JP2016110801A - Insulated electric wire and method for producing insulated electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated electric wire that achieves a low dielectric constant while at the same time maintaining mechanical strength and flexibility.SOLUTION: The insulated electric wire has a linear conductor and an insulation layer coated onto an outer peripheral surface side of the conductor. The insulation layer has a sea phase and an island phase scattered in the sea phase to form a sea-island structure. The island phase includes pores and the porosity of the island phase is higher than that of the sea phase. The porosity of the island phase is preferably not less than 5 vol% to not more than 80 vol% and the porosity of the sea phase is preferably less than 5 vol%. The average size of the pores is preferably not less than 0.1 μm to not more than 10 μm. The ratio of the volume of the island phase to the total volume of the insulation layer is preferably not less than 20% to not more than 60%. The average thickness of the insulation layer is preferably not less than 30 μm to not more than 200 μm. The average size of the island phase is preferably not more than 50% of the average thickness of the insulation layer.SELECTED DRAWING: Figure 1

Description

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

  In an electric device having a high applied voltage, such as a motor used at a high voltage, a high voltage is applied to an insulated wire constituting the electric device, and partial discharge (corona discharge) is likely to occur 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 portions become pores. Low dielectric constant of insulating coating is realized.

JP 2012-224714 A

  In the conventional insulated wire, pores are formed directly in the coating film forming resin forming the insulating film. That is, pores in contact with the inner wall surface of the coating film constituting resin are formed. For this reason, the pores are easily distorted, and the coating film-constituting resin is affected by the distortion of the pores, and the flexibility may be impaired.

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

  An insulated wire according to an aspect of the present invention made to solve the above problems is an insulated wire comprising a linear conductor and an insulating layer coated on an outer peripheral surface side of the conductor, and the insulating layer However, a sea island structure is formed by having a sea phase and island phases scattered in the sea phase, the island phase includes pores, and the porosity of the island phase is higher than the porosity of the sea phase. .

  Another method for producing an insulated wire according to one aspect of the present invention is a method for producing an insulated wire comprising a linear conductor and an insulating layer having a sea-island structure coated on the outer peripheral surface side of the conductor, The island phase is formed rather than the compatibility with the main polymer forming the sea phase in the main polymer forming the sea phase of the insulating layer and the main polymer forming the island phase of the insulating layer diluted with a solvent. It includes a step of preparing a varnish by mixing a foaming agent having higher compatibility with the main polymer, a step of applying the varnish to the outer peripheral surface of the conductor, and a step of baking the varnish.

  A method for producing an insulated wire according to another aspect of the present invention is a method for producing an insulated wire comprising a linear conductor and an insulating layer having a sea-island structure coated on the outer peripheral surface side of the conductor, A step of kneading the resin composition forming the sea phase of the insulating layer with the resin composition forming the island phase of the insulating layer and containing a foaming agent or a hollow filler; and And a step of extruding to cover the surface.

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

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

[Description of Embodiment of the Present Invention]
An insulated wire according to an aspect of the present invention is an insulated wire including a linear conductor and an insulating layer coated on an outer peripheral surface side of the conductor, and the insulating layer includes a sea phase and the sea phase. The island phase scattered in the inside forms a sea-island structure, the island phase includes pores, and the porosity of the island phase is higher than the porosity of the sea phase.

  In the insulated wire, when the island phase of the sea-island structure formed in the insulating layer includes pores, the insulating layer can have a low dielectric constant, and the corona discharge starting voltage is improved. In addition, the insulated wire is locally present in the insulating layer because the pores are mainly in the island phase, so that the expansion and contraction of the sea phase due to the distortion of the pores compared to the insulating layer having a structure in which the pores are entirely included. The suppression effect of characteristics can be reduced, and the flexibility of the insulating layer can be maintained. Moreover, the said insulated wire maintains the mechanical strength excellent in the sea phase whose porosity is lower than an island phase. Here, the “porosity” means a percentage of the volume of the pores in the island phase or the sea phase with respect to the volume including the pores of the island phase or the sea phase.

  The porosity of the island phase is preferably 5% by volume or more and 80% by volume or less. Thus, by setting the porosity of the island phase within the above range, the dielectric constant of the insulating layer can be reliably reduced, and the corona discharge start voltage can be more reliably improved.

  The porosity of the sea phase is preferably less than 5% by volume. Thus, by making the porosity of the sea phase less than the above upper limit, it is possible to suppress the influence of a decrease in mechanical strength due to the pores in the sea phase, and to maintain the mechanical strength of the insulating layer more reliably.

  The average diameter of the pores is preferably 0.1 μm or more and 10 μm or less. Thus, by setting the average diameter of the pores within the above range, it is possible to suppress the local increase in the dielectric constant of the insulating layer, and it is possible to more reliably maintain the corona discharge start voltage at a high value. Here, the “average diameter of the pores” means an average value of the diameter of the true sphere corresponding to the volume of the pores.

  The volume ratio of the island phase to the total volume of the insulating layer is preferably 20% or more and 60% or less. Thus, by setting the volume ratio of the island phase within the above range, the dielectric constant of the insulating layer can be lowered and the mechanical strength and flexibility can be more reliably maintained.

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

  The average diameter of the island phase is preferably 50% or less of the average thickness of the insulating layer. Thus, by setting the average diameter of the island phase to be equal to or smaller than the above upper limit, the dielectric constant of the insulating layer can be suppressed from being locally increased, and the corona discharge start voltage can be more reliably maintained at a high value. Here, the “average diameter of the island phase” means an average value of the diameter of the true sphere corresponding to the volume of the island phase including the pores.

  A method of manufacturing an insulated wire according to an aspect of the present invention is a method of manufacturing an insulated wire including a linear conductor and an insulating layer having a sea-island structure that is coated on an outer peripheral surface side of the conductor. The main polymer that forms the island phase rather than the compatibility of the main polymer that forms the sea phase and the main polymer that forms the island phase of the insulating layer with a solvent. A step of preparing a varnish by mixing a foaming agent having higher compatibility with the above, a step of applying the varnish to the outer peripheral surface of the conductor, and a step of baking the varnish.

  The method for producing the insulated wire is to prepare a varnish mixed with a foaming agent having a higher compatibility with the main polymer that forms the island phase than with the main polymer that forms the sea phase. Since the surface is coated and baked, an insulating layer having a sea-island structure in which the porosity of the island phase is higher than the porosity of the sea phase can be formed. Thereby, in the insulated wire manufactured by the method for manufacturing the insulated wire, the dielectric constant of the insulating layer is reduced, and the corona discharge start voltage is improved. In addition, the insulated wire produced by the method for producing an insulated wire is locally present in the insulating layer because the pores are mainly in the island phase. Thus, the effect of suppressing the expansion and contraction characteristics of the sea phase due to the distortion of the pores can be reduced, and the flexibility of the insulating layer is maintained. Moreover, the mechanical strength excellent in the insulated wire manufactured with the manufacturing method of the said insulated wire is maintained by the sea phase whose porosity is lower than an island phase. Here, the “main polymer” means a polymer having the highest content among the polymers forming the sea phase or the island phase.

  Another method for producing an insulated wire according to one aspect of the present invention is a method for producing an insulated wire comprising a linear conductor and an insulating layer having a sea-island structure coated on the outer peripheral surface side of the conductor, A step of kneading the resin composition forming the sea phase of the insulating layer with the resin composition forming the island phase of the insulating layer and containing a foaming agent or a hollow filler, and the kneaded product on the outer peripheral surface of the conductor And a step of extruding to coat.

  In the method for producing the insulated wire, the outer peripheral surface of the conductor is coated with a kneaded product obtained by kneading the resin composition forming the sea phase and the resin composition forming the island phase and containing the foaming agent or the hollow filler. Since extrusion is performed, pores are formed in the island phase by the foaming agent or the hollow filler, and an insulating layer having a sea-island structure in which the porosity of the island phase is higher than the porosity of the sea phase can be formed. Thereby, in the insulated wire manufactured by the method for manufacturing the insulated wire, the dielectric constant of the insulating layer is reduced, and the corona discharge start voltage is improved. In addition, the insulated wire produced by the method for producing an insulated wire is locally present in the insulating layer because the pores are mainly in the island phase. Thus, the effect of suppressing the expansion and contraction characteristics of the sea phase due to the distortion of the pores can be reduced, and the flexibility of the insulating layer is maintained. Moreover, the mechanical strength excellent in the insulated wire manufactured with the manufacturing method of the said insulated wire is maintained by the sea phase whose porosity is lower than an island phase.

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

[Insulated wire]
The insulated wire in FIG. 1 includes a linear conductor 1 and an insulating layer 2 that covers the outer peripheral surface of the conductor 1. The insulating layer 2 has a sea-island structure by having a sea phase 3 and island phases 4 scattered in the sea phase 3. The island phase 4 includes pores 5, and the sea phase 3 does not include pores. That is, the porosity of the sea phase 3 is 0, the porosity of the island phase 4 is more than 0, and is higher than the porosity of the sea phase 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, iron, steel, and stainless steel. The conductor 1 is a material in which these metals are formed in a linear shape, or a multilayer structure in which such a linear material is coated with another metal, such as a nickel-coated copper wire, a silver-coated copper wire, or a copper-coated aluminum. Wire, copper-coated steel wire, etc. can be used.

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

<Insulating layer>
As shown in FIG. 1, the insulating layer 2 includes a sea phase 3 and island phases 4 scattered in the sea phase 3 to form a sea-island structure.

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

(Sea phase)
The sea phase 3 is formed of an insulating resin composition. As shown in FIG. 1, there are no pores in the sea phase 3.

  The main component resin of the resin composition forming the sea phase 3 is not particularly limited. For example, polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy, thermosetting polyester, thermosetting polyester imide, thermosetting polyester. Thermosetting resins such as amideimide, aromatic polyamide, thermosetting polyamideimide, and thermosetting polyimide, and thermoplastic resins such as polyetherimide, polyetheretherketone, and polyethersulfone can be used. Here, the “main component” is a component having the largest content, for example, a component contained in an amount of 50% by mass or more.

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

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

(Island Phase)
As shown in FIG. 1, the island phases 4 are scattered in the sea phase 3 and include pores 5 therein.

  The island phase 4 is formed of an insulating resin composition. The resin as the main component of the resin composition forming the island phase 4 is not particularly limited. For example, polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy, thermosetting polyester, thermosetting polyester imide, thermosetting polyester amide Thermosetting resins such as imide, aromatic polyamide, thermosetting polyamideimide, and thermosetting polyimide, and thermoplastic resins such as polyetherimide, polyetheretherketone, and polyethersulfone can be used. However, in order to disperse the island phase 4 in the sea phase 3, it is preferable to use a resin having a low compatibility with the resin of the main component of the sea phase 3 as the resin of the main component of the island phase 4.

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

  The lower limit of the volume ratio of the island phase 4 to the total volume of the insulating layer 2 is preferably 20% and more preferably 30%. On the other hand, the upper limit of the volume ratio of the island phase 4 is preferably 60%, and more preferably 50%. When the volume ratio of the island phase 4 is less than the lower limit, the dielectric constant of the insulating layer 2 may not be sufficiently lowered. On the contrary, when the volume ratio of the island phase 4 exceeds the upper limit, there is a possibility that sufficient mechanical strength of the insulating layer 2 cannot be secured.

  The upper limit of the average diameter of the island phase 4 with respect to the average thickness of the insulating layer 2 is preferably 50%, more preferably 30%. On the other hand, the lower limit of the average diameter of the island phase 4 with respect to the average thickness of the insulating layer 2 is preferably 1% and more preferably 2%. When the average diameter of the island phase 4 with respect to the average thickness of the insulating layer 2 exceeds the upper limit, the distribution of the island phase 4 in the sea phase 3 is likely to be biased, and as a result, the distribution of the pores 5 in the insulating layer 2 is The bias and the dielectric constant distribution are likely to be biased. On the contrary, when the average diameter of the island phase 4 with respect to the average thickness of the insulating layer 2 is less than the lower limit, the pores 5 are easily in direct contact with the sea phase 3, and the effect of improving the mechanical strength by the sea phase 3 is reduced. There is a risk.

<Porosity>
The pore 5 exists in the island phase 4 as shown in FIG. The pore 5 has a resin composition that forms a sea phase 3 with this resin composition by adding a foaming agent to the resin composition that forms the island phase 4, for example, as in a second manufacturing method of an insulated wire described later. It can be generated by covering the conductor 1 with a kneaded product obtained by kneading a product and foaming a foaming agent. Moreover, it replaces with the said foaming agent, a hollow filler may be included in the resin composition which forms the said island phase 4, and the pore 5 may be formed with a hollow filler.

  When the pores 5 are formed by the hollow filler, the hollow portion inside the hollow filler becomes the pores 5 of the insulated wire. Examples of the hollow filler include shirasu balloons, glass balloons, ceramic balloons, and organic resin balloons. When flexibility is required for the insulated wire, an organic resin balloon is preferable among them. In the case of an insulated wire in which mechanical strength is important, a glass balloon is preferable because it is easily available and is not easily damaged.

  As a minimum of the porosity of island phase 4, 5 volume% is preferred and 10 volume% is more preferred. On the other hand, the upper limit of the porosity of the island phase 4 is preferably 80% by volume, and more preferably 50% by volume. When the porosity of the island phase 4 is less than the lower limit, the dielectric constant of the insulating layer 2 is not sufficiently lowered, and the corona discharge start voltage may not be sufficiently improved. On the other hand, when the porosity of the island phase 4 exceeds the upper limit, sufficient mechanical strength of the insulating layer 2 may not be ensured.

  The lower limit of the average diameter of the pores 5 is preferably 0.1 μm, and more preferably 1 μm. On the other hand, the upper limit of the average diameter of the pores 5 is preferably 10 μm, and more preferably 8 μm. When the average diameter of the pores 5 is less than the above lower limit, the formation of the pores 5 may be difficult. On the contrary, when the average diameter of the pores 5 exceeds the upper limit, it is difficult to make the distribution of the pores 5 in the insulating layer 2 uniform, and the distribution of the dielectric constant is likely to be biased.

[First manufacturing method of insulated wire]
Next, the 1st manufacturing method of the said insulated wire is demonstrated. The first manufacturing method of the insulated wire is obtained by diluting the main polymer forming the sea phase 3 of the insulating layer 2 and the main polymer forming the island phase 4 of the insulating layer 2 with a solvent. A step of preparing a varnish by mixing a foaming agent having a higher compatibility with the main polymer that forms the island phase 4 than a compatibility with the main polymer that forms the phase 3 (varnish preparation step); The process of apply | coating to the outer peripheral surface of 1 (varnish application process), and the process (baking process) of baking the said varnish are provided.

<Varnish preparation process>
In the varnish preparation step, a varnish is prepared by further mixing a foaming agent with the main polymer forming the sea phase 3 and the main polymer forming the island phase 4 diluted with a solvent.

As the foaming agent to be mixed with the varnish, a chemical foaming agent is preferable. For example, a thermally decomposable substance such as azobisisobutyronitrile that generates nitrogen gas (N ₂ gas) by heating is suitably used.

  Moreover, the said foaming agent uses the thing whose compatibility with the main polymer which forms the island phase 4 is higher than the compatibility with the main polymer which forms the sea phase 3. Thereby, the foaming agent can be included in the main polymer that forms the island phase 4 in the varnish, and the pores 5 can be formed only in the island phase 4.

The upper limit of the difference between the solubility parameter (SP value) of the blowing agent and the SP value of the main polymer forming the island phase 4 is preferably 3, and more preferably 2. When the difference in SP value exceeds the above upper limit, the compatibility between the foaming agent and the main polymer forming the island phase 4 decreases, and the foaming agent moves from the main polymer forming the island phase 4 into the sea phase 3. It becomes easy to do. Here, the “solubility parameter (SP value)” is a parameter that is a measure of the solubility of a binary solution defined by the regular solution theory introduced by Hildebrand, and is the SP value of the two components. It is empirically known that the smaller the difference, the higher the solubility. Here, the solubility parameter δ is the square root of the cohesive energy density CED (Cohesive Energy Density), and is obtained by the following formula (1). CED is the amount of energy required to evaporate 1 ml. In the following formula (1), E is the molecular cohesive energy (cal / mol), and E = Σei when the evaporation energy ei is used. V is molecular volume (cm ³ / mol), and V = Σvi (vi: molar volume).
Solubility parameter δ = (CED) ^1/2 = (E / V) ^1/2 (1)

  Moreover, as a minimum of the difference of SP value of the said foaming agent, and SP value of the main polymer which forms the said sea phase 3, 5 is preferable and 7 is more preferable. When the difference between the SP values is less than the lower limit, the compatibility between the foaming agent and the main polymer forming the sea phase 3 is improved, and the foaming agent easily enters the main polymer forming the sea phase 3.

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

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

  In addition, as a minimum of the resin solid content density | concentration of the varnish prepared by diluting with these organic solvents, 20 mass% is preferable and 22 mass% is more preferable. On the other hand, the upper limit of the resin solid content concentration of the varnish is preferably 50% by mass, more preferably 30% by mass. When the resin solid content concentration of the varnish is less than the lower limit, the amount of application at one time when applying the varnish decreases, and therefore the number of repetitions of the varnish application step for forming the insulating layer 2 having a desired thickness is reduced. There is a risk that the time for the varnish application process will be increased. On the contrary, when the resin solid content concentration of the varnish exceeds the upper limit, it is difficult to uniformly mix the main polymer that forms the sea phase 3, the main polymer that forms the island phase 4, and the foaming agent, and the time required for dilution is long. There is a risk.

<Varnish application process>
In the varnish application step, after the 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.

  The coating die has an opening. When the conductor 1 coated with the 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 uniform and uniform electrical insulation is obtained.

<Baking process>
Next, in the baking step, the conductor 1 coated with the varnish is passed through a baking furnace to burn the varnish, thereby forming the insulating layer 2 on the surface of the conductor 1. At the time of baking, the foaming agent contained in the varnish is foamed, and pores 5 are mainly generated in the island phase 4.

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

  In addition, in the first manufacturing method of the insulated wire described above, instead of the varnish prepared by mixing the foaming agent, the compatibility with the main polymer that forms the island phase 4 rather than the compatibility with the main polymer that forms the sea phase 3 You may manufacture the said insulated wire using the varnish prepared by mixing the heat-decomposable resin with higher compatibility. That is, in the varnish preparation step, the main polymer forming the sea phase 3 and the main polymer forming the island phase 4 are diluted with a solvent, and a thermally decomposable resin is further mixed to prepare a varnish.

  A resin having higher compatibility with the main polymer forming the island phase 4 than the main polymer forming the sea phase 3 is used as the thermally decomposable resin. Thereby, in the varnish, the main polymer forming the island phase 4 can be encapsulated in the thermally decomposable resin, and the pores 5 generated by the thermal decomposition of the thermally decomposable resin are mainly contained only in the island phase 4. Can be formed.

  As the thermally decomposable resin, for example, resin particles that thermally decompose at a temperature lower than the baking temperature of the main polymer that forms the island phase 4 are used. The baking temperature of the main polymer forming the island phase 4 is appropriately set according to the type of resin, but is usually about 200 ° C. or higher and 350 ° C. or lower. Accordingly, the lower limit of the thermal decomposition temperature of the thermally decomposable resin used for the varnish is preferably 200 ° C., and the upper limit is preferably 300 ° C. Here, the thermal decomposition temperature means a temperature at which the temperature is increased from room temperature to 10 ° C./min in a nitrogen atmosphere and the mass reduction rate becomes 50%. The thermal decomposition temperature can be measured, for example, by measuring the thermogravimetry using a thermogravimetry-differential thermal analyzer (“TG / DTA” manufactured by SII Nano Technology Co., Ltd.).

  The heat-decomposable resin used in the varnish is not particularly limited, but 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, poly (meta) ) Alkyl ester polymer of 1 to 6 carbon atoms of (meth) acrylic acid, such as methyl acrylate, poly (meth) ethyl acrylate, poly (meth) acrylic acid propyl, poly (meth) acrylic acid butyl, urethane oligomer , Urethane polymer, urethane (meth) acrylate, epoxy (meth) acrylate, polymer of modified (meth) acrylate such as ε-caprolactone (meth) acrylate, poly (meth) acrylic acid, cross-linked products thereof, polystyrene, cross-linked polystyrene Etc. Among these, a crosslinked product of a (meth) acrylic polymer is preferable, and a crosslinked poly (meth) acrylate is more preferable. Moreover, it is preferable that the thermally decomposable resin can be evenly distributed in the main polymer forming the island phase 4. Accordingly, the thermally decomposable resin used for the varnish is preferably a resin that is excellent in compatibility with the main polymer that forms the island phase 4 and is formed into a spherical shape, and specifically, a crosslinked resin.

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

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

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

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

  When using the resin particles to be thermally decomposed, the resin particles are preferably spherical. The lower limit of the average particle diameter of the resin particles is preferably 0.1 μm, more preferably 0.5 μm, and even more preferably 1 μm. On the other hand, the upper limit of the average particle diameter of the resin particles is preferably 100 μm, more preferably 50 μm, further preferably 30 μm, and particularly preferably 10 μm. The resin particles are thermally decomposed when the varnish is baked to form pores 5 in the portions existing in the main polymer forming the island phase 4. Therefore, when the average particle diameter of the resin particles is less than the lower limit, it is difficult to form pores in the insulating layer 2. On the contrary, when the average particle diameter of the resin particles exceeds the upper limit, the distribution of the pores 5 in the insulating layer 2 is difficult to be uniform, and the distribution of the dielectric constant is likely to be biased. Here, the average particle diameter of the resin particles means a particle diameter showing the highest volume content in the particle size distribution measured with a laser diffraction particle size distribution measuring apparatus.

  As a solvent for dilution, the same kind as that used for the varnish prepared by mixing the above-mentioned foaming agent can be used. Moreover, the resin solid content density | concentration of the varnish prepared by diluting with an organic solvent can be made the same as the resin solid content density | concentration of the varnish adjusted by mixing the foaming agent mentioned above.

  After the varnish is prepared by mixing the thermally decomposable resin, the varnish prepared by mixing the thermally decomposable resin is applied to the outer peripheral surface of the conductor 1 in the same manner as the varnish applying step, and then applied. The application amount of the varnish of the conductor 1 is adjusted by a die and the applied varnish surface is smoothed.

  Next, in the baking step, the conductor 1 coated with the varnish is passed through a baking furnace, and the varnish is baked, so that the thermally decomposable resin contained in the varnish is thermally decomposed to form the island phase 4. The pore 5 is produced | generated in the part in which the thermally decomposable resin existed.

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

[Second manufacturing method of insulated wire]
Next, the 2nd manufacturing method of the said insulated wire is demonstrated. The second method for producing the insulated wire includes a resin composition that forms the sea phase 3 of the insulating layer 2 and a resin composition that forms the island phase 4 of the insulating layer 2 and includes a foaming agent or a hollow filler. And a step of extruding the outer periphery of the conductor 1 (insulating layer coating step).

<Kneaded product production process>
In the kneaded product forming step, the island phase 4 and the resin composition forming the sea phase 3 are formed so that the resin composition forming the island phase 4 is uniformly dispersed in the resin composition forming the sea phase 3. The resin composition to be kneaded is kneaded.

  The resin composition forming the island phase 4 contains a foaming agent or a hollow filler. That is, the resin composition forming the island phase 4 is obtained by kneading the main polymer forming the island phase 4 and the foaming agent or the hollow filler before kneading with the resin composition forming the sea phase 3. .

  As the foaming agent contained in the resin composition forming the island phase 4, the same type of foaming agent as that used in the first method for producing an insulated wire can be used.

  Moreover, it is preferable to use the said hollow filler whose compatibility with the main polymer of the resin composition which forms the island phase 4 is higher than compatibility with the main polymer of the resin composition which forms the sea phase 3. . Thereby, it can suppress that the hollow filler contained in the island phase 4 moves into the sea phase 3.

  The upper limit of the difference between the SP value of the outer shell of the hollow filler and the SP value of the main polymer of the resin composition forming the island phase 4 is preferably 3, and more preferably 2. When the difference in SP value exceeds the upper limit, the compatibility between the hollow filler and the resin composition forming the island phase 4 decreases, and the hollow filler forms the island phase 4 from the resin composition in the sea phase 3. It becomes easy to move to.

  Moreover, as a minimum of the difference of SP value of the outer shell of a hollow filler, and SP value of the main polymer of the resin composition which forms the said sea phase 3, 5 is preferable and 7 is more preferable. When the difference in SP value is less than the lower limit, the compatibility between the hollow filler and the resin composition forming the sea phase 3 is improved, and the hollow filler easily enters the resin composition forming the sea phase 3.

  Moreover, since the insulating layer 2 is formed by extrusion molding in the second manufacturing method of the insulated wire, it is preferable to use a thermoplastic resin as the main polymer of the resin composition for forming the sea phase 3 and the island phase 4.

<Insulating layer coating process>
In the insulating layer coating step, after the kneaded product obtained in the kneaded product generating step is put into a melt extruder, the insulating layer 2 is formed by extruding the outer peripheral surface of the conductor 1 by extrusion molding. And forming the insulated wire.

  When the resin composition forming the island phase 4 contains a foaming agent, the foaming agent foams by heating at the time of extrusion for softening the resin composition forming the sea phase 3 and the island phase 4, and the inside of the island phase 4 The pores 5 are generated.

  When the resin composition forming the island phase 4 includes a hollow filler, the hollow filler is present in the island phase 4 of the insulating layer 2, and the hollow portion inside the hollow filler becomes the pores 5.

[advantage]
In the insulated wire, when the island phase 4 of the sea-island structure formed in the insulating layer 2 includes the pores 5, the dielectric constant of the insulating layer 2 can be reduced and the corona discharge starting voltage can be improved. Moreover, since the said insulated wire has the island phase 4 containing the pore 5, and the sea phase 3 which does not contain a pore, since a pore exists locally in the insulating layer 2, the insulation of the structure by which a pore is contained entirely Compared to the layer, it is possible to reduce the effect of suppressing the expansion and contraction characteristics of the sea phase 3 due to the distortion of the pores, and the flexibility of the insulating layer can be maintained. Moreover, since the sea wire 3 does not include pores 5 in the insulated wire, excellent mechanical strength is maintained by the sea phase 3.

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

  That is, in the above-described embodiment, the configuration in which the pores 5 are included only in the island phase 4 and not in the sea phase 3 has been described. However, if the island phase has a higher porosity than the sea phase, the ocean phase May contain pores. Even when pores are contained in the sea phase, the pores contained in the sea phase and the island phase can achieve the effect of lowering the dielectric constant, and the dielectric constant of the insulating layer can be lowered. In addition, since the pores are mainly in the island phase and locally exist in the insulating layer, the sea phase expansion and contraction characteristics due to the distortion of the pores can be suppressed compared to the insulating layer having the pores as a whole. And the flexibility of the insulating layer can be maintained. In addition, since the porosity of the sea phase is lower than the porosity of the island phase, the effect of improving the mechanical strength by the pores contained in the sea phase is small, and the excellent mechanical strength of the insulating layer can be maintained. . Here, “the porosity of the sea phase” means the percentage of the volume of the pores in the sea phase with respect to the volume including the pores in the sea phase but not the island phase.

  The porosity of the sea phase is preferably less than 5% by volume and more preferably less than 2% by volume. When the porosity of the sea phase 3 is greater than or equal to the above upper limit, the action of suppressing the mechanical strength improvement effect due to the pores contained in the sea phase is increased, and the mechanical strength of the insulating layer may not be sufficiently maintained.

  Moreover, although the manufacturing method which produces | generates a pore using a foaming agent was demonstrated in the said embodiment, it is good also as a manufacturing method which uses a thermally expansible microcapsule as a foaming agent and forms pores with a thermally expansible microcapsule. . For example, in the first production method, a varnish is prepared by mixing a thermally expandable microcapsule with a main polymer that forms a sea phase and a main polymer that forms an island phase diluted with a solvent. May be applied and baked on the outer peripheral surface of the conductor to form an insulating layer. During baking, the thermally expandable microcapsules contained in the varnish expand or foam, and pores are generated by the thermally expandable microcapsules. In this case, the compatibility between the main polymer forming the island phase and the outer shell of the thermally expandable microcapsule is higher than the compatibility between the main polymer forming the sea phase and the outer shell of the thermally expandable microcapsule. A main polymer that forms an island phase, a main polymer that forms a sea phase, and a thermally expandable microcapsule are used.

  Further, for example, in the second manufacturing method, the resin composition forming the sea phase and the resin composition forming the island phase including the thermally expandable microcapsules are kneaded, and the kneaded material is coated on the outer peripheral surface of the conductor. The insulating layer may be formed by extrusion. The heat-expandable microcapsule contained in the resin composition forming the island phase expands or foams by heating during extrusion to soften the resin composition that forms the sea phase and the island phase. Pores are generated.

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

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

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

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

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

  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. When the average thickness of the primer treatment layer is less than the above lower limit, there is a possibility that sufficient adhesion with the conductor cannot be exhibited. Conversely, when the average thickness of the primer-treated layer exceeds the above upper limit, the insulated wire may be unnecessarily increased in diameter.

  Further, for example, in the insulated wire, a second insulating layer that further has insulating properties and does not include pores may be laminated on the outer peripheral surface side of the insulating layer. As a resin composition which forms a 2nd insulating layer, what has the same kind as resin mentioned as a main component of the resin composition of the sea phase mentioned above as a main component can be used. Since the second insulating layer does not contain pores and is excellent in insulation, the insulation of the insulated wire is further improved by forming the second insulating layer as the outermost layer.

  When the second insulating layer is formed, the thickness of the second insulating layer can be freely designed according to the required characteristics of the breakdown voltage, but as a lower limit of the average thickness of the second insulating layer, for example, 0.5 μm is preferable, and 1 μm is more preferable. On the other hand, the upper limit of the average thickness of the second insulating layer is preferably 20 μm, for example, and more preferably 15 μm. When the average thickness of the second insulating layer is less than the above lower limit, there is a possibility that the effect of improving the insulating property may not be sufficiently obtained although the manufacturing process is complicated. Conversely, when the average thickness of the second insulating layer exceeds the upper limit, the insulated wire becomes too thick, and the volume efficiency of a coil or the like formed using the insulated wire may be reduced.

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

1 Conductor 2 Insulating Layer 3 Sea Phase 4 Island Phase 5 Pore

Claims (9)

An insulated wire comprising a linear conductor and an insulating layer coated on the outer peripheral surface side of the conductor,
The said insulating layer forms a sea-island structure by having a sea phase and island phases scattered in this sea phase,
An insulated wire in which the island phase includes pores, and the porosity of the island phase is higher than the porosity of the sea phase.   The insulated wire according to claim 1, wherein the island phase has a porosity of 5% by volume to 80% by volume. Please change the upper limit.   The insulated wire according to claim 1 or 2, wherein the porosity of the sea phase is less than 5% by volume.   The insulated wire according to claim 1, wherein the average diameter of the pores is 0.1 μm or more and 10 μm or less.   The insulated wire according to any one of claims 1 to 4, wherein a volume ratio of the island phase to a total volume of the insulating layer is 20% or more and 60% or less.   The insulated wire according to any one of claims 1 to 5, wherein an average thickness of the insulating layer is not less than 30 µm and not more than 200 µm.   The insulated wire according to any one of claims 1 to 6, wherein an average diameter of the island phase is 50% or less of an average thickness of the insulating layer. A method for producing an insulated wire comprising a linear conductor and an insulating layer having a sea-island structure coated on the outer peripheral surface side of the conductor,
The island phase is formed rather than the compatibility with the main polymer that forms the sea phase in the main polymer that forms the sea phase of the insulating layer and the main polymer that forms the island phase of the insulating layer diluted with a solvent. A step of preparing a varnish by mixing a foaming agent having higher compatibility with the main polymer
A method for producing an insulated wire, comprising: applying the varnish to an outer peripheral surface of the conductor; and baking the varnish. A method for producing an insulated wire comprising a linear conductor and an insulating layer having a sea-island structure coated on the outer peripheral surface side of the conductor,
A step of kneading the resin composition forming the sea phase of the insulating layer with the resin composition forming the island phase of the insulating layer and containing a foaming agent or a hollow filler; and A method of manufacturing an insulated wire comprising a step of extruding to cover a surface.

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