Insulated wire and method for producing the same

Abstract

To provide a technique capable of improving watertight properties, adhesion and peel-off properties in a good balance.SOLUTION: When hydraulic pressure at atmospheric pressure of 0.5 is applied for 24 hours onto one end in an axial direction of an insulated wire cut at a prescribed length, a water penetration distance from the one end of the insulated wire is 1000 mm or less. When a tensile test is conducted to the insulated wire held by an electric wire holding implement under a condition with a tensile load of 4.17 kN and application time of 10 minutes, a length of a deviation of an insulator layer is 50 mm or less. When an outer layer watertight material and the insulator layer are peeled off over an entire circumference of a conductor in the axial direction of the insulated wire by 15 cm, remnant parts of the outer layer watertight material remaining in a manner across conductor strands are 5 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a resin composition for an outer layer watertight material, an insulated electric wire, and a method for producing an insulated electric wire. [Background technology]

[0002] In overhead wiring applications, insulated electric wires are used in which a waterproof material is provided between the conductor strands of the conductor and between the conductor and the insulating layer in order to suppress corrosion of the conductor due to the infiltration of rainwater. Of the waterproof materials for insulated electric wires, the outer waterproof material provided between the conductor and the insulating layer is required to have watertight properties, adhesion to bond the conductor and the insulating layer, and peelability to strip the waterproof material and the insulating layer from the conductor (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3688319 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a technology that can improve watertightness, adhesion, and peelability in a well-balanced manner. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, A resin composition for an outer layer water-tight material forming an outer layer water-tight material for an insulated electric wire, When a water pressure of 0.5 atmospheres is applied to one axial end of the insulated electric wire cut to a predetermined length for 24 hours, the permeation distance of water from the one end of the insulated electric wire is 1000 mm or less; When the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less, When the outer layer watertight material and the insulating layer are stripped off over the entire outer circumference of the conductor by 15 cm in the axial direction of the insulated wire, the remaining portion of the outer layer watertight material remaining across the conductor wires is 5 or less. A resin composition for an outer layer watertight material is provided.

[0006] According to another aspect of the present disclosure, a conductor formed by twisting together a plurality of conductor wires; An outer watertight material provided to cover the outer periphery of the conductor; An insulating layer provided to cover the outer periphery of the outer layer watertight material; An insulated wire having When a water pressure of 0.5 atmospheres is applied to one axial end of the insulated electric wire cut to a predetermined length for 24 hours, the permeation distance of water from the one end of the insulated electric wire is 1000 mm or less; when the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less; When the outer layer watertight material and the insulating layer are stripped off over the entire outer circumference of the conductor by 15 cm in the axial direction of the insulated wire, the remaining portion of the outer layer watertight material remaining across the conductor wires is 5 or less. An insulated wire is provided.

[0007] According to another aspect of the present disclosure, A step of stranding a plurality of conductor wires to form a conductor; forming an outer layer watertight material so as to cover an outer periphery of the conductor; forming an insulating layer so as to cover the outer periphery of the outer layer watertight material; cross-linking at least the insulating layer; having In the step of forming the outer layer water-tight material, The conductor is preheated to a temperature of 20°C to 40°C, and the outer layer watertight material is extruded. In the step of cross-linking the insulating layer, The insulating layer is cross-linked with water at a cross-linking temperature of 75°C to 82°C. A method for making an insulated wire is provided. Effect of the Invention

[0008] According to the present disclosure, it is possible to improve watertightness, adhesion, and peelability in a well-balanced manner. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view perpendicular to the axial direction of an insulated wire according to one embodiment of the present disclosure. [Figure 2A] FIG. 2A is a schematic diagram illustrating a method for producing an insulated wire according to one embodiment of the present disclosure. [Figure 2B] FIG. 2B is a schematic diagram illustrating a method for producing an insulated wire according to an embodiment of the present disclosure. [Figure 2C] FIG. 2C is a schematic diagram illustrating a method for producing an insulated wire according to an embodiment of the present disclosure. [Figure 2D] FIG. 2D is a schematic diagram illustrating a method for making an insulated wire according to one embodiment of the present disclosure. [Figure 3A] FIG. 3A is a schematic diagram showing an insulated wire of Sample 1 that was subjected to a peelability test. [Figure 3B] FIG. 3B is a schematic diagram showing an insulated wire of Sample 3 that was subjected to a peelability test. [Figure 3C] FIG. 3C is a schematic diagram showing an insulated wire of Sample 4 that was subjected to a peelability test. [Figure 3D] FIG. 3D is a schematic diagram showing an insulated wire of Sample 5 that was subjected to a peeling property test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Description of the embodiments of the present disclosure] <Knowledge gained by the inventors> First, the findings of the inventors will be described.

[0011] Of the three characteristics required for an outer layer waterproofing material, watertightness (rainwater infiltration prevention or water running prevention) is a characteristic to suppress the propagation of rainwater between conductor strands and between the conductor and the insulating layer, and to suppress corrosion of the conductor due to rainwater. Adhesion (wire gripping property, Camler property) is a property to prevent the insulating layer from shifting or breaking when the insulated wire is pulled with a wire gripping tool (wire gripper, Camler) by adhering the conductor and the insulating layer. Strippability is a property to strip the outer layer waterproofing material and insulating layer from the conductor at the end of the insulated wire when a pair of insulated wires are compressed and connected through a compression sleeve.

[0012] Regarding the peelability required for an outer layer waterproof material, it has been considered in the past that even if at least a portion of the conductor remains, there is no problem as long as electrical continuity is established between the conductor and the compression sleeve when a pair of insulated electric wires are compressed and connected via the compression sleeve.

[0013] However, in recent years, from the viewpoint of improving power transmission efficiency and installation stability, it is desired to reduce the contact resistance between the conductor and the compression sleeve when a pair of insulated electric wires are compressed and connected via the compression sleeve, and to improve the gripping property (grip strength) of the compression sleeve, so that stricter stripping property of the insulated electric wire is required.

[0014] Here, the inventors have found that depending on the shape of the remaining portion of the outer layer watertight material that remains when the insulating layer is peeled off, the following problems may occur.

[0015] For example, if a large amount of the outer layer waterproofing material remains across the conductor strands when the insulation layer is stripped away, it becomes difficult for the conductor strands to be connected to the compression sleeve via the remaining portion, which may increase the contact resistance between the conductor and the compression sleeve.

[0016] In addition, for example, if many of the grooves formed between adjacent conductor strands when the insulation layer is stripped away contain residual outer layer watertight material, the remaining outer layer watertight material in the grooves may cause the compression sleeve to come into uneven contact with the outer circumference of the conductor when the compression sleeve is compressed and connected, making it difficult to sufficiently compress the compression sleeve. This may result in a decrease in gripping ability of the compression sleeve.

[0017] In order to solve such problems, the inventors have conducted intensive research and have found that the above-mentioned peelability can be improved compared to the conventional method by, for example, preheating (preheating) the conductor to a predetermined temperature in the outer layer waterproofing material forming process of the insulated wire manufacturing process.

[0018] The present disclosure is based on the above-mentioned new findings discovered by the inventors.

[0019] <Embodiments of the present disclosure> Next, embodiments of the present disclosure will be listed and described.

[0020] [1] The resin composition for an outer layer watertight material according to one embodiment of the present disclosure comprises: A resin composition for an outer layer water-tight material forming an outer layer water-tight material for an insulated electric wire, When a water pressure of 0.5 atmospheres is applied to one axial end of the insulated electric wire cut to a predetermined length for 24 hours, the permeation distance of water from the one end of the insulated electric wire is 1000 mm or less; When the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less; When the outer layer watertight material and the insulating layer are stripped off over 15 cm in the axial direction of the insulated wire around the entire outer circumference of the conductor, the remaining portions of the outer layer watertight material remaining across the conductor wires are 5 or less. According to this configuration, it is possible to improve watertightness, adhesion and peelability in a well-balanced manner.

[0021] [2] An insulated wire according to another aspect of the present disclosure includes: A resin composition for an outer layer water-tight material forming an outer layer water-tight material for an insulated electric wire, a conductor formed by twisting together a plurality of conductor wires; An outer watertight material provided to cover the outer periphery of the conductor; An insulating layer provided to cover the outer periphery of the outer layer watertight material; An insulated wire having When a water pressure of 0.5 atmospheres is applied to one axial end of the insulated electric wire cut to a predetermined length for 24 hours, the permeation distance of water from the one end of the insulated electric wire is 1000 mm or less; when the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less; When the outer layer watertight material and the insulating layer are stripped off over 15 cm in the axial direction of the insulated wire around the entire outer circumference of the conductor, the remaining portions of the outer layer watertight material remaining across the conductor wires are 5 or less. According to this configuration, it is possible to improve watertightness, adhesion and peelability in a well-balanced manner.

[0022] [3] The insulated wire according to [2] above, When the outer layer watertight material and the insulating layer are stripped off over 15 cm in the axial direction of the insulated wire around the entire outer circumference of the conductor, the ratio of the number of grooves in which the outer layer watertight material remains to the total number of grooves formed between adjacent conductor wires is 7 / 12 or less. This configuration improves the grip of the compression sleeve.

[0023] [4] The insulated wire according to the above [2] or [3], The outer layer watertight material is made of a resin composition containing an ethylene-(meth)acrylate copolymer. According to this configuration, it is possible to preferably achieve a well-balanced watertightness, adhesion and peelability.

[0024] [5] A method for producing an insulated wire according to still another aspect of the present disclosure includes: A step of stranding a plurality of conductor wires to form a conductor; forming an outer layer watertight material so as to cover an outer periphery of the conductor; forming an insulating layer so as to cover the outer periphery of the outer layer watertight material; cross-linking at least the insulating layer; having In the step of forming the outer layer water-tight material, The conductor is preheated to a temperature of 20°C to 40°C, and the outer layer watertight material is extruded. In the step of cross-linking the insulating layer, The insulating layer is cross-linked with water at a cross-linking temperature of 75°C or more and 82°C or less. According to this configuration, it is possible to improve watertightness, adhesion and peelability in a well-balanced manner.

[0025] [Details of the embodiment of the present disclosure] Next, an embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0026] <One embodiment of the present disclosure> (1) Insulated wire (watertight insulated wire) An insulated wire according to an embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the insulated wire according to the embodiment, taken perpendicular to its axial direction.

[0027] As shown in FIG. 1, the insulated electric wire 10 of the present embodiment is configured to be used as an electric wire for outdoor power distribution, and has, for example, from the center toward the outside, a conductor 100, an inner layer watertight material 220, an outer layer watertight material 240, and an insulating layer (insulator, insulating coating layer) 300.

[0028] The conductor 100 is provided by twisting together a plurality of conductor wires 110. The conductor 100 is made of, for example, a hard copper wire, a hard copper stranded wire, a hard aluminum stranded wire, an aluminum-core stranded wire (ACSR), etc. The plurality of conductor wires 110 are, for example, concentrically twisted, and the number of conductor wires 110 is, for example, 19.

[0029] It should be noted that the conductor 100 may or may not be compressed.

[0030] The inner layer watertight material 220 is filled between the plurality of conductor wires 110. The inner layer watertight material 220 is configured to improve the watertightness between the plurality of conductor wires 110. The inner layer watertight material 220 will be described later.

[0031] The outer layer watertight material 240 is provided so as to cover the outer periphery of the conductor 100 (and the inner layer watertight material 220). The outer layer watertight material 240 is also configured to mainly improve the watertightness between the conductor 100 and the insulating layer 300. The outer layer watertight material 240 will be described in detail below together with the inner layer watertight material 220.

[0032] The insulating layer 300 is provided so as to cover the outer periphery of the outer-layer waterproof material 240 (and the conductor 100). The insulating layer 300 is made of, for example, a resin composition for insulating layers containing polyolefin as a base resin. The base resin of the resin composition for insulating layers is, for example, polyethylene.

[0033] The insulating layer 300 is configured to be crosslinked by, for example, a silane graft water crosslinking method. The resin composition for insulating layer constituting the insulating layer 300 contains, for example, a silane coupling agent, a crosslinking agent (a free radical generator), and a catalyst (a silanol condensation catalyst). In addition, the resin composition for insulating layer may contain, for example, a color batch, an antiaging agent, and the like.

[0034] (Dimensions, etc.) The outer diameter of the conductor wire 110 is, for example, 1 mm or more and 5 mm or less. The cross-sectional area of ​​the conductor 100 is, for example, 14 mm 2More than 500mm 2 The thickness of the outer waterproof material 240 is, for example, 0.1 mm or more and 2 mm or less. The thickness of the insulating layer 300 is, for example, 1 mm or more and 5 mm or less. The nominal voltage of the insulated wire 10 is, for example, 6.6 kV or more and 33 kV or less.

[0035] (2) Characteristics of insulated wire As a result of intensive research by the inventors, for example, an insulated wire 10 having the following characteristics has been realized for the first time.

[0036] In the insulated electric wire 10 of the present embodiment, when a water pressure of 0.5 atmospheres is applied to one end of the insulated electric wire 10 in the axial direction cut to a predetermined length for 24 hours, the water permeation distance from one end of the insulated electric wire 10 is, for example, 1000 mm or less, preferably 600 mm or less. If the water permeation distance exceeds 1000 mm, the conductor 100 may corrode due to the penetration of rainwater. In contrast, in the insulated electric wire 10 of the present embodiment, the water permeation distance is 1000 mm or less, so that the corrosion of the conductor 100 can be suppressed. This allows the insulated electric wire 10 to be stably maintained as a product. Furthermore, the water permeation distance is 600 mm or less, so that the corrosion of the conductor 100 can be stably suppressed.

[0037] In addition, the shorter the water permeation distance, the better. In other words, the lower limit of the water permeation distance is preferably 0 mm, that is, it is preferable that no water permeates from one end of the insulated electric wire 10 at all.

[0038] In addition, in the insulated electric wire 10 of the present embodiment, when the insulated electric wire 10 is held by a predetermined electric wire gripper (e.g., Camlar manufactured by Nagaki Seiki Co., Ltd.) and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer 300 is, for example, 50 mm or less, and preferably 5 mm or less. If the length of displacement of the insulating layer 300 exceeds 50 mm, for example, when the insulated electric wire 10 is held by a wire gripper during a work of replacing the insulated electric wire 10, the insulating layer 300 may slip along the conductor 100, and the insulated electric wire 10 may come off the wire gripper. This may increase the risk of the insulated electric wire 10 falling off. In contrast, in the insulated wire 10 of the present embodiment, the length by which the insulating layer 300 is displaced is 50 mm or less, and therefore, when the insulated wire 10 is held by a wire gripper, slippage of the insulating layer 300 is suppressed, and the insulated wire 10 can be suppressed from coming off the wire gripper. As a result, the insulated wire 10 can be prevented from falling off. Furthermore, the length by which the insulating layer 300 is displaced is 5 mm or less, and therefore, the insulated wire 10 can be reliably prevented from coming off the wire gripper.

[0039] It is to be noted that the shorter the length of displacement of the insulating layer 300, the better. In other words, the lower limit of the length of displacement of the insulating layer 300 is preferably 0 mm, that is, it is preferable that the insulating layer 300 does not displace.

[0040] Moreover, the insulated wire 10 of the present embodiment satisfies stricter strippability requirements than conventional insulated wires.

[0041] Specifically, in the insulated wire 10 of the present embodiment, when the outer-layer water-tight material 240 and the insulating layer 300 are stripped off over 15 cm in the axial direction of the insulated wire 10 around the entire outer periphery of the conductor 100, the remaining portion of the outer-layer water-tight material 240 remaining so as to straddle the conductor wires 110 is, for example, 5 or less, preferably 3 or less, and more preferably 0. Note that the "remaining portion of the outer-layer water-tight material 240 remaining so as to straddle the conductor wires 110" refers to the remaining portion of the outer-layer water-tight material 240 remaining so as to connect from one conductor wire 110 (groove on the side) of a pair of conductor wires 110 adjacent to a specific conductor wire 110 on the outer periphery of the conductor 100 to the other conductor wire 110 (groove on the side) sandwiching the specific conductor wire 110 therebetween. If the number of remaining parts of the outer layer watertight material 240 remaining so as to straddle the conductor wires 110 is more than five, the conductor wires 110 with the remaining parts and the compression sleeve are difficult to connect through the remaining parts. This may increase the contact resistance between the conductor 100 and the compression sleeve. In contrast, in the insulated electric wire 10 of the present embodiment, the number of remaining parts of the outer layer watertight material 240 remaining so as to straddle the conductor wires 110 is five or less, that is, the number of remaining parts of the outer layer watertight material 240 interposed between the conductor wires 110 and the compression sleeve is reduced, so that each conductor wire 110 and the compression sleeve can be well connected. As a result, it is possible to prevent the contact resistance between the conductor 100 and the compression sleeve from increasing. Furthermore, the number of remaining parts of the outer layer watertight material 240 remaining so as to straddle the conductor wires 110 is preferably three or less, more preferably zero, so that each conductor wire 110 and the compression sleeve can be well and reliably connected.

[0042] In addition, in the insulated wire 10 of the present embodiment, when the outer layer watertight material 240 and the insulating layer 300 are stripped off over 15 cm in the axial direction of the insulated wire 10 over the entire outer circumference of the conductor 100, the ratio of the number of grooves in which the outer layer watertight material 240 remains to the total number of grooves formed between adjacent conductor wires 110 (on the outer circumference of the conductor 100) is, for example, 7 / 12 or less, and preferably 3 / 12 or less. If the ratio of the number of grooves in which the outer layer watertight material 240 remains exceeds 7 / 12, when the compression sleeve is compressed and connected, the compression sleeve comes into uneven contact with the outer circumference of the conductor 100 due to the remaining outer layer watertight material 240 in the grooves, making it difficult to sufficiently compress the compression sleeve. This may reduce the gripping ability of the compression sleeve. In contrast, in the insulated wire 10 of the present embodiment, the ratio of the number of grooves in which the outer-layer watertight material 240 remains is 7 / 12 or less, so that when the compression sleeve is compressed and connected, the compression sleeve can be uniformly abutted against the outer periphery of the conductor 100, and the compression sleeve can be sufficiently compressed. As a result, the gripping ability of the compression sleeve can be improved. Furthermore, the ratio of the number of grooves in which the outer-layer watertight material 240 remains is 3 / 12 or less, so that the compression sleeve can be firmly compressed.

[0043] In addition, the lower the ratio of the number of grooves where the outer-layer watertight material 240 remains, the better. In other words, the lower limit of the ratio of the number of grooves where the outer-layer watertight material 240 remains is preferably 0.

[0044] (3) Watertight material (Outer layer watertight material) Next, a description will be given of the outer layer watertight material 240. The outer layer watertight material 240 of this embodiment is configured, for example, as follows.

[0045] The outer layer watertight material 240 of this embodiment is made of a resin composition containing an ethylene-(meth)acrylate copolymer as a base resin (hereinafter, also referred to as a "resin composition for the outer layer watertight material"). Note that "(meth)acrylate" here means acrylate or methacrylate.

[0046] Specifically, examples of the base resin of the resin composition for the outer layer watertight material include ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl methacrylate copolymer (EMMA), and the like.

[0047] The base resin of the resin composition for the outer-layer watertight material of this embodiment is, for example, EMMA, which has the structure shown in the following formula (1).

[0048] [ka]

[0049] EMMA has the same flexibility as ethylene vinyl acetate copolymer (EVA), rubber-like elasticity, excellent low-temperature properties, and excellent electrical properties, but is formulated to not corrode in acids like EVA.

[0050] In addition, the base resin of the outer-layer watertight material 240 of this embodiment is formed by mixing two resins (first resin and second resin) containing, for example, EMMA and having different properties. The first resin has, for example, high mechanical strength, hard properties, and good peelability, but poor adhesion. On the other hand, the second resin has, for example, low mechanical strength, soft properties, good watertightness and adhesion, but poor peelability. In this embodiment, the outer-layer watertight material 240 contains a base resin formed by mixing the first resin and the second resin, so that the watertightness, adhesion, and peelability of the insulated electric wire 10 can be improved in a well-balanced manner.

[0051] Here, the first resin and the second resin will be described in detail.

[0052] The first resin has, for example, the following properties. MMA content: 18% by weight or more, but less than 22% by weight Melt flow rate: 1g / 10min or more and less than 3g / 10min Durometer hardness for Type A: 75 or more and less than 92 Vicat softening temperature: 54℃ or higher and 66℃ or lower Melting temperature: 77℃ or higher and less than 95℃

[0053] Here, MMA stands for methyl methacrylate. The melt flow rate (MFR) is measured in accordance with JIS K7210, and is the value at a measurement temperature of 190°C and a load of 2.12N. The durometer hardness of Type A is measured in accordance with JIS K7215. The Vicat softening temperature is measured in accordance with JIS K7206. The melting temperature is measured by a differential scanning calorimeter (DSC) in accordance with JIS K7121.

[0054] On the other hand, the second resin has, for example, the following properties. MMA content: 22% by weight or more, but less than 28% by weight Melt flow rate: 6g / 10min or more and less than 8g / 10min Durometer hardness for Type A: 70 or more and less than 86 Vicat softening temperature: 42℃ or higher and 52℃ or lower Melting temperature: 72℃ or higher and less than 88℃

[0055] In this embodiment, the ratio B / A of the weight B of the second resin to the weight A of the first resin in the base resin of the outer-layer watertight material 240 is 1 / 4 or more and 4 or less (A:B=80:20-20:80). If the ratio B / A of the weight B of the second resin to the weight A of the first resin is less than 1 / 4, that is, if the weight B of the second resin is smaller than the weight A of the first resin by a certain ratio, the outer-layer watertight material 240 becomes excessively hard, and while the peelability is improved, the adhesion is reduced. On the other hand, by setting the ratio B / A of the weight B of the second resin to the weight A of the first resin to 1 / 4 or more, the outer-layer watertight material 240 is prevented from becoming excessively hard, and the watertightness and adhesion can be improved while maintaining the peelability. On the other hand, if the ratio B / A of the weight B of the second resin to the weight A of the first resin exceeds 4, that is, if the weight B of the second resin is greater than the weight A of the first resin by a certain ratio, the outer-layer watertight material 240 becomes excessively soft, improving the watertightness and adhesion while decreasing the peelability. In contrast, by setting the ratio B / A of the weight B of the second resin to the weight A of the first resin to 4 or less, the outer-layer watertight material 240 is prevented from becoming excessively soft, and the peelability can be improved while maintaining the watertightness and adhesion.

[0056] Furthermore, in this embodiment, the ratio B / A of the weight B of the second resin to the weight A of the first resin in the base resin of the outer-layer watertight material 240 is preferably 1 or more and 7 / 3 or less (A:B=50:50-30:70). In this way, by mixing a larger amount of the relatively soft second resin than the first resin in the base resin of the outer-layer watertight material 240, it is possible to stably improve the watertightness and adhesion while maintaining the peelability.

[0057] The resin composition constituting the outer layer watertight material 240 contains, in addition to the above-mentioned base resin, for example, the following various additives.

[0058] The outer layer watertight material 240 is configured to be colored, for example. The resin composition constituting the outer layer watertight material 240 includes, for example, a color batch. The color batch includes, for example, a color batch base resin made of EMMA, carbon black, and a dispersant. For example, the content of the color batch base resin is 50 parts by weight, the content of the carbon black is 20 parts by weight, and the content of the dispersant is 30 parts by weight. The content of the color batch in the outer layer watertight material 240 is 0.5 parts by weight or more and 5 parts by weight or less when the base resin of the outer layer watertight material 240 is 100 parts by weight. By including a predetermined amount of the color batch in the outer layer watertight material 240, the outer layer watertight material 240 can be colored to make the peeling property easier to visually recognize, and the deterioration of the outer layer watertight material 240 over time can be suppressed.

[0059] The outer layer watertight material 240 is configured to be crosslinked by, for example, a silane graft water crosslinking method. The resin composition constituting the outer layer watertight material 240 contains, for example, a silane coupling agent, a crosslinking agent (free radical generator), a catalyst (silanol condensation catalyst), and an antiaging agent. An alkoxysilane compound is used as the silane coupling agent. Specifically, the silane coupling agent is, for example, vinyltrimethoxysilane. The content of the silane coupling agent in the outer layer watertight material 240 is 0.5 parts by weight or more and 5 parts by weight or less when the base resin is 100 parts by weight. An organic peroxide is used as the crosslinking agent. Specifically, the crosslinking agent is, for example, dicumyl peroxide (DCP). The content of the crosslinking agent in the outer layer watertight material 240 is 0.05 parts by weight or more and 0.5 parts by weight or less when the base resin is 100 parts by weight. As the catalyst, a carboxylate of a metal such as tin, zinc, iron, lead, or cobalt, an organic base, an inorganic acid, or an organic acid is used. Specifically, the catalyst is, for example, dibutyltin dilaurate. The content of the catalyst in the outer layer water-tight material 240 is 0.01 parts by weight or more and 0.1 parts by weight or less when the base resin is 100 parts by weight. As the anti-aging agent, for example, a phenol-based anti-aging agent is used. Specifically, the anti-aging agent is, for example, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The content of the anti-aging agent in the outer layer water-tight material 240 is 0.01 parts by weight or more and 0.3 parts by weight or less when the base resin is 100 parts by weight.

[0060] (Inner layer water tight material) Next, the inner watertight material 220 will be described.

[0061] The resin composition for the inner layer watertight material that constitutes the inner layer watertight material 220 of this embodiment is not particularly limited, but for example, similar to the resin composition for the outer layer watertight material, it contains an ethylene-(meth)acrylate copolymer as a base resin.

[0062] The inner layer watertight material 220 is filled between the conductor wires 110 and is not in contact with the insulating layer 300. Therefore, the inner layer watertight material 220 is not required to have peelability like the outer layer watertight material 240. Therefore, the inner layer watertight material 220 may be made of a material softer than the outer layer watertight material 240 so that it can easily penetrate between the conductor wires 110.

[0063] In addition, the resin composition for the inner layer watertight material contains a color batch, for example, similar to the resin composition constituting the outer layer watertight material 240.

[0064] The inner layer water-tight material 220 may be configured to be cross-linked by a silane graft water cross-linking method, or may be configured not to be cross-linked by the cross-linking method.

[0065] (4) Manufacturing method of insulated electric wire Next, a method for producing the insulated wire 10 according to this embodiment will be described with reference to Figures 2A to 2D. Figures 2A to 2D are schematic diagrams showing a method for producing the insulated wire according to this embodiment.

[0066] (Step 1: Conductor wire formation process) First, a predetermined number of conductor wires 110 made of, for example, hard copper wire are formed by a wire drawing machine (not shown).

[0067] (Step 2: Conductor formation process and inner layer water sealing material formation process) 2A, one conductor wire 110 that will form the center of the conductor 100 is fed out from a bobbin 511. After the conductor wire 110 is fed out from the bobbin 511, the conductor wire 110 is passed through a first inner-layer watertight material extruder 522 into which a resin composition for the inner-layer watertight material is charged while being conveyed along the axial direction. As a result, an inner-layer watertight material 220 is extruded to cover the outer periphery of the conductor wire 110.

[0068] After the inner layer watertight material 220 is formed so as to cover the outer periphery of the conductor wire 110, the six bobbins 512 are rotated around the conductor wire 110 covered with the inner layer watertight material 220, and the conductor wire 110 is fed out from each of the six bobbins 512. After the conductor wire 110 is fed out from each of the six bobbins 512, these conductor wires 110 are passed through a predetermined die 532 having a circular opening. In this way, the six conductor wires 110 are twisted together so as to cover the outer periphery of the conductor wire 110 covered with the inner layer watertight material 220, thereby forming the conductor intermediate body 120. After the conductor intermediate body 120 is formed, the conductor intermediate body 120 is wound up on a drum 542.

[0069] Next, as shown in Fig. 2B, the conductor intermediate 120 is sent out from the drum 542, and while conveying the conductor intermediate 120 along the axial direction, it is passed through the second inner-layer watertight material extruder 524 into which the resin composition for the inner-layer watertight material is charged. As a result, the inner-layer watertight material 220 is extruded so as to cover the outer periphery of the conductor intermediate 120.

[0070] After the inner layer watertight material 220 is formed so as to cover the outer periphery of the conductor intermediate body 120, the conductor wires 110 are fed out from each of the 12 bobbins 513 while rotating the 12 bobbins 513 around the conductor intermediate body 120 covered with the inner layer watertight material 220. After the conductor wires 110 are fed out from each of the 12 bobbins 513, these conductor wires 110 are passed through a predetermined die 534 having a circular opening. In this way, the 12 conductor wires 110 are twisted together so as to cover the outer periphery of the conductor intermediate body 120 covered with the inner layer watertight material 220, thereby forming the conductor 100. After the conductor 100 is formed, the conductor 100 is wound around a drum 544.

[0071] Immediately after the conductor 100 is formed, the temperature of the conductor 100 rises to a predetermined temperature by passing through the heated second inner layer water-tight material extruder 524. However, after the conductor 100 is wound around the drum 544, the drum 544 is stored at room temperature for a predetermined time, whereby the conductor 100 is cooled, and the temperature of the conductor 100 drops to, for example, less than 20°C.

[0072] (Step 3: Outer layer water tight material formation process) 2C, the conductor 100 is fed from the drum 544, and while being conveyed in the axial direction, the conductor 100 is preheated to a predetermined temperature by the heater 552. The term "preheating" here means that the conductor 100 is heated in advance before the outer layer watertight material 240 is extruded.

[0073] At this time, the temperature to which the conductor 100 is preheated is set to, for example, 20° C. or higher and 40° C. or lower.

[0074] At this time, for example, a lamp heater that irradiates infrared rays is used as the heater 552. This makes it possible to easily preheat the conductor 100 to a predetermined temperature while transporting the conductor 100 along the axial direction.

[0075] Next, the conductor 100 is passed through an outer-layer water-tight material extruder 526 into which a resin composition for the outer-layer water-tight material is charged while being conveyed along the axial direction. As a result, the outer-layer water-tight material 240 is extruded so as to cover the outer circumference of the conductor 100.

[0076] At this time, as described above, the outer layer watertight material 240 is extrusion molded in a state where the conductor 100 is preheated to a temperature of, for example, 20°C or more and 40°C or less. If the conductor 100 is not preheated and the temperature at which the conductor 100 is preheated is less than 20°C, it becomes difficult to coat the resin composition for the outer layer watertight material according to the outer peripheral shape of the conductor 100 in which the conductor wires 110 are twisted together in a spiral shape when the outer layer watertight material 240 is extruded by the outer layer watertight material extruder 526. The reason for this is that fine gaps are formed between the conductor 100 and the outer layer watertight material 240, and the conductor 100 and the outer layer watertight material 240 may not adhere well to each other. As a result, the watertightness and adhesion of the insulated electric wire 10 may be reduced. In contrast, by setting the temperature for preheating the conductor 100 to 20°C or higher, the covering property of the resin composition for the outer layer water-tight material on the outer periphery of the conductor 100 can be improved when extruding the outer layer water-tight material 240. This is because the formation of fine gaps between the conductor 100 and the outer layer water-tight material 240 can be suppressed, and the conductor 100 and the outer layer water-tight material 240 can be well adhered to each other. As a result, the water-tight property and adhesion of the insulated electric wire 10 can be improved. On the other hand, if the temperature for preheating the conductor 100 is higher than 40°C, the fluidity of the resin composition for the outer layer water-tight material increases when extruding the outer layer water-tight material 240, and the resin composition for the outer layer water-tight material may excessively adhere to the outer periphery of the conductor 100. For this reason, the peeling property of the outer layer water-tight material 240 may be reduced. In contrast, by setting the temperature for preheating the conductor 100 to 40°C or lower, the resin composition for the outer layer water-tight material can be suppressed from excessively adhering to the outer periphery of the conductor 100. As a result, the peelability of the outer layer watertight material 240 can be ensured.

[0077] Also, at this time, for example, pellets of the first resin and pellets of the second resin are mixed in advance by a metering mixer (not shown) so that the ratio B / A of the weight B of the second resin to the weight A of the first resin is 1 / 4 or more and 4 or less. After the first resin and the second resin are mixed, a resin composition for the outer layer watertight material, which is a mixture of a base resin containing the first resin and the second resin and predetermined additives (color batch, silane coupling agent, crosslinking agent, catalyst, antiaging agent), is poured into a hopper of the outer layer watertight material extruder 526. At this time, the silane coupling agent and the like to be added are poured into the lower part of the hopper by injection method.

[0078] In addition, at this time, for example, by the so-called one-shot method (also called the monosil method), the outer layer water-tight material 240 is extruded while grafting the silane coupling agent to the base resin in the outer layer water-tight material extruder 526. This can simplify the manufacturing process.

[0079] In addition, at this time, the extrusion temperature of the outer layer water-tight material 240 in the outer layer water-tight material extruder 526 is, for example, 180 ° C or more and 240 ° C or less. If the extrusion temperature of the outer layer water-tight material 240 is less than 180 ° C, the covering property of the resin composition for the outer layer water-tight material on the outer circumference of the conductor 100 may decrease. In addition, the graft rate of the silane coupling agent to the base resin may be reduced. In contrast, by setting the extrusion temperature of the outer layer water-tight material 240 to 180 ° C or more, the covering property of the resin composition for the outer layer water-tight material on the outer circumference of the conductor 100 can be improved. In addition, the graft rate of the silane coupling agent to the base resin can be set to a predetermined value or more. On the other hand, if the extrusion temperature of the outer layer water-tight material 240 is more than 240 ° C, the fluidity of the resin composition for the outer layer water-tight material increases, and the resin composition for the outer layer water-tight material may be excessively adhered to the outer circumference of the conductor 100. In response to this, by setting the extrusion temperature of the outer-layer water-tight material 240 to 240° C. or lower, it is possible to prevent the resin composition for the outer-layer water-tight material from excessively adhering to the outer periphery of the conductor 100 .

[0080] (Step 4: Insulation layer formation process) 2C, the conductor 100 coated with the outer-layer water-tight material 240 is conveyed in the axial direction and passed through an insulating layer extruder 528 into which an insulating layer resin composition having a base resin containing polyolefin and a predetermined additive is charged. In this way, an insulating layer 300 is extruded to cover the outer periphery of the outer-layer water-tight material 240, and an insulated electric wire intermediate body 12 is formed in which the outer-layer water-tight material 240 and the insulating layer 300 are in an uncrosslinked state. After the insulated electric wire intermediate body 12 is formed, the insulated electric wire intermediate body 12 is wound around a drum 546.

[0081] At this time, for example, by the so-called one-shot method, the insulating layer 300 is extruded while grafting the silane coupling agent to the base resin of the insulating layer resin composition in the insulating layer extruder 528. This can simplify the manufacturing process.

[0082] (Step 5: Cross-linking process) 2D, the drum 546 around which the insulated wire intermediate body 12 is wound is immersed for a predetermined time in a hot water bath 560 containing hot water. This causes water cross-linking of at least the insulating layer 300 (in this embodiment, both the outer water-tight material 240 and the insulating layer 300).

[0083] At this time, the outer layer water-tight material 240 and the insulating layer 300 are water-crosslinked at a crosslinking temperature of, for example, 75°C or more and 82°C or less. If the crosslinking temperature is less than 75°C, the outer layer water-tight material 240 and the insulating layer 300 may not be sufficiently water-crosslinked. In contrast, by setting the crosslinking temperature to 75°C or more, the outer layer water-tight material 240 and the insulating layer 300 can be sufficiently water-crosslinked. In addition, by combining the preheating in step 3, the resin composition for the outer layer water-tight material that is moderately adhered to the outer circumference of the conductor 100 can be melted to an optimal temperature, and the peelability of the outer layer water-tight material 240 can be ensured while also satisfying the water-tightness characteristics.

[0084] On the other hand, if the crosslinking temperature exceeds 82°C, the outer layer water-tight material 240 may melt excessively again during the crosslinking process of step 5, and the outer layer water-tight material 240 may flow into and become stuck in the grooves formed between adjacent conductor wires 110. In contrast, by setting the crosslinking temperature to 82°C or lower, the outer layer water-tight material 240 can be prevented from melting excessively again during the crosslinking process of step 5, and the outer layer water-tight material 240 can be prevented from flowing into and becoming stuck in the grooves.

[0085] In addition, when the inner-layer water-tight material 220 is configured to be cross-linked by the silane grafting water cross-linking method, a silane coupling agent is grafted to the base resin of the inner-layer water-tight material 220 in advance in the conductor forming process of step 2 and the inner-layer water-tight material forming process, and the inner-layer water-tight material 220 is water-cross-linked together with the outer-layer water-tight material 240 and the insulating layer 300 in the cross-linking process of step 5.

[0086] In this manner, the insulated wire 10 of the present embodiment is manufactured.

[0087] (5) Effects of this embodiment According to this embodiment, one or more of the following advantages are achieved.

[0088] (a) In the outer layer water-tight material forming process of step 3 of this embodiment, the conductor 100 is preheated to a temperature of 20°C or more and 40°C or less, and the outer layer water-tight material 240 is extrusion molded. By setting the temperature for preheating the conductor 100 to 20°C or more, the covering property of the resin composition for the outer layer water-tight material on the outer periphery of the conductor 100 can be improved when extruding the outer layer water-tight material 240. This can suppress the formation of fine gaps between the conductor 100 and the outer layer water-tight material 240, and the conductor 100 and the outer layer water-tight material 240 can be closely adhered to each other. As a result, the water-tight property and adhesion of the insulated electric wire 10 can be improved. In addition, by setting the temperature for preheating the conductor 100 to 40°C or less, the resin composition for the outer layer water-tight material can be suppressed from excessively adhering to the outer periphery of the conductor 100. As a result, the peelability of the outer layer water-tight material 240 can be ensured. Specifically, when the insulating layer 300 is peeled off, it is possible to reduce the remaining portion of the outer-layer watertight material 240 that remains across the conductor wires 110. In this way, according to the present embodiment, it is possible to improve the watertightness, adhesion, and peelability of the insulated wire 10 in a well-balanced manner.

[0089] (b) In the crosslinking process of step 5 of this embodiment, the outer layer watertight material 240 and the insulating layer 300 are water-crosslinked at a crosslinking temperature of 75°C or more and 82°C or less. By setting the crosslinking temperature to 75°C or more, the outer layer watertight material 240 and the insulating layer 300 can be sufficiently water-crosslinked. In addition, by setting the crosslinking temperature to 82°C or less, excessive remelting of the outer layer watertight material 240 during the crosslinking process of step 5 can be suppressed, and the outer layer watertight material 240 can be suppressed from flowing excessively into the groove formed between the adjacent conductor wires 110 and becoming stuck there. As a result, the peelability of the outer layer watertight material 240 can be improved. Specifically, when the insulating layer 300 is peeled off, the remaining part of the outer layer watertight material 240 remaining in the groove between the adjacent conductor wires 110 can be reduced. In this way, in this embodiment, it is possible to meet the recent strict requirements for peelability while improving the watertightness and adhesion.

[0090] (c) In the insulated wire 10 of the present embodiment, when a water pressure of 0.5 atmospheres is applied for 24 hours to one axial end of the insulated wire 10 cut to a predetermined length, the penetration distance of water from one end of the insulated wire 10 is 1000 mm or less. This makes it possible to suppress corrosion of the conductor 100. As a result, the insulated wire 10 can be stably maintained as a product.

[0091] (d) When the insulated wire 10 of the present embodiment is held by a predetermined wire gripping tool and subjected to a tensile test under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer 300 is 50 mm or less. This makes it possible to prevent the insulating layer 300 from slipping when the insulated wire 10 is held by the wire gripping tool, and to prevent the insulated wire 10 from coming off the wire gripping tool. As a result, it is possible to prevent the insulated wire 10 from falling off.

[0092] (e) In the insulated wire 10 of the present embodiment, when the outer-layer water-tight material 240 and the insulating layer 300 are stripped off over 15 cm in the axial direction of the insulated wire 10 around the entire outer circumference of the conductor 100, the remaining portions of the outer-layer water-tight material 240 remaining to straddle the conductor wires 110 are 5 or less. In other words, by reducing the remaining portions of the outer-layer water-tight material 240 interposed between the conductor wires 110 and the compression sleeve, each conductor wire 110 and the compression sleeve can be well connected. As a result, the contact resistance between the conductor 100 and the compression sleeve can be prevented from increasing.

[0093] (f) In the insulated wire 10 of this embodiment, when the outer-layer watertight material 240 and the insulating layer 300 are stripped off over 15 cm in the axial direction of the insulated wire 10 around the entire outer circumference of the conductor 100, the ratio of the number of grooves in which the outer-layer watertight material 240 remains to the total number of grooves formed between adjacent conductor wires 110 is 7 / 12 or less. This allows the compression sleeve to be uniformly abutted against the outer circumference of the conductor 100 and sufficiently compressed when the compression sleeve is compressed and connected. As a result, the gripping ability of the compression sleeve can be improved.

[0094] <Other embodiments of the present disclosure> Although the embodiments and modified examples of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and modified examples, and various modifications are possible without departing from the gist of the present disclosure.

[0095] In the above embodiment, the case where the number of conductor wires 110 is 19 has been described, but the number of conductor wires 110 is not limited to this number and may be, for example, seven.

[0096] In the above-described embodiment, the base resin of the outer layer watertight material 240 is described as being only EMMA, but the base resin of the outer layer watertight material 240 may be a material other than EMMA, or may be a mixture of EMMA and other materials.

[0097] In the above-described embodiment, a case has been described in which the base resin of the outer layer watertight material 240 is composed of a mixture of a first resin and a second resin, but the base resin of the outer layer watertight material 240 may be composed of one resin or three or more types of resin.

[0098] In the above-described embodiment, the outer layer water-tight material 240 is configured to be cross-linked by the silane grafting water cross-linking method, but the outer layer water-tight material 240 may be configured not to be cross-linked.

[0099] In the above-described embodiment, the resin composition for the outer layer watertight material contains vinyltrimethoxysilane as a silane coupling agent, but the resin composition for the outer layer watertight material may contain other materials as the silane coupling agent.

[0100] In the above embodiment, the resin composition for the outer layer watertight material contains dicumyl peroxide as a crosslinking agent, but the resin composition for the outer layer watertight material may contain other materials as crosslinking agents.

[0101] In the above embodiment, the case where the resin composition for the outer layer watertight material contains dibutyltin dilaurate as a catalyst has been described, but the resin composition for the outer layer watertight material may contain other materials as catalysts.

[0102] In the above-described embodiment, the resin composition for the outer layer watertight material contains thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] as an anti-aging agent. However, the resin composition for the outer layer watertight material may contain other materials as anti-aging agents.

[0103] In the above embodiment, a case has been described in which the conductor forming process and the inner layer water-tight material forming process are performed simultaneously in step 2, but the inner layer water-tight material may be pressed in from the outside of the conductor after the conductor forming process is performed.

[0104] In the above embodiment, the case where the conductor intermediate body 120 is formed in step 2 and then wound around the drum 542 has been described, but the conductor intermediate body 120 may be passed through the second inner layer watertight material extruder 524 while being conveyed along the axial direction without being wound around the drum 542. In other words, the conductor 100 may be continuously formed without being wound around the drum.

[0105] In the above embodiment, a lamp heater is used as the heater 552 in the outer layer water-tight material forming process in step 3 to preheat the conductor 100, but the heater 552 may be something other than a lamp heater. For example, a thermostatic bath that heats the entire drum 544 to a predetermined temperature may be used as the heater 552, and then processing may be performed immediately in the process after the outer layer water-tight material extruder 526 in step 3.

[0106] In the above-described embodiment, in the outer layer watertight material forming process in step 3, the case where pellets of the first resin and pellets of the second resin are mixed using a measuring mixer is described, but resin pellets in which the first resin and the second resin are mixed in a predetermined ratio may be prepared in advance.

[0107] In the above embodiment, the case where the outer water-tight material 240 and the insulating layer 300 are extrusion-molded by the one-shot method in steps 3 and 4 has been described, but the present invention is not limited to this case. For example, the outer water-tight material 240 and the insulating layer 300 may be extrusion-molded by the two-shot method by feeding a base resin to which a silane coupling agent has been grafted in advance, a master batch containing a silanol condensation catalyst, and other additives into an extruder. EXAMPLES

[0108] Next, examples according to the present disclosure will be described together with comparative examples.

[0109] (1) Manufacture of insulated wires Insulated wires according to Samples 1 to 6 were produced as follows.

[0110] [Insulated wire configuration] In Samples 1 to 6, the insulated wire had the following common configuration. (conductor) Conductor wire: hard copper wire Conductor wire outer diameter: 2.00mm Number of conductor wires: 19 Conductor cross-sectional area: 80mm 2 (Inner layer water tight material) Base resin: Second resin The additives are the same as those for the outer layer water-tight material below. (Outer layer watertight material) Base resin: Mixture of first resin and second resin (total 100 parts by weight) First resin: Acryft (registered trademark) WH206 manufactured by Sumitomo Chemical Co., Ltd. Second resin: Acryft (registered trademark) WK307 manufactured by Sumitomo Chemical Co., Ltd. Ratio of weight B of the second resin to weight A of the first resin: B / A: 1 / 4 to 4 Color batch: PE-M 10H397 (1.2 parts by weight) manufactured by Dainichi Seika Color & Chemicals Co., Ltd. Silane coupling agent: KBM-1003 (1.25 parts by weight) manufactured by Shin-Etsu Chemical Co., Ltd. Crosslinking agent: DCP (0.094 parts by weight) manufactured by NOF Corporation Catalyst: Neostan (registered trademark) U-100 (0.05 parts by weight) manufactured by Nitto Kasei Co., Ltd. Anti-aging agent: BASF Irganox (registered trademark) 1035 (0.15 parts by weight) Outer watertight material thickness: 0.2mm (insulating layer) Material: Cross-linked polyethylene Insulation layer thickness: 2.5mm

[0111] [Insulated wire manufacturing conditions] (Inner layer water tight material formation process) Extrusion temperature: 180~240℃ (Outer layer watertight material formation process) Conductor preheating temperature: no heating (approx. 18°C), 25-50°C Extrusion temperature: 180~240℃ (Insulation layer formation process) Extrusion temperature: 180~240℃ (Crosslinking process) Method: hot water bath immersion Crosslinking temperature: 73~85℃

[0112] The manufacturing conditions of the insulated wires in Samples 1 to 6 and the evaluation results thereof are shown in Table 1 below.

[0113] [Table 1]

[0114] (2) Evaluation (Watertightness characteristic test (rainwater infiltration test)) The insulated electric wires of Samples 1 to 6 were cut to a predetermined length (for example, 2.0 m). A water pressure of 0.5 atmospheres was applied to one axial end of the cut insulated electric wire for 24 hours, and the permeation distance of water from the one end was measured.

[0115] (Adhesion test (wire gripping tool tensile test)) The insulated wires of Samples 1 to 6 were held by a wire holder (Camlar, manufactured by Nagaki Seiki Co., Ltd.) and subjected to a tensile test under the following conditions: temperature 40°C, tensile load 4.17 kN, and application time 10 minutes. As a result of the test, the cases where the length of the insulation layer displacement was 0 mm or more and 50 mm or less were evaluated as "A", and the cases where the length of the insulation layer displacement was more than 50 mm were evaluated as "B".

[0116] (Skin peeling test) A peeling test was conducted on the insulated wires of samples 1 to 6, in which the outer layer of waterproof material and the insulating layer were peeled off with a knife at a temperature of 40°C. However, the speed at which the outer layer of waterproof material and the insulating layer were peeled off by 15 cm was set to 60 seconds or less. When peeling off at a speed exceeding 60 seconds, the remaining outer layer of waterproof material tends to decrease, but considering the work efficiency at the site where the wire is used, it is difficult to apply this method.

[0117] As a result of the test, the shape of the remaining outer layer waterproofing material when the insulation layer was peeled off was evaluated in two categories.

[0118] (i) Straddle section When the insulation layer was peeled off, the number of remaining parts of the outer layer watertight material that remained straddling the conductor wires (hereinafter also referred to as "straddling parts") was 0 to 5, and was evaluated as "A", and the number of parts was more than 5, as "B". Note that when the remaining parts of the outer layer watertight material that remained straddling the conductor wires covered a wide area, the area of ​​a square with one side equal to the diameter of the conductor wires was counted as 1 part.

[0119] (ii) Remainder groove When the insulation layer was peeled off, the ratio of the number of grooves in which the outer layer watertight material remained (hereinafter also referred to as "grooves with remaining parts") to the total number of grooves formed between adjacent conductor wires was 7 / 12 or less, and was evaluated as "A", and the ratio of the number exceeding 7 / 12 was evaluated as "B". Note that in Samples 1 to 5, the number of conductor wires in the outermost layer of the conductor was 12, so the total number of grooves was 12.

[0120] (3) Results Referring to the above Table 1 and Figs. 3A to 3D, Figs. 3A to 3D are schematic diagrams showing insulated electric wires of Samples 1 and 3 to 5, respectively, which were subjected to a peelability test.

[0121] (Sample 2) In Sample 2, in which the conductor was not preheated in the outer layer water-tight material forming process and the crosslinking temperature was set to 78 to 82°C in the crosslinking process, good results equivalent to those of Sample 1 described later were obtained in the peelability test.

[0122] However, in the watertightness test, the water penetration distance of Sample 2 was more than 2000 mm, and the results of the watertightness test were significantly inferior to those of the other samples. In addition, in the adhesion test, the length of displacement of the insulating layer of Sample 2 was more than 50 mm, and the results of the adhesion test were inferior to those of the other samples.

[0123] In Sample 2, the crosslinking temperature in the crosslinking process was appropriate, but the conductor preheating was not performed in the outer layer watertight material forming process. Therefore, it is considered that it was difficult to coat the resin composition for the outer layer watertight material according to the outer peripheral shape of the conductor when extruding the outer layer watertight material. As a result, it is considered that the watertightness and adhesion of Sample 2 were reduced.

[0124] (Sample 3) In sample 3, in which the conductor preheating temperature in the outer layer watertight material forming process was set to over 50°C and the crosslinking temperature in the crosslinking process was set to 78 to 82°C, good results were obtained in the watertight property test and the adhesion test.

[0125] However, in the case of Sample 3, the results shown in FIG. 3B were obtained in the peelability test. As shown in FIG. 3B, in Sample 3, many remnants 242 of the outer-layer water-tight material 240 were found on the surface of the conductor 100 from which the insulating layer 300 of the insulated electric wire 10 was stripped. The number of "straddling portions 244" which are the remnants 242 of the outer-layer water-tight material 240 remaining across the conductor wires 110 was more than five. In addition, the ratio of the number of "groove portions 112a with remnants" which are the groove portions 112 in which the remnants 242 of the outer-layer water-tight material 240 remain to the total number of groove portions 112 formed between adjacent conductor wires 110 was more than 7 / 12. Thus, the results of the peelability test for Sample 3 were inferior to those of the other samples.

[0126] In Sample 3, the crosslinking temperature in the crosslinking process was appropriate, but the conductor preheating temperature in the outer layer watertight material forming process was set to over 50°C. This is thought to have increased the fluidity of the resin composition for the outer layer watertight material when extruding the outer layer watertight material, causing the resin composition for the outer layer watertight material to adhere excessively to the outer circumference of the conductor. As a result, it is thought that Sample 3 had improved watertightness and adhesion, but reduced peelability.

[0127] (Sample 4) In sample 4, in which the conductor was not preheated in the outer layer watertight material forming process and the crosslinking temperature was set to 85°C in the crosslinking process, good results were obtained in the watertightness property test and the adhesion test.

[0128] In the peelability test, the results shown in FIG. 3C were obtained for Sample 4. As shown in FIG. 3C, the number of straddling portions 244 of the outer layer watertight material 240 was six. Also, there were many remaining groove portions 112a, and the ratio was more than 7 / 12 (specifically, about 10 / 12). Thus, the results of the peelability test for Sample 4 were inferior to those of Sample 1 described later.

[0129] In Sample 4, the conductor was not preheated in the outer layer watertight material formation process, so the outer layer watertight material did not necessarily cover the conductor's outer circumference at the time of this process. However, the crosslinking temperature in the crosslinking process was set to over 82°C, so the outer layer watertight material is thought to have melted again during this process. Therefore, while the adhesion of the outer layer watertight material to the conductor's outer circumference improved, the outer layer watertight material flowed into the grooves between adjacent conductor wires and became fixed. As a result, in Sample 4, the watertightness and adhesion improved, but the peelability decreased.

[0130] (Sample 5) In sample 5, in which the conductor preheating temperature was set to 25 to 35°C in the outer layer watertight material forming process and 85°C in the crosslinking process, good results were obtained in the watertight property test and the adhesion test.

[0131] However, in the peeling property test, the results shown in FIG. 3D were obtained for Sample 5. As shown in FIG. 3D, the number of straddling portions 244 of the outer layer watertight material 240 was 11. Also, there were many remaining groove portions 112a, and the ratio was more than 7 / 12 (specifically, about 12 / 12). Thus, the peeling property test results for Sample 5 were inferior to those for Sample 1 described later.

[0132] In sample 5, the conductor preheating was performed at an appropriate temperature in the outer layer watertight material forming process, so the outer layer watertight material was considered to have had good coverage on the conductor's outer circumference at the time of this process. However, the crosslinking temperature in the crosslinking process was set to over 82°C, so the outer layer watertight material is considered to have melted again during this process. This is thought to have increased the adhesion of the outer layer watertight material to the conductor's outer circumference, and the outer layer watertight material flowed into and fixed in the grooves formed between adjacent conductor wires. As a result, it is thought that in sample 5, the watertightness and adhesion were improved, but the peelability was reduced.

[0133] (Sample 6) In sample 6, in which the conductor preheating temperature was set to 25 to 35°C in the outer layer water-tight material forming process and 73°C in the crosslinking process, good results were obtained in the adhesion test and peelability.

[0134] However, in the case of sample 6, the water penetration distance in the watertightness property test was more than 1000 mm, and the results of the watertightness property test were inferior to those of the other samples.

[0135] In sample 6, the conductor preheating was performed at an appropriate temperature in the outer water-tight material forming process, so the outer water-tight material was considered to have had good coverage over the conductor's outer circumference at that stage. However, the crosslinking temperature in the crosslinking process was set below 75°C, so the outer water-tight material and the insulating layer were not sufficiently water-crosslinked, and the outer water-tight material was not optimally remelted sufficiently. As a result, the water-tightness of sample 6 was considered to have deteriorated.

[0136] (Sample 1) In comparison with the above-mentioned Samples 2 to 5, Sample 1, in which the conductor preheating temperature was set to 25 to 35°C in the outer layer watertight material forming process and 78 to 82°C in the crosslinking process, showed good results in the watertightness property test and the adhesion test.

[0137] Moreover, in the peelability test, the results shown in Fig. 3A were obtained for Sample 1. As shown in Fig. 3A, the outer layer watertight material 240 had no straddling portions 244 at all, or at most 5 or less. The number of remnant groove portions 112a was also small, with the proportion being 7 / 12 or less (at most about 2 / 12). Furthermore, the length of the remnant 242 in the remnant groove portion 112a was 10 mm or less. Thus, Sample 1 had the best results in the peelability test.

[0138] In sample 1, it was confirmed that the covering property of the resin composition for the outer layer watertight material on the outer circumference of the conductor could be improved when extruding the outer layer watertight material by setting the conductor preheating temperature at 20°C or higher in the outer layer watertight material forming process. As a result, it was confirmed that the watertightness and adhesion of the insulated wire could be improved.

[0139] In addition, in sample 1, it was confirmed that excessive adhesion of the resin composition for the outer layer water-tight material to the outer circumference of the conductor could be suppressed by setting the conductor preheating temperature to 40°C or less in the outer layer water-tight material forming process. As a result, it was confirmed that the peelability of the outer layer water-tight material could be ensured. Specifically, it was confirmed that the straddling portion could be reduced in the peelability test.

[0140] In addition, in sample 1, by setting the crosslinking temperature in the crosslinking process to 75°C or higher and 82°C or lower, the outer layer watertight material and the insulating layer could be sufficiently water-crosslinked. It was also confirmed that during the crosslinking process, excessive melting of the outer layer watertight material was suppressed, and the outer layer watertight material was prevented from flowing into and adhering to the grooves between adjacent conductor wires. As a result, it was confirmed that the peelability of the outer layer watertight material could be improved while improving the watertightness of the insulated wire. Specifically, it was confirmed that the number of remaining grooves in the peelability test could be reduced.

[0141] Thus, it was confirmed that Sample 1 can improve watertightness and adhesion while satisfying recent strict requirements for peelability.

[0142] <Preferred aspects of the present disclosure> Preferred aspects of the present disclosure are described below.

[0143] (Appendix 1) A resin composition for an outer layer water-tight material forming an outer layer water-tight material for an insulated electric wire, When a water pressure of 0.5 atmospheres is applied to one axial end of the insulated electric wire cut to a predetermined length for 24 hours, the permeation distance of water from the one end of the insulated electric wire is 1000 mm or less; When the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less; When the outer layer watertight material and the insulating layer are stripped off over the entire outer circumference of the conductor by 15 cm in the axial direction of the insulated wire, the remaining portion of the outer layer watertight material remaining across the conductor wires is 5 or less. Resin composition for outer layer watertight material.

[0144] (Appendix 2) a conductor formed by twisting together a plurality of conductor wires; An outer watertight material provided to cover the outer periphery of the conductor; An insulating layer provided to cover the outer periphery of the outer layer watertight material; An insulated wire having When a water pressure of 0.5 atmospheres is applied to one axial end of the insulated electric wire cut to a predetermined length for 24 hours, the permeation distance of water from the one end of the insulated electric wire is 1000 mm or less; when the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less; When the outer layer watertight material and the insulating layer are stripped off over the entire outer circumference of the conductor by 15 cm in the axial direction of the insulated wire, the remaining portion of the outer layer watertight material remaining across the conductor wires is 5 or less. Insulated wire.

[0145] (Appendix 3) When the outer layer water-tight material and the insulating layer are stripped off over 15 cm in the axial direction of the insulated wire around the entire outer circumference of the conductor, the ratio of the number of grooves in which the outer layer water-tight material remains to the total number of grooves formed between adjacent conductor wires is 7 / 12 or less. 2. An insulated wire as described in Appendix 2.

[0146] (Appendix 4) The outer layer watertight material is composed of a resin composition containing an ethylene-(meth)acrylate copolymer. 1. An insulated electric wire according to claim 2 or 3.

[0147] (Appendix 5) The resin composition comprises a first resin including an ethylene methyl methacrylate copolymer having a methyl methacrylate content of 18% by weight or more and less than 22% by weight; and a second resin including an ethylene methyl methacrylate copolymer having a methyl methacrylate content of 22% by weight or more and less than 28% by weight, In the base resin, the ratio B / A of the weight B of the second resin to the weight A of the first resin is 1 / 4 or more and 4 or less. 5. An insulated wire according to any one of claims 2 to 4.

[0148] (Appendix 6) A step of stranding a plurality of conductor wires to form a conductor; forming an outer layer watertight material so as to cover an outer periphery of the conductor; forming an insulating layer so as to cover the outer periphery of the outer layer watertight material; cross-linking at least the insulating layer; having In the step of forming the outer layer water-tight material, The conductor is preheated to a temperature of 20°C to 40°C, and the outer layer watertight material is extruded. In the step of cross-linking the insulating layer, The insulating layer is cross-linked with water at a cross-linking temperature of 75°C to 82°C. A method for manufacturing insulated electric wire. [Explanation of symbols]

[0149] 10 Insulated wire 12 Insulated wire intermediate body 100 Conductor 110 Conductor wire 112 Groove 112a Remainder groove 120 Conductor Intermediate 220 Inner layer watertight material 240 Outer layer watertight material 242 Remainder 244 Straddle 300 Insulation layer 511 Bobbin 512 Bobbin 513 Bobbin 522 No. 1 inner layer watertight material extrusion machine 524 No. 2 inner layer water tight material extrusion machine 526 Outer layer water tight material extrusion machine 528 Insulation Layer Extrusion Machine 532,534 Dice 542,544,546 drums 552 Heater 560 Hot water tank

Claims

1. a conductor formed by twisting together a plurality of conductor wires; An outer watertight material provided to cover the outer periphery of the conductor; An insulating layer provided to cover the outer periphery of the outer layer watertight material; An insulated wire having The conductor is made of a hard copper wire, a hard copper stranded wire, a hard aluminum stranded wire, or a steel-core aluminum stranded wire; The outer layer watertight material is A first resin including an ethylene-methyl methacrylate copolymer having a methyl methacrylate content of 18% by weight or more and less than 22% by weight; a second resin including an ethylene-methyl methacrylate copolymer having a methyl methacrylate content of 22% by weight or more and less than 28% by weight; The base resin is a mixture of a ratio B / A of a weight B of the second resin to a weight A of the first resin in the base resin is 1 / 4 or more and 4 or less; The melting temperature of the base resin is greater than 80° C. and less than 86° C. the insulating layer comprises polyethylene; The outer layer watertight material is extruded in a state where the conductor is preheated to a temperature of 20°C or more and 40°C or less, The outer water-tight material and the insulating layer are crosslinked by a silane graft water crosslinking method at a crosslinking temperature of 75° C. or more and 82° C. or less; when a water pressure of 0.5 atmospheres is applied for 24 hours to one axial end of the insulated electric wire cut to a predetermined length, a water permeation distance from the one end of the insulated electric wire is 1000 mm or less; when the insulated wire is held by a wire holder and a tensile test is performed under conditions of a tensile load of 4.17 kN and an application time of 10 minutes, the length of displacement of the insulating layer is 50 mm or less; When the outer watertight material and the insulating layer are stripped off over a distance of 15 cm in the axial direction of the insulated wire around the entire outer circumference of the conductor at a temperature of 40° C. and at a speed of 60 seconds or less using a knife, the number of remnants of the outer watertight material remaining across the conductor strands is 5 or less. Insulated wire.

2. When the outer layer water-tight material and the insulating layer are stripped off over 15 cm in the axial direction of the insulated wire around the entire outer circumference of the conductor, the ratio of the number of grooves in which the outer layer water-tight material remains to the total number of grooves formed between adjacent conductor wires is 7 / 12 or less. The insulated wire according to claim 1 .

3. The melt flow rate of the first resin is 1 g / 10 min or more and less than 3 g / 10 min when the measurement temperature is 190° C. and the load is 2.12 N, The melt flow rate of the second resin is 6 g / 10 min or more and less than 8 g / 10 min when the measurement temperature is 190° C. and the load is 2.12 N. The insulated wire according to claim 1 or 2.

4. The melting temperature of the first resin is 77° C. or higher and lower than 95° C. The melting temperature of the second resin is 72° C. or higher and lower than 88° C. The insulated wire according to claim 1 .

5. A step of stranding a plurality of conductor wires to form a conductor; forming an outer layer watertight material so as to cover an outer periphery of the conductor; forming an insulating layer so as to cover the outer periphery of the outer layer watertight material; A step of cross-linking the outer layer water-tight material and the insulating layer by a silane grafting / water cross-linking method; having In the step of forming a conductor, The conductor is formed of a hard copper wire, a hard copper stranded wire, a hard aluminum stranded wire, or a steel-core aluminum stranded wire; In the step of forming the outer layer water-tight material, A first resin including an ethylene-methyl methacrylate copolymer having a methyl methacrylate content of 18% by weight or more and less than 22% by weight; a second resin including an ethylene-methyl methacrylate copolymer having a methyl methacrylate content of 22% by weight or more and less than 28% by weight; The outer layer watertight material is formed so as to include a base resin obtained by mixing a ratio B / A of a weight B of the second resin to a weight A of the first resin in the base resin is set to 1 / 4 or more and 4 or less; The melting temperature of the base resin is more than 80° C. and less than 86° C. The conductor is preheated to a temperature of 20°C to 40°C, and the outer layer watertight material is extruded. In the step of forming the insulating layer, forming the insulating layer to include polyethylene; In the step of cross-linking the outer water-tight material and the insulating layer, The outer water-tight material and the insulating layer are cross-linked with water at a cross-linking temperature of 75° C. or more and 82° C. or less. A method for manufacturing insulated wire.

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