Patent ID: 8569412

Claim:
Process for the preparation of heterophasic polypropylene compositions, comprising the steps of: producing a polypropylene polymer matrix (A) in the presence of a catalyst system comprising a Ziegler-Natta procatalyst in combination with an external donor and a cocatalyst in at least one slurry reactor transferring the slurry reactor product into a first gas phase reactor (GPR), (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester as internal donor and (ii) an organometallic cocatalyst and (iii) an external donor represented by formula (III) Si(OCH 2 CH 3 ) 3 (NR 1 R 2 ) wherein R 1 and R 2 can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms or formula (IV) R 3n R 4 m Si(OR 6 ) z wherein R 3 and R 4 are identical or different hydrocarbon residues, R 5 is methyl or ethyl, z is 2 or 3; m is 0 or 1; n is 0 or 1; with the proviso that n+m+z=4, said procatalyst being modified by polymerizing it with a vinyl compound of the formula CH 2 ═CH—CHR 6 R 7 wherein R 6 and R 7 together form a 5- or 6-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising 1 to 4 carbon atoms, in the presence of the cocatalysts and the external donor, wherein the slurry reactor product is further polymerized in the presence of the catalyst system in said first GPR transferring the first GPR product into a 2 nd GPR producing an ethylene/propylene-copolymer (B) in the polymer matrix (A) in the presence of the catalyst system in said 2 nd GPR transferring the 2 nd GPR product into a 3 rd GPR and further producing an ethylene/propylene-copolymer (B) in the polymer matrix (A) in the presence of the catalyst system in said 3 rd GPR, said ethylene/propylene copolymers having the same composition ratios and recovering the polymer product for further processing, yielding a polypropylene polymer matrix (A) containing said ethylene/propylene copolymers (B) having the same composition ratios, respectively having same ethylene content and intrinsic viscosities, so that an unimodal rubber composition is obtained adding (C) 0-15 wt % of an elastomeric ethylene/alpha-olefin random copolymer and (D) 3-25 parts per weight of inorganic filler.