JP5155771B2 - Fluoropolymer-wrapped gasket - Google Patents

Description

  The present invention relates to a fluororesin-wrapped gasket in which the outer periphery of a core body, which is a cushion material, is coated with a fluororesin film, and more particularly relates to a fluororesin-wrapped gasket having excellent crush characteristics at room temperature and airtight characteristics at high temperatures. .

Conventionally known gaskets having excellent chemical resistance include a gasket made of a fluororesin alone, a fluororesin-wrapped gasket, and the like.
A gasket made of a single fluororesin has excellent chemical resistance, but has a large creep and stress relaxation, so when using it alone as a gasket, provide a groove in the flange and place the gasket in the groove. In addition, it is necessary to manage the stress load such as preventing the gasket end from expanding to the inside of the piping, and not applying an excessive stress load to the gasket made of a single fluororesin. There are many restrictions on use, such as significant stress relaxation at high temperatures, and there are problems in use.

  On the other hand, for example, as shown in FIG. 8, the fluororesin-wrapped gasket uses an annular core 1 such as a joint sheet or asbestos as a cushioning material, and the outer periphery of the annular core 1 is made of tetrafluoroethylene resin (PTFE). The structure is covered with a fluororesin film 2 having a thickness of 0.5 mm or less and excellent in heat resistance and chemical resistance, such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA).

  Therefore, many of these types of gaskets have been conventionally used as gaskets for sealing between the flanges of pipes, and have been widely used especially for chemical fluids that are highly corrosive or for food industries that do not like contamination or pure water.

  Further, depending on the purpose of use, as shown in FIG. 9, the annular core 1 may be configured by laminating a plurality of annular sheets 3, 4, 3. As the annular joint sheet 3, an asbestos-based or non-asbestos-based joint sheet is used, and as the annular sheet 4, for example, an asbestos-based or non-asbestos-based felt sheet is used.

Since such a fluororesin-wrapped gasket has a structure in which a core material is usually covered with a fluororesin jacket having a thickness of 0.5 mm or less, the elasticity and strength as a gasket are mainly the core. As a result, creep and stress relaxation are smaller than those of the above-mentioned gasket made of a single fluororesin, so that it is frequently used in applications where chemical resistance is required. As for general use conditions, the maximum use temperature is about 200 ° C., and the maximum pressure is about 20 kgf / cm ^2. )

On the other hand, in recent years, in consideration of the environment, non-asbestos materials have been used instead of asbestos materials as joint sheets and felt materials that are core materials.
However, in the fluororesin-wrapped gasket, the friction coefficient of the fluororesin that is the outer sheath is small, so when an excessive load is applied, slippage occurs between the core material and the fluororesin outer sheath. Joint sheets and felt materials, which are materials, sometimes collapsed.

  This crushing phenomenon occurs when the initial tightening is excessive, and the core material undergoes a creep phenomenon before the fluororesin jacket breaks, resulting in an extremely low gasket stress. This is a phenomenon in which the sealing performance cannot be exhibited.

  Moreover, such a crushing phenomenon was particularly remarkable in a non-asbestos gasket having a low core strength.

  The present invention is intended to solve the problems associated with the prior art as described above, and an object thereof is to provide a non-asbestos-based fluororesin-wrapped gasket having excellent crushing properties and good sealing properties. It is said.

  The fluororesin-wrapped gasket according to the present invention is a fluororesin-wrapped gasket in which an annular core formed by laminating a single layer (single layer) or a plurality of annular members is inserted in an annular groove of a fluororesin jacket. Thus, at least one layer of the annular member (a) constituting the annular core includes organic fibers, inorganic fibers, inorganic powders, and a binder.

  In the present invention, when the annular member (a) includes one layer or two or more layers, the two layers of the one-layer or two or more layers of the annular member are in close contact with the fluororesin jacket, respectively. Is preferred. In other words, the annular member in contact with the fluororesin jacket preferably includes organic fibers, inorganic fibers, inorganic powder, and a binder.

  In the present invention, the inorganic powder contained in the annular member may be uniformly dispersed or may be unevenly distributed on the surface of the annular member on the fluororesin jacket side, but the inorganic powder is unevenly distributed. The powder layer (the surface on which the powder is unevenly distributed) is preferably in close contact with the fluororesin jacket. When the annular member (b) has only one layer, the surface of the powder, and when a plurality of (b) is used, the two powder-side surfaces of (b) are respectively coated with the fluororesin jacket. It is preferable to contact.

  In the present invention, the inorganic powder is selected from barium sulfate, talc, clay, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, silicic acid, silicon dioxide, calcium carbonate, sodium carbonate, calcium hydroxide, and magnesium carbonate. It is preferably at least one compound selected from the group consisting of barium sulfate.

  An annular member for a fluororesin-wrapped gasket according to the present invention is an annular member composed of one or a plurality of layers constituting an annular core body that is fitted into an annular groove of a fluororesin jacket. At least one annular member among the one-layer or plural-layer annular members constituting the core body includes an organic fiber, an inorganic fiber, an inorganic powder, and a binder.

  In the annular core for a fluororesin-wrapped gasket of the present invention, the inorganic powder comprises barium sulfate, talc, clay, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, silicic acid, silicon dioxide, calcium carbonate, It is preferably at least one compound selected from sodium carbonate, calcium hydroxide, and magnesium carbonate, and more preferably barium sulfate.

  In the present invention, the average particle size of the inorganic powder is preferably 1.5 μm or less. The fluororesin-wrapped gasket according to the present invention is excellent in the crushing property at normal temperature and the airtight property at high temperature.

  In the present invention, the organic fiber in the annular member is 5 to 40% by weight, the inorganic fiber is 20 to 85% by weight, the inorganic powder is 10% by weight or more, and the remaining amount of the binder (however, the weight of each annular member) Is 100% by weight).

In the present invention, the inorganic fiber preferably has a fiber diameter of 20 μm or less and a fiber length of 0.01 mm or more.
The core material (non-asbestos-based felt material) for fluororesin-wrapped gaskets or the annular member for the core material according to the present invention is excellent in crushing characteristics at normal temperature and airtight characteristics at high temperatures.

  Hereinafter, the fluororesin-wrapped gasket and the core material (felt) for the gasket according to the present invention will be specifically described with reference to preferred embodiments shown in the drawings. In addition, in this specification and an accompanying drawing, the same code | symbol is attached | subjected to the same member.

  FIG. 1 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to an embodiment of the present invention. FIG. 2 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to another embodiment of the present invention.

  A first fluororesin-wrapped gasket 10 shown in FIG. 1 has an annular core body 14 and a fluororesin jacket 12 to which the annular core body 14 is attached. In the annular groove 19 of the fluororesin jacket 12, the annular core body 14 formed by sequentially laminating a plurality of, in particular, three layers of annular members 18a, 16, 18b is fitted.

<Fluororesin jacket>
First, the fluororesin jacket 12 mainly contributes to the improvement of chemical resistance of the gasket, and is modified polytetrafluoroethylene (see Japanese Patent Publication No. 3-39105), tetrafluoroethylene resin (PTFE), tetrafluoroethylene-par. Fluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer resin (EPE), tetrafluoride It is made of a fluororesin such as ethylene-ethylene copolymer resin (ETEE) or vinylidene fluoride resin (PVDF).

These fluororesins can be used alone or in combination of two or more.
<Annular member>
In the fluororesin-wrapped gasket 10, the annular core body 14 is mainly responsible for improving the elasticity and strength of the gasket, and is formed by laminating a plurality of annular sheets (annular members) 18a, 16, 18b as described above. ing. Of the annular members 18a, 16, and 18b that constitute the annular core body 14, the annular members 18a and 18b that are in close contact with the jacket 12 contain organic fibers, inorganic fibers, inorganic powder, and a binder.

  The inorganic powder contained in the annular members 18a and 18b may be uniformly dispersed in the annular members as shown in FIG. 1, and the outer coverings of the annular members 27 and 28 as shown in FIG. It may be unevenly distributed on the side surfaces 27b and 28b.

  In particular, when the inorganic powder contained is uniformly dispersed in the annular member as shown in FIG. 1, the inorganic powder adheres to the fiber surface, so that organic fiber-organic fiber, organic fiber-inorganic By improving the adhesion of fibers such as fibers and inorganic fibers-inorganic fibers, the effect of obtaining a gasket having excellent crushing characteristics can be obtained, and the outer surface of the annular members 27 and 28 as shown in FIG. If it is unevenly distributed in 27b and 28b, the adhesion between the fluororesin jacket and the annular member is improved, and the effect of suppressing the creep of the jacket and obtaining a gasket with excellent sealing characteristics can be obtained. In FIG. 2, reference numerals 27a and 28a indicate felt layers made of organic fibers, inorganic fibers and a binder, and reference numerals 27b and 28b indicate inorganic powder layers mainly made of an inorganic powder and a binder.

  The felt layer 27a and the inorganic powder layer 27b are laminated to form the annular member 27, and the felt layer 28a and the inorganic powder layer 28b are laminated to form the annular member 28.

  In these annular members, the inorganic powder content may continuously decrease in the thickness direction of the layer from the outer member 12 side surface 11b, 13b of the annular member toward the annular sheet 16 side.

  The annular sheet (annular member) 16 is composed of a rubber plate, a cork plate, and a joint sheet material, and is preferably composed of a joint sheet material. The joint sheet material is not particularly limited. For example, (i) a material made of aramid fiber and rubber, and (ii) an organic fiber such as an aramid fiber and an inorganic fiber, like the annular members 18a and 18b in FIG. And inorganic powder and a binder such as rubber, and the composition ratio thereof is different from the annular members 18a, 18b, etc. of FIG. The annular sheet (annular member) 16 is connected to a communication hole or the like that communicates the annular groove back part 5 and the outside in the radial direction so that the gas and liquid in the annular groove back part 5 can be discharged to the outside. Means may be provided.

  Hereinafter, the annular members 18a and 18b will be described in detail. As described above, the annular members 18a and 18b contain organic fibers, inorganic fibers, inorganic powder, and a binder.

  As the organic fiber, an organic fiber (heat-resistant organic fiber) having an initial strength of 50% or more even after heating at 200 ° C. for 100 hours is preferable. Examples of such heat-resistant organic fibers include aramid fibers, carbon fibers, Teflon fibers, and the like, and these organic fibers can be used alone or in combination of two or more. Among these organic fibers, fibers that can be fibrillated and have a pulp shape (branched shape) are particularly desirable.

  As the inorganic fiber, conventionally known ones such as glass fiber, zirconia fiber, ceramic fiber, rock wool and the like can be widely used, and these inorganic fibers can be used alone or in combination of two or more.

  Among these inorganic fibers, those having a relatively small fiber diameter (fiber diameter of 20 μm or less, preferably 0.1 to 5 μm) and a fiber length of 0.01 mm or more, preferably 0.1 to 10 mm are desirable. As a desirable inorganic fiber having a relatively small fiber diameter and a fiber length in the above range, rock wool is exemplified.

  Examples of the inorganic powder include talc, clay, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, silicic acid, silicon dioxide, calcium carbonate, sodium carbonate, calcium hydroxide, and magnesium carbonate. Species or a combination of two or more can be used. Of these inorganic powders, barium sulfate is preferred. Among the inorganic powders, those having an average particle size of usually 1.5 μm or less, preferably 0.5 μm or less, more preferably 0.2 μm or less are desirable. By using inorganic powder having such a particle size, the surface energy of the inorganic powder can be used to enhance the adhesion between fibers and improve the strength of the annular member (felt material), and the annular member can be moderately flexible. And density can be imparted, and the sealing characteristics and crushing characteristics can be improved.

  The binder is not particularly limited, and conventionally known binders can be widely used, and examples thereof include rubber-based banders such as natural rubber and NBR; resin-based binders such as acrylic resins; and acrylic resins are preferably used.

  In such annular members 18a and 18b, the organic fiber is usually 5 to 40% by weight, preferably 10 to 40% by weight, and the inorganic fiber is usually 20 to 85% by weight, preferably 30 to 70%. In the amount of wt%, the inorganic powder is usually contained in an amount of 10 wt% or more, preferably 30 wt% or more, and the binder is contained in the remaining amount (provided that the weight of each annular member is 100 wt%). It is desirable.

  When organic fiber is included in the above amount, the resulting gasket has a moderate stress relaxation at high temperature, good airtightness at high temperature, and tends to have excellent breaking strength at normal temperature. When the inorganic fiber is contained in the above amount, the fiber diameter of the inorganic fiber is relatively large (for example, fiber diameter of 5 to 10 μmφ). There is a tendency that the relaxation becomes small, the flexibility is hardly lowered, and the airtight property at high temperature is excellent.

  Further, when the inorganic powder is uniformly dispersed in the annular member in the above amount, the adhesion between the inorganic fiber and the organic fiber, between the organic fibers, or between the inorganic fibers can be increased. Since the strength of the annular member obtained by blending both the organic fiber and the fiber can be increased more effectively, and the adhesion strength between the fibers can be increased, the obtained gasket is the annular member 18a constituting the gasket. , 18b can be increased in strength (felt part strength), stress relaxation can be reduced, gasket sealing performance at high temperatures can be stabilized, and the surface layer 11b of the annular members (felt materials) 18a, 18b. , 13b increases the frictional resistance between the felt materials 18a and 18b and the fluororesin outer sheath 12, thereby improving the crushing strength of the gasket. There is a direction.

<Manufacture of annular member>
In order to manufacture the annular members 18a and 18b in which such inorganic powder is uniformly dispersed, conventionally known methods can be used. For example, the above-mentioned amounts of organic fiber, inorganic fiber, and inorganic powder are used. In addition, it can be produced by a papermaking process in which an unvulcanized binder is blended, dispersed in water, finished in multiple stages, and dried with a hot roll at 100 ° C to 200 ° C.

  Further, as shown in FIG. 2, a conventionally known method is used to manufacture an annular member in which inorganic powder is unevenly distributed only on the outer sheath 22a side of the annular member 27, ie, 27b, and on the outer sheath 22b side of the annular member 28, ie, 28b. For example, after blending the above-mentioned amounts of organic fiber, inorganic fiber and unvulcanized binder, making paper by the same process as the above paper making process, spraying inorganic powder dispersed in water Can be manufactured by spraying.

<Manufacture of gaskets>
In order to manufacture the fluororesin-wrapped gasket 10 as shown in FIG.

  The annular members 18a and 18b are bonded to both surfaces of the annular sheet 16 using an adhesive mainly composed of resin or rubber, for example, and the annular core body 14 is formed. Further, as shown in FIG. 1, the surface (in particular, the inner peripheral surface and the upper and lower surfaces) of the annular core body 14 is covered with a fluororesin jacket 12 cut out from a fluororesin sleeve of a predetermined size by lathing. The fluororesin jacket 12 having such a shape is cut out by pressing the cutting bite from the outer diameter side of the fluororesin sleeve. In order to form the annular groove 19, the cutting bit pressed from the outer diameter side is provided at the position of 6. It is sufficient to process it so that the inner diameter side end portion 15a remains. Further, the annular core body 14 may be formed by laminating the annular sheet 16 and the annular members 18a and 18b as described above, and the sheet-like material before being processed into an annular shape has a layer structure as shown in FIG. After pasting together, it can also be punched into a ring of a predetermined size.

  In such a fluororesin-wrapped gasket 10, even when a load is excessively applied at the time of initial tightening, the annular core material does not collapse. That is, when the initial tightening is excessive, the core material 14 does not cause a creep phenomenon before the fluororesin sheath 12 is broken, and the gasket stress is appropriately maintained. The sealing performance is excellent.

  Further, in such a gasket 10, as shown in FIGS. 6 and 7, which will be described later, the annular core bodies 64 and 74 are composed of only one-layer annular sheets (annular members) 68 and 78. Compared to those having no joint sheet layer 16, the crushing strength is particularly excellent. In addition, since the annular core 14 can be sandwiched between two fluororesin jackets 12a and 12b and the inner peripheral side ends thereof can be joined together, a U-shaped cross section ( Compared to a gasket having a U-shaped outer cross-section (see reference numeral 32 in FIG. 3 to be described later), it has an effect that it is easy to manufacture.

  The fluororesin-wrapped gasket according to the present invention is not limited to the embodiment described above, and can be variously modified. For example, as shown by the number 32 in FIG. 3, the shape of the fluororesin jacket may be a U-shaped cross section, and as shown by the number 42 in FIG. The cross section may be U-shaped. Of these, the fluororesin jacket 32 as shown in FIG. 3 has the effect of preventing the fluid from staying in use by adjusting the gasket inner diameter to the flange inner diameter, and as shown in FIG. In the fluororesin sheath 42, even if an external fluid (including both liquid and gas) enters the annular groove back part 5 and is confined in the part, the inner part of the annular groove as shown in the gasket 10 shown in FIG. Since the acute angle portion 6 of the portion 5 is not provided, the innermost portion 6c of the fluororesin jacket 42 has an effect that it is difficult to break.

  Further, as indicated by reference numeral 52 in FIG. 5, the shape of the fluororesin jacket may be a bag shape in which the inner diameter side end portion 55a and the outer diameter side end portion 55b are sealed. Such a fluororesin-wrapped gasket 50 has a structure in which the opening on the outer diameter side end portion 15b of the fluororesin-wrapped gasket 10 shown in FIG. 1 is also sealed. This fluid is preferable because it can prevent the fluid from entering the annular core body 54 of the gasket 50 and can prevent a decrease in strength due to the annular member 54 getting wet.

  The shape of the fluororesin-wrapped gasket is not limited to the shape shown in FIG. 1, but may be a jacket shape as shown in FIG. 3 or FIG. 4, or the structure shown in FIG. 5 in which the opening on the outer diameter side is sealed. May be.

  In the above description, an embodiment in which the annular core is composed of a plurality of (three layers) annular members has been shown. However, the fluororesin-wrapped gasket according to the present invention is not limited to the above-described embodiment, and For example, as shown in FIGS. 6 and 7, the core body may be composed of one layer (one sheet) of annular members 68 and 78. That is, in FIG. 6, instead of the three-layered annular core body 14 shown in FIG. 1, an annular core body 64 composed of one annular member 68 is fitted into the annular groove 69 of the fluororesin jacket 62. The embodiment shown is shown. Further, in FIG. 7, instead of the three-layered annular core body 44 shown in FIG. 4, an annular core body 74 composed of one annular member 78 is fitted in the annular groove 79 of the fluororesin jacket 72. The embodiment shown is shown. In such an annular member (annular core body), inorganic powder typified by barium sulfate may be unevenly distributed on the outer surface and the outer surface (not shown).

  The materials of these annular members 68 and 78 are the same as the annular members 18a and 18b in FIG. As described above in detail, in the present invention, the annular member constituting the annular core material of the fluororesin-wrapped gasket includes organic fibers, non-asbestos inorganic fibers, inorganic powder (preferably barium sulfate), and a binder. Therefore, it has excellent environmental safety and excellent crushing properties. The fluororesin-wrapped gasket of the present invention in which one or more (one layer) of the annular member is incorporated as a constituent material for the annular core material is used at a high temperature (about 200 ° C.) when used at room temperature. In this case, stress relaxation hardly increases, moderate flexibility, good airtightness is maintained, and it can withstand use at high temperatures.

  On the other hand, in the conventional non-asbestos-based fluororesin-wrapped gasket using a non-asbestos felt material as a core material, the crushing phenomenon was remarkable. The cause is considered as follows. Traditionally, asbestos felt material used for fluororesin-wrapped gaskets is a mixture of asbestos fibers with a small amount of rubber binder, and the asbestos fibers have a small fiber diameter and each fiber is shrunk and intricately intertwined. Therefore, the strength was relatively high.

  In contrast, non-asbestos felt materials for core members that replace asbestos felt materials have heretofore been composed of inorganic fibers as the main component, blended with inorganic powder and a small amount of organic binder. It was. That is, asbestos fiber is replaced with inorganic powder and inorganic fiber among the blended components of the conventional asbestos felt material.

  However, since these non-asbestos felt materials are mainly composed of rigid and large-diameter inorganic fibers and inorganic powders, these non-asbestos felt materials have little entanglement between fibers and low strength. .

  ADVANTAGE OF THE INVENTION According to this invention, the fluororesin wrapped gasket excellent in the crushing characteristic at normal temperature and the airtight characteristic under high temperature is provided.

  The core material (non-asbestos-based felt material) for a fluororesin-wrapped gasket according to the present invention and the annular member for the core material are excellent in crushing characteristics at normal temperature and airtight characteristics at high temperature. In particular, in the above fluororesin-wrapped gasket, by using a modified PTFE or a PFA resin having a reduced amount of unstable end groups and having only -CF3 end groups as the jacket material, Not only is the fracture strength improved, the crushing strength of the core material has also been improved, the safety against over-tightening when tightening the gasket has been improved, and the flow of fluid inside the pipe body at high temperatures, repeated shut-off, etc. As a result, the bending resistance to pressure cycles and the seal retention characteristics at high temperatures are significantly improved.

  In particular, a fluororesin-wrapped gasket in which inorganic powder, preferably barium sulfate is unevenly distributed on the surface of the annular core material (felt surface) has high airtightness performance at high temperatures.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited at all by this Example.

<Measurement method of crushing stress (when dry)>
A sample gasket was mounted between the flanges, and a load was applied with a hydraulic compression tester so that the gasket stress was 10 MPa, and the load was maintained for 5 minutes. Thereafter, the gasket was taken out, and it was visually confirmed whether or not a minute crack was generated on the surface of the core material. Thereafter, the gasket stress was increased every 5 MPa, and the above confirmation test was repeated while increasing the gasket stress until a minute crack was generated on the surface of the core.

<Method of measuring crushing stress (when wet)>
The crushing measurement when wet is the same as the crushing measurement when drying, except that the gasket is immersed in water for 24 hours in advance.

[Example 1]
PTFE (trade name “Polyflon M12”, Daikin Industries, Ltd.), which is generally used as the jacket material, is used, and the following three-layer non-asbestos core is used as the core material. Gasket dimensions: “JIS” A 10K 100A "fluororesin-wrapped gasket was manufactured (FIG. 1).

The thickness of each layer is as follows. Outer coating: 0.4 mm thick Core: annular member / joint sheet / annular member = 0.8 mm / 0.8 mm / 0.8 mm three-layer structure, thickness of the entire core 2.4 mm
(A) Two annular members:
(1) Heat-resistant organic fiber (aramid fiber, trade name "Conex" (manufactured by Teijin Limited)
(2) Inorganic fiber (rock wool, trade name “S Fiber Fiber” (manufactured by Nippon Steel Chemical Co., Ltd.)
(3) Inorganic powder (barium sulfate, average particle size 0.1 to 0.2 μm)
(4) Binder (NBR latex)
(1) / (2) / (3) / (4) (ratio by weight) = 20/50/26/4
(B) Joint sheet (aramid fiber 10% by weight / rubber 40% by weight / inorganic filler 50% by weight, thickness 0.8 mm) A plurality of the above fluororesin-wrapped gaskets were prepared. The fluororesin-wrapped gasket is attached to a flange (flange material: “SUS 304”, flange surface roughness: Rmax 18-25 μm), applied with various gasket surface pressures, held for 5 minutes for each surface pressure, and then taken out. The surface pressure at which minute cracks occurred on the surface of the core material was defined as the intermediate core collapse surface pressure.

  The core collapse surface pressure of the obtained fluororesin-wrapped gasket was 120 MPa when dried and 100 MPa when wet. The results are also shown in Table 1.

  Further, this fluororesin-wrapped gasket was attached to the same flange as described above, and the hermetic internal pressure (measured by applying nitrogen gas after heating at 200 ° C. for 100 hours) was 3.5 MPa.

[Example 2]
A fluororesin-wrapped gasket was produced in the same manner as in Example 1 except that modified PTFE (trade name “Polyflon M-112”, Daikin Industries, Ltd.) was used as the jacket material.

As a result, the core collapse surface pressure of the fluororesin-wrapped gasket obtained in Example 2 was 130 MPa when dried and 120 MPa when wet. The airtight internal pressure was 3.0 MPa.
The results are also shown in Table 1.

[Comparative Example 1]
In Example 1, a fluororesin-wrapped gasket was prepared in the same manner as in Example 1 except that the composition was changed to 65 parts by weight of rock wool, 31 parts by weight of sepiolite, and 4 parts by weight of binder as shown in Table 1.

The obtained fluororesin-wrapped gasket had a crushing stress (when dried) of 70 MPa and a crushing stress (when wet) of 40 MPa. Further, this fluororesin-wrapped gasket was attached to the same flange as described above, and the hermetic internal pressure (measured by applying nitrogen gas after heating at 200 ° C. for 100 hours) was 3.0 MPa.
The results are also shown in Table 1.

[Comparative Example 2]
In Example 1, as shown in Table 1, a fluororesin-wrapped gasket was prepared in the same manner as in Example 1 except that asbestos fiber was replaced by 80 parts by weight, sepiolite 16 parts by weight, and binder 4 parts by weight.

The resulting fluororesin-wrapped gasket had a crushing stress (when dried) of 110 MPa and a crushing stress (when wet) of 60 MPa. Further, this fluororesin-wrapped gasket was attached to the same flange as described above, and the hermetic internal pressure (measured by applying nitrogen gas after heating at 200 ° C. for 100 hours) was 3.0 MPa.
The results are also shown in Table 1.

FIG. 1 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to an embodiment of the present invention. FIG. 2 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to another embodiment of the present invention. FIG. 3 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to another embodiment of the present invention. FIG. 4 is a cross-sectional view of a fluororesin-wrapped gasket according to another embodiment of the present invention. FIG. 5 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to another embodiment of the present invention. FIG. 6 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket according to another embodiment of the present invention. FIG. 7 is a cross-sectional view of a fluororesin-wrapped gasket according to another embodiment of the present invention. FIG. 8 is a cross-sectional view of a conventional fluororesin-wrapped gasket. FIG. 9 is a cross-sectional view of a conventional fluororesin-wrapped gasket.

Explanation of symbols

5: Annular groove depth 6: An acute angle part 6c: Annular groove depth: 10, 20, 30, 40, 50, 60, 70 ...... Fluoropolymer-wrapped gasket 11a, 21a, 31a, 41a, 51a, 61a, 71a ... Upper cover side surface (surface) of annular member
11b, 21b, 31b, 41b, 51b, 61b, 71b...
12, 22, 32, 42, 52, 62, 72... Fluororesin jacket 12a, 22a, 32a, 42a, 52a, 62a, 72a... )
12b, 22b, 32b, 42b, 52b, 62b ... Upper fluororesin jacket (upper jacket)
13a, 23a, 33a, 43a, 53a, 63a ... The outer side surface (surface) of the annular member or annular core
13b, 23b, 33b, 43b, 53b, 63b, 73b ... The outer side surface (surface) of the annular member or annular core
14, 24, 34, 44, 54, 64, 74 ... annular core 15b ... gasket outer diameter side end 16, 26, 36, 46, 56 ... annular Sheet (joint sheet)
27... An annular member in which inorganic powder is unevenly distributed on the outer surface side 27 a, 28 a... Layer mainly composed of organic fiber, inorganic fiber and binder 28. Ring members 27b, 28b ... unevenly distributed on the outer surface of the jacket 27b ... Layers containing inorganic powder (barium sulfate) and binder as main components 18a, 38a, 48a, 58a, 68a, 78a ... Ring members (Lower surface side annular member)
18b, 38b, 48b, 58b, 68b, 78b ... annular member (upper surface side annular member)
19, 29, 39, 49, 59, 69, 79... Annular groove 55a... Inner diameter side end portion of fluororesin jacket 15b, 25b, 35b, 45b, 55b. Outer diameter side end of resin jacket or gasket

Claims (6)

A fluororesin-wrapped gasket in which an annular core, an annular sheet and an annular member are laminated in this order in an annular groove of the fluororesin jacket,
The annular member includes organic fiber, inorganic fiber, inorganic powder and binder,
The annular sheet is composed of at least one selected from the group consisting of a rubber plate, a cork plate and a joint sheet material,
A fluororesin-wrapped gasket, wherein the inorganic powder is uniformly dispersed in an annular member. A fluororesin-wrapped gasket in which an annular core, an annular sheet and an annular member are laminated in this order in an annular groove of the fluororesin jacket,
The annular member includes organic fiber, inorganic fiber, inorganic powder and binder,
The annular sheet is composed of at least one selected from the group consisting of a rubber plate, a cork plate and a joint sheet material,
A fluororesin-wrapped gasket, wherein the inorganic powder is unevenly distributed on the surface of the fluororesin jacket side in an annular member.   The inorganic powder is at least selected from barium sulfate, talc, clay, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, silicic acid, silicon dioxide, calcium carbonate, sodium carbonate, calcium hydroxide, and magnesium carbonate. The fluororesin-wrapped gasket according to any one of claims 1 and 2, wherein the gasket is one kind of compound.   The fluororesin-wrapped gasket according to any one of claims 1 to 3, wherein an average particle size of the inorganic powder is 1.5 µm or less.   When the weight of the annular member in the annular member is 100% by weight, the organic fiber is 5 to 40% by weight, the inorganic fiber is 20 to 85% by weight, the inorganic powder is 10% by weight or more, and the binder is The fluororesin-wrapped gasket according to any one of claims 1 to 4, wherein the gasket is contained in the remaining amount.   The fluororesin-wrapped gasket according to any one of claims 1 to 5, wherein the inorganic fiber has a fiber diameter of 20 µm or less and a fiber length of 0.01 mm or more.

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