Insulated wires and cables

Abstract

To provide insulated wires and cables that are small in diameter yet highly resistant to bending and other forces. [Solution] The insulated wire 1 comprises a conductor 2 and a coating layer 5 formed on the outermost surface so as to cover the conductor 2. The coating layer 5 has an outer diameter of 0.6 mm or less and a thickness of 0.005 mm or more and 0.05 mm or less. The coating layer 5 is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and the coating layer 5 contains titanium dioxide, with the amount of Ti contained in the coating layer 5 being 0.2 mass% or less.

Description

Technical Field

[0001] The present invention relates to insulated wires and cables.

Background Art

[0002] As a cable used in medical devices, there is a cable that is inserted into the body, such as a cable for an endoscope. In such a cable, repeated heat sterilization is performed. Therefore, as the coating layer of the insulated wire used in the cable, a resin having high heat resistance, such as PFA (ethylene tetrafluoride-perfluoroalkoxyethylene copolymer), is used. Various additives such as colorants are added to the coating layer.

[0003] Note that Patent Document 1 is available as prior art document information related to the invention of this application.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above conventional insulated wire, foaming occurs during the molding of the coating layer, and there is a problem that the foamed portion becomes brittle. In particular, in a thin-diameter insulated wire with a thin coating layer, the decrease in mechanical strength when foaming occurs is remarkable.

[0006] In a cable inserted into the body, such as a cable for an endoscope, mechanical stresses such as bending and twisting are repeatedly applied in the body. Therefore, resistance to repeated bending and twisting (resistance to bending, etc.) is required.

[0007] Therefore, the present invention aims to provide insulated wires and cables that are small in diameter but have high resistance to bending and other forces. [Means for solving the problem]

[0008] The present invention aims to solve the above problems and provides an insulated wire comprising a conductor and a covering layer formed on the outermost surface so as to cover the conductor, wherein the covering layer has an outer diameter of 0.6 mm or less and a thickness of 0.005 mm or more and 0.05 mm or less, the covering layer is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), the covering layer contains titanium dioxide, and the amount of Ti contained in the covering layer is 0.2 mass% or less.

[0009] Furthermore, the present invention aims to solve the above problems by providing a cable comprising an assembly composed of a plurality of insulated wires and a sheath that covers the periphery of the assembly, wherein at least one of the insulated wires constituting the assembly is an insulated wire according to any one of claims 1 to 4.

[0010] Furthermore, the present invention aims to solve the above problems and provides a cable comprising: an assembly composed of a plurality of insulated wires; and a sheath formed on the outermost surface that covers the periphery of the assembly collectively, wherein the sheath has an outer diameter of 2 mm or less and a thickness of 0.005 mm or more and 0.12 mm or less; the sheath is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer); the sheath contains titanium dioxide; and the amount of Ti contained in the coating layer is 0.2 mass% or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide insulated wires and cables that are small in diameter yet highly resistant to bending and other forces. [Brief explanation of the drawing]

[0012] [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 the relationship between the amount of Ti in the coating layer and the amount of gas generated in the color masterbatch. [Figure 3] This is a cross-sectional view showing a section perpendicular to the longitudinal direction of a cable according to one embodiment of the present invention. [Modes for carrying out the invention]

[0013] [Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0014] Figure 1 is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of an insulated wire 1 according to this embodiment. The insulated wire 1 comprises a conductor 2 and a covering layer 5 formed on the outermost surface so as to cover the conductor 2. In this embodiment, the insulated wire 1 is a coaxial cable 10 further comprising an insulator 3 covering the conductor 2 and a shielding layer 4 covering the insulator 3 between the conductor 2 and the covering layer 5.

[0015] The coaxial cable 10 is used as a medical insulated wire 1 that is inserted into the human body, such as in an endoscope or catheter. The coaxial cable 10 is made very thin in diameter to minimize the burden on the human body, and its outer diameter (outer diameter of the coating layer 5) is 0.6 mm or less, more preferably 0.4 mm or less, and even more preferably 0.2 mm or less.

[0016] (Conductor 2) The conductor 2 is composed of a stranded conductor formed by stranding a plurality of metal strands 2a. As the metal strand 2a, one made of copper or a copper alloy can be used, and plating may be applied to its surface. In this embodiment, seven metal strands 2a made of silver-plated copper alloy wires with an outer diameter of 0.013 mm are concentrically stranded to form a conductor 2 with an outer diameter of 0.039 mm. The stranding pitch of the conductor 2 was set to 0.7 mm. Note that the stranding pitch of the conductor 2 is the interval along the longitudinal direction of the insulated wire 1 at points where the positions of the metal strands 2a are the same in the circumferential direction of the insulated wire 1.

[0017] The conductor 2 may be composed of a compressed stranded conductor in which the stranded conductor is compressed so that its cross-sectional shape is circular. As a result, the outer diameter of the conductor can be made smaller, enabling further reduction in the diameter of the insulated wire 1. Also, since the contact area between adjacent metal strands 2a increases, the conductivity of the entire conductor 2 improves, and the transmission characteristics can be enhanced.

[0018] (Insulator 3) The insulator 3 is preferably composed of a fluororesin capable of thin-wall molding. Here, an insulator 3 made of PFA (ethylene tetrafluoride-perfluoroalkoxyethylene copolymer) with a thickness of 0.023 mm was used. The insulator 3 had an outer diameter of 0.085 mm.

[0019] (Shield layer 4) The shield layer 4 is composed of a horizontally wound shield in which a plurality of metal strands 4a are spirally wound around the insulator 3. As the metal strand 4a, one made of copper or a copper alloy can be used, and plating may be applied to its surface. In this embodiment, the shield layer 4 was formed using 16 metal strands 4a made of silver-plated copper alloy wires with an outer diameter of 0.020 mm. The stranding direction of the shield layer 4 is preferably the same as the stranding direction of the conductor 2. Thereby, when bending or twisting is applied to the coaxial line 10, the stranding can be appropriately loosened according to the bending or twisting to release stress, and the resistance to bending and twisting is improved. Note that the stranding direction of the conductor 2 and the shield layer 4 is the direction in which the metal strands 2a, 4a rotate from one end to the other end as viewed from one end of the coaxial line 10.

[0020] (Coating layer 5) The coating layer 5 constitutes the outermost layer of the coaxial line 10. As the coating layer 5, similar to the insulator 3, it is preferably composed of a fluororesin that can be formed into a thin wall. In this embodiment, a coating layer 5 made of a resin composition mainly composed of PFA is used. For the purpose of reducing the diameter of the coaxial line 10, the thickness of the coating layer 5 is preferably at least 0.05 mm or less, more preferably 0.04 mm or less, and even more preferably 0.02 mm or less. Also, if it is made too thin, it is likely to be damaged, so the thickness of the coating layer 5 is preferably 0.005 mm or more, more preferably 0.01 mm or more. The outer diameter of the coating layer 5, that is, the outer diameter of the coaxial line 10, is set to a thin diameter of at least 0.6 mm or less, more preferably 0.4 mm or less, and even more preferably 0.2 mm or less. In this embodiment, the thickness of the coating layer 5 is 0.02 mm, and the outer diameter of the entire coaxial line 10 is 0.165 mm.

[0021] When the coating layer 5 is thin, the discharge amount of the resin during extrusion molding decreases, so the resin stays in the extruder for a long time, and the resin is decomposed and foamed by the excessive heat in the extruder, resulting in pinholes in the formed coating layer 5, etc., and the mechanical strength (resistance to bending, etc.) of the coating layer 5 decreases. As a result of the study by the present inventors, it was found that especially when the coating layer 5 contains titanium oxide as a colorant, titanium oxide acts as a catalyst and promotes the decomposition of the resin. Titanium oxide is a white colorant and is generally used when coloring the coating layer 5, for example, white or gray. In addition, if the molding temperature is lowered to suppress foaming, the orientation of the molecules of the resin constituting the coating layer 5 becomes uniform due to the strain during molding, and the coating layer 5 becomes easily torn along the longitudinal direction. Therefore, it is necessary to maintain the molding temperature at a temperature at which it does not become easily torn.

[0022] Therefore, in this embodiment, titanium dioxide is used as a coloring agent in the coating layer 5, but the amount used is reduced. More specifically, the amount of Ti contained in the coating layer 5 is preferably 0.2 mass% or less, more preferably 0.1 mass% or less, and more preferably 0.07 mass% or less. This suppresses the decomposition and foaming of the resin during extrusion molding, suppresses the decrease in mechanical strength, including resistance to bending, and also suppresses the decrease in insulating properties. Furthermore, since it becomes possible to perform extrusion molding while suppressing foaming even at relatively high temperatures, it is also possible to suppress the coating layer 5 from becoming prone to cracking.

[0023] Furthermore, in order to further suppress foaming, the viscosity of the PFA used in the coating layer 5 must be appropriately selected. Specifically, the PFA contained in the coating layer 5 should have a melt flow rate (MFR) of 20 to 80, more preferably 25 to 40, under conditions of 372±1℃ and a load of 5000g, in accordance with the ASTM standard ASTM D 3307. This will further suppress the decomposition and foaming of the resin during extrusion molding. If the MFR is less than 20, the viscosity will be high, and foaming will be promoted due to self-heating caused by shear stress during molding. Also, if the MFR is greater than 80, the molecular weight will be too low, which may adversely affect product functions such as flexural resistance.

[0024] (Consideration of the amount of Ti in coating layer 5) Coating layers 5 were formed using color masterbatches adjusted to various hues with different titanium dioxide content, and insulated wires 1 of Examples 1-3 and Comparative Examples 1 and 2 were formed. First, elemental analysis was performed on each color masterbatch used in Examples 1-3 and Comparative Examples 1 and 2 to determine the amount of Ti contained in the color masterbatch (Ti content of the color masterbatch). In addition, for each color masterbatch used in Examples 1-3 and Comparative Examples 1 and 2, the weight loss was measured using a TG-DTA (thermogravimetric-differential thermal analyzer) when held at 385°C for 120 minutes under N2 flow, and the amount of generated gas (amount of gas generated in the color masterbatch) was determined. A larger amount of generated gas indicates that foaming is more likely to occur during extrusion molding.

[0025] Furthermore, the color masterbatches of Examples 1-3 and Comparative Examples 1 and 2 were each added to a base resin (uncolored (natural color) PFA) and extruded to form coating layers 5. The base resin and color masterbatches were mixed in a ratio of 10:3. The amount of Ti contained in coating layer 5 (Ti amount in coating layer) was obtained by (Ti amount in color masterbatch) × (3 / 13). The extrusion conditions were a cylinder temperature of 265°C to 340°C, a crosshead temperature of 385°C, and a rotation speed of 2 rpm. The presence or absence of foaming was visually confirmed in the coating layers 5 obtained by extrusion molding. The results are summarized in Table 1. Figure 2 shows the relationship between the Ti amount in coating layer 5 and the amount of gas generated in the color masterbatch.

[0026] [Table 1]

[0027] As shown in Table 1 and Figure 2, it can be seen that the lower the amount of Ti in the coating layer 5, the lower the amount of gas generated and the less likely the coating layer 5 is to foam. In Examples 1 to 3, where the amount of Ti in the coating layer 5 was 0.2 mass% or less, no foaming occurred in the coating layer 5. In contrast, in Comparative Examples 1 and 2, where the amount of Ti in the coating layer 5 was greater than 0.2 mass%, foaming was confirmed to have occurred in the coating layer 5.

[0028] (cable) Next, a cable 110 using the insulated wire 1 according to this embodiment will be described. The cable 110 comprises an assembly 111 composed of multiple insulated wires 1, and a sheath 113 that covers the entire assembly 111. In this embodiment, a binding tape 112 is wrapped around the assembly 111, and the sheath 113 is provided around the binding tape 112.

[0029] In cable 110, at least one of the insulated wires 1 constituting the bundle 111 may be an insulated wire 1 according to this embodiment, and other insulated wires may be included. In the illustrated example, four insulated wires 1 according to this embodiment are twisted together to form the bundle 111.

[0030] Nonwoven fabric tape, paper tape, resin tape, etc., can be used as the binding tape 112. In this embodiment, a polyester tape with copper vapor-deposited on one side was used as the binding tape 112. The copper layer formed by vapor deposition acts as a shielding layer. This makes it possible to reduce the outer diameter of the cable 110 compared to the case where a shielding layer is provided separately from the binding tape 112. The thickness of the binding tape 112 was set to 0.01 mm and the width to 2.0 mm. The binding tape 112 is wound in a spiral shape so that a portion of it overlaps in the width direction.

[0031] The twisting direction of the bundle 111 and the winding direction of the binding tape 112 are set to be in opposite directions. This prevents the twisted cores from unraveling and improves durability against repeated bending. The twisting direction of the bundle 111 is the direction in which the insulated wire 1 rotates from one end to the other when viewed from one end of the cable 110. The winding direction of the binding tape 112 is the direction in which the binding tape 112 rotates from one end to the other when viewed from one end of the cable 110.

[0032] The sheath 113 is preferably made of a fluororesin that can be molded into a thin wall. Here, a sheath 113 made of PFA with a thickness of 0.025 mm was used. The overall outer diameter of the cable 110 is approximately 0.47 mm.

[0033] (Operation and Effects of the Embodiment) As described above, in the insulated wire 1 according to this embodiment, the outer diameter of the coating layer 5 is 0.6 mm or less, and the thickness is 0.005 mm or more and 0.05 mm or less. The coating layer 5 is made of a resin composition mainly composed of PFA and contains titanium oxide, and the amount of Ti contained in the coating layer 5 is 0.2 mass% or less.

[0034] This makes it possible to suppress the decomposition and foaming of the resin during the extrusion molding of the coating layer 5, enabling the realization of an insulated wire 1 that is small in diameter and has a thin coating layer 5, while still being highly resistant to bending and other forces. Furthermore, by suppressing the foaming of the coating layer 5, it is also possible to suppress the decrease in the insulation properties of the coating layer 5. In addition, since it becomes possible to perform extrusion molding while suppressing foaming even at relatively high temperatures, the alignment of the resin molecules constituting the coating layer 5 due to distortion during extrusion molding is suppressed, resulting in an insulated wire 1 in which the coating layer 5 is less likely to crack.

[0035] (modified version) In the above embodiment, the amount of Ti in the outermost coating layer 5 of the insulated wire 1 was set to 0.2 mass% or less. However, the present invention is not limited to the insulated wire 1, but can also be applied to small-diameter multi-core cables. That is, in a cable comprising an assembly composed of multiple insulated wires and a sheath formed on the outermost surface that covers the assembly as a whole, the sheath may be made of a resin composition mainly composed of PFA and containing titanium oxide, and the amount of Ti contained in the sheath may be set to 0.2 mass% or less. In particular, when the outer diameter of the cable (outer diameter of the sheath) is small, such as 2 mm or less, and the thickness of the sheath is thin, such as 0.005 mm or more and 0.12 mm or less, the decrease in mechanical strength due to foaming becomes significant. In contrast, by setting the amount of Ti in the sheath to 0.2 mass% or less, preferably 0.1 mass% or less, and more preferably 0.07 mass% or less, it is possible to suppress foaming during extrusion molding and suppress the decrease in mechanical strength.

[0036] (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.

[0037] [1] An insulated electric wire (1) comprising a conductor (2) and a covering layer (5) formed on the outermost surface so as to cover the periphery of the conductor (2), wherein the covering layer (5) has an outer diameter of 0.6 mm or less and a thickness of 0.005 mm or more and 0.05 mm or less, the covering layer (5) is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), the covering layer (5) contains titanium dioxide, and the amount of Ti contained in the covering layer (5) is 0.2 mass% or less.

[0038] [2] The insulated wire (1) according to [1], wherein the amount of Ti contained in the coating layer (5) is 0.07 mass% or less.

[0039] [3] The insulated wire (1) described in [1], wherein the PFA contained in the coating layer (5) has a melt flow rate of 20 or more and 80 or less under the conditions specified in ASTM D 3307.

[0040] [4] The insulated wire (1) described in [1], wherein the conductor (2) is a compressed stranded conductor obtained by twisting together a plurality of metal strands (2a) and compressing them so that the cross-sectional shape is circular.

[0041] [5] A cable (100) comprising an assembly (111) composed of multiple insulated wires and a sheath (113) that covers the assembly (111) collectively, wherein at least one of the insulated wires constituting the assembly (111) is an insulated wire (1) as described in any one of items [1] to [4].

[0042] [6] A cable comprising an assembly composed of multiple insulated wires, and a sheath formed on the outermost surface that covers the entire assembly, wherein the sheath has an outer diameter of 2 mm or less and a thickness of 0.005 mm or more and 0.12 mm or less, the sheath is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), the sheath contains titanium dioxide, and the amount of Ti contained in the sheath is 0.2 mass% or less.

[0043] (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. In addition, the present invention can be implemented with appropriate modifications without departing from its spirit. [Explanation of Symbols]

[0044] 1…Insulated wire 10…Coaxial line 2... Conductor 3…Insulator 4…Shield layer 5…Covering layer 110... Cable 111…Aggregation 112... Bind Tape 113...Sheath

Claims

1. A conductor and The conductor comprises a covering layer formed on the outermost surface so as to cover the periphery of the conductor, The coating layer has an outer diameter of 0.6 mm or less and a thickness of 0.005 mm or more and 0.05 mm or less. The coating layer is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), The coating layer contains titanium oxide, and the amount of Ti contained in the coating layer is 0.2 mass% or less. Insulated wire.

2. The amount of Ti contained in the coating layer is 0.07 mass% or less. The insulated wire according to claim 1.

3. The PFA contained in the coating layer has a melt flow rate of 20 to 80 under the conditions specified in ASTM D 3307. The insulated wire according to claim 1.

4. The conductor consists of a compressed stranded conductor formed by twisting together multiple metal strands and compressing them so that the cross-sectional shape is circular. The insulated wire according to claim 1.

5. A collection of multiple insulated wires, The assembly comprises a sheath that covers the entire surroundings of the assembly, At least one of the insulated wires constituting the assembly is an insulated wire according to any one of claims 1 to 4. cable.

6. A collection of multiple insulated wires, The assembly comprises a sheath that covers the entire surroundings and is formed on the outermost side, The sheath has an outer diameter of 2 mm or less and a thickness of 0.005 mm or more and 0.12 mm or less. The sheath is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), The sheath contains titanium oxide, and the amount of Ti contained in the sheath is 0.2 mass% or less. cable.

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