JP4747647B2 - POLYMER ELECTROLYTE MEMBRANE AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

The present invention relates to a polymer electrolyte membrane and a method for producing the same .

  The polymer electrolyte membrane is a main constituent material of electrochemical elements such as a solid polymer fuel cell, a humidity sensor, a gas sensor, and an electrochromic display element. Among these electrochemical devices, polymer electrolyte fuel cells are expected as a pillar of future new energy technologies. A polymer electrolyte fuel cell (PEFC) using a polymer electrolyte membrane having proton conductivity is characterized by its ability to operate at a low temperature and to be reduced in size and weight, such as a moving body such as an automobile, a home cogeneration system, and Application to consumer small portable devices is under consideration. In particular, direct methanol fuel cells (DMFC) using methanol as a fuel have a simple structure, ease of fuel supply and maintenance, and high energy density, and are portable as an alternative to lithium ion secondary batteries. Applications to small portable devices such as telephones and notebook computers are expected.

  As a polymer electrolyte membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been developed, and its application to many electrochemical devices such as PEFC has been proposed. ing. The perfluorocarbon sulfonic acid membrane has high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance. However, there are drawbacks that it is difficult to manufacture and is very expensive. Furthermore, the permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol, which is regarded as promising as a fuel for fuel cells for small portable devices, is large, so-called chemical short reaction occurs. As a result, not only the cathode potential is lowered, but also fuel efficiency is lowered, which is a main factor of cell characteristic degradation. Therefore, there are many problems in using such a perfluorocarbon sulfonic acid membrane as a polymer electrolyte membrane of a direct liquid fuel cell or a direct methanol fuel cell.

  Against this background, various sulfonates of aromatic polymer compounds have been proposed as polymer electrolyte membranes that are easy to manufacture and cheaper. However, proton conductivity is insufficient for use as a polymer electrolyte membrane of PEFC that requires high proton conductivity. In order to improve this, increasing the amount of proton-conductive substituents such as sulfonic acid groups increases the mechanical properties (strength and elongation), water solubility, and the water absorption rate of the membrane. As a result, the handling property is significantly impaired. Moreover, the same tendency is shown with respect to methanol which is promising as a fuel for fuel cells for small portable devices, and its use may be restricted.

  For example, Patent Document 1 discloses a method for producing a polymer electrolyte membrane made of a sulfonated aromatic polymer such as sulfonated polyphenylene sulfide. In this method for producing a polymer electrolyte membrane, it is described that chlorosulfonic acid is used as a sulfonating agent and dichloromethane is used as a solvent. However, in order to obtain high proton conductivity, proton conductive substitution such as a sulfonic acid group is described. Increasing the amount of introduction of the group is easily assumed to increase methanol permeation. Thus, polymer electrolyte membranes of direct methanol fuel cells are required to suppress methanol permeation without reducing proton conductivity, but there is a trade-off relationship between proton conductivity and methanol barrier properties. Therefore, it is difficult to achieve both of these characteristics.

  Patent Document 2 describes a proton conductive composite containing a layered / reticulated silicate. However, silicates may not have sufficient effects such as methanol blocking properties, and there is a problem that it is difficult to achieve both proton conductivity and methanol blocking properties, as described above.

International Publication No. 02/062896 Pamphlet Special table 2003-501516 gazette

An object of the present invention is to provide a polymer electrolyte membrane useful for solid polymer fuel cells, direct liquid fuel cells, and direct methanol fuel cells.

The polymer electrolyte membrane of the present invention, a polymer electrolyte fuel cell, a polymer electrolyte membrane to be used in liquid electrolyte fuel cells or direct methanol fuel cells directly, (A) a polyphenylene sulfide and (B) flaky titanium Proton-conducting substituents are introduced into a polymer film composed of a polymer composition composed of an acid, chemical stability, and fuel shielding properties such as hydrogen and methanol, and oxidant shielding properties, In addition, it is preferable because excellent proton conductivity can be expressed.

  The scaly titanic acid is nanosheeted layered titanic acid obtained by treating layered titanate with acid or warm water to form layered titanic acid, and then intercalating an organic basic compound having an interlayer swelling action. However, it is preferable because the dispersibility with respect to at least one polymer compound selected from the group consisting of polyphenylene sulfide, polyphenylene ether and modified polyphenylene ether is improved, and the fuel blocking property and the oxidizing agent blocking property are excellent.

The layered titanate has the general formula A _X MY _{Y Z} Ti _{[2- (Y + Z)]} O ₄ (wherein A and M represent 1 to 3 valent metals different from each other, and X is a positive real number satisfying 0 <X <1.0, and Y and Z are preferably 0 or a positive real number satisfying 0 <Y + Z <1).

Furthermore, it is preferable that the layered titanate is represented by K _0.5 to _0.8 Li _0.27 Ti _1.73 O _3.85 to ₄ from the viewpoint of industrial availability and ease of intercalation of organic basic compounds.

The method for producing a polymer electrolyte membrane of the present invention is a method for producing a polymer electrolyte membrane for use in a solid polymer fuel cell, a direct liquid fuel cell or a direct methanol fuel cell, which comprises (A) polyphenylene sulfide. And (B) a chemical film formed by bringing a polymer film made of a polymer composition composed of flaky titanic acid into contact with a sulfonating agent in the presence of a solvent to introduce a sulfonic acid group . Furthermore, it is preferable because a polymer electrolyte membrane capable of exhibiting excellent proton conductivity in addition to the fuel barrier properties such as hydrogen and methanol and the oxidant barrier properties can be obtained .

According to the present invention, it is possible to provide a polymer electrolyte membrane capable of achieving both high proton conductivity and excellent methanol blocking properties.

The polymer composition used in the present invention will be specifically described. The polymer compound of the present invention is a material for a polymer electrolyte membrane used in a solid polymer fuel cell, a direct liquid fuel cell, and a direct methanol fuel cell, and comprises (A) polyphenylene sulfide and (B) phosphorous fragments. What consists of a structure of a titanic acid is preferable.

Here, polyphenylene sulfide is used to impart dispersibility of flaky titanate, various physical properties such as mechanical properties and handling properties of a polymer film prepared when obtaining a polymer electrolyte membrane, and proton conductivity. It is preferable because it is easy to introduce a proton conductive substituent such as a sulfonic acid group to be introduced, proton conductivity as a polymer electrolyte membrane, and a blocking property of a hydrogen-containing liquid such as hydrogen or methanol. In addition, polyphenylene sulfide is more preferable because the obtained polymer electrolyte membrane is excellent in hydrolysis resistance and chemical stability typified by oxidation resistance.

The flake titanic acid used in the present invention is a layered titanic acid obtained by treating layered titanate with acid or warm water to form layered titanic acid, and then intercalating an organic basic compound having an interlayer swelling action. An acid is preferable because it is easily dispersed in the polymer compound.
The layered titanate is prepared by mixing potassium carbonate, lithium carbonate and titanium dioxide at a ratio of K / Li / Ti = 3/1 / 6.5 (molar ratio), for example, according to the method disclosed in WO99 / 11574. K _0.8 L _0.27 Ti _1.73 O ₄ is obtained by grinding and baking at 800 ° C.

Furthermore, according to the method disclosed in Japanese Patent No. 3062497, a mixture in which an alkali metal or an alkali metal halide or sulfate is used as a flux and the weight ratio of the flux / raw material is 0.1 to 2.0 is mixed. the general formula _{a X M Y □ Z Ti 2-} (Y + Z) O 4 ( wherein a and M are different monovalent to trivalent metals obtained by calcining at 700 to 1200 ° C., □ is the Ti X represents a positive real number satisfying 0 <X <1.0, and Y and Z are 0 or a positive real number satisfying 0 <Y + Z <1.0, respectively. Titanates are mentioned. A in the above general formula is a valence 1-3 metal, preferably at least one selected from K, Rb, and Cs, and M is a valence 1-3 valence different from the metal A. It is a metal, and preferably at least one selected from Li, Mg, Zn, Cu, Fe, Al, Ga, Mn, and Ni. As a specific example,
K _0.80 Li _0.27 Ti _1.73 O ₄ ,
Rb _0.75 Ti _1.75 Li _0.25 O ₄ ,
Cs _0.70 Li _0.23 Ti _1.77 O ₄ ,
Ce _0.70 □ _0.18 Ti _1.83 O ₄ ,
Ce _0.70 Mg _0.35 Ti _1.65 O ₄ ,
K _0.8 Mg _0.4 Ti _1.6 O ₄ ,
K _0.8 Ni _0.4 Ti _1.6 O ₄ ,
K _0.8 Zn _0.4 Ti _1.6 O ₄ ,
K _0.8 Cu _0.4 Ti _1.6 O ₄ ,
K _0.8 Fe _0.8 Ti _1.2 O ₄ ,
K _0.8 Mn _0.8 Ti _1.2 O ₄ ,
K _0.76 Li _0.22 Mg _0.05 Ti _1.73 O ₄ ,
K _0.67 Li _0.2 Al _0.07 Ti _1.73 O _{4 and the} like.

Further, according to the method disclosed in International Publication No. 03/037797, pickled and _{K 0.8 L 0.27 Ti 1.73 O 4} , is _{K 0.5 ~ 0.7 Li 0.27 Ti 1.73} O 3.85 ~ 3.95 obtained by firing the like .

  The layered titanic acid can be obtained, for example, by acid-treating the layered titanate and replacing a replaceable metal cation with a hydrogen ion or a hydronium ion. The acid used for the acid treatment is not particularly limited, and may be a mineral acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, or an organic acid.

  Nanosheeted layered titanic acid is obtained, for example, by allowing an organic basic compound having an interlayer swelling action to act on the layered titanic acid. As the organic basic compound having an interlayer swelling action, known compounds can be applied, and examples thereof include amine-based compounds, ammonium-based compounds, and phosphorus-based compounds. More specifically, distearyldimethylammonium, octadecylamine, octadecylaminetrimethylammonium, alkylmethylbishydroxyethylammonium, 12-aminododecanoic acid, 1,2-dimethyl-3-hexadecylimidazolium, dodecyltributylphosphonium And hexadecyltributylphosphonium, dodecyltriphenylphosphonium, distearyldimethylammonium, alkylmethylbis (hydroxyethyl) ammonium and the like.

  In order to make an organic basic compound having an interlayer swelling action act, a basic compound or a basic compound is added to an aqueous system under stirring in a suspension in which layered titanic acid after acid treatment or hot water treatment is dispersed in an aqueous medium. What is diluted with a medium may be added. Alternatively, the layered titanic acid or a suspension thereof may be added to an aqueous solution of the basic compound with stirring.

  The aqueous medium or aqueous solution means water, a solvent soluble in water, a mixed solvent of water and a solvent soluble in water, or a solution thereof.

  Examples of the water-soluble solvent include alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, ketones such as acetone, ethers such as tetrahydrofuran and dioxane, nitriles such as acetonitrile, ethyl acetate, propylene carbonate and the like. Of these esters.

The addition amount of the basic compound is 0.3 to 10 equivalents, preferably 0.5 to 2 equivalents, of the ion exchange capacity of the layered titanate. Here, the ion exchange capacity is the exchangeable metal cation amount. For example, when the layered titanate is represented by the general formula A _{X MY} □ _Z Ti _{2− (Y + Z)} O ₄ , A value expressed by mX + nY where m is the valence and n is the valence of M.

In the polymer composition of the present invention, the mixing method of polyphenylene sulfide and flaky titanic acid can be appropriately selected according to the properties of the polymer compound and flaky titanic acid. For example, flaky titanic acid is mixed with a raw material monomer or oligomer of a polymer compound in a solvent and polymerized to obtain a polymer compound in which flaky titanic acid is dispersed, or flaky titanic acid is polymerized. And a method in which a scaly titanic acid-dispersed polymer compound is obtained by mixing in a solution, or a scaly titanic acid-dispersed polymer compound obtained by melt-kneading a scaly titanic acid and a polymer compound The method of obtaining can be enumerated. At this time, melt-kneading may be carried out a plurality of times so that the flaky titanic acid is easily dispersed in the polymer compound, and the flaky titanic acid is added to the polymer compound in advance of a desired composition ratio. A master batch mixed in a large amount may be prepared, and this and a polymer compound may be melt-kneaded. Moreover, you may mix scaly titanic acid and a polymer at the time of film preparation. In the present invention, it is preferable to mix the flake titanic acid and the polymer compound by a melt kneading method from the viewpoint of reducing the environmental load simply and without using a solvent. Specific examples include a method of obtaining the desired polymer composition by mixing the scaly titanic acid in a molten state of the polymer compound with a plastmill or a twin screw extruder.

The flake titanic acid to be used is preferably the nanosheet-formed layered titanic acid which is excellent in dispersibility in polyphenylene sulfide and barrier property of hydrogen-containing liquid such as hydrogen or methanol as a polymer electrolyte membrane.

  The polymer film of the present invention is a polymer electrolyte membrane material used for a solid polymer fuel cell, a direct liquid fuel cell, and a direct methanol fuel cell, and is a polymer composition obtained by the method described above. Can be used for dispersibility of flaky titanate, various physical properties such as mechanical properties and handling properties of polymer films, ease of introduction of proton conductive substituents such as sulfonic acid groups, polymers Preferred because of excellent proton conductivity as an electrolyte membrane, fuel barrier properties such as hydrogen-containing liquids such as hydrogen and methanol, and chemical stability typified by hydrolysis resistance and oxidation resistance of the resulting polymer electrolyte membrane . As a method for producing the polymer film of the present invention, a known method can be applied. For example, an inflation method, a T-die method, a calendar method, a casting method, a cutting method, an emulsion method, a hot press method, and the like can be listed as applicable. Further, post-treatment such as biaxial stretching may be performed to control molecular orientation and the like, or heat treatment may be performed to control crystallinity. Among these, the melt extrusion method represented by the inflation method, the T-die method, and the calendar method is preferable because of high productivity.

  As the thickness of the polymer film of the present invention, any thickness can be selected depending on the application. In consideration of uniformly introducing proton conductive groups, particularly sulfonic acid groups, into the film and reducing the internal resistance of the resulting polymer electrolyte membrane, the thinner the raw material film, the better. On the other hand, considering the fuel barrier property, the oxidant barrier property, the handling property, etc., it is not preferable that the film thickness is too thin. Considering these, the thickness of the polymer film is preferably 1.2 to 350 μm. If the thickness of the film is less than 1.2 μm, it is difficult to manufacture, and the handling property tends to be wrinkled or broken at the time of processing. Sulfonation is difficult, and the internal resistance of the obtained polymer electrolyte membrane is increased, which may reduce proton conductivity.

The polymer electrolyte membrane of the present invention is used for a solid polymer fuel cell, a direct liquid fuel cell, and a direct methanol fuel cell, and has a proton conductive substituent in the polymer composition described above. Is. Examples of proton conductive substituents that can be used in the present invention include sulfonic acid groups, phosphoric acid groups, carboxylic acid groups, and phenolic hydroxyl groups. Among these, considering the ease of introduction of substituents and the characteristics typified by proton conductivity of the obtained polymer electrolyte membrane, a sulfonic acid group and / or a substituent containing a sulfonic acid group is preferable.

  In the present invention, the sulfonic acid group means a substituent containing a sulfonic acid group represented by the following formula (1) or a sulfonic acid group represented by the following general formula (2).

［式中、Ｒはアルキレン、ハロゲン化アルキレン、アリーレン、ハロゲン化アリーレンからなる群から選択される少なくとも１種の結合単位からなる２価の有機基、またはエーテル結合を含んでいてもよい］

[In the formula, R may contain a divalent organic group composed of at least one bond unit selected from the group consisting of alkylene, halogenated alkylene, arylene, and halogenated arylene, or an ether bond.]

  Hereinafter, the introduction of a sulfonic acid group as a preferable example of a proton conductive group will be described as an example, but the present invention is not limited thereto.

  As the sulfonating agent, known sulfonating agents such as chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, sulfur trioxide-triethyl phosphate, concentrated sulfuric acid, trimethylsilylchlorosulfate, and trimethylbenzenesulfonic acid can be used. Considering the ease of industrial availability, the ease of introduction of sulfonic acid groups and the properties of the resulting polymer electrolyte membrane, at least one selected from the group consisting of chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide and concentrated sulfuric acid Preferably it is. In particular, in the present invention, it is more preferable to use chlorosulfonic acid from the viewpoint of easy introduction of a sulfonic acid group, characteristics of the obtained membrane, industrial availability, and the like.

  In addition, by optimizing the reaction system, cyclic sulfur-containing compounds such as propane sultone and 1,4-butane sultone and hydrocarbon polymer compounds in the presence of a catalyst such as aluminum chloride according to the Friedel-Crafts reaction A method of introducing a substituent containing a sulfonic acid group such as a sulfopropyl group or a sulfobutyl group by bringing the aromatic unit inside into contact with each other can also be used.

  Furthermore, the polymer electrolyte membrane of the present invention is preferably produced by bringing a polymer film comprising the polymer composition into contact with a sulfonating agent in the presence of a solvent. Examples of the solvent include dichloromethane, 1,2-dichloroethane, chloroform, 1-chloropropane, 1-bromopropane, 1-iodopropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 1-bromobutane. 2-bromobutane, 1-bromo-2-methylpropane, 1-iodobutane, 2-iodobutane, 1-iodo-2-methylpropane, 1-chloropentane, 1-bromopentane, 1-iodopentane, 1-chlorohexane 1-bromohexane, 1-iodohexane, chlorocyclohexane, bromocyclohexane, iodocyclohexane and the like. In the present invention, as compared with the use of a halide having 2 or less carbon atoms, the boiling point is higher and it is difficult to volatilize. Therefore, ancillary equipment for preventing the volatilization of the solvent and recovering the volatilized solvent is necessary. Therefore, it is preferable to use a halide having 3 or more carbon atoms, because 1-chloropropane, 1-bromopropane, 1-iodopropane, 1-chlorobutane is preferable. 2-chlorobutane, 1-chloro-2-methylpropane, 1-bromobutane, 2-bromobutane, 1-bromo-2-methylpropane, 1-iodobutane, 2-iodobutane, 1-iodo-2-methylpropane, 1- Chloropentane, 1-bromopentane, 1-iodopentane, 1-chlorohexane, 1-bromohexane, 1-iodohexane, black Cyclohexane, bromo cyclohexane, iodocyclohexane can be exemplified. Considering especially the ease of handling of the solvent used and the characteristics of the polymer electrolyte membrane obtained, 1-chloropropane, 1-bromopropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 1-bromobutane , 2-bromobutane, 1-bromo-2-methylpropane, 1-chloropentane, 1-bromopentane, 1-chlorohexane, 1-bromohexane, chlorocyclohexane and bromocyclohexane Preferably there is. Furthermore, at least one selected from 1-chloropropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 1-chloropentane, 1-chlorohexane and chlorocyclohexane because of industrial availability. It is preferable that Among the solvents, 1-chlorobutane is preferable from the viewpoints of industrial availability and characteristics of the obtained polymer electrolyte membrane.

  As a usage-amount of a sulfonating agent, it is preferable that it is 0.5-30 equivalent with respect to the aromatic unit in the said high molecular compound, Furthermore, it is preferable that it is 0.5-15 equivalent. When the amount of the sulfonating agent used is less than 0.5 equivalent, the amount of sulfonic acid group introduced tends to decrease, or the time required for introduction tends to increase. On the other hand, when it exceeds 30 equivalents, the polymer film is chemically deteriorated, the mechanical strength of the resulting polymer electrolyte membrane is lowered, handling becomes difficult, and the amount of sulfonic acid groups introduced increases. However, the practical properties of the polymer electrolyte membrane tend to be impaired, for example, the methanol barrier property is lowered.

  The concentration of the sulfonating agent in the solvent may be appropriately set in consideration of the target introduction amount of sulfonic acid groups and reaction conditions (temperature / time). Specifically, it is preferably 0.1 to 10% by weight, and a more preferable range is 0.2 to 5% by weight. If it is lower than 0.1% by weight, the sulfonating agent and the aromatic unit in the polymer compound are difficult to contact, and the desired sulfonic acid group cannot be introduced or it takes a long time to introduce. is there. On the other hand, when the content exceeds 10% by weight, the introduction of sulfonic acid groups tends to be uneven, and the mechanical properties of the obtained polymer electrolyte membrane tend to be impaired.

  The reaction temperature and reaction time for contacting are not particularly limited, but are set within the range of 0 to 100 ° C., further 10 to 30 ° C., 0.5 hour or more, and further 2 to 100 hours. preferable. When the reaction temperature is lower than 0 ° C, measures such as cooling on the equipment are necessary, and the reaction tends to take more time than necessary. When the reaction temperature exceeds 100 ° C, the reaction proceeds excessively or side reactions occur. Or the like, and the film characteristics tend to deteriorate. In addition, when the reaction time is shorter than 0.5 hours, the contact between the sulfonating agent and the aromatic unit in the polymer compound becomes insufficient, and the desired sulfonic acid group tends to be difficult to be introduced. When the time exceeds 100 hours, the productivity tends to be remarkably lowered, and a great improvement in film properties tends not to be expected. In actuality, if the setting is made so that a polymer electrolyte membrane having desired characteristics can be efficiently produced in consideration of a reaction system such as a sulfonating agent and a solvent to be used and a target production amount. Good.

  The method for producing a polymer electrolyte membrane of the present invention is preferably washed with water in order to remove the unreacted sulfonating agent and solvent after the sulfonic acid group introduction step. At this time, it is preferable that the polymer electrolyte membrane is obtained by continuously washing with water and drying under appropriate conditions without recovering the polymer electrolyte membrane after the sulfonic acid group introduction step. Further, instead of washing with water, the polymer electrolyte membrane may be obtained by performing neutralization washing with a sodium hydroxide aqueous solution or the like and then performing acid treatment.

  Further, when the polymer electrolyte membrane produced by the production method of the present invention is produced, the polymer membrane is provided with a plasticizer, an antioxidant, an antistatic agent, an antibacterial agent, a lubricant, a surfactant, and various organic fillers. An appropriate amount of additives such as may be contained.

  The ion exchange capacity of the polymer electrolyte membrane of the present invention is preferably 0.3 meq / g or more, more preferably 0.5 meq / g or more, and further preferably 1.0 meq / g. That's it. If the ion exchange capacity is lower than 0.3 meq / g, the desired proton conductivity may not be exhibited, which is not preferable.

The proton conductivity of the polymer electrolyte membrane of the present invention at room temperature is preferably 1.0 × 10 ⁻³ S / cm or more, more preferably 1.0 × 10 ⁻² S / cm or more. When the proton conductivity is lower than 1.0 × 10 ⁻³ S / cm, when the polymer electrolyte membrane of the present invention is used as an electrolyte membrane of a solid polymer fuel cell or a direct methanol fuel cell, There is a risk of not showing sufficient power generation characteristics.

  As the thickness of the polymer electrolyte membrane of the present invention, any thickness can be selected depending on the application. When considering reducing the internal resistance of the membrane, the range has practical mechanical strength, and when used for an electrolyte membrane of a polymer electrolyte fuel cell, the range has a blocking property of fuel and oxidant. And the thinner each, the better. As the characteristics of the electrolyte membrane, as the ion exchange capacity and proton conductivity are equal, the resistance value as the membrane decreases as the thickness decreases. Therefore, the thickness of the film is preferably 5 to 200 μm, more preferably 20 to 150 μm. When this thickness is less than 5 μm, pinholes and film cracking tend to occur during use. Further, when used as an electrolyte membrane of a polymer electrolyte fuel cell, the barrier property of the fuel and the oxidant is insufficient, which tends to cause performance deterioration. Further, when used as an electrolyte membrane of a direct methanol fuel cell, the methanol barrier property is insufficient, and there is a tendency that performance is deteriorated due to methanol permeation. On the other hand, when it exceeds 200 μm, the resistance of the polymer electrolyte membrane is increased, which tends to cause a performance deterioration.

  The sulfonated polymer membrane obtained by the production method of the present invention has proton conductivity, chemical / thermal stability, and mechanical properties, and uses alcohols such as solid polymer fuel cells and methanol. It is preferable as a membrane for a fuel cell that can be used for a direct alcohol fuel cell. Actually, when used as a membrane for a fuel cell, a catalyst or an electrode is joined on the membrane by a known method applied to a perfluorocarbon sulfonic acid membrane represented by Nafion, and these are combined with a fuel and an oxidant. A fuel cell can be constructed from the supply path and current collector. In order to obtain a required output, a plurality of cells can be arranged to form a stack and used. As the fuel, pure hydrogen, reformed hydrogen gas such as methanol, natural gas, and gasoline, alcohols such as methanol, dimethyl ether, and the like can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

Example 1
(Preparation of nanosheet layered titanic acid A)
A raw material in which 27.64 g of potassium carbonate, 4.91 g of lithium carbonate, 69.23 g of titanium dioxide and 74.56 g of potassium chloride were pulverized and mixed in a dry process was calcined at 1100 ° C. for 4 hours. The fired sample was immersed in 10 kg of pure water, stirred for 20 hours, separated, washed and dried at 110 ° C. The obtained white powder was layered titanate K _0.8 Li _0.27 Ti _1.73 O ₄ and had an average major axis of 44 μm.

  65 g of this layered titanate was dispersed in 1 kg of deionized water, and 28 g of 35% hydrochloric acid was added. After stirring for 1.5 hours, separation and washing were performed to obtain layered titanic acid in which K ions and Li ions were exchanged with hydrogen ions or hydronium ions. The exchange rate of K ions was 72 equivalent% and the exchange rate of Li ions was 99 equivalent% or more. According to XRD analysis, the interlayer distance was 9.2 mm.

  50 g of this layered titanic acid was further dispersed in 4 kg of deionized water, and a solution prepared by dissolving 130 g of dodecyltriphenylphosphonium bromide in 500 g of deionized water was added while stirring at 80 ° C. After continuing heating and stirring for 1 hour, it was filtered out. After thoroughly washing with deionized water at 80 ° C., it was dried at 40 ° C. in air. Furthermore, it dried at 160 degreeC under pressure reduction for 12 hours, and obtained nanosheet-formation layered titanic acid with an average major axis of 42 micrometers. The interlayer distance was 23.7 mm by XRD analysis, and it was confirmed that dodecyltriphenylphosphonium was inserted between the layers. The organic content was 34.7 wt% due to thermal decomposition loss with TG / DTA.

(Preparation of polymer composition)
97 parts by weight of polyphenylene sulfide resin (manufactured by Dainippon Ink & Chemicals, Inc .: ML320p) and 3 parts by weight of nanosheet-layered layered titanic acid A obtained by the above method were mixed and melt extruded at 290 ° C. with a twin screw extruder. Pellets of molecular composition (ash content 1.5% by weight) were obtained.

(Production of polymer film)
The polymer composition pellets obtained by the above method were melt-extruded at 290 ° C. by a T-die method to prepare a polymer film.

(Preparation of polymer electrolyte membrane)
In a glass container, 147 g of 1-chlorobutane and 1.47 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. In this solution, 0.34 g of the polymer film prepared by the above method was immersed and allowed to stand at room temperature for 20 hours (the amount of chlorosulfonic acid added was 4 equivalents with respect to the aromatic unit of polyphenylene sulfide). After standing at room temperature for 20 hours, the polymer film was recovered and washed with ion-exchanged water until neutral.

  The polymer film after washing was dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, A polymer electrolyte membrane (thickness: 90 μm) was prepared.

  Various characteristics of this polymer electrolyte membrane were measured by the following methods. The results are shown in Table 1.

(Measurement method of ion exchange capacity)
A polymer electrolyte membrane (about 10 mm × 40 mm, thickness: arbitrary) is immersed in a saturated aqueous solution of sodium chloride and reacted in a water bath at 60 ° C. for 3 hours. After cooling to room temperature, the sample was thoroughly washed with ion-exchanged water, titrated with 0.01N aqueous sodium hydroxide solution using a phenolphthalein solution as an indicator, and the ion-exchange capacity was calculated.

(Proton conductivity)
A polymer electrolyte membrane (10 mm × 40 mm) stored in ion-exchanged water was taken out, and water on the surface of the test specimen was wiped off with a filter paper. An electrode was placed on the surface of the test body so that the distance between the electrodes was 30 mm, and the electrode was attached to a two-pole non-sealed Teflon (registered trademark). The resistance between the electrodes on the membrane surface was measured by the AC impedance method (frequency: 42 Hz to 5 MHz) under the condition of a voltage of 0.2 V at 25 ° C., and the proton conductivity was calculated.

(Methanol permeability coefficient)
Using a membrane test apparatus manufactured by Beadrex, ion-exchanged water and a 64 wt% aqueous methanol solution were separated from each other by a polymer electrolyte membrane. The amount of methanol permeated to the ion-exchanged water after a predetermined time was quantified with a gas chromatograph. From this, the methanol permeation rate was calculated by the following formula (3) to obtain the methanol permeation coefficient of the membrane.

(Example 2)
(Preparation of nanosheeted layered titanate B)
A raw material in which 27.64 g of potassium carbonate, 4.91 g of lithium carbonate, and 69.23 g of titanium dioxide were pulverized and mixed in a dry process was calcined at 1050 ° C. for 4 hours. The fired sample was immersed in 10 kg of pure water, stirred for 20 hours, separated, washed and dried at 110 ° C. 79.2 L of 10.9% aqueous slurry of the obtained layered titanate was adjusted, 4.7 kg of 10% aqueous sulfuric acid solution was added and stirred for 2 hours, and the pH of the slurry was adjusted to 7.0. What was separated and washed with water was dried at 110 ° C. and then calcined at 600 ° C. for 12 hours. The obtained white powder was a layered titanate K _0.6 Li _0.27 Ti _1.73 O _3.9 and had an average major axis of 28 μm.

  Using this layered titanate, treatment was carried out in the same manner as in Example 1 except that the organic basic compound was changed to octadecyldimethylbenzylammonium chloride to obtain nanosheeted layered titanic acid having an average major axis of 27 μm. The distance between layers was 24.7 mm by XRD analysis, and it was confirmed that octadecyldimethylbenzylammonium was inserted between layers. The organic content was 41.5 wt% due to thermal decomposition loss with TG / DTA.

(Preparation of polymer composition)
93 parts by weight of polyphenylene sulfide resin (manufactured by Dainippon Ink and Chemicals, Inc .: ML320p) and 7 parts by weight of nanosheet-layered layered titanic acid B obtained by the above method were mixed and melt extruded at 290 ° C. with a twin screw extruder. Pellets of molecular composition (ash content 3.0% by weight) were obtained.

(Production of polymer film)
The polymer composition pellets obtained by the above method were melt-extruded at 290 ° C. by a T-die method to prepare a polymer film.

(Preparation of polymer electrolyte membrane)
In a glass container, 129 g of 1-chlorobutane and 1.29 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. In this solution, 0.30 g of the polymer film produced by the above method was immersed and allowed to stand at room temperature for 20 hours (the amount of chlorosulfonic acid added was 4 equivalents relative to the aromatic unit of polyphenylene sulfide). After standing at room temperature for 20 hours, the polymer film was recovered and washed with ion-exchanged water until neutral.

  The polymer film after washing was dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, A polymer electrolyte membrane (thickness: 89 μm) was prepared.

  Various characteristics of this polymer electrolyte membrane were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
Nafion 115 (registered trademark) manufactured by DuPont was used as the polymer electrolyte membrane.

  Various characteristics of this polymer electrolyte membrane were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
(Production of polymer film)
A polymer film was produced in the same manner as in Example 1 except that only the polyphenylene sulfide resin (Dainippon Ink & Chemicals, Inc .: ML320p) was used without using the nanosheeted layered titanic acid.

(Preparation of polymer electrolyte membrane)
In a glass container, 133 g of 1-chlorobutane and 1.66 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. In this solution, 0.31 g of the polymer film prepared by the above method was immersed and allowed to stand at room temperature for 20 hours (the amount of chlorosulfonic acid added was 5 equivalents with respect to the aromatic unit of polyphenylene sulfide). After standing at room temperature for 20 hours, the polymer film was recovered and washed with ion-exchanged water until neutral.

  The polymer film after washing was dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, A polymer electrolyte membrane (thickness: 101 μm) was prepared.

  Various characteristics of this polymer electrolyte membrane were measured in the same manner as in Example 1. The results are shown in Table 1.

  From comparison between Examples 1 and 2 and Comparative Example 1, the polymer electrolyte membrane of the present invention has a proton conductivity equal to or higher than that of Nafion (registered trademark) manufactured by DuPont, which is known as a polymer electrolyte membrane for fuel cells. It has been shown that it is useful as a polymer electrolyte membrane for fuel cells.

Further, from the comparison between Examples 1 and 2 and Comparative Examples 1 and 2, it is clear that the polymer electrolyte membrane of the present invention has a low methanol permeability coefficient and excellent methanol barrier properties. It was shown to be useful as a polymer electrolyte membrane for fuel cells.

Claims (5)

A polymer electrolyte membrane for use in a solid polymer fuel cell, a direct liquid fuel cell or a direct methanol fuel cell , the polymer composition comprising (A) polyphenylene sulfide and (B) flaky titanic acid A polymer electrolyte membrane obtained by introducing a proton-conductive substituent into a polymer film comprising: The flaky titanic acid is nanosheeted layered titanic acid obtained by treating a layered titanate with an acid or warm water and then intercalating an organic basic compound having an interlayer swelling action. Item 12. The polymer electrolyte membrane according to Item 1. The layered titanate has a general formula A _{X MY} □ _Z Ti _{[2- (Y + Z)]} O ₄ (wherein A and M represent 1 to 3 valent metals different from each other; X is a positive real number satisfying 0 <X <1.0, and Y and Z are 0 or a positive real number satisfying 0 <Y + Z <1). The polymer electrolyte membrane according to claim 2 . The polymer electrolyte membrane according to claim 2 , wherein the layered titanate is represented by K _0.5 to _0.8 Li _0.27 Ti _1.73 O _3.85 to ₄ . A method for producing a polymer electrolyte membrane for use in a solid polymer fuel cell, a direct liquid fuel cell or a direct methanol fuel cell, comprising: (A) polyphenylene sulfide and (B) scaly titanic acid A method for producing a polymer electrolyte membrane, wherein a polymer film comprising a molecular composition is brought into contact with a sulfonating agent in the presence of a solvent to introduce a sulfonic acid group .