| 摘要 |
PURPOSE:To obtain a vulcanized rubber having excellent impact resilience and flexing resistance, by vulcanizing a compsn. comprising a specific raw material rubber, a filler, sulfur and a vulcanizing accelerator. CONSTITUTION:A compsn. obtd. by compounding 100pts.wt. raw material rubber contg. not less than 30wt% branched polybutadiene rubber obtd. by polymn. using a lithium base catalyst (e.g. n-propyl-lithium) and then by coupling reaction with a branching agent (e.g. tetrachlorosilane) having 0.2-1.5 equivalent wt. to the catalyst whose weight-average MW (MW) measured by gel permeation chromatography is 50,000-500,000, having a monomodal MW distribution where the ratio of MW to number-average MW is 1.5-4.0, whose Mooney viscosity (ML) measured at 100 deg.C by using an L rotor is 20-90, whose soln. viscosity (SV) in 5wt% styrene at 25 deg.C is 20-100 cps and where the relation of (ML) and (SV) satisfies formula I, with 20-150pts.wt. filler, sulfur in doubled quantity (pts.wt.) of formula II of a straight chain polybutadiene rubber in which log SV/log MW relation is 1.30-1.35 and vulcanizing accelerator, is vulcanized at 130-200 deg.C to obtain a vulcanized rubber whose impact resiliences measured at 70 deg.C and 20 deg.C satisfy formula III.
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