# US 8,771,816 B2 · Controlling melt fracture in bimodal resin pipe

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- Number: US 8,771,816 B2
- Document ID: US8771816B2
- Status: Granted
- Kind: B2
- Application number: 13/660,777
- Filed: 2012-10-25
- Published: 2013-12-05
- Granted: 2014-07-08
- Earliest claimed: 2012-05-31
- Assignees: Chevron Phillips Chemical Company LP
- Applicants: Chevron Phillips Chemical Company LP
- Inventors: Paul J. DesLauriers; Yongwoo Inn; Qing Yang; Ashish M. Sukhadia; David C. Rohlfing; Pamela L. Maeger
- Web page: https://patentgrep.com/patent/US8771816B2

## CPC

- C08F 110/02: Ethene
- C08L 23/06: Polyethylene
- F16L 9/00: Rigid pipes
- G01N 3/24: by applying steady shearing forces (G01N3/26, G01N3/28 take precedence)
- G01N 11/04: through a restricted passage, e.g. tube, aperture
- G06F 17/10: Complex mathematical operations {(function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544)}
- G16C 20/20: Identification of molecular entities, parts thereof or of chemical compositions
- C08L 23/04: Homopolymers or copolymers of ethene
- F16L 9/12: of plastics with or without reinforcement (F16L9/16 - F16L9/22 take precedence)
- Y10T 428/139: Open-ended, self-supporting conduit, cylinder, or tube-type article
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)
- F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G16C: COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A method of preparing a medium-density polyethylene pipe comprising melting a multimodal metallocene-catalyzed polyethylene resin to form a molten polyethylene, wherein the multimodal metallocene-catalyzed polyethylene resin has a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition of greater than about 90 kPa of stress, and a shear rate for smooth to matte transition greater than about 10 s−1, wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test; and forming the molten polyethylene resin into pipe. A pipe prepared from a multimodal metallocene-catalyzed polyethylene resin having a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi; a stress for smooth to matte transition of greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s−1, wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test.

## Claims

### Claim 1

A method of preparing a medium-density polyethylene pipe comprising: melting a multimodal metallocene-catalyzed polyethylene resin to form a molten polyethylene, wherein the multimodal metallocene-catalyzed polyethylene resin has a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition of greater than about 90 kPa of stress, and a shear rate for smooth to matte transition greater than about 10 s−1, wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test; and forming the molten polyethylene resin into pipe.

### Claim 2 (depends on 1)

The method of claim 1 wherein the polyethylene resin has a density of from about 0.928 g/ml to about 0.940 g/ml.

### Claim 3 (depends on 1)

The method of claim 1 wherein the polyethylene resin has a melt flow rate of less than about 0.4 g/10 min.

### Claim 4 (depends on 1)

The method of claim 1 wherein the pipe has a PENT value of from about 500 hours to about 20,000 hours.

### Claim 5 (depends on 1)

The method of claim 1 wherein the pipe has a Charpy Tdb of less than about −25° C.

### Claim 6 (depends on 1)

The method of claim 1 wherein the pipe has a Charpy impact energy of from about 1.0 J to about 3.0 J.

### Claim 7 (depends on 1)

The method of claim 1 wherein the pipe has a flexural modulus, 2% secant of from about 80 kpsi to about 110 kpsi.

### Claim 8 (depends on 1)

The method of claim 1 wherein the pipe has an elongation at break of greater than about 450%.

### Claim 9 (depends on 1)

The method of claim 1 wherein the pipe has a Young's modulus of from about 120 kpsi to about 190 kpsi.

### Claim 10 (depends on 1)

The method of claim 1 wherein the pipe has a tensile strength at yield of from about 2600 psi to less than about 3,000 psi.

### Claim 11 (depends on 1)

The method of claim 1 wherein the pipe has a tensile strength at break of greater than about 3000 psi.

### Claim 12 (depends on 1)

The method of claim 1 wherein the pipe has a thermal stability of greater than about 220° C.

### Claim 13 (depends on 1)

The method of claim 1 wherein the pipe has a critical temperature value (Tc) of equal to or less than about 0° C.

### Claim 14 (depends on 1)

The method of claim 1 wherein the pipe has a critical pressure value (Pc) of greater than about 12 bar.

### Claim 15 (depends on 1)

The method of claim 1 wherein the pipe has a tensile natural draw ratio of less than about 500%.

### Claim 16 (depends on 1)

The method of claim 1 wherein the pipe has a hydrostatic design basis at 23° C. of from about 1200 psi to less than about 1530 psi and at 60° C. of from about 960 psi to less than about 1200 psi.

### Claim 17 (depends on 1)

The method of claim 1 wherein the pipe has a minimum required strength of from about 8≦σLPL<10 MPa.

### Claim 18

A pipe prepared from a multimodal metallocene-catalyzed polyethylene resin having a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi; a stress for smooth to matte transition of greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s−1, wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test.

### Claim 19 (depends on 18)

The pipe of claim 18 having a PENT value of from about 500 hours to about 20,000 hours.

### Claim 20 (depends on 18)

The pipe of claim 18 having a Charpy Tdb of less than about −25° C.