Propylene random copolymer for use in film applications
AssigneeBorealis AG
InventorsJingbo WANG, Markus GAHLEITNER, Klaus BERNREITNER, Pauli LESKINEN, Peter NIEDERSÜSS
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Abstract
The present invention is directed to a polypropylene composition (P) comprising a bimodal copolymer of propylene and 1-hexene prepared in the presence of a metallocene catalyst, said bimodal copolymer having a melt flow rate MFR2 in the range of 4.0 to 20.0 g/10 min. Further, the present invention is directed to a method for preparing the copolymer (C) and an article comprising said polypropylene composition (P).
Claims18
1-17. (canceled)
A polypropylene composition (P), comprising at least 90.0 wt.-%, based on the overall weight of the polypropylene composition (P), of a copolymer (C) of propylene and 1-hexene, having
- i) an overall 1-hexene content in the range of 2.0 to 10.0 wt.-%,
- ii) a melt flow rate MFR2 determined according to ISO 1133 (2.16 kg, 230° C.) in the range of 4.0 to 20.0 g/10 min, and
- iii) an amount of 2,1 erythro regio-defects of at least 0.2 mol.-%,
- wherein the copolymer (C) has been visbroken with a visbreaking ratio (VR) in the range of 1.5 to 15.0, wherein the visbreaking is determined according to equation (2)
- VR
- =
- MFR
- final
- MFR
- start
- (
- 2
- )
- wherein “MFRfinal” is the melt flow rate MFR2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C) after visbreaking and “MFRstart” is the melt flow rate MFR2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C) before visbreaking.
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) has a xylene soluble content (XCS) of at least 8.0 wt.-%.
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) comprises
- a) a first random propylene copolymer (A) of propylene and a 1-hexene having a comonomer content in the range of 0.1 to 4.0 wt.-%, and
- b) a second random propylene copolymer (B) of propylene and 1-hexene having a higher comonomer content than the first random propylene copolymer (A).
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) has a 1-hexene content of the xylene soluble fraction C6(XCS) in the range of 2.0 to 15.0 wt.-%.
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) comprises 30.0 to 70.0 wt.-% of the first random propylene copolymer (A) and 30.0 to 70.0 wt.-% of the second random propylene copolymer (B), based on the overall weight of the copolymer (C).
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) has a melting temperature Tm below 140° C.
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) fulfills in-equation (1)
- 4.50
- ≤
- C
-
-
- 6
-
- (
- C
- )
- C
-
-
- 6
-
- (
- A
- )
- *
- [
- A
- ]
- [
- C
- ]
- ≤
- 9.00
- (
- 1
- )
- 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 copolymer (C) based on the total weight of the copolymer (C) [in wt.-%];
- and
- [A]/[C] is the weight ratio between the first random propylene copolymer (A) and the copolymer (C) [in g/g].
The polypropylene composition (P) according to claim 17, wherein the copolymer (C) has a melt flow rate MFR2 determined according to ISO 1133 (230° C., 2.16 kg) before visbreaking in the range of 0.4 to below 4.0 g/10 min.
The polypropylene composition (P) according to claim 17, wherein
- i) the first random propylene copolymer (A) has a melt flow rate MFR2 (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in the range of 0.3 to 6.0 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 before visbreaking in the range of 0.1 to 4.0 g/10 min.
A process for the preparation of a copolymer (C) of propylene and 1-hexene, comprising the steps of
- a) preparing a copolymer (C′) of propylene and 1-hexene having an overall 1-hexene content in the range of 2.0 to 10.0 wt.-% in the presence of a metallocene catalyst (MC),
- b) visbreaking the copolymer (C′) obtained in step a) with a visbreaking ratio (VR) in the range of 1.5 to 15.0, thereby obtaining the copolymer (C), wherein the visbreaking is determined according to equation (3)
- VR
- =
- MFR
-
- (
- C
- )
- MFR
-
- (
- C
- ′
- )
- (
- 3
- )
- wherein “MFR(C)” is the melt flow rate MFR2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C) after visbreaking and “MFR(C′)” is the melt flow rate MFR2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C′).
An article comprising at least 90.0 wt.-% of the polypropylene composition (P) according to claim 17.
Dependencies are inferred from the claim text.