摘要 |
The present invention relates in particular to a preparation process for a copolymer having two blocks usable in a sulphur-cross-linkable rubber composition of reduced hysteresis in the cross-linked state, such a block copolymer in which one of the blocks is constituted of a polyisoprene and the other of a diene elastomer other than a polyisoprene, and this rubber composition for tyre treads. A process for the preparation of this copolymer consists of copolymerising one or more monomers comprising a conjugated diene other than isoprene using a catalytic system comprising at least one hydrocarbon solvent, a compound A of a metal of group IIIA, a compound B of an alkaline-earth metal and a polymeric initiator C comprising a C-Li bond which is constituted of a monolithiated polyisoprene intended to form said polyisoprene block, the number-average molecular weight Mn1 of said polyisoprene block being between 2,500 and 20,000 g/mol, in order to obtain said copolymer in which the other block consisting of said diene elastomer has a number-average molecular weight Mn2 of between 65,000 and 350,000 g/mol and a content of trans-1,4 linkages equal to or greater than 70%.
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