Paint-Making Processes

Varnishes are usually colorless but may be slightly colored due to the intrinsic color of the binders, driers, or other additives. Colored transparent varnishes contain soluble dyes or a small amount of finely dispersed pigments. Matt varnishes may be opaque (milky), colorless, or transparent after drying they have a matt to semigloss surface due to the presence of dulling (mainly inorganic) additives. 

Liquid raw materials are mixed in a specific sequence in slow- to high-speed stirrers or mixers to give a homogeneous, streak-free mixture (see Section 7.3.3). In larger mixers and tanks (up to 50000 L capacity) the mixing device is permanently installed in the vessels. Precondensates and wax solutions are prepared in heatable and coolable vessels equipped with stirrers. 

Solids are usually dissolved in liquids using high-speed stirring equipment. If the formulation contains dissolving and nondissolving solvents (diluents), then the nondissolving solvents are often added first, followed by the solid raw materials (e.g., powders, granules, fibers), and then finally the true solvent. With this order of 

Dispersion. The liquid semifinished products (intermediates) used in paint making are prepared in a similar manner to varnishes (see Section 7.2.1). The most important stage in the production of pigment-containing paints is complete wetting and uniform distribution (i.e., dispersion) of the solid pigment particles in the liquid, film- 

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In general the paint-making process can be subdivided into four main stages ... 

Quality Assurance. Almost every aspect of the paint-making process is subjected to quality assurance measures. Depending on the type of product, this involves a number of eorrection stages and delay periods, particularly in the adjustment tanks. 

The wide variety of paint formulations are reflected in the variety of paint-making processes. Figure 7.3 summarizes the essential features of these processes. Only a few special products (e.g., putties, plasters, or underbody protection materials) are not covered by this scheme they are produced by special proprietary procedures (generally of the one-pot type). 

Figure 7.3. General flow diagram of the paint-making process...

The use of calcium carbonate in paint, paper, and plastics make up the principal part of the market. In the paper industry calcium carbonate products find two uses as a filler in the papermaking process and as a part of the coating on paper. 

Surfaces. Essentially any electrically conductive surface can be electroplated, although special techniques may be required to make the surface electrically conductive. Many techniques ate used to metalline nonconductive surfaces. These are weU-covered ia the Hterature (3) and can range from coating with metallic-loaded paints or reduced-silver spray, to autocatalytic processes on tin—palladium activated surfaces or vapor-deposited metals. Preparation steps must be optimized and closely controlled for each substrate being electroplated. 

When the problem is to disrupt Ughtly bonded clusters or agglomerates, a new aspect of fine grinding enters. This may be iUustrated by the breakdown of pigments to incorporate them in liquid vehicles in the making of paints, and the disruption of biological cells to release soluble produces. Purees, food pastes, pulps, and the like are processed by this type of mill. Dispersion is also associated with the formation of emulsions which are basically two-fluid systems. Syrups, sauces, milk, ointments, creams, lotions, and asphalt and water-paint emulsions are in this categoiy. 

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