JPH0423881A - Gasket material - Google Patents

Abstract

PURPOSE:To obtain a gasket material capable of suppressing the reduction of sealed surface pressure after long-term use and of improving durability by incorporating dicyandiamide in a combination of a synthetic rubber and cork granules. CONSTITUTION:The objective gasket material can be obtained by incorporating (A) 1.0 pt.wt. of a rubber component consisting of pref. nitrile rubber (in addition, chloroprene rubber, silicone rubber, hydrin rubber, etc., can be used) with (B) normally 0.6-1.5 pts.wt. of a ground product of natural cork and (C) pref. 0.1-10 (esp. 2-5)wt.%, based on the component B, of dicyandiamde. The component C may be blended with the component B in advance, or blended simultaneously when mixing the components A with B.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for clipping, for example, a joint surface of a container or piping, etc.
This invention relates to improvements in gasket materials used to prevent fluid leakage.

[Prior art] Rubber elastic bodies such as chloroprene rubber, nitrile rubber, or silicone rubber are used as gasket materials to prevent fluid leakage when clamped with scissors or bolts to joint surfaces of containers, piping, etc. . Since these gasket materials produce cross flow when compressed, they are often used in a grooved flange structure, housed in a groove.

On the other hand, in the case of a joint surface with a flat surface structure without grooves,
Gasket materials such as those described above cannot be used because they do not provide sufficient sealing surface pressure due to cross flow.

Cork rubber made of a mixture of synthetic rubber and cork grains is often used as the packing material for the joint surfaces of such a flat seat structure. Cork grains have independent voids inside, and when tightened, these voids are compressed, which has the advantage of changing the necessary sealing surface pressure without causing lateral flow.

[Problem to be solved by the invention] When the gasket material sandwiched between the joint surfaces is used in a compressed state for a long time, it is heated by the heat of the fluid, and stress relaxation is promoted. Seal pressure may be lost. In that case, fluid leakage will occur, the gasket material will no longer function as a gasket, and it will need to be replaced. Replacing gaskets can be costly if the scale of a plant that uses gaskets such as containers and piping becomes large, requiring the plant to be shut down. Therefore, it is desirable that the gasket installed twice can be used for as long as possible without being replaced. - The present invention was made to meet such needs, and aims to create a gasket material that does not lose its sealing function even after long-term use.

[Means for Solving the Problems] The gasket material of the present invention is characterized in that it is made of synthetic rubber and cork particles, and further contains dicyandiamide.

[Function] In the present invention, since a gasket material containing dicyandiamide mixed with cork grains is used, permanent deformation will not occur when the gasket material is sandwiched between joint surfaces of pipes and the like and tightened with bolts. Stress relaxation is difficult to occur. Therefore, the reduction in seal surface pressure after long-term use is suppressed.

[Example] The gasket material of the present invention is a mixture of synthetic rubber and cork particles, and as the synthetic rubber, nitrile rubber is preferable because it has good oil resistance. In addition, chloroprene rubber, silicone rubber, hydrin rubber, etc. may be used. Cork grains are obtained by crushing natural cork, and are usually mixed in an amount of 0.6 to 1.5 parts per 1.0 parts (parts by weight, same hereinafter) of synthetic rubber.

The method for adding dicyandiamide to cork grains is as follows:
Dicyandiamide may be blended in advance with the cork grains alone, or may be blended together when the synthetic rubber and the cork grains are mixed. A small amount of dicyandiamide may be used. For example, 0.1 per cork grain weight
~10% is preferred, and 2-5% is more preferred. When dicyandiamide is less than 0.1%, the effect tends to be lost, and when it exceeds 10%, although it is effective, it tends to not be blended uniformly.

Next, the durability effect of the gasket material of the present invention will be explained by giving specific examples and comparative examples.

In an example, 1.0 part of trill rubber, 1.0 part of natural cork crushed to a particle size of 6 to 40 mesh, and 2% dicyandiamide based on the weight of the cork grains were mixed to produce a commonly used rubber. The sheet-shaped gasket material of Example 1 was obtained by compression molding it to a thickness of 61 m using a sheet manufacturing machine.

Comparative Example 1 A conventionally used gasket material (cork gasket manufactured by Toyo Takasago Battery ■) was used as Comparative Example 1.

The gasket materials of Example 1 and Comparative Example 1 were each cut to a width of 25sui and a length of 50Iam to prepare test pieces. In order to keep the thickness constant after tightening, set them to ′!
Depth (T) 4ms, width (W) 30 as shown in s1 diagram
■, flange model with a groove of length (L) 50-■ (
P) and heated in a hot air circulation furnace at 120° C., test pieces were taken out at predetermined intervals, and the compression set rate was measured.

The compression set rate was calculated by the formula: % formula % based on the compression set test specified in JIS K6301, Section 10.

Here, C8 is the compression set rate (%), % to is the thickness of the test piece, tl is the thickness after 30 minutes have passed since the test piece was taken out from the compression device, and tl is the thickness of the spacer. This JIS standard indicates a method for evaluating the durability of gasket materials when they are inserted into joint surfaces of pipes and used for long periods of time, and measures the compression set after heating at a specified temperature and time. However, in order to evaluate the long-term durability of gasket materials, we investigated the long-term durability of gasket materials by changing the heating temperature corresponding to the usage conditions and examining the change in compression set rate with respect to the heating time corresponding to the usage period. I decided to evaluate the durability.

The results are shown in the graph of FIG.

From the results shown in FIG. 2, it can be seen that the gasket material of Example 1 has improved durability compared to that of Comparative Example 1.

In general, when gasket materials are used on the joint surfaces of flat seat structures, their functionality deteriorates, causing fluid leakage, etc., and the lifespan limit at which the gasket material loses its functionality is considered to be when the permanent strain rate reaches 90%. It is being From this experimental result, it takes 300 hours for the gasket material of Example 1 to reach a compression set rate of 90%, and 150 hours for the gasket material of Comparative Example 1. It can be seen that it has twice the durability compared to conventional products.

[Effects of the Invention] As explained above, the present invention has the effect of improving the durability of the gasket material during long-term use by incorporating dicyandiamide into the cork grains.

[Brief explanation of the drawing]

'W-1 is a perspective view of the flange model used for testing the gasket material of the present invention, and Figure 2 shows the changes over time in the compression set rates of the gasket material according to the embodiment of the present invention and the conventional gasket material. This is a graph showing comparison. Agent Masuo Oiwa Saizusai 2 Figure-O-: Example 112 Comparative Example Heating time (Hr)

Claims (1)

[Claims] (1) A gasket material made by mixing synthetic rubber and cork particles, and further containing dicyandiamide.