Manufacture of catalysts for polymerization of olefins

Claim 1

In a process for the production of solid catalysts based on titanium trichloride used in the polymerization of alpha-olefins wherein titanium tetrachloride is reduced by an organoaluminum compound to form a precipitate, and then the precipitate is aged in the presence of its formation media, the improvement comprising reducing the titanium tetrachloride with the organoaluminum compound such that the ratio of the number of titanium tetrachloride moles to the number of organic gram equivalents of the organoaluminum compound is at least equal to 1.8, with the organoaluminum compound being a compound having the general formula AlR n X 3-n in which R is an alkyl, cycloalkyl, aryl or aralkyl group containing 1 to 12 carbon atoms, X is a hydrogen or halogen atom, and n is an integer or fraction which can assume any value between 1 and 3, the process being performed in the presence of 2 to 5 moles, per mole of organoaluminum compound, of one or several aliphatic ethers of formula R'--O--R" in which R' and R" are alkyl groups containing 1 to 5 carbon atoms, at least a portion of said ether being mixed with the organoaluminum compoound in the absence of the titanium tetrachloride, the ratio of the number of moles of ether to the number of moles of the organoaluminum compound in said mixture being between 0.3 and 5, the reduction of the titanium tetrachloride is performed between -10° and +60° C, and the aging of the precipitate is performed between 20° and 100° C, for a period between 15 minutes and 24 hours, and recovering the solid catalyst.