Process for bulk alternating copolymerization of propylene and butadiene

A process for bulk alternating copolymerization of propylene and butadiene which comprises contacting propylene and butadiene in liquid phase in the presence of a catalyst system containing (A) a trialkylaluminum compound represented by the general formula AlP.sup.1 R.sup.2 R.sup.3 and (B) (i) VOX.sub.3 and Al(OR')(OR")(OR"'), (ii) VO(OR').sub.m (OR").sub.n X.sub.3-m-n or (iii) VO(OR')(OR")(OR"') and a halogen component other than fluorine, under a pressure sufficient to keep the monomers in liquid phase at a temperature within the range of -100.degree.-+50.degree. C., wherein the trialkylaluminum compound and (i) VOX.sub.3 and Al(OR')--(OR")(OR"'), (ii) VO(OR').sub.m (OR"').sub.n X.sub.3-m-n or (iii) VO(OR')(OR")(OR"') are brought into contact in the presence of a monomer or monomers at a temperature within the range of -100.degree.-+50.degree. C., the molar ratio of propylene/butadiene in the feed is within the range of 20/1-1/10 and the ratio of the number of moles of trialkylaluminum compound to the number of moles of vanadyl component in the catalyst system is within the range of 0.5-100, wherein R.sup.1, R.sup.2, and R.sup.3, are the same or different and each is selected independently from the group consisting of a straight chain, a branched chain and a cyclic, monovalent aliphatic hydrocarbon radical with 4 to 9 carbon atoms, and R', R" and R"' of the alkoxyl group are the same or different and each is selected independently from the group consisting of a straight chain, a branched chain and a cyclic, monovalent aliphatic hydrocarbon radical with three to nine carbon atoms, X is chlorine or bromine, and m+n is 0.2-2.