Components and catalysts for the polymerization of olefins

A solid component to be employed, in combination with metallorganic Al compounds and with electron-donor compounds which are not completely complexed with Al-triethyl at the equivalent point of a potentiometric titration under standard conditions but reactive toward anhydrous Mg chloride, to form catalysts for the polymerization of alpha-olefins CH.sub.2 =CHR, said component comprising a titanium compound having at least a Ti-halogen bond and an electron-donor compound both supported on an anhydrous Mg dihalide, the electron-donor compound being selected from the group consisting of diisoamyl ether, triphenyl phosphite, .alpha.-methyl-.alpha.-phenyl-.gamma.-butyrolactone and the following classes of esters:

• (1) di-n-butyl succinate and di-isobutyl succinate;
• (2) esters of unsaturated polycarboxylic acids in which two carboxyl groups are linked to vicinal, double bond-forming carbon atoms and in which the hydrocarbyl radical or radicals of the COOR groups are linear saturated or unsaturated radicals or cycloaliphatic radicals with 2-20 carbon atoms or hydrocarbyl esters of unsaturated linear or branched polycarboxylic acids with 1-20 carbon atoms in which the carboxy groups are not linked to vicinal double bond-forming carbon atoms;
• (3) hydrocarbyl esters of aromatic meta- and paradicarboxylic acids and hydrocarbyl esters of polycarboxylic aromatic acids containing more than two carboxyl groups;
• (4) hydrocarbyl esters of aromatic hydroxy compounds containing the OH groups in meta- or para-position and esters of aromatic hydroxy acids the OH groups of which are in meta- or para-position with respect to the carboxyl group;
• (5) hydrocarbyl esters of polycarboxylic acids in which at least one carboxyl group is linked to an aromatic ring and at least one other is linked to carbon atom of an aliphatic chain or to a cycloaliphatic ring or at least two carbonyl groups are linked to an aromatic ring through an alkylene group;
• (6) esters of aromatic polycarboxylic acids containing at least two non-condensed aromatic rings, each bearing a carboxyl group;
• (7) esters of carbonic acid with glycols, and carbonic acid derivatives of formula RO--CO--OR' wherein R and R' are the same or different acyl groups with 1-20 carbon atoms;
• (8) esters of polyols and of monohydroxy-phenols;
• and
• (9) hydrocarbyl esters of acetylenic acids;
• the electron-donor compounds being extractable from the solid for at least 70% by mols with Al-triethyl under standard measurement conditions, and the surface area of the solid subjected to extraction being higher than 20 m.sup.2 /g.