CATALYSEURS POUR LA POLYMERISATION ET LA COPOLYMERISATION DU PROPYLENE ET PROCEDES DE POLYMERISATION UTILISANT CES CATALYSEURS

CATALYSEURS UTILISABLES POUR LA POLYMERISATION ET LA COPOLYMERISATION, AVEC D'AUTRES ALPHA-OLEFINES, DU PROPYLENE, CARACTERISES EN CE QU'ILS COMPORTENT UN SUPPORT DE CHLORURE DE MAGNESIUM, DE FORME SPHERIQUE, PRESENTANT UNE DISTRIBUTION GRANULOMETRIQUE ETROITE ET UNE GRANULOMETRIE MOYENNE COMPRISE ENTRE 10 ET 100MICRONS, AYANT UNE SURFACE LISSE ET UNE DENSITE COMPRISE ENTRE 1,1 ET 1,6, SUPPORT QUI A ETE TRAITE PAR UN DONNEUR D'ELECTRONS CHOISI PARMI LES ETHERS ET LES ESTERS D'UN ACIDE ORGANIQUE AROMATIQUE ET QUI, IMPREGNE DE TETRACHLORURE DE TITANE, COMPORTE 0,5 A 3 D'ATOMES DE TITANE PAR ATOME DE MAGNESIUM, ET UN PROCEDE POUR LA MISE EN OEUVRE DESDITS CATALYSEURS. The present invention relates to catalysts which can be used for the polymerization and copolymerization of propylene with other alpha-olefins, characterized in that they comprise a support containing essentially magnesium chloride and possibly a chlorinated aluminium derivative, 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 to the means diameter by number is less than or equal to 3, which support has been treated by an electron donor compound chosen from among the aromatic ethers and aromatic acid esters and which when impregnated with titanium tetrachloride comprises 0.5 to 3% of atoms of titanium per atom of magnesium, and process for utilizing the said catalyst.