JP2571483B2 - Method for forming a conductive layer on an epoxy resin insulating molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a conductive layer on the surface of an insulator formed of an epoxy resin composition.

[0002]

2. Description of the Related Art Epoxy resin compositions are used for molding insulators such as porcelain tubes because of their excellent electrical strength, mechanical strength and moldability.

[0003] In this epoxy resin composition, an inorganic filler is often added to improve various properties such as thermal expansion / shrinkage rate, mechanical strength, electric properties, heat resistance, etc., and reduce costs.

In an electric insulator such as the above-mentioned porcelain tube, depending on the state of electric field distribution, it is necessary to adjust the electric field distribution acting on the insulator to reduce electric stress and to improve electric strength. There is.

[0005] When molding an insulator using the epoxy resin composition, a casting method is usually used. In such a casting method, burrs are generated, and grinding for removing the burrs is required. Further, in order to cope with dimensional deformation due to curing shrinkage and heat shrinkage of the epoxy resin during molding, it may be necessary to perform dimensioning by cutting after molding.

[0006] Conventionally, in order to adjust the electric field distribution acting on the epoxy resin molded insulator, to reduce the electric stress and to improve the electric strength, a predetermined portion of the surface of the insulator is coated with a conductive paint to form an electrode. It is known to form layers.

Normally, a considerably high electric stress acts on the interface between the electric field distribution adjusting electrode layer and the insulator, and when the interface is separated, the portion where the interface is separated becomes an electrical weak point, and the dielectric breakdown causes the dielectric breakdown. It is well known that the film develops from the peeling point and causes a decrease in electric strength.

For this reason, the importance of stabilizing the bonding at the interface between the electric field distribution adjusting electrode layer and the insulator or increasing the bonding strength is widely recognized. For example, when the insulator is formed from a hardly-adhesive resin such as a fluororesin, the surface of the insulator is subjected to a base treatment for improving the adhesion in order to strengthen the adhesion between the insulator and the electric field distribution adjusting electrode layer. It has been proposed to apply

However, in epoxy resins,
It has extremely good adhesion, strong adhesion between the electric field distribution adjusting electrode layer provided by applying the conductive paint and the insulator, and the interface between the epoxy resin molded insulator and the electric field distribution adjusting electrode layer. It is not normally assumed that the condition will cause a decrease in the electrical strength of the insulator.

[0010]

By the way, in order to form an electrode layer by applying a conductive paint to an epoxy resin molded insulator, the above-described processing such as dimensional accuracy, deburring, etc., and a cut surface or a ground surface are required. Must be coated with a conductive paint.

[0011] The inventors of the present invention, however, apply a conductive paint to a cutting surface or a ground surface after applying an undercoat of an insulating paint, and then directly apply the conductive paint to the cutting surface without applying an undercoat. In addition, it has been experimentally found that the electric strength of the insulator can be remarkably improved as compared with the case of coating on a ground surface.

The present inventors conducted various experiments in order to elucidate the reason, and found that the inorganic filler added to the epoxy resin (large, about 0.1 mm ).
In addition, due to its brittleness, hard cracks occur on the cut surface or ground surface of the insulator, or the inorganic filler is chipped on the cut surface or ground surface and falls off by 0.01 m.
It was observed by SEM that a sharp concave portion of the order of m was generated, and it could be inferred that the cause was that the conductive paint entered the hard crack and the sharp concave portion to form an electrode needle.

As described above, in the epoxy resin molded insulator, even if the electric field distribution adjusting electrode layer can be firmly fixed due to its excellent adhesiveness, the electric field distribution adjusting electrode layer can be fixed to the cut surface of the insulator. Or by applying a conductive paint on the ground surface, the concentration of electric stress (electrode needle) due to intrusion of the conductive paint into the cracks or the like on the cut surface or the ground surface of the inorganic filler. Therefore, it is difficult to properly cope with an increase in the working voltage only by strengthening the adhesion between the electric field distribution adjusting electrode layer and the insulator.

An object of the present invention is to provide an epoxy resin composition by strengthening the electric strength at the interface between a molded insulator of an epoxy resin composition containing an inorganic filler and an electric field distribution adjusting electrode layer based on the above findings. An object of the present invention is to provide a method capable of forming an electric field distribution adjusting electrode layer on an insulating molded body.

[0015]

The method for forming a conductive layer on an epoxy resin insulating molded article according to the present invention comprises cutting or grinding a predetermined outer surface of an insulator molded from an epoxy resin composition to which an inorganic filler has been added. , An insulating paint is applied to the processed surface, and a conductive paint is applied to the applied surface.

[0016]

The insulating filler has a crack formed on the surface of the insulator or a crack formed on the surface of the insulating filler during chipping or grinding. A paint is applied. Accordingly, it is possible to prevent the conductive paint from penetrating into a hair crack or a sharp concave portion, to eliminate generation of an electrode needle, and to avoid electric breakdown due to concentration of electric stress at the electric needle.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an insulation reinforcing body used by attaching to a cable terminal, 1 is an epoxy resin insulation molding, and 2 is an insulating paint.
Of a coating layer, 3 indicates an electric field distribution adjusting bellmouth electrodes formed by coating a conductive paint, respectively.

This epoxy resin insulating molded body is molded by casting an epoxy resin composition to which, for example, silica powder has been added, and the entire body including the bell mouth surface 11 is cut.

In order to form the bell mouth electrode 3 for adjusting the electric field distribution according to the present invention, first, an insulating paint is applied to the bell mouth surface 11, and hair cracks and inorganic filling generated in the inorganic filler during the above-mentioned cutting process. The sharp recesses of the chipped or dropped material are filled with an insulating paint, and after the paint is solidified, a conductive paint is applied on the paint film.

It is preferable to use a filler-free liquid resin or a solvent-diluted resin having the same level of insulating performance as the epoxy resin composition for the insulating coating.

The conductive paint is applied after the insulating paint applied to the bellmouth surface is sufficiently solidified.
This is performed so as not to dissolve in the conductive paint.

According to the present invention, the hair crack of the inorganic filler or the chipping or falling off of the inorganic filler on the cut surface or the ground surface of the molded insulator molded with the epoxy resin composition is filled with the insulating paint. In addition, since the bellmouth electrode layer is provided by applying a conductive paint, the formation of electrode needles due to the penetration of the conductive paint into the hair cracks and the like can be eliminated, and the insulation strength of the epoxy resin insulating molded body is improved well. it can. This is also evident from the results of the pressure test of the following examples and comparative examples.

Example 1 An epoxy resin composition was prepared by adding a silica powder (200 parts by weight) to a bisphenol-based epoxy resin (100 parts by weight) and an acid-based curing agent (20 parts by weight) as a filler. As shown in FIG. 2, the above-mentioned epoxy resin composition was cast on the conductor rod 4 and the center portion was cut into a curved surface 11 (t: 3 mm, I ₁ : 100 mm, I ₂ : 60 mm). . Room temperature liquid bisphenol-based epoxy resin Room temperature curing type Araldite AY103: 100 parts and HY956: 18 parts
An insulating paint (no filler added) obtained by diluting with a 0% ketone-based organic solvent is applied to the cut surface, and this applied layer is
The composition was cured at 3 ° C. for 3 hours, and a conductive paint was applied on the cured layer 2 to form an electrode layer 3.

Example 2 In contrast to Example 1, a room temperature-cured polyurethane liquid paint (no filler added) was used as an insulating paint, and the coating layer of this paint was cured at 80 ° C. for 3 hours. Other than this, Example 1
And the same.

Example 3 In contrast to Example 1, bisphenol type epoxy resin (Epicoat 1004): 160 parts and a resin were used as insulating coatings.
Xylene phenol resin: 160 parts with cellosolve acetate: 100 parts, xylene: 120 parts with butanol
: Insulating paint obtained by dissolving with 60 parts (no filler added)
The coating layer of this paint was cured at 120 ° C. for 3 hours. Except for this, it was the same as Example 1.

Comparative Example In Example 1, the application of the insulating paint was omitted, and the conductive paint was directly applied to the cut surface. Except for this, it was the same as Example 1.

With respect to these examples and comparative examples,
AC withstand voltage test to apply AC voltage in insulating oil by 10KV / 1 minute step-up method and negative polarity 20KV
When an impulse withstand voltage test in which an impulse voltage was applied by a step-up method / 3 times was performed (the number of samples was 5 for each), in the comparative example, the AC breakdown voltage was 100 KV on average, and the impulse breakdown voltage was only 196 KV. However, in the example products, the AC breakdown voltage was 120 KV or more on average (Example 1: 134 KV on average, Example 2: 124 KV on average, and Example 3: 126 KV on average), and the impulse breakdown voltage was 250 KV or more (implemented). Example 1:
(Average: 257 KV, Example 2: average 252 KV, Example 3: average 251 KV), which was much better than the comparative example. Note that each of the examples and comparative examples
To remove the conductive paint layer and expose the epoxy resin surface,
Observation by SEM showed that the epoxy resin was
Conduction in hard cracks or sharp recesses on grease-cut surfaces
The electrode needle was formed due to the penetration of the conductive paint.
Then the cracks or sharp recesses are filled with insulating paint
No electrode needle formation was observed. Therefore, insulating paint
When conductive paint is used instead of
It is clear that it is not substantially different from the comparative example.

[0028]

According to the method for forming a conductive layer on an epoxy resin insulating molded article of the present invention, when an electric field distribution adjusting electrode layer is formed by applying a conductive paint, only an insulating paint is applied to the base. Can dramatically improve the insulation strength of the epoxy resin insulation molded product, and can be precisely dimensioned by cutting or grinding.
It is possible to enhance and reduce the insulation reliability of the epoxy resin insulating molded body while guaranteeing the degree .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an epoxy resin molded insulator on which an electric field distribution adjusting electrode is formed according to the present invention.

FIG. 2 is a sectional view showing a sample used for a withstand voltage test of an epoxy resin molded insulator on which an electric field distribution adjusting electrode is formed according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Epoxy resin molded insulator 11 Cutting surface 2 Insulation paint application layer 3 Conductive paint application layer

Claims (1)

(57) [Claims] An insulator molded from an epoxy resin composition to which an inorganic filler has been added is processed by cutting or grinding a predetermined outer surface, an insulating paint is applied to the worked surface, and a conductive paint is applied on the applied surface. A method for forming a conductive layer on an epoxy resin insulating molded article, characterized by applying a coating.