Process for producing of a capacitor film comprising the steps of (a) polymerizing propylene in the presence of a catalyst comprising a solid catalyst system obtaining a polypropylene, (b) subjecting said polypropylene to a film forming process obtaining a capacitor film, wherein during the polymerization step (a) said catalyst comprising the solid catalyst system fragments into nanosized catalyst fragments being distributed in said polypropylene, said solid catalyst system comprises a transition metal, a metal which is selected from one of the groups 1 to 3 of the periodic table (IUPAC), and an internal electron donor.