KR100645233B1 - Proton-Conducting Membrane, Method For Producing The Same, And Fuel Cell Using The Same - Google Patents

Abstract

An object of the present invention is to provide a proton conductive membrane having excellent resistance to heat and sustainability at high temperatures and exhibiting excellent proton conductivity. Still another object of the present invention is to provide a method of manufacturing such a conductive film and a fuel cell using the same.

The present invention comprises an organic material (A), a three-dimensional crosslinked structure (B) comprising a specific metal-oxygen bond, a proton conductivity granter (C) and water (D), wherein the organic material (A) is 56 to It has a number average molecular weight of 30,000 and at least four carbon atoms continuously connected to the main chain, and the organic material (A) and the three-dimensional crosslinked structure (B) provide a proton conductive membrane bonded to each other by covalent bonds.

Description

Proton-Conducting Membrane, Method For Producing The Same, And Fuel Cell Using The Same}

1 is a graph showing the output power performance of a fuel cell using a proton conductive membrane of the present invention, determined using an electrochemical impedance meter.

The present invention relates to a proton conductive membrane, a method for manufacturing the same, and a fuel cell using the same. More particularly, the present invention provides excellent proton conductivity at high temperature and excellent resistance to heat and durability. The present invention relates to a visible proton conductive membrane, a method for manufacturing the same, and a fuel cell using the same.

Recently, attention has been focused on fuel cells as a next generation power generation device that can contribute to solving environmental and energy problems that are currently emerging as serious social problems. This is because fuel cells are highly power efficient and environmentally friendly.

Fuel cells fall into three or four categories depending on the type of electrolyte. Of these, polyelectrolyte fuel cells (PEFCs), which are smaller and produce higher outputs than other types, serve a variety of purposes, such as small-size on-site facilities, and driveability (ie, , Automotive power sources) and portable cells are considered to be the leading fuel cell type in the future.

However, despite its inherent advantages in principle, PEFC is still in the development or testing phase, due to the lack of a realistic electrolyte membrane that can meet all requirements, for example, heat resistance, durability and proton conductivity. And it is not yet commercialized. Currently, the electrolyte membrane for PEFC is mainly used a fluorine-based membrane having perfluoroalkylene at the main skeleton and partially having an ion-exchange group such as a sulfone group or a carboxyl group at the end of the perfluorovinyl ether side chain. . As three or four types of these fluorine-based membranes, for example, Nafion membrane (Nafion R membran, Du Pont, US Patent No. 4,330,654), Dow membrane (Dow membrane, Dow Chemical, JP-A-4-366137) Aciplex membranes (Aciplex membrane, Asahi Chemical, Japanese Patent Laid-Open No. 6-342665), Flemion membrane, Asahi Glass, and the like have been proposed.

Current PEFCs using such fluorine-based membranes as electrolytes usually operate in a relatively low temperature range, for example in the region of 80 ° C from room temperature, whereby the fluorine-based membranes themselves, above which destroy the ion channel structure involved in ion conductivity. This is because it has a glass transition temperature (Tg) near 130 ° C. It is not desirable for fuel cells to operate at low temperature ranges, for example due to low power generation efficiency and some serious problems such as significant poisoning of the catalyst with carbon monoxide.

In order to avoid the problems resulting from operation at low temperatures, fuel cells operating over a high temperature range have been continuously developed. The possibility of operating at high temperatures has three or four benefits. For example, when operating at a temperature of 100 ° C. or higher, the power generation efficiency increases, while heat can be used to improve energy efficiency. When the operating temperature increases to 140 ° C., in addition to the above, other advantages can be expected, such as, for example, a reduction in fuel cell fabrication costs due to an increased range of catalytic materials.

Various electrolyte membranes have been developed so far to increase the operating temperature of PEFC.

Among the more representative are heat-resistant aromatic polymers that will replace traditional fluorine-based films. These include polybenzimidazole (Japanese Patent Laid-Open No. 9-110982), polyether sulfones (Japanese Patent Laid-Open Nos. 10-21943 and 10-45913) and polyether ether ketones (JP-A-9- 87510). However, each of these aromatic polymers is very rigid and likely to cause damage when the membrane-electrode assembly (MEA) is formed.

These also have other types of disadvantages. For example, it is modified with an acidic group (e.g. sulfonic or phosphoric acid group) to have the proton conductivity necessary for the electrolyte membrane, resulting in swelling in water or in the presence of water. Water-soluble ones cannot be applied to fuel cells because water is produced there. On the other hand, swelling in the presence of water may cause problems, since swelling may cause the membrane to have enough stress to damage the electrode or to deteriorate the strength of the membrane to the extent that the membrane breaks down.

On the other hand, the following inorganic materials have been proposed as proton conducting materials. For example, Minami et al. Incorporated various acids into hydrolysable silyl compounds to prepare inorganic proton conductive materials (Solid State Ionics, 74 (1994), pp. 105). It has shown proton conductivity safely at high temperatures, but it has some problems, for example, tends to break when produced in thin films, is unwieldy, and difficult to make into MEA. Several methods have been proposed to overcome these problems. For example, the proton conducting material is pulverized and mixed with an elastomer (Japanese Patent Laid-Open No. 8-249923) or mixed with a sulfone group-containing polymer (Japanese Patent Laid-Open No. 10-69817). However, these methods have their own problems. For example, in each of these methods, the polymer as a binder does not have an inorganic crosslinking compound, a bond, or the like, and has a basic thermal property that is not very different from that of the polymer itself, resulting in a structural change in the high temperature range. It does not stably express proton conductivity.

Numerous research investments have been made on various electrolyte membranes to solve these problems associated with typical PEFCs. However, none of these have succeeded in developing a proton conductive membrane that exhibits sufficient sustainability at high temperatures (eg, 100 ° C. or higher) and meets mechanical requirements.

An object of the present invention is to provide a proton conductive membrane, a method for manufacturing the same, and a fuel cell using the same, which are excellent in resistance to heat and sustainability, and exhibit excellent proton conductivity at high temperature, thereby solving the problems inherent in traditional PEFC. will be.

The inventors of the present invention have conducted extensive research on various electrolyte membranes that can solve the above problems, and as essential components, a specific organic material, a three-dimensional crosslinked structure containing a specific metal-oxygen bond, a proton conductivity providing agent, and a specific proton conducting material It has now been found that innovative organic / inorganic mixture membranes can be obtained by including selective binding of. It exhibits higher resistance to heat and persistence than conventional membranes and proton conductivity at higher temperatures, because the covalent bonds formed between the organic material and the three-dimensional crosslinked structure disperse them very finely at the molecular level (nano dispersion).

The first invention comprises an organic material (A), a three-dimensional crosslinked structure (B) comprising a specific metal-oxygen bond, a proton conductivity granter (C), and water (D), wherein

(i) the organic material (A) has a number average molecular weight of 56 to 30,000 and at least four carbon atoms continuously connected to the main chain,

(ii) The organic material (A) and the three-dimensional crosslinked structure (B) are proton conductive membranes which are connected to each other by covalent bonds.

In the second invention, the organic material (A) is a polyether in the proton conductive film of the first invention.

In the third invention, the organic material (A) in the proton conductive film of the second invention is polytetramethylene oxide.

In the fourth invention, the organic material (A) is polymethylene in the proton conductive film of the first invention.

In the fifth invention, the organic material (A) is octamethylene in the proton conductive film of the fourth invention.

The sixth invention includes a water-containing resin (E) having up to four carbon atoms in which the organic material (A) is continuously connected in the main chain in the proton conductive film of the first invention.

In the seventh invention, the water-containing resin (E) in the proton conductive film of the sixth invention is polyethylene oxide.

In the eighth invention, in the proton conductive membrane of the first invention, the organic material (A) is a mixture of polytetramethylene oxide and polyethylene oxide.

In the ninth invention, in the proton conductive film of the first invention, a three-dimensional crosslinked structure (B) is formed by silicon-oxygen bonds.

In the tenth invention, in the proton conductive membrane of the first invention, the proton conductivity imparting agent (C) is an inorganic solid acid.

In the eleventh invention, in the proton conductive membrane of the tenth invention, the inorganic solid acid is tungstophosphoric acid.

In the twelfth invention, the proton conductive film of the first invention includes 5 to 500 parts by weight of the proton conductivity-imparting agent (C) based on 100 parts by weight of the total of the organic material (A) and the three-dimensional crosslinked structure (B).

In the thirteenth invention, the proton conductive membrane of the first invention comprises 1 to 60% by weight of water (D) relative to the total proton conductive membrane.

In the fourteenth invention, the proton conductive membrane of the first invention further includes a reinforcing agent (F).

In the fifteenth invention, the reinforcing agent (F) in the proton conducting film of the fourteenth invention is glass fiber.

The sixteenth invention comprises the steps of preparing a reaction system comprising a mixture of an organic material (A), a hydrolyzable inorganic compound forming a three-dimensional crosslinked structure (B), and a proton conductivity imparting agent (C); Forming the reaction system into a film; And forming a three-dimensional crosslinked structure (B) by metal-oxygen bonds in the film by sol-gel reaction of the film in the presence of water vapor or liquid water (D).

The seventeenth invention includes preparing a reaction system comprising a mixture of an organic material (A), a hydrolyzable inorganic compound forming a three-dimensional crosslinked structure (B), and a proton conductivity imparting agent (C); Forming the reaction system into a film; Three-dimensional crosslinked structure (B) by metal-oxygen bonds in the film by sol-gel reaction of the film in the presence of vapor or liquid water (D) and vapor or liquid alcohol of an alcohol having four or less carbons Method for producing a proton conductive film comprising the step of forming a.

In the eighteenth invention, in the method for producing a proton conductive film of the sixteenth or seventeenth invention, the organic material (A) and the hydrolyzable inorganic compound forming the three-dimensional crosslinked structure (B) are mixed with each other in the organic solvent (G). .

In the ninth invention, in the method for producing a proton conductive film of the eighteenth invention, a compound (H) having a relative dielectric constant of 20 or more and a boiling point of 100 ° C. or more is further added to the organic solvent (G).

In the twentieth invention, in the method for preparing a proton conductive film of the ninth invention, a compound (H) having a relative dielectric constant of 20 or more and a boiling point of 100 ° C. or more is composed of ethylene carbonate, propylene carbonate and butylene carbonate. It is selected.

The twenty-first invention is a fuel cell using any one of the first to fifth invention proton conductive membranes.

One. Organic matter (A)

The proton conductive film of the present invention includes an organic material (A), a three-dimensional crosslinked structure (B) containing a specific metal-oxygen bond, a proton conductivity providing agent (C), and water (D).

The organic material (A) is used in the present invention in order to impart proper flexibility to the proton conductive film, improving the convenience of the MEA and facilitating manufacture. It is important to simultaneously satisfy that these organic materials (A) have two requirements, namely a number average molecular weight of 56 to 30,000 and at least four carbon atoms connected continuously to the main chain.

The organic material (A) is not particularly limited as long as the two requirements are satisfied. In view of the fact that the proton conductivity imparting agent (C) used together in the present invention is an acidic component, it is preferable that these structures are not destroyed by an acid.

Organic materials that do not meet the requirement of having at least four carbon atoms in series in the backbone are undesirable, because they cannot form a film of sufficient flexibility. Organics with heteroatoms, such as oxygen, nitrogen, sulfur, or the like, may provide sufficient flexible membranes even if they do not have at least four carbon atoms bonded in series in the main chain. Nevertheless, they are still undesirable because polar interactions that tend to occur in chains containing 3 or less carbon atoms make the membrane very sensitive to hydrolysis by protons and water present therein. . Organic materials having at least four carbon atoms connected in series to the main chain are useful in the present invention because they can significantly control polar interactions even when they have heteroatoms, such as oxygen, nitrogen or sulfur, in the structure.

The organic material (A) is not particularly limited as long as it has at least four carbon atoms continuously bonded to the main chain. It may be straight chain or branched or may have a heteroatom such as oxygen, nitrogen or sulfur in its structure.

The simplest structural organic material having four carbon atoms connected in series and useful in the present invention is butylene and its molecular weight is 56. The carbon number of the main chain is not limited. However, the organic material preferably has a number average molecular weight of 30,000 or less in order to realize the heat resistance effect generated by bonding the organic material (A) and the three-dimensional crosslinked structure (B) to each other.

Compounds useful in the present invention as organic material (A) include, but are not limited to, polyethers such as polytetramethylene oxide, polyhexamethylene oxide, and the like; Polyacrylic and polymethacrylic acids (hereinafter referred to as the generic name "poly (meth) acrylic acid"), for example n-propyl poly (meth) acrylate, isopropyl poly (meth) acrylate, n-butyl poly (Meth) acrylate, isobutyl poly (meth) acrylate, sec-butyl poly (meth) acrylate, tert-butyl poly (meth) acrylate, n-hexyl poly (meth) acrylate, cyclohexyl poly (meth ) Acrylate, n-octyl poly (meth) acrylate, isooctyl poly (meth) acrylate, 2-ethylhexyl poly (meth) acrylate, decyl poly (meth) acrylate, lauryl poly (meth) acrylate Isononyl poly (meth) acrylate, isoboroyl poly (meth) acrylate, benzyl poly (meth) acrylate and stearyl poly (meth) acrylate; Acrylamides such as polyacrylamide, poly N-alkyl acrylamide, and poly2-acrylamide-2-methylpropane sulfonic acid; Vinyl esters such as polyvinyl acetate, polyvinyl formate, polyvinyl propionate, polyvinyl butyrate, polyvinyl n-caprorate, polyvinyl isocarate, polyvinyl octoate, polyvinyl laurate, poly Vinyl palmitate, polyvinyl stearate, polyvinyl trimethyl acetate, polyvinyl chloroacetate, polyvinyl trichloroacetate, polyvinyl trifluoroacetate, polyvinyl benzoate and polyvinyl pibarate; Polyvinyl alcohol; Acetal resins such as polyvinyl butyral; Polymethylenes such as tetramethylene, hexamethylene, octamethylene, decamethylene, dodecamethylene and tetradecamethylene; Polyolefins such as long chain polyethylene, polypropylene and polyisobutylene; And fluorine resins such as polytetrafluoroethylene, polyvinylidene fluoride, and the like. Copolymers thereof and mixtures of two or more of the above organic polymers may be used in the present invention. Because of acid resistance and heat resistance, polyethers, polyolefins, fluororesins and the like are particularly preferable among these organic materials. In view of imparting flexibility to the membrane and compatibility with the three-dimensional crosslinked structure and the proton conductivity imparting agent, for example, polyethers such as polytetramethylene oxide and polyhexamethylene oxide are more preferable. Polyethers have adequate flexibility and are well compatible with three-dimensional crosslinked structures and proton conductivity granters due to the polarity of the ether bonds. As a result, they enable higher amounts of proton conductivity giving agents to be added, which is very advantageous for obtaining high proton conductivity.

In view of its heat resistance in addition to the above preferred properties, polytetramethylene oxide is also more preferred. Controlled molecular weight polytetramethylene oxide can be used commercially at an affordable price. It may be suitable for use for the proton conductive membrane of the present invention, because it gives the membrane sufficient flexibility and does not discolor to 160 ° C. and is not cut.

The polytetramethylene oxide is not particularly limited in terms of molecular weight, but one having a weight average molecular weight of 200 to 2000 is suitably used.

Polymethylene chains having no ether bonds, or so-called olefin chains, are also suitably used in the present invention when considering resistance to heat and acid. These include tetramethylene, hexamethylene, octamethylene, decamethylene, dodecamethylene, tetradecamethylene, long chain polyethylenes, branched isobutylenes, isoprene, mixtures thereof, and the like. Particularly because of their high conductivity, those containing a methylene chain having 4 to 20 carbon atoms are suitably used.

The organic material of the present invention may be combined with a polar group such as a carboxyl group, a hydroxyl group, a sulfone group or a phosphor group to enhance compatibility with an ion conductive medium and an inorganic crosslinking compound. It is preferable that polyethylenes and fluororesins have a polar group by copolymerization or the like.

As long as the heat resistance is not impaired, a water-containing resin (E) having up to 4 carbon atoms continuously bonded to the chain in addition to the organic material (A), for example, polyethylene oxide or polypropylene It may also be mixed with an oxide or the like. Water-containing resins are defined as resins that may contain 5% by weight or more. Although not particularly limited in terms of molecular weight, it is particularly preferable to be dissolved in water. Such a water-containing resin (E) functions to hold water (D) as a proton conducting material, thereby contributing to the stable proton conduction properties being expressed from a low temperature over a wide range of temperatures.

The content of the water-containing resin (E) is usually 5 to 95 parts by weight, preferably 10 to 80, based on 100 parts by weight of the organic material (A), although it varies depending on, for example, its thermal stability and acid resistance. Parts by weight. If the content is 5 parts by weight or less, sufficient moisture retention can not be imparted to the membrane, and if it is 95 parts by weight or more, the heat resistance of the film may deteriorate.

One preferred embodiment of the organic material (A) is a combination of polytetramethylene oxide and polyethylene oxide. In such cases, the polytetramethylene oxide has a weight average molecular weight of about 200 to 2000, and the polyethylene oxide has a weight average molecular weight of about 100 to 1000. The ratio can be chosen selectively so as not to impair the heat resistance of the membrane.

It is necessary in the present invention that the organic material (A) and the three-dimensional crosslinked structure (B) having a metal-oxygen bond are bonded to each other by covalent bonds, as described later. Covalent bonds can be introduced by either of the following two methods:

1) Substituents capable of bonding themselves to the three-dimensional crosslinked structure (B), for example, hydrolyzable cyryl groups or metal alkoxides, etc., are introduced in advance into the organic material (A) and used to generate covalent bonds,

2) Substituents capable of reacting with the organic material (A), for example, isocyanate, vinyl, amino, hydroxyl, carboxyl or epoxy groups are introduced into the three-dimensional crosslinked structure (B) in advance, and this is the organic material (A). Reacts with to form a covalent bond.

Of the two methods, the former is more preferred, where components (A) and (B) can be very finely dispersed (nano dispersion) more easily at the molecular level and can be used simply. In this case, it is preferable that the organic substance (A) is incorporated into the hydrolyzable silyl group.

Hydrolyzable silyl groups are groups that react with water to form silanol (Si-OH) and include one or more alkoxy groups (eg, methoxy, ethoxy, n-propoxy, isopropoxy or n-butoxide). Or the like) or silicone to which the chlorine is bound.

Examples of the organic material (A) in which the hydrolyzable silyl group is incorporated include bis (triethoxysilyl) butane, bis (triethoxysilyl) hexane, bis (triethoxysilyl) octane and bis (triethoxysilyl) nonane , Bis (triethoxysilyl) decane, bis (triethoxysilyl) dodecane, bis (triethoxysilyl) tetradodecane, general formula R ¹ _3-x -R ² _x -Si- (CH ₂ ) _n -Si-R ¹ _3-x -R ² _x [R ¹ Silver hydroxy, methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, isobutoxy, t-butoxy group or chlorine; R ² is a methyl, ethyl, n-propyl or isopropyl group; (x) is an integer from 0 to 2; (n) is an integer from 4 to 20], a commercially available polypropylene oxide (KANEKA CORPORATION, SILYL ^™ ) having a hydrolyzable silyl group at the terminal, and having a hydrolyzable silyl group at the terminal and / or side chain Polyisobutylene (KANEKA CORPORATION, EPION ^TM ), polyacrylates having hydrolyzable cyryl groups at the ends and / or side chains (KANEKA CORPORATION, GEMLAC ^TM ), and poly (ethylene-co-alkoxyvinylsilane) (Aldrich) Include.

The organic material is reacted with commercially available 3-triethoxysilylpropyl isocyanate (Shin-Etsu Silicone, KBE9007) when it has a hydroxyl or amino group, or 3-triethoxy when it has a halogen The hydrolyzable silyl group can be coalesced by reacting with silylpropylamine. When it has an unsaturated bond, it is reacted with a silyl hydride such as trialkoxysilane or dialkoxy monoalkylsilane in the presence of a catalyst such as chloroplatinic acid. Hydrolyzable silyl groups can also be easily incorporated. When the organic material is a polymer, a hydrolyzable silyl compound having a functional group (e.g., a polymerizable unsaturated bond) and an organic polymer monomer are copolymerized to easily generate an organic polymer having a hydrolyzable silyl group at the terminal and / or side chain. Can be.

Most of the organic materials have two or more hydrolyzable cyryl groups. It is desirable to have two or more hydrolyzable cyryl groups, because it provides a tough membrane. However, as long as the membranes they provide are strong enough, having one hydrolyzable silyl group can also be useful in the present invention.

The organic material having one hydrolyzable silyl group is preferably at least one acidic group (e.g., sulfonic or phosphoric group), hydroxyl group, hydrophilic group (e.g., weakly basic salt such as ammonium salt) Etc.). The hydrophilic group serves to enhance the water retention of the membrane and promote proton conductivity. Although there is no particular limitation on the number of carbon atoms and the molecular weight, generally speaking, an organic material having one hydrolyzable silyl group has a molecular weight of 1000 or less. Having a molecular weight of 1000 or more can degrade the strength or heat resistance of the membrane. The content of such organic materials is not particularly limited as long as the film has sufficient strength and heat resistance, but is 80% by weight or less with respect to the total solid component of the film, and preferably 60% by weight or less.

When the hydrolyzable silyl group is incorporated, the organic material need not be further incorporated with the precursor for the three-dimensional crosslinked structure (B). This is because the silyl group itself can produce such a structure by hydrolysis or the like. Nevertheless, it may also be incorporated with such precursors.

Thus, when hydrolyzable silyl groups are coalesced, organic materials can be bonded to the three-dimensional crosslinked structure via covalent bonds, providing a so-called inorganic / organic mixture membrane, where they are at the molecular level via metal-oxygen bonds. Mixed. Such membranes are well suited as proton conductive membranes that can be operated at high temperatures because the potential thermal stability in three-dimensional crosslinked structures is further improved. Moreover, the crosslinked organic material makes the film more stable at high temperatures, otherwise it will dissolve or suffer structural changes.

The proton conductive membranes of the present invention have sufficient resistance to heat and at the same time have the flexibility and ease of manufacture that are convenient to use MEAs, which are combined in the membranes as three-dimensional crosslinked structures (B) and organic as flexible components. From substance (A). Sufficient resistance to heat means a very high acceptable and operable temperature of 100 ° C. or higher, preferably 140 ° C. or higher.

2. Three-dimensional crosslinked structure with specific metal-oxygen bonds (B)

As described above, the proton conductive film of the present invention includes an organic material (A), a three-dimensional crosslinked structure (B) having a specific metal-oxygen bond, a proton conductivity providing agent (C), and water (D).

The three-dimensional crosslinked structure (B) of the present invention having a specific metal-oxygen bond is responsible for two main functions, one to impart high heat resistance to the proton conductive membrane, which is a component (A) and (B) The strong bond comes from the covalent bond, and the other is to hold the proton conductivity imparting agent (C) as described later.

Three-dimensional crosslinked structure (B) having a specific metal-oxygen bond means a structure formed by a metal oxide, for example, silicon, titanium, zirconium oxide, or the like. Such structures (B) can usually be readily prepared by so-called sol-gel reactions, in which metallic compounds (eg metal alkoxides or metal halides) as precursors with hydrolyzable metal containing groups are hydrolyzed and condensed .

The hydrolyzable metal-containing group is not necessarily present in the precursor, and may exist as a substituent in the organic material (A). When it is present in the organic material (A), the precursor may be replaced by the organic material (A) having a hydrolyzable metal containing group.

Of the three-dimensional crosslinked structures (B) having specific metal-oxygen bonds, those having silicon-oxygen bonds are particularly preferable. It can be readily prepared by a sol-gel process using alkoxy silicates or halogenated silyl groups as stocks. Silicone compounds as raw materials are inexpensive and can easily control their activity, which makes the process more economical and processable.

The ratio of the organic material (A) to the three-dimensional crosslinked structure (B) is not particularly limited, but is preferably 3:97 to 99: 1 by weight, more preferably 10:90 to 97: 3. The organic material (A) does not provide sufficient flexibility to the film at 3% by weight or less, and the three-dimensional crosslinked structure (B) does not give sufficient heat resistance to the film at 1% by weight or less.

3. Proton Conductor (C)

As described above, the proton conductive film of the present invention, in addition to the three-dimensional crosslinked structure (B) containing the organic material (A) and a specific metal-oxygen bond, a proton conductivity providing agent (C) and water (D) Include.

The proton conductivity imparting agent (C) of the present invention is used to increase the proton concentration in the proton conductive membrane. Increased proton concentration is essential for high proton conductivity for the present invention, given the increased proton conductivity and the concentration of the proton conducting medium (water (D) in the present invention) which is proportional to the proton concentration.

So-called acidic compounds which release protons are used as proton conductivity imparting agents (C). Acidic compounds useful as proton conductivity imparting agents (C) include phosphoric acid, sulfuric acid, sulfurous acid, carboxylic acids, boric acid, inorganic solid acids, and derivatives thereof. Two or more of these acids or derivatives thereof may be used in the present invention.

Among these, inorganic solid acid is more preferable. These include, for example, acid with a Keggin structure such as tungstophosphoric acid, tungstosilicic acid, and molybdophosphoric acid, and Dawson. It is an inorganic oxo acid, including polyhetero acid of structure).

These inorganic solid acids have a molecular size large enough to control the elution of the acid to a significant extent from the membrane, even in the presence of water and the like. Moreover, they have ionic polarity, are retained in the membrane by interaction with metal-oxygen bonds, and serve to regulate the dissolution of acids from the membrane. They are particularly desirable properties for proton conducting membranes when operating at elevated temperatures for extended periods of time.

Among the solid inorganic acids, tungstophosphoric acid is particularly preferred given the high acidity, large size and magnitude of polar interaction with the metal-oxygen bond. The inorganic solid acid may be used together with another acid for the proton conductivity imparting agent (C) of the present invention. Two or more organic and inorganic acids may also be used as the imparting agent (C).

The content of the proton conductivity imparting agent (C) is preferably 5 parts by weight or more per 100 parts by weight of the total of the organic compound (A) and the three-dimensional crosslinked structure (B). At 5 parts by weight or less, good proton conductivity of the membrane cannot be expected due to insufficient proton concentration. There is no upper limit to the content of the proton conductivity imparting agent (C), and many may be used as long as the film properties are not impaired by it. At 500 parts by weight or more relative to 100 parts by weight of the components (A) and (B) in total, the membrane is usually too rigid and brittle when a solid acid is used, and conversely too soft when a liquid acid is used. Therefore, it is suitable to make the content 500 parts by weight or less.

4. Water (D)

The proton conductive film of the present invention, as described above, includes water (D) in addition to an organic material (A), a three-dimensional crosslinked structure (B) containing a specific metal-oxygen bond, and a proton conductivity providing agent (C). do.

In the present invention, water (D) serves as a medium for effectively conducting protons. There are three or four reactors in which water conducts protons. For example, water accepts protons and becomes H ₃ O ⁺ and moves on its own. In another reactor, protons hop over water molecules. Any reactor is useful in the present invention.

When fuel cells are used or tested in a humid atmosphere, water is introduced into the membrane. Thus, the membrane may be pre-soaked into water to introduce water. When formed in the presence of water or steam, water can be introduced into the membrane.

In order to effectively introduce water into the proton conductive membrane, it is recommended to impart moisture retentivity to the membrane. Therefore, it is desirable to form a three-dimensional crosslinked structure under water or steam to contain water during the manufacturing step, in particular during the sol-gel reaction.

As the water (D) content increases, the membrane tends to have higher proton conductivity. However, the content is usually in the range of 1 to 60% by weight. When less than 1% by weight, the membrane does not have sufficient proton conductivity. A content of more than 60% by weight is also undesirable because the membrane may be excessively porous or swell. When the fuel cell membrane is excessively porous, hydrogen as fuel leaks out of the anode (a phenomenon known as chemical shorting), resulting in a significant loss of energy efficiency. On the other hand, when the membrane is excessively swelled by water, it may also undergo a volume change that can generate enough stress to damage the electrode or the membrane itself. Therefore, the moisture content is preferably maintained at 60% by weight or less.

The moisture content can be controlled by adjusting the composition of the organic material content of the three-dimensional crosslinked structure, the content of the proton conductivity imparting agent, or the process conditions under which the film is formed.

One or more known proton conducting materials may be added to water (D) to further promote proton conductivity by being used in the present invention. These materials include ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butylolactone, gamma-valerolactone, sulfolane, 3-methylsulolane, dimethyl sulfoxide, dimethylformamide and N-methylloxazolidinone ( N-methyloxazolidinone) and the like. The content of these proton conducting materials is not particularly limited as long as the strength of the membrane is not degraded. However, it is usually 50% by weight or less with respect to the whole film. The combination of water and one or more proton conducting materials conducts protons more effectively than water alone, resulting in high proton conductivity as well as increasing the compatibility of the organic material with the proton conducting agent.

5. Other optional ingredients

The proton conductive membrane of the present invention is an optional component in addition to the above-described organic material (A), three-dimensional crosslinked structure (B), proton conductivity providing agent (C) and water (D) as long as the object of the present invention is not impaired. It may also include. These optional ingredients include reinforcing agents, surfactants, dispersants, reaction promoters, stabilizers, colorants, antioxidants, inorganic or organic fillers, and the like.

Taking the reinforcing agent (F) as an example, the proton conductive film of the present invention is a fiber reinforcing agent because it may be brittle depending on the composition of the film, even if it has an appropriate strength mainly due to the three-dimensional crosslinked structure having a metal-oxygen bond. It is possible to use as.

Various materials include polymeric fibers (eg, acrylic, polyester, polypropylene, and fluorine resins) fibers, natural substrates (eg, silk, cotton, and paper), and glass, and reinforcing fibers or fabrics thereof. Can be used as fabrics. Among them, glass fibers and fabrics are particularly preferable in view of their strength and compatibility with the film composition.

Glass fibers may or may not be surface treated. The fiber diameter is not particularly limited as long as it is uniformly dispersed in the membrane. When considering the relationship with the thickness of the film, it is preferably 100 µm or less, more preferably 20 µm or less. The fiber length is not particularly limited. Glass fibers of various sizes or their fabrics can be used commercially (eg from Nitto Boseki).

Glass fibers can be easily introduced by adding to the film forming composition in the form of powder or yarn. When a fabric of glass fiber is used, it can be impregnated into the membrane composition and cured by a sol-gel method or adhered to a previously prepared membrane.

Glass fibers may be reinforced with long, crystalline fibers, whiskers and the like in themselves.

6. Proton Conductive Membrane And Its Manufacture

As described above, the proton conductive film of the present invention includes an organic material (A), a three-dimensional crosslinked structure (B) having a specific metal-oxygen bond, a proton conductivity providing agent (C), water (D), and, if necessary, Comprises one or more optional components (eg, glass fibers). The main feature is that the organic material (A) and the three-dimensional crosslinked structure (B) are strongly bonded to each other by covalent bonds.

As described previously in the description of the prior art, simple mixing of structures and organic materials crosslinked by metal-oxygen bonds is known. However, such mixing is insufficient to realize both flexibility and heat resistance by the three-dimensional crosslinked structure by the organic materials required for the film. In the case of simple mixtures, the content of organic matter should be increased to ensure the flexibility of the membrane. If the organic material present in the membrane in a very high content is not proton conductive, it will block the proton pathway and reduce the proton conductivity of the membrane. On the other hand, even when it is proton conductivity, a significant improvement in heat resistance cannot be expected, and it is difficult to maintain higher heat resistance than a typical fluororesin film.

The organic material and the three-dimensional crosslinked structure are bonded to each other by crosslinking in the proton conductive film of the present invention, and as a result, they are very finely dispersed at the molecular level (nano dispersion). Thus, even when the organic material is present in a sufficient amount required to ensure the flexibility of the membrane, the proton conduction path will not be interrupted. Since it is bonded to a highly heat resistant three-dimensional crosslinked structure, the cleavage of its molecules (ie, thermal decomposition, etc.) under heating is controlled. As a result, the proton conductive membrane is flexible and at the same time heat resistant.

In addition, the organic material is essentially crosslinked to stabilize the film at high temperatures that would otherwise dissolve or become structurally uncrosslinked.

The proton conductive membrane of the present invention can be prepared by various methods, for example, any one of the following five methods.

1) A reaction system of a composition comprising an organic material, a hydrolyzable inorganic compound capable of forming a three-dimensional crosslinked structure, and a proton conductivity-imparting agent is prepared and made into a thin film by a known method. The sol-gel reaction takes place in this thin film reaction system in the presence of water or steam.

2) A reaction system of a composition comprising an organic material, a hydrolyzable inorganic compound capable of forming a three-dimensional crosslinked structure, and a proton conductivity-providing agent is prepared and made into a thin film by a known method. The sol-gel reaction takes place in such thin film reaction systems in the presence of water or water vapor and alcohols having 4 or less carbon atoms or vapors thereof.

3) A membrane comprising a structure three-dimensionally crosslinked by an organic material and a metal-oxygen bond is prepared, and the membrane is immersed in a liquid containing a proton conductivity imparting agent to dope the component.

4) A porous inorganic crosslinked structure is prepared and immersed in a solution of organic compounds for composition. The composite is then doped with a proton conductivity imparting agent.

5) A film of organic compound is prepared and swollen with a precursor solution to form a three-dimensional crosslinked structure with metal-oxygen bonds. The sol-gel reaction is carried out in the swollen film and then doped with a proton conductivity imparting agent.

In methods 1) and 2), organic materials and hydrolyzable inorganic compounds capable of forming a three-dimensional crosslinked structure do not need to be added as individual stocks, as described above. For example, when the organic compound has a hydrolyzable silyl group or a hydrolyzable metal containing group (eg, metal alkoxide), the latter hydrolyzable inorganic compound may be omitted.

In method 5), the organic compound may have a crosslinked structure by covalent bonds or similar crosslinked structures such as, for example, hydrogen bonds or crystallization. It may be crosslinked during the sol-gel reaction, or may be made into a thin film and then irradiated with an electron beam or ultraviolet ray for crosslinking.

The object of the present invention is, as described above, to an organic material (A), a three-dimensional crosslinked structure (B) having a specific metal-oxygen bond, a proton conductivity imparting agent (C), water (D), and, if necessary, To provide one or more optional ingredients (eg, glass fibers). Therefore, the method for producing such a film is not particularly limited as long as the present object is satisfied. However, the methods 1) and 2) are preferred, for example, because of their ease of handling, certainty and cost of investment.

The method 1) and 2) are described according to the process sequence for a more detailed description of the method for producing a proton conductive membrane of the present invention.

The first step is to mix the organic material with hydrolyzable silyl groups and, for example, a metal alkoxide hydrolyzable inorganic compound to form a three-dimensional crosslinked structure as needed. The hydrolyzable inorganic compound is preferably added separately to 100% by weight or less with respect to the organic compound, otherwise the membrane may be too rigid and the flexible effect of the organic compound may not be fully expressed.

Hydrolyzable inorganic compounds useful in the present invention include alkoxysilicates such as tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetra-t-butoxysilane, and these Monoalkyl and dialkyl derivatives of; Phenyltriethoxysilane, halogenated silane, tetraethoxy titanate, tetraisopropoxy titanate, tetra-n-butoxy titanate, tetra-t-butoxy titanate, and monoalkyl and dialkyl derivatives thereof; Compounds substituted with groups for controlling the rate of crosslinking reaction, for example, alkoxy titanate including acetylacetone and oligomers thereof; And alkoxy zirconates. When the hydrolyzable inorganic compound includes an alkyl group, the alkyl group may be substituted with a hydrophilic group, for example, a carboxyl, sulfone, sulfate ester, phosphate, amine salt or hydroxyl group. Hydrophilic groups increase the moisture content of the membrane and also promote proton conductivity.

In the first step, a suitable solvent may be used as component (G). Solvents useful in the present invention include alcohols (eg, methanol, ethanol, isopropanol, n-butanol, and t-butanol, etc.), and ethers (eg, tetrahydrofuran, dioxane, etc.). The solvent is not limited to the above, and any solvent may be used as long as it dissolves or mixes organic materials, metal alkoxides, and the like.

In the first step, a compound having a relative dielectric constant of 20 or more and a boiling point of 100 ° C. or more may be used in addition to the component (G) as a solvent. Compounds with a relative dielectric constant of 20 or more are preferred because they have adequate surface-active functions and can help disperse organic and inorganic compounds. On the other hand, compounds having a boiling point of 100 ° C. or higher are preferred because they remain in the membrane after the heating / curing step and are replaced by water when washed with water to increase the moisture content of the membrane. Moreover, when a compound having a relatively low molecular weight (eg, 100 or less) is used as the organic material to make the film soft, the residual compound can act as a plasticizer.

Compounds satisfying these two properties include ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butylolactone, gamma-valerolactone, sulfolane, 3-methylsulfolane, dimethyl sulfoxide, dimethylformamide and N-methyl Siloxane oxazolidinones and the like.

In the second step, a proton conductivity imparting agent is added to the solution obtained in the first step to prepare a reaction system containing a precursor solution, i.e., a raw material mixture for film formation. The first and second steps may be incorporated to simplify the manufacturing process by simultaneously mixing the raw materials.

The third step produces a film of the precursor solution by known methods, for example casting or coating. The fourth step is a so-called sol-gel process wherein the film is treated in the presence of water or steam and at a selective temperature in the range from room temperature to 300 ° C. to produce the desired film. The film may be heated in the fourth step by known methods, for example by heating in an oven or under a high pressure reaction vessel under pressure.

In the method 1), water or water vapor is introduced into the reaction system obtained in the third step, i.e., the precursor film, and the precursor is brought into contact with water by heating it in water after being cured in the water vapor atmosphere or to the extent that it is not soluble in water. to be. When heated in the presence of water or steam at these conditions, hydrolysis and condensation of the precursor film are effectively effected, resulting in a higher heat resistant film. Moreover, the silanol groups formed as a result of hydrolysis will enhance the water holding capacity of the membrane and promote proton conductivity.

Films containing water condense and cure more effectively in the presence of water or water vapor to increase its water content.

Water vapor atmosphere means an atmosphere having a relative humidity of 10 to 100%. The increase in water vapor promotes hydrolysis.

In method 2), a reaction system (i.e., the precursor film obtained in the third step described above) comprising a mixture of an organic material, a hydrolyzable inorganic compound forming a three-dimensional crosslinked structure and a proton conductivity imparting agent, Together with alcohol having 4 or less carbon atoms or vapor thereof. In this case, as in method 1), the precursor film may be heated in a water / alcohol vapor atmosphere after it is cured to such an extent that it does not dissolve in solution. Hydrolysis and condensation of the precursor film are effectively effected when heated in the presence of water / alcohol solution or vapor while it is swollen, creating a film with adequate flexibility and higher heat resistance.

Alcohol compounds useful for method 2) are alcohol compounds having 4 or less carbon atoms and include methanol, ethanol, isopropanol, n-propanol, n-butanol, t-butanol, ethylene glycol, propylene glycol, glycerin and the like. Preferred alcohol / water ratios are 1/99 to 90/10.

A water / alcohol mixed vapor atmosphere means an atmosphere with a relative humidity of 10 to 100%. It is desirable to increase the humidity, because as the relative humidity approaches 100%, the membrane swells more adequately and hydrolyzes more effectively.

The temperature level of the fourth step is not particularly limited as long as the three-dimensional crosslinked structure can be formed by the sol-gel reaction and the organic material is decomposed at that temperature level. The thickness of the film is not particularly limited, but is usually in the range of 10 μm to 1 mm.

In order to promote the formation of the three-dimensional crosslinked structure, a catalyst such as hydrochloric acid, sulfuric acid or phosphoric acid may be previously incorporated into the reaction system. The formation of the three-dimensional crosslinked structure can also be promoted in the presence of alkali, so that the use of a basic catalyst, for example ammonia, may be used. However, acid catalysts are more preferred because the basic catalyst may react with the proton conductivity imparting agent.

Thus, the resulting proton conductive membrane is an innovative organic / inorganic composite membrane having absolutely high unexpected heat resistance and sustainability and high proton conductivity even at high temperatures, and can be suitably used as a fuel cell membrane. When the proton conductive membrane of the present invention is used in a fuel cell, a so-called membrane / electrode assembly is formed that includes a membrane bonded to a catalyst carrying electrode. The method for producing the membrane / electrode assembly is not particularly limited; It can be produced by any suitable method, for example by heating or compressing or coating a membrane or electrode with a proton conducting combination.

The proton conductive membrane of the present invention can be applied not only to PEFC but also to chemical sensors or ion exchange membranes.

EXAMPLE

The present invention will be described in more detail by way of examples, which do not limit the invention. All compounds and solvents used in the examples and comparative examples below are commercial. They were used directly, i.e. not processed for these examples.

Analytical Method :

(1) Determination of moisture content in the film

The cross section of the proton conductive membrane was measured by a thermogravimetric analyzer (Seiko Instruments, TG / DTA320). Membranes generally showed weight loss at 90 to 130 ° C., which is believed to be the result of water evaporation since such phenomena were not observed in membranes without water completely. Thus, the moisture content of the membrane herein means the weight loss divided by the weight of the entire membrane.

Evaluation method :

(1) heat resistance evaluation

The proton conductive membrane was heated to 140 ° C. for 24 hours in an oven under a nitrogen atmosphere. The treated film was evaluated for its heat resistance by visual and bending function tests, and was classified as follows.

ｏ: Flexible film, does not bend when folded

×: easily collapses, disintegrates or melts when folded

(2) Evaluation of Proton Conductivity

The proton conductive film of the present invention was coated on both sides with silver paste and dried to form an electrode, thereby producing a membrane / electrode assembly (MEA). The proton conductivity was determined by testing the 4-terminal impedance with an electrochemical impedance meter (Solartron, Model 1260) at a frequency of 0.1 Hz to 2 MHz.

In this analysis, the MEA sample was supported in an electrically insulated closed container and its proton conductivity was measured at varying temperatures under a steam atmosphere, where the temperature of the cell was increased from room temperature to 160 ° C. by a thermostat. The values measured at 140 ° C. are shown as representative values herein. The measuring tank was pressurized to 5 atmospheres at 140 ° C. to determine proton conductivity.

Example 1

(Synthesis of Polytetramethylene Oxide with Triethoxysilyl Group at the End)

75.0 g of polytetramethylene glycol # 650 (Wako Pure Chemical Industries, weight average molecular weight: 650) was placed in a dry glass container and 57.1 g of 3-triethoxysilylpropyl isocyanate (Shin-Etsu Silicone, KBE-9007) After addition, the mixture was slowly stirred for 120 h at 60 ° C. under a nitrogen atmosphere for the next process. The viscous liquid obtained was tested by H ¹ -NMR (BRUKER, Japan, DRX-300). A spectral pattern was thought to be related to the polytetramethylene oxide with the triethoxysilyl group at the end. The product was considered to be nearly pure and no impurity signal was observed at the detectable sensitivity of NMR. Thus, the resulting compound had 4.9% by weight of silicon atoms derived from the hydrolyzable silyl group (triethoxysilyl group) relative to the total composition.

HO (CH ₂ CH ₂ CH ₂ CH ₂ O) _n H + 2OCNCH ₂ CH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ →

(OC ₂ H ₅ ) ₃ SiCH ₂ CH ₂ CH ₂ NHCOO (CH ₂ CH ₂ CH ₂ CH ₂ O) _n CONHCH ₂ CH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃

Synthesis of Other Compounds with Hydrolysable Cyryl Group at the Terminal

Except for using polytetramethylene glycol # 1000 (Wako Pure Chemical Industries, weight average molecular weight: 1000) or polyethylene glycol (Wako Pure Chemical Industries, weight average molecular weight: 600) instead of polytetramethylene glycol # 650 , The same process as used in Example 1 was repeated, to prepare a compound having a hydrolyzable silyl group at its terminal.

Preparation of Mixed Solution and Preparation of Film

1.0 g of polytetramethylene oxide having a triethoxysilyl group at the end was mixed with 1.0 g of isopropanol. Separately from this solution, 1.0 g of tungstophosphoric acid (Wako Pure Chemical Industries) was dissolved in 1.0 g of isopropanol to prepare a solution. These solutions were mixed with each other for 1 minute with vigorous stirring, and the mixed solution was placed in a polystyrene petri dish (Yamamoto MFG) having an inner diameter of 9 cm. The dish was placed in a container maintained at 60 ° C., and the contents were heated for 12 hours by introducing steam generated at 70 ° C. This produced a colorless, transparent flexible film.

Example 2

The membrane was prepared by repeating the same process as used in Example 1, except that 0.5 g of tungstophosphoric acid was used.

Example 3

Polytetramethylene glycol # 250 (Aldrich) was used in place of Polytetramethylene glycol # 650 and 1.17 g of tungstophosphoric acid was used and was used in Example 1 except that no water vapor was introduced upon heating. The same process was repeated to prepare a membrane.

Example 4

 The membrane was repeated in the same process as used in Example 1, except that 0.5 g of tungstophosphoric acid was used, 0.5 g of ethylene carbonate (Wako Pure Chemical Industries) was added, and no water vapor was introduced for heating. Prepared.

Example 5

 The membrane was prepared in the same manner as in Example 1, except that 0.75 g of tungstophosphoric acid was used, 0.5 g of ethylene carbonate was added and no water vapor was introduced for heating.

Example 6

The membrane was prepared using the same process as used in Example 2 except that 0.5 g of ethylene carbonate was added.

Example 7

0.67 g of polytetramethylene having a triethoxysilyl group and 0.33 g of phenyltriethoxysilane (Toshiba Silicone) prepared in a similar manner as in Example 1 were dissolved in 1.0 g of isopropanol. Apart from this solution, 0.57 g of tungstophosphoric acid and 0.28 g of propylene carbonate (Wako Pure Chemical Industries) were dissolved in 1.0 g of isopropanol, respectively, to prepare a solution. These solutions were mixed with each other for 1 minute with vigorous stirring, and the mixed solutions were placed in a polystyrene petri dish having an inner radius of 9 cm. This dish was heated to 60 ° C. in an oven for 12 hours. This produced a colorless, transparent flexible membrane.

Example 8

The membrane was prepared by repeating the same process as used in Example 1, except that a 90/10 mixture of steam produced at 80 ° C. and n-butanol vapor was used instead of steam produced at 70 ° C.

Example 9

The membrane was repeated by the same process as used in Example 1 except that 0.1 g of glass fiber (Nitto Boseki, PF70E-001, fiber major axis: 70 μm, fiber diameter: 10 μm) was added to the membrane composition. Prepared.

The membrane produced was proton conductive and had a high strength as that prepared in Example 1.

Example 10

The membrane was prepared in the same manner as used in Example 1 except that polytetramethylene glycol # 1000 (Wako Pure Chemical Industries) was used instead of polytetramethylene glycol # 650.

The membrane was coated 3 μm thick with polytetramethylene glycol # 1000 by a bar coater, and gas diffusion electrodes (E-TEK, platinum content: 0.30 mg / cm 2, diameter 20 mm) were coated on both sides. . This membrane was assembled into a test cell and the output performance of the fuel cell was evaluated. Here, hydrogen and oxygen flowing at 60 ml / min were reacted with each other at a battery temperature of 100 ° C. and a gas pressure of 3 atmospheres. Hydrogen was wetted by passing it through a water bubbler in advance.

Cell output runs were tested with an electrochemical impedance meter (Solartron, model 1260). The result is shown in FIG.

Comparative Example 1

Dupont's Nafion 117 was used directly.

Comparative Example 2

Polytetramethylene glycol # 600 (Wako Pure Chemical Industries) was used instead of polyterramethylene glycol # 650, except that 0.5 g of propylene carbonate and 0.5 g of tungstophosphoric acid were used in the film preparation step. The membrane was prepared by repeating the same process as used in Example 7.

Comparative Example 2 used an organic material mainly characterized by a chain of two carbon atoms.

Comparative Example 3

The membrane was prepared by repeating the same process as used in Example 1 except that 0.25 g of tungstophosphoric acid was used. The membrane thus prepared was heated to 140 ° C. for 3 hours under a dry nitrogen atmosphere to remove moisture from the membrane. Proton conductivity was measured while not wet.

Thermogravimetric analysis (Seiko Instruments, TG / DTA320) up to 200 ° C. showed no weight loss, indicating that the membrane is essentially water free.

[Comparative Example 4]

The membrane was prepared in the same manner as in Example 1, except that 0.5 g of 1N hydrochloric acid was used as the curing catalyst instead of tungstophosphoric acid as the proton conductivity imparting agent. During the heat treatment for curing hydrochloric acid was completely evaporated and no residual acid was observed.

Example 11

(Synthesis of dodecanediol having a triethoxysilyl group at the end)

20.2 g (100 mmol) of 1,12-dodecanediol (100 mmol) and 3-triethoxysilylpropyl isocyanate (amount equal to the amount of hydroxyl groups) instead of polytetramethylene glycol # 650 49.5 g (200 mmol) The same process as used in Example 1 was used except that was used, and the target compound was prepared quantitatively. Its chemical structure was determined by NMR analysis.

The compound produced is an olefin organic material that does not have an ether bond, unlike that made using polytetramethylene glycol.

In addition to dodecanol, other diols (eg, decandiol, octanediol, hexanediol and butanediol, etc.) have been used to confirm that they can provide compounds with triethoxysilyl groups at their ends. The same is true for dodecanediamine and hexanediamine. When amines were used, the triethoxysilyl groups were bound via urea bonds, not urethanes.

Preparation of Mixed Solution and Preparation of Film

The same process as used in Example 2 was repeated except that 1.0 g of the dodecanediol having a triethoxysilyl group at the end was used instead of the polytetramethylene oxide having the triethoxysilyl group at the end. The membrane was prepared. The film produced was colorless, transparent and stiffer than that prepared in Example 1.

Example 12

Preparation of Mixed Solution and Preparation of Film

The membrane was prepared in the same manner as used in Example 2 except that commercial bis (triethoxysilyl) octane (AZmax) was used instead of polytetramethylene oxide having a triethoxysilyl group at the end. . The resulting film was colorless, transparent and stiffer than that prepared in Example 2.

Bis (triethoxysilyl) octane has no ether or urethane bonds and has a methylene chain olefin body having eight carbon atoms between the terminal triethoxysilyl groups.

Example 13

The membrane was prepared using the same process as used in Example 12 except that 0.78 g of tungstophosphoric acid was used. The resulting membrane was relatively rigid as prepared in Example 12.

Example 14

The same process as used in Example 12 was used except that bis (triethoxysilyl) hexane (AZmax) was used in place of bis (triethoxysilyl) octane and 1.04 g of tungstophoric acid was used. To prepare the membrane. The membrane produced was relatively rigid as prepared in Example 12.

Example 15

Preparation of Mixed Solution and Preparation of Film

The membrane was prepared using the same process as used in Example 2 except that molybdophosphoric acid (Wako Pure Chemical Industries) was used instead of tungstophosphoric acid. The film prepared was yellowish and transparent, and as flexible as that prepared in Example 2.

[Comparative Example 5]

The same process as that used in Example 2 was repeated except that polyethylene oxide having a triethoxysilyl group at the terminal (average molecular weight: 600) was used instead of polytetramethylene oxide having a triethoxysilyl group at the terminal. The membrane was prepared. The membrane produced was as flexible as the membrane prepared in Example 2.

Example 16

0.30 g of polytetramethylene glycol # 650 having a hydrolyzable silyl group at the end and 0.70 g of polyethylene glycol # 600 having a hydrolyzable silyl group at the end were dissolved in 1.0 g of isopropanol. Apart from this solution, 0.25 g of tungstophosphoric acid (Wako Pure Chemical Industries) and 0.25 g of ethylene carbonate were dissolved in 1.0 g of isopropanol. These solutions were mixed with each other for 1 minute by vigorous stirring, and the mixed solutions were placed in a polystyrene petri dish having an inner diameter of 9 cm. This dish was heated to 60 ° C. for 12 h in a saturated steam atmosphere. This produced a thick film of 100 μm.

Example 17

0.30 g of polytetramethylene glycol # 1000 having a hydrolyzable silyl group at the end and 0.70 g of polyethylene glycol # 600 having a hydrolyzable silyl group at the end were dissolved in 1.0 g of isopropanol, which were prepared in Example 1 Membrane was prepared by repeating the same process as used in Example 16.

Example 18

0.50 g of polytetramethylene glycol # 1000 having two hydrolyzable silyl groups at the end and 0.50 g of polyethylene glycol # 600 having hydrolyzable silyl groups at the end were dissolved in 1.0 g of isopropanol. Membrane was prepared by repeating the same process as that used in Example 16.

Example 19

0.70 g of polytetramethylene glycol # 1000 having two hydrolyzable cyryl groups at the end and 0.30 g of polyethylene glycol # 600 having hydrolyzable cyril groups at the end were dissolved in 1.0 g of isopropanol. Then, the same process as in Example 16 was repeated to prepare a membrane.

Example 20

The membrane was prepared using the same process as used in Example 2, except that 0.1 g of tetraisopropoxy titanate (Wako Pure Chemical Industries) was used as the precursor of the three-dimensional crosslinked structure. The prepared membrane had almost the same physical properties as those prepared in Example 2.

Tables 1 to 3 summarize the compositions used in the examples, the heating conditions and the physical properties of the membranes produced in these examples. Table 4 summarizes the comparative examples.

As shown in Tables 1 to 4, the proton of the present invention comprises an organic material (A), a three-dimensional crosslinked structure (B) containing a specific metal-oxygen bond, a proton conductivity imparting agent (C) and water (D) It is apparent that each of the conductive films exhibits high heat resistance and proton conductivity at 140 ° C. On the contrary, the fluorine-based resin (Comparative Example 1) used as one of the typical electrolytic membranes exhibits deteriorated physical properties. Each of the components (A) to (D) (Comparative Example 1) which do not satisfy the requirements of the present invention are clearly inferior to the present invention as electrolyte membrane in proton conductivity, heat resistance or mechanical properties. When the organic material is incorporated with a water-containing resin having four carbon atoms continuously bonded in the main chain (Examples 16 to 19), it has been found that the membrane has improved resistance to heat and enhanced water content to enhance proton conductivity.

Comparing the results of Example 1 with the results of Example 3, the use of water vapor for curing in the manufacturing process increases the efficiency of the sol-gel reaction and also increases the water content in the membrane, leading to enhanced proton conductivity. Power generation of the fuel cell using the proton conductive membrane of the present invention is also confirmed (Example 10).

Table 1

Table 2

Table 3

Table 4

The proton conductive film of the present invention has sufficient heat resistance by hybridization of an inorganic crosslinked structure and an organic material. When combined with a proton conductivity imparting agent and water, this results in an excellent proton conductive membrane that exhibits high proton conductivity at high temperatures.

The proton conductive membrane of the present invention can raise the operating temperature of PEFC to 100 ° C. or higher, which is currently of interest, leading to improved power generation efficiency and reduced CO toxicity. Elevated operating temperatures will make PEFCs applicable to cogeneration systems using waste heat, which will lead to a significant increase in energy efficiency.

Claims (21)

Organic material (A), three-dimensional crosslinked structure (B) having a specific metal-oxygen bond, proton conductivity providing agent (C) and water (D), (Iii) the organic material (A) has a number average molecular weight of 56 to 30,000 and at least four carbon atoms continuously connected to the main chain, (Ii) The organic material (A) and the three-dimensional crosslinked structure (B) are bonded to each other by covalent bonds. The proton conductive film according to claim 1, wherein the organic material (A) is polyether. The proton conductive film according to claim 2, wherein the organic material (A) is polytetramethylene oxide. The proton conductive film according to claim 1, wherein the organic material (A) is polymethylene. The proton conductive film according to claim 4, wherein the organic material (A) is octamethylene. The proton conductive film according to claim 1, wherein the organic material (A) comprises a water-containing resin (E) having four or less carbon atoms connected in series in a chain. The proton conductive film according to claim 6, wherein the water-containing resin (E) is polyethylene oxide. The proton conductive film according to claim 1, wherein the organic material (A) is a mixture of polytetramethylene oxide and polyethylene oxide. The proton conductive film according to claim 1, wherein the three-dimensional crosslinked structure (B) is formed by silicon-oxygen bonds. The proton conductive film according to claim 1, wherein the proton conductivity providing agent (C) is an inorganic solid acid. The proton conductive membrane according to claim 10, wherein the inorganic solid acid is tungstophosphoric acid. The proton conductive film according to claim 1, comprising 5 to 500 parts by weight of a proton conductivity-imparting agent (C) based on 100 parts by weight of the organic material (A) and 100 parts by weight of the three-dimensional crosslinked structure (B). The proton conductive membrane according to claim 1, comprising 1 to 60% by weight of water (D) based on the total proton conductive membrane. The proton conductive membrane according to claim 1, further comprising a reinforcing agent (F). The proton conductive film according to claim 14, wherein the reinforcing agent (F) is glass fiber. Preparing a reaction system comprising a mixture of an organic material (A), a hydrolyzable inorganic compound forming a three-dimensional crosslinked structure (B), and a proton conductivity providing agent (C); Forming a reaction system into a film; And forming a three-dimensional crosslinked structure (B) by metal-oxygen bonds in the film by a sol-gel reaction of the film in the presence of water vapor or liquid water (D). Preparing a reaction system comprising a mixture of an organic material (A), a hydrolyzable inorganic compound forming a three-dimensional crosslinked structure (B), and a proton conductivity providing agent (C); Forming a reaction system into a film; And a three-dimensional crosslinked structure (B) by metal-oxygen bonds in the film, by sol-gel reaction of the film in the presence of vapor or liquid water (D) and vapor or liquid of an alcohol having 4 or less carbon atoms. Comprising the step of forming a, proton conductive film manufacturing method. The method for producing a proton conductive film according to claim 16 or 17, wherein the organic material (A) and the hydrolyzable inorganic compound forming the three-dimensional crosslinked structure (B) are mixed with each other in an organic solvent (G). The method for producing a proton conductive film according to claim 18, wherein the organic solvent (G) is further incorporated with a compound (H) having a relative boiling point of 20 or more and a boiling point of 100 ° C or more. 20. The method of claim 19, wherein the compound (H) having a relative dielectric constant of 20 or more and a boiling point of 100 ° C or more is selected from the group consisting of ethylene carbonate, propylene carbonate and butylene carbonate. A fuel cell using the proton conducting membrane according to claim 1.

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