PROCESS FOR THE PRODUCTION OF POLYOLEFINS WITH BROAD MOLECULAR WEIGHT DISTRIBUTION

1 . A propylene homo- or copolymer having

a polydispersity index, determined according ISO 6721-1, of at least 7.0 Pa −1 , and

a tensile modulus, determined according to ISO 527-2, of at least 1600 MPa measured on a test specimen prepared by injection molding according to ISO 1873-2; and

a weight average molecular weight (Mw) of at least 400,000 g/mol.

2 . The propylene homo- or copolymer according to claim 1 having an impact strength in a charpy notch test according to ISO 179/1eA:2000 at +23° C. of at least 3.0 kJ/m 2 measured on a test specimen prepared by injection molding according to ISO 1873-2.

3 . (canceled)

4 . A composition comprising the homo- or copolymer according to claim 1 .

5 . A process for the production of a propylene homo- or copolymer in one or more reactors, wherein in at least one reactor the process comprises the following steps:

(c) feeding one or more (co)monomers and hydrogen to said at least one reactor, whereby the hydrogen concentration in said at least one reactor is periodically varied;

(d) preparing an olefin homo- or copolymer in the presence of an olefin polymerization catalyst;

(e) withdrawing the olefin homo- or copolymer from said at least one reactor whereby

the following relation is fulfilled

P

H

τ

>

2.0

wherein

P H is the time of one variation period of the hydrogen concentration in said at least one reactor; and

τ is the average residence time of the polymer in said at least one reactor.

6 . The process according to claim 4 wherein the hydrogen concentration in said at least one reactor is varied within the range of 10 and 20000 ppm.

7 . The process according to claim 4 wherein the polyolefin is subjected to not more than one variation period in said at least one reactor.

8 . The process according to claim 4 wherein the average residence time (τ) is from 0.25 hours to 3.0 hours in said at least one reactor.

9 . The process according to claim 4 wherein the time of one variation period (P) is from 4.0 h to 50 h in said at least one reactor.

10 . The process according to claim 4 wherein the olefin polymerization catalyst in step d) is a Ziegler-Natta catalyst.

11 . The process according to claim 4 wherein process steps (c), (d) are carried out at a temperature of 40° C. to 110° C.

12 . The process according to claim 4 wherein step (c) is preceded by the following step:

(a) prepolymerising the olefin polymerization catalyst with one or more comonomer(s).

13 . The process according to claim 4 wherein the produced polymers are continuously withdrawn from said reactor during step (d).

14 . The process according to claim 4 wherein the periodical variation of the hydrogen concentration in said at least one reactor starts with an increase of the hydrogen concentration in said reactor.

15 . A composition comprising a propylene homo- or copolymer having

a polydispersity index, determined according ISO 6721-1, of at least 7.0 Pa −1 ;

whereby

a test specimen prepared by injection molding according to ISO 1873-2 has a tensile modulus determined according to ISO 527-2 of at least 1600 MPa; and

talc

the composition having an impact strength in a charpy notch test according to ISO 179/1eA:2000 at +23° C. measured on a specimen consisting of the composition and prepared by injection molding according to ISO 1873-2 of at least 3.8 kJ/m 2 and a tensile modulus determined according to ISO 527-2 on a specimen consisting of the composition and prepared by injection molding according to ISO 1873-2 of at least 2000 MPa.