JP2015168724A - Seal material and hot-melt adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hot-melt adhesive superior in resistance to moist heat to provide a seal material for fuel cells superior in resistance to moist heat.SOLUTION: A seal material used to seal around an electrolyte membrane of a fuel cell generating electricity by reaction of hydrogen and oxygen contains crystalline polyester resin, amorphous polyester resin, epoxy resin and isocyanate-based crosslinking agent. A melting point of the crystalline polyester resin is lower than a softening point of the epoxy resin. A sealing surface of the seal material is molded from hot-melt adhesive that the crystalline polyester resin and the amorphous polyester resin are crosslinked by the isocyanate-based crosslinking agent.

Description

  The present invention relates to a sealing material and a hot melt adhesive, and more particularly, a sealing material used for sealing the periphery of an electrolyte membrane of a fuel cell that generates power by reaction of hydrogen and oxygen, and the sealing material. The present invention relates to a hot-melt adhesive that can be suitably used as a forming material for the above.

In recent years, a power generation system called a fuel cell that generates electricity by supplying oxygen to one of reaction spaces partitioned by an electrolyte membrane and supplying hydrogen to the other and reacting the hydrogen with oxygen has been a clean energy source. Is widely used.
As a sealing material for sealing around the electrolyte membrane in order to isolate the reaction space of the fuel cell from the external environment, an elastic member such as a fluorine rubber ring is used as shown in the following Patent Document 1 (see paragraph 0016). ing.
Further, the sealing in the fuel ionization is sometimes performed by a hot melt adhesive as shown in the following Patent Document 2 (see paragraph 0045).

The hot melt adhesive is easy to follow the surface shape of the mating material, while it is difficult to exert sufficient sealing performance when the mating material with which the elastic member is in contact has fine irregularities. It can be said that it is advantageous in demonstrating.
In addition, the elastic member exhibits sealing performance by the restoring force against elastic deformation, whereas the hot melt adhesive exhibits sealing performance by the adhesive force. It can be said that it is advantageous also in making it.

By the way, in a fuel cell, since hydrogen and oxygen usually react with heat generation, the reaction space is in a high temperature and high humidity state.
That is, the sealing material is used in a situation where it is susceptible to wet heat degradation.
If this sealing material causes wet heat deterioration on the sealing surface, the sealing performance may be greatly reduced.
Therefore, at least the sealing surface of the sealing material is required to be excellent in wet heat resistance.
In response to such a demand, the conventional hot melt adhesives cannot sufficiently satisfy the demand for moisture and heat resistance.
Such a demand for moisture and heat resistance is not only required when the hot melt adhesive is used as a material for forming a sealing material for a fuel cell, but is generally required for the hot melt adhesive. It is a matter.

JP 2012-89330 A JP 2007-66768 A

  The present invention has been made to satisfy the above-described demand, and an object of the present invention is to provide a hot melt adhesive excellent in wet heat resistance so as to provide a sealing material for fuel cells excellent in wet heat resistance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors cross-linked a resin composition containing a crystalline polyester resin, an amorphous polyester resin, and an epoxy resin with a predetermined cross-linking agent. The inventors have found that the resin composition can be excellent in heat and humidity resistance, and have completed the present invention.

  That is, the present invention relating to a sealing material for solving the above-mentioned problems is a sealing material used for sealing the periphery of an electrolyte membrane of a fuel cell that is generated by a reaction between hydrogen and oxygen, which is a crystalline polyester resin. An amorphous polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent, and the melting point of the crystalline polyester resin is lower than the softening point of the epoxy resin, and the crystalline polyester resin and the amorphous resin The sealing surface is formed by a hot melt adhesive in which the conductive polyester resin is crosslinked with the isocyanate-based crosslinking agent.

  In addition, the present invention according to a hot melt adhesive for solving the above-mentioned problems includes a crystalline polyester resin, an amorphous polyester resin, an epoxy resin, and an isocyanate crosslinking agent, and the melting point of the crystalline polyester resin. However, the temperature is lower than the softening point of the epoxy resin, and the crystalline polyester resin and the amorphous polyester resin are crosslinked with the isocyanate-based crosslinking agent.

ADVANTAGE OF THE INVENTION According to this invention, the hot melt adhesive excellent in heat-and-moisture resistance is provided, and the sealing material for fuel cells excellent in the reliability with respect to sealing performance can be provided.
In addition, since the melting point of the crystalline polyester resin is set to be lower than the softening point of the epoxy resin, a large amount of epoxy groups derived from the epoxy resin can be present in the hot melt adhesive. The melt adhesive can be made particularly excellent in wet heat resistance.

(A) The schematic plan view which shows the sealing material of one Embodiment. (B) The schematic sectional drawing which showed the mode of the A-A 'arrow cross section in the said top view. The schematic plan view which showed the shape of the sample for shear adhesive force measurement, and a schematic front view.

  Hereinafter, for a preferred embodiment of the present invention, a sealing material used to seal the periphery of the electrolyte membrane by contacting the seal surface so as to circulate along the outer peripheral portion of the electrolyte membrane having a rectangular shape in plan view, or An example is a sealing material that is used to seal the periphery of an electrolyte membrane by contacting the sealing surface to the member so that the adherend surrounds the electrolyte membrane from the outside instead of the electrolyte membrane. I will give you a description.

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 is provided on a base material layer 10 made of a polymer sheet and both surfaces of the base material layer 10. It has a three-layer structure having the adhesive layer 20 formed.
And as for the sealing material 1 of this embodiment, the said adhesive bond layer 20 is formed of the hot-melt-adhesive.
That is, the sealing material 1 of the present embodiment is used as a sealing surface where the surface of the adhesive layer 20 is bonded to an adherend, and the sealing surface is formed by the hot melt adhesive.

First, the hot melt adhesive will be described.
The hot melt adhesive forming the adhesive layer 20 includes a crystalline polyester resin (A), an amorphous polyester resin (B), and an epoxy resin (C).
The hot melt adhesive further contains an isocyanate crosslinking agent (X), and contains the crystalline polyester resin and the amorphous polyester resin in a state of being crosslinked by the isocyanate crosslinking agent.

(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.

(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, polytetramethylene glycol; 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 a higher melting point and a higher degree of crystallinity are advantageous in terms of the heat and moisture resistance of the hot melt adhesive.
On the other hand, if the crystalline polyester resin, which is the main component of the hot melt adhesive, has an excessively high melting point, the hot melt adhesive may not be adhered to the adherend unless heated to a high temperature.
Therefore, the crystalline polyester resin preferably has a melting point of more than 90 ° C. and less than 150 ° C. in that the hot melt adhesive can have both excellent heat and moisture resistance and excellent bonding workability. 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, particularly in the range of −70 ° C. or higher and 10 ° C. or lower. More preferably,

By using a crystalline polyester resin having a Tg in the above range, the hot melt adhesive can be given further rubber elasticity, and the cohesive force as an adhesive can be further improved.
That is, by setting the Tg of the crystalline polyester resin to 30 ° C. or less, more preferably 10 ° C. or less, and further preferably 5 ° C. or less, a hot melt adhesive having excellent cold resistance can be formed.
Further, by setting the Tg of the crystalline polyester resin to 30 ° C. or less, more preferably 10 ° C. or less, and further preferably 5 ° C. or less, the low-temperature adhesive property can be improved, and the melt viscosity can be lowered during bonding. The temperature condition can be lowered.
When such a suitable crystalline polyester resin is contained in the adhesive layer of the sealing material, the electrolyte membrane is damaged by heat when the periphery of the electrolyte membrane of the fuel cell is sealed using the sealing material. It is possible to provide a reliable seal while suppressing the risk of being lost.

Moreover, it can suppress that a hot-melt-adhesive becomes too flexible by employ | adopting that Tg is -100 degreeC or more as said crystalline polyester resin, More preferably, it is -70 degreeC or more.
In addition, by adopting the crystalline polyester resin as described above, it is possible to suppress the softening point of the hot melt adhesive from becoming too low, and high adhesion to the adhesive layer even at room temperature or under heated conditions. Can exert strength.
Moreover, it can suppress that the flowability of the hot-melt-adhesive becomes large at the time of heating by employ | adopting the above crystalline polyester resins.
That is, by using the crystalline polyester resin as described above, it is possible to suppress the use conditions such as the bonding temperature and the bonding time from becoming narrow, and the sealing material can be used to seal the periphery of the electrolyte membrane. It is possible to improve the workability during the process.

The melting point and the glass transition temperature (Tg) can be measured using, for example, a differential scanning calorimeter (DSC).
More specifically, the temperature of the sample (crystalline polyester resin) is increased at a rate of 5 ° C./min while flowing nitrogen gas from a temperature lower than 30K or higher of 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 at this time.
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 has such a molecular weight. By setting the molecular weight of the crystalline polyester resin to 10,000 or more, the hot melt adhesive can be prevented from becoming brittle, and the hot melt adhesive can be used. This is because excellent toughness can be imparted.
On the other hand, by adopting a crystalline polyester resin having a number average molecular weight of 50000 or less, it is possible to prevent the softening point of the hot melt adhesive from becoming too high, and to make the sealing material excellent in low-temperature adhesiveness. Can do.
That is, by adopting such a crystalline polyester resin, the sealing material can exhibit excellent sealing properties while suppressing the possibility of damaging the electrolyte membrane of the fuel cell with heat. .

  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) Amorphous polyester resin The amorphous polyester resin blended in the hot melt adhesive together with the crystalline polyester resin while the crystalline polyester shows a clear crystallization or crystal melting peak as measured by DSC, This is a polyester resin that does not show a clear crystallization or crystal melting peak as measured by DSC. As the amorphous polyester resin of this embodiment, a polyvalent carboxylic acid (a1) and a polyol (a2) are used in the same manner as the crystalline polyester resin. ) Can be employed, and the polycarboxylic acid (a1) and the polyol (a2) can be employed in any one or both, and a plurality of types can be employed for crystallinity. What was made not to express can be employ | adopted.

The hot melt adhesive of the present embodiment is blended with an amorphous polyester resin in order to increase its cohesive force and to exhibit the role of adjusting the rubber elasticity of the crystalline polyester resin.
That is, in this embodiment, by blending an amorphous polyester resin with a hot melt adhesive, the flexibility (hardness) of the hot melt adhesive is adjusted and peeling from the bonded member occurs. The effect to prevent is demonstrated.
For example, when the sealing material of the present embodiment is used as a sealing material for a fuel cell, there is a difference in thermal expansion between a member that contacts one surface of the sealing material and a member that contacts the other surface during operation of the fuel cell. When stress is applied to the sealing material, it is possible to prevent peeling from the bonded member by causing moderate stress relaxation inside the hot melt adhesive.

  The amorphous polyester resin in the present embodiment preferably has a Tg in the range of 50 ° C. or higher and 100 ° C. or lower, and particularly preferably has a Tg in the range of 60 ° C. or higher and 75 ° C. or lower.

The amorphous polyester resin has a Tg of preferably 50 ° C. or higher, and particularly preferably 60 ° C. or higher, in order to prevent the tackiness from being expressed in a normal storage state. This is because it is possible to reduce the possibility that dust or the like adheres to the exposed portion of the agent and deteriorates the appearance, or problems such as blocking occur, and good handling properties can be imparted.
On the other hand, the Tg of the amorphous polyester resin is preferably 100 ° C. or less, and particularly preferably 75 ° C. or less. The softening point of the hot melt adhesive is high, and the hot melt adhesive in a molten state is used. This is because the viscosity of the agent can be prevented from becoming too high, and the bonding conditions such as the bonding temperature can be suppressed from being restricted to high temperatures.
That is, by including an amorphous polyester resin having a Tg of 100 ° C. or less in the hot melt adhesive, the sealing material of this embodiment can be made excellent in bonding workability and excellent in sealing properties.

Moreover, it is preferable that the number average molecular weights of the amorphous polyester resin used for the hot melt adhesive of this embodiment are 15000-35000.
An amorphous polyester resin having a number average molecular weight of 15000 or more can impart excellent toughness to the hot melt adhesive, and can make the hot melt adhesive excellent in cohesive strength and adhesive strength.
Moreover, the amorphous polyester resin having a number average molecular weight of 35000 or less can suppress the temperature at the time of bonding the hot melt adhesive from being limited to a high temperature.

As the amorphous polyester resin exhibiting the above properties, those obtained by reacting terephthalic acid, isophthalic acid, ethylene glycol, neopentyl glycol, and diethylene glycol are suitable.
Among them, terephthalic acid is composed of 20 to 30 mol%, isophthalic acid is composed of 20 to 25 mol%, ethylene glycol is composed of 20 to 30 mol%, neopentyl glycol is composed of 20 to 30 mol%, and diethylene glycol is composed of 0.1 to 5 mol%. Amorphous polyester resin is preferred.

  The blending ratio of the crystalline polyester resin (A) and the amorphous polyester resin (B) is not particularly limited, but these polyester resins have a mass ratio (A: B) of 50:50. ˜90: 10 and preferably contained in the hot melt adhesive, and particularly preferably contained in the hot melt adhesive at a mass ratio of 70:30 to 80:20.

  It is preferable that the blending ratio of the crystalline polyester resin and the amorphous polyester resin is in the above range. If the blending amount of the amorphous polyester resin with respect to the crystalline polyester resin is too small, the effect of the blending On the other hand, if an amorphous polyester resin is added excessively, the elasticity of the crystalline polyester resin becomes difficult to be expressed in the hot melt adhesive, and the hot melt adhesive has excellent adhesion. This is because there is a possibility that it is difficult to exert strength and toughness.

(C) Epoxy resin Examples of the epoxy resin in the present embodiment include a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a cresol novolac type epoxy resin, an alicyclic epoxy resin, and a phenol novolac type epoxy resin. .

Among these, the epoxy resin is preferably a bisphenol A type epoxy resin in that it is effective for imparting tackiness and toughness to a hot melt adhesive and imparting excellent wet heat resistance.
For example, in the case of conventional hot melt adhesives, especially in the joining of metal members, etc., due to the polarity of metals and the size of thermal expansion, the interface with the adhesive in a high temperature and high humidity atmosphere. Is significantly affected by moisture, and in environments where the temperature changes drastically as in a fuel cell, the shearing force is repeatedly generated at the adhesive interface due to the difference in expansion coefficient between the adhesive and the adherend. Therefore, the adhesive force may decrease, and the service life tends to be shortened.
On the other hand, since the hot melt adhesive of this embodiment contains an epoxy resin, the wet heat resistance of the hot melt adhesive is improved as compared with the conventional hot melt adhesive.

The epoxy resin used for the hot melt adhesive of this embodiment has a softening point determined by the ring and ball method of JIS K 7234 that is higher than the melting point of the crystalline polyester resin.
More specifically, in the present embodiment, one or both of the crystalline polyester resin and the amorphous polyester resin are cross-linked by an isocyanate-based cross-linking agent to be described later, for example, when producing a hot melt adhesive. The melting point of the crystalline polyester resin is softened to prevent the isocyanate group of the cross-linking agent from being consumed in the reaction with the epoxy group and being effectively utilized in the reaction with the hydroxyl group of the polyester resin. It is an important requirement that the temperature is lower than the point.
For example, when the melting point (Tm) of the crystalline polyester resin is more than 100 ° C and less than 140 ° C, or when the melting point (Tm) of the crystalline polyester resin is more than 105 ° C and less than 130 ° C, The softening point of the epoxy resin is preferably 135 ° C. or higher and 150 ° C. or lower and (Tm + 5 ° C.) to (Tm + 40 ° C.), preferably 135 ° C. or higher and 150 ° C. or lower and (Tm + 10 ° C.) to (Tm + 30 ° C.). It is more preferable.

Thus, by including the epoxy resin which has a softening point higher than melting | fusing point of crystalline polyester resin, the said epoxy resin can be contained in a hot-melt-adhesive in the state in which an epoxy group is unreacted.
When the epoxy resin is contained in the hot melt adhesive so that the epoxy group is not opened, the polyester resin is hydrolyzed and becomes a short chain having a hydroxyl group or a carboxyl group at the molecular end. The group can be reacted to make it long again.
Therefore, the presence of the epoxy group prevents the hot melt adhesive from deteriorating in wet heat and lowering physical properties such as adhesive strength and tensile strength.
The presence of an unreacted epoxy group in the hot melt adhesive indicates that when hot melt adhesion is analyzed using a Fourier transform infrared spectrophotometer (FTIR), a peak indicating the presence of the epoxy group is 925 to 899 cm. It can be confirmed by appearing at ^-1 .
Whether the peak appearing at 925 to 899 cm ⁻¹ is due to an epoxy group or not is determined before and after thermal adhesion to the adherend of the hot melt adhesive and the peak height due to a hydroxyl group appearing at 3650 to 3140 cm ^−1. It can be confirmed by the change in relation to Sato.

The epoxy resin preferably has a molecular weight of 3000 to 5000, and preferably has an epoxy equivalent of 2400 to 3800 g / eq.
In addition, this epoxy equivalent can be calculated | required by JISK7236.
The blending ratio of the epoxy resin in the hot melt adhesive of the present embodiment is 10 parts by mass or more and 50 parts by mass or less with respect to a total of 100 parts by mass of the crystalline polyester resin and the amorphous polyester resin. It is preferable that it is 20 mass parts or more and 30 mass parts or less.

  It is preferable that the blending ratio of the epoxy resin is in the above range by setting the blending amount of the epoxy resin to 10 parts by mass or more with respect to 100 parts by mass in total of the crystalline polyester resin and the amorphous polyester resin. The effect of improving the heat-and-moisture resistance of the hot melt adhesive can be more reliably exhibited. By setting it to 50 parts by mass or less, an appropriate melt viscosity can be imparted to the hot melt adhesive, and the bonding workability is good. It is because it can be made to be a thing.

(X) Isocyanate-based crosslinking agent The isocyanate-based crosslinking agent may be a crystalline polyester resin, an amorphous polyester resin, or a compound having reactivity with a polar group such as a hydroxyl group. For example, hexamethylene diisocyanate ( And aliphatic isocyanates such as HDI), isophorone diisocyanate (IPDI), and xylylene diisocyanate (XDI), and aromatic isocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and tolidine diisocyanate (TODI). .

  Further, as the isocyanate-based crosslinking agent in the hot melt adhesive of this embodiment, xylylene diisocyanate is preferable, and the blending ratio of the isocyanate-based crosslinking agent is that of the crystalline polyester resin and the amorphous polyester resin. The total amount is preferably 0.1 parts by mass or more and 15 parts by mass or less, and particularly preferably 1 part by mass or more and 8 parts by mass or less with respect to 100 parts by mass in total.

(Z) Other components The hot-melt adhesive of the present embodiment contains the resin components other than the crystalline polyester resin, amorphous polyester resin, and epoxy resin shown above as long as the effects of the present invention are not impaired. For example, when initial tackiness is required, a tackifier such as a terpene resin can be added.
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.

Among these, in order to improve the cohesive force of the hot melt adhesive and improve the water vapor barrier property and gas barrier property, it is preferable to contain an inorganic filler such as plate-like mineral particles.
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.
The talc powder to be included in the hot melt adhesive may be surface-treated with a fatty acid or a silane coupling agent, but the cohesive strength of the hot melt adhesive is increased by utilizing the functional group on the surface. In terms of improvement, it is preferable to use an untreated one.

  When this talc powder is contained in the hot melt adhesive, it is contained so as to have a ratio of 10 parts by mass to 50 parts by mass with respect to 100 parts by mass in total of the crystalline polyester resin and the amorphous polyester resin. It is preferable to make it contain so that it may become 20 to 30 mass parts.

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”). Second adhesive layer 20b ") is not required to be formed by the same hot melt adhesive, and the first adhesive layer 20a and the second adhesive layer 20b are formed by hot melt adhesives having different blending contents. May be.
The first adhesive layer 20a and the second adhesive layer 20b may have the same formation thickness or different thicknesses.
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 when a sealing material is used for sealing a fuel cell.

The base material layer 10 carrying the adhesive layer 20 on both sides is usually constituted by a film-like sheet made of a resin having good affinity with a hot melt adhesive or a fiber sheet made of the resin. it can.
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 hot melt adhesive such as a crystalline polyester resin, an amorphous polyester resin, an epoxy resin, an isocyanate-based crosslinking agent, and an inorganic filler, such as the crystalline polyester. Melt and knead at a temperature above the melting point of the resin and below the softening point of the epoxy resin, and if necessary, prepare an application liquid by adding an organic solvent, and apply the application liquid on both sides of the polymer sheet. It can be formed by coating.
In addition, about the bridge | crosslinking of the said crystalline polyester resin and the said amorphous polyester resin, it is made to react by making the hydroxyl group of a polyester resin react with the isocyanate group of a crosslinking agent by the heating in the case of adjustment of the said coating liquid. Can do.

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 has two layers of a base material layer and an adhesive layer. The structure may be a single layer structure having only an adhesive layer.
Moreover, in this embodiment, although the aspect which utilizes a hot-melt-adhesive as a forming material of a sealing material is illustrated, the hot-melt adhesive of this invention has the adhesiveness outstanding also in uses other than a sealing material. It can be suitably used in applications where moisture and heat resistance is required.

  Moreover, the sealing material and hot melt adhesive of this embodiment can employ conventionally known technical matters in these technical fields in addition to the matters exemplified above within a range not significantly impairing the effects of the present invention.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
(Materials used)
A hot melt adhesive was prepared using the following materials, and heat resistance was evaluated.

(Crystalline polyester resin (A))
A1: Crystalline polyester resin having a number average molecular weight of about 30000, Tg: −60 ° C., Tm: 107 ° C. A2: Crystalline polyester resin having a number average molecular weight of about 35000, Tg: −70 ° C., Tm: 126 ° C. A3: Number average molecular weight: about 35000, Tg: 8 ° C., Tm: 138 ° C. crystalline polyester resin

(Amorphous polyester resin (B))
B1: Number average molecular weight: about 23000, Tg: 67 ° C. amorphous polyester resin

(Epoxy resin (C))
C1: Bisphenol A type epoxy resin having a molecular weight of about 3800 and a softening point of 144 ° C. C2: Bisphenol A type epoxy resin having a molecular weight of about 70,000 and a softening point of 80 ° C.

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

(Other additives (Z))
Z1: Talc powder

Example 1
A varnish containing a crystalline polyester resin A1, an amorphous polyester resin B1, an epoxy resin C1, an isocyanate-based crosslinking agent X1, and a talc powder Z1 in an organic solvent with a composition shown in Table 1 below is prepared. Was coated on a release film and dried to prepare a hot melt adhesive sheet having a dry thickness of about 50 μm.
From this hot melt adhesive sheet, a square sheet piece having a side of 10 mm was cut out and used as an evaluation material.

(Shear adhesive strength evaluation: hot water resistance)
The sheet piece of 10 mm square was evaluated using two strip-shaped metal pieces S1 and S2 as shown in FIG.
The metal pieces S1 and S2 are formed of the same material and in the same shape, and are formed of stainless steel (SUS304) to be 13 mm wide × 35 mm long × 0.1 mm thick.
The metal piece is shifted in the length direction, and the end portions are arranged so as to overlap each other over about 13 mm, and the test piece S is positioned so as to be located at the approximate center of the overlapping 13 mm square region. I was caught.
This was hot-pressed at 150 ° C. for 60 seconds to obtain a shear adhesive strength evaluation sample.
In addition, this hot press was implemented so that the pressure which might be set to 2 MPa in conversion of the area of the sheet piece S was added.

This evaluation sample was naturally cooled in a room at room temperature of 25 ° C. for 3 hours and then subjected to a tensile test.
The tensile test was performed at a tensile speed of 50 mm / min by chucking one metal piece S1 and the other metal piece S2 to a tensile tester.
Then, a tensile test was performed until the sample for evaluation broke, and a value obtained by dividing the observed maximum stress by the adhesion area by the hot melt adhesive sheet was evaluated as an initial shear adhesive force (Table 1 “Initial” ").
Moreover, the evaluation sample produced similarly was immersed in distilled water of 95 degreeC for 14 days, and the hot water test was done (Table 1 "after 14 days").
The evaluation sample after the hot water test was wiped off and dried, and then naturally cooled in a room at 25 ° C. for 3 hours. After that, the shear adhesive force was measured in the same manner as described above, and the initial shear adhesive value was measured. The value of the shear adhesive strength after the hot water test was calculated as a percentage when the value was 100%, and the residual ratio of the shear adhesive strength was determined (Table 1 “Residual ratio”).
In addition, the measurement of the shear adhesive force in the initial stage and after the hot water test was carried out using three evaluation samples, and the arithmetic average value of each was obtained.

(Example 2-3, Comparative Examples 1 and 2)
A hot melt adhesive sheet was prepared in the same manner as in Example 1 except that the material used was changed to the formulation shown in Table 1, and evaluated in the same manner as in Example 1.
The evaluation results are shown in Table 1 below.
In all Examples, the residual epoxy group could be confirmed by FTIR measurement even after the metal pieces were bonded.

From the above results, it can be seen that according to the present invention, a hot-melt adhesive having excellent heat and heat resistance can be obtained.
In addition, it can be understood from the above results that a sealing material for a fuel cell having excellent heat resistance can be obtained by using a hot melt adhesive that hardly causes wet heat degradation.

1 Sealing material 10 Base material layer 20 Adhesive layer

Claims (6)

A sealing material used to seal the periphery of an electrolyte membrane of a fuel cell that generates electricity by the reaction between hydrogen and oxygen,
A crystalline polyester resin, an amorphous polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent, wherein the crystalline polyester resin has a melting point lower than the softening point of the epoxy resin; A sealing material is characterized in that a sealing surface is formed by a hot melt adhesive in which the amorphous polyester resin is crosslinked with the isocyanate-based crosslinking agent.   The sealing material according to claim 1, wherein the epoxy resin is contained in the hot melt adhesive in a state having an unreacted epoxy group.   The sealing material according to claim 1 or 2, wherein the hot melt adhesive further contains an inorganic filler, and talc powder that is not surface-treated is contained as the inorganic filler.   A crystalline polyester resin, an amorphous polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent, wherein the crystalline polyester resin has a melting point lower than the softening point of the epoxy resin; And a hot melt adhesive, wherein the amorphous polyester resin is crosslinked by the isocyanate-based crosslinking agent.   The hot melt adhesive according to claim 4, wherein the epoxy resin is contained in a state having an unreacted epoxy group.   The hot melt adhesive according to claim 4 or 5, further comprising an inorganic filler, and containing talc powder that has not been surface-treated as the inorganic filler.

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