Abstract: Catalysts for polymerization and copolymerization of olefins to form polymers having a high degree of isotacticity and fast rate of crystal transformation. The catalysts embody a component made by chlorinating a magnesium alkyl with chlorine or a mixture of chlorine and alkyl chloride to form a carrier, contacting the carrier first with liquid TiCl.sub.4, then with a Lewis base, and after that at least once with TiCl.sub.4 in the absence of Lewis base.

Abstract: Catalysts for polymerization and copolymerization of olefins to form polymers having a high degree of isotacticity and fast rate of crystal transformation. The catalysts embody a component made by chlorinating a magnesium alkyl with chlorine or a mixture of chlorine and alkyl chloride to form a carrier, contacting the carrier first with liquid TiCl.sub.4, then with a Lewis base, and after that at least once with TiCl.sub.4 in the absence of Lewis base.

Abstract: New highly active and highly stereospecific catalysts for the polymerization of alpha-olefins are disclosed, the starting components of which are(a) an organometallic-compound of Al free from halogen atoms bound directly to the Al atom;(b) an electron-donor compound (such as a Lewis base) in an amount such that 15% to 100% of the organometallic Al compound (a) is combined with the electron-donor compound; and(c) a solid component comprising, at least on surface, the reaction product of a halogen. Mg compound with a tetravalent Ti compound and with an electron-donor compound, the molar ratio electron-donor compound/Ti being higher than 0.2, and the molar ratio halogen atoms/Ti being higher than 4.Processes for polymerizing the alpha-olefins and mixtures thereof with ethylene in contact with the new catalysts are also disclosed.

Abstract: New components of catalysts for polymerizing alpha-olefins, and the catalysts formed from the new components are disclosed. Said catalyst components are prepared by reacting Ti compounds with a carrier in the form of spheroidal particles of specified characteristics and which consists of or comprises an Mg compound, or mixture of Mg compounds of the formulaX.sub.n Mg(OR).sub.2-n (I)in which 0.ltoreq.n.ltoreq.2, R is an alkyl, aryl, cycloalkyl radical containing from 1 to 20 carbon atoms, X is halogen or a group OR' in which R' is an alkyl, aryl or cycloalkyl radical containing from 1 to 20 carbon atoms and is the same or different from R in formula (I).

Abstract: New highly active and highly stereospecific catalysts for the polymerization of alpha-olefins are disclosed, the starting components of which are(a) an organometallic-compound of Al free from halogen atoms bound directly to the Al atom;(b) an electron-donor compound (such as a Lewis base) in an amount such that 15% to 100% of the organometallic Al compound (a) is combined with the electron-donor compound; and(c) a solid component comprising, at least on the surface, the reaction product of a halogenated Mg compound with a tetravalent Ti compound and with an electron-donor compound, the molar ratio electron-donor compound/Ti being higher than 0.2, and the molar ratio halogen atoms/Ti being higher than 4.Processes for polymerizing the alpha-olefins and mixtures thereof with ethylene in contact with the new catalysts are also disclosed.

Abstract: New components of catalysts for polymerizing alpha-olefins, and the catalysts formed from the new components are disclosed. Said catalyst components are prepared by reacting Ti compounds with a carrier in the form of spheroidal particles of specified characteristics and which consists of or comprises an Mg compound, or mixture of Mg compounds of the formulaX.sub.n Mg(OR).sub.2-n (I)in which 0.ltoreq.n.ltoreq.2, R is an alkyl, aryl, cycloalkyl radical containing from 1 to 20 carbon atoms, X is halogen or a group OR' in which R' is an alkyl, aryl or cycloalkyl radical containing from 1 to 20 carbon atoms and is the same or different from R in formula (I).

Abstract: There are disclosed new catalysts for the stereospecific polymerization of alpha-olefins having the formula CH.sub.2 .dbd.CHR in which R is an alkyl radical containing from 1 to 4 carbon atoms and the starting components of which comprise (a) a halogenated organometallic Al compound and (b) reduction products of TiCl.sub.4 comprising TiCl.sub.3 in the crystalline beta form.

Abstract: New catalyst components comprising compounds containing titanium, magnesium and halogens, and catalysts for polymerizing olefins obtained by mixing said components with organometallic Al compounds are disclosed.

Abstract: There is disclosed a new and improved process for preparing compositions consisting for at least 50% by weight of isotactic polypropylene and having high impact strength at low temperatures.The process comprises three or more steps. In the first step propylene is polymerized in an inert liquid hydrocarbon medium and in contact with a stereospecific catalyst prepared by mixing a titanium trihalide with a dialkyl aluminum monohalide to obtain a slurry. In subsequent steps ethylene, or an ethylene/propylene mixture, is fed to the polymerization suspension of first step and the polymerization is continued until the amount of ethylene polymerized is, at most, 20% by weight of the total, final polymeric composition obtained.

Abstract: Polypropylene obtained by polymerizing propylene in contact with stereospecific catalysts supported on anhydrous magnesium dihalides is purified, and the magnesium content thereof is reduced, by treating a suspension of the polypropylene in a hydrocarbon solvent with an aliphatic alcohol containing from 3 to 8 carbon atoms, followed by centrifuging to remove both the hydrocarbon solvent and the catalyst residues solubilized by the alcohol treatment.

Abstract: New catalyst components comprising compounds containing titanium, magnesium and halogens, and catalysts for polymerizing olefins obtained by mixing said components with organometallic Al compounds are disclosed.