JP6346832B2 - Sealing material - Google Patents

Description

  The present invention relates to a sealing material, and more particularly, to a sealing material used for sealing the periphery of a polymer electrolyte membrane of a fuel cell that generates power by a reaction between hydrogen and oxygen.

In recent years, a power generation system called a fuel cell that generates electricity by supplying oxygen to one of reaction spaces partitioned by a polymer electrolyte membrane and supplying hydrogen to the other and reacting the hydrogen with oxygen has been clean. Widely used as an energy source.
This type of fuel cell is configured by contacting an annular sealing material along the outer periphery of the polymer electrolyte membrane so as to isolate the reaction space from the external environment. As shown in (paragraph 0016), an elastic member such as a fluorine rubber ring is used.
Further, the sealing in the fuel cell is sometimes performed by a hot melt adhesive as shown in the following Patent Document 2 (see paragraph 0045).

Among such sealing methods, when an elastic member such as a fluoro rubber ring is used, it is advantageous in that an operation for heat-bonding to a polymer electrolyte membrane is not required unlike a hot melt adhesive.
On the other hand, an elastic member such as a fluorine rubber ring usually hardly exhibits an adhesive force with respect to the polymer electrolyte membrane, so that the sealing performance is not sufficiently exhibited.
On the other hand, the hot melt adhesive has an advantage that it can easily exert a sealing performance excellent in adhesion to the polymer electrolyte membrane, although it needs to be thermally bonded to the polymer electrolyte membrane as described above.

JP 2012-89330 A JP 2007-66768 A

For the above reasons, a sealing material for a fuel cell is conventionally required to exhibit a high adhesive force.
In a fuel cell, since hydrogen and oxygen usually react with heat generation, the reaction space for sealing is in a high-temperature and high-humidity state. It is required to have excellent thermal properties.

By the way, as the polymer electrolyte membrane, those made of a perfluorocarbon sulfonic acid resin having a sulfonic acid group and a main chain having a perfluorocarbon structure have been widely used.
In recent years, instead of such polymer electrolyte membranes made of perfluorocarbon sulfonic acid resin, polymer electrolyte membranes made of polyphenylene-based resin are increasing their demand.
As a polyphenylene resin used for this type of application, those having a sulfonic acid group and a main chain having a polyphenylene structure are generally used, but exhibit good adhesion to such a polyphenylene resin. At the same time, a sealing material excellent in moisture and heat resistance has not been found so far.
Therefore, a sealing material that exhibits a good sealing property for this type of polymer electrolyte membrane has not been found.
The present invention has been made in order to satisfy the above-mentioned demand, and an object of the present invention is to provide a sealing material that exhibits good adhesion to this type of polymer electrolyte membrane and is excellent in moisture and heat resistance. .

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a specific resin composition exhibits excellent adhesion to a polyphenylene resin and has excellent wet heat resistance, thereby completing the present invention. It is what led to it.

  That is, in order to solve the above-mentioned problems, the present invention provides a polyphenylene resin having a sulfonic acid group, which is a sealing material used in contact with a polymer electrolyte membrane of a fuel cell that generates electricity by reaction of hydrogen and oxygen. And at least the surface in contact with the polymer electrolyte membrane is made of a polyester resin composition, the polyester resin composition is a crystalline polyester resin, and the softening point is 60 ° C. The polyester resin composition contains an epoxy resin having a temperature of 100 ° C. or less and an isocyanate crosslinking agent, and the polyester resin composition contains the crystalline polyester resin crosslinked with the isocyanate crosslinking agent. The content of the epoxy resin in the resin composition is based on 100 parts by mass of the crystalline polyester resin. Providing a sealing material is less than 30 parts by mass or more 20 parts by weight.

  ADVANTAGE OF THE INVENTION According to this invention, the sealing material for fuel cells excellent in wet heat resistance and normal temperature adhesiveness can be provided.

(A) The schematic plan view which shows the sealing material of one Embodiment. (B) The schematic sectional drawing which showed the AA arrow cross section in the said top view.

  Hereinafter, a preferred embodiment of the present invention is a sealing material used for sealing the periphery of a polymer electrolyte membrane of a fuel cell that generates power by reaction of hydrogen and oxygen, and has a sulfonic acid group. An example of the sealing material used for the sealing by contacting the surface of a polymer electrolyte membrane made of polyphenylene resin will be described.

As shown in FIG. 1, the sealing material in the present embodiment is a sheet-like member having a rectangular frame shape in plan view, and more specifically, a rectangular shape whose outer peripheral shape is slightly smaller than that of the polymer electrolyte membrane. It has a frame shape.
The sealing material 1 has a three-layer structure including a base material layer 10 made of a polymer sheet and an adhesive layer 20 provided on both surfaces of the base material layer 10.
That is, the sealing material 1 of the present embodiment functions as a sealing surface in which the surface of one adhesive layer 20 is bonded to the polymer electrolyte membrane, and the adhesive layer 20 constituting the sealing surface is crystalline. It is formed with the polyester resin composition which has a polyester resin (A) as a main component.

The polyester resin composition forming the adhesive layer 20 (hereinafter also simply referred to as “resin composition”) includes an epoxy resin (B) and an isocyanate-based crosslinking agent (X) in addition to the crystalline polyester resin. And the crystalline polyester resin (A) in a state of being crosslinked by the isocyanate-based crosslinking agent.
Hereinafter, the individual components will be described in more detail.

(A) Crystalline polyester resin As the crystalline polyester resin in the present embodiment, a resin obtained by dehydration condensation of a polyvalent carboxylic acid (a1) and a polyol (a2) can be employed.
It should be noted that a polyester resin generally called an amorphous polyester resin is made crystalline by adopting a plurality of types in either one or both of the polyvalent carboxylic acid (a1) and the polyol (a2). While the expression is suppressed, for example, the crystalline polyester resin is adjusted so as not to show a clear crystallization peak or crystal melting peak by differential scanning calorimetry (DSC) analysis, the crystalline polyester resin is subjected to DSC analysis. The polyvalent carboxylic acid (a1) and the polyol (a2) are selected in the synthesis so that the crystallization peak and the crystal melting peak are clearly shown in FIG.
Therefore, when it is necessary to determine whether or not the polyester resin is a crystalline polyester resin, it is only necessary to confirm whether or not a crystallization peak or a crystal melting peak is clearly shown by DSC analysis.

(A1) Polyvalent carboxylic acid Examples of the polyvalent carboxylic acid constituting the crystalline polyester resin include terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, Aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid and biphenyldicarboxylic acid; aromatic oxycarboxylic acids such as p-oxybenzoic acid and p- (hydroxyethoxy) benzoic acid; succinic acid , Saturated aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and dodecane dicarboxylic acid; unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid and itaconic acid; unsaturated alicyclic dicarboxylic acids such as tetrahydrophthalic acid Hexahydrophthalic acid, 1,2-cyclohexanedicarboxylic acid, 1,3- Examples thereof include alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and tricarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

(A2) Polyol Examples of the polyol constituting the crystalline polyester resin include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl Aliphatic glycols such as 1,3-propanediol; oligoalkylene glycols such as diethylene glycol, triethylene glycol and dipropylene glycol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedi Alicyclic glycols such as methanol; Polyalkylene ether glycols such as reethylene glycol, polypropylene glycol and polytetramethylene glycol; triols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol; ethylene oxide adducts and propylene oxide adducts of bisphenol A, hydrogenated bisphenol A And ethylene oxide adducts and propylene oxide adducts.

It is considered that the crystalline polyester resin is less susceptible to attack by water in the crystalline region than in the amorphous region, and is less likely to deteriorate due to hydrolysis or the like.
Therefore, as the crystalline polyester resin, it can be said that the higher the melting point and the higher the degree of crystallinity are advantageous in that the adhesive layer 20 can be excellent in wet heat resistance.
On the other hand, if the crystalline polyester resin, which is the main component of the resin composition for forming the adhesive layer 20, is made to have a high melting point with an excessively high degree of crystallinity, the resin composition has excellent room temperature adhesion. It becomes difficult.
Accordingly, the crystalline polyester resin preferably has a melting point of more than 90 ° C. and less than 150 ° C. in that the adhesive layer 20 can have both excellent heat and moisture resistance and excellent room temperature adhesion. Is more preferably higher than 100 ° C. and lower than 140 ° C., particularly preferably higher than 105 ° C. and lower than 130 ° C.
The crystalline polyester resin preferably has a glass transition temperature (hereinafter also referred to as “Tg”) in the range of −100 ° C. or higher and 30 ° C. or lower, and particularly in the range of −80 ° C. or higher and −20 ° C. or lower. More preferably, it is in the range.

By adopting a crystalline polyester resin having a Tg within the above range as a main component of the resin composition, the adhesive layer 20 has a single layer of rubber as compared with the case where a crystalline polyester resin having a Tg outside the above range is used. Elasticity can be exhibited, and the cohesive force can be improved to exhibit excellent adhesiveness.
In addition, the adhesive layer 20 excellent in cold resistance can be formed by setting Tg of crystalline polyester resin to 10 degrees C or less.
Moreover, the adhesive layer 20 can make a normal temperature adhesive characteristic favorable by having as a main component the crystalline polyester resin whose Tg is 10 degrees C or less.
When such a suitable crystalline polyester resin is contained in the adhesive layer of the sealing material, the polymer electrolyte membrane is sealed when the periphery of the polymer electrolyte membrane of the fuel cell is sealed using the sealing material. A reliable seal can be applied while suppressing the possibility of heat damage.

Moreover, it can suppress that the said adhesive bond layer 20 becomes too flexible by employ | adopting the crystalline polyester resin whose Tg is -100 degreeC or more as a main component of the said resin composition.
Moreover, since it is possible to suppress the softening temperature of the entire resin composition from becoming too low by adopting the crystalline polyester resin as described above, the fuel cell is operating at room temperature when the operation is stopped, The adhesive layer can exhibit high adhesive strength even under heating conditions during battery operation.

The melting point and the glass transition temperature (Tg) can be measured using, for example, a DSC analyzer.
More specifically, the sample (crystalline polyester resin) is heated at a rate of 5 ° C./min while flowing nitrogen gas from a temperature lower than 30K or higher than the predicted melting point or glass transition temperature to a temperature higher than 30K. The melting point and glass transition temperature can be determined from the DSC curve obtained when the temperature is raised.
The glass transition temperature (Tg) can be determined by determining the midpoint glass transition temperature based on the method described in JIS K7121: 1987 “Method for measuring plastic transition temperature”.

The number average molecular weight of the crystalline polyester resin is preferably 10,000 to 50,000.
It is preferable that the crystalline polyester resin as the main component of the resin composition has such a molecular weight. By setting the molecular weight of the crystalline polyester resin to 10,000 or more, the adhesive layer 20 can be prevented from becoming brittle. This is because the adhesive layer 20 can exhibit excellent toughness.
On the other hand, by adopting a crystalline polyester resin having a number average molecular weight of 50000 or less, the adhesive layer 20 can be made excellent in normal temperature adhesiveness.
That is, by adopting such a crystalline polyester resin, it is possible to make the sealing material less likely to cause thermal damage to the polymer electrolyte membrane of the fuel cell and to exhibit excellent sealing properties.

  In addition, the number average molecular weight of crystalline polyester resin can be calculated | required as a styrene conversion value by a gel permeation chromatography (GPC) method.

As the crystalline polyester resin exhibiting the above characteristics, those obtained by reacting terephthalic acid, isophthalic acid, butanediol, and polyoxytetramethylene glycol are preferable.
Among them, terephthalic acid is composed of 25 to 40 mol%, isophthalic acid is composed of 10 to 20 mol%, butanediol is composed of 35 to 50 mol%, and polyoxytetramethylene glycol having an average number of repetitions of 10 to 20 is composed of 5 to 15 mol%. The crystalline polyester resin is preferred.

(B) Epoxy resin The resin composition in the present embodiment contains an epoxy resin having a softening point of 60 ° C. or higher and 100 ° C. or lower as an essential component determined by the ring and ball method of JIS K 7234, and the softening point is lower than 60 ° C. And an epoxy resin having a softening point exceeding 100 ° C. are optional components.
Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, phenol novolac type epoxy resin and the like.
In addition, when making the said epoxy resin which is an arbitrary component contain in the said resin composition, it is preferable to set it as the ratio of 1/10 or less of the epoxy resin which is an essential component, and it is especially preferable to set it as the ratio of 1/20 or less. .
Moreover, it is preferable that the resin composition does not substantially contain an optional epoxy resin.
The epoxy resin, which is an essential component, is an effective component for causing the resin composition forming the adhesive layer 20 to exhibit tackiness.

  The epoxy resin is preferably a bisphenol A type epoxy resin in that it is effective for imparting tackiness and toughness to the resin composition and imparting excellent moisture and heat resistance, and the epoxy resin has a molecular weight of 600 to 600. It is preferable that the epoxy equivalent calculated | required by JISK7236 by 1500 is 400-800 g / eq.

The crystalline polyester resin is preferably contained in the resin composition in a proportion of 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.
When the amount of the crystalline polyester resin is 100 parts by mass, the epoxy resin as the essential component may be contained in the resin composition so as to be 20 parts by mass or more and 30 parts by mass or less. It is important in making it excellent in heat-and-moisture resistance, and can be contained in the resin composition so as to be 22 parts by mass or more and 28 parts by mass or less.

The epoxy resin is a short chain having a hydroxyl group or a carboxyl group at the molecular end because the crystalline polyester resin is hydrolyzed by containing at least part of the epoxy group in the resin composition so as not to open the ring. In such a case, these can be reacted with an epoxy group to make it long again.
Therefore, the adhesive layer 20 of the present embodiment is capable of suppressing degradation of physical properties such as adhesive strength and tensile strength due to wet heat degradation of the resin composition used for the formation due to the presence of the epoxy group, It is preferable that at least a part of the epoxy groups contain the epoxy resin in an unreacted state.
In addition, it can confirm that an epoxy group remains without ring-opening using a Fourier transform infrared spectrophotometer (FTIR), and specifically, the peak which shows presence of an epoxy group is 925. It can be confirmed by appearing at ˜899 cm ⁻¹ .
Further, if it is necessary to confirm whether the peak appearing at 925 to 899 cm ⁻¹ is due to an epoxy group, the resin composition may be heated again to a temperature above the softening point of the epoxy resin and then subjected to FTIR measurement. It can be confirmed that the peak is due to the epoxy group by changing in relation to the peak height and the peak height due to the hydroxyl group appearing at 3650 to 3140 cm ⁻¹ .

(X) Isocyanate-based crosslinking agent As the isocyanate-based crosslinking agent, those having reactivity with polar groups such as hydroxyl groups possessed by the crystalline polyester resin can be used. For example, hexamethylene diisocyanate (HDI), isophorone diisocyanate ( Examples thereof include aliphatic isocyanates such as IPDI) and xylylene diisocyanate (XDI), and aromatic isocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and tolidine diisocyanate (TODI).

  Moreover, as said isocyanate type crosslinking agent contained in the said resin composition, xylylene diisocyanate is preferable, and the compounding ratio of this isocyanate type crosslinking agent is 3 mass parts or more and 12 masses with respect to 100 mass parts of said crystalline polyester resins. The amount is preferably 5 parts by mass or less and particularly preferably 5 parts by mass or more and 10 parts by mass or less.

(Z) Other components In the resin composition of the present embodiment, the crystalline polyester resin shown above and a resin component other than the epoxy resin can be contained in a range that does not significantly impair the effects of the present invention. For example, when further room temperature adhesiveness is required, a tackifier such as a terpene resin can be added.
Further, an amorphous polyester resin or the like may be contained in the resin composition of the present embodiment as an optional component.
However, if the amorphous polyester resin is excessively contained, the excellent characteristics of the crystalline polyester resin, which is the base polymer of the resin composition, may not be manifested as the characteristics of the resin composition.
Therefore, when the amorphous polyester resin is contained in the resin composition, the ratio is preferably 1/10 or less of the crystalline polyester resin, and more preferably 1/20 or less.
In addition, general plastic compounding agents such as anti-aging agents, antioxidants, flame retardants, fillers, colorants, processing aids and the like can be appropriately contained within a range not impairing the effects of the present invention.

Especially, in order to improve the cohesive force of a resin composition and to improve water vapor | steam barrier property and gas barrier property, it is preferable to contain an inorganic filler like a plate-like mineral particle.
In particular, talc powder having an average particle diameter (median diameter by laser diffraction method) of 1 to 10 μm is preferable in that it can be obtained at low cost.
Further, the talc powder to be contained in the resin composition may be surface-treated with a fatty acid or a silane coupling agent, but improves the cohesive strength of the resin composition by using the functional group on the surface. Above, it is preferable to use an untreated one.

  When the talc powder is contained in the resin composition, the talc powder is preferably contained so as to have a ratio of 10 parts by mass to 50 parts by mass with respect to 100 parts by mass of the crystalline polyester resin, and 20 parts by mass. It is preferable to contain talc powder so that it may be 30 parts by mass or less.

The sealing material of this embodiment includes an adhesive layer 20 (hereinafter also referred to as “first adhesive layer 20a”) formed on one side of the base material layer 10 and an adhesive layer 20 (hereinafter referred to as “first adhesive layer 20a”). It is not necessary to form the second adhesive layer 20b ") by the same resin composition, and the first adhesive layer 20a and the second adhesive layer 20b may be formed by resin compositions having different blending contents. good.
In addition, the first adhesive layer 20a and the second adhesive layer 20b can usually have a thickness of 10 μm or more and 200 μm or less, and both may have the same thickness or different thicknesses.

It should be noted that the adhesive layer 20 is difficult to exhibit an adhesive force at room temperature if the storage elastic modulus is excessively low, but is also bonded as a result of insufficient adhesion to the polymer electrolyte membrane if the storage elastic modulus is excessively high. It becomes difficult to exert power.
Accordingly, at least the adhesive layer 20 on the side in contact with the polymer electrolyte membrane can exhibit excellent adhesion to the polymer electrolyte membrane at room temperature (for example, 23 ° C.) and storage modulus (G ′) at 40 ° C. Is preferably 2.5 MPa or more and 5 MPa or less.

About this storage elastic modulus, it calculates | requires by the measurement on the following conditions.

<Measurement conditions of storage elastic modulus (G ')>
・ Equipment used: manufactured by TA Instruments Japan, Inc., trade name "ARES-2 KFRT"
・ Measurement mode: Temperature dependence test of dynamic viscoelasticity, using 8mm parallel plate ・ Measurement temperature range: 30 ° C to 200 ° C
・ Raising rate: 10 ° C / min
・ Vibration frequency: 1Hz
・ Distortion: 0.5%

In addition, it is preferable that the sealing material of this embodiment exhibits a peel strength of 0.1 N / 10 mm with respect to a polymer electrolyte membrane made of a polyphenylene resin, and particularly preferably has a peel strength of 3 N / 10 mm or more. .
Whether or not the sealing material has such a peeling strength can be determined by actually measuring the peeling strength of the sealing material by the method described in the examples.

The base material layer 10 for supporting the adhesive layer 20 on both sides can be usually constituted by a film-like sheet made of a resin having good affinity with the resin composition or a fiber sheet made of the resin. .
Among them, a film or a nonwoven fabric made of polyethylene terephthalate resin or polyethylene naphthalate resin and having a thickness of 10 μm or more and 200 μm or less is suitable as a constituent material of the base material layer 10.
It is possible to use not only such a polyester resin sheet, but also other resins such as polyamide resin and polyimide resin, and polymer sheets made of polymers such as silicone rubber and fluorine rubber as a constituent material of the base material layer 10. is there.
Furthermore, a laminate sheet obtained by laminating different materials may be used as the material for forming the base material layer 10.

The sealing material of the present embodiment includes a compounding agent for forming a resin composition such as a crystalline polyester resin, an epoxy resin, an isocyanate-based crosslinking agent, and an inorganic filler, for example, at a temperature equal to or higher than the melting point of the crystalline polyester resin. A coating liquid can be prepared by melt-kneading and adding an organic solvent as necessary, and the coating liquid can be applied to both surfaces of a polymer sheet.
In addition, about bridge | crosslinking of the said crystalline polyester resin, it can be made to react by making the hydroxyl group of a polyester resin and the isocyanate group of a crosslinking agent react by the heating in the case of adjustment of the said coating liquid.

In addition, as a polymer electrolyte membrane made of polyphenylene resin that is sealed with the sealing material of the present embodiment, for example, on the surface of a sheet body made of a single polyphenylene resin or a base material sheet made of resin other than polyphenylene resin. Examples include a sheet body in which polyphenylene resin sheets are laminated.
In the polymer electrolyte membrane, as the polyphenylene resin constituting the surface portion to which the adhesive layer 20 is bonded, for example, the main chain is a polymer having a polyphenylene structure and is bonded to the main chain. Examples thereof include those having a sulfonic acid group as a functional group and those having a sulfonic acid group in a part of the side chain bonded to the main chain.

  The polyphenylene resin is preferably a polymer having a number average molecular weight of about 1000 to 20000 determined by the GPC method, and a polymer having a sulfonic acid group in the side chain. For example, a repeat represented by the following general formula (1) Polymers having units are preferred.

“X ¹ ” represents a direct bond, an ether bond (—O—), a sulfide bond (—S—), or any one of the following bonds (a) to (e). Yes.

“Y ¹ ” represents a direct bond, an ether bond (—O—), or a sulfide bond (—S—).

Furthermore, “R ¹ ” and “R ² ” represent a divalent group in which a hydrogen atom is removed from any of alkylene having 1 to 10 carbon atoms, phenylene, the following (f), or the following (g). .

Note that “R ¹ ” and “R ² ” do not need to have the same structure, and may be different.

“P” and “q” represent a rational number of 0 or more and 1 or less, and at least one of “p” and “q” is a value exceeding 0.
Here, when “p” or “q” is an intermediate value between 0 and 1, all the repeating units are side chains (“—R ¹ —SO ₃ H”, “—R ² —SO ₃ H”). ).
That is, “p” or “q”, for example, “0.1” means that the number of side chains (“—R ¹ —SO ₃ H” of 1/10 of the number of repetitions (n) in one polymer. "" ^- R 2 -SO ₃ H ") means that is provided.

In the polyphenylene resin of the present embodiment, the X ¹ and the Y ¹ are preferably a direct bond and have a sulfonic acid group in a form as shown in (fx) or (gx) below.

  Moreover, as said preferable polyphenylene-type resin of this embodiment, what is represented by following General formula (2) can be mentioned, for example.

“X ² ” represents a direct bond, an ether bond (—O—), a sulfide bond (—S—), or any one of the following bonds (a) to (e). Yes.
Also, ^{"X 3"} is a direct bond, an ether bond (-O-), sulfide linkages (-S-), and, among any of the following (a) ~ (e), and ^{"X 2"} Represents different bonds.

“Y ² ” and “Y ³ ” represent a direct bond, an ether bond (—O—), or a sulfide bond (—S—).
“Y ² ” and “Y ³ ” may be the same or different from each other.

Furthermore, “R ³ ” to “R ⁶ ” represent a divalent group in which a hydrogen atom is removed from any one of alkylene having 1 to 10 carbon atoms, phenylene, the following (f), or the following (g). .

Note that “R ³ ”, “R ⁴ ”, “R ⁵ ”, and “R ⁶ ” do not need to have the same structure and may be different from each other.

“P” and “q” represent a rational number of 0 or more and 1 or less, and at least one of “p” and “q” is a value exceeding 0.
Further, “s” and “t” represent rational numbers of 0 or more and 1 or less, and at least one of “s” and “t” is a value exceeding 0.
Here, “p”, “q”, “s”, “t” and the like are intermediate values between 0 and 1, as described above, that all the repeating units do not have side chains. means.
The sealing material of the present embodiment exhibits excellent moisture and heat resistance and adhesion with respect to the polymer electrolyte membrane made of polyphenylene resin as described above because the adhesive layer is made of a predetermined resin composition. It will be.

  Note that the sealing material of the present embodiment does not necessarily have to be adhered to the polymer electrolyte membrane at room temperature when sealing, for example, the polymer electrolyte membrane is heated to a temperature below the melting point of the crystalline polyester resin. You may make it adhere | attach.

Further, in the present embodiment, the sealing material has a three-layer structure of adhesive layer / base material layer / adhesive layer, but the sealing material of the present invention includes a base material layer, an adhesive layer, Or a single-layer structure having only an adhesive layer.
Further, the sealing material of the present invention can employ conventionally known technical matters in addition to the matters exemplified above as long as the effect is not significantly impaired.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
(material)
The materials used for the evaluation and the details are shown below.
(A Crystalline polyester resin)
(A1):
Number average molecular weight: 30000
Glass transition temperature (Tg): -60 ° C
Melting point (Tm): 107 ° C
Crystalline polyester resin.

(B Epoxy resin)
(B1):
Number average molecular weight (epoxy equivalent): about 900 (450 to 500 g / eq)
Softening point (Ts): 69 ° C
Bisphenol A type epoxy resin.

(B2):
Number average molecular weight (epoxy equivalent): about 1300 (670-770 g / eq)
Softening point (Ts): 89 ° C
Bisphenol A type epoxy resin.

(B3):
Number average molecular weight (epoxy equivalent): about 1650 (875-975 g / eq)
Softening point (Ts): 97 ° C
Bisphenol A type epoxy resin.

(X Isocyanate-based crosslinking agent)
(X1): Xylylene diisocyanate

Example 1
Resin composition containing crystalline polyester resin (A1), epoxy resin (B2, B3), and isocyanate-based crosslinking agent (X1) in the ratio shown in Table 1 on one side of a 25 μm-thick polyethylene terephthalate (PET) film A sheet sample was prepared by forming an adhesive layer having a thickness of 20 μm with the object.

(Evaluation of room temperature adhesive strength: Sample preparation method and evaluation)
A strip-shaped sample having a width of 10 mm and a length of 200 mm was cut out from the sheet sample for a peel test.
Also, a plate-like sample in which a polyphenylene-based resin sheet (commercial product manufactured by JSR) was attached to one side of a hard plate, and the same size as the strip sample was prepared.

The plate-shaped sample and the strip-shaped sample are superposed in such a manner that the polyphenylene resin sheet surface of the plate-shaped sample and the adhesive layer forming surface of the strip-shaped sample are brought into contact with each other. The rubber roller at 25 ° C. rotated at a peripheral speed of min was supplied so that the longitudinal direction was the moving direction, and passed through the rubber roller.
At this time, the pressure (linear pressure) of the rubber roller was 51.2 MPa / cm.
In addition, the above bonding is performed so that the bonding section between the two is a section of about 40 mm from one end in the longitudinal direction, and the strip-shaped sample and the plate-shaped sample are not bonded to each other in the remaining section of about 160 mm. Was carried out.
Then, the strip-like sample and the plate-like sample on the non-bonded side are respectively chucked on the upper and lower chucks of a tensile tester, and a 180 degree peel test is performed to obtain an average value of tensile stress (N / cm), This sample was evaluated as “room temperature adhesive strength”.

(Hot water adhesion test: Sample preparation method and evaluation)
A 22 mm square sheet piece (sheet piece A) was cut out from a polyphenylene resin sheet (commercially available from JSR).
Then, two 20 mm square sheet pieces (sheet piece B) that were slightly smaller than the above were cut out from the sheet sample (20 μm adhesive layer / 25 μm PET).
The two sheet pieces B are so formed that the adhesive layer of the sheet piece B is in contact with the sheet piece A and the sheet piece B protrudes uniformly with a width of about 1 mm around the sheet piece A. A laminate was prepared by sandwiching the sheet piece A therebetween.
This laminated body is supplied to a rubber roller at 25 ° C. rotated at a peripheral speed of 0.5 m / min, and a pressure (linear pressure) of 25.6 MPa / cm is applied by the rubber roller to obtain sheet pieces A and B. Was bonded at room temperature to obtain a hot water adhesion test sample.
The sample for hot water adhesion test was evaluated by immersing in boiling water that had been boiled for 3 hours.
Then, as a result of the evaluation, the case where there was no peeling between the sheet pieces A and B was determined as “◯”, the case where partial peeling was seen as “Δ”, and the case where peeling occurred as “×”. .

The evaluation results and the results of measuring the storage elastic modulus of the resin composition are shown in Table 1.

(Example 2, Comparative Examples 1 and 2)
Evaluation was carried out in the same manner as in the Examples except that the resin composition used for forming the adhesive layer was formulated as shown in Table 1. The results are shown in Table 1.

  From the above results, it can be seen that according to the present invention, a sealing material having excellent heat and moisture resistance and room temperature adhesion can be obtained.

1 Sealing material 10 Base material layer 20 Adhesive layer

Claims (1)

A sealing material used in contact with a polymer electrolyte membrane of a fuel cell that is generated by a reaction between hydrogen and oxygen,
Used in contact with a polymer electrolyte membrane formed by a polyphenylene resin having a sulfonic acid group,
At least the surface in contact with the polymer electrolyte membrane is made of a polyester resin composition,
The polyester resin composition includes a crystalline polyester resin, an epoxy resin having a softening point of 60 ° C. or higher and 100 ° C. or lower, and an isocyanate-based crosslinking agent.
The polyester resin composition contains the crystalline polyester resin in a state of being crosslinked by the isocyanate-based crosslinking agent,
And the sealing material whose content of the said epoxy resin in this polyester resin composition is 20 to 30 mass parts with respect to 100 mass parts of said crystalline polyester resins.

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