Multi-stage process for the polymerization of olefins

A multi-stage process for the polymerization of ethylene, and optionally one or more α-olefins comprising from 3 to 10 carbon atoms, for producing a polymer having broad MWD, said process comprising the following stages:

• (A) polymerizing ethylene, and optionally an α-olefin, in one or more reactors, in the presence of a catalyst comprising the reaction product between:
• (i) a solid component comprising a compound of a transition metal MI selected from Ti and V, not containing MI-π bonds, and a halide of Mg in active form, optionally further comprising an electron-donor compound (internal donor);
• (ii) an alkyl-Al compound and optionally an electron-donor compound (external donor);
• (B) contacting the product obtained in stage (A), in any order whatever, with:
• (a) a compound capable of deactivating the catalyst of stage (A);
• (b) a zirconocene compound of formula (I):
• wherein R1, R2 R3 and R4, the same or different from each other, are selected from the group consisting of hydrogen, linear or branched, saturated or unsaturated, C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl radicals, optionally containing one or more Si or Ge atoms, or wherein two substituents of R1, R2, R3 and R4 form a ring having from 4 to 8 carbon atoms;
• R5 and R6, the same or different from each other, are selected from the group consisting of linear or branched, saturated or unsaturated C1-C20, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl radicals, optionally containing one or more Si or Ge atoms, or wherein one pair of vicinal R6 substituents of the same indenyl group forms a ring having from 4 to 8 carbon atoms;
• m is an integer ranging from 0 to 2;
• n is an integer ranging from 0 to 4;
• the groups X, the same or different from each other, are hydrogen, halogen, —R, —OR, —SR, —NR2 or —PR2, wherein R is selected from the group consisting of linear or branched, saturated or unsaturated, C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl radicals, optionally containing one or more Si or Ge atoms;
• and
• (c) optionally an activating cocatalyst;
• (C) polymerizing ethylene, and optionally an α-olefin, in one or more reactors, in the presence of the polymer obtained from stage (B).