JP2002373528A - Insulated electric wire and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halogen free insulated electric wire with which the holding power of the electric wire does not decline, by deforming an insulator substance 12, in a strain-relief part 4 of a pressure contact connector, even if the connection is made by using a pressure contact connector, and the tear of an insulator does not grow up (notch propagation) even to a portion except where a pressure welding edge and the electricity feeding conductor touch in the slot part 3 of the pressure welding connector. SOLUTION: As a resin composite covered on an electricity feeding conductor, the resin composite which is combined with metal hydrate, such as magnesium hydrate or the like, as a fire-retardant agent to the resin component, which makes a styrene system thermoplastic elastomer and styrene butadiene rubber a main substance. Cross-linking is carried out by irradiation of ionization radiation, such as an electron ray, so that 100% modulus of the concerned covering layer in 200 deg.C may be set to 0.2 MPa or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated wire used for, for example, in-machine wiring, and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the growing public interest in global environmental issues, there has been a movement to replace PVC (polyvinyl chloride), which has been used in a large amount as a coating material for electric wires and cables, with a halogen-free material. The same is true for in-machine wiring wires and the like applied to internal wiring of electronic devices.

[0003] Electric wires for in-machine wiring are manufactured by UL (Underwrit) in the United States.
ers Laboratories) standards and the vertical flame retardancy test described in the Japanese Electrical Appliance and Material Control Law, etc., and the coating material is required to have high flame retardancy. So, conventionally,
PVC has been widely used as a coating material.
There are various resin compositions in which a polyolefin-based polypropylene, polyethylene, ethylene-based copolymer (such as EVA or EEA) is blended as a halogen-free material with a metal hydroxide such as aluminum hydroxide or magnesium hydroxide as a flame retardant. Are being considered.

On the other hand, the efficiency of the internal wiring work of electronic equipment has been improved.
Due to the demand for high-density wiring, crimp connectors and press-fit connectors have come to be used frequently for connecting printed wiring boards and insulated wires. FIG. 1 is a perspective view of a board-to-wire press-connecting connector 2. The electric wire 1 is fitted into a portion called a strain relief portion 4 and, in the slot portion, the electric wire 1 is bunched 5 as shown in FIG.
This connector is a connector of a type that is pressed into a pressure contact blade (a terminal serving as a conductive member with a circuit pattern of a printed wiring board), breaks the insulator with the pressure contact blade, and makes electrical contact between the conductor of the electric wire and the pressure contact blade.

[0005]

FIG. 3 is a sectional view showing a state where the electric wire is fitted into the strain relief. When a press-fit connector is applied to a polyolefin-based halogen-free wire,
As shown in (b), the insulator of the electric wire is deformed, which causes a problem such as a decrease in the holding force of the electric wire. Further, although not shown, the insulator is broken in the slot portion. But,
In some cases, the pressure contact blade and the conductor grow to a position other than where they come into contact with each other (notch propagation), causing problems such as impairing aesthetic appearance and reducing reliability. for that reason,
Halogen-free electric wires that do not deform at the strain relief portion even when using a crimping connector or crimping connector and that do not allow the insulation to grow at the slot other than where the crimping blade and the conductor are in contact are required. Have been.

[0006]

Means for Solving the Problems As a result of diligent studies on the above-mentioned problems, the present inventors have found that a resin composition containing at least a styrene-based thermoplastic elastomer or styrene-butadiene rubber is used as an insulating layer of an electric wire. 100% modulus at 200 ° C of the insulating layer is 0.2 MPa
As described above, it was found that crosslinking treatment by irradiation with ionizing radiation such as an electron beam can solve problems such as deformation of the insulator at the strain relief portion and growth of the insulation coating at the slot portion. Invented the invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The styrene-based thermoplastic elastomer referred to in the present invention is a styrene / ethylene butylene / styrene copolymer, a styrene / ethylene butylene copolymer,
Styrene / ethylene / butylene / olefin copolymer, styrene / isoprene copolymer, styrene / ethylene / isoprene copolymer, styrene / isoprene / styrene copolymer, styrene / ethylene / isoprene / styrene copolymer, and the like, These hydrogenated polymers, partially hydrogenated polymers, and chemically modified polymers such as those modified with maleic anhydride or epoxy can be exemplified. Examples of the styrene-butadiene rubber include a copolymer of styrene and butadiene having a styrene content of 20 to 60% by weight, and examples thereof include a maleic anhydride-modified product and an epoxy-modified product. Or a combination with the above-mentioned styrene-based thermoplastic elastomer.

The above-mentioned styrene-based elastomer and styrene-butadiene rubber include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, and copolymers of ethylene and a polar comonomer such as EVA and EEA. Known polymers such as coalesced polypropylene (homopolymers, random polymers, block polymers), propylene-based thermoplastic elastomers, polyolefin-grafted polyolefins, etc., as required, do not exceed the above-mentioned styrene-based elastomer and styrene-butadiene rubber amounts. Can be blended. It is not preferable that the amount of the styrene-based elastomer or the styrene-butadiene rubber is blended in excess of the amount of the styrene-based elastomer or the styrene-butadiene rubber to lose the characteristics of the styrene-based elastomer or the styrene-butadiene rubber.

A metal hydroxide can be added to the resin composition used for the insulating layer of the electric wire of the present invention in order to impart flame retardancy, and the metal hydroxide may be magnesium hydroxide. In addition, aluminum hydroxide, calcium hydroxide and the like can be exemplified, and one or more of these may be used in combination. In addition, these metal hydroxides, fatty acids, fatty acid salts, surfactants, those surface-treated with a wax-based treatment agent can also be used,
Further, those surface-treated with a coupling agent such as a silane-based, titanate-based, aluminum-based, zircoaluminum-based, carboxylic acid-based, or phosphoric acid-based can also be used.

From the viewpoint of flame retardancy, the amount of the metal hydroxide is preferably 50 to 250 parts, more preferably 90 to 250 parts, per 100 parts by weight of the resin containing the styrene-based thermoplastic elastomer or styrene-butadiene rubber. A range of 220 parts by weight is preferred. If the amount is less than 50 parts by weight, it is difficult to pass a vertical combustion test such as UL standard VW-1 test regardless of the size of the electric wire.
If the amount exceeds 0 parts by weight, the melting torque increases and the extrudability deteriorates.

The above resin composition may contain, if necessary, antimony trioxide, zinc sulfide, borate, molybdate, stannate, carbonate, acetate, silicate, zirconium compound, Add flame retardant such as expanded graphite, nitrogen-based flame retardant such as melamine compound, silicone-based flame retardant such as polysiloxane, phosphoric ester-based or polyphosphate-based compound, or phosphorus-based flame retardant such as red phosphorus-based Can also.

Further, in order to improve the extrudability and the dispersibility of the metal hydroxide, the additive and the filler during mixing,
It is also possible to add a lubricant such as paraffin or hydrocarbon resin, fatty acid amide type, fatty alcohol type, fatty acid type, fatty acid ester type, etc., for the purpose of improving heat resistance and weather resistance, amine type, hydroquinone derivative type, Polyphenol-based, quinoline-based, phenol-based, thiobisphenol-based, hindered phenol-based, phosphite-based, salicylic acid derivative-based, benzotriazole-based, hindered amine-based, benzophenone-based ultraviolet absorbers and copper damage inhibitors Addition is also possible.

The insulated wire of the present invention is also characterized in that the coating layer on the conductor is cross-linked by irradiation with ionizing radiation. In order to crosslink the resin, a thermal vulcanization method and a water crosslinking method are known in addition to the crosslinking by ionizing radiation. However, the thermal vulcanization method is used when the insulation thickness is large and electron beam irradiation is difficult to crosslink.However, for relatively thin wires such as in-machine wiring, electron beam irradiation crosslink is faster. It is advantageous. In addition, the water crosslinking method requires a dedicated production line capable of strictly controlling the water content of the resin composition, and is not very suitable for a system in which a large amount of a metal hydroxide having a high water absorption is blended. . Further, since the crosslinking speed is low, it is not suitable as a method for crosslinking an in-machine wiring wire.

On the other hand, a so-called dynamic vulcanization for partially crosslinking a resin component in an extruder or vulcanizing only a specific polymer component in a blend system of a plurality of polymers, and a reactor for performing the same in a polymerization reactor. Cross-linking systems and the like are also known, but these cross-linking materials generally have problems such as an increase in the melting torque of the resin component and a decrease in extrudability.

On the other hand, in the cross-linking method by irradiation with ionizing radiation, the degree of cross-linking of the coating layer of the present invention can be freely controlled only by changing the irradiation dose, and an unvulcanized material having a low melting torque can be obtained. Since the extrusion can be performed, the line speed at the time of extrusion is high, and the speed of the cross-linking treatment is also high. Therefore, it is the most suitable method for cross-linking the coating layer of the thin insulated wire used for the in-machine wiring of the present invention.

In the above-mentioned crosslinking of the coating layer by irradiation with ionizing radiation, a polyfunctional monomer having a plurality of carbon-carbon double bonds in the same molecule, for example, 1,6, in order to further increase the crosslinking rate. -Hexanediol dimethacrylate, trimethylolpropane trimethacrylate,
It is also possible to add triallyl isocyanurate, triallyl cyanurate and the like.

Examples of the ionizing radiation source include accelerated electron beams, gamma rays, X-rays, α-rays, ultraviolet rays, etc., but from the viewpoint of industrial use such as simplicity of use of the source, thickness of ionizing radiation permeation, and speed of crosslinking treatment. The most preferred is an accelerated electron beam.

If necessary, an inorganic foaming agent, an azo compound foaming agent and a nitroso compound sulfonylhydrazide compound are added to the resin composition of the present invention to form a foamed layer. The capacitance between them can be reduced. This is effective when a shield layer is provided outside the insulating layer to form a shielded electric wire.

The present inventors have found that, as the degree of cross-linking of the coating layer is increased, the tendency of deformation at the strain relief portion and growth of tearing of the coating at the slot portion when connecting to the press-connecting connector is reduced. As an index of the degree of cross-linking, using a 100% modulus when the coating layer was subjected to a tensile test at 200 ° C., such that the value becomes 0.2 MPa or more,
If the coating layer is cross-linked by irradiation with ionizing radiation, deformation at the strain relief part when fitting into the insulation displacement connector,
It has been found that a unique effect is achieved in that the growth of the tearing of the coating in the slot portion is eliminated.

Generally, the degree of crosslinking (vulcanization degree) of a vulcanized rubber is
At low elongation of the tensile test at room temperature (for example, 100% or less)
It is known that the higher the modulus, the higher the degree of crosslinking. When this correlation is applied to a crosslinked thermoplastic resin having crystallinity, it is necessary to measure the modulus at a temperature exceeding the melting point of the crystal of the thermoplastic resin.

In the coating layer of the insulated wire according to the present invention, when the resin component is amorphous, for example, when a styrene-based thermoplastic elastomer alone or a styrene-butadiene rubber alone is used, the measurement was performed at room temperature. The low elongation modulus can be used as an index of the degree of crosslinking of the coating layer.However, in a system in which various polymers having crystallinity are blended with a styrene-based thermoplastic elastomer or styrene-butadiene rubber, a polymer to be added is used. It is necessary to measure the modulus at a temperature higher than the crystal melting point of. The present inventors have found that the highest melting point of the polypropylene homopolymer among the polymers used in the present invention is 160 to 170 ° C., and therefore, in the present invention, even in the composition where the crystalline polymer exists, It is thought that all components are molten 2
00 ° C. was taken as the measurement temperature of the 100% modulus.

[0022]

The present invention will be described below with reference to examples. Table 1
The compounded compositions shown in Tables 1 to 3 were melt-kneaded in a pressure kneader set at 150 ° C., and the obtained kneaded material was formed into pellets using a feeder ruder. In addition, in the compounding compositions described in Tables 1 to 3, 0.5 parts by weight of oleamide was added to 100 parts by weight of the resin component, and pentaerythritol-tetrakis [3- (3,5-di-t-butyl-) was used. 4-hydroxyphenyl) propionate] in an amount of 1 part by weight.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

Using a melt extruder (45 mmφ, L / D = 24, compression ratio 2.5, full flight type), pellets having the composition shown in Tables 1 to 3 were used to form a 0.16 φ tinned annealed copper wire. Extrusion coating was performed on a conductor obtained by twisting seven wires to a thickness of 0.27 mm, and a predetermined amount of an electron beam having an acceleration voltage of 2 MeV was irradiated to produce an insulated wire.

The degree of crosslinking of the coating layer was determined by a method in which a 100% modulus was measured at a temperature of 200 ° C. and a tensile speed of 50 mm / min using a tensile tester equipped with a thermostat.
The press-working processability is determined by using a hand-press type simple jig or press-fitting pistol tool with JST KR connector or AM.
The insulated wire was fitted into the slot portion and the strain relief portion by mounting a P-made CT connector and pressing the insulated wire. The crimping workability was evaluated based on the presence or absence of deformation of the insulating coating at the strain relief portion after fitting and the presence or absence of tearing of the insulating coating at the slot portion.

The tensile test of the coating layer (tensile speed 500 mm
/ Min), the tensile strength and the tensile elongation at break were measured at each of the three points, and the average value was determined. The modulus of elasticity was determined by the modulus at 2% elongation in a tensile test (tensile speed: 50 mm / min). The value obtained by multiplying by 50 was determined as n = 3, the average value was obtained, and this was used as an index of the elastic modulus.

To investigate the flame retardancy of this insulated wire, U
The LW standard VW-1 test was performed on each of the five samples.
Judgment was made that even if one of the five points burned for 60 seconds or more, the cotton wool laid at the bottom burned down by burning falling objects, or the kraft paper attached to the top of the sample burned or burned, it was rejected. did.

Examples 1 to 8 In Examples 1 to 8 in Table 1, styrene / ethylene / butylene / styrene copolymers, styrene / butadiene copolymers, or styrene / ethylene / butadiene / olefin copolymers were used. Magnesium hydroxide (average particle size of 0.
It is an insulated wire using a resin composition containing 7 μm, a BET specific surface area of 8 m ² / g, and stearic acid surface treatment), and is irradiated with an electron beam having an acceleration voltage of 2 MeV in a range of 50 to 200 kGy. The 100% modulus at 200 ° C. of the coating layer of these insulated wires is 0.2 to 0.9.
In the range of MPa, the crimping workability was evaluated using two types of connectors. As a result, no deformation of the coating at the strain relief portion and no breakage of the coating at the slot portion were observed for any of the insulated wires. It was found that it was press-workable.

Comparative Examples 1 to 5 Comparative examples 1 to 5 shown in Table 2 were obtained from styrene / ethylene / butylene / styrene copolymer, styrene / butadiene copolymer, or styrene / ethylene / butadiene / olefin copolymer. Magnesium hydroxide (average particle size of 0.
It is an insulated wire using a resin composition containing 7 μm, a BET specific surface area of 8 m ² / g, and stearic acid surface treatment), and is irradiated with an electron beam having an acceleration voltage of 2 MeV in a range of 50 to 200 kGy. The 100% modulus at 200 ° C. of the coating layer of these insulated wires is 0.05 to 0.
It is in the range of 16MPa, and as a result of evaluating the press-welding workability of the connector, the evaluation results vary, such as breakage at the slot part and deformation of the coating at the strain relief part, depending on the type of connector, It turned out to be inferior.

Comparative Examples 6 and 7 Comparative Examples 6 and 7 in Table 3 show that ethylene / vinyl acetate copolymer and ethylene / ethyl acrylate copolymer had an average particle size of 0.7 μm and water It is an insulated wire using a resin composition blended with magnesium oxide (average particle size 0.7 μm, BET specific surface area 8 m ² / g, stearic acid surface treatment), and irradiated with 100 kGy of an electron beam having an acceleration voltage of 2 MeV. is there. The 100% modulus at 200 ° C. of the coating layer of these insulated wires was 0.3 to 0.6 MPa. However, as a result of evaluating the crimpability of the connector,
Depending on the type of connector, tearing at the slot,
The evaluation results were scattered, such as deformation of the coating at the strain relief portion, and it was found that the pressure welding workability was poor.
That is, ethylene-vinyl acetate copolymer, ethylene
It was found that, in a system mainly composed of an ethyl acrylate copolymer, even if the degree of cross-linking was increased, the press-bonding processability was not improved.

Comparative Examples 8 to 9 Comparative Examples 8 to 9 in Table 3 show that an ethylene / vinyl acetate copolymer and an ethylene / ethyl acrylate copolymer were prepared by adding magnesium hydroxide (average particle size 0.7 μm , A BET specific surface area of 8 m ² / g, and an insulated wire using a resin composition containing stearic acid surface treatment), Comparative Example 8 was irradiated with an electron beam of 100 kGy at an acceleration voltage of 2 MeV, and Comparative Example 9 was not irradiated. Things. As a result of evaluating the crimping workability of the connector, it was found that, depending on the type of the connector, the evaluation results varied, such as breakage at the slot portion and deformation of the coating at the strain relief portion, indicating that the crimping processability was poor. .

Comparative Examples 10 to 11 Comparative Examples 10 to 11 are conventional PVC insulated wires. Comparative Example 10 did not perform the electron beam irradiation treatment, and Comparative Example 11
Was subjected to irradiation crosslinking treatment with an electron dose of 50 kGy. The connector was good in terms of press-contact workability without any breakage of the coating at the slot portion and no deformation of the coating at the strain relief portion. However, switching is required due to harmful gases generated during combustion.

In summary, as can be seen by comparing Examples 1 to 8 and Comparative Examples 1 to 5, styrene / ethylene / butylene / styrene copolymer, styrene / butadiene copolymer or styrene・ Pressure processability of insulated wires using a resin composition containing magnesium hydroxide in an ethylene / butadiene / olefin copolymer shows correlation with the elastic modulus, tensile strength and tensile elongation at break of the covering material. However, it was found that those subjected to cross-linking treatment by electron beam irradiation so that the 100% modulus at 200 ° C. became 0.2 MPa or more had excellent press-contact workability regardless of the type of connector.

(Production of shielded electric wire) Next, pellets of the resin composition shown in Table 4 were melt extruded (45 mmφ, L / D = 2
4, compression ratio 2.5, full flight type)
An insulated wire having an outer diameter of 1.20 mm was extruded onto a conductor obtained by twisting seven strands of 0.127φ tin-plated soft copper wire while checking the capacitance with a capacitance monitor. After irradiating the obtained insulated wire with an electron beam having an accelerating voltage of 2 MeV in a predetermined amount, an outer conductor is formed by wrapping a wire of 0.127φ tinned soft copper wire around the outer periphery of the coating layer, and further forming an outer conductor on the outer periphery. Then, a pellet of the same resin composition as that of the coating layer is extrusion-coated with a melt extruder (45 mmφ, L / D = 24, compression ratio 2.5, full flight type) so as to have a thickness of 0.2 mm, and the shielded electric wire is formed. I got Next, the sheath layer and the outer conductor layer of the end of the obtained shielded wire are cut off, press-workability to the connector of the insulated wire, tensile strength of the insulating coating layer,
Elongation, modulus, 100% modulus at 200%, and flame retardancy were evaluated in the same manner as in the examples.

[0037]

[Table 4]

Example 9 Example 9 in Table 4 is a shielded insulated wire using the same resin composition as in Example 7, and was irradiated with an electron dose of 100 kGy. The end of this shielded wire was cut off, and the press-workability of the exposed insulated wire was evaluated.As a result, no deformation of the coating at the strain relief portion and no breakage of the coating at the slot portion were observed at all. It turned out to be excellent. Further, when the flame retardancy of the obtained shielded insulated wire was examined, it was found that it passed the VW-1 test.

Comparative Example 12 Comparative Example 12 in Table 4 is a shielded electric wire using the same resin composition as Comparative Example 1 and was irradiated with an electron dose of 150 kGy. The end of this shielded wire was cut off, and the press-workability of the exposed insulated wire was evaluated. As a result, the press-workability of any of the connectors showed no breakage of the coating at the slot, but the strain was observed. Deformation of the coating was observed at the relief portion, which proved to be inferior in press-welding workability.

[0040]

As described above, according to the present invention,
There is no problem of harmful gas generation during combustion, and it is possible to obtain insulated wires or shielded insulated wires that are excellent in pressure welding processability and flame retardant. Some are very large.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state where an insulated wire according to the present invention has been press-welded.

FIG. 2 shows the electric wire of the present invention in the slot portions (a), (b) and (c).
Are shown in the order of pressure welding.

FIG. 3 is a cross-sectional view showing a state of the insulated wire fitted into the strain relief portion. (A) shows a good example, and (b) shows an example in which the insulating layer may not be deformed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric wire 11 Conductor 12 Insulation 2 Pressure welding connector 3 Slot part 4 Strain relief part 5 Bunch 6 Pressure welding blade 7 Contact part of pressure welding blade and conductor

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Claims (2)

[Claims] 1. An insulated wire in which an insulating layer is made of at least a resin composition containing a styrene-based thermoplastic elastomer or a styrene-butadiene rubber, wherein the insulating layer has a 100% modulus at 200 ° C. of 0. .2MPa
An insulated wire characterized by the above. 2. Extruding and coating a resin composition containing at least a styrene-based thermoplastic elastomer or a styrene-butadiene rubber as an insulating layer on a conductor, and irradiating the resin composition with ionizing radiation to form an insulating layer. ° C
A method for producing an insulated wire having a 100% modulus of 0.2 MPa or more.