JPH03106982A - High-temperatuer gasket and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a high-temperature gasket showing excellent sealing properties and heat resistance even at temperature as high as 950 deg.C or above and suitable for application to an automobile engine, etc., by using ceramic fibers, an unexpanded vermiculite, an organic elastic material and an inorganic binder as the constituents. CONSTITUTION:A high-temperature gasket consisting of 35-80wt.% inorganic ceramic fibers (preferably having a diameter smaller than 12mum and a shot content of at most 20%) (e.g. silica/alumina ceramic fibers); 5-20wt.% unexpanded vermiculite (preferably having a particle diameter of 0.1-2.8mm and preferably treated with a sodium salt of an organic acid); 5-25wt.% organic elastic material (e.g. a natural or synthetic rubber latex): and 5-35wt.% inorganic binder (e.g. an activated sodium montmorillonite). The gasket is produced by wet mixing a specified composition to form a sheet, removing it from a press, drying it, and hot pressing it.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a high-temperature gasket and a method for manufacturing the same, and in particular to a gasket that exhibits excellent sealing properties and heat resistance even under temperature conditions exceeding 950°C. This is a proposal for Lukaskeft, which is suitable for use in automobile engines, etc., and is constructed with ceramisox as the main ingredient instead of asbestos. [Prior Art] Conventional high-temperature gaskets used in the above-mentioned applications use asbestos as the main raw material, as well as natural rubber, nitrile rubber (NBR), and styrene-butadiene rubber (SBR) to impart elasticity. It is common to use an isoelastic material and an auxiliary agent such as a vulcanizing agent added as necessary. By the way, Gas Kent for such uses include joint sheet-shaped Gas Kent obtained by heating and shaping asbestos and an elastic substance, and slurry made by mixing and fixing asbestos and an elastic substance such as emulsion latex. There was a beater seat-shaped gas keft obtained by

These known gaskets mainly contain 60% to 95% asbestos fibers, and because the asbestos fibers are scattered not only during the gasket manufacturing process but also at the construction facility, they are considered to be at risk of causing health problems. , improvement was desired. For this reason, even in our country, the handling of cancer has been regulated through various laws and regulations since the signing of the International Cancer Convention in 1971. For example, April 1, 1975
The establishment of the "Ordinance on Prevention of Hazards from Specified Chemical Substances, etc."
On March 30, 1971, a part of the Labor Standards Enforcement Regulations was amended, and it was established that diseases caused by carcinogenic substances or factors,
or for work-related illnesses in carcinogenic processes;
This includes the designation of ``lung cancer or mesothelioma resulting from work that involves exposure to asbestos.''

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, with the approval of OMB (Office of Management and Budget), a proposal was made to ban the use of asbestos products from January 1988, and in 1991 They are proposing a complete ban on its use starting in 2020.

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

In addition, not only in the above two countries, but also internationally, in June 1986,
Based on a proposal by the International Labor Organization (ILO) in February, the ``Convention and Recommendations on Safety in the Use of Asbestos'' is being discussed and deliberated, and in Sweden in particular, the use of asbestos products is expected to be banned as early as 1985.

In response to this international situation, recently, inorganic fibers such as Seviolite fiber, glass fiber, carbon fiber, and stainless steel fiber, as well as aromatic boria fiber, phenolic fiber, polyethylene fiber, etc., have been introduced as alternative fibers to asbestos. Attempts have been made to produce gaskent using "organic fibers."

[Problem that the invention seeks to solve]

As mentioned above, gas kefts using asbestos fibers have the problem of pollution, and although they can maintain good physical properties up to around 600°C, at higher temperatures, such as 950°C or higher, crystallization occurs. The drawback was that dehydration caused strength deterioration.

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

For example, among the above-mentioned inorganic fibers, for example, Seviolite has water of crystallization, and therefore, like the above-mentioned asbestos, strength deterioration occurs in a high temperature range. Moreover, when a gasket is manufactured using only this inorganic fiber, there is a problem in that the tensile strength and the like are inferior, similar to gaskets using asbestos. In particular, carbon fibers among inorganic fibers, aromatic polyamide fibers, phenol fibers, polyethylene fibers among organic fibers, etc., deteriorate significantly in their fiber properties at around 200°C, and at temperatures above 400°C they completely carbonize or It is known that it is characterized by burning out and deterioration of the bond, and therefore there is a problem that it cannot be used at high temperatures of 400° C. or higher.

The purpose of the present invention is to propose a high-temperature gasket that does not have the problems of high-temperature gaskets made of asbestos as described above, and also does not have the problems of high-temperature gaskets made of various inorganic fibers. , and an advantageous manufacturing method thereof. [Means for Solving the Problems] The present invention solves the lack of performance as a gasket due to insufficient tensile strength and recovery rate, that is, the lack of sealing function, durability, reliability, etc. First, we decided to improve the heat resistance of Gaskent by using ceramic inorganic fibers, and then to improve the recovery rate and heat resistance of Gaskent by using unexpanded vermiculite. This method is characterized in that the strength of the gasket in the high temperature range is compensated for by using a suitable inorganic binder.

In addition, in manufacturing such a gasket, a method is adopted in which the ceramic inorganic fiber, unexpanded vermiculite, inorganic binder, and organic elastic material are wet-mixed, dehydrated, pressed, dried, and then hot-pressed. , it was decided to overcome the problems of the above-mentioned prior art all at once.

In particular, in the present invention, since ceramic inorganic fibers and unexpanded vermiculite are used as materials,
Gaskesoto with high heat resistance and high recovery rate is obtained.

That is, the present invention provides a beater sheet-like gas get obtained by making a paper from a slurry of a mixture of fibers, elastic substances, etc.
5-20 wt% of unexpanded verculite, 5-25 wt% of organic elastic material, and 5-35 wt% of inorganic binder.
A high-temperature gasket, characterized in that it is produced by wet-mixing such a blend, drying it after dehydration pressing, and then real-pressing it. [Function] The gasket according to the present invention is basically obtained by mixing and fixing an aqueous solution in which Cerafukus inorganic fibers, unexpanded vermiculite, an organic elastic substance, and an inorganic binder are dispersed. This is a beater sheet-like gasket made by laminating a slurry to a certain thickness by forming a slurry with a paper-making machine using a slurry, in which auxiliary additives such as a vulcanizing agent are added as necessary. In recent years, this beater sheet-shaped gasket has been widely used because it can provide a gasket with higher uniformity than a jointed sheet-shaped gasket.

Now, one of the main components of the gasket structure of the present invention is ceramic inorganic fiber. As the ceramic inorganic fibers, artificial inorganic fibers such as silica-alumina ceramic fibers, crystalline fibers of alumina and mullite, and silica fibers are used. In addition, ultrafine glass fibers can also be used for those that have low requirements for heat resistance, for example, when the operating temperature is 300° C. or lower.

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 gaskesoto, 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 (ratio to the amount of inorganic fibers).

Moreover, it is desirable that the fiber diameter of this ceramic inorganic fiber is less than 12 μm. The reason for this is that when the fiber diameter is 12 μm or more, the number of fibers per unit volume decreases, the sheet density decreases, and it is easy to break in the press process after papermaking in the manufacturing process, resulting in poor airtightness.
This is because it deteriorates the sealing performance) or tensile strength.

In particular, a size of 1 to 3 μm is advantageous.

Furthermore, this inorganic fiber needs to have excellent rigidity and holdability as a sheet-like product. This is because gaskets generally must have excellent compression and recovery characteristics.

Now, the high-temperature gasket of the present invention must contain 35 to 80 wt% of ceramic inorganic fibers having the above-mentioned properties. This is because if the amount of such ceramic inorganic fibers is less than 35% or 1 lt%, the recovery rate and tensile strength at high temperatures will decrease, while if it is more than 80 wt%, the fibers will easily break and the tensile strength will decrease. In addition to this, airtightness is also reduced. Next, in the high temperature gasket of the present invention, it is necessary to contain a predetermined amount of unexpanded vermiculite in order to improve the recovery rate and heat resistance. This unexpanded vermiculite is a particulate material with a flake multilayer structure, consisting of a Si-0 tetrahedral layer and Mg-0 (OH) or AI.
- It is a hydrated mineral with excellent elasticity and heat insulation properties due to its mica-like structure, which is based on a 2:l type layer structure with 0 octahedral layers and is connected through water between the layers. Therefore, when heated, it dehydrates, peels and expands, and stretches 10 to 25 times.

However, because the bond between the eyebrows is poor, it becomes flaky with the slightest external force, making it difficult to maintain its shape by itself.

Therefore, in the present invention, it is advantageous to treat this vermiculite with sodium organic acid. The reason for this is that the expansion rate and expansion force of unexpanded vermiculite are
It increases in proportion to the particle size. In particular, when manufacturing sheets, particles with a small particle size that have good dispersibility are preferred;
Therefore, the sheet of the present invention has a small particle size of 0.1 to 2.8.
I'm going to use a related one. A sheet using vermiculite with such a small particle size has low expansion force and elasticity.

Therefore, the present inventors previously discovered that by replacing the cations between the layers of vermiculite particles with organic acid sodium, the expansion force and elasticity increase, and furthermore, the vermiculite expands from a lower temperature than unsubstituted vermiculite. (Japanese Unexamined Patent Publication No. 59-230737).

This is because it was found that even when vermiculite with a small particle size is used as in the present invention, the same effect can be obtained by treating it with sodium organic acid, resulting in a sheet with excellent properties. be.

The reason why the expansion power of the unexpanded vermiculite is improved by the treatment with the organic acid sodium, that is, the treatment of immersing the unexpanded vermiculite in the organic acid sodium aqueous solution is considered to be as follows. That is, by replacing the calcium ions or magnesium ions between the eyebrows with sodium ions, water between the eyebrows becomes difficult to drain 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 such unexpanded vermiculite is less than 5 wt %, the expansion force of the sheet decreases, making it difficult to obtain a high recovery rate. On the other hand, 20wt
If it exceeds %, the tensile strength will drop significantly because verculite becomes granular. Next, the high temperature gas keft of the present invention contains an organic elastic material. The organic elastic material as a gasket material is
Particularly useful materials include commonly used organic elastomers, such as natural rubber emulsions or NBR. S
A Hewei rubber latex binder such as BR is suitable.
Note that in order to improve the durability and strength of the rubber latex, a rubber vulcanizing agent or the like (eg, sulfur, sulfur chloride) can be used. However, in the present invention, strength, elastic modulus, and recovery rate are ensured by an inorganic binder such as montmorillonite, ceramic inorganic fibers, and unexpanded vermiculite, so this organic elastic material is used as an auxiliary material. It can be said that the amount of the organic elastic material to be blended is preferably as small as possible because it burns or carbonizes at high temperatures and deteriorates the properties.
The range is 5% by weight.

Next, the high-temperature gas keft of the present invention also contains the above-mentioned inorganic binder. As such an inorganic binder, montmorillonite, clay, talc, kaolinite, amorphous tetrasilicified fluorine mica, etc. are used. Among these, montmorillonite easily swells in water and has excellent bonding strength, so
It is effective and suitable for maintaining strength at temperatures above 00°C. This montmorillonite is usually the main component of naturally occurring bentonite ore. These can be broadly divided into: (1) Na-montmorillonite, which is rich in Na ions and exhibits high swelling properties by absorbing a large amount of water, and (2) Ca-montmorillonite, which is rich in Ca and Mg ions and has low swelling properties. In addition, there is also Na-montmorillonite, which is activated by treating Ca-montmorillonite with soda.
However, all montmorolinites exhibit swelling properties to varying degrees, unlike other hydrous silicate alfructium minerals such as kaolinite and talc. Among them, activated Na-montmorillonite has particularly excellent swelling properties and binding properties, and thus satisfies the purpose of the present invention. Its chemical formula is expressed as follows.

(OH)msi(A131aMgo.hh)Ozo
Nao. bb Furthermore, as swelling inorganic binding substances, Seviolite, Gekai tetrasilicified fluorine mica, ball clay, etc. are known as substances that exhibit the same performance as the above-mentioned montmorillonite, and may be used in place of the montmorillonite. ．． The amount of this inorganic binder blended is limited by the required performance and manufacturing method, but if the amount is insufficient and becomes less than 5%, not only will strength not be obtained, but the paper will not be formed properly. The sheet becomes uneven. Furthermore, if a large amount of inorganic binder is used, such as exceeding 35%, the rubber latex will not aggregate sufficiently due to its swelling property in water, resulting in poor freeness and making it impossible to produce a sheet-like product. Furthermore, since the blending ratio of the fibrous material is also limited, the strength and elasticity are also adversely affected.

From this, the amount of the inorganic binder is 5 to 35 wt%.
A range of is appropriate.

In addition to the above-mentioned compounding materials, the high-temperature gas keft of the present invention further contains kaolinite (Al■SizOs).
Inorganic substances such as (OH)4) which do not have swelling properties but can be expected to have binding strength may be blended as reinforcing agents.

Now, when a composition compounded at the above-mentioned ratio is shaped and pressed into a sheet as described later, it has a density of 1.0 g 7 cm3 to 2.0 g/CIm"
It shows 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. In particular, the gasket of the present invention has a density of 2.0 g/c.
When it is larger than 1, the inorganic fibers may break, and the tensile strength, elastic modulus, and recovery rate may decrease. In our research, 1.2g/cm3 to 1.68/el
A density range of m' was preferred.

The production of the gasket of the present invention having such a density is characterized by wet-mixing the compounded materials to form a slurry, paper-forming the slurry, dehydrating it, and hot-pressing the slurry after drying. That is, when hot pressing is employed, fluidity is generated in the organic 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.

In addition, regarding the above-mentioned gaskets of the present invention, SOS
It is also effectively applied to a gasket wrapped in a metal plate such as 304, a steel best gasket with a metal plate as a core, and a gasket sheet whose opening is processed with a metal grommet.

〔Example〕

Example I SiClz: 50wt%, AhOz: 50W
Silica-aluminium-based ceramic fiber with an average fiber diameter of 1.8 μm (trade name: Ibiwool,
(manufactured by IBIDEN Co., Ltd.) was subjected to shot removal processing to reduce the shot content of 44 μm or more to 20% or less, and this was further defibrated in 69 g of water 301.

Next, 12 g of unexpanded vermiculite and 30 g of Na-Montomori Kuchinite were added to 30 N of the above-mentioned water in which Ibiwool had been defibrated, and mixed well. Then, NBR latex (trade name: 22 Ball 1562. 27g of Nippon Zeon Co., Ltd. (manufactured by Zeon Co., Ltd., tH content: 41%) was added thereto, and the slurry was agglomerated with sulfuric acid band.

Next, this slurry was made into a wet sheet with a thickness of 8 mm by using a hand paper machine measuring 340 m x 340 m. This sheet-like material was pressed with a surface pressure of 300 kg/C-, and
It was dried under the conditions of 0°C and 1hr. The dried sheet was hoft-pressed at a surface pressure of 60 kg/am'' and a temperature of 300°C for 15 minutes.The ends of this sheet were cut to give a thickness of 0.
A sheet-like product measuring 8 m square, 300 m square, and having a density of 1.25 g/c1 was obtained. Table 1 shows the mechanical properties of this sheet-like material.

Example 2 The same raw materials used in Example 1 were used, and the blending ratio of those raw materials was changed to silica-alumina ceramic fiber 6.
A mixture consisting of 9 g of unexpanded vermiculite, 30 g of Na-montmorillonite, and 27 g of NBR latex was treated in the same manner as in Example 1, and the thickness was 0.9 g.
A sheet-like product with a size of 75 mm, 300 nm square, and a density of 1.26 g/c was produced. Its mechanical properties are shown in Table 1.

Example 3 Using the same raw materials as used in Example 1, the blending ratio was changed to 69g of silica-alumina ceramic fiber.
A compound consisting of 27 g of unexpanded vermiculite, 30 g of Na-montmorillonite, and 27 g of NBR latex was treated in the same manner as in Example 1, and the thickness was Q, 9 m.
A sheet-like product having a square dimension of 1.248/c+s' and a density of 1.248/c+s' was produced. Its mechanical properties are also shown in Table 1.

Comparative Example 1 Using the same raw materials as used in Example 1, the blending ratio was changed to 69 g of silica-alumina-based ceramic fiber.
1 A mixture consisting of 3 g of unexpanded barculite, 30 g of Na montmolyte, and 27 g of NBR latex was treated in the same manner as in Example 1 to give a thickness of 0.
A sheet-like product measuring 75 m, 300 mm square, and having a density of 1.23 g/c1 was produced. Its mechanical properties are shown in Table 1.

Comparative Example 2 The same raw materials as in Example 1 were used, and their blending ratio was 69g of silica-alumina ceramic fiber, 45g of unexpanded vermiculite, and 30g of SNa-montmoriteite.
, and 27 g of NBR-based latex was treated in the same manner as in Example 1 to obtain a 300
A sheet-like product with a va angle and a density of 1.27 g/cts was produced. Its mechanical properties are shown in Table 1.

Comparative Example 3 The same raw materials as in Example 1 were used, but the difference was that the unexpanded vermiculite was not used, and 69 g of silica-alumina-based ceramic fiber, Na
-Montmorillonite 30g, NBR Latinx 27g
By applying the same treatment as in Example 1, a compound consisting of
A sheet-like product with a weight of 100 g/cn+" was produced. Its mechanical properties are shown in Table 1.

As can be seen from Table 1, those using unexpanded vermiculite have a high recovery rate in the high temperature range. Therefore, it can be seen that it is possible to prevent torque down. However, if unexpanded vermiculite is used outside the range prescribed in the present invention, for example in a large amount, the tensile strength will drop significantly because unexpanded vermiculite is in the form of particles. Therefore, when used in an engine body, for example, it cannot follow the expansion and contraction of the engine body due to heat. On the other hand, if it is not added at all, the recovery rate in the high temperature range will be extremely low and torque down will occur. Therefore, good sealing performance cannot be obtained.

Therefore, for this unexpanded vermiculite, 5~
It can be seen that it must be used within a range of 20 wt%.

Next, in order to investigate 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 and installed as a gasket between the head and exhaust manifold of an automobile engine.
A durability test was conducted by flowing exhaust gas into the exhaust manifold of a 000 cc, D O H C turbo engine for 100 hours at an exhaust gas temperature of 900°C. During this durability test, no serious problems such as gas leakage occurred, and the gasket of Example 1 performed a sufficient gasket function.

〔Effect of the invention〕

As explained above, the high-temperature gasket of the present invention can be obtained without using asbestos, which is considered to be harmful to the human body. In addition, it has high strength and is superior in terms of gas sealing properties, heat insulation properties, wind erosion properties, etc. because the fibers do not disappear or become powder (bond deterioration) due to combustion oxidation even at high temperatures of 950°C.

As a result, there will be the following ripple effects:

Firstly, for automobiles, (1) exhausts and manifolds are used for cylinders and
Since the amount of heat transferred to the head is reduced, the amount of heat transferred to the cooling water flowing through the cylinder head is reduced, allowing for a smaller radiator, lower costs, and more effective use of the engine room.

(2) The temperature of the flange surface where the exhaust and manifold are in contact with the cylinder head is higher than that of conventional technology, and the temperature is uniformly distributed, so the cost is reduced by reducing the thickness of the flange part by reducing thermal strain on the flange surface. Furthermore, since the gas temperature in the exhaust manifold also rises, exhaust system tension 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 the engine output can be improved.

Claims (1)

[Claims] 1. Ceramic inorganic fiber 35-80 wt%, unexpanded vermiculite 5-20 wt%, organic elastic material 5-25 wt%
A high-temperature gasket comprising 5 to 35 wt% of an inorganic binder and an inorganic binder. 2. A method for producing a high-temperature gasket, which comprises wet-mixing a mixture of ceramic inorganic fibers, unexpanded vermiculite, an organic elastic material, and an inorganic binder, dehydrating and pressing, drying, and then hot pressing.