JP2579374B2 - Gasket for high temperature - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gasket for high temperature, and particularly to a gasket for an automobile, which has excellent sealing properties and heat resistance even under a temperature condition exceeding 950 ° C. This is a proposal for the gasket shown, which is composed mainly of ceramics instead of asbestos.

[Prior art] The high-temperature gasket used for the above-mentioned applications is made of asbestos as a main raw material, and natural rubber or nitrile rubber (NBR) for imparting elasticity, styrene-butadiene rubber (S
BR) In general, it is composed of a material using an elastic material and an auxiliary agent such as a vulcanizing agent added as needed.

By the way, a casquette for such an application is obtained by forming and forming a “joint sheet” -shaped gasket obtained by heating and molding asbestos and an elastic substance, and a slurry in which substances such as asbestos and emulsion latex are mixed and fixed. There was a "beater sheet" shaped gasket.

These known gaskets mainly contain asbestos fibers in an amount of 60 to 95% by weight. Therefore, not only the gasket manufacturing process but also the asbestos fibers are scattered from a construction facility, which may cause a health hazard. As a result, improvements have been desired.

For this reason, the handling of such regulations has been regulated by various laws and regulations in Japan following the signing of the International Cancer Treaty in 1974. For example, the “Regulations for the Prevention of Disorders of Specific Chemical Substances” was established on April 1, 1976, and a part of the Labor Standards Enforcement Rules was revised on March 30, 1978. For example, the designation of "lung cancer or mesothelioma caused by asbestos-related work" for a source factor or a disease caused by work in the cancer-source process.

In the United States EPA (Environmental Protection Agency),
In June, a proposal was made to prohibit the use of asbestos products. In June 1986, with the consent of the OMB (Administrative and Budget), a proposal was made to prohibit the use of asbestos products in January 1988.
It proposes a total ban from 1991.

And in July 1986, the three largest gasket manufacturers in the United States made a declaration to accept the proposal in stages.

In addition to the above two countries, internationally, the IL of June 1986
O (International Labor Organization) proposal discusses and discusses "Conventions and Recommendations on Safety in the Use of Asbestos".

In response to this international situation, recently, as an asbestos substitute fiber, 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 have been used. Attempts have been made to manufacture gaskets.

[Problems to be solved by the invention]

As described above, a gasket using asbestos fiber has a problem of pollution, and can retain a good substance up to around 600 ° C., but at a higher temperature, for example, at a temperature of 950 ° C. or higher, the The drawback is that strength degradation occurs due to dehydration of water.

On the other hand, a gasket using an inorganic fiber or an organic fiber as the asbestos substitute fiber also has the following problems.

That is, among the inorganic fibers, for example, sepiolite and the like have water of crystallization, so that the strength is deteriorated in the high temperature region as in the case of the asbestos. In addition, when a gasket is manufactured using only inorganic fibers, there is a problem that the tensile strength and the like are inferior as in a gasket using asbestos. In particular, among the inorganic fibers, for example, carbon fibers,
Organic fibers, such as aromatic polyamide fibers, phenol fibers, and polyethylene fibers, have significantly degraded fiber properties from around 200 ° C. Above 400 ° C, they are completely carbonized or burned and bond deterioration occurs. However, there is a problem that it cannot be used at high temperatures.

[Means for solving the problem]

The present invention uses ceramic-based inorganic fibers to overcome the deterioration of properties as a gasket, that is, the deterioration of sealing function, durability, and reliability due to deterioration of properties such as tensile strength and elastic modulus. To improve durability, to improve tensile strength, elastic modulus, restoration rate, heat resistance, etc. by using wollastonite, and to compensate for strength in high temperature range by using an appropriate inorganic binder. By
It was decided to overcome the problems of the prior art at once.

Particularly, in the present invention, wollastenite is used, so that a gasket having high heat resistance and high recovery rate can be obtained.

The present invention developed under such a concept provides a beater sheet-like gasket formed by laminating and forming a mixture slurry from fibers, elastic materials, and the like, using 35 to 80 wt% of ceramic inorganic fibers and 2 to 50 wt% of wollastenite. ,
2-25wt% of organic elastic material and 5-35wt of inorganic binder
% Gasket for high temperature, characterized in that the gasket is composed of a composition containing 0.1% by weight.

(Operation)

The gasket according to the present invention basically comprises an emulsion obtained by mixing ceramic inorganic fibers, wollastenite, an organic elastic substance and an inorganic binder in an aqueous solution, and mixing the resulting mixture with an organic elastic substance. This is a beater sheet-like gasket obtained by forming an emulsion obtained by adding an auxiliary additive such as a vulcanizing agent to a papermaking machine and laminating the emulsion to a predetermined thickness. In recent years, the beater sheet-shaped gasket has been widely used since a gasket having higher uniformity than that of a joint sheet-shaped gasket can be obtained.

One of the main constituents of the gasket of the present invention is a ceramic inorganic fiber. The fibers are artificial inorganic fibers, such as silica-alumina ceramic fibers, crystalline fibers of alumina and mullite, and silica fibers. In addition, for those having low heat resistance requirements, for example, those used at a use temperature of 300 ° C. or lower, ultrafine glass fibers can be used.

Such a ceramic inorganic fiber may contain a non-fibrous material commonly called “shot”. This non-fibrous substance "shot" does not contribute much to the improvement of the properties of the gasket, so it is better not to include it.
Therefore, it is desirable that the non-fibrous material having a size of 44 μm or more contained in the fibers be suppressed to 20% or less (non-inorganic fibers). The fiber diameter of this ceramic inorganic fiber is 12
Desirably, it is less than μm. The reason for limiting to this size is as follows. That is, when the fiber diameter is 12 μm or more, the number of fibers per unit volume decreases, the sheet density decreases, and the fiber is easily broken in a pressing step after papermaking in a manufacturing process, and has an airtightness (sealing property) or a tensile strength. Is worse. The fiber diameter is advantageously from 1 to 5 μm.

In addition, since the gasket generally needs to have excellent compression-recovery properties, the properties of the inorganic fiber to be compounded need to be excellent in rigidity and excellent in holding properties as a sheet-like material. .

The high-temperature gasket of the present invention contains 35 to 80% by weight of ceramic inorganic fibers having the above-mentioned properties. If the amount of such inorganic fibers is less than 35 wt%, the restoration rate and tensile strength at high temperatures decrease, whereas if it is more than 80 wt%, the fibers are liable to breakage, and in addition to the decrease in tensile strength, airtightness That is, there is a drop in sex.

Next, in the gasket for high temperature of the present invention, in order to improve tensile strength, elastic modulus, recovery rate and heat resistance,
2 to 50 wt% of wollastenite is contained.

That is, since wolastenide does not have water of crystallization, it does not cause shrinkage due to structural changes such as dehydration and crystallization and does not lose fiber strength even at high temperatures, unlike asbestos and sepiolite. It is more excellent in heat resistance than plastic fibers and carbon fibers. Moreover, it does not adversely affect the human body like asbestos.

Such wollastenite has been conventionally produced in India, China, and the like, and has two types of scaly α-type and acicular β-type.
There are types. In the present invention, considering the need to entangle the fibers, a needle-shaped β-type is preferable. That is, β
This is because, since wollastonite is needle-shaped, its use promotes entanglement with ceramic inorganic fibers, and cotton having tensile strength and elastic modulus is advantageous.

Further, since wollastenite is a natural mineral, it contains at least a small amount of impurities, and the type or amount of impurities differs depending on the place of production. Therefore, depending on the nameplate, the characteristics of the sheet-like material are slightly affected. In view of this point, it is advantageous to use β-type and relatively pure Indian wollastenite.

It is necessary that the wollastenite is contained in the gasket composition in a proportion of 2 to 50% by weight. If the content of wollastenite is less than 2%, the effect of improving the strength and the elastic modulus cannot be obtained. On the other hand, if the content is too large, the fiber length is very short in the case of wollastenite. Since it shows characteristics similar to powder, it leads to a reduction in wind erosion resistance and vibration resistance, so it must be 50% by weight or less.
35% by weight is more preferred. The average asbestos ratio is
It is desirable to use fibers having 15 or more.

Next, montmorillonite, clay, talc, kaolinite, synthetic fluorine tetrasilicide mica, or the like is used as the inorganic binder. Of these, montmorillonite easily swells in water and has excellent bonding strength,
It is effective and suitable for maintaining the above strength. This montmorillonite is usually a major component of naturally occurring bentonite ore, and is roughly divided into Na-montmorillonite, which is rich in Na ions and absorbs a large amount of water and has high swelling properties, and is rich in Ca ions and Mg ions. There is Ca-montmorillonite with low swelling property. In addition, there is Na-montmorillonite obtained by activating the Ca-montmorillonite by soda treatment. However, any of the montmorolinites, unlike the other hydrated aluminum silicate minerals such as kaolinite and talc, exhibit swelling properties to varying degrees. Among them, activated Na-montmorillonite is particularly excellent in swelling property and binding property and well fulfills the object of the present invention. Its chemical formula is represented by the following formula.

_{(OH) 4 Si (Al 3.34} Mg 0.66) O 20 -Na 0.66 Further, as swellable inorganic binding agent, wherein the montmorillonite and sepiolite as an indication of similar performance, synthetic four silicide fluorine type mica, such as a ball clay It is known and can be used in place of the montmorillonite.

Next, the organic elastic substance used in the present invention is particularly useful as a gasket composition.
A commonly used organic elastic material, for example, an emulsion of natural rubber, or a synthetic rubber latex binder such as NBR.SBR is suitable. In order to improve the durability and strength of the rubber latex, a rubber vulcanizing agent (for example, sulfur or sulfur chloride) can be used. However, in the present invention, the inorganic binder such as montmorillonite and wollastenite can be used as an auxiliary material because the strength, elastic modulus and restoration rate can be secured.

The compounding ratio of the organic elastic substance is preferably small because it is burned or carbonized at a high temperature, and particularly the restoring property is deteriorated. However, from the necessity of sheet molding, 2 to 25% by weight is preferable.

Next, the inorganic binding substance will be described. The mixing ratio of the inorganic binding substance is limited by the required performance and the production method. However, if the amount is insufficient, not only the strength cannot be obtained but also the formed sheet becomes uneven. On the other hand, if used in an excessively large amount, the aggregation of the rubber latex becomes insufficient due to the swelling property with respect to water, so that the drainage becomes poor and a sheet-like material cannot be produced. Further, since the compounding ratio of the fiber substance is also limited, the strength and elasticity are adversely affected, so that there is a limitation. From this, the amount of the inorganic binder is 5
A range of ~ 35% by weight is suitable.

In the present invention, in addition to the above-mentioned components, inorganic materials such as kaolinite (Al ₂ Si ₂ O ₅ (OH) ₄ ) which does not have swelling properties but can be expected to have a binding force, such as colloidal silica, Corodil alumina and the like can also be added as a reinforcing agent.

By the way, the composition blended in the above-described blending ratio is molded and pressed into a sheet-like material (gasket).
Is in the range of density of ^{0.4g / cm 3 ~2.0g / cm 3} , a high temperature gasket showing excellent heat resistance, tensile strength, modulus of elasticity, the recovery rate and the like.

Generally, properties such as tensile strength, elastic modulus, and recovery rate of a gasket depend on density.
In particular, when the density of the gasket of the present invention is higher than 2.0 g / cm ³ , the inorganic fibers may be broken, and the tensile strength, the elastic modulus, and the restoration rate may be reduced. In our studies, density range of 0.6g / cm ³ ~1.4g / cm ³ was preferred.

In order to manufacture a gasket having such a density, hot pressing is preferably performed in a press after wet mixing, papermaking, dewatering, and drying. That is, when a hot press is adopted, fluidity is generated in an organic elastic substance such as rubber, so that the inorganic fibers are not pulverized and the asbestos ratio of the fibers is not reduced, and the preferred density can be easily obtained. Because.

As for the gasket of the present invention as described above, a graphite sheet having a solid forward activity is bonded to the surface, or a solid is used by impregnating MoS ₂ or carbon particles as a lubricant on the surface of the sheet. Wrapped gasket wrapped in metal plate such as 304, steel vest gasket with metal plate core, power vest gasket,
It is also effectively used when the opening of the gasket sheet is processed using a metal grommet.

〔Example〕

Example 1 The average fiber diameter was 50% by weight of SiO _{2 and} 50% by weight of Al ₂ O _3.
1.8 μm silica-alumina ceramic fiber (manufactured by IBIDEN Co., Ltd.) is subjected to de-shot processing to reduce the content of shots having a size of 44 μm or more to 20% or less, and further defibrated in 30 l of 55 g water. I let it.

Next, wollastenite (produced by Maruwa Biochemical Co., Ltd.) having an average fiber diameter of 8 μm and an aspect ratio of 30
g, 30 g of Na-montmorillonite was added to the water 30 and mixed well. Further, 54 g of NBR-based latex (manufactured by Nippon Zeon Co., Ltd., solid content 41%) was added to the water and coagulated with a sulfuric acid band. This was made into a slurry.

Next, this slurry was applied to a hand paper machine of 340 mm × 340 m with a thickness of 8 mm.
mm wet sheet. The end of the sheet was cut into a sheet having a thickness of 1.0 mm, a square of 300 mm, and a density of 1.06 g / cm ³ . Table 1 shows the mechanical properties of the sheet.

Example 2 61 g of crystalline alumina fiber (manufactured by ICI) having an alumina crystallinity of 70% and an average fiber diameter of 3 μm, wollastenite 24 g, silica sol (manufactured by Nissan Chemical Co., Ltd., solid content 20
%) 120 g and NBR-based latex 29 g were subjected to the same treatment as in Example 1 to give a sheet having a thickness of 1.0 mm, 300 mm square, and a density of 1.05 g / cm ³ . Table 1 shows the mechanical properties of the sheet.

Comparative Example 1 The same raw materials as those used in Example 1 were used, except that the same raw materials were used and the mixing ratio of the raw materials was 36 g of silica-alumina fiber, 25 g of wollastenite, 24 g of Na-montmorillonite, and 90 g of NBR latex. By performing the treatment, a sheet having a thickness of 1.0 mm, a square of 300 mm, and a density of 1.06 g / cm ³ was obtained. Table 1 shows the mechanical properties of the sheet.

Comparative Example 2 Using the same raw materials as used in Example 1, the raw material mixing ratio was 100 g of silica-alumina fiber, 9 g of wollastenite, 12 g of Na-montmorillonite, and NBR latex.
2 g was processed in the same manner as in Example 1 to obtain a sheet having a thickness of 1.0 mm, a square of 300 mm and a density of 1.06 g / cm ³ . Table 1 shows the mechanical properties of the sheet.

Comparative Example 3 The same raw materials as used in Example 1 were used, and the mixing ratio of the raw materials was 61 g of silica-alumina fiber, 55 g of Na-montmorillonite, and 15 g of NBR-based latex. By performing the same processing as in Example 1, the thickness is 1.0 mm, the square is 300 mm, and the density is 1.06.
g / cm ^{3 as} a sheet. Table 1 shows the mechanical properties of the sheet.

Comparative Example 4 The same raw materials as those used in Example 1 were used, and the mixing ratio of the raw materials was 49 g of silica-alumina fiber, 67 g of wollastenite, 15 g of NBR-based latex, and the above-mentioned Na-montmorillonite was not used. 1.0mm thickness, 300mm square, density 1.06g /
cm ³ sheet-like material. Table 1 shows the mechanical properties of the sheet.

Regarding the results of Examples 1 and 2 and Comparative Examples 1 to 4; As is clear from Table 1, in the case where only a small amount of the ceramic-based inorganic fiber was added (Comparative Example 1), the fiber amount was small, and the high-temperature recovery Bad rate. On the other hand, the one to which a large amount of the ceramic inorganic fiber was added (Comparative Example 2) had a poor tensile strength because the fiber was significantly broken in the pressing step during molding. Therefore, it is understood that the amount of the ceramic inorganic fiber in the present invention must be used in the range of 35 to 80 wt%.

In addition, it is understood that the amount of wollastenite must be used in the range of 2 to 50% by weight in the present invention because the same properties as those of the ceramic inorganic fiber are exhibited. (Comparative Examples 3 and 4) Next, with respect to the amount of the inorganic binder added, only a small amount was added (Comparative Example 4), so that the bonding strength of Na-montmorillonite was weakened, so that the tensile strength was reduced. However, the restoration rate is improved by an increase in the amount of fibers. On the other hand, when a large amount of this inorganic binder was added (Comparative Example 3), the binding force of Na-montmorillonite was strong, and the tensile strength was good. However, the restoration rate is reduced by the amount of the fiber. Therefore, it is understood that the amount of the inorganic binder in the present invention must be used in the range of 5 to 35% by weight.

As for the amount of the organic elastic substance, the one in which only a small amount was added (Comparative Example 2) had insufficient tensile strength due to insufficient sheet formability. On the other hand, in the case where a large amount of the organic elastic substance is added (Comparative Example 1), the organic elastic substance is carbonized or burned off at a high temperature, so that the high-temperature tensile strength and the high-temperature recovery rate are extremely low. Therefore, it is understood that the amount of the organic elastic substance in the present invention must be used in the range of 2 to 25% by weight.

Example 4 Next, in order to examine the performance of the sheet-like gasket of the present invention, the gasket-like sheet of Example 1 was punched out to a predetermined size, attached as a gasket between a head of an automobile engine and an exhaust manifold, and the displacement was reduced.
Exhaust gas was flowed into the exhaust manifold with a 2000cc DOHC turbo engine at an exhaust gas temperature of 900 ° C for 100 hours, and a durability test was performed. During this durability test, no serious problem such as gas leakage occurred, and the gasket of Example 1 performed a sufficient gasket function.

Example 5 Further, after processing the gasket-like sheet of Example 1 to a predetermined size, it was mounted as a power vest gasket using a metal plate of SUS 304 as a gasket for a turbo engine and an elbow building of an automobile engine, and the same durability test as described above. However, no serious problem such as gas leakage occurred during the durability test, and the gasket-like sheet of Example 1 performed a sufficient gasket function.

〔The invention's effect〕

As described above, according to the present invention, a high-temperature gasket that does not use asbestos that is harmful to the human body can be obtained. Moreover, even at a high temperature of 950 ° C., the fibers are not lost and powdered due to combustion oxidation, so that they are excellent in gas sealing properties, heat insulation properties, wind erosion properties and the like.

 As a result, there are the following ripple effects.

First, as an automobile, (1) Since the exo-sheet manifold reduces the amount of heat to the cylinder head, the amount of heat transferred to the cooling water flowing through the cylinder head is reduced, and the radiator is downsized. The engine room can be effectively used at low cost.

(2) The temperature of the flange surface where the exo-sheet / manifold contacts the cylinder head is higher than that of the conventional technology, and the temperature distribution becomes uniform. Therefore, the cost reduction can be achieved by reducing the thickness of the flange portion by reducing the thermal distortion of the flange surface. Since the temperature of the gas in the exhaust manifold also increases, the exhaust emission can be reduced, and the catalyst can be highly activated.

(3) Due to the rise in the exhaust gas temperature in (2), the exhaust heat is converted into the work amount in the supercharged engine.
The engine output can be improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiko Shiratani 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Takehisa Yaegashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 56) References JP-A-61-200192 (JP, A) JP-A-62-103132 (JP, A)

Claims (1)

(57) [Claims] 1. A beater sheet-like gasket formed by paper-mixing a slurry of fibers, elastic materials, and the like, and laminating the mixture into ceramic-inorganic fibers of 35 to 80% by weight, wollastenite of 2 to 50% by weight, and organic elastic material of 2 to 25% by weight. %, And a high-temperature gasket comprising a composition containing 5-35 wt% of an inorganic binder.