JP2001035257A - Insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester insulating wire having heat resistance, humidity resistance and solar peeling property, by overcoming defects of conventional polyester insulated wires. SOLUTION: An acid component, composed of not less than 10 equivalent % of 2,6-naphthalene-dicarboxylic acid or its derivative (A) and at least one kind (B) selected from among less than 90 equivalent % of terephthalic acid, trimelitic acid anhydride, their derivatives and diimide-carboxylic acid composed of trimelitic acid anhydride and 4'-diamino-diphenylmethane are reacted with an alcohol component (C) of at least one kind of aliphatic polyhydric alcohol, having 2-8 carbons in the condition where the quantity of the alcohol component (C) become 1.2-2.0 times the total acid component equivalent, in order to obtain insulating paint containing a polyester resin, and a polyester insulated wire having solder peeling property is obtained by painting and baking it on a conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester-based insulated wire having heat resistance, heat and moisture resistance and solder releasability.

[0002]

In recent years, electric devices such as motors and transformers have been significantly reduced in size and weight and improved in performance. The heat resistance of insulated wires, which are used materials, has been improved in order to improve the reliability of electrical equipment, and polyester-based insulated wires (PEW, EIW) and polyamide-imide insulated wires (AIW) of heat resistance class F or higher have been developed. Has been put to practical use.

[0003] In addition, as the electrical equipment is hermetically sealed, the use temperature of the electrical equipment in an atmosphere where moisture is confined inside the electrical equipment often rises, and it is a material used for improving the reliability of the electrical equipment. Moisture and heat resistance of insulated wires is also desired. On the other hand, electrical equipment manufacturers are trying to rationalize processes such as labor-saving automation mainly for the purpose of cost reduction, and insulated wires require not only the heat resistance and moisture-heat resistance described above, but also various characteristics that lead to labor-saving automation. It has come to be.

[0004] One of the various characteristics leading to labor-saving automation is a line of terminal stripping of insulated wires. Methods of terminal stripping of insulated wires include (1) mechanical stripping, (2) pyrolysis stripping, (3) chemical stripping, and (4) solder stripping. Considering the processing and the like, the method of (4) by solder peeling is considered to be the most preferable. For this reason, electrical equipment manufacturers have demanded an insulated wire having heat resistance, moisture heat resistance, and solder releasability.

[0005]

Among the above-mentioned insulated wires, polyester-based insulated wires which have not only various properties such as heat resistance but also productivity and economy are most widely used. However, in practical polyester-based insulated wires, those having heat resistance and heat and moisture resistance do not have solder peeling property, and those having heat resistance and solder peeling property have insufficient moisture and heat resistance. There is a demand for an insulated wire satisfying both of the characteristics. Accordingly, an object of the present invention is to overcome the above-mentioned drawbacks of the conventional polyester-based insulated wires, and to provide a polyester-based insulated wire having heat resistance, wet heat resistance, and solder releasability.

The present inventors have conducted intensive studies to achieve the above object. As a result, the polyester resin obtained by using an acid component containing at least 10 equivalent% of 2,6-naphthalenedicarboxylic acid or a derivative thereof and an alcohol component was insulated. Polyester insulated wires made by coating and baking an insulating paint used as a film-forming resin on a conductor overcomes the drawbacks of conventional polyester insulated wires, and has excellent heat resistance, moisture-heat resistance, and solder releasability. It has been found that the present invention has been completed.

[0007]

The above object is achieved by the present invention described below. That is, the present invention relates to a method for preparing 10-equivalent or more of 2,6-naphthalenedicarboxylic acid or its derivative (A) and less than 90-equivalent of terephthalic acid and its derivative, trimellitic anhydride and its derivative, and trimellitic anhydride. An acid component comprising at least one component (B) selected from diimide dicarboxylic acids comprising 4,4'-diaminodiphenylmethane; and an alcohol component (C) which is at least one component of an aliphatic polyhydric alcohol having 2 to 8 carbon atoms. Is applied in an organic solvent by dissolving a polyester resin obtained by reacting the alcohol component (C) in an amount equivalent to 1.2 to 2.0 times the equivalent of the total acid component with an organic solvent. And a polyester-based insulated wire having solder releasability characterized by being baked.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to embodiments of the present invention. The insulated wire according to the present invention comprises:
6-Naphthalenedicarboxylic acid or a derivative thereof (A) and terephthalic acid or a derivative thereof, trimellitic anhydride or a derivative thereof, or a diimide dicarboxylic acid composed of trimellitic anhydride and 4,4'-diaminodiphenylmethane or a mixture thereof An insulating paint containing, as an insulating film forming resin, a polyester resin obtained by reacting an acid component consisting of (B) and at least one aliphatic polyhydric alcohol having 2 to 8 carbon atoms as an alcohol component (C) as a conductor. It is characterized by being baked.

In the above polyester resin, the proportion of the component (A) in the acid component is at least 10 equivalent%, preferably 20 to 100 equivalent%, and the proportion of the component (B) is 90%.
%, Preferably 80 to 0% by equivalent (however, the sum of the components (A) and (B) is 100% by weight), and the use ratio of the alcohol component (C) is 1% of the total acid component equivalent. .
The equivalent weight of 2 to 2.0 times is necessary for forming an insulating film having both heat resistance, moisture heat resistance and solder peelability. When the proportion of the component (A) in the acid component is less than 10 equivalent%, not only the moisture and heat resistance of the obtained insulated wire becomes insufficient, but also the solder peeling property itself may not be imparted depending on the type of the component (B). .

In view of the prior art, 2,6,
-It can be sufficiently predicted that the preparation of a polyester resin using naphthalenedicarboxylic acid or its derivative (A) can improve the heat resistance and wet heat resistance of the resin. It is easily predicted that the solder peeling property, which is a property contradictory to the property, is impaired. However, as described above, by using 2,6-naphthalenedicarboxylic acid or a derivative thereof as the acid component in the above-described amount, in addition to heat resistance and wet heat resistance, solder-peeling is expected to be prevented from being given to a polyester-based resin. It was unexpected that soldering properties were imparted despite the heat resistance of the polyester resin having heat resistance.

As an acid component constituting the polyester resin used in the present invention, terephthalic acid or a derivative thereof, trimellitic anhydride or a derivative thereof, trimellitic anhydride together with 2,6-naphthalenedicarboxylic acid or a derivative thereof (A) It is necessary to use any one of a diimide dicarboxylic acid composed of an acid and 4,4'-diaminodiphenylmethane or a mixture thereof (B) to impart heat resistance to the obtained insulated wire. Use of the component is not preferred because it hinders heat resistance. 2,6-Naphthalenedicarboxylic acid derivatives include 2,6-naphthalenedicarboxylic acid dimethyl ester, and terephthalic acid derivatives include terephthalic acid dimethyl ester. Further, diimide dicarboxylic acid composed of trimellitic anhydride and 4,4′-diaminodiphenylmethane is
It is a diimidedicarboxylic acid obtained by subjecting 2 mol of trimellitic anhydride and 1 mol of 4,4'-diaminodiphenylmethane to a dehydration reaction.

As the alcohol component (C) to be reacted with the acid component in the present invention, an aliphatic polyhydric alcohol having 2 to 8 carbon atoms is suitable. Aliphatic polyhydric alcohols having 9 or more carbon atoms are not preferred because they reduce heat resistance. Also, the use of a polyhydric alcohol having an aromatic or heterocyclic ring is not preferred because it hinders solder peelability. In order to obtain the polyester resin used in the present invention, the use ratio of the alcohol component (C) to the acid components (A) and (B) is such that the alcohol component (C) is used in an amount of 1.2 to 1.2 with respect to the total acid component equivalent.
It is necessary to use 2.0 times equivalent, and if it is less than 1.2 times, it is easy to cause gelation during the synthesis reaction of the polyester-based resin, and practical application is difficult. The degree of polymerization of the base resin is too low, and the film forming ability when baked as an insulating paint is inferior.

Examples of the aliphatic polyhydric alcohol having 2 to 8 carbon atoms include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,2-propylene glycol, 1,3-butanediol and the like can be mentioned.

The polyester resin used in the present invention comprises:
The acid components (A) and (B) and the alcohol component (C) are used in the above-mentioned amounts, and can be synthesized (produced) by a conventionally known method such as an esterification reaction or a transesterification reaction. Is not particularly limited. The synthesis reaction is usually performed in the presence of a solvent. Examples of the solvent for the synthesis reaction and the solvent for dilution include, for example, polar solvents such as phenol, cresol, cresylic acid, xylenol, dimethylformamide, and N-methyl-2-pyrrolidone, alone or in combination. Further, as the auxiliary solvent at the time of dilution, for example, a hydrocarbon solvent such as toluene, xylene, solvent naphtha, methyl ethyl ketone, and cyclohexanone can be used. Particularly useful are aromatic hydrocarbons such as xylene and solvent naphtha, which can improve the workability when an insulating paint is baked on a conductor to produce an insulated wire.

The insulating coating used in the present invention is produced by dissolving the polyester resin obtained as described above in a solvent. Usually, the solution after the synthesis reaction of the resin is used as it is or diluted. In addition, adding a small amount of a metal desiccant or a compound of titanic acid to the insulating paint when baking it on a conductor to produce an insulated wire can speed up the production of the insulated wire and increase the speed of insulated wire. It is preferable because the surface smoothness is further improved. Examples of the metal desiccant include zinc octenoate and lead naphthenate. Most useful are compounds of titanic acid, for example, tetrabutyl titanate, tetraisopropyl titanate, and the like. The amount of addition is 0.1 to 100 parts by weight based on the solid content of the insulating paint.
It is 8.0 parts by weight, preferably 1.0 to 6.0 parts by weight.

In addition to the metal desiccant, the insulating paint used in the present invention may be a stabilized isocyanate in which the isocyanate group of the polyisocyanate is blocked with phenol or the like, polyamide, polyester, polysulfone or the like as long as the characteristics of the present invention are not impaired. Such as thermoplastic resin, melamine resin,
Thermosetting resins such as phenolic resins, dyes, pigments, lubricants, and other paint additives can be appropriately added.

The insulated wire of the present invention is prepared by adjusting the above-mentioned insulating paint to a viscosity suitable for work with an appropriate solvent, and then applying and baking it on a conductor such as a soft copper wire according to a conventionally known method. ). Further, the insulated wire of the present invention can be coated with lubricant such as liquid paraffin or solid paraffin for winding properties on the upper layer of the above-mentioned insulating layer, and is generally used for imparting other properties. As is practiced, other insulating paints can be applied and baked to provide the insulating layer. For example, when further heat resistance is required, a polyimide-based insulating coating or polyamide-imide-based insulating coating is required. When winding property is required, a polyamide-based coating such as 6,6 nylon is required. In such a case, a self-fusing paint such as polyvinyl butyral, phenoxy, polyester, polyamide, or polysulfone paint is used.

[0018]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. The percentages in the text are based on weight.

Production Example 1 In a 5-liter flask equipped with a stirrer, a nitrogen introducing tube, a condenser and a thermometer, 1,220 g (5 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester, 233 g (3.75 mol) of ethylene glycol, glycerin 233g
(2.5 mol), and heating was performed while blowing in nitrogen. At 160 ° C., methanol removal accompanying transesterification started. After raising the temperature to 240 ° C. over 10 hours, the reaction was carried out at 240 ° C. for 3 hours.
The reaction was stopped by charging 0 g. In addition, Cresol 43
After diluting with 1 g and 185 g of xylene, 68 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating paint-1 having a resin content of 40%.

Production Example 2 In the same manner as in Production Example 1, 610 g (2.5 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester and 485 g of terephthalic acid dimethyl ester (2.5 g) were placed in a flask.
Mol), 116 g (1.88 mol) of ethylene glycol, 169 g (1.88 mol) of 1,3-butanediol, and 233 g (2.5 mol) of glycerin, and the reaction was carried out. To stop the reaction. Further, 407 g of cresol, 17 of xylene
After dilution with 4 g, 65 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating paint-2 having a resin content of 40%.

Production Example 3 In the same manner as in Production Example 1, 244 g (1 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester, 776 g (4 mol) of terephthalic acid dimethyl ester, and 233 g (3.75 mol) of ethylene glycol were placed in a flask. Then, 233 g (2.5 mol) of glycerin was charged to carry out the reaction, and 1,160 g of cresol was added to stop the reaction. After dilution with 368 g of cresol and 158 g of xylene, 10
At 0 ° C., 58 g of tetrabutyl titanate was blended to obtain an insulating paint-3 having a resin content of 40%.

Production Example 4 In the same manner as in Production Example 1, 427 g (1.75 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester, 326 g (5.25 mol) of ethylene glycol,
When 171 g (2.25 mol) of propylene glycol was charged and heated while blowing in nitrogen, demethanol accompanying the transesterification reaction started at 160 ° C. After the temperature was raised to 200 ° C. over 8 hours, 760 g of cresol was added to temporarily stop the reaction. After setting the system to 120 ° C,
When 416 g (2.17 mol) of trimellitic anhydride was charged and heated again, dehydration accompanying the esterification reaction started at 180 ° C. After the reaction was performed while raising the temperature from 180 ° C. to 240 ° C. over 6 hours, 383 g of cresol was charged to stop the reaction. Further, after diluting with 363 g of cresol and 155 g of xylene, 57 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating paint-4 having a resin content of 40%.

Example 5 In the same manner as in Production Example 4, 488 g (2 mol) of dimethyl 2,6-naphthalenedicarboxylate, 291 g (1.5 mol) of dimethyl terephthalate were placed in a flask.
After charging and reacting 326 g (5.25 mol) of ethylene glycol and 140 g (1.5 mol) of glycerin,
287 g of cresol was added to temporarily stop the reaction, 192 g (1 mol) of trimellitic anhydride was charged into the system and reacted again, and 882 g of cresol was charged to stop the reaction. After dilution with 370 g of cresol and 159 g of xylene, at 100 ° C., 59 g of tetrabutyl titanate was diluted.
Was blended to obtain an insulating paint-5 having a resin content of 40%.

Production Example 6 In the same manner as in Production Example 4, 366 g (1.5 mol) of dimethyl 2,6-naphthalenedicarboxylate, 485 g (2.5 mol) of dimethyl terephthalate, and 279 g (4.5 mol) of ethylene glycol were used. Mol), glycerin 18
After charging 6 g (2 mol) into a flask and reacting, 263 g of cresol was added to temporarily stop the reaction. 10
After cooling to 0 ° C or lower, trimellitic anhydride 38
4 g (2 mol) and 198 g (1 mol) of 4,4'-diaminodiphenylmethane were charged and heated again.
Dehydration accompanying the imidation reaction starts at 0 ° C., and then dehydration starts at 180 ° C. accompanying the esterification reaction. After the temperature was raised from 140 ° C. to 210 ° C. over 6 hours, and further reacted at 210 ° C. for 3 hours, 286 g of cresol was charged to stop the reaction. Further, after dilution with 494 g of cresol and 212 g of xylene, 79 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating paint-6 having a resin content of 40%.

Production Example 7 In the same manner as in Production Example 6, 366 g (1.5 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester, 372 g (6 mol) of ethylene glycol, and 93 g (1 mol) of glycerin
Mol) was charged into a flask and reacted, and cresol 64
The reaction was once stopped by adding 4 g. After adding 704 g (3.67 mol) of trimellitic anhydride and 198 g (1 mol) of 4,4'-diaminodiphenylmethane to this system and reacting again, 860 g of cresol was added to stop the reaction. 475 g of cresol, 203 g of xylene
After dilution at 100 ° C, tetrabutyl titanate 75 g
Was blended to obtain an insulating paint-7 having a resin content of 40%.

Production Example 8 In the same manner as in Production Example 6, 732 g (3 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester, 233 g (3.75 mol) of ethylene glycol, and 233 g (2.5 mol) of glycerin were placed in a flask. After charging and reacting, 1,655 g of cresol was added to temporarily stop the reaction. To this system, 768 g (4 mol) of trimellitic anhydride,
After charging 396 g (2 mol) of 4,4'-diaminodiphenylmethane and reacting again, 368 g of cresol was obtained.
Was added to stop the reaction. 638 g of cresol,
After dilution with 274 g of xylene, 101 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating paint-8 having a resin content of 40%.

Production Example 9 In the same manner as in Production Example 6, 366 g (1.5 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester, 233 g (3.75 mol) of ethylene glycol,
After charging and reacting 114 g (1.5 mol) of propylene glycol and 140 g (1.5 mol) of glycerin,
The reaction was once stopped by adding 669 g of cresol. In this system, 512 g (2.67 mol) of trimellitic anhydride,
After charging 198 g (1 mol) of 4,4'-diaminodiphenylmethane and reacting again, 894 g of cresol was added.
To stop the reaction. In addition, cresol 494
g, diluted with 212 g of xylene, and mixed with 78 g of tetrabutyl titanate at 100 ° C. to obtain an insulating paint-9 having a resin content of 40%.

Production Example 10 In the same manner as in Production Example 1, 970 g (5 mol) of dimethyl terephthalate and ethylene glycol 2 were added to a flask.
33 g (3.75 mol), glycerin 233 g (2.5
Mol), and the reaction was carried out.
8 g was charged to stop the reaction. In addition, Cresol 351
After diluting with 151 g of xylene, 56 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating coating composition with a resin content of 40%.

Production Example 11 In the same manner as in Production Example 1, 61 g (0.25 mol) of 2,6-naphthalenedicarboxylic acid dimethyl ester and 922 g of terephthalic acid dimethyl ester (4.7 g) were placed in a flask.
5 mol), 233 g (3.75 mol) of ethylene glycol, and 233 g (2.5 mol) of glycerin, and the reaction was carried out. Then, 1,120 g of cresol was added to stop the reaction. 355 g of cresol, 152 of xylene
g and diluted at 100 ° C. with tetrabutyl titanate 5
6 g were blended to obtain an insulating paint ratio of 2 with a resin content of 40%.

Comparative Production Example 12 In the same manner as in Production Example 4, 679 g (3.5 mol) of dimethyl terephthalate and 372 g of ethylene glycol
(6 mol), 93 g (1 mol) of glycerin were charged into a flask to carry out a reaction, and 1,068 g of cresol was added to temporarily stop the reaction, followed by 192 g of trimellitic anhydride.
(1 mol) and react again, and cresol 1,0
The reaction was stopped by charging 68 g. More cresol 3
After diluting with 39 g and xylene 145 g, 54 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating coating material having a resin content of 40% and a ratio of 3.

Production Example 13 In the same manner as in Production Example 4, 582 g (3 mol) of dimethyl terephthalate and 233 g of ethylene glycol
(3.75 mol), 233 g (2.5 mol) of glycerin
Was charged in a flask and reacted, and then 698 g of cresol was added.
Was added to stop the reaction. After 768 g (4 mol) of trimellitic anhydride and 396 g (2 mol) of 4,4'-diaminodiphenylmethane were added to this system and reacted again, 341 g of cresol was added to stop the reaction. Further, after diluting with 591 g of cresol and 253 g of xylene, 94 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating coating composition with a resin content of 40%-ratio 4.

Production Example 14 In the same apparatus as in Production Example 1, trimellitic anhydride 1,2 was used.
80 g (6.67 mol), 465 g ethylene glycol
(7.5 mol), 495 g (2.5 mol) of 4,4'-diaminodiphenylmethane and 1,634 g of cresol were charged and reacted, and 364 g of cresol was added to stop the reaction. Furthermore, 630 g of cresol and 27 of xylene
After dilution with 0 g, 100 g of tetrabutyl titanate was blended at 100 ° C. to obtain an insulating paint ratio of 5 with a resin content of 40%.

Comparative Production Example 15 Using the same apparatus as in Production Example 1, 776 g (4 mol) of dimethyl terephthalate and 233 g of ethylene glycol
(3.75 mol), 653 g (2.5 mol) of tris (2-hydroxyethyl) isocyanurate, 384 g (2 mol) of trimellitic anhydride, 198 g (1 mol) of 4,4'-diaminodiphenylmethane and 211 g of cresol After the charging reaction, 1,702 g of cresol was charged to stop the reaction. Further, after diluting with 603 g of cresol and 259 g of xylene, 96 g of tetrabutyl titanate was blended at 100 ° C., and an insulating coating material having a resin content of 40% -a ratio of 6
I got

Examples 1 to 9 and Comparative Examples 1 to 6 Each of the above insulating paints was applied to a horizontal baking furnace having a furnace length of 2.5 m.
A copper wire with a conductor diameter of 0.32 mm was heated to a furnace temperature of 500 ° C and a die 6
It was applied and baked at a take-up speed of 22 m / min to produce an insulated wire having a film thickness of 0.018 mm. The appearance, adhesion, pinhole, flexibility, softening point, breakdown voltage and solder peelability of the obtained insulated wire were measured according to JIS C.
Tested according to 3003 (Test method for enameled copper wire and enameled aluminum wire). 700ml moist heat resistance
The two-twisted sample in the dielectric breakdown voltage test of JIS C3003 was sealed together with 0.2 vol% of water in an autoclave, and left in a thermostat at 120 ° C. for 168 hours.
C3003 was performed in accordance with the dielectric breakdown voltage test, and the holding ratio with respect to the initial value was measured. Tables 1 and 2 show the above test results.

Table 1 (Insulated wire characteristics part 1)

Table 2 (Insulated wire characteristics part 2)

The results in Tables 1 and 2 show that the insulated wire of the present invention overcomes the drawbacks of the conventional polyester-based insulated wire and has heat resistance, wet heat resistance and solder peelability. .

[0038]

According to the present invention, there is provided an insulated wire having solder peelability and heat resistance and wet heat resistance. INDUSTRIAL APPLICABILITY The insulated wire of the present invention can sufficiently meet the requirements for polyester-based insulated wires used for electric equipment in recent years.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 7/02 H01B 7/02 B (72) Inventor Masao Ikeda 1-7-6 Nihombashi Bakurocho, Chuo-ku, Tokyo Dai Nissin Chemical Industry Co., Ltd. (72) Inventor Setsuo Terada 1-7-6 Nihombashi Bakurocho, Chuo-ku, Tokyo Dai Nissin Chemical Industry Co., Ltd. F term (reference) 4J029 AA01 AB01 AB07 AC02 AE11 BA02 BA03 BA04 BA05 BA08 BA09 BF09 CB06A CC06A CH01 DA15 FC36 KB02 4J038 DD071 DD131 DD171 KA06 NA04 NA10 NA14 NA21 PA19 PB09 PC02 5G305 AA02 AA11 AB24 AB26 AB36 AB40 BA09 BA22 CA11 5G309 MA11

Claims (1)

[Claims] 1. An amount of 10 equivalent% or more of 2,6-naphthalenedicarboxylic acid or its derivative (A) and less than 90 equivalent% of terephthalic acid and its derivative, trimellitic anhydride and its derivative, and trimellitic anhydride and 4 An acid component comprising at least one component (B) selected from diimidodicarboxylic acids comprising 4,4'-diaminodiphenylmethane;
The alcohol component (C), which is at least one of aliphatic polyhydric alcohols having 2 to 8 carbon atoms, is reacted in an amount such that the alcohol component (C) becomes 1.2 to 2.0 equivalents of the total acid components. A polyester-based insulated wire having solder releasability, which is obtained by applying and baking an insulating paint obtained by dissolving a polyester-based resin obtained in an organic solvent on an electric conductor.