Patent ID: 8901259

Claim:
Process for the preparation of heterophasic polypropylene copolymers comprising the steps of: producing a polypropylene polymer matrix (A) in the presence of a catalyst system in a first slurry reactor and optionally in a second slurry reactor or in a 1 st gas phase reactor (GPR), yielding a first polymerisation product, wherein the catalyst system comprises: i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester; (ii) optionally an organometallic cocatalyst; and (iii) an external donor represented by formula (I) or (II) Si(OCH 2 CH 3 ) 3 (NR 1 R 2 ) (I) or R 3 n R 4 m Si(OR 5 ) z (II) wherein R 1 and R 2 can be the same or different and represent a hydrocarbon group having 1 to 12 carbon atoms, R 3 and R 4 are identical or different hydrocarbon residues having 1 to 12 carbon atoms, 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; transferring the first polymerisation product into a 1 st GPR or a 2 nd GPR, if the matrix is produced in a slurry/GPR combination; producing an ethylene/propylene-copolymer in the polymer matrix in the presence of the catalyst system in said 1 st or 2 nd GPR; optionally transferring the 1 st or 2 nd GPR product into a 2 nd respectively 3 rd GPR and producing a second ethylene/propylene-copolymer in the polymer matrix in the presence of the catalyst system in said 2 nd or 3 rd GPR, said 1 st and 2 nd ethylene/propylene mixtures may have the same or different composition ratios; and recovering the polymer product for further processing, the recovered polymer product including heterophasic polypropylene copolymers having an MFR 2 (2.16 kg, 230° C.) of 15 to 200 g/10 min, determined according to ISO 1133 comprising a propylene homo- or copolymer matrix (A) with an MFR 2 (2.16 kg, 230° C.) of 80 to 500 g/10 min, determined according to ISO 1133 and an ethylene or C 4 -C 10 -alpha-olefin propylene rubber phase (B) dispersed within the matrix, wherein the heterophasic polypropylene copolymers have a fraction soluble in p-xylene at 25° C. (XCS), having an intrinsic viscosity of 2.85 to 4.00 dl/g, determined according to DIN EN ISO 1628-1 and -3 and being composed of propylene monomer units in an amount of 70 wt % to 90 wt %.