Multi-stage process for the (CO) polymerization of olefins

A multi-stage process for the polymerization of olefins comprising:

• (I) a first polymerization stage, wherein one or more olefins of the formula CH2═CHR, wherein R is selected from the group consisting of hydrogen, a linear or branched, saturated or unsaturated C1–C10 alkyl, a cycloalkyl and an aryl radical, are polymerized in one or more reactors, in the presence of a catalyst comprising the product of the reaction between an alkyl-Al compound and a solid component comprising at least one compound of a transition metal MI chosen from Ti and V, and not containing MI-π bonds, and a halide of Mg, in order to produce an olefinic polymer having porosity, expressed as the percentage of voids, greater than 5%;
• (II) a treatment stage, wherein the product obtained in said first polymerization stage (I) is, in any order whatever:
• (a) contacted with a compound capable of deactivating the catalyst used in stage (I);
• and
• (b) contacted with a late transition metal complex, optionally in the presence of a suitable activating agent;
• and
• (III) a second polymerization stage, wherein one or more olefinic monomers are polymerized in one or more reactors, in the presence of the product obtained from stage (II);
• wherein the amount of polymer produced in the first polymerization stage (I) is between 10 and 90% by weight relative to the total amount of polymer produced in stages (I) and (III).