A novel binder suitable for cationic electrodeposition coatings based on a non-isocyanate chemistry

A non-polyisocyanate resin system that can be applied to cationic electrodeposition (CED) paint has been developed. Most of the compositions of binders currently on the market as CED coatings are composed of modified epoxy resins and blocked polyisocyanates, their crosslinking essentially being polyurethane or polyurea formation. This report deals with a new resin system of which crosslinking is based on a ring-opening/etherification reaction between epoxy groups and hydroxyl groups. The ring-opening addition reaction has very low emissions during the baking process. However, it is difficult to attain a compromise between satisfactory reactivity at elevated temperatures and stability in aqueous composition. By a series of careful investigations, we have established the composition of CED coatings that are sufficiently stable and can be satisfactorily cured. The CED paint formulated on this resin system has such desirable properties as low weight loss upon baking, outstanding weatherability, and excellent chipping resistance. Other characteristics are comparable to existing polyisocyanate based CED coatings.