WO2009105070A1

WO2009105070A1 - Ultra high molecular weight polyethylene articles

Info

Publication number: WO2009105070A1
Application number: PCT/US2008/002359
Authority: WO
Inventors: Stanley P. Dudek
Original assignee: Dudek Stanley P
Priority date: 2008-02-22
Filing date: 2008-02-22
Publication date: 2009-08-27

Abstract

The present invention describes an advantageous way of processing ultra high molecular weight polyethylene during an extrusion process. The ultra high molecular weight polyethylene may be formed into pipes and other useful articles.

Description

1 Ultra High Molecular Weight Polyethylene Articles

0₀

2 Inventor. Stanley P. Dudek

3 of

4 811 14^th Street

5 Galveston, TX 77550

6

7

9

10

11 BACKGROUND OF THE INVENTION

12 Field of the invention. This invention relates to the manufacture of articles from ultra high molecular weight polyethylene especially pipe. A problem in the processing of ultra high molecular weight polyethylene from the powdered state is the speed of fusion of the ultra high molecular weight polyethylene. The present invention obtains an article such as pipe from a pellet rather than a powder.

13 Description of the art practices.

14 Lee, et at. In United States Patent 4,355,116 issued October 19, 1982, is stated to disclose stable single film bipolar membranes of prolonged life and improved performance particularly for use in electrodialysis water splitting process, are prepared by introducing a more stable interface in the membrane structure. After the cationic exchange groups are preformed on an insoluble cross-linked aromatic polymeric matrix, the dissociable anionic exchange groups may be introduced more intimately chemically bonded in position by using multi- functional compounds containing mixed tertiary, secondary and primary amine groups, so that the resulting interface is comparatively more stable, and is less likely to be neutralized, therefore, attaining longer life- time and a higher level of performance. 15 United States Patent 5,079,287 issued January 7, 1992 to Takeshi, et al., describes an olefin resin composition for injection molding, which comprises (A) an olefin resin composition comprising ultra-high-molecular-weight polyethylene having an intrinsic viscosity of 10 to 40 dl/g as measured in decalin as the solvent at 135 ° C. and low- molecular-weight or high-molecular-weight polyethylene having an intrinsic viscosity lower than that of the ultra-high-molecular-weight polyethylene, in which the ultra-high-molecular-weight polyethylene is present in an amount of 15 to 40% by weight based on the sum of both of the polyethylenes and the two polyethylenes as a whole have an intrinsic viscosity [.eta.] c of 3.5 to 15 dl/g and a melt torque T lower than 4.5 kg.cm, and (B) 1 to 70% by weight based on the olefin resin composition, of an additive selected from the group consisting of fine particulate inorganic fillers, fibrous fillers and liquid and solid lubricants. 16 United States Patent 6,328,681 issued December 11 , 2001 , to Stephens, discloses industrial roll of the present invention comprises a substantially cylindrical core, an adhesive layer overlying the core, and a cover overlying the adhesive layer. The cover comprises: a polymeric base layer overlying the adhesive layer; and a top stock layer overlying the base layer. The top stock layer comprises a mixture of an elastomeric material and ultra high molecular weight polyethylene (UHMWPE), with the mixture including 100 parts elastomeric material by weight and between about 25 and 50 parts UHMWPE by weight. With these components in the recited ratios, the roll can be formulated to a desired hardness within the desired 10 to 50 P&J hardness range while maintaining release properties suitable for papermaking in the papermaking environment 17 United States Patent 6,521 ,709 issued February 18, 2003, to Pitteri, et al., s discloses a polyolefin composition comprising from 10 to 95% by weight of a crystalline propylene polymer, A) having an MFR value equal to or lower than 60 g/10 min., and from 5 to 90% by weight of an ultra high molecular weight polyethylene, B) in form of particles having a mean particle size of from 300 to 10 .mu.m.. 18 In United States Patent 6,780,361 issued August 24, 2004, to Sridharan, et al., there is disclosed a method including forming a pseudo-gel of a semi-crystalline polymer material and a solvent. The pseudo-gel is shaped into a first form and stretched. A portion of the solvent is removed to create a second form. The second form is stretched into a microstructure including nodes interconnected by fibrils. A method including forming a first form of a pseudo-gel including an ultra-high molecular weight polyethylene material and a solvent; stretching the first form; removing the solvent to form a second form; stretching the second form into a microstructure including nodes interconnected by fibrils; and annealing the stretched second form. An apparatus including a body portion formed of a dimension suitable for a medical device application and including a polyolefin polymer including a node and a fibril microstructure. An apparatus including a body portion including an ultra-high molecular weight polyolefin material including a node and a fibril microstructure. 19 United States Patent 6,790,923 issued September 14, 2004, to Smith, et al., discloses melt-processible, thermoplastic polyethylene compositions of high resistance against wear are disclosed and methods for making and processing same. Additionally, products comprising these compositions are described. 20 In United States Patent 6,855,785 issued February 15, 2005, to Baumgart, et al., there is disclosed a heat-curable composition comprising (I) at least one constituent whose molecule comprises on average (A) at least one functional group containing at least one bond which may be activated by means of heat and/or actinic radiation, and/or (B) at least one reactive functional group which is able to undergo thermal crosslinking reactions with groups of its own kind and/or with complementary reactive functional groups, with the proviso that there are always groups (A) and (B) in the composition; said constituent excluding the polyurethane dispersion synthesized from aliphatic polyisocyanates, compounds containing isocyanate-reactive functional groups and containing bonds that may be activated with actinic radiation, low molecular mass aliphatic compounds containing isocyanate-reactive functional groups, compounds containing isocyanate-reactive functional groups and dispersing functional groups, neutralizing agents for the dispersing functional groups, blocking agents for isocyanate groups, and/or compounds containing blocked isocyanate groups, the blocked isocyanate groups being introduced into the polyurethane dispersion by the reaction of the blocking agents with isocyanato-containing polyurethane prepolymers; and (II) from 0.5 to 15% by weight, based on the solids of the heat-curable composition, of at least one C-C-cleaving initiator.. 21 United States Patent 6,855,787 issued February 15, 2005, to Funaki, et al., discloses a multi-layer hose which is excellent in the interlayer adhesion strength and the fuel barrier property and which exhibits fuel resistance of the excellent interlayer adhesion strength over a long period of time. A component utilized by Funaki, et al., is UHMWPE. 22 In United States Patent 6,989, 198 issued January 24, 2006, to Masuda, et al., there is described a multi-layer structure excellent in the alcohol gasoline permeation-preventing properties and, particularly, hydrocarbon component permeation-preventing properties, and also excellent in the interiayer adhesion, low-temperature impact resistance, heat resistance and chemical resistance. A component utilized by Masuda, et al., is UHMWPE. 23 In United States Patent 7,019,042 issued March 28, 2006, to Rockmart, et al., the coating, bonding or sealing of primed or unprimed plastics parts is disclosed, for example, of ABS, AMMA, ASA, CA, CAB₁ EP, UF, CF, MF, MPF, PF, PAN, PA, PE, HDPE, LDPE, LLDPE, UHMWPE, PC, PC/PBT, PC/PA, PET, PMMA, PP₁ PS, SB, PUR, PVC, RF, SAN, PBT₁ PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM and UP (abbreviations to DIN 7728P1 ). Unfunctionalized and/or nonpolar substrate surfaces may be subjected to conventional pre-coating treatment, such as with a plasma or by a flaming, or may be given a water-based primer. 24 In United States Patent 7,037,970 issued Mehta, et al., to May 2, 2006, there is disclosed ethylene polymer composites, concentrates and a process utilized for their preparation are provided. The composites of the invention have increased melt strength compared to the base resin and other improved physical characteristics. The composites contain an organically modified clay and may also contain a compatibilizng agent, depending on the base resin used. 25 Throughout the specification and claims, percentages and ratios are by weight temperatures are in degrees Celsius, and pressures are in Kpa gauge unless otherwise indicated. Tp the extent that any of the references cited herein are applicable, they are hereby specifically incorporated by reference. Ranges and ratios given herein may be combined. 26 SUMMARY OF THE INVENTION 27 The present invention describes a composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having an MFR 250° C value at 2.5 Kg from 0.1 to 6 as measured by ASTM D1238. 28 The present invention also describes a composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having a tensile strength as measured by ASTM D-638 of less than 2850 psi. 29 The present invention further describes a composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having a tensile modulus as measured by ASTM D-638 of less than 110,000 psi. 30 The present invention also describes a composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having a flexural modulus as measured by ASTM D-790 of less than 130,000 psi . 31 The compositions of the present invention provide an easy to use pellet that provides an end use product such as pipe having improved abrasion resistance. That is, when the pipe is employed in an environment where abrasive materials are present the pipe may be used for a significant period of time before it must be replaced. Such an environment is, for example, a water intake pipe. 32 The compositions of the present invention behave as a thermoplastic thereby permitting melt processing to obtain an end use product rather than by compression processing. Historically, ultra high molecular weight polyethylene has been processed into various shapes, such as blocks, rods, and sheet, by compression, molding or ram extrusion. This type of processing was required because the ultra high molecular weight polyethylene alone does not have flow characteristics, such as melt index, which other polymers exhibit 33 It has been suggested that materials such as oils, waxes and other lubricants can be compounded into ultra high molecular weight poly-ethylene to help it obtain flow characteristics. These other materials, however, lower the physical properties of the ultra high molecular weight polyethylene when these materials are used at a level that would allow a melt index to be measured. The foregoing issues have essentially precluded the use of ultra high molecular weight polyethylene that is processed into a pellet that is then useful for injection molding or extrusion. 34 To accomplish the desired flow characteristics for ultra high molecular weight polyethylene a processing aid has is included to permit extrusion processing and to speed the fusion of the ultra high molecular weight polyethylene. The improved fusion characteristics permits the ultra high molecular weight polyethylene to be processed on standard plastic processing equipment such as single or twin screw extruders and injection molding machines. Molded parts produced from the modified ultra high molecular weight polyethylene pellets of the present invention exhibit excellent abrasion resistance, an important characteristic that ultra high molecular weight polyethylene is known to exhibit in compression molding. 35 An objective of this invention is to show that ultra high molecular weight polyethylene may be processed with desirable flow characteristics without the need for oils, waxes, or lubricants. Furthermore, such an ultra high molecular weight polyethylene pellets may be processed on standard plastic compounding equipment such as injection molding machines and extruders to produce various shaped articles such as pipe. 1 DETAILED DESCRIPTION OF THE INVENTION

2 36 The Thermoplastic Rubber Component

3 37 The thermoplastic rubber component is preferably a propylene

4 homopolymer, but it can also be a propylene copolymer containing

5 amounts of comonomers, in particular selected from ethylene and

6 .alpha.-olefins C ₄ -Ci₀, as 1-butene, l-pentene, 1-hexene, 4-methyM-

7 pentene, 1-octene, -|_d_eCene. The thermoplastic rubber may also be a

8 styrene block copolymer.

9 38 When a propylene homopolymer is employed, the thermoplastic

I o rubber component preferably contains an amount of fraction insoluble

I 1 in xylene at 25 ° C. equal to or greater than 94% by weight, more

12 preferably equal to or greater than 96% by weight; when it is a

13 copolymer, it prefer-ably contains an amount of fraction insoluble in

14 xylene at 25 ° C. equal to or greater than 85% by weight. The

15 thermoplastic rubber component can have narrow to broad molecular

16 weight distribution, provided that its MFR be within the above said

17 limits.

18 39 The Mw /M_n values for the thermoplastic rubber component

19 preferably can range from 2 to 60. The value of flexural modulus of the

20 thermoplastic rubber component as measured by ASTM D-790 of less

21 than 130,000 psi measured according to ASTM D-790. Preferably, the

22 flexural modulus is less than 120,000 psi.

23 40 A particular example of the thermoplastic rubber component is a

24 propylene polymer, in particular a homopolymer, having a broad

25 molecular weight distribution in terms of M_w /M_n namely having Mw /M_n

26 values equal to or higher than 5, in particular from 5 to 60, more

27 preferably from 6 to 30.

28 41 In particular, the flexural modulus, the tensile strength at yield

29 and the spiral flow (which is a test method commonly used to evaluate

30 the flowability in the molten state and, consequently, the melt-

31 processability) of the compositions of the invention are improved when the thermoplastic rubber component with broad molecular weight distribution is used. The above propylene polymers constituting the thermoplastic rubber compon-ent are well known in the art and commercially available. They can be prepared by using, for instance, the catalysts and polymerization processes described in the European patent No 45977. 42 The Ultra High Molecular Weight Polyethylene Component 43 The ultra high molecular weight polyethylene component is an ethylene homopolymer or a copolymer of ethylene containing 40% by weight or less, preferably 20% by weight or less of comonomers, selected in particular from alpha-olefins C₃ -Cio, as propylene, 1- butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene. Other comonomers that can be present in the copolymer are dienes. 44 The ultra high molecular weight polyethylene has a molecular weight between 1 ,000,000 and 8,000,000 preferably having a molecular weight between 2,000,000 and 7,500,000. 45 Component Usage and Processing 46 The components of the present invention are mixed together thoroughly and processed through an extruder. Typically, the extruder will achieve a temperature of 140° C to 220° C, preferably 150° C to 200 ° C. 47 Typically, the thermoplastic rubber is present in a weight ratio to the ultra high molecular weight polyethylene at about 1 :50 to about 1 :5. Preferably, the thermoplastic rubber is present in a weight ratio to the ultra high molecular weight polyethylene at about 1 :40 to about 1 :4. In use an ultra high molecular weight polyethylene powder is blended with the thermoplastic rubber and extruded into pellets. The pellets range are generally cylindrical in shape with a diameter of about 3/32 inch to about 5/32 inch with a length of 5/32 inch to 7/32 inch. The pellet size is ideal for the processing as later described. 48 Additional Components 49 Typically, many additional components may be utilized in the processing of the ultra high molecular weight polyethylene. Generally, any of the normally used components in the ultra high molecular weight polyethylene processing which do not materially interfere with the functioning of the system and the desired properties of the finished product may be employed. For instance, normally used components may be utilized herein at from 1 to 40 weight parts per 100 parts of the ultra high molecular weight polyethylene. Fillers and pigments may also be utilized herein typically at from 3 to 30 weight parts per 100 parts of the ultra high molecular weight polyethylene. 50 Composition Properties 51 The extruded composition has an MFR 250° C value at 2.5 Kg from 0.1 to 6 as measured by ASTM D1238. Preferably, the extruded comp-osition has an MFR 250° C value at 2.5 Kg from 0.2 to 5.5 as measured by ASTM D1238. 52 The extruded composition has a tensile strength as measured by ASTM D-638 of less than 2850 psi. Preferably, the extruded composition has a tensile strength as measured by ASTM D-638 of about 2600 psi to about 2825 psi. 53 The extruded composition has a tensile modulus as measured by ASTM D-638 of less than 130,000 psi. Preferably, the extruded composition has a tensile modulus as measured by ASTM D-638 of less than 110,000 psi. 54 From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims. 55 Certain portions of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

Claims

56 What is claimed is: Claim 1. A composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having an MFR 250° C value at 2.5 Kg from 0.1 to 6 as measured by ASTM D1238.

Claim 2. The composition according to claim 1 wherein said ultra high molecular weight polyethylene has a molecular weight between 1 ,000,000 and 8,000,000.

Claim 3. The composition according to claim 1 wherein said thermoplastic rubber is a styrene block copolymer.

Claim 4. The composition according to claim 1 wherein said ultra high molecular weight polyethylene has a molecular weight between 2,000,000 and 7,500,000.

Claim 5. The composition according to claim 1 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 : 50 to about 1 :5.

Claim 6. The composition according to claim 1 wherein said composition has an MFR 250° C value at 2.5 Kg from 0.2 to 5.5 as measured by ASTM D1238.

Claim 7. The composition according to claim 1 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 :40 to about 1 A. Claim 8. A composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having a tensile strength as measured by ASTM D-638 of less than 2850 psi.

Claim 9. The composition according to claim 8 wherein said ultra high molecular weight polyethylene has a molecular weight between 1 ,000,000 and 8,000,000.

Claim 10. The composition according to claim 8 wherein said thermoplastic rubber is a styrene block copolymer.

Claim 11. The composition according to claim 8 wherein said ultra high molecular weight polyethylene has a molecular weight between 2,000,000 and 7,500,000.

Claim 12. The composition according to claim 8 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 :50 to about 1 :5.

Claim 13. The composition according to claim 8 wherein said composition has an MFR 250° C value at 2.5 Kg from 0.2 to 5.5 as measured by ASTM D1238.

Claim 14. The composition according to claim 8 wherein said composition has a tensile strength as measured by ASTM D-638 of about 2600 psi to about 2825 psi.

Claim 15. The composition according to claim 8 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 :40 to about 1 :4. Claim 16. A composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having a tensile modulus as measured by ASTM D-638 of less than 130,000 psi.

Claim 17. The composition according to claim 16 wherein said ultra high molecular weight polyethylene has a molecular weight between 1 ,000,000 and 8,000,000.

Claim 18. The composition according to claim 16 wherein said thermoplastic rubber is a styrene block copolymer.

Claim 16. The composition according to claim 16 wherein said ultra high molecular weight polyethylene has a molecular weight between 2,000,000 and 7,500,000.

Claim 20. The composition according to claim 16 wherein said composition has a tensile modulus as measured by ASTM D-638 of less than 110,000 psi.

Claim 21. The composition according to claim 16 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 : 50 to about 1 :5.

Claim 22. The composition according to claim 16 wherein said composition has an MFR 250° C value at 2.5 Kg from 0.2 to 5.5 as measured by ASTM D1238.

Claim 23. The composition according to claim 16 wherein said composition has a tensile modulus as measured by ASTM D-638 of about 2600 psi to about 2825 psi. Claim 24. The composition according to claim 16 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 :40 to about 1 :4.

Claim 25. A composition comprising a pellet of a thermoplastic rubber and an ultra high molecular weight polyethylene said composition having a flexural modulus as measured by ASTM D-790 of less than 130,000 psi.

Claim 26. The composition according to claim 25 wherein said ultra high molecular weight polyethylene has a molecular weight between 1 ,000,000 and 8,000,000.

Claim 27. The composition according to claim 25 wherein said thermoplastic rubber is a styrene block copolymer.

Claim 28. The composition according to claim 25 wherein said ultra high molecular weight polyethylene has a molecular weight between 2,000,000 and 7,500,000.

Claim 29. The composition according to claim 25 wherein said composition has a flexural modulus as measured by ASTM D-790 of less than 120,000 psi.

Claim 30. The composition according to claim 25 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 :50 to about 1 :5. Claim 31. The composition according to claim 25 wherein said composition has an MFR 250° C value at 2.5 Kg from 0.2 to 5.5 as measured by ASTM D1238.

Claim 33. The composition according to claim 25 wherein said composition has a tensile modulus as measured by ASTM D-638 of about 2600 psi to about 2825 psi.

Claim 34. The composition according to claim 25 wherein said thermoplastic rubber is present in a weight ratio to said ultra high molecular weight polyethylene at about 1 :40 to about 1 :4.

Claim 35. The composition according to claim 25 wherein said composition has a tensile modulus as measured by ASTM 0-638 of less than 110,000 psi.