JPH0354286A - Sealing material composition - Google Patents

Abstract

PURPOSE:To improve sealing properties over a wide temp. range, heat resistance, mechanical characteristics and compression recovery by incorporating a ceramic inorg. fiber, a three-dimensional whisker, an org. elastic substance and/or an inorg. binder. CONSTITUTION:A ceramic inorg. fiber containing 20 % or less non-fibrous substance with a length of 44 mum or larger and having a fiber diameter of 12 mum or less (e.g. a silica-alumina ceramic fiber), a three-dimensional whisker (e.g. a tetrapod-shaped ZnO whisker), an org. elastic substance (e.g. natural rubber) and/or or inorg. binder (e.g. montmorillonite) are compounded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a sealing material that exhibits excellent sealing properties and heat resistance even under conditions of low temperatures to high temperatures of around 1000'C. Instead, this is a proposal for a sealing material assembly that is suitably used for fuel and exhaust gas of internal combustion engines, chemical plant piping, etc., which are mainly composed of ceramics.

[Conventional technology]

The sealing material used for the above-mentioned purposes uses asbestos as its main raw material, and also natural rubber, nitrile rubber (NBR), or styrene-butadiene rubber (SBR) to impart elasticity.
It is generally made of an isoelastic material and an auxiliary agent such as a vulcanizing agent added as necessary.

By the way, sealing materials for such uses include joint sheet-shaped sealing materials obtained by heating and forming asbestos and an elastic substance, and slurry in which asbestos and elastic substances such as emulsion latex are mixed and fixed. There was a sheet-shaped sealing material obtained by molding. These known sealing materials mainly contain 60 to 95% by weight of asbestos fibers, and therefore, there is a risk of health problems not only during the manufacturing process of the sealing materials but also because the asbestos fibers are scattered from the construction facilities. It was hoped that improvements would be made. For this reason, in our country as well, with the signing of the International Cancer Convention in 1971, various laws and regulations have been put in place to regulate the handling of cancer. For example, the ``Specified Chemical Substances Hazard Prevention Regulations'' were established on April 1, 1975, and the Labor Standards Enforcement Regulations were partially revised on March 30, 1973, and This includes the designation of ``persimmon cancer or mesothelioma caused by work that exposes asbestos'' to diseases caused by work-related factors or carcinogenic processes. In addition, the US EPA (Environmental Protection Agency) has 198
In January 1986, a proposal was made to ban the use of asbestos products, and in June 1986, the ○MB (Bureau of Management and Budget)
With the consent of the government, the government proposed banning it from use in building materials starting in January 1988, and proposed a complete ban on its use starting in 1991. In July 1986, the three largest gasket manufacturers in the United States declared that they would accept this proposal in stages. In addition, not only in the two countries mentioned above, but also internationally, the "Convention and Recommendation on Safety in the Use of Asbestos" is being discussed and deliberated based on the proposal of the ILO (International Labor Organization) in June 1986, and in Sweden in particular, It is expected that a ban on the use of asbestos products will be implemented in 1985. In response to this international situation, inorganic fibers such as Seviolite fiber, glass fiber, carbon fiber, and stainless steel fiber, as well as organic woven fibers such as aromatic polyamide fiber, phenol fiber, and polyethylene fiber, have recently been introduced as alternative fibers to asbestos. Attempts have been made to manufacture sealing materials using this method.

[Problem that the invention seeks to solve]

As mentioned above, sealing materials using asbestos fibers have problems with pollution, and although they can maintain good physical properties up to around 600°C, they deteriorate at higher temperatures, such as 950°C or higher. The disadvantage of this method was that strength deterioration occurred due to dehydration of crystal water.

On the other hand, sealing materials using inorganic fibers or organic fibers as asbestos substitute fibers also have the following problems.

That is, among the inorganic fibers, for example, Seviolite has water of crystallization, and therefore its strength deteriorates in the same way as asbestos in a high temperature range. Moreover, when a sealing material is manufactured using only this inorganic fiber, there is a problem in that it has inferior tensile strength, etc., similar to sealing materials using asbestos. In particular, among inorganic fibers, for example, carbon fiber,
Organic fibers such as aromatic polyamide fibers, phenolic fibers, polyethylene fibers, etc. deteriorate significantly at around 200°C, and at temperatures above 400°C they are completely carbonized or burnt out and bond deterioration occurs. The problem was that it could not be used at high temperatures. Furthermore, the asbestos substitute fibers have extremely smooth fiber surfaces and linear fiber shapes, as typified by glass fibers, carbon fibers, stainless steel fibers, and general artificial organic fibers. Therefore, when used as a substitute for textured fibers such as asbestos, the strength due to the intertwining of the fibers cannot be expected, and when used as a sealing material, there is a problem in that the tensile strength and recovery rate decrease.
The purpose of the present invention is to propose a sealing material assembly that does not have the above-mentioned problems of seal materials made of asbestos, and also does not have the problems of sealing materials made of various inorganic fibers. It's there. (Means for Solving the Problems) The present invention overcomes the deterioration of properties as a sealing material due to deterioration of properties such as tensile strength and elastic modulus, that is, deterioration of sealing function, durability, and reliability. As something to do,
Heat resistance is improved by using ceramic-based EA-free woven fibers, and tensile strength, elastic modulus, recovery rate, heat resistance, etc. are improved by using three-dimensional structure whiskers, and a suitable inorganic binder is used. By using , the strength in high temperature range can be compensated, and by adding an organic binder, it is possible to set the handleability at room temperature and the compressibility as a sealing material to a predetermined value.
The aim was to overcome all the problems of the conventional technology mentioned above all at once. In particular, in the present invention, since three-dimensional whiskers are used, a sealing material having high temperature thermal properties, high compressibility, and also high recovery rate can be obtained.

The present invention, developed based on such a concept, mainly contains ceramic inorganic fibers and whiskers with a three-dimensional structure, and is TXTed with one or a combination of two or more of an organic elastic material and an inorganic binder. A sealing material characterized by
It's in the TIi thing. [Function] The sealant composition according to the present invention mainly contains ceramic fibers and whiskers with a three-dimensional structure, and contains one or more of an organic elastic substance and an inorganic binder in an aqueous solution. Further, if necessary, auxiliary additives such as a vulcanizing agent are added to the slurry dispersed in the slurry, and the slurry is agglomerated.
A sheet-shaped sealing material made into a sheet of a certain thickness by a paper-making machine, or a sealing material containing the ceramic inorganic fibers and whiskers with a three-dimensional structure, and optionally containing a vulcanizing agent, an inorganic binder, or an inorganic A rubber base with filler added and dissolved in a solvent and rubber chemicals are thoroughly mixed with a stirrer to create a clay-like joint sheet raw material, and the raw material is made into a joint sheet shape using hot rolls and cooling rolls. It is used as a sealing material.

Therefore, existing technology and equipment can be easily applied to the manufacturing method, but the manufacturing method of the peak sheet-shaped sealing material is particularly superior in terms of anisotropy due to the orientation of the ceramic inorganic fibers. It works. Now, one of the main constituents of the seal material assembly of the present invention is:
It is a ceramic inorganic fiber. This fiber is a man-made inorganic fiber, including silica alumina ceramic fiber,
Alumina and mullite crystalline fibers and silica fibers are used. In addition, for products with low heat resistance requirements, for example those used at temperatures below 300°C, it is also possible to use ultra-fine glass fibers. Such ceramic inorganic fibers may contain a non-fibrous material commonly called "shiwosoto". This non-fibrous material "Shosoto" does not contribute much to improving the properties of the sealing material, so it is better not to include it. Therefore, the non-fibrous material with a diameter of 44 μm or more contained in this fiber is approximately 20%. It is desirable to suppress the amount below (ratio to the amount of inorganic fiber).

Further, it is desirable that the fiber diameter of this ceramic inorganic fiber is less than 12 μm. The reason is that the fiber diameter is 1
When the diameter is 2 μm or more, the number of fibers per unit volume decreases, the sheet density decreases, and it is likely to break in the press process after papermaking in the manufacturing process, resulting in poor airtightness (
This is because it deteriorates sealing performance) or tensile strength.
It is particularly advantageous for the fiber diameter to be between 1 and 3 μm. Furthermore, this ceramic inorganic fiber must have excellent rigidity and holdability as a sheet-like material. This is because sealing materials generally need to have excellent compression and recovery properties. In addition, since the above-mentioned Ceramic ivy inorganic fiber exhibits tensile strength and folding strength after forming into sheets, it is possible to have an appropriate fiber length (average fiber length and fiber length distribution) as necessary. desirable. Next, the sealing material M1* of the present invention needs to contain whiskers having a three-dimensional structure. As the whisker having a three-dimensional structure, for example, a tetrapod-shaped zinc oxide whisker, a spiral-shaped SixNa whisker, etc. can be used. In other words, it is fundamentally important for the present invention to have a three-dimensional structure, and the constituent material is not particularly limited, and various materials may be selected depending on the heat resistance, reactivity, or cost of the sealing material used. do it. The reason for this is that general inorganic whiskers have simple two-dimensional needle-like crystals, and the above-mentioned method for manufacturing beater sheets and twin-point sheets produces two-dimensional needle-like crystal whiskers, inorganic fibers, or organic fibers. In addition, in the case of continuous production, the whiskers and fibers have the property of being oriented parallel to the sheet flow direction. Moreover, since the whiskers are short fibers, no reinforcing effect can be expected due to mutual entanglement of the whiskers, and after the sheet is formed, the compression recovery rate against force in the thickness direction is poor, and the tensile strength etc. in the longitudinal and lateral directions of the sheet are poor. Because the characteristics of the seals are different, that is, they are anisotropic, after punching into a ring shape, an imbalance in strength occurs in the seal pankin, etc.
There was a risk of problems such as gas leaks. On the other hand, since the present invention uses whiskers with a three-dimensional structure, strength can be expected from the intertwining of the whiskers with each other, and after sheeting or shaping, it has a remarkable effect on improving the compression recovery ratio, especially against forces in the thickness direction. be. Next, the sealing material set If7.115 of the present invention contains one or more of an organic elastic substance and an inorganic binder.

The organic elastic substance is used as appropriate to provide sealing properties at relatively low temperatures and to improve handling performance. Examples of the organic elastic substance include natural rubber, NBRSSBR, silicone rubber, etc. can be used. The inorganic binder is used as appropriate to reinforce the intertwining of the three-dimensionally structured whiskers and inorganic fibers, and examples of the inorganic binder include montmori stylinite, clay, and talc, which can also be expected to have a filler effect. , kaolinite, Hewei fluorine tetrasilicide mica, general inorganic binders, silica sol, alumina sol, etc. can be used.

In addition, the above-mentioned seal &
It can also be effectively applied when wrapped in a metal plate such as, processed with a metal grommet if necessary, or used in combination with a graphite sheet, etc. Example 1 SiOz: 50wt%, AI! OS: 50
In terms of wt% composition ratio, the average fiber diameter is 1. 8 μm silica-aluminum ceramic fiber (trade name: IBI WOOL, manufactured by IBIDEN Co., Ltd.) is processed to remove soyotto, reducing the content of soyots of 44 μm or more to 20% or less, and further adding it to 55 g of 30 ffi water. It was defibrated with

Next, 15 g of tetrapot-shaped zinc oxide whiskers (trade name: Banatetra, manufactured by Matsushita Electric Industrial ■) were added together with 30 g of Na-Montmoly Kuchinite to 30 ffi of the water in which Ibi wool had been defibrated, and mixed well. 54 g of NBR-based Latinx (trade name 22 Ball 1562, manufactured by Nippon Zeon Co., Ltd., i4 degree 41%) was added to the above solution, and a slurry was made by coagulating with sulfuric acid band. Next, this slurry was made into a wet sheet with a thickness of 8 m2 using a hand paper machine of 340 ms + 340 mm. This sheet-like material was pressed with a surface pressure of 300 kg/d, and
It was dried under CXlhr conditions. After drying, the sheet was subjected to a surface pressure of 60 kg/cj and a temperature of 300°C'? ! I really breathed for 15 minutes. Cut the end of this sheet-like material to a thickness of 0.
A sheet-like material having a size of 8sim, 300w++ square, and a density of 1.25g/cd was obtained. Its mechanical properties are shown in Table 1. Example 2 E glass chopped strand (diameter 12 μm length 5 mm
) 40% by weight, 10% by weight of tetrapot-shaped zinc oxide whiskers (trade name: Banatetra, manufactured by Matsushita Electric Industrial ■), 15% by weight of natural rubber, 1% by weight of sulfur, 1% by weight of zinc white,
0.2% superposition of accelerator and 32.8% clay as filler
Toluene was added to 1 kg of the mixture containing %
．． After adding the rubber at a ratio of 8f and swelling the rubber in the solvent, the mixture was mixed in a kneader for about 50 minutes and shaped using hot rolls and cooling rolls to form a joint sheet with a thickness of 1 mm, a density of 1, and 8 g/d. I got something like that. Its mechanical properties are shown in Table 1.

Comparative Example 1 A sheet-like product was obtained in the same manner as in Example 1, except that the same amount of acicular SiC whiskers was used instead of the tetrabond zinc oxide whiskers. Its mechanical properties are shown in Table 1. Comparative Example 2 A joint sheet-like product was obtained in the same manner as in Example 2, except that acicular Si,N-whiskers were used in place of the tetrabond zinc oxide whiskers.

Its mechanical properties are shown in Table 1. As is clear from Table 1, mechanical properties vary depending on density, but mechanical properties are improved by using whiskers with a three-dimensional structure. [Effects of the Invention] As explained above, the sealing material composition of the present invention can provide a sealing material with excellent properties without using asbestos, which is considered to be harmful to the human body. Furthermore, even at high temperatures of 700°C, there is no deterioration of the inorganic fibers due to combustion oxides, and good sealing performance and reliability are always achieved. that's all

Claims (1)

[Claims] A sealing material composition mainly containing ceramic inorganic fibers and three-dimensional whiskers, and comprising one or more of an organic elastic substance and an inorganic binder.