JPH07282645A - Heat resistant insulated wire and its manufacture - Google Patents

Abstract

PURPOSE:To provide a heat resistant insulated wire, which can be used under an environment of high temperature, excellent in adhesiveness and flexibility of an insulating film. CONSTITUTION:A heat resistant insulated wire 10 comprises a conductor 1 and an inorganic film 2 covering the conductor 1 for insulation. The inorganic film 2 is formed of a compound material comprising a matrix consisting of a metal oxide and a metal particle uniformly dispersed in the matrix. A content of the metal particle in the compound material is 10 to 100 pts.wt. relating to 100 pts.wt. the metal oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant insulated electric wire used as an electric wire for wiring, an electric wire for winding, etc. in high vacuum equipment, equipment used at high temperature, etc.

[0002]

2. Description of the Related Art Insulated wires are sometimes used in equipment such as heating equipment and fire alarms that require safety at high temperatures. The insulated wire is also used in an environment where the vehicle is heated to a high temperature. As an insulated wire used in such an environment, an insulated wire in which a conductor is coated with a heat-resistant organic resin such as polyimide or fluororesin has been conventionally used.

When used in applications requiring high heat resistance or in environments where a high degree of vacuum is required, only the coating of the above-mentioned organic substance is effective in terms of heat resistance and gas releasing property. Is insufficient. Therefore, an insulated wire of a type in which a conductor is passed through a ceramic insulator tube, or an MI cable of a type in which a conductor is passed through a tube made of a heat-resistant alloy made of stainless alloy or the like filled with metal oxide fine particles such as magnesium oxide (Mineral Insulated Cable)
Have been used for such purposes.

Further, as a heat resistant electric wire which is required to have heat resistance and flexibility, a glass braided electric wire using a glass fiber spun fabric as an insulating member, and JP-A-3-958.
There is also a wire rod provided with an electrically insulating covering layer by a technique such as a vapor deposition method, as disclosed in Japanese Patent Laid-Open No. 09-2009.

[0005]

The insulated wire whose heat resistance is increased by using a ceramic insulator tube has drawbacks such as poor flexibility. Since the MI cable is composed of a heat-resistant alloy tube and a conductor, the outer shape of the cable becomes large. Therefore, the MI cable is a cable having a relatively large cross section with respect to the amount of electric power allowed by the conductor passed through the heat-resistant alloy pipe. Also, MI
In order to use the cable as a wire for winding a coil around a bobbin or the like, a tube made of a heat-resistant alloy needs to be bent with a predetermined curvature, but this bending has a problem that it is difficult. Further, when wound in a coil, the MI cable has a large diameter, so that it is difficult to improve the winding density.

In the case of a glass braid insulated electric wire, when the glass braid is arranged in a predetermined shape depending on the application, a gap may occur in the glass braid, and the braid is relatively thickly coated to ensure insulation. There is. Also, the glass braided strands are 40
At temperatures above 0 ° C, it becomes brittle and may damage the coating. Therefore, when the glass braided insulated wire is used at a high temperature, a method of hardening the glass braided insulated wire with a cementitious material is used.

[0007] As disclosed in Japanese Patent Laid-Open No. 3-95809, a wire rod provided with an electrically insulating coating layer by a technique such as a vapor deposition method has a manufacturing speed limited to a film forming rate of the vapor deposition method. The deposition rate of the vapor deposition method is generally 1 μm / min or less, which results in a high-cost insulated wire. In addition, in order to develop the adhesion of the film, it is necessary to preheat the base material at a temperature of 900 ° C. or higher before coating and to heat the base material to a high temperature during the film formation. Then, a copper wire, a nickel-plated copper wire, or other plated wire that causes an increase in electrical resistance due to oxidation or alloying cannot be used as a base material. When coating is carried out in a short time by the vapor deposition method, only a very thin coating can be obtained, and sufficient electric insulation cannot be imparted.

An object of the present invention is to provide a heat resistant insulated wire having the following features. (A) It has insulation in a high temperature environment.

(B) Excellent flexibility. (C) The adhesion of the insulating film is excellent.

(D) Low cost.

[0011]

A heat-resistant insulated electric wire according to the present invention is a heat-resistant insulated electric wire comprising a conductor and an inorganic coating covering the conductor for insulation, wherein the inorganic coating is a matrix made of a metal oxide, and It is characterized in that it is composed of a composite material consisting of metal particles uniformly dispersed in the composite material, and the content of the metal particles in the composite material is 10 to 100 parts by weight with respect to 100 parts by weight of the metal oxide.

According to the manufacturing method of the present invention described later, metal oxide can be formed around the conductor at a relatively low temperature. Then, a heat-resistant insulated wire can be provided by using a conductor having a melting point that is considerably lower than the melting point of the metal oxide contained in the composite material. In this case, it is possible to provide a heat-resistant insulated wire in which the melting point of the conductor is 1200 ° C. or lower and the melting point of the metal oxide is 1600 ° C. or higher.

The conductor may be, for example, copper (melting point about 1030).
℃), copper alloy, aluminum (melting point about 660 ℃), aluminum alloy, silver (melting point about 1064 ℃), silver alloy, gold (melting point about 1064 ℃), gold alloys and combinations thereof. It can be preferably formed of metal. The conductor is usually a wire forming a core in the heat resistant insulated electric wire according to the present invention.

Preferred metal oxides constituting the matrix of the composite material in the present invention include, for example, silicon oxide, zirconium oxide, aluminum oxide,
Mention may be made of compounds selected from the group consisting of titanium oxides and combinations thereof. The melting point of silicon oxide is about 1700 ° C., the melting point of zirconium oxide is about 2760 ° C., the melting point of aluminum oxide is about 2060 ° C., and the melting point of titanium oxide is about 1640 ° C., for example.

From the above, in the present invention, for example, a metal oxide having a melting point 500 to 1200 ° C. higher than that of the conductor or 1.2 to 1.5 times the melting point of the conductor is used as the surface of the conductor. Can be adhered to.

In the composite material, the metal particles dispersed in the metal oxide matrix are preferably, for example, a metal selected from the group consisting of copper, aluminum, zinc, and tin. The particle size of the metal particles is preferably 0.5 to 20 μm, more preferably 1 to 10 μm. The content of the metal particles in the composite material is 10 to 100 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the metal oxide.
Parts by weight.

In the electric wire of the present invention, the thickness of the inorganic coating made of the composite material is, for example, 1 to 100 μm, preferably 5 to 30 μm.

In the present invention, in order to improve the adhesion between the conductor and the inorganic film, a layer containing chromium oxide as a main component can be formed on the surface of the conductor, and the inorganic film can be formed on this layer. The thickness of the layer containing chromium oxide as a main component can be, for example, 0.1 to 10 μm, preferably 0.5 to 1 μm. This layer can be formed by a plating method as described later.

An electric wire according to the present invention has a temperature of 800 at room temperature.
It has a breakdown voltage of V or higher. Further, the electric wire according to the present invention is resistant to bending, and for example, even if a coil having an inner diameter of 10 cm is bent, the insulating layer does not crack, and the electric wire has a dielectric breakdown voltage of 400 V or more at room temperature in a coil state. it can.

The method for producing a heat-resistant insulated wire according to the present invention comprises the steps of hydrolyzing a compound in an aqueous solution or suspension containing a compound selected from the group consisting of metal alkoxides and metal organic acid salts as a main component. A step of preparing a liquid containing an organometallic polymer as a main component by a polycondensation reaction, a step of mixing the prepared solution with a metal powder, a step of applying the mixed solution to a conductor, and a conductor to which the mixed solution is applied. Is heated at a temperature lower than the melting point of the conductor and the metal powder to form a film of a composite material composed of a matrix made of a metal oxide and metal particles uniformly dispersed in the matrix around the conductor. Prepare

In this manufacturing method, the particle size of the metal powder can be 0.5 to 20 μm, preferably 1 to 10 μm. The surface of the metal powder is preferably surface-treated in advance with a compound selected from the group consisting of a silane coupling agent, benzotriazole and a benzotriazole derivative before the mixing step. On the other hand, the surface of the metal powder may be previously coated with an organic resin that thermally decomposes at a temperature of 300 ° C. or lower before the mixing step. When the metal powder is coated with the organic resin, the conductor coated with the mixed liquid is heated at a temperature of 300 ° C. or higher to form the composite material.

Before applying the mixed liquid to the conductor, a layer containing chromium oxide as a main component can be formed on the surface of the conductor by electroplating. This improves the adhesion of the composite material formed on the surface of the conductor.

The conductor coated with the mixed solution is heated at a temperature of 300 to 900 ° C., preferably 400 to 600 ° C. for forming a film made of a composite material.

[0024]

From the viewpoint of electrical insulation, it is considered preferable to use only an inorganic insulating material such as silicon oxide, aluminum oxide or silicon carbide as the insulating material. However, in this case, in addition to the fact that the coating must be made quite thin, the flexibility of the coating becomes poor. This is because the inorganic insulator (ceramics) has low fracture toughness, and therefore cracks are generated and propagated even with a small bending stress, and are easily broken.

In the present invention, a composite material containing metal particles in a metal oxide is used as the insulating film instead of ceramics. Due to the metal powder contained in the composite material, bending stress is relaxed against bending deformation. Further, even if a crack occurs, the tip of the crack stops at the portion of the metal powder, and the propagation of the crack can be hindered.

The content of the metal powder in the composite material should not exceed 100 parts by weight with respect to 100 parts by weight of the metal oxide, because the film made of the composite material functions as an insulator. The addition of an excessive amount of metal powder brings about a great decrease in electrical insulation. It has also been confirmed by experiments that the amount of metal particles of 10 parts by weight or less relative to 100 parts by weight of metal oxide does not sufficiently fulfill the function of inhibiting crack propagation.

As a method for producing a metal oxide of an insulating film, a method of producing a metal oxide by firing a precursor solution obtained by hydrolysis and polycondensation reaction of a metal alkoxide or a metal organic acid salt is preferable. Used. The method using a metal alkoxide is a so-called sol-gel method. The method using a metal organic acid salt is a so-called thermal decomposition method. In this method, a metal powder is uniformly dispersed in a precursor solution, which is applied onto a conductor and then fired. Thereby, the insulating layer in which the metal oxide and the metal powder are compounded is formed. Further, since this method only applies the solution and fires it, it is possible to manufacture the inorganic insulated wire at low cost.

Further, in order to prevent the metal powder from being excessively oxidized during firing, it is preferable that the metal powder is surface-treated with a silane coupling agent, benzotriazole or a benzotriazole derivative in advance. Further, in order to prevent the metal powders from agglomerating with each other to form an electric circuit and lower the electrical insulation property, the surface of the metal powders should be 3
It is preferable to coat with an organic resin that is thermally decomposed by heating at a temperature of 00 ° C. or less.

A layer containing chromium oxide as a main component may be formed on the surface of the conductor by electroplating for the purpose of enhancing the adhesion of the film. The chromium oxide method is formed by an electrochemical method. When the chromium oxide layer is formed by the electroplating method, an aqueous solution of chromic acid to which a small amount of organic acid is added is used. Generally, as an electrolytic bath used when performing chrome plating, a Sargent bath mainly containing chromic acid and sulfuric acid is known, but it is different from this bath in the following points. The mineral acid mixed in the electrolytic bath has a function of dissolving chromium oxide generated on the plating surface during electroplating, and a metallic chromium layer having gloss is plated by using the Sargent bath. On the other hand, in a bath with a small amount of organic acid added to the chromic acid aqueous solution,
Chromium oxide can be plated preferentially.

The chromium oxide layer has good wettability with the organic metal polymer used for forming the insulating film or its solution, and firmly adheres to the metal oxide obtained by heating it. Further, in order to further enhance the wettability and the adhesion of the film, it is preferable that the surface of the layer mainly containing chromium oxide is rough and velvety. Therefore, the processing current density and the like are different from those of the bright plating that is generally performed. In bright plating, a current density of 10 to 60 A / dm ² is used depending on the treatment temperature, but in the present invention, 100 to 200 A / dm 2.
Use a current density of ² to get a rough surface.

According to the present invention, it is possible to provide a heat-resistant insulated wire which is excellent in flexibility and adhesion of an insulating film and can be used for a long time in a high temperature environment at a relatively low cost. it can.

[0032]

【Example】

Example 1 A copper wire having a diameter of 1.0 mm was used as a conductor. To a mixed solution of 4 mol% of tetraethyl orthosilicate, 40 mol% of water and 56 mol% of ethyl alcohol, nitric acid was added dropwise in an amount of 1/100 of the mole number of tetraethyl orthosilicate, and the mixture was reacted at 80 ° C for 2 hours. To prepare a sol.

As the metal powder, aluminum powder having an average particle size of 10 μm was washed with a 1N sodium hydroxide aqueous solution and then treated with an alcohol solution of dimethylethoxysilane as a silane coupling agent. Furthermore, the surface was coated with PVA by immersing in 30% polyvinyl alcohol and drying.

150 g of the obtained metal powder and 1 l of sol solution
20 g of butyl cellosolve as a thickener,
A coating liquid was prepared by adding 120 g of glycerin.

The conductor is dipped in the coating liquid and the pulling speed is 10 m.
The application was done by pulling up the conductor at m / min.
The conductor coated with the coating solution on the outer surface in this manner was subjected to a step of heating for 10 minutes at a temperature of 450 ° C. in a nitrogen atmosphere three times to form a film having a thickness of 25 μm.

In order to evaluate the insulation of the obtained insulated wire, the breakdown voltage was measured. The dielectric breakdown voltage was 800 V at room temperature. Further, the obtained insulated wire was heated at 600 ° C. for 100 hours, then allowed to cool to room temperature and evaluated, and the insulation breakdown voltage was 800 V. Furthermore, on the outer peripheral surface of a cylinder with a diameter of 10 cm,
Even when the obtained insulated electric wire was wound, no crack was generated in the insulating layer.

Example 2 A copper wire having a diameter of 1.0 mm was coated with a layer containing chromium oxide as a main component.
It was formed by the following process. No electroplating layer
Hydrochromic acid 200 g / l, glacial acetic acid 6.5 g / l, dichloride
80g / l of shell and 5g / l of sodium nitrate
Was used. The plating condition is to use a copper wire as the cathode,
Bath temperature 40 ℃, current density 100A / dm ², Processing time 2
It was a minute. In this way, the outer surface of the copper wire is oxidized with black oxide.
A layer containing aluminum as a main component was formed to a thickness of about 1 μm.

On the other hand, a mixed solution of 15 mol% sec-tributoxyaluminum, 80 mol% water and 5 mol% hydrogen chloride was reacted at a temperature of 50 ° C. for 4 hours to prepare a sol. As the metal powder, zinc powder having an average particle size of 5 μm,
Ethanol 1% by weight of 1,1,1-benzotriazole
The solution was washed.

200 g of the obtained metal powder and 1 l of sol solution
Were mixed and 20 g of butyl cellosolve and 120 g of glycerin were added as a thickener to prepare a coating solution.

The copper wire is dipped in the coating solution and the pulling speed is 10 m.
The application was done by pulling up the copper wire at m / min.
The copper wire coated with the coating solution on the outer surface in this manner was heated three times at a temperature of 450 ° C. for 10 minutes in a nitrogen atmosphere to form a film having a thickness of 30 μm.

In order to evaluate the insulating property of the obtained insulated wire, the breakdown voltage was measured. The dielectric breakdown voltage was 1100 V at room temperature. The obtained insulated wire was heated at 400 ° C. for 100 hours, then allowed to cool to room temperature and evaluated, and the insulation breakdown voltage remained at 1100 V. Also, on the outer peripheral surface of a cylinder with a diameter of 5 cm,
Even when this insulated wire was wound, no crack was generated in the insulating layer.

FIG. 1 schematically shows the structure of the insulated wire manufactured in the above examples. A conductor 1 is provided at the center of the heat-resistant insulated wire 10, and an inorganic film 2 of a composite material composed of a metal oxide and metal particles is in close contact with the periphery of the conductor 1.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a structure of an electric wire according to the present invention.

[Explanation of symbols]

 1 conductor 2 inorganic film 10 heat resistant insulated wire

Claims (8)

[Claims] 1. A heat-resistant insulated wire comprising a conductor and an inorganic coating for covering the conductor for insulation, wherein the inorganic coating comprises a matrix made of a metal oxide,
The composite material is composed of metal particles uniformly dispersed in the matrix, and the content of the metal particles in the composite material is 10 to 100 parts by weight based on 100 parts by weight of the metal oxide. A heat-resistant insulated wire characterized by: 2. The heat resistant insulated wire according to claim 1, wherein the melting point of the conductor is 1200 ° C. or lower and the melting point of the metal oxide is 1600 ° C. or higher. 3. The conductor comprises a metal selected from the group consisting of copper, copper alloys, aluminum, aluminum alloys, silver, silver alloys, gold, gold alloys and combinations thereof, and the metal oxide is The heat resistant insulated wire according to claim 1, wherein the heat resistant insulated wire is made of a compound selected from the group consisting of silicon oxide, zirconium oxide, aluminum oxide, titanium oxide, and combinations thereof. 4. The heat resistant insulated wire according to claim 1, wherein a layer containing chromium oxide as a main component is formed on the surface of the conductor, and the inorganic film is formed on the layer. 5. A method for producing a heat-resistant insulated wire comprising a conductor and an inorganic coating covering the conductor for insulation, the method mainly comprising a compound selected from the group consisting of metal alkoxides and metal organic acid salts. In an aqueous solution or water suspension containing as a component, a step of preparing a liquid containing an organometallic polymer as a main component by hydrolysis and polycondensation reaction of the compound, and a step of mixing a metal powder in the prepared liquid, A step of applying the mixed liquid to the conductor, and heating the conductor to which the mixed liquid is applied at a temperature lower than the melting points of the conductor and the metal powder, and a matrix made of a metal oxide and the matrix in the matrix around the conductor. And a step of forming a composite material film composed of metal particles uniformly dispersed in the heat-resistant insulated wire. 6. The surface of the metal powder is previously surface-treated with a compound selected from the group consisting of a silane coupling agent, a benzotriazole and a benzotriazole derivative before the mixing step. The method for producing a heat resistant insulated wire according to claim 5. 7. The surface of the metal powder is previously coated with an organic resin that thermally decomposes at a temperature of 300 ° C. or lower before the mixing step, and the temperature of 300 ° C. is formed to form the composite material.
The method for producing a heat-resistant insulated wire according to claim 5, wherein the conductor is heated at the above temperature. 8. Before applying the mixed solution to the conductor,
The method for producing a heat-resistant insulated wire according to claim 5, wherein a layer containing chromium oxide as a main component is formed on the surface of the conductor by an electroplating method.