Лако-красочные материалы — производство

Powder coatings are absolutely free of organic solvents and should therefore be con­sidered as the most environmentally beneficial coating systems. In additional to the absence of solvents, the overspray can be recycled and reused, supporting the ecological targets even more.

For the processing of metallic effect pigments in powder coatings, there are basi­cally three possible technologies: coextrusion, dry blending and bonding.

The “classic” method for making powder coatings, coextrusion, is not recom­mended for the application of metallic pigments. The high shear forces during ex­trusion would mechanically destroy the pigment flakes and thereby spoil the metallic effect.

“Dry blending”, i. e. the addition of metallic pigments to the ready-made powder coating in a final blending step, was for a long time the only recommended method to make metallic powder coatings. The advantage of this method is the gentle handling of the flakes giving the best metallic appearance. The disadvantage, however, is that the metallic particles seem to be differently charged compared with the resin particles, and therefore tend to separate in the overspray. A reuse of the overspray without color matching could be problematic.

In the so-called “bonding-process”, the metallic flakes are thermally and mechan­ically bonded to the surface of the resin powder, avoiding separation in the overspray and thereby giving problem-free reuse of the material. Furthermore there are op­tical advantages in bonded metallic powder coatings due to the very homogeneous distribution of the metallic flakes.

Today, there are many applications for metallic effect powder coatings, such as steel furniture, tools, transportation, household equipment, architectural coatings etc.

Besides regular aluminum and gold bronze pigments in powdered form there are specially treated (coated) metal pigments available for powder coatings, achieving chemical resistance, good chargeability, compatibility and pigment distribution.

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