Improvements relating to polymerization catalysts and their use

A polymerization catalyst comprises (1) an organometallic compound, a metal hydride, an organometallic hydride, or an organometallic halogen compound of a metal of Group I, II or III, of the Mendelgeeff Periodic Table and a component (2) consisting of two halides in intimate admixture, each in a lower than normal valency state, and selected from halides of two different metals of "A" sub-groups IV to VII, and VIII, of the Periodic Table. Component (2) is made by reacting under anhydrous conditions a halide of a metal of IVa, Va, VIa, VIIa or VIII, in its highest normal valency state, with a metal of Group I to III, or a hydride, or an organo-metallic compound of such a metal to reduce the halide to a lower halide, mixing the lower halide with another higher halide of another metal of Group IVa to VIIa or VIII, and reacting this other halide with the same classes of reducing agents as used in the previous reduction, thereby reducing this other halide to a lower halide. The polymerization may be effected in presence of diisopropyl ether. Specified higher halides are TiC,4, ZrCl4, WCl6 and VCl4. Exemplified catalysts systems are Al(C2H5)3 and a mixture of TiCl3 and VCl3. In the examples, the following polymers are prepared, polyisoprene, polyethylene, a copolymer of ethylene and propylene, a copolymer of ethylene, propylene, and bicyclopentadiene, poly-pentadiene-1,3, and a copolymer of isoprene and butadiene.ALSO: Mixtures of two halides each in a lower than normal valency state, and selected from two different metals of "A" sub-groups IV to VII, and VIII, of the Mendelgeeff Periodic Table, are made by (1) reacting under anhydrous conditions a halide of a metal selected from one of the above groups, and in its highest normal valency state, with a metal Group I to III, or a hydride, or an organometallic compound of such a metal, to reduce the halide to a lower halide, and (2) mixing (1) with another higher halide of another metal of Groups IV(a) to VII(a), or VIII, and reducing this other halide with the same classes of reducing agents as used in (1). When TiCl4 is used in step (1), the TiCl3 formed is converted into the alpha-form by heating to between 135 DEG and 225 DEG C. The following preparations are exemplified, (1) a mixture of TCl3 and VCl3 is obtained by dispersing TiCl4 in liquid paraffin, treated with Al(C2H5)3 for 30 minutes, heated to 170 DEG C. for 1 hour, cooled, VCl4 added, Al(C2H5)3 added, and mixture heated for 1 ho