Insulated wire, cable, and method for manufacturing insulated wire

Abstract

To provide insulated wires and cables that are extremely thin in diameter while exhibiting improved resistance to damage to the insulator. [Solution] The insulated wire 1 comprises a conductor 11 and an insulator 12 that surrounds the conductor 11, with an outer diameter of 0.1 mm or less, the insulator 12 being made of a resin composition mainly composed of fluororesin, having a thickness of 10 μm or more and 30 μm or less, and having a crush strength of 15 N / 50 mm or more in accordance with the UL standard UL2556.

Description

[Technical Field]

[0001] The present invention relates to an insulated wire, a cable, and a method for manufacturing an insulated wire. [Background Art]

[0002] It is desirable for cables used in endoscopes and catheters to have as small a diameter as possible in order to reduce the burden on patients. For such cables, very thin insulated wires, for example having a diameter of 0.10 mm or less, are used.

[0003] As the aforementioned very thin insulated wire, a magnet wire in which an insulator is formed by applying an enamel paint made of polyurethane or the like around a conductor and baking the paint has been conventionally used. However, in magnet wires, high-temperature heat treatment is performed when baking the enamel paint, which causes the conductor to be annealed by the heat during the heat treatment, leading to a problem that the tensile strength of the conductor decreases.

[0004] In order to solve such problems, it is conceivable to use an insulated wire in which an insulator is formed by coating a fluororesin around a conductor via extrusion molding. Fluororesin can be molded into thin walls, and its molding temperature is lower than the temperature during heat treatment of enamel paint. Therefore, while maintaining a small outer diameter of the insulated wire, the decrease in tensile strength of the conductor caused by annealing is suppressed, and an insulated wire that is less prone to wire breakage can be achieved.

[0005] As prior art document information related to the invention of this application, there is Patent Document 1. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] U.S. Patent No. 12040108 Specification [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] However, in order to realize extremely thin insulated wires, such as those with an outer diameter of 0.10 mm or less, it is necessary to form the insulator, made of fluororesin, very thinly. When the insulator is formed very thinly, the resistance to external damage to the insulator decreases, and the insulator becomes more susceptible to tearing under external force. Therefore, damage to the insulator is more likely to occur when twisting insulated wires together or when processing the ends, and countermeasures were desired.

[0008] Therefore, the present invention aims to provide an insulated wire, a cable, and a method for manufacturing an insulated wire that are extremely small in diameter while having improved resistance to damage to the insulator. [Means for solving the problem]

[0009] The present invention aims to solve the above problems by providing an insulated electric wire comprising a conductor and an insulator covering the conductor, wherein the outer diameter is 0.1 mm or less, the insulator is made of a resin composition mainly composed of fluororesin, has a thickness of 10 μm or more and 30 μm or less, and has a crush strength of 15 N / 50 mm or more in accordance with the UL standard UL2556.

[0010] Furthermore, the present invention aims to solve the above problems by providing a cable that includes the insulated wire.

[0011] Furthermore, the present invention aims to solve the above problems and provides a method for manufacturing an insulated electric wire comprising a conductor and an insulator covering the conductor, with an outer diameter of 0.1 mm or less, comprising an extrusion molding step of providing the insulator, which is made of a resin composition mainly composed of fluororesin, around the conductor by extrusion molding, wherein the molding temperature in the extrusion molding step is set to be between +5°C and +25°C above the melting point of the fluororesin, and the conductor is preheated to above the melting point of the fluororesin before performing the extrusion molding to form the insulator with a thickness of 10 μm or more and 30 μm or less. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an insulated wire, a cable, and a method for manufacturing an insulated wire that are extremely small in diameter while having improved resistance to damage to the insulator. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of an insulated electric wire according to one embodiment of the present invention. [Figure 2] This figure shows an example of a Raman spectrum of an insulator. [Figure 3] This is a diagram illustrating the manufacturing method of insulated wires. [Figure 4] (a) and (b) are cross-sectional views showing an example of a cable using insulated wires. [Figure 5] This is a cross-sectional view showing an example of a cable using insulated wires. [Modes for carrying out the invention]

[0014] [Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0015] Figure 1 is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of the insulated wire 1 according to this embodiment. The insulated wire 1 is used, for example, as the core wire of a cable used in endoscopes and catheters, and its outer diameter is very small, less than 0.10 mm.

[0016] The insulated electric wire 1 includes a conductor 11 and an insulator 12 covering the periphery of the conductor 11. The conductor 11 is formed of a single-wire conductor. As the conductor 11, it is preferable to use one made of a hard copper alloy having high tensile strength. In the present embodiment, the conductor 11 made of silver-plated copper alloy is used. More specifically, the tensile strength of the conductor 11 is desirably 700 MPa or higher. With this configuration, even when the conductor 11 has a small diameter, wire breakage is less likely to occur. In order to increase the overall tensile strength of the insulated electric wire 1, the outer diameter of the conductor 11 is preferably 1 / 2 or more of the outer diameter of the insulated electric wire 1. Here, the outer diameter of the conductor 11 is set to 0.04 mm, and the outer diameter of the insulated electric wire 1 is set to 0.07 mm.

[0017] The insulator 12 is formed of a resin composition containing a fluororesin as a main component, and is formed by extrusion molding. As the fluororesin used for the insulator 12, it is preferable to use PFA (perfluoroalkoxyalkane), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), and ETFE (tetrafluoroethylene-ethylene copolymer). In particular, it is desirable to use PFA or FEP, which have good insulation performance when thinned.

[0018] The thickness of the insulator 12 is preferably 10 μm or more and 30 μm or less. By setting the thickness of the insulator 12 to 10 μm or more, the mechanical strength of the insulator 12 can be improved. In addition, by setting the thickness of the insulator 12 to 30 μm or less, an increase in the diameter of the insulated electric wire 1 can be suppressed.

[0019] Figure 2 is an example of a Raman spectrum obtained with the insulator 12 (Nichias Technical Report No.393, 2nd Issue, 2021, p.7). As shown in Figure 2, when PFA is used as the fluororesin, the peak P assigned to C-C stretching vibration in the Raman spectrum has a Raman shift of 1365 cm -1 or more and 1387 cm -1 or less, which is a peak derived from a crystalline component of PFA (referred to as a crystalline peak) Pc, and the Raman shift is 1343 cm -1 or more and 1365 cm -1The amorphous component of PFA can be separated into the following peaks (called amorphous peaks) Pa. The insulator 12 should have a crystallinity Ic / Ia ratio of 1.56 or higher, which is the ratio of the intensity Ic of the crystalline peak Pc to the intensity Ia of the amorphous peak Pa. A crystallinity Ic / Ia ratio of 1.56 or higher for the insulator 12 increases the proportion of crystallized PFA in the insulator 12, improving its resistance to trauma.

[0020] The insulated wire 1 according to this embodiment has a crush strength of 15N or more in accordance with the UL standard UL2556. This improves the resistance of the insulator 12 to external damage. To determine the crush strength, a pair of metal plates positioned opposite each other are used. The insulated wire 1 is placed on the lower plate, and the upper plate is gradually moved downward to compress the insulated wire 1 between the pair of plates. The insulated wire 1 is crushed by the compression, and the load applied between the pair of plates when the metal plates and the conductor 11 come into contact and conduct electricity is determined as the crush strength.

[0021] Furthermore, in the insulated wire 1 according to this embodiment, the ratio TB / OD of the tensile strength TB of the entire insulated wire 1, including the conductor 11 and the insulator 12, to the outer diameter OD of the insulator 12 (i.e., the outer diameter of the insulated wire 1) is 10 N / mm or more. This makes it possible to realize an insulated wire 1 that is small in diameter but resistant to breakage.

[0022] (Method of manufacturing insulated electric wire 1) Figure 3 illustrates the manufacturing method of the insulated wire 1. As shown in Figure 3, when manufacturing the insulated wire 1, an extrusion molding process is performed in which an insulator 12 is provided around the conductor 11 by extrusion molding using an extruder 20. In the extrusion molding process, first, raw material pellets are put into the hopper 21a of the extruder 20. Then, kneading is performed by a screw inside the extruder body 21, and the molten resin is extruded from the die 22a via the crosshead 22. In this embodiment, a resin composition mainly composed of fluororesin (here, PFA) is used as the raw material pellets.

[0023] The resin extruded from the die 22a coats the surface of the conductor 11 as it moves along the running line. As the resin coating the surface of the conductor 11 cools, an insulator 12 is formed, and an insulated wire 1 is obtained. In this embodiment, an insulator 12 with a thickness of 10 μm to 30 μm is formed by extrusion molding, and an insulated wire 1 with an outer diameter of 0.10 mm or less is manufactured. Hereinafter, when simply referred to as "fluororesin," it means the fluororesin used for the insulator 12.

[0024] The inventors' investigations revealed that if the molding temperature during extrusion molding is too high, the melt viscosity of the resin becomes too high, causing the outer diameter of the insulated wire 1 to become unstable. Conversely, if the molding temperature during extrusion molding is too low, although the outer diameter of the insulated wire 1 remains stable, the molding distortion increases, preventing the fluororesin (in this case, PFA) crystals from growing sufficiently and reducing the resistance of the insulator 12 to external damage. In this embodiment, "molding temperature" refers to the molding temperature downstream of the extruder 20, which is close to the temperature of the resin discharged from the extruder 20. More specifically, it refers to the temperature of the crosshead 22 and mold (die and nozzle 22a) installed at the tip of the extruder 20.

[0025] Further investigations by the inventors revealed that even when the molding temperature is set relatively low, if the conductor 11 is sufficiently preheated before extrusion molding, molding distortion can be suppressed and the resistance of the insulator 12 to damage can be improved. Therefore, in this embodiment, a preheating device 23 is provided to preheat the conductor 11 before it is introduced into the extruder 20, and the conductor 11 is introduced into the extruder 20 in a preheated state.

[0026] More specifically, the molding temperature in the extruder 20 is set to a relatively low temperature, between 5°C and 25°C above the melting point of the fluororesin. Then, the conductor 11 is preheated to above the melting point of the fluororesin by the preheating device 23 and introduced into the extruder 20. It is sufficient that the temperature of the conductor 11 at the time of introduction into the extruder 20 is above the melting point of the fluororesin. When PFA is used as the fluororesin, the melting point of PFA is around 300°C to 310°C, so it is advisable to set the temperature of the preheating device 23 so that the temperature of the conductor 11 at the time of introduction into the extruder 20 is at least 310°C. In this embodiment, the conductor 11 is preheated to 350°C in the preheating device 23, and the molding temperature in the extruder 20 is set to 315°C. The preheating temperature of the conductor 11 in the preheating device 23 is set to a higher temperature than the molding temperature in the extruder 20.

[0027] In this embodiment, the screw rotation speed was set to 0.5 rpm and the linear velocity to 23 m / min. Furthermore, the resin after extrusion molding was cooled by inline air cooling at a temperature of 20°C to 25°C without water cooling to form an insulator 12 and obtain an insulated wire 1. Note that the resin after extrusion molding retains molding distortion, so if it is rapidly cooled with water, the molecular motion of the PFA molecules is suppressed, and the insulator 12 is formed with the molding distortion remaining, making the insulator 12 susceptible to damage. Therefore, in this embodiment, the resin after extrusion molding is slowly cooled by air cooling without rapid water cooling. As a result, the molecular motion of the PFA molecules in the resin after extrusion molding is not suppressed and attempts are made to return to a state where the molding distortion is relieved, so that molding distortion does not remain in the insulator 12 and the insulator 12 is less likely to be damaged.

[0028] (Cable 3 using insulated wire 1) Figures 4(a), (b), and 5 are cross-sectional views showing an example of a cable 3 including an insulated wire 1.

[0029] The cable 3 shown in Figure 4(a) is a paired wire 3a formed by twisting together two insulated wires 1. In the example in Figure 4(a), no other components are provided around the two insulated wires 1, but for example, a jacket or the like that covers them all together may be provided around the two insulated wires 1. It is also possible to construct the cable 3 by twisting together two or more insulated wires 1.

[0030] The cable 3b shown in Figure 4(b) comprises an assembly 31 formed by twisting together a single insulated wire 1 and a tension member (tensile fiber) 30, a binding tape 32 spirally wrapped around the assembly 31, and a jacket 33 covering the binding tape 32. The tension member 30 can be made of, for example, liquid crystal polyester. The binding tape 32 can be made of, for example, resin tape. Here, a copper polyester tape with a thickness of 0.01 mm, in which a metal layer made of copper is formed on one side of a resin tape made of polyester, is used as the binding tape 32. In this case, the metal layer of the binding tape 32 acts as a shielding layer. The jacket 33 is constructed by spirally wrapping resin tape around the binding tape 32. Here, the jacket 33 is constructed using a resin tape made of polyester with a thickness of 0.01 mm. The outer diameter of the cable 3b is 0.22 mm.

[0031] The assembly 31 may include two or more insulated wires 1. For example, two insulated wires 1 may be used, and the assembly 31 may be constructed by alternately arranging the insulated wires 1 and tension members 30 in the circumferential direction of the cable 3b.

[0032] The cable 3c shown in Figure 5 comprises an assembly 34 made by twisting together five stranded wires 3a, a binding tape 35 spirally wrapped around the assembly 31, a shielding layer 36 covering the binding tape 35, and a sheath 37 covering the shielding layer 36.

[0033] The assembly 34 is constructed by twisting together a fiber intervening 38 and five stranded wires 3a. More specifically, the assembly 34 is constructed by placing the fiber intervening 38 at the center of the cable and arranging the five stranded wires 3a around the fiber intervening 38 in a circumferential direction. The fiber intervening 38 is made of bundled resin fibers. As the resin fibers constituting the fiber intervening 38, for example, those made of liquid crystal polyester can be used. As the binding tape 35, for example, a resin tape can be used. Here, a 0.40 mm thick resin tape made of polyimide was used as the binding tape 35.

[0034] The shield layer 36 consists of a horizontally wound shield formed by spirally winding multiple metal strands 361. The metal strands 361 used are extremely thin, with an outer diameter of 0.05 mm. To suppress breakage of the metal strands 361 and improve conductivity, it is desirable to use silver-plated copper alloy wires for the metal strands 361. Here, the shield layer 36 was constructed using metal strands 361 made of silver-plated copper alloy wire with an outer diameter of 0.03 mm. The sheath 37 should be made of a fluororesin that can be molded into a thin wall. Here, a sheath 37 made of PFA with a thickness of 0.05 mm was used. The outer diameter of the cable 3c is 0.56 mm.

[0035] (Examples) An insulated wire 1 of the example was fabricated using an extruder 20 with a core diameter of 2.5 mm, a nozzle diameter of 4.0 mm, and a screw diameter of 15 mm. An insulator 12 made of PFA (P-61XP manufactured by AGC Inc.) with a thickness of 0.015 mm was formed around a conductor 11 with an outer diameter of 0.04 mm. The extrusion molding conditions were a molding temperature of 315°C, a screw rotation speed of 0.5 rpm, and a wire speed of 23 m / min. The resin after extrusion molding was cooled by in-line air cooling at a temperature between 20°C and 25°C without water cooling to form the insulator 12, and the insulated wire 1 shown in Figure 1 was obtained. In this example, the conductor 11 introduced into the extruder 20 was heated to 350°C using a preheating device 23.

[0036] A crush test was performed on the insulated wire 1 of the obtained example in accordance with the UL standard UL2556 to determine the crush strength, and the tensile strength was also measured. In addition, Raman spectroscopy was performed on the insulator 12 of the insulated wire 1 to determine the degree of crystallinity.

[0037] Furthermore, the cable 3c shown in Figure 5 was fabricated using the insulated wire 1 from the example. First, two insulated wires 1 were twisted together with a twisting pitch of 0.5 mm to form a paired wire 3a. Then, five paired wires 3a were twisted together with a fiber interposition 38 made of 440dTEX liquid crystal polyester to form an assembly 34. The assembly 34 was twisted using a planetary twisting machine with a die diameter of 0.5 mm and a rotation speed of 50 rpm. After that, a binding tape 35 made of polyimide with a width of 2.2 mm was wrapped around the assembly 34, a shield layer 36 was formed around the binding tape 35, and a sheath 37 made of PFA was formed around the shield layer 36 by extrusion molding at a molding temperature of 315°C. Then, the resistance between the conductors 11 of the two insulated wires 1 constituting the paired wires 3a was measured in the obtained cable 3c. If the measured resistance is small, it is considered that damage occurred to the insulator 12 during the manufacturing process of the cable 3c. Furthermore, the cable 3c was disassembled and visually inspected for any damage to the insulator 12 of the insulated wire 1.

[0038] Furthermore, a comparative example insulated wire was fabricated under the same conditions as the example, but without heating the conductor 11 introduced into the extruder 20, and the crush strength, tensile strength, and degree of crystallinity were measured. In addition, a cable was fabricated using the fabricated comparative example insulated wire, similar to the example, and the resistance between the conductors 11 was measured, and the presence or absence of damage to the insulator 12 was visually checked. The results are summarized in Table 1.

[0039] [Table 1]

[0040] As shown in Table 1, the crush strength was 15N or higher in the examples, while it was lower than 15N in the comparative example. Furthermore, the crystallinity of the insulator 12 was 1.56 or higher in the examples, while it was lower than 1.56 in the comparative example. In the examples, where the crush strength was sufficiently high and the crystallinity of the insulator 12 was also high, it was confirmed that no damage occurred to the insulator 12 during the formation of the cable 3c, and the insulation resistance between the conductors 11 was maintained. In contrast, in the comparative example, where the crush strength was low and the crystallinity of the insulator 12 was also low, it was confirmed that damage occurred to the insulator 12 during the formation of the cable, and the insulation resistance between the conductors 11 was extremely low. It is desirable that the insulation resistance between the conductors 11 be at least 1000 Mohm-km. Also, the ratio of the tensile strength TB to the outer diameter OD of the insulated wire 1, TB / OD, was 10N / mm or higher in both the examples and the comparative example, confirming that a state of resistance to breakage was maintained.

[0041] (Operation and Effects of the Embodiment) As described above, in the insulated wire 1 according to this embodiment, the insulator 12 is made of a resin composition mainly composed of fluororesin, the thickness of the insulator 12 is 10 μm or more and 30 μm or less, and the crush strength in accordance with the UL standard UL2556 is 15 N / 50 mm or more.

[0042] This configuration makes it possible to improve the resistance of the insulator 12 to external damage while maintaining a very small diameter. As a result, for example, when twisting the insulated wires 1 together or when processing the ends, the insulator 1 is less likely to be damaged, making it easier to handle the insulated wires 1 and suppressing a decrease in yield.

[0043] (Summary of the embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0044] [1] An insulated electric wire (1) comprising a conductor (11) and an insulator (12) covering the conductor (11), wherein the outer diameter is 0.1 mm or less, the insulator (12) is made of a resin composition mainly composed of fluororesin, has a thickness of 10 μm or more and 30 μm or less, and has a crush strength of 15 N / 50 mm or more in accordance with the UL standard UL2556.

[0045] [2] The insulated wire (1) according to [1], wherein the ratio TB / OD of the overall tensile strength TB including the conductor (11) and the insulator (12) to the outer diameter OD of the insulator (12) is 10 N / mm or more.

[0046] [3] The insulated wire (1) according to [2], wherein the tensile strength of the conductor (11) is 700 MPa or more.

[0047] [4] The fluororesin is PFA (perfluoroalkoxyalkane), and the insulator (12) has a Raman shift of 1365 cm² among the peaks attributed to CC stretching vibration in the Raman spectrum. -1 Over 1387cm -1 The intensity Ic of the crystal peaks derived from the crystalline components of PFA within the following range, and the Raman shift of 1343 cm⁻¹ -1 1365cm -1 An insulated wire (1) as described in [1], wherein the crystallinity Ic / Ia, which is the ratio of the intensity Ia of the amorphous peak derived from the amorphous component of the PFA within the following range, is 1.56 or greater.

[0048] A cable (3) comprising an insulated wire (1) as described in any one of paragraphs [5][1] to [4].

[0049] [6] A method for manufacturing an insulated electric wire (1) comprising a conductor (11) and an insulator (12) covering the conductor (11), the insulator having an outer diameter of 0.1 mm or less, the method comprising an extrusion molding step of providing the insulator (12) made of a resin composition mainly composed of fluororesin around the conductor (11) by extrusion molding, wherein in the extrusion molding step the molding temperature is set to be between +5°C and +25°C above the melting point of the fluororesin, and the conductor (11) is preheated to above the melting point of the fluororesin before performing the extrusion molding to form the insulator (12) having a thickness of 10 μm or more and 30 μm or less.

[0050] (Note) Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. Moreover, the present invention can be implemented with appropriate modifications without departing from its spirit. [Explanation of symbols]

[0051] 1...Insulated wire 11...Conductor 12…Insulator 3… Cable

Claims

1. A conductor and The conductor comprises an insulator covering the periphery of the conductor, The outer diameter is 0.1 mm or less. The insulator is made of a resin composition mainly composed of fluororesin, and has a thickness of 10 μm or more and 30 μm or less. The crash strength conforms to the UL standard UL2556 and is 15N / 50mm or higher. Insulated wire.

2. The ratio TB / OD of the total tensile strength TB including the conductor and the insulator to the outer diameter OD of the insulator is 10 N / mm or more. The insulated wire according to claim 1.

3. The tensile strength of the conductor is 700 MPa or more. The insulated wire according to claim 2.

4. The fluororesin is PFA (perfluoroalkoxyalkane), The insulator has a Raman shift of 1365 cm² among the peaks attributed to C-C stretching vibrations in the Raman spectrum. －１ 1387cm or more －１ The intensity Ic of the crystal peaks originating from the crystalline components of PFA within the following range, and the Raman shift of 1343 cm⁻¹ －１ 1365cm －１ The crystallinity Ic / Ia, which is the ratio of the intensity Ia of the amorphous peak derived from the amorphous component of the PFA within the following range, is 1.56 or higher. The insulated wire according to claim 1.

5. The insulated wire includes the one described in any one of claims 1 to 4. cable.

6. A method for manufacturing an insulated electric wire comprising a conductor and an insulator covering the conductor, wherein the outer diameter is 0.1 mm or less, The process includes an extrusion molding step in which the insulator, made of a resin composition mainly composed of fluororesin, is provided around the conductor by extrusion molding, In the extrusion molding process, the molding temperature is set to be between +5°C and +25°C above the melting point of the fluororesin, and the conductor is preheated to above the melting point of the fluororesin before the extrusion molding is performed to form the insulator with a thickness of 10 μm to 30 μm. A method for manufacturing insulated electric wires.

Images