Patent ID: 7550176
Filing Date: 2009-06-23
Classification: B05D,C09D

Abstract:
1. A method of forming a coating film on an aluminum substrate, comprising the steps of: (1) coating an aluminum substrate with a thermosetting polyester resin lustrous powder base coating composition (a) containing a lustrous material, and baking the resulting base coat layer; and (2) coating the base coat layer with a thermosetting acrylic resin clear powder coating composition (b), and baking the resulting clear coat layer to obtain a lustrous multilayer coating film; the lustrous powder base coating composition (a) comprising a carboxyl-containing polyester resin as a base resin, and a β-hydroxyalkylamide as a crosslinking agent: the clear powder coating composition (b) comprising an epoxy-containing acrylic resin as a base resin, and a polycarboxylic acid and/or anhydride thereof as a crosslinking agent; the ratio of the β-hydroxyalkylamide to the carboxyl-containing polyester resin being such that the number of β-hydroxyalkylamide hydroxyl groups is about 1.2 to about 1.6 per polyester resin carboxyl group; and the ratio of the polycarboxylic acid and/or anhydride thereof to the epoxy-containing acrylic resin being such that the total number of carboxyl groups and anhydride groups thereof in the polycarboxylic acid and/or anhydride thereof is about 0.6 to about 0.9 per acrylic resin epoxy group.