SOLID POLYMERS BINDERS FOR HEAT-HARDENING POWDER VARNISHES BASED ON CARBOXYL GROUP-CONTAINING POLYURETHANE PRE-POLYMERS WITH CAPTED ISOCYANATE GROUPS, THIS BINDER CONTAINING POWDER LACQUER METALS AND VARNISHES.

摘要

A solid polymer binder for thermosetting powder coating compositions obtained by combining (A) a polyurethane prepolymer containing carboxyl groups and derived from polyisocyanates, hydroxycarboxylic acids and blocking agents different from oximes, containing 1 to 40% by weight of blocked isocyanate groups and having an acid number of 1 to 80, with (B) at least one homo- and/or heterofunctional compound which either contains hydroxyl groups or is capable of forming them by reaction, component (B) being present in an amount such that cross-linked products are formed under stoving conditions, in which the content of COOH-groups is not higher than 1.5% referred to the weight of components (A) and (B), a thermosetting powder composition containing such binder, a metal object coated with such thermosetting powder coating composition, and a process for the manufacture of coatings on metal substrates with such powder coating composition.