JP2010070672A - Coating for insulating film, and insulated electric wire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating for an insulating film capable of forming the insulating film exhibiting adhesive strength of a conductor to the insulating film formed on the conductor surface, particularly excellent adhesiveness not only in a state before carrying out winding processing but also even after the winding processing and a varnish impregnating treatment, and to provide an insulated electric wire having the insulating film formed by using the coating. <P>SOLUTION: The coating for the insulating film is used for forming a primer layer, and contains a resin and a polysulfide polymer comprising the primer layer. The polysulfide polymer preferably has SH as a terminal, and a main chain comprising a repeating unit of -R<SP>1</SP>-O-R<SP>2</SP>-O-R<SP>1</SP>-S-S- (wherein, R<SP>1</SP>and R<SP>2</SP>are each 1-3C alkylene). The polysulfide polymer is preferably contained in an amount of 0.5-25 pts.mass based on 100 pts.mass of the resin comprising the primer layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating for an insulating coating suitable for forming an insulating coating such as a magnet wire, particularly a primer layer, and more specifically, an initial mechanical strength such as wear resistance and adhesion, and an adhesive strength after holding at a high temperature. The present invention relates to a coating for an insulating coating that can form an excellent insulating coating, and an insulated wire having a primer layer formed of the coating.

  As an insulated wire used for a motor winding or a transformer winding, a copper wire is generally used in which an insulating coating is formed by baking a resin such as polyesterimide, polyamide, polyurethane, or polyester. .

Insulated wires that form coils of various electrical equipment, the insulation coating that covers the conductors must also have good adhesion to the conductors, high heat resistance, mechanical strength, and chemical resistance as a premise to exhibit excellent insulation. Is required. In particular, in the winding process, automation and speeding-up have progressed, and when an automatic winding machine is used, winding is performed under bending, friction, etc. while applying strong tension to the processed wire. The possibility of damaging the insulation film of the wire is increased. Furthermore, with the demand for higher output, reduction in size, and power saving of various electric devices, higher space factor has been advanced, and the processing load applied to the winding has become severe.
In order to prevent the insulating coating from being damaged against such severe winding processing, a coating excellent in winding resistance is demanded.

  Winding workability is considered to be greatly related to the lubricity and wear resistance of the wire surface. For this reason, an insulating film is formed on the conductor, and a polyamide resin or polyamideimide resin having excellent lubricity and mechanical strength is overcoated on the insulating film to provide a surface layer portion having excellent surface lubricity. This is the actual situation.

  For example, in Japanese Patent Application Laid-Open No. 9-45142 (Patent Document 1), a lubricating polyester or lubricating polyesterimide layer in which a lubricant such as wax is blended with a polyester or polyesterimide coating is provided on an insulating coating.

  On the other hand, in order to improve the adhesion between the conductor and the insulating coating, at least selected from the group consisting of acetylenes, aldehydes, amines, mercaptans, and thioureas, which can form a complex compound with a metal. Japanese Patent No. 3766447 (Patent Document 2) discloses an insulating paint to which one kind of metal deactivator is added.

JP-A-9-45142 Japanese Patent No. 3766447

  However, the winding process has become severer year by year. Moreover, when varnish impregnation processing is performed after winding processing, it is calculated | required that the adhesiveness outstanding after heat processing at high temperature is hold | maintained.

  The present invention has been made in view of such circumstances, and the object of the present invention is only the adhesion strength between the conductor and the insulating coating formed on the conductor surface, particularly the state before the winding process is performed. And providing a coating for an insulating coating that can form an insulating coating that can exhibit excellent adhesion even after winding and varnish impregnation, and an insulated wire having an insulating coating formed using the coating. It is in.

  That is, the coating material for insulating coating of the present invention is a coating material for insulating coating used for forming the primer layer of an insulated wire having a conductor and a primer layer formed on the conductor, and is a resin constituting the primer layer. And a polysulfide polymer.

The polysulfide polymer has an SH group at the end and a main chain of —R ¹ —O—R ² —O—R ¹ —SS— (wherein R ¹ and R ² are alkylene having 1 to 3 carbon atoms) It is preferably composed of a repeating unit of (a group). The polysulfide polymer is preferably contained in an amount of 0.5 to 25 parts by mass per 100 parts by mass of the primer layer constituting resin.

  The primer layer-constituting resin is preferably one kind selected from the group consisting of a polyesterimide resin, a polyimide resin, a polyamide resin, a polyamideimide resin, an epoxy resin, a polyester resin, and a polyurethane resin. More preferably, it is a polyesterimide resin.

  Further, the primer layer-constituting resin may contain a curing agent.

  The insulated wire of the present invention has a conductor; a primer layer formed by baking and curing the coating material for insulating coating of the present invention; and at least one overcoat layer formed on the primer layer. The insulated wire of the present invention according to another aspect is such that a primer layer having a polysulfide polymer content of 0.49 to 20% by mass is formed on a conductor surface.

  The primer layer formed using the insulated wire paint of the present invention can exhibit excellent adhesion to the conductor due to the inclusion of the polysulfide polymer, and can maintain excellent adhesion even at high temperatures.

  Although embodiments of the present invention will be described below, it should be considered that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Insulation coating]
The coating material for insulating coating of the present invention is a coating material for insulating coating used for forming the primer layer of an insulated wire having a conductor and a primer layer formed on the conductor, and the resin and polysulfide constituting the primer layer Contains polymer.

<Primer layer constituent resin>
The primer layer-constituting resin contained in the paint of the present invention is a resin that forms a primer layer directly formed on the conductor of the insulating film of the magnet wire, and a known resin conventionally used for an insulating varnish is used. Can do. For example, a polyesterimide resin, a polyamideimide resin, a polyimide resin, a polyurethane resin, a polyester resin, a polyamide resin, an epoxy resin, or the like can be used. Among these, in particular polyesterimide resins that are excellent in heat resistance, softening resistance, solvent resistance, etc., but are required to improve wear resistance, which is an indicator of severe winding workability, The remarkable effect can be acquired about adhesive improvement.

The primer layer-constituting resin may contain a resin base polymer curing agent.
The base polymer curing agent depends on the type of the base polymer. For example, in the case of a polymer having an OH group, a COOH group, or an NH ₂ group at the terminal, such as polyesterimide, an isocyanate curing agent is preferably used. .

  Examples of isocyanate curing agents include aromatic diisocyanates such as tolylene diisocyanate (TDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate, and the like. Of aliphatic diisocyanates having 3 to 12 carbon atoms; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidene Dicyclohexyl-4,4′-diisocyanate, 1,3-diisocyanatotomylcyclohexane (hydrogenated XDI), hydrogenated TDI, 2,5-bis (isosina Tomyl) -bicyclo [2.2.1] heptane, 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane, and the like. (XDI), aliphatic diisocyanates having an aromatic ring such as tetramethylxylylene diisocyanate (TMXDI); blocked isocyanates in which isocyanate groups such as modified products of these diisocyanates are blocked, each of which is used alone or in combination of two or more It can be used by mixing. Such an isocyanate type hardening | curing agent may be contained normally 1-20 mass parts per 100 mass parts of polyesterimide.

  In a base polymer having a functional group capable of reacting with an amine such as an OH group, a COOH group, or an epoxy group at the terminal, a melamine compound can be used as a curing agent. Examples of the melamine compound include methyl melamine, butylated melamine, methylolated melamine, butyrolated melamine and the like, and these can be used alone or in combination of two or more. The melamine compound can be usually contained in an amount of 1 to 20 parts by mass per 100 parts by mass of the polyesterimide.

  In addition, it may contain a crosslinking agent such as a silane coupling agent or a titanate coupling agent. For OH group-containing resins, tetrapropyl titanate, tetraisopropyl titanate, tetramethyl titanate, tetrabutyl titanate, tetrahexyl A titanium alkoxide such as titanate is preferably used.

  Instead of the primer layer constituent resin, a commercially available resin containing a curing agent or the like may be used. Furthermore, a commercially available insulating varnish can also be used. Specifically, Isomid 40SM45 manufactured by Hitachi Chemical Co., Ltd., EH402-45 manufactured by Dainichi Seika Co., Ltd., FS304, FS201, Isomid manufactured by Nichichu Schenectady, Imidex manufactured by General Electric Co., Ltd .; Pile ML manufactured by Deyupon Torays # 2000, # 3000 polyimide paints of those skilled in the art; Hitachi Chemical's polyamide-imide paints such as HI-400, HI-405, HI-406, and the like.

<Polysulfide polymer>
The polysulfide polymer used in the present invention is a liquid polymer having a disulfide bond (—S—S—) in the main chain and having a terminal SH group.
Preferably, the main chain is a polymer having a repeating unit of —R ¹ —O—R ² —O—R ¹ —S—S— and has rubber elasticity.

In the repeating ^unit, R 1, ^{R 2} is methylene, ethylene, an alkylene group having 1 to 4 carbon atoms such as propylene, more preferably _{-C 2 H 4 -O-CH 2} -O-C 2 H 4 - S—S—, HS— (C ₂ H ₄ —O—CH ₂ —O—C ₂ H ₄ —S—S) _n —C ₂ H ₄ —O—CH ₂ —O—C ₂ H ₄ — It is a polysulfide polymer represented by SH.

  Although the polysulfide polymer used by this invention is not specifically limited, It is preferable that it is a weight average molecular weight 400-50000, More preferably, it is 800-10000, More preferably, it is 800-8000.

  The mechanism of such a polysulfide polymer is not clear, but the adhesion strength of the insulating film to the conductor, particularly when the insulating film is composed of a primer layer and one or more overcoat layers formed on the primer layer In addition, the wear resistance strength can be improved. The SH group at the end of the polysulfide polymer forms a chelate bond with the conductor, and the SH group at the other end reacts with the functional group at the end of the resin (primer layer-constituting resin) in the coating for insulating coating to form a bond. It seems to form. That is, it is considered that the polysulfide polymer is crosslinked between the conductor and the resin constituting the insulating film. Since polysulfide polymer has rubber elasticity, the insulation coating constituent resin follows the external stress applied at the time of the winding process, that is, the frictional force applied to the insulation coating. Even if the insulation coating (especially the overcoat layer) moves relatively, the polysulfide polymer intervening between the conductor and the insulation coating constituent resin (particularly the primer layer constituent resin) plays a role as a buffer. Therefore, it is considered that the insulating coating constituent resin (particularly the overcoat layer) can be prevented from peeling off from the conductor surface.

  The polysulfide polymer is preferably contained in an amount of about 0.5 to 25 parts by mass, more preferably 1.0 to 20 parts by mass, per 100 parts by mass of the primer layer constituting resin contained in the paint. If the amount is less than 0.5 part by mass, the effect of adding the polysulfide polymer is small. On the other hand, if the amount is too large, the conductor, particularly copper, is easily oxidized by sulfur contained in the polysulfide polymer.

  In addition, for commercially available insulating varnishes, as an adhesive strength improving agent with a metal conductor, for example, a metal deactivator capable of forming a complex compound with a metal as disclosed in Japanese Patent No. 3766447, acetylenes , Alkynols, aldehydes, amines, mercaptans, thioureas, and other metal deactivators. The polysulfide polymer used in the present invention can also obtain an effect equal to or higher than that of these adhesive strength improvers with respect to the initial adhesive strength. Furthermore, there is also an advantage that there is no problem of a decrease in adhesion strength when held at a high temperature for a long time, which is a weak point of the currently known high adhesion polyesterimide. In other words, when polysulfide polymer is used as an adhesive strength improver, the adhesive strength is reduced even if it is kept at a high temperature for a long time even though the abrasion resistance is improved to the same level or higher as that of the highly adhesive polyesterimide. Is small, and there is a remarkable effect that excellent adhesion strength can be maintained even after the impregnating varnish treatment.

<Other ingredients>
In addition to the primer layer constituting resin and the polysulfide polymer, the coating material for insulating coating of the present invention may contain a polysulfide polymer curing agent. Examples of the polysulfide polymer curing agent include paraquinone dioxime, zinc peroxide, lead dioxide, manganese dioxide, and calcium peroxide.

  Furthermore, the coating material for insulating coating of the present invention contains an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it can dissolve the primer layer-constituting resin. For example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, In addition to polar organic solvents such as tetramethylurea, hexaethylphosphoric triamide, and γ-butyrolactone, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; methyl acetate, ethyl acetate, butyl acetate, diethyl oxalate, etc. Esters such as diethyl ester, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol methyl ether, tetrahydrofuran, etc. Ethers; hydrocarbon compounds such as hexane, heptane, benzene, toluene and xylene; halogenated hydrocarbon compounds such as dichloromethane and chlorobenzene; phenols such as cresol and chlorophenol; tertiary amines such as pyridine; These organic solvents can be used alone or in admixture of two or more.

  Furthermore, various additives such as pigments, dyes, inorganic or organic fillers, lubricants, antioxidants, leveling agents, and the like may be contained as necessary, as long as the object of the present invention is not impaired.

The coating material for insulating coating of the present invention is produced by blending a primer layer-constituting resin, a polysulfide polymer and other additives and diluting with an organic solvent so that the solid content is about 30 to 60% by mass. .
When a commercially available insulating varnish is used as the primer layer constituent resin, the insulating varnish is 0.5 to 25 parts by mass, preferably 1.0 to 20 parts by mass with respect to 100 parts by mass of the solid content of the insulating varnish. Thus, it can also be produced by adding a polysulfide polymer.

  The coating for insulating coatings of the present invention having the above composition not only forms an insulating coating, but also has excellent adhesion to the conductor even under stress, so it can be used as a primer layer coating for insulated wires. Is useful.

  The primer layer can be formed by applying the insulating coating paint of the present invention directly to a conductor and then baking and curing. The baking temperature is a temperature at which the organic solvent contained in the paint can be volatilized, and when a curing agent is included, the temperature of the curing agent and the base polymer of the primer layer constituting resin can be reacted. Therefore, it is appropriately selected.

[Insulated wire]
The insulated wire of this invention has a primer layer formed with the coating material for insulation films of the said invention on the conductor surface.

  As a conductor, it is a well-known conductor normally used for an electric wire conductor, and metal conductors, such as a copper wire and an aluminum wire, are used.

  The baking of the coating material for insulating coating of the present invention is appropriately selected depending on the type of base polymer. For example, in the case of a polyesterimide-based coating material, an oven at about 350 to 500 ° C. is used for 10 seconds to 30 seconds per pass ( It is preferable to carry out by letting it pass 10 times (100 seconds to 300 seconds). By baking, a primer layer having excellent heat resistance and wear resistance can be obtained.

  Although the thickness of a primer layer is not specifically limited, 1-20 micrometers is preferable, More preferably, it is 1-10 micrometers. This is because this thickness is sufficient for the primer layer.

  The primer layer formed by applying and baking the insulating coating paint of the present invention contains a cured product of the primer layer constituting resin and the polysulfide polymer contained in the paint. The content of the polysulfide polymer in the primer layer corresponds to the content of the polysulfide polymer with respect to the total solid content of the paint, and is preferably about 0.49 to 20% by mass, more preferably about 1 to 17% by mass.

The insulated wire of the present invention has at least one overcoat layer on the primer layer as described above.
The composition of the overcoat layer is not particularly limited, and polyesterimide resins, polyamideimide resins, polyimide resins, polyurethane resins, polyester resins, polyamide resins, phenoxy resins, and the like conventionally used for insulating coatings Can be used. The topcoat layer-constituting resin may be the same as or different from the primer layer-constituting resin, and is appropriately selected according to the use of the insulated wire.

  The thickness of the overcoat layer is preferably about 10 to 30 μm. When the top coat layer is composed of two or more layers, the top coat layer of the insulated wire is preferably composed of a film having lubricity, for example, a highly lubricated polyimide, a highly lubricated amide imide or the like.

  The best mode for carrying out the present invention will be described with reference to examples. The examples are not intended to limit the scope of the invention.

[Measurement evaluation method]
First, the evaluation method performed in this example will be described.

(1) Adhesion (1-1) Initial length According to JIS C3003 “8.1a) Rapid extension”, the produced insulated wire was cut by rapid extension, and the length of the film floating conductor that was not cut (Mm) and the conductor length (mm) exposed when the coating was peeled off at the cut portion were measured. As the measured value is smaller, the coating layer is not peeled off even on the rapidly extending cut surface, indicating that the adhesiveness is excellent.
For each insulated wire, the average value of the results of measuring three wires each is shown.

(1-2) Adhesion after heating After the created insulated wire was held at 160 ° C. for 6 hours, the length of the membrane floating conductor (mm) after rapid elongation was measured in the same manner as in (1-1). did. This becomes an index of adhesion after the impregnation varnish treatment, and indicates that the smaller the film floating conductor length, the better the adhesion after the heat treatment.
In addition, about each insulated wire, the average value of the result measured 3 each is shown.

(2) Abrasion resistance The unidirectional wear value (g) was measured in accordance with the abrasion resistance test described in JIS C3003-1999. This is an investigation of how much force is applied to break the coating, and it is an index of coating strength against stress during shoreline.
In addition, about each insulated wire, the average value of the result of having measured 9 pieces is shown.

(3) Softening temperature The softening temperature (° C.) was measured according to JIS C3003 “Test method for enameled copper wire and enameled aluminum wire”. For each of a load (700 g), a double load (1400 g), and a triple load specified in JIS, the temperature (softening temperature) when the wire was conducted was measured.
In addition, about each insulated wire, the average value of the maximum value and the minimum value of the result of measuring four each is shown.

(4) Dielectric breakdown voltage Create a stranded wire using the two insulated wires produced, measure the dielectric breakdown voltage (V) according to JIS C2002 10, average the measured values of 10 samples The average breakdown voltage was determined.
In addition, the average value of the result of having measured each 10 insulated wires is shown.

(5) Flexibility The insulated wire was stretched by 20% with respect to the initial length, and after stretching, it was tested according to JIS C3003 7.1.1 flexibility test. Specifically, after winding the electric wire 30 times so that the electric wire and the electric wire are in contact with each other along a round bar having a self-diameter (1d) of the insulated electric wire, the presence or absence of cracks was observed and the number of cracks was counted. .
The number of cracks after winding was also counted in the same manner for the diameter of the round bar to be wound twice (2d) and 3 times (3d) of the self-diameter of the insulated wire.

(6) Heat Shock Test The insulated wire was stretched by 20% with respect to the initial length, and after stretching, the insulated wire was tested according to the impact resistance test of JIS C3003-20. Specifically, after heating at 240 ° C. for 1 hour, after winding the wire 30 times so that the wire and the wire are in contact with each other along a round bar having the self-diameter (1d) of the insulated wire, there is no crack The number of cracks was counted.
The number of cracks after winding was also counted in the same manner for the diameter of the round bar to be wound twice (2d) and 3 times (3d) of the self-diameter of the insulated wire.

[Manufacture of paint for esterimide insulating coating and insulated wire]
No. 1-5:
To 100 parts by mass of solid content contained in a general-purpose ester imide varnish (Isomid 40SM45 manufactured by Hitachi Chemical Co., Ltd.), Toray Fine Chemical Co., Ltd. Thiocol LP3 (trade name) is added in an amount shown in Table 1 as a liquid polysulfide. An insulating coating material was prepared by mixing at 30 ° C. for 60 minutes.
The prepared coating material for insulating coating was applied to a copper wire having a diameter of 0.898 mm or 0.899 mm and baked (furnace temperature 350 to 500 ° C.) to form a primer layer having a coating thickness of 3 μm.
Next, a general-purpose ester imide (Hitachi Chemical Industry's Isomid 40SM45) is applied and baked to form a second layer with a film thickness of 25 μm, and a general-purpose amide imide varnish (Hitachi Chemical Industry's HI-406E-34) is applied and baked. A third layer having a thickness of 5 μm was formed, and a highly lubricated amideimide resin (Sumitomo Electric Wintec) was further applied and baked to form a fourth layer having a thickness of 2 μm. Thus, an insulated wire having a total coating thickness shown in Table 1 was produced. .
The adhesion, wear resistance, dielectric breakdown voltage, softening temperature, flexibility, and heat shock resistance of the prepared insulated wires were measured and evaluated according to the above evaluation methods. The results are shown in Table 1.

No. 6:
Except that the primer layer was formed only with a commercially available general-purpose esterimide varnish (Isomid 40SM45 manufactured by Hitachi Chemical Co., Ltd.), No. In the same manner as in Example 1, an insulated wire was prepared. Adhesion, abrasion resistance, dielectric breakdown voltage, softening temperature, flexibility and heat shock resistance of the produced insulated wire were measured and evaluated according to the above evaluation methods. The results are shown in Table 1.

No. 7:
Except that the primer layer was formed only with a commercially available highly adhesive polyesterimide paint (EH402-45 manufactured by Dainichi Seika Co., Ltd.), No. In the same manner as in Example 1, an insulated wire was prepared. Adhesion, abrasion resistance, dielectric breakdown voltage, softening temperature, flexibility and heat shock resistance of the produced insulated wire were measured and evaluated according to the above evaluation methods. The results are shown in Table 1.

  In Table 1, no. 6 and no. As can be seen from the comparison with No. 7, the insulated wire (No. 6) in which the primer layer is formed with a general-purpose esterimide varnish has high adhesion in all of unidirectional wear, softening resistance, flexibility, and heat shock. It was inferior to the insulated wire (No. 7) which formed the primer layer with the ester imide varnish. However, an insulated wire (No. 7) having a primer layer formed of a highly adhesive esterimide varnish is superior to an insulated wire having a primer layer formed of a general-purpose esterimide varnish in terms of mechanical strength. On the other hand, in the adhesion test after the heat treatment at 160 ° C. for 6 hours, the film floated as much as 150 mm, which was reduced to a level not recognized in the insulated wire having the primer layer formed of the general-purpose esterimide varnish.

  On the other hand, no. 1 to 5 are insulated wires in which a primer layer is formed using a coating material for an insulating film in which a polysulfide polymer is added to a general-purpose ester imide. As the amount of polysulfide added increases, initial adhesion and initial mechanical strength improve. It was. Furthermore, the adhesiveness after the heat treatment was also slightly lower than the initial adhesiveness, but was not problematic. Therefore, by including the polysulfide polymer in the primer layer, both the initial mechanical strength and the adhesion after the heat treatment can be improved.

  The coating material for insulating coating of the present invention is excellent in initial adhesion, wear resistance, heat resistance, and excellent adhesion after being held at high temperature for a long time. It is useful as a magnet wire to be processed, for example, an insulated wire for a motor winding or a transformer coil that meets the demand for miniaturization and power saving.

Claims (8)

A coating for an insulating film used for forming the primer layer of an insulated wire having a conductor and a primer layer formed on the conductor,
A coating material for insulating coating containing a resin constituting the primer layer and a polysulfide polymer. The polysulfide polymer has an SH group at the end and a main chain of —R ¹ —O—R ² —O—R ¹ —SS— (wherein R ¹ and R ² are alkylene having 1 to 3 carbon atoms) The coating material for insulating coatings according to claim 1, wherein the coating material is a repeating unit. The paint for insulating coatings according to claim 1 or 2, wherein the polysulfide polymer is contained in an amount of 0.5 to 25 parts by mass per 100 parts by mass of the primer layer constituting resin. The primer layer-constituting resin is one selected from the group consisting of a polyesterimide resin, a polyimide resin, a polyamide resin, a polyamideimide resin, an epoxy resin, a polyester resin, and a polyurethane resin. The coating material for insulating coatings according to any one of -3. The said primer layer structure resin is a polyesterimide-type resin, The coating material for insulation films of any one of Claims 1-3. The coating material for insulating coatings according to claim 1, wherein the primer layer-constituting resin contains a curing agent. An insulated wire having a conductor; a primer layer formed by baking and curing the insulating film paint according to any one of claims 1 to 6; and at least one overcoat layer formed on the primer layer. An insulated wire in which a primer layer having a polysulfide polymer content of 0.49 to 20% by mass is formed on a conductor surface.