UHMWPE paste extrusion pipe

Abstract

The present invention generally relates to ultra high molecular weight polyethylene ("UHMWPE") pipes having an average wall thickness of 0.02 mm or less; the fracture tensile stress is greater than 40MPa; and a storage modulus at 23 DEG C greater than 500 MPa. The invention further relates to the preparation and use of such a tube, as well as to constructions (e.g., catheter constructions) comprising such a tube and components thereof.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 401,208, filed on August 26, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates generally to the field of pipes comprising ultra high molecular weight polyethylene (UHMWPE), for use, for example, as thin wall catheter liners, and to methods relating to such pipes. Background Art

[0004] Vascular therapy uses minimally invasive, catheter-based surgery and special devices and techniques. The catheter used in these surgeries usually adopts coating or lining on the inner wall to provide a lubricated inner surface. The lubricated inner diameter (ID) associated with these devices is conducive to reducing friction with them when they are pushed through the tight limits of the catheter cavity in different catheter technologies such as stents, balloons, atherectomy or thrombectomy devices. If the catheter ID does not have enough lubricity, the device such as stent will cause the liner to collapse in an accordion-like manner when the device is pushed through the catheter cavity. The effect of the increased lubricity of the catheter ID is to reduce their spreading force when the catheter device passes through the lumen, which increases the possibility of successful surgery. The mechanical properties of the catheter lining are also crucial for their success. For example, when some devices (such as shunts, embolic coils, aneurysm bridging devices and stents (scaffolding) and thrombectomy devices) pass microcatheters in a compressed state, high tensile and yield strengths will be required. The compressed shape exerts an outward radial force, which causes friction with the ID, generally making it difficult to pass the device through the lumen. On the other hand, when the catheter must pass through a vasculature involving sharp twists and turns, such as the cerebrovascular system and below-the-knee (BTK) applications, high flexibility of the liner is generally desired.

[0005] Among the different materials sought for the inner wall (base lining) material in such catheter devices, there is polytetrafluoroethylene (PTFE) because of its excellent chemical resistance, high temperature resistance, biocompatibility and very low friction coefficient / high lubricity. A major disadvantage of PTFE is that it is not radiation stable. Radiation sterilization (i.e., gamma rays or electron beams) is one of the most widely used and safe sterilization methods for medical devices. Radiation sterilization improves the manufacturability of catheters because it can be performed quickly on the production line, while the ethylene oxide gas sterilization (ETO) procedure commonly used with PTFE-lined catheters requires storage for up to 48 hours to allow the gas to diffuse out of the sterilization device. In addition, ethylene oxide gas needs to be handled carefully due to its flammability and toxicity. Strict handling requirements and technically complex sterilization processes make ETO sterilization technology generally undesirable. Recently, medical regulatory organizations around the world have also been encouraging the medical industry to reduce or replace the use of ETO with alternative sterilization methods.

[0006] Although several other polymers can withstand gamma radiation, none can match the lubricity or low coefficient of friction of PTFE. Ultra-high molecular weight polyethylene (UHMWPE) comes close. UHMWPE is a linear polymer with -CH2-CH2- repeating units. Medical grade UHMWPE has long chains with a molecular weight greater than 1×10 6g / mol, is a semi-crystalline polymer. UHMWPE has a very low coefficient of friction, excellent wear resistance, good toughness, high impact strength, high resistance to corrosive chemicals, excellent biocompatibility and low cost. In addition, UHMWPE has a low processing temperature, so it can be easily combined with a variety of other polymer catheter components. UHMWPE has been used clinically for joint implants for more than 40 years, especially as a joint lining in total hip replacement and a tibial insert in total knee replacement. One disadvantage of UHMWPE is that it has a very high viscosity due to its extremely high molecular weight. When UHMWPE is raised to a temperature higher than its melting point, it does not flow like lower molecular weight polyethylene or traditional melt-processable polymers. Therefore, many thermoplastic processing techniques such as injection molding, screw extrusion or blow molding are not practical for UHMWPE. U.S. Patent No. 6,837,890 describes a catheter construction using foamed UHMWPE as an inner layer / liner formed by compacting UHMWPE powder into a billet, deforming the billet through a die, and further orienting the extrudate by uniaxial or biaxial stretching to impart a microporous node and fibril structure. Such a foamed UHMWPE liner has lower strength, potential for fluid absorption, and lower wear resistance than an unfoamed, non-porous UHMWPE liner due to its microporosity. International Patent Application Publication No. WO 2023 / 114080A1 discusses a method for making membranes and porous structures with UHMWPE using a belt calendering process. However, there is currently no practical processing technology available for producing very thin, high-strength, non-porous UHMWPE tubes for catheter linings.

[0007] The gel spinning process is widely used to process UHMWPE into high-strength oriented polyolefin fibers, which can be used to make products such as ropes, tennis lines, fishing nets, filters, bulletproof molded products, medical textiles and high-strength medical sutures. Gel spinning of UHMWPE traditionally involves organic solvents such as decalin, tetralin, toluene, lower alkanes, paraffin oil, mineral oil, paraffin, etc., of which decalin and paraffin oil are the most widely used. Many of these solvents are generally considered to be unsafe or environmentally unfriendly for close contact. However, gel spinning of UHMWPE is generally only used to produce fibers and membranes. See, for example, International Patent Application Publication No. WO 2019 / 143899A1 (describing a composition comprising UHMWPE and 0.001-15wt% of cyclic terpenes / d-limonene, which is used to form a polymer gel, which is spun into fibers, membranes, filters and diaphragms). The document does not teach any method for producing thin-walled pipes or liners with UHMWPE at a high polymer concentration.

[0008] It would be a great benefit for both medical and industrial applications if radiation sterilizable polymer materials such as UHMWPE could be processed with environmentally friendly solvents into thin-walled tubes, liners or other polymer structures with good mechanical properties. Summary of the invention

[0009] The present invention provides a UHMWPE tube produced by a paste extrusion process, having an average wall thickness of less than 0.1 mm (preferably less than 0.05 mm) with a high longitudinal orientation of the UHMWPE polymer chains (which produces a high tensile strength). Due to the thin walls of the disclosed tubes and their high tensile modulus, they can exhibit high ID lubricity and wear resistance in some embodiments. In different embodiments, the combination of properties exhibited by the disclosed tubes can make them particularly suitable for use in catheters, including catheters designed for flexibility, because the thin walls of the disclosed tubes provide a significantly flexible lining that can be sterilized by irradiation (e.g., by a gamma or electron beam radiation source), unlike PTFE liners. In some embodiments, the paste extruded tube can be further oriented in the longitudinal and transverse directions to change and / or enhance mechanical, thermal and barrier properties. In addition, the polyethylene tube of the present invention can be used as a liner for metal tubes such as laser-cut hypotubes.

[0010] The present invention includes but is not limited to the following embodiments:

[0011] Embodiment 1: An ultra-high molecular weight polyethylene (UHMWPE) pipe comprising: a) an average wall thickness of 0.2 mm or less; and b) a tensile stress at break greater than 40 MPa; and c) a storage modulus greater than 500 MPa at 23°C.

[0012] Embodiment 2: The UHMWPE pipe of Embodiment 1, wherein the UHMWPE pipe is prepared by extruding a billet comprising a lubricant and a UHMWPE resin through an annular die.

[0013] Embodiment 3: The UHMWPE pipe of Embodiment 2, wherein the lubricant is selected from d-limonene, naphtha, Isopar G, Isopar M or any combination thereof.

[0014] Embodiment 4: The UHMWPE pipe of any one of Embodiments 1-3, wherein the UHMWPE pipe is prepared by extrusion on a metallic or non-metallic wire or mandrel.

[0015] Embodiment 5: The UHMWPE tube of Embodiment 4, wherein the metallic or non-metallic wire or mandrel and the UHMWPE tube are both substantially cylindrical in shape.

[0016] Embodiment 6: The UHMWPE tube of any one of Embodiments 1-5, wherein the average wall thickness is 0.1 mm or less.

[0017] Embodiment 7: The UHMWPE tube of any one of Embodiments 1-5, wherein the average wall thickness of the tube is 0.005 mm to 0.1 mm.

[0018] Embodiment 8: The UHMWPE pipe of any one of Embodiments 1-7, wherein the pipe exhibits a storage modulus variation of 70 MPa / °C or less between 23°C and 40°C.

[0019] Embodiment 9: The UHMWPE pipe of any one of Embodiments 1-8, comprising an inner surface having a coefficient of friction with stainless steel less than 0.2.

[0020] Embodiment 10: The UHMWPE pipe of Embodiment 9, wherein the difference in the coefficient of friction between 23°C and 40°C is ≤ 0.1.

[0021] Embodiment 11: The UHMWPE pipe of any of Embodiments 1-10, comprising an inner surface having a coefficient of friction with stainless steel in saline of less than 0.1.

[0022] Embodiment 12: The UHMWPE pipe of Embodiment 11, wherein the difference in friction coefficient in saline between 23°C and 40°C is ≤ 0.1.

[0023] Embodiment 13: The UHMWPE pipe of any one of Embodiments 1-12, consisting essentially of UHMWPE.

[0024] Embodiment 14: The UHMWPE pipe of any one of Embodiments 1-12, comprising UHMWPE and a particulate filler, wherein the particulate filler is present in a concentration of less than 50 wt %, based on the weight of the UHMWPE pipe.

[0025] Embodiment 15: The UHMWPE pipe of any one of Embodiments 1-12, comprising UHMWPE and a particulate filler, wherein the particulate filler is present in a concentration of less than 20 wt %, based on the weight of the UHMWPE pipe.

[0026] Embodiment 16: The UHMWPE tube of Embodiment 14 or 15, wherein the particulate filler is a filler imparting radiopacity, strength or hydrophilicity.

[0027] Embodiment 17: The UHMWPE pipe of any one of Embodiments 1-12 or 14-16, further comprising one or more additives selected from antioxidants, antimicrobial agents, processing aids, lubricants and colorants.

[0028] Embodiment 18: The UHMWPE pipe of any one of Embodiments 1-12 or 14-17, wherein the UHMWPE pipe comprises one or more additional polymer materials other than UHMWPE, wherein the one or more additional polymer materials are present in a concentration of less than 50 wt. % based on the weight of the UHMWPE pipe.

[0029] Embodiment 19: The UHMWPE pipe of any one of Embodiments 1-12 or 14-17, wherein the UHMWPE pipe comprises one or more additional polymer materials other than UHMWPE, wherein the one or more additional polymer materials are present in a concentration of less than 20 wt. % based on the weight of the UHMWPE pipe.

[0030] Embodiment 20: The UHMWPE pipe of Embodiment 18 or 19, wherein the one or more additional polymeric materials are selected from modified polyethylene and ethylene vinyl acetate tie resins.

[0031] These and other features, aspects and advantages of the present invention will become clear by reading the following specific embodiments and the accompanying drawings briefly described below. The present invention includes any combination of two, three, four or more of the above-mentioned embodiments, and any combination of two, three, four or more features or elements set forth in the present invention, regardless of whether such features or elements are clearly combined in the specific embodiments of this specification. The present invention is intended to be read as a whole, so that any separable features or elements of the disclosed invention in any of its different aspects and embodiments should be considered to be intended to be combinable, unless the context clearly specifies otherwise. Other aspects and advantages of the present invention will become clear from the following content. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To provide an understanding of embodiments of the invention, reference is made to the accompanying drawings, which are not necessarily drawn to scale and in which reference numerals refer to components of exemplary embodiments of the invention. The drawings are merely exemplary and should not be construed as limiting the invention.

[0033] Figure 1 is a general schematic diagram of a tube of the present invention with relevant parameters, and an enlarged schematic diagram of a cross-sectional end face of the tube. DETAILED DESCRIPTION

[0034] The present invention will now be described more fully below. However, the present invention can be implemented in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided so that the present invention will be comprehensive and complete and will fully convey the scope of the invention to those skilled in the art. As used in this specification and claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0035] The present invention provides UHMWPE pipes produced by a paste extrusion process having certain physical properties such as those more fully outlined below. A general schematic diagram of an exemplary pipe is provided in Figure 1 The tube is generally cylindrical. "L" represents the length of the produced tube, which can be processed, such as cut, to provide a tube of the desired length "l" (not shown). Figure 1 The enlarged area on the right is a cross-sectional view of the interior of the tube. As shown, the "lumen" is the interior area of ​​the tube, i.e., the open passage / cavity (e.g., through which a catheter device can pass when the tube is introduced as part of a medical device). The inner diameter of the tube (shown as "ID") is the average distance from a point on the inner wall of the tube to the relative / farthest point on the inner wall of the tube. The outer diameter of the tube (shown as "OD") is the average distance from a point on the outer wall of the tube through the lumen of the tube to the relative / farthest point on the outer wall of the tube. Therefore, the OD value minus half of the value provided by the ID value provides the average wall thickness of the tube. Figure 1 Also shown are representative "Wall Thickness", "Inner Wall Surface" and "Outer Wall Surface" of the tube.

[0036] In certain embodiments, the present invention provides a UHMWPE tube having a thin wall (i.e., wherein Figure 1 The "wall thickness" shown is relatively small). For example, in some embodiments, the average thickness of the wall is less than about 0.2 mm, or less than 0.100 mm, preferably less than about 0.075 mm, and more preferably less than 0.050 mm. For example, the average thickness can be about 0.005 mm to about 0.2 mm, about 0.005 mm to about 0.1 mm, about 0.005 mm to about 0.075 mm, or about 0.005 mm to about 0.05 mm. In preferred embodiments, the wall of the disclosed tube is substantially uniform in thickness along the length of the tube and / or around the circumference of the tube.

[0037] As shown, there is no particular restriction on the length L, and Figure 1The tube schematically shown in the figure can be optionally processed, for example, cut into a plurality of tubes of any desired length l. In some embodiments, the length l of the tube provided herein is a length suitable for catheter applications, for example, as a liner. For example, in some embodiments, the length l is about 150mm-about 2000mm. Similarly, ID (which determines the diameter of the lumen) can vary, and in some embodiments, has a size suitable for catheter applications, for example, as a liner, for example, about 1mm-about 11mm.

[0038] The pipe provided herein generally comprises UHMWPE.Different UHMWPE resins are commercially available and can be used in certain embodiments of the UHMWPE pipe provided herein.In some embodiments, UHMWPE is unique polymer in the disclosed pipe.In other embodiments, one or more other polymers can be included in the disclosed pipe, for example, with the following amount: less than 50% by weight, less than 40% by weight, less than 30% by weight, less than 20% by weight, less than 10% by weight, less than 5% by weight, less than 1% by weight, less than 0.5% by weight, less than 0.1% by weight, less than 0.05% by weight, or less than about 0.01% by weight, based on the gross weight of the pipe (for example, about 0.01% by weight-about 50% by weight, about 0.01% by weight-about 30% by weight, about 0.01% by weight-about 10%, about 0.01% by weight-about 1% by weight, or about 20% by weight-about 50% by weight, about 30% by weight-about 50% by weight, or about 40% by weight-about 50% by weight).

[0039] In some embodiments, optionally one or more additional polymers can be a bonding resin. In some embodiments, optionally one or more additional polymers can be, for example, modified polyethylene and / or ethylene vinyl acetate (EVA) bonding resins. In some embodiments, optionally one or more additional polymers can be, for example, grafted polyethylene, such as maleic anhydride grafted HDPE. In the case of incorporating one or more additional polymers into the disclosed pipe, it is generally in the form of an intimate mixture / blend with UHMWPE so that the composition of the material of the pipe is substantially uniformly distributed. In some embodiments, a second (or additional) polymer can be incorporated to change the physical properties of the pipe, such as mechanical properties, heat and barrier properties, crystallinity and / or friction coefficient.

[0040] Advantageously, in various embodiments, the tube consists essentially of UHMWPE (alone or in combination with one or more additional polymers, as described above), i.e., no significant amount of additional components (e.g., fillers) are contained in the tube. In other embodiments, the disclosed tube may contain one or more additives or fillers, such as particulate fillers, in a concentration of up to about 50% by weight, based on the total weight of the tube, such as about 0.01% to about 50%, such as about 0.01% to about 10%, about 0.01% to about 10%, about 0.01% to about 20%, about 10% to about 50%, about 20% to about 50%, about 20% to about 50%, about 20% to about 30%, or about 30% to about 50% by weight, based on the total weight of the tube. Suitable particulate fillers may vary and may include, for example, fillers designed to impart specific properties such as radiopacity, strength, and / or hydrophilicity. In some embodiments, one or more additives such as antioxidants, antimicrobial agents, processing aids, lubricants, and / or colorants are included in the disclosed tube. In some embodiments, the filler may be a heat stabilizer, an oxidation stabilizer, or a light stabilizer. In some embodiments, an amount of lubricant or other processing aid (e.g., a low molecular weight polyethylene or wax, such as polyethylene wax, erucamide, oleamide, or stearate) may be included in the tube, although in preferred embodiments, the tube contains only trace or undetectable amounts of lubricant or other processing aid.

[0041] In some embodiments, the UHMWPE pipe has high lubricity and wear resistance. These features can be characterized in different ways. Wear is generally understood as the material being worn away due to friction. Friction is caused by rubbing or scratching the initial material. Wear resistance is a material property that prevents wear when friction is applied to the surface. Wear resistance is understood to be material-dependent and processing-dependent. There are a variety of methods for quantifying abrasion and wear, depending on the sample geometry and application. In certain embodiments, the material or sample to be tested is positioned relative to another material so that the two surfaces are in contact. Other materials can be selected based on the desired test conditions. Some common materials include polished metal surfaces, metal pins, sandpaper, or the same material as the test sample. Then, one or both materials are moved so that friction is caused between the contacting surfaces. Depending on the test method, the end point of the test can be defined after a certain amount of time, after a defined number of times the surface is rubbed, or until a specified failure mode is reached. Some failure modes include reaching: a defined mass loss, a defined material thickness relative to the reduction of the initial material thickness, a loss of tensile properties, or a loss of insulation properties. Regardless of the selected test method, the relative wear resistance of two or more materials can be determined by subjecting the samples to the same test conditions and comparing the effects of the test conditions on the materials tested. Some methods of detecting sample wear are weight loss, visual inspection, and microscope images. Different methods that can be used to define the evaluation wear resistance of the tubes of the present invention include, but are not limited to, those disclosed herein by reference (including, for example, pin wear test (e.g., using ASTM G132), rubber wheel wear test (e.g., using ASTM G65), Taber wear test (e.g., using ASTM D1044 and ASTM D4060), blade-block wear test, medical device wear test, and pin-disc wear test (e.g., using ASTM G99, ASTM G133, and ASTM F732)). Another exemplary method is EN 3475 method 511, which generally includes placing the material in a fixture so that it contacts another sample of the same type; fixing the ends in place and vibrating / rubbing the sample itself.

[0042] Suitable wear resistance / lubricity values ​​for the disclosed tubes can vary, but advantageously, such values ​​are quite high. For example, in some embodiments, at least the inner wall surface of the disclosed tube can be described as "wear resistant" and / or "lubricated", and in some embodiments, both the inner wall surface and the outer wall surface can be described similarly. For example, in some embodiments, the inner wall and / or outer wall of the tube is a lubricated surface having a coefficient of friction less than about 0.2 or less than about 0.1 (e.g., about 0.05-about 0.2, or about 0.05-about 0.1). In some embodiments, the inner wall and / or outer wall of the tube is a lubricated surface having a coefficient of friction less than about 0.2 or less than about 0.1 (e.g., about 0.02-about 0.2, or about 0.02-about 0.1) in saline. In some embodiments, the lubricated surface of the disclosed tube exhibits a difference in the coefficient of friction less than or equal to about 0.1 (e.g., about 0.01-about 0.1) between 23°C and 40°C. In some embodiments, the lubricated surface of the disclosed tubes exhibits a difference in coefficient of friction of less than or equal to about 0.1 (eg, about 0.01 to about 0.1) in saline between 23° C. and 40° C. The values ​​given above may be, for example, coefficients of friction against stainless steel.

[0043] In some embodiments, the disclosed tubes exhibit physical properties that make them suitable for a wide range of applications. In some embodiments, the disclosed tubes exhibit high tensile stress at break values, such as greater than 40 MPa. For example, in some embodiments, the tubes exhibit tensile stress at break values ​​of about 40 MPa-400 MPa, such as 40 MPa-200 MPa. In some embodiments, the disclosed tubes exhibit high storage modulus values. For example, in some embodiments, the disclosed tubes can exhibit a storage modulus at 23°C of greater than 500 MPa, such as in some embodiments greater than 750 MPa at 23°C, greater than 1000 MPa at 23°C, greater than 1,200 MPa at 23°C, greater than 1,500 MPa at 23°C, greater than 2,000 MPa at 23°C, greater than 2,200 MPa at 23°C, or greater than 2,500 MPa at 23°C, such as about 500 MPa to about 5,000 MPa, about 500 MPa to about 2,500 MPa, or about 1,000 MPa to about 5,000 MPa at 23°C. In some embodiments, the change in storage modulus is lower, for example such that the tube exhibits a change in storage modulus between 23°C and 40°C of 500 MPa / °C or less, 200 MPa / °C or less, 100 MPa / °C or less, or 70 MPa / °C or less, for example, about 10 MPa / °C-500 MPa / °C, or about 10 MPa / °C-70 MPa / °C.

[0044] In some embodiments, the disclosed tubes may be referred to as "paste extruded" tubes. The method of preparing these tubes (as described below) produces certain physical properties that distinguish such tubes from, for example, free extruded tubes. For example, in some embodiments, tubes uniquely prepared by this method (e.g., paste extrusion of UHMWPE on a substrate / core, subsequent sintering and removal of the formed UHMWPE tube from the substrate / core) exhibit low longitudinal orientation of the UHMWPE polymer chains, e.g., much lower than the longitudinal orientation exhibited by free extruded tubes. In addition, the tubes may uniquely exhibit particularly beneficial properties (e.g., which may be produced at least in part by the production method), including, for example, excellent strength and flexibility characteristics even at very low wall thicknesses.

[0045] In some embodiments, the UHMWPE tube produced may be described as being "unstretched" and / or "undrawn", i.e., it has not been stretched after production to impart molecular orientation. In some embodiments, the UHMWPE tube produced may be described as being "stretched" and / or "drawn" after production, and may therefore exhibit longitudinal molecular orientation, and accordingly exhibit increased tensile strength and reduced wall thickness (relative to the corresponding produced tube). In some embodiments, the UHMWPE tube produced may be described as being "stretched" and / or "drawn" in both the longitudinal and transverse directions.

[0046] It is noted that in some embodiments, the properties of a given tube may vary somewhat relative to the properties when the disclosed fillers and / or other polymers are included therein. For example, in some embodiments, a tube comprising one or more of the above-described bonding resins may enhance or impart one or more specific properties, such as lubricity, toughness, or adhesion. In some embodiments, a tube comprising one or more added fillers and / or polymers other than UHMWPE may have different properties, such as mechanical properties, thermal properties, and barrier properties, crystallinity, and coefficient of friction, among others. In addition, the inclusion of, for example, an antioxidant or antimicrobial agent will provide the tube with corresponding characteristics, and a colorant will impart a relevant color to the tube.

[0047] The present invention further provides a method for producing UHMWPE profiles such as monofilaments, multifilaments, tapes and tubes exhibiting the above-mentioned physical properties. The method generally comprises using a paste extrusion process, wherein the UHMWPE is extruded freely or on a metal or non-metal substrate, which includes, for example, but is not limited to, a wire or a PTFE core / mandrel. The paste extrusion method for UHMWPE may involve several steps, including: (1) paste preparation or mixing of resin and lubricant; (2) preform preparation; (3) extrusion; (4) lubricant evaporation; and (5) curing / annealing / sintering, as further described below. It should be understood that for some paste extrusion methods, it is not necessary to prepare a preform prior to extrusion.

[0048] Finely powdered UHMWPE resins suitable for the extrusion process disclosed herein generally have a molecular weight of generally greater than 1×10 6 g / mol (usually calculated from IV / intrinsic viscosity measurements) of homopolymers. Exemplary resins suitable for this purpose include, but are not limited to, Celanese [ 2024, 2122, 2122-5, 2126, 4012, 4012F, 4020-3, 4022, 4022-6, 4032, 4050-3, 4056-3, 4112, 4113, 4120, 4122, 4122-5, 4130, 4150, 4150-3, 4152, 4170, 4523, 4550, 5113, 5129, 5523, X161, X195, X204, X214, X217], Mitsui's [MipelonPM200, XM220, XM221U, XM330], Hi-Zex Million 030S, 145M, 240S, 320MU, 630M, Braskem's UTEC3040, UTEC3041, UTEC4040, UTEC4041, UTEC5540, UTEC5541, UTEC6540, UTEC6540G, UTEC6541, Rochling's Polystone, LyondellBasell's Lupolen UHM5000 and Asahi Kasei's Sunfine UH. Copolymers of ethylene or other polyethylene resins such as radiation or chemically modified polyethylene resins can also be used in the extrusion process.

[0049] It should be understood that in the following discussion, the term "lubricant" can be applied to any compound that at least partially wets the UHMWPE resin. Wettability / surface tension and viscosity are two properties of lubricants that significantly affect the pressure at which the UHMWPE paste is extruded, and can therefore be varied accordingly. Lubricants that wet the UHMWPE are more helpful in reducing extruder pressure. Similarly, lubricants with low viscosity will help reduce extruder pressure.

[0050] The paste preparation step includes mixing UHMWPE fine powder with a suitable lubricant (or a combination of lubricants). The non-limiting examples of suitable lubricants include xylene, cyclohexane, benzene, toluene, carbon tetrachloride, tetrahydrofuran, chloroform, dodecane, naphthalene, naphtha, Isopar G, Isopar M, p-xylene, 1,2,4-trichlorobenzene, kerosene, camphene, paraffin oil, decalin, polybutene, sunflower oil, palm oil, orange oil (terpene), other oleophilic hydrocarbons and combinations thereof. Environmentally friendly solvents such as D-limonene [CAS No. 5989-27-5] can also be used for the above-mentioned paste preparation step. D-limonene is a cyclic terpene found in citrus extract / oil, and is also referred to as limonene or 1-limonene or dl-limonene or (+)-limonene or (+)-dipentene or (+)-(R)-limonene or (R)-4-isopropenyl-1-methyl-1-cyclohexene.

[0051] The ratio of resin to lubricant can vary from 1:1 to 15:1 (weight grams / volume mL). In order to form a suitable paste, the polymer can be mixed with the lubricant by mechanical stirring, heated or not (up to 100°C). The paste can be subjected to an optional filtering step to remove large agglomerates. In addition, the paste can be optionally aged over an extended period of time, heated or not (up to 100°C) to enhance the wettability of the resin with the lubricant. Before the extrusion step, it is usually important to remove at least some air (advantageously, as much air as possible) from the UHMWPE paste to prevent defects in the extrudate. Unlike PTFE paste extrusion, the preforming step in UHMWPE may not always be necessary. Instead, the paste can be loaded into a machine barrel in a single step and pressed to eliminate the entrained air. If a preforming step is used, the mixture is usually pressed into a solid or hollow shape (e.g., a cylindrical or annular profile), which is referred to as a preform or blank. These preforms are usually quite weak and can easily break or deform, and should be handled with care. For example core-sheath structure can be used for having different materials and / or properties on the inner layer and outer layer of extruded tube profile for each layer having the multilayer preform of different paste formula.In some embodiments, a plurality of preforms with different lubricants or different amounts of lubricants can be manufactured, and are loaded into the extruder.In such an embodiment, the different parts of the preform have different lubricants or different amounts of lubricants, which changes the extrusion pressure in the production process.

[0052] In certain embodiments, the cylindrical preform is inserted into the extrusion cylinder / barrel of the paste extruder, and then pressed by the die head by means of a plunger. The barrel and / or the die head can be in ambient temperature or heated to a temperature lower than the resin degradation temperature. The extrusion of the pipe (with or without a core) usually requires the presence of a mandrel in the barrel, which is connected to the rear portion. According to the present invention, a metal / non-metallic, smooth or textured core is fed through this mandrel. Such a core can be in room temperature or preheated to above room temperature before entering the mandrel. There is no particular restriction on the material of the core adopted in this paste extrusion process, and in some embodiments, it can be metallic or non-metallic. When core coating is not required, if the mandrel exists as described above, the free extruded pipe can still be produced.

[0053] The extruded paste coats the core (in the case of core coating) while being directed through the extruder head. If the extrusion pressure changes during processing and the coating thickness (or wall thickness of the free extruded tube) deviates from the target, the design of the machine ensures that the plunger speed can be adjusted (manually / automatically) to ensure uniform coating or wall thickness of the free extruded tube on the mandrel.

[0054] During the extrusion process, based on the drafting of the material, the molecular / chain orientation can be imparted to the extruded product (e.g., the final component). It is known that the orientation imparted to the material affects the tensile properties, especially the modulus, tensile strength, and elongation. With the changes shown in the modulus, the coefficient of friction (COF) will also change. Generally, increasing the drafting will increase the axial orientation of the polymer, thereby increasing the modulus and tensile strength, and reducing the elongation and COF. The extrudate can be optionally processed, for example, long tubes are cut into shorter lengths as desired, for example, for certain specific applications.

[0055] After extrusion, the residual lubricant in the extruded UHMWPE pipe or profile must be completely removed by heating to above the boiling point or flash point of the lubricant. This step is performed, for example, by sending the product through a devolatilization oven.

[0056] After the devolatilization step, the product is heated in a higher temperature sintering / annealing oven, which is usually set at a temperature equal to or higher than the melting point of UHMWPE. Depending on the line speed and thickness of the UHMWPE, the oven is usually set at a temperature far above this melting temperature. It is important that the product in the sintering oven is completely free of lubricants / solvents. In the sintering oven, the UHMWPE particles melt and adhere to each other. When the product cools (for example, when leaving / taking out of the sintering oven), the UHMWPE changes from a molten state to a solid state. The second stretching / orientation (in MD / TD) can also be performed in the same manner as described above. In addition, a bonding material can be coated or extruded onto the UHMWPE layer to help combine with materials such as PI, PU, ​​nylon or PEBA.

[0057] In another embodiment, the devolatilization, sintering / annealing, and stretching / orientation operations can be performed in the same oven.

[0058] The inventors have found that by extruding UHMWPE on a substrate / core, the longitudinal orientation of the UHMWPE polymer chains is reduced. This feature is in contrast to, for example, freely extruded tubes which exhibit a high longitudinal orientation. By extruding and sintering a UHMWPE coating in this manner, followed by removal of the coating, a tube exhibiting a particularly beneficial combination of properties (as described above) can be readily obtained. In particular, the inventors have surprisingly found that a tube having a very low wall thickness can be obtained in this manner, which exhibits the above-mentioned strength and flexibility characteristics, which provides a particularly beneficial means for producing, for example, very thin-walled UHMWPE tubes for catheter applications.

[0059] The produced UHMWPE pipe or profile can also be optionally stretched and pulled in the longitudinal direction (heated or not) to impart molecular orientation and thus increase tensile strength and further reduce wall thickness. The longitudinally oriented pipe can then be further oriented (heated or not) by stretching, for example, 1.1-10 times in the TD (transverse direction) mechanically or pneumatically (e.g., applying air on the ID). Alternatively, the unstretched pipe can be mechanically / pneumatically or combined (e.g., a balloon blower) oriented simultaneously in the longitudinal and transverse directions (heated or not). The stretching process can be used to produce different structural and mechanical effects in the pipe.

[0060] In some embodiments, UHMWPE can be extruded into different profiles such as monofilaments, tubes and bands without the use of lubricants. One or more UHMWPE resins and any desired fillers such as bonding resins can be loaded into the extruder barrel with or without making preforms. The resin material can then be sent through a high temperature (higher than the melting temperature of the resin) die to extrude, and additional steps such as annealing, stretching, orientation, etc. are performed.

[0061] It should be understood that any UHMWPE tube of the present invention may contain fillers to impart specific properties, such as radiopacity, strength and hydrophilicity. It should also be understood that any UHMWPE tube of the present invention may contain one or more polymers other than UHMWPE, such as modified polyethylene (maleic anhydride grafted / copolymerized polyethylene) and ethylene vinyl acetate (EVA) bonding resin, to impart specific properties such as lubricity, toughness or adhesion. Tubes to which fillers and polymers other than UHMWPE are added may have different properties, such as mechanical properties, thermal properties and barrier properties, crystallinity and friction coefficient, etc. It should be understood that the tube of the present invention may contain additives such as antioxidants, antimicrobial agents, processing aids, lubricants and colorants, as well as other particles designed to impart specific properties to the tube.

[0062] The pipe of extrusion can be subjected to radiation such as electron beam or gamma processing, and the dosage is 50kGy-15MGy. Radiation treatment can change the polymer chain structure of pipe, and affect some physical properties, mechanical properties or thermal properties of liner, such as lubricity, toughness, modulus etc. Usually, radiation treatment can give polyethylene chain crosslinking, which increases modulus and tensile strength. Alternatively, irradiated UHMWPE resin can be added to UHMWPE paste / preform as filler to give and / or enhance specific function. The pipe of extrusion can also carry out surface modification, such as plasma treatment to improve the combination with other polymer materials such as catheter sheath.

[0063] In some embodiments, the tube disclosed herein is particularly useful for use as a catheter sleeve. Conventional three-layer catheters include a liner as the innermost layer, and the tube of the present invention is particularly useful for it. The liner itself generally has a wall thickness of about 0.025mm-about 0.070mm and an inner diameter of about 0.380mm-about 4.300mm. The braided layer encapsulates the liner, and the sheath encapsulates the braided encapsulation. The braided layer can be constructed with wires or filaments of metal or non-metallic materials (such as stainless steel, liquid crystal polymers, UHMWPE, etc.). Therefore, the present invention not only provides the tube described herein, but also provides a tube configured as a liner (for example, it can only include the tube, or it can include one or more other components except the tube, such as a braided layer and / or other layers associated with the catheter structure such as the sheath).

[0064] In order to use the disclosed pipe to construct a catheter, an instrument such as a Beahm 810A vertical laminator can be used. The polyethylene tube provided herein can be combined with a catheter sheath made of materials such as PEBA (polyether block amide), nylon, polyurethane, etc. The disclosed pipe can also be stretched to reduce the wall thickness of the pipe, without reducing their associability, and then used to construct the catheter. The elongation of the tubing can affect some physical properties, mechanical properties or thermal properties of the liner, such as lubricity, toughness, modulus, etc. Usually, increasing the elongation can increase the axial orientation of the pipe, thereby increasing modulus and tensile strength and reducing elongation. Constructed catheters and catheter components such as liner and sheath can be tested using an interventional device tester such as the IDTE3000 from MSI, which can measure and record device performance characteristics, such as pushability, flexibility, torsion, etc.

[0065] The lubricant, solvent and UHMWPE resin used in the paste extrusion process can also be used in different concentrations to produce 3D printed monofilaments for polymer structures / devices / products for different applications.

[0066] experiment

[0067] The tensile properties of the UHMWPE samples were determined using an Instron 5965 dual-column mechanical tester running Bluehill 3v3.73.4823 operating software. For the strip samples, a 1kN load cell and a 12.7mm gauge length were used and tested at a rate of 25.4mm / min with a V-type dog bone. The tensile test of the tube samples was performed using a 50.8mm gauge length and a 50.8mm / min test rate and a 1kN load cell. As described in the specific embodiments, different test parameters were used to measure the mechanical properties of the monofilament samples. The average tensile values ​​of the UHMWPE profiles are listed in Tables 2 and 3.

[0068] Thermomechanical properties of UHMWPE profiles were determined using a TA Instruments Q800 DMA with a film tension fixture. The main property of interest was the storage modulus (E'). A temperature scan was performed from -100°C to 130°C and held isothermally at -100°C for 5 minutes. The sample was heated at a constant rate of 3°C / min while being displaced with a constant amplitude of 15 μm and a fixed frequency tensile oscillation of 1 Hz. The resulting DMA data were imported into TA Instruments TRIOS software v4.3 and the average values ​​of the storage modulus at 23°C and 40°C are listed in Tables 2 and 3.

[0069] The flexural properties of the UHMWPE pipe samples were determined using a TA Instruments Q800 DMA with a 3-point bend fixture. The test was operated at room temperature with a sample size of 5 mm x 50 mm and a span length of 15 mm, with a strain increase of 1% / min to 5% strain. The results are listed in Table 3.

[0070] The tribological properties of the UHMWPE samples were determined using a TA Instruments Discovery Hybrid Rheometer (DHR-3) rheometer with a tribological rheometer attachment. One of the main properties of interest during this test was COF. The samples were prepared using a ring-plate tribological rheometer fixture by attaching three 5 mm × 16.5 mm tube segments each to three teeth of a half ring. The ring with the mounted sample was then attached to a ring-plate upper geometry holder and lowered to contact the sample with a mirror-polished stainless steel plate under a specified axial force. Tribological tests were performed at room temperature (23°C) with an axial load of 1 N at sliding speeds of 750 μm / s to 7650 μm / s. Additional tribological tests were performed in a saline bath at room temperature (23°C) with an axial load of 1 N at sliding speeds of 750 μm / s to 7650 μm / s. The minimum COF over the sliding speed range was calculated by TA Instruments TRIOS software v4.3. For each blend, multiple samples were tested and the average values ​​are reported in Tables 2 and 3.

[0071] A combination of adequate parameters such as COF, tensile strength, modulus and bending stress is generally important for linings for catheter applications. As a non-limiting example, for linings for neurovascular applications, a combination of low COF, high strength and low bending stress is generally desired.

[0072] Example

[0073] Aspects of the present invention are more fully illustrated by the following examples, which are presented for the purpose of illustrating certain aspects of the present invention and should not be construed as limiting thereof.

[0074] Use Malvern Advanced Capillary Rheometer RH7, vertical paste extruder and horizontal paste extruder to prepare multiple UHMWPE samples with different profiles according to the specific embodiment content provided below. Further information about the resin (or multiple resins) used in these embodiments is provided in the following table 1. According to the above method, mechanical and lubricity test samples are carried out. Any changes in sample production or test methods should be noted in the specific embodiments. In all embodiments, the measurement unit of weight is gram, and the measurement unit of volume is milliliter.

[0075] Tape and Monofilament Examples

[0076] Embodiment 1:

[0077] UHMWPE PM-200 was mixed with d-limonene lubricant in a 1:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. All heating zones in the rheometer (including barrel and die) were set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 200% under tension in a secondary process at about 110°C.

[0078] Embodiment 2:

[0079] UHMWPE PM-200 was mixed with PTFE (wt / wt) accounting for 2% of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a ratio of 1:1 (wt / vol). The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. All heating zones in the rheometer (including barrel and die) were set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 200% under tension in a secondary process at about 110°C.

[0080] Embodiment 3:

[0081] UHMWPE PM-200 was mixed with 5% PTFE (wt / wt) of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a 1:1 ratio (wt / vol). The mixture was added to the rheometer barrel and a flat ribbon profile was extruded using a ribbon die with a length of 10.8 mm and a width of 1.5 mm. All heating zones in the rheometer (including the barrel and die) were set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 200% under tension in a secondary process at about 110°C.

[0082] Embodiment 4:

[0083] UHMWPE PM-200 was mixed with d-limonene lubricant in a 1:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 300% under tension in a secondary process at about 110°C.

[0084] Embodiment 5:

[0085] UHMWPE PM-200 was mixed with 2% PTFE (wt / wt) of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a 1:1 ratio (wt / vol). The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 300% under tension in a secondary process at about 110°C.

[0086] Embodiment 6:

[0087] UHMWPE PM-200 was mixed with 5% PTFE (wt / wt) of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a 1:1 ratio (wt / vol). The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 300% under tension in a secondary process at about 110°C.

[0088] Embodiment 7:

[0089] UHMWPE PM-200 was mixed with d-limonene lubricant in a 2:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 400% under tension in a secondary process at about 110°C.

[0090] Embodiment 8:

[0091] UHMWPE PM-200 was mixed with 10% EVA (wt / wt) of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a ratio of 2:1 (wt / vol). The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 400% under tension in a secondary process at about 110°C.

[0092] Embodiment 9:

[0093] UHMWPE PM-200 was mixed with 10% UHMWPE XM-221U (wt / wt) of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a ratio of 2:1 (wt / vol). The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 400% under tension in a secondary process at about 110°C.

[0094] Embodiment 10:

[0095] UHMWPE PM-200 was mixed with irradiated (10MRad) UHMWPE PM-200 (wt / wt) accounting for 10% of the polymer in a wide-mouth bottle. D-limonene lubricant was added to the resin mixture in a ratio of 2: 1 (wt / vol). The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 400% under tension in a secondary process at about 110°C.

[0096] Embodiment 11:

[0097] UHMWPE PM-200 was mixed with d-limonene lubricant in a 2: 1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and a ribbon die with a length of 10.8 mm and a width of 1.5 mm was used to extrude a flat ribbon profile. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded ribbon was heat-drawn by about 400% under tension in a secondary process at about 110°C. The drawn ribbon was irradiated with an electron beam of 10 MRad dose.

[0098] Embodiment 12:

[0099] UHMWPE GUR 4056-3 was compressed into a solid cylindrical billet in a preforming press without using any lubricant. The billet was loaded into a vertical paste extruder and a flat ribbon profile was extruded using a ribbon die with a length of 12.7 mm and a width of 3.17 mm. Only the die of the extruder was heated to a set temperature of 260°C. The extruded ribbon was hot-drawn by about 200% under tension in a secondary process at about 130°C.

[0100] Embodiment 13:

[0101] UHMWPE GUR 4056-3 was mixed with Isopar M lubricant in a ratio of 4:1 (wt / vol) in a wide-mouth bottle. The mixture was compressed into a solid cylindrical billet in a preforming press. The billet was loaded into a vertical paste extruder and a flat ribbon profile was extruded using a ribbon die with a length of 12.7 mm and a width of 3.17 mm. Only the die of the extruder was heated to a set temperature of 260°C. The extruded ribbon was hot-drawn by about 300% under tension in a secondary process at about 130°C.

[0102] Embodiment 14:

[0103] UHMWPE GUR 4056-3 was mixed with Isopar G lubricant in a ratio of 10:1 (wt / vol) in a wide-mouth bottle. The mixture was compressed into a solid cylindrical billet in a preforming press. The billet was loaded into a vertical paste extruder and a flat ribbon profile was extruded using a ribbon die with a length of 12.7 mm and a width of 3.17 mm. Only the die of the extruder was heated to a set temperature of 260°C. The extruded ribbon was hot-drawn by about 200% under tension in a secondary process at about 130°C.

[0104] Embodiment 15:

[0105] UHMWPE GUR 4022-6 was mixed with Isopar M lubricant in a 4:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was compressed into a solid cylindrical billet in a preforming press. The billet was loaded into a vertical paste extruder and a flat ribbon profile was extruded using a ribbon die with a length of 12.7 mm and a width of 3.17 mm. Only the die of the extruder was heated to a set temperature of 260°C. The extruded ribbon was hot-drawn by about 300% under tension in a secondary process at about 130°C.

[0106] Embodiment 16:

[0107] UHMWPE PM 200 and irradiated UHMWPE PM 200 (10MRad) resins were mixed in a 4:1 ratio (wt / wt) in a wide-mouth bottle, and 5% (wt / wt) Epolene C-16P was added to the UHMWPE resin mixture. D-limonene was added to the resin mixture in a 3:1 ratio (wt / vol) as a lubricant. The mixture was compressed into a solid cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder, and a strip die with a length of 19.95 mm and a width of 0.09 mm was used to extrude the strip. The die had multiple heating zones, which were heated to a set temperature of 30°C-160°C. The strip was tested after extrusion without any additional drawing process.

[0108] Embodiment 17:

[0109] UHMWPE PM-200 was mixed with d-limonene lubricant in a 5:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and the monofilaments were extruded using a 1.5 mm die. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded monofilaments were heat-drawn by about 200% under tension in a secondary process at about 110°C.

[0110] Embodiment 18:

[0111] UHMWPE PM-200 was mixed with d-limonene lubricant in a 2:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and the monofilaments were extruded using a 1.5 mm die. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded monofilaments were heat-drawn about 700% under tension in a secondary process at about 110°C. Tensile tests were performed on an Instron using a 152.4 mm gauge length and a 304.8 mm / min test rate.

[0112] Embodiment 19:

[0113] UHMWPE PM-200 is mixed with d-limonene lubricant in a 2: 1 ratio (wt / vol) in a wide-mouth bottle. The mixture is compressed into a solid cylindrical billet in a preforming press. The billet is loaded into a horizontal paste extruder and a 2.3mm die is used to extrude the monofilament. Only the die of the extruder is heated to a set temperature of 200°C. The extruded monofilament is heat-drawn about 1000% under tension in a secondary process at about 110°C. A tensile test is performed on an Instron using a 101.6mm gauge length and a test rate of 203.2mm / min.

[0114] Embodiment 20:

[0115] UHMWPE PM-200 was compressed into a solid cylindrical billet in a preforming press without using any lubricant. The billet was loaded into a vertical paste extruder and monofilaments were extruded using a 7.37 mm die. Only the die of the extruder was heated to a set temperature of 300°C. The extruded monofilaments were hot-drawn 200% under tension in a secondary process at about 120°C.

[0116] Embodiment 21:

[0117] UHMWPE GUR 4022-6 was compressed into a solid cylindrical billet in a preforming press without any lubricant. The billet was loaded into a vertical paste extruder and the monofilament was extruded using a 0.635 mm die. Only the die of the extruder was heated to a set temperature of 260°C. The extruded strip was hot-drawn 200% under tension in a secondary process at about 130°C. Tensile testing was performed on an Instron using a 25.4 mm gauge length and a test rate of 12.7 mm / min.

[0118] Pipe Example

[0119] Embodiment 22:

[0120] UHMWPE PM-200 was mixed with d-limonene lubricant in a 2:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and a large-size tube was extruded using a 6.35 mm spider die with a 4.83 mm mandrel. Only the die heating zone of the rheometer was turned on and set to a temperature of 165°C. The extruded tube was heat-drawn by about 400% under tension in a secondary process at about 120°C.

[0121] Embodiment 23:

[0122] UHMWPE PM-200 was mixed with d-limonene lubricant in a 2:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder and a 6.35 mm pipe die with a 3.2 mm mandrel was used to extrude large-size pipes. The die had multiple heating zones that were heated to a set temperature of 130°C-240°C. The extruded pipe was heat-drawn 600% at 120°C under tension.

[0123] Embodiment 24:

[0124] UHMWPE XM 221U was mixed with Isopar G lubricant in a 1:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was added to the rheometer barrel and a large-size tube was extruded using a 9.78 mm spider die with a 9.27 mm mandrel. Only the die heating zone of the rheometer was turned on and set to a temperature of 180°C. The extruded tube was hot-drawn about 700% under tension in a secondary process at about 120°C.

[0125] Embodiment 25:

[0126] UHMWPE XM 221U was mixed with d-limonene lubricant in a ratio of 3: 1 (wt / vol) in a wide-mouth bottle. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder and the pipe was extruded using a 6.35 mm pipe die with a 6.22 mm mandrel. The die had multiple heating zones that were heated to a set temperature of 60°C-220°C. The pipe was hot-drawn by about 600% under tension in a secondary process at about 120°C.

[0127] Embodiment 26:

[0128] UHMWPE XM 221U was mixed with d-limonene lubricant in a ratio of 3: 1 (wt / vol) in a wide-mouth bottle. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder and the pipe was extruded using a 6.35 mm pipe die with a 6.22 mm mandrel. The die had multiple heating zones that were heated to a set temperature of 60°C-220°C. The pipe was hot-drawn in-line at about 120°C during extrusion.

[0129] Embodiment 27:

[0130] The UHMWPE XM 221U extruded tube from Example 24 was hot drawn by about 400% under tension in a secondary process at about 120°C without in-line drawing.

[0131] Embodiment 28:

[0132] UHMWPE XM 221U and GUR 211 resins were mixed in a 1:2 ratio (wt / wt) in a wide-mouth bottle, and d-limonene was added to the resin mixture as a lubricant in a 2:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder, and a 6.35 mm pipe die with a 6.09 mm mandrel was used to extrude the pipe. The die had multiple heating zones, which were heated to a set temperature of 60°C-240°C. The extruded pipe was heat-drawn by about 300% under tension in a secondary process at about 120°C.

[0133] Embodiment 29:

[0134] UHMWPE XM 221U and GUR 211 resins were mixed in a 1:2 ratio (wt / wt) in a wide-mouth bottle, and Isopar G was added to the resin mixture as a lubricant in a ratio of 3:1 (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder, and a 6.35 mm pipe die with a 6.09 mm mandrel was used to extrude the pipe. The die had multiple heating zones, which were heated to a set temperature of 60°C-240°C. The extruded pipe was heat-drawn by about 300% under tension in a secondary process at about 120°C.

[0135] Embodiment 30:

[0136] UHMWPE PM-200 was mixed with d-limonene lubricant in a 2:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder and the pipe was extruded using a 6.35mm pipe die with a 6.09mm mandrel. The die had multiple heating zones that were heated to a set temperature of 60°C-240°C. The extruded pipe was heat-drawn 500% under tension in a secondary process at about 120°C.

[0137] Embodiment 31:

[0138] UHMWPE PM-200 was mixed with d-limonene lubricant in a 3:1 ratio (wt / vol) in a wide-mouth bottle. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder and a 6.35 mm pipe die with a 6.09 mm mandrel was used to extrude the pipe. The die had multiple heating zones that were heated to a set temperature of 60°C-260°C. The extruded pipe was heat-drawn 400% under tension in a secondary process at about 120°C.

[0139] Embodiment 32:

[0140] UHMWPE PM-200 and 5% (wt / wt) Epolene C-16P were mixed in a wide-mouth bottle, and d-limonene was added to the resin mixture as a lubricant in a ratio of 3:1 (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder, and the pipe was extruded using a 6.35mm pipe die with a 6.22mm mandrel. The die had multiple heating zones, which were heated to a set temperature of 30°C-180°C. The extruded pipe was heat-drawn by about 300% under tension in a secondary process at about 120°C.

[0141] Embodiment 33:

[0142] UHMWPE PM 200 and irradiated UHMWPE PM 200 (10MRad) resins were mixed in a 1:1 ratio (wt / wt) in a wide-mouth bottle, and 5% (wt / wt) Epolene C-16P was added to the UHMWPE resin mixture. D-limonene was added to the resin mixture in a 3:1 ratio (wt / vol) as a lubricant. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder, and a 6.35mm pipe die with a 6.09mm mandrel was used to extrude the pipe. The die had multiple heating zones, which were heated to a set temperature of 30°C-180°C. The extruded pipe was heat-drawn by about 300% under tension in a secondary process at about 120°C.

[0143] Embodiment 34:

[0144] UHMWPE XM 221U was mixed with 10% (wt / wt) of powdered Orevac 18300M in a wide-mouth bottle, and d-limonene was added to the resin mixture as a lubricant in a ratio of 3:1 (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder, and a 6.35mm pipe die with a 6.09mm mandrel was used to extrude the pipe. The die had multiple heating zones, which were heated to a set temperature of 30°C-180°C. The extruded pipe was heat-drawn by about 500% under tension in a secondary process at about 120°C.

[0145] Embodiment 35:

[0146] UHMWPE PM 200 and irradiated UHMWPE PM 200 (10MRad) resins were mixed in a 4:1 ratio (wt / wt) in a wide-mouth bottle, and 5% (wt / wt) Epolene C-16P was added to the UHMWPE resin mixture. D-limonene was added to the resin mixture in a 3:1 ratio (wt / vol) as a lubricant. The mixture was compressed into a hollow cylindrical billet in a preforming press. The billet was loaded into a horizontal paste extruder and a 6.35 mm pipe die with a 6.22 mm mandrel was used to extrude the pipe. The die had multiple heating zones that were heated to a set temperature of 30°C-180°C. The pipe was tested after extrusion without any additional drawing process.

[0147] Table 1. List of resins used

[0148]

[0149]

[0150]

[0151] With the benefit of the teachings provided by the foregoing description, those skilled in the art will appreciate many variations and other embodiments of the present invention. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, and variations and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used only in a general and descriptive sense, not for limitation.

Claims

1. An ultra-high molecular weight polyethylene (UHMWPE) pipe comprising: a. Average wall thickness of 0.2 mm or less; and b. a tensile stress at break greater than 40 MPa; and c. Storage modulus greater than 500 MPa at 23°C.

2. The UHMWPE pipe according to claim 1, wherein the UHMWPE pipe is prepared by extruding a billet comprising a lubricant and a UHMWPE resin through an annular die.

3. The UHMWPE pipe according to claim 2, wherein the lubricant is selected from d-limonene, naphtha, Isopar G, Isopar M or any combination thereof.

4. The UHMWPE pipe according to claim 1, wherein the UHMWPE pipe is prepared by extrusion on a metallic or non-metallic wire or mandrel.

5. A UHMWPE pipe according to claim 4, wherein the metallic or non-metallic wire or mandrel and the UHMWPE pipe are both substantially cylindrical in shape.

6. The UHMWPE pipe according to any one of claims 1 to 5, wherein the average wall thickness is 0.1 mm or less.

7. The UHMWPE pipe according to any one of claims 1 to 5, wherein the average wall thickness of the pipe is 0.005 mm to 0.1 mm.

8. The UHMWPE pipe according to any one of claims 1 to 5, wherein the pipe exhibits a storage modulus variation of 70 MPa / °C or less between 23°C and 40°C.

9. The UHMWPE pipe according to any one of claims 1 to 5, comprising an inner surface having a coefficient of friction with stainless steel of less than 0.

2.

10. The UHMWPE pipe according to claim 9, wherein the difference in the coefficient of friction between 23°C and 40°C is ≤ 0.

1.

11. The UHMWPE pipe according to any one of claims 1 to 5, comprising an inner surface having a coefficient of friction with stainless steel in saline of less than 0.

1.

12. The UHMWPE pipe according to claim 11, wherein the difference in friction coefficient in salt water between 23°C and 40°C is ≤ 0.

1.

13. A UHMWPE pipe according to any one of claims 1 to 12, consisting essentially of UHMWPE.

14. The UHMWPE pipe according to any one of claims 1 to 12, comprising UHMWPE and a particulate filler, wherein the particulate filler is present in a concentration of less than 50 wt.-%, based on the weight of the UHMWPE pipe.

15. The UHMWPE pipe according to any one of claims 1-12, comprising UHMWPE and a particulate filler, wherein the particulate filler is present in a concentration of less than 20 wt.-%, based on the weight of the UHMWPE pipe.

16. A UHMWPE pipe according to claim 14 or 15, wherein the particulate filler is a filler imparting radiopacity, strength or hydrophilicity.

17. The UHMWPE pipe according to any one of claims 1 to 12, further comprising one or more additives selected from antioxidants, antimicrobial agents, processing aids, lubricants and colorants.

18. The UHMWPE pipe according to any one of claims 1-12, wherein the UHMWPE pipe comprises one or more additional polymeric materials other than UHMWPE, wherein the one or more additional polymeric materials are present in a concentration of less than 50 wt.-%, based on the weight of the UHMWPE pipe.

19. The UHMWPE pipe according to any one of claims 1-12, wherein the UHMWPE pipe comprises one or more additional polymeric materials other than UHMWPE, wherein the one or more additional polymeric materials are present in a concentration of less than 20 wt.-%, based on the weight of the UHMWPE pipe.

20. A UHMWPE pipe according to claim 18 or 19, wherein the one or more further polymeric materials are selected from modified polyethylene and ethylene vinyl acetate bonding resins.

Images