This invention relates to a process for the stereospecific polymerization of .alpha.-olefins and a catalyst therefor.
Methods of supporting the titanium compound of Ziegler-Natta catalysts on a carrier to improve the catalyst activity have been developed in a commercial scale for polymerization of .alpha.-olefins and generally, have being employed for a catalyst for polymerization of ethylene.
However, in case of polymerization of .alpha.-olefins such as propylene and butene, a useful, crystalline polymer can not be obtained unless the polymeric chain has an isotactic structure in which alkyl groups such as methyl or ethyl are stereospecifically regulated. Accordingly, catalysts improved only in polymerization activity as the case of ethylene polymerization cannot be considered to be a useful catalyst for polymerization of .alpha.-olefins and thus, regulating the stereospecificity of polymer is a significant matter.
In connection with this, there is, for example in British Pat. No. 1,435,768 provided a catalyst comprising a titanium composition, an organoaluminum compound and an electron donative compound, said titanium composition being prepared by copulverizing magnesium halide, a solid organic substance, an organic acid ester and titanium halide. Also, Japanese Patent Publication No. 52-50037 discloses a catalyst comprising a titanium composition and an organoaluminum compound, said titanium composition being obtained by reacting a copulverized product of magnesium halide and an organic acid ester with titanium tetrachloride. These catalysts are, however, still insufficient in a polymerization activity and a crystallinity of polymers obtained.