MANUFACTURE OF PAINT

(Graduation project)

2016

Supervised by: prof.Dr Farag Abd El-hai

Prepared by: Mohamed Abu Bakr Elgharib

Al-Azhar University Faculty of science Chemistry Department Applied Chemistry Branch

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‘Acknowledgement’ I would like to express my gratitude for everyone who

helped me during the graduation project starting with

endless thanks for my supervisor prof.Dr/Farag Abd El-

hai who didn’t keep any effort in encouraging me to do a

great job, providing me with valuable information and

advices to be better each time. Thanks for the continuous

support and kind communication which had a great effect

regarding to feel interesting about what I am working on.

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TABLE OF CONTENTS Content page

i. Abstract 3

ii. Introduction 3

iii. Classification of paints 5

iv. Paint raw materials 6

v. Factors influencing the paint formula 6

vi. General Rules on Drawing up Formulations 7

vii. Material Flow in a Paint Factory 10

viii. Theory of Dispersion 10

ix. Production of Coating Materials 16

x. Quality control in paint industry 29

xi. Paint defects and application problems 32

xii. Arabic summary 33

xiii. References 37

xiv. Communication information 38

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i. Abstract:

The manufacture of coating materials is a technical process which has been optimized

from economic and environmental perspectives and which is composed of numerous

basic operations.

Transportation, metering, homogenization in agitators and dispersers with subsequent

separation processes by sieving, filtration and centrifugation are the most important

processes during the journey from raw material to coating material.

All the production stages are subject to scrutiny by relevant laboratories. Formulations

developed by the labs address not only the economic aspects but also the quality

standards and environmental regulations.

The specific task for a paint manufacturer–manufacturing a semi-finished product

which will be converted into a coating at a later.

The central task of pigment dispersion forms part of the complex sequence of wetting,

thorough moistening of the agglomerates with the film forming agent solution and the

subsequent mechanical stress in viscous laminar flow gradients.

When it comes to rapid and complete dispersion, the pigment type, size and form are

variables in just the same way as the polarity, size and form of the polymer molecules.

The latter play a fundamental role in shaping the rheological properties and the

surface tension of the film forming agent solution.

The pigment stabilization necessary if pigmented coating materials are to be usable

can be achieved by coating with ions and the associated formation of electrical double

layers or with sufficiently long mobile and well solvated polymer chains with as

complete a coating as possible.

Optimum conditions can only be identified to a limited extent by theoretical

considerations. Experimentation is therefore still the indispensable way of determining

the optimum grinding conditions.

ii. Introduction: The task of coating technology is to provide surface protection, decorative finishes and

numerous special functions for commodities and merchandise by means of organic

coatings. Many everyday products are only made usable and thus saleable because of

their surface treatment.

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To achieve this, relevant coating

formulations, their production plant, the

coating material and suitable coating

processes for the product must be available.

However, the quality to be achieved by means

of the coating process is not the only function

of the coating material used. The object to be

painted or coated itself with its specific

material and design and an appropriate

application process are further variables

which play a significant role. Also taken into

account as the framework defining the conditions in which work is carried out from

development to application.

Two of the most important of the many functions which coatings have to meet are

protection and decoration. Other noteworthy features are the informative tasks and the

achievement of special physical effects.

The conspicuousness of emergency service vehicles, the camouflaging of military

equipment, and road or airport markings are just some of the informative tasks required

of coatings.

Floors and steps can be made nonslip by means of rough or high grip coatings, thereby

increasing their utility value.

By contrast, surface friction can be reduced by use of smooth coatings to produce a high

degree of nonadhesiveness.

Flammable materials can be rendered safe by means of flame retardant coatings.

Antibacterial coatings help maintain sterile surfaces in production and storage facilities in

dairies and breweries or prevent the growth of barnacles and algae on ships’ hulls.

In the electrical engineering sector insulating coatings provide effective and lasting

insulation for wire, windings and condenser materials.

On the other hand, conductive coatings can be used to make insulating substrates

electrically conductive or even to print electrical circuits.

Furthermore, organic coatings can help to reduce noise pollution. Acoustical insulation

coatings for machines and underbody protection coatings for passenger cars are examples

of this.

Fig.1 Factors determining the quality of coatings.

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iii. Classification of paints: Classification of paints by physical type:

1) Solvent-borne paints contain up to 80% of solid constituents (binders, pigments and

additives) dispersed in the organic solvent. Solvent-borne paints dry fast and may contain

a wide range of binders. The main disadvantages of the solvent-borne paints are their

toxicity and combustibility.

2) Water-borne paints contain water as the paint solvent. Waterborne paints are non-

toxic and noncombustible but they are characterized by long drying time due to slow

evaporation rate of water.

Water-borne paints based on water-soluble binders contain low molecular

weight polymeric binders dispersed in water in form of true solutions. Water-

soluble binders contain up to 15% of organic oxygen containing solvents soluble in

water (alcohols, glycol ethers, etc.).

Water-borne paints based on polymer dispersions (Emulsion paints)

contain 50-60% of high molecular weight polymeric binders dispersed in water in

form of Colloids. Emulsion paint contain up to 5% of organic oxygen containing

solvents soluble in water (alcohols, glycol ethers, etc.).

3) High-solids paints (Low VOC paints) contain more than 80% of solid constituents

(binders, pigments) dispersed in an organic solvent. VOC - volatile organic

compounds.

4) Powder coatings are obtained from powdered resin, particles of which are attracted

by the electrostatic force to the substrate surface (electrodeposition). No solvent is

involved in the process therefore powder coatings produce no/low toxic waste. The

main disadvantage of powder coatings is high cost of equipment.

5) Radiation curable coatings are formed from a mixture of prepolymers, monomers

and additives, which is cured under ultra-violet radiation. Radiation curable coatings

harden fast and contain no solvents. The main disadvantage is relatively high cost.

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Classification of painting products

by their functions:

1) Paint - colored non-transparent

protective coating.

2) Varnish - transparent or semi-

transparent protective coating. A

varnish is made of binder, solvent

and additives. Some varnishes

contain small amounts of pigment.

3) Enamel - hard protective coating

with glossy finish.

4) Primer - the first coating applied to the

surface in order to enhance the adhesion of the final paint (topcoat) and to seal the

substrate surface. Primer may be formulated to impart additional protection to the

substrate (e.g. anti-rust primer for steel substrates).

iv. PAINT RAW MATERIALS: Paints is made up of numerous components such as:

1) Resins or Binder.

2) Pigment.

3) Extender.

4) Solvent.

5) Additives.

v. Factors influencing

the paint formula: The paint and coating raw

materials manufactured out of

them meet the varied

requirements of practical

applications. The formulations

which have to be developed for

this contain not only detailed

information on the raw

materials to be used, but also

provide precise details on the

Fig.2 Typical composition of coatings.

Fig.3 Factors influencing the paint formula.

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quantitative proportions, the sequence in which the formulation ingredients are to be

combined and the settings for the machines to be used in production. The correct selection of the raw materials must be based on accurate knowledge of the

interaction in the product used for its later purpose, knowledge of the processing methods

and the available plant and machinery at the paint manufacturer. The varying

requirements of the processor or end user relating to final product quality, in conjunction

with the environmental demands, the application processes and the prices to be achieved

in the market place are variables which have to be covered by a diverse range of raw

materials. The composition to be selected for a coating material is therefore subject to

preconditions, requirements and external influences.

Bearing in mind that in the automotive sector alone the number of producible

formulations together with the necessary raw materials is hugely increased as a result of

the desired variety of colors and effects, it is no wonder that major paint factories have to

have many thousands of formulations on hand.

vi. General Rules on Drawing up Formulations: 1. Purpose and Quality:

If the customer merely wishes decorative goals to be met, more attention will have to be

paid to the pigmentation and the selection of the effect materials than to the other raw

materials. With many pigments a high gloss requires a low pigment level, which results

in an inadequate hiding power.

In order to achieve a large amount of room for manoeuvre in terms of color and gloss a

certain separation of functions in the form of two coats has become accepted The hiding

power is provided by a base coat, irrespective of gloss requirements, while the gloss itself

is delivered by an additional clear coat on top of the base coat.

If the purpose of the paint or coating is the protection of commodities, the selection

criteria are aimed initially at the film forming agent. Special demands are made on low

water vapor and ion permeability for coatings subject to long term outdoor exposure for

the protection of metal objects.

Further selection criteria include excellent adhesion under extreme climatic conditions

combined with the physical and chemical effect of anticorrosive pigments. If, for

example, zinc dust is used for active corrosion control, the pigmentation level is a

decisive factor. Only at weight concentrations of more than 90% do the metal particles

touch each other, thereby permitting their protective effect to develop.

2. Production Resources, Application Systems and Object to be Painted:

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When it comes to pigment dispersion formulations for the manufacture of colored coating

materials where dissolvers are used differ considerably from those produced in agitator

mills. The pigment-binder ratio and the rheological properties have to be adapted to the

particular machines by use of appropriate solvents and additives.

The processing systems in operation at the paint customer also have a significant impact

on the formulation. It is obvious that roller requires different material properties from the

spray guns or dip baths of industrial scale paint processors.

If more complex objects incorporating cavities with difficult access have to be coated,

dip-coating processes are the only alternative to the standard spray application. If the

latest electrocoating process is chosen, all the formulation ingredients have to be matched

to the electrochemical precipitation process.

Watersoluble resins can be made to coagulate on the objects to be painted, which are

connected to form electrodes, by means of changes in the pH value, and these determine

the formulation.

3. Function in Paint System:

Primers, whose main task is corrosion control, are provided with resins from the raw

material side which feature excellent adhesion even under extreme climatic conditions.

Aromatic epoxy resins, aromatic polyurethanes or modifications of these can therefore be

used because of their good adhesion, despite the lack of light fastness, as no account

needs to be taken of the lack of light fastness in the aromatic structural elements. These

are always optically covered by a further functional layer, the primer surfacer. This

second layer provides everything needed to make the topcoat optically attractive while at

the same time meeting all the demands on mechanical-technological properties

Primer surfacers therefore have to prime the surface, i.e. even out any unevenness and

be well sandable so that its surface can be smoothed, if required. Primer surfacers also

take on the function of protection against stone chipping as an intermediate coat in

conjunction with the topcoat. With this purpose in mind, resins have to be selected whose

glass temperature is in the operating temperature range. Furthermore, extenders have to

be used which create predetermined breaking points under extreme impact loads. This

prevents the coating from separating from the substrate.

The light fastness requirements on the primer surfacer coat are not as rigorous as those

on topcoats.

As with the primer coat, epoxy ester resin and polyurethanes are the standard film

forming agents for the functional intermediate coating. The tasks of the last coat, the

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topcoat, are quite different. The emphasis here is on the visual properties, provided that

the mechanical-technological properties have been addressed. A high level of gloss and

pronounced optical color effects are the usual requirements for the topcoat.

The functionability of the coating depends also on good adhesion to the primer surfacer

and a high degree of hardness with good wear and scratch resistance at the same time.

When it comes to selecting the raw materials for topcoats, resistance to sunlight and

outdoor exposure, but also to chemicals from industrial emissions and natural

atmospheric effects such as tree resins and bird droppings, are the primary considerations,

in addition to the abovementioned factors.

Topcoat formulations differ significantly, therefore, from the abovementioned items.

Weather resistant alkyd-melamine resin or acrylic-melamine resin paints or

polyurethanes based on polyester or acrylic resins are the standard film forming agents.

By contrast with primer surfacers, the principle with single film topcoats is to use the

minimum necessary amount of pigment.

4. Cost Effectiveness and Availability:

The demands for cost effective production have a particular impact on formulation

design.

In the manufacture of pigmented paints the incorporation of pigments in the paint

formulation causes the greatest production input. The goal, therefore, is to identify the

combination of pigments, film forming agents, additives and solvents which permits

rapid dispersion of the pigments with the highest possible pigment component and thus

the smallest possible volume.

In addition to manufacturers’ demands relating to cost effective production the processor

also requires coating materials which enable large areas to be covered at a low

consumption rate. Paints always have a high yield if a high hiding power with a low dry

film density at the same time makes it possible to apply thin film thicknesses.

5. Occupational Health, Safety and Environmental Protection Regulations:

Paint raw materials are regularly replaced by others for occupational health, safety and

environmental protection reasons as new knowledge becomes available.

However, great efforts are still required to achieve emission free, physiologically

harmless paint technology which is reflected in the paint types and their formulations.

The replacement of volatile organic solvents by water, the reduction of solvents by

increasing the solid content, or the replacement of volatile solvents by reactive diluents,

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but also the complete omission of solvents in the use of powder coatings has brought new

formulation principles to the process of developing paints.

Novel film forming agents, new additives and physiologically less harmful pigments are

superseding the existing range of raw materials continuously.

Environmentally polluting emissions of organic solvents and additives containing heavy

metals are being avoided by means of new environmentally compatible painting

technologies.

vii. Material Flow in a Paint Factory: Unlike plants operating continuous production processes the paint and coatings industry

has to operate in batch production mode as this is the only way of handling the

production demands of the variety of products.

Since customer orders differ in terms not only of the formulation itself but also of the

order quantity, the plants must have an appropriate range of production systems.

Fig.4 Process map for paint manufacturing.

viii. Theory of Dispersion: 1) Pigment Specific Properties for Dispersion Processes:

Whereas the manufacture of clearcoats is limited to the mixing of various film forming

agents with solvents and additives, the production process of pigmented systems is based

on complex wetting and stabilization processes.

The interaction of the pigments with the incident light results in selective shares being

removed from the white light and the remaining being scattered as widely as possible.

The first property results in Chroma, while the second is the prerequisite for good hiding

power. The ability to produce Chroma is proportional to the pigment surface area which

can interact with the light.

This means that for a specified pigment quantity the degree of selective absorption

increases with decreasing particle size up to a discrete stage. This stage is reached when

the particles are completely penetrated by light.

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The scattering power increases with the number of dipoles in the pigments which can be

excited by light. For this reason the scattering power increases initially with increasing

particle size.

However, this increase only continues as long as all the dipoles can interact in each

pigment particle with the incident light. But this is only possible up to a specific particle

size for each pigment. Above this critical size the dipoles inside the pigment become

optically inactive. Furthermore, interference occurs, resulting ultimately in a decrease in

scattering power. There is, therefore, an optimum particle size or particle diameter for the

scattering power.

Such small particles tend to combine to form larger units as a function of their shape and

polarity. If the primary particles are in contact with each other along edges and at corners,

the conglomerations with diameters of more than 100 µm can become very large, though

the forces of attraction remain relatively low. Such particles are termed agglomerates.

If the primary particles are connected via common surfaces, the forces of attraction

increase to such an extent that separation via mechanical means is only possible with

difficulty. However, the volume of such aggregates is much lower. The cavities in the

agglomerates and the cavities in the pigment powder in the delivery form can represent

up to 75% of the overall volume, depending on the pigment form and size. The pigment

volume concentration (PVC) is then only 25%.

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The forces of

attraction among the

pigments themselves

are an addition of

Coulomb forces, van-

der-Waals’ forces

and hydrogen bridge

bonds, depending on

the chemical

structure. The range

and strength of the

forces of attraction

are very greatly

influenced by the

type of interaction.

2) Wetting and Decomposition of Agglomerates:

Wetting of the pigments is a

surface energy process. The

matching of the surface tension

of the pigment to be dispersed

with the interacting binder

solution is thus the decisive

fundamental prerequisite for

successful pigment processing.

The surface tension is the

surface related work which has

to be performed to form the

surface which is newly created

by the wetting of the pigments.

Thorough wetting of the pigment

surfaces by resin solutions is

only possible if the energy gain

Fig.5 Scheme of dispersing and stabilizing of pigments.

Fig.6 Schemes of the most important dispersing equipments.

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resulting from the interaction of fluid and pigment is greater than the work which has to

be performed to increase the surface area of the liquid.

The wetting of the outer agglomerate is therefore followed by the penetration of the resin

solution into the cavities of the agglomerates.

Various features are used to describe the material specific dispersion properties of

pigments. These include the oil absorption value and the wetting volume.

The type and quantity of solvents and solvent combinations also have a bearing on

viscosity and surface tension, while also determining the configuration of the resin

molecules which are in the form of coils.

Since the low molecular solvent molecules have much greater mobility than the film

forming agents, they also penetrate the agglomerate cavities more quickly. They generate

a preliminary wetting of the pigment surfaces, termed pseudo wetting, during dispersion.

The solvent type and the film forming agent polarity must therefore be matched to each

other such that the pseudowetting by solvents is then converted to real stabilization by

replacing them with film forming agent molecules. Only part of the agglomerates can be

destroyed by the physicochemical interactions of the pigments with the resin solution.

Complete conversion to the primary particle with the best possible pigment wetting at the

same time can only be achieved by the additional transmission of mechanical forces to

the pigments.

Numerous dispersers have been developed to transmit shear forces to pigment

agglomerates by laminar flows of viscous fluids. The most important are dissolvers,

which are suitable for easily dispersible pigments, three roll mills for highly viscous

pastes and the very effective agitator mills for universal use. A small number of ball mills

are also in use, though these are uneconomic by comparison with agitator mills and

dissolvers.

3) Stabilization of Pigment Dispersions:

The uniform distribution of the pigments brought about by the dispersion process is only

a feasible technical solution if the distribution state is also retained during formulation,

storage, processing and the subsequent film formation. The reagglomeration of the

primary particles would result in a reduction in gloss and a change in the tinting strength.

Other side effects would include color shifts in pigment mixtures, specks and

sedimentation.

Stabilization by means of electrical double layers This is a relatively simple method of

describing surface energies when there is a polar, i.e. ion forming environment, which

makes it a useful method for practical operations. The mathematical correlations which

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are known by the term DLVO theory show that a pigment dispersion is stable if the

repulsive forces acting on the surface as a result of ion adsorption exceed the van-der-

Waals’ forces of attraction.

VT = VA + VR

The total potential surface energy VT is composed of the attraction VA and the electrically

induced repulsion VR energy levels. Steric stabilization while the DLVO theory allows calculations to describe conditions

with a good fit when assessing pigment stabilization in aqueous media, this method is

ineffective in a nonpolar environment.

To permit stabilization, the pigment must be surrounded by polymer chains which are

fixed punctually but which otherwise can move freely. When two particles stabilized in

this way approach, the mobility of the polymer chains and thus the entropy are reduced.

The selection of a suitable solvent is also important when stabilizing pigments. Because

of the greater mobility of the solvent molecules the primary wetting of the pigment

cavities is initially achieved by solvent molecules. A subsequent complete wetting

conversion is only achieved if a gain in free enthalpy is identified through the wetting

process of an adequate concentration of film forming agent molecules.

The use of relatively nonpolar solvents enhances the immediate wetting process with

polar binder molecules and at the same time the wetting conversion of the already

adsorbed solvent components.

Mixed stabilization the process of correlating theoretical considerations on the

stabilization of pigment surfaces with practical operations is made more difficult by the

fact that different stabilization

mechanisms can overlap. Mixed

forms of particle stabilization were

discovered during the calculation of

electrically stabilized gold sols after

the addition of nonionic

polyethylene glycol. Heller and

Pugh, for example, discovered that

the existing stabilization of

electrically stabilized gold sols can

be further improved by adding

polyethylene glycol.

Fig.7 Mixed stabilizations of pigments and their effect on the zeta-potential.

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The zeta-potential, which is an indicator of the stability of pigment distributions.

Stabilization limits despite the best possible stabilization the primary particles can

approach the range of the forces of attraction if the kinetic energy is sufficiently high, for

example at relatively high temperatures. This leads to pigment flocculation.

Flocculation as a result of solvent loss and inadequate covering of the pigment surfaces

can occur despite optimum dispersion and the best possible stabilization if the material to

be dispersed is wrongly handled when lacquering pigment concentrates.

Pigment shock and solvent shock in particular are commonly encountered in coating

technology.

Fig.8 Pigment shock by differences in solvent concentrations of dispersion and lacquer.

Fig.9 Solvent shock by unprofessional addition of solvents to the dispersion.

4) Optimum Mill Base Formulation:

This is done by determining the solid content of a film forming agent solution at which a

specified pigment quantity can be converted into a flowable mixture with the minimum

amount of resin solution.

The pigment absorption capability is quantified using indicators for better evaluation. An

important indicator for determining the optimum mill base composition is the yield value.

This is defined as the volume of a film forming agent solution which is required to

convert a specified pigment quantity into a flowable state. The characterizing feature of

this property is that the mixture flows in a continuous thread from a glass rod.

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If the compositions of the ternary

mixtures of film forming agent, solvent

and pigment determined from the

individual yield points are plotted in a

concentration triangle, the ranges of the

flowable mixtures can be attractively

presented in graphical form.

If the two ends of the yield point curve

are extended to the triangle sides and the

area of the supercritical pigmentation is

hatched, the area enclosed by the curve

with the exception of the hatched,

supercritical area contains all the flowable

binder/solvent/pigment mixtures.

Super critically pigmented mill base compositions lie above the critical pigment volume

concentration (CPVC), at which the volume of the film forming agent is lower than that

of the spaces between the pigments. The CPVC can be calculated from the bulk volume

of the pigments and must be converted into the critical pigment weight concentrations

(CPWC) for entering in the concentration triangle.

ix. Production of Coating Materials: The formulations drawn up by the laboratory must be supplemented by further detailed

standards of operation and test specifications for large scale production. The latter refer

equally to technical processing requirements and to quality.

Manufacturing instructions contain information on the order in which raw materials are

added, machine settings and temperatures for homogenization, dispersion and filtration

systems, information on process monitoring and interim tests. Information on approval

tests, instructions for filling methods, the container type and size to be chosen, together

with safety information and labeling on the containers must be clearly specified in the

manufacturing instructions.

Modern make-to-order production can then use one of three methods:

i. Direct dispersion

ii. Production of pastes with later lacquering

iii. The production of mixing paints

Fig.10 concentration triangle of film forming agent, solvent

and pigment to demonstrate the flow curves.

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While the mixing paint principle has won through for the very varied color requirements

of decorative and automotive refinishing paints, paste production and direct dispersion

are commonly used for production for large scale users.

Mixing paints are coating materials with a standardized color and tinting strength which

mostly contain only one pigment and are turned into the final product by simply stirring

together, without the addition of a binder. They are stored by paint users such as dealers

in specially developed mixing machines and converted into the end products in

accordance with given formulations.

Direct dispersions and products made from pastes are manufactured by the paint

manufacturer and sold as ready-to-use paint. Paste production of individual pigments has

proved its worth, despite the expense of storing the standardized pastes, because of the

advantages of the more effective and thus more economical dispersion of batches for

grinding. The individual pigment pastes are combined in particular mixing ratios as per

the color requested by the processor, with completion to form the coating material as per

the specification involving the addition of film forming agent solutions and additives.

1) Agitation and Agitators:

Visitors to a paint plant will see the basic mechanical process engineering operations to

combine materials via agitation in the dissolving of resins, the mixing of liquids, the

premixing of material to be dispersed or the tinting of color pastes.

In all cases the aim is to eliminate inhomogeneities in material mixtures. These can reveal

themselves in differences in concentration, density or color. Temperature differentials or

different refractive indices can also be used to characterize the mixing quality.

The homogenization of liquids or liquid-solid mixtures is carried out by generating flows

which are as irregular as possible with the aim of achieving the desired degree of

homogenization as quickly as possible with

minimum energy input.

If, because of excessively high viscosities, random

shifts in position can no longer be achieved by free

product flow but only by means of pressure or shear

forces, this is termed kneading.

The task of homogenizing free flowing material

mixtures is achieved by agitation using vertical and

horizontal flows. These are generated by rotating

agitator blades. Numerous types of agitator have Fig.11 Characteristic flow in a stirring vessel.

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proved their practical value, depending on the type of material and the desired degree of

homogenization.

Homogenization which has to be carried out under economic conditions is best achieved

if horizontal and vertical circular motions are present in the mixing vessel at the same

time. When homogenizing materials of different density it is recommended that vertical

flow be used because of the tendency towards sedimentation of the heavier components.

Wherever possible, movement of the entire amount of material together in the mixing

vessel, which occurs frequently during the agitation process, should be avoided because

of the unwanted separation caused by centrifugal forces.

The mixing time is short if the components to be mixed undergo a large number of

changes of location. This can take the form of movement of the agitator itself or of

material flows generated by the agitator. They can be achieved by impact, flow around

obstacles, crossing directions of flow and speed differentials at the interfaces of parallel

flows.

Two different agitator designs have become established. Either the entire contents of the

vessel are circulated by means of a large agitator surface area and slow material motionor

small partial quantities are transported at high speed by means of impact and mixing

eddies with a small agitator surface area and a high rotational speed. The first concept is

represented by blade agitators, and the second by propeller agitators. At high agitation

speeds the occurrence of conical eddies can be observed which entrain air into the

mixture. To avoid this, baffles are fitted in the agitators or the agitator shafts are

configured eccentrically.

A broad range of different consistencies has to be covered in the paint and coatings

industry when homogenizing materials. The viscosity of the material to be agitated is

therefore adjusted continually by altering the rotational speed or by means of gear

mechanisms and interchangeable agitator blades.

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The anchor mixer is an old design which is unsuitable from an economic

perspective. It rotates slowly and is now only still used in resin reactors for better heat

transfer and to eliminate vapour bubbles. It is not suitable for homogenization tasks

because of its lack of vertical flow. The blade agitator is also a simple agitator design. It is mainly used to maintain

already homogenized mixtures. Because of the size of the agitator blades there is the

danger of radial motion being induced in the agitated material. Such motion can be

prevented or reduced by means of baffles. Vertical flow is not very pronounced in blade

agitators. Flow is different in the beater or the modern variant, the multistage impulse

agitator both achieve intensive vertical motion.

The propeller agitator moves part of the mill base at high speed. It entrains the

material

axially and discharges it in turn axially, this ensures good vertical flow, and the undesired

circular motion can be prevented by rotating rings. The propeller agitator copes with a

broad range of consistencies and has therefore become accepted in practical paint

production operations as a universal machine. Its disadvantage is that the generated flow

is often insufficiently turbulent, as a result of which long mixing times have to be

accepted.

Safety regulations must be observed when operating agitators and other mixing

equipment. Explosion protection systems, rigorous earthing of all agitators and vessels,

Fig.12 Different agitator types.

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and the fitting of grilles in vessel openings are important measures to take to ensure

accident free operation.

2) Dispersersing and Dispersers:

The task of dispersers is to separate pigment agglomerates in viscous fluids from each

other by the transmission of shear forces.

At the same time the conditions required for the stabilizing covering of the pigment

surfaces which is also necessary are created by suitable raw material selection and

formulation. The shear forces generated in the machines by flow are enhanced by

supplementary rotation of the particles by centrifugal forces.

In addition, there are also tensile and compressive loads at work which help in breaking

down the agglomerates. Since the transmission of shear forces right to the level of the

primary particle must be possible, flow states must be ensured which enable the

transmission of forces irrespective of particle size.

The machines used for pigment dispersal are varied, and there is a wide range of designs.

Nonetheless, all have the same operating principle. They transmit high shear forces in

laminar flow gradients to separate the agglomerates. The most important machines used

commonly in large scale production are dissolvers, agitator mills and roll mills.

Dissolvers: Are disc agitators which can transmit shear stresses to pigments under

certain conditions which are sufficiently high to ensure dispersion.

The necessary conditions for this are met if the agitator disc and the agitator vessel are

matched in size and this is complemented by appropriate agitator disc sizes and shapes,

an adequate rotational speed, an optimized fill level and adapted mill base formulations.

Even when all the conditions are met, the shear forces transmitted by dissolvers are not

high. Dissolvers are therefore only suitable for the dispersion of easily dispersed

pigments, such as for dispersion paints and decorative paints. Different dispersion

systems must be used if requirements are more demanding.

Dissolvers are then only used for preliminary homogenization or preliminary dispersion.

This enables the throughputs of the actual dispersion systems to be significantly

increased. To generate the necessary laminar flow the sizes of the vessels and agitator

discs and the fill level and disc configuration must, as mentioned above, be matched to

each other.

Optimum dispersion results are achieved if the vessel diameter is 2.5 to 3 times the size

of the disc diameter, and the distance from the agitator disc to the base corresponds to 0.5

and the fill level to 2 disc diameters.

{21}

Under such conditions dispersions are

possible once the tangential speed UA at the

periphery of the disc has reached 24 m/s.

The limit speed is therefore a function of

the disc size.

Apart from conventional dissolvers

numerous special designs will be found in

paint plants. They differ in the type and

number of agitator discs and in the

configuration of the agitator vessels. Of the

multishaft machines, the twinshaft dissolver

is the most commonly encountered

disperser. It has agitator discs which are

offset in height, mounted on two separate

shafts, and thus better agitation properties.

Fig.14 Schemes of different dissolver types.

Rotor-stator agitators (inline dissolvers) have also proved successful for high speed

homogenization, particularly for the manufacture of waterbased paints. Because of the

high rotational speed of the rotor fast and effective distribution of the formulation

ingredients is achieved with these, particularly when systems with a high pseudoplasticity

Fig.13 Scheme of flow in dissolvers and pictures of dissolver

equipment and a dissolver disc.

{22}

have to be processed. They

feature small dispersion

chambers and are mainly used

for continuous processes.

The principle of dispersion by

means of friction rolls or roll

mill is implemented in single-

roll, two-roll, three-roll and

multiroll mills. The only one of

any significance for the paint and coatings industry is the three-roll mill which has

become less important because of its relatively low throughput by comparison with other

types of dispersing systems.

Its use is now limited to the manufacture of fillers, highly viscous printing inks and,

because of its gentle treatment of the pigment surfaces, to the dispersion of sensitive

surface treated pigments and temperature sensitive pastes. Three-roll mills consist in

essence of three metal or plastic cylinders configured one after the other. The middle roll

has a fixed mount, while the two outer ones are pressed against the middle one with

pressures of up to 1,000 bars. High shear forces can be transmitted by viscous liquids in

the narrow gaps between the rolls as a result of the different rotational speeds of the

individual rolls.

A speed ratio of 1:3:9 yields the best and most cost effective dispersing results, as has

been repeatedly confirmed in numerous experiments.

The rolls themselves generally have an

extremely hard, 1 cm thick outer

lining. Beneath this there are softer

elements on the inside. These enable

better heat transfer to the cooling hoses

inside the rolls.

Before a three-roll mill is used, the mill

base should undergo preliminary

dispersion in a dissolver or kneader,

depending on its consistency. The mill

base is then transferred to a feed device Fig.16 Picture of a three-roll mill.

Fig.15 Scheme and function of an inline dissolver.

{23}

between the first two rolls. The mill base is drawn into the gap as it adheres to the wall of

the rolls.

Because of the shear stress in the direction of flow and the diminishing gap opening a

pressure is generated in addition to the shear load which promotes dispersion. This

external pressure also causes pressure rises inside the agglomerates which may still

contain air and promotes the decomposition processes.

The width and height of the pressure profile depends on the diameter of the rolls and the

viscosity of the mill base. It is all the narrower, the thinner the mill base and the smaller

the roll diameter. The effect is enhanced by the shear of the material, caused by the

differing roll speeds.

The pressure is at its maximum shortly before the narrowest part of the gap. This is

followed directly by a zone of under pressure, as a result of which a sudden pressure drop

causes pigment wetting which is advantageous for the mill base.

The mill base is then separated at the exit of the gap and distributed onto both rolls in a

ratio corresponding to the rotational speed. With a speed ratio of 1:3 an appropriate

amount of material is transferred to the second roll.

Corresponding processes also take place between the second and third rolls. The

dispersed mill base adhering to the third roll is then removed from the roll by a doctor

blade and transferred to a storage container. As with the other disperser types, the

viscosity of the material to be dispersed must be adjusted to the three-roll process. If the

viscosity is too low, this results in spraying in the filling gap and in inadequate shear

forces; high viscosities, on the other hand, do not cause problems by comparison.

However, because of the high energy dissipation and the corresponding heat buildup,

appropriate measures must be taken to ensure good cooling or supplementary high

boiling liquids must be added to prevent the rolls from drying out. The latter would cause

irrevocable damage in the form of grooves in the roll surface.

Another application nowadays for the three-roll mill is the flushing of pigments. The

pigment cake, which is generally aqueous, still wet and therefore not yet or only slightly

agglomerated during pigment production, is not dried using the otherwise normal process

during flushing, but is converted from the aqueous to the organic phase by treating it with

organic binder solutions in kneaders.

The intention of the subsequent roll dispersion is less to decompose the agglomerates but

more to remove the residual water completely. Consequently, the rolls are not cooled, but

are heated with steam to ensure faster removal of the water. This method enables high

tinting strengths and good fineness levels to be achieved with pigments that are hard to

{24}

disperse. Carbon black pastes manufactured in

this way, for example, are used to produce haze

free, glossy, deep black topcoats.

Ball mills: the ball mills have been displaced

more and more by agitator mills because of their

poor economy. Their use is now limited to just a

few applications in dispersing. Ball mills are

hollow cylinders which rotate about a horizontal

axis in operation. They are filled to about 40%

of their volume with mill base and grinding

media, generally porcelain or steel balls with a

diameter of 20 – 30 mm, in a given ratio. As a result of the relative motion of the

grinding balls passing each other at different speeds, friction surfaces are generated

which enable the dispersion of the pigments. Above a certain rotational speed the moving

grinding media are lifted and cause an additional unwanted impact load on the pigment

agglomerates as they fall back down. This results in decomposition of the primary

particle, which is associated with deterioration in the optical power of the pigments. The

drum is therefore set to rotate more slowly for roll friction.

The actual dispersion process occurs whenever grinding media pass each other at

different speeds and generate the shear stress necessary for dispersion at the point where

they are closest together.

Because of their closed design, however, ball mills

have the benefit of being able to use low boilers as

solvents. A further advantage of ball mills worth

mentioning is their low maintenance during the

dispersion process.

The attritor: This consists of an upright milling

vessel in which 3 – 5 mm thick balls are artificially

moved by means of an agitator. The mill base is fed

into the mill chamber at the bottom and drawn off

again at the top. The cycle carries on continually

until the required particle fineness or tinting strength

has been achieved.

Fig.17 Function of a three-roll mill and pressure

profile in the milling gap.

Fig.18 Function of a ball mill.

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The continuing shortcomings of a high level of wear and the

high power consumption were largely eradicated by

changing the shape and the type of the agitation tools and by

making the grinding media even smaller. The attritor became

slimmer and taller, with the outcome that it was possible to

achieve adequate dispersion after one pass. In principle,

therefore, the agitator mill had been invented.

Agitator mills: which were usually open and fitted with

wedge wire sieves were increasingly replaced by closed

systems. By a closed system we mean a disperser which

enables the separation of the mill base from the grinding

media by means of friction gaps. Such closed agitator mills

bring numerous additional benefits. Dispersion can take place at increased pressure, thereby

making higher throughputs possible. Material feed or

material throughput can be varied by means of infinitely

adjustable pumps in

order to achieve better

adaptation of the

disperser to material

specific features in

many areas. As with

ball mills, steps must

be taken to provide an

effective cooling

system in agitator

mills too.

Dyno Mill: Dyno Mill is mainly used in ink industry, paint making plant, food plant

and medicine industries.

Fig.19 From ball mills via attritor to

agitator mills.

Fig.20 Scheme of an agitator mill.

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Basket Mill: The basket mill is a submersible

milling unit that will achieve particle size reduction

without the use of hard to clean pumps, hoses, and

tanks. The basket mill allows a greater amount of

material to pass through the milling chamber more

often resulting in a narrower particle size distribution

and stronger pigment strength in a shorter amount of

time.

Sand Mill: It uses a different type of impeller and

it is charged with glass or ceramic as a grinding

media. Pigments are ground by shear and attrition and the finesse of the dispersion is

determined by the length of time the paste is in the mill, or residency time. This mill

consists of a high-speed shaft with one or two solid disc impellers rotating off center in a

cylindrical tank with a cone-shaped bottom, filled with small grinding beads.

3) Separation Processes in the Manufacture of Paint:

In the paint manufacturing industry

numerous separation processes also

have to be carried out during the

production of pigmented and non-

pigmented coating materials. Examples

include the partial or complete removal

of solid particles from liquids, the

separation of grinding media in the

wedge wire sieves of agitator mills, the

recovery of hard agglomerates or the

removal of foreign matter before the

coating materials which are ready for

dispatch are transferred to their relevant containers. The separating operations are carried

out in sieveing and filtration units or by accelerated sedimentation in centrifuges.

Sieving and filtration Sieving or screening is a sizing process and is used for

fractionating mixtures of solids. This can take place in the gaseous phase or in a liquid

phase. The principle of separation by sieves lies in offering up the solid particles to be

separated as frequently as possible to the openings of the sieve surface.

The aim is to permit smaller particles to pass through, while holding larger ones back.

Fig.22 Different forms of sieves.

Fig 21 basket mill.

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The sieves with their defined openings are made of metal, organic fibres or plastics.

These are divided into perforated, woven or clamped sieve surfaces, depending on the

design. To ensure a consistent long-term separating effect it is important to ensure that

the sieve design does not permit any shift, i.e. any enlargement of the openings.

The necessary stability in the sieve surface is achieved by the use of monofilament yarn,

a fixed weave in the fabric and nonswelling materials.

It is also important in practice to use materials which are not attacked by the material

being separated. Depending on the material to be separated, solvent, acid, alkali or

bacteria resistant sieve fabrics should be used.

When dealing with hot materials ensure that the heat resistance of the used materials is

adequate.

High specific separation performance is achieved when all particles are offered up to the

sieve openings as frequently as possible by inducing movement of the material to be

separated. The frequency with which material is offered up can be increased by

horizontal or vertical motion and by vibration.

Filtration is the separation of solid particles from suspensions with the aid of porous

filter media. Strictly speaking, therefore, the filtration process is the complete separation

of solids (filter cake) from the liquid phase (filtrate).

Depending on the purpose of the filtration process, the treatment of the liquid is termed

clarification, and separation of the solids is termed cake filtration.

Because of the small size of the pigments the term ”filtration” is applied when fine and

extremely fine sieves are used although the dispersed pigment is still in the filtrate.

Whether such processes are termed sieveing or filtration in the paint and coatings

industry depends merely on the degree of fineness of the separation system.

Filtration processes are divided into surface filtration, cake filtration and deep bed

filtration, depending on the separation method employed.

Surface or sieve filtration is a method of solids separation which obeys the laws of

sieveing. It is used when only small quantities of solids have to be separated by means of

fine sieve bags with pore sizes of up to just a few micrometers (clarification).

Cake filtration is a separation process in which the solid cake accumulating on the

partition also serves as a filter aid at the same time. It enables the isolation of large

quantities of solids. With a pure surface filtration system all the solid particles are larger

than the openings in the perforated plate. With cake filtration this is only partially true. In

the course of the filtration process the solids form a cake which then enables the

{28}

separation of finer particles. In both processes the solids are deposited above the filter

medium.

Fig.23 Principles of filtration techniques.

The principle of deep bed filtration is quite different. This uses thicker filter media with

larger pores than the diameter of the solids to be separated. As a result these penetrate the

labyrinth of the channels in the filter medium where they are lodged either mechanically

in relatively narrow side passages or adsorptively on the internal walls of the capillaries.

Because of the fineness of the pore labyrinth deep bed filtration is not generally carried

out with pigmented paints.

Deep bed filtration is mainly used for purifying clearcoats and binder solutions. The

mechanical choking of the channels, by contrast with purely adsorptive separation, results

in a decrease in filter performance. On the other hand, the adsorptively retained particles

can be transported more or less quickly through the channels if filtered for long enough,

depending on the size of the attractive forces, with the result that deep bed filters can

”blow” after excessively long use. Deep bed filtration allows even relatively small gel

particles, i.e. deformable particles, to be separated if their diameter is small enough.

Larger gel particles, on the other hand, choke the pores of the filter medium and result in

a rapid drop in filter performance. To prevent blockages in the fine filter channels,

supplementary

filter aids are

frequently used to

clear critical

suspensions.

Fig.24 Scheme and picture of a plate-and-frame filter press.

{29}

The main differences between the plate-and-frame filter press

and the chamber filter press are its larger chamber volume of

the former and the option of carrying out flushing and washing

operations. It is therefore used for filtering suspensions with a

high solid content, such as in cake filtration for recovering

pigment powder during the manufacture of pigments.

The reasons for the increasing importance of bag filters

are essentially commercial. Higher throughputs, lower costs for

rigging, lower material costs and less waste merit particular

mention.

Sedimentation Solid particles of different sizes can be

separated from the liquid phase selectively or completely if

there is a difference in density between the liquid and dispersed phases. With gravity

sedimentation the acceleration due to gravity g and, in the opposite direction, the

frictional forces of the fluids act on the solid particles.

x. Quality control in paint industry:

Quality control is a set of procedures carried out to ensure that a manufactured product

and performed service adheres to a defined set of criteria and standard

values, before, during and after manufacturing, to ensure customer satisfaction and

conformance with statutory regulations.

The raw materials, manufacturing process and finished products undergo stringent QC

checks.

1. Paint manufacturing process:

The 1st thing should be ensuring that raw materials are available.

Then, batch sheet is issued, based on the quantity of raw materials available & sales

request.

Next thing is to ensure that the container and HSD and Grinding machine is very

clean.

Manufacturing instruction has to be adhered to in order to achieve the desired

results.

2. Water based paints manufacturing process:

Water based paints is processed in a HSD (high-speed dispersion) tank, in which a

circular, toothed blade attached to a rotating shaft agitates the mixture of pigment,

Fig.25 bag filter equipment.

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extenders, wetting & dispersing agents, little quantity of water, and defoamer until

the pigment particles are fully dispersed.

Once the dispersion is certified okay, by the Quality Control, the temperature of the

mixture is controlled to 300▫C, before adding the binder & other raw materials

remaining in the Batch sheet.

The paint is then mixed and sampled to the laboratory to check Quality Control

parameters (viscosity, S.G (Specific gravity), Colour, Opacity, drying, texture -

consistency, gloss or sheen, NVC (nonvolatile content) etc.) to ensure conformance

with the set standard.

Thinning & Tinting occurs.

Once the paint is certified okay by QC, it is then PASSED & PACKED as finished

product. However, QC ensures that packaging containers are properly labelled, free

from dirt & that products are packed to level.

3. Oil-based paint manufacturing process:

The first step in making oil-based paint involves mixing the pigment and fillers with

little resin, little solvent, wetting and dispersing agent to form a paste.

It is then routed into a sand mill or grinding machine (a large cylinder that agitates

and grinds the pigment and filler particles, making them smaller and dispersing them

throughout the mixture).

After about 30minutes, the fineness of grind is checked by the Quality Control

Personnel. If okay, the paint is discharged & made-up. At this stage, the remaining

raw materials yet to be added are added.

Thinning & tinting then starts.

Quality Control parameters (viscosity, S.G, Colour, Opacity, drying, gloss, NVC etc.)

are checked to ensure conformance with the set standard.

Once the paint is certified okay by QC, it is then PASSED & PACKED as finished

product.

However, QC has to ensure that packaging containers are properly labelled, free from

dirt and that products are packed to level.

4. In-process/finished product analysis:

Specific gravity

PH: 7.5 – 9.0

Dispersion & Fineness of Grind

Viscosity determined by Ford Cup (seconds) for low viscous products and

Rotothinner (Poises) for highly viscous products.

{31}

Bleed resistance/ flocculation

Drying

The Texture of the paint is determined by applying it on the wall using a Texcote

roller to check for sagging.

Color – using spectrophotometer

Opacity or Hiding power is measured by painting it over a black surface and a white

surface. The ratio of coverage on the black surface to coverage on the white surface is

then determined.

Non-volatile matter.

Gloss or Sheen is measured by determining the amount of reflected light given off a

painted surface, using a Gloss meter.

Adhesion is tested by making a crosshatch on a dried paint surface. A piece of tape is

applied to the crosshatch, and then pulled off. A good paint will remain on the surface.

Resistance to soapy water is tested by a machine that rubs a soapy brush over the

paint's surface. – Wet Abrasion Scrub Tester

Weathering and Resistance of the color to fading is determined by exposing a

portion of a painted surface to outdoor conditions i.e. sunlight, water, extreme

temperature, humidity, and comparing the amount of fading to a painted surface that

was not exposed.

Stability Test

Coarse particle and foreign matter – stick, rope, sack etc.

Flash Point is the temperature at which the mixture of the paint vapour and air can

ignite in the presence of a spark. The higher the flash point, the safer a solvent-based

paint is considered for storage.

xi. Paint defects and application problems:

{32}

DEFECTS CAUSES

1 Settling Low dispersion 2 Paint Separation Incompatibility 3 Foaming Mixing at high speed, insufficient defoamer. 4 Foul smell& Mould growth Micro-organisms 5 Sagging, no texture/ pattern Too much water, sand omitted 6 Low viscosity Excess solvent 7 High Viscosity Insufficient solvent 8 High Specific gravity

Insufficient solvent

9 Low Specific gravity

Excess solvent, foaming

11 Foreign matter Adding foreign contaminants without manufacturers specification (lead to film defect)

11 Chalking (is the progressive powdering of the paint film on the painted surface).

Polymer degradation of the paint matrix, due to exposure from UV radiation.

12 Erosion (Erosion is a very quick chalking)

due to external agents like rainfall

13 Peeling/Blistering

Improper surface treatment before application& dampness present in the substrate.

14 Cracking When paint coatings are not allowed to cure/dry completely before the next coat is applied.

15 Pigment Flocculation

The pigment, after dispersion, reverts to a greater or lesser degree, when rubbed. (Colour change)

16 Tacking/ not drying Insufficient drier

{33}

xii. Arabic summary:

ة(والمىسلي بسهب المريب )الصىبعيةإوتبج البىيبت التي أسأوالً:

.........( المقاومة لمحرارة المواد المالصقة والمجففات والمواد(ام واإلضافات خواد التختمف البويات التى أساسيا المذيب حسب استخداماتيا، وبالتالى تختمف الم المستخدمة فى إنتاجيا.

صناعية مثل دىان السيارات والغساالت وعمميات طالء المواسير. ألغراض ويضم ىذا النوع كل من البويات الصناعية والمنزلية. ويتم استخدام البويات الصناعية العمميات الصناعية األساسية فى خطوط إنتاج البويات الصناعية والمنزلية ( 2،1 الشكالنرض )ويع .لبويات المنزلية فيتم استخداميا لطالء المبانى واألثاثأما ا

. التى أساسيا المذيب ، والمدخالت إلى الوحدات ومصادر التموث

:الخمط .1

(وكربونات الكالسيوممك ت(والمواد المالئة (ثانى أكسيد التيتانيوم)والمخضباتواألحماض الدىنية ي(الكتان المغم زيت)نباتية الالزيوت أو يتم وزن راتنجات االلكيد .إلى الخالطات الميكانيكية والممدنات ويتم نقميا أتوماتيكيا

ن:الطح .2

.ع الطاحونة المستخدمة بنوع المخضبات واألوساط الحاممة والمواد المالئةالتجانس. ويرتبط نو و إلى الطواحين لمزيد من الخمط ( الدفعة ) وبعد الخمط يتم نقل الخميط

:الوسيطالتخزين .3

. قد تكون الدفعة بحاجة إلى مزيد من الطحن لمحصول عمى درجة التجانس المطموبةوه المصانع يتم نقل الدفعة بعد الطحن إلى خزان تخزين وسيط ألعض فى ب

:التخفيف .4

.من خزان التخزين الوسيط إلى خالط من أجل تخفيفيا حيث يتم إضافة المذيبات اإلضافات األخرى نقل الدفعةك يتم بعد ذل

يب:الترشيح والتشط .5

، كوبالت)لسيولة التجفيف ح معدنية المنتشرة وأى مواد صمبة متبقية . ويتم إضافة اكاسيد وأمالغير إلزالة المخضباتح فى المرشح الدفعة وبعد التخفيف يتم ترشي ). زركونيوم، ورصاص

التعبئة والتخزين: .6

يتم صب البوية وتعبئتيا في صفائح أو براميل ثم تغميفيا ونقميا إلي المخازن.

17 Skinning Absence of anti-skinning agent, excess drier 18 Low sheen Excess pigment/extender

{34}

.خط انتاج البويات التي أساسها مذيب )المنزلية( 1شكل

{35}

.خط انتاج البويات التي أساسها مذيب )الصناعية( 2شكل

:مبئًال ذات األسبش البىيبتج إوتبثبويبً:

خطوات بو مدخالت كل وحدة ومصادر التموث . وتتشاح العمميات األساسية التى تجرى فى خط إنتاج البويات ذات األساس المائى، كما يوض( 3يوضح) شكل م إضافتيا إلى الخميط بترتيب مختمف ، المستخدمة إلنتاج البويات التى أساسيا المذيب، باستثناء المواد الخام والتى يت مك تصنيع البويات ذات األساس المائى مع ت

.من المذيب كمخفف لقوام البويات كما يستخدم الماء بدال

:الخمط والتخفيف .1

{36}

المخضبات )العضوية غير حيث يتم خمط المواد المشتتة والمواد (خمط فائق السرعة)يحدث الخمط فى البويات ذات األساس المائى عمى خطوتين فى الخطوة األولى ضافات أخرى وخمطيا جميعا. جيدا ، والمواد المبممة خمطا( المالئة والمواد أما فى الخطوة الثانية، يتم إضافة كل من البوليمر والجميكول، وعامل مذيب التجمد وا

ت فيما بينيا فى نسبة االنتشار فى والمواد المالئة المستخدمة، فيى مكونة من مواد وعناصر تتفاو يك المخضبات وراتنجات اإلكريم معظم منخفضة وبالنسبة ل بسرعة .غىسيىموالميثوفون، كبريتات الباريوم ، والميكا، السيميكون، الطفمة، وسيميكات الما كالماء، وىذه العناصر ىى ثانى أكسيد التيتانيوم، وكبريتيد الزن

حن:الط .2

لطواحين لزيادة خمطيا وطحنيا وتحقيق التجانس المطموب بينيا. وترتبط نوعية الطاحونة المستخدمة بنوعية انتياء خطوة الخمط، يتم إرسال الدفعة إلى ابعد .المخضبات واألوساط الحاممة والمواد المالئة

اإلضافات: خمط .3

، ثم (التى سبق خمطيا وطحنيا فى الطاحونة) يتم إرسال الدفعة إلى الخالط، حيث تتم إضافة النشادر والمواد المشتتة إلى الماء، يمييا المخضبات لك بعد ذ المطموبة، تستخدم اإلضافات ثم البولى فينيل اسيتات، لموصول إلى الخواص( الفينوالت المعالجة بالكمورظة )غالبا ما تكون ، ثم المواد الحافمرغوةالعوامل المضادة ل

.األخرى إلكساب البويات خواص معينة

:الوسيطخزين الت .4

وسيط، حيث من الممكن أن تحتاج الدفعة إلى مزيد من الطحن لمحصول عمى درجة ن آت، يتمو الخطوة السابقة إرسال الدفعة إلى خزان تخزيالمنشعض فى ب .التجانس المطموبة

ب النهائي:التشطي الترشيح و .5

.بالخميطيتم انتشارىا أو أية مواد صمبة عالقة م لمخضبات من أيةشح لمتخمص الخميط فى مر ح ثم يتم ترشي

:لتخزينبئة واتعال .6

.يتم صب البويات فى عبوات ، ثم يتم تعبئتيا ونقميا إلى المخزنك بعد ذل

{37}

.إنتاج البويات ذات األساس المائيخط 3شكل

xiii. References: [1] Prof. Dr. A. Goldschmidt and Dr. H.-J. Streitberger Wiedenbrück, BASF

Handbook on Basics of Coating Technology ,July 2007.

[2] http://www.substech.com/dokuwiki/doku.php?id=classification_of_paints

البىيبت صىبعة - دليل التفتيش - المشروع المصري للحد مه التلىث - جهبز شئىن البيئة [3]

{38}

[4] other free PDFs from Google & web sites.

xiv. communication information: Mobile: 010 134 296 21 or 012 126 847 14

E-mail: mohamedabobakr2143@gmail. com