Process for production of polyolefins
AssigneeE. I. Du Pont de Nemours and Company
InventorJoel David Citron
Life of this patent
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Abstract
Polyolefins, especially branched polyethylenes, can be made by combining a catalyst that can oligomerize ethylene to one or more alpha-olefins and a polymerization catalyst which can copolymerize ethylene and α-olefins, by first carrying out the process in, for example, a continuous stirred tank reactor or its equivalent, and then in a plug flow reactor or its equivalent. The process minimizes the occurrence of (unreacted) α-olefins in the final polymer product.
Claims20
A process for the production of a branched polyethylene comprising the steps of contacting, under polymerization conditions:
- (a) ethylene;
- (b) an oligomerization catalyst that oligomerizes ethylene to one or more α-olefins of the formula R20CH═CH2, wherein R20 is n-alkyl containing an even number of carbon atoms, and
- (c) a transition metal polymerization catalyst that copolymerizes ethylene and one or more of the α-olefins produced by the oligomerization catalyst,
- to produce a first product comprising a predominant amount of a branched polyethylene, a first residual α-olefin content and, optionally, an amount of unreacted ethylene;
- then
- (2) allowing the first product to further react under conditions to (co)polymerize at least a portion of the first residual α-olefin content, in the substantial absence of added ethylene, to result in a second product comprising a branched polyolefin having a second residual α-olefin content, provided that said second residual α-olefin content is at least 20% less than said first residual α-olefin content.
A process for the production of a branched polyethylene, comprising the step of contacting, under polymerizing conditions:
- (a) ethylene,
- (b) an ethylene oligomerization catalyst which is capable under the process conditions of producing one or more olefins of the formula R20CH═CH2 wherein R20 is n-alkyl containing an even number of carbon atoms, and
- (c) a polymerization catalyst which contains one or more transition metals and which is capable under process conditions of copolymerizing ethylene and one or more olefins of the formula R21CH═CH2, wherein R21 is n-alkyl, provided that a major portion of the branched polyethylene is produced first in a continuous stirred tank reactor, and that a minor portion of said branched polyethylene is produced subsequently in a plug flow reactor.
Dependencies are inferred from the claim text.