Process for the preparation of a polypropylene molding composition

Claim 1

A process for the preparation of a polypropylene molding composition consisting essentially (1) 20 to 99% bv weight of a crystalline polymer which is comprised to the extent of at least 95% by weight of polymerized propylene and (2) 1 to 80% by weight of a non-crystalline ethylene-propylene copolymer having an ethylene content of 20 to 90% by weight, in which first the polymer (1) is prepared in one or more stages in liquid propylene over a residence time of 15 to 400 minutes under a pressure of 5 to 100 bar and at a temperature of 0 to 100° C., and the polymer (2) is prepared in a second stage over a residence time of 10 to 180 minutes, under a pressure of 5 to 100 bar and at a temperature of 0 to 100° C. in the presence of ethylene in the gas phase, in the presence of a catalyst which is comprised of a transition metal compound and an organoaluminum compound, which comprises carrying out the polymerization in the second stage in the gas phase, and using a transition metal compound which is a metallocene of the formula I ##STR10## in which M 1 is a metal of group IVb, Vb or VIb of the periodic table, R 1 and R 2 are identical or different and are a hydrogen atom, a C 1 -C 10 -alkyl group, a C 1 -C 10 -alkoxy group, a C 6 -C 10 -aryl group, a C 6 -C 10 -aryloxy group, a C 2 -C 10 -alkenyl group, a C 7 -C 40 -arylalkyl group, a C 7 -C 10 -alkylaryl group, a C 8 -C 40 -arylalkenyl group or a halogen atom, R 3 , r 4 , R 5 and R 6 are identical or different and are a hydrogen atom, a halogen atom, a C 1 -C 10 -alkyl group, --NR 10 , --SR 10 , --OSiR 3 10 , --SiR 3 10 or PR 2 10 , in which R 10 is a halogen atom or a C 1 -C 10 -alkyl group, or in each case two adjacent R 3 , R 4 , R 5 or R 6 form a ring with the carbon atoms joining them, R 7 is ##STR11## R 11 , R 12 , R 13 , R 14 and R 15 are identical or different and are a hydrogen atom, a halogen atom, a C 1 -C 10 -alkyl group, a C 1 -C 10 -fluoroalkyl group, a C 6 -C 10 -aryl group, a C 6 -C 10 -fluoroaryl group, a C 1 -C 10 -alkoxy group, a C 2 -C 10 -alkenyl group, a C 7 -C 40 -arylalkyl group, a C 8 -C 40 -arylalkenyl group or a C 7 -C 40 -alkylaryl group, or R 11 and R 12 or R 11 and R 13 form a ring, in each case with the atoms joining them, M 2 is silicon, germanium or tin, p is 1, 2 or 3, R 8 and R 9 are identical or different and are a group ═CR 11 R 12 , in which R 11 and R 12 have the abovementioned meaning, and m and n are identical or different and are zero, 1 or 2, m+n being zero, 1 or 2, and an organoaluminum compound which is an aluminoxane of the formula II ##STR12## for the linear type and/or of the formula III ##STR13## for the cyclic type, in which R 16 is a C 1 -C 6 -alkyl group and q is an integer from 2 to 50.