Tear-off tube made of fluororesin

Abstract

To provide a fluororesin tube excellent in tearability and inner surface smoothness.SOLUTION: A fluororesin tube, which has tearability in a lengthwise direction, is formed from one kind of thermoplastic fluororesin different from polytetrafluoroethylene, and provided with a weld line in the lengthwise direction. In the fluororesin tube having heat shrinkability, a heat shrinkage rate of an inside diameter during heating for five minutes in a gas phase at 200°C is 20% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fluororesin tube having tearability and useful as a temporary covering tube for products and a method for producing the same.

Background Art

[0002] Conventionally, in various products such as electric wires, lead wires, catheters, and guide wires, a temporary covering tube that temporarily covers these products and is removed from the products after achieving the intended purpose has been widely used. Such a temporary covering tube is generally formed of synthetic resin, synthetic rubber, or the like.

[0003] Although synthetic resin and synthetic rubber have excellent product protection characteristics, the tearing force required for removal from the product is large. For this reason, it is difficult to tear by hand, it takes a long time to remove, or a large force is applied to the product when tearing, resulting in damage to the product. In addition, a method of tearing after damaging the tube with a cutter or the like has also been adopted, but there has been a case where the product inside the covering tube is damaged by the cutter or the like.

[0004] As a technique for solving such problems, for example, Patent Document 1 discloses a temporary covering tube having a uniform thickness and a transverse tensile strength of 80% or less of the longitudinal tensile strength by using a special silicone rubber. However, Patent Document 1 describes that although the transverse tensile strength is 80% or less of the longitudinal tensile strength by using a special silicone rubber, the reason is unclear, and the technique of Patent Document 1 is applicable only when using a special silicone rubber.

[0005] On the other hand, temporary covering tubes made of fluororesin are known to have excellent heat resistance, chemical resistance, water and oil repellency, and high mechanical strength. As a technique to improve the tearability of fluororesin tubes, for example, Patent Document 2 discloses a method in which multiple thermoplastic fluororesins of different types are melt-extruded and formed into a tube. Also, for example, Patent Document 3 discloses a method using a low molecular weight fluororesin relative to polytetrafluoroethylene. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-208448 [Patent Document 2] Japanese Patent Publication No. 2008-20037 [Patent Document 3] Japanese Utility Model Publication No. 6-74148 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the inventors have investigated and found that even with the tear tubes disclosed in Patent Documents 2 and 3, the force required for tearing is not stable, and the tearability may be insufficient in some cases. For example, as disclosed in Patent Document 3, if polytetrafluoroethylene is used for the tear tube, the force required for tearing becomes large, which may result in insufficient tearability.

[0008] Furthermore, tear-off tubes require high inner surface smoothness. That is, high inner surface smoothness of the tear-off tube makes it possible to maintain high surface smoothness of the product covered by the tear-off tube. Also, by heating the tear-off tube to a temperature above the melting point of the product's surface and then thermally shrinking the tear-off tube to cover the product, it is possible to transfer the high inner surface smoothness of the tear-off tube to the product's surface. For example, catheters are inserted into the body, so tear-off tubes used in catheters and the like require particularly high inner surface smoothness. However, the inventors have investigated and found that As described in Patent Documents 2 and 3, it has become clear that when different types of fluororesins are mixed, phase separation occurs between the fluororesins, forming an uneven surface on the inner surface of the tear tube, which can result in reduced inner surface smoothness.

[0009] Under these circumstances, the main objective of the present invention is to provide a fluororesin tube with excellent tear resistance and inner surface smoothness, and a method for manufacturing the same. [Means for solving the problem]

[0010] The inventors of this invention conducted diligent research to solve the above problems. As a result, they discovered that by forming a fluororesin tube from a single type of thermoplastic fluororesin different from polytetrafluoroethylene, a fluororesin tube with excellent tear resistance in the longitudinal direction and smooth inner surface can be obtained. The present invention was completed by further research based on this finding.

[0011] In other words, the present invention provides the following inventions. Item 1. A fluororesin tube having tearability in the longitudinal direction, A fluororesin tube made from a single type of thermoplastic fluororesin, distinct from polytetrafluoroethylene. Item 2. A fluororesin tube as described in Item 1, which is heat-shrinkable. Item 3. A fluoropolymer tube according to item 1 or 2, wherein the thermal shrinkage rate of the inner diameter when heated in a gas phase at 200°C for 5 minutes is 20% or more. Item 4. A fluororesin tube according to any one of items 1 to 3, wherein the thermoplastic fluororesin is a tetrafluoroethylene-hexafluoropropylene copolymer. Item 5. A fluororesin tube according to any one of items 1 to 3, wherein the thermoplastic fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Item 6. A fluoropolymer tube according to any one of items 1 to 5, whose inner diameter can be expanded by applying pressure from the inside while heated. Item 7. A fluoropolymer tube according to any one of items 1 to 6, having a weld line in the longitudinal direction. Item 8. A method for manufacturing a fluororesin tube that has tear properties, It includes a process for melt-extrude molding a single type of thermoplastic fluororesin, which is different from polytetrafluoroethylene. A method for manufacturing a fluororesin tube, comprising temporarily branching the flow path of the molten thermoplastic fluororesin during the melt extrusion molding process to form a weld line in the longitudinal direction of the fluororesin tube. Item 9. The method for manufacturing a fluororesin tube according to Item 8, further comprising the step of expanding the inner diameter by applying pressure from the inside while the fluororesin tube on which the weld line is formed is heated. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a fluororesin tube with excellent tear resistance in the longitudinal direction and smooth inner surface. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a fluororesin tube with excellent tear resistance in the longitudinal direction and smooth inner surface. Moreover, according to the present invention, it is possible to provide various products such as electric wires, lead wires, catheters, and guide wires coated with the fluororesin tube of the present invention. [Brief explanation of the drawing]

[0013] [Figure 1] It is a schematic cross-sectional view of the fluororesin tube of the present invention in the inner diameter and outer diameter directions. [Figure 2] It is a schematic cross-sectional view of the mold used for melt extrusion molding of the manufacturing method of the fluororesin tube of the present invention (a cross-section perpendicular to the melt extrusion direction, at the part where the legs exist). [Figure 3] It is an image obtained by observing the inner surface of the fluororesin tube obtained in Example 1 with a laser microscope. [Figure 4] It is an image obtained by observing the inner surface of the fluororesin tube obtained in Example 2 with a laser microscope. [Figure 5] It is an image obtained by observing the inner surface of the fluororesin tube obtained in Comparative Example 1-1 with a laser microscope. [Figure 6] It is an image obtained by observing the inner surface of the fluororesin tube obtained in Comparative Example 2-1 with a laser microscope. [Figure 7] It is a photograph when a white nylon wire is inserted inside the fluororesin tube (before expansion) obtained in Example 1. [Figure 8] It is a photograph when a white nylon wire is inserted inside the fluororesin tube (before expansion) obtained in Example 2. [Figure 9] It is a photograph when a white nylon wire is inserted inside the fluororesin tube (before expansion) obtained in Comparative Example 1-1. [Figure 10] It is a photograph when a white nylon wire is inserted inside the fluororesin tube (before expansion) obtained in Comparative Example 2-1.

Mode for Carrying Out the Invention

[0014] The fluororesin tube of the present invention is characterized in that its inner surface is smooth, has tearability in the length direction, and is formed of one kind of thermoplastic fluororesin different from polytetrafluoroethylene. Hereinafter, the fluororesin tube of the present invention will be described in detail.

[0015] The fluororesin tube of the present invention is formed from a single type of thermoplastic fluororesin different from polytetrafluoroethylene. The thermoplastic fluororesin is not particularly limited as long as it is different from polytetrafluoroethylene, but it is preferably a thermoplastic resin that can be molded into a tube shape by melt extrusion molding at a temperature of approximately 260 to 450°C, preferably 280 to 420°C.

[0016] Specific examples of thermoplastic fluororesins include, preferably, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE). Among these, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) are particularly preferred from the viewpoint of providing excellent tear resistance and inner surface smoothness.

[0017] The fluororesin tube of the present invention preferably has heat-shrinkability. Heat-shrinkability of the fluororesin tube can be suitably imparted, for example, by expanding the inner diameter by applying pressure from the inside while the fluororesin tube is heated. For example, when covering (temporarily covering) products such as electric wires, lead wires, catheters, and guide wires with the fluororesin tube of the present invention, these products can be inserted into the heat-shrinkable fluororesin tube, and by heat-shrinking the fluororesin tube, the fluororesin tube can be suitably fitted and covered with these products. By using, for example, a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer as one of the thermoplastic fluororesins, particularly excellent heat shrinkage properties can be imparted.

[0018] In the present invention, the heat shrinkage rate of the fluororesin tube to which heat shrinkability has been imparted is not particularly limited, but the heat shrinkage rate of the inner diameter when heated in the gas phase (specifically in air) at 200°C for 5 minutes is preferably 20% or more, more preferably 30-60%. This allows the product to be suitably coated with the fluororesin tube.

[0019] The melt flow rate (MFR) of the thermoplastic fluororesin constituting the fluororesin tube of the present invention is not particularly limited, but from the viewpoint of improving the tearability and surface smoothness of the fluororesin tube, and further improving the heat shrinkage, it is preferably about 1.0 to 25.0. In this invention, the MFR of the thermoplastic fluororesin is JIS The values ​​were measured using a method compliant with the provisions of K7210:1999.

[0020] The fluororesin tube of the present invention, being formed from a single type of thermoplastic fluororesin different from polytetrafluoroethylene, exhibits excellent tear resistance and inner surface smoothness, and furthermore, excellent heat shrinkage. The detailed mechanism by which the fluororesin tube of the present invention exhibits excellent tear resistance, inner surface smoothness, and furthermore, excellent heat shrinkage can be considered as follows. That is, since the fluororesin tube of the present invention is formed from a single type of thermoplastic fluororesin different from polytetrafluoroethylene, phase separation of the fluororesin constituting the tube does not occur. The tube exhibits high uniformity throughout, including tear resistance, inner surface smoothness, and heat shrinkage, resulting in a tube with excellent properties in these areas.

[0021] Furthermore, the fluororesin tube of the present invention can exhibit high transparency because it is formed from a single type of thermoplastic fluororesin different from polytetrafluoroethylene. In other words, the fluororesin tube of the present invention can be a transparent fluororesin tube. Products such as catheters that are coated with the fluororesin tube of the present invention are required to be positioned within the tube with high positional accuracy when coated with the tube. In this case, by using the highly transparent fluororesin tube of the present invention, it becomes possible to easily position the product within the tube with high positional accuracy. On the other hand, multiple thermoplastics of different types Conventional tubes, such as those formed by melt-extruding fluororesin into a tubular shape or those made of polytetrafluoroethylene, have low transparency and are cloudy, making it difficult to position objects within the tube with high accuracy. In this invention, a transparent fluororesin tube refers to one that is evaluated as having high transparency in the transparency evaluation described in the examples.

[0022] In the fluororesin tube of the present invention, "one type of thermoplastic fluororesin" means that, from the viewpoint of suppressing phase separation and improving tear resistance and inner surface smoothness, it is sufficient to have only one type of thermoplastic fluororesin. For example, it may be a mixed resin of resins with different weight-average molecular weights or polymerization forms (e.g., block polymers, random polymers, etc.) or resins with different polymerization ratios of multiple monomers. That is, even if thermoplastic resins with different weight-average molecular weights or polymerization forms or resins with different polymerization ratios of multiple monomers are included in "one type of thermoplastic fluororesin," as long as there is only one type of thermoplastic fluororesin, phase separation is suppressed, and a fluororesin tube with excellent tear resistance and inner surface smoothness can be made. However, as mentioned above, polytetrafluoroethylene has the problem of poor tear resistance, so it is not substantially included in "one type of thermoplastic fluororesin" of the present invention.

[0023] In this invention, the thermoplastic fluororesin does not need to be made entirely of one type of thermoplastic fluororesin, as long as it achieves the effects of the present invention; it is sufficient if it is substantially made of one type of thermoplastic fluororesin.

[0024] Furthermore, the fluororesin tube of the present invention may contain fillers and the like in addition to one type of thermoplastic fluororesin. If the fluororesin tube of the present invention is to be photographed by X-ray, it may contain a contrast agent such as barium sulfate in addition to one type of thermoplastic fluororesin.

[0025] Preferably, the fluororesin tube of the present invention can be expanded in inner diameter (and outer diameter) by applying pressure from the inside while heated. This makes it easier to insert various products such as electric wires, lead wires, catheters, and guide wires into the expanded fluororesin tube of the present invention. Furthermore, since the expanded fluororesin tube has heat-shrinkability, the expanded fluororesin tube of the present invention can be heat-shrinked to suitably cover these products with the fluororesin tube. A typical method involves heating the fluororesin tube of the present invention to approximately 100-180°C and then pressurizing it from the inside with pressurized nitrogen or the like. Since the fluororesin tube of the present invention, with its expanded inner diameter, has enhanced heat shrinkability, it can more effectively coat products by heat shrinkage.

[0026] Furthermore, the fluororesin tube of the present invention, with its expanded inner diameter, is provided to facilitate the insertion of various products. Therefore, in the fluororesin tube of the present invention, excellent tear resistance is mainly required for the fluororesin tube before its inner diameter is expanded, or for the fluororesin tube after its inner diameter has been expanded and then heat-shrunk. The tear resistance of the fluororesin tube after its inner diameter has been expanded and then heat-shrunk depends on the dimensions after shrinkage, but it is intermediate between the tear resistance of the fluororesin tube before its inner diameter is expanded and the tear resistance of the fluororesin tube before its inner diameter is expanded and then heat-shrunk.

[0027] The tear strength of the fluororesin tube of the present invention is preferably less than 8.0 N / mm, more preferably 7.5 N / mm or less, even more preferably 6.8 N / mm or less, and particularly preferably 5.0 N / mm or less, as measured by the following method. The lower limit of the tear strength is typically 1.0 N / mm.

[0028] (Measurement of tear strength) A 40 mm cut is made at one end of a fluororesin tube (100 mm in length), and it is torn using a tensile testing machine at a speed of 200 mm / min. The maximum force at which this occurs is measured and defined as the tear strength (N). Three measurements are taken, and the tear resistance (N / mm) of the fluororesin tube is determined from the average weighted value and the wall thickness of the fluororesin tube.

[0029] Examples of the expansion ratio of the inner diameter include 20% or more, preferably around 20-200%.

[0030] The inner diameter Wa and outer diameter Wb (before expanding the inner diameter) of the fluororesin tube of the present invention are not particularly limited and can be appropriately set according to the product to be coated. For example, the inner diameter Wa is about 0.2 to 10.0 mm, preferably about 0.2 to 5.0 mm. For example, the outer diameter Wb is about 0.3 to 11.0 mm, preferably about 0.3 to 6.0 mm.

[0031] When the fluororesin tube of the present invention is used after heat shrinking, the inner diameter Wa of the fluororesin tube of the present invention before covering the product (i.e., after expanding the inner diameter but before heat shrinking) is, for example, about 0.3 to 20.0 mm, preferably about 0.3 to 10.0 mm, and the outer diameter Wb is, for example, about 0.5 to 25.0 mm, preferably about 0.5 to 12.0 mm. Furthermore, the inner diameter Wa in the state after covering the product (i.e., after expanding the inner diameter and then heat shrinking) is, for example, about 0.2 to 10.0 mm, preferably about 0.2 to 5.0 mm, and the outer diameter Wb is, for example, 0.3 A length of approximately 11.0 mm is preferred, preferably between 0.3 and 6.0 mm.

[0032] Furthermore, the wall thickness D of the fluororesin tube of the present invention (before expanding the inner diameter) is not particularly limited and can be set appropriately depending on the product to be coated. Examples of wall thickness D include approximately 0.03 to 1.0 mm, preferably approximately 0.05 to 0.5 mm. The length of the fluororesin tube of the present invention (before expanding the inner diameter) can also be set appropriately depending on the product to be coated, for example, 0.1 m or more, preferably approximately 0.1 to 2.5 m.

[0033] When the fluororesin tube of the present invention is used after heat shrinking, the wall thickness D of the fluororesin tube of the present invention before it covers the product (i.e., after the inner diameter has been expanded but before heat shrinking) is, for example, about 0.02 to 0.7 mm, preferably about 0.02 to 0.5 mm. Furthermore, the wall thickness D in the state after it has covered the product (i.e., after the inner diameter has been expanded and then heat-shrinked) is, for example, about 0.03 to 1.0 mm, preferably about 0.05 to 0.5 mm.

[0034] The fluororesin tube of the present invention preferably has a weld line in the longitudinal direction. This allows it to exhibit particularly excellent tear resistance. In the fluororesin tube of the present invention, the weld line may or may not be visible to the naked eye. In the fluororesin tube of the present invention, the weld line is usually not visible to the naked eye.

[0035] When weld lines are formed along the length of the fluororesin tube of the present invention, there are no particular limitations on the number of weld lines, but from the viewpoint of further improving tear resistance, it is preferable to have about 1 to 10 lines, and more preferably about 2 to 8 lines.

[0036] The fluororesin tube of the present invention is formed from a single type of thermoplastic fluororesin different from polytetrafluoroethylene, and further, when it has weld lines in the longitudinal direction, it can be made into a fluororesin tube that is not only particularly excellent in tear resistance and inner surface smoothness, but also in heat shrinkage. That is, because the fluororesin tube of the present invention, which has weld lines in the longitudinal direction, is formed from a single type of thermoplastic fluororesin, even when the inner diameter is expanded by applying pressure from the inside while heated, cracks and the like are less likely to occur in the part where the weld lines are formed, and the inner diameter can be suitably expanded. Furthermore, by heating the fluororesin tube of the present invention with an expanded inner diameter, it can be suitably heat-shrinked. As a specific method for forming weld lines in the fluororesin tube of the present invention, for example, the method described in "2. Method for Manufacturing a Fluororesin Tube" below can be used.

[0037] The fluororesin fluorotube of the present invention can be suitably used for covering (temporarily covering) various products such as electric wires, lead wires, catheters, and guide wires. By being covered with the fluororesin fluorotube (temporarily covered tube) of the present invention, various products such as electric wires, lead wires, catheters, and guide wires have their surfaces suitably protected.

[0038] The method for manufacturing the fluororesin tube of the present invention is not particularly limited, but it can be suitably manufactured by, for example, the following manufacturing method.

[0039] 2. Method for manufacturing fluororesin tubes The present invention relates to a method for manufacturing a fluororesin tube, which includes a step of melt-extruding a single type of thermoplastic fluororesin, different from polytetrafluoroethylene. Furthermore, in the present invention's method for manufacturing a fluororesin tube, it is preferable to temporarily branch the flow path of the molten thermoplastic fluororesin during melt-extrusion molding to form a weld line in the longitudinal direction of the fluororesin tube. This results in a fluororesin tube that is excellent not only in tear resistance and inner surface smoothness but also in heat shrinkage. The present invention's method for manufacturing a fluororesin tube will be described in detail below.

[0040] In the manufacturing method of the present invention, the thermoplastic fluororesin used for melt extrusion molding is as described in the section "1. Fluororesin Tube" above.

[0041] In melt extrusion molding, the temperature at which the thermoplastic fluororesin is melted (the set temperature of the extruder die) is not particularly limited as long as it is a temperature at which the thermoplastic fluororesin can be melted and molded into a tube shape. For example, a temperature of about 260 to 450°C, preferably about 280 to 420°C, is used. Furthermore, by mixing fillers and the like with the thermoplastic fluororesin and performing melt extrusion molding, fillers and the like can be incorporated into the fluororesin tube, as explained in the "2. Fluororesin Tubes" section above.

[0042] For melt extrusion molding, known extrusion machines can be used, such as a single-screw extruder.

[0043] In the manufacturing method of the present invention, when melt extrusion molding, a mold 2 having a cross-section such as that shown in Figure 2 (a cross-section perpendicular to the direction in which the molten resin flows) can be used. Depending on the shape of the mold 2, the flow path of the molten thermoplastic fluororesin can be temporarily branched, and a weld line can be formed along the length of the fluororesin tube. For example, when using a mold 2 having a cross-section as shown in Figure 2, the multiple legs 22 provided in the flow path 21 temporarily branch the flow path of the molten thermoplastic fluororesin. The branched thermoplastic resin is extruded from the mold with a weld line formed at the point where it merges, and is cooled to become a fluororesin tube. Therefore, when forming a weld line using a mold having a structure in which the flow path 21 is branched by the legs 22, such as mold 2, the number of legs 22 is important. A corresponding number of weld lines are formed. In the mold 2 of Figure 2, eight legs 22 are provided.

[0044] Such weld lines can effectively improve the tear resistance of the fluororesin tube in the longitudinal direction. As mentioned above, in the present invention, since the fluororesin tube is formed from a single type of thermoplastic fluororesin, it is possible to improve tear resistance by forming weld lines while also improving the inner surface smoothness and thermal shrinkage rate.

[0045] Furthermore, the manufacturing method of the present invention may also include a step of expanding the inner diameter by applying pressure from the inside while the fluororesin tube on which the weld line has been formed is heated. By expanding the inner diameter of the fluororesin tube, it is possible to manufacture a fluororesin tube with enhanced heat shrinkability. [Examples]

[0046] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0047] (Example 1) As the fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP, FEP-130J manufactured by Mitsui DuPont Fluorochemicals) was used, and fluororesin tubes were manufactured by melt extrusion molding. In melt extrusion molding, a single-screw extruder with a cylinder diameter of 30 mm and a mold was assembled, and tube molding was performed using the sizing plate method at a screw rotation speed of 2.0 rpm and a die temperature of 330°C to produce fluororesin tubes (original tubes, before expansion) with an inner diameter of 0.5 mm, an outer diameter of 1.2 mm, and a wall thickness of 0.35 mm. As the mold, a mold was used with a leg width of 5 mm, a leg length (length of branched flow path) of 10 mm, a number of legs of 8, and a distance of 10 mm from the mold outlet side of the legs to the mold outlet. Next, the obtained raw tube was inserted into a cylinder with an inner diameter of 1.7 mm and heated at 150°C while pressurized nitrogen was added to expand its diameter, resulting in a fluororesin tube (after expansion) with an inner diameter of 1.25 mm, an outer diameter of 1.65 mm, and a wall thickness of 0.2 mm.

[0048] (Example 2) A fluororesin tube (original tube, before expansion) was prepared in the same manner as in Example 1, except that tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA, PFA950HPplus manufactured by Mitsui DuPont Fluorochemicals) was used as the fluororesin instead of tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Furthermore, expansion was performed in the same manner as in Example 1 to obtain a fluororesin tube (after expansion) with an inner diameter of 1.25 mm, an outer diameter of 1.65 mm, and a wall thickness of 0.2 mm.

[0049] (Comparative Example 1-1) A fluororesin tube (original tube, before expansion) was prepared in the same manner as in Example 1, except that a mixture of the tetrafluoroethylene-hexafluoropropylene copolymer used in Example 1 and the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer used in Example 2 was used as the fluororesin, in a mass ratio of 1:1. Furthermore, expansion was performed in the same manner as in Example 1, but the tube burst during pressurization / heating, making it impossible to expand the tube to the inner diameter of the cylinder.

[0050] (Comparative Example 1-2) A fluororesin tube (original tube, before expansion) was prepared in the same manner as in Comparative Example 1-1. Next, the obtained original tube was inserted into a cylinder with an inner diameter of 1.5 mm and heated at 150°C while pressurized nitrogen was added to expand its diameter, thereby obtaining a fluororesin tube (after expansion) with an inner diameter of 0.90 mm, an outer diameter of 1.45 mm, and a wall thickness of 0.25 mm.

[0051] (Comparative Example 2-1) As the fluororesin, 80 parts by mass of polytetrafluoroethylene (PTFE, Teflon® 6J powder manufactured by Mitsui DuPont Fluorochemicals) and 20 parts by mass of low molecular weight polytetrafluoroethylene (PTFE, TLP10F-1 powder manufactured by Mitsui DuPont Fluorochemicals) were mixed. 17.5% by mass of an extrusion aid (Exxon Chemicals Isobar G) was added to the total volume and mixed, and the mixture was aged at 24°C for 24 hours to prepare the raw material for tube molding. Using this raw material, tubes molded in a paste extrusion machine were continuously fired in a drying oven and firing oven at 400-450°C to produce fluororesin with an inner diameter of 0.5 mm, an outer diameter of 1.2 mm, and a wall thickness of 0.35 mm. A resin tube (original tube, before expansion) was fabricated. Furthermore, expansion was carried out in the same manner as in Example 1, except that the heating temperature was set to 280°C, but the tube burst during pressurization / heating, making it impossible to expand the tube to the inner diameter of the cylinder.

[0052] (Comparative Example 2-2) As the fluororesin, 80 parts by mass of polytetrafluoroethylene (PTFE, Teflon® 6J powder manufactured by Mitsui DuPont Fluorochemicals) and 20 parts by mass of low molecular weight polytetrafluoroethylene (PTFE, TLP10F-1 powder manufactured by Mitsui DuPont Fluorochemicals) were mixed. 17.5% by mass of an extrusion aid (Exxon Chemicals Isobar G) was added to the total volume and mixed, and the mixture was aged at 24°C for 24 hours to prepare the raw material for tube molding. Using this raw material, tubes molded in a paste extrusion machine were continuously fired in a drying oven and firing oven at 400-450°C to produce fluororesin with an inner diameter of 0.5 mm, an outer diameter of 1.2 mm, and a wall thickness of 0.35 mm. A resin tube (original tube, before expansion) was fabricated. Next, the obtained original tube was inserted into a cylinder with an inner diameter of 1.5 mm and heated at 280°C while pressurized nitrogen was added to expand its diameter, resulting in a fluororesin tube (after expansion) with an inner diameter of 0.90 mm, an outer diameter of 1.45 mm, and a wall thickness of 0.25 mm.

[0053] (Evaluation of tear resistance) A 40 mm cut was made at one end of each fluororesin tube (100 mm in length), and the tubes were torn using a tensile testing machine at a speed of 200 mm / min. The maximum force at which the tear strength was measured was defined as the tear strength (N). Three measurements were taken, and the tear resistance (N / mm) of the tube was determined from the average weighted value and the tube wall thickness. The results are shown in Table 1.

[0054] (Evaluation of inner surface smoothness) The inner surface of each fluororesin tube (before expansion) was observed using a laser microscope (Keyence VK-9510 laser microscope, 400x magnification). A circle (○) indicated a smooth inner surface with few irregularities, while a cross (×) indicated a smooth inner surface with many irregularities. The results are shown in Table 1. Images from Example 1 are shown in Figure 3, from Example 2 in Figure 4, from Comparative Example 1-1 in Figure 5, and from Comparative Example 2-1 in Figure 6.

[0055] (Evaluation of thermal shrinkage) Each fluororesin tube (after expansion) obtained in Examples 1 and 2 and Comparative Examples 1-2 and 2-2 was heated in an oven (under air) at 200°C for 5 minutes. Next, the inner diameter before and after heating was measured with a pin gauge, and the shrinkage rate was calculated using the following formula. The results are shown in Table 1. Radial heat shrinkage rate (%) = [(Inner diameter of fluororesin tube before expansion) - (Inner diameter of fluororesin tube after expansion)] / (Inner diameter of fluororesin tube before expansion) × 100

[0056] (Transparency assessment) A white nylon wire was inserted inside each fluororesin tube (before expansion), and observed from the outside of each fluororesin tube. If the white nylon wire inside was visible, it was evaluated as having high transparency (○), and if it was not visible, it was evaluated as having low transparency (×). Photographs of the fluororesin tubes (before expansion) obtained in Examples 1 and 2, Comparative Example 1-1, and Comparative Example 2-1 with the white nylon wire inserted inside are shown in Figures 7-10. The evaluation results are shown in Table 1.

[0057] [Table 1]

[0058] As shown in Table 1, the fluororesin tubes in Examples 1 and 2, which are made from a single type of thermoplastic fluororesin different from polytetrafluoroethylene, require little force to tear. In fact, when the fluororesin tubes obtained in Examples 1 and 2 were torn by hand along their length, they could be easily torn. Furthermore, the fluororesin tubes in Examples 1 and 2 showed almost no irregularities on their inner surface and exhibited excellent inner surface smoothness (Figures 3 and 4).

[0059] On the other hand, the fluororesin tube (before expansion) of Comparative Example 1-1, which was formed from two types of thermoplastic fluororesins, had excellent tear resistance, but it could not be expanded to the same high magnification as Examples 1 and 2. Furthermore, as shown in Figure 5, the fluororesin tube of Comparative Example 1-1 had numerous small irregularities on its inner surface, and its inner surface smoothness was inferior to that of Examples 1 and 2. In Comparative Example 1-2, a fluororesin tube (before expansion) obtained in the same manner as in Comparative Example 1-1 was expanded to the extent that it did not burst during expansion to produce a fluororesin tube (after expansion), but its thermal shrinkage rate was inferior to that of Examples 1 and 2.

[0060] The fluororesin tube (before expansion) of Comparative Example 2-1 had poor tear resistance, and depending on the degree of cutting at the end and the tearing method, it exhibited unstable tearing properties that would break midway. Furthermore, the fluororesin tube (before expansion) of Comparative Example 2-1 could not be expanded to the same high magnification as Examples 1 and 2. In Comparative Example 2-2, the fluororesin tube (before expansion) obtained in the same manner as in Comparative Example 2-1 was expanded to a degree that did not burst during expansion to produce a fluororesin tube (after expansion), but the heat shrinkage rate was inferior to that of Examples 1 and 2. Moreover, the fluororesin tube (after expansion) of Comparative Example 2-2 had excessively high tear strength, making it difficult to tear. I couldn't do it.

[0061] Furthermore, while each of the fluororesin tubes in the examples exhibited high transparency, each of the fluororesin tubes in the comparative examples exhibited low transparency (Figures 7 to 10).

Claims

1. A fluororesin tube having tearability in the longitudinal direction, It is made of a single type of thermoplastic fluororesin, which is different from polytetrafluoroethylene. The thermoplastic fluororesin is a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene-ethylene copolymer (ETFE), or an ethylene-chlorotrifluoroethylene copolymer (ECTFE). A transparent fluoropolymer tube with weld lines running lengthwise.

2. A fluororesin tube according to claim 1, which is heat-shrinkable.

3. A fluororesin tube according to claim 1 or 2, wherein the thermal shrinkage rate of the inner diameter when heated in a gas phase at 200°C for 5 minutes is 20% or more.

4. The fluororesin tube according to any one of claims 1 to 3, wherein the thermoplastic fluororesin is a tetrafluoroethylene-hexafluoropropylene copolymer.

5. The fluororesin tube according to any one of claims 1 to 3, wherein the thermoplastic fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

6. A fluororesin tube according to any one of claims 1 to 5, wherein the inner diameter can be expanded by applying pressure from the inside while it is heated.

7. A method for manufacturing a fluororesin tube that has tear properties, It includes a process for melt-extrude molding a single type of thermoplastic fluororesin, which is different from polytetrafluoroethylene. A method for manufacturing a transparent fluororesin tube according to any one of claims 1 to 6, wherein during the melt extrusion molding, the flow path of the molten thermoplastic fluororesin is temporarily branched to form a weld line in the longitudinal direction of the fluororesin tube.

8. The method for manufacturing a fluororesin tube according to claim 7, further comprising the step of expanding the inner diameter by applying pressure from the inside while the fluororesin tube on which the weld line is formed is heated.

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