| abstract |
Process for the preparation of a polypropylene molding composition n A propylene block copolymer having good flow properties and a very good low temperature impact strength is obtained in a high yield if a catalyst which consists of a chiral metallocene, containing a bridge, of the formula I ##STR1## and an aluminoxane is used for the polymerization of propylene and the comonomers. n The polymerization is carried out in two stages, a crystalline propylene polymer being prepared in the first stage. |