| abstract |
The rubber for high-performance tire tread of the invention basically includes: (a) about 10%-50% weight percentage low molecular weight coupled copolymer of aromatic vinyl compound and conjugated diene or conjugated diene monopolymer, having a molecular weight of 5X10<SP>4</SP>#35X10<SP>4</SP>,(b) about 10%#60% weight percentage middle molecular weight uncoupled copolymer of aromatic vinyl compound and conjugated diene, having a molecular weight of 10X10<SP>4</SP>#80X10<SP>4</SP>, and ( c) 5#60% weight percentage high molecular weight coupled copolymer of aromatic vinyl compound and conjugated diene, having a molecular weight of 45X10<SP>4</SP>#200X10<SP>4</SP> . The coupling agent used for the polymer parts [a] and [c] is a compound of the formula R m MX n-m or (RO) k MX n-k , M = Sn, P, Ga or Is; X = halide; R = paraffin HC, cyclane or aromatic and n is the valency no of M and = 3 or 4, and m#2 and k#4. In the examples the polymer is prepared by sequential polymerisation in organic solvent using organometallic initiators. |