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US 5,852,143 AGranted
Production of polyethylene using stereoisomeric metallocenes
AssigneeUnion Carbide Chemicals & Plastics Technology Corporation
InventorsPurna Chand Sishta, Eric Paul Wasserman, Frederick John Karol
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Abstract
Polyethylene having a broad molecular weight distribution, a narrow comonomer distribution and excellent processability is easily and cost effectively made using stereoisomeric mixtures of bridged metallocene catalysts containing cycloalkadienyl ligands with facial chirality.
Claims5
A process for producing polyethylene, which comprises contacting under gas phase polymerization conditions ethylene and optionally a higher alpha-olefin with an unsupported, liquid catalyst composition comprising:
- a) racemic and meso stereoisomers of a bridged metallocene catalyst containing two cycloalkadienyl ligands joined by a bridging linkage and complexed to a metal atom, each cycloalkadienyl ligand having facial chirality, and
- b) a cocatalyst selected from the group consisting of methylaluminoxane and modified methylaluminoxane, wherein the polyethylene produced has a Polydispersity Index of at least about 3.0, a melt index, MI, and Relaxation Spectrum Index, RSI, such that (RSI)(MI.sup..alpha.)>about 26 when .alpha. is about 0.7, a Crystallizable Chain Length Distribution Index, L.sub.w /L.sub.n, of less than about 3, and at least about 0.3 long chain branches per 1000 main chain carbon atoms.
Dependencies are inferred from the claim text.