JP2008031466A - Manufacturing method of polyelectrolyte emulsion and polyelectrolyte emulsion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyelectrolyte emulsion that manifests high power-generating properties when used as an ion-conductive membrane or an electrode binder which are a member for a fuel cell. <P>SOLUTION: [1] The manufacturing method of the polyelectrolyte emulsion comprises subjecting a polyelectrolyte dispersion, comprising polyelectrolyte particles dispersed in a dispersing medium, to a membrane treatment with a separating membrane. [2] In the manufacturing method of [1], the membrane treatment is a membrane treatment using a dialysis membrane. [3] The polyelectrolyte emulsion is manufactured by either one of the methods above. [4] The polyelectrolyte electrode for a fuel cell is obtained by using the above [3]. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a treatment method using membrane separation of a polymer electrolyte dispersion. Furthermore, the present invention relates to a polymer electrolyte emulsion that is obtained by the treatment method and gives a fuel cell having excellent power generation performance.

  Conventionally, a polymer having a hydrophilic group such as a sulfonic acid group, a carboxyl group, or a phosphonic acid group is a polymer electrolyte emulsion including a polymer solid electrolyte, a proton conductive membrane or a platinum-supporting carbon that is a member of a fuel cell. And used as a binder to form a catalyst layer. For example, as a polymer electrolyte to be applied to a fuel cell, Nafion (registered trademark) manufactured by Dupont, Aciplex (registered trademark) manufactured by Asahi Kasei, Flemion (registered trademark) manufactured by Asahi Glass, and the like are commercially available. These are so-called fluorine-based polymer electrolytes, and have an advantage that the dispersion stability is relatively good when a polymer electrolyte emulsion is formed. On the other hand, from the viewpoint of consideration for the environment and cost reduction, it is composed of a polymer electrolyte called a non-fluorine polymer electrolyte that has few fluorine atoms in the molecule, more preferably a hydrocarbon polymer electrolyte. A polyelectrolyte emulsion has been eagerly desired.

As such a polymer electrolyte emulsion, for example, Patent Document 1 discloses providing an aqueous dispersion with improved water resistance and film-forming properties by containing polyorganosiloxane. Patent Document 2 discloses a dispersion containing hydrocarbon fine particles having an ionic group on the surface in order to reduce fuel crossover of a direct methanol fuel cell.
However, the polymer electrolyte emulsion disclosed in Patent Document 1 or Patent Document 2 requires the addition of an emulsifier because the dispersion stability of the polymer electrolyte particles is not good.
Japanese Patent Laying-Open No. 2005-132996 (Claims) JP-A-2004-319353 (Example)

When a polymer electrolyte membrane is produced using the polymer electrolyte emulsion disclosed in Patent Documents 1 and 2, the emulsifier tends to remain in the membrane, and there has been a concern about deterioration in characteristics due to the remaining of the emulsifier. . When the present inventors examined in detail, when such a polymer electrolyte emulsion was applied to the electrode for fuel cells, it became clear that electric power generation performance fall by presence of an emulsifier.
Accordingly, an object of the present invention is to provide a method for producing a polymer electrolyte emulsion capable of exhibiting high power generation characteristics when used as an ion conductive membrane or electrode binder as a fuel cell member, and a polymer electrolyte emulsion. It is to provide.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention
[1] To provide a method for producing a polymer electrolyte emulsion, characterized in that a polymer electrolyte dispersion obtained by dispersing polymer electrolyte particles in a dispersion medium is subjected to membrane separation with a separation membrane.

Furthermore, the following [2] to [6] are provided as preferred embodiments according to the above [1].
[2] The production method of [1], wherein the separation membrane is a dialysis membrane or an ultrafiltration membrane [3] The production method of [1], wherein the membrane treatment is a dialysis membrane [4] The polymer electrolyte particles The production method of any one of [1] to [3], wherein the polymer electrolyte contained is a polymer electrolyte having a fluorine atom content of 15% by weight or less in its elemental composition. [5] The polymer electrolyte dispersion liquid Is a dispersion obtained through the following steps (1) and (2), the production method of any one of [1] to [4] (1) a polymer electrolyte, a good solvent for the polymer electrolyte Mixing step [6] above, wherein the polymer electrolyte solution obtained in the preparation step (2) (1) and the poor solvent of the polymer electrolyte are dissolved in a solvent containing Good solvents for polymer electrolytes are N-methylpyrrolidone, N, N-dimethylacetoa De, N, characterized in that an aprotic polar solvent selected from the group consisting of N- dimethylformamide and dimethyl sulfoxide, the production method of [5]

In addition, the present invention provides the following [7] to [9] related to any one of the above production methods.
[7] Polymer electrolyte emulsion produced using the production method of any one of [1] to [6] [8] The content of the good solvent of the polymer electrolyte constituting the polymer electrolyte emulsion is 200 ppm or less. The polymer electrolyte emulsion of [7], wherein the volume average particle size determined by the dynamic light scattering method is 100 nm to 200 μm, [7] or [8]

Said polymer electrolyte emulsion is suitable when manufacturing the member which comprises a solid polymer type fuel cell, and provides the following [10]-[12].
[10] Electrode for polymer electrolyte fuel cell comprising the polymer electrolyte emulsion of [7] to [9] [11] [10] Membrane electrode junction comprising electrode for polymer electrolyte fuel cell of [10] Solid polymer fuel cell fuel cell comprising a membrane electrode assembly of bodies [12] and [11]

  ADVANTAGE OF THE INVENTION According to this invention, the polymer electrolyte emulsion suitable for the electrode which gives the fuel cell excellent in electric power generation characteristic can be manufactured easily.

Hereinafter, the present invention will be sequentially described.
<Preparation of polymer electrolyte dispersion>
The present invention relates to a method for producing a polymer electrolyte emulsion that can be suitably used for a fuel cell, particularly a fuel cell electrode binder, and is characterized by performing membrane separation using a separation membrane. A method for preparing a polymer electrolyte dispersion liquid in which polymer electrolyte particles are dispersed in a dispersion medium, which is a target for membrane separation, is not particularly limited, but preferred embodiments include the following ( A dispersion obtained through the steps 1) and (2) is preferred.
(1) Preparation step (2) for preparing a polymer electrolyte solution by dissolving a polymer electrolyte in a solvent containing a good solvent for the polymer electrolyte, and the polymer electrolyte solution obtained in (1), Mixing step of mixing the poor solvent of the molecular electrolyte (2) In the mixing step, the polymer electrolyte is put into the poor solvent of the polymer electrolyte by stirring and adding the polymer electrolyte solution to the poor solvent. It is preferable that it is a step of precipitating in the form of particles and preparing a dispersion.
The polymer electrolyte particle means a particle containing a polymer electrolyte. When an additive is used as will be described later, a polymer electrolyte and an additive are used. It contains the contained particles.
Here, the definition of “good solvent” and “poor solvent” is defined by the weight of the polymer electrolyte that can be dissolved in 100 g of the solvent at 25 ° C. The good solvent is a solvent in which 0.1 g or more of the polymer electrolyte is soluble, and the poor solvent is a solvent in which the polymer electrolyte can dissolve only 0.05 g or less. These solvents can be selected in consideration of the solubility depending on the applied polymer electrolyte.
The amount of the good solvent and the poor solvent for producing the dispersion can also be optimized as long as the polymer electrolyte to be used can be deposited in the form of particles, but preferably (1) the polymer electrolyte solution in the adjustment step The concentration of the polymer electrolyte is more preferably 0.1 to 10% by weight, and further preferably 0.5 to 5% by weight. In addition, in the mixing step (2), the poor solvent to be used is preferably 4 to 99 times by weight, more preferably 6 to 99 times by weight with respect to parts by weight of the polymer electrolyte solution to be mixed, It is more preferable that it is 9 to 99 times by weight. When the concentration of the polymer electrolyte in the polymer electrolyte solution and the amount of the poor solvent used are within the above ranges, there is an advantage that it is easier to obtain a polymer electrolyte dispersion.

  As described above, the good solvent for preparing the polymer electrolyte solution can be selected in consideration of the solubility in the polymer electrolyte to be used, but preferably N, N dimethylacetamide, N, N-dimethyl. Examples include formamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone, and two or more of these may be used in combination. These have an advantage that the solubility is relatively high with respect to a hydrocarbon-based polymer electrolyte, which is a preferable polymer electrolyte described later.

  The poor solvent can also be selected in consideration of solubility. Examples of the poor solvent include water, alcohol solvents such as methanol and ethanol, nonpolar organic solvents such as hexane and toluene, polar organic solvents such as acetone, methyl ethyl ketone, methylene chloride, and ethyl acetate, or a mixture thereof. However, from the viewpoint of reducing environmental burden when used industrially, water or a solvent containing water as a main component is preferably used.

<Polymer electrolyte>
The polymer electrolyte used in the present invention includes, for example, a sulfonic acid group (—SO ₃ H), a carboxyl group (—COOH), a phosphonic acid group (—PO (OH) ₂ ), a phosphinic acid group (—POH (OH )), Sulfonimide groups (—SO ₂ NHSO ₂ —), phenolic hydroxyl groups (—Ph (OH) (Ph represents a phenyl group)), and the like. Alternatively, it has an anion exchange group such as a primary to tertiary amine group. Among them, a polymer electrolyte having a sulfonic acid group or a phosphonic acid group is more preferable, and a polymer electrolyte having a sulfonic acid group is more preferable.

  Representative examples of such a polymer electrolyte include, for example, (A) a polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group are introduced into a polymer whose main chain is composed of an aliphatic hydrocarbon; (B) the main chain is an aromatic ring A polyelectrolyte in which a sulfonic acid group and / or a phosphonic acid group are introduced into a polymer having the following: (C) a sulfonic acid group and a polymer such as polysiloxane and polyphosphazene substantially free of carbon atoms in the main chain And / or polyelectrolyte into which a phosphonic acid group has been introduced; (D) any two or more selected from repeating units constituting the polymer before introduction of the sulfonic acid group and / or phosphonic acid group in (A) to (C) A polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group is introduced into a copolymer comprising repeating units of: (E) a basic nitrogen atom in the main chain or side chain, and sulfuric acid Such polyelectrolytes introduced by ionic bonding of the acidic compound such as phosphoric acid.

  Examples of the polymer electrolyte (A) include polyvinyl sulfonic acid, polystyrene sulfonic acid, poly (α-methylstyrene) sulfonic acid, and the like.

  The polymer electrolyte (B) is a polymer in which aromatic rings are connected directly or by a divalent group to form a main chain, and has an ion exchange group. Here, examples of the divalent group include an oxy group, a thioxy group, a carbonyl group, and a sulfonyl group. Examples of such a polymer electrolyte include polyetheretherketone, polysulfone, polyethersulfone, poly (arylene ether), polyimide, poly ((4-phenoxybenzoyl) -1,4-phenylene), polyphenylene sulfide, and polyphenyl. Those in which a sulfonic acid group is introduced into each of homopolymers such as quinoxalen, sulfoarylated polybenzimidazole, sulfoalkylated polybenzimidazole, phosphoalkylated polybenzimidazole (Japanese Patent Laid-Open No. 9-110882), And phosphonated poly (phenylene ether) (J. Appl. Polym. Sci., 18, 1969 (1974)).

  Examples of the polymer electrolyte (C) include those obtained by introducing sulfonic acid groups into polyphosphazene, polysiloxanes having phosphonic acid groups (Polymer Prep., 41, No. 1, 70 (2000)). Etc.

  As the polymer electrolyte of (D) above, a sulfonic acid group and / or a phosphonic acid group is introduced into a random copolymer, but a sulfonic acid group and / or a phosphonic acid group is introduced into an alternating copolymer. The sulfonic acid group and / or the phosphonic acid group may be introduced into the block copolymer. Examples of the sulfonic acid group introduced into the random copolymer include a sulfonated polyethersulfone-dihydroxybiphenyl copolymer described in JP-A-11-116679.

  In the polymer electrolyte of the above (D), as the block copolymer, a block copolymer having a sulfonated aromatic polymer block described in JP-A-2001-250567, JP-A-2003-32322, Examples include block copolymers having a main chain structure of polyetherketone and polyethersulfone described in JP-A-2004-359925, JP-A-2005-232439, and JP-A-2003-113136. It is done. Moreover, the block copolymer which substituted some or all of the sulfonic acid group of these block copolymers by the phosphonic acid group is mentioned.

  The block copolymer preferably has a segment having an ion exchange group and a segment substantially not having an ion exchange group, and is a block copolymer having one of these segments. Alternatively, it may be a block copolymer having two or more of any one segment, or may be any of a multi-block copolymer having two or more of both segments.

  Examples of the polymer electrolyte (E) include polybenzimidazole containing phosphoric acid described in JP-T-11-503262.

  Among those exemplified above, the polymer electrolyte applied to the present invention is referred to as a polymer electrolyte (hereinafter referred to as “hydrocarbon polymer electrolyte”) having a fluorine atom content of 15 wt% or less in its elemental composition. It is preferable that a fluorine atom content exceeding 15 wt% in the elemental composition is called “fluorine polymer electrolyte”). Such hydrocarbon-based polymer electrolytes have a lower dissociation degree of sulfonic acid groups than conventional fluorine-based polymer electrolytes, or are poorly dispersible in an aqueous medium, so that an emulsifier for stabilizing an emulsion is used. I needed it. When the present inventors use an emulsion containing an emulsifier as a binder in the production of a fuel cell catalyst layer, the emulsifier is adsorbed and poisoned on the platinum surface as a catalyst component. It has been found that the properties are significantly impaired. The preferred polymer electrolyte dispersion exemplified above is a dispersion in which polymer electrolyte particles composed of a hydrocarbon polymer electrolyte are dispersed in a dispersion medium without using such an emulsifier, and membrane separation is performed. In addition to a high degree of dispersion stability, the polymer electrolyte emulsion obtained by performing the step makes it possible to improve the power generation performance when used in a fuel cell catalyst layer or the like.

  Furthermore, the production method of the present invention provides a polymer that provides a fuel cell electrode with excellent power generation performance while maintaining a high degree of dispersibility even when an emulsifier is not substantially used for a hydrocarbon polymer electrolyte. Although it is particularly effective in producing an electrolyte emulsion, it is expected to contribute to improvement in power generation performance with respect to conventional fluorine-based polymer electrolytes. As such a fluorine-based polymer electrolyte, in addition to the commercially available fluorine-based polymer electrolyte described in the background art, copolymerization of a fluorine-containing vinyl monomer and a hydrocarbon-based vinyl monomer described in JP-A-9-102322 is performed. A sulfonic acid type polystyrene-graft-ethylene-tetrafluoroethylene copolymer (ETFE) composed of a main chain thus prepared and a hydrocarbon side chain having a sulfonic acid group, and U.S. Pat. No. 4,012,303 No. 4 or US Pat. No. 4,605,685, obtained by graft polymerization of α, β, β-trifluorostyrene onto a copolymer of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer, Examples thereof include resins obtained by introducing sulfonic acid groups with a sulfonating agent such as chlorosulfonic acid and fluorosulfonic acid. That.

<Membrane separation>
Next, a preferred embodiment of the membrane separation applied to the present invention will be described.
Here, the membrane separation method is convenient depending on the pore size of the membrane to be used, such as microfiltration, ultrafiltration, dialysis, electrodialysis, nanofiltration, etc. It is classified. Here, microfiltration blocks particles larger than 0.1 μm, ultrafiltration blocks particles in the range of 0.1 μm to 2 nm, and nanofiltration particles smaller than 2 nm. Is to prevent. Reverse osmosis is to move the solvent in the opposite direction to the osmotic pressure difference by pressurization. Any of these separation means can be used in the present invention, but preferably membrane separation using a dialysis membrane and / or membrane separation using an ultrafiltration membrane is preferable, and among them, a dialysis membrane is used. It is more preferable to use conventional membrane separation. Among the dialysis membranes, a regenerated cellulose membrane can be suitably used.
The method using a dialysis membrane is characterized in that it can be processed without applying pressure as compared with the filtration method, and the membrane thickness can be made very thin. There are various pore sizes ranging from ultrafiltration membranes to reverse osmosis membranes. As the material of the dialysis membrane, regenerated cellulose, cellulose acetate, polyacrylonitrile and the like are used. Any of them can be preferably used in the present invention.
As a preferred implementation condition related to the dialysis method, a regenerated cellulose membrane was used, and the first phase in which the polymer electrolyte dispersion was added to one side across the membrane, and the other was used for preparation of the applied polymer electrolyte dispersion. A second phase charged with a poor solvent is provided. From the first phase side, the good solvent used for the preparation of the polymer electrolyte solution, unreacted monomer components at the time of polymer electrolyte production, other impurities, etc. permeate the membrane and move to the second phase side. From the second phase side, the poor solvent moves to the first phase side, so that the polymer electrolyte dispersion is purified while the impurities and the poor solvent are exchanged to obtain a suitable polymer electrolyte emulsion. It is done. Such membrane separation is usually preferred because it is simple to carry out at about room temperature (20 to 30 ° C.).

  In the membrane separation, what is separated from the first phase side is assumed to impair the power generation performance when applied to a fuel cell member. Although it is not certain, the good solvent of the polymer electrolyte used by the preparation of the said polymer electrolyte dispersion liquid is assumed as one of them. When a dialysis membrane that is suitable membrane separation is used, the removal amount of such a good solvent can be removed by 80% by weight or more when the total amount of the good solvent contained in the polymer electrolyte dispersion is 100% by weight. It turns out. The removal amount is more preferably 90% or more, and even more preferably substantially 100%. When expressed by the content of the good solvent remaining in the polymer electrolyte emulsion obtained through such membrane separation, the good solvent is preferably 200 ppm or less, and 100 ppm or less, based on the total weight of the dispersion medium of the polymer electrolyte emulsion. It is more preferable that the good solvent is not substantially contained, that is, it is particularly preferable to remove the good solvent so that it is not detected by a known analysis means.

<Polymer electrolyte emulsion>
In the polymer electrolyte emulsion obtained through the production method of the present invention, the average particle diameter of the particles including the polymer electrolyte particles contained is represented by a volume average particle diameter determined by a dynamic light scattering method, and is 100 nm to The range is 200 μm. The average particle size is preferably in the range of 150 nm to 10 μm, and more preferably in the range of 200 nm to 1 μm. When the average particle diameter of the polymer electrolyte particles is within the above range, the resulting polymer electrolyte emulsion has a higher degree of storage stability, and when the film is formed, the uniformity of the film is relatively good. There is an advantage to become.

Furthermore, in addition to the above polymer electrolyte, other components may be contained within a range in which catalyst poisoning does not occur when applied to a fuel cell electrode according to desired characteristics. Examples of such other components include plasticizers, stabilizers, adhesion assistants, mold release agents, water retention agents, inorganic or organic particles, sensitizers, leveling agents, colorants, and the like used in ordinary polymers. The presence or absence of catalyst poisoning ability of these components can be determined by a known method using a cyclic voltammetry method.
As described above, when the polymer electrolyte emulsion obtained by the present invention is used as a constituent component of a fuel cell electrode, during the operation of the fuel cell, a peroxide is generated at the electrode. May be converted into radical species while diffusing, and this may move to the ion conductive film bonded to the electrode, thereby deteriorating the ion conductive material (polymer electrolyte) constituting the ion conductive film. In this case, in order to avoid such inconvenience, it is preferable to add a stabilizer capable of imparting radical resistance to the polymer electrolyte emulsion.
These other components can be applied to the production method of the present invention by preparing a polymer electrolyte solution by dissolving in a solvent together with the polymer electrolyte in the preparation step.
Further, such other components may be contained in the polymer electrolyte particles constituting the polymer electrolyte emulsion, dissolved in the dispersion medium, or separately from the polymer electrolyte particles. The fine particles may be present as other components.

<Application>
The polymer electrolyte emulsion obtained through the production method of the present invention can obtain an accurate film by various film forming methods. As the film forming method, for example, cast film forming, spray coating, brush coating, roll coater, flow coater, bar coater, dip coater and the like can be used. The coating film thickness varies depending on the use, but is usually a dry film thickness of 0.01 to 1,000 μm, preferably 0.05 to 500 μm.
This polymer electrolyte emulsion is suitably used as a proton conductive membrane for fuel cells as a dry membrane, a fuel cell electrode combined with carbon or platinum catalyst, or applied to a substrate surface as a modifier or adhesive. be able to.

  An electrode called a catalyst layer containing a catalyst such as platinum that promotes the oxidation-reduction reaction between hydrogen and air is formed on both surfaces of the polymer electrolyte membrane. Further, in the MEA, a structure having a gas diffusion layer for efficiently supplying gas to the catalyst layer outside both catalyst layers is usually a membrane electrode gas diffusion layer assembly (hereinafter referred to as “ It is also called “MEGA”.)

  Such MEA is a method of directly forming a catalyst layer on a polymer electrolyte membrane, or a catalyst layer is formed on a flat support substrate, which is transferred to the polymer electrolyte membrane, and then the support substrate is peeled off. It is manufactured using a method or the like. Moreover, after forming a catalyst layer on the base material used as gas diffusion layers, such as carbon paper, this is joined with a polymer electrolyte membrane, and the method of manufacturing with the form of MEGA is also mentioned.

The polymer electrolyte emulsion obtained by the method of the present invention can be applied to various uses such as a primer, an adhesive, a binder resin, and a polymer solid electrolyte membrane.
For example, if an MEA is formed by applying a catalyst ink blended with the polymer electrolyte emulsion obtained in the present invention and platinum-supported carbon on an ion conductive membrane, an MEA with extremely excellent power generation characteristics can be obtained. it can. Alternatively, if the MEA is formed by applying the polymer electrolyte emulsion obtained by the present invention on the ion conductive membrane and placing the composite particles of the electrolyte and platinum-supported carbon before drying the emulsion coating film, the power generation characteristics An extremely excellent MEA can be obtained. Alternatively, when the membrane electrode assembly and the gas diffusion layer are joined, even when the polymer electrolyte emulsion of the present invention is used as an adhesive, an MEA having extremely excellent power generation characteristics can be obtained.

  Next, a fuel cell provided with MEA obtained by the polymer electrolyte emulsion of the present invention will be described.

FIG. 1 is a diagram schematically showing a cross-sectional configuration of a fuel cell according to a preferred embodiment. As shown in FIG. 1, the fuel cell 10 has catalyst layers 14a and 14b sandwiching the ion conductive membrane 12 on both sides, and this is the MEA 20 obtained by the manufacturing method of the present invention. Furthermore, the catalyst layers on both sides are provided with gas diffusion layers 16a and 16b, respectively, and separators 18a and 18b are formed in the gas diffusion layers.
Here, the MEGA includes the MEA 20 and the gas diffusion layers 16a and 16b.

  Here, the catalyst layers 14a and 14b are layers that function as electrode layers in the fuel cell, and either one of them serves as an anode catalyst layer and the other serves as a cathode catalyst layer.

  The gas diffusion layers 16a and 16b are provided so as to sandwich both sides of the MEA 20, and promote the diffusion of the raw material gas into the catalyst layers 14a and 14b. The gas diffusion layers 16a and 16b are preferably made of a porous material having electron conductivity. For example, a porous carbon non-woven fabric or carbon paper is preferable because the raw material gas can be efficiently transported to the catalyst layers 14a and 14b.

  Separator 18a, 18b is formed with the material which has electronic conductivity, As this material, carbon, resin mold carbon, titanium, stainless steel etc. are mentioned, for example. Although not shown, the separators 18a and 18b are preferably provided with grooves serving as flow paths for fuel gas or the like on the catalyst layers 14a and 14b.

  The fuel cell 10 can be obtained by sandwiching MEGA as described above between a pair of separators 18a and 18b and joining them together.

  The fuel cell of the present invention is not necessarily limited to the above-described configuration, and may have a different configuration as long as it does not depart from the spirit of the fuel cell.

  The fuel cell 10 may be one having the above-described structure sealed with a gas seal body or the like. Furthermore, a plurality of the fuel cells 10 having the above structure can be connected in series to be put to practical use as a fuel cell stack. The fuel cell having such a configuration can operate as a solid polymer fuel cell when the fuel is hydrogen, and as a direct methanol fuel cell when the fuel is an aqueous methanol solution.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Measurement method of ion exchange capacity)
The polymer electrolyte used for the measurement was made into a membrane using a solution casting method. The dry weight of this membrane was determined using a halogen moisture meter set at a heating temperature of 105 ° C. Next, this membrane was immersed in 5 mL of a 0.1 mol / L sodium hydroxide aqueous solution, and then 50 mL of ion-exchanged water was added and left for 2 hours. Thereafter, titration was performed by gradually adding 0.1 mol / L hydrochloric acid to the solution in which the membrane was immersed, and the neutralization point was determined. Then, the ion exchange capacity (unit: meq / g) of the membrane was calculated from the dry weight of the membrane and the amount of hydrochloric acid required for the neutralization.

(Measurement method of weight average molecular weight)
The weight average molecular weight was calculated by measuring by gel permeation chromatography (GPC) and performing polystyrene conversion. The measurement conditions of GPC are as follows.
GPC conditions and GPC measurement device HLC-8220 manufactured by TOSOH
・ Two columns AT-80M made by Shodex are connected in series ・ Column temperature 40 ℃
Mobile phase solvent DMAc (added LiBr to 10 mmol / dm ³ )
・ Solvent flow rate 0.5mL / min

(Average particle size measurement method)
The average particle size of the particles present in the produced emulsion was measured using a dynamic light scattering method (concentrated particle size analyzer FPAR-1000 [manufactured by Otsuka Electronics]). The measurement temperature is 30 ° C., the integration time is 30 minutes, and the wavelength of the laser used for the measurement is 660 nm. The obtained data is analyzed by the CONTIN method by using the analysis software (FPAR system VERSION 5.1.7.2) attached to the above apparatus, and the scattering intensity distribution is obtained. did.

Production Example 1 [Synthesis of dipotassium 4,4′-difluorodiphenylsulfone-3,3′-disulfonate]
To a reactor equipped with a stirrer, 467 g of 4,4′-difluorodiphenylsulfone and 3500 g of 30% fuming sulfuric acid were added and reacted at 100 ° C. for 5 hours. The obtained reaction mixture was cooled and then added to a large amount of ice water, and 470 mL of a 50% aqueous potassium hydroxide solution was further added dropwise thereto.
Next, the precipitated solid was collected by filtration, washed with ethanol, and dried. The obtained solid was dissolved in 6.0 L of deionized water, 50% aqueous potassium hydroxide solution was added to adjust the pH to 7.5, and then 460 g of potassium chloride was added. The precipitated solid was collected by filtration, washed with ethanol, and dried.
Thereafter, the obtained solid was dissolved in 2.9 L of dimethyl sulfoxide (hereinafter referred to as “DMSO”), insoluble inorganic salts were removed by filtration, and the residue was further washed with 300 mL of DMSO. To the obtained filtrate, 6.0 L of a solution of ethyl acetate / ethanol = 24/1 was added dropwise, and the precipitated solid was washed with methanol, dried at 100 ° C., and 4,4′-difluorodiphenylsulfone-3,3. 482 g of dipotassium dipotassium disulfonate was obtained.

Production Example 2 [Production of polymer electrolyte A]
(Synthesis of polymer compound having sulfonic acid group)
In a flask equipped with an azeotropic distillation apparatus, 9.32 parts by weight of dipotassium 4,4′-difluorodiphenylsulfone-3,3′-disulfonate obtained in Production Example 1 in an argon atmosphere, 2,5-dihydroxybenzene 4.20 parts by weight of potassium sulfonate, 59.6 parts by weight of DMSO, and 9.00 parts by weight of toluene were added, and argon gas was bubbled for 1 hour while stirring these at room temperature.
Thereafter, 2.67 parts by weight of potassium carbonate was added to the obtained mixture, and azeotropic dehydration was performed by heating and stirring at 140 ° C. Thereafter, heating was continued while distilling off toluene, and a DMSO solution of a polymer compound having a sulfonic acid group was obtained. Total heating time was 14 hours. The resulting solution was allowed to cool at room temperature.

(Synthesis of polymer compounds substantially free of ion exchange groups)
In a flask equipped with an azeotropic distillation apparatus, in an argon atmosphere, 8.32 parts by weight of 4,4′-difluorodiphenylsulfone, 5.36 parts by weight of 2,6-dihydroxynaphthalene, 30.2 parts by weight of DMSO, N-methyl- 20.2 parts by weight of 2-pyrrolidone (hereinafter referred to as “NMP”) and 9.81 parts by weight of toluene were added, and argon gas was bubbled for 1 hour while stirring at room temperature.
Thereafter, 5.09 parts by weight of potassium carbonate was added to the obtained mixture, and azeotropic dehydration was performed by heating and stirring at 140 ° C. Thereafter, heating was continued while toluene was distilled off. Total heating time was 5 hours. The resulting solution was allowed to cool at room temperature to obtain a NMP / DMSO mixed solution of a polymer compound substantially free of ion exchange groups.

(Synthesis of block copolymer)
While stirring the obtained NMP / DMSO mixed solution of the polymer compound having substantially no ion exchange group, the total amount of the DMSO solution of the polymer compound having the sulfonic acid group and 80.4 parts by weight of NMP were added thereto. DMSO (45.3 parts by weight) was added, and a block copolymerization reaction was carried out at 150 ° C. for 40 hours.
The obtained reaction solution was dropped into a large amount of 2N hydrochloric acid and immersed for 1 hour. Thereafter, the produced precipitate was filtered off and then immersed again in 2N hydrochloric acid for 1 hour. The obtained precipitate was filtered and washed with water, and then immersed in a large amount of hot water at 95 ° C. for 1 hour. And this solution was dried at 80 degreeC for 12 hours, and the polymer electrolyte A which is a block copolymer was obtained. The obtained polymer electrolyte A had an ion exchange capacity of 1.9 meq / g and a weight average molecular weight of 4.2 × 10 ⁵ .
The structure of this polymer electrolyte A is shown below. In addition, description of "block" in a following formula represents having at least one block each having a sulfonic acid group and no block having an ion exchange group. n and m represent the copolymerization mole fraction of each structural unit.

得られた高分子電解質Ｂのイオン交換容量は２．３ｍｅｑ／ｇであり、重量平均分子量は、２．７×１０⁵であった。なお、ｔ、ｕは各ブロックを構成する括弧内の繰返し単位の平均重合度を表すものである。 Production Example 3 [Production of polymer electrolyte B]
Under an argon atmosphere, in a flask equipped with an azeotropic distillation apparatus, DMSO 600 ml, toluene 200 mL, sodium 2,5-dichlorobenzenesulfonate 26.5 g (106.3 mmol), the following polyethersulfone having a terminal chloro type (manufactured by Sumitomo Chemical) Sumika Excel PES5200P, Mn = 5.4 × 10 ⁴ , Mw = 1.2 × 10 ⁵ ) 10.0 g and 2,2′-bipyridyl 43.8 g (280.2 mmol) were added and stirred. Thereafter, the bath temperature was raised to 150 ° C., and water in the system was azeotropically dehydrated by distilling off toluene, followed by cooling to 60 ° C. Next, 73.4 g (266.9 mmol) of bis (1,5-cyclooctadiene) nickel (0) was added thereto, the temperature was raised to 80 ° C., and the mixture was stirred at the same temperature for 5 hours. After allowing to cool, the reaction solution is poured into a large amount of 6 mol / L hydrochloric acid to precipitate a polymer, which is filtered off. Thereafter, washing and filtration operations with 6 mol / L hydrochloric acid were repeated several times, followed by washing with water until the filtrate became neutral and drying under reduced pressure to obtain 16.3 g of the following polyarylene block copolymer. . This is designated as polymer electrolyte B (the following formula). In addition, description of "block" in a following formula represents having at least one block each having a sulfonic acid group and no block having an ion exchange group.

The obtained polymer electrolyte B had an ion exchange capacity of 2.3 meq / g and a weight average molecular weight of 2.7 × 10 ⁵ . T and u represent the average degree of polymerization of the repeating units in parentheses constituting each block.

Production Example 4 [Production of Stabilizer Polymer d]
Synthesis of polymer a A 2 L separable flask equipped with a vacuum azeotropic distillation apparatus was purged with nitrogen, and 63.40 g of bis-4-hydroxydiphenylsulfone, 70.81 g of 4,4′-dihydroxybiphenyl, and 955 g of NMP were added to obtain a homogeneous solution. did. Thereafter, 92.80 g of potassium carbonate was added, and dehydrated under reduced pressure at 135 ° C. to 150 ° C. for 4.5 hours while NMP was distilled off. Thereafter, 200.10 g of dichlorodiphenylsulfone was added and the reaction was carried out at 180 ° C. for 21 hours.
After completion of the reaction, the reaction solution was added dropwise to methanol, and the precipitated solid was filtered and collected. The recovered solid was further washed with methanol, washed with water, and washed with hot methanol and dried to obtain 275.55 g of polymer a. The structure of this polymer a is shown below. The polymer a had a polystyrene-reduced weight average molecular weight of 18000 by GPC measurement, and the ratio of n and m determined from the integrated value of NMR measurement was n: m = 7: 3. In addition, the following "random" description shows that the structural unit which forms the following polymer a is copolymerized at random.

Synthesis of Polymer b The 2 L separable flask was purged with nitrogen, and 101.12 g of nitrobenzene and 80.00 g of polymer a were added to obtain a uniform solution. Thereafter, 50.25 g of N-bromosuccinimide was added and cooled to 15 ° C. Subsequently, 106.42 g of 95% concentrated sulfuric acid was added dropwise over 40 minutes, and the reaction was carried out at 15 ° C. for 6 hours. Six hours later, 450.63 g of a 10 w% aqueous sodium hydroxide solution and 18.36 g of sodium thiosulfate were added while cooling to 15 ° C. The 2 L separable flask was purged with nitrogen, and 1014.12 g of nitrobenzene and 80.00 g of polymer a were added to obtain a uniform solution. Thereafter, 50.25 g of N-bromosuccinimide was added and cooled to 15 ° C. Subsequently, 106.42 g of 95% concentrated sulfuric acid was added dropwise over 40 minutes, and the reaction was carried out at 15 ° C. for 6 hours. Six hours later, 450.63 g of a 10 w% aqueous sodium hydroxide solution and 18.36 g of sodium thiosulfate were added while cooling to 15 ° C. Thereafter, this solution was added dropwise to methanol, and the precipitated solid was collected by filtration. The recovered solid was washed with methanol, washed with water, washed again with methanol and dried to obtain 86.38 g of polymer b.

Synthesis of Polymer c A 2 L separable flask equipped with a reduced-pressure azeotropic distillation apparatus was purged with nitrogen, and 116.99 g of dimethylformamide and 80.07 g of polymer b were added to obtain a uniform solution. Thereafter, dehydration under reduced pressure was performed for 5 hours while distilling off dimethylformamide. After 5 hours, the mixture was cooled to 50 ° C., 41.87 g of nickel chloride was added, the temperature was raised to 130 ° C., and 69.67 g of triethyl phosphite was added dropwise, and the reaction was carried out at 140 ° C. to 145 ° C. for 2 hours. After 2 hours, an additional 17.30 g of triethyl phosphite was added, and the reaction was carried out at 145 ° C. to 150 ° C. for 3 hours. After 3 hours, the mixture was cooled to room temperature, a mixed solution of 1161 g of water and 929 g of ethanol was added dropwise, and the precipitated solid was collected by filtration. Water was added to the collected solid and sufficiently pulverized, washed with 5 w% hydrochloric acid and washed with water to obtain 86.83 g of polymer c.

Synthesis of Polymer d A 5 L separable flask was purged with nitrogen, and 1200 g of 35 wt% hydrochloric acid aqueous solution, 550 g of water and 75.00 g of polymer c were added, and the mixture was stirred at 105 ° C. to 110 ° C. for 15 hours. After 15 hours, the mixture was cooled to room temperature and 1500 g of water was added dropwise. Thereafter, the solid in the system was filtered and collected, and the obtained solid was washed with water and hot water. After drying, 72.51 g of the target polymer d was obtained. The phosphorus content determined from elemental analysis of polymer d was 5.91%, and the value of x (number of phosphonic acid groups per biphenylyleneoxy group) calculated from the elemental analysis value was 1.6.

(Production method of ion conductive membrane)
The polymer electrolyte obtained in Synthesis Example 1 was dissolved in N-methylpyrrolidone to a concentration of 13.5 wt% to prepare a polymer electrolyte solution. Next, this polymer electrolyte solution was dropped on a glass plate. Then, the polymer electrolyte solution was uniformly spread on the glass plate using a wire coater. At this time, the coating thickness was controlled using a wire coater having a 0.25 mm clearance. After application, the polymer electrolyte solution was dried at 80 ° C. under normal pressure. Then, the obtained membrane was immersed in 1 mol / L hydrochloric acid, washed with ion-exchanged water, and further dried at room temperature to obtain an ion conductive membrane 1 having a thickness of 30 μm.

Example 1 (Preparation of polymer electrolyte emulsion 1)
The polymer electrolyte A 0.9 g obtained in Production Example 2 and the polymer d0.1 g which is the stabilizer obtained in Production Example 4 are dissolved in N-methylpyrrolidone (NMP) to prepare 100 g of a 1 wt% solution. did. Next, 100 g of this polymer electrolyte solution was dropped into 900 g of distilled water at a dropping rate of 3 to 5 g / min to dilute the polymer electrolyte solution. This diluted polymer electrolyte solution was sealed in a dialysis membrane dialysis cellulose tube (UC36-32-100, manufactured by Sanko Junyaku Co., Ltd .: molecular weight cut off 14,000), exposed to running water for 72 hours, and subjected to membrane separation. Processed. The polymer electrolyte solution after the treatment was concentrated using an evaporator so as to have a concentration of 2.0 wt% to prepare a polymer electrolyte emulsion. The average particle diameter of this polymer electrolyte emulsion was 394 nm. In addition, it was 4 ppm when the residual amount of NMP was performed by the gas chromatograph-mass spectrometry (GC-MASS).

(Create MEA)
0.696 g of platinum-supported carbon (SA50BK, manufactured by N.E. Chemcat) carrying 50 wt% platinum in 5.0 mL of Nafion 5 wt% solution (manufactured by Aldrich) on the anode side was added, and 11 mL of ethanol was further added. . The obtained mixture was subjected to ultrasonic treatment for 1 hour and then stirred for 5 hours with a stirrer to obtain a catalyst ink. Subsequently, in accordance with a method described in Japanese Patent Application Laid-Open No. 2004-089976, a catalyst ink was applied to a 5.2 cm square region on one side of the ion conductive membrane 1. The distance from the discharge port to the film was set to 6 cm, and the stage temperature was set to 75 ° C. After eight times of overcoating, the mixture was left on the stage for 15 minutes to remove the solvent and form a catalyst layer. Similarly, the catalyst ink was applied to the other surface to form a catalyst layer. From the composition of the catalyst layer and the applied weight, MEA in which 0.6 mg / cm ² of platinum was arranged was obtained.
When the cathode side electrode is applied to the opposite side of the MEA on which the catalyst ink is applied to the anode side on the cathode side, platinum-supported carbon (50 wt% platinum supported on 2.561 g of the polymer electrolyte emulsion 1) 1.50 g of SA50BK (manufactured by N.E. Chemcat) was added, and 16.87 g of ethanol was further added. The obtained mixture was subjected to ultrasonic treatment for 1 hour and then stirred for 5 hours with a stirrer to obtain a catalyst ink. Subsequently, in accordance with the method described in Japanese Patent Application Laid-Open No. 2004-089976, a catalyst ink was applied to a 5.2 cm square region at the center of one side of the polymer electrolyte membrane 1. The distance from the discharge port to the film was set to 6 cm, and the stage temperature was set to 75 ° C. After eight times of overcoating, the mixture was left on the stage for 15 minutes to remove the solvent and form a catalyst layer. Similarly, the catalyst ink was applied to the other surface to form a catalyst layer. From the composition of the catalyst layer and the applied weight, MEA in which 0.6 mg / cm ² of platinum was arranged was obtained.

(Fuel cell creation)
A fuel cell was manufactured using a commercially available JARI standard cell. That is, carbon cloth serving as a gas diffusion layer is disposed on both outer sides of the membrane-electrode assembly obtained using the polymer electrolyte membrane of each Example or Comparative Example, and a gas passage groove is cut on the outer side. A processed carbon separator was disposed, and a current collector and an end plate were sequentially disposed on the outside thereof, and these were tightened with bolts, thereby assembling a fuel cell having an effective membrane area of 25 cm ² .

(Power generation test)
While keeping the obtained fuel cells at 80 ° C., humidified hydrogen was supplied to the anode and humidified air was supplied to the cathode. At this time, the back pressure at the gas outlet of the cell was set to 0.1 MPaG. Each source gas was humidified by passing the gas through a bubbler. The water temperature of the hydrogen bubbler was 80 ° C., and the water temperature of the air bubbler was 80 ° C. Here, the hydrogen gas flow rate was 529 mL / min, and the air gas flow rate was 1665 mL / min. And the value of the cell voltage when a current density was set to 0.2 A / cm < ² > was measured, and the electric power generation performance of each fuel cell was evaluated. The higher the cell voltage, the better the power generation performance of the fuel cell.

Reference example 1
<When Nafion solution is used>
In Example 1, an electrode was formed on the cathode side in the same manner as the anode side, and power generation performance was evaluated.

Comparative Example 1
The power generation performance was evaluated in the same manner as in Example 1 except that dialysis was not used.

  Since the fuel cell obtained by the polymer electrolyte emulsion obtained by the method of the present invention does not contain an emulsifier, it has no catalyst poisoning and thus exhibits high power generation performance.

It is a figure which shows typically the cross-sectional structure of the fuel cell which concerns on suitable embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 12 ... Ion conduction membrane, 14a, 14b ... Catalyst layer, 16a, 16b ... Gas diffusion layer, 18a, 18b ... Separator, 20 ... MEA

Claims (12)

  A method for producing a polymer electrolyte emulsion, comprising separating a polymer electrolyte dispersion obtained by dispersing polymer electrolyte particles in a dispersion medium with a separation membrane.   The production method according to claim 1, wherein the separation membrane is a dialysis membrane or an ultrafiltration membrane.   The manufacturing method according to claim 1, wherein the membrane treatment is a dialysis membrane.   The production method according to any one of claims 1 to 3, wherein the polymer electrolyte contained in the polymer electrolyte particles is a polymer electrolyte having a fluorine atom content of 15 wt% or less in its elemental composition. The manufacturing method in any one of Claims 1-4 whose said polymer electrolyte dispersion liquid is a dispersion liquid obtained through the process of following (1) and (2).
(1) A preparation step (2) of preparing a polymer electrolyte solution by dissolving a polymer electrolyte in a solvent containing a good solvent for the polymer electrolyte, and the polymer electrolyte solution obtained in (1), Mixing process of mixing molecular electrolyte with poor solvent   6. The good solvent of the polymer electrolyte is an aprotic polar solvent selected from N-methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide and dimethylsulfoxide. The manufacturing method as described.   The polymer electrolyte emulsion obtained using the manufacturing method in any one of Claims 1-6.   The polymer electrolyte emulsion according to claim 7, wherein the content of the good solvent of the polymer electrolyte constituting the polymer electrolyte emulsion is 200 ppm or less.   The polymer electrolyte emulsion according to claim 7 or 8, wherein the volume average particle size determined by a dynamic light scattering method is 100 nm to 200 µm.   An electrode for a polymer electrolyte fuel cell comprising the polymer electrolyte emulsion according to any one of claims 7 to 9.   A membrane electrode assembly comprising the polymer electrolyte fuel cell electrode according to claim 10.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 9.

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