MINIMIZING NITROSAMINES USING STERICALLY HINDERED THIURAM DISULFIDES DITHIOCARBAMATES

Sulfenamide accelerators and sulfur donors based on secondary amines must liberate all of their amine in order to function. Consequently, they are capable of producing relatively large amounts of nitrosamines. Thiuram disulfides and dithiocarbamates, on the other hand, only liberate their amines because of undesired side reactions. Accordingly, compared to sulfenamides, they produce significant, but much lower levels of nitrosamines during the cure. In an effort to reduce these side reactions, and thus the amount of nitrosamine which forms, we investigated the effect of steric factors on nitrosamine formation. We find that thiurams and dithiocarbamates made from sterically bulky amines, like diisobutylamine, produce orders of magnitude lower levels of nitrosamine than TMTD. At the same time, when used as a kicker for 2-benzothiazole sulfenamides, N,N,N',N-tetraisobutylthiuram disulfide has better scorch safety but cures at the same rate as TMTD. Uniquely, N,N,N',N-tetraisobutylthiuram monosulfide acts as a retarder as well as a kicker for 2-benzothiazole sulfenamides.