JP2017045662A - Insulated wire and varnish for forming insulating layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated wire capable of suppressing deterioration of strength and solvent resistance of an insulating layer while decreasing a dielectric constant.SOLUTION: An insulated wire according to one aspect of the present invention includes a linear conductor and one or more insulating layers laminated on an outer peripheral surface of the conductor. At least one of the one or more insulating layers contains a plurality of hollow inorganic particles, and the pressure resistant strength of the hollow inorganic particles measured by the glycerol method according to ASTM D3102-78 is 10 MPa or more. The average shell thickness of the hollow inorganic particles is preferably 1.0 μm or less. The material of shells of the hollow inorganic particles is preferably glass. The hollow inorganic particles are preferably spherical. The average particle diameter of the hollow inorganic particles is preferably 30 μm or less. The hollow ratio of the hollow inorganic particles is preferably 50 vol% or more and 95 vol% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulated wire and an insulating layer forming varnish.

  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 reduce the dielectric constant of an insulating coating, a heat-cured film (insulating coating) is formed by an insulating varnish containing a coating film constituent resin and a thermally decomposable resin that decomposes at a temperature lower than the baking temperature of the coating film constituent resin ) Has been proposed (see JP 2012-224714 A). In this insulated wire, pores are formed in the heat-cured film by utilizing the fact that the thermally decomposable resin is thermally decomposed during baking of the coating film constituting resin and the portion becomes pores. Low dielectric constant of insulating coating is realized.

JP 2012-224714 A

  However, in the insulated wire proposed in the above publication, for example, when pores formed in the insulating coating are localized, or when the size of these pores varies, the insulating coating is derived from a thermally decomposable resin. The pores can easily communicate with each other, and pores larger than the particle size of the thermally decomposable resin may be generated. When such continuous pores are generated, the strength and solvent resistance of the insulating film may be reduced.

  This invention is made | formed based on the above situations, and provides the insulated wire and insulating layer formation varnish which can suppress the fall of the intensity | strength and solvent resistance of an insulating layer, reducing a dielectric constant. Objective.

  An insulated wire according to one aspect of the present invention made to solve the above problems is an insulated wire comprising a linear conductor and one or more insulating layers laminated on the outer peripheral surface of the conductor, It is an insulated wire in which at least one layer of the one or more insulating layers includes a plurality of hollow inorganic particles, and the pressure resistance of the hollow inorganic particles measured by the glycerol method in accordance with ASTM D3102-78 is 10 MPa or more. .

  Another insulating layer forming varnish according to one aspect of the present invention is an insulating layer forming varnish used for forming at least one layer of one or more insulating layers constituting an insulated wire, and a resin composition forming a matrix And a hollow inorganic particle dispersed in the resin composition, and the insulating layer forming varnish having a compressive strength of the hollow inorganic particle measured by a glycerol method according to ASTM D3102-78 of 10 MPa or more It is.

  The insulated wire and insulating layer forming varnish of the present invention can suppress a decrease in strength and solvent resistance of the insulating layer while lowering the dielectric constant.

It is a typical sectional view of an insulated wire concerning an embodiment of the present invention. It is a typical end view of the hollow inorganic particle contained in the insulated wire of FIG. It is a typical end view of hollow inorganic particles contained in an insulated wire according to another embodiment of the present invention. FIG. 3C is a schematic end view of hollow inorganic particles different from FIG. 3A included in an insulated wire according to another 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 one or more insulating layers stacked on an outer peripheral surface of the conductor, and includes at least one of the one or more insulating layers. One layer includes a plurality of hollow inorganic particles, and the insulation strength of the hollow inorganic particles measured by the glycerol method in accordance with ASTM D3102-78 is 10 MPa or more.

  The insulated wire includes an insulating layer including a plurality of hollow inorganic particles, and pores of the hollow inorganic particles are surrounded by a shell made of an inorganic material. Is difficult to communicate. Thus, since the said insulated wire cannot connect the hollow parts in each hollow inorganic particle easily, even if it increases a hollow inorganic particle, it is hard to produce a coarse pore. Therefore, the said insulated wire can suppress the fall of the intensity | strength of an insulating layer and solvent resistance, reducing a dielectric constant. In addition, the insulated wire is made of an inorganic material due to shrinkage of the varnish when the insulating layer is formed because the pressure resistance of the hollow inorganic particles measured by the glycerol method in accordance with ASTM D3102-78 is equal to or higher than the lower limit. The cracking of the shell is suppressed, and the effect of suppressing the decrease in insulation and solvent resistance is promoted. Here, the “porosity” means the percentage of the volume of the pores by the hollow inorganic particles with respect to the volume of the insulating layer containing the hollow inorganic particles.

  The average thickness of the hollow inorganic particle shell is preferably 1.0 μm or less. Thus, the porosity of an insulating layer can be raised because the average thickness of the shell of a hollow inorganic particle is below the said upper limit.

  The shell of the hollow inorganic particles is preferably glass. Thus, the strength of the insulating layer can be further increased by using hollow inorganic particles having a glass shell.

  The hollow inorganic particles are preferably spherical. Thus, since the hollow inorganic particles are spherical, the external force applied to the shell surface is easily dispersed due to the shrinkage of the varnish during the formation of the insulating layer, and as a result, the cracks of the shell hardly occur and coarser pores are generated. hard. Here, “spherical” is not limited to a true sphere, and means a sphere shape having a sphericity of 1.0 to 1.3, for example.

  The average particle size of the hollow inorganic particles is preferably 30 μm or less. Thus, when the average particle diameter of the hollow inorganic particles is not more than the above upper limit, formation of irregularities on the surface of the insulating layer is suppressed. Here, an average particle diameter means the median diameter prescribed | regulated to JIS-Z8825 (2013).

  As a hollow rate of the said hollow inorganic particle, 50 volume% or more and 95 volume% or less are preferable. Thus, when the hollow ratio of the hollow inorganic particles is within the above range, the porosity can be efficiently increased with respect to the volume occupied by the hollow inorganic particles. Moreover, since the volume ratio which the hollow inorganic particle in an insulating layer occupies can be made small, the inhibitory effect of an insulation fall is accelerated | stimulated. Here, the “hollow ratio” means a percentage of the volume of the hollow portion with respect to the apparent volume of the entire hollow inorganic particle.

  An insulating layer forming varnish according to one aspect of the present invention is an insulating layer forming varnish used for forming at least one of one or more insulating layers constituting an insulated wire, and a resin composition that forms a matrix; And an insulating layer forming varnish containing hollow inorganic particles dispersed in the resin composition and having a compressive strength of the hollow inorganic particles measured by the glycerol method according to ASTM D3102-78 of 10 MPa or more. .

  Since the insulating layer-forming varnish thus contains the hollow inorganic particles dispersed in the resin composition forming the matrix, an insulating layer including pores formed by these hollow inorganic particles can be formed. The insulating layer forming varnish is a shell in which each pore formed in the insulating layer is made of an inorganic material even if the volume ratio of the hollow inorganic particles to the resin composition is increased so that the porosity of the insulating layer is increased. Therefore, it is difficult for the hollow portions in each hollow inorganic particle to communicate with each other, and as a result, coarse pores are hardly generated in the insulating layer. Therefore, the insulating layer forming varnish can suppress the decrease in the strength and solvent resistance of the insulating layer while decreasing the dielectric constant of the insulated wire. In addition, the insulating layer forming varnish contains hollow inorganic particles having a pressure strength measured by the glycerol method in accordance with ASTM D3102-78 that is equal to or higher than the lower limit, thereby causing shrinkage of the varnish when forming the insulating layer. The cracking of the shell made of an inorganic material is suppressed, and the effect of suppressing the decrease in insulation and solvent resistance is promoted.

[Details of the embodiment of the present invention]
Hereinafter, an insulated wire and an insulating layer forming varnish according to an embodiment of the present invention will be described with reference to the drawings.

[Insulated wire]
The insulated wire in FIG. 1 includes a linear conductor 1 and a single insulating layer 2 laminated on the outer peripheral surface of the conductor 1. The insulating layer 2 includes a plurality of hollow inorganic particles 3.

<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. If 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, if 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 a plurality of hollow inorganic particles 3 as shown in FIG. That is, the insulating layer 2 includes a plurality of pores due to the hollow inorganic particles 3.

  The insulating layer 2 is formed of a resin composition having insulating properties and hollow inorganic particles 3 scattered in the resin composition. The insulating layer 2 is formed by applying and baking an insulating layer forming varnish, which will be described later, on the outer peripheral surface of the conductor 1.

(Hollow inorganic particles)
The hollow inorganic particles 3 have a hollow shell 4 as shown in FIG.

  The shell 4 is made of an inorganic material. Examples of such inorganic materials include single crystal materials, ceramics, and glass. Among these, the material of the shell 4 is preferably glass. By making the material of the shell 4 glass, it is easy to improve the strength of the insulating layer 2 of the insulated wire.

  Although the shape of the hollow inorganic particle 3 is not specifically limited, For example, the spherical shape as shown in FIG. 2 is preferable. By using the spherical hollow inorganic particles 3, the external force applied to the surface of the shell 4 is easily dispersed due to the shrinkage of the varnish when the insulating layer 2 is formed, so that the shell 4 is hardly cracked. As a result, pores due to the hollow inorganic particles 3 are difficult to communicate and coarse pores are not easily generated.

  When the spherical hollow inorganic particles 3 are used, the lower limit of the average particle diameter of the hollow inorganic particles 3 is preferably 0.5 μm and more preferably 1 μm. On the other hand, the upper limit of the average particle diameter of the hollow inorganic particles 3 is preferably 30 μm, and more preferably 25 μm. If the average particle diameter of the hollow inorganic particles 3 is less than the above lower limit, the upper limit of the hollow ratio is reduced and the hollow ratio cannot be increased beyond a predetermined level, so that the volume ratio of the hollow inorganic particles 3 contained in the insulating layer 2 is increased. As a result, the insulating property of the insulating layer 2 may be reduced. On the contrary, if the average particle diameter of the hollow inorganic particles 3 exceeds the above upper limit, the hollow v particles 3 become too large with respect to the thickness of the insulating layer 2, so that unevenness may be easily formed on the surface of the insulating layer 2. There is.

  The lower limit of the average thickness of the shell 4 made of an inorganic material is preferably 0.05 μm, and more preferably 0.1 μm. On the other hand, the upper limit of the average thickness of the shell 4 is preferably 1.0 μm, and more preferably 0.8 μm. If the average thickness of the shell 4 is less than the above lower limit, the shell 4 is liable to crack due to shrinkage of the varnish when the insulating layer 2 is formed, and the pore communication suppression effect by the hollow inorganic particles 3 may not be sufficiently obtained. There is. On the contrary, if the average thickness of the shell 4 exceeds the above upper limit, the volume of pores formed with respect to the volume of the hollow inorganic particles 3 becomes too small, so the volume ratio of the hollow inorganic particles 3 contained in the insulating layer 2 Becomes larger. As a result, the insulating property of the insulating layer 2 may be reduced.

  The lower limit of the pressure strength of the hollow inorganic particles 3 is 10 MPa, preferably 20 MPa, and more preferably 30 MPa as measured by the glycerol method in accordance with ASTM D3102-78. If the pressure resistance of the hollow inorganic particles 3 is less than the above lower limit, the shell 4 is liable to crack due to varnish contraction when the insulating layer 2 is formed, and the effect of suppressing pore communication by the hollow inorganic particles 3 cannot be sufficiently obtained. There is a fear. In addition, although there is no restriction | limiting in particular as an upper limit of the pressure strength of the hollow inorganic particle 3, For example, 250 MPa is preferable. If the pressure resistance of the hollow inorganic particles 3 exceeds the above upper limit, the cost of the hollow inorganic particles 3 increases, and the product cost of the insulated wire may increase.

  As a minimum of the hollow rate of hollow inorganic particle 3, 50 volume% is preferred and 60 volume% is more preferred. On the other hand, the upper limit of the hollow ratio of the hollow inorganic particles 3 is preferably 95% by volume, more preferably 90% by volume. If the hollow ratio of the hollow inorganic particles 3 is less than the above lower limit, the volume ratio occupied by the hollow inorganic particles 3 in the insulating layer 2 becomes too large, and there is a possibility that the insulation deterioration cannot be sufficiently suppressed. On the contrary, when the hollowness ratio of the hollow inorganic particles 3 exceeds the above upper limit, the shear due to the stirring at the time of varnish preparation and the crack of the shell 4 due to the shrinkage of the varnish at the time of forming the insulating layer 2 easily occur. There is a possibility that the effect of suppressing communication is not sufficiently obtained.

  As an upper limit of the dielectric constant of the hollow inorganic particle 3, 2.5 is preferable and 2.0 is more preferable. When the relative dielectric constant of the hollow inorganic particles 3 exceeds the above upper limit, the amount of the hollow inorganic particles 3 necessary for lowering the dielectric constant of the insulating layer 2 increases, which may increase the product cost of the insulated wire. On the other hand, the lower limit of the dielectric constant of the hollow inorganic particles 3 is not particularly limited, but is preferably 1.2, for example. If the relative dielectric constant of the hollow inorganic particles 3 is less than the lower limit, it may be difficult to ensure the pressure resistance of the hollow inorganic particles 3. The “relative permittivity of the hollow inorganic particles 3” is a relative permittivity calculated from the relative permittivity of the material constituting the shell 4, the relative permittivity of air, and the hollow permittivity of the hollow inorganic particles 3.

  As a minimum of average thickness of insulating layer 2, 15 micrometers is preferred and 20 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 above lower limit, the insulating property may be lowered, and the presence of the hollow inorganic particles 3 may easily form an uneven shape on the surface of the insulating layer 2. Conversely, if 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 reduced.

  As a minimum of the porosity of the insulating layer 2, 5 volume% is preferable and 8 volume% is more preferable. On the other hand, the upper limit of the porosity of the insulating layer 2 is preferably 80% by volume, and more preferably 50% by volume. If the porosity of the insulating layer 2 is less than the lower limit, the dielectric constant of the insulating layer 2 is not sufficiently lowered, and the corona discharge starting voltage may not be sufficiently improved. Conversely, if the porosity of the insulating layer 2 exceeds the above upper limit, the mechanical strength of the insulating layer 2 may not be maintained.

  In the insulated wire, the pores included in the insulating layer 2 are thus formed by the hollow inorganic particles 3. Since the pores of the hollow inorganic particles 3 are surrounded by the shell 4 made of an inorganic material, even if the shells 4 come into contact with each other, the hollow portions in the hollow inorganic particles 3 are difficult to communicate with each other. Larger pores than the particles 3 are unlikely to occur. Thereby, the said insulated wire can suppress the fall of the intensity | strength and solvent resistance of an insulating layer, reducing a dielectric constant.

[Insulation layer forming varnish]
The insulating layer forming varnish is a varnish used for forming the insulating layer 2 of the insulated wire. The insulating layer forming varnish contains a resin composition forming a matrix and hollow inorganic particles 3 dispersed in the resin composition.

<Resin composition>
The resin composition is a composition containing a main polymer, a diluent solvent, a curing agent, and the like. Although it does not specifically limit as said main polymer, When using a thermosetting resin, a polyvinyl formal precursor, a thermosetting polyurethane precursor, a thermosetting acrylic resin precursor, an epoxy resin precursor, a thermosetting polyester precursor, for example A thermosetting polyesterimide precursor, a thermosetting polyesteramideimide precursor, a thermosetting polyamideimide precursor, a polyimide precursor, or the like can be used. Moreover, when using a thermoplastic resin as a main polymer, polyether imide, polyether ether ketone, polyether sulfone, polyimide etc. can be used, for example. Among these, a polyimide precursor is preferable because it can easily apply the insulating layer forming varnish and can easily improve the strength and heat resistance of the insulating layer 2.

  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.

  Moreover, you may make the said resin composition contain a hardening | curing agent. Curing agents include titanium-based curing agents, isocyanate compounds, blocked isocyanates, urea and melamine compounds, amino resins, acetylene derivatives, alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, aliphatic acid anhydrides, and aromatics. An acid anhydride etc. are illustrated. These curing agents are appropriately selected according to the type of main polymer 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. Examples of the acetylene derivative include ethynyl aniline and enethyl phthalic anhydride.

  The lower limit of the resin solid content concentration of the insulating layer forming varnish prepared by diluting with the organic solvent and dispersing the hollow inorganic particles 3 is preferably 15% by mass, more preferably 20% by mass. On the other hand, the upper limit of the resin solid content concentration of the insulating layer forming varnish is preferably 50% by mass, and more preferably 30% by mass. If the resin solid content concentration of the varnish for forming the insulating layer is less than the lower limit, the thickness that can be formed by a single varnish application is reduced, so that the varnish application for forming the insulating layer 2 having a predetermined thickness is performed. There is a possibility that the number of repetitions of the process increases and the time for the varnish application process becomes long. Conversely, if the resin solids concentration of the insulating layer forming varnish exceeds the above upper limit, the varnish may be thickened, which may deteriorate the storage stability of the varnish and the adhesiveness during varnish application. There is.

[Insulated wire manufacturing method]
Next, the manufacturing method of the said insulated wire is demonstrated. This method for producing an insulated wire includes a step of preparing an insulating layer forming varnish by dispersing hollow inorganic particles 3 in a resin composition obtained by diluting a main polymer for forming the insulating layer 2 with a solvent (varnish preparation). Step), a step of applying the insulating layer forming varnish to the outer peripheral surface of the conductor 1 (varnish applying step), and a step of baking the insulating layer forming varnish (baking step).

<Varnish preparation process>
In the varnish preparation step, first, a resin composition that forms a matrix of the insulating layer 2 is prepared by diluting the main polymer that forms the insulating layer 2 with a solvent. Next, the hollow inorganic particles 3 are dispersed in the resin composition to prepare an insulating layer forming varnish. Instead of dispersing the hollow inorganic particles 3 in the resin composition, the insulating layer forming varnish may be prepared by simultaneously mixing the hollow inorganic particles 3 when the main polymer is diluted with a solvent.

<Varnish application process>
In the varnish application step, the insulating layer forming varnish prepared in the varnish preparation step is applied to the outer peripheral surface of the conductor 1.

<Baking process>
Next, in the baking step, the conductor 1 coated with the insulating layer forming varnish is passed through a baking furnace to burn the insulating layer forming varnish, thereby forming a baking layer on the surface of the conductor 1.

  By repeating the varnish coating step and the baking step until the total thickness of the plurality of baking layers laminated on the surface of the conductor 1 reaches a predetermined thickness, the insulating layer 2 composed of a plurality of baking layers is formed, and the insulation An electric wire is obtained. The hollow inorganic particles 3 contained in the formed insulating layer 2 form pores in the insulating layer 2.

  In addition, when repeating the said varnish application | coating process and baking process, it replaces with the said varnish for insulating layer formation containing the hollow inorganic particle 3 in at least any varnish application | coating process, and does not contain the hollow inorganic particle 3. A varnish may be applied. That is, after applying and baking the insulating layer forming varnish containing the hollow inorganic particles 3, the insulating layer forming varnish not containing the hollow inorganic particles 3 may be applied, or the insulating layer not containing the hollow inorganic particles 3 may be applied. After the application and baking of the forming varnish, the insulating layer forming varnish containing the hollow inorganic particles 3 may be applied. For example, when the average thickness of the baked layer formed by applying the insulating layer forming varnish once is smaller than the average particle diameter of the hollow inorganic particles 3, the insulating layer not containing the hollow inorganic particles 3 is formed. By applying the varnish for use, the formation of irregularities on the surface of the insulating layer 2 due to the shape of the hollow inorganic particles 3 can be suppressed.

  Moreover, when applying the insulating layer forming varnish that does not contain the hollow inorganic particles 3 in the varnish applying step after the predetermined varnish applying step as described above, the insulating layer forming varnish that does not contain the hollow inorganic particles 3 is applied. In the varnish application step, after applying the varnish, the application amount of the varnish of the conductor 1 may be adjusted and the applied varnish surface may be smoothed by an application die.

  The coating die has an opening, and when the conductor 1 coated with the insulating layer forming varnish passes through the opening, the excess varnish is removed, and the coating amount of the varnish is adjusted. Thereby, as for the said insulated wire, the thickness of the insulating layer 2 becomes easy easily and it becomes easy to obtain uniform electrical insulation.

  Thus, the insulating layer 2 produced using the insulating layer forming varnish includes pores due to the hollow inorganic particles 3. Since the pores are surrounded by the shell 4 made of an inorganic material, the pores are difficult to communicate with each other, and even if the hollow inorganic particles 3 are increased so that the porosity of the insulating layer 2 is increased, coarse pores are hardly generated. As described above, the insulating layer forming varnish can increase the porosity of the insulating layer 2 while suppressing a decrease in insulation and solvent resistance.

[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

  In the said embodiment, although the insulated wire in which one insulating layer was laminated | stacked on the outer peripheral surface of a conductor was demonstrated, it is good also as an insulated wire by which a some insulating layer is laminated | stacked on the outer peripheral surface of a conductor. That is, one or a plurality of insulating layers may be laminated between the conductor 1 of FIG. 1 and the insulating layer 2 including pores, or one or a plurality of insulating layers may be provided on the outer peripheral surface of the insulating layer 2 including the pores of FIG. Layers may be stacked, or one or a plurality of insulating layers may be stacked on both the outer peripheral surface and the inner peripheral surface of the insulating layer 2 including the pores of FIG. In the insulated electric wire in which a plurality of insulating layers are laminated in this way, it is only necessary that at least one insulating layer includes pores due to hollow inorganic particles. That is, pores due to hollow inorganic particles may be included in two or more insulating layers. When two or more insulating layers contain pores due to hollow inorganic particles, each of these insulating layers contributes to a reduction in dielectric constant. Thus, the insulated wire in which a plurality of hollow inorganic particles are contained in at least one of the plurality of insulating layers is also within the scope of the present invention. Moreover, the mechanical strength of an insulated wire can be improved by laminating | stacking a some insulating layer on the outer peripheral surface of a conductor in this way. In addition, the same kind may be used as a resin composition which forms these some insulating layers, and a mutually different thing may be used.

  Further, in the above embodiment, spherical inorganic particles are used as the hollow inorganic particles, but other than spherical, as long as the shell is difficult to break due to shrinkage of the varnish during mixing and baking of the hollow inorganic particles. You may use the thing of a shape. That is, as the hollow inorganic particles for forming pores in the insulating layer, for example, the hollow inorganic particles 13 constituted by a rectangular parallelepiped shell 14 as shown in FIG. 3A or the shell having a plurality of pores as shown in FIG. 3B inside. You may use the hollow inorganic particle 23 comprised by 24. FIG. Specifically, as the rectangular parallelepiped hollow inorganic particles 13 as shown in FIG. 3A, for example, the average particle diameter is about 80 nm to 130 nm, and the average thickness of the shell 14 made of an inorganic material is about 5 nm to 15 nm. Particles having a pressure strength of about 100 MPa can be used. Further, as the hollow inorganic particles 23 having a plurality of pores inside as shown in FIG. 3B, for example, the hollow inorganic particles 23 have a plurality of pores formed with a two-dimensional hexagonal structure, and an average particle diameter of about 2.4 μm. The distance between the facing surfaces of the hexagonal peripheral wall surrounding the hole is about 4 nm, and particles having a pressure strength of about 100 MPa can be used.

  Although there is no restriction | limiting in particular as a minimum of the average particle diameter of the hollow inorganic particle in the case of having shapes other than a sphere, For example, 50 nm is preferable and 60 nm is more preferable. On the other hand, the upper limit of the average particle diameter of the hollow inorganic particles other than spherical is preferably 30 μm, and more preferably 25 μm. If the average particle diameter of the hollow inorganic particles other than the spherical shape is less than the above lower limit, the upper limit of the hollow ratio becomes small and the hollow ratio cannot be increased beyond a predetermined level, so that the volume ratio of the hollow inorganic particles contained in the insulating layer increases. As a result, the insulating properties of the insulating layer may be reduced. On the contrary, if the average particle diameter of the hollow inorganic particles other than the spherical shape exceeds the upper limit, the hollow inorganic particles become too large with respect to the thickness of the insulating layer, so that the surface of the insulating layer is likely to be uneven. is there. The “particle diameter” of the hollow inorganic particles other than spherical means the equivalent diameter of a true sphere having the same volume as the apparent volume of the hollow inorganic particles.

  In the above embodiment, the hollow inorganic particles 4 having a smooth surface as shown in FIG. 2 are used as the hollow inorganic particles for forming pores. For example, the hollow inorganic particles 23 shown in FIG. 3B are used. In addition, particles having an uneven shape on the surface may be used.

  Moreover, although the said embodiment demonstrated the structure which repeats the said varnish application | coating process and baking process, it is good also as a structure which forms an insulating layer by one application | coating process and baking process. For example, when a baked layer having the thickness of the insulating layer can be formed by one coating and baking by using a highly viscous insulating layer forming varnish, the insulating layer is thus repeated without repeating the coating process and baking process. Can be formed. In this case, the insulating layer is formed of one baking layer.

  Further, for example, in the insulated wire, an additional layer such as a primer treatment layer may be provided between the conductor and the insulating layer. 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 treatment layer between a conductor and an insulating layer, the resin composition forming this primer treatment layer is, for example, one or more kinds of resins selected from polyimide, polyamideimide, polyesterimide, polyester and phenoxy resin. It is good to include. 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. If the average thickness of the primer-treated layer is less than the above lower limit, there is a possibility that sufficient adhesion with the conductor cannot be exhibited. Conversely, if the average thickness of the primer-treated layer exceeds the above upper limit, the insulated wire may unnecessarily increase in diameter.

  With the insulated wire and the insulating layer forming varnish according to the present invention, it is possible to suppress a decrease in the strength and solvent resistance of the insulating layer while reducing the dielectric constant. Therefore, an insulated wire having such an insulating layer can be suitably used for forming a coil, a motor, or the like.

DESCRIPTION OF SYMBOLS 1 Conductor 2 Insulating layer 3, 13, 23 Hollow inorganic particle 4, 14, 24 Shell

Claims (7)

An insulated wire comprising a linear conductor and one or more insulating layers laminated on the outer peripheral surface of the conductor,
At least one of the one or more insulating layers includes a plurality of hollow inorganic particles;
An insulated wire in which the pressure resistance of the hollow inorganic particles measured by the glycerol method in accordance with ASTM D3102-78 is 10 MPa or more.   The insulated wire according to claim 1, wherein an average thickness of the shell of the hollow inorganic particles is 1.0 µm or less.   The insulated wire according to claim 1 or 2, wherein a material of the shell of the hollow inorganic particles is glass.   The insulated wire according to claim 1, wherein the hollow inorganic particles are spherical.   The insulated wire according to claim 4, wherein the hollow inorganic particles have an average particle size of 30 μm or less.   The insulated wire according to claim 4 or 5, wherein a hollow ratio of the hollow inorganic particles is 50% by volume or more and 95% by volume or less. An insulating layer forming varnish used for forming at least one of one or more insulating layers constituting an insulated wire,
A resin composition forming a matrix;
Hollow inorganic particles dispersed in the resin composition,
A varnish for forming an insulating layer, wherein the hollow inorganic particles have a pressure strength of 10 MPa or more as measured by a glycerol method according to ASTM D3102-78.

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