JP2007184116A - Ion conductive polymer electrolyte membrane and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion conductive polymer electrolyte membrane demonstrating a superior durability and having high ion conductivity in thickness direction, and suitable for a solid polymer fuel cell, and its manufacturing method. <P>SOLUTION: The ion conductive polymer electrolyte membrane is formed of an ion conductive composition including a first polymer containing an ionic dissociation group and a second polymer different from the first polymer. The intrinsic viscosity of the second polymer is established to be 2-15 dL/g. The molecule chains of each polymer are oriented in an certain direction, and the orientation α along the certain direction of the molecule chains of each polymer obtained by the following formula (1) by X-ray diffraction measurement is established to be 0.3 or more and less than 1. The ion conductivity in the thickness direction of the electrolyte membrane is established higher than that in a direction parallel to the surface of the membrane. The formula (1): orientation α=(180-Δβ)/180, provided that Δβ expresses a half width when the X-ray diffraction intensity distribution from 0 to 360° azimuth angle direction is measured by fixing a peak scattering angle in the X-ray diffraction measurement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ion conductive polymer electrolyte membrane which is used in, for example, a polymer electrolyte fuel cell and allows hydrogen ions generated on the fuel electrode side to permeate to the air electrode side.

  In recent years, with the development of electronic devices, there is a demand for a small power supply with high power output density and a low pollution and high efficiency for solving environmental problems. Fuel cells are attracting attention as satisfying these demands. Unlike conventional power generation systems, fuel cells use, for example, hydrogen or methanol as fuel, and obtain electric energy by electrochemically reacting the fuel with oxygen contained in air. Fuel cells are classified into solid polymer type, solid oxide type, molten carbonate type, phosphoric acid type, etc., depending on the electrolyte. Among these, the polymer electrolyte fuel cell is actively researched as a power source for movement because it operates at room temperature (100 ° C. or lower), has a short start-up time, and can be easily downsized.

  The polymer electrolyte fuel cell includes a fuel electrode and an air electrode, and a polymer electrolyte membrane such as an ion conductive polymer electrolyte membrane is provided between them. The peripheral edge of the polymer electrolyte membrane is exposed from each electrode and is sandwiched between a pair of separators via a plurality of gaskets. In this polymer electrolyte fuel cell, for example, hydrogen or methanol as fuel supplied from the fuel electrode side is dissociated into hydrogen ions and electrons by the catalyst. The hydrogen ions permeate the polymer electrolyte membrane and reach the air electrode, and react with oxygen in the air by the catalyst to generate water. At this time, electric energy is obtained by a series of these reactions.

  The polymer electrolyte membrane is required to have high ion conductivity, and various polymer electrolyte membranes have been proposed at present. For example, fluorine-based polymer electrolyte membranes into which acidic groups such as perfluorocarbon sulfonic acid are introduced are widely used. However, it is difficult for fluorine-based polymer electrolyte membranes to retain moisture at around 100 ° C., which is the upper limit of the operating temperature of a polymer electrolyte fuel cell, because of its low glass transition temperature. There was a problem that sex was not exhibited. Furthermore, the fluorine polymer electrolyte membrane has a problem of high methanol permeability.

  In order to overcome the above-mentioned problems of fluorine polymer electrolyte membranes, non-fluorine-containing aliphatic polymer electrolyte membranes (hereinafter referred to as hydrocarbon polymer electrolyte membranes) into which strong acid groups have been introduced have been proposed. ing. Specifically, a polymer electrolyte membrane in which a sulfonic acid group that is a strong acid group is introduced into an aromatic polymer such as polyether ketone, polysulfone, and polybenzimidazole having chemical resistance and heat resistance has been reported.

  However, the hydrocarbon-based polymer electrolyte membrane hydrates and swells more easily than the fluorine-based polymer electrolyte membrane, and thus tends to contract over time while repeating expansion and contraction. For this reason, there is a possibility that a gap is generated between the hydrocarbon polymer electrolyte membrane and the gasket due to contraction of the portion of the hydrocarbon polymer electrolyte membrane that is sandwiched by the gasket, and fuel or the like may leak.

Therefore, in order to overcome the above-mentioned problems that the hydrocarbon polymer electrolyte membrane has, Patent Document 1 discloses a mixture of polybenzoxazole or polybenzthiazole having an acidic group and a basic polymer having a sulfonic acid group or the like. A blend polymer electrolyte membrane is disclosed. Patent Document 2 discloses a blend polymer electrolyte membrane made of a mixture of a polymer having an acidic group and a basic inorganic compound. These blend polymer electrolyte membranes have improved durability by a basic polymer or a basic inorganic compound. Patent Document 3 discloses a polymer electrolyte membrane in which a molecular chain of a polymer having an ionic dissociation group is oriented in a certain direction by applying an electric field. This polymer electrolyte membrane has improved ion conductivity due to the orientation of the molecular chain of the polymer.
JP 2003-22709 A JP 2003-22708 A JP 2003-234015 A

  However, the blend polymer electrolyte membrane described in Patent Document 1 and Patent Document 2 has a problem of low ion conductivity. Patent Document 3 has a problem that the durability of the polymer electrolyte membrane is low because the polymer electrolyte membrane easily breaks along the orientation direction of the molecular chains of the polymer.

  The present invention has been made paying attention to such problems existing in the prior art. An object of the present invention is to provide an ion conductive polymer electrolyte membrane that exhibits excellent durability, has high ion conductivity in the thickness direction, and is suitable for a polymer electrolyte fuel cell, and a method for producing the same. is there.

  In order to achieve the above object, an invention according to claim 1 is an ion including a first polymer containing an ionic dissociation group and a second polymer different from the first polymer. An ion conductive polymer electrolyte membrane formed from a conductive composition, wherein the intrinsic viscosity of the second polymer is set to 2 to 15 dL / g, and the molecular chains of the first and second polymers Is oriented in a certain direction, and the degree of orientation α along the certain direction of the molecular chains of the first and second polymers obtained from the following formula (1) from X-ray diffraction measurement is 0.3 or more and less than 1. Provided is an ion conductive polymer electrolyte membrane which is set and has an ionic conductivity in the thickness direction of the membrane set higher than an ionic conductivity in a direction parallel to the surface of the membrane.

Orientation degree α = (180−Δβ) / 180 (1)
(However, Δβ represents the half width when the X-ray diffraction intensity distribution from 0 to 360 degrees in the azimuth direction is measured with the peak scattering angle determined by X-ray diffraction measurement fixed.)
The invention according to claim 2 provides the ion conductive polymer electrolyte membrane according to claim 1, wherein the second polymer is a basic polymer.

  The invention according to claim 3 is the polymer according to claim 2, wherein the basic polymer is a polymer having a primary or secondary amino group in a constituent unit of the polymer, or an azole polymer. An ion conductive polymer electrolyte membrane is provided.

The invention according to claim 4 provides the ion conductive polymer electrolyte membrane according to claim 2 or 3, wherein the basic polymer is polybenzimidazole.
Invention of Claim 5 is formed from the ion conductive composition containing the 1st polymer | macromolecule containing an ionic dissociation group, and the 2nd polymer | macromolecule different from this 1st polymer | macromolecule, The intrinsic viscosity of the second polymer is set to 2 to 15 dL / g, the molecular chains of the first and second polymers are oriented in a certain direction, and are obtained by the following formula (1) from X-ray diffraction measurement. The degree of orientation α along the certain direction of the molecular chains of the first and second polymers is set to 0.3 or more and less than 1, and the ionic conductivity in the thickness direction of the film is parallel to the surface of the film A method for producing an ion conductive polymer electrolyte membrane set higher than the ionic conductivity in a direction, a preparation step for preparing the ion conductive composition, and first and second in the ion conductive composition An alignment step of aligning molecular chains of the two polymers in a certain direction, and first and second heights It provides a method of producing an ionic conductive polymer electrolyte membrane and a solidifying step of solidifying the ion conductive composition while maintaining the orientation of the molecular chains of the child.

Orientation degree α = (180−Δβ) / 180 (1)
(However, Δβ represents the half width when the X-ray diffraction intensity distribution from 0 to 360 degrees in the azimuth direction is measured with the peak scattering angle determined by X-ray diffraction measurement fixed.)
According to a sixth aspect of the present invention, the first and second polymers are liquid crystalline polymers, and the manufacturing method includes the step of preparing the first conductive composition in the ion conductive composition after the preparation step and before the alignment step. The manufacturing method of the ion conductive polymer electrolyte membrane of Claim 5 further equipped with the expression process which expresses the liquid crystallinity of the 1st and 2nd polymer | macromolecule.

  According to a seventh aspect of the present invention, the alignment step is a step of aligning the molecular chains of the first and second polymers in a certain direction by applying a magnetic field to the ion conductive composition. The manufacturing method of the ion conductive polymer electrolyte membrane of Claim 5 or Claim 6 is provided.

  According to the present invention, it is possible to provide an ion conductive polymer electrolyte membrane that exhibits excellent durability and has high ion conductivity in the thickness direction and is suitable for a polymer electrolyte fuel cell. Moreover, according to this invention, the manufacturing method of such an ion conductive polymer electrolyte membrane is also provided.

Hereinafter, an ion conductive polymer electrolyte membrane (hereinafter simply referred to as an electrolyte membrane) embodying the present invention will be described in detail.
As shown in FIG. 1, the electrolyte membrane 11 of the present embodiment is formed into a sheet shape from an ion conductive composition (hereinafter simply referred to as a composition). This electrolyte membrane 11 is interposed between the fuel electrode and the air electrode of the polymer electrolyte fuel cell, and allows hydrogen ions generated on the fuel electrode side to permeate to the air electrode side.

  The electrolyte membrane 11 has durability and ion conductivity. The durability of the electrolyte membrane 11 is attributed to physical defects such as cracks, chips, and holes in the electrolyte membrane 11 and the swelling rate of the electrolyte membrane 11. When a physical defect occurs in the electrolyte membrane 11, not only the durability of the electrolyte membrane 11 is lowered, but also the power generation efficiency of the fuel cell is lowered. When the expansion coefficient of the electrolyte membrane 11 is high, not only the durability of the electrolyte membrane 11 is lowered, but also the electric power output from the fuel cell is lowered.

  On the other hand, ionic conductivity is an index representing the ease of permeation of hydrogen ions, and is attributed to the ionic conductivity of the electrolyte membrane 11. As the ionic conductivity is higher, the electrolyte membrane 11 can easily transmit hydrogen ions and has higher ionic conductivity. Hydrogen ions usually permeate in the thickness direction of the electrolyte membrane 11 (Z-axis direction in FIG. 1). For this reason, the electrolyte membrane 11 particularly increases the ionic conductivity in the thickness direction of the membrane, and is higher than the ionic conductivity in the X-axis direction or Y-axis direction parallel to the surface of the membrane. A direction parallel to the film surface, such as the X-axis direction, is orthogonal to the thickness direction of the film.

  The composition includes a first polymer containing an ionic dissociation group and a second polymer. The first polymer increases the ionic conductivity of the electrolyte membrane 11 by increasing the ionic conductivity of the electrolyte membrane 11 due to the ionic dissociation group. The ionic dissociation group has a characteristic that a hydrogen ion is bonded to the ionic dissociation group in a polar solvent or a hydrogen ion bonded to the ionic dissociation group is dissociated. The ionic dissociation group is covalently bonded to the main chain or side chain of the first polymer. In the first polymer, the binding site with the ionic dissociation group is not particularly limited.

  Examples of the ionic dissociation group include a proton acid group and a basic group, and a proton acid group is preferable because it has an excellent effect of increasing the ionic conductivity of the electrolyte membrane 11. Examples of the proton acid group include a sulfonic acid group, a phosphonic acid group, a carboxylic acid group, and a salt such as an alkaline earth metal salt and an ammonium salt thereof. These may be bonded to the main chain or side chain of the first polymer alone, or two or more may be bonded to the main chain or side chain. Among these, since the effect | action which raises the ionic conductivity of the electrolyte membrane 11 is more excellent, a sulfonic acid group and a phosphonic acid group are preferable, and a sulfonic acid group is more preferable. Examples of the basic group include polar groups such as primary or secondary amino groups, or salts such as alkaline earth metal salts and ammonium salts.

  The ionic dissociation group is bonded to the main chain or side chain of the first polymer by, for example, synthesizing a liquid crystal monomer containing a sulfonic acid group as an ionic dissociation group and then polymerizing the liquid crystal monomers. . The ionic dissociation group is bonded to the main chain or side chain of the first polymer by immersing the first polymer in a protonic acid solution that is a strong acid. The immersion of the first polymer in the protonic acid solution is performed by, for example, immersing the electrolyte membrane 11 in the protonic acid solution after the electrolyte membrane 11 is formed from a composition containing the first polymer that does not contain an ionic dissociation group. Is done. The binding of the ionic dissociation group to the first polymer may be performed by dispersing the first polymer in the proton acid solution. Furthermore, the ionic dissociation group may be bonded to the main chain or side chain of the first polymer via a linker. Examples of the linker include alkylene, alkylene ether, alkylene ether ketone, arylene, arylene ether, and arylene ether ketone. These may be used alone or in combination of two or more. In addition, the linker may be fluorinated.

  Examples of a method for bonding an ionic dissociation group to the main chain or side chain of the first polymer via a linker include phenolic hydroxyl groups generated by irradiation with electron beams or the like, or sodium salts of phenolic hydroxyl groups generated by chemical reaction Or after forming a potassium salt, the method of alkylene-etherifying with sultone is mentioned. In addition, a method in which the sodium salt is reacted with an alkenyl halide by, for example, a Williamson reaction and then sulfonated. For example, when the main chain of the first polymer is imidazole, it is dehydrogenated using a reducing agent such as lithium hydride and then reacted with sultone to sulfonate the main chain of the first polymer. be able to.

  The number of ionic dissociation groups in the structural unit (repeating unit) of the first polymer containing an ionic dissociation group is preferably 0.1 or more, and more preferably 0.5 or more. When the number of ionic dissociation groups is less than 0.1, the electrolyte membrane 11 has low ionic conductivity and cannot exhibit sufficient ionic conductivity.

  The first polymer is not particularly limited as long as it contains an ionic dissociation group, but is preferably one that exhibits liquid crystallinity because the orientation control of the molecular chain of the first polymer is easy. In the following description, a polymer that exhibits liquid crystallinity is referred to as a liquid crystal polymer. The first polymer containing an ionic dissociation group and exhibiting liquid crystallinity is composed of an ionic dissociation group and a liquid crystal polymer.

  The liquid crystalline polymer is a polymer that exhibits optical anisotropy by regularly arranging molecular chains in a liquid crystal state. The molecular chain of the liquid crystalline polymer is a main chain or a side chain having a liquid crystalline expression site. The liquid crystalline polymer may have a liquid crystalline expression site only in the main chain or only in the side chain, or may have a liquid crystalline expression site in both the main chain and the side chain. The optical anisotropy of the liquid crystalline polymer is confirmed by the strong birefringence inherent in the liquid crystal when observed with a normal polarization microscope using an orthogonal polarizer. Examples of the liquid crystalline polymer include a thermal liquid crystalline polymer (thermotropic liquid crystalline polymer) and a lyotropic liquid crystalline polymer.

  The thermal liquid crystalline polymer refers to a liquid crystalline polymer that exhibits an optically anisotropic molten phase in a predetermined temperature range. The thermal liquid crystalline polymer is classified into a main chain type, a side chain type, and a composite type. The main chain type thermal liquid crystalline polymer is a thermal liquid crystalline polymer in which a mesogenic group having a rigid molecular structure that causes liquid crystallinity development is contained in the main chain. On the other hand, the side chain type thermal liquid crystalline polymer is a thermal liquid crystalline polymer in which the mesogenic group is contained in the side chain. For example, a mesogenic group is present in a hydrocarbon or siloxane main chain. The structure connected as a side chain is included as a repeating unit. The composite type thermal liquid crystalline polymer is a thermal liquid crystalline polymer in which the main chain type and the side chain type are combined.

  On the other hand, the lyotropic liquid crystalline polymer is a liquid crystalline polymer that exhibits an optically anisotropic phase and is in a liquid crystal state when dissolved in a solvent. The liquid crystalline polymer is preferably a lyotropic liquid crystalline polymer because the composition can be easily prepared by being easily mixed with the second polymer. The lyotropic liquid crystalline polymer exhibits excellent heat resistance and chemical resistance. Here, being excellent in heat resistance means that the structure of the lyotropic liquid crystalline polymer does not change in the temperature range in which the fuel cell is used. On the other hand, being excellent in chemical resistance means that the structure of the lyotropic liquid crystalline polymer does not change when the electrolyte membrane 11 comes into contact with the chemical. Examples of chemical resistance include acid resistance and alkali resistance. However, since the electrolyte membrane 11 is often used in an acidic atmosphere, the lyotropic liquid crystalline polymer preferably exhibits excellent acid resistance.

  The solvent is not particularly limited as long as it forms a liquid crystal state when the lyotropic liquid crystalline polymer is dissolved, and specific examples thereof include N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, N- Examples include aprotic solvents such as methyl-2-pyrrolidone, pyridine, quinoline, triethylamine, ethylenediamine, and hexamethylphosphonamide, and protic solvents such as trifluoromethanesulfonic acid, trifluoroacetic acid, methanesulfonic acid, polyphosphoric acid, and sulfuric acid. . These may be used alone or in combination of two or more. When two or more types are used in combination, it is preferable that the acidic solvent and the basic solvent are not combined in order to suppress the reaction between the solvents. Further, for example, a Lewis acid catalyst may be added to the solvent in order to enhance the solubility of the lyotropic liquid crystalline polymer.

  As the lyotropic liquid crystalline polymer, main chain type such as polybenzazole, polyimide, polyparaphenylene terephthalamide, polymetaphenylene isophthalamide or a copolymer thereof, polyarylene polymer containing a mesogenic group, terminal And a side chain type in which a hydrophilic group is bonded to a polymer chain in which the hydrophilic group is a lipophilic group (hydrophobic group). Among these, polybenzazole and polyimide are preferable because they exhibit excellent chemical resistance in addition to heat resistance. Furthermore, the lyotropic liquid crystalline polymer may be fluorinated. Fluorination of a lyotropic liquid crystalline polymer means that the main chain or side chain of the lyotropic liquid crystalline polymer contains a fluorine atom.

  The polybenzazole is a polymer composed of at least one selected from polybenzoxazole, polybenzimidazole, and polybenzthiazole. Polybenzimidazole is a polymer composed of a repeating unit having at least one imidazole ring bonded to an aromatic group, and specific examples thereof include poly (phenylenebenzobisimidazole). Polybenzoxazole is a polymer composed of a repeating unit having at least one oxazole ring bonded to an aromatic group, and specific examples thereof include poly (phenylenebenzobisoxazole). Polybenzthiazole is a polymer composed of a repeating unit having at least one thiazole ring bonded to an aromatic group, and specific examples thereof include poly (phenylenebenzobisthiazole).

Examples of the repeating unit of polybenzazole containing an ionic dissociation group include those represented by the following general formulas (2) to (7). In the following general formulas (2) to (7), Ar ^{1 to} Ar ⁶ represent an aromatic hydrocarbon group, and X ¹ and X ² are a sulfur atom, an oxygen atom, an imino group, or —N (RSO ₃ H) — ( Wherein R represents alkylene, alkylene ether, alkylene ether ketone, arylene, arylene ether or arylene ether ketone), Z represents an ionic dissociation group or a salt thereof, and k represents an integer of 1 to 10. The polybenzazole may be composed of only a repeating unit represented by at least one selected from the following general formulas (2), (3) and (4), but the general formulas (2), (3) and ( It may be composed of a combination of at least one repeating unit selected from 4) and at least one repeating unit selected from general formulas (5), (6) and (7). The repeating units represented by the following general formulas (2) to (7) may constitute polybenzazole by random polymerization or may constitute polybenzazole by block polymerization. The degree of polymerization of the repeating unit represented by the following general formula (2), (3) or (4) (hereinafter referred to as polymerization degree m) and the repetition represented by the general formula (5), (6) or (7) The degree of polymerization of units (hereinafter referred to as polymerization degree n) is preferably 1 to 600.

ここで、Ａｒ^１〜Ａｒ^６で示される芳香族炭化水素基は、１個の芳香族環または芳香族複素環により構成されてもよいし、複数の芳香族環または芳香族複素環が互いに直接結合することにより、若しくはイオウ原子、酸素原子、窒素原子などのヘテロ原子を有する官能基を介して結合することにより構成されてもよい。さらに芳香族炭化水素基を構成するベンゼン環の各炭素原子と結合している水素原子が、例えばメチル基、エチル基、ｔ−ブチル基などのブチル基からなる炭素数１〜１０のアルキル基、又はフェニル基などの芳香族炭化水素基に置換されてもよい。加えて、前記芳香族炭化水素基が複数の芳香族環または芳香族複素環により構成されているときには、各芳香族炭化水素基および芳香族複素環の結合部位としては、ポリベンズアゾールの主鎖が直線状をなしてその配向制御が容易になるためにパラ位が好ましい。Ａｒ¹又はＡｒ^４で示される芳香族炭化水素基の具体例を下記表１に示し、Ａｒ²又はＡｒ^５で示される芳香族炭化水素基の具体例を下記表２に示し、Ａｒ^３又はＡｒ^６で示される芳香族炭化水素基の具体例を下記表３に示す。表２の各芳香族炭化水素基がＡｒ²の具体例を示すとき、及び表３の各芳香族炭化水素基がＡｒ^３の具体例を示すときには、ベンゼン環の少なくとも１つの炭素原子と結合している水素原子がイオン性解離基に置換されている。

Here, the aromatic hydrocarbon group represented by Ar ^{1 to} Ar ⁶ may be composed of one aromatic ring or aromatic heterocyclic ring, or a plurality of aromatic rings or aromatic heterocyclic rings may be directly connected to each other. You may be comprised by couple | bonding through the functional group which has hetero atoms, such as a sulfur atom, an oxygen atom, and a nitrogen atom. Further, the hydrogen atom bonded to each carbon atom of the benzene ring constituting the aromatic hydrocarbon group is an alkyl group having 1 to 10 carbon atoms, for example, a butyl group such as a methyl group, an ethyl group, or a t-butyl group, Alternatively, it may be substituted with an aromatic hydrocarbon group such as a phenyl group. In addition, when the aromatic hydrocarbon group is composed of a plurality of aromatic rings or aromatic heterocycles, the bonding site of each aromatic hydrocarbon group and aromatic heterocycle is the main chain of polybenzazole. The para position is preferable because it forms a straight line and its orientation control becomes easy. Specific examples of the aromatic hydrocarbon group represented by Ar ¹ or Ar ⁴ are shown in the following Table 1, specific examples of the aromatic hydrocarbon group represented by Ar ² or Ar ⁵ are shown in the following Table 2, and Ar ³ or Ar Specific examples of the aromatic hydrocarbon group represented by ⁶ are shown in Table 3 below. When each aromatic hydrocarbon group in Table 2 shows a specific example of Ar ² and each aromatic hydrocarbon group in Table 3 shows a specific example of Ar ³ , it binds to at least one carbon atom of the benzene ring. Hydrogen atoms are replaced by ionic dissociation groups.

ポリベンズアゾールが前記一般式（２）、（３）及び（４）から選ばれる少なくとも一つで示される繰返し単位と、前記一般式（５）、（６）及び（７）から選ばれる少なくとも一つで示される繰返し単位との組み合わせにより構成されるときには、重合度ｍは重合度ｎよりも大きい値であることが好ましい。さらに、重合度ｍと重合度ｎとの合計は、好ましくは１０以上６００未満の範囲である。重合度ｍと重合度ｎとの合計が１０未満では、電解質膜１１中における液晶性高分子の各分子同士の絡み具合が弱くなり、電解質膜１１の強度が低下するおそれがある。重合度ｍと重合度ｎとの合計が６００以上の場合、液晶性高分子の分子鎖の配向制御が困難になる。

The polybenzazole is a repeating unit represented by at least one selected from the general formulas (2), (3) and (4), and at least one selected from the general formulas (5), (6) and (7). The degree of polymerization m is preferably a value greater than the degree of polymerization n. Furthermore, the total of the polymerization degree m and the polymerization degree n is preferably in the range of 10 or more and less than 600. When the sum of the polymerization degree m and the polymerization degree n is less than 10, the degree of entanglement between the molecules of the liquid crystalline polymer in the electrolyte membrane 11 becomes weak, and the strength of the electrolyte membrane 11 may be reduced. When the sum of the polymerization degree m and the polymerization degree n is 600 or more, it becomes difficult to control the alignment of the molecular chains of the liquid crystalline polymer.

  The intrinsic viscosity of the first polymer containing an ionic dissociation group is preferably 0.5 to 25 dL / g, more preferably 1 to 20 dL / g, and even more preferably 1 to 15 dL / g. The value of the intrinsic viscosity of the first polymer is a value at 25 ° C. measured according to American Society for Testing and Materials standard ASTM D2857-95 using methanesulfonic acid as a solvent and using an Ostwald viscometer. If the intrinsic viscosity of the first polymer is less than 0.5 dL / g, since the molecular weight of the first polymer is small, the strength of the manufactured electrolyte membrane 11 may be reduced and become brittle. When the intrinsic viscosity of the first polymer exceeds 25 dL / g, the viscosity of the composition becomes high, and it becomes difficult to orient the molecular chains of the first polymer when manufacturing the electrolyte membrane 11.

  The second polymer enhances the durability of the electrolyte membrane 11 by reinforcing the electrolyte membrane 11 due to its physical properties. The second polymer is different from the first polymer. Here, “the second polymer is different from the first polymer” includes the following concepts (a) to (c). That is, the first and second polymers are distinguished by the presence or absence of the ionic dissociation group or the type of polymer.

(A) The first and second polymers are different types of polymers, and only the first polymer contains the ionic dissociation group.
(B) The first and second polymers are different types of polymers, and the first and second polymers contain the ionic dissociation group.

(C) The first and second polymers are the same type of polymer, and only the first polymer contains the ionic dissociation group.
Although it will not specifically limit if it exhibits the said effect | action as a 2nd polymer | macromolecule, Since a swelling of the electrolyte membrane 11 can be suppressed in addition to the said effect | action, a basic polymer is preferable. The basic polymer includes an azole polymer such as polybenzazole. Furthermore, among basic polymers, polymers having a primary or secondary amino group in the repeating unit of the polymer or azole polymers are preferred, and polybenzimidazole is more preferred. The basic polymer having a primary or secondary amino group in the structural unit can effectively suppress the swelling of the electrolyte membrane 11, and the azole polymer exhibits excellent acid resistance. Polybenzimidazole exhibits excellent acid resistance and can effectively suppress swelling of the electrolyte membrane 11.

  The polybenzazole used as the second polymer is composed of, for example, the repeating unit represented by the general formula (5), (6) or (7), and the polymerization degree n is preferably 50 or more and less than 600. It is. If the degree of polymerization n is less than 50, the degree of entanglement between the molecules of the second polymer in the electrolyte membrane 11 becomes weak, the reinforcing effect of the electrolyte membrane 11 by the second polymer decreases, and the strength of the electrolyte membrane 11 May decrease. When the degree of polymerization n is 600 or more, it becomes difficult to control the orientation of the molecular chains of the second polymer.

  In addition to polyimidazole, polyvinylimidazole, polybenzbisimidazole, polyquinoxaline, polyquinoline, polyvinylamine, and poly (4-vinylpyridine), the polymer having a primary or secondary amino group in the structural unit includes: Examples include polybenzimidazole which is also included in the concept of polybenzazole.

  The second polymer may contain the ionic dissociation group as described above. In this case, the second polymer exhibits ionic conductivity in addition to the reinforcing action of the electrolyte membrane 11. Further, the second polymer may exhibit liquid crystallinity like the first polymer. That is, the second polymer may be composed of the liquid crystalline polymer in the same manner as the first polymer. In this case, the orientation of the molecular chain of the second polymer is easily controlled.

For example, when polybenzimidazole containing an ionic dissociation group is used as the second polymer, the polybenzimidazole is at least one selected from the general formulas (2), (3) and (4). It is comprised by the combination of the repeating unit shown and the repeating unit shown by at least 1 chosen from the said General formula (5), (6) and (7). At this time, X ¹ and X ² represent an imino group. The polymerization degree m is preferably larger than the polymerization degree n. Furthermore, the total of the polymerization degree m and the polymerization degree n is preferably in the range of 10 or more and less than 600. When the sum of the polymerization degree m and the polymerization degree n is less than 10, the degree of entanglement between the molecules of the second polymer in the electrolyte membrane 11 becomes weak, and the strength of the electrolyte membrane 11 may be reduced. When the sum of the polymerization degree m and the polymerization degree n is 600 or more, it becomes difficult to control the orientation of the molecular chain of the second polymer.

  When the second polymer does not contain an ionic dissociation group, the second polymer is preferably the same type of polymer as the first polymer or a polymer having a structure close to that of the first polymer. When it contains a dissociating group, it is preferably a polymer having a structure close to that of the first polymer. In this case, since the molecular chains of the second polymer are oriented in the same manner as the molecular chains of the first polymer, the molecular chains of the first and second polymers are oriented under the same conditions. Therefore, the first and second polymers can be easily oriented.

  Furthermore, the molecular chains of the second polymer may be cross-linked with each other, or may be bonded to each other by graft polymerization resulting from generation of radical species by irradiation with radiation or electron beam. In addition, when the main chain of the first and second polymers contains a polar group such as a hydroxyl group, a carboxyl group, a primary or secondary amino group, the activated alkylene or arylene terminal group is activated with them. The molecular chain of the first polymer and the molecular chain of the second polymer may be cross-linked by reaction with the carbocation. In this case, the second polymer is preferably a basic polymer because it is easily cross-linked with the first polymer. Swelling of the electrolyte membrane 11 can be effectively suppressed by crosslinking between the molecular chains of the second polymer or by crosslinking the molecular chains of the first polymer and the second polymer.

  The intrinsic viscosity of the second polymer is 2 to 15 dL / g, and preferably 7.5 to 13 dL / g. The intrinsic viscosity of the second polymer is measured in the same manner as the intrinsic viscosity of the first polymer. When the intrinsic viscosity of the second polymer is less than 2 dL / g, since the molecular weight of the second polymer is small, the strength of the manufactured electrolyte membrane 11 is lowered and becomes brittle. When the intrinsic viscosity of the second polymer exceeds 15 dL / g, the viscosity of the composition becomes high, and it becomes difficult to orient the molecular chains of the second polymer when the electrolyte membrane 11 is manufactured.

  The composition may contain a basic inorganic compound. Known basic inorganic compounds are used, and specific examples include hydrotalcite, aluminum hydroxide gel, magnesium oxide, alkaline silicate, and zinc oxide. The inorganic compound may be subjected to a surface treatment in order to enhance dispersibility in the composition.

  Since the electrolyte membrane 11 is formed of the composition, the electrolyte membrane 11 contains the first and second polymers. Further, the electrolyte membrane 11 has enhanced ion conductivity in the thickness direction of the electrolyte membrane 11 by orienting molecular chains of the first and second polymers in a certain direction. Here, the ion conductivity is improved because the ionic dissociation groups are arranged in the thickness direction of the electrolyte membrane 11, so that the ion channel is formed so as to extend in the thickness direction and the ionic conductivity in the same direction is increased. This is probably because of this. Therefore, the orientation direction of the molecular chain of the polymer containing the ionic dissociation group is preferably the direction in which the ionic dissociation groups are arranged in the thickness direction. For example, when the ionic dissociation group is bonded to the main chain of the first polymer, the main chain of the ion conductive polymer may be regularly oriented so as to extend in the thickness direction of the electrolyte membrane 11. preferable.

  The degree of orientation α along the certain direction of the molecular chains of the first and second polymers obtained from the following formula (1) from the X-ray diffraction measurement of the electrolyte membrane 11 is 0.3 or more and less than 1. If the degree of orientation α is less than 0.3, the ionic conductivity in the certain direction of the electrolyte membrane 11 is lowered, so that the ionic conductivity in the same direction is lowered. On the other hand, since the half-value width Δβ always shows a positive value, the degree of orientation α cannot take a value of 1 or more from the following formula (1).

Orientation degree α = (180−Δβ) / 180 (1)
(However, Δβ represents the half width when the X-ray diffraction intensity distribution from 0 to 360 degrees in the azimuth direction is measured with the peak scattering angle determined by X-ray diffraction measurement fixed.)
Here, how to determine the orientation degree α of the first and second polymers will be specifically described.

  In order to obtain the orientation degree α of the first and second polymers, wide-angle X-ray diffraction measurement (transmission) is performed on the electrolyte membrane 11. In an X-ray diffractometer, when a sample is irradiated with X-rays, a concentric arc-shaped diffraction pattern (Debye ring) is obtained when the particles (molecular chains) contained in the sample are oriented. Therefore, when the first and second polymers are oriented in the thickness direction of the electrolyte membrane 11 as the fixed direction, in order to obtain the orientation degree α, first, a plurality of electrolyte membranes 11 are laminated, and then the electrolyte The laminate of the film 11 is cut in the thickness direction to form a cut surface extending in the thickness direction. Next, the Debye ring is obtained by irradiating the cut surface with X-rays. Here, the X-ray irradiation direction is a direction perpendicular to the cut surface. Next, a diffraction pattern showing an X-ray diffraction intensity distribution in the radial direction from the center of the Debye ring is obtained.

  Subsequently, 2θ (hereinafter referred to as peak scattering angle) having the highest intensity in the range of 2θ = 15 to 30 degrees is obtained from the diffraction pattern. The peak scattering angle appears at 26 degrees, for example. Next, by fixing this peak scattering angle and measuring the X-ray diffraction intensity distribution from 0 to 360 degrees in the azimuth direction (circumferential direction of the Debye ring), the X in the azimuth direction as shown in FIG. A line diffraction intensity distribution is obtained. Next, in the X-ray diffraction intensity distribution in the azimuth angle direction, a width at half the peak height (half-value width Δβ) is obtained, and the half-value width Δβ is substituted into the equation (1) to obtain the orientation degree α Ask for. In the case of the X-ray diffraction intensity distribution in the azimuth direction shown in FIG. 2, the degree of orientation α is 0.57.

  The electrolyte membrane 11 has an ionic conductivity in the thickness direction of the membrane higher than that in a direction parallel to the surface of the membrane. Here, the ionic conductivity is obtained by, for example, an AC impedance method. Specifically, the resistance value is measured by changing the distance between the two electrodes (distance between the electrodes), and the influence of the contact resistance is determined from the slope value of the graph obtained by plotting the distance between the electrodes and the measured resistance value. The ionic conductivity is determined by removing. Furthermore, the electrolyte membrane 11 has a range in which the ionic conductivity ratio γ determined by the following formula (8) exceeds 1, preferably 2 or more and less than 60, and more preferably 6 or more and less than 30. When the ionic conductivity ratio γ is 1 or less, the ionic conductivity in the thickness direction of the electrolyte membrane 11 cannot be sufficiently increased. When the ionic conductivity ratio γ is 60 or more, it is difficult to manufacture the electrolyte membrane 11.

Ionic conductivity ratio γ = ionic conductivity in the thickness direction of the electrolyte membrane 11 / ionic conductivity in a direction parallel to the surface of the electrolyte membrane 11 (8)
Next, as a method for manufacturing the electrolyte membrane 11, a method for manufacturing the electrolyte membrane 11 in which the first and second polymers are liquid crystalline polymers will be described. This manufacturing method includes a preparation process, an expression process, an alignment process, and a solidification process. The preparation step is a step of preparing a composition by blending the respective components such as the first and second polymers. In this preparation process, the blending order of each component is not particularly limited.

  The expression step is a step for expressing the liquid crystal properties of the first and second polymers in the composition. In this expression step, when the first and second polymers are thermal liquid crystalline polymers, liquid crystallinity is exhibited by heating and melting the composition. On the other hand, when the first and second polymers are lyotropic liquid crystalline polymers, the solvent is added to the composition to prepare a solvent-containing composition. At this time, the lyotropic liquid crystalline polymer is dissolved in a solvent and exhibits liquid crystallinity when the solvent-containing composition is heated.

  The concentration of the lyotropic liquid crystalline polymer in the solvent-containing composition is preferably 2 to 60% by mass. If the concentration of the lyotropic liquid crystalline polymer is less than 2% by mass, the lyotropic liquid crystalline polymer has a low concentration, so that it becomes difficult to exhibit liquid crystallinity. On the other hand, when the concentration of the lyotropic liquid crystalline polymer exceeds 60% by mass, the viscosity of the solvent-containing composition increases, and it becomes difficult to align the molecular chain of the lyotropic liquid crystalline polymer in the alignment step. The concentration of the lyotropic liquid crystalline polymer in the solvent-containing composition is the sum of the concentration of the lyotropic liquid crystalline polymer constituting the first polymer and the concentration of the lyotropic liquid crystalline polymer constituting the second polymer. It is.

  The temperature of the solvent-containing composition is preferably 40 to 250 ° C, more preferably 40 to 200 ° C, and still more preferably 60 to 150 ° C. If the temperature of the solvent-containing composition is less than 40 ° C. or exceeds 250 ° C., the lyotropic liquid crystalline polymer cannot sufficiently exhibit liquid crystallinity. The heating means of the solvent-containing composition is not particularly limited, and examples thereof include a method using radiant heat such as an electric heater and an infrared lamp, and a dielectric heating method. The solvent-containing composition is preferably heated under an inert gas atmosphere. Furthermore, the solvent-containing composition is once heated to a temperature range that does not exhibit liquid crystallinity, thereby transferring the lyotropic liquid crystalline polymer to a uniform isotropic phase and then cooling to a temperature range that exhibits liquid crystallinity. May be. In this case, the liquid crystal phase of the lyotropic liquid crystalline polymer can be grown as compared with the case where the solvent-containing composition is only heated to a temperature range that exhibits liquid crystallinity.

  The alignment step is a step of aligning the molecular chains of the first and second polymers exhibiting liquid crystallinity in a certain direction. As a method for orienting the molecular chains of the first and second polymers in a certain direction, a method of orienting the compositions by self-orientation of the first and second polymers in a molten state or a liquid state with a solvent. And a method of aligning with at least one kind of field selected from a fluid field, a shear field, a magnetic field and an electric field. Among these alignment methods, a method of aligning by at least one field selected from a fluid field, a shear field, a magnetic field, and an electric field is preferable, and a method of aligning by a magnetic field is more preferable.

  For example, in the method of aligning by a magnetic field, a magnetic field is applied to the composition using a magnetic field generator. At this time, the molecular chains of the first and second polymers are oriented in a direction extending in parallel to the magnetic field lines. Examples of the magnetic field generator include a permanent magnet, an electromagnet, a superconducting magnet, and a coil. Among these, the superconducting magnet is preferable because it can easily generate a magnetic field having a high magnetic flux density.

  The magnetic flux density of the magnetic field applied to the composition is preferably 1 to 30 Tesla (T), more preferably 2 to 25 T, and even more preferably 3 to 20 T. If the magnetic flux density is less than 1T, the molecular chains of the first and second polymers cannot be sufficiently oriented, and conversely if it exceeds 30T, it is not practical. When the first and second polymers are lyotropic liquid crystalline polymers, a magnetic field is applied to the solvent-containing composition.

  The solidification step is a step of solidifying the composition while maintaining the orientation of the molecular chains of the first and second polymers. In this solidification step, when the first and second polymers are thermal liquid crystalline polymers, the composition is cooled and solidified. On the other hand, when the first and second polymers are lyotropic liquid crystalline polymers, the solvent-containing composition may be heated to remove the solvent to solidify (coagulate) the composition. It is preferred to use to solidify the composition. The coagulation liquid preferably has compatibility with the solvent and the lyotropic liquid crystalline polymer exhibits poor solubility. Specific examples include water, aqueous phosphoric acid, aqueous sulfuric acid, aqueous sodium hydroxide, methanol, ethanol, Acetone and ethylene glycol are mentioned. These may be used alone or in combination of two or more.

  When the solvent-containing composition is solidified, the coagulation liquid is brought into contact with the solvent-containing composition. At this time, only the solvent dissolves in the coagulating liquid and moves from the solvent-containing composition into the coagulating liquid. As a result, the lyotropic liquid crystalline polymer is precipitated and the composition is solidified. For this reason, since the planarity of the surface of the manufactured electrolyte membrane 11 can be improved by gently moving the solvent among the specific examples of the coagulating liquid, a 10 to 70% by mass phosphoric acid aqueous solution can be obtained. And lower alcohols such as methanol and ethanol are preferred.

  The temperature of the coagulation liquid is preferably −60 to 60 ° C., more preferably −30 to 30 ° C., and further preferably −20 to 0 ° C. When the temperature of the coagulation liquid is less than −60 ° C., the solidification of the solvent-containing composition is slow, and the production efficiency of the electrolyte membrane 11 may be reduced. On the other hand, when the temperature of the coagulating liquid exceeds 60 ° C., the planarity of the surface of the electrolyte membrane 11 may be lowered, or the density of the lyotropic liquid crystalline polymer in the electrolyte membrane 11 may be biased. In the solidification step, it is preferable to apply the magnetic field to the composition or the solvent-containing composition in order to positively maintain the orientation of the molecular chains of the first and second polymers.

  After the solidification step, the solidified composition is washed and dried. Cleaning of the solidified composition is performed by immersing the composition in a cleaning liquid or spraying the cleaning liquid on the composition. Examples of the cleaning liquid include polar solvents such as water. The solidified composition is dried by a method using a heated gas such as air, nitrogen or argon, a method using radiant heat such as an electric heater or an infrared lamp, or a dielectric heating method. At this time, the shrinkage may be limited by restraining the outer edge of the solidified composition. The drying temperature is preferably 100 to 500 ° C, more preferably 100 to 400 ° C, and further preferably 100 to 200 ° C. If the drying temperature is less than 100 ° C., the composition is not sufficiently dried. Conversely, if the drying temperature exceeds 500 ° C., the liquid crystalline polymer may be decomposed. Each process may be performed continuously, for example, so that the preparation process and the expression process are performed simultaneously.

Hereinafter, as an example, a method for producing the electrolyte membrane 11 from a composition containing the thermal liquid crystalline polymer as the first and second polymers will be described.
Here, the metal mold | die 21 for manufacturing the electrolyte membrane 11 is demonstrated. As shown in FIG. 3, the mold 21 includes a cavity 22 having a shape corresponding to the shape of the electrolyte membrane 11. Further, the mold 21 includes a heating device (not shown).

  When manufacturing the electrolyte membrane 11, first, as a preparation step and an expression step, a thermal liquid crystalline polymer containing an ionic dissociation group as a first polymer, and a thermal liquid crystalline polymer as a second polymer, After preparing a composition by mixing with other components, the composition is heated and melted to exhibit liquid crystallinity. Subsequently, the intermediate body 13 is formed by filling the cavity 22 of the mold 21 with the composition melted by heating. The composition is filled by a synthetic resin material heat molding apparatus such as an injection molding apparatus, an extrusion molding apparatus, or a press molding apparatus. The intermediate body 13 is maintained in a molten state by a heating device provided in the mold 21.

  Subsequently, a pair of permanent magnets 23 a and 23 b are disposed above and below the mold 21 as an alignment step. At this time, a magnetic force line M extending in a straight line is generated between the upper permanent magnet 23a and the lower permanent magnet 23b. As a result, a magnetic field is applied to the intermediate 13. At this time, the molecular chain of each thermal liquid crystalline polymer is oriented in the thickness direction (vertical direction) of the intermediate body 13 because the magnetic lines of force M extend in parallel with the thickness direction of the intermediate body 13.

  Next, as a solidification step, the intermediate body 13 is solidified by cooling the mold 21 in a state where the alignment state of the molecular chains of each of the thermal liquid crystalline polymers is maintained. Next, after removing the intermediate 13 from the mold 21, the intermediate 13 is washed and dried to manufacture the electrolyte membrane 11.

A method for producing the electrolyte membrane 11 from a composition containing lyotropic liquid crystalline polymers as the first and second polymers will be described.
When manufacturing the electrolyte membrane 11, first, as a preparation step and an expression step, a lyotropic liquid crystalline polymer containing an ionic dissociation group as a first polymer, and a lyotropic liquid crystalline polymer as a second polymer, After mixing with other components to prepare a composition, a solvent is added to the composition to prepare a solvent-containing composition. Next, as shown in FIG. 4, the intermediate 13 is formed by casting the solvent-containing composition on the substrate 24 using a slit die or the like. Examples of the substrate 24 include an endless belt, an endless drum, an endless film, and a plate. Examples of the material of the substrate 24 include glass, a synthetic resin material, and a metal material, but a corrosion-resistant material such as stainless steel, hastelloy alloy, and tantalum is preferable.

  Subsequently, by placing another substrate 24 on the intermediate body 13, the intermediate body 13 is sandwiched between the pair of substrates 24. At this time, the intermediate body 13 is sandwiched between the pair of substrates 24, so that the contact area with the moisture contained in the air is reduced, and deterioration due to the air can be suppressed.

  Subsequently, as an alignment step, a pair of permanent magnets 23 a and 23 b are disposed above and below each substrate 24. At this time, a magnetic force line M extending in a straight line is generated between the upper permanent magnet 23a and the lower permanent magnet 23b. As a result, a magnetic field is applied to the intermediate 13. At this time, the molecular chain of each lyotropic liquid crystalline polymer is oriented in the thickness direction (vertical direction) of the intermediate body 13 because the magnetic lines of force M extend in parallel with the thickness direction of the intermediate body 13. Further, a heating device (not shown) is disposed around each substrate 24, and the intermediate 13 is heated to a temperature at which liquid crystallinity is exhibited.

  Next, as a solidification step, after the intermediate 13 is peeled from each substrate 24 in a state where the molecular chain alignment state of each lyotropic liquid crystalline polymer is maintained, the solvent-containing composition is heated to remove the solvent. To solidify the intermediate 13. Next, the intermediate body 13 is washed and dried to manufacture the electrolyte membrane 11.

The effects exhibited by the above embodiment will be described below.
-The electrolyte membrane 11 of this embodiment is formed from the composition containing the 1st polymer | macromolecule containing an ionic dissociation group, and the 2nd polymer | macromolecule different from this 1st polymer | macromolecule. The molecular chains of the first and second polymers are oriented in a certain direction, and the degree of orientation α in the certain direction and the intrinsic viscosity of the second polymer are set in the above ranges. In addition, the ionic conductivity in the thickness direction of the electrolyte membrane 11 is set higher than the ionic conductivity in the direction parallel to the surface of the membrane.

  Therefore, the electrolyte membrane 11 can increase the ionic conductivity by the ionic dissociation group to increase the ionic conductivity, and has durability due to the second polymer whose intrinsic viscosity is set in the above range. Can be increased. Furthermore, the electrolyte membrane 11 can particularly enhance the ionic conductivity in the thickness direction by setting the orientation degree α and the ionic conductivity in the thickness direction within the above ranges.

  The liquid crystalline polymer is preferably polybenzazole, that is, at least one selected from polybenzoxazole, polybenzimidazole, and polybenzthiazole. In this case, the electrolyte membrane 11 can improve heat resistance and chemical resistance. For example, even when used in an acidic atmosphere, it is possible to prevent a decrease in ion conductivity.

In addition, this embodiment can also be changed and embodied as follows.
-You may comprise the said 1st and 2nd polymer | macromolecule from polymers other than a liquid crystalline polymer. In this case, the expression step is omitted in manufacturing the electrolyte membrane 11. Further, the electrolyte membrane 11 may be manufactured from the composition containing the thermal liquid crystalline polymer using the substrate 24, or the electrolyte membrane using the mold 21 from the composition containing the lyotropic liquid crystalline polymer. 11 may be manufactured. Furthermore, the electrolyte membrane 11 may be manufactured using only one substrate 24. In this case, in order to prevent deterioration due to moisture contained in the air, it is preferable to place the intermediate body 13 in a dry air atmosphere.

  -When orienting the molecular chains of the first and second polymers by a flow field or shear field, by using a molding apparatus such as an injection molding apparatus, an extrusion molding apparatus, or a press molding apparatus in the alignment process and the solidification process. The electrolyte membrane 11 may be manufactured by shaping a block in which the molecular chains of the first and second polymers are oriented in an arbitrary direction and then slicing the block. At this time, the block is sliced so that the direction of highest ion conductivity is the thickness direction of the electrolyte membrane 11. Examples of the method for slicing the block include a method using a rotary blade such as a diamond cutter, a cutting board, a water ablation cutter, a wire cutter and the like.

The intermediate body 13 may be formed by, for example, compression molding, extrusion molding, injection molding, cast molding, calendar molding, painting, printing, dispenser, or potting.
-The electrolyte membrane 11 is made to have conductivity of cations such as hydrogen ions, such as batteries other than solid polymer fuel cells such as lithium ion secondary batteries (polymer batteries), seawater electrolysis, ion conductive actuators, etc. You may use for the various use for which the electrolyte membrane which has is used suitably.

Next, the embodiment will be described more specifically with reference to examples and comparative examples. The intrinsic viscosity of each polymer used in Examples and Comparative Examples is a value at 25 ° C. when methanesulfonic acid is used as a solvent and an Ostwald viscometer is used, and the concentration of the polymer in the solution is 0.05 g / dL. It is.
(Examples 1-6 and Comparative Examples 1-9)
In Example 1, as a preparation process and an expression process, 39.06 g of polyphosphoric acid (condensation rate of P ₂ O ₅ 115%), phosphorus pentoxide was added to a reaction vessel equipped with a stirrer, a nitrogen introduction tube, and a dryer. A reaction solution was prepared by charging 11.52 g, 6.39 g (30.0 mmol) of 4,6-diaminoresorcinol dihydrochloride, and 8.05 g (30.0 mmol) of 2-sulfoterephthalic acid. The mixture was stirred at 70 ° C. for 0.5 hours under a nitrogen atmosphere. Next, while stirring the reaction solution, each component in the reaction solution is allowed to react by heating in steps of 120 ° C. for 3 hours, 130 ° C. for 10 hours, 165 ° C. for 10 hours, and 190 ° C. for 15 hours. Thus, a crude sulfonated polybenzoxazole solution was obtained. Observation using a polarizing microscope confirmed that the crude sulfonated polybenzoxazole solution exhibited liquid crystallinity.

  Subsequently, the crude sulfonated polybenzoxazole solution is washed with methanol, acetone, and water in order, so that a scraped sulfonated polybenzoxazole (sulfone as a first polymer containing an ionic dissociation group) is obtained. PBO) was obtained. After washing the crude sulfonated polybenzoxazole solution, the pH of the crude sulfonated polybenzoxazole solution was confirmed to be neutral using a pH test. The intrinsic viscosity of the sulfonated PBO was 2.01 dL / g.

On the other hand, in a reaction vessel equipped with a stirrer, a nitrogen introduction tube, and a dryer, 300 g of polyphosphoric acid (condensation rate of P ₂ O ₅ 115%), 5 g (23.4 mmol) of 4,6-diaminoresorcinol dihydrochloride, After the reaction solution was prepared by charging 4.76 g (23.4 mmol) of terephthalic acid dichloride, the reaction solution was stirred at 70 ° C. for 16 hours. The reaction solution is then heated stepwise in the order of 90 ° C. for 5 hours, 130 ° C. for 3 hours, 150 ° C. for 16 hours, 170 ° C. for 3 hours, 185 ° C. for 3 hours, and 200 ° C. for 48 hours. By reacting each component in the reaction solution, a crude polybenzoxazole solution was obtained. Subsequently, a crude polybenzoxazole solution was reprecipitated using methanol, acetone, and water in this order to obtain scraped polybenzoxazole (PBO-I) as a second polymer. The intrinsic viscosity of PBO-I was 7.5 dL / g.

  Next, after mixing sulfonated PBO and PBO-I in the ratio shown in Table 4 below, polyphosphoric acid was added to prepare a 25 mass% sulfonated PBO / PBO-I mixed solution as a solvent-containing composition. Observation with a polarizing microscope confirmed that the mixed solution exhibited liquid crystallinity.

  Subsequently, the mixed solution was applied between two substrates 24 to obtain an intermediate 13 having a film shape. Subsequently, as an alignment step, the two substrates 24 were arranged between the pair of upper and lower permanent magnets 23a and 23b so that the magnetic lines of force M extended in parallel with the thickness direction of the intermediate body 13. And it heated at 100 degreeC for 25 minutes, applying the magnetic field of 10T to the intermediate body 13. FIG.

  Next, as a solidification step, the intermediate 13 was naturally cooled to room temperature (25 ° C.) and solidified while standing. Subsequently, the solidified intermediate 13 was immersed in a mixed solution of methanol and water while being sandwiched between the substrates 24. In the mixed solution, one of the substrates 24 was removed, and the intermediate 13 was further solidified. The solidified intermediate 13 is immersed in the mixed solution for 1 hour, further immersed in water for 1 hour, and then dried at 110 ° C. for 2 hours to form a sulfonated PBO / PBO-I film (thickness) as the electrolyte membrane 11. Obtained: 150 μm). The direction in which the magnetic field is applied in the alignment step corresponds to the Z-axis direction shown in FIG. 1 with respect to the sulfonated PBO / PBO-I film spreading on the substrate 24.

  In Example 2, polybenzoxazole (PBO-II) having an intrinsic viscosity of 10 dL / g was used as the second polymer, and sulfonated PBO and PBO-II were mixed at a ratio shown in Table 4 below. Obtained a sulfonated PBO / PBO-II film (thickness: 150 μm) in the same manner as in Example 1.

  In Example 3, polybenzoxazole (PBO-III) having an intrinsic viscosity of 13 dL / g was used as the second polymer, and sulfonated PBO and PBO-III were mixed at the ratio shown in Table 4 below. Obtained a sulfonated PBO / PBO-III film (thickness: 150 μm) in the same manner as in Example 1.

  In Example 4, sulfonated polybenzimidazole (sulfonated PBI-I) having an intrinsic viscosity of 2.2 dL / g was used as the second polymer containing an ionic dissociation group. A sulfonated PBO / sulfonated PBI-I film (thickness: 150 μm) was obtained in the same manner as in Example 1 except that sulfonated PBO and sulfonated PBI-I were mixed at the ratio shown in Table 4 below. It was.

  In Example 5, sulfonated polybenzimidazole (sulfonated PBI-II) having an intrinsic viscosity of 5.2 dL / g was used as the second polymer containing an ionic dissociation group. A sulfonated PBO / sulfonated PBI-II film (thickness: 150 μm) was obtained in the same manner as in Example 1 except that sulfonated PBO and sulfonated PBI-II were mixed at the ratio shown in Table 4 below. It was.

  In Example 6, polybenzimidazole (PBI) having an intrinsic viscosity of 8.2 dL / g was used as the second polymer, and sulfonated PBO and PBI were mixed in the ratio shown in Table 4 below. In the same manner as in Example 1, a sulfonated PBO / PBI film (thickness: 150 μm) was obtained.

  In Comparative Example 1, polybenzoxazole (PBO-IV) having an intrinsic viscosity of 27 dL / g was used as the second polymer, and sulfonated PBO and PBO-IV were mixed at a ratio shown in Table 4 below. Obtained a sulfonated PBO / PBO-IV film (thickness: 150 μm) in the same manner as in Example 1.

  In Comparative Example 2, a sulfonated PBO / PBO-I film (thickness: 150 μm) was prepared in the same manner as in Example 1 except that the application of the magnetic field was omitted and the heating time in the alignment step was changed to 20 minutes. Obtained.

  In Comparative Example 3, a sulfonated PBO / PBO-II film (thickness: 150 μm) was obtained in the same manner as in Example 2 except that the application of the magnetic field was omitted and the heating time in the alignment step was changed to 20 minutes. Obtained.

  In Comparative Example 4, a sulfonated PBO / PBO-III film (thickness: 150 μm) was obtained in the same manner as in Example 3 except that the application of the magnetic field was omitted and the heating time in the alignment step was changed to 20 minutes. Obtained.

  In Comparative Example 5, sulfonated PBI-II was used as the second polymer. And sulfonated PBO and sulfonated PBI-II were mixed in the ratio shown in Table 5 below, and further, the application of the magnetic field was omitted and the heating time in the alignment step was changed to 20 minutes. Similarly, a sulfonated PBO / sulfonated PBI-II film (thickness: 150 μm) was obtained.

  In Comparative Example 6, PBI was used as the second polymer. Then, sulfonated PBO and PBI were mixed at the ratio shown in Table 5 below, and the application of a magnetic field was omitted, and the heating time in the alignment step was changed to 20 minutes. A PBO / PBI film (thickness: 150 μm) was obtained.

In Comparative Example 7, a sulfonated PBO film (thickness: 150 μm) was obtained in the same manner as in Example 1 except that the second polymer was omitted.
In Comparative Example 8, sulfonated polybenzimidazole (sulfonated PBI-III) having an intrinsic viscosity of 1.5 dL / g was used as the second polymer containing an ionic dissociation group. A sulfonated PBO / sulfonated PBI-III film (thickness: 150 μm) was obtained in the same manner as in Example 1 except that sulfonated PBO and sulfonated PBI-III were mixed at the ratio shown in Table 5 below. It was.

  In Comparative Example 9, sulfonated perfluorocarbon (Nafion 112 manufactured by DuPont) was used as the first polymer, and the second polymer was omitted. A sulfonated perfluorocarbon film (thickness: 150 μm) was obtained in the same manner as in Example 1 except that the application of the magnetic field was omitted and the heating time in the alignment step was changed to 20 minutes.

  And about the film of each example, it measured or evaluated regarding the following each item. The results are shown in Tables 4 and 5. In Table 4 and Table 5, the unit of the numerical value in the column which shows each compound is a weight part. “-” In the “Orientation degree α” column indicates that the molecular chain of each polymer was not oriented in a certain direction. “−” In each column other than the “Orientation degree α” column indicates that the item in the column could not be measured or calculated.

<Orientation degree α>
Using an X-ray diffractometer (RINT-RAPID manufactured by Rigaku Corporation), X-ray diffraction in the azimuth direction that appears in the vicinity of 2θ = 15 to 25 degrees obtained by irradiating X-rays from the X-axis direction of FIG. Based on the half-value width Δβ of the peak in the intensity distribution, the degree of orientation α was calculated by the above formula (1). FIG. 2 shows the X-ray diffraction intensity distribution in the azimuth direction when the peak scattering angle is 26 degrees in Example 1.

<Ionic conductivity and ionic conductivity ratio>
The film of each example was cut into a certain shape, the cut film was sandwiched between plate-like platinum probes (10 mm × 10 mm), and allowed to stand in a high-temperature and high-humidity atmosphere at 80 ° C. and 90% RH. The alternating current impedance measured using this was taken as the ionic conductivity in the thickness direction of the electrolyte membrane. The ionic conductivity in the direction parallel to the film surface was determined in the same manner as in the thickness direction, except that the platinum probe was pressed against the film surface to change the distance of the platinum probe. And the ionic conductivity ratio was computed by the said Formula (8) from the obtained ionic conductivity of the direction parallel to the thickness direction and the surface.

<Swelling rate>
The film of each example was immersed in pure water at 80 ° C. for 12 hours. And swelling rate was computed by following formula (9) based on the mass of the film before and behind immersion.

Swelling ratio (% by mass) = (W ₁ −W ₂ ) / W ₂ × 100 (9)
(W ₁ indicates the mass of the film after immersion, and W ₂ indicates the mass of the film before immersion.)
<State of film>
The state of the film after drying in each example was visually evaluated. In the “Film Status” column of Tables 4 and 5, “◯” indicates that no physical defect such as chipping has occurred in the film and the film is in good condition, and “X” indicates the film. Is brittle, and physical defects such as cracks are easily generated.

表４に示すように、実施例１〜６においては各項目について優れた結果が得られた。そのため、各実施例のフィルムはイオン伝導性を高めることができ、特に厚さ方向のイオン伝導性を高めることができた。さらに、各実施例のフィルムは、フィルムの状態が良好であることから耐久性も高めることができた。従って、各実施例のフィルムは、固体高分子形燃料電池に好適に使用可能である。

As shown in Table 4, in Examples 1 to 6, excellent results were obtained for each item. Therefore, the film of each Example was able to improve ionic conductivity, and especially the ionic conductivity in the thickness direction. Furthermore, since the film of each Example had the favorable state of a film, it could also improve durability. Therefore, the film of each Example can be suitably used for a polymer electrolyte fuel cell.

  Furthermore, in Example 6, by using PBI as the second polymer, the swelling rate of the film was effectively reduced and the durability could be further increased. In Examples 4 and 5, by using sulfonated PBI as the second polymer, not only the swelling rate of the film is effectively reduced and the durability is increased, but also the ions in each direction as compared with Example 6. It was possible to increase the conductivity and increase the ionic conductivity.

  In Comparative Example 1, since the intrinsic viscosity of PBO-IV exceeded 15 dL / g, the first and second polymers could not be oriented. In Comparative Examples 2 to 6 and 9, since no magnetic field was applied in the alignment step, the molecular chains of each polymer were not aligned in a certain direction, and the ionic conductivity in the thickness direction was compared to each example. It was low. In Comparative Example 7, since the second polymer was not contained, the film easily cracked and the like, and the durability was low as compared with each Example. In Comparative Example 8, since the intrinsic viscosity of the second polymer was less than 2 dL / g, the film easily cracked, and the durability was lower than in each Example.

The principal part perspective view which shows the electrolyte membrane of embodiment. The graph which shows X-ray diffraction intensity distribution of an azimuth angle direction. The conceptual diagram which shows the manufacturing process of an electrolyte membrane. The conceptual diagram which shows the manufacturing process of an electrolyte membrane.

Explanation of symbols

  Δβ: Half width, 11: Ion conductive polymer electrolyte membrane.

Claims (7)

An ion conductive polymer electrolyte membrane formed from an ion conductive composition comprising a first polymer containing an ionic dissociation group and a second polymer different from the first polymer. ,
The intrinsic viscosity of the second polymer is set to 2 to 15 dL / g;
The molecular chains of the first and second polymers are oriented in a certain direction;
The degree of orientation α along the certain direction of the molecular chains of the first and second polymers determined from the following formula (1) from the X-ray diffraction measurement is set to 0.3 or more and less than 1.
An ion conductive polymer electrolyte membrane, wherein the ion conductivity in the thickness direction of the membrane is set higher than the ion conductivity in a direction parallel to the surface of the membrane.
Orientation degree α = (180−Δβ) / 180 (1)
(However, Δβ represents the half width when the X-ray diffraction intensity distribution from 0 to 360 degrees in the azimuth direction is measured with the peak scattering angle determined by X-ray diffraction measurement fixed.)   The ion conductive polymer electrolyte membrane according to claim 1, wherein the second polymer is a basic polymer.   The ion conductive polymer electrolyte membrane according to claim 2, wherein the basic polymer is a polymer having a primary or secondary amino group in a structural unit of the polymer or an azole polymer.   The ion conductive polymer electrolyte membrane according to claim 2 or 3, wherein the basic polymer is polybenzimidazole. Formed from an ion-conductive composition comprising a first polymer containing an ionic dissociation group and a second polymer different from the first polymer, and the intrinsic viscosity of the second polymer is The first and second polymers are set to 2 to 15 dL / g, the molecular chains of the first and second polymers are oriented in a certain direction, and are obtained from the following formula (1) from X-ray diffraction measurement The degree of orientation α along the certain direction of the molecular chain is set to 0.3 or more and less than 1, and the ionic conductivity in the thickness direction of the film is set higher than the ionic conductivity in the direction parallel to the surface of the film. A method for producing an ion conductive polymer electrolyte membrane,
A preparation step of preparing the ion conductive composition;
An alignment step of aligning the molecular chains of the first and second polymers in the ion conductive composition in a certain direction;
And a solidifying step of solidifying the ion conductive composition while maintaining the orientation of the molecular chains of the first and second polymers. A method for producing an ion conductive polymer electrolyte membrane, comprising:
Orientation degree α = (180−Δβ) / 180 (1)
(However, Δβ represents the half width when the X-ray diffraction intensity distribution from 0 to 360 degrees in the azimuth direction is measured with the peak scattering angle determined by X-ray diffraction measurement fixed.) The first and second polymers are liquid crystalline polymers;
6. The ion conduction according to claim 5, wherein the production method further comprises an expression step for expressing the liquid crystallinity of the first and second polymers in the ion conductive composition after the preparation step and before the alignment step. For producing a conductive polymer electrolyte membrane.   The ion according to claim 5 or 6, wherein the alignment step is a step of aligning molecular chains of the first and second polymers in a certain direction by applying a magnetic field to the ion conductive composition. A method for producing a conductive polymer electrolyte membrane.

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