Polypropylene film with improved slip performance

A process for preparing a film, comprising the steps of:

• i) preparing a propylene homopolymer (HPP) having a melting temperature (Tm) measured by differential scanning calorimetry (DSC) according to ISO 11357 in a range from 152 to 162° C., a xylene cold soluble fraction (XCS) determined at 25° C. according to ISO 16152 of equal or below 1.5 wt % and a content of 2,1 erythro regiodefects as determined from 13C-NMR spectroscopy in a range from 0.01 to 1.00 mol % in a multistage process wherein a loop reactor is followed by a gas phase reactor, in the presence of a catalyst system comprising a cocatalyst comprising a compound of a group 13 metal, and a metallocene catalyst complex of formula (I):
• wherein
• Mt is Hf or Zr;
• each X is a sigma-ligand,
• each R1 independently is the same or may be different and is a CH2—R7 group, where R7 is H or linear or branched C1-6-alkyl group, C3-8 cycloalkyl group, C6-10 aryl group,
• each R2 is independently a —CH═, —CY═, —CH2-, —CHY— or —CY2-group, wherein Y is a C1-10 hydrocarbyl group and where n is 2-6,
• each R3 and R4 is independently the same or may be different and is hydrogen, a linear or branched C1-C6-alkyl group, an OY group or a C7-20 arylalkyl, C7-20 alkylaryl group or C6-20 aryl group, whereby at least one R3 per phenyl group and at least one R4 is not hydrogen, and optionally two adjacent R3 or R4 groups may be part of a ring including the phenyl carbons to which they are bonded,
• R5 is a linear or branched C1-C6-alkyl group, C7-20 arylalkyl, C7-20 alkylaryl group or C6-C20-aryl group,
• R6 is a C (R8)3 group, where R8 is a linear or branched C1-C6 alkyl group,
• each R is independently a C1-C20-hydrocarbyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl,
• ii) forming the propylene homopolymer (HPP) obtained in step i into a film together with 0.1-0.4 wt % of a slip agent, and 0.0-0.5 wt % of an anti-block agent.