Catalysts for the polymerization and copolymerization of propylene and polymerization processes using these catalysts

Claim 1

Process for the polymerisation of propylene, or the copolymerisation of propylene with other alpha-olefins, in the presence of a catalyst, characterised in that the said catalyst comprises a support containing essentially magnesium chloride, or magnesium chloride with a chlorinated derivative of aluminum, and an electron donor compound, but no product comprising a Mg--C bond, this support having a density comprised between 1.2 and 2.1 and a specific surface area comprised between 20 and 60 m 2 /g (BET), and occurring in the form of spheroidal particles, having a mean diameter by mass comprised between 10 and 100 microns and a particle size distribution such that the ratio of the mean diameter by mass, Dm, to the mean diameter by number, Dn, is less than or equal to 3, which support has been treated with an electron donor compound chosen from among the aromatic ethers and the esters of an aromatic acid, and which when impregnated with titanium tetrachloride comprises 0.5 to 3% of atoms of titanium per atom of magnesium, and further characterised in that the said polymerisation or copolymerisation is carried out in the presence of a co-catalyst of the formula Al(R 7 ) 3 , in which R 7 is an alkyl radical having 2 to 12 carbon atoms.