JP2008214508A - Compound consisting of solid acid and hyperbranched polymer and use thereof - Google Patents

Abstract

[Problem] To provide a compound excellent in handling property in film formation, stability and durability of a film, and proton conductivity, and usable in a polymer electrolyte membrane, a solid acid catalyst, an ion exchange membrane and the like.
A compound comprising a solid acid and a hyperbranched polymer, wherein the solid acid is bonded to the hyperbranched polymer by an electrophilic substitution reaction, preferably the solid An acid is an amorphous carbon having a sulfonic acid group introduced by heat-treating polycyclic aromatic hydrocarbons in concentrated sulfuric acid or fuming sulfuric acid and condensing and sulfonating the polycyclic aromatic hydrocarbons. The problem can be solved by a compound in which the multi-branched polymer is a multi-branched polymer having an aromatic structure having oxidation resistance in the main chain and having a sulfone group at the terminal.
[Selection] Figure 1

Description

  The present invention relates to a compound comprising a solid acid and a multi-branched polymer and use thereof. More specifically, the present invention is excellent in handling properties in film formation, stability and durability of the film, and proton conductivity. The present invention relates to a compound comprising a solid acid and a multi-branched polymer that can be used for a molecular electrolyte membrane, a solid acid catalyst, an ion exchange membrane, and the like.

In recent years, fuel cells having high energy efficiency and low environmental impact have attracted attention. A fuel cell is one that converts chemical energy of fuel into electrical energy by electrochemically oxidizing fuel such as hydrogen or methanol using oxygen or air.
Such fuel cells are classified into a solid polymer type, a phosphoric acid type, a molten carbonate type, a solid oxide type, an alkaline type, and the like depending on the type of electrolyte used. Among these, a polymer electrolyte fuel cell using a cation exchange membrane as an electrolyte can be operated at a high current because the internal resistance in the fuel cell can be reduced by thinning the electrolyte membrane to be used, and can be miniaturized. Because of these advantages, research on solid polymer types has become active.

The electrolyte membrane used in the polymer electrolyte fuel cell is required to have high proton conductivity with respect to protons involved in the electrode reaction of the fuel cell. As such proton conductive polymer electrolyte membrane materials, sulfonic acid group-containing fluororesins such as Nafion (registered trademark of DuPont) are known.
However, these polymer electrolyte materials have a problem that they are difficult to handle fluorine-based resins, have a complicated synthesis route, and are very expensive.
In addition, since the sulfonic acid group-containing fluororesin has a low glass transition temperature and low heat resistance, there is a risk that the resin will deteriorate when the operating temperature is increased (see Patent Document 1).

On the other hand, it has been proposed to produce a fuel cell electrolyte membrane using a multi-branched polymer having a sulfone group (see Patent Document 2).
However, since this multibranched polymer is unlikely to cause molecular entanglement, when attempting to form an electrolyte membrane with only a multibranched polymer, the mechanical strength of the film is weak or the film itself is difficult to form. There is a problem that there is.

The present inventors have found that a solid acid which is amorphous carbon (sulfonic acid group-introduced amorphous carbon) having a sulfonic acid group introduced has excellent properties as an electrolyte membrane for a fuel cell, and filed an application earlier. (See Patent Document 3).
Japanese Patent Laid-Open No. 2004-238111 JP 2003-183244 A International application number: PCT / JP2004 / 13035

The solid acid has high proton conductivity, excellent heat resistance, low production cost, and exhibits extremely excellent properties as a polymer electrolyte membrane material. However, since this substance is in a powder form, it is usually necessary to form a film by mixing with a binder resin in order to produce an electrolyte membrane having sufficient strength.
When mixing with the binder resin to form a film, it is necessary to adjust the varnish by dispersing or dissolving the binder resin together with the binder resin in some solvent. However, sulfonic acid group-introduced amorphous carbon does not dissolve in a solvent, so there are great restrictions in adjusting the varnish. Further, depending on the selection of the binder resin, the affinity with the binder is low, and there is a possibility of elution after film formation.

The first object of the present invention is to provide a compound that is excellent in handling properties in film formation, stability and durability of the film, and proton conductivity, and can be used for a polymer electrolyte membrane, a solid acid catalyst, an ion exchange membrane, and the like. Is to provide
A second object of the present invention is to provide the use and use of such compounds.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a film by binding a multibranched polymer having a high affinity between a solid acid and a solvent by an electrophilic substitution reaction. It has been found that the handling properties can be improved, the stability and durability of the film can be improved, and the proton conductivity can be improved, and the present invention has been completed.

  The invention according to claim 1 of the present invention is a compound comprising a solid acid and a multibranched polymer, wherein the solid acid is bonded to the multibranched polymer by an electrophilic substitution reaction.

  According to a second aspect of the present invention, in the compound according to the first aspect, the solid acid is a heat-treated polycyclic aromatic hydrocarbon in concentrated sulfuric acid or fuming sulfuric acid to condense the polycyclic aromatic hydrocarbon and sulfone. Amorphous carbon into which a sulfonic acid group obtained by conversion is introduced.

According to a third aspect of the present invention, in the compound according to the second aspect, the amorphous carbon into which the sulfonic acid group is introduced is bonded to a condensed aromatic carbon 6-membered ring and a sulfonic acid group in a ¹³ C nuclear magnetic resonance spectrum. Amorphous carbon into which a sulfonic acid group capable of detecting a chemical shift of a condensed aromatic carbon 6-membered ring is introduced.

  According to a fourth aspect of the present invention, in the compound according to the second or third aspect, the amorphous carbon into which the sulfonic acid group is introduced is a carbon having a half-value width of 5 to 30 ° in powder X-ray diffraction (002 ) Amorphous carbon having a sulfonic acid group in which at least a diffraction peak of the surface is detected is introduced.

  According to a fifth aspect of the present invention, in the compound according to any one of the second to fourth aspects, the amorphous carbon into which the sulfonic acid group is introduced is a diffraction peak on a carbon (002) plane in powder X-ray diffraction. Amorphous carbon into which a sulfonic acid group that can only be detected is introduced.

  According to a sixth aspect of the present invention, in the compound according to any one of the second to fifth aspects, the sulfonic acid density of the amorphous carbon having the sulfonic acid group introduced is 0.5 to 14 mmol / g. It is an amorphous carbon having a sulfonic acid group introduced therein.

  According to a seventh aspect of the present invention, in the compound according to any one of the first to sixth aspects, the multi-branched polymer has an aromatic structure having oxidation resistance in the main chain and a sulfone group at the terminal. It is a multi-branched polymer having

According to an eighth aspect of the present invention, in the compound according to any one of the first to seventh aspects, the multi-branched polymer is synthesized by sequential polymerization of an AB _X type monomer (where X is 2 or 3). A dendritic polymer having a number average degree of polymerization of 2 to 100, and AB _X type monomer has one aromatic structure A and X number of sulfone groups B, and aromatic structure A Each of the sulfone groups B is sequentially polymerized by electrophilic substitution reaction.

According to a ninth aspect of the present invention, in the compound according to any one of the first to eighth aspects, the multi-branched polymer has at least the following formulas (A) to (D) and formulas (E) to (H): It is a multi-branched polymer synthesized from a monomer selected from
(However, Ar in formulas (A) to (D) and formulas (E) to (H) represents at least one group selected from formulas (I) to (K).)

According to a tenth aspect of the present invention, in the compound according to any one of the first to ninth aspects, the multi-branched polymer has at least the following formulas (A ′) to (D ′) and a formula (E ′): It is a multi-branched polymer containing a group selected from ~ (H ').
(However, Ar in the formulas (A ′) to (D ′) and the formulas (E ′) to (H ′) represents at least one group selected from the formulas (I ′) to (K ′)). )

  An eleventh aspect of the present invention is the compound according to any one of the first to tenth aspects, wherein the multibranched polymer includes a group selected from the following formulas (L) to (M): It is a polymer.

  According to a twelfth aspect of the present invention, in the compound according to any one of the first to eleventh aspects, a proton conductivity of the compound comprising the solid acid and the multi-branched polymer is 0.01 to 0.30 S /. cm (according to the alternating current impedance method at a temperature of 80 ° C. and a humidity of 100%).

  A thirteenth aspect of the present invention is a polymer electrolyte membrane using the compound according to any one of the first to twelfth aspects.

  A fourteenth aspect of the present invention is a membrane / electrode assembly using the compound according to any one of the first to twelfth aspects.

  A fifteenth aspect of the present invention is a fuel cell using the compound according to any one of the first to twelfth aspects.

The invention according to claim 1 of the present invention is a compound comprising a solid acid and a multibranched polymer, wherein the solid acid is bonded to the multibranched polymer by an electrophilic substitution reaction. It is difficult to obtain sufficient proton conductivity with only a multi-branched polymer, but by combining the multi-branched polymer with a solid acid, the proton conductivity is high and the heat resistance is excellent. Because of its excellent affinity, it is easy to handle when it is made into a film, and it is also excellent in the stability and durability of the solid acid in the film. In addition, a large amount of industrially discarded sulfuric acid pitch is recycled as a solid acid. A polymer electrolyte membrane with membrane strength, a membrane electrode assembly and a fuel that have the effect of being able to reduce the environmental burden significantly when used, and that have membrane strength, efficiency that does not decrease even at high temperature operation Pond brings solid acid catalyst, a remarkable effect that can be utilized such as an ion exchange membrane.
Even after the multi-branched polymer is bonded to the solid acid, there is a remarkable effect that the characteristics capable of greatly reducing the environmental load are maintained.

According to a second aspect of the present invention, in the compound according to the first aspect, the solid acid is a heat-treated polycyclic aromatic hydrocarbon in concentrated sulfuric acid or fuming sulfuric acid to condense the polycyclic aromatic hydrocarbon and sulfone. It is characterized by being an amorphous carbon into which a sulfonic acid group obtained by conversion is introduced,
It is possible to provide a compound with more excellent proton conductivity, and to achieve a further remarkable effect that the environmental load can be greatly reduced.
This solid acid can be synthesized in a very simple step of sulfonation and carbonization, and does not necessarily require refined starting materials. Heavy oil, pitch, tar, asphalt, etc. can be used as starting materials, greatly reducing costs. There is a further remarkable effect of becoming.

According to a third aspect of the present invention, in the compound according to the second aspect, the amorphous carbon into which the sulfonic acid group is introduced is bonded to a condensed aromatic carbon 6-membered ring and a sulfonic acid group in a ¹³ C nuclear magnetic resonance spectrum. Amorphous carbon into which a sulfonic acid group capable of detecting a chemical shift of a condensed aromatic carbon 6-membered ring is introduced,
There is a further remarkable effect that a compound having a more excellent proton conductivity can be provided.

According to a fourth aspect of the present invention, in the compound according to the second or third aspect, the amorphous carbon into which the sulfonic acid group is introduced is a carbon having a half-value width of 5 to 30 ° in powder X-ray diffraction (002 ) Amorphous carbon introduced with a sulfonic acid group in which at least the diffraction peak of the surface is detected,
There is a further remarkable effect that a compound having a more excellent proton conductivity can be provided.

According to a fifth aspect of the present invention, in the compound according to any one of the second to fourth aspects, the amorphous carbon into which the sulfonic acid group is introduced is a diffraction peak on a carbon (002) plane in powder X-ray diffraction. It is characterized by being amorphous carbon into which only a sulfonic acid group that can be detected is introduced,
When the amorphous solid acid having such a high purity is surely superior in proton conductivity, the power generation performance is further improved when applied to a fuel cell.

According to a sixth aspect of the present invention, in the compound according to any one of the second to fifth aspects, the sulfonic acid density of the amorphous carbon having the sulfonic acid group introduced is 0.5 to 14 mmol / g. It is an amorphous carbon having a sulfonic acid group introduced,
There is a further remarkable effect that a compound having a more excellent proton conductivity can be provided.

According to a seventh aspect of the present invention, in the compound according to any one of the first to sixth aspects, the multi-branched polymer has an aromatic structure having oxidation resistance in the main chain and a sulfone group at the terminal. It is characterized by being a multi-branched polymer having
Surface modification of sulfonic acid group-introduced amorphous carbon with this multi-branched polymer has high affinity with solvents, excellent heat resistance, improved handling when forming into a film, and stability and durability of the film It is possible to improve the property and to further improve the proton conductivity.

Claim 8 of the present invention is the compound according to any one of claims 1 to 7, wherein the multi-branched polymer is synthesized by sequential polymerization of an AB _X type monomer (where X is 2 or 3), A dendritic polymer having a number average degree of polymerization of 2 to 100, AB _X type monomer having one aromatic structure A and X sulfone groups B, and aromatic structure A and sulfone Each of the groups B is one that is sequentially polymerized by electrophilic substitution reaction,
The film can be easily synthesized and has higher affinity with the solvent. By combining this multi-branched polymer with sulfonic acid group-introduced amorphous carbon through an electrophilic substitution reaction, the handling property when forming a film is improved. It is possible to improve the stability and durability of the resin and to further improve the proton conductivity.

According to a ninth aspect of the present invention, in the compound according to any one of the first to eighth aspects, the multi-branched polymer is at least the formulas (A) to (D) and the formulas (E) to (H). It is characterized by being a multi-branched polymer synthesized from monomers selected from
There is a further remarkable effect that the multi-branched polymer can be easily synthesized at low cost.

A tenth aspect of the present invention is the compound according to any one of the first to ninth aspects, wherein the multi-branched polymer is at least the formulas (A ′) to (D ′) and the formula (E ′) to It is a multi-branched polymer containing a group selected from (H ′),
There is a further remarkable effect that the stability and durability of the film can be further improved and the proton conductivity can be further improved.

The eleventh aspect of the present invention is the compound according to any one of the first to tenth aspects, wherein the hyperbranched polymer contains a group selected from the formulas (L) to (M). It is characterized by being a molecule,
There is a further remarkable effect that the stability and durability of the film can be further improved and the proton conductivity can be further improved.

According to a twelfth aspect of the present invention, in the compound according to any one of the first to eleventh aspects, a proton conductivity of the compound comprising the solid acid and the multi-branched polymer is 0.01 to 0.30 S /. cm (according to the alternating current impedance method at a temperature of 80 ° C. and a humidity of 100%),
There is a further remarkable effect that proton conductivity can be reliably improved.

  A thirteenth aspect of the present invention is a polymer electrolyte membrane characterized by using the compound according to any one of the first to twelfth aspects, and has excellent handling properties when formed into a film, The solid acid is excellent in stability and durability, excellent in proton conductivity, durability, mechanical strength, excellent in heat resistance, and exhibits excellent performance.

  A fourteenth aspect of the present invention is a membrane / electrode assembly comprising the compound according to any one of the first to twelfth aspects, and the stability and durability of the solid acid in the membrane. It is excellent in proton conductivity, durability, mechanical strength, heat resistance, operation at high temperature, and excellent performance.

  A fifteenth aspect of the present invention is a fuel cell using the compound according to any one of the first to twelfth aspects, and the environment of the fuel cell material itself used as next-generation clean energy. The load can be reduced, the durability is excellent, the operation is possible at a high temperature, and excellent power generation characteristics are exhibited.

Hereinafter, the present invention will be described in detail.
The compound of the present invention is characterized by comprising a solid acid and a hyperbranched polymer.
The solid acid used in the present invention is not particularly limited as long as it is insoluble in water and has a functional group that functions as an acid. Examples of functional groups that function as acids include functional groups having Bronsted acid properties such as OH, SO ₃ H, COOH, NO ₃ H, and NO ₂ H, and Lewis acid properties such as BF ₃ and AlCl _3. Functional groups are included, but are not limited to these.

  Examples of suitable solid acid include amorphous carbon having a sulfone group introduced therein, and other inorganic materials such as zeolite, silicate of group IV element, hydrous zirconium oxide, hydrous zirconium oxide, organic solid acid, and mordenite. Examples thereof include system solid acids.

The sulfone group-introduced amorphous carbon used as the solid acid may be any substance having a sulfonic acid group and exhibiting properties as amorphous carbon.
Here, “amorphous carbon” refers to a substance made of carbon and does not have a clear crystal structure such as diamond or graphite, and more specifically, a clear peak in powder X-ray diffraction. Means a substance in which no or a broad peak is detected.

  Suitable sulfonic acid group-introduced amorphous carbon is (1) sulfonic acid group-introduced amorphous carbon having the following properties (A), (B) and (C), and (2) the following (A), ( B) and (C), and sulfonic acid group-introduced amorphous carbon having the following properties (D) and / or (E): (3) No sulfonic acid group-introducing, having the following properties (C): An example is regular carbon.

(A) A chemical shift of a condensed aromatic carbon 6-membered ring and a condensed aromatic carbon 6-membered ring to which a sulfonic acid group is bonded is detected in the ¹³ C nuclear magnetic resonance spectrum.
(B) In powder X-ray diffraction, at least a diffraction peak on the carbon (002) plane having a half width of 5 to 30 ° is detected.
(C) shows proton conductivity.
(D) The sulfonic acid density is 0.5 to 14 mmol / g.
(E) Sulfur content is 0.3-15 atm%.

Regarding the property (A), the peak of the condensed aromatic carbon 6-membered ring is detected at 130 ppm, and the peak shift of the condensed aromatic carbon 6-membered ring to which the sulfonic acid group is bonded is detected at 140 ppm. Therefore, if the condensed aromatic carbon 6-membered ring has a sulfone group, a chemical shift to 140 ppm will be detected. ^{In the 13} C nuclear magnetic resonance spectrum, since quantitative handling is not considered, it is only necessary to detect a peak shift to 140 ppm.
Although the diffraction peak detected for the property (B) may be other than the (002) plane, it is preferable that only the (002) plane diffraction peak is detected. In amorphous powder X-ray diffraction, amorphous carbon shows poor performance unless it shows a diffraction peak on the carbon (002) plane, and those showing a peak show excellent performance. When such an amorphous solid acid having a high purity is used, further excellent power generation characteristics are exhibited.

With respect to the property (C), the proton conductivity is not particularly limited, but is preferably 0.01 to 0.30 Scm ⁻¹ (the proton conductivity is AC under conditions of a temperature of 80 ° C. and a humidity of 100%. It is a value measured by the impedance method.) If the proton conductivity is less than 0.01 Scm ⁻¹ , battery characteristics may be insufficient, and if the proton conductivity exceeds 0.30 Scm ⁻¹ , the yield may decrease.

  Regarding the property (D), the sulfonic acid density is preferably 0.5 to 14 mmol / g. If the sulfone group density is less than 0.5 mmol / g, the proton conductivity may be insufficient, and if the sulfone group density exceeds 14 mmol / g, the yield may decrease. More desirably, the sulfonic acid density is 1 to 8 mmol / g.

  Regarding the property (E), the sulfur content is preferably 0.3 to 15 atm%, more preferably 3 to 10 atm%. When the sulfur content is low, the density of the sulfone group is low and the proton conductivity may be insufficient. When the sulfur content is high, the yield in the synthesis of amorphous carbon itself having a sulfonic acid group introduced may be low.

The sulfonic acid group-introduced amorphous carbon can be produced, for example, by heat-treating an organic compound in concentrated sulfuric acid or fuming sulfuric acid. An outline of this manufacturing method is shown in FIG.
As shown in FIG. 1, when an organic compound is heat-treated in concentrated sulfuric acid or fuming sulfuric acid, carbonization, sulfonation, and condensation between rings occur. As a result, sulfonic acid group-introduced amorphous carbon as shown in FIG. 1 can be obtained.

  Heat treatment of organic compounds in concentrated sulfuric acid or fuming sulfuric acid is necessary to produce amorphous carbon with a high sulfonic acid density in an inert gas stream such as nitrogen or argon, or in a dry air stream. . A more preferable treatment is to perform heating while blowing an inert gas such as nitrogen or argon or dry air into concentrated sulfuric acid or fuming sulfuric acid to which an organic compound is added.

  Aromatic sulfonic acid and water are produced by the reaction of concentrated sulfuric acid and an aromatic compound, and this reaction is an equilibrium reaction. Therefore, as the amount of water in the reaction system increases, the reverse reaction proceeds faster, so the amount of sulfonic acid introduced into amorphous carbon is significantly reduced.

  Amorphous carbon with a high sulfonic acid density is synthesized by reacting in an inert gas or in a dry air stream, or reacting while blowing these gases into the reaction system, and actively removing water from the reaction system. can do.

In the heat treatment, partial carbonization, cyclization, condensation and the like of the organic compound are allowed to proceed and sulfonation is caused. Therefore, the heat treatment temperature is not particularly limited as long as the reaction proceeds, but industrially, 100 to 350 ° C is preferable, and 150 to 250 ° C is more preferable.
If the treatment temperature is less than 100 ° C., the condensation and carbonization of the organic compound may not be sufficient, and carbon formation may be insufficient. If the treatment temperature exceeds 350 ° C., thermal decomposition of the sulfonic acid group may occur. It may happen.

  Although heat processing time can be suitably selected according to the organic compound to be used, processing temperature, etc., 5 to 50 hours are preferable normally, More preferably, it is 10 to 20 hours.

  The amount of concentrated sulfuric acid or fuming sulfuric acid to be used is not particularly limited, but is usually 2.6 to 50.0 mol, more preferably 6.0 to 36.0 mol with respect to 1 mol of the organic compound. is there.

As the organic compound, aromatic hydrocarbons can be used, but other organic compounds such as glucose, sugar (sucrose), natural products such as cellulose, synthetic polymers such as polyethylene and polyacrylamide. A compound may be used.
The aromatic hydrocarbons may be polycyclic aromatic hydrocarbons or monocyclic aromatic hydrocarbons, and for example, benzene, naphthalene, anthracene, perylene, coronene, etc. can be used, preferably Naphthalene or the like can be used. Only one type of organic compound may be used, but two or more types may be used in combination.
Further, it is not always necessary to use a purified organic compound, and for example, heavy oil containing aromatic hydrocarbons, pitch, tar, asphalt, and the like may be used.

When using natural products such as glucose and cellulose or synthetic polymer compounds as raw materials, these materials are heated in an inert gas stream and partially carbonized before heat treatment in concentrated sulfuric acid or fuming sulfuric acid. It is preferable to keep it.
The heating temperature at this time is usually preferably 100 ° C. to 350 ° C., and the treatment time is usually preferably 1 to 20 hours.
The state of partial carbonization is preferably such that a (002) plane diffraction peak with a half width of 30 ° is detected in the powder X-ray diffraction pattern of the heat-treated product.

When using aromatic hydrocarbons or heavy oil containing the same, pitch, tar, asphalt, etc. as raw materials, it is preferable to heat the product in vacuum after heat treatment in concentrated sulfuric acid or fuming sulfuric acid. This removes excess sulfuric acid, promotes carbonization and solidification of the product, and increases the yield of the product.
For evacuation, it is preferable to use an evacuation apparatus having an evacuation speed of 10 L / min or more and an ultimate pressure of 100 torr or less.
A preferable heating temperature is 140 to 300 ° C, and a more preferable temperature is 200 to 280 ° C. The evacuation time at this temperature is usually 2 to 20 hours.

Next, the hyperbranched polymer used in the present invention will be described.
The multibranched polymer preferably used in the present invention is a multibranched polymer characterized by having an aromatic structure having oxidation resistance in the main chain and having a sulfone group at the terminal.
First, a monomer for synthesizing a hyperbranched polymer will be described.
The monomer for synthesizing the multi-branched polymer is a monomer selected from the above formulas (A) to (D) and formulas (E) to (H).

Next, the hyperbranched polymer will be described. This multi-branched polymer is synthesized from the above-mentioned monomers. This multi-branched polymer has a sulfone group.
The hyperbranched polymer includes a skeleton structure including at least a group selected from the above formulas (A ′) to (D ′) and formulas (E ′) to (H ′).

  Moreover, the above-mentioned multibranched polymer includes an end group selected from the above formulas (L) to (M).

  Further, in the above-described multibranched polymer, the terminal is not a terminal group selected from the above formulas (L) to (M), and the terminal is a sulfonic acid group or a sulfonate (Na, K, or Li).

As described above, the polymerization reaction of the multi-branched polymer is synthesized from the monomers of the formulas (A) to (D) and the formulas (E) to (H). This polymerization repeats the electrophilic substitution reaction with the aromatic structure and the sulfone group. Therefore, the aromatic structures of the above formulas (A) to (D) are simply expressed as A and the sulfone group as B, and expressed as an AB ₂ type monomer. In the case of the monomers of formulas (E) to (H) having three sulfone groups, they are represented as AB ₃ type monomers. From the above, the hyperbranched polymer is a dendritic polymer synthesized by sequential polymerization of an AB _X type monomer (where X is 2 or 3) by electrophilic substitution reaction.

  The number average degree of polymerization of the multi-branched polymer is preferably 2 to 100. If the number average degree of polymerization is less than 2, the mechanical strength may be insufficient. If the number average degree of polymerization exceeds 100, the mechanical strength may be excellent, but the handling property may be poor when forming a film.

Next, a monomer for synthesizing the multibranched polymer and a method for synthesizing the multibranched polymer will be described.
First, a method for synthesizing monomers will be described. The method for synthesizing this monomer is as follows.
That is, potential attraction of a cyano group, a nitro group, a chloro group, a fluoro group, etc. as shown in Formula (1) [wherein X may be Cl alone, F alone, or Cl and F in Formula (1)] A monomer can be synthesized by reacting a group having a chloro group or fluoro group on one benzene ring with a phenol having a sulfonic acid group (or sulfonic acid group).

  The method for synthesizing the monomer is not limited to the method described above. In addition, the following method can be adopted as a method for synthesizing the monomer. That is, as shown in the reaction of p-chloro or p-fluorobenzenesulfonic acid (or sulfonate) with bisphenols as shown in formula (2), p-chloro or p-fluorobenzenesulfonic acid of bisphenols Monomers can be synthesized by electrophilic substitution to (or sulfonate).

Next, a method for synthesizing a multibranched polymer will be described. The method for synthesizing this multi-branched polymer is as follows.
That is, the above AB ₂ type monomer and, for example, a mixed liquid of methanesulfonic acid and phosphorus pentoxide are added to the eggplant flask and heated to a predetermined temperature in a nitrogen atmosphere and reacted for a predetermined time. Thereafter, an end-capping agent such as Anisole is added to the reaction solution, heated to a predetermined temperature and reacted for a predetermined time to modify the end.
The method for synthesizing the hyperbranched polymer is not limited to the above-described method. In addition, the following two methods can be employed for the synthesis method of the sulfonic acid resin.

  One is that the monomer is 0 in a single liquid of sulfuric acid, phosphoric acid, polyphosphoric acid, phosphorus pentoxide, or sulfonic acids such as methanesulfonic acid, trichloromethanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and fluorosulfonic acid. ˜200 ° C. (preferably 30 ° C. to 150 ° C. The reaction is too slow at low temperatures and side reactions such as gelation occur at high temperatures) for 0.1 to 72 hours (preferably 3 to 48 hours). This is because if the length is too short, a sufficient molecular weight cannot be obtained, and if the length is too long, the rate of increase in molecular weight will be small.)

  In another one, the monomers are sulfuric acid, phosphoric acid, polyphosphoric acid, phosphorus pentoxide, and sulfonic acids such as methanesulfonic acid, trichloromethanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and fluorosulfonic acid. It is 0 to 200 ° C. (preferably 30 to 150 ° C.) in a mixture containing 95% (preferably 30 to 70%) because the reaction is too slow at low temperatures and side reactions such as gelation occur at high temperatures. For 0.1 to 72 hours (preferably 3 to 48 hours. If the length is too short, a sufficient molecular weight cannot be obtained, and if the length is too long, the increase rate of the molecular weight is small.) Stirring method.

As described above, the hyperbranched polymer is synthesized.
This multi-branched polymer has only two terminal portions at both ends in a linear polymer, whereas the number of terminal portions is proportional to the molecular weight. This multi-branched polymer has an aromatic structure in which the main chain is oxidation-resistant, and has a sulfonic acid (or sulfonate) group at the terminal portion. Therefore, it also has excellent solvent affinity.

Next, a method of synthesizing a compound by reacting a solid acid with a hyperbranched polymer will be described. For example, when synthesizing a hyperbranched polymer, it is only necessary to mix the solid acid at the same time. Alternatively, a solid acid may be mixed during the synthesis of the multibranched polymer. The sulfone group of the solid acid is bonded to the aromatic structure of the multi-branched polymer by an electrophilic substitution reaction.
Alternatively, a side reaction may occur in which the sulfo group of the multi-branched polymer undergoes an electrophilic substitution reaction into the aromatic structure of the solid acid. There is no particular problem even if such a side reaction occurs. This is because in both cases, a bond is formed by an electrophilic substitution reaction between the aromatic structure and the sulfone group. In this way, the solid acid and the hyperbranched polymer are bonded by an electrophilic substitution reaction.

The proton conductivity of the compound composed of the solid acid and the multi-branched polymer synthesized in this manner is measured by the AC impedance method under the conditions of 0.01 to 0.30 Scm ⁻¹ (temperature 80 ° C., humidity 100%). Value). If the proton conductivity is less than 0.01 Scm ⁻¹ , battery characteristics may be insufficient, and if the proton conductivity exceeds 0.30 Scm ⁻¹ , the yield may decrease. is there.
The compound composed of the solid acid and the multi-branched polymer thus synthesized has excellent proton conductivity and heat resistance, and therefore can be used as a polymer electrolyte for fuel cells.
Moreover, since it has excellent solvent affinity, it is very excellent in handling when adjusting the varnish of the polymer electrolyte for fuel cells by mixing with a binder resin.
The use of this compound is not limited to the polymer electrolyte for fuel cells described above. In addition to this, the use of this compound can also include a polymer electrolyte for electrolysis, an ion exchange resin for producing pure water, an antistatic agent, and the like.

  The compound of the present invention is excellent as proton conductivity and a solid acid catalyst, and also has excellent durability (heat resistance, acid resistance, chemical stability) and cost performance. It is very useful as a proton conductive material, an electrolyte membrane, a solid acid catalyst carrier and the like. Furthermore, it is possible to produce a solid electrolyte membrane using the compound of the present invention, and to produce a membrane electrode assembly and a fuel cell using this.

  As an example of a method for producing an electrolyte membrane using the compound of the present invention, first, the compound of the present invention is laminated on a support and dried to produce an electrolyte membrane. If necessary, a protective film is laminated thereon and stored.

  The method for producing a membrane electrode assembly using the electrolyte membrane of the present invention is, for example, in use, after peeling off the support and the protective film, on both sides of the electrolyte, Nafion (registered trademark of Nafion, DuPont) A membrane electrode assembly can be obtained by applying a proton conductive resin solution such as a binder as a binder, combining the gas diffusion electrodes with a catalyst layer, and hot pressing. The present invention is not limited to this.

A fuel cell can be manufactured by assembling a separator or an auxiliary device (a gas supply device or a cooling device) in a single or stacked manner.
That is, the fuel cell of the present invention can be obtained by sandwiching the membrane electrode assembly obtained by the above method with a gas separator or the like.

  The fuel cell of the present invention can be used alone or in a stack of a plurality of layers.

FIG. 6 is a cross-sectional explanatory view of one embodiment of the membrane electrode assembly of the present invention.
The membrane electrode assembly 12 is formed by joining and laminating the electrode catalyst layers 2 and 3 on both surfaces of the electrolyte membrane 1 by a conventional method.

  FIG. 7 is an exploded cross-sectional view showing the configuration of an embodiment of a single cell of a polymer electrolyte fuel cell equipped with the membrane electrode assembly 12. The air electrode side gas diffusion layer 4 having a structure in which a mixture of carbon black and polytetrafluoroethylene (PTFE) is applied to carbon paper, facing the electrode catalyst layer 2 and the electrode catalyst layer 3 of the membrane electrode assembly 12, and The fuel electrode side gas diffusion layer 5 is disposed. Thereby, the air electrode 6 and the fuel electrode 7 are comprised, respectively. A set of conductive and gas-impermeable materials having a gas flow path 8 for reaction gas flow facing a single cell and a cooling water flow path 9 for cooling water flow on the opposing main surface. A single cell 11 is formed by being sandwiched by the separator 10.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to a following example.
(Example 1)
(Production of solid acid)
A black liquid was obtained by adding 20 g of naphthalene to 300 mL of 96% concentrated sulfuric acid and heating the mixture at 250 ° C. for 15 hours while blowing nitrogen gas at 30 ml / min.
The liquid is heated at 250 ° C. for 5 hours while being evacuated with a high vacuum rotary pump with an exhaust speed of 50 L / min and an ultimate pressure of 1 × 10 ⁻² torr or less, thereby removing excess concentrated sulfuric acid and promoting carbonization. A black powder was obtained.
This black powder is heated at 180 ° C. for 12 hours in an inert air flow, then washed with 300 mL of distilled water, and the sulfuric acid in the distilled water after washing is detected by the elemental analyzer using flash combustion as described above. This operation was repeated until the following was obtained to obtain a solid acid. The obtained solid acid was insoluble in water.

(Analysis of solid acid)
Measurement of ¹³ CMAS (Magnetic angle spinning) nuclear magnetic resonance spectrum of sulfonic acid group-introduced amorphous carbon: Measurement was performed using ASX200 (manufactured by Bruker, measurement frequency: 50.3 MHz).
FIG. 4 is a graph showing the measurement results of ¹³ CMAS (Magnetic Angle Spinning) nuclear magnetic resonance spectrum of amorphous carbon introduced with sulfonic acid groups.
A chemical shift due to the condensed aromatic carbon 6-membered ring appeared near 130 ppm, and a chemical shift due to the condensed aromatic carbon 6-membered ring bonded with the sulfonic acid group appeared near 140 ppm.
X-ray analyzer for sulfonic acid group-introduced amorphous carbon: Geigerflex RAD-B, CuKα (manufactured by Rigaku Corporation) was used.
FIG. 5 is a graph showing the results of X-ray analysis of sulfonic acid group-introduced amorphous carbon.
The diffraction peaks of the carbon (002) plane and (004) plane were confirmed. The half width of the diffraction peak on the (002) plane was 11 °.
Moreover, the measurement of a sulfonic acid density is as follows. 1 g of the produced material was dispersed in 100 mL of distilled water and determined by titrating with a 0.1 M aqueous sodium hydroxide solution. The neutralization point was determined using a pH meter. It was 4.9 mmol / g.

(Performance evaluation of solid acid)
A solid acid powder is pressure-molded (manufactured by JASCO Corporation, 10 mmΦ tablet molding machine, molding conditions: 400 kg / cm ² , room temperature, 1 minute) to produce a disk having a thickness of 0.7 mm and a diameter of 10 mm. After depositing platinum on one side, proton conductivity was measured by an AC impedance method using an impedance analyzer (HYP4192A).
The absolute value and phase angle of the cell impedance were measured at a frequency of 5 to 13 MHz, an applied voltage of 12 mV, a temperature of 80 ° C., and a humidity of 100%. The obtained data was subjected to complex impedance measurement using a computer at an oscillation level of 12 mV. The proton conductivity was confirmed to be 2.2 × 10 ⁻¹ Scm ⁻¹ .
This result indicates that the sulfonic acid group-introduced amorphous carbon has proton conductivity comparable to that of Nafion.

(Synthesis of monomers to synthesize hyperbranched polymers)
First, a monomer was synthesized according to the formula (3) by the following method.
A 300 ml three-necked flask was equipped with a Dean-stark extractor and a nitrogen inlet tube, and under a nitrogen stream, 11.8 g of p-phenolic sulfonic acid salt and 6.6 g of potassium carbonate, 150 ml of dimethyl sulfoxide (DMSO) and 60 ml of toluene. (Toluene) was added and azeotropic dehydration was performed at 165 ° C. for 2 hours.
After the toluene was distilled off, 3.4 g of 2,6-dichlorobenzonitrile (2,6-dichlorobenzonitrile) was added and reacted at 150 ° C. for 48 hours.
The reaction solution was filtered through a glass filter, and then poured into 800 ml of chloroform to precipitate. The obtained precipitate was refluxed and washed with methanol for 1 hour and then recrystallized twice with water to obtain AB type ₂ monomer.
The yield was 46%. The structure of the obtained AB ₂ type monomer was confirmed by 1H-NMR and IR.

(Synthesis of multi-branched polymer and synthesis of compound of the present invention consisting of solid acid and multi-branched polymer)
Next, a multi-branched polymer was synthesized from the obtained AB ₂ type monomer by the following method.
That is, a mixed solution of 0.4 g of the AB type ₂ monomer, 5 ml of methanesulfonic acid and phosphorus pentoxide was added to a 50 ml eggplant flask and reacted at 120 ° C. for 48 hours in a nitrogen atmosphere to synthesize a multibranched polymer. .
FIG. 2 (a) shows the molecular structure of the synthesized manifold polymer, and (b) is an image diagram showing the molecular chain of the manifold polymer.
Next, 0.05 g of solid acid was added to the obtained reaction solution containing the multibranched polymer by the following method, and the reaction was further performed at 120 ° C. for 24 hours to modify the ends.
After completion of the reaction, the reaction product was poured into 800 ml of water, washed with refluxing with methanol for 1 hour, and dried under reduced pressure at 100 ° C. overnight to obtain the compound of the present invention consisting of a solid acid and a hyperbranched polymer. It was. The resulting compound of the present invention dissolved with good affinity for aqueous solvents.
FIG. 3 is an explanatory diagram showing the molecular structure of the compound of the present invention comprising a solid acid and a variety of polymers.

(Analysis of the compound of the present invention consisting of solid acid and various polymers)
Measurement of ¹³ CMAS (Magnetic Angle Spinning) nuclear magnetic resonance spectrum of the compound of the present invention: Measurement was performed using ASX200 (manufactured by Bruker, measurement frequency: 50.3 MHz).
A chemical shift due to the condensed aromatic carbon 6-membered ring appeared near 130 ppm, and a chemical shift due to the condensed aromatic carbon 6-membered ring bonded with the sulfonic acid group appeared near 140 ppm.
X-ray analyzer for the compound of the present invention: Geigerflex RAD-B, CuKα (manufactured by Rigaku Corporation) was used.
The diffraction peaks of the carbon (002) plane and (004) plane were confirmed. The half width of the diffraction peak on the (002) plane was 11 °.
Moreover, the measurement of the sulfonic acid density of the compound of this invention is as follows. 1 g of the produced material was dispersed in 100 mL of distilled water and determined by titrating with a 0.1 M aqueous sodium hydroxide solution. The neutralization point was determined using a pH meter. The sulfonic acid density was 5.5 mmol / g.

(Performance evaluation of the compound of the present invention comprising a solid acid and a hyperbranched polymer)
By subjecting the powder of the compound of the present invention to pressure molding (manufactured by JASCO Corporation, 10 mmΦ tablet molding machine, molding conditions: 400 kg / cm ² , room temperature, 1 minute), a disk having a thickness of 0.7 mm and a diameter of 10 mm is produced. Then, after depositing platinum on one surface of the disk, proton conductivity was measured by an AC impedance method using an impedance analyzer (HYP4192A).
The absolute value and phase angle of the cell impedance were measured at a frequency of 5 to 13 MHz, an applied voltage of 12 mV, a temperature of 80 ° C., and a humidity of 100%. The obtained data was subjected to complex impedance measurement using a computer at an oscillation level of 12 mV. The proton conductivity was confirmed to be 2.4 × 10 ⁻¹ Scm ⁻¹ . This result indicates that the compound of the present invention has proton conductivity comparable to that of Nafion.

  The compound of the present invention is a compound comprising a solid acid and a hyperbranched polymer, wherein the solid acid is bonded to the hyperbranched polymer by an electrophilic substitution reaction. While it is difficult to obtain sufficient proton conductivity with a polymer alone, by combining a multi-branched polymer with a solid acid by an electrophilic substitution reaction, the proton conductivity is high and the heat resistance is excellent. Because of its excellent affinity, it has excellent handling properties when it is made into a film, is excellent in the stability and durability of the solid acid in the film, and uses sulfuric acid pitch, which is industrially discarded in large quantities, as a solid acid. Recycling has the effect of lowering the cost and significantly reducing the environmental impact, and has a polymer electrolyte membrane having membrane strength, a membrane electrode assembly operable at high temperatures, and a fuel cell, Body acid catalyst, since a marked effect that can be utilized such as an ion exchange membrane, a high industrial value.

It is explanatory drawing which shows notionally the process of manufacturing sulfonic acid group introduction | transduction amorphous carbon. (A) shows the molecular structure of a manifold polymer formed by polymerizing an AB2 type monomer (A: benzene ring, B: sulfone group), and (B) is an image diagram showing the molecular chain of the manifold polymer. It is explanatory drawing which shows the molecular structure of the compound of this invention which consists of a solid acid and various polymers. It is a graph which shows the measurement result of the ¹³ CMAS (Magnetic Angle Spinning) nuclear magnetic resonance spectrum of sulfonic acid group introduction | transduction amorphous carbon. It is a graph which shows the X-ray-analysis result of a sulfonic acid group introduction | transduction amorphous carbon. It is sectional explanatory drawing of one embodiment of the membrane electrode assembly which formed the electrode catalyst layer on both surfaces of the electrolyte membrane. FIG. 7 is an exploded cross-sectional view showing the configuration of a single cell of a polymer electrolyte fuel cell equipped with the membrane electrode assembly shown in FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2, 3 Electrode catalyst layer 4 Air electrode side gas diffusion layer 5 Fuel electrode side gas diffusion layer 6 Air electrode 7 Fuel electrode 8 Gas flow path 9 Cooling water flow path 10 Separator 11 Single cell 12 Membrane electrode assembly

Claims (15)

  A compound comprising a solid acid and a hyperbranched polymer, wherein the solid acid is bound to the hyperbranched polymer by an electrophilic substitution reaction.   Amorphous carbon into which the solid acid is introduced, obtained by heat-treating polycyclic aromatic hydrocarbons in concentrated sulfuric acid or fuming sulfuric acid, and condensing and sulfonating the polycyclic aromatic hydrocarbons The compound according to claim 1, wherein Amorphous carbon into which the sulfonic acid group is introduced is a sulfonic acid in which a chemical shift of a condensed aromatic carbon 6-membered ring and a condensed aromatic carbon 6-membered ring to which a sulfonic acid group is bonded is detected in ¹³ C nuclear magnetic resonance spectrum 3. The compound according to claim 2, wherein the compound is an amorphous carbon having a group introduced therein.   The amorphous carbon into which the sulfonic acid group is introduced is amorphous carbon into which a sulfonic acid group in which at least a diffraction peak of a carbon (002) plane having a half width of 5 to 30 ° in powder X-ray diffraction is detected is introduced. The compound according to claim 2 or 3, wherein   The amorphous carbon into which the sulfonic acid group is introduced is amorphous carbon into which a sulfonic acid group in which only a diffraction peak of the carbon (002) plane is detected in powder X-ray diffraction is introduced. The compound according to any one of claims 2 to 4.   The amorphous carbon into which the sulfonic acid density of the amorphous carbon into which the sulfonic acid group is introduced is 0.5 to 14 mmol / g is an amorphous carbon into which the sulfonic acid group has been introduced. The compound in any one of.   7. The multi-branched polymer according to claim 1, wherein the multi-branched polymer is a multi-branched polymer having an aromatic structure having oxidation resistance in a main chain and having a sulfone group at a terminal. The described compound. The multi-branched polymer is a dendritic polymer synthesized by sequential polymerization of an AB _X type monomer (where X is 2 or 3), and the number average degree of polymerization is 2 to 100, and the AB _X type The monomer is characterized in that it has one aromatic structure A and X sulfone groups B, and each of the aromatic structure A and the sulfone group B is sequentially polymerized by electrophilic substitution reaction. The polymer according to any one of claims 1 to 7. The multibranched polymer is a multibranched polymer synthesized from a monomer selected from at least the following formulas (A) to (D) and formulas (E) to (H). The compound according to any one of claims 8 to 9.
(However, Ar in formulas (A) to (D) and formulas (E) to (H) represents at least one group selected from formulas (I) to (K).)

The multi-branched polymer is a multi-branched polymer including at least a group selected from the following formulas (A ′) to (D ′) and formulas (E ′) to (H ′). Item 10. The compound according to any one of Items 1 to 9.
(However, Ar in the formulas (A ′) to (D ′) and the formulas (E ′) to (H ′) represents at least one group selected from the formulas (I ′) to (K ′)). )

The compound according to any one of claims 1 to 10, wherein the multi-branched polymer is a multi-branched polymer including a group selected from the following formulas (L) to (M).

  The proton conductivity of the compound comprising the solid acid and the multi-branched polymer is 0.01 to 0.30 S / cm (according to an alternating current impedance method at a temperature of 80 ° C. and a humidity of 100%). The compound in any one of Claims 1-11.   A polymer electrolyte membrane comprising the compound according to any one of claims 1 to 12.   A membrane-electrode assembly comprising the compound according to any one of claims 1 to 12.   A fuel cell using the compound according to any one of claims 1 to 12.

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