JPS5854274A - Gasket and manufacture thereof - Google Patents

Abstract

PURPOSE:To have a gasket endurable against high temperature usage over 300 deg.C by shaping the gasket that it contains 100-200pts.wt. of synthetic resin per 100pts.wt. of granular expansible graphite. CONSTITUTION:Synthetic resin is dissolved and mixed in granular expansible graphite by the effect of solvent and the resultant mixture may be prepared as the material of a gasket. Fluorine rubber, for example, which has high heat resistance may be preferable as the material of the synthetic resin and the mixture ratio of the fluorine rubber to the granular expansible graphite may be 100-200pts. per 100pts.wt. After preliminarily dried, the material of the gasket is subjected to press shaping by use of a specified metal mold, that is, preliminarily shaped to prepare a preliminary work which is shaped in the desired a gasket form. Further, after dried at a temperature as high as in the preliminary shaping process, the preliminary work is subjected to press shaping by use of a metal mold, that is, to final shaping to prepare a desired gasket.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gasket that can be suitably used even at high temperatures and a method for manufacturing the same.

Rubber gaskets are generally well known as conventional gaskets, but such gaskets have poor heat resistance and, when used at high temperatures, harden or carbonize and fail to perform a good gasket function. There is a drawback that there is no

Therefore, in recent years, as a gasket that can be used well even at high temperatures, graph oil (registered trademark), that is, graphite, is treated with an oxidizing medium called an intercalation compound, and the expanded graphite obtained by heating is continuously rolled using a roll etc. A tape-shaped tape has been developed that is simply compression molded.

However, such gaskets are anisotropic in strength and brittle due to the characteristics of tape-shaped expanded graphite, and therefore the edges are easily peeled off or damaged during use, making them extremely difficult to handle. Moreover, it is necessary to increase the gasket coefficient during use, which poses a problem in terms of the tightening strength of the gasket.

The present invention eliminates the drawbacks of the conventional ones as described above,
The present invention was made in order to provide a gasket that can be suitably used even at high temperatures exceeding 600° C., and a manufacturing method that can easily manufacture such a gasket.

First, to explain the method for manufacturing a gasket according to the present invention, first, the expanded graphite particles C density in a cotton-like state before being formed into a tape shape are 0.01 to 0.005 F'.
/cm3, which has expanded 150 to 600 times the original graphite particles) is dissolved and mixed with synthetic rubber using a solvent to obtain a gasket raw material which is a mixture thereof.

Preferably, a rubber material with high heat resistance, such as fluororubber, is used as the synthetic rubber, and this fluororubber is mixed with expanded graphite particles C.
At 2.5 to 1.5 parts by volume C to parts by weight,
(100 to 200 parts by weight per 100 parts by weight of expanded graphite particles), liquefy it with a solvent such as methyl ethyl ketone to give it fluidity, and gradually add this liquid to the expanded graphite particles while stirring. to obtain a gasket raw material that is uniformly mixed throughout. Of course, this fluororubber is not vulcanized. Please note that the gasket is heated to 200℃.
When used in a relatively high temperature atmosphere, unvulcanized nitrile rubber or the like may be used instead of fluororubber as the synthetic rubber, and can be selected depending on the intended specification and purpose. Further, when providing corrosion resistance and further lubricity, an appropriate amount of Teflon dispersion can be added.

Next, the gasket raw material is pre-dried and then pressure-molded, that is, pre-formed, using a predetermined mold to obtain a pre-formed product formed into a substantially desired gasket shape.

Pre-drying is carried out at room temperature (23[deg.]C) to 120[deg.]C, and if the process is desired to be carried out in a short period of time, it is preferable to carry out the preliminary drying at a temperature of about 100[deg.]C. The purpose is to granulate the aforementioned gasket raw material mixture and vaporize the solvent, but the gasket raw material is not completely dried. In other words, unless the solvent is evaporated to some extent to reduce the amount of residual solvent in the preform, the preform will undergo many dimensional changes or changes in surface condition; When preforming is performed, it is difficult to obtain a preform with uniform properties. One purpose of pre-drying is to satisfy these two opposing conditions.

Therefore, pre-drying not only granulates the mixture, but also improves fluidity during pre-forming, reduces the amount of solvent remaining in the pre-formed product, and prevents dimensional changes and changes in surface condition. Although a preformed product with a small number of holes and uniform properties can be obtained, the solvent is vaporized even during preforming.

Further, the preformed product is dried at a temperature similar to that used in the predrying, and then pressure molded, that is, main molded, using the mold to obtain a desired gasket.

In this drying step, the solvent remaining in the preformed product is completely removed, but it is more preferable to completely dry it at the final stage of main molding.

Further, most of the gasket is formed through the preforming, and the main forming is only a final finishing step, and the main forming corrects the dimensions of the gasket and corrects the surface roughness.

Note that, if necessary, heat treatment may be performed at the same time as the main molding to perform vulcanization.

Therefore, according to the manufacturing method of the present invention, it is possible to easily manufacture a gasket that has uniform properties, has small grain and surface roughness, and has accurate dimensions. Moreover, since the gasket raw material is made by adding a liquid (synthetic rubber solution) to the expanded graphite particles instead of using only expanded graphite particles, the volume of the gasket is reduced to about 1/sum or less compared to the case of using only expanded graphite particles. The mold can be made smaller.

The gasket manufactured as described above, in which synthetic rubber is uniformly contained in expanded graphite particles, contains synthetic rubber in a range of 100 to 200 weight RIgB per 100 parts by weight of expanded graphite particles. It was confirmed that the gasket of the present invention had the best properties.

In other words, if the proportion of synthetic rubber is less than 100 parts by weight, the disadvantage of expanded graphite's brittleness will become more pronounced, and the gasket itself will become brittle, and if the proportion of synthetic rubber exceeds 200 parts by weight, the disadvantages of synthetic rubber will become more pronounced. As a result, the gasket itself becomes poor in heat resistance and suffers from hardening or carbonization.

Therefore, the gasket of the present invention has both the conformability and elasticity, which are the advantages of rubber materials, and the heat resistance and corrosion resistance, which are the advantages of expanded graphite, and has the heat resistance, which is the disadvantages of rubber materials. This covers the weaknesses in mechanical strength and the brittleness and anisotropy of strength of expanded graphite. In other words, it has improved heat resistance compared to conventional rubber gaskets, making it suitable for use even at high temperatures.Also, since expanded graphite particles are bonded with synthetic rubber, conventional rubber gaskets have improved heat resistance. Unlike gaskets that use graphite alone, the edges do not peel off or break, making them easy to handle.

Moreover, since it is filled with synthetic rubber, the fluid to be sealed will not leak through the gasket or leak from the seal contact surface during use.
A good sealing function can be expected. Furthermore, compared to conventional gaskets made of expanded graphite alone, synthetic rubber is evenly contained, so the gasket coefficient is small enough and there are no problems with tightening strength. The gasket of the present invention can be suitably used as a general gasket used at high temperatures or as a gasket requiring chemical resistance (excluding those with oxidizing power).

Example (1) G ZhangjiJU) Ako 2700cc (about 20yr
) (2) Fluororubber 27.5fr 11.
8) (3) Methyl ethyl ketone (1 liter of solution) 150
fr above (11(2) (31) is mixed to obtain a gasket raw material.

Next, this gasket raw material is pre-dried for 5 to 1 hour at a temperature of 100 to 1.20°C, and then heated to 100 to 170 KP for 3 to 60 seconds at room temperature using a specified mold.
A preformed product is obtained by applying a surface pressure of r/cm2 and preforming.

Furthermore, this preformed product was dried at a temperature of room temperature (23°C) to 40°C for 5 to 24 hours, and then dried for 3 to 60 seconds at room temperature (or between the tracks for vulcanization).
A desired gasket was obtained by processing the surface pressure of oo to 4oo Kgr/cIn2 and then performing main molding.

The gasket thus obtained exhibited the above-mentioned effects, and was used as a secondary seal (gasket) of a mechanical seal for a pump under the following conditions, for example, as a gasket provided in a fixed sealing ring. At that time, we obtained a track record of approximately one year of use.

Usage conditions Pump used Normal pressure residue pump Pump rotation speed 357 Or, p, m Suction side pressure
8.4~10.4 Instant bill 472 Discharge side pressure 1
60.5 Kf/an Twin shaft sealing chamber temperature 288℃ Shaft sealing chamber pressure 8.4 to 10.4 KF”7.2 Patent Applicant Agent: Nippon Pillar Industries Co., Ltd.
Patent attorney Takashi Suzue −

Claims (1)

[Claims] 1. 100 to 200 parts by weight of expanded graphite particles
A gasket containing synthetic rubber by weight. 2. Dissolve synthetic rubber into expanded graphite particles using a solvent.
A method for producing a gasket, comprising: mixing the mixture, pre-drying the mixture to granulate it, pre-forming it, drying the pre-form and molding it into a desired gasket shape. .