Polypropylene composition with improved optical properties and whitening resistance

1. A polypropylene composition comprising:

a) propylene homopolymer (H-PP) and

b) propylene copolymer (C-PP) of propylene and 1-hexene, wherein

i. the propylene copolymer (C-PP) has an overall 1-hexene content in the range of 3.8 to 10.0 wt.-%,

ii. the propylene copolymer (C-PP) comprises:

b-1) a first random propylene copolymer (A) of propylene and a 1-hexene having a 1-hexene content in the range of 0.1 to below 3.5 wt.-%, and

b-2) a second random propylene copolymer (B) of propylene and 1-hexene having a higher 1-hexene content than the first random propylene copolymer (A),

iii. the propylene copolymer (C-PP) has a xylene soluble content (XCS) in the range of 8.0 to 30.0 wt.-%, and

iv. the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer (C-PP) to the propylene homopolymer (H-PP) is in the range of 10/90 to 45/55.

2. The polypropylene composition according to claim 1 , wherein the propylene copolymer (C-PP) fulfils inequation (1)

MFR(C-PP)/MFR(A)<1.0  (1),

wherein MFR(A) is the melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 (in g/10 min) of the first random propylene copolymer (A) and MFR(C-PP) is the melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 (in g/10 min) of the propylene copolymer (C-PP).

3. The polypropylene composition according to claim 1 , wherein the propylene copolymer (C-PP) has a melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 0.4 to 100.0 g/10 min.

4. The polypropylene composition according to claim 1 , wherein the weight ratio between the first random propylene copolymer (A) and the second random propylene copolymer (B) within the propylene copolymer (C-PP) is in the range of 30:70 to 70:30.

5. The polypropylene composition according to claim 1 , wherein the propylene copolymer (C-PP) has an amount of 2,1 erythro regio-defects in the range of 0.1 to 2.0 mol.-%.

6. The polypropylene composition according to claim 1 , wherein:

i) the first random propylene copolymer (A) has a melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 0.3 to 12.0 g/10 min, and/or

ii) the second random propylene copolymer (B) has a melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 0.2 to 9.0 g/10 min.

7. The polypropylene composition according to claim 1 , wherein the propylene copolymer (C-PP) fulfills in-equation (2)

4.5

≤

C

⁢

6

⁡

(

C

)

C

⁢

6

⁡

(

A

)

*

[

A

]

[

C

]

≤

9.0

(

2

)

wherein

C6(A) is the 1-hexene content of the first random propylene copolymer (A) based on the total weight of the first random propylene copolymer (A) (in wt.-%);

C6(C) is the 1-hexene content of the propylene copolymer (C-PP) based on the total weight of the propylene copolymer (C-PP) (in wt.-%); and

[A]/[C] is the weight ratio between the first random propylene copolymer (A) and the propylene copolymer (C-PP) (in g/g).

8. The polypropylene composition according to claim 1 , wherein the propylene homopolymer (H-PP) has a melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 1.5 to 100.0 g/10 min.

9. The polypropylene composition according to claim 1 , wherein the polypropylene composition has a melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 1.5 to 100.0 g/10 min.

10. The polypropylene composition according to claim 1 , wherein the polypropylene composition has a xylene soluble content (XCS) in the range of 0.5 to 12.0 wt.-%.

11. An article comprising at least 90.0 wt.-% of the polypropylene composition according to claim 1 .

12. The article according to claim 11 , wherein the article is a film.

13. The article according to claim 12 , wherein the film has

i) a haze before steam sterilization determined according to ASTM D 1003-00 measured on a 50 μm cast film below 10.0%, and

ii) a haze after steam sterilization determined according to ASTM D 1003-00 measured on a 50 μm cast film below 12.0%.

14. The article according to claim 11 , wherein the article is a moulded article.

15. The article according to claim 14 , wherein the article is an injection moulded article.

16. A polypropylene composition comprising:

a) a propylene homopolymer (H-PP) and

b) a propylene copolymer (C-PP) of propylene and 1-hexene, wherein

i. the propylene copolymer (C-PP) has an overall 1-hexene content in the range of 3.8 to 10.0 wt.-%,

ii. the propylene copolymer (C-PP) has a xylene soluble content (XCS) in the range of 8.0 to 30.0 wt.-%,

iii. the propylene copolymer (C-PP) has an amount of 2,1 erythro regio-defects in the range of 0.1 to 2.0 mol.-%, and

iv. the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer (C-PP) to the propylene homopolymer (H-PP) is in the range of 10/90 to 45/55.

17. An article, comprising at least 90.0 wt.-% of a polypropylene composition, the polypropylene composition comprising:

a) a propylene homopolymer (H-PP) and

b) a propylene copolymer (C-PP) of propylene and 1-hexene, wherein

i. the propylene copolymer (C-PP) has an overall 1-hexene content in the range of 3.8 to 10.0 wt.-%,

ii. the propylene copolymer (C-PP) has a xylene soluble content (XCS) in the range of 8.0 to 30.0 wt.-%, and

iii. the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer (C-PP) to the propylene homopolymer (H-PP) is in the range of 10/90 to 45/55, wherein the article is a film, and wherein the film has

i′) a haze before steam sterilization determined according to ASTM D 1003-00 measured on a 50 μm cast film below 10.0%, and

ii′) a haze after steam sterilization determined according to ASTM D 1003-00 measured on a 50 μm cast film below 12.0%.