Patent ID: 8299188

Claim:
A method for the production of an isotactic ethylene propylene copolymer comprising: (a) providing a supported metallocene catalyst comprising: (i) an isospecific metallocene catalyst component of the formula: B′(Cp′R′aR′b)(Fl′)M′Q′ n (2) wherein: Cp′ is a substituted cyclopentadienyl group, Fl′ is a fluorenyl group, B′ is an isopropylidene group, R′a is a substituent on the cyclopentadienyl group which is in a distal position to the bridge and comprises a bulky group of the formula XR* 3 in which X is carbon or silicon and R* is the same or different and is chosen from hydrogen or a hydrocarbyl group having from 1-20 carbon atoms, provided that at least one R* is not hydrogen, R′b is a substituent on the cyclopentadienyl ring which is proximal to the bridge and positioned non-vicinal to the distal substituent and is of the formula YR# 3 in which Y is silicon or carbon and each R# is the same or different and chosen from hydrogen or a hydrocarbyl group, an alkoxy group, a thioalky group or an amino, alkyl group containing from 1 to 7 carbon atoms and is less bulky than the substituent R′a M′ is a transition metal selected from the group consisting of titanium, zirconium, hafnium and vanadium, Q′ is a halogen or a C 1 -C 4 alkyl group; and n′ is an integer of from 0-4, (ii) an alkylalumoxane cocatalyst component, and (iii) a particulate silica support characterized by a particle size of 20-35 microns, a surface area of 200-400 m 2 /gram, a pore volume within the range of 1.3-1.6 ml./gram and a pore diameter within the range of 200-240 Å, (b) contacting said catalyst in a polymerization reaction zone with a mixture of propylene and ethylene in an amount within the range of 0.01-20 mole percent of ethylene in said ethylene-propylene mixture, and; (c) operating said reaction zone under a temperature and pressure conditions effective to provide for the isospecific polymerization of said propylene in the presence of said ethylene at a production of at least 1000 grams of polymer per gram of catalyst to produce an isotactic ethylene propylene copolymer having a melting temperature of no more than 150° C.