Development of novel crosslinking system based on equilibrium reaction of thermal dissociation of hemiacetal ester

Novel thermal latent hardeners containing blocked carboxyl groups with alky l vinyl ethers ie. hemiacetal esters, have been developed. They showed liqu id form or lower melting point and excellent solubility and compatibility. Although the blocked carboxyl groups were stable under usual condition, the y could regenerate the corresponding free carboxyl groups by thermal dissoc iation of hemiacetal ester. A novel crosslinking system between blocked car boxyl group and epoxide was examined. The new one-package thermosetting coa tings provided by the system have been applied to practical automotive and coil coatings line production. The formed coatings have high level of acid resistance, corrosion resistance and weatherability with reduction of VOCs.