raw-materials, that is pigment and medium, can be directly charged. 46

Onyenekenwa Cyprian Eneh Ene A guide for thee paint maker The sequence could be illustrated as follows:

Fig 4: Flow chhart for paint manufacture using mills Direct Charge Dispersion Mills The Ball Mill (For Oil Paint): This is the most favoured paint production unit for many years, mainly because they can produce a wide range of paints containing very volatile solvents, such as cellulose lacquers and quick drying synthetic enamels. When using porcelain balls, the charge of balls should occupy about 45% of the total volume of the mill, but the charge for steel balls is somewhat less. The speed o the mill is a critical factor. When a mill is running the balls are carr carried ied up on one side and 47

Onyenekenwa Cyprian Eneh A guide for the paint maker ‘cascade’ under gravity. The mill speed should be high enough to give the maximum degree of cascading, but not sufficiently high to carry the balls round b centrifugal force. Other factors of importance in ball milling are the size of the charge of mill base at its consistency. The dispersion of pigment takes place mainly as a result of shear or rubbing of the balls and, to a lesser extent, by impact. The mill base charge, manufacture using Mills in theory, should be just sufficient to fill the voids between the balls, but in practice about 10% extra is used. The volume of the voids depends on the size of the balls employed and is generally of the order of 20%. The raw-materials, that is pigment and medium, are charged directly into the ball mill and, since the object is to disperse the maximum amount of pigment in each operation, the composition of the mill base is of great importance. Too low a consistency can result in excessive wear on the mill lining, while an unduly high consistency will impair the cascading action of the mills and lead to prolonged milling times. The mixture (paint) in the ball mill is tested for thorough dispersion using the Hegman gauge, which if passed, is thinned down with appropriate solvents and mixed in the machine for some minutes. The paint is then run out for laboratory tests. STRAINING Most paints after processing contain small amounts of foreign matter and, in air- drying types, small quantities of skin. They are, therefore strained or filtered immediately before filling. A number 48

Onyenekenwa Cyprian Eneh A guide for the paint maker of straining materials are used, such as muslin, nylon gauge of fine wire sieves of 80-120-mesh. FILLING Paints are sold by volume or weight utilizing the specific gravity of the paint. Filling by weight is the normal practice. PAINT APPLICATIONS Paints can be applied to a surface by a variety of methods and devices, such as: Padding: This involves the fluff-free of cloth with which coatings of shellac solution are applied to furniture and decorative wood work which is characteristic of French polish. Spraying Paint can be applied to a surface by means of a sprayer or spray-gun. The method is, however, not economical in terms of the consumption of paint, particularly with guns operated by airpressure since the spray does not deposit only on the object being coated but also spreads itself beyond and around, necessitating the pr ion of special plant to trap the overspray and also prevent it from contaminating the factory atmosphere. Airless Spraying: Mainly used in ship building and maintenance of vessels, railway and heavy road vehicles. The paint is sprayed by pumping it at very high pressure to force it through a minute orifice in the tip of the spray-gun. Others: Other applications include dipping, Alot spray technique, roller coating, electro-deposition (electro-painting), etc. 49

Onyenekenwa Cyprian Eneh

A guide for the paint maker

BIBLIOGRAPHY Eneh, O.C. (1981). SIWES Report for B.Sc. lndustrial Chemistry, submitted to the Department of Pure & Industrial Chemistry, University of Nigeria, Nsukka.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER SEVEN PAINT QUALITIES AND QUALITY CONTROL Quality control in an industry ensures good qualities for the raw material as well as satisfactory and consistent qualities for the finished product. Some of the paint qualities watched out for include: COLOUR A good paint has colour. The colour is brought about during production by (a) using the pigment of the same or similar colour to that of the paint which is intended for production (b) addition of colourants with the same or similar colour to that of the required paint in order to supplement the efforts of the pigment in producing the wanted colour. Colourants are not always necessary, especially for white paints. In evaluating the colour, the paint may be run down the brushdown sheet and the colour compared with the universal colour in the colour chart (for initial production) or the old product (for a repeat production). Spectrophotometers and colorimeters are now used and this eliminates the human error in visual comparison with a standard or control. More colourant may be needed. A white paint may be prepared and added if the colour is deeper than required.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

HIDING POWER OR OPACITY Paints should be able to give a new look to the substrate by way of a good degree of obliteration. This is a function of the pigment used as part of the base materials. Titanium dioxide has a high refractive index and accounts for the greater part of the hiding property of the paints. To reduce cost, yet extend and supplement the hiding action of the dioxide, calcium carbonate may be added together with Atagel 50, etc. These, in addition to acting as extenders or extender- pigments, help to improve the thickness of the paint. The opacity is assessed m the industry by applying the paint on a smooth background of alternating white and black often referred to as diamond chart. A view is then taken to see if the paint has obliterated equally well the alternating black and white lines. The brush-down sheet can also be used. Titanium dioxide or extender-pigments in combination with colourant may be needed to improve the opacity. DENSITY This is an indication of the bubble-content of a certain volume of the paint. No buyer would like to pay for bubbles in the name of paint. The relative density (specific gravity) per gallon of the paint is measured to control the foam (bubble) contained in the paint. The greater the bubbles the smaller the density. Recalling that 52

Onyenekenwa Cyprian Eneh mass density = volume

A guide for the paint maker

it is easy to measure this variable of paints in a number of ways. More defoamers or bubble breakers which act through surface tension, may be needed. They include tri-n-butyl phosphate, noctyl alcohol, and other higher alcohols VISCOSITY Paints are viscous substances. The viscosity is built up by the addition of tylose or methyl celulose (for emulsion) and alkyd (for alkyd paints). This does not affect the colour of the paint. On the other hand, viscosity can be thinned down by the addition of such solvents as mineral spirit (for alkyd paints) and water (for emulsion). Other solvents include ethyl benzene, etc. Viscosity control is by alkyd solvent-ratio. A viscometer is used for measuring viscosity of the paint at 25°C. CRACKING AND ADHESION This is an unwanted break in the paint film that extends from the surface to the underlying material. It reflects a loss or lack of adhesion. A good paint should be adhesive. In oil paint alkyd takes care of this quality, while in the emulsion paint the polyvenylacetate copolymer (PVAC) does the job. They can be added as appropriate during quality control.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHECKING This denotes a very fine type of surface cracking. CHALKING, ABRASION, HARDNESS & ADHERENCE A good paint is adherend and hard, not abrasive and chalking. These qualities are tested by use of finger nails or mechanical testers. Alkyd may be added to oil paint and PVAC to emulsion in order to improve the quality. FINENESS A good paint contains only well ground materials. The agitators or palers or mixers do the “grinding” work. The grinding work here is just the dispersion of already ground/milled materials. Dispersing agents for pigments may be added. These are tetrasodium pyrophosphate, soya lecithin, and others. Also, during canning, the palm is also sieved to improve the fineness quality. Fineness can be simply assessed by spreading the paint on a smooth background. For oil Paint the precision guage is used, while brush-down sheet is used for emulsion. Grind guage is used for both oil and emulsion paints. Appropriate measures are then taken to arrest a deviation from good quality. FLOODING OF FLOATING A good paint should not exhibit flooding (floating or flotation), which results in the separation of individual pigment particles into streaks or layers of the liquid paint and non-uniform colour of dried film. This is due to unbalanced wetting and is common in green, grey and brown shades. It is aggravated by over thinning, and the remedy is change of pigment or introduction of more effective wetting agents. 54

Onyenekenwa Cyprian Eneh A guide for the paint maker This defect can also be combated by the addition of anti-floading agents or of coalescing agents which coalesce the discrete particles of resin during evaporation of water in emulsion paint. Such materials as hexylene glycol and ethylene glycol monobutyl ether acetate are used. Most coalescing agents in use volatilize quite slowly, but ultimately evaporate from the film. THIXOTROPISM AND BRUSHIBILITY Paints should not be difficult to brush: it should be brushible, thixotropic and exhibit shear-thinning. This property is tested by brushing the paint on a surface. To improve this quality, polyamides, Atagel, etc. may be added. If the paint is too thick, water and PVAC are added (emulsion) or mineral spirit for gloss paint. Poor brushbility may be due to excess calcium carbonate. LEVELING A good paint should flow in a way as to cover the marks of the painting brush. This is leveling. Wetting agents improve this quality. UNIFORMITY Although many materials of different nature are used for making paints, the paint should possess uniform quality. This is achieved by the addition of binders, such as the PVAC (for emulsion) and alkyd resins (for gloss paint). The binders articulate these materials as an aid to the mixing. The binders also bind the paint to the substrate.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

BLISTERING Coats should not blister. Insufficient attention to the cleanliness of the surface on to which the paint is applied is often a cause of blistering. Blistering can also be caused by the reaction products, such as carbon dioxide evolved during the curing of a polyurethane paint, which is occasionally due to the use of resin with a high acid value. Blistering can also be due to entrapped solvent being released from within a paint film after the surface has set at the initial stages of curing in a storing oven. The last cause is also called solvent propping. The blisters that sometimes appear on exterior painted work, on wood in particular, are usually the effect of the sun which heats and softens the paint coating and develops vapour pressure under the dried top layer from the volatile matter trapped by too rapid drying and skinning over of the top surface of the film. The heat-expanded vapour causes the soft film to blister. The volatile matter in the film may arise from the resinous constituent of the wood carrying the coating, from solvent residues, or from moisture. The sealing of resinous knots in wood by coatings of shellac or manila resin is helpful towards eliminating one cause of blistering. Paints on a metal substrate are not so liable to blister, particularly if the metal surface is properly cleaned and primed. FLAKING (PEELING OR ALLIGATORING) This is the breaking away of the complete paint coating, including primer, undercoat and finish from small or large areas of the surface to which the system has been applied. It may be the result of chemical action or physical change at the interface between priming coat and the surface beneath. Studies of the conditions that effect adhesive forces between solid surfaces form an important 56

Onyenekenwa Cyprian Eneh A guide for the paint maker part of the work of the paint research laboratories in their endeavour to analyse the causes of flaking. It can frequently be attributed to porous surface containing moisture in the pores. Increased penetration of moisture explains the greater susceptibility to blistering and flaking shown by paint coatings on soft, open grained woods than by those on the hard, close grained varieties. Moisture entering wood at weakly protected points may seek to escape through areas covered by paint; if the paint coating is impermeable to moisture the water pressure underneath will push the coating away from its support, and blistering will appear, followed eventually by flaking. Correctly formulated primers can minimize these defects. Plaster walls insufficiently dried out provide surfaces on which paint is likely to blister and flake. Similar trouble may arise in paint on wood into which moisture has penetrated through joints, and grain, etc. And the importance of preventing ingress of moisture at these weak points is obvious. CORROSION On ferrous metals and light alloys not perfectly protected by primers of the appropriate type corrosion is likely to occur. The corrosion products such as the white rust of light alloys distend the film above them and can eventually lead to the cracking of the film. Through the cracks, water and any dissolved salts can- reach the bare metal, allowing corrosion to colour. DRYING Paints should not take too long a period to dry. To ensure this, metallic driers may be added to the paint.

57

Onyenekenwa Cyprian Eneh A guide for the paint maker The drying of paint is a chemical change of oxidation and polymerization hastened by pretreatment of the oil and by adding diers, or catalysts, predominantly heavy-metalic soaps, which are oxygen earners, usually soluble in oil. These driers need be used only in small amounts (1 to 2% by weight). Oil paints need no driers. SKINNING A good paint should not skin. To ensure this, anti-skin agents (ASA) are added to the paint. They include oxime and ketoxime, eg. methyl ethyl ketoxime, phenolic ketoxime, etc. FREEZING Good paints should not freeze. The anti-freezing agents added to the emulsion paint include high-boiling solids, such as ethylene glycol and benzyl alcohol. These solids prevent the polymerization of the materials in the paint. RUSTING Paints should neither rust nor induce rusting on their containers or substrate. Sodium benzoate is the anti-rusting material added to emulsion paints. Gloss paints need no anti-rusting agents, since oil does not rust.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

GLOSS The gloss paints are shinny or glassy and not dull. The alkyd resins added to the paint are responsible for this quality, as well as acting as a binder. The paint is run down the brush-down sheet and the gloss compared as in colour. To eliminate visual errors, gloss is now measured with photometers, the reference being a theoretically perfect minor, to which is assigned an arbitraiy value of 1000 so that gloss figures are parts per thousand. The practical standard is a polished black glass plate having a value of 95. THICKNESS AND WETTING The paint should not be too thick as to hamper the brushibility and leveling properties. The paint is brushed on a vertical smooth surface and this property evaluated. Sulphonated glyceride (S.G. I) and napthanates of Magnesium (Mg), Lead (Pb) and Cobalt (Co) may be needed as appropriate. RESISTANCE TO BACTERIAL AND FUNGAL ATTACKS Paints, should be resistant to bacterial and flingal attacks. This is ensured by the addition of mildewcides and preservatives, such as mercurial, copper, and phenolic compounds. LIVERING The appearance in paint of semi-solid, jelly-like masses resembling raw liver is called livering. It is caused by chemical reactions which may occur between certain pigments and vehicles e.g. zinc 59

Onyenekenwa Cyprian Eneh A guide for the paint maker oxide and acidic vehicle or between atmospheric oxygen and oxidizable and polymerizable oils in the vehicles. A paint that has set to a livery mass that will not disperse on stirring even with added solvent is entirely useless. pH CONTROL Latex compositions are aqueous and the pH must be carefully controlled, to prevent de-emulsification. Generally, ammonium hydroxide is used for adjustment, but the exact pH specification varies according to the nature of the resin and other ingredients in the formula. ODOUR Paints must not have objectionable odours. Deodorants may, therefore, be necessarily added to the paint. Other tests may be required depending on the end use of the paint and the material involved. The actual tests undertaken depend on the formulation. BIBLIOGRAPHY Cyprian O. Eneh (1986). Introduction to Paint Technology. Sunday Satellite, 20 October, p. 10. Taylor, C.J.A. and Marks, S. (1965). The Testing of Paints. Paint Technology Manuals, Part Five. Chapman & Hall, London.

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

CHAPTER EIGHT ORGANIZATION OF A PAINT FACTORY The paint factory can be divided into the following departments or sections for effective operations: Production: This section is in charge of production, and is usually headed by an Industrial Chemist, a Polymer Chemist, a Chemical Engineer, a Paint Chemist or a Paint Technologist. He should have an assistant of similar qualification with lower number of years of experience. Working with them are production staff whose strength will depend on the scope of production. The staff are headed by a supervisor. It is sub-divided into milling, mixing, tinting and canning sub-sections. Quality Control Laboratory: This section is headed by the Quality Control Manager of similar qualifications as above who will also have an assistant. The section analyses all in-coming rawmaterials before use and all out going products before sales, to ensure conformity to set standards. This section must be strict and not easily given to compromise with suppliers or production staff Administration: This section, headed by the General Manager, is responsible for the overall administration of the factory. He works with other administrative staff, example, Secretary, Receptionist, Messengers, etc. Stores and Marketing: This department plays the role of procuring the raw-materials and other needs of the factory, stores them and issues them out on approval of requisitions. In the same vein, it takes delivery, from Production Department of all products 61

Onyenekenwa Cyprian Eneh A guide for the paint maker and makes sales arrangements to trade them off for cash at the earliest possible time. For effective sales of the products, sales strategies: advert, promotions, displacement, etc. are necessary. Store-keepers and marketers staff this section which must have a head. Accounts: This section handles all the financial matters in the factory: sale proceeds, purchases, salaries, and other income/expenditure. It also calculates the’ annual depreciation of the industrial plant/machinery. An Accountant heads the section Security: This section is in charge of the security of the establishment It is made up of day and night guards headed by Chief Security Officer. It controls in coming visitors and searches all out-going vehicles.

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Onyenekenwa Cyprian Eneh Ene

A guide for thee paint maker

Fig. 5:: An outlay of paint factory

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

SAMPLE QUESTIONS 1.

While paint makers decry the proliferation of paint industries in the eastent Nigeria, a university professor of development economics says we need more. Rationalize. (Chapter 1).

2.

Distinguish between Surface Coating and Paint industries. (Chapter 1)

3.

What do you know about Colour, and how does Colour apply to Paint. What is metamerism? (Chapter 2)

4.

Outline the basic (i) functions and composition of paint (ii) Paint formulation (iii) Paint factory equipment (Chapter 3)

5.

What do you understand by opacity, thixotropism, sagging, drying and livering? (Chapter 4).

6.

Distinguish between (i) density and viscosity (ii) finish and primer (iii) latex and intergard (iv) enamel and emulsion (v) exterior and interior (vi) chalking and leveling (Chapter 4).

7.(a)

State the functions of pigments 64

Onyenekenwa Cyprian Eneh (b)

A guide for the paint maker

Name any 30 pigments and their colours (Chapter 5)

8.

Outline any three specialty paints (Chapter 5)

9.

Write on operations and practice of paint production and application (Chapter 6).

10.

How do you control the qualities of a paint product? (Chapter 7)

11.

Suggest a workplan or profile and an organizational layout for N5m paint factory. (Chapter 8)

12(a) What are the components of the white light that are visible to human eye? (b)

What s the colour of a “light-repelling object that reflects all light components that fail on it?

(c)

A “light-greedy” object absorbs all light components incident on it, what is its colour?

(d)

What is the colour of a “light-stable” object which neither reflects nor absorbs but permits the passage of all light components through it? (Chapter 2)

13.

Okenwa, a paint-dealer, has five colours: white, blue, yellow, red and black in his stock. But his customer wants brown paint. How could he attempt to meet his customer’s demand? What are his constraints? (Chapter 2)

4.

What is pigment-volume concentration and its significance in paint formulation? (Chapter 3) 65

Onyenekenwa Cyprian Eneh A guide for the paint maker 15. What do you understand by the term paint Outline its composition. (Chapter 3) 16.

What technology would you apply in painting a house of timber and asbestos materials? (Chapter 4)

17.

Considering solvent only, why can’t a painter interchange an exterior paint with an interior? (Chapter 4).

18.

Explain the drying mechanism(s) of a paint coating. (Chapter 4)

19.

Compare and contrast titanium dioxide, white lead and zinc oxide as pigments for exterior white paints (Chapter 5).

20

What do you understand by rutile and anatase (Chapter 5)?

21 (a) What is an extender? (b) Name four extenders known to you (Chapter 5). 22.

What is a primer? Why would you advocate its adoption in paint technology? Contrast its formulation with that of an exterior finish coat (Chapter 5).

23.

What is the significance of resin in interior paint? (Chapter 4).

24.

Discuss briefly how you can obtain other colours than white for paints (Chapter 5).

25(a) Name any 24 qualities to watch out for in paints. 66

Onyenekenwa Cyprian Eneh A guide for the paint maker (b) Concisely state how you can control any 20 of them (Chapter 7).

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Onyenekenwa Cyprian Eneh Ene

A guide for thee paint maker

Plate I: Diamond Chart C 68

Onyenekenwa Cyprian Eneh Ene

A guide for thee paint maker

Plate II: Brushdown Brus sheet

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Onyenekenwa Cyprian Eneh

A guide for the paint maker

INDEX Colour - charts ... ... ... ... - complementary ... ... ... - harmonious ... ... ... - of paint ... ... ... ... - wheel ... ... ... ... Light - absorption, reflection, transmission - dispersion ... ... ... ... - seven components of ... ... Metamerism ... ... ... ... ... Paint - abrasion ... ... ... ... - additive ... ... ... ... - adherence ... ... ... ... - adhesion ... ... ... ... - ancient industry ... ... ... - anatase ... ... ... ... - application ... ... ... ... - as part of surface coating industry - blistering ... ... ... ... - casein ... ... ... ... - cement ... ... ... ... - chalking ... ... ... ... - checking ... ... ... ... - chemical resistant ... ... ... - colour ... ... ... ... - critical pigment-volume concentration (CPVC) - cracking ... ... ... ... - defoamer ... ... ... ... - drier ... ... ... ... - drying ... ... ... ... 70

13 5 6 5 5 4 3 3 6 18 22 18 18 1 26 49 2 19 16 16 18 18 38 8, 13 10 18 30 23 20

Onyenekenwa Cyprian Eneh A guide for the paint maker - drying oil ... ... ... ... 23 - economic importance ... ... 1-2 - emulsion ... ... ... ... 8, 15, 17 - enamel ... ... ... ... 17 - extender ... ... ... ... 8, 23 - exterior ... ... ... ... 17, 25 - fatty acid ... ... ... ... 23 - filler ... ... ... ... 14 - fineness ... ... ... ... 18 - finish ... ... ... ... 15 - floading ... ... ... ... 18 - flooding ... ... ... ... 18 - flow ... ... ... ... 19 - freezing ... ... ... ... 21 - function ... ... ... ... 1-2, 8 - galvanized ... ... ... ... 40 - gloss ... ... ... ... 8, 15, 17, 21,58 - glossmeter ... ... ... ... 33 - hardness ... ... ... ... 18 - hiding power ... ... ... 49 - intergard ... ... ... ... 15 - interior ... ... ... ... 17 - latex ... ... ... ... 16, 29 - leveling ... ... ... ... 19 - linseed ... ... ... ... 16 - livering ... ... ... ... 20, 54 - manufactruring equipment ... 9 - machinery ... ... ... ... 11 - marine ... ... ... ... 41 71

Onyenekenwa Cyprian Eneh A guide for the paint maker - mildewcide ... ... ... 26 - opacity ... ... ... ... 8, 13 - pigment ... ... ... ... 8, 23 - pighment volume concentration, pvc 10 - plasticizer ... ... ... ... 23 - polyvinylacetate, pva ... ... 34 - preservative ... ... ... 30 - primer ... ... ... ... 14 - resin ... ... ... ... 22 - rusting ... ... ... ... 58 - rutile ... ... ... ... 26 - sagging ... ... ... ... 19 - sealer ... ... ... ... 13 - skinning ... ... ... ... 20 - solvent ... ... ... ... 23 - specialties ... ... ... ... 42 - splash zone compound ... ... 15 - stopper ... ... ... ... 14 - structural-steel ... ... ... 37 - thinner ... ... ... ... 28 - thixothropy ... ... ... 19 - traffic ... ... ... ... 41 - undercoat ... ... ... ... 14, 28 - varnish ... ... ... ... 15 - vehicle ... ... ... ... 8 - viscosity ... ... ... ... 13 - washability ... ... ... 35 - wetting agent, surfactant ... ... 13 - whitewash ... ... ... ... 16 72

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