Polyethylene pipes

• US 20060275571A1
• Filed: 06/02/2005
• Published: 12/07/2006
• Est. Priority Date: 06/02/2005
• Status: Abandoned Application

• Current Assignee: Univation Technologies LLC (Dow, Inc.)
• Original Assignee: Univation Technologies LLC (Dow, Inc.)
• Inventors: Liu, Han-Tai, Mure, Cliff Robert
• Application Number:
  US11/143,039
• Publication Number:
  US 20060275571A1
• Time in Patent Office: Days
• US Class Current: 428/36.900
• CPC Class Codes: B29C 2948/9219 Density, e.g. per unit length or area
• CPC Class Codes: B29C 2948/922 Viscosity; Melt flow index [MFI]; Molecular weight
• CPC Class Codes: B29C 2948/92209 Temperature
• CPC Class Codes: B29C 2948/92676 Weight
• CPC Class Codes: B29C 2948/92695 Viscosity; Melt flow index [MFI]; Molecular weight
• CPC Class Codes: B29C 2948/92704 Temperature
• CPC Class Codes: B29C 35/16 Cooling cooling extruded material B29C48/911; cooling preforms for blow moulding B29C49/6427; cooling blown articles B29C49/66; cooling tyres during post cure inflation B29D30/0643
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/10 flexible, e.g. blown foils
• CPC Class Codes: B29C 48/92 Measuring, controlling or regulating
• CPC Class Codes: B29K 2023/06 PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/065 HDPE, i.e. high density polyethylene
• CPC Class Codes: B29K 2105/16 Fillers
• CPC Class Codes: B29L 2023/22 Tubes or pipes, i.e. rigid bent tubes not for use as pipe couplings B29L2023/004
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 23/04 Homopolymers or copolymers of ethene
• CPC Class Codes: C08L 23/06 Polyethene
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: F16L 9/127 the walls consisting of a single layer
• CPC Class Codes: Y10T 428/139 : Open-ended, self-supporting conduit, cylinder, or tube-type article

Abstract

A pipe composition comprising, in one embodiment, from 80 to 99 wt % of a high density polyethylene by weight of the composition and from 1 to 20 wt % of a filler by weight of the composition; the polyethylene having a density of from 0.940 to 0.980 g/cm³, and an 121 of from 2 to 18 dg/min; characterized in that the pipe composition extrudes at an advantageously low melt temperature and at an advantageously high specific throughput. Also provided is a method of forming a pipe comprising in embodiment providing a filler composition comprising from 5 to 50 wt % of a filler and from 95 to 50 wt % of a low density polyethylene and from 0 to 3 wt % of one or more stabilizers; then melt blending the filler composition and a high density polyethylene having a density of from 0.940 to 0.980 g/cm³, and an I₂₁ of from 2 to 18 dg/min to a target drop temperature of from 16° C. to 185° C. to form a pipe composition, melt blending such that the pipe composition comprises from 1 to 20 wt % of the filler by weight of the pipe composition; and extruding the pipe composition to form a pipe.

Claims

1. A pipe composition comprising from 80 to 99 wt % of a high density polyethylene by weight of the composition and from 1 to 20 wt % of a filler by weight of the composition;

the polyethylene having a density of from 0.940 to 0.980 g/cm³, and an I₂₁ of from 2 to 18 dg/min;

characterized in that the pipe composition extrudes at a melt temperature, T_m, that satisfies the following relationship;

T_m≦

230−

3.3(I₂₁)

wherein the composition also extrudes at a specific throughput of from greater than 1.38 kg/hr/rpm to form the pipe.

2. The pipe of claim 1, having a resistance to rapid crack propagation (RCP) characterized by a critical pressure of greater than 10 bars tested by the S-4 test (ISO 13477) at 0°

C.

3. The pipe of claim 1, wherein the polyethylene comprises at least one high molecular weight component, the high molecular weight component having a short chain branching index ranging from 1.8 to 10.

4. The pipe of claim 2, wherein there is one high molecular weight component having a weight average molecular weight ranging from greater than 60,000 Daltons.

5. The pipe of claim 1, wherein the density of the polyethylene ranges from 0.943 to 0.970 g/cm³.

6. The pipe of claim 1, wherein the I₂₁ of the polyethylene ranges from 4 to 16 dg/min.

7. The pipe of claim 1, wherein the polyethylene has a molecular weight distribution ranging from 20 to 200.

8. The pipe of claim 1, wherein the composition is extruded through a pipe die having a diameter of from 10 to 500 mm to form the pipe.

9. The pipe of claim 1, wherein the specific throughput ranges from 1.38 to 5 kg/hr/rpm.

10. The pipe of claim 1, wherein the pipe has a wall thickness ranging from 5 to 30 mm.

11. The pipe of claim 1, wherein the filler is carbon black.

12. The pipe of claim 1, wherein the polyethylene is produced in a single reactor.

13. The pipe of claim 12, wherein the reactor is a gas phase reactor.

14. The pipe of claim 12, comprising combining a bimetallic catalyst composition with ethylene and one or more α

-olefins in the reactor and isolating the polyethylene.

15. The pipe of claim 14, wherein the bimetallic catalyst composition comprises at least one metallocene compound and at least one Group 3 to Group 10 coordination compound.

16. A method of forming a pipe comprising:

(a) providing a filler composition comprising from 5 to 50 wt % of a filler and from 95 to 50 wt % of a low density polyethylene and from 0 to 3 wt % of one or more stabilizers;

(b) melt blending the filler composition and a high density polyethylene having a density of from 0.940 to 0.980 g/cm³, and an I₂₁ of from 2 to 18 dg/min to a target drop temperature of from 165°

C. to 185°

C. to form a pipe composition, melt blending such that the pipe composition comprises from 1 to 20 wt % of the filler by weight of the pipe composition; and

(c) extruding the pipe composition to form the pipe.

17. The method of claim 16, wherein the pipe composition extrudes at a melt temperature, T_m, that satisfies the following relationship:

T_m≦

230−

3.3(I₂₁)

wherein the composition also extrudes at a specific throughput of from greater than 1.38 kg/hr/rpm to form the pipe.

18. The method of claim 16, wherein the filler composition comprises from 10 to 40 wt % filler by weight of the filler composition.

19. The method of claim 16. wherein the pipe composition comprises from 1.5 to 10 wt % of the filler by weight of the pipe composition.

20. The method of claim 16, wherein the polyethylene comprises at least one high molecular weight component, the high molecular weight component having a short chain branching index ranging from 1.8 to 10.

21. The method of claim 20, wherein there is one high molecular weight component having a weight average molecular weight ranging from greater than 60,000 Daltons.

22. The method of claim 16, wherein the density of the polyethylene ranges from 0.943 to 0.970 g/cm³.

23. The method of claim 16, wherein the I₂₁ of the polyethylene ranges from 4 to 10 dg/min.

24. The method of claim 16, wherein the polyethylene has a molecular weight distribution ranging from 30 to 100.

25. The method of claim 16, wherein the filler is carbon black.