Polytetrafluoroethylene tube and medical tube using same

Abstract

This invention provides a thin-walled PTFE tubing with moderate elongation and sufficient strength, good uniformity during elongation, and excellent flexibility and dimensional accuracy for medical use. The PTFE tubing of this invention has a wall thickness of 0.005 mm or more and 0.04 mm or less, and the wetting tension of either or both of its outer and inner surfaces is 46 mN / m or more. In the stress-strain curve obtained by a tensile test conducted under ambient gas at 200°C, the 20% strain tensile stress σ of the PTFE tubing is... 20 (N / mm) 2) The 50% strain tensile stress σ of the PTFE pipe fitting 50 (N / mm) 2) Satisfies 2.0≦0.1×σ 20+0.3×σ 50 < 5.5 (Equation (1)).

Description

Technical Field

[0001] Field of the Invention The present invention relates to a fluororesin pipe fitting, and more particularly to a thin-walled pipe fitting made of polytetrafluoroethylene (hereinafter referred to as "PTFE"). Prior Art

[0002] Background Art Intravascular surgery, which involves inserting a catheter into a blood vessel to remove or treat lesions, is becoming increasingly mainstream due to its minimal burden on patients. Catheters used for this purpose are inserted percutaneously, and the distal end of the tube must pass through the blood vessels to reach the lesion. Therefore, catheters are required to have the ability to navigate straight within the vessel and to communicate the procedures performed by the surgeon. To meet these requirements, catheters are constructed using layers with varying properties. Because the interior of the catheter must accommodate procedures such as the insertion of a treatment clip and the injection of medication, it requires a low-friction, high-strength inner surface, resulting in a maximum inner diameter. Meanwhile, the outer diameter of the catheter must be minimized to minimize the burden on the patient. Therefore, the layers that comprise the catheter are designed to be as thin as possible.

[0003] PTFE tubing is suitable for medical applications due to its excellent properties, including chemical resistance, non-stick properties, and low friction. One method for manufacturing catheter tubing involves coating a core wire with PTFE, forming an outer resin layer thereon, and then removing the core wire to produce the catheter tubing. Other methods for coating the core wire with PTFE include applying a PTFE dispersion onto the core wire and then sintering it (hereinafter referred to as the "impregnation method") and directly extruding the paste onto the core wire. This method also includes a method of coating a core wire with a thin-walled PTFE tube. This method involves inserting the core wire into the PTFE tube and, while still in this state, stretching the PTFE tube to reduce its diameter so that the PTFE tube contacts the surface of the core wire. In this method, the PTFE tube must possess both strength to withstand stretching and elongation to sustain stretching. Furthermore, in catheter manufacturing processes requiring high dimensional accuracy, the PTFE layer on the core wire preferably has a uniform wall thickness, and the stretched PTFE tube is required to exhibit high dimensional accuracy and uniform elongation.

[0004] PTFE has a very high melt viscosity, and long PTFE molded products are generally formed using paste extrusion rather than melt extrusion. However, paste extrusion makes it difficult to form thin-walled tubing. Therefore, to form thin-walled PTFE tubing, the dipping method is often used. This involves coating a PTFE dispersion onto a core wire, sintering it, and then removing the core wire to produce the tubing (see, for example, Patent Document 1). However, tubing formed using the dipping method can have defects such as pinholes and can also suffer from problems such as poor strength. Patent Document 2 discloses a method for producing thin-walled tubing by paste extruding PTFE resin onto a metal core wire. Paste extrusion promotes the flow and orientation of PTFE particles, increasing the tensile strength of the tubing. However, it does not achieve sufficient strength to improve catheter performance.

[0005] Patent Document 3 discloses a method of forming a PTFE tube by paste extrusion and then stretching the tube in the longitudinal direction to thin the tube's walls. However, while stretching the PTFE tube achieves thinner walls and ensures tube strength, it also compromises the tube's elongation and flexibility.

[0006] Prior Art Literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2000-316977 Patent Document 2: Japanese Patent Application Laid-Open No. 2013-176583 Patent Document 3: Japanese Patent Application Laid-Open No. 2004-340364 Summary of the Invention

[0007] Summary of the Invention Problems that the invention aims to solve To address the aforementioned problems of conventional thin-walled PTFE tubing, the present invention provides a thin-walled PTFE tubing having moderate elongation and sufficient strength, while also exhibiting good uniformity during the elongation required when the PTFE tubing is used to coat core wires, etc., and providing a medical tubing having excellent flexibility and dimensional accuracy.

[0008] Means used to solve problems To solve the above-mentioned problems, a structure as described in the patent application can be adopted. For example, a polytetrafluoroethylene (PTFE) pipe fitting is characterized by having a wall thickness of 0.005 mm or more and 0.04 mm or less, a wet tension of 46 mN / m or more on either or both of the outer and inner surfaces of the PTFE pipe fitting, and a stress-strain curve obtained by a tensile test in an ambient atmosphere at 200°C, wherein the 20% strain tensile stress σ 20 (N / mm 2 ) of the PTFE pipe fitting and the 50% strain tensile stress σ 50 (N / mm 2 ) of the PTFE pipe fitting satisfy 2.0≦0.1×σ 20 + 0.3×σ 50 <5.5 (Equation (1)).

[0009] A preferred embodiment is a polytetrafluoroethylene pipe having a tensile fracture strain of 200% or more in a tensile test conducted in an atmosphere of 200°C, and a 20% strain tensile stress σ 20 of 4.0 (N / mm 2) or more in a tensile test conducted in an atmosphere of 200°C.

[0010] Alternatively, a structure as described in the following patent claims may be employed. For example, a polytetrafluoroethylene (PTFE) pipe fitting is characterized in that: the wall thickness is not less than 0.005 mm and not more than 0.04 mm, the inner diameter of the polytetrafluoroethylene (PTFE) pipe fitting is not less than 0.2 mm and not more than 3.0 mm, and in a stress-strain curve obtained by a tensile test in an atmosphere at 200°C, the 20% strain tensile stress σ 20 (N / mm 2 ) of the polytetrafluoroethylene (PTFE) pipe fitting and the 50% strain tensile stress σ 50 (N / mm 2 ) of the polytetrafluoroethylene (PTFE) pipe fitting satisfy 2.0≦0.1×σ 20 + 0.3×σ 50 <5.5 (Equation (1)).

[0011] Another example is a medical tube, which uses a polytetrafluoroethylene tube, and the wall thickness of the polytetrafluoroethylene tube is not less than 0.005 mm and not more than 0.04 mm, and the wet tension of either or both of the outer surface and the inner surface of the polytetrafluoroethylene tube is not less than 46 mN / m. In the stress-strain curve obtained by a tensile test in an ambient gas at 200°C, the 20% strain tensile stress σ20 (N / mm2) of the polytetrafluoroethylene tube and the 50% strain tensile stress σ50 (N / mm2) of the polytetrafluoroethylene tube satisfy the above formula (1). A medical tubing is provided, wherein the wall thickness of the polytetrafluoroethylene tubing is not less than 0.005 mm and not more than 0.04 mm, and the inner diameter of the polytetrafluoroethylene tubing is not less than 0.2 mm and not more than 3.0 mm. In a stress-strain curve obtained by a tensile test in an atmosphere at 200° C., the 20% strain tensile stress σ 20 (N / mm 2 ) of the polytetrafluoroethylene tubing and the 50% strain tensile stress σ 50 (N / mm 2 ) of the polytetrafluoroethylene tubing satisfy the above-mentioned formula (1). Furthermore, another example is a medical tube, which includes a tube inner layer material processed from a polytetrafluoroethylene tube, and the wall thickness of the tube inner layer material is less than 0.04 mm, and the inner diameter of the tube inner layer material is less than 3.0 mm, and in the stress-strain curve of the tube inner layer material obtained by a tensile test in an ambient gas at 200°C, the 20% strain tensile stress σ'20 (N / mm2) of the tube inner layer material and the 50% strain tensile stress σ'50 (N / mm2) of the tube inner layer material satisfy 2.4≦0.1×σ'20+0.3×σ'50<6.6 (Formula (2)) Formula (2).

[0012] Effects of the Invention The PTFE tubing of the present invention possesses strength and moderate elongation, and furthermore, exhibits excellent uniformity during stretching, making it suitable for applications where PTFE tubing is stretched. The PTFE tubing coated on the core wire is uniform with minimal dimensional variation, and exhibits excellent flexibility and dimensional accuracy. The PTFE tubing of the present invention can be used in products requiring high dimensional accuracy, and is particularly suitable as an inner layer material for medical tubing. Simple diagram description

[0013] FIG1 is a schematic cross-sectional view of a PTFE tube for explaining the dimensions of the tube of the present invention. FIG2 is a graph showing the relationship between the median value of formula (1) and the outer diameter variation (coefficient of variation CV) of the PTFE pipe of the present invention. Implementation Method

[0014] Mode for carrying out the invention The following describes in detail the PTFE pipe fittings according to the embodiments of the present invention. The embodiments described below are not intended to limit the scope of the invention, and the entire combination of features described in the embodiments is not necessarily required to establish the present invention.

[0015] In an embodiment of the present invention, the wall thickness of the PTFE tubing is approximately 0.04 mm or less. Specifically, it is approximately 0.005 mm to approximately 0.04 mm, preferably approximately 0.01 mm to approximately 0.04 mm, and more preferably approximately 0.01 mm to approximately 0.03 mm. A thinner wall thickness, when used as part of a catheter layer, does not hinder the functionality of the catheter and can contribute to a thinner catheter diameter. The wall thickness should at least be sufficient to ensure airtightness within the tubing. The wall thickness of the PTFE tubing can be confirmed by measuring a cross-section perpendicular to the long axis of the PTFE tubing using a microscope or other device. Alternatively, if the inner diameter of the PTFE tubing can be measured using a pin gauge, the inner diameter can also be measured using the pin gauge. With the pin gauge inserted into the end of the tubing, the outer diameter can be measured from above using a dial gauge or other device. The outer diameter can then be calculated using the formula: wall thickness = (outer diameter - inner diameter) / 2. Furthermore, in embodiments of the present invention, the inner diameter of the PTFE tubing is preferably between approximately 0.20 mm and 3.0 mm, more preferably between approximately 0.25 mm and 2.0 mm. Figure 1 is a schematic diagram of a cross-section 1 of a PTFE tubing and serves as an illustration of the tubing's dimensions. When the tubing's cross-section is circular, the inner diameter of the tubing refers to the diameter of the inside of the tubing's cross-section. Using Figure 1 as an example, the inner diameter is the inner circle diameter, which is the straight line distance between points A and B on the inner circle, along a line passing through the center C of the inner circle. The inner diameter is measured evenly at approximately two locations (two locations where the angle of the straight line is changed by approximately 90°) to four locations (four locations where the angle of the straight line is changed by approximately 45°), and the average value is used as the inner diameter of the PTFE tubing. The wall thickness of the PTFE tubing is the distance between points A and A' on the inner circle, along a line passing through the center C of the circle, and also the distance between points A' and B' on the outer circle. The wall thickness is measured evenly at 4 to 8 locations, and the average value is used as the wall thickness of the PTFE pipe.

[0016] In the stress-strain curve obtained by the tensile test in an atmosphere of 200°C, if the tensile stress at the elongation of the polytetrafluoroethylene tube is 20% (20% strain tensile stress) is σ 20 (N / mm 2) and the tensile stress at the elongation of the polytetrafluoroethylene tube is 50% (50% strain tensile stress) is σ 50 (N / mm 2), the PTFE tube of the present invention (when its wall thickness is 0.04 mm or less) satisfies formula (1), the problem of the present invention can be solved. Formula (1) is the result of data analysis 2.0≦0.1×σ 20+0.3×σ 50<5.5 Formula (1) The result shows a high correlation with the uniformity of the PTFE tube during extension. The right-hand side value of formula (1) is preferably 5.5, preferably 5.0. If the left-hand side value of formula (1) is too small, the strength of the PTFE tube during extension cannot be fully obtained. The left-hand side value of formula (1) is preferably 2.0, preferably 3.0. In addition, when the inner diameter of the PTFE tube of the present invention is less than about 3.0 mm, if formula (1) is satisfied, the effect tends to be further improved. When an outer resin layer is formed on a PTFE tube, the right-hand and left-hand values ​​of equation (1) for the inner layer material of the tube after the PTFE tube has been processed tend to increase by approximately 20%. Therefore, the value obtained for the inner layer material of the tube can be treated as the value of the PTFE tube of the present invention by subtracting approximately 20%.

[0017] Furthermore, the polytetrafluoroethylene tubing of the present invention preferably exhibits a tensile strain at break of 200% or greater in a tensile test conducted in an atmosphere at 200°C. Furthermore, the 20% strain tensile stress σ20 of the polytetrafluoroethylene tubing in a tensile test conducted in an atmosphere at 200°C is preferably at least 4.0 (N / mm²). Furthermore, the 20% strain tensile stress σ20 of the polytetrafluoroethylene tubing is preferably less than 11.0 (N / mm²).

[0018] Furthermore, in a tensile test conducted in an atmosphere at 200°C, the PTFE tubing of the present invention preferably has a 50% strain tensile stress (σ50) of 6.0 (N / mm²) or greater. Furthermore, the 50% strain tensile stress (σ50) of the PTFE tubing is preferably less than 14.0 (N / mm²). Medical tubing using the PTFE tubing of the present invention having strength and moderate elongation can be made into tubing with good flexibility.

[0019] The PTFE tubing of the present invention has a wetting tension of at least 46 mN / m on either or both of its outer and inner surfaces, preferably at least 60 mN / m. The wetting tension of the PTFE tubing surface can be adjusted by etching (physical or chemical modification). Specifically, etching can be performed using plasma, corona discharge, or ion beams; or etching using a mixture of metallic sodium and ammonia or naphthalene. For example, etching using a solution of naphthalene, metallic sodium, and dimethyl ether can also achieve a wetting tension of at least 70 mN / m on the tubing surface. The PTFE tubing of the present invention has a wetting tension of at least 46 mN / m on its outer surface. This makes it easier to maintain the strength of the inner layer (PTFE layer) against loads applied to the inner surface of medical tubing, particularly when used as the inner layer of medical tubing.

[0020] Hereinafter, embodiments of the present invention will be described in detail. PTFE powder used in pipe molding includes both fine powder and molding powder. The fine powder used in embodiments of the present invention preferably exhibits the following properties: it deforms as it fibrillates when shear stress is applied. The polytetrafluoroethylene resin used in embodiments of the present invention can be a homopolymer of tetrafluoroethylene (hereinafter referred to as "TFE") or modified PTFE. Modified PTFE is a product obtained by polymerizing TFE with a small amount of monomers other than TFE. Examples of such monomers other than TFE include chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and perfluoroalkyl vinyl ether (PAVE). Generally, modified PTFE is used to enhance the heat resistance, wear resistance, and flex resistance of molded products. The polytetrafluoroethylene resin used in embodiments of the present invention can be a single type of PTFE listed above or a blend of multiple types. Furthermore, the polytetrafluoroethylene pipe of the present invention may contain a small amount of polymers other than the polytetrafluoroethylene resin listed above, as long as this does not impair its functionality.

[0021] PTFE fine powder is generally composed of primary particles with an average particle size of 0.2-0.5 μm agglomerated to form secondary particles with an average particle size of 400-700 μm. It has the property of being easily fibrillated even at room temperature by vibration and other means, and easily forms lumps. Paste extrusion is a method that utilizes this property. Generally speaking, paste extrusion involves mixing PTFE with an organic solvent known as an additive (lubricant), compressing it to form a preliminary molded body. This preliminary molded body is then fed into an extruder, pressure is applied, and extruded into a film, tube, or linear coating. In the PTFE tubing of the present invention, since uniformity of the extruded PTFE tubing is crucial, the preliminary molded body is preferably formed to achieve a uniform internal structure. Specifically, for example, the PTFE fine powder mixed with the additive before forming the preliminary molded body is preferably treated to prevent lumps from forming. Any formed lumps are removed using a sieve before feeding the preliminary molded body into the compression mold.

[0022] The additive is added to the PTFE fine powder to form a paste, which can then be formed using an extruder. The additive used in the embodiment of the present invention is preferably an organic solvent with high lubricity. After adding the additive to the PTFE fine powder, it is formed into a tube through a die in an extruder. However, if the additive volatilizes during forming, stable forming becomes difficult and less than ideal. The additive used in the embodiment of the present invention preferably has an initial boiling point (IBP) of 150°C or higher. After the PTFE fine powder and the additive are formed into the shape of the tube, the additive is removed by volatilization before the tube is fired. To reliably remove the additive at this time, the IBP of the additive is preferably below 250°C. Petroleum-based solvents are often used as organic solvents with high lubricity and an IBP of 150°C to 250°C.

[0023] The additive used in the embodiments of the present invention preferably has an interfacial tension that is at least 3 mN / m higher than the interfacial tension of PTFE, which is 18.5 mN / m. It is believed that the high interfacial tension of the additive prevents excessive migration between PTFE particles and tends to remain on the particle surface. During PTFE paste extrusion, the PTFE particles slide against each other within the die, and the particle surfaces become fibrillated. This fibril entanglement hinders flow, increasing extrusion pressure. The additive surrounding the PTFE particles enhances lubricity between the PTFE particles and between the PTFE particles and the die wall, moderately suppressing entanglement between the PTFE particles and preventing excessive increases in extrusion pressure. For example, when extruding PTFE tubing with a wall thickness of 0.04 mm or less, the flow path within the die is extremely narrow, and the resin flows under high reduction ratios (RR), increasing shear forces between the die wall and the PTFE particles, as well as between the PTFE particles themselves. If high shear stress is applied to PTFE particles rapidly, they will fibrillate, increasing extrusion pressure. However, additives retained between PTFE particles reduce the shear forces between the particles and between the particles and the mold wall, thus suppressing excessive fibrillation.

[0024] The pipe fittings according to embodiments of the present invention may also contain fillers or other resins in polytetrafluoroethylene resin. Examples of fillers include metal oxides such as carbon and alumina, calcined PTFE, and resin fillers composed of fluororesins other than PTFE or other resins. One or more of these fillers may be mixed with PTFE. Furthermore, PTFE pipe fittings may be constructed with multiple layers, with the filler or other resin layer being disposed in only one of the layers.

[0025] Hereinafter, a method for manufacturing a pipe fitting according to an embodiment of the present invention will be described. [Forming of preliminary molded body] Mix the PTFE fine powder and additives using a rotating drum. If fillers are added to the PTFE, they can be added in this step. The PTFE fine powder is used after removing any lumps using a sieve or other method. After the PTFE and additive mixture is sieved to remove any lumps, it is compressed and formed into a preliminary molded body. The preliminary molded body should be uniformly compressed throughout its interior. When constructing PTFE tubing in multiple layers, for example, preliminary molded bodies of different sizes can be combined to create a multi-layer preliminary molded body. [Extrusion molding] The prepared preformed body is placed in an extruder and formed into a tube shape through a die. The die outlet temperature of the extruder is preferably between 80°C and 150°C, preferably between 90°C and 120°C. High die temperatures promote surface fibrillation of the PTFE particles, strengthening the entanglement of the resulting fibrils. Furthermore, the cooling rate of the extruded tube from the die may affect the values ​​of the 20% strain tensile stress σ20 and 50% strain tensile stress σ50 of the polytetrafluoroethylene (PTFE) tubing. For example, by covering the die periphery after the PTFE is extruded from the die outlet with a heater, the temperature of the PTFE tubing around the die outlet can be adjusted. For the PTFE tubing of the present invention, this temperature is found to be suitable between 60°C and 120°C. The extrusion speed and temperature of the preliminary molded body are preferably adjusted to maintain a constant extrusion pressure, and molding is performed at a constant extrusion pressure. The extrusion of the pipe is carried out under a certain stable state, and the balance between the pipe output and the pickup (winding) is adjusted. From the pipe extrusion forming step to the drying step and the pipe sintering step, the processing can be carried out in a way that does not impose a load on the formed pipe. [Drying step] PTFE formed into the tubing shape is heated in a furnace set to a temperature below the PTFE melting point, volatilizing the additive. During the subsequent sintering step, the PTFE is left with a significant amount of additive, which is unsatisfactory for the tubing quality. Therefore, sufficient volatilization is required. Using an additive with an IBP of 150°C to 250°C facilitates its removal during the drying step. To minimize tubing elongation during the drying step, line tension should be adjusted to achieve a balance between tubing delivery and pickup. [Pipe Firing Steps] The dried PTFE formed into the tubing is then calcined by heating it to a temperature above the melting point of PTFE. This temperature is typically around 400°C. When the PTFE forming the tubing is heated above its melting point, the PTFE particles fuse together, forming the tubing. [Etching process step] The surface of the PTFE tube is etched physically and / or chemically.

[0026] The present invention will be described in more detail with reference to the following examples. The following examples are provided to illustrate the present invention and are not intended to limit the present invention.

[0027] Example Tensile test at 200°C Tensile tests were performed using a testing machine capable of controlling the sample temperature in a constant temperature chamber, in an atmosphere of 200°C using the following test conditions. [Tensile test conditions] Test temperature 200℃±3℃ Initial distance between chucks 50mm Test speed 50mm / min Cut the pipe into a length suitable for measurement and use it directly as the test specimen. Continue measuring until the pipe fractures, and obtain data. The number of test specimens should be set to at least 5, and the stress values ​​should be calculated using the arithmetic mean of these measured values. The tensile strain ε (%) is calculated by dividing the increase in the distance between the chucks, ΔL (mm), by the initial distance between the chucks, L 0 (mm), using the formula ε (%) = (ΔL / L 0) × 100. When the pipe placed in the chucks of the testing machine is elongated by 20% in the longitudinal direction (at an elongation of 10 mm), the stress is 20% strain tensile stress σ 20, σ' 20. When the pipe is elongated by 50% in the longitudinal direction (at an elongation of 25 mm), the stress is 50% strain tensile stress σ 50, σ' 50. When testing the inner layer of a PTFE tube with an outer resin layer, the outer resin layer can be peeled off and removed with a solvent, and only the inner layer of the tube can be used for tensile testing. <Heating Extension Test> A core wire approximately 20 mm shorter than the tube was inserted through a sample tube cut to a length of at least 1000 mm (20 samples were prepared). One end of the core wire was fixed to the lamination machine, aligned with the tube and the leading end of the core wire. The other end was fixed to the tube and hung with a weight. The weight was set to 150 g per 0.1 mm² of the tube's cross-sectional area. A heater heated to 300°C was moved downward from above the suspended tube, stretching the PTFE tubing and laminating it onto the core wire. The heater's movement speed was set at 100 mm / min. The core wire with the PTFE tubing laminated onto it (hereinafter referred to as the coated core wire) was cooled and its dimensions were measured. Since a core wire with a fixed outer diameter was used, the wall thickness of the coated PTFE tubing could be calculated from the outer diameter of the coated core wire and the outer diameter of the core wire. Variation in the outer diameter of the coated core wire was evaluated as variation in the elongation of the coated PTFE tubing. Since several tens of millimeters of the ends of the covered core wire may be damaged during lamination, the dimensions of the covered core wire are measured by deducting these tens of millimeters of the ends. The outer diameter is measured at six or more locations as evenly as possible along the entire length of the covered core wire. Measurements are made evenly in the radial direction (cross-sectional direction) at each measurement point, from two points (two points at which the measurement angle is changed by 90°) to four points (four points at which the measurement angle is changed by 45°). The arithmetic average of these measurements is defined as the outer diameter D0 at that measurement point. Furthermore, measurements are made at six or more locations along the entire length of a specimen, and the arithmetic average of the outer diameter D0 at each measurement point is defined as the outer diameter average value D of the specimen. The outer diameter variation within the specimen is confirmed by calculating the coefficient of variation within the specimen. The coefficient of variation (CVD) of the outer diameter for a single specimen is calculated by combining the outer diameter deviation (outer diameter at the measurement point, D0 - average outer diameter, D) and the outer diameter variation (the mean square of the outer diameter deviation). The outer diameter standard deviation (the square root of the outer diameter variation) is then divided by the average outer diameter, D. Repeat the same process for the remaining 19 specimens. The arithmetic mean of the coefficients of variation (CVD) for each of the 20 specimens is designated as the "coefficient of variation (CV)." <Wet tension test> Wetting tension is measured in accordance with ISO 8296. Specifically, a test mixture (wetting tension test mixture) is applied to the surface of the PTFE tubing using a swab, and the state of the liquid film is evaluated. If the line drawn with the swab does not change within two seconds, the surface tension of the PTFE tubing is determined to be greater than the surface tension of the wetting tension test mixture. Conversely, if the line drawn with the swab shrinks or the liquid film breaks within two seconds, the evaluation is performed using a mixture with a lower surface tension than the wetting tension test mixture.

[0028] Example 1 100 parts by mass of PTFE fine powder (delumped) and 18 parts by mass of an additive are placed in a container and mixed. After delumping, the mixture is compressed to form a preliminary molded body. This preliminary molded body is fed into an extruder with a cylinder diameter of 20 mm and a mandrel diameter of 10 mm and extruded at a die temperature of 100°C to form a tube. A heater covers the periphery of the die after the PTFE is discharged from the die outlet, and the temperature around the die outlet is adjusted to 90°C. The formed tube is dried and calcined in a first drying furnace set at 150°C, a second drying furnace set at 220°C, and a calcining furnace set at 430°C. The resulting tube has an inner diameter of 0.60 mm and a wall thickness of 0.028 mm. The surface of the resulting tube is coated with TETRA-ETCH (registered trademark), washed with alcohol and water, and then etched to produce a PTFE tube according to an embodiment of the present invention. The resulting PTFE tubing was cut into approximately 100 mm lengths to prepare tensile test specimens. Tensile testing was performed in an atmosphere at 200°C, following the aforementioned method. Furthermore, the resulting PTFE tubing was cut into approximately 1000 mm lengths to prepare evaluation specimens. Separately, a core wire with an outer diameter of 0.51 mm and a length of approximately 980 mm was prepared and subjected to a heated elongation test, following the aforementioned method. Furthermore, wet tension was measured, following the aforementioned method. Example 2 A preliminary molded body, prepared in the same manner as in Example 1, was placed into an extruder with a cylinder diameter of 30 mm and a mandrel diameter of 10 mm and extruded at a die temperature of 90°C to form a tube. A heater was placed around the die after the PTFE was extruded from the die outlet, and the temperature around the die outlet was maintained at 80°C. As in Example 1, the formed tube was dried and calcined in a drying and calcining furnace. The resulting tube had an inner diameter of 1.72 mm and a wall thickness of 0.038 mm. The surface of the resulting tube was coated with TETRA-ETCH (registered trademark), washed with alcohol and water, and then etched to produce a PTFE tube according to an embodiment of the present invention. The resulting PTFE tube was cut into approximately 100 mm lengths to prepare tensile test specimens. Tensile tests were performed in an atmosphere at 200°C according to the above method. Furthermore, the resulting PTFE tube was cut into approximately 1000 mm lengths to prepare evaluation specimens. Separately, a core wire with an outer diameter of 1.45 mm and a length of approximately 980 mm was prepared and subjected to a heat extension test according to the above method. Furthermore, the wet tension was measured according to the above method. Example 3 A preliminary molded body, prepared in the same manner as in Example 1, was placed into an extruder and extruded at a die temperature of 100°C to form a tube. A heater was placed around the die after the PTFE was discharged from the die outlet, and the temperature around the die outlet was adjusted to 80°C. As in Example 1, the formed tube was dried and sintered in a drying and sintering furnace. The resulting tube had an inner diameter of 0.475 mm and a wall thickness of 0.028 mm. The surface of the resulting tube was plasma treated by passing it through a plasma generated at a voltage of 10 kV, a frequency of 18 kHz, and an excitation gas of Ar gas at a speed of 6.0 m / min, thereby producing a PTFE tube according to an embodiment of the present invention. The resulting PTFE tube was cut into approximately 100 mm lengths to prepare tensile test specimens. Tensile testing was performed in an atmosphere at 200°C according to the above method. The resulting PTFE tube was also cut into approximately 1000 mm lengths to prepare evaluation specimens. Separately, a core wire with an outer diameter of 0.41 mm and a length of approximately 980 mm was prepared and subjected to a heat extension test according to the above method. Furthermore, the wet tension was measured according to the above method. Example 4 A preliminary molded body, prepared in the same manner as in Example 1, was placed into an extruder and extruded at a die temperature of 100°C to form a tube. A heater was placed around the die after the PTFE was extruded from the die outlet, and the temperature around the die outlet was maintained at 100°C. As in Example 1, the formed tube was dried and calcined in a drying and calcining furnace. The resulting tube had an inner diameter of 0.49 mm and a wall thickness of 0.038 mm. The surface of the resulting tube was coated with TETRA-ETCH (registered trademark), washed with alcohol and water, and then etched to produce a PTFE tube according to an embodiment of the present invention. The resulting PTFE tube was cut into approximately 100 mm lengths to prepare tensile test specimens. Tensile tests were performed in an atmosphere at 200°C, following the above method. The resulting PTFE tube was also cut into approximately 1000 mm lengths to prepare evaluation specimens. Separately, a core wire with an outer diameter of 0.41 mm and a length of approximately 980 mm was prepared and subjected to a heat extension test according to the above method. Furthermore, the wet tension was measured according to the above method. Example 5 A preliminary molded body, prepared in the same manner as in Example 1, was placed into an extruder and extruded at a die temperature of 80°C to form a tube. A heater was placed around the die after the PTFE was discharged from the die outlet, and the temperature around the die outlet was adjusted to 60°C. As in Example 1, the formed tube was passed through a drying furnace and a sintering furnace for drying and sintering. The resulting tube had an inner diameter of 0.50 mm and a wall thickness of 0.022 mm. The surface of the resulting tube was plasma treated by passing it through a plasma generated at an applied voltage of 10 kV, a frequency of 18 kHz, and an excitation gas of Ar gas at a speed of 2 m / min, thereby producing a PTFE tube according to an embodiment of the present invention. The resulting PTFE tube was cut into approximately 100 mm lengths to prepare tensile test specimens. Tensile tests were performed in an atmosphere at 200°C according to the above method. The resulting PTFE tube was also cut into approximately 1000 mm lengths to prepare evaluation specimens. Separately, a core wire with an outer diameter of 0.41 mm and a length of approximately 980 mm was prepared and subjected to a heat extension test according to the above method. Furthermore, the wet tension was measured according to the above method. Example 6 A preliminary molded body, prepared in the same manner as in Example 1, was placed into an extruder with a cylinder diameter of 44 mm and extruded at a die temperature of 100°C to form a tube. A heater was placed around the die after the PTFE was extruded from the die outlet, and the temperature around the die outlet was maintained at 80°C. As in Example 1, the formed tube was dried and calcined in a drying and calcining furnace. The resulting tube had an inner diameter of 2.68 mm and a wall thickness of 0.033 mm. The surface of the resulting tube was coated with TETRA-ETCH (registered trademark), washed with alcohol and water, and then etched to produce a PTFE tube according to an embodiment of the present invention. The resulting PTFE tube was cut into approximately 100 mm lengths to prepare tensile test specimens. Tensile tests were performed in an atmosphere at 200°C, following the above method. The resulting PTFE tube was also cut into approximately 1000 mm lengths to prepare evaluation specimens. Separately, a core wire with an outer diameter of 2.42 mm and a length of approximately 980 mm was prepared and subjected to a heat extension test according to the above method. Furthermore, the wet tension was measured according to the above method.

[0029] Table 1 shows the results of each example.

[0030] [Table 1] In all examples, it was confirmed that the 20% strain tensile stress σ 20 (N / mm 2) and the 50% strain tensile stress σ 50 (N / mm 2) of the polytetrafluoroethylene tubing satisfy the above formula (1). Furthermore, the outer diameter variation (outer diameter variation coefficient CV) when the core wire is covered with the PTFE tubing is small, indicating uniform elongation. FIG2 is a graph of the median value of formula (1) and the outer diameter variation (outer diameter variation coefficient CV) for the PTFE tubing of the example. This graph confirms that the relationship formula (1) is highly correlated with the uniform elongation when the core wire is covered with the PTFE tubing.

[0031] Industrial applicability The PTFE tube of the present invention can be suitably used as an inner layer material of a tube, and the tube using the PTFE tube of the present invention can be suitably used in medical tubes, etc.

[0032] 1:PTFE pipe fittings (cross section) A,A',B,B':point C: Center

Claims

1. A polytetrafluoroethylene (PTFE) pipe fitting, characterized in that: the wall thickness is 0.005 mm or more and 0.04 mm or less, and the wetting tension of either or both of the outer and inner surfaces of the PTFE pipe fitting is 46 mN / m or more; in the stress-strain curve obtained by a tensile test conducted under an ambient gas temperature of 200°C, the 20% strain tensile stress σ20 (N / mm2) of the PTFE pipe fitting and the 50% strain tensile stress σ50 (N / mm2) of the PTFE pipe fitting satisfy Equation (1): 2.0 ≦ 0.1 × σ20 + 0.3 × σ50 < 5.5 Equation (1).

2. The PTFE pipe fittings as requested in item 1 have a tensile fracture strain of more than 200% in a tensile test conducted in an ambient gas at 200°C.

3. For the polytetrafluoroethylene (PTFE) fittings as requested in item 1, wherein in a tensile test conducted in an ambient gas at 200°C, the tensile stress σ20 of the aforementioned PTFE fitting at 20% strain is 4.0 (N / mm2) or higher.

4. A medical fitting that uses a polytetrafluoroethylene fitting as claimed in any one of claims 1 to 3.

5. A polytetrafluoroethylene (PTFE) pipe fitting, characterized in that: the wall thickness is 0.005 mm or more and 0.04 mm or less, and the inner diameter of the PTFE pipe fitting is 0.2 mm or more and 3.0 mm or less; in the stress-strain curve obtained by a tensile test conducted under an ambient gas temperature of 200°C, the 20% strain tensile stress σ20 (N / mm2) of the PTFE pipe fitting and the 50% strain tensile stress σ50 (N / mm2) of the PTFE pipe fitting satisfy Equation (1): 2.0 ≦ 0.1 × σ20 + 0.3 × σ50 < 5.5 Equation (1).

6. The PTFE pipe fittings as requested in item 5 have a tensile fracture strain of more than 200% in a tensile test conducted in an ambient gas at 200°C.

7. For the polytetrafluoroethylene (PTFE) fittings as requested in item 5, wherein in a tensile test conducted in an ambient gas at 200°C, the tensile stress σ20 of the aforementioned PTFE fitting at 20% strain is 4.0 (N / mm2) or higher.

8. A medical fitting that uses a polytetrafluoroethylene fitting as described in any one of claims 5 to 7.

9. A medical tubing, characterized in that: it comprises an inner layer material of a tubing having been processed from a polytetrafluoroethylene tubing, wherein the wall thickness of the inner layer material is less than 0.04 mm and the inner diameter of the inner layer material is less than 3.0 mm, and in the stress-strain curve obtained by a tensile test conducted under an ambient gas at 200°C, the 20% strain tensile stress σ'20 (N / mm2) of the inner layer material and the 50% strain tensile stress σ'50 (N / mm2) of the inner layer material satisfy Equation (2): 2.4≦0.1×σ'20+0.3×σ'50<6.6 Equation (2).

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