Patent ID: 7115693

Claim:
A process for preparing Bernoulli's statistical random copolymers of butadiene and isoprene, said process comprising copolymerizing butadiene and isoprene in the presence of a catalyst system comprising: (a) a conjugated diene monomer; (b) an organic phosphoric acid salt of at least one rare earth metal; (c) an alkylaluminum alkylating agent of the formula AlR 3 or HAlR 2 where R is an alkyl group; and (d) an alkylaluminum halide halogen donor, said salt being in suspension in at least one inert, saturated and aliphatic or alicyclic hydrocarbon solvent which is included in said catalytic system, the alkylating agent:rare earth salt molar ratio having a value of from 1 to 8, and wherein the copolymerization reaction optionally is conducted in an inert hydrocarbon solvent.