UHMWPE paste extrusion tube

Abstract

The present disclosure generally relates to ultra-high molecular weight poly(ethylene) ("UHMWPE") tubing having an average wall thickness of 0.2 mm or less, a tensile stress at break greater than 40 MPa, and a storage modulus greater than 500 MPa at 23° C. The disclosure further relates to the preparation and use of such tubing, as well as structures (e.g., catheter structures) and components thereof comprising such tubing.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 401,208, filed August 26, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This application relates generally to the field of tubing comprising ultra-high molecular weight poly(ethylene) (UHMWPE), for example, as used as thin-walled catheter liners, and methods relating to such tubing. [Background technology]

[0003] Vascular treatments involve minimally invasive, catheter-based procedures as well as specialized equipment and techniques. Catheters used in such procedures typically utilize a coating or liner on their inner wall to provide a lubricious inner surface. The lubricious inner diameter (ID) associated with these devices is beneficial in reducing friction against various catheter technologies, such as stents, balloons, and atherectomy or thrombectomy devices, as they are advanced through the narrow confines of the catheter lumen. If the catheter ID is not sufficiently lubricious, devices such as stents may accordion-like collapse against the liner as they are advanced through the catheter lumen. The effect of improving the lubricity of the catheter ID is to reduce the deployment forces exerted on the catheter device as it is threaded through the lumen, increasing the likelihood of a successful procedure. The mechanical properties of the catheter liner are also crucial to its success. For example, high tensile and yield strengths may be required when certain devices (e.g., flow diversion tubing, embolization, aneurysm bridging, and scaffolding and thrombectomy devices) are threaded through microcatheters in a compressed state. The compressed shape exerts an outward radial force, which causes friction with the ID and generally makes delivery of the device through the lumen difficult. On the other hand, when the catheter must navigate vasculature containing sharp twists and bends (e.g., cerebral vasculature and below-the-knee (BTK) applications), high liner flexibility is often desirable.

[0004] For example, among the various materials that have been pursued as the base liner material for use within such catheter devices, polytetrafluoroethylene (PTFE) has been chosen due to its excellent chemical resistance, high-temperature resistance, biocompatibility, and very low coefficient of friction / high lubricity. One major drawback of PTFE is that it is not radiation stable. Radiation sterilization (i.e., gamma radiation or electron beam) is one of the most widely used and safe sterilization processes for medical devices. While radiation sterilization improves catheter manufacturability because it can be performed quickly on the manufacturing line, the ethylene oxide gas sterilization (ETO) method commonly used for PTFE-lined catheters requires storage for up to 48 hours to allow the gas to diffuse from the sterilized device. Furthermore, ETO gas requires careful handling due to its flammability and toxicity. Stringent handling requirements and technically complex sterilization processes often make ETO sterilization undesirable. Recently, medical regulatory agencies around the world have also encouraged the medical industry to minimize ETO use or replace it with alternative sterilization methods.

[0005] While some other polymers can withstand gamma irradiation, none can match PTFE's lubricity or low coefficient of friction. Ultra-high molecular weight polyethylene (UHMWPE) comes close. UHMWPE is a linear polymer with repeating units of -CH2-CH2-. Medical-grade UHMWPE has a 1×10 6It is a semi-crystalline polymer with long chains and a molecular mass greater than 1000 g / mol. UHMWPE has a very low coefficient of friction, excellent abrasion resistance, good toughness, high impact strength, high resistance to aggressive chemicals, excellent biocompatibility, and low cost. Furthermore, UHMWPE's low processing temperature allows it to be easily bonded to a variety of other polymeric catheter components. UHMWPE has been used clinically in joint implants for over 40 years, particularly as articular liners in total hip replacements and tibial inserts in total knee replacements. One drawback of UHMWPE is its extremely high molecular weight, resulting in very high viscosity. Above its melting temperature, UHMWPE does not flow as well as lower molecular weight polyethylene resins or conventional melt-processable polymers. For this reason, many thermoplastic processing techniques, such as injection molding, screw extrusion, or blow molding, are impractical for UHMWPE. Patent Document 1 describes a catheter structure using expanded UHMWPE as an inner layer / liner, formed by compressing 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 nodule and fibril structure. Due to its microporosity, the expanded UHMWPE liner has lower strength, potential for fluid absorption, and lower abrasion resistance compared to unexpanded, nonporous UHMWPE liners. Patent Document 2 discusses a method for producing films and porous structures using UHMWPE using a tape calendering process. However, practical processing techniques for producing very thin, high-strength, nonporous UHMWPE tubes for catheter liners are currently unavailable.

[0006] The gel spinning process has been widely used to process UHMWPE into high-strength oriented polyolefin fibers, which can be used to make articles such as ropes, tennis strings, fishing nets, filters, bulletproof moldings, medical textiles, and high-strength medical sutures. Gel spinning of UHMWPE traditionally utilizes organic solvents such as decalin, tetralin, toluene, lower alkanes, paraffin oil, mineral oil, and paraffin wax, with decalin and paraffin oil being the most widely used. Many of these solvents are often considered unsafe for close contact or environmentally unfriendly. However, gel spinning of UHMWPE has generally been used to produce only fibers and films. See, for example, U.S. Patent No. 5,929,499 (which describes a composition comprising UHMWPE and 0.001 to 15 wt% cyclic terpene / d-limonene used to form a polymer gel that is spun into fibers, films, filters, and membranes). The literature does not teach how to produce thin-walled tubes or liners with high polymer concentrations of UHMWPE.

[0007] The ability to process radiation-sterilizable polymeric materials such as UHMWPE into thin-walled tubing, liners, or other polymeric structures with excellent mechanical properties using environmentally friendly solvents would be of great benefit to both medical and industrial applications. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 6,837,890 [Patent Document 2] International Patent Application Publication No. WO2023 / 114080A1 [Patent Document 3] International Patent Application Publication No. WO2019 / 143899A1 Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure provides UHMWPE tubes manufactured by paste extrusion, having an average wall thickness of less than 0.1 mm (preferably less than 0.05 mm) and a high machine direction orientation of the UHMWPE polymer chains (resulting in high tensile strength). Due to the thin walls and high tensile modulus of the disclosed tubes, they can, in some embodiments, exhibit high ID lubricity and abrasion resistance. In various embodiments, the combination of properties exhibited by the disclosed tubes may make them particularly suitable for use in catheters, including those designed for flexibility, because the thin walls of the disclosed tubes result in a significantly more flexible liner that, unlike PTFE liners, can be sterilized by irradiation, such as with a gamma or electron beam irradiation source. In some embodiments, paste-extruded tubes may be further oriented in the machine and cross directions to alter and / or enhance their mechanical, thermal, and barrier properties. Furthermore, the polyethylene tubes of the present invention may be used as liners for metal tubes, such as laser-cut hypotubes. [Means for solving the problem]

[0010] The present disclosure includes, but is not limited to, the following embodiments.

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

[0012] Embodiment 2: A UHMWPE tube as described in embodiment 1, prepared by extrusion of a billet comprising a lubricant and UHMWPE resin through an annular die.

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

[0014] Embodiment 4: A UHMWPE tube according to any one of embodiments 1 to 3, prepared by extrusion over 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.

[0016] Embodiment 6: A UHMWPE tube according to any one of embodiments 1 to 5, having an average wall thickness of 0.1 mm or less.

[0017] Embodiment 7: A UHMWPE tube according to any one of embodiments 1 to 5, wherein the average wall thickness of the tube is from 0.005 mm to 0.1 mm.

[0018] Embodiment 8: A UHMWPE tube according to any one of embodiments 1 to 7, exhibiting a change in storage modulus between 23°C and 40°C of 70 MPa / °C or less.

[0019] Embodiment 9: A UHMWPE tube according to any one of embodiments 1 to 8, comprising an inner surface having a coefficient of friction against stainless steel of less than 0.2.

[0020] Embodiment 10: A UHMWPE tube according to embodiment 9, having a difference in coefficient of friction between 23°C and 40°C of ≦0.1.

[0021] Embodiment 11: A UHMWPE tube according to any one of embodiments 1 to 10, comprising an inner surface having a coefficient of friction against stainless steel in saline of less than 0.1.

[0022] Embodiment 12: A UHMWPE tube according to embodiment 11, having a difference in coefficient of friction in saline between 23°C and 40°C of ≦0.1.

[0023] Embodiment 13: A UHMWPE tube according to any one of embodiments 1 to 12, consisting essentially of UHMWPE.

[0024] Embodiment 14: A UHMWPE tube according to any one of embodiments 1 to 12, comprising UHMWPE and a particulate filler, wherein the particulate filler is present at a concentration of less than 50% by weight based on the weight of the UHMWPE tube.

[0025] Embodiment 15: A UHMWPE tube according to any one of embodiments 1 to 12, comprising UHMWPE and a particulate filler, wherein the particulate filler is present at a concentration of less than 20% by weight based on the weight of the UHMWPE tube.

[0026] Embodiment 16: A UHMWPE tube according to embodiment 14 or 15, wherein the particulate filler is a filler for imparting radiopacity, strength or hydrophilicity.

[0027] Embodiment 17: The UHMWPE tube of any one of embodiments 1 to 12 or 14 to 16, further comprising one or more additives selected from the group consisting of antioxidants, antimicrobial agents, processing aids, slip aids, and colorants.

[0028] Embodiment 18: A UHMWPE tube according to any one of embodiments 1 to 12 or 14 to 17, wherein the UHMWPE tube comprises one or more additional polymeric materials other than UHMWPE, and the one or more additional polymeric materials are present in a concentration of less than 50% by weight based on the weight of the UHMWPE tube.

[0029] Embodiment 19: A UHMWPE tube according to any one of embodiments 1 to 12 or 14 to 17, wherein the UHMWPE tube comprises one or more additional polymeric materials other than UHMWPE, and the one or more additional polymeric materials are present at a concentration of less than 20% by weight based on the weight of the UHMWPE tube.

[0030] Embodiment 20: A UHMWPE tube according to embodiment 18 or 19, wherein the one or more additional polymeric materials are selected from modified polyethylene and ethylene vinyl acetate tie resin.

[0031] These and other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description read in conjunction with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, as well as combinations of any two, three, four, or more features or elements described in this disclosure, whether or not such features or elements are explicitly combined in the description of a particular embodiment herein. The present disclosure is intended to be read holistically, and therefore, in any of its various aspects and embodiments, separable features or elements of the disclosed invention should be considered as intended to be combinable unless the context clearly dictates otherwise. Other aspects and advantages of the present invention will become apparent from the following.

[0032] To provide an understanding of embodiments of the present 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 illustrative only and are not to be construed as limiting the invention. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a general schematic diagram of a tube of the present disclosure with associated parameters and an enlarged schematic diagram of one cross-sectional end face of the tube. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will now be described more fully below. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough 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 disclosure provides UHMWPE tubing manufactured by a paste extrusion process, having specific physical properties that are more fully outlined herein below. A general schematic diagram of an exemplary tubing provided is shown in Figure 1. The tubing is generally cylindrical. "L" indicates the length of the manufactured tubing, which can be processed, e.g., cut, to provide a tubing of desired length "1" (not shown). The enlarged area on the right side of Figure 1 is a cross-sectional view of the interior of the tubing. As shown, the "lumen" is the interior region of the tubing, i.e., the open channel / cavity (through which, for example, a catheter device may be threaded if the tubing is incorporated as part of a medical device). The inner diameter of the tubing, designated "ID," is the average distance from a point on the inner wall of the tubing to the opposite / farthest point on the inner wall of the tubing. The outer diameter of the tubing, designated "OD," is the average distance from a point on the outer wall of the tubing through the lumen of the tubing to the opposite / farthest point on the outer wall of the tubing. Therefore, the average wall thickness of the tubing is half the value obtained by subtracting the ID value from the OD value. Figure 1 also shows representative "wall thicknesses," "inner wall surfaces," and "outer wall surfaces" of the tubing.

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

[0037] As mentioned above, the length L is not particularly limited, and the tube shown schematically in FIG. 1 may be processed as desired, for example, cut into multiple tubes of any desired length 1. In some embodiments, the length 1 of the tubes provided herein is a length suitable for catheter applications, for example, use as a liner. For example, in some embodiments, the length 1 is from about 150 mm to about 2000 mm. Similarly, the ID (which determines the diameter of the lumen) may vary, and in some embodiments, is a size suitable for catheter applications, for example, use as a liner, such as from about 1 mm to about 11 mm.

[0038] The tubing provided herein generally comprises UHMWPE. Various UHMWPE resins are commercially available and can be used in certain embodiments of the UHMWPE tubing provided herein. In some embodiments, UHMWPE is the only polymer in the disclosed tubing. In other embodiments, one or more other polymers may be included in the disclosed tubing in an amount of, for example, less than 50 wt%, less than 40 wt%, less than 30 wt%, less than 20 wt%, less than 10 wt%, less than 5 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.1 wt%, less than 0.05 wt%, or less than about 0.01 wt% based on the total weight of the tubing (e.g., from about 0.01 wt% to about 50 wt%, from about 0.01 wt% to about 30 wt%, from about 0.01 wt% to about 10 wt%, from about 0.01 wt% to about 1 wt%, or from about 20 wt% to about 50 wt%, from about 30 wt% to about 50 wt%, or from about 40 wt% to about 50 wt%).

[0039] In some embodiments, the optional one or more additional polymers may be tie resins. In some embodiments, the optional one or more additional polymers may be, for example, modified polyethylene and / or ethylene vinyl acetate (EVA) tie resins. In some embodiments, the optional one or more additional polymers may be, for example, grafted polyethylene, such as maleic anhydride-grafted HDPE. When one or more additional polymers are incorporated into the disclosed tubes, they are typically in the form of an intimate mixture / blend with UHMWPE so that the material composition of the tube is substantially uniform throughout. In some embodiments, a second (or additional) polymer may be incorporated to modify the physical properties of the tube, such as mechanical properties, thermal and barrier properties, crystallinity, and / or coefficient of friction.

[0040] Advantageously, in various embodiments, the tubing consists essentially of UHMWPE (alone or in combination with one or more of the additional polymers mentioned above), i.e., no significant amount of additional components (e.g., fillers) are included within the tubing. In other embodiments, the disclosed tubing may include one or more additives or fillers, e.g., particulate fillers, at a concentration of up to about 50% by weight based on the total weight of the tubing, e.g., from about 0.01% to about 50% by weight, e.g., from about 0.01% to about 10% by weight, from about 0.01% to about 10% by weight, from about 0.01% to about 20% by weight, from about 10% to about 50% by weight, from about 20% to about 50% by weight, from about 20% to about 30% by weight, or from about 30% to about 50% by weight based on the total weight of the tubing. 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, slip aids, and / or colorants, are included in the disclosed tubes. In some embodiments, the filler may be a heat, oxidation, or light stabilizer. In some embodiments, a certain amount of lubricant or other processing aid (such as a wax, such as low molecular weight polyethylene or polyethylene wax, erucamide, oleamide, or stearates) may be included in the tube, although in preferred embodiments, the tube contains only trace amounts of lubricants or other processing aids, or no detectable amounts thereof.

[0041] In some embodiments, UHMWPE tubing has high lubricity and abrasion resistance. These characteristics may be characterized in various ways. Abrasion is generally understood as the wear of a material due to friction. Friction occurs by scraping or scraping against the original material. Abrasion resistance is the property of a material that prevents wear when friction is applied to its surface. Abrasion resistance is understood to be material-dependent as well as process-dependent. Various methods are used to quantify abrasion and wear, depending on the specimen geometry and application. In certain embodiments, the material or specimen being tested is positioned relative to another material so that the two surfaces are in contact. The other material can be selected based on the required test conditions. Some common materials include a polished metal surface, a metal pin, sandpaper, or the same material as the test specimen. One or both materials are then moved to create friction between the contacting surfaces. Depending on the test method, the end of the test may be defined as a certain time, after the surfaces have been scraped a specified number of times, or until a specified failure mode is reached. Some failure modes include reaching a specified loss of mass, a reduction in a specified material thickness relative to the initial material thickness, a loss of tensile properties, or a loss of insulating properties. Regardless of the test method selected, the relative abrasion resistance of two or more materials can be determined by subjecting samples to the same test conditions and comparing the effect of the test conditions on the tested materials. Some methods for detecting sample abrasion are weight loss, visual inspection, and microscopic imaging. Various methods for assessing abrasion resistance that can be used to define the tubing of the present disclosure include, but are not limited to, those disclosed herein, which are incorporated by reference, including, for example, pin abrasion tests (e.g., using ASTM G132), rubber wheel abrasion tests (e.g., using ASTM G65), Taber abrasion tests (e.g., using ASTM D1044 and ASTM D4060), blade-on-block abrasion tests, medical device abrasion tests, and pin-on-disk abrasion tests (e.g., using ASTM G99, ASTM G133, and ASTM F732).A further exemplary method is EN 3475 Method 511, which generally involves placing a material in a fixture in contact with another specimen of the same type, with both ends fixed in position and the specimen vibrated / rubbed against itself.

[0042] Suitable wear-resistance / lubricity values ​​for the disclosed tubing may vary, but advantageously, the values ​​are somewhat higher. For example, in some embodiments, at least the inner wall surface of the disclosed tubing may be described as "wear-resistant" and / or "lubricious," and in some embodiments, both the inner and outer wall surfaces may be similarly described. For example, in some embodiments, the inner and / or outer wall of the tubing is a lubricious surface having a coefficient of friction of less than about 0.2 or less than about 0.1 (e.g., from about 0.05 to about 0.2 or from about 0.05 to about 0.1). In some embodiments, the inner and / or outer wall of the tubing is a lubricious surface having a coefficient of friction in saline of less than about 0.2 or less than about 0.1 (e.g., from about 0.02 to about 0.2 or from about 0.02 to about 0.1). In some embodiments, the lubricious surface of the disclosed tubing exhibits a difference in the coefficient of friction between 23°C and 40°C of about 0.1 or less (e.g., from about 0.01 to about 0.1). In some embodiments, the lubricious surface of the disclosed tubing exhibits a difference in coefficient of friction of about 0.1 or less (e.g., about 0.01 to about 0.1) in saline between 23° C. and 40° C. Such values ​​may be, for example, coefficients of friction against stainless steel.

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

[0044] In some embodiments, the disclosed tubes may be referred to as "paste-extruded" tubes. The methods for preparing these tubes (described below) result in particular physical properties that distinguish them from, for example, freely extruded tubes. For example, in some embodiments, tubes inherently prepared by this method (e.g., paste-extrusion of UHMWPE onto a substrate / core, followed by sintering and removal of the resulting UHMWPE tube from the substrate / core) exhibit low machine direction orientation of UHMWPE polymer chains, much lower than that exhibited by, for example, freely extruded tubes. Furthermore, the tubes can inherently exhibit particularly beneficial properties (e.g., properties attributable, at least in part, to the manufacturing method), including, for example, exceptional strength and flexibility characteristics even at very low wall thicknesses.

[0045] The produced UHMWPE tube, in some embodiments, can be described as "unstretched" and / or "unoriented," i.e., not stretched after manufacture to impart molecular orientation. In some embodiments, the produced UHMWPE tube can be described as "stretched" and / or "oriented" after manufacture and can therefore exhibit molecular orientation in the machine direction and a corresponding increased tensile strength and decreased wall thickness (relative to the corresponding produced tube). In some embodiments, the produced UHMWPE tube can be described as "stretched" and / or "oriented" in the machine and transverse directions.

[0046] It should be noted that the properties of a given tube may, in some embodiments, vary somewhat from those disclosed if fillers and / or other polymers are included therein. For example, in some embodiments, a tube containing one or more tie resins mentioned above may enhance or impart one or more specific properties, such as lubricity, toughness, or adhesion. In some embodiments, a tube containing one or more added fillers and / or polymers other than UHMWPE may have different properties, such as mechanical, thermal, and barrier properties, crystallinity, and coefficient of friction. Furthermore, the inclusion of, for example, antioxidants or antimicrobial agents may impart corresponding characteristics to the tube, and colorants may impart associated colors to the tube.

[0047] The present disclosure further provides methods for producing UHMWPE profiles, such as monofilaments, multifilaments, ribbons, and tubes, exhibiting the physical properties described herein. The methods generally involve utilizing a paste extrusion process, in which UHMWPE is extruded free or onto a metallic or non-metallic substrate, including, but not limited to, a wire or a PTFE core / mandrel. UHMWPE paste extrusion methods may include several steps, including (1) paste preparation or resin mixing with a lubricant, (2) preform preparation, (3) extrusion, (4) lubricant evaporation, and (5) curing / annealing / sintering, as discussed in more detail below. It should be understood that some paste extrusion methods do not require the preparation of a preform prior to extrusion.

[0048] Fine powder UHMWPE resin suitable for the extrusion process disclosed herein is typically in the range of 1×10 6Exemplary resins suitable for this purpose include homopolymers having a molecular weight (usually calculated from IV / intrinsic viscosity measurements) greater than 1000 g / mol. Exemplary resins suitable for this purpose include Celanese's GUR® 2024, GUR® 2122, GUR® 2122-5, GUR® 2126, GUR® 4012, GUR® 4012 F, GUR® 4020-3, GUR® 4022, GUR® 4022-6, GUR® 4032, GUR® 4050-3, GUR® 4056-3, GUR® 4112, GUR® 4113, GUR® 4120, GUR® 4122, GUR® 4122-5, GUR® 4130, GUR® 4150, GUR® 4160, GUR® 4170, GUR® 4180, GUR® 4190, GUR® 4200, GUR® 4210, GUR® 4222, GUR® 4222-5, GUR® 4130, GUR® 4150, GUR® 4212, GUR® 4213, GUR® 4214, GUR® 4215, GUR® 4216, GUR® 4217, GUR® 4218, GUR® 4219, GUR® 4220, GUR® 4221, GUR® 4222-5, GUR® 4130, GUR® 4150, GUR® 4219, GUR® 4222-6, GUR® 4032, GUR® 4050-3, GUR® 4056-3, GUR® GUR® 4150-3, GUR® 4152, GUR® 4170, GUR® 4523, GUR® 4550, GUR® 5113, GUR® 5129, GUR® 5523, GUR® X161, GUR® X195, GUR® X204, GUR® X214, GUR® X217], and Mitsui Chemicals' [Mipelon Examples of suitable polyethylene resins include, but are not limited to, PM200, 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 UHM 5000, and Asahi Kasei Corporation's Sunfine UH. Copolymers of ethylene or other polyethylene resins, such as irradiated or chemically modified polyethylene resins, may also be used in the extrusion process.

[0049] In the following discussion, the term "lubricant" is understood to apply to any compound that at least partially wets the UHMWPE resin. Wetting / surface tension and viscosity are two properties of a lubricant that can significantly affect the pressure of UHMWPE paste extrusion and can therefore be modified accordingly. A lubricant that wets UHMWPE better will help reduce extruder pressure. Similarly, a lubricant with a lower viscosity can help reduce extruder pressure.

[0050] The paste preparation process involves mixing the UHMWPE fine powder with a suitable lubricant (or a combination of lubricants). 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 lipophilic hydrocarbons, and combinations thereof. Environmentally friendly solvents such as D-limonene [CAS No. 5989-27-5] can also be used in the paste preparation process. D-Limonene is a cyclic terpene found in citrus extracts / oils and is also known as limonene or 1-limonene or dl-limonene or (+)-limonene or (+)-dipentene or (+)-(R)-limonene or (R)-4-isopropenyl-l-methyl-1-cyclohexene.

[0051] The resin to lubricant ratio may vary from 1:1 to 15:1 (wt. in grams / vol. in mL). To form a suitable paste, the polymer may be mixed with the lubricant by mechanical agitation, with or without the addition of heat (as high as 100°C). The paste may undergo an optional filtration step to remove large agglomerates. Additionally, the paste may be optionally aged for extended periods, with or without the addition of heat (as high as 100°C), to enhance the wetting of the resin by the lubricant. Prior to the extrusion step, it is generally important to remove at least some air (preferably as much air as possible) from the UHMWPE paste to prevent defects in the extrudate. Unlike the extrusion of PTFE paste, a preforming step for UHMWPE may not always be necessary. Instead, the paste can be loaded into the machine barrel in a single step and pressed to eliminate entrapped air. If a preforming step is used, the mixture is typically pressed into a solid or hollow shape (e.g., a cylindrical or annular profile) called a preform or billet. These preforms are generally very weak and can easily break or deform, so they must be handled carefully. Multilayer preforms, such as core-sheath structures, with separate paste formulations for each layer may be used to create extruded tubing profiles with different materials and / or properties for the inner and outer layers. In some embodiments, multiple preforms with different lubricants or different amounts of lubricant may be made and loaded into an extruder. In such embodiments, different portions of the preform may have different lubricants or different amounts of lubricant to vary the extrusion pressure during the manufacturing process.

[0052] In certain embodiments, the cylindrical preform is inserted into the extrusion cylinder / barrel of a paste extruder and pressed through a die using a ram. The barrel and / or die may be at ambient temperature or may be heated to a temperature below the resin decomposition temperature. Extrusion of a tube (with or without a core) generally requires the presence of a mandrel within the barrel, which is attached to the rear. According to the present disclosure, a metallic / non-metallic, smooth or textured core is fed through this mandrel. The core may be at room temperature or may be preheated above room temperature before entering the mandrel. The core material utilized in this paste extrusion process is not particularly limited and, in some embodiments, may be metallic or non-metallic. Even if a core coating is not intended, the presence of a mandrel as described above still allows for the production of a free-extrusion tube.

[0053] The extruded paste material simultaneously coats the core that is guided into the extruder head (in the case of core coating). If the extrusion pressure changes during processing and the coating thickness (or wall thickness of the freely extruded tube) deviates from the target, ensure that the machine design allows for adjustment of the ram speed (manual / automatic) to ensure a uniform coating on the mandrel or wall thickness of the freely extruded tube.

[0054] During extrusion, molecular / chain orientation may be imparted to the extruded product (e.g., the final part) based on the stretching of the material. The orientation imparted to the material is known to affect tensile properties, particularly modulus, tensile strength, and elongation. The perceived change in modulus may also change the coefficient of friction (COF). Generally, increasing stretching increases the axial orientation of the polymer, thereby increasing modulus and tensile strength and decreasing elongation and COF. The extrudate can be optionally processed, for example, by cutting long tubes into shorter lengths as desired, for specific applications.

[0055] After extrusion, any remaining lubricant in the extruded UHMWPE tube or profile must be completely removed by heating above the boiling or flash point of the lubricant. This can be done, for example, by passing the product through a devolatilizing oven.

[0056] After the devolatilization step, the product is heated in a higher-temperature sintering / annealing oven, typically 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 generally set well above this melting temperature. It is important that the product in the sintering oven be completely free of lubricants / solvents. Within the sintering oven, the UHMWPE particles melt and bond together. Once the product cools (e.g., upon exiting / removal from the sintering oven), the UHMWPE transitions from a molten state to a solid state. Secondary stretching / orientation (in the MD / TD) can also be performed using the same methods described above. Additionally, tie materials may be coated or extruded onto the UHMWPE layer to aid in bonding with materials such as PI, PU, ​​nylon, or PEBA.

[0057] The devolatilization, sintering / annealing, and stretching / orientation operations may, in another embodiment, be carried out in the same oven.

[0058] The inventors have discovered that extruding UHMWPE onto a substrate / core reduces the machine direction orientation of the UHMWPE polymer chains. This characteristic is in contrast to, for example, freely extruded tubing, which exhibits high machine direction orientation. By extruding a UHMWPE coating in this manner, sintering, and then removing the coating, tubing exhibiting a particularly advantageous combination of properties (as outlined hereinabove) can be readily obtained. In particular, the inventors have unexpectedly discovered that in this manner, tubing with a very low wall thickness can be obtained. This tubing exhibits the strength and flexibility characteristics outlined above, providing a particularly advantageous means for producing very thin-walled UHMWPE tubing for use in, for example, catheter applications.

[0059] The produced UHMWPE tube or profile may also be optionally stretched and drawn in the machine direction (with or without heating) to impart molecular orientation and thus increase tensile strength and further reduce wall thickness. The machine-direction oriented tube may be further oriented (with or without heating) by mechanically or pneumatically stretching (e.g., by applying air to the ID), for example, by 1.1 to 10 times in the TD (transverse direction). Alternatively, the unstretched tube may be simultaneously oriented in the machine and transverse directions (with or without heating) mechanically / pneumatically, or a combination thereof (e.g., in a balloon blower). The stretching process can be used to produce various structural and mechanical effects in the tube.

[0060] In some embodiments, UHMWPE may be extruded into various profiles, such as monofilaments, tubes, and ribbons, without the use of lubricants. One or more UHMWPE resins may be loaded into an extruder barrel along with desired fillers, such as tie resins, with or without preform creation. The resin material is then extruded by forcing it through a die at an elevated temperature (above the melting temperature of the resin) and may be subjected to additional processes, such as annealing, stretching, and orientation.

[0061] It should be understood that any of the UHMWPE tubing of the present invention may contain fillers to impart specific properties, such as radiopacity, strength, and hydrophilicity. It should also be understood that any of the UHMWPE tubing of the present invention may contain one or more polymers other than UHMWPE, such as modified polyethylene (maleic anhydride-grafted / copolyethylene) and ethylene vinyl acetate (EVA) tie resin, to impart specific properties, such as lubricity, toughness, or adhesion. Tubing containing fillers and polymers other than UHMWPE may have different properties, such as mechanical, thermal, and barrier properties, crystallinity, and coefficient of friction. It should also be understood that the tubing of the present invention may contain additives, such as antioxidants, antimicrobial agents, processing aids, slip aids, and colorants, as well as other particulate materials designed to impart specific properties to the tubing.

[0062] The extruded tubing may be subjected to radiation, such as e-beam or gamma irradiation, at doses between 50 kGy and 15 MGy. Radiation treatment alters the polymer chain structure of the tubing, potentially affecting certain physical, mechanical, or thermal properties of the liner, such as lubricity, toughness, and modulus. Typically, radiation treatment crosslinks the polyethylene chains, improving modulus and tensile strength. Alternatively, irradiated UHMWPE resin can be added as a filler to UHMWPE pastes / preforms to impart and / or enhance specific functionality. The extruded tubing may also be subjected to surface modification, such as plasma treatment, to improve bonding to other polymeric materials, such as catheter jackets.

[0063] In some embodiments, the tubes disclosed herein are particularly advantageous for use as catheter liners. Conventional three-layer catheters include a liner as the innermost layer, making the tubes of the present invention particularly useful. The liner itself typically has a wall thickness of about 0.025 mm to about 0.070 mm and an inner diameter of about 0.380 mm to about 4.300 mm. A braided layer encases the liner, and a jacket surrounds the braided encasement. The braided layer can be constructed using wire or filaments of metallic or non-metallic materials, such as stainless steel, liquid crystal polymer, or UHMWPE. Thus, the present disclosure provides not only the tubes described herein, but also tubes configured as liners (e.g., which may include only the tube or may include one or more additional components in addition to the tube, e.g., additional layers associated with catheter construction, such as the braided layer and / or jacket).

[0064] Equipment such as a Beahm 810A vertical laminator can be used to construct catheters using the disclosed tubing. The polyethylene tubing provided herein can be bonded to catheter jackets made from materials such as PEBA (polyether block amide), nylon, and polyurethane. The disclosed tubing can also be stretched to reduce the wall thickness of the tubing without compromising its integrity, and then used to construct catheters. The degree of stretching of the tubing can affect certain physical, mechanical, or thermal properties of the liner, such as lubricity, toughness, and modulus. Typically, increasing the degree of stretching increases the axial orientation of the tubing, thereby improving modulus and tensile strength and reducing elongation. Constructed catheters and catheter components, such as liners and jackets, can be tested using interventional device testing equipment such as the MSI IDTE3000, which can measure and record device performance characteristics such as pushability, flexibility, and torqueability.

[0065] The lubricants, solvents and UHMWPE resins used in the paste extrusion process may also be used in different concentrations to produce monofilaments for 3D printing of polymer structures / devices / products for various applications.

[0066] experiment To determine the tensile properties of UHMWPE samples, an Instron 5965 dual-column mechanical testing machine with Bluehill 3 v3.73.4823 operating software was used. For ribbon samples, tests were performed at a speed of 25.4 mm / min using a 1 kN load cell, a 12.7 mm gauge length, and a Type V dogbone. Tensile tests for tube samples were performed using a 50.8 mm gauge length, a 50.8 mm / min test speed, and a 1 kN load cell. The mechanical properties of monofilament samples were measured using different test parameters, as described in the specific examples. Average tensile values ​​for UHMWPE profiles are listed in Tables 2 and 3.

[0067] A TA Instruments Q800 DMA equipped with a film tension fixture was used to determine the thermomechanical properties of the UHMWPE profiles. The primary property of interest was the storage modulus (E'). Temperature scans were performed from -100 °C to 130 °C, with a 5-minute isothermal hold at -100 °C. The samples were heated at a constant rate of 3 °C / min while undergoing a constant 15 µm amplitude displacement with a fixed 1 Hz tensile oscillation. The resulting DMA data was 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.

[0068] A TA Instruments Q800 DMA equipped with a three-point bending fixture was used to determine the flexural properties of the UHMWPE tubing samples. Tests were conducted at room temperature using a 5 mm x 50 mm sample size, a 15 mm span length, and a 1% / min strain ramp up to 5% strain. The results are listed in Table 3.

[0069] A TA Instruments Discovery Hybrid Rheometer (DHR-3) equipped with a tribo-rheometer accessory was used to determine the tribological properties of UHMWPE samples. The primary property of interest in this test was COF. Samples were prepared by attaching three 5 mm x 16.5 mm tube sections to the three prongs of a half ring for use with a ring-on-plate tribo-rheometry fixture. The ring with the sample attached was then attached to the ring-on-plate upper placement holder, and the sample was lowered into contact with a mirror-finish stainless steel plate at a specified axial force. Tribological tests were conducted at room temperature (23 °C) with sliding speeds ranging from 750 μm / s to 7650 μm / s under an axial load of 1 N. Additional tribological tests were conducted in a saline bath at room temperature (23 °C) with sliding speeds ranging from 750 μm / s to 7650 μm / s under an axial load of 1 N. The minimum COF over the stated range of sliding speeds was calculated by TRIOS software v4.3 from TA instruments. Multiple specimens were tested for each sample and the averages are listed in Tables 2 and 3.

[0070] A sufficient combination of parameters such as COF, tensile strength, modulus, and bending stress are generally important for liners for catheter applications. As a non-limiting example, a combination of low COF, high strength, and low bending stress is often desirable for liners used in neurovascular applications. [Example]

[0071] Aspects of the present invention are described to illustrate certain aspects of the invention, as more fully illustrated by the following examples, which are not to be construed as limitations thereof.

[0072] Several UHMWPE samples with different profiles were prepared using a Malvern Advanced Capillary Rheometer RH7, a vertical paste extruder, and a horizontal paste extruder, as described in the specific examples below. Further information regarding the resin(s) used in these examples is provided in Table 1 below. The samples were subjected to mechanical and lubricity testing according to the methods described above. Modifications to the sample preparation or testing methods are described in the specific examples. In all examples, the unit of measurement for weight was grams, and the unit of measurement for volume was milliliters.

[0073] Ribbon and Monofilament Examples Example 1: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. All heating zones within the rheometer, including the barrel and die, were set to a temperature of 165°C. The extruded ribbon was hot-stretched approximately 200% under tension in a secondary process at approximately 110°C.

[0074] Example 2: UHMWPE PM-200 was mixed with 2% PTFE (wt / wt) of the polymer in a jar. d-Limonene lubricant was added to the resin mixture at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. All heating zones within the rheometer, including the barrel and die, were set to a temperature of 165°C. The extruded ribbon was hot-stretched approximately 200% under tension in a secondary process at approximately 110°C.

[0075] Example 3: UHMWPE PM-200 was mixed with 5% PTFE (wt / wt) of the polymer in a jar. d-Limonene lubricant was added to the resin mixture at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, 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 within the rheometer, including the barrel and die, were set to a temperature of 165°C. The extruded ribbon was hot-stretched approximately 200% under tension in a secondary process at approximately 110°C.

[0076] Example 4: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 300% under tension in a secondary process at approximately 110°C.

[0077] Example 5: UHMWPE PM-200 was mixed with 2% PTFE (wt / wt) of the polymer in a jar. d-Limonene lubricant was added to the resin mixture at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 300% under tension in a secondary process at approximately 110°C.

[0078] Example 6: UHMWPE PM-200 was mixed with 5% PTFE (wt / wt) of the polymer in a jar. d-Limonene lubricant was added to the resin mixture at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 300% under tension in a secondary process at approximately 110°C.

[0079] Example 7: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 400% under tension in a secondary process at approximately 110°C.

[0080] Example 8: UHMWPE PM-200 was mixed with 10% EVA (wt / wt) of the polymer in a jar. d-Limonene lubricant was added to the resin mixture at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 400% under tension in a secondary process at approximately 110°C.

[0081] Example 9: UHMWPE PM-200 was mixed in a jar with 10% UHMWPE XM-221 U (wt / wt) polymer. d-Limonene lubricant was added to the resin mixture at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die measuring 10.8 mm in length and 1.5 mm in width. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 400% under tension in a secondary process at approximately 110°C.

[0082] Example 10: UHMWPE PM-200 was mixed with 10% irradiated (10 MRad) UHMWPE PM-200 (wt / wt) in a jar. d-Limonene lubricant was added to the resin mixture at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die measuring 10.8 mm in length and 1.5 mm in width. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 400% under tension in a secondary process at approximately 110°C.

[0083] Example 11: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a flat ribbon profile was extruded using a ribbon die 10.8 mm long and 1.5 mm wide. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded ribbon was hot-stretched approximately 400% under tension in a secondary process at approximately 110°C. The stretched ribbon was subjected to e-beam irradiation at a dose of 10 MRad.

[0084] Example 12: UHMWPE GUR 4056-3 was compressed into a solid cylindrical billet in a preform press without lubrication. The billet was loaded into a vertical paste extruder, and a flat ribbon profile was extruded using a ribbon die measuring 12.7 mm in length and 3.17 mm in width. The extruder die alone was heated to a set temperature of 260°C. The extruded ribbon was hot-stretched approximately 200% under tension in a secondary process at approximately 130°C.

[0085] Example 13: UHMWPE GUR 4056-3 was mixed in a jar with Isopar M lubricant at a 4:1 ratio (wt / vol). The mixture was compressed into a solid cylindrical billet in a preform press. The billet was loaded into a vertical paste extruder, and a flat ribbon profile was extruded using a ribbon die measuring 12.7 mm in length and 3.17 mm in width. The extruder die alone was heated to a set temperature of 260°C. The extruded ribbon was hot-stretched under tension by approximately 300% in a secondary process at approximately 130°C.

[0086] Example 14: UHMWPE GUR 4056-3 was mixed in a jar with Isopar G lubricant at a 10:1 ratio (wt / vol). The mixture was compressed into a solid cylindrical billet in a preform press. The billet was loaded into a vertical paste extruder, and a flat ribbon profile was extruded using a ribbon die measuring 12.7 mm in length and 3.17 mm in width. The extruder die alone was heated to a set temperature of 260°C. The extruded ribbon was hot-drawn approximately 200% under tension in a secondary process at approximately 130°C.

[0087] Example 15: UHMWPE GUR 4022-6 was mixed in a jar with Isopar M lubricant at a 4:1 ratio (wt / vol). The mixture was compressed into a solid cylindrical billet in a preform press. The billet was loaded into a vertical paste extruder, and a flat ribbon profile was extruded using a ribbon die measuring 12.7 mm in length and 3.17 mm in width. The extruder die alone was heated to a set temperature of 260°C. The extruded ribbon was hot-drawn approximately 300% under tension in a secondary process at approximately 130°C.

[0088] Example 16: UHMWPE PM 200 and irradiated UHMWPE PM 200 (10 MRad) resins were mixed in a jar at a 4:1 ratio (wt / wt), and 5% (wt / wt) of Epolene C-16P was added to the UHMWPE resin mixture. d-Limonene was added as a lubricant to the resin mixture at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and ribbons were extruded using a ribbon die measuring 19.95 mm in length and 0.09 mm in width. The die had multiple heating zones, which were heated to set temperatures between 30°C and 160°C. The ribbons were tested as extruded without further stretching.

[0089] Example 17: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 5:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and monofilaments were extruded using a 1.5 mm die. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded monofilaments were hot-stretched approximately 200% under tension in a secondary process at approximately 110°C.

[0090] Example 18: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and monofilaments were extruded using a 1.5 mm die. Only the die heating zone of the rheometer was turned on and set at a temperature of 165°C. The extruded monofilament was hot stretched approximately 700% under tension in a secondary process at approximately 110°C. Tensile testing was performed on an Instron using a 152.4 mm gauge length and a test speed of 304.8 mm / min.

[0091] Example 19: UHMWPE PM-200 was mixed in a jar with d-limonene lubricant at a 2:1 ratio (wt / vol). The mixture was compressed into a solid cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and monofilaments were extruded using a 2.3 mm die. Only the extruder die was heated to a set temperature of 200°C. The extruded monofilament was hot-stretched approximately 1000% under tension in a secondary process at approximately 110°C. Tensile testing was performed on an Instron using a 101.6 mm gauge length and a test speed of 203.2 mm / min.

[0092] Example 20: UHMWPE PM-200 was compressed into a solid cylindrical billet in a preform press without lubrication. The billet was loaded into a vertical paste extruder, and a 7.37 mm die was used to extrude monofilaments. The extruder die alone was heated to a set temperature of 300°C. The extruded monofilaments were hot-drawn 200% under tension in a secondary process at approximately 120°C.

[0093] Example 21: UHMWPE GUR 4022-6 was compressed into a solid cylindrical billet in a preform press without any lubricant. The billet was loaded into a vertical paste extruder, and a 0.635 mm die was used to extrude the monofilament. Only the extruder die was heated to a set temperature of 260°C. The extruded ribbon was hot stretched 200% under tension in a secondary process at approximately 130°C. Tensile testing was performed on an Instron using a 25.4 mm gauge length and a test speed of 12.7 mm / min.

[0094] Example of a tube Example 22: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 2:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a large 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 at a temperature of 165°C. The extruded tube was hot-stretched approximately 400% under tension in a secondary process at approximately 120°C.

[0095] Example 23: UHMWPE PM-200 was mixed in a jar with d-limonene lubricant at a 2:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and large-size tubes were extruded using a 6.35 mm tube die with a 3.2 mm mandrel. The die contained multiple heating zones, which were heated to set temperatures between 130°C and 240°C. The extruded tubes were hot-stretched 600% under tension at 120°C.

[0096] Example 24: UHMWPE XM 221U was mixed with Isopar G lubricant in a jar at a 1:1 ratio (wt / vol). The mixture was added to the barrel of a rheometer, and a large 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 at a temperature of 180°C. The extruded tube was hot-stretched approximately 700% under tension in a secondary process at approximately 120°C.

[0097] Example 25: UHMWPE XM 221U was mixed with d-limonene lubricant in a jar at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder and extruded using a 6.35 mm tube die with a 6.22 mm mandrel. The die contained multiple heating zones, which were heated to set temperatures between 60°C and 220°C. The tube was hot-stretched approximately 600% under tension in a secondary process at approximately 120°C.

[0098] Example 26: UHMWPE XM 221U was mixed in a jar with d-limonene lubricant at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubing was extruded using a 6.35 mm tubing die with a 6.22 mm mandrel. The die contained multiple heating zones, which were heated to set temperatures between 60°C and 220°C. The tubing was hot-stretched in-line during extrusion at approximately 120°C.

[0099] Example 27: The UHMWPE XM 221U extruded tubing of Example 24 was hot stretched under tension by about 400% in a secondary process at about 120° C. without being subjected to in-line stretching.

[0100] Example 28: UHMWPE XM 221U and GUR211 resins were mixed in a jar at a 1:2 ratio (wt / wt), and d-limonene was added to the resin mixture as a lubricant at a 2:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubes were extruded using a 6.35 mm tube die with a 6.09 mm mandrel. The die had multiple heating zones, which were heated to set temperatures between 60°C and 240°C. The extruded tubes were then hot-stretched to approximately 300% under tension in a secondary process at approximately 120°C.

[0101] Example 29: UHMWPE XM 221U and GUR211 resins were mixed in a jar at a 2:1 ratio (wt / wt), and Isopar G was added to the resin mixture as a lubricant at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubes were extruded using a 6.35 mm tube die with a 6.09 mm mandrel. The die contained multiple heating zones, which were heated to set temperatures between 60°C and 240°C. The extruded tubes were then hot-stretched to approximately 300% under tension in a secondary process at approximately 120°C.

[0102] Example 30: UHMWPE PM-200 was mixed in a jar with d-limonene lubricant at a 2:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder and extruded using a 6.35 mm tube die with a 6.09 mm die. The die had multiple heating zones, which were heated to set temperatures between 60°C and 240°C. The extruded tube was hot-stretched 500% under tension in a secondary process at approximately 120°C.

[0103] Example 31: UHMWPE PM-200 was mixed with d-limonene lubricant in a jar at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder and extruded using a 6.35 mm tube die with a 6.09 mm die. The die had multiple heating zones, which were heated to set temperatures between 60°C and 260°C. The extruded tube was hot-stretched 400% under tension in a secondary process at approximately 120°C.

[0104] Example 32: UHMWPE PM-200 was mixed with 5% (wt / wt) Epolene C-16P in a jar, and d-limonene was added as a lubricant to the resin mixture at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubes were extruded using a 6.35 mm tube die with a 6.22 mm mandrel. The die had multiple heating zones, which were heated to set temperatures between 30°C and 180°C. The extruded tubes were then hot-stretched to approximately 300% under tension in a secondary process at approximately 120°C.

[0105] Example 33: UHMWPE PM 200 and irradiated UHMWPE PM 200 (10MRad) resins were mixed in a jar at a 1:1 ratio (wt / wt), and 5% (wt / wt) of Epolene C-16P was added to the UHMWPE resin mixture. d-Limonene was added as a lubricant to the resin mixture at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubes were extruded using a 6.35 mm tube die with a 6.09 mm mandrel. The die had multiple heating zones, which were heated to set temperatures between 30°C and 180°C. The extruded tubes were then hot-stretched to approximately 300% under tension in a secondary process at approximately 120°C.

[0106] Example 34: UHMWPE XM 221U was mixed in a jar with 10% (wt / wt) powdered Orevac 18300M, and d-limonene was added as a lubricant to the resin mixture at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubes were extruded using a 6.35 mm tube die with a 6.09 mm mandrel. The die had multiple heating zones, which were heated to set temperatures ranging from 30 °C to 180 °C. The extruded tube was then hot-stretched to approximately 500% under tension in a secondary process at approximately 120 °C.

[0107] Example 35: UHMWPE PM 200 and irradiated UHMWPE PM 200 (10 MRad) resins were mixed in a jar at a 4:1 ratio (wt / wt), and 5% (wt / wt) of Epolene C-16P was added to the UHMWPE resin mixture. d-Limonene was added as a lubricant to the resin mixture at a 3:1 ratio (wt / vol). The mixture was compressed into a hollow cylindrical billet in a preform press. The billet was loaded into a horizontal paste extruder, and tubes were extruded using a 6.35 mm tube die with a 6.22 mm mandrel. The die had multiple heating zones, which were heated to set temperatures between 30°C and 180°C. The tubes were tested as extruded without further stretching.

[0108] [Table 1]

[0109] [Table 2]

[0110] [Table 3]

[0111] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description. It is to be understood, therefore, that the invention is not limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. 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 at 23°C greater than 500 MPa 1. An ultra-high molecular weight poly(ethylene) (UHMWPE) tube comprising:

2. 10. The UHMWPE tube of claim 1 prepared by extrusion of a billet containing a lubricant and UHMWPE resin through an annular die.

3. 3. The UHMWPE tube of claim 2, wherein the lubricant is selected from the group consisting of d-limonene, naphtha, Isopar G, Isopar M, or any combination thereof.

4. 10. The UHMWPE tube of claim 1 prepared by extrusion onto a metallic or non-metallic wire or mandrel.

5. 5. The UHMWPE tube of claim 4, wherein the metallic or non-metallic wire or mandrel and the UHMWPE tube are both substantially cylindrical.

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

7. 6. An UHMWPE tube according to any one of the preceding claims, wherein the average wall thickness of the tube is from 0.005 mm to 0.1 mm.

8. 6. An UHMWPE tube according to any one of claims 1 to 5, which exhibits a change in storage modulus between 23°C and 40°C of 70 MPa / °C or less.

9. 6. An UHMWPE tube according to any one of claims 1 to 5, comprising an inner surface having a coefficient of friction against stainless steel of less than 0.

2.

10. 10. An UHMWPE tube according to claim 9, wherein the difference in coefficient of friction between 23°C and 40°C is ≦0.

1.

11. 6. An UHMWPE tube according to any one of claims 1 to 5, comprising an inner surface having a coefficient of friction against stainless steel in saline of less than 0.

1.

12. 12. The UHMWPE tube of claim 11, wherein the difference in coefficient of friction in saline between 23°C and 40°C is ≦0.

1.

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

14. 13. A UHMWPE tube according to any one of claims 1 to 12, comprising UHMWPE and a particulate filler, the particulate filler being present at a concentration of less than 50 wt% based on the weight of the UHMWPE tube.

15. 13. A UHMWPE tube according to any one of claims 1 to 12, comprising UHMWPE and a particulate filler, the particulate filler being present at a concentration of less than 20 wt% based on the weight of the UHMWPE tube.

16. 16. The UHMWPE tube of claim 14 or 15, wherein the particulate filler is a filler for imparting radiopacity, strength or hydrophilicity.

17. 13. The UHMWPE tube according to any one of claims 1 to 12, further comprising one or more additives selected from the group consisting of antioxidants, antimicrobial agents, processing aids, slip aids and colorants.

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

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

20. 20. A UHMWPE tube according to claim 18 or 19, wherein the one or more additional polymeric materials are selected from modified polyethylene and ethylene vinyl acetate tie resin.

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