Process for the Production of a Bimodal Polypropylene Having Low Ash Content

A process for production of propylene polymers with improved properties and a low ash content comprising:

• polymerizing propylene and one or more optional comonomers in at least two sequential polymerization reactors in presence of:
• a Ziegler-Natta catalyst comprising a titanium compound having at least one titanium-halogen bond, and an internal electron donor, both supported on a magnesium halide in active form;
• triethyl aluminium;
• an optional external electron donor (ED);
• and
• hydrogen,
• wherein the internal electron donor comprises at least 80 wt % of a diether, the molar ratio Al/Ti is at most 40, the propylene polymers are recovered from the polymerization reactor without any washing, as a powder and optionally converted to pellets, and wherein the propylene polymer fractions produced in the at least two of the sequential polymerization reactors differ in average molecular weight such that the ratio of the melt flow indices of the propylene polymer fractions with the highest and the lowest melt flow index is at least 10.