JPS6113322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a conductive sheet or tape suitable for preventing corona breakdown of an insulating layer in a high voltage coil.

In high-voltage coils of 3KV class or higher, which have heat resistance of class F or higher among electrical equipment insulation, high voltage is applied for a long period of time during the operation of the equipment, so the insulation layer is eroded by the corona generated, resulting in corona destruction. It is known that its lifespan is significantly shortened.

Conventionally, in order to prevent such corona destruction, a so-called conductive paint is prepared by mixing conductive particles such as carbon into natural or synthetic resin paint, and a conductive sheet or tape is made from this paint and wrapped around the conductor surface. Measures have been taken.

However, with conventional sheets or tapes of this kind, the resistance value of the conductive layer formed therefrom is unstable, and a uniform resistance value cannot be obtained over the entire surface of the layer. In general, the surface resistance that is effective for preventing corona damage is 10 ² to ^{10 3} Ω・cm, which has a relatively narrow tolerance range, so materials with such unstable resistance values cannot sufficiently prevent corona damage. .

The inventor believes that the cause of this problem lies in the resin content of paints such as epoxy resins and polyester resins that have been widely used in the past, and that these resins make it difficult to uniformly disperse and bind conductive particles. As a result of extensive research into selecting a heat-resistant resin with excellent mechanical strength and elongation suitable for use in high-voltage coils, we found that a certain type of water-soluble polymer is extremely suitable for this purpose. I learned that.

This invention was made based on the above knowledge, and its gist is 1.2.
An acid obtained by a condensation reaction between a polybasic acid component consisting of 3,4-butanetetracarboxylic acid (or one that partially contains a derivative thereof) and a diamine in a water-soluble solvent or in the coexistence of a water-soluble solvent and water. A condensate with a residual value of 3 to 50% is made into a water-soluble salt (hereinafter referred to as a water-soluble aliphatic condensation polymer salt) with a nitrogenous basic compound, and if required, the above-mentioned In an aqueous solution containing the above solvent to which a carbonate or organic carboxylate of a nitrogenous compound is added,
It is a conductive sheet or tape made by impregnating a fiber base material with excellent heat resistance with a conductive paint in which conductive particles are uniformly dispersed.

When the water-soluble aliphatic condensation polymer salt used in this invention is heated at high temperatures, it becomes imidized through a ring-closing reaction between the amide bond and the carboxyl group in the molecule, resulting in excellent heat resistance, freon resistance, and radiation resistance. It becomes an insoluble and infusible resin.

Such water-soluble polymer salts are already known per se. In the present invention, this type of salt has excellent affinity with conductive particles having hydrophilic groups on the particle surface, and by blending the above particles into an aqueous solution containing the above solvent in which the salt is dissolved, the particles can be formed. A paint with uniform dispersion and stability over time can be obtained, and as a result, when a sheet or tape is made from this, which is wrapped around a conductor surface and applied, and further imidized, a stable resistance value is obtained over the entire conductive layer. Especially for carbon particles, 10 ² ~
It has been found to be extremely suitable for preventing corona damage in high-voltage coils, as it exhibits a stable resistance value in the range of 10 ³ Ω, and the conductive layer has excellent mechanical strength and elongation. It is something.

By the way, other water-soluble polymer salts are known which can ultimately provide a polyimide layer with excellent heat resistance. For example, there is an aromatic condensation type polymer salt that uses an aromatic tetracarboxylic acid as a polybasic acid component and makes it water-soluble by reacting a basic compound with a polyamic acid as a polyimide precursor obtained by a condensation reaction of this with a diamine. .

Although this polymer salt can be expected to have some degree of affinity with conductive particles, it generally lacks stability in an aqueous solution state, lowers the degree of polymerization due to chemical changes, and deteriorates layer properties. It also has problems in mechanical strength and elongation, making it practically unsuitable for use as a paint resin component for preventing corona damage in the high-voltage coil of the present invention.

Similarly, coatings that can ultimately form a heat-resistant imidized conductive layer include those in which conductive particles are dispersed in various polyamic acid compositions conventionally synthesized in organic solvents. However, when this type of paint is made into a sheet or tape and wrapped around the conductor surface to imidize it, the dispersion and binding of the resin and conductive particles is not very good, and the high-voltage coil It has been difficult to expect the high resistance stability of the conductive layer required for this purpose.

In this way, in this invention, among the various polymers that can ultimately form a heat-resistant polyimide layer, the above-mentioned water-soluble aliphatic condensation polymer salt can be used for the first time to meet the requirements for high-voltage coils. The present invention has succeeded in obtaining a heat-resistant conductive layer having high resistance stability and good layer strength or elongation that is practically desired.

In this invention, among such water-soluble aliphatic condensation polymer salts, 1, 2, 3, and 4
- The acid value residual rate of the condensate obtained by the reaction of a polybasic acid component consisting of butanetetracarboxylic acid (or a derivative thereof that partially contains monoanhydride, dianhydride, ester, amide, etc.) and diamine. 3
~30%, and a water-soluble polymer salt made into an ammonium salt with ammonia or a quaternary ammonium compound (hereinafter referred to as an aliphatic condensed ammonium salt) is preferably used.

This aliphatic condensed ammonium salt makes it possible to obtain a paint with better dispersibility of conductive particles and stability over time, resulting in even better results in resistance stability as a conductive layer. The flexibility and heat resistance of the imidized conductive layer are further improved. This type of paint also has the advantage of not being toxic or having a harmful odor.

Regarding the production method of these water-soluble aliphatic condensation polymer salts, the present applicant previously proposed a method for producing them in JP-A-50
It is described in detail in JP-A-76196 and JP-A-53-42241.

In general, the molar ratio of the polybasic acid component and diamine during the condensation reaction is usually in the range of 0.55 to 1.8 mol of diamine per 1 mol of the polybasic acid component, and also in the water-soluble solvent of both or between the water-soluble solvent and water. The concentration during the reaction in a mixed solvent is not particularly limited, but is preferably about 50 to 95% by weight. The reaction temperature is preferably 60°C or higher, up to the boiling point under normal pressure.

The diamine component used in this condensation reaction includes various diamines such as aliphatic, alicyclic, and aromatic diamines, and among them, aromatic diamines are preferably used. Further, water-soluble solvents include monoalcohols, glycols, glycol ethers, glycol esters, glycerin, etc., and preferably those other than monoalcohols are used.
These include a wide range of known ones described in the above-mentioned publications and the like.

The condensate formed by such a reaction has a residual acid value of 3 to 50%, especially 3 to 30% when it is an aliphatic condensed ammonium salt. It shows how many acid groups remain after the reaction, assuming that the acid value of the polybasic acid component in the initial system (mg equivalent of carboxyl group per 1 g of sample) is 100%.

The nitrogenous basic compounds used to make this condensate water-soluble include ammonia and quaternary ammonium compounds to form ammonium salts, as well as primary amines, secondary amines, tertiary amines, and tertiary amines. There are various nitrogen compounds that act as bases, including polycyclic compounds that act similarly.
These include a wide range of known compounds described in the above-mentioned Japanese Patent Application Laid-Open No. 53-42241. The temperature during salt formation is from 0℃ to 200℃, especially from room temperature to 120℃
is sufficient.

The conductive paint according to the present invention contains various conductive materials such as carbon and silver powder depending on the required surface resistance in an aqueous solution containing the above-mentioned water-soluble solvent in which such a water-soluble aliphatic condensation polymer salt is dissolved. Add solid particles and mix with stirring until the solid content concentration is usually 30 to 40.
It can be obtained by diluting with water to give a concentration of 100 parts by weight, but the proportion of conductive particles is generally 20 to 40 parts by weight, preferably 13 to 20 parts by weight, per 100 parts by weight of the polymer salt. be.

In addition, if it is desired to further improve the storage stability of the resulting conductive paint, carbonates of nitrogenous basic compounds such as formic acid, acetic acid, propionic acid, etc., are added to the paint at any stage of its production.
What is necessary is just to add the organic carboxylic acid salt of No. 7. Regarding these salts, those disclosed in JP-A-53-42241 can be used as desired.

In the present invention, such a conductive paint is used as a conductive sheet or tape coated on a base material. The base material used to form this sheet or tape may be a synthetic film having excellent heat resistance, but preferably a heat-resistant fiber base material having arbitrary voids is selected. By impregnating and coating such a base material, it is possible to fully exhibit its flexibility as a sheet or tape and its function as a conductive layer. Specifically, glass cloth, glass nonwoven fabric, cloth made of synthetic fibers with excellent heat resistance such as polyester,
Examples include nonwoven fabrics.

The conductive sheet or tape of this invention is suitable for preventing corona damage in high-voltage coils, but it can also be widely used for other applications that require high resistance stability, good layer strength, elongation, heat resistance, etc. be able to.

Examples of this invention will be described below. Note that in the following, parts mean parts by weight.

Example 1, 2, 3, 4 in a 500ml three-necked flask equipped with a thermometer, a condenser with a trap, and a stirring device.
117 parts of -butanetetracarboxylic acid, 99 parts of 4,4'-diaminodiphenylmethane, and 70 parts of triethylene glycol were added and stirred with heating. Distillation of water began around 100°C, and the reaction system gradually became homogeneous and turned dark brown. As heating continued, the temperature in the system rose and the viscosity increased. In this way, the temperature in the system remained constant for about 1 hour after water began to distill.
The reaction was terminated when the temperature reached 130°C.

The acid value residual rate of the obtained condensate was 22.0%. Aqueous ammonia was further added dropwise to this condensate solution at 80 to 100°C to form an aliphatic condensed ammonium salt. Here, the ammonia water is commercially available at 28% by weight.
A solution prepared by diluting 35 parts of concentrated ammonia water with approximately 1.5 times the amount of purified water was used, and the excess ammonia was scattered out of the system after salt formation.

Next, add 13.3 parts of Carbon HS-500 (manufactured by Nippon Carbon Co., Ltd.) to 100 parts of this ammonium salt solution (solid content 40% by weight), mix well with a paint roll, and then add 33.4 parts of water to coat. The conductive paint according to the present invention was prepared by adjusting the viscosity to a suitable viscosity.

Apply this paint to glass cloth (manufactured by FRP Kogyo Co., Ltd.)
SECO50gfey, 0.05mm thickness, 47g/ ^m2 ) 10~50
The conductive tape of the present invention was prepared by applying 2 g/m ² coating, heating and drying at 130 to 150°C for 10 to 30 minutes, and cutting to a predetermined width. The resistance value of this tape was in the range of 10 ² to ^{10 3} Ω·cm over the entire length of the tape. Furthermore, the conductive layer that was actually applied to the surface of the insulating layer of a high-voltage coil and imidized by high-temperature heating after installation had excellent heat resistance with suppressed corona destruction and excellent mechanical strength and flexibility. .

Claims (1)

[Claims] 1. A polybasic acid component consisting of 1,2,3,4-butanetetracarboxylic acid (or one containing a portion of its derivative) and a diamine in a water-soluble solvent or in combination with a water-soluble solvent and water. A condensate with a residual acid value of 3 to 50% obtained by condensation reaction in the coexistence of A conductive sheet or tape in which a heat-resistant fiber base material is impregnated with a conductive paint made by uniformly dispersing conductive particles in an aqueous solution containing the above-mentioned solvent to which a salt or organic carboxylic acid salt has been added. . 2. The conductive sheet or tape according to claim 1, wherein the residual acid value of the condensate is 3 to 30%, and a nitrogenous basic compound capable of converting the above condensate into an ammonium salt is used.