Patent Number: 6,293,325

Title: Technique for reducing the cold flow of rubbers

Abstract: Cold flow is a problem that is commonly encountered in the handling andstorage of low molecular weight linear rubbers, such as low vinylpolybutadiene rubber and isoprene-butadiene rubber. This invention isbased upon the unexpected discovery that the cold flow of such rubberypolymers can be greatly reduced by incorporating a small block ofpolystyrene therein. The rubbery polymers of this invention which exhibita low level of cold flow can be synthesized by simply terpolymerizing1,3-butadiene, isoprene and from about 0.5 phm to about 3 phm of styreneunder anionic polymerization conditions in the absence of a polarmodifier. It is preferred to utilize batch .polymerization techniques.However, continuous polymerization techniques can also be utilized. Thisinvention more specifically disclosed a rubbery polymer which is comprisedof polymer chains containing repeat units which are derived from1,3-butadiene, isoprene and from about 0.5 weight percent to about 3weight percent styrene, wherein the repeat units which are derived fromstyrene are in blocks at the ends of the polymer chains, wherein therubbery polymer has a glass transition temperature which is within therange of about -105.degree. C. to about -65.degree. C. and wherein therubbery polymer has a number average molecular weight which is within therange of about 50,000 to about 600,000.

Inventors: Hsu; Wen-Liang (Cuyahoga Falls, OH), Halasa; Adel Farhan (Bath, OH)

Assignee:

International Classification:

Expiration Date: 09/25/2013