Catheter comprising PTFE liner

Abstract

To provide catheters comprising polytetrafluoroethylene (PTFE) tubes with advantageous combinations of strength, flexibility, and size.SOLUTION: The present disclosure provides catheters comprising polytetrafluoroethylene (PTFE) tubes. Such tubes can exhibit features including an average wall thickness of 0.001 inch or less, a tensile stress at break of greater than 5000 psi, and a storage modulus of less than 100,000 psi at all temperatures between 21°C and 37°C, inclusive of 21°C and 37°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This application relates generally to the field of catheters having thin-walled catheter liners comprising poly(tetrafluoroethylene) (PTFE) and methods relating to such catheters. [Background technology]

[0002] Vascular treatments employ minimally invasive catheter-based procedures, specialized instruments, and techniques. Catheters used in these procedures generally use a coating or liner on the inner wall to provide a smooth inner surface. The smooth inner diameter (ID) associated with these devices is beneficial for various catheter techniques such as stents, balloons, atherectomy or thrombectomy devices to reduce friction as they are pushed into the tight confines of the catheter lumen. If the catheter ID does not have sufficient lubricity, devices such as stents may cause damage to the liner as they are pushed through the catheter lumen. The effect of increased lubricity of the catheter ID is a reduction in the deployment force of the catheter device as it passes through the lumen, increasing the likelihood of a successful procedure. The mechanical properties of the catheter liner are also crucial. For example, high tensile and yield strengths may be required when certain devices (e.g., shunt tubing, embolization, aneurysm bridging, scaffolding, and thrombectomy devices) are passed through the catheter in a compressed state. The compressed shape creates an outward radial force that creates friction with the ID, generally making delivery of the device therethrough difficult. On the other hand, high liner flexibility is often desirable when the catheter must pass through vasculature with sharp twists and turns (e.g., cerebral vasculature and below the knee (BTK) applications), in which a highly flexible liner with moderate tensile strength is often more desirable than a high tensile liner with low flexibility / high stiffness.

[0003] For example, various materials have been pursued as an inner wall (base liner) material for use in such catheter devices. One material under consideration is polytetrafluoroethylene (PTFE). PTFE is beneficial because it has many beneficial properties including excellent chemical resistance, high temperature resistance, biocompatibility, and very low coefficient of friction / high lubricity.

[0004] Known PTFE-based materials for use within catheter applications have various drawbacks. For example, certain extruded PTFE tubes can be manufactured with sufficiently thin walls and sufficiently high tensile strength, but exhibit high stiffness and high tensile modulus values, making them unsuitable, for example, in applications where flexibility is important. See, for example, U.S. Pat. No. 5,399,363. Similarly, improved extruded PTFE tubes have been reported to have high tensile strength but undesirable stiffness due to the method by which the high tensile strength is obtained. See, for example, U.S. Pat. No. 5,399,363. Dip-coated and thin-skin expanded PTFE-based liners have been prepared from PTFE dispersions and exhibit higher flexibility but relatively low tensile strength. Furthermore, the dip-coating method is cumbersome and has low productivity (requiring repeated painting and sintering). Furthermore, dip-coated tubes typically have relatively low abrasion resistance as a result of separation of PTFE particles, and therefore the IDs of these tubes often have poor lubricity.

[0005] It would be advantageous to provide a flexible PTFE-based tube having sufficient strength and a method for preparing such a tube, such that the material is suitable for use in, for example, interior wall (base liner) applications. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 10,183,098 [Patent Document 2] US Patent Application Publication No. 2015 / 0025562 Summary of the Invention

[0007] The present disclosure provides extruded polytetrafluoroethylene (PTFE) tubes with an average wall thickness of less than 0.001 inches, with limited orientation of the PTFE fibrils in the machine direction (resulting in intermediate tensile strength and low tensile modulus). Due to the very thin walls of the disclosed tubes and the low modulus values ​​of such tubes, in some embodiments, they can exhibit better ID lubricity and abrasion resistance than dip-coated PTFE liners, while desirably having similar flexibility as dip-coated PTFE liners. In various embodiments, the combination of properties exhibited by the disclosed tubes can make them particularly suitable for use in catheters, including in catheters designed for flexibility, as the thin wall thickness and low modulus of the disclosed tubes provide a tube / liner product that is significantly more flexible than conventional thin-wall extruded ("free extrusion") PTFE liners, as described in more detail below. It should be noted that portions of this specification are described with particular reference to tubes such as catheter liners. However, it is understood that the tubes and methods disclosed herein are applicable in other contexts and are not limited to use in catheters.

[0008] In one aspect, a catheter is provided having a walled passageway and further comprising a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break of greater than 5000 psi, and c) a storage modulus of less than 100,000 psi at all temperatures between and including 21° C. and 37° C. In one aspect, a catheter is provided having a walled passageway and further comprising a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break of greater than 5000 psi, and c) a storage modulus of less than 100,000 psi at 23° C. In one aspect, a catheter is provided having a walled passageway and further comprising a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break of greater than 5000 psi, and c) a storage modulus of less than 100,000 psi at 37° C. In some embodiments, the average wall thickness of the PTFE tubular liner is 0.0002 inches to 0.0008 inches. In some embodiments, the PTFE tubular liner exhibits a change in storage modulus of 3,000 psi / ° C. or less between 21° C. and 37° C. In some embodiments, the PTFE tubular liner exhibits a change in storage modulus of 3,000 psi / ° C. or less between 23° C. and 37° C. In some embodiments, the PTFE tubular liner has an abrasion resistant surface and / or a lubricious surface.

[0009] In another aspect, a polytetrafluoroethylene (PTFE) tube is provided having an average wall thickness of 0.001 inches or less, a tensile stress at break of greater than 5000 psi, and a storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., including 21° C. and 37° C. In another aspect, a polytetrafluoroethylene (PTFE) tube is provided having an average wall thickness of 0.001 inches or less, a tensile stress at break of greater than 5000 psi, and a storage modulus of less than 100,000 psi at 23° C. In some embodiments, the average wall thickness is about 0.0002 inches to about 0.0008 inches. In some embodiments, the tube exhibits a change in storage modulus of 3,000 psi / ° C. or less between 21° C. and 37° C. In some embodiments, the tube exhibits a change in storage modulus of 3,000 psi / ° C. or less between 23° C. and 37° C. In some embodiments, the tube has a wear-resistant surface and / or a lubricious surface. Such tubes may be included, for example, in medical devices, including but not limited to catheters.

[0010] In another aspect, a PTFE layer is provided on a metal core, the PTFE layer having an average thickness of 0.001 inches or less, exhibiting an average tensile stress at break of greater than 5,000 psi, and an average storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., including 21° C. and 37° C. For example, such a PTFE layer may exhibit a storage modulus of less than 100,000 psi at 23° C. and / or 37° C. In some embodiments, the metal core and the PTFE layer are both substantially cylindrical in shape. In some embodiments, the PTFE layer on the metal core has a minimum continuous length of 50 feet. In some embodiments, the PTFE layer exhibits a change in storage modulus of less than 3,000 psi / ° C. between 21° C. and 37° C. In some embodiments, the PTFE layer exhibits a change in storage modulus of less than 3,000 psi / ° C. between 23° C. and 37° C. The PTFE layer on the metal core may, in some embodiments, be wear resistant and / or have a lubricated surface. In preferred embodiments, the values ​​reported for these embodiments are measured by removing the metal core (so that the values ​​reported characteristically relate to the PTFE layer).

[0011] In another aspect, a polytetrafluoroethylene (PTFE) tube is provided having a characteristic tensile curve having two distinct segments between 0 and 50% elongation with a first segment having an average tensile modulus of 100,000 psi or less and a second segment having a tensile modulus of 25,000 psi or less but greater than 2,500 psi, the PTFE tube having a tensile stress of 3000 psi or less at 5% elongation. In some such embodiments, the tensile stress is 4000 psi or less at 10% elongation.

[0012] The present disclosure includes, but is not limited to, the following embodiments. Embodiment 1: A catheter having a walled passageway and further having a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner having: a) an average wall thickness of 0.001 inches or less; and b) a tensile stress at break of greater than 5000 psi; and c) a storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., inclusive. Embodiment 2: A catheter having a walled passageway and further having a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break greater than 5000 psi, and c) a storage modulus at 23° C. of less than 100,000 psi. Embodiment 3: A catheter having a walled passageway and further having a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break greater than 5000 psi, and c) a storage modulus at 37° C. of less than 100,000 psi. Embodiment 4: The catheter of any preceding embodiment, wherein the PTFE tubular liner has an average wall thickness of 0.0002 inches to 0.0008 inches. Embodiment 5: The catheter of any preceding embodiment, wherein the PTFE tubular liner exhibits a change in storage modulus between 21° C. and 37° C. of 3,000 psi / ° C. or less. Embodiment 6: The catheter of any preceding embodiment, wherein the PTFE tubular liner exhibits a change in storage modulus between 23° C. and 37° C. of 3,000 psi / ° C. or less. Embodiment 7: The catheter of any preceding embodiment, wherein the PTFE tubular liner has an abrasion-resistant surface. Embodiment 8: The catheter of any preceding embodiment, wherein the PTFE tubular liner has a lubricious surface. Embodiment 9: A polytetrafluoroethylene (PTFE) tubing having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break greater than 5000 psi, and c) a storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., inclusive. Embodiment 10: A polytetrafluoroethylene (PTFE) tubing having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break of greater than 5000 psi, and c) a storage modulus of less than 100,000 psi at 23° C. Embodiment 11: A polytetrafluoroethylene (PTFE) tubing having a) an average wall thickness of 0.001 inches or less, and b) a tensile stress at break of greater than 5000 psi, and c) a storage modulus of less than 100,000 psi at 37° C. Embodiment 12: The PTFE tubing of any preceding embodiment, wherein the average wall thickness is from 0.0002 inches to 0.0008 inches. Embodiment 13: The PTFE tubing of any preceding embodiment, wherein the tubing exhibits a change in storage modulus between 21° C. and 37° C. of 3,000 psi / ° C. or less. Embodiment 14: The PTFE tubing of any preceding embodiment, wherein the tubing exhibits a change in storage modulus between 23° C. and 37° C. of 3,000 psi / ° C. or less. Embodiment 15: The PTFE tube of any preceding embodiment, having an abrasion resistant surface. Embodiment 16: The PTFE tube of any preceding embodiment, having a lubricious surface. Embodiment 17: The PTFE tube of any preceding embodiment, comprised in a medical device. Embodiment 18: The PTFE tube of any of the above embodiments, wherein the medical device is a catheter. Embodiment 19: The PTFE tube of any preceding embodiment, having a characteristic tensile curve having two distinct segments between 0 and 50% elongation, with a first segment having an average tensile modulus of 100,000 psi or less and a second segment having a tensile modulus of 25,000 psi or less but greater than 2,500 psi, and wherein the PTFE tube has a tensile stress of 3000 psi or less at 5% elongation. Embodiment 20: A polytetrafluoroethylene (PTFE) tube having a characteristic tensile curve having two distinct segments between 0 and 50% elongation with a first segment having an average tensile modulus of 100,000 psi or less and a second segment having an average tensile modulus of 25,000 psi or less but greater than 2,500 psi, the PTFE tube having a tensile stress of 3000 psi or less at 5% elongation. Embodiment 21: The PTFE tubing of the preceding embodiments, wherein the tensile strength is less than or equal to 4000 psi at 10% elongation. Embodiment 22: A PTFE layer on a metal core, the PTFE layer having an average thickness of about 0.001 inches or less, an average tensile stress at break greater than 5,000 psi, and an average storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., inclusive. Embodiment 23: A PTFE layer on a metal core, the PTFE layer having an average thickness of about 0.001 inches or less, an average tensile stress at break greater than 5,000 psi, and an average storage modulus at 23° C. of less than 100,000 psi. Embodiment 24: A PTFE layer on a metal core, the PTFE layer having an average thickness of about 0.001 inches or less, an average tensile stress at break greater than 5,000 psi, and an average storage modulus at 37° C. of less than 100,000 psi. Embodiment 25: The PTFE layer on a metal core of any preceding embodiment, wherein both the metal core and the PTFE layer are substantially cylindrical in shape. Embodiment 26: The PTFE layer on a metal core of any preceding embodiment, wherein said metal core and PTFE layer have a minimum continuous length of 50 feet. Embodiment 27: The PTFE layer on a metal core of any preceding embodiment, wherein the PTFE layer has a change in storage modulus between 21° C. and 37° C. of 3,000 psi / ° C. or less. Embodiment 28: The PTFE layer on a metal core of any preceding embodiment, wherein the PTFE layer has a change in storage modulus between 23° C. and 37° C. of 3,000 psi / ° C. or less. Embodiment 29: A PTFE layer on a metal core of any preceding embodiment having wear resistance. Embodiment 30: A PTFE layer on the metal core of any preceding embodiment having a lubricious surface.

[0013] These and other features, aspects, and advantages of the present disclosure will become apparent upon reading the following detailed description and the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, as well as any combination of any two, three, four, or more features or elements described in this disclosure, whether or not such features or elements are explicitly combined in the description of a specific embodiment herein. The present disclosure is intended to be read as a whole such that any separable features or elements of the disclosed invention are intended to be combinable in any of its various aspects and embodiments, unless the context clearly dictates otherwise. Other aspects and advantages of the present invention will become apparent from the following.

[0014] To provide an understanding of embodiments of the present invention, reference is made to the accompanying drawings, which are not necessarily drawn to scale and in which reference numerals refer to components of exemplary embodiments of the present invention. The drawings are illustrative only and are not to be construed as limiting the present invention. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is a general schematic diagram of a tube of the present disclosure, with associated parameters, and an enlarged schematic diagram of one cross-sectional end of the tube. [Diagram 2] 1 is a table of various physical parameters associated with certain tubes within the scope of the present disclosure as compared to those associated with comparative tubes. [Diagram 3] 1 is a graph of tensile stress versus tensile strain (elongation) for a tube of the present disclosure (Example 1) and three comparative examples. [Figure 4] FIG. 4 is an enlarged view of a region of the graph in FIG. [Diagram 5] 1 is a graph of tensile stress versus tensile strain (elongation) for a tube of the present disclosure (Example 2) and two comparative examples. [Figure 6] FIG. 6 is an enlarged view of a region of the graph in FIG. 5. [Figure 7] 1 is a graph of storage modulus versus temperature for tubes of the present disclosure (Examples 1 and 2) and a comparative example. [Figure 8] FIG. 8 is an enlarged view of a region of the graph in FIG. [Figure 9] FIG. 9 is an enlarged view of a region of the graph in FIG. 8. [Figure 10] FIG. 10 is an enlarged view of a region of the graph in FIG. [Figure 11] 1 is a table of data comparing storage modulus versus temperature for tubing of the present disclosure (Examples 1 and 2) and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in more detail below. However, the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present 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.

[0017] The present disclosure provides extruded tubing comprising polytetrafluoroethylene (PTFE) and having certain physical properties as more fully outlined herein below. Embodiments of the present disclosure have certain properties related to average wall thickness, storage modulus values, and tensile strength (e.g., tensile strength at break), which are particularly relevant to the present disclosure and are described in more detail below.

[0018] A general schematic of the tubes provided is shown in FIG. 1. The tubes are generally cylindrical in shape. "L" indicates the length of the tube as manufactured, which can be processed, e.g., cut, to provide a tube of a desired length "1" (not shown). The enlarged area on the right side of FIG. 1 is a cross-sectional view of the interior of the tube. As shown, the "lumen" is the interior region of the tube, i.e., the open passage / cavity (e.g., through which a catheter device can be passed). The inner diameter of the tube, designated as "ID," is the average distance from a point on the inner wall of the tube to the opposite / farthest point on the inner wall of the tube. The outer diameter of the tube, designated as "OD," is the average distance from a point on the outer wall of the tube through the lumen of the tube to the opposite / farthest point on the outer wall of the tube. Thus, subtracting the ID value from the OD value and dividing by two gives the average wall thickness of the tube. Also shown in FIG. 1 are representative "wall thickness," "inner wall surface," and "outer wall surface" of the tube.

[0019] In certain embodiments, the present disclosure provides thin-walled extruded PTFE tubing. For example, the average wall thickness in some embodiments is less than about 0.001 inches. In some embodiments, the average wall thickness of the disclosed tubing can be from about 0.0001 inches to about 0.001 inches, such as from about 0.0002 inches to about 0.001 inches, from about 0.0003 inches to about 0.001 inches, from about 0.0004 inches to about 0.001 inches, or from about 0.0005 inches to about 0.001 inches.

[0020] The wall thickness typically does not vary significantly around the circumference of the tube or along the length (L or 1) of the tube. Thus, the wall thickness can generally be described as substantially uniform. Wall tolerances in some embodiments can be, for example, + / - 0.0001 inches to + / - 0.0003 inches for a nominal wall of 0.0003 inches to 0.001 inches or less. In some embodiments, at any given point on a tube provided in accordance with the present disclosure, the wall thickness is less than about 0.001 inches. In some embodiments, at any point on a tube provided in accordance with the present disclosure, the wall thickness is about 0.0001 inches to about 0.001 inches, such as about 0.0002 inches to about 0.001 inches, about 0.0003 inches to about 0.001 inches, about 0.0004 inches to about 0.001 inches, or about 0.0005 inches to about 0.001 inches. In some embodiments, the wall thickness may be, for example, from about 0.0001 inches to about 0.0008 inches, from about 0.0002 inches to about 0.0008 inches, or from about 0.0002 inches to about 0.0006 inches.

[0021] The length of the tube may vary. In some embodiments, the as-manufactured tube may be at least about 50 feet long. As mentioned above, the length L is not particularly limited, and the tube as shown in FIG. 1 may be processed, such as cut into a plurality of tubes of several desired lengths 1. In some embodiments, the length 1 of the tube provided herein is a length suitable for catheter applications, such as use as a liner. For example, in some embodiments, the length 1 is about 6 inches to about 20 inches, such as about 12 inches to about 20 inches. Similarly, the ID (which determines the diameter of the lumen) may vary, and in some embodiments, is a size suitable for catheter applications, such as use as a liner.

[0022] The tubes provided herein generally comprise polytetrafluoroethylene (PTFE). A variety of PTFE resins are commercially available and may be used in certain embodiments to provide the PTFE tubes provided herein. Advantageously, in various embodiments, the tubes consist essentially of PTFE, i.e., no additional components (such as fillers) are intentionally added to the tubes. The tubes provided herein typically do not include any significant amount of lubricant (which may be used in some embodiments in the method of preparing the tubes, as described more fully below).

[0023] The extruded tubes provided herein generally do not exhibit the high machine direction orientation exhibited by typical PTFE tubes (which are generally stretched to provide and increase the desired strength as a secondary step after manufacture). Standard free extrusion liners are also tough due to the inherent machine direction orientation imposed by the paste extrusion process used to form them. Typically, extruded tubes have PTFE fibrils that are at least partially, e.g., substantially aligned, in the machine direction. The tubes provided herein, in some embodiments, can exhibit unique flexibility, which is particularly useful in applications where the tube must bend around corners and curves, including, but not limited to, certain catheter applications. Some methods for quantifying the degree of orientation of polymer molecules include, but are not limited to, X-ray diffraction, differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and birefringence spectroscopy. Tensile testing is also an indirect method for qualitatively identifying the orientation of polymeric materials.

[0024] As an example, the degree of orientation of fibrils can be quantified in PTFE extrudates in some embodiments using Raman spectroscopy. For materials with little or no orientation, Raman spectroscopy generally shows no difference in scattering intensity at all Raman shifts between the two polarization geometries (i.e., parallel or perpendicular to the extrusion direction), indicating no preferred orientation (isotropy). For extruded materials that show orientation, there is often a difference in scattering intensity between the two polarization geometries at the major Raman shifts. Thus, in some embodiments, the ratio of Raman scattering intensity at the major Raman shifts between the two polarization geometries can be used to provide an indication (e.g., a quantitative measure) of preferred fibril orientation. A ratio of 1 indicates isotropy or no preferred orientation. On the other hand, a ratio greater than 1 indicates a preferred orientation in the direction parallel to the extrusion direction.

[0025] The tubes provided herein are generally of low stiffness (eg, at body temperature of about 37° C.) and are suitable for use within the body.

[0026] The tubing embodiments described above (having the referenced average wall thicknesses) can have a variety of storage modulus values ​​at specific temperatures. Storage modulus values ​​over a range of temperatures (including but not limited to the specific values ​​below) are clearly shown in Figures 7 and 8 and more clearly in the blown-up / blow-up views shown in Figures 9 and 10. Some of such tubing embodiments have a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at 37°C. Some tubing have a storage modulus of less than 90 ksi (i.e., less than 90,000 psi), less than 80 ksi (i.e., less than 80,000 psi), or less than 70 ksi (i.e., less than 70,000 psi) at 37°C.

[0027] Certain tubing embodiments exhibit a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at all temperatures ranging from 21° C. to 37° C., for example, without limitation, some tubing has a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at 35° C. Some tubing has a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at 30° C., some tubing has a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at 25° C., some tubing has a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at 23° C., and some tubing has a storage modulus of less than 100 ksi (i.e., less than 100,000 psi) at 21° C.

[0028] For example, some tubes provided herein have a storage modulus of about 20,000 psi to about 100,000 psi at 23° C., e.g., about 30,000 psi to about 100,000 psi at 23° C., about 40,000 psi to about 100,000 psi at 23° C., or about 50,000 psi to about 100,000 psi at 23° C. Some tubes provided herein have a storage modulus of about 20,000 psi to about 100,000 psi at 37° C., e.g., about 30,000 psi to about 100,000 psi at 37° C., about 40,000 psi to about 100,000 psi at 37° C., about 20,000 psi to about 90,000 psi at 37° C., about 20,000 psi to about 80,000 psi at 37° C., or about 20,000 psi to about 70,000 psi at 37° C.

[0029] In some embodiments, the disclosed tubes (e.g., having reference average wall thickness and / or general storage modulus values ​​as set forth above) exhibit a storage modulus that remains insensitive to temperature changes of about 3,000 psi / °C (3 ksi / °C) or less between 21°C and body temperature (37°C), including room temperature (~23°C) and body temperature (37°C). Some such tubes exhibit a change in storage modulus between 21°C and 37°C, more particularly between 23°C and 37°C, of ​​2,800 psi / °C or less, 2,500 psi / °C or less, 2,200 psi / °C or less, 2,000 psi / °C or less, or 1,800 psi / °C or less (e.g., a change in storage modulus between 23°C and 37°C of 1,000 psi / °C to 3,000 psi / °C, e.g., 1,000 psi / °C to 2,000 psi / °C). In some such tubes, the total change in storage modulus between these temperature values ​​(i.e., between 23°C and 37°C) is about 30,000 psi or less (e.g., about 25,000 psi or less), such as about 10,000 psi to about 30,000 psi or about 10,000 psi to about 25,000 psi. In some embodiments, the tube can have a flexibility similar to that exhibited by a dip-coated PTFE liner having similar characteristics (e.g., comparable size, wall thickness, etc.).

[0030] The tubes described in this disclosure have, in some embodiments, a tensile strength that is considered moderate (e.g., in addition to the referenced average wall thickness and storage modulus values). In some embodiments, the PTFE tube has a tensile strength at break of about 5,000 psi (about 5 ksi) or more. Furthermore, in some embodiments, the tube has a tensile stress value at 5% elongation of about 3,000 psi or less and a tensile strength value at 10% elongation of about 4,000 psi or less. In certain embodiments, the product also has a characteristic tensile curve with two distinct segments between 0 and 50% elongation, with a first segment having an average tensile modulus of 100 ksi or less and a second segment having a tensile modulus of 25 ksi or less but greater than 2,500 psi.

[0031] In some embodiments, the PTFE tube has high lubricity and wear resistance. Such characteristics can be characterized in various ways. Wear is generally understood to be the wear of a material due to friction. Friction occurs by rubbing or scratching the initial material. Wear resistance is the material property that prevents wear when friction is applied to the surface. Wear resistance is understood to be material- and process-dependent.

[0032] The methods used to quantify wear and abrasion vary depending on the geometry and application of the sample. In certain embodiments, the material or sample being tested is positioned against another material so that the two surfaces are in contact. One material can be almost anything as long as it is specified. Common materials include polished metal surfaces, metal pins, sandpaper, or the same material. Then, one or both materials are moved so that friction occurs between the contacting surfaces. Depending on the test method, the end of the test can be defined after a certain amount of time, a defined number of times, or until a specified failure mode is reached. Some failure modes include a certain mass loss, a certain reduction in material thickness relative to the initial material thickness, a loss of tensile properties, or a loss of insulating properties. Regardless of the test method selected, the relative wear resistance of two or more materials can be determined by subjecting two samples to the same test conditions and comparing the effect of the test conditions on the test materials. Various methods of evaluating wear resistance that can be used to define the tubes of the present disclosure include: www.element.com / materials-testing-services / abrasion-and-wear, www.lectromec.com / test / cable-cable-abrasion, and https: / / www.en-standard.eu / csn-en-3475-51l-aerosdace-series-cables-electrical-aircraft-use-test-methods-part-511-cable-to-cable-abrasion / Examples of such methods include, but are not limited to, those disclosed in EN3475. References include, for example, pin abrasion tests (e.g., using ASTM G132), rubber wheel abrasion tests (e.g., using ASTM G65), Taber abrasion tests (e.g., using ASTM D1044 and ASTM D4060), blade-on-block abrasion tests, medical device abrasion tests, and pin-on-disk abrasion tests (e.g., using ASTM G99, ASTM G133, and ASTM F732). Another illustrative method is EN3475 Method 511, which generally involves placing a material (e.g., a wire-coated PTFE or comparative sample provided herein) in a fixture in contact with another sample of the same type, clamping both ends and allowing the sample to vibrate / rub on itself until a current is detected between the wires at the insulation fault.

[0033] The tubes provided according to the present disclosure, in various embodiments, exhibit higher wear resistance and lubricity than commercially available tubes, including dip-coated tubes, which generally have problems with delamination and / or wear resistance. See, for example, Examples 3 to 5 below. Moreover, such tubes, in various embodiments, exhibit higher flexibility than conventional PTFE "free extrusion" PTFE liners, as shown, for example, in Examples 1 and 2 (see, in particular, the tensile modulus and DMA cumulative modulus data shown therein). Advantageously, such improved properties are exhibited by the tubes of the present disclosure, particularly those with thin average wall thicknesses, e.g., within the ranges described herein (e.g., less than 0.001 inches). Thus, the tubes are widely applicable, including, for example, for use as PTFE catheter liners.

[0034] The present disclosure further provides a method for producing a PTFE tube, for example, a tube exhibiting the physical properties described above. The method generally involves a paste extrusion process, in which PTFE is extruded onto a metal substrate, for example, including, but not limited to, a wire. The paste extrusion process of PTFE is generally known and includes several steps, such as: (1) paste preparation or resin mixing with a lubricant; (2) pretreatment; (3) paste extrusion; (4) degassing; and (5) sintering. Fine powder PTFE resins suitable for wire coating paste extrudates disclosed herein are typically non-homopolymers and can be extruded at reduction ratios of >300. Exemplary resins suitable for this purpose include, but are not limited to, Daikin F205, F201, F201L, F208, and F207 resins, Dynon TF2071, TF2072, and TF2053 resins, Chemoasteflon 640XT X, 641XT X, CFP6000 X, 62XT X, 6C X, and 6CN X, and Asahi Glass CD090E and CD097E. It is to be understood that the products and methods described herein are not limited to such resins, and any PTFE resin may be reasonably used within the scope of the present disclosure. See, for example, Fluoroplastics, Vol. 1 (Ebne Sajad, South Dakota, USA), Applied Polymer Rheology (Kontopoulou, M), Processing of Dyneon PTFE Fine powder (3M™ Dyneon™), Processing Guide: Fine Powder PTFE (INOFLON), Paste Extrusion of Polytetrafluoroethylene fine powder resin (Ariawan, AB, Ph.D. Doctoral dissertation, University of British Columbia), U.S. Patent No. 10,183,098 to Ohshika et al., and U.S. Patent No. 8,377,352 to Inamoto et al., which are incorporated herein by reference in their entireties.

[0035] Even when refrigerated and handled with care, PTFE micropowder can compact slightly during shipping and storage, resulting in clumping. Sifting the cold resin through a coarse wire mesh helps break up these clumps. PTFE micropowder is sheared and must be handled with extreme care. In some embodiments, the PTFE micropowder can be extruded using a mixture of Isopar (C, E, G, H, J, K, L, M, N, P, V), Novec (7100, 7200, 7300, 7500, 7700), naphtha, Shellsol 340HT, Shellsol 142HT, Mineral Spirits 200HT, Methyl Nonafluorobutyl Ether, Methyl Nonafluoro-2-Butyl Ether, Ethyl Nonafluorobutyl Ether, Ethyl Nonafluoro-2-Butyl Ether, Pentane, 1,1,1,2,2,3,4,5,5,5-Decafluoro-3-Methoxyprop ... The lubricant or organic solvent such as oxy-4-(trifluoromethyl)-, 2-trifluoromethyl-3-ethoxydodefluorohexane, furan, 2,3,3,4,4-pentafluorotetrahydro-5-methoxy-2,5-bis[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]-, perfluorooctane, perfluoro(2-butyltetrahydrofuran), perfluorotributylamine, 1,1,2,2,3,3,4,4,4-nonafluoro-N,N-bis(nonafluorobutyl)butan-1-amine, C5-18, Perfluoro N-Alkyl Morpholimes, 3M (trademark) Fruorinert (FC-770, FC-3283, FC-40, FC-43, FC-70, FC-75, FC-77), etc., is uniformly mixed. The lubricant used is not particularly limited in the context of the disclosed method.See, for example, Fluoroplastics, Vol. 1 (Ebne Sajad, South Dakota, USA), Applied Polymer Rheology (Kontopoulou, M), Processing of Dyneon PTFE Fine powder (3M™ Dyneon™), Processing Guide: Fine Powder PTFE (INOFLON), Paste Extrusion of Polytrafluoro ethylene (Ariawan, AB, Ph.D. Doctoral dissertation, University of British Columbia), 3M™ Thermal management fluids (3M), US Patent No. 10,183,098 to Ohshika et al., and US Patent No. 8,377,352 to Inamoto et al., all of which are incorporated herein by reference in their entireties.

[0036] The lubricant content is generally (but not limited to) about 35 to 45% by total volume of the mixture. The lubricant content should be as low as possible to make the devolatilization step easy and quick, but not so low that the extrusion pressure becomes excessively high, which is often a problem in the thin-wall extrusion of PTFE. Increasing the amount of lubricant in the paste mixture helps to keep the extruder pressure within reasonable / maximum limits. Wetting / surface tension and viscosity are two properties of the lubricant that can have a large effect on the pressure of PTFE paste extrusion and therefore can be modified accordingly. Lubricants that wet the PTFE more help to reduce the extruder pressure. Similarly, using a lubricant with a lower viscosity can reduce the extruder pressure.

[0037] Prior to the extrusion step, it is generally important to remove at least some air (preferably as much air as possible) from the PTFE / lubricant paste to prevent defects in the extrudate. Thus, in the preforming step, the mixture is typically pressed into a shape (e.g., a cylindrical shape) called a preform or billet. These preforms are generally very weak and can easily break or deform, so care must be taken when handling them. The preforms are advantageously loaded into the extruder immediately (e.g., immediately) after production to prevent evaporation of the lubricant.

[0038] In certain embodiments, the cylindrical preform is inserted into the extrusion cylinder / barrel of a paste extruder and then pressed through a die with the aid of a ram. Tube and wire extrusion generally requires the presence of a mandrel in the rear-mounted barrel. According to the present disclosure, a metal substrate (e.g., wire) is fed through this mandrel. The material of the metal substrate (e.g., wire) used in this paste extrusion process is not particularly limited and in some embodiments can be copper (e.g., annealed copper wire), plated copper (e.g., silver-plated copper wire), nickel, stainless steel, nitinol, etc.

[0039] The extruded paste material simultaneously coats the wire which is guided through the extruder head. In a preferred embodiment, the machine design ensures that the ram speed and extrusion rate are maintained at a constant level while the extrusion pressure is varied during processing.

[0040] After extrusion, any residual lubricant in the insulation / PTFE coating must be completely removed by heating above the boiling point of the lubricant / solvent, for example by passing the product through (or placing the product in) a devolatilizing oven.

[0041] After devolatilization, the product is heated in a sintering furnace, typically set above the melting point of PTFE (about 345°C). Depending on the production line speed and the thickness of the PTFE layer, the oven is generally set at a temperature significantly higher than this. It is important that the product in the sintering furnace is completely free of lubricant. In the sintering furnace, the PTFE particles melt and adhere. When the product cools (e.g., upon exiting / removal from the sintering furnace), the PTFE goes from the molten state to a solid state. It is understood that the PTFE layer / coating thus applied can advantageously have the physical properties (e.g., wall thickness, storage modulus value, tensile strength properties) as described herein for the PTFE tube removed therefrom.

[0042] The cooled coated wire is then stretched to remove the PTFE coating from the wire. One method for removing the PTFE coating involves removing small portions of the PTFE coating at two distal locations of the coated wire, exposing the metal wire. The two exposed metal locations can be clamped (e.g., using an Instron tensile machine) and the wire stretched. The degree of stretching targeted during this process is usually at least about 5%, with a maximum stretch percentage of 30% (or until the wire is about to break or until the outer diameter of the coated wire is small enough to break the bond between the PTFE and the metal wire). Once the wire is stretched sufficiently, the PTFE coating usually slides off easily in a tubular form. The removed coating is preferably in the form of a free-standing tube (length L). This tube can be optionally processed, for example, by cutting the long tube into shorter lengths 1 as desired for a particular application.

[0043] The inventors have found that extruding PTFE onto a metal substrate such as a wire introduces very little machine direction orientation of the PTFE fibrils. This feature is in contrast to, for example, a freely extruded tube, which exhibits high machine direction orientation. By extruding / sintering the PTFE coating in this manner and then removing the coating, a tube exhibiting a particularly advantageous combination of properties (as described herein above) can be readily obtained. In particular, the inventors have unexpectedly discovered that a tube having a very low wall thickness can be obtained in this manner, which exhibits the strength and flexibility characteristics outlined above, providing a particularly advantageous means for producing very thin-walled PTFE tubes, for example for use in catheter applications. EXAMPLES

[0044] PTFE tubes were prepared according to the specific examples described below. Tensile properties of the PTFE tubes were measured using an Instron 5965 dual column mechanical tester running the Bluehill 3 v3.73.4823 operating system. Tests were performed at a speed of 2 inches / min using a 20Ibf load cell attached to pneumatic grips with smooth-faced insets set at a 2 inch gauge length. At least five samples were tested and average results are reported in the table of FIG. 2. During the analysis, a line was fitted between 0 and 5% elongation / tensile strain to determine the tensile modulus of the first segment. A line was fitted between 10 and 50% elongation / tensile strain to determine the tensile modulus of the second segment. Comparative Examples 1 and 2 did not have a second separate segment. As a result, a line could not be properly fitted between 10 and 50% tensile strain, resulting in no modulus data for the second segment.

[0045] The thermomechanical properties of the PTFE tube separated from the metal core were measured using a TA Instruments Q800 DMA with a film tension fixture. The primary property of interest was the storage modulus (E'). A temperature scan from -100°C to 300°C was performed with an isothermal hold at -100°C for 5 minutes. The sample was heated at a constant rate of 3°C / min and displaced at a constant amplitude of 15 pm with a fixed frequency tensile oscillation of 1 Hz. The resulting DMA data was imported into TA Instruments TRIOS software v4.3. Data comparing the properties of Example 1 with Comparative Examples 1, 4, and 5 (see below) are shown in Figures 3 and 4 (10 represents Example 1, 12 represents Comparative Example 1, 14 represents Comparative Example 4, and 16 represents Comparative Example 5). Data comparing the properties of Example 2 with Comparative Examples 2 and 3 (see below) are shown in Figures 5 and 6 (where 18 represents Example 2, 20 represents Comparative Example 2, and 22 represents Comparative Example 3). The storage modulus properties of all tubes produced (including Examples 1 and 2 as well as all Comparative Examples) are shown in Figures 7 through 11 (where 24 represents Example 1, 26 represents Example 2, 28 represents Comparative Example 1, 30 represents Comparative Example 2, 32 represents Comparative Example 3, 34 represents Comparative Example 4, and 36 represents Comparative Example 5).

[0046] Example 1: A 0.0005 inch thick PTFE layer was extruded onto an annealed 0.0169 inch OD copper wire using a PTFE paste extrusion process (using a medium to high reduction low molecular weight grade resin), followed by evaporation of the lubricant and sintering of the PTFE onto the wire. The thickness of the PTFE layer was measured as follows: The outer diameter (OD) of the coated wire was measured with a laser. The PTFE coating was removed in one location without stretching the wire. The OD of the exposed wire was measured with a laser. Based on these OD values, the wall thickness of the PTFE tube was calculated. It was confirmed that there were no voids between the wire and the PTFE layer, and that the coating was smooth and well bonded to the wire. The annealed coated wire was then stretched as described above, and the PTFE coating (in tubular form) was removed from the wire without deforming or damaging the PTFE layer, resulting in a free-standing PTFE product in tubular form. The sample was then cut to appropriate lengths, e.g., for tensile and DMA testing. See Figures 3 and 4.

[0047] Example 2 The process described in Example 1 was also used to manufacture PTFE tubing, except the metal core used was annealed copper wire with an outer diameter / OD of 0.071 inches. Tensile and DMA tests were also performed on this sample. See Figures 5 and 6.

[0048] Comparative Example 1 A thin-walled PTFE tube with an ID of 0.0167 inches and a wall thickness of 0.00057 inches ("free extrusion tube") was produced using a PTFE paste extrusion process generally based on the process of Examples 1 and 2, except that no wire substrate was used. Tensile and DMA tests were also performed on this sample.

[0049] Comparative Example 2 Thin wall PTFE tubing with an ID of 0.0684 inches and a wall thickness of 0.00052 inches was produced using the PTFE paste extrusion process referenced in Comparative Example 1. Tensile and DMA tests were also performed on this sample.

[0050] Comparative Example 3 A PTFE layer was coated onto an annealed copper wire with an outer diameter of 0.071 inches using a PTFE dip coating / cast film process. The thickness of the PTFE layer was measured as follows and was 0.00068. The outer diameter (OD) of the coated wire was measured by laser. The PTFE coating was removed in one place without stretching the wire. The OD was measured again by laser. Based on these OD values, the wall thickness of the PTFE tube was calculated. It was confirmed that there were no voids between the wire and the PTFE layer, and that the coating was smooth and well bonded to the wire. The annealed wire was then stretched and the PTFE layer was removed without deformation or damage. The PTFE product thus obtained was in the form of a tube. The samples were then cut to appropriate lengths for tensile and DMA testing.

[0051] Comparative Example 4 Using the same process as in Comparative Example 3, a PTFE layer was coated onto an annealed copper wire with an outer diameter of 0.0169 inches. The thickness of the PTFE layer was 0.00057 inches. The annealed wire was then stretched and the PTFE layer was removed without deformation or damage to obtain a tubular PTFE product. The sample was then cut to an appropriate length for tensile and DMA testing.

[0052] Comparative Example 5 This was a competitive sample, procured from an outside vendor, and had a PTFE layer on annealed copper wire having an outer diameter of 0.0169 inches with the thickness of the PTFE layer being 0.00067 inches. The annealed wire was stretched and the PTFE layer was removed without deformation or damage. The resulting PTFE product was in the form of a tube. The sample was then cut to appropriate lengths for tensile and DMA testing.

[0053] result As shown in Figures 2 through 6, Examples 1 and 2 (lines 10 and 18, respectively) had "intermediate" tensile strengths compared to the comparative samples. For both Examples 1 and 2, the tensile strength was 4000 psi or less at 10% elongation. As shown in the data in the figures, Examples 1 and 2 (lines 24 and 26, respectively) had storage moduli of less than 100,000 psi at all temperatures between 21°C and 37°C, including 23°C and 37°C. These examples had an overall change in storage modulus from 23°C to 37°C of about 30,000 psi or less (e.g., about 25,000 psi or less) and / or a change in storage modulus between 23°C and 37°C of 3,000 psi / °C or less.

[0054] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description. It is to be understood, therefore, that the invention is not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. 1. A catheter having a walled passageway and further having a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner comprising: a. an average wall thickness of 0.001 inches or less; and b. A tensile stress at break of greater than 5000 psi; and c. A catheter having a storage modulus of less than 100,000 psi at all temperatures between and including 21° C. and 37° C.

2. 1. A catheter having a walled passageway and further having a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner comprising: a. an average wall thickness of 0.001 inches or less; and b. A tensile stress at break of greater than 5000 psi; and c. A catheter having a storage modulus of less than 100,000 psi at 23° C.

3. 1. A catheter comprising a walled passageway and further comprising a polytetrafluoroethylene (PTFE) tubular liner within the passageway, the PTFE tubular liner comprising: a. an average wall thickness of 0.001 inches or less; and b. A tensile stress at break of greater than 5000 psi; and c. a storage modulus of less than 100,000 psi at 37° C.; A catheter having

4. The catheter of any one of claims 1 to 3, wherein the PTFE tubular liner has an average wall thickness of 0.0002 to 0.0008 inches.

5. 5. The catheter of claim 1, wherein the PTFE tubular liner exhibits a change in storage modulus between 21°C and 37°C of 3,000 psi / °C or less.

6. 6. The catheter of claim 1, wherein the PTFE tubular liner exhibits a change in storage modulus of less than or equal to 3,000 psi / °C between 23°C and 37°C.

7. The catheter of any one of claims 1 to 6, wherein the PTFE tubular liner comprises an abrasion resistant surface.

8. The catheter of any one of claims 1 to 7, wherein the PTFE tubular liner comprises a lubricious surface.

9. A polytetrafluoroethylene (PTFE) tube, a. an average wall thickness of 0.001 inches or less; and b. A tensile stress at break of greater than 5000 psi; and c. A polytetrafluoroethylene (PTFE) tubing having a storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., inclusive.

10. A polytetrafluoroethylene (PTFE) tube, a. an average wall thickness of 0.001 inches or less; and b. A tensile stress at break of greater than 5000 psi; and c. Polytetrafluoroethylene (PTFE) tubing having a storage modulus of less than 100,000 psi at 23° C.

11. A polytetrafluoroethylene (PTFE) tube, a. an average wall thickness of 0.001 inches or less; and b. A tensile stress at break of greater than 5000 psi; and c. Polytetrafluoroethylene (PTFE) tubing having a storage modulus of less than 100,000 psi at 37° C.

12. The PTFE tube of any one of claims 9 to 11, wherein the average wall thickness is from 0.0002 inches to 0.0008 inches.

13. 13. The PTFE tube according to any one of claims 9 to 12, wherein the tube exhibits a change in storage modulus of 3,000 psi / °C or less between 21°C and 37°C.

14. 14. The PTFE tube according to any one of claims 9 to 13, wherein the PTFE tubular liner exhibits a change in storage modulus of 3,000 psi / °C or less between 23°C and 37°C.

15. The PTFE tube according to any one of claims 9 to 14, wherein the PTFE tube has an abrasion resistant surface.

16. The PTFE tube according to any one of claims 9 to 15, wherein the PTFE tube has a lubricious surface.

17. The PTFE tube according to any one of claims 9 to 16, wherein the PTFE tube is provided in a medical device.

18. 18. The PTFE tube of claim 17, wherein the medical device is a catheter.

19. 19. The PTFE tube according to any of claims 9 to 18, having a characteristic tensile curve having two distinct segments between 0 and 50% elongation, with a first segment having an average tensile modulus of 100,000 psi or less and a second segment having a tensile modulus of 25,000 psi or less but greater than 2,500 psi, the PTFE tube having a tensile stress of 3000 psi or less at 5% elongation.

20. 1. A polytetrafluoroethylene (PTFE) tube having a characteristic tensile curve having two distinct segments between 0 and 50% elongation, with a first segment having an average tensile modulus of 100,000 psi or less and a second segment having a tensile modulus of 25,000 psi or less but greater than 2,500 psi, wherein the PTFE tube has a tensile stress of 3000 psi or less at 5% elongation.

21. 21. The PTFE tube of claim 20, wherein the tensile strength is less than or equal to 4000 psi at 10% elongation.

22. A PTFE layer on a metal core, the PTFE layer having an average thickness of about 0.001 inches or less, an average tensile stress at break of greater than 5,000 psi, and an average storage modulus of less than 100,000 psi at all temperatures between 21° C. and 37° C., inclusive.

23. A PTFE layer on a metal core, the PTFE layer having an average thickness of about 0.001 inches or less, an average tensile stress at break of greater than 5,000 psi, and an average storage modulus at 23° C. of less than 100,000 psi.

24. A PTFE layer on a metal core, the PTFE layer having an average thickness of about 0.001 inches or less, an average tensile stress at break of greater than 5,000 psi, and an average storage modulus at 37° C. of less than 100,000 psi.

25. A PTFE layer on a metal core according to any of claims 22 to 24, wherein both the metal core and the PTFE layer are substantially cylindrical in shape.

26. 26. The PTFE layer on a metal core of any of claims 22-25, wherein the PTFE layer on a metal core has a minimum continuous length of 50 feet.

27. 27. The PTFE layer on a metal core according to any of claims 22 to 26, wherein the PTFE layer exhibits a change in storage modulus of less than 3,000 psi / s between 21°C and 37°C.

28. 28. A PTFE layer on a metal core according to any of claims 22 to 27, wherein the PTFE layer exhibits a change in storage modulus between 23°C and 37°C of 3,000 psi / °C or less.

29. A PTFE layer on a metal core according to any one of claims 22 to 28, which has abrasion resistance.

30. A PTFE layer on a metal core according to any one of claims 22 to 29, having a lubricating surface property.

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