| abstract |
There are disclosed catalyst components for polymerizing olefins, consisting of the product obtained by successively reacting n (A) a Mg compound (halide, alcoholate, haloalcoholate, carboxylate, oxyde, hydroxyde, salt of an inorganic oxygen containing acid, Grignard reagent or reaction product of a Grignard reagent with a silicon compound), optionally in the form of a complex with an electron-donor compound, with n (B) a compound having general formula [MO x (OR) y ] n , wherein M=Ti, V or Zr, R=an alkyl, an aryl or a cycloalkyl containing 1 to 20 carbon atoms, x may be zero, y is an integer not lower than 2, 2x+y=a valence of M, and n=an integer from 1 to 6 (inclusive), and with n (C) a compound, other than the aluminium halides, exerting on component (B) a halogenating action and a reducing action, or a mixture of a halogenating compound with a reducing substance. n These components, used to prepare the final catalysts by mixing them with organometallic compounds of metals belonging to Groups I, II and III of the Mendelyeev Periodic Table, provide catalysts which are particularly active in the polymerization of ethylene, alpha-olefins having at least three carbon atoms, and mixtures of ethylene with alpha-olefins and/or with diolefins or multiolefins. |