ETHYLENE/PROPYLENE COPOLYMER RUBBERS

A process for the production of EPRs comprising contacting ethylene, propylene, and, optionally, a diene, under polymerization conditions, with a catalyst system comprising: (A) a catalyst precursor comprising: (i) a vanadium compound, which is the reaction product of (a) VX3 wherein each X is independently chlorine, bromine, or iodine; and (b) an electron on donor, which is a liquid, organic Lewis base in which VX3 is soluble; (ii) a modifier having the formula BX3 or AlR(3-a)Xa wherein each R is independently alkyl having 1 to 14 carbon atoms; each X is as defined above; and a is 1 or 2; and (iii) a support for said vanadium compound and modifier, said catalyst precursor being in an independent or prepolymerized state, wherein said in independent catalyst precursor or said prepolymerized catalyst precursor have been pre-oxidized with an oxidant in an amount sufficient to increase the oxidation state of the vanadium by at least one; (B) a cocatalyst consisting essentially of a compound having the formula AlR(3-a)Xa and, optionally, a compound having the formula AlR3 wherein R, X, and a are as defined above; and, (C) optionally, a promoter, which is a chlorinated ester having at least 2 chlorine atoms; a saturated or unsaturated aliphatic halocarbon having at least 3 carbon atoms and at least 6 halogen atoms; or a haloalkyl substituted aromatic hydrocarbon wherein the haloalkyl has at least 3 halogen atoms.