JP6842962B2 - Sealing material and its manufacturing method - Google Patents

Description

The present invention relates to a sealing material used for a fuel path of an engine and a method for manufacturing the sealing material.

Rubber elastic bodies such as O-rings, packings, and gaskets are used as sealing materials used in engine fuel paths. The rubber elastic body is required to have fuel oil resistance in order to prevent fuel oil such as gasoline from leaking from a fuel path such as a fuel tank or a carburetor. As a rubber elastic body having fuel oil resistance, those having an annular sealing base material made of rubber and a coating film made of a fluororesin coated on the surface of the annular sealing base material are known ( See Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-344038

Although the fluorine-based coating film in the conventional rubber elastic body is considered to have fuel oil resistance, it does not sufficiently follow the expansion and contraction of the annular sealing base material made of rubber, and it becomes a fluorine-based coating film over time. Cracks may occur. When the rubber constituting the annular sealing base material is exposed to the fuel oil through the cracks or the like, the plasticizer and the antiaging agent are extracted from the rubber. When a plasticizer or an antiaging agent is extracted from rubber, there is a problem that the metal used in the fuel path (for example, a fuel tank) of an engine is corroded.

In view of such a problem, the present invention provides a sealing material used for a fuel path of an engine and a method for producing the same, which has a barrier property against fuel oil and can maintain the barrier property for a long period of time. With the goal.

In order to solve the above problems, the present invention provides a sealing material for use in fuel lines of the engine, comprising an annular seal backing material made of rubber, and the film you covering the sealing substrate, wherein coating contains at least fluorine rubber, and wherein the follow-up possible der Rukoto as not to cause cracks on the coating when the sealing substrate is extended 50% the surface area of the sealing substrate as a reference Provide a sealing material.

The coating film that can follow the expansion and contraction of the sealing base material means that cracks and the like do not occur in the coating material when the sealing base material expands and contracts. Specifically, the sealing base material is 50% based on the surface area thereof. It is meant that the coating does not crack when stretched, preferably no cracks occur when stretched by 80%.

In the sealing material, the film thickness is preferably 5 to 50 μm, the fluororubber is preferably a binary or ternary copolymer, and the film is used as a solid lubricant. It is preferable that the polytetrafluoroethylene (PTFE) of the above is further contained .

Further, the present invention is a method for producing a sealing material used for a fuel path of an engine, in which a step of applying a surface treatment agent containing a film-forming composition to an annular sealing base material made of rubber and the surface thereof. By heating the sealing base material coated with the treatment agent in a temperature range of 130 to 150 ° C., there is a step of forming a film capable of following the expansion and contraction of the sealing base material on the surface of the sealing base material. The coating composition contains at least fluororubber so that cracks do not occur when the sealing base material is stretched by 50% based on the surface area of the sealing base material in the step of forming the coating material. Provided is a method for producing a sealing material, which comprises forming the coating film that can be followed.

In the method for producing a sealing material, it is preferable to heat the sealing base material coated with the surface treatment agent in a temperature range of 130 to 150 ° C. so that the film thickness is 5 to 50 μm. It is preferable to apply the surface treatment agent to the seal base material, and the fluororubber is a binary copolymer obtained by copolymerizing vinylidene fluoride (VDF) and tetrafluoroethylene (TFE). , A binary or ternary fluororubber such as a ternary copolymer obtained by copolymerizing vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). The film-forming composition preferably further contains tetrafluoroethylene (PTFE) as a solid lubricant. The rubber constituting the sealing base material is preferably acrylonitrile butadiene rubber or hydrogenated nitrile rubber.

According to the present invention, it is possible to provide a sealing material used in a fuel path of an engine and a method for producing the same, which has a barrier property against fuel oil and can maintain the barrier property for a long period of time.

FIG. 1 is a partial cross-sectional view showing a schematic configuration of a fuel tank having a sealing material according to an embodiment of the present invention. FIG. 2 is a perspective view (FIG. 2 (A)) and a cut end view (FIG. 2 (B)) showing a schematic configuration of a sealing material according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial cross-sectional view showing a schematic configuration of a fuel tank having a sealing material according to the present embodiment, and FIG. 2 is a perspective view showing a schematic configuration of the sealing material according to the present embodiment (FIG. 2 (A)). ) And the cut end view (FIG. 2 (B)).

As shown in FIG. 1, the fuel tank 1 in the present embodiment is a container for accommodating fuel oil, which forms a part of the fuel path of the engine, and includes an upper container 11 and a lower container 12. The upper container 11 and the lower container 12 are made of a metal material that is not easily corroded by gasoline as fuel oil, light oil, or the like, and are preferably a rust-preventive metal such as aluminum, copper, chromium, or nickel-plated alloy. , Stainless steel and other conventionally known materials.

Recessed grooves 11B and 12B are formed on the facing surfaces 11A and 12A of the upper container 11 and the lower container 12 of the fuel tank 1 along the circumferential direction thereof so that the facing surfaces 11A and 12A face each other. By combining the upper container 11 and the lower container 12, the O-ring accommodating portion 13 as a space formed by the concave groove portions 11B and 12B is formed.

The sealing material 2 according to the present embodiment is provided so as to fit into the O-ring accommodating portion 13 composed of the concave groove portions 11B and 12B. As a result, the contained fuel oil is sealed from between the upper container 11 and the lower container 12 (between the facing surfaces 11A and 12A) so as not to leak.

As shown in FIGS. 2A and 2B, the sealing material 2 according to the present embodiment is an O-ring having a substantially annular shape in a plan view and a substantially circular cross section, but is limited to this embodiment. is not it. The sealing material 2 according to the present embodiment may have a plan view shape or a cross-sectional shape corresponding to the object to be attached. The shape of the sealing material 2 is, for example, a shape conventionally known as a sealing material for O-rings, packings, gaskets, etc., which is a substantially rectangular shape, a substantially rectangular shape, a substantially angular cross section, and is molded at regular intervals on an annular side surface. Examples thereof include a shape having protrusions. Further, the dimensions and the like of the sealing material 2 are not particularly limited, and can be appropriately set according to the object to which the sealing material 2 is attached.

The sealing material 2 according to the present embodiment includes an annular sealing base material 21 and a coating film 22 that covers the surface of the annular sealing base material 21. The annular sealing base material 21 may be composed of a rubber elastic body that functions as a sealing material. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), and butyl rubber. (IIR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), ethylene propylene rubber (EPM, EPDM), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), silicone rubber (VMQ, FVMQ), urethane rubber (AU, EU), fluororubber (FKM, FEPM), hydride nitrile rubber (HNBR) and the like can be used, and particularly preferably acrylonitrile butadiene rubber (NBR) and hydride nitrile rubber (HNBR). Is. Since NBR is excellent in mechanical properties (aging resistance, durability), it is a suitable material as an elastomer constituting the annular sealing base material 21. In addition, NBR and HNBR are generally excellent in oil resistance and are used as a material for a sealing material in the fuel path of an engine. However, they swell when exposed to fuel oil for a long time, and plasticizers and antiaging agents are used. It will be extracted. As a result, there is a risk of causing corrosion of the metal material constituting the fuel path of the fuel tank 1 and the like. The sealing material 2 according to the present embodiment can exhibit a barrier property against fuel oil by providing a coating film 22 that covers the surface of the annular sealing base material 21 made of rubber.

The coating film 22 that covers the surface of the annular sealing base material 21 contains at least fluororubber. By containing the fluororubber, as is clear from the examples described later, it has an appropriate followability and maintains a barrier property against the fuel oil even if the sealing material 2 is exposed to the fuel oil for a long period of time. can do.

The fluororubber contained in the coating film 22 is not particularly limited as long as it can be cured at a relatively low temperature (for example, about 130 to 150 ° C.), and is not particularly limited, for example, vinylidene fluoride (VDF) / hexafluoro. Binary copolymers such as propylene (HFP) copolymers, vinylidene fluoride (VDF) / hexafluoropropylene (HFP) / tetrafluoroethylene (TFE) copolymers, tetrafluoroethylene / propylene / vinylidene fluoride Copolymers, tetrafluoroethylene / propylene / vinyl fluoride copolymers, tetrafluoroethylene / propylene / trifluoroethylene copolymers, tetrafluoroethylene / propylene / pentafluoropropylene copolymers, tetrafluoroethylene / propylene / chloro Examples thereof include ternary copolymers such as a trifluoroethylene copolymer and a tetrafluoroethylene / propylene / ethylidene norbornene copolymer. Of these, as the fluororubber contained in the coating film 22, those obtained by copolymerizing vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene are preferable.

The coating 22 preferably contains a solid lubricant. By containing the solid lubricant, it is possible to impart non-adhesiveness and low friction to the sealing material 2. Examples of the solid lubricant include polytetrafluoroethylene (PTFE), hexafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, molybdenum disulfide, and organic molybdenum compound. Examples thereof include graphite, graphite fluoride, boron nitride, tungsten disulfide and the like, and polytetrafluoroethylene (PTFE) is particularly preferable. The content of the solid lubricant in the coating film 22 may be about 1 to 50 parts by mass, preferably about 1 to 10 parts by mass with respect to 100 parts by mass of the fluororubber.

The coating 22 preferably contains carbon black. The inclusion of carbon black can increase the strength of the coating 22. Examples of carbon black include channel black, furnace black, thermal black, acetylene black, conductive carbon black and the like. The content of carbon black may be about 5 to 30 parts by mass, preferably about 5 to 10 parts by mass with respect to 100 parts by mass of the fluororubber. The carbon black is also contained in the coating film 22 for the purpose of coloring (black or the like). From the viewpoint of coloring the coating film 22, the coating film 22 may contain a pigment (black pigment or the like), a dye (black dye or the like) or the like in place of carbon black or together with carbon black.

The coating film 22 may contain a cross-linking agent, and as the cross-linking agent, for example, a polyol cross-linking agent can be used. Specifically, bis (4-hydroxyphenyl), 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) perfluoropropane, 2,2-bis (4-hydroxy). Examples thereof include phenyl) methane, 4,4'-dihydroxydiphenyl, and 2,2-bis (4-hydroxyphenyl) butane. The content of the cross-linking agent may be about 0.1 to 5 parts by mass with respect to 100 parts by mass of the fluororubber.

The coating 22 may contain a cross-linking aid. Examples of the cross-linking aid include magnesium oxide, calcium hydroxide, 5-benzyl-1,5-diazabicyclo [4.3.0] -5-nonenium tetrafluoroborate as a quaternary ammonium salt, and the like. .. The content of the cross-linking aid may be about 1 to 100 parts by mass with respect to 100 parts by mass of the fluororubber.

In addition, as other additives, the coating 22 contains a filler such as glass fiber and carbon fiber; a plasticizer; a processing aid such as stearate and laurate; a flame retardant; an antistatic agent; a colorant and the like. It may be included.

The film thickness of the coating film 22 in the present embodiment is, for example, about 5 to 50 μm, preferably about 5 to 26 μm. If the film thickness of the coating film 22 is less than 5 μm, it becomes difficult to uniformly coat the surface of the annular sealing base material 21, and it may be difficult to achieve the desired barrier property against the fuel oil. Further, if the film thickness of the coating film 22 exceeds 50 μm, it becomes difficult for the coating film 22 to follow the expansion and contraction of the annular sealing base material 21, and the coating film 22 may easily crack when the annular sealing base material 21 expands and contracts. ..

In the sealing material 2 according to the present embodiment, the volume resistance value (Ω · cm) after being immersed in FeelC containing 50% by mass of toluene and 50% by mass of isooctane in a temperature environment of 40 ° C. for 48 hours, and the FuelC. It is preferable that the volume resistance value (Ω · cm) before immersion is substantially the same. The fact that the volume resistance values (Ω · cm) before and after immersion in FuelC are substantially the same means that the barrier property of the coating film 22 against fuel oil is maintained. The volume resistance value after immersion in FuelC ^{is preferably 1.0 × 10 6} (Ω · cm) or more, and more preferably 1.0 × 10 ⁷ (Ω · cm) or more. If the volume resistance value of the sealing material 2 after being immersed in Fuel C for 48 hours ^{is less than 1.0 × 10 6} (Ω · cm), the fuel tank 1 may be easily corroded.

In the sealing material 2 according to the present embodiment, the coating film 22 has a predetermined followability. The sealing material 2 (annular sealing base material 21) may expand and contract due to a decrease in fuel oil contained in the fuel tank 1, swelling due to continuous exposure to the fuel oil, and the like. If the coating film 22 cannot follow the expansion and contraction of the sealing material 2 (annular sealing base material 21), the coating film 22 may crack and the annular sealing base material 21 may be directly exposed to the fuel oil. However, since the coating film 22 has a predetermined followability (it can follow the expansion and contraction of the annular sealing base material 21), it is possible to prevent the coating film 22 from being cracked.

In the present embodiment, "having a predetermined followability (capable of following the expansion and contraction of the annular sealing base material 21)" means that the sealing material 2 is stretched by 50% (1.5 times) with respect to its surface area. Occasionally, it means that the coating 22 follows to the extent that cracks do not occur, and when the sealing material 2 is stretched by 80% (1.8 times) based on its surface area, it follows to the extent that the coating 22 does not crack. It is preferable to do so.

The adhesive strength of the surface of the sealing material 2 (the surface of the coating film 22) according to the present embodiment is more preferably 1 to 100 gf, and particularly preferably 1 to 50 gf. If the adhesive force on the surface of the sealing material 2 exceeds 100 gf, the difficulty of assembling the sealing material 2 to the O-ring accommodating portion 13 of the fuel tank 1 may increase. The adhesive strength of the surface of the sealing material 2 (the surface of the coating film 22) according to the present embodiment is obtained after the sealing material 2 is immersed in fuel oil at a predetermined temperature (for example, 40 ° C.) for a predetermined time (for example, 48 hours). However, it is preferable that the temperature does not change substantially as compared with that before the immersion. Since the tack value after immersion does not substantially change from that before immersion, the sealing material 2 can be easily removed even when the fuel path of the engine is overhauled.

The "adhesive strength" in this embodiment can be measured by the following method.
The sealing material 2 is attached to a probe tack tester (product name: tacking tester TAC-II, manufactured by Reska), and a probe (cylindrical probe made by SUS) is applied for 3 seconds while applying a load of 100 gf to the surface of the sealing material 2. After the probe is brought into contact with the diameter: 5.1 mm)), the probe is peeled off at a speed of 600 mm / min in the vertical direction, and the adhesive force (gf) is required as the force required for the peeling.

The sealing material 2 according to the present embodiment can be manufactured as follows.
First, the annular seal base material 21 is produced. For the annular seal base material 21, a mold including an upper mold and a lower mold having a cavity conforming to the shape is prepared, and the unvulcanized seal base material 21 constituting the annular seal base material 21 is formed in the cavity of the mold. The rubber composition is filled and heat vulcanized. In this way, the annular sealing base material 21 made of rubber is produced.

Next, a surface treatment agent containing a film-forming composition is applied to the surface of the annular sealing base material 21 made of rubber to form an uncured coating film. For the surface treatment agent containing the film-forming composition, a solid lubricant (PTFE, etc.), carbon black, and other additives are added to a solvent (for example, butyl acetate, etc.) together with the above-mentioned fluororubber, and 3 to 12 at room temperature. It can be prepared by stirring for a time, then adding a cross-linking agent, a cross-linking aid, and other additives dissolved in ethanol, and stirring at room temperature for about 5 to 10 minutes.

The method of applying the surface treatment agent containing the film-forming composition to the surface of the annular seal base material 21 is particularly limited as long as a homogeneous coating film can be formed on the surface of the annular seal base material 21. Instead, a conventionally known coating method can be used. For example, a spray coating method, a dipping method, a tumbling method and the like can be mentioned.

Subsequently, the annular sealing base material 21 having the coating film formed on the surface is heated at 130 to 150 ° C. for about 10 to 30 minutes. As a result, the coating film is cured to form a coating film 22 that covers the surface of the annular sealing base material 21.

Generally, when a film is formed on the surface of a rubber base material using a fluororubber-based surface treatment agent, the coating film formed by applying the surface treatment agent is fired at about 160 to 280 ° C. and cured. However, when the rubber base material is made of NBR, there is a problem that the NBR is deteriorated and the hardness is increased by being exposed to the temperature atmosphere. In the production method of the present embodiment, since the coating film can be cured by firing at a relatively low temperature, it is possible to suppress an increase in the hardness of rubber such as NBR constituting the annular sealing base material 21. Further, since the coating film 22 formed by the coating film forming composition contained in the surface treatment agent has a property of being able to follow the expansion and contraction of the annular sealing base material 21 made of rubber, the expansion and contraction of the annular sealing base material 21 There is no possibility that the coating film 22 will be cracked due to such factors. Therefore, according to the sealing material 2 produced by the production method in the present embodiment, it is possible to exhibit a barrier property against fuel oil and maintain the barrier property for a long period of time.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

As an embodiment of the sealing material 2 in the above embodiment, the embodiment used for the fuel tank 1 forming a part of the fuel path of the engine has been described as an example, but the present invention is not limited to this embodiment. For example, the sealing material 2 may be an O-ring used for a carburetor.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to the following Examples and the like.

[Example 1]
Fluororubber (VDF / HFP / TFE copolymer) 5 parts by mass, solid lubricant (Kitamura Co., Ltd., PTFE powder KTL-8F) 2 parts by mass, carbon black 0.1 parts by mass, cross-linking aid (magnesium oxide) 1 The parts by mass and 90 parts by mass of the solvent (butyl acetate) were stirred at room temperature for 5 hours, and then the cross-linking agent (2,2-bis (4-hydroxyphenyl) hexafluoropropane) 0 was added to 0.72 parts by mass of ethanol. A solution in which .48 parts by mass was dissolved was added, and the mixture was stirred at room temperature for 5 minutes to prepare a surface treatment agent containing a film-forming composition.

A test piece (100 mm × 100 mm) made of NBR rubber is prepared, and a surface treatment agent containing the above film-forming composition is spray-coated on both sides of the test piece (spray pressure: 0.2 MPa), and then at 150 ° C. By firing for 30 minutes, the coating film was cured and a film (thickness 5 μm) was formed on the test piece.

[Example 2]
A test piece in which a coating was formed was prepared in the same manner as in Example 1 except that the thickness of the coating was changed to 8 μm.

[Example 3]
A film-forming composition solution was prepared in the same manner as in Example 1 except that fluororubbers having different monomer compositions were used, and a film (thickness 5 μm) was formed on the test piece.

[Example 4]
A test piece in which a coating was formed was prepared in the same manner as in Example 3 except that the thickness of the coating was changed to 7 μm.

[Example 5]
A test piece in which a coating was formed was prepared in the same manner as in Example 3 except that the thickness of the coating was changed to 10 μm.

[Example 6]
A test piece in which a coating was formed was prepared in the same manner as in Example 3 except that the thickness of the coating was changed to 14 μm.

[Example 7]
A test piece in which a coating was formed was prepared in the same manner as in Example 3 except that the thickness of the coating was changed to 24 μm.

[Comparative Example 1]
A film (thickness 5 μm) was formed in the same manner as in Example 1 except that GLS-213L manufactured by Daikin Industries, Ltd. was used as the surface treatment agent and the test piece spray-coated with the surface treatment agent was fired at 280 ° C. for 20 minutes. The formed test piece was prepared.

[Comparative Example 2]
A test piece having a coating film (thickness 5 μm) formed was prepared in the same manner as in Example 1 except that Marvel Coat RFH-10 manufactured by Ryoe Chemical Co., Ltd. was used as the surface treatment agent.

[Comparative Example 3]
A test piece having a coating film (thickness 5 μm) formed was prepared in the same manner as in Example 1 except that an obligato SS0063 manufactured by AGC Cortec Co., Ltd. was used as the surface treatment agent.

[Comparative Example 4]
A test piece was prepared in the same manner as in Comparative Example 3 except that the thickness of the coating film was 129 μm.

[Test Example 1]
The volume resistance values (40 ° C.) of the test pieces of Examples 1 to 7 and Comparative Examples 1 to 4 and the test pieces having no coating (Reference Example 1) before and after immersion in FuelC for 48 hours (40 ° C.). Ω · cm) was measured according to JIS K 6271. The results are shown in Table 1.

[Test Example 2]
Followability of the test pieces of Examples 1 to 7 and Comparative Examples 1 to 4 and the test pieces having no coating (Reference Example 1) before and after immersion in Fuel C (40 ° C.), respectively. Was tested. This test was carried out by observing with a scanning microscope whether or not the coating of the test piece had cracks while extending the test piece to 25% and 50% on an area basis. The results are shown in Table 1. In the item of "followability" in Table 1, the one in which the coating was not cracked by 50% elongation was designated as "○", and the one in which the coating was cracked by 50% elongation was designated as "x". did.

[Test Example 3]
The test pieces of Examples 1 to 7 and Comparative Examples 1 to 4 and the test pieces having no coating (Reference Example 1) were used in a probe tack test device (product name: tacking tester TAC-II, manufactured by Resca). After mounting and contacting the probe (SUS cylindrical probe (diameter: 5.1 mm)) for 3 seconds while applying a load of 100 gf to the surface of the test piece, the probe is placed at 600 mm / in the direction perpendicular to the surface of the test piece. The peeling was performed at a speed of min, and the force (adhesive strength, gf) required for peeling was measured. The results are shown in Table 1.

As shown in Table 1, it was confirmed that by forming a fluororubber-based film on the surface of the base material made of NBR, the effect of substantially not changing the volume resistance value before and after immersion in FuelC is exhibited. It was. Further, in Examples 1 to 7, the followability before and after immersion in WheelC was good, and no crack was generated in the coating film even at the time of 80% elongation, but in Comparative Examples 1 to 4, the followability was improved. The result was inferior. In particular, in Comparative Example 1, cracks were generated at the time of 20% elongation in the state before immersion in WheelC, and the test piece was broken. It is presumed that the test piece of Comparative Example 1 was fired at a high temperature when the film was formed, so that the hardness of NBR increased and the rubber elasticity decreased.

1 ... Fuel tank 11 ... Upper container 12 ... Lower container 2 ... Sealing material 21 ... Sealing base material 22 ... Coating

Claims (13)

A sealing material used in the fuel path of an engine.
An annular seal base made of rubber and
A target film you covering the sealing substrate,
The film has a feature tracking can der Rukoto as not to cause cracks on the coating when at least fluororubber containing, said sealing substrate is extended 50%, based on the surface area of the sealing substrate Sealing material to be used. The sealing material according to claim 1, wherein the film thickness is 5 to 50 μm. The sealing material according to claim 1 or 2, wherein the fluororubber is a binary or ternary fluororubber. The sealing material according to any one of claims 1 to 3, wherein the coating film further contains a solid lubricant. The sealing material according to claim 4, wherein the solid lubricant is polytetrafluoroethylene (PTFE). The sealing material according to any one of claims 1 to 5 , wherein the rubber constituting the sealing base material is an acrylonitrile butadiene rubber or a hydrogenated nitrile rubber. A method of manufacturing sealing materials used in engine fuel paths.
A step of applying a surface treatment agent containing a film-forming composition to an annular sealing base material made of rubber, and
By heating the sealing base material coated with the surface treatment agent in a temperature range of 130 to 150 ° C., a step of forming a film capable of following the expansion and contraction of the sealing base material is formed on the surface of the sealing base material. Have and
The film-forming composition contains at least a fluororubber and contains.
In the step of forming the coating material, the sealing material is characterized in that the coating material is formed so as not to cause cracks when the sealing base material is stretched by 50% based on the surface area of the sealing base material. Manufacturing method. The method for producing a sealing material according to claim 7 , wherein the sealing base material coated with the surface treatment agent is heated in a temperature range of 130 to 150 ° C. The method for producing a sealing material according to claim 7 or 8 , wherein the surface treatment agent is applied to the sealing base material so that the film thickness of the coating film is 5 to 50 μm. The method for producing a sealing material according to any one of claims 7 to 9 , wherein the fluororubber is a binary or ternary fluororubber. The method for producing a sealing material according to any one of claims 7 to 10 , wherein the film-forming composition further contains a solid lubricant. The method for producing a sealing material according to claim 11 , wherein the solid lubricant is tetrafluoroethylene (PTFE). The method for producing a sealing material according to any one of claims 7 to 12 , wherein the rubber constituting the sealing base material is an acrylonitrile butadiene rubber or a hydrogenated nitrile rubber.

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