Process for the preparation of a polypropylene molding composition

Claim 1

A process for the preparation of a polypropylene molding composition consisting of 65 to 95% by weight of a polypropylene and 35 to 5% by weight of an ethylene propylene copolymer by continuous polymerization in two stages in liquid propylene, which comprises preparing a crystalline polypropylene or a polypropylene modified by small amounts of another 1-olefin in the first state at a temperature between about 40° C. and about 85° C. and a pressure higher than the pressure of the second stage and a residence time of 40 to 90 minutes and preparing an ethylene/propylene copolymer in the second stage at a temperature between about 40° C. and about 85° C. and under a pressure of 23 to 64 atmospheres and a residence time of 10 to 90 minutes in the presence of 10 to 55 mole % of ethylene, based on the ethylene/propylene mixture present, a mixed catalyst which has been formed by bringing into contact (A) the reaction product of (a1) a reaction product of a magnesium halide with an electron donor and/or a cyclopolyene and (a21) a compound formed by reduction of titanium tetrachloride by means of an organometallic compound of main groups I to III of the periodic table or (a22) titanium tetrachloride with (B) a halogen-free organoaluminum compound and (C) a compound from the group comprising cyclopolyenes and aromatic carboxylic acid esters, wherein the mixed catalyst being used in both stages is composed of about 0.001 to 1 mole/liter of liquid of component (A) about 0.01 to 40 moles/liter of liquid of component (B) and 0.003 to 12 moles/liter of liquid of component (C).