New insight into the kinetics of diisocyanate-alcohol reactions by high-performance liquid chromatography and mass spectrometry

摘要

The uncatalyzed reactions of 2,4-TDI (2,4-toluenediisocyanate) and MDI (4,4-diphenylmethane-diisocyanate) with alcohols including butan-1-ol, butan-2-ol, diethylene glycol monomethylether (DEGME) were studied by high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS). The reactions were carried out at different temperatures from 22 degrees C to 75 degrees C using high molar ratios of alcohols to diisocyanates. It was found that the first isocyanate group of the MDI reacts about 1.5 times faster with the alcohols than the second one. The relative reactivities of the isocyanate groups (para and ortho) of 2,4-TDI as a function of the temperature was also deduced. From the temperature dependence of the rate constants the apparent activation energies were determined. Furthermore, the dependence of the apparent rate constant on the concentration of alcohols was also investigated and a mechanism was proposed for the reaction of diisocyanates with alcohols. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42127.