COPOLIMERO CAUCHUTOSO DE ETILENO/PROPILENO

UN PROCESO PARA LA PRODUCCION DE CAUCHOS DE ETILENO Y PROPILENO QUE CONSISTE EN PONER EN CONTACTO ETILENO, PROPILENO Y, OPCIONALMENTE, UN DIENO, BAJO CONDICIONES DE POLIMERIZACION CON UN SISTEMA CATALIZADOR QUE COMPRENDE: (A) UN PRECURSOR CATALITICO QUE CONTIENE: UN COMPUESTO DE VANADIO; UN MODIFICADOR; Y UN SOPORTE EN DONDE DICHO PRECURSOR CATALITICO SE HA PREOXIDADO CON UN OXIDANTE EN UNA CANTIDAD SUFICIENTE COMO PARA QUE AUMENTE EL ESTADO DE OXIDACION DEL VANADIO EN AL MENOS UNO; (B) UN COCATALIZADOR; Y (C) OPCIONALMENTE UN PROMOTOR. The prodn. of ethylene/propylene rubbers (EPR) comprises contacting ethylene, propylene and, optionally, a diene, under polymerisation conditions with a catalyst system comprising: (A) a catalyst precursor comprising: (i) a vanadium cpd. comprising the reaction prod. of: (a) VX3, where X = Cl, Br or I; and (b) an electron donor comprising a liq. organic Lewis base in which (a) is soluble; (ii) a modifier of formula BX3 or AIR(3-a)Xa, where R = 1-14C alkyl and a = m1 or 2; and (iii) a support for (i) and (ii); the catalyst precursor is in an independent or pre-polymerised state and has been pre-oxidised with sufficient oxidant to raise the oxidn. state of the vanadium by at least one; (B) a cocatalyst of formula AIR(3-a)Xa; and (C) optionally, a promoter comprising a chlorinated ester with 2 or more Cl-atoms, a 3C or more (un)satd. aliphatic halocarbon contg. 6 or more halogen atoms or a haloalkyl-substd. aromatic hydrocarbon contg. 3 or more halogen atoms in the haloalkyl substituent. Also claimed is a process comprising contacting ethylene, propylene and optionally, a diene under polymerisation conditions in the presence of a catalyst.