GB795971A - Improved polymerisation process - Google Patents

Abstract

<PICT:0795971/III/1> <PICT:0795971/III/2> <PICT:0795971/III/3> <PICT:0795971/III/4> <PICT:0795971/III/5> Catalysts for the polymerization of ethylene comprise the vapour of an organometallic compound of beryllium, aluminium, gallium or indium mixed with the vapour of a tetravalent compound of titanium or vanadium, e.g. the tetrachlorides. Organo-metallic compounds specified are triethyl and trimethyl aluminium or gallium, dimethylaluminium chloride, trimethyl indium and dimethyl beryllium. The vapours may be supplied separately in streams of ethylene, obtained for instance by blowing or sucking the liquid component or a solution thereof into an ethylene stream, and then mixing the streams, e.g. in a venturi, at the point of entry into the polymerization chamber. The polymerization apparatus described is constructed to prevent polymer adhering to the internal walls and may be as described in Specification 740,054, [Group II], or as illustrated in Fig. 1 wherein 1 is the polymerization chamber fitted with a scraper 5, or with a helical screw, and with a rotary valve exit 8 which excludes air; or as illustrated in Fig. 5 wherein a rotating polymerization chamber 1 contains spheres 39, e.g. of glass. In Fig. 2 ethylene is supplied by line 20, nitrogen by line 28 and catalyst components by lines 24, 25. Numerals 26, 27 indicate equipment for saturating ethylene with the respective vapours, said equipment being further illustrated in Figs. 3 and 4. The polymerization process may be carried out continuously.ALSO:Polyethylene of high softening point is produced catalytically by mixing the vapours of an organometallic compound of beryllium, aluminium, gallium or indium and a tetravalent compound of titanium or vanadium, e.g. the tetrachlorides, in the presence of ethylene, and preferably in the absence of oxygen and water. Organometallic compounds specified are triethyl <PICT:0795971/IV (a)/1> <PICT:0795971/IV (a)/2> and trimethyl aluminium or gallium, dimethyl aluminium chloride, trimethyl indium and dimethyl beryllium. The molecular weight of the product may be controlled by means of the molar ratio of the catalyst components. Further ethylene may be added during the polymerization, which may be batchwise or continuous. The temperature is preferably maintained below the sintering temperature of the product, which is thus obtained in powder form, by controlling the rate of polymerization, e.g. by dilution with an inert gas, such as nitrogen, or by cooling. The vapours may be supplied separately in streams of ethylene, obtained for instance by blowing or sucking the liquid component or a solution thereof into an ethylene stream, and then mixing the streams, e.g. in a venturi, at the point of entry into the polymerization chamber. Catalyst component solvents specified are methyl cyclohexane and petroleum ether. The polymerization apparatus described is constructed to prevent polymer adhering to the internal walls and may be as described in Specification 740,054, [Group II]; or as illustrated in Fig. 1, wherein 1 is a polymerization chamber fitted with a scraper 5, or with a helical screw, and with a rotary valve exit 8 which excludes air; or as illustrated in Fig. 5, wherein a rotating polymerization chamber 1 contains spheres 39, e.g. of glass. The polymerization chamber is also preferably so filled with powdered polymer, e.g. by recycling the product, that the fresh reactants tend to contact the powder rather than the vessel. The product may be purified, continously if desired, with materials such as methanol and ethanol.