Cathode electrodeposition paint to form a film with improved surface smoothness

摘要

A negative electrode electrodeposition paint containing an epoxy resin modified with a cation dispersed in an aqueous medium of an acid and a crosslinking agent is disclosed. The paint contains an auxiliary resin component which can improve the surface smoothness of the cured paint film. The auxiliary resin is a reaction product produced by reacting an active hydrogen compound with a t-alkylphenol novolac epoxy resin to open all the epoxy rings. When there is a hydroxyl group introduced into the auxiliary resin by reaction with an active hydrogen compound, the lactone or the alkylene oxide is additionally reacted with the hydroxyl group to graft the soft portion to the auxiliary resin. By grafting the soft part, the auxiliary resin not only improves the surface smoothness of the paint film but also the impact strength.