JPH08193164A - Epoxy resin composition for apparatus insulated with sulfur hexafluoride gas - Google Patents

Abstract

PURPOSE: To obtain an epoxy resin compsn. which has a high crack resistance and a high resistance to a gas generated by the electric discharge decomposition of SF6 and which is suitable for an SF6 -insulated apparatus. CONSTITUTION: This compsn. is prepd. by compounding an epoxy resin mixture used for producing a cast epoxy article for an SF6 -insulated apparatus with a filler and short 1iq.-crystal polyester fibers. The amt. of the filler compounded is pref. 100-300wt.% of the resin mixture. and the amt. of the fibers compounded is pref. 1-20wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition used for producing an epoxy cast product for gas insulation equipment, which is filled with sulfur hexafluoride gas (hereinafter referred to as "SF ₆ gas"). is there.

[0002]

2. Description of the Related Art SF ₆ gas is excellent in electrical insulation and arc extinguishing properties, and can be made compact and lightweight. Therefore, electrical equipment such as circuit breakers, disconnectors, transformers, cable terminal bushings, busbars, etc. Widely used for insulation. This SF ₆ gas is decomposed by an arc or corona discharge generated in the equipment to generate a highly reactive decomposed product. For this reason,
Epoxy cast products used for electric equipment are required to maintain stable properties for many years without being eroded by the decomposition products or undergoing alteration. Regarding the durability of the epoxy cast product against insulation gas decomposition products, the characteristics of the filler, which is one of the main components of the epoxy cast product, are greatly related, and normally, the filling is performed for the purpose of maintaining durability. Aluminum oxide (alumina) is used as the agent.

[0003]

By the way, recently, in order to increase the voltage and size of electric equipment, there is a demand for an epoxy cast product which can withstand more severe conditions than before. In particular, if the epoxy resin composition used has a high relative dielectric constant, local electric field concentration may occur depending on the insulation design of the electrical equipment or the shape of the epoxy cast product, so that the desired dielectric breakdown characteristics are satisfied. There are things I can't do. The reason why the relative dielectric constant of the epoxy resin composition becomes a relatively large value is that the epoxy resin composition contains about 70% by weight of alumina.

Therefore, as a filler having a relative dielectric constant smaller than that of alumina and resistant to insulating gas decomposition products,
Aluminum fluoride, magnesium fluoride, calcium fluoride, calcium carbonate, calcium sulfate and the like are mentioned. However, epoxy resin cured products containing these fillers are generally inferior in mechanical strength, and metal conductors, electrodes,
Epoxy cast products with mounting hardware embedded had the drawback of being prone to cracking.

Further, as the electric equipment becomes higher in voltage, larger in capacity and smaller in size, the heat generation temperature of the electric equipment increases, so that the epoxy resin cured product is required to have higher heat resistance than ever before. It's coming. Generally, the high temperature mechanical and electrical properties of cured epoxy resin tend to decrease significantly when the heat distortion temperature of the resin is exceeded. Although an epoxy resin cured product of this kind tends to cause cracks more easily, it has been a very difficult technical problem to achieve both crack resistance and heat resistance.

As a means for improving the crack resistance of a cured epoxy resin product, it has been proposed to mix glass fibers or to add a scaly filler such as talc powder or mica powder (Japanese Patent Laid-Open No. HEI-2). -97553 gazette), since these contain silica as a component, it was recognized that the SF ₆ discharge decomposition gas resistance is lowered.

The present invention has been made in view of these circumstances, and an object thereof is to provide an epoxy resin composition for SF ₆ gas insulation equipment having good SF ₆ discharge decomposition gas resistance and crack resistance. To provide.

[0008]

In order to achieve the above-mentioned object, the epoxy resin composition for SF ₆ gas insulation equipment of the present invention is used for producing an epoxy cast product for sulfur hexafluoride gas insulation equipment. A filler and a liquid crystal polyester short fiber are added to an epoxy resin mixture.

The amount of the filler added is an epoxy resin mixture.
It is 100 to 300 parts by weight with respect to 100 parts by weight, and the addition amount of liquid crystalline polyester short fibers is 1
It is preferably 1 to 20 parts by weight with respect to 00 parts by weight.

That is, the epoxy resin composition used in the present invention is obtained by adding a filler and a liquid crystal polyester short fiber to an epoxy resin mixture (epoxy resin base) comprising an epoxy resin and an acid anhydride type curing agent. After defoaming this epoxy resin composition under reduced pressure, it is poured into a mold and cured by heating to obtain an epoxy cast product.

As the epoxy resin, those having two or more epoxy groups in the molecule are preferable, and examples thereof include bisphenol epoxy resin, cycloaliphatic epoxy resin, novolac epoxy resin, naphthalene epoxy resin, and the like. Two or more types of resins can be mixed and used accordingly.

As the acid anhydride type epoxy resin curing agent,
Phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, trimellitic anhydride, and the like. Two or more of these Can also be used together. As the filler, powders of inorganic compounds excluding boron compounds and silicon compounds are suitable, and examples thereof include calcium fluoride, magnesium fluoride, aluminum fluoride, magnesium oxide, aluminum oxide, calcium carbonate, calcium sulfate, and the like. Two or more of these may be used in combination.

The amount of the filler to be added is preferably 100 to 300 parts by weight with respect to 100 parts by weight of the epoxy resin base composed of epoxy resin, acid anhydride curing agent, etc., in particular casting workability and mechanical strength. If the filler is used in an amount as large as possible within the range in which the decrease in the temperature is allowed, the shrinkage amount at the time of curing and the expansion coefficient of the cured resin become smaller, and the crack resistance and heat dissipation are improved. If the amount of the filler added is less than 100 parts by weight, the crack resistance becomes insufficient, and if it is more than 300 parts by weight, the casting operation becomes difficult.

The liquid crystal polyester short fibers used as a crack preventing reinforcing material in the present invention are liquid crystal polymers obtained by copolymerizing a monomer containing para-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid as main components. High strength made by melt spinning and heat treating
High-modulus fiber, "Vectran" from Kuraray Co., Ltd.
It is marketed under the brand name of.

It has been found that the short fibers are excellent in electrical insulation properties, tensile properties, creep resistance properties, moisture absorption properties, chemical resistance properties, and have sufficient stability against decomposition products of SF ₆ gas.

The addition amount of the liquid crystal polyester short fibers is preferably 1 to 20 parts by weight with respect to 100 parts by weight of an epoxy resin base composed of an epoxy resin, an acid anhydride curing agent, etc., when the addition amount is less than 1 part by weight. The reinforcing effect for preventing cracks becomes insufficient, and if the amount is more than 20 parts by weight, the increase in viscosity becomes large and casting work becomes difficult.

If necessary, a curing accelerator, a coloring agent, an antioxidant and the like can be added to the epoxy resin composition of the present invention.

Therefore, by adding the filler and the liquid crystal polyester short fibers to the epoxy resin mixture (epoxy resin base) consisting of the epoxy resin, the acid anhydride type curing agent, etc., the liquid crystal polyester short fibers are resistant to SF ₆ discharge. Good S resistance as it contributes to the improvement of decomposition gas resistance and crack resistance.
An epoxy resin composition suitable for SF ₆ gas insulation equipment having F ₆ discharge decomposition gas resistance and crack resistance can be obtained.

[0019]

Embodiments of the present invention will be described below.

Various components were blended according to the blending composition shown in each column of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1.

The epoxy resin is 80 parts by weight of bisphenol liquid resin Epicoat 828 [made by Shell Chemical Co., Ltd.] and rubber-dispersed bisphenol liquid resin Eposet BPA-328.
[Manufactured by Nippon Shokubai Co., Ltd.] A mixed resin consisting of 20 parts by weight was used.

As the acid anhydride type curing agent, tetrahydrophthalic anhydride type curing agent Araldite HT903 [manufactured by Nippon Ciba Geigy Co., Ltd.] was used.

Benzyldimethylamine was used as the curing accelerator. The liquid crystal polyester short fibers are Vectran short fibers manufactured by Kuraray Co., Ltd., diameter 22 μm, length 0.5 mm and diameter 2
Two kinds of short fibers having a length of 2 μm and a length of 1.0 mm were used.

The glass fiber used for comparison is E glass fiber, which is a short fiber having a diameter of 9 μm and a length of 0.5 mm.

The ratio of the compounding agents in Table 1 is parts by weight.

The composition blended as described above was defoamed under reduced pressure, poured into a mold and cured by heating to prepare a cured resin. The casting workability and the characteristics of the cured resin at this time were investigated, and the results are shown in the lower column of Table 1. Each evaluation method is as follows.

The casting workability was determined by observing the fluidity at 120 ° C. and the defoaming property at the time of defoaming under reduced pressure and categorizing into three stages of excellent, good and good.

The characteristics of the cured resin were evaluated with respect to SF ₆ discharge decomposition gas resistance and crack resistance. The composition degassed under reduced pressure at 120 ° C. was poured into a mold, and after primary curing at 120 ° C. for 20 hours, secondary curing at 150 ° C. for 20 hours, a test piece prepared was tested.

The SF ₆ gas used in SF ₆ gas-insulated equipment is decomposed by the arc and corona discharge generated in the _{apparatus, SF 2, SF 4, S} 2 F 2, SOF 2, SOF 4 , etc. reactive It produces strong decomposition products. The most produced of these decomposition products is SF ₄ , and in the case of SF ₄ ,
Upon contact with water or water vapor, a decomposition reaction such as SF ₄ + H ₂ O➝SOF ₂ + 2HF SOF ₂ + H ₂ O➝SO ₂ + 2HF is carried out to generate hydrofluoric acid which is highly corrosive.

Therefore, the SF ₆ discharge decomposition gas resistance and the hydrogen fluoride acid resistance of the insulating material have a close correlation, and the HF resistance
Resistance test can predict SF ₆ discharge decomposition gas resistance.
Here, place a reagent grade hydrofluoric acid with a concentration of 46% in a vat on the bottom of a plastic desiccator in the room, and place a 100 mmφ x 3 mmt test piece on a shelf with a hydrogen fluoride atmosphere inside the desiccator. Allow to stand for a period of time, then remove it, wipe this surface, dry it in a draft for 24 hours, and then measure the dielectric constant, dielectric loss tangent, and volume resistivity to determine the HF resistance.
It was compared with the initial value before the sex test. The dielectric constant, dielectric loss tangent and volume resistivity were measured according to JIS K6911. The dielectric constant and dielectric loss tangent were measured at 60 Hz and 1000 V by a Schering bridge, and the volume resistivity was measured at DC500V for 1 minute with an ultra-insulator.

The crack resistance was determined by performing the heat cycle test shown in Table 2 on a test piece having a diameter of 28 mm and a length of 50 mm which was embedded with a M12 steel bolt having a length of 40 mm as the number of cracked steps. It was The low temperature side of the heat cycle test used an ethanol tank cooled by a refrigerator, and the high temperature side used an air constant temperature layer.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from Table 1, all of the epoxy resin compositions of Examples 1 to 3 according to the present invention have improved crack resistance and less deterioration in electrical characteristics in the HF resistance test. It is useful for SF ₆ gas insulation equipment. On the other hand, Comparative Example 1 in which the liquid crystal polyester short fibers are less than the specified value is inferior in crack resistance, and Comparative Example 2 in which the compounding amount is large is inferior in castability. Also,
Comparative Example 3 uses short glass fibers, and the deterioration of the electrical characteristics after the HF resistance test is larger than that of Examples 1 to 3, and the measured value exceeds the measurement limit (dielectric loss tangent: 100%) of the Shasong Bridge. I wasn't asked.

[0035]

As described above, according to the present invention, an epoxy resin composition having good SF ₆ discharge decomposition gas resistance and crack resistance and suitable for SF ₆ gas insulation equipment can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Ito 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable FM Co., Ltd.

Claims (2)

[Claims] 1. A hexafluoride characterized by comprising a filler and a liquid crystal polyester short fiber added to an epoxy resin mixture used for producing an epoxy cast product for sulfur hexafluoride gas insulation equipment. Epoxy resin composition for sulfur gas insulation equipment. 2. The amount of the filler added is 100 to 300 parts by weight with respect to 100 parts by weight of the epoxy resin mixture, and the amount of the liquid crystal polyester short fibers added is 1 with respect to 100 parts by weight of the epoxy resin mixture. The composition according to claim 1, which is about 20 parts by weight.