Basell Polyolefine Gmbh

Thomas Dröge

Andrei Gonioukh

Lars Wittkowski

Gernot Köhler

Andreas Deckers

Dieter Littmann

Roger G Klimesch

Wilhelm Weber

Philipp Rosendorfer

Frank-Olaf Mähling

Ernst Fischer

Theo Teuber

The invention relates to a process for the continuous preparation of ethylene homopolymers or copolymers in the presence of free-radical polymerization initiators and, if desired, molecular weight regulators at from 120&#xb0; C. to 350&#xb0; C. and pressures in the range from 100 to 4000 bar, in which the polymer is separated from unpolymerized ethylene in a high-pressure stage at a pressure of from 100 to 500 bar and at least one low-pressure stage at a pressure of from 1 to 100 bar and the ethylene separated off in the high-pressure stage is separated from remaining monomeric, oligomeric and/or polymeric constituents and recirculated to the inlet of the tube reactor in a high-pressure circuit and the ethylene separated off in the low-pressure stage is separated from remaining monomeric, oligomeric and/or polymeric constituents and recirculated to the inlet of the tube reactor in a low-pressure circuit. The initiator is used as a solution in an isoparaffinic solvent having a boiling point of not more than 160&#xb0; C. and the solvent is separated from the other monomeric, oligomeric and/or polymeric constituents in the low-pressure circuit. The solvent is then, if appropriate after being admixed with fresh solvent, reused for dissolving initiator.

Continuous preparation of ethylene homopolymers or copolymers

A process for preparing ethylene polymers by the high-pressure method comprises dissolving one or more free-radical initiators in one or more ketones of the formula Iwhere Rand Rare identical or different and are selected from among C-C-alkyl and C-C-cycloalkyl and Rand Rmay also be covalently linked to one another to form a 4- to 13-membered ring, prior to the polymerization,compressing the solution, metering it into the polymerization reactor at one or more points and subsequently carrying out the polymerization at from 150 to 380&#xb0; C. and from 500 to 4500 bar.

Preparation of ethylene polymers by the high-pressure method

Ethylene homopolymers and copolymers are prepared in a tube reactor at from 160&#xb0; C. to 350&#xb0; C. and pressures in the range from 500 to 5000 bar, with or without use of molar mass regulators, using a peroxide mixture comprising from 1 to 95 mol %, based on the total amount of the peroxide mixture, of at least one cyclic peroxide of the formula I,where the radicals R are identical or different and are selected from among alkyl groups and aryl groups, as polymerization initiator.

Preparation of polyethylene

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Neustadt, Germany

Thomas Dröge