Storage-stable PU powder coating compositions and their use for flexible, low-haze polyurethane coatings

Abstract

The present invention relates to PU powder coating compositions based on semi-crystalline polyesters, amorphous polyesters and blocked polyisocyanates and to their use for flexible, low-haze polyurethane powder coatings and more particularly for powder coil coatings.

Description

technical field [0001] The present invention relates to PU powder coating compositions based on semi-crystalline polyesters, amorphous polyesters and blocked polyisocyanates, and their use in low haze, tough polyurethane powder coating materials, more particularly in powder coil coatings application. Background technique [0002] Thermosetting powder coating compositions are widely used in the production of crosslinked coatings on a wide variety of substrates. Compared to thermoplastic compositions, thermoset coating materials are generally harder, more resistant to solvents and detergents, have better adhesion to metal substrates, and do not soften when exposed to high temperatures. [0003] Thermosetting powdery materials obtained by reaction between hydroxyl-containing resins and externally or internally blocked polyisocyanates have been known since 1970. Such powders are described - for example - in DE 27 35 497 . With this powder, ready-formed metal parts are coated ...

AI Technical Summary

Problems solved by technology

[0015] It has been shown that the use of (semi)crystalline polyesters in powder coating materials increases the flexibility but at the same time brings with it 2 serious disadvantages: The crystalline component has a lowering of the glass transition point of the powder coating formulation Propensity

However, this product has a tendency to crystallize the cured paint film and thus cause the paint film to be cloudy