High purity heterophasic polypropylene copolymers comprising (A) 73 to 98 wt % of a propylene homo- or copolymer matrix with an MFR2 in accordance with ISO 1133 (230° C., 2.16 kg load) of ≧45 g/10 min and (B) 2 to 27 wt % of an elastomeric copolymer, comprising propylene in an amount of at least 50 wt % of component (B) and at least ethylene and/or one other C4 to C10 alpha olefin in an amount of up to 50 wt % of component (B), the heterophasic polypropylene copolymers being obtainable by a multistage polymerization process in the presence of a catalyst system comprising (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester and (ii) optionally an organometallic cocatalyst and (iii) an external donor represented by formula (I) Si(OCH2CH3)3(NR1R2) wherein R1 and R2 can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms, their production and use.