Crosslinking with malonate blocked isocyanates and with melamine resins

Automotive clearcoats with improved acid etch resistance are being formulated using a combination of a dialkyl malonate blocked polyisocyanate, a melamine crosslinker, and an acrylic polyol,^1,2 These coatings contain lower levels of melamine crosslinker compared to conventional acrylic/HMMM systems and show excellent acid etch resistance. We explored the reaction mechanism of this complex crosslinking system and found explanations for the good chemical resistance properties. Presented at the 25th International Waterborne, High-Solids, and Powder Coatings Symposium, February 18–20, 1998, New Orleans, LA. Science Rd., Norwalk, CT 06852; E-mail: AlexHe@Kingindustries.com and Wblank@Kingindustries.com.