Patent GB-799392-A (GB)
Title: High molecular polyethylenes
IPC: B65G65/00
Filed: 1954-11-16
Abstract: Catalysts for the polymerization of ethylene comprise a mixture of aluminium trialkyl and a compound of a metal of the a-sub groups of Groups IV to VI of the Periodic Table.  Aluminium trialkyls with alkyl radicals containing from 2 to 12 carbon atoms, such as may be obtained by the union of ethylene with triethylaluminium and corresponding to trioctyl or dodecyl aluminium are used preferably in an amount formed by mixing from 2 mm. to 3 mm. mols. of aluminium trialkyl with n mols. of metal compound where n is the valency of the metal in the compound. Compounds of titanium, zirconium, hafnium, thorium, uranium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten such as zirconium or titanium, tetrachloride, oxychloride and acetyl acetonate are mentioned.  In examples, titanium and uranium tetrachloride, zirconium tetrabromide, tantalum pentachloride, tungsten hexachloride, potassium titanium hexafluoride, zirconium and titanium oxyhydrate, zirconium tetrabutylate, and zirconium, thorium, vanadium, chromium and molybdenum acetyl acetonates are used and the mixtures may be prepared in suspension or solution by the addition, optionally dropwise, of the metal compound to the trialkylaluminium in solvents such as liquid paraffin, pentane, hexane, cyclohexane, diesel oil, tetrahydronaphthalene, decahydronaphthalene, benzene, xylene, o-dichlorobenzene, chlorinated naphthalene, dibutyl ether, dioxane and tetrahydrofurane.  The reaction is carried out in the presence of solvents at pressures below 100 atmospheres and below 100 DEG  C. High molecular weight polyethylenes, preferably above 10,000 and from 300,000 to 3,000,000, with a melting point above 130 DEG  C. and insoluble in the usual organic solvents, and with a highly crystalline linear structure are obtained, and films and fibres may be extruded.  Specifications 713,081 and 773,536, [both in Group IV (a)], are referred to.ALSO:High molecular weight polyethylenes are prepared by contacting gaseous ethylene with a mixture of an aluminium trialkyl and a compound of the a sub-group of Groups IV to VI of the Periodic Table, at low pressure and temperature, e.g. below 100 atmospheres and 100 DEG  C.  Pure ethylene or mixtures obtained by cracking mixtures of saturated hydrocarbons, e.g. ethane and propane, or of petroleum and its fractions or gases from the Fischer-Tropsch synthesis may be used.  The catalysts comprise aluminium trialkyl preferably in which the alkyl group contains 2 to 12 carbon atoms, such as is produced by the union of ethylene with triethylaluminium corresponding to trioctyl, and dodecyl, and in an amount of from 2 mm. to 3 mm. mols. of aluminium trialkyl with m. mols. of metal compound where n is the valency of the metal in the compound.  Compounds of titanium, zirconium, hafnium, thorium, uranium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten such as zirconium or titanium tetrachloride, oxychloride and acetyl acetonate are mentioned. In examples, titanium and uranium tetrachloride, zirconium tetrabromide, tantalum pentachloride, tungsten hexachloride, potassium titanium hexafluoride, titanium and zirconium oxyhydrate, zirconium tetrabutylate, and zirconium, thorium vanadium, chromium and molybdenum acetyl acetonates are used in suspension or solution in solvents such as liquid paraffin, pentane, hexane, cyclohexane, diesel oil, tetrahydronaphthalene, decahydronaphthalene, benzene, xylene, o - dichlorobenzene, chlorinated naphthalene, dibutyl ether, dioxane and tetrahydrofurane. The reactions are performed in an autoclave in the absence of air or under nitrogen to which the catalyst or ethylene may be added portionwise or in one amount, and the polymer is extracted with solvents, e.g. methanol, methanol-hydrochloric acid, acetone and benzene and filtered to yield a powdered or filament product.  The products have a highly crystalline linear structure, with practically no branched chains and not more than three methyl groups per hundred methylene groups, a molecular weight preferably above 10,000, which may range from 300,000 to 3,000,000, a melting point above 130 DEG C. and are insoluble in the usual organic solvents.  Films or strips may be extruded and filaments spun from the molten material. Specifications 763,081 and 773,536 are referred to.