Patent ID: 7872066

Claim:
A rubber composition for belt use, comprising: (A) 90-5 mass % of a vinyl-cis-polybutadiene rubber including (b) 1-30 mass % of specific syndiotactic 1,2-polybutadiene crystal fibers having an average fiber length of crystal fibers equal to 200 nm or below, an average aspect ratio of 10 or lower, the number of crystal fibers having a fiber length of 200 nm or below equal to 90 or more per 25 μm 2 , and a melting point of 170° C. or higher, and (a) 99-70 mass % of a cis-polybutadiene rubber; (B) 10-95 mass % of a diene-based rubber other than (A); and (C) 20-70 parts by mass of a rubber reinforcing agent compounded on the basis of 100 parts by mass of the rubber components (A)+(B), wherein the rubber reinforcing agent (C) contains at least carbon black and silica, wherein the compounding amount of the silica in the rubber reinforcing agent is 70 mass % or less.