THE KINETICS OF DISSOCIATION OF BLOCKED 2,4-DIISOCYANATOTOLUENE (TDI)IN AMINES

The kinetics of dissociation of blocked diisocyanates based on commerc ial diisocyanatotoluene (TDI) (80/20 mixture of 2,4- and 2,6- isomers) in the presence of amino compounds was studied by a volumetric method and Fourier Transform IR (FTIR) spectral data. Second-order rate cons tants for the dissociation of TDI adducts (with phenol, thiophenol and p-chlorophenol) in the presence of amines (dibenzyl, benzyl, cyclohex yl, n-hexyl and di-n-butyl) in cyclohexanone solvent are reported. The relative effects of various blocking agents, basicity of the amines a nd temperature on the dissociation of blocked TDI have been determined . An FTIR spectroscopic method was used to study the dissociation of b locked TDI (with blocking agents such as phenol, thiophenol, p-chlorop henol, p-nitrophenol, p-cresol, alpha-naphthol and resorcinol) in the presence of excess triethylamine and in cyclohexanone solvent. Pseudo- first-order rate constants were calculated from NCO concentrations as determined from FTIR spectra.