Preventing the yellowing of clear coats in multilayer color and effect paints, involves incorporation of blocked polyisocyanate in the primer, applying thermally curable clear coat and curing primer and clear coat

摘要

Preventing the yellowing of clear coats involves (1) application of a pigmented primer paint containing an isocyanate reactive group and a blocked polyisocyanate as crosslinker, (2) application of a thermally curable clear coat, via epoxide groups or thermally cured via epoxide groups to give a clear coat layer and (3) mutual curing of the primer and clear coat. A process for retarding the yellowing of clear coats in multilayer color and effect paints deposited by a wet on wet process by: (1) application of at least one pigmented primer paint containing (A) at least one independently crosslinked primer binder and at least one isocyanate reactive group and (B) at least one blocked polyisocyanate as crosslinker, (AB) at least one self-crosslinked primer binder with at least one isocyanate reactive group and at least one blocked polyisocyanate group, to an optionally primed base, where at least one primer layer is the resu (2) application of at least one thermally curable clear coat, via epoxide groups or thermally cured via epoxide groups and with actinic radiation to the primer layer, to give at least one clear coat layer; and (3) mutual curing of the primer layer or layers and the clear coat layer or layers. The blocking agent is selected from: pyrazole, 2,2,4-triazole, and substituted 1,2,4-triazoles.