Supported metallocene catalysts

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(CpRaRb)(FlR′)MQn (1)
• wherein:
• Cp is a substituted cyclopentadienyl group,
• Fl is a fluorenyl group substituted at the 2 and 7 positions,
• B is an isopropylidene group
• Ra is a substituent on the cyclopentadienyl group which is in a distal position to the bridge and comprises a bulky group of the formula XR3 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,
• Rb 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 thioalkyl group, or an amino, alkyl group containing from 1 to 7 carbon atoms and is less bulky than the substituent Ra,
• each R′ is the same or different and is a hydrocarbyl group having from 4-20 carbon atoms and is more bulky than the substituted Rb with one R′ being substituted at the 2 position on the fluorenyl group and the other R′ being substituted at the 7 position on the fluorenyl group,
• M is a transition metal selected from the group consisting of titanium, zirconium hafnium and vanadium;
• Q is a halogen or a C1-C4 alkyl group,
• n is an integer of from 0-4,
• (ii) an alkylalumoxane cocatalyst component, and
• (iii) a particulate silica support,
• (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.

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 housing a bridged cyclopentadienyl fluorenyl ligand characterized by the formula:
• wherein Ra is a bulky hydrocarbyl group containing from 4 to 20 carbon atoms, Rb is a methyl group or ethyl group, R′ is a bulky hydrocarbyl group containing from 4 to 20 carbon atoms, M is a transition metal selected from the group consisting of titanium, zirconium, hafnium, and vanadium, Q is a halogen or a C1-C4 hydrocarbyl group, n is an integer of from 0 to 4, B is a structural bridge extending between the cyclopentadienyl and fluorenyl groups, and is an ethylene group or is characterized by the formula:
• wherein:
• b is a C1-C4 alkyl group or a phenyl group,
• (ii) an alkylalumoxane cocatalyst component, and
• (iii) a particulate silica support,
• (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 temperature and pressure conditions effective to provide for the isospecific polymerization of said propylene in the presence of said ethylene at an activity of at least 1000 grams of polymer per gram of catalyst to produce an isotactic ethylene propylene copolymer having a melt flow rate of no more than 80 grams per 10 minutes and a melting temperature of no more than 120° C.