UHMWPE dip-coated pipe

Abstract

The present invention provides a pipe comprising ultra high molecular weight polyethylene (UHMWPE). Such tubes may have thin walls and are suitable for applications, for example, as catheter liners. The method of making such a tube comprises dip-coating the core in a dispersion comprising UHMWPE, where the dispersion advantageously further comprises an environmentally friendly solvent, and may optionally comprise one or more additional components (e.g., fillers and / or other polymers). In one aspect, a UHMWPE tube is provided that includes an average wall thickness of 0.004 ''or less, and a tensile stress at break of greater than 6 MPa, and a storage modulus of greater than 60 MPa at 37 DEG C. In some embodiments, the tube exhibits a change in storage modulus between 23 DEG C and 37 DEG C of 5 MPa / DEG C or less.

Description

Technical Field

[0001] The present application relates generally to the field of pipes comprising ultra-high molecular weight polyethylene (UHMWPE), for use, for example, as thin-walled conduit liners, and to methods relating to such pipes. Background Art

[0002] Vascular therapy uses minimally invasive, catheter-based surgery and specialized devices and techniques. The catheters used in these procedures are usually coated or lined on the inner wall to provide a lubricated inner surface. The lubricated inner diameter (ID) associated with these devices is conducive to reducing friction with them when they are pushed through the tight confines of the catheter lumen in different catheter technologies such as stents, balloons, atherectomy or thrombectomy devices. If the catheter ID does not have enough lubricity, the device, such as stent, will cause the liner to collapse in an accordion-like manner when the device is pushed through the catheter lumen. The effect of the increased lubricity of the catheter ID is to reduce their spreading force when the catheter device is sent through the lumen, which increases the possibility of successful surgery. The mechanical properties of the catheter lining are also extremely important. For example, when some devices (such as shunts, embolic coils, aneurysm bridging devices, stents and thrombectomy devices) are sent through microcatheters in a compressed state, high tensile and yield strengths will be required. The compressed shape applies an outward radial force, which causes friction with the ID, which usually makes it difficult to send the device through the lumen. On the other hand, high flexibility of the liner is often desired when the catheter must be routed through a vasculature involving sharp twists and turns, such as the cerebrovascular system and below-the-knee (BTK) applications.

[0003] Among the different materials used for the inner wall (base lining) material in such catheter devices, there is polytetrafluoroethylene (PTFE), which is due to its excellent chemical resistance, high temperature resistance, biocompatibility and very low friction coefficient / high lubricity. A major disadvantage of PTFE is that it is not radiation stable. Radiation sterilization (i.e., gamma rays or electron beams) is one of the most widely used and safe sterilization methods for medical devices. Radiation sterilization improves the manufacturability of catheters because it can be performed quickly on the production line, while the ethylene oxide gas sterilization (ETO) procedure commonly used with PTFE-lined catheters requires storage for up to 48 hours to allow the gas to diffuse out of the sterilization device. In addition, ETO gas requires careful handling due to its flammability and toxicity. Strict handling requirements and technically complex sterilization processes make ETO sterilization technology generally undesirable. Recently, medical regulatory organizations around the world have also been encouraging the medical industry to minimize or replace the use of ETO with alternative sterilization methods.

[0004] While several other polymers can withstand gamma radiation, none can match the lubricity or low coefficient of friction of PTFE. Ultra-high molecular weight polyethylene (UHMWPE) comes close to doing so. UHMWPE is a linear polymer with -CH2-CH2- repeating units. Medical grade UHMWPE has long chains with a molecular weight greater than 1×10 6 g / mol, and is a semi-crystalline polymer. UHMWPE has a very low coefficient of friction, excellent wear resistance, good toughness, high impact strength, high resistance to corrosive chemicals, excellent biocompatibility and low cost. In addition, UHMWPE has a low processing temperature, so it can be easily combined with a variety of other polymer catheter components. UHMWPE has been used clinically for joint implants for more than 40 years, especially as joint linings in total hip replacements and tibial inserts in total knee replacements. One disadvantage of UHMWPE is its very high viscosity due to its extremely high molecular weight. When UHMWPE is raised above its melting temperature, it does not flow like lower MW polyethylene or traditional 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, there are currently few practical processing techniques available for the production of very thin-walled tubes necessary for catheter linings.

[0005] Gel spinning process is widely used in processing UHMWPE into high-strength oriented polyolefin fibers, which can be used to manufacture products such as ropes, tennis ropes, fishing nets, filters, anti-ballistic molded products, medical textiles and high-strength medical sutures. The gel spinning of UHMWPE traditionally involves organic solvents such as decalin, tetralin, toluene, lower alkanes, paraffin oil, mineral oil, paraffin etc., among which decalin and paraffin oil are the most widely used. Many of these solvents are generally considered to be unsafe or environmentally unfriendly for close contact. However, the gel spinning of UHMWPE is usually only used to produce fibers and films.

[0006] It would be a great benefit for both medical and industrial applications if radiation sterilizable polymer materials such as UHMWPE could be processed with environmentally friendly solvents into thin-walled tubes, liners or other polymer structures with good mechanical properties. Summary of the invention

[0007] The present invention provides a UHMWPE tube produced by dip coating, which exhibits an average wall thickness of less than 0.004 inches (preferably less than 0.002 inches). Advantageously, in some embodiments, such a tube can exhibit a low longitudinal orientation of the UHMWPE polymer chain (which achieves a medium tensile strength and a low tensile modulus). Due to the thin wall of the disclosed tube and the low modulus value of such a tube, they can desirably have high flexibility in some embodiments while exhibiting high ID lubricity and wear resistance. In different embodiments, the combination of properties exhibited by the disclosed tube can make them particularly suitable for use in catheters, including catheters designed to be flexible, because the thin tube wall and low modulus value of the disclosed tube provide a significantly flexible tube / liner product that is also radiation-resistant and sterilizable (unlike PTFE liners). In some embodiments, the dip-coated tube can be further oriented in the longitudinal and transverse directions to enhance mechanical, thermal and barrier properties. In addition, the UHMWPE tube provided herein can be used as a liner for a metal tube (e.g., a laser-cut hypotube) in some embodiments.

[0008] In one aspect, a UHMWPE pipe is provided, comprising: an average wall thickness of 0.001" or less; and a tensile stress at break greater than 9 MPa; and a storage modulus greater than 60 MPa at 37°C. In some embodiments, the pipe exhibits a storage modulus change of 5 MPa / °C or less between 23°C and 37°C.

[0009] In another aspect, a UHMWPE layer on a metallic or non-metallic core is provided, wherein: the UHMWPE layer has an average thickness of 0.002" or less; it exhibits an average tensile stress at break greater than 7 MPa and an average storage modulus greater than 150 MPa at 37°C. In certain embodiments, both the metallic or non-metallic core and the UHMWPE layer are substantially cylindrical in shape. In some embodiments, the UHMWPE layer on the metallic or non-metallic core comprises a minimum continuous length of 50 feet.

[0010] In another aspect, there is provided a porous / semi-sintered tube having a tensile strength greater than 3 MPa at 5% elongation and greater than 5 MPa at 10% elongation and a storage modulus greater than 65 MPa at 37°C.

[0011] The solvent and UHMWPE resin used for the dip coating method can also be used in different concentrations for 3D printing of polymer structures / devices / products for different applications.

[0012] The present invention includes, but is not limited to, the following embodiments.

[0013] Embodiment 1: A tube comprising ultra high molecular weight polyethylene (UHMWPE), the tube exhibiting: 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.

[0014] Embodiment 2: The tube of Embodiment 1, wherein at least about 50 wt% of the tube comprises UHMWPE.

[0015] Embodiment 3: The pipe of any of Embodiments 1-2, further comprising HDPE and / or LDPE in an amount less than about 50 wt %, based on the total weight of the pipe.

[0016] Embodiment 4: The tube of any of Embodiments 1-3, further comprising one or more particulate fillers in an amount less than about 50 wt %, based on the total weight of the tube.

[0017] Embodiment 5: The tube of any one of Embodiments 1-4, wherein the tube is free of solvent.

[0018] Embodiment 6: The tube of any of Embodiments 1-5, wherein the average wall thickness is 0.0002" - 0.002".

[0019] Embodiment 7: The tube of any of Embodiments 1-6, wherein the tube exhibits a storage modulus change of 10 MPa / °C or less between 23°C and 37°C.

[0020] Embodiment 8: The tube of any of Embodiments 1-7, wherein the tube has a wear resistant inner surface.

[0021] Embodiment 9: The tube of any of Embodiments 1-8, wherein the tube has a lubricated inner surface having a coefficient of friction less than 0.2.

[0022] Embodiment 10: A coated core comprising a continuous UHMWPE layer on a core, wherein the UHMWPE layer has an average thickness of about 0.002" or less when measured after removal from the core, an average tensile stress at break greater than 7 MPa, and an average storage modulus at 37°C greater than 50 MPa.

[0023] Embodiment 11: The coated core of Embodiment 10, wherein both the core and the UHMWPE layer are substantially cylindrical in shape.

[0024] Embodiment 12: The coated core of any of Embodiments 10-11, having a minimum continuous length of 50 feet.

[0025] Embodiment 13: The coated core of any of Embodiments 10-12, wherein the contact angle of the core is less than 120 degrees.

[0026] Embodiment 14: The coated core of any of Embodiments 10-13, wherein the contact angle of the core is less than 100 degrees.

[0027] Embodiment 15: The coated core of any of Embodiments 10-14, wherein the UHMWPE layer exhibits a storage modulus change of 10 MPa / °C or less between 23°C and 37°C.

[0028] Embodiment 16: A pipe comprising UHMWPE prepared by dip coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dispersion has a dynamic viscosity at 110°C of less than 3000 cP.

[0029] Embodiment 17: The pipe of Embodiment 16, wherein the dispersion further comprises one or more additional modified polyethylene resins.

[0030] Embodiment 18: The tube of any of Embodiments 16-17, wherein the dispersion further comprises one or more particulate fillers.

[0031] Embodiment 19: The tube of any of Embodiments 16-18, wherein the dip coating is performed at a temperature of about 20°C to about 100°C.

[0032] Embodiment 20: A method of making a pipe comprising UHMWPE, comprising dip coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dispersion has a dynamic viscosity at 110°C of less than 3000 cP.

[0033] These and other features, aspects and advantages of the present invention will become clear by reading the following specific embodiments and the accompanying drawings briefly described below. The present invention includes any combination of two, three, four or more of the above-mentioned embodiments, as well as any combination of two, three, four or more features or elements set forth in the present invention, regardless of whether such features or elements are clearly combined in the specific embodiments of this specification. The present invention is intended to be read as a whole, so that any separable features or elements of the disclosed invention in any of its different aspects and embodiments should be considered to be intended to be combined, unless the context clearly stipulates otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] To provide an understanding of embodiments of the invention, reference is made to the accompanying drawings, which are not necessarily drawn to scale and in which reference numerals refer to components of exemplary embodiments of the invention. The drawings are merely exemplary and are not to be construed as limiting the invention.

[0035] Figure 1 is a general schematic diagram of a tube of the present invention with relevant parameters, and an enlarged schematic diagram of a cross-sectional end face of the tube;

[0036] Figure 2 is a graph of temperature versus viscosity for a dispersion ("A") used to make certain UHMWPE pipes according to one non-limiting embodiment of the present invention;

[0037] Figure 3 is a graph of temperature versus viscosity for a dispersion ("B") used to make certain UHMWPE pipes according to one non-limiting embodiment of the present invention;

[0038] Figure 4 is a graph of temperature versus viscosity for dispersions ("C" and "D") used to make certain UHMWPE pipes according to certain non-limiting embodiments of the present invention;

[0039] Figure 5 is a graph of temperature versus viscosity for dispersions ("E" and "F") used to make certain comparative ethylene vinyl acetate (EVA) tubes;

[0040] Figure 6 is a graph of temperature versus viscosity for a dispersion ("G") used to make certain pipes comprising UHMWPE and EVA according to one non-limiting embodiment of the present invention;

[0041] Fig. 7A is a scanning electron microscope (SEM) image of the partially sintered tube of Example 4; and Figure 7B is a SEM image of the fully sintered tube of Example 4. DETAILED DESCRIPTION

[0042] The present invention will now be described more fully below. However, the present invention can be implemented in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided so that the present invention will be 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.

[0043] The present invention provides a pipe comprising ultra-high molecular weight polyethylene (UHMWPE) produced by a dip coating method, having certain physical properties such as those more fully outlined below. "UHMWPE pipe" refers to a pipe provided herein comprising UHMWPE, consisting essentially of it, or consisting of it. In some embodiments, a major part of the pipe (e.g., about 50 wt % or more, about 60 wt % or more, about 70 wt % or more, about 80 wt % or more, about 90 wt % or more, about 95 wt % or more, or about 98 wt % or more) is UHMWPE. Different UHMWPE resins are commercially available and can be used in certain embodiments to provide a UHMWPE pipe as described herein.

[0044] In certain embodiments, in addition to UHMWPE, the tube also includes one or more additional components (e.g., fillers such as particulate fillers, or other polymers). For example, in some embodiments, the tube includes a bonding resin, such as a polyethylene-based bonding 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). Other suitable polyethylene-based bonding resins include but are not limited to anhydride-modified polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ethylene-acrylate-maleic anhydride terpolymers, etc. In some embodiments, the tube is essentially composed of UHMWPE and bonding resins and optionally fillers. In some embodiments, the filler is a particulate filler. Fillers can be incorporated, which can impart specific properties to the tube, such as non-radioactive properties, strength and / or hydrophilicity. In some embodiments, additional polymers can be included in the tube to impart specific properties such as lubricity, toughness or adhesion. Pipes with added fillers and / or polymers other than UHMWPE may have different properties, such as different mechanical, thermal and barrier properties, different crystallinity, different coefficient of friction, etc.

[0045] The UHMWPE pipe provided herein does not generally include any appreciable amount of solvent (in some embodiments, it can be used in the method for preparing the pipe, as described more fully below). Therefore, in some embodiments, the pipe provided herein can be described as comprising less than about 5% by weight, less than about 4% by weight, less than about 3% by weight, less than about 2% by weight, less than about 1% by weight, less than about 0.5% by weight, less than about 0.1% by weight, or less than about 0.05% by weight of solvent, based on the gross weight of a given pipe. In a preferred embodiment, the pipe does not substantially include residual solvent (for example, less than about 0.01% by weight, or less than 0.001% by weight), or does not include residual solvent (i.e., the solvent for producing this pipe is completely removed). In the case of retaining any amount of solvent in the pipe, it is advantageously an environmentally friendly non-toxic solvent. Therefore, in some embodiments, the pipe provided herein does not include any solvent, such as decalin, tetralin, toluene, lower alkanes, paraffin oil, mineral oil or paraffin.

[0046] A general schematic diagram of a representative tube is provided in Figure 1. The tube is generally cylindrical. "L" represents the length of the produced tube, which can be processed, for example, cut, to provide a tube of desired length "l" (not shown). Therefore, there is no particular limitation on the length of the tube provided herein. In some embodiments, the length l of the tube provided herein is a length suitable for catheter applications, for example, as a liner. For example, in some embodiments, the length l is from about 6" to about 20", for example, from about 12" to about 20".

[0047] Figure 1 The enlarged area on the right is a cross-sectional view of the interior of the tube. As shown, the "lumen" is the interior area of ​​the tube, i.e., the open passage / cavity (e.g., the catheter device can be sent therethrough). The internal diameter of the tube (shown as "ID") is the average distance from a point on the inner wall of the tube to the relative / farthest point on the inner wall of the tube. The ID (which determines the diameter of the lumen) can vary, and in some embodiments, has a size suitable for catheter applications, such as as a liner. The outer diameter of the tube (shown as "OD") is the average distance from a point on the outer wall of the tube through the inner cavity of the tube to the relative / farthest point on the outer wall of the tube. Therefore, the OD value minus half of the ID value provides the average wall thickness of the tube. Figure 1 Also shown are the representative "Wall Thickness", "Inner Wall Surface" and "Outer Wall Surface" of the tube.

[0048] In certain embodiments, the present invention provides UHMWPE tubes with thin walls. For example, in some embodiments, the average wall thickness is less than about 0.004 inches. In some embodiments, the average wall thickness of the disclosed tubes can be about 0.0001" to about 0.004", such as about 0.0002" to about 0.001", about 0.0002" to about 0.002", about 0.0002" to about 0.003", or about 0.0005" to about 0.001".

[0049] Wall thickness generally does not change significantly around the circumference of the tube or along the length (L or L) of the tube. Therefore, wall thickness can be generally described as being substantially uniform. In some embodiments, for a nominal wall thickness of 0.001 "-0.004" or lower, the wall tolerance (i.e., the variance with reference to the average wall thickness) can be, for example, + / -0.0002" to + / -0.001". In some embodiments, at any given point on the tube provided according to the present invention, the wall thickness is less than about 0.001". In some embodiments, at any given point on the tube provided according to the present invention, the wall thickness is about 0.0001 "-about 0.004", for example, about 0.0002 "-about 0.001", about 0.0002 "-about 0.002", about 0.0002 "-about 0.003", or about 0.0002 "-about 0.004".

[0050] 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, a coefficient of friction of less than 0.2.

[0051] In some embodiments, the tubes provided herein have low storage modulus values, such as greater than 50MPa at 37°C. Some tubes have higher storage modulus values ​​(e.g., in the case where they undergo secondary processing such as orientation / stretching). Advantageously, in some embodiments, the UHMWPE tubes provided herein have high flexibility, which makes them particularly suitable for certain medical applications, such as linings in catheters (which can be properly sterilized by radiation). In some embodiments, the tube exhibits low storage modulus changes when heated, such as 10MPa / °C or less storage modulus changes between 23°C and 37°C. In certain embodiments, the average tensile stress at break of the tubes provided herein is greater than 7MPa. In some embodiments, the minimum tensile modulus of the tubes provided herein is about 100MPa or greater.

[0052] In some embodiments, the dip-coated tube provided herein is completely sintered. This completely sintered tube generally comprises completely sintered / melted particles, and shows a continuous transparent structure. In some embodiments, this dip-coated tube shows little or no porosity, as demonstrated by SEM / electron microscope images.

[0053] When the coated core is subjected to lower temperatures in the oven (compared to the annealing / sintering temperature), the resulting tube is typically partially sintered, and the individual particles partially melt to form a porous / semi-porous structure. At higher temperatures (e.g., near, at, or above the sintering temperature), the individual particles typically fuse completely and produce a continuous transparent structure with minimal or no porosity. SEM / electron microscopy images support this observation.

[0054] In some embodiments, the dip-coated tube provided herein is incompletely sintered, and can be regarded as, for example, semi-sintered. Semi-sintered tube can be more combined with other materials than corresponding sintered tube due to its microporosity. Compared with the continuous structure of complete sintering / fusion, these semi-sintered tubes can have different mechanical or thermal properties and / or different crystallinity or lubricity. This tubing with porous / semi-porous structure and different mechanical properties can be used for different applications.

[0055] The dip-coated tube provided herein does not show high longitudinal (MD) molecular orientation usually, as the highly oriented UHMWPE fiber of typical gel spinning usually shows.In some embodiments, the dip-coated tube provided herein shows little or no MD molecular orientation.Orientation in the polymer chain is mainly given in the processing method.Extrusion process makes the chain parallel to the longitudinal alignment, but solvent casting / dip coating is not like this.A way to distinguish the two is the anisotropy of some physical properties, such as the modulus on MD and TD.

[0056] In some embodiments, the dip-coated tube undergoes secondary stretching in the machine direction (MD) and / or transverse direction (TD) to impart molecular orientation, change crystallinity, and thereby change mechanical, thermal, barrier, or electrical / piezoelectric properties in the corresponding directions. Thus, in some embodiments, a dip-coated UHMWPE tube is provided that does exhibit significant MD and / or TD orientation.

[0057] The present invention further provides a method for producing a UHMWPE tube (e.g., a tube exhibiting the chemical and physical properties described above). This method is generally referred to herein as a "dip coating" method; however, in different embodiments, this method may also be characterized as "dispersion coating", "solution coating" or "solvent casting". The dip coating method for UHMWPE may involve several steps, including: (1) dispersion (or solution) preparation, or mixing of the resin with one or more solvents; (2) dipping / coating; (3) solvent evaporation; (4) sintering / curing; and (5) removal of the core / mandrel, as further described in detail below.

[0058] First, a dispersion or solution is prepared (e.g., one or more resins are mixed with one or more solvents). The dispersion or solution typically comprises one or more UHMWPE resins, a solvent, and optionally any additives mentioned above (e.g., fillers and / or bonding layer materials). It should be understood in the following discussion that the term "solvent" may be applicable to any compound that at least partially dissolves the UHMWPE resin. It may also be used to refer to a dispersant or suspension medium or continuous phase of a dipping medium. In some embodiments, a mixture of a UHMWPE resin and a solvent (and optionally additional additives) produces a dispersion. In some embodiments, a mixture of a UHMWPE resin and a solvent (and optionally additional additives) produces a solution. There is no particular limitation on the method for combining these components, and different mixing methods and equipment may be used.

[0059] In some embodiments, the dispersion used in the disclosed methods has a dynamic viscosity of less than about 3000 cP at 110°C.

[0060] Non-limiting fine powder UHMWPE resins suitable for use in the dip coating method disclosed herein are generally homopolymeric and typically have a particle size greater than 1×106 The molecular weight is usually calculated from IV (intrinsic viscosity) measurements. Exemplary resins suitable for this purpose include, but are not limited to, [GUR® 2024, GUR® 2122, GUR® 2122-5, GUR® 2126, GUR® 4012, GUR® 4012-6, GUR® 4012-7, GUR® 4012-8, GUR® 4012-9, GUR® 4012-10, GUR® 4012-11, GUR® 4012-12, GUR® 4012-13, GUR® 4012-14, GUR® 4012-15, GUR® 4012-16, GUR® 4012-17, GUR® 4012-18, GUR® 4012-19, GUR® 4012-20, GUR® 4012-21 F, GUR®4020-3, GUR®4022, GUR®4022-6, GUR®4032, GUR®4050-3, GUR®4056-3, GU R®4112, GUR®4113, GUR®4120, GUR®4122, GUR®4122-5, GUR®4130, GUR®4150, 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], manufactured by Mitsui [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's Sunfine UH.

[0061] As described above, in some embodiments, other additives may be included with the UHMWPE resin (and incorporated into the pipe produced therefrom). For example, polyethylene-based bonding resins may be included with the UHMWPE resin, such as LDPE, LLDPE, HDPE, VLDPE, anhydride-modified polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ethylene-acrylate-maleic anhydride terpolymers, and the like.

[0062] The dispersion / solution preparation step involves combining the UHMWPE resin (and optionally, any additional resins and / or other additives) into a suitable solvent (or solvent composition). 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 mentioned herein (e.g., as much heat as 10°C lower than 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 11-16 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, an environmentally friendly solvent is 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 used in the dispersion / solution preparation step. D-limonene is a cyclic terpene found in citrus extracts / oils, also known as limonene or 1-limonene or dl-limonene or (+)-limonene or (+)-dipentene or (+)-(R)-limonene or (R)-4-isopropenyl-1-methyl-1-cyclohexene. In some embodiments, the solvent is primarily 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, the dispersion or solution provided according to the present invention consists essentially of one or more UHMWPE resins, limonene, and optionally any additional tie layer resins and / or fillers, as described above.

[0063] To form a suitable dispersion, the polymer resin may be mixed in a solvent by mechanical stirring with or without heating (up to 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 the component. Typically, the dispersion / suspension containing UHMWPE is coated on a metal or non-metallic core / substrate, such as, but not limited to, a wire or mandrel. In some embodiments, the core / substrate may include a surface containing poly(tetrafluoroethylene), filled poly(tetrafluoroethylene) or silver-clad copper. There are no particular restrictions on the shape and size and composition of the core / substrate. In some embodiments, the shape of the core / substrate is cylindrical. In some embodiments, the core / substrate is smooth; in other embodiments, the core / substrate is patterned (in some embodiments, it may impart such patterning to the ID of the formed tube). It should be understood that in some embodiments, reference to "UHMWPE" coated on the core / substrate also includes additional components, such as bonding layer materials, fillers, solvents, etc.

[0064] The UHMWPE coating on the core / substrate is generally adhered to the underlying substrate to some extent; the adhesion of the UHMWPE coating to the core / substrate generally depends on the relative surface tensions of the core / substrate and the UHMWPE coating. One method of measuring the surface tension of a metal / non-metallic core / substrate / mandrel is the contact angle. In some embodiments, an appropriate core / mandrel may be selected based on its contact angle value (generally less than 120 degrees, preferably less than 100 degrees). The contact angle value may be evaluated, for example, as described in U.S. Pat. No. 5,268,733 to Wright et al., which is incorporated herein by reference in its entirety.

[0065] The dip coating step can be a batch or continuous process.

[0066] In the intermittent process, the storage device contains a dispersion or solution. For example, in one embodiment, the mandrel / core is immersed in the dispersion / solution momentarily (when it is in a rotation mode of being stationary or around its central axis), and is pulled out manually or by an automatic method. In some embodiments, the pulled material can be sent through a sizing die after dipping to remove excess coating and ensure a uniform coating around the circumference. The coated core is then usually heated (e.g., placed in an oven) to dry / devolatilize / drive out the solvent at a set temperature. Suitable temperature will depend on, for example, the solvent to be removed at this stage. The drying / devolatilization oven temperature can vary at 100°C-230°C, depending on the boiling point of the solvent used to produce the dispersion. Advantageously, drying / devolatilization results in the removal of substantially all solvents. In some embodiments, the coated core can then undergo other (e.g., higher) temperatures for sintering / tempering / melt fusion of polymer particles, or annealing. The temperature of the sintering oven can be set at 120°C-250°C, depending on the molecular weight or viscosity / fluidity grade of the UHMWPE resin. In some embodiments, these steps (i.e., dipping and heating) can be repeated multiple times to increase the coating thickness (and accordingly, the wall thickness of the tube produced therefrom) to the desired value.

[0067] In a continuous coating process, the core is 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 a higher temperature (e.g., in an oven). Likewise, in some embodiments, it may be advantageous to further increase the coating thickness; in such embodiments, the coating material leaving the sintering oven may be returned to the same or another coating reservoir in the loop, passed through a different appropriately sized sizing die, and then heated again (e.g., in an oven).

[0068] The inner surface of a hollow metal or non-metallic tube can also be coated with the dispersion in a similar manner while the hollow tube is stationary or in a rotational mode about its axis. If the UHMWPE coating is to be removed and subsequently combined with another material such as polyimide (PI), polyurethane (PU), nylon or polyamide ether copolymer (PEBA) or any other polymer or copolymer, the dispersion may also contain a bonding resin, including but not limited to anhydride-modified polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ethylene-acrylate-maleic anhydride terpolymer or other similar resins. Where included, the amount of the bonding layer resin may be up to about 50% by weight of the resin of the dispersion.

[0069] As described above, when the coated core is subjected to a lower temperature in the oven (compared to the annealing / sintering temperature), the resulting tube is typically partially sintered, and the individual particles are partially fused to form a porous / semi-porous structure. At higher temperatures (e.g., near, at, or above the sintering temperature), the individual particles are typically completely fused and a continuous transparent structure with minimal or no porosity is produced. Thus, in some embodiments, physical properties (e.g., mechanical properties, thermal properties, crystallization properties, lubricity, etc.) can be adjusted by selecting a suitable temperature for heat treatment.

[0070] Once the coated core leaves the oven and cools (either in air or quenched in water), the product can be used as is for further processing, which generally depends on the intended use. For example, in some embodiments, different materials can be added to the outer surface of the coating; in certain embodiments, different metal / non-metallic fibers can be woven onto the outer surface.

[0071] In some embodiments, coating is removed from the following core to obtain pipe, for example, coating is removed from the core by stretching the coated core.A non-limiting method for removing coating relates to removing a small portion of coating at two distal positions of the coated core, thereby exposing the core portion.The two exposed positions can be clamped (for example, using an Instron stretcher), and then the core can be stretched.During this step, the target stretching degree is generally for example at least about 5%, and the maximum stretching percentage is 30% (or until the outer diameter of just core fracture or coated core is reduced to be enough to destroy the combination between coating and core).After the core is fully stretched, coating is usually easy to slide off in the form of pipe.The removed coating is advantageously in the form of a free-standing pipe (length is L).This pipe can optionally be processed, for example, by cutting a long tube into a shorter length l as required, for example, for some specific applications.

[0072] The coated tube or independent tube can be further processed as follows in some embodiments: stretching (e.g., 1.1-10 times) in the longitudinal direction (heating or not) to impart molecular orientation. Such stretching can be used to increase the tensile strength of the coating / tube, and further reduce the wall thickness. If the coated tube is stretched, the core can then be separated from the coating, for example, by the same method as described above. The longitudinally oriented tube can then optionally be further oriented (heating or not) by stretching, for example, 1.1-10 times in the transverse direction (TD) mechanically or pneumatically (e.g., applying air in the ID of the tube). Alternatively, the unstretched tube (e.g., after removing the coating from the core) can be mechanically or pneumatically or in combination (e.g., via a balloon blow molding machine) oriented simultaneously in the longitudinal and transverse directions (heating or not). The stretching method can be used for partially sintered and fully sintered tubes to produce different structural and mechanical effects in the tube. In some embodiments, the partially sintered tube may also undergo a stretching-post-sintering process to produce a sintered tube, which may have different properties than a fully sintered-post-stretched corresponding tube.

[0073] experiment

[0074] Embodiments of the present invention are more fully illustrated by the following examples, which are presented for the purpose of illustrating aspects of the invention and should not be construed as limiting thereof.All parts and percentages are by weight unless otherwise indicated.

[0075] UHMWPE pipes were prepared according to the specific example records provided below. The temperature versus viscosity curves of the different dispersions used in the specific examples were drawn using a Brookfield viscometer LVDVII+Pro. For all dispersions, the rotor was used at a setting of 100 rpm, and the test was conducted at a temperature from 20°C to a temperature at least 10°C lower than the melting temperature of the resin, because the dispersion began to gel and agglomerate when it was close to the melting temperature of the resin. It should be noted that the suitable dispersions for preparing UHMWPE pipes as generally described in this application are not limited to the specific dispersions in the examples.

[0076] The tensile properties of the dip coated UHMWPE pipe were determined using an Instron 5965 dual column mechanical tester running Bluehill 3 v3.73.4823 operating software. Testing was performed at room temperature at a rate of 20" / min using a 1 kN load cell attached to a pneumatic grip with a serrated face insert set to a 2 inch gauge length. The average tensile properties are listed in Table 2.

[0077] Thermomechanical properties of dip-coated UHMWPE pipes separated from the core were determined using a TA Instruments Q800 DMA with a film tension fixture. The main property of interest was the storage modulus (E'). A temperature scan was performed from -100°C to 130°C and held isothermally at -100°C for 5 minutes. The sample was heated at a constant rate of 3°C / min while being displaced with a constant amplitude of 15 μm and a fixed frequency tensile oscillation of 1 Hz. The resulting DMA data was imported into TA Instruments TRIOS software v4.3, and the average storage modulus at 23°C and 37°C is listed in Table 2.

[0078] Constructed catheters and catheter components such as liners and sheaths can be tested using interventional device testing equipment (such as the IDTE3000 from MSI, which can measure and record device performance characteristics such as pushability, flexibility, torquability, etc.).

[0079] Several dispersions were prepared at different concentrations from 1% wt / vol to 100% wt / vol using Mipelon™ PM200 UHMWPE resin and d-limonene solvent. Dispersions were also made at different concentrations from 1% wt / vol to 100% wt / vol using Microthene FE53200 ethylene vinyl acetate (EVA) and d-limonene solvent. Another dispersion was prepared by adding EVA to a dispersion of UHMWPE and d-limonene. All dispersions were tested with a Brookfield viscometer as described above to obtain their temperature versus viscosity curves, which are shown in FIG. Figure 2-6 middle.

[0080] Embodiment 1:

[0081] A 0.109" OD PTFE mandrel was dip coated with dispersion A at 80°C, followed by devolatilization of the solvent at 170°C. The partially sintered tube was dip coated with dispersion G at 50°C, followed by another round of devolatilization of the solvent at 170°C. The coated tube was then sintered on 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 layer to yield a freestanding UHMWPE product in tubular form.

[0082] Embodiment 2:

[0083] A 0.109" OD PTFE mandrel was dip coated with dispersion B at 80°C, followed by devolatilization of the solvent at 170°C. The partially sintered tube was dip coated with dispersion G at 50°C, followed by another round of devolatilization of the solvent at 170°C. The coated tube was then sintered on 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 layer to yield a freestanding UHMWPE product in tubular form.

[0084] Embodiment 3:

[0085] A 0.109" OD PTFE mandrel was dip coated with Dispersion C at 10°C and then the solvent was devolatilized at 170°C. The partially sintered tube was dip coated again with Dispersion C at 10°C and then subjected to another round of solvent devolatilization at 170°C. The coated tube was then sintered on 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 layer to yield a freestanding UHMWPE product in tubular form.

[0086] Embodiment 4:

[0087] A 0.109" OD PTFE mandrel was dip coated with dispersion C at 80°C and the solvent was then devolatilized at 170°C. The coated tube was then sintered on 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 layer to give a freestanding UHMWPE product in tubular form. SEM images of partially and fully sintered forms of this material were taken at 1000x magnification using a ZEISS EVO 40, as shown in Figure 2, respectively. Fig. 7A and 7B shown.

[0088] Embodiment 5:

[0089] A 0.109" OD PTFE mandrel was dip coated with Dispersion F at 50°C and then the solvent was devolatilized at 130°C. The partially sintered tube was again dip coated with Dispersion F at 50°C and then subjected to another round of solvent devolatilization at 130°C. The coated tube was then sintered on the core at 160°C and quenched in cold water. The core was then stretched as described above and the coating (in tubular form) removed from the core without deforming or damaging the layer to yield a freestanding product in tubular form.

[0090] Embodiment 6:

[0091] A 0.109" OD PTFE mandrel was dip coated with Dispersion G at 50°C and then the solvent was devolatilized at 150°C. The partially sintered tube was dip coated again with Dispersion G at 50°C and then subjected to another round of devolatilization of the solvent at 150°C. The coated tube was then sintered on the 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 layer to give a freestanding UHMWPE product in tubular form.

[0092] Embodiment 7:

[0093] A 0.109" OD PTFE mandrel was dip coated with Dispersion C at 80°C, followed by devolatilization of the solvent at 170°C. The partially sintered tube was again dip coated with Dispersion E at 50°C, followed by another round of devolatilization of the solvent at 170°C. The coated tube was then sintered on 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 layer to yield a freestanding UHMWPE product in tubular form.

[0094] Embodiment 8:

[0095] A 0.109" OD PTFE mandrel was dip coated with dispersion D at 80°C and the solvent was then devolatilized at 170°C. The coated tube was then sintered on the core at 200°C and quenched in cold water. The core was then stretched as described above and the coating removed from the core (in tubular form) without deforming or damaging the layer to yield a freestanding UHMWPE product in tubular form.

[0096] Embodiment 9:

[0097] A 0.109" OD PTFE mandrel was dip coated with Dispersion B at 80°C and then the solvent was devolatilized at 170°C. The partially sintered tube was dip coated again with Dispersion B at 80°C and then subjected to another round of solvent devolatilization at 170°C. The coated tube was then sintered on 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 layer to yield a freestanding UHMWPE product in tubular form.

[0098] Embodiment 10:

[0099] A 0.060" OD silver-plated copper (SPC) mandrel was dip coated with Dispersion B at 80°C and then the solvent was devolatilized at 170°C. The partially sintered tube was dip coated again with Dispersion B at 80°C and then subjected to another round of solvent devolatilization at 170°C. The coated tube was then sintered on a core at 200°C. Due to the affinity of polyethylene to metal, it was difficult to separate the UHMWPE tube from the SPC mandrel without damaging the tubular form.

[0100] Embodiment 11:

[0101] A 0.088" OD textured glass-filled PTFE mandrel was dip coated with Dispersion B at 80°C, followed by devolatilization of the solvent at 170°C. The partially sintered tube was dip coated again with Dispersion B at 80°C, followed by another round of devolatilization of the solvent at 170°C. The coated tube was then sintered on 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 layer to yield a freestanding UHMWPE product in tubular form.

[0102] Embodiment 12:

[0103] A 0.109" OD PTFE mandrel was dip coated with Dispersion C at 80°C and then the solvent was devolatilized at 170°C. The partially sintered tube was dip coated again with Dispersion C at 80°C and then subjected to another round of solvent devolatilization at 170°C. The coated tube was then sintered on a core at 200°C and quenched in cold water. The core was then stretched as described above and the coating (in tubular form) removed from the core without deforming or damaging the layer to yield a freestanding UHMWPE product in tubular form.

[0104] Embodiment 13:

[0105] The UHMWPE tube of Example 12 was stretched by about 300% at 120°C to improve axial orientation and mechanical properties.

[0106] Embodiment 14:

[0107] A 0.125" OD PTFE mandrel was dip coated with Dispersion C at 80°C in a continuous process, followed by devolatilization of the solvent at 170°C. The partially sintered tube was again dip coated with Dispersion C at 80°C, followed by another round of devolatilization of the solvent at 170°C. The coated tube was then sintered on a 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 layer to yield a freestanding UHMWPE product in tubular form. Approximately 50 feet of the mandrel was coated with the dispersion.

[0108] Table 1. List of dispersions and their components

[0109]

[0110] EVA was used to demonstrate that a bonding resin could be added to the dispersion, or that a multilayer coating could be formed where one layer was UHMWPE and another layer was EVA.

[0111] Table 2. Dimensions and mechanical properties

[0112]

[0113] With the benefit of the teachings of the foregoing description, those skilled in the art will appreciate many changes and other embodiments of the present invention. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, and changes and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used only in a general and descriptive sense, not for limiting purposes.

Claims

1. A pipe comprising ultra high molecular weight polyethylene (UHMWPE), the pipe exhibiting: a. 0.004” or less average wall thickness; and b. a tensile stress at break greater than 6 MPa; and c. Storage modulus greater than 20 MPa at 37°C.

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

3. The pipe according to claim 1, further comprising HDPE and / or LDPE in an amount less than about 50 wt. %, based on the total weight of the pipe.

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

5. The tube of claim 1, wherein the tube is free of solvent.

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

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

8. The tube of claim 1, wherein the tube has a wear resistant inner surface.

9. The tube of claim 1, wherein the tube has a lubricated inner surface with a coefficient of friction less than 0.

2.

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

11. A coated core according to claim 10, wherein both the core and the UHMWPE layer are substantially cylindrical in shape.

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

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

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

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

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

17. The pipe according to claim 16, wherein the dispersion further comprises one or more other modified polyethylene resins.

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

19. The tube of claim 16, wherein the dip coating is performed at a temperature of about 20°C to about 100°C.

20. A method of making a pipe comprising UHMWPE comprising dip coating a core in a dispersion comprising UHMWPE resin and d-limonene, wherein the dispersion has a dynamic viscosity of less than 3000 cP at 110°C.

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