JPH0124920B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a gasket material that is a stationary sealing material that seals between stationary members such as piping flanges, and in particular to a gasket material made of carbon fiber paper. It is related to.

[Background of the invention]

As is well known, carbon fiber has high elasticity, chemical resistance,
Because it has excellent properties such as heat resistance, it is used in many industrial applications such as sealing materials such as gaskets and packing, heat insulation materials, and heating elements.

However, although carbon fiber itself has high elasticity, it is not flexible and stiff (just like
It resembles a taut steel wire) and generally has poor leakage (hydrophilicity) to water. For this reason, conventionally, thin (0.5~
There was no gasket material made of carbon fiber paper, which has paper-like properties such as about 2 mm), pliability, and high density. The reason for this is mainly due to the above-mentioned properties of carbon fibers, and furthermore, because carbon fibers (short fibers) are not aggregated at all in the paper making liquid, this is combined with the high apparent elasticity of carbon fibers. This is because it is extremely difficult to make paper made of thick carbon fiber.

Therefore, in order to obtain carbon fiber paper, it is first necessary to improve the leakage properties of the carbon fiber itself.
For example, as seen in Utility Model Publication No. 54-5842,
It was necessary to activate the carbon fibers (short fibers).

However, in order to make it usable as a gasket material, it must be able to withstand high clamping surface pressure and sufficiently exhibit the high elasticity (young modulus) and heat resistance inherent in carbon fiber to prevent creep. Therefore, the filler containing fiber materials other than activated carbon fiber as impurities must be as small as possible.In order to increase the shape ratio as a gasket material, a paper-like and thin material is used. preferable.

As a sealing material, issues remained, such as the need for a gasket material that would not allow fluid to penetrate or leak.

[Object of the present invention]

The present invention was made to solve these problems, and aims to provide a gasket material made of thin carbon fiber paper with good sealing properties and high density.

[Summary of the invention]

In order to achieve the above object, the gasket material of the present invention is particularly a thin carbon fiber paper made of activated short carbon fibers and having a density of 1.6 to 1.8 gr/ ^cm3 . A small amount of an additive made of fluorine resin is added to fill the holes.

The density of carbon fiber paper (hereinafter simply referred to as "carbon fiber paper" refers to carbon fiber paper without additives), which is the main gasket material, is 1.6 to 18 gr/ ^cm3 . This is because it exhibits a good sealing function even for gases such as nitrogen gas, which are difficult to seal compared to liquids such as water.

In other words, as will be described in detail later, as is clear from the experimental results shown in Figure 1, when a gasket material made of carbon fiber paper with a density of less than 1.6gr/cm ³ is used, the gasket material has a density of 1.6gr/cm ³ or more. When the fluid to be sealed is a liquid,
This is because when the fluid to be sealed is gas, the amount of leakage increases rapidly, and a good sealing function cannot be achieved for gas. In addition, the upper limit of density is 1.8gr/
cm ³ was chosen not because it was said that sealing performance would be impaired if the density was higher than that, but because the theoretical density of carbon fiber is approximately 2gr/cm ³ , and because of the relationship with the porosity of carbon fiber paper. This is because it is difficult to actually produce carbon fiber paper with a density exceeding 1.8gr/cm ³ . Therefore, in order to improve the sealing performance of gasket materials, it is important to increase the density of carbon fiber paper.
The fact that it is less than 1.8gr/cm ³ is not so important, but the fact that it is more than 1.6gr/cm ³ is significant.

By the way, according to carbon fibers that are not activated, even when using pitch type, acrylonitrile type, phenol resin fiber type (novolac), etc.
Although the density of carbon fiber paper can only be increased to about 1.4 gr/cm ³ at most, the present invention has been able to increase the density of carbon fiber paper to 1.6 gr/cm ³ or more as described above. This is mainly due to the following reasons.

That is, while unactivated carbon fibers have a specific surface area of less than 50 m ² /gr, activated carbon fibers can have a specific surface area of 200 to 1000 m ² /gr. Therefore, if activated carbon fiber is used, compared to the case where non-activated carbon fiber is used,
Due to the Van der Wals force, the cohesive force during paper formation during the papermaking process becomes significantly greater, and carbon fiber paper with extremely high density can be obtained. As described above, activated carbon fibers have a large physical adsorption force, and therefore it is possible to obtain high-density carbon fiber paper that cannot be obtained with non-activated carbon fibers.

Further, the additive is used for the purpose of improving the conformability of the gasket material and for the purpose of filling microholes in the carbon fiber itself and voids between the fibers. As such additives, it is necessary to use ones that do not easily flow even when heat and load are generated, and rubber, gelatin, and phenolic resins are suitable in addition to fluorine resins. However, as is clear from the experimental results shown in Figure 2, which will be described later, when rubber or gelatin is used, the amount of compression changes significantly with respect to the clamping surface pressure, making it difficult to use gasket materials that can withstand high clamping surface pressure. On the other hand, when phenolic resin is used, the change in the amount of compression is extremely small, it lacks compatibility with the mating member such as a flange, and the sealing surface of the mating member has low flatness or distortion. It is difficult to exhibit a good sealing function. Gasket materials using fluororesin do not have such drawbacks. For these reasons, and also because fluorine resins have excellent corrosion resistance, fluorine resins are used as additives for filling holes.

By the way, as mentioned above, unactivated carbon fibers do not coagulate in the paper making solution and it is difficult to obtain carbon fiber paper of uniform thickness, but in the case of activated carbon fibers, they coagulate well on their own. Therefore, no binder for papermaking is required. Therefore, additives made of fluororesin are not used for the purpose of acting as such a binder. Therefore, the amount of the additive added may be small enough to achieve the purpose of filling the holes described above, for example, about 5% by weight based on the total weight of the gasket material. Note that since the carbon fibers are activated, even if the additive is used in a small amount, the pores are uniformly and well filled by capillary action.

〔Example〕

Commercially available carbon fiber (manufactured by Kureha Chemical Co., Ltd., #Y-103
(fiber thickness 12 μm)) is focused and then
Activation was carried out by passing through the oven in a stream of steam at 1 to 5 minutes. The activated carbon fibers had a specific surface area of 200 to 1000 m ² /gr.

The thus activated carbon fibers were cut into short fibers with an average fiber length of 10 to 15 using a beating machine.

Then, the activated carbon fibers in the form of short fibers were soaked in an aqueous suspension of tetrafluoroethylene resin to make it wet, and then made into paper using a 150-mesh paper-making mesh.
This was heated to 70°C and dried to obtain a gasket material made of carbon fiber paper filled with pores filled with tetrafluoroethylene resin.

The gasket material thus obtained was thin, approximately 2 mm thick, pliable and flexible, and had an extremely smooth surface. Further, the density of the carbon fiber paper was 1.7 gr/cm ³ and the content of tetrafluoroethylene resin was 5% by weight. Note that the thickness of the carbon fiber paper can be freely adjusted by controlling the paper making time.

In addition to the above-mentioned gasket material, the density of carbon fiber paper was increased to 1.4 using the above-mentioned paper-making method (excluding the fact that density-determining factors such as the degree of mesh of the paper-making network were changed).
Multiple types of gasket materials were obtained, varying in the range of ~1.8 gr/cm ³ . Among these, the gasket material group having a density of less than 1.6 gr/cm ³ is a gasket material as a comparative example, and the other gasket material groups (including gasket materials) are gasket materials according to the present invention.

Then, several sheets of each of these gasket materials were stacked and interposed between pipe flanges, and a 5 kg/cm ² water pressure leak test and a nitrogen gas (20 kg/cm ² ) gas leak test were conducted, and the following results were obtained. The results were obtained.

That is, in the hydraulic leakage test, all gasket materials, including carbon fiber paper with a low density of about 1.4 gr/cm ³ , showed no leakage, and were extremely suitable for use as stationary sealing materials. From these test results, it was found that using activated carbon fiber paper material as the main gasket material and adding an additive made of fluorine resin to carbon fiber paper to fill the holes.
It was confirmed that this method is highly effective in sealing liquids.

On the other hand, in the gas leak test, as shown in Figure 1, for gasket materials in which carbon fiber paper has a density of 1.6 to 1.8 gr/cm ³ , the leakage rate exceeded the allowable standard value (0.1 cc/Hr). ) below. but,
For the gasket material group in which the carbon fiber paper density was less than 1.6 gr/cm ³ , the amount of leakage exceeded the above-mentioned allowable standard value, and the amount of leakage increased rapidly as the density decreased. Therefore, the latter group of gasket materials cannot be suitably used as a gas sealing material.

As is clear from these test results, keeping the density of carbon fiber paper at 1.6 to 1.8gr/ ^cm3 is an important condition for exhibiting a good sealing function against both liquids and gases. It was confirmed that there is.

Furthermore, a gasket material as a comparative example was obtained by the same paper making method as above except that the additives were changed. As additives, rubber was used for the gasket material, gelatin was used for the gasket material, and phenolic resin was used for the gasket material. The density and thickness of the carbon fiber paper in these gasket materials and the amount of additives added were all the same as those of the gasket materials described above.

For each gasket material, the change in compression amount with respect to the tightening surface pressure was measured, and the results shown in FIG. 2 were obtained. In FIG. 2, the gasket material is shown by a solid line, the gasket material by a chain line, the gasket material by a chain double-dot line, and the gasket material by a broken line.

As is clear from these measurement results, the gasket material has extremely large changes in the amount of compression and cannot withstand high tightening surface pressure.On the contrary, the gasket material has extremely small changes in the amount of compression and is not compatible with the mating member. In other words, it cannot exhibit a good sealing function depending on the smoothness or distortion of the gasket mounting surface of a mating member such as a flange. However, the gasket material exhibits an amount of compression depending on the tightening surface pressure, and can exhibit a good sealing function.

From this, it was confirmed that fluorine-based resin is optimal as an additive.

〔Effect of the invention〕

As can be easily understood from the above description, according to the present invention, a gasket material with good sealing properties without permeation leakage can be provided for both liquids and gases.

Further, since the main component is substantially activated carbon fiber, it is possible to provide a gasket material having heat resistance and high elasticity (high strength).

Furthermore, the microholes in the carbon fibers themselves and the gaps between the fibers in the carbon fiber paper are filled with fluorine-based resin, which is difficult to flow out even when heat or load is generated. sex)
It is possible to provide a pliable and flexible gasket material with significantly improved gasket properties.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the density of carbon fiber paper and gas sealing performance (leakage amount) in gasket material, and Figure 2 is a graph showing the relationship between tightening surface pressure and compression amount in gasket material. It is.

Claims (1)

[Claims] 1 A small amount of additive made of fluorine-based resin is added to a thin carbon fiber paper made of activated short carbon fibers and has a density of 1.6 to 1.8 gr/cm ³ as a hole filler. A gasket material made of carbon fiber paper characterized by the addition of.