GB815161A - Improvements in or relating to polymerization process - Google Patents

Abstract

Ethylene is polymerized in an inert solvent and using as catalyst a mixture of a compound of Ti, Zr, Hf, V, Cb, Ta, Cr, Mo, W, Th or U, with a compound RR1AlX, wherein R and R1 are hydrogen, alkyl or aryl, and X is hydrogen, halogen, alkoxy, aryloxy, alkyl, secondary amino, mono-N-substituted amido, mercapto, thiophenyl, or a radical of a carboxylic or sulphonic acid; the process being characterized in that polymer slurry is withdrawn from the reaction zone, the polyethylene is separated in the absence of air, moisture and other catalyst poisons (e.g. under a blanket of nitrogen) and the liquid residue of catalyst and solvent is then reused in subsequent runs, whereby the total amounts of catalyst and solvent required are reduced. The solvents specified are heptane, hexane, pentane, propane, cyclohexane, tetrahydronaphthalene, decahydronaphthalene, benzene, xylene, dichloro-benzene, chlorinated naphthalene, dibutylether, dioxane and tetrahydrofurane, and particular catalyst components used are titanium-tetrachloride, -oxychloride and -acetylacetonate, diethyl aluminium chloride, di-isobutyl aluminium-chloride and -hydride, and triethyl-, triisobutyl- and trioctyl-aluminium, the preferred mol. ratios and amounts of these being stated. The polymers obtained may be purified with methanol and methanolic hydrochloric acid. An advantage of the process is that the molecular weights of the materials produced in different runs become stabilized. The examples illustrate the continuous addition of the reaction components and the continuous withdrawal of polyethylene slurry.