JP6619614B2 - 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) 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, in addition to excellent insulation, mechanical strength, etc., an insulated wire used for an electric device having a high applied voltage is required to increase the corona discharge start voltage.

  In order to increase the corona discharge starting voltage, it is effective to reduce the dielectric constant of the insulating coating. As an insulated wire that achieves such a low dielectric constant of an insulating coating, an insulated wire having a foamed resin layer containing bubbles formed by foaming of a foaming agent on the outer peripheral surface of a conductor has been proposed (Japanese Patent Laid-Open No. 10-101). -168-248).

Japanese Patent Laid-Open No. 10-168248

  However, in the insulated wire described in the above publication, flexibility may be reduced due to the foamed resin layer, and the wire winding process may not be easy, or bubbles in the foamed resin layer are expected to be crushed during the winding process. There is a possibility that low dielectric constant cannot be realized.

  This invention is made | formed based on the above situations, and it aims at providing the insulated wire which can accelerate | stimulate low dielectric constant, suppressing the fall of flexibility.

  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, At least one of the one or more insulating layers has a matrix mainly composed of a synthetic resin and a plurality of pores dispersed in the matrix, and the average diameter of the plurality of pores is 0.1 μm. The porosity of the insulating layer having the plurality of pores is 10% by volume or more and 30% by volume or less.

  The insulated wire of the present invention can promote a reduction in dielectric constant while suppressing a decrease in flexibility.

It is a typical sectional view showing the insulated wire concerning one embodiment of the present invention. It is typical sectional drawing which shows the insulated wire which concerns on embodiment different from the insulated wire of FIG. It is typical sectional drawing which shows the insulated wire which concerns on embodiment different from the insulated wire of FIG.1 and FIG.2.

[Description of Embodiment of the Present Invention]
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, At least one of the one or more insulating layers has a matrix mainly composed of a synthetic resin and a plurality of pores dispersed in the matrix, and the average diameter of the plurality of pores is 0.1 μm. The porosity of the insulating layer having the plurality of pores is 10% by volume or more and 30% by volume or less.

  The insulated wire includes an insulating layer having a plurality of pores, and the average diameter of the plurality of pores dispersed in the matrix of the insulating layer and the porosity of the insulating layer are within the above range. A plurality of pores are likely to be distributed moderately and substantially uniformly. Therefore, the insulated wire can promote a reduction in dielectric constant while suppressing a decrease in flexibility.

  The insulating layer directly laminated on the conductor does not have pores, and the insulating layer having the plurality of pores may be laminated outside the insulating layer having no pores. As described above, the insulating layer directly laminated on the conductor does not have pores, and the insulating layer having the plurality of pores is laminated outside the insulating layer not having the pores. Adhesion with the insulating layer having pores can be increased.

  The plurality of pores may be derived from a plurality of thermally decomposable resin particles. Thus, when the plurality of pores are derived from the plurality of thermally decomposable resin particles, it is possible to prevent the insulating layer having the plurality of pores from expanding outwardly when the plurality of pores are formed. As a result, the uniform dispersibility of the plurality of pores can be improved, and the decrease in flexibility can be further suppressed.

  The insulating layer having a plurality of pores is preferably composed of one or a plurality of baking layers, and the ratio of the average diameter of the plurality of pores to the average thickness of the one baking layer is 0.05 or more and 0.9 or less. Is preferred. As described above, the insulating layer having the plurality of pores is composed of one or a plurality of baking layers, and the ratio of the average diameter of the plurality of pores to the average thickness of the one baking layer is within the above range. It is easy to further improve the uniform dispersibility of the pores and suppress the decrease in flexibility.

  The average thickness of the insulating layer having a plurality of pores is preferably 50 μm or more and 200 μm or less. The ratio of the average thickness of the insulating layer having no pores to the average thickness of the insulating layer having the plurality of pores is as follows. 0.005 to 0.35 is preferable. Thus, the ratio of the average thickness of the insulating layer having the plurality of pores and the average thickness of the insulating layer having no pores to the average thickness of the insulating layer having the plurality of pores is within the above range. It is possible to easily and reliably promote the reduction of the dielectric constant while enhancing the adhesion between the conductor and the insulating layer having a plurality of pores.

  The elongation percentage of the entire insulating layer or layers is preferably 40% or more and 150% or less. Thus, when the elongation percentage of the whole of the one or more insulating layers is within the above range, lowering of the dielectric constant can be promoted while sufficiently suppressing the decrease in flexibility.

  In the present invention, the “main component” means a component having the highest content, for example, a component contained in an amount of 50% by mass or more. “Does not have pores” means that pores are not positively formed unless they are inevitably included, for example, that there are no pores having a diameter of 0.1 μm or more. This means that there are no pores having a diameter of 01 μm or more. The “average diameter of pores” means a value obtained by calculating and averaging the diameters of true spheres corresponding to the volume of the pores for 10 pores of the insulating layer having a plurality of pores. “The porosity of the insulating layer having a plurality of pores” is a percentage of the volume of the gas in the insulating layer with respect to the volume of the insulating layer having a plurality of pores, and is a solid such as a matrix of the insulating layer having a plurality of pores. When the actual volume calculated from the mass and density of the minute is V0 and the apparent volume including the pores of the insulating layer having a plurality of pores is V1, the value calculated by (V1−V0) / V1 × 100 means. “Thermal decomposable resin particles” refers to resin particles that are decomposed by heating and at least one part disappears in the region occupied before heating. “Elongation rate of the entire insulating layer” means that a 3 cm long insulating layer peeled off from a conductor in a cylindrical shape was pulled at a tensile speed of 50 mm / min in a longitudinal direction in a 25 ° C. environment in an environment of 25 ° C. It means the elongation at break in the case.

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

[Insulated wire]
An insulated wire 1 in FIG. 1 includes a linear conductor 2 and a plurality of insulating layers (first insulating layer 3 and second insulating layer 4) stacked on the outer peripheral surface of the conductor 2.

<Conductor>
The conductor 2 is, for example, a round wire having a circular cross section, but may be a square wire having a circular cross section or a stranded wire obtained by twisting a plurality of strands.

  The material of the conductor 2 is preferably a metal having high conductivity and high mechanical strength. Examples of such metals include copper, copper alloys, aluminum, nickel, silver, soft iron, steel, and stainless steel. The conductor 2 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 2, preferably 0.01 mm ^2, 0.1 mm ² is more preferable. Moreover, as an upper limit of the average cross-sectional area of the conductor 2, 10 mm < ² > is preferable and 5 mm < ² > is more preferable. When the average cross-sectional area of the conductor 2 is less than the above lower limit, the total volume of the first insulating layer 3 and the second insulating layer 4 with respect to the conductor 2 is increased, and the volume efficiency of a coil or the like formed using the insulated wire 1 May be low. On the other hand, if the average cross-sectional area of the conductor 2 exceeds the above upper limit, the first insulating layer 3 and the second insulating layer 4 must be formed thick in order to sufficiently reduce the dielectric constant. There is a risk of increasing the diameter as necessary.

<Insulating layer>
At least one of the plurality of insulating layers (the first insulating layer 3 and the second insulating layer 4) (the second insulating layer 4 in this embodiment) includes a matrix 5 mainly composed of a synthetic resin, and the matrix 5 includes And a plurality of pores 6 to be dispersed. The plurality of pores 6 are derived from a plurality of thermally decomposable resin particles. Further, the first insulating layer 3 directly laminated on the conductor 2 does not have pores. That is, in this embodiment, the insulating layer 3 having no pores is directly laminated on the conductor 2, and the insulating layer 4 having a plurality of pores 6 is laminated outside the insulating layer 3 having no pores (note that Hereinafter, “insulating layer 4 having a plurality of pores 6” is referred to as “pore layer 4”, and “insulating layer 3 having no pores” is also referred to as “solid layer 3”). Since the plurality of pores 6 are derived from the plurality of thermally decomposable resin particles, the insulated wire 1 can suppress the expansion of the pore layer 4 when the plurality of pores 6 are formed. As a result, the insulated wire 1 can improve the uniform dispersibility of the plurality of pores 6 and can further suppress the decrease in flexibility.

  The lower limit of the average thickness of the plurality of insulating layers (the average thickness of the entire insulating layer including the solid layer 3 and the pore layer 4) is preferably 50 μm, and more preferably 80 μm. On the other hand, the upper limit of the average thickness of the plurality of insulating layers is preferably 300 μm, and more preferably 200 μm. When the average thickness of the plurality of insulating layers is less than the lower limit, the effect of increasing the corona discharge start voltage may be insufficient. Conversely, if the average thickness of the plurality of insulating layers exceeds the upper limit, the insulated wire 1 may be unnecessarily increased in diameter.

  The lower limit of the elongation rate of the entire plurality of insulating layers (the elongation rate of the entire insulating layer including the solid layer 3 and the pore layer 4) is preferably 40%, more preferably 50%, and even more preferably 70%. If the elongation percentage of the entire plurality of insulating layers is less than the lower limit, flexibility may be insufficient. In addition, although it does not specifically limit as an upper limit of the elongation rate of the whole some insulating layer, For example, it can be 150%.

  The upper limit of the relative dielectric constant of the entire plurality of insulating layers (the relative dielectric constant of the entire insulating layer including the solid layer 3 and the pore layer 4) is preferably 3.3, and more preferably 3. When the relative dielectric constant of the entire plurality of insulating layers exceeds the above upper limit, the corona discharge start voltage may not be sufficiently increased. On the other hand, the lower limit of the relative dielectric constant of the entire plurality of insulating layers is not particularly limited, but may be 1.5, for example. If the relative dielectric constant of the entire plurality of insulating layers is less than the lower limit, the breaking strength of the entire plurality of insulating layers may be insufficient. The “relative dielectric constant of the insulating layer” refers to the ratio between the dielectric constant of the insulating layer and the dielectric constant of vacuum.

(Solid layer)
The solid layer 3 is laminated between the conductor 2 and the pore layer 4 to enhance the adhesion between the conductor 2 and the pore layer 4. Further, the solid layer 3 enhances the partial discharge prevention function of the insulated wire 1.

  The solid layer 3 is mainly composed of synthetic resin. Examples of the synthetic resin include thermosetting such as phenoxy resin, butyral resin, polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy resin, thermosetting polyester, thermosetting polyester imide, thermosetting polyester amide imide, thermosetting polyamide imide, and the like. Resins, such as polyimide, polyphenylsulfone, polyphenylene sulfide, polyetherimide, polyetheretherketone, polyethersulfone, copolyester, polybutylene terephthalate, polyethylene terephthalate, thermoplastic polyurethane, polycarbonate, polyphenylene oxide, polysulfone And thermoplastic resins such as polyetherketone, semi-aromatic polyamide, aromatic polyamide, and thermoplastic polyamideimide. Among these, polyimide, polyamideimide, or polyesterimide, which can easily ensure breaking strength and heat resistance, is preferable, and polyimide is particularly preferable. The solid layer 3 may be a composite or laminate of two or more types of resin compositions, for example, a composite or laminate of a thermosetting resin and a thermoplastic resin. Furthermore, it is also possible to make a part of the thermosetting type by crosslinking by adding a thermoreactive curing agent such as epoxy resin, melamine resin, phenol resin, isocyanate or the like to the thermoplastic resin. In addition, in the case of a thermosetting resin, it can be used as a semi-cured state or a cured state by combining with a curing agent. Further, the solid layer 3 may contain additives such as an adhesion improver.

  The lower limit of the average thickness of the solid layer 3 is preferably 0.5 μm, and more preferably 1 μm. On the other hand, the upper limit of the average thickness of the solid layer 3 is preferably 40 μm, more preferably 20 μm, and even more preferably 5 μm. If the average thickness of the solid layer 3 is less than the lower limit, the adhesion between the conductor 2 and the pore layer 4 and the partial discharge prevention function of the insulated wire 1 may not be sufficiently enhanced. Conversely, if the average thickness of the solid layer 3 exceeds the above upper limit, the insulated wire 1 may unnecessarily increase in diameter.

(Porous layer)
The pore layer 4 is composed of one or a plurality of baking layers. Each baking layer is formed by applying and baking an insulating varnish containing a plurality of thermally decomposable resin particles. In the insulated wire 1, when the pore layer 4 is composed of a plurality of seizure layers, each seizure layer is sequentially laminated on the outer peripheral surface side of the conductor 2, and the plurality of pores 6 are dispersed in each seizure layer. . That is, the plurality of pores 6 are arranged in a multiple ring shape around the conductor 2 in a cross section perpendicular to the axis of the conductor 2. In the insulated wire 1, the plurality of pores 6 are arranged in a multiple ring shape in this manner, and thus the plurality of pores 6 are easily dispersed uniformly in the pore layer 4. Moreover, according to this structure, when curving the said insulated wire 1, it suppresses that the pores 6 interfere, and it is easy to suppress a fall of flexibility.

Examples of the material of the thermally decomposable resin particles include 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 ester having an alkyl group having 1 to 6 carbon atoms, such as poly (meth) acrylate methyl, poly (meth) ethyl acrylate, poly (meth) acrylate propyl, poly (meth) acrylate butyl, etc. Polymers of;
Polymers of modified (meth) acrylates such as urethane oligomers, urethane polymers, urethane (meth) acrylates, epoxy (meth) acrylates, and ε-caprolactone (meth) acrylates;
Poly (meth) acrylic acid;
These cross-linked products;
Examples thereof include polystyrene and cross-linked polystyrene. The thermally decomposable resin particles are preferably dispersed uniformly in the resin composition constituting the matrix 5 so that closed cells can be formed in each baking layer. From this point, it is preferable to use a crosslinked resin such as the crosslinked product or crosslinked polystyrene as the material of the thermally decomposable resin particles.

  As a minimum of the thermal decomposition temperature of the said thermally decomposable resin particle, 150 degreeC is preferable and 200 degreeC is more preferable. On the other hand, as an upper limit of the thermal decomposition temperature of the said thermally decomposable resin particle, 330 degreeC is preferable and 300 degreeC is more preferable. If the thermal decomposition temperature of the thermally decomposable resin particles is less than the lower limit, there is a risk that the thermal decomposition may occur unintentionally when the insulated wire 1 is manufactured. Conversely, if the thermal decomposition temperature of the thermally decomposable resin particles exceeds the above upper limit, the energy cost required for thermally decomposing the thermally decomposable resin particles may be excessive. The “thermal decomposition temperature” means a temperature at which the temperature is increased from room temperature to 10 ° C./mim in a nitrogen atmosphere and the mass reduction rate becomes 50%. For example, a differential manufactured by SII Nanotechnology Co., Ltd. It can be measured by measuring the thermogravimetry using a thermothermal gravimetric simultaneous measurement device “TG / DTA”.

  The lower limit of the average thickness of each seizure layer is preferably 0.2 μm, and more preferably 0.8 μm. On the other hand, the upper limit of the average thickness of each baking layer is preferably 30 μm, more preferably 20 μm, and even more preferably 10 μm. If the average thickness of each baking layer is less than the lower limit, it may be difficult to disperse the plurality of pores 6 in each baking layer. Conversely, if the average thickness of each seizure layer exceeds the above upper limit, the production of the seizure layer may be difficult.

  The lower limit of the ratio of the average diameter of the plurality of pores 6 to the average thickness of 1 of the above-mentioned seizure layer is preferably 0.05, more preferably 0.1. On the other hand, the upper limit of the ratio of the average diameter of the plurality of pores 6 to the average thickness of one of the above-mentioned seizure layers is preferably 0.9, and more preferably 0.7. If the ratio of the average diameter of the plurality of pores 6 to the average thickness of one of the above baking layers is less than the lower limit, the particle diameter of the thermally decomposable resin particles becomes too small and the thermally decomposable resin particles may be aggregated. There is. Conversely, if the ratio of the average diameter of the plurality of pores 6 to the average thickness of one of the above-mentioned baking layers exceeds the above upper limit, it becomes difficult to form the pores 6 in one baking layer and exists in the adjacent baking layer. There is a risk that the pores 6 to be connected to each other.

  The lower limit of the average diameter of the plurality of pores 6 is 0.1 μm, preferably 0.5 μm, and more preferably 1 μm. On the other hand, the upper limit of the average diameter of the plurality of pores 6 is 10 μm, preferably 5 μm, and more preferably 3 μm. If the average diameter of the plurality of pores 6 is less than the lower limit, the porosity of the pore layer 4 may not be sufficiently increased, and the reduction of the dielectric constant may not be sufficiently promoted. When the average diameter of the plurality of pores 6 is less than the lower limit, the plurality of pores 6 may be connected due to aggregation of the plurality of thermally decomposable resin particles. On the contrary, if the average diameter of the plurality of pores 6 exceeds the upper limit, the distribution of the plurality of pores 6 in the pore layer 4 varies, and the dielectric constant distribution tends to be biased. Moreover, when the average diameter of the plurality of pores 6 exceeds the upper limit, the flexibility of the insulated wire 1 may be reduced.

  The lower limit of the porosity of the pore layer 4 is 10% by volume, and more preferably 20% by volume. On the other hand, the upper limit of the porosity of the pore layer 4 is 30% by volume. If the porosity of the pore layer 4 is less than the above lower limit, the reduction of the dielectric constant may not be promoted sufficiently. On the other hand, when the porosity of the pore layer 4 exceeds the above upper limit, flexibility and dielectric breakdown voltage may be insufficient.

  As a main component of the matrix 5, for example, a thermosetting resin such as polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy resin, thermosetting polyester, thermosetting polyester imide, thermosetting polyester amide imide, thermosetting polyamide imide, Examples thereof include thermoplastic resins such as polyimide and aromatic polyamide. Among these, polyimide, thermosetting polyamideimide, or thermosetting polyesterimide, which can easily ensure breaking strength and heat resistance, are preferable, and polyimide is particularly preferable. In particular, the main component of the matrix 5 is preferably the same as the main component of the solid layer 3 from the viewpoint of improving the adhesion with the solid layer 3.

  In addition to the above main components, the matrix 5 includes polyphenylsulfone, polyphenylene sulfide, polyetherimide, polyetheretherketone, polyethersulfone, copolymer polyester, polybutylene terephthalate, polyethylene terephthalate, thermoplastic polyurethane, Thermoplastic resins such as polycarbonate, polyphenylene oxide, polysulfone, polyetherketone, semi-aromatic polyamide, thermoplastic polyamideimide may be included. The insulated wire 1 can improve the flexibility of the pore layer 4 when the matrix 5 contains a thermoplastic resin in addition to the main component.

  When the matrix 5 contains a thermoplastic resin in addition to the main component, the lower limit of the content of the thermoplastic resin in the matrix 5 is preferably 5% by mass, and more preferably 10% by mass. On the other hand, the upper limit of the thermoplastic resin content in the matrix 5 is preferably 40% by mass, more preferably 30% by mass. If the content of the thermoplastic resin is less than the lower limit, the effect of improving the flexibility of the pore layer 4 may not be sufficiently obtained. Conversely, if the content of the thermoplastic resin exceeds the upper limit, the strength of the pore layer 4 may be insufficient.

  As a minimum of average thickness of pore layer 4, 50 micrometers is preferred and 70 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the pore layer 4 is preferably 200 μm, and more preferably 150 μm. If the average thickness of the pore layer 4 is less than the lower limit, it may be difficult to promote the reduction of the dielectric constant while maintaining a sufficient breaking strength. Conversely, if the average thickness of the pore layer 4 exceeds the above upper limit, the volume efficiency of a coil or the like formed using the insulated wire 1 may be lowered.

  The lower limit of the ratio of the average thickness of the solid layer 3 to the average thickness of the pore layer 4 is preferably 0.005, and more preferably 0.01. On the other hand, the upper limit of the ratio of the average thickness of the solid layer 3 to the average thickness of the pore layer 4 is preferably 0.35, and more preferably 0.1. If the ratio of the average thickness of the solid layer 3 to the average thickness of the pore layer 4 is less than the lower limit, the adhesion between the conductor 2 and the pore layer 4 and the partial discharge prevention function of the insulated wire 1 are sufficiently enhanced. There is a risk that it will not be possible. On the contrary, when the ratio of the average thickness of the solid layer 3 to the average thickness of the pore layer 4 exceeds the upper limit, when the thickness of the pore layer 4 is maintained and low dielectric constant is promoted, the insulation There exists a possibility that volumetric efficiency, such as a coil formed using the electric wire 1, may become low.

  Moreover, as for the said insulated wire 1, it is more preferable that both ratio of the average thickness of the pore layer 4 and the average thickness of the solid layer 3 with respect to the average thickness of the pore layer 4 is in the said range. The insulated wire 1 has the average thickness of the pore layer 4 and the ratio of the average thickness of the solid layer 3 to the average thickness of the pore layer 4 within the above range. It is possible to easily and reliably promote the reduction of the dielectric constant while sufficiently enhancing the adhesion force and the partial discharge prevention function of the insulated wire 1. Further, the insulated wire 1 has a reduced flexibility even when the average thickness of the pore layer 4 is relatively large because the plurality of pores 6 are substantially uniformly dispersed in each of the seizure layers as described above. Can be suppressed. Therefore, the said insulated wire 1 makes it easy to raise the breaking strength of the whole some insulating layer (the solid layer 3 and the pore layer 4) by making the average thickness of the pore layer 4 into the said range.

<Insulated wire manufacturing method>
The manufacturing method of the insulated wire 1 includes, for example, a step of preparing a solid layer forming resin composition, a step of forming the solid layer 3 on the outer peripheral surface of the conductor 2, and a pore layer forming resin composition. And a step of forming the pore layer 4 outside the solid layer 3.

(Process for preparing solid layer forming resin composition)
In the solid layer forming resin composition preparation step, a solid layer varnish (insulating varnish) is prepared by diluting the resin composition constituting the solid layer 3 with a solvent.

  As said solvent for dilution, the well-known organic solvent conventionally used for the 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 Examples include halogenated hydrocarbons such as dichloromethane and chlorobenzene, phenols such as cresol and chlorophenol, and tertiary amines such as pyridine. These organic solvents are used alone or in admixture of two or more. It is done.

  By diluting with such a solvent, the resin composition can be easily applied to the conductor 2. The solvent is volatilized by heating in the solid layer forming step.

  As a minimum of the boiling point of the said solvent, 140 degreeC is preferable and 160 degreeC is more preferable. Moreover, as an upper limit of the boiling point of the said solvent, 230 degreeC is preferable and 210 degreeC is more preferable. If the boiling point of the solvent is less than the lower limit, the volatile solvent evaporates before heating, and the wire workability of the insulated wire 1 may be reduced. On the other hand, if the boiling point of the solvent exceeds the upper limit, it takes time for the solvent to volatilize, and the formation time of the solid layer 3 may be long.

(Solid layer forming process)
In the solid layer forming step, the solid layer varnish prepared in the solid layer forming resin composition preparing step is applied to the outer peripheral surface of the conductor 2 and then baked to solidify the outer peripheral surface of the conductor 2. Layer 3 is formed. The baking temperature is appropriately set according to the type of resin used, and is, for example, 200 ° C. or higher and 600 ° C. or lower. In the solid layer forming step, application and baking of the solid layer varnish may be repeated until the solid layer 3 has a predetermined thickness.

(Process for preparing pore layer forming resin composition)
In the pore layer forming resin composition preparation step, the resin composition constituting the matrix 5 of the pore layer 4 is diluted with a solvent, and the thermally decomposable resin particles are mixed to form a pore layer varnish (insulating varnish). To prepare. Examples of the solvent used in the pore layer forming resin composition preparing step include the same solvents as those used in the solid layer forming resin composition preparing step.

  As a minimum of resin solid content concentration of a varnish for pore layers prepared by diluting with the above-mentioned solvent, 20 mass% is preferred and 22 mass% is more preferred. On the other hand, the upper limit of the resin solid content concentration of the pore layer varnish is preferably 50% by mass, and more preferably 30% by mass. When the resin solid content concentration of the pore layer varnish is less than the above lower limit, the amount of application at one time when the pore layer varnish is applied decreases, so that the pore layer 4 having a desired thickness is formed. There is a possibility that the number of repetitions of the varnish application process increases and the time of the varnish application process becomes longer. Conversely, when the resin solid content concentration of the pore layer varnish exceeds the upper limit, it is difficult to uniformly mix the thermally decomposable resin particles, and the time required for dilution may be increased.

(Porous layer forming step)
In the pore layer forming step, the pore layer varnish prepared in the pore layer forming resin composition preparation step is applied to the outer periphery of the solid layer 3 formed in the solid layer forming step, and then baked to form the pore layer. 4 is formed. The baking temperature is appropriately set according to the type of resin used, and is, for example, 200 ° C. or higher and 350 ° C. or lower. By this baking, the thermally decomposable resin particles are thermally decomposed to form a plurality of pores 6 in the pore layer 4.

  In the pore layer forming step, the coating and baking of the pore layer varnish are repeated until the pore layer 4 formed on the outer periphery of the solid layer 3 has a predetermined thickness. Thus, the plurality of pores 6 are arranged in a multiple ring shape around the conductor 2 in a cross section perpendicular to the axis of the conductor 2. In the pore layer forming step, it is preferable to repeatedly apply and bake the varnish for the pore layer, but it is not always necessary to repeatedly apply and bake the varnish for the pore layer. You may perform application | coating and baking of the insulating varnish which does not contain a degradable resin particle.

[advantage]
The insulated wire 1 includes a pore layer 4 having a plurality of pores 6, and the average diameter of the plurality of pores 6 dispersed in the matrix 5 of the pore layer 4 and the porosity of the pore layer 4 are within the above range. Therefore, the plurality of pores 6 are easily and appropriately uniformly dispersed in the pore layer 4. Therefore, the insulated wire 1 can promote a reduction in dielectric constant while suppressing a decrease in flexibility.

[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 scope and meaning equivalent to the scope of the claims. The

  In the above embodiment, the configuration in which the solid layer is directly laminated on the conductor has been described. However, in the insulated wire, the solid layer is not necessarily laminated directly on the conductor. As a specific configuration of the insulated wire, for example, configurations as shown in FIGS.

  In the insulated wire 11 of FIG. 2, the pore layer 13 is directly laminated on the conductor 12, and the solid layer 14 is laminated outside the pore layer 13. The configuration of the pore layer 13 and the solid layer 14 can be the same as that of the pore layer 4 and the solid layer 3 of FIG. Even with such a configuration, the insulated wire 11 can promote a reduction in dielectric constant while suppressing a decrease in flexibility, like the insulated wire 1.

  3, the first solid layer 23 is directly laminated on the conductor 22, the pore layer 24 is laminated outside the first solid layer 23, and the second solid layer 25 is outside the pore layer 24. Are stacked. The configuration of the pore layer 24 can be the same as that of the pore layer 4 of FIG. Further, the configuration of the first solid layer 23 and the second solid layer 25 can be the same as that of the solid layer 3 in FIG. That is, the insulated wire 21 has a configuration in which a solid layer is further laminated outside the pore layer 4 of the insulated wire 1 of FIG. Even with such a configuration, the insulated wire 21 can promote a reduction in dielectric constant while suppressing a decrease in flexibility, like the insulated wire 1. Further, since the insulated wire 21 includes the second solid layer 25 outside the pore layer 24 in addition to the first solid layer 23, the partial discharge prevention function can be further enhanced.

  In addition, the said insulated wire is not limited to the structure shown in FIG. 1 thru | or FIG. 3, It may be provided with the other layer as needed, for example, is provided with the several pore layer. Also good. Moreover, the said insulated wire may be comprised only from a linear conductor and one pore layer laminated | stacked on the outer peripheral surface of this conductor.

  The pore layer is not necessarily constituted by one or a plurality of baking layers. For the insulated wire, for example, instead of the thermally decomposable resin particles, a foaming agent such as a chemical foaming agent or a thermal expansion microcapsule, or a hollow filler such as a shirasu balloon, a glass balloon, a ceramic balloon, or an organic resin balloon may be used. Is possible. Hereinafter, the chemical foaming agent and the thermal expansion microcapsule will be described in detail.

  The chemical foaming agent is decomposed by heating to generate, for example, nitrogen gas, carbon dioxide gas, carbon monoxide, ammonia gas or the like, and an organic foaming agent or an inorganic foaming agent can be used.

  Examples of the organic blowing agent include azo blowing agents such as azodicarbonamide (ADCA) and azobisisobutyronitrile (AIBN), such as dinitrosopentamethylenetetramine ( D.P.T.), N, N′dinitroso-N, N′-dimethylterephthalamide (D.N.D.M.T.A) and the like, for example, P-toluenesulfonyl hydrazide (T. Hydrazides such as S.H), P, P-oxybisbenzenesulfonyl hydrazide (O.B.S.H), benzenesulfonyl hydrazide (B.S.H), and others, trihydrazinotriazine (T.H). .T), acetone-P-sulfonylhydrazone, etc., are exemplified, and these can be used alone or in combination of two or more.

  Examples of the inorganic foaming agent include sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, sodium borohydride, sodium boron hydride, silicon oxyhydride and the like. In general, an inorganic foaming agent has a slower gas generation rate than an organic foaming agent, and adjustment of gas generation is difficult. Therefore, an organic foaming agent is preferable as the chemical foaming agent.

  The lower limit of the foaming start temperature of the chemical foaming agent, that is, the thermal decomposition temperature, is preferably 140 ° C, and more preferably 160 ° C. On the other hand, the upper limit of the foaming start temperature of the chemical foaming agent is preferably 250 ° C, more preferably 220 ° C. If the foaming start temperature of the chemical foaming agent is less than the lower limit, the chemical foaming agent may unintentionally foam during production of the insulated wire. On the contrary, if the foaming start temperature of the chemical foaming agent exceeds the upper limit, the energy cost required for foaming the foaming agent may be excessive.

  In the pore layer, a foaming aid may be blended together with the chemical foaming agent. The foaming aid is not particularly limited as long as it promotes thermal decomposition of the chemical foaming agent. For example, a vulcanization accelerator, a filler, a vulcanization acceleration aid, a PVC stabilizer, an anti-aging agent, A sulfurizing agent, a urea compound, etc. are mentioned. Such a foaming aid accelerates the decomposition of the chemical foaming agent and lowers the foaming temperature.

  Examples of the vulcanization accelerator include guanidine, aldehyde-ammonia, sulfenamide, thiuram, xanthate, aldehyde-amine, thiazole, thiourea, and dithiocarbamate. Examples of the filler include silica, magnesium carbonate, calcium carbonate, magnesium silicate, aluminum carbonate, talc, barium sulfate, aluminum sulfate, and calcium sulfate. Examples of the vulcanization acceleration aid include zinc white, activated zinc white, zinc carbonate, magnesium oxide, lead monoxide, basic lead carbonate, calcium hydroxide, stearic acid, oleic acid, lauric acid, diethylene glycol, diethylene glycol. -N-Butylamine, dicyclohexylamine, diethanolamine, organic amine, etc. are mentioned. Examples of the stabilizer for PVC include tribasic lead sulfate, dibutyltin dilaurate, dibutyltin dimaleate, zinc stearate, cadmium stearate, barium stearate, calcium stearate and the like. Examples of the anti-aging agent include naphthylamine, diphenylamine, P-phenylene, quinoline, monophenol, polyphenol, thiobisphenol, and phosphite esters. Examples of the vulcanizing agent include triallyl isocyanate and ammonium sulfur benzoate. Examples of other chemicals include phthalic anhydride, salicylic acid, benzoic acid, antimony trioxide, white petrolatum, titanium oxide, cadmium oxide, borax, glycerin, and dibutyltin dimaleate. Of these, zinc oxide, tribasic lead sulfate, and various vulcanization accelerators are preferable as the foaming aid.

  As a minimum of the compounding quantity with respect to 100 mass parts of chemical foaming agents of these foaming adjuvants, 5 mass parts are preferred and 50 mass parts are more preferred. On the other hand, the upper limit of the blending amount of the foaming aid is preferably 200 parts by weight, and more preferably 150 parts by weight. If the blending amount of the foaming aid is less than the lower limit, the effect of decomposing the chemical foaming agent may be insufficient. Conversely, if the blending amount of the foaming aid exceeds the upper limit, the pore layer may unintentionally expand during the production of the insulated wire.

  The thermal expansion microcapsule has a core material (inner package) made of an internal foaming agent and an outer shell that encloses the core material, and the outer shell expands due to the expansion of the core material.

  The internal foaming agent of the above-mentioned thermally expandable microcapsules may be any one that expands or generates gas when heated, and its principle is not limited. As the internal foaming agent of the thermally expandable microcapsule, for example, a low boiling point liquid, a chemical foaming agent and 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 thermally decomposable substance such as azobisisobutyronitrile that generates N ₂ gas by heating is preferably used.

  The foaming start temperature of the internal foaming agent of the thermally expandable microcapsule, that is, the boiling point of the low-boiling liquid or the thermal decomposition temperature of the chemical foaming agent is equal to or higher than the softening temperature of the outer shell of the thermally expandable microcapsule described later.

  More specifically, the lower limit of the foaming start temperature of the internal foaming agent of the thermally expandable microcapsule is preferably 140 ° C., more preferably 160 ° C. On the other hand, the upper limit of the foaming start temperature of the internal foaming agent of the thermally expandable microcapsule is preferably 250 ° C., more preferably 220 ° C. If the foaming start temperature of the internal foaming agent of the thermally expandable microcapsule is less than the lower limit, the thermally expandable microcapsule may expand unintentionally during the production of the insulated wire. On the contrary, if the foaming start temperature of the internal foaming agent of the thermally expandable microcapsule exceeds the 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 internal foaming agent is foamed and can 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 an acrylonitrile copolymer. In this case, the decomposition temperature of the internal foaming agent is 70 ° C. or higher and 250 ° C. or lower.

  The lower limit of the average diameter of the thermally expandable microcapsules before heating is preferably 1 μm and more preferably 5 μm. On the other hand, the upper limit of the average diameter of the thermally expandable microcapsules before heating is preferably 150 μm, and more preferably 100 μm. If the average diameter of the heat-expandable microcapsules before heating is less than the lower limit, a sufficient expansion rate may not be obtained. Conversely, if the average diameter of the thermally expandable microcapsules before heating exceeds the upper limit, the pore layer may become unnecessarily thick or the pore layer may not be uniformly expanded. The “average diameter of the thermally expandable microcapsule” is an average value of the maximum diameter in a plan view when 10 or more samples of the thermally expandable microcapsule are observed with a microscope and the diameter in a direction perpendicular to the maximum diameter. It shall be said.

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

[Example]
[No. 1]
Copper was cast, drawn, drawn and softened to obtain a conductor having a circular cross section and a diameter of 1.0 mm. Next, a solid layer varnish was prepared by using a polyimide precursor as a main component and N-methyl-2-pyrrolidone as a solvent and diluting the main component with this solvent. The solid layer varnish is applied to the outer peripheral surface of the conductor, and the average thickness is applied to the outer peripheral surface of the conductor by baking under conditions of a linear velocity of 4.0 m / min, a heating furnace inlet temperature of 250 ° C., and a heating furnace outlet temperature of 350 ° C. A solid layer having a thickness of 3 μm was formed. Next, an insulating varnish was prepared by using a polyimide precursor as a main component, N-methyl-2-pyrrolidone as a solvent, and diluting the main component with this solvent. Further, a foaming agent (“SSX-102” manufactured by Sekisui Plastics Kogyo Co., Ltd.) was dispersed in this insulating varnish so that the porosity of the pore layer was 10% by volume, thereby preparing a pore layer varnish. The porous layer varnish is applied to the outer periphery of the solid layer, and the solid layer is repeatedly subjected to the baking process under the conditions of a linear velocity of 4.0 m / min, a heating furnace inlet temperature of 250 ° C., and a heating furnace outlet temperature of 350 ° C. A pore layer having an average thickness of 97 μm is formed on the outer peripheral surface of 1 insulated wire was obtained. When this insulated wire was cut perpendicular to the axis and the cut surface was observed using a scanning electron microscope (SEM), the average diameter of the plurality of pores in this pore layer was 2.5 μm. It was.

[No. 2-No. 4]
No. 1 except that the average thickness of the solid layer and the pore layer, the porosity of the pore layer, and the average diameter of the pores were as shown in Table 1. In the same manner as in No. 1, 2-No. 4 insulated wires were obtained.

[Comparative example]
[No. 5]
No. 1 except that the average thickness of the solid layer and the pore layer, the porosity of the pore layer, and the average diameter of the pores were as shown in Table 1. In the same manner as in No. 1, 5 insulated wires were obtained.

[No. 6]
No. except that the average thickness was as shown in Table 1. In the same manner as in Example 1, a solid layer was formed on the outer peripheral surface of the conductor. Furthermore, no. Instead of 1 varnish for the pore layer, a polyimide precursor is used as a main component, N-methyl-2-pyrrolidone is used as a solvent, and an insulating varnish diluted with this solvent is applied to the outer periphery of the solid layer. , No. No. 1 is used to form a second solid layer having an average thickness of 3 μm on the outer peripheral surface of the solid layer. 6 insulated wires were obtained.

<Adhesion>
No. 1-No. Two cuts having a length of about 2 cm were made at intervals of 0.5 mm in the longitudinal direction of the insulated wire No. 6. One end of the band-shaped portion delimited by the two cuts was peeled off from the conductor using tweezers, and the adhesion between the conductor and the insulating layer was evaluated. The evaluation results are shown in Table 2.
A: Unable to peel off (good adhesion)
B: Peelable (poor adhesion)

<Elongation>
No. 1-No. For the insulated wire No. 6, the insulating layer was peeled off from the conductor in a cylindrical shape, and the insulating layer having a length of 5 cm was peeled off from the conductor, and the tensile speed was 50 mm / min in the longitudinal direction in an environment of 25 ° C. The elongation percentage [%] at the time of pulling when pulled by was measured. In addition, the measurement of elongation rate was implemented by n = 5, and calculated | required the average value. The measurement results are shown in Table 2.

<Flexibility>
A round bar having a diameter of 1.0 mm was prepared. 1-No. The insulated wire 6 was bent 90 ° while being in contact with the round bar so that the shaft of the insulated wire and the shaft of the round bar were perpendicular to each other with the initial length extended or not extended. Furthermore, the flexibility of the insulated wire was evaluated according to the following criteria by visually observing the folded insulated wire with a microscope and observing the presence or absence of cracks. The evaluation results are shown in Table 2.
A: Cracks do not occur even when 30% of the initial length is extended.
B: Cracks do not occur even when stretched by 20% of the initial length, but cracks occur when stretched by 30%.
C: Cracks do not occur even when stretched 10% of the initial length, but cracks occur when stretched 20%.

<Dielectric breakdown voltage>
No. 1-No. With respect to 6 insulated wires, in accordance with JIS-C3216-5: 2011, an alternating voltage was applied between the two twisted wires, the voltage was increased at 500 V / sec, and the voltage [kV] when dielectric breakdown was measured. The dielectric breakdown voltage was measured at n = 5, and the average value was obtained. The measurement results are shown in Table 2.

<Relative permittivity>
No. 1-No. For the insulated wire No. 6, the dielectric constant of the insulating layer was measured according to JIS-C2138: 2007. The measurement results are shown in Table 2.

<Solvent immersion test>
Since the insulated wire becomes a high temperature in use where a high voltage is applied, in such a case, for example, the insulated wire may be used by being immersed in a solvent in order to cool the insulated wire. Thus, even when the insulated wire was immersed in a solvent and used, a solvent immersion test was performed in order to confirm that desired characteristics were obtained. Specifically, no. 1-No. After the 6 insulated wires were immersed in the test oil IRM903 at 150 ° C. for 72 hours, the relative dielectric constant of each wire was measured. This solvent immersion test was carried out with n = 3, and the average value was obtained and compared with the relative dielectric constant before immersion in the solvent. Specifically, an evaluation result A was defined as a case where the relative dielectric constant difference before and after the solvent immersion test was less than 0.05, and no increase in the relative dielectric constant was observed. In addition, when the relative dielectric constant after the solvent immersion test is greater than 0.05 and less than 0.2 than before the solvent immersion test, the evaluation result B is regarded as the relative dielectric constant slightly increased, and the ratio after the solvent immersion test is An evaluation result C was defined as a case where the dielectric constant was 0.2 or greater and the relative dielectric constant was significantly increased. Table 2 shows the determination results of the increase in relative dielectric constant.

[Evaluation results]
As shown in Table 1 and Table 2, It can be seen that the insulated wire No. 5 has insufficient flexibility because the porosity of the pore layer is as high as 50% by volume. No. In the insulated wire No. 5, since the porosity of the pore layer is as high as 50% by volume, a plurality of pores communicate with each other. As a result, permeation of the solvent into the insulation layer is also observed, and the solvent has a higher dielectric constant than that before the solvent immersion. The relative dielectric constant after immersion is high. From this, No. The insulated wire No. 5 is not suitable for use by being immersed in a solvent, and is not suitable for use where a high voltage is applied. On the other hand, no. In the insulated wire No. 6, since the insulating layer does not have a plurality of pores, it can be seen that the relative dielectric constant is high. On the other hand, no. 1-No. In the insulated wire No. 4, since the porosity of the pore layer is 10% by volume to 30% by volume, it can be seen that both the flexibility and the relative dielectric constant are good. Furthermore, no. 1-No. The insulated wire No. 4 shows little change in the dielectric constant before and after immersion in the solvent, so it is considered suitable for use in immersion in a solvent or application of a solvent.

  Since the insulated wire according to the present invention can promote a reduction in dielectric constant while suppressing a decrease in flexibility, it can be applied to an electric device having a high applied voltage such as a motor used at a high voltage.

1,11,21 Insulated wire 2,12,22 Conductor 3 Insulating layer (solid layer)
14, 23, 25 Solid layer 4 Insulating layer (porous layer)
13,24 Pore layer 5 Matrix 6 Pore

Claims (5)

An insulated wire comprising a linear conductor and a plurality of insulating layers laminated on the outer peripheral surface of the conductor,
At least one of the plurality of insulating layers has a matrix mainly composed of a synthetic resin and a plurality of pores dispersed in the matrix,
The average diameter of the plurality of pores is 0.1 μm or more and 10 μm or less,
The insulating layer having a plurality of pores has a porosity of 10% by volume to 30% by volume,
The insulating layer directly laminated on the conductor does not have pores,
The insulating layer having the plurality of pores is laminated outside the insulating layer having no pores,
The main component of the insulating layer having no pores is polyimide,
The main component of the matrix of the insulating layer having pores is polyimide,
The dielectric constant of the entire insulating layer Ri der 3 or less,
It said plurality of insulating layers overall elongation Ru der 70% insulated wire.   The insulated wire according to claim 1, wherein the plurality of pores are derived from a plurality of thermally decomposable resin particles. The insulating layer having a plurality of pores is composed of one or more baking layers,
The insulated wire according to claim 1 or 2, wherein a ratio of an average diameter of the plurality of pores to an average thickness of the seizure layer is 0.05 or more and 0.9 or less.   The average thickness of the insulating layer having a plurality of pores is 50 μm or more and 200 μm or less, and the ratio of the average thickness of the insulating layer having no pores to the average thickness of the insulating layer having the plurality of pores is 0.005. The insulated wire according to claim 1, claim 2, or claim 3, which is 0.35 or less. Insulated wire as claimed in any one of claims 4 above Kifuku number of insulating layers total elongation of not more than 1 50%.

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