JPH03229785A - High-temperature gasket and its manufacture - Google Patents

Abstract

PURPOSE:To obtain the title gasket improved in sealing properties, heat resistance, and wind erosion resistance by wet mixing ceramic inorganic fibers, wollastonite, unexpanded vermiculite, an organic elastic substance, and an inorganic binder to form a sheet, drying it, and hot pressing it. CONSTITUTION:35-80wt.% ceramic inorganic fibers having a diameter of 12mum or smaller and containing at most 20% nonfibrous material of 44mum or larger in size, 2-50wt.% wollastonite having a particle diameter of 0.1-2.8mm and an average aspect ratio of 15 or greater, 5-20wt.% unexpanded vermiculite having a particle diameter of 0.1-2.8mm, 5-35wt.% inorganic binder (e.g. montmorillonite), and 2-25wt.% organic elastic substance (e.g. natural rubber emulsion) are wet mixed to form a sheet. The sheet is dewatered by pressing, dried, and hot pressed to give a high-temperature gasket having a density of 0.4-2.0g/cm<3>.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a high temperature cassette and a method for producing the same, and in particular has excellent sealing properties and heat resistance even under high temperature conditions exceeding 950°C. A gasket,
This is a proposal for a gasket suitable for use in automobile engines, etc., which is made of a material whose main component is ceramic instead of asbestos.

[Conventional technology]

High-temperature gaskets used in the above-mentioned applications are made mainly of asbestos, and are also made of natural rubber, nitrile rubber (NBR), or styrene-butadiene rubber (for imparting elasticity).
It is generally made of an elastic material such as SBR) and an auxiliary agent such as a vulcanizing agent added as necessary.

By the way, gas get used for such purposes include "joint sheet"-like scum and throat obtained by heating and molding asbestos and an elastic material, and gas get obtained by mixing asbestos and an elastic material such as emulsion latte nox. There were "heater root"-shaped gaskets obtained by paper-forming slurry.

These known gaskets contain 60-95% by weight of primarily asbestos fibers. As a result, asbestos powder is scattered not only during the production of gaskets, but also from facilities where the asbestos fibers are installed, posing a risk of health problems, and improvements have been desired.

Therefore, in Japan, following 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 specifying ``lung 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, 9i was passed to ban the use of 7th Hest products, and in June 1986, with the approval of OMB (Office of Management and Budget), a ban on building materials was proposed from January 1988. They are proposing a complete ban on its use starting in 1991.

In July 1986, the three major gas and toy manufacturers in the United States declared that they would accept this proposal in stages.

In addition, not only in these countries, but also internationally, in June 1986,
The ``Convention and Recommendations on Safety in the Use of Asbestos'' is being discussed and deliberated based on a proposal by the ILO (International Labor Organization) in February.

Under these international circumstances, recently, inorganic fibers such as sepiolite fiber, glass fiber, carbon fiber, and stainless steel fiber, or organic fibers such as aromatic polyamide fiber, phenol fiber, and polyethylene fiber are being used as substitute fibers for asbestos. There are attempts to manufacture gaskets using these fibers.

[Problem that the invention seeks to solve]

As mentioned above, gaskets made of asbestos fibers are said to have problems with pollution, and although they can maintain good physical properties up to around 600°C, they fail at higher temperatures, such as 950°C or higher. had the disadvantage that strength deterioration occurred due to dehydration of crystal water.

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

That is, among the inorganic fibers, for example, sepiolite has water of crystallization, and therefore its strength deteriorates in the same way as asbestos in a high temperature range. Furthermore, when a gasket is manufactured using only this inorganic fiber, there is a problem in that the tensile strength and recovery rate are inferior, similar to gaskets using asbestos.

In particular, among inorganic fibers, for example carbon fibers, and organic fibers9 such as aromatic polyamide fibers, phenol fibers, and polyethylene fibers, their properties deteriorate significantly from around 200°C, and in particular, they completely carbonize or burn out at temperatures above 400°C. There was a problem in that it could not be used at high temperatures of 400° C. or higher because bond deterioration occurs.

The purpose of the present invention is to solve the above-mentioned problems such as environmental pollution of high-temperature suspensions made of asbestos, as well as to reduce the tensile strength and elastic modulus due to the use of various inorganic fibers, and the accompanying decline in gasket function. The purpose of the present invention is to provide a high-temperature gasket that can overcome problems such as lack of sealing function, reliability, and durability.

[Means for solving problems]

The present invention deals with non-asbestos gaskets, and furthermore, the properties as a gasket are deteriorated due to the deterioration of properties such as tensile strength and elastic modulus, that is, the sealing function, reliability, etc.
In order to overcome the decrease in durability, we decided to improve the heat resistance of the gasket by blending it with ceramic inorganic fibers, and in particular to improve its tensile strength and elastic modulus by using wolastenite. It is characterized by the use of an inorganic binder to compensate for the strength in the high temperature range, and the use of unexpanded vermiculite to further improve the recovery rate at high temperatures.

In addition, in manufacturing such a gasket, a mixture consisting of the ceramic inorganic fiber, wolastenite, unexpanded vermiculite organic elastic 'pA' material, and an inorganic binder is wet-mixed, and then paper-formed; By adopting a method of dehydration pressing, drying, and then hot pressing, they were able to overcome the problems of the above-mentioned conventional techniques all at once.

In particular, in the present invention, since wolastenite and unexpanded vermiculite are used in combination, a gasket with high heat resistance, high recovery rate, and high strength can be obtained due to their synergistic effect.

The present invention, which was developed based on such a concept, is a beater sheet-like gasket made by laminating and laminating a slurry of a mixture of fibers and elastic substances. 2-25wt of substance
%, an inorganic binder is blended at a ratio of 5 to 35%, and further, 2 to 5Qwt% of wolastenite and 5 to 35% of
The present invention relates to a high-temperature gasket and a method for producing the same, characterized in that it is composed of a compound S containing 20% unexpanded vermiculite.

[Function] The gasket according to the present invention includes ceramic inorganic fibers,
An organic elastic substance and an inorganic binder, in addition to which wolastenite and unexpanded vermiculite are dispersed in an aqueous solution, that is, an emulsion obtained by mixing an organic elastic substance, or a vulcanizing agent if necessary. This is a beater sheet-like gasket obtained by forming an emulsion containing auxiliary additives, such as auxiliary additives, using a paper-making machine and laminating them to a certain thickness.

In recent years, beater sheet-shaped gaskets have been widely used because they provide higher uniformity than joint sheet-shaped gaskets.

Now, one of the main components constituting the gasket of the present invention is ceramic inorganic fiber. This fiber is an artificial inorganic fiber, and silica-alumina ceramic fibers, crystalline fibers of alumina and mullite, silica fibers, and the like are used. 7. In addition, for those that require low heat resistance, for example, for use at temperatures below 300°C, it is also possible to use glass fiber as a seed wire.

Such ceramic inorganic fibers may contain a non-fibrous material commonly called "shot." This non-fibrous material "shot" does not contribute much to improving the properties of the gasket, so it is better not to include it. Therefore, it is desirable that the amount of non-fibrous substances substantially larger than 44 μm contained in the fibers be suppressed to 20% or less (non-inorganic fibers).

Further, it is desirable that the fiber diameter of this ceramic inorganic fiber is less than 12 μm. When the fiber diameter exceeds 12 μm, the number of fibers per unit volume decreases, resulting in a decrease in sheet density. This is because it deteriorates the properties (resistance) or tensile strength. The fiber diameter is preferably in the range from 1 to 3 μm.

Now, gaskets generally need to have excellent compression and recovery properties, so the inorganic fibers used need to have excellent rigidity and retention as a sheet-like material. be. The high-temperature gasket of the present invention contains 35 to 80 L% of ceramic inorganic fibers having the properties described above. If the amount of such inorganic fibers is less than 35 wt%, the recovery rate and tensile strength at high temperatures will decrease. On the other hand, the blending amount is 80%
If the amount is larger than this, the fibers are likely to break and the tensile strength decreases, as well as the airtightness decreases.

Next, in the high temperature gasket of the present invention, a predetermined amount of unexpanded vermiculite is blended in order to improve the recovery rate and heat resistance at high temperatures. This unexpanded vermiculite is a particulate material with a flake multilayer structure, and is 5i-
It is a hydrated mineral with a mica-like structure based on a 2:1 type layer structure of a 0 tetrahedral layer and a Mg-0(OH) or Am-0 octahedral layer, and these are connected through water between the eyebrows, It is a substance with excellent elasticity and heat insulation properties. Moreover, when this unexpanded vermiculite is heated, it dehydrates, exfoliates and expands.
It has the property of elongating up to 25 times. Due to the poor binding strength between the tatami and the glabella, it becomes flaky with the slightest external force, making it difficult to maintain its shape by itself.

In the present invention, as a result of studying the usage of vermiculite having such characteristics, it was found that treatment with organic acid sodium is effective. The reason is explained below.

Generally, the expansion rate and elasticity of unexpanded vermiculite are
It is known that it is proportional to the particle size. However, vermiculite for sheet production is preferably one with good dispersibility and small particle size.

Therefore, in the present invention, it was decided to use small vermiculite with a particle size of 0.1 to 2.8 m. However, when vermiculite with a small particle size was used, the resulting sheet had a smaller expansion force and elastic force in proportion to the particle size of the vermiculite. This is not something that should be welcomed.

Now, the present inventors previously discovered that by replacing the cations between the layers of vermiculite particles with organic acid sodium, the expansion force 1 elastic force increases, and furthermore, vermiculite expands from a lower temperature than unsubstituted vermiculite. I know that. (Unexamined Japanese Patent Publication No. 59-230737). This means that even if the particle size of vermiculite is small, the same effect can be obtained by treating it with sodium organic acid.

Therefore, in the present invention, we focused on this phenomenon and used unexpanded vermiculite treated with organic acid sodium to produce a sheet with excellent properties.

The reason why the expansion power of unexpanded vermiculite is improved by treatment with such organic acid sodium, that is, by immersing unexpanded vermiculite in the organic acid sodium aqueous solution, is because calcium ions or This seems to be because magnesium ions are replaced with sodium ions, making it difficult for water between the eyebrows to drain out during heating.

As explained above, the high-temperature gasket of the present invention uses unexpanded vermiculite having the above-mentioned properties, and the amount thereof is 5 to 20 wt%. If the amount of unexpanded vermiculite is less than 5%, the expansion force of the sheet decreases, making it difficult to obtain a sheet with a high recovery rate. On the other hand, 20
If the content exceeds wt%, vermiculite becomes granular and its tensile strength significantly decreases.

Next, in the high temperature gasket of the present invention, 2 to 50 wt % of wolastenite is further blended in order to improve tensile strength, modulus of elasticity, recovery rate, and heat resistance. This is because scaly unexpanded vermiculite alone cannot be expected to provide strong bonding strength between vermiculites, and even when mixed with ceramic inorganic fibers of small fiber diameter, the fibers and vermiculite are well entangled. This is because it is difficult to form a matrix.

That is, the particle size of vermiculite (0.1 to 2.8 m
) is relatively rougher than ceramic-based inorganic fibers.

Therefore, in the present invention, it became necessary to add a filler of intermediate size.

In order to meet such demands, the present invention has decided to use wolastenite as an intermediate filler. Since this wollastenite does not contain water of crystallization, it does not shrink due to structural changes such as dehydration, oxidation and crystallization, even under high temperatures, unlike asbestos and sepiolite, and has the property of not losing fiber strength. It is something. Furthermore, it has superior heat resistance compared to plastic fibers, carbon fibers, etc. In addition, this wolastenite has a relatively high aspect ratio and does not have an adverse effect on the human body like asbestos, so it is optimal as the above-mentioned filler.

Such wolastenite needs to be blended so that the proportion thereof in the gasket composition is 2 to 50 wt%. The content of this wolastenite is 2imt%
If the amount is less than 50 wt%, the effect of improving strength and elastic modulus cannot be obtained. On the other hand, if the amount exceeds 50 wt%, the fiber length of wolastenite is very short, so the properties are similar to those of powder. This leads to a decrease in wind corrosion resistance. Among these, a blending amount of 10 to 35% is more suitable. Further, it is desirable to use a filler having an average aspect ratio of 15 or more.

Next, in the present invention, an inorganic binder is blended. The blending ratio of this inorganic binder is limited by the required performance and manufacturing method, but if the amount of this inorganic binder is insufficient, not only will strength not be obtained, but the sheet produced will be non-uniform. On the other hand, if it is used in too large a quantity, it will lead to poor aggregation of rubber latex etc. due to its swellability in water, impairing water freeness and making it difficult to manufacture sheet-like products.

Furthermore, since the blending ratio of the fibrous material is also limited, strength and elasticity are also adversely affected, so there is a limit to the use of large amounts. The amount of the inorganic binder determined in this way is between 5 and 35
A range of wt% is appropriate.

Suitable examples of such an inorganic binder include montmorillonite, clay, talc, kaolinite, and synthetic fluorine tetrasilicide type mica. Among them, montmorillonite easily swells in water and has excellent bonding strength, so it can be heated to 400°C.
It is effective and suitable for maintaining the strength in the above conditions. This montmorillonite is usually an earth component of naturally occurring bentonite raw ore, and can be roughly divided into Na-montmorillonite, which is rich in Na ions and absorbs a large amount of water and exhibits high swelling properties, and Na-montmorillonite, which is rich in Na ions and exhibits high swelling properties, and Ca ion! I! There is Ca-montmorillonite which is rich in g ions and has low swelling properties. In addition, Sea Ca
Sodium activated by treating montmorillonite with soda
There is also montmorillonite. However, unlike other hydrous silicate aluminum minerals such as kaolinite and talc, all montmorilloids exhibit swelling properties to varying degrees. Among them, activated Na-montmorillonite has particularly excellent swelling properties and binding properties, and satisfies the purpose of the present invention well, and its chemical formula is expressed as follows.

(DH) asi (A l :+, zaMgo,
66) 020 Nao, bbAs an inorganic binder that exhibits swelling properties, sepiolite, synthetic fluorine tetrasilicide type mica, ball clay, etc. are known as exhibiting the same performance as the above-mentioned montmorillonite. can be used instead of montmorillonite.

Next, in the present invention, an organic elastic material is used. This material is particularly useful as a gasket composition;
For example, a natural rubber emulsion or a synthetic rubber latex binder such as NBR or SBR is suitable.

It is preferable that the blending ratio of such an organic elastic material is small, since it burns or carbonizes at high temperatures and deteriorates its properties.
Due to the necessity of sheet forming, 2 to 25% is preferable.

Furthermore, in the present invention, the durability of rubber latex,
To improve strength, rubber vulcanizing agents and the like (eg, sulfur, sulfur chloride) can be used.

However, in the present invention, an inorganic binder such as montmorillonite and wolastenite are used as auxiliary materials because the strength, elastic modulus, and recovery rate can be ensured.

δ, in the present invention, in addition to the above-mentioned compounding materials,
Furthermore, kaolinite (Al□Sl zQs (OH)
Inorganic substances such as a) that do not have so-called swelling properties but can be expected to have binding strength can also be added as reinforcing agents.

Now, a sheet-like product (gasket) formed by molding and pressing the composition blended at the above-mentioned ratio is as follows:
The density is in the range of 0.4 g/cm3 to 2.0 g/cm3, resulting in a high-temperature gasket that exhibits excellent heat resistance, tensile strength, elastic modulus, recovery rate, etc.

Generally, properties such as tensile strength, elastic modulus, and recovery rate of gaskets are influenced by density. Regarding the gasket of the present invention, if the density is greater than 2.0 g/cm', the inorganic fibers will break and the tensile strength will decrease.
There is a risk that the elastic modulus and recovery rate will decrease. In our research, 0.6g/cm3 to 1.4g/
A density range of c+a:l was preferred.

In order to produce a gasket having such a density, it is advantageous to perform hot pressing after wet mixing, paper forming, dehydration, and drying. That is, when hot pressing is employed, fluidity is generated in the ionic elastic material such as rubber, so the inorganic fibers are not crushed and the aspect ratio of the fibers is not reduced, and the preferred density can be easily achieved. Because you can get it.

In addition, regarding the gasket of the present invention as described above, SO5
A walnut gasket wrapped in a metal plate such as 304, and a steel heist gasket with a metal plate as the core.

When using metal grommets for the openings of gasket sheets, adhering carbon sheets to each surface to provide solid lubricity, or impregnating carbon or similar solid lubricants. It can also be used effectively.

〔Example〕

Example 1 SiOz: 50wt%, Al2O3: 50wt%
By de-shotting silica-alumina ceramic fibers (trade name: Ibiwool, manufactured by Ibiden Co., Ltd.) with an average fiber diameter of 1.8 μm,
A sample was prepared in which the shot content of 4 μm or more was reduced to 20% or less. 52g of the thus obtained ceramic fiber was placed in 30n of water and defibrated.

Next, 18 g of wollastenite having an average fiber diameter of 8 μm and an aspect ratio of 30, Na-montmorillonite: 2
After adding 3 g of unexpanded permiculite l-, which had been previously treated with sodium organic acid, to the water 3ON and mixing well, NBR latex (trade name: Nipole 1562, manufactured by Nippon Zeon Co., Ltd.) was added. , with a concentration of 41%) was added thereto and agglomerated using a sulfuric acid hand to prepare a slurry.

Next, the slurry was fed to a 340 m x 340 fl hand paper machine and made into a wet sheet with a thickness of 8 fl. This sheet-like material is subjected to a surface pressure of 300 kg/c
It was pressed at a temperature of m 2 and dried at 120° C. for 1 hr.

After drying, the sheet is subjected to a surface pressure of 60 kg/cm” and a temperature of 300°C.
Hot pressed for 15 minutes. The end of this sheet-like material was cut to a thickness of 0.8fi, a square of 300fi, and a density of 1.25.
A sheet-like product of g/CI' was obtained. Table 1 shows the mechanical properties of this sheet-like material. In addition, the following durability test was conducted to investigate the performance of the sheet gasket.

The sheet was punched out to a predetermined size and was installed as a gasket between the head and exhaust manifold of an automobile engine. And displacement 2000cc,
Exhaust gas temperature of 900℃ with DOHC turbo engine
Exhaust gas was allowed to flow into the exhaust manifold for 200 hours.

As a result, it was found that heat caused a distortion of about Q, about 1 mm, between the flanges, and that the engine body expanded by about 0.4 B due to heating. However, no serious problems such as gas leakage occurred during the durability test.

Comparative Example 1 This comparative example uses the blended raw materials of Example 1 excluding unexpanded vermiculite, that is, 52 g of silica-alumina ceramic fiber and 25 g of wolastenite.
A mixture of 28 g of Na-montmorillonite and 25 g of NBR-based latetex was treated in the same manner as in Example 1, and the plate thickness was 0.8 B, 300 fi square, and density 1.25.
A sheet of g/cm3 was produced.

The mechanical properties of this sheet gasket are shown in Table 1, and the same durability test as in Example 1 was conducted.

As a result, although the amount of strain between the flanges and the amount of expansion of the flange body were the same as in Example 1, gas leakage occurred approximately 50 hours after the start of the test.

Comparative Example 2 This comparative example uses the blended raw materials of Example 1 except that wolastenite is removed, that is, 65 g of silica-alumina ceramic fiber and 12 g of unexpanded vermiculite.
, 28g of Na-montmorillonite.

A compound of 25 g of NBR-based latetex was subjected to the same treatment as in Example 1, with a thickness of 0.8 tsuru, 300 day angle,
A sheet material having a density of 1.25 g/cm3 was produced.

The mechanical properties of this sheet gasket are shown in Table 1, and the same durability test as in Example 1 was conducted.

As a result, although the amount of strain between the flanges and the amount of expansion of the flange body were the same as in Example 1, gas leakage occurred approximately 20 hours after the start of the test.

Comparative Example 3 In this comparative example, a sheet-like product similar to that in Example 1 was manufactured using unexpanded vermiculite, which was not treated with organic acid sodium, among the raw materials blended in Example 1. The mechanical properties of this sheet gasket are shown in Table 1, and the same durability test as in Example 1 was conducted.

As a result, although the amount of strain between the flanges and the amount of expansion of the engine body were the same as in Example 1, gas leakage occurred approximately 100 hours after the start of the test.

From the results of the above Examples and Comparative Examples, it was found that the blended raw materials in which wolastenite and unexpanded vermiculite treated with sodium organic acid were used in combination within a predetermined range had good performance as a gasket.

However, in those that do not contain unexpanded vermiculite, the recovery rate at high temperatures is significantly reduced, making it impossible to sufficiently seal the strain between the flanges. on the other hand,
Products that do not contain wolastenite will have a significant drop in tensile strength regardless of temperature, and will not be able to follow the expansion of the engine body due to heat, resulting in cracks around the bolt holes and insufficient strength. Sealability could not be obtained.

In addition, in the case of blending unexpanded vermiculite that had not been treated with organic acid sodium, the recovery rate at high temperatures was slightly lower. Therefore, it was found that although sufficient sealing performance was exhibited when the amount of strain was small, gas leakage occurred as the amount of strain increased as the test time progressed.

Therefore, unexpanded vermiculite treated with wolastenite and sodium organic acid has a weight of 2 to 50 w, respectively.
It was found that t% must be used in the range of 5 to 201%.

C. Effects of the Invention] As explained above, the high temperature gasket of the present invention does not require the use of asbestos, which is considered to be harmful to the human body. In addition, it has high strength, and even at high temperatures of 950°C, there is no loss of fiber or powdering (bond deterioration) due to combustion oxidation.
Excellent properties such as gas sealing properties, heat insulation properties, and resistance to wind erosion can also be obtained.

As a result, the present invention has the following ripple effects.

First, for automobiles, (11) since the amount of heat transferred from the exhaust manifold to the cylinder head is reduced, the amount of heat transferred to the cooling water flowing through the cylinder head is reduced, making it possible to downsize the radiator. , low cost, and effective use of the engine room.

(2) The temperature of the flange surface of the exhaust manifold in contact with the cylinder head is higher than in conventional technology, and the temperature is uniformly distributed, so it is possible to reduce costs by reducing the thickness of the flange part by reducing thermal strain on the flange surface. In addition, the temperature of the gas in the exhaust manifold can also be increased, so that exhaust emissions can be reduced and the catalyst can be highly activated.

(3) Due to the increase in exhaust gas temperature in (2) above, exhaust heat is converted into work in a supercharged engine, and engine output can be improved.

Claims (1)

[Claims] 1. In a beater sheet-like gasket containing at least inorganic fibers, elastic substances, binders, etc., the ceramic inorganic fibers are contained in an amount of 35 to 80 wt%, and the organic elastic substance is contained in an amount of 2 to 2 wt%.
5 wt% and an inorganic binder at a ratio of 5 to 35 wt%, and further contains 2 to 50 wt% of wollastenite and 5 to 20 wt% of unexpanded vermiculite. High-temperature gasket with special features. 2. A compound consisting of ceramic inorganic fibers, wollastenite, unexpanded vermiculite, an organic elastic material, and an inorganic binder is wet-mixed, then paper-formed, then dehydrated and pressed, then dried, and then hot-pressed. A method for manufacturing a high-temperature gasket.