JP2016110847A - Insulated electric wire and method for producing insulated electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated electric wire that achieves a low dielectric constant while at the same time maintaining mechanical strength and flexibility.SOLUTION: The insulated electric wire has a linear conductor and an insulation layer coated onto an outer peripheral surface side of the conductor. The insulation layer has one or a plurality of porous layers including pores and one or a plurality of solid layers including no pores laminated on an outer peripheral surface side of the porous layer and the solid layer is composed mainly of a thermoplastic resin. The porous layer may be composed mainly of a thermoplastic resin. The thermoplastic resin may be a polyethylene terephthalate, a polyether ether ketone, a polyphenylene sulfide or a combination thereof. The porosity of the porous layer is preferably not less than 5 vol% to not more than 80 vol%. The average size of the pores is preferably not less than 0.1 μm to not more than 10 μm. The ratio of an average thickness of the total of one or a plurality of porous layers to an average thickness of the insulation layer is preferably not less than 20% to not more than 60%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulated wire and a method for producing an insulated wire.

  In an electric device having a high applied voltage, such as a motor used at a high voltage, a high voltage is applied to an insulated wire constituting the electric device, and partial discharge (corona discharge) easily occurs on the surface of the insulating coating. When a local temperature rise, ozone generation, ion generation, or the like is caused by the generation of corona discharge, dielectric breakdown occurs at an early stage, and the life of the insulated wire and thus the electrical equipment is shortened. For this reason, the insulated wire used for the electric equipment with a high applied voltage is also required to improve the corona discharge starting voltage in addition to excellent insulation and mechanical strength.

  As a device for increasing the corona discharge starting voltage, it is effective to lower the dielectric constant of the insulating coating. In order to realize a low dielectric constant of an insulating coating, an insulated wire has been proposed in which an insulating coating having a layer containing bubbles and a layer not containing bubbles is formed on a conductor by baking a thermosetting resin varnish. (See Japanese Patent No. 5391365). This insulated wire achieves a low dielectric constant by forming a layer containing bubbles.

Japanese Patent No. 5391365

  Since the conventional insulated wire has an insulating coating formed of a thermosetting resin, the insulating coating is difficult to stretch and the flexibility of the insulated wire is likely to be impaired.

  This invention is made | formed based on the above situations, and it aims at providing the insulated wire which can make mechanical strength and flexibility maintenance and low dielectric constant compatible.

  An insulated wire according to an aspect of the present invention made to solve the above problems is an insulated wire comprising a linear conductor and an insulating layer coated on an outer peripheral surface side of the conductor, and the insulating layer Has one or more pore layers containing pores and one or more solid layers laminated on the outer peripheral surface side of the pore layers and does not contain pores, and the main component of the solid layer is thermoplastic. Resin.

  Another method for manufacturing an insulated wire according to an aspect of the present invention includes a linear conductor and an insulating layer that is covered on the outer peripheral surface side of the conductor and includes an insulating layer having a pore layer and a solid layer in order from the conductor side. A method for producing an electric wire, comprising: a step of preparing a pore layer varnish by mixing a resin forming a pore layer with a solvent and a pore-forming agent; and a thermoplastic resin forming the solid layer. A step of preparing a solid layer varnish by diluting with a solvent, a step of forming a pore layer by applying and baking the varnish for pore layer on the outer peripheral surface side of the conductor, and the conductor having the pore layer formed thereon And forming the solid layer by applying and baking the varnish for the solid layer on the outer peripheral surface side.

  Yet another method of manufacturing an insulated wire according to an aspect of the present invention includes a linear conductor and an insulating layer that is coated on an outer peripheral surface side of the conductor and has a pore layer and a solid layer in order from the conductor side. A method of manufacturing an insulated wire comprising: a step of coating the outer peripheral surface side of the conductor with a pore layer and a solid layer by coextrusion, the pore layer including pores, and the solid layer including pores The main component of the solid layer is a thermoplastic resin.

  The insulated wire of the present invention can achieve both maintenance of mechanical strength and flexibility and reduction in dielectric constant. Moreover, the manufacturing method of the insulated wire of this invention can manufacture the insulated wire which can make mechanical strength and flexibility maintenance, and low dielectric constant compatible.

It is a typical sectional view of an insulated wire concerning an embodiment of the present invention.

[Description of Embodiment of the Present Invention]
An insulated wire according to an aspect of the present invention is an insulated wire including a linear conductor and an insulating layer coated on an outer peripheral surface side of the conductor, and the insulating layer includes one or more pores. It has a pore layer and one or a plurality of solid layers that are laminated on the outer peripheral surface side of the pore layer and do not contain pores, and the main component of the solid layer is a thermoplastic resin.

  In the insulated wire, the insulating layer has one or a plurality of pore layers including pores, so that the dielectric layer can have a low dielectric constant, and the corona discharge starting voltage is improved. Further, in the insulated wire, since the main component of one or more solid layers of the insulating layer is a thermoplastic resin, the solid layer is easily stretched and the flexibility of the insulating layer can be maintained. Moreover, since the solid layer in which the said insulated wire does not contain a pore is laminated | stacked on the outer peripheral surface side of a pore layer, the mechanical strength of an insulating layer is maintained by a solid layer. Here, the “main component” is a component having the largest content, for example, a component contained in an amount of 50% by mass or more.

  The main component of the pore layer is preferably a thermoplastic resin. As described above, the thermoplastic layer is also used as the main component of the pore layer, so that the pore layer is easily elongated together with the solid layer, so that the flexibility of the insulating layer can be more reliably maintained.

  The thermoplastic resin may be polyethylene terephthalate, polyetheretherketone, polyphenylene sulfide, or a combination thereof. Since these resins have a low dielectric constant, the dielectric constant of the insulating layer can be more reliably lowered and the corona discharge starting voltage can be improved.

  The thermoplastic resin is preferably crosslinked. Thus, since the thermoplastic resin is crosslinked, the mechanical strength of the solid layer is improved, and the mechanical strength of the insulating layer is easily maintained. Moreover, since the chemical resistance and heat resistance of the solid layer are improved, the chemical resistance and heat resistance of the insulating layer can be improved.

  The porosity of the pore layer is preferably 5% by volume or more and 80% by volume or less. Thus, by setting the porosity of the pore layer within the above range, the dielectric constant of the insulating layer can be reliably reduced, and the corona discharge start voltage can be more reliably improved. Here, the “porosity” means a percentage of the volume of the pores with respect to the volume including the pores of the pore layer.

  The average diameter of the pores is preferably 0.1 μm or more and 10 μm or less. Thus, by setting the average diameter of the pores within the above range, it is possible to suppress the local increase in the dielectric constant of the insulating layer, and it is possible to more reliably maintain the corona discharge start voltage at a high value. Here, the “average diameter of the pores” means the average value of the diameters of the true spheres corresponding to the volume of the pores for all the pores included in the pore layer. Therefore, when the insulating layer has a plurality of pore layers, the “average pore diameter” means the average value of the pores contained in all the pore layers.

  The ratio of the total average thickness of the one or more pore layers to the average thickness of the insulating layer is preferably 20% or more and 60% or less. Thus, by setting the ratio of the total average thickness of the pore layers within the above range, the dielectric constant of the insulating layer can be reduced, and the mechanical strength and flexibility of the insulating layer can be more reliably maintained. it can.

  The average thickness of the insulating layer is preferably 30 μm or more and 200 μm or less. Thus, by making the average thickness of the insulating layer within the above range, the conductor can be reliably insulated and a decrease in the volumetric efficiency of the coil when forming the coil or the like can be suppressed.

  An insulated wire manufacturing method according to an aspect of the present invention includes a linear conductor and an insulating layer that is coated on an outer peripheral surface side of the conductor and has a pore layer and a solid layer in order from the conductor side. A method of preparing a pore layer varnish by mixing a resin that forms the pore layer with a solvent and a pore-forming agent, and a thermoplastic resin that forms the solid layer as a solvent. The step of preparing a varnish for a solid layer by dilution with the step of forming a pore layer by applying and baking the varnish for a pore layer on the outer peripheral surface side of the conductor, and the step of forming the pore layer And a step of forming the solid layer by applying and baking the varnish for the solid layer on the outer peripheral surface side.

  The method for producing an insulated wire includes preparing a varnish for a pore layer by mixing a resin for forming a pore layer with a solvent and mixing a pore-forming agent, applying the varnish for the pore layer to the outer peripheral surface side of the conductor, and Since the pore layer including pores is formed by baking, the insulated wire manufactured by the method for manufacturing an insulated wire can realize a low dielectric constant of the insulating layer, and the corona discharge starting voltage is improved. In addition, the method for manufacturing the insulated wire forms the solid layer by applying and baking the solid layer varnish on the outer peripheral surface side of the conductor in which the pore layer is formed. In the insulated wire, the mechanical strength of the insulating layer is maintained by the solid layer. Moreover, since the manufacturing method of the said insulated wire forms a solid layer with a thermoplastic resin, the insulated wire manufactured by the said manufacturing method of the insulated wire is easy to extend a solid layer, and the flexibility of an insulating layer is made. Can be maintained.

  Another method for manufacturing an insulated wire according to an aspect of the present invention includes a linear conductor and an insulating layer that is coated on an outer peripheral surface side of the conductor and has a pore layer and a solid layer in order from the conductor side. A method of manufacturing an insulated wire, comprising a step of coating the outer peripheral surface side of the conductor with a pore layer and a solid layer by coextrusion, the pore layer including pores, and the solid layer not including pores The main component of the solid layer is a thermoplastic resin.

  In the method for manufacturing the insulated wire, the insulated wire is manufactured by coextrusion, so that the outer peripheral surface side of the conductor can be simultaneously covered with the pore layer and the solid layer, and the manufacturing time can be shortened. Moreover, since the pore layer includes pores in the method for producing the insulated wire, the insulated wire produced by the method for producing the insulated wire can realize a low dielectric constant of the insulation layer, and the corona discharge starting voltage is improved. . Moreover, since the solid layer does not contain pores in the method for manufacturing the insulated wire, the mechanical strength of the insulating layer is maintained by the solid layer in the insulated wire manufactured by the method for manufacturing the insulated wire. In addition, since the main component of the solid layer in the method for manufacturing the insulated wire is a thermoplastic resin, the insulated wire manufactured by the method for manufacturing the insulated wire has a solid layer that is easily stretched and the insulating layer is flexible. Can maintain sex.

[Details of the embodiment of the present invention]
Hereinafter, an insulated wire and a method for manufacturing an insulated wire according to an embodiment of the present invention will be described with reference to the drawings.

[Insulated wire]
The insulated wire shown in FIG. 1 includes a linear conductor 1 and an insulating layer 2 that covers the outer peripheral surface of the conductor 1. The insulating layer 2 mainly includes a pore layer 3 including pores 6 and a solid layer 4 which is laminated on the outer peripheral surface side of the pore layer 3 and does not include pores. The insulating layer 2 has an auxiliary layer 5 that does not include pores on the inner surface side of the pore layer 3. The main component of the solid layer 4 and the auxiliary layer 5 is a thermoplastic resin.

<Conductor>
The conductor 1 is, for example, a round wire having a circular cross section, but may be a square wire having a square cross section or a stranded wire obtained by twisting a plurality of strands.

  The material of the conductor 1 is preferably a metal having high electrical conductivity and high mechanical strength. Examples of such metals include copper, copper alloys, aluminum, nickel, silver, soft iron, steel, and stainless steel. The conductor 1 is a material in which these metals are formed in a linear shape, or a multilayer structure in which such a linear material is coated with another metal, such as a nickel-coated copper wire, a silver-coated copper wire, or a copper-coated aluminum. Wire, copper-coated steel wire, etc. can be used.

The lower limit of the average cross-sectional area of the conductor 1, preferably from 0.01 mm ^2, 0.1 mm ² is more preferable. In contrast, the upper limit of the average cross-sectional area of the conductor 1, preferably from 10 mm ^2, 5 mm ² is more preferable. When the average cross-sectional area of the conductor 1 is less than the lower limit, the volume of the insulating layer 2 with respect to the conductor 1 increases, and the volume efficiency of a coil or the like formed using the insulated wire may be reduced. Conversely, when the average cross-sectional area of the conductor 1 exceeds the above upper limit, the insulating layer 2 must be formed thick in order to sufficiently reduce the dielectric constant, and the insulated wire may be unnecessarily increased in diameter. is there.

<Insulating layer>
The insulating layer 2 includes an auxiliary layer 5 that does not include pores, a pore layer 3 that is stacked on the outer peripheral surface side of the auxiliary layer 5 and includes pores 6, and a solid that is stacked on the outer peripheral surface side of the porous layer 3 and does not include pores. Layer 4.

  As a minimum of average thickness of insulating layer 2, 30 micrometers is preferred and 50 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the insulating layer 2 is preferably 200 μm, and more preferably 150 μm. If the average thickness of the insulating layer 2 is less than the lower limit, the insulating layer 2 may be broken and the conductor 1 may be insufficiently insulated. On the contrary, when the average thickness of the insulating layer 2 exceeds the upper limit, the volume efficiency of a coil or the like formed using the insulated wire may be lowered.

(Porous layer)
The pore layer 3 includes a plurality of pores 6.

  The main component resin of the resin composition forming the pore layer 3 is not particularly limited, but examples thereof include polyethersulfone, polyetherimide, polycarbonate, polyphenylsulfone, polysulfone, polyethylene terephthalate, polyetheretherketone, polyphenylene. Thermoplastic resins such as sulfide, for example, polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy, thermosetting polyester, thermosetting polyester imide, thermosetting polyester amide imide, aromatic polyamide, thermosetting polyamide imide, thermosetting polyimide A thermosetting resin such as can be used. Note that a thermoplastic resin is more preferable than a thermosetting resin as the resin for forming the pore layer 3 in that the flexibility of the insulating layer 2 can be easily maintained. Among these thermoplastic resins, polyethylene terephthalate, polyether ether ketone, and polyphenylene sulfide are particularly preferable because they have a low dielectric constant and can easily reduce the dielectric constant of the insulating layer 2.

  Moreover, it is preferable to use a crosslinkable thermoplastic resin as the main component resin of the resin composition forming the pore layer 3. Examples of the crosslinkable thermoplastic resin include cyclic olefin monomers such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, cyclopentene, 2-norbornene, and cyclotetradodecene monomers in addition to the above thermoplastic resins. A cyclic polyolefin obtained by polymerization is preferred.

  Moreover, you may make the resin composition which forms the pore layer 3 contain a hardening | curing agent with the said resin. Curing agents include titanium-based curing agents, isocyanate compounds, blocked isocyanates, urea and melamine compounds, amino resins, alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, aliphatic acid anhydrides, and aromatic acid anhydrides. Etc. are exemplified. These curing agents are appropriately selected according to the type of resin contained in the resin composition to be used. For example, in the case of polyamideimide, imidazole, triethylamine and the like are preferably used as the curing agent.

  Examples of the titanium-based curing agent include tetrapropyl titanate, tetraisopropyl titanate, tetramethyl titanate, tetrabutyl titanate, and tetrahexyl titanate. Examples of the isocyanate compound include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane isocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, C3-C12 aliphatic diisocyanate such as lysine diisocyanate, 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidene Dicyclohexyl-4,4′-diisocyanate, 1,3-diisocyanatomethylcyclohexane (hydrogenated XD ), Hydrogenated TDI, carbon such as 2,5-bis (isocyanatomethyl) -bicyclo [2,2,1] heptane, 2,6-bis (isocyanatomethyl) -bicyclo [2,2,1] heptane Examples thereof include aliphatic diisocyanates having an aromatic ring such as alicyclic isocyanate, xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI), and modified products thereof. Examples of the blocked isocyanate include diphenylmethane-4,4′-diisocyanate (MDI), diphenylmethane-3,3′-diisocyanate, diphenylmethane-3,4′-diisocyanate, diphenylether-4,4′-diisocyanate, and benzophenone-4,4. '-Diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, naphthylene-1,5-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, etc. Is exemplified. Examples of the melamine compound include methylated melamine, butylated melamine, methylolated melamine, and butyrololized melamine.

  Further, the resin in the resin composition forming the pore layer 3 is preferably crosslinked. By cross-linking the resin in the resin composition forming the pore layer 3, the mechanical strength of the pore layer 3 is improved, and the action of suppressing the mechanical strength due to the inclusion of the pores 6 can be reduced. Mechanical strength is easily maintained. Moreover, chemical resistance and heat resistance can also be improved by crosslinking the resin in the resin composition forming the pore layer 3.

  For example, the above-described crosslinkable thermoplastic resin can be used as the main component of the resin composition forming the pore layer 3 and the resin can be crosslinked by, for example, irradiation with ionizing radiation.

  As a minimum of average thickness of pore layer 3, 20% of average thickness of insulating layer 2 is preferred, and 30% is more preferred. On the other hand, the upper limit of the average thickness of the pore layer 3 is preferably 60% of the average thickness of the insulating layer 2, and more preferably 50%. When the average thickness of the pore layer 3 is less than the lower limit, the dielectric constant of the insulating layer 2 may not be sufficiently lowered. On the other hand, when the average thickness of the pore layer 3 exceeds the upper limit, the thickness of the pore layer 3 having a low mechanical strength becomes relatively large, and the mechanical strength of the insulating layer 2 may not be maintained.

  The lower limit of the porosity of the pore layer 3 is preferably 5% by volume, and more preferably 10% by volume. On the other hand, the upper limit of the porosity of the pore layer 3 is preferably 80% by volume, more preferably 50% by volume. When the porosity of the pore layer 3 is less than the lower limit, the dielectric constant of the insulating layer 2 is not sufficiently lowered, and the corona discharge start voltage may not be sufficiently improved. On the other hand, when the porosity of the porous layer 3 exceeds the upper limit, the mechanical strength of the porous layer 3 is too low, and the mechanical strength of the insulating layer 2 may not be maintained.

  The lower limit of the average diameter of the pores 6 is preferably 0.1 μm, and more preferably 1 μm. On the other hand, the upper limit of the average diameter of the pores 6 is preferably 10 μm, more preferably 8 μm. When the average diameter of the pores 6 is less than the above lower limit, the generation of the pores 6 may be difficult. On the other hand, when the average diameter of the pores 6 exceeds the upper limit, it is difficult to make the distribution of the pores 6 in the pore layer 3 uniform, and the dielectric constant distribution is likely to be biased.

(Solid layer)
The solid layer 4 is laminated on the outer peripheral surface side of the pore layer 3 and does not include pores.

  The resin as the main component of the resin composition forming the solid layer 4 is not particularly limited. For example, polyethersulfone, polyetherimide, polycarbonate, polyphenylsulfone, polysulfone, polyethylene terephthalate, polyetheretherketone, A thermoplastic resin such as polyphenylene sulfide can be used. Among these thermoplastic resins, polyethylene terephthalate, polyether ether ketone, and polyphenylene sulfide are particularly preferable because they have a low dielectric constant and can easily reduce the dielectric constant of the insulating layer 2. The solid layer 4 is easily stretched by using a thermoplastic resin as a main component, and the flexibility of the insulating layer 2 is easily maintained.

  Moreover, it is preferable to use a crosslinkable thermoplastic resin as the main component resin of the resin composition forming the solid layer 4. Examples of the crosslinkable thermoplastic resin include cyclic olefin monomers such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, cyclopentene, 2-norbornene, and cyclotetradodecene monomers in addition to the above thermoplastic resins. A cyclic polyolefin obtained by polymerization is preferred.

  Moreover, you may make the resin composition which forms the solid layer 4 contain a hardening | curing agent with the said resin. As a hardening | curing agent, the same kind as the hardening | curing agent contained in the resin composition which forms the pore layer 3 mentioned above is mentioned.

  Further, the resin in the resin composition forming the solid layer 4 is preferably crosslinked. By cross-linking the resin in the resin composition forming the solid layer 4, the mechanical strength of the solid layer 4 is improved, and the mechanical strength of the insulating layer 2 is easily maintained. Moreover, chemical resistance and heat resistance can also be improved by crosslinking the resin in the resin composition forming the solid layer 4.

  For example, the above-mentioned crosslinkable thermoplastic resin as a main component of the resin composition forming the solid layer 4 can be used for the cross-linking of the resin, for example, by irradiation with ionizing radiation.

  As a minimum of the average thickness of the solid layer 4, 20% of the average thickness of the insulating layer 2 is preferable, and 25% is more preferable. On the other hand, the upper limit of the average thickness of the solid layer 4 is preferably 80% of the average thickness of the insulating layer 2 and more preferably 70%. If the average thickness of the solid layer 4 is less than the lower limit, the mechanical strength of the insulating layer 2 may not be maintained. On the other hand, when the average thickness of the solid layer 4 exceeds the upper limit, the thickness of the pore layer 3 that contributes to lowering the dielectric constant is relatively small, and the dielectric constant of the insulating layer 2 is not sufficiently lowered. There is a fear.

  Moreover, as a minimum of the average thickness of the solid layer 4, 1 micrometer is preferable and 1.5 micrometers is more preferable. On the other hand, the upper limit of the average thickness of the solid layer 4 is preferably 80 μm, and more preferably 60 μm. When the average thickness of the solid layer 4 is less than the lower limit, the solid layer 4 may be broken and the pore layer 3 having low mechanical strength may be exposed. Conversely, when the average thickness of the solid layer 4 exceeds the upper limit, the insulated wire may unnecessarily increase in diameter.

(Auxiliary layer)
The auxiliary layer 5 is laminated between the conductor 1 and the pore layer 3 and does not include pores. The auxiliary layer 5 compensates for a decrease in the insulating properties and mechanical strength of the insulating layer 2 due to the pores 6.

  The resin as the main component of the resin composition forming the auxiliary layer 5 is not particularly limited. For example, polyethersulfone, polyetherimide, polycarbonate, polyphenylsulfone, polysulfone, polyethylene terephthalate, polyetheretherketone, polyphenylene A thermoplastic resin such as sulfide can be used. Among these thermoplastic resins, polyethylene terephthalate, polyetheretherketone, and polyphenylene sulfide are particularly preferable because they have a low dielectric constant and can easily reduce the dielectric constant of the insulating layer 2. The auxiliary layer 5 is easily stretched by using a thermoplastic resin as a main component, and the flexibility of the insulating layer 2 is easily maintained.

  Moreover, you may make the resin composition which forms the auxiliary | assistant layer 5 contain a hardening | curing agent with the said resin. As a hardening | curing agent, the same kind as the hardening | curing agent contained in the resin composition which forms the pore layer 3 mentioned above is mentioned.

  As a minimum of average thickness of auxiliary layer 5, 1% of average thickness of insulating layer 2 is preferred, and 1.5% is more preferred. On the other hand, the upper limit of the average thickness of the auxiliary layer 5 is preferably 20% of the average thickness of the insulating layer 2 and more preferably 10%. When the average thickness of the auxiliary layer 5 is less than the lower limit, the insulating property may not be maintained when the pore layer 3 is broken. On the other hand, when the average thickness of the auxiliary layer 5 exceeds the upper limit, the thickness of the pore layer 3 contributing to lowering the dielectric constant is relatively small, and the dielectric constant of the insulating layer 2 may not be sufficiently reduced. There is.

[First manufacturing method of insulated wire]
Next, the 1st manufacturing method of the said insulated wire shown in FIG. 1 is demonstrated. The first manufacturing method of the insulated wire includes a step of preparing a pore layer varnish by mixing a resin for forming the pore layer 3 with a solvent and a pore-forming agent (pore layer varnish preparation step); The step of preparing a solid layer varnish by diluting the thermoplastic resin forming the solid layer 4 with a solvent (solid layer varnish preparation step), and the solid layer on the outer peripheral surface of the conductor 1 The step of forming the auxiliary layer 5 by applying and baking the varnish for use (auxiliary layer forming step), and the pore layer by applying and baking the varnish for the pore layer on the outer peripheral surface side of the conductor 1 on which the auxiliary layer 5 is formed 3 (porous layer forming step) and a step of forming the solid layer 4 by applying and baking the solid layer varnish on the outer peripheral surface of the conductor 1 on which the porous layer 3 has been formed (in the middle) Real layer forming step).

<Porosity layer varnish preparation process>
In the pore layer varnish preparation step, the main polymer forming the pore layer 3 is diluted with a solvent, and further mixed with a pore forming agent to prepare a pore layer varnish.

As the pore forming agent to be mixed with the pore layer varnish, a chemical foaming agent is preferable. For example, a thermally decomposable material such as azobisisobutyronitrile that generates nitrogen gas (N ₂ gas) by heating is preferable. Used for.

  As a minimum of foaming temperature of the above-mentioned chemical foaming agent, 180 ° C is preferred and 210 ° C is more preferred. On the other hand, the upper limit of the foaming temperature is preferably 300 ° C, and more preferably 260 ° C. When the said foaming temperature is less than the said minimum, it is easy to produce foam before baking and there exists a possibility that adjustment of the thickness of the insulating layer 2 may become difficult. On the other hand, when the foaming temperature exceeds the upper limit, an increase in the baking temperature and an increase in the baking time may be caused, and the manufacturing cost of the insulated wire may increase. Here, the “foaming temperature” is a temperature at which the foaming agent starts foaming. The “baking time” is a time for holding the conductor 1 coated with the varnish at the baking temperature in the baking process.

  As the solvent for dilution, a known organic solvent conventionally used for insulating varnish can be used. Specifically, polar organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, tetramethylurea, hexaethylphosphoric triamide, and γ-butyrolactone are used. First, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, diethyl oxalate, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether (butyl cellosolve) ), Ethers such as diethylene glycol dimethyl ether and tetrahydrofuran, hydrocarbons such as hexane, heptane, benzene, toluene and xylene , Halogenated hydrocarbons such as dichloromethane and chlorobenzene, phenols such as cresol and chlorophenol, and tertiary amines such as pyridine. These organic solvents may be used alone or in combination of two or more. Used.

  In addition, as a minimum of the resin solid content density | concentration of the varnish for pore layers prepared by diluting with these organic solvents, 20 mass% is preferable and 22 mass% is more preferable. On the other hand, the upper limit of the resin solid content concentration of the pore layer varnish is preferably 50% by mass, and more preferably 30% by mass. When the resin solid content concentration of the pore layer varnish is less than the above lower limit, the amount of application at one time when the pore layer varnish is applied decreases, so that the varnish for forming the pore layer 3 having a desired thickness is formed. There is a possibility that the number of repetitions of the coating process increases and the time for the varnish coating process becomes long. Conversely, when the resin solid content concentration of the pore layer varnish exceeds the above upper limit, it is difficult to uniformly mix the main polymer and the pore forming agent forming the pore layer 3, and the time required for preparing the varnish may be long. There is.

<Solid layer varnish preparation process>
In the solid layer varnish preparation step, the solid polymer varnish is prepared by diluting the main polymer forming the solid layer 4 with a solvent. In addition, the varnish for solid layers prepared here is used also for formation of the auxiliary | assistant layer 5 so that it may mention later.

  As the solvent for diluting the pore layer varnish, known organic solvents conventionally used for insulating varnishes can be used, and specifically, the same kind as the solvent for diluting used in the preparation of the pore layer varnish described above. Can be mentioned.

  In addition, as a minimum of the resin solid content concentration of the varnish for solid layers prepared by diluting with these organic solvents, 20 mass% is preferable and 22 mass% is more preferable. On the other hand, the upper limit of the resin solid content concentration of the solid layer varnish is preferably 50% by mass, and more preferably 30% by mass. When the resin solid content concentration of the solid layer varnish is less than the lower limit, the amount of application at one time when the solid layer varnish is applied decreases, so that the solid layer 4 or the auxiliary layer having a desired thickness is formed. The number of repetitions of the varnish application process for forming 5 may increase, and the time of the varnish application process may become longer. On the contrary, when the resin solid content concentration of the solid layer varnish exceeds the upper limit, the time required for dilution may be increased.

<Auxiliary layer forming step>
In the auxiliary layer forming step, the solid layer varnish prepared in the solid layer varnish preparation step is applied to the outer peripheral surface of the conductor 1 and then baked to form the auxiliary layer 5 on the surface of the conductor 1.

  If the auxiliary layer 5 having a desired thickness cannot be formed by one application and baking of the solid layer varnish, the solid layer varnish is used until the auxiliary layer 5 formed on the surface of the conductor 1 has a predetermined thickness. Repeat application and baking.

<Porosity layer forming step>
In the pore layer forming step, after applying the pore layer varnish prepared in the pore layer varnish preparation step to the outer peripheral surface of the conductor 1 on which the auxiliary layer 5 is formed, the conductor 1 is baked. The pore layer 3 is formed outside the auxiliary layer 5 formed in the above. During the baking, the chemical foaming agent contained in the pore layer varnish is foamed, and pores 6 are generated in the pore layer 3.

  When the pore layer 3 having a desired thickness cannot be formed by applying and baking the pore layer varnish once, the pore layer varnish is repeatedly applied and baked until the pore layer 3 has a predetermined thickness.

<Solid layer forming process>
In the solid layer forming step, the solid layer varnish prepared in the solid layer varnish preparation step is applied to the outer peripheral surface of the conductor 1 on which the pore layer 3 is formed, and then baked. The solid layer 4 is formed outside the pore layer 3 formed in the conductor 1.

  When the solid layer 4 having a desired thickness cannot be formed by applying and baking the solid layer varnish once, the solid layer varnish is repeatedly applied and baked until the solid layer 4 reaches a predetermined thickness. Do. By forming the solid layer 4 having a predetermined thickness, the insulated wire can be obtained.

  In the first method for producing an insulated wire, the solid layer varnish is shared as the varnish for forming the solid layer 4 and the auxiliary layer 5, but different varnishes are used for the solid layer 4 and the auxiliary layer 5. It may be used. Since the insulated wire is required to have higher mechanical strength on the outer surface side, for example, a varnish capable of obtaining higher mechanical strength than the auxiliary layer 5 is used as a solid layer varnish for forming the solid layer 4. You may adjust separately from the varnish for forming the layer 5. FIG.

  In addition, in the 1st manufacturing method of the said insulated wire mentioned above, it replaced with the said pore layer varnish prepared by mixing the pore formation agent, and prepared by mixing a thermally decomposable resin as a pore layer varnish. A varnish may be used. That is, in the pore layer varnish preparation step, a pore layer varnish is prepared by further mixing a thermally decomposable resin with the main polymer that forms the pore layer 3 diluted with a solvent.

  As the thermally decomposable resin, for example, resin particles that thermally decompose at a temperature lower than the baking temperature of the main polymer that forms the pore layer 3 are used. The baking temperature of the main polymer forming the pore layer 3 is appropriately set according to the type of resin, but is usually about 200 ° C. or higher and 350 ° C. or lower. Accordingly, the lower limit of the thermal decomposition temperature of the thermally decomposable resin used in the pore layer varnish is preferably 200 ° C., and the upper limit is preferably 300 ° C. Here, the thermal decomposition temperature means a temperature at which the temperature is increased from room temperature to 10 ° C./min in a nitrogen atmosphere and the mass reduction rate becomes 50%. The thermal decomposition temperature can be measured, for example, by measuring the thermogravimetry using a thermogravimetry-differential thermal analyzer (“TG / DTA” manufactured by SII Nano Technology Co., Ltd.).

  The thermally decomposable resin used for the pore layer varnish is not particularly limited, but for example, one of polyethylene glycol, polypropylene glycol, etc., a compound in which both ends or a part thereof are alkylated, (meth) acrylated or epoxidized, C1-C6 alkyl ester polymers of (meth) acrylic acid such as poly (meth) acrylate methyl, poly (meth) ethyl acrylate, poly (meth) acrylate propyl, poly (meth) acrylate butyl, etc. , Urethane oligomers, urethane polymers, urethane (meth) acrylates, epoxy (meth) acrylates, polymers of modified (meth) acrylates such as ε-caprolactone (meth) acrylate, poly (meth) acrylic acid, cross-linked products thereof, polystyrene And cross-linked polystyrene. Among these, a crosslinked product of a (meth) acrylic polymer is preferable, and a crosslinked poly (meth) acrylate is more preferable. Further, it is preferable that the thermally decomposable resin can be uniformly distributed as an island phase of fine particles in the sea phase of the resin forming the pore layer 3. Therefore, the thermally decomposable resin used for the pore layer varnish is preferably a resin that is excellent in compatibility with the resin that forms the pore layer 3 and that is formed into a spherical shape. Specifically, a crosslinked resin is preferred. .

  The crosslinked poly (meth) acrylic polymer can be obtained, for example, by polymerizing a (meth) acrylic monomer and a polyfunctional monomer by emulsion polymerization, suspension polymerization, solution polymerization, or the like.

  Here, as the (meth) acrylic monomer, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate, stearyl acrylate, acrylic acid 2 -Ethylhexyl, tetrahydrofurfuryl acrylate, diethylaminoethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate , Dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, diethylaminoethyl methacrylate and the like.

  Examples of the polyfunctional monomer include divinylbenzene, ethylene glycol di (meth) acrylate, trimethylolpropane triacrylate, and the like.

  In addition to the (meth) acrylic monomer and multifunctional monomer, other monomers may be used as the constituent monomer of the crosslinked poly (meth) acrylic polymer. Other monomers include glycol esters of (meth) acrylic acid such as ethylene glycol mono (meth) acrylate and polyethylene glycol mono (meth) acrylate, alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, vinyl acetate and vinyl butyrate Vinyl esters, N-alkyl substituted (meth) acrylamides such as N-methylacrylamide, N-ethylacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide, nitriles such as acrylonitrile and methacrylonitrile, styrene, p -Styrene monomers such as methylstyrene, p-chlorostyrene, chloromethylstyrene, and α-methylstyrene.

  When using the resin particles to be thermally decomposed, the resin particles are preferably spherical. The lower limit of the average particle diameter of the resin particles is preferably 0.1 μm, more preferably 0.5 μm, and even more preferably 1 μm. On the other hand, the upper limit of the average particle diameter of the resin particles is preferably 100 μm, more preferably 50 μm, further preferably 30 μm, and particularly preferably 10 μm. The resin particles form pores 6 in portions where they were thermally decomposed during baking of the resin forming the pore layer 3. Therefore, when the average particle diameter of the resin particles is less than the lower limit, the pores 6 may not be easily formed in the pore layer 3. On the contrary, when the average particle diameter of the resin particles exceeds the upper limit, the distribution of the pores 6 in the pore layer 3 is difficult to be uniform, and the distribution of the dielectric constant may be easily biased. Here, the average particle diameter of the resin particles means a particle diameter showing the highest volume content in the particle size distribution measured with a laser diffraction particle size distribution measuring apparatus.

  As a solvent for dilution, the same kind as that used for the varnish for the pore layer prepared by mixing the above-described pore forming agent can be used. Moreover, the resin solid content concentration of the varnish prepared by diluting with an organic solvent can be the same as the resin solid content concentration of the varnish for the pore layer adjusted by mixing the pore forming agent described above.

  After preparing the pore layer varnish by mixing the thermally decomposable resin, in the same manner as in the pore layer forming step, the thermally decomposable resin is further applied to the outer peripheral surface of the conductor 1 on which the auxiliary layer 5 is formed. The pore layer 3 is formed on the outside of the auxiliary layer 5 formed on the conductor 1 by applying the pore layer varnish prepared by mixing and then baking. At the time of baking, the thermally decomposable resin contained in the pore layer varnish is thermally decomposed, and pores 6 are generated in portions where the thermally decomposable resin is present in the pore layer 3.

  Next, after applying the solid layer varnish prepared in the solid layer varnish preparation step to the outer peripheral surface side of the conductor 1 in which the pore layer 3 is formed, as in the solid layer formation step. By baking, a solid layer 4 is formed outside the pore layer 3 formed in the conductor 1. The insulated wire is obtained by repeatedly applying and baking the varnish for the solid layer until the solid layer 4 has a predetermined thickness.

[Second manufacturing method of insulated wire]
Next, the 2nd manufacturing method of the said insulated wire shown in FIG. 1 is demonstrated. The second manufacturing method of the insulated wire includes a step of covering the outer peripheral surface side of the conductor 1 with the auxiliary layer 5, the pore layer 3 and the solid layer 4 (extrusion coating step) by coextrusion. The pore layer 3 includes pores, and the solid layer 4 and the auxiliary layer 5 do not include pores.

<Extrusion coating process>
In the extrusion coating step, the pore layer resin composition for forming the pore layer 3 and the solid layer resin composition for forming the solid layer 4 and the auxiliary layer 5 are charged into a melt extruder. Here, the resin composition for a pore layer includes a thermoplastic resin as a main component and a pore forming agent. The solid layer resin composition contains a thermoplastic resin as a main component and does not contain a pore forming agent. And after throwing these resin compositions into a melt extruder, these resin compositions are coextruded so that it may laminate | stack in order of the auxiliary | assistant layer 5, the pore layer 3, and the solid layer 4 from the conductor 1 side. That is, the solid layer resin composition for forming the auxiliary layer 5 on the outer periphery of the conductor 1, the pore layer resin composition so as to surround the outer peripheral side, and the solid layer 4 so as to surround the outer peripheral side thereof. The insulated wire is obtained by extruding the conductor 1 and these resin compositions so that the solid layer resin composition to be formed is disposed.

  Here, the pores 6 in the pore layer 3 are generated by foaming a chemical foaming agent contained in the pore layer resin composition by heating at the time of co-extrusion for softening the resin composition. Thereby, the said insulated wire provided with the insulating layer 2 which has the pore layer 3 containing the pore 6, and the solid layer 4 which does not contain a pore is obtained.

  In addition, the resin composition for the pore layer may be one having a thermosetting resin as a main component, but as described above, the one having a thermoplastic resin as the main component is heated during coextrusion. Since the control can be easily performed, it is easy to manufacture the insulated wire.

  In the second manufacturing method of the insulated wire, the solid layer resin composition is used as the resin composition for forming the solid layer 4 and the auxiliary layer 5. Different resin compositions may be used.

  Moreover, it is preferable to bridge | crosslink the said resin composition in the 2nd manufacturing method of the said insulated wire. When the resin composition is crosslinked, for example, a crosslinkable thermoplastic resin is used as the resin composition, and the resin composition is disposed on the outer peripheral side of the conductor 1 by coextrusion, and then irradiated with ionizing radiation. The resin composition is crosslinked. By irradiating with ionizing radiation, the resin forming the auxiliary layer 5, the pore layer 3 and the solid layer 4 is cross-linked, and the mechanical strength of the insulated wire can be improved.

  Here, examples of the ionizing radiation include charged particle beams such as electron beams and high-energy ion beams, high-energy electromagnetic waves such as γ-rays and X-rays, and neutral beams. Among these, electron beams are preferable. This is because the electron beam generator is relatively inexpensive, a high-power electron beam can be obtained, and the degree of crosslinking can be easily controlled.

  When using a polymer compound having an aromatic or heterocyclic ring in the molecule as the resin composition, it is preferable to irradiate an ion beam before irradiation with ionizing radiation in order to crosslink these resin compositions. . In other words, ring opening reaction occurs in the case of containing a benzene ring by ion beam irradiation, and paraffin and olefin are generated. When radicals are generated, the radicals react with oxygen to generate a large amount of reactive groups such as hydroxyl groups and carnyl groups. Thus, since the polymer partially reacts with paraffin, olefin, hydroxyl group, etc. by ion beam irradiation and becomes reactive, when using such a resin composition, ion beam is irradiated by ion beam irradiation in advance. Crosslinking by irradiation can be promoted.

  As described above, in the first manufacturing method and the second manufacturing method of the insulated wire, the pores 6 are formed when the pore layer 3 is formed. On the other hand, in the conventional method for producing an insulated wire described in, for example, International Publication No. 2011/118717, pores are formed by coating an insulating layer on a conductor and then filling with gas under pressure. This conventional manufacturing method requires a special apparatus such as a pressure vessel and a long process such as 24-hour gas filling. Therefore, by using the method for manufacturing an insulated wire, the equipment cost can be reduced and the time for producing the insulated wire can be greatly shortened. Moreover, since the insulating layer of the insulated wire manufactured with the said conventional manufacturing method is a thermoplastic resin, it is difficult to make only the predetermined layer of the insulated wire which has a several laminated structure into a layer which does not contain a pore. On the other hand, in the method for manufacturing an insulated wire, only a predetermined layer such as the solid layer 4 can be a layer that does not include pores.

[advantage]
In the insulated wire, since the insulating layer 2 includes the pore layer 3 including the pores 6, the dielectric constant of the insulating layer 2 can be reduced, and the corona discharge start voltage can be improved. In the insulated wire, since the main component of the solid layer 4 and the auxiliary layer 5 of the insulating layer 2 is a thermoplastic resin, these layers are easily stretched and the flexibility of the insulating layer 2 can be maintained. Moreover, since the solid layer 4 that does not include pores is laminated on the outer peripheral surface side of the pore layer 3 in the insulated wire, the solid layer 4 can maintain the mechanical strength of the insulating layer 2. In addition, in the insulated wire, the auxiliary layer 5 compensates for a decrease in the insulating properties and mechanical strength of the insulating layer 2 due to the pores 6.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  That is, in the said embodiment, although the said insulated wire in which the insulating layer has an auxiliary layer, a pore layer, and a solid layer was demonstrated, it is good also as the said insulated wire in which an insulating layer does not have an auxiliary layer. Even if the insulating layer does not have an auxiliary layer, the outer surface of the insulated wire is protected by the solid layer, and the mechanical strength can be maintained. In addition, when manufacturing the insulated wire in which an insulating layer does not have an auxiliary | assistant layer, an auxiliary | assistant layer formation process is abbreviate | omitted in the said 1st manufacturing method. Moreover, in the said 2nd manufacturing method, co-extrusion is performed without arrange | positioning the resin composition for forming an auxiliary | assistant layer on the outer periphery of a conductor.

  Moreover, in the said embodiment, although the said insulating wire has demonstrated the said insulated wire which has a pore layer and a solid layer one each, the solid layer which has a thermoplastic resin as a main component is laminated | stacked on the outer peripheral surface side of a pore layer. The insulating layer may be an insulated wire having a plurality of pore layers, or the insulating layer may be an insulated wire having a plurality of solid layers. Moreover, it is good also as an insulated wire which has an insulating layer by which a pore layer and a solid layer are laminated | stacked alternately. When the insulating layer has a plurality of pore layers, each of the pore layers contributes to lowering the dielectric constant of the insulating layer. Further, when the insulating layer has a plurality of solid layers, the plurality of solid layers collectively contribute to the improvement of the mechanical strength of the insulating layer.

  When the insulating layer has a plurality of pore layers, the lower limit of the total average thickness of the pore layers is preferably 20% of the average thickness of the insulating layer, and more preferably 30%. On the other hand, the upper limit of the total average thickness of the pore layers is preferably 60% of the average thickness of the insulating layer, and more preferably 50%. When the total average thickness of the pore layer is less than the lower limit, the dielectric constant of the insulating layer may not be sufficiently lowered. On the other hand, when the total average thickness of the pore layers exceeds the upper limit, the total thickness of the pore layers having low mechanical strength becomes relatively large, and the mechanical strength of the insulating layer may not be maintained.

  When the insulating layer has a plurality of solid layers, the lower limit of the total average thickness of the solid layers is preferably 40% of the average thickness of the insulating layer, and more preferably 50%. On the other hand, the upper limit of the total average thickness of the solid layers is preferably 80% of the average thickness of the insulating layer, and more preferably 70%. When the total average thickness of the solid layer is less than the lower limit, the mechanical strength of the insulating layer may not be maintained. Conversely, if the total average thickness of the solid layer exceeds the upper limit, the total thickness of the pore layer that contributes to lowering the dielectric constant is relatively small, and the dielectric constant of the insulating layer may not be sufficiently reduced. There is.

  When the insulating layer has a plurality of solid layers, the lower limit of the average thickness of the outermost solid layer is preferably 1 μm and more preferably 1.5 μm. On the other hand, the upper limit of the average thickness of the solid outermost layer is preferably 70 μm, and more preferably 50 μm. When the average thickness of the solid layer of the outermost layer is less than the lower limit, the solid layer of the outermost layer may be broken to expose a pore layer having low mechanical strength. When the average thickness of the solid layer of the outermost layer exceeds the upper limit, the insulated wire may be unnecessarily increased in diameter.

  In the above embodiment, the production method for generating pores by using a chemical foaming agent as the pore forming agent has been described. However, the thermally expandable microcapsule is used as the pore forming agent, and the pores are formed by the thermally expandable microcapsule. It is good also as a manufacturing method which forms. For example, in the first production method, a resin for forming a pore layer diluted with a solvent is mixed with a thermally expandable microcapsule to prepare a pore layer varnish, and the outer peripheral surface side of the conductor of the pore layer varnish The pore layer may be formed by coating and baking. During baking, the thermally expandable microcapsule contained in the pore layer varnish expands or foams, and pores are formed in the pore layer by the thermally expandable microcapsule. Further, for example, in the second production method, the resin composition for the pore layer may contain thermally expandable microcapsules. In this case, the heat-expandable microcapsule contained in the resin composition for pore layer expands or foams by heating at the time of co-extrusion, and a pore layer including pores formed by the heat-expandable microcapsule is formed.

  The thermally expandable microcapsule has a core material (inner package) made of a thermal expansion agent and an outer shell that wraps the core material. The thermal expansion agent of the heat-expandable microcapsules may be any one that expands or generates a gas by heating, and the principle thereof does not matter. As the thermal expansion agent of the thermally expandable microcapsule, for example, a low boiling point liquid, a chemical foaming agent, or a mixture thereof can be used.

As the low boiling point liquid, for example, alkanes such as butane, i-butane, n-pentane, i-pentane and neopentane, and freons such as trichlorofluoromethane are preferably used. As the chemical foaming agent, a material having thermal decomposability such as azobisisobutyronitrile that generates N ₂ gas by heating is preferably used.

  The expansion start temperature of the thermal expansion agent of the thermal expansion microcapsule, that is, the boiling point of the low-boiling liquid or the thermal decomposition temperature of the chemical foaming agent is set to be equal to or higher than the softening temperature of the outer shell of the thermal expansion microcapsule described later. More specifically, the lower limit of the expansion start temperature of the thermal expansion agent of the thermally expandable microcapsule is preferably 60 ° C, more preferably 70 ° C. On the other hand, the upper limit of the expansion start temperature of the thermal expansion agent of the thermally expandable microcapsule is preferably 200 ° C, and more preferably 150 ° C. When the expansion start temperature of the thermal expansion agent of the thermally expandable microcapsule is less than the lower limit, the thermally expandable microcapsule may expand unintentionally during production, transportation or storage of the insulated wire. On the other hand, when the expansion start temperature of the thermal expansion agent of the thermally expandable microcapsule exceeds the above upper limit, the energy cost required for expanding the thermally expandable microcapsule may be excessive.

  On the other hand, the outer shell of the thermally expandable microcapsule is formed of a stretchable material that can expand without breaking when the thermally expandable agent expands to form a microballoon containing the generated gas. As a material for forming the outer shell of the thermally expandable microcapsule, a resin composition mainly composed of a polymer such as a thermoplastic resin is usually used.

  Examples of the thermoplastic resin used as the main component of the outer shell of the thermally expandable microcapsule are formed from monomers such as vinyl chloride, vinylidene chloride, acrylonitrile, acrylic acid, methacrylic acid, acrylate, methacrylate, and styrene. A polymer formed from two or more types of monomers is preferably used. An example of a preferred thermoplastic resin is a vinylidene chloride-acrylonitrile copolymer. In this case, the expansion start temperature of the thermal expansion agent is 80 ° C. or higher and 150 ° C. or lower.

  Moreover, although the said embodiment demonstrated the said insulated wire of the structure by which the pore contained in a pore layer is formed with a hole formation agent, it is good also as the said insulated wire of the structure which formed the said pore with the hollow filler, for example. . In the case of forming the pores with a hollow filler, for example, the insulated wire can be produced by kneading a resin composition forming a pore layer and a hollow filler and coating the kneaded product on a conductor by coextrusion molding.

  When the pores are formed by the hollow filler, the hollow portion inside the hollow filler becomes the pores included in the pore layer. Examples of the hollow filler include shirasu balloons, glass balloons, ceramic balloons, and organic resin balloons. When flexibility is required for the insulated wire, an organic resin balloon is preferable among them. In the case of the insulated wire where mechanical strength is important, a glass balloon is preferable because it is easily available and is not easily damaged.

  For example, in the insulated wire, a primer treatment layer may be formed on the outer peripheral surface of the conductor, and a pore layer may be formed on the outer peripheral surface side of the conductor on which the primer treatment layer is formed. A primer process layer is a layer provided in order to improve the adhesiveness between layers, for example, can be formed with a well-known resin composition.

  When providing a primer processing layer in a conductor outer peripheral surface, it is good for the resin composition which forms this primer processing layer to contain 1 type or multiple types of resin in a polyimide, a polyamideimide, a polyesterimide, polyester, and a phenoxy resin, for example. Moreover, the resin composition forming the primer treatment layer may contain an additive such as an adhesion improver. By forming the primer treatment layer between the conductor and the insulating layer with such a resin composition, it is possible to improve the adhesion between the conductor and the insulating layer. Properties such as flexibility, abrasion resistance, scratch resistance, and workability can be effectively enhanced.

  Moreover, the resin composition which forms a primer process layer may contain other resin, for example, an epoxy resin, a phenoxy resin, a melamine resin, etc. with the said resin. Moreover, you may use a commercially available liquid composition (insulation varnish) as each resin contained in the resin composition which forms a primer process layer.

  As a minimum of the average thickness of a primer processing layer, 1 micrometer is preferable and 2 micrometers is more preferable. On the other hand, the upper limit of the average thickness of the primer treatment layer is preferably 20 μm, and more preferably 10 μm. When the average thickness of the primer treatment layer is less than the above lower limit, there is a possibility that sufficient adhesion with the conductor cannot be exhibited. Conversely, when the average thickness of the primer-treated layer exceeds the above upper limit, the insulated wire may be unnecessarily increased in diameter.

  Since the insulated wire according to the present invention can maintain both mechanical strength and flexibility and achieve a low dielectric constant, it can be suitably used for forming a coil, a motor, and the like.

DESCRIPTION OF SYMBOLS 1 Conductor 2 Insulation layer 3 Porous layer 4 Solid layer 5 Auxiliary layer 6 Pore

Claims (10)

An insulated wire comprising a linear conductor and an insulating layer coated on the outer peripheral surface side of the conductor,
The insulating layer has one or more pore layers including pores, and one or more solid layers laminated on the outer peripheral surface side of the pore layers and not including pores,
An insulated wire in which the main component of the solid layer is a thermoplastic resin.   The insulated wire according to claim 1, wherein a main component of the pore layer is a thermoplastic resin.   The insulated wire according to claim 1 or 2, wherein the thermoplastic resin is polyethylene terephthalate, polyetheretherketone, polyphenylene sulfide, or a combination thereof.   The insulated wire according to claim 1, 2 or 3, wherein the thermoplastic resin is crosslinked.   The insulated wire according to any one of claims 1 to 4, wherein the porosity of the pore layer is 5 vol% or more and 80 vol% or less.   The insulated wire according to any one of claims 1 to 5, wherein an average diameter of the pores is 0.1 µm or more and 10 µm or less.   The insulated wire according to any one of claims 1 to 6, wherein a ratio of a total average thickness of the one or more pore layers to an average thickness of the insulating layer is 20% or more and 60% or less.   The insulated wire according to any one of claims 1 to 7, wherein an average thickness of the insulating layer is not less than 30 µm and not more than 200 µm. A method for producing an insulated wire comprising a linear conductor and an insulating layer that is coated on the outer peripheral surface side of the conductor and has a pore layer and a solid layer in order from the conductor side,
A step of preparing a varnish for a pore layer by mixing a resin forming the pore layer with a solvent and a pore-forming agent;
A step of diluting the thermoplastic resin forming the solid layer with a solvent to prepare a varnish for the solid layer;
A step of forming a pore layer by applying and baking the varnish for the pore layer on the outer peripheral surface side of the conductor; and
Forming a solid layer by applying and baking the varnish for the solid layer on the outer peripheral surface side of the conductor having the pore layer formed thereon. A method for producing an insulated wire comprising a linear conductor and an insulating layer that is coated on the outer peripheral surface side of the conductor and has a pore layer and a solid layer in order from the conductor side,
The step of coating the outer peripheral surface side of the conductor with a pore layer and a solid layer by coextrusion,
The pore layer includes pores;
The solid layer does not contain pores,
The manufacturing method of the insulated wire whose main component of the said solid layer is a thermoplastic resin.

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