Random propylene polymer composition and use in extrusion blow moulding

1. A propylene polymer composition comprising at least one propylene copolymer (C-PP), and an α-nucleating agent (N), wherein the propylene copolymer (C-PP) comprises two propylene copolymer fractions (PP1) and (PP2), wherein

propylene copolymer fraction (PP1) is contained in the propylene copolymer (C-PP) in an amount of 30 to 70 wt. % and the propylene copolymer fraction (PP2) is contained in the propylene copolymer (C-PP) in an amount of 70 to 30 wt. %,

the comonomer content of propylene copolymer fraction (PP1) is in the range of 0.5 to 2.6 wt.-% and the comonomer content of the propylene copolymer fraction (PP1) is lower compared to the comonomer content of the propylene copolymer fraction (PP2), and the propylene polymer composition has

(a) a melt flow rate MFR 2 (230° C.) measured according to according to ISO 1133 of 1 to 5 g/10 min.,

(b) a comonomer content of 4.0 to 8.0 wt. %, the comonomer(s) being ethylene and/or at least one C 4 to C 12 α-olefin, and

(c) a soluble fraction (SF), determined by CRYSTEC fractionation with CRYSTEX QC, Polymer Char (Valencia, Spain), of from 8 to 20 wt. %,

wherein propylene copolymer (C-PP) is obtained in a multi-stage polymerization process in the presence of

(a) a Ziegler-Natta catalyst (ZN-C) that comprises a titanium compound (TC), a magnesium compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic acid ester,

(b) optionally a co-catalyst (Co), and

(c) optionally an external donor (ED),

wherein the ratio C 2 (SF)/C 2 (CF) between the ethylene content C 2 (SF) of soluble fraction of the propylene copolymer (C-PP) and the ethylene content C 2 (CF) of crystalline fraction of the propylene copolymer (C-PP) is 4.0 to 6.0.

2. The propylene polymer composition according to claim 1 having

(a) a melting temperature Tm in the range of from 148 to 162° C.; and/or

(b) a crystallization temperature Tc of not less than 115° C.

3. The propylene polymer composition according to claim 1 which has

(c) a Charpy notched impact strength according to ISO 179 1eA at +23° C. in the range of from 20 to 100 kJ/m 2 .

4. The propylene polymer composition according to any one of claims 1 to 3 wherein the comonomer content of propylene copolymer fraction (PP2) is in the range of 6 to 20 wt. %.

5. The propylene polymer composition according to claim 1 wherein propylene copolymer fraction (PP1) and propylene copolymer fraction (PP2) differ in their melt flow rate MFR 2 (230° C.) measured according to according to ISO 1133.

6. The propylene polymer composition according to claim 1 wherein the melt flow rate MFR 2 (230° C.) of the propylene copolymer fraction (PP1) to the melt flow rate MFR 2 (230° C.) of the propylene copolymer (C-PP) differ by no more than 6.0 g/10 min., measured according to ISO 1133, respectively.

7. The propylene polymer composition according to claim 1 comprising an α-nucleating agent (N) selected from the group consisting of

(i) salts of monocarboxylic acids and polycarboxylic acids,

(ii) dibenzylidenesorbitol and C 1 -C 8 -alkyl-substituted dibenzylidenesorbitol derivatives, or substituted nonitol-derivatives,

(iii) salts of diesters of phosphoric acid,

(iv) polymeric α-nucleating agent, and

(v) mixtures thereof.

8. The propylene polymer composition according to claim 7 , wherein the α-nucleating agent is selected from vinylcycloalkane polymers and vinylalkane polymers.

9. A method of producing the propylene polymer composition according to claim 1 , wherein propylene copolymer (C-PP) is obtained in a multi-stage polymerization process in the presence of

(a) a Ziegler-Natta catalyst (ZN-C) comprises a titanium compound (TC), a magnesium compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic acid ester,

(b) optionally a co-catalyst (Co), and

(c) optionally an external donor (ED),

wherein the ratio C 2 (SF)/C 2 (CF) between the ethylene content C 2 (SF) of soluble fraction of the propylene copolymer (C-PP) and the ethylene content C 2 (CF) of crystalline fraction of the propylene copolymer (C-PP) is 4.0 to 6.0.

10. The method according to claim 9 , wherein the internal donor (ID) is selected from the group consisting of optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives and/or mixtures thereof.

11. An extrusion blow molded article comprising the propylene polymer composition according to claim 1 .

12. The extrusion blow molded article according to claim 11 having a Charpy notched impact strength according to ISO 179 1eA at +23° C. in the range of from 20 to 100 kJ/m 2 .

13. The extrusion blow molded article according to claim 11 being a bottle or a container.

14. A method of preparing an extrusion blow molded article comprising extrusion blow molding of a propylene polymer composition according to claim 1 .