| 摘要 |
A catalyst used for the polymerization of ethylenically unsaturated hydrocarbons (see Group IV (a)), comprises a compound of Ti, Zr, Ce, V, Nb, Ta, Cr, Mo or W, together with a lithium aluminium tetraalkyl and wherein the molar ratio of the catalyst components is in the range from 2.5 to 4.5. Catalyst components disclosed are titanium trichloride, tetrachloride and tetrafluoride, zirconium and vanadium tetrachlorides, niobium and molybdenum pentachlorides, tantalum pentabromide, cerium trichloride, tungsten hexachloride, tetra-(2-ethylhexyl)-titanate, tetrapropyl titanate, octylene glycol titanate, triethanolamine titanate, tetraethyl zirconate, tetra-(chloroethyl) zirconate, and the lithium aluminium tetraalkyls wherein the alkyl is n-butyl, heptyl, n-octyl or ethylcyclohexenyl. Catalyst preparation and polymerization are preferably effected in an inert medium, e.g. cyclohexane, n-heptane, benzene, toluene, or xylene. Specifications 682,420, [Group IV (a)], 776,326, 777,414, [Group IV (a)], 777,538 and 778,639 are referred to.ALSO:The degree of polymerization of an ethylenically unsaturated hydrocarbon is controlled by maintaining the initial molar ratio of the Ti, Zr, Ce, V, Nb, Ta, Cr, Mo or W compound to the lithium aluminium tetraalkyl in the catalyst, at from 2.5 to 4.5. Monomers specified are ethylene, propylene, butene, isobutylene, styrene and mixtures thereof, and the catalyst components disclosed are titanium tetrachloride and tetrafluoride, titanium trichloride, zirconium tetrachloride, niobium pentachloride, vanadium tetrachloride, tantalum pentabromide, cerium trichloride, molybdenum pentachloride, tungsten hexachloride, tetra-(2-ethylhexyl)-titanate, tetrapropyl titanate, octylene glycol titanate, triethanolamine titanate, tetraethyl zirconate, tetra-(chloroethyl)-zirconate, and the lithium aluminium tetraalkyls wherein the alkyl is n-butyl, heptyl, n-octyl or ethylcyclohexenyl. An inert medium, e.g. cyclohexane, n-heptane, benzene, toluene or xylene is preferably present, and the polymerization is preferably carried out until the catalyst loses activity. Small quantities of hydrogen and oxygen may be included as additional methods of molecular weight control. In an example, ethylene is added continuously. The products are linear polymers of melt index from 0.05 to 1 and may be used in the manufacture of films, fibres, mouldings and extruded wire coverings. Specifications 682,420, 776,326, 777,414, 777,538 and 778,639 are referred to.
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