| abstract |
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 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 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 substituent has at least 3 halogen atoms. |