Thermoplastic polyolefins with high flowability and excellent surface quality produced by a multistage process

A catalyst system for the production of reactor grade thermoplastic polyolefins in a multistage polymerization process with at least 3 polymerization steps, said catalyst system comprises

• (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester and
• (ii) an organometallic cocatalyst and
• (iii) external donor represented by the formula
• Si(OCH2CH3)3(NxRy)
• wherein Rx and Ry can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms,
• said reactor grade thermoplastic polyolefins have high flowability and excellent surface quality and comprise
• (A) 40-90 wt % of a propylene homo- or copolymer matrix with an MFR2 in accordance with ISO 1133 (230° C., 2.16 kg load) of 200 g/10 min and
• (B) 2-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of ≦2.8 dl/g and an ethylene content of >50 to 80 wt % and
• (C) 8-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 3.0-6.5 dl/g and an propylene content of 50 to 80 wt %.

Process for producing reactor grade thermoplastic polyolefins with high flowability and excellent surface quality, wherein the process is a multistage process with at least 3 polymerization steps in the presence of a catalyst system, said process comprises either a combination of one loop and two or three gas phase reactors or a combination of two loops and two gas phase reactors, said catalyst system comprises

• (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester and
• (ii) an organometallic cocatalyst and
• (iii) external donor represented by the formula
• Si(OCH2CH3)3(NRxRy)
• wherein Rx and Ry can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms,
• and wherein further said reactor grad thermoplastic polyolefins comprises
• (A) 40-90 wt % of a propylene homo- or copolymer matrix with an MFR in accordance with ISO 1133 (230° C., 2.16 kg load) of ≧200 g/10 min and
• (B) 2-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of ≦2.8 dl/g and an ethylene content of >50 to 80 wt % and
• (C) 8-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 3.0-6.5 dl/g and a propylene content of 50 to 80 wt %.