Reaction kinetics of dicyclohexylmethane-4,4'-dilsocyanate with 1-and 2-butanol: A model study for polyurethane formation

摘要

Reactions of dicyclohexylmethane-4,4-diisocyanate (H12MDI) with 1- or 2-butanol in N,N-dimethylformamide using dibutyltin dilaurate (DBTDL), stannous octoate (SnOct), or triethylamine (TEA) as catalyst were conducted in stirred reactors at 40 degrees C. Reactor contents were circulated through an external loop containing a temperature-con trolled FTIR transmission cell; reaction progress was monitored by observing decrease in height of the isocyanate peak at 2266 cm(-1). Catalyzed reactions were second order as indicated by linear 1/[NCO]plots; uncatalyzed reactions yielded nonlinear plots. In all cases, the reaction with a primary alcohol was faster than that with a secondary alcohol. DBTDL dramatically increased the reaction rate with both primary and secondary alcohols. For [DBTDL] = 5.3 x 10(-5) mol/L (300 ppm Sn) the second-order rate constant, k, was 5.9 x 10(-4) (primary OH) and 1.8 x 10(-4) L/(mol s) (secondary OH); for both alcohols, this represents an increase in initial reaction rate on the order of 2 x 10(1) when compared with the uncatalyzed reactions. The second-order rate constant was observed to increase linearly with DBTDL concentration in the range 100-700 ppm Sn. SnOct and TEA showed little to no catalytic activity with the primary alcohol and only a slight increase in reaction rate with the secondary alcohol. (c) 2008 Wiley Periodicals, Inc.