Ethylene/propylene copolymer rubbers

摘要

A process comprises contacting a mixt. comprising ethylene. propylene and opt. a diene, in the gas phase, under polymerisation conditions, with a catalyst system. The catalyst system comprises: (a) a catalyst precursor, in independent or prepolymer form, consisting of vanadium (acetylacetonate)3; (b) opt. a support for (a); (c) a cocatalyst consists of (i) an alkylaluminium halide of formula ALR(3-a)Xa (R = 1-14C alkyl, X = Cl, Br or I and a = 1 or 2) and (ii) opt. a trialkylaluminium in a molar ratio of at least 1.5:1; and (d) a promoter which is a chlorinated ester having at least 2 Cl atoms; an (un)satd. aliphatic halocarbon having at least 3C atoms and at least 6 halogen atoms; or a haloalkyl substd. aromatic hydrocarbon wherein the haloalkyl substit. has at least 3 halogen atoms. Also claimed are: (1) a process as above comprising contacting in a fluidised bed, where the catalyst system comprises (a), (b) a silica support, (c) diethylaluminium chloride and (d) ethyl trichloroacetate (pref. 800-1400 pts. per million polymer in fluidised bed) and the amt. of cocatalyst is 1000-10,000) (pref. 1500-5000) pts. per million pts.wt. of polymer in fluidised bed; and (2) a process for preparing homogeneous polyethylene by contacting a mixt. comprising ethylene and an alpha-olefin(s) in the presence of the above catalyst system. The cocatalyst is pref. an alkylaluminium halide, esp. diethylaluminium chloride or it is an alkylaluminium halide and trialkylaluminium mixt. in a molar ratio of 2:1-3:1 (pref. diethyl aluminium chloride and triethyl aluminium mixt.). The promoter is pref. ethyl trichloroacetate. The molar ratio of cocatalyst to vanadium is pref. 10:1-500:1.