Abstract: A method for producing a propylene-.alpha.-olefin block copolymer, which comprises polymerizing propylene in the presence of a catalyst and then polymerizing in a gas phase an .alpha.-olefin other than propylene, or propylene and other .alpha.-olefin without deactivating the catalyst, wherein at least one compound selected from the group consisting of an aromatic carboxylic acid ester, a phosphorous ester, an unsaturated dicarboxylic acid diester, an amine compound and an amide compound, is supplied to the latter gas phase polymerization system.

Abstract: A method for producing an .alpha.-olefin block copolymer, which comprises polymerizing propylene alone or together with a small amount of other .alpha.-olefin in the presence of a catalyst comprising a titanium-containing solid catalyst component and an organoaluminum compound, and then polymerizing the resulting propylene polymer with an .alpha.-olefin other than propylene, alone or together with propylene in a gas phase without deactivating the catalyst, characterized in that the gas phase polymerization is conducted in the presence of a siloxane or a polysiloxane in an amount of from 1.times.10.sup.-6 to 0.1 by weight ratio relative to the weight of said propylene polymer.

Abstract: A process for preparing solid titanium trichloride useful for the polymerization of an .alpha.-olefin, which comprises precipitating violet-colored fine solid particles of titanium trichloride at a temperature of not higher than 150.degree. C. from a liquid of titanium trichloride liquefied in the presence of an ether, characterized in that after the amount of the precipitated violet-colored fine solid particles of titanium trichloride reaches at least 80% based on the total amount of titanium trichloride in the system, titanium tetrachloride is added in an amount within a molar ratio of from 0.2 to 10 based on the total amount of titanium trichloride in the system, followed by aging at a temperature of from 60.degree. to 120.degree. C.

Abstract: The present invention relates to a process for producing a polypropylene-ethylene block copolymer by a continuous multi-stage polymerization comprising a first stage in which polypropylene is polymerized in a first polymerization vessel in the presence of a propylene polymerization catalyst, and a second stage in which propylene and ethylene are copolymerized in a second polymerization vessel, wherein the polypropylene slurry discharged from the first polymerization vessel is supplied to a concentrator to separate said slurry into a concentrated polypropylene slurry and a supernatant liquid, the concentrated polypropylene slurry is then introduced through an upper part of a hydraulic sedimentation classifier to be contacted with a countercurrent of the upward flowing of the supernatant fluid introduced through a lower part of said classifier to obtain hydraulically sedimented polypropylene, and non-hydraulically sedimented polypropylene; the thus obtained hydraulically-sedimented polypropylene is then supplie

Abstract: A process for producing a polyolefin characterized by polymerizing an olefin in the presence of a catalytic system composed of solid titanium trichloride, an organic aluminum compound, an aromatic hydrocarbon and a monocarboxylic acid ester having an olefinic double bond or an aromatic ring in the molecule thereof.

Abstract: A solid titanium trichloride, produced by precipitation from a homogeneous solution or mixture with an ether, is treated by prepolymerization with propylene at a partial pressure of less than 1 kg/cm.sup.2. The pretreated titanium trichloride containing a propylene polymer is then admixed with an organoaluminum compound and the admixture is used as a catalyst in the polymerization of propylene.

Abstract: A process for producing stabilized polyolefins comprising adding an epoxide to a polyolefin slurry obtained through polymerization of .alpha.-olefins in the presence of a catalyst containing a halide of a transition metal and an organoaluminum compound to render the catalyst remaining in the polymer inactive, and then subjecting the polyolefin slurry after the above inactivation treatment to an evaporation treatment. The process is extremely simple and results in polyolefins and molded products which are highly stable against discoloration and heat.

Abstract: Solid titanium trichloride in the form of fine granules having low aluminum compound content, which is suitable as a catalyst for polymerization of .alpha.-olefins, especially, propylene is obtained as a precipitate by heating liquefied titanium trichloride in the presence of a liberating agent, and separating the thus formed precipitate. The liquefied titanium trichloride is preferably prepared with an reducing titanium tetrachloride by organic aluminium compound in the presence of ether and hydrocarbon.

Abstract: Solid titanium trichloride in the form of fine granules having low aluminum compound content, which is suitable as a catalyst for polymerization of .alpha.-olefins, especially, propylene is obtained as a precipitate by heating liquefied titanium trichloride in the presence of a liberating agent, and separating the thus formed precipitate. The liquified titanium trichloride is preferably prepared with an reducing titanium tetrachloride by organic aluminum compound in the presence of ether and hydrocarbon.

Abstract: Solid titanium trichloride in the form of fine granules having low aluminum compound content, which is suitable as a catalyst for polymerization of .alpha.-olefins, especially, propylene is obtained as a precipitate by heating liquefied titanium trichloride in the presence of a liberating agent, and separating the thus formed precipitate. The liquefied titanium trichloride is preferably prepared with an reducing titanium tetrachloride by organic aluminium compound in the presence of ether and hydrocarbon.