JP2007146124A - Proton-exchanging membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton-exchanging membrane having high durability even under a high temperature and low humidified condition [e.g. 100°C operation temperature and 50°C humidification (corresponding to a relative humidity of 12%RH)]. <P>SOLUTION: This proton-exchanging membrane is characterized by containing a perfluorocarbon polymer compound A having an ion-exchanging group and sulfur B. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a proton exchange membrane suitable for a polymer electrolyte fuel cell.

A fuel cell is one that converts the chemical energy of fuel directly into electrical energy by electrochemically oxidizing hydrogen, methanol, etc. in the battery, and is attracting attention as a clean electrical energy supply source. ing. In particular, polymer electrolyte fuel cells are expected to be used as alternative power sources for automobiles, home cogeneration systems, portable generators, and the like because they operate at a lower temperature than others.
Such a polymer electrolyte fuel cell includes at least a membrane electrode assembly in which a gas diffusion electrode in which an electrode catalyst layer and a gas diffusion layer are laminated is bonded to both surfaces of a proton exchange membrane. The proton exchange membrane here is a material having a strong acidic group such as a sulfonic acid group and a carboxylic acid group in the polymer chain and a property of selectively transmitting protons. As such a proton exchange membrane, a perfluoro proton exchange membrane represented by Nafion (registered trademark, manufactured by DuPont) having high chemical stability is preferably used.

  During operation of the fuel cell, fuel (for example, hydrogen) is supplied to the gas diffusion electrode on the anode side, and an oxidant (for example, oxygen or air) is supplied to the gas diffusion electrode on the cathode side. Operates by connecting. Specifically, when hydrogen is used as a fuel, hydrogen is oxidized on the anode catalyst to generate protons, and after passing through the proton conductive polymer in the anode catalyst layer, the protons move in the proton exchange membrane, It reaches the cathode catalyst through the proton conducting polymer in the cathode catalyst layer. On the other hand, electrons generated simultaneously with protons by oxidation of hydrogen reach the cathode side gas diffusion electrode through an external circuit, and react with the protons and oxygen in the oxidant on the cathode catalyst to generate water, At this time, electric energy can be taken out.

At this time, the proton exchange membrane also needs to play a role as a gas barrier. When the gas permeability of the proton exchange membrane is high, leakage of anode-side hydrogen to the cathode side and leakage of cathode-side oxygen to the anode side, that is, A cross leak occurs, so that a so-called chemical short circuit occurs and a good voltage cannot be taken out.
Such a polymer electrolyte fuel cell is usually operated near 80 ° C. in order to obtain high output characteristics. However, when used for automobiles, the fuel cell can be operated even under high-temperature and low-humidification conditions (operating temperature near 100 ° C., 50 ° C. humidification (corresponding to a humidity of 12 RH%)) assuming that the vehicle is driven in summer. It is desired.

However, when a fuel cell is operated for a long time under a high temperature and low humidity condition using a conventional perfluoro proton exchange membrane, there is a problem that pinholes are generated in the proton exchange membrane, and cross leaks occur. Is not obtained.
As methods for improving the durability of perfluoro proton exchange membranes, reinforcement using fibrillar polytetrafluoroethylene (PTFE) (Patent Documents 1 and 2) and reinforcement using a stretched PTFE porous membrane (Patent Documents) 3) An investigation by reinforcement with addition of inorganic particles (Patent Documents 4, 5, and 6) is disclosed. In addition, a study for improving durability by crosslinking a perfluoro proton exchange membrane via a strongly acidic crosslinking group is also disclosed (Patent Document 7). Furthermore, the examination of the durability improvement by the proton exchange membrane which made the perfluoro type proton exchange membrane contain silica using the sol-gel reaction is also disclosed (nonpatent literature 1). However, in these methods, it has not been achieved to obtain a durability sufficient to solve the above problems.

  On the other hand, a proton exchange membrane (Patent Document 8) in which a perfluoro proton exchange membrane is doped with low molecular weight polypropylene glycol or the like, and a membrane (Patent Document 9) in which a membrane containing nitrogen is bonded to a perfluoro proton exchange membrane It is disclosed. However, the membranes obtained by these methods do not have good proton conductivity and have not been able to extract a sufficient voltage.

  In addition, it has been reported that a proton exchange membrane (hereinafter referred to as a strong acid-doped membrane) in which a polybenzimidazole having high heat resistance is doped with a strong acid such as phosphoric acid (hereinafter referred to as a strong acid doped membrane) can be operated at a high temperature of 100 ° C. or higher. (Patent Document 10). Further, a strong acid doped film in which polybenzimidazole having high heat resistance is doped with a low molecular weight acidic polymer has been reported (Patent Document 11). However, since there is water in the fuel cell operation at less than 100 ° C., the strong acid is eluted from the membrane into the water and the output is reduced. Therefore, the fuel cell operation under the high temperature and low humidification condition maintains a high voltage for a long time. I can't.

  Furthermore, a membrane obtained by blending a perfluorocarbon polymer having no ion exchange group with a hydrocarbon polymer having an ion exchange group is used as a proton exchange membrane (Patent Document 12), and a hydrocarbon having an ion exchange group A membrane obtained by blending a sulfonated aromatic polyether ketone or a sulfonated aromatic polyamide and a basic polymer as a polymer is used as a proton exchange membrane (Patent Documents 13 and 14), in the presence of an aprotic solvent. The use of a proton exchange membrane obtained by blending a hydrocarbon polymer having an ion exchange group and a basic polymer and then casting it has been studied (Patent Documents 15 and 16), but the chemical stability is insufficient. However, sufficient durability has not been achieved.

JP-A-53-149981 Japanese Examined Patent Publication No. 63-61337 JP-A-8-162132 JP-A-6-1111827 JP-A-9-219206 US Pat. No. 5,523,181 JP 2000-188013 A JP 2001-236773 A JP 2001-167775 A Japanese National Patent Publication No. 11-503262 Special Table 2000-517462 JP 2002-294087 A JP 2002-529546 A US Pat. No. 5,290,884 Japanese translation of PCT publication No. 2002-512285 Japanese translation of PCT publication No. 2002-512291 K. A. Mauritz, R.A. F. Story and C.I. K. Jones, in Multiphase Polymer Materials: Blends and Ionomers, L .; A. Utracki and R. A. Weiss, Editors, ACS Symposium Series No. 395, p. 401, American Chemical Society, Washington, DC (1989)

  An object of the present invention is to provide a proton exchange membrane having high durability even under high temperature and low humidification conditions (for example, at an operating temperature of 100 ° C. and 50 ° C. humidification (corresponding to a humidity of 12 RH%)).

As a result of intensive studies to solve the above problems, the present inventors have found that a proton exchange membrane comprising a perfluorocarbon polymer compound A having an ion exchange group and sulfur B has a high temperature and low humidity. However, it has been found to have high durability.
That is, the present invention is as follows.
(1) A proton exchange membrane comprising a perfluorocarbon polymer compound (A) having an ion exchange group and sulfur (B).
(2) The mass ratio (A / B) between the perfluorocarbon polymer compound (A) having an ion exchange group and sulfur (B) is 50/50 to 99.99 / 0.01. The proton exchange membrane according to (1) above.
(3) A membrane electrode assembly including the proton exchange membrane according to (1) or (2).
(4) A polymer electrolyte fuel cell comprising the membrane electrode assembly according to (3).

The proton exchange membrane of the present invention exhibits excellent durability with no cross leak even when the fuel cell is operated for a long period of time at an operating temperature of 100 ° C. and humidified at 50 ° C. (equivalent to a humidity of 12 RH%).
The proton exchange membrane obtained by the present invention can also be used for direct methanol fuel cells, chloralkali, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen concentrators, humidity sensors, gas sensors, and the like. .

The present invention is described in detail below.
As the perfluorocarbon polymer compound A having an ion exchange group used in the present invention, a perfluorocarbon sulfonic acid polymer, a carboxylic acid polymer, a phosphoric acid polymer, or an amine salt or a metal salt thereof is preferably used. A polymer represented by the general formula (1) is given as a typical example.
^{_{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 4)]}} g - (1)
(Wherein X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms, 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, b is 0 An integer of 8 or less, c is 0 or 1, d, e and f are each independently an integer of 0 or more and 6 or less (where d + e + f is not equal to 0), and R ¹ and R ² are each independently A halogen element, a perfluoroalkyl group or a fluorochloroalkyl group having 1 to 10 carbon atoms, and X ⁴ is COOZ, SO ₃ Z, PO ₃ Z ₂ , PO ₃ HZ (Z is a hydrogen atom, an alkali metal atom, Alkaline earth metal atoms, amines (NH ₄ , NH ₃ R, NH ₂ R ₂ , NHR ₃ , NR ₄ (R is an alkyl group or arene group))

Among these, a perfluorocarbon sulfonic acid polymer represented by the general formula (2) or (3) or a metal salt thereof is particularly preferable.
_{- [CF 2 CF 2] a} - [CF 2 -CF (-O-CF 2 -CF (CF 3)) b -O- (CF 2) c -SO 3 X]] d - ··· (2)
(Wherein 0 ≦ a <1, 0 ≦ d <1, a + d = 1, b is an integer of 1 to 8, c is an integer of 0 to 10, and X is a hydrogen atom or an alkali metal atom)
_{- [CF 2 CF 2] e} - [CF 2 -CF (-O- (CF 2) f -SO 3 Y)] g - ··· (3)
(Wherein 0 ≦ e <1, 0 ≦ g <1, e + g = 1, f is an integer of 0 to 10 and Y is a hydrogen atom or an alkali metal atom)

The perfluorocarbon polymer compound A having an ion exchange group of the present invention can be produced, for example, by polymerizing a precursor polymer represented by the chemical formula (4) and then performing alkali hydrolysis, acid treatment and the like.
^{_{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 5)]}} g - ··· (4)
(Wherein X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms, 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, b Is an integer of 0 to 8, c is 0 or 1, d, e and f are each independently an integer of 0 to 6 (where d + e + f is not equal to 0), R ¹ and R ² Are each independently a halogen element, a perfluoroalkyl group or fluorochloroalkyl group having 1 to 10 carbon atoms, X ⁵ is COOR ³ , COR ⁴ or SO ₂ R ⁴ (R ³ is a carbon number of 1 to 3) Hydrocarbon alkyl group, R ⁴ is a halogen element))

The precursor polymer that can be used in the present invention is produced by copolymerizing a fluorinated olefin compound and a vinyl fluoride compound.
Specific examples of the fluorinated olefin compound include CF ₂ = CF ₂ , CF ₂ = CFCl, CF ₂ = CCl _{2 and the} like.
In addition, as a specific vinyl fluoride compound,
_{CF 2 = CFO (CF 2)} z -SO 2 F, CF 2 = CFOCF 2 CF (CF 3) O (CF 2) z -SO 2 F, CF 2 = CF (CF 2) z -SO 2 F, CF _{2 = CF (OCF 2 CF (} CF 3)) z - (CF 2) z -1-SO 2 F, CF 2 = CFO (CF 2) z -CO 2 R, CF 2 = CFOCF 2 CF (CF 3) _{O (CF 2) z -CO 2} R, CF 2 = CF (CF 2) z -CO 2 R, CF 2 = CF (OCF 2 CF (CF 3)) z - (CF 2) 2 -CO 2 R ( Z represents an integer of 1 to 8, and R represents a hydrocarbon alkyl group having 1 to 3 carbon atoms).

As a polymerization method of the precursor polymer, a solution polymerization method in which a vinyl fluoride compound is dissolved in a solvent such as chlorofluorocarbon and then reacted with a gas of a fluorinated olefin compound to perform polymerization, or a block shape in which polymerization is performed without using a solvent such as chlorofluorocarbon General polymerization methods such as a polymerization method, an emulsion polymerization method in which a vinyl fluoride compound is mixed with a surfactant in water and emulsified, and then reacted with a gas of a fluorinated olefin compound for polymerization.
In the present invention, in addition to a vinyl fluoride compound and a fluorinated olefin compound, a copolymer containing a third component such as a perfluoroolefin such as hexafluoropropylene or chlorotrifluoroethylene or a perfluoroalkyl vinyl ether may be used. Good.

  The melt index MI (g / 10 min) of the precursor polymer that can be used in the present invention, measured at 270 ° C., load 21.2 N, orifice inner diameter 2.09 mm based on JIS K-7210 is 0.00. 001 or more and 1000 or less are preferable, more preferably 0.01 or more and 100 or less, and most preferably 0.1 or more and 10 or less.

Next, the precursor polymer that can be used in the present invention is immersed in a basic reaction liquid and subjected to an alkali hydrolysis treatment. The reaction liquid is preferably an aqueous solution of an alkali metal or alkaline earth metal hydroxide such as potassium hydroxide or sodium hydroxide. The content of alkali metal or alkaline earth metal hydroxide is preferably 10% by mass or more and 30% by mass or less. The reaction liquid preferably contains a swellable organic compound such as dimethyl sulfoxide or methanol. The content of the swellable organic compound is preferably 1% by mass or more and 30% by mass or less.
After the precursor polymer is subjected to an alkali hydrolysis treatment, the perfluorocarbon polymer compound A having an ion exchange group is produced by further performing an acid treatment with hydrochloric acid or the like as necessary.

Next, as the sulfur B used in the present invention, any isotope or allotrope can be suitably used.
Examples of isotope compositions include 32S, 33S, 34S, and 36S.
As an allotrope, solid sulfur is roughly classified into cyclic sulfur and chain catena sulfur (amorphous sulfur). Examples of cyclic sulfur include orthorhombic sulfur and monoclinic sulfur. Amorphous sulfur includes rubbery sulfur, white sulfur, precipitated sulfur, colloidal sulfur and the like. In addition, as the solid sulfur, sulfur white is also included.

There are also artificially synthesized cyclo-S6, cyclo-S7, cyclo-S9, cyclo-S10, cyclo-S11, cyclo-S12, cyclo-S18, cyclo-S20 and the like.
In addition to solids, liquid sulfur and gaseous sulfur can also be suitably used in the present invention.
Next, the composition ratio of the proton exchange membrane of the present invention will be described. The mass ratio (A / B) between the perfluorocarbon polymer compound A having an ion exchange group and sulfur B is preferably 50/50 to 99.99 / 0.01, more preferably 70/30 to 99. .95 / 0.05, more preferably 80/20 to 99.9 / 0.1, and most preferably 90/10 to 99/1.

When the mixing ratio of the polymer compound A is 50 wt% or more, sufficient proton conductivity can be obtained and good battery characteristics can be obtained. On the other hand, when the mixing ratio of sulfur B is 0.01 wt% or more, a significant difference is observed in durability in battery operation under high temperature and low humidification conditions.
About the proton exchange membrane of this invention, various additives, such as antioxidant, antioxidant, and a flame retardant, can be added as needed. The mass ratio (electrolyte composition / additive) of the proton exchange membrane and the additive of the present invention is preferably 80/20 to 99.999 / 0.001, more preferably 90/10 to 99.99 /. 0.01, more preferably 95/5 to 99.9 / 0.1.

Next, a method for producing a polymer electrolyte composition necessary for producing the proton exchange membrane of the present invention will be described. The method for obtaining the polymer electrolyte composition used in the present invention is not particularly limited, and a general method for mixing polymer compositions can be suitably applied.
Examples thereof include a method in which perfluorocarbon polymer compound A or its precursor polymer and sulfur B are heated and kneaded with a kneading extruder, a lab plast mill, a kneading roll, a Banbury mixer, or the like. However, since sulfur B may ignite at 250 ° C. or higher, it is necessary to take measures such as putting it in a nitrogen atmosphere when melting. When the precursor polymer is used in place of the perfluorocarbon polymer compound A, the polymer electrolyte composition used in the present invention is converted into a form having an ion exchange group by performing an alkali hydrolysis treatment and an acid treatment after kneading. You can get things. Similarly, in this case, when melting, it is necessary to take measures such as putting under a nitrogen atmosphere.

  Further, there may be mentioned a method of dissolving the perfluorocarbon polymer compound A or its precursor polymer and sulfur B in an appropriate solvent, mixing them together to prepare a solution, and then removing the solvent. Also in this case, when the precursor polymer is used instead of the polymer compound A, after removing the solvent, it is converted into a form having an ion exchange group by performing an alkali hydrolysis treatment and an acid treatment. The polymer electrolyte composition used in the above can be obtained.

  Next, a method for producing a proton exchange membrane of the present invention will be described. The film forming means is not particularly limited, and a general polymer composition film forming method can be suitably applied. For example, known film forming methods such as calendar molding, press molding, T-die extrusion, and inflation extrusion can be used. However, since sulfur B ignites at 250 ° C. or higher, it is necessary to take measures such as placing it in a nitrogen atmosphere when melting. In addition, after the polymer composition comprising the precursor polymer of perfluorocarbon polymer compound A and sulfur B is formed using the above-described film forming method, an appropriate post-treatment such as alkali hydrolysis treatment or acid treatment is performed. The proton exchange membrane of the present invention can also be obtained by converting to a form having an ion exchange group. Similarly, in this case, when melting, it is necessary to take measures such as putting under a nitrogen atmosphere.

In addition, a perfluorocarbon polymer compound A and sulfur B are dissolved in an appropriate solvent and then mixed to prepare a solution. After casting the solution, the solvent is removed to obtain a proton exchange membrane. Can do. However, when sulfur B is used as a liquid, it is not necessary to dissolve in a solvent, and only the perfluorocarbon polymer compound A may be dissolved in the solvent.
As a casting method, a known coating method such as a method of casting into a petri dish, a gravure roll coater, a natural roll coater, a reverse roll coater, a knife coater, or a dip coater can be used. The base material used for the casting method is a general polymer film, a metal foil, a substrate made of alumina, silicon or the like, a porous film obtained by stretching a PTFE film described in Patent Document 3, and Patent Document 1 and Patent Document 2. A fibrillated fiber or the like can be used.

As a method for removing the solvent, a method such as heat treatment or reduced pressure treatment at room temperature to 200 ° C. can be used. When heat treatment is performed, the solvent can be removed by raising the temperature stepwise.
In the production of the proton exchange membrane of the present invention, reinforcement by adding inorganic particles such as glass fiber, reinforcement by crosslinking, and the like can be performed in combination with the above production method.
In addition, stretching orientation can be imparted by carrying out lateral uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching.
In the proton exchange membrane of the present invention, the mechanical properties can also be improved by heat treatment at 160 ° C. or higher in air or in an oxygen atmosphere.

The equivalent mass EW of the proton exchange membrane produced according to the present invention (dry mass in grams of proton exchange membrane per equivalent of proton exchange group) is preferably 250 or more and 2000 or less, more preferably 400 or more and 1200 or less, most preferably. Is 500 or more and 1000 or less. By using a proton conductive polymer with a lower EW, that is, a large proton exchange capacity, it exhibits excellent proton conductivity even under high temperature and low humidity conditions, and when used in a fuel cell, a high output can be obtained during operation. .
The thickness of the proton exchange membrane produced according to the present invention is preferably 1 μm to 500 μm, more preferably 0 to 2 μm to 100 μm, and most preferably 5 μm to 50 μm.

  The change in wet and dry dimensions of the proton exchange membrane produced according to the present invention is preferably 0% to 100%, more preferably 0% to 50%, and most preferably 0% to 10%. The term “wet and dry dimensional change” as used herein refers to the ratio of the change in dimension when left in water at 80 ° C. for 1 hour with respect to the dimension when left at 25 ° C. and 20 RH% for 1 hour. The dimension is the length in the vertical direction or the horizontal direction of the proton exchange membrane, and both preferably satisfy the above range.

In order to evaluate the durability of the proton exchange membrane of the present invention as a fuel cell, the evaluation method will be described below.
(Membrane electrode assembly)
When the proton exchange membrane obtained by the present invention is used in a polymer electrolyte fuel cell, it is used as a membrane electrode assembly (hereinafter abbreviated as “MEA”) in which two types of electrode catalyst layers are joined to an anode and a cathode. A structure in which a pair of gas diffusion layers are bonded to the outer side of the electrode catalyst layer so as to face each other is also called MEA.
The electrode catalyst layer is composed of fine particles of a catalytic metal and a conductive agent supporting the catalyst metal, and a water repellent is included as necessary. The catalyst used for the electrode may be any metal that promotes the oxidation reaction of hydrogen and the reduction reaction by oxygen. Platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten , Manganese, vanadium, alloys thereof, etc., among which platinum is mainly used.
As the MEA manufacturing method, for example, the following method is performed. First, a platinum-supported carbon serving as an electrode material is dispersed in a solution obtained by dissolving an ion exchange resin in a mixed solution of alcohol and water to form a paste. A certain amount of this is applied to a PTFE sheet and dried. Next, the application surface of the PTFE sheet faces each other, the proton exchange membrane of the present invention is sandwiched therebetween, and transfer bonding is performed by hot pressing at 100 ° C. to 200 ° C. to obtain an MEA.

(Fuel cell)
The MEA obtained above and, in some cases, a structure in which a pair of gas diffusion electrodes are opposed to each other via the MEA are further combined with components used for general solid polymer fuel cells such as bipolar plates and backing plates. Thus, a polymer electrolyte fuel cell is constructed.
Bipolar plates are graphite or resin composite materials, metal plates, etc. that have grooves on the surface for the flow of gas such as fuel and oxidant, and are used to transmit electrons to an external load circuit. In addition, it has a function as a flow path for supplying fuel and oxidant to the vicinity of the electrode catalyst. A fuel cell is manufactured by inserting and stacking a plurality of MEAs between such bipolar plates.
The method for evaluating the durability of the proton exchange membrane obtained from the solution for producing the fuel cell of the present invention has been described above.

Hereinafter, the present invention will be specifically described by way of examples.
The evaluation method and measurement method used in the present invention are as follows.
(Fuel cell evaluation)
(1) Manufacture of fuel cell First, a proton exchange membrane is sandwiched between two gas diffusion electrodes coated on a mount and hot pressed at 180 ° C. and a pressure of 10 MPa to transfer and bond the gas diffusion electrode to the proton exchange membrane. To produce an MEA.
As a gas diffusion electrode, a platinum-supported catalyst manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., trade name, TEC10E40E (platinum support ratio 40 wt%), perfluorosulfonic acid polymer solution (polymer mass ratio 5 wt%, solvent composition (mass ratio): Ethanol / water = 50/50) concentrated to 12 wt% and ethanol were added, mixed, stirred and applied in ink form on a PTFE sheet, then dried and fixed at 150 ° C in an air atmosphere Use the converted one. This gas diffusion electrode has a platinum loading of 0.4 mg / cm ² and a polymer loading of 0.5 mg / cm ² .
Carbon paper or carbon cloth subjected to water repellent treatment is disposed on both sides of the MEA, and is incorporated into an evaluation cell and set in an evaluation apparatus. A single cell characteristic test is performed using hydrogen gas as a fuel and air gas as an oxidizing agent at a cell temperature of 100 ° C. and 0.1 MPa. A water bubbling method is used for gas humidification, and both hydrogen gas and air gas are humidified at 50 ° C. and supplied to the cell.

(2) Measurement of fluorine elution rate The waste water discharged together with the anode exhaust gas and the cathode exhaust gas during the single cell characteristic test is respectively collected for a predetermined time, and then weighed. The fluorine composite electrode 9609BNionplus (trade name) is attached to a bench top type pH ion meter 920Aplus (trade name) manufactured by Meditrial Co., Ltd., and the fluorine ion concentration in the anode drainage and the cathode drainage is measured. The elution rate G is derived.
G = (Wa × Fa + Wc × Fc) / (T × A)
G: Fluorine elution rate (μg / Hr / cm ² )
Wa: Mass of captured and recovered anode drainage (g)
Fa: Fluorine ion concentration (ppm) in anode drainage
Wc: Mass of cathode drainage collected and recovered (g)
Fc: Fluorine ion concentration in the cathode drainage (ppm)
T: Time for collecting and collecting wastewater (Hr)
A: MEA electrode area (cm ² )

(3) Measurement of cross leak amount Part of the cathode exhaust gas during the single cell characteristic test was introduced into GL Sciences' micro gas chromatograph Micro GC CP-4900 (trade name), and the hydrogen gas concentration in the cathode exhaust gas was measured. The hydrogen gas permeability is derived from the following equation.
L = (X × V × T) × (5-U / 100) / (3 × A × P) × 10 −8
L: Hydrogen gas permeability (ml · cm / cm ² / sec / Pa)
X: Hydrogen gas concentration (ppm) in cathode exhaust gas
V: Cathode gas flow rate (ml / min)
T: thickness of proton exchange membrane (cm)
U: Cathode gas utilization rate (%)
A: Hydrogen permeation area of the proton exchange membrane (cm ² )
P: Hydrogen partial pressure difference between the cathode and anode (Pa)

[Example 1]
Perfluorosulfonic acid polymer solution (polymer mass ratio 5 wt%, solvent composition (mass ratio): ethanol / water = 50/50) was solvent-substituted with isopropyl alcohol and concentrated to 9 wt% to butanol with a polymer ratio of 5 wt%. % Of orthorhombic sulfur dissolved therein was mixed and sufficiently stirred, then poured into a petri dish and finally dried at 160 ° C. to obtain a cast film having a thickness of 50 μm. Next, it was immersed in a 2N hydrochloric acid aqueous solution at 60 ° C. for 3 hours, washed with ion-exchanged water and dried to obtain a proton exchange membrane.
When the fuel cell evaluation of this proton exchange membrane was performed, the average value of the fluorine elution rate in the waste water from the start to 200 hours was as low as 0.048 (μg / Hr / cm 2), Further, the cross leak amount after 200 hours was 8.3 × 10 −13 (ml × cm / cm 2 / sec / Pa), and the cross leak amount at the start (6.8 × 10 −13 (ml × cm / cm 2). / Sec / Pa)) and was found to exhibit excellent durability.

[Example 2]
Perfluorosulfonic acid polymer solution (polymer mass ratio 5 wt%, solvent composition (mass ratio): ethanol / water = 50/50) was solvent-substituted with isopropyl alcohol, and the solution was concentrated to 9 wt% to butanol with a polymer ratio of 1 wt. % Of rubber-like sulfur dissolved therein was mixed and stirred sufficiently, then poured into a petri dish and finally dried at 160 ° C. to obtain a cast film having a thickness of 50 μm. Next, it was immersed in a 2N hydrochloric acid aqueous solution at 60 ° C. for 3 hours, washed with ion-exchanged water and dried to obtain a proton exchange membrane.
When the fuel cell evaluation of this proton exchange membrane was performed, the average value of the fluorine elution rate in the waste water from the start to 200 hours was as low as 0.051 (μg / Hr / cm ² ). Moreover, the cross leak amount after 200 hours is 8.5 × 10 −13 (ml × cm / cm ² / sec / Pa), and the cross leak amount at the start (6.5 × 10 −13 (ml × cm / Cm ² / sec / Pa)), and it was found that excellent durability was exhibited.

[Example 3]
Perfluorosulfonic acid polymer solution (polymer mass ratio 5 wt%, solvent composition (mass ratio): ethanol / water = 50/50) was solvent-substituted with isopropyl alcohol, and the solution was concentrated to 9 wt% with a polymer ratio of 3 wt%. After liquid sulfur was mixed and sufficiently stirred, it was poured into a petri dish and finally dried at 160 ° C. to obtain a cast film having a thickness of 50 μm. Next, it was immersed in a 2N hydrochloric acid aqueous solution at 60 ° C. for 3 hours, washed with ion-exchanged water and dried to obtain a proton exchange membrane.
When the fuel cell evaluation of this proton exchange membrane was performed, the average value of the fluorine elution rate in the waste water from the start to 200 hours was as low as 0.040 (μg / Hr / cm ² ). Moreover, the cross leak amount after 200 hours is 7.5 × 10 −13 (ml × cm / cm ² / sec / Pa), and the cross leak amount at the start (6.0 × 10 −13 (ml × cm / Cm ² / sec / Pa)), and it was found that excellent durability was exhibited.

[Comparative Example 1]
Perfluorosulfonic acid polymer solution (polymer mass ratio 5 wt%, solvent composition (mass ratio): ethanol / water = 50/50) was solvent-substituted with isopropyl alcohol, and the solution concentrated to 9 wt% was poured into a petri dish. And dried at 160 ° C. to obtain a cast film having a thickness of 50 μm. Next, it was immersed in a 2N hydrochloric acid aqueous solution at 60 ° C. for 3 hours, washed with ion-exchanged water and dried to obtain a proton exchange membrane.
As a result of the fuel cell evaluation of this proton exchange membrane, the average value of the fluorine elution rate in the waste water from the start to 200 hours was as high as 0.506 (μg / Hr / cm ² ). Cross leak amount at the start when the cross leak amount is 2.1 × 10 −11 (ml × cm / cm ² / sec / Pa) (6.0 × 10 −13 (ml × cm / cm ² / sec / Pa)) Thus, sufficient durability was not obtained.

  The present invention is a proton exchange membrane having high durability even at high temperatures, and is suitable for the fields of ion exchange membranes and fuel cells. The proton exchange membrane obtained by the present invention can also be used for chloralkali, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen concentrator, humidity sensor, gas sensor and the like.

Claims (4)

  A proton exchange membrane comprising a perfluorocarbon polymer compound (A) having an ion exchange group and sulfur (B).   The mass ratio (A / B) between the perfluorocarbon polymer compound (A) having an ion exchange group and sulfur (B) is 50/50 to 99.99 / 0.01. 1. The proton exchange membrane according to 1.   A membrane electrode assembly comprising the proton exchange membrane according to claim 1.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 3.