Patent ID: 6858686

Claim:
A process for obtaining a polyisoprene from a steam-cracked C5 naphtha fraction enriched with isoprene comprising: reacting the steam-cracked C5 naphtha fraction enriched with isoprene in the presence of a catalytic system, wherein said C5 fraction has a mass fraction of isoprene in a range of from 30% to 95%, and wherein said catalytic system is based on at least: (a) a conjugated diene monomer, (b) an organic phosphoric acid salt of a rare earth metal, (c) an alkylating agent consisting of a trialkylaluminum compound or a dialkylaluminum hydride, and (d) a halogen donor consisting of an alkylaluminum halide, wherein said rare earth salt is suspended in at least one inert saturated aliphatic or alicyclic hydrocarbon solvent which is included in said catalytic system, and the molar ratio of alkylating agent:rare earth salt is in a range of from 1 to 5.