JPH06114855A - Production of injection molded product composed of epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain an injection-molded product enhanced in dielectric breakdown strength using an epoxy resin compsn. CONSTITUTION:In producing an injection-molded product by stirring and kneading an epoxy resin and an inorg. filler to obtain a kneaded compsn. and compounding a curing agent with the kneaded compsn. and injecting the obtained epoxy resin compsn. in a mold to cure the same, the kneading of the epoxy resin and the inorg. filler is performed in electrically negative gas and curing is performed in electrically negative gas with a pressure of 5kg/cm<2> or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an epoxy resin cast product having improved characteristics, which is applied to a large-scale electric insulation device and used particularly in a portion having high electric stress.

[0002]

2. Description of the Related Art Epoxy resins are used in various devices as insulating structural members for electric devices because of their excellent electrical properties, mechanical properties, heat resistance properties, etc. Various fillers are generally blended in the epoxy resin base for the purpose of reducing the expansion coefficient. Typical fillers to be blended with the epoxy resin for this purpose include inorganic fillers such as silica, alumina, hydrated alumina, dolomite, etc., but low dielectric constant, low dielectric loss tangent and low linear expansion coefficient are possible. Fused silica is known as an inorganic filler to be used. There are various methods for kneading the filler with the epoxy resin, but for kneading the solid epoxy resin and the inorganic filler at room temperature,
Epoxy resin with a universal mixer and stirrer at 120-140 ℃
Generally, an inorganic filler is mixed and kneaded while being heated to a certain degree and melted. At this time, in order to eliminate the gas existing in the resin, the surface of the inorganic filler, etc., 1 to 3
Kneading is generally performed under a low pressure of about mmHg.

When the epoxy resin and the inorganic filler are kneaded, the gas is removed from the resin and the surface of the inorganic filler to reduce the defects in the cured product. It is effective for improving the dielectric breakdown characteristics of. Therefore, conventionally, mixing and stirring of the epoxy resin and the inorganic filler and vacuum casting of the composition have been performed in a vacuum. This is an effective method to prevent air from being entrained during kneading and casting, and to eliminate voids in the cured product by removing the gas from the resin and the surface of the inorganic filler. is there. By producing a cast cured product of voidless, the dielectric breakdown characteristics of the cast product are improved.

However, depending on the type of resin or filler, it may be difficult to completely remove air or the like from the resin composition by evacuation. For example, the shape of the filler is complicated, or the viscosity of the resin composition is high. When air or the like remains in the resin composition as described above, it is considered that the residual air is crushed when released from the vacuum to the atmospheric pressure and diffused into the resin. Further, air that cannot be completely diffused in the resin may remain in the cured product as fine voids. The presence of such residual air is not preferable because it lowers the dielectric breakdown strength of the cured casting.

On the other hand, along with the recent miniaturization of electrical equipment, there is a demand for downsizing of structural members for electrical insulation. As a result, the electrical stress applied to the electrical insulating structural member tends to increase, and it has become necessary to improve the dielectric breakdown strength of the epoxy resin composition, which has not been a problem in the past.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of intensive studies in view of the above points, and an epoxy resin having a significantly improved dielectric breakdown strength as compared with a conventionally cast epoxy resin composition casting product. It is intended to provide a manufacturing method capable of obtaining a composition cast product.

[0007]

Means for Solving the Problems That is, according to the present invention, an epoxy resin and an inorganic filler are kneaded with stirring, and the obtained kneading composition is mixed with a curing agent, and this is mixed in a mold by a vacuum casting method. In a method for producing a cast product of an epoxy resin composition by injecting into an epoxy resin and curing the mixture, the epoxy resin and the inorganic filler are kneaded in an electrically negative gas. As the electrically negative gas used in the present invention, for example, SF ₆ gas, Freon gas, etc. can be used, and among them, SF ₆ gas is preferable because it can impart high electrical insulation.

[0008]

In the present invention, since the epoxy resin and the inorganic filler are kneaded in the electrically negative gas, the air remaining in the kneaded material is replaced with the electrically negative gas having good electric insulation, In addition, even if an electrically negative gas with good electrical insulation diffuses into the kneaded product, and even if a minute void occurs, the electrically negative gas with good electrical insulation is filled inside the void. Therefore, the cast product obtained by cast-curing the kneaded product has high dielectric breakdown strength. In addition,
Further, if casting is carried out under a high-pressure electrically negative gas of 5 kg / cm ² or more, a high pressure is applied to the resin in a molten state, and the fine gas in the resin composition is crushed. Therefore, the characteristics can be further improved. Also in the present invention, if the epoxy resin and the inorganic filler are kneaded in an electrically negative gas, if the kneading system is subjected to a vacuuming treatment,
This is preferable because the air in the composition is eliminated, and the subsequent filling of the electrically negative gas can be easily and completely performed.

[0009]

EXAMPLES Examples and comparative examples of the present invention will be shown below. (Example 1) Epoxy resin (trade name: Araldite CT
200, manufactured by Ciba Geigy, bisphenol A type epoxy resin, epoxy equivalent 400) to 100 parts by weight,
200 parts by weight of fused silica (trade name: Hugh Rex Y-60, manufactured by Tatsumori Co., Ltd.) is kneaded by a universal mixing stirrer. Evacuate the kneading container for 1 hour from the start of kneading, and
The pressure was set to 3 mmHg. Next, the container was filled with SF ₆ gas, the pressure was set to 5 Kg / cm ^2, and kneading was performed for 30 minutes. Finally, the container is evacuated again to 1 to 3 mmHg
Under pressure. Here, the inside of the container was temporarily returned to atmospheric pressure, 30 parts by weight of phthalic anhydride melted as a curing agent was mixed with 100 parts by weight of the epoxy resin, and the container was evacuated again under a pressure of 5 to 8 mmHg. Stirring was performed.
The resin composition thus prepared was injected into a mold by a vacuum casting method, then returned to atmospheric pressure and cured to prepare a dielectric breakdown test sample having a shape and dimensions as shown in FIG.

(Example 2) An epoxy resin composition prepared in the same manner as in Example 1 was injected into a mold by a vacuum casting method, and then the epoxy resin was pressurized to 5 Kg / cm ² with SF ₆ gas. The resin composition was cured to prepare a dielectric breakdown test sample having a shape and dimensions as shown in FIG. (Example 3) Pressurization with SF ₆ gas at the time of casting and curing is 10K
A dielectric breakdown test sample having a shape and dimensions as shown in FIG. 1 was prepared in the same manner as in Example 3 except that g / cm ² was used.

(Comparative Example 1) 200 parts by weight of fused silica (trade name: Hugh Rex) was added to 100 parts by weight of epoxy resin (trade name: Araldite CT200, manufactured by Ciba Geigy, bisphenol A type epoxy resin, epoxy equivalent 400). Y-60, manufactured by Tatsumori Co., Ltd.) was evacuated in a kneading container by a universal mixing stirrer, and kneading was performed while maintaining a pressure of 1 to 3 mmHg. After mixing phthalic acid, the inside of the container was evacuated again and stirred under a pressure of 5 to 8 mmHg. The resin composition thus obtained was injected into a mold by a vacuum casting method, then returned to atmospheric pressure and cured to prepare a dielectric breakdown test sample having a shape and dimensions as shown in FIG.

(Comparative Example 2) The epoxy resin composition obtained in the same manner as in Comparative Example 1 was injected into a mold by a vacuum casting method, and then the epoxy resin was pressurized to 5 Kg / cm ² with SF ₆ gas. The resin composition was cured to prepare a dielectric breakdown test sample having a shape and dimensions as shown in FIG. (Comparative Example 3) A dielectric breakdown test sample having a shape and dimensions as shown in FIG. 1 was prepared in the same manner as in Example 2 except that the pressure during curing was 3 Kg / cm ² .

An AC breakdown test was performed on each of the dielectric breakdown test samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3 as described above. The test was conducted in RT and SF ₆ gas, and the voltage was applied at a step pressure of 50 KV to 5 KV / 5 min. As the dielectric breakdown strength, a value obtained by dividing the breakdown voltage by the insulation thickness (minimum distance between electrodes) was used. The results obtained are shown in Table 1.

[0014]

[Table 1]

As is apparent from Table 1, the epoxy resin composition cast product of Comparative Example 1 produced by the conventional method is insulated from the epoxy resin composition cast product of Example 1 produced by the method of the present invention. High breaking strength. Further, as can be seen from Examples 1, 2 and Comparative Example 3, the pressure of the electrically negative gas (SF ₆ gas) in the universal mixing stirrer at the time of kneading the epoxy resin and the inorganic filler was 5 Kg / cm. ² or more is required. Further, as can be seen from Examples 1 and 3, when the epoxy resin composition is cured, pressurization with an electrically negative gas of 5 kg / cm ² or more improves the dielectric breakdown strength of the cast product obtained. However, as in Comparative Example 2, pressing with an electrically negative gas only during curing does not contribute to the improvement of dielectric breakdown strength.

[0016]

According to the method of the present invention, an epoxy resin composition cast product having a much higher dielectric breakdown strength than the epoxy resin composition cast product obtained by the conventional method can be produced. The target value is extremely large.

[Brief description of drawings]

FIG. 1 is a sectional explanatory view of a dielectric breakdown test sample made of an epoxy resin composition.

Claims (2)

[Claims] 1. An epoxy resin composition in which an epoxy resin and an inorganic filler are kneaded with stirring, a curing agent is added to the resulting kneaded composition, and the mixture is injected into a mold by a vacuum casting method and cured. A method for producing a cast product of an epoxy resin composition, which comprises kneading an epoxy resin and an inorganic filler in an electrically negative gas. 2. An epoxy resin composition obtained by stirring and kneading an epoxy resin and an inorganic filler, mixing the obtained kneading composition with a curing agent, injecting this into a mold by a vacuum casting method, and curing it. In the method for producing a cast product, kneading the epoxy resin and the inorganic filler in an electrically negative gas,
A method for producing a cast product of an epoxy resin composition, which comprises curing in an electrically negative gas having a pressure of 5 kg / cm ² or more.