JP2014049433A - Production and production method of fire proof layer of heat proof/fire proof insulation electric wire or cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire proof layer as follow: if a fire proof layer formed on a surface of a conductor satisfies the following five requirements, the future hardest standard of a fire proof layer is not only satisfied, but also a present fire proof layer is substituted by a fire proof layer having further safety and further cheap price: first, a fire proof layer has a heat proof property of at least 1,420°C that is the melting point of a hard steel wire, second, being an insulation body even at 1,420°C, third, a fire proof layer can be formed on a surface of a conductor by the same means not depending on a thickness or a material of a conductor, fourth, a fire proof layer can be formed by very simple continuous processing, and fifth, a fire proof layer can be formed by a cheaply priced industrial material.SOLUTION: An organic iron compound that forms iron oxide (II) by heat decomposition is made to be adsorbed to a conductor, the adsorbed organic iron compound is heat-treated in an atmosphere to make a maghemite fine particle precipitate on a surface of a conductor, a coat comprising maghemite is formed on a surface of a conductor by magnetism adsorption of the maghemite fine particles as a fire proof layer, thereby a fire proof layer in which five requirements are satisfied can be realized.

Description

  The present invention relates to the manufacture and manufacturing method of a refractory layer formed on the surface of a conductor of a heat- and fire-resistant insulated electric wire or cable.

Due to the painful accidents that killed many precious human lives in a building fire, it was important to maintain fire-fighting equipment, especially to secure an emergency power source in the event of a fire. In 1946, standards for fireproof wires for high-power circuits were set by the Fire and Disaster Management Agency. Since then, the standards have been revised several times. These heat- and fire-resistant insulated wires or cables have a special fire-resistant layer compared to ordinary wires or cables, so that the insulation performance in the fire-resistant layer is maintained even in the event of a fire, enabling energization for a certain period of time. It is used for the wiring of various emergency facilities (emergency elevators, indoor fire hydrant facilities, smoke exhaust facilities, etc.) defined by the Building Standard Law.
There are the following six types of such heat-resistant / fire-resistant insulated wires or cables, and each has fire-resistant / heat-resistant performance in accordance with the standards determined by the Japan Electric Wire Industry Association JCS. The first type is a low-pressure fireproof cable, and the rating is 600V75 ° C. according to the standard of JCS4506. The second type is a high-pressure fireproof cable, and the rating is 6600V90 ° C. according to the standard of JCS4507. A third type is a heat-resistant electric wire for a small force circuit, and the rating is 60 V in accordance with the standard of JCS3501. There is a heat-resistant fiber optic cable in the fourth type, which is a fiber optic cable with heat resistance performance that conforms to the notification from the Ministry of Fire, Disaster Prevention Agency Preliminary No. 178 of the Ministry of Home Affairs of Japan on December 12, 1986. Used for operation. This heat-resistant optical fiber has a rating of 60V75 ° C. according to the standard of JCS4396. The fifth type is heat-resistant type leaky coaxial cable and heat-resistant coaxial cable, and fire prevention preliminary number 45 of fire prevention agency prevention section notice on March 17, 1997 "about self-management such as leaky coaxial cable used for radio communication auxiliary equipment" This is a leaky coaxial cable and heat-resistant coaxial cable with the heat resistance specified in JIS. In accordance with the JCS4504 standard, it is laid in underground streets, subways, basements of underground buildings, underground parking lots, etc. Used for wireless communication for activities and police security activities. The sixth type is a highly flame-retardant non-halogen fire-resistant / heat-resistant wire or cable. There are three types of fire-resistant / heat-resistant wires or cables: a low-pressure fire-resistant cable, a high-pressure fire-resistant cable, and a heat-resistant wire. Furthermore, it is a fire-resistant and heat-resistant electric wire or cable that reduces the generation of smoke and gas even in the event of a fire, and was newly specified in the Fire and Disaster Management Agency Notification Nos. 10 and 11 on December 18, 1997. A general fire-resistant / heat-resistant electric wire or cable passes a combustion test (JCS3005: Inclination test) using a single electric wire or cable as a specimen, and is equivalent to the flame resistance of general electric wires such as CV cables or cables. On the other hand, the highly flame-retardant non-halogen refractory / heat-resistant electric wire or cable is intended for the electric wire group or cable group, and is an electric wire or cable that conforms to the vertical tray combustion test (IEEE Std. 383). In order to improve the flame retardancy of ordinary electric wires or cables, materials with halogen-based flame retardants added were used. However, high flame retardant non-halogen fire-resistant / heat-resistant electric wires or cables do not contain halogen elements. The use of non-contained materials has greatly reduced the generation of toxic gases, corrosive gases and smoke.
In addition, according to JCS, a fire-resistant wire or cable is a wire or cable that has been certified in accordance with the regulations of the Fire and Disaster Management Agency (Ministry of Fire and Disaster Management Agency Notification No. 10 and technical standards based on December 18, 1997). It has insulation performance that can withstand even when heated in a fire temperature curve that reaches 840 ° C in 30 minutes, and it is approved for use in emergency power circuits. Furthermore, a heat-resistant electric wire or cable is an electric wire or cable certified in accordance with the above-mentioned regulations of the Fire and Disaster Management Agency, and has an insulation performance that can withstand a heating temperature curve that reaches 380 ° C in 15 minutes. It is approved for use in wiring of weak electric circuits such as emergency broadcast speakers and emergency bell activation devices.

All of the above-mentioned low-voltage fire-resistant cable, high-pressure fire-resistant cable, heat-resistant wire for small force circuit, and heat-resistant / fire-resistant insulated wire or cable related to highly flame-retardant non-halogen fire-resistant / heat-resistant wire have a fire-resistant layer on the outer periphery of the conductor, A structure having an insulating layer outside the layer and a sheath outside the layer is a basic structure. That is, the insulation performance of the conductor is ensured for a certain period of time by the fireproof layer even in the event of a fire, and the conductor has a function of enabling energization for a certain period of time. According to JIS-A1304, fire resistance performance with an insulation resistance of 0.1 MΩ or higher is specified for low-pressure fireproof cables when heated at a fire temperature curve that reaches 380 ° C after 15 minutes of heating. Heat resistance performance having an insulation resistance of 0.4 MΩ or more when the wire is heated by a flame temperature curve reaching a temperature of 840 ° C. after 30 minutes of heating is defined. On the other hand, the insulating layer bears the insulating performance between the conductors before heating. According to JIS-A1304, the insulation resistance of 50 MΩ or more and the insulation strength capable of withstanding 1500 VAC for 1 minute are prescribed for low-voltage fireproof cables, and the insulation resistance of 50 MΩ or more and 250 VAC can be withstanding for heat-resistant wires for small force circuits. Dielectric strength is specified. Therefore, the heat resistance and fire resistance of the low-voltage fire-resistant cable, high-voltage fire-resistant cable, heat-resistant electric wire for small force circuit, and heat-resistant / fire-resistant insulated wire or cable related to highly flame-retardant non-halogen fire-resistant / heat-resistant wire are formed on the outer circumference of the conductor. The fireproof layer will be responsible.
Various technical improvements have been made on the heat-resistant and fire-resistant layers of the heat-resistant and fire-resistant insulated wires or cables. For example, Patent Document 1 discloses an insulated wire or an insulated cable that can maintain electrical characteristics even when exposed to a temperature of 800 ° C. in a fire, and a fireproof layer formed by wrapping a glass mica tape is provided on the tape. Like the film which covers the surface, the inorganic powder by sodium tetraborate which melts in the range of the heating temperature of 600-800 degreeC and vitrifies is carry | supported. For this reason, when exposed to 600-800 degreeC by a fire etc., even if an insulator burns out, only a conductor and a refractory layer remain, and the structure which can protect an electrical property by a refractory layer protecting a conductor is described.
Further, Patent Document 2 has a configuration in which an insulating layer in which inorganic powder is mixed is formed between a refractory layer and an insulating layer. When the insulating layer mixed with the inorganic powder burns due to a fire, the inorganic powder mixed in the insulating layer adheres to the refractory layer. As a result, the inorganic powder adhering to the refractory layer acts as a barrier, prevents intrusion of the conductive combustion product generated by burning the insulating layer into the conductor, and provides an insulated wire or cable that ensures fire resistance. Have been described.
Patent Document 3 discloses a heat-resistant electric wire that is improved in heat resistance and chemical durability by covering the conductor directly with glass as compared with a case in which silica mica tape or glass fiber is wound around the conductor. Or a heat-resistant cable is described.

The techniques described in Patent Documents 1 to 3 relating to the heat-resistant and fire-resistant performance of the heat-resistant / fire-resistant insulated electric wire or cable described above are all 840 ° C. for 30 minutes described in the test method of JIS-A1304. It is an improved technology related to fire resistance standards when heated with a fire temperature curve that reaches On the other hand, the technique described in Patent Document 4 is based on fire resistance standards that comply with the guidelines for the installation and operation of road tunnels (RABT) established by the German Ministry of Transport, and tunnel inner walls that withstand high-temperature heating at 1200 ° C. Describes the fireproof protection structure of the cable pipe installed in. In other words, in the case of a tunnel fire, the generated heat has little escape, and in the case of an accident in which gasoline burns, the maximum temperature reaches about 1200 ° C in about 10 minutes, which reflects such a fire accident in the tunnel. Patent Document 4 discloses a fireproof protective structure for a cable line.
Furthermore, the technique described in Patent Document 5 is based on the data that the temperature reaches 930 ° C after 1 hour for the fire temperature curve reaching 840 ° C in 30 minutes described in the test method of JIS-A1304. Describes technologies related to fire-resistant layers that can withstand In other words, the technology of Patent Document 5 is based on the idea that the safety standards change according to social demands, and the refractory layer responsible for heat resistance and fire resistance is based on the prediction that stricter standards will be established in the future. It can be said that this is a preliminary technology.

On the other hand, there are various heat-resistant / insulated electric wires or cables according to the environment in which they are used, unlike the above-mentioned viewpoint of ensuring the insulation of the conductor in the event of a fire. For example, a heat-resistant insulated wire described in Patent Document 6 includes a sensor and a measurement circuit for measuring temperature and strain of parts and members used at high temperature and high rotation in a rotating machine of a gas turbine engine and a steam turbine. Used for connecting lead wires. Since this heat-resistant insulated wire is exposed to a high temperature environment of 900 ° C. and bent inside the engine, heat resistance, flexibility, strength, and insulation are required. For this reason, a lead wire made of a conductor, an insulating layer obtained by horizontally winding an insulating wire in which a plurality of inorganic fibers are bundled and twisted together, a protective layer obtained by braiding and winding the insulating wire on the insulating layer, It is comprised from the exterior part which further piled up on the protective layer and braided the stainless steel wire.
Further, the heat-resistant insulated wire described in Patent Document 7 is used as a lead wire of an oxygen sensor mounted on an automobile exhaust manifold, and has heat resistance and insulation that can be used even in a high temperature range of 700 ° C. or higher. . This electric wire is insulated by applying a secondary coating with a fiber having excellent heat resistance and insulation on a bundle of insulated wire cores with a primary coating with fibers having excellent heat resistance and insulation on a conductor. It consists of an electric wire and a metal sheath coated thereon.
Furthermore, the heat-resistant insulated wire or cable described in Patent Document 8 is a heat-resistant insulated wire or cable having a conductor whose tensile strength and conductivity do not decrease even when used at a high temperature up to 1000 ° C. An insulator of a mica / glass bonding tape is provided on the outer periphery of the alloy wire conductor, a silica glass yarn braid is formed on the outer periphery, and a metal wire reinforcing layer is formed on the outer periphery.

JP 2002-324439 A JP 2005-347053 A JP 2006-156293 A JP 2007-244073 A JP 2000-331546 A JP 2000-149672 A JP-A-10-223061 JP 2006-19225 A

The heat resistance and fire resistance of heat-resistant and fire-insulated wires or cables are that the fire-resistant layer has heat resistance even if it is burned or thermally decomposed by exposure of the insulator and sheath formed outside the fire-resistant layer to high temperatures. Thus, even at high temperatures, the refractory layer is bonded to the conductor, ensuring the insulation of the conductor for a certain period of time, and allowing the conductor to be energized for a certain period of time. That is, the heat resistance is the heat resistance of the refractory layer, and the fire resistance is the insulation of the refractory layer at a high temperature. Accordingly, the heat resistance and fire resistance of the heat / fire resistant insulated wire or cable are determined by the heat resistance of the fire resistant layer and the insulation at high temperatures. However, as described above, the standards for the heat resistance and fire resistance of heat-resistant / fire-resistant insulated wires or cables vary depending on social demands, and it is predicted that safer and stricter standards will be required in the future. For this reason, a refractory layer that meets the most stringent standards is the best preliminary technology for insulated wires or cables.
Now consider the most stringent standards for refractory layers in the future. The strictest standard is that the refractory layer first has heat resistance exceeding the melting point of the conductor, and secondly it has insulation even at the melting point of the conductor, and the refractory layer combines these two properties. Even when the temperature is close to the melting point, the refractory layer is bonded to the conductor to ensure the insulation of the conductor. This is because if the conductor melts, it loses its function as a conductor. Since many conductors in insulated wires or cables are made of electrolytic copper, the refractory layer has a heat resistance of 1085 ° C or higher, which is the melting point of copper, and the refractory layer is bonded to the conductor as an insulator at a temperature close to 1085 ° C. In this case, the fireproof layer has fireproof performance at a temperature close to 1085 ° C. This makes the refractory layer the best preliminary technology that meets the most stringent standards for future insulated wires or cables. Moreover, it can be used also as an excellent fireproof layer of an insulated wire or an insulated cable for high temperature applications as described in Patent Documents 6 to 8. Furthermore, the refractory layer has a heat resistance performance of 1390 ° C. to 1420 ° C., which is the melting point of the hard steel wire constituting the copper-clad steel wire used for the central conductor of the coaxial cable, and the refractory layer is 1420 If it is bonded as an insulator to the hard steel wire at a temperature close to ℃, the refractory layer will have a fire resistance performance at a temperature close to 1420 ℃. Thereby, the fire resistance performance as a fireproof layer for all conductor materials in the electric wire or cable can be exhibited. By the way, there are electric copper, oxygen-free copper, copper alloy and copper-clad steel wire as the conductor material in the electric wire or cable, and the conductor having the highest melting point is a hard steel wire constituting the copper-clad steel wire.

Furthermore, if the refractory layer meets the following five requirements, it will not only become the best preliminary technology that will meet the strictest refractory layer standards of the future, but it will also be a safer and cheaper refractory layer that can be used in the current refractory layer. Can be replaced. The first requirement is heat resistance of 1420 ° C. or higher, which is the melting point of hard steel wire. The second requirement is an insulator even at 1420 ° C. The third requirement is that refractory layers can be formed on the surface of various conductors by the same means regardless of the thickness or material of the conductor. The fourth requirement is that a refractory layer can be formed on the surface of the conductor by a very simple continuous process. The fifth requirement is that a fireproof layer can be formed using inexpensive industrial materials. A fire-resistant layer that satisfies these five requirements dramatically improves the safety of current insulated wires or cables as an excellent preliminary technology. The problem in the present invention is to realize a fireproof layer that satisfies these five requirements.
On the other hand, the technique described in Patent Document 4 described above is a technique related to the fireproof layer of the fireproof protective case of the cable conduit installed on the inner wall of the tunnel, and is not a technique of the fireproof layer of the insulated wire or the insulated cable. The fireproof layer of this fireproof protective case contains synthetic zonotlite, blast furnace cement and wollastonite as solids, and vinylon fibers and pulp are added to these solids and kneaded with water. The obtained slurry is formed by dehydration press molding. Thereafter, the obtained molded body is dried at 180 ° C. to produce a calcium silicate fireproof layer. Since this technology is a technology for forming a refractory layer by subjecting a slurry-like substance to dehydration press molding, the slurry-like substance can be dehydrated and press-molded inside a container that is not a case, but the conductor A slurry-like substance cannot be dehydrated and pressed into such a wire. That is, even if calcium silicate is excellent in heat resistance, it is limited to a manufacturing method in which a slurry-like substance is subjected to dehydration press molding due to restrictions on the manufacturing method of calcium silicate. By this manufacturing method, the object for providing the refractory layer is limited, and the refractory layer cannot be formed on a wire such as a conductor. Moreover, heat resistance is 1200 degreeC.
The technique described in Patent Document 5 described above is a technique related to a refractory layer formed on the surface of a conductor. A composite insulating tape is manufactured by backing laminated mica with an alumina cloth, and this composite insulating tape is used as a conductor. Wrap to form a refractory layer. The composite insulating tape is lined by creating a laminated mica powder obtained by crushing a layered crystal of fluorine phlogopite to a scaly shape and adhering the assembled mica powder to an alumina cloth with a silicone adhesive. Alumina cloth is an extremely expensive material, and laminated mica is an expensive material. Furthermore, since the process of lining the laminated mica on the alumina cloth is complicated, the manufacturing cost of the composite insulating tape increases. Furthermore, since it consists of the complicated process of manufacturing a composite insulating tape and the process of winding a composite insulating tape around a conductor, the manufacturing process of a refractory layer is divided. On the other hand, if the alumina fiber content is too small, the alumina crystal is not formed during the heat action and becomes amorphous, resulting in insufficient heat resistance. On the other hand, if the alumina fiber content is excessive, the accumulated mica is insufficient and the fire resistance is lowered. Furthermore, the fiber diameter of the alumina long fiber and the thickness of the alumina cloth must be changed according to the thickness of the conductor. When the fiber diameter of the alumina long fiber and the thickness of the alumina cloth are changed, the size of the powder constituting the laminated mica must also be changed. Furthermore, if the size of the powder constituting the laminated mica is changed, it is necessary to change the proportion of the alumina fiber. In this way, the present technology forms a refractory layer by wrapping the composite insulating tape around the surface of the conductor, so that the insulating layer having uniform properties is wound around the surface of the conductor having an extremely long length under the same conditions. There are difficulties. In addition, the material used as a raw material is extremely expensive, and the manufacturing process for manufacturing the composite insulating tape is complicated. Therefore, the manufacturing cost is high, and the refractory layer cannot be formed at a low cost. Therefore, this technology cannot replace the current refractory layer as an excellent preliminary technology. Moreover, heat resistance is 1000 degreeC.

  The first characteristic means of the refractory layer formed on the surface of the conductor in the heat- and fire-resistant insulated electric wire or cable according to the present invention is to form a film made of maghemite, which is an iron oxide, on the surface of the conductor, and the film made of the maghemite Thus, a refractory layer is formed on the surface of the conductor.

That is, maghemite, which is an iron oxide, is a substance represented by the chemical formula γ-Fe ₂ O ₃ and has the following two properties. Therefore, a film made of maghemite is formed on the surface of the conductor. Among the five requirements necessary as a fireproof layer, it acts as a fireproof layer that simultaneously satisfies the first and second requirements. Maghemite is a γ phase of iron oxide (III) Fe ₂ O ₃ .
First, an insulating material having a specific resistance of 10 ⁶ Ωm. For this reason, if the surface of a conductor is coat | covered with maghemite, the surface of a conductor will become an insulator. Incidentally, the specific resistance of copper is 1.68 × 10 ⁻⁸ Ωm.
Second, the phase transitions to hematite α-Fe ₂ O ₃ which is the α phase of iron (III) Fe ₂ O ₃ at a temperature of 450 ° C. or higher. Hematite is an insulating material having a specific resistance of 10 ⁷ Ωm and has a single-digit insulating property higher than that of maghemite. Furthermore, since hematite is an extremely stable oxide, it is passive even at high temperatures and has heat resistance close to the melting point of 1566 ° C. In other words, if a film made of maghemite is formed as a heat-resistant layer for heat-resistant and fire-resistant insulated wires or cables, it will undergo a phase transition to a film made of hematite when exposed to a temperature of 450 ° C. or higher in the event of a fire. It has a heat resistance of 1420 ° C. or higher, which is the melting point of the wire, and since it is passive, it exhibits a specific resistance close to 10 ⁷ Ωm even at the melting point of the hard steel wire. If maghemite having such properties is formed as a coating on the surface of the conductor, among the five requirements necessary as a refractory layer formed on the surface of the conductor, a refractory layer that simultaneously satisfies the first and second requirements. As a maghemite film acts.

  The second characteristic means of the refractory layer formed on the surface of the conductor in the heat- and fire-resistant insulated electric wire or cable according to the present invention is the maghemite film formed on the surface of the conductor in the first characteristic means described above. The film is formed by gathering.

In other words, according to this feature means, maghemite is a ferrimagnetic material, which is a kind of ferromagnetic material, so that the maghemite fine particles deposited on the surface of the conductor are strongly magnetically adsorbed to each other, depending on the thickness and material of the conductor. First, a film made of maghemite fine particles having a strong binding force is formed on the surface of the conductor. That is, regardless of the material of the electric copper, oxygen-free copper, copper alloy, and copper-coated steel wire used as the conductor material, a film made of maghemite fine particles can be easily formed on the surface of the conductor. In addition, surface treatments such as tin plating, silver plating, and nickel plating have been applied to the electrical copper that is most commonly used as a conductor material to prevent oxidation and make soldering easier. A film made of maghemite fine particles can be easily formed on the surface of electrolytic copper subjected to various surface treatments. Thus, the film made of maghemite fine particles becomes a refractory layer that satisfies the third requirement among the five requirements necessary as the refractory layer formed on the surface of the conductor.
In addition, the film composed of a collection of maghemite fine particles is hardly peeled off from the surface of the conductor because the maghemite fine particles are magnetically adsorbed to each other. Even when various loads are applied to the refractory layer when the insulating layer is formed on the surface of the refractory layer, the refractory layer is unlikely to peel off from the surface of the conductor. When an excessive load is applied to the surface of the refractory layer, after forming a coating made of maghemite fine particles on the surface of the conductor, the magnetic adsorption force of the maghemite fine particles can be increased by passing the conductor through the magnetizer. A film consisting of maghemite fine particles that remarkably increases and has a stronger binding force is formed. Thereby, even if an excessive load is applied to the refractory layer, the refractory layer is more difficult to peel off from the surface of the conductor.
Furthermore, since the amount of maghemite fine particles deposited on the surface of the conductor can be freely changed, the thickness of the film made of maghemite fine particles or hematite fine particles after phase transition can be freely changed, and the refractory layer formed on the surface of the conductor The insulation resistance can be changed in any way. As a result, the insulation resistance necessary to insulate the conductor can be easily realized not only at room temperature but also at a temperature close to 1420 ° C., which is the melting point of the hard steel wire. Thus, if a film composed of a collection of maghemite fine particles is formed on the surface of the conductor as a refractory layer, among the five requirements necessary for the refractory layer formed on the surface of the conductor, the first to third requirements are satisfied. A film composed of a collection of maghemite fine particles acts as a refractory layer that is simultaneously filled.

  In the heat-resistant / fire-resistant insulated electric wire or cable according to the present invention, the third characteristic means of the refractory layer formed on the surface of the conductor is a film composed of maghemite fine particles formed on the surface of the conductor in the second characteristic means described above. An organic iron compound that generates iron (II) oxide by thermal decomposition is adsorbed on a conductor, and the adsorbed organic iron compound is heat-treated in the atmosphere, whereby maghemite fine particles are deposited on the surface of the conductor, and the maghemite fine particles The point is that a film composed of a collection of maghemite fine particles is formed on the surface of the conductor by magnetic attraction between them.

That is, according to this characteristic means, a film made of maghemite fine particles can be very easily formed on the surface of the conductor. As a result, a refractory layer satisfying the fourth requirement among the five requirements necessary as the refractory layer formed on the surface of the conductor can be realized.
First, an organic iron compound that generates iron (II) oxide (chemical formula is FeO) by thermal decomposition is dispersed in a solvent, and the conductor is immersed in this dispersion. Thereafter, when the conductor is exposed to a temperature equal to or higher than the vaporization point of the solvent, the organic iron compound is adsorbed on the surface of the conductor. The conductor having the organic iron compound adsorbed is continuously subjected to the following two-stage heat treatment in an air atmosphere.
First, the conductor is subjected to a heat treatment in which the organic iron compound is pyrolyzed to iron (II) oxide, and then the iron (II) oxide generated by pyrolysis is maghemite (chemical formula is γ-Fe ₂ O ₃ ). ) Is subjected to oxidation heat treatment. That is, when the boiling point of the organic substance constituting the organic iron compound is exceeded, the organic iron compound is thermally decomposed into an organic substance and iron (II) oxide. The organic matter generated by pyrolysis takes the heat of vaporization and vaporizes. On the other hand, when the iron (II) oxide generated by thermal decomposition is exposed to a higher temperature, an oxidation reaction in which the divalent iron ion Fe ²⁺ becomes the trivalent iron ion Fe ³⁺ proceeds. When the oxidation reaction in which the divalent iron ion Fe ²⁺ becomes the trivalent iron ion Fe ³⁺ is completed, all the divalent iron ions Fe ²⁺ in the iron (II) oxide become trivalent iron ions Fe ^3+. Iron (II) FeO is oxidized to iron (III) Fe ₂ O ₃ . This iron (III) Fe ₂ O ₃ is maghemite γ-Fe ₂ O ₃ which is a γ phase of iron (III) Fe ₂ O ₃ . Since maghemite is a ferrimagnetic material among ferromagnetic materials, the produced maghemite fine particles are strongly magnetically adsorbed to each other, and a film made of maghemite fine particles is formed on the surface of the conductor as a refractory layer.
As described above, a coating made of maghemite is formed on the surface of the conductor as a refractory layer by an extremely simple continuous treatment in which an organic iron compound is adsorbed on the surface of the conductor and the conductor is passed through a heat treatment furnace consisting of an atmospheric atmosphere. Formed as. The temperature of the heat treatment is about 430 ° C. at the maximum. For this reason, an insulating film made of maghemite having a heat resistance well above 1420 ° C. can be formed on the surface of the conductor as a refractory layer at a much lower cost than conventional. Thus, a fireproof layer that simultaneously satisfies the first to fourth requirements among the five requirements necessary for the fireproof layer formed on the surface of the conductor can be realized.

  The fourth characteristic means of the refractory layer formed on the surface of the conductor in the heat- and fire-resistant insulated electric wire or cable according to the present invention is an organic iron compound that generates iron (II) oxide by pyrolysis in the third characteristic means described above. The point is that the ion is an organic iron compound coordinated with an oxygen ion.

In other words, according to this characteristic means, when an organic iron compound in which iron ions coordinate with oxygen ions forming a ligand is thermally decomposed in the atmosphere, iron (II) oxide is generated. When II) is oxidized, maghemite precipitates. That is, in the thermal decomposition reaction of such an organic iron compound in the atmosphere, thermal decomposition starts when the boiling point of the organic substance constituting the organic iron compound is exceeded, and decomposes into iron (II) oxide and the organic substance. That is, the oxygen ion constituting the organic iron compound becomes a ligand and coordinates with the iron ion so that the distance between the iron ion and the oxygen ion that is the ligand is short. For this reason, in the thermal decomposition of the organic iron compound, first, the binding site opposite to the short-distance site where the oxygen ion, which is the ligand, binds to the iron ion, that is, the site with the long binding distance is cut. Thereby, the organic iron compound is decomposed into iron (II) FeO in which iron ions are combined with oxygen ions and organic matter. Thereafter, the organic matter is vaporized while taking the heat of vaporization. On the other hand, when iron (II) FeO is exposed to a higher temperature, the oxidation reaction of divalent iron ions Fe ²⁺ becomes trivalent iron ions Fe ³⁺ proceeds. When this oxidation reaction is completed, iron (II) FeO Becomes a γ phase of iron (III) Fe ₂ O ₃ , that is, maghemite. Thus, when the oxidation reaction of iron (II) is completed, maghemite fine particles are deposited on the surface of the conductor. Since maghemite is a ferromagnetic substance, maghemite fine particles are strongly magnetically adsorbed to form a maghemite film as a refractory layer on the surface of the conductor. As a result, a film made of maghemite fine particles is formed as a refractory layer on the surface of the conductor. As described above, the organic iron compound in which iron ions coordinate with oxygen ions are adsorbed on the surface of the conductor, and the conductor is heat-treated, so that the five requirements necessary as a fireproof layer formed on the surface of the conductor are described. Among these, the fireproof layer that satisfies the first to fourth requirements at the same time can be specifically realized.

  The fifth characteristic means of the refractory layer formed on the surface of the conductor in the heat- and fire-resistant insulated electric wire or cable according to the present invention is such that the iron ions in the fourth characteristic means are coordinated with oxygen ions forming a ligand. The organic iron compound is an organic iron compound of iron carboxylate or acetylacetone iron among iron acetate, iron benzoate, iron caprylate, and iron naphthenate.

That is, according to this means, iron (II) acetate (chemical formula is Fe (CH ₃ COO) ₂ ), iron (II) benzoate (chemical formula is Fe (C ₆ H ₅ COO) ₂ ), capryl Carboxylic acid comprising iron (II) acid (chemical formula is Fe (CH ₃ (CH ₂ ) ₆ COO) ₂ ) or iron (II) naphthenate (chemical formula is Fe (C ₆ H ₅ COO) ₂ ) In each of the acid irons, oxygen ions constituting the carboxyl group COOH of the carboxylic acid act as a ligand to approach the divalent iron ion, and the oxygen ion coordinates with the iron ion. Further, acetylacetone iron (III) (chemical formula is Fe (C ₅ H ₇ O ₂ ) ₃ ) is acetylacetonate (chemical formula is C) which is a conjugate base of acetylacetone (chemical formula is C ₅ H ₈ O ₂ ). ₅ H ₇ O ₂ ^— ) is an organic iron compound in which two oxygen ions form a ligand and bind to an iron ion, and acetylacetonate forms a six-membered ring. When such iron carboxylate or acetylacetone iron exceeds the boiling point of the carboxylic acid or acetylacetone, thermal decomposition starts and decomposes into iron (II) FeO and carboxylic acid or acetylacetone. That is, the oxygen ion constituting the carboxyl group of the carboxylic acid or the oxygen ion constituting the acetylacetonate approaches the iron ion and forms a coordinate bond, so the distance between the iron ion and the oxygen ion that is the ligand is short. For this reason, in thermal decomposition, the site | part of the long distance of the opposite side where the oxygen ion which is a ligand couple | bonds with an iron ion cuts first. By this thermal decomposition, iron ions are decomposed into iron (II) FeO in which oxygen ions are combined with carboxylic acid or acetylacetone. In addition, acetylacetone iron (III) is an organic iron compound in which three molecules of trivalent iron ion Fe ³⁺ and acetylacetonate C ₅ H ₇ O ₂ ^— are bonded, but thermal decomposition of acetylacetone iron (III) occurs. At temperature, since the divalent iron ion Fe ²⁺ is more stable than the trivalent iron ion Fe ³⁺ , in the thermal decomposition of acetylacetone iron (III), iron oxide (II) FeO composed of the divalent iron ion Fe ^2+. Is generated. Thereafter, the carboxylic acid or acetylacetone vaporizes while taking heat of vaporization. On the other hand, in the iron oxide (II) FeO, the oxidation reaction proceeds from the divalent iron ion Fe ²⁺ to the trivalent iron ion Fe ³⁺ as the temperature rises, and the iron (II) FeO is converted into iron (III) Fe ₂ O _3. Γ phase, that is, maghemite. Thus, after the oxidation reaction of iron oxide (II) is completed, maghemite fine particles are precipitated. Since maghemite is a ferromagnetic substance, maghemite fine particles are strongly magnetically adsorbed to form a maghemite film as a refractory layer on the surface of the conductor.
The iron carboxylate or iron acetylacetone described above is an industrial chemical that is easy to synthesize and inexpensive because it is a compound of general-purpose carboxylic acid or general-purpose organic matter and iron. Because a film made of maghemite is formed on the surface of the conductor by continuous treatment in which an inexpensive industrial chemical is adsorbed on the conductor and this conductor is heat-treated in the atmosphere, the heat resistance is hard at a much lower manufacturing cost than before. A refractory layer higher than the melting point of the steel wire can be formed. Thus, a fireproof layer that simultaneously satisfies the first to fifth requirements among the five requirements necessary for the fireproof layer formed on the surface of the conductor can be realized.

  The characteristic means of the forming method for forming a refractory layer composed of a maghemite film on the surface of a conductor in a heat- and fire-resistant insulated wire or cable according to the present invention is a first method for preparing a dispersion by dispersing an organic iron compound in an organic solvent. A second step of immersing the conductor in the dispersion of the organic iron compound, and a third step of evaporating the organic solvent to evaporate the organic solvent to adsorb the organic iron compound on the surface of the conductor. And maghemite is deposited on the surface of the conductor by the four steps consisting of the above step and the fourth step of heat-treating the conductor on which the organic iron compound is adsorbed in the atmosphere, whereby a film made of maghemite is formed on the surface of the conductor. It is in the point which is the formation method formed as a fireproof layer.

That is, according to the forming method for forming the refractory layer made of the maghemite film, the film made of maghemite is formed on the surface of the conductor by a very simple continuous four-step manufacturing method. Thereby, a refractory layer can be formed on the surface of the conductor at a very low manufacturing cost.
That is, the first step is a step in which an organic iron compound is filled in a container, an organic solvent is added thereto, and the mixture is stirred. Thereby, a dispersion liquid in which the organic iron compound is dispersed in the organic solvent can be prepared. The second step is simply a step of immersing the conductor in the dispersion. Thereby, the dispersion liquid of the organic iron compound adheres to the surface of the conductor. The third step is simply a step of raising the temperature of the conductor to the boiling point of the organic solvent. As a result, the organic iron compound is adsorbed on the surface of the conductor. In the fourth manufacturing process, a heat treatment furnace at a temperature at which the reaction in which the organic iron compound is thermally decomposed and the iron (II) oxide generated by the pyrolysis is oxidized to iron (III) in an air atmosphere is completed. It is a process that only passes. Thereby, the film made of maghemite formed on the surface of the conductor acts as a fireproof layer. Thus, a refractory layer that simultaneously satisfies the first to fifth requirements among the five requirements necessary as the refractory layer formed on the surface of the conductor can be manufactured.

It is a figure explaining the manufacturing process which forms a fireproof layer using an organic iron compound. It is a figure explaining the manufacturing process which forms a fireproof layer using iron naphthenate. It is a figure explaining the process of forming a fireproof layer using acetylacetone iron.

Embodiment 1 for forming a refractory layer

Embodiment 1 in which a refractory layer made of a maghemite film is formed on the surface of a conductor is used as a raw material, and a manufacturing process for forming a refractory layer on the surface of the conductor using an organic iron compound that generates iron (II) oxide by thermal decomposition. As shown in FIG. A dispersion in which an organic iron compound is dispersed in n-butanol as 10% by weight is prepared in advance, and this n-butanol dispersion is filled in a liquid tank. First, the conductor is immersed in a liquid tank containing an n-butanol dispersion of an organic iron compound for a certain period of time and passed through this liquid tank. Thereby, the n-butanol dispersion of the organic iron compound adheres to the surface of the conductor. Next, the conductor is passed through the low-temperature firing chamber A set at 120 ° C. in a short time to vaporize n-butanol in the n-butanol dispersion of the organic iron compound adsorbed on the conductor, and the vaporized n-butanol is recovered. Collect with machine D. As a result, the organic iron compound is adsorbed on the surface of the conductor. Further, the conductor passes through the high-temperature firing chamber B in a certain time. The high temperature baking chamber B includes a low temperature baking part B1 set at a relatively low temperature and a high temperature baking part B2 set at a relatively high temperature. The low-temperature fired part B1 is set to a temperature slightly higher than the boiling point of the organic substance constituting the organic iron compound, and the conductor passes through the low-temperature fired part B1, so that the organic iron compound adsorbed on the surface of the conductor becomes the organic substance and iron oxide. Pyrolysis to (II). Thereby, iron (II) oxide is adsorbed on the surface of the conductor. The organic matter generated by this thermal decomposition is collected by the organic matter collecting machine E. The high-temperature fired part B2 is set to a temperature at which an oxidation reaction in which iron (II) oxide is oxidized to iron (III) proceeds, and the conductor passes through the high-temperature fired part B2 in a relatively long time, thereby oxidizing All of the iron (II) is oxidized to iron (III) oxide, and maghemite fine particles are deposited on the surface of the conductor. Since maghemite is a ferromagnetic material, the maghemite fine particles are strongly magnetically adsorbed to form a film made of a collection of maghemite fine particles on the surface of the conductor.
As described above, the manufacturing process for forming a refractory layer made of maghemite on the surface of the conductor includes a process of immersing the conductor in an n-butanol dispersion of an organic iron compound, and a process of heat-treating the conductor in an air atmosphere. These two steps are performed in succession. Moreover, the process of heat-treating the conductor consists of three consecutive heat treatment processes. For this reason, the manufacturing process which forms the refractory layer which consists of maghemite on the surface of a conductor can manufacture a refractory layer at a very cheap manufacturing cost.

Embodiment 2 for forming a refractory layer

Embodiment 2 in which a refractory layer composed of a maghemite film is formed on the surface of a conductor uses iron (II) naphthenate (chemical formula is Fe (C ₆ H ₅ COO) ₂ ), which is a kind of iron carboxylate. This is an embodiment in which a refractory layer made of a maghemite film is formed on the surface of a copper wire. Iron (III) naphthenate is a kind of iron carboxylate that is easily generated when two molecules of naphthenic acid (chemical formula is C ₆ H ₅ COOH) react with iron, and the carboxyl group ( The chemical formula is COOH), which is generated by the separation of the hydrogen ions easily and the divalent iron ions bonded to the oxygen ion sites where the hydrogen ions are separated. The structural formula is C ₆ H ₅ COO-Fe represented by -OOCC ₆ H _5.
FIG. 2 shows a manufacturing process for forming a refractory layer made of a maghemite film on the surface of a copper wire. First, iron (II) naphthenate and a copper wire are prepared (step S10). Next, a dispersion in which iron (II) naphthenate is dispersed in n-butanol at a ratio of 10% by weight is prepared, and this dispersion is filled in a liquid tank (step S11). After such preparation, the copper wire is immersed in an n-butanol dispersion of iron (II) naphthenate (step S12). As a result, the n-butanol dispersion of iron (II) naphthenate adheres to the surface of the copper wire. Next, the copper wire passes through the following three heat treatment furnaces in succession. First, the copper wire passes through a low-temperature firing chamber A at 120 ° C. in 1 minute, n-butanol is vaporized, and the vaporized n-butanol is collected by the collecting machine D (step S13). Thereby, iron (II) naphthenate is adsorbed on the surface of the copper wire. In this embodiment, in order to increase the insulation resistance of the refractory layer, as shown in FIG. 2, the copper wire is immersed again in the n-butanol dispersion of iron (II) naphthenate, and the low-temperature firing chamber A is further provided. By passing, the adsorption amount of iron (II) naphthenate was increased, and as a result, the insulation resistance of the refractory layer was increased. Thereafter, the copper wire passes through the high-temperature firing chamber B and is subjected to a two-stage heat treatment. First, it passes through the low-temperature fired part B1 set at 300 ° C. for 5 minutes, and iron (II) naphthenate adsorbed on the surface of the copper wire is thermally decomposed to precipitate iron (II) oxide, thereby vaporizing naphthene. The acid is recovered by the organic acid recovery machine E (step S14). Thereafter, it passes through the high-temperature calcined part B2 set at 400 ° C. for 10 minutes, and the iron (II) oxide generated by thermal decomposition is oxidized to iron (III), and the produced maghemite fine particles are magnetically adsorbed to each other. Then, a film made of maghemite is formed on the surface of the copper wire (step S15). Thus, the copper wire that has passed through the high-temperature firing chamber B has a maghemite film as a refractory layer formed on the surface.

Embodiment 3 for forming a refractory layer

In Embodiment 3, in which a refractory layer made of a maghemite film is formed on the surface of a conductor, acetylacetone iron (III) Fe (C ₅ H ₇ O ₂ ) ₃ , which is a kind of acetylacetone metal, is used as a raw material. The fireproof layer is formed on the surface of the copper wire. Acetylacetone iron (III) Fe (C ₅ H ₇ O ₂ ) ₃ is an organic iron compound that is easily produced by the reaction of three molecules of acetylacetone C ₅ H ₈ O ₂ with iron. Acetylacetone C ₅ H ₈ O 2 An organic iron compound in which two oxygen ions constituting acetylacetonate C ₅ H ₇ O ₂ ^— , which is a conjugate base of ₂ , binds to iron ions as a ligand and acetylacetonate forms a six-membered ring It is.
In this embodiment, since the thermal decomposition temperature of acetylacetone iron (III) is different from the thermal decomposition temperature of iron (II) naphthenate, the conditions for the heat treatment temperature are higher than those in Embodiment 2 using iron (II) naphthenate. It is only different. FIG. 3 shows a manufacturing process in which a film made of maghemite is formed as a refractory layer on the surface of copper wire using acetylacetone iron (III) as a raw material. First, acetylacetone iron (III) and a copper wire are prepared (step S20). Next, a dispersion liquid in which acetylacetone iron (III) is dispersed in n-butanol at a ratio of 10% by weight is prepared, and this dispersion liquid is filled in a liquid tank (step S21). After such preparation, a copper wire is immersed in an n-butanol dispersion of acetylacetone iron (III) (step S22). Next, the copper wire passes through the low-temperature firing chamber A in 1 minute, n-butanol is vaporized, and the vaporized n-butanol is collected by the recovery machine D (step S23). In this embodiment, in order to increase the insulation resistance of the refractory layer, as shown in FIG. 3, the copper wire is again immersed in the n-butanol dispersion of acetylacetone iron (III) and further passes through the low-temperature baking chamber A. As a result, the adsorption amount of acetylacetone iron (III) was increased, and as a result, the insulation resistance of the refractory layer was increased. Further, the copper wire passes through the high-temperature firing chamber B, and two-stage heat treatment is performed. First, the acetylacetone iron (III) adsorbed on the surface of the conductor is thermally decomposed by passing through the low-temperature fired part B1 set at 330 ° C. in 5 minutes, and iron (II) oxide is generated. It collects with the acid recovery machine E (step S24). Thereafter, it passes through the high-temperature firing part B2 set at 430 ° C. for 10 minutes to oxidize iron (II) oxide generated by pyrolysis to iron (III) oxide, and the generated maghemite fine particles are magnetically adsorbed to each other. Then, a film made of maghemite is formed on the surface of the copper wire (step S25). Thus, the copper wire that has passed through the high-temperature firing chamber B has a maghemite film as a refractory layer formed on the surface.

Example 1 in which a refractory layer is formed on the surface of a conductor according to the present invention is the surface of a copper wire using iron (II) naphthenate, which is a kind of iron carboxylate, and a coating composed of a collection of maghemite fine particles as a refractory layer. It is the Example formed in. In addition, the manufacturing process of a refractory layer is based on Embodiment 2 demonstrated in 23 paragraphs.
First, iron (II) naphthenate and n-butanol as raw materials, and an annealed copper wire based on JIS C 3102 are prepared as electric wires. As iron (II) naphthenate, iron (II) naphthenate commercially available as a metal soap (for example, a product of Toei Chemical Co., Ltd.) was used. For n-butanol, a reagent first grade was used. Commercially available annealed copper wire was used.
Next, iron (II) naphthenate is weighed so as to have a ratio of 10% by weight with respect to n-butanol, and this iron (II) naphthenate is mixed with n-butanol and stirred, and iron naphthenate (II N-butanol dispersion was prepared. This dispersion was filled in a container. Further, the electrical annealed copper wire was immersed in a container containing n-butanol dispersion of iron (II) naphthenate for 30 seconds. As a result, the n-butanol dispersion of iron (II) naphthenate adheres to the surface of the electrical annealed copper wire.
Next, the annealed copper wire was passed through three heat treatment furnaces in succession. First, a low-temperature baking chamber at 120 ° C. was passed in 1 minute to vaporize n-butanol. As a result, iron (II) naphthenate is adsorbed on the surface of the electrical annealed copper wire. Furthermore, the annealed copper wire was dipped in the n-butanol dispersion of iron (II) naphthenate again for 30 seconds, and then passed through the low-temperature firing chamber for 1 minute. Thereafter, the electrical annealed copper wire passes through the low temperature firing part of the high temperature firing chamber set at 300 ° C. in 5 minutes, and iron (II) naphthenate adsorbed on the surface of the electrical annealed copper wire is thermally decomposed to iron oxide. (II) was precipitated. Thereafter, the high-temperature baking part of the high-temperature baking chamber set at 400 ° C. is passed in 10 minutes, and iron (II) oxide generated by thermal decomposition is oxidized to iron (III), and the generated maghemite fine particles are A film made of maghemite was formed on the surface of the annealed copper wire by magnetic adsorption.
Next, observation and measurement were performed on a sample of an electrical annealed copper wire manufactured under the above-described conditions, and it was determined whether or not the intended treatment was reliably performed. First, the sample surface was observed with an electron microscope. The electron microscope used was an ultra-low acceleration voltage SEM from JFE Techno-Research Corporation. This apparatus is capable of observing the surface with an extremely low acceleration voltage from 100 V, and further has a feature that the surface of the sample can be directly observed without forming a conductive film on the sample. A secondary electron beam between 900 V and 1 kV of the reflected electron beam was taken out and subjected to image processing to observe irregularities on the sample surface. It was confirmed that an extremely large number of granular fine particles having a size of 40 nm to 60 nm were uniformly formed on the entire surface of the electrical annealed copper wire in the sample. Next, the energy and intensity of characteristic X-rays were subjected to image processing, and the types of elements constituting the film formed on the sample surface and the distribution state thereof were analyzed. Both iron atoms and oxygen atoms were uniformly present on the surface, and no particularly uneven locations were found, confirming that the particles were made of iron oxide. Furthermore, an EBSP analysis function was added to the function of the extremely low acceleration voltage SEM, and the crystal structure was analyzed. From this result, it was confirmed that the fine particles formed on the sample surface were maghemite γ-Fe ₂ O ₃ which is a γ phase of iron (III) oxide. The EBSP analysis function means that when a sample is irradiated with an electron beam, the reflected electrons are diffracted by the atomic plane in the sample to form a band-shaped pattern, and the symmetry of this band corresponds to the crystal system. Since the band interval corresponds to the atomic plane interval, the function of measuring the crystal orientation and the crystal system by analyzing this pattern.
From the observation results of the sample surface described above with an electron microscope, it was confirmed that an extremely large number of maghemite particles were magnetically adsorbed on the entire surface of the electrical annealed copper wire. From this result, it was confirmed that the maghemite fine particles were evenly magnetically adsorbed on the surface of the electrical annealed copper wire by heat-treating iron (II) naphthenate under the conditions described above.
Next, the insulation resistance of the sample was measured. For measuring the insulation resistance, an insulation resistance meter of a Kyoritsu electric meter was used. The length of the sample was 1 m, and the electrical resistance between the annealed copper wire and the refractory layer was measured. The insulation resistance showed a value close to 1 MΩ. Therefore, it was found that a film made of maghemite fine particles was formed to have the insulation resistance required for the refractory layer.
As explained above, iron naphthenate (II), which is an inexpensive industrial chemical, is used as a raw material, and iron (II) naphthenate is thermally decomposed in an air atmosphere to thereby form maghemite on the surface of an electrical annealed copper wire. A refractory layer was formed from the collection of fine particles. Maghemite undergoes a phase transition to hematite at a temperature of 450 ° C. Since hematite is an extremely stable oxide passivity, it has heat resistance close to the melting point of 1566 ° C. and is an insulator having a specific resistance close to 10 ⁷ Ωm even at a temperature close to the melting point. For this reason, the refractory layer from the collection of maghemite fine particles satisfies all the five requirements necessary for the refractory layer formed on the surface of the conductor.

Example 2 of forming a refractory layer on the surface of a conductor according to the present invention uses acetylacetone iron (III), which is a kind of acetylacetone metal, to form a film composed of a collection of maghemite fine particles on the surface of a copper wire as a refractory layer. This is an example. In addition, the manufacturing process of a refractory layer is based on Embodiment 3 demonstrated in 24 paragraphs.
First, acetylacetone iron (III) and n-butanol as raw materials and an electric annealed copper wire based on JIS C 3102 are prepared as electric wires. As acetylacetone iron (III), acetylacetone iron (III) commercially available as a metal soap (for example, nursem ferric, a product of Nippon Chemical Industry Co., Ltd.) was used. For n-butanol, a reagent first grade was used. Commercially available annealed copper wire was used.
Next, acetylacetone iron (III) is weighed so as to have a ratio of 10% by weight with respect to n-butanol, this acetylacetone iron (III) is mixed with n-butanol and stirred, and n of acetylacetone iron (III) is stirred. -A butanol dispersion was made. This dispersion was filled in a container. Further, the electrical annealed copper wire was immersed in a container containing an n-butanol dispersion of acetylacetone iron (III) for 30 seconds. As a result, an n-butanol dispersion of acetylacetone iron (III) adheres to the surface of the electrical annealed copper wire.
Next, the annealed copper wire was passed through three heat treatment furnaces in succession. First, a low-temperature baking chamber at 120 ° C. was passed in 1 minute to vaporize n-butanol. Thereby, acetylacetone iron (III) is adsorbed on the surface of the electrical annealed copper wire. Furthermore, the annealed copper wire was immersed again in an n-butanol dispersion of acetylacetone iron (III) for 30 seconds, and then passed through a low-temperature firing chamber for 1 minute. Thereafter, the electrical annealed copper wire passes through the low temperature firing part of the high temperature firing chamber set at 330 ° C. in 5 minutes, and acetylacetone iron (III) adsorbed on the surface of the electrical annealed copper wire is thermally decomposed to iron oxide ( II) was precipitated. Furthermore, the high temperature baking part of the high temperature baking chamber set to 430 degreeC is passed over 10 minutes, the iron (II) oxide produced | generated by thermal decomposition is oxidized to iron (III), and the produced | generated maghemite fine particles mutually A film made of maghemite was formed on the surface of the annealed copper wire by magnetic adsorption.
Next, observation and measurement were performed on a sample of an electrical annealed copper wire manufactured under the above-described conditions, and it was determined whether or not the intended treatment was reliably performed. First, the sample surface was observed with an electron microscope. The electron microscope used was an ultra-low acceleration voltage SEM from JFE Techno-Research Corporation. A secondary electron beam between 900 V and 1 kV of the reflected electron beam was taken out and subjected to image processing to observe irregularities on the sample surface. It was confirmed that an extremely large number of granular fine particles having a size of 40 nm to 60 nm were uniformly formed on the entire surface of the electrical annealed copper wire in the sample. Next, the energy and intensity of characteristic X-rays were subjected to image processing, and the types of elements constituting the film formed on the sample surface and the distribution state thereof were analyzed. Both iron atoms and oxygen atoms were present uniformly on the surface, and no particularly uneven locations were found, so it was confirmed that they were granular fine particles made of iron oxide. Furthermore, an EBSP analysis function was added to the function of the extremely low acceleration voltage SEM, and the crystal structure was analyzed. From this result, it was confirmed that the fine particles formed on the sample surface were maghemite γ-Fe ₂ O ₃ which is a γ phase of iron (III) oxide.
From the observation results of the sample surface described above with an electron microscope, it was confirmed that an extremely large number of maghemite particles were magnetically adsorbed on the entire surface of the electrical annealed copper wire. From this result, it was confirmed that the maghemite fine particles were uniformly magnetically adsorbed on the surface of the electrical annealed copper wire by heat-treating acetylacetone iron (III) under the conditions described above.
Next, the insulation resistance of the sample was measured. For measuring the insulation resistance, an insulation resistance meter of a Kyoritsu electric meter was used. The length of the sample was 1 m, and the electrical resistance between the annealed copper wire and the refractory layer was measured. The insulation resistance showed a value close to 1 MΩ. Therefore, it has been found that the coating made of maghemite fine particles has an insulation resistance required as a refractory layer.
As described above, acetylacetone iron (III), which is an inexpensive industrial chemical, is used as a raw material, and acetylacetone iron (III) is thermally decomposed in an air atmosphere, whereby maghemite fine particles are formed on the surface of an electric annealed copper wire. A refractory layer was formed from the gathering. Maghemite undergoes a phase transition to hematite at a temperature of 450 ° C. Since hematite is an extremely stable oxide passivity, it has heat resistance close to the melting point of 1566 ° C. and is an insulator having a specific resistance close to 10 ⁷ Ωm even at a temperature close to the melting point. For this reason, the refractory layer from the collection of maghemite fine particles satisfies all the five requirements necessary for the refractory layer formed on the surface of the conductor.

Claims (6)

  Regarding the formation of a refractory layer formed on the surface of a heat-resistant / fire-resistant insulated wire or cable conductor, a film made of maghemite, which is an iron oxide, is formed on the surface of the conductor, and the surface of the conductor is refractory by the film made of the maghemite. Formation of a refractory layer formed on the surface of a heat- and fire-resistant insulated electric wire or cable conductor, characterized by forming a layer.   The refractory layer comprising a maghemite film according to claim 1, wherein the refractory layer comprising a maghemite film is a film formed by a collection of maghemite fine particles.   The film formed by the collection of maghemite fine particles according to claim 2 adsorbs an organic iron compound that generates iron (II) oxide by thermal decomposition on a conductor, and heat-treats the adsorbed organic iron compound in the air to form the conductor. 3. The formation of a film comprising a collection of maghemite fine particles according to claim 2, wherein maghemite fine particles are deposited on the surface of the maghemite and a film comprising the collection of maghemite fine particles is formed by magnetic adsorption between the maghemite fine particles.   The organic iron compound that produces iron (II) oxide by thermal decomposition in claim 3 is an organic iron compound in which iron ions coordinate with oxygen ions, and is oxidized by thermal decomposition according to claim 3. An organic iron compound that produces iron (II).   The organic iron compound in which the iron ion is coordinated to the oxygen ion in claim 4 is an organic iron compound of iron acetate, iron benzoate, iron caprylate, or iron naphthenate or iron acetylacetone. The organic iron compound in which the iron ion according to claim 4 is coordinated with an oxygen ion.   The method for forming a refractory layer comprising a maghemite film formed on the surface of a conductor according to any one of claims 1 to 5, wherein a dispersion liquid is prepared by dispersing an organic iron compound in an organic solvent. A second step of immersing the conductor in the dispersion of the organic iron compound, and a third step of evaporating the organic solvent to evaporate the organic solvent to adsorb the organic iron compound on the surface of the conductor. And the fourth step of heat treating the conductor on which the organic iron compound is adsorbed in the atmosphere, maghemite is deposited on the surface of the conductor, and a film made of the maghemite is formed on the surface of the conductor. A method for forming a refractory layer comprising a maghemite film formed on the surface of a conductor according to any one of claims 1 to 5, wherein the refractory layer is formed as a refractory layer.

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