Sumitomo Chemical Company, Limited

The Japan Steel Works, Ltd.

Setsuo Nakai

Hiroshi Ochi

Shinichiro Kita

Masayuki Shimizu

Fumihiko Hiki

A method for removing unreacted monomer (or monomers) from an ethylene homopolymer or a copolymer of ethylene and at least one monomer copolymerizable with ethylene during the course of pelletization by use of an extruder, said polymer having been formed by high-pressure polymerization by use of a radiation or a radical initiator, discharged from the reactor by way of a separator, and fed to said extruder to be pelletized, which method comprises injecting into said extruder 0.1 to 10% by weight (based on said polymer) of water or steam intermixing the polymer and the water or steam in the mixing section of the extruder screw, and subjecting the resulting mix to a subatmospheric pressure of 500 mmHg (absolute) or less in the venting zone provided in the extruder. This method permits efficient removal of the unreacted ethylene or the unreacted ethylene and comonomer contained in a homopolymer or copolymer of ethylene.

Method for removing unreacted monomer

In a process for polymerizing ethylene in a two-zone autoclave reactor comprising a top reaction zone and a bottom reaction zone which process comprises polymerizing ethylene in said top reaction zone at 130.degree. to 200.degree. C and at a reaction pressure of 1,000 to 1,800 kg/cm.sup.2 using an initiator, sending the resulting reaction mixture from the top reaction zone to the bottom reaction zone, and further promoting the polymerization at 220.degree. to 280.degree. C using an initiator which is same as or different from the initiator in the top reaction zone, the improvement which comprises feeding 75% or more of the ethylene to the top reaction zone of the two-zone reactor, said two-zone reactor being constructed so that the volume ratio of top reaction zone to bottom reaction zone is 1.5 to 6 and being provided with two or more feed inlets for each of the ethylene and the initiator in the top reaction zone in the direction extending through the two reaction zones.

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Niihama, Japan

Setsuo Nakai