Process for the polymerization of a polyolefin

Abstract

The present invention relates to a process for the polymerization of a polyolefin, preferably polypropylene, in a polymerization reactor by contacting one or more olefins, preferably propylene, with a catalyst system in said reactor while stirring, said catalyst system comprising: * a procatalyst comprising 1) a magnesium-containing support, 2) titanium, 3) a phthalate-free internal electron donor; and 4) optionally an activator; wherein said procatalyst is obtained by the following process: i) contacting a compound R, MgX—, with an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product, being a solid Mg(OR)X-x, Ris the same as Rbeing a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has between 1 and 20 carbon atoms; wherein Xand Xare each independently a halide; z is in a range of larger than 0 and smaller than 2, being 0<z<2; x is in a range of larger than 0 and smaller than 2, being 0<x<2; ii) optionally contacting the solid Mg(OR)X-x obtained in step ii) with at least one activating compound selected from the group formed by activating electron donors and metal alkoxide compounds of formula M'(OR),(OR)or M(OR)v-(R), to obtain a second intermediate product; wherein: Mis a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valency of M; Mis a metal being Si; v is the valency of M; Rand Rare each independently a hydrocarbyl group; w is smaller than v, v is preferably 3 or 4; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with the halogen-containing Ti-compound, the internal electron donor and optionally an activator; * optionally an external electron donor; and * a co-catalyst, being a alkyl aluminum co-catalyst preferably having formula AlHR-n, wherein H is a hydride; n is 0, 1 or 2, preferably 0; wherein R is a C1-C12 alkyl group, preferably ethyl; wherein a portion of the co-catalyst and optionally a portion of the external electron donor is (are) pre-contacted with the procatalyst prior to the addition of the catalyst system to the polymerization reactor. The present invention also relates to a polyolefin and a shaped article comprising said polyolefin.