Propylene random copolymer for use in film applications

Patent metadata

Field	Value
Publication number	US-12006426-B2
Application number	US-201917273700-A
Country	US
Kind code	B2
Filing date	Sep 9, 2019
Priority date	Sep 26, 2018
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

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).

First claim

The invention claimed is:

1. A polypropylene composition (P), comprising at least 90.0 wt-%, based on an overall weight of the polypropylene composition (P), of a copolymer (C) of propylene and 1-hexene, having
i) an overall 1-hexene content in a range of 2.0 to 10.0 wt-%,
ii) a melt flow rate MFR 2 determined according to ISO 1133 (2.16 kg, 230° C.) in a 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 a range of 1.5 to 15.0, wherein the visbreaking ratio is determined according to equation (2)

VR
=

MFR
final

MFR
start

(
2
)

wherein “MFR final ” is the melt flow rate MFR 2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C) after visbreaking and “MFR start ” is the melt flow rate MFR 2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C) before visbreaking.

2. The polypropylene composition (P) according to claim 1 , wherein the copolymer (C) has a xylene soluble content (XCS) of at least 8.0 wt-%.

3. The polypropylene composition (P) according to claim 1 , wherein the copolymer (C) comprises
a) a first random propylene copolymer (A) of propylene and a 1-hexene having a comonomer content in a 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 that of the first random propylene copolymer (A).

4. The polypropylene composition (P) according to claim 1 , wherein the copolymer (C) has a 1-hexene content of a xylene soluble fraction C6(XCS) in a range of 2.0 to 15.0 wt-%.

5. The polypropylene composition (P) according to claim 3 , 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 an overall weight of the copolymer (C).

6. The polypropylene composition (P) according to claim 3 , wherein the copolymer (C) has a melting temperature Tm below 140° C.

7. The polypropylene composition (P) according to claim 3 , 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 1-hexene content of the first random propylene copolymer (A) based on a total weight of the first random propylene copolymer (A) in wt-%;
C6(C) is 1-hexene content of the copolymer (C) based on a total weight of the copolymer (C) in wt-%; and
[A]/[C] is weight ratio between the first random propylene copolymer (A) and the copolymer (C) in [g/g].

8. The polypropylene composition (P) according to claim 1 , wherein the copolymer (C) has a melt flow rate MFR 2 determined according to ISO 1133 (230° C., 2.16 kg) before visbreaking in a range of 0.4 to 3.5 g/10 min.

9. The polypropylene composition (P) according to claim 1 , wherein
i) a first random propylene copolymer (A) has a melt flow rate MFR 2 (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in a range of 0.3 to 6.0 g/10 min, and/or
ii) a second random propylene copolymer (B) has a melt flow rate MFR 2 (230° C., 2.16 kg) determined according to ISO 1133 before visbreaking in a range of 0.1 to 4.0 g/10 min.

10. 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 a 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 a range of 1.5 to 15.0, thereby obtaining the copolymer (C),
wherein the visbreaking ratio is determined according to equation (3)

VR
=

MFR
⁡

(
C
)

MFR
⁡

(

C
′

)

(
3
)

wherein “MFR(C)” is a melt flow rate 1MFR 2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C) after visbreaking and “MFR(C′)” is melt flow rate MFR 2 determined according to ISO 1133 (230° C., 2.16 kg) of the copolymer (C′).

11. The process according to claim 10 , wherein the copolymer (C′) of propylene and 1-hexene is prepared by
a1) polymerizing propylene and 1-hexene in a first reactor (R-1) in the presence of the metallocene catalyst (MC), thereby obtaining a first random propylene copolymer (A) having a 1-hexene content in a range of 0.1 to 4.0 wt-%,
a2) transferring said first random propylene copolymer (A) and unreacted comonome

Assignees

• Borealis Ag

Inventors

• Wang Jingbo
• Gahleitner Markus
• Bernreitner Klaus
• Leskinen Pauli
• Niedersüss Peter

Classifications

• C08L23/30

  by oxidation · CPC title

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• C08F2500/12

  Melt flow index or melt flow ratio · CPC title

• C08F2810/10

  including a reactive processing step which leads, inter alia, to morphological and/or rheological modifications, e.g. visbreaking · CPC title

• C08F210/06 Primary

  Propene · CPC title