Kinetics and Catalysis of Urethane Foam Reactions

Abstract

Since the rates of chemical reactions in volved in cellular urethane formation are decisive for product quality, model reactions were kinetically investigated and the mech anism of catalysis was studied. A simple rela tionship found between the specific rate con stant and the molar ratio of alcohol/catalyst for an alcohol/isocyanate reaction catalyzed by stannous octoate suggests the formation of an activated intermediate complex. The balance between the alcohol/isocyan ate and water/isocyanate reaction rates is important. Organotin compounds promote the former rate more than the latter whereas the reverse holds for amine catalysts. The rates of both reactions, catalyzed by amines with and without stannous octoate as co catal yst, demonstrate a synergistic effect ex plained by the extra stability imparted to the activated intermediate complex by attach ment of the amine.