Patent GB-811633-A (GB)
Title: Process for the polymerisation of ethylene
IPC: F16J1/22
Filed: 1955-05-26
Abstract: Catalysts used in the polymerization of ethylene (see Group IV (a)) comprise one or more of activated titanium or zirconium, and titanium or zirconium compounds in which the metals have a valency of less than 3 and which are free of metal organic compounds. Activated Ti or Zr is produced by treating the metal with small amounts of halogen or a substance yielding halogen, e.g. aluminium or titanium or zirconium halide, such that a surface layer of lower halide, especially dihalide is formed (any aluminium halide may then be removed before the catalyst is used).  Other catalyst systems specified are: Ti and/or Zr dihalides, disproportionated Ti and/or Zr trihalides, Ti and/or Zr compounds reduced with metals of Groups 1, 2 or 3 (e.g. TiCl4 or TiCl3 with Na or iodine activated Al), and Ti or Zr+Al+ a titanium and/or zirconium halide (followed by complete or partial removal of residual aluminium halide).  In the above catalysts the preferred halides used are the chlorides.  Optionally a Friedel-Crafts catalyst, such as aluminium halide, may be included with any specified catalyst, as a polymer of lower molecular weight is thereby obtained.  An aliphatic, cycloaliphatic or aromatic hydrocarbon is preferably the solvent used in the catalyst preparation and in the polymerization, and oxygen and water are desirably excluded.  Catalyst residues may be removed by treating the products obtained with methanol and/or hydrochloric acid, aqueous ammonia, benzyl alcohol, or o-dichlorobenzene.ALSO:Ethylene is polymerized in a solvent in the presence of one or more of the following catalysts; activated titanium or zirconium, and titanium or zirconium compounds in which the metals have a valency of less than 3 and which are free of metal organic compounds.  Activated Ti or Zr is produced by treating the metal with small amounts of halogen or a substance yielding halogen, e.g. aluminium or titanium or zirconium halide, such that a surface layer of lower halide, especially dihalide, is formed (any aluminium halide may then be removed before the catalyst is used). Other catalyst systems specified are: Ti and/or Zr dihalides, disproportionated Ti and/or Zr trihalides, Ti and/or Zr compounds reduced with metals of Groups I, II or III (e.g. TiCl4 or TiCl3 with Na or iodine activated Al), and Ti or Zr+Al+ a Ti halide and/or a Zr halide (followed by complete or partial removal of residual aluminium halide).  In the above catalysts the preferred halides used are the chlorides.  Optionally, a Friedel-Crafts catalyst, such as aluminium halide, may be included with any specified catalyst, as a product of lower molecular weight is thereby obtained.  Solvents which are used in the preparation of the catalysts and in the polymerization are benzene, xylene, tetrahydronaphthalene, methyl cyclohexane, gasoline, petroleum ether, paraffin oil and paraffin wax. Polymerization is desirably in the absence of oxygen and water and may be effected continuously or intermittently, e.g. with ethylene being added during reaction, or by a continuous flow process (see Examples 11 and 12).  Subsequent to polymerization the products may be purified (catalyst destroyed) with methanol and/or hydrochloric acid, aqueous ammonia benzyl alcohol or o-dichloro benzene.  The products range from waxes to high molecular weight plastics and find application as films, foils, coatings, tubes, mouldings, electrical insulation and as lubricating oil additives.  The polymers may be stretched, may be dry distilled to give higher paraffins, and may be fractionated with xylene and methanol, or by distillation.