阅读说明：本技术 绝缘电线 (Insulated wire ) 是由 古川丰贵 于 2019-09-19 设计创作，主要内容包括：提供一种绝缘电线,用使绝缘包覆部中的阻燃剂的含量增加以外的方法也能够提高绝缘电线的阻燃性。绝缘电线具有电线导体和将所述电线导体的外周包覆的由树脂组合物构成的绝缘包覆部,定义为所述绝缘包覆部相对于导体截面积S1的截面积S2的比S2/S1的截面积比S、和构成所述绝缘包覆部的所述树脂组合物的氧指数OI满足S≤OI-17.2的关系。(Provided is an insulated wire, which can improve the flame retardance of the insulated wire by a method other than increasing the content of a flame retardant in an insulating coating. An insulated wire has a wire conductor and an insulating coating portion composed of a resin composition for coating the outer periphery of the wire conductor, and a cross-sectional area ratio S defined as a ratio S2/S1 of a cross-sectional area S2 of the insulating coating portion with respect to a conductor cross-sectional area S1 and an oxygen index OI of the resin composition constituting the insulating coating portion satisfy a relationship of S ≦ OI-17.2.)

1. An insulated wire comprising a wire conductor and an insulating coating part made of a resin composition for coating the outer periphery of the wire conductor,

a cross-sectional area ratio S defined as a ratio S2/S1 of a cross-sectional area S2 of the insulating coating portion to a conductor cross-sectional area S1, and an oxygen index OI of the resin composition constituting the insulating coating portion satisfy a relationship of S ≦ OI-17.2.

2. The insulated wire according to claim 1,

the cross-sectional area ratio S is 2.5 or less.

3. The insulated wire according to claim 1 or claim 2,

the cross-sectional area ratio S is 1.5 or less.

4. The insulated wire according to any one of claims 1 to 3,

the resin composition constituting the insulating coating portion contains polypropylene and polyphenylene ether.

5. The insulated wire according to any one of claims 1 to 4,

the resin composition constituting the insulating coating portion contains a flame retardant composed of a phosphate ester compound, and the content of the flame retardant is less than 30 parts by mass with respect to 100 parts by mass of the resin component.

6. The insulated wire according to claim 5,

the cross-sectional area ratio S is 2.5 or less, and the content of the flame retardant in the resin composition is 10 parts by mass or less with respect to 100 parts by mass of the resin component.

7. The insulated wire according to claim 5 or claim 6,

the cross-sectional area ratio S is 1.5 or less, and the content of the flame retardant in the resin composition is 5 parts by mass or less with respect to 100 parts by mass of the resin component.

8. The insulated wire according to any one of claims 1 to 7,

the conductor sectional area S1 is 0.10mm²The following.

Technical Field

The present disclosure relates to an insulated wire.

Background

Insulated wires used in vehicles such as automobiles and various devices are required to have high flame retardancy. For example, when a halogen-free resin such as a polyolefin resin is used as the insulating coating portion constituting the insulated wire, flame retardancy can be secured by mixing a flame retardant composed of a phosphorus compound or the like. For example, patent document 1 describes the following: the flame retardant is contained in an amount of 30 parts by mass or more per 100 parts by mass of the polyolefin resin having a predetermined composition.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-66345

Disclosure of Invention

Problems to be solved by the invention

As described in patent document 1, the flame retardancy of the insulating coating portion can be improved by incorporating a flame retardant into the insulating coating portion constituting the insulated wire. However, since the insulating coating portion contains a large amount of flame retardant, there is a possibility that the mechanical properties and the like of the resin material constituting the insulating coating portion are affected. Therefore, it is preferable to suppress the content of the flame retardant to a small amount within a range capable of ensuring necessary flame retardancy. Therefore, a method for improving the flame retardancy of the insulated wire in addition to increasing the content of the flame retardant is desired.

Therefore, an object is to provide an insulated wire which comprises: the flame retardancy of the insulated wire can be improved by a method other than increasing the content of the flame retardant in the insulating coating portion.

Means for solving the problems

An insulated wire of the present disclosure has a wire conductor and an insulating coating portion composed of a resin composition covering the outer periphery of the wire conductor, and a sectional area ratio S defined as a ratio S2/S1 of a sectional area S2 of the insulating coating portion with respect to a conductor sectional area S1, and an oxygen index OI of the resin composition constituting the insulating coating portion satisfy a relationship of S ≦ OI-17.2.

Effects of the invention

The insulated wire of the present disclosure can improve the flame retardancy of the insulated wire by a method other than increasing the content of the flame retardant in the insulating coating portion.

Drawings

Fig. 1A and 1B are diagrams illustrating an insulated wire according to an embodiment of the present disclosure. Fig. 1A is a perspective view, and fig. 1B is a circumferential sectional view.

FIG. 2 is a graph showing the relationship between the oxygen index and the cross-sectional area ratio and the flame retardancy with respect to the experimental data.

Fig. 3A is a graph showing the relationship between the oxygen index and the flame retardancy with respect to the experimental data. Fig. 3B is a graph showing the relationship between the oxygen index and the insulation thickness and flame retardancy with respect to the experimental data.

Detailed Description

[ description of embodiments of the present disclosure ]

First, embodiments of the present disclosure will be described.

An insulated wire of the present disclosure has a wire conductor and an insulating coating portion composed of a resin composition covering the outer periphery of the wire conductor, and a sectional area ratio S defined as a ratio S2/S1 of a sectional area S2 of the insulating coating portion with respect to a conductor sectional area S1, and an oxygen index OI of the resin composition constituting the insulating coating portion satisfy a relationship of S ≦ OI-17.2.

In the insulated wire, the cross-sectional area ratio S and the oxygen index OI of the insulating coating portion satisfy the relationship of S.ltoreq.OI-17.2. Since the sectional area of the insulating coating portion is reduced relative to the sectional area of the conductor, heat of the insulating coating portion is easily released to the conductor of the electric wire, and the temperature of the insulating coating portion is not easily increased. As a result, the flame retardancy of the insulated wire is improved. Even when the oxygen index of the resin composition constituting the insulating coating portion is low by containing only a small amount of flame retardant or the like, high flame retardancy can be secured in the insulated wire when the sectional area ratio S is reduced so as to satisfy the above relational expression by reducing the sectional area S2 of the insulating coating portion with respect to the conductor sectional area S1 by forming the insulating coating portion thin.

The reduction of the diameter of the insulated wire is also related to the reduction of the thickness of the insulating coating portion. When the insulating coating portion is made thin, if a large amount of flame retardant is contained, there is a possibility that the mechanical properties of the insulating coating portion, such as abrasion resistance, are lowered, but in the insulated wire described above, the content of the flame retardant can be suppressed to a small level because the oxygen index may be low when the cross-sectional area ratio is sufficiently small. Therefore, the influence on the mechanical properties of the resin component due to the addition of the flame retardant can be suppressed to a small extent.

Here, the cross-sectional area ratio S may be 2.5 or less. Therefore, even when the oxygen index of the insulating material constituting the insulating coating portion is considerably low, high flame retardancy can be easily obtained in the insulated wire. Further, the insulating coating portion is made thin, so that the diameter of the insulated wire can be easily reduced.

Further, the cross-sectional area ratio S may be 1.5 or less. Therefore, the effect of improving the flame retardancy of the insulated wire and the effect of reducing the diameter of the insulated wire are particularly excellent.

The resin composition constituting the insulating coating portion may contain polypropylene and polyphenylene ether. Therefore, even if the insulating coating portion is formed to be thin in order to reduce the cross-sectional area ratio to improve the flame retardancy of the insulated wire, it is easy to ensure high abrasion resistance. In addition, the chemical resistance and heat resistance of the insulating coating portion are also increased.

The resin composition constituting the insulating coating portion may contain a flame retardant composed of a phosphate ester compound, and the content of the flame retardant may be less than 30 parts by mass with respect to 100 parts by mass of the resin component. Thus, although the oxygen index of the resin composition can be increased by containing the flame retardant, the decrease in the mechanical properties of the insulating coating portion, such as abrasion resistance, due to the large amount of the flame retardant contained can be suppressed by suppressing the content of the flame retardant to less than 30 parts by mass.

In this case, the cross-sectional area ratio S may be 2.5 or less, and the content of the flame retardant in the resin composition may be 10 parts by mass or less with respect to 100 parts by mass of the resin component. Thus, the flame retardancy and the abrasion resistance of the insulated wire can be achieved at the same time, and the thickness of the insulating coating portion can be effectively reduced.

Further, the cross-sectional area ratio S may be 1.5 or less, and the content of the flame retardant in the resin composition may be 5 parts by mass or less with respect to 100 parts by mass of the resin component. Therefore, the effect of making the flame retardancy and the abrasion resistance of the insulated wire compatible and making the insulating coating portion thin is particularly excellent.

The conductor sectional area S1 can also be 0.10mm²The following. Therefore, the effect of reducing the diameter of the entire insulated wire by reducing the diameter of the conductor is particularly excellent together with the effect of reducing the thickness of the insulating coating portion.

[ details of embodiments of the present disclosure ]

Hereinafter, an insulated wire according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In the present specification, unless otherwise specified, various physical properties of the material are values measured at room temperature or in the atmosphere.

[1] Constitution of insulated wire

Fig. 1 shows an outline of an insulated wire 10 according to an embodiment of the present disclosure. As shown in fig. 1, the insulated wire 10 includes a wire conductor 12 and an insulating coating portion 14 made of a resin composition for coating the outer periphery of the wire conductor 12. The insulated wire 10 can be obtained by extrusion-coating the resin composition to be the insulating coating portion 14 on the outer periphery of the wire conductor 12.

In the insulated wire 10 of the present embodiment, the sectional area ratio S and the oxygen index OI of the resin composition constituting the insulating coating 14 satisfy the following formula (1) when a is 17.2.

S≤OI-A (1)

Here, assuming that the conductor cross-sectional area, that is, the cross-sectional area of the wire conductor 12 in the cross-section (fig. 1B) orthogonal to the axis of the insulated wire 10 is S1, and the insulation cross-sectional area, that is, the cross-sectional area of the insulating coating 14 in the cross-section is S2, the cross-sectional area ratio S of the insulated wire 10 is expressed as follows.

S＝S2/S1 (2)

The oxygen index OI is the minimum oxygen concentration (% by volume) required for sustained combustion of the material, and can be measured, for example, in accordance with JIS K7201-2.

In the insulated wire 10 of the present embodiment, the sectional area ratio S and the oxygen index OI satisfy the formula (1) when a is 17.2, whereby the insulated wire 10 is a high flame retardant insulated wire that is sufficiently usable in vehicles such as automobiles. Assuming that a >17.2, when formula (1) is made to be satisfied, further high flame retardancy can be secured. For example, a may be 17.5, and further a may be 18.0.

In the insulated wire 10, even if the insulating coating 14 is heated by an external environment or by self-ignition, heat of the insulating coating 14 is released to the wire conductor 12, and the wire conductor 12 absorbs the heat of the insulating coating 14. This phenomenon can suppress the temperature increase (heat extraction) of the insulating coating 14. The greater the volume of the wire conductor 12 relative to the volume of the insulating coating 14, the greater the heat extraction effect. In other words, the thinner the insulating coating 14 is with respect to the wire conductor 12, the higher the heat-extracting effect. That is, the smaller the cross-sectional area ratio S defined by the formula (2), the more the heat-extracting effect can be improved.

The higher the oxygen index OI of the resin composition constituting the insulated wire 10 is, the less likely the insulating coating 14 is to cause burning. However, even when the oxygen index OI of the resin composition is low, the insulating coating 14 is less likely to burn by heat extraction of the wire conductor 12. Even if the insulating coating 14 catches fire, the flame can be extinguished at an early stage. In the insulated wire 10, the insulation coating portion 14 is formed to be thin so as to reduce the cross-sectional area ratio S in the ratio to the conductor cross-sectional area S1, whereby the heat extraction effect can be increased and the flame retardancy of the insulated wire 10 can be improved.

When the insulating coating portion 14 is made thin, the effect of making the diameter of the insulated wire 10 small can be obtained in addition to the effect of increasing the cross-sectional area ratio S and improving the flame retardancy of the insulated wire 10. In automobiles and the like, there is a high demand for reducing the diameter of the insulated wire 10 from the viewpoint of space saving.

When the cross-sectional area ratio S of the insulated wire 10 is suppressed to the upper limit value or less determined in the relationship with the oxygen index OI of the resin composition as in the formula (1), sufficient flame retardancy can be secured in the insulated wire 10 even if the insulating coating 14 is formed of a resin composition having a low oxygen index OI as the resin composition. The oxygen index OI of the resin composition depends on the type and formulation of the resin component and the additive components other than the resin component, but as a method for effectively increasing the oxygen index OI, the addition of a flame retardant may be mentioned. However, when a large amount of flame retardant is added, the mechanical properties of the resin component constituting the insulating coating portion 14, such as abrasion resistance, are easily affected.

When the amount of the flame retardant to be added is suppressed in order to maintain the mechanical properties, the oxygen index OI of the resin composition constituting the insulating coating portion 14 decreases. However, in this case as well, by making the insulating coating 14 thin, sufficient flame retardancy can be secured in the insulated wire 10 by utilizing heat extraction. When the insulating coating portion 14 is made thin, the wear resistance of the insulating coating portion 14 tends to decrease, but the decrease in wear resistance due to the addition of the flame retardant can be suppressed by suppressing the addition amount of the flame retardant to be small. That is, by making the thickness of the insulating coating 14 thin and decreasing the amount of the flame retardant to be added within a range satisfying the relationship between the cross-sectional area ratio S and the oxygen index OI defined by the formula (1), it is possible to achieve a reduction in the diameter of the insulated electric wire 10 while maintaining both the flame retardancy and the wear resistance of the insulated electric wire 10.

The insulated wire 10 of the present embodiment is not particularly limited in use, and can be used in various applications, such as vehicles such as automobiles, machine tools, information communication, power tools, ships, aircrafts, and the like. Among them, it can be suitably used as an electric wire for automobiles. In the field of automotive electric wires, the insulated electric wire 10 is required to have high flame retardancy in order to meet the requirements for avoiding fire and the like. In addition, the diameter of the insulated wire 10 is also required to be reduced from the viewpoint of space saving. Further, in the electric wire for an automobile, excellent abrasion resistance is required because it is likely to come into contact with a vehicle body or other parts at the time of assembly and to generate friction with the vehicle body or other parts at the time of use. In the insulated wire 10 of the present embodiment, the diameter of the insulated wire 10 can be reduced while achieving both flame retardancy and abrasion resistance, and the above-described characteristics required for an automotive wire can be satisfied.

The insulated wire 10 of the present embodiment may be used in a single wire state or in a bundle including a plurality of insulated wires. All the insulated wires constituting the wire harness may be constituted by the insulated wire 10 of the present embodiment, or a part thereof may be constituted by the insulated wire 10 of the present embodiment.

The constituent materials and specific dimensions of the wire conductor 12 and the insulating coating 14 constituting the insulated wire 10 according to the present embodiment are not particularly limited as long as they satisfy the relationship of the above formula (1), and examples of suitable configurations are listed below.

[2] Electric wire conductor

As the wire conductor 12, various metal materials generally used as conductors constituting the electric wire can be used. Examples of such a metal material include copper, aluminum, iron, magnesium, and alloys of those metals and other metals. Among these metals, copper or copper alloys can be most suitably used. Copper and copper alloys have high thermal conductivity among various metal materials, and provide a particularly high effect of improving the flame retardancy of the insulated electric wire 10 by heat extraction.

The wire conductor 12 may be formed of a single wire or a stranded wire obtained by stranding a plurality of wires 12 a. From the viewpoint of ensuring flexibility of the insulated wire 10, the wire conductor 12 is preferably formed of a twisted wire. In this case, it is possible to use both wires 12a composed of the same material and wires 12a composed of a plurality of different materials.

The conductor cross-sectional area S1 of the wire conductor 12 is not particularly limited as long as the ratio S of the insulation cross-sectional area S2 to the oxygen index OI of the insulating coating 14 satisfies the relationship of the formula (1). However, from the viewpoint of reducing the diameter of the insulated wire 10, it is preferableThe conductor cross-sectional area S1 is small. When set to 0.15mm²Below, further 0.10mm²Below, 0.05mm²In the following, the insulated wire 10 can be effectively reduced in diameter by utilizing the effect of the fineness of the wire conductor 12 itself and the effect of satisfying the formula (1) by reducing the thickness of the insulating coating 14 with the reduction in diameter of the wire conductor 12. The lower limit of the conductor cross-sectional area S1 is not particularly limited, but is preferably 0.03mm from the viewpoint of enhancing the heat extraction effect and the like²The above.

[3] Insulating coating

The thickness of the insulating coating 14 is not particularly limited as long as the ratio S of the conductor cross-sectional area S1 to the oxygen index OI of the insulating coating 14 satisfies the relationship of formula (1). However, the insulating coating 14 is preferably thin in order to reduce the cross-sectional area ratio S as much as possible to improve flame retardancy and to reduce the diameter of the insulated wire 10. When the thickness of the insulating coating 14 is 0.20mm or less, further 0.15mm or less, and 0.10mm or less, the flame retardancy and the small diameter property of the insulated wire 10 can be effectively improved. The lower limit of the thickness is not particularly limited, but is preferably 0.08mm or more from the viewpoint of easily ensuring the wear resistance of the insulating coating 14.

The specific value of the cross-sectional area ratio S is also not particularly limited. However, by setting 4.0 or less, the effect of improving flame retardancy and the effect of reducing the diameter of the insulated wire 10 tend to be excellent. When the cross-sectional area ratio S is further set to 2.5 or less and 1.5 or less, the relationship of the formula (1) is easily satisfied with respect to the oxygen index OI of each resin composition assumed as the material of the insulating coating portion 14, and high flame retardancy can be secured in the insulated wire 10.

The composition of the resin composition constituting the insulating coating 14 exerts an influence on the flame retardancy of the insulated wire 10 through the oxygen index OI. However, the component composition of the resin composition can be arbitrarily selected as long as the desired cross-sectional area ratio S is given an oxygen index OI satisfying the formula (1).

Various polymer materials can be used as the resin component which is the main component of the resin composition. Examples of such polymer materials include polyolefins such as polyethylene and polypropylene, engineering plastics such as polyvinyl chloride, polyphenylene ether and polyamide, thermoplastic elastomers, and rubbers. The polymer material may be used alone or in combination of two or more.

Among the above-listed materials, a mixture of polyolefin and engineering plastic can be mentioned as a suitable resin component. Those mixtures tend to impart a relatively high oxygen index OI in various polymeric materials. Further, since polyolefin is excellent in chemical resistance and oil resistance and engineering plastic is excellent in abrasion resistance, even if the insulating coating 14 is formed to be thin and the cross-sectional area ratio S is reduced by using a mixture of them, the insulating coating 14 which is easy to secure abrasion resistance and is excellent in chemical resistance and oil resistance can be formed.

Examples of the polyolefin constituting the mixture include polypropylene (PP) and Polyethylene (PE). Examples of the engineering plastic include polyphenylene ether (PPE), Polyamide (PA), polybutylene terephthalate (PBT), and Polycarbonate (PC). The polyolefin and the engineering plastic preferably constitute a polymer alloy. The mixing ratio of the polyolefin and the engineering plastic is preferably a ratio of polyolefin: the mass ratio of the engineering plastics is 30: 70-70: 30.

among the above, as a particularly suitable example, a mixture (PP/PPE) of Polypropylene (PP) and polyphenylene ether (PPE), particularly a polymer alloy thereof can be exemplified. PP/PPE is a relatively inexpensive material, but is excellent in abrasion resistance, chemical resistance, and oil resistance.

It is also possible to further add further polymeric materials to the mixture of polyolefin and engineering plastic. Examples of such a polymer material include thermoplastic elastomers such as SEBS. By adding the thermoplastic elastomer, the flexibility and mechanical properties of the insulating coating 14 can be improved. The amount of the thermoplastic elastomer added may be 5 parts by mass or more based on 100 parts by mass of the total resin components constituting the resin composition, from the viewpoint of sufficiently obtaining the effect of addition. On the other hand, from the viewpoint of ensuring sufficient wear resistance, it is not more than 20 parts by mass.

The resin composition constituting the insulating coating 14 may contain various additives in addition to the resin component. As the additive, a flame retardant can be exemplified. The type of the flame retardant is not particularly limited, and examples thereof include phosphorus flame retardants such as phosphate compounds, bromine flame retardants, nitrogen flame retardants, and metal compound flame retardants. Among these flame retardants, from the viewpoint of improving compatibility with the resin component and suppressing a decrease in mechanical properties, a flame retardant composed of a phosphate ester compound is preferably used.

The oxygen index OI of the resin composition can be improved by adding the flame retardant. However, as described above, when the content of the flame retardant is increased, mechanical properties of the resin component such as abrasion resistance are easily impaired. In particular, when the insulating coating portion 14 is formed to be thin, it is difficult to ensure sufficient abrasion resistance when a large amount of flame retardant is contained. Therefore, it is preferable that the flame retardancy of the insulated wire 10 can be improved by reducing the cross-sectional area ratio S by thinning the insulating coating 14 without increasing the content of the flame retardant. That is, the content of the flame retardant is preferably reduced.

For example, when a flame retardant composed of a phosphate ester compound is used, the content thereof in the resin composition is preferably less than 30 parts by mass, and more preferably 20 parts by mass or less, per 100 parts by mass of the resin component. In particular, when the cross-sectional area ratio S of the insulated wire 10 is 2.5 or less, the insulated wire 10 satisfying the formula (1) and having high flame retardancy can be easily configured even if the content of the flame retardant composed of the phosphate compound is 10 parts by mass or less. Further, when the cross-sectional area ratio S of the insulated wire 10 is 1.5 or less, the insulated wire 10 having high flame retardancy satisfying the formula (1) can be easily configured even if the content of the flame retardant composed of the phosphate ester compound is 5 parts by mass or less.

The specific value of the oxygen index OI itself is not particularly limited. However, the oxygen index OI of the resin component assumed to be used as the insulating coating portion 14 is approximately 18 or more. Further, the oxygen index OI may be 21 or more. On the other hand, from the viewpoint of avoiding a form containing a large amount of the flame retardant, the oxygen index OI may be 23 or less.

The resin composition constituting the insulating coating 14 may contain various additives in addition to the flame retardant. Examples of such additives include fillers, antioxidants, lubricants, plasticizers, and pigments. However, from the viewpoint of easily ensuring the abrasion resistance when the insulating coating portion 14 is thinned, the content of the additive other than the flame retardant is preferably small. For example, the content of each additive that also contains a flame retardant is less than 30 parts by mass, and is further 20 parts by mass or less and 10 parts by mass or less with respect to 100 parts by mass of the resin component.

The insulating coating 14 may be formed by laminating a plurality of layers made of different resin compositions. In this case, when the formula (1) is applied, the total value of the sectional areas of the respective layers may be used as the insulation sectional area S2. The oxygen index OI may be a value obtained by weighted-averaging the oxygen indexes of the materials constituting each layer according to the cross-sectional area.

Examples

The following illustrates embodiments of the present invention. The present invention is not limited to these examples. Here, flame retardancy and abrasion resistance were evaluated for insulated wires in which the conductor cross-sectional area and the oxygen index and thickness of the insulating coating portion were variously changed.

[ test methods ]

(1) Preparation of samples

First, a copper alloy stranded wire is prepared as a wire conductor. Here, three kinds of wire conductors having different conductor cross-sectional areas are prepared. In particular, the nominal size of the conductor is 0.05mm²(wire diameter of 0.11mm, number of wires of seven) and 0.13mm²(wire diameter of 0.18mm, number of wires of seven) and 0.35mm²Three types (wire diameter of 0.26mm, number of wires of seven).

Further, the components shown in tables 1 and 2 were mixed at 280 ℃ in a predetermined content ratio to prepare resin compositions for preparing samples a1 to a13 and samples B1 to B5. The obtained resin composition was pressed to the outer periphery of the wire conductor by the thickness shown in tables 1 and 2 to form an insulating coating portion.

The following materials were used as the respective components of the resin composition constituting the insulating coating portion.

PPE: "ZYLON (ザイロン) S201A" manufactured by Asahi Kasei K.K.) "

PP: NOVATEC (ノバテック) EC9 manufactured by JAPAN POLYPROPYLENE CORPORATION "

SEBS: asahi Kasei K.K.)

Flame retardant: phosphoric ester flame retardant (aromatic condensed phosphoric ester) 'PX-200' manufactured by Kyowa Kagaku K.K.) "

Antioxidant: irganox (イルガノックス)1010 manufactured by BASF, a hindered phenol antioxidant "

(2) Evaluation of oxygen index

Resin compositions having the component compositions shown in tables 1 and 2 were molded into a sheet, and the oxygen index was evaluated in accordance with JIS K7201-2 on an IV test piece.

(3) Evaluation of flame retardancy

The flame retardancy of the insulated wire was evaluated according to ISO 6722. Specifically, each wire was cut to 600mm, fixed in a state of being inclined at an angle of 45 degrees with respect to the horizontal plane, and the flame of the gas torch was ignited at a position 500mm from the upper end. Then, the case where the combustion time until the flame is extinguished is 70 seconds or less was evaluated as "a" having high flame retardancy. On the other hand, the case where the combustion time until the flame was extinguished exceeded 70 seconds and the case where the flame was not extinguished were evaluated as "B" having low flame retardancy.

(4) Evaluation of wear resistance

The wear resistance of the insulating coating was evaluated by the reciprocating knife edge method in accordance with ISO 6722. At this time, the nominal size of the conductor is 0.05mm²Or 0.13mm²In the case of (3), the load applied to the blade was set to 4N, and the conductor nominal size was 0.35mm²In the case of (3), the load applied to the blade is set to 7N. Then, the number of reciprocating times of the blade until the conductor is exposed is set to a predetermined reference or more to evaluateThe "a" was evaluated as "a" having high wear resistance, and the "B" was evaluated as "B" having low wear resistance. The predetermined reference is 0.05mm in conductor nominal size²In the case of (2), 50 times, and 0.13mm in the conductor nominal size²In the case of (2), 100 times, and 0.35mm in the conductor nominal size²In the case of (2), 150 times.

[ results ]

In tables 1 and 2, the results of evaluation of flame retardancy and abrasion resistance of the samples a1 to a13 and the samples B1 to B5 are shown together with the content (unit: part by mass) of each component in the resin composition constituting the insulating coating portion, the Oxygen Index (OI), the conductor cross-sectional area (S1), and the insulation thickness. The table also shows the insulation sectional area (S2) and the sectional area ratio (S). The insulation cross-sectional area (S2) is calculated by subtracting the conductor cross-sectional area (S1) from the measured value of the cross-sectional area of the insulated wire. The cross-sectional area ratio (S) is calculated by dividing the insulation cross-sectional area (S2) by the conductor cross-sectional area (S1).

[ Table 1]

[ Table 2]

Fig. 2 shows the relationship between the cross-sectional area ratio and the oxygen index and the evaluation result of flame retardancy. The vertical axis is the cross-sectional area ratio, the horizontal axis is the oxygen index, the data points of samples a1 to a13 having an evaluation result of "a" are shown by circular symbols (●), and the data points of samples B1 to B5 having an evaluation result of "B" are shown by square symbols (□).

As can be seen from fig. 2: in each oxygen index, high flame retardancy can be obtained in a region where the cross-sectional area ratio is small. That is, the flame retardancy of the insulated wire can be improved by making the insulating coating portion thinner than the conductor cross-sectional area.

However, the cross-sectional area ratio that can achieve high flame retardancy evaluated as "a" differs depending on the oxygen index, and high flame retardancy can be obtained even if the cross-sectional area ratio is larger as the oxygen index is higher. As shown by the solid line in the figure, the case where high flame retardancy is evaluated as "a" and the case where high flame retardancy is not evaluated as "a" can be divided by the straight line on the upper right where OI is S + a where a is 17.2, and high flame retardancy can be obtained in the lower region of the straight line, that is, the region where the cross-sectional area ratio is small. In this way, the relationship between the cross-sectional area ratio and the flame retardancy can be evaluated using the linear function of the oxygen index, and the insulated wire having high flame retardancy can be obtained by using the cross-sectional area ratio of a value defined by the linear function or less. In the figure, the straight lines a to 17.5 and a to 18.0 are also indicated by the broken lines and dotted lines, respectively, and the regions having high flame retardancy can be more strictly sorted by these straight lines.

In the resin composition, when the content of the flame retardant is reduced, the oxygen index tends to be lowered, but in this case, sufficient flame retardancy can be secured by reducing the cross-sectional area ratio. For example, when the cross-sectional area ratio is 2.5 or less, high flame retardancy can be obtained even if the content of the flame retardant is reduced to 10 parts by mass or less (samples a1, a2, a5 to a7, a9, a 13). Further, when the cross-sectional area ratio is set to 1.5 or less, high flame retardancy can be obtained even if the content of the flame retardant is reduced to 5 parts by mass or less (samples a1, a5, a6, a 13).

The combustion time obtained by the test for flame retardancy evaluation is shown relative to the oxygen index in fig. 3A. As a result, even if the oxygen index is the same, data points are distributed in regions where the combustion times are greatly different. The oxygen index is an index having a correlation with the flame retardancy of the resin composition, but it can be said from fig. 3A that the flame retardancy of the insulated wire cannot be sufficiently evaluated only with the oxygen index of the resin composition constituting the insulating coating portion.

Further, fig. 3B shows the relationship between the insulation thickness and the evaluation results of the oxygen index and the flame retardancy. This figure corresponds to the replacement of the cross-sectional area ratio of the vertical axis of fig. 2 by the insulation thickness. Referring to fig. 3B, unlike the case of fig. 2, the data point (●) evaluated as having high flame retardancy and the data point (□) evaluated as having reduced flame retardancy are not distributed in clearly distinguished regions on the graph. For example, at two locations where the insulation thickness is 0.20mm, the high flame retardancy data point (●) and the low flame retardancy data point (□) overlap. From this, it can be said that as an index for evaluating the flame retardancy of the insulated wire together with the oxygen index of the resin composition, it is necessary to use the ratio to the conductor cross-sectional area, not the values of the thickness and the cross-sectional area of the insulating coating portion itself.

Finally, when the results of the wear resistance evaluations were compared for the respective samples in tables 1 and 2, the wear resistance was reduced in the samples a12 and B4 containing 30 parts by mass of the flame retardant. In sample a11, the number of reciprocations in the evaluation was also relatively small. From the viewpoint of obtaining sufficiently high abrasion resistance, the content of the flame retardant is preferably suppressed to less than 30 parts by mass in advance. While sample a6 and sample a13 differ in the content of SEBS, but have the same oxygen index, the same flame retardancy is obtained, but the abrasion resistance is increased in sample a13 having a small content of SEBS.

The embodiments of the present invention have been described above in detail, but the present invention is not limited to the above embodiments at all, and various changes can be made without departing from the scope of the present invention.

Description of the symbols

10 insulated wire

12 electric wire conductor

12a wire rod

14 insulating coating part