Bimetal catalyst for the (co) polymerization of α-olefins

A process for the preparation of a solid component of catalyst for the (co)polymerization of α-olefins, comprising at least 95% by weight, based on the total weight of the solid component of catalyst, of titanium, magnesium, aluminum, chlorine, carboxylate (R—COO−) and at least one metal selected from the group consisting of hafnium and zirconium, in the following molar ratios:

• M/Ti=0.1-10.0;
• Mg/Ti=1.0-20.0:
• Al/Ti=0.01-6.0
• Cl/Ti=2.0-70.0;
• R—COO−/Ti=0.1-10.0
• wherein:
• R is an aliphatic, cycloaliphatic or aromatic hydrocarbon radical, containing from 1 to 30 carbon atoms, and
• M is hafnium, zirconium or mixtures thereof,
• wherein said process comprises the following steps in succession:
• (i) preparing a mixture of at least one compound of magnesium, a compound of titanium and at least one compound of a metal M selected from zirconium and hafnium, in the appropriate proportions, in a medium consisting of an inert organic liquid, in which at least one of said compounds is insoluble;
• (ii) preparing a substantially limpid solution by the addition to said mixture of step (i) of a sufficient quantity of a carboxylic acid having the formula R—COOH (I), wherein R is an aliphatic, cycloaliphatic or aromatic hydrocarbon radical, containing from 1 to 30 carbon atoms, and maintaining this, under suitable conditions of pressure and temperature, and with no significant removal of hydrochloric acid, if formed, until the substantial dissolution of all the insoluble compound;
• (iii) adding and reacting with the solution obtained in step (ii) an alkyl aluminum chloride which can be represented with the following general formula (II):
• AlR′nCl(3−n) (II)
• wherein R′ is a linear or branched alkyl radical, containing from 1 to 20 carbon atoms, and “n” is a decimal number having values ranging from 0.5 to 2.5, in a quantity which is at least sufficient to make at least 70% of the titanium present in the solution of said step (ii) precipitate into the form of a solid compound, and
• (iv) separating the solid precipitated in step (iii) from the residual liquid to obtain said solid component of catalyst.