Automotive boots chloroprene rubber composition for chloroprene rubber, formed by using the same, and chloroprene rubber composition excellent in dynamic fatigue resistance

摘要

PROBLEM TO BE SOLVED: To obtain the subject chloroprene rubber for chloroprene rubber composition having excellent dynamic fatigue resistance without deteriorating the scorch time of unvulcanized compound or the mechanical properties of vulcanized product by polymerizing chloroprene in such a manner as to get an elastic stress fall-ing within a prescribed range. SOLUTION: The objective chloroprene rubber is produced by carrying out emulsion polymerization of 2-chloro-1,3-butadiene and =50 wt.% of a comonomer copolymerizable therewith such as 2,3-dichloro-1,3-butadiene at a palymerization temperature of 5-50 deg.C while controlling the Mooney viscosity using ndodecyl- mercaptan as a molecular weight controlling agent and suppressing the formation of branched structure in the presence of an emulsifier such as rosic acid potassium salt under a condition to get an elastic stress Y satisfying the formula Y=0.023X+5.28 (X is Mooney viscosity; 55=X=85). The chloroprene rubber is useful e.g. for a uniform velocity joint boot of automobile.