Catalysts for the polymerisation of alpha-olefins

Claim 1

Process for the manufacture of titanium trichloride-based catalysts suitable for alpha-olefin polymerisation, characterised in that it comprises successively: (a) in a first stage, forming a suspension of solid particles by reducing titanium tetrachloride at a temperature of between -10 and 80°C, by means of at least one organoaluminium compound of the formula AlR n X₃ -n in which R is an alkyl, cycloalkyl, aryl or aralkyl group containing 1 to 12 carbon atoms, X a hydrogen, chlorine or bromine atom, and n an integer or fraction capable of assuming any value from 1 to 3, the organoaluminium compound(s) being used in such quantity that the ratio of the number of moles of titanium tetrachloride to the number of organic gram-equivalents of the organoaluminium compound(s) is between 1.2 and 50, and the reduction being carried out in a liquid hydrocarbon, in the presence of 2 to 5 moles, per mole of organoaluminium compound, of one or more aliphatic ethers of formula RʹORʺ in which Rʹ and Rʺ are identical or different alkyl groups containing from 1 to 12 carbon atoms; (b) in a second stage, keeping the suspension of solid particles obtained in the first stage, at a temperature of between 20 and 115°C, for a period of between 15 minutes and 24 hours; (c) in a third stage, washing the solid particles resulting from the second stage by means of a liquid hydrocarbon, and (d) in the fourth stage, bringing the solid particles resulting from the third stage into contact with one or more alpha-olefins in such quantity that the solid catalyst obtained contains from 0.05 to 10g of polyalpha-olefin per milligram-atom of titanium, this contact being performed at a temperature of between 0 and 60°C, in the presence of at least one organoaluminium compound of formula AlR n X₃ -n in which R, X and n correspond to the same definitions as previously, this organoaluminium compound being identical to, or different from, that used in the first stage.