Abstract: Modifiers based on high-pressure polyethylenes or low-pressure ethylene copolymers or highly amorphous olefin elastomers or mixtures of these with polyethylenes or isotactic polypropylenes are added to highly amorphous polypropylenes to reduce their surface tack.

Abstract: Procedure for the preparation of a solid catalyst component which is active in the polymerization of olefins, comprising the steps:a) contacting a dehydrated silica support with a solution of Mg-halide or Mg-alkyl-halide or a mixture of both, optionally in the presence of and Ti-alkoxyde or Ti-halogen-alkoxyde or a mixture of both,b) contacting the catalyst-precursor obtained in (a) with Mg-alkyl or Mg-alkyl-halide or a mixture of both, optionally in presence of electron-donors (Lewis bases),c) halogenating the catalyst-precursor obtained in (b) by contact of said activated support with halogenating agents,d) titanating the catalyst-precursor obtained in (c) with Ti-tetrahalide in the presence of electron-donors,e) recovering the solid catalyst-component from the reaction products of step (d).The catalyst component, which is obtained according to the above procedure, may also be used together with Al-trialkyl or Al-alkyl-halides and a Lewis base, as a catalyst for the polymerization of olefins.