Multimodal polyethylene composition with high pressure resistance

Patent metadata

Field	Value
Publication number	US-9920190-B2
Application number	US-201515323915-A
Country	US
Kind code	B2
Filing date	Jul 6, 2015
Priority date	Jul 7, 2014
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

The present invention relates to a multimodal polyethylene composition which can be manufactured into pipes showing improved pressure resistance comprising a high density multimodal ethylene polymer component (A) having a density of at least 930 kg/m 3 , and a MFR 21 of not more than 15 g/10 min, wherein said composition exhibits a LAOS-NLF defined as

L
⁢

⁢
A
⁢

⁢
O
⁢

⁢
S

-

N
⁢

⁢
L
⁢

⁢
F

=



G
1
′

G
3
′



where G 1 ′—first order Fourier Coefficient
G 3 ′—third order Fourier Coefficient

of at least 1.7. Such a polyethylene composition is useful for the manufacture of pressure pipes that exhibit improved pressure resistance and creep resistance and do not undergo sagging. Further disclosed is a process for the production of a pipe using such a multimodal polyethylene composition and a pipe comprising such a multimodal polyethylene composition.

First claim

The invention claimed is:

1. A multimodal polyethylene composition comprising a high density multimodal ethylene polymer component (A) having a density of at least 930 kg/m 3 , and a MFR 21 of not more than 15 g/10 min,
wherein said composition exhibits a LAOS-NLF defined as

L
⁢

⁢
A
⁢

⁢
O
⁢

⁢
S

-

N
⁢

⁢
L
⁢

⁢
F

=



G
1
′

G
3
′



where G′ 1 —first order Fourier Coefficient
G′ 3 —third order Fourier Coefficient

of at least 1.7.

2. The multimodal ethylene polymer composition according to claim 1 , which has a viscosity at a shear stress of 747 Pa (eta747) of 1,000 kPa·s or higher.

3. The multimodal polyethylene composition according to claim 1 whereby the polypropylene base resin has a F30 melt strength of 10 cN or higher at 200° C. measured according to ISO 16790:2005.

4. The multimodal polyethylene composition according to claim 1 having a ratio (eta 0.05 )/(eta 300 ) of the complex viscosity, in Pa·s, at a frequency of 0.05 rad/s (eta 0.05 ), to the complex viscosity, in Pa·s, at a frequency of 300 rad/s (eta 300 ) of at least 190.

5. The multimodal polyethylene composition according to claim 1 obtainable by melt-mixing a high density multimodal ethylene polymer component (A) having a density of at least 930 kg/m 3 , and a MFR 21 of not more than 15 g/10 min, and extruding said high density multimodal ethylene polymer component (A) in the presence of up to 10 wt. % of additives, based on the weight of the mixture so as to form said multimodal polyethylene composition.

6. The multimodal polyethylene composition according to claim 1 further comprising an ultrahigh molecular weight ethylene polymer component (B).

7. The multimodal polyethylene composition according to claim 6 , wherein the ultrahigh molecular weight ethylene polymer component (B) has a nominal viscosity molecular weight (Mv) according to ASTM D 4020-05 in the range of from 1,000,000 to 6,000,000 g/mol.

8. Process for the production of a pipe comprising the steps of
(a) melt-mixing a high density multimodal ethylene polymer component (A) having a density of at least 930 kg/m 3 , and a MFR 21 of not more than 15 g/10 min,
(b) extruding the high density multimodal ethylene polymer component (A) so as to form a multimodal polyethylene composition in the presence of up to 10 wt. % of additives, based on the extruded mixture, the multimodal polyethylene composition having an MFR 21 of not more than 15 g/10 min, a density of at least 925 kg/m 3 and a LAOS-NLF defined as

L
⁢

⁢
A
⁢

⁢
O
⁢

⁢
S

-

N
⁢

⁢
L
⁢

⁢
F

=



G
1
′

G
3
′



where G′ 1 —first order Fourier Coefficient
G′ 3 —third order Fourier Coefficient

of at least 1.7, and

(c) forming said multimodal ethylene polymer composition into a pipe.

9. The process according to claim 8 , wherein an ultrahigh molecular weight polymer component (B) is added to the melt-mixing step (a).

10. The process according to claim 8 , wherein at least a part of the additives is added in step (b) at a position situated with 50% of the length from the downstream end of the extruder.

11. The process according to claim 8 , wherein at least an antioxidant and/or an acid scavenger is added at a position situated within 50% of the length from the downstream end of the extruder.

12. A pipe comprising the multimodal polyethylene composition according to claim 1 .

13. The pipe according to claim 12 having a hydrostatic pressure resistance according to ISO 1167-1:2006 with a failure time at 13.9 MPa stress and at 20° C. of at least 30 h.

14. A method for the production of a pipe wherein a multimodal polyethylene composition as defined in claim 1 is extruded and cooled.

Assignees

• Borealis Ag

Inventors

• Liu Yi
• Albunia Alexandra Romina
• Piel Tanja
• Dou Qizheng
• Prokschi Hermann

Classifications

• B29K2023/0683

  UHMWPE, i.e. ultra high molecular weight polyethylene · CPC title

• C08F2500/05

  Bimodal or multimodal molecular weight distribution · CPC title

• C08L2207/068

  Ultra high molecular weight polyethylene · CPC title

• C08F110/02

  Ethene · CPC title

• B29C47/0004

  Operations & Transport · mapped topic