UHMWPE dip coated tubing

Abstract

The present disclosure provides tubing comprising ultra-high molecular weight polyethylene (UHMWPE). The tubing can have a thin wall, making it suitable for use, for example, as a catheter liner. A method for preparing the tubing includes dip-coating a core in a dispersion comprising UHMWPE, which advantageously further comprises an environmentally friendly solvent and may optionally contain one or more additional ingredients (e.g., fillers and / or other polymers). In one aspect, a UHMWPE tubing is provided having an average wall thickness of 0.001" or less, a tensile stress at break greater than 9 MPa, and a storage modulus at 37°C greater than 60 MPa. In some embodiments, the tubing exhibits a change in storage modulus between 23°C and 37°C of 5 MPa / °C or less.

Description

[Technical Field]

[0001] 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]

[0002] 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 successful procedures. The mechanical properties of the catheter liner are also crucial. For example, high tensile and yield strengths may be required when certain devices (e.g., flow shunts, 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.

[0003] 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.

[0004] 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 joint liners for total hip replacements and tibial inserts for 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 like low-MW polyethylene or conventional melt-processable polymers. For this reason, many thermoplastic processing techniques, such as injection molding, screw extrusion, or blow molding, are not practical for UHMWPE. For the same reason, practical processing techniques for producing the ultra-thin-walled tubing essential for catheter liners are currently unavailable.

[0005] 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 rope, tennis string, 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 or environmentally unfriendly for close use. However, gel-spinning of UHMWPE has generally been used to produce only fibers and films.

[0006] 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]

[0007] [Patent Document 1] U.S. Patent No. 5,268,733 Summary of the Invention [Problem to be solved by the invention]

[0008] The present disclosure provides UHMWPE tubing produced by dip coating, the tubing exhibiting an average wall thickness of less than 0.004 inches (preferably less than 0.002 inches). Advantageously, in some embodiments, the tubing may exhibit low machine direction orientation of the UHMWPE polymer chains (resulting in moderate tensile strength and low tensile modulus). Due to the thin walls and low modulus values ​​of the disclosed tubing, the tubing can, in some embodiments, be highly flexible while desirably exhibiting high ID lubricity and abrasion resistance. In various embodiments, the combination of properties exhibited by the disclosed tubing may make it particularly suitable for use in catheters, including in catheters designed for flexibility, because the thin tube walls and low modulus values ​​of the disclosed tubing result in a significantly flexible tubing / liner product that is also radiation-resistant and sterilizable (unlike PTFE liners). In some embodiments, the dip-coated tubing may be further oriented in the machine and cross directions to enhance mechanical, thermal, and barrier properties. Additionally, the UHMWPE tubing provided herein may, in some embodiments, be used as a liner for metal tubing, such as laser-cut hypotubes.

[0009] In one aspect, a UHMWPE tube is provided having an average wall thickness of 0.001" or less, a tensile stress at break greater than 9 MPa, and a storage modulus at 37°C greater than 60 MPa. In some embodiments, the tube exhibits a change in storage modulus between 23°C and 37°C of 5 MPa / °C or less.

[0010] In another aspect, there is provided a UHMWPE layer on a metallic or non-metallic core, the UHMWPE layer having an average thickness of 0.002" or less and exhibiting an average tensile stress at break greater than 7 MPa and an average storage modulus at 37°C greater than 150 MPa. In certain embodiments, the metallic or non-metallic core and the UHMWPE layer are both substantially cylindrical. In some embodiments, the UHMWPE layer on the metallic or non-metallic core comprises a minimum continuous length of 50 ft.

[0011] In another embodiment, a porous / semi-sintered tube is provided having a tensile strength greater than 3 MPa at 5% elongation, greater than 5 MPa at 10% elongation, and a storage modulus greater than 65 MPa at 37°C.

[0012] The solvents and UHMWPE resins used in the dip-coating process can also be used in different concentrations for 3D printing of polymer structures / devices / products for various applications. [Means for solving the problem]

[0013] The present invention includes, but is not limited to, the following embodiments.

[0014] Embodiment 1: A tubing comprising ultra-high molecular weight poly(ethylene) (UHMWPE), the tubing exhibiting: a. an average wall thickness of less than or equal to 0.004″; and b. a tensile stress at break greater than 6 MPa; and c. a storage modulus at 37° C. greater than 20 MPa.

[0015] Embodiment 2: The tube of embodiment 1, wherein at least about 50% by weight of the tube comprises UHMWPE.

[0016] Embodiment 3: The tube of embodiment 1 or 2, further comprising HDPE and / or LDPE in an amount less than about 50% by weight, based on the total weight of the tube.

[0017] Embodiment 4: The tube of any one of embodiments 1 to 3, further comprising one or more particulate fillers in an amount of less than about 50% by weight, based on the total weight of the tube.

[0018] Embodiment 5: The tube of any one of embodiments 1 to 4, which is solvent-free.

[0019] Embodiment 6: The tube of any one of embodiments 1 to 5, wherein the average wall thickness is from 0.0002" to 0.002".

[0020] Embodiment 7: A tube according to any one of embodiments 1 to 6, exhibiting a change in storage modulus between 23°C and 37°C of 10 MPa / °C or less.

[0021] Embodiment 8: A tube according to any one of embodiments 1 to 7, having an abrasion-resistant inner surface.

[0022] Embodiment 9: A tube described in any one of embodiments 1 to 8, having a lubricious inner surface with a coefficient of friction of less than 0.2.

[0023] Embodiment 10: A coated core comprising a continuous UHMWPE layer on a core, said UHMWPE layer having an average thickness of about 0.002" or less, an average tensile stress at break of greater than 7 MPa, and an average storage modulus at 37°C of greater than 50 MPa, when measured after removal from said core.

[0024] Embodiment 11: A coated core according to embodiment 10, wherein the core and the UHMWPE layer are both substantially cylindrical.

[0025] Embodiment 12: The coated core of embodiment 10 or 11 having a minimum continuous length of 50 ft.

[0026] Embodiment 13: The coated core of any one of embodiments 10 to 12, wherein the core has a contact angle of less than 120 degrees.

[0027] Embodiment 14: The coated core of any one of embodiments 10 to 13, wherein the core has a contact angle of less than 100 degrees.

[0028] Embodiment 15: A coated core according to any one of embodiments 10 to 14, wherein the UHMWPE layer exhibits a change in storage modulus between 23°C and 37°C of 10 MPa / °C or less.

[0029] Embodiment 16: A tubing comprising UHMWPE prepared by dip-coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dynamic viscosity of said dispersion is less than 3000 cP at 110°C.

[0030] Embodiment 17: The tube of embodiment 16, wherein the dispersion further comprises one or more other modified polyethylene resins.

[0031] Embodiment 18: The tube of embodiment 16 or 17, wherein the dispersion further comprises one or more particulate fillers.

[0032] Embodiment 19: A tube according to any one of embodiments 16 to 18, wherein the dip coating is carried out at a temperature between about 20°C and about 100°C.

[0033] Embodiment 20: A method for preparing a tubing comprising UHMWPE, comprising dip-coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dynamic viscosity of the dispersion is less than 3000 cP at 110° C.

[0034] 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 whereby 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.

[0035] 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]

[0036] [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. [Figure 2] 1 is a plot of temperature versus viscosity of a dispersion ("A") utilized to make a particular UHMWPE tubing according to one non-limiting embodiment of the present disclosure. [Figure 3] 1 is a plot of temperature versus viscosity of a dispersion ("B") utilized to make a particular UHMWPE tubing according to one non-limiting embodiment of the present disclosure. [Figure 4] 1 is a plot of temperature versus viscosity for dispersions ("C" and "D") utilized to make certain UHMWPE tubing according to certain non-limiting embodiments of the present disclosure. [Figure 5] 1 is a plot of viscosity versus temperature for dispersions ("E" and "F") utilized to make ethylene vinyl acetate (EVA) tubing for certain comparative examples. [Figure 6] 1 is a plot of temperature versus viscosity of a dispersion (“G”) utilized to make a particular tubing comprising UHMWPE and EVA according to one non-limiting embodiment of the present disclosure. [Figure 7A] 1 is a scanning electron microscope (SEM) image of the partially sintered tube of Example 4. [Figure 7B] 1 is an SEM image of the fully sintered tube of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0037] 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.

[0038] The present disclosure provides tubing comprising ultra-high molecular weight poly(ethylene) (UHMWPE) produced by a dip-coating process, having certain physical properties more fully outlined herein below. "UHMWPE tubing" means that the tubing provided herein comprises, consists essentially of, or consists of UHMWPE. In some embodiments, a majority of the tubing (e.g., about 50% by weight or more, about 60% by weight or more, about 70% by weight or more, about 80% by weight or more, about 90% by weight or more, about 95% by weight or more, or about 98% by weight or more) is UHMWPE. Various UHMWPE resins are commercially available and may be used in certain embodiments to provide the UHMWPE tubing described herein.

[0039] In certain embodiments, the tube comprises, in addition to UHMWPE, one or more additional components (e.g., fillers, such as particulate fillers, or other polymers). For example, in some embodiments, the tube comprises a tie resin such as a polyethylene-based tie resin (e.g., including, but not limited to, low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), and derivatives, copolymers, and combinations thereof). Additional suitable polyethylene-based tie resins include, but are not limited to, anhydride-modified polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ethylene-acrylic acid ester-maleic anhydride terpolymer, and the like. In some embodiments, the tube consists essentially of UHMWPE and tie resin, and optionally, a filler. In some embodiments, the filler is a particulate filler. Fillers may be incorporated that may impart certain properties to the tube, such as radiopacity, strength, and / or hydrophilicity. In some embodiments, additional polymers may be included within the tube to impart certain properties, such as lubricity, toughness, or adhesion. Tubing with added fillers and / or polymers other than UHMWPE may have different properties, such as different mechanical, thermal and barrier properties, different crystallinity, different coefficients of friction, etc.

[0040] The UHMWPE tubes provided herein typically do not contain significant amounts of solvent, which, in some embodiments, may be used in methods for preparing the tubes, as described more fully herein below. Thus, the tubes provided herein may, in some embodiments, be described as containing less than about 5 wt. %, less than about 4 wt. %, less than about 3 wt. %, less than about 2 wt. %, less than about 1 wt. %, less than about 0.5 wt. %, less than about 0.1 wt. %, or less than about 0.05 wt. % of solvent, based on the total weight of a given tube. In preferred embodiments, the tubes are substantially free of residual solvent (e.g., less than about 0.01 wt. % or less than 0.001 wt. %) or free of residual solvent (i.e., the solvent used in producing the tubes is completely removed). If there is any amount of solvent retained within the tube, it is advantageously an environmentally friendly, non-toxic solvent. Thus, in some embodiments, the tubes provided herein are free of solvents such as decalin, tetralin, toluene, lower alkanes, paraffin oil, mineral oil, or paraffin wax.

[0041] A general schematic diagram of a representative tube provided is shown in FIG. 1. The tube is generally cylindrical. "L" indicates the length of the produced tube, which may be processed, e.g., cut, to provide a tube of a desired length "1" (not shown). Thus, the length of the tubes provided herein is not particularly limited. In some embodiments, length 1 of the tubes provided herein is a length suitable for catheter applications, e.g., for use as a liner. For example, in some embodiments, length 1 is from about 6" to about 20", e.g., from about 12" to about 20".

[0042] The enlarged area on the right side of Figure 1 is a cross-sectional view of the interior of the tube. As shown, the "lumen" is the interior region of the tube, i.e., the open channel / cavity (e.g., through which a catheter device may be threaded). The inner diameter of the tube, designated "ID," is the average distance from a point on the inner wall of the tube to the opposite / farthest point on the inner wall of the tube. The ID (which determines the diameter of the lumen) may vary and, in some embodiments, is sized appropriately for catheter applications, e.g., for use as a liner. The outer diameter of the tube, designated "OD," is the average distance from a point on the outer wall of the tube through the lumen of the tube to the opposite / farthest point on the outer wall of the tube. Therefore, the average wall thickness of the tube is half the OD value minus the ID value. Figure 1 also shows representative "wall thicknesses," "inner wall surfaces," and "outer wall surfaces" of the tube.

[0043] In certain embodiments, the present disclosure provides UHMWPE tubing having thin walls. For example, the average wall thickness in some embodiments is less than about 0.004 inches. In some embodiments, the average wall thickness of the disclosed tubing may be from about 0.0001 inches to about 0.004 inches, such as from about 0.0002 inches to about 0.001 inches, from about 0.0002 inches to about 0.002 inches, from about 0.0002 inches to about 0.003 inches, or from about 0.0005 inches to about 0.001 inches.

[0044] The wall thickness typically does not vary significantly around the circumference of the tube or along the length (L or l) of the tube. Thus, the wall thickness may generally be described as substantially uniform. The wall tolerance (i.e., variation from a referenced average wall thickness) in some embodiments may be + / −0.0002″ to + / −0.001″, for example, where the nominal wall thickness is 0.001″ to 0.004″ or less. In some embodiments, at any given point on a tube provided in accordance with the present disclosure, the wall thickness is less than about 0.001″. In some embodiments, at any given point on a tube provided in accordance with the present disclosure, the wall thickness is about 0.0001″ to about 0.004″, e.g., about 0.0002″ to about 0.001″, about 0.0002″ to about 0.002″, about 0.0002″ to about 0.003″, or about 0.0002″ to about 0.004″.

[0045] In some embodiments, the UHMWPE tubes provided herein have a wear-resistant inner surface. In some embodiments, the UHMWPE tubes provided herein have a lubricious inner surface, for example, with a coefficient of friction of less than 0.2.

[0046] In some embodiments, the tubing provided herein has a low storage modulus value, e.g., greater than 50 MPa at 37°C. Some tubing has a higher storage modulus value (e.g., when subjected to secondary processing such as orientation / stretching). Advantageously, in some embodiments, the UHMWPE tubing provided herein has high flexibility, making it particularly suitable for certain medical applications, e.g., in catheters as liners (which can be suitably sterilized by radiation). In some embodiments, the tubing exhibits a low change in storage modulus upon heating, e.g., a change in storage modulus of 10 MPa / °C or less between 23°C and 37°C. In certain embodiments, the tubing provided herein has an average tensile stress at break of greater than 7 MPa. In some embodiments, the tubing provided herein has a minimum tensile modulus of about 100 MPa or greater.

[0047] In some embodiments, the dip-coated tubes provided herein are fully sintered. The fully sintered tubes generally contain fully sintered / fused particles and exhibit a continuous, transparent structure. In some embodiments, the dip-coated tubes exhibit little or no porosity as shown in SEM / electron microscope images.

[0048] When the coated core is subjected to lower temperatures in an oven (compared to the annealing / sintering temperature), the resulting tube is generally partially sintered, with the individual particles partially fused together to form a porous / semi-porous structure. At higher temperatures (e.g., near, at, or above the sintering temperature), the individual particles generally fuse completely, forming a continuous, transparent structure with minimal or no porosity. SEM / electron microscope images support this observation.

[0049] In some embodiments, the dip-coated tubes provided herein may not be fully sintered, but may be considered, for example, semi-sintered. Semi-sintered tubes may bond better to other materials than corresponding sintered tubes due to their microporous nature. These semi-sintered tubes may have different mechanical or thermal properties and / or different crystallinity or lubricity compared to fully sintered / fused continuous structures. Tubes with the porous / semi-porous structures and different mechanical properties may be used for different applications.

[0050] The dip-coated tubing provided herein generally does not exhibit high machine direction (MD) molecular orientation, as typically exhibited by typical gel-spun highly oriented UHMWPE fibers. In some embodiments, the dip-coated tubing provided herein exhibits little or no MD molecular orientation. Polymer chain orientation is primarily imparted by the processing method. The extrusion process aligns chains parallel to the machine direction, while solvent casting / dip coating does not. One way to distinguish the two is the anisotropy of certain physical properties, such as MD and TD modulus.

[0051] In some embodiments, the dip-coated tubing is subjected to secondary stretching in the machine direction (MD) and / or transverse direction (TD) to impart molecular orientation and alter the crystallinity, thereby altering the mechanical, thermal, barrier, or electrical / piezoelectric properties in the corresponding direction. Thus, in some embodiments, dip-coated UHMWPE tubing is provided that exhibits significant MD and / or TD orientation.

[0052] The present disclosure further provides methods for producing UHMWPE tubing, such as tubing exhibiting the chemical and physical properties described herein above. Such methods are generally referred to herein as "dip-coating" methods. However, such methods may also be characterized, in various embodiments, as "dispersion coating," "solution coating," or "solvent casting." UHMWPE dip-coating methods may include several steps, including (1) dispersion (or solution) preparation or resin mixing with one or more solvents, (2) dipping / coating, (3) solvent evaporation, (4) sintering / curing, and (5) core / mandrel removal, as discussed in more detail below.

[0053] First, a dispersion or solution is prepared (e.g., one or more resins are mixed with one or more solvents). The dispersion or solution generally includes one or more UHMWPE resins, a solvent, and optionally any of the additives mentioned hereinabove (e.g., fillers and / or tie layer materials). In the following discussion, it is understood that the term "solvent" can apply to any compound that at least partially solubilizes the UHMWPE resin. The term can also be used to refer to a dispersant or a suspension medium or the continuous phase of a dip-coating medium. In some embodiments, a mixture of UHMWPE resin and a solvent (and optionally additional additives) results in a dispersion. In some embodiments, a mixture of UHMWPE resin and a solvent (and optionally additional additives) results in a solution. The method for combining the above components is not particularly limited, and various mixing methods and equipment can be utilized.

[0054] In some embodiments, the dynamic viscosity of the dispersions used in the disclosed methods is less than about 3000 cP at 110°C.

[0055] Non-limiting fine powder UHMWPE resin suitable for the dip coating process disclosed herein typically ranges from about 1×10 6 The resins are homopolymeric and have 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® 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 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.

[0056] As noted above, in some embodiments, other additives may be included with the UHMWPE resin (and incorporated into the tubing produced therefrom). For example, polyethylene tie resins may be included with UHMWPE resins such as LDPE, LLDPE, HDPE, VLDPE, anhydride-modified polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ethylene-acrylic acid ester-maleic anhydride terpolymer, and the like.

[0057] The dispersion / solution preparation step involves combining the UHMWPE resin (and optionally additional resins and / or other additives) with a suitable solvent (or combination of solvents). The solvent typically at least partially dissolves the UHMWPE resin, and in some embodiments, substantially or completely dissolves the UHMWPE resin, for example, at room temperature or at a temperature referred to herein (e.g., elevated heat 10°C below the melting temperature of the resin). Suitable solvents include, but are not limited to, xylene, cyclohexane, benzene, toluene, carbon tetrachloride, tetrahydrofuran, chloroform, dodecane and other hydrocarbon chains (e.g., having 11 to 16 carbons), naphthalene, p-xylene, 1,2,4-trichlorobenzene, kerosene, camphene, paraffin oil, decalin, polybutene, sunflower oil, palm oil, and / or orange oil (terpenes). In some embodiments, environmentally friendly solvents are used to prepare the solution / dispersion. For example, in some embodiments, a solvent such as D-limonene [CAS No. 5989-27-5] can be advantageously utilized in the dispersion / solution preparation step. 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. In some embodiments, the solvent is predominantly limonene, e.g., the solvent comprises about 50% or more, about 60% or more, about 70% or more, about 80% or more, about 90% or more, about 95% or more, about 98% or more, or about 99% or more limonene by weight. In some embodiments, dispersions or solutions provided in accordance with the present disclosure consist essentially of one or more UHMWPE resins, limonene, and optionally additional tie layer resins and / or fillers as mentioned hereinabove.

[0058] To form a suitable dispersion, the polymer resin can be mixed in the solvent by mechanical agitation with or without the addition of heat (as high as 10°C below the melting temperature of the resin). In some embodiments, the disclosed method may further include subjecting the dispersion to an optional filtration step to remove large agglomerates. The dispersion or solution is then used to dip-coat a part. Typically, the UHMWPE-containing dispersion / suspension is coated onto a metallic or non-metallic core / substrate, including, but not limited to, a wire or mandrel. In some embodiments, the core / substrate can include a surface comprising poly(tetrafluoroethylene), filled poly(tetrafluoroethylene), or silver-coated copper. The shape, size, and composition of the core / substrate are not particularly limited. In some embodiments, the core / substrate is cylindrical. In some embodiments, the core / substrate is smooth. In other embodiments, the core / substrate is patterned (which, in some embodiments, can impart the above-mentioned patterning to the ID of the resulting tube). In some embodiments, reference to "UHMWPE" coated onto a core / substrate is understood to include additional components, such as tie layer materials, fillers, solvents, and the like.

[0059] The UHMWPE coating on the core / substrate generally adheres to the underlying substrate to some degree. The adhesion of the UHMWPE coating to the core / substrate typically depends on the relative surface tensions of the core / substrate and the UHMWPE coating. One method for measuring the surface tension of a metallic / non-metallic core / substrate / mandrel is contact angle. In some embodiments, a suitable core / mandrel may be selected based on its contact angle value, typically less than 120 degrees, and preferably less than 100 degrees. The contact angle value may be evaluated, for example, as described in U.S. Patent No. 6,299,499 to Wright et al., which is incorporated herein by reference in its entirety.

[0060] The dip coating step may be a batch or continuous process.

[0061] In a batch process, the reservoir contains the dispersion or solution. For example, in one embodiment, the mandrel / core is momentarily immersed in the dispersion / solution (while stationary or in rotational mode around its central axis) and then drawn off by manual or automated processes. In some embodiments, the drawn material may pass through a sizing die after immersion to remove excess coating material and ensure uniform coating around the circumference. The coated core is then typically heated (e.g., placed in an oven) to dry / devolatilize / remove the solvent at a set temperature. The suitable temperature depends, for example, on the solvent to be removed in this step. The drying / devolatilization oven temperature can vary from 100°C to 230°C, depending on the boiling point of the solvent used to create the dispersion. Advantageously, the drying / devolatilization removes substantially all of the solvent. In some embodiments, the coated core may then be subjected to other (e.g., higher) temperatures for sintering / tempering / melt-fusing or annealing of the polymer particles. The temperature of the sintering oven may be set between 120° C. and 250° C. depending on the viscosity / flowability of the molecular weight or grade of UHMWPE resin. These steps (i.e., dip coating and heating) may be repeated multiple times in some embodiments to increase the coating thickness (and correspondingly, the wall thickness of the tubing produced therefrom) to a desired value.

[0062] In a continuous coating process, the cores are passed through a bath of the dispersion / solution to be coated, then through a sizing die, followed by devolatilization and sintering and / or heating at higher temperatures (e.g., in an oven). Again, in some embodiments, it may be advantageous to further increase the coating thickness. In the above embodiments, the coated material exiting the sintering oven may be returned to the same or another coating reservoir in a loop, passed through a different appropriately sized sizing die, and then heated again (e.g., in an oven).

[0063] The interior surface of hollow metallic or non-metallic tubes can also be coated with the dispersion in a similar manner while the hollow tube is stationary or in rotation about its axis. If the UHMWPE coating is intended to be removed and subsequently bonded to another material, such as polyimide (PI), polyurethane (PU), nylon or polyamide ether copolymer (PEBA), or other polymers or copolymers, the dispersion may also contain a tie resin, including, but not limited to, anhydride-modified polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ethylene-acrylic acid ester-maleic anhydride terpolymer, or other similar resins. If included, the amount of tie layer resin may be up to about 50% by weight of the resin in the dispersion.

[0064] As described above, when the coated core is subjected to lower temperatures in an oven (compared to the annealing / sintering temperature), the resulting tube generally undergoes partial sintering, with the individual particles partially fused together to form a porous / semi-porous structure. At higher temperatures (e.g., near, at, or above the sintering temperature), the individual particles generally fuse together completely, producing a continuous, transparent structure with minimal or no porosity. Thus, in some embodiments, physical properties (e.g., mechanical properties, thermal properties, crystallinity properties, lubricity, etc.) can be tailored by selecting an appropriate temperature for heat treatment.

[0065] Once the coated core is removed from the oven and cooled (either in air or quenched with water), the product is ready for further processing, generally depending on the intended use. For example, in some embodiments, various materials can be added to the outer surface of the coating, and in certain embodiments, different metallic / non-metallic fibers can be woven onto the outer surface.

[0066] In some embodiments, the coating is removed from the underlying core to obtain a tube, for example, by stretching the coated core to remove the coating from the core. One non-limiting method for removing the coating includes removing small portions of the coating at two distal locations of the coated core to expose the core portion. The two exposed locations may be clamped (e.g., using an Instron tensile machine) and the core may be stretched. The degree of stretching targeted in this step is typically, for example, at least about 5%, with a maximum stretch percentage of 30% (or just before the core breaks or the outer diameter of the coated core is reduced sufficiently to break the bond between the coating and the core). After the core has been sufficiently stretched, the coating typically slides off easily in the form of a tube. The removed coating is advantageously in the form of a self-supporting tube (of length L). This tube may optionally be processed, for example, by cutting the long tube into shorter lengths 1 as desired, for example, for certain specific applications.

[0067] In some embodiments, the coated or single tube may be further processed by stretching (e.g., 1.1 to 10 times) in the machine direction (with or without heating) to impart molecular orientation. Such stretching may serve to increase the tensile strength of the coating / tube and also further reduce the wall thickness. When the coated tube is stretched, the core may be separated from the coating, for example, by the same methods described above. Tubes oriented in the machine direction may optionally be further oriented (with or without heating) by stretching (e.g., mechanically or pneumatically) in the transverse direction (TD) by 1.1 to 10 times (with or without heating), for example, mechanically or pneumatically (e.g., by applying air to the ID of the tube). Alternatively, unstretched tubes (e.g., after removing the coating from the core) may be simultaneously oriented in the machine and transverse directions (with or without heating), mechanically or pneumatically, or in combination (e.g., via a balloon blower). Stretching processes may be used on partially sintered and fully sintered tubes to impart different structural and mechanical effects to the tube. In some embodiments, the partially sintered tube may also be subjected to a post-stretching sintering process to produce a sintered tube that may have different properties than a corresponding tube that has been stretched after full sintering. [Example]

[0068] Embodiments of the present disclosure are more fully illustrated by the following examples, which are set forth to illustrate aspects of the disclosure and are not to be construed as limiting thereof. Unless otherwise indicated, all parts and percentages are by weight.

[0069] UHMWPE tubing was prepared as described in the following examples. A Brookfield Viscometer LVDV 11+ Pro was used to map the temperature vs. viscosity profile of the various dispersions used in the examples. All dispersions were tested using a spindle set at 100 rpm, from 20°C to at least 10°C below the resin's melting temperature, as the dispersions begin to gel and coagulate near the resin's melting temperature. It should be noted that the dispersions suitable for preparing UHMWPE tubing generally described in this application are not limited to the specific dispersions in the examples.

[0070] Tensile properties of dip-coated UHMWPE tubing were determined using an Instron 5965 dual-column mechanical testing machine running Bluehill 3 v3.73.4823 operating software. Tests were conducted at room temperature at a rate of 20" / min using a 1 kN load cell attached to pneumatic grips with serrated face inserts set at a 2" gauge length. Average tensile properties are listed in Table 2.

[0071] The thermomechanical properties of the dip-coated UHMWPE tubing separated from the core were determined using a TA Instruments Q800 DMA equipped with a film tension fixture. 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 sample was heated at a constant rate of 3 °C / min while being subjected to a constant amplitude displacement of 15 µm in a tensile oscillation with a fixed frequency of 1 Hz. The resulting DMA data was imported into TA Instruments TRIOS software v4.3, and the average storage moduli at 23 °C and 37 °C are listed in Table 2.

[0072] Constructed catheters and catheter components, such as liners and jackets, may 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.

[0073] Several dispersions were made using Mipelon™ PM200 UHMWPE resin and d-limonene solvent at concentrations varying from 1% wt. / vol. to 100% wt. / vol. Additionally, dispersions were made using Microthene FE53200 ethylene vinyl acetate (EVA) and d-limonene solvent at concentrations varying from 1% wt. / vol. to 100% wt. / vol. Another dispersion was made by adding EVA to the UHMWPE and d-limonene dispersion. All dispersions were tested on a Brookfield Viscometer as described above to obtain the viscosity vs. temperature profiles shown in Figures 2 through 6.

[0074] Example 1: A 0.109" OD PTFE mandrel was dip coated with Dispersion A at 80°C, followed by solvent evaporation at 170°C. A partially sintered tube was dip coated with Dispersion G at 50°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0075] Example 2: A 0.109" OD PTFE mandrel was dip coated with Dispersion B at 80°C, followed by solvent evaporation at 170°C. The partially sintered tube was dip coated with Dispersion G at 50°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0076] Example 3: A 0.109" OD PTFE mandrel was dip coated with Dispersion C at 10°C, followed by solvent evaporation at 170°C. The partially sintered tube was again dip coated with Dispersion C at 10°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0077] Example 4: A 0.109" OD PTFE mandrel was dip-coated with Dispersion C at 80°C, followed by solvent evaporation at 170°C. The coated tube was then sintered onto a core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article. SEM images of this material in partially sintered and fully sintered forms were taken using a ZEISS EVO 40 at 1000x magnification and are shown in Figures 7A and 7B, respectively.

[0078] Example 5: A 0.109" OD PTFE mandrel was dip coated with Dispersion F at 50°C, followed by solvent evaporation at 130°C. The partially sintered tube was again dip coated with Dispersion F at 50°C, followed by another solvent evaporation at 130°C. The coated tube was then sintered onto a core at 160°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0079] Example 6: A 0.109" OD PTFE mandrel was dip coated with Dispersion G at 50°C, followed by solvent evaporation at 150°C. The partially sintered tube was again dip coated with Dispersion G at 50°C, followed by another solvent evaporation at 150°C. The coated tube was then sintered onto a core at 180°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0080] Example 7: A 0.109" OD PTFE mandrel was dip coated with Dispersion C at 80°C, followed by solvent evaporation at 170°C. The partially sintered tube was again dip coated with Dispersion E at 50°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0081] Example 8: A 0.109" OD PTFE mandrel was dip coated with Dispersion D at 80°C, followed by solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0082] Example 9: A 0.109" OD PTFE mandrel was dip coated with Dispersion B at 80°C, followed by solvent evaporation at 170°C. The partially sintered tube was again dip coated with Dispersion B at 80°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0083] Example 10: A 0.060" OD silver-plated copper (SPC) mandrel was dip-coated with Dispersion B at 80°C, followed by solvent evaporation at 170°C. The partially sintered tube was again dip-coated with Dispersion B at 80°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C. Due to polyethylene's affinity for metals, it was difficult to separate the UHMWPE tube from the SPC mandrel without damaging the tube shape.

[0084] Example 11: A 0.088" OD textured glass-filled PTFE mandrel was dip-coated with Dispersion B at 80°C, followed by solvent evaporation at 170°C. The partially sintered tube was again dip-coated with Dispersion B at 80°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto a core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0085] Example 12: A 0.109" OD PTFE mandrel was dip coated with Dispersion C at 80°C, followed by solvent evaporation at 170°C. The partially sintered tube was again dip coated with Dispersion C at 80°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and quenched in cold water. The core was then stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article.

[0086] Example 13: The UHMWPE tube of Example 12 was stretched approximately 300% at 120° C. to improve axial orientation and mechanical properties.

[0087] Example 14: A 0.125" OD PTFE mandrel was dip coated with Dispersion C at 80°C in a continuous process, followed by solvent evaporation at 170°C. The partially sintered tube was again dip coated with Dispersion C at 80°C, followed by another solvent evaporation at 170°C. The coated tube was then sintered onto the core at 200°C and cooled in air. The coated core was then cut into smaller lengths and stretched as described above, and the coating (in tubular form) was removed from the core without deforming or damaging the layers, resulting in a tubular, free-standing UHMWPE article. Approximately 50 feet of mandrel was coated with the dispersion.

[0088] [Table 1]

[0089] EVA was used to demonstrate that a tie resin can be added to the dispersion or a multi-layer coating can be formed where one layer is UHMWPE and another layer is EVA.

[0090] [Table 2]

[0091] 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. 1. A tube comprising ultra-high molecular weight poly(ethylene) (UHMWPE), a. an average wall thickness of 0.004″ or less; and b. A tensile stress at break greater than 6 MPa; and c. A storage modulus greater than 20 MPa at 37°C Showing the tube.

2. 10. The tube of claim 1, wherein at least about 50% by weight of the tube comprises the UHMWPE.

3. 10. The tube of claim 1, further comprising HDPE and / or LDPE in an amount less than about 50% by weight, based on the total weight of the tube.

4. 10. The tube of claim 1, further comprising one or more particulate fillers in an amount of less than about 50% by weight, based on the total weight of the tube.

5. 10. The tubing of claim 1, which is solvent-free.

6. 10. The tube of claim 1, wherein the average wall thickness is from 0.0002" to 0.002".

7. 2. The tube of claim 1, which exhibits a change in storage modulus between 23°C and 37°C of 10 MPa / °C or less.

8. 10. The tube of claim 1 having an abrasion-resistant inner surface.

9. 10. The tube of claim 1 having a lubricious inner surface having a coefficient of friction of less than 0.

2.

10. A coated core comprising a continuous UHMWPE layer on the core, said UHMWPE layer having an average thickness of about 0.002" or less, an average tensile stress at break of greater than 7 MPa, and an average storage modulus at 37°C of greater than 50 MPa, when measured after removal from said core.

11. 11. The coated core of claim 10, wherein the core and UHMWPE layer are both substantially cylindrical.

12. 11. The coated core of claim 10 having a minimum continuous length of 50 ft.

13. 11. The coated core of claim 10, wherein the core has a contact angle of less than 120 degrees.

14. The coated core of claim 10, wherein the core has a contact angle of less than 100 degrees.

15. 11. The coated core of claim 10, wherein the UHMWPE layer exhibits a change in storage modulus between 23°C and 37°C of 10 MPa / °C or less.

16. 1. A tube comprising UHMWPE prepared by dip-coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dynamic viscosity of said dispersion is less than 3000 cP at 110°C.

17. 17. The tubing of claim 16, wherein the dispersion further comprises one or more other modified polyethylene resins.

18. 17. The tube of claim 16, wherein the dispersion further comprises one or more particulate fillers.

19. 17. The tubing of claim 16, wherein the dip coating is performed at a temperature between about 20°C and about 100°C.

20. 1. A method for preparing a tubing comprising UHMWPE, comprising dip-coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dynamic viscosity of the dispersion is less than 3000 cP at 110°C.

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