JP2883293B2 - Joint sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a petrochemical plant,
The present invention relates to a joint sheet used as a base material of a gasket 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 at a low fastening pressure for automobiles and the like.

[0002]

2. Description of the Related Art A joint sheet is prepared by sufficiently kneading a rubber swollen in a solvent (or a mixture of powdered rubber or latex and a solvent) with a base fiber, a filler and a rubber chemical using a Henschel mixer or the like. A composition for forming (hereinafter referred to as a kneaded material) is prepared, and then the kneaded material is put between a pair of rolls (calender rolls) composed of a hot roll (about 150 ° C.) and a cold roll (about 20 ° C.) It has been manufactured by laminating the sheet on the hot roll side while heating and rolling, evaporating and vulcanizing the solvent, and peeling off the sheet laminated to a predetermined thickness. Depending on the product, secondary vulcanization may be further performed on the sheet-like material obtained for vulcanization in an autoclave or the like. In addition, depending on the application, a small amount of a softener, a plasticizer, a water swelling agent 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 gaskets for piping and equipment for water, oil, air, steam, etc., utilizing the unique shape of asbestos fibers and excellent heat resistance. It has been stamped and used. Asbestos fibers are very flexible and highly fibrillated while being inorganic fibers, and the asbestos joint sheet is made of such thin, large surface area asbestos fibers.
About 85% by weight, asbestos fibers are sufficiently dispersed and adhered to the rubber material, so the surface of the sheet laminated while heated and rolled is smooth and has good fit with the flange, and low tightening surface pressure However, good sealing properties were maintained.

However, asbestos fibers are natural minerals, and there is a concern that resources may be depleted, and health disorders presumed to be caused by asbestos fibers are social issues, and the use of asbestos fibers is restricted worldwide. It has become. By those things,
Recently, asbestos-free joint sheets using at least one of inorganic fibers and / or organic fibers other than asbestos fibers (hereinafter referred to as asbestos-free joint sheets or non-asbestos joint sheets, hereinafter abbreviated as NA joint sheets) ) Has come to be used.

[0005]

As the fiber 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. In many cases, the fiber diameter is large and rigid. Therefore, in the NA joint sheet, undulation due to a lump of fibers occurs on the surface of the sheet,
There was a tendency for the surface roughness to increase, and with a low tightening surface pressure, it was difficult to break into the flange, and there was a case where leakage occurred at the interface between the flange and the gasket. In addition, in the industrial field such as the automobile industry in recent years, the thickness of the flange to be sealed has become thinner due to the reduction in size and weight of parts, and the diameter of the tightening bolts of the flange has become smaller and the number of bottles has become smaller. It is not possible to apply sufficient tightening surface pressure to
Leaks are more likely to occur. Therefore, depending on the application, various measures have been taken to improve the sealing performance by giving the internal fluid swelling properties, but for punching processors and wholesalers, the number of varieties for each application will increase, so punching waste 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 problem, such as disposal problems.

[0006]

The present invention relates to a base fiber,
A kneaded product consisting of rubber, rubber chemicals and filler is cooled
A multi-layer joint sheet manufactured by putting it between heat rolls
A is, filler kneaded material constituting at least one surface layer, kaolinite, carbon black, either alone or in combination of two or more of the white carbon, or other kaolinite with fillers, carbon black or white carbon A joint sheet wherein the amount of kaolinite, carbon black and white carbon in the surface layer is 30% by weight or more based on the total filler amount in the surface layer.

Here, it is desirable that the filler composition on both the front and back surfaces of the joint sheet be a predetermined one and both surfaces be smooth to enhance the sealing property. However, at least one surface may be smooth depending on the purpose. In order to obtain a predetermined filler composition in the surface layer or the backside layer, a kneaded material different from the core portion, which greatly affects the physical properties such as tensile strength and stress relaxation rate, is used for the surface layer or the backside layer. virtuous preferable to a joint sheet layers.

The base fibers used in the joint sheet of the present invention include rock wool, carbon fiber, glass fiber, sepiolite, ceramic fiber, fused quartz fiber, chemically treated high silica fiber, fused silicate alumina fiber, alumina continuous fiber, and stable fiber. Zirconia fiber, boron nitride fiber, alkali titanate fiber, wollastonite, whisker, boron fiber, inorganic fiber such as metal fiber, aromatic polyamide fiber, polyamide fiber, polyolefin fiber, polyester fiber, polyacrylonitrile 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 includes acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, acrylic rubber, ethylene propylene rubber, styrene butadiene rubber, chloroprene rubber, butadiene rubber, butyl rubber,
Rubbers such as fluorine rubber, silicone rubber, chlorosulfonated polyethylene, ethylene vinyl acetate rubber, polyethylene chloride, butyl chloride rubber, epichlorohydrin rubber, nitrile isoprene rubber, natural rubber, and isoprene rubber can be used.

As rubber chemicals, sulfur, zinc oxide, magnesium oxide, peroxides, vulcanizing agents such as dinitrosobenzene, polyamine compounds, aldehydeamine 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, anti-scorch agents, plastics Conventionally known rubber chemicals such as an agent and a coloring agent are widely used as rubber chemicals for forming a joint sheet.

As the filler, besides kaolinite, carbon black and white carbon, clay, talc, barium sulfate, sodium bicarbonate, mica, graphite, sericite, wollastonite, calcined clay and the like are used.

[0012]

The present inventors have been conducting research on the sealing properties of the NA joint sheet and have found that the roughness of the gasket surface affects the sealing properties. Although we have always paid attention, it has been very difficult to obtain a sheet having excellent surface roughness while satisfying basic properties such as tensile strength, compressibility, and stress relaxation rate.

[0013] In order to solve such a problem, a study was conducted on the filler in the surface layer. As a result, the total amount of the filler, or 30% by weight or more of the total amount of the filler was changed to kaolinite, carbon black, white carbon or the like. By doing
It has been found 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, so that kaolinite, carbon black,
It is considered that a 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 a direction parallel to the surface of the sheet due to shearing force during plate-making, and the surface roughness
It was also found that a sheet having a smoother surface condition of 20 μm level could be obtained.

An appropriate amount of the above kaolinite, carbon black and white carbon relative to the total filler 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 the weight%.

[0016] In general, in the NA joint sheet, the amount of filler added is as large as 20 to 60% of the total material, and the type of filler greatly affects basic physical properties such as tensile strength, stress relaxation rate, and compressibility. Therefore, a mixture of kaolinite, carbon black, and white carbon, alone or in combination, in which 30% by weight or more of the filler is added 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,
Desirable since it is possible to improve the sealing property.

[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 and processed to a thickness of 0.2 mm with a rubber kneading roll was weighed, immersed in 300 parts by weight of toluene, and left for 24 hours to sufficiently swell. I let it.

Next, the base fiber, the swollen rubber, the rubber chemicals and the filler having the following composition were mixed together in a Henschel mixer for 80 minutes 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 containing kaolinite as a filler was prepared in the same manner as in the case of the core material using the composition shown in Example 1 in Table 1.
First, the surface material is put between a hot roll at 150 ° C and a cold roll at 20 ° C, and then the core material and finally the surface material are pressed and vulcanized, and a three-layer joint sheet with a thickness of 1.5 mm is formed. It was created.

Examples 2 to 6 Three-layer joint sheets were produced in the same manner as in Example 1 using the surface materials having the formulations shown in Examples 2 to 6 in Table 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 only the core material was used without using the surface material.
A single-layer joint sheet was produced in the same manner as in 1.

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

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 ratio, restoration ratio, and stress relaxation ratio of the joint sheet are based on JIS R
It was measured according to 3453. The surface roughness was measured using a universal surface profiler manufactured by Kosaka Seisakusho in accordance with JIS BO601. With respect to the sealing performance, the amount of leakage when the N ₂ gas was pressurized at an internal pressure of 15 kgf / cm ² for 1 hour with a gasket punched in a ring shape sandwiched between flanges was determined by an underwater replacement method.

As a result of the measurement, it is understood that Examples 1 to 6 have good general physical properties such as tensile strength, and also have good sealing properties and small surface roughness. In particular, Examples 1 and 7 using kaolinite having a hexagonal plate shape are excellent in surface smoothness.
In Example 7, the sealability is good although the compression ratio and the stress relaxation ratio are slightly reduced. On the other hand, it can be seen that Comparative Examples 1 to 4 all 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.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-20587 (JP, A) JP-A-2-77483 (JP, A) JP-A-7-102242 (JP, A) JP-A-7-102 11236 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 3/10

Claims (1)

(57) [Claims] 1. A multi-layer joint sheet produced by introducing a kneaded material comprising a base fiber, rubber, a rubber chemical and a filler between a pair of cold and hot rolls, wherein at least one surface layer is formed. The filler of the kneaded material contains kaolinite, carbon black, or white carbon alone or in combination of two or more, or contains kaolinite, carbon black, or white carbon together with another filler. A joint sheet wherein the amount of knight, carbon black and white carbon is at least 30% by weight based on the total filler amount in the surface layer.