JP6912253B2 - Manufacturing method of insulated wire - Google Patents

Description

The present invention relates to an insulated wire, a resin composition for forming an insulating layer, and a method for manufacturing an insulated wire.

In an electric device having a high applied voltage, for example, a motor used at a high voltage, a high voltage is applied to an insulated wire constituting the electric device, and a partial discharge (corona discharge) may occur on the surface of the insulating coating. When the occurrence of corona discharge causes a local temperature rise, ozone generation, ion generation, etc., dielectric breakdown occurs at an early stage, and the life of the insulated wire and thus the electrical equipment is shortened. Therefore, an insulated wire used for an electric device having a high applicable voltage is required to improve the corona discharge starting voltage in addition to excellent insulating properties and mechanical strength.

As a device to raise the corona discharge start voltage, it is effective to reduce the dielectric constant of the insulating coating. In order to reduce the dielectric constant of the insulating coating, a heat-curing film (insulating coating) is provided with an insulating varnish containing a coating resin and a thermally decomposable resin that decomposes at a temperature lower than the baking temperature of the coating resin. ) Has been proposed (see JP-A-2012-224714). In this insulated wire, pores are formed in the heat-cured film by utilizing the fact that the thermally decomposable resin is thermally decomposed at the time of baking the coating resin and the portion becomes pores, and the formation of the pores causes the pores to be formed. Achieves a low dielectric constant of the insulating coating.

Japanese Unexamined Patent Publication No. 2012-224714

However, in the insulated wire proposed in the above publication, for example, when the pores formed in the insulating coating are localized or when the sizes of these pores vary, the insulating coating is derived from a pyrolytic resin. The pores are easily communicated with each other, and there is a possibility that pores larger than the particle size of the pyrolytic resin may be generated. If such continuous pores are generated, the strength of the insulating film may decrease.

The present invention has been made based on the above circumstances, and is an insulated wire and insulation capable of lowering the dielectric constant of the insulating coating and improving the corona discharge starting voltage while suppressing a decrease in the strength of the insulating layer. An object of the present invention is to provide a resin composition for layer formation and a method for producing an insulated electric wire.

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

Another resin composition for forming an insulating layer according to another aspect of the present invention is a resin composition for forming an insulating layer used for forming at least one of one or a plurality of insulating layers constituting an insulated electric wire, and comprises a matrix. The compressive strength of the hollow inorganic particles, which contains the thermoplastic resin composition to be formed and a plurality of hollow inorganic particles dispersed in the thermoplastic resin composition, and is measured by the glycerol method in accordance with ASTM D3102-78. Is a resin composition for forming an insulating layer having a value of 10 MPa or more.

Another method for manufacturing an insulated wire according to one aspect of the present invention is a method for manufacturing an insulated wire including a linear conductor and one or a plurality of insulating layers laminated on the outer peripheral surface of the conductor. , A step of kneading the thermoplastic resin composition forming a matrix of at least one layer of the above one or a plurality of insulating layers with the above-mentioned extruder using an extruder with a side feeder, and a plurality of steps from the side feeder of the above-mentioned extruder. It is a method for manufacturing an insulated electric wire including a step of mixing hollow inorganic particles with the thermoplastic resin composition and a step of extruding the resin composition for forming an insulating layer after the mixing step toward the outer peripheral surface side of the conductor.

The method for producing an insulated wire, a resin composition for forming an insulating layer, and an insulated wire of the present invention can reduce the dielectric constant of an insulating coating while suppressing a decrease in the strength of the insulating layer, and can improve the corona discharge start voltage. ..

It is a schematic cross-sectional view which shows the insulated wire which concerns on 1st Embodiment of this invention. It is a schematic end view of the hollow inorganic particle contained in the insulated wire of FIG. It is a schematic cross-sectional view which shows the insulated wire which concerns on 2nd Embodiment of this invention.

[Explanation of Embodiments of the Present Invention]
The insulated wire according to one aspect of the present invention is an insulated wire including a linear conductor and one or more insulating layers laminated on the outer peripheral surface of the conductor, and is at least one or more of the above insulating layers. An insulated wire in which one layer contains a plurality of hollow inorganic particles and the withstand voltage strength of the hollow inorganic particles measured by the glycerol method in accordance with ASTM D3102-78 is 10 MPa or more.

Since the insulated wire has a withstand voltage of 10 MPa or more measured by the glycerol method in accordance with ASTM D3102-78 of hollow inorganic particles contained in the insulating layer, a force is applied in the insulating layer manufacturing process. As a result, cracking of the shell is suppressed, and an insulating layer in which hollow inorganic particles are stably dispersed can be provided. As a result, since each pore formed in the insulating layer is surrounded by a shell made of an inorganic material, it is difficult for the hollow portions in each hollow inorganic particle to communicate with each other, and it becomes difficult for coarse pores to be generated in the insulating layer. Therefore, the corona discharge starting voltage can be improved by reducing the dielectric constant of the insulating coating while suppressing the decrease in strength of the insulating layer due to the coarse pores. Furthermore, surge resistance can be imparted due to the effect of the hollow inorganic particles as an inorganic filler, and deterioration due to heating when an overvoltage (surge voltage) is applied during use can be suppressed. For example, even when the insulating layer is formed by extrusion molding, cracking of the shell due to the application of force is suppressed, and an insulating layer in which hollow inorganic particles are stably dispersed can be provided.

The withstand strength of the hollow inorganic particles is preferably 20 MPa or more. By setting the compressive strength of the hollow inorganic particles to 20 MPa or more, cracking of the shell can be further suppressed and the dispersibility of the hollow inorganic particles can be improved.

The average thickness of the shell of the hollow inorganic particles is preferably 0.5 μm or more and 2.0 μm or less. By setting the average thickness of the shell of the hollow inorganic particles within the above range in this way, it is possible to increase the porosity of the insulating layer while suppressing the decrease in the strength of the insulating layer. Here, the "porosity" means a percentage of the volume of pores by the hollow inorganic particles with respect to the volume of the insulating layer containing the hollow inorganic particles.

The median diameter of the hollow inorganic particles is preferably 50 μm or less. By setting the median diameter of the hollow inorganic particles within the above range in this way, the decrease in the compressive strength of the hollow inorganic particles is suppressed. Here, the median diameter means the median diameter defined in JIS-Z8825 (2013).

The specific gravity of the hollow inorganic particles is preferably 0.3 or more and 0.7 or less. As described above, when the specific gravity of the hollow inorganic particles is within the above range, the porosity can be efficiently increased with respect to the volume occupied by the hollow inorganic particles. In addition, the hollow ratio of the hollow inorganic particles does not become too large, and the decrease in the compressive strength of the hollow inorganic particles is suppressed. Here, the "specific gravity" means the specific gravity defined in JIS-K0061 (2001).

It is preferable that the matrix of the insulating layer containing the hollow inorganic particles contains a thermoplastic resin. As described above, since the matrix of the insulating layer containing the hollow inorganic particles contains the thermoplastic resin, the insulating layer containing the hollow inorganic particles can be satisfactorily formed even in extrusion molding.

The resin composition for forming an insulating layer according to one aspect of the present invention is a resin composition for forming an insulating layer used for forming at least one of one or a plurality of insulating layers constituting an insulated electric wire, and forms a matrix. The pressure resistance strength of the hollow inorganic particles containing the thermoplastic resin composition and a plurality of hollow inorganic particles dispersed in the thermoplastic resin composition and measured by the glycerol method in accordance with ASTM D3102-78 is 10 MPa. This is the resin composition for forming an insulating layer.

The resin composition for forming an insulating layer has a compressive strength of 10 MPa or more as measured by the glycerol method in accordance with ASTM D3102-78 of a plurality of hollow inorganic particles dispersed in the thermoplastic resin composition. .. As a result, cracking of the shell due to force applied in the insulating layer manufacturing process is suppressed, and an insulating layer in which hollow inorganic particles are stably dispersed can be provided. Since each pore formed in the insulating layer is surrounded by a shell made of an inorganic material, it is difficult for the hollow portions in each hollow inorganic particle to communicate with each other, and it is difficult for coarse pores to be generated in the insulating layer. Therefore, it is possible to reduce the dielectric constant of the insulating coating while suppressing the decrease in strength of the insulating layer due to the coarse pores.

The method for manufacturing the insulated wire is a method for manufacturing an insulated wire including a linear conductor and one or a plurality of insulating layers laminated on the outer peripheral surface of the conductor, using an extruder with a side feeder. The step of kneading the thermoplastic resin composition forming a matrix of at least one layer of one or a plurality of insulating layers with the extruder, and the plurality of hollow inorganic particles from the side feeder of the extruder are formed into the thermoplastic resin composition. This is a method for manufacturing an insulated electric wire, which comprises a step of mixing with the conductor and a step of extruding the resin composition for forming an insulating layer after the mixing step toward the outer peripheral surface side of the conductor.

In the method for manufacturing the insulated wire, the thermoplastic resin composition is first kneaded by the extruder with a side feeder, and then a plurality of hollow inorganic particles are mixed from the side feeder of the extruder to form the thermoplastic resin composition. Since it is mixed with the substance, it is possible to form an insulating layer in which the hollow inorganic particles are uniformly dispersed while suppressing the cracking of the hollow inorganic particles. Therefore, it is possible to manufacture an insulated wire capable of lowering the dielectric constant of the insulating coating and improving the corona discharge starting voltage while suppressing a decrease in the strength of the insulating layer.

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

[First Embodiment]
<Insulated wire>
The insulated wire of FIG. 1 includes a linear conductor 1 and a single layer of the first insulating layer 2 laminated on the outer peripheral surface of the conductor 1. The first insulating layer 2 contains a plurality of hollow inorganic particles 3. Further, the matrix of the first insulating layer 2 containing the hollow inorganic particles 3 contains a thermoplastic resin.

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

As the material of the conductor 1, a metal having high conductivity and high mechanical strength is preferable. Examples of such metals include copper, copper alloys, aluminum, nickel, silver, soft iron, steel, stainless steel and the like. The conductor 1 is a material in which these metals are linearly formed, or a material having a multilayer structure in which such a linear material is coated with another metal, for example, nickel-coated copper wire, silver-coated copper wire, or copper-coated aluminum. Wires, copper-coated steel wires, etc. can be used.

As the lower limit of the average cross-sectional area of the conductor 1, 0.01 mm ² is preferable, and 0.1 mm ² is more preferable. On the other hand, as the upper limit of the average cross-sectional area of the conductor 1, 10 mm ² is preferable, and 5 mm ² is more preferable. If the average cross-sectional area of the conductor 1 is less than the above lower limit, the volume of the first insulating layer 2 with respect to the conductor 1 may increase, and the volumetric efficiency of the coil or the like formed by using the insulated wire may decrease. On the contrary, when the average cross-sectional area of the conductor 1 exceeds the above upper limit, the first insulating layer 2 must be formed thick in order to sufficiently reduce the dielectric constant, and the diameter of the insulated wire becomes unnecessarily large. There is a risk.

<Insulation layer>
The first insulating layer 2 contains a plurality of hollow inorganic particles 3 as shown in FIG. That is, the first insulating layer 2 includes a plurality of pores due to the hollow inorganic particles 3.

The first insulating layer 2 is formed of an insulating resin composition and hollow inorganic particles 3 scattered in the resin composition. The first insulating layer 2 is formed on the outer peripheral surface of the conductor 1 by extrusion molding using the resin composition for forming an insulating layer, which will be described later.

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

The upper limit of the dielectric constant of the first insulating layer 2 is preferably 3.0, more preferably 2.9. If the dielectric constant of the first insulating layer 2 exceeds the above upper limit, the corona discharge starting voltage may not be sufficiently improved.

The lower limit of the average thickness of the first insulating layer 2 is preferably 100 μm, more preferably 120 μm. On the other hand, the upper limit of the average thickness of the first insulating layer 2 is preferably 500 μm, more preferably 450 μm. If the average thickness of the first insulating layer 2 is less than the above lower limit, the insulating property may be lowered. The presence of the hollow inorganic particles 3 may easily form an uneven shape on the surface of the first insulating layer 2. On the contrary, when the average thickness of the first insulating layer 2 exceeds the above upper limit, the volumetric efficiency of the coil or the like formed by using the insulated wire may be lowered.

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

The shell 4 is made of an inorganic material. Examples of such inorganic materials include single crystal materials, ceramics, and glass. Among these, glass is preferable as the material of the shell 4. By using glass as the material of the shell 4, the strength of the first insulating layer 2 of the insulated wire can be further improved.

The shape of the hollow inorganic particles 3 is not particularly limited, but for example, a spherical shape as shown in FIG. 2 is preferable. By using the spherical hollow inorganic particles 3, cracking of the shell 4 due to the force applied to the surface of the shell 4 during kneading of the hollow inorganic particles and the thermoplastic resin composition in the insulating layer manufacturing process is unlikely to occur. As a result, it is difficult for the pores of the hollow inorganic particles 3 to communicate with each other, and it is difficult for coarse pores to be generated. Here, the “sphere” is not limited to a true sphere, but means, for example, the shape of a sphere having a sphericity of 1.0 or more and 1.3 or less.

The compressive strength of the hollow inorganic particles 3 is the pressure when the volume of the hollow inorganic particles is reduced by 10% as measured by the glycerol method based on ASTM D3102-78. The lower limit of the compressive strength of the hollow inorganic particles 3 is 10 MPa, preferably 20 MPa, more preferably 25 MPa, and even more preferably 30 MPa. If the compressive strength of the hollow inorganic particles 3 does not meet the above lower limit, the shell 4 is likely to crack due to the force applied to the surface of the shell 4 during kneading of the hollow inorganic particles and the thermoplastic resin composition in the insulating layer manufacturing process. Therefore, there is a possibility that the effect of suppressing the communication of pores by the hollow inorganic particles 3 cannot be sufficiently obtained. The upper limit of the withstand voltage of the hollow inorganic particles 3 is not particularly limited, but is preferably 250 MPa, for example. If the withstand voltage strength of the hollow inorganic particles 3 exceeds the above upper limit, the cost of the hollow inorganic particles 3 increases, and the product cost of the insulated wire may increase.

The lower limit of the median diameter of the hollow inorganic particles 3 is preferably 0.5 μm, more preferably 1 μm. On the other hand, the upper limit of the median diameter of the hollow inorganic particles 3 is preferably 50 μm, more preferably 45 μm. If the median diameter of the hollow inorganic particles 3 does not meet the above lower limit, the upper limit of the hollow ratio becomes small and the hollow ratio cannot be increased more than a predetermined value, so that the volume ratio of the hollow inorganic particles 3 contained in the first insulating layer 2 becomes large. .. As a result, the insulating property of the first insulating layer 2 may decrease. On the contrary, if the median diameter of the hollow inorganic particles 3 exceeds the above upper limit, the hollow ratio becomes too large, and the compressive strength of the hollow inorganic particles may decrease.

The lower limit of the average thickness of the shell 4 of the hollow inorganic particles made of an inorganic material is preferably 0.5 μm, more preferably 0.6 μm. On the other hand, the upper limit of the average thickness of the shell 4 is preferably 2.0 μm, more preferably 1.8 μm. If the average thickness of the shell 4 is less than the above lower limit, the shell 4 is likely to be cracked due to the force applied to the surface of the shell 4 during kneading of the hollow inorganic particles and the thermoplastic resin composition in the insulating layer manufacturing process. , The effect of suppressing the communication of pores by the hollow inorganic particles 3 is not sufficiently obtained, and there is a possibility that the strength of the insulating layer is lowered due to the coarse pores. On the contrary, when the average thickness of the shell 4 exceeds the above upper limit, the volume of the pores formed is too small with respect to the volume of the hollow inorganic particles 3, so that the hollow inorganic particles 3 contained in the first insulating layer 2 The volume ratio increases. As a result, the insulating property of the first insulating layer 2 may decrease.

As the lower limit of the specific gravity of the hollow inorganic particles 3, 0.3 is preferable, and 0.4 is more preferable. On the other hand, the upper limit of the specific gravity of the hollow inorganic particles 3 is preferably 0.7, more preferably 0.6. If the specific gravity of the hollow inorganic particles 3 does not reach the above lower limit, the hollow ratio of the hollow inorganic particles becomes too large, and the compressive strength of the hollow inorganic particles may decrease. On the contrary, if the specific gravity of the hollow inorganic particles 3 exceeds the above upper limit, the porosity of the insulating layer may decrease, and the dielectric constant of the insulating layer may not be sufficiently reduced.

The lower limit of the blending amount of the hollow inorganic particles 3 is preferably 20% by volume, more preferably 25% by volume, based on the thermoplastic resin composition. On the other hand, the upper limit of the blending amount is preferably 40% by volume, more preferably 35% by volume, based on the thermoplastic resin composition. If the blending amount of the hollow inorganic particles 3 does not reach the above lower limit, the dielectric constant of the insulating layer may not be sufficiently lowered, and the corona discharge starting voltage may not be sufficiently improved. On the contrary, if the blending amount of the hollow inorganic particles 3 exceeds the above upper limit, the mechanical strength of the insulating layer may not be maintained.

(Resin composition for forming an insulating layer)
The resin composition for forming an insulating layer is a resin composition used for forming the first insulating layer 2 of the insulated electric wire. The resin composition for forming an insulating layer contains a thermoplastic resin composition forming a matrix and a plurality of hollow inorganic particles 3 dispersed in the thermoplastic resin composition.

As the thermoplastic resin composition, for example, one containing a thermoplastic resin as a main component such as polyether sulfone, polyphenylene sulfide, polyetherimide, and polyetheretherketone can be used.

<Manufacturing method of insulated wire>
Next, a method of manufacturing the insulated wire will be described. In the insulated wire, the first insulating layer 2 is formed by extrusion molding. The method for producing an insulated electric wire is a resin composition for forming an insulating layer (also referred to as a resin composition for forming a first insulating layer) by dispersing hollow inorganic particles 3 in a thermoplastic resin composition forming a matrix. A step of preparing a resin composition for forming a first insulating layer (a step of preparing a resin composition for forming a first insulating layer) and a step of extruding and coating the outer peripheral surface of the conductor 1 with the resin composition for forming the first insulating layer (extrusion step).

(Step of preparing resin composition for forming first insulating layer)
More specifically, the step of preparing the resin composition for forming the first insulating layer includes a step of uniformly kneading the thermoplastic resin composition while heating the thermoplastic resin composition to a temperature equal to or higher than the melting point with an extruder, and a plurality of steps. It has a step of mixing the hollow inorganic particles with the thermoplastic resin composition. A normal twin-screw or triaxial multi-screw extruder or single-screw extruder equipped with a side feeder or a side hopper can be used for preparing the resin composition for forming the first insulating layer. As a method for preparing the resin composition for forming the first insulating layer, for example, the thermoplastic resin composition is melt-kneaded using a twin-screw extruder or the like, the thermoplastic resin composition is uniformly kneaded, and then a side feeder or a side feeder or the like. Hollow inorganic particles are charged from the side hopper and mixed with the molten thermoplastic resin composition. When mixing the thermoplastic resin composition and the hollow inorganic particles, the side feeder of the extruder can be efficiently and uniformly dispersed in the thermoplastic resin composition while suppressing cracking of the hollow inorganic particles. A method of mixing a plurality of hollow inorganic particles with the thermoplastic resin composition is preferable.

The resin composition for forming the first insulating layer may be added with various additives such as a lubricant, an antioxidant and a light stabilizer, and various additives such as a modifier, if necessary.

The hollow inorganic particles may be mixed with the thermoplastic resin as the main raw material in advance by a separate mixing device to prepare the resin composition for forming the first insulating layer as a masterbatch, and then put into the extruder.

(Extrusion process)
In the extrusion step, extrusion molding is performed in which the resin composition for forming the first insulating layer after the mixing step of the resin composition for forming the first insulating layer is extruded to the outer peripheral surface side of the conductor. In this way, the outer peripheral surface of the conductor 1 is covered with the first insulating layer 2. By extrusion molding, the first insulating layer 2 containing hollow inorganic particles is formed to obtain the insulated electric wire. The hollow inorganic particles 3 contained in the first insulating layer 2 formed in the extrusion step form pores in the first insulating layer 2.

In the insulated wire, the pores contained in the first insulating layer 2 are formed by the hollow inorganic particles 3. Since the pores formed by the hollow inorganic particles 3 are surrounded by the shell 4 made of an inorganic material, it is difficult for the hollow portions in the hollow inorganic particles 3 to communicate with each other even if the shells 4 come into contact with each other. Pore larger than particle 3 is unlikely to occur. As a result, the insulating electric wire can reduce the dielectric constant of the insulating coating while suppressing the decrease in strength of the insulating layer due to the coarse pores.

As the lower limit of the partial discharge start voltage of the insulated wire, 1200 Vp is preferable, and 1300 Vp is more preferable. If the partial discharge start voltage does not reach the lower limit, dielectric breakdown may occur at an early stage and the life of the insulated wire may be shortened.

As the lower limit of the dielectric breakdown voltage of the insulated wire, 10 kV is preferable, and 11 kV is more preferable. If the breakdown voltage does not reach the lower limit, the insulated wire may not be used for equipment used under high voltage.

<Advantage>
The insulated wire includes an insulating layer in which cracking of the shell of hollow inorganic particles in the insulating layer manufacturing process is suppressed and hollow inorganic particles having pores are stably dispersed. Therefore, it is possible to reduce the dielectric constant of the insulating coating while suppressing a decrease in the strength of the insulating layer, and it is possible to improve the corona discharge starting voltage. Further, surge resistance can be imparted by the effect of the hollow inorganic particles as an inorganic filler. Further, in the resin composition for forming an insulating layer, cracking of the shell of the hollow inorganic particles in the insulating layer manufacturing process is suppressed, and the hollow inorganic particles can be stably dispersed. Therefore, it is possible to reduce the dielectric constant of the insulating coating while suppressing the decrease in the strength of the insulating layer. Further, in the method for manufacturing the insulated wire, the thermoplastic resin composition is first kneaded with an extruder with a side feeder, and then a plurality of hollow inorganic particles are mixed with the thermoplastic resin composition from the side feeder of the extruder. It is possible to form an insulating layer in which the hollow inorganic particles are uniformly dispersed while suppressing the cracking of the hollow inorganic particles. Therefore, it is possible to manufacture an insulated wire capable of lowering the dielectric constant of the insulating coating and improving the corona discharge starting voltage while suppressing a decrease in the strength of the insulating layer.

[Second Embodiment]
<Insulated wire>
The insulated wire according to the second embodiment includes a second insulating layer (hereinafter, also referred to as a second insulating layer) that does not contain hollow inorganic particles due to seizure between the first insulating layer containing hollow inorganic particles and the conductor. It is a laminated product.

The insulated wire according to the second embodiment of FIG. 3 is formed on a linear conductor 1, a second insulating layer 5 laminated on the outer peripheral surface of the conductor 1 by baking, and an outer peripheral surface of the second insulating layer 5. It includes a first insulating layer 2 that is laminated and constitutes the outermost layer. Further, the first insulating layer 2 contains hollow inorganic particles 3, whereas the second insulating layer 5 does not contain hollow inorganic particles. Since the conductor 1 and the first insulating layer 2 are the same as those in the first embodiment, they are numbered the same and the description thereof will be omitted.

(Second insulating layer)
The second insulating layer 5 is laminated on the peripheral surface side of the conductor 1 so as to cover the conductor 1. The second insulating layer 5 is formed by applying and baking an insulating layer forming varnish, which will be described later. In the insulated wire according to the second embodiment of the present invention, the insulating layer forming varnish is applied and baked to form the second insulating layer 5, so that the adhesion between the second insulating layer 5 and the conductor 1 is excellent. ..

The upper limit of the dielectric constant of the second insulating layer 5 is preferably 3.7, more preferably 3.6. If the dielectric constant of the second insulating layer 5 exceeds the above upper limit, the corona discharge start voltage may not be sufficiently improved.

The lower limit of the average thickness of the second insulating layer 5 is not particularly limited, but is preferably 10 μm, more preferably 15 μm. The upper limit of the average thickness is preferably 150 μm, more preferably 100 μm. If the average thickness is less than the above lower limit, sufficient electrical insulation, scratch resistance, work resistance, etc. may not be exhibited. On the other hand, if the average thickness exceeds the upper limit, foaming may occur when the solvent is volatilized.

(Varnish for forming an insulating layer)
The insulating layer forming varnish is a resin composition used for producing the second insulating layer 5 formed by baking. The insulating layer forming varnish is a composition containing a main polymer, a diluting solvent, a curing agent, and the like. The main polymer is not particularly limited, but a thermosetting resin is preferable. When a thermosetting resin is used, for example, a polyvinyl formal precursor, a thermosetting polyurethane precursor, a thermosetting acrylic resin precursor, an epoxy resin precursor, a thermosetting polyester precursor, a thermosetting polyesterimide precursor, a thermosetting polyesteramide. An imide precursor, a thermosetting polyamide imide precursor, a polyimide precursor and the like can be used. Among these, the polyimide precursor is preferable in that the varnish for forming the insulating layer can be easily applied and the strength and heat resistance of the second insulating layer 5 can be easily improved.

As the diluting solvent, an organic solvent known for insulating varnish can be used. Specifically, for example, polar organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, tetramethylurea, hexamethylphosphate triamide, and γ-butyrolactone are used. First, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate and 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 pyridine and the like. Examples thereof include tertiary amines, and these organic solvents are used alone or in admixture of two or more.

Further, the resin composition may contain a curing agent. Examples of the curing agent include titanium-based curing agents, isocyanate-based compounds, blocked isocyanates, urea and melamine compounds, amino resins, acetylene derivatives, alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, aliphatic acid anhydrides, and aromatics. Acid anhydrides and the like are exemplified. These curing agents are appropriately selected according to the type of the main polymer contained in the resin composition used. For example, in the case of a polyamide-imide type, 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-based compound include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexanediisocyanate, and the like. Aliphatic diisocyanate having 3 to 12 carbon atoms such as lysine diisocyanate, 1,4-cyclohexanediisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexanediisocyanate, isopropylidene Dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane (hydrogenated XDI), hydrogenated TDI, 2,5-bis (isocyanatomethyl) -bicyclo [2,2,1] heptane, 2 , 6-Bis (isocyanatomethyl) -bicyclo [2,2,1] heptane and other alicyclic isocyanates with 5 to 18 carbon atoms, and tetramethylxylylene diisocyanates (TMXDI) and other aliphatic diisocyanates having an aromatic ring. Examples of these modified products are used. 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, tolylen-2,4-diisocyanate, tolylen-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, butyrolylated melamine and the like. Examples of the acetylene derivative include ethynylaniline and ethynylphthalic anhydride.

The lower limit of the resin solid content concentration of the insulating layer forming varnish diluted with the organic solvent is preferably 15% by mass, more preferably 20% by mass. On the other hand, the upper limit of the resin solid content concentration of the insulating layer forming varnish is preferably 50% by mass, more preferably 30% by mass. If the resin solid content concentration of the insulating layer forming varnish does not reach the above lower limit, the thickness that can be formed by one application of the varnish becomes small, so that the varnish for forming the second insulating layer 5 having a predetermined thickness is formed. The number of repetitions of the coating process increases, and the time of the varnish coating process may become long. On the contrary, if the resin solid content concentration of the varnish for forming the insulating layer exceeds the above upper limit, the varnish may be thickened, which may deteriorate the storage stability of the varnish or the adhesiveness at the time of applying the varnish. be.

<Manufacturing method of insulated wire of the second embodiment>
As a method of manufacturing the insulated wire of the second embodiment, for example, after laminating the second insulating layer 5 on the outer peripheral surface of the conductor 1, the resin for forming the first insulating layer of the method of manufacturing the insulated wire of the first embodiment. Examples thereof include a method of performing a composition preparation step and an extrusion step.

(Method of forming the second insulating layer 5)
The method for forming the second insulating layer 5 is a step of preparing the insulating layer forming varnish for forming the second insulating layer 5 (varnish preparation step), and applying the insulating layer forming varnish to the outer peripheral surface of the conductor 1. A step of applying (varnish coating step) and a step of baking the above-mentioned insulating layer forming varnish (baking step) are provided.

<Varnish preparation process>
In the varnish preparation step, first, a varnish for forming an insulating layer forming the second insulating layer 5 is prepared by diluting the main polymer forming the second insulating layer 5 with a solvent.

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

<Baking process>
Next, in the baking step, a baking layer is formed on the surface of the conductor 1 by passing the conductor 1 coated with the insulating layer forming varnish through a baking furnace and baking the insulating layer forming varnish.

The second insulating layer 5 composed of the plurality of baking layers is formed by repeating the varnish coating step and the baking step until the total thickness of the plurality of baking layers laminated on the surface of the conductor 1 reaches a predetermined thickness. ..

In the varnish coating step, after coating the varnish, the coating amount of the varnish on the conductor 1 may be adjusted and the coated varnish surface may be smoothed by using a coating die. The coating die has an opening, and the conductor 1 coated with the insulating layer forming varnish passes through the opening to remove excess varnish and adjust the coating amount of the varnish. As a result, the thickness of the second insulating layer 5 of the insulated wire tends to be uniform, and uniform electrical insulation can be easily obtained.

After laminating the second insulating layer 5 on the surface of the conductor 1, the second insulation is performed by performing the first insulating layer forming resin composition preparation step and the extrusion step of the method for manufacturing the insulated wire of the first embodiment described above. The first insulating layer 2 containing hollow inorganic particles can be laminated on the outer peripheral surface of the layer 5 to obtain the insulated wire of the second embodiment.

<Advantage>
Since the insulated wire includes an insulating layer formed from the resin composition for forming the insulating layer containing hollow inorganic particles, the insulating layer is suppressed from being lowered in strength as in the case of the insulated wire according to the first embodiment. , The dielectric constant of the insulating film can be lowered, and the corona discharge starting voltage can be improved. Further, surge resistance can be imparted by the effect of the hollow inorganic particles as an inorganic filler. Further, since the insulated wire is provided with a baking insulating layer having good adhesion to the conductor between the insulating layer containing hollow inorganic particles and the conductor, the adhesion between the conductor and the insulating layer is improved. can do. Further, the mechanical strength of the insulated wire can be improved by providing the insulated wire with a plurality of insulating layers laminated on the outer peripheral surface of the conductor.

[Third Embodiment]
<Insulated wire>
The insulated wire according to the third embodiment is obtained by laminating a second insulating layer containing no hollow inorganic particles between a first insulating layer containing hollow inorganic particles and a conductor by extrusion molding.

The thermoplastic resin composition used for forming the second insulating layer laminated between the first insulating layer containing hollow inorganic particles and the conductor is the heat used for the resin composition for forming the first insulating layer of the first embodiment. It is the same as the plastic resin composition.

The lower limit of the average thickness of the second insulating layer is not particularly limited, but is preferably 50 μm, more preferably 60 μm. On the other hand, the upper limit of the average thickness of the second insulating layer is preferably 500 μm, more preferably 450 μm. If the average thickness of the second insulating layer is less than the above lower limit, the insulating property may decrease. On the other hand, if the average thickness of the second insulating layer exceeds the above upper limit, the volumetric efficiency of the coil or the like formed by using the insulated wire may decrease.

<Manufacturing method of insulated wire of the third embodiment>
As a method for manufacturing an insulated wire of the third embodiment, for example, the second insulating layer is laminated by extrusion molding the thermoplastic resin composition on the outer peripheral surface of the conductor 1, and then the first insulating layer 2 is formed. Examples thereof include a method of laminating a resin composition for forming a first insulating layer containing the hollow inorganic particles 3 to be used by extrusion molding.

<Advantage>
Since the insulated wire includes an insulating layer formed from the resin composition for forming the insulating layer containing hollow inorganic particles, the insulating layer is suppressed in strength as in the case of the first embodiment. The dielectric constant of the insulating coating can be lowered, and the corona discharge starting voltage can be improved. Further, surge resistance can be imparted by the effect of the hollow inorganic particles as an inorganic filler. Further, the mechanical strength of the insulated wire can be improved by providing the insulated wire with a plurality of insulating layers laminated on the outer peripheral surface of the conductor.

[Other Embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. NS.

In the above embodiment, the second insulating layer of 1 is laminated between the insulated wire and the conductor 1 in which the first insulating layer of one layer is laminated on the outer peripheral surface of the conductor and the first insulating layer containing the hollow inorganic particles 3. Although the insulated wire to be provided has been described, a plurality of insulating layers may be laminated between the conductor 1 and the first insulating layer containing hollow inorganic particles. Further, one or more insulating layers formed in the extrusion step may be laminated on the outer peripheral surface of the first insulating layer containing hollow inorganic particles. As described above, in an insulated wire in which a plurality of insulating layers are laminated, it is sufficient that at least one insulating layer contains hollow inorganic particles. That is, hollow inorganic particles may be contained in two or more insulating layers. When two or more insulating layers contain hollow inorganic particles, each of these insulating layers contributes to lowering the dielectric constant. An insulated wire in which at least one of the plurality of insulating layers contains a plurality of hollow inorganic particles is also within the scope of the present invention. Further, by laminating a plurality of insulating layers on the outer peripheral surface of the conductor in this way, the mechanical strength of the insulated wire can be improved.

Further, the adhesion between the hollow inorganic particles and the thermoplastic resin composition forming the matrix may be improved by performing the surface treatment of the hollow inorganic particles.

Further, for example, in the insulated wire, a further layer such as a primer-treated layer may be provided between the conductor and the insulating layer. The primer-treated layer is a layer provided for enhancing the adhesion between layers, and can be formed by, for example, a known resin composition.

When a primer-treated layer is provided between the conductor and the insulating layer, the resin composition forming the primer-treated layer may be, for example, one or more resins among polyimide, polyamide-imide, polyesterimide, polyester and phenoxy resins. It should be included. Further, the resin composition forming the primer-treated layer may contain an additive such as an adhesion improver. By forming a primer-treated 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, and as a result, the insulating electric wire can be used. Properties such as flexibility, wear resistance, scratch resistance, and work resistance can be effectively enhanced.

Further, the resin composition forming the primer-treated layer may contain other resins such as epoxy resin and melamine resin in addition to the above resin. Further, a commercially available liquid composition (insulating varnish) may be used as each resin contained in the resin composition forming the primer-treated layer.

As the lower limit of the average thickness of the primer-treated layer, 1 μm is preferable, and 2 μm is more preferable. On the other hand, the upper limit of the average thickness of the primer-treated layer is preferably 20 μm, more preferably 10 μm. If the average thickness of the primer-treated layer is less than the above lower limit, sufficient adhesion to the conductor may not be exhibited. On the contrary, if the average thickness of the primer-treated layer exceeds the above upper limit, the diameter of the insulated wire may be unnecessarily increased.

Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limitedly interpreted based on the description of this Example.

[Insulated wire No. 1-No. 12]
By laminating an insulating layer on the outer peripheral surface of a conductor having a conductor diameter (diameter) of 1 mm according to the conditions shown in Table 1, the insulated wire No. 1-No. 12 was prototyped. The insulating layer was laminated in the order of a second insulating layer containing no hollow inorganic particles and a first insulating layer containing hollow inorganic particles on the outer peripheral surface of the conducting wire. In addition, No. In No. 9, in forming the first insulating layer, hollow inorganic particles were mixed with the thermoplastic resin composition from the side feeder of the extruder to prepare a resin composition for forming the first insulating layer.

(1) Formation of second insulating layer (second insulating layer by extrusion molding)
As the thermoplastic resin composition used for forming the second insulating layer by extrusion molding containing no hollow inorganic particles, a polyether sulfone or a polyether ether ketone was used. The thermoplastic resin composition was put into a twin-screw extruder and kneaded while being heated to a temperature equal to or higher than the melting point to prepare a resin composition for forming a first insulating layer. Next, the resin composition for forming the second insulating layer was put into a twin-screw extruder, kneaded while heating above the melting point, and then extruded on the outer peripheral surface of the conducting wire to form the second insulating layer. ..

(Second insulating layer by baking)
As a thermosetting resin composition used for forming the second insulating layer by baking, a polyimide precursor obtained by reacting an aromatic tetracarboxylic dianhydride with an aromatic diamine is converted into N-methyl-2-pyrrolidone. It was prepared by dissolving it. Next, the thermosetting resin composition for baking was applied to the surface of the conducting wire and then heated (baked), and this was repeated a plurality of times to form a second insulating layer.

(2) Formation of first insulating layer (hollow inorganic particles)
As the hollow inorganic particles, "Glass Bubbles iM30K, iM16K, S42XHS, S38, S22, K20" of 3M Japan Ltd. was used.

(Physical characteristics of hollow inorganic particles)
Table 1 shows the compressive strength (MPa), the average thickness of the shell (μm), the median diameter (μm), and the specific gravity as the physical property values of the hollow inorganic particles used. As described above, the compressive strength was measured by the glycerol method based on ASTM D3102-78, and showed the pressure when the volume of the hollow inorganic particles was reduced by 10%. The specific gravity was determined from the true density (g / cm ^{3) of the hollow inorganic particles.}

(Formation of the first insulating layer containing hollow inorganic particles by extrusion molding)
As the resin composition for forming the first insulating layer used for forming the first insulating layer containing the hollow inorganic particles, the hollow inorganic particles are sided with the resin composition for forming the second insulating layer heat-kneaded by a twin-screw extruder. After being charged from the hopper, it was heated and kneaded to prepare a resin composition for forming a first insulating layer. The blending amount of the hollow inorganic particles was 30% by volume with respect to the resin composition for forming the first insulating layer. Next, the resin composition for forming the first insulating layer was laminated on the outer peripheral surface of the conducting wire or the second insulating layer by extrusion molding to prepare an insulated electric wire.

<Evaluation>
The insulated wire No. obtained as described above. 1-No. Table 1 shows the evaluation results of (1) dielectric constant, (2) partial discharge start voltage, (3) dielectric breakdown voltage, and (4) appearance of No. 12.

(1) Dielectric constant Each insulated wire obtained is placed in a constant temperature bath at a temperature of 100 ° C., dried for 1 hour, and then silver paste is applied to any three places on the surface of the insulating layer constituting the outermost layer for measurement. Samples were prepared. Next, the capacitance between the conductor and the silver paste was measured with an LCR meter (“Impiness Analyzer ZA5405” manufactured by NF Circuit Design Block Co., Ltd.), and the dielectric constant was determined from the average value of the measured capacitance and the average thickness of the insulating layer. Was calculated. The measurement was performed under the conditions of a temperature of 30 ° C. and a relative humidity of 50%.

(2) Partial discharge start voltage Two of the manufactured insulated wires were twisted together, an AC voltage was applied to both ends of the two insulated wires to raise the voltage at a rate of 10 V / sec, and discharge of 50 pC or more continued for 3 seconds. The voltage at that time was used as the measured value. In the evaluation, 1200 Vp or more was designated as A, and less than 1200 Vp was designated as B.

(3) Insulation breakdown voltage Insulation breakdown voltage is measured by immersing an insulating wire in a glycerin solution in which glycerin and saturated saline are mixed at a mass ratio of 17: 3 by 1 m, and then using the conductor of the insulating wire and the glycerin solution. In the meantime, the breaking voltage when an AC voltage having a waveform close to a sinusoidal wave of 50 Hz or 60 Hz was boosted at 500 V / s and applied was measured. Here, the detection current of dielectric breakdown was set to 5 mA. This measurement was carried out continuously at 30 m of insulated wires every 1 m at a total of 30 points. The average value of the dielectric breakdown voltage at 30 points was calculated and used as the measured value of the dielectric breakdown voltage. In the evaluation, 10 kV or more was designated as A, and less than 10 kV was designated as B.

(4) Appearance (4-1) Surface of insulating layer, (4-2) Dispersibility of hollow inorganic particles and (4-3) Cracking of hollow inorganic particles were evaluated.
(4-1) Surface of Insulation Layer As for the surface of the insulation layer, the one that is smooth and has no unevenness by visual judgment is designated as A, the one that has a partially rough feeling is designated as B, and the one that has unevenness as a whole is designated as C.
(4-2) Dispersibility of Hollow Inorganic Particles Regarding the dispersibility of hollow inorganic particles, a cross-sectional observation of the wire coating was performed with a scanning electron microscope (SEM), and the case where the hollow inorganic particles were uniformly dispersed was A. The case where a small amount of agglomeration of hollow inorganic particles was present was designated as B, and the case where agglomeration of hollow inorganic particles was present at a plurality of locations was defined as C.
(4-3) Cracking of hollow inorganic particles For cracking of hollow inorganic particles, observe the cross section of the wire film with a scanning electron microscope (SEM), and if there are no cracks, A, if there are slight cracks, B, the case where a large number of cracks were present was designated as C.

The evaluation results of the above characteristics are shown in Table 1.

From the results in Table 1 above, the insulated wire No. 1-No. Regarding No. 9, it was confirmed that good results were obtained in all of (1) dielectric constant, (2) partial discharge start voltage, (3) dielectric breakdown voltage and (4) appearance. On the other hand, the insulated wire No. 1 in which the withstand voltage strength of the hollow inorganic particles is less than 10 MPa and the specific gravity is less than 0.3. In No. 10, many cracks of hollow inorganic particles were present. Further, the insulated wire No. having a withstand voltage of less than 10 MPa, a specific gravity of less than 0.3, and a median diameter of more than 50 μm of the hollow inorganic particles. In No. 11, a large number of cracks in the hollow inorganic particles were present, and the partial discharge start voltage was less than 1200 Vp. No. that does not contain hollow inorganic particles in the insulating layer. At 12, the partial discharge start voltage was less than 1200 Vp.

The insulated wire according to the present invention can improve the corona discharge start voltage by lowering the dielectric constant of the insulating coating while suppressing the decrease in the strength of the insulating layer, and is therefore used in electrical equipment having a high applicable voltage. It can be suitably used as an insulated electric wire.

1 Conductor 2 First insulating layer 3 Hollow inorganic particles 4 Shell 5 Second insulating layer

Claims (1)

A linear conductor and one or more insulating layers laminated on the outer peripheral surface of the conductor are provided.
A method for manufacturing an insulated wire having a partial discharge start voltage of 1200 Vp or more and a dielectric breakdown voltage of 10 kV or more.
Using an extruder with a side feeder,
The step of kneading the thermoplastic resin composition forming a matrix of at least one layer of the above one or a plurality of insulating layers with the above extruder.
A step of mixing a plurality of hollow inorganic particles from the side feeder of the extruder into the thermoplastic resin composition, and
A method for manufacturing an insulated electric wire, comprising a step of extruding a resin composition for forming an insulating layer after the mixing step toward the outer peripheral surface side of the conductor.

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