Abstract: A process for polymerizing or copolymerizing .alpha.-olefins having at least 3 carbon atoms or copolymerizing .alpha.-olefins having at least 3 carbon atoms with not more than 50 mole % of ethylene in the presence of a catalyst composed of an organometallic compound of a metal of Groups I to III of the periodic table and a titanium catalyst component supported on a halogen-containing magnesium compound, said titanium catalyst component being a solid reaction product obtained by treating (i) a mechanically copulverized product of a halogen-containing compound and an organic acid ester with (ii) an organo-metallic compound of a metal of Groups I to III of the periodic table, and then reacting the resulting solid product with (iii) a titanium compound in the absence of mechanical pulverization.

Abstract: Highly stereoregular polymers or copolymers of .alpha.-olefins containing at least 3 carbon atoms are prepared in high yields by polymerizing or copolymerizing the .alpha.-olefins in the presence of a catalyst composed of (a) an improved solid transition metal catalyst component prepared by reacting (1) a magnesium-containing reaction product derived from a member of the group consisting of (i) a magnesium halide, (ii) an active hydrogen-containing compound, (iii) an organic acid ester and (iv) a silicon or tin compound containing at least one halogen atom or hydrocarbon group bonded directly to silicon or tin with (2) a titanium compound, and (b) an organometallic compound of a metal selected from aluminum, magnesium and zinc.

Abstract: A process for preparing a highly stereoregular olefin polymer or copolymer in high yield and with good reproducibility of quality and yield, which comprises polymerizing or copolymerizing an olefin containing at least 3 carbon atoms in the presence of a catalyst comprising(a) a solid titanium catalyst component obtained by reacting a solid magnesium component with a titanium compound in the absence of a free organometallic compound of a metal of Groups I to III of the periodic table and separating the solid component of the resulting reaction product, said magnesium component being obtained by separating a solid from a suspension of a reaction product derived from (i) a magnesium dihalide, (ii) an active hydrogen-containing organic compound, (iii) an organic acid ester and (iv) an organometallic compound of a metal of Groups I to III of the periodic table, and(b) an organometallic compound of a metal of Groups I to III of the periodic table.