JPH10102036A - Joint sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sealing properties under a low surface pressure without using a swelling agent and a plasticizer in a non-asbosto(NA) joint sheet. SOLUTION: This NA joint sheet is obtained by inserting a composition for forming a joint sheet obtained by mixing and kneading a composition comprising a base fiber consisting of an inorganic fiber and/or an organic fiber, a rubber, a filler and rubber chemicals consisting of a vulcanizer a vulcanization-accelerator, etc., with a solvent between a pair of heated roller and cold roller, laminating to the heated roller to a predetermined thickness and separating the laminated composition from the heated roller. A sub is added to the composition in 1-20%, preferably 5-10% weight ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 petrochemical plants, various industrial machinery, automobiles, and home electric appliances, and particularly to a low fastening for automobiles and the like. The present invention relates to an improvement in an NA joint sheet suitable as a joint sheet used under pressure.

[0002]

2. Description of the Related Art Joint sheets are made of rubber swelled in a solvent (or powdered rubber or latex added with a solvent) to a base material fiber, filler, rubber chemicals such as a vulcanizing agent and a vulcanization accelerator. Is kneaded sufficiently with a Henschel mixer or the like to prepare a composition for forming a joint sheet (hereinafter abbreviated as a kneading material). Then, the kneading material is separated from a hot roll (about 150 ° C.) and a cold roll (about 20 ° C.). It has been manufactured by putting between a pair of rolls (calender rolls), laminating while heating and rolling on the hot roll side, evaporating and vulcanizing the solvent, and peeling off the laminated sheet to a predetermined thickness. Was. 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, as a constituent material, in addition to the above, a softener, a plasticizer, a water swelling agent,
A small amount of an oil swelling agent may be added, and a pigment may be added for storage and identification.

[0003] Conventionally, asbestos joint sheets have been used as joint sheets. By utilizing the unique shape of asbestos fibers and excellent heat resistance, they can be used as gaskets for piping such as water, oil, air, steam, etc. and equipment. It has been stamped and used. This asbestos joint sheet contains about 60 to 85% by weight of an inorganic material, which is very flexible and highly fibrillated, and has a large surface area of about 60 to 85% by weight, and the asbestos fiber is sufficiently dispersed and adhered to the rubber material. Because of this state, the surface of the sheet laminated while being heated and rolled was smooth and had good conformity with the flange, and good sealing properties were maintained even with a low tightening surface pressure.

However, asbestos fibers are natural minerals, and there is a concern that resources may be depleted. For example, recently, asbestos fibers have not been used at all, and inorganic and / or organic fibers other than asbestos fibers have been used. Joint sheets (referred to as asbestos-free joint sheets or non-asbestos joint sheets, hereinafter abbreviated as NA joint sheets) have come to be used.

[0005]

In recent years, in the industrial field such as the automobile industry, the thickness of a flange to be sealed has been reduced due to the reduction in size and weight of parts, and the diameter of a tightening bolt for the flange is small and the number of bolts is small. Therefore, it is becoming impossible to apply a sufficient tightening surface pressure to the gasket, and leakage is likely to occur. In particular, there is a problem that the surface of the NA joint sheet is swelled due to the fact that the fibers used are rigid and the fiber diameter is often large, and the sealing property is likely to be worse than that of the asbestos joint sheet.

In view of this, many studies have been made on the compounding aspect to improve the sealing properties. For example, a swelling agent is used to impart swelling properties to an internal fluid, or a plasticizer is used to soften a sheet. It is designed to improve the familiarity with the flange. However, although the swelling agent softens the sheet due to its swelling action, it cannot be used for all applications because the strength is lowered or the sheet must be used properly depending on the fluid used. In addition, the plasticizer is liable to elute components to the outside when it comes into contact with a fluid such as oil, and has a problem that the sealability gradually decreases and the components eluted in oil cause sludge.

An object of the present invention is to improve the sealability of an NA joint sheet without using a swelling agent or a plasticizer.

[0008]

In order to achieve the above object, the present invention provides a joint sheet comprising a base fiber comprising inorganic fibers and / or organic fibers, a composition comprising rubber, a filler and a rubber chemical. In the above, the gist is that a sub is contained in the composition. In addition, the above-mentioned sub may be blended only with the composition on the front surface and / or the back surface of the sheet.
% Is preferable.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention include a composition comprising a base fiber composed of inorganic fibers and / or organic fibers, a rubber, a filler, and a rubber chemical such as a vulcanizing agent and a vulcanization accelerator. The composition for forming a joint sheet obtained by kneading the product with a solvent is put between a pair of rolls composed of a hot roll and a cold roll, and laminated to a predetermined thickness on the hot roll side, and then peeled from the hot roll. In the joint sheet manufactured by the above method, the above composition contains a sub, and the added amount is 1 to 20% by weight, preferably 5 to 10%. Here, the sub (ruffer substitute) used in the joint sheet of the present invention is a compounding chemical that has been used as a rubber softener or filler, and a brown black sub that is obtained by heating and vulcanizing oxidized vegetable oil with sulfur, A white or slightly yellowish white vulcan obtained by vulcanizing vegetable oil such as rapeseed oil or castor oil with sulfur chloride at room temperature, or an amber transparent candy vulcanized by vulcanizing vegetable oil with sulfur chloride can be used.

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 alumina silicate 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.

Examples of rubber chemicals include vulcanizing agents such as sulfur, zinc oxide, magnesium oxide, peroxide, 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 Known rubber chemicals such as agents and colorants are widely used as conventional rubber chemicals for forming a joint sheet.

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

The present inventor has been conducting research on the improvement of NA joint sheets, and in particular, in order to improve the sealability at low contact pressures such as automotive joint sheets, various compounding chemicals have been added to improve the effect. Investigation revealed that the addition of one kind of softener could significantly improve the sealability without adversely affecting other properties. The reason is that the sub is solid unlike many other softeners, and because it is vulcanized with sulfur, it is common to mix the compounding material after swelling the rubber with a solvent like a joint sheet It is presumed that a part of the sub will be crosslinked with rubber through sulfur if made by a completely different manufacturing method from rubber products. That is, vegetable oil-based softeners such as mineral oil-based softeners such as conventional process oils and castor oil,
Or, even if a plasticizer such as a phthalate ester is blended, the sealing property at room temperature can be improved, but since the amount of elution in the heating oil is large and the stress relaxation rate is large, it is used as a gasket for an oil pan, for example, to seal the oil. In some cases, long-term sealing properties are uneasy. On the other hand, if the sub is blended, the dispersion of the fiber and filler during mixing will be better
The undulation on the front and back surfaces is also reduced, and the rubber is softened and the surface is softened, so that the familiarity with the flange is improved and the sealing property is improved.

Further, even in hot oil, since the components are less eluted and the stress relaxation rate is not lowered, the sealing property can be maintained. When the amount of the sub-addition is 1% or less, the effect of improving the sealing property is hardly observed, and when it exceeds 20%, the sheet easily flows and the stress relaxation rate also decreases. A desirable addition amount of the sub is 5 to 10%, which is considerably large as compared with the case where it is used as a normal rubber softener. In addition, since the sealing property of the joint sheet at low surface pressure often leaks from the contact surface between the sheet and the flange, it is affected by the state of the front and back surfaces. It is most desirable to have a three-layer structure in which is added. However, even if a single composition is used, the addition of the sub is effective even if a single composition is used, since even if the sub is added, the other physical properties are relatively low. Needless to say.

[0016]

The present invention will be described below in detail with reference to examples. (Example 1) A predetermined amount of acrylonitrile butadiene rubber which had been thinned and processed to a thickness of 0.2 mm by a rubber kneading roll was weighed, immersed in 300 parts by weight of toluene, and left for 24 hours to be sufficiently swollen. Example 1 in Table 1
The mixture was mixed with a fiber material, a rubber chemical, a filler, and a candy sub of the composition shown in the above for 80 minutes using a Henschel mixer to prepare a material. The material was pressed and vulcanized while being put between a hot roll at 150 ° C. and a cold roll at 20 ° C., and was 1.5 mm thick.
Was manufactured. (Example 2) A joint sheet was manufactured in the same manner as in Example 1 using the materials having the composition shown in Example 2 of Table 1.

(Comparative Example 1) A joint sheet was manufactured in the same manner as in Example 1 using the materials having the composition shown in Comparative Example 1 in Table 1. (Comparative Example 2) Example 1 was performed using a material having the composition shown in Comparative Example 2 in Table 1 using a process oil as a petroleum-based softening agent.
A joint sheet was manufactured in the same manner as described above. (Comparative Example 3) A joint sheet was produced in the same manner as in Example 1 by using a material having the composition shown in Comparative Example 3 in Table 1 using castor oil as a vegetable oil-based softener. (Comparative Example 4) Dioctyl phthalate (D
A joint sheet was manufactured in the same manner as in Example 1 using the materials having the composition shown in Comparative Example 4 in Table 1 using OP).

Table 2 shows the physical properties of the joint sheets of Examples 1 and 2 and Comparative Examples 1 to 4. The tensile strength, compressibility, restoration rate, and oil resistance test of the joint sheet were measured according to JIS R3453. Regarding the sealability, a gasket punched in a ring shape having an outer diameter of 80 mm and an inner diameter of 72 mm was sandwiched between flanges, assuming an engine oil seal of an automobile. 30 il at 1 kgf internal pressure
/ Cm ² , and the time until leakage occurred was visually measured. Regarding the sealability after oil immersion, the gasket punched in a ring shape was used for No. 30i
1 for 5 hours, then lifted up, gently wiped with acetone and sandwiched between flanges, and measured similarly.

As a result of the measurement, Examples 1 and 2 were compared with Comparative Example 1.
Compared with, the sealability is remarkably improved, the tensile strength is not reduced, and the stress relaxation rate is not much different. Thus, it is understood that the addition of the sub does not adversely affect the general physical properties. Also,
Even when compared with Comparative Examples 2 to 4, the sealability is the same, the stress relaxation rate and the tensile strength are not reduced, and the weight change rate after oil immersion is small, so that the plasticizer or the softener component is introduced into the oil. It can be seen that there is little outflow. Further, with respect to the sealing property after oil immersion, in Comparative Example 1, the expansion due to oil was small and the sealing property was not so improved, and in Comparative Examples 2 to 4, the sealing property was lower than in the normal state. No decrease is seen.

[0020]

[Table 1]

[Table 2]

[0021]

As described above, according to the present invention, by adding a sub into a joint sheet, an NA joint sheet having excellent sealing properties even with low tightening surface pressure and good other physical properties can be obtained. Obtainable.

Claims (3)

[Claims] 1. A joint sheet comprising a composition comprising a base fiber composed of inorganic fibers and / or organic fibers, rubber, a filler and a rubber chemical, characterized in that the composition contains a sub. Joint sheet. 2. The joint sheet according to claim 1, wherein the sub is blended only with the composition on the front surface and / or the back surface of the sheet. 3. The joint sheet according to claim 1, wherein the sub is added in an amount of 1 to 20% by weight.