| 摘要 |
<p>Catalysts used in the polymerization of ethylene (see Group IV (a)) comprise an alkali metal or an alkaline earth metal, and a Group 5A metal oxide which has been activated by partial reduction and which is preferably supported on a difficultly reducible metal oxide such as silica, alumina, titania, zirconia or a clay. The 5A metal oxide may be V2O5, Nb2O5 or Ta2O5 and these may be pre-reduce (e.g. in the presence of the support and the metal) with materials such as hydrogen, carbon monoxide, sulphur dioxide, hydrogen sulphide; sodium, calcium or lithium aluminium hydride; and hydrocarbons such as acetylene, methane, benzene toluene, xylenes, polymethylenes, polyethylenes and paraffin waxes. The catalyst may be treated from time to time with solvents to remove polymer, following which the catalyst may be reactivated or regenerated with materials such as water, ammonium salts, dilute acids, oxygen, permolybdic, pervanadic or pertungstic acids and hydrogen. The polymerization is preferably conducted in an inert medium, preferably benzene, toluene, xylenes or "Decalin" or "Tetralin" (Registered Trade Marks). Specifications 753,349 and 776,326 are referred to.ALSO:Ethylene is polymerized by contacting with an alkali metal or an alkaline earth metal, and a Group Va metal oxide which has been activated by partial reduction and which is preferably supported on a difficulty reducible metal oxide such as silica, alumina, titania, zirconia or a clay. Other monomers and inert gases which may be included in the gas stream are propylene, n-butylenes, isobutylene, t-butylethylene, acetylene, butadiene, isoprene, methane, ethane, propane and hydrogen. The Va metal oxide may be V2O5, Nb2O5 or Ta2O5 and these may be pre-reduced with materials such as hydrogen, carbon monoxide, sulphur dioxide, hydrogen sulphide; sodium, calcium or lithium aluminium hydride; and hydrocarbons such as acetylene, methane, benzene, toluene, xylenes, polymethylenes, polyethylenes and paraffin waxes. The polymerization may be in bulk in the gas phase, with catalyst being treated from time to time with solvents to remove polymer-followed by reactivation or regeneration of said catalyst, or may be in a liquid hydrocarbon medium (preferably purified before use) of which many aliphatic and aromatic examples are specified, preferred media being benzene, toluene, xylenes, "Decalins" (Registered Trade Mark) and "Tetralins" (Registered Trade Mark). The process may be continuous or batchwise with intermittent repressurization of ethylene, and suitable space velocities and contact times are given. Polymerization is preferably in the absence of oxygen, carbon dioxide, water and sulphur compounds, but the presence of hydrogen is used to eliminate the induction period. Comparison is made with polymerizations in the absence of the metal promoter. The products range from greases and waxes to highmolecular weight materials and may be mixed with antioxidants, stabilizers, fillers, extenders, plasticisers, pigments, insecticides, fungicides, polyethylenes, polybutylenes, hydrocarbon oils, xylene and paraffin, petrolatum and ester waxes. The polymers may be extruded, milled, filmed, cast, halogenated, halogenated then dehalogenated, sulphohalogenated, sulphonated, converted to sponges or latices, and subjected to ionizing radiation. Applications specified are as coating materials, gas barriers and binders. Specifications 753,349 and 776,326 are referred to.</p> |
