The thermal degradation of a polythiolcarbamate

On pyrolysis at 300° under nitrogen the polythiolcarbamate from methylenebis(4‐phenyl isocyanate) and 1,6‐hexanedithiol decomposed into carbon dioxide, carbonyl sulfide, 6‐mercapto‐1‐hexene, tetrahydro‐2‐methyl‐1‐thiapyran, thiepane, 1,6‐hexanedithiol, and an intractable residue. Carbodiimide and amine groups were shown to be intermediates in the formation of the residue. A quantitative study of the degradation indicated that about 80% of the thiolcarbamate groups decomposed by splitting into isocyanate and mercaptan moieties. Further reaction of the isocyanate moiety produced the carbon dioxide and carbodiimide groups. The remaining thiolcarbamate groups formed carbonyl sulfide, and amine and olefin groups, probably by a direct ester type of degradation. The resulting 6‐mercapto‐1‐hexene was the source of the cyclic sulfides.