JP7666171B2 - Insulated Wire - Google Patents

Description

This disclosure relates to insulated wire.

Patent Document 1 discloses an automobile wire harness having a layer made of a resin coating material crosslinked from a resin composition containing 90 to 100 parts by mass of ethylene-vinyl acetate copolymer (A), 15 to 30 parts by mass of a bromine-based flame retardant (B), 5 to 15 parts by mass of antimony trioxide (C), 6 to 12 parts by mass of a benzimidazole-based antioxidant (D), 2 to 4 parts by mass of a phenol-based antioxidant (E), 2 to 4 parts by mass of a thioether-based antioxidant (F), 0.5 to 2 parts by mass of a copper inhibitor (G), and 3 to 6 parts by mass of a crosslinking assistant (H).

JP 2019-014794 A

An insulated wire comprises a conductor and an insulating layer that covers the outer surface of the conductor.

Insulated electric wires are also used in automobiles, for example, as in the automotive wire harness disclosed in Patent Document 1. However, when an insulated electric wire is used, for example, for wiring for an automobile light, and the insulated electric wire is heated by the light for a long period of time, clouding may occur in the translucent member of the light located around the wire.

Therefore, the present disclosure aims to provide an insulated electric wire that can suppress clouding of the surrounding translucent material even when heated.

The insulated wire of the present disclosure comprises a conductor and
an insulating layer covering an outer surface of the conductor;
The insulating layer contains a resin component and stearic acid as a lubricant,
The resin component contains polyethylene as a main component,
The resin component has a melting temperature of 110° C. or less and a heat of fusion of 80 J/g or less.

The present disclosure provides an insulated electric wire that can prevent clouding of the surrounding translucent material even when heated.

FIG. 1 is a cross-sectional view of an insulated wire according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. FIG. 2A is an explanatory diagram of the relationship between the crystallinity of a resin component and an additive. FIG. 2B is an explanatory diagram of the relationship between the crystallinity of the resin component and the additives. FIG. 3 is an explanatory diagram of a haze test device.

The form for implementing this is explained below.

[Description of the embodiments of the present disclosure]
First, the embodiments of the present disclosure will be described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

(1) An insulated wire according to one aspect of the present disclosure includes a conductor,
an insulating layer covering an outer surface of the conductor;
The insulating layer contains a resin component and stearic acid as a lubricant,
The resin component contains polyethylene as a main component,
The resin component has a melting temperature of 110° C. or less and a heat of fusion of 80 J/g or less.

When the resin component contains polyethylene as a main component and has a melting temperature of 110°C or lower, the crystallinity of the resin component is sufficiently low and the side chains of the resin component can contain a sufficient amount of branched structure. Therefore, even when the insulated wire is heated and exposed to high temperatures, the additive is prevented from being released outside the insulating layer, and gas generation and clouding of translucent members such as lights placed around the wire due to the generated gas can be prevented.

When the resin component contains polyethylene as a main component and has a heat of fusion of 80 J/g or less, the resin component has a sufficiently low crystallinity and can contain a sufficient amount of branched structure in the side chain of the resin component. Therefore, even when the insulated wire is heated and exposed to high temperatures, the additive is prevented from being released outside the insulating layer, and gas generation and clouding of translucent members such as lights placed around the wire due to the generated gas can be prevented.

In addition, when the insulating layer contains stearic acid as a lubricant, gas generation when the insulated wire is heated and clouding of the surrounding translucent member due to the generated gas are particularly likely to occur. In contrast, according to an insulated wire according to one aspect of the present disclosure, the generation of such gas and clouding of the surrounding translucent member can be suppressed even when the wire is heated. Therefore, when the insulating layer contains stearic acid as a lubricant, it is particularly effective in suppressing clouding of the surrounding translucent member.

(2) In accordance with ISO 6452, when the glass plate is placed in a container covered with a glass plate, heated at 100°C for 16 hours, and then left in the air for 1 hour, the haze value of the glass plate may be 15% or less.

When the above test is performed, if the haze value of the glass plate is 15% or less, the insulated wire can be said to be able to suppress the generation of gas even when heated for a long period of time, and to be particularly able to suppress the occurrence of clouding of the translucent member arranged around it.

(3) The resin component may have a melt mass flow rate of greater than 1.0 g/10 min.

When the melt mass flow rate of the resin component is greater than 1.0 g/10 min, the fluidity of the resin component increases when forming the insulated wire, improving processability when forming the insulated wire.

(4) It may also be used for wiring in automobile headlights.

The wiring of an automobile headlight may be heated by the headlight during use. It is particularly required that the translucent member used in the headlight not become cloudy. According to an insulated electric wire according to one embodiment of the present disclosure, even when heated for a long period of time, gas generation is suppressed, and clouding of the translucent member arranged around the wire can be suppressed. Therefore, the insulated electric wire according to one embodiment of the present disclosure can be particularly effective when used in the wiring of an automobile headlight.

[Details of the embodiment of the present disclosure]
Specific examples of an insulated wire according to an embodiment of the present disclosure (hereinafter, referred to as the present embodiment) will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.
[Insulated wire]
1 shows an example of the cross section of an insulated electric wire according to the present embodiment, the cross section being perpendicular to the longitudinal direction of the wire. The direction perpendicular to the paper surface of FIG. 1 is the longitudinal direction of the insulated electric wire.

As shown in FIG. 1 , an insulated wire 10 of the present embodiment can have a conductor 11 and an insulating layer 12 that covers the outer surface of the conductor 11 .
(1) Components Contained in the Insulated Wire Components contained in the insulated wire of the present embodiment will be described.
(1-1) Conductor The conductor 11 can be composed of a single metal wire or multiple metal wires. When the conductor 11 has multiple metal wires, the multiple metal wires can be twisted together. In other words, when the conductor 11 has multiple metal wires, the conductor 11 can be a twisted wire of multiple metal wires.

The material of the conductor 11 is not particularly limited, but may be one or more conductor materials selected from, for example, copper, soft copper, silver-plated soft copper, nickel-plated soft copper, tin-plated soft copper, and the like.
(1-2) Insulating Layer (1-2-1) Resin Component As shown in Fig. 1, the insulating layer 12 can cover the outer surface of the conductor 11, specifically, the outer surface along the longitudinal direction of the insulated wire 10. The insulating layer 12 can contain a resin component. The resin component contains polyethylene as a main component. The resin component may be crosslinked or may not be crosslinked.

The resin component containing polyethylene as a main component means that the resin component contains polyethylene in the largest amount by mass. In this case, the resin component preferably contains 65 mass% or more of polyethylene. Since the resin component can be composed of only polyethylene, the resin component can contain 100 mass% or less of polyethylene.
(Melting temperature, heat of fusion)
The inventors of the present invention have investigated the cause of clouding of the light-transmitting member of an automobile light when the insulated electric wire is used for wiring the light and heated for a long time by the light. The light-transmitting member refers to a member that protects a light source such as a light, is disposed on an optical path through which light from the light passes, and transmits the light. As a result, they have found that when the insulated electric wire is heated, additives such as lubricants contained in the insulating layer of the insulated electric wire volatilize and become gas, which condenses or solidifies and adheres to the light-transmitting member, causing the light-transmitting member to cloud.

Based on the above findings, the inventors of the present invention conducted further research. They discovered that the crystallinity of the resin component contained in the insulating layer can control the volatility of additives such as lubricants, and that even when the insulated electric wire is heated for a long period of time by a light or the like, gas generation and the clouding of the translucent member that accompanies gas generation can be suppressed, leading to the completion of the present invention.

The relationship between the crystallinity of the resin component of the insulating layer and the additives is shown using Figures 2A and 2B. Figures 2A and 2B show a schematic diagram of an additive 21 such as a lubricant, and a resin component 22. As shown in Figures 2A and 2B, the resin component 22 has a main chain 221 and a side chain 222. Note that the resin component may be crosslinked, and in the case of crosslinking, bonds will also be included between the main chains 221, etc.

The insulating layer 201 shown in FIG. 2A and the insulating layer 202 shown in FIG. 2B have different crystallinity of the resin component 22 contained therein, and the resin component contained in the insulating layer 201 has a lower crystallinity than the insulating layer 202.

As described above, in the insulating layer 202 shown in FIG. 2B, the resin component contained therein has high crystallinity, so that the branched structure in the side chains 222 is reduced. Therefore, when the insulating layer 202 is heated and exposed to high temperatures, the molecular motion of the additive 21 becomes active, and the additive 21 is easily released to the outside through the gaps in the resin component.

In contrast, in the insulating layer 201 shown in FIG. 2A, the crystallinity of the resin component contained therein is low, so the side chains 222 of the resin component 22 contain a branched structure as shown in FIG. 2A. Therefore, even if the insulating layer 201 is heated and exposed to high temperatures, causing active molecular motion of the additive 21, the molecular motion is inhibited by the side chains 222 having a branched structure. As a result, even if the insulating layer 201 is heated, the additive 21 is less likely to be released to the outside.

Therefore, it is preferable that the resin component contained in the insulating layer 12 has low crystallinity. The crystallinity of the resin component contained in the insulating layer can be evaluated by the melting temperature and heat of fusion. The melting temperature and heat of fusion of the resin component can be determined by performing DSC (Differential Scanning Calorimetry) measurement on the insulating layer.

The melting temperature of the resin component is preferably 110°C or less, and more preferably 107°C or less.

When the resin component contains polyethylene as a main component and has a melting temperature of 110°C or lower, the crystallinity of the resin component is sufficiently low and the side chains of the resin component can contain a sufficient amount of branched structure. Therefore, even when the insulated wire is heated and exposed to high temperatures, the additive is prevented from being released outside the insulating layer, and gas generation and clouding of translucent members such as lights placed around the wire due to the generated gas can be prevented.

The lower limit of the melting temperature of the resin component is not particularly limited, but is preferably 55°C or higher, and more preferably 60°C or higher.

The heat of fusion of the resin component is preferably 80 J/g or less, and more preferably 75 J/g or less.

When the resin component contains polyethylene as a main component and has a heat of fusion of 80 J/g or less, the resin component has a sufficiently low crystallinity and can contain a sufficient amount of branched structure in the side chain of the resin component. Therefore, even when the insulated wire is heated and exposed to high temperatures, the additive is prevented from being released outside the insulating layer, and gas generation and clouding of translucent members such as lights placed around the wire due to the generated gas can be prevented.

The lower limit of the heat of fusion of the resin component is not particularly limited, but is preferably, for example, 30 J/g or more, and more preferably 32 J/g or more.
(Melt Mass Flow Rate)
The resin component preferably has a melt mass flow rate (MFR) of more than 1.0 g/10 min, more preferably 1.1 g/10 min or more. When the resin component has a melt mass flow rate of more than 1.0 g/10 min, the resin component has high fluidity when forming the insulated electric wire, and the processability when forming the insulated electric wire can be improved.

The upper limit of the melt mass flow rate of the resin component is not particularly limited, but is preferably 5.0 g/10 min or less, and more preferably 2.0 g/10 min or less, for example. By setting the melt mass flow rate in the above range, the fluidity of the resin component can be prevented from becoming excessively high when forming the insulated electric wire, and the processability when forming the insulated electric wire can be particularly improved.
(1-2-2) Additives In addition to the above-mentioned resin components, the insulating layer 12 may contain various additives. The insulating layer 12 may contain, as the additive, one or more selected from, for example, a flame retardant, an antioxidant, a lubricant, an acid acceptor, and the like.
(Lubricant)
As described above, the raw material of the gas that is generated when the insulated wire is heated and causes the clouding of the light-transmitting member is mainly a lubricant such as stearic acid. For this reason, it is preferable that the insulating layer 12 contains stearic acid as a lubricant. When the insulating layer 12 contains stearic acid as a lubricant, the generation of gas when the insulated wire is heated and the clouding of the light-transmitting member associated therewith are likely to occur. In contrast, according to the insulated wire of the present embodiment, even when heated, the generation of such gas and the clouding of the light-transmitting member disposed around the wire can be suppressed. For this reason, when the insulating layer contains stearic acid as a lubricant, a particularly high effect can be exhibited in suppressing the clouding of the light-transmitting member around the wire.

In this specification, stearic acid does not include stearates such as zinc stearate and calcium stearate formed by reacting with a base.

The amount of stearic acid contained in the insulating layer 12 is not particularly limited. For example, when the resin component is 100 parts by mass, the insulating layer 12 preferably contains stearic acid in an amount of more than 0 parts by mass and not more than 2.0 parts by mass, and more preferably contains stearic acid in an amount of 0.1 parts by mass or more and not more than 1.5 parts by mass.

When the insulating layer 12 has a resin component of 100 parts by mass, the content of stearic acid is more than 0 parts by mass, which makes it easier to peel the insulating layer 12 from the conductor 11 and improves the processability of the insulated wire. When the insulating layer 12 has a resin component of 100 parts by mass, the content of stearic acid is 2.0 parts by mass or less, which makes it possible to prevent precipitation of stearic acid on the surface of the insulating layer 12, etc.
(Flame retardant)
The flame retardant is not particularly limited, and for example, a halogen-based flame retardant can be used.

The halogen-based flame retardant imparts flame retardancy to the insulating layer of the insulated electric wire. Examples of halogen-based flame retardants include bromine-based flame retardants and chlorine-based flame retardants.

Examples of bromine-based flame retardants include ethylene bis tetrabromophthalimide, ethylene bis (pentabromophenyl), tetrabromoethane, tetrabromobisphenol A, hexabromobenzene, decabromo biphenyl ether, tetrabromophthalic anhydride, polydibromophenylene oxide, hexabromocyclodecane, and ammonium bromide.

Examples of chlorine-based flame retardants include chlorinated paraffin, chlorinated polyethylene, chlorinated polyphenol, and perchlorpentacyclodecane.

Among these halogen-based flame retardants, bromine-based flame retardants are preferred, with ethylene bis(tetrabromophthalimide) (e.g., Albemarle's "Scitex BT93") and ethylene bis(pentabromophenyl) (e.g., Albemarle's "Scitex 8010") being more preferred. The halogen-based flame retardants may be used alone or in combination of two or more types.

The lower limit of the content of the halogen-based flame retardant in the insulating layer 12 is not particularly limited. For example, when the resin component is 100 parts by mass, the insulating layer 12 preferably contains 1 part by mass or more of the halogen-based flame retardant, preferably 5 parts by mass or more, and more preferably 10 parts by mass or more. When the resin component is 100 parts by mass, the insulating layer 12 contains 1 part by mass or more of the halogen-based flame retardant, so that the insulating layer 12 can be provided with sufficient flame retardancy.

The upper limit of the content of the halogen-based flame retardant in the insulating layer 12 is not particularly limited. For example, when the resin component is 100 parts by mass, the insulating layer 12 preferably contains 30 parts by mass or less of the halogen-based flame retardant, and more preferably 25 parts by mass or less. When the resin component is 100 parts by mass, the insulating layer 12 contains 30 parts by mass or less of the halogen-based flame retardant, thereby improving the adhesion between the insulating layer and the conductor.

In addition to the above halogen-based flame retardants, the insulating layer 12 may contain a phosphorus-based flame retardant, a nitrogen-based flame retardant, or a non-halogen-based flame retardant such as magnesium hydroxide, aluminum hydroxide, antimony trioxide, etc. The content of the non-halogen-based flame retardant is also not particularly limited, but the content of the non-halogen-based flame retardant is preferably 10 parts by mass or less when the resin component is taken as 100 parts by mass.
(Antioxidants)
The antioxidant is preferably a hindered phenol-based antioxidant. Examples of the hindered phenol-based antioxidant include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide], benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate, and the like. hydroxy, C7-C9 side chain alkyl ester, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 3,3',3",5,5'5"-hexa-tert-butyl-a,a',a"-(mesitylene-2,4,6-tolyl)tri-p-cresol, calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-tert-butyl-4-(4,6-bis(oxazone) butylthio)-1,3,5-triazin-2-ylamino)phenol, 2,6-di-tert-butyl-4-methylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 3,9-bis[2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propynox)-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro(5,5)undecane, etc. These may be used alone or in combination of two or more.

The lower limit of the antioxidant content of the insulating layer 12 is not particularly limited. For example, when the resin component is 100 parts by mass, the insulating layer 12 preferably contains 0.5 parts by mass or more of the antioxidant, and more preferably 1 part by mass or more. When the resin component is 100 parts by mass, the insulating layer 12 contains 0.5 parts by mass or more of the antioxidant, so that the insulating layer 12 can be given sufficient antioxidant properties.

There is no particular upper limit to the content of the antioxidant in the insulating layer 12. For example, when the resin component is taken as 100 parts by mass, the content of the antioxidant in the insulating layer 12 is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less. When the resin component is taken as 100 parts by mass, the insulating layer 12 contains 10 parts by mass or less of the antioxidant, thereby making it possible to suppress blooming and the like.
(Acid Acceptor)
As the acid acceptor, one or more materials selected from the group consisting of iron oxide, titanium oxide, magnesium oxide, aluminum oxide, silicon dioxide, and zinc oxide can be used.

The lower limit of the content of the acid acceptor in the insulating layer 12 is not particularly limited. For example, when the resin component in the insulating layer 12 is 100 parts by mass, the content of the acid acceptor in the insulating layer 12 is preferably 0.1 parts by mass or more, and more preferably 5 parts by mass or more.

There is no particular upper limit on the content of the acid acceptor in the insulating layer 12. For example, when the resin component in the insulating layer 12 is taken as 100 parts by mass, the content of the acid acceptor in the insulating layer 12 is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.
(2) Characteristics and Suitable Uses of the Insulated Wire (2-1) Haze According to the insulated wire of the present embodiment, even when heated, gas generation can be suppressed and the generation of haze on a translucent member disposed around the insulated wire can be suppressed.

There are no particular limitations on the degree to which the generation of such gases is suppressed and the occurrence of fogging on the translucent member is suppressed. For example, in accordance with ISO 6542, when an insulated electric wire is placed in a container covered with a glass plate, heated at 100°C for 16 hours, and then left in the air for 1 hour, the haze value of the glass plate is preferably 15% or less, and more preferably 14% or less.

When the above test is carried out, if the haze value of the glass plate is 15% or less, it can be said that the generation of gas is suppressed even when heated for a long period of time, and the clouding of the translucent material arranged around it is sufficiently suppressed.

The lower limit of the haze value of the glass plate when the above test is performed is not particularly limited, but it should be 0 or more. However, since it may be difficult to achieve a haze value of 0, it is preferable that the haze value be 1% or more.

The above test can be carried out based on the ISO 6542 standard, for example, using the haze test device shown in Figure 3. Figure 3 shows a schematic cross-sectional view of the haze test device taken along a plane passing through the central axis.

The haze test device is structured by stacking a beaker 31 with an inner diameter of φ83 mm and a height of 190 mm, a silicon packing 32, a 100 mm x 100 mm glass plate 33, filter paper 34, and a cooling plate 35. The haze value can be measured by the following procedure.

Fill the oil bath with silicone oil to a height of 130 mm and heat it to 100°C.

Next, the insulated wire 10 to be evaluated is placed in the beaker 31 of the haze test device, and the packing 32, glass plate 33, filter paper 34, and cooling plate 35 are stacked at the upper opening of the beaker 31 and the lid is placed. The cooling plate 35 can be configured so that water at 21°C flows inside to cool the glass plate 33, etc.

Then, place the haze test device in an oil bath and heat it for 16 hours.

Next, remove the haze test device from the oil bath and leave it in an air environment, for example, at a temperature of 23°C and a relative humidity of 50% RH, for one hour.

The glass plate 33 can then be removed and the haze measured.
(2-2) Suitable Uses There are no particular limitations on the uses of the insulated wire of the present embodiment, but it is preferable that the insulated wire be used for wiring in automobile headlights.

The wiring of an automobile headlight may be heated by the headlight during use. It is particularly required to prevent the occurrence of fogging in the translucent members used in the headlights. The insulated wire of this embodiment can suppress the generation of gas even when heated for a long period of time, and can suppress the occurrence of fogging in the translucent members arranged around it. For this reason, the insulated wire of this embodiment can be particularly effective when used in the wiring of an automobile headlight.

The present invention will be described below with reference to specific examples, but is not limited to these examples.
(Evaluation Method)
First, the evaluation method of the insulated wires produced in the following experimental examples will be described.
(1) Melting Temperature and Heat of Fusion The melting temperature and heat of fusion of the resin component contained in the insulating layer were measured and calculated using a DSC (Shimadzu Corporation; heat flux differential scanning calorimeter DSC-50) according to the method described below.

The insulating layer was peeled off from the insulated electric wires produced in each of the following experimental examples. Then, in a DSC, 5 mg of the insulating layer was heated from room temperature to 200°C at a rate of 10°C/min under a nitrogen gas flow.

The melting temperature and heat of fusion were determined from the DSC curve obtained. Specifically, the temperature at the point where the endothermic peak with the greatest maximum intensity appears on the DSC curve was taken as the melting temperature, and the area of the peak was converted per gram of the sample evaluated to determine the heat of fusion.

The point where the peak rises means the intersection point between the baseline and the tangent line at the inflection point.
(3) Melt Mass Flow Rate The melt mass flow rate of the resin component contained in the insulating layer was measured under conditions of a temperature of 190° C. and a test load of 2.16 kg using a melt indexer (melt flow rate measuring device) manufactured by Toyo Seiki Seisakusho Co., Ltd. Note that the insulating layer peeled off from the insulated wire was used as the test piece in the same manner as in the case of the melting temperature, etc. The evaluation results are shown in the column "MFR (g/10 min)" in Table 2.
(4) Specific Gravity Based on JIS K 7112 (1999), the specific gravity (density) of the resin component used in producing the insulating layer was measured by an underwater displacement method.
(5) Haze Value and Haze Evaluation The haze value was evaluated based on the standard ISO 6542. Specifically, a glass plate for measuring the haze value was prepared using a haze tester shown in FIG.

The haze test device has a structure in which a beaker 31 with an inner diameter of φ83 mm and a height of 190 mm, a silicon packing 32, a 100 mm x 100 mm glass plate 33, filter paper 34, and a cooling plate 35 are stacked.

The oil bath was filled with silicone oil to a height of 130 mm and heated to 100°C.

Then, the insulated wire 10 to be evaluated was placed in the beaker 31 of the haze test device, and the packing 32, glass plate 33, filter paper 34, and cooling plate 35 were stacked at the upper opening of the beaker 31 and the lid was placed. Three insulated wires of the same sample were prepared with lengths of 230 mm, 225 mm, and 220 mm. The three insulated wires were then arranged in a circular ring shape at the bottom of the beaker 31 without overlapping. The cooling plate 35 was configured so that water at 21°C would flow inside to cool the glass plate 33, etc.

The haze test device was then placed in an oil bath and heated for 16 hours.

Next, the haze test device was removed from the oil bath and left in an air atmosphere, specifically an environment with a temperature of 23°C and a relative humidity of 50% RH, for one hour.

Then, the glass plate was removed and the haze was measured. The haze was measured using a haze measuring device (Murakami Color Research Laboratory, Model: Haze Meter HM-150L2).

For the same experimental sample, heating using the haze test device and measuring the haze on the glass plate were performed twice under the same conditions, and the average of the two measurements was taken as the haze value for that experimental example.

If the obtained haze value was 15% or less, the haze rating was rated as A, and if it was greater than 15%, the haze rating was rated as B. A haze rating of A means that the insulated wire is capable of preventing the occurrence of clouding on the surrounding translucent members even when heated.

The insulated wires used in each experimental example are described below.

In the following experimental examples, insulated wires were produced according to experimental examples 1 to 8. Experimental examples 1 to 4 are working examples, and experimental examples 5 to 8 are comparative examples.
[Experimental Example 1]
In Experimental Example 1, an insulated wire was produced that had a conductor 11 and an insulating layer 12 covering the outer surface of the conductor 11, as shown in FIG. 1, in a cross section perpendicular to the longitudinal direction.

Specifically, the components were mixed in the hopper of an extruder in the blending ratio (mass ratio) shown in Table 1, and extrusion was performed by setting the temperature of the extruder to 180°C. In all of Experimental Examples 1 to 8, the resin component contained 100% polyethylene by mass. The extrusion was performed by extruding an insulating layer onto a conductor with an outer diameter of 0.75 mm. After extrusion, a cross-linking treatment was performed using an electron beam. A single wire of tin-plated soft copper was used as the conductor, and the outer diameter of the obtained insulated wire was 1.4 mm.

The insulated wire thus obtained was subjected to the above-mentioned evaluations. The evaluation results are shown in Table 2.
[Experimental Examples 2 to 8]
Insulated wires were produced and evaluated in the same manner as in Experimental Example 1, except that the blending ratio (mass ratio) of each material supplied to the extrusion molding machine was changed to the value shown in Table 1. The evaluation results are shown in Table 2.

上記結果によれば、絶縁層に用いた樹脂成分の融解温度が１１０℃以下、融解熱量が８０Ｊ／ｇ以下であり、滑剤としてステアリン酸を含有する実験例１～実験例４の絶縁電線では、ヘイズ値が１５％以下となり、ヘイズ評価がＡになることを確認できた。すなわち、加熱された場合でも周囲の透光部材への曇りの発生を抑制できる絶縁電線であることを確認できた。

According to the above results, it was confirmed that the insulated wires of Experimental Examples 1 to 4, in which the resin component used in the insulating layer had a melting temperature of 110° C. or less, a heat of fusion of 80 J/g or less, and contained stearic acid as a lubricant, had a haze value of 15% or less and a haze evaluation of A. That is, it was confirmed that these insulated wires were capable of suppressing the generation of clouding on the surrounding light-transmitting member even when heated.

REFERENCE SIGNS LIST 10 Insulated wire 11 Conductor 12, 201, 202 Insulating layer 21 Additive 22 Resin component 221 Main chain 222 Side chain 31 Beaker 32 Gasket 33 Glass plate 34 Filter paper 35 Cooling plate

Claims (4)

A conductor;
an insulating layer covering an outer surface of the conductor;
The insulating layer contains a resin component and stearic acid as a lubricant,
The resin component contains polyethylene as a main component,
The resin component has a melting temperature of 110° C. or lower and a heat of fusion of 80 J/g or lower. The insulated wire according to claim 1, which is placed in a container covered with a glass plate, heated at 100°C for 16 hours, and then left in the air for 1 hour in accordance with ISO 6452, has a haze value of 15% or less. The insulated wire according to claim 1 or 2, wherein the resin component has a melt mass flow rate of greater than 1.0 g/10 min. An insulated electric wire according to any one of claims 1 to 3, which is used for wiring an automobile headlight.

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