JPH06287542A - Joint sheet - Google Patents

Abstract

PURPOSE:To prepare a flexible joint sheet having an improved compression ratio and good sealing properties by incorporating a specified amt. of cork having a grain size finer than 50 meshes into the sheet. CONSTITUTION:This flexible joint sheet is prepd. by incorporating cork having a grain size finer than 50 meshes into a joint sheet comprising an org. fiber, an inorg. fiber other than asbestos, an inorg. filler, a rubber, and rubber chemicals in an ant. of the cork of 2-4wt.% based on the total solid content of the sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-asbestos joint sheet (hereinafter abbreviated as NA joint sheet) used as a heat resistant soft gasket.

[0002]

2. Description of the Related Art A soft gasket refers to a gasket that is flexible and has good compression / restoration properties. By design, flanges, bolts, etc. are limited in strength and only low surface pressure can be applied. It is used in places where the finishing accuracy is poor. As a typical soft gasket, various rubber sheets,
Known plant fiber processed sheets, cork sheets, asbestos beater sheets, asbestos joint sheets and the like are known.

Of the above-mentioned soft gaskets, various rubber sheets are various rubber sheets, and a mixture of rubber and a rubber compounding material such as a filler and a vulcanizing agent is mainly vulcanized to form a sheet, and a cloth or the like is used. It is laminated with a reinforcing core material. The plant fiber processed sheet is of a type in which plant fibers are mixed with water in a water together with a filler, a binder and the like to form a slurry and paper. The cork sheet is obtained by mixing cork particles as a main material, mixing a synthetic rubber and a rubber compounding material such as a filler and a vulcanizing agent, and molding and vulcanizing into a sheet by a pressing method or an extrusion method.

Since all of the soft gasket materials up to this point are mainly composed of organic substances such as rubber, vegetable fiber and cork, the gasket generally lacks the heat resistance required and can be used only at a relatively low temperature. Since the stress relaxation rate, which greatly affects the aging of the gasket, is large, there is still concern about durability.

The above-mentioned asbestos beater sheets and asbestos joint sheets are examples of those having improved heat resistance.

Asbestos beater sheets are obtained by wet-opening asbestos as the main component in a beater with a large amount of water.
Add additives such as rubber latex and vulcanizing agent to the asbestos slurry, mix evenly, and
After being machined by a machine (paper making machine), it is manufactured through processes such as drying, pressing and vulcanization.

On the other hand, asbestos joint sheet is prepared by sufficiently kneading asbestos, filler, rubber chemicals and rubber swollen in a solvent in a mixer to prepare a joint sheet forming composition (hereinafter referred to as kneading material). Then, this composition was charged between a pair of rolls consisting of a hot roll (150 ° C.) and a cold roll (20 ° C.), the solvent was evaporated and vulcanized while being laminated on the hot roll side, and finally laminated. It has been manufactured by peeling a sheet material. Depending on the product, in order to complete the vulcanization, the obtained sheet-like material may be subjected to secondary vulcanization in an autoclave or the like. As constituent materials, in addition to the above, small amounts of additives such as coupling agents, softeners, plasticizers, water swelling agents, oil swelling agents, etc. are compounded according to the application, and pigments are compounded from the viewpoint of storage and identification There are many things that have been done.

Since these asbestos-based sheets are mainly composed of asbestos which is an inorganic material, they have higher heat resistance than the above-mentioned various rubber sheets, plant fiber processed sheets, cork sheets, etc. -Because of its excellent properties such as good restoration characteristics and easy processing, it has been widely used for gaskets for water / oil seals of internal combustion engines and equipment flange gaskets.

Since the asbestos beater sheet has a merit that the fibers are well dispersed and is flexible and the price is low because it is manufactured by a paper-making method, it has a mechanical strength because it evaporates water after being formed into a sheet. It also has the disadvantage that sealing properties are inferior to those of joint sheets. For this reason, the proportion of asbestos joint sheets is gradually increasing in response to the trend of adopting high performance ones even if the price is a little higher recently.

However, asbestos fiber is a natural mineral, and it is difficult to obtain it due to depletion of resources, rising mining costs and transportation costs, and health problems caused by asbestos fibers are a social problem. As a result, the use of asbestos has become regulated worldwide. Due to these factors, recently, asbestos fibers are not used at all, and joint sheets (NA joint sheets) using inorganic fibers and / or organic fibers other than asbestos have come to be used.

The fiber materials used for the NA joint sheet are roughly classified into organic fibers and inorganic fibers (other than asbestos fibers). Since the organic fiber is relatively flexible and the SP value (solubility parameter) is close to that of the rubber material, the organic fiber is likely to be entangled, bonded or joined with the rubber material or the filler, and has a high reinforcing effect. On the other hand, in the case of inorganic fiber, it is more rigid and S
Since the P value is different from the rubber material that is the binder,
Although the entanglement with the rubber material and the filler and the bondability / bondability are poor, the reinforcing effect cannot be expected so much, but the resilience and stress relaxation resistance are good due to the rigidity of the inorganic fiber. In consideration of this, the NA joint sheet is often used by combining these organic and inorganic fiber materials according to the intended use.

However, in the case of using these organic / inorganic fiber materials, the point that is greatly different from the asbestos joint sheet is the amount of fibers in the compound. The asbestos joint sheet refers to one containing 65% or more of asbestos fibers as specified in JIS-R3453, and the amount of fibers may be about 80% for the purpose of increasing the compression rate.

On the other hand, in the case of the NA joint sheet, since the entanglement between the fibers and the adhesiveness between the fiber and the rubber are not so good as described above, in consideration of the manufacturability, a fiber obtained by combining the organic fiber and the inorganic fiber is used. The total amount is at most 50%, usually 10 to 30%.

Recently, however, in automobiles, to improve running performance, reduction of engine weight has become a problem, and application of light alloy to joint structure, downsizing and simplification of design are rapidly progressing. Since the shape of the joint is complicated, it is becoming difficult to obtain the proper tightening surface pressure originally required by the gasket and to obtain a uniform tightening surface pressure distribution. In response to such a situation, even in the NA joint sheet, a sheet having a high compressibility that absorbs the distortion of the joint portion and having a good fit to the joint surface has been demanded.

However, it is very difficult to increase the compression ratio of the NA joint sheet because it is impossible to increase the blending amount of fibers as described above. There was a risk that durability and heat resistance would decrease due to the stress relaxation rate.

Therefore, conventionally, a swelling type in which an oil swelling agent or a water swelling agent was added was used, but the NA joint sheet has less mechanical strength than the asbestos joint sheet, and there is a concern that the strength after swelling will decrease. , Oil water depending on the application
There was a problem that two types of sheets had to be used properly and that they had to be stored carefully so as not to get oil or water.

[0017]

That is, in such a conventional NA joint sheet, since the amount of fibers and rubber cannot be increased as compared with the asbestos joint sheet, the compressibility is poor and the joint It was difficult to follow the distortion of the part, and the sealing property at low surface pressure was not so good.

Further, the swelling type has a problem in that there is a fear of a decrease in strength after swelling, and it is necessary to pay attention to the proper use and storage of the sheet.

It is an object of the present invention to provide an NA joint sheet which improves the compressibility and flexibility of the NA joint sheet and follows the distortion of the joint portion and has a good sealability at a low surface pressure. .

[0020]

The present invention has been made in view of the above-mentioned conventional problems. As a result of intensive studies, the present inventors have found that a sheet having a very high compression rate can be obtained by using fine cork for the NA joint sheet.

Conventionally, cork packing has been used as a gasket for low surface pressure and low pressure. The present inventors have paid attention to the good sealing property of cork, and by applying cork to the joint sheet, the cork packing I thought that it would be possible to give the joint sheet the characteristics.

As a result of various experiments, it was found that manufacturability was improved when the content of cork was 40% or less by weight of the total composition. This is because when 40% or more of cork is added, it is used for rubber swelling in the manufacture of joint sheets as described above, but the solvent is absorbed by the porous cork and the material after kneading becomes viscous. It became impossible to produce a sheet by using this kneaded material. Furthermore, if the amount of solvent is increased in anticipation of the amount absorbed in cork, the kneaded material will be in a viscous and manufacturable state, but this time it is not possible to completely evaporate the solvent while manufacturing the sheet on the roll. , Air bubbles remain in the sheet. In addition to it,
It was found that those having a cork content of 40% or more had a markedly reduced stress relaxation rate, and when the amount of rubber was the same, the tensile strength also considerably decreased, and it was found that they are not suitable as gaskets.

Considering this, the addition amount of fine cork is slightly affected by the particle size, but 40% by weight%
The following is desirable, and it has been found that 3 to 30% is particularly preferable in view of characteristics such as compression characteristics as a gasket.

Regarding the particle size of the fine cork, if the particle size is 50 mesh or more, the particle size is too large. Therefore, even if the kneading is sufficiently carried out, the soul of the cork remains during the compounding, and a sheet having a smooth surface cannot be obtained.

As a result of repeating these studies, the present inventors were able to obtain a joint sheet having a high compressibility which was not obtained by the conventional NA joint sheet, by adding fine cork.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 After the latex and toluene having the compounding amounts shown in Table 1 were kneaded with a Henschel mixer (rotation speed: 1000 RPM) for 10 minutes, the cork particles having the compounding amounts shown in Table 1 (passed through 200 mesh)・ Fiber materials, fillers and rubber chemicals were added and kneaded for 20 minutes. The joint sheet forming composition thus obtained was pressure-vulcanized and molded by a heat roll (150 ° C) and a cold roll (20 ° C) calender rolls to a thickness of 1.5 mm.
I got a joint sheet of.

The joint sheets of Examples 2 to 4 and Comparative Examples 1 to 3 had the formulations shown in Table 1 and Table 2,
It was manufactured in the same manner as.

The manufacturability and main physical properties of each of the examples and comparative examples thus obtained are also shown in Tables 1 and 2. The tensile strength, compression rate, restoration rate and stress relaxation rate of the joint sheet were measured according to JIS-R3453. In addition, the sealing property is 20 kgf / cm ² in contact pressure,
It was evaluated in the leak state when a pressure of 3 kgf / cm ^{2 of} distilled water was applied.

[0030]

[Table 1] * 1: The weight part of latex is calculated as solid content, * 2: ◯: extremely good, Δ: good, * 3: ◯: extremely good, Δ: good.

[0031]

[Table 2] * 1: Latex weight part is calculated as solid content * 2: ○: Very good, △: Good, ×: Plate making failure * 3: ○: Very good, ×: Bad.

[0032]

As can be seen from Tables 1 and 2, Examples 1 to 4 have improved sealability as compared with Comparative Example 1 in which no cork is used, and comparatively large amounts of cork are used. Examples 2, 3 and 4 were particularly good. In addition, Comparative Example 3 in which the amount of cork is larger than that of the present invention cannot be manufactured. Similarly, Comparative Example 2 has a tensile strength higher than those of Examples 1 to 4.
The stress relaxation rate tends to decrease.

As described above, the joint sheet obtained by the present invention has an improved compression ratio by blending a specific amount of cork finer than 50 mesh,
A joint sheet with good sealing properties can now be obtained.

Claims (1)

[Claims] 1. A joint sheet comprising organic fibers, inorganic fibers other than asbestos, inorganic filler, rubber and rubber chemicals, in addition to the inorganic filler as filler, cork particles finer than 50 mesh are used in the total composition of the joint sheet. A joint sheet characterized by being mixed in a ratio of 2 to 40% by weight based on the solid content.