JP2017199478A - Insulated wire and method for manufacturing insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated wire excellent in welding resistance and insulating properties.SOLUTION: An insulated wire according to one embodiment of the present invention includes a conductor and an insulating layer covering an outer peripheral surface of the conductor, where the insulating layer has a hole layer which contains a hole and is laminated directly on the conductor and a solid layer containing no hole. A porosity of the porous layer is preferably 5 vol.% or more and 80 vol.% or less. An average diameter of the holes is preferably 0.1 μm or more and 30 μm or less. A ratio of the average thickness of the solid layer to the average thickness of the hole layer is preferably 5% or more and 700% or less. A method for manufacturing an insulated wire according to another embodiment of the present invention is a method for manufacturing an insulated wire including a conductor and an insulating layer covering an outer peripheral surface of the conductor, where the insulating layer has a hole layer which contains a hole and is laminated directly on the conductor and a solid layer containing no hole, the method including a first application step of applying a first resin composition containing a resin and a hole forming agent onto the conductor.SELECTED DRAWING: Figure 1

Description

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

  A coil formed by winding an insulated wire is used for components such as general household electric appliances and automobiles such as a motor, an alternator, and an ignition. The insulated wire forming such a coil is generally composed of a conductive metal conductor and a resin insulating layer covering the conductive conductor.

  For example, when an insulated wire is used for a coil used in an automobile motor or the like, a method of joining short insulated wires together by welding to form a long coil may be employed. Welding is performed by electric welding such as TIG welding, and the conductor is connected by raising the temperature of the welded portion by passing a constant current. Usually, a high current is used to increase the working efficiency of welding. However, for example, when the insulation resistance of the insulating layer is low, foaming may occur in the insulating layer and the insulating layer may be deteriorated. Therefore, an insulated wire with high weld resistance is required. In addition to such weld resistance, there is a demand for high insulation that does not cause dielectric breakdown even when a high current is passed.

  On the other hand, the insulated wire which improved the welding resistance and insulation by selecting each monomer which comprises the polyimide contained in an insulating layer suitably is developed (refer Unexamined-Japanese-Patent No. 2014-007065). ).

JP 2014-007065 A

  However, the above-described conventional insulated wire has insufficient weld resistance, and there is a limit to improving the weld resistance and insulation by selecting materials.

  This invention is made | formed based on the above situations, and it aims at providing the insulated wire excellent in weld resistance and insulation.

  An insulated wire according to one aspect of the present invention made to solve the above problems is an insulated wire comprising a conductor and an insulating layer covering the outer peripheral surface of the conductor, and the insulating layer has pores. An insulated wire including a hole layer that is directly stacked on the conductor and a solid layer that does not include a hole.

  The manufacturing method of the insulated wire which concerns on another one aspect | mode of this invention is equipped with a conductor and the insulating layer which coat | covers the outer peripheral surface of this conductor, and the said insulating layer contains a void | hole and is laminated | stacked directly on the said conductor. A method of manufacturing an insulated wire having a hole layer and a solid layer not including holes, a first application step of applying a first resin composition containing a resin and a hole forming agent on a conductor; A first heating step for heating the first layer applied in the first application step, and a second resin composition containing a resin on the pore layer formed in the first heating step. It is a manufacturing method of an insulated wire provided with the 2 application | coating process and the 2nd heating process which heats the 2nd layer formed at the said 2nd application | coating process.

  Since the insulated wire includes a hole layer in which an insulating layer is directly laminated on a conductor and a solid layer provided on the outside thereof, the insulated wire is excellent in welding resistance and insulation. Moreover, according to the manufacturing method of the said insulated wire, such an insulated wire can be manufactured easily and reliably.

FIG. 1 is a schematic cross-sectional view of an insulated wire according to an embodiment of the present invention. FIG. 2 is a schematic diagram schematically showing a welding resistance test method.

[Description of Embodiment of the Present Invention]
An insulated wire according to an aspect of the present invention is an insulated wire including a conductor and an insulating layer covering an outer peripheral surface of the conductor, and the insulating layer includes a hole and is directly laminated on the conductor. It is an insulated wire having a hole layer and a solid layer not including holes.

  The said insulated wire can suppress deterioration by the heat | fever of an insulating layer because the insulating layer has the hole layer which has high heat insulation in contact with a conductor. Therefore, the insulated wire is excellent in weld resistance. Moreover, since the said insulated wire is provided with the solid layer in which an insulating layer does not contain a void | hole, the insulation of an insulating layer can be improved and a dielectric breakdown can be suppressed. Furthermore, the said insulated wire can provide flexibility to an insulating layer because an insulating layer is provided with a void layer. Thus, since the said insulated wire is provided with the void | hole layer by which an insulating layer is directly laminated | stacked on a conductor, and a solid layer, it is excellent in welding resistance, insulation, and flexibility.

  The porosity of the pore layer is preferably 5% by volume or more and 80% by volume or less. Thus, the deterioration by the heat | fever of an insulating layer can be effectively suppressed by making the porosity of a void | hole layer into the said range. Here, “porosity” means the ratio of the total volume of all the pores contained in the pore layer to the volume of the pore layer, and is expressed as a percentage.

  The average diameter of the holes is preferably 0.1 μm or more and 30 μm or less. Thus, by making the average diameter of the pores within the above range, deterioration of the insulating layer due to heat can be reliably suppressed, and the weld resistance can be improved. Here, the “average diameter of the holes” means a value obtained by averaging the diameters of the true spheres corresponding to the volume of the holes for all the holes included in the hole layer. In the case where the insulating layer has a plurality of pore layers, the “average diameter of the pores” means a value obtained by averaging the diameters of the pores included in all the pore layers.

  The ratio of the average thickness of the solid layer to the average thickness of the pore layer is preferably 5% or more and 700% or less. Thus, welding resistance, insulation, and flexibility can be improved by setting the ratio of the average thickness of the solid layer to the average thickness of the pore layer in the above range.

  The manufacturing method of the insulated wire which concerns on another one aspect | mode of this invention is equipped with a conductor and the insulating layer which coat | covers the outer peripheral surface of this conductor, and the said insulating layer contains a void | hole and is laminated | stacked directly on the said conductor. A method of manufacturing an insulated wire having a hole layer and a solid layer not including holes, a first application step of applying a first resin composition containing a resin and a hole forming agent on a conductor; A first heating step for heating the first layer applied in the first application step, and a second resin composition containing a resin on the pore layer formed in the first heating step. It is a manufacturing method of an insulated wire provided with the 2 application | coating process and the 2nd heating process which heats the 2nd layer formed at the said 2nd application | coating process.

  In the method for manufacturing the insulated wire, a hole layer including holes is directly laminated on a conductor. Since air having a high heat insulating effect is confined in the holes, the hole layer including such holes has excellent heat resistance, and thus the insulated wire has excellent weld resistance. Moreover, the manufacturing method of the said insulated wire forms the solid layer which does not contain a hole on the above-mentioned hole layer. Since the solid layer does not have pores, the obtained insulated wire is excellent in insulation. Therefore, the manufacturing method of the said insulated wire can manufacture the insulated wire which is excellent in welding resistance and insulation.

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

[Insulated wire]
The insulated wire in FIG. 1 includes a conductor 1 and an insulating layer 2 that covers the outer peripheral surface of the conductor 1. The insulating layer 2 mainly includes a hole layer 3 that includes holes 5 and is directly stacked on the conductor 1, and a solid layer 4 that is stacked on the outer peripheral surface of the hole layer 3 and does not include holes. .

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

  The material of the conductor 1 is preferably a metal having high electrical conductivity and high mechanical strength. Examples of such metals include copper, copper alloys, aluminum, nickel, silver, iron, steel, and stainless steel. The conductor 1 is a material in which these metals are formed in a linear shape, or a multilayer structure in which such a linear material is coated with another metal, such as a nickel-coated copper wire, a silver-coated copper wire, or a copper-coated aluminum. Wire, copper-coated steel wire, etc. can be used.

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

<Insulating layer>
The insulating layer 2 includes a hole layer 3 that includes holes 5 and is directly stacked on the conductor 1, and a solid layer 4 that is stacked on the outer peripheral surface of the hole layer 3 and does not include holes.

  As a minimum of average thickness of insulating layer 2, 30 micrometers is preferred and 40 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the insulating layer 2 is preferably 200 μm and more preferably 180 μm. If the average thickness of the insulating layer 2 is less than the lower limit, the insulating layer 2 may be broken and the conductor 1 may be insufficiently insulated. On the contrary, when the average thickness of the insulating layer 2 exceeds the upper limit, the volume efficiency of a coil or the like formed using the insulated wire may be lowered.

(Hole layer)
The hole layer 3 is composed of a resin composition and holes 5.

  The main component resin of the resin composition forming the pore layer 3 is not particularly limited, but examples thereof include polyether sulfone, polyether imide, polycarbonate, polyphenyl sulfone, polysulfone, polyethylene terephthalate, polyether ether ketone, and the like. Thermoplastic resins such as polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy, thermosetting polyester, thermosetting polyester imide, thermosetting polyester amide imide, aromatic polyamide, thermosetting polyamide imide, thermosetting polyimide, etc. A thermosetting resin can be used. Note that a thermoplastic resin is more preferable than a thermosetting resin as the resin for forming the pore layer 3 in that the flexibility of the insulating layer 2 can be easily maintained. Among these thermoplastic resins, polyethylene terephthalate is particularly preferable because it has a low dielectric constant and can easily reduce the dielectric constant of the insulating layer 2. Here, the “main component” is a component having the largest content, for example, a component contained in an amount of 50% by mass or more.

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

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

  Further, the resin in the resin composition forming the pore layer 3 is preferably crosslinked. By cross-linking the resin in the resin composition forming the pore layer 3, the mechanical strength of the pore layer 3 is improved, and the action of suppressing the mechanical strength due to the inclusion of the pores 5 can be reduced. It becomes easy to maintain the mechanical strength of the layer 2. Moreover, chemical resistance and weld resistance can also be improved by crosslinking the resin in the resin composition forming the pore layer 3.

  The lower limit of the average thickness of the pore layer 3 is preferably 5 μm and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the pore layer 3 is preferably 180 μm, and more preferably 160 μm. If the average thickness of the pore layer 3 is less than the above lower limit, the weld resistance may be reduced. On the contrary, when the average thickness of the hole layer 3 exceeds the upper limit, the insulated wire may be unnecessarily enlarged.

  The lower limit of the porosity of the pore layer 3 is preferably 5% by volume, more preferably 10% by volume, and still more preferably 20% by volume. On the other hand, the upper limit of the porosity of the pore layer 3 is preferably 80% by volume, more preferably 70% by volume, and still more preferably 60% by volume. When the porosity of the hole layer 3 is less than the above lower limit, the heat insulating effect of the hole layer 3 is lowered, and the weld resistance may not be sufficiently improved. Conversely, if the porosity of the pore layer 3 exceeds the above upper limit, the insulation may not be sufficiently improved, or the mechanical strength of the pore layer 3 is too low, and the mechanical strength of the insulating layer 2 is maintained. It may not be possible.

  The lower limit of the average diameter of the pores 5 is preferably 0.1 μm, more preferably 1 μm, and even more preferably 5 μm. On the other hand, the upper limit of the average diameter of the holes 5 is preferably 30 μm, more preferably 20 μm, and even more preferably 15 μm. When the average diameter of the holes 5 is less than the lower limit, the heat insulating effect of the hole layer 3 is lowered, and the weld resistance may not be sufficiently improved. On the contrary, if the average diameter of the holes 5 exceeds the upper limit, the insulation cannot be sufficiently improved, and the distribution of the holes 5 in the hole layer 3 is difficult to be uniform, and the distribution of the dielectric constant is biased. May occur easily.

(Solid layer)
The solid layer 4 is laminated on the outer peripheral surface of the pore layer 3. The solid layer 4 is composed of a resin composition, and the solid layer 4 does not include pores.

  The main component resin of the resin composition forming the solid layer 4 is not particularly limited, but examples thereof include polyethersulfone, polyetherimide, polycarbonate, polyphenylsulfone, polysulfone, polyethylene terephthalate, polyetheretherketone, and the like. Thermoplastic resins such as polyvinyl formal, thermosetting polyurethane, thermosetting acrylic, epoxy, thermosetting polyester, thermosetting polyester imide, thermosetting polyester amide imide, aromatic polyamide, thermosetting polyamide imide, thermosetting polyimide, etc. A thermosetting resin can be used. Among these thermoplastic resins, polyethylene terephthalate is particularly preferable because it has a low dielectric constant and can easily reduce the dielectric constant of the insulating layer 2.

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

  The resin in the resin composition forming the solid layer 4 is preferably crosslinked. By cross-linking the resin in the resin composition forming the solid layer 4, the mechanical strength of the solid layer 4 is improved, and the mechanical strength of the insulating layer 2 is easily maintained. Moreover, chemical resistance and weld resistance can also be improved by crosslinking the resin in the resin composition forming the solid layer 4.

  Moreover, as a minimum of the average thickness of the solid layer 4, 10 micrometers is preferable and 20 micrometers is more preferable. On the other hand, the upper limit of the average thickness of the solid layer 4 is preferably 180 μm, and more preferably 160 μm. When the average thickness of the solid layer 4 is less than the above lower limit, the insulation may not be sufficiently improved. Conversely, when the average thickness of the solid layer 4 exceeds the upper limit, the insulated wire may unnecessarily increase in diameter.

  Further, the lower limit of the ratio of the average thickness of the solid layer 4 to the average thickness of the pore layer 3 is preferably 5%, more preferably 10%, and even more preferably 20%. On the other hand, the upper limit of the ratio is preferably 700%, more preferably 650%, and still more preferably 600%. If the ratio is less than the lower limit, the mechanical strength of the insulating layer 2 may be lowered and the insulating property of the insulating layer 2 may be lowered. Conversely, if the ratio exceeds the upper limit, the effect of suppressing the thermal degradation of the insulating layer 2 may be reduced.

[First manufacturing method of insulated wire]
Next, the 1st manufacturing method of the said insulated wire shown in FIG. 1 is demonstrated. The method for manufacturing an insulated wire heats a first coating step in which a first resin composition containing a resin and a pore-forming agent is applied onto the conductor 1, and the first layer applied in the first coating step. A first heating step; a second coating step of applying a second resin composition containing a resin on the pore layer 3 formed in the first heating step; and a second coating step formed in the second coating step. A second heating step for heating the two layers.

<First application process>
In the first coating step, the resin for forming the pore layer 3 is diluted with a solvent and further mixed with a pore-forming agent to prepare a first resin composition (hereinafter also referred to as “a varnish for the pore layer”). To do. Thereafter, the void layer varnish is applied onto the conductor 1 to form the first layer.

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

  As a minimum of foaming temperature of the above-mentioned chemical foaming agent, 180 ° C is preferred and 210 ° C is more preferred. On the other hand, the upper limit of the foaming temperature is preferably 300 ° C, and more preferably 260 ° C. When the said foaming temperature is less than the said minimum, it is easy to produce foaming before baking and there exists a possibility that adjustment of the thickness of the void | hole layer 3 may become difficult. On the other hand, when the foaming temperature exceeds the upper limit, an increase in the baking temperature and an increase in the baking time may be caused, and the manufacturing cost of the insulated wire may increase. Here, the “foaming temperature” is a temperature at which the foaming agent starts foaming. The “baking time” is a time for holding the conductor 1 coated with the varnish at the baking temperature in the baking process.

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

  In addition, as a minimum of the resin solid content density | concentration of the varnish for hole layers prepared by diluting with these organic solvents, 20 mass% is preferable and 22 mass% is more preferable. On the other hand, the upper limit of the resin solid content concentration of the void layer varnish is preferably 50% by mass, and more preferably 48% by mass. When the resin solid content concentration of the varnish for vacancies is less than the lower limit, the amount of coating at one time when the varnish for vacancies is applied is reduced, so that the pore layer 3 having a desired thickness is formed. Therefore, the number of repetitions of the varnish application process increases, and the time of the varnish application process may be increased. On the contrary, when the resin solid content concentration of the varnish for the pore layer exceeds the above upper limit, it is difficult to uniformly mix the resin for forming the pore layer 3 and the pore-forming agent, and it may take a long time to prepare the varnish. There is.

<First heating step>
In the first heating step, the first layer applied in the first application step is heated and baked. Thereby, the hole layer 3 is formed outside the conductor 1. During baking, the holes 5 are formed by foaming or decomposition of the hole forming agent contained in the first layer.

  When the pore layer 3 having a desired thickness cannot be formed by applying and baking the varnish for the pore layer once, the application and baking of the varnish for the pore layer are repeated until the pore layer 3 reaches a predetermined thickness. Do.

<Second application process>
In the second application step, the resin forming the solid layer 4 is diluted with a solvent to prepare a second resin composition (hereinafter also referred to as “solid layer varnish”). Thereafter, the solid layer varnish is applied onto the pore layer 3 to form a second layer.

  As the solvent for diluting the solid layer varnish, known organic solvents conventionally used for insulating varnishes can be used, and specifically, the diluting solvent used for preparing the above-described pore layer varnish. And the same kind.

  In addition, as a minimum of the resin solid content concentration of the varnish for solid layers prepared by diluting with these organic solvents, 20 mass% is preferable and 22 mass% is more preferable. On the other hand, the upper limit of the resin solid content concentration of the solid layer varnish is preferably 50% by mass, and more preferably 48% by mass. When the solid content concentration of the solid layer varnish is less than the above lower limit, the amount of application at one time when the solid layer varnish is applied is reduced, so that the solid layer 4 having a desired thickness is formed. Therefore, the number of repetitions of the varnish application process increases, and the time of the varnish application process may be increased. On the contrary, when the resin solid content concentration of the solid layer varnish exceeds the upper limit, the time required for dilution may be increased.

<Second heating step>
In the second heating step, the second layer applied to the outer peripheral surface of the pore layer 3 in the second application step is heated and baked. Thereby, the solid layer 4 is formed on the outer peripheral surface of the hole layer 3 formed in the conductor 1. A layer other than the hole layer 3 and the solid layer 4 constituting the insulating layer 2 may be formed between the hole layer 3 and the solid layer 4. This layer may be a single layer or a plurality of layers.

  When the solid layer 4 having a desired thickness cannot be formed by applying and baking the solid layer varnish once, the solid layer varnish is repeatedly applied and baked until the solid layer 4 reaches a predetermined thickness. Do. By forming the solid layer 4 having a predetermined thickness, the insulated wire can be obtained.

[Second manufacturing method of insulated wire]
Next, the 2nd manufacturing method of the said insulated wire shown in FIG. 1 is demonstrated. The second manufacturing method of the insulated wire includes a step of covering the outer peripheral surface of the conductor 1 with the hole layer 3 and the solid layer 4 (extrusion coating step) by coextrusion. The hole layer 3 includes holes 5, and the solid layer 4 does not include holes.

<Extrusion coating process>
In the extrusion coating step, the hole layer resin composition for forming the hole layer 3 and the solid layer resin composition for forming the solid layer 4 are charged into a melt extruder. Here, the resin composition for a pore layer includes a thermoplastic resin as a main component and a pore-forming agent. The solid layer resin composition contains a thermoplastic resin as a main component and does not contain a pore forming agent. Then, after these resin compositions are put into a melt extruder, these resin compositions are coextruded so as to be laminated in the order of the hole layer 3 and the solid layer 4 from the conductor 1 side. That is, by extruding the resin composition for the pore layer on the outer peripheral surface of the conductor 1 and further extruding these resin compositions so that the resin composition for the solid layer is disposed so as to surround the outer peripheral surface. Get an insulated wire.

  Here, the holes 5 in the hole layer 3 are generated by foaming or decomposition of the hole forming agent contained in the resin composition for the hole layer by heating at the time of co-extrusion for softening the resin composition. Is done. Thereby, the said insulated wire provided with the insulating layer 2 which has the void | hole layer 3 containing the void | hole 5, and the solid layer 4 which does not contain a void | hole is obtained.

  In addition, the resin composition for the pore layer may be one having a thermosetting resin as a main component, but the one using a thermoplastic resin as a main component as described above is more suitable for coextrusion. Since heating control can be easily performed, it is easy to manufacture the insulated wire.

[advantage]
The said insulated wire can suppress deterioration by the heat | fever of the insulating layer 2 because the insulating layer 2 has the hole layer 3 which has high heat insulation in contact with the conductor 1. FIG. Therefore, the insulated wire is excellent in weld resistance. Moreover, since the said insulated wire is provided with the solid layer 4 in which the insulating layer 2 does not contain a void | hole, the insulation of the insulating layer 2 can be improved and a dielectric breakdown can be suppressed. Furthermore, the insulated wire can give flexibility to the insulating layer 2 because the insulating layer 2 includes the hole layer 3. Thus, since the said insulated wire is provided with the void | hole layer 3 with which the insulating layer 2 is directly laminated | stacked on the conductor 1, and the solid layer 4, it is excellent in weld resistance, insulation, and 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 meaning and scope equivalent to the scope of the claims. The

  In the above embodiment, the insulated wire has been described in which the insulating layer has one hole layer and one solid layer, but at least one hole layer is directly laminated on the conductor, and the outside of the hole layer. If at least one solid layer exists, the insulating layer may be an insulated wire having a plurality of hole layers, or the insulating layer may be an insulated wire having a plurality of solid layers. Moreover, it is good also as an insulated wire which has an insulating layer by which a void | hole layer and a solid layer are laminated | stacked alternately. When the insulating layer has a plurality of pore layers, each of the pore layers contributes to improving the weld resistance of the insulating layer. Further, when the insulating layer has a plurality of solid layers, the plurality of solid layers collectively contribute to the improvement of the mechanical strength of the insulating layer and also to the improvement of the insulating properties.

  When the insulating layer has a plurality of hole layers, the lower limit of the total average thickness of the hole layers is preferably 10%, more preferably 20%, with respect to the average thickness of the insulating layer. On the other hand, the upper limit of the total average thickness is preferably 95% and more preferably 90% with respect to the average thickness of the insulating layer. When the total of the average thickness is less than the lower limit, the weld resistance may not be sufficiently improved. On the other hand, if the total of the average thickness exceeds the upper limit, the insulation may not be sufficiently improved, or the total thickness of the pore layer with low mechanical strength becomes relatively large, and the mechanical strength of the insulating layer May not be maintained.

  When the insulating layer has a plurality of solid layers, the lower limit of the total average thickness of each solid layer is preferably 5% and more preferably 10% with respect to the average thickness of the insulating layer. On the other hand, the upper limit of the total average thickness is preferably 90% and more preferably 80% with respect to the average thickness of the insulating layer. When the total of the average thickness is less than the lower limit, there is a possibility that the insulating property cannot be sufficiently improved or the mechanical strength of the insulating layer cannot be maintained. Conversely, if the total average thickness exceeds the upper limit, the weld resistance may not be sufficiently improved.

  When the insulating layer has a plurality of solid layers and the outermost solid layer is formed, the lower limit of the average thickness of the outermost solid layer is preferably 10 μm, more preferably 20 μm. On the other hand, the upper limit of the average thickness of the solid layer on the outermost layer is preferably 180 μm, and more preferably 160 μm. If the average thickness of the solid layer of the outermost layer is less than the lower limit, the insulation may not be sufficiently improved. On the other hand, when the average thickness of the outermost solid layer exceeds the upper limit, the insulated wire may unnecessarily increase in diameter.

  When the insulating layer has a plurality of pore layers, the “average thickness of the pore layers” in “the ratio of the average thickness of the solid layer to the average thickness of the pore layers” is the average of the pore layers. Means the average thickness of the innermost layer, and when the insulating layer has a plurality of solid layers, the above-mentioned “average thickness of the solid layers” means the sum of the average thicknesses of the respective solid layers.

  In the above embodiment, the production method for generating pores using a chemical foaming agent as a pore forming agent has been described. However, a thermally expandable microcapsule is used as the pore forming agent, and It is good also as a manufacturing method which forms a void | hole. For example, in the first manufacturing method, a resin for forming a pore layer diluted with a solvent is mixed with a thermally expandable microcapsule to prepare a varnish for the pore layer, and the conductor of the varnish for the pore layer is prepared. The pore layer may be formed by coating and baking on the outer peripheral surface side. During baking, the thermally expandable microcapsules contained in the varnish for the pore layer expand or foam, and pores are formed in the pore layer by the thermally expandable microcapsules. Further, for example, in the second production method, the resin composition for a pore layer may contain a thermally expandable microcapsule. In this case, the heat-expandable microcapsules contained in the resin composition for a pore layer expand or foam by heating during coextrusion, and a pore layer including pores formed by the thermally-expandable microcapsules is formed. The

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

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

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

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

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

  Further, a thermally decomposable resin may be used as the pore forming agent. That is, as the first resin composition of the first production method, a resin in which the pore layer is formed may be diluted with a solvent and further mixed with a thermally decomposable resin. Moreover, as a resin composition for a pore layer of the second production method, a resin in which a thermally decomposable resin is mixed with a resin that forms a pore layer may be used.

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

  The thermally decomposable resin used for the pore layer is not particularly limited. For example, a compound obtained by alkylating, (meth) acrylated or epoxidizing one or both ends or part of polyethylene glycol, polypropylene glycol, or the like, poly (Meth) acrylic acid methyl ester, poly (meth) ethyl acrylate, poly (meth) acrylic acid propyl, poly (meth) acrylic acid and other alkyl ester polymers having 1 to 6 carbon atoms, Urethane oligomer, urethane polymer, urethane (meth) acrylate, epoxy (meth) acrylate, polymer of modified (meth) acrylate such as ε-caprolactone (meth) acrylate, poly (meth) acrylic acid, cross-linked products thereof, polystyrene, Examples include crosslinked polystyrene. Among these, a crosslinked product of a (meth) acrylic polymer is preferable, and a crosslinked poly (meth) acrylate is more preferable. Moreover, it is preferable that the thermally decomposable resin can be uniformly distributed as an island phase of fine particles in the sea phase of the resin forming the pore layer. Therefore, the thermally decomposable resin used for the pore layer is preferably a resin that is excellent in compatibility with the resin that forms the pore layer and is gathered into a spherical shape, and specifically, a crosslinked resin.

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

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

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

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

  When using the resin particles to be thermally decomposed, the resin particles are preferably spherical. The lower limit of the average particle diameter of the resin particles is preferably 0.1 μm, more preferably 0.5 μm, and even more preferably 1 μm. On the other hand, the upper limit of the average particle diameter of the resin particles is preferably 100 μm, more preferably 50 μm, further preferably 30 μm, and particularly preferably 10 μm. The resin particles are thermally decomposed when the resin forming the pore layer is baked to form pores in the existing portions. Therefore, when the average particle diameter of the resin particles is less than the lower limit, there is a risk that it is difficult to form holes in the hole layer. On the contrary, when the average particle diameter of the resin particles exceeds the upper limit, the distribution of vacancies in the vacancy layer is difficult to be uniform, and the distribution of dielectric constant may be easily biased. Here, the average particle diameter of the resin particles means a particle diameter showing the highest volume content in the particle size distribution measured with a laser diffraction particle size distribution measuring apparatus.

  Further, for example, the holes may be formed with a hollow filler. In the case of forming the pores with a hollow filler, for example, the insulated wire can be produced by kneading a resin composition forming a pore layer and a hollow filler and coating the kneaded product on a conductor by coextrusion molding.

  When holes are formed by the hollow filler, the hollow portions inside the hollow filler become holes included in the hole layer. Examples of the hollow filler include shirasu balloons, glass balloons, ceramic balloons, and organic resin balloons. Among these, an organic resin balloon that can improve the flexibility of the insulated wire is preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

<Example 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, an insulating varnish was prepared by dissolving a polyimide precursor formed by polymerization of pyromellitic dianhydride and diaminodiphenyl ether in N-methyl-2-pyrrolidone. Further, a pore forming agent (foaming agent) was dispersed in this insulating varnish so that the porosity of the pore layer was 10% by volume, thereby preparing a pore layer varnish. By applying this void layer varnish to the outer peripheral surface of the conductor and repeatedly baking it under the conditions of a linear speed of 3.0 m / min, a heating furnace inlet temperature of 350 ° C., and a heating furnace outlet temperature of 450 ° C., the outer peripheral surface of the conductor A pore layer having an average thickness of 20 μm was formed on the substrate. Next, a solid layer varnish was prepared by dissolving a polyimide precursor formed by polymerization of pyromellitic dianhydride and 4- (4-aminophenoxy) phenyl in N-methyl-2-pyrrolidone. The solid layer varnish is applied to the outer peripheral surface of the pore layer and baked under the conditions of a linear speed of 3.0 m / min, a heating furnace inlet temperature of 350 ° C., and a heating furnace outlet temperature of 250 ° C. A solid layer having an average thickness of 30 μm was formed on the surface to obtain an insulated wire of Example 1.

<Example 2 and Example 3>
Insulated wires of Example 2 and Example 3 were obtained in the same manner as Example 1 except that the average thicknesses of the pore layer and the solid layer and the porosity of the pore layer were as shown in Table 1.

<Comparative Example 1>
An insulated wire of Comparative Example 1 was produced in the same manner as in Example 1 except that no holes were formed in the lower layer.

<Welding resistance>
The weld resistance of the insulated wires of Examples 1 to 3 and Comparative Example 1 was evaluated. FIG. 2 shows a schematic diagram of a method for evaluating weld resistance. The insulated wires of Examples 1 to 3 and Comparative Example 1 made of a conductor and an insulating layer were cut to a length of 100 mm to form test pieces, and the insulating layer was peeled off from one end of each test piece to a position of 5.0 mm. did. A portion 2.5 mm from the end on the side where the insulating layer was peeled off is sandwiched between two chrome copper grounding rods 15 having a cross-sectional dimension of 1.5 mm × 2.0 mm, and 1.25 mm from the end of the end of the test piece. The tip position of the welding torch 14 was aligned with a distant position (position where the distance t from the end of the end of the test piece of FIG. 2 to the tip of the welding torch 14 was 2.5 mm), and energization was performed by a TIG welding machine. . The energization current was increased by 10A from 60A to a maximum of 100A. The energization time for each energization was 0.3 seconds. The surface in the vicinity of the energized portion of each test piece after energization was visually confirmed, and the maximum value of the energization current that could be satisfactorily welded without the occurrence of film floating or foaming was determined. The above evaluation results are shown in Table 1. In Table 1, “A” described in the column of materials indicates a polyimide precursor formed by polymerization of pyromellitic dianhydride and diaminodiphenyl ether, and “B” indicates pyromellitic dianhydride and 4- The polyimide precursor formed by superposition | polymerization with (4-aminophenoxy) phenyl is shown.

[Evaluation results]
As shown in Table 1, Example 1, Example 2 and Example in which the insulating layer has a hole layer directly laminated on the conductor and the porosity is 10% by volume, 30% by volume and 50% by volume, respectively. In Example 3, the weld resistance was 90 A or more. The insulated wires of Examples 1 to 3 had higher weld resistance than the insulated wire of Comparative Example 1 in which the lower layer did not have pores. Moreover, it was found from the comparison between Example 1 and Example 2 that the weld resistance can be improved by increasing the porosity from 10% by volume to 30% by volume.

  Since the insulated wire according to the present invention is excellent in weld resistance and insulation, it can be suitably used as a wire joined by welding.

DESCRIPTION OF SYMBOLS 1 Conductor 2 Insulation layer 3 Hole layer 4 Solid layer 5 Hole 14 Welding torch 15 Ground rod

Claims (5)

An insulated wire comprising a conductor and an insulating layer covering the outer peripheral surface of the conductor,
The insulating layer is
A hole layer including holes and directly laminated on the conductor;
An insulated wire having a solid layer that does not include pores.   The insulated wire according to claim 1, wherein the porosity of the pore layer is 5% by volume or more and 80% by volume or less.   The insulated wire according to claim 1 or 2, wherein an average diameter of the holes is 0.1 µm or more and 30 µm or less.   The insulated wire according to claim 1, wherein the ratio of the average thickness of the solid layer to the average thickness of the pore layer is 5% or more and 700% or less. A conductor and an insulating layer covering the outer peripheral surface of the conductor, the insulating layer including a hole and including a hole layer directly stacked on the conductor and a solid layer including no hole; A method of manufacturing an insulated wire,
A first coating step of coating a first resin composition containing a resin and a pore-forming agent on a conductor;
A first heating step of heating the first layer applied in the first application step;
A second application step of applying a second resin composition containing a resin on the pore layer formed in the first heating step;
A method for manufacturing an insulated wire, comprising: a second heating step for heating the second layer formed in the second coating step.

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