Components of catalysts useful for the polymerization of α-olefins, and catalysts prepared therefrom

Claim 1

A solid catalyst component for preparing catalysts for polymerizing alpha-olefins containing at least three carbon atoms, which comprises Mg dihalide and, combined with the dihalide, a Ti compound and a hydrocarbyl electron-donor free of active hydrogen atoms, the molar ratio Mg/Ti in said catalyst component being from 5 to 100 and the g moles of the electron-donor compound being from 0.4 to 3.5 per 1 g atom of Ti, and the content of Ti compounds soluble in TiCl 4 at 80° C. present in the catalyst component being less than 50% by weight with respect to the total content of Ti compounds, said catalyst component being obtained by reacting: (a) a halogenated Ti compound soluble in hydrocarbons and containing at least a Ti-halogen bond; (b) a product comprising a Mg dihalide, obtained by decomposition of an adduct between a Mg dihalide and at least 0.5 moles per mole of Mg dihalide of an electron-donor compound selected from the group consisting of hydrocarbyl electron-donors, ammonia, POCl 3 and PSCl 3 , the decomposition of the adduct being carried out with a substance capable of reacting with the electron-donor compound of the adduct and selected from the group consisting of organometallic compounds of metals of Groups I to III of the Mendelyeev Periodic Table or of Si, and, when the electron-donor of the adduct contains active hydrogen atoms, also from the group consisting of halides of tetravalent Si, trihalides of Al and B and halides of Sn and Sb, said decomposition product being characterized in that, in its X-rays powder spectrum instead of the maximum intensity line appearing in the normal Mg dihalide spectrum, a halo appears the intensity maximum of which is shifted with respect to said line; and (c) a hydrocarbyl electron-donor free of active hydrogen atoms, which may be also reacted with (a) or combined with (b) before reacting (a) with (b).