JPH0711236A - Electrical insulating gasket - Google Patents

Abstract

PURPOSE:To provide the subject gasket giving adequate sealing performance even in its use at elevated temperatures and ensuring excellent electrical insulating performance to be retained. CONSTITUTION:The objective gasket made up of (A) a total of 80-84wt.% of inorganic mineral composed of cakeable and sinterable mineral and/or talc and (B) the rest of inorganic fibers such as ceramic fibers plus a small amount of an organic binder, so as to be 1.3-2.5g/cm<3> in bulk density and 1X10<6> to 1X10<100>OMEGA.cm in volume resistivity as insulation resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating gasket used for electric equipment such as a fuel cell which operates at a high temperature and a connecting portion of electric piping.

[0002]

2. Description of the Related Art Asbestos joint sheet gaskets have hitherto been generally known as non-metal gaskets used in electric equipment operating at high temperatures, but this asbestos joint sheet gasket has a maximum operating temperature of 500 ° C. Therefore, at a higher temperature than that, a predetermined sealing performance cannot be exhibited.

By increasing the limit of such operating temperature, 10
As one of the non-metal gaskets which exhibits excellent sealing performance even at a high temperature of about 00 ° C., JP-A-64-623 has been proposed.
As disclosed in Japanese Patent Publication No. 81, glass fiber or glass powder 5 to 40 wt%, inorganic powder 30 to 90 w
One having a porosity of 50% or less with t% and 30 wt% of an organic binder (hereinafter referred to as a first conventional gasket) is known.

In addition to the above, the applicant of the present invention has a fiber diameter of 2
5 to 15 wt% of glass-based fibers of μm or less, 5 to 30 wt% of sepiolite mineral, 50 to 80 wt% of talc mineral
%, The organic binder is 6 wt% and the porosity is 50
% Or less of high temperature gasket (hereinafter referred to as second conventional gasket) or ceramic fiber of 5 to 15 wt%
%, 50-80 wt% of talc mineral, 10-30 wt% of sepiolite mineral, and 10-15 wt% of organic binder, and a high-temperature gasket having a bulk density of 1.0 g / cm ³ (hereinafter referred to as the third Conventionally called a gasket).

[0005]

However, the first conventional gasket among the conventional non-metallic gaskets having the above-mentioned composition is the glass fiber or glass powder softened during use in a high temperature range. In order to fill the voids, while exhibiting excellent sealing performance even when used in a high temperature range of about 1000 ° C., since it contains a large amount of an organic binder that serves to retain the shape of the gasket at initial room temperature, The organic binder is decomposed by heat and disappears,
As a result, the shape retention force of the gasket is reduced, the gasket is scattered by the sealing fluid, and there is concern about the sealing performance in that respect, and the organic binder is carbonized in a high temperature range of about 1000 ° C. There is a drawback that the insulation performance deteriorates.

Further, the second conventional gasket among the conventional non-metallic gaskets has a small amount of organic binder,
Although it is possible to suppress deterioration of electrical insulation performance when used in high temperature range, due to the large heat shrinkage and heat loss of sepiolite mineral, strain deformation easily occurs during heat cycle, and sealing during use in high temperature range The performance cannot be fully exerted. Further, the third conventional gasket, like the first conventional gasket described above, has a large amount of the organic binder compounded, and therefore lacks the shape retention and electrical insulation of the gasket when used in a high temperature range. At the same time, great concern remains in terms of sealing performance.

The present invention has been made in view of the above circumstances, and is excellent in shape retention performance and sealing performance when used in a high temperature range and has high reliability in terms of electrical insulation performance. The purpose is to provide an electrically insulating gasket that can be secured.

[0008]

In order to achieve the above object, the electric insulating gasket according to the present invention contains 80 to 84 wt% of the inorganic mineral composed of solidifying / sintering mineral and / or talc. A sheet-like gasket containing the balance of inorganic fibers such as ceramic fibers and a small amount of an organic binder, and having a bulk density of 1.3 to 2.5 g.
/ Cm ³ , volume resistivity as insulation resistance is 1 × 10 ⁶ ~
It has a structure of 1 × 10 ¹⁰⁰ Ω · cm.

In the above electric insulating gasket, the solidifying / sintering mineral is one kind or a combination of two or more kinds of kaolin mineral, sepiolite mineral, sericite mica mineral and montmorillonite mineral. is there.

[0010]

In the electric insulating gasket having the above structure, each compounding material plays the following role.
Solidifying and sinterable minerals are 100% like porcelain and pottery.
Not complete sintering at temperatures above 0 ° C, but from room temperature to 10
It is a mineral that stably plays the role of retaining the shape of the gasket up to 00 ° C. As a method of selecting a mineral having such consolidation and sinterability, powders of various minerals are kneaded with water to form a mud dumpling, which is dried and then placed in an electric furnace at 1000 ° C. for 3 hours. throw into. Then, a test was conducted in which the dried mud balls were crushed with fingers to check the solidification property, and the mud balls taken out from the electric furnace were crushed with fingers to check the sinterability. The results are shown in Fig. 1. As is clear from Fig. 1, kaolin minerals, sepiolite minerals, sericite mica minerals, and montmorillonite minerals are effective as minerals having both consolidation and sinterability. It turned out that

The talc mineral is a very soft mineral having a plate-like shape and a Mohs hardness of 1, and has a role as a flexible and high-density packing material for the gasket and seals the gasket. It is intended to improve the property, has little heat shrinkage, and has no sinterability. Therefore, as described above, the combination with the mineral having both the solidifying property and the sinterability is very effective for improving the sealing property as a gasket.

The ceramic fiber as the inorganic fiber retains its shape by fiber-reinforcing the gasket and prevents heat shrinkage. Further, the organic binder has a role of maintaining the shape of the gasket at the initial room temperature, but when it is heated, it is thermally decomposed and disappears to increase the porosity of the gasket. In order to prevent carbonization at the time of use and deterioration of the electric insulation performance, the compounding amount thereof is preferably as small as possible, and is preferably about 2 to 6 wt%. The organic binder is preferably an ethylene-based multicomponent copolymer such as an ethylene-acrylic triester copolymer or an ethylene-vinyl chloride terpolymer. It has excellent skeleton forming functions such as hardness and adhesive strength, and has good emulsion polymerization stability and workability.

[0013]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Sheet-shaped sample gaskets (outer diameter 55 mm, inner diameter 35 mm, having a bulk density of 1.44 g / cm ³⁾ were produced by pressing the sheets of Examples 1 to 4 and Comparative Example having the composition shown in FIG. 1mm thick)
It was created.

The materials used for each sample gasket having the composition shown in FIG. 2 are as follows. Kaolin minerals (made by Shiraishi calcium: brand name Burgess # 10), salicite mica minerals (made by Murakami Sericite), sepiolite minerals (made by Showa Mining: brand name Milcon MS-2-2), montmorillonite minerals (Dalian bentonite), talc Minerals (manufactured by Nippon Talc: trade name Talc MS), ceramic fibers (manufactured by Toshiba: trade name Toshiba Monoflux HSA Fiber),
Hemp pulp (Ogura trade: Manila hemp pulp), ethylene copolymer (Sumitomo Chemical: trade name Sumikaflex).

A sealing test was conducted on each of the sample gaskets prepared from the above composition using the sealing test apparatus shown in FIG. In FIG. 3, 1 is an electric furnace, and 2 and 3
Is a flange which is made of a high nickel alloy or the like and constitutes a seal bearing surface, and a sample gasket M is sandwiched between the upper and lower flanges 2 and 3. The weight 4 is placed on the upper flange 2. 5 the vulcanizing pressure pipe 6 and N ₂ gas cylinder for supplying N ₂ gas to the machine 7 via the valve 8, 9 is a pressure gauge.

The test method is as follows: tightening surface pressure 0.3 kgf / c
After the sample gasket M was tightened at m ² , the inside of the machine was sealed with N ₂ gas at a pressure of 0.1 kgf / cm ² ,
The valve 8 is closed, and the leak amount is measured from the pressure decrease rate with the pressure gauge 9. At normal temperature → 1000 ° C
-> Normal temperature-> 1000 ° C-> Normal temperature-> The amount of leak when a thermal cycle of 1000 ° C is applied is measured. On the other hand, the volume resistivity and the surface resistivity of each of the above sample gaskets were also measured by an electrical insulation test. As its electrical insulation measuring method, a high voltage Schering bridge,
The zero method such as the transformer bridge and the parallel resistance bridge, the conductance change method, the capacitance change method, the resonance method such as the Q meter method, and the volt-ampere method are conceivable. The description will be omitted.

The volume resistivity ρ (Ω · m) and the surface resistivity δ (Ω) are calculated by the following equations, respectively. ρ = (A / d) Rv {A: area of main electrode, d: thickness of sample gasket, R
v: volume resistance obtained from measured current value and voltage} δ = (P / g) R6 {P: effective length of main electrode, g: distance between electrodes, R6: surface resistance obtained from measured current value and voltage}

FIG. 4 shows the results of each of the above tests. As is clear from the results of the tests, in the comparative example, the shape retention of the gasket is insufficient after the organic binder is thermally decomposed by heating. The gasket scatters due to the fluid to be sealed, and blowout occurs in the 1000 ° C. sealing test. On the other hand, in Examples 1 to 4 of the present invention, 10
It can be seen that the amount of leakage is small at both high temperature of 00 ° C. and normal temperature, and excellent sealing performance is maintained. Also, regarding the electrical insulation, in Examples 1 to 4 of the present invention, 1 × 10
^It has a volume resistivity in the range of ⁶ to 1 × 10 ¹⁰⁰ Ω · m and exhibits excellent electrical insulation performance even when used in high temperature regions.

[0019]

As described above, according to the present invention, 1000
Not only the excellent sealing performance can be exhibited even in a high temperature range of about 0 ° C., but also the leak amount at room temperature can be extremely reduced. In addition, by reducing the amount of the organic binder compounded, the decrease in electrical resistance due to carbonization of the organic binder during use in the high temperature range is suppressed, resulting in excellent electrical insulation performance even in the high temperature range. Can be secured.

[Brief description of drawings]

FIG. 1 is a diagram showing the solidification and sintering characteristics of various minerals that were the subject of a test for selecting minerals with solidifying and sinterability used in an electrically insulating gasket according to an embodiment of the present invention. Is.

FIG. 2 is a chart showing the composition of each sample gasket of Examples 1 to 4 and Comparative Example.

FIG. 3 is a schematic view of a sealing test device used for a sealing test of each sample gasket according to the formulation of FIG.

FIG. 4 is a chart showing the sealing test results and electric resistance test results of each sample gasket according to the formulation of FIG.

[Explanation of symbols]

 1 Electric furnace 2,3 Flange 5 Pressure tank 8 Pressure gauge M Sample gasket

Claims (2)

[Claims] 1. A total of 80 to 84 of inorganic minerals composed of caking / sintering minerals and / or talc minerals.
A sheet-shaped gasket containing wt%, which contains inorganic fibers such as ceramic fibers and a small amount of an organic binder as the balance, has a bulk density of 1.3 to 2.5 g / cm ³ , and has a volume resistivity of 1 as insulation resistance. × 10 ⁶ to 1 × 10 ¹⁰⁰ Ω · cm
An electrically insulating gasket, which is characterized in that 2. The electrical insulation according to claim 1, wherein the solidifying / sintering mineral comprises any one kind of kaolin mineral, sepiolite mineral, sericite mica mineral and montmorillonite mineral or a combination of two or more kinds thereof. gasket.