Лако-красочные материалы — производство

Slip is a term used to describe the smoothness, feel and slipability of a coating surface. It may also be related to the friction or lubricating aspect (feel) of the coating surface. Mar resistance is the ability of the coating to withstand mechanical abuse, such as abrasion. In many practical circumstances, an additive that provides better slip to the coating is also likely to give better mar resistance, improved scratch and scrub resistance, reduced metal and black heel marking and better anti-blocking properties. These additives modify the surface

rather than bulk of the coating to impart such properties; there­fore, such additives should migrate to the surface for effectiveness.

Waxes and silicone-based oils are the most common materials used to improve slip and mar resistance.

Pure polydimethylsiloxane (low MW) or modified polysiloxanes are widely used as slip and mar additives in both solventborne and waterborne systems. Most are surface active and hence migrate to the surface and reduce surface irregularities, giving a much smoother film. The organic modifications in the additive molecule are oriented inside the coating film, while the polysiloxane units orient outside the paint surface. The presence of such a thin film of the silicone reduces sliding friction, which results in better feel and improved mar resistance. Similarly to other silicone additives discussed, their overdosing may result in many film defects and possible recoating problems.

The waxes used as slip additives are incompatible with the binder and hence migrate to the surface of the film, where they improve the lubricity and feel of the coating. The waxes that are most commonly used in modern coatings are synthetic waxes such as polyethylene, polypropylene, Fischer-Tropsch waxes, or ethylene vinyl acetate waxes. For easy incorporation in coatings, waxes are supplied as fine dispersions in a carrier such as water or organic solvents, as well as micronized waxes in fine powder form. Waxes with different degrees of hardness, melting points and polarities are used in these preparations in order to meet the various requirements of different applications. Normal dosage levels for wax-based slip additives are higher (1 to 3 %) than silicones.