Pigment Coat

Its components are pigments, binders and auxiliaries such as waxes and fillers. The pigment coat imparts the desired appearance to the leather and levels out the leather surface. The choice of binders is made according to the finishing effect and fastness profile desired. Generally, polyacrylate dispersions are used in the pigment coat. 

Polyurethane dispersions are used in the pigment coat in particular when very high fastness properties are required. 

The top coat determines the ultimate appearance and the feel of the leather surface. It further substantially influences the fastness properties of the finish. Instead of organic, solvent-containing lacquers and top coats (e.g., nitrocellulose emulsions), today there is an increasing trend towards waterborne top coat systems. These are usually polyurethane dispersions which, owing to their specific properties (no emulsifier, good film formation despite relatively high hardness), are superior to polyacrylate dispersions in appHcation terms. 

The degree of luster of the finish is controlled using matting agents (e.g., silica derivatives). 

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Titanium dioxide pigment coated with pentaerythritol, trimethylolpropane, or trim ethyl ol eth an e exhibits improved dispersion characteristics when used in paint or plastics formulations. The polyol is generally added at levels of 0.1—0.5% (96). 

Pigment-coated printing papers usually are required to have high brightness to achieve contrast between the printed and unprinted areas. The coatings frequendy have a glossy surface. There also is a demand for duU-coated papers and for dull papers upon which glossy ink films can be printed. 

Pigmented Coating Processes for Paper and Board, TAPPI Press BookNo. 28, Technical Association of the Pulp and Paper Industry, Atianta, Ga., 1962. 

Advantages of the electron beam processor are its abiUty to penetrate thick and highly pigmented coatings. It is used to cross-link reactive unsaturated polymers, nonreactive thermoplastic polymers, iasulation, and wire-cable covetings (4,9,16) (see Insulation, electric-wire and cable COVERDIGS). 

The exceUent adhesion to primed films of polyester combined with good dielectric properties and good surface properties makes the vinyhdene chloride copolymers very suitable as binders for iron oxide pigmented coatings for magnetic tapes (168—170). They perform very weU in audio, video, and computer tapes. 

Strontium. Strontium 2-ethyIhexanoate [2457-02-5] is a candidate to replace lead in lead-free paints. It functions well under adverse weather conditions and promotes through drying. Outdoor performance of low pigmented coatings like stains may be effected negatively by using strontium instead of zirconium. 

Alternatively, the same coatings can be cured by electrons from an electron accelerator without the use of photoinitiators. Electrons from a 150-600 kV accelerator are energetic enough to create free radicals on impact with the polymer molecules and curing ensues. Clear and pigmented coatings can be cured. Electron accelerators are extremely expensive, but are cheap to run. 

Figure 14. Ti02 anatase pigmented coating, chalk rating 4, general view (2)...

Pigmented Coatings Cured with Visible Light... 

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