Technique for stablizing tin-coupled elastomers

Abstract

The process of this invention can be utilized to stabilize tin-coupled rubbery polymers. It is particularly useful for stabilizing rubbery polymers that do not contain bound styrene. This invention more specifically discloses a process for improving the stability of a tin-coupled rubbery polymer which comprises (1) adding 0.1 phr to about 4 phr of styrene to a living rubbery polymer to produce a styrene capped rubbery polymer, (2) adding a tin halide to the styrene capped living rubbery polymer to produce the tin-coupled rubbery polymer, and (3) optionally, adding a tertiary chelating alkyl 1,2-ethylene diamine or a metal salt of a cyclic alcohol to the tin-coupled rubbery polymer. The use of metal salts of cyclic alcohols is preferred because they do not lead to recycle stream contamination. This is because cyclic alcohols do not co-distill with hexane or form compounds during steam-stripping which co-distill with hexane. In other words, the boiling points of these metal salts of cyclic alcohols are very high, so they do not co-distill with hexane and contaminate recycle streams. Additionally, metal salts of cyclic alcohols are considered to be environmentally safe. In fact, sodium mentholate is used as a food additive.

Dependencies are inferred from the claim text.