Liquid paint is a composite of a finely divided pigment dispersed in a liquid composed of a resin or binder and a volatile solvent. Therefore, paints are manufactured from three main constituents; pigments, binders, and solvents. In addition to give the paints specific properties for specific purposes or applications some additives are also used.
The liquid portion of the paints is known as the vehicle. Vehicles are composed of nonvolatile and volatile parts:
- Solvent-based paints: oils and/ or resins plus driers and additives.
- Lacquers: celluloses, resins, plasticizers, and additives.
- Water-based paints: styrene-butadiene, polyvinyl acetate, acrylic, other polymers and emulsions, copolymers plus additives.
- Ketones , esters, alcohol, aromatics, and aliphatics
The pigment is one of the main and important constituent of the paint. In general, pigments should be opaque to ensure good covering power and chemically inert to secure stability, hence long life. Pigments should be nontoxic, or at least of very low toxicity, to both the painter and the inhabitants. Finally, pigments must be wet by the film-forming constituents and be of low cost. Different pigments possess different covering power perunit weight.
Table below shows the different paints constituents.
|Pigments are usually: · An inorganic substance, such as titanium dioxide, chrome pigment, earths, lead pigments, zinc pigments. · A pure, insoluble organic dye known as a toner. An organic dye precipitated on an inorganic carrier such as aluminum hydroxide, barium sulfate or clay.||The function of pigments and fillers is to provide simply a colored surface, pleasing for its aesthetic appeal. The solid particles in paint reflect light rays, and thus help to prolong the life of the paints, and protect metals from corrosion.|
|Binders or vehicles. Those are resins or oils.||Its function is binding the pigment to the substrate.|
|Thinners and solvents; such as petroleum ether, toluene, xylene.||It is the volatile part of the vehicle. Its function is to dissolve the binders, adjust the paint viscosity, and give homogeneous, regular, and uniform thickness on the coated surface.|
|Fillers; such as clay, talc, gypsum, and calcium carbonate.||Pigment extender, or fillers, reduce the paint cost and control the rheorological properties (viscosity) of paints.|
|Driers, as cobalt, lead, zinc, zirconium, manganese, calcium, barium.||To accelerate the drying of the paints.|
|Anti-skinning agents||It is added to the paints (unsaturated), to prevent the solidification of paints surface during storage.|
|Anti-settling agents||To improve the dispersion efficiency of the pigments into the vehicle, to prevent the settling of pigments during storage.|
|Plasticizers; These materials are special types of oils, phthalate esters or chlorinated paraffins.||To improve the elasticity of paint films, and to minimize the paint films tendency for cracking.|
|Dispersants, wetting agents, fire retarding, anti-floating, anti-foaming,…etc.||To give the paint specific property for specific purpose or application|
2. Other Raw Materials
· Preservatives are also used in the manufacture of water-based paints to prolong their life time.
· Water-alkali solutions and solvents for equipment cleaning and washing, between batches.
· Detergents and antiseptics for floor cleaning.
Packaging materials; different types of packaging materials are used (aluminum foil, metallic and plastic containers, tin sheets, and cartons).
Steam; is generated in boilers that use either Mazot (fuel oil), solar (gas oil) or natural gas as fuel. Steam is used for providing heat requirements and in some large facilities for electric power generations.
Water; is used as process water, as rinse water for equipment and floor, as boiler feed water, as cooling water and for domestic purposes. Boiler feed water is pretreated in softeners to prevent scale formation. Water may be supplied from public water lines, wells or canals. The type of water supply will dictate the type of pretreatment.