CN107833688B

CN107833688B - Insulated wire

Info

Publication number: CN107833688B
Application number: CN201710390899.6A
Authority: CN
Inventors: 加贺雅文; 木部有; 梶山元治
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 2016-09-15
Filing date: 2017-05-27
Publication date: 2021-07-20
Anticipated expiration: 2037-05-27
Also published as: EP3340257A1; EP3340257B1; CN107833688A

Abstract

The invention provides an insulated wire, and provides a technology capable of realizing the reduction of the diameter of the insulated wire while obtaining high insulation and high flame retardance. The insulated wire has a conductor and a coating layer disposed on the outer periphery of the conductor, the coating layer having a laminated structure composed of an inner flame-retardant layer disposed on the outer periphery of the conductor and formed of a flame-retardant-containing polymer composition, and a coating layer disposed on the outer periphery of the inner flame-retardant layer and having a thickness of 1 × 10¹⁶The high-electric-power-generating insulating layer is formed by laminating a high-electric-power-generating insulating layer formed of a polymer composition having a volume resistivity of not less than Ω cm and an outer flame-retardant layer formed of a flame-retardant-containing polymer composition and disposed on the outer periphery of the high-electric-power-generating insulating layer, wherein the high-electric-power-generating insulating layer shares not less than 80% of a voltage applied in the thickness direction of the laminated structure, and the thickness of the high-electric-power-generating insulating layer is thinner than at least one of the thickness of the inner flame-retardant layer and the thickness of the outer flame-retardant layer.

Description

Insulated wire

Technical Field

The present invention relates to an insulated wire.

Background

Insulated wires used as wiring for railway vehicles, automobiles, and the like are required to have flame retardancy that is difficult to burn in case of fire, in addition to insulation. Therefore, a flame retardant is added to the coating layer of the insulated wire. For example, patent document 1 discloses an insulated wire in which a flame retardant layer containing a flame retardant is laminated on the outer periphery of an insulating layer having insulation properties to form a coating layer.

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. 2010-97881

Disclosure of Invention

Problems to be solved by the invention

In recent years, for example, from the viewpoint of weight reduction, the diameter of an insulated wire is required to be reduced. However, it is difficult to achieve a reduction in diameter while achieving high insulation and high flame retardancy.

An object of the present invention is to provide a technique for reducing the diameter of an insulated wire while achieving high insulation and high flame retardancy.

Means for solving the problems

According to one aspect of the present invention, there is provided an insulated wire including a conductor and a coating layer disposed on an outer periphery of the conductor,

the coating layer has a laminated structure in which,

the laminated structure is composed of:

an inner flame-retardant layer disposed on the outer periphery of the conductor and formed of a flame-retardant-containing polymer composition (A),

Is arranged on the periphery of the inner flame-retardant layer and has a thickness of 1 × 10¹⁶A high-electric-insulation layer formed of a polymer composition (B) having a volume resistivity of not less than Ω cm, and

an outer flame-retardant layer disposed on the outer periphery of the high-electric-insulation layer and formed of a flame-retardant-containing polymer composition (C)

The composite material is formed by laminating,

the high-electric-power insulating layer shares 80% or more of a voltage applied in a thickness direction of the laminated structure, and the thickness of the high-electric-power insulating layer is thinner than at least one of the thickness of the inner flame-retardant layer and the thickness of the outer flame-retardant layer.

According to another aspect of the present invention, there is provided an insulated wire including a conductor and a coating layer disposed on an outer periphery of the conductor,

the coating layer has:

a conductor disposed on the outer periphery of the conductor and containing a conductive agent and having a size of 1 × 10⁹A semiconductive layer comprising a polymer composition (A) having a volume resistivity of not more than Ω cm,

Is arranged on the outer periphery of the semi-conductive layer and has a thickness of 1 × 10¹⁶A high-electric-insulation layer formed of a polymer composition (B') having a volume resistivity of not less than Ω cm, and

a flame-retardant layer which is disposed at least on the outer periphery of the high-electric-insulation layer and is formed of a polymer composition (C') containing a flame retardant,

the thicknesses of the high-electric-insulation layer and the semiconductive layer are respectively thinner than the thickness of the flame-retardant layer.

Effects of the invention

According to the present invention, the insulated wire can be made smaller while achieving high insulation and high flame retardancy.

Drawings

Fig. 1 is a cross-sectional view perpendicular to a longitudinal direction of an insulated electric wire according to an embodiment of the present invention;

fig. 2 is a cross-sectional view perpendicular to the longitudinal direction of an insulated electric wire according to another embodiment of the present invention;

fig. 3 is a cross-sectional view perpendicular to the longitudinal direction of an insulated wire according to another embodiment;

fig. 4 is a cross-sectional view of a conventional insulated wire perpendicular to the longitudinal direction.

Description of the symbols

100 insulated wire

110 conductor

120 coating layer

130 integral flame retardant layer

131 inner flame-retardant layer

132 outer flame retardant layer

130' semi-conducting layer

140 high electric insulation layer

150. 150a, 150b flame retardant layer

160 laminated structure

Detailed Description

The present inventors have studied the structure of an insulated wire that can achieve a reduction in diameter while achieving high insulation and high flame retardancy.

First, a conventional electric wire structure will be described, and a view of the electric wire structure in the embodiment of the present invention will be described. Fig. 4 is a cross-sectional view of a conventional insulated wire perpendicular to the longitudinal direction.

The insulated wire 200 of the conventional structure includes a conductor 210, an insulating layer 220 disposed on the outer periphery of the conductor 210, and a flame retardant layer 230 disposed on the outer periphery of the insulating layer 220 and containing a flame retardant.

In the insulated wire 200 having a conventional structure, an additive having (a certain degree of) flame retardancy (for example, an inorganic filler such as calcium carbonate or clay) is blended into the polymer composition forming the insulating layer 220 in order to impart a certain degree of flame retardancy to the insulating layer 220 itself.

The insulating property of the polymer composition forming the insulating layer 220 is lower than that of the base polymer of the polymer composition due to the blending of an additive having flame retardancy and the like. For example, when polyethylene is used as the matrix polymer of the polymer composition forming the insulating layer 220, 1 × 10, for example, can be obtained¹⁶Volume resistivity of the matrix polymer in the order of Ω cm. By blending an additive having flame retardancy or the like into the polymer composition, the volume resistivity of the polymer composition forming the insulating layer 220 is reduced to, for example, 1 × 10¹⁴In the order of magnitude of Ω cm.

The inventors of the present invention have studied thinning the flame retardant layer 230 in order to reduce the diameter of the insulated wire 200. However, if the flame retardant layer 230 is merely thinned (without changing the thickness of the insulating layer 220), high flame retardancy of the insulated wire 200 cannot be obtained.

Thus, thinning of the insulating layer 220 is studied. However, if only the insulating layer 220 is made thin, high insulation of the insulated wire 200 cannot be obtained. Therefore, it has been studied to reduce the thickness of the insulating layer 220 required to obtain a desired insulating property by suppressing the amount of additives having flame retardancy or the like added to the insulating layer 220 to make the insulating property of the polymer composition forming the insulating layer 220 close to the high insulating property of the matrix polymer. However, sufficient flame retardancy of the insulating layer 220 cannot be obtained by merely reducing the amount of additives or the like having flame retardancy to be added to the insulating layer 220.

Then, a new structure in which the insulating layer 220 is divided into a flame-retardant layer disposed on the inner side (conductor side) and containing an additive having flame retardancy and an insulating layer disposed on the outer side (opposite side to the conductor) and containing a suppressed amount of the additive having flame retardancy and the like has been studied. The insulating layer in which the amount of additives having flame retardancy and the like is suppressed is referred to as a "high-electric insulating layer". The flame-retardant layer disposed on the inner side with respect to the high-electric-insulation layer is referred to as an "inner flame-retardant layer", and the flame-retardant layer disposed on the outer side with respect to the high-electric-insulation layer is referred to as an "outer flame-retardant layer".

According to such a configuration, by using the high-voltage insulating layer in which the insulating property of the polymer composition is improved (the decrease in the insulating property is suppressed) by suppressing the blending amount of the flame retardant additive or the like, the thickness of the high-voltage insulating layer for obtaining a desired insulating property can be reduced. In addition, by disposing the inner flame-retardant layer and the outer flame-retardant layer, desired flame retardancy can be obtained. Further, as the thickness of the high-electric-power insulating layer which is easily combustible can be made thin, the thickness of the inner flame-retardant layer and the outer flame-retardant layer, that is, the thickness of the entire flame-retardant layer can be made thin.

The volume resistivity of the polymer composition forming the high-electric-insulation layer can be greatly increased to, for example, about 100 times as high as the volume resistivity of the original polymer composition forming the insulation layer 220 by suppressing the amount of additives having flame retardancy and the like to be blended. Therefore, it can be said that it is easier to make the insulating layer thinner than the flame-retardant layer by increasing the volume resistivity to obtain a desired insulation property.

The conductor generally has a stranded structure in which bare wires are stranded, and has irregularities on the surface. If the high-potential insulating layer is disposed directly above the conductor, the high-potential insulating layer is easily broken due to electric field concentration caused by irregularities on the surface of the conductor, and it is difficult to make the high-potential insulating layer thin. By disposing the inner flame-retardant layer directly above the conductor to cover the irregularities, the inner flame-retardant layer functions as an irregularity relaxing layer, and the high-electric-insulation layer disposed on the inner flame-retardant layer can be made thin.

Here, the following new structure was also studied: an insulating layer in which the amount of additives having flame retardancy and the like is suppressed is used, and a semiconductive layer containing a conductive agent is disposed on the inner side (conductor side) of the insulating layer and directly above the conductor. The insulating layer in which the amount of additives having flame retardancy and the like is suppressed is referred to as a "high-electric insulating layer".

With such a configuration, by using the high-voltage insulating layer having improved insulation properties (reduced insulation property degradation) while suppressing the amount of additives having flame retardancy and the like, the thickness of the high-voltage insulating layer for obtaining desired insulation properties can be reduced. The semiconductive layer can also serve as an irregularity relaxing layer by covering irregularities on the surface of the conductor, and thus the high-electric-insulation layer disposed on the semiconductive layer can be made thin. Further, as the high-electric-insulation layer which is easily combustible can be made thin, the thickness of the flame-retardant layer for obtaining desired flame retardancy can be made thin.

Thus, a wire structure capable of achieving high insulation and high flame retardancy and a reduction in diameter can be obtained.

As the small-diameter insulated wire preferably used for such a wire structure, for example, an insulated wire having an outer diameter (diameter) of 3mm or less or 7mm or less is assumed. The insulation of the insulated wire can be evaluated by, for example, a dc stability test as described later. The flame retardancy of the insulated wire can be evaluated by, for example, the VFT test and the VTFT test described below. The use of the insulated wire is not particularly limited, and examples thereof include railway vehicle use, automobile use, and medical use.

Next, embodiments of the present invention will be explained.

Embodiment mode 1

Referring to fig. 1, an insulated wire 100 according to an embodiment of the present invention is illustrated. Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction showing an example of the structure of an insulated wire 100.

< construction of insulated electric wire >

The insulated wire 100 includes a conductor 110 and a coating layer 120 disposed on the outer periphery of the conductor 110.

[ conductor ]

As the conductor 110, for example, a stranded wire obtained by twisting a plurality of bare wires (metal wires) can be used. As the bare wire, for example, in addition to a copper wire and a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like may be used, and a material plated with a metal such as tin or nickel on the outer periphery may be used. The outer diameter (diameter) of the conductor 110 is, for example, 0.70mm to 1.70 mm. The bare wire has an outer diameter (diameter) of, for example, 0.10mm to 0.30 mm. The material, structure, size, etc. of the conductor 110 may be appropriately selected according to the required characteristics of the conductor 110 in the insulated electric wire 100.

[ coating layer ]

The coating layer 120 has a laminated structure 160 in which an inner flame-retardant layer 131 disposed on the outer periphery of the conductor 110, a high-potential insulating layer 140 disposed on the outer periphery of the inner flame-retardant layer 131, and an outer flame-retardant layer 132 disposed on the outer periphery of the high-potential insulating layer 140 are laminated. The inner flame retardant layer 131 and the outer flame retardant layer 132 constitute an integrated flame retardant layer 130.

(inner flame-retardant layer)

The inner flame-retardant layer 131, that is, the flame-retardant layer 131 disposed on the inner side (conductor 110 side) of the high-electric-insulation layer 140 is formed of a polymer composition (a) containing a flame retardant. The inner flame-retardant layer 131 is formed by, for example, extruding the polymer composition (a) on the outer periphery of the conductor 110.

Examples of the matrix polymer used in the polymer composition (a) include polyolefin resins. As the polyolefin resin, for example, a polyethylene resin or the like can be used. Examples of the polyethylene resin include polyethylene such as Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), and High Density Polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and ethylene-glycidyl methacrylate copolymer. One kind of the polyolefin resin may be used alone, or two or more kinds may be used in combination.

The matrix polymer used in the polymer composition (a) preferably contains EVA, for example. EVA is preferred because it has a high filler acceptance, so that a flame retardant can be easily added, and the resin itself has a certain degree of flame retardancy.

As the flame retardant used in the polymer composition (a), a non-halogen flame retardant is preferable since no toxic gas is generated, and for example, a metal hydroxide can be preferably used. Examples of the metal hydroxide include magnesium hydroxide, aluminum hydroxide, calcium hydroxide, and metal hydroxides having nickel dissolved therein. One kind of the flame retardant may be used alone, or two or more kinds may be used in combination.

The flame retardant is preferably surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, a fatty acid salt such as a stearate, a fatty acid metal salt such as calcium stearate, or the like, from the viewpoint of controlling the mechanical properties (balance between tensile strength and elongation) of the inner flame retardant layer 131.

The amount of the flame retardant to be blended is preferably, for example, 100 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the base polymer. If the blending amount is less than 100 parts by mass, there is a fear that the desired high flame retardancy cannot be obtained. If the blending amount exceeds 250 parts by mass, there is a fear that the mechanical properties of the inner flame-retardant layer 131 are lowered and the elongation is lowered.

In order to improve flame retardancy and heat resistance, the inner flame retardant layer 131 is preferably composed of a crosslinked polymer composition (a). Examples of the crosslinking method include irradiation crosslinking, chemical crosslinking, and silane crosslinking. The polymer composition (A) may contain a crosslinking assistant or a crosslinking agent for satisfactory crosslinking. As described later, irradiation crosslinking is preferable for crosslinking of the high-potential insulating layer 140, and therefore, irradiation crosslinking of the inner flame-retardant layer 131 is performed simultaneously with irradiation crosslinking of the high-potential insulating layer 140, that is, in the same step as irradiation crosslinking of the high-potential insulating layer 140, which is efficient.

The inner flame-retardant layer 131 is, for example, a polymer composition (A) having 1X 10¹⁴An electrically insulating layer having a volume resistivity of the order of Ω cm (above). Note that when the inner flame-retardant layer 131 is composed of the crosslinked polymer composition (a), the volume resistivity of the polymer composition (a) shows the volume resistivity of the crosslinked polymer composition (a).

The polymer composition (a) may contain other additives such as carbon fiber, talc, clay, and the like as necessary within a range that does not impair the characteristics of the inner flame-retardant layer 131.

(high electric insulation layer)

The high electric insulation layer 140 is made of a material having a thickness of 1 × 10¹⁶Polymer group having volume resistivity of not less than Ω cmCompound (B) is formed. The high electric insulation layer 140 is formed, for example, by extruding the polymer composition (B) on the outer periphery of the inner flame retardant layer 131.

The matrix polymer used in the polymer composition (B) may have a volume resistivity of 1X 10¹⁶And polymers having an Ω cm or more, for example, polyolefin resins. As the polyolefin resin, for example, polyethylene such as LDPE, LLDPE, HDPE, etc. can be used. One kind of the polyolefin resin may be used alone, or two or more kinds may be used in combination.

The matrix polymer used in the polymer composition (B) preferably contains polyethylene, for example. Polyethylene is preferred because it can increase the volume resistivity by crosslinking. As the polyethylene, any of LDPE, LLDPE, and HDPE can be used. From the viewpoint of easy crosslinking, LDPE may be used.

In order to increase the volume resistivity, the high-electric-insulation layer 140 is preferably composed of the crosslinked polymer composition (B). Examples of the crosslinking method include irradiation crosslinking, chemical crosslinking, and silane crosslinking. The polymer composition (B) may contain a crosslinking assistant or a crosslinking agent for satisfactory crosslinking. However, from the viewpoint of not lowering the electrical insulation, it is preferable that irradiation crosslinking by adding an additive is not required.

Note that when the high-electric-insulation layer 140 is composed of the crosslinked polymer composition (B), the volume resistivity of the polymer composition (B) shows the volume resistivity of the crosslinked polymer composition (B).

From the viewpoint of suppressing the decrease in the volume resistivity, the polymer composition (B) preferably contains no additives as much as possible, but the volume resistivity may be maintained at 1 × 10¹⁶In the range of not less than Ω cm, various additives are contained as required. Examples of the additive include an antioxidant and a copper inhibitor.

From the viewpoint of suppressing the decrease in the volume resistivity of the polymer composition (B), it is preferable that the polymer composition (B) does not contain inorganic fillers such as calcium carbonate, clay, talc, silica, wollastonite (wollastonite), zeolite, diatomaceous earth, silica sand, pumice powder, slate powder, alumina, aluminum sulfate, palladium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and flame retardants such as metal hydroxides.

(outer flame-retardant layer)

The outer flame-retardant layer 132, that is, the flame-retardant layer 132 disposed on the outer side (the side opposite to the conductor 110) with respect to the high-electric-insulation layer 140 is formed of a polymer composition (C) containing a flame retardant. The outer flame retardant layer 132 is formed, for example, by extruding the polymer composition (C) on the outer periphery of the high electric insulation layer 140.

The base polymer used in the polymer composition (C) may be, for example, the same as the base polymer of the polymer composition (a) forming the inner flame-retardant layer 131, and preferably, an EVA-containing material, for example. The base polymer of the polymer composition (C) forming the outer flame-retardant layer 132 may be the same as or different from the base polymer of the polymer composition (a) forming the inner flame-retardant layer 131.

Examples of the flame retardant used in the polymer composition (C) include the same flame retardants as those of the polymer composition (a) forming the inner flame-retardant layer 131, and preferably include, for example, metal hydroxides. The amount of the flame retardant to be blended may be, for example, the same as the amount of the flame retardant to be blended in the polymer composition (a) forming the inner flame-retardant layer 131. The flame retardant of the polymer composition (C) forming the outer flame-retardant layer 132 may be the same as or different from the flame retardant of the polymer composition (a) forming the inner flame-retardant layer 131. The same applies to the amount of the flame retardant, and the polymer composition (C) may be the same as or different from the polymer composition (A).

In order to improve flame retardancy and heat resistance, the outer flame retardant layer 132 is preferably composed of a crosslinked polymer composition (C). Examples of the crosslinking method include irradiation crosslinking, chemical crosslinking, and silane crosslinking. The polymer composition (C) may contain a crosslinking assistant or a crosslinking agent for satisfactory crosslinking. Since irradiation crosslinking is preferable for crosslinking of the high-potential insulating layer 140, irradiation crosslinking of the outer flame-retardant layer 132 is performed simultaneously with irradiation crosslinking of the high-potential insulating layer 140, that is, in the same step as irradiation crosslinking of the high-potential insulating layer 140, which is efficient.

The outer flame-retardant layer 132 is, for example, a polymer composition (C) having 1X 10¹⁴An electrically insulating layer having a volume resistivity of the order of Ω cm (above). Note that when the outer flame-retardant layer 132 is composed of the crosslinked polymer composition (C), the volume resistivity of the polymer composition (C) shows the volume resistivity of the crosslinked polymer composition (C).

The polymer composition (C) may contain other additives such as carbon fiber, talc, clay, and the like as necessary within a range that does not impair the characteristics of the outer flame-retardant layer 132.

(laminated Structure of coating layer)

Next, the laminated structure 160 of the inner flame-retardant layer 131, the high-electric-insulation layer 140, and the outer flame-retardant layer 132 in the coating layer 120 will be further described.

The high-potential insulating layer 140 is configured to share preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more of the voltage applied in the thickness direction of the laminated structure 160.

Thereby, the voltage applied to the inner flame-retardant layer 131 and the outer flame-retardant layer 132, respectively, can be suppressed to be relatively low. The inner flame-retardant layer 131 and the outer flame-retardant layer 132 contain a large amount of additives such as flame retardants, and the insulation properties are more likely to be deteriorated than those of the high-electric-insulation layer 140. By suppressing the voltage applied to the inner flame-retardant layer 131 and the outer flame-retardant layer 132 to be low, high insulation of the insulated wire 100 can be obtained.

The high-electric-insulation layer 140 is thinner than at least one of the inner flame-retardant layer 131 and the outer flame-retardant layer 132.

This makes it easy to suppress the combustibility of the laminated structure 160 due to the high-electric-insulation layer 140 by the inner flame-retardant layer 131 and the outer flame-retardant layer 132, thereby achieving high flame retardancy, and also makes the laminated structure 160 thin, thereby reducing the diameter of the insulated wire 100. As the high-electric-insulation layer 140 that is easily combustible is made thinner, the entire flame-retardant layer 130 (the inner flame-retardant layer 131 and the outer flame-retardant layer 132) can be made thinner.

In order to allow the high electric insulation layer 140 to share more than 80% of the voltage applied to the laminated structure 160, and to allow the high electric insulation layer 140 to share the voltageThe high-electric-insulation layer 140 is thinner than at least one of the inner flame-retardant layer 131 and the outer flame-retardant layer 132, and the volume resistivity of the polymer composition (B) forming the high-electric-insulation layer 140 is preferably set to 1 × 10¹⁶Omega cm or more, more preferably 1X 10¹⁷Omega cm or more. The upper limit of the volume resistivity of the polymer composition (B) is not particularly limited.

In order to allow the high electric insulation layer 140 to share 80% or more of the voltage applied to the laminated structure 160 and to make the high electric insulation layer 140 thinner than at least one of the inner flame retardant layer 131 and the outer flame retardant layer 132, the volume resistivity of the polymer composition (B) forming the high electric insulation layer 140 is preferably 10 times or more, more preferably 50 times or more, and still more preferably 100 times or more the volume resistivity of each of the polymer composition (a) forming the inner flame retardant layer 131 and the polymer composition (C) forming the outer flame retardant layer 132.

From the viewpoint of achieving high flame retardancy and reduction in diameter, the thickness of the high-electric-power insulating layer 140 is more preferably 1/2 or less of the thickness of the entire flame-retardant layer 130 (the sum of the thickness of the inner flame-retardant layer 131 and the thickness of the outer flame-retardant layer 132), and still more preferably 1/2 or less of at least one of the thickness of the inner flame-retardant layer 131 and the thickness of the outer flame-retardant layer 132.

From the viewpoint of the small diameter insulated wire, the outer diameter (diameter) of the insulated wire 100 is preferably 3mm or less, more preferably 2.5mm or less, and the rated voltage (ac) of the insulated wire 100 is, for example, 660V or less (600V as an example). Further, the small diameter also has an advantage that the inner flame-retardant layer 131, the high-potential insulating layer 140, and the outer flame-retardant layer 132 are easily crosslinked at the same time by irradiation crosslinking.

The upper limit of the thickness of the high-voltage insulating layer 140 is, for example, preferably 0.2mm or less, and more preferably 0.15mm or less, from the viewpoint of reducing the diameter. The lower limit of the thickness of the high-potential insulating layer 140 is not particularly limited as long as the desired insulating property can be obtained, and is preferably 0.05mm or more, for example, from the viewpoint of improving the uniformity of the thickness of the high-potential insulating layer 140 and obtaining stable insulating property.

The flame retardancy of the insulated wire 100 is obtained by setting the entire flame retardant layer 130 to a sufficient thickness in a balance that can suppress the burning of the high-electric-insulation layer 140. Therefore, the thicknesses of the inner flame-retardant layer 131 and the outer flame-retardant layer 132 may be appropriately changed as needed in balance with the overall flame-retardant layer 130 having a sufficient thickness. For example, the outer flame-retardant layer 132 may be thicker than the inner flame-retardant layer 131, and the inner flame-retardant layer 131 and the outer flame-retardant layer 132 may be made to have the same thickness. However, from the viewpoint of making the flame retardancy higher, the outer flame-retardant layer 132 is preferably thicker than the inner flame-retardant layer 131. The thickness of the entire flame retardant layer 130 is preferably 2 times or more of the thickness of the high-voltage insulating layer 140, for example.

The upper limit of the thickness of the entire flame-retardant layer 130 is preferably 0.4mm or less, for example, from the viewpoint of reducing the diameter. The lower limit of the thickness of the entire flame retardant layer 130 is not particularly limited as long as it is a thickness that can provide flame retardancy according to the thickness of the high-voltage insulating layer 140, but is preferably 0.2mm or more from the viewpoint of, for example, obtaining stable flame retardancy.

The inner flame retardant layer 131 is disposed directly above (in contact with) the conductor 110, and covers the irregularities on the surface of the conductor 110, thereby functioning as an irregularity moderating layer that suppresses electric field concentration. This can reduce the thickness of the high-potential insulating layer 140 disposed on the inner flame-retardant layer 131. The thickness of the inner flame-retardant layer 131 is represented by the thickness of the convex portion (thinnest portion) of the twist on the surface of the conductor 110, that is, the thickness outside the outer diameter of the conductor 110.

The upper limit of the thickness of the inner flame-retardant layer 131 is not particularly limited, and may be appropriately selected within the range of the thickness of the entire flame-retardant layer 130. The lower limit of the thickness of the inner flame-retardant layer 131 is not particularly limited, but is preferably 0.05mm or more, for example, from the viewpoint of sufficiently covering the irregularities on the surface of the conductor 110, improving the uniformity of the thickness of the inner flame-retardant layer 131, and obtaining stable flame retardancy.

The upper limit of the thickness of the outer flame-retardant layer 132 is not particularly limited, and may be appropriately selected within the range of the thickness of the entire flame-retardant layer 130. The lower limit of the thickness of the outer flame-retardant layer 132 is not particularly limited, but is preferably 0.05mm or more, for example, from the viewpoint of improving the uniformity of the thickness of the outer flame-retardant layer 132 and obtaining stable flame retardancy.

From the viewpoint of reducing the diameter, it is preferable that no other layer is disposed between the inner flame retardant layer 131 and the high-potential insulating layer 140. That is, the high-potential insulating layer 140 is preferably disposed directly above the inner flame-retardant layer 131 (in contact with the inner flame-retardant layer 131). It is preferable that no other layer is disposed between the high-electric-insulation layer 140 and the outer flame-retardant layer 132. That is, the outer flame retardant layer 132 is preferably disposed directly above the high-potential insulating layer 140 (in contact with the high-potential insulating layer 140). Further, it is preferable that no other layer is disposed on the outer periphery of the outer flame-retardant layer 132. That is, the outer flame retardant layer 132 is preferably an outermost layer of the coating layer 120, that is, the insulated wire 100.

The inner flame retardant layer 131, the high electric insulation layer 140, and the outer flame retardant layer 132 are preferably formed on the outer circumference of the conductor 110 by simultaneous extrusion. This can prevent dust in the atmosphere, which causes electric field concentration, from adhering to the interface between the inner flame retardant layer 131 and the high-potential insulating layer 140 and the interface between the high-potential insulating layer 140 and the outer flame retardant layer 132.

The inner flame-retardant layer 131 may have a laminated structure of a plurality of flame-retardant layers (sub flame-retardant layers) as needed. The high-potential insulating layer 140 may have a laminated structure of a plurality of insulating layers (sub-insulating layers) as necessary. The outer flame-retardant layer 132 may have a laminated structure of a plurality of flame-retardant layers (sub flame-retardant layers) as needed.

Embodiment mode 2

Next, referring to fig. 2, an insulated electric wire 100 according to another embodiment of the present invention is explained. Fig. 2 is a cross-sectional view perpendicular to the longitudinal direction showing another example of the structure of the insulated wire 100.

< construction of insulated electric wire >

[ conductor ]

As the conductor 110, for example, a stranded wire obtained by twisting a plurality of bare wires (metal wires) can be used. As the bare wire, for example, in addition to a copper wire and a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like may be used, and a material plated with a metal such as tin or nickel on the outer periphery may be used. The outer diameter (diameter) of the conductor 110 is, for example, 1mm to 6 mm. The bare wire has an outer diameter (diameter) of, for example, 0.1mm to 0.5 mm. The material, structure, size, etc. of the conductor 110 may be appropriately selected according to the required characteristics of the conductor 110 in the insulated electric wire 100.

[ coating layer ]

The coating layer 120 has a laminated structure 160 in which a semiconductive layer 130 'disposed on the outer periphery of the conductor 110, a high-electric-power insulating layer 140 disposed on the outer periphery of the semiconductive layer 130', and a flame retardant layer 150 disposed on the outer periphery of the high-electric-power insulating layer 140 are laminated.

(semi-conductive layer)

The semiconductive layer 130' is made of a conductive material and has a thickness of 1 × 10⁹A volume resistivity of not more than Ω cm. The semiconductive layer 130 'is formed, for example, by extruding the polymer composition (a') on the outer circumference of the conductor 110.

Examples of the matrix polymer used in the polymer composition (a') include polyolefin resins. As the polyolefin resin, for example, a polyethylene resin or the like can be used. Examples of the polyethylene resin include polyethylene such as Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), and High Density Polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-glycidyl methacrylate copolymer, ethylene-butene-hexene terpolymer, ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer (EOR), ethylene-propylene copolymer (EPR), ethylene-styrene copolymer, styrene-butadiene copolymer, and modified with an acid such as maleic acid. One kind of the polyolefin resin may be used alone, or two or more kinds may be used in combination.

The matrix polymer used in the polymer composition (A') preferably contains EVA, for example. EVA is preferred because it has a high filler acceptance, so that it is easy to add a conductive agent, and the resin itself has a certain degree of flame retardancy. The VA content of EVA is preferably 15% or more, for example, from the viewpoint of filler acceptance, and is preferably 80% or less, for example, from the viewpoint of manufacturability such as adhesion.

Examples of the conductive agent used in the polymer composition (a') include carbon black and carbon nanotubes, and carbon black is preferably used. As the carbon black, for example, furnace black, channel black, acetylene black, thermal black, or the like can be used, and acetylene black is preferably used in order to impart high conductivity with a small amount. One kind of the conductive agent may be used alone, or two or more kinds may be used in combination.

The amount of the conductive agent is such that the volume resistivity of the polymer composition (A ') forming the semiconductive layer 130' is 1X 10⁹The amount of Ω cm or less is not particularly limited. For example, the amount of carbon black blended is 30 parts by mass or more per 100 parts by mass of the matrix polymer. For example, since there is a possibility that the mechanical properties of the semiconductive layer 130' are lowered and the elongation is lowered, it is preferable that the amount of the conductive agent is not excessively increased. For example, the amount of carbon black blended is 150 parts by mass or less per 100 parts by mass of the matrix polymer.

In order to improve heat resistance, the semiconductive layer 130 'is preferably composed of the crosslinked polymer composition (a'). Examples of the crosslinking method include irradiation crosslinking, chemical crosslinking, and silane crosslinking. For good crosslinking, the polymer composition (A') may contain a crosslinking assistant or a crosslinking agent. As described later, since the crosslinking of the high-electric-insulation layer 140 is preferably irradiation crosslinking, it is effective to perform irradiation crosslinking of the semiconductive layer 130' simultaneously with irradiation crosslinking of the high-electric-insulation layer 140, that is, in the same step as the irradiation crosslinking of the high-electric-insulation layer 140.

Note that, when the semiconductive layer 130 'is constituted of the crosslinked polymer composition (a'), the volume resistivity of the polymer composition (a ') shows the volume resistivity of the crosslinked polymer composition (a').

The polymer composition (a ') may contain other additives such as flame retardants, antioxidants, copper inhibitors, reinforcing agents, process oils, and the like, as necessary, within a range that does not impair the characteristics of the semiconductive layer 130'.

(high electric insulation layer)

The high electric insulation layer 140 is made of a material having a thickness of 1 × 10¹⁶A volume resistivity of not less than Ω cm. The high-electric-insulation layer 140 is formed, for example, by extruding the polymer composition (B ') on the outer periphery of the semiconductive layer 130'.

The matrix polymer used in the polymer composition (B') may have a volume resistivity of 1X 10¹⁶And polymers having an Ω cm or more, for example, polyolefin resins. As the polyolefin resin, for example, polyethylene such as LDPE, LLDPE, HDPE, etc. can be used. One kind of the polyolefin resin may be used alone, or two or more kinds may be used in combination.

The matrix polymer used in the polymer composition (B') preferably contains polyethylene, for example. Polyethylene is preferred because it can increase the volume resistivity by crosslinking. As the polyethylene, any of LDPE, LLDPE, and HDPE can be used. From the viewpoint of easy crosslinking, LDPE may be used.

In order to increase the volume resistivity, the high-electric-insulation layer 140 is preferably composed of the crosslinked polymer composition (B'). Examples of the crosslinking method include irradiation crosslinking, chemical crosslinking, and silane crosslinking. For good crosslinking, the polymer composition (B') may contain a crosslinking assistant or a crosslinking agent. However, from the viewpoint of not lowering the electrical insulation, it is preferable that irradiation crosslinking by adding an additive is not required.

Note that when the high-electric-insulation layer 140 is composed of the crosslinked polymer composition (B '), the volume resistivity of the polymer composition (B ') shows the volume resistivity of the crosslinked polymer composition (B ').

From the viewpoint of suppressing the decrease in the volume resistivity, the polymer composition (B') preferably contains no additives as much as possible, but the volume resistivity may be maintained at 1 × 10¹⁶In the range of not less than Ω cm, various additives are added according to needAdding the agent. Examples of the additive include an antioxidant and a copper inhibitor.

From the viewpoint of suppressing the decrease in the volume resistivity of the polymer composition (B '), it is preferable that the polymer composition (B') does not contain, for example, inorganic fillers such as calcium carbonate, clay, talc, silica, wollastonite (wollastonite), zeolite, diatomaceous earth, silica sand, pumice powder, slate powder, alumina, aluminum sulfate, palladium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and flame retardants such as metal hydroxides.

(flame retardant layer)

The flame-retardant layer 150 is formed, for example, from a polymer composition (C') containing a flame retardant. The flame retardant layer 150 is formed, for example, by extruding the polymer composition (C') on the outer circumference of the high electric insulation layer 140.

Examples of the matrix polymer used in the polymer composition (C') include polyolefin resins. As the polyolefin resin, for example, a polyethylene resin or the like can be used. Examples of the polyethylene resin include polyethylene such as LDPE, LLDPE, and HDPE, EVA, ethylene-ethyl acrylate copolymers, ethylene-methyl acrylate copolymers, ethylene-glycidyl methacrylate copolymers, ethylene-butene-hexene terpolymers, ethylene-propylene-diene terpolymers (EPDM), ethylene-octene copolymers (EOR), ethylene-propylene copolymers (EPR), ethylene-styrene copolymers, styrene-butadiene copolymers, and those obtained by modifying these with an acid such as maleic acid. One kind of the polyolefin resin may be used alone, or two or more kinds may be used in combination.

The matrix polymer used in the polymer composition (C') preferably contains EVA, for example. EVA is preferred because it has a high filler acceptance, so that a flame retardant can be easily added, and the resin itself has a certain degree of flame retardancy. The VA content of EVA is preferably 15% or more, for example, from the viewpoint of filler receptivity, and is preferably 60% or less, for example, from the viewpoint of suppressing a decrease in low-temperature properties.

The flame retardant used in the polymer composition (C') is preferably a non-halogen flame retardant since no toxic gas is generated, and for example, a metal hydroxide can be preferably used. Examples of the metal hydroxide include magnesium hydroxide, aluminum hydroxide, calcium hydroxide, and metal hydroxides in which nickel is dissolved. One kind of the flame retardant may be used alone, or two or more kinds may be used in combination.

The flame retardant is preferably surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, a fatty acid salt such as a stearate, a fatty acid metal salt such as calcium stearate, or the like, from the viewpoint of controlling the mechanical properties (balance between tensile strength and elongation) of the flame retardant layer 150.

The amount of the flame retardant to be blended is preferably, for example, 100 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the base polymer. If the blending amount is less than 100 parts by mass, there is a fear that the desired high flame retardancy cannot be obtained. If the blending amount exceeds 250 parts by mass, there is a fear that the mechanical properties of the flame retardant layer 150 are lowered and the elongation is lowered.

In order to improve flame retardancy and heat resistance, the flame retardant layer 150 is preferably composed of the crosslinked polymer composition (C'). Examples of the crosslinking method include irradiation crosslinking, chemical crosslinking, and silane crosslinking. For good crosslinking, the polymer composition (C') may contain a crosslinking assistant or a crosslinking agent. Since irradiation crosslinking is preferable for crosslinking of the high-potential insulating layer 140, irradiation crosslinking of the flame retardant layer 150 is performed simultaneously with irradiation crosslinking of the high-potential insulating layer 140, that is, in the same step as irradiation crosslinking of the high-potential insulating layer 140, which is efficient.

The flame-retardant layer 150 is, for example, a polymer composition (C') having 1X 10¹⁴Of the order of Ω cm (1X 10)¹³Omega cm or more or 1X 10¹⁴Omega cm or more) volume resistivity. Note that when the flame-retardant layer 150 is composed of the crosslinked polymer composition (C '), the volume resistivity of the polymer composition (C ') shows the volume resistivity of the crosslinked polymer composition (C ').

The polymer composition (C') may contain other additives such as an antioxidant, a copper harm inhibitor, a lubricant, an inorganic filler, a compatibilizer, a stabilizer, carbon black, a colorant, and the like as necessary within a range that does not impair the characteristics of the flame-retardant layer 150.

(laminated Structure of coating layer)

Next, the laminated structure 160 of the semiconductive layer 130', the high-electric insulation layer 140, and the flame retardant layer 150 in the coating layer 120 will be further described.

The high electric insulation layer 140 is configured to be thinner than the flame retardant layer 150. This makes it easy to suppress the combustibility of the laminated structure 160 due to the high-voltage insulating layer 140 by the flame-retardant layer 150, thereby achieving high flame retardancy, and also makes the laminated structure 160 thin, thereby reducing the diameter of the insulated wire 100. The flame retardant layer 150 can be made thinner as the high-voltage insulating layer 140, which is easily combustible, is made thinner.

In order to obtain high insulation and to make the high-electric-insulation layer thin, the volume resistivity of the polymer composition (B') forming the high-electric-insulation layer 140 is preferably set to 1 × 10¹⁶Omega cm or more, more preferably 1X 10¹⁷Omega cm or more. The upper limit of the volume resistivity of the polymer composition (B') is not particularly limited.

From the viewpoint of achieving high flame retardancy and reduction in diameter, the thickness of the high-electric-power insulating layer 140 is more preferably 1/2 or less of the thickness of the flame-retardant layer 150, and still more preferably 1/3 or less of the thickness of the flame-retardant layer 150.

The semiconductive layer 130' is disposed directly above (in contact with) the conductor 110 and covers irregularities on the surface of the conductor 110, thereby functioning as an irregularity moderating layer that suppresses electric field concentration. This can make the high-voltage insulating layer 140 disposed on the semiconductive layer 130' thin. In order to improve the conductivity of the semiconductive layer 130 ', the volume resistivity of the polymer composition (a ') forming the semiconductive layer 130 ' is preferably set to 1 × 10⁹Omega cm or less. The lower limit of the volume resistivity of the polymer composition (a') is not particularly limited.

The semiconductive layer 130 'may cover the irregularities on the surface of the conductor 110 (i.e., fill the recesses and smooth the surface), and the thickness of the semiconductive layer 130' may be as thin as desired. Here, the thickness of the semiconductive layer 130' is represented by the thickness on the convex portion (the thinnest portion) of the twist on the surface of the conductor 110, that is, the thickness outside the outer diameter of the conductor 110.

If the semiconductive layer 130' is too thick, the diameter reduction and flame retardancy are inhibited. Therefore, the thickness of the semiconductive layer 130' is preferably smaller than that of the flame-retardant layer 150, more preferably 1/2 or less of the thickness of the flame-retardant layer 150, and still more preferably 1/3 or less of the thickness of the flame-retardant layer 150.

From the viewpoint of achieving high flame retardancy and reducing the diameter, the thickness of the laminated portion of the semiconductive layer 130 'and the high-electric-insulation layer 140, that is, the sum of the thickness of the semiconductive layer 130' and the thickness of the high-electric-insulation layer 140 is more preferably smaller than the thickness of the flame-retardant layer 150, and still more preferably equal to or less than 2/3 of the thickness of the flame-retardant layer 150.

The high-potential insulating layer 140 is preferably configured to share 80% or more, more preferably 90% or more, and still more preferably 95% or more of the voltage applied in the thickness direction of the laminated portion of the high-potential insulating layer 140 and the flame retardant layer 150.

Thereby, the voltage applied to the flame retardant layer 150 can be suppressed to be relatively low. The flame retardant layer 150 contains a large amount of additives such as a flame retardant, and the insulation property is more likely to be deteriorated than that of the high-electric-insulation layer 140. By suppressing the voltage applied to the flame retardant layer 150 to be low, high insulation of the insulated wire 100 can be obtained.

In order to allow the high-potential insulating layer 140 to share 80% or more of the voltage applied to the laminated portion of the high-potential insulating layer 140 and the flame retardant layer 150 and to make the high-potential insulating layer 140 thin, the volume resistivity of the polymer composition (B') forming the high-potential insulating layer 140 is preferably 1 × 10¹⁶Omega cm or more, more preferably 1X 10¹⁷Omega cm or more.

In order to allow the high-potential insulating layer 140 to share 80% or more of the voltage applied to the laminated portion of the high-potential insulating layer 140 and the flame retardant layer 150 and to make the high-potential insulating layer 140 thin, the volume resistivity of the polymer composition (B ') forming the high-potential insulating layer 140 is preferably 10 times or more, more preferably 50 times or more, and still more preferably 100 times or more the volume resistivity of the polymer composition (C') forming the flame retardant layer 150.

From the viewpoint of the insulated wire having a small diameter, the outer diameter (diameter) of the insulated wire 100 is preferably 7mm or less. The rated voltage (ac) of the insulated wire 100 is 3600V or less, for example. The small diameter also has an advantage that the semiconductive layer 130', the high-electric-insulation layer 140, and the flame-retardant layer 150 can be easily crosslinked at the same time by irradiation crosslinking.

The upper limit of the thickness of the semiconductive layer 130' (the thickness of the thinnest portion on the projection of the twist seam on the surface of the conductor 110) is preferably 0.10mm or less, for example, from the viewpoint of reducing the diameter. The lower limit of the thickness of the semiconductive layer 130 'is not particularly limited as long as it can cover the irregularities on the surface of the conductor 110, and is preferably 0.05mm or more, for example, from the viewpoint of improving the uniformity of the thickness of the semiconductive layer 130' and obtaining stable withstand voltage characteristics. The thickness of the portion of the recess that fills the recess, which is the twist seam on the surface of the conductor 110, is preferably equal to or greater than 1/2, which is the outer diameter of the bare wire.

The upper limit of the thickness of the high-voltage insulating layer 140 is, for example, preferably 0.15mm or less, and more preferably 0.10mm or less, from the viewpoint of reducing the diameter. The lower limit of the thickness of the high-potential insulating layer 140 is not particularly limited as long as the desired insulating property can be obtained, and is preferably 0.05mm or more, for example, from the viewpoint of improving the uniformity of the thickness of the high-potential insulating layer 140 and obtaining a stable insulating property.

The upper limit of the thickness of the flame retardant layer 150 is preferably 0.30mm or less, for example, from the viewpoint of reducing the diameter. The lower limit of the thickness of the flame retardant layer 150 is not particularly limited as long as flame retardancy can be obtained from the thickness of the high-electric-insulation layer 140 (and the semiconductive layer 130'), but is preferably 0.10mm or more, for example, from the viewpoint of improving the uniformity of the thickness of the flame retardant layer 150 and obtaining stable flame retardancy.

From the viewpoint of reducing the diameter, it is preferable that no other layer is disposed between the semiconductive layer 130' and the high-electric-insulation layer 140. That is, the high-electric-insulation layer 140 is preferably disposed directly above (in contact with) the semiconductive layer 130'. In addition, it is preferable that no other layer is disposed between the high electric insulation layer 140 and the flame retardant layer 150. That is, the flame retardant layer 150 is preferably disposed directly above the high-potential insulating layer 140 (in contact with the high-potential insulating layer 140). Further, it is preferable that no other layer is disposed on the outer periphery of the flame retardant layer 150. That is, the flame retardant layer 150 is preferably the outermost layer of the coating layer 120, that is, the insulated wire 100.

The semiconductive layer 130', the high-electric insulation layer 140, and the flame retardant layer 150 are preferably formed on the outer circumference of the conductor 110 by simultaneous extrusion. This can prevent dust in the atmosphere, which causes electric field concentration, from adhering to the interface between the semiconductive layer 130' and the high-potential insulating layer 140 and the interface between the high-potential insulating layer 140 and the flame retardant layer 150.

The semiconductive layer 130' may have a laminated structure of a plurality of semiconductive layers (sub-semiconductive layers) as needed. The high-potential insulating layer 140 may have a laminated structure of a plurality of insulating layers (sub-insulating layers) as necessary. The flame-retardant layer 150 may have a laminated structure of a plurality of flame-retardant layers (sub flame-retardant layers) as needed.

As described above, according to the present embodiment, the insulated wire can be made smaller while obtaining high insulation and high flame retardancy.

The insulated wire according to the embodiment is not limited to being used as a single insulated wire, and may be used for a core of a cable or the like, or may be used in combination with other members as necessary.

< other embodiment of the present invention >

The two embodiments of the present invention have been specifically described above by way of example, but the present invention is not limited to the above embodiments, and can be appropriately modified within a range not departing from the gist thereof. For example, other embodiments as described below are also possible.

Referring to fig. 3, an insulated wire 100 according to other embodiments is illustrated. Fig. 3 is a cross-sectional view perpendicular to the longitudinal direction showing an example of the structure of the insulated electric wire 100 according to another embodiment.

In another embodiment, the coating layer 120 disposed on the outer periphery of the conductor 110 has a laminated structure 160 in which a semiconductive layer 130 ', a flame-retardant layer 150a disposed on the outer periphery of the semiconductive layer 130 ', a high-voltage insulating layer 140 disposed on the outer periphery of the flame-retardant layer 150a (disposed on the outer periphery of the semiconductive layer 130 ' with the flame-retardant layer 150a interposed therebetween), and a flame-retardant layer 150b disposed on the outer periphery of the high-voltage insulating layer 140 are laminated. Flame retardant layer 150a and flame retardant layer 150b comprise integral flame retardant layer 150.

That is, in another embodiment, the flame retardant layer 150 includes a flame retardant layer 150a disposed on the inner side (conductor 110 side) of the high-electric-property insulating layer 140 in addition to a flame retardant layer 150b disposed on the outer side (opposite side to the conductor 110) of the high-electric-property insulating layer 140. The flame retardant layer 150a is formed of a polymer composition containing a flame retardant, as in the flame retardant layer 150b, and is formed, for example, by extruding the polymer composition onto the outer periphery of the semiconductive layer 130'. The flame retardant layer 150 having such a configuration may be provided as necessary, for example, to further improve flame retardancy.

In this way, the flame retardant layer 150 may be disposed only on the outer side of the high-voltage insulating layer 140, or may be disposed on both the outer side and the inner side of the high-voltage insulating layer 140. However, in order to improve the flame retardancy of the insulated wire 100, the flame retardant layer 150 is preferably disposed at least on the outer side (on the outer periphery) of the high-electric-insulation layer 140.

Examples

Next, the present invention will be described in further detail based on examples thereof, but the present invention is not limited to these examples.

[ production of insulated wire ]

(example 1, example 2 and comparative examples 1 to 4)

Insulated wires of example 1 and example 2 and comparative examples 1 to 4 were produced as follows.

A polymer composition (A) for forming an inner flame-retardant layer, a polymer composition (B) for forming a high-electric-insulation layer, and a polymer composition (C) for forming an outer flame-retardant layer were prepared. As the polymer composition (a) forming the inner flame-retardant layer and the polymer composition (C) forming the outer flame-retardant layer, a common polymer composition was prepared. As the polymer composition (B) for forming the high-electric-insulation layer, three polymer compositions (composition 1 to composition 3) having different volume resistivities were prepared according to the difference in volume resistivity of the high-electric-insulation layer of each sample. The compounding ratios of the polymer compositions (a) and (C) are shown in table 1, and the compounding ratio of the polymer composition (B) is shown in table 2.

[ Table 1]

[ Table 2]

As a conductor, a conductor having an outer diameter of 1.23mm (a conductor obtained by stranding 37 bare tin-plated copper wires having an outer diameter of 0.18 mm) was prepared. On the outer periphery of the conductor, the polymer composition (a), the polymer composition (B), and the polymer composition (C) are extruded simultaneously, and crosslinked by electron ray irradiation, thereby forming an inner flame-retardant layer, a high-electric insulation layer, and an outer flame-retardant layer.

The insulated wires of examples 1 and 2 and comparative examples 1 to 4 were different in the volume resistivity of the high-electric-insulation layer, that is, the blending of the polymer composition (B). In addition, the thickness of the outer flame-retardant layer and the high-electric-insulation layer are made different. The volume resistivity of the inner flame-retardant layer and the outer flame-retardant layer were the same, and were constant in the insulated wires of example 1, example 2, and comparative examples 1 to 4. The thickness of the inner flame-retardant layer is set to be constant.

As the configurations of the insulated wires of examples 1 and 2 and comparative examples 1 to 4, the volume resistivity of the polymer composition forming the flame-retardant layer (volume resistivity of the flame-retardant layer), the volume resistivity of the polymer composition forming the high-electric-insulation layer (volume resistivity of the high-electric-insulation layer), the thickness of the high-electric-insulation layer, the thickness of the inner flame-retardant layer, and the thickness of the outer flame-retardant layer are shown in table 3.

Table 3 shows the voltage share ratio of the high-electric-insulation layer in the laminated structure of the inner flame-retardant layer, the high-electric-insulation layer, and the outer flame-retardant layer, that is, the ratio of the electric resistance of the high-electric-insulation layer to the sum of the electric resistance of the inner flame-retardant layer, the electric resistance of the high-electric-insulation layer, and the electric resistance of the outer flame-retardant layer in the thickness direction of the laminated structure.

[ Table 3]

(examples 3 to 5 and comparative examples 5 to 7)

Insulated wires having a laminated structure shown in fig. 2 were produced as examples 3 to 5 and comparative examples 5 to 7 in the following manner.

A semiconductive layer-forming polymer composition (A '), a high-electric insulation layer-forming polymer composition (B '), and a flame-retardant layer-forming polymer composition (C ') were prepared. The compounding ratios of the polymer compositions (A ') to (C') are shown in tables 4 to 6, respectively.

[ Table 4]

[ Table 5]

[ Table 6]

As a conductor, a conductor having an outer diameter of 1.23mm (a conductor obtained by stranding 37 bare tin-plated copper wires having an outer diameter of 0.18 mm) was prepared. The polymer composition (a '), the polymer composition (B ') and the polymer composition (C ') are simultaneously extruded on the outer periphery of the conductor, and crosslinked by electron beam irradiation to form a semiconductive layer, a high-electric insulation layer and a flame-retardant layer, thereby producing an insulated wire.

In the insulated wires of examples 3 to 5 and comparative examples 5 to 7, the thicknesses of the semiconductive layer, the high-electric-insulation layer, and the flame-retardant layer were varied. In comparative example 5, no semiconductive layer was formed. The thickness of each layer and the total coating thickness are shown in table 7.

[ Table 7]

[ evaluation of insulated wire ]

The insulated wires of examples 1 and 2 and comparative examples 1 to 4 were evaluated for insulation (electrical characteristics) and flame retardancy as follows. The evaluation results are shown in table 3. The insulated wires of examples 3 to 5 and comparative examples 5 to 7 were evaluated for insulation (electrical characteristics) and flame retardancy as follows. The evaluation results are shown in table 7.

(DC stability test)

The electrical characteristics of the insulated wire, i.e., the insulation reliability, were evaluated by a dc stability test in which 300V dc power was applied to 85 ℃ and 3% NaCl aqueous solution according to EN50305.6.7. The case where 10 days did not short circuit, that is, the time taken until short circuit was 240 hours or longer was regarded as pass (o), and the case where short circuit occurred in less than 10 days, that is, the case where the time taken until short circuit was less than 240 hours was regarded as fail (x).

(flame retardancy)

The flame retardancy of the insulated wire was evaluated by the vertical flame test (VFT test and VTFT test) shown below.

The VFT test was carried out according to the Vertical flame test for single insulated wires or cables as specified in EN 60332-1-2. Specifically, an insulated wire having a length of 600mm was held vertically, and a flame was brought into contact with the insulated wire for 60 seconds. After removing the flame, the flame was extinguished within 30 seconds and designated as acceptable with a margin (. circleincircle.), the flame was extinguished within 60 seconds and designated as acceptable (. largecircle.), and the flame was not extinguished within 60 seconds and designated as unacceptable (. largecircle.).

The VTFT test was carried out according to the multiple cable vertical burn test (Flame propagation (bundled cables)) specified in EN 50266-2-4. Specifically, 7 insulated wires having a total length of 3.5m were twisted into 1 bundle, 11 bundles were vertically arranged at equal intervals, and were burned for 20 minutes, and after self-extinguishing, the carbonization length from the lower end was measured. When the carbonization length is 1.5m or less, it is regarded as acceptable with margin (. circleincircle.), when the carbonization length is 2.5m or less, it is regarded as acceptable (. largecircle.), and when the carbonization length exceeds 2.5m, it is regarded as unacceptable (X).

(comprehensive evaluation)

The overall evaluation was rated as good (o) for the insulated wires that passed both the dc stability test and the flame retardancy, and rated as bad (x) for the other insulated wires.

< example 1, example 2>

Regarding the volume resistivity of the flame-retardant layer, both example 1 and example 2 were 4 × 10¹⁴Ω cm, volume resistivity of the high electric insulating layer, example 1 was 1.34X 10¹⁷Omega cm, 9.48X 10 for example 2¹⁶Omega cm. Regarding the voltage sharing rate of the high-electric-insulation layer 140, example 1 was 98.9%, and example 2 was 99.1%. The thickness of the inner flame retardant layer was 0.1mm in both examples 1 and 2, and the thickness of the outer flame retardant layer was 0.3mm in both examples 1 and 2. The thickness of the high electric insulating layer was 0.11mm in example 1 and 0.18mm in example.

In examples 1 and 2, the volume resistivity of the high-electric-insulation layer was 1 × 10¹⁶Omega cm or more, the voltage sharing rate of the high electric insulation layer is 80% or more, and further, the high electric insulation layer has a structure thinner than at least one of the inner flame-retardant layer and the outer flame-retardant layer, so that both the electric characteristics and the flame retardancy are acceptable. In example 1 and example 2, the voltage sharing rate of the high-voltage insulating layer satisfied not only the condition of 80% or more but also the conditions of 90% or more and 95% or more.

The thickness of the integrated flame-retardant layers (inner flame-retardant layer and outer flame-retardant layer) was 0.4mm in each of examples 1 and 2, and the thickness of the high-electric-insulation layer was 0.4mm in each of examples 1 and 2The thickness of the flame-retardant layer in each of examples 2 was 1/2 or less (specifically, 0.2mm or less). In example 1, the high-electric-power insulating layer had a thickness of 1/2 or less (more specifically, 0.15mm or less) which was at least one of the thickness of the inner insulating layer and the thickness of the outer insulating layer, and thus higher flame retardancy was obtained than in example 2, and the diameter was also reduced. In example 1, the volume resistivity of the high-electric-insulation layer was 1X 10¹⁷Omega cm or more, thereby making it possible to make a high electric insulation layer thinner than that of example 2.

The ratio of the volume resistivity of the high-electric-insulation layer to the volume resistivity of the flame-retardant layer was 335 times in example 1 and 237 times in example 2, and the conditions of 10 times or more, 50 times or more, and 100 times or more were satisfied in both example 1 and example 2.

< comparative example 1, comparative example 2>

As for the volume resistivity of the flame-retardant layer, comparative example 1 and comparative example 2 were each 4X 10¹⁴Ω cm, volume resistivity of high electric insulating layer, 1.60 × 10 in each of comparative examples 1 and 2¹⁵Omega cm. The voltage sharing rate of the high-electric-insulation layer 140 was 52.4% in comparative example 1 and 66.7% in comparative example 2. The thickness of the inner flame-retardant layer was 0.1mm in each of comparative examples 1 and 2, and the thickness of the outer flame-retardant layer was 0.3mm in each of comparative examples 1 and 2. The thickness of the high electric insulating layer was 0.11mm in comparative example 1 and 0.2mm in comparative example 2.

In comparative examples 1 and 2, the volume resistivity of the high-electric-insulation layer was less than 1X 10¹⁶Ω cm, the voltage sharing rate of the high electric insulation layer is less than 80%, and thus the electric characteristics become unqualified. The high-electric-insulation layer is thinner than at least one of the inner flame-retardant layer and the outer flame-retardant layer, and the flame retardancy is acceptable. In addition, the ratio of the volume resistivity of the high-electric-insulation layer to the volume resistivity of the flame-retardant layer was 4 times and less than 10 times in each of comparative examples 1 and 2.

< comparative example 3, comparative example 4>

As to the volume resistivity of the flame-retardant layer, comparative example 3 and comparative example 4 were each 4X 10¹⁴Omega cm, volumetric electricity with respect to high electric insulationResistivity, comparative examples 3 and 4 were 1.60X 10¹⁵Omega cm. Regarding the voltage sharing rate of the high-electric-insulation layer 140, the voltage sharing rate of comparative example 3 was 68.8%, and the voltage sharing rate of comparative example 4 was 74.2%. The thickness of the inner flame-retardant layer was 0.1mm in both comparative examples 3 and 4, and the thickness of the outer flame-retardant layer was 0.1mm in comparative example 3 and 0.15mm in comparative example 4. The thickness of the high-electric-insulation layer was 0.11mm in comparative example 3 and 0.18mm in comparative example 4.

In comparative examples 3 and 4, the volume resistivity of the high-electric-insulation layer was less than 1 × 10¹⁶Ω cm, the voltage sharing rate of the high electric insulation layer is less than 80%, and thus the electric characteristics become unqualified. Further, the high-electric-insulation layer is thicker than either of the inner flame-retardant layer and the outer flame-retardant layer, and the flame retardancy is also unsatisfactory. In addition, the ratio of the volume resistivity of the high-electric-insulation layer to the volume resistivity of the flame-retardant layer was 4 times and less than 10 times in each of comparative examples 3 and 4.

< examples 3 to 5>

In example 3, the thickness of the semiconductive layer was 0.10mm, the thickness of the high-electric-insulation layer was 0.11mm, and the thickness of the flame-retardant layer was 0.29 mm. In example 4, the thickness of the semiconductive layer was 0.05mm, the thickness of the high-electric-insulation layer was 0.15mm, and the thickness of the flame-retardant layer was 0.30 mm. In example 5, the thickness of the semiconductive layer was 0.10mm, the thickness of the high-electric-insulation layer was 0.08mm, and the thickness of the flame-retardant layer was 0.29 mm.

In examples 3 to 5, the thickness of the high-electric-insulation layer was smaller than that of the flame-retardant layer, and the thickness of the semiconductive layer was smaller than that of the flame-retardant layer, thereby achieving both flame retardancy and a reduction in diameter. In addition, since the semiconductive layer is formed, good insulation is obtained.

The thickness of the high-electric-insulation layer is 1/2 or less of the thickness of the flame-retardant layer in examples 3 to 5, and 1/3 or less of the thickness of the flame-retardant layer in example 5. The thickness of the semiconductive layer is 1/2 or less of the thickness of the flame-retardant layer in examples 3 to 5, and 1/3 or less of the thickness of the flame-retardant layer in example 4. The sum of the thickness of the semiconductive layer and the thickness of the high-electric-insulation layer is smaller than the thickness of the flame-retardant layer in examples 3 to 5, and is 2/3 or less of the thickness of the flame-retardant layer in examples 4 and 5. In example 5, the thickness of the high-electric-insulation layer was smaller than that of the semiconductive layer.

< comparative examples 5 to 7>

In comparative example 5, the semiconductive layer was not formed, the thickness of the high-electric-insulation layer was 0.11mm, and the thickness of the flame-retardant layer was 0.4 mm. In comparative example 6, the thickness of the semiconductive layer was 0.10mm, the thickness of the high-electric-insulation layer was 0.20mm, and the thickness of the flame-retardant layer was 0.20 mm. In comparative example 7, the thickness of the semiconductive layer was 0.20mm, the thickness of the high-electric-insulation layer was 0.10mm, and the thickness of the flame-retardant layer was 0.20 mm.

In comparative example 5, the high-electric-insulation layer was thin and therefore good in flame retardancy, but the insulation was not satisfactory because no semiconductive layer was formed.

In comparative examples 6 and 7, the semiconductive layer was formed and the insulation property was satisfactory, but in comparative example 6, the high-electric-insulation layer and the flame-retardant layer were equal in thickness, and in comparative example 7, the semiconductive layer and the flame-retardant layer were equal in thickness and the flame retardancy was unsatisfactory.

Insulated wires of other examples were also produced in which the blend of the polymer composition (a ') for forming a semiconductive layer, the polymer composition (B ') for forming a high-electric-insulation layer, and the polymer composition (C ') for forming a flame-retardant layer was varied in the same thickness as in example 3, and the same characteristics as in examples 3 to 5 were obtained for these insulated wires. For example, made with a volume resistivity of 10¹⁶An insulated wire having a high electrical insulation layer of the polymer composition (B ') of the order of Ω cm, as the polymer composition (B '), it is possible to use a wire having a high electrical insulation layer of the polymer composition (B ') of the order of 1X 10¹⁶A volume resistivity of not less than Ω cm. In addition, for example, the product has a volume resistivity of 10⁸An insulated wire having a semiconductive layer of the polymer composition (A ') in the order of Ω cm, as the polymer composition (A'), it is possible to use a wire having a semiconductive layer of 1X 10⁹A material having a volume resistivity of not more than Ω cm.

The present invention has been described above with reference to the embodiments, but the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various changes, modifications, combinations, and the like can be made.

< preferred embodiment of the present invention >

Hereinafter, preferred embodiments of the present invention will be described.

(Note 1)

An insulated wire having a conductor and a coating layer disposed on an outer periphery of the conductor,

the coating layer has a laminated structure in which,

the laminated structure is composed of:

The composite material is formed by laminating,

(Note 2)

The insulated wire according to supplementary note 1, wherein the high-electric-power insulating layer shares more preferably 90% or more, and still more preferably 95% or more of the voltage applied in the thickness direction of the laminated structure.

(Note 3)

The insulated wire according to note 1 or 2, wherein the polymer composition (B) has a molecular weight of 1X 10¹⁷Volume resistivity of not less than Ω cm.

(Note 4)

The insulated wire according to any one of supplementary notes 1 to 3, wherein the volume resistivity of the polymer composition (B) forming the high electric insulation layer is preferably 10 times or more, more preferably 50 times or more, and further preferably 100 times or more the volume resistivity of the polymer composition (A) forming the inner flame retardant layer.

(Note 5)

The insulated wire according to any one of supplementary notes 1 to 4, wherein the volume resistivity of the polymer composition (B) forming the high electric insulation layer is preferably 10 times or more, more preferably 50 times or more, and further preferably 100 times or more the volume resistivity of the polymer composition (C) forming the inner flame retardant layer.

(Note 6)

The insulated wire according to any one of supplementary notes 1 to 5, wherein the thickness of the high-electric-power insulating layer is 1/2 or less of the sum of the thickness of the inner flame-retardant layer and the thickness of the outer flame-retardant layer.

(Note 7)

The insulated wire according to any one of supplementary notes 1 to 6, wherein the thickness of the high-electric-power insulating layer is 1/2 or less of at least one of the thickness of the inner flame-retardant layer and the thickness of the outer flame-retardant layer.

(Note 8)

The insulated wire according to any one of supplementary notes 1 to 7, wherein an outer diameter of the insulated wire is preferably 3mm or less, and more preferably 2.5mm or less.

(Note 9)

The insulated wire according to any one of supplementary notes 1 to 8, wherein the thickness of the high-electric-power insulating layer is preferably 0.2mm or less, and more preferably 0.15mm or less.

(Note 10)

The insulated wire according to any one of supplementary notes 1 to 9, wherein a sum of a thickness of the inner flame-retardant layer and a thickness of the outer flame-retardant layer is 0.4mm or less.

(Note 11)

The insulated wire according to any one of supplementary notes 1 to 10, wherein the inner flame retardant layer is disposed directly above (in contact with) the conductor.

(Note 12)

The insulated wire according to any one of supplementary notes 1 to 11, wherein the high-electric-power insulating layer is disposed directly above (in contact with) the inner flame-retardant layer.

(Note 13)

The insulated wire according to any one of supplementary notes 1 to 12, wherein the outer flame retardant layer is disposed directly above (in contact with) the high-electric-insulation layer.

(Note 14)

The insulated wire according to any one of supplementary notes 1 to 13, wherein the outer flame-retardant layer is an outermost layer of the insulated wire.

(Note 15)

The insulated wire according to any one of supplementary notes 1 to 14, wherein the conductor is a stranded wire formed by stranding a plurality of bare wires.

(Note 16)

The insulated wire according to any one of supplementary notes 1 to 15, wherein the inner flame retardant layer is such that the polymer composition (A) has a thickness of 1X 10¹⁴An electrical insulating layer having a volume resistivity of not less than Ω cm.

(Note 17)

The insulated wire according to any one of supplementary notes 1 to 16, wherein the outer flame retardant layer is such that the polymer composition (C) has a molecular weight of 1X 10¹⁴An electrical insulating layer having a volume resistivity of not less than Ω cm.

(Note 18)

the coating layer has:

a conductor disposed on the outer periphery of the conductor and containing a conductive agent and having a size of 1 × 10⁹A semiconductive layer comprising a polymer composition (A') having a volume resistivity of not more than Ω cm,

(Note 19)

In the insulated wire according to supplementary note 18, the thickness of the high electric insulation layer is more preferably 1/2 or less of the thickness of the flame retardant layer, and still more preferably 1/3 or less of the thickness of the flame retardant layer.

(Note 20)

In the insulated wire according to supplementary note 18 or 19, the thickness of the semiconductive layer is more preferably 1/2 or less of the thickness of the flame retardant layer, and still more preferably 1/3 or less of the thickness of the flame retardant layer.

(Note 21)

An insulated wire according to any one of supplementary notes 18 to 20, wherein a sum of a thickness of the semiconductive layer and a thickness of the high-electric-insulation layer is preferably smaller than a thickness of the flame-retardant layer, and more preferably 2/3 or less of the thickness of the flame-retardant layer.

(Note 22)

The insulated wire according to any one of supplementary notes 18 to 21, wherein the high-electric-power insulating layer shares preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more of the voltage applied in the thickness direction of the laminated portion of the high-electric-power insulating layer and the flame retardant layer.

(Note 23)

The insulated wire according to any one of supplementary notes 18 to 22, wherein the polymer composition (B') has a molecular weight of 1X 10¹⁷Volume resistivity of not less than Ω cm.

(Note 24)

An insulated wire according to any one of supplementary notes 18 to 23, wherein a volume resistivity of the polymer composition (B ') forming the high electric insulation layer is preferably 10 times or more, more preferably 50 times or more, and further preferably 100 times or more a volume resistivity of the polymer composition (C') forming the flame retardant layer.

(Note 25)

The insulated wire according to any one of supplementary notes 18 to 24, wherein an outer diameter of the insulated wire is 7mm or less.

(Note 26)

An insulated wire according to any one of supplementary notes 18 to 25, wherein the thickness of the semiconductive layer is 0.10mm or less.

(Note 27)

The insulated wire according to any one of supplementary notes 18 to 26, wherein the thickness of the high electric insulation layer is preferably 0.15mm or less, and more preferably 0.10mm or less.

(Note 28)

The insulated wire according to any one of supplementary notes 18 to 27, wherein the flame retardant layer has a thickness of 0.30mm or less.

(Note 29)

An insulated wire according to any one of supplementary notes 18 to 28, wherein the semiconductive layer is disposed directly above (in contact with) the conductor.

(Note 30)

The insulated wire according to any one of supplementary notes 18 to 29, wherein the high-electric-power insulating layer is disposed directly above (in contact with) the semiconductive layer.

(Note 31)

The insulated wire according to any one of supplementary notes 18 to 30, wherein the flame retardant layer is further disposed between the semiconductive layer and the high-electric-insulation layer.

(Note 32)

The insulated wire according to any one of supplementary notes 18 to 31, wherein the flame retardant layer is disposed directly above (in contact with) the high-electric-insulation layer.

(Note 33)

The insulated wire according to any one of supplementary notes 18 to 32, wherein the flame retardant layer is an outermost layer of the insulated wire.

(Note 34)

The insulated wire according to any one of supplementary notes 18 to 33, wherein the conductor is a stranded wire formed by stranding a plurality of bare wires.

(attached note 35)

The insulated wire according to any one of supplementary notes 18 to 34, wherein the flame retardant layer is such that the polymer composition (C') has a composition of 1X 10¹³Omega cm or more or 1X 10¹⁴An electrical insulating layer having a volume resistivity of not less than Ω cm.

Claims

1. An insulated wire having a conductor and a coating layer disposed directly above the conductor,

the coating layer has a laminated structure in which,

the laminated structure is composed of:

an inner flame-retardant layer disposed on the outer periphery of the conductor and formed of a flame-retardant-containing polymer composition A,

Is arranged on the periphery of the inner flame-retardant layer and has a thickness of 1 × 10¹⁶A high-electric-insulation layer made of a polymer composition B having a volume resistivity of not less than Ω cm, and

an outer flame-retardant layer disposed on the outer periphery of the high-electric-insulation layer and formed of a flame-retardant-containing polymer composition C

The composite material is formed by laminating,

2. The insulated wire according to claim 1, wherein a thickness of the high-electric-insulation layer is 1/2 or less of a sum of the thickness of the inner flame-retardant layer and the thickness of the outer flame-retardant layer.

3. The insulated wire according to claim 1 or 2, wherein the thickness of the high-electric-power insulating layer is 1/2 or less of at least one of the thickness of the inner flame-retardant layer and the thickness of the outer flame-retardant layer.