JPH08311433A - Joint sheet - Google Patents

Abstract

PURPOSE: To obtain a joint sheet which is excellent both in general physical properties and in sealability and is suitable for being used under a low tightening pressure. CONSTITUTION: This mono- or multilayer joint sheet is produced by charging a kneaded mixture comprising substrate fibers, rubbers, rubber chemicals, and fillers into between a pair of cold and hot rolls, subject to the conditions that the mixture in at least one surface layer contains at least one filler selected from among kaolinite, carbon black, and white carbon, optionally together with other fillers; and that the sum of the amts. of kaolinite, carbon black, and white carbon in the surface layer accounts for at least 30wt.% of the total amt. of all the fillers in the layer.

Description

Detailed Description of the Invention

[0001]

This invention relates to a petrochemical plant,
The present invention relates to a joint sheet used as a base material for gaskets used in a wide range of fields such as various industrial machinery, automobiles and home appliances, and is particularly suitable as a joint sheet used for automobiles with a low tightening pressure.

[0002]

2. Description of the Related Art A joint sheet is a joint sheet prepared by thoroughly kneading a base fiber, a filler, a rubber chemical, and a rubber swollen with a solvent (or powder rubber or latex with a solvent added) with a Henschel mixer or the like. A forming composition (hereinafter referred to as a kneaded product) is prepared, and then the kneaded product is charged between a pair of rolls (calender rolls) including a hot roll (about 150 ° C.) and a cold roll (about 20 ° C.), It has been manufactured by laminating while heating and rolling on a hot roll side, evaporating and vulcanizing a solvent, and peeling a sheet laminated to a predetermined thickness. Depending on the product, the sheet-like material obtained in order to promote vulcanization may be further subjected to secondary vulcanization in an autoclave or the like. In addition to the above materials, a small amount of a softening agent, a plasticizer, a water swelling material or an oil swelling agent may be added as a constituent material, and a pigment may be blended from the viewpoint of storage and identification.

Conventionally, asbestos joint sheets have been used exclusively as joint sheets, and by utilizing the unique shape of asbestos fibers and excellent heat resistance, gaskets for pipes and equipment such as water, oil, air, and water vapor. Has been punched and used. Although asbestos fiber is an inorganic fiber, it is extremely flexible and highly fibrillated, and asbestos joint sheet uses 60 asbestos fibers that are thin and have a large surface area.
Approximately 85% by weight, the asbestos fibers are well dispersed and adhered to the rubber material, so the sheet surface laminated while heating and rolling is smooth and fits well with the flange. However, it retained good sealing properties.

However, asbestos fibers are natural minerals, and there is a concern that resource depletion will occur, and health problems that are presumed to be caused by asbestos fibers will become social problems and the use of asbestos tends to be restricted worldwide. Has become. By those things,
Recently, a joint sheet that does not use asbestos fibers at all and uses inorganic fibers and / or organic fibers other than asbestos fibers (called asbestos-free joint sheet or non-asbestos joint sheet, hereinafter abbreviated as NA joint sheet) ) Has come to be used.

[0005]

As the fibrous material used for this NA joint sheet, various organic fibers and inorganic fibers (other than asbestos) are used in combination according to the application, but compared with asbestos fibers. Most of them are thick and rigid. Therefore, in the NA joint sheet, swelling occurs due to fiber clumps on the surface of the sheet,
The surface roughness tended to increase, and it was difficult to fit in with the flange at a low tightening surface pressure, and there were cases where leakage occurred at the interface between the flange and the gasket. In addition, in recent years, in the industrial field such as the automobile industry, the thickness of the flange to be sealed has become thinner due to the reduction in size and weight of parts, the tightening bolt diameter of the flange tends to be thinner, and the number of bottles also tends to decrease. It is becoming impossible to apply sufficient tightening surface pressure to
Leakage is more likely to occur. Therefore, depending on the application, we are trying to improve the sealing property by giving swelling property to the internal fluid, but for punching processors and wholesalers, it will increase the variety of products by application, so punching scraps will be increased. The amount of waste has increased and the burden of inventory management has increased, and the amount of industrial waste has also increased, which has recently become a major environmental issue such as a treatment problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a single-layer or multi-layer joint sheet produced by charging a kneaded material comprising a base fiber, rubber, a rubber chemical and a filler between a pair of cold and hot rolls. In the above, the filler of the kneaded material constituting at least one surface layer contains kaolinite, carbon black, white carbon alone or in combination of two or more, or kaolinite, carbon black or white carbon together with other fillers. The joint sheet is characterized in that the amount of kaolinite, carbon black and white carbon in the surface layer is 30% by weight or more based on the total amount of the filler in the surface layer.

Here, it is desirable that the filler composition on both the front and back surfaces of the joint sheet be set to be predetermined so that both surfaces are smooth to enhance the sealing property, but at least one surface may be smooth depending on the purpose. In order to make the filler composition in the front surface layer or the back surface layer predetermined, it is necessary to use a kneaded material different from the core portion, which has a large effect on physical properties such as tensile strength and stress relaxation rate, in the front surface layer or the back surface layer. It is preferable to use a layered joint sheet, but when using a kneaded product of a single composition from the viewpoint of productivity etc., use the same kneaded material as the surface layer for the core part to form a single layer joint sheet. Also included in the present invention.

The base fiber used in the joint sheet of the present invention includes rock wool, carbon fiber, glass fiber, sepiolite, ceramic fiber, fused silica fiber, chemically treated high silica fiber, fused silica silicate fiber, alumina continuous fiber, stable fiber. Zirconia fibers, boron nitride fibers, alkali titanate fibers, wollastonite, whiskers, boron fibers, inorganic fibers such as metal fibers, aromatic polyamide fibers, polyamide fibers, polyolefin fibers, polyester fibers, polyacrylonitrile fibers Organic fibers such as fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, polyurea fibers, polyurethane fibers, polyfluorocarbon fibers, phenol fibers, and cellulose fibers can be used alone or in combination.

The rubber is acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, acrylic rubber, ethylene propylene rubber, styrene butadiene rubber, chloroprene rubber, butadiene rubber, butyl rubber,
Fluorine rubber, silicone rubber, chlorosulfonated polyethylene, ethylene vinyl acetate rubber, polyethylene chloride, butyl chloride rubber, epichlorohydrin rubber, nitrile isoprene rubber, natural rubber, isoprene rubber and the like can be used.

As rubber chemicals, vulcanizing agents such as sulfur, zinc oxide, magnesium oxide, peroxides and dinitrosobenzene, polyamine compounds, aldehyde amine compounds,
Vulcanization accelerators such as thiuram-based compounds, dithiocarbamate-based compounds, sulfenamide-based compounds, thiazole-based compounds, guanidine-based compounds, thiourea-based compounds, xanthate-based compounds, anti-aging agents, scorch inhibitors, plasticizers Conventionally known rubber chemicals such as agents and coloring agents are widely used as the rubber chemicals for forming a joint sheet.

As the filler, clay, talc, barium sulfate, sodium bicarbonate, mica, graphite, sericite, wollastonite, calcined clay, etc. may be used in addition to kaolinite, carbon black and white carbon.

[0012]

The present inventors have been researching the sealing properties of NA joint sheets, and it has been known that the roughness of the gasket surface affects the sealing properties. Therefore, regarding the surface roughness of the joint sheets, Although attention has always been paid, it has been extremely difficult to obtain a sheet having excellent surface roughness while satisfying the basic properties such as tensile strength, compressibility and stress relaxation rate.

As a result of studying the filler for the surface layer in order to solve such a point, kaolinite, carbon black, and white carbon were used for the entire amount of the filler, or 30% by weight or more of the total amount of the filler. By
It was discovered that the surface condition of the joint sheet is greatly affected.

This is because the fibers of the NA joint sheet are often thick and rigid, so that the sealing fluid often leaks through the gaps between the fibers, such as kaolinite, carbon black,
It is considered that the filler having a small particle size such as white carbon fills the gap with the rubber of the binder and improves the sealing property. In the case of hexagonal plate-like particles such as kaolinite, the plate-like particles are oriented in the direction parallel to the surface of the sheet by the shearing force at the time of plate making, and the surface roughness Rmax
It was also found that a sheet having a smoother surface condition of 20 μm was obtained.

A suitable blending amount of the above-mentioned kaolinite, carbon black and white carbon is 30% by weight or more, preferably 50% by weight or more.
It was confirmed that the surface condition was not significantly improved when the content was less than 10% by weight.

Generally, in the NA joint sheet, the amount of the filler added is as large as 20 to 60% of the total material, and the type of the filler greatly affects basic physical properties such as tensile strength, stress relaxation rate and compressibility. Therefore, kaolinite, carbon black, and white carbon are used individually or in combination, and a kneaded mixture containing 30% by weight or more of the filler is thinly laminated only on the front surface and / or the back surface of the base material to form a multilayer structure. Can maintain good surface smoothness while maintaining good basic properties of the joint sheet,
It is desirable because the sealing property can be improved. However, the kneaded product is not limited to this, and the kneaded product may be used in a single-layer structure.

[0017]

The present invention will be described below in detail with reference to examples.

Example 1 A predetermined amount of an acrylonitrile-butadiene rubber material thinned by a rubber masticating roll to a thickness of 0.2 mm was weighed, then immersed in 300 parts by weight of toluene, and allowed to stand for 24 hours for sufficient swelling. Let

Next, a base fiber having the following composition, swollen rubber, a rubber chemical and a filler were mixed together for 80 minutes in a Henschel mixer to prepare a core material.

Base fiber Aromatic polyamide fiber 10% by weight Glass fiber 10% by weight Rock wool 10% by weight Acrylonitrile butadiene rubber 15% by weight Rubber chemicals 5% by weight Filler talc 20% by weight Silica clay 15% by weight Calcium carbonate 15% by weight Next, a surface material having kaolinite as a filler was prepared by the same method as that for the core material, with the composition shown in Example 1 in Table 1.
Then, the surface material is placed between a hot roll of 150 ° C and a cold roll of 20 ° C, then the core material and finally the surface material are pressure-vulcanized and molded to form a three-layer joint sheet with a thickness of 1.5 mm. It was created.

Examples 2 to 6 Using the surface materials having the formulations shown in Examples 2 to 6 in Table 1, a three-layer joint sheet was produced in the same manner as in Example 1.

Example 7 A material having the same composition as the surface material of Example 1 in Table 1 was used as the core material, and the surface material was not used.
A single-layer joint sheet was manufactured in the same manner as in.

Comparative Examples 1 to 4 Using the surface materials having the compositions shown in Comparative Examples 1 to 4 in Table 1, a three-layer joint sheet was produced in the same manner as in Example 1.

Table 2 shows the physical properties of the joint sheets of Examples 1 to 7 and Comparative Examples 1 to 4. The tensile strength, compression rate, restoration rate and stress relaxation rate of the joint sheet are JIS R
It was measured according to 3453. For the measurement of the surface roughness, Rmax was measured according to JIS BO601 using a universal surface profiler manufactured by Kosaka Seisakusho. Regarding the sealing property, the leakage amount when N ₂ gas was pressurized at an internal pressure of 15 kgf / cm ² for 1 hour with a gasket punched in the shape of a ring sandwiched between the flanges was determined by an underwater substitution method.

As a result of the measurement, it can be seen that Examples 1 to 6 have good general physical properties such as tensile strength, and also have good sealing property with small surface roughness. Particularly, Examples 1 and 7 using kaolinite having a hexagonal plate shape are excellent in surface smoothness.
In Example 7, the compressibility and the stress relaxation rate are slightly lowered, but the sealing property is good. On the other hand, it can be seen that Comparative Examples 1 to 4 have large surface roughness and poor sealing properties.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

As described above, it can be seen that the joint sheet obtained by the present invention has good general physical properties and excellent sealing properties, and is suitable as a joint sheet used at a low tightening pressure.

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[Procedure amendment]

[Submission date] July 21, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

Comparative Examples 1 to 4 Using the surface materials having the compositions shown in Comparative Examples 1 to 4 in Table 1, a three-layer joint sheet was produced in the same manner as in Example 1.
It was

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Segawa 4-1000-4G, Matsumi-cho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (1)

[Claims] 1. A single-layer or multi-layer joint sheet produced by charging a kneaded material composed of a base fiber, rubber, a rubber chemical and a filler between a pair of cold and hot rolls, and at least one surface layer of the joint sheet. The filler of the kneaded material to be used contains kaolinite, carbon black, white carbon alone or in combination of two or more kinds, or contains kaolinite, carbon black or white carbon together with other fillers, and A joint sheet characterized in that the amount of kaolinite, carbon black and white carbon is 30% by weight or more based on the total amount of filler in the surface layer.