Composition and process

Patent metadata

Field	Value
Publication number	US-11427670-B2
Application number	US-201716348376-A
Country	US
Kind code	B2
Filing date	Nov 15, 2017
Priority date	Nov 25, 2016
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

A polymer composition and a process for the production of this composition comprising a base resin is disclosed herein. The base resin includes a very high molecular weight component, a low molecular weight component, and a high molecular weight component having a weight average molecular weight higher than the weight average molecular weight of the low molecular weight component but lower than the weight average molecular weight of the very high molecular weight component. An amount of the very high molecular weight component in the base resin is 0.5 to 8 wt %. The very high molecular weight component has a viscosity average molecular weight of greater than 1100 kg/mol. The composition has FRR21/5 of equal to or greater than 38, a melt flow rate MFR21 of equal to or greater than 6.5 g/10 min and a viscosity at a shear stress of 747 Pa (eta747) of 450 to 3000 kPas.

First claim

The invention claimed is:

1. A polymer composition comprising a base resin which comprises at least three polymer components:
(a) a very high molecular weight polyethylene component as fraction A1;
(b) a low molecular weight polyethylene component as fraction A2 having a weight average molecular weight lower than a weight average molecular weight of the very high molecular weight polyethylene component; and
(c) a high molecular weight polyethylene component as fraction A3 having a weight average molecular weight higher than the weight average molecular weight of the low molecular weight polyethylene component but lower than the weight average molecular weight of the very high molecular weight component,
wherein:
(I) an amount of the very high molecular weight polyethylene component in the base resin is 0.5 to 8 wt %, and a viscosity average molecular weight (M v ) of the very high molecular weight polyethylene component is greater than 1100 kg/mol;
(II) the composition has FRR 21/5 of equal to or greater than 38, a melt flow rate MFR 21 of equal to or greater than 6.5 g/10 min, a viscosity at a shear stress of 747 Pa (eta747) of 450 to 3000 kPas, and a strain hardening modulus of more than 50 MPa; and
(III) the composition has a hexene content of 0.1 to 1.0 mol %, measured using NMR.

2. A polyethylene composition according to claim 1 , wherein the composition comprises carbon black in an amount of 8 wt % or below of the total composition.

3. A polyethylene composition according to claim 1 , wherein:
(i) an amount of the very high molecular weight polyethylene component in the base resin is 1 to 7 wt %, which very high molecular weight polyethylene component is an ethylene homopolymer or copolymer having at least one C3-C20 alpha olefin comonomer;
(ii) an amount of the low molecular weight polyethylene component in the base resin is 30 to 70 wt %, which low molecular weight polyethylene component is an ethylene homopolymer or copolymer with at least one C3-C20 alpha olefin comonomer; and
(iii) an amount of the high molecular weight polyethylene component in the base resin is 25 to 65 wt %, which high molecular weight polyethylene component is an ethylene homopolymer or copolymer with at least one C3-C20 alpha olefin comonomer.

4. A polyethylene composition according to claim 1 , wherein the composition has a density of 945 to 975 kg/m 3 .

5. A polyethylene composition according to claim 1 , wherein the composition has MFR 21 of equal to or greater than 7.0 g/10 min.

6. A polyethylene composition according to claim 1 , wherein the composition has MFR 5 of equal to or greater than 0.1 g/10 min.

7. A polyethylene composition according to claim 1 , wherein the composition has FRR 21/5 of equal to or greater than 40.

8. A polyethylene composition according to claim 1 , wherein the polyethylene composition has a viscosity at a shear stress of 747 Pa (eta747) of 500 to 2500 kPas.

9. A polyethylene composition according to claim 1 , wherein a melt flow rate MFR 5 of the mixture of fractions A1, A2 and A3 forming the base resin determined according to ISO 1133 is equal to or less than 0.30 g/10 min.

10. A polyethylene composition according to claim 1 , wherein the very high molecular weight polyethylene component of fraction A1 has a viscosity average molecular weight (M v ) of greater than 1400 kg/mol.

11. An article made of the polyethylene composition as defined in claim 1 .

12. A process for the production of a polymer composition comprising a base resin, which comprises steps of:
(a) polymerising ethylene and optionally at least one comonomer in the presence of a polymerisation catalyst to form a very high molecular weight polyethylene component of fraction A1; and
(b) polymerising ethylene and optionally at least one comonomer in the presence of same or different polymerisation catalyst(s) as polymerising the very high molecular weight polyethylene component to form a low molecular weight polyethylene component of fraction A2 having a weight average molecular weight lower than a weight average molecular weight of the very high molecular weight polyethylene component; and
(c) polymerising ethylene and optionally at least one comonomer in the presence of same or different polymerisation catalyst(s) as polymerising the very high molecular weight polyethylene component to form a high molecular weight polyethylene component of fraction A3 having a weight average molecular weight higher than the weight average molecular weight of the low molecular weight polyethylene component but lower than the weight average molecular weight of the very high molecular weight component,
wherein
(I) an amount of the very high molecular weight polyethylene component in the base resin is 0.5 to 8 wt %;
(II) the very high molecular weight polyethylene component of fraction A1 has a viscosity average molecular weight (M v ) of greater than 1100 kg/mol;
(III) the composition has FRR 21/5 of equal to or greater than 38, a melt flow rate MFR 21 of equal to or greater than 6.5 g/10 min, a viscosity at a shear stress of 747 Pa (eta747) of 450 to 3000 kPas, and a strain hardening modulus of more than 50 MPa; and
(IV) the composition has a hexene content of 0.1 to 1.0 mol %, measured using NMR.

13. A process according to claim 12 , wherein at least one of the catalyst(s) is a Ziegler-Natta (ZN) catalyst.

14. The process according to claim 12 , wherein the composition has a white spot rating (WSR) determined according to ISO 18553 after a single compounding step of 5 to 10.

15. The polyethylene composition according to claim 1 , wherein the composition has a white spot rating (WSR) determined according to ISO 18553 after a single compounding step of 5 to 10.

Assignees

• Borealis Ag

Inventors

• Roos Peter
• Cheng Joy
• Jeruzal Mark
• Duo Qizheng
• Eriksson Erik

Classifications

• C08L23/04 Primary

  Homopolymers or copolymers of ethene · CPC title

• C08F210/16

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

• C08L23/06

  Polyethylene · CPC title

• C08K3/04

  Carbon · CPC title

• C08F2500/17

  Viscosity · CPC title