Technique for reducing the cold flow of rubbers

Details Technique for reducing the cold flow of rubbers Technique for reducing the cold flow of rubbers

1997-06-13

2000-11-14

Henderson, Christopher

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

526340, C08F29300

Patent

active

06147164&

ABSTRACT:
Cold flow is a problem that is commonly encountered in the handling and storage of low molecular weight linear rubbers, such as low vinyl polybutadiene rubber and isoprene-butadiene rubber. This invention is based upon the unexpected discovery that the cold flow of such rubbery polymers can be greatly reduced by incorporating a small block of polystyrene therein. The rubbery polymers of this invention which exhibit a low level of cold flow can be synthesized by simply terpolymerizing 1,3-butadiene, isoprene and from about 0.5 phm to about 3 phm of styrene under anionic polymerization conditions in the absence of a polar modifier. It is preferred to utilize batch polymerization techniques. However, continuous polymerization techniques can also be utilized. This invention more specifically disclosed a rubbery polymer which is comprised of polymer chains containing repeat units which are derived from 1,3-butadiene, isoprene and from about 0.5 weight percent to about 3 weight percent styrene, wherein the repeat units which are derived from styrene are in blocks at the ends of the polymer chains, wherein the rubbery polymer has a glass transition temperature which is within the range of about -105.degree. C. to about -65.degree. C. and wherein the rubbery polymer has a number average molecular weight which is within the range of about 50,000 to about 600,000.

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