JP4851757B2 - Electrolyte membrane and polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to an electrolyte membrane in which a proton conductive polymer is filled in pores of a porous substrate containing polyolefins, and a polymer electrolyte fuel cell using the electrolyte membrane.

  A polymer electrolyte fuel cell (PEFC) has an excellent characteristic that only water is generated by low temperature operation, high power density, and power generation reaction. Since PEFC using pure hydrogen can provide high output, it is expected to be used especially for automobiles, and hydrogen energy environments such as hydrogen stations are being promoted. In addition, methanol fuel PEFC can be supplied as liquid fuel in the same way as gasoline, so it is considered promising as a power supply source for electric vehicles and portable devices.

  In addition to the type using pure hydrogen gas, the above polymer electrolyte fuel cell uses a reformer that converts methanol into hydrogen-based gas using a reformer, and uses methanol directly without a reformer It is divided into two types: direct type (DMFC, Direct Mathanol Polymer Fuel Cell). The reforming type requires a reformer, but has a large output and a wide range of applicable equipment. On the other hand, since the direct type does not require a reformer, it can be reduced in size and weight.

  As the PEFC electrolyte membrane, an electrolyte membrane made of a perfluorocarbon sulfonic acid polymer has been conventionally used because of its high durability. However, the electromotive force is generated by the crossover phenomenon in which the electrolyte swells in the wet state, which is the atmosphere when the fuel cell is operated, and the dimensional stability is impaired and the interface between the electrolyte and the electrode is broken. It has been pointed out that it will decline. In addition, the perfluorocarbon film is generally very expensive.

  Therefore, as a membrane for a polymer electrolyte fuel cell, an aromatic hydrocarbon porous membrane as a support membrane, and an electrolyte membrane (for example, see Patent Document 1) filled with a polyether electrolyte in the gap, An electrolyte membrane (see, for example, Patent Document 2) in which a PTFE membrane is used as a supporting membrane and perfluorocarbon sulfonic acid is filled in the voids is disclosed. However, these use unstretched porous membranes, the piercing strength and elastic modulus of the membrane are low, and it cannot be said that suppression of swelling of the electrolyte with water or methanol is sufficient.

  Regarding improvement of mechanical strength, an electrolyte membrane in which a porous membrane made of aromatic polyamide is used as a support membrane and perfluorocarbon sulfonic acid is filled in the voids is disclosed (for example, see Patent Document 3). However, since the proton conductivity of the electrolyte to be used is low, it is considered that sufficient proton conductivity cannot be obtained, and as a result, sufficient fuel cell output characteristics are not obtained.

  Further, an electrolyte membrane in which various electrolytes are interpenetrated into a support membrane made of polyaramid is known (see, for example, Patent Document 4). However, since the porous membrane as the support membrane is formed by a casting method using polyaramid, it is unlikely that an electrolyte membrane having sufficient strength and flexibility can be obtained.

  Further, a cation exchange membrane is disclosed in which a cation exchange resin is filled in pores of a high molecular weight polyolefin porous membrane having a weight average molecular weight of 500,000 or more (see, for example, Patent Document 5). However, since perfluorocarbon sulfonic acid is used as the ion exchange resin, it is considered that there is a problem in the shape maintenance property and methanol permeability during swelling.

  In addition, an example in which an electrolyte membrane is obtained using sulfonated polyetheretherketone as an acidic electrolyte component and vinylimidazole as a basic electrolyte component is known (see, for example, Patent Document 6). However, the basic component in this case is used for pseudo-crosslinking of the electrolyte component by the association of acidic group-basic group, and since the film is formed by the casting method of the electrolyte component, a support material is used. The strength for proper handling cannot be obtained.

  In addition, various electrolyte membranes other than perfluorocarbon membranes have been proposed, but perfluorocarbon sulfonic acid is widely used as an electrode binder, and the interfacial resistance between the membrane and the electrode can be improved by applying the electrode directly to the electrolyte membrane. An example of improving the increase in the above has been disclosed (see, for example, Patent Document 7). However, with respect to the hydrocarbon-based electrolyte membrane, an electrolyte membrane that has improved the decrease in bondability with the electrode and the accompanying increase in the interfacial resistance between the membrane and the electrode of the membrane-electrode assembly without using an electrode binder separately. Not obtained.

  As described above, PEFC electrolyte membranes are as follows: 1) Permeability of hydrogen and methanol, etc. (hydrogen and methanol must not permeate the electrolyte), 2) Durability and heat resistance, 3) Activation and termination of the membrane There is no or little area change due to liquid wetting and drying. An electrolyte membrane that satisfies 4) proton conductivity, 5) chemical resistance, and 6) prevents bonding with an electrode has not been obtained.

JP 2004-143388 A Japanese Patent Laid-Open No. 06-029032 JP 2000-149965 A Special table 2003-528420 gazette JP-A-1-22932 Special table 2003-535940 gazette JP 2005-11590 A

  Accordingly, an object of the present invention is to provide an electrolyte membrane that has good proton conductivity and methanol permeation-preventing properties, has high bonding properties with the electrode, and does not easily peel off from the electrode even when a methanol aqueous solution is flowed. Another object of the present invention is to provide a polymer electrolyte fuel cell using the above.

  The inventors of the present invention have intensively studied to achieve the above object. As a result, the second polymer having a reactive functional group having a weight average molecular weight of 2 million or more and the weight average molecular weight having a reactive functional group of less than 2 million. By using together with the fourth polymer, it has been found that the bondability with the electrode is improved, and the present invention has been completed.

That is, the electrolyte membrane of the present invention includes a first polymer containing a polyolefin having a weight average molecular weight of 500,000 or more, a second polymer having a double bond and a weight average molecular weight of 2 million or more, and a weight average molecular weight having a double bond of 200. into the pores of the porous substrate obtained by crosslinking a resin composition comprising a fourth polymer less than one million, tare and filling the third polymer having proton conductivity is, the said third polymer the 4 polymers are bonded to each other . The various physical property values in the present invention are specifically values measured by the measuring methods described in the examples.

  According to the electrolyte membrane of the present invention, a polyolefin-based porous substrate is used, and the pores are filled with a third polymer having proton conductivity, so that proton conductivity and methanol permeation blocking properties are excellent. Become. In addition, since the fourth polymer having a weight average molecular weight of less than 2 million is used in combination with the second polymer, the bondability between the electrode and the electrolyte membrane is improved as shown in the results of the examples.

In the above, it is preferable that the second polymer is a polynorbornene rubber and the fourth polymer is a terpolymer of ethylene, propylene and a diene monomer. In such a polymer combination, the fourth polymer often binds to the third polymer in the polymerization step of the third monomer described later to obtain proton conductivity, and the fourth polymer flows due to high temperature. It is thought that it penetrates into the gaps in the surface layer of the electrode, the adhesiveness is improved by the anchor effect, and the proton conductive component of the electrode and the electrolyte membrane can be adhered. It is considered that when the proton conducting part is in close contact, protons easily move between the electrode and the electrolyte membrane, and the interface resistance is reduced.
it can.

Moreover, it is preferable that the said 3rd polymer is what the polymerizable monomer containing a sulfonic acid group and a vinyl group was bridge | crosslinked with the crosslinking agent. When the third polymer is cross-linked, dissolution and swelling of the third polymer at the time of use are suppressed, and the methanol permeation blocking property can be more reliably increased.

  At that time, the polymerizable monomer is preferably vinyl sulfonic acid. When vinyl sulfonic acid is used as a constituent component, the sulfone groups are easily arranged in a straight line at a high density, proton conductivity is improved, and the main chain is likely to be packed, resulting in a harder polymer. Changes in swelling between chains are less likely to occur.

  On the other hand, the polymer electrolyte fuel cell of the present invention uses any one of the electrolyte membranes described above. For this reason, the polymer electrolyte fuel cell of the present invention has good proton conductivity and methanol permeation-preventing property of the electrolyte membrane, and also has high bonding properties between the electrode and the electrolyte membrane, and a methanol aqueous solution as a fuel is flowed. Even in this case, the polymer electrolyte fuel cell is difficult to peel off from the electrode.

  Embodiments of the present invention will be described below.

  The porous substrate used in the present invention comprises a first polymer containing a polyolefin having a weight average molecular weight of 500,000 or more, a second polymer having a reactive functional group and a weight average molecular weight of 2 million or more, and a reactive functional group. It is obtained by crosslinking a resin composition containing a fourth polymer having a weight average molecular weight of less than 2 million.

  Of these, polyethylenes are preferred as the first polymer for reasons such as contamination resistance, corrosion resistance, and low cost. In particular, high density polyethylene, low density polyethylene, ultra high molecular weight polyethylene and the like are preferable. High-density polyethylene or ultrahigh molecular weight polyethylene is more preferable from the viewpoint of the strength of the porous substrate to be obtained. Among these, it is preferable to use an ultrahigh molecular weight polyethylene having a weight average molecular weight of 500,000 or more, particularly a weight average molecular weight of 1,000,000 or more, particularly from the viewpoint of increasing the strength of the porous film. Further, one or more kinds of polyolefins grafted with a carbonyl group or an acid anhydride group may be used. These polyolefin resins may be used alone or in admixture of two or more.

  Examples of the second polymer and the fourth polymer having a reactive functional group include a polymer having a double bond, a polymer grafted with an acid anhydride group, and the like, and a polymer having an epoxy group. The types of the second polymer and the fourth polymer may be the same or different.

  As a 2nd polymer etc. which have a double bond in a polymer, it is good to have at least 1 sort (s) of 2nd polymer among polynorbornene, an ethylene propylene terpolymer, and polybutadiene, for example. Examples of the second polymer include bicyclo [3.2.0] hept-6-ene, bicyclo [4.2.0] oct-7-ene, and ring-opening polymers of these derivatives; bicyclo [2.2. 1] norbornene derivatives such as hept-5-ene (also referred to herein as “norbornene”), bicyclo [2.2.1] hept-5-ene-2,3-dicarboxymethyl ester; [2.2.2] Ring-opening polymer of oct-2-ene and derivatives thereof; and ring-opening polymer of dicyclopentadiene, tetracyclododecene and derivatives thereof, ethylene-propylene-terpolymer, polybutadiene, etc. Can be mentioned.

  The ethylene-propylene-terpolymer is composed of a terpolymer of ethylene, propylene and a diene monomer, and has an aliphatic ring derived from the diene monomer unit and a double bond in the main chain. The polymer may be hydrogenated at a part of the double bond. In the terpolymer of ethylene, propylene and diene monomer, examples of the diene monomer include dicyclopentadiene, ethylidene norbornene, and hexadiene. Of these, an aliphatic ring skeleton is preferable, and ethylidene norbornene is more preferable from the viewpoint of crosslinking reactivity. The ternary copolymer using these diene monomers may be a polymer used alone or in admixture of two or more.

  As the polyolefin resin composition, the ethylene-propylene-terpolymer desirably has a complex molecular chain entanglement structure in a three-dimensional crosslinked structure, and an ethylene-propylene-terpolymer having a high molecular weight with a molecular weight of a certain level or more is preferable.

  When polybutadiene is used, examples of the polybutadiene include cis-type 1,4-polybutadiene, trans-type 1,4-polybutadiene, and 1,2-polybutadiene. A polybutadiene having a large cis-type 1,4-polybutadiene skeleton is preferable in that it easily takes a flexible structure and a reaction of a double bond easily proceeds. In particular, polybutadiene having a cis-type 1,4-polybutadiene skeleton ratio of 30 mol% or more is preferable.

  Examples of the grafted polymer include graft-polymerized polyolefins-high density polyethylene, low density polyethylene, polypropylene, EVA and the like, but maleic anhydride graft polyethylene can be more preferably used from the viewpoint of compatibility. . These polyolefin graft polymers may be used in combination as the first polymer.

  Among these, as the second polymer having a reactive functional group and a weight average molecular weight of 2 million or more, a polynorbornene rubber having a high molecular weight and capable of being easily cross-linked by oxidation by heat treatment in air is preferable. In addition, the fourth polymer having a reactive functional group and a weight average molecular weight of less than 2 million has a weight average molecular weight of 1 million or less and can easily flow at a bonding temperature at the time of producing a membrane-electrode assembly. An ethylene-propylene-terpolymer having a double bond that can be copolymerized during crosslinking and polymerization is preferably used.

  The amount of the second polymer and the fourth polymer is 1 to 30 parts by weight, preferably 1 to 20 parts by weight when the total of the first polymer, the second polymer and the fourth polymer is 100 parts by weight. More preferably, it is 1 to 15 parts by weight. The fourth polymer may be 3 to 30 parts by weight, more preferably 3 to 20 parts by weight.

  The reason why the electrolyte membrane using the membrane added with the fourth polymer improves the bondability when the electrode-membrane assembly is produced and reduces the interfacial resistance of the electrode-membrane assembly is as follows. It seems like. That is, the fourth polymer is bonded to the third polymer in the polymerization step of the third monomer to be described later to obtain proton conductivity, and the fourth polymer to which the third monomer is added flows at a high temperature to cause a gap between the surface layers of the electrodes. It is considered that the adhesion is improved by the penetration and anchor effect, and the proton conductive components of the electrode and the electrolyte membrane are brought into close contact with each other. It is considered that when the proton conducting part is in close contact, protons easily move between the electrode and the electrolyte membrane, and the interface resistance is reduced.

  In addition, in the resin composition of the porous substrate, additives such as an antioxidant, an ultraviolet absorber, a dye, a pigment, an antistatic agent, a nucleating agent, and the like are added as necessary for the purpose of the present invention. It can add in the range which does not impair.

  Next, the manufacturing method of the porous base material used for this invention is demonstrated. In the production of the porous substrate in the present invention, a known method such as a heat-induced or non-solvent-induced wet film forming method or a dry film forming method can be used. For example, it can be produced by mixing the resin composition with a solvent, forming into a sheet while kneading and heating and dissolving, rolling, stretching in a uniaxial direction or more, and extracting and removing the solvent.

  The solvent that can be used in the present invention is not particularly limited as long as it can dissolve the polyolefin resin, but a solvent having a freezing point of −10 ° C. or lower is preferably used. Preferable specific examples of such a solvent include, for example, aliphatic or alicyclic hydrocarbons such as decane, decalin, and liquid paraffin, and mineral oil fractions having boiling points corresponding to these.

  The mixing ratio of the polyolefin and the solvent cannot be generally determined, but the resin concentration is preferably 5 to 30% by weight. When the resin concentration is higher than this, kneading is insufficient and it becomes difficult to obtain sufficient entanglement of polymer chains.

  The porosity of the porous substrate thus obtained is 10 to 70%, preferably 15 to 60%. Moreover, the thickness of a base material is 100 micrometers or less, Preferably it is 1-80 micrometers, More preferably, it is good that it is 5-70 micrometers.

  In addition, when performing a crosslinking treatment using heat, a one-stage heat treatment method in which heat treatment is performed once, a multistage heat treatment method in which the heat treatment is performed first at a low temperature and then at a higher temperature, or a temperature rise heat treatment method in which the temperature is increased, Various methods can be used. However, in consideration of the reactivity of the filled polymer or monomer present in the substrate, it is desirable to perform the treatment without impairing various properties of the substrate film and the inner filling film of the present invention. The heat treatment temperature is 40 to 140 ° C, preferably 90 to 140 ° C. The treatment time is preferably about 0.5 to 14 hours. These can be further optimized by appropriately changing the reaction temperature and time depending on the properties of the third polymer or monomer to be filled.

  The electrolyte membrane of the present invention is obtained by filling the surface of a substrate made of the porous material, particularly the pore inner surface with a third polymer having proton conductivity, but having a proton conductivity. It is preferable that the third monomer is filled into the pores and copolymerized by a crosslinking reaction or a polymerization reaction to be integrated. At this time, in particular, it is preferable that the third monomer and the fourth polymer are copolymerized to impart proton conductivity to the fourth polymer. Thereby, the proton conductivity with respect to the electrode can be improved as well as the bonding property with the electrode (decrease in the resistance value).

As the third polymer, as acidic functional groups having proton conductivity, for example, -SO 3 _H group derived from -SO ₃ ^-, etc., has a functional group of the held and released easily acidic proton, Those having a polymerizable functional group such as a vinyl group are preferred. That is, a compound having an acidic functional group as a side chain after polymerization is preferred.

  Examples of monomers that can be used as the third monomer include vinyl sulfonic acid (VSA), sodium allyl sulfonate (SAS), sodium methacryl sulfonate (SMS), sodium p-styrene sulfonate (SSS), and acrylic acid (AA). Can be mentioned. However, the monomers that can be used in the present invention are not limited to the above, and are allylamine, allylsulfonic acid, allylphosphonic acid, methallylsulfonic acid, methallylphosphonic acid, vinylphosphonic acid, styrenesulfonic acid, styrenephosphonic acid. The structure may be a vinyl group, a strong acid group such as sulfonic acid or phosphonic acid, or a weak acid group such as a carboxyl group, such as an acid, a sulfonic acid or phosphonic acid derivative of acrylamide, or methacrylic acid. Particularly preferred is vinyl sulfonic acid or sodium vinyl sulfonate which is a salt type.

  When a salt type such as a sodium salt is used as a monomer, it is preferable to make the salt into a proton type after forming a polymer. Moreover, it is preferable that the vinyl sulfonic acid to be used is highly pure, a crosslinking polymerization is accelerated | stimulated and a delicate polymer is easy to be obtained. The purity of this vinyl sulfonic acid is preferably 90% or more, more preferably 95% or more.

  The reason why a polymer using vinyl sulfonic acid is particularly preferable is not clear, but the sulfone groups are easily arranged in a straight chain at a high density, and proton conductivity can be improved. For example, main chain packing is likely to occur, and the polymer becomes harder, so that swelling changes between molecular chains are less likely to occur.

  A linear polymer may be formed using only the above-mentioned monomers, but by introducing a cross-linked structure, it is possible to form a cross-linked polymer that is insoluble in water, methanol, etc. that are permeated when used in a fuel cell. desirable.

  The method for introducing a crosslinked structure into the polymer is not particularly limited, and a known method can be used. For example, there are a method of performing a polymerization reaction using a polymerizable crosslinking agent having two or more double bonds, and a method of performing self-crosslinking by drawing hydrogen during polymerization, but a polymerization having two or more double bonds It is easier and more preferable to perform the polymerization reaction using a functional crosslinking agent.

  Examples of the crosslinking agent that causes the crosslinking reaction of the monomer constituting the third polymer include N, N-methylenebis (meth) acrylamide, trimethylolpropane diallyl ether, pentaerythritol triallyl ether, oligoethylene oxide diallyl ether, divinylbenzene, and bis (vinyl). Phenyl) methane, triallylamine, vinylsulfone, 1,3,5-triacroyl-hexahydro-s-triazine and the like. These crosslinking agents can be used alone or in combination of two or more as required.

  The amount of the crosslinking agent used is preferably 4 to 40% by weight, more preferably 4 to 25% by weight, in the monomer solution for filling. If the amount of the cross-linking agent is too small, the uncrosslinked polymer is likely to be eluted, and if it is too large, the cross-linking agent component is hardly compatible and a uniform cross-linked polymer cannot be obtained, and the relative amount of the proton conductive component is reduced. For this reason, the efficiency of proton conduction decreases.

  In the present invention, the above-mentioned third monomer, crosslinking agent, polymerization initiator and the like are mixed and dissolved to obtain an electrolyte monomer solution. In this case, by using a high concentration electrolyte monomer solution, cross-linking polymerization, which has been difficult to polymerize so far, is promoted, and a fine polymer is obtained. In the concentration of the electrolyte containing the third monomer, the concentration of the third monomer in the solution is preferably 30 to 95%, and more preferably 50 to 90% by weight. If the concentration of the vinyl sulfonic acid in the solution is too low, the porous membrane is not sufficiently filled, resulting in poor electrolyte membrane uniformity and proton conductivity. On the other hand, if the concentration in the solution is too high, the viscosity of the monomer solution for filling will be too high, making it difficult to penetrate into the porous substrate, and there will be problems such as the formation of bubbles. Flexibility is lost.

  The electrolyte monomer solution described above is preferably an aqueous solution, but depending on the solubility of the components used, it may be removed after polymerization using an organic solvent in part or in whole. When impregnating the porous substrate with this electrolyte monomer solution, depending on the affinity between the porous substrate and the electrolyte monomer solution, the porous substrate may be hydrophilized beforehand with an aqueous surfactant solution, etc. It is necessary to sufficiently penetrate the electrolyte monomer solution into the pores. Further, when a surfactant is added to the electrolyte monomer solution, or when the substrate is impregnated with the monomer solution, vacuum degassing or ultrasonic treatment may be performed. When impregnating the porous substrate with the electrolyte monomer solution, a known method such as a method of immersing the substrate in the electrolyte monomer solution or a method of applying using a spray or a coating machine is appropriately selected.

  As the polymerization initiator, radical polymerization initiators such as water-soluble azo initiators and peroxide initiators are preferable. Specifically, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2 , 2′-azobis [2- [N- (2-carboxyethyl) amino] propane] n-hydrate and the like.

  In the present invention, when the polymerization treatment is performed after impregnating the porous substrate with the monomer solution, one or more known methods selected from the group consisting of heat, ultraviolet rays, visible rays, and electron beams may be used. it can. At that time, a glass plate, polyimide, polyester, PET, PTFE, or other film was impregnated with the monomer solution so that the solvent of the monomer solution would not volatilize and oxygen that would inhibit radical polymerization would not enter the system. The base material is sandwiched, and the above-described polymerization treatment is preferably performed in a nitrogen atmosphere. The polymerization treatment conditions are appropriately selected according to the monomer, the crosslinking agent, the initiator and the like. The first, second, and third polymers are preferably partially or wholly crosslinked in terms of heat resistance and film strength. In addition, 1 or more types of well-known methods chosen from the group which consists of a heat | fever, an ultraviolet-ray, visible light, and an electron beam can be used for bridge | crosslinking.

  Thus, when the porous substrate is filled with the electrolyte and polymerized, the weight increase rate after filling and polymerization is 60% or more, more preferably 80% or more, based on the weight of the original porous substrate. Is good. This rate of weight increase indicates the degree of electrolyte filling in the pores of the porous substrate. If this is too low, the density of ion exchange groups contained in the electrolyte will be low, and sufficient proton conduction will occur. Sex cannot be obtained.

  The electrolyte membrane of the present invention is a solid polymer fuel cell, that is, a methanol fuel cell including a direct methanol solid polymer fuel cell or a reformed methanol solid polymer fuel cell, or a pure hydrogen gas fuel cell using hydrogen gas. It is preferable to use for.

  Here, the configuration of the solid polymer fuel cell will be briefly described. The solid polymer fuel cell includes a cathode electrode, an anode electrode, and an electrolyte membrane sandwiched between the electrodes. The fuel cell may be a reforming methanol fuel cell having a reformer on the anode electrode side.

  The cathode electrode may have a conventionally known configuration, and may include, for example, a catalyst layer and a support layer that supports the catalyst layer in order from the electrolyte side. The anode electrode can also have a conventionally known configuration, and for example, can have a catalyst layer and a support layer that supports the catalyst layer in order from the electrolyte side.

  The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the test method in an Example is as follows.

(Weight average molecular weight)
Using a gel permeation chromatography (GPC) apparatus, the molecular weight distribution was measured under the conditions of a column temperature of 140 ° C. and an eluent of o-dichlorobenzene.

(Film thickness)
1 / 10,000 Measured with a direct reading dial type film thickness measuring instrument.

(Porosity)
1/10000 Using thickness measured by a direct-reading dial type film thickness measuring device, weight W (g) per unit area S (cm ² ), average thickness t (μm), density d (g / cm ³ ) The value calculated from the following equation A was used.
Porosity (%) = (1- (10 ⁴ × W / S / t / d)) × 100 Formula A

(Weight increase rate)
The weight increase rate α at the time of filling was calculated by the following formula B, where the dry weight of the porous substrate before filling the electrolyte was ma and the dry weight after filling polymerization was mb.
α = (mb−ma) / ma × 100 Formula B

(Proton conductivity measurement)
The membrane was swollen in water (temperature: 25 ° C.), and then a membrane for proton conductivity measurement was prepared by sandwiching the membrane between two platinum foil electrodes, and impedance measurement was performed using HP4192A manufactured by Hewlett-Packard Company. The measurement frequency range was 10 kHz to 1 MHz. The obtained impedance was plotted with the real part on the horizontal axis and the imaginary part on the vertical axis, and the value of the real part of the minimum value was taken as the membrane resistance R (Ω). The proton conductivity σ (S / cm) can be obtained from the formula C, where t (μm) is the thickness of the membrane when swollen.
σ = 10 ⁻⁴ × t / R Formula C

(Methanol permeability evaluation test)
Methanol permeation performance at 25 ° C. was determined by a diffusion experiment using a chamber diffusion cell. The feed liquid was 140 g of water and 200 g of water placed in both ends of an L-shaped cell (permeable membrane area 8.04E-4m ² ) sandwiching the membrane, and the membrane surface was blended and stabilized at 25 ° C. with stirring. . Next, 60 g of methanol was quickly added to a cell containing 140 g of water, and the sample was sampled at regular intervals with the addition time set to 0 (1 ml was sampled, and 1 ml of water was added to correct the concentration by dilution later). The sampled solution was evaluated by Yanaco gas chromatography to determine each methanol concentration. The change in methanol weight concentration per unit membrane area and unit time was calculated as the methanol permeation flow rate.

(MEA production)
Platinum-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd .: TEC10E50E) is used for the oxygen electrode and platinum ruthenium alloy-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd .: TEC61E54) is used for the fuel electrode. An electrolyte solution (manufactured by DuPont: Nafion 5% solution) and polytetrafluoroethylene dispersion were blended, and water was added as appropriate to stir to obtain a reaction layer coating material. This was printed on one side of a carbon paper (manufactured by Toray Industries, Inc .: TGP-H-060) by screen printing and dried to obtain an electrode. At that time, the platinum amount on the oxygen electrode side was 1 mg / cm ² , and the total amount of platinum and ruthenium on the fuel electrode side was 3 mg / cm ² . These were superposed on the center of the electrolyte membrane with the paint surface facing inward, and heated and pressed at 135 ° C. and 0.25 MPa for 5 minutes to prepare a fuel cell membrane-electrode assembly (MEA).

(Fuel cell test using methanol as fuel)
Regarding the operating conditions when the MEA prepared in Examples and Comparative Examples was directly incorporated into a single methanol fuel cell, the fuel was a 5 mol% methanol aqueous solution and the oxidant was air. The cell temperature was 70 ° C. The voltage and output characteristics were measured by operating with an electronic loader at a current density of 0.1 A / cm ² .

(Membrane-electrode assembly peelability test)
The membrane-electrode assembly was immersed in a 30% aqueous methanol solution and taken out after 2 hours. At that time, the bonding / peeling state of the membrane and the electrode was evaluated in the following three stages. ◯: The film and the electrode are kept in a bonded state, Δ: Easily peeled, X: Completely peeled.

[Example 1]
More than 20% by weight of norbornene ring-opening polymer powder (norsolex NB, weight average molecular weight of 2 million or more), 10% by weight of EPDM rubber (EPDM553 manufactured by Sumitomo Chemical Co., Ltd., weight average molecular weight of about 1 million), and a weight average molecular weight of over 1.5 million 15 parts by weight of a polymer composition composed of 70% by weight of high molecular weight polyethylene and 85 parts by weight of liquid paraffin were uniformly mixed in a slurry state and dissolved and kneaded at a temperature of 160 ° C. using a small kneader for about 60 minutes. Thereafter, these kneaded materials were sandwiched between rolls or metal plates cooled to 0 ° C. and rapidly cooled into a sheet shape. These quenched resin sheets are heat-pressed at a temperature of 115 ° C. until the sheet thickness reaches 0.5 mm, and simultaneously biaxially stretched 4.5 × 4.5 times in length and width at a temperature of 115 ° C. Used to remove the solvent. Then, the obtained microporous film was heat-treated in air at 85 ° C. for 6 hours, and then heat-treated at 116 ° C. for 2 hours to obtain a porous substrate A-1 according to the present invention.

  The porous substrate A-1 was weighed and then impregnated with a 0.5 wt% sodium dodecylbenzenesulfonate aqueous solution, subjected to ultrasonic treatment and vacuum degassing treatment, and the substrate membrane was hydrophilized. While maintaining a 0.5 wt% sodium dodecylbenzenesulfonate aqueous solution at 20 ° C. or lower, vinyl sulfonic acid (hereinafter abbreviated as “VSA”, purity 98%) 70.0 wt%, cross-linking agent: N, N′-methylene- After mixing each so that it may become 10 wt% of bisacrylamide (it abbreviates as "MBA" hereafter), water-soluble azo initiator V-50 (Wako Pure Chemical Industries) with respect to the total amount of 100 mol% of VSA, VP, and MBA. An electrolyte monomer solution for filling was prepared by adding 1 mol% of Kogyo Kogyo). While maintaining this monomer solution at 20 ° C. or lower, a depressurization operation was performed to perform deaeration treatment. The membrane substrate A-1 is immersed in this liquid, further degassed by depressurization, irradiated with visible light for 7 minutes, and then heated in an oven at 80 ° C. for 1 hour to polymerize the electrolyte monomer. went. This film substrate was immersed twice in the monomer solution, degassed by a decompression operation, and polymerized by heating.

  Then, the obtained electrolyte membrane was immersed in 1N hydrochloric acid aqueous solution, and ion exchange was performed over 2 minutes of ultrasonic waves. Finally, excess hydrochloric acid was removed using ultrapure water, and after vacuum drying at 50 ° C. for 5 hours, a proton exchange membrane B-1 was obtained. The weight increase rate of this membrane was calculated, and proton conductivity, methanol permeation rate, and membrane-electrode assembly peelability were evaluated.

[Example 2]
10% by weight of norbornene ring-opening polymer powder (norsolex NB, weight average molecular weight of 2,000,000 or more), 20% by weight of EPDM rubber (Sumitomo Chemical, EPDM553, weight average molecular weight of about 1,000,000), weight average molecular weight of 1,500,000 A slurry was obtained using 15 parts by weight of a polymer composition composed of 70% by weight of ultrahigh molecular weight polyethylene and 85 parts by weight of liquid paraffin, and the obtained microporous film was heat-treated in air at 85 ° C. for 6 hours. Subsequently, it produced like Example 1 except having heat-processed at 118 degreeC for 2 hours, and obtained porous base material A-2 by this invention. After weighing the porous substrate A-2, the electrolyte monomer solution was charged and polymerized in the same manner as in Example 1 to obtain a proton exchange membrane B-2. The weight increase rate of this membrane was calculated, and proton conductivity, methanol permeation rate, and membrane-electrode assembly peelability were evaluated.

[Comparative Example 1]
Norbornene ring-opening polymer powder (Norsolex NB, weight average molecular weight of 2,000,000 or more) 20% by weight, polymer composition comprising 70% by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,500,000 and liquid paraffin 85 Prepared in the same manner as in Example 1 except that the slurry was obtained using parts by weight, and the obtained microporous film was heat-treated in air at 85 ° C. for 6 hours and then heat-treated at 124 ° C. for 2 hours. As a result, a porous substrate C-1 according to the present invention was obtained. After weighing the porous substrate C-1, the electrolyte monomer solution was charged and polymerized in the same manner as in Example 1 to obtain a proton exchange membrane D-1. The weight increase rate of this membrane was calculated, and proton conductivity, methanol permeation rate, and membrane-electrode assembly peelability were evaluated.

  The results obtained above are shown in Table 1.

  As shown in Table 1, the electrolyte membranes of Examples 1 and 2 are hydrocarbon electrolyte membranes having high electrolyte membrane characteristics equivalent to those of the comparative example and excellent in bondability with electrodes. . For this reason, when a fuel cell having this electrolyte membrane, particularly a polymer electrolyte fuel cell, is produced, an excellent fuel cell having high output characteristics can be provided at a low cost.

Claims (5)

Contains a first polymer containing a polyolefin having a weight average molecular weight of 500,000 or more, a second polymer having a double bond and a weight average molecular weight of 2 million or more, and a fourth polymer having a double bond and a weight average molecular weight of less than 2 million to the pores of the resin composition obtained by crosslinking a porous substrate, tare and filling the third polymer having proton conductivity is, electrolyte and said third polymer with said fourth polymer is attached film.   The electrolyte membrane according to claim 1, wherein the second polymer is polynorbornene rubber, and the fourth polymer is a terpolymer of ethylene, propylene, and a diene monomer. The electrolyte membrane according to claim 1 or 2, wherein the third polymer is obtained by crosslinking a polymerizable monomer containing a sulfonic acid group and a vinyl group with a crosslinking agent.   The electrolyte membrane according to claim 3, wherein the polymerizable monomer is vinyl sulfonic acid. A polymer electrolyte fuel cell comprising the electrolyte membrane according to claim 1.