SUPPORTED METALLOCENE CATALYSTS

摘要

Supported metallocene catalysts and processes for the use of such catalysts in isotactic polymerization of a C3+ ethylenically unsaturated monomer. The supported catalysts comprise a particulate silica support, an alkyl alumoxane component, and a metallocene catalyst component. The support has an average particle size of 10-50 microns, a surface area of 200-800 m<2>/g and a pore volume of 0.9-2.1 milliliters per gram (ml/g). alumoxane is incorporated onto the support to provide a weight ratio of alumoxane to silica of at least 0.8:1. The metallocene is present in an amount of at least 1 weight percent of the silica and the alumoxane and is of the formula B(CpRaRb)(Fl')MQ2 in which Fl' is an unsubstituted fluorenyl group or a fluorenyl group symmetrically substituted at the 3 and 6 positions, B is a structural bridge between Cp and Fl', Ra is a bulky substituent in a distal position, Rb is a less bulky substituent in a distal position, Rb is a less bulky substituent proximal to the bridge and non-vicinal to the distal substituent, M is a Group IVB transition metal or vanadium, and Q is a halogen or a C1-C4 alkyl group.