Polymerisation process and catalysts therefor

Unsaturated aliphatic compounds containing a group are polymerized using a catalyst formed from (a) a compound of a Group IVa, Va, VIa, VII or VIII metal and (b) an organo-compound of a Group I, II, IIIb or IVb metal, or a hydride of a Group Ia metal, the catalyst or component (a) and/or (b) being dispersed in an inert solid which dissolves in the polymerization reaction mixture so as to release the catalyst or component. The invention also comprises the catalyst composition as just defined, wherein the inert solid is soluble in a liquid hydrocarbon at 50 DEG C. to an extent of at least 2% by wt. The preferred inert solids are straight or branched-chain paraffins of m.p. up to 110 DEG C., preferably 20 DEG -80 DEG C., ceresine wax, petroleum jelly and paraffin wax are specified. In examples, the following catalysts are stated to have been used for polymerizing butadiene and ethylene/propylene mixture: (I) TiCl3 in ceresine wax, p (II) TiCl4/Al(i-Bu)3 product in paraffin wax, (III) ZrCl4/PbEt4 product in paraffin wax, (IV) TiCl4/NaH product in paraffin wax; and the polymerization of butadiene using the following catalysts is described: (V) VCl4/AlEt2Br product in paraffin wax, (VI) TiCl4/Al(iBu)3 product in ceresine wax, (VII) TiCl4 in ceresine wax plus Al(iBu)3 in ceresine wax and (VIII) VCl4/Al(iBu)2\t H product in paraffin wax.