WO2017104032A1 - 耐熱性絶縁電線とその絶縁層の形成に用いる電着液 - Google Patents

耐熱性絶縁電線とその絶縁層の形成に用いる電着液 Download PDF

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WO2017104032A1
WO2017104032A1 PCT/JP2015/085291 JP2015085291W WO2017104032A1 WO 2017104032 A1 WO2017104032 A1 WO 2017104032A1 JP 2015085291 W JP2015085291 W JP 2015085291W WO 2017104032 A1 WO2017104032 A1 WO 2017104032A1
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Prior art keywords
insulating layer
heat
particles
resistant
resin
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PCT/JP2015/085291
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English (en)
French (fr)
Inventor
慎太郎 飯田
礼子 泉
桜井　英章
研 林井
桂子 芦田
Original Assignee
三菱マテリアル株式会社
三菱電線工業株式会社
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Application filed by 三菱マテリアル株式会社, 三菱電線工業株式会社 filed Critical 三菱マテリアル株式会社
Priority to EP15910722.6A priority Critical patent/EP3392886B1/en
Priority to CN201580085302.6A priority patent/CN108475562B/zh
Priority to KR1020187016421A priority patent/KR102515689B1/ko
Priority to PCT/JP2015/085291 priority patent/WO2017104032A1/ja
Priority to US16/060,715 priority patent/US10395798B2/en
Publication of WO2017104032A1 publication Critical patent/WO2017104032A1/ja

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/29—Protection against damage caused by extremes of temperature or by flame
    • H01B7/292—Protection against damage caused by extremes of temperature or by flame using material resistant to heat
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
    • C09D5/4488—Cathodic paints
    • C09D5/4492—Cathodic paints containing special additives, e.g. grinding agents
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/66—Additives characterised by particle size
    • C09D7/67—Particle size smaller than 100 nm
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/66—Additives characterised by particle size
    • C09D7/68—Particle size between 100-1000 nm
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/12—Electrophoretic coating characterised by the process characterised by the article coated
    • C25D13/16—Wires; Strips; Foils
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/002—Inhomogeneous material in general
    • H01B3/006—Other inhomogeneous material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/02—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances
    • H01B3/10—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances metallic oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/303—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups H01B3/38 or H01B3/302
    • H01B3/306—Polyimides or polyesterimides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/447—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from acrylic compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/02—Disposition of insulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/29—Protection against damage caused by extremes of temperature or by flame
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C08K2003/2244—Oxides; Hydroxides of metals of zirconium
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica

Definitions

  • the present invention relates to an insulated wire having a heat-resistant insulating layer and an electrodeposition liquid for forming the insulating layer.
  • the present application is based on Japanese Patent Application No. 2014-138113 filed in Japan on July 3, 2014, the contents of which are incorporated herein by reference.
  • Insulated wires are widely used for magnet coils and the like.
  • An immersion method and an electrodeposition method are known as methods for forming an insulating layer of an insulated wire.
  • the dipping method is a method of forming an insulating coating on the surface of a wire by dipping a conductive wire used as a core material of an insulated wire in a paint such as a resin varnish, lifting it, and drying it.
  • the wire is placed in an electrodeposition solution containing a paint component such as a resin varnish, and the wire is used as an anode or a cathode and energized between a counter electrode and the paint component is electrodeposited on the surface of the wire and then baked.
  • an insulating layer is formed by treatment (see Patent Document 1 and Patent Document 2).
  • the dipping method has a drawback in that the paint hardly adheres to the corners of the flat electric wire, and the layer thickness of the corners becomes thinner than the layer thickness of the flat part.
  • the electrodeposition method has an advantage that an insulating layer having the same thickness as the flat portion or a thickness equal to or larger than the flat portion can be formed at the corner portion because the paint is sufficiently electrodeposited also at the corner portion of the flat electric wire.
  • Patent Document 3 A coating material for enameled wire containing bismuth is known (Patent Document 3).
  • the paint described in Patent Document 3 is for the dipping method, and cannot be used for the electrodeposition method with the liquid composition or liquid state of the disclosed paint.
  • the dipping method it is necessary to repeat dipping and drying many times in order to reach a desired layer thickness. For example, seven dippings are repeated to form a coating having a layer thickness of 35 ⁇ m that is practically used. For this reason, productivity is low. Further, the dipping method cannot solve the disadvantage that the layer thickness of the corner portion becomes thinner than that of the flat portion in the flat wire.
  • an organic solvent is used as a solvent / dispersion medium for resin and oxide fine particles, the environmental load is large.
  • the immersion method when silica fine particles are contained in the insulating layer, since the immersion is repeated in the paint containing the silica fine particles, the silica fine particles are included in each layer, and the silica fine particles are dispersed throughout the insulating layer. Become. However, since the surface of the insulating layer is most exposed to heat at a high temperature, the surface of the insulating layer is likely to be damaged if there are few silica particles near the surface of the insulating layer.
  • the present invention solves the above-mentioned problems in the conventional insulated wire by the dipping method and its manufacturing method, and has a heat-resistant insulated wire with excellent heat resistance near the surface of the insulating layer and an electric wire for forming the insulating layer. Provide the landing liquid.
  • Each aspect of the present invention has the following configuration.
  • An insulated wire having a heat-resistant insulating layer characterized in that the insulating layer contains heat-resistant particles, and the heat-resistant particles are concentrated in a surface layer thickness portion of the insulating layer.
  • Heat resistant insulated wire The heat-resistant insulating layer is usually formed on the surface of the conductive wire.
  • the “dense” means that heat-resistant particles are dispersed in the surface layer thickness portion of the insulating layer at a relatively higher density than other portions of the insulating layer.
  • the amount (concentration) of the heat-resistant particles contained in a layer thickness portion of 0.5 ⁇ m from the surface of the insulating layer is the amount of the heat-resistant particles contained in the central portion in the thickness direction of the insulating layer (
  • the average particle size of the resin particles is more preferably 10 to 100 nm, and the average particle size of the heat-resistant particles is more preferably 0.5 to 400 nm.
  • the rate of increase in the softening temperature resistance of the insulating layer is more preferably 1.2 to 1.6.
  • metal oxide one or a mixture of two or more selected from alumina, zirconia and the like, and as the metal nitride, one or a mixture of two or more selected from aluminum nitride, boron nitride and the like can be used.
  • the heat-resistant insulated wire since the heat-resistant particles are concentrated on the surface portion of the insulating layer, the heat resistance of the surface portion of the insulating layer that is most exposed to heat at high temperature is high. For this reason, even if the total amount of heat-resistant particles contained in the entire insulating layer is small, excellent heat resistance can be obtained.
  • the electrodeposition liquid according to another aspect of the present invention can form an insulating layer with dense heat-resistant particles on the surface portion. Therefore, it is possible to obtain an insulation coated electric wire having a high softening temperature.
  • the rate of increase in the softening temperature represented by the formula [softening temperature of insulating layer (° C.)] / [Softening temperature of insulating layer resin (° C.)] is 1.2 or more, preferably 1.2 to 1. .6, more preferably 1.3 to 1.5 heat resistant insulation coating.
  • the above electrodeposition liquid is used in the electrodeposition method, a desired layer thickness can be obtained by a single electrodeposition process.
  • an insulating coating can be uniformly formed at the corners of the flat electric wire.
  • water can be used as a dispersion medium for the electrodeposition liquid, the load on the environment is small.
  • 2 is a partial cross-sectional photograph of an insulated wire formed in Example 1.
  • 2 is an EDS analysis chart at a position where a distance from the surface of the insulating layer is 0.25 ⁇ m on a perpendicular line connecting the surface of the copper wire 10 and the surface of the insulating layer 20 in FIG. 1.
  • 2 is an EDS analysis chart at a position where the distance from the surface of the insulating layer is a half of the thickness of the entire insulating layer on a perpendicular line connecting the surface of the copper wire 10 and the surface of the insulating layer 20 in FIG.
  • a heat-resistant insulated wire is an insulated wire having a conductive wire and a heat-resistant insulating layer provided on the surface of the conductive wire, wherein the heat-resistant particles are contained in the insulating layer. And the heat-resistant particles are densely packed in the surface layer thickness portion of the insulating layer.
  • the conductive wire may be any commonly used metal such as copper, copper alloy, silver, silver alloy, aluminum, aluminum alloy.
  • the shape may be any shape such as a circular cross-section, a cross-sectional ellipse, a cross-sectional quadrangle, and a cross-sectional flat plate shape.
  • the insulating layer is formed on the surface of the conductive wire with a substantially uniform thickness.
  • the corners are formed relatively thicker (for example, about 10 to 30% thicker) than other parts.
  • the surface layer thickness portion of the insulating layer is a layer whose distance (depth) from the surface of the insulating layer is 0.5 ⁇ m on the perpendicular connecting the surface of the conductive wire of the insulated wire and the surface of the insulating layer. Thick part. In general, the thickness of the entire insulating layer is generally 2 to 50 ⁇ m, and usually 3 to 30 ⁇ m.
  • the amount (concentration) of heat-resistant particles contained in the layer thickness portion of 0.5 ⁇ m from the surface of the insulating layer is in the central portion in the thickness direction of the insulating layer. It is at least twice the amount (concentration) of heat-resistant particles contained.
  • the central portion in the thickness direction of the insulating layer is a vertical line connecting the surface of the conductive wire and the surface of the insulating layer, and 1/3 ⁇ from the surface of the insulating layer with respect to the layer thickness L of the entire insulating layer. The range from the position of L to the position of 2/3 ⁇ L.
  • FIG. 1 is a partial cross-sectional view of a heat-resistant insulated wire according to this embodiment.
  • the heat-resistant insulated wire has a conductive wire 10 (copper wire 10 in the illustrated example) and a heat-resistant resin insulating layer 20 that covers the copper wire 10 with a certain thickness.
  • grains 30 are contained.
  • the white spots inside the insulating layer 20 are the heat-resistant particles 30.
  • the heat-resistant particles 30 in the illustrated example are silica fine particles. As shown in the figure, white spots are concentrated in the 0.5 ⁇ m thick portion from the surface of the insulating layer 20, and it can be seen that the heat-resistant particles 30 are unevenly distributed in this portion.
  • FIG. 2 and FIG. 3 show the results of elemental analysis by energy dispersive X-ray spectroscopic analysis (hereinafter referred to as EDS analysis) for the elements contained in the cross-sectional portion shown in FIG.
  • FIG. 2 is a chart of an EDS analysis result at a position where the distance from the surface of the insulating layer is 0.25 ⁇ m on a perpendicular line connecting the surface of the copper wire 10 and the surface of the insulating layer 20.
  • FIG. 3 shows an EDS analysis result at a position where the distance from the surface of the insulating layer is a half (thickness center) of the entire insulating layer on a perpendicular line connecting the surface of the copper wire 10 and the surface of the insulating layer 20. It is a chart.
  • the analysis region on the sample surface is a circle having a diameter of 1 ⁇ m.
  • the heat-resistant particles contained in the insulating layer are concentrated in the surface layer thickness portion of the insulating layer.
  • the heat-resistant insulated wire is included in the surface layer thickness portion of the insulating layer. Since the amount of silica fine particles is about four times the amount of silica fine particles contained in the central portion of the insulating layer, the heat resistance of the surface layer thickness portion that is most exposed to heat at high temperatures is high. For this reason, even if there is little quantity of the heat resistant particle contained in the whole insulating layer, the outstanding heat resistance can be obtained.
  • the insulating layer is made of acrylic resin, polyesterimide resin, polyimide resin, or the like, and the heat-resistant particles contained in the insulating layer are metal oxide fine particles, metal nitride fine particles, boron nitride fine particles, and One type or two or more types selected from silica fine particles.
  • the metal oxide is, for example, one or a mixture of two or more selected from alumina and zirconia
  • the metal nitride is one or a mixture of two or more selected from aluminum nitride and boron nitride. Particularly preferred are alumina and zirconia.
  • the insulating layer can be formed by the following electrodeposition liquid.
  • the electrodeposition liquid of this embodiment is a suspension in which resin particles and heat-resistant particles are dispersed in a solvent. This electrodeposition liquid can be obtained by mixing a suspension in which heat-resistant particles are dispersed in a suspension in which resin particles are dispersed.
  • the dispersion medium of the resin particle suspension may be any liquid used in the electrodeposition method, and may be water, water-N, N dimethylformamide mixed solution, water-N methylpyrrolidone mixed solution, water-dimethyl sulfoxide mixed solution, etc. A mixture of water and aprotic polar solvent is used.
  • a dispersion medium having good compatibility with the resin particle suspension is suitable for the dispersion of the heat-resistant particle suspension. For example, one or a mixture of two or more selected from water, methanol, methyl ethyl ketone, and the like are used.
  • the electrodeposition liquid of this embodiment is a suspension having a turbidity of 1 mg / L or more, preferably 10 to 600 mg / L, in which resin particles and heat-resistant particles are dispersed. Turbidity can be measured with a commercially available integrating sphere turbidimeter. If the turbidity of the electrodeposition liquid is less than 1 mg / L, the dispersion state of the resin particles and heat-resistant particles in the liquid is insufficient, and the amount of the resin particles and heat-resistant particles is insufficient. It is difficult to form a thick insulating layer.
  • the turbidity of the electrodeposition liquid is 1 mg / L or more, the dispersion state of the resin particles and heat-resistant particles in the liquid is good, and since a sufficient amount of resin particles and heat-resistant particles are contained, good heat resistance An insulating layer can be formed.
  • a direct current is mainly passed between the conductive wire immersed in the electrodeposition liquid and the counter electrode, and the resin particles and the heat-resistant particles in the liquid are electrically moved to the surface of the wire to be electrodeposited.
  • the electrodeposition solution is required to have a low viscosity so that the solution does not solidify. If the viscosity of the electrodeposition liquid is too high, the liquid is solidified and cannot be used for film formation.
  • the viscosity of the electrodeposition liquid is preferably 100 cP or less, and more preferably 0.5 to 90 cP. If the viscosity of the electrodeposition liquid is 100 cP or less, a good insulating layer can be formed without solidifying the liquid.
  • a coating material that forms an insulating layer is used in the dipping method.
  • a highly viscous liquid is used so that the paint does not flow down.
  • the viscosity of a coating forming paint used in the dipping method is 1000 cP or more. Since the resin component of the coating composition for dipping coating is dissolved in the paint and is not a suspension in which resin particles are dispersed in the liquid, the turbidity of the paint is generally less than 0.01 mg / L, It is a light transmissive liquid.
  • the viscosity of these paints is 1000 cP or more and turbidity.
  • the viscosity is less than 0.01 mg / L, and the viscosity and turbidity of the liquid are completely different from the electrodeposition liquid for forming an insulating layer of the present invention.
  • the electrodeposition liquid of this embodiment has a markedly lower viscosity than the insulating layer paint used in the dipping method.
  • the type of resin particles contained in the electrodeposition liquid of this embodiment is one or a mixture of two or more selected from acrylic resin, polyesterimide resin, polyimide resin, or the like.
  • the average particle diameter of the resin particles is preferably 1 ⁇ m or less, more preferably 10 to 100 nm. If resin particles having an average particle diameter of 1 ⁇ m or less are used, the dispersion stability of the resin particles is improved.
  • the content of the resin particles contained in the electrodeposition liquid of the present invention is preferably 1 to 30% by mass. Since the electrodeposition liquid of the present invention contains the resin particles having the above content, an insulating layer having a sufficient thickness can be formed.
  • the shape of the resin particles may be spherical, elliptical, or other different shapes.
  • the average particle size of the resin particles can be determined by a commercially available dynamic light scattering particle size distribution measuring device.
  • heat-resistant particles are dispersed together with the resin particles.
  • the heat-resistant particles are one or more selected from metal oxide fine particles, metal nitride fine particles, boron nitride fine particles, and silica fine particles.
  • metal oxide for example, one or a mixture of two or more selected from alumina and zirconia, and one or a mixture of two or more selected from aluminum nitride and boron nitride can be used as the metal nitride.
  • the heat-resistant particles are dispersed in advance in a dispersion medium having good compatibility with the suspension, and the dispersion is used as a suspension of the resin particles. To be mixed.
  • the heat resistant particles are preferably colloidal particles of 500 nm or less, and more preferably 0.5 to 400 nm. Since the colloidal particles having the above particle diameter are dispersed without being settled in the liquid, a heat resistant coating in which the heat resistant particles are uniformly contained can be formed.
  • the shape of the heat-resistant particles may be spherical, elliptical, or other irregular shapes.
  • the average particle diameter of the heat-resistant particles can also be determined by a commercially available dynamic light scattering particle size distribution measuring apparatus.
  • the content of the heat resistant particles is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the resin particles.
  • the content is less than 1 part by mass, the heat resistance of the insulating layer becomes insufficient, and when it exceeds 100 parts by mass, the flexibility of the insulating layer is lowered.
  • the electrodeposition liquid of the present invention contains the above-mentioned heat-resistant particles, an insulating layer having sufficient heat resistance and flexibility can be formed. More preferably, it is 20 to 80 parts by mass with respect to 100 parts by mass of the resin particles.
  • an electrodeposition film is formed by energization between the conductive wire immersed in the electrodeposition liquid and the counter electrode.
  • the energization conditions at this time are not different from the case of using a general electrodeposition liquid.
  • electrodeposition can be performed at a DC voltage of 5 to 100 V, an electrodeposition time of 0.1 to 30 seconds, and an electrodeposition liquid temperature of 5 to 40 ° C.
  • the charged state of the heat-resistant particles and the resin particles are different, and the resin particles are more easily electrodeposited than the heat-resistant particles. Therefore, the concentration of the heat-resistant particles is higher on the surface of the electrodeposition film.
  • the baking conditions may be the same as when a general electrodeposition solution is used.
  • the conductive wire on which the electrodeposition film is formed may be placed in a baking furnace, heated at 200 to 600 ° C. for 2 to 120 seconds, and baked to form an insulating film.
  • an insulating layer in which heat-resistant particles are densely formed in the surface layer thickness portion can be formed.
  • the heat-resistant insulated wire of the present embodiment since the heat-resistant particles are concentrated on the surface portion of the insulating layer, the heat resistance of the surface portion of the insulating layer that is most exposed to heat at high temperature is high. For this reason, even if there is little quantity of the heat resistant particle contained in the whole insulating layer, the outstanding heat resistance can be obtained.
  • the electrodeposition liquid of the present embodiment can form an insulating layer in which heat-resistant particles are dense on the surface portion. Therefore, it is possible to obtain an insulation coated electric wire having a high softening temperature.
  • the rate of increase in the softening temperature represented by the formula of [softening temperature of insulating layer (° C.)] / [Softening temperature of insulating layer resin (° C.)] is 1.2 or more, preferably A heat resistant insulation coating of 1.3 to 1.5 can be formed.
  • the electrodeposition liquid of this embodiment is used for the electrodeposition method, a desired layer thickness can be obtained by a single electrodeposition process.
  • An insulating coating can be uniformly formed on the corner of the flat electric wire.
  • water or a water mixture can be used as a dispersion medium for the electrodeposition liquid, the burden on the environment is small.
  • Example 1 Acrylic resin particles having an average particle diameter of 50 nm were dispersed in water to obtain an aqueous suspension having a resin particle concentration of 20% by mass. Silica particles having an average particle size of 10 nm or an average particle size of 360 nm were dispersed in water to obtain a silica sol having a silica particle concentration of 30% by mass and water of 70% by mass. Furthermore, the water suspension and the silica sol were mixed at various ratios to prepare a plurality of water-dispersed electrodeposition solutions. Table 1 shows parts by mass of the silica particles with respect to 100 parts by mass of the resin particles in the electrodeposition liquid.
  • Table 1 shows the turbidity, viscosity, liquid state, resin particle concentration, and average particle size of the resin particles of each electrodeposition solution.
  • the amount of water in each electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 1.
  • the average particle diameters of the acrylic resin particles and the silica particles were measured by a dynamic light scattering particle size distribution analyzer (LB550: trade name) manufactured by HORIBA.
  • the turbidity of the electrodeposition solution was measured with an integrating sphere turbidimeter (ANA-148: trade name) manufactured by Tokyo Photonic Co., Ltd.
  • the viscosity of the electrodeposition liquid was measured with a capillary viscometer according to JIS (Z8803: 2011-6).
  • Each electrodeposition solution is placed in an electrodeposition bath at 25 ° C., and a copper wire having a diameter of 0.1 mm is passed through the electrodeposition bath at a wire speed of 15 m / min.
  • the copper wire is used as an anode, and the electrodeposition bath is used as a cathode.
  • Acrylic resin and silica particles were electrodeposited on the wire surface.
  • a mist treatment with DMF was performed, the treated wire was passed through a baking furnace, and a baking treatment was performed at a heating temperature of 300 ° C. for a heating time of 10 seconds to form an insulating layer having a thickness of 10 ⁇ m on the copper wire surface.
  • the flexibility, softening temperature, softening temperature increase rate, and ratio of the heat-resistant particle amount of the insulating layer surface layer thickness portion to the heat-resistant particle amount of the central portion of the insulating layer were measured.
  • the results are shown in Table 1.
  • self-diameter winding was performed according to JIS (C3005: 2000-4.20.1), and the presence or absence of peeling of the insulating layer was examined with an optical microscope.
  • the softening temperature was measured according to JIS (C3216-6: 2011-4).
  • the rate of increase in the softening temperature was determined by the formula [softening temperature of insulating layer (° C.)] / [Softening temperature of insulating layer resin (° C.)].
  • the ratio of the heat-resistant particle amount in the insulating layer surface layer thickness portion to the heat-resistant particle amount in the central portion of the insulating layer was measured in the same manner as the above-described Si / C ratio measurement method.
  • Example 14 to 23 Zirconia particles having an average particle diameter of 100 nm were dispersed in water to obtain a zirconia sol having a zirconia particle concentration of 30% by mass and water of 70% by mass. Further, alumina particles having an average particle diameter of 50 nm were dispersed in water to obtain an alumina sol having an alumina particle concentration of 30% by mass and water of 70% by mass. A water-dispersed electrodeposition solution was prepared in the same manner as in Examples 1 to 13 except that these sols were used. Table 2 shows the parts by mass of zirconia particles or alumina particles with respect to 100 parts by mass of the resin particles in the electrodeposition liquid.
  • Table 2 shows the turbidity, viscosity, liquid state, resin particle concentration, and average particle diameter of the resin particles.
  • the amount of water in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 2.
  • the average particle diameter of the acrylic resin particles and silica particles, the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13. Using these electrodeposition solutions, an insulating layer having a thickness of 10 ⁇ m was formed in the same manner as in Examples 1 to 13.
  • Polyesterimide resin particles having an average particle diameter of 200 nm were dispersed in water to obtain an aqueous suspension having a resin particle concentration of 20% by mass.
  • Silica particles having an average particle diameter of 10 nm were dispersed in water to obtain a silica sol having a silica particle concentration of 30% by mass and water of 70% by mass. Furthermore, these were mixed at various ratios to prepare a plurality of water-dispersed electrodeposition solutions.
  • Table 3 shows parts by mass of the silica particles with respect to 100 parts by mass of the resin particles in each electrodeposition liquid. The turbidity, viscosity, liquid state, resin particle concentration, and average particle diameter of the resin particles were measured. The results are shown in Table 3.
  • the amount of water in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 3.
  • the average particle diameter of the polyesterimide resin particles and silica particles, the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13.
  • an insulating layer having a thickness of 10 ⁇ m was formed in the same manner as in Examples 1 to 13.
  • the flexibility, softening temperature, softening temperature increase rate, and ratio of the heat-resistant particle amount of the insulating layer surface layer thickness portion to the heat-resistant particle amount of the central portion of the insulating layer were measured.
  • the results are shown in Table 3.
  • the ratios of flexibility, softening temperature, softening temperature rise rate, and heat-resistant particle amount in the insulating layer surface layer thickness portion to heat-resistant particle amount in the central portion of the insulating layer are the same as in Examples 1 to 13. It was measured.
  • Example 31 to Example 35 Polyimide resin particles having an average particle diameter of 400 nm were dispersed in water to obtain an aqueous suspension having a resin particle concentration of 20% by mass. Silica particles having an average particle diameter of 10 nm were dispersed in water to obtain a silica sol having a silica particle concentration of 30% by mass and water of 70% by mass. Furthermore, these were mixed and the water dispersion type electrodeposition liquid was prepared. Table 3 shows parts by mass of the silica particles with respect to 100 parts by mass of the resin particles in the electrodeposition liquid. Table 3 shows the turbidity, viscosity, liquid state, resin particle concentration, and average particle diameter of the resin particles.
  • the amount of water in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 3.
  • the average particle diameter of the polyimide resin particles and silica particles, the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13.
  • an insulating layer having a thickness of 10 ⁇ m was formed in the same manner as in Examples 1 to 13.
  • the flexibility, softening temperature, softening temperature increase rate, and ratio of the heat-resistant particle amount of the insulating layer surface layer thickness portion to the heat-resistant particle amount of the central portion of the insulating layer were measured.
  • the results are shown in Table 3.
  • the ratios of flexibility, softening temperature, softening temperature rise rate, and heat-resistant particle amount in the insulating layer surface layer thickness portion to heat-resistant particle amount in the central portion of the insulating layer are the same as in Examples 1 to 13. It was measured.
  • Example 36 to 40 Polyamideimide resin particles having an average particle diameter of 300 nm were dispersed in water to obtain an aqueous suspension having a resin particle concentration of 20% by mass. Silica particles having an average particle diameter of 10 nm were dispersed in water to obtain a silica sol having a silica particle concentration of 30% by mass and water of 70% by mass. Furthermore, these were mixed and the water dispersion type electrodeposition liquid was prepared. Table 4 shows parts by mass of the silica particles with respect to 100 parts by mass of the resin particles in the electrodeposition liquid. Table 4 shows the turbidity, viscosity, liquid state, resin particle concentration, and average particle diameter of the resin particles.
  • the amount of water in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 4.
  • the average particle diameter of the polyimide resin particles and silica particles, the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13.
  • an insulating layer having a thickness of 10 ⁇ m was formed in the same manner as in Examples 1 to 13.
  • the flexibility, softening temperature, softening temperature increase rate, and ratio of the heat-resistant particle amount of the insulating layer surface layer thickness portion to the heat-resistant particle amount of the central portion of the insulating layer were measured.
  • the results are shown in Table 4.
  • the ratios of flexibility, softening temperature, softening temperature rise rate, and heat-resistant particle amount in the insulating layer surface layer thickness portion to heat-resistant particle amount in the central portion of the insulating layer are the same as in Examples 1 to 13. It was measured.
  • the turbidity of the electrodeposition solution is 30 mg / L or more, the viscosity is 100 cP or less, and the softening temperature of the formed insulating layer is 400 ° C. or more.
  • the softening temperature increase rate was 1.2 or more, and the heat resistance was high.
  • the softening temperature and the softening temperature increase rate increased according to the content of the heat-resistant particles.
  • the amount of the heat-resistant particles is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the resin particles.
  • Acrylic resin particles having an average particle size of 50 nm, polyesterimide resin particles having an average particle size of 200 nm, polyimide resin particles having an average particle size of 400 nm, and polyamideimide resin particles having an average particle size of 300 nm are each dispersed in water to obtain a resin particle concentration of 20 A mass% aqueous suspension was obtained and used as an electrodeposition solution.
  • Table 5 shows the turbidity, viscosity, liquid state, resin particle concentration, and average particle diameter of the resin particles. The amount of water in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 5.
  • the average particle diameter of the resin particles, the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13. Using these electrodeposition solutions, an insulating layer having a thickness of 10 ⁇ m was formed in the same manner as in Examples 1 to 13. About these insulated wires, the flexibility, softening temperature, and softening temperature increase rate were measured. The results are shown in Table 5. The flexibility, softening temperature, and softening temperature increase rate were measured in the same manner as in Examples 1 to 13. In Comparative Examples 1 to 4, the insulating layer was formed by the electrodeposition method, but since it does not contain heat-resistant particles, the softening temperature does not increase and the softening temperature increase rate is 1.
  • silica particles having an average particle diameter of 10 nm were dispersed in a mixed solution of xylene and butanol to obtain a silica sol.
  • the silica sol was mixed with the paint while stirring the paint, and dispersed so that the silica particles were 20 parts by mass with respect to 100 parts by mass of the resin content of the paint.
  • Table 5 shows the turbidity, viscosity, liquid state, and resin concentration of the electrodeposition liquid. The amount of xylene and butanol in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 5.
  • the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13. Using this electrodeposition solution, an insulating layer was formed in the same manner as in Examples 1 to 13. However, the turbidity of the electrodeposition solution was less than 0.01 mg / L and the viscosity exceeded 1000 cP. A layer could not be formed.
  • Polyesterimide resin particles having an average particle diameter of 200 nm were dispersed in water to obtain an aqueous suspension having a resin particle concentration of 40% by mass.
  • Silica particles having an average particle diameter of 10 nm were dispersed in water to obtain a silica sol having a silica particle concentration of 30% by mass and water of 70% by mass.
  • the water suspension and the silica sol were mixed so as to obtain 1 part by mass of silica particles with respect to 100 parts by mass of the polyesterimide resin, thereby obtaining an electrodeposition solution.
  • Table 5 shows the turbidity, viscosity, liquid state, resin particle concentration, and average particle diameter of the resin particles.
  • the amount of water in the electrodeposition solution was adjusted so that the resin particle concentration was the value shown in Table 5.
  • the average particle diameter of the resin particles, the turbidity and viscosity of the electrodeposition solution were measured in the same manner as in Examples 1 to 13. An attempt was made to form an insulating layer using these electrodeposition solutions in the same manner as in Examples 1 to 13. However, since the resin particle concentration was high and the viscosity of the electrodeposition solution was too high, the solution solidified and could be electrodeposited. There wasn't.
  • the present invention provides a heat-resistant insulated wire excellent in heat resistance near the surface of the insulating layer, and an electrodeposition liquid for forming the insulating layer. Therefore, it has industrial applicability.

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Abstract

　耐熱性の絶縁層を有する絶縁電線であって、上記絶縁層中に耐熱性粒子を含有し、上記耐熱性粒子が上記絶縁層の表面層厚部分に密集している。例えば、上記絶縁層の表面から０．５μｍの層厚部分に含まれる耐熱性粒子の量は、上記絶縁層の中央部分に含まれる耐熱性粒子の量の２倍以上である。上記絶縁層の形成に用いる電着液は、樹脂粒子が分散した懸濁液に、耐熱性粒子を分散させてなり、粘度は１００ｃＰ以下であり、かつ濁度は１ｍｇ／Ｌ以上である。

Description

耐熱性絶縁電線とその絶縁層の形成に用いる電着液
　本発明は、耐熱性の絶縁層を有する絶縁電線と上記絶縁層を形成する電着液に関する。
　本願は、２０１４年７月３日に日本出願された特願２０１４－１３８１１３号に基づき、その内容をここに援用する。
　絶縁電線はマグネットコイルなどに広く用いられている。絶縁電線の絶縁層を形成する方法として浸漬法と電着法が知られている。浸漬法は絶縁電線の心材になる導電性の線材を樹脂ワニス等の塗料に浸漬して引き上げ、乾燥させて線材表面に絶縁被覆を形成する方法である。電着法は上記線材を樹脂ワニス等の塗料成分を含む電着液に入れ、上記線材を陽極あるいは陰極にして対極との間に通電し、上記線材表面に塗料成分を電着させた後に焼付処理して絶縁層を形成する方法である（特許文献１、特許文献２参照）。
　浸漬法は平角電線の角部に塗料が付着し難く、角部の層厚が平坦部の層厚に比べて薄くなるという欠点がある。一方、電着法では平角電線の角部にも塗料が十分に電着するので、角部にも平坦部と同じ厚さ、もしくは平坦部以上の厚さの絶縁層を形成できる利点がある。
　近年、広範な用途に対応するために耐電圧強度や耐熱性に優れた絶縁電線が求められており、絶縁層の耐熱性を高める手段として、絶縁層の樹脂中に金属酸化物微粒子やシリカ微粒子を含有させたエナメル線用塗料が知られている（特許文献３）。
　しかし、特許文献３に記載されている塗料は浸漬法用であり、開示されている塗料の液組成や液状態のものでは電着法に用いることができない。浸漬法では所望の層厚に達するため何度も浸漬と乾燥を繰り返す必要があり、例えば、実用に供される程度の層厚３５μｍの被覆を形成するために７回の浸漬を繰り返している。このため生産性が低い。さらに浸漬法は平角線材では角部の層厚が平坦部に比べて薄くなる欠点を解消できない。また、樹脂や酸化物微粒子の溶媒・分散媒として有機溶剤を使用しているため環境負荷が大きい。
　さらに浸漬法では、絶縁層にシリカ微粒子を含有させる場合、シリカ微粒子を含む塗料に浸漬を繰り返すので、各層ごとにシリカ微粒子が含まれることになり、絶縁層全体にシリカ微粒子が分散された状態になる。しかし、高温下で最も熱に曝されるのは絶縁層表面であるため、絶縁層表面付近のシリカ微粒子が少ないと絶縁層表面が損傷を受けやすくなる。
特開昭６２－０３７３９６号公報 特開平０３－２４１６０９号公報 特開２００１－３０７５５７号公報
　本発明は、従来の浸漬法による絶縁電線およびその製造方法における上記問題を解決したものであり、絶縁層の表面付近の耐熱性が優れた耐熱性絶縁電線と上記絶縁層を形成するための電着液を提供する。
　本発明の各態様は以下の構成を有する。
　［１］耐熱性の絶縁層を有する絶縁電線であって、上記絶縁層中に耐熱性粒子を含有し、上記耐熱性粒子が上記絶縁層の表面層厚部分に密集していることを特徴とする耐熱性絶縁電線。上記耐熱性の絶縁層は、通常、導電性線材の表面上に形成されている。上記「密集」とは、上記絶縁層の表面層厚部分に、上記絶縁層の他の部分よりも相対的に高い密度で耐熱性粒子が分散されていることをいう。
　［２］上記絶縁層の表面から０．５μｍの層厚部分に上記耐熱性粒子が密集している上記［１］に記載の耐熱性絶縁電線。
　［３］上記絶縁層の表面から０．５μｍの層厚部分に含まれる上記耐熱性粒子の量（濃度）が、上記絶縁層の厚さ方向の中央部分に含まれる上記耐熱性粒子の量（濃度）の２倍以上である上記［１］または上記［２］に記載の耐熱性絶縁電線。より好ましくは、０．５μｍの層厚部分に含まれる上記耐熱性粒子の密度が、上記絶縁層の厚さ方向の中央部分に含まれる上記耐熱性粒子の密度の２～６倍とされる。
　［４］［１］に記載した絶縁電線の上記絶縁層の形成に用いる絶縁層形成用電着液であって、樹脂粒子が分散した懸濁液に上記耐熱性粒子を分散させてなり、粘度が１００ｃＰ以下であって、かつ濁度が１ｍｇ／Ｌ以上であることを特徴とする絶縁層形成用電着液。より好ましくは、電着液の粘度は０．５～５０ｃＰであり、濁度は１０～６００ｍｇ／Ｌである。
　［５］上記樹脂粒子の含有量が１～３０質量％であって、上記樹脂粒子１００質量部に対して上記耐熱性粒子が１～１００質量部含有されている上記［４］に記載の絶縁層形成用電着液。
　［６］上記樹脂粒子の平均粒子径が１μｍ以下であり、上記耐熱性粒子の平均粒子径が５００ｎｍ以下である上記［４］または上記［５］に記載の絶縁層形成用電着液。上記樹脂粒子の平均粒子径は、より好ましくは１０～１００ｎｍであり、上記耐熱性粒子の平均粒子径は、より好ましくは０．５～４００ｎｍである。
　［７］上記絶縁層の耐軟化温度上昇率が１．２以上の絶縁層を形成する上記［４］～上記［６］の何れかに記載の絶縁層形成用電着液。上記絶縁層の耐軟化温度上昇率は、より好ましくは１．２～１．６である。
　［８］上記樹脂粒子がアクリル樹脂、ポリエステルイミド樹脂、ポリイミド樹脂、またはポリアミドイミド樹脂から選択される一種または２種以上である上記［５］～上記［７］の何れかに記載の絶縁層形成用電着液。
　［９］上記耐熱性粒子が金属酸化物の微粒子、金属窒化物の微粒子、窒化ホウ素の微粒子、およびシリカの微粒子から選択される１種または２種以上である上記［５］～上記［８］の何れかに記載の絶縁層形成用電着液。金属酸化物としては、アルミナ、ジルコニアなどから選択される１種または２種以上の混合物、金属窒化物としては窒化アルミニウム、窒化ホウ素などから選択される１種または２種以上の混合物が使用できる。
　本発明の一態様に係る耐熱性絶縁電線は、絶縁層の表面部分に耐熱性粒子が密集しているので、高温下で最も熱に曝される絶縁層の表面部分の耐熱性が高い。このため絶縁層全体に含まれる耐熱性粒子の総量が少なくても優れた耐熱性を得ることができる。
　本発明の他の態様に係る電着液は、表面部分に耐熱性粒子が密集した絶縁層を形成することができる。従って、耐軟化温度の高い絶縁被覆電線を得ることができる。例えば、［絶縁層の耐軟化温度（℃）］／［絶縁層樹脂の耐軟化温度（℃）］の式によって表される耐軟化温度上昇率が１．２以上、好ましくは１．２～１．６、より好ましくは１．３～１．５の耐熱性の絶縁被覆を形成できる。
　上記電着液は電着法に用いられるので、所望の層厚を一回の電着処理によって得ることができる。また、平角電線の角部にも均一に絶縁被覆を形成することができる。さらに、電着液の分散媒として水を用いることができるので、環境に対する負荷が小さい。
実施例１において形成した絶縁電線の部分断面写真である。 図１の銅線１０の表面と上記絶縁層２０の表面を結んだ垂線上において上記絶縁層表面からの距離が０．２５μｍの位置のＥＤＳ分析チャートである。 図１の銅線１０の表面と上記絶縁層２０の表面を結んだ垂線上において上記絶縁層表面からの距離が上記絶縁層全体の層厚の１／２の位置のＥＤＳ分析チャートである。
　本発明の一実施形態に係る耐熱性絶縁電線は、導電性線材と、この導電性線材の表面に設けられた耐熱性の絶縁層を有する絶縁電線であって、上記絶縁層中に耐熱性粒子を含有し、上記耐熱粒子が上記絶縁層の表面層厚部分に密集していることを特徴とする。導電性線材は、銅、銅合金、銀、銀合金、アルミニウム、アルミニウム合金など通常用いられるいかなる金属でもよい。また、その形状は断面円形、断面楕円形、断面四角形、断面平板状などいかなる形状であってもよい。前記絶縁層は、導電性線材が断面円形または断面楕円形の場合には導電性線材の表面にほぼ均一の厚さで形成される。一方、導電性線材が角部のある断面形状の場合には、角部において他の部分よりも相対的に厚く（例えば１０～３０％程度厚く）形成されている。
　上記絶縁層の表面層厚部分とは、上記絶縁電線の導電性線材の表面と上記絶縁層表面を結んだ垂線上で、上記絶縁層表面からの距離（深さ）が０．５μｍまでの層厚部分である。一般に絶縁層全体の層厚は概ね２～５０μｍであり、通常は３～３０μｍである。
　本実施形態の耐熱性絶縁電線では、好ましくは、上記絶縁層の表面から０．５μｍの層厚部分に含まれる耐熱性粒子の量（濃度）が、上記絶縁層の厚さ方向の中央部分に含まれる耐熱性粒子の量（濃度）の２倍以上である。上記絶縁層の厚さ方向の中央部分とは、導電性線材の表面と上記絶縁層表面を結んだ垂線上で、上記絶縁層全体の層厚Ｌに対して上記絶縁層表面から１／３・Ｌの位置から２／３・Ｌの位置までの範囲である。
　本実施形態の耐熱性絶縁電線の一例を図１に示す。図１は本実施形態に係る耐熱性絶縁電線の部分断面図である。この耐熱性絶縁電線は、導電性線材１０（図示する例では銅線１０）と、この銅線１０を一定の厚さで覆う耐熱樹脂製の絶縁層２０とを有し、絶縁層２０に耐熱性粒子３０が含まれている。図中、絶縁層２０の内部の白い斑点が耐熱性粒子３０である。図示する例の耐熱性粒子３０はシリカ微粒子である。図示するように、絶縁層２０の表面から０．５μｍの層厚部分に白い斑点が密集しており、この部分に耐熱性粒子３０が偏在していることが分かる。
　図１に示す断面部分に含まれる元素について、エネルギー分散型Ｘ線分光分析（以下、ＥＤＳ分析と云う）による元素分析の結果を図２および図３に示す。図２は、銅線１０の表面と絶縁層２０の表面を結んだ垂線上において上記絶縁層表面からの距離が０．２５μｍの位置のＥＤＳ分析結果のチャートである。図３は銅線１０の表面と絶縁層２０の表面を結んだ垂線上において上記絶縁層表面からの距離が上記絶縁層全体の層厚の１／２（厚さ中心）の位置のＥＤＳ分析結果のチャートである。試料表面における被分析領域は、直径１μｍの円形である。
　炭素の強度ピーク（図中Ｃ）に対するケイ素の強度ピーク（図中Ｓｉ）の比（Ｓｉ／Ｃ）は、分析５回の平均値で、図２ではＳｉ／Ｃ＝２０／８０であるが、図３ではＳｉ／Ｃ＝５／９５であり、図２に示す上記絶縁層の表面層厚部分に含まれるシリカ微粒子量が、図３に示す上記絶縁層中央部分に含まれるシリカ微粒子量の約４倍であった。
　本実施形態の耐熱性絶縁電線は、絶縁層に含まれる耐熱性粒子が上記絶縁層の表面層厚部分に密集しており、例えば図示する例では、上記絶縁層の表面層厚部分に含まれるシリカ微粒子量は上記絶縁層中央部分に含まれるシリカ微粒子量の約４倍であるので、高温下で最も熱に曝される表面層厚部分の耐熱性が高い。このため絶縁層全体に含まれる耐熱性粒子の量が少なくても優れた耐熱性を得ることができる。
　上記絶縁層はアクリル樹脂、ポリエステルイミド樹脂、またはポリイミド樹脂などによって形成されており、上記絶縁層に含まれる上記耐熱性粒子は金属酸化物の微粒子、金属窒化物の微粒子、窒化ホウ素の微粒子、およびシリカの微粒子から選択される１種または２種以上などである。上記金属酸化物は例えばアルミナ、ジルコニアから選択される１種または２種以上の混合物、金属窒化物としては窒化アルミニウム、窒化ホウ素から選択される１種または２種以上の混合物などである。特に好ましいのは、アルミナおよびジルコニアである。
　上記絶縁層は、下記の電着液によって形成することができる。本実施形態の電着液は、溶媒中に樹脂粒子および耐熱性粒子が分散した懸濁液である。この電着液は、樹脂粒子が分散した懸濁液に、耐熱性粒子を分散させた懸濁液を混合して得ることができる。樹脂粒子懸濁液の分散媒は、電着法に用いる液体であればよく、水、水－Ｎ，Ｎジメチルホルムアミド混合液、水－Ｎメチルピロリドン混合液、水－ジメチルスルホキシド混合液などの、水－非プロトン性極性溶媒の混合液などが用いられる。耐熱性粒子懸濁液の分散煤は樹脂粒子懸濁液と相溶性のよい分散媒が適し、例えば水、メタノール、メチルエチルケトンなどから選択される１種または２種以上の混合物などが用いられる。
　本実施形態の電着液は、樹脂粒子および耐熱性粒子が分散している濁度１ｍｇ／Ｌ以上、好ましくは濁度１０～６００ｍｇ／Ｌの懸濁液である。濁度は市販の積分球式濁度計などで測定可能である。電着液の濁度が濁度１ｍｇ／Ｌ未満では液中の樹脂粒子および耐熱性粒子の分散状態が不十分であり、また樹脂粒子や耐熱性粒子の量が不十分であるので、十分な厚さの絶縁層を形成することが難しい。電着液の濁度が１ｍｇ／Ｌ以上であれば、液中の樹脂粒子および耐熱性粒子の分散状態が良好であり、十分な量の樹脂粒子および耐熱性粒子を含むので、良好な耐熱性を有する絶縁層を形成することができる。
　電着法では、電着液に浸漬した導電性線材と対電極の間に主として直流電流を通電し、液中の樹脂粒子および耐熱性粒子を上記線材表面に電気的に移動させて電着させることによって絶縁層を形成するが、液が固化しないように、電着液は低粘度であることが求められる。電着液の粘度が高すぎると液が固化してしまい成膜に使用することができない。電着液の粘度は１００ｃＰ以下が好ましく、粘度０．５～９０ｃＰがより好ましい。電着液の粘度が１００ｃＰ以下であれば、液が固化することなく良好な絶縁層を形成することができる。
　一方、浸漬法では絶縁層を形成する塗料が用いられる。この塗料は絶縁電線の導電性線材の表面に塗布されたときに、塗料が流れ落ちないように粘度の高い液が用いられる。一般に浸漬法で用いる被覆形成用塗料の粘度は１０００ｃＰ以上である。浸漬法の被覆形成用塗料の樹脂成分は塗料中に溶解しており、液中に樹脂粒子が分散した懸濁液ではないので、上記塗料の濁度は一般に０．０１ｍｇ／Ｌ未満であり、光透過性の液である。
　また、浸漬法では、具体的には、ポリウレタン樹脂、ポリエステル樹脂、ホルマール樹脂、ポリエステルイミド樹脂、ポリアミドイミド樹脂、ポリイミド樹脂を用いた塗料が用いられており、これらの塗料の粘度は１０００ｃＰ以上、濁度０．０１ｍｇ／Ｌ未満であり、本発明の絶縁層形成用の電着液とは、液の粘度および濁度が全く異なる。本実施形態の電着液は浸漬法で用いる絶縁層用塗料に比べて粘度が格段に低い。
　本実施形態の電着液に含まれる樹脂粒子の種類は、アクリル樹脂、ポリエステルイミド樹脂、またはポリイミド樹脂などから選択される１種または２種以上の混合物である。上記樹脂粒子の平均粒子径は１μｍ以下が好ましく、１０～１００ｎｍがより好ましい。平均粒子径が１μｍ以下の樹脂粒子を用いれば樹脂粒子の分散安定性が向上する。本発明の電着液に含まれる樹脂粒子の含有量は１～３０質量％が好ましい。本発明の電着液は上記含有量の樹脂粒子を含むので十分な厚さの絶縁層を形成することができる。樹脂粒子の形状は、球形であっても、楕円球であっても、その他の異形状であってもよい。樹脂粒子の平均粒径は、市販の動的光散乱式粒径分布測定装置によって求めることができる。
　本実施形態の電着液には上記樹脂粒子と共に耐熱性粒子が分散している。上記耐熱性粒子は金属酸化物の微粒子、金属窒化物の微粒子、窒化ホウ素の微粒子、およびシリカの微粒子から選択される１種または２種以上である。金属酸化物は例えばアルミナ、ジルコニアから選択される１種または２種以上の混合物、金属窒化物としては窒化アルミニウム、窒化ホウ素から選択される１種または２種以上の混合物などが使用できる。上記耐熱性粒子を上記樹脂粒子の懸濁液に均一に分散させるには、上記懸濁液と相溶性のよい分散媒に予め耐熱性粒子を分散させ、この分散液を樹脂粒子の懸濁液に混合すればよい。
　耐熱性粒子は５００ｎｍ以下のコロイド粒子が好ましく、０．５～４００ｎｍの粒子がより好ましい。上記粒子径のコロイド粒子は液中で沈降せずに分散するので、耐熱性粒子が均一に含まれる耐熱性被覆を形成することができる。耐熱性粒子の形状は、球形であっても、楕円球であっても、その他の異形状であってもよい。耐熱性粒子の平均粒径も、市販の動的光散乱式粒径分布測定装置によって求めることができる。
　耐熱性粒子の含有量は上記樹脂粒子１００質量部に対して１～１００質量部が好ましい。この含有量が１質量部未満では絶縁層の耐熱性が不十分になり、１００質量部を超えると絶縁層の可撓性が低下する。本発明の電着液は上記含有量の耐熱性粒子を含むので十分な耐熱性および可撓性を有する絶縁層を形成することができる。より好ましくは上記樹脂粒子１００質量部に対して２０～８０質量部である。
　本実施形態の電着液を用い、上記電着液に浸漬した導電性線材と対電極の間で通電して電着膜を形成する。このときの通電条件は一般の電着液を用いた場合と変わらない。例えば、直流電圧５～１００Ｖ、電着時間０．１～３０秒、電着液温度５～４０℃で電着を行うことができる。耐熱性粒子と樹脂粒子の帯電状態は異なり、耐熱性粒子よりも樹脂粒子の方が電着され易いため、電着膜の表面の方が耐熱性粒子の濃度が高くなる。
　上記電着後に焼き付けを行う。焼き付け条件は一般の電着液を用いた場合と同様でよい。例えば、電着膜を形成した導電性線材を焼付け炉に入れ、２００～６００℃で、２～１２０秒間加熱し、焼付け処理して、絶縁膜を形成すればよい。
　上記のように、本実施形態の電着液を用いることによって、表面層厚部分に耐熱性粒子が密集した絶縁層を形成することができる。
　本実施形態の耐熱性絶縁電線は、絶縁層の表面部分に耐熱性粒子が密集しているので、高温下で最も熱に曝される絶縁層の表面部分の耐熱性が高い。このため絶縁層全体に含まれる耐熱性粒子の量が少なくても優れた耐熱性を得ることができる。
　本実施形態の電着液は、表面部分に耐熱性粒子が密集した絶縁層を形成することができる。従って、耐軟化温度の高い絶縁被覆電線を得ることができる。具体的には、例えば、［絶縁層の耐軟化温度（℃）］／［絶縁層樹脂の耐軟化温度（℃）］の式によって表される耐軟化温度上昇率が１．２以上、好ましくは１．３～１．５の耐熱性の絶縁被覆を形成することができる。
　本実施形態の電着液は電着法に用いられるので、所望の層厚を一回の電着処理によって得ることができる。平角電線の角部にも均一に絶縁被覆を形成することができる。さらに、電着液の分散媒として水もしくは水混合物を用いることができるので、環境に対する負荷が小さい。
　本発明の実施例を比較例と共に以下に示す。
［実施例１～実施例１３］
　平均粒子径５０ｎｍのアクリル樹脂粒子を水に分散し、樹脂粒子濃度２０質量％の水懸濁液を得た。平均粒子径１０ｎｍまたは平均粒子径３６０ｎｍのシリカ粒子を水に分散し、シリカ粒子濃度３０質量％および水７０質量％のシリカゾルを得た。さらに上記水懸濁液と上記シリカゾルを種々の割合で混合して水分散型の電着液を複数種調製した。上記電着液中の樹脂粒子１００質量部に対するシリカ粒子の質量部を表１に示す。上記各電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を表１に示す。
　樹脂粒子濃度が表１の値になるように上記各電着液の水量を調整した。アクリル樹脂粒子およびシリカ粒子の平均粒子径は、ＨＯＲＩＢＡ社の動的光散乱式粒径分布測定装置（ＬＢ５５０：商品名）によって測定した。電着液の濁度は東京光電株式会社の積分球式濁度計（ＡＮＡ－１４８：商品名）で測定した。電着液の粘度はＪＩＳ（Ｚ８８０３：２０１１－６）に従って細管粘度計により測定した。
　各電着液を２５℃の電着槽に入れ、電着槽にφ０．１ｍｍの銅線を線速１５ｍ／ｍｉｎで通過させ、銅線を陽極とし、電着槽を陰極として通電し、銅線表面にアクリル樹脂とシリカ粒子を電着塗装した。電着後にＤＭＦによるミスト処理を行い、処理後の線材を焼付炉に通過させて加熱温度３００℃、加熱時間１０秒で焼付処理を行い、銅線表面に厚さ１０μｍの絶縁層を形成した。
　これらの絶縁電線について、可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比を測定した。その結果を表１に示した。
　可撓性はＪＩＳ（Ｃ３００５：２０００－４．２０．１）に従って自己径巻付後、光学顕微鏡で絶縁層の剥離の有無を調べ、剥離なしを○印、剥離ありを×印で示した。耐軟化温度はＪＩＳ（Ｃ３２１６－６：２０１１－４）に従って測定した。耐軟化温度上昇率は［絶縁層の耐軟化温度（℃）］／［絶縁層樹脂の耐軟化温度（℃）］の式によって求めた。絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比は、前述したＳｉ／Ｃ比率の測定方法と同様にして測定した。
　［実施例１４～実施例２３］
　平均粒子径１００ｎｍのジルコニア粒子を水に分散し、ジルコニア粒子濃度３０質量％および水７０質量％のジルコニアゾルを得た。また、平均粒子径５０ｎｍのアルミナ粒子を水に分散し、アルミナ粒子濃度３０質量％および水７０質量％のアルミナゾルを得た。これらのゾルを用いた以外は実施例１～実施例１３と同様にして水分散型電着液を調製した。上記電着液中の樹脂粒子１００質量部に対するジルコニア粒子またはアルミナ粒子の質量部を表２に示す。上記電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を表２に示す。樹脂粒子濃度が表２の値になるように上記電着液の水量を調整した。アクリル樹脂粒子およびシリカ粒子の平均粒子径、電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。
　これらの電着液を用い、実施例１～実施例１３と同様にして、厚さ１０μｍの絶縁層を形成した。この絶縁電線について、可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比を測定した。その結果を表２に示した。可撓性、耐軟化温度、耐軟化温度上昇率は実施例１～実施例１３と同様にして測定した。絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比は前述したＳｉ／Ｃ比率の測定方法において、実施例１４～実施例１８はＳｉをＺｒに置き換え、実施例１９～実施例２３はＳｉをＡｌに置き換えて同様に測定した。
　［実施例２４～実施例３０］
　平均粒子径２００ｎｍのポリエステルイミド樹脂粒子を水に分散し、樹脂粒子濃度２０質量％の水懸濁液を得た。平均粒子径１０ｎｍのシリカ粒子を水に分散し、シリカ粒子濃度３０質量％および水７０質量％のシリカゾルを得た。さらに、これらを種々の割合で混合して複数の水分散型電着液を調製した。各電着液中の樹脂粒子１００質量部に対するシリカ粒子の質量部を表３に示す。電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を測定した。その結果を表３に示す。樹脂粒子濃度が表３の値になるように上記電着液の水量を調整した。ポリエステルイミド樹脂粒子およびシリカ粒子の平均粒子径、上記電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。
　これらの電着液を用い、実施例１～実施例１３と同様にして、厚さ１０μｍの絶縁層を形成した。これらの絶縁電線について、可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比を測定した。その結果を表３に示した。可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比は実施例１～実施例１３と同様にして測定した。
　［実施例３１～実施例３５］
　平均粒子径４００ｎｍのポリイミド樹脂粒子を水に分散し、樹脂粒子濃度２０質量％の水懸濁液を得た。平均粒子径１０ｎｍのシリカ粒子を水に分散し、シリカ粒子濃度３０質量％および水７０質量％のシリカゾルを得た。さらに、これらを混合して水分散型電着液を調製した。上記電着液中の樹脂粒子１００質量部に対するシリカ粒子の質量部を表３に示す。上記電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を表３に示す。樹脂粒子濃度は表３の値になるように上記電着液の水量を調整した。ポリイミド樹脂粒子およびシリカ粒子の平均粒子径、電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。
　これらの電着液を用い、実施例１～実施例１３と同様にして、厚さ１０μｍの絶縁層を形成した。これらの絶縁電線について、可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比を測定した。その結果を表３に示した。
　可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比は実施例１～実施例１３と同様にして測定した。
　［実施例３６～実施例４０］
　平均粒子径３００ｎｍのポリアミドイミド樹脂粒子を水に分散し、樹脂粒子濃度２０質量％の水懸濁液を得た。平均粒子径１０ｎｍのシリカ粒子を水に分散し、シリカ粒子濃度３０質量％および水７０質量％のシリカゾルを得た。さらに、これらを混合して水分散型電着液を調製した。上記電着液中の樹脂粒子１００質量部に対するシリカ粒子の質量部を表４に示す。上記電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を表４に示す。樹脂粒子濃度は表４の値になるように上記電着液の水量を調整した。ポリイミド樹脂粒子およびシリカ粒子の平均粒子径、電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。
　これらの電着液を用い、実施例１～実施例１３と同様にして、厚さ１０μｍの絶縁層を形成した。これらの絶縁電線について、可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比を測定した。その結果を表４に示した。
　可撓性、耐軟化温度、耐軟化温度上昇率、および絶縁層中央部分の耐熱性粒子量に対する絶縁層表面層厚部分の耐熱性粒子量の比は実施例１～実施例１３と同様にして測定した。
　実施例１～実施例４０の電着液は、何れも電着液の濁度は３０ｍｇ／Ｌ以上、粘度は１００ｃＰ以下であり、形成された絶縁層の耐軟化温度は４００℃以上であり、耐軟化温度上昇率は１．２以上であって、高い耐熱性を有していた。また何れの樹脂種においても、耐熱性粒子の含有量に応じて耐軟化温度および耐軟化温度上昇率が高くなった。実施例８はシリカ粒子の含有量が多いので可撓性試験において絶縁層の剥離が生じた。この結果から耐熱性粒子の量は樹脂粒子１００質量部に対して１～１００質量部が好ましいことが解った。
　［比較例１～比較例４］
　平均粒子径５０ｎｍのアクリル樹脂粒子、平均粒子径２００ｎｍのポリエステルイミド樹脂粒子、平均粒子径４００ｎｍのポリイミド樹脂粒子、および平均粒子径３００ｎｍのポリアミドイミド樹脂粒子を、それぞれ水に分散し、樹脂粒子濃度２０質量％の水懸濁液を得て、電着液として用いた。上記電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を表５に示す。樹脂粒子濃度は表５の値になるように上記電着液の水量を調整した。上記樹脂粒子の平均粒子径、電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。
　これらの電着液を用い、実施例１～実施例１３と同様にして、厚さ１０μｍの絶縁層を形成した。これらの絶縁電線について、可撓性、耐軟化温度、耐軟化温度上昇率を測定した。その結果を表５に示した。可撓性、耐軟化温度、耐軟化温度上昇率は実施例１～実施例１３と同様にして測定した。
　比較例１～比較例４は電着法によって絶縁層が形成されたが、耐熱性粒子を含まないので、耐軟化温度が上昇せず、耐軟化温度上昇率は何れも１である。
　［比較例５］
　平均粒子径１０ｎｍのシリカ粒子をキシレンとブタノールの混合液に分散し、シリカゾルを得た。ポリエステルイミド樹脂が溶解した塗料を用い、この塗料を撹拌しながら、上記シリカゾルを上記塗料に混合し、塗料の樹脂分１００質量部に対してシリカ粒子が２０質量部になるように分散させた。
　上記電着液の濁度、粘度、液の状態、樹脂濃度を表５に示す。樹脂粒子濃度は表５の値になるように上記電着液のキシレンとブタノール量を調整した。電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。この電着液を用い、実施例１～実施例１３と同様にして絶縁層の形成を試みたが、電着液の濁度０．０１ｍｇ／Ｌ未満および粘度１０００ｃＰを超えるので、電着によって絶縁層は形成できなかった。
　［比較例６］
　平均粒子径２００ｎｍのポリエステルイミド樹脂粒子を水に分散し、樹脂粒子濃度４０質量％の水懸濁液を得た。平均粒子径１０ｎｍのシリカ粒子を水に分散し、シリカ粒子濃度３０質量％および水７０質量％のシリカゾルを得た。上記ポリエステルイミド樹脂１００質量部に対してシリカ粒子１質量部になるように、上記水懸濁液と上記シリカゾルを混合し、電着液を得た。上記電着液の濁度、粘度、液の状態、樹脂粒子濃度、樹脂粒子の平均粒子径を表５に示す。樹脂粒子濃度は表５の値になるように上記電着液の水量を調整した。上記樹脂粒子の平均粒子径、電着液の濁度および粘度は実施例１～実施例１３と同様にして測定した。これらの電着液を用い、実施例１～実施例１３と同様にして絶縁層の形成を試みたが、樹脂粒子濃度が高く電着液の粘度が高すぎるので液が固化し、電着できなかった。
　［比較例７］
　平均粒子径１０ｎｍのシリカ粒子をキシレンとブタノールの混合液に分散し、シリカゾルを得た。トリス－ヒドロキシエチルイソシアヌレート変性ポリエステルイミドが溶解した塗料を用い、この塗料を撹拌しながら、上記シリカゾルを上記塗料に混合し、塗料の樹脂分１００質量部に対してシリカ粒子が２０質量部になるように分散させた。この塗料を用い、実施例１～実施例１３と同様にして電着法によって絶縁層の形成を試みたが、樹脂成分が溶解した液であるため電着法では絶縁層を形成することができなかった。
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
　本発明は、絶縁層の表面付近の耐熱性が優れた耐熱性絶縁電線と、上記絶縁層を形成するための電着液を提供する。よって、産業上の利用可能性を有する。
　１０　銅線
　２０　絶縁層
　３０　耐熱性粒子

Claims (9)

  1. 　耐熱性の絶縁層を有する絶縁電線であって、上記絶縁層中に耐熱性粒子を含有し、上記耐熱性粒子が上記絶縁層の表面層厚部分に密集していることを特徴とする耐熱性絶縁電線。
  2. 　上記絶縁層の表面から０．５μｍの層厚部分に上記耐熱性粒子が密集している請求項１に記載の耐熱性絶縁電線。
  3. 　上記絶縁層の表面から０．５μｍの層厚部分に含まれる上記耐熱性粒子の量が、上記絶縁層の厚さ方向の中央部分に含まれる上記耐熱性粒子の量の２倍以上である請求項１または請求項２に記載の耐熱性絶縁電線。
  4. 　請求項１に記載した絶縁電線の上記絶縁層の形成に用いる絶縁層形成用電着液であって、樹脂粒子が分散した懸濁液に上記耐熱性粒子を分散させてなり、粘度が１００ｃＰ以下であって、かつ濁度が１ｍｇ／Ｌ以上であることを特徴とする絶縁層形成用電着液。
  5. 　上記樹脂粒子の含有量が１～３０質量％であって、上記樹脂粒子１００質量部に対して上記耐熱性粒子が１～１００質量部含有されている請求項４に記載の絶縁層形成用電着液。
  6. 　上記樹脂粒子の平均粒子径が１μｍ以下であり、上記耐熱性粒子の平均粒子径が５００ｎｍ以下である請求項４または請求項５に記載の絶縁層形成用電着液。
  7. 　上記絶縁層の耐軟化温度上昇率が１．２以上の絶縁層を形成する請求項４～請求項６の何れかに記載の絶縁層形成用電着液。
  8. 　上記樹脂粒子がアクリル樹脂、ポリエステルイミド樹脂、ポリイミド樹脂、またはポリアミドイミド樹脂である請求項５～請求項７の何れかに記載の絶縁層形成用電着液。
  9. 　上記耐熱性粒子が金属酸化物微粒子またはシリカ微粒子の少なくとも一種である請求項５～請求項８の何れかに記載の絶縁層形成用電着液。
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EP3392886A1 (en) 2018-10-24
EP3392886A4 (en) 2019-07-31
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