JPH06207163A - Composite gasket and sealing method using the same gasket - Google Patents

Abstract

PURPOSE:To provide a gasket capable of following the change of gap with temperature at a joint part of a device or an equipment of a chemical plant, an automobile, etc., and of constantly and sufficiently exhibiting a sealing function. CONSTITUTION:This gasket has a composite structure produced by using an expanded material composed of a polymer material having <=0 deg.C glass transition temperature as a base material and forming a fluororesin layer on each of both the sides of the base material. In case a gap at a joint part is extended, this gasket can keep the sealing state following it by the elasticity of the expanded material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite gasket used for various devices such as chemical plants and automobile engines, joints (for example, flanges) of equipment, and a sealing method using the composite gasket.

[0002]

2. Description of the Related Art Gaskets are incorporated and arranged at the joints of various devices and equipment such as chemical plants and automobile engines to prevent leakage of fluid inside the equipment and equipment. Most of such gaskets were made of asbestos, but due to their harmful effect on the human body due to scattering, those made of expanded graphite ("Introduction to Gasket", p. 95, 19).
82.2.10, published by Kobunshi Publishing Co., Ltd., or made of polytetrafluoroethylene (hereinafter referred to as "PTFE") (above "Introduction to Gasket", No. 115).
Page).

[0003]

When the gap at the joint changes, these conventional gaskets may not be able to follow the change in the gap and may not sufficiently exhibit the sealing function. For example, when incorporated in a joint of a chemical plant in which a high-temperature fluid flows, it is not uncommon for the difference in fluid temperature to be about 300 ° C. during operation and after operation is stopped. Although it becomes large, the gasket cannot follow this gap change, and as a result, the sealing function may be insufficient. In order to deal with this, "re-tightening" work may be performed, but this work is troublesome.

Further, the expanded graphite gasket is fragile and is easily damaged when it is incorporated into a joint of a device or equipment.
There is also a problem that surface peeling is likely to occur due to vibration of the device or equipment after being incorporated. On the other hand, since the PTFE gasket easily causes a creep phenomenon, there is a problem that it is difficult to apply the gasket to a joint where high airtightness is required.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a composite gasket characterized in that a fluororesin layer is provided on both sides of a foam made of a polymer having a glass transition point of 0 ° C. or lower.

An example of the present invention will be described below with reference to the drawings. The composite gasket shown in FIGS. 1 and 2 is a disk-shaped one having a through hole 6 in the center thereof, and the fluororesin layers 3 and 4 are provided on both surfaces of the foam 1. This composite gasket can be obtained by, for example, sandwiching both sides of a foam with two fluororesin films and adhering or fusing both ends of these films. At this time, an adhesive may be provided on the entire surface of one side of the fluororesin film so that the films are adhered to each other at their both ends and the film and the foam are adhered.

As the foam, one made of a polymer having a glass transition point of 0 ° C. or lower (preferably -10 ° C. or lower) is used. Specific examples of such a polymer include silicone rubber, acrylic rubber, natural rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, isoprene rubber and the like. Of these polymer foams, silicone rubber foams are particularly suitable because they can be used in a wide temperature environment of about -60 to 250 ° C. When a foam made of a polymer having a glass transition temperature higher than 0 ° C. is used as this foam, elasticity is lost at a low temperature and the sealing function cannot be sufficiently exhibited, which is not preferable.

In the present invention, the polymer is used as a foam in order to impart elasticity to follow the change in the gap at the joint of the device or equipment, and the expansion ratio is about 1.5 to 10 times. It has been found preferable to Practically preferable thickness of this foam is about 0.1 to 10 mm. In addition, this foam is preferably of the independent foaming type in order to follow the gap change and prevent the fluid from penetrating.

The fluororesin layers provided on both sides of this foam are not particularly limited, and examples thereof include PTFE, tetrafluoroethylene-perfluoroalkylvinylether copolymer (hereinafter referred to as "PFA"), tetrafluoroethylene-hexafluoro. Propylene copolymer, ethylene-
It may be formed of any fluororesin such as tetrafluoroethylene copolymer.

The fluororesin layers are formed on both sides of the foam in order to impart chemical resistance and to ensure the peeling workability when it becomes unnecessary after being incorporated in the joint portion of the device or equipment. . The thickness of each fluororesin layer is not particularly limited, but is usually about 5 to 100 μm. If it is too thin, the mechanical strength will be insufficient, and if it is too thick, the fit property for the surface shape of the joint will be insufficient. By making the fluororesin layer porous, it is possible to increase its flexibility and improve the fitting property to the surface shape of the joint.

FIG. 3 shows another embodiment of the present invention, in which the support 5
Two pieces (the number of which is not limited) between the foams 1,
2 and fluororesin layers 3 and 4 are provided on both surfaces thereof. By interposing the support in this manner, the handling property and dimensional stability of the gasket can be improved. As the support, a plastic film such as polyimide, polyphenylene sulfide, polyether / ether ketone, polyethylene terephthalate, or a metal foil can be used. The foam and the support may be integrated by adhesion or the like.

In the composite gasket shown in FIG. 3, the two foams have different expansion ratios or different bubble diameters.
Alternatively, the thickness can be varied to provide different flexibility. By doing so, it becomes easy to incorporate into a joint part such as one having a flat surface and the other having an uneven surface. That is, in this type of gasket, if the assembling work is performed so that the highly flexible foam side corresponds to the uneven surface of the joint and the low flexible foam side corresponds to the flat surface of the joint, the Also has good fit to the surface.
The position of the support is not limited to that shown in FIG. 3, and may be between the foam and the fluororesin layer, for example.

In the examples shown in FIGS. 2 and 3, the fluororesin layers provided on both sides of the foam are fused and adhered to each other at their ends. However, in the present invention, the fusion and adhesion are not always necessary. As shown in FIG. 4, the side surface of the foam 1 may be exposed.

The composite gasket according to the present invention is arranged at the joint portion of the device or equipment, and its thickness is 80 to 10% of the original thickness.
By compressing and using so that it will exhibit an excellent sealing function. When the compression is insufficient and the thickness is greater than 80% of the original thickness, the gap cannot be followed when the gap becomes wide and the sealing property becomes insufficient. If the compressed state is smaller than 10%, the gasket may be damaged when the gap becomes small.

[0015]

EXAMPLES Examples of the present invention will be described in more detail below with reference to examples.

Example 1 Foam made of polybutyl acrylate having a glass transition point of -15 ° C. (foaming ratio 3 times, thickness 4 mm) and thickness 10 μm
2 pieces of PTFE are prepared. Incidentally, one side of the PTFE film was subjected to a known adhesion treatment, and the polyacrylic adhesive solution was applied to the entire treated surface and dried. The thickness of the adhesive layer is 20 μm.

Then, the foam is sandwiched between two PTFE films, both ends of the filler are adhered to each other, and the film and the foam are adhered to each other, whereby a composite gasket having the same structure as shown in FIGS. 1 and 2 is formed. Got

Example 2 A foam made of silicone rubber having a glass transition point of −55 ° C. (foaming ratio of 2 times, thickness of 8 mm) and 2 having a thickness of 50 μm.
Prepare a sheet of PFA film. In addition, one side of the PFA film is subjected to a well-known adhesive treatment, and a silicone adhesive (manufactured by Toray Dow Corning, trade name S
E9166) was applied and dried. The thickness of the adhesive layer is 30μ
m.

Then, the foam is sandwiched between two foams, the films are adhered to each other at both ends thereof, and the film and the foam are adhered to each other, whereby a composite gasket having the same structure as shown in FIGS. 1 and 2 is formed. Got

Example 3 A foam made of silicone rubber having a glass transition point of -50 ° C. (foaming ratio: 5 times, thickness: 9 mm) is adhered to both surfaces of a stainless steel foil.

Next, a 25 μm thick PTFE film 2
An integrated product of the above-mentioned stainless steel foil and foam was sandwiched between the sheets and the PTFE films were adhered to each other at both ends thereof to obtain a composite gasket having the same structure as shown in FIG.

Comparative Example 1 A composite gasket was prepared in the same manner as in Example 2 except that a foam having a glass transition point of 28 ° C. and containing polyvinyl acetate as a main component (foaming ratio: 5 times, thickness: 4 mm) was used. Obtained.

Comparative Example 2 Expanded graphite having a thickness of 4 mm was processed into a shape shown in FIG. 1 to obtain a gasket.

Comparative Example 3 A gasket having a thickness of 3 mm was processed into a shape shown in FIG.

The composite gaskets obtained in the above Examples and Comparative Examples (both of which have an outer diameter of 130 mm and a through hole diameter of 70 mm).
mm) is placed on a flange portion having an outer diameter of 140 mm, an inner diameter of 70 mm and a surface roughness of 10 μm, and the thickness thereof is 50% of the original thickness (however, in Comparative Example 3, 8% of the original thickness is used).
It was compressed to 0%) and sealed.

Then, this was placed in a thermal cycle tester to test whether the pressure inside the seal (adjusted to 10 atm) did not change. This tester has a low temperature of -10 ℃ and 150
A high temperature of ℃ was maintained for 10 hours each, and it was adjusted so that the transition from the low temperature state to the high temperature state or from the high temperature state to the low temperature state took 4 hours (the temperature change from the low temperature to the high temperature or from the high temperature to the low temperature). In that case, the flange gap was designed to vary by 30%). Table 1 below shows the results of measuring the internal pressure every 10 cycles, with 24 hours as one cycle.

[0027]

[Table 1]

[0028]

Since the present invention is constructed as described above and uses the foam having a specific glass transition point as the base material of the gasket, even if the gap changes, the change can be followed and the sealing function can be obtained. It can be fully demonstrated.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a composite gasket according to the present invention.

FIG. 2 is a cross-sectional view taken along the line AB in FIG.

FIG. 3 is a cross-sectional view showing another example of the composite gasket according to the present invention.

FIG. 4 is a cross-sectional view showing another example of the composite gasket according to the present invention.

[Explanation of symbols]

 1 Foam 2 Foam 3 Fluororesin Layer 4 Fluororesin Layer

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[Procedure amendment]

[Submission date] April 8, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Example 1 Foam made of polybutyl acrylate having a glass transition point of -15 ° C. (foaming ratio 3 times, thickness 4 mm) and thickness 10 μm
m two PTFE films are prepared. In addition, PTF
One side of the E film was subjected to a known adhesion treatment, and a polyacrylic adhesive solution was applied to the entire treated surface and dried. The thickness of the adhesive layer is 20 μm.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Then, the foam is sandwiched between two PFA films, the films are adhered to each other at both ends thereof, and the film and the foam are adhered to each other, whereby a composite gasket having the same structure as shown in FIGS. 1 and 2 is formed. Got

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Akira Asakami 1-2-1, Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (2)

[Claims] 1. A composite gasket, characterized in that a fluororesin layer is provided on both sides of a foam made of a polymer having a glass transition point of 0 ° C. or lower. 2. A composite gasket characterized in that a fluororesin layer is provided on both sides of a foam made of a polymer having a glass transition point of 0 ° C. or less, and the composite gasket is arranged at a joint portion, and the gasket has the original thickness. A sealing method of compressing to a thickness of 80 to 10%.