Hafnium metallocene catalyst for the polymerization of olefins
AssigneeFina Technology, Inc.
InventorJohn A. Ewen
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Abstract
The present invention provides a catalyst system for the polymerization and copolymerization of olefins with the system comprising a chiral, stereorigid hafnium metallocene catalyst in combination with an aluminum compound. The aluminum compound is preferably an alumoxane and may be a mixture of alumoxane and trimethyl aluminum. It was discovered that this mixture causes a transformation of the catalyst over time. The catalyst system may also include a solvent to increase the solubility of the metallocene catalyst. It was discovered that these catalyst systems produce useful polymer products with molecular weights greater than 10,000.
Claims8
A catalyst for the polymerization and copolymerization of olefins comprising a an alumoxane and chiral, stereorigid hafnium metallocene catalyst described by the formula
- R"(C.sub.5 (R').sub.4).sub.2 HfQ.sub.p
- wherein (C.sub.5 (R').sub.4) is a cyclopentadienyl or substituted cyclopentadienyl ring;
- each R' is the same or different and is a hydrogen or a hydrocarbyl radical having from 1-20 carbon atoms;
- R" is a structural bridge between the two (C.sub.5 (R').sub.4) rings imparting stereorigidity to said catalyst and R" is selected from the group consisting of an alkylene radical having 1-4 carbon atoms, a silicon hydrocarbyl radical, a germanium hydrocarbyl radical, a phosphorus hydrocarbyl radical, a nitrogen hydrocarbyl radical, a boron hydrocarbyl radical, and an aluminum hydrocarbyl radical;
- each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen;
- and O.ltoreq.P.ltoreq.3.
Dependencies are inferred from the claim text.