GB910132A - Process for making linear polyethylenes having controlled melt flow properties - Google Patents

Abstract

High molecular weight polyethylene is made by polymerizing ethylene at a temperature of from 0 DEG to 100 DEG C., in an inert diluent and in the presence of a catalyst comprising a mixture of (a) a metal hydride or organometallic compound, and (b) a compound of a transition metal, and a control agent selected from alphaolefins, alpha-acetylenes, n-alkadienes containing at least four carbon atoms, 2-alkyl-1,3-butadienes, and 2-halo-1,3-butadienes, in an amount corresponding to from 0.01 to 30 milligram-moles per gram-mole of ethylene. Components (a) and (b) of the catalyst, are used in amounts corresponding to from 0,25 to 4 atoms of the metal in (a) to one atom of the metal in (b). The control agent may be acetylene, methylacetylene, vinyl acetylene, phenyl acetylene, 1,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, 2,4-hexadiene, 1,5-hexadiene, propylene, 1-butene, 3-methyl-1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, styrene or, o-, m-, or p-methyl styrene. The metal of the hydride or organometallic compound may be zinc, aluminium, germanium, tin, lead, or magnesium. Specified compounds are trimethyl-, triethyl-, tripropyl-, trisobutyl-, or trioctyl-aluminium, lithium aluminium hydride, lithium aluminium tetrahexyl, and diethylaluminium chloride or bromide. The preferred transition metal compounds are titanium tetrachloride, titanium trichloride, titanium tetrabromide or tribromide. The polymerization is generally effected in the presence of an inert hydrocarbon medium. Specifications 799,392, 819,867 and 827,517 are referred to.