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US 4,786,697 AGranted
Molecular weight distribution modification in a tubular reactor
AssigneeExxon Research & Engineering Co.
InventorsCharles Cozewith, Shiaw Ju, Gary W. Verstrate
Life of this patent
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Abstract
Polymodal MWD ethylene copolymer comprising at least two modes of differing molecular weights. Each mode has at least one of M.sub.w /M.sub.n of less than 2.0, and a M.sub.z /M.sub.w of less than 1.8. The polymodal character of the copolymer is achieved by either (1) withdrawing polymer modes from the reactor from at least one takeoff port, and blending such modes with the reactor effluent, or (2) utilizing at least two catalyst species in the reaction to produce modes of differing molecular weights.
Claims24
A method for preparing a polymodal MWD ethylene copolymer which comprises:
- (a) conducting the polymerization in a substantially mix free reactor;
- (b) using at least two catalyst species each of which initiates a polymer chain of a different molecular weight than the other catalyst species;
- (c) using at least one reaction mixture comprising ethylene and at least one alpha-olefin monomer, said reaction mixture being essentially transfer-agent free;
- (d) in such a manner and under such conditions sufficient to initiate propagation of essentially all copolymer chains simultaneously;
- the resulting polymer comprising at least two modes of differing molecular weights, each mode having at least one of M.sub.w /M.sub.n of less than 2 and M.sub.z /M.sub.w of less than 1.8, the resulting polymer being a polymodal MWD ethylene copolymer.
2 more elements
Dependencies are inferred from the claim text.