JP2016003263A - Coating liquid for insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating liquid for an insulated wire capable of obtaining a porous insulating coating film having a small average pore diameter and a high porosity.SOLUTION: There is provided a coating liquid for an insulated wire which comprises a polyamide-imide and a mixed solvent containing an amide-based solvent and an ether-based solvent, wherein the blending amount of the ether-based solvent is 200 mass% or more and 800 mass% or less based on the mass of the polyamide-imide. There is provided the coating liquid for an insulated wire in which an isolated solid polyamide-imide is used as the polyamide-imide. There is provided the coating liquid for an insulated wire in which the isolated solid polyamide-imide is a polyamide-imide resin containing 4,4'-diphenyletherdiamine and m-phenylenediamine as a diamine component.

Description

The present invention relates to a coating liquid for insulated wires used in various electric devices.

Insulated wires whose conductors are covered with an insulating film are used in electric coils for various electric devices such as motors and transformers. The insulated wire forming this electric coil is required to have adhesion to the conductor, electrical insulation and heat resistance. In particular, in space electrical equipment, aircraft electrical equipment, nuclear electrical equipment, energy electrical equipment, automotive electrical equipment, etc., there is a demand for higher performance as well as reduction in size and weight. The rotating electrical machines and transformers require higher output than ever before.

Since a high voltage is applied to the rotating electrical machine or the like during operation, an insulated wire that does not easily cause partial discharge is required. A partial discharge start voltage is known as an index for measuring the likelihood of partial discharge. As a method for improving the partial discharge start voltage, an insulated wire provided with a coating made of porous polyamideimide has been proposed. (Patent Documents 1 to 3) This method can form a thick insulating film with a small number of coatings, and can reduce the dielectric constant of the film, which is effective for improving the partial discharge start voltage. Is the method.

In the said patent document, as a coating liquid for forming the insulating film which consists of porous polyamideimide, it is 30-150 mass% with respect to the mass of a polyamideimide to the polyamideimide solution containing the amide-type solvent prepared beforehand. A method using a polyamideimide solution to which an ether solvent is added is disclosed.

JP 2013-187029 A International Publication No. 2013/133334 Japanese Patent No. 5391365

However, when the coating liquid is used, the average pore diameter of the formed insulating film of porous polyamideimide tends to be slightly large as 5 μm or more, so that there is a problem that mechanical characteristics are easily impaired. Moreover, it was not easy to increase the porosity sufficiently. Then, this invention solves the said subject, and aims at provision of the coating liquid for insulated wires from which the porous insulating film which has a small average pore diameter and high porosity is obtained.

The present inventors have found that the above problems can be solved by a coating liquid for insulated wires having a specific composition, and have completed the present invention.
The present invention has the following objects.
<1> It consists of a polyamideimide and a mixed solvent containing an amide solvent and an ether solvent, and the blending amount of the ether solvent is 200% by mass or more and 800% by mass or less with respect to the mass of the polyamideimide. Characteristic coating solution for insulated wires.
<2> The insulated wire coating liquid, wherein an isolated solid polyamideimide is used as the polyamideimide.
<3> The insulated wire coating liquid, wherein the isolated solid polyamideimide is a polyamideimide resin containing 4,4′-diphenyl ether diamine and m-phenylene diamine as diamine components.

Since an insulating coating made of porous polyamideimide having a small pore diameter and high porosity can be easily obtained from the coating liquid of the present invention, it is suitably used as a coating liquid for insulated wires with improved partial discharge characteristics. can do.

Hereinafter, the present invention will be described in detail.
The present invention relates to a coating liquid for an insulated wire comprising a polyamideimide and a mixed solvent containing an amide solvent and an ether solvent.

Here, the polyamide-imide is a heat-resistant polymer having both an imide bond and an amide bond in the main chain, and by drying a coating film obtained from a solution containing this, heat resistance with excellent mechanical properties Films can be easily obtained.

Among these polyamideimides, aromatic polyamideimides excellent in mechanical properties and heat resistance are preferable. The aromatic polyamideimide may be thermoplastic or non-thermoplastic, but an aromatic polyamideimide having a glass transition temperature of 200 ° C. or higher can be preferably used.

As the polyamideimide, an isolated solid polyamideimide is preferably used as the polyamideimide.

The isolated solid polyamideimide can be obtained, for example, by the following method. That is, the raw material trimellitic acid component (trimellitic anhydride chloride, trimellitic anhydride, etc.) and diamine component (various diamines or diisocyanate derivatives thereof) are blended in approximately equimolar amounts, and this is mixed in, for example, an amide solvent. To the solution obtained by the polymerization reaction, for example, a polyamide imide such as water is added as a poor solvent to precipitate the polyamide imide as a precipitate, and this is filtered and dried, and if necessary, a hot imide Can be obtained. The methods for producing these isolated solid polyamideimides are described in detail, for example, in JP-B-56-16171, JP-A-58-91724, JP-A-2007-246680, and the like. Therefore, it can manufacture with reference to these literatures.

As the trimellitic acid component, trimellitic anhydride chloride is preferable. Further, as the trimellitic acid component, a part of which is substituted with a component such as pyromellitic acid, benzophenone tetracarboxylic acid, or biphenyl tetracarboxylic acid may be used.

Examples of the diamine component include m-phenylenediamine, p-phenylenediamine, 4,4′-diphenylmethanediamine, 4,4′-diphenyletherdiamine, diphenylsulfone-4,4′-diamine, and diphenyl-4,4. '-Diamine, o-tolidine, 2,4-tolylenediamine, 2,6-tolylenediamine, xylylenediamine, naphthalenediamine or their diisocyanate derivatives can be used. These may be used alone or in combination of two or more. Among these, 4,4′-diphenyl ether diamine and m-phenylene diamine are preferable in that the porosity of the coating can be increased.

As the isolated solid polyamideimide, commercially available polyamideimide powder (for example, Torlon AI-10, Torlon AI-30, Torlon AI-50, Torlon 4000T, Torlon 4000TF, etc. manufactured by Solvay Advanced Polymers Co., Ltd.) is used. It can also be used.

The coating liquid of the present invention can be obtained, for example, by dissolving the isolated solid polyamideimide in a mixed solvent containing an amide solvent and an ether solvent. Examples of the amide solvent include N-methyl-2-pyrrolidone (NMP boiling point: 202 ° C.), N, N-dimethylformamide (DMF boiling point: 153 ° C.), N, N-dimethylacetamide (DMAc boiling point: 166 ° C.). Is mentioned. These may be used alone or in combination of two or more. Among these, NMP is preferable.

As the ether solvent, a solvent having a boiling point higher than that of the amide solvent is preferably used, and the difference in boiling point is preferably 5 ° C. or higher, more preferably 20 ° C. or higher, and further preferably 50 ° C. or higher. Specifically, diethylene glycol dimethyl ether (DEGM boiling point: 162 ° C.), triethylene glycol dimethyl ether (TRGM boiling point: 216 ° C.), tetraethylene glycol dimethyl ether (TEGM boiling point: 275 ° C.), diethylene glycol (DEG boiling point: 244 ° C.), triethylene A solvent such as glycol (TEG boiling point: 287 ° C.) can be used. These may be used alone or in combination of two or more. Among these, TEGM is preferable.

In the coating liquid of the present invention, the blending amount of the ether solvent is 200% by mass or more and 800% by mass or less, preferably 300% by mass or more and 700% by mass or less with respect to the mass of the polyamideimide. Here, it is preferable to set it as 5-30 mass% as a polyamideimide density | concentration in a coating liquid, and it is more preferable to set it as 10-20 mass%. Such a composition can be easily achieved by using a solid polyamideimide as described above.

The coating composition of the present invention having the coating composition described above is applied to a conductor for an electric wire to form a coating film, and then the coating film is baked at a temperature of 300 ° C. or higher, preferably 400 ° C. or higher. It is possible to obtain an insulated wire in which a film made of a porous polyamideimide is formed. During this baking, the phase separation efficiently occurs due to the action of the ether solvent remaining in the coating film at a high concentration, whereby an insulating coating made of porous polyamideimide having a small pore diameter and a high porosity is formed. Can be obtained. Here, as a conductor of an insulated wire, what was used conventionally, such as copper, copper alloy, aluminum, aluminum alloy, or those combinations, can be used, for example. For details of the coating method, for example, JP-A-2013-187029 can be referred to. In addition, as thickness of the insulating film formed, it is preferable to set it as 10-200 micrometers. In order to obtain such a thickness, the coating and baking as described above can be repeated twice or more.

The average pore diameter is preferably less than 5 μm, and more preferably less than 3 μm. Moreover, as a porosity, it is preferable to set it as 40 volume% or more, and it is more preferable to set it as 50 volume% or more. Here, the average pore diameter can be confirmed by observing an SEM image of the coating film cross section. The porosity can be calculated from the apparent density of the coating film and the true density (specific gravity) of the polyamideimide. An insulating coating having such an average pore diameter and porosity can be easily obtained from the coating liquid of the present invention.

You may add well-known additives, such as various surfactant and an organic silane coupling agent, to the coating liquid of this invention in the range which does not impair the effect of this invention. Moreover, you may add other polymers other than a polyamideimide to a coating liquid as needed in the range which does not impair the effect of this invention.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples.

<Example 1>
As a polyamideimide powder obtained by copolymerization of trimellitic anhydride chloride, 4,4′-diphenyl ether diamine and m-phenylene diamine, Torlon 4000T manufactured by Solvay Advanced Polymers Co., Ltd. (this powder is referred to as “P-1”). Abbreviated). 15 g of P-1 was dissolved in a mixed solvent composed of 25 g of NMP and 60 g of TEGM at 30 ° C., and the TEGM blending ratio was 15% by mass with respect to the coating liquid mass, and the solid content concentration of polyamideimide was ether-based. The uniform coating liquid (A-1) whose compounding quantity of a solvent is 400 mass% with respect to the polyamidoimide mass was obtained. The coating liquid was applied to the outer periphery of a copper wire having a diameter of 1 mm and baked in a continuous firing furnace set at 480 ° C., thereby obtaining an electric wire on which a film made of porous polyamideimide having a thickness of 30 μm was formed. . Table 1 shows the measurement results of the average pore diameter and porosity of this coating.

<Examples 2 to 5>
In the same manner as in Example 1, coating liquids (A-2 to A-5) having the composition shown in Table 1 were prepared, and using these coating liquids, the thickness was 30 μm under the same conditions as in Example 1. An electric wire on which a film made of porous polyamideimide was formed was obtained. Table 1 shows the measurement results of the average pore diameter and the porosity of these coatings.

<Example 6>
Polyamideimide powder obtained by copolymerizing trimellitic anhydride chloride with 60 mol% of 4,4′-diphenyl ether diamine and 40 mol% of m-phenylene diamine according to Example 1 of JP-A-2007-246680 A body (this powder is abbreviated as “P-2”) was obtained. The intrinsic viscosity of P-2 was 0.82 dL / g, and the glass transition temperature was 280 ° C. 15 g of P-2 was dissolved in a mixed solvent composed of 25 g of NMP and 60 g of TEGM at 30 ° C., and the TEGM blending ratio was 15% by mass with respect to the coating liquid mass, and the solid content concentration of polyamideimide was ether. A uniform coating solution (A-6) was obtained in which the amount of the system solvent was 400% by mass relative to the mass of polyamideimide. The coating liquid was applied to the outer periphery of a copper wire having a diameter of 1 mm and baked in a continuous firing furnace set at 480 ° C., thereby obtaining an electric wire on which a film made of porous polyamideimide having a thickness of 30 μm was formed. . Table 1 shows the measurement results of the average pore diameter and porosity of this coating.

<Example 7>
Polyamideimide powder obtained by copolymerizing trimellitic anhydride chloride with 70 mol% of 4,4'-diphenyl ether diamine and 30 mol% of m-phenylenediamine based on the description in Example 2 of JP2007-246680A A body (this powder is abbreviated as “P-3”) was obtained. The intrinsic viscosity of P-3 was 0.85 dL / g, and the glass transition temperature was 270 ° C. 15 g of P-3 was dissolved in a mixed solvent consisting of 25 g of NMP and 60 g of TEGM at 30 ° C., and the TEGM compounding ratio was 15% by mass with respect to the mass of the coating liquid with respect to the solid content concentration of the polyamideimide. The uniform coating liquid (A-7) whose compounding quantity of a system solvent is 400 mass% with respect to the polyamidoimide mass was obtained. The coating liquid was applied to the outer periphery of a copper wire having a diameter of 1 mm and baked in a continuous firing furnace set at 480 ° C., thereby obtaining an electric wire on which a film made of porous polyamideimide having a thickness of 30 μm was formed. . Table 1 shows the measurement results of the average pore diameter and porosity of this coating.

<Examples 8 to 10>
Sollon Advanced Polymers Co., Ltd. Torlon AI-10 as a polyamideimide powder obtained by polymerizing trimellitic anhydride chloride and 4,4'-diphenylmethanediamine (this powder is abbreviated as "P-4") Prepared. In the same manner as in Example 1, coating liquids (A-8 to A-10) were prepared with the compositions shown in Table 1, and using these coating liquids, the thickness was 30 μm under the same conditions as in Example 1. An electric wire on which a film made of porous polyamideimide was formed was obtained. Table 1 shows the measurement results of the average pore diameter and the porosity of these coatings.

<Comparative Examples 1-5>
In the same manner as in Example 1, coating liquids (B-1 to B-5) were prepared with the compositions shown in Table 1, and a porous material having a thickness of 30 μm was prepared from these coating liquids under the same conditions as in Example 1. An electric wire on which a film made of polyamideimide was formed was obtained. Table 1 shows the average pore diameter and porosity measurement results of these coating films.

The average pore diameter of the porous polyamideimide coating obtained from the coating liquid used in the examples was as small as less than 5 μm, and the porosity was as high as 40% by volume or more. Therefore, the coating liquid of the present invention can be suitably used for an insulated wire having improved partial discharge characteristics. On the other hand, it can be seen that the insulating coating obtained from the coating liquid shown in the comparative example has a large average pore diameter and a low porosity.

Claims (3)

It consists of a polyamideimide and a mixed solvent containing an amide solvent and an ether solvent, and the blending amount of the ether solvent is 200% by mass or more and 800% by mass or less with respect to the mass of the polyamideimide. Insulated wire coating solution. 2. The insulated wire coating liquid according to claim 1, wherein an isolated solid polyamideimide is used as the polyamideimide. 3. The isolated solid polyamideimide is a polyamideimide resin containing 4,4'-diphenyl ether diamine and m-phenylenediamine as a diamine component. .