JPS58138757A - Electrical insulating coating material composition - Google Patents

Abstract

PURPOSE:The titled composition useful as a resistor, etc. for high-voltage switch preventing thermal deterioration, deterioration of applied voltage, etc., having improved bond strength, strength of film and durability, comprising an electrical insulating material of highly active aluminum oxide, a binder of a phosphate, etc. CONSTITUTION:For example, (A) 75wt% aluminum oxide having >=99.9% purity and <=1mum average particle diameter and (B) 10wt% phosphate (e.g., aluminum phosphate) are dispersed into (C) 15wt% water, to give the desired composition. It is applied to a substrate to form a dried film, which is heated at <=300 deg.C to form a cured film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrically insulating coating composition for high voltage switchgear resistors and the like.

Conventionally, inorganic insulating base materials (for example, purity 80 to 90%) were blended with organic binders such as CMC and silicone resin;
Alternatively, it was coated with electrical insulation using a mixture of glaze and the like. Coating using this organic binder is performed at, for example, 500K.

1000 K, ylt class ultra-high voltage switch resistor element.

When applied to the outer circumferential surface and inner circumferential surface, opening/closing surge energy (
500J/cc), the coating changed color.

Spots, etc. occur and gradually deteriorate, causing flash holes from spark discharge and deteriorating insulation properties, or heat generated by opening/closing surges reduces the adhesive strength with the resistor element, making the coating easy to peel off. , there are defects such as flash holes occurring in the peeled parts and deterioration of insulation properties. On the other hand, in order to coat the resistor element with a glaze, it is done at the same time as the firing of the resistor element, so that a part of the alkali metal oxide, which is a flux component, contained in the glaze may be reduced. However, the insulation properties deteriorate, and furthermore, it contains a lot of glass.

The resistance value changes due to the temperature rise associated with the opening/closing surge.

The coating film has defects that can lead to discharge breakdown due to a decrease in insulation properties.

The present invention focuses on finding a suitable coating material without using organic binders or inorganic binders containing a large amount of glass or alkali metal salts, which cause deterioration of insulation properties at high temperatures. This was done with this in mind.

To solve this problem, it is necessary to use a binder that does not harm the insulation properties, to have high adhesive strength during coating, and to ensure that the insulation properties do not deteriorate under harsh conditions of 150°C or higher. 〇The present inventors used highly active aluminum oxide with a purity of 99.9 cm or more and an average particle size of 1 μm or less as an insulating base material due to thermal deterioration, moisture absorption deterioration, weight deterioration, and chemical deterioration.

It is said that it is very good at preventing such things.

It was discovered that the adhesion strength to the object is high, the paint film does not peel off, and the paint film has excellent strength and durability.

Moreover, it has been found that phosphate is effective as a binder for advantageously forming the above-mentioned highly active aluminum oxide coating. An example of this is aluminum phosphate, which is uniformly dispersed in water, used as a paint vehicle component, and mixed with the highly active aluminum oxide.

Grind and knead into this vehicle to ensure uniform dispersion.

Highly active aluminum oxide before dispersion exists in the form of secondary particles that are agglomerated primary particles, but because it is once returned to primary particles by grinding here, it can be uniformly dispersed. becomes.

The mixture thus obtained is uniformly applied to the coated surface to be electrically insulated to form a coating film. Next, as water evaporates from this coating film, the highly active aluminum oxide particles are aggregated and fused together via aluminum phosphate, forming a dry coating film. This coating film is uncured. Furthermore, the cured coating film is formed by heating and curing at a temperature of 300° C. or lower. Here, the aluminum phosphate functions as a matrix that interconnects the aluminum oxide crystal grains. Heat curing temperature to 30
The reason for setting the temperature below 0℃ is that the temperature is suitable for aluminum phosphate to function as a hardening agent, and it is necessary to avoid affecting the resistance value as it is a component of the resistor element that should be insulated.
It is also to make it easier. This temperature is the temperature reached when the resistor element itself to be insulated generates heat from the heat sink, and is also a temperature that the coating film itself can withstand sufficiently.

As mentioned above, since the composition of the present invention is composed of aluminum oxide and phosphate with a purity of 99.9% or more and an average particle size of 1 μm, the object to be insulated is a resistive element made of carbon as a conductive material. Even when used in locations where surge energy reaches approximately 500 J/cc, it can withstand a temperature rise of 150 to 200°C on its surface, and has sufficient resistance to creeping discharge. Since aluminum oxide is highly active and the phosphate promotes this activity, it has sufficient adhesive strength to the object to be applied.

won. Furthermore, since the coating method of the present invention has a curing temperature of 300°C or less, even if the object to be coated uses Cursen as a conductive material and there is a limit to the heating temperature, it can be applied within the limit range. This means that an inorganic insulating coating can be formed. Also, since it is a combination process of natural drying and forced heating in a curing oven, the coating film before drying is 1,000,000,000,000,000,000.
When the thickness is 0.05 to 0.15 mm, the coating film can be formed as a homogeneous film because rapid evaporation of water is not accompanied.

The present invention will be explained in more detail below using examples.

Example 1 75% by weight of aluminum oxide with a purity of 99.9% and an average particle size of 1 μm or less, 10% by weight of aluminum phosphate, and 15% by weight of water are mixed and treated in a Zeel mill to obtain a paint-like product. This paint-like material is applied to the outer peripheral surface and inner peripheral surface of the ultra-high voltage resistor to a thickness of 0.05 to 0.15 mm using a roller, and after drying, it is heated in a curing oven at a temperature of 300 °C or less to harden the coating. A film was formed on the outer circumferential surface and inner circumferential surface of the resistor.

Next, as a test similar to that of applying a surge to this insulating coating, an ultra-high voltage of % 1000 K = ylt class was applied.

Electrical energy application test of 500 J/cc was applied once (increased to 160 to 170°C), twice at 5-minute intervals (23
The test was carried out by applying (280°C) % (increased to 0°C) three times at 5-minute intervals, and for comparison, tests were also conducted for glaze (glaze coat) Comparative Example 1 and organic binder (CMC) Comparative Example 20. The results are shown in the table below.

table As is clear from the table above, in the case of the present invention.

Even if the temperature rises to 280° C. when the voltage is applied three times at 5-minute intervals, the insulating coating remains in good condition and maintains its insulating properties. On the other hand, in the comparative example of the conventional technology,
In the case of glaze coating, cracking occurs after one application, resulting in C
In the case of MC.

Peeling (-ms) and discolored spots occur, making it impossible to maintain the insulation properties.

As described above, the insulating coating film of the present invention is good, and aluminum phosphate has no effect on the insulation properties of the insulating coating film, whereas in the case of glaze coating, the flux component contained in the glaze is Since the alkali metal oxide is partially reduced during firing, the insulation properties of the insulating coating are reduced, and cracks are thought to occur due to creeping discharge on the coating surface.In the case of CMC, Since it is itself an organic substance and has low heat resistance, and its adhesive strength with the resistive leaf is also low in heat resistance, it is thought that peeling will occur in some parts, and discoloration spots (for example, carbonization) will also occur.

Claims (2)

[Claims] (1) An electrically insulating coating material composition comprising electrically insulating powder of aluminum oxide having a purity of 99.9% or more and an average particle size of 1 μm or less, a phosphate binder, and a water dispersant. (2) The composition according to claim 1, wherein the phosphate binder is aluminum phosphate.