JP4633569B2 - Cross-linked proton conductive block copolymer, cross-linked product thereof, and proton conductive membrane and fuel cell using the same - Google Patents

Description

  The present invention relates to an ion-conductive cross-linked proton-conductive block copolymer aromatic resin used in a fuel cell using hydrogen, alcohol or the like as a fuel, a polymer membrane obtained using the same, and a fuel cell.

A polymer electrolyte fuel cell is a fuel cell that uses a proton-conducting polymer as an electrolyte, and the chemical energy of the fuel is converted into electrical energy by electrochemically oxidizing hydrogen or methanol or other fuel using oxygen or air. It is to be converted and extracted. The polymer electrolyte fuel cell includes a type using pure hydrogen supplied from a cylinder, a pipe, or the like as a fuel, and a type using hydrogen generated from gasoline or methanol by a reformer. In addition, a direct methanol fuel cell (DMFC) that directly generates power using a methanol aqueous solution as a fuel has been developed. Since this DMFC does not require a reformer for generating hydrogen, a simple and compact system can be constructed, and it is especially attracting attention as a power source for portable devices.
A polymer electrolyte fuel cell includes a polymer electrolyte membrane and a positive electrode and a negative electrode arranged in contact with both sides thereof. Fuel hydrogen or methanol is electrochemically oxidized at the negative electrode to generate protons and electrons. This proton moves in the polymer electrolyte membrane to the positive electrode to which oxygen is supplied. On the other hand, electrons generated at the negative electrode pass through a load connected to the battery and flow to the positive electrode, where protons and electrons react to generate water at the positive electrode. Therefore, high proton conductivity is required for the electrolyte membrane.

As a polymer electrolyte membrane having high proton conductivity, development of a non-fluorine polymer compound has been promoted, but tertiary carbon having a main chain structure is easily subjected to radical attack, and is easily α-positioned in a battery. This causes a problem that the battery characteristics deteriorate over time. For this reason, a large number of protonic acid group-containing polymers having no aliphatic chain in the main chain, that is, aromatic hydrocarbons, have been developed. Among them, it has been reported that a membrane made of sulfonated polyether ether ketone is excellent in heat resistance and chemical durability and can withstand long-time use as a polymer electrolyte (for example, Non-Patent Document 1). .
In order to increase the proton conductivity of these proton acid group-containing aromatic hydrocarbon polymer membranes, it is necessary to increase the amount of proton acid groups introduced, that is, to reduce the ion exchange group equivalent. It is known that when the introduction amount is increased, the hydrophilicity is increased at the same time, and the water absorption is increased or becomes water-soluble (for example, Patent Document 1). Since a fuel cell by-produces water by the reaction of fuel and oxygen, a water-soluble resin cannot be used as a polymer electrolyte membrane for a fuel cell. In addition, even if it is not water-soluble, when water absorption is high, problems such as swelling of the film, a decrease in strength, and permeation of methanol from the negative electrode to the positive electrode through the absorbed water occur.

Therefore, a method for improving water resistance and reducing water absorption by introducing a crosslinked structure into the polymer electrolyte membrane has been developed.
For example, a crosslinking method using a sulfonate bond obtained by desulfurization condensation of sulfonic acids in a polyether ether ketone membrane has been reported (for example, Patent Document 2), which is a crosslinking mechanism accompanied by elimination of sulfuric acid, There are problems that the crosslink density is different between the film surface and the inside of the film or the back surface of the film, it is difficult to increase the film thickness, voids are formed in the film, and the production apparatus is corroded by the desorbed acidic gas. Further, the membrane obtained by the crosslinking mechanism using these protonic acid groups has a problem that when the crosslinking density is improved, the protonic acid groups decrease (the ion exchange group equivalent increases) and the ionic conductivity decreases.

  As a crosslinking mechanism that does not involve elimination of sulfuric acid or hydrochloric acid, the chlorosulfonic acid group of chlorosulfonated polyetherketone and allylamine are reacted to form an allyl group bonded with a sulfonamide group. Although the mechanism of making it report is reported (for example, patent document 3), in order to improve a crosslinking density, it is necessary to reduce a proton acid group (increase an ion exchange group equivalent). In addition, the sulfonamide bond that binds the crosslinking group has a problem that it is susceptible to hydrolysis.

A method of crosslinking a carbonyl group and an alkyl group directly bonded to an aromatic ring is disclosed as one having a crosslinking mechanism that is not derived from a proton acid group and does not involve a leaving component (for example, Patent Document 4). Since the part into which the group is introduced is not specified, if the crosslinking proceeds too much in the part where the proton acid group exists, the movement of the polymer chain is restricted by the crosslinking, or the water absorption necessary for proton conduction decreases. In some cases, the conductivity was reduced.
However, in any of the methods, a polymer electrolyte membrane that sufficiently satisfies water resistance, low water absorption, low methanol permeability and high proton conductivity has not been obtained, and further performance improvement has been demanded.

Japanese Patent Laid-Open No. 10-45913 JP 2000-501223 Gazette JP-A-6-93114 JP 2003-217342 A Masaru Honma, Abstracts of Lectures of the 3rd Separation of Sciences and Technology "Basics and Applications of Polymer Membrane Fuel Cells" p17 (1999)

  An object of the present invention is to provide a crosslinked proton-conductive block copolymer for use in a fuel cell, particularly a direct methanol fuel cell, which has both water resistance, low water absorption, low methanol permeability and high proton conductivity for a long period of time. An object of the present invention is to provide a crosslinked body, a proton conductive membrane and a fuel cell using the same.

The present inventors have found that a polymer electrolyte membrane obtained from a cross-linked proton conductive block copolymer having a specific block structure is compatible with water resistance, low water absorption, low methanol permeability and high proton conductivity over a long period of time. As a result, the present invention has been completed.
That is, this invention is specified by the matter described in the following [1]-[9].

[1] Repeating a block (A) having repeating structural units represented by the general formula (1) and a structural unit containing a protonic acid group directly bonded to the aromatic ring and not containing an alkyl group directly bonded to the aromatic ring A crosslinked proton-conductive block copolymer comprising the block (B).


[In formula (1), _{R 1} is _-C m _{H 2m +} 1 (m is an integer of from 1 to 10). A ₁ and A ₂ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. , G and h each independently represent 0 or 1. Hydrogen atoms of the aromatic ring in formula (1) _{may, -C m H 2m + 1 (} m is an integer of from 1 to _{10), - F, -CF 3,} -Si (CH 3) 3, -OSi (CH 3) 3 Alternatively, it may be substituted with -CN. ]

[2] The crosslinked proton-conductive block copolymer according to the above [1], wherein the block (B) comprises a repeating structural unit represented by the general formula (2) or (3).


[In the formulas (2) and (3), R ₂ , R ₃ , R ₄ and R ₅ are each independently H or a proton acid group, and at least one is a proton acid group. In formulas (2) and (3), A ₃ , A ₄ , A ₅ and A ₆ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) _2. -, - O -, - SO 2 - or a -CO-, showing i, j, k and m are each independently 0 or 1. The hydrogen atom of the aromatic ring of the formulas (2) and (3) is substituted with a proton acid group, -F, -CF ₃ , -Si (CH ₃ ) ₃ , -OSi (CH ₃ ) ₃ or -CN Also good. ]
[3] The crosslinked proton conductive block according to the above [1] or [2], wherein the block (A) is represented by the general formula (4) and the block (B) is represented by the general formula (5). Polymer.


Wherein (4), _{R 6} is _-C m _{H 2m +} 1 (m is an integer of from 1 to 10). A ₇ is a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. H atom of an aromatic ring in formula (4) _{is, -C m H 2m + 1 (} m is an integer of from 1 to 10), - F, may be substituted in the -CF _3. ]




[In Formula (5), at least one of R ₇ and R ₈ is a proton acid group, and the others are H atoms. A _{8 in} Formula Y is a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—, and an aromatic ring The hydrogen atom is not replaced by another atom. ]
[4] protonic acid _{group, -C n H 2n -SO 3 Z} , -C n H 2n -PO 2 Z 2, -C n H 2n -COOZ (n is an integer of 0, Z is H, Na Or K)). The crosslinked proton-conductive block copolymer according to any one of [1] to [3] above.
[5] A proton-conductive block copolymer crosslinked product obtained by crosslinking a crosslinking group of any one of the crosslinked proton-conductive block copolymers described in [1] to [4] above.
[6] A proton conductive membrane for a fuel cell comprising the cross-linked proton conductive block copolymer or proton conductive block copolymer cross-linked product according to [1] to [5] above.
[7] A fuel cell using the proton conducting membrane according to [6].
[8] The fuel cell as described in [7] above, wherein alcohol is directly used as fuel.

  The crosslinked proton-conductive block copolymer of the present invention and the crosslinked product thereof have a crosslinking group that is not derived from a protonic acid group and can be crosslinked without generation of a leaving component only in the hydrophobic block. It is suitable as a material for an electrolyte membrane that can achieve both low water absorption, low methanol permeability and high proton conductivity over a long period of time. The electrolyte membrane using the cross-linked proton conductive block copolymer of the present invention is composed of a phase composed of a hydrophilic block having a protonic acid group responsible for proton conduction and a hydrophobic structure having excellent water resistance, low water absorption expansion and a cross-linked structure. Since the phase interface is bonded with the same molecule while appropriately phase-separating with the functional block, dissolution of the block responsible for proton conduction in water and water absorption expansion are suppressed, and further, there is no separation of the phase interface. Therefore, the proton conducting membrane has a high proton acid group content and high proton conductivity, and is excellent in water resistance and low water absorption, and can suppress the permeation amount of methanol propagating with water. In addition, by crosslinking only the hydrophobic block portion, the water absorption expansion of the hydrophobic block phase can be reduced and the solvent resistance can be improved. On the other hand, since the hydrophilic block portion does not have a crosslinked structure, there is no need to worry about a decrease in hydrophilicity, that is, a decrease in proton conductivity associated with the formation of the crosslinking. Further, by blocking and partially crosslinking, generation of cracks due to detachment of protonic acid groups and expansion / contraction due to changes in temperature and humidity associated with power generation and shutdown of the fuel cell are suppressed. Therefore, by using the cross-linked proton conductive block copolymer of the present invention for the proton conductive membrane, it is difficult for a decrease in proton conductivity and a decrease in power generation efficiency due to an increase in methanol permeation amount, and a high efficiency and excellent reliability. A fuel cell can be obtained. In particular, a fuel cell using alcohol directly as a fuel can be suitably obtained.

Hereinafter, the cross-linked proton conductive block copolymer according to the present invention, the cross-linked product thereof, and the proton conductive membrane for fuel cell and the fuel cell using them will be described in detail.
The proton conductive block copolymer according to the present invention is characterized by comprising a block (A) having a specific structural unit having excellent water resistance and low water absorption expansion, and a block (B) having a proton acid group. To do.

Block (A)
The block (A) according to the present invention repeatedly has a structural unit represented by the following general formula (1).

[In formula (1), _{R 1} is _-C m _{H 2m +} 1 (m is an integer of from 1 to 10). A ₁ and A ₂ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. , G and h each independently represent 0 or 1. Hydrogen atoms of the aromatic ring in formula (1) _{may, -C m H 2m + 1 (} m is an integer of from 1 to _{10), - F, -CF 3,} -Si (CH 3) 3, -OSi (CH 3) 3 Alternatively, it may be substituted with -CN. ]

The structural unit has a carbonyl group and an alkyl group directly bonded to an aromatic ring, and a bridging group can be formed at this portion. The presence of a cross-linking group is preferred because the resin has excellent water resistance and has a small water absorption expansion, so that the membrane does not swell or decrease in strength when used as a proton conductive membrane. Since the block (B) does not have an alkyl group capable of forming a crosslinking group, the block (A) is more hydrophobic than the block (B). Furthermore, it is preferable to have a structural unit represented by the following general formula (4) repeatedly because of high water resistance and low water absorption expansion.

Wherein (4), _{R 6} is _-C m _{H 2m +} 1 (m is an integer of from 1 to 10). A ₇ is a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. H atom of an aromatic ring in formula (4) _{is, -C m H 2m + 1 (} m is an integer of from 1 to 10), - F, may be substituted in the -CF _3. ]

  The block (A) according to the present invention can form a crosslinking group, and the polymer chains are bonded to each other through a covalent bond. In the present invention, the term “crosslinking” does not include the interaction between polymer chains due to ionic bonds or hydrogen bonds that repeatedly dissociate and recombine.

  The bridging group in the present invention is a group that is not derived from a protonic acid group and can be cross-linked without generation of a leaving component, and among them, an alkyl group having 1 to 10 carbon atoms that is directly bonded to a carbonyl group and an aromatic ring. It is desirable that Although various methods are known as the crosslinking method, the crosslinking composed of a carbonyl group and an alkyl group according to the present invention is a crosslinking not derived from a protonic acid group, and a protonic acid group is used for bonding polymer chains to each other. In other words, the group or chain that bonds the polymer chains after crosslinking is not a group or chain derived from a protonic acid group. That is, in the cross-linking not derived from the protonic acid group of the present invention, the cross-linking in which the protic acid group chemically reacts during the cross-linking reaction, as well as the cross-linking in which the cross-linking group is introduced in advance through the protonic acid group in advance Is not included. The cross-linking as in the present invention is preferable because the cross-linking density of the resin can be controlled without decreasing the amount of proton acid groups of the resin (increasing the ion exchange group equivalent). On the other hand, cross-linking derived from protonic acid groups is not preferable because it is necessary to use more protonic acid groups in order to increase the cross-linking density, and as a result, the ionic conductivity of the resulting cross-linked resin decreases. .

  The cross-linking of the present invention bonds polymer chains by a reaction that does not generate a leaving component. Here, the elimination component is, for example, a by-product which is generated in the reaction and is not bonded to the resin chain, such as a halogenated hydrocarbon or salt in the Friedel-Craft reaction, water, hydrogen halide or salt in the condensation reaction. Indicates. Crosslinking that does not generate a desorbing component as in the present invention does not cause modification or deterioration of the electrode material due to the desorbing component, has a uniform crosslink density in the film thickness direction, is easy to thicken, and corrodes the manufacturing equipment. This is preferable because no generated gas is generated. On the other hand, the cross-linking that generates the desorbing component requires a desorbing component removal operation, the cross-linking density is different between the film surface and the inside of the film or the back surface of the film having different desorbing component removal efficiencies, and it is difficult to increase the film thickness. There are problems such as the formation of voids in the film and the corrosion of the electrode material and the manufacturing apparatus due to the desorbed acidic gas.

  The bridging group consists of a carbonyl group and an alkyl group having 1 to 10 carbon atoms directly bonded to the aromatic ring, and one protonic acid group, one carbonyl group and one alkyl group are simultaneously contained in one repeating unit constituting the resin. Since it can be contained above and a remarkably high crosslinking density can be obtained, it is particularly preferable. Further, this crosslinking mechanism is particularly preferred because it does not contain hydrogen at the α-position of the tertiary carbon that is susceptible to radical attack in the bond formed by crosslinking.

The crosslinking mechanism between the carbonyl group according to the present invention and the alkyl group having 1 to 10 carbon atoms directly bonded to the aromatic ring will be described. It is presumed that the carbonyl group in the polymer and the alkyl group having 1 to 10 carbon atoms directly bonded to the aromatic ring in the polymer are involved in the crosslinking reaction in the following manner. The following reaction formula shows the case where the alkyl group is a methyl group.

  As shown in the above reaction formula, radicals are generated on benzophenone by supplying energy by ultraviolet irradiation or heat treatment, and this extracts hydrogen from the methyl group. Subsequently, it is presumed that cross-linking of the polymers is caused by reactions such as dimerization of benzyl radical, reaction of benzyl radical and alcoholic carbon radical coupling, and dimerization of alcoholic carbon radical.

  Further, in the cross-linked proton conductive block copolymer of the present invention, since these cross-linking groups exist only in the block (A), the proton conduction in the block (B) containing a proton acid group may be inhibited. Less preferred. That is, the movement of the polymer chain in the portion where the protonic acid group exists is restricted due to crosslinking, and the water absorption necessary for proton conduction decreases, which is considered to cause a decrease in proton conductivity. Therefore, the cross-linked proton conductive block copolymer according to the present invention suppresses the swelling of the membrane and the strength, and the permeation of fuel such as alcohol from the negative electrode to the positive electrode by cross-linking without causing a decrease in proton conductivity. can do. Therefore, the cross-linked proton conductive block copolymer according to the present invention is more preferably used in a fuel cell using alcohol or the like as a direct fuel, for example, a direct methanol fuel cell.

The molecular weight of the block (A) according to the present invention is not particularly limited and can be any molecular weight.
The hydrophobic block according to the present invention may be composed of a plurality of types of repeating structural units other than the block (A), but the hydrophobic block is susceptible to expansion due to hydrolysis or water absorption, amide bond, imide When it contains a bond or a protonic acid group, the solubility of the block copolymer in water and water absorption may be increased, which is not preferable.

Block (B)
The block (B) according to the present invention has a structural unit that includes a protonic acid group directly bonded to an aromatic ring and does not include an alkyl group bonded directly to the aromatic ring. Since the block (B) is composed of a structural unit that does not contain an alkyl group directly bonded to an aromatic ring, in the block (B), a crosslinked structure composed of a carbonyl group and an alkyl group is not generated. Therefore, the block (B) absorbs moisture necessary for proton conduction, and the movement of the polymer chain is not limited in this block (B). Therefore, the block (B) is more hydrophilic than the block (A). The repeating structural unit (B) constituting the hydrophilic block according to the present invention preferably has the following general formula (2) or (3).

[In the formulas (2) and (3), R ₂ , R ₃ , R ₄ and R ₅ are each independently H or a proton acid group, and at least one is a proton acid group. In formulas (2) and (3), A ₃ , A ₄ , A ₅ and A ₆ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) _2. -, - O -, - SO 2 - or a -CO-, showing i, j, k and m are each independently 0 or 1. The hydrogen atom of the aromatic ring of the formulas (2) and (3) is substituted with a proton acid group, -F, -CF ₃ , -Si (CH ₃ ) ₃ , -OSi (CH ₃ ) ₃ or -CN Also good. ]
The protonic acid groups of the general formulas (2) and (3) are bonded to an aromatic ring directly bonded to —SO ₂ — or —CO— which is an electron withdrawing group, and the protonic acid bonded to another aromatic ring It is particularly preferred because it has a stronger binding force than a group and is less susceptible to decomposition and dissociation.

In addition, when an existing aromatic polyether is sulfonated with fuming sulfuric acid or the like, a sulfonic acid group must be introduced into an aromatic ring to which —SO ₂ — or —CO— which is an electron withdrawing group is not directly bonded. It has been known.

Specific examples of the proton acid group according to the present invention include sulfonic acid groups, carboxylic acid groups, and phosphonic acid groups represented by the following formulas (6) to (8). Among them, a sulfonic acid group represented by the following formula (6) is preferable, and a sulfonic acid group represented by Z = H in the following formula (6) is particularly preferable.
_{-C n H 2n -SO 3 Z (} n is an integer of 0, Z is H, Na or K) (6)
-C _n H _2n -COOZ _(n is an integer of 0, Z is H, Na or K) (7)
_{-C n H 2n -PO 3 Z 2} (n is an integer of 0, Z is H, Na or K) (8)

  The molecular weight of the block (B) according to the present invention is preferably 0.05 to 0.4 dl / g in terms of reduced viscosity (concentration 0.5 g / dl, measured at 35 ° C.), 0.1 to 0.3 dl / g. Is more preferable, and 0.15-0.25 dl / g is especially preferable. When the molecular weight of the block is too small, the block (B) and the block (A) are not separated from each other to form a single phase, which may reduce water resistance or increase water absorption. Absent. When the molecular weight of the block is too large, the hydrophobic block and the hydrophilic block are difficult to form a fine phase separation structure, and some of the molecular chains are formed only from blocks having a proton acid group. There is a possibility that the chain may be eluted in water, which is not preferable.

  The block (B) according to the present invention may have a plurality of types of repeating structural units in addition to the structural unit, and they may not contain a protonic acid group. In this case, the content of the repeating structural unit having a protonic acid group is preferably 100 to 30 mol%, particularly preferably 100 to 50 mol%, based on the entire block (B). When the content of the repeating structural unit (B) having a proton acid group is small, the proton conductivity is too low, which is not preferable.

Cross-linked proton conductive block copolymer The cross-linked proton conductive block copolymer of the present invention comprises a block (B) bearing proton conductivity having a protonic acid group, water resistance and low water absorption expansion, and cross-linking groups. Block (A). The block (B) responsible for proton conduction is easy to dissolve or absorb water and expand in water, and the block (A) has excellent water resistance and small water absorption and expansion, so even if trying to dissolve or absorb water in the block (B) Block (A) suppresses this. For example, when the crosslinked proton conductive block copolymer of the present invention is used for a proton conductive membrane, the block (A) and the block (B) are appropriately phase-separated. Since the interface between the two phases is bonded by the same molecule, even if the phase consisting of the block (B) is dissolved or absorbs water, the block (A) is excellent in water resistance and has a small water absorption expansion and is crosslinked. The phase suppresses this. As a result, the proton conducting membrane has a high proton acid group content, high proton conductivity, excellent water resistance and low water absorption, and can suppress the amount of methanol permeating with water. Further, since the two phase interfaces are bonded by the same molecule, the difference in expansion and contraction between the two phases due to changes in temperature and humidity is suppressed, and the generation of cracks due to the difference in expansion and contraction is suppressed.

When the cross-linked proton conductive copolymer is a random copolymer, the hydrophilic portion and the hydrophobic portion do not separate from each other to form a single phase. Therefore, when the composition of repeating structural units responsible for proton conduction increases Dissolution in water and water absorption expansion occur, and high proton conductivity, water resistance, and low water absorption cannot be achieved at the same time.
In addition, a composite membrane composed of a cross-linked proton conductive block copolymer and a resin having excellent water resistance and low water absorption expansion is difficult to form a fine phase separation structure because the polarities of the two resins are extremely different. Are not bonded by molecular chains, so the proton conductive resin cannot be dissolved in water and the water absorption expansion can be suppressed, and the phase interface cracks due to the difference in expansion and contraction between the two phases due to changes in temperature and humidity. Yes, not preferred.

  The molecular weight of the cross-linked proton conductive block copolymer of the present invention is not particularly limited, but the reduced viscosity (concentration: 0.5 g / dl, measured at 35 ° C.) ranges from 0.5 to 2.0 dl / g. A range of 0.7 to 1.5 dl / g is particularly preferable. If the molecular weight is too low, the resin strength is low, and the resulting film may crack due to shrinkage / expansion during drying and moisture absorption. On the other hand, if the molecular weight is too high, the solvent solubility of the resin becomes insufficient, which may cause problems in film formation.

  In the cross-linked proton conductive block copolymer of the present invention, the ratio of the block (B) having a proton acid group and the block (A) having a cross-linking group is not particularly limited. It is preferably 200 to 1500 g / mol, particularly preferably 300 to 1000 g / mol, in terms of the ion exchange group equivalent of the coalescence. Here, the ion exchange group equivalent is defined by the resin weight per mole of proton acid groups and means the reciprocal of the number of moles of proton acid groups per resin unit weight. That is, the smaller the ion exchange group equivalent, the higher the composition of the block (B) having a proton group, and the larger the ion exchange group equivalent, the lower the composition of the block (B) having a proton acid group. When the ion exchange group equivalent is too small, the ratio of the block (A) is too small, so that the water resistance and low water absorption of the crosslinked proton conductive block copolymer may be insufficient. When the ion exchange group equivalent is too large, the composition of the block having a proton group is too small, so that sufficient proton conductivity may not be obtained.

  The water absorption of the cross-linked proton conductive block copolymer of the present invention is 3 to 30 wt%. Here, the water absorption can be determined from the weight ratio of the dried resin before and after immersion in pure water at 25 ° C. for 24 hours. The cross-linked proton conductive block copolymer according to the present invention has a smaller water absorption expansion and a lower water absorption rate than a random copolymer having an equivalent ion exchange group equivalent or a block copolymer having no cross-linking group.

  The cross-linked proton conductive block copolymer of the present invention comprises the block (A) and the block (B), and these blocks are preferably composed of an aromatic polyether structure. Aromatic polyether structures do not have linking groups that are susceptible to hydrolysis such as hot water, acids, alkalis, and alcohols, and groups that have low heat resistance and radical resistance, so they deteriorate or denature when used in fuel cells. There is almost no. On the other hand, ester bonds, carbonate bonds, amide bonds, imide bonds that are susceptible to hydrolysis of hot water, acids, alkalis, alcohols, etc., alkylene bonds that have α-hydrogen that is less heat resistant and susceptible to radical attack, aliphatic ethers Resins having bonds and the like are not preferable because they are deteriorated when used in a fuel cell.

  The form of the cross-linked proton conductive block copolymer of the present invention is not particularly limited, and may be in the form of a powder, a varnish dissolved or dispersed in a solvent, a film obtained by applying and drying the varnish, and the like. . When the crosslinked proton conductive block copolymer is a varnish dissolved or dispersed in a solvent, the solvent is not particularly limited. For example, water, methanol, ethanol, 1-propanol, 2-propanol, Alcohols such as butanol, hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methyl chloride and methylene chloride, ethers such as dichloroethyl ether, 1,4-dioxane and tetrahydrofuran, methyl acetate, ethyl acetate, etc. Fatty acid esters, ketones such as acetone and methyl ethyl ketone, as well as aprotic polar solvents such as N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and dimethyl carbonate. Can be used.

Production Method of Crosslinked Proton Conductive Block Copolymer Although there is no particular limitation on the production method of the crosslinkable proton conductive block copolymer of the present invention, specific production methods are exemplified below by taking an aromatic polyether structure as an example. To do.
1. Aromatic dihydroxy compound and aromatic dihalide compound having proton acid group, aromatic dihalide compound and aromatic dihydroxy compound having proton acid group, or aromatic dihydroxy compound having proton acid group and aromatic dihydroxy compound having proton acid group The compound is subjected to condensation polymerization to synthesize a protonic acid group-containing oligomer having a repeating structural unit having a reduced viscosity at 35 ° C. of 0.05 to 0.4 dl / g. Aromatic dihydroxy compound and aromatic dihalide compound having a crosslinking group, aromatic dihalide compound and aromatic dihydroxy compound having a crosslinking group, or aromatic dihydroxy compound having a crosslinking group and aromatic dihydroxy compound having a crosslinking group, respectively. A block copolymer is obtained by addition and condensation polymerization.
2. Aromatic dihydroxy compound and aromatic dihalide compound having proton acid group, aromatic dihalide compound and aromatic dihydroxy compound having proton acid group, or aromatic dihydroxy compound having proton acid group and aromatic dihydroxy compound having proton acid group The compounds are each subjected to condensation polymerization to synthesize a protonic acid group-containing oligomer having a repeating structural unit having a reduced viscosity at 35 ° C. of 0.05 to 0.4 dl / g. Separately, an aromatic dihydroxy compound and an aromatic dihydroxy compound having a crosslinking group, an aromatic dihydroxy compound having an aromatic dihydroxy compound and a crosslinking group, or an aromatic dihydroxy compound having a crosslinking group and an aromatic dihydroxy compound having a crosslinking group, Each is polycondensed to obtain a hydrophobic oligomer.
The hydrophobic oligomer is added to the protonic acid group-containing oligomer and subjected to condensation polymerization to obtain a block copolymer.

  Here, although there is no restriction | limiting in particular in the monomers used in manufacture of the bridge | crosslinking type proton conductive block copolymer concerning this invention, A typical example is illustrated below. However, the compound forming the repeating structural unit of the block (B) of the present invention excludes those containing an alkyl group directly bonded to an aromatic ring.

  Examples of the aromatic dihalide compound include 4,4′-difluorobenzophenone, 3,3′-difluorobenzophenone, 4,4′-dichlorobenzophenone, 3,3′-dichlorobenzophenone, 4,4′-difluorodiphenyl sulfone, 4,4'-dichlorodiphenyl sulfone, 1,4-difluorobenzene, 1,3-difluorobenzene, 2,6-dichlorobenzonitrile, 4,4'-difluorobiphenyl, 3,3'-dibromo-4,4 ' -Difluorobiphenyl, 4,4'-difluorodiphenylmethane, 4,4'-dichlorodiphenylmethane, 4,4'-difluorodiphenyl ether, 2,2-bis (4-fluorophenyl) propane, 2,2-bis (4-chlorophenyl) ) Propane, α, α'-bis (4-fluoropheny) ) -1,4-diisopropylbenzene, 3,3′-dimethyl-4,4′-difluorobenzophenone, 3,3′-diethyl-4,4′-difluorobenzophenone, 3,3 ′, 5,5′- Tetramethyl-4,4′-difluorobenzophenone, 3,3′-dimethyl-4,4′-dichlorobenzophenone, 3,3 ′, 4,4′-tetramethyl-5,5′-dichlorobenzophenone, 3,3 '-Dimethyl-4,4'-difluorodiphenylsulfone, 3,3'-dimethyl-4,4'-dichlorodiphenylsulfone, 2,5-difluorotoluene, 2,5-difluoroethylbenzene, 2,5-difluoro-p -Xylene etc. are mentioned, It can use individually or in mixture of 2 or more types.

Examples of the aromatic dihydroxy compound include hydroquinone, resorcin, catechol, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenyl ether, 4, 4′-dihydroxydiphenylsulfone, 4,4′-dihydroxybenzophenone, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 1,4-bis (4 -Hydroxyphenyl) benzene, α, α'-bis (4-hydroxyphenyl) -1,4-dimethylbenzene, α, α'-bis (4-hydroxyphenyl) -1,4-diisopropylbenzene, α, α ' -Bis (4-hydroxyphenyl) -1,3-diisopro Rubenzene, 4,4'-dihydroxybenzophenone, 1,4-bis (4-hydroxybenzoyl) benzene, 3,3-difluoro-4,4'-dihydrobiphenyl, 2-methylhydroquinone, 2-ethylhydroquinone, 2- Isopropyl hydroquinone, 2-octyl hydroquinone, 2,3-dimethyl hydroquinone, 2,3-diethyl hydroquinone, 2,5-dimethyl hydroquinone, 2,5-diethyl hydroquinone, 2,5-diisopropyl hydroquinone, 2,6-dimethyl hydroquinone, 2,3,5-trimethylhydroquinone, 2,3,5,6-tetramethylhydroquinone, 3,3′-dimethyl-4,4′-dihydroxybiphenyl, 3,3 ′, 5,5′-tetramethyl-4 , 4'-dihydroxybiphenyl, 3,3'- Methyl-4,4′-dihydroxydiphenylmethane, 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane, 3,3 ′, 5,5′-tetraethyl-4,4′-dihydroxydiphenylmethane 3,3′-dimethyl-4,4′-dihydroxydiphenyl ether, 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenyl ether, 3,3′-dimethyl-4,4′-dihydroxy Diphenyl sulfide, 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenyl sulfide, 3,3′-dimethyl-4,4′-dihydroxydiphenyl sulfone, 3,3 ′, 5,5 ′ -Tetramethyl-4,4'-dihydroxydiphenylsulfone, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3- 4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, α, α′-bis (3-methyl-4-hydroxyphenyl) -1,4-diisopropyl Benzene, α, α′-bis (3,5-dimethyl-4-hydroxyphenyl) -1,4-diisopropylbenzene, α, α′-bis (3-methyl-4-hydroxyphenyl) -1,3-diisopropyl Examples thereof include benzene and α, α′-bis (3,5-dimethyl-4-hydroxyphenyl) -1,3-diisopropylbenzene, which can be used alone or in combination of two or more.
Examples of the aromatic dihalide compound having a proton acid group include sulfonated products and alkylsulfonated products of the above-mentioned aromatic dihalide compounds, 2,5-dichlorobenzoic acid, 2,5-difluorobenzoic acid, and 5,5′-carbonyl. Bis (2-fluorobenzoic acid), 5,5′-sulfonylbis (2-fluorobenzoic acid), 2,5-dichlorophenylphosphonic acid, 5,5′-carbonylbis (2-fluorobenzenephosphonic acid) and alkalis thereof A metal salt etc. can be mentioned.

Examples of the aromatic dihydroxy compound having a proton acid group include sulfonated products and alkylsulfonated products of the above aromatic dihydroxy compounds, 2,5-dihydroxybenzoic acid, 2,5-dihydroxyterephthalic acid, and 5,5′-methylene. Examples thereof include aromatic dihydroxy compounds having a phosphate group such as disalicylic acid, 5,5′-thiodisalicylic acid, and 2,5-dihydroxyphenylphosphonic acid, and alkali metal salts thereof.
The aromatic dihalide compound and aromatic dihydroxy compound sulfonated product and alkyl sulfonated product are obtained by sulfonating the aromatic dihalide compound and the aromatic dihydroxy compound with a known sulfonating agent such as fuming sulfuric acid (Macromol. Chem. Phys., 199, 1421 (1998)).

Proton Conducting Membrane The proton conducting membrane of the present invention is a proton conducting membrane comprising the crosslinked proton conductive block copolymer of the present invention. Here, the proton conducting membrane of the present invention includes not only a self-supporting membrane but also a coating film in close contact with a substrate, an electrode membrane, other proton conducting membranes, and the like. Here, although there is no restriction | limiting in particular in the thickness of the proton conductive film concerning this invention, when it is a self-supporting film | membrane, it is preferable that it is 10-100 micrometers in the case of being a coating film.
The proton conductive membrane of the present invention only needs to contain the cross-linked proton conductive block copolymer of the present invention, such as a conductive material having electrical conductivity, a hydrogen oxidation reaction, a catalyst for promoting oxygen reduction reaction, etc. It may be combined.

As the conductive material, any conductive material may be used, and various metals, carbon materials, and the like can be used. Examples thereof include carbon black such as acetylene black, activated carbon, graphite and the like, and these are used alone or mixed and used in the form of powder or sheet.
The catalyst is not particularly limited as long as it promotes hydrogen oxidation reaction and oxygen reduction reaction. For example, lead, iron, manganese, cobalt, chromium, gallium, vanadium, tungsten, ruthenium, iridium, palladium, platinum, Rhodium or an alloy thereof.

Fuel cell The proton conductive membrane of the present invention can be used as an electrolyte membrane of various known fuel cells. As the fuel source of the fuel cell, for example, natural gas, alcohol such as hydrogen, methanol or the like is used. be able to. Of these, those using alcohol directly as fuel are preferred. The fuel cell using the proton conducting membrane of the present invention is excellent in power generation efficiency and reliability, because it does not easily cause membrane degradation, resin elution, proton acid group elimination, or fuel crossover, resulting in a decrease in output.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited at all by this.
Test methods of various tests in the examples are as follows.
(I) Reduced viscosity (ηinh)
A proton conductive block copolymer or oligomer thereof (0.50 g) was dissolved in 100 ml of dimethyl sulfoxide by heating, and then measured at 35 ° C. with an Ubbelohde viscometer.
(Ii) Ion exchange group equivalent (EW)
The proton conductive block copolymer or proton conductive membrane was precisely weighed in a glass container that could be sealed, and an excess amount of calcium chloride aqueous solution was added thereto and stirred overnight. The hydrogen chloride generated in the system was titrated with a 0.1N sodium hydroxide standard aqueous solution using a phenolphthalein indicator and calculated.
(Iii) Water Absorption Rate A proton conductive block copolymer or proton conductive membrane dried at 120 ° C. for 12 hours under nitrogen ventilation was immersed in pure water at 23 ° C. for 24 hours, and the weight change was calculated.
(Iv) Proton conductivity (25 ° C., film thickness direction)
The sample film wetted with 1M sulfuric acid was sandwiched between two measuring cells each having a platinum electrode on one side of a 100 μm thick PET film having 1 cm ² pores, and the pores were filled with 1M sulfuric acid water. This was installed in a constant temperature bath at 25 ° C., and the resistance value was measured. The resistance value of the sample film alone was determined from the difference from the resistance value when the sample film was not sandwiched, and the ionic conductivity (25 ° C., film thickness direction) was calculated. The film thickness necessary for the calculation of proton conductivity was measured using a micrometer in a dry state.
(V) Methanol permeability Distilled water and a 1 mol / L aqueous methanol solution were brought into contact with each other through a proton conductive membrane having a diameter of 23 mmφ at room temperature, and the change in methanol concentration on the distilled water side up to 3 hours was measured by gas chromatography. The methanol permeation rate at a film thickness of 50 μm was calculated from the slope of the obtained methanol concentration increasing line, and this was defined as methanol permeability.

Example 1
Into a flask equipped with a nitrogen inlet tube, a thermometer, a cooler equipped with a separator filled with toluene, and a stirrer, 147,802 g (0,3,3′-carbonylbis (6-fluorobenzenesulfonic acid sodium salt)) 0.035 mol), 9.9877 g (0.043 mol) of 2,2-bis (4-hydroxyphenyl) propane and 5.80 g (0.042 mol) of anhydrous potassium carbonate were precisely weighed. To this was added 99.0 g of dimethyl sulfoxide (hereinafter abbreviated as DMSO) and 40.0 g of toluene, and the mixture was heated to 140 ° C. while stirring through nitrogen gas, and then reacted for 5 hours. The reaction was performed under toluene return distillation, and the distilled water was separated and collected by a separator. After cooling, a part of the reaction mass was sampled, diluted with DMSO, the supernatant was discharged into methanol, the oligomer was precipitated, washed with acetone, and then dried at 150 ° C. for 4 hours under nitrogen flow to obtain the oligomer. The obtained oligomer is a compound containing a protonic acid group (sodium sulfonate group) directly bonded to the aromatic ring and no alkyl group directly bonded to the aromatic ring, and its reduced viscosity is 0.20 dl / g ( DMSO).

  To the reaction mass, 14.4830 g (0.065 mol) of 4,4′-difluorobenzophenone, 14.4197 g (0.05625 mol) of 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane, Anhydrous potassium carbonate (10.76 g, 0.12 mol), DMSO (114.0 g), and toluene (46.0 g) were added, and the mixture was heated to 140 ° C. with stirring through nitrogen gas. The reaction was continued for 4 hours.

The obtained viscous reaction mass (110 ° C.) was discharged into 3 L of acetone using a homomixer, and the precipitated polymer was collected by filtration, twice with 4 L of distilled water and once with 4 L of acetone, each for 1 hour each. And then collected by filtration. It was dried at 50 ° C. for 8 hours and at 150 ° C. for 4 hours (both in a nitrogen atmosphere) to obtain a crosslinked proton-conductive block copolymer having a proton acid group (sodium sulfonate group). The resulting block copolymer was 46.2 g (93.5% yield), and the reduced viscosity was 1.45 dl / g (N-methylpyrrolidone).
4 g of the obtained block copolymer was dissolved in 18.2 g of N-methylpyrrolidone to obtain a varnish having a polymer concentration of 18%. The obtained varnish was cast on a glass substrate using a blade having a spacer and dried by heating from room temperature to 200 ° C. over 2 hours under a nitrogen flow to obtain a film having a thickness of 50 μm.
The obtained film was peeled off from the glass substrate, and irradiated with light of 7000 mJ / cm ² on both sides using a metal halide lamp to be crosslinked to obtain a film-like proton conductive block copolymer crosslinked product.
The crosslinked film was immersed in a 2N aqueous sulfuric acid solution and distilled water for 1 day to perform proton exchange of sodium sulfonate groups to obtain a film having free sulfonic acid groups.
The film obtained had an ion exchange group equivalent of 770 g / mol, a water absorption of 11%, a proton conductivity of 0.011 S / cm, and a methanol permeability of 0.54 μmol / cm ² · min.

(Example 2)
Into a flask equipped with a nitrogen inlet tube, a thermometer, a cooler equipped with a separator filled with toluene, and a stirrer, 147,802 g (0,3,3′-carbonylbis (6-fluorobenzenesulfonic acid sodium salt)) 0.035 mol), 4,4′-dihydroxyphenylmethane 8.7606 g (0.043 mol) and anhydrous potassium carbonate 5.80 g (0.042 mol) were precisely weighed. Dimethyl sulfoxide 94.0g and toluene 38.0g were added to this, and it heated up to 140 degreeC, stirring through nitrogen gas, Then, reaction was performed for 4 hours and 40 minutes. The reaction was performed under toluene return distillation, and the distilled water was separated and collected by a separator. After cooling, a part of the reaction mass was sampled, diluted with DMSO, the supernatant was discharged into methanol, the oligomer was precipitated, washed with acetone, and then dried at 150 ° C. for 4 hours under nitrogen flow to obtain the oligomer. The obtained oligomer is a compound containing a protonic acid group (sodium sulfonate group) directly bonded to the aromatic ring and not containing an alkyl group directly bonded to the aromatic ring, and the reduced viscosity of the oligomer is 0.20 dl / g. (DMSO).

  To the reaction mass, 14.4830 g (0.065 mol) of 4,4′-difluorobenzophenone, 14.4197 g (0.05625 mol) of 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane, Anhydrous potassium carbonate (10.76 g, 0.12 mol), DMSO (114.0 g), and toluene (46.0 g) were added. While stirring through nitrogen gas, the temperature was raised to 140 ° C., and after 5 hours and 30 minutes, toluene was distilled off. The temperature was raised to 160 ° C. and the reaction was performed for 4 hours.

The obtained viscous reaction mass (110 ° C.) was discharged into 3 L of acetone using a homomixer, and the precipitated polymer was collected by filtration, twice with 4 L of distilled water and once with 4 L of acetone, each for 1 hour each. And then collected by filtration. It was dried at 50 ° C. for 8 hours and at 150 ° C. for 4 hours (both in a nitrogen atmosphere) to obtain a crosslinked proton-conductive block copolymer having a proton acid group (sodium sulfonate group). The obtained block copolymer was 42.2 g (yield 87.7%), and the reduced viscosity was 1.50 dl / g (N-methylpyrrolidone).
4 g of the obtained block copolymer was dissolved by heating in 19.5 g of N-methylpyrrolidone to obtain a varnish having a polymer concentration of 17%. The obtained varnish was cast on a glass substrate using a blade having a spacer and dried by heating from room temperature to 200 ° C. over 2 hours under a nitrogen flow to obtain a film having a thickness of 50 μm.
The obtained film was peeled off from the glass substrate, and irradiated with light of 7000 mJ / cm ² on both sides using a metal halide lamp to be crosslinked to obtain a film-like proton conductive block copolymer crosslinked product.
The crosslinked film was immersed in a 2N aqueous sulfuric acid solution and distilled water for 1 day to perform proton exchange of sodium sulfonate groups to obtain a film having free sulfonic acid groups.
The film obtained had an ion exchange group equivalent of 733 g / mol, a water absorption of 10%, a proton conductivity of 0.013 S / cm, and a methanol permeability of 0.48 μmol / cm ² · min.

(Example 3)
Into a flask equipped with a nitrogen inlet tube, a thermometer, a cooler equipped with a separator filled with toluene, and a stirrer, 147,802 g (0,3,3′-carbonylbis (6-fluorobenzenesulfonic acid sodium salt)) 0.035 mol), 2,2-bis (4-hydroxyphenyl) hexafluoropropane (14.7802 g, 0.043 mol) and anhydrous potassium carbonate (5.80 g, 0.042 mol) were precisely weighed. To this, 118.0 g of DMSO and 47.0 g of toluene were added, the temperature was raised to 140 ° C. while stirring through nitrogen gas, and then the reaction was performed for 9 minutes. The reaction was performed under toluene return distillation, and the distilled water was separated and collected by a separator. After cooling, a part of the reaction mass was sampled, diluted with DMSO, the supernatant was discharged into methanol, the oligomer was precipitated, washed with acetone, and then dried at 150 ° C. for 4 hours under nitrogen flow to obtain the oligomer. The oligomer obtained was a compound containing a protonic acid group (sodium sulfonate group) directly bonded to the aromatic ring and not containing an alkyl group directly bonded to the aromatic ring, and the reduced viscosity of the oligomer was 0.17 dl / g ( DMSO).

  To the reaction mass, 14.1830 g (0.065 mol) of 4,4′-difluorobenzophenone, 14.4197 g (0.05625 mol) of 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane, Anhydrous potassium carbonate (10.76 g, 0.12 mol), DMSO (114.0 g), and toluene (46.0 g) were added, and the mixture was heated to 140 ° C. with stirring through nitrogen gas. The temperature was raised to 160 ° C., and the reaction was performed for 6 hours and 30 minutes.

The obtained viscous reaction mass (110 ° C.) was discharged into 3 L of acetone using a homomixer, and the precipitated polymer was collected by filtration, twice with 4 L of distilled water and once with 4 L of acetone, each for 1 hour each. And then collected by filtration. It was dried at 50 ° C. for 8 hours and at 150 ° C. for 4 hours (both in a nitrogen atmosphere) to obtain a crosslinked proton-conductive block copolymer having a proton acid group (sodium sulfonate group). The obtained block copolymer was 45.8 g (yield 84.7%), and the reduced viscosity was 0.99 dl / g (N-methylpyrrolidone).
4 g of the obtained block copolymer was dissolved by heating in 14.2 g of N-methylpyrrolidone to obtain a varnish having a polymer concentration of 22%. The obtained varnish was cast on a glass substrate using a blade having a spacer and dried by heating from room temperature to 200 ° C. over 2 hours under a nitrogen flow to obtain a film having a thickness of 50 μm.
The obtained film was peeled off from the glass substrate, and irradiated with light of 7000 mJ / cm ² on both sides using a metal halide lamp to be crosslinked to obtain a film-like proton conductive block copolymer crosslinked product.
The crosslinked film was immersed in a 2N aqueous sulfuric acid solution and distilled water for 1 day to perform proton exchange of sodium sulfonate groups to obtain a film having free sulfonic acid groups.
The obtained film had an ion exchange group equivalent of 791 g / mol, a water absorption rate of 9%, a proton conductivity of 0.012 S / cm, and a methanol permeability of 0.64 μmol / cm ² · min.

(Comparative Example 1)
Into a flask equipped with a nitrogen inlet tube, a thermometer, a cooler equipped with a separator filled with toluene, and a stirrer, 147,802 g (0,3,3′-carbonylbis (6-fluorobenzenesulfonic acid sodium salt)) 0.035 mol), 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane, 11.153 g (0.043 mol), and 5.80 g (0.042 mol) of anhydrous potassium carbonate were precisely weighed. To this, 104.0 g of dimethyl sulfoxide and 42.0 g of toluene were added, the temperature was raised to 140 ° C. while stirring through nitrogen gas, and a reaction was carried out for 8 hours. The reaction was performed under toluene return distillation, and the distilled water was separated and collected by a separator. After cooling, a part of the reaction mass was sampled, diluted with DMSO, the supernatant was discharged into methanol, the oligomer was precipitated, washed with acetone, and then dried at 150 ° C. for 4 hours under nitrogen flow to obtain the oligomer. The obtained oligomer was a compound in which a protonic acid group and an alkyl group were directly bonded to an aromatic ring, and the reduced viscosity was 0.20 dl / g (DMSO).

  To the reaction mass, 14.1830 g (0.065 mol) of 4,4′-difluorobenzophenone, 14.4197 g (0.05625 mol) of 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane, Anhydrous potassium carbonate (10.76 g, 0.12 mol), DMSO (114.0 g), and toluene (46.0 g) were added, and the mixture was heated to 140 ° C. with stirring through nitrogen gas. The reaction was continued for 8 hours.

The obtained viscous reaction mass (110 ° C.) was discharged into 3 L of acetone using a homomixer, and the precipitated polymer was collected by filtration, twice with 4 L of distilled water and once with 4 L of acetone, each for 1 hour each. And then collected by filtration. It was dried at 50 ° C. for 8 hours and at 150 ° C. for 4 hours (both in a nitrogen atmosphere) to obtain 46.1 g (yield 91.1%) of a block copolymer having a proton acid group (sodium sulfonate group). .
The reduced viscosity of the obtained block copolymer was 1.10 dl / g (N-methylpyrrolidone).
4 g of the obtained block copolymer was dissolved by heating in 14.2 g of N-methylpyrrolidone to obtain a varnish having a polymer concentration of 22%. The obtained varnish was cast on a glass substrate using a blade having a spacer and dried by heating from room temperature to 200 ° C. over 2 hours under a nitrogen flow to obtain a film having a thickness of 50 μm.
The obtained film was peeled off from the glass substrate and cross-linked by irradiating each surface with light of 7000 mJ / cm ² using a metal halide lamp.
The crosslinked film was immersed in a 2N aqueous sulfuric acid solution and distilled water for 1 day to perform proton exchange of sodium sulfonate groups to obtain a film having free sulfonic acid groups.
The film obtained had an ion exchange group equivalent of 761 g / mol, a water absorption of 19%, a proton conductivity of 0.013 S / cm, and a methanol permeability of 0.85 μmol / cm ² · min.

From Table 1, when Examples 1 to 3 are compared with Comparative Example 1, it can be seen that the proton conductivity is maintained in each of the Examples although the water absorption rate and methanol permeability are reduced. From this, it is considered that methanol permeability can be reduced by introducing a crosslinking group only in the hydrophobic block without causing a decrease in proton conductivity.

Claims (8)

A block (A) having repeating structural units represented by the general formula (1) and a block having repeating structural units containing a protonic acid group directly bonded to the aromatic ring and not containing an alkyl group directly bonded to the aromatic ring ( B) A cross-linked proton conductive block copolymer.
[In formula (1), R ₁ is -C _m H _{2m +} 1 _(m is an integer of from 1 to 10). A ₁ and A ₂ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. , G and h each independently represent 0 or 1. Hydrogen atoms of the aromatic ring in formula (1) _{may, -C m H 2m + 1 (} m is an integer of from 1 to _{10), - F, -CF 3,} -Si (CH 3
) ₃ , —OSi (CH ₃ ) ₃ or —CN may be substituted. ] The crosslinked proton-conductive block copolymer according to claim 1, wherein the block (B) comprises a repeating structural unit represented by the general formula (2) or (3).
[In the formulas (2) and (3), R ₂ , R ₃ , R ₄ and R ₅ are each independently H or a proton acid group, and at least one is a proton acid group. In formulas (2) and (3), A ₃ ,
A ₄ , A ₅ and A ₆ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO. -, I, j, k and m each independently represent 0 or 1. The hydrogen atom of the aromatic ring of formulas (2) and (3) is substituted with a proton acid group, -F, -CF ₃ , -Si (CH ₃ ) ₃ , -OSi (CH ₃ ) ₃ or -CN Also good. ] The crosslinked proton-conductive block copolymer according to claim 1 or 2, wherein the block (A) is represented by the general formula (4) and the block (B) is represented by the general formula (5 ) .
Wherein (4), R ₆ is -C _m H _{2m +} 1 _(m is an integer of from 1 to 10). A ₇ is a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. H atom of an aromatic ring in formula (4) _{is, -C m H 2m + 1 (} m is an integer of from 1 to 10), - F, may be substituted in the -CF _3. ]
[In Formula (5), at least one of R ₇ and R ₈ is a protonic acid group, and the others are H atoms. A _{8 in} Formula Y is a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —,
It is —O—, —SO ₂ — or —CO—, and the hydrogen atom of the aromatic ring is not substituted with another atom. ] Protonic acid _{group, -C n H 2n -SO 3 Z} , -C n H 2n -PO 2 Z 2, -C n H 2n -COOZ (n is an integer of 0, Z is H, with Na or K crosslinked proton conducting block copolymer according to any one of claims 1 to 3, characterized in that either there one Tsude of a).   A proton-conductive block copolymer crosslinked product obtained by crosslinking a crosslinking group of any one of the crosslinked proton-conductive block copolymers according to claim 1. A proton conductive membrane comprising the crosslinked proton conductive block copolymer according to any one of claims 1 to 4 or the proton conductive block copolymer crosslinked product according to claim 5 .   A fuel cell comprising the proton conducting membrane according to claim 6.   8. The fuel cell according to claim 7, wherein alcohol is directly used as fuel.