PTFE liner with reduced coefficient of friction

Abstract

To provide an extruded PTFE composite tube with a reduced coefficient of friction (COF).SOLUTION: There is provided a PTFE composite tube. An extruded PTFE composite tube may exhibit reduction of a change in coefficient of friction between about 20°C and about 40°C by obtaining an inclusion of a secondary polymeric particle with a small particle size (less than 100 μm) at a loading percentage of less than about 50 wt.%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application generally relates to the field of poly(tetrafluoroethylene) (PTFE) liners and products comprising such PTFE liners.

Background Art

[0002] Poly(tetrafluoroethylene) (PTFE) resin is used in a paste extrusion process for manufacturing products such as sheets, profiles, monofilaments, and tubes. Paste extrusion of PTFE generally involves several steps including (1) preparation of the paste, i.e., mixing of the resin and lubricant, (2) preforming, (3) paste extrusion through one or more die heads, and (4) removal of volatiles. PTFE is commonly used as an inner liner of catheters, for example, due to its chemical resistance, biocompatibility, and low coefficient of friction (COF). PTFE exhibits unique properties not found in other polymers in this field. Due to the low COF associated with PTFE materials, use of PTFE materials can provide a tube having an inner diameter through which various catheter technologies such as stents, balloons, atherectomy devices or thrombectomy devices can be easily pushed through a small-diameter catheter lumen. The effect of increasing the lubricity of the catheter inner diameter is to reduce the deployment force of the catheter device as it passes through the lumen, enhancing the likelihood of success of procedures using such devices. During typical medical procedures, the difference between the operating room temperature (between 65°F and 75°F, i.e., in the range of 18°C to 24°C) and body temperature (98.6°F, i.e., 37°C) can cause significant changes in the properties of the materials of medical members, particularly PTFE members such as catheter liners. Since PTFE has significant thermal transitions at approximately 19°C and 30°C, the modulus of elasticity changes greatly near the operating room temperature, and the overall COF of the PTFE-based materials used can depend on the modulus of elasticity of the material. These thermal transitions affect the physical properties in a way that is detrimental to the performance of the PTFE liner within the catheter during minimally invasive medical procedures where the liner is exposed to temperatures that vary from less than 20°C to about 40°C.

[0003] There is a desire to provide a method for reducing the coefficient of friction (COF) of extruded polymer films, profiles, and tubes composed of PTFE and improving the lubricity of such extruded polymer films, profiles, and tubes used in various catheter technologies. It has been previously studied in the art to add certain fillers such as glass particles, polyarylene particles, and polyimide polymer particles to PTFE materials using a paste extrusion process to improve the wear resistance and creep resistance of such composite PTFE materials. Various methods known in the art involve obtaining thick-walled (e.g., wall thickness of about 10 mm) composite tubes having improved wear resistance and / or creep resistance by thermoplastic processing, paste extrusion, and molding of polymer particles. However, it has been found that current methods of adding polymer-based fillers or particles to PTFE sheets, profiles, and tubes have little effect on the COF of the resulting PTFE composite materials and extrudates formed using such methods. It is considered advantageous to provide a further method for preparing PTFE-based products using a paste extrusion process such that the resulting products exhibit practical COF characteristics. SUMMARY OF THE INVENTION

[0004] The present disclosure provides composite PTFE materials (e.g., in the form of sheets, profiles, tubes, etc.) having a reduced coefficient of friction (COF) compared to corresponding PTFE products (not the composite materials described herein). The composite PTFE tubes provided herein can exhibit a significant reduction in COF relative to equivalent PTFE tubes and can exhibit a lower storage modulus compared to equivalent PTFE tubes and can be in the form of thin-walled tubes having a wall thickness of less than about 0.1 mm, for example. Further, the present disclosure provides a method for obtaining such thin-walled composite PTFE tubes having a reduced COF and storage modulus compared to equivalent PTFE tubes, as well as methods of using such thin-walled composite PTFE tubes.

[0005] In one aspect, the present disclosure provides a PTFE composite tube having a reduced coefficient of friction and / or a lower storage modulus as compared to an equivalent virgin PTFE tube. In some embodiments, for example, the PTFE composite tube according to the present disclosure may include PTFE and a second polymer. In such embodiments, the second polymer may be present at a concentration of less than about 50 wt% of the PTFE composite tube. In certain embodiments, the concentration of the second polymer is less than 10 wt% of the PTFE composite tube. The PTFE composite tube according to the present disclosure may exhibit one or more beneficial properties when compared to a virgin PTFE tube. Such properties include, but are not limited to, a lower coefficient of friction when tested at 23° C. as compared to an equivalent PTFE tube and / or a smaller change in the coefficient of friction from about 23° C. to about 40° C. as compared to an equivalent PTFE tube.

[0006] In one or more embodiments, the PTFE composite tube according to the present disclosure may exhibit a coefficient of friction of about 0.07 or less at 23° C. and an increase in the coefficient of friction of about 0.02 or less from about 23° C. to about 40° C. In certain embodiments, the PTFE composite tube exhibits a lower storage modulus at 20° C. as compared to a PTFE tube and a decreased change in the storage modulus between 20° C. and 40° C. as compared to a PTFE tube. In some embodiments, the PTFE composite tube according to the present disclosure has a storage modulus of about 15×10 8 Pa or less at 20° C. and a decrease in the storage modulus of about 7.5×10 8 Pa or less from about 20° C. to about 40° C.

[0007] Generally, the PTFE composite tube according to the present disclosure may include a second polymer different from PTFE. For example, in some embodiments, the second polymer is a polyolefin or a modified polyolefin. In some embodiments, the second polymer is a fluoropolymer or a modified fluoropolymer. In some embodiments, the second polymer is a polyarylene ketone (PAEK), a polyether ether ketone (PEEK), or a modified PAEK or modified PEEK. In certain specific embodiments, the second polymer is a polyester or a modified polyester, or a polyurethane or a modified polyurethane. In some embodiments, the second polymer is a polyimide, a polyamide, a polyamine, or a copolymer thereof. In some embodiments, the second polymer may be in the form of a plurality of particles or in the form of a powder, and these particles may have a certain particle size. In some embodiments, for example, the second polymer may be in the form of a plurality of polymer particles having an average particle size of less than about 100 microns.

[0008] In one or more embodiments, the second polymer in the PTFE composite tube is a second different PTFE selected from the group consisting of sintered PTFE, ground recycled PTFE, different grades of PTFE, chemically modified PTFE, and combinations thereof. In still other embodiments, the second polymer may be selected from the group consisting of polyarylene ether ketone (PAEK), modified polyarylene ether ketone (modified PAEK), polyether ether ketone (PEEK), modified polyether ether ketone (modified PEEK), polyimide (PI), ultra-high molecular weight polyethylene (UHMWPE), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), and any combination or copolymer of two or more of them.

[0009] In some embodiments, the PTFE composite tube according to the present disclosure has a wall thickness of less than about 0.1 mm. As described herein, in some embodiments, the PTFE composite tube according to the present disclosure may exhibit certain beneficial properties or characteristics when compared to equivalent PTFE tubes. Typically, the equivalent PTFE tubes described herein may be unfilled filler PTFE tubes or virgin PTFE tubes.

[0010] Some aspects of the present disclosure provide a medical device comprising a PTFE composite tube prepared according to one or more embodiments of the present disclosure. For example, the medical device can be a catheter or other catheter technology. In some embodiments, for example, the present disclosure provides a medical device comprising a PTFE composite tube. In such embodiments, the PTFE composite tube can comprise PTFE and a second polymer, wherein the concentration of the second polymer is less than about 50 wt% of the PTFE composite tube. In such embodiments, the PTFE composite tube and / or the medical device can exhibit one or both of a lower storage modulus at 20°C compared to a PTFE tube and a reduced change in storage modulus between 20°C and 40°C compared to a PTFE tube.

[0011] The present disclosure includes, but is not limited to, the following embodiments.

[0012] Embodiment 1: A PTFE composite tube comprising PTFE and a second polymer, wherein the second polymer is present at a concentration of less than about 50 wt% of the PTFE composite tube, and wherein the PTFE composite tube exhibits one or both of a lower coefficient of friction and a smaller change in coefficient of friction between about 23°C and about 40°C compared to an equivalent PTFE tube when tested at 23°C.

[0013] Embodiment 2: The PTFE composite tube according to Embodiment 1, wherein the concentration of the second polymer is less than 10 wt% of the PTFE composite tube.

[0014] Embodiment 3: The PTFE composite tube is the PTFE composite tube according to Embodiment 1 or 2, showing a coefficient of friction of about 0.07 or less at 23°C and an increase in the coefficient of friction of about 0.02 or less from about 23°C to about 40°C.

[0015] Embodiment 4: The PTFE composite tube is the PTFE composite tube according to any one of Embodiments 1 to 3, showing a lower storage modulus at 20°C compared to the PTFE tube and a change in the storage modulus between 20°C and 40°C that is decreased compared to the PTFE tube.

[0016] Embodiment 5: The PTFE composite tube is the PTFE composite tube according to any one of Embodiments 1 to 4, showing a storage modulus of about 15×10 8 Pa or less at 20°C and a decrease in the storage modulus of about 7.5×10 8 Pa or less from about 20°C to about 40°C.

[0017] Embodiment 6: The second polymer is a polyolefin or a modified polyolefin in the PTFE composite tube according to any one of Embodiments 1 to 5.

[0018] Embodiment 7: The second polymer is a fluoropolymer or a modified fluoropolymer in the PTFE composite tube according to any one of Embodiments 1 to 6.

[0019] Embodiment 8: The second polymer is a polyarylene ketone (PAEK), a polyether ether ketone (PEEK), or a modified PAEK or modified PEEK in the PTFE composite tube according to any one of Embodiments 1 to 7.

[0020] Embodiment 9: The second polymer is a polyester or a modified polyester in the PTFE composite tube according to any one of Embodiments 1 to 8.

[0021] Embodiment 10: The PTFE composite tube according to any one of Embodiments 1 to 9, wherein the second polymer is polyurethane or modified polyurethane.

[0022] Embodiment 11: The PTFE composite tube according to any one of Embodiments 1 to 10, wherein the second polymer is polyimide, polyamide, polyamine, or a copolymer thereof.

[0023] Embodiment 12: The PTFE composite tube according to any one of Embodiments 1 to 11, wherein the second polymer is in the form of a plurality of polymer particles having an average particle size of less than about 100 microns.

[0024] Embodiment 13: The PTFE composite tube according to any one of Embodiments 1 to 12, wherein the second polymer is a second different PTFE selected from the group consisting of sintered PTFE, ground recycled PTFE, different grades of PTFE, chemically modified PTFE, and combinations thereof.

[0025] Embodiment 14: The PTFE composite tube according to any one of Embodiments 1 to 13, wherein the second polymer is selected from the group consisting of polyaryletherketone (PAEK), modified polyaryletherketone (modified PAEK), polyetheretherketone (PEEK), modified polyetheretherketone (modified PEEK), polyimide (PI), ultra-high molecular weight polyethylene (UHMWPE), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), and combinations or copolymers of any two or more thereof.

[0026] Embodiment 15: The PTFE composite tube according to any one of Embodiments 1 to 14, wherein the PTFE composite tube has a wall thickness of less than about 0.1 mm.

[0027] Embodiment 16: The PTFE composite tube according to any one of Embodiments 1 to 15, wherein the equivalent PTFE tube is an unfilled PTFE tube.

[0028] Embodiment 17: The equivalent PTFE tube is the PTFE composite tube according to any one of Embodiments 1 to 16, which is a virgin PTFE tube.

[0029] Embodiment 18: A medical device comprising the PTFE composite tube according to any one of Embodiments 1 to 17.

[0030] Embodiment 19: The medical device according to Embodiment 18, wherein the medical device is a catheter.

[0031] Embodiment 20: A PTFE composite tube comprising PTFE and a second polymer, wherein the second polymer is present at a concentration of less than about 50% by weight of the PTFE composite tube, and the PTFE composite tube exhibits one or both of a lower storage modulus at 20°C compared to a PTFE tube and a smaller change in storage modulus at 20°C to 40°C compared to a PTFE tube.

[0032] Embodiment 21: The PTFE composite tube according to Embodiment 20, having a storage modulus of about 15×10 8 Pa or less at 20°C and a decrease in storage modulus of about 7.5×10 8 Pa or less from about 20°C to about 40°C.

[0033] Embodiment 22: A medical device comprising a PTFE composite tube, wherein the PTFE composite tube comprises PTFE and a second polymer, the concentration of the second polymer is less than about 50% by weight of the PTFE composite tube, and the PTFE composite tube exhibits one or both of a lower storage modulus at 20°C compared to a PTFE tube and a decreased change in storage modulus at 20°C to 40°C compared to a PTFE tube.

[0034] These and other features, aspects, and advantages of the present disclosure may become apparent by reading the following detailed description in conjunction with the accompanying drawings described briefly below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, and any combination of two, three, four, or more features or elements described in the specific embodiments herein, regardless of whether such features or elements are specifically identified and combined in the description of the embodiments. The present disclosure is intended to be read comprehensively, and thus any separable feature or element of the present invention disclosed, unless explicitly stated in the context, is intended to be combinable in any of its various aspects and embodiments. Other aspects and advantages of the present invention will become apparent hereinafter.

[0035] To understand the embodiments of the present invention, reference is made to the accompanying drawings. These are not necessarily drawn to scale, and in the drawings, reference numerals represent components of exemplary embodiments of the present invention. The drawings are merely illustrative and are not to be construed as limiting the present invention.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0037] Here, the present invention will be described in more detail below. However, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments shown herein. Rather, these embodiments are provided to make the present disclosure thorough and complete and to fully convey the scope of the invention to those skilled in the art. As used in this specification and the claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0038] The present disclosure provides PTFE composite tubes (including, for example, PTFE and one or more additional polymers), such as extruded PTFE composite tubes. The PTFE composite tubes provided herein are at least partially characterized by a reduced coefficient of friction (COF) compared to equivalent PTFE tubes and a lower storage modulus compared to equivalent PTFE tubes. In some embodiments, the PTFE composite tubes provided herein can be at least partially characterized as "thin-walled" tubes having a wall thickness of, for example, less than about 0.1 mm. As used herein, "equivalent PTFE tube" refers to a tube having the same size, shape, and wall thickness as the PTFE composite tubes described herein but containing no second polymer therein. For example, an equivalent PTFE tube can be characterized as consisting essentially of virgin PTFE containing no fillers. Also provided herein are methods of providing PTFE composite tubes, as well as methods of using such PTFE composite tubes and products comprising such PTFE composite tubes.

[0039] A general schematic diagram of one non-limiting embodiment of a method based on paste extrusion for manufacturing a PTFE composite tube, for example, a PTFE composite tube exhibiting the physical properties described hereinabove, is shown in FIG. 1. As shown in FIG. 1, one method for preparing a PTFE composite tube according to the present disclosure includes preparing a PTFE composite material 12, subjecting the PTFE composite material to a compression / compounding step 14 to produce a preform, subjecting the preform to an extrusion process 16, for example, by a paste extrusion apparatus, and forming a film, tube, or rod by sintering 20 of the extrudate, thereby incorporating a second polymer into the extruded product (e.g., film, tube, rod, etc.) to produce a PTFE composite extrudate (e.g., a PTFE composite tube). In FIG. 1, method 10 is shown as also including a further step 22 of performing a secondary process on the PTFE composite extrudate, which step is optional, as will be discussed in more detail hereinafter in this specification.

[0040] In one or more embodiments, a method 10 of preparing a PTFE composite tube begins with the preparation 12 of a PTFE composite material by mixing a PTFE resin, a second polymer, and a lubricant or an organic solvent. As used herein, "PTFE resin" generally refers to polytetrafluoroethylene ("PTFE") or a synthetic fluoropolymer of tetrafluoroethylene called virgin PTFE because it is not chemically modified. A fine powder PTFE resin suitable for a paste extrusion process can be extruded, for example, at a reduction ratio exceeding 300. Exemplary resins suitable for this purpose include, but are not limited to, Daikin's F205 resin, F201 resin, F201L resin, F208 resin, and F207 resin, Dyneon's TF 2071 resin, TF 2072 resin, and TF 2053 resin, Chemours' Teflon 640XT X, 641XT X, CFP 6000 X, 62XT X, 6C X, and 6CN X, and Asahi Glass's CD 090E and CD 097E. It should be understood that the products and methods described herein are not limited to such resins and that any PTFE resin can be reasonably used within the scope of the present disclosure. Although the present disclosure refers herein, for example, to "PTFE" resins and "PTFE tubes", it should be noted that these materials may not contain 100% PTFE but are still encompassed by the present disclosure. For example, PTFE resins commonly used in paste extrusion can be homopolymers or non-homopolymers (for example, modified resins containing a small amount of comonomer are commonly used because they have a lower transition temperature), and all such resins are intended to be encompassed within the scope of the present disclosure.

[0041] Examples of suitable lubricants and organic solvents include, but are not limited to, Isopar (C, E, G, H, J, K, L, M, N, P, V), Novec (7100, 7200, 7300, 7500, 7700), naphtha, Shell Sol 340 HT, Shell Sol 142 HT, Mineral Spirit 200 HT, methyl nonafluorobutyl ether, methyl nonafluoro-2-butyl ether, ethyl nonafluorobutyl ether, ethyl nonafluoro-2-butyl ether, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane, 2-trifluoromethyl-3-ethoxidedodecafluorohexane, 2,3,3,4,4-pentafluorotetrahydro-5-methoxy-2,5-bis[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]-furan, perfluorooctane, perfluoro(2-butyltetrahydrofuran), perfluorotributylamine, 1,1,2,2,3,3,4,4,4-nonafluoro-N,N-bis(nonafluorobutyl)butane-1-amine, perfluoro N-alkylmorpholine (C5-18), 3M's Fluorinert (FC-770, FC-3283, FC-40, FC-43, FC-70, FC-75, FC-77), and combinations thereof, include.

[0042] Generally, the amount of lubricant or organic solvent blended with PTFE resin and the second polymer can vary widely. For example, in some embodiments, the lubricant or organic solvent is present in the mixture of PTFE, the second polymer, and the lubricant (referred to herein as "PTFE composite material") in an amount between about 25% by volume and about 55% by volume, about 30% by volume and about 50% by volume, or about 35% by volume and about 45% by volume, based on the total volume of the PTFE composite. Without intending to be bound by theory, it should be noted that the content of the lubricant / organic solvent should be kept as low as possible (while achieving the desired lubricating effect) to minimize the amount of lubricant / organic solvent that has to be removed in the subsequent devolatilization step discussed in more detail herein. Similarly, it should be noted that an increase in the amount of lubricant / organic solvent in the PTFE composite material can help maintain the pressure of the extruder within reasonable / maximum limits during the extrusion process. For example, the use of lubricant / organic solvent in the PTFE composite material can affect the wettability / surface tension and viscosity of the PTFE composite material and thus can be varied to have a desirable effect on the pressure during the extrusion process.

[0043] The second polymer can vary widely and can include one or more types of polymers. Certain non-limiting examples of suitable second polymers include, but are not limited to, polyolefins, modified polyolefins, fluoropolymers, modified fluoropolymers, polyesters, modified polyesters, polyurethanes, modified polyurethanes, polyimides, polyamides, polyamines, and various derivatives, combinations, and copolymers thereof. In some embodiments, the second polymer can include a modified or unmodified polyaryletherketone (PAEK), or a modified or unmodified polyetheretherketone (PEEK). In some embodiments, the second polymer can include a polyimide (PI), ultra-high molecular weight polyethylene (UHMWPE), fluorinated ethylene propylene (FEP), or perfluoroalkoxy alkane (PFA).

[0044] In some embodiments, a second PTFE that is somehow different from the PTFE resin component can be used as the second polymer. For example, in some embodiments, the second polymer includes sintered PTFE, ground recycled PTFE (e.g., ground after extrusion to obtain it in particulate form, such as powder form), PTFE chemically modified in some way, or PTFE corresponding to two or more of these classifications. Examples of chemical modification to PTFE or other polymers include, but are not limited to, grafting, oxidation, defluorination, etching, plasma treatment, and irradiation.

[0045] The second polymer generally exists in the form of a plurality of polymer particles, for example, as a finely ground powder of a plurality of polymer particles. It is advantageous to introduce the second polymer (e.g., the polymer particles of the second polymer) to incorporate a desired percentage of the second polymer in the resulting preform and the final PTFE composite tube. In such embodiments, those polymer particles can have a particle size of less than about 150 microns, less than about 100 microns, or less than about 50 microns. In some embodiments, the polymer particles can have a particle size in the range of about 1 micron to about 150 microns, about 1 micron to about 100 microns, or about 1 micron to about 50 microns. In some embodiments, the second polymer / polymer particles can be present in an amount of less than about 50 wt%, less than about 40 wt%, less than about 30 wt%, less than about 20 wt%, or less than about 10 wt% based on the total weight of the PTFE composite tube. In some embodiments, the second polymer / polymer particles can be present in an amount of about 1 wt% to about 50 wt%, about 1 wt% to about 25 wt%, or about 1 wt% to about 10 wt% based on the total weight of the PTFE composite tube.

[0046] The order of mixing the various components of the PTFE composite is not intended to be limiting, and the individual components of the PTFE composite material can be combined and mixed in any desired order. For example, in certain embodiments, the second polymer can be blended with the PTFE resin either before or after the addition of the lubricant or organic solvent. Subsequently, the mixture of the PTFE resin, the second polymer, and the lubricant or organic solvent can be mixed using, for example, a low shear blending mixer. It should be noted that since the PTFE resin is susceptible to the influence of shear, it is important to be careful when mixing the components of the PTFE composite material. For example, in some embodiments, the lubricant or organic solvent is added prior to mixing to ensure uniform mixing of the PTFE composite material.

[0047] For example, if a PTFE composite material is provided in accordance with step 12 described herein, this material is subjected to a compression / compounding step 14 to produce a preform. Any method known in the art can be used to compound or compress the PTFE composite material, and it is not intended to be particularly limited. For example, in some embodiments, a compressor can be used to compound the PTFE composite material to obtain a compounded PTFE composite material suitable for extrusion in operation 16. Generally, in order to prevent defects in the extrudate, it may be beneficial to remove at least some of the air from the compounded PTFE composite material prior to extrusion. For example, such air removal is achieved by preforming the PTFE composite material into various shapes (e.g., cylindrical shape) or a preform called a billet, for example, during the compounding process. The billet is typically loaded into the extruder immediately after manufacture to prevent evaporation of the lubricant / organic solvent. In some embodiments, other additives such as pigments, stabilizers, colorants, and / or other fillers can be added to the PTFE composite material during compounding to elicit certain specific properties such as color, radiation opacity, etc.

[0048] After compounding the PTFE composite material, the compounded PTFE composite material is extruded, for example, via a multi-stage extrusion process. The extrusion can generally be carried out, for example, via a paste extrusion process. For example, after subjecting a preform or billet to extrusion 16, for example, by a paste extruder, sintering 20 is performed to form a film, tube, or rod, thereby incorporating the second polymer into the extruded product (for example, film, tube, rod, etc.) and producing a PTFE composite extrudate (for example, a PTFE composite tube). Typically, during the extrusion process, a few percent of molecular chain orientation can be imparted to the extruded product (for example, a PTFE composite tube) based on, for example, the drawdown of the material, which is very similar to other polymer extrusion processes. The orientation imparted to the material can affect tensile properties such as modulus of elasticity, tensile strength, and elongation. Since the melt viscosity of the PTFE resin is very high, typically, a PTFE composite tube cannot be manufactured by melt extrusion, so paste extrusion is a useful approach.

[0049] During the extrusion step 16, the billet can be inserted into the extrusion cylinder / barrel of the paste extruder and then compressed through the die with the assistance of the ram. In some embodiments, the extrusion tube requires the presence of a mandrel within the barrel, and a metal substrate (for example, a wire substrate, etc.) can be supplied through the mandrel. The material of the metal substrate is not particularly limited. For example, the metal substrate can include copper (for example, annealed copper wire, etc.), plated copper (for example, silver-plated copper wire, etc.), nickel, stainless steel, nitinol, etc. Next, the extruded paste material is formed into a tube through the extruder head.

[0050] As referred to herein, the paste extrusion process generally involves extruding the extruded paste material through one or more dies to shape it, and then removing volatiles and sintering the resulting shaped material. In some embodiments, when the extrusion pressure changes during processing, the machine design ensures that the ram speed and extrusion speed are maintained at a constant level. The extruder design, such as the barrel size, extruder size and design, and the operating conditions, such as the barrel zone temperature, ram speed, and throughput, can be adjusted. In some embodiments, such parameters are manipulated to affect the rate and extent of polymer degradation. One of ordinary skill in the art will recognize the considerations associated with selecting appropriate parameters for extrusion, for example, based on the rheology of the polymer resin, to ensure the reliable production of a suitable extrudate.

[0051] After the extrusion step 16, the residual lubricant / organic solvent in the extruded PTFE composite material is removed (advantageously, completely removed) by heating the extruded PTFE composite material above the boiling point of the lubricant / organic solvent. As shown in FIG. 1, this process can be achieved using an evaporation step or a devolatilization step 18. In some embodiments, for example, the extruded PTFE composite material is passed through a devolatilization furnace to heat the extruded PTFE composite material, thereby removing all of the residual lubricant or organic solvent.

[0052] Following the evaporation / volatilization removal step, the extruded PTFE composite material can be subjected to a sintering step 20, as shown, for example, in FIG. 1. For example, the extruded PTFE composite material can be heated in a sintering furnace to sinter the PTFE resin in the extruded PTFE composite material, and thus the PTFE resin particles can be adhered to each other. In some embodiments, the sintering furnace can be set to a temperature above the melting point of PTFE (e.g., approximately 327° C.). However, it should be noted that the temperature in the sintering furnace can vary as desired, based, for example, on the line speed associated with passing the extruded PTFE composite material through the furnace and the thickness of the PTFE composite layer. As described above, any amount of lubricant or organic solvent is typically removed during the evaporation step 18, so generally it is possible to operate the sintering furnace without containing any remaining lubricant or organic solvent therein. It should be noted that the second polymer described herein can generally withstand the sintering temperature during this step without excessive decomposition. The sintered extrudate can be cooled using various known methods. For example, the extrudate can be passively cooled over a specific time using, for example, air, cooled through a water bath at a set temperature, or cooled by the action of a blower or fan.

[0053] After sintering and cooling, the PTFE composite tube can be subjected to one or more secondary processes 22 to impart one or more additional properties and characteristics to the PTFE composite tube. In certain embodiments, the PTFE composite tube can optionally be further processed, for example, by cutting a longer tube to a shorter length for a particular application or end use, if desired. This step is shown as the final step of the process in FIG. 1, but it should be noted that various secondary processes can be performed at other stages of the process (e.g., the tube can be cut to a shorter length before or after sintering). Thus, the order of the steps shown in FIG. 1 is not strictly limited to the order shown therein. Examples of secondary processes include, but are not limited to, drawdown, entrainment, helical cutting, folding, etching, stretching, punching / perforating, spreading, flanging, sealing, imprinting, overmolding, pad printing, scoring, skiving, slitting, tapering, and chipping. Such processes can be performed, for example, as generally known in the art.

[0054] It should be noted that during any step of the extrusion process of the PTFE composite, the extruded PTFE composite can be drawn down or dimensionally reduced by pulling the extrudate at a speed faster than the speed at which it is extruded by the extrusion ram. In some embodiments, the degree of drawdown can be correlated with the amount of orientation imparted to the extrudate, for example, to vary its mechanical properties to desired specifications including, but not limited to, storage modulus, yield stress, ultimate tensile stress, and elongation. The degree and / or amount of drawdown can vary widely as will be understood by those skilled in the art. In some embodiments, for example, the degree of drawdown of the extruded PTFE composite tube can be at least about 5 times its original length, at least about 10 times its original length, at least about 15 times its original length, at least about 20 times its original length, at least about 25 times its original length, or at least about 30 times its original length.

[0055] The PTFE composite tubes obtained from the disclosed process uniquely exhibit a lower coefficient of friction compared to equivalent PTFE tubes and a lower storage modulus compared to equivalent PTFE tubes. In particular, by extruding a PTFE tube containing a second polymer (e.g., in the form of particles) and thus obtaining a PTFE composite tube, a liner for a catheter or a PTFE composite tube used as another application that exhibits particularly advantageous properties, for example, within a temperature range of about 20 °C to about 40 °C, can be provided. For example, the PTFE composite tubes described herein advantageously have the following beneficial properties when compared to equivalent PTFE tubes that are not prepared according to the methods and processes described herein: A lower coefficient of friction compared to equivalent PTFE tubes at 23 °C, A lower change in the coefficient of friction at about 23 °C to about 40 °C compared to equivalent PTFE tubes, A coefficient of friction of about 0.07 or less at 23 °C, An increase in the coefficient of friction of about 0.02 or less at about 23 °C to about 40 °C, A lower storage modulus compared to equivalent PTFE tubes at 20 °C, A decreased change in the storage modulus between 20 °C and 40 °C compared to equivalent PTFE tubes, A storage modulus of about 15×10 8 Pa or less at 20 °C, A reduction in the storage modulus of about 7.5×10 8 Pa or less at about 20 °C to about 40 °C, and can exhibit one or more of the above.

[0056] It should be noted that the change in the coefficient of friction (COF) can be determined based on the following formula (1), and the change in the storage modulus can be determined based on the following formula (2).

[0057] Formula: (1) ΔCOF = COF 40℃ - COF 23℃ (2) ΔE’ = ΔE’ 40℃ - ΔE’20℃

[0058] These and other features of the disclosed PTFE composite tubes are beneficial, for example, in applications that require PTFE-based extruded polymer films, profiles, and improved lubricity of tubes, such as in various catheter technologies and the like. As an example, in one implementation of the embodiments disclosed herein, a reduction in the variation of the elastic modulus is desirable in providing consistency to the feel of a catheter during minimally invasive procedures. Similarly, in one or more implementations of the embodiments disclosed herein, a reduction in the COF is desirable in enhancing the lubricity in a PTFE composite tube that can be used in catheter technology (e.g., functioning as a liner). The effect of increasing the lubricity of a PTFE composite tube when used in catheter-based applications is a reduction in the deployment force of a catheter device when passing through the lumen of the catheter inner diameter, which can, for example, increase the likelihood of success of a procedure. In addition to the specific benefits described herein, it should be noted that PTFE composite tubes with reduced COF (e.g., increased lubricity) and lower variation in elastic modulus can provide benefits when used in a variety of other applications, as will be understood by those skilled in the art.

Examples

[0059] Aspects of the present invention are more fully described by the following examples, which are shown to illustrate certain aspects of the present invention and should not be construed as limiting the present invention.

[0060] Example 1 Two sets of PTFE composite tubes were ram extruded to an outer diameter (OD) of 0.080 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% PEEK based on the total weight of the tubes. This is represented as EX1 (2% PEEK) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% PEEK. This is represented as EX1 (4% PEEK) in Table 1 below. The particle size of the PEEK polymer for both sets of tubes was 10 μm.

[0061] The tensile properties of the PTFE composite tubes were determined using an Instron 5965 dual-column mechanical testing machine running Bluehill 3 (version 3.73.4823) operating software. A pneumatic grip with a smooth surface insert set to a 2-inch gauge length was used, and a 1 kN (224.8 lb f ) load cell was used to conduct the tests at a speed of 20 inches per minute. At least five specimens were tested for each load amount, and the average of the results was reported in Table 1.

[0062] To determine the thermomechanical properties of the PTFE composite tubes, the storage modulus (E’) was obtained using a TA instruments Q800 Dynamic Mechanical Analysis (「DMA」) with a film tensile fixture. A temperature scan was performed from -100 °C to 300 °C with an isothermal hold at -100 °C for 5 minutes. The sample was heated at a constant rate of 3 °C / min while being displaced at a constant amplitude of 15 μm with a fixed frequency of 1 Hz in tensile vibration. An additional temperature scan was performed from -20 °C to 100 °C at 3 °C / min with a fixed frequency of 1 Hz in tensile vibration at a constant amplitude of 15 μm. The obtained DMA data was imported into TA instruments TRIOS software (version 4.3). The average values are listed in Table 1.

[0063] The coefficient of friction (COF) was obtained using a tribometer accessory with a TA Instruments Discovery Hybrid Rheometer (DHR-3) to determine the tribological properties of PTFE tubes. Three tube sections measuring 5 mm × 16.5 mm were prepared by attaching them to three teeth of a half-ring used with a ring-on-plate tribometry fixture. Next, the ring with the sample attached was mounted in a ring-on-plate upper geometry holder and lowered so that the sample contacted a mirror-finished stainless steel plate with a specific axial force. Tribological tests were conducted at room temperature (23 °C) with a sliding speed of 750 μm / s to 7650 μm / s under an axial load of 1 N. Additional tribological tests were conducted at 40 °C with a dwell time of 5 minutes at a sliding speed of 750 μm / s to 7650 μm / s under an axial load of 1 N. The minimum COF over the entire specified range of sliding speeds was calculated by TA Instruments' TRIOS software (version 4.3). At least three samples were tested for each load and temperature. The averages are listed in Table 1.

[0064] Example 2 Two sets of PTFE composite tubes were ram extruded with a wall thickness of 0.002 inches and an OD of 0.080 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% PFA based on the total weight of the tube. This is represented as EX2 (2% PFA) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% PFA. This is represented as EX2 (4% PFA) in Table 1 below. The particle size of the PFA polymer was 30 μm. Tests for each tube were conducted as in Example 1. The averages are reported in Table 1.

[0065] Example 3 Two sets of PTFE composite tubes were ram extruded to an OD of 0.080 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% FEP based on the total weight of the tube. This is represented as EX3(2% FEP) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% FEP. This is represented as EX3(4% FEP) in Table 1 below. The particle size of the FEP polymer was 20 μm. Tests for each tube were conducted as in Example 1. The averages are reported in Table 1.

[0066] Example 4 Two sets of PTFE composite tubes were ram extruded to an OD of 0.080 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% UHMWPE based on the total weight of the tube. This is represented as EX4(2% UHMWPE) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% UHMWPE. This is represented as EX4(4% UHMWPE) in Table 1 below. The particle size of the UHMWPE polymer was 10 μm. Tests for each tube were conducted as in Example 1. The averages are reported in Table 1.

[0067] Example 5 Four sets of PTFE composite tubes were ram extruded to an OD of 0.095 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% PTFE-A based on the total weight of the tube. This is represented as EX5 (2% PTFE-A) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% PTFE-A. This is represented as EX5 (4% PTFE-A) in Table 1 below. The first set of PTFE composite tubes was prepared using 90 wt% PTFE and 10 wt% PTFE-A based on the total weight of the tube. This is represented as EX5 (10% PTFE-A) in Table 1 below. The second set of PTFE composite tubes was prepared using 75 wt% PTFE and 25 wt% PTFE-A. This is represented as EX5 (25% PTFE-A) in Table 1 below. The particle size of the PTFE-A polymer was 5 μm and it was a fully sintered PTFE fine powder. Tests for each tube were conducted as in Example 1. The averages are reported in Table 1.

[0068] Example 6 Two sets of PTFE composite tubes were ram extruded to an OD of 0.095 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% PTFE-B based on the total weight of the tube. This is represented as EX6 (2% PTFE-B) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% PTFE-B. This is represented as EX6 (4% PTFE-B) in Table 1 below. The particle size of the PTFE-B polymer was 38 μm and it was an unsintered PTFE powder. Tests for each tube were conducted as in Example 1. The averages are reported in Table 1.

[0069] Example 7 Two sets of PTFE composite tubes were ram extruded to an OD of 0.100 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% PTFE-C based on the total weight of the tube. This is represented as EX7 (2% PTFE-C) in Table 1 below. The second set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% PTFE-C. This is represented as EX7 (2% PTFE-C) in Table 1 below. The particle size of the PTFE-C polymer was 5 μm and it was a fully sintered chemically modified PTFE fine powder. Tests for each tube were conducted in the same manner as in Example 1. The averages are reported in Table 1.

[0070] Comparative Example 1 Using the procedure of Example 1, a PTFE control tube (e.g., virgin PTFE) was extruded. The PTFE control tube was prepared using 100 wt% virgin PTFE based on the total weight of the tube. This is represented as CE1 (control) in Table 1 below. Tests for this tube were conducted in the same manner as in Example 1. The averages are reported in Table 1. This comparative example is a control tube.

[0071] Comparative Example 2 Two sets of PTFE composite tubes were ram extruded to an OD of 0.080 inches with a wall thickness of 0.002 inches. The first set of PTFE composite tubes was prepared using 98 wt% PTFE and 2 wt% spherical glass based on the total weight of the tube. This is represented as CE2 (2% glass) in Table 1 below. The second set of PTFE composite tubes was prepared using 96 wt% PTFE and 4 wt% PEEK. This is represented as CE2 (4% glass) in Table 1 below. The particle size of the glass filler was 10 μm.

[0072] Tests on each tube were conducted in the same manner as in Example 1. The averages are reported in Table 1. This comparative example provides a clue to understanding why an inorganic filler under the same processing conditions with an equivalent particle size cannot elicit a response similar to that of an organic filler / polymer particle with respect to the parameters of COF and modulus of elasticity.

[0073] Comparative Example 3 A PTFE composite tube was ram extruded to an OD of 0.060 inches with a wall thickness of 0.002 inches. The PTFE composite tube was prepared using 98 wt% PTFE and 4 wt% PEEK based on the total weight of the tube. This is represented as CE3(4% PEEK-LDD) in Table 1 below. The particle size of the PEEK polymer was 10 μm. This extrusion deviated from Example 1 in that the process parameters of this extrusion showed a significantly lower drawdown (an approximate 23% reduction in drawdown), causing a reduction in the machine direction / axial orientation of the PTFE tube.

[0074] Tests on each tube were conducted in the same manner as in Example 1. The averages are reported in Table 1 as "4% PEEK-LDD". This comparative example provides a clue to understanding why different processing of the same PTFE / PEEK formulation would result in different responses with respect to the parameters of COF and modulus of elasticity.

[0075]

Table 1

[0076] Summary of the Drawings Figure 2 shows a plot of the COF versus the sliding speed for a PTFE composite tube (e.g., containing 98% PTFE and 2% PFA by weight) prepared according to Example 2 above, compared to a control tube (e.g., containing 100% virgin PTFE by weight) prepared according to Comparative Example 1 above. As shown in Figure 2, the PTFE composite tube prepared according to Example 2 showed a significantly lower COF compared to the control tube, regardless of the sliding speed.

[0077] Figure 3 shows a plot of the COF versus the sliding speed for a PTFE composite tube (e.g., containing 96 wt% PTFE and 4 wt% UHMWPE by weight) prepared according to Example 4 above at 23 °C and 40 °C, respectively. As shown in Figure 3, the COF of the samples remained substantially the same at both temperatures regardless of the sliding speed, so the observed COF of both samples was not significantly affected by the change in temperature.

[0078] Figure 4 shows a plot of the storage modulus (E’) versus the temperature for a PTFE composite tube (e.g., containing 96% PTFE and 4% PEEK by weight) prepared according to Example 1 above, compared to a control tube (e.g., containing 100% virgin PTFE by weight) prepared according to Comparative Example 1 above. As shown in Figure 4, the PTFE composite tube prepared according to Example 1 showed a significantly lower storage modulus compared to the control tube, regardless of the temperature.

[0079] Many variations and other embodiments of the present invention will occur to those skilled in the art of the technology related to the present invention, which have the benefit of the teachings presented in the above description. Therefore, it is to be understood that the present invention is not limited to the specific embodiments disclosed, and that variations and other embodiments are intended to be included within the scope of the appended claims. Specific terms are used in this specification, but they are used for general and descriptive meanings only, not for purposes of limitation.

Claims

1. A PTFE composite tube comprising PTFE and a second polymer, the second polymer is present in a concentration of less than about 50% by weight of the PTFE composite tube; and The PTFE composite tube is A lower coefficient of friction compared to a comparable PTFE tube when tested at 23°C; and A smaller change in coefficient of friction from about 23° C. to about 40° C. compared to a comparable PTFE tube; 1. A PTFE composite tube exhibiting one or both of the following:

2. 10. The PTFE composite tube of claim 1, wherein the concentration of the second polymer is less than 10% by weight of the PTFE composite tube.

3. 10. The PTFE composite tube of claim 1, wherein the PTFE composite tube exhibits a coefficient of friction of about 0.07 or less at 23°C, and an increase in coefficient of friction of about 0.02 or less from about 23°C to about 40°C.

4. 2. The PTFE composite tube of claim 1, wherein the PTFE composite tube exhibits a lower storage modulus at 20° C. compared to a PTFE tube, and a reduced change in storage modulus between 20° C. and 40° C. compared to a PTFE tube.

5. The PTFE composite tube has a viscosity of about 15×10 at 20° C. ８ A storage modulus of about 7.5×10 Pa or less at about 20° C. to about 40° C. ８ 2. The PTFE composite tube of claim 1, which exhibits a reduction in storage modulus of less than 10 Pa.

6. The PTFE composite tube of claim 1 , wherein the second polymer is a polyolefin or a modified polyolefin.

7. The PTFE composite tube of claim 1 , wherein the second polymer is a fluoropolymer or a modified fluoropolymer.

8. 2. The PTFE composite tube of claim 1, wherein the second polymer is a polyarylketone (PAEK), a polyetheretherketone (PEEK), or a modified PAEK or PEEK.

9. The PTFE composite tube of claim 1 , wherein the second polymer is a polyester or a modified polyester.

10. The PTFE composite tube of claim 1 , wherein the second polymer is a polyurethane or a modified polyurethane.

11. 10. The PTFE composite tube of claim 1, wherein the second polymer is a polyimide, a polyamide, a polyamine, or a copolymer thereof.

12. 10. The PTFE composite tube of claim 1, wherein the second polymer is in the form of a plurality of polymer particles having an average particle size of less than about 100 microns.

13. 10. The PTFE composite tube of claim 1, wherein the second polymer is a second different PTFE selected from the group consisting of sintered PTFE, regrind PTFE, different grades of PTFE, chemically modified PTFE, and combinations thereof.

14. 2. The PTFE composite tube of claim 1, wherein the second polymer is selected from the group consisting of polyaryletherketone (PAEK), modified polyaryletherketone (modified PAEK), polyetheretherketone (PEEK), modified polyetheretherketone (modified PEEK), polyimide (PI), ultra-high molecular weight polyethylene (UHMWPE), fluorinated ethylene propylene (FEP), perfluoroalkoxyalkane (PFA), and combinations or copolymers of any two or more thereof.

15. 10. The PTFE composite tube of claim 1, wherein the PTFE composite tube has a wall thickness of less than about 0.1 mm.

16. 2. The PTFE composite tube of claim 1, wherein the equivalent PTFE tube is an unfilled PTFE tube.

17. 2. The PTFE composite tube of claim 1, wherein the equivalent PTFE tube is a virgin PTFE tube.

18. A medical device comprising the PTFE composite tube of any one of claims 1 to 17.

19. The medical device of claim 18 , wherein the medical device is a catheter.

20. A PTFE composite tube comprising PTFE and a second polymer, the second polymer is present in a concentration of less than about 50% by weight of the PTFE composite tube; and The PTFE composite tube is A lower storage modulus compared to a comparable PTFE tube at 20° C., and Smaller change in storage modulus from 20°C to 40°C compared to comparable PTFE tubing; 1. A PTFE composite tube exhibiting one or both of the following:

21. The PTFE composite tube has a viscosity of about 15×10 at 20° C. ８ A storage modulus of about 7.5×10 Pa or less at about 20° C. to about 40° C. ８ 21. The PTFE composite tube of claim 20, which exhibits a reduction in storage modulus of less than 1 Pa.

22. 1. A medical device comprising a PTFE composite tube, The PTFE composite tube is a composite PTFE tube having a second polymer, the second polymer being present in a concentration of less than about 50% by weight of the composite PTFE tube; A lower storage modulus compared to a comparable PTFE tube at 20° C., and Reduced change in storage modulus from 20°C to 40°C compared to comparable PTFE tubing; A medical device comprising:

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