Abstract: A solid catalyst for olefin polymerization which is obtained by the catalytic treatment of a titanium trichloride composition with a mixture of a halogenated hydrocarbon and an ether, the composition being produced by subjecting a solid reduction product, which is obtained by reduction of titanium tetrachloride with an organo-aluminum compound, to heat treatment or to catalytic treatment with a specific organo-aluminum compound, aluminum halide, an ether and the like. In the polymerization of an olefin, combined catalyst systems of this solid catalyst and organo-aluminum compounds as activators can be used for efficient production of olefin polymers having a high crystallinity.

Abstract: A process for producing a homopolymer of propylene or a copolymer of propylene which comprises polymerizing propylene or a mixture of propylene and another unsaturated hydrocarbon monomer such as ethylene in liquid propylene, in the presence of a catalyst system consisting essentially of (a) an activated titanium compound obtained by reducing titanium tetrachloride with an organic aluminum compound and activating the resulting titanium compound and (b) an organic aluminum compound to produce a polymer slurry, introducing the polymer slurry into an upper part of a counter-current washing zone, such as a washing tower, and counter-currently contacting the polymer slurry with liquid propylene which is introduced into a lower part of the washing zone, whereby the polymer and catalyst residues dissolved in the polymer slurry are removed.

Abstract: A process for preparing a solid catalyst for the polymerization of olefins which comprises the steps of (1) reducing titanium tetrachloride with an organoaluminum compound, (2) treating the resulting .beta.-type titanium trichloride with a complexing agent, (3) treating the solid catalyst thus obtained with an organoaluminum compound, and (4) treating the resulting solid catalyst with a complexing agent, and a solid catalyst for the polymerization of olefins prepared by the above process.

Abstract: A process for polymerizing .alpha.-olefins in a solvent under conditions such that the polymer formed grows as particles, in which the process comprises reusing a greater part of the solvent used for the polymerization by recycling the solvent to the polymerization zone without carrying out any purification treatment.