PAINT PRODUCTION
Abstract
Increasing student skills in the field work, and linking theory with application,
become the motivation to students to join to factories and companies for
achieving this target. One of chemical process industries is the paints industry.
Paints is a main part of coatings, paints composed of five components which are;
resin (binder), solvent, filler, pigments, and additives. From the point of view of
chemical engineering; paints manufacturing, requires number of unit operation
which are mixing, milling, and filtration. These of operations done using several
industrial units which are; mixers, mills, and screen filters.
Paints manufacturing done by adding binders, solvents, and thickeners to
provide a gel phase which its existence is a mark for starting of adding fillers and
pigment, through and after manufacturing processes a samples send to
laboratory to done some tests, by which the manufacturer be sure from his
products quality, the main tests are density, viscosity, and hiding power test,
there several tests can be done also such as wash-ability and impact test.
1
INGREDIENT
 Water
200kg
 Calcium
200kg
Carbonate/kaolin(white)
 Titan
10kg
 Polyvinyl Acetate (P.V.A)
20kg
 Nitrosol or Antisol
4kg
 Defoamer
2kg
 Jenepour
1kg
 Formalin
1kg
 Calgon
1kg
 Ammonia
0.5kg
 Silicate
1kg
 Marble Dust
20kg
2
Introduction
Paint is any liquid, liquefiable, or mastic composition which after application to a
substrate in a thin layer is converted to an opaque solid film. It is most commonly
used to protect, colour or provide texture to objects.
Surface coating industry is one of the most popular industries. Paints, varnishes
and lacquers industry is gaining ground at a rapid pace in modern time
accompanied with closed advance in surface coating technology. They are
formulated for specific purposes: outside house paints and exterior varnishes are
intended to give good service when exposed to weathering; interior wall paints
are formulated to give excellent coverage and good wash ability; and lacquers
are formulated for rapid drying.
Varnish is one of the important parts of surface coating industry. Varnish is a
transparent, hard, protective finish or film primarily used in wood finishing but
also for other materials. They are used to change the surface gloss, making the
surface more matte or higher gloss, or to provide the various areas of a painting
with a more unified finish. Varnishes are also applied over wood stains as a final
step to achieve a film for gloss and protection. Some products are marketed as a
combined stain and varnish.
3
The paint and coatings industry plays an integral role in sustainability; coatings
protect the objects we depend on every day, preserve our possessions, so they
last longer and provide for a sustainable future. They are indispensable products
that extend the useful life of everyday objects by acting as a protective barrier.
These newer products have enabled paint manufacturers to improve the
performance properties of their paints and coatings and so satisfy the more
stringent requirements of our modern industrial society. The future for industrial
paints, varnishes and lacquers is bright. In the next few years its value will go up
gradually in line with the global trend.
Paints products
Epoxy paints
Most of epoxy paints are working as two-component system (2K), and used
for several applications most of it for coating; concrete, steel structure, and
wooden grounds as primer and finish also coating metal surfaces such as; petrol
pipes and tanks. One of important coating missions is coating pipes and tanks for
water and oil.
Polyurethane paints
As epoxy its work depend usually on the 2K system with high wash-ability
weathering and chemicals resistance, which make it suitable for applying steel,
wooden, and concrete surfaces.
TV & Phones Paints
It's thermoplastic acrylic finishing coat with high adhesion and weathering,
water and aliphatic hydrocarbons resistance, which make it suitable for air
spraying for TV and phones.
Aluminium Paints
4
It’s a metallic paint used in protection purposes, it depends on aluminium paste
as pigment, which give it corrosion resistance.
Primers
It can be manufactured from alkyds, or resins such as epoxy, it used for
covering surface pores, and levelling surface to be painted with other type of
paints
such as lake
Varnish
It is a colour less paint used for protection, and disappearing the primed surface
under it.
Instrumentation
5
Fig. 1: Production procedure for water-based paints
Fig. 2: Paint mixer/distributor tank
Fig. 3: Paint colour combination
6
Fig. 4: Paint production process
Fig. 5: A mixer distributing paints in the production plant
7
Fig. 6: Finished product
Procedures
Firstly, surface active agents, usually thickeners added to give a gel stage
after that binders or oils added, in addition to adding pigment and fillers also
amount of solvent added, this procedure called premixing, after that a sample
sent to the laboratory to get a report about its fineness, viscosity, and density.
If the fineness not meet the required specifications, the mixture charged to the
milling unit, after that the other additives and the rest amount of solvent added
and mixed in a procedure called thinning, after this procedure another sample
sent to the laboratory to done some tests such as, viscosity, density, and hiding
power, if test results meet the required specification the quality lab. Permission is
given to start packaging, and before that the final mixture purified using a bar
screen, after that it packaged manually, semi-automatic, or automatic according
production volume.
Laboratory
Before production starts each separate paint has a unique formula developed for
it in the laboratory. During this development stage the paint's quality aspects are
comprehensively tested. The laboratory is also responsible for inspecting the raw
8
materials before they go into the product and monitoring the quality during the
production process. In addition to the above activities, particular attention is also
given to research into new raw materials and paint systems.
Weighing the raw materials
The central warehouse stores all the dry raw materials. This includes pigments
and extenders, as well as binders such as dextrine and Gum arabic which is later
made liquid through dilution. At the start of the production process the dry raw
materials are weighed here accurately to the gram and prepared for transport to
the next department, the pre-mixing department. The pre-mixing department
stores the liquid binders and additives. The correct amount is tapped off, after
which the weighed dry raw materials are added. As small amounts of dry raw
materials are left behind in the sacks during this process, the paint has to be
checked at each subsequent production step against standards for the relevant
product according to colour and viscosity, and is adjusted if necessary.
Dispersion
Pigments are insoluble in the binder. They therefore have to be regularly
dispersed in the binder, that is to say finely distributed. This dispersal occurs in
two steps: first through pre-mixing with a mixer and then the final fineness is
determined with a triple roll mill.
Pre-mixing
The pigments are supplied in dry powder form, with the pigment components
held together in clusters. During the pre-mixing these are turned to smaller
clusters and homogenously distributed throughout the binder. The tinting
strength of the paint is now relatively low, but this will increase as the pigment is
ground finer in the next production phase.
Grinding the pigments
9
In the triple roll mill the pigment clusters are ground further to the desired
fineness. During this process the pigment particles must not get damaged as this
may result in a change of colour. The three rollers rotate in opposite directions
with different speeds. The first roller turns relatively slowly, the second 3 times as
fast and the third 9 or 12 times as fast, depending on the type of mill. The
difference in speed helps to grind the pigment lumps and the paint goes from one
roller to the other. The paint is finally removed using a scraper.
Fineness inspection
The distance between the rollers determines the fineness of the grind. This
process is run through for a maximum of five times. The finer the grind, the
greater the tinting strength of the paint. The rollers are hollow and are cooled on
the inside with water, as the pigments would otherwise burn through the heat of
the friction. Depending on the nature of the pigment and the purpose of the paint
or ink, the pigments are ground to between 2 and 55 microns (1 micron = 1/1000
mm). After the last grinding the paint finally has the required viscosity.
After the grinding the fineness is checked using the Hegman bar. The depth of
the groove in the bar gradually increases, indicated in microns. The paint is
thinned to a certain viscosity and then applied to the groove and levelled off. At
the point where the pigment particles are larger than the thickness of the paint
layer they stick up above the surface of the paint film. At this point, visible to the
human eye under skimming light, the fineness is read off.
Colour inspection
The new colour is now compared against the standard colour. Both are applied
thick as well as thin so that both the mass tone and the undertone of the colour
can be seen. There must not be a difference between the new colour and the
standard colour.
Stability inspection
10
In order to ensure that only quality products are sold, each batch is left to stand
for a certain time in order to check the stability. After this period another
laboratory check is carried out, and after approval the paint is filled into
containers.
Filling
Tubes are filled from the underside, with the top already in place. Plastic tubes
are closed by melting the material, while the aluminium tubes are folded step-bystep and squeezed shut. Bottles are filled, closed and then labelled. The final
step is to check that the packaging contains the right amount of paint.
Discussions
Paint is made from a coloured pigment which is usually a powder. The powder is
made from different chemicals.[1] Some of the pigments come straight from
natural things like clay. The pigment must be made wet by mixing it with
something that will make it stick onto the surface and not come off easily. The
wet stuff is called the "medium" or "vehicle". Some paints are just mixed with
water. Other paints are mixed with oils or chemicals of different sorts. Most
painters buy paint that is already mixed. House-painters use paint already mixed
in large cans. Artists buy paint in tubes. Some artists buy dry pigment and mix it
for themselves.
The paint is usually put onto the surface with a paint brush. Paint brushes are
used by painters of all sorts. House painters also use rollers and spray-guns to
put on paint. A modern invention is paint in a pressurized can which can be
sprayed on. Some modern artists also use spray paint. In factories there are
machines which spray paint onto objects. Cars are usually painted in this way.
Paint must be allowed to dry. Some paints such as watercolour, dries in a few
minutes. Other paints, such as artist's oil paint, can take days or even weeks to
dry. Most other types of paints fit between these two. Many types of paint are
11
best if they are put on in several layers. The painter must first prepare the
surface so it is smooth, clean and dry. The first layer of paint is often an
"undercoat" or "ground" which is smooth and sticks very well. The coloured
paints are put on over the top. A house-painter who is using oil paint on a
wooden window frame might used three layers of paint to give very good
protection from the weather. Other types of modern house paint only need one
layer, particularly on the inside. Artists using oil paint and tempera often use
many layers to get just the right effect.
Paints Application
There are four main methods of applying paint:
1. By spreading, e.g. by brush, roller, paint pad, or doctor blade;
2. By spraying, e.g. air-fed spray, airless spray, hot spray, and electrostatic
spray;
3. By flow coating, e.g. dipping, curtain coating, roller coating, and reverse roller
coating;
4. By electro deposition.
Paints Unit Operations & Equipment
Mixing operation
In paints manufacturing several ingredients used to formulate paint system,
each of them has properties differ from others which mean that there is no
homogeneity between all these several components, mixing process has a vital
role in achieving homogeneity to the mentioned components to get the final paint
system. All paints components are in solid or in liquid state so the used mixing
techniques, will be depends on; solid - liquid mixing, and liquid – liquid mixing.
Liquid - liquid Mixing
12
Most of paints components are liquids for providing a final liquid state for paint
applying, three processes occur simultaneously to achieve homogeneity which
are; coalescence, dispersion, and suspension. Coalescence and Dispersion;
occur dependence on shear or velocity gradient which resulted from mixing
speed of liquids drops, which force drops to deform, to daughter drops increasing
due to high energies that produced by dispersion, after deformation they
disperse,
collide
with
each
other,
and
then
coalesce.
Suspension; occur depending on flow movement inside mixing vessel,
which come from speed of mixing, so high-speed mixers are used to achieve
coalesce drops suspension.
Solid- liquid mixing
Solid content of paint system varies, and may reaching to 50% or more
from contents of paint formula, and usually added in the middle stages of mixing
after adding some liquidous components. This mentioned solid content is a finite
powder, dissolved in other liquidous components by three processes which are;
suspension, distribution, and drawing down of solids by agitation.
Suspension; the condition where no particle remains on the bottom of the vessel
(or upper surface of the liquid) for longer than 1-2 sec. this position achieved by
existence
of
anti-settling
agents
and
high
rotating
speed.
Distribution; it means that there’s no particles in flocculated state usually in
bottom of mixing vessel, this achieves by using dispersing agents which led for
particles
distribution
in
all
directions
inside
vessel.
Drawing down of solids; it achieved by agitation, and represented in mixing by a
cone shape around agitator.
Conclusions
13
1. Paint is a main type of coatings, used in purposes of protection, and
decoration. An example is epoxy and poly urethane system, paints has
several methods for applying such as spray gun.
2. Paints composed mainly of five components; resin (binder), which collect all
the rest of paint components, it classified to convertible binders such as;
epoxy,
and polyurethane. The other classification is non-convertible binders such as;
cellulose, and nitro-cellulose.
3. The second component is the solvent; which used to dissolve all components
of paint. Other components used such as pigment which give the paint its
colour,
the filler which perform usually half of formula amount, and finally some
additives such as thickeners, dryers, anti-foaming agents, and other additives
4. Paints manufacturing depend on three-unit operations which are; mixing,
milling, and filtration. Mixing operation used for mixing all components and
homogenizing it, by using two mechanisms which are; liquid-liquid mixing, and
solid-liquid mixing. Milling operation is used to damaging all agglomerated
particles to prevent its settling. Filtration is used to remove any agglomerated
particles or anything before filtration.
5. Equipment used in paints manufacturing are mixers, mills, and filters. Mixers
is consisting of impeller, consist of axis and radial or axial disk, and vessel
which
must not contain baffles inside it for not reducing vortex, which is important in
solid-liquid mixing. Mills used to damage any coagulated particles, by crashing
it
with macro balls manufactured from several materials such as; glass, and
ceramics. Screen filters are used for purification of paint.
6. Paints manufacturing pass through several procedures, be in cleaning of
industrial units, and start adding the resin, solvent, thickener, and anti-settling
14
agent to provide pre gel phase to contain powders, that will be added and
mixed.
After that, a sample sent to QCL to test it fineness, and after that the rest
components added, mixed well and milled, filtrated, and packaged. During
and
after manufacturing processes several test done such as density, and
viscosity test
References
1. R. Norris Shreve, 1956, the chemical process industries, second edition,
McGraw-Hill book company, Tokyo.
2. Rodger Talbert, 2008, Paints Technology Handbook, Taylor & Francis
group, Boca Raton & New York & London.
3. R. LAMBOURNE and T.A. STRIVENS, 1999, Paint and surface Coatings
theory and practice, second edition, Woodhead Publishing Ltd, Cambridge.
4. Charles A. Harper and Edward M. Petrie, 2003, Plastics Materials and
Processes A Concise Encyclopedia, John Wiley & Sons, New Jersey.
5. Robert O. Ebewele, 2000, Polymer Science and Technology, CRC Press,
Florida.
6. BRYAN ELLIS, 1993, Chemistry and Technology of Epoxy Resins,
Springer Science + Business Media Dordrecht, United Kingdom.
7. Charles E. Carraher, Jr., 2003, Polymer Chemistry, MARCEL DEKKER,
NEW YORK and BASEL.
8. Lyle F. Albright, 2009, Albright’s Chemical Engineering Handbook, Taylor
& Francis Group, Boca Raton & New York & London.
15
9. James R. Couper, W. Roy Penney, James R. Fair, and Stanley M. Walas,
2012, Chemical Process Equipment Selection and Design, Third edition,
Elsevier, united states of America.
10.
Ministry of state for environmental affairs, 2002, Paint Industry- Self-
Monitoring Manual, Egypt
16