Supported metallocene catalysts

A supported metallocene catalyst useful in the polymerization of olefins comprising:

• a. a particulate silica support having an average particle size within the range of 10-50 microns, a surface area within the range of 200-800 m2/g, and a pore volume within the range of 0.9-2.1 ml/g;
• b. an alkylalumoxane cocatalyst component incorporated onto said silica support to provide a weight ratio of alkylalumoxane to silica within the range of 1:1-2:1;
• c. a metallocene catalyst component supported on said particulate silica support in an amount of at least 1 weight percent of said silica and said alkylalumoxane and characterized by the formula:
• wherein:
• Ra is a bulky hydrocarbyl group containing from 4 to 20 carbon atoms, Rb is a methyl, ethyl or isopropyl group, wherein the Rb is less bulky than the Ra;
• 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, 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.

A supported metallocene catalyst composition useful in the polymerization of olefins comprising:

• a. a particulate silica support of a spheroidal shape having an average particle size of about 21 microns, a pore volume of about 1.7 ml/g, and a surface area of about 600 m2/g;
• b. an alkylalumoxane cocatalyst component incorporated onto said silica support to provide a weight ratio of alkylalumoxane to silica of at least 0.8:1;
• c. a metallocene catalyst component supported on said particulate silica support in an amount of at least 1 weight percent of said silica and said alkylalumoxane and characterized by the formula:
• B(CpRaRb)(Fl′)MQ2
• wherein:
• Cp is a substituted cyclopentadienyl group, Fl′ is an unsubstituted fluorenyl group or a fluorenyl group which is symmetrically substituted at the 3 and 6 positions with C1-C4 hydrocarbyl groups, and B is a structural bridge between Cp and Fl′ imparting stereorigidity to said catalyst, 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 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, 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 containing from 1 to 7 carbon atoms and is less bulky than the substituent Ra, M is a Group IVB transition metal or vanadium;
• Q is a halogen or a C1-C4 alkyl group;
• and
• d. said alkylalumoxane component and said metallocene component being present in relative amounts to provide an Al/M mole ratio of at least 150.

In a method for the isospecific propagation of a polymer chain derived from an ethylenically-unsaturated monomer, comprising:

• a. providing a supported metallocene catalyst comprising an isospecific metallocene catalyst component of the formula:
• B(CpRaRb)(FlR′2)MQ2
• wherein:
• Cp is a substituted cyclopentadienyl group, Fl is a substituted fluorenyl group, and B is a structural bridge between Cp and Fl imparting stereorigidity to said catalyst, 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 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 Rb 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 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 1-20 carbon atoms with one R′ being substituted at a non-proximal position on the fluorenyl group and the other R′ being substituted at an opposed non-proximal position on the fluorenyl group, M is a Group IVB transition metal or vanadium;
• an alkylalumoxane cocatalyst component;
• a particulate silica support having an average particle size within the range of 10-50 microns and a surface area within the range of 200-800;
• and said metallocene catalyst component and said alumoxane cocatalyst component being supported on said particulate silica support in an amount to provide a weight ratio of said alumoxane to said silica support of at least 0.8 and a metallocene loading of at least 1 weight percent;
• contacting said catalyst in a polymerization reaction zone with an ethylenically-unsaturated monomer which contains 3 or more carbon atoms or which is a substituted vinyl compound;
• and
• b. operating said reaction zone under a temperature within the range of 55-70° C. to provide isospecific polymerization of said monomer at an activity of at least 1000 g/g/hr to produce a polymer having a melting temperature of at least 155° C.

In a method for the isospecific propagation of a polymer chain derived from an ethylenically-unsaturated monomer, comprising:

• a. providing a supported metallocene catalyst comprising an isospecific metallocene catalyst component of the formula:
• B(CpRaRb)(Fl′)MQ2
• wherein:
• Cp is a substituted cyclopentadienyl group, Fl′ is an unsubstituted fluorenyl group or a fluorenyl group which is symmetrically substituted at the 3 and 6 positions with C1-C4 alkyl groups, phenyl groups or 2,6 substituted phenyl groups, and B is a structural bridge between Cp and Fl′ imparting stereorigidity to said catalyst, 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 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, 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 containing from 1 to 7 carbon atoms and is less bulky than the substituent Ra, M is a Group IVB transition metal or vanadium;
• Q is a halogen or a C1-C4 alkyl group;
• and
• (ii) an alkylalumoxane cocatalyst component;
• (iii) a particulate silica support having an average particle size of about 21 microns, a pore volume of about 1.7 ml/g, and a surface area of about 600 m2/g;
• and
• (iv) said metallocene catalyst component and said alumoxane cocatalyst component being supported on said particulate silica support in an amount to provide a weight ratio of said alumoxane to said silica support of at least 0.8 and a metallocene loading of at least 1 weight percent.
• b. contacting said catalyst in a polymerization reaction zone with an ethylenically-unsaturated monomer which contains 3 or more carbon atoms or which is a substituted vinyl compound;
• and
• c. operating said reaction zone under a temperature within the range of 65-70° C. to provide isospecific polymerization of said monomer at an activity of at least 1000 g/hr. to produce a polymer having a melting temperature of at least 140° C.

In a method for the isospecific propagation of a polymer chain derived from an ethylenically-unsaturated monomer, comprising:

• a. providing a supported metallocene catalyst comprising an isospecific metallocene catalyst component of the formula:
• wherein:
• Ra is a bulky hydrocarbyl group containing from 4 to 20 carbon atoms, Rb is a methyl 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, 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, an alkylalumoxane cocatalyst component;
• a particulate silica support having an average particle size within the range of 10-50 microns and a surface area within the range of 200-800;
• and said metallocene catalyst component and said alumoxane cocatalyst component being supported on said particulate silica support in an amount to provide a weight ratio of said alumoxane to said silica support of at least 0.8 and a metallocene loading of at least 1 weight percent;
• b. contacting said catalyst in a polymerization reaction zone with propylene;
• and
• C. operating said reaction zone under a temperature within the range of 60-70° C. to provide isospecific polymerization of said propylene at an activity of at least 1000 g/g/hr to produce a polymer having a melting point of at least 155° C.