GB840916A - Polymerization of ethylene - Google Patents

Abstract

Ethylene is polymerized by means of a catalyst which comprises a borohydride (preferably of an alkali metal e.g. N, Na or Li), AlX3 (X = halogen, preferably Cl) and a Group IVa metal halide preferably TiCl4. Polymerization is preferably carried out in an inert solvent for ethylene such as a hydrocarbon which may be aromatic (e.g. benzene, toluene, xylene), aliphatic (e.g. dodecane) or cycloaliphatic (e.g. cyclohexane, decahydronaphthalene); it is preferable, when using a solvent, to pass a stream of ethylene continuously and to agitate the reaction mixture vigorously, and unreacted ethylene may be recovered and returned to the reaction. The polytthylenes produced have m.p.s. in the range 125-170 DEG C., the m.p. being defined as the p temperature at which a sample begins to become clear and lose its crystallinity. The reaction is quenched with methanol and the polymers purified by means of dilute aqueous KOH, dilute alcoholic KOH, water and methanol.ALSO:A catalyst for ethylene polymerization comprises a (preferably alkali) metal borohydride (e.g. of Na, K or Li), an Al halide (preferably chloride) and a halide of Ti, Zr, Hf or Th (preferably TiCl4). Preferably the catalyst is formed in an inert liquid (particularly a hydrocarbon especially when cyclic e.g. xylene) which is a solvent for ethylene, in the absence of free oxygen and in a nitrogen atmosphere; particularly a mixture of borohydride and Al halide is heated in the solvent at 60-110 DEG C. for at least 30 minutes before adding the second metal halide. The preferred molar ratio AlCl3: TiCl4:NaBH4 is 0.1-1:0.1-1:1. Optionally, the catalyst may be deposited on a carrier such as cryolite, clays, silica-alumina cracking catalysts and charcoal and the deposition may be carried out in e.g. xylene or decahydronaphthalene.