GB864772A - Process for the manufacture of polyethylenes - Google Patents

Abstract

Polyethylene of molecular weight below 100,000 is made by polymerizing ethylene in the presence of hydrogen and a catalyst system comprising a bis-cyclopentadienyl-titanium compound and an organometallic compound of a metal of Group 1(a), II(a), II(b) and III(a) of the Mendeleeff Periodic Table. The polymerization is preferably effected in the presence of an inert diluent. The polymerization may also be effected in the presence of a small amount of oxygen. Exemplified bis-cyclopentadienyl-titanium compounds are bis-cyclopentadienyl-titanium dichloride, bis-cyclopentadienyl-dimethyl-titanium, and bis-cyclopentadienyl-methyl-titanium chloride. The preferred organo-metallic compounds are of the type R3Al, R2 Al Cl, and R Al Cl2 where R is an alkyl group of 1 to 8 carbon atoms. Exemplified organometallic compounds are dimethyl and dimethylaluminium chloride. The inert diluent may be pentane, hexane, benzene, toluene, ethyl-benzene, xylenes tetrahydronaphthalene, chlorobenzene, chloronaphthalene, methylene chloride, butyl chloride, and dichlorethane. A small proportion of oxygen may also be added to the polymerization system. The polyethylene may be purified by treatment with an alcohol such as methanol or butanol, or acetone, or an ether, and if desired steam distilled under acid, neutral, or alkaline conditions. Specifications 799,392, 799,823 and 801,031 are referred to.