Process for producing improved random propylene copolymers

摘要

A process for preparing random propylene copolymers containing copolymerized C2-C10-alk-1-enes by polymerization of propylene and C2-C10-alk-1-enes in the presence of a Ziegler-Natta catalyst system comprising a titanium-containing solid component a) comprising a compound of magnesium, a halogen, silica gel as support and a carboxylic ester as electron donor compound, and also, as cocatalysts, an aluminum compound b) and a further electron donor compound c), where propylene and the C2-C10-alk-1-enes are polymerized with one another at from 50 to 100 DEG C. at pressures in the range from 15 to 40 bar and mean residence times of from 0.5 to 5 hours and the support used in the titanium-containing solid component is a silica gel which has a mean particle diameter of from 5 to 200 mu m, a mean particle diameter of the primary particles of from 1 to 10 mu m and voids or channels having a mean diameter of from 1 to 10 mu m, which voids or channels have a macroscopic proportion by volume based on the total particle in the range from 5 to 20%.