Fire-resistant cable and method for manufacturing a fire-resistant cable

Abstract

To provide a fire-resistant cable that is fire-resistant and can reduce the generation of voids even when bent before the insulating layer is formed. [Solution] The fire-resistant cable comprises a conductor, a plurality of mica tapes wrapped around the conductor, an insulating layer covering the plurality of mica tapes, a semiconducting layer covering the insulating layer, a metal shielding layer covering the semiconducting layer, and a sheath covering the metal shielding layer. The plurality of mica tapes can be wound horizontally or vertically via a cured adhesive.

Description

Technical Field

[0001] The present invention relates to a fire-resistant cable and a method for manufacturing the same.

Background Art

[0002] Fire-resistant cables are used, for example, in electrical wiring for disaster prevention equipment in buildings, underground shopping arcades, etc. Fire-resistant cables are known to have the ability to supply electricity for a certain period of time even during a fire (see, for example, Patent Document 1).

[0003] Patent Document 1 describes a high-voltage fire-resistant cable in which a fire-resistant layer, an insulator layer, a semiconductive layer, a metal shielding layer, and a sheath are sequentially provided on a conductor. The fire-resistant layer has a glass mica tape covering the conductor and a film mica tape covering the glass mica tape. The glass mica tape is formed by attaching synthetic mica or natural mica to a glass cloth. On the other hand, the film mica tape is formed by attaching synthetic mica or natural mica to a resin film. To manufacture the high-voltage fire-resistant cable described in Patent Document 1, first, a glass mica tape and a film mica tape are wound around a conductor in layers, and then an insulator layer is formed by extrusion molding. Next, a semiconductive layer and a metal shielding layer are formed on the insulator layer, and then a sheath is formed by extrusion molding. When manufacturing a fire-resistant cable having a glass mica tape as a fire-resistant layer, such as the high-voltage fire-resistant cable described in Patent Document 1, due to the heat during extrusion molding of the insulator layer, the gas contained in the glass cloth expands and rises, and voids (spaces) may occur inside or around the insulator. In a high-voltage fire-resistant cable with voids, the electrical characteristics during a fire are likely to deteriorate. In the high-voltage fire-resistant cable described in Patent Document 1, by winding the film mica tape horizontally after winding the glass mica tape horizontally as the fire-resistant layer, the film mica tape inhibits the gas contained in the glass cloth from moving to the insulator layer side, preventing the occurrence of voids (spaces) inside or around the insulator.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-305389 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When an exposed fire resistance test simulating an actual fire is conducted using the high-voltage fire-resistant cable described in Patent Document 1, conductive carbides can enter through gaps created by the deformation of the high-voltage fire-resistant cable under the test load, potentially leading to a decrease in insulation resistance and short circuits. Thus, the high-voltage fire-resistant cable described in Patent Document 1 had room for improvement in terms of fire resistance. Furthermore, when manufacturing the high-voltage fire-resistant cable described in Patent Document 1, due to manufacturing equipment and other factors, the cable may be wound onto a drum or similar device after the fire-resistant layer is formed, and then the insulating layer may be formed while the wound cable is fed out. In this case, the cable bends when wound onto the drum, creating gaps in the film mica tape. Then, when the wound cable is fed out, the film mica tape may twist, and gases contained in the glass cloth may reach the insulating layer, creating voids inside or around the insulating layer.

[0006] The object of the present invention is to provide a fire-resistant cable and a method for manufacturing the same, which have fire resistance and can reduce the generation of voids even when bent before forming an insulating layer. [Means for solving the problem]

[0007] To solve the above problems, according to one aspect of the present invention, A fire-resistant cable comprising a conductor, a plurality of mica tapes wrapped around the conductor, an insulating layer covering the plurality of mica tapes, a semiconducting layer covering the insulating layer, a metal shielding layer covering the semiconducting layer, and a sheath covering the metal shielding layer, The winding method of the aforementioned plurality of mica tapes includes horizontal winding and vertical winding via a cured adhesive. Fireproof cables will be provided.

[0008] To solve the above problems, according to one aspect of the present invention, A method for manufacturing a fire-resistant cable comprising a conductor, a plurality of mica tapes wrapped around the conductor, an insulating layer covering the plurality of mica tapes, a semiconducting layer covering the insulating layer, a metal shielding layer covering the semiconducting layer, and a sheath covering the metal shielding layer, The process of wrapping the plurality of mica tapes around the conductor, A step of heating the plurality of mica tapes wrapped around the conductor, A step of forming the insulating layer on the plurality of mica tapes after heating, It has, A method for manufacturing a fire-resistant cable is provided, characterized in that, in the step of winding the plurality of mica tapes around the conductor, the plurality of mica tapes are wound by horizontal winding and vertical winding with an adhesive. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a fire-resistant cable that has fire resistance and can reduce the generation of voids even when bent before forming an insulating layer, as well as a method for manufacturing the same. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a cross-sectional view of a fire-resistant cable according to an embodiment of the present invention. [Figure 2] Figures 2A-D are diagrams illustrating horizontal winding. [Figure 3] Figures 3A and 3B are diagrams illustrating the vertical winding technique. [Figure 4] Figure 4 is a flowchart of the manufacturing method for fire-resistant cables. [Modes for carrying out the invention]

[0011] The following describes a fire-resistant cable according to an embodiment of the present invention, but the fire-resistant cable of the present invention is not limited to the following embodiments. In this specification, the "~" indicating a numerical range includes both an upper and lower limit.

[0012] Figure 1 is a cross-sectional view of a fire-resistant cable 10 according to an embodiment of the present invention. As shown in Figure 1, the fire-resistant cable 10 includes a conductor 20, a fire-resistant layer (multiple mica tapes 31) 30 covering the conductor 20, an insulating layer 40 covering the fire-resistant layer 30, a semiconducting layer 50 covering the insulating layer 40, a metal shielding layer 60 covering the semiconducting layer 50, a winding layer 70 covering the metal shielding layer 60, and a sheath 80 covering the winding layer 70. Multiple fire-resistant cables 10 may be used in combination, or they may be used individually. In this embodiment, three fire-resistant cables 10 are twisted together to form a single cable. Furthermore, the fire-resistant cable 10 may be made up of multiple insulated wires, each having a conductor 20, a fire-resistant layer 30, an insulating layer 40, a semiconducting layer 50, a metal shielding layer 60, and a winding layer 70, and these multiple insulated wires may be covered by a single common sheath 80.

[0013] The conductor 20 is not particularly limited as long as it can conduct electricity. Examples of materials for the conductor 20 include copper. In this embodiment, the conductor 20 is a copper wire.

[0014] The fire-resistant layer 30 is a layer that imparts fire resistance to the fire-resistant cable 10. The fire-resistant layer 30 is formed by wrapping multiple mica tapes 31 around the conductor 20. Examples of mica tapes 31 include glass mica tape, which is made by bonding mica to glass cloth, and film mica tape, which is made by bonding mica to a plastic film made of polyethylene or the like. In the case of glass mica tape, the glass cloth and mica are integrated through adhesive impregnation treatment, resulting in good adhesion and excellent mechanical strength, making it difficult to peel off.

[0015] FIG. 2A is a schematic diagram for explaining a horizontal winding, FIG. 2B is a schematic diagram for explaining another horizontal winding, and FIGS. 2C and 2D are schematic diagrams for explaining still another horizontal winding. FIG. 3A is a schematic diagram for explaining a vertical winding, and FIG. 3B is a schematic diagram for explaining another vertical winding.

[0016] Examples of the winding method of the mica tape 31 include a horizontal winding (FIGS. 2A to 2D) and a vertical winding (FIGS. 3A and 3B). Here, the "horizontal winding" means winding the mica tape 31 spirally around the winding object. Also, the "vertical winding" means winding the mica tape 31 such that the length direction of the winding object is parallel to the length direction of the mica tape 31. When the mica tape 21 is arranged in a vertical winding, an adhesive is applied to each inner surface of the mica tape 21. The material of the adhesive may contain a thermosetting resin or a thermoplastic resin. Examples of the adhesive include an adhesive polyolefin and a silicone adhesive. By applying the adhesive, peeling of the mica tape 31 can be suppressed. That is, the fire-resistant cable 10 has a cured product of the adhesive. Here, the cured product of the adhesive includes the adhesive cured after heating when the adhesive contains a thermosetting resin, and the adhesive solidified after melting when the adhesive contains a thermoplastic resin.

[0017] Each of the plurality of mica tapes 31 is preferably arranged so as not to overlap within the same mica tape 31. As shown in FIGS. 2A to 2D, for example, when the mica tape 31 is wound horizontally, the mica tape 31 may be arranged such that the side surfaces of the same mica tape 31 contact each other (the distance between the side surfaces in the width direction of the mica tape 31 is zero) (FIG. 2A), or the mica tape 31 may be arranged such that the distance between the side surfaces of the same mica tape 31 is less than 10% of the width of the mica tape 31 (FIG. 2B). After arranging a certain mica tape 31 in a spiral shape with a predetermined gap (FIG. 2C), other mica tapes 31 may be arranged to fill the gap (FIG. 2D). The distance between the side surfaces of the mica tape 31 is preferably within the range of 0 to 2 mm. Here, the distance between the side surfaces of the mica tape 31 refers to the distance between the opposing side surfaces, which may be the distance between the opposing side surfaces of the same mica tape 31 or the distance between the opposing side surfaces of different mica tapes 31.

[0018] Also, as shown in FIGS. 3A and 3B, when the mica tape 31 is wound vertically, the mica tape 31 may be arranged such that the side surfaces of the same mica tape 31 contact each other (the distance between the side surfaces in the width direction of the mica tape 31 is zero) (FIG. 3A), or the mica tape 31 may be arranged such that the distance between the side surfaces of the same mica tape 31 is less than 2% of the width of the mica tape 31 (FIG. 3B). The distance between the side surfaces in the width direction of the mica tape 31 is preferably within the range of 0 to 10 mm.

[0019] Although not particularly illustrated, the winding method of the mica tape 31 only needs to include vertical winding and horizontal winding. The winding method of the mica tape 31 may, for example, alternately perform vertical winding and horizontal winding, or may perform horizontal winding continuously after continuously performing vertical winding.

[0020] In this embodiment, the mica tape 31 may have a first mica tape 32 that is wrapped around the conductor 20 and a second mica tape 33 that is wrapped around the first mica tape 32. Here, the first mica tape 32 and the second mica tape 33 may be different types of mica tapes or the same type of mica tape.

[0021] The first mica tape 32 is wrapped around the conductor 20. The first mica tape 32 may be, for example, a glass mica tape or a film mica tape. In this embodiment, the first mica tape 32 is a glass mica tape. The number of first mica tapes 32 is not particularly limited, as long as there are multiple tapes. Preferably, the number of first mica tapes 32 is in the range of 2 to 20, more preferably in the range of 2 to 10, and even more preferably in the range of 4 to 6. Using two or more first mica tapes 32 makes it easier to ensure sufficient fire resistance. On the other hand, using 20 or fewer first mica tapes 32 makes it easier to ensure the thinness and flexibility of the fire-resistant cable 10. In this embodiment, five first mica tapes 32 are laminated. The method of wrapping the first mica tape 32 around the conductor 20 is as follows: if the fire-resistant cable 10 has both vertical and horizontal wrapping, it may be vertical wrapping or horizontal wrapping. It is preferable that the ends of the different first mica tapes 32 are arranged so that they do not overlap (are offset) in the width direction.

[0022] The second mica tape 33 is wrapped around the first mica tape 32. The second mica tape 33 may be the same as or different from the first mica tape 32. The second mica tape 33 may be, for example, a glass mica tape or a film mica tape. In this embodiment, the second mica tape 33 is a film mica tape. The number of second mica tapes 33 is not particularly limited, as long as there are multiple tapes. Preferably, the number of second mica tapes 33 is in the range of 2 to 20, more preferably in the range of 2 to 10, and even more preferably in the range of 4 to 6. Using two or more second mica tapes 33 makes it easier to ensure sufficient fire resistance. On the other hand, using 20 or fewer second mica tapes 33 makes it easier to ensure the thinness and flexibility of the fire-resistant cable 10. In this embodiment, the number of second mica tapes 33 is 5. The method of wrapping the second mica tape 33 around the first mica tape 32 is not limited by the method of wrapping the first mica tape 32, as long as the fire-resistant cable 10 has both vertical and horizontal re-wrapping. If the first mica tape 32 is arranged with vertical re-wrapping, the second mica tape 33 may be arranged with horizontal wrapping or with vertical re-wrapping. Also, if the first mica tape 32 is arranged with horizontal wrapping, the second mica tape 33 may be arranged with horizontal wrapping. It is preferable that the ends of different second mica tapes 33 in the width direction do not overlap (are offset). It is preferable that the outermost layer of the second mica tape 33 is wrapped horizontally. By wrapping the outermost layer of the second mica tape 33 horizontally, the mica tape 31 becomes less likely to peel off.

[0023] Thus, in this embodiment, the mica tape 31 has both vertical and horizontal windings, and is arranged so that identical (single) mica tapes 31 do not overlap, and it is preferable that the sides of identical mica tapes 31 are in contact with each other. In this case, during the manufacture of the fire-resistant cable 10, when the cable is wound onto a drum during manufacturing, the cable may bend, creating gaps between the sides of identical mica tapes 31. However, when the wound cable is fed out, the gaps between the sides of identical mica tapes 31 are substantially closed.

[0024] The insulating layer 40 is a layer that imparts insulating properties to the fire-resistant cable 10. The insulating layer 40 is formed by extruding a thermoplastic resin such as polyvinyl chloride or polyolefin. Examples of polyolefins include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), very low-density polyethylene (VLDPE), linear low-density polyethylene (LLDPE), polypropylene, polyisobutylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, and ethylene-butene copolymer. In addition, materials obtained by copolymerizing ethylene with α-olefins or cyclic olefins such as propylene, butene, pentene, hexene, and octene using a metallocene catalyst can also be used. These resins may be used alone or in combination. Additives such as antioxidants and ultraviolet stabilizers may be added to the insulating material forming the insulating layer 40 as needed. The thickness of the insulating layer 40 is not particularly limited. The thickness of the insulating layer 40 is in the range of 3 to 5 μm, and more preferably in the range of 3.5 to 4.5 μm.

[0025] The semiconductive layer 50 covers the insulating layer 40. The semiconductive layer 50 is formed, for example, by wrapping a semiconductive tape around it. Examples of semiconductive tapes include tapes in which a conductive material is laminated on a base material. Examples of base materials include various nonwoven fabrics and glass cloth. Examples of conductive materials include carbon, aluminum, and silicon carbide. The thickness of the semiconductive layer 50 is not particularly limited. The thickness of the semiconductive layer 50 is in the range of 0.1 to 0.5 μm, and more preferably in the range of 0.15 to 0.30 μm.

[0026] The metal shielding layer 60 covers the semiconducting layer 50. The metal shielding layer 60 is formed, for example, by wrapping a metal tape around it. Examples of metal tapes include soft copper tape and soft iron tape. The thickness of the metal shielding layer 60 is in the range of 0.1 to 0.5 mm, and more preferably in the range of 0.15 to 0.3 mm. Note that aluminum cannot be used as the metal for the metal tape.

[0027] The backing layer 70 covers the metal shielding layer 60. Examples of materials for the backing layer 70 include resin or glass. Examples of materials for the backing layer 70 include nonwoven tapes made of one or more of the following: polyester, polypropylene, aramid fiber, nylon, acrylic fiber, or glass fiber. In this embodiment, the material for the backing layer 70 is a polyester nonwoven tape. The thickness of the backing layer 70 is not particularly limited. The thickness of the backing layer 70 is in the range of 0.05 to 0.3 mm, and more preferably in the range of 0.1 to 0.2 mm.

[0028] The sheath 80 covers the metal shielding layer 60. The sheath 80 is formed, for example, by extruding a predetermined composition. The composition includes compositions in which a flame retardant is blended with an ethylene copolymer such as polyvinyl chloride resin, flame-retardant polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), or ethylene-methyl acrylate copolymer (EMA). These compositions are preferred from the viewpoint of flame retardancy, fire resistance, trauma resistance, and light resistance. Furthermore, from the viewpoint of ease of removing the coating (sheath) during terminal processing, flame-retardant polyethylene is particularly preferred as the resin included in the composition. Examples of flame retardants contained in Sheath 80 include metal oxides such as antimony oxide and molybdenum oxide, metal hydrates such as aluminum hydroxide and magnesium hydroxide, halogen-based flame retardants, and phosphorus-based flame retardants such as red phosphorus. From the viewpoint of environmental protection, non-halogen-based flame retardants are preferred, for example, metal hydrates such as aluminum hydroxide and magnesium hydroxide are preferred. Furthermore, Sheath 80 may further contain crosslinking agents, crosslinking aids, antioxidants, lubricants, etc., as needed. Sheath 80 may also be crosslinked with electron beams or organic peroxides. The thickness of Sheath 80 is not particularly limited. The thickness of Sheath 80 is in the range of 2 to 4 mm, and more preferably in the range of 2.5 to 3 mm.

[0029] (How to manufacture fire-resistant cables) Next, the manufacturing method of the fire-resistant cable 10 of this embodiment will be described. Figure 4 is a flowchart of the manufacturing method of the fire-resistant cable 10. The fire-resistant cable 10 can be manufactured, for example, by the following method.

[0030] As shown in Figure 4, the method for manufacturing the fire-resistant cable 10 includes the steps of preparing the conductor 20 (S110), winding the mica tape 31 (S120), heating the mica tape 31 (S130), forming the insulating layer 40 (S140), forming the semiconducting layer 50 (S150), forming the metal shielding layer 60 (S160), forming the winding layer 70 (S170), and forming the sheath 80 (S180).

[0031] In the step of preparing the conductor 20 (S110), a copper wire of a predetermined diameter is prepared as the conductor 20.

[0032] In the process of wrapping the mica tape 31 (S120), the mica tape 31 is wrapped around the prepared conductor 20. For example, multiple mica tapes 31 are wrapped vertically and horizontally around the prepared conductor 20 to form a fire-resistant layer. The first mica tape 32 may be wrapped horizontally or vertically. In this embodiment, five first mica tapes 32 are wrapped vertically, and then five second mica tapes 33 are wrapped horizontally. At this time, the first mica tapes 32 and the second mica tapes 33 are arranged so that the same mica tape 31 does not overlap. After this, for example, when the cable is wrapped around a drum or the like according to the manufacturing equipment, the cable may bend during manufacturing, and gaps may occur between the first mica tape 32 and the second mica tape 33.

[0033] In the step of heating the mica tape 31 (S130), the gas inside the mica tape 31 is removed by heating the mica tape 31. The gas inside the mica tape 31 expands when the mica tape 31 is heated and is released to the outside through the gaps between the mica tapes 31. The method for heating the mica tape 31 is not particularly limited as long as it can release the gas inside the mica tape 31 to the outside. Examples of methods for heating the mica tape 31 include using a hot jet, an incandescent lamp, or passing it through an oven chamber. In this embodiment, the gas inside the mica tape 31 is removed by heating it at 150-250°C for 15-60 seconds using a hot jet. For example, once a cable is wrapped around a drum or similar device and then sent out, the bend is released, and the gaps between the mica tapes 31 are effectively sealed. By heating the mica tapes 31 in this state, the gas inside the mica tapes 31 can be removed.

[0034] In the step of forming the insulating layer 40 (S140), the insulating layer 40 is formed by extruding a thermoplastic resin onto the refractory layer 30. In this embodiment, it is formed by extruding crosslinked polyethylene onto the refractory layer 30.

[0035] In the step of forming the semiconducting layer 50 (S150), the semiconducting layer 50 is formed by wrapping a semiconducting tape around the insulating layer 40. In this embodiment, the semiconducting layer 50 is formed by wrapping a carbon-impregnated nonwoven fabric tape around the insulating layer 40.

[0036] In the step of forming the metal shielding layer 60 (S160), the metal shielding layer 60 is formed by winding a metal tape around the semiconducting layer 50. In this embodiment, the metal shielding layer 60 is formed by winding a soft copper tape horizontally.

[0037] In the step of forming the press-wrap layer 70 (S170), the press-wrap layer 70 is formed on the surface of the metal shielding layer 60. The method of forming the press-wrap layer 70 is not particularly limited. In this embodiment, the press-wrap layer 70 is formed by horizontally winding a nonwoven soft copper tape.

[0038] In the process of forming the sheath (S180), the sheath 80 is formed on the surface of the pressed layer 70. The method of forming the sheath 80 is not particularly limited. In this embodiment, the sheath 80 is formed by extruding flame-retardant polyethylene.

[0039] Through the above process, a fire-resistant cable 10 can be manufactured.

[0040] (effect) As described above, according to this embodiment, the same mica tapes 31 are arranged so as not to overlap, and the mica tapes 31 are heated before forming the insulating layer 40. Therefore, even if the cable is bent during manufacturing before forming the insulating layer 40, voids are less likely to form inside or around the insulating layer 40. [Examples]

[0041] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0042] (Manufacturing of fire-resistant cables) (1) Manufacturing of the fire-resistant cable of Example 1 The fire-resistant cable in Example 1 first has a conductor with a cross-sectional area of ​​150 mm². 2 A copper wire was prepared. Next, five sheets of glass mica tape, with adhesive applied to the inside, were wrapped lengthwise around the conductor as the first mica tape. The five sheets of first mica tape were wrapped lengthwise so that the sides of the glass mica tape were in contact with each other. The positions of the sides of the five sheets of first mica tape were all different. Next, film mica tape was wrapped horizontally around the first mica tape as the second mica tape. Five sheets of second mica tape were wrapped horizontally so that the sides of the film mica tape were in contact with each other. The positions of the sides of the five sheets of second mica tape were all different.

[0043] Next, the fire-resistant layered cable was wound onto a drum and left to stand overnight. Then, the cable unwound from the drum was heated at 200°C for 30 seconds using a hot jet to remove air bubbles contained in the first mica tape. The heating also cured the adhesive of the vertically wound mica tape.

[0044] Next, an insulating layer was formed by extruding low-density polyethylene onto the fire-resistant layer. A semiconducting layer was formed by longitudinally winding semiconducting tape onto the insulating layer. A metal shielding layer was formed by transversely winding soft copper tape onto the semiconducting layer. A pressed-wrap layer was formed by transversely winding polyester nonwoven fabric onto the metal shielding layer. Finally, a sheath was formed by extruding flame-retardant polyethylene onto the pressed-wrap layer.

[0045] (2) Manufacturing of fire-resistant cables for Examples 2-6 and Comparative Examples 1-4 Except for the changes in the method of wrapping the mica tape, the presence or absence of adhesive, and the presence or absence of heating as shown in Table 1, the fire-resistant cables of Examples 2-6 and Comparative Examples 1-4 were manufactured in the same manner as the fire-resistant cable of Example 1.

[0046] (evaluation) (1) Performance evaluation The manufactured fire-resistant cables were evaluated by twisting three cables together to form a test specimen, in accordance with Fire and Disaster Management Agency Notification No. 10 (December 18, 1997), JCS 4507 "High-Voltage Fire-Resistant Cables", and JCS 7502 Cable Fire Resistance Test Method (Small Heating Furnace). First, a withstand voltage test of 17,000V was performed for 10 minutes before heating, and it was confirmed that all fire-resistant cables in Examples 1-6 and Comparative Examples 1-4 passed the test. Next, the test specimens were heated to 840°C over 30 minutes, during which time the withstand voltage characteristics at 4400V (dielectric strength during heating), insulation resistance of 1.0MΩ or more (insulation resistance), and the withstand voltage characteristics at 7600V (dielectric strength after heating) were evaluated for 10 minutes after heating. The evaluation criteria for dielectric strength during heating are as follows: ○: No dielectric breakdown occurred. ×: Dielectric breakdown occurred. The evaluation criteria for insulation resistance are as follows. A result of "○" or "△" was considered a pass. ○: The resistance was 100 MΩ or higher. △: The resistance was between 1 MΩ and 100 MΩ. ×: Less than 1 MΩ The evaluation criteria for dielectric strength after heating are as follows: ○: No dielectric breakdown occurred. ×: Dielectric breakdown occurred.

[0047] (2) Evaluation of the presence or absence of voids For voids, each fire-resistant cable was cut perpendicular to its length, and the cut surface of the insulation layer was observed with a microscope. The presence or absence of voids was evaluated according to the following criteria. Evaluation Criteria ○: No voids were observed. ×: A void was observed.

[0048] (3) Overall evaluation Each fire-resistant cable was comprehensively evaluated according to the following criteria. ○: There were no "×" marks in any of the categories. ×: One of the items was marked with "×".

[0049] Table 1 shows the components of each cable and the evaluation results for each fire-resistant cable.

[0050] [Table 1]

[0051] As shown in Table 1, the fire-resistant cables of Examples 1 to 6, in which multiple mica tapes were wrapped around the cable without overlapping and then heated, showed good results in terms of dielectric strength during heating, insulation resistance, dielectric strength after heating, and presence or absence of voids. In particular, the fire-resistant cables of Examples 1, 3, and 5, in which the outermost layer of mica tape was wrapped horizontally, showed even better insulation resistance.

[0052] On the other hand, in Comparative Example 1, where the mica tape was only wound vertically and not heated, the dielectric strength during heating was poor. This is thought to be because the adhesive peeled off during the test. Insulation resistance and dielectric strength after heating were not tested because the dielectric strength during heating was poor. Furthermore, in Comparative Example 2, where the mica tape was only wound horizontally and not heated, the insulation resistance was poor. This is thought to be because vertical winding was not included. Note that the dielectric strength after heating was not measured because the insulation resistance results were poor. Furthermore, voids were generated in Comparative Examples 3 and 4, which were not heated. This is thought to be because voids were generated inside the insulating layer due to the lack of heating. [Industrial applicability]

[0053] The fire-resistant cable of the present invention is useful as wiring in environments where high fire resistance is required. [Explanation of Symbols]

[0054] 10 Fireproof Cables 20 Conductors 30 Fireproof layer 31 Mica Tape 32 First mica tape 33. Second mica tape 40 Insulator layer 50 Semiconductive layer 60 Metal shielding layer 70. Pressed layer 80 Sheath

Claims

1. A fire-resistant cable comprising a conductor, a plurality of mica tapes wrapped around the conductor, an insulating layer covering the plurality of mica tapes, a semiconducting layer covering the insulating layer, a metal shielding layer covering the semiconducting layer, and a sheath covering the metal shielding layer, The winding method of the aforementioned plurality of mica tapes includes horizontal winding and vertical winding via a cured adhesive. Fireproof cable.

2. In the fire-resistant cable described in claim 1, Of the aforementioned multiple mica tapes, the outermost mica tape is wound horizontally. Fireproof cable.

3. In the fire-resistant cable described in claim 1, Each of the aforementioned plurality of mica tapes is arranged so that no identical mica tapes overlap. Fireproof cable.

4. In the fire-resistant cable described in claim 3, A fire-resistant cable characterized in that the identical mica tapes are arranged so that their sides are in contact with each other.

5. In the fire-resistant cable of claim 1, A fire-resistant cable characterized in that each of the plurality of mica tapes is either a glass mica tape or a film mica tape.

6. A method for manufacturing a fire-resistant cable comprising a conductor, a plurality of mica tapes wrapped around the conductor, an insulating layer covering the plurality of mica tapes, a semiconducting layer covering the insulating layer, a metal shielding layer covering the semiconducting layer, and a sheath covering the metal shielding layer, The process of wrapping the plurality of mica tapes around the conductor, A step of heating the plurality of mica tapes wrapped around the conductor, A step of forming the insulating layer on the plurality of mica tapes after heating, It has, A method for manufacturing a fire-resistant cable, characterized in that, in the step of winding the plurality of mica tapes around the conductor, the plurality of mica tapes are wound by horizontal winding and vertical winding with an adhesive.

7. In the method for manufacturing a fire-resistant cable according to claim 6, A method for manufacturing a fire-resistant cable, characterized in that, in the step of wrapping the plurality of mica tapes around the conductor, each of the plurality of mica tapes is arranged so as not to overlap on the same mica tape.

8. In the method for manufacturing a fire-resistant cable according to claim 6, Each of the aforementioned plurality of mica tapes is either a glass mica tape or a film mica tape. A method for manufacturing a fire-resistant cable, characterized in that the heating temperature in the step of heating the plurality of mica tapes is within the range of 150 to 250°C.

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