JP2005154710A - Polymer solid electrolyte, method for producing the same, and solid polymer type fuel cell by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer solid electrolyte having a small fuel cross over such as with methanol, and capable of achieving a high output, to prepare a polymer solid electrolyte film, to provide a method for producing the same and a solid polymer type fuel cell, or the like, by using the same. <P>SOLUTION: The polymer solid electrolyte is constituted with at least a crosslinked material consisting of a polymeric polyfunctional alcohol, a polyfunctional crosslinking agent capable of reacting with hydroxy groups and a polymer having an ionic group. Also, the polymer solid electrolyte is constituted with at least the crosslinked material consisting of a polymeric polyfunctional alcohol and an inorganic proton-conductive material. The electrolyte film consisting of the electrolyte material, and the solid polymer type fuel cell by using the electrolyte film are also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer solid electrolyte material, an electrolyte membrane comprising the same, a method for producing the same, and a polymer electrolyte fuel cell using the same.

  A fuel cell is a power generation device with low emissions, high energy efficiency, and low burden on the environment. For this reason, it is in the spotlight again in recent years to the protection of the global environment. Compared to conventional large-scale power generation facilities, this is a power generation device expected in the future as a relatively small-scale distributed power generation facility, and as a power generation device for mobile objects such as automobiles and ships. It is also attracting attention as a power source for small mobile devices and portable devices, and is expected to be installed in mobile phones and personal computers in place of secondary batteries such as nickel metal hydride batteries and lithium ion batteries.

  In a polymer electrolyte fuel cell, in addition to a conventional polymer electrolyte fuel cell using hydrogen gas as a fuel (hereinafter also referred to as PEFC), a direct methanol fuel cell (hereinafter also referred to as DMFC) that directly supplies methanol. ) Is also attracting attention. Although the DMFC has a lower output than the conventional PEFC, the fuel is liquid and does not use a reformer. Therefore, the energy density is high, and the use time of the portable device per filling is long. is there.

  In a fuel cell, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs, and an electrolyte membrane serving as an ion conductor between the anode and the cathode constitute a membrane-electrode complex (MEA). A cell sandwiched between separators is configured as a unit. Here, the electrode is composed of an electrode substrate (also referred to as a gas diffusion electrode or a current collector) that promotes gas diffusion and collects (supply) electricity, and an electrode catalyst layer that actually becomes an electrochemical reaction field. ing. For example, in an anode electrode of a polymer electrolyte fuel cell, a fuel such as hydrogen gas reacts with a catalyst layer of the anode electrode to generate protons and electrons, the electrons are conducted to the electrode substrate, and the protons are conducted to the electrolyte membrane. . For this reason, the anode electrode is required to have good gas diffusibility, electron conductivity, and ion conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air is produced in the catalyst layer of the cathode electrode, and protons conducted through the electrolyte membrane react with electrons conducted from the electrode substrate to generate water. For this reason, in the cathode electrode, it is necessary to efficiently discharge the generated water in addition to gas diffusibility, electron conductivity, and ion conductivity.

  In particular, among solid polymer fuel cells, in an electrolyte membrane for DMFC using an organic solvent such as methanol as a fuel, in addition to the performance required for a conventional electrolyte membrane for PEFC using hydrogen gas as a fuel, Inhibition of methanol aqueous solution permeation is also required. Methanol permeation of the electrolyte membrane is also referred to as methanol crossover (hereinafter sometimes abbreviated as MCO) or chemical short, and causes a problem that battery output and energy efficiency are lowered.

  In the past, for example, “Nafion” (Nafion, a registered trademark of DuPont), which is a perfluorosulfonic acid polymer membrane, has been used in an electrolyte membrane of a polymer electrolyte fuel cell. However, "Nafion" is a very expensive film because it is a fluoropolymer film manufactured through multi-step synthesis, and methanol, which has a high affinity for water, is used to form a cluster structure. There is a problem that the fuel easily permeates the membrane, that is, the fuel crossover of methanol or the like is large. There is also a problem that the mechanical strength of the film is reduced by swelling. Therefore, in order to put these polymer membranes into practical use as electrolyte membranes, there has been a demand from the market for polymer solid electrolyte membranes that are inexpensive and suppress fuel crossover such as methanol.

  Some efforts have already been made on polymer proton conductors based on non-fluorinated polymers. In the 1950s, styrene-based cation exchange resins were studied. However, since the strength as a membrane, which is a form used in a normal fuel cell, was not sufficient, a sufficient battery life could not be obtained. A fuel cell using a sulfonated aromatic polyetheretherketone as an electrolyte membrane has also been studied. In Non-Patent Document 1, an aromatic polyether ether ketone (hereinafter sometimes abbreviated as PEEK), which is sparingly soluble in an organic solvent, becomes highly soluble in an organic solvent by being highly sulfonated to form a film. It is introduced that it becomes easy. However, these sulfonated PEEKs simultaneously improve hydrophilicity, become water-soluble, or cause a decrease in strength during water absorption. Fuel cells usually produce water as a by-product by the reaction of fuel and oxygen, or in DMFC, the fuel itself is a fuel aqueous solution such as methanol. Therefore, when sulfonated PEEK becomes water-soluble, it is used as it is for fuel cells. Not suitable for use in electrolyte membranes.

  Non-Patent Document 2 describes PSF (UDELP-1700) which is an aromatic polyethersulfone and a sulfonated product of PES. PSF and PES are polymers having structures of the following formula (F1) and the following formula (F2), respectively.

  Non-Patent Document 2 describes that sulfonated PSF is completely water-soluble and cannot be evaluated as an electrolyte membrane. Although sulfonated PES is not water-soluble, it has been proposed to introduce a crosslinked structure due to the problem of high water absorption. However, none of these satisfy the above-mentioned high proton conductivity, the effect of suppressing fuel crossover such as methanol, and the economy at the same time, and the development of a polymer material that satisfies a higher level of demand has been awaited.

  What cross-linked polyvinyl alcohol (hereinafter also referred to as PVA) represented by the following general formula (I) can be used for a water / alcohol pervaporation separation membrane (see Non-Patent Document 3).

(General formula I)

  However, PVA has extremely low proton conductivity for use as a polymer solid electrolyte.

  Therefore, in Non-Patent Document 4, a cation exchange membrane obtained by heat-treating a homogeneous membrane composed of polystyrene sulfonic acid and PVA has been studied. This PVA-based crosslinked membrane becomes insoluble in water due to intermolecular dehydration condensation of PVA using polystyrene sulfonic acid as an acid catalyst as it is heat-treated, but at the same time, its flexibility is reduced and it becomes hard and brittle. It has been proposed to use

  Further, in Non-Patent Document 4, an electrolyte membrane using a sulfonic acid group-containing PVA obtained by heat-treating a mixture of PVA, a sulfonating agent and a cross-linking agent has been studied. However, in the cross-linked PVA, the proton conductivity is only one digit lower than that of “Nafion” even if the amount of sulfonating agent is increased, and the use as a composite membrane with “Nafion” is proposed. ing.

  Further, in Non-Patent Document 5, an electrolyte membrane obtained by heat-treating a mixture of PVA and tungstic acid has been studied. However, in the tungstic acid / PVA film, only 48% of the tungstic acid is introduced at the maximum with respect to the PVA weight, so that only a film having an extremely low conductivity of 1 mS / cm or less at room temperature is obtained. Moreover, although the amount of the silicic acid compound is not specified, it is described that only a small amount is added, and the heat treatment temperature is also carried out at 100 ° C., and sufficient crosslinking reaction proceeds to suppress the swelling of the film. It is difficult to think. As a result, only MCO larger than “Nafion” has been obtained, and suppression of swelling by treatment with isobutyraldehyde has been proposed.

JP 2001-158806 A Polymer, vol. 28, 1009 (1987) Journal of Membrane Science, 83 (1993) 211-220 Ji-Won Rhimet et al., Journal of Applied Polymer Science, Vol.68, 1717 (1998) Occupational Chemical Journal, Vol. 70, No. 3, 393 (1967) Proceedings of the 44th Battery Symposium 246 (2002)

  In these conventional techniques, there are problems that the obtained electrolyte membrane is expensive, the ion conductivity is insufficient, or the effect of suppressing the crossover of fuel such as methanol is insufficient. An object of the present invention is a high-performance fuel cell that is inexpensive, has good mechanical strength, does not swell in a fuel aqueous solution such as methanol, and has both high proton conductivity and a fuel crossover suppression effect such as methanol. It is an object to provide a polymer solid electrolyte material suitable for the above, an electrolyte membrane comprising the same, and a high-performance solid polymer fuel cell using the same.

In order to achieve the above object, the present invention is specified as follows.
That is, “a polymer solid electrolyte material comprising at least a polymer polyfunctional alcohol and a crosslinked product composed of a polyfunctional crosslinking agent capable of reacting with a hydroxyl group, and a polymer having an ionic group” or It is “a polymer solid electrolyte material comprising at least a crosslinked product composed of a polymer polyfunctional alcohol and an inorganic proton conductor”, and various derivatives or improvements thereof. .

  ADVANTAGE OF THE INVENTION According to this invention, the novel polymer electrolyte material which suppresses fuel crossovers, such as methanol, has high ion conductivity, and can achieve high output, the electrolyte membrane consisting thereof, its manufacturing method, and the high performance using the same A solid polymer fuel cell can be provided, and its practicality is high.

Hereinafter, embodiments for carrying out the present invention will be described in detail.
One aspect of the polymer solid electrolyte material of the present invention is composed of at least a polymer polyfunctional alcohol, a crosslinked product composed of a polyfunctional crosslinking agent capable of reacting with a hydroxyl group, and a polymer having an ionic group. Features.

  That is, in the polymer solid electrolyte material of the present invention, the polymer having an ionic group is retained in a three-dimensional crosslinked body derived from a polyfunctional crosslinking agent capable of reacting with at least a polymeric polyfunctional alcohol and a hydroxyl group. Therefore, the molecular chain of the polymer having an ionic group that easily swells in a fuel aqueous solution such as methanol is normally mixed with a three-dimensional crosslinked product that does not swell in a fuel aqueous solution such as methanol at the molecular level. However, it is restrained and exists. By being constrained by the three-dimensional crosslinked body in this way, while maintaining high proton conductivity, swelling with respect to an aqueous fuel solution such as methanol is suppressed, fuel permeation such as MCO is reduced, and a decrease in membrane strength is also suppressed. This is an effect.

  The reason why the fuel permeation reduction such as MCO is achieved in the present invention is not necessarily clear at the present stage, but is estimated as follows. When a conventional polymer having an ionic group is used alone as a polymer solid electrolyte material, if the content of the ionic group is increased in order to obtain high ionic conductivity, the polymer solid electrolyte material swells inside. A cluster of water having a large diameter is formed, and free water increases in the polymer solid electrolyte material. Methanol and other fuels move easily in free water, so a sufficient fuel crossover suppression effect such as methanol cannot be obtained. Conventional ones have a high ion conductivity and a fuel crossover suppression effect such as methanol. It was not possible to achieve both. On the other hand, in the polymer solid electrolyte material of the present invention, since the molecular chain of the polymer having an ionic group is constrained by the three-dimensional crosslinked body, swelling with respect to an aqueous fuel solution such as methanol can be suppressed. It is possible to achieve both the conductivity and the effect of suppressing the fuel crossover such as methanol. In addition, there is an effect of preventing the fuel cell performance from being lowered due to swelling deformation or the like.

  The three-dimensional crosslinked product in the polymer solid electrolyte material of the present invention is a product obtained by crosslinking a polymer polyfunctional alcohol with a polyfunctional crosslinking agent, and the polymer polyfunctional alcohol is not particularly limited. It is necessary to have a large number of hydroxyl groups. When the number of hydroxyl groups is insufficient, the degree of cross-linking is also insufficient, the swelling of the electrolyte material cannot be suppressed and the permeation of fuel such as MCO cannot be suppressed, and the mechanical strength may even decrease when containing water.

  Specific examples of the polymer polyfunctional alcohol include a saponified polyvinyl acetate such as polyvinyl alcohol, a saponified polyvinyl acetate copolymer such as an ethylene-vinyl alcohol copolymer, and a hydroxyalkyl such as hydroxyethyl cellulose and hydroxypropyl cellulose. Examples include polysaccharides such as cellulose, chitin, chitosan and the like. Among these, polyvinyl alcohol is preferably used because of its excellent hydrolysis resistance under acidic conditions.

  In this polymer polyfunctional alcohol, at least a part of the hydroxyl group may be modified. Here, the modification means that the hydroxyl group is converted to another substituent. Specific examples of the modification include urethanization, esterification and etherification of a hydroxyl group. As an example of a method for urethanizing a hydroxyl group, there may be mentioned a method of reacting a hydroxyl group with urea and a method of reacting a hydroxyl group with various isocyanate compounds. An example of a method for esterifying a hydroxyl group is a method of reacting a hydroxyl group with various acid compounds or various acid halide compounds. Examples of the method for etherifying a hydroxyl group include a method of reacting a compound having a hydroxyl group and a halogen group and a method of reacting a compound having a hydroxyl group and a carbon-carbon multiple bond.

  Various physical properties can be imparted to the solid polymer electrolyte material by modifying the hydroxyl group. For example, when urethanization is performed, effects such as an improvement in heat resistance by the provision of hydrogen bonds, a reduction in fuel crossover, and suppression of swelling can be obtained. When esterification or etherification is performed, although it depends on the type of esterification agent or etherification agent, in general, there are effects such as improved solubility in solvents, suppression of swelling by imparting hydrophobicity, and reduction of fuel crossover. can get. In particular, urethanization is a preferred modification because it has a large effect of improving heat resistance.

  When the hydroxyl group is modified, the modification rate is preferably 0.5% to 95%, more preferably 1% to 75%, and even more preferably 2 to 50%. If the modification rate is too low, the effect of modification cannot be sufficiently obtained, and if the modification rate is too high, proton conductivity tends to decrease, which is not preferable.

  In the present invention, the modification rate is the ratio of the number of modified hydroxyl groups to the total number of hydroxyl groups in the polymer polyfunctional alcohol. It is assumed that the number of hydroxyl groups spent on the crosslinking reaction described later is not included in the number of modified hydroxyl groups.

  Next, the polyfunctional crosslinking agent used for crosslinking of the polymer polyfunctional alcohol in the present invention will be described. The polyfunctional crosslinking agent is not particularly limited as long as it has a plurality of functional groups capable of reacting with a hydroxyl group.

  Examples of such functional groups include carboxylic acid groups, carboxylic acid ester groups, carboxylic acid halide groups, isocyanate groups, aldehyde groups, epoxy groups, silanol groups, haloalkyl groups, hydroxyl groups, sulfonic acid ester groups, alkenyl groups, and the like. It is done. Two or more kinds of these functional groups can be contained in the cross-linking agent, and may be preferable by combining them. The combination is appropriately determined depending on the handleability, the mechanical strength of the electrolyte material, and the effect of suppressing fuel crossover such as methanol. Among these, those containing at least a carboxylic acid group and an isocyanate group are more preferably used from the viewpoints of handleability and hydrolysis resistance.

  The polyfunctional carboxylic acid crosslinking agent used in the present invention is not particularly limited, and may be a bifunctional carboxylic acid crosslinking agent or a trifunctional or higher polyfunctional carboxylic acid crosslinking agent. Specific examples of the bifunctional carboxylic acid crosslinking agent include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, polyacrylic acid, phthalic acid, isophthalic acid, terephthalic acid Acids, naphthalenedicarboxylic acids, diphenylenedicarboxylic acids, diphenoxyethanedicarboxylic acids, aliphatic, aromatic and alicyclic bifunctional carboxylic acids such as 1,4-cyclohexanedicarboxylic acid and, for example, tetrafluorosuccinic acid Examples thereof include those obtained by fluorinating the carbon chain portion of these bifunctional carboxylic acids, and sulfonated products of these bifunctional carboxylic acids such as sulfosuccinic acid.

  Among these, a bifunctional carboxylic acid having 2 to 8 carbon atoms is more preferable from the balance of the mechanical strength of the electrolyte material, proton conductivity, and the fuel crossover suppression effect such as methanol. Specifically, oxalic acid, malonic acid, succinic acid, Examples include glutaric acid and adipic acid. Further, from the viewpoint of ion conductivity, specifically, a fluorinated carbon chain part of a bifunctional carboxylic acid having 2 to 8 carbon atoms is more preferably used. Ion conductivity and fuel crossover such as methanol Tetrafluorosuccinic acid is most preferable from the viewpoint of the inhibitory effect.

  In the present invention, the polyfunctional isocyanate crosslinking agent used for crosslinking of the polymeric polyfunctional alcohol is not particularly limited, and may be a bifunctional isocyanate crosslinking agent or a trifunctional or higher polyfunctional isocyanate crosslinking agent. Absent. Examples of the bifunctional isocyanate crosslinking agent include compounds having two or more isocyanato groups in the molecule described in “Network Polymer”, Vol. 17 (No. 2), pages 19 to 26 (1996), “ Examples thereof include compounds having two or more isocyanato groups in a molecule described in “Functional polyurethane” (publishing office; CMC Co., Ltd., publication year; 1989), pages 3 to 24.

  Among them, the compounds of the following formulas (1) to (20) are more preferable, and the compounds of the formulas (1) to (12) are more preferable. The same applies to isocyanate-modified products of these compounds, uretidinedione-modified products of these compounds, biuret-modified products of these compounds, and urethane prepolymers obtained by adding these compounds (excess amount) to active hydrogen-containing compounds. It is suitable for.

Next, the polymer having an ionic group used in the present invention will be described. The ionic group present in the polymer is not particularly limited as long as it is a negatively charged atomic group, but is preferably one having proton exchange ability. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, and a phosphoric acid group are preferably used. Here, the sulfonic acid group is —SO ₂ (OH), the sulfonimide group is —SO ₂ NHSO ₂ R (where R represents an organic group), the sulfuric acid group is —OSO ₂ (OH), The phosphonic acid group means —PO (OH) ₂ , and the phosphoric acid group means —OPO (OH) ₂ and salts thereof. Two or more kinds of these ionic groups can be contained in the polymer solid electrolyte material, and may be preferable by combining them. The combination is appropriately determined depending on the structure of the polymer. Among them, it is more preferable to have at least one of sulfonic acid group, sulfonimide group, sulfuric acid group and phosphonic acid group from the viewpoint of high proton conductivity, and at least sulfonic acid from the viewpoint of hydrolysis resistance and cost. Most preferably it has a group.

  Examples of the monomer for forming such a polymer include acrylic acid, methacrylic acid, vinyl sulfonic acid, styrene sulfonic acid, maleic acid, 2-acrylamido-2-methylpropane sulfonic acid, and ethylene glycol methacrylate phosphate. Although a monomer can be used, it is not limited to these. It is also possible to copolymerize a monomer having no ionic group with such a monomer having an ionic group. Preferable specific examples of such a copolymer include styrene / styrene sulfonic acid copolymer, acrylonitrile / 2-acrylamido-2-methylpropane sulfonic acid copolymer, styrene / 2-acrylamido-2-methylpropane sulfonic acid. Examples thereof include a copolymer and a styrenesulfonic acid / (meth) acrylic acid copolymer.

  It is also possible to introduce an ionic group into the aromatic polymer by a polymer reaction. Introduction of a phosphonic acid group into an aromatic polymer can be performed, for example, by a method described in Polymer Preprints, Japan, 51, 750 (2002). Introduction of a phosphate group into an aromatic polymer is possible by, for example, phosphate esterification of a polymer having a hydroxyl group. Introduction of sulfate groups into the aromatic polymer is possible, for example, by sulfate esterification of a polymer having hydroxyl groups. Introduction of a sulfonimide group into an aromatic polymer is possible, for example, by treating a polymer having a sulfonic acid group with an alkylsulfonamide.

  As a method for sulfonating an aromatic polymer, that is, a method for introducing a sulfonic acid group, for example, a method described in JP-A-2-16126 or JP-A-2-208322 is known. Specifically, for example, the aromatic polymer can be sulfonated by reacting with a sulfonating agent such as chlorosulfonic acid in chloroform or by reacting in concentrated sulfuric acid or fuming sulfuric acid. The sulfonating agent is not particularly limited as long as it sulfonates an aromatic polymer. In addition to the above, sulfur trioxide and the like can be used. When the aromatic polymer is sulfonated by this method, the degree of sulfonation can be easily controlled by the amount of the sulfonating agent used, the reaction temperature and the reaction time.

  The degree of sulfonation can be expressed as a value of sulfonic acid group density. The sulfonic acid group density in the polymer solid electrolyte material of the present invention is not particularly limited, but is preferably 0.1 to 5.0 mmol / g, more preferably from the viewpoint of proton exchange ability and water resistance. 1.0 to 3.5 mmol / g. When the sulfonic acid group density is lower than 0.1 mmol / g, the output performance may be lowered due to low conductivity, and when it is higher than 5.0 mmol / g, it is sufficient for use as an electrolyte membrane for a fuel cell. Since the water resistance of the polymer and the mechanical strength when containing water may not be obtained, they are not preferable.

Here, the sulfonic acid group density is the molar amount of sulfonic acid groups introduced per unit gram of the dried polymer solid electrolyte material, and the larger the value, the higher the degree of sulfonation. The sulfonic acid group density can be measured by ¹ H-NMR spectroscopy, elemental analysis, neutralization titration, atomic absorption photometry, etc., but in the present invention, the sulfone group density is not limited regardless of the solubility of the polymer solid electrolyte material. Since the acid group density can be measured, it is specified by elemental analysis or neutralization titration.

The procedure for neutralization titration is as follows. The measurement shall be performed three times or more and the average shall be taken.
(1) The polymer solid electrolyte material is pulverized by a mill, and is passed through a 50-mesh mesh screen to make the particle size uniform.
(2) Weigh the sample tube (with lid) with a precision balance.
(3) About 0.1 g of the electrolyte material of (1) is put in a sample tube and vacuum dried at 40 ° C. for 16 hours.
(4) Weigh the sample tube containing the polymer solid electrolyte material and determine the dry weight of the polymer solid electrolyte material.

(5) Dissolve sodium chloride in a 30 wt% aqueous methanol solution to prepare a saturated saline solution.
(6) Add 25 mL of the saturated salt solution of (5) above to the solid polymer electrolyte material, and stir for 24 hours for ion exchange.
(7) Titrate the resulting hydrochloric acid with 0.02 mol / L aqueous sodium hydroxide. Two drops of a commercially available titration phenolphthalein solution (0.1% by volume) as an indicator are added, and the point at which light reddish purple is obtained is the end point.
(8) The sulfonic acid group density is determined by the following formula.
Sulfonic acid group density (mmol / g) =
[Concentration of sodium hydroxide aqueous solution (mmol / ml) × Drip amount (ml)] / Dry weight of sample (g)

  The polymer having an ionic group used in the present invention is not particularly limited. Specific examples thereof include polystyrene sulfonic acid, polyacrylamide alkane sulfonic acid, polyvinyl sulfonic acid, and polyvinyl alcohol sulfonic acid ester. A hydrocarbon-based polymer having an aliphatic chain, a perfluorosulfonic acid polymer such as “Nafion”, a sulfonated polyphenylene oxide, a sulfonated polyether ketone, a sulfonated polyether ether ketone, a sulfonated polyether sulfone, Sulfonated polyetherethersulfone, sulfonated polyphenylene sulfide, sulfonated polyamide, sulfonated polyimide, sulfonated polyetherimide, sulfonated polyimidazole, sulfonated polyoxazol , The backbone, such as sulfonated polyphenylene include hydrocarbon polymers aromatic. Among these, at least one selected from polystyrene sulfonic acid, polyacrylamide alkane sulfonic acid, polyvinyl sulfonic acid, polyvinyl alcohol sulfonic acid ester, and perfluorosulfonic acid polymer is more preferable from the viewpoint of having a high sulfonic acid group density. Further, at least one selected from a styrene sulfonic acid (co) polymer, an acrylamide alkane sulfonic acid (co) polymer, a vinyl sulfonic acid (co) polymer, and a perfluorosulfonic acid polymer is preferable.

  Another aspect of the polymer solid electrolyte material of the present invention is characterized in that it is composed of at least a crosslinked product composed of a polymer polyfunctional alcohol and an inorganic proton conductor.

  That is, in the polymer solid electrolyte material of the present invention, the inorganic proton conductor is held and held in at least a three-dimensional crosslinked body composed of at least a polymer polyfunctional alcohol. An inorganic proton conductor that dissolves in the aqueous fuel solution and elutes from the solid polymer electrolyte material is mixed with a three-dimensional crosslinked body that does not swell at all even when using an aqueous fuel solution such as methanol and is restrained. To do. By being constrained by the three-dimensional crosslinked body in this way, while maintaining high proton conductivity, swelling with respect to an aqueous fuel solution such as methanol is suppressed, fuel permeation such as MCO is reduced, and a decrease in membrane strength is also suppressed. This is an effect.

  The reason why the fuel permeation reduction such as MCO is achieved in the present invention is not necessarily clear at the present stage, but is estimated as follows. When an inorganic proton conductor is used for a polymer solid electrolyte material, if the content of the inorganic proton conductor is increased in order to obtain high ionic conductivity, the polymer solid electrolyte material swells and has a large diameter inside. A cluster of water is formed, and free water increases in the polymer solid electrolyte material. Since fuel such as methanol easily moves in free water, a sufficient fuel crossover suppression effect such as methanol cannot be obtained. In addition, since the inorganic proton conductor is also eluted from the polymer solid electrolyte material, high conductivity could not be obtained, so the conventional one can achieve both high ionic conductivity and fuel crossover suppression effect such as methanol. There wasn't. On the other hand, in the solid polymer electrolyte material of the present invention, as a result of intensive studies on the type of crosslinked body, inorganic proton conductor, and film forming conditions, a three-dimensional crosslinked body composed of a polymer polyfunctional alcohol is heat-treated at high temperature. By doing so, it was found that the crosslinked body was densified and a large amount of inorganic proton conductors could be included and fixed. As a result, it was possible to achieve both high proton conductivity and the effect of suppressing the crossover of fuel such as methanol. In addition, there is an effect of preventing the fuel cell performance from being lowered due to swelling deformation or the like.

  The inorganic proton conductor in the polymer solid electrolyte material of the present invention is not particularly limited as long as it is a substance exhibiting high proton conductivity near room temperature, but the characteristics of these substances include hydration or It is stably present in a state where moisture is retained, and the water becomes a proton supply source and a conduction path and exhibits high proton conductivity.

Specific examples of such compounds include α-Zr (HPO ₄ ) · nH ₂ O, γ-Zr (PO ₄ ) (H ₂ PO ₄ ) · 2H ₂ O, α-Zr sulfophenyl phosphate, Alternatively, a layered compound such as γ-Zr sulfophenyl phosphate, a hydrated oxide such as SnO ₂ .2H ₂ O, Sb ₂ O ₅ .5.4H ₂ O, or the like, generally represented by the structural formula Ha [ XM ₁₂ O ₄₀ ] · nH ₂ O (where a is an integer, X is a hetero element such as Si, P, As, S, Fe, and Co, and M is a poly element such as Mo, W, and V) And compounds having no hydrate such as CsHSO ₄ , Rb ₃ H (SeO ₄ ) _2, etc., are preferably used.

  Among them, the heteropolyacid has a sufficiently large molecular size and forms a hydrogen bond or a covalent bond with a hydroxyl group of a polymer polyfunctional alcohol, so that it is possible to prevent elution from a membrane in a fuel aqueous solution such as methanol. Therefore, it can be particularly preferably used in a polymer solid electrolyte membrane used in a fuel aqueous solution such as methanol for a long period of time.

  Among the heteropolyacids, tungstosilicic acid, tungstophosphoric acid, or molybdophosphoric acid has the highest acidity and can be most preferably used.

  The amount of the heteropolyacid used is preferably a molar ratio of M / C contained in the polymer solid electrolyte material (where M represents a poly element such as Mo, W, and V, and C represents carbon), and is preferably 0. 0.04 or more and 0.24 or less, more preferably 0.08 or more and 0.2 or less, and particularly preferably 0.11 or more and 0.17 or less. If it is less than 0.04, proton conductivity will be insufficient. On the other hand, if it exceeds 0.24, the cross-linked membrane material may become brittle and easily cracked, or the inorganic proton conductor may be eluted. The M / C molar ratio can be easily analyzed by elemental analysis, ICP emission analysis, or the like.

  The solid polymer electrolyte material of the present invention contains other components, for example, an inert polymer or an organic or inorganic compound that does not have conductivity or ionic conductivity, as long as the object of the present invention is not impaired. It doesn't matter.

  When the polymer solid electrolyte material of the present invention is used for a fuel cell, it is usually used in the form of a membrane, but may be used in other shapes. Hereinafter, an electrolyte membrane made of the polymer solid electrolyte material of the present invention will be described.

  The polymer solid electrolyte membrane of the present invention comprises: (A) a polymer solid electrolyte comprising at least a three-dimensional cross-linker composed of a polyfunctional alcohol capable of reacting with a polymer polyfunctional alcohol and a hydroxyl group; and a polymer having an ionic group. Material or (B) a polymer solid electrolyte material composed of at least a crosslinked product composed of a polymer polyfunctional alcohol and an inorganic proton conductor, and there is no particular limitation on the method for producing the membrane, A method of forming a film from the state and then cross-linking by heat treatment is employed. An example of the manufacturing method will be specifically described.

  First, the case (A) will be described. A polyfunctional cross-linking agent is added together with a polymer having an ionic group to an aqueous solution of a polymer polyfunctional alcohol that is uniformly dissolved, and the mixture is stirred to obtain a casting solution. The PVA concentration of the casting solution is preferably 1 to 50% by weight, more preferably 5 to 30% by weight, and particularly preferably around 10% by weight. The casting liquid is cast on a glass plate or a resin plate, the moisture is evaporated, and then vacuum-dried. Casting can be performed using a doctor blade or the like. Water evaporation is performed by heating with a hot plate or a vacuum drying furnace, and the heating temperature is preferably 100 ° C. or lower, more preferably 40 ° C. or lower. The temperature during vacuum drying is preferably 100 ° C. or lower, more preferably 40 ° C. or lower. If the heating temperature and the temperature during vacuum drying are too high, the fuel crossover suppressing effect such as methanol may be insufficient.

  Subsequently, in order to perform a crosslinking process, the obtained film | membrane is heat-processed. The temperature of this heat treatment is preferably 50 to 250 ° C, more preferably 80 to 230 ° C, and particularly preferably 120 to 220 ° C. The heat treatment time is preferably 5 minutes to 12 hours, more preferably 30 minutes to 6 hours, and particularly preferably around 1 hour. If the heat treatment temperature is too low, the degree of crosslinking is insufficient. On the other hand, if it is too high, the film material tends to deteriorate. If the heat treatment time is less than 5 minutes, the degree of crosslinking is insufficient. On the other hand, when it exceeds 12 hours, the film material tends to deteriorate.

  In particular, when a film is formed at 40 ° C. or lower and then heat-treated at 80 ° C. or higher, a particularly high-performance polymer solid electrolyte having excellent mechanical strength, low swelling rate, and high proton conductivity and low MCO is obtained. It is done. Further, this condition is preferable because the total light transmittance described later can be 40% or less and 0% or more.

  Since the polymer solid electrolyte membrane obtained by the above preparation contains a polymer polyfunctional alcohol crosslinked structure together with a polymer having an ionic group, it can be used as an electrolyte membrane immersed in water. Although there is no restriction | limiting in particular in the film thickness of a polymer solid electrolyte membrane, Usually a 10-500 micrometers thing is used suitably. A thickness of more than 10 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 500 μm is preferable to reduce membrane resistance, that is, to improve power generation performance.

  The amount of the crosslinking agent to be used is preferably 1 to 50 mol%, more preferably 1 to 20 mol%, particularly preferably 3 to 10 mol%, based on the hydroxyl group in the polymer polyfunctional alcohol. If it is less than 1 mol%, the crosslinked film material becomes water-soluble. On the other hand, if it exceeds 50 mol%, the crosslinked film material becomes brittle and easily cracked.

  Next, (B) will be described. An inorganic proton conductor is added to an aqueous solution of a polymer polyfunctional alcohol that is uniformly dissolved, and the mixture is stirred and used as a casting solution. The PVA concentration of the casting solution is preferably 1 to 50% by weight, more preferably 5 to 30% by weight, and particularly preferably around 10% by weight. The casting liquid is cast on a glass plate or a resin plate, the moisture is evaporated, and then vacuum-dried. Casting can be performed using a doctor blade or the like. Water evaporation is performed by heating with a hot plate or a vacuum drying furnace, and the heating temperature is preferably 100 ° C. or lower, more preferably 40 ° C. or lower. The temperature during vacuum drying is preferably 100 ° C. or lower, more preferably 40 ° C. or lower. If the heating temperature and the temperature during vacuum drying are too high, the fuel crossover suppressing effect such as methanol may be insufficient.

  Subsequently, in order to perform a crosslinking process, the obtained film | membrane is heat-processed. The temperature of this heat treatment is preferably 105 to 200 ° C, more preferably 105 to 150 ° C, particularly preferably 105 to 130 ° C. The heat treatment time is preferably 5 minutes to 12 hours, more preferably 30 minutes to 6 hours, and particularly preferably 1 to 2 hours. When the heat treatment temperature is less than 105 ° C., the degree of crosslinking is insufficient, and the fuel crossover suppressing effect and swelling suppression may be insufficient. On the other hand, if it is too high, the film material tends to deteriorate. If the heat treatment time is less than 5 minutes, the degree of crosslinking is insufficient. On the other hand, when it exceeds 12 hours, the film material tends to deteriorate.

  In particular, when a film is formed at 40 ° C. or lower and then heat-treated at 105 ° C. or higher, a particularly high-performance polymer solid electrolyte is obtained that has excellent mechanical strength, low swelling rate, and high proton conductivity and low MCO. It is done. Further, this condition is preferable because the total light transmittance described later can be 40% or less and 0% or more.

  Since the polymer solid electrolyte membrane obtained by the above preparation contains a crosslinked structure of a polymer polyfunctional alcohol together with an inorganic proton conductor, it can be used as an electrolyte membrane in a state immersed in water. Although there is no restriction | limiting in particular in the film thickness of a polymer solid electrolyte membrane, Usually a 10-500 micrometers thing is used suitably. A thickness of more than 10 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 500 μm is preferable to reduce membrane resistance, that is, to improve power generation performance.

  The amount of the inorganic proton conductor used is preferably 50 to 300% by weight, more preferably 100 to 250% by weight, particularly preferably 140 to 2100% by weight, based on the polyfunctional alcohol. If it is less than 50% by weight, proton conductivity will be insufficient. On the other hand, if it exceeds 300% by weight, the crosslinked membrane material may become brittle and easily cracked, or the inorganic proton conductor may be eluted.

  The solid polymer electrolyte membrane composed of the solid polymer electrolyte material of the present invention preferably has a total light transmittance of 40% or less, preferably 0% or more, and more preferably 35% or less, 0% or more. . When the total light transmittance is 40% or less and 0% or more, it is easier to visually recognize the solid polymer electrolyte membrane as compared with the colorless case. For example, the polymer immersed in water When picking up the solid electrolyte membrane, the operation is remarkably facilitated, which leads to reduction in manufacturing cost, which is preferable.

  Here, the total light transmittance is the ratio of the total transmitted light beam to the parallel incident light beam of the test piece. In the present invention, the total light transmittance of the polymer solid electrolyte membrane is measured according to ASTM-D1003 using a digital SM color computer (manufactured by Suga Test Instruments: SM-7-CH).

  Since the polymer solid electrolyte membrane of the present invention is composed of the polymer solid electrolyte material of the present invention described above, it has a feature that the swelling rate when the dried membrane is immersed in water is small. Specifically, the swelling ratio when the dry film is immersed in water is preferably 101% to 140%, more preferably 101% to 130%, and even more preferably 101% to 125%. If the swelling rate is too large, the size of the polymer solid electrolyte membrane is greatly changed during use as a fuel cell, so that the catalyst may peel off and the output may decrease or the output may not be stable. From this point of view, it is most preferable that the swelling rate is 100%, that is, it does not swell at all, but if it does not swell at all, the conductivity tends to be too small, so it is preferably 101% or more.

  Here, the swelling rate means the area (S1) of a polymer solid electrolyte membrane (with a size of about 3 cm × 3 cm) dried at 50 ° C. and a pressure of 10 hPa or less for 24 hours or more, It is a ratio calculated | required from the area (S2) of the film | membrane immediately after being immersed in water at 25 degreeC for 48 hours or more, Comprising: It represents as follows by a formula.

Swelling rate (%) = 100 × S2 / S1
In addition, when the electrolyte material (membrane) of the present invention is manufactured, additives such as plasticizers, stabilizers, mold release agents and the like used in ordinary polymers are within the range that does not contradict the purpose of the present invention. Can be used together.

  Since the polymer solid electrolyte material of the present invention is excellent in proton conductivity and fuel barrier properties such as methanol, it is very useful as a polymer solid electrolyte membrane material of a fuel cell, particularly a liquid supply type DMFC. In addition, the polymer solid electrolyte membrane of the present invention has high catalytic activity when combined with an electrode containing catalyst fine particles supported on porous particles, and is particularly useful for a liquid supply type DMFC particularly in terms of methanol resistance. It is.

  There is no particular limitation on the method for joining the electrolyte membrane and the electrode when the electrolyte membrane comprising the polymer solid electrolyte material of the present invention is used as an electrolyte membrane in a fuel cell, and a known method (for example, Electrochemistry, 1985, 53). 269, chemical plating method described in J. Electrochem. Soc .: Electrochemical Science and Technology, 1988, 135 (9), 2209. .

  Solid polymer fuel cells include those using hydrogen as fuel and those using an organic solvent such as methanol (liquid supply type DMFC) as a fuel. The polymer solid electrolyte membrane of the present invention is particularly preferably used for a direct fuel cell using at least one selected from alcohol, dimethyl ether, and an aqueous solution or water suspension thereof as a fuel.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. In addition, the measurement conditions of each physical property are as follows.

(1) Measuring method of sulfonic acid group density The sulfonic acid group density was measured by elemental analysis about the polymer electrolyte membrane sample dried after washing sufficiently with pure water. Analysis of C, H, and N was performed by a fully automatic elemental analyzer varioEL, and analysis of S was performed by a flask combustion method and barium acetate titration. The sulfonic acid group density (mmol / g) per gram of the polymer solid electrolyte was calculated from the composition ratio.

(2) Measuring method of ionic conductivity of polymer solid electrolyte membrane Using LCR meter (AG-4411B) manufactured by Ando Electric Co., Ltd., conducting constant potential impedance measurement at 25 ° C by the two-terminal method, and ionic conduction from Nykist diagram I asked for a degree. The AC amplitude was 500 mV. As the sample, a membrane having a width of about 10 mm and a length of about 10 to 30 mm was used. The sample used was immersed in water until immediately before the measurement. Platinum electrodes (two wires) having a diameter of 100 μm were used as electrodes. The electrodes were arranged on the front side and the back side of the sample film so as to be parallel to each other and perpendicular to the longitudinal direction of the sample film.

(3) Measuring method of methanol permeation amount (MCO) of polymer solid electrolyte membrane A sample membrane was sandwiched between H-type cells, pure water was put into one cell, and 1M methanol aqueous solution was put into the other cell. The cell capacity was 80 mL each. The area of the opening between the cells was 1.77 cm ² . Both cells were stirred at 20 ° C. The amount of methanol eluted in pure water at the time of 1 hour, 2 hours and 3 hours was measured and quantified with a gas chromatography (GC-2010) manufactured by Shimadzu Corporation. The methanol permeation amount per unit time and unit area was determined from the slope of the graph.

(4) Measuring method of total light transmittance of solid polymer electrolyte membrane Using digital SM color computer (manufactured by Suga Test Instruments: SM-7-CH), measuring total light transmittance (%) according to ASTM-D1003 did.

(5) Measuring method of swelling rate of polymer solid electrolyte membrane Immediately after a polymer solid electrolyte membrane sample (with a size of about 3 cm × 3 cm) was dried at 50 ° C. and a pressure of 10 hPa or less for 24 hours or more The area (S1) was measured, and immediately after the dried film was immersed in pure water at 25 ° C. for 48 hours or longer, the area (S2) of the film was measured, and the swelling ratio was calculated from the following formula.
Swelling rate (%) = 100 × S2 / S1

(6) Measuring method of molar ratio of M / C in polymer solid electrolyte membrane (M is poly element in heteropolyacid, C is carbon) Measured by elemental analysis on membrane which has been thoroughly washed with water did. The analysis of C was quantified and calculated by a fully automatic analyzer vioEL, and the analysis of polyelements (Mo, W, etc.) in the heteropolyacid was quantified and calculated by a Hitachi ICP emission analyzer P-4010.

[Comparative Example 1] (Evaluation of “Nafion 117”)
A commercially available perfluorosulfonic acid polymer electrolyte membrane “Nafion 117” (manufactured by DuPont) was used to evaluate ion conductivity, MCO, and total light transmittance. “Nafion 117” was measured after being immersed in 5% hydrogen peroxide solution at 100 ° C. for 30 minutes, then in 5% dilute sulfuric acid at 100 ° C. for 30 minutes, and thoroughly washed with deionized water at 100 ° C. . The sulfonic acid group density was 0.9 mmol / g, the methanol permeation amount was 5.6 μmol / cm ² / min, and the ionic conductivity was 5.4 S / cm ² . Further, the total light transmittance was 92%, which was poor in visual visibility. In fact, it was very difficult to visually check and pick up a 5 cm square “Nafion 117” film immersed in water. The swelling rate was 128%.

[Example 1] (Production of cross-linked membrane from PVA / tetrafluorosuccinic acid / polystyrene sulfonic acid)
Polyvinyl alcohol (PVA) (Mw = 14,000 to 186,000, manufactured by Aldrich Corporation), tetrafluorosuccinic acid (manufactured by ACROS ORGANICS) and sodium polystyrene sulfonate (Mw = 1,000,000, manufactured by Aldrich Corporation) ) Is mixed with water at a ratio of PVA / tetrafluorosuccinic acid / sodium polystyrene sulfonate = 67.5 / 7.5 / 25 to form a 7 wt% aqueous solution, and this aqueous solution is applied onto a glass plate, 25 Casting was performed at 200 ° C for 2 days at ℃. The obtained cast film was heat-treated at 200 ° C. for 1 hour to prepare a PVA-based crosslinked film. The obtained film was immersed in 1M hydrochloric acid to form an acid form, and then thoroughly washed with water. The film thickness of the obtained PVA-based crosslinked membrane (polymer solid electrolyte membrane) was 70 μm.

The electrolyte membrane had a sulfonic acid group density of 1.3 mmol / g, a methanol permeation amount of 0.8 μmol / cm ² / min, and an ionic conductivity of 4.5 S / cm ² . Although the ionic conductivity was slightly inferior to that of “Nafion 117”, the MCO was considerably suppressed. Further, the total light transmittance was 28%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 116%.

[Example 2] (Production of cross-linked membrane from PVA / sulfosuccinic acid / polystyrene sulfonic acid)
PVA (Mw = 124,000 to 186,000, manufactured by Aldrich Co., Ltd.), sulfosuccinic acid (manufactured by Aldrich Co., Ltd.), and sodium polystyrene sulfonate (Mw = 1,000,000, manufactured by Aldrich Co., Ltd.) were converted into PVA / sulfosuccinic acid. Acid / sodium polystyrene sulfonate = 67.5 / 7.5 / 25 mixed with water to form a 7 wt% aqueous solution. This aqueous solution was applied onto a glass plate and cast at 25 ° C and 200 hPa for 2 days. did. The obtained cast film was heat-treated at 200 ° C. for 1 hour to prepare a PVA-based crosslinked film. The obtained film was immersed in 1M hydrochloric acid to form an acid form, and then thoroughly washed with water. The film thickness of the obtained PVA-based crosslinked membrane (polymer solid electrolyte membrane) was 70 μm.

The electrolyte membrane had a sulfonic acid group density of 1.5 mmol / g, a methanol permeation amount of 2.7 μmol / cm ² / min, and an ionic conductivity of 5.7 S / cm ² . Compared with “Nafion 117”, the ionic conductivity was the same and the MCO was low. Moreover, the total light transmittance was 31%, and it was excellent in visual visibility. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 117%.

[Example 3] (Production of cross-linked membrane from PVA / hexamethylene diisocyanate / polystyrene sulfonic acid)
PVA (Mw = 124,000 to 186,000, manufactured by Aldrich Co., Ltd.), hexamethylene diisocyanate (manufactured by Aldrich Co., Ltd.) and polystyrene sulfonate (Mw = 1,000,000, manufactured by Aldrich Co., Ltd.) Hexamethylene diisocyanate / polystyrene sodium sulfonate = 67.5 / 7.5 / 25 mixed with water to make a 3% by weight aqueous solution, this aqueous solution was coated on a glass plate and taken at 25 ° C. and 200 hPa for 2 days And cast. The obtained cast film was heat-treated at 200 ° C. for 1 hour to prepare a PVA-based crosslinked film. The obtained film was immersed in 1M hydrochloric acid to form an acid form, and then thoroughly washed with water. The film thickness of the obtained PVA-based crosslinked membrane (polymer solid electrolyte membrane) was 70 μm.

The electrolyte membrane had a sulfonic acid group density of 1.2 mmol / g, a methanol permeation amount of 2.9 μmol / cm ² / min, and an ionic conductivity of 5.2 S / cm ² . Compared with “Nafion 117”, the ionic conductivity was the same and the MCO was low. Further, the total light transmittance was 33%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 116%.

[Example 4] (Production of crosslinked membrane from PVA / polyacrylic acid / poly-2-acrylamido-2-methyl-1-propanesulfonic acid)
PVA (Mw = 124,000 to 186,000, manufactured by Aldrich Co.), polyacrylic acid (Mw = 2,000, manufactured by Aldrich Co.) and sodium poly-2-acrylamido-2-methyl-1-propanesulfonate (A product obtained by substituting Na-2-type poly-2-acrylamido-2-methyl-1-propanesulfonic acid (Mw = 2,000,000) manufactured by Aldrich Co.) with PVA / polyacrylic acid / poly-2-acrylamide Sodium 2-methyl-1-propanesulfonate = 56/14/30 and mixed with water to form a 7% by weight aqueous solution. This aqueous solution was applied onto a glass plate and cast at 40 ° C. for 7 days. . The obtained cast film was heat-treated at 200 ° C. for 1 hour to prepare a PVA-based crosslinked film. The obtained film was immersed in 1M hydrochloric acid to form an acid form, and then thoroughly washed with water. The film thickness of the obtained PVA-based crosslinked membrane (polymer solid electrolyte membrane) was 70 μm.

The electrolyte membrane had a sulfonic acid group density of 1.4 mmol / g, a methanol permeation amount of 3.9 μmol / cm ² / min, and an ionic conductivity of 5.2 S / cm ² . Compared with “Nafion 117”, the ionic conductivity was the same and the MCO was low. Further, the total light transmittance was 34%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 114%.

[Example 5]
Sodium styrenesulfonate (0.03 mol) and acrylic acid (0.03 mol) were dissolved in water (100 mL), and radical polymerization was performed at 50 ° C. for 8 hours using potassium peroxodisulfate (0.6 mmol) as an initiator. . The polymerization solution was put into acetone to precipitate a polymer. The precipitate was thoroughly washed with acetone, sufficiently dried in vacuum, then dissolved again in water and poured into acetone. The precipitate was washed with acetone and again sufficiently dried in vacuum. The obtained copolymer is hereinafter referred to as P (SSNa-AA).

  PVA (Mw = 124,000 to 186,000, manufactured by Aldrich Co., Ltd.), P (SSNa-AA) and sulfosuccinic acid were converted to PVA / P (SSNa-AA) / sulfosuccinic acid = 70/30/16 (weight ratio). This was mixed with water to make a 7 wt% aqueous solution, this aqueous solution was applied on a polystyrene petri dish, and cast at 25 ° C. for 7 days. The obtained cast film was peeled off from the polystyrene petri dish, placed on a glass plate, and further heat-treated at 130 ° C. for 1 hour (normal pressure) to produce a PVA-based crosslinked film. The obtained film was immersed in 1M hydrochloric acid for 1 hour to form an acid form, and then thoroughly washed with water. The film thickness of the obtained crosslinked membrane (polymer solid electrolyte membrane) was 80 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 3.4 μmol / cm ² / min and an ionic conductivity of 8.0 S / cm ² . Compared with “Nafion 117”, the ionic conductivity was larger and the MCO was smaller. Further, the total light transmittance was 27%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 113%.

[Examples 6 to 11]
The same procedure as in Example 5 was performed except that the composition ratio of PVA / P (SSNa-AA) / sulfosuccinic acid in the aqueous solution and the heat treatment conditions during film production were changed as shown in Table 1. Table 1 shows the methanol permeability, ionic conductivity, and total light transmittance of the obtained crosslinked membrane (polymer solid electrolyte membrane).

[Example 12]
PVA: urea (molar ratio 1: 1) was reacted at 150 ° C. for about 30 minutes in a nitrogen atmosphere, and then precipitated in methanol, and further purified by repeated reprecipitation in a water-methanol system. The modification rate (degree of urethanization) of the obtained urethanized PVA was determined from elemental analysis values and was 3.3%. Hereinafter, this urethanized PVA is referred to as U-PVA-L.

  U-PVA-L, sodium polystyrene sulfonate (PSSSNa) and tetrafluorosuccinic acid used in Example 1 were mixed at a ratio of U-PVA-L / PSSSNa / tetrafluorosuccinic acid = 72/20/8 (weight ratio). The mixture was mixed with water to make a 7% by weight aqueous solution, and this aqueous solution was applied onto a polystyrene petri dish and cast at 25 ° C. for 7 days. The obtained cast film was peeled off from the polystyrene petri dish, placed on a glass plate, and further heat-treated at 250 ° C. for 1.5 hours (normal pressure) to produce a PVA-based crosslinked film. The obtained membrane was immersed in 1M dilute sulfuric acid for 12 hours to form an acid form, and then thoroughly washed with water. The film thickness of the obtained crosslinked membrane (polymer solid electrolyte membrane) was 55 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 0.22 μmol / cm ² / min and an ionic conductivity of 1.2 S / cm ² . Although the ionic conductivity was smaller than that of “Nafion 117”, the MCO was very small, and the ratio of conductivity to MCO was superior to “Nafion 117”. Further, the total light transmittance was 23%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 117%.

[Example 13]
U-PVA-L, sodium polystyrene sulfonate (PSSSNa) and sulfosuccinic acid used in Example 1 were mixed with water at a ratio of U-PVA-L / PSSSNa / sulfosuccinic acid = 72/20/8 (weight ratio). The aqueous solution was applied on a polystyrene petri dish and cast at 25 ° C. for 7 days. The obtained cast film was peeled off from the polystyrene petri dish, placed on a glass plate, and further heat-treated at 220 ° C. for 1 hour (normal pressure) to produce a PVA-based crosslinked film. The obtained membrane was immersed in 1M dilute sulfuric acid for 12 hours to form an acid form, and then thoroughly washed with water. The film thickness of the obtained crosslinked membrane (polymer solid electrolyte membrane) was 55 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 0.45 μmol / cm ² / min and an ionic conductivity of 3.1 S / cm ² . Although the ionic conductivity was smaller than that of “Nafion 117”, the MCO was very small, and the ratio of conductivity to MCO was superior to “Nafion 117”. Further, the total light transmittance was 25%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 113%.

[Example 14]
PVA, sulfosuccinic acid, tetrafluorosuccinic acid and polystyrene polystyrene sulfonate (PSSSNa) used in Example 1 were mixed with water at a ratio of 63.75 / 7.5 / 3.75 / 25 (weight ratio), A 7 wt% aqueous solution was applied, and this aqueous solution was applied onto a polystyrene petri dish and cast at 25 ° C for 7 days. The obtained cast film was peeled off from the polystyrene petri dish, placed on a glass plate, and further heat treated at 200 ° C. for 3 hours (normal pressure) to prepare a PVA-based crosslinked film. The obtained film was immersed in 0.1M hydrochloric acid for 12 hours to form an acid form, and then thoroughly washed with water. The film thickness of the obtained crosslinked membrane (polymer solid electrolyte membrane) was 40 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 1.4 μmol / cm ² / min and an ionic conductivity of 9.0 S / cm ² . Compared with “Nafion 117”, the ionic conductivity was larger, the MCO was smaller, and it had excellent characteristics. Further, the total light transmittance was 15%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 117%.

[Example 15 and Comparative Example 2] (Production and Evaluation of Membrane Electrode Composite)
The carbon fiber cloth base material was subjected to a water repellent treatment using a 20% polytetrafluoroethylene (PTFE) suspension, and then fired to prepare an electrode base material. On this electrode base material, an anode electrode catalyst coating solution composed of Pt—Ru-supported carbon and “Nafion” solution is applied and dried to form an anode electrode, and a cathode electrode catalyst composed of Pt-supported carbon and “Nafion” solution. The coating solution was applied and dried to prepare a cathode electrode.

  The polymer solid electrolyte membrane produced in Example 14 was held between the produced anode and cathode electrodes and heated and pressed to produce a membrane electrode assembly (MEA) (Example 15). A commercially available electrolyte membrane “Nafion 117” used in Comparative Example 1 was sandwiched between the produced anode electrode and cathode electrode and heated and pressed to produce a membrane electrode assembly (MEA) (Comparative Example 2).

The obtained MEA was sandwiched between cells manufactured by Electrochem, and a MEA evaluation was performed by flowing a 30 wt% methanol aqueous solution on the anode side, air on the cathode side, and a constant current through the MEA, and measuring the voltage at that time. went. The measurement was performed until the current was increased successively until the voltage became 10 mV or less. The product of the current and voltage at each measurement point is the output, but the MEA using the polymer electrolyte membrane of Example 14 (Example 15) is the MEA using the “Nafion 117” membrane (Comparative Example 2). The maximum output (mW / cm ² ) was about twice, and the energy capacity (Wh) was about three times, indicating excellent characteristics.

[Example 16]
PVA, ethylene glycol, and sodium polystyrene sulfonate (PSSSNa) used in Example 1 were mixed with water at a ratio of PVA / ethylene glycol / PSSSNa = 64/7/29 (weight ratio) to form a 7 wt% aqueous solution. This aqueous solution was applied onto a polystyrene petri dish and cast at 25 ° C. for 7 days. The obtained cast film was peeled off from the polystyrene petri dish, placed on a glass plate, and further heat-treated at 130 ° C. for 1 hour (normal pressure) to produce a PVA-based crosslinked film. The obtained membrane was immersed in 1M dilute sulfuric acid for 12 hours to form an acid form, and then thoroughly washed with water. The film thickness of the obtained crosslinked membrane (polymer solid electrolyte membrane) was 55 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 1.2 μmol / cm ² / min and an ionic conductivity of 3.2 S / cm ² . Although the ionic conductivity was smaller than that of “Nafion 117”, the MCO was sufficiently small, and the ratio of conductivity and MCO was superior to that of the “Nafion 117” membrane. The total light transmittance was 29%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the solid polymer electrolyte membrane immersed in water. The swelling rate was 119%.

[Example 17]
Chitosan (manufactured by Nacalai Tesque), tetrafluorosuccinic acid (manufactured by ACROS ORGANICS) and sodium polystyrene sulfonate (Mw = 1,000,000, manufactured by Aldrich Co., Ltd.), chitosan / tetrafluorosuccinic acid / sodium polystyrene sulfonate = 67.5 / 7.5 / 25 mixed with water to make a 7 wt% aqueous solution, this aqueous solution was applied onto a glass plate and cast at 25 ° C and 200 hPa for 2 days. The obtained cast film was heat-treated at 200 ° C. for 1 hour to prepare a PVA-based crosslinked film. The obtained film was immersed in 1M hydrochloric acid to form an acid form, and then thoroughly washed with water. The film thickness of the obtained PVA-based crosslinked membrane (polymer solid electrolyte membrane) was 70 μm.

The electrolyte membrane had a methanol permeation rate of 1.5 μmol / cm ² / min and an ionic conductivity of 3.2 S / cm ² . Although the ionic conductivity was slightly inferior to that of “Nafion 117”, the MCO was considerably suppressed. Further, the total light transmittance was 28%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 120%.

[Example 18]
U-PVA-L, Tungstosilicic acid hydrate (STA, manufactured by MERCK) was mixed with water at a ratio of U-PVA-L / STA = 40/60 (weight ratio) to form a 7 wt% aqueous solution. The aqueous solution was applied on a polystyrene dish and cast at 25 ° C. for 7 days. The obtained transparent cast film was peeled off from the polystyrene petri dish, sandwiched between “Teflon” (registered trademark) sheets, and heat-treated at 120 ° C. for 1 hour (normal pressure) to obtain a PVA-based crosslinked film. The obtained film was blackened. The thickness of the obtained crosslinked film was 20 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 0.18 μmol / cm ² / min and an ionic conductivity of 7.0 S / cm ² . Despite the higher ionic conductivity compared to “Nafion 117”, the MCO was very small and the ratio of conductivity to MCO was much better than “Nafion 117”. In particular, the MCO was greatly reduced. Further, the total light transmittance was 24%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 113%. The molar ratio of M / C (= W / C) was 0.12.

[Example 19]
PVA (Mw = 124,000 to 186,000, manufactured by Aldrich), tungstophosphoric acid hydrate (PWA, manufactured by Nacalai Tesque), and water in a ratio of PVA / PWA = 33/67 (weight ratio) The mixture was mixed to form a 7% by weight aqueous solution, and this aqueous solution was coated on a polystyrene petri dish and cast at 25 ° C. for 7 days. The obtained transparent cast film was peeled off from the polystyrene petri dish, sandwiched between “Teflon” (registered trademark) sheets, and heat-treated at 105 ° C. for 1 hour (reduced pressure) to obtain a PVA-based crosslinked film. The obtained film was blackened. The thickness of the obtained crosslinked film was 35 μm.

The electrolyte membrane had a methanol permeation rate (MCO) of 0.81 μmol / cm ² / min and an ionic conductivity of 3.4 S / cm ² . Although the ionic conductivity was smaller than that of “Nafion 117”, the MCO was very small, and the ratio of conductivity to MCO was superior to “Nafion 117”. In particular, the MCO was greatly reduced. Further, the total light transmittance was 28%, and the visual visibility was excellent. Actually, it was easy to visually check and pick up the electrolyte membrane immersed in water. The swelling rate was 118%. The molar ratio of M / C (= W / C) was 0.16.

  The polymer solid electrolyte material of the present invention is applied to polymer solid electrolyte parts (for example, polymer solid electrolyte membranes) used in various electrochemical devices (for example, fuel cells, water electrolysis devices, chloroalkali electrolysis devices, etc.). Is possible. Among them, it is very useful for a polymer electrolyte membrane in a fuel cell, further a polymer electrolyte fuel cell, particularly a liquid supply type DMFC.

  Further, the application of the polymer electrolyte fuel cell of the present invention is not particularly limited, but a power supply source for a mobile body is preferable. In particular, it is preferably used as a power supply source for mobile devices such as mobile devices such as mobile phones, personal computers, PDAs (Personal Digital Assistants), home appliances such as vacuum cleaners, passenger cars, buses and trucks, ships, and railways.

Claims (26)

A solid polymer electrolyte material comprising at least a polymer polyfunctional alcohol, a crosslinked product comprising a polyfunctional crosslinking agent capable of reacting with a hydroxyl group, and a polymer having an ionic group. A polymer solid electrolyte material comprising at least a crosslinked body composed of a polymer polyfunctional alcohol and an inorganic proton conductor. 3. The polymer polyfunctional alcohol is one or more selected from polyvinyl acetate saponified products, polyvinyl acetate copolymer saponified products, hydroxyalkyl cellulose, chitin, and chitosan. The polymer solid electrolyte material described in 1. 3. The polymer solid electrolyte material according to claim 1, wherein the polymer polyfunctional alcohol is polyvinyl alcohol. The polymer solid electrolyte material according to any one of claims 1 to 4, wherein at least a part of hydroxyl groups of the polymer polyfunctional alcohol is modified. The polymer solid electrolyte material according to any one of claims 1 to 4, wherein at least a part of hydroxyl groups of the polymer polyfunctional alcohol is urethanized. The polymer solid electrolyte material according to claim 1, wherein the polyfunctional crosslinking agent is a polyfunctional carboxylic acid. The polymer solid electrolyte material according to claim 7, wherein the polyfunctional carboxylic acid is a bifunctional carboxylic acid having 2 to 8 carbon atoms and / or a derivative thereof. The polymer solid electrolyte material according to claim 8, wherein the bifunctional carboxylic acid having 2 to 8 carbon atoms and / or a derivative thereof contains fluorine. The polymer solid electrolyte material according to claim 1, wherein the polyfunctional crosslinking agent is a polyfunctional isocyanate. The polymer having an ionic group has at least one kind or two or more kinds selected from a sulfonic acid group, a sulfonimide group, a sulfuric acid group, and a phosphonic acid group. A polymer solid electrolyte material according to claim 1. 11. The polymer solid electrolyte material according to claim 1, wherein the polymer having an ionic group has at least a sulfonic acid group. The polymer solid electrolyte material according to claim 12, wherein the sulfonic acid group density is 0.1 to 5.0 mmol / g. The polymer solid electrolyte material according to claim 12, wherein the sulfonic acid group density is 1.0 to 3.5 mmol / g. The polymer having an ionic group is at least one selected from a styrenesulfonic acid (co) polymer, an acrylamide alkanesulfonic acid (co) polymer, a vinylsulfonic acid (co) polymer, and a perfluorosulfonic acid polymer. The polymer solid electrolyte material according to claim 12, wherein the polymer solid electrolyte material is a solid polymer electrolyte material. The polymer having an ionic group is at least one selected from polystyrene sulfonic acid, polyacrylamide alkane sulfonic acid, polyvinyl sulfonic acid, polyvinyl alcohol sulfonic acid ester, and perfluorosulfonic acid polymer. Item 15. The polymer solid electrolyte material according to any one of Items 12 to 14. The polymer solid electrolyte material according to claim 2, wherein the inorganic proton conductor is a heteropolyacid. The polymer solid electrolyte material according to any one of claims 2 to 6, wherein the inorganic proton conductor is at least one selected from tungstosilicic acid, tungstophosphoric acid, and molybdophosphoric acid. The polymer solid electrolyte material according to any one of claims 2 to 6, 17 and 18, characterized in that it contains 50% by weight or more of an inorganic proton conductor based on the weight of the polymer polyfunctional alcohol. The molar ratio of M / C contained in the solid polymer electrolyte material (where M is a poly element in the heteropolyacid, and C is carbon) is 0.04 or more. The polymer solid electrolyte material in any one of -19. A polymer solid electrolyte membrane comprising the polymer solid electrolyte material according to claim 1. The solid polymer electrolyte membrane according to claim 21, wherein the total light transmittance of the polymer solid electrolyte membrane is 40% or less and 0% or more. Claimed by performing a heat treatment at 80 ° C. or higher after forming a mixture of at least a polymer polyfunctional alcohol, a polyfunctional crosslinking agent capable of reacting with a hydroxyl group and a polymer having an ionic group at 40 ° C. or lower. Item 23. A method for producing a solid polymer electrolyte membrane, comprising producing the solid polymer electrolyte membrane according to Item 21 or 22. The polymer solid according to claim 21 or 22, wherein a polymer solid functional alcohol and an inorganic proton conductor are formed at a temperature of 40 ° C or lower and then heat-treated at 105 ° C or higher. A method for producing a polymer solid electrolyte membrane, comprising producing an electrolyte membrane. A solid polymer fuel comprising the solid polymer electrolyte component comprising the solid polymer electrolyte material according to any one of claims 1 to 20, or the solid polymer electrolyte membrane according to claim 21 or 22. battery. 26. The polymer electrolyte fuel cell according to claim 25, wherein at least one selected from alcohols having 1 to 3 carbon atoms, dimethyl ether, and aqueous solutions or suspensions thereof is used as a fuel.