Process for producing olefinic copolymer rubber with improved titanium compound containing catalyst system

In a process for producing a rubbery olefin copolymer which comprises random copolymerization of at least two olefins in the presence of a catalyst composed of (A) a titanium compound and (B) an organometallic compound of a metal of Groups I to III of the periodic table, the improvement wherein the titanium compound (A) is a liquid product obtained by treating a titanium tetrahalide of the general formula TiX.sub.4 in which X represents Cl, Br or I in a hydrocarbon, a halogenated hydrocarbon or a mixture of both in the presence of an ether with at least one member selected from the group consisting of (1) an organoaluminum compound, (2) an organomagnesium compound and (3) hydrogen with at least one metal or metal compound, said metal selected from the group consisting of metals of Group IB, IIB, IVB and VIII of the Periodic Table, said ether being represented by the general formula:

• R.sup.1 O R.sup.2
• wherein R.sup.1 and R.sup.2, independently form each other, represent an alkyl, alkenyl or aralkyl group having 2-12 carbon atoms with the proviso the alkyl, alkenyl or aralkyl group contains at least 6 carbon atoms if a hydrocarbon is used.