GB813221A - Improvements in or relating to ethylene polymerization process - Google Patents

Abstract

Polyethylene made by polymerizing ethylene in the presence of a catalyst comprising a mixture of (A) a compound of the general formula RR1AlX in which R is hydrogen, an alkyl, or an aryl radical, R1 is hydrogen, an alkyl, or an aryl radical and X is hydrogen, halogen, alkyl, alkyloxy, aryloxy, a secondary amino radical, a secondary acid amide radical, a mercapto radical, a thiophenyl radical, or a radical of a carboxylic or sulphonic acid; and (B) a halide of a metal of Group IVa, Va or VIa of the Mendeleeff Periodic Table, is purified by treating the polymer with an alkoxide, filtering the slurry, and washing the purified polymer with an alcohol. The alkoxides have the general formula R-O-M, where R is an alkyl radical selected from methyl, ethyl, propyl, isopropyl, butyl or isobutyl and M is an alkali metal, e.g. sodium, potassium, or lithium. Exemplified alkoxides are sodium and potassium isopropoxides, sodium methoxide and ethoxide, and sodium tert. butoxide. Alcohols mentioned are methanol, ethanol, propanol and isopropanol. The polyethylene is preferably prepared in the presence of an inert solvent or diluent such as heptane, hexane, pentane, cyclohexane, tetrahydronaphthalene, decahydronaphthalene, benzene, xylene, o-dichlorobenzene, chlorinated naphthalene, or dibutylether. Specified catalysts are a mixture of diethylaluminium chloride and titanium tetrachloride in a mol. ratio of 1.1 : 1, di-isobutyl aluminium chloride and titanium tetrachloride in a 1.1 : mol. ratio, and dipropyl aluminium chloride and titanium tetrachloride in a mol. ratio of 1.1 : 1.