JP2015011838A - Solid oxide fuel battery cell and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel battery cell including a member comprising porous ceramic and having excellent cell strength and high generation power, and a method for manufacturing the solid oxide fuel battery cell.SOLUTION: In a solid oxide fuel battery cell, at least one of a support, a fuel electrode and an air electrode constituting a fuel battery cell comprises porous ceramic that is obtained by using a water-containing medium and crosslinkable water-absorbing resin fine particles, as a pore-forming agent, The water absorption amount of the crosslinkable water-absorbing resin fine particles is preferably in a range of 3-100 ml/g.

Description

  The present invention relates to a solid oxide fuel cell (hereinafter also referred to as “SOFC”) cell. More specifically, the present invention relates to a SOFC cell having excellent cell strength and high power generation and a method for manufacturing the same.

In general, the SOFC cell has a structure in which a laminated power generation element in which a solid electrolyte layer is sandwiched between a fuel electrode layer and an air electrode layer is disposed on a support having gas permeability. In many cases, the support and the fuel electrode or air electrode are integrated.
Here, fuel gas such as hydrogen, carbon monoxide or propane is supplied to the fuel electrode, and air (oxygen) is supplied to the air electrode to generate power. Various materials and cell structures have been proposed for the purpose of enhancing the power generation characteristics of SOFC, but in any case, each member of the support, fuel electrode layer, and air electrode layer should have high gas permeability. Is required.

  In order to ensure the gas permeability, when forming each member of the support, the fuel electrode layer, and the air electrode layer, a pore forming agent (also referred to as a pore-forming agent or a pore agent) is used to make it porous. Porosity) has been performed. However, since the strength of the cell decreases due to the porosity, problems such as a decrease in yield during manufacturing of the cell or a decrease in durability of the cell are likely to occur. Therefore, the pore-forming agent is required to have characteristics that can increase the porosity and do not decrease the cell strength.

In general, pore-forming agents include starch, phenolic resin, carbon fiber, carbon powder, celluloses such as polyvinyl alcohol, carboxymethylcellulose and methylcellulose, other polysaccharides, polyolefin polymers such as polyethylene and polypropylene, and polymethylmethacrylate. Acrylic or styrenic polymers obtained by emulsion polymerization or suspension polymerization of polystyrene or the like are known.
Among these, (1) dispersibility in slurry and miscibility with ceramics, (2) solvent resistance, (3) no burning residue when fired (fireability), (4) obtained by firing From the viewpoint of high electrode strength, SOFCs obtained using specific crosslinked polymer fine particles as pore forming agents have been proposed.

  Patent Document 1 discloses a SOFC material using a cross-linked polymer fine particle aggregate having an average particle size of 0.5 to 100 μm in which cross-linked polymer fine particles having an average particle size of 0.01 to 30 μm are aggregated as a pore forming agent. ing. Patent Document 2 describes an SOFC cell obtained by using a spherical resin and a fibrous resin in combination as pore forming agents. Further, Patent Document 3 discloses a method for producing an SOFC material using crosslinked polymer fine particles having a specific particle diameter and a specific coefficient of variation as a pore-forming agent.

JP 2005-327511 A JP 2006-331743 A JP 2011-34819 A

  However, in the inventions described in Patent Documents 1 to 3, it is necessary to use a relatively large amount of pore-forming agent when trying to increase the porosity. For this reason, when the pore-forming agent is burned out in a degreasing process or the like at the time of ceramic production, there is a case in which a rapid generation of decomposition heat or decomposition gas occurs, causing a problem that distortion or cracks occur in the ceramic molded body. Moreover, in order to avoid such a problem, since it is necessary to perform the treatment at a moderate temperature rise rate before and after the degreasing step, improvement has been desired from the viewpoint of productivity.

  The present invention has been made in view of the above problems. That is, it is an object of the present invention to provide an SOFC cell having excellent cell strength and high power generation obtained by using a pore-forming agent capable of obtaining a high porosity even with a small addition amount, and a method for producing the same. .

  As a result of intensive studies in view of the above problems, the present inventors have found that when a porous ceramic obtained using a water-containing medium and crosslinked water-absorbing resin fine particles as a pore-forming agent is used as a material for SOFC, it is high. The inventors have found that even if the porosity is excellent cell strength, the present invention has been completed.

The present invention is as follows.
[1] Solid oxide fuel cell, wherein at least one of a support, a fuel electrode and an air electrode constituting the fuel cell is a medium containing water and crosslinked water-absorbent resin fine particles as a pore-forming agent A solid oxide fuel cell characterized by being a porous ceramic obtained by using
[2] The solid oxide fuel cell according to [1], wherein the cross-linked water-absorbing resin fine particles have a water absorption amount of 3 to 100 ml / g at normal pressure.
[3] The solid oxide form according to the above [1] or [2], wherein the crosslinked water-absorbent resin fine particles have an average particle diameter of 1 to 100 μm when saturated and swollen with ion exchange water. Fuel cell.
[4] In air, from room temperature to 600 ° C., the rate of temperature increase is 10 ° C./min. The above-mentioned [1], wherein the decrease in heating weight in an arbitrary section where the temperature difference is 100 ° C. is 50% by mass or less when the decrease in heating weight of the crosslinked water-absorbing resin fine particles is measured under the conditions. ] The solid oxide fuel cell according to any one of [3] to [3].
[5] The solid oxide fuel cell according to any one of [1] to [4], wherein the content of sulfur element in the crosslinked water-absorbent resin fine particles is 500 mass ppm or less. .
[6] The above porous ceramic is obtained by using a binder having a structure in which a part or all of hydroxyl groups of cellulose is substituted with methoxy groups and / or hydroxyalkoxyl groups. The solid oxide fuel cell according to any one of 1] to [5].
[7] A method for producing a solid oxide fuel cell, wherein at least one of a support, a fuel electrode and an air electrode constituting the fuel cell has a water-containing medium and a cross-linking type as a pore forming agent A method for producing a solid oxide fuel cell, comprising using a porous ceramic obtained through steps including kneading, molding, drying and degreasing using water absorbent resin fine particles.

  The solid oxide fuel cell according to the present invention includes a porous ceramic whose member is made highly porous with a small amount of a pore forming agent. For this reason, it has excellent cell strength and can exhibit high power generation.

It is a figure which shows the apparatus used for the measurement of the amount of water absorption of bridge | crosslinking type water-absorbent resin fine particles. The graph which shows the heating weight decreasing behavior of the pore formation agent (crosslinked water-absorbent resin fine particles) used in the examples The graph which shows the heating weight decreasing behavior of the pore formation agent (crosslinked water-absorbent resin fine particles) used in the examples The graph which shows the heating weight reduction | decrease behavior of the pore formation agent (crosslinked water-absorbent resin fine particles) used in the comparative example 1 is a specific structural example of a solid oxide fuel cell according to the present invention. It is a figure which shows the equivalent circuit of a solid oxide fuel cell.

An embodiment of the present invention will be described as follows, but the present invention is not limited to this. In the present specification, acrylic acid or methacrylic acid is represented as (meth) acrylic acid.
<Solid oxide fuel cell (SOFC)>
The solid oxide fuel cell (SOFC) in the present invention can take various forms such as a solid electrolyte support type, an electrode support type, a flat plate type, and a cylindrical type. The structure of SOFC is generally a structure in which a cell having a structure in which a solid electrolyte is sandwiched between a fuel electrode and an air electrode, and separators for separating and distributing fuel gas and air are stacked in layers. It is.

<Support>
The support is a member for supporting a power generating element composed of a fuel electrode, a solid oxide, and an air electrode, and having a strength or form necessary for actual use as a SOFC cell. In many cases, the support is integrated with the fuel electrode or the air electrode. In this case, the support is a gas flow for passing and diffusing fuel gas, air, or gas generated during power generation. It consists of a porous ceramic with a channel.
The support preferably has a thickness of about 0.5 to 3 mm, and is generally the thickest member in the SOFC cell configuration. In addition, it is very important to control the gas permeability (porosity) of the support in order to ensure the supply of fuel and the like and the flow path of the generated gas and to ensure high power generation. The porosity of the support is preferably as high as possible within a range that maintains the required strength, and the preferable porosity is 30% or more, more preferably 35% or more, and even more preferably 40% or more.
The constituent components of the support are not particularly limited as long as the strength and redox resistance necessary for the SOFC cell can be secured. For example, iron, cobalt or nickel as well as oxides thereof may be included.

The support preferably has a coefficient of thermal expansion that matches the power generation element as much as possible. Thereby, generation | occurrence | production of a power generation element and generation | occurrence | production of a crack are suppressed.
In order to adjust the coefficient of thermal expansion, one or more of zirconia, alumina, titania, ceria, aluminum magnesium spinel, aluminum nickel spinel and the like may be used as a component of the support. Of these, stabilized zirconia is the most versatile. Examples of the stabilized zirconia include zirconia, alkaline earth metal oxides such as MgO, CaO, SrO, and BaO as stabilizers; Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , Nd Oxides of rare earth elements such as ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ ; One or two or more oxides selected from Sc ₂ O ₃ , Bi ₂ O ₃ , In ₂ O ₃ , or the like, or alumina, titania, Ta ₂ O as a dispersion strengthener ₅ , dispersion-strengthened zirconia to which Nb ₂ O ₅ or the like is added is exemplified as a preferable example.
In general, the support constituting raw material is preferably used as a powder having an average particle size of 0.1 to 3 μm, more preferably 0.5 to 1.5 μm.

<Fuel electrode>
The fuel electrode has a conductive component for imparting conductivity as an essential component, and the conductive component powder used as the material is a conductive metal in a reducing atmosphere such as iron oxide, nickel oxide, and cobalt oxide when the fuel cell is operated. Or a composite metal oxide such as nickel ferrite or cobalt ferrite containing two or more of these oxides. These may be used alone or in combination of two or more as necessary. Among these conductive components, iron oxide, cobalt oxide, and nickel oxide are highly versatile in consideration of cost and conductive characteristics, and nickel oxide is the most common.
Actually, from the viewpoint of preventing sintering between nickel particles, matching the thermal expansion coefficient with the electrolyte, and making the electrode three-dimensional, nickel is obtained by mixing the electrolyte zirconia or ceria oxide with nickel and making it porous. Cermet electrodes are often used.

  The fuel electrode may be formed on the surface of the support, for example, or may be integrated with the support. The fuel electrode is porous and preferably has a thickness of 1 to 150 μm.

<Air electrode>
As an air electrode material which comprises an air electrode, what is used as an air electrode material in a well-known solid oxide fuel cell can be used without specifically limiting. For example, a metal oxide made of Co, Fe, Ni, Cr or Mn having a perovskite structure or the like can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) MnO ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. The average particle size of the air electrode material powder is preferably 10 nm or more and 100 μm or less, more preferably 50 nm or more and 50 μm or less, and further preferably 100 nm or more and 10 μm or less. In addition, an average particle diameter can be measured according to JISR1619, for example.

  The air electrode may be formed on the surface of the support, for example, or may be integrated with the support. The air electrode is porous and preferably has a thickness of 20 to 100 μm.

<Pore forming agent>
The pore forming agent according to the present invention is an organic material that burns away at a degreasing to firing temperature of the electrode material, and is for forming pores in the electrode material.
In the present invention, crosslinked water-absorbing resin fine particles are used as the pore-forming agent. In the SOFC cell of the present invention, at least one of the support, fuel electrode and air electrode constituting the cell is kneaded, molded and dried using crosslinked water-absorbing resin fine particles as a pore-forming agent in a medium containing water. It is obtained through the steps of degreasing and firing. Moreover, you may provide the temporary baking process by the temperature lower than a baking temperature before a baking process. By using crosslinked water-absorbing resin fine particles as a pore-forming agent in a medium containing water, it becomes possible to increase the porosity of the molded body even with a small amount of pore-forming agent. The calorific value and gas generation amount can be suppressed. Therefore, distortion and cracks are less likely to occur in the obtained porous ceramic, and a sufficiently strong molded body can be obtained. As a result, the yield during SOFC cell production is improved, and the durability and gas permeability of the cell are improved. It leads to.

The crosslinked water-absorbent resin fine particles are obtained by polymerizing a radically polymerizable hydrophilic vinyl monomer by a known polymerization method such as solution polymerization, suspension polymerization, bulk polymerization, and drying and pulverizing as necessary. Although it can be obtained, the reverse phase suspension polymerization method is preferred in that it is easy to obtain micron-sized hydrophilic cross-linked resin fine particles.
In the reversed-phase suspension polymerization method, resin fine particles are obtained by w / o type suspension polymerization in which an aqueous phase (aqueous solution of hydrophilic vinyl monomer) is suspended in the form of water droplets in the oil phase in the presence of a dispersion stabilizer. Can be manufactured.
Specific examples of the dispersion stabilizer include macromonomer type dispersion stabilizers, sorbitan fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, sorbitol fatty acid esters, polyoxyethylene alkyl ethers and other nonionic surfactants.
Among these, it is preferable to use a macromonomer type dispersion stabilizer. Macromonomer type dispersion stabilizers are those having a radical polymerizable unsaturated group at the end of a polymer derived from a vinyl monomer. Also, macromonomer type dispersion stabilizers, sorbitan monooleate, sorbitan monopalmitate, etc. It is preferable to use a nonionic surfactant having a relatively high hydrophobicity with an HLB of 3 to 8, and these may be used alone or in combination of two or more.

The dispersion stabilizer is preferably added to the polymerization system after being dissolved or uniformly dispersed in a hydrophobic organic solvent forming a dispersion medium (oil phase).
In order to obtain hydrophilic polymer fine particles having a uniform particle size while maintaining good dispersion stability, the amount of the dispersion stabilizer used is 0.1 with respect to a total of 100 parts by mass of the vinyl monomer. It is preferable that it is -50 mass parts, It is more preferable that it is 0.2-20 mass parts, It is still more preferable that it is 0.5-10 mass parts. If the amount of the dispersion stabilizer used is too small, the dispersion stability of the vinyl monomer in the polymerization system and the generated polymer particles will be poor, and the generated polymer particles will aggregate, settle, and the particle size will vary. Is likely to occur. On the other hand, if the amount of the dispersion stabilizer used is too large, the amount of by-product fine particles (1 μm or less) produced may increase.

  The structural unit constituting the crosslinked water-absorbing resin fine particles of the present invention is not particularly limited as long as it is a radical polymerizable hydrophilic vinyl monomer. For example, a hydrophilic vinyl monomer having a hydrophilic group such as a carboxyl group, an amino group, a phosphoric acid group, a sulfonic acid group, an amide group, a hydroxyl group, or a quaternary ammonium group can be used. Among these, hydrophilic vinyl monomers having a carboxyl group, a sulfonic acid group, an amino group, and an amide group are preferable because polymer fine particles having high hydrophilicity and excellent water absorption performance and water retention performance can be obtained.

  Specific examples of hydrophilic vinyl monomers include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, monobutyl itaconic acid, monobutyl maleate, cyclohexanedicarboxylic acid, and other vinyl monomers having a carboxyl group. Monomers or their (partial) alkali neutralized products; N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N , N-dimethylaminopropyl (meth) acrylamide and other vinyl monomers having amino groups, or (partial) acid neutralized products or (partial) quaternized products; N-vinylpyrrolidone, acryloylmorpholine; Oxyethyl methacrylate, acid phosphooxypropi Methacrylate, vinyl monomers having a phosphate group such as 3-chloro-2-acid phosphooxypropyl methacrylate, or their (partially) alkali neutralized products; 2- (meth) acrylamide-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, 2- (meth) acryloylethanesulfonic acid, allyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl phosphonic acid, vinyl phosphonic acid and other vinyl-based phosphonic acid groups Monomers or their (partially) alkali neutralized products; (meth) acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N-methylol (meth) acrylamide, N-alkoxymethyl (meth) acrylamide, (meta ) Acrylonitrile Can be used (meth) acrylate, hydroxypropyl can be mentioned nonionic hydrophilic monomers such as (meth) acrylic acid hydroxypropyl, one or more of these

  Among these, it is excellent in polymerizability to perform reverse phase suspension polymerization using one or more of (meth) acrylic acid, (meth) acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. In addition, the obtained resin fine particles are preferable from the viewpoint of excellent water absorption characteristics, and particularly preferable are acrylic acid or acrylic resin from the viewpoint of the thermal decomposition characteristics of the polymer to be formed and the absence of poisoning elements (sulfur, phosphorus, etc.). A combination of acid and acrylamide.

  Moreover, the crosslinked water-absorbent resin fine particles of the present invention include, as a vinyl monomer, one or more of the above-described monofunctional hydrophilic vinyl monomers and a radical polymerizable unsaturated group. It can be obtained by using a polyfunctional vinyl monomer having 2 or more.

  The polyfunctional vinyl monomer may be any vinyl monomer having at least two radically polymerizable groups with the hydrophilic vinyl monomer. Specific examples thereof include polyethylene glycol di (meta ) Acrylate, polypropylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide modified tri (meth) acrylate and other di- or tri- (meta) ) Bisamides such as acrylate and methylene bis (meth) acrylamide, divinylbenzene, allyl (meth) acrylate, and the like, and one or more of these may be used.

  Among these, as the polyfunctional vinyl monomer, polyethylene glycol diacrylate and methylene bisacrylamide are excellent in solubility in a mixed solution of hydrophilic vinyl monomer and water, and are used in a large amount to obtain a high crosslinking density. And is preferably used, and particularly preferably polyethylene glycol di (meth) acrylate.

The proportion of the polyfunctional vinyl monomer used may vary depending on the type of vinyl monomer used, the intended use of the resulting polymer fine particles, etc., but the total of monofunctional vinyl monomers used The amount is preferably 0.1 to 100 mol, more preferably 0.2 to 50 mol, and still more preferably 0.5 to 10 mol with respect to 100 mol.
By using cross-linked water-absorbing resin fine particles using polyfunctional vinyl monomers, the pore-forming agent has appropriate water absorption, and has the strength to withstand the load during kneading and molding of ceramics even in the water-absorbing state. Thus, the designed porosity can be ensured. In addition, the solvent resistance of the pore forming agent is improved.

In the present invention, at least one of the support, the fuel electrode, and the air electrode constituting the SOFC cell is a porous ceramic obtained using a water-containing medium and crosslinked water-absorbing resin fine particles as a pore-forming agent. is necessary.
Porous ceramics are made by kneading, forming and drying ceramic materials such as metal oxides and inorganic compounds, pore formers, media, binders, etc., and then the organic matter containing pore formers is burned away in the degreasing to firing process. It is manufactured by forming holes in the molded body. Therefore, according to the conventional pore forming agent, it is necessary to use a large amount of the pore forming agent in order to increase the porosity. However, if the amount of pore-forming agent used is large, the amount of heat (decomposition heat) and decomposition gas generated in the degreasing to firing process increases, so that the resulting molded body is subjected to strain and load, and cracks may occur in some cases. There was a problem in terms of strength and yield of the molded body.

On the other hand, in the present invention, a porous ceramic having a high porosity can be obtained with a small amount of crosslinked water-absorbent resin fine particles (pore forming agent). The pore formation process assumed in the present invention will be described below.
In the present invention, the water-absorbent resin fine particles are present in the molded body in a swollen state due to water absorption at the time when the respective raw materials are kneaded and molded. In the drying step, moisture that has not been absorbed by the water-absorbent resin fine particles, that is, moisture in the matrix portion is preferentially evaporated, so that the periphery of the water-absorbent resin fine particles contains water and is fixed. Thereafter, when the drying is further advanced, the water in the water-absorbent resin fine particles is also evaporated, but since the periphery is fixed, pores corresponding to the evaporated water are formed. The water-absorbent resin fine particles remaining in the pores are burned off in the subsequent degreasing to firing steps. For this reason, in the present invention, a porous ceramic having a higher porosity can be produced with a smaller amount of pore-forming agent than in the prior art. In addition, since the amount of pore-forming agent used is small, there is little generation of heat and decomposition gas due to decomposition heat in the degreasing to firing process, and the pore-forming agent is greatly reduced from a water-swollen state to a dry state, so that the surrounding area is sufficient. Since it is thermally decomposed after forming a void, it is difficult to receive stress due to generation of decomposition heat or decomposition gas. Therefore, the obtained porous ceramic has excellent molded body strength.

In the present invention, the crosslinked water-absorbing resin fine particles preferably have an ionic functional group. By having an ionic functional group, it is excellent in water absorption and further has good dispersibility in water, so that it becomes easy to stably disperse in a clay containing water in the medium.
The ionic functional group is preferably an acidic functional group neutralized with an alkali, and the neutralization rate is preferably 10 to 100 mol%, more preferably 20 to 80 mol%. As the alkali, ammonia and amine compounds such as triethylamine and (mono, di, tri) ethanolamine are preferable from the viewpoint that a residue that affects battery performance does not remain after degreasing.
Here, the acidic functional group is introduced by using a vinyl monomer having an acidic group such as carboxylic acid (salt) or sulfonic acid (salt). Alternatively, a polymer can be obtained using an alkyl ester (meth) acrylate or the like and then saponified with an alkali.

  The amount of the ionic functional group in the crosslinked water-absorbent resin fine particles is preferably in the range of 0.5 to 15 mmol / g, more preferably 2 to 12 mmol / g. When the ionic functional group is 0.5 mmol / g or more, the water absorption performance is good and the dispersibility in water can be sufficiently imparted. Moreover, if it is 12.0 mmol / g or less, even when a microwave is used at the time of heat drying, the absorption difference is small and drying unevenness can be suppressed.

  In the present invention, the cross-linked water-absorbing resin fine particles preferably have a water absorption amount of 3 to 100 mL / g, more preferably a range of 10 to 50 mL / g, at normal pressure. When the amount of water absorption is less than 3 mL / g, the amount of pore-forming agent used to increase the porosity increases, and when it exceeds 100 mL / g, the moldability and the retention of the clay are compatible. It may be difficult to reduce the yield.

The crosslinked water-absorbent resin fine particles preferably have an average particle diameter in the range of 1 to 200 μm in a state of being saturated and swollen with ion exchange water, more preferably in the range of 2 to 100 μm, and further in the range of 5 to 50 μm. preferable. When the average particle size is less than 1 μm, it may be difficult to increase the porosity, and when it exceeds 200 μm, the strength of the molded product may be reduced.
The average particle diameter in the state of saturated swelling with the ion-exchanged water can be adjusted by the water absorption amount of the crosslinked water-absorbent resin fine particles, the particle diameter in the dry state, and the like. Here, the amount of water absorption depends on the hydrophilicity and the degree of crosslinking of the water-absorbent resin fine particles. In addition, the particle size in the dry state can be adjusted by, for example, the type and amount of the dispersion stabilizer, the stirring rotation speed, or the like in the reverse phase suspension polymerization.

Furthermore, the crosslinked water-absorbent resin fine particles of the present invention have a temperature rising rate of 10 ° C./min. When the weight loss by heating of the crosslinked water-absorbent resin fine particles under the conditions is measured, the weight loss by heating in an arbitrary section where the temperature difference is 100 ° C. is preferably 50% by mass or less.
The degreasing and pre-baking steps are performed under a high temperature condition of about 400 to 1300 ° C., and the crosslinked resin fine particles as the pore forming agent are burned off as described above. Here, when the pore-forming agent burns out, if it suddenly loses weight (pyrolysis) in a specific temperature range, this also increases the amount of heat generated per unit time, and cracks occur in the molded body. Or distortion may remain. If the calorific value is large, there is a method to prevent the generation of cracks and residual strain by raising the temperature very slowly near the decomposition temperature of organic matter, but it is extremely difficult to control the temperature, and the manufacturing time becomes extremely long. Therefore, there is a problem that productivity is greatly reduced. For this reason, as the pore forming agent, those exhibiting a behavior in which decomposition gradually proceeds as the temperature rises are preferable.
The weight reduction behavior due to heating of the water-absorbent resin fine particles can be controlled by, for example, the types of monomers constituting the water-absorbent resin fine particles and the blending of a stabilizer such as an antioxidant.

  The cross-linked water-absorbent resin fine particles may contain components such as sulfur, phosphorus and sodium derived from raw materials for producing the fine particles. Since these can be poisoning components of nickel, which is an electrode component, there is a concern that electrode performance such as power generation characteristics and durability may be deteriorated when included in a large amount. In particular, since sulfur has a great influence, the amount contained in the crosslinked water-absorbent resin fine particles is preferably 500 ppm by mass or less, and more preferably 100 ppm by mass or less.

<Method for producing porous ceramic>
Next, a method for producing a porous ceramic will be described.
First, ceramic raw materials composed of metal, metal oxide, inorganic compound powder, etc. are mixed, and then the mixture, crosslinked polymer fine particles which are pore forming agents, a medium containing water and a binder are blended at a predetermined ratio. Knead. If necessary, a lubricant such as an olefin wax may be blended. The kneading can be performed by using a known kneader such as a pressure kneader or a double arm kneader.
Next, the kneaded product is formed into a desired molded body by extrusion molding or the like.

In the obtained molded body, after moisture contained in the molded body is evaporated by a drying process, in the degreasing and pre-baking processes, organic substances such as cross-linked water-absorbing resin fine particles and binders as pore-forming agents are burned off, and the subsequent baking is performed. Ceramic sintering is performed in the process.
The drying to firing process may be performed by a known method, and devices such as a high-frequency dielectric heating type heating device, a hot air dryer, a heated floor dryer, a mangle dryer, and a tunnel dryer can be used. Drying is usually performed at a temperature of 150 ° C. or lower, and it is preferable to dry to a state that does not substantially contain moisture. The pre-baking and baking steps are performed by heating to a temperature exceeding 150 ° C., preferably 800 ° C. or higher, but generally 800 to 1500 ° C.

  The ratio of the amount of the ceramic raw material and the cross-linked water-absorbing resin fine particles used is 0.1 to 20 mass of the cross-linked water-absorbent resin fine particles based on 100 parts by mass of the ceramic raw material in a dry state (a state containing no water). Part is preferable, and 0.5 to 10 parts by mass is more preferable. If the amount of the crosslinked water-absorbent resin fine particles used is less than 0.1 parts by mass, a sufficient porosity may not be obtained. If it exceeds 20 parts by mass, a large amount of organic gas is generated in the degreasing and pre-baking processes, and the gas composition in the baking apparatus exceeds the explosion limit, the baking time becomes too long, or the volume change during baking is large. There may be a problem that the ceramic molded product is likely to be distorted or cracked.

As a method for adding the crosslinked water-absorbing resin fine particles in the raw material mixing, either a method of adding a water-containing state (water absorption state) or a method of adding a dry state may be used. The appearance of the water-containing crosslinked fine water-absorbing resin fine particles may be in the form of a powder or a paste.
When using crosslinked water-absorbing resin fine particles in a water-containing state, the water content is not particularly limited, but the crosslinked water-absorbing resin fine particles can be handled as a powder, that is, the crosslinked water-absorbing resin fine particle powder has fluidity. It is preferable that the water content is within the range. The reason for this is that resin fine particles with a high water content and in a gel state are difficult to handle, and mixing and dispersion with ceramic raw materials are insufficient, resulting in insufficient strength and porosity of the fired ceramic molded product. This is because there are cases.
The crosslinked water-absorbing resin fine particles in a dried powder state or a powder state in which the moisture content is adjusted are easy to mix with the ceramic raw material powder, and the resulting mixture of the cross-linked water-absorbing resin fine particles and the ceramic raw material powder is It tends to have high uniform dispersibility. That is, a method in which water is added to and mixed with the powdery mixture of the cross-linked water-absorbing resin fine particles and the ceramic raw material in which the powdered cross-linked water-absorbing resin fine particles and the powdered ceramic raw material are mixed and dispersed in advance is obtained. The resulting raw material kneaded product is likely to be uniform, and a ceramic molded product obtained by drying and firing the formed raw material kneaded material is preferred because it is likely to have high strength and uniform pore distribution. On the other hand, the powdered water-absorbing polymer particles and the powdered ceramic raw material are obtained in a method in which the crosslinked water-absorbing resin fine particles, the ceramic raw material and water are mixed substantially simultaneously without being mixed in advance. The raw material kneaded product may be non-uniform, and the ceramic molded product obtained by drying and firing the formed raw material kneaded product may have insufficient strength and pore distribution uniformity. .

  In the present invention, the medium used when kneading the ceramic raw material or the like needs to contain water. The medium may be water alone or a mixed medium of water and an organic solvent that can be mixed therewith. Examples of the organic solvent that can be mixed with water include alcohols such as methanol, ethanol, and isopropanol; acetone and the like.

Examples of the binder include a polymer containing a hydroxyl group-containing polyvinyl alcohol, polyvinyl butyral, and hydroxyethyl (meth) acrylate as a structural unit; a polymer having a carboxyl group as a structural unit containing (meth) acrylic acid; , Celluloses such as hydroxypropylmethylcellulose and hydroxyethylmethylcellulose; and other polysaccharides.
Among these, when a compound having a structure in which a part or all of hydroxyl groups of cellulose, such as methylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose, is substituted with a methoxy group and / or a hydroxyalkoxyl group, is used as a binder. Since the gelation at the time of drying is fast, the periphery of the water-absorbent resin fine particles as the pore-forming agent is likely to be fixed before the water is removed. For this reason, compared with other binders, the balance between formability and shape retention is good, which is advantageous in terms of increasing the porosity.

In addition to the above components, surfactants, dispersants, plasticizers, antifoaming agents, and the like may be used as necessary.
Among these, a surfactant can be added to adjust the plasticity of the clay, and a nonionic surfactant is particularly preferable.
The dispersing agent can be used for unraveling the raw material powder and promoting dispersion, for example, polyelectrolytes such as polyacrylic acid and ammonium polyacrylate; organic acids such as citric acid and tartaric acid; isobutylene or styrene and anhydrous Examples thereof include copolymers with maleic acid, ammonium salts thereof, amine salts, copolymers of butadiene and maleic anhydride, and the like.

<Method for producing electrode cell>
In the present invention, a SOFC cell having a solid oxide layer sandwiched between a fuel electrode and an air electrode, wherein at least one of a support, a fuel electrode and an air electrode constituting the cell is obtained by the above method. It is characterized by being. Especially, since the intensity | strength of a SOFC cell can be made sufficient, it is preferable to apply the said porous ceramic to a support body. In this case, the support and the fuel electrode or the air electrode may be integrated. The SOFC cell of the present invention may have a structure having an intermediate layer between the solid oxide layer and the fuel electrode or the air electrode.
When the porous ceramic is not used for the fuel electrode or the air electrode, these electrode material layers are made of organic materials such as glycerin, dibutyl phthalate, dioctyl phthalate, and polyethylene glycol as a plasticizer in addition to a conductive component, a skeleton component, and a pore forming agent. Can be formed into a paste and formed by a screen printing method, a dip coating method, a knife coating method, a spin coating method, a spray coating method or a green sheet method.

  Examples of the dispersion medium used during green sheet production and coating / printing include alcohols such as water, methanol, ethanol, isopropanol, 1-butanol, 1-hexanol and 1-hexanol; ketones such as acetone and 2-butanone. Aliphatic hydrocarbons such as pentane, hexane and heptane; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; and acetates such as methyl acetate, ethyl acetate and butyl acetate can be appropriately selected and used. . These dispersion media can also be used alone or in combination of two or more as necessary. The most common of these dispersion media is isopropanol, toluene, ethyl acetate and the like.

  As the solid electrolyte, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria-based oxides doped with samarium or gadolinium, lanthanum galade-based oxides doped with strontium or magnesium, An oxygen ion conductive ceramic material such as zirconia oxide containing scandium or yttrium can be used.

  In addition, a plurality of the SOFC cells of the present invention can be electrically connected to each other via a current collecting member to form a fuel cell stack. According to the cell stack composed of the SOFC cell of the present invention, it is excellent in mechanical strength and can ensure high power generation performance.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to the following examples at all. In the following description, “part” means part by mass, and “%” means mass%.
In the following examples, evaluation of the crosslinked water-absorbent resin fine particles was performed by the following method.

(1) About 1 g of a solid content measurement sample was weighed (a), then the residue after drying for 60 minutes at 150 ° C. in an airless dryer was measured (b), and calculated from the following formula. A weighing bottle was used for the measurement. Other operations were in accordance with JIS K 0067-1992 (chemical product weight loss and residue test method).
Solid content (%) = (b / a) × 100

(2) Water absorption The water absorption was measured by the following method. The measuring device is shown in FIG.
The measuring device is composed of <1> to <3> in FIG.
<1> Consists of a burette 1 with a branch pipe for venting air, a pinch cock 2, a silicon tube 3, and a polytetrafluoroethylene tube 4.
<2> A support cylinder 8 having a large number of holes in the bottom surface on the funnel 5, and a filter paper 10 for the apparatus is installed on the support cylinder 8.
<3> The sample 6 of polymer fine particles is sandwiched between two sample fixing filter papers 7, and the sample fixing filter papers are fixed by an adhesive tape 9. All filter papers used are ADVANTEC No. 2 The inner diameter is 55 mm.
<1> and <2> are connected by the silicon tube 3.
Further, the funnel 5 and the column cylinder 8 are fixed to the burette 1 at a fixed height, and the lower end of the polytetrafluoroethylene tube 4 installed inside the buret branch pipe and the bottom surface of the column cylinder 8 have the same height. (Dotted line in FIG. 1).

The measurement method will be described below.
The pinch cock 2 in <1> is removed, and ion exchange water is introduced from the upper part of the burette 1 through the silicon tube 3 so that the burette 1 to the apparatus filter paper 10 are filled with the ion exchange water 12. Next, the pinch cock 2 is closed, and air is removed from the polytetrafluoroethylene tube 4 connected to the buret branch pipe with a rubber stopper. In this way, the ion exchange water 12 is continuously supplied from the burette 1 to the filter paper 10 for the apparatus.
Next, after removing the excess ion-exchanged water 12 that oozes from the filter paper for apparatus 10, the reading (a) of the scale of the burette 1 is recorded.
Weigh 0.1 to 0.2 g of the dry powder of the measurement sample and place it uniformly on the center of the sample fixing filter paper 7 as shown in <3>. The sample is sandwiched with another filter paper, and the two filter papers are fastened with the adhesive tape 9 to fix the sample. The filter paper on which the sample is fixed is placed on the apparatus filter paper 10 shown in <2>.
Next, the reading (b) of the scale of the bullet 1 after 30 minutes from the time when the lid 11 is placed on the filter paper 10 for apparatus is recorded.
The sum (c) of the amount of water absorption of the measurement sample and the amount of water absorption of the two sample fixing filter papers 7 is obtained by (ab). By the same operation, the water absorption of only two filter papers 7 not including the polymer fine particle sample is measured (d).
The above operation was performed, and the water absorption was calculated from the following formula. In addition, the value measured by the method of (1) was used for solid content used for calculation.
Water absorption (mL / g) = (cd) / {measurement sample weight (g) × (solid content% ÷ 100)}

(3) Water saturation swelling particle diameter 20 ml of ion exchange water was added to 0.02 g of the measurement sample, and the sample was uniformly dispersed by shaking sufficiently. Further, in order to make the particles saturated and swollen with ion-exchanged water, the dispersion liquid dispersed for 30 minutes or more was irradiated with ultrasonic waves for 1 minute using a laser diffraction scattering type particle size distribution meter (manufactured by Nikkiso, MT-3000). Later, the particle size distribution was measured. Ion exchange water was used as the circulating dispersion medium at the time of measurement, and the refractive index of the dispersion was 1.53. The median diameter (μm) was calculated from the particle size distribution on the basis of the volume obtained by the measurement, and was defined as the water-swelled particle diameter.

(4) Reduction in heating weight The thermal decomposition characteristics of the crosslinked water-absorbent resin fine particles were measured with a differential thermothermal weight simultaneous measurement apparatus (TG-DTA, manufactured by SII NanoTechnology, SII EXSTAR6000). In air, the temperature was raised from room temperature to 600 ° C. at a heating rate of 10 ° C./min, and the weight reduction behavior due to heating was evaluated.
In the measured temperature range, the case where the weight loss in an arbitrary section where the temperature difference is 100 ° C. is 50% by mass or less is “◯”, and the weight loss in the section where the temperature difference is 100 ° C. may exceed 50% by mass. The thing was judged as "x".

(5) Amount of sulfur element The sulfur element content (wtppm) in the crosslinked water-absorbent resin fine particles was measured using a trace chlorine sulfur analyzer (manufactured by Mitsubishi Chemical Corporation, "TOX-100").

Production Example 0: Production of Macromonomer Composition UM-1 The temperature of the oil jacket of a 1000 ml capacity pressurized stirred tank reactor equipped with an oil jacket was kept at 240 ° C.
75.0 parts of lauryl methacrylate (hereinafter referred to as “LMA”) as a monomer, 25.0 parts of acrylic acid (hereinafter referred to as “AA”), 10.0 parts of methyl ethyl ketone as a polymerization solvent, ditertiary butyl as a polymerization initiator A monomer mixed liquid adjusted at a ratio of 0.45 parts of peroxide was charged into a raw material tank.
Start supplying the monomer mixture from the raw material tank to the reactor, and supply the monomer mixture and remove the reaction mixture so that the weight in the reactor is 580 g and the average residence time is 12 minutes. went. The reactor internal temperature was adjusted to 235 ° C., and the reactor internal pressure was adjusted to 1.1 MPa. The reaction mixture extracted from the reactor is decompressed to 20 kPa, continuously supplied to a thin film evaporator maintained at 250 ° C., and discharged as a macromonomer composition from which monomers and solvents are distilled off. . Distilled out monomers and solvents were cooled with a condenser and recovered as a distillate. After the start of the monomer mixture supply, 60 minutes after the reactor internal temperature was stabilized at 235 ° C., the recovery start point was set, and the reaction was continued for 48 minutes to recover the macromonomer composition UM-1. During this time, 2.34 kg of the monomer mixture was supplied to the reactor, and 1.92 kg of the macromonomer composition was recovered from the thin film evaporator. In addition, 0.39 kg of distillate was recovered in the distillate tank.
When the distillate was analyzed by gas chromatography, LMA 31.1 parts, AA 16.4 parts, other solvents, etc. were 52.5 parts with respect to 100 parts of distillate.
From the amount and composition of the monomer mixture, the recovered amount of the macromonomer composition, the recovered amount and composition of the distillate, the monomer reaction rate is 90.2%, and the composition of the macromonomer composition UM-1 The monomer composition ratio was calculated as LMA: AA = 76.0 / 24.0 (mass ratio).

Further, when the molecular weight of the macromonomer composition UM-1 was measured by gel permeation chromatograph (hereinafter referred to as “GPC”) using tetrahydrofuran as an eluent, the weight average molecular weight (hereinafter referred to as “Mw”) in terms of polystyrene was measured. And number average molecular weight (hereinafter referred to as “Mn”) were 3800 and 1800, respectively. Moreover, the density | concentration of the terminal ethylenically unsaturated bond in a macromonomer composition was measured from the < ¹ > H-NMR measurement of a macromonomer composition. As a result of calculating the terminal ethylenically unsaturated bond introduction rate of the macromonomer composition UM-1 from the concentration of the terminal ethylenically unsaturated bond by ¹ H-NMR measurement, Mn by GPC, and the constituent monomer composition ratio, 97 %Met. The solid content of the heating residue after heating at 150 ° C. for 60 minutes was 98.3%.
In addition, about each raw material, such as a monomer, a polymerization solvent, and a polymerization initiator, the commercially available industrial product was used as it was, without performing processes, such as refinement | purification.

(Production Example 1: Production of crosslinked water-absorbent resin fine particles PA-1)
For the polymerization, a reactor having a stirring mechanism comprising a stirring blade and a baffle, and further equipped with a thermometer, a reflux condenser, and a nitrogen introduction tube was used.
In the reactor, 1.5 parts of UM-1 as a dispersion stabilizer, 2.0 parts of sorbitan trioleate (trade name “Leodol AO-10V” manufactured by Kao Corporation), and 395 parts of n-heptane as a polymerization solvent. The oil phase in which the dispersion stabilizer was completely dissolved was prepared by charging and stirring. The oil phase was adjusted to 15 ° C.
On the other hand, AA 100.0 parts, Aronix M-243 (manufactured by Toagosei Co., Ltd., polyethylene glycol diacrylate, average molecular weight 425) 13.0 parts (corresponding to 2.2 mol% with respect to the monofunctional monomer) in another container ), And 94.9 parts of ion-exchanged water were added and stirred and dissolved uniformly. Further, while cooling so that the temperature of the mixed solution was kept at 40 ° C. or lower, 70.8 parts of 25% ammonia water was slowly added to neutralize to obtain a monomer mixed solution (a total of 148 parts of water).
While stirring the oil phase at a predetermined stirring speed, the monomer mixture was charged into the reactor to prepare a dispersion in which the monomer mixture was dispersed in the oil phase. After maintaining the reactor internal temperature at 15 ° C. and purging the reactor with nitrogen, a solution prepared by dissolving 0.07 part of hydrosulfite sodium in 2.3 parts of ion-exchanged water was added to the reactor. Three minutes later, Parkmill H80 (manufactured by NOF Corporation, 80% solution of cumene hydroperoxide) diluted with 5.0 parts of n-heptane was added to the reactor. An increase in temperature was observed. After reaching the peak temperature, the internal temperature was cooled to 25 ° C., and then a solution obtained by dissolving 0.05 part of hydrosulfite sodium in 1.7 parts of ion-exchanged water was added to the reactor. When a solution obtained by diluting 0.015 part of H69 (manufactured by NOF Corporation, 69% solution of t-butyl hydroperoxide) with 1.5 parts of ion exchange water was added to the reactor, The temperature rose. After reaching the peak temperature, the mixture was cooled to 20 ° C. to obtain a dispersion in water of crosslinked water-absorbent resin fine particles PA-1 (including water in the particles). Thereafter, the reactor was heated to azeotropically circulate water and n-heptane, and after removing water from the water separator until the dehydration rate reached 95%, the slurry in the reactor was filtered, and further n-heptane was filtered. After rinsing with n, n-heptane was removed by heating to obtain powder of crosslinked water-absorbent resin fine particles PA-1.
Table 1 shows the analysis results of the obtained crosslinked water-absorbent resin fine particles PA-1. Moreover, the result of the heating weight reduction | decrease measurement of PA-1 is shown in FIG. As is clear from the results of FIG. 2, PA-1 had a weight loss of 50% by mass or less in an arbitrary section where the temperature difference was 100 ° C. in the measured temperature range.

(Production Examples 2 and 4-8)
From Production Example 1, only the stirring speed was changed to obtain crosslinked water-absorbent resin fine particles PA-2 and PA-4 to 8 having different water saturated swelling particle diameters. The results of each analysis are shown in Table 1. Moreover, the behavior of the weight loss by heating of PA-2 and PA-4 to 8 was almost the same as PA-1.

(Production Example 3)
For the polymerization, a reactor having a stirring mechanism comprising a stirring blade and a baffle, and further equipped with a thermometer, a reflux condenser, and a nitrogen introduction tube was used.
The reactor is charged with 1.5 parts of UM-1 as a dispersion stabilizer, 2.0 parts of sorbitan trioleate (trade name “Leodol SP-O30V” manufactured by Kao Corporation), and 395 parts of n-heptane as a polymerization solvent. The oil phase in which the dispersion stabilizer was completely dissolved was prepared by stirring. The oil phase was adjusted to 15 ° C.
On the other hand, AA 50.0 parts, concentration 40% acrylamide aqueous solution (hereinafter referred to as “40% AMD”) 125 parts (50.0 parts as AMD), Aronix M-243 8.3 parts (monofunctional) Equivalent to 1.4 mol% with respect to the monomer), and 46.4 parts of ion-exchanged water were added and stirred and uniformly dissolved. Further, while cooling so as to keep the temperature of the mixed solution at 40 ° C. or lower, 35.4 parts of 25% ammonia water was slowly added to neutralize to obtain a monomer mixed solution (total of 148 parts of water).
While stirring the oil phase at a predetermined stirring speed, the monomer mixture was charged into the reactor to prepare a dispersion in which the monomer mixture was dispersed in the oil phase. The reactor internal temperature was maintained at 15 ° C., the inside of the reactor was replaced with nitrogen, and then a solution prepared by dissolving 0.07 part of hydrosulfite sodium in 0.23 part of ion-exchanged water was added to the reactor. After a minute, a solution obtained by diluting 0.03 part of Park Mill H80 (manufactured by NOF Corporation, 80% solution of cumene hydroperoxide) with 5.0 parts of n-heptane was immediately added to the reactor. An increase was confirmed. After reaching the peak temperature, the internal temperature was cooled to 25 ° C., and then a solution obtained by dissolving 0.05 part of hydrosulfite sodium in 1.7 parts of ion-exchanged water was added to the reactor. When a solution obtained by diluting 0.015 part of H69 (manufactured by NOF Corporation, 69% solution of t-butyl hydroperoxide) with 1.5 parts of ion-exchanged water was added to the reactor, the internal temperature gradually increased due to polymerization of the residual monomer. Rose. After reaching the peak temperature, the mixture was cooled to 20 ° C. to obtain a dispersion of crosslinked water-absorbent resin fine particles PA-3 (including water in the particles) in oil. Thereafter, the reactor was heated to azeotropically circulate water and n-heptane, and after removing water from the water separator until the dehydration rate reached 95%, the slurry in the reactor was filtered, and further n-heptane was filtered. After rinsing with n, n-heptane was removed by heating to obtain powder of crosslinked water-absorbent resin fine particles PA-3.
Table 1 shows the analysis results of the obtained crosslinked water-absorbent resin fine particles PA-3. Moreover, the result of the heating weight reduction | decrease measurement of PA-3 is shown in FIG. As is apparent from the results of FIG. 3, PA-3 had a weight loss of 50% by mass or less in an arbitrary section where the temperature difference was 100 ° C. in the measured temperature range.

(Production Examples 9 to 11)
From Production Example 3, the monomer composition and the amount of 25% ammonia water were changed as shown in Table 2, and the amount of ion-exchanged water was changed so that the total amount of water in the monomer mixture was 148 parts. did. In addition, the stirring speed was also adjusted so as to achieve the target water-swelled particle size. Otherwise, the same operation as in Production Example 3 was performed to obtain crosslinked water-absorbent resin fine particles PA-9 to 11 having different ionic functional group concentrations and water absorption amounts. Table 2 shows the results of each analysis. Moreover, the behavior of PA-9 to 11 in reducing the heating weight was almost the same as that of PA-3.

(Production Examples 12-14)
From Production Example 1, the amount of M-243 was changed as described in Table 2. In addition, the stirring speed was also adjusted so as to achieve the target water-swelled particle size. Otherwise, the same operation as in Production Example 1 was performed to obtain crosslinked water-absorbing resin fine particles PA-12 to 14 having different water absorption amounts. Table 2 shows the results of each analysis. In addition, the heating weight reduction behavior of PA-12 to 14 was almost the same as that of PA-1.

(Production Examples 15 and 16)
From Production Example 2, the monomer composition and the amount of 25% ammonia water were changed as shown in Table 2, and the amount of ion-exchanged water was changed so that the total amount of water in the monomer mixture was 148 parts. did. In the table, ATBS means 2-acrylamido-2-methylpropanesulfonic acid (ATBS, manufactured by Toagosei Co., Ltd.). Otherwise, the same operation as in Production Example 2 was performed to obtain crosslinked water-absorbing resin fine particles PA-15 and 16 having different types and concentrations of ionic functional groups.
Table 2 shows the analysis results of the obtained crosslinked water-absorbent resin fine particles PA-15 and 16. Moreover, the behavior of the weight loss by heating of PA-15 and 16 was almost the same as PA-1.

(Production Example 17)
From Production Example 2, hydrosulfite sodium was changed to ascorbic acid, and the amount used was 0.14 parts for the first addition and 0.10 parts for the second addition. Otherwise, the same operation as in Production Example 2 was performed to obtain crosslinked water-absorbent resin fine particles PA-17.
Table 2 shows the analysis results of the obtained crosslinked water-absorbent resin fine particles PA-17. Moreover, the behavior of heating weight reduction of PA-17 was almost the same as PA-1.

(Comparative polymer fine particles)
As the polymer fine particles for comparison of the pore-forming agent, commercially available true spherical crosslinked polymethyl methacrylate fine particles having no water absorption performance, 3 types, PN-1 (manufactured by Sekisui Chemical Co., Ltd., Techpolymer MBX-5, average particle size 5 μm) ), PN-2 (same, MBX-12, average particle size 12 μm), and PN-3 (same, MBX-30, average particle size 30 μm).
The weight loss by heating was measured for each polymer fine particle, and the results are shown in Table 3. Moreover, the result of the heating weight reduction | decrease measurement of PN-1 is shown in FIG. As is clear from the results of FIG. 4, PN-1 decomposes rapidly from around 270 ° C., and the weight loss in the temperature range of 100 ° C. up to 370 ° C. is 92.4% by mass, which is much higher than 50% by mass. It was a thing. A similar behavior was observed for the reduced heating weight of PN-2 and 3.

Example 1
As metal oxide powder, 60 parts of NiO powder and 40 parts of 8YSZ (yttria-stabilized zirconia: (Y ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 ) powder, hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., product) (Name “60SH-4000”: hereinafter “HPMC”) 8 parts, 1 part of powder of the crosslinked water-absorbent resin fine particles PA-1 as a pore-forming agent was mixed and charged into a kneader, and further 1 part of a nonionic surfactant, And 35 parts of water was added and kneaded to prepare a clay having plasticity suitable for extrusion molding. This clay is processed into a cylindrical shape by extrusion molding, dried under hot air at 100 to 200 ° C., then degreased (thermal decomposition and removal of organic matter) and pre-baked at 1000 ° C. in an air atmosphere, and an outer diameter of 4 mm. A calcined molded body of a cylindrical fuel electrode / support having an inner diameter of 2 mm and a length of 40 mm was obtained. The appearance of the obtained molded body was visually observed, evaluated according to the following criteria, and the results are shown in Table 4.
○: Deformation was not observed and cracks were not generated as compared with before pre-firing.
Δ: Slight deformation or cracking is observed.
X: A remarkable deformation | transformation or a crack is recognized.

The temporary fired body was fired at 1400 ° C. for 3 hours in an air atmosphere to obtain a single molded body (molded body 1) of the fuel electrode / support. The porosity (%) of the obtained fuel electrode support was measured by mercury porosimetry. Further, the three-point bending strength (MPa) was measured in accordance with JIS R 1601. The results are shown in Table 4.
Further, a slurry prepared by mixing 8YSZ powder, an acrylic binder, and toluene was applied to the temporary fired molded body by a dip coating method, dried, and further fired at 1400 ° C. for 3 hours to obtain a molded body 1 A molded body (molded body 2) in which the electrolyte layer was laminated with a thickness of 25 μm on the surface of was obtained. Next, a slurry comprising LSM-20 / 8YSZ ((La _0.80 Sr _0.20 ) MnO ₃ : (Y ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 = 1: 1) powder, an acrylic binder, and toluene is formed into the above molded body 2. And then dried by dip coating, and further fired at 1100 ° C. for 3 hours to laminate an intermediate layer on the surface of the molded body 2, followed by LSM-20 ((La _0.80 Sr _0.20 ) MnO ₃ ) powder Then, a slurry composed of acrylic binder and toluene was laminated in the same manner to obtain a molded body (molded body 3) in which the intermediate layer and the air electrode layer were laminated on the surface of the molded body 2 with a total thickness of 25 μm. In the molded body 3, the length of the air electrode layer was 20 mm. A front view and a side view of the molded body 3 are shown in FIG.
Next, a power generation experiment was performed using the obtained molded body 3 as a cell. Silver wire and silver paste were used for current collection. The cell used was reduced with hydrogen at 750 ° C. immediately before the power generation experiment. Hydrogen diluted with nitrogen as a fuel was allowed to flow inside the cell heated to 700 ° C. by an electric furnace. The flow rates were 40 cc / min hydrogen and 40 cc / min nitrogen. In addition, air was passed as an oxidant at 1000 cc / min outside the cell. The electric resistance of the cell was measured by the 4-terminal method, and AC impedance measurement was performed at a frequency of 0.2 Hz to 20 kHz at a current of 0.1 A to obtain an impedance spectrum. The internal resistance of the cell can be separated into an ohmic resistance Rohm, a high frequency component Rh, and a low frequency component Rl by fitting the impedance spectrum to the equivalent circuit shown in FIG. Rh (Ω) was calculated from the high frequency side arc of the obtained impedance spectrum, and Rl (Ω) was calculated from the low frequency side arc. The results are shown in Table 4. Rh corresponds to the activation polarization of the fuel electrode and depends on the state of Ni at the fuel electrode. Rl corresponds to the concentration dispersion of the fuel electrode and depends on the pore formation state of the fuel electrode. It can be determined that the smaller the Rh and Rl, the smaller the internal resistance and the better the power generation characteristics.

(Examples 2 to 8)
Except for changing the cross-linked water-absorbing resin fine particles used as the pore-forming agent to the type shown in Table 4, the same operation as in Example 1 was performed, and the porosity (%) of the single molded body of the fuel electrode / support was determined. , And three-point bending strength (MPa). Further, the same operation as in Example 1 was performed to calculate Rh (Ω) and Rl (Ω) of the cell. These results are shown in Table 4.

(Comparative Examples 1-4)
The same procedure as in Example 1 was performed except that the polymer fine particles used as the pore-forming agent were changed to the types and addition amounts shown in Table 4, and the porosity (% ) And three-point bending strength (MPa). Further, the same operation as in Example 1 was performed to calculate Rh (Ω) and Rl (Ω) of the cell. These results are shown in Table 4.

(Comparative Example 5)
Except not using a pore formation agent, operation similar to Example 1 was performed and the porosity (%) and the three-point bending strength (MPa) were measured about the single molded object of the fuel electrode and support body. Further, the same operation as in Example 1 was performed to calculate Rh (Ω) and Rl (Ω) of the cell. These results are shown in Table 4.

(Examples 9 to 14)
Except for changing the crosslinked water-absorbing resin fine particles used as the pore-forming agent to the type shown in Table 5, the same operation as in Example 1 was performed, and the porosity (%) of the single molded body of the fuel electrode / support was determined. , And three-point bending strength (MPa). Further, the same operation as in Example 1 was performed to calculate Rh (Ω) and Rl (Ω) of the cell. These results are shown in Table 5.

(Examples 15 to 17)
The same procedure as in Example 1 was carried out except that the crosslinked water-absorbent resin fine particles used as the pore-forming agent were changed to PA-15 to 17 having a different impurity element amount compared to PA-2. The porosity (%) and three-point bending strength (MPa) of the single molded body of the support were measured. Further, the same operation as in Example 1 was performed to calculate Rh (Ω) and Rl (Ω) of the cell. These results are shown in Table 5.

(Example 18)
Except for changing the binder type from HPMC to PVA (manufactured by Kuraray, PVA-124), the same operation as in Example 1 was performed, and the porosity (%) and 3 The point bending strength (MPa) was measured. Further, the same operation as in Example 1 was performed to calculate Rh (Ω) and Rl (Ω) of the cell. These results are shown in Table 5.

As is clear from the results in Table 4, in Examples 1 to 8 using the cross-linked water-absorbent resin as the pore-forming agent, the porosity of the fuel electrode support is sufficiently high, and Rl is remarkably reduced as an effect. It was. Furthermore, the strength was also excellent.
When Examples 1, 2, 4 and 5 were compared, it was confirmed that the larger the particle size, the larger the porosity and the smaller Rl. This is presumed to be due to a decrease in the proportion of small-diameter particles that do not participate in pore formation. However, the strength tended to decrease slightly. Further, in Examples 6 to 8 having a large particle diameter, Rl tended to be rather large. This is considered to be because the decrease in the number of pore-forming agents affects the increase in Rl in the region where the small particles not involved in pore formation are almost eliminated.

  On the other hand, Comparative Examples 1 to 4 using polymer fine particles that do not exhibit water absorption as a pore-forming agent are difficult to obtain a ceramic with a high porosity, and in order to obtain a porosity comparable to the Examples, a large amount of addition Although the amount was necessary, the reduction in the strength of the molded product was significant. This is thought to be due to the effect of heat of decomposition during degreasing.

Examples 9 to 14 are experimental examples when cross-linked water-absorbing resin fine particles having different ionic functional group concentrations and water absorption properties were used as pore-forming agents. The cell characteristics were excellent. The tendency of Examples 9 to 11 is that when the water-saturated swelling particle diameter is almost the same, the larger the ionic functional group concentration and the water absorption amount, the larger the number of pore-forming agents even when the same weight is added, and the higher the porosity. Conceivable. On the other hand, in Examples 12 to 14, the porosity does not depend on the water absorption amount when the water absorption amount is increased to about 100 ml / g, and the porosity tends to decrease rather at 100 ml / g or more. This is presumably because the pore-forming agent with a high water absorption amount has a small force for retaining water in the clay.
From the results of Examples 15 to 17 and other examples, the other examples show better Rh values compared to Example 16 having a relatively large amount of sulfur element, and are superior in power generation characteristics. A result was obtained.
From the comparison of Examples 2 and 18, it is more preferable to use a compound having a structure in which part or all of the hydroxyl groups of cellulose such as HPMC are substituted with methoxy groups and / or hydroxyalkoxyl groups as a binder. And excellent results in terms of Rl values.

  The solid oxide fuel cell of the present invention is excellent in cell strength because at least one of the support, the fuel electrode and the air electrode is made of a porous ceramic whose porosity has been increased by a small amount of a pore forming agent. ing. Thereby, it is possible to obtain a solid oxide fuel cell having excellent power generation characteristics and excellent durability.

1 Burette 2 Pinch cock 3 Silicone tube 4 Polytetrafluoroethylene tube 5 Funnel 6 Sample (polymer fine particles)
7 Sample (polymer fine particle) fixing filter paper 8 Support cylinder 9 Adhesive tape 10 Device filter paper 11 Lid 12 Ion exchange water 21 Fuel electrode / support 22 Electrolyte layer 23 Intermediate layer + Air electrode layer

Claims (7)

A solid oxide fuel cell, wherein at least one of a support, a fuel electrode and an air electrode constituting the fuel cell uses a medium containing water and crosslinked water-absorbent resin fine particles as a pore-forming agent. A solid oxide fuel cell, which is a porous ceramic obtained. 2. The solid oxide fuel cell according to claim 1, wherein the water-absorbing amount of ion-exchanged water at normal pressure of the crosslinked water-absorbent resin fine particles is 3 to 100 ml / g. 3. The solid oxide fuel cell according to claim 1, wherein an average particle diameter of the crosslinked water-absorbent resin fine particles in a state of being saturated and swollen with ion-exchanged water is 1 to 100 μm. In air, from room temperature to 600 ° C., the rate of temperature increase is 10 ° C./min. 2. The heating weight reduction in an arbitrary section where the temperature difference is 100 ° C. when measuring the heating weight reduction of the crosslinked water-absorbent resin fine particles under the conditions is 50% by mass or less. The solid oxide fuel cell according to any one of -3. The solid oxide fuel cell according to any one of claims 1 to 4, wherein the content of sulfur element in the crosslinked water-absorbent resin fine particles is 500 mass ppm or less. The porous ceramic is obtained by using a binder having a structure in which part or all of hydroxyl groups of cellulose are substituted with methoxy groups and / or hydroxyalkoxyl groups. The solid oxide fuel cell according to any one of the above. A method for producing a solid oxide fuel cell, wherein at least one of a support, a fuel electrode and an air electrode constituting the fuel cell includes a water-containing medium and a crosslinked water-absorbing resin as a pore-forming agent A method for producing a solid oxide fuel cell, comprising using a porous ceramic obtained through steps including kneading, molding, drying and degreasing using fine particles.

Images