JP6249079B1 - Insulated wire - Google Patents

Abstract

To reduce the outer diameter of an insulated wire while maintaining high flame retardancy and DC stability. A conductor and a coating layer disposed on the outer periphery of the conductor, the coating layer being formed from a flame retardant resin composition, and having a plurality of oxygen indexes defined by JIS K7201-2 exceeding 45 It includes a flame retardant layer and a water shielding layer having a saturated water absorption rate of 0.5% or less. The water shielding layer is interposed between the plurality of flame retardant layers, and the outermost layer is formed as a flame retardant layer. An insulated wire is provided. [Selection] Figure 1

Description

  The present invention relates to an insulated wire.

  Insulated electric wires used as wiring for railway vehicles and automobiles are required to have not only insulating properties but also flame resistance that does not easily burn in a fire. Therefore, a flame retardant is mix | blended with the coating layer of an insulated wire. For example, Patent Document 1 discloses an insulated wire in which a coating layer is formed by laminating a flame retardant layer containing a flame retardant on the outer periphery of an insulating layer having insulation properties. According to Patent Document 1, insulation and flame retardancy can be obtained at a high level with a good balance.

JP 2013-214487 A

  By the way, in recent years, an insulated wire is required to have a thin outer diameter from the viewpoint of weight reduction. Therefore, reducing the thickness of the insulating layer located inside and the flame retardant layer located outside has been studied.

  However, if the thickness of the flame retardant layer is reduced, it becomes difficult to maintain high flame retardancy. On the other hand, when the thickness of the insulating layer is reduced, the insulation reliability is lowered, and it is difficult to maintain high DC stability. That is, in an insulated wire, it is difficult to achieve both high flame retardance and high DC stability while reducing the outer diameter.

  This invention is made | formed in view of the said subject, and it aims at providing the technique which makes an outer diameter thin, maintaining a flame retardance and DC stability high in an insulated wire.

According to one aspect of the invention,
Conductors,
A coating layer disposed on the outer periphery of the conductor,
The coating layer is formed from a flame retardant resin composition, a plurality of flame retardant layers having an oxygen index defined by JIS K7201-2 of greater than 45, and a water shielding layer having a saturated water absorption rate of 0.5% or less, An insulated wire is provided in which the water shielding layer is interposed between the plurality of flame retardant layers, and the outermost layer is the flame retardant layer.

  According to the present invention, it is possible to reduce the outer diameter while maintaining high flame retardancy and DC stability in an insulated wire.

It is sectional drawing perpendicular | vertical to the length direction of the insulated wire which concerns on one Embodiment of this invention. It is sectional drawing perpendicular | vertical to the length direction of the insulated wire which concerns on other embodiment of this invention. It is sectional drawing perpendicular | vertical to the length direction of the insulated wire which concerns on other embodiment of this invention. It is sectional drawing perpendicular | vertical to the length direction of the cable using the insulated wire of this invention. It is sectional drawing perpendicular | vertical to the length direction of the conventional insulated wire.

  First, a conventional insulated wire will be described with reference to FIG. FIG. 5 is a cross-sectional view perpendicular to the length direction of a conventional insulated wire.

  As shown in FIG. 5, a conventional insulated wire 100 includes a conductor 110, an insulating layer 120 disposed on the outer periphery of the conductor 110, a flame retardant layer 130 that is disposed on the outer periphery of the insulating layer 120, and contains a flame retardant. , And is configured.

  In the conventional insulated wire 100, since the flame retardant layer 130 is formed of a resin like the insulating layer 120, it exhibits a predetermined insulation property but has a low insulation reliability and does not contribute to DC stability. As will be described later, DC stability is one of the electrical characteristics evaluated by a DC stability test based on EN 50305.6.7, and a predetermined voltage is applied by immersing the insulated wire 100 in water. Sometimes it shows that dielectric breakdown does not occur even after a predetermined time, and serves as an index for insulation reliability.

  According to the study by the present inventors, it has been found that the flame retardant layer 130 does not contribute to the direct current stability because the water absorption rate is increased by the addition of the flame retardant. As one of the factors, in the flame retardant layer 130, a minute gap may be formed around the flame retardant due to low adhesion between the resin forming the flame retardant layer 130 and the flame retardant. Conceivable. The formation of the gap makes it easy for water to penetrate into the flame retardant layer 130 and absorb water. In such a flame retardant layer 130, when the insulated wire 100 is immersed in water and DC stability is evaluated, Since the conductive path is formed by the permeation and the dielectric breakdown is likely to occur, the insulation reliability tends to be low. In this way, the flame retardant layer 130 is liable to deteriorate in insulation properties due to water absorption, and does not contribute to direct current stability.

  On the other hand, since the insulating layer 120 is covered with the flame retardant layer 130, it is not necessary to add a flame retardant. Therefore, although the insulating layer 120 does not exhibit flame retardance unlike the flame retardant layer 130, the insulating layer 120 is configured to have a low water absorption rate and contributes to DC stability.

  Thus, in the conventional insulated wire 100, the insulating layer 120 contributes to DC stability, and the flame retardant layer 130 contributes to flame retardancy. Therefore, in order to achieve both DC stability and flame retardancy at a high level, it is necessary to increase the thickness of the insulating layer 120 and the flame retardant layer 130, respectively, and to reduce the diameter of the insulated wire 100 in order to reduce the diameter. It has become difficult.

  In the conventional insulated wire 100, the present inventor has a direct current stability (insulation reliability) lowered by providing a flame retardant layer 130 that easily absorbs water on the surface, so that water does not penetrate into the flame retardant layer 130. With this configuration, the flame retardant layer 130 can contribute not only to flame retardancy but also to DC stability. Finally, the thickness of the insulating layer 120 is reduced and the outer diameter of the insulated wire 100 is reduced. I thought it was possible.

  Therefore, a method for suppressing the penetration of water into the flame retardant layer 130 was examined. As a result, it was found that a water shielding layer having a low water absorption rate should be provided on the outer periphery of the flame retardant layer. According to the water shielding layer, since the penetration of water into the flame retardant layer can be suppressed, the flame retardant layer can function as a resin layer having not only flame retardancy but also DC stability. Thereby, the conventionally formed insulating layer 120 can be omitted. That is, a conventional laminated structure composed of the insulating layer 120 and the flame retardant layer 130 can be constituted by the flame retardant layer and the water shielding layer. The water shielding layer has a thickness that prevents water permeation, and does not need to be formed thick like the conventional insulating layer 120. Therefore, the outer diameter of the insulated wire can be reduced.

  However, since the water shielding layer does not substantially contain a flame retardant and is inferior in flame retardancy, if such a water shielding layer is provided on the surface of the insulated wire, the flame resistance of the insulated wire as a whole may be reduced. is there.

  In this regard, by interposing a water-impervious layer inferior in flame retardance between the flame-retardant layers, for example, the coating layer is arranged in order from the conductor side, the first flame-retardant layer, the water-impervious layer, and the second flame-retardant layer. By forming the three layers, it is possible to maintain high DC stability by suppressing flooding of the first flame retardant layer by the water shielding layer while maintaining flame retardancy in the coating layer.

  In addition, by forming each flame retardant layer so that the oxygen index, which is an indicator of flame retardancy, exceeds 45, the desired high flame retardance is maintained in the coating layer while making each flame retardant layer thinner. can do.

  The present invention has been made based on the above findings.

<Configuration of insulated wire>
Hereinafter, an insulated wire according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view perpendicular to the length direction of an insulated wire according to an embodiment of the present invention. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  As shown in FIG. 1, the insulated wire 1 according to this embodiment includes a conductor 11 and a coating layer 20.

〔conductor〕
As the conductor 11, a commonly used metal wire, for example, a copper wire, a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like can be used. Moreover, you may use what gave metal plating, such as tin and nickel, to the outer periphery of a metal wire. Further, a collective stranded conductor obtained by twisting metal wires can be used. The cross-sectional area and the outer diameter of the conductor 11 can be appropriately changed according to the electrical characteristics required for the insulated wire 1. For example, the cross-sectional area is 1 mm ^{2 to} 10 mm ² and the outer diameter is 1.25 mm to 3. 9 mm.

(Coating layer)
A coating layer 20 is provided on the outer periphery of the conductor 11. In this embodiment, the coating layer 20 is formed by interposing a single water shielding layer 22 between two flame retardant layers 21 and 21 and laminating so that the outermost layer becomes the flame retardant layer 21. Yes. That is, the coating layer 20 is formed by laminating three layers of the flame retardant layer 21, the water shielding layer 22, and the flame retardant layer 21 in order from the conductor 11 side. Hereinafter, in the coating layer 20, the flame retardant layer 21 covered with the water shielding layer 22 and positioned inside is described as the internal flame retardant layer 21a, and the flame retardant layer 21 positioned as the outermost layer is described as the external flame retardant layer 21b.

(Internal flame retardant layer)
The internal flame retardant layer 21 a is formed, for example, by extruding a flame retardant resin composition on the outer periphery of the conductor 11, and has an oxygen index greater than 45. In the present embodiment, the internal flame retardant layer 21 a is formed so that the oxygen index exceeds 45, and contributes to the flame retardancy of the coating layer 20. Further, since the internal flame retardant layer 21a is covered with the water shielding layer 22, the penetration of water is suppressed when the DC stability is evaluated by immersing the insulated wire 1 in water, so that the insulation reliability is high. This also contributes to the direct current stability of the coating layer 20. That is, the internal flame retardant layer 21a contributes not only to flame retardancy but also to DC stability, and functions as a flame retardant insulating layer.

  The oxygen index of the internal flame retardant layer 21a is not particularly limited as long as it is larger than 45, and is preferably as large as possible from the viewpoint of flame retardancy. The oxygen index is an index of flame retardancy, and is defined by JIS K7201-2 in this embodiment.

  The flame retardant resin composition forming the internal flame retardant layer 21a contains a resin and, if necessary, a flame retardant.

  The resin forming the internal flame retardant layer 21a may be appropriately changed depending on the characteristics required for the insulated wire 1, such as elongation and strength. For example, polyolefin, polyimide, polyether ether ketone (PEEK), or the like can be used. When polyolefin is used, it is preferable to add a large amount of flame retardant to increase the oxygen index of the flame retardant layer 21. When polyimide or PEEK is used, the flame retardant of the resin itself is high, so no flame retardant is added. Also good. Polyolefin has a low molding temperature and excellent moldability of the flame retardant layer 21 as well as polyimide and the like, and has a large elongation at break and excellent bendability of the flame retardant layer 21.

  As the polyolefin, a polyethylene resin, a polypropylene resin, or the like can be used, and a polyethylene resin is particularly preferable. Examples of the polyethylene resin include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene-α olefin copolymer, and ethylene-vinyl acetate copolymer (EVA). , Ethylene-acrylic acid ester copolymers, ethylene-propylene-diene copolymers, and the like can be used. These resins may be used alone or in combination of two or more. From the viewpoint of obtaining higher flame retardancy in the internal flame retardant layer 21a, EVA is particularly preferable among polyolefin resins.

  As the flame retardant, a non-halogen flame retardant is preferable because it does not generate a toxic gas. For example, a metal hydroxide can be used. When the internal flame retardant layer 21a is heated and burned, the metal hydroxide decomposes and dehydrates, lowers the temperature of the internal flame retardant layer 21a by the released moisture, and suppresses the combustion. . Examples of the metal hydroxide that can be used include magnesium hydroxide, aluminum hydroxide, calcium hydroxide, and metal hydroxides in which nickel is dissolved. These flame retardants may be used alone or in combination of two or more.

  The flame retardant is a silane coupling agent, titanate coupling agent, fatty acid such as stearic acid, fatty acid such as stearate from the viewpoint of controlling the mechanical properties (balance between tensile strength and elongation) of the internal flame retardant layer 21a. It is preferable that the surface is treated with a salt, a fatty acid metal such as calcium stearate, or the like.

  It is preferable that the compounding quantity of a flame retardant is 150 mass parts-250 mass parts with respect to 100 mass parts of resin from a viewpoint of making the oxygen index of the flame retardant layer 21 higher than 45. There exists a possibility that desired high flame retardance may not be acquired in the insulated wire 1 as a compounding quantity is less than 150 mass parts. If the blending amount exceeds 250 parts by mass, the mechanical properties of the internal flame retardant layer 21a may be reduced, and the elongation may be reduced.

  The internal flame retardant layer 21a may be cross-linked. For example, the resin composition forming the internal flame retardant layer 21a is blended with a crosslinking aid, extruded, and then irradiated with an electron beam for crosslinking. Also good.

(Water shielding layer)
The water shielding layer 22 has a saturated water absorption rate of 0.5% or less, and is configured so that the water absorption amount and the water diffusion coefficient are small. Since the water shielding layer 22 has high water shielding properties and is difficult for water to permeate, water penetration into the internal flame retardant layer 21a located inside the coating layer 20 can be suppressed. Although the water shielding layer 22 does not substantially contain a flame retardant and is inferior in flame retardancy, it is covered and protected by an external flame retardant layer 21b described later.

  The material for forming the water shielding layer 22 may be a material having a saturated water absorption rate of 0.5% or less, and the lower limit value of the saturated water absorption rate is not particularly limited, and may be 0%. If it exceeds 0.5%, the water shielding layer 22 is likely to absorb water, and water penetration into the internal flame retardant layer 21a cannot be suppressed. In the present specification, the saturated water absorption is a water saturation obtained from Fick's law based on JIS K7209: 2000.

  As a material for forming the water shielding layer 22, a resin is preferable from the viewpoint of the moldability of the water shielding layer 22, and the same resin as the internal flame retardant layer 21a can be used. In the water shielding layer 22, polyolefin is more preferable, and among them, other properties such as low water absorption, good moldability, relatively high elongation at break, and oil resistance (solvent resistance) are excellent. Linear low density polyethylene (LLDPE) is particularly preferred because of its low cost and low cost.

  In the case of forming the water shielding layer 22 from a resin such as LLDPE, for example, a resin composition containing LLDPE may be formed by extrusion molding on the outer periphery of the internal flame retardant layer 21a. From the viewpoint of further improving the water shielding property of the water shielding layer 22, it is preferable that the water shielding layer 22 is formed of a crosslinked body by blending the resin composition with a crosslinking agent or a crosslinking aid. By crosslinking, the molecular structure of the resin can be strengthened, and the water shielding property of the water shielding layer 22 can be improved. In addition, since the strength of the water shielding layer 22 can also be improved, even if the thickness of the water shielding layer 22 is reduced, the water shielding property can be maintained high without impairing the strength.

  The cross-linked body forming the water shielding layer 22 is preferably cross-linked so that the gel fraction is 40% to 100%. Since the water-impervious layer 22 can increase strength and water-imperviousness by increasing the gel fraction of the crosslinked body, the thickness can be reduced.

  In the case of cross-linking the water-impervious layer 22, a known cross-linking agent or cross-linking aid may be added to the resin composition. As a crosslinking agent, an organic peroxide, a silane coupling agent, etc. can be used, for example. As the crosslinking aid, for example, polyfunctional monomers such as triallyl isocyanurate and trimethylol propantoacrylate can be used. These compounding quantities are not specifically limited, For example, it is good to change suitably so that the crosslinking degree of the water-impervious layer 22 may be 40%-100% in a gel fraction. In addition, as a crosslinking method, it can carry out by well-known methods, such as chemical crosslinking and electron beam crosslinking, according to the kind of crosslinking agent.

(External flame retardant layer)
The external flame retardant layer 21b is formed by, for example, extruding a flame retardant resin composition containing a flame retardant to the outer periphery of the conductor 11, and is configured to have an oxygen index greater than 45, as with the internal flame retardant layer 21a. . The external flame retardant layer 21b is located on the surface of the coating layer 20 and is not covered with the water shielding layer 22 like the internal flame retardant layer 21a, so that water easily penetrates and does not contribute to DC stability. The water-impervious layer 22 which is inferior in properties is coated to suppress a reduction in flame retardancy as the entire coating layer 20.

  In addition, the flame-retardant resin composition which forms the external flame-resistant layer 21b can use the same thing as the internal flame-resistant layer 21a. The external flame retardant layer 21b may be cross-linked similarly to the internal flame retardant layer 21a. The cross-linking of the external flame retardant layer 21b may be performed, for example, by blending a resin composition that forms the external flame retardant layer 21b with a cross-linking agent or a cross-linking aid, extrusion molding, and then performing a cross-linking treatment. The crosslinking method is not particularly limited, and can be performed by a conventionally known method.

(Laminated structure of coating layer)
Subsequently, a laminated structure of the coating layer 20 will be described.

  In the coating layer 20, the thickness of the water shielding layer 22 is not particularly limited and is preferably 0.05 mm or more from the viewpoint of water shielding. By setting it as 0.05 mm or more, the intensity | strength of the water shielding layer 22 can be made high and the tearing of the water shielding layer 22 at the time of bending the insulated wire 1 can be suppressed. Thereby, the water imperviousness of the water impervious layer 22 can be maintained, and the internal flame retardant layer 21a can be contributed to DC stability. On the other hand, the upper limit value of the thickness of the water shielding layer 22 is not particularly limited, but is preferably 0.1 mm or less from the viewpoint of flame retardancy of the insulated wire 1. Since the water shielding layer 22 does not substantially contain a flame retardant, the flame resistance of the insulated wire 1 may be reduced. However, by setting the thickness of the water shielding layer 22 to 0.1 mm or less, the insulated wire 1 It can be kept high without impairing the flame retardancy. Moreover, by setting it as such thickness, the outer diameter of the insulated wire 1 can be made thin.

Moreover, in the coating layer 20, each thickness of the some flame retardant layer 21 is not specifically limited, It is good to change suitably according to the flame retardance and DC stability which are calculated | required by the coating layer 20, and high flame retardance From the viewpoint of obtaining the above, the total thickness of the plurality of flame retardant layers 21 is preferably 0.35 mm or more.
Since the internal flame retardant layer 21a contributes to the flame retardance and DC stability of the coating layer 20, from the viewpoint of obtaining desired DC stability, at least the thickness of the wire of the metal wire constituting the conductor 11 If the diameter is 0.5 times or more or the wire diameter is 0.2 mm or less, it is preferably 0.1 mm or more. When the thickness of the internal flame retardant layer 21a is excessively thin, the conductor 11 cannot sufficiently absorb the surface unevenness of the conductor 11 caused by the metal wire when the metal 11 is formed by twisting a plurality of metal wires, and the internal flame retardant layer The surface of the water-impervious layer 22 provided on 21a is formed uneven, and there is a risk that the direct current stability will be reduced. However, by setting the thickness of the internal flame retardant layer 21a within the above range, the internal flame retardant layer 21a can be formed flat to reduce the surface irregularities of the water shielding layer 22 and improve the direct current stability. it can. On the other hand, the upper limit is not particularly limited, and can be appropriately changed in consideration of the flame retardance of the coating layer 20 and the diameter reduction of the insulated wire 1.
Since the external flame retardant layer 21b covers the water shielding layer 22 and suppresses its combustion, the thickness is preferably at least 0.25 mm or more. On the other hand, the upper limit is not particularly limited, and can be appropriately changed in consideration of the flame retardance of the coating layer 20 and the diameter reduction of the insulated wire 1.
Therefore, in the coating layer 20, by setting the thickness of each layer within the above range, it is possible to obtain high flame resistance as well as direct current stability while reducing the diameter of the insulated wire 1.

<Effect according to this embodiment>
According to the present embodiment, the following one or more effects are achieved.

In the present embodiment, the water shielding layer 22 having a saturated water absorption rate of 0.5% or less is provided so as to be interposed in the flame retardant layer 21 having an oxygen index greater than 45, and the inner flame retardant layer 21a in order from the conductor 11 side. A coating layer 20 is formed in which the water shielding layer 22 and the external flame retardant layer 21b are laminated.
According to the water shielding layer 22 having a saturated water absorption rate of 0.5% or less, the penetration of water into the internal flame retardant layer 21a can be suppressed, and the insulation reliability of the internal flame retardant layer 21a can be maintained. The layer 21a can function as a flame retardant insulating layer that contributes not only to flame retardancy but also to DC stability. Thereby, the desired DC stability can be maintained without forming the insulating layer 120 that contributes to DC stability as in the conventional insulated wire 100 shown in FIG. The insulating layer 120 needs to be formed thick in order to obtain a desired direct current stability, whereas the water shielding layer 22 may be formed thin enough to show water shielding. By forming the layer 22, the outer diameter of the insulated wire 1 can be reduced by the difference in thickness.
Further, the water shielding layer 22 does not substantially contain a flame retardant and may reduce the flame retardance of the coating layer 20. However, the coating layer is formed by coating the water shielding layer 22 with the external flame retardant layer 21 b. The flame retardance as a whole can be maintained high.
Further, since each of the plurality of flame retardant layers 21 is made highly flame retardant so that the oxygen index exceeds 45, even if the thickness of each of the flame retardant layers 21 is reduced, the desired flame retardant in the entire coating layer 20. It becomes possible to maintain sex.
Therefore, according to the present embodiment, in the insulated wire 1, it is possible to reduce the outer diameter while achieving both high flame retardance and high DC stability.

In the case of the conventional insulated wire 100 shown in FIG. 5, for example, when both high flame retardance conforming to EN455545-2 and direct current stability conforming to EN50305.6.7 are achieved, the outer diameter is 1.25 mm-3. the conductor 110 of 9 mm (cross-sectional area ^{1 mm} 2 to 10 mm ^2), the thickness of the coating layer including the insulating layer 120 and the flame retardant layer 130 is not blended with flame retardants (coating thickness) needs to be at least 0.6mm Yes, the outer diameter of the electric wire is 2.6 mm or more.
On the other hand, in this embodiment, the coating thickness of the coating layer 20 including the internal flame retardant layer 21a and the water shielding layer 22 is thinned to about 0.45 mm to 0.5 mm with respect to the conductor 11 having the same outer diameter. The outer diameter of the electric wire can be reduced to 2.1 mm to 2.3 mm.

  The flame retardant resin composition forming the flame retardant layer 21 includes linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene-α olefin copolymer, ethylene-vinyl acetate. It is preferable to contain at least one resin of a copolymer (EVA), an ethylene-acrylic acid ester copolymer, and an ethylene-propylene-diene copolymer. According to such a resin, even when a large amount of the flame retardant is blended so that the oxygen index of the flame retardant layer 21 is larger than 45, the elongation of the flame retardant layer 21 due to the blending of the flame retardant or A decrease in strength or the like can be suppressed to a small level. Among these, EVA contains vinyl acetate and is excellent in flame retardancy. Therefore, the flame retardance of the flame retardant layer 21 can be improved.

  The flame retardant resin composition forming the flame retardant layer 21 preferably contains 150 parts by mass or more and 250 parts by mass or less of a flame retardant with respect to 100 parts by mass of the resin. By setting it as such a compounding quantity, high flame retardance that an oxygen index exceeds 45 can be acquired, without impairing the mechanical characteristics (for example, elongation, intensity | strength, etc.) of the flame retardant layer 21.

  The water shielding layer 22 is preferably formed from a resin, and is preferably formed from linear low density polyethylene (LLDPE). According to LLDPE, the water shielding layer 22 can be easily formed by extrusion. Further, according to LLDPE, it is easy to adjust the saturated water absorption rate of the water shielding layer 22 to 0.5% or less when crosslinked, and it is possible to enhance water shielding and improve other properties such as oil resistance.

  The water shielding layer 22 is formed from a crosslinked body obtained by crosslinking HDPE, and the gel fraction of the crosslinked body is preferably 40% to 100%. By setting it as such a gel fraction, since the intensity | strength and water imperviousness of the water shielding layer 22 can be improved, the thickness of the water shielding layer 22 can be formed thinly. Thereby, it becomes possible to make the outer diameter of the insulated wire 1 thinner.

  In addition, according to this embodiment, you may form so that the insulated wire 1 may become the same outer diameter as before, without reducing the diameter. In this case, by increasing the thickness of the flame retardant insulating layer 21, it is possible to further improve the flame retardancy and DC stability.

<Other Embodiments of the Present Invention>
As mentioned above, although one Embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the summary, it can change suitably.

  In the above-described embodiment, the case where the flame retardant layer 21, the water shielding layer 22, and the flame retardant layer 21 are sequentially laminated on the outer periphery of the conductor 11 to form the three-layer coating layer 20 is illustrated. It is not limited to. For example, as shown in FIG. 2, a plurality of flame retardant layers 21 and water barrier layers 22 are provided so that a water barrier layer 22 is interposed between three flame retardant layers 21 to form a five-layer structure. It may be provided. In FIG. 2, among the three flame retardant layers 21, the one located on the surface of the coating layer 20 is the external flame retardant layer 21 b, and the one coated with the other water shielding layer 22 is the internal flame retardant layer 21 a. .

  In the insulated wire 1 shown in FIG. 2, the thickness of each layer is not particularly limited. For example, the total thickness of the water shielding layer 22 is 0.05 mm to 0.1 mm, and the thickness of the internal flame retardant layer 21 a is 0.00 mm. The thickness of the external flame retardant layer 21b is preferably 0.25 mm or more. As described above, in order to form the outer water shielding layer 22 flat and ensure the DC stability of the coating layer 20, the total thickness of the layers located inside the outer water shielding layer 22 is determined by the conductor 11. The thickness of each layer may be adjusted to be 0.5 mm or more of the wire diameter of the metal wire constituting the wire or 0.1 mm or more if the wire diameter is 0.2 mm or less. For example, in the insulated wire 1 shown in FIG. 2, when a stranded conductor having an outer diameter of 1.25 mm obtained by twisting a metal wire having a strand diameter of 0.18 mm is used as the conductor 11, the thickness of each layer is as follows: Good. That is, from the conductor 11 side, the inner flame retardant layer 21a is 0.05 mm, the water shielding layer 22 is 0.05 mm, the inner flame retardant layer 21a is 0.05 mm, the water shielding layer 22 is 0.05 mm, and the outer flame retardant layer 21b. Is 0.25 mm. By setting the total thickness of the layers inside the outer water-impervious layer 22 to 0.15 mm and 0.5 times or more of the strand diameter of the metal wire, the outer impermeable layer 22 can be formed flat, Higher DC stability can be ensured.

Moreover, although the above-mentioned embodiment demonstrated the case where the water shielding layer 22 was formed with resin, such as LLDPE, this invention is not limited to this. The water shielding layer 22 may be formed of a material other than resin, and may be formed of, for example, ceramics or glass.
When forming the water shielding layer 22 from ceramics or glass, for example, the outer periphery of the flame retardant insulating layer 21 can be formed by surface treatment with alumina, zirconia, or diamond-like carbon (DLC) by a plasma CVD method or the like. At this time, the thickness of the water shielding layer 22 is preferably 0.005 mm to 0.01 mm.

  Moreover, each resin composition which forms the flame retardant layer 21 and the water shielding layer 22 may contain other additives as necessary. For example, a flame retardant aid, an antioxidant, a lubricant, a softener, a plasticizer, an inorganic filler, a compatibilizer, a stabilizer, carbon black, a colorant, and the like may be contained. These can be contained in the range which does not impair each characteristic of the flame-resistant layer 21 and the water-impervious layer 22.

  Moreover, although the above-mentioned embodiment demonstrated the case where the coating layer 20 was formed with the flame retardant layer 21 and the water shielding layer 22, the coating layer 20 has characteristics different from those of the flame retardant layer 21 and the water shielding layer 22. You may provide the resin layer which has. For example, as shown in FIG. 3, a semiconductive layer 23 may be provided between the conductor 11 and the internal flame retardant layer 21a in order to improve electrical characteristics. The thickness of each layer is, for example, 0.1 mm for the semiconductive layer 23, 0.05 mm for the internal flame retardant layer 21a, 0.075 mm for the water shielding layer 22 and 0. It can be 25 mm.

  The insulated wire 1 described above may be used as it is, for example, as a wiring for a railway vehicle or an automobile, but can also be used as a cable core. Specifically, as shown in FIG. 4, a flame retardant sheath 70 is provided on the outer periphery of a core 60 including three insulated wires 1, for example, a core 60 in which three insulated wires 1 are twisted together. Thus, the cable 50 can be configured. FIG. 4 shows the case where the core 60 includes three insulated wires 1, but the number of insulated wires 1 is not limited to three, and one or a plurality of two or more wires can be used.

  EXAMPLES Next, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

The materials used in Examples and Comparative Examples are as follows.
・ Ethylene-vinyl acetate copolymer (EVA): Mitsui DuPont Polychemical Co., Ltd. “Evaflex EV170”
-Maleic acid modified polymer: "Tuffmer MH7020" manufactured by Mitsui Chemicals, Inc.
・ Thermoplastic polyimide: “Aurum PL450C” manufactured by Mitsui Chemicals, Inc.
Silicone-modified polyetherimide: “STM1500” manufactured by Savic Co., Ltd.
・ Linear low density polyethylene (LLDPE): “Evolue SP2030” manufactured by Prime Polymer Co., Ltd.
-Polyetheretherketone (PEEK): “Keta Spire KT-820NT” manufactured by Solvay Specialty Polymers Co., Ltd.
・ Flame retardant (magnesium hydroxide): “Kisuma 5A” manufactured by Kyowa Chemical Industry Co., Ltd.
・ Mixed antioxidant: “ADEKA STAB AO-18” manufactured by ADEKA CORPORATION
・ Phenolic antioxidant: “Irganox 1010” manufactured by BASF Corporation
・ Carbon black: “Asahi Thermal” manufactured by Asahi Carbon Co., Ltd.
・ Lubricant (zinc stearate)
・ Crosslinking aid (trimethylol propantoacrylate (TMPT)): Shin-Nakamura Chemical Co., Ltd.

<Preparation of flame retardant resin composition>
First, a flame retardant resin composition was prepared by blending the above materials with the composition shown in Table 1 below.
Specifically, first, 75 parts by weight of EVA, 25 parts by weight of maleic acid-modified polymer, 150 parts by weight of magnesium hydroxide, 2 parts by weight of a crosslinking aid, and 2 parts by weight of a mixed antioxidant 2 parts by mass of carbon black and 1 part by mass of lubricant were mixed and kneaded using a 75 L wonder kneader. After kneading, it was extruded using an extruder to form a strand, which was then cooled with water and cut to obtain pellet-shaped flame retardant resin composition 1 (also referred to as flame retardant material 1). This pellet had a cylindrical shape with a diameter of about 3 mm and a height of about 5 mm. In addition, the oxygen index of the flame retardant material 1 was 45.5, and it was confirmed that the saturated water absorption exceeds 0.5%.
Similarly, the composition was appropriately changed as shown in Table 1 to prepare flame retardant material 2 to flame retardant material 7, respectively. Table 1 shows the oxygen index and saturated water absorption of each material.

<Preparation of water shielding material>
Then, the water shielding materials 1 and 2 were prepared as a resin composition for forming a water shielding layer.
Specifically, the water shielding material 1 was prepared by dry blending 100 parts by mass of LLDPE and 1 part by mass of a phenol-based antioxidant and kneading them using a wonder kneader. Further, PEEK was prepared as the water shielding material 2.

<Production of insulated wires>
Example 1
Then, the insulated wire was produced using the above-mentioned flame retardant material and water shielding material.
Specifically, three layers of flame retardant material 1, water shielding material 1 and flame retardant material 1 are simultaneously extruded to the outer periphery of a tin-plated copper conductor having an outer diameter of 1.25 mm to absorb an electron beam. Irradiation was performed so that the dose was 75 kGy to crosslink each material, and the insulated wire of Example 1 was produced. The produced insulated wire has an inner flame retardant layer thickness of 0.1 mm, a water shielding layer thickness of 0.1 mm, an external flame retardant layer thickness of 0.27 mm, and the entire coating layer in order from the conductor side. The thickness was 0.47 mm, and the outer diameter of the electric wire was 2.19 mm. Moreover, it was confirmed that the water shielding layer has a saturated water absorption of 0.5% or less. Table 3 below summarizes each configuration of the insulated wire of Example 1. Table 3 shows that the resin layer (1), the resin layer (2), and the resin layer (3) are formed in order from the conductor side. The three-layer coextrusion was performed by using three short-shaft extruders and joining them in a crosshead.

(Examples 2-9)
In Examples 2 to 9, Example 1 except that the types of the flame retardant material and the water shielding material, the thickness of each of the internal insulating layer, the water shielding layer, and the external flame retardant layer were appropriately changed as shown in Table 3. Similarly, an insulated wire was produced. In addition, it was confirmed that the water shielding layer in each Example has a gel fraction similar to that in Example 1 and a saturated water absorption rate of 0.5% or less.

(Comparative Examples 1-4)
In Comparative Examples 1 to 4, as shown in Table 3 below, Example 1 except that at least one of the internal flame retardant layer and the external flame retardant layer was formed of the flame retardant material 7 having an oxygen index of 44.5. An insulated wire was produced by forming a coating layer with the same laminated structure as in FIG.

(Comparative Examples 5 and 6)
In Comparative Examples 5 and 6, the water shielding material 1, the flame retardant material 4 and the water shielding material 1 are simultaneously extruded to the outer periphery of the tin-plated copper conductor wire at respective predetermined thicknesses. An insulated wire was produced in the same manner as in Example 1 except that a coating layer in which a fuel layer and a water shielding layer were laminated was formed.

(Comparative Examples 7-9)
In Comparative Examples 7 to 9, two layers of the water shielding material 1 and the flame retardant material 4 or the flame retardant material 1 are simultaneously extruded on the outer periphery of the tin-plated copper conductor wire with respective predetermined thicknesses, and the water shielding layer and the difficulty are sequentially formed from the conductor side. An insulated wire was produced in the same manner as in Example 1 except that a coating layer in which a fuel layer was laminated was formed.

(Comparative Example 10)
In the comparative example 10, the flame retardant material 4 and the water shielding material 1 are simultaneously extruded on the outer periphery of the tin-plated copper conducting wire with respective predetermined thicknesses, and the flame retardant layer and the water shielding layer are sequentially laminated from the conductor side. An insulated wire was produced in the same manner as in Example 1 except that the layer was formed.

(Comparative Examples 11 and 12)
In Comparative Examples 11 and 12, one layer of the flame retardant material 2 or the water shielding material 1 was extruded at a predetermined thickness on the outer periphery of the tin-plated copper conductor, and only one layer of the flame retardant layer or the water shielding layer was formed on the outer periphery of the conductor. Except for the above, an insulated wire was produced in the same manner as in Example 1.

<Evaluation method>
The produced insulated wire was evaluated by the following method. The evaluation results are summarized in Tables 2 and 3.

(Flame retardance)
The flame retardancy of the insulated wire was evaluated by the vertical combustion test shown below. First, a VFT test was performed according to a vertical flame propagation for a single insulated wire or cable defined in EN50265-2-1. Specifically, an insulated wire having a length of 600 mm was held vertically, and a flame was applied to the insulated wire for 60 seconds. Pass / fail was determined according to the above criteria.

(DC stability)
The DC stability of the insulated wire was evaluated by a DC stability test according to EN50305.6.7. Specifically, the insulated wire was immersed in 3% strength salt water at 85 ° C., 1500 V was applied, and the time until dielectric breakdown was measured. In this example, if the time until dielectric breakdown was 240 hours or more, ◯ was evaluated as having high DC stability, and if it was less than 240 hours, X was evaluated as having low DC stability.

<Evaluation results>
As shown in Table 2, in Examples 1 to 9, it was confirmed that both DC stability and flame retardancy can be achieved at a high level while reducing the outer diameter of the electric wire.

On the other hand, in Comparative Examples 1 to 4, since at least one of the internal flame retardant layer and the external flame retardant layer is formed so that the oxygen index is smaller than 45, the flame retardancy as the coating layer may be insufficient. confirmed.
In Comparative Examples 5 and 6, a water shielding layer, a flame retardant layer, and a water shielding layer were laminated in order from the conductor side to form a three-layer coating layer, and a flame barrier layer was provided on the surface of the coating layer. It was confirmed that the property was insufficient. Moreover, in Comparative Example 6, it was confirmed that the DC stability could be maintained high, but the coating layer was thick and it was difficult to reduce the diameter.
In Comparative Examples 7 to 9, since the flame retardant layer was provided on the water shielding layer and the coating layer had a two-layer structure, it was confirmed that the coating layer easily absorbs water and was inferior in DC stability. Moreover, since the flame retardant layer was thinner in Comparative Example 7 than in Comparative Examples 8 and 9, it was confirmed that the flame retardancy was inferior.
In Comparative Example 10, a water shielding layer was provided on the flame retardant layer to form a coating layer having a two-layer structure, and the DC layer stability was maintained high because the water shielding layer was located on the surface of the coating layer. It was confirmed that the layer was inferior in flame retardancy because it easily burned.
In Comparative Examples 11 and 12, since the coating layer is composed of only one layer of a flame retardant layer or a water shielding layer, it is confirmed that at least one of flame retardancy and DC stability can be obtained at a high level, but they are not compatible. It was.

  As described above, by forming the coating layer so that the water shielding layer having a low water absorption rate is interposed between the flame retardant layer having a high oxygen index, the entire thickness of the coating layer is reduced and the insulated wire is thinned. It was confirmed that both flame retardancy and DC stability can be achieved at a high level while the diameter is increased.

<Preferred embodiment of the present invention>
Hereinafter, preferred embodiments of the present invention will be additionally described.

[Appendix 1]
According to one aspect of the invention,
Conductors,
A coating layer disposed on the outer periphery of the conductor,
The coating layer is formed from a flame retardant resin composition, a plurality of flame retardant layers having an oxygen index defined by JIS K7201-2 of greater than 45, and a water shielding layer having a saturated water absorption rate of 0.5% or less, An insulated wire is provided in which the water shielding layer is interposed between the plurality of flame retardant layers, and the outermost layer is the flame retardant layer.

[Appendix 2]
In the insulated wire of appendix 1, preferably,
The flame retardant resin composition forming the flame retardant layer is composed of high density polyethylene, linear low density polyethylene, low density polyethylene, ethylene-α olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid. It contains at least one resin of an ester copolymer and an ethylene-propylene-diene copolymer.

[Appendix 3]
In the insulated wire of appendix 1 or 2,
The flame retardant resin composition forming the flame retardant layer contains a flame retardant, and contains 150 parts by mass or more and 250 parts by mass or less of the flame retardant with respect to 100 parts by mass of the resin.

[Appendix 4]
In any one of the supplementary wires 1 to 3, preferably,
The water shielding layer is formed from a crosslinked body obtained by crosslinking a resin composition.

[Appendix 5]
In the insulated wire of appendix 4, preferably,
The resin composition forming the water shielding layer includes high density polyethylene.

[Appendix 6]
In the insulated wire of appendix 3 , preferably,
The flame retardant is a metal hydroxide.

[Appendix 7]
According to another aspect of the invention,
A core including at least one insulated wire;
A sheath disposed on the outer periphery of the core,
The insulated wire is
A conductor, and a coating layer disposed on the outer periphery of the conductor,
The coating layer is formed from a flame retardant resin composition, a plurality of flame retardant layers having an oxygen index defined by JIS K7201-2 of greater than 45, and a water shielding layer having a saturated water absorption rate of 0.5% or less, The cable is provided such that the water shielding layer is interposed between the plurality of flame retardant layers, and the outermost layer is the flame retardant layer.

1 Insulated wire 11 Conductor 20 Cover layer 21 Flame retardant layer 21a Internal flame retardant layer 21b External flame retardant layer 22 Water shielding layer

Claims (6)

Conductors,
A coating layer disposed on the outer periphery of the conductor,
The coating layer is formed from a flame retardant resin composition, a plurality of flame retardant layers having an oxygen index defined by JIS K7201-2 of greater than 45, and a water shielding layer having a saturated water absorption rate of 0.5% or less, The insulated wire is formed such that the water shielding layer is interposed between the plurality of flame retardant layers, and the outermost layer is the flame retardant layer.   The flame retardant resin composition forming the flame retardant layer is composed of high density polyethylene, linear low density polyethylene, low density polyethylene, ethylene-α olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid. The insulated wire according to claim 1, comprising at least one resin of an ester copolymer and an ethylene-propylene-diene copolymer.   The said flame-retardant resin composition which forms the said flame-resistant layer contains a flame retardant, and contains the said flame retardant with respect to 100 mass parts of resin at 150 mass parts or more and 250 mass parts or less. Insulated wires.   The insulated wire according to any one of claims 1 to 3, wherein the water shielding layer is formed from a crosslinked body obtained by crosslinking a resin composition.   The insulated wire according to claim 4, wherein the resin composition forming the water shielding layer includes high-density polyethylene. The insulated wire according to claim 3, wherein the flame retardant is a metal hydroxide.

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