JP2021182464A - Non-halogen flame-retardant heat-resistant wire and non-halogen flame-retardant heat-resistant cable - Google Patents

Abstract

To provide a non-halogen flame-retardant heat-resistant wire having direct current stability and low toxicity while securing fire resistance.SOLUTION: A non-halogen flame-retardant heat-resistant wire has a conductor, a fire-resistant layer 2 on its outer periphery, and a coating layer on its outer periphery. The coating layer has a low toxic layer 3 which is arranged on an outer periphery of the fire-resistant layer 2 and is formed of a polymer composition (A) containing an inorganic filler, a high insulation layer 4 which is arranged on its outer periphery and is formed of a polymer composition (B) having volume resistivity at 25°C of 5×1015 Ω cm or more, and a flame-retardant layer 5 which is arranged on its outer periphery and is formed of a polymer composition (C) containing a flame retardant, and a volume fraction of the high insulation layer 5 in the coating layer is 25% or less. Since the coating layer on the fire-resistant layer 2 has a three-layer structure of low toxic layer 3, high insulation layer 4 and flame-retardant layer 5, and the volume fraction of the high insulation layer 4 in the coating layer is set at 25% or less, a non-halogen flame-retardant heat-resistant wire having direct current stability and low toxicity can be obtained while securing fire resistance.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-halogen flame-retardant refractory electric wire and a non-halogen flame-retardant refractory cable.

In addition to insulating properties, electric wires and cables used in railway vehicles are flame-retardant, prevent fire spread, emit less smoke when the resin insulator burns, and emit highly toxic gases such as halogen compounds and cyanide compounds. Various fire safety is required, such as not occurring. In addition, in evacuation guidance and other important circuits, in addition to the above-mentioned fire safety, there are restrictions on the wire structure such as the thickness of the insulating layer, and the wire has fire resistance that can ensure short-time energization after a fire occurs. And cables (fireproof wires / cables) are used.

For example, Patent Document 1 describes a non-halogen crosslinkable resin composition as a material for a crosslinked molded product having excellent flame retardancy and excellent mechanical properties, as well as excellent fuel resistance, cold resistance and room temperature storage, and a crosslinked molding thereof. Insulated electric wires and cables (particularly, insulated electric wires and cables for vehicles) having a body and a coating layer made of the crosslinked molded product are disclosed.

Further, Patent Document 2 describes a polybutylene naphthalate-based resin composition and polybutylene naphthalate, which have heat resistance, flame retardancy, hydrolysis resistance, and abrasion resistance and do not contain a halogen compound capable of achieving low smoke emission. An electric wire using a based resin composition is disclosed.

Further, Patent Document 3 describes a refractory cable having high flame retardancy and excellent refractory characteristics, in which an insulator is coated on a conductor via a refractory layer made of glass mica, and an interposition is provided around the conductor. A refractory cable comprising a sheath covering is disclosed.

Japanese Unexamined Patent Publication No. 2015-021120 Japanese Unexamined Patent Publication No. 2013-049869 Japanese Unexamined Patent Publication No. 7-321120

As electric wires and cables used for railway vehicles, electric wires and cables compliant with EN (European standard) are recognized worldwide. In addition to the above fire safety, this EN (European standard) has excellent environmental resistance (oil resistance, fuel resistance, acid resistance, alkali resistance, ozone resistance, etc.) of insulating materials used for electric wires and cables. It requires excellent electrical insulation and the like. Therefore, it can be said that the EN-compliant electric wire is an electric wire that clears the extremely technically difficult items that are established under the trade-off in which various requirements are intricately intertwined.

Furthermore, as mentioned above, in evacuation guidance and other important circuits, high fire resistance of electric wires is required, and it is very technically difficult to achieve both this fire resistance and the items required for conventional EN compliant electric wires. The degree is high.

For example, according to a study example of the present inventor described later, in an insulated wire in which a refractory layer made of mica tape is formed directly above a conductor and a covering layer is provided on the outer periphery thereof, EN ( It has been found that the DC stability required in (European standard) is reduced. Further, it was found that even if the DC stability was improved by improving the layer structure of the coating layer, the toxicity test result was rejected due to the balance of each layer.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a non-halogen flame-retardant refractory electric wire or a non-halogen flame-retardant refractory cable having good DC stability and low toxicity while ensuring fire resistance. do.

A brief description of the representative inventions disclosed in the present application is as follows.

[1] The non-halogen flame retardant fireproof electric wire of the present invention has a conductor, a fireproof layer arranged on the outer periphery of the conductor, and a coating layer arranged on the outer periphery of the fireproof layer. A first layer formed of the polymer composition (A) containing an inorganic filler, which is arranged on the outer periphery of the fire resistant layer, and 5 × 10 ¹⁵ Ω at 25 ° C., which is arranged on the outer periphery of the first layer. A second layer formed of the polymer composition (B) having a volume fraction of cm or more, and a second layer arranged on the outer periphery of the second layer and formed of the polymer composition (C) containing a flame retardant. It has three layers, and the volume fraction of the second layer in the covering layer is 25% or less.

[2] In [1], the average thickness of the second layer is 0.05 mm or more.

[3] In [1], the polymer composition (A) contains 40 parts by mass or more and 200 parts by mass or less of the inorganic filler with respect to 100 parts by mass of the polymer.

[4] In [1], the refractory layer contains mica.

[5] In [1], the total thickness of the coating layer is 0.6 mm or more.

[6] In [1], the polymer composition (B) contains an ethylene / α-olefin copolymer having a melting point of 90 ° C. or lower.

[7] The cable of the present invention has an electric wire and a sheath layer covering the electric wire, and the electric wire has a non-halogen flame-retardant fire-resistant electric wire according to any one of [1] to [6]. It is a fuel-resistant cable.

According to the present invention, it is possible to provide a non-halogen flame-retardant refractory electric wire or cable having DC stability while ensuring fire resistance.

It is sectional drawing of the non-halogen flame-retardant refractory electric wire which concerns on embodiment of this invention. It is sectional drawing of the cable which concerns on embodiment of this invention.

(to be considered)
First, before explaining the embodiment, the matters examined by the present inventor will be described. The present inventor is studying an insulated wire using a laminated body of a medium insulating layer and a flame-retardant layer as a coating layer on a conductor, and further, in order to improve fire resistance, a fire resistant layer is interposed on the conductor. It was considered to provide a covering layer. Hereinafter, this insulated wire will be referred to as an "insulated wire of a study example". The insulated wire of this study example corresponds to Comparative Example 1 described later.

The insulated wire of the study example has a conductor, a fire-resistant layer coated on the conductor, and a laminated body of a medium insulating layer and a flame-retardant layer, which are coating layers coated on the fire-resistant layer.

The medium insulating layer is an insulating layer having a lower volume resistivity than the “high insulating layer” described later, and a small amount of an inorganic filler having a low dielectric constant such as clay or talc is added to a polymer having a low dielectric constant such as polyolefin (for example). , 30 to 150 parts by mass) added to 100 parts by mass of the polymer. The addition of such an inorganic filler reduces the proportion of the polymer and improves the toxicity test results described later. Further, a flame retardant is blended in the flame retardant layer.

However, the DC stability of the insulated wire of the study example was unacceptable. This is due to the overlapping part of the mica tape coated on the conductor as a refractory layer by wrapping, the unevenness of the glass cloth itself of the mica tape base material, the "fluff" at the end, etc. It is considered that there was a place where the layer thickness became small and the dielectric breakdown started from the place (Problem 1). Further, it is considered that the inorganic filler of the medium insulating layer becomes a conductive path and lowers the DC stability. Specifically, due to the low adhesion between the polymer constituting the medium insulating layer and the inorganic filler, minute gaps are formed around the inorganic filler, and water easily permeates into the gaps. Therefore, when the insulated wire is immersed in an aqueous NaCl solution to evaluate the DC stability, a conductive path is formed by the permeation of water, and dielectric breakdown is likely to occur (Problem 2). In particular, it is considered that dielectric breakdown due to the conductive path is likely to occur in a place where the layer thickness of the coating layer is locally reduced due to unevenness of the glass cloth itself of the mica tape base material.

Further, in order to mitigate the influence of the unevenness of the glass cloth itself of the mica tape base material, it is possible to adjust the layer thickness of the medium insulating layer and the flame-retardant layer constituting the coating layer, but in the coating layer, It is required to set EN50264-3-1 so as to have a specified average wall thickness, and it is difficult to establish a coating layer and balance each layer due to restrictions on the thickness of the coating layer. there were.

Therefore, in order to solve the above problems, on the premise of adopting a fireproof layer, the coating layer has a three-layer structure consisting of a low-toxicity layer, a high-insulation layer, and a flame-retardant layer, and the balance of each layer is achieved to stabilize DC. The toxicity test results and the flame-retardant test results have led to the finding of good insulated wires without deteriorating the properties. It will be described in detail below.

(Embodiment)
(Composition of non-halogen flame-retardant refractory electric wire)
FIG. 1 is a cross-sectional view of a non-halogen flame-retardant refractory electric wire according to an embodiment of the present invention.

As shown in FIG. 1, the non-halogen flame-retardant refractory electric wire 10 according to the embodiment of the present invention has a conductor 1, a fire-resistant layer 2 coated on the conductor 1, and a coated layer coated on the fire-resistant layer 2. .. The coating layer is a low toxicity layer 3 in which the polymer composition (A) containing an inorganic filler is coated on the fire resistant layer 2, and a high insulation layer in which the polymer composition (B) is coated on the low toxicity layer 3. In the polymer composition (C) which is arranged on the outer periphery of the high insulating layer 4 having a volume resistivity of 5 × 10 ^{15 Ω · cm or more at 25 ° C. and the high insulating layer 4 and contains a flame retardant.} It has a flame retardant layer 5 formed.

As described above, by forming the coating layer on the refractory layer 2 into a three-layer laminated structure of the low toxicity layer 3, the high insulation layer 4, and the flame retardant layer 5, the fire resistance of the refractory layer 2 is maintained and the toxicity is low. The layer 3 can smooth the surface of the refractory layer 2 such as mica tape, and can improve the DC stability of the insulated wire by suppressing the local decrease in the layer thickness. Further, since the high insulating layer 4 serves as a barrier, it is possible to avoid a decrease in DC stability due to the inorganic filler in the low toxicity layer 3. Further, the flame retardancy can be ensured by the flame retardant layer 4 of the outermost layer.

Further, by adding the inorganic filler to the low toxicity layer 3, the ratio of the inorganic filler in the coating layer can be secured, and the toxicity test result becomes good.

Hereinafter, the conductor 1, the fire-resistant layer 2, and the coating layer (low-toxicity layer 3 / high-insulation layer 4 / flame-retardant layer 5) of the non-halogen flame-retardant refractory electric wire according to the embodiment of the present invention will be described in detail.

As the conductor 1, a conductor generally used in an insulated electric wire can be used.

As the refractory layer 2, a layer containing mica is used. Specifically, mica tape is used. The mica tape has a base material and a mica layer provided on the base material. There are no restrictions on the base material, mica composition, mica layer thickness, etc., and there are no restrictions on the winding method or number of mica tapes, but at least one mica tape having a mica layer on a glass cloth base material. It is preferable to wind it. Although it is possible to use mica tape using a resin film base material, it is preferable to use mica tape using a glass cloth base material because the resin film base material decomposes when burned. Further, as a method of winding the mica tape, wrap winding is preferable from the viewpoint of flexibility and the like.

The coating layer (three layers of low toxicity layer 3 / high insulation layer 4 / flame retardant layer 5) will be described below.

[Low toxicity layer]
The low toxicity layer (innermost layer, first layer) 3 is made of the polymer composition (A) containing an inorganic filler.

As the polymer (resin) used in the polymer composition (A), it is preferable to use a copolymer of polyolefin or olefin. Specifically, polyethylene, polypropylene, ethylene / α-olefin copolymer (including ethylene / propylene rubber), ethylene / vinyl acetate copolymer, ethylene / acrylic acid-based copolymer (including acrylic rubber) and the like can be used. preferable. Further, an acid-modified polymer may be added to these polymers.

As the inorganic filler used in the polymer composition (A), it is preferable to use an inorganic filler that does not contain halogen. Specifically, it is preferable to use clay, talc, alumina, silica, aluminum hydroxide, magnesium hydroxide, boehmite, various silicates and the like. Further, those obtained by surface-treating the particles of the inorganic filler may be used. For example, the particles of the inorganic filler can be surface-treated with vinylsilane or the like.

The amount of the inorganic filler added is preferably 40 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the polymer.

In addition, as long as the effect of the present invention is exhibited, the polymer composition (A) may contain additives such as a cross-linking agent, a cross-linking aid, an antioxidant, a colorant, and a lubricant.

By using the above-mentioned polyolefin or olefin copolymer as the polymer (resin) used in the polymer composition (A), it is possible to reduce the production of toxic gas during combustion. Examples of the toxic gas include CO, CO ₂ , SO ₂ , NO _X , HCN and the like. Further, by adding the above-mentioned inorganic filler to the polymer composition (A), the generation of toxic gas at the time of combustion can be further reduced.

[High insulation layer]
The high insulation layer (high electrical insulation layer, intermediate layer, second layer) 4 is made of the polymer composition (B).

As the polymer (resin) used in the polymer composition (B), it is preferable to use a non-polar polymer such as polyethylene, ethylene / propylene rubber, or an ethylene / α-olefin copolymer. In particular, it is preferable to use an ethylene / α-olefin copolymer having a melting point of 90 ° C. or lower. The high insulating layer 4 refers to an insulating layer having a volume resistivity [Ω · cm] at 25 ° C. of 5.0 × 10 ¹⁵ or more, more preferably 1.0 × 10 ¹⁶ or more.

Here, as shown in the above-mentioned study example, a medium insulating layer may be used instead of the laminate of the low toxicity layer 3 and the high insulating layer 4. As described above, the medium insulating layer is a layer obtained by adding a small amount (for example, 30 to 150 parts by mass) of an inorganic filler having a low dielectric constant such as clay or talc to a polymer having a low dielectric constant such as polyolefin. Compared with such a medium insulating layer, the highly insulating layer 4 (polymer composition (B)) is a non-polar polymer containing no inorganic filler.

The polymer composition (B) may contain additives such as a cross-linking agent, a cross-linking aid, an antioxidant, a colorant, and a lubricant, as long as the effects of the present invention are exhibited.

For the high insulating layer 4, the layer thickness (average layer thickness, average thickness) is preferably 0.05 mm or more. Further, it is preferable that the volume fraction of the high insulating layer 4 in the covering layer (three layers of the low toxicity layer 3 / the high insulating layer 4 / the flame retardant layer 5) is 25% or less. If the layer thickness is less than 0.05 mm, the electrical characteristics, especially the DC stability, cannot be satisfied. On the other hand, if the volume fraction is larger than 25%, the amount of combustibles increases, and the toxicity test and the combustion test become unsatisfactory.

Further, even when the above layer thickness and volume fraction are satisfied, if a high insulation layer is formed directly above the refractory layer, the overlapping portion of the mica tape by wrapping the mica tape and mica are similar to the case of the above study example. Due to the unevenness of the glass cloth itself of the tape base material, "fluffing" at the edges, etc., there may be a place where the layer thickness is locally reduced, which may cause dielectric breakdown starting from such a place. However, by arranging the highly insulating layer 4 on the refractory layer 2 via the low toxicity layer 3, the surface of the mica tape can be smoothed and the toxicity worsened by the high insulating layer 4 can be supplemented.

[Flame-retardant layer]
The flame-retardant layer (outermost layer, third layer) 5 is made of the polymer composition (C).

As the polymer (resin) used in the polymer composition (C), it is preferable to use a polyolefin-based polymer. It is sufficient if the flame retardancy is satisfied, but it is preferable to use a polymer having an oxygen index of 35 or more, more preferably 40 or more, as the polymer composition (C). Specifically, polyethylene, an ethylene / vinyl acetate copolymer, an ethylene / acrylic acid-based copolymer (including acrylic rubber), an ethylene / α-olefin copolymer (including ethylene / propylene rubber) and the like can be used. Further, an acid-modified polymer may be added to these polymers.

As the flame retardant used in the polymer composition (C), it is preferable to use a metal hydroxide. Specifically, it is preferable to use aluminum hydroxide, magnesium hydroxide, or the like. Here, among the inorganic fillers, those having flame retardancy are referred to as "flame retardants".

The amount of the metal hydroxide added is preferably 120 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the polymer.

Further, a halogen-free organic flame retardant such as a phosphorus flame retardant or a nitrogen flame retardant may be contained as long as it satisfies the required characteristics such as low toxicity and smoke emission.

In addition, as long as the effect of the present invention is exhibited, the polymer composition (C) may contain additives such as a cross-linking agent, a cross-linking aid, an antioxidant, a colorant, and a lubricant.

The total thickness of the coating layer (low toxicity layer 3 / high insulation layer 4 / flame retardant layer 5) is preferably 0.6 mm or more.

As described above, in the present embodiment, the coating layer on the refractory layer 2 has a three-layer laminated structure of the above-mentioned low toxicity layer 3 / high insulation layer 4 / flame-retardant layer 5, and the high insulation layer 4 in the coating layer. Since the volume fraction of the above was set to 25% or less, the fire resistance, DC stability, toxicity test results, and flame retardancy can be improved.

(Cable configuration using non-halogen flame-retardant refractory electric wire)
FIG. 2 is a cross-sectional view of a cable according to an embodiment of the present invention.

As shown in FIG. 2, the cable (non-halogen flame-retardant fire-resistant cable) 20 according to the embodiment of the present invention includes a three-core stranded wire obtained by twisting three non-halogen flame-retardant fire-resistant electric wires 10 described above and a periphery of the three-core stranded wire. It is provided with a metal shield braided layer 6 provided in the above, and a sheath (sheath layer) 7 extruded and coated around the metal shield braided layer 6. The non-halogen flame-retardant refractory electric wire 10 may be used with a single core, or a multi-core stranded wire other than the three cores may be used. Further, the sheath 7 may have a multi-layer structure. Further, as a constituent member of the cable, a separator, a shield tape made of metal leaf, or the like may be incorporated.

(Example)
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Preparation of compound for coating layer material)
The compounding composition of the compound of the coated layer material examined is shown in Table 1, and the materials used are shown in Table 2. The compound of each coating layer material was formed as follows. Each compounding agent (polymer composition) excluding the peroxide and the cross-linking agent was put into the kneader kept at 100 ° C., melt-kneaded while raising the temperature to 160 ° C., and then put into a single-screw extruder. The kneaded product extruded into strands from a single-screw extruder was passed through a pelletizer and molded into pellets. Further, for the coating layer material containing a peroxide or a cross-linking agent, the molded pellets are placed in a stirring blender, the peroxide or the cross-linking agent is added, and the mixture is mixed and impregnated with stirring to form a compound. bottom. As a reference evaluation of the characteristics of the coating layer material, the compound was formed into a sheet, and the volume resistivity and the oxygen index were measured.

(Taping of mica tape)
Using a taping machine, one glass mica tape (OMF-8 manufactured by Okabe Mica) was wrapped around a conductor as mica tape so as to be 1/2 wrap.

(Preparation of insulated wire sample)
[Examples 1 and 2, Comparative Examples 1, 4, 5]
The compound (each polymer composition) of each coating layer material was coated on the conductor around which the glass mica tape was wound by using an extruder, and three layers constituting the coating layer were simultaneously formed. The thickness of the coating layer was set to be the average wall thickness of the 600V structure in EN50264-3-1. Then, by irradiating with an electron beam of 8M Mad, the polymer composition of each layer was crosslinked to prepare an insulated wire sample.

[Comparative Examples 2 and 3]
The compound (each polymer composition) of each coating layer material was directly coated on the conductor using an extruder without using glass mica tape, and three layers constituting the coating layer were simultaneously formed. The thickness of the coating layer was set to be the average wall thickness of the 600V structure in EN50264-3-1. Then, by irradiating with an electron beam of 8M Mad, the polymer composition of each layer was crosslinked to prepare an insulated wire sample.

[Examples 3, 4, 5, Comparative Examples 6, 7]
The compound (each polymer composition) of each coating layer material was coated on the conductor around which the glass mica tape was wound by using an extruder, and three layers constituting the coating layer were simultaneously formed. The thickness of the coating layer was set to be the average wall thickness of the 600V structure in EN50264-3-1. Then, by continuously applying 1.5 MPa high-pressure steam, the polymer composition of each layer was crosslinked to prepare an insulated wire sample.

(evaluation)
1. 1. Outer diameter The outer diameter of the insulated wire sample was measured.

2. 2. Fire resistance test A test was conducted based on EN50200, and the durability (PH120) for 120 minutes was passed.

3. 3. DC stability test Based on EN50305.6.7, DC ± 1500V was applied to 5 insulated wire samples in a 3% NaCl aqueous solution at 85 ° C. The charge was continued for 10 days, and all 5 positive and negative charges that did not break down were passed, and those that did not break down even one of them were rejected.

4. Toxicity test Based on EN5035.9.2, 1 g of the coating layer of the insulated wire sample is burned at 800 ° C., and 5 types of generated gas (CO, CO ₂ , HCN, SO ₂ , NO _X ) are quantitatively analyzed and determined. It was evaluated by converting it into a toxicity index (ITC value) by weighting. Those with an ITC value of 3 or less were rejected, and those with an ITC value greater than 3 were rejected.

5. Vertical combustion test [Ichijo]
Based on EN60332-1-2, a strip of insulated wire sample was laid, burned using a burner, and the carbonization length was measured. Those whose carbonization length conforms to the standard are regarded as acceptable, and those whose carbonization length does not conform to the standard are rejected.

6. Vertical combustion test [Multi-row]
Based on EN50264-3-1, an insulated wire sample was laid in multiple rows so that the amount of non-metal was a specified value, burned using a burner, and the carbonization length was measured. Those whose carbonization length conforms to the standard are regarded as acceptable, and those whose carbonization length does not conform to the standard are rejected.

Specifically, in the case of an insulated wire sample having an outer diameter of 12 mm or more, the test was carried out under the conditions of EN50266-2-4 and NMV 1.5 l / m, and a carbonization length of 2.5 m or less was accepted. For the insulated wire sample having an outer diameter of more than 6 mm and less than 12 mm, it was carried out under the conditions of EN50266-2-5 and NMV 0.5 l / m, and a carbonization length of 2.5 m or less was accepted. For insulated wire samples with an outer diameter of 6 mm or less, the procedure was carried out under the conditions of EN50305 9.1.2, and carbonization lengths of 1.5 m or less were accepted.

Table 3 shows the conductor diameter, the presence / absence of a refractory layer, the type / thickness of the innermost layer, the type / thickness of the intermediate layer, the type / thickness of the outermost layer, the volume fraction of the highly insulating layer, and the above evaluation.

[About Examples 1 and 2, Comparative Examples 1, 2, 3 and 4]
In Comparative Example 1 in which a coating layer (medium insulating layer / flame-retardant layer) having a two-layer structure was formed on a conductor via mica tape, both positive and negative DC stability were unacceptable. This is because, as explained in detail in the section of the above-mentioned considerations, the layer thickness of the medium insulating layer is locally reduced due to the “fluff” of the mica tape coated on the conductor as the refractory layer. It is considered that a place was generated and dielectric breakdown occurred. Further, it is considered that the inorganic filler in the medium insulating layer becomes a conductive path and reduces the DC stability.

Further, in Comparative Example 2 in which the coating layer (medium insulating layer / flame-retardant layer) having a two-layer structure is formed on the conductor without using mica tape, the coating layer thickness is kept uniform, so that the DC stability is improved. Both + charge and-charge pass, but the fire resistance test result (fire resistance characteristics) fails because there is no mica tape that is a fire resistance layer.

Further, in Comparative Example 3 in which the coating layer (medium insulating layer / flame retardant layer) having a two-layer structure was formed on the conductor without using mica tape, the medium insulating layer was thicker than that in Comparative Example 2, so that the DC was stable. Both positive and negative properties pass, but the vertical combustion test result [Ichijo] (flame retardant) fails due to the large amount of combustibles.

According to the above Comparative Examples 1 to 3, when a coating layer having a two-layer structure (medium insulating layer / flame-retardant layer) is provided, all of flame retardancy, fire resistance, and DC stability cannot be satisfied. found.

On the other hand, in Example 1 in which a coating layer (low toxicity layer / high insulation layer / flame retardant layer) having a three-layer structure is formed on a conductor via mica tape, high insulation is provided by providing the low toxicity layer. By coating the layer on the low toxicity layer with a uniform wall thickness, it is possible to prevent the local thinning of the highly insulating layer by mica tape, and by using the highly insulating layer, the DC stability test can be performed. In the above, the inorganic filler did not become a conductive path, and further, the flame retardancy was improved by using the flame retardant layer, and it was possible to satisfy all of the flame retardancy, the fire resistance, and the DC stability.

Further, even when a coating layer (low toxicity layer / high insulation layer / flame retardant layer) having a three-layer structure is formed on the conductor via mica tape, the comparison is made by increasing the high insulation layer to 0.2 mm. In Example 4, the volume fraction of the highly insulating layer became large, and the toxicity test results and the vertical combustion test results (both [one row] and [multi-row]) were rejected.

However, in the case where a coating layer (low toxicity layer / high insulation layer / flame retardant layer) having a three-layer structure is formed on the conductor via mica tape, the example in which the high insulation layer is increased to 0.15 mm. In No. 2, it was possible to satisfy all of flame retardancy, fire resistance, and DC stability.

[About Examples 3, 4, 5 and Comparative Examples 5, 6 and 7]
An example in which a coating layer (low toxicity layer / high insulation layer / flame retardant layer) having a three-layer structure is formed on a conductor via mica tape, and the volume fraction of the high insulation layer is 25% or less. In 3 to 5, it was possible to satisfy all of flame retardancy, fire resistance, and DC stability.

Further, in the case where a coating layer (low toxicity layer / high insulation layer / flame retardant layer) having a three-layer structure is formed on the conductor via mica tape, the volume fraction of the high insulation layer exceeds 25%. In Example 5, the vertical combustion test results (both [Ichijo] and [Multi-row]) were passed by thickening the flame-retardant layer, but the toxicity test results were unsuccessful.

Further, in Comparative Example 6 in which a coating layer (medium insulating layer / flame retardant layer) having a two-layer structure was formed on the conductor via mica tape, even if the medium insulating layer was thickened, the positive charge of DC stability was obtained. It was a failure. Also, as explained in detail in the section of the above-mentioned considerations, the layer thickness of the medium insulating layer is locally reduced due to the “fluff” of the mica tape coated on the conductor as the refractory layer. It is considered that a place was generated and dielectric breakdown occurred. Further, it is considered that the inorganic filler in the medium insulating layer becomes a conductive path and reduces the DC stability.

Further, even when a coating layer (low toxicity layer / high insulation layer / flame retardant layer) having a three-layer structure is formed on the conductor via mica tape, the volume fraction of the high insulation layer exceeds 25%. In Comparative Example 7, the toxicity test result was unacceptable.

The present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the gist thereof.

1 Conductor 2 Fire-resistant layer 3 Low-toxic layer 4 High-insulation layer 5 Flame-retardant layer 6 Metal shield braided layer 7 Sheath 10 Non-halogen flame-retardant fire-resistant wire 20 Cable

Claims (7)

It has a conductor, a refractory layer arranged on the outer periphery of the conductor, and a coating layer arranged on the outer periphery of the refractory layer.
The covering layer is
A first layer arranged on the outer periphery of the refractory layer and formed of the polymer composition (A) containing an inorganic filler.
A second layer arranged on the outer periphery of the first layer and formed of the polymer composition (B) having a volume resistivity ^{of 5 × 10 15 Ω · cm or more at 25 ° C.}
It has a third layer arranged on the outer periphery of the second layer and formed of the polymer composition (C) containing a flame retardant.
A non-halogen flame-retardant refractory electric wire having a volume fraction of the second layer in the covering layer of 25% or less. In the non-halogen flame-retardant refractory electric wire according to claim 1.
A non-halogen flame-retardant refractory electric wire having an average thickness of 0.05 mm or more in the second layer. In the non-halogen flame-retardant refractory electric wire according to claim 1.
The polymer composition (A) is a non-halogen flame-retardant refractory electric wire containing 40 parts by mass or more and 200 parts by mass or less of the inorganic filler with respect to 100 parts by mass of the polymer. In the non-halogen flame-retardant refractory electric wire according to claim 1.
The refractory layer is a non-halogen flame-retardant refractory electric wire containing mica. In the non-halogen flame-retardant refractory electric wire according to claim 1.
A non-halogen flame-retardant refractory electric wire having a total thickness of the coating layer of 0.6 mm or more. In the non-halogen flame-retardant refractory electric wire according to claim 1.
The polymer composition (B) is a non-halogen flame-retardant refractory electric wire containing an ethylene / α-olefin copolymer having a melting point of 90 ° C. or lower. In a cable having an electric wire and a sheath layer covering the electric wire,
A non-halogen flame-retardant refractory cable having the non-halogen flame-retardant refractory electric wire according to any one of claims 1 to 6 as the electric wire.

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