High activity carbenium-activated polymerization catalysts
AssigneeExxonMobil Chemical Patents Inc.
InventorsDonna Jean Crowther, Bernard Jean Folie
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Abstract
This application discloses triphenyl carbenium NCA's as catalyst activators for a class of asymmetrically bridged hafnocene catalyst precursors. These catalyst precursors are activated into olefin polymerization catalysts and are suitable for gas, solution, and slurry-phase polymerization reactions. The disclosed bridge is methylenyl- or silanylenyl-based and is optionally, alkyl or aryl substituted. The catalytic activity of the disclosed hafnocene catalyst precursors is substantially enhanced over identical catalysts that are activated with other activators.
Claims4
A metallocene catalyst system comprising an ion pair formed by contacting a metallocene and an activator wherein:
- (a) the metallocene is described by the formula T(CpRn)(Cp′R′m)HfQ2 wherein
- (i) Cp and Cp′ are cyclopentadienyl ligands
- (ii) Each R and R′ are the same or different hydrocarbyl radicals having 1-20 carbon atoms;
- (iii) T is a bridge between Cp and Cp′, and comprises a substituted or unsubstituted methylene or silylene radical;
- (iv) each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen
- (v) n is the number of hydrocarbyl substituents on Cp and n=0-4;
- (vi) m is the number of hydrocarbyl substituents on Cp′ and m=0-4;
- and
- (b) the activator is described by the formula:
- [Ar3C][NCA] wherein
- (i) Ar is an aryl ligand
- (ii) Ar3C is a triarylcarbenium;
- and
- (iii) NCA is a non-coordinating anion.
Dependencies are inferred from the claim text.