Patent ID: 8258213

Claim:
A rubber composition for a breaker topping comprising 15 to 50 parts by weight of carbon black, 5 to 50 parts by weight of silica and 1.0 to 3.0 parts by weight of benzothiazolyl sulfenamide represented by the chemical formula (1): wherein R 1 is a hydrocarbon group selected from tert-butyl, 2-ethylhexyl, 2-methylhexyl, 3-ethylhexyl, 3-methylhexyl, 2-ethylpropyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylheptyl and 2-ethyloctyl and R 2 is a hydrocarbon group selected from tert-butyl, 2-ethylhexyl, 2-methylhexyl, 3-ethylhexyl, 3 methylhexyl, 2-ethylpropyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylheptyl and 2-ethyloctyl or a benzothiazolyl sulfide group, based on 100 parts by weight of a rubber component (provided that a butadiene rubber containing 1,2-syndiotactic polybutadiene crystals is not included) consisting of 10 to 45% by weight of a modified butadiene rubber and/or a modified styrene-butadiene rubber and 55 to 90% by weight of a natural rubber and/or an isoprene rubber, wherein the modified butadiene rubber is the modified butadiene rubber obtained by carrying out the polymerization of 1,3-butadiene by a lithium initiator and then adding a tin compound or the modified butadiene rubber modified with a compound represented by the formula (2): wherein R 3 , R 4 and R 5 are an alkyl group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof, R 6 and R 7 are a hydrogen group or an alkyl group and n represents an integer, and wherein the modified styrene-butadiene rubber is the modified styrene-butadiene rubber coupled with tin and silicon or the modified styrene-butadiene rubber having a primary amino group and an alkoxysilyl group.