Nucleated propylene polymer composition with high toughness

1. A propylene homopolymer composition, comprising

(a) not less than 90 wt. %, based on the weight of the total propylene homopolymer composition, of a propylene homopolymer (A) having

(i) a pentad isotacticity (mmmm) of equal or more than 98.0 mol.-%, determined by quantitative 13C NMR spectroscopy, as described herein,

(ii) a relative amount of <2,1> erythro regio-defects of not more than 2.0 mol.-%, determined by quantitative 13C NMR spectroscopy, as described herein, and

(b) a nucleating agent (B) selective for the beta-modification of isotactic polypropylene in an amount of from 0.001 to 1.0 wt. %, based on the weight of the total propylene homopolymer composition,

wherein said propylene homopolymer composition has a melt flow rate MFR 2 (230° C., 2.16 kg) according to ISO 1133 of 0.1 to 10 g/10 min., a beta-phase content of not less than 80%, measured by wide angle x-ray scattering (WAXS).

2. The propylene homopolymer composition according to claim 1 , which has a relative Charpy notched impact strength improvement ΔNIS (23° C.) of not less than 4.0, wherein ΔNIS (23° C.) is defined by:

ΔNIS=(NIS nuc −NIS PP )/NIS PP

where NIS nuc is the Charpy notched impact strength at 23° C. of the β-nucleated propylene homopolymer composition and NIS PP is the Charpy notched impact strength at 23° C. of the non-nucleated propylene homopolymer (a), the Charpy notched impact strength at 23° C. being measured according to ISO 179 1eA.

3. The propylene homopolymer composition according to claim 1 , which has an absolute Charpy notched impact strength at 23° C., measured according to ISO 179 1eA, of not less than 30 KJ/m 2 .

4. The propylene homopolymer composition according to claim 1 , which has a flexural modulus determined according to ISO 178 in the range of 1200 to 2000 MPa.

5. The propylene homopolymer composition according to claim 1 , which has a main melting temperature (Tm) of at least 140° C. and/or a crystallization temperature (T c ) of at least 114° C., T m and T c being measured by differential scanning calorimetry (DSC).

6. The propylene homopolymer composition according to claim 1 , which has a relative content of the gamma-modification of less than 5.0%, determined by wide-angle X-ray scattering (WAXS).

7. The propylene homopolymer composition according to claim 1 , which has a beta-phase content of not less than 85%, measured by wide angle x-ray scattering (WAXS).

8. The propylene homopolymer composition according to claim 1 , wherein the propylene homopolymer (A) has a weight average molecular weight M w of more than 300 kg/mol and a ratio between weight and number average molecular weight, M w /M n , of not more than 4.0, both M w and M n being determined by size exclusion chromatography (SEC).

9. The propylene homopolymer composition according to claim 1 , wherein the propylene homopolymer (A) has a content of xylene cold solubles (XCS) fraction of less than 1.5 wt. %.

10. The propylene homopolymer composition according to claim 1 , wherein the nucleating agent (B) selective for the beta-modification of isotactic polypropylene is selected from quinacridone type compounds and dicarboxylic acid salts of metals from group IIa of the periodic table.

11. A process for the preparation of a propylene homopolymer composition according to claim 1 , comprising the steps of:

(i) polymerizing propylene in the presence of a single-site polymerization catalyst into a propylene homopolymer (A) as defined in claim 1 ,

(ii) melt mixing a suitable amount of the nucleating agent (B) selective for the beta-modification of isotactic polypropylene with said propylene homopolymer (A) in a melt mixing device, and

(iii) solidifying the resulting melt in a strand or underwater pelletization process.

12. The process according to claim 11 , wherein the propylene homopolymer composition is produced in the presence of a supported metallocene catalyst.

13. The process according to claim 11 , wherein the propylene homopolymer composition is produced in the presence of a catalyst system comprising

(i) a complex of formula (I)

wherein

M is zirconium or hafnium;

each X is a sigma ligand;

L is a divalent bridge selected from —R′ 2 C—, —R′ 2 C—CR′2-, —R′ 2 Si—, —R′ 2 Si—SiR′ 2 —, and

R′ 2 Ge—, wherein each R′ is independently a hydrogen atom, C 1 -C 20 -hydrocarbyl, tri (C 1 -C 20 -alkyl) silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl;

each R1 is independently a C 1 -C 20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16 of the periodic table of elements, or is a C 4 -C 20 hydrocarbyl radical branched at the B-atom to the cyclopentadienyl ring, optionally containing one or more heteroatoms belonging to groups 14-16 of the periodic table of elements, or is a C 3 -C 20 hydrocarbyl radical branched at the B-atom to the cyclopentadienyl ring where the β-atom is an Si-atom;

each R a is independently hydrogen or an aliphatic C 1 -C 20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 of the periodic table of elements;

each R b is independently hydrogen or an aliphatic C 1 -C 20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 of the periodic table of elements; or

an R a and R b group on adjacent carbon atoms can be taken together to form a 5-membered saturated carbon ring which is optionally substituted by n groups R 2 , n being from 0 to 3;

each R 2 is same or different and may be a C 1 -C 20 hydrocarbyl group, or a C 1 -C 20 hydrocarbyl radical optionally containing one or more heteroatoms belonging to groups 14-16 of the periodic table of elements;

each R 4 is independently an aliphatic C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 of the periodic table of elements or is a hydrogen atom;

each W group is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 3

each R 3 is the same or different and is a C 1 -C 20 hydrocarbyl group optionally containing one or more heteroatoms belonging to groups 14-16 of the periodic table of elements;

or two R 3 groups on adjacent carbon atoms taken together can form a fused 5- or 6-membered non aromatic ring with the W group, said ring being itself optionally substituted with one or more C 1 -C 20 hydrocarbyl group(s), or two adjacent R 5 groups taken together can form a further mono-or multicyclic ring condensed to W optionally substituted by one or two groups R 3 ,

and

(ii) optionally a co-catalyst comprising a compound of a metal of group 13 of the periodic table of elements.

14. A moulded propylene homopolymer product obtained by compression moulding or extrusion of the propylene homopolymer composition according to claim 1 .

15. The moulded propylene homopolymer product according to claim 14 selected from the group consisting of a pipe, a filter plate, a fitting or any other part of a fluid transportation system, filtration system and fluid storage system.