JP6406332B2 - Insulated wire - Google Patents

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, insulating properties and flame retardancy can be obtained in a balanced manner at a high level by forming an insulated wire by laminating a flame retardant layer on the outer periphery of the insulating layer.

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.

  On the other hand, since the coating layer easily deteriorates due to oxidation or metal damage under a high temperature environment, improvement in heat resistance is also required.

  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, DC stability, and heat resistance 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, in order from the conductor side, is formed by alternately laminating a flame retardant layer formed from a resin composition containing a flame retardant and a water shielding layer so that the outermost layer becomes the flame retardant layer,
An insulated wire is provided in which the water shielding layer is formed from a resin composition containing a resin, an antioxidant, and a copper damage inhibitor .

  According to the present invention, the outer diameter of the insulated wire can be reduced while maintaining high flame retardancy, DC stability, and heat resistance.

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 conventional insulated wire.

  First, a conventional insulated wire will be described with reference to FIG. FIG. 3 is a cross-sectional view perpendicular to the length direction of a conventional insulated wire.

  As shown in FIG. 3, the conventional insulated wire 100 includes a conductor 110, an insulating layer 120 disposed on the outer periphery of the conductor 110, and a flame retardant layer 130 containing a flame retardant disposed on the outer periphery of the insulating layer 120. 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 insulating property, but its insulation reliability is low and does not contribute much to DC stability. As will be described later, the DC stability is one of the electrical characteristics evaluated by a DC stability test in accordance with EN50305.6.7. This indicates that the dielectric breakdown does not occur even when a predetermined time elapses when the voltage is applied, 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. More specifically, in the flame retardant layer 130, a minute gap is formed around the flame retardant due to low adhesion between the resin forming the flame retardant layer 130 and the flame retardant. Formation of this gap makes it easy for water to penetrate into the flame retardant layer 130 and to absorb water. In such a flame retardant layer 130, when the DC stability is evaluated by immersing the insulated wire 100 in water, a conductive path is formed by the penetration of water, and dielectric breakdown is likely to occur, so that the insulation reliability is low. There is a tendency. Thus, the flame retardant layer 130 is liable to be reduced in insulation due to water absorption, and does not contribute much to DC 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 the flame retardant layer 130 which is easy to absorb water in the outermost layer, 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 to reduce the outer diameter of the insulated wire 100. I thought I could make it thinner.

  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 in the outermost layer of the insulated wire, the flame retardancy of the insulated wire as a whole may be reduced. There is. In this respect, a water-impervious layer inferior in flame retardancy is interposed between the flame-retardant layers. For example, the coating layer is composed of the first flame-retardant layer, the water-impervious layer, and the second flame-retardant layer in order from the conductor side. By forming it with a layer, it is possible to maintain high DC stability by suppressing water infiltration into the first flame retardant layer by the water shielding layer while maintaining flame retardancy. That is, the outer diameter of the insulated wire can be reduced while maintaining high flame retardancy and DC stability.

  Moreover, when the method of improving the heat resistance of a coating layer was examined, it turned out that it is good to mix | blend antioxidant and a copper damage inhibitor with a water shielding layer. As described above, since the water shielding layer is provided so as to be interposed between the two flame retardant layers, it is not easily affected by oxidation or metal damage (copper damage). By blending an inhibitor, the heat resistance of the entire coating layer can be greatly improved.

  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 outer diameter of the conductor 11 can be appropriately changed according to the electrical characteristics required for the insulated wire 1, and is, for example, 1.0 mm to 6.0 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 from a resin composition containing a flame retardant, and is formed, for example, by extruding a resin composition containing a flame retardant to the outer periphery of the conductor 11. The internal flame retardant layer 21 a containing a flame retardant 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 resin composition forming the internal flame retardant layer 21a contains a resin and 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 resin or polyamideimide resin (PAI resin) can be used. As the polyolefin resin, 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 low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), and ethylene-ethyl acrylate copolymer. , Ethylene-methyl acrylate copolymer, ethylene-glycidyl methacrylate copolymer, and the like can be used. These polyolefin resin may be used individually by 1 type, and may use 2 or more types together. From the viewpoint of obtaining higher flame retardancy in the internal flame retardant layer 21a, EVA is particularly preferable, and EVA having a vinyl acetate content (VA amount) of 10% to 40% is more preferable.

  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.

  From the viewpoint of controlling the mechanical properties (balance between tensile strength and elongation) of the internal flame retardant layer 21a, the flame retardant is a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, or a fatty acid such as stearate. 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 50 mass parts-300 mass parts with respect to 100 mass parts of resin from a flame-retardant viewpoint. 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 50 mass parts. If the blending amount exceeds 300 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 crosslinked by a conventionally known method. The crosslinking of the internal flame retardant layer 21a is performed by, for example, crosslinking by radiation such as an electron beam, or by performing a crosslinking treatment after extrusion molding by adding a crosslinking agent or a crosslinking aid to the resin composition forming the internal flame retardant layer 21a. It is good to give.

(Water shielding layer)
It is preferable that the water-impervious 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%. 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 molding processability of the water shielding layer 22. The resin, from the viewpoint of safety is preferably a polyolefin resin is halogen-free, resin density in terms of impermeability and mechanical properties are 0.85g ^/ cm ³ ~1.20g ^/ cm 3 are preferred. For example, high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or the like can be used. Further, for example, a fluorine-containing resin (for example, PFA) may be used because of its low water absorption rate.

  When the water shielding layer 22 is formed from a resin such as LDPE or 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 properties of the water shielding layer 22, it is preferable that the resin composition is blended with a crosslinking agent and crosslinked to form the water shielding layer 22 with a crosslinked body. 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 preferably 10% to 100%, more preferably 40% to 100%. In the water-impervious layer 22, the strength and the water-imperviousness can be increased as the gel fraction of the crosslinked body is increased, so that 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 the crosslinking agent, for example, an organic peroxide such as dicumyl peroxide can be used. As the crosslinking aid, for example, trimethylol propanthate methacrylate (TMPT) or triallyl isocyanurate (TAIC) 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 10%-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.

Moreover, the resin composition which forms the water-impervious layer 22 contains an antioxidant and a copper damage inhibitor . Impermeable layer 22 is less susceptible to deterioration due to oxidation and metal damage because it is sandwiched between the flame retardant layer 21 (e.g., copper damage, etc.). However, the water shielding layer 22 is responsible for most of the DC stability of the insulated wire 1, and if the water shielding layer 22 deteriorates due to oxidation or metal damage (for example, copper damage), the DC stability of the insulated wire 1 is improved. The nature will be greatly impaired. Therefore, in the present embodiment, the heat resistance of the coating layer 20 as a whole, for example, the heat resistance at 120 ° C., can be improved by adding an antioxidant and a copper damage inhibitor to the water shielding layer 22.

Although it does not specifically limit as antioxidant, For example, antioxidants, such as a phenol type, sulfur type, an amine type, and a phosphorus type, can be used.
Examples of the phenolic antioxidant include dibutylhydroxytoluene (BHT), pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 1,3,5-tris (3 , 5-di-t-butyl-4-hydroxy-benzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione, thiodiethylenebis- [3- (3,5-di-tert -Butyl-4-hydroxyphenyl) propionate] can be used, and among them, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] is preferable.
Examples of the sulfur-based antioxidant include didodecyl 3,3′-thiodipropionate, ditridecyl 3,3′-thiodipropionate, dioctadecyl 3,3′-thiodipropionate, tetrakis [methylene-3- ( Dodecylthio) propionate] methane and the like can be used, among which tetrakis [methylene-3- (dodecylthio) propionate] methane is preferable.
These antioxidants may be used alone or in combination of two or more.

  The copper damage inhibitor can stabilize copper and other metal ions by chelating action and suppress oxidative deterioration. For example, N- (2H-1,2,4-triazol-5-yl) salicylamide, dodecanedioic acid bis [N2- (2-hydroxybenzoyl) hydrazide], 2 ', 3-bis [[3- [3 , 5-di-tert-butyl-4-hydroxyphenyl] propionyl]] propionohydrazide and the like, among which 2 ′, 3-bis [[3- [3,5-di-tert-butyl- 4-hydroxyphenyl] propionyl]] propionohydrazide is preferred.

  Although these compounding quantities are not specifically limited, It is preferable that at least 1 of antioxidant and copper damage inhibitor shall be 0.1 mass part-5 mass parts with respect to 100 mass parts of resin. When using together, it is preferable to make these total compounding quantity into the said range.

(External flame retardant layer)
The external flame retardant layer 21b is formed from a resin composition containing a flame retardant, similarly to the internal flame retardant layer 21a. For example, the external flame retardant layer 21b is formed by extruding a resin composition containing a flame retardant to the outer periphery of the conductor 11. Although 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, water easily penetrates and does not contribute to direct current 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.

  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 50 μm or more from the viewpoint of water shielding. By setting it as 50 micrometers or more, while being able to obtain a desired high water-blocking property, the intensity | strength of the water-blocking layer 22 can be made high. Thereby, since the breakage of the water shielding layer 22 when the insulated wire 1 is bent can be suppressed, the water shielding property of the water shielding layer 22 can be maintained, and the internal flame retardant layer 21a can contribute to the 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 150 μm or less from the viewpoint of flame retardancy of the insulated wire 1.

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, it is preferable that the total thickness of the plurality of flame retardant layers 21 is 300 μm to 500 μm.
The internal flame retardant layer 21a preferably has a thickness of 50 μm to 150 μm.
Since the external flame retardant layer 21b covers the water shielding layer 22 and suppresses its combustion, the thickness is preferably 200 μm or more. On the other hand, the upper limit is preferably 400 μm or less.

  Moreover, in the coating layer 20, it is preferable that the ratio of the sum total of the thickness of the some flame-resistant layer 21 and the thickness of the water shielding layer 22 is 2: 1-10: 1.

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

In the present embodiment, a 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, and the internal flame retardant layer 21 a, the water shielding layer 22, and the external difficulty are sequentially formed from the conductor 11 side. The coating layer 20 in which the fuel layer 21b is laminated is formed.
According to the water shielding layer 22, since 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 internal flame retardant layer 21a is not only flame retardant, It can function as a flame retardant insulating layer that also contributes 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, while the water shielding layer 22 may be formed thin enough to show water shielding, so that the water shielding layer 22 is formed instead of the insulating layer 120. By forming, 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.
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 conventional insulated wire 100 shown in FIG. 3, for example, when both high flame resistance conforming to EN455545-2 and direct current stability conforming to EN50305.6.7 are achieved, the outer diameter is 1.0 mm to 6. For the 0 mm conductor 110, the thickness of the insulating layer 120 must be 0.3 mm to 0.4 mm, and the thickness of the flame retardant layer 130 containing the flame retardant must be 0.4 mm to 0.5 mm. The outer diameter of the electric wire 100 is 2.6 mm to 6.7 mm.
On the other hand, in this embodiment, the inner flame retardant layer 21a having a thickness of 0.05 mm to 0.15 mm and the water shielding layer having a thickness of 0.05 mm to 0.15 mm are provided for the conductor 11 having the same outer diameter. 22 and an external flame retardant layer 21b having a thickness of 0.2 mm to 0.4 mm may be laminated, and the outer diameter of the insulated wire 1 may be reduced to a range of 2.2 mm to 5.7 mm. Can do.
For example, in the conventional insulated wire 100, when the conductor size is 1 SQ (conductor diameter 1.25 mm), the thickness of the covering layer including the insulating layer 120 and the flame retardant layer 130 provided on the outer periphery of the conductor 110 (covering thickness) However, in this embodiment, the coating thickness of the coating layer including the internal flame retardant layer 21a and the water shielding layer 22 is 0.45 mm to 0 mm. The outer diameter of the electric wire can be reduced to 2.2 mm to 2.3 mm.

  The water shielding layer 22 is preferably formed from a resin such as HDPE, LDPE, or LLDPE, and more preferably from LDPE. This is because LDPE can be cross-linked more easily than HDPE or LLDPE, so that the gel fraction of the water-impervious layer 22 can be increased and the water-impervious property can be further increased.

  The water shielding layer 22 is formed from a crosslinked body obtained by crosslinking a resin such as LDPE or LLDPE, and the gel fraction of the crosslinked body is preferably 10% 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.

The resin composition for forming the water shield layer 22, you containing resin and the antioxidant and copper inhibitor. Since the water shielding layer 22 is sandwiched between the flame retardant layers 21, it is not easily affected by deterioration due to oxidation or metal damage (such as copper damage), but by blending an antioxidant and a copper damage inhibitor, For example, the heat resistance at 120 ° C. can be improved.

  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. . The thickness of each water shielding layer 22 may be at least 25 μm, and is preferably 25 μm to 75 μm. At this time, from the viewpoint of flame retardancy of the coating layer 20, the total thickness of the plurality of water shielding layers 22 is preferably 50 μm to 150 μm. Of the plurality of flame retardant layers 21, the thickness of the external flame retardant layer 21 b is preferably at least 50 μm, and preferably 50 μm to 120 μm. The thickness of the internal flame retardant layer 21a is preferably 50 μm to 150 μm. From the viewpoint of flame retardancy of the coating layer 20, the total thickness of the plurality of flame retardant layers 21 is preferably 200 μm to 400 μm.

  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, a semiconductive layer may be provided between the conductor 11 and the internal flame retardant layer 21a in order to improve electrical characteristics.

  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 (EVA1): Mitsui DuPont Polychemical Co., Ltd. “Evaflex EV260” (VA amount: 28%, MFR: 6)
Ethylene-vinyl acetate copolymer (EVA2): Mitsui DuPont Polychemical Co., Ltd. “Evaflex EV170” (VA amount: 33%, MFR: 1)
High density polyethylene (HDPE, d: 0.951 g / cm ³ , MFR: 0.8): “Hi-Zex 5305E” manufactured by Prime Polymer Co., Ltd.
Low density polyethylene (LDPE, d: 0.921 g / cm ³ , MFR: 1): “UBE C450” manufactured by Ube Industries, Ltd.
Linear low density polyethylene (LLDPE, d: 0.922 g / cm ³ , MFR: 2.5): “SP2030” manufactured by Prime Polymer Co., Ltd.
-Maleic acid modified polymer: "Tuffmer MH7020" manufactured by Mitsui Chemicals, Inc.
Magnesium hydroxide (Silane treatment): Albemarle “H10A”
Magnesium hydroxide (fatty acid treatment): “H10C” manufactured by Albemarle Co., Ltd.
Aluminum hydroxide (fatty acid treatment): “OL107C” manufactured by Albemarle Co., Ltd.
・ Mixed antioxidant: “AO-18” manufactured by Adeka Co., Ltd.
・ Phenolic antioxidant: “Irganox 1010” manufactured by BASF Corporation
Copper damage inhibitor: “Irganox MD1024” manufactured by BASF Corporation
・ Colorant: “FT Carbon” manufactured by Asahi Carbon Co., Ltd.
・ Lubricant (zinc stearate): Nitto Kasei Co., Ltd.

<Preparation of flame retardant materials>
A flame retardant material for forming a flame retardant layer was prepared by blending the above materials with the composition shown in Table 1 below. Specifically, 85 parts by weight of EVA1, 15 parts by weight of maleic acid-modified polymer, 80 parts by weight of silane-treated magnesium hydroxide, 120 parts by weight of fatty acid-treated magnesium hydroxide, and a mixed antioxidant 1 part by weight, 2 parts by weight of a colorant and 1 part by weight of a lubricant were kneaded with a pressure kneader to obtain a pellet-shaped flame retardant material 1.
Similarly, the composition was appropriately changed as shown in Table 1 to prepare flame retardant material 2 to flame retardant material 7, respectively.
In the pressure kneader, kneading was performed at a start temperature of 40 ° C. and an end temperature of 190 ° C.

<Preparation of water shielding material>
Then, the above-mentioned material was mix | blended with the composition shown in following Table 2, and the water shielding material for forming a water shielding layer was prepared. Specifically, the water shielding material 1 was prepared by kneading 100 parts by mass of HDPE, 1 part by mass of a phenolic antioxidant and 0.5 part by mass of a copper damage inhibitor with a pressure kneader.
Similarly, the composition was appropriately changed as shown in Table 2 to prepare water shielding material 2 to water shielding material 4, respectively.
In the pressure kneader, kneading was performed at a start temperature of 40 ° C. and an end temperature of 190 ° C.

<Production of insulated wires>
Example 1
Subsequently, an insulated wire was produced using the prepared flame retardant material and water shielding material.
Specifically, three layers of the flame retardant material 1, the water shielding material 1 and the flame retardant material 1 are simultaneously extruded at a predetermined thickness on the outer periphery of a tin-plated copper conductor having an outer diameter of 1.25 mm, and the electron beam is 8 Mrad. By irradiating with, each material was bridge | crosslinked and the insulated wire of Example 1 was produced. The manufactured insulated wire has an internal flame retardant layer thickness of 50 μm, a water shielding layer thickness of 50 μm, an external flame retardant layer thickness of 400 μm, an overall coating layer thickness of 500 μm, and an outer diameter of the wire of 2 .25 mm. Moreover, it was confirmed that the water-impervious layer has a degree of cross-linking such that the gel fraction is 36% and the saturated water absorption is 0.3%. Table 3 below summarizes each configuration of the insulated wire of Example 1. The three-layer coextrusion was performed by using three short-shaft extruders and joining them in a crosshead. The temperature of each crosshead was 190 ° C.

(Examples 2 to 10)
In Examples 2 to 10, 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 changed as shown in Table 3 as appropriate in Example 1. Similarly, an insulated wire was produced.

(Comparative Examples 1 and 2)
In Comparative Example 1, an insulated wire was prepared in the same manner as in Example 1 except that the external flame retardant layer was not formed as shown in Table 3 and a coating layer was formed by providing a water shielding layer on the internal flame retardant layer. did.
In Comparative Example 2, an insulated wire was produced in the same manner as in Example 1 except that the water shielding layer was not formed as shown in Table 3 and the coating layer was formed of one flame retardant layer.

<Evaluation method>
The produced insulated wire was evaluated by the following method. Each evaluation result is summarized in Table 3.

(DC stability)
The DC stability of the insulated wire was evaluated by a DC stability test in accordance with 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.

(Flame retardance)
The flame retardancy of the insulated wire was evaluated by a vertical combustion test in accordance with EN455545-2.
Specifically, after the flame of the burner was applied for 1 minute to the insulated wire supported vertically, the flame was removed, and the distance between the upper fixed portion and the carbonized upper end portion was 50 mm or more, and the upper fixed portion and the carbonized portion If the distance from the lower end is less than 540 mm, “◯” is indicated as being excellent in flame retardancy, and “X” is indicated otherwise.

(Heat-resistant)
The heat resistance of the insulated wire was evaluated by a test based on EN50264-1.
Specifically, first, a conductor (tin-plated copper conducting wire) was drawn from the produced insulated wire to produce a sample. This sample was put into a constant temperature bath at 135 ° C. for 168 hours. And the tension test was done with respect to each of the sample of the initial state before a heating, and the sample after a heating, and the tensile strength residual rate and the elongation residual rate were calculated | required as a change rate from an initial state. In this example, each was within ± 30%, and “◯” was indicated as being excellent in heat resistance, and otherwise, it was determined as being low in heat resistance and indicated as “X”.

<Evaluation results>
As shown in Table 3, in Examples 1 to 10, 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.
In Example 3, the saturated water absorption rate of the water shielding layer was lowered to 0.1%, and the blending amount of the flame retardant in the flame retardant layer was set to 100 parts by mass. Example 1 (200 parts by mass) and Example 4 (150) It was confirmed that the coating layer was less likely to absorb water by being less than (part by mass), so that the time until short-circuiting could be increased and the DC stability could be increased.

On the other hand, in Comparative Example 1, although high DC stability was obtained, it was confirmed that the flame retardance of the entire coating layer was insufficient because the external flame retardant layer was not formed.
Moreover, in Comparative Example 2, since the coating layer was formed only with the flame retardant layer without providing the water shielding layer, although high flame retardancy was obtained, the time until short-circuiting was short and the DC stability was insufficient. It was confirmed. In addition, since the water shielding layer containing the antioxidant and the copper damage preventing material is not formed, it has been confirmed that the heat resistance as the entire coating layer cannot be secured sufficiently.

<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, in order from the conductor side, is formed by alternately laminating a flame retardant layer formed from a resin composition containing a flame retardant and a water shielding layer so that the outermost layer becomes the flame retardant layer,
An insulated wire is provided in which the water shielding layer is formed from a resin composition containing a resin, an antioxidant, and a copper damage inhibitor .

[Appendix 2]
In the insulated wire of appendix 1, preferably,
The barrier tree fat compositions that form a water layer, said containing antioxidant and the copper deactivator than 2 parts by weight 0.1 parts by weight relative to the resin 100 parts by mass.

[Appendix 3]
In the insulated wire of appendix 2, preferably,
The water shielding layer is formed from a crosslinked body obtained by crosslinking the resin composition forming the water shielding layer, and the gel fraction of the crosslinked body is 40% or more and 100% or less.

[Appendix 4]
In any one of the supplementary wires 1 to 3, preferably,
The resin forming the water shielding layer is low density polyethylene.

[Appendix 5]
In the insulated wire of any one of supplementary notes 1 to 4,
The coating layer is formed by laminating three layers of the flame retardant layer, the water shielding layer and the flame retardant layer in order from the conductor side,
The thickness of the flame retardant layer on the inner side of the water shielding layer is 50 μm or more and 150 μm or less
The thickness of the water shielding layer is 50 μm or more and 150 μm or less,
The thickness of the flame retardant layer outside the water shielding layer is 200 μm or more and 400 μm or less.

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 (5)

Conductors,
A coating layer disposed on the outer periphery of the conductor,
The coating layer, in order from the conductor side, is formed by alternately laminating a flame retardant layer formed from a resin composition containing a flame retardant and a water shielding layer so that the outermost layer becomes the flame retardant layer,
An insulated wire, wherein the water shielding layer is formed from a resin composition containing a resin, an antioxidant, and a copper damage inhibitor.   The resin composition which forms the said water shielding layer contains the said antioxidant and the said copper damage inhibitor with respect to 100 mass parts of said resin of 0.1 mass part or more and 2 mass parts or less of Claim 1. Insulated wire. The said water shielding layer is formed from the crosslinked body which bridge | crosslinked the resin composition which forms the said water shielding layer, The gel fraction of the said crosslinked body is 40% or more and 100% or less, The Claim 1 or 2 characterized by the above-mentioned. Insulated wires.   The insulated wire according to any one of claims 1 to 3, wherein the resin forming the water shielding layer is low-density polyethylene. The coating layer is formed by laminating three layers of the flame retardant layer, the water shielding layer and the flame retardant layer in order from the conductor side,
The thickness of the flame retardant layer on the inner side of the water shielding layer is 50 μm or more and 150 μm or less
The thickness of the water shielding layer is 50 μm or more and 150 μm or less,
The insulated wire according to any one of claims 1 to 4, wherein a thickness of the flame retardant layer outside the water shielding layer is 200 µm or more and 400 µm or less.

Images