ALIPHATIC ISOCYANATES BLOCKED WITH VOLATILE ALCOHOLS FOR DECORATIVE COATINGS

Aliphatic polyisocyanates blocked with simple aliphatic alcohols, such as methanol and ethanol, are widely thought to require baking tempera tures and times that are too high and/or too long for application of d ecorative coatings under production conditions. Here we show that poly isocyanates blocked with these alcohols can, when catalyzed with organ otin catalysts, crosslink an acrylic polyol at temperatures comparable to those of commercial epsilon-caprolactam blocked crosslinkers. With 0.5% of dibutyl tin diacetate catalyst, methanol blocked 1,3-bis (1-i socyanato-1-1methylethyl) benzene (TMXDI) and methanol blocked hexamet hylene diisocyanate isocyanurate are effective crosslinkers for an acr ylic polyol at 145 to 155 degrees C. It is theorized that physical fac tors (blocking agent diffusion rate and volatility) strongly influence cure response.