Aminoplast-based crosslinkers and powder coating compositions containing such crosslinkers

摘要

A crosslinking agent having reactive benzoxazine groups is provided. The crosslinking agent is the ungelled reaction product of a polyhydric aromatic compound and an aminotriazine compound having one or less non-alkylated NH bond per triazine ring. The crosslinking agent is essentially free of hydroxyl functionality and has a glass transition temperature of at least 10° C. Additionally provided is a method for preparing the crosslinking agent. Also provided is a curable powder coating composition including a solid particulate, film-forming mixture of a polymer having functional groups reactive with benzoxazine groups and the crosslinking agent. Further provided is a multilayer composite coating composition having a base coat layer deposited from a film-forming base coating composition and a topcoat layer deposited from the curable powder coating composition. Coated substrates are also provided.