Catalyst precursor and catalyst for the high-temperature (co)polymerization of alpha-olefin

A catalyst precursor for the (co)polymerization of alpha-olefins, comprising titanium, magnesium, aluminum, chlorine and at least one metal M selected from hafnium and zirconium characterized in that it is obtained by means of a process comprising the following steps:

• (i) heating a mixture in a liquid hydrocarbon solvent comprising a magnesium chloride, a compound of titanium, a compound of said metal M, a carboxylic acid R—COOH, wherein R is an organic group having from 2 to 30 carbon atoms, in such quantities as to respect the following atomic or molar ratio ranges:
• M/Ti=0.2-5.0;
• Mg/Ti=3.0-20.0;
• R—COOH/(Mg+M)=1-8
• at a temperature ranging from 50 to 200° C. for at least one minute and separating the possible solid residue remaining undissolved, to obtain a solution;
• (ii) adding to the solution obtained in step (i), an aluminum alkyl chloride having the following general formula (I):
• AlR′nCl(3−n) (I)
• 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 an amount sufficient for precipitating in the form of a solid compound at least 70% of the metals Mg, M and Ti present in said solution, and heating the mixture thus obtained to a temperature ranging from 40 to 130° C. for a time ranging from 5 to 240 minutes to obtain a solid precipitate comprising Mg, M, Al and Cl in atomic ratios with respect to the Ti within the following ranges:
• M/Ti=0.2-5.0;
• Mg/Ti=3.0-15.0;
• Al/Ti=0.1-4.0;
• Cl/Ti=15.0-60.0;
• (iii) separating the solid precipitate thus formed from the residual liquid solution;
• and
• (iv) putting said solid precipitate obtained in step (iii) in contact with a siloxane compound A, having from 2 to 40 carbon atoms and from 1 to 15 silicon atoms, comprising at least one siloxane group selected from the following formulae:
• O—Si—C and Si—O—Si,
• in such an amount that the atomic ratio Si/Ti between the Si atoms in the siloxane compound A and the Ti atoms in the solid precipitate, is higher than or equal to 0.1 to obtain said catalyst precursor.