JP5108376B2 - Adhesive seal member for fuel cell - Google Patents

Description

  The present invention relates to an adhesive seal member that adhesively seals members constituting a fuel cell.

  A fuel cell that generates electricity by an electrochemical reaction of gas has high power generation efficiency, clean gas discharged, and extremely little influence on the environment. Among these, the polymer electrolyte fuel cell can be operated at a relatively low temperature and has a large power density. For this reason, various uses, such as a power generation and a power supply for automobiles, are expected.

  In a polymer electrolyte fuel cell, a cell in which an electrolyte membrane electrode assembly (MEA), a gas diffusion layer, and the like are sandwiched by separators serves as a power generation unit. The MEA includes a polymer membrane (electrolyte membrane) serving as an electrolyte and a pair of electrodes (fuel electrode and oxygen electrode) disposed on both sides of the electrolyte membrane. A fuel gas such as hydrogen or hydrocarbon is supplied to the fuel electrode, and an oxidant gas such as oxygen or air is supplied to the oxygen electrode. Power generation is performed by an electrochemical reaction at the three-phase interface between the supplied gas, electrolyte, and electrode. The polymer electrolyte fuel cell is configured by fastening a cell stack in which a plurality of the cells are stacked with end plates or the like disposed at both ends in the cell stacking direction.

The separator is formed with a flow path of gas supplied to each electrode and a flow path of refrigerant for relaxing heat generation during power generation. For example, when the gas supplied to each electrode is mixed, problems such as a decrease in power generation efficiency occur. The electrolyte membrane has proton conductivity in a state containing water. For this reason, it is necessary to keep the electrolyte membrane in a wet state during operation. Therefore, in order to prevent gas mixing, gas and refrigerant leakage, and to keep the inside of the cell moist, a sealing property such as between the electrolyte membrane and the separator or between adjacent separators is secured. It becomes important. For example, an adhesive made of a thermosetting resin is known as an adhesive seal member that adhesively seals the constituent members of the fuel cell (see, for example, Patent Document 1).
JP 2005-129343 A JP 2005-347256 A

  Usually, when an adhesive made of a thermosetting resin is used, the adhesive is applied between the members to be bonded, and heated and pressed in a state where it is fixed as it is. In this case, it is necessary to cure the adhesive with a load applied, and it takes a long time of several tens of minutes to one hour or more to complete the curing. For this reason, the productivity of the fuel cell is low. In addition, when curing, if there are impurities or the like, curing failure may occur, so care should be taken in handling such as working environment. In addition, it is necessary to consider the pot life of the thermosetting resin.

  On the other hand, Patent Document 2 introduces a polyolefin-based adhesive seal member modified with an acid or the like. If this adhesive seal member is used, the above-mentioned problems derived from the thermosetting resin are solved. However, the adhesion in the operating environment of the fuel cell is still not sufficient. That is, when the fuel cell is operated for a long period of time, in the adhesive seal member introduced in Patent Document 2, the adhesive force may decrease with the passage of time.

  For example, a polymer electrolyte fuel cell operates at a temperature of about 70 ° C to 90 ° C. Further, the fuel gas and the oxidant gas are often humidified and supplied to each electrode in order to maintain the proton conductivity of the electrolyte membrane. Furthermore, water is produced from hydrogen and oxygen at the oxygen electrode. Further, a coolant such as water flows in the coolant channel. Thus, in the polymer electrolyte fuel cell, the adhesive seal member is used in an environment where it comes into contact with moisture at a temperature of about 70 ° C. to 90 ° C. Accordingly, the adhesive seal member is required to have a low adhesive strength even when used for a long time in an environment where it comes into contact with warm water or steam.

  Further, the adhesive seal member introduced in Patent Document 2 does not have sufficient compression creep resistance (hereinafter simply referred to as “creep resistance”). As described above, in the polymer electrolyte fuel cell, the cell stack is compressed with a predetermined load from both ends in the cell stacking direction. In addition, heat is generated during operation. For this reason, if the creep resistance of the adhesive seal member is low, the adhesive seal member may be gradually deformed during the operation of the fuel cell, and the air tightness and liquid tightness (sealability) of the adhesive seal portion may be reduced. is there. Further, when the adhesive seal member is compressed and deformed, the distance between the adhesive seal portions, that is, the constituent members is reduced. The change in the interval between the constituent members in the individual cells acts on the cell stack in a total manner. Thereby, the load added to a cell laminated body will fall. As a result, the contact between the electrolyte membrane, the electrode, the separator and the like becomes insufficient, and the battery performance may be deteriorated. Therefore, the adhesive seal member is required not to be deformed even when the fuel cell is operated for a long period of time, that is, to have high creep resistance.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an adhesive seal member for a fuel cell that has a low creep strength and high creep resistance in the operating environment of the fuel cell. .

The fuel cell adhesive seal member of the present invention (hereinafter appropriately referred to as “the adhesive seal member of the present invention”) is mainly composed of an olefin-based thermoplastic resin modified with an acid, a silane coupling agent, and a crosslinking agent . And a resin particle comprising at least one selected from an acrylic polymer and a crosslinked styrene polymer, and is characterized by adhesively sealing the constituent members of the fuel cell.

  The adhesive seal member of the present invention is mainly composed of an olefin-based thermoplastic resin modified with an acid (hereinafter referred to as “acid-modified olefin-based thermoplastic resin” as appropriate). For this reason, it is not necessary to harden for a long time like the adhesive which consists of the conventional thermosetting resin. Therefore, the bonding operation can be completed in a short time, and the fuel cell productivity can be improved. In addition, thermoplastic resins are unlikely to be hardened due to impurities, dirt, and the like. For this reason, the adhesive seal member of the present invention is easy to handle. Moreover, there is no need to consider pot life. Furthermore, the acid-modified olefin-based thermoplastic resin has good water resistance and acid resistance. Therefore, the adhesive seal member of the present invention is excellent in adhesiveness in the presence of moisture. In addition, the adhesive seal member of the present invention has good wettability with respect to the surface of the constituent member (metal or resin) of the fuel cell. Therefore, it is easy to ensure desired adhesiveness and sealability. Here, “mainly composed of an olefin-based thermoplastic resin modified with an acid” means that the content of the acid-modified olefin-based thermoplastic resin when the entire adhesive seal member of the present invention is 100% by weight. It means that the ratio is 50% by weight or more.

  In addition, the adhesive seal member of the present invention contains a silane coupling agent. A silane coupling agent has reactivity with respect to each of an inorganic material and an organic material. Therefore, for example, when the constituent member of the fuel cell is made of an inorganic material such as a metal or a carbon material, the constituent member and the adhesive seal member (organic material) of the present invention are strongly fixed by the silane coupling agent. Chemical bonds are formed. As a result, the adhesive force of the adhesive seal member of the present invention is further increased, and the adhesive force is unlikely to decrease even in the operating environment of the fuel cell. Moreover, the adhesive force of the polymer which comprises the adhesive seal member of this invention, and the resin particle mentioned later is improved by including a silane coupling agent. Therefore, compared with the case where only resin particles are contained, the adhesive force is less likely to be reduced. As described above, according to the adhesive seal member of the present invention having high adhesion reliability, even when the fuel cell is operated for a long period of time, good sealability is ensured. For this reason, the operation reliability of the fuel cell can be improved.

  Furthermore, the adhesive seal member of the present invention includes resin particles. By including the resin particles, the interface at the time of peeling becomes a so-called cohesive failure state in which the adhesive seal member remains on the surface of the adherend (component). For this reason, the adhesive sealing member of this invention is excellent in adhesive reliability. Further, since the resin particles serve as spacers, the adhesive seal member of the present invention is difficult to compress and creep. Therefore, even in the operating environment of the fuel cell, the adhesive seal member of the present invention is not easily deformed, and good sealability can be ensured. In addition, according to the adhesive seal member of the present invention, since a decrease in load applied to the cell laminate is suppressed, it is possible to maintain a good contact state of the electrolyte membrane, electrode, separator, etc., resulting in a decrease in battery performance. Can be suppressed.

  Below, embodiment of the adhesive seal member for fuel cells of this invention is described. The adhesive seal member for a fuel cell according to the present invention is not limited to the following embodiment, and various modifications and improvements that can be made by those skilled in the art without departing from the gist of the present invention. It can be implemented in the form.

<Adhesive sealing material for fuel cells>
As described above, the adhesive seal member of the present invention contains an acid-modified olefin thermoplastic resin as a main component. Here, the olefin-based thermoplastic resin includes an olefin homopolymer, an olefin copolymer, and a copolymer of an olefin and a substance other than an olefin. Specifically, the olefin homopolymer includes a polymer composed of a single unsaturated olefin having 2 to 20 carbon atoms (for example, polyethylene, polypropylene, polybutene, etc.). The olefin copolymer includes a polymer comprising one or more unsaturated or polyunsaturated hydrocarbons having 2 to 20 carbon atoms. For example, ethylene / propylene copolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / octene copolymer, ethylene / styrene copolymer, ethylene / butene / octene copolymer, ethylene / propylene / Examples include norbornadiene copolymer and propylene / butene copolymer. Non-olefins (those that can be copolymerized with olefins (in principle, ethylene)) include vinyl acetate, acrylic acid or methacrylic acid esters having 1 to 20 carbon atoms, and unsaturated anhydrides (for example, maleic anhydride, Itaconic anhydride, etc.) and unsaturated acids (eg, maleic acid, fumaric acid, acrylic acid, methacrylic acid, itaconic acid, etc.). Examples of the copolymer of olefin and non-olefin include ethylene / vinyl acetate, ethylene / methyl acrylate, ethylene / butyl acrylate, and the like.

  For example, olefinic thermoplastic resin can be high density polyethylene (HDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), ultra low density polyethylene (ULDPE), high density polypropylene (HDPP), low density polypropylene. (LDPP) and mixtures thereof are preferred. In addition, it is desirable to employ a propylene resin as a main component as the olefin thermoplastic resin for reasons such as excellent balance between the bonding processing temperature of the adhesive seal member of the present invention and the hot strength during use. . Here, “mainly composed of a propylene-based resin” means that the content of the propylene-based resin is 50% by weight or more when the entire olefin-based thermoplastic resin is 100% by weight.

  The olefinic thermoplastic resin modified with an acid means the olefinic thermoplastic resin modified with an acid, an acid anhydride, an acid ester, a metallocene or the like. Modification with an acid may be carried out by grafting an acid component onto an olefinic thermoplastic resin, copolymerizing it, or a combination thereof. For reasons such as relatively easy modification, modification by grafting is preferred. The amount of modification by acid (weight ratio of the acid component contained in the acid-modified olefin-based thermoplastic resin) is not particularly limited. What is necessary is just to determine suitably so that desired adhesiveness and sealing performance may be acquired. In general, if the amount of modification by acid is small, it becomes difficult to obtain desired adhesiveness and sealability. On the contrary, if the predetermined amount of modification is exceeded, the adhesiveness is saturated. Therefore, for example, it is preferable that the amount of modification with an acid is 0.01% by weight or more, further 0.3% by weight or more when the total amount of the acid-modified olefinic thermoplastic resin is 100% by weight. Further, it is preferable that the amount of modification by acid is 1.6% by weight or less. The amount of modification by acid can be measured, for example, by infrared absorption spectroscopy.

  As the acid, for example, one or more selected from unsaturated carboxylic acids and derivatives thereof can be used. Specifically, maleic acid, fumaric acid, acrylic acid, methacrylic acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, nadic acid (endo-cis-bicyclo [2.2.1] hept- Acid anhydrides such as unsaturated carboxylic acids such as 5-ene-2,3-dicarboxylic acid), maleic anhydride, itaconic anhydride, citraconic anhydride, maleenyl chloride, maleimide, monomethyl maleate, dimethyl maleate, glycidyl maleate, etc. Products, halides, amides, imides, esters and the like. In particular, when an acid-modified olefin-based thermoplastic resin modified with maleic acid or maleic anhydride is included, the wettability to the surface of the metal or resin is further improved. More improved.

  The organic component which becomes the skeleton of the adhesive seal member of the present invention may consist only of an acid-modified olefin thermoplastic resin. In addition, one or more kinds selected from other thermoplastic resins, rubbers, thermoplastic elastomers, etc., as necessary, as long as they do not impair the adhesiveness, sealing properties, elasticity, etc. of the adhesive sealing member of the present invention. May be included. Examples of such auxiliary components include nylon resin, ethylene-propylene rubber, butadiene rubber, isoprene rubber, styrene-based thermoplastic elastomer (styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-styrene). Block copolymer (SBS), styrene-ethylene-propylene-styrene block copolymer (SEPS)) and the like. Further, the thermoplastic resin, rubber, thermoplastic elastomer and the like may be modified with an acid in the same manner as the olefin-based thermoplastic resin.

  Moreover, the adhesive sealing member of this invention contains a silane coupling agent. The silane coupling agent may be appropriately selected from a group of compounds having an epoxy group, an amino group, a vinyl group or the like as a functional group in consideration of adhesiveness. A silane coupling agent may be used individually by 1 type, and 2 or more types may be mixed and used for it. For example, when one or more selected from the group of compounds having an epoxy group is used, the adhesive force is further improved, and the adhesive force is hardly reduced even in the operating environment of the fuel cell. Specifically, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Etc.

  Although the content rate of a silane coupling agent is not specifically limited, For example, it is desirable to set it as 0.5 weight% or more when the whole adhesive seal member of this invention is 100 weight%. This is because when the silane coupling agent is less than 0.5% by weight, the effect of suppressing a decrease in the adhesive force accompanying the long-term operation of the fuel cell is reduced. More preferably, it is 3% by weight or more. The content ratio of the silane coupling agent is desirably 10% by weight or less when the entire adhesive seal member of the present invention is 100% by weight. This is because if the silane coupling agent exceeds 10% by weight, the processability may be lowered when the adhesive seal member of the present invention is produced.

  The adhesive seal member of the present invention contains resin particles. The resin particles may have a heat resistant temperature equal to or higher than the melting point of the polymer constituting the adhesive seal member of the present invention. Here, the measurement of the heat-resistant temperature of the resin particles is based on the following method. That is, using a displacement thermobalance, 15 mg of resin particles are heated in air at a heating rate of 10 ° C./min, and the temperature when the weight is reduced by 3 wt% is defined as the heat resistant temperature. The measurement of the melting point of the polymer may be performed in accordance with differential scanning calorimetry (heat flux DSC) in JIS K7121. When the adhesive seal member of the present invention is used in, for example, a polymer electrolyte fuel cell, it is desirable to employ resin particles having a heat resistant temperature of 150 ° C. or higher. It is more preferable that the heat resistant temperature is 200 ° C. or higher, and further 250 ° C. or higher. In addition, the upper limit of heat-resistant temperature is not specifically limited. Even if the heat resistant temperature of the resin particles is high, there is little risk of impairing the effect of improving adhesiveness and creep resistance.

The resin particles may be constituted by particles made of the same type of resin, or may be constituted by mixing particles made of different resins. As the resin , one or more selected from a cross-linked acrylic polymer and a cross-linked styrene polymer are used from the viewpoint that the degree of freedom of the particle diameter is large and an increase in weight can be suppressed due to a relatively low specific gravity.

  The “acrylic polymer” of the cross-linked acrylic polymer refers to a polymer having an acrylic acid ester polymer, a methacrylic acid ester polymer, an acrylic acid ester or a methacrylic acid ester as a main component.

  Specific examples of the acrylate ester include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, s-butyl acrylate, t-butyl acrylate, hexyl acrylate, Examples include octyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, and the like.

  Specific examples of the methacrylic acid ester include, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, hexyl methacrylate, Examples include octyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, decyl methacrylate, dodecyl methacrylate, and the like.

  As the cross-linked acrylic polymer, cross-linked polymethyl acrylate, cross-linked polymethyl methacrylate, and the like are preferable because of relatively low cost.

  The “styrene polymer” of the crosslinked styrene polymer refers to a styrene polymer and a polymer containing styrene as a main component. One of these, or two or more may be selected. Of these, polystyrene and the like are preferable because of relatively low cost. As the cross-linked styrene polymer, cross-linked polystyrene, cross-linked acrylonitrile-styrene resin, cross-linked acrylonitrile-butadiene-styrene resin and the like are suitable.

  For the crosslinking of the resin, a known method such as electron beam irradiation crosslinking or ultraviolet (UV) crosslinking may be used. Further, the resin may contain various additives such as a crosslinking agent, a crosslinking aid, and an antioxidant.

  The content ratio of the resin particles is not particularly limited, and may be appropriately determined so that desired creep resistance can be obtained. For example, the content ratio of the resin particles may be changed according to the adhesive seal portion of the fuel cell. When the content ratio of the resin particles exceeds a predetermined ratio, the effect of improving creep resistance is saturated. Moreover, when there are too many resin particles, the tendency for adhesive force to fall is seen. On the other hand, when there are too few resin particles, desired creep resistance cannot be obtained. Considering these points, the content ratio of the resin particles is desirably 50% by weight or less when the entire adhesive sealing member of the present invention is 100% by weight. More preferable upper limit values include 45% by weight, 40% by weight, 35% by weight, and 30% by weight. The content ratio of the resin particles is preferably 0.5% by weight or more when the entire adhesive seal member of the present invention is 100% by weight. More preferable lower limit values include 1% by weight, 2% by weight, 3% by weight, 4% by weight, and 5% by weight.

  The shape of the resin particles is not particularly limited, and examples thereof include a spherical shape, a column shape, a needle shape, a plate shape, and a lump shape. Among them, it is desirable to use spherical resin particles because the effect of suppressing a decrease in load applied to the cell laminate is high, and it is easy to disperse in the polymer. In particular, substantially spherical resin particles are suitable. The resin particles may be composed of particles having the same shape, or may be composed by mixing particles having different shapes.

  The size of the resin particles may be appropriately determined in consideration of the size of the gap between the constituent members of the fuel cell. For example, when spherical resin particles are used, the average particle size is desirably 50 μm or less. More preferable upper limit values of the average particle diameter include 40 μm, 30 μm, 20 μm, and 10 μm. Moreover, 3 micrometers, 6 micrometers, 9 micrometers, 12 micrometers, and 15 micrometers can be mentioned as a suitable lower limit which can be combined with these suitable upper limits. The particle size of the resin particles may be measured using a commercially available particle size distribution measuring device (for example, “Coulter Counter” manufactured by Beckman Coulter, Inc.).

  Furthermore, the adhesive seal member of the present invention may contain various additives usually used together with thermoplastic resins, rubbers, thermoplastic elastomers and the like. Examples of the additive include an antioxidant, a tackifier, a softener, a processing aid, and a wax.

  What is necessary is just to set the melting | fusing point of the adhesive sealing member of this invention so that favorable adhesiveness and sealing performance may be maintained in the operating environment of a fuel cell. On the other hand, the adhesive sealing member of the present invention is heated and melted (hot melted) to exhibit adhesiveness and sealing properties. For this reason, at the time of manufacturing the fuel cell, heat is applied to the constituent members to be adhesively sealed together with the adhesive seal member of the present invention. Therefore, it is necessary to set the melting point of the adhesive seal member of the present invention in consideration of the heat resistance of the constituent members of the fuel cell.

  In consideration of these, for example, when used in a polymer electrolyte fuel cell, the melting point of the adhesive seal member of the present invention is 120 ° C. or higher and 180 ° C. or lower, preferably 130 ° C. or higher and 170 ° C. or lower. In order to adjust the melting point of the adhesive seal member of the present invention within the above range, an acid-modified olefin thermoplastic resin whose melting point is originally within the above range may be selected. Alternatively, a method such as mixing an acid-modified olefin-based thermoplastic resin, another thermoplastic resin, rubber, a thermoplastic elastomer or the like polymer or disrupting the polymer chain of the contained polymer so that the melting point is within the above range. Use it. In addition, the measurement of melting | fusing point should just be performed based on the differential scanning calorimetry (heat flux DSC) in JISK7121 as mentioned above.

  Moreover, the storage longitudinal elastic modulus of the adhesive seal member of the present invention decreases as the temperature increases. For example, when the adhesive seal member of the present invention is used for a polymer electrolyte fuel cell, the temperature at which the storage longitudinal elastic modulus at 23 ° C. of the adhesive seal member decreases to 1/10 or less is 90 ° C. or higher. It is desirable that In this case, since the adhesive seal member of the present invention has a suitable elastic modulus, it exhibits good adhesiveness and sealability during operation of the fuel cell. In order to adjust the storage longitudinal elastic modulus of the adhesive seal member of the present invention so as to satisfy the above-mentioned conditions, an acid-modified olefin-based thermoplastic resin that originally satisfies the above-mentioned conditions is selected, or an acid-modified olefin-based so as to satisfy the above-mentioned conditions What is necessary is just to mix polymers, such as a thermoplastic resin, another thermoplastic resin, rubber | gum, and a thermoplastic elastomer. In addition, the value measured by the following method is employ | adopted for the "storage longitudinal elastic modulus" in this specification. First, a plate-shaped test piece having a width of 5 mm, a length of 20 mm, and a thickness of 50 μm is prepared from the adhesive seal member of the present invention. Next, vibration strain (frequency: 10 Hz, dynamic strain: ± 10 μm) is applied to the prepared test piece in the length direction, and the storage length is measured by a dynamic viscoelasticity measuring apparatus (“Rheogel-E4000” manufactured by UBM Co., Ltd.). Measure the elastic modulus.

  Further, the melt mass flow rate (MFR) at 230 ° C. of the adhesive seal member of the present invention is desirably 2 g / 10 minutes or more. Preferably it is 7 g / 10 min or more, more preferably 10 g / 10 min or more. When this condition is satisfied, the adhesive seal member of the present invention is excellent in flowability, so that excellent adhesiveness can be obtained even when the surface of the constituent member of the fuel cell is uneven. Note that the MFR measurement may be performed according to JIS K7210.

<Method for Producing Adhesive Seal Member for Fuel Cell>
The adhesive seal member of the present invention can be produced by, for example, a kneading method, a dry blend method or the like. Among these, the kneading method is preferable because the acid-modified olefinic thermoplastic resin and the like and the silane coupling agent are easily reacted. In addition, according to the kneading method, the silane coupling agent is dispersed in the acid-modified olefin thermoplastic resin, so that there is an advantage that the functional group of the silane coupling agent is not easily deteriorated until adhesion. Hereinafter, the manufacturing method of the adhesive seal member of the present invention by the kneading method will be described.

  First, an acid-modified olefin thermoplastic resin is heated and melted at a predetermined temperature. When other thermoplastic resin, rubber, or thermoplastic elastomer is added, it may be heated and melted together with the acid-modified olefin thermoplastic resin. Next, a silane coupling agent and resin particles are put into the heated melt and kneaded by heating for a predetermined time. Then, it shape | molds in a predetermined shape and obtains the adhesive seal member of this invention. Here, the series of operations of heating and melting and heating and kneading may be performed, for example, in an inert gas atmosphere. Moreover, what is necessary is just to add various additives, such as antioxidant, a radical initiator, etc. in each process of the said heat melting and heat kneading | mixing as needed. In addition, when an olefinic thermoplastic resin or the like is modified with an acid, an acid such as an unsaturated carboxylic acid is divided or added all at once to the heated melt before adding the silane coupling agent and the resin particles. What is necessary is just to heat-knead at the temperature of.

  The adhesive seal member of the present invention may be formed into a film, for example. When it is formed into a film, it is possible to easily bond the constituent members to each other only by attaching the adhesive seal member of the present invention to the constituent members of the fuel cell. Moreover, the complicated alignment conventionally performed becomes unnecessary and it becomes easy to perform continuous processing. Further, if the adhesive seal member of the present invention is laminated on the constituent members in advance, the bonding process is further facilitated. Thus, the productivity of the fuel cell can be further improved by forming the adhesive seal member of the present invention into a film shape. In order to form the film, a known press method, extrusion method (T-die method), inflation method or the like may be used. Further, the thickness of the film may be appropriately set according to the size of the gap between the constituent members to be adhesively sealed.

<Application to fuel cells>
The adhesive seal member of the present invention provides an adhesive seal between the constituent members of the fuel cell. The fuel cell to be applied is at a temperature at which organic components (acid-modified olefin thermoplastic resin, other thermoplastic resins, rubber, thermoplastic elastomer, etc.) that serve as the skeleton of the adhesive seal member of the present invention can be used. Anything that works. For example, a polymer electrolyte fuel cell (PEFC) (including a direct methanol fuel cell (DMFC)) is suitable.

  The part to be bonded and sealed (between constituent members) varies depending on the type and structure of the fuel cell. That is, the adhesive seal member of the present invention is required to be airtight and liquid-tight, and can be used for any part where the adhesive seal member has been used conventionally. In addition, the adhesive seal member of the present invention may be used for all parts that require an adhesive seal in a fuel cell, or may be used for a part of a part that requires an adhesive seal. Examples of the adhesive seal portion include a separator between the separators facing each other across the MEA, a frame supporting the MEA and the separator, and between the separators and separators constituting adjacent cells. The adhesive sealing method may be performed by, for example, interposing the adhesive sealing member of the present invention between the constituent members of the fuel cell and thermocompression bonding at a temperature of about 140 ° C. to 200 ° C. and a pressure of about 1 MPa to 3 MPa. The adhesive seal member of the present invention may be used alone or in combination with a primer or the like.

  An embodiment of a polymer electrolyte fuel cell using the adhesive seal member of the present invention will be shown below. FIG. 1 is a perspective view of a polymer electrolyte fuel cell using the adhesive seal member of the present invention. As shown in FIG. 1, the polymer electrolyte fuel cell 1 is configured by stacking a number of cells C. FIG. 2 shows a perspective view of the stacked cells C (for only three cells). FIG. 3 shows an exploded perspective view of a single cell C. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. As shown in FIGS. 2 to 4, the cell C includes an MEA 2, a separator 3, and a frame 4.

  The MEA 2 includes an electrolyte membrane 20 and a pair of electrodes 21a and 21b. The electrolyte membrane 20 has a rectangular thin plate shape. The pair of electrodes 21a and 21b has a rectangular thin plate shape. The pair of electrodes 21a and 21b are arranged on both sides with the electrolyte membrane 20 in between. The frame 4 is made of metal and has a rectangular frame shape. The frame 4 holds the periphery of the electrolyte membrane 20.

  The separator 3 is made of metal and has a rectangular thin plate shape. The separator 3 has a total of six grooves extending in the longitudinal direction. Due to the groove, the cross section of the separator 3 has an uneven shape (see FIG. 4). The separator 3 is disposed opposite to both sides of the MEA 2 (also both sides of the frame 4). A gas flow path 30 for supplying gas to the electrodes 21a and 21b is defined between the MEA 2 and the separator 3 by using an uneven shape. Further, between the separators 3 facing each other in the cell C adjacent to each other in the stacking direction, a refrigerant flow path 31 for flowing a refrigerant is defined using an uneven shape.

  The adhesive seal member 5 (adhesive seal member of the present invention) is arranged at the following two locations. That is, the adhesive seal member 5 is interposed between the frame 4 and the separator 3. Moreover, it is interposed between the separators 3 facing each other in the cells C adjacent in the stacking direction. A conventional adhesive 7 made of a thermosetting resin is disposed between the electrolyte membrane 20 and the frame 4.

  During operation of the polymer electrolyte fuel cell 1, fuel gas and oxidant gas are supplied through the gas flow paths 30. Further, the refrigerant flows through the refrigerant flow path 31 in order to relieve the heat generated during power generation. Here, the frame 4 and the separator 3 are adhesively sealed with an adhesive seal member 5. For this reason, gas mixing and leakage do not occur. Further, the separators 3 facing each other in the cell C adjacent in the stacking direction are similarly adhesively sealed by the adhesive seal member 5. For this reason, the refrigerant does not leak. Furthermore, the adhesiveness of the adhesive seal member 5 is good, and it is difficult to deteriorate even in the operating environment of the polymer electrolyte fuel cell 1. For this reason, good sealing performance is ensured over a long period of time. Moreover, the creep resistance of the adhesive seal member 5 is high. For this reason, even if the polymer electrolyte fuel cell 1 is operated for a long time, the adhesive seal member 5 is not easily deformed. Moreover, since the fall of the load added to the laminated body of the cell C is suppressed, the favorable contact state of the electrolyte membrane 20, electrode 21a, 21b, and the separator 3 is maintained. That is, according to the adhesive seal member 5, the polymer electrolyte fuel cell 1 can be stably operated over a long period of time.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(1) Production of adhesive seal member (a) Examples 1-4
First, 60 g of polypropylene (“Sumitomo Noblen (registered trademark)” manufactured by Sumitomo Chemical Co., Ltd.) and 0.6 g of maleic anhydride (manufactured by Kanto Chemical Co., Ltd.) were combined into a small-sized closed kneader (Toyo Seiki Co., Ltd.). The product was put into a “lab plast mill” (capacity 100 cc), and an organic peroxide (“Park Mill (registered trademark) D” manufactured by NOF Corporation) was further added and heated and melted at 240 ° C. Next, 3 g (5 wt%) of a silane coupling agent (“KBE402”: 3-glycidoxypropylmethyldiethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) is charged into the heated melt, and the temperature is 220 ° C. Kneaded for 5 minutes. Subsequently, resin particles made of crosslinked polymethyl methacrylate (“Kemisnow (registered trademark) MX” manufactured by Soken Chemical Co., Ltd.) were added and kneaded at 220 ° C. for 5 minutes. This was formed into a film having a thickness of 50 μm by a pressing method to obtain an adhesive seal member. The amount of resin particles charged is 0.3 g (0.5 wt%), 3 g (5 wt%), 6 g (10 wt%), and 18 g (30 wt%). Four types of adhesive seal members with different s were obtained. The obtained adhesive seal members were numbered as Examples 1, 2, 3, and 4 in the order of decreasing resin particle content.

  Moreover, the heat-resistant temperature of the used resin particle was measured as follows. That is, when using a thermobalance (“TGA-50” manufactured by Shimadzu Corporation), 15 mg of resin particles were heated in air at a heating rate of 10 ° C./min, and the weight decreased by 3% by weight. The temperature of was measured. As a result, the heat resistant temperature was 260 ° C. Furthermore, when the average particle diameter of the resin particles was measured by “Coulter Counter” manufactured by Beckman Coulter, Inc., it was 30 μm.

(B) Example 5
In the production of the adhesive seal member of Example 3, the adhesive seal member was produced by changing only the kind of the resin particles. That is, 6 g (10 wt%) of resin particles made of crosslinked polystyrene (“Kemisnow (registered trademark) SGP” manufactured by Soken Chemical Co., Ltd.) were contained to produce an adhesive seal member. When the heat-resistant temperature of the resin particles was measured in the same manner as described above, it was 255 ° C. The average particle diameter was 25 μm.

(C) As an example, for the adhesive seal member of Example 1, the amount of maleic anhydride modified in the maleic anhydride-modified polypropylene was measured using an infrared absorption spectrum method. Specifically, first, the infrared absorption spectrum of the adhesive seal member of Example 1 was measured by a transmission method. Next, a calibration curve was prepared from the peak intensity of maleic anhydride near 1800 cm ⁻¹ and the amount of maleic anhydride determined by titration, and the amount of modification was determined. As a result, the amount of modification in the maleic anhydride-modified polypropylene was 0.8% by weight.

  The melting point of the adhesive seal member of Example 1 was measured by differential scanning calorimetry (heat flux DSC) based on JIS K7121. As a result, the melting point was 135 ° C. Since the melting point is 30 ° C. or more higher than the operating upper limit temperature (90 ° C.) of the polymer electrolyte fuel cell, it can be said that the adhesive seal member of Example 1 can be safely used for the polymer electrolyte fuel cell.

Furthermore, regarding the adhesive seal member of Example 1, the relationship between the temperature and the storage longitudinal elastic modulus was measured. First, a plate-shaped test piece having a width of 5 mm, a length of 20 mm, and a thickness of 50 μm was prepared from the adhesive seal member of Example 1. Next, the produced test piece was installed in a dynamic viscoelasticity measuring apparatus (“Rheogel-E4000” manufactured by UBM Co., Ltd.), and the relationship between temperature and storage longitudinal elastic modulus was measured. The measurement conditions were tensile mode, frequency: 10 Hz, initial load: automatic mode, dynamic strain: ± 10 μm, temperature range: −40 to 200 ° C., temperature increase rate: 3 ° C./min, measurement: every 2 ° C. As a result, the storage longitudinal elastic modulus at 23 ° C. was 5.80 × 10 ⁸ (Pa). The temperature at which the storage longitudinal elastic modulus at 23 ° C. decreased to 1/10 or lower was 104 ° C., which was higher than the upper limit temperature (90 ° C.) of the polymer electrolyte fuel cell.

  Moreover, when the MFR at 230 ° C. was measured for the adhesive seal member of Example 1, it was 6 g / 10 min.

(D) Comparative Examples 1-5
On the other hand, an adhesive seal member (two-component type, “EP331” manufactured by Cemedine Co., Ltd.) mainly composed of a conventional epoxy resin was prepared and used as Comparative Example 1. For the adhesive seal member of Comparative Example 1, the relationship between temperature and storage longitudinal elastic modulus was measured in the same manner as described above. As a result, the storage longitudinal elastic modulus at 23 ° C. was 1.50 × 10 ⁸ (Pa). The temperature at which the storage longitudinal elastic modulus at 23 ° C. was reduced to 1/10 or lower was 45 ° C., which was lower than the operating temperature of the polymer electrolyte fuel cell.

  Moreover, in manufacture of the adhesive seal member of the Example mentioned above, the adhesive seal member was manufactured without including a silane coupling agent and resin particles. The obtained adhesive seal member was referred to as Comparative Example 2.

  Moreover, in manufacture of the adhesive seal member of Example 3 mentioned above, the adhesive seal member was manufactured without including the resin particle. The obtained adhesive seal member was referred to as Comparative Example 3.

  Moreover, in manufacture of the adhesive seal member of Example 3 mentioned above, the adhesive seal member was manufactured without including a silane coupling agent. The obtained adhesive seal member was referred to as Comparative Example 4.

  Moreover, in manufacture of the adhesive seal member of Example 5 mentioned above, the adhesive seal member was manufactured without including a silane coupling agent. The obtained adhesive seal member was referred to as Comparative Example 5.

(2) Evaluation of Adhesiveness and Creep Resistance The adhesiveness of each adhesive seal member in Examples and Comparative Examples was evaluated by the following (a) and (b). Moreover, creep resistance was evaluated by the following (c).

(A) Adhesion time About each adhesive sealing member, the adhesion time in 150 degreeC was measured. Specifically, each adhesive seal member was interposed between the stainless steel base materials, and pressure bonding was performed at 150 ° C., and the time required to complete the adhesion was measured.

(B) T-shaped peel test First, a test piece used for the T-shaped peel test was produced. That is, a required number of strip-shaped stainless steel plates having a width of 1 cm and a thickness of 0.1 mm were prepared, and the surface was degreased. Two stainless steel plates are placed facing each other, each adhesive seal member is interposed on one side of the gap between the stainless steel plates, and compressed by 10-30 μm in the thickness direction at a temperature of 150 ° C. to bond the stainless steel plates together did. Thus, each test piece was produced.

  Next, each produced test piece was attached to the tensile test apparatus, and the T-shaped peeling test was done. FIG. 5 schematically shows the state of the T-peel test. As shown in FIG. 5, the test piece 60 includes a pair of stainless steel plates 61 a and 61 b and an adhesive seal member 62 that adheres between them. The end of the stainless steel plate 61a that is not bonded is sandwiched by the gripping tool 63a and is bent in the peeling direction (indicated by an upward white arrow in the figure) at an angle of about 90 ° with respect to the bonding surface. . Similarly, the end of the stainless steel plate 61b that is not bonded is sandwiched by the gripping tool 63b and bent in the peeling direction (indicated by a downward white arrow in the figure) at an angle of about 90 ° with respect to the bonding surface. It has been. That is, the adhesive seal member 62 between the stainless steel plates 61a and 61b was peeled off by pulling the free ends of the stainless steel plates 61a and 61b in the opposite directions of about 180 ° with the gripping tools 63a and 63b. In addition, this test was performed under 23 degreeC (room temperature), and the moving speed of the holding tools 63a and 63b was 10 mm / min. The T-peel strength of each test piece in the T-peel test was determined according to JIS K6854-3. Further, the T-peeling strength of the test piece using the adhesive seal member (conventional product) of Comparative Example 1 is used as a reference (100), and the ratio of the T-peeling strength of each test piece to the test piece is calculated, and T-peeling The strength index was used. It can be said that the larger the T-shaped peel strength index, the greater the adhesive strength.

  Furthermore, in order to evaluate the adhesion reliability of each adhesive seal member, an environmental resistance test was performed on each test piece, and then a T-shaped peel test was performed in the same manner as described above. The environmental resistance test was performed by immersing each test piece in 90 ° C. warm water for 2000 hours. Also in this case, the ratio of the T-shaped peel strength (T-shaped peel strength index) of each test piece was calculated in the same manner as described above.

(C) Creep Test First, each adhesive seal member was cut into a square shape having a length of 1 cm and a width of 1 cm, and five test pieces were prepared for each adhesive seal member. Next, six stainless steel plates having a length of 1 cm, a width of 1 cm, and a thickness of 100 μm were prepared for each adhesive seal member. And the laminated body sample was produced by interposing the test piece of the said adhesive sealing member one by one between each stainless steel plate.

  Next, a creep test was performed on the manufactured laminate sample. That is, first, the laminate sample was held in an atmosphere at a temperature of 90 ° C. for 30 minutes. Thereafter, in the same atmosphere, a load of 0.01 MPa was applied from above the laminate sample, and zero point adjustment in thickness measurement was performed. Subsequently, a load of 3 MPa was applied to the laminate sample in the same atmosphere, and the thickness of the laminate sample immediately after (after about 15 seconds) was measured to obtain an initial thickness. After holding as it is for 500 hours, the thickness of the laminate sample was measured again to obtain the post-test thickness. The difference between the initial thickness and the thickness after the test was taken as the creep amount. Further, the creep amount of the laminate sample using the adhesive seal member (conventional product) of Comparative Example 1 was used as a reference (100), and the ratio of the creep amount of each laminate sample to that was calculated as the creep index. It can be said that the smaller the creep index, the higher the creep resistance.

  Table 1 below summarizes the contents of the adhesive seal members of the examples and comparative examples, and the adhesiveness and creep resistance evaluation of these adhesive seal members.

  As shown in Table 1, the adhesion time of the adhesive seal member of Comparative Example 1 mainly composed of a conventional epoxy resin is as long as 60 minutes, whereas maleic anhydride-modified polypropylene (in Table 1, “acid-modified”). The adhesion time of the adhesive seal members of Examples 1 to 5 having “PP” as a main component was shortened to 10 minutes. That is, according to the adhesive seal member of the present invention, the adhesion time can be shortened and the productivity of the fuel cell can be improved. Moreover, the adhesive sealing member of Examples 1-5 is a film form. For this reason, it was able to adhere | attach easily only by sticking between base materials. That is, when formed into a film shape, the bonding work is facilitated as compared with the adhesive seal member of Comparative Example 1 of the two-component type. Further, the extrudability of the adhesive seal members of Examples 1 to 5 was extremely good.

  Moreover, the T-shaped peel strength index of the adhesive seal members of Examples 1 to 5 is the same as that of Comparative Example 1 having a conventional epoxy resin as a main component, both in the initial stage and after the environmental resistance test. In comparison, it became bigger. From this, it can be seen that the adhesive seal member of the present invention has an excellent adhesive force, and even when used for a long time in an operating environment of a fuel cell in contact with hot water or steam, the adhesive force is unlikely to decrease. . Moreover, the creep index of the adhesive seal members of Examples 1 to 5 was smaller than that of the adhesive seal member of Comparative Example 1. From this, it can be seen that the adhesive seal members of Examples 1 to 5 are excellent in creep resistance.

  Hereinafter, the adhesive seal members of Examples 1 to 5 and each of the adhesive seal members of Comparative Examples 2 to 5 are compared. First, in the adhesive seal member of Comparative Example 2 that does not contain a silane coupling agent and resin particles, the T-shaped peel strength index after the environmental resistance test is as small as less than 700, and the creep index is greater than 100 (conventional). It is larger than the adhesive seal member of Comparative Example 1). Compared with the results of Comparative Example 2, the adhesive seal members of Examples 1 to 5 contain a silane coupling agent and resin particles, so that adhesion reliability and creep resistance in the operating environment of the fuel cell are improved. It can be seen that it has improved.

  Next, in the adhesive seal member of Comparative Example 3 that does not contain resin particles, the T-peel strength index after the environmental resistance test is larger than 700, but the creep index is larger than 100 (Conventional Comparative Example 1). Larger than the adhesive seal member). Compared with the results of Comparative Example 3, it can be seen that the adhesive seal members of Examples 1 to 5 have improved creep resistance by containing resin particles in addition to the silane coupling agent.

  Next, in the adhesive seal members of Comparative Examples 4 and 5 that do not contain a silane coupling agent, the creep index is small, but the T-peel strength index after the environmental resistance test is as small as less than 700. In particular, comparing Comparative Example 4 with Example 3 having the same type and content of resin particles, the adhesive seal member of Example 3 has a larger T-peel strength index after the environmental resistance test, and The creep index is smaller. From this, it can be seen that, in the adhesive seal member of Example 3, the adhesion reliability and creep resistance in the operating environment of the fuel cell are improved by containing the silane coupling agent in addition to the resin particles. . Similarly, when Comparative Example 5 and Example 5 having the same kind and content of resin particles are compared, the adhesive seal member of Example 5 has a larger T-shaped peel strength index after the environmental resistance test, and The creep index is smaller. From this, it can be seen that the adhesive seal member of Example 5 has improved adhesion reliability and creep resistance in the operating environment of the fuel cell by containing a silane coupling agent in addition to the resin particles. .

  As described above, the adhesive seal members of Examples 1 to 5 of the present invention have an excellent adhesive force, and have an adhesive force even when used for a long time in an operating environment of a fuel cell in contact with hot water or steam. It was confirmed that it was difficult to decrease. In addition, it was confirmed that the adhesive seal members of Examples 1 to 5 of the present invention have high creep resistance.

  Moreover, when the adhesive seal members of Examples 1 to 5 were peeled from the base material (the adherend), the interface was in a state of cohesive failure. On the other hand, the interface at the time of peeling of the adhesive seal members of Comparative Examples 1 and 2 that did not contain resin particles was a so-called interface fracture state in which the adhesive seal member did not remain on the substrate surface. Also from this point, it can be seen that the adhesive seal member of the present invention is excellent in adhesion reliability.

(3) Application to solid polymer fuel cells Using the adhesive seal members of Examples 1 to 5, solid polymer fuel cells were produced. As shown in FIG. 4, the adhesive seal members were arranged at two locations, between the frame and the separator, and between the separators facing away from each other in the stacking direction. The adhesive seal member was bonded by pressure bonding at a temperature of 150 ° C. and a pressure of 2 MPa for 10 minutes. The polymer electrolyte fuel cell was operated for 24 hours, and the sealing property of the adhesive seal member was confirmed. As a result, it was confirmed that gas mixing and leakage and refrigerant leakage did not occur, and good adhesion was ensured.

1 is a perspective view of a polymer electrolyte fuel cell using an adhesive seal member of the present invention. It is a perspective view of the laminated | stacked cell. It is a disassembled perspective view of a single cell. It is IV-IV sectional drawing of FIG. It is a schematic diagram which shows the mode of the T-shaped peeling test in an Example.

Explanation of symbols

1: Solid polymer fuel cell 2: MEA 20: Electrolyte membrane 21a, 21b: Electrode 3: Separator 30: Gas flow path 31: Refrigerant flow path 4: Frame 5: Adhesive seal member 7: Adhesive 60: Test piece 61a, 61b: stainless steel plate 62: adhesive seal members 63a, 63b: gripping tool C: cell

Claims (7)

As a main component modified olefin thermoplastic resin by acid, wherein the silane coupling agent, and the resin particles consisting of one or more selected from crosslinked acrylic polymers and crosslinked styrene polymer, a configuration of a fuel cell An adhesive seal member for a fuel cell that seals the seal between members.   The adhesive seal member for a fuel cell according to claim 1, wherein the olefin-based thermoplastic resin includes a propylene-based resin.   The adhesive seal member for a fuel cell according to claim 1 or 2, wherein the silane coupling agent is at least one selected from the group of compounds having an epoxy group.   The fuel according to any one of claims 1 to 3, wherein a content ratio of the silane coupling agent is 0.5 wt% or more and 10 wt% or less when the entire adhesive seal member is 100 wt%. Adhesive sealing member for batteries. The fuel cell content according to any one of claims 1 to 4 , wherein a content ratio of the resin particles is 0.5% by weight or more and 50% by weight or less when the entire adhesive seal member is 100% by weight. Adhesive seal member. The adhesive seal member for a fuel cell according to any one of claims 1 to 5 , wherein the resin particles have a spherical shape. The adhesive seal member for a fuel cell according to any one of claims 1 to 6 , wherein the adhesive seal member is formed in a film shape.

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