JP2005337401A - Gasket coated with fluororesin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gasket coated with fluororesin to be used for in a wide temperature range, easy to be handled without requiring excessive fastening force when using, and improved in service life. <P>SOLUTION: This gasket coated with fluororesin is formed by fitting an annular center core body formed of a single layer of an annular member or a plurality of laminated annular members in an annular groove of a fluororesin cover. At least one layer of the annular member (a) structuring the annular center core body is formed of an expansion graphite sheet, and in order to prevent the generation of slip between the fluororesin cover and the annular member (a), at least one layer of other annular member (b) is laminated or coated on each of the obverse and reverse of the annular member (a). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluororesin-wrapped gasket, and more particularly to a fluororesin-wrapped gasket that has a wide usable temperature range, does not require an excessive tightening force during use, has excellent handleability, and has a long life.

  Conventionally, a fluororesin-wrapped gasket is composed of a fluororesin jacket excellent in corrosion resistance and a core (core body) made of a joint sheet excellent in elasticity and flexibility, which is covered with the jacket. It tends to be excellent in corrosion resistance and elasticity.

  Fluororesin wrapping gaskets, especially fluorinated resin wrapping gaskets that use a non-ass joint sheet as the core, are not sufficiently heat resistant, and when used for a long time at high temperatures, the non-ass joint sheet cures and sealability decreases. There is a problem that it is not suitable for use at high temperatures.

On the other hand, the fluororesin-wrapped gasket described in Japanese Patent Application Laid-Open No. 2000-104732 (Patent Document 1) previously proposed by the applicant of the present application has a single layer or a plurality of annular gaskets in the annular groove of the fluororesin jacket A fluororesin-wrapped gasket in which an annular core body formed by laminating members is inserted, wherein at least one layer of the annular member constituting the annular core body includes an organic fiber, an inorganic fiber, an inorganic powder, and a binder. It has excellent crushing properties at room temperature and airtightness properties at high temperatures.

  However, even if this fluororesin-wrapped gasket is used as a gasket for a highly corrosive chemical fluid that requires corrosion resistance and chemical resistance, it is a gasket for the food industry or pure water that does not want to be contaminated. To be used as a gasket used in the region exceeding ℃, as a binder for the annular core, natural rubber that melts and decomposes at a relatively low temperature, rubber binder such as NBR, resin binder such as acrylic resin Is not sufficient in terms of heat resistance, and instead a spiral gasket using PTFE as a filler has been used.

However, this spiral gasket has a problem that it is more expensive than a fluororesin-wrapped gasket, requires an excessive tightening force, and is inferior in handleability.
Further, in the graphite sheet gasket described in Japanese Utility Model Publication No. 60-154664 (Patent Document 2), the surface of the graphite sheet is peeled off by forming a fluororesin film on the surface of the graphite sheet by impregnation or the like. A graphite sheet gasket that prevents the above is disclosed.

  The film thickness is 5 to 20 μm, and the coating is formed by spraying the coating member on the graphite sheet, coating, or dipping (immersing) the graphite sheet on the coating member (solution). Etc. are also described.

However, the graphite sheet gasket described in Patent Document 2 has problems such as generation of graphite scraps when mounted and used, and is used in places where corrosion resistance and chemical resistance are required in terms of basic quality and performance. In addition, it is not suitable for use as a gasket for the food industry or for pure water, which does not want to be contaminated.
JP 2000-104832 A Japanese Utility Model Publication No. 60-154664

  The present invention is intended to solve the problems associated with the prior art as described above, has a wide usable temperature range, does not require excessive tightening force during use, and is excellent in handleability, An object of the present invention is to provide a fluororesin-wrapped gasket having a long life.

  A first fluororesin-wrapped gasket according to the present invention is a fluororesin-wrapped gasket in which an annular core body formed by laminating a single layer or a plurality of annular members is inserted into an annular groove of a fluororesin sheath, At least one layer of the annular member (a) constituting the annular core is made of an expanded graphite sheet.

  In a preferred embodiment of the present invention, the annular core is further laminated or coated with at least one other annular member (b) on the front and back surfaces of the annular member (a) made of the expanded graphite sheet. It is desirable to be made.

In the present invention, it is particularly preferable that the “other annular member” (b) is made of a felt sheet containing organic fibers, inorganic fibers and a binder.
In the present invention, the “other annular member” (b) is preferably made of a felt sheet further containing an inorganic powder.

  In the second fluororesin-wrapped gasket according to the present invention, the annular member (a) is composed of two layers, and a metal plate (foil) is interposed between the annular member (a) and the annular member (a). It is preferable to be interposed.

  According to the first fluororesin-wrapped gasket according to the present invention, there is provided a fluororesin-wrapped gasket that has a wide usable temperature range, does not require an excessive tightening force during use, has excellent handleability, and has a long life. Can be provided.

  In particular, the second fluororesin-wrapped gasket in which a metal plate such as a SUS plate is inserted between the annular member (a) and the annular member (a) is more portable than the first fluororesin-wrapped gasket. In addition, the shape retainability can be further improved, and excellent sealing properties can be exhibited in the same manner as the first fluororesin-wrapped gasket.

Hereinafter, the fluororesin-wrapped gasket according to the present invention will be specifically described with reference to the accompanying drawings.
In the following description, the same members are denoted by the same reference numerals.

[Fluoropolymer-wrapped gasket]
FIG. 1 is a partial perspective view including a cross section of a main part of a fluororesin-wrapped gasket 10 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 20 according to another embodiment of the present invention.
<Figure 1>
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 fluororesin-wrapped gasket 10, the annular core body 14 having a structure in which a plurality of, in particular, three layers of the annular members 18 a, 16, 18 b are sequentially stacked is fitted in the annular groove 19 of the fluororesin jacket 12. Has been. In other words, in this fluororesin-wrapped gasket 10, the annular core 14 is laminated or coated with the other annular members 18 a and 18 b one by one on the front and back surfaces of the annular member 16 made of the expanded graphite sheet. The three-layer annular members 18a, 16, 18b are joined to each other by sticking / adhesion, occlusion, or the like.

  The fluororesin jacket 12 bears chemical resistance of the gasket, and the annular member 16 made of an expanded graphite sheet in the annular core 14 bears elasticity and strength as a gasket. ) 18a and 18b are located between the fluororesin jacket 12 and the annular member 16 made of an expanded graphite sheet, and have a function of preventing the mutual slipping and preventing the annular member 16 and the like from being crushed.

  The dimensions of the fluororesin-wrapped gasket 10 are not particularly limited. For example, the outer diameter is approximately 40 to 1800 mm, the inner diameter is approximately 10 to 1500 mm, and the difference between the outer diameter and the inner diameter (outer diameter−inner diameter) is approximately 10 to 1500 mm. The thickness is about 20 to 60 mm.

The thickness of the annular member (a) 16 is preferable in terms of the handleability and portability of the fluororesin-wrapped gasket obtained to be about 0.5 to 5.0 mm. The thicknesses of the “two other annular members” (b) 18a and 18b of the two layers are each preferably about 0.3 to 2.0 mm.
<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), tetrafluoroethylene-ethylene copolymer resin (ETEE) And made of a fluororesin such as vinylidene fluoride resin (PVDF). Among these fluororesins, PTFE, PFA, and the like are preferable in terms of heat resistance and chemical resistance of the obtained fluororesin-wrapped gasket.

These fluororesins can be used alone or in combination of two or more.
<Annular core>
The annular core body 14 is mainly responsible for improving the elasticity and strength of the gasket, and as described above, a plurality of annular sheets (annular member (a) and other annular members (b)) 18a, 16, 18b are laminated. It is configured. Of the annular members 18a, 16, 18b constituting the annular core body 14, the annular member 16 inserted so as to be sandwiched between the two "other annular members" (b) 18a, 18b. Is made of an expanded graphite sheet as described above.
<Annular member (a)>
The expanded graphite sheet is not particularly limited, and expanded graphite sheet or graphite sheet produced by rolling expanded graphite or graphite with a roll or the like can be used. Furthermore, graphite or expanded graphite is a base material. These include, for example, a sheet containing rubber and a sheet described in Japanese Patent Application No. 2003-121407.

  Furthermore, when forming a sheet based on expanded graphite or graphite, by blending butyl rubber or the like, the same intention and function as in the case of the following <other annular member (b)>, that is, friction of the above sheet The thing which aimed at the slip prevention by raising a coefficient may be used.

Moreover, the laminated product formed by sticking an expanded graphite to a metal plate (foil) may be sufficient.
Thus, the expanded graphite may be used as an expanded graphite sheet by itself, for example, as shown in FIG. 6 described later, expanded graphite sheets 66a and 66b on both surfaces of a stainless steel plate (foil) 100, (i) Affixed with an adhesive or the like, or (ii) A large number of hooks that can be engaged and locked on the front and back surfaces of a metal plate, and a mating member such as an expanded graphite sheet without using an adhesive Using a metal plate such as “hook metal” that can be joined together, and (iii) mesh (metal mesh) or punched stainless steel plate (foil) However, in the present invention, a laminated product of expanded graphite and a metal plate is preferable because it is excellent in handleability. The method for joining / adhering the expanded graphite and the metal plate is not particularly limited, but those that are joined / adhered by hook metal or the like without using an adhesive are less likely to cause deterioration in sealing performance at high temperatures. And more preferable. In addition, when expanded graphite and metal plate are bonded / bonded with an adhesive / adhesive, the adhesive in the gasket decomposes / disappears when the gasket is heated, and the area becomes hollow, resulting in reduced sealing performance due to permeation leakage. There is a risk of causing.

<Other annular member (b)>
In addition, the above-mentioned two-layer “other annular members” (b) 18a and 18b may be the same as or different from each other, but are preferably the same, and are an annular member made of a fluororesin jacket 12 and an expanded graphite sheet. It is sufficient that it has a function of preventing the mutual slippage and preventing the crushing of the annular member 16 and the like, and is arranged by lamination or application. In this fluororesin-wrapped gasket 10, two layers of “other annular members” (b) 18 a and 18 b are sandwiched between the annular member (a) and the fluororesin jacket 12. One layer is disposed on each of the front and back surfaces.

  The material of the other annular member (b) may be a material having a large friction coefficient for preventing slipping, such as glass, ceramic sheet and cloth, organic or inorganic coated material, and the like. It is done. Alternatively, a rubber material such as butyl rubber may be applied to the expanded graphite sheet to form another annular member layer on the surface of the expanded graphite sheet.

Furthermore, as described in (a) above, when forming a sheet based on expanded graphite or graphite, butyl rubber or the like may be added to increase the friction coefficient of the sheet.
Further, as the other annular member (b), a felt sheet containing organic fibers, inorganic fibers, and a binder is preferably used from the viewpoint of processability and pressure resistance, and further includes inorganic powder. It is more preferable.

  In the first fluororesin-wrapped gasket 10, as the “other annular member (b)” 18 a and 18 b of two layers of the fluororesin jacket 12, Japanese Patent Laid-Open No. 2000-104732 previously proposed by the present applicant. The thing similar to the thing described in (patent document 1) is used suitably.

  Hereinafter, the annular members 18a and 18b will be described in detail. The annular members 18a and 18b preferably contain organic fibers, inorganic fibers, and a binder as described above, and further contain inorganic powder as necessary.

  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 (registered trademark) 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.

  The inorganic powder preferably includes talc, clay, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, silicic acid, silicon dioxide, calcium carbonate, sodium carbonate, calcium hydroxide, magnesium carbonate, and the like. A body can be used 1 type or in combination of 2 or more types. 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. Examples thereof include natural rubber, rubber-based binders such as 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 the inorganic powder is uniformly dispersed as shown in FIG. 1, a conventionally known method can be used, for example, Japanese Patent Laid-Open No. 2000-104732 ( Patent Document 1) As described in the column “0038”, the above-mentioned amounts of organic fiber, inorganic fiber, inorganic powder and unvulcanized binder were blended, dispersed in water, and finished in multiple stages. Then, it can manufacture by the papermaking process dried with a 100 degreeC-200 degreeC hot roll.

  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, that is, 27b, and only on the outer sheath 22b side of the annular member 28, that is, 28b. For example, as described in the “0039” column of JP-A-2000-104732 (Patent Document 1), the above-mentioned amounts of organic fiber, inorganic fiber, and unvulcanized binder are mixed. The paper can be produced by spraying and spraying inorganic powder dispersed in water after paper making by the same process as the above paper making process.

[Manufacture of gaskets]
Moreover, what is necessary is just to follow the method of Unexamined-Japanese-Patent No. 2000-104832 (patent document 1) in order to manufacture the fluororesin wrapped gasket 10 as shown in FIG.

  That is, the annular cores 14 are formed by bonding the annular members 18a and 18b to both surfaces of the annular sheet 16 made of expanded graphite using an adhesive mainly composed of resin or rubber, for example. 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.

  In addition, such a gasket 10 can be manufactured by sandwiching the annular core body 14 so as to be sandwiched between two fluororesin jackets 12a and 12b, and joining the inner peripheral side ends thereof. Therefore, it has an effect that it is easier to manufacture than a gasket having a U-shaped cross section (see 42 in FIG. 4 described later) and a U-shaped cross section (see 32 in FIG. 3 described later).

  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, in the fluororesin-wrapped gasket 50 according to a preferred embodiment of the present invention, as shown by the reference numeral 52 in FIG. 5, the shape of the fluororesin jacket is such that the inner diameter side end portion 55a and the outer diameter side end portion 55b are sealed. It may be in the form of a bag.

  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.

In the above description, each of the annular cores is composed of a plurality (three layers) of annular members, and one layer of “annular members (a)” 16, 26 located in the middle in the direction perpendicular to the front and back surfaces. Each of 36, 46 and 56 is made of an expanded graphite sheet, and each of two layers of “other annular members (b)” (18a and 18b)
, (28a, 28b), (38a, 38b), (48a, 48b), (58a, 58b) play a role of preventing slippage between the expanded graphite sheet and the fluororesin jacket. , An embodiment comprising a felt sheet containing inorganic fibers, inorganic powder and a binder,
The fluororesin-wrapped gasket according to the present invention is not limited to the above embodiment, and a metal plate (metal layer) 100 may be further interposed in the annular core as shown in FIG. . This metal plate (metal layer) 100 may consist of only one layer (sheet) or may be provided with a plurality of layers (sheets).
<Fig. 6>
FIG. 6 is a partial perspective view including a cross section of the main part of the second fluororesin-wrapped gasket 20 according to the present invention.

  The fluororesin-wrapped gasket 60 shown in FIG. 6 is a metal plate (foil) 100 having substantially the same plane shape as the annular member 16 in the annular member 16 made of the expanded graphite sheet in the fluororesin-wrapped gasket 10 shown in FIG. 1 is the same as the fluororesin-wrapped gasket 10 shown in FIG.

  In other words, in this fluororesin-wrapped gasket 60, the annular member (a) 16 made of the expanded graphite sheet in the first fluororesin-wrapped gasket is composed of two layers (66a, 66b). A planar metal plate 100 substantially the same as the annular member (a) is interposed between the member 66b.

  Such a fluororesin-wrapped gasket 60 is further improved in portability and shape retention as compared with the first fluororesin-wrap gasket 10 shown in FIG. As with, excellent sealing performance can be exhibited.

  The metal plate 100 is not particularly limited, and those conventionally used in the manufacture of gaskets can be used. For example, the metal plate 100 is described in columns "0018" to "0019" of JP-A-7-27231. Various metal foils can be used without any particular limitation, such as stainless steel, steel, aluminum, copper, nickel, and the like. In the present invention, among these, considering heat resistance, chemical resistance, corrosion resistance, and the like, stainless steel (SUS) steel foil, particularly austenitic stainless steel foil is desirable. In the case of a metal foil that is easily corroded, the surface thereof may be subjected to a surface treatment such as galvanization.

  The thickness and planar dimensions of these metal plates are not particularly limited as long as the portability and shape retention can be improved, but considering workability and the like, usually 0.01 to 0.2 mm, preferably 0.01 to It is desirable to be 0.1 mm.

  Moreover, as a metal plate, the planar shape has a concentric circular shape which is a planar shape similar to the planar shape of the annular member 64, and one piece without a seam is preferable in terms of sealing properties. In the present invention, one to a plurality of such metal plates (foil) may be appropriately laminated so as to have a desired thickness or the like.

  In general, the metal plate 100 is often used for manufacturing the fluororesin-wrapped gasket 60 in a state of being bonded (joined) to the adjacent expanded graphite sheets 66a and 66b from the viewpoint of convenience of handling and the like. In that case, the bonding (bonding) method of the expanded graphite and the metal plate is not particularly limited, and is a method using an adhesive, a method of bonding (bonding) with an adhesive-less hook metal, a mesh (metal mesh) or punching. Examples include a method in which an expanded graphite sheet is bitten into a metal plate and joined. In the present invention, those that are bonded (joined) with an adhesive-less hook metal or the like are preferable in that they do not easily cause deterioration in sealing performance at high temperatures.

  Such a metal plate is not limited to the case where the metal plate is inserted into the annular member 16 made of the expanded graphite sheet of FIG. 1 as shown in FIG. 6, but the annular plate made of the expanded graphite sheet shown in FIGS. The members 26, 36, 46, and 56 may be inserted in the same manner as the metal plate 100 of FIG.

  In order to manufacture such a fluororesin-wrapped gasket 60, the above-described fluororesin-wrapped gasket 10 is used except that an expanded graphite sheet with a metal plate 100 interposed is used in place of the expanded graphite sheet in the manufacture of the fluororesin-wrapped gasket 10. What is necessary is just to make it the same as the case of manufacture of the resin wrapping gasket 10.

  As described above in detail, in the present invention, one layer of the annular member constituting the annular core material of the fluororesin-wrapped gasket is made of an expanded graphite sheet. For example, two layers of “other annular members” are preferably Organic fiber, non-asbestos inorganic fiber, inorganic powder (preferably barium sulfate) and binder are included, so it has excellent environmental safety, excellent crushing properties, and normal temperature (15-25 ° C) ~ Excellent airtightness at high temperatures (eg, about 200 to 260 ° C.), and the residual torque (%) is kept high even when used by repeatedly changing the temperature from room temperature to high temperature as described above for several cycles. Excellent compressibility.

  The magnitude of the residual torque indicates the magnitude of deterioration due to stress relaxation of the gasket. That is, it can be expected that a gasket having a large residual torque rate is less deteriorated due to stress relaxation than a gasket having a small residual torque, and can be used for a longer time (long life). However, if the residual torque is doubled, it cannot be said that the gasket life is also doubled (there is a proportional relationship).

The fluororesin-wrapped gasket of the present invention has a large (high) residual torque.
For example, an annular core 14 as shown in FIG. 1 has a three-layer structure, and a fluororesin-wrapped gasket having the same gasket size as defined in “JIS 10K 100A” is manufactured, and a flange (flange material: SUS304, flange surface roughness: Rmax 18 to 25 μm) and bolts to have an initial gasket clamping surface pressure of 24.5 MPa (250 kgf / cm ² ) at normal temperature (25 ° C.) (0 to 40 ° C. is also acceptable) In this state, nitrogen gas is sealed in the flange fastening body so as to obtain a desired gas pressure so that gas leakage does not occur. In this state, the flange fastening body is submerged and held for 15 minutes. Conducts a test (nitrogen gas seal test) that identifies gas leakage at gas pressure based on the presence or absence of underwater foaming, and gradually increases the gas pressure and repeats the same test. When the test is performed until gas leakage can be confirmed, the hermetic internal pressure is, for example, about 3.5 to 4.5 MPa, preferably about 3.8 to 4.5 MPa.

  Also, the fluororesin-wrapped gasket is attached to the flange, tightened with an initial gasket clamping surface pressure of 24.5 MPa, and held at high temperature (200 ° C. or 260 ° C.) for 48 hours, then allowed to cool and return to room temperature. After the operation of “confirming leakage” is repeated a total of three times (three cycles), the airtight internal pressure measured at room temperature is, for example, about 3.5 to 4.5 MPa, preferably about 3.8 to 4.5 MPa.

Further, the residual torque after repeating the above “3 cycles” is 65 to 84%, preferably about 70 to 84%.
In addition, in the fluororesin wrapping gasket 60 (Example 2) shown in FIG. 6 in which the metal plate 100 such as a SUS plate is inserted, the fluororesin wrapping gasket 10 (Example 1) shown in FIG. Although there is an improvement in portability and shape retention, the presence or absence of a metal plate in terms of airtight internal pressure at room temperature, airtight internal pressure after several cycles at room temperature to high temperature, and residual torque that is a measure of compression sag Regardless, both are good and show similar values.

In particular, as an asbestos-based gasket (Comparative Example 1) using a combination of an asbestos joint sheet and the above-mentioned two layers [other annular members (felt)] as a core material (annular core), a non-asbestos joint Conventional non-asbestos-based wrapping gasket (Comparative Example 2) that uses a sheet (non-ass joint sheet) and the above-mentioned two layers [other annular member (felt)], and a conventional gasket using an expanded graphite sheet containing SUS plate Compared to (Comparative Example 3)
The above-mentioned fluororesin-wrapped gaskets of the present invention (Examples 1 and 2) have good airtightness at room temperature, and airtightness (sealability) at high temperatures, particularly after repeated several cycles from room temperature to high temperature. Airtightness and residual torque are extremely high (stress relaxation is remarkably small), and even when subjected to repeated temperature changes over a long period of time, it is difficult to sag and has excellent heat resistance.

  Specifically, with a fluororesin-wrapped gasket made of PTFE, the fluororesin-wrapped gasket of the present invention can be used for a long time at a high temperature up to the continuous use temperature (260 ° C) of the cover PTFE, and has high sealing characteristics. Have.

  Even if the outer cover is made of a fluororesin, if the core is only expanded graphite as shown in Japanese Utility Model Laid-Open No. 60-154664 (Patent Document 2), a flow (slip) of the fluororesin will occur and the outer The material will be crushed and the sealing performance will be reduced.

  On the other hand, in the fluororesin-wrapped gasket of the present invention, the expanded graphite sheet and the specific felt material are used in combination as the annular core (core), and the fluororesin jacket and the core material are used. This prevents the core material from collapsing and improves the sealing performance.

  Thus, the fluororesin-wrapped gasket of the present invention not only has a high sealing property even at high temperatures (particularly 200 to 260 ° C.), but can be used for a long time (long life) as compared with conventional products.

Moreover, this fluororesin-wrapped gasket can be used in a wide temperature range from room temperature to the above high temperature, and is of high quality.
[Example]
Hereinafter, the fluororesin-wrapped gasket according to the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.

(The core is a “expanded graphite sheet + felt” fluororesin wrapped gasket)
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 produced (FIG. 1).

The thickness of each layer is as follows.
Outer coating: 0.4 mm thick.
Middle core: annular member / expanded graphite sheet / annular member = 0.8 mm / 1.6 mm
/ Three-layer structure of 0.8 mm, the thickness of the entire core is 3.2 mm.
(A) Two annular members:
(I) Heat-resistant organic fiber (aramid fiber, trade name “Conex” (manufactured by Teijin Limited),
(Ii) Inorganic fibers (rock wool, trade name “S Fiber Fiber” (manufactured by Nippon Steel Chemical Co., Ltd.))
(Iii) inorganic powder (barium sulfate, average particle size 0.1-0.2 μm),
(iv) Binder (NBR latex).
(I) / (ii) / (iii) / (iv) blending ratio (parts by weight) = 20/50/26/4. (B) Expanded graphite sheet (overall sheet thickness 1.6 mm).
A plurality of the fluororesin-wrapped gaskets were prepared.

A fluororesin-wrapped gasket is attached to a flange (flange material: “SUS 304”, flange surface roughness: Rmax 18 to 25 μm), and an initial clamping surface pressure of 24.5 MPa (
The flange was tightened so as to be 250 kgf / cm ² ).

In this state, a “nitrogen gas seal test” at room temperature (25) ° C. was first performed.
In the “nitrogen gas seal test”, nitrogen gas is sealed in a flange fastening body so that a predetermined gas pressure is obtained, and in this state, the flange fastening body is submerged and held for 15 minutes. This is a test that discriminates by presence or absence. When there is no gas leakage at the gas internal pressure (no foaming), the nitrogen gas internal pressure is increased again to confirm the presence or absence of underwater foaming. In this series of operations, the internal pressure is gradually increased until underwater foaming is confirmed, and the test is repeated to obtain the highest internal pressure (airtight internal pressure) at which underwater foaming does not occur.

As a result, the hermetic internal pressure of this fluororesin-wrapped gasket at normal temperature was 4.4 MPa.
Next, when the fluororesin wrapping gasket is attached to the flange of the flange fastening body and is tightened at an initial gasket clamping surface pressure of 24.5 MPa, nitrogen gas is applied so that a desired gas pressure is obtained so that no gas leakage occurs. Was sealed in a flange fastening body, heated in an electric furnace at a temperature of “200 ° C. or 260 ° C.” for 48 hours in this state, allowed to cool, and the sealing performance was confirmed at room temperature.

  In addition, the leakage confirmation is the same as the above “nitrogen gas seal test” (that is, the flange fastening body attached with the fluorine resin-wrapped gasket and sealed with nitrogen gas is submerged, held for 15 minutes, and the gas pressure is In the case where no underwater foaming was observed, the nitrogen gas internal pressure was further increased, and the above nitrogen gas seal test was conducted.

When nitrogen gas leakage was observed, the amount of leakage was measured by substituting in water.
A series of these steps (heating to leakage check) was set as one cycle, and this cycle was repeated three times.

The leak detectable range is 1.7 × 10 ^{−4 to} 1.7 × 10 ⁰ Pa · m ³ / s (0.1 to
1000 cc / min) and less than the leak detectable range was determined as “Seal”.

Further, the residual torque was measured after the “3 cycles”.
The sealability of the obtained fluororesin-wrapped gasket is 4.4 MPa (45 kg) at room temperature.
f / cm ² ) showed sealing (Seal), but no deterioration was observed after 200 ° C. × 48 hours (h) × 3 cycles, and 4.4 MPa (45 kgf / cm ² ) was sealed. .

Furthermore, even after 260 ° C. × 48 hours (h) × 3 cycles, no deterioration was observed, and an internal pressure of 4.4 MPa (45 kgf / cm ² ) was sealed.
The residual torque was 80% after 200 ° C. × 48 hours (h) × 3 cycles, and 70% after 260 ° C. × 48 hours (h) × 3 cycles.

  The results are also shown in Table 1.

(The core is "expanded graphite sheet with SUS plate + felt" series fluororesin wrapped gasket)
In Example 1, a fluororesin-wrapped gasket as shown in FIG. 6 was prepared instead of the fluororesin-wrapped gasket as shown in FIG.

That is, the following core was used as the core in Example 1, and instead of the above (b) expanded graphite sheet (total sheet thickness 1.6 mm), (b) -1 “expanded graphite with stainless steel sheet Except for using a sheet (expanded graphite sheet / stainless steel sheet / expanded graphite sheet), stainless steel sheet thickness: 0.05 mm ”, a fluororesin-wrapped gasket was prepared in the same manner as in Example 1, and the same test as above was performed. Went.
<Core>:
2. cyclic member / expanded graphite sheet with stainless steel sheet (expanded graphite sheet / stainless steel sheet / expanded graphite sheet) / annular member = 0.8 mm / 1.6 mm / 0.8 mm, three core thickness 2 mm.

As a result, the hermetic internal pressure of this fluororesin-wrapped gasket at normal temperature was 4.4 MPa.
The sealability of the obtained fluororesin-wrapped gasket is 4.4 MPa (45 kg) at room temperature.
f / cm ² ) showed sealing (Seal), but no deterioration was observed after 200 ° C. × 48 hours (h) × 3 cycles, and 4.4 MPa (45 kgf / cm ² ) was sealed. .

Furthermore, even after 260 ° C. × 48 hours (h) × 3 cycles, no deterioration was observed, and an internal pressure of 4.4 MPa (45 kgf / cm ² ) was sealed.
The residual torque was 80% after 200 ° C. × 48 hours (h) × 3 cycles, and 70% after 260 ° C. × 48 hours (h) × 3 cycles.

The results are also shown in Table 1.
[Comparative Example 1]
(The core is an asbestos joint sheet + felt-based fluororesin-wrapped gasket)
In Example 1 above, (b) -2: “joint sheet (component composition: 80% by weight of asbestos / butyl rubber-based vulcanization) instead of (b) an expanded graphite sheet with a stainless steel thin plate constituting a part of the core in Example 1 A fluororesin-wrapped gasket was prepared in the same manner as in Example 1 except that 10% by weight of rubber / 10% by weight of inorganic filler) was used, and a test similar to the above was performed.

As a result, the sealing performance of the fluororesin-wrapped gasket shown in Comparative Example 1 showed sealing (Seal) at 4.4 MPa (45 kgf / cm ² ) at room temperature, but 200 ° C. × 48 hours (h) × 3 cycles. After that, only a seal at an internal pressure of 2.9 MPa (30 kgf / cm ² ) was shown.

The residual torque was 50% for 200 ° C. × 48 hours × 3 cycles and 40% for 260 ° C. × 48 hours × 3 cycles.
The results are also shown in Table 1.
[Comparative Example 2]
(The core is a "non-ass joint sheet + felt" fluororesin wrapped gasket)
As a fluororesin-wrapped gasket, a fluororesin-wrapped gasket described in the “0059” column of Japanese Patent Application Laid-Open No. 2000-104832 (Patent Document 1) was prepared, and a test similar to the above was performed.

That is, in Example 1 described above, instead of (ii) an expanded graphite sheet containing a stainless steel thin plate that constitutes a part of the core, “0059” of Japanese Patent Laid-Open No. 2000-104832 (Patent Document 1).
(B) -3: “joint sheet (component composition: 10% by weight of aramid fiber / 40% by weight of rubber / 50% by weight of inorganic filler, thickness 0.8 mm)” is used. Except for the above, a fluororesin-wrapped gasket was prepared in the same manner as in Example 1, and a test similar to the above was performed.

As a result, the sealing performance of this fluororesin-wrapped gasket is 4.4 MPa (
45 kgf / cm ² ) showing sealing (sealing) is 200 ° C. × 48 hours (h) ×
After 3 cycles, the seal was only shown with an internal pressure of 2.5 MPa (25 kgf / cm ² ).

The residual torque was 30% when 200 ° C. × 48 hours × 3 cycles, and 25% when 260 ° C. × 48 hours × 3 cycles.
The results are also shown in Table 1.
[Comparative Example 3]
Comparative Example 3 is not a fluororesin-coated gasket but a numerical value of an expanded graphite sheet gasket containing SUS having only a core.

That is, in Example 1, a test similar to the above was performed using an expanded graphite sheet gasket containing SUS made of only a core without providing a fluororesin jacket.
The sealing performance of this expanded graphite sheet gasket containing SUS is 4.4 MPa at room temperature (4
Although 5 kgf / cm ² ) was sealed, after 200 ° C. × 48 hours (h) × 3 cycles, internal pressure 2.5 MPa (25 kgf / cm ² ) was only sealed. The residual torque was 40% when 200 ° C. × 48 hours × 3 cycles, and 30% when 260 ° C. × 48 hours × 3 cycles.

The results are also shown in Table 1.
From the above, the fluororesin-wrapped gaskets of the present invention shown in Examples 1 and 2 show better sealing properties at higher temperatures than the fluororesin-wrapped gaskets (comparative products) shown in any of the comparative examples. It can be predicted that it can be used for a longer time than the comparative product.

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.

Explanation of symbols

5 ... annular groove deep part 6 ... acute angle part 6c of annular groove deep part ... innermost part 10, 20, 30, 40, 50, 60 ... of annular groove deep part ... Fluoro-resin-wrapped gaskets 11a, 21a, 31a, 41a, 51a, 61a ... Upper outer cover side surface (surface) of another annular member (b)
11b, 21b, 31b, 41b, 51b, 61b... Lower outer side surface (surface) of another annular member (b)
12, 22, 32, 42, 52, 62... Fluororesin jacket 12a, 22a, 32a, 42a, 52a, 62a... Fluororesin jacket (lower jacket)
12b, 22b, 32b, 42b, 52b, 62b ... Upper fluororesin jacket (upper jacket)
13a, 23a, 33a, 43a, 53a, 63a ... other annular member (b) or expanded graphite sheet of annular core (a) side surface (surface)
13b, 23b, 33b, 43b, 53b, 63b ... Other annular member (b) or outer side surface (surface) of annular core
14, 24, 34, 44, 54, 64, 74 ... annular core bodies 16, 26, 36, 46, 56 ... annular sheet (annular member (a), expanded graphite sheet)
27... Annular members 27a, 28a in which inorganic powder is unevenly distributed on the outer surface of the jacket side... Layer 28 containing organic fiber, inorganic fiber and binder as main components. Ring members 27b and 28b that are unevenly distributed on the outer surface of the jacket side. Layers 18a, 38a, 48a, 58a, and 68a mainly composed of inorganic powder (barium sulfate) and a binder. Side annular member, other annular member (b))
18b, 38b, 48b, 58b, 68b ... annular member (upper surface side annular member, other annular member (b))
19, 29, 39, 49, 59, 69 ... annular grooves 15a, 25a, 55a ... inner diameter side ends 15b, 25b, 35b, 45b, 55b ... · Fluororesin jacket or gasket outer diameter side end 66a ... Expanded graphite sheet (expanded graphite layer) on the lower surface side of the metal plate
66b... Expanded graphite sheet on the upper surface side of the metal plate (expanded graphite layer)
100 ... Metal plate (layer) such as stainless steel plate

Claims (5)

  A fluororesin-wrapped gasket having an annular core formed by laminating a single layer or a plurality of annular members in an annular groove of a fluororesin jacket, wherein at least one layer constituting the annular core A fluororesin-wrapped gasket, wherein the annular member (a) is made of an expanded graphite sheet.   The annular core is formed by laminating or applying at least one layer of another annular member (b) on the front and back surfaces of the annular member (a) made of the expanded graphite sheet. 1. A fluororesin-wrapped gasket according to 1.   The fluororesin-wrapped gasket according to claim 2, wherein the other annular member (b) is made of a felt sheet containing organic fibers, inorganic fibers, and a binder.   The fluororesin-wrapped gasket according to claim 3, wherein the other annular member (b) is made of a felt sheet further containing an inorganic powder.   The said annular member (a) consists of two layers, The metal plate is inserted between these annular members (a) and an annular member (a), The Claims 1-4 characterized by the above-mentioned. A fluororesin-wrapped gasket according to any one of the above.

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