JP2009140878A - Insulating electric wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulating electric wire which has a high thermal resistance and is superior in suppression of a corona discharge at a high frequency region. <P>SOLUTION: The insulating electric wire has an insulating coating formed by coating and baking an insulating varnish having imide-based resin varnish as a main component on a conductor. The insulating varnish has a hollow silica dispersant in which hollow silica is dispersed in a mixed solvent of an amide-based polarorganic solvent and a silane coupling agent, mixed in the imide-based resin varnish. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an insulated wire used for an electric device such as a motor or a transformer, an enameled wire used as an insulated wire, and an insulating paint used therefor.

Generally, an enameled wire used as an insulated wire has an insulating film formed by applying and baking an enamel paint on a conductor. A coil for an electric device obtained by winding the enameled wire is widely used in a large capacity and large heavy electric device.
When manufacturing an electric device such as a motor or a transformer by using the enamel wire used for the coil for the electric device, generally the enamel wire is continuously coiled in the slot of the core (magnetic core) of the motor. The mainstream method is to form the coil by winding it in a coil or by fitting and inserting a coil of enameled wire into a slot in the core.

  On the other hand, in the case of an enameled wire with a large cross-sectional area, that is, a large outer diameter or an enameled wire having a rectangular conductor, the enameled wire is not continuously wound to form a long coil with a large number of turns, but the number of turns A method has been proposed in which a plurality of short small-diameter coils with a small number are formed, and enameled wire ends of these small-diameter coils are welded together to form a long coil. The coil formed in this way is used for a coil of an electric device that requires a small and high-density magnetic flux, such as a coil of an automobile generator.

Also, for motors used in inverter control devices for automobiles, an insulating film is formed by applying and baking polyesterimide varnish around the conductor, and polyamideimide varnish is applied around the polyesterimide insulating film. A double-coated wire provided with an insulating film formed by coating and baking, and a single-coated wire provided with an insulating film formed by applying and baking a polyamideimide varnish around a conductor are mainly used.
In addition, an insulation film is formed by applying and baking polyimide varnish around the conductor, and a polyamide-imide insulation film is provided around the polyimide insulation film to improve heat resistance and mechanical strength. Are also used (see, for example, Patent Document 1).

However, polyamide-imide and polyimide-based insulation films have high heat resistance, but because of their high polarity, they have a high dielectric constant. For example, in the case of inverter control, a high surge voltage generated from the inverter enters the motor, and the motor insulation system. Adversely affect. Specifically, when there is not sufficient insulation between the enamel wires wound in a coil shape, the deterioration of the insulating film is promoted by corona discharge.
At this time, as a method for improving the inverter surge resistance of the enameled wire, a method of extending the life of the enameled wire even when corona discharge occurs can be considered. As a technique for extending the life, it is known to provide an enameled wire with an insulating film in which silica sol is dispersed in an electrically insulating varnish (see, for example, Patent Document 2).

  Moreover, if the corona discharge start voltage of the insulating film is higher than the inverter surge voltage during high frequency voltage application, corona discharge does not occur and the life is prolonged. Examples of a method for increasing the corona discharge start voltage include increasing the thickness of the insulating film and decreasing the dielectric constant. In order to reduce the dielectric constant of an insulating film, it has been proposed to form an insulating film by applying and baking an insulating varnish made of fluorine-based polyimide on a conductor surface (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 5-130759 JP 2004-22831 A JP 2002-56720 A

However, increasing the thickness of the insulating film is not preferable because the space factor increases and the motor becomes larger.
In addition, although the insulating film made of a fluorine-based insulating varnish has a low dielectric constant, there is a risk of generating a harmful fluorine-based gas during high-temperature baking.

  An object of the present invention is to provide an insulated wire that solves the above-described problems of the prior art, has high heat resistance, and is excellent in suppressing the occurrence of corona discharge in a high-frequency region.

  A first aspect of the present invention is an insulated wire in which an insulating varnish mainly composed of an imide resin varnish is applied and baked on a conductor to form an insulating film. The insulating varnish is an amide polar organic solvent. A hollow silica dispersion in which hollow silica is dispersed in a mixed solvent of silane coupling agent and silane coupling agent is mixed with the imide resin varnish.

  According to a second aspect of the present invention, in the invention according to the first aspect, the hollow silica has a porosity of 30 vol% or more.

  According to a third aspect of the present invention, in the invention according to the first or second aspect, the hollow silica is 10 parts by weight or more and 50 parts by weight of silica with respect to 100 parts by weight of the resin content of the insulating varnish. It is characterized by being included in less than.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the hollow silica has an average particle diameter of less than 200 nm.

  According to a fifth aspect of the present invention, in the invention according to the first aspect, the silane coupling agent is contained in an amount of 0.01 parts by weight or more and less than 10 parts by weight with respect to the amount of silica of the hollow silica. It is characterized by.

  According to a sixth aspect of the present invention, in the invention according to the first aspect, the imide-based resin varnish is a polyamide-imide resin or a polyimide resin.

  According to the present invention, an insulated wire that is highly heat resistant and excellent in suppressing the occurrence of corona discharge in a high frequency region can be obtained.

Hereinafter, the best mode for carrying out the present invention will be described.
The insulated wire in the present embodiment is a conductor of insulating varnish obtained by mixing a hollow silica dispersion in which hollow silica is dispersed in a mixed solvent composed of a silane coupling agent and an amide polar organic solvent into an imide resin varnish. It is applied and baked to provide an insulating film.
Examples of the metal used for the conductor include copper and aluminum. Further, the cross-sectional shape of the conductor may be any cross-sectional shape such as a circular shape or a flat rectangular shape as long as it can be used as an insulated wire.
The imide-based resin varnish specifically uses one or more types of polyamide-imide resin or polyimide resin.

  The hollow silica is mainly composed of silicon oxide and is amorphous. As the silica source, silicon oxide and its precursor, which can be finally converted to silica by condensation or polymerization can be used. Specifically, alkoxides such as tetraethoxysilane, methyltriethoxysilane, dimethyltriethoxysilane, 1,2-bis (triethoxysilyl) ethane, and activated silica can be used alone or in combination. Activated silica is particularly preferred because it is inexpensive and highly safe. The active silica can be prepared by ion exchange of water glass or extraction from water glass with an organic solvent.

Moreover, the said hollow silica contains the silica fine particle which has a nanosize hollow.
Since the silica fine particles form a composite dielectric with air, the dielectric constant of the insulating film can be lowered. By mixing the hollow silica with other materials, the dielectric space of the insulating film can be reduced using the internal space of the hollow silica, that is, air. In addition, since the internal space of the hollow silica is a nano-sized space, dielectric breakdown hardly occurs.

Specifically, the hollow silica preferably has a fine particle porosity of 30 vol% or more and 30 vol% or less and 50 vol% or less obtained from the silica particle diameter and the hollow silica shell thickness in transmission electron microscopy. It is more preferable that
When the porosity is less than 30 vol%, the effect of suppressing the occurrence of corona discharge in the high frequency region and the dielectric breakdown characteristics tend to decrease. When the porosity exceeds 50 vol%, the porosity is between 30 vol% and 50 vol% This is because the mechanical strength of the hollow silica becomes weaker than that of the hollow silica, and the hollow silica may be broken during dispersion.

Specifically, it is preferable that the hollow silica is contained in an amount of 10 parts by weight or more and less than 50 parts by weight with respect to 100 parts by weight of the resin component of the imide resin varnish.
When the amount is less than 10 parts by weight, the effect of lowering the dielectric due to the hollow structure of the hollow silica is not exhibited. When the amount is 50 parts by weight or more, precipitation of the silica in the varnish component, thickening of the varnish due to silica blending This is because it occurs.

  Furthermore, specifically, it is preferable that the average particle diameter of the fine particles determined by transmission electron microscopy is less than 200 nm. This is because hollow silica having an average particle diameter of 200 nm or more has poor dispersibility in the imide resin varnish and is very poor in stability.

  The silane coupling agent is not limited as a compound as long as it exhibits a dispersion stabilizing action with the imide resin varnish by adsorbing onto the hollow silica. Specific examples include 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxy. Silane, N-2- (aminoethyl) -3-aminopropylpropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane and the like are preferable.

Further, the silane coupling agent is preferably contained in an amount of 0.01 parts by weight or more and less than 10 parts by weight with respect to the silica amount of the hollow silica.
When the amount is less than 0.01 parts by weight, silica sedimentation occurs in an amide polar organic solvent, and uniform dispersion becomes difficult. When the amount is 10 parts by weight or more, condensation of the silane coupling agent proceeds, and This is because a decrease in stability occurs.

The amide polar organic solvent is not limited as a compound as long as the hollow silica can be uniformly dispersed in the solvent by a silane coupling agent and is soluble with the imide resin varnish. Specific examples include dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAC), N-methylpyrrolidone (N
MP) and the like can be used, but it is particularly preferable to use N-methylpyrrolidone (NMP) and / or dimethylacetamide (DMAC).

It describes about the manufacturing method of the insulated wire in this embodiment.
An example of a method for producing hollow silica used in the method for producing an insulated wire will be described below.
First, a surfactant is adjusted at a predetermined concentration and a predetermined temperature to prepare a molecular assembly solution. Separately, a solution in which a silica source is dissolved or dispersed in a solvent is prepared.
Next, both these liquids are stirred and mixed uniformly to bring the aggregate-containing liquid to a temperature of 100 ° C. or lower for a predetermined time, and the silica source is condensed and polymerized on the molecular aggregate formed by the surfactant. . And a hollow silica is obtained by removing a molecular assembly using a baking process or a cation exchange resin.
The hollow silica obtained here is mixed in an amide polar organic solvent and silane coupling agent mixed solvent to obtain a hollow silica dispersion. At this time, it is preferable to perform ultrasonic treatment to uniformly disperse the hollow silica in the mixed solvent. Since hollow silica has a strong mutual cohesion and becomes a secondary aggregate, the aggregation is loosened by ultrasonic treatment. The ultrasonic treatment can obtain a good dispersion effect by treating at a frequency of 20 kHz for about 5 to 120 minutes, but the ultrasonic conditions of the present invention are not limited to this, and are suitably good. You can choose the method. As the ultrasonic power is higher and the treatment time is longer, the agglomeration is loosened, but the hollow silica is also broken, so the dielectric constant reduction effect is lowered. By setting the ultrasonic treatment time to about 10 to 60 minutes, it is possible to produce a hollow silica dispersion in which secondary aggregation hardly occurs and the hollow silica is uniformly dispersed.
And after mixing and stirring the said hollow silica dispersion and an imide resin varnish, a solvent is volatilized so that it may become optimal viscosity, and an insulating varnish is obtained.
Finally, this insulating varnish is applied and baked around the conductor to provide an insulating film, thereby producing an insulated wire.
Here, a plurality of insulated wires may be brought close together and covered to form a single insulated wire.

It describes about the effect which the insulated wire in this embodiment brings.
The insulated wire in the present embodiment is a hollow silica dispersion in which particulate hollow silica is dispersed by ultrasonic treatment in a mixed solvent composed of a silane coupling agent and an amide polar organic solvent, and the hollow silica dispersion Is provided with an insulating film formed by applying a resin varnish on a conductor and baking it, and thus has high heat resistance and excellent suppression of generation of corona discharge and high dielectric breakdown characteristics in a high frequency region. The insulated wire is particularly suitable for coils such as motors and transformers.

  A method for producing an insulated wire having an insulating film in which the hollow silica of the present invention is dispersed will be described below according to specific examples.

(Examples 1-3)
Table 1 (below) shows the characteristics of hollow silica, blending amounts of silica and silane coupling, stability of insulating varnish, 5% weight loss temperature, dielectric constant, and dielectric breakdown voltage in Examples and Comparative Examples. Example 1 will be described below.
From Table 1, hollow silica (5 g) having an average particle diameter of 180 nm and a porosity of 50 vol% was converted into NMP (N-methylpyrrolidone) solvent (100 g) and a silane coupling agent (3-aminopropyltrimethoxysilane) (0.05 g). ) And mixed with an ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd.) for 30 minutes at a frequency of 20 kHz and an output of 150 W to obtain a hollow silica dispersion.
Next, a polyamideimide resin 10 having a solid content concentration of 20 parts by weight obtained by synthesizing trimellitic anhydride and diaminodiphenylmethane as the hollow silica dispersion and an imide resin varnish.
0 g was mixed and stirred.
Then, the solvent was volatilized so that it might become optimal viscosity as an insulated wire application | coating varnish, and the insulating varnish which consists of polyamideimide resin in which the hollow silica was disperse | distributed was obtained.
And after apply | coating this insulating varnish around the rectangular copper conductor, it baked and provided the insulating film whose film thickness is 30 micrometers, and produced the insulated wire.
In Example 2, an insulated wire was produced in the same manner as in Example 1, except that the hollow silica dispersion and 62.5 g of polyamideimide resin having a solid content of 20 parts by weight were mixed and stirred.
In Example 3, the hollow silica was mixed with a mixed solvent of NMP (N-methylpyrrolidone) solvent (100 g) and silane coupling agent (0.005 g) in the same manner as in Example 1. An insulated wire was produced.
As shown in Table 1, the hollow silica of the samples in Examples 1 to 3 has an average particle size of less than 200 nm and a porosity of 30 vol% or more.
Further, the blending amount of the hollow silica with respect to 100 parts by weight of the resin of the insulating varnish is 10 to 50 parts by weight, and the blending amount of the silane coupling agent with respect to 100 parts by weight of the hollow silica is 0.01 to 1 part by weight. Less than.

(Comparative Examples 1-5)
In Comparative Example 1, an insulated wire was produced in the same manner as in Example 1 except that a polyesterimide resin containing neither hollow silica nor a silane coupling agent was used as the insulating varnish.
In Comparative Example 2, an insulated wire was prepared in the same manner as in Example 1 except that the hollow silica dispersion and 40 g of polyamideimide paint having a solid content of 20 parts by weight were mixed and stirred.
In Comparative Example 3, an insulated wire was produced in the same manner as in Example 1 except that the void ratio of the hollow silica was 0 vol%, that is, granular silica having no hollow was used.
In Comparative Example 4, an insulated wire was produced in the same manner as in Example 1 except that the blending amount of the silane coupling agent was 0 parts by weight, that is, no silane coupling agent was blended.
In Comparative Example 5, an insulated wire was produced in the same manner as in Example 1 except that the average particle diameter of the hollow silica was 200 nm.

Insulation varnishes in Examples and Comparative Examples and insulated wires using the varnishes were evaluated by the following methods, and the results are shown in Table 1.
(1) Stability of insulating varnish The insulating varnishes produced in the examples and comparative examples were placed in a room at room temperature of 30 ° C. where they were not exposed to direct sunlight for one month, and were judged by the presence of varnish resin and hollow silica sedimentation. .
(2) 5% weight reduction temperature It heated in the thermogravimetric balance with respect to the insulation film of the insulated wire produced in the Example and the comparative example, and the temperature in case 5% of weight was lost was measured.
(3) Dielectric constant The insulating varnishes produced in the examples and comparative examples were molded into a film, and a 2 mm × 100 mm test strip was measured using the cavity resonator perturbation method (S-parameter network analyzer 8720ES; manufactured by Agilent), and the frequency A dielectric constant of 10 GHz was measured.
(4) Dielectric breakdown voltage Insulated wires produced in the examples and comparative examples are sandwiched between brass parallel plate electrodes (diameter: 30 mm), and the voltage is applied by increasing the initial charge from 1 kV to 0.5 kV / min. The voltage at that time was measured.

In the insulated wires obtained in Examples 1 to 3 and Comparative Examples 1 and 3, the stability of the insulating varnish is good, but from the result of the 5% weight loss temperature, the insulated wires of Examples 1 to 3 are It can be seen that the heat resistance is superior to the conventional insulated wire obtained in Comparative Example 1.
Moreover, in Examples 1-3, the dielectric constant of an insulating film is lower than Comparative Examples 1 and 3, and generation | occurrence | production of the corona discharge in a high frequency area | region can be suppressed rather than before.
Furthermore, in Examples 1-3, it turns out that a dielectric breakdown voltage is higher than Comparative Examples 1 and 3, and it is excellent in a dielectric breakdown characteristic.
On the other hand, in the insulated wires obtained in Comparative Examples 1 and 3, silica fine particles containing neither hollow silica nor a silane coupling agent or voids are blended, and the dielectric constant compared to Examples 1-3. It becomes difficult to effectively suppress the occurrence of corona discharge in the high frequency region.
Moreover, in Comparative Example 2 and Comparative Example 4, although the same hollow silica as in Examples 1 to 3 is used, in Comparative Example 2, the amount of silica with respect to 100 parts by weight of the insulating varnish resin exceeds 50 parts by weight. 62.5 parts by weight, and in Comparative Example 4, the stability of the insulating varnish was very poor due to the absence of the silane coupling agent. Moreover, in the comparative example 5, compared with Example 1, the average particle diameter of hollow silica was 200 nm, and varnish stability became very bad.
In addition, this invention is not limited to the said embodiment and Example, A various deformation | transformation is possible within the range which does not change the summary. For example, the combination of the components of the embodiment can be arbitrarily performed.

Claims (6)

  In an insulated wire in which an insulating varnish mainly composed of an imide resin varnish is applied and baked on a conductor to form an insulating film, the insulating varnish is a mixed solvent of an amide polar organic solvent and a silane coupling agent. An insulated wire comprising a hollow silica dispersion in which hollow silica is dispersed in the imide resin varnish.   The insulated wire according to claim 1, wherein the hollow silica has a porosity of 30 vol% or more.   The insulated wire according to claim 1 or 2, wherein the hollow silica is contained in an amount of 10 parts by weight or more and less than 50 parts by weight with respect to 100 parts by weight of the resin content of the insulating varnish.   The insulated wire according to any one of claims 1 to 3, wherein the hollow silica has an average particle diameter of less than 200 nm.   The insulated wire according to claim 1, wherein the silane coupling agent is contained in an amount of 0.01 parts by weight or more and less than 10 parts by weight with respect to the silica amount of the hollow silica.   The insulated wire according to claim 1, wherein the imide-based resin varnish is a polyamide-imide resin or a polyimide resin.