JPH02180982A - Production of gasket for high-temperature use - Google Patents

Abstract

PURPOSE:To obtain the title gasket which is a nonasbesitine beater sheet type, can withstand high-temperature conditions and has highly heat-insulating properties by mixing a material for gasket containing an inorganic fiber other than asbestos and an elastic substance in water, making the mixing into a sheet, pressing this sheet and drying and hot-pressing the sheet. CONSTITUTION:A material for gasket based on an inorganic fiber other than asbestos (e.g. alumina, silica fiber or carbon fiber) and an elastic substance (e.g. montmorillonite or NBR emulsion latex) is mixed in water and the obtained mixture is made into a sheet, which is dewatered by pressing and dried and hot-pressed desirably at a temperature of 50-350 deg.C under a pressure of 5-150Kg/cm<2>.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a high-temperature gasket, which is resistant to high-temperature conditions, has high heat insulation properties, and is made of asbestos-free to make it harmless. The present invention relates to a method of manufacturing a gasket.

[Conventional technology]

Conventionally, sheets containing asbestos as a main component, such as asbestos beater sheets and joint sheets, have been widely used as gaskets. These sheets have base fibers such as
Contains asbestos in a proportion of 60-95% by weight. Therefore, asbestos fibers were scattered not only during the sheet manufacturing process but also from the equipment used, posing a risk of health problems.

However, in recent years, interest in asbestos pollution has increased, and research has been conducted to manufacture beater sheets or joint sheets using asbestos alternative fiber base materials. As substitute fibers for asbestos, attempts have been made to manufacture sheet materials using inorganic fibers such as glass fiber, carbon fiber, potassium titanate fiber, and stainless steel fiber, or organic fibers such as aromatic polyamide fiber, phenol fiber, and polyethylene fiber. being done.

Furthermore, as a method for manufacturing such a gasket, a beater sheet method has been disclosed in which gasket raw materials are wet-mixed by high-speed stirring, followed by paper forming, dehydration pressing, drying, and molding (British Patent No. 1023425). .

[Problem to be solved by the invention]

However, the conventional manufacturing method has the following problems. First, in the process of manufacturing a joint sheet, it is difficult to uniformly disperse and knead a binder that binds inorganic or organic fibers. In addition, when the joint sheet raw material is heated and rolled using a hot roll and a cooling roll, the binder adheres to the cooling roll, causing wrinkles and other problems in the joint sheet, as well as significant uneven thickness. Furthermore, there is a problem that it may become impossible to form into a sheet, resulting in poor processability.

On the other hand, although the beater sheet method is superior in processability and cost compared to the joint sheet method, it has the following problems.

That is, during press processing after papermaking, the fibers serving as the base material are crushed, resulting in a decrease in the aspect ratio of the fibers, and the tensile strength of the formed sheet becomes significantly inferior or varies. or,
It is impossible to completely remove moisture during pressing, and if dehydration is performed in the post-process, continuous pores will form after the moisture has passed through, reducing airtightness, that is, gas sealing.
Tensile strength also decreases. Therefore, an object of the present invention is to solve such problems and provide a good gasket that can withstand high-temperature use.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for manufacturing a non-asbestos beater sheet type gasket mainly composed of inorganic fibers and elastic substances, including mixing raw materials for gaskets containing inorganic fibers and elastic substances in water; Make paper,
A method for producing a high-temperature gasket is provided, which comprises the steps of pressing, drying, and hot-pressing the resulting sheet.

The gasket raw material used in the present invention contains inorganic fibers other than asbestos and an elastic material.

Inorganic fibers include alumina fibers, silica fibers,
A single fiber or a combination of fibers with high heat resistance such as mullite fiber, carbon fiber, potassium titanate fiber, etc. are used, but glass fiber can also be used when the requirement for heat resistance is low. As a gasket-like material, it is necessary to use rigid fibers to have compression recovery properties and to have excellent retention properties as a sheet-like material, so the diameter of this inorganic fiber is 1.
It is desirable that the thickness is μm or more. In addition, the fiber diameter is 12 μm
It has been found that the above method is not suitable because it will be crushed in the subsequent hot press step.

Elastic substances include inorganic binding substances and organic elastic substances. The present invention is particularly directed to the manufacture of high-temperature gaskets using inorganic binding materials, and the use of such inorganic binding materials has been disclosed by the present inventors in Japanese Patent Application No. 257,275/1983. However, this inorganic binding substance is particularly an inorganic substance that swells in water and has binding strength, and examples thereof include montmorillonite, seviolite, synthetic silicified fluorine-type mica, and ball clay. Organic elastic materials are also commonly used because they are useful in gasket sheets. These include natural rubber emulsions and synthetic rubber emulsion latexes such as NOR and SBH, but rubber vulcanizing agents (eg, silicone), vulcanization accelerators, etc. are also used in combination.

The present invention relates to a method of manufacturing a beater sheet type gasket using a raw material containing inorganic fibers and an elastic substance, or C, I,
Direct Blue 273 etc.) may also be included.

Further, although not limited thereto, the present invention is particularly suitable for manufacturing the high-temperature gasket disclosed in the above-mentioned Japanese Patent Application No. 62-257275. This high temperature gasket contains 35-80% by weight of ceramic inorganic fibers and 2-30% of carbon fibers.
% by weight, 5-25% by weight of an organic elastic material, and 5-35% by weight of an inorganic binding material.

Next, the manufacturing process of the high temperature gasket of the present invention will be explained.

The manufacturing process includes a wet mixing process, a papermaking process, a dehydration process, a drying process, a hot press process, and a punching process.

The wet mixing process of the present invention is a process in which raw materials containing inorganic fibers and elastic substances (inorganic binding substances and/or organic elastic substances) are uniformly stirred and mixed in water. However, in this wet mixing step, after the raw material slurry is mixed uniformly, the slurry is coagulated and fixed using a polymer flocculant such as polyacrylamide or an ionic flocculant such as aluminum sulfate.

In this step, the slurry concentration is desirably 3% by weight or less in order to prevent the base fibers from being broken and the aspect ratio of the base fibers to decrease and to uniformly mix the slurry IJ-.

The papermaking process is a process in which the slurry prepared in the wet mixing process is formed into a paper layer, forcedly dehydrated, and wet sheets of a predetermined thickness are continuously or intermittently made.From the viewpoint of productivity, thick sheets are made continuously. It is preferable to use a single-mesh continuous paper making machine.

The dehydration pressing process is a process of dehydrating the wet sheet formed in the papermaking process using a batch or roller press. The press used in this step is preferably a batch type press in order to prevent the base fibers in the wet sheet from being oriented and to reduce the water content in the sheet as much as possible. In the present invention, in order to avoid pulverizing the inorganic fibers as much as possible in this pressing process, the pressure is significantly lower than the conventional press pressure of 350 mm.
Press at a pressure of about kg/ctj.

The drying process is a process of drying the wet sheet that has been dehydrated and pressed to a predetermined thickness in the pressing process.

In the drying step of the present invention, the sheet-like material is sufficiently dried to reduce its moisture content. In this process, it is desirable to dry at a temperature of 250°C or lower to prevent the organic polymer contained in the elastic material (inorganic bond, organic elastic material) in the sheet from deteriorating. In order to quickly evaporate moisture, a drying temperature of 100° C. or higher is desirable.

The present invention is characterized in that hot pressing is performed after the drying step. By this hot pressing, the matrix portion of the sheet-like material, that is, the elastic material, is given plasticity, and by pressing, the properties of the gasket can be improved without crushing the inorganic fibers. In the hot press, the dried sheet material is pressed at a temperature of 50°C or more and less than 350°C and 5kg/c11! The above is carried out at a press pressure of 150 kg/ci without swirling. In order to prevent the inorganic fibers from being crushed (decreasing the aspect ratio), the inorganic fibers themselves need to respond to the press pressure within the sheet-like material during the hot pressing process, and for this purpose the elastic material is made to have plasticity. At temperatures below 50°C, it is difficult to impart plasticity to elastic substances, while at temperatures above 350°C, some elastic substances harden and inhibit plasticity.
A temperature range of 50-350°C is preferred. In addition, if the press pressure is less than 5 kg/crI, the required bulk density as a gasket-like material cannot be obtained, and if it is more than 150 kg/ct1, the base fibers will be crushed, so the pressure should be 5 to 150 kg/c.
It is desirable that the press pressure be within the range of i.

Then, punch out the shape of the gasket to be used.

[For production]

In the present invention, in the manufacture of beater sheet type gaskets, dehydration pressing is performed at a sufficiently low pressing pressure that the inorganic fibers are not crushed in the papermaking, dehydration, and drying processes, and the moisture content is sufficiently reduced in the subsequent drying process. The airtightness of the sheet-like material decreases due to the holes during water removal, but hot pressing is then performed to impart plasticity to the elastic material in the sheet-like material and improve the airtightness. In addition, in this hot pressing process, the elastic material is pressed with plasticity, so the inorganic fibers respond without being crushed.
The bulk density of the sheet material is improved. Furthermore, since the inorganic fibers are not ultimately crushed, the tensile strength of the sheet material is also improved synergistically with the plasticizing effect of the elastic material. In addition, hot pressing raises the temperature of the elastic material to a point close to hardening, so
The high temperature strength of the gasket is also improved.

〔Example〕

Next, the present invention will be explained below by way of examples.

Example 1 7 kg of alumina-silica fibers with a diameter of 2 μm (trade name Ibiwool Bulk) and carbon fibers with a diameter of IO μm (fiber length 3
0 ma + > 3 kg of base fiber, 4 kg of montmorillonite (trade name: Kunivia G) as an inorganic binding substance, and 5 kg of NBR emulsion latex (trade name: Pole L
kg was added to 1000 β of water, stirred and mixed using a pulper for 10 minutes, and then made into aluminum sulfate and coagulated to create a gasket slurry.

Next, the obtained slurry was passed through a single-mesh continuous paper machine to a width of 300 mm.
A continuous sheet with a thickness of 10 mm and a thickness of 10 mm was formed. This was cut into a length of 600 mm using a guillotine cutter, and then dehydrated using a hydraulic press at 340 kg/cnf. Then, dry it in a hot air dryer at 130℃ to a thickness of 1
．． A sheet-like product having a size of 2 mm, a width of 310 mm, and a length of 620 mm was created.

Then, the dried sheet material was hot-pressed at a hot plate temperature of 290°C and a surface pressure (press pressure) of 60 kg/crd for 10 minutes to give a thickness of 1.2 ff1m and a bulk density of 1.1 g/crd.
A gasket-like sheet of c++t was obtained.

The tensile strength of this gasket-like sheet is JIS-63.
According to 01 hot-flow rubber physical test method (3), room temperature, 200°C
Measurement was performed after X2Hr heat treatment and 400°C X2Hr heat treatment. Table 1 shows the relationship between heat treatment temperature and tensile strength.

Example 2 7 kg of alumina-silica fiber (trade name Ibiwool Bulk) with a diameter of 2 μm, 3 kg of rock wool with a diameter of 5 μm,
Using 4 kg of montmorillonite (trade name Knipia G) as an inorganic binding substance, 5 kg solid content of NBR emulsion latex (trade name Kopol L X-1562) as an organic elastic substance, and 1 kg of fibrillated aromatic polyamide fiber A gasket-like sheet was prepared in the same manner as in Example 1, and the tensile strength was measured in the same manner as in Example 1. Table 1 shows the relationship between heat treatment temperature and tensile strength.

Comparative Example 1 Using an asbestos beater sheet, tensile strength was measured in the same manner as in Example 1. The results are shown in Table-■.

Table 1 Example 3 The gasket-like sheet of Example 1 was punched out to the specified dimensions and installed as a gasket between the head and exhaust manifold of an automobile engine, with a displacement of 2000c.
c. A 100-hour durability test was conducted using a DOHC turbo engine at a temperature of 850°C for the exhaust gas flowing into the exhaust manifold.

During this durability test, no serious problems such as gas leakage occurred, and the gasket of Example 1 performed a sufficient gasket function.

In addition, results equivalent to those of Example 1 in Table 1 were obtained regarding tensile strength, and it was confirmed that the product was highly durable.

FIGS. 1 and 2 show the relationship between the hot pressing temperature and pressure and the tensile strength, and the relationship between the hot pressing time and the tensile strength when a gasket was produced in the same manner as in Example 1. The method for measuring tensile strength was also the same as in Example 1, and the measured value was at room temperature.

FIG. 3 shows an electron micrograph of a gasket sheet produced in the same manner as in Example 1 (hot press 290° C. x 60 kg/cnf) at a magnification of 1000 times. FIG. 4 shows an electron micrograph of a gasket produced in the same manner as in Example 1 but hot pressed at 170° C. and 150 kg/an. Figure 5 shows the same procedure as in Example 1, except that the weight is 350 kg.
Dehydrated and pressed with /cut, dried at 150°C,
Electron micrograph of a gasket that was not hot pressed,
FIG. 6 is an electron micrograph of a gasket prepared in accordance with Example 1, except that it was dehydrated and pressed at 350 kg/cm, dried at 150° C., and then pressed at room temperature at 80 kg/ctl. From these photos, it can be seen that those that were not hot pressed (Figure 5) lacked compactness compared to those that were hot pressed (Figures 3 and 4), and that they did not stand at room temperature after drying. It can be seen that the fibers of the pressed sheet (Figure 6) are folded within the sheet.

〔Effect of the invention〕

In the high-temperature gasket manufactured by the method of the present invention, plasticity is imparted to the inorganic binding substance and organic elastic substance contained in the sheet by hot pressing, and since the inorganic fibers are not crushed, the quality of the gasket (tensile strength, water content, The organic elastic material in the sheet is dried and sufficiently cured by hot pressing, which eliminates leakage and adhesion to mating materials (seizure) during high-temperature use. be able to. Furthermore, the manufacturing process is simple and the manufacturing cost is low.

[Brief explanation of the drawings] Figure 1 is a diagram showing the relationship between hot pressing temperature and pressure and the tensile strength of the gasket, Figure 2 is a diagram showing the relationship between hot pressing time and the tensile strength of the gasket, and Figures 3 to 6 are electron micrographs (1000x magnification) showing the shapes of fibers in gaskets produced under various conditions.

Claims (1)

[Scope of Claims] 1. A method for producing a non-asbestos beater sheet type gasket mainly composed of inorganic fibers and elastic substances, which is obtained by mixing raw materials for gaskets containing inorganic fibers and elastic substances in water and forming paper. A method of manufacturing a high temperature gasket, comprising the steps of pressing, drying, and hot pressing a sheet.