Polytetrafluoroethylene tube and medical tube using the same

Abstract

The present invention provides a thin-walled PTFE tube having moderate stretchability and sufficient strength and good uniformity during stretching, and also provides a medical tube having excellent flexibility and dimensional accuracy. The polytetrafluoroethylene tube of the present invention is a polytetrafluoroethylene tube having a wall thickness of about 0.04 mm or less, the wetting tension of one or both of the outer surface and the inner surface of the polytetrafluoroethylene tube being 46 mN / m or more, and the 20% strain tensile stress σ of the polytetrafluoroethylene tube being 0.01 mm or less in a stress-strain curve obtained by a tensile test conducted in an atmosphere at 200°C. 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 (N / mm 2 ) satisfies 2.0≤0.1σ 20 +0.3σ 50 <5.5(Formula (1)).

Description

Technical Field

[0001] The present invention relates to a fluororesin tube, and more particularly to a thin-walled tube made of polytetrafluoroethylene (hereinafter referred to as "PTFE"). Background Art

[0002] Intravascular surgery, which involves inserting a catheter into a blood vessel to remove and treat the diseased area inside the blood vessel, has become the mainstream because it places little burden on the patient. The catheter used for this purpose needs to be inserted into the body percutaneously, and the front end of the tube reaches the diseased area through the blood vessel. Therefore, the catheter is required to have the ability to advance straight in the blood vessel, and the ability to transmit the operation of the operator performing the treatment. In order to meet these requirements, the catheter is composed of layers with different characteristics stacked on top of each other. The inside of the catheter needs to cope with operations such as the insertion of the treatment clamp and the injection of the drug solution, so the inner surface is required to have low friction, high strength, and the inner diameter is as large as possible. On the other hand, considering the burden on the patient, it is required to reduce the outer diameter of the catheter. Therefore, it is hoped that each layer that constitutes the catheter is as thin as possible.

[0003] PTFE tubes are suitable for medical applications due to their excellent properties such as chemical resistance, non-stickiness, and low friction. As one of the methods for manufacturing catheters, there is a method in which a core wire is coated with PTFE, an outer resin layer is formed thereon, and then the core wire is removed to obtain a catheter. As a method for coating a core wire with PTFE, there is a method in which a PTFE dispersion is coated on the core wire and sintered (hereinafter referred to as "impregnation method"), and a method in which a paste is directly extruded and coated on the core wire.

[0004] In addition, there is also a method of coating a PTFE tube formed into a thin wall on a core wire. In this method, the core wire is passed through the PTFE tube, and the PTFE tube is stretched in this state to reduce its diameter so that the PTFE tube contacts the surface of the core wire. In this method, as the characteristics of the PTFE tube used, it is required to have both strength that can withstand stretching and stretchability that can be stretched. In addition, in the catheter manufacturing process that requires high dimensional accuracy, it is desired that the PTFE layer on the core wire has a uniform wall thickness, and the stretched PTFE tube is required to have high dimensional accuracy and uniform stretchability.

[0005] The melt viscosity of PTFE is very large, and long strips of PTFE molded products are generally not formed by melt extrusion but by paste extrusion molding. However, paste extrusion is difficult to form into thin-walled tubes. Therefore, in order to form thin-walled PTFE tubes, the impregnation method of applying PTFE dispersion on the core wire and sintering, and then removing the core wire to obtain the tube is often used in the past (for example, refer to patent document 1). However, the tube formed by the impregnation method may produce defects such as pinholes, and there are also problems such as poor strength. In addition, patent document 2 discloses a method for extruding PTFE resin paste on a metal core wire to obtain a thin-walled tube. Although paste extrusion can promote the flow orientation of PTFE particles and improve the tensile strength of the tube, it cannot obtain sufficient strength to improve the performance of the catheter.

[0006] Patent Document 3 discloses a method of forming a PTFE tube by paste extrusion and then stretching the PTFE tube in the length direction to thin the tube. However, although the PTFE tube can be thinned and the strength of the tube can be ensured by stretching the PTFE tube, there is a problem that the stretchability and flexibility of the tube are lost.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2000-316977

[0010] Patent Document 2: Japanese Patent Application Publication No. 2013-176583

[0011] Patent Document 3: Japanese Patent Application Publication No. 2004-340364 Summary of the invention

[0012] Technical problem to be solved by the invention

[0013] The present invention aims to solve the above problems of conventional thin-walled PTFE tubes, and to provide a thin-walled PTFE tube having appropriate stretchability and sufficient strength, and having good uniformity during stretching required when the PTFE tube is used for covering a core wire, etc., and to provide a medical tube having excellent flexibility and dimensional accuracy.

[0014] Technical solutions adopted to solve technical problems

[0015] In order to solve the above problems, the technical solutions described in the claims can be adopted. For example, a polytetrafluoroethylene tube having a wall thickness of about 0.04 mm or less, characterized in that the wetting tension of one or both of the outer surface and the inner surface of the polytetrafluoroethylene tube is 46 mN / m or more, and in the stress-strain curve obtained by the tensile test in an atmosphere of 200°C, the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20(N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 (N / mm 2 ) satisfies 2.0≤0.1×σ 20 +0.3×σ 50 <5.5(Formula (1)).

[0016] A preferred embodiment is a polytetrafluoroethylene tube having a tensile fracture strain of more than 200% in a tensile test conducted at 200°C, and a 20% strain tensile stress σ 20 At 4.0(N / mm 2 )above.

[0017] In addition, the following technical solutions described in the claims can be adopted. For example, a polytetrafluoroethylene tube having a wall thickness of about 0.04 mm or less, characterized in that the inner diameter of the polytetrafluoroethylene tube is about 3.0 mm or less, and in a stress-strain curve obtained by a tensile test conducted at 200° C., the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 (N / mm 2 ) satisfies 2.0≤0.1σ 20 +0.3σ 50 <5.5(Formula (1)).

[0018] In another example, a medical tube is provided, wherein a polytetrafluoroethylene tube is used, wherein the wall thickness of the polytetrafluoroethylene tube is about 0.04 mm or less, and the wetting tension of one or both of the outer surface and the inner surface of the polytetrafluoroethylene tube is 46 mN / m or more, and in a stress-strain curve obtained by a tensile test conducted in an atmosphere at 200° C., the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 (N / mm 2 ) satisfies the above formula (1).

[0019] In addition, there is a medical tube using a polytetrafluoroethylene tube, wherein the wall thickness of the polytetrafluoroethylene tube is about 0.04 mm or less, and the inner diameter of the polytetrafluoroethylene tube is about 3.0 mm or less, and in a stress-strain curve obtained by a tensile test conducted in an atmosphere at 200° C., the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube50 (N / mm 2 ) satisfies the above formula (1).

[0020] Still another example is a medical tube comprising a polytetrafluoroethylene liner obtained by processing a polytetrafluoroethylene tube, wherein the wall thickness of the polytetrafluoroethylene liner is less than about 0.04 mm, the inner diameter of the polytetrafluoroethylene liner is less than about 3.0 mm, and the 20% strain tensile stress σ' of the polytetrafluoroethylene liner in a stress-strain curve obtained by a tensile test conducted at 200° C. is less than about 0.04 mm. 20 (N / mm 2 ) and the 50% strain tensile stress σ' of the polytetrafluoroethylene liner 50 (N / mm 2 ) satisfies 2.4≤0.1×σ' 20 +0.3×σ' 50 <6.6(Formula (2)).

[0021] Effects of the Invention

[0022] The PTFE tube of the present invention has strength and appropriate stretchability, and has good uniformity during stretching, so it can be suitably used for applications where the PTFE tube is stretched for use. The PTFE tube coated on the core wire is uniform, has small dimensional deviation, and is excellent in flexibility and dimensional accuracy. The PTFE tube of the present invention can be used for products requiring high dimensional accuracy, and is particularly suitable as a liner for medical tubes, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a tube cross section for explaining the dimensions of the PTFE tube of the present invention.

[0024] Figure 2 This is a graph showing the relationship between the value on the intermediate side of the formula (1) and the fluctuation (coefficient of variation CV) of the outer diameter related to the PTFE tube of the present invention. DETAILED DESCRIPTION

[0025] The PTFE tube according to the embodiment of the present invention is described in detail below. The embodiment described below is not intended to limit the invention described in the claims, and all combinations of features described in the embodiment are not essential to the establishment of the present invention.

[0026] In an embodiment of the present invention, the wall thickness of the PTFE tube is below about 0.04 mm. Specifically, about 0.005 mm to about 0.04 mm, preferably about 0.01 mm to about 0.04 mm, and more preferably about 0.01 mm to about 0.03 mm. If the wall thickness is thin, when used as a part of the layer of the catheter, it can help reduce the diameter of the catheter without hindering the function of the catheter. It is preferably a wall thickness that is at least sufficient to ensure the airtightness of the inside of the tube. The wall thickness of the PTFE tube can be confirmed by measuring the cross section cut perpendicular to the long axis direction of the PTFE tube using a microscope or the like. Alternatively, in the case where the inner diameter of the PTFE tube can be measured with a needle gauge, the inner diameter can also be measured with a needle gauge, and the outer diameter is measured from above it with a micrometer or the like when the needle gauge is inserted into the end of the tube, and calculated by the formula (wall thickness = (outer diameter-inner diameter) / 2). In addition, in an embodiment of the present invention, the inner diameter of the PTFE tube is below about 3.0 mm. Specifically, it is preferably about 0.20 mm to about 3.0 mm, and more preferably about 0.25 mm to about 2.0 mm. Figure 1 1 is a schematic diagram of a cross section of a PTFE tube, and is a diagram for explaining the dimensions of the tube. When the cross section of the tube is circular, the inner diameter of the tube refers to the diameter of the inner side of the cross section of the tube. Figure 1 To explain, the inner diameter refers to the diameter of the inner circle, which is the straight line distance between point A and point B on the inner circle on the straight line passing through the center C of the inner circle. The inner diameter is evenly measured at about 2 places (2 places where the angle of the straight line changes by about 90°) to 4 places (4 places where the angle of the straight line changes by about 45°), and the average value is used as the inner diameter of the PTFE tube. The wall thickness of the PTFE tube is the distance between point A on the inner circle and point A' on the outer circle on the straight line passing through the center C of the circle, and is also the distance between point A' on the inner circle and point B' on the outer circle. The wall thickness is evenly measured at about 4 places to 8 places, and the average value is used as the wall thickness of the PTFE tube.

[0027] In the stress-strain curve obtained from the tensile test conducted at 200°C, the tensile stress (20% strain tensile stress) when the elongation of the polytetrafluoroethylene tube reaches 20% is recorded as σ 20 (N / mm 2 ), the tensile stress (50% strain tensile stress) when the elongation of the polytetrafluoroethylene tube reaches 50% is recorded as σ 50 (N / mm 2 ), if the PTFE tube of the present invention (when its wall thickness is less than 0.04 mm) satisfies formula (1), the problem of the present invention can be solved. Formula (1) is the result of data analysis

[0028] 2.0≤0.1×σ 20 +0.3×σ 50 <5.5 Formula (1)

[0029] The obtained formula has a high correlation with the uniformity of the PTFE tube when stretched. The value on the right side of formula (1) is preferably 5.5, and more preferably 5.0. If the value on the left side of formula (1) is too small, the strength of the PTFE tube when stretched may not be fully obtained. The value on the left side of formula (1) is preferably 2.0, and more 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, there is a tendency that the effect is more easily improved.

[0030] When an outer resin layer is formed on a PTFE tube, the value on the right side and the value on the left side of the formula (1) of the PTFE liner obtained by processing the PTFE tube tend to increase by about 20%. Therefore, the value obtained by subtracting about 20% from the above value obtained by the PTFE liner can be used as the value of the PTFE tube of the present invention.

[0031] In addition, in a tensile test conducted at 200°C, the tensile fracture strain of the polytetrafluoroethylene tube of the present invention is preferably 200% or more. In addition, the 20% strain tensile stress σ of the polytetrafluoroethylene tube in a tensile test conducted at 200°C is 20 Preferably at 4.0 (N / mm 2 ) or more. In addition, the 20% strain tensile stress σ of the polytetrafluoroethylene tube 20 Preferably less than 11.0 (N / mm 2 ).

[0032] In addition, in a tensile test of the polytetrafluoroethylene tube of the present invention in an atmosphere at 200°C, the 50% strain tensile stress σ of the polytetrafluoroethylene tube is 50 Preferably at 6.0 (N / mm 2 ) or more. In addition, the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 Preferably less than 14.0 (N / mm 2 ).

[0033] The medical tube using the PTFE tube of the present invention having strength and appropriate stretchability can be a tube having good flexibility.

[0034] The wetting tension of one or both of the outer surface and the inner surface of the PTFE tube of the present invention is above 46mN / m, more preferably above 60mN / m. The wetting tension of the PTFE tube surface can be adjusted by etching the surface (physical or chemical modification). Specifically, etching using plasma, corona discharge or ion beam, etching using a mixture of metallic sodium and ammonia or naphthalene, etc. can be implemented. For example, by etching using a naphthalene+metallic sodium+diethylene glycol dimethyl ether solution, the wetting tension of the tube surface can also be made to reach above 70mN / m. The wetting tension of the outer surface of the PTFE tube of the present invention is above 46mN / m, and particularly when used as an inner liner of a medical tube, it is easy to maintain the strength of the inner layer (PTFE layer) for the load applied to the inner surface of the medical tube.

[0035] Hereinafter, embodiments of the present invention will be described in detail.

[0036] There are two types of PTFE powder used in tube forming: fine powder and plastic powder. In the embodiment of the present invention, fine powder is preferably used, and the fine powder has the property that deformation accompanied by fibrillation will occur if shear stress is applied. The polytetrafluoroethylene resin used in the embodiment of the present invention can be a homopolymer of tetrafluoroethylene (hereinafter referred to as "TFE"), or it can be modified PTFE. Modified PTFE is polymerized by TFE and a small amount of monomers other than TFE. Monomers other than a small amount of TFE can be exemplified by chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), perfluoroalkyl vinyl ether (PAVE), etc. In general, modified PTFE can be used to improve the heat resistance, wear resistance, bending resistance and other properties of the molded product. The polytetrafluoroethylene resin used in the embodiment of the present invention can be a single type of the PTFE types listed above, or it can be a mixture of multiple types. In addition, the polytetrafluoroethylene tube of the present invention can also contain polymers other than the above-mentioned polytetrafluoroethylene resin, as long as the amount is small enough not to damage its function.

[0037] PTFE fine powder is generally formed by agglomerating primary particles with an average particle size of 0.2 to 0.5 μm to form secondary particles with an average particle size of 400 to 700 μm. It has the property of being easily fibrillated due to vibration or the like at room temperature, and is easy to form lumps. Paste extrusion molding utilizes this property. Generally speaking, paste extrusion molding refers to the following method: PTFE and an organic solvent called an auxiliary agent (lubricant) are mixed and compressed to form a preform, and the preform is put into an extruder to apply pressure, thereby extruding into a film, a tube, a linear coating material, and the like. In the PTFE tube of the present invention, the uniformity of the extruded PTFE tube is very important, so it is preferred to make the preform under the condition that the internal structure of the PTFE preform is uniform. Specifically, for example, for the PTFE fine powder mixed with the auxiliary agent before making the preform, it is preferably operated under the condition that no lumps are formed, and the formed lumps are removed with a sieve before being put into the compression mold of the preform.

[0038] An auxiliary agent can be added to the PTFE fine powder to make it into a paste and formed by an extruder. The auxiliary agent used in the embodiment of the present invention is preferably an organic solvent with high lubricity. After adding the auxiliary agent to the PTFE fine powder, a tube is formed by a die in an extruder, but if the auxiliary agent volatilizes during the forming process, it is difficult to form stably and is therefore not preferred. The auxiliary agent used in the embodiment of the present invention is preferably an auxiliary agent with an initial boiling point (IBP) above 150°C. After the PTFE fine powder and the auxiliary agent are formed into a tube, the auxiliary agent is volatilized and removed before the tube is calcined. At this time, in order to effectively remove the auxiliary agent, the IBP of the auxiliary agent is preferably below 250°C. As an organic solvent with high lubricity and an IBP of 150°C to 250°C, petroleum-based solvents and the like are commonly used.

[0039] The auxiliary agent used in the embodiment of the present invention preferably has a surface tension higher than 18.5mN / m of the surface tension of PTFE by more than 3mN / m. It is believed that if the surface tension of the auxiliary agent is high, the auxiliary agent will not move excessively between the PTFE particles and will easily remain on the particle surface. In the paste extrusion molding of PTFE, the PTFE particles in the mold slide against each other during extrusion, and the particle surface fibrillates. The fibrils are entangled with each other and become difficult to flow, and the extrusion pressure increases. At this time, the auxiliary agent present around the PTFE particles can improve the lubricity between the PTFE particles and between the PTFE particles and the inner wall of the mold, appropriately suppress the mutual entanglement between the PTFE particles, and prevent the excessive increase of the extrusion pressure. For example, in the case of extrusion molding into a PTFE tube with a wall thickness of less than 0.04mm, the flow path in the mold is extremely narrow, and the resin flows under the condition of a high attenuation ratio (Reduction Ratio, hereinafter referred to as "RR"), and the shear force between the inner wall of the mold and the PTFE particles and between the PTFE particles increases. If a high shear force is suddenly applied to the PTFE particles, the PTFE particles will fibrillate at once, and the extrusion pressure increases. However, the additive retained between PTFE particles reduces the shear force between PTFE particles and between PTFE and the inner wall of the mold, and is expected to play an effect of inhibiting excessive fibrillation of PTFE.

[0040] The tube of the embodiment of the present invention may also contain fillers or other resins in the polytetrafluoroethylene resin. Examples of fillers include metal oxides such as carbon and aluminum oxide, sintered PTFE, and resin fillers composed of fluororesins or other resins other than PTFE. One or more of the above fillers may be mixed in PTFE for use. In addition, the PTFE tube may also be composed of multiple layers, and a layer containing fillers or other resins may be configured only at any one layer.

[0041] Hereinafter, a method for producing a pipe according to an embodiment of the present invention will be described.

[0042] [Forming of preform]

[0043] PTFE fine powder and auxiliary agent are mixed in a drum or the like. When filler etc. is added to PTFE, it is preferable to add it in this process. PTFE fine powder is used after removing lumps with a sieve or the like. After the mixture of PTFE and auxiliary agent is sieved to remove lumps, it is compressed and pressed to form a preform. It is preferable that the preform is uniformly compressed inside. When the PTFE tube is composed of multiple layers, for example, preforms of different sizes can be combined to form a preform composed of multiple layers.

[0044] [Extrusion molding]

[0045] The produced preform is loaded into an extruder and formed into a tube shape through a die.

[0046] The outlet temperature of the die of the extruder is preferably 80°C to 150°C, more preferably 90°C to 120°C. If the temperature of the die is high, the fibrillation of the surface of the PTFE particles can be promoted, and the mutual entanglement of the formed fibrils tends to be enhanced. In addition, the cooling rate of the tube extruded from the die also affects the 20% strain tensile stress σ of the polytetrafluoroethylene tube. 20 The value of 50% strain tensile stress σ 50 value. For example, by covering the periphery of the die after the PTFE is discharged from the die outlet with a heater, the temperature of the tubular PTFE around the die outlet can be adjusted. For the PTFE tube of the present invention, it is considered that the appropriate temperature is 60°C to 120°C. It is preferred to adjust the extrusion speed and extrusion temperature of the preform to be constant, and to perform the forming under the condition of constant extrusion pressure. The extrusion of the tube is carried out in a constant stable state, and the balance between the delivery and drawing (winding) of the tube is adjusted so that the operation is performed in a manner that no load is applied to the formed tube from the tube extrusion forming process to the drying process and the tube sintering process.

[0047] [Drying process]

[0048] The PTFE formed into a tube is heated by a heating furnace set at a temperature below the melting point of PTFE to volatilize the additive. When the PTFE is calcined in the subsequent process, the state of a large amount of additive remaining is not good for the quality of the tube, so it is necessary to fully volatilize it. If an additive with an IBP of 150°C to 250°C is used as an additive, it is easy to fully remove the additive in the drying process. In order to prevent the tube from being stretched in the drying process, it is preferable to maintain a balance between the delivery and pulling of the tube and adjust the line tension.

[0049] [Tube Firing Process]

[0050] The dried PTFE formed into a tube is calcined by heating to a temperature above the melting point of PTFE. The calcination temperature is usually around 400° C. When the PTFE constituting the tube is heated to a temperature above the melting point, the PTFE particles are fused to each other, forming a PTFE tube.

[0051] [Etching process]

[0052] The surface of the PTFE tube is subjected to physical and / or chemical etching treatment.

[0053] The invention is described in more detail by the following examples. The following examples are used to illustrate the invention, but are not intended to limit the content of the invention by the following examples.

[0054] Example

[0055] <Tensile test at 200°C>

[0056] The tensile test was performed under the following test conditions in an atmosphere of 200° C. using a testing machine capable of performing a tensile test by controlling the temperature of a sample in a constant temperature chamber.

[0057] [Tensile test conditions]

[0058] Test temperature 200℃±3℃

[0059] Initial chuck spacing 50mm

[0060] Test speed: 50 mm / min

[0061] The tube cut into a length suitable for measurement is directly used as the measurement tube, and the measurement is continued until the tube breaks to obtain data. The number of test samples should be as large as possible, and the arithmetic mean of these measured values ​​is used for each stress value. The tensile stress ε (%) is the value obtained by dividing the increase in the chuck spacing ΔL (mm) by the initial chuck spacing L0 (mm), and is calculated as ε (%) = (ΔL / L0) × 100. The stress when the tube mounted on the chuck of the testing machine is stretched 20% in the length direction (when stretched 10 mm) is recorded as the 20% strain tensile stress σ 20 ,σ' 20 , the stress when stretched 50% along the length direction (when stretched 25 mm) is recorded as the 50% strain tensile stress σ 50 ,σ' 50 When measuring the inner lining of a tube having a PTFE tube as an inner lining and an outer resin layer or the like formed thereon, the outer resin layer may be peeled off with a solvent or the like and only the inner lining portion may be subjected to a tensile test.

[0062] <Heating tensile test>

[0063] A core wire about 20 mm shorter than the tube was inserted into a tube sample cut to a length of 1000 mm or more (20 samples were prepared). The tube and the core wire were aligned at one end and fixed to the laminator, and a weight fixed only to the tube was hung at the other end. The weight of the weight was 0.1 mm. 2The cross-sectional area of ​​the tube is 150g. A heater heated to 300°C is moved downward from the top of the suspended tube to heat it, and the PTFE tube is stretched and laminated on the core wire. The moving speed of the heater is 100mm / min. The core wire laminated with the PTFE tube (hereinafter referred to as the coated core wire) is cooled and its size is measured. Because a core wire with a constant outer diameter is used, the wall thickness of the coated PTFE tube can be calculated from the outer diameter of the coated core wire and the outer diameter of the core wire. Here, the change in the outer diameter of the coated core wire is regarded as a change in the tensile properties of the coated PTFE tube for evaluation. Several tens of millimeters at both ends of the coated core wire may be damaged during the lamination process, so several tens of millimeters at both ends should be removed when measuring the size of the coated core wire. The outer diameter is measured at more than 6 locations as evenly as possible over the entire length of a coated core wire. Each measurement point is measured evenly in the radial direction (cross-sectional direction) at 2 points (2 points where the measurement angle changes by 90°) to 4 points (4 points where the measurement angle changes by 45°), and the arithmetic average of these measurement values ​​is taken as the outer diameter D0 of the measurement point. In addition, the above measurement is performed at more than 6 locations within the entire length of a sample, and the arithmetic average of the outer diameter D0 of each measurement point is taken as the outer diameter average value D of the sample. In addition, the variation of the outer diameter within the sample is determined by calculating the coefficient of variation of the outer diameter within the sample. Coefficient of variation of the outer diameter within a sample CV D The outer diameter deviation (outer diameter D0 of the measuring point minus the outer diameter average value D) and the outer diameter variance (the average of the square of the outer diameter deviation) are calculated, the outer diameter standard deviation (the square root of the outer diameter variance) is calculated, and the outer diameter standard deviation is divided by the outer diameter average value D. The same operation is repeated for the remaining 19 samples. The coefficient of variation CV of the outer diameter of each of the 20 samples is calculated. D The arithmetic mean is taken as the coefficient of variation CV of the outer diameter.

[0064] <Wetting tension test>

[0065] Wetting tension is measured in accordance with ISO 8296. Specifically, a test mixed solution for wetting tension measurement (mixed solution for wetting tension test) is quickly applied to the surface of the PTFE tube with a cotton swab, and the state of the liquid film is used for judgment. If the state of the line drawn by the cotton swab does not change within 2 seconds, it is judged that the surface tension of the PTFE tube is greater than the surface tension of the mixed solution for wetting tension test. On the contrary, if the width of the line of the mixed solution for wetting tension test drawn by the cotton swab shrinks or the liquid film breaks within less than 2 seconds, a mixed solution with a lower surface tension than the mixed solution for wetting tension test is used for evaluation.

[0066] Example 1

[0067] 100 parts by mass of PTFE fine powder and 18 parts by mass of auxiliary agent from which lumps were removed by sieving were added to a container and mixed. After removing lumps by sieving, the mixture was compressed to form a preform. The preform was put into an extruder with a barrel diameter of 20 mm and a mandrel diameter of 10 mm, and extruded into a tubular shape at a mold temperature of 100 ° C. The mold periphery after PTFE was ejected from the mold outlet was covered with a heater, and the temperature around the mold outlet was adjusted to 90 ° C. The formed tube was passed through a first drying furnace set at 150 ° C, a second drying furnace set at 220 ° C, and a sintering furnace set at 430 ° C for drying and sintering. The inner diameter of the obtained tube was 0.60 mm and the wall thickness was 0.028 mm. TETRA-ETCH (registered trademark) was applied to the surface of the obtained tube, washed with alcohol and water, and etched to form a PTFE tube according to an embodiment of the present invention. The obtained PTFE tube was cut into a length of about 100 mm as a sample for tensile testing. A tensile test was performed in an atmosphere at 200°C according to the above method. In addition, the obtained PTFE tube was cut into pieces of about 1000 mm as a sample for evaluation. On the other hand, a core wire with an outer diameter of 0.51 mm and a length of about 980 mm was prepared and a heated tensile test was performed according to the above method. In addition, the wetting tension was measured according to the above method.

[0068] Example 2

[0069] The preformed body prepared in the same manner as in Example 1 is put into an extruder with a barrel diameter of 30 mm and a mandrel diameter of 10 mm, and extruded into a tubular shape at a mold temperature of 90°C. Cover the periphery of the mold after PTFE is ejected from the mold outlet with a heater, and adjust the temperature around the mold outlet to 80°C. The formed tube is passed through a drying furnace and a sintering furnace in the same manner as in Example 1 for drying and sintering. The inner diameter of the obtained tube is 1.72 mm and the wall thickness is 0.038 mm. TETRA-ETCH (registered trademark) is applied to the surface of the obtained tube, washed with alcohol and water, and etched to form a PTFE tube according to an embodiment of the present invention. The obtained PTFE tube is cut into a length of about 100 mm as a sample for tensile test. A tensile test is performed in an atmosphere at 200°C according to the above method. In addition, the obtained PTFE tube is cut into about 1000 mm as a sample for evaluation. On the other hand, a core wire with an outer diameter of 1.45 mm and a length of about 980 mm is prepared, and a heated tensile test is performed according to the above method. In addition, the wetting tension was measured according to the above method.

[0070] Example 3

[0071] The preformed body prepared in the same manner as in Example 1 is put into an extrusion molding machine and extruded into a tubular shape at a die temperature of 100°C. Cover the periphery of the die after PTFE is discharged from the die outlet with a heater, and adjust the temperature around the die outlet to 80°C. The formed tube is passed through a drying furnace and a sintering furnace in the same manner as in Example 1 for drying and sintering. The inner diameter of the obtained tube is 0.475mm and the wall thickness is 0.028mm. The surface of the obtained tube is subjected to plasma treatment at a speed of 6.0m / min through a plasma generated by applying a voltage of 10kV, a frequency of 18kHz, and using Ar gas as an excitation gas to prepare a PTFE tube according to an embodiment of the present invention. The obtained PTFE tube is cut into a length of about 100mm as a sample for tensile test. A tensile test is performed in an atmosphere at 200°C according to the above method. In addition, the obtained PTFE tube is cut into about 1000mm as a sample for evaluation. On the other hand, a core wire with an outer diameter of 0.41mm and a length of about 980mm is prepared, and a heated tensile test is performed according to the above method. In addition, the wetting tension was measured according to the above method.

[0072] Example 4

[0073] The preformed body prepared in the same manner as in Example 1 is put into an extrusion molding machine and extruded into a tubular shape at a die temperature of 100°C. The periphery of the die after the PTFE is discharged from the die outlet is covered with a heater, and the temperature around the die outlet is adjusted to 100°C. The formed tube is passed through a drying furnace and a sintering furnace in the same manner as in Example 1 for drying and sintering. The inner diameter of the obtained tube is 0.49 mm and the wall thickness is 0.038 mm. TETRA-ETCH (registered trademark) is applied to the surface of the obtained tube, washed with alcohol and water, and etched to form a PTFE tube according to an embodiment of the present invention. The obtained PTFE tube is cut into a length of about 100 mm as a sample for tensile test. A tensile test is performed in an atmosphere at 200°C according to the above method. In addition, the obtained PTFE tube is cut into about 1000 mm as a sample for evaluation. On the other hand, a core wire with an outer diameter of 0.41 mm and a length of about 980 mm is prepared, and a heated tensile test is performed according to the above method. In addition, the wetting tension is measured according to the above method.

[0074] Example 5

[0075] The preformed body prepared in the same manner as in Example 1 is put into an extrusion molding machine and extruded into a tubular shape at a die temperature of 80°C. Cover the periphery of the die after PTFE is discharged from the die outlet with a heater, and adjust the temperature around the die outlet to 60°C. The formed tube is passed through a drying furnace and a sintering furnace in the same manner as in Example 1 for drying and sintering. The inner diameter of the obtained tube is 0.50mm and the wall thickness is 0.022mm. The surface of the obtained tube is subjected to plasma treatment at a speed of 2m / min through a plasma generated by applying a voltage of 10kV, a frequency of 18kHz, and using Ar gas as an excitation gas to prepare a PTFE tube according to an embodiment of the present invention. The obtained PTFE tube is cut into a length of about 100mm as a sample for tensile test. A tensile test is performed in an atmosphere at 200°C according to the above method. In addition, the obtained PTFE tube is cut into about 1000mm as a sample for evaluation. On the other hand, a core wire with an outer diameter of 0.41mm and a length of about 980mm is prepared, and a heated tensile test is performed according to the above method. In addition, the wetting tension was measured according to the above method.

[0076] Example 6

[0077] The preformed body prepared in the same manner as in Example 1 is put into an extruder with a barrel diameter of 44 mm and extruded into a tubular shape at a die temperature of 100°C. Cover the periphery of the die after PTFE is ejected from the die outlet with a heater, and adjust the temperature around the die outlet to 80°C. The formed tube is passed through a drying furnace and a sintering furnace in the same manner as in Example 1 for drying and sintering. The inner diameter of the obtained tube is 2.68 mm and the wall thickness is 0.033 mm. TETRA-ETCH (registered trademark) is applied to the surface of the obtained tube, washed with alcohol and water, and etched to form a PTFE tube according to an embodiment of the present invention. The obtained PTFE tube is cut into a length of about 100 mm as a sample for tensile test. A tensile test is performed in an atmosphere at 200°C according to the above method. In addition, the obtained PTFE tube is cut into about 1000 mm as a sample for evaluation. On the other hand, a core wire with an outer diameter of 2.42 mm and a length of about 980 mm is prepared, and a heated tensile test is performed according to the above method. In addition, the wetting tension is measured according to the above method.

[0078] The results of each example are shown in Table 1.

[0079] [Table 1]

[0080]

[0081] In the embodiment, the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube50 (N / mm 2 ) all satisfy the above formula (1), and it can be confirmed that the change in the outer diameter (coefficient of variation of the outer diameter CV) when the core wire is covered with a PTFE tube is small, showing uniform stretchability. Figure 2 This is a graph in which the value of the middle side of the formula (1) and the change in the outer diameter (coefficient of variation of the outer diameter CV) are plotted for the PTFE tube of the example. From this graph, it can be confirmed that the relationship formula (1) has a high correlation with the uniform stretchability when the core wire is covered with a PTFE tube.

[0082] Possibility of industrial application

[0083] The PTFE tube of the present invention can be suitably used for linings of tubes and the like, and a multilayer tube using the PTFE tube of the present invention is particularly suitably used for medical tubes and the like.

[0084] Explanation of symbols

[0085] 1PTFE tube (section)

Claims

1. A polytetrafluoroethylene tube having a wall thickness of about 0.04 mm or less, characterized in that: The wetting tension of one or both of the outer surface and the inner surface of the polytetrafluoroethylene tube is above 46 mN / m, In the stress-strain curve obtained from the tensile test conducted at 200°C, the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 (N / mm 2 ) satisfies formula (1): 2.0≤0.1×σ 20 +0.3×σ 50 <5.5Formula (1).

2. The polytetrafluoroethylene tube according to claim 1, characterized in that: In a tensile test conducted in an atmosphere at 200°C, the tensile fracture strain is 200% or more.

3. The polytetrafluoroethylene tube according to claim 1, characterized in that: In the tensile test conducted at 200°C, the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 At 4.0(N / mm 2 )above. 4 . A medical tube using the polytetrafluoroethylene tube according to claim 1 .

5. A polytetrafluoroethylene tube having a wall thickness of about 0.04 mm or less, characterized in that: The inner diameter of the polytetrafluoroethylene tube is less than about 3.0 mm. In the stress-strain curve obtained from the tensile test conducted at 200°C, the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 (N / mm 2 ) and the 50% strain tensile stress σ of the polytetrafluoroethylene tube 50 (N / mm 2 ) satisfies formula (1): 2.0≤0.1×σ 20 +0.3×σ 50 <5.5Formula (1).

6. The polytetrafluoroethylene tube according to claim 5, characterized in that In a tensile test conducted in an atmosphere at 200°C, the tensile fracture strain is 200% or more.

7. The polytetrafluoroethylene tube according to claim 5, characterized in that: In the tensile test conducted at 200°C, the 20% strain tensile stress σ of the polytetrafluoroethylene tube is 20 At 4.0(N / mm 2 )above. 8 . A medical tube using the polytetrafluoroethylene tube according to claim 5 .

9. A medical tube comprising a polytetrafluoroethylene liner obtained by processing a polytetrafluoroethylene tube, wherein the wall thickness of the polytetrafluoroethylene liner is less than about 0.04 mm, characterized in that: The inner diameter of the polytetrafluoroethylene liner is less than about 3.0 mm. In the stress-strain curve obtained from the tensile test conducted at 200°C, the 20% strain tensile stress σ' of the polytetrafluoroethylene liner is 20 (N / mm 2 ) and the 50% strain tensile stress σ' of the polytetrafluoroethylene liner 50 (N / mm 2 ) satisfies formula (2): 2.4≤0.1×σ' 20 +0.3×σ' 50 <6.6Formula (2).

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