Basell Polyolefine Gmbh

Gernot Köhler

Dieter Littmann

Andrei Gonioukh

Frank-Olaf Mähling

Lars Wittkowski

Thomas Dröge

Andreas Deckers

Roger G Klimesch

Philipp Rosendorfer

Ernst Fischer

Michael Hoppach

Eckhard Häffner

Theo Teuber

Axel Schmitz

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 homopolymers and copolymers in a tubular reactor having two or more polymerization zones at temperatures of between 150&#xb0; C. and 350&#xb0; C. and pressures in the range from 500 to 5000 bar, using oxygen as initiator, which comprises using, as molar mass regulator, one or more aliphatic ketones of the formula I, where the variable Ris a C-C-alkyl or C-C-cycloalkyl, ethylene homopolymers and copolymers obtainable therefrom and their user for producing injection-molded products in the cosmetics, medical and food sectors are described.

Nonodorous ethylene homopolymers and copolymers having good mechanical properties

In a process for polymerizing ethylene and, if desired, further monomers in a high-pressure reactor at from 140 to 320&#xb0; C. and pressures of from 1000 to 4000 bar, but in any case under pressure and temperature conditions under which water displays supercritical behavior, water is introduced continuously or intermittently into the reactor.

Method for high pressure polymerization of ethylene in the presence of supercritical water

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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Meckenheim, Germany

Gernot Köhler