JP2012224654A - Fluororubber composition and rubber-metal laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluororubber composition that can follow microvibration, thermal expansion, and thermal contraction and maintain adhesion to metal even if calcium metasilicate is mixed therein, and a rubber-metal laminate using the fluororubber composition.SOLUTION: In the fluororubber composition that contains at least a fluororubber polymer, a crosslinking agent, a crosslinking accelerator, calcium metasilicate, and carbon black, the calcium metasilicate is contained at 1 pts.wt. or more and less than 10 pts.wt. with respect to 100 pts.wt. of the fluororubber polymer. In the rubber-metal laminate, the fluororubber composition is used as a rubber layer forming composition to form a rubber layer or layers on one or both surfaces of a metal plate.

Description

  The present invention relates to a fluororubber composition and a rubber metal laminate, and more specifically, a fluororubber composition capable of following microvibration, thermal expansion and contraction, and maintaining adhesion to metal, and rubber using the same. The present invention relates to a metal laminate.

  Rubber cylinder laminates are used as cylinder head gaskets for automobiles, and vinylidene fluoride fluororubber (FKM) is widely used as rubber for rubber metal laminates because the use environment becomes high.

  A cylinder head gasket of a cast iron engine seals combustion gas, oil, LLC (Long Life Coolant), etc. by compressing the gasket with high surface pressure by utilizing the rigidity of cast iron.

  Therefore, compression resistance is indispensable for the rubber metal laminate used as a cylinder head gasket of a cast iron engine, and MT carbon or silica is filled to obtain compression resistance.

  In Example 3 of Patent Document 1, 40 parts by weight of MT carbon black, 20 parts by weight of silica, and 10 parts by weight of calcium metasilicate are added to 100 parts by weight of fluororubber, and the compression resistance is extremely excellent. A rubber metal laminate is described.

  However, recently, in order to reduce the weight of the engine, there has been a movement to introduce an aluminum engine instead of a cast iron engine.

  The aluminum engine is less rigid than the cast iron engine, so the head block is lifted by the combustion pressure in the cylinder, creating a gap between the cylinder block, causing slight vibrations (tack phenomenon) It is characterized by large expansion and contraction due to heat.

  Therefore, a cylinder head gasket for an aluminum engine is required to follow the housing vibration and thermal contraction.

  The rubber metal laminate of Patent Document 1 is suitable for a cast iron engine because of its high compression resistance. However, when applied to an aluminum engine having a slight vibration or thermal contraction of the housing, the rubber vibration or heat of the housing is suitable. There is a concern that rubber peeling may occur due to failure to follow the shrinkage.

JP 2007-186536 A

  The present inventors can follow a slight movement such as microvibration and heat shrinkage, while fluororubber as a base material can follow, whereas calcium metasilicate cannot follow because it is a fibrous filler. It has been found that a deviation occurs between the rubber and the filler, and that the deviation is the starting point and the rubber is peeled off.

  However, a fluororubber composition containing no calcium metasilicate for preventing rubber peeling is not suitable for a rubber metal laminate used as a gasket because the compression resistance is lowered.

  Accordingly, an object of the present invention is to provide a fluororubber composition capable of following microvibration, thermal expansion and thermal contraction and maintaining adhesion to metal even when calcium metasilicate is blended, and a rubber metal laminate using the same To provide a body.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
In a fluororubber composition comprising at least a fluororubber polymer, a crosslinking agent, a crosslinking accelerator, calcium metasilicate, and carbon black,
A fluororubber composition comprising 1 part by weight or more and less than 10 parts by weight of the calcium metasilicate with respect to 100 parts by weight of the fluororubber polymer.

(Claim 2)
The fluororubber composition according to claim 1, further comprising silica.

(Claim 3)
A rubber metal laminate in which a rubber layer is formed on one side or both sides of a metal plate using the fluororubber composition according to claim 1 as a rubber layer forming component.

  According to the present invention, even when calcium metasilicate is blended, a fluororubber composition that can follow microvibration, thermal expansion and thermal contraction, and can maintain adhesion to metal, and a rubber metal laminate using the same Can be provided.

Diagram showing the method of micro vibration and thermal shrinkage evaluation test

  Embodiments of the present invention will be described below.

<Fluorine rubber composition>
As the fluororubber polymer that can be used in the present invention, a polymer or copolymer of one or more fluorine-containing olefins can be used.

  Specific examples of the fluorine olefin include, for example, vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylic acid ester, and acrylic acid perfluoroacrylate. Examples include fluoroalkyl, perfluoromethyl vinyl ether, and perfluoropropyl vinyl ether. These fluorine-containing olefins can be used alone or in combination of two or more.

  In the present invention, preferred as the fluororubber polymer is a vinylidene fluoride-hexafluoropropylene binary copolymer (abbreviation: VDF-HFP), a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer (abbreviation). : VDF-HFP-TFE) and the like. These polymers can be obtained by solution polymerization, suspension polymerization or emulsion polymerization by a conventionally known method, and can be obtained as commercial products (for example, Viton A and Viton B manufactured by DuPont).

  As the crosslinking system, either amine crosslinking or polyol crosslinking or a combination thereof can be used.

  As a crosslinking agent for amine crosslinking, 4,4'-methylenebis (cyclohexylamine) carbamate, hexamethylenediamine carbamate, N, N'-dicinenamylidene-1,6-hexanediamine or the like is used.

  As a crosslinking agent for polyol crosslinking, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (4-hydroxyphenyl) perfluoropropane [bisphenol AF], bis (4-hydroxyphenyl) ) Polyhydroxy aromatics such as sulfone [bisphenol S], bisphenol A-bis (diphenyl phosphate), 4,4′-dihydroxydiphenyl, 4,4′-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl) butane Bisphenol A, bisphenol AF, etc. are preferably used. These may be in the form of alkali metal salts or alkaline earth metal salts.

  The amount of the crosslinking agent is preferably in the range of 1 to 10 parts by weight, more preferably in the range of 3 to 9 parts by weight per 100 parts by weight of the fluororubber polymer.

  When a polyol-based crosslinking agent is used, a quaternary onium salt such as a quaternary ammonium salt or a quaternary phosphonium salt or an equimolar molecular compound of the quaternary phosphonium salt and an active hydrogen-containing aromatic compound is used as a crosslinking accelerator. And quaternary phosphonium salts are preferably used.

Examples of the quaternary phosphonium salt include compounds represented by [PR ¹ R ² R ³ R ⁴ ] ⁺ X ⁻ .
In the formula, R ^{1 to} R ⁴ are an alkyl group having 1 to 25 carbon atoms, an alkoxyl group, an aryl group, an alkylaryl group, an aralkyl group, or a polyoxyalkylene group, or 2 to 3 of them together with P Multiple ring structures can also be formed.
X ⁻ represents an anion such as Cl ⁻ , Br ⁻ , I ⁻ , HSO ₄ ⁻ , H ₂ PO ₄ ⁻ , RCOO ⁻ , ROSO ₂ ⁻ or CO ₃ ⁻ .

  Specifically, tetraphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, triphenylmethoxymethylphosphonium chloride, triphenylmethylcarbonylmethylphosphonium chloride, triphenylethoxycarbonylmethylphosphonium chloride, trioctylbenzylphosphonium chloride , Trioctylmethylphosphonium chloride, trioctylethylphosphonium acetate, tetraoctylphosphonium chloride, trioctylethylphosphonium dimethyl phosphate, and the like.

The quaternary ammonium salt is a compound represented by the general formula [NR ¹ R ² R ³ R ⁴ ] ⁺ X ⁻ (wherein R ^{1 to} R ⁴ and X ⁻ are the same as described above), for example, 1 -Alkyl pyridinium salts, 5-aralkyl-1,5-diazabicyclo [4,3,0] -5-nonenium salts, 8-aralkyl-1,8-diazabicyclo [5,4,0] -7-undecenium salts, etc. Used.

  These quaternary onium salts are used in combination of one kind or two or more kinds at a ratio of about 1 to 10 parts by weight, preferably about 2 to 8 parts by weight, per 100 parts by weight of the fluororubber.

<Calcium metasilicate>
As calcium metasilicate, those having an average diameter (fiber diameter) of about 1 to 50 μm, preferably about 5 to 35 μm and an aspect ratio of 3 or more, preferably 3 to 15 are used. The aspect ratio is obtained from (fiber length) / (fiber diameter).

  Examples of commercially available products include “NYAD400” and “NYAD325” manufactured by NYCO.

  Calcium metasilicate is used in a proportion of 1 to 10 parts by weight, preferably 2 to 8 parts by weight, more preferably 4 to 7 parts by weight, per 100 parts by weight of the fluororubber. It is done.

  By using it in the range of 1 part by weight or more and less than 10 parts by weight, it is possible to obtain both protrusion resistance (compression resistance) and followability to micro vibrations and heat shrinkage.

  When the compounding amount of calcium metasilicate is less than 1 part by weight, it is impossible to prevent the rubber from protruding (flowing) due to compression under high temperature and high surface pressure (Comparative Example 1), but 10 parts by weight or more. As a result, it is not possible to follow micro vibrations and heat shrinkage, and rubber peeling occurs (Comparative Examples 2 and 4).

<Carbon black>
As the carbon black, carbon black having a large average particle diameter is preferably used, and thermal black, particularly MT carbon is preferable.

  By blending carbon black, the compression resistance desirable as a gasket can be provided even when the blending of calcium metasilicate is 1 to 10 parts by weight. In addition, there is also an effect of suppressing rubber stickiness and improving rubber kneadability.

  The carbon black is preferably used in an amount of 15 to 40 parts by weight, more preferably 20 to 35 parts by weight, and still more preferably 20 to 30 parts by weight per 100 parts by weight of the fluororubber. If the blending amount of carbon black is less than 15 parts by weight, a reinforcing effect cannot be obtained, and if it exceeds 40 parts by weight, followability to micro vibrations and heat shrinkage is deteriorated.

  In the present invention, it is preferable to further add silica.

Silica can be produced by the pyrolysis method of halogenated silicic acid or organosilicon compounds, dry silica produced by heat reduction of silica sand and air oxidation of vaporized SiO, etc., produced by pyrolysis method of sodium silicate, etc. An amorphous silica can be used, and commercially available products such as Nippon Sil (nip seal) LP manufactured by Tosoh Silica Industry Co., Ltd. are used as they are. The specific surface area is about 20 to 250 m ² / g, preferably about 30 to 100 m ² / g. The same effect can be obtained by using natural silica having an average particle size of about 20 μm or less, preferably natural silica surface-treated with a silane coupling agent or the like.

  Silica is effective in preventing peeling of the adhesive layer during high-temperature immersion, and exhibits an effect of improving water resistance.

  Silica is preferably used in an amount of 5 to 30 parts by weight, more preferably 10 to 25 parts by weight, and still more preferably 10 to 15 parts by weight per 100 parts by weight of the fluororubber.

  Besides the above components, it is generally used in the rubber industry such as metal salts of fatty acids such as stearic acid and heptanoic acid, fillers such as hydrotalcite, processing aids, anti-aging agents and acid acceptors. Various compounding agents are appropriately added and used.

  The fluororubber composition of the present invention is prepared by kneading using a kneader such as an intermix, a pressure kneader, a Banbury mixer or an open roll.

  Further, when the fluororubber composition of the present invention is used as a rubber layer of a rubber metal laminate, kneading is not performed, or only a part of raw materials is kneaded by an intermix, kneader, Banbury mixer, or an open roll. Then, the fluororubber composition is dissolved or dispersed in a solvent having a boiling point of 250 ° C. or less, for example, aromatic hydrocarbons, ketones, or a mixed solvent thereof to prepare a coating solution.

<Rubber metal laminate>
The rubber metal laminate of the present invention is obtained by forming the fluororubber composition of the present invention as a rubber layer on one side or both sides of a metal plate through a primer layer and an adhesive layer as necessary.

  As the metal plate, stainless steel plate, SPCC steel plate, aluminum plate, etc. whose surface is roughened by shot blasting, scotch blasting, hairline, dull finish, etc. In general, after solvent degreasing and alkali degreasing, they may be used as they are or after being subjected to a chemical conversion treatment for forming an inorganic or organic rust preventive film.

  The above-mentioned chemical conversion treatment is necessary to prevent the rubber layer after being crushed for a long time with a high-temperature antifreeze or oil, and the film formed by the chemical conversion treatment includes zinc phosphate coating, phosphoric acid Iron coating, chromate coating, vanadium, zirconium, titanium, molybdenum, tungsten, manganese, zinc, cerium and other metal compounds, especially inorganic coatings such as oxides of these metals, silane, phenolic resin, epoxy resin, polyurethane, etc. Examples include organic coatings.

  In the case of an SPCC steel plate, a zinc phosphate coating and an iron phosphate coating are also formed.

  In the present invention, the metal plate is preferably a metal plate which has been degreased by alkaline degreasing treatment or the like and then formed with a rust-proof rust-proof treatment or non-chromate-type rust-proof treatment. An iron phosphate coating or a similar coating may be formed.

  The thickness of the metal plate is preferably about 0.1 to 1 mm, and more preferably about 0.2 to 0.8 mm, for gasket material applications.

  The adhesive solution is obtained by dissolving an adhesive resin, a cured resin and an unvulcanized rubber composition for an adhesive in an organic solvent by a general method, applying the adhesive solution on a metal plate, drying and A baking process is performed to form an adhesive layer.

  As the adhesive resin, it is preferable to use one or two or more resins selected from phenol resin, epoxy resin, and xylene resin.

  As a phenol resin, arbitrary thermosetting phenol resins, such as a cresol novolak type, a cresol resol type, an alkyl modified type, are mentioned.

  As the epoxy resin, a cresol novolak modified epoxy resin is generally used, and a bisphenol novolac type phenol resin is suitably used as the curing agent, and an imidazole compound is suitably used as the curing catalyst.

  The xylene resin includes any modified xylene resin such as a phenol-modified type.

  As the rubber composition for the adhesive, a fluororubber composition is used, and preferably the same fluororubber composition as that used for forming the rubber layer is used. Good adhesion to the rubber coat layer is ensured without being affected by the drying and baking temperature of the primer.

  The organic solvent is not limited as long as it dissolves the adhesive resin, the crosslinking agent, the crosslinking accelerator, and the rubber composition for the unvulcanized adhesive at the same time. Examples thereof include aromatic hydrocarbons such as toluene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, alcohol organic solvents such as isopropyl alcohol, and mixed solvents of two or more of these.

  The adhesive solution is prepared so as to have a solid content concentration of 0.5 to 20% with an organic solvent, and is applied onto a metal plate, preferably a metal plate on which a primer layer is formed. Thereafter, the adhesive layer is formed by air drying at room temperature and further drying at about 100 to 250 ° C. for about 5 to 30 minutes (cross-linking reaction may be performed).

  The fluororubber composition of the present invention is dissolved in an organic solvent to form a coating solution, and this coating solution is applied onto a metal plate, preferably an adhesive layer formed on the metal plate, and subjected to press crosslinking or oven crosslinking. A rubber layer is used.

  The fluororubber composition of the present invention is not kneaded, or only a part of raw materials are kneaded using a kneader such as an intermix, kneader, Banbury mixer or an open roll, and then dissolved or dispersed in an organic solvent. And prepared as a coating solution.

  The organic solvent is not limited as long as it dissolves the fluororubber composition. For example, the fluororubber composition is dissolved in a mixed solvent of two or more of alcohols such as methanol and n-butanol and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and the solid content concentration is about 10 to 10%. The coating solution is 40% by weight, preferably about 10-30% by weight.

  The coating solution is coated so that the thickness after drying is 20 to 150 μm. Multiple coatings may be performed as necessary.

  As the coating method, in addition to roll coating, die coating, knife coating, etc., partial printing by screen printing, dispenser or ink jet is also possible. The coating liquid is prepared to have a viscosity suitable for each coating method. For example, in a roll coat, the viscosity is preferably about 200 to 500 cps, and the solid content concentration is appropriately adjusted according to the air temperature and the liquid temperature.

The crosslinking of the fluororubber composition is performed after applying the coating solution and then dried. In the case of press crosslinking, the crosslinking is performed at about 160 to 230 ° C., about 20 to 100 kgf / cm ² (about 1.96 to 9.8 MPa), about 0 In the case of using heated air (oven crosslinking) under a condition of 5 to 30 minutes, heat treatment is performed under conditions of about 160 to 230 ° C. and about 5 to 30 minutes under normal pressure to cause crosslinking.

  On the crosslinked rubber layer, lubricating components such as graphite, PTFE, molybdenum dioxide, carbon black and paraffin wax are the main components, and cellulose resin, acrylic resin, polybutadiene resin, urethane resin, etc. are added as binders to this, and toluene is added. By applying a dispersion liquid dispersed in an organic solvent such as water or the like to form a non-adhesive layer having a thickness of about 1 to 10 μm, seizure prevention and adhesion prevention are achieved.

  The rubber metal laminate (gasket material) thus obtained is processed into a desired shape by, for example, a punch, and is suitably used as a gasket.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

Example 1
Fluororubber composition Binary fluororubber polymer (DuPont Dow Elastomer “Viton A-500”; Mooney viscosity ML _{1 + 10} (121 ° C.) 45) 100 parts by weight MT carbon (Cancarb product “Thermax N990” ] 20 parts by weight Silica (“Nipseal LP” primary particle size 16 nm, manufactured by Tosoh Silica Corporation) 10 parts by weight Calcium metasilicate (“Nyad400” manufactured by NYCO) 5 parts by weight Hydrotalcite (“DHT-4A, manufactured by Kyowa Chemical Co., Ltd.) ] 2 parts by weight Sodium stearate (manufactured by NOF Corporation) 0.5 parts by weight Magnesium oxide (“Kyowa Mag 30” manufactured by Kyowa Chemical Co., Ltd.) 6 parts by weight Crosslinking agent:
Bisphenol AF (“Curative VC # 30” manufactured by DuPont Dow Elastomer Co., Ltd .; master batch of 50 wt% and fluororubber [Viton E-45] 50 wt%)
5 parts by weight (rolling)
Cross-linking accelerator:
Triphenylbenzylphosphonium chloride (Curative VC # 20 manufactured by DuPont Dow Elastomer Co., Ltd .; masterbatch of 33 wt% crosslinking accelerator and 67 wt% fluororubber [Viton E-45]) 2 parts by weight (rolled)

  The above blending components were kneaded using a closed pressure kneader and an open roll. The kneadability at this time was evaluated according to the criteria described later.

  The fluororubber composition was dissolved in a mixed solvent of methyl ethyl ketone: methanol = 8: 2 to prepare a coating solution having a fluororubber composition concentration of 25% by weight.

Rubber metal laminate A Zr / Al-based primer (Nippon Parkerizing product) was applied to an alkali-degreasing stainless steel plate (Nisshin Steel Products SUS301, thickness 0.2 mm) to form a lower primer layer.

  Adhesive solution (Methyl ethyl ketone solution of epoxy phenol resin (Dainippon Ink and Chemicals product cresol novolak modified epoxy resin) is used as the main agent. (Shikoku Chemicals product) 7% by weight, 3% by weight of the above fluororubber composition and 90% by weight of methyl ethyl ketone are dipped on both sides of the steel sheet and heated in an oven at 150 ° C for about 5 minutes. The adhesive layer having a thickness of 2.5 μm on one side was formed on both sides.

On the formed double-sided adhesive layer, the above coating solution was applied at a thickness of 25 μm on one side using a roll coater and dried at 60 ° C. for 10 minutes, and then at 220 ° C. for 1 minute, 35 kgf / cm ² ( The cross-linking was performed under the condition of 3.43 MPa).

  Then, for the purpose of preventing the adhesion of the crosslinked rubber, a toluene dispersion of polyethylene wax to which a polybutadiene resin binder is added is applied and heat-treated at 200 ° C. for 3 minutes to form a 5 μm thick anti-sticking layer (surface coat layer). Formed.

  The following evaluation was performed about the fluororubber composition and rubber metal laminated body which were prepared and manufactured as mentioned above.

1. Rubber kneadability The ease of kneading at the time of preparing the dough was evaluated according to the following criteria.
(Evaluation criteria)
◎: Can be kneaded well ○: Sticked to the roll ×: Could not be kneaded

2. Evaluation of micro-vibration and thermal shrinkage (trackability)
As shown in FIG. 1, the rubber metal laminate 1 was sandwiched between a jig A (reference numeral 2) and a jig B (reference numeral 3) so as to be at an angle of 45 ° with respect to the plane. Under a temperature environment of 200 ° C., the rubber metal laminate is pressurized with the vibrator 4 while changing the surface pressure between 100 MPa to 300 MPa, and a minute vibration with a frequency of 100 Hz is given, and the state after 10 minutes is as follows: Evaluated by criteria.
(Evaluation criteria)
◎: No rubber peeling ○: Some rubber peeling, but no problem ×: Large rubber peeling

3. Protrusion resistance: Flow resistance of gasket material at high temperature and pressure High pressure of 300 MPa is applied to the gasket material with a stainless steel convex jig in a press heated to 150 ° C. It was evaluated with.
It can be determined that the smaller the peeling and protrusion, the better the compressibility.
(Evaluation criteria)
◎: Rubber exfoliation and no protrusion ○: Slight exfoliation and protrusion, but metal plate is not exposed, and there is no problem in practical use ×: Rubber is exfoliated and protruding excessively, metal plate is exposed Stuff

4). LLC Resistance After immersing the rubber metal laminate in a 50% LLC solution in a pressure vessel at 120 ° C. for 500 hours, a cross-cut test was conducted according to JIS K5600, and the following criteria were evaluated.
(Evaluation criteria)
: Rubber remaining rate is 100%
○: Residual rate of rubber is 65% or more and less than 100% ×: Residual rate of rubber is less than 65%

5. Oil resistance After immersing the rubber metal laminate in IRM903 oil at 150 ° C. for 500 hours, a cross-cut test was conducted in the same manner as in the LLC resistance test, and evaluation was performed based on the same criteria.

6). Heat resistance After placing the rubber metal laminate in a thermostatic bath at 200 ° C. for 500 hours, a cross-cut test was conducted in the same manner as the LLC resistance test, and evaluation was performed based on the same criteria.

  The evaluation results are shown in Table 1.

(Example 2)
A rubber metal laminate was obtained in the same manner as in Example 1 except that MT carbon was 30 parts by weight and silica was 20 parts by weight.

(Comparative Example 1)
A rubber metal laminate was obtained in the same manner as in Example 1 except that calcium metasilicate was not blended.

(Comparative Example 2)
A rubber metal laminate was obtained in the same manner as in Example 1 except that MT carbon was 40 parts by weight, silica was 20 parts by weight, and calcium metasilicate was 10 parts by weight.

(Comparative Example 3)
In Example 1, a rubber metal laminate was obtained in the same manner as in Example 1 except that MT carbon was 10 parts by weight and calcium metasilicate was 10 parts by weight.

(Comparative Example 4)
A rubber metal laminate was obtained in the same manner as in Example 1 except that the calcium metasilicate was changed to 10 parts by weight.

(Comparative Example 5)
In Comparative Example 2, a rubber metal laminate was obtained in the same manner except that calcium metasilicate was not blended.

  Example 2 and Comparative Examples 1 to 5 were evaluated in the same manner as Example 1, and the evaluation results are shown in Table 1.

  The fluororubber composition according to the present invention is suitably used as a cross-linking molding material such as a gasket, and the rubber metal laminate according to the present invention is suitably used as a gasket, particularly an engine cylinder head gasket, a compressor gasket, and the like. .

1: Rubber metal laminate 2: Jig A
3: Jig B
4: Exciter

Claims (3)

In a fluororubber composition comprising at least a fluororubber polymer, a crosslinking agent, a crosslinking accelerator, calcium metasilicate, and carbon black,
A fluororubber composition comprising 1 part by weight or more and less than 10 parts by weight of the calcium metasilicate with respect to 100 parts by weight of the fluororubber polymer.   The fluororubber composition according to claim 1, further comprising silica. A rubber metal laminate in which a rubber layer is formed on one side or both sides of a metal plate using the fluororubber composition according to claim 1 as a rubber layer forming component.

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