GB869534A - Improvements in the manufacture of polyethylene - Google Patents

Abstract

A process for polymerizing ethylene at a pressure of at least 15,000 p.s.i. and a temperature of 80 DEG to 180 DEG C., in the presence of a nonmetallic ethylene polymerization catalyst and from 5% to 50% by weight based on the weight of ethylene, of a saturated acyclic aliphatic hydrocarbon containing 3-7 carbon atoms and in the absence of any other diluent or solvent, yields solid homopolymers of a molecular weight of at least 20,000; a density of at least 0,930; a stiffness of at least 25,000 p.s.i.; a heat distortion temperature of at least 110 DEG C.; and an inherent melt viscosity in the range 0,5 to 1,5 decilities per gram in tetralin at 100 DEG C. The hydrocarbons exemplified are n-propane, n- or iso-butane, pentane or iso-pentane, hexane or n-heptane, and are used in preferred proportion of 10% to 15% of the ethylene. Catalysts mentioned are peroxy compounds such as benzoyl, lauroyl, and di-t-butyl peroxides and t-butyl perbenzoate, and compounds such as azobisisobutyronitrile, methyl azobisisobutyrate and diethyl 2 : 21-azobis-(2-methyl propionate), in amounts of from 5 parts per million to 5% by weight. The polymerization may be carried out in a single or multi-stage process, in an autoclave or tubular reactor.