JP6613163B2 - Insulated wire - Google Patents

Description

  The present invention relates to 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 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.

  Moreover, an overvoltage (surge voltage) may be temporarily applied to the insulated wire during use. When surge voltage is applied, the insulating layer deteriorates due to heat dissipation and the product life is shortened. Therefore, an insulated wire in which inorganic fine particles (silica) are contained in the insulating layer to improve surge resistance has been proposed (see Japanese Patent Application Laid-Open No. 2007-141507).

JP 2012-224714 A JP 2007-141507 A

  In the above-described conventional insulated wire, silica used for the insulating layer is difficult to disperse in the resin and is likely to be unevenly distributed, so that the surge resistance may be insufficiently improved. Moreover, the varnish containing a silica has the inconvenience that the sedimentation of a silica occurs easily and handling is difficult, and the manufacturability of an insulated wire is lowered.

  This invention is made | formed based on the above situations, and it aims at providing the insulated wire which is excellent in surge resistance, maintaining manufacturability.

  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, The insulating layer contains silicone.

  The insulated wire of the present invention is excellent in surge resistance while maintaining manufacturability.

It is typical sectional drawing of the insulated wire of one Embodiment of this invention. It is typical sectional drawing of the insulated wire of embodiment different from FIG. It is typical sectional drawing of the insulated wire of embodiment different from FIG.1 and FIG.2.

[Description of Embodiment of the Present Invention]
The insulated wire which concerns on 1 aspect of this invention is an insulated wire provided with a linear conductor and 1 or several insulating layer laminated | stacked on the outer peripheral surface of this conductor, Comprising: The said insulating layer contains silicone.

  The insulated wire contains silicone in the insulating layer, and this silicone is denatured into silica by heat dissipation when a surge voltage is applied. In other words, unlike insulated silica, the insulated wire contains silicone that is unlikely to be unevenly distributed in the insulating layer and that is denatured into silica after heat dissipation, thereby maintaining the manufacturability and improving the surge resistance of the insulating layer uniformly. , Can significantly improve the product life. “Silicone” means a polymer containing a repeating structure of a siloxane bond in which a silicon atom and an oxygen atom are bonded.

  At least one of the insulating layers may contain a matrix and silicone dispersed in the matrix. Thus, surge resistance can be improved easily and reliably by the silicone containing and dispersing the silicone in the matrix.

  At least one of the insulating layers may contain silicone as a main component. Thus, even if the insulating layer includes a layer mainly composed of silicone, surge resistance can be easily and reliably improved.

  At least one of the insulating layers may contain a plurality of pores and an outer shell around the pores, and the outer shell may contain silicone as a main component. When the insulating layer contains such pores and outer shells, surge resistance can be improved while lowering the dielectric constant of the insulating layer. In addition, since the pores included in the insulating layer are surrounded by the outer shell, the pores are difficult to communicate with each other and coarse pores are difficult to be generated. Therefore, it is possible to reduce the dielectric constant while suppressing a decrease in insulation and solvent resistance.

  The “main component” means a component that is contained most, for example, a component that is contained by 50% by mass or more.

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

[First embodiment]
The insulated wire 10 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 contains a matrix and silicone 3 dispersed in the matrix.

<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>
As shown in FIG. 1, the insulating layer 2 contains a matrix and silicone 3 dispersed in the matrix.

  As a minimum of average thickness of insulating layer 2, 5 micrometers is preferred and 10 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 100 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. Conversely, when the average thickness of the insulating layer 2 exceeds the above upper limit, the volume efficiency of a coil or the like formed using the insulated wire 10 may be lowered.

  The matrix of the insulating layer 2 is formed of a resin other than the silicone 3.

  The main component (main polymer) of the matrix is not particularly limited, but when a thermosetting resin is used, for example, polyvinyl formal, thermosetting polyurethane, thermosetting acrylic resin, epoxy resin, phenoxy resin, thermosetting polyester, Thermosetting polyester imide, thermosetting polyester amide imide, thermosetting polyamide imide, polyimide and 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, polyimide is preferable because it can easily apply the varnish for forming the insulating layer and can easily improve the strength and heat resistance of the insulating layer 2.

  Silicone 3 is in the form of particles and is dispersed in the matrix. The shape of the silicone 3 may be spherical or flat.

  As the silicone, for example, organopolysiloxane such as polymethylsiloxane is used.

  The lower limit of the average particle size of the silicone 3 is not particularly limited, but is preferably 0.1 μm, more preferably 1 μm, and even more preferably 1.5 μm. On the other hand, the upper limit of the average particle diameter of the silicone 3 is preferably 10 μm, more preferably 8 μm, and even more preferably 6 μm. When the average particle diameter of the silicone 3 is smaller than the above lower limit, the dispersibility is lowered, and the effect of improving surge resistance may be lowered. On the contrary, when the average particle diameter of the silicone 3 exceeds the above upper limit, the insulating layer 2 may become unnecessarily thick in addition to the risk that the dielectric constant of the insulating layer 2 will increase or the mechanical strength will decrease. The “average particle size” means a particle size indicating the highest volume content in the particle size distribution measured with a laser diffraction particle size distribution analyzer.

  Although the content rate of the silicone 3 in the insulating layer 2 can be arbitrarily changed according to the overvoltage (surge voltage) and life time assumed when the insulated wire is used, the lower limit of the content rate of the silicone 3 in the insulating layer 2 is the matrix 100. 5 mass parts is preferable with respect to a mass part, 15 mass parts is more preferable, and 20 mass parts is still more preferable. On the other hand, as an upper limit of the content rate of the silicone 3 in the insulating layer 2, 60 mass parts is preferable with respect to 100 mass parts of matrices, 50 mass parts is more preferable, and 40 mass parts is further more preferable. When the content rate of silicone 3 is smaller than the said minimum, there exists a possibility that the improvement effect of surge resistance may become inadequate. On the contrary, when the content rate of the silicone 3 exceeds the above upper limit, the dielectric constant of the insulating layer 2 may increase, the mechanical strength, and the like may decrease.

  As a minimum of the content rate in the whole insulating layer 2 of silicone 3 in insulating layer 2, 3 mass% is preferred, 10 mass% is more preferred, and 15 mass% is still more preferred. On the other hand, as an upper limit of the content rate in the whole insulating layer 2 of the silicone 3 in the insulating layer 2, 50 mass% is preferable, 40 mass% is more preferable, and 30 mass% is further more preferable. When the content rate of silicone 3 is smaller than the said minimum, there exists a possibility that the improvement effect of surge resistance may become inadequate. On the contrary, when the content rate of silicone 3 exceeds the said upper limit, in addition to the possibility that the mechanical strength etc. of the insulating layer 2 will fall, there exists a possibility that the insulating layer 2 may become thick unnecessarily.

  Moreover, you may make the resin composition which forms the insulating layer 2 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 compounds 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 include aliphatic diisocyanates having an aromatic ring such as alicyclic isocyanate, xylylene diisocyanate (XDI), 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 ethynylaniline and ethynylphthalic anhydride.

<Insulated wire manufacturing method>
Next, a method for manufacturing the insulated wire 10 will be described. The method of manufacturing the insulated wire 10 includes a step of preparing an insulating layer forming varnish by dispersing silicone 3 in a resin composition obtained by diluting the resin forming the insulating layer 2 with a solvent (varnish preparing step); A step of applying and heating the insulating layer forming varnish to the outer peripheral surface of the conductor 1 (varnish applying step).

(Varnish preparation process)
In the varnish preparation step, first, a resin composition that forms the matrix of the insulating layer 2 is prepared by diluting the resin that forms the matrix of the insulating layer 2 (a precursor in the case of a thermosetting resin) with a solvent. . Next, silicone 3 is dispersed in this resin composition to prepare an insulating layer forming varnish. Instead of dispersing the silicone 3 in the resin composition, the insulating layer forming varnish may be prepared by simultaneously mixing the silicone 3 when the resin is diluted with a solvent.

  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.

  As a minimum of the resin solid content concentration of the varnish for insulating layer formation, 15 mass% is preferred and 20 mass% is more preferred. 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. When the resin solid content concentration of the insulating layer forming varnish is less than the lower limit, the thickness that can be formed by applying the varnish once is reduced, so that the varnish applying step for forming the insulating layer 2 having a desired thickness is performed. There is a possibility that the number of repetitions of the varnish increases and the time of the varnish application process becomes longer. On the contrary, when the resin solid content concentration of the insulating layer forming varnish exceeds the upper limit, the storage stability of the varnish may be deteriorated due to thickening of the varnish.

(Varnish application process)
In the varnish application step, first, the insulating layer forming varnish prepared in the varnish preparation step is applied to the outer peripheral surface of the conductor 1, and then the application amount of the varnish of the conductor 1 is adjusted and the applied varnish surface of the conductor 1 is applied. Perform smoothing.

  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 10, the thickness of the insulating layer 2 becomes uniform and uniform electrical insulation is obtained.

  Next, the insulating layer 2 is formed on the surface of the conductor 1 by passing the conductor 1 coated with the insulating layer forming varnish through a baking furnace and baking the insulating layer forming varnish.

  By repeating the varnish application step and the heating step until the insulating layer 2 laminated on the surface of the conductor 1 has a predetermined thickness, the insulated wire 10 is obtained.

<Advantages>
In the insulated wire 10, the silicone 3 dispersed in the matrix of the insulating layer 2 is denatured into silica by heat dissipation when a surge voltage is applied. This silica can improve surge resistance and suppress deterioration of the insulating layer 2 due to surge voltage. Accordingly, since the insulated wire 10 has silica derived from the silicone 3 in the insulating layer 2 after being radiated, the surge resistance of the insulating layer 2 is uniformly increased while maintaining the manufacturability and the product life is increased. It can be significantly improved.

  In the insulated wire 10, the insulating layer 2 may have a multilayer structure. In this case, at least one layer of the insulating layer 2 may contain the silicone 3.

[Second Embodiment]
The insulated wire 20 in FIG. 2 includes a linear conductor 1 and a multilayer insulating layer 22 laminated on the outer peripheral surface of the conductor 1. The insulating layer 22 has an inner layer 22a and an outer layer 22b. Since the conductor 1 is the same as the conductor 1 of the insulated wire 10 of FIG. 1, it attaches | subjects the same code | symbol and abbreviate | omits description.

<Insulating layer>
As shown in FIG. 2, the insulating layer 22 has an inner layer 22a laminated on the outer circumferential surface of the conductor 1, and an outer layer 22b laminated on the outer circumferential surface of the inner layer 22a and forming the outermost layer.

  The outer layer 22b has silicone as a main component. The outer layer 22b may contain other insulating resins and additives in addition to silicone.

  As a minimum of the content rate of silicone in outer layer 22b, 2 mass% is preferred and 5 mass% is still more preferred. On the other hand, the upper limit of the silicone content in the outer layer 22b is not particularly limited, and is usually 100% by mass. When the content rate of silicone is smaller than the said minimum, there exists a possibility that the improvement effect of surge resistance may become inadequate.

  The lower limit of the average thickness of the outer layer 22b is preferably 1 μm and more preferably 3 μm. On the other hand, the upper limit of the average thickness of the outer layer 22b is preferably 200 μm, and more preferably 100 μm. If the average thickness of the outer layer 22b is less than the lower limit, the effect of improving surge resistance may be insufficient. Conversely, when the average thickness of the outer layer 22b exceeds the above upper limit, the dielectric constant of the insulating layer 2 may increase, or the volume efficiency of a coil or the like formed using the insulated wire 20 may be reduced.

  The inner layer 22a is formed of an insulating resin composition. As this resin composition, it can be set as the same as the resin composition which forms the insulating layer 2 of the insulated wire 10 of FIG. 1, for example. The resin composition forming the inner layer 22a may or may not contain silicone.

  The lower limit of the average thickness of the inner layer 22a is preferably 5 μm and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the inner layer 22a is preferably 200 μm, and more preferably 100 μm. When the average thickness of the inner layer 22a is less than the lower limit, the inner layer 22a may be broken and the conductor 1 may be insufficiently insulated. Conversely, when the average thickness of the inner layer 22a exceeds the upper limit, the volume efficiency of a coil or the like formed using the insulated wire 20 may be lowered.

<Insulated wire manufacturing method>
The insulated wire 20 forms the outer layer 22b by applying and heating a resin composition obtained by diluting a resin or the like for forming the inner layer 22a with a solvent on the outer peripheral surface of the conductor 1 and the outer layer 22b. And a step of applying and heating a resin composition obtained by diluting a resin or the like with a solvent to the outer peripheral surface of the inner layer 22a (outer layer varnish applying step).

<Advantages>
In the insulated wire 20, the silicone contained in the outer layer 22b is denatured into silica by heat dissipation when a surge voltage is applied. Accordingly, since the silica derived from silicone is present in the insulating layer 22 after the heat dissipation once, the insulated wire 20 uniformly improves the surge resistance of the insulating layer 22 while maintaining the manufacturability, thereby extending the product life. It can be significantly improved.

  In the insulated wire 20, the insulating layer 2 may have a multilayer structure of three or more layers, and the layer mainly composed of silicone is not limited to the outermost layer, and may be an innermost layer or an intermediate layer. .

[Third embodiment]
The insulated wire 30 in FIG. 3 includes a linear conductor 1 and a single insulating layer 32 laminated on the outer peripheral surface of the conductor 1. The insulating layer 32 includes a plurality of pores 4 and an outer shell 5 at the peripheral edge of the pores. Since the conductor 1 is the same as the conductor 1 of the insulated wire 10 of FIG. 1, it attaches | subjects the same code | symbol and abbreviate | omits description.

<Insulating layer>
As shown in FIG. 3, the insulating layer 32 contains a plurality of pores 4 derived from hollow-forming particles having a core-shell structure, which will be described later, and an outer shell 5 mainly composed of silicone.

  The insulating layer 32 is formed of an insulating resin composition, pores 4 scattered in the resin composition, and the outer shell 5 at the peripheral edge of the pores 4. As this resin composition, it can be set to be the same as that of the resin composition which forms the insulating layer 2 of the insulated wire 10 of FIG. The resin composition forming the insulating layer 32 may or may not contain silicone.

  As shown in FIG. 3, the plurality of pores 4 are each covered with an outer shell 5, and the outer shell 5 is constituted by a shell that is hollowed by removing the core of the hollow-forming particles having a core-shell structure. That is, the outer shell 5 is derived from a shell of hollow-forming particles having a core-shell structure. Further, at least a part of the plurality of outer shells 5 has a defect.

  The plurality of pores 4 are preferably flat spheres as shown in FIG. In addition, when the minor axis of the pore 4 is oriented in the direction perpendicular to the surface of the conductor 1, the pores are less likely to come into contact with each other in the vertical direction in which external force is likely to act, so that the independent pores are more easily maintained. Therefore, the larger the proportion of the pores 4 whose minor axis is oriented in the direction perpendicular to the surface of the conductor 1, the better. The lower limit of the ratio of the number of pores 4 whose minor axis is oriented in the direction perpendicular to the surface of the conductor 1 with respect to the total number of pores 4 is preferably 60%, more preferably 80%. If the ratio of the pores 4 whose minor axis is oriented in the direction perpendicular to the surface of the conductor 1 is less than the above lower limit, the pores 4 that come into contact with the pores may increase, and the generation of continuous pores may not be sufficiently suppressed.

  The lower limit of the ratio of the length of the minor axis to the major axis in the cross section including the minor axis and the major axis of the pore 4 is preferably 0.2, and more preferably 0.3. On the other hand, the upper limit of the average of the above ratio is preferably 0.95, more preferably 0.9. If the average of the above ratios is less than the lower limit, it is necessary to increase the amount of shrinkage in the thickness direction during varnish baking, which may reduce the flexibility of the insulated wire 30. On the contrary, when the average of the ratio exceeds the upper limit, when the porosity is increased, the pores are easily brought into contact with each other in the thickness direction of the insulating layer 32 where the external force easily acts, and the communication suppression effect of the pores 4 is obtained. There is a possibility that it cannot be obtained sufficiently. The ratio can be adjusted by changing the pressure applied to the hollow particles by shrinkage during baking of the resin composition contained in the insulating layer forming varnish. The pressure applied to the hollow forming particles can be changed depending on, for example, the type of the material that is the main component of the resin composition, the thickness of the insulating layer 32, the material of the hollow forming particles, the baking conditions, and the like.

  The lower limit of the average major axis of the pores 4 is preferably 0.1 μm and more preferably 1 μm. On the other hand, the upper limit of the average of the major axis is preferably 10 μm, and more preferably 8 μm. If the average of the major axis is less than the lower limit, the insulating layer 32 may not have a desired porosity. On the contrary, if the average of the major axis exceeds the upper limit, it is difficult to make the distribution of the pores 4 in the insulating layer 32 uniform, and the dielectric constant distribution may be easily biased.

  The plurality of outer shells 5 present at the peripheral edge portions of the plurality of pores 4 have at least some defects. The pores 4 and the outer shell 5 are derived from hollow particles having a core mainly composed of a thermally decomposable resin and a shell having a higher thermal decomposition temperature than the thermally decomposable resin. That is, when the varnish containing the hollow forming particles is baked, the thermally decomposable resin, which is the main component of the core, is gasified by thermal decomposition and scattered through the shell to form the pores 4 and the outer shell 5. At this time, the passage of the thermally decomposable resin in the shell exists in the outer shell 5 as a defect. The shape of this defect varies depending on the material and shape of the shell, but from the viewpoint of enhancing the effect of preventing the pores 4 from communicating with the outer shell 5, cracks, cracks and holes are preferred.

  Note that the insulating layer 32 may include the outer shell 5 having no defect. Depending on the outflow conditions of the core thermally decomposable resin to the outside of the shell, there is a case where no defect is formed in the shell (outer shell 5). The insulating layer 32 may include pores 4 that are not covered by the outer shell 5.

  The average thickness of the outer shell 5 is the same as the average thickness of the shell of the hollow-forming particles described later.

  The lower limit of the average thickness of the insulating layer 32 is preferably 5 μm and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the insulating layer 32 is preferably 200 μm, and more preferably 100 μm. If the average thickness of the insulating layer 32 is less than the lower limit, the insulating layer 32 may be broken, and the conductor 1 may be insufficiently insulated. Conversely, when the average thickness of the insulating layer 32 exceeds the above upper limit, the volume efficiency of a coil or the like formed using the insulated wire 30 may be reduced.

  The lower limit of the porosity of the insulating layer 32 is preferably 5% by volume, and more preferably 10% by volume. On the other hand, the upper limit of the porosity of the insulating layer 32 is preferably 80% by volume, and more preferably 50% by volume. If the porosity of the insulating layer 32 is less than the lower limit, the dielectric constant of the insulating layer 32 is not sufficiently lowered, and the corona discharge starting voltage may not be sufficiently improved. Conversely, if the porosity of the insulating layer 32 exceeds the above upper limit, the mechanical strength of the insulating layer 32 may not be maintained. Here, the “porosity” means a percentage of the volume of the pores with respect to the volume of the insulating layer including the pores.

  The upper limit of the ratio of the dielectric constant of the insulating layer 32 to the dielectric constant of a layer that is the same material as the insulating layer 32 and does not contain pores is 95%, preferably 90%, and more preferably 80%. If the dielectric constant ratio exceeds the upper limit, the corona discharge starting voltage may not be sufficiently improved.

<Insulated wire manufacturing method>
Next, a method for manufacturing the insulated wire 30 will be described. The method of manufacturing the insulated wire 30 includes a step of preparing a varnish for forming an insulating layer by dispersing hollow-forming particles having a core-shell structure in a resin composition obtained by diluting the resin forming the insulating layer 32 with a solvent (preparation of varnish) 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 removing the core of the hollow forming particles by heating (heating step).

(Varnish preparation process)
In the varnish preparation step, first, a resin composition that forms a matrix of the insulating layer 32 is prepared by diluting the resin that forms the insulating layer 32 with a solvent. Next, hollow forming particles are dispersed in this resin composition to prepare an insulating layer forming varnish. Instead of dispersing the hollow-forming particles in the resin composition, the insulating layer-forming varnish may be prepared by simultaneously mixing the hollow-forming particles when the resin is diluted with a solvent.

  The hollow forming particles have a core mainly composed of a thermally decomposable resin and a shell having a higher thermal decomposition temperature than the thermally decomposable resin.

  As the thermally decomposable resin used as the main component of the core, for example, resin particles that thermally decompose at a temperature lower than the baking temperature of the resin forming the insulating layer are used. The baking temperature of the insulating layer forming resin is appropriately set according to the type of the resin, but is usually about 200 ° C. or higher and 600 ° C. or lower. Therefore, the lower limit of the thermal decomposition temperature of the thermally decomposable resin used for the core of the hollow forming particles is preferably 200 ° C., and the upper limit is preferably 400 ° C. Here, the thermal decomposition temperature means a temperature at which the temperature is increased from room temperature to 10 ° C./min in an air 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 core of the hollow-forming particles is not particularly limited. For example, a compound obtained by alkylating, (meth) acrylated or epoxidizing one or both ends or part of polyethylene glycol, polypropylene glycol or the like. (Meth) acrylic acid having an alkyl group having 1 to 6 carbon atoms, such as poly (meth) methyl acrylate, poly (meth) ethyl acrylate, poly (meth) acrylate propyl, poly (meth) acrylate butyl, etc. Polymers of esters, urethane oligomers, urethane polymers, urethane (meth) acrylates, epoxy (meth) acrylates, modified (meth) acrylate polymers such as ε-caprolactone (meth) acrylate, poly (meth) acrylic acid, these Cross-linked product, polystyrene, cross-linked polystyrene, etc. And the like. Among these, a polymer of a (meth) acrylic acid ester having an alkyl group having 1 to 6 carbon atoms is preferable in that it is easily pyrolyzed at the baking temperature of the insulating layer forming resin and easily forms pores 4 in the insulating layer 2. preferable. An example of such a (meth) acrylic acid ester polymer is polymethyl methacrylate (PMMA).

  The core is preferably spherical. In order to make the core shape spherical, for example, spherical heat-decomposable resin particles may be used as the core. When spherical heat-decomposable resin particles are used, the lower limit of the average particle diameter of the resin particles is not particularly limited, but 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 15 μm and more preferably 10 μm. If the average particle diameter of the resin particles is less than the lower limit, it may be difficult to produce hollow-forming particles having the resin particles as a core. Conversely, if the average particle diameter of the resin particles exceeds the upper limit, hollow-forming particles having the resin particles as a core become too large, so that the distribution of the pores 4 in the insulating layer 32 becomes difficult to be uniform, and the dielectric There is a risk that the distribution of the rate is likely to be biased.

  Silicone is used as the main component of the shell.

  Although there is no restriction | limiting in particular as a minimum of the average thickness of a shell, For example, 0.01 micrometer is preferable and 0.02 micrometer is more preferable. On the other hand, the upper limit of the average thickness of the shell is preferably 0.5 μm, and more preferably 0.4 μm. If the average thickness of the shell is less than the above lower limit, the communication suppression effect of the pores 4 may not be sufficiently obtained. On the other hand, if the average thickness of the shell exceeds the above upper limit, the volume of the pores 4 becomes too small, so that the porosity of the insulating layer 32 may not be increased beyond a predetermined level. Note that the shell may be formed of one layer or a plurality of layers. When the shell is formed of a plurality of layers, the average of the total thickness of the plurality of layers may be within the range of the thickness.

  The upper limit of the CV value (coefficient of variation) of the hollow-forming particles is preferably 30% and more preferably 20%. If the CV value of the hollow-forming particles exceeds the above upper limit, the insulating layer 32 includes a plurality of pores 4 having different sizes, and thus the dielectric constant distribution may be easily biased. In addition, although there is no restriction | limiting in particular as a minimum of CV value of hollow formation particle, For example, 1% is preferable. If the CV value of the hollow-forming particles is less than the lower limit, the cost of the hollow-forming particles may be too high.

  The hollow-forming particles may have a structure in which the core is formed by one thermally decomposable resin particle, or the core is formed by a plurality of thermally decomposable resin particles, and the shell resin is formed by the plurality of thermally decomposable particles. The resin resin particles may be covered. Further, the surface of the hollow forming particles may be smooth without irregularities, or irregularities may be formed.

  In addition to the hollow-forming particles, a pore-forming agent such as thermally decomposable particles may be mixed with the insulating layer-forming varnish in order to form pores. In order to form pores, the insulating layer forming varnish may be prepared by combining diluting solvents having different boiling points. The pores formed by the pore-forming agent and the pores formed by the combination of dilution solvents having different boiling points are difficult to communicate with the pores derived from the hollow-forming particles. Therefore, even when pores that are not covered with the outer shell 5 are included, coarse pores are hardly generated in the insulating layer 32 due to the presence of the pores covered with the outer shell 5.

(Varnish application process)
In the varnish application step, after the insulating layer forming varnish prepared in the varnish preparation step is applied to the outer peripheral surface of the conductor 1, the application amount of the varnish of the conductor 1 is adjusted and the applied varnish surface is smoothed by an application die. I do.

  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 32 becomes uniform and uniform electrical insulation is obtained.

(Heating process)
Next, in the above heating step, the insulating layer 32 is formed on the surface of the conductor 1 by passing the conductor 1 coated with the insulating layer forming varnish through a baking furnace and baking the insulating layer forming varnish. At the time of baking, the thermally decomposable resin of the core of the hollow forming particles contained in the insulating layer forming varnish is gasified by thermal decomposition, and the gasified thermally decomposable resin passes through the shell and is scattered. Thus, the core of the hollow particles is removed by heating during baking. As a result, hollow particles (shell-only particles) derived from the hollow-forming particles are formed in the insulating layer 32, and pores 4 due to the hollow particles are formed in the insulating layer 2. Thus, the said heating process doubles as the baking process of the insulating layer formation varnish.

  The insulated wire 30 is obtained by repeating the varnish coating step and the heating step until the insulating layer 32 laminated on the surface of the conductor 1 has a predetermined thickness.

  In addition, you may perform the said heating process before a varnish preparation process. In this case, for example, by heating the hollow-forming particles using a thermostat or the like, the thermally decomposable resin of the core is gasified by thermal decomposition to obtain hollow-forming particles from which the core has been removed, that is, hollow particles. In the varnish preparation step, hollow particles are dispersed in the resin composition forming the matrix of the insulating layer 32 to prepare an insulating layer forming varnish. Even after the coating and baking of the insulating layer forming varnish, the hollow forming particles from which the core has been removed, that is, the hollow structure of the hollow particles are maintained. 4 can be formed. However, when performing a heating process before a varnish preparation process in this way, the process of baking the varnish for insulating layer formation is performed after a varnish application process separately from a heating process.

  Thus, when performing a heating process before a varnish preparation process, compared with the case where the core of hollow formation particle | grains is lose | disappeared by the heating at the time of baking, it is easy to lose | disappear a core more reliably. Therefore, pores can be more reliably formed in the insulating layer 32, and foaming of the insulating layer 32 due to the decomposition gas of the thermally decomposable resin can be suppressed.

<Advantages>
In the insulated wire 30, silicone contained in the outer shell 5 is denatured into silica by heat dissipation when a surge voltage is applied. Accordingly, since the silica derived from silicone is present in the insulating layer 32 after heat radiation once, the insulated wire 30 uniformly improves the surge resistance of the insulating layer 32 and maintains the product life while maintaining the manufacturability. It can be significantly improved.

  Further, in the insulated wire 30, the pores 4 included in the insulating layer 32 are surrounded by the outer shell 5, and even if the outer shell 5 comes into contact, the pores 4 are difficult to communicate with each other, so that coarse pores are not easily generated. Thereby, the said insulated wire 30 can raise the porosity of the insulating layer 32, suppressing the fall of 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

  The configurations of the above embodiments can be appropriately combined. For example, in the insulated wire of the first embodiment or the second embodiment, at least one of the insulating layers may have the bubbles of the third embodiment.

  In the third embodiment, the insulated wire in which one insulating layer is laminated on the outer circumferential surface of the conductor has been described. However, an insulated wire in which a plurality of insulating layers are laminated on the outer circumferential surface of the conductor may be used. That is, one or a plurality of other insulating layers may be laminated between the conductor 1 in FIG. 3 and the insulating layer 32 including the pores 4, and 1 is provided on the outer peripheral surface of the insulating layer 32 including the pores 4 in FIG. 3. Alternatively, a plurality of other insulating layers may be stacked, or one or a plurality of other insulating layers may be stacked on both the outer peripheral surface and the inner peripheral surface of the insulating layer 32 including the pores 4 in FIG.

  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-treated layer is preferably 30 μm and more preferably 20 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Examples 1 to 5]
First, copper was cast, drawn, drawn and softened to obtain a conductor having a circular cross section and an average diameter of 1 mm. An average thickness shown in Table 1 is obtained by applying and baking a varnish containing polyamideimide and a silicone filler (polymethylsilsesquioxane particles; polymethyltrimethoxysilane powder) shown in Table 1 on the outer peripheral surface of the conductor. Insulating wires of Examples 1 to 5 were obtained. In the insulated wires of Examples 4 and 5, the insulating layer had a two-layer structure of a lower layer and an upper layer, and a silicone filler was contained only in one of the lower layer and the upper layer. In addition, content of the filler in Table 1 is a content rate with respect to 100 mass parts of polyamideimides.

[Example 6]
Insulated wires were obtained in the same manner as in Examples 1 to 3, except that a varnish containing hollow-forming particles having an average particle diameter of 2 Pm and a core of PMMA and silicone was used instead of the silicone filler.

[Comparative Example 1]
Insulated wires were obtained in the same manner as in Examples 1 to 3, except that the varnish for forming the insulating layer did not contain a silicone filler.

[Comparative Example 2]
An insulated wire was obtained in the same manner as in Examples 1 to 3, except that the silica filler shown in Table 1 was used instead of the silicone filler.

[Evaluation]
The following evaluation was performed about Examples 1-5 and Comparative Examples 1 and 2. The results are shown in Table 1.

<Varnish stability>
After the insulating layer forming varnishes of Examples 1 to 5 and Comparative Example 2 were stored at 25 ° C. for 30 days, the appearance of the varnish was confirmed. The case where there was no difference in the density of the solution between the upper layer and the lower layer of the varnish was designated as A, and the case where there was a difference in shade such as sedimentation was designated as B.

<Flexibility>
In accordance with “winding test” defined in 5.1 of JIS-C3216-3 (2011), the insulated wires of Examples 1 to 5 and Comparative Examples 1 and 2 are rounded with the same diameter while being stretched by 0%. A sample was wound 30 times along the rod and A was not cracked, and B was cracked.

<Vt characteristics (h)>
For the insulated wires of Examples 1 to 5 and Comparative Examples 1 and 2, a sine wave voltage of 10 kHz and 1 kV was applied to a sample obtained by twisting the same insulated wires in pairs, and the time until short-circuiting (maximum 100 hours) was measured. did.

  From Table 1, Examples 1-6 provided with the insulating layer containing silicone are excellent in Vt characteristic, having an equivalent BDV with respect to the comparative example 1 in which an insulating layer does not contain silicone. In Comparative Example 2 in which silica was contained in the insulating layer, although the Vt characteristic was high, sedimentation occurred in the varnish, making it difficult to handle, and the flexibility of the obtained insulated wire was insufficient. . From these, it can be seen that the inclusion of silicone in the insulating layer can increase the surge resistance of the insulating layer uniformly while maintaining the manufacturability, thereby significantly improving the product life.

[Confirmation of modification to silica]
In the part (test piece 1) where the white powder of the insulating layer of the insulated wire of Example 2 after the Vt characteristic test was deposited and the insulating layer (test piece 2) of the insulated wire of Example 2 before the test On the other hand, XPS analysis was performed using “Quantera SXM” manufactured by ULVAC PHI. The results (atomic concentration) are shown in Table 2.

As shown in Table 2, in the insulated wire (test piece 1) in which a short circuit occurred, more silica (SiO ₂ ) was detected than in the insulation layer (test piece 2) before the test, and the silicone was modified to silica. It was confirmed that

  Since the insulated wire according to the present invention is excellent in surge resistance while maintaining manufacturability, it can be suitably used for forming coils, motors, and the like.

DESCRIPTION OF SYMBOLS 1 Conductor 2, 22, 32 Insulating layer 3 Silicone 4 Pore 5 Outer shell 10, 20, 30 Insulated wire 22a Inner layer 22b Outer layer

Claims (4)

An insulated wire comprising a linear conductor and one or more insulating layers laminated on the outer peripheral surface of the conductor,
The insulating layer contains silicone ;
At least one of the insulating layers is mainly composed of silicone,
An insulated wire in which a primer treatment layer is provided between the conductor and the insulating layer . An insulated wire comprising a linear conductor and a plurality of insulating layers laminated on the outer peripheral surface of the conductor,
The insulating layer contains silicone;
An insulated wire in which at least one of the outermost layer and the intermediate layer in the plurality of insulating layers contains silicone as a main component. The insulated wire according to claim 1 or 2 , wherein at least one of the insulating layers contains a matrix and silicone dispersed in the matrix. The insulated wire according to claim 1 or 2 , wherein at least one of the insulating layers contains a plurality of pores and an outer shell of a peripheral portion of the pores, and the outer shell contains silicone as a main component.

Images