CATIONIC RESIN CONTAINING BLOCKED ISOCYANATE GROUPS SUITABLE FOR USE IN ELECTRODEPOSITION

摘要

A cationic resin containing blocked isocyanate groups which is suitable for use in electrodeposition is disclosed. The cationic resin is derived from an epoxy resin and contains in the resin molecule cationic salt groups, active hydrogen groups and blocked isocyanate groups. The blocked isocyanate groups are incorporated into the resin molecule by reacting the epoxy resin with a compound selected from the class consisting of mercapto compounds and acid group-containing compounds where the compounds also contain blocked isocyanate groups. The resin can be formulated into an electrocoating composition which is free of lead and yet provides outstanding corrosion resistance when electrodeposited over steel substrates. The outstanding corrosion resistance can be attained when the substrate has not been given a chrome rinse which is conventional in pretreating the steel substrate before electrodeposition.