Catalyst components and catalysts for polymerizing olefins prepared from the catalysts

Claim 1

Components for catalysts for the polymerization of olefins, consisting of the product obtained by reacting the product of reaction between (A) a magnesium compound selected from the groups (1) compounds having formula XnMg(OR).sub.2-n wherein X is a halogen atom, a hydroxyl group or an alkyl, aryl or cycloalkyl radical containing 1-20 carbon atoms; R is an alkyl, aryl or cycloalkyl radical containing 1-20 carbon atoms, or a --COR' radical in which R' has the same meaning as R; 0≦n≦2; or products of reaction of said compounds with hydrocarbyl electron-donor compounds; (2) compounds having formula RMgX wherein X is a halogen atom, and R is an alkyl, aryl or cycloalkyl radical containing 1-20 carbon atoms, or products of reaction of said compounds with polysiloxane compounds containing from 2 to 1000 monomeric units ##STR3## in which R is the same or different from R', R being an alkyl, aryl, alkoxy or aryloxy radical, and R' being hydrogen, halogen or an alkyl, aryl or cycloalkyl radical containing 1-20 carbon atoms; (3) Mg oxide, Mg hydroxide, Mg hydroxy halides, or Mg salts of inorganic oxygen containing acids, and (B) a compound of Ti, V or Zr containing at least two --OR groups linked to a Ti, V or Zr atom through the oxygen atom, and in which R is an alkyl, aryl or cycloalkyl radical having 1-20 carbon atoms, with (C) a silicon compound capable of substituting, in compound (B), at least one --OR group with a halogen atom and to reduce the valence of the metal of compound (B) to a lower valence, or a mixture of a compound capable of substituting, in compound (B), at least one --OR group with a halogen atom and a compound capable of reducing the metal of compound (B) to a lower valence; with reaction between compounds (A) and (B) being conducted in the presence of a hydrocarbyl electron-donor compound when compound (A) is an (A)(3) compound, and component (C) being a halogenating, but not necessarily a reducing compound when (A) is an (A)(2) compound.