Catalysts and catalyst components useful for polymerizing olefins

Claim 1

Components for catalysts for polymerizing olefins comprising the product of the reaction between at least the following substances: (a) a halogenated Ti compound selected from the group consisting of Ti tetrahalides and Ti haloalcoholates; (b) a solid support comprising the following essential components or mixtures thereof: component (b1) containing (A) an oxygenated Mg compound selected from the group consisting of MgO, mixed oxides of Mg, Al and/or Si, Mg hydroxide, Mg hydroxychloride or bromide, Mg nitrate, Mg phosphates, Mg silicates, Mg carboxylates and the products obtained from the dehydration, under hydrolysis conditions, of hydrated Mg halides, and (B) an adduct between a Mg dihalide and at least one hydrocarbyl electron-donor compound or the product of the decomposition of said adduct to Mg dihalide; or component (b2) obtained by reacting an oxygenated Mg compound as defined in (A) with a hydrocarbyl electron-donor compound free from active hydrogen atoms (component ED) or with mixtures thereof with an electron-donor compound containing active hydrogen atoms (compound HED); the reaction system comprising also a compound ED, at least when said compound ED or derivatives thereof are not used in preparing support (b), the amount of compound ED present in the catalyst component, in a form non-extractable with TiCl 4 at 80° C., being in the range of from 0.05 to 5 moles per mole of Ti compound existing after the treatment at 80° C.