JP5275704B2 - Proton conductive material and method for producing the same - Google Patents

Description

  The present invention relates to a proton conductive material that maintains high proton conductivity and is excellent in thermal stability and hot water elution, and a method for producing the same.

  A fuel cell directly converts chemical energy into electrical energy by supplying fuel and an oxidant to two electrically connected electrodes and causing the fuel to be oxidized electrochemically. Unlike thermal power generation, fuel cells are not subject to the Carnot cycle, and thus exhibit high energy conversion efficiency. A fuel cell is usually formed by laminating a plurality of single cells having a basic structure of a membrane / electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes. Among them, a solid polymer electrolyte fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane has advantages such as easy miniaturization and operation at a low temperature. It is attracting attention as a power source for the body.

In the solid polymer electrolyte fuel cell, when hydrogen is used as the fuel, the reaction of the formula (1) proceeds at the anode (fuel electrode).
H ₂ → 2H ⁺ + 2e ⁻ (1)
The electrons generated by the equation (1) reach the cathode (oxidant electrode) after working with an external load via an external circuit. Then, the proton generated in the formula (1) moves by electroosmosis from the anode side to the cathode side in the solid polymer electrolyte membrane in a state of being hydrated with water.

Further, when oxygen is used as the oxidizing agent, the reaction of the formula (2) proceeds at the cathode.
2H ⁺ + (1/2) O ₂ + 2e ⁻ → H ₂ O (2)
The water produced at the cathode mainly passes through the gas diffusion layer and is discharged to the outside. As described above, the fuel cell is a clean power generation device that has no emissions other than water.

  A polymer electrolyte membrane operable in a temperature range of a commonly used solid polymer electrolyte fuel cell is composed of an organic polymer type proton conductive material having a polymer as a basic skeleton or main chain. Problems with the proton-conducting material include dimensional changes such as expansion and contraction of the membrane during water absorption and drainage, and creep or thermal contraction due to heat. It is known that the balance of water and heat changes frequently under load and external environment under the operating environment of the fuel cell, but the accompanying dimensional change of the membrane is an important issue that shortens the life of the electrolyte. In addition, current organic polymer type proton conductive materials cannot be solved in principle.

  Based on the above problems, development of inorganic polymer type proton conductive materials has been actively conducted in recent years. Patent Document 1 discloses a technique related to a proton conductive material using a mechanical pulverization method for a crystalline metal phosphate such as zirconium phosphate and the like.

  Patent Document 2 discloses a technique relating to a proton conductive material obtained by adding a metal phosphate to phosphosilicate gel or silica gel.

  Further, Patent Document 3 discloses a technique related to a proton conductive material obtained by adding zirconium phosphate to a polymer compound having ion conductivity.

  In addition, an unprecedented organic polymer type proton conductive material has been developed. Patent Document 4 discloses a technique related to a fullerene polymer having proton conductivity in which a sulfonic acid group is introduced into fullerene, which is a carbon allotrope, and fullerene derivatives are crosslinked with biphenyl or the like.

JP 2003-289311 A JP 2004-55181 A JP 2006-147478 A JP 2002-193861 A

Among the above, Patent Documents 1 to 3 use a metal phosphate that is an inorganic material. In general, in an inorganic material, when a proton conductive group is added to improve proton conductivity, the shape retention is extremely poor because it is hydrated to become a liquid with high fluidity. Therefore, metal phosphate has a limit in improving proton conductivity.
In Patent Document 4, there is a limit to the proton conductive group that can be directly introduced onto one fullerene molecule consisting of only a finite number of carbon atoms. Therefore, there is a limit in improving proton conductivity in this case as well.

As a result of intensive studies on the proton conductive material, the present inventors have developed a material in which hollow inorganic fine particles having through holes on the surface are filled with an electrolyte resin, and the material impairs mechanical properties and shape. It has been found that high proton conductivity is exhibited without any patent application (Japanese Patent Application No. 2007-246203).
In the above patent application, hollow inorganic fine particles having through holes on the surface are mixed with a monomer having a sulfonic acid group or a precursor group thereof, and the monomer is filled in the inorganic fine particles under reduced pressure. A method for producing a proton conductive material for polymerizing the monomer is also proposed. According to this method, the polymer is filled into the inorganic fine particles by the subsequent polymerization reaction by a simple operation of filling the inorganic fine particles into the inorganic fine particles from the through holes of the inorganic fine particles, without impairing the mechanical properties and shape. A proton conductive material capable of improving proton conductivity can be provided.

  The present inventors further studied the proton conductive material, and found a proton conductive material excellent in thermal stability and hot water elution and a method for producing the same. That is, the present invention has been accomplished through the above-described research, and a proton conductive material that maintains a high proton conductivity and is excellent in thermal stability and heat-resistant water elution, and a method for producing the same. The purpose is to provide.

In the proton conductive material of the present invention, hollow inorganic fine particles having through holes on the surface are filled with an electrolyte resin having a Si-O skeleton, and the inorganic fine particles and the electrolyte resin are cross -linked by Si-O bonds. It is characterized by.

In the proton conductive material having such a configuration, the infinite number of proton conductive groups of the electrolyte resin filled in the cavity of the inorganic fine particles, which are the outer shell of the proton conductive material, have through holes on the surface of the inorganic fine particles. Since the proton conductivity is high and the electrolyte resin is confined in the inorganic fine particles having a fixed particle size, the proton conductive material does not swell and contract. Further, even if the proton conductive material of the present invention is usually in a state of high fluidity such as introducing a large amount of proton conductive groups into the structure of the electrolyte resin, Since it is held in the cavities of the inorganic fine particles, it is possible to achieve both improvement in shape retention and proton conductivity in the proton conductive material.
Further, the proton conductive material of the present invention, the said inorganic particulate electrolyte and the resin, because it is cross-linked by chemically stable and rigid Si-O bond, more excellent thermal stability, and thermal Even in water, the electrolyte resin does not elute from the inorganic fine particles, and a more stable shape can be maintained.
In addition, the proton conductive material of the present invention can easily cause a polymerization reaction when the inorganic fine particles are filled with a monomer as a raw material of the electrolyte resin and polymerized to synthesize the electrolyte resin. Easy to manufacture. In the proton conductive material of the present invention, since the monomer has a high affinity with the inorganic fine particles and can be easily filled, the proton conductive material can be synthesized quickly.

In the proton conductive material of the present invention, the inorganic fine particles are preferably SiO ₂ .

The proton conductive material having such a structure has mechanical characteristics because the inorganic fine particles that are the outer shell of the proton conductive material are formed of SiO ₂ that is a chemically stable and rigid inorganic material. Excellent, stable shape can be maintained without shrinking / expanding due to water and heat balance.

  The proton conductive material of the present invention preferably has an ion exchange capacity larger than that of the inorganic fine particles.

  The proton conductive material having such a configuration can ensure proton conductivity higher than that of the inorganic fine particles by filling the electrolyte resin in the inorganic fine particles.

  The proton conductive material of the present invention preferably has an ion exchange capacity of 0.5 meq / g or more.

  The proton conductive material having such a configuration can have sufficient proton conductivity.

  The proton conductive material of the present invention preferably has an average particle size of 0.05 to 10 μm.

  The proton conductive material having such a configuration can be formed into an appropriate thickness.

  In the proton conductive material of the present invention, the bulk density of the inorganic fine particles is preferably 20% or less of the true density of the inorganic fine particles.

  The proton conductive material having such a structure can fill the inorganic fine particles with a sufficient amount of the electrolyte resin.

  In the method for producing a proton conductive material of the present invention, hollow inorganic fine particles having through-holes on the surface and a monomer having a sulfonic acid group are mixed, and the inorganic fine particles are filled in the inorganic fine particles under reduced pressure. The monomer is polymerized, and after the polymerization, a binder is added and repolymerized to crosslink the inorganic fine particles and the polymerized electrolyte resin by chemical bonding.

  The proton conductive material according to the present invention can be obtained by the method for producing a proton conductive material having such a configuration. Further, the method for producing a proton conductive material of the present invention fills the monomer from the through-holes of the inorganic fine particles into the inorganic fine particles by a simple operation of placing both the inorganic fine particles and the monomer under reduced pressure. Further, the polymer can be polymerized in the inorganic fine particles by the subsequent polymerization reaction. In addition, the method for producing a proton conductive material of the present invention is characterized in that the inorganic fine particles and the above-mentioned inorganic fine particles, which are one of the characteristics of the proton conductive material according to the present invention, are obtained by further adding a binder and repolymerizing after monomer polymerization Crosslinks of chemical bonds with the electrolyte resin can be easily formed.

  In the method for producing a proton conductive material of the present invention, at least one selected from a hydrocarbonoxysilane compound, a bis (trihydrocarbonoxysilyl) alkane compound, and a bis (trihydrocarbonoxysilyl) aryl compound is used as the binder. It is preferable to use it.

  In the method for producing a proton conductive material having such a structure, a Si—O bond bridge is formed between the inorganic fine particles and the electrolyte resin by using a compound having a Si—O bond as the binder. Proton conductive material is obtained.

  In the method for producing a proton conductive material of the present invention, the amount of the binder added is preferably 5 to 40 parts by weight when the amount of the inorganic fine particles added is 100 parts by weight.

  With the method for producing a proton conductive material having such a configuration, a proton conductive material in which cross-linking of Si—O bonds is appropriately formed can be obtained.

According to the present invention, innumerable proton conductive groups of the electrolyte resin filled in the cavity of the inorganic fine particles that are the outer shell of the proton conductive material of the present invention are exposed from the through holes on the surface of the inorganic fine particles. Therefore, since the proton conductivity is high and the electrolyte resin is confined in the inorganic fine particles having a fixed particle diameter, the proton conductive material does not swell and contract. Further, according to the present invention, even if the fluidity is normally high, such as introducing a large amount of proton conductive groups into the structure of the electrolyte resin, Since it is held in the cavity, it is possible to achieve both improvement in shape retention and proton conductivity in the proton conductive material.
Furthermore, according to the present invention, since the inorganic fine particles and the electrolyte resin are cross-linked by a chemical bond, they are excellent in thermal stability, and the electrolyte resin is contained in the inorganic fine particles even in hot water. A stable shape can be maintained without elution.

  The proton conductive material of the present invention is characterized in that hollow inorganic fine particles having through holes on the surface thereof are filled with an electrolyte resin, and the inorganic fine particles and the electrolyte resin are crosslinked by chemical bonds.

Hereinafter, the proton conductive material of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a typical example of the proton conductive material of the present invention, and is a diagram in which a particulate proton conductive material is cut into circles. The lower right circle is an enlarged view of the cross section, and is a diagram schematically showing the structural formulas of the inorganic fine particles and the electrolyte resin. The broken line connecting the silicon atom and the sulfonic acid group in the lower right circle represents an alkyl chain. The proton conductive material 100 includes an electrolyte resin 1 and inorganic fine particles 2, and the hollow inorganic fine particles 2 are filled with the electrolyte resin 1. The inorganic fine particles 2 have innumerable through holes, and the electrolyte resin 1 is exposed on the particle surface through the through holes.
Further, the electrolyte resin 1 and the inorganic fine particles 2 are cross-linked by a chemical bond (Si—O bond in FIG. 1).

  As in the structural formula schematically shown in the lower right circle of FIG. 1, the electrolyte resin 1 preferably has a Si—O skeleton. The electrolyte resin 1 has a proton conductive group such as a sulfonic acid group. The sulfonic acid group is preferably exposed on the surface of the proton conductive material 100 through the through holes of the inorganic fine particles 2 as shown in the lower right circle of FIG.

  A typical example of the electrolyte resin having a Si—O skeleton is a polymer in which a Si—O skeleton is formed by polymerizing a monomer. Such a polymer can easily cause a polymerization reaction when the inorganic fine particles are filled with a monomer as a raw material of the electrolyte resin and polymerized to synthesize the electrolyte resin. Further, since the monomer has a high affinity with the inorganic fine particles and can be easily filled, the proton conductive material can be synthesized quickly. Furthermore, since the electrolyte resin has a strong polymer chain called a Si—O skeleton, proton conductive groups do not leak out of the proton conductive material.

  In addition, the electrolyte resin 1 may be a polymer electrolyte usually used in a fuel cell. Polyelectrolyte here refers to polyether polymer ketone, polyether ketone, polyether sulfone, polyphenylene sulfide, in addition to fluorine-based polymer electrolytes such as perfluorocarbon sulfonic acid resin represented by Nafion (trade name). Protonic acid groups such as sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, and boronic acid groups on hydrocarbon polymers such as engineering plastics such as polyphenylene ether and polyparaphenylene, and general-purpose plastics such as polyethylene, polypropylene, and polystyrene ( Hydrocarbon polymer electrolytes into which proton conductive groups) have been introduced.

  The inorganic fine particles 2 are required to have a sufficient filling amount inside the particles, and have a low internal resistance to flow and are easy to be filled when the monomer as the raw material of the electrolyte resin 1 is filled. It is not necessarily limited to a complete hollow body, and may have some internal structures in the form of partitions on the pillars.

  In addition, the through-holes on the surface of the inorganic fine particles 2 have a low resistance to flow when the monomer as the raw material of the electrolyte resin 1 is filled, and the monomer is addition-polymerized or polycondensed inside the particles. It is required that the electrolyte resin produced in this way has a size in an appropriate range that does not easily flow out.

In order to satisfy the properties of the inside of the inorganic fine particles 2 and the through holes as described above, the inorganic fine particles 2 are preferably SiO ₂ . Since the proton conductive material 100 has a rigid shell made of SiO _2, it has an advantage of excellent mechanical properties.

The proton conductive material 100 preferably has an ion exchange capacity larger than the ion exchange capacity of the inorganic fine particles 2 itself, and the ion exchange capacity of the proton conductive material 100 is 0.5 meq / g or more. Is preferred.
If the ion exchange capacity of the proton conductive material 100 is smaller than the ion exchange capacity of the inorganic fine particles 2, no improvement in ion conductivity can be expected even if an ion conductive group is added. If the ion exchange capacity of the proton conductive material 100 is less than 0.5 meq / g, sufficient power generation efficiency can be expected when the proton conductive material 100 is used, for example, in an electrolyte membrane of a fuel cell. Absent.

  The holding power of the electrolyte resin of the proton conductive material after polymerization depends on either the average diameter or the number of through-holes of the inorganic fine particles, or the fluidity of the polymerized electrolyte resin. It is difficult to measure or observe. Even if these values can be obtained, it must be comprehensively evaluated from the relationship with the proton conductivity proportional to the filling amount of the electrolyte fat filled in the cavity of the inorganic fine particles. From such a viewpoint, the ion exchange capacity of the proton conductive material remaining in the particle cavity without flowing out even in hot water, that is, the residual ion exchange capacity after the hydrothermal treatment test is 0.5 meq / g or more. Is more preferable.

The proton conductive material 100 preferably has an average particle size of 0.05 to 10 μm.
If the average particle size of the proton conductive material 100 is less than 0.05 μm, it is not large enough to hold a sufficiently filled electrolyte resin. On the other hand, when the average particle diameter of the proton conductive material 100 exceeds 10 μm, it becomes impossible to use it for an electrolyte membrane having an appropriate thickness, for example.

The bulk density of the inorganic fine particles 2 is preferably 20% or less of the true density of the inorganic fine particles 2. If the bulk density of the inorganic fine particles 2 exceeds 20% of the true density of the inorganic fine particles 2, a sufficient amount of electrolyte resin cannot be filled.
More preferably, from the viewpoint of avoiding particle destruction, the bulk density of the inorganic fine particles 2 may be 5% or more of the true density of the inorganic fine particles 2.

The chemical bond referred to in the present invention refers to a connection between atoms, and includes both a covalent bond that shares electrons between atoms and an ionic bond that does not share electrons between atoms. In detail, it includes coordination bonds in which electrons are provided from only one atom, metal bonds that are mainly maintained by valence electrons, and bonds by intermolecular electrostatic interactions, van der Waals mutuals. It includes bonds by action, hydrogen bonds, and bonds by charge transfer interactions.
Among these, in the present invention, the inorganic fine particles and the electrolyte resin are preferably crosslinked by a covalent bond.

The chemical bond is preferably a Si—O bond. This is because the inorganic fine particles and the electrolyte resin are cross-linked by a chemically stable and rigid Si—O bond, and thus are more excellent in thermal stability and hot water elution.
The electrolyte resin 1 and the inorganic fine particles 2 may be bonded to each other by a silicon atom and an oxygen atom, and directly crosslinked by a Si—O bond, or indirectly through a binder. May be cross-linked by -O bond

According to the present invention, the countless proton conductive groups of the electrolyte resin filled in the cavities of the inorganic fine particles are exposed from the through holes on the surface of the inorganic fine particles, so that the proton conductivity is high, and the electrolyte resin is Since it is confined to inorganic fine particles with a fixed particle size, there is no swelling or shrinkage of the proton conductive material. Further, according to the present invention, even if the fluidity is normally high, such as introducing a large amount of proton conductive groups into the structure of the electrolyte resin, Therefore, it is possible to achieve both improvement in shape retention and proton conductivity in the proton conductive material.
Furthermore, according to the present invention, since the inorganic fine particles and the electrolyte resin are cross-linked by chemical bonding, the thermal stability is excellent, and the electrolyte resin does not elute from the inorganic fine particles even in hot water. , Can keep a stable shape.

  In the method for producing a proton conductive material of the present invention, hollow inorganic fine particles having through-holes on the surface and a monomer having a sulfonic acid group are mixed, and the inorganic fine particles are filled in the inorganic fine particles under reduced pressure. The monomer is polymerized, and after the polymerization, a binder is added and repolymerized to crosslink the inorganic fine particles and the polymerized electrolyte resin by chemical bonding.

As the inorganic fine particles, it is preferable to use microcapsules (trade name: Washin microcapsules) whose main component is SiO ₂ , but other inorganic fine particle porous hollow bodies may be used. Specifically, in addition to the above SiO ₂ , silsesoxane, zeolite, and the like can be given. However, mesoporous silica does not correspond to the hollow inorganic fine particles used in the present invention because the electrolyte resin easily flows out from the inside of the particles and it is difficult to hold the electrolyte resin.
As a method for producing inorganic fine particles, styrene monomer is polymerized in the presence of a vinyl monomer having a cationic surfactant group to obtain polystyrene fine particles having an ionic group on the surface. The polystyrene fine particles are subjected to a hydrolytic condensation reaction of tetraethoxysilane to form silica on the surfaces of the polystyrene fine particles. Next, hollow silica microcapsules are obtained by dissolving and removing polystyrene with a solvent.
The microcapsules must be treated with an acid such as hydrochloric acid prior to the production of the proton conductive material to remove impurities in advance.

  The polymerization of the monomer here includes addition polymerization and polycondensation. In addition, a resin that is a polymer having a large molecular weight from the beginning cannot be used because it is difficult to fill at the time of decompression. Therefore, a monomer can be used for filling.

As the monomer, a compound that is a repeating unit of the electrolyte resin to be filled in the cavity of the hollow inorganic fine particles is used.
For example, when it is desired to fill inorganic fine particles with perfluorocarbon sulfonic acid conventionally used in the field of polymer electrolyte fuel cells, a monomer that forms a fluorocarbon skeleton such as fluoroethylene can be used.
When it is desired to fill the inorganic fine particles with an electrolyte resin having a Si—O skeleton, a hydrocarbonoxysilane compound and / or a silanol compound having a sulfonic acid group or a precursor group thereof can be used. The hydrocarbonoxysilane compound that can be used here is a sulfonic acid group or a precursor group thereof bonded directly or indirectly to a silicon atom, and a hydrocarbonoxy group that may contain a different atom is bonded to the same silicon atom. A compound having a bonded structure. The hydrocarbonoxy group is a group in which an oxygen atom is bonded to an aliphatic or aromatic hydrocarbon group such as an alkoxy group or an aryloxy group, and the oxygen atom is bonded to a silicon atom. is there. The hydrocarbonoxy group may contain a hetero atom. When the sulfonic acid group or its precursor group is indirectly bonded to the silicon atom, it may be bonded via, for example, an aliphatic or aromatic hydrocarbon group, and the hydrocarbon group is bonded to a hetero atom. May be included. The silanol compound that can be used here is a compound having a structure in which a sulfonic acid group or a precursor group thereof is bonded directly or indirectly to a silicon atom and a hydroxyl group is bonded to the same silicon atom.
Examples of the hydrocarbonoxysilane compound and / or the silanol compound include, for example, a Si atom, a sulfonic acid hydrocarbon group (which may contain a different atom), a hydroxyl group (—OH) and / or an alkoxy group or an aryl group. A silicon compound bonded to an oxy group (which may contain a different atom) is preferably used. More specifically, those having a structure represented by the following formula (1), formula (2) and formula (3) can be mentioned.

（式中、Ｒ^１は炭素数１〜４の脂肪族炭化水素基又は炭素数６〜１０の芳香族炭化水素基であり、且つ、ｎ＝１〜４である。）

(In the formula, R ¹ is an aliphatic hydrocarbon group having 1 to 4 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms, and n = 1 to 4).

  As the monomer having a sulfonic acid group precursor group, a compound that can be derived from the above-described monomer having a sulfonic acid group can be used. For example, in the above formulas (1), (2), and (3) Examples of the corresponding monomer include those having a structure represented by the following formula (4), formula (5), and formula (6).

（式中、Ｒ^２〜Ｒ^９は互いに独立であり、水素原子、異種原子を含んでいてもよく好ましくは炭素数１〜４の脂肪族炭化水素基、及び異種原子を含んでいてもよく好ましくは炭素数６〜１０の芳香族炭化水素基からなる群から選択される官能基である。また、ｎ＝１〜４である。Ｘ^１〜Ｘ^４は互いに独立であり、チオール基、スルフィニル基、スルホン酸フルオリド、スルホン酸クロリド、スルホン酸ブロミド、スルホン酸ヨージド、スルホン酸リチウム、スルホン酸カリウム又はスルホン酸ナトリウム等のスルホン酸基の前駆体基のうちのいずれかから選択される官能基である。）

(In the formula, R ^{2 to} R ⁹ are independent of each other, and may contain a hydrogen atom, a heteroatom, or preferably an aliphatic hydrocarbon group having 1 to 4 carbon atoms and a heteroatom. Is a functional group selected from the group consisting of aromatic hydrocarbon groups having 6 to 10 carbon atoms, and n = 1 to ^4. X ^{1 to} X ⁴ are independent of each other, and are a thiol group or a sulfinyl group. , Sulfonic acid fluoride, sulfonic acid chloride, sulfonic acid bromide, sulfonic acid iodide, lithium sulfonic acid, potassium sulfonate, sodium sulfonate, and other functional groups selected from precursor groups of sulfonic acid groups .)

  In synthesizing the electrolyte resin, two or more monomers may be used.

As a method for converting a precursor group of a sulfonic acid group into a sulfonic acid group, for example, when the precursor group is a thiol group or a sulfinyl group, it is converted into a sulfonic acid group by adding an oxidizing agent such as hydrogen peroxide. Or when the precursor group is sulfonic acid fluoride, sulfonic acid chloride, sulfonic acid bromide, sulfonic acid iodide, lithium sulfonic acid, potassium sulfonic acid, sodium sulfonic acid or the like, an acid such as hydrochloric acid or sulfuric acid, or It can be converted to a sulfonic acid group by adding a base such as an aqueous sodium hydroxide solution.
Further, the precursor group of the sulfonic acid group is not limited to the above, and includes, for example, the case where X ^{1 to} X ⁴ in the above formulas (4) to (6) are terminal olefins. In this case, it can be converted into an alkyl group having a sulfonic acid group at the terminal by treating with sulfur trioxide and then treating with a base.

The filling conditions of the monomer into the inorganic fine particles are preferably 1 to 200 mmHg as a degree of vacuum, 20 to 100 ° C., and 1 to 6 hours. Moreover, as polymerization conditions in the inorganic fine particles of the monomer, it is preferable to perform heat treatment at 80 to 150 ° C. for 2 to 24 hours under reduced pressure.
In addition, the chemical bond may be already formed between the electrolyte resin and the inorganic fine particles during the filling and polymerization. However, as shown by the TGA measurement and hot water resistance test in the later examples, the proton conductive material of the example that had undergone repolymerization with the binder and the proton of the comparative example that had not undergone repolymerization with the binder Due to the difference in thermal stability and hot water resistance with conductive materials, the number of chemical bonds that affect the physical properties of the proton conductive material itself during the filling and polymerization described above are It is reasonable to think that it is not formed.

  As the binder, it is preferable to use at least one selected from a hydrocarbonoxysilane compound, a bis (trihydrocarbonoxysilyl) alkane compound, and a bis (trihydrocarbonoxysilyl) aryl compound.

  As the hydrocarbonoxysilane compound, for example, a compound in which an alkoxy group or an aryloxy group (which may contain a different atom) is bonded to a Si atom is preferably used. More specifically, those having a structure represented by the following formula (7) can be mentioned.

（式中、Ｒ^１０〜Ｒ^１３は互いに独立であり、異種原子を含んでいてもよく好ましくは炭素数１〜４の脂肪族炭化水素基、及び異種原子を含んでいてもよく好ましくは炭素数６〜１０の芳香族炭化水素基からなる群から選択される官能基である。）

(In the formula, R ^{10 to} R ¹³ are independent of each other and may contain a heteroatom, preferably an aliphatic hydrocarbon group having 1 to 4 carbon atoms, and may contain a heteroatom, preferably a carbon number. It is a functional group selected from the group consisting of 6 to 10 aromatic hydrocarbon groups.)

  The bis (trihydrocarbonoxysilyl) alkane compound is a compound in which two silicon atoms are bonded to an aliphatic hydrocarbon group, and three hydrocarbonoxy groups are bonded to the silicon atom. is there. As the bis (trihydrocarbonoxysilyl) alkane compound, for example, a compound in which an alkoxy group or an aryloxy group (which may contain a different atom) is bonded to an Si atom is preferably used. More specifically, those having a structure represented by the following formula (8) can be mentioned.

（式中、Ｒ^１４〜Ｒ^１９は互いに独立であり、異種原子を含んでいてもよく好ましくは炭素数１〜４の脂肪族炭化水素基、及び異種原子を含んでいてもよく好ましくは炭素数６〜１０の芳香族炭化水素基からなる群から選択される官能基である。また、Ｒ^２０は脂肪族炭化水素基であり、好ましくは、炭素数１〜９の脂肪族炭化水素基である。）

(In the formula, R ^{14 to} R ¹⁹ are independent of each other and may contain a heteroatom, preferably an aliphatic hydrocarbon group having 1 to 4 carbon atoms, and may contain a heteroatom, preferably a carbon number. A functional group selected from the group consisting of 6 to 10 aromatic hydrocarbon groups, and R ²⁰ is an aliphatic hydrocarbon group, preferably an aliphatic hydrocarbon group having 1 to 9 carbon atoms. .)

  The bis (trihydrocarbonoxysilyl) aryl compound is a compound in which two silicon atoms are bonded to an aromatic hydrocarbon group, and three hydrocarbonoxy groups are bonded to the silicon atom. is there. As the bis (trihydrocarbonoxysilyl) aryl compound, for example, a compound in which an alkoxy group or an aryloxy group (which may contain a different atom) is bonded to a Si atom is preferably used. More specifically, those having a structure represented by the following formula (9) can be mentioned.

（式中、Ｒ^２１〜Ｒ^２６は互いに独立であり、異種原子を含んでいてもよく好ましくは炭素数１〜４の脂肪族炭化水素基、及び異種原子を含んでいてもよく好ましくは炭素数６〜１０の芳香族炭化水素基からなる群から選択される官能基である。また、Ｒ^２７は芳香族炭化水素基であり、好ましくは、炭素数６〜１０の芳香族炭化水素基である。）

(In the formula, R ^{21 to} R ²⁶ are independent of each other and may contain a heteroatom, preferably an aliphatic hydrocarbon group having 1 to 4 carbon atoms, and may contain a heteroatom, preferably a carbon number. A functional group selected from the group consisting of 6 to 10 aromatic hydrocarbon groups, and R ²⁷ is an aromatic hydrocarbon group, preferably an aromatic hydrocarbon group having 6 to 10 carbon atoms. .)

  In the method for producing a proton conductive material having such a structure, a Si—O bond bridge is formed between the inorganic fine particles and the electrolyte resin by using a compound having a Si—O bond as the binder. Proton conductive material is obtained.

  The amount of the binder added is preferably 5 to 40 parts by weight when the amount of the inorganic fine particles added is 100 parts by weight. This is because if the amount of the binder added is less than 5 parts by weight, sufficient crosslinking of the Si—O bond between the inorganic fine particles and the electrolyte resin is not formed, and the amount of the binder added temporarily. When the amount exceeds 40 parts by weight, the binder-derived non-proton conductive layer is formed thick on the surface of the inorganic fine particles, and the proton conductivity decreases.

  As a preparatory stage for performing repolymerization, a binder is added in advance to a container different from that in which the above-described filling / polymerization reaction has been performed, and further an alcohol such as methanol and ethanol, and an aqueous acid solution such as hydrochloric acid, sulfuric acid, and nitric acid. It is preferable to slowly drop the mixed solvent and stir at 20 to 60 ° C. for 3 to 24 hours. By this procedure, the binder can be uniformly distributed inside and on the surface of the inorganic fine particles added during the subsequent repolymerization.

  As a procedure for repolymerization, the inorganic fine particles filled with the polymer described above are added to the container after the preparation step described above, and after stirring at 20 to 60 ° C. for 2 to 24 hours, the solvent is distilled off under reduced pressure. The heat treatment is performed at 80 to 150 ° C. for 2 to 24 hours. After heat treatment, homogenized with a mortar, etc., washed several times with an appropriate solvent, and dried under reduced pressure at 60 to 120 ° C. for 2 to 6 hours, whereby the proton conductive material of the present invention described above Is obtained.

  According to the present invention, the above-described proton conductive material is obtained. In addition, according to the present invention, the monomer can be filled from the through-holes of the inorganic fine particles into the inorganic fine particles by a simple operation of placing both the inorganic fine particles and the monomer under reduced pressure, and the subsequent polymerization reaction Thus, the polymer can be polymerized in the inorganic fine particles. In addition, according to the present invention, a chemical bond cross-linking between the inorganic fine particles and the electrolyte resin, which is one of the features of the proton conductive material according to the present invention, is performed by adding a binder and repolymerizing after the monomer polymerization. Can be easily formed.

1. Pretreatment of inorganic fine particles 10.0 g of microcapsules (trade name: Washin Microcapsule) as hollow inorganic fine particles having through-holes on the surface were added to 200 mL of 0.1N hydrochloric acid and stirred for one day. Thereafter, the mixture was allowed to stand to precipitate microcapsules, and the supernatant was removed. After adding 200 mL of distilled water and stirring well, it was allowed to stand and the supernatant was removed in the same manner. Thus, addition of distilled water, stirring, and removal of the supernatant were repeated until pH = 7.
Finally, the remaining precipitate was dried under reduced pressure at 120 ° C. under vacuum for 6 hours.

2. Production of proton conductive material [Example 1]
0.10 g (100 parts by weight) of the inorganic fine particles after the pretreatment described above are used as a monomer having a sulfonic acid group, a 3- (trihydroxysilyl) -1-propanesulfonic acid solution (manufactured by Gelest) 1.54 g having a concentration of 30 wt%. Added to. Then, pressure reduction (100 mmHg, 25 degreeC, 2 hours) was performed in order to fill the inorganic fine particles with the monomer. The pressure was further reduced for 3 hours to remove moisture, and the monomer was polymerized by performing heat treatment at 80 ° C. for 1 day under reduced pressure.
Next, 0.034 g (34 parts by weight) of tetraethoxysilane as a binder was added to another flask, and a 1: 1 mixed solvent of ethanol and 0.01 N hydrochloric acid was slowly added dropwise. After stirring at room temperature for 24 hours, the polymerized polymer was added, and the mixture was further stirred at 60 ° C. for 24 hours. Thereafter, the solvent was distilled off under reduced pressure, and repolymerization was carried out by heating at 80 ° C. for 12 hours under reduced pressure.
Then, after homogenizing using a mortar, it wash | cleaned 3 times with ion-exchange water, and dried under reduced pressure (120 degreeC, 6 hours). As a result, 0.23 g of a proton conductive material which was a white solid was obtained.

[Comparative Example 1]
0.10 g of the inorganic fine particles after the pretreatment described above were added to 1.54 g of a 3- (trihydroxysilyl) -1-propanesulfonic acid solution (manufactured by Gelest) having a concentration of 30 wt% as a monomer having a sulfonic acid group. Then, pressure reduction (100 mmHg, 25 degreeC, 2 hours) was performed in order to fill the inorganic fine particles with the monomer. The pressure was further reduced for 3 hours to remove moisture. Subsequently, the monomer was polymerized by heat treatment at 80 ° C. for 12 hours under reduced pressure. Then, after homogenizing using a mortar, it wash | cleaned 3 times with ion-exchange water, and dried under reduced pressure (120 degreeC, 6 hours). As a result, 0.36 g of a proton conductive material which was a white solid was obtained.

3. TGA measurement and evaluation of proton conductive material TGA (Thermogravimetric) with respect to the proton conductive material of Example 1 and Comparative Example 1 and the pre-treated inorganic fine particles (that is, the particles immediately before filling the electrolyte resin). analysis). FIG. 2 is a graph showing TGA curves of the proton conductive materials of Example 1 and Comparative Example 1 and inorganic fine particles after pretreatment.
The proton conductive materials of Example 1 and Comparative Example 1 have less weight loss between 0 ° C. and 150 ° C. compared to the inorganic fine particles after the pretreatment. Since it is considered that the weight loss in this temperature section is due to the desorption of moisture, the proton conductive materials of Example 1 and Comparative Example 1 have a temperature of 0 to 150 ° C. compared to inorganic fine particles not having an electrolyte resin. It is considered that moisture is moderately retained in the meantime.
Moreover, the weight reduction between 250-400 degreeC is considered to be based on detachment | desorption of a sulfonic acid group, Furthermore, the weight reduction above 400 degreeC is considered to be based on decomposition | disassembly of an organic part. Therefore, the proton conductive materials of Example 1 and Comparative Example 1 can maintain thermal stability up to 200 ° C., and the proton conductive material of Example 1 is compared with that of Comparative Example 1. Thus, it was found that the effect of suppressing the elimination of the sulfonic acid group and the decomposition of the organic portion was great.

4). Hot water resistance test of proton conductive material and its evaluation The proton conductive material of Example 1 and Comparative Example 1 was immersed in hot water at 80 ° C. for 30 minutes, and then the weight was measured. The weight loss rate was calculated. Table 1 is a table showing the weight reduction rate of the proton conductive materials of Example 1 and Comparative Example 1.

  From Table 1, the weight reduction rate of the proton conductive material of Comparative Example 1 was 34%, whereas the weight reduction rate of the proton conductive material of Example 1 was only 26%. Therefore, it was found that the proton conductive material of Example 1 was further improved in hot water resistance as compared with that of Comparative Example 1.

5. Production of electrolyte membrane having proton conductive material [Example 2]
Polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) 0.10 g (50 parts by weight), which is a type of polymer for improving film-forming properties, is added to dimethylacetamide (50 parts by weight) in an eggplant flask under nitrogen. (DMA) In a volume of 1.5 mL, 0.10 g (50 parts by weight, average particle size of 3 to 5 μm) of the proton conductive material synthesized in Example 1 was added and stirred at room temperature for one day under nitrogen. After completion of the stirring, the stirring bar was taken out and stirred for 30 minutes using an ultrasonic homogenizer, and PVDF-HFP and the proton conductive material of Example 1 were monodispersed in the solution.
The monodispersed solution was cast on a Teflon (registered trademark) petri dish and allowed to stand under a nitrogen stream at 60 ° C. for 24 hours to obtain a wet gel film. In order to remove the residual solvent in the wet gel film, it was dried under reduced pressure for 12 hours under the condition of 120 ° C. under vacuum, and 0.2 g of a translucent and flexible electrolyte film was obtained.

[Comparative Example 2]
In an eggplant flask under nitrogen, 0.10 g (50 parts by weight) of PVDF-HFP, which is a kind of polymer for improving the film forming property, was dissolved in 1.5 mL of dimethylacetamide (DMA) and synthesized in Comparative Example 1. 0.10 g (50 parts by weight, average particle size 3 to 5 μm) of the proton conductive material was added and stirred at room temperature for 1 day under nitrogen. After completion of the stirring, the stirring bar was taken out and stirred for 30 minutes using an ultrasonic homogenizer, and PVDF-HFP and the proton conductive material of Comparative Example 1 were monodispersed in the solution.
The treatment of the monodispersed solution was the same as in Example 2 described above, and 0.2 g of a translucent and flexible electrolyte membrane was obtained after the treatment.

6). Measurement of proton conductivity of electrolyte membrane having proton conductive material Before and after hydrothermal treatment, the electrolyte membranes of Example 2 and Comparative Example 2 were immersed in hot water at 80 ° C. for 30 minutes. The proton conductivity of was measured. Table 1 is a table comparing the proton conductivity of the electrolyte membranes of Example 2 and Comparative Example 2 before and after the hydrothermal treatment.

  From Table 2, it can be seen that the proton conductivity of the electrolyte membrane of Comparative Example 2 changes significantly before and after the hydrothermal treatment, and therefore the electrolyte membrane of Comparative Example 2 has low hot water resistance. On the other hand, the proton conductivity of the electrolyte membrane of Example 2 hardly changes before and after the hot water treatment, and thus it can be seen that the electrolyte membrane of Example 2 has high hot water resistance. From these results, it was found that the electrolyte membrane of Example 2 was further improved in hot water resistance as compared with that of Comparative Example 2, and maintained high proton conductivity even after the hydrothermal treatment.

6). Summary From the above TGA measurement and hot water resistance test results, it was found that the proton conductive material of Example 1 had improved thermal stability and hot water resistance compared to the proton conductive material of Comparative Example 1. From the proton conductivity measurement results, it was found that the electrolyte membrane of Example 2 kept high proton conductivity even after the hot water treatment as compared with the electrolyte membrane of Comparative Example 2.

It is the figure which showed the typical example of the proton-conductive material contained in the electrolyte membrane for fuel cells of this invention, and is the figure which cut the particulate proton-conductive material into pieces. It is the graph which showed the TGA curve of the proton-conductive material of Example 1 and Comparative Example 1, and the inorganic fine particle after a pretreatment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st electrolyte resin 2 ... Inorganic fine particle 100 ... Proton conductive material

Claims (9)

Protons characterized in that hollow inorganic fine particles having through-holes on the surface are filled with an electrolyte resin having a Si-O skeleton, and the inorganic fine particles and the electrolyte resin are crosslinked by Si-O bonds. Conductive material. The proton conductive material according to claim 1 , wherein the inorganic fine particles are SiO ₂ . The proton conductive material according to claim 1 or 2 , which has an ion exchange capacity larger than that of the inorganic fine particles. The proton conductive material according to any one of claims 1 to 3 , wherein the ion exchange capacity is 0.5 meq / g or more. The proton conductive material according to any one of claims 1 to 4 , wherein the average particle size is 0.05 to 10 µm. The proton conductive material according to any one of claims 1 to 5 , wherein a bulk density of the inorganic fine particles is 20% or less of a true density of the inorganic fine particles.   After mixing hollow inorganic fine particles having through holes on the surface and a monomer having a sulfonic acid group, filling the monomer in the inorganic fine particles under reduced pressure, polymerizing the monomer, and adding a binder after the polymerization A method for producing a proton conductive material, wherein the inorganic fine particles and the polymerized electrolyte resin are cross-linked by chemical bonding by repolymerization. The proton conductive material according to claim 7 , wherein at least one selected from a hydrocarbonoxysilane compound, a bis (trihydrocarbonoxysilyl) alkane compound, and a bis (trihydrocarbonoxysilyl) aryl compound is used as the binder. Manufacturing method. The method for producing a proton conductive material according to claim 7 or 8 , wherein the amount of the binder added is 5 to 40 parts by weight when the amount of the inorganic fine particles added is 100 parts by weight.

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