Effect of catalysts on the reaction between a cycloaliphatic diisocyanate (H‐MDI) and n‐butanol

Kinetics of the reaction between bis(4‐isocyanatocyclohexyl)methane, H‐MDI, and n‐butanol was studied in toluene at 100°C. Effects of various catalysts, such as Hg(CH3COO)2, Zn(CH3COO)2 · 2H2O, SnCl4 · 5H2O, and dibutyltindilaurate on the reaction rate and kinetics were also investigated. Reactions were followed by determining the unreacted isocyanate as a function of reaction time, using the standard dibutylamine back titration method. All catalysts seem to be very effective in increasing of the rate of the reaction compared to the uncatalyzed system. Depending on the initial stoichiometric ratio of (NCO) and (OH) and the concentration of the catalyst used, it seems possible to have preferential catalysis of the primary reaction between (NCO) and (OH) over the side reactions.