JP2003055568A - Ion exchanger resin dispersion and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an ion exchanger resin dispersion capable of giving such an ion-exchange membrane that has a uniform and small thickness so as to be reduced in electrical resistance, has low hydrogen gas permeability, is reduced in dimensional change caused by heating or moistening, exhibits no anisotropy and has high tear strength so as to be excellent in handleability, and is mass- producible. SOLUTION: In this ion exchanger resin dispersion, an ion exchanger polymer having sulfonate groups, preferably a fluorine-containing polymer having the sulfonate groups, and a fibrillar fluorocarbon polymer are dispersed into a dispersion medium. The ion exchanger resin dispersion is obtained, for example, by mixing a fluorine-containing polymer having precursor groups of the sulfonate groups and a fluorocarbon polymer capable of being fibrillated, fibrillating the fluorocarbon polymer capable of being fibrillated, changing the precursor groups of the sulfonate groups into the sulfonate groups, and dispersing the treated mixture into the dispersion medium.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to ion exchanger polymer dispersions.

[0002]

2. Description of the Related Art A hydrogen / oxygen fuel cell has been attracting attention as a power generation system that has a reaction product of only water in principle and has almost no adverse effect on the global environment. The polymer electrolyte fuel cell was once installed in a spacecraft under the Gemini and biosatellite projects, but the cell power density at that time was low. Later, higher performance alkaline fuel cells were developed, and alkaline fuel cells have been adopted for space use up to the present space shuttle.

However, polymer electrolyte fuel cells have been receiving attention again due to technological progress in recent years. The reasons are as follows. (1) A highly conductive membrane has been developed as a solid polymer electrolyte. (2) By supporting the catalyst used in the gas diffusion electrode layer on carbon and coating it with an ion exchange resin, high activity can be obtained.

In order to further improve the performance, it is considered that the electrical resistance is reduced by increasing the concentration of sulfonic acid groups and reducing the thickness of the solid polymer electrolyte membrane. However, a significant increase in the concentration of sulfonic acid groups reduces the mechanical strength and tear strength of the electrolyte membrane, causes dimensional changes during handling, and causes the electrolyte membrane to creep easily during long-term operation, resulting in reduced durability. Problems such as occur. On the other hand, the reduction in thickness causes problems such as reduction in mechanical strength and tear strength of the electrolyte membrane, and further deterioration in workability and handleability when the membrane is bonded to a gas diffusion electrode.

[0005]

As a method for solving the above problems, polytetrafluoroethylene (hereinafter referred to as PT
It is called FE. ) A method of impregnating a porous ion exchange polymer having a sulfonic acid group into a porous membrane has been proposed (Japanese Patent Publication No. 5-75835). However, although the thickness can be reduced, the electrical resistance of the porous PTFE is high. There was a problem that it did not fall sufficiently. Further, in this method, since the interface between the PTFE porous membrane and the ion exchange polymer is not completely adhered, when used as an electrolyte membrane of a polymer electrolyte fuel cell, hydrogen gas leaks due to poor adhesion after long-term use. However, there is a problem that the battery performance increases and the battery performance decreases.

As a method for solving the problem of high electric resistance of the membrane, a cation exchange membrane reinforced with a perfluorocarbon polymer in the form of fibril, woven fabric or non-woven fabric has been proposed (JP-A-6-231779). . This membrane had a low resistance, and the fuel cell produced using this membrane had relatively good power generation characteristics, but the thickness was at most 100-200 μm.
However, the thickness was not sufficiently thin and the thickness was uneven, so that it was insufficient in terms of power generation characteristics and mass productivity. Further, the adhesion between the perfluorocarbon polymer and the fluorinated ion exchanger polymer having a sulfonic acid group was not sufficient, and the hydrogen gas permeability was relatively high, so the output when the fuel cell was constructed was insufficient. .

Therefore, the present invention has a uniform thickness and a low resistance, a low hydrogen gas permeability, a small dimensional change due to heat and humidification, and has no anisotropy and a high tear strength and an excellent handling property. An object of the present invention is to provide an ion-exchanger polymer dispersion liquid for obtaining an ion-exchange membrane that can be mass-produced and a method for producing the same.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an ion-exchanger polymer dispersion characterized in that an ion-exchanger polymer having a sulfonic acid group and a fibril-like fluorocarbon polymer are dispersed in a dispersion medium. The manufacturing method is provided.

An ion-exchanger polymer dispersion liquid (hereinafter referred to as the present dispersion liquid) in which the ion-exchanger polymer of the present invention and a fibrillar fluorocarbon polymer are dispersed in a dispersion medium.
The ion-exchange membrane formed by using (1) contains a reinforcing material (hereinafter referred to as the present reinforcing material) made of a fibril-like fluorocarbon polymer uniformly in the in-plane direction of the membrane. Normally, when a membrane containing this reinforcing material is produced by extrusion, the MD direction (the direction of extrusion when the membrane is formed) depends on the orientation of the fibrils.
And TD direction (direction perpendicular to MD direction) cause anisotropy of different strength. With the ion exchange membrane obtained using this dispersion, such anisotropy can be reduced, and the anisotropy can be substantially eliminated, and the mechanical strength such as tear strength and tensile strength of the membrane can be improved. It can be improved without directionality.

Therefore, for example, a membrane-electrode assembly for a solid polymer electrolyte fuel cell provided with this membrane as an electrolyte membrane is excellent in handleability, and the dimensional change due to heat or humidification can be extremely isotropic and small. As a result, a membrane with a thin cation exchange membrane, which was difficult with the conventional technology,
The electrode assembly can be easily manufactured.

Furthermore, the film produced using this dispersion is M
Since the mechanical strength is high without anisotropy in the D and TD directions,
The membrane / electrode assembly including the membrane is also excellent in durability. In the polymer electrolyte fuel cell, the gas supplied to the anode and the cathode is usually humidified to near the saturated water vapor pressure in order to ensure the proton conductivity of the electrolyte. However, when the current density and water vapor concentration in the membrane / electrode assembly were simulated, the current density distribution, temperature distribution, and water vapor pressure distribution were not uniform on all surfaces of the membrane / electrode assembly, and It is known that there is a high possibility that the catalyst layer resin in the membrane or the catalyst layer is partially dried due to a specific heat generation to cause nonuniform and local shrinkage or swelling. In such a case, if the reinforcing material is uniformly dispersed in the film, mechanical deformation or crack due to local shrinkage or swelling is less likely to occur, and a membrane / electrode assembly including a thin film is provided. However, it is considered to have excellent durability.

Further, the present dispersion can be used for forming an electrode of a membrane / electrode assembly by mixing a catalyst powder. That is, an electrode containing the present reinforcing material can be obtained by using a liquid obtained by mixing the present dispersion liquid and the catalyst powder.

In the present invention, examples of the fibril-like fluorocarbon polymer include copolymers containing at least 95 mol% of polymerized units based on PTFE and tetrafluoroethylene. In the case of a copolymer, it must be a fibrillizable copolymer, preferably a copolymer of tetrafluoroethylene and a fluorine-containing monomer, and containing 99% or more of polymer units based on tetrafluoroethylene. Is preferred. Specifically, PTFE, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-perfluoro (2,2
-Dimethyl-1,3-dioxole) copolymers, tetrafluoroethylene-perfluoro (butenyl vinyl ether) copolymers and other tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymers, and the like, but especially PTFE Is preferred.

The fibrillar fluorocarbon polymer is
It is preferable that 0.5 to 15 mass% of the total solid content of the present dispersion is contained. If it is less than 0.5% by mass, the reinforcing effect is not sufficiently exhibited, and if it is more than 15% by mass, the resistance tends to increase. When the fibrillar fluorocarbon polymer is 2 to 10% by mass based on the total solid content, the resistance does not increase and the reinforcing effect is sufficiently expressed, and the viscosity of the dispersion is not too high, and the electrolyte membrane or It is particularly preferable because the catalyst layer can be easily formed. The content of the fibrillar fluorocarbon polymer referred to here is the content of all the fibrillated or fibrillizable fluorocarbon polymers, the polymer contained without fibrillation and the fibrillated It also includes the amount of polymer present. That is, for example, when PTFE is used as the polymer, it indicates the content of PTFE in the total mass of the solid content.

Well-known polymers are widely used as the ion-exchange polymer in the present invention. In particular, when used as a constituent material of a membrane / electrode assembly of a fuel cell, sulfonic acid is used from the viewpoint of durability and the like. It is preferably made of a fluorine-containing polymer having a group, and particularly preferably made of a perfluorocarbon polymer having a sulfonic acid group.

Specific examples of the perfluorocarbon polymer having a sulfonic acid group include the general formula CF ₂ ═CF.
_{(OCF 2 CFX) m -O p} - (CF 2) n SO 3 H
(Here, X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 0 to 12, p is 0 or 1, and when n = 0, p = A copolymer containing a polymerized unit based on a perfluorovinyl compound represented by 0) and a polymerized unit based on a perfluoroolefin or a perfluoroalkyl vinyl ether is preferable. Specific examples of the perfluorovinyl compound include compounds represented by any one of formulas 1 to 4. However, in Formulas 1-4, q is an integer of 1-9, r is an integer of 1-8, s is an integer of 0-8, and z is 2 or 3.

[0017]

[Chemical 1]

A polymer containing polymerized units based on a perfluorovinyl compound having a sulfonic acid group is usually -SO ₂
It is polymerized using a perfluorovinyl compound having an F group. A perfluorovinyl compound having a —SO ₂ F group can be homopolymerized, but since it has low radical polymerization reactivity, it is usually used by copolymerizing with a comonomer such as perfluoroolefin or perfluoro (alkyl vinyl ether). To be Examples of the perfluoroolefin serving as a comonomer include tetrafluoroethylene, hexafluoropropylene and the like, and usually tetrafluoroethylene is preferably used.

As perfluoro (alkyl vinyl ether) as a comonomer, CF ₂ = CF- (OCF ₂
A compound represented by CFY) _t- O-R ^f is preferable. However, in the formula, Y is a fluorine atom or a trifluoromethyl group, t is an integer of 0 to 3, R ^f is a perfluoroalkyl group (1 represented by C _{u F} 2u _{+ 1} linear or branched ≦ u ≦ 12). CF ₂ = CF- (OCF ₂ C
Preferred examples of the compound represented by FY) _t- O-R ^f include compounds represented by any one of formulas 5 to 7. However, in formulas 5-7, v is an integer of 1-8,
w is an integer of 1 to 8 and x is an integer of 1 to 3.

[0020]

[Chemical 2]

Further, in addition to perfluoroolefin and perfluoro (alkyl vinyl ether), a fluorine-containing monomer such as perfluoro (3-oxahepta-1,6-diene) is a perfluorovinyl compound having a --SO ₂ F group as a comonomer. It may be copolymerized with.

From the viewpoint of heat resistance and the like, a non-fluorine type polymer or a partial fluorine type polymer is preferable to a perfluorocarbon polymer having a sulfonic acid group, and such an ion exchange polymer is, for example, represented by the formula 8 Examples thereof include copolymers containing the polymerized units represented by the formula 9 and the polymerized units represented by the formula 9. Here, P ¹ is a phenyltolyl group, a biphenyltolyl group, a naphthalent reel group, a phenanthrene reel group or an anthracent reel group, and P ²
Is a phenylene group, a biphenylene group, a naphthylene group, a phenanthrylene group or an anthracylene group, and A ² is S
An O ₃ M group (M is a hydrogen atom or an alkali metal atom) or a group which is converted into these groups by hydrolysis, B ¹ ,
B ² is each independently an oxygen atom, a sulfur atom, a sulfonyl group or an isopropylidene group. Structural isomers of P ¹ and ^{P 2} are not particularly limited, one hydrogen atom of the ^{P 1} and ^{P 2}
Fluorine atom, chlorine atom, bromine atom or 1 carbon atom
It may be substituted with an alkyl group of ~ 3.

[0023]

[Chemical 3]

In the present invention, the concentration of sulfonic acid groups in the ion exchanger polymer, that is, the ion exchange capacity, is 0.5 to 2.0 meq / g dry resin, particularly 0.7.
It is preferably ˜1.6 meq / g dry resin.
When the ion exchange capacity is lower than this range, for example, when it is used for producing an electrolyte membrane or an electrode for a polymer electrolyte fuel cell, the resistance of the obtained electrolyte membrane or the electrode becomes large,
On the other hand, when it is high, the mechanical strength of the electrolyte membrane and the electrode becomes insufficient.

The dispersion medium of the present dispersion liquid is not particularly limited, but examples thereof include the following. Methyl alcohol, ethyl alcohol, n-propyl alcohol, n
-Monohydric alcohols such as butyl alcohol and isopropyl alcohol. Polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin. 2,2,2-
Trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 2,2,3,3-tetrafluoro-1-propanol, 2,2,3,4,4,4
-Hexafluoro-1-butanol, 2,2,3,3,
4,4,4-heptafluoro-1-butanol, 1,
Fluorine-containing alcohols such as 1,1,3,3,3-hexafluoro-2-propanol.

Perfluoro oxygen-containing or nitrogen-containing compounds such as perfluorotributylamine and perfluoro-2-n-butyltetrahydrofuran, chlorofluorocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane , 3,3-dichloro-1,1,1,2,2-
Pentafluoropropane, 1,3-dichloro-1,1,
In addition to hydrochlorofluorocarbons such as 2,2,3-pentafluoropropane, polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and water can be used. These dispersion media may be used alone or in combination of two or more.

The concentration of the present dispersion liquid is preferably 0.3 to 30% by mass of the ion exchange polymer based on the total mass of the dispersion liquid. If it is less than 0.3% by mass, it takes time to volatilize the dispersion medium, or high temperature heating is required to shorten the time, and if heated at high temperature, ion clusters in the ion exchange resin become irreversibly small. , The proton conductivity is reduced. When it exceeds 30% by mass, the viscosity of the present dispersion becomes high and the coatability at the time of forming the electrolyte membrane or the catalyst layer becomes poor. When the concentration is 5 to 25% by mass,
Particularly preferred.

Next, a method for producing the present dispersion liquid will be described. This dispersion can be produced by the method (1) or (2). (1) A fluorinated polymer having a sulfonic acid group precursor group and a fibrillizable fluorocarbon polymer are used.
A mixing step of mixing at a temperature of 0 ° C. or higher and a melting point of the fibrillizable fluorocarbon polymer or less, a fibrillation step of fibrillating the fibrillizable fluorocarbon polymer, or a sulfonic acid precursor group. An acid-forming step of obtaining a fluoropolymer having a sulfonic acid group by conversion into an acid group, and a fibrillated fluorocarbon polymer and a fluoropolymer having a sulfonic acid group in a dispersion medium. A method of manufacturing through a dispersion step of dispersing.

(2) A step of mixing a solution or dispersion of a polymer having a sulfonic acid group with a dispersion of a fibrillatable fluorocarbon polymer, and a shearing force applied to the mixture obtained in the above step. A step of applying and fibrillating the fibrillizable fluorocarbon polymer.

In the method (1), the precursor group of sulfonic acid group means a group which can be converted into a sulfonic acid group by hydrolysis or acid type treatment, and specifically, -S.
An O ₂ F group, a —SO ₂ Cl group and the like are shown. The method (1) will be specifically described below. The mixing step and the fibrillation step can be carried out simultaneously, and first, -S is performed with a twin-screw extruder.
A fluorine-containing polymer having an O ₂ F group and a powder of a fibrillatable fluorocarbon polymer (PTFE, etc.) were mixed with 1
Kneading is performed at a temperature of 50 ° C. or higher and a melting point of the fibrillizable fluorocarbon polymer or lower. At this time, -SO ₂
A fluorine-containing polymer having an F group and a fibrillizable fluorocarbon polymer powder are uniformly mixed, and the fibrillizable fluorocarbon polymer is fibrillated to obtain pellets. The temperature at this time is 150 ° C
If the amount is less than the above, it is difficult to uniformly mix the fluoropolymer having a —SO ₂ F group and the fibrillatable fluorocarbon polymer or to fibrillate the fibrillatable fluorocarbon polymer.

If it is desired to further fibrillate the fluorocarbon polymer in the fibrillation step, the pellets may be extruded and formed into a film. Here, the fluorocarbon polymer which can be fibrillated when kneaded with a twin-screw extruder (and when extrusion-molded into a film) is given a shearing force to be fibrillated.

Next, the process proceeds to the acid-forming step, and the obtained pellets or film are subjected to hydrolysis and acid-forming treatment, and --SO ₂ F
Converting the group into a sulfonic acid group (-SO ₃ H group). Further, the dispersion process is started, and the pellet or film that has undergone the acid-forming process is dispersed in a dispersion medium to obtain the present dispersion liquid. Before dispersing the pellets or the film in the dispersion medium, 100 μm to 1 mm with a pulverizer such as a freeze pulverizer.
It is preferable to pulverize the powder into powder having a particle size of a certain degree because it can be easily dispersed.

In the dispersion step, the temperature of the dispersion medium may be any temperature at which the fluorinated polymer having a sulfonic acid group can be dissolved or uniformly dispersed, but the temperature is higher than the boiling point of the dispersion medium at normal pressure. When it is high, the dispersion step may be performed under pressure. Generally, the dispersion treatment is carried out while maintaining the temperature of the dispersion medium in the temperature range from room temperature to 270 ° C.
It is preferable to hold the temperature at 50 ° C. If the temperature is too low, it may be difficult to uniformly disperse the fluorinated polymer having a sulfonic acid group and the fibrillated fluorocarbon polymer in the dispersion medium, or it may take time to disperse them uniformly. On the other hand, if the temperature is too high, the sulfonic acid group concentration may decrease. The time for performing the dispersion treatment is usually about 1 minute to 1 day. For quick dispersion, stirring or ultrasonic irradiation may be performed.

Next, the method (2) will be specifically described.
In the method (2), first, a solution obtained by dissolving or dispersing a polymer having an acidified sulfonic acid group in a solvent (dispersion medium) and a fibrillizable fluorocarbon polymer are dispersed in the dispersion medium. Mix with the allowed dispersion. This method can be adopted regardless of whether the ion-exchange polymer is a fluorine-containing polymer or a non-fluorine-based polymer. The solvent and the dispersion medium used here are not particularly limited, and the dispersion medium of the present dispersion liquid exemplified above can be used. Next, a shearing force is applied to the obtained mixed liquid to fibrillate the fibrillizable fluorocarbon polymer. Specifically, the fibrillizable fluorocarbon polymer is agitated so that a shearing force is applied. The stirring device is not particularly limited as long as it can apply a shearing force to the fibrillizable fluorocarbon polymer. By stirring, the fluorocarbon polymer capable of fibrillation in the dispersion can be fibrillated, and the present dispersion can be obtained.

Since the transition temperature of a fibrillatable fluorocarbon polymer is usually around room temperature, it is considered that fibrillation is easy at temperatures above room temperature, but depending on the molecular weight and the proportion of copolymerization components, etc. When the temperature is raised, the viscosity is remarkably lowered, and it becomes difficult to apply a sufficient shearing force, and as a result, the fibrillation of the fluorocarbon polymer may not be accelerated. In such a case, it is preferable to stir around room temperature. In general, a fibrillizable fluorocarbon polymer is more likely to be fibrillated as the molecular weight is higher and the particle size is smaller. Therefore, it is preferable to use a fluorocarbon polymer having a high molecular weight and a small particle size.

The presence of the fibrillar fluorocarbon polymer in the present dispersion can be confirmed by, for example, removing the dispersion medium from the present dispersion and observing with a scanning electron microscope (SEM). Specifically, it can be confirmed by the following method.

The thickness of this dispersion when dried is approximately uniform to about 3
A cast film is formed by dropping it on a petri dish so as to have a thickness of 0 μm and holding it in an oven at 60 ° C. for 3 hours.
After peeling this cast film from the petri dish, the surface was subjected to plasma etching treatment and observed by SEM at a magnification of 5,000 to 10,000 times, and it was confirmed that the fibrillated fluorocarbon polymer had a short fiber shape. it can.

In the fibrils observed here, it is preferable that fibrils having a fiber diameter of 1 μm or less occupy 70% or more, particularly 95% or more of the total number of fibrils. 70
In the film obtained by using the present dispersion liquid of less than%,
The reinforcing effect may be reduced.

[0039]

EXAMPLES [Example 1 (Example) polymerized units based on tetrafluoroethylene and _{CF 2 = CF-OCF 2 CF} (CF
₃ ) 9730 g of a copolymer powder consisting of polymerized units based on O (CF ₂ ) ₂ SO ₂ F (ion exchange capacity 1.1 meq / g dry resin, hereinafter referred to as copolymer A) and PTFE powder ( 270 g of product name: Fluon CD-1, manufactured by Asahi Glass Co., Ltd.) was mixed and biaxial extrusion molding was performed to obtain 9500 g of pellets. 30% of the total mass of the solution was mixed with dimethyl sulfoxide and 1% of the total mass of the solution.
Hydrolyze in an aqueous solution containing 5% potassium hydroxide to give 1
It was immersed in mol / L hydrochloric acid for 16 hours at room temperature to convert it into an acid form (sulfonic acid group), washed with water and dried.

This was dispersed in ethanol, the solid content concentration was 10% of the total mass of the solution, and the fibril-like fluorocarbon polymer (2.7% of the total solid content) and sulfonic acid group-containing perfluorocarbon. A fibril-like fluorocarbon polymer-containing ion exchanger polymer dispersion containing a polymer was obtained.

Using this ion exchanger polymer dispersion,
An ion exchange membrane having a thickness of 30 μm and containing 2.7% by mass of a reinforcing material made of a fibril-like fluorocarbon polymer was applied on a polyethylene terephthalate (PET) film surface-treated with a silicone release agent by a die coater. Formed.

In order to measure the tear strength of the above ion-exchange membrane, after dipping in pure water at 90 ° C. for 16 hours, a width of 5 was obtained.
A rectangular sample having a length of cm and a length of 15 cm was cut out. Each sample was cut in half along the length direction from the center of the short side to 7.5 cm, which is a half of the length of 15 cm. One of the cut ends was attached to the upper chuck of the tensile tester and the other was attached to the lower chuck so as to be torn from the cut portion, and the gap between the chucks was widened at a speed of 200 mm / min at 25 ° C. to measure the tear load. The tear strength was calculated by dividing the tear load by the thickness of the sample, and the average value of 5 samples was taken. The tear strength of the obtained fibril-containing ion exchange membrane was 2 N / mm.

5 m from the fibril-containing ion exchange membrane
A strip-shaped film sample with a width of m was prepared, and a platinum wire (diameter: 0.2 mm) was placed on the surface of the sample for 5 m so that it was parallel to the width direction.
AC specific resistance was calculated | required by pressing five samples at m intervals, holding a sample in a thermostat / humidity device of 80 degreeC and 95% of relative humidity, and measuring the AC impedance between platinum wires in an alternating current of 10 kHz. Since 5 platinum wires are pressed at 5 mm intervals, the distance between poles is 5, 10, 15, 20 mm
The contact resistance between the platinum wire and the membrane can be excluded by measuring the AC resistance at each inter-electrode distance and calculating the specific resistance of the film from the inter-electrode distance and the gradient of the resistance. did. A good linear relationship was obtained between the distance between the poles and the measured resistance value, and the specific resistance was calculated from the following equation from the gradient and the thickness. Specific resistance ρ (Ω · cm) = width of sample (cm) × thickness of sample (cm) × gradient between resistance electrodes (Ω / cm) The specific resistance of the obtained fibril-containing ion exchange membrane is 4Ω.
It was cm.

Example 2 (Example) Pellets were obtained in the same manner as in Example 1 except that the amount of the copolymer A powder was changed to 9600 g and the amount of the PTFE powder was changed to 400 g. A fibril-like fluorocarbon polymer-containing ion-exchanger polymer dispersion was obtained in the same manner as in Example 1 except for the above.

Using this ion-exchanger polymer dispersion, an ion-exchange membrane was formed in the same manner as in Example 1. When the obtained fibril-containing ion exchange membrane was evaluated in the same manner as in Example 1, the number of fibrils having a fiber diameter of 1 μm or less was 96% of the total number of fibrils. When the specific resistance and the tear strength of this ion exchange membrane were measured, the specific resistance was 4 Ω · cm and the tear strength was 4 N / mm.

[Example 3 (Example)] A dispersion liquid having a solid content concentration was obtained in the same manner as in Example 1 except that a dispersion medium of ethanol and ion-exchanged water having a mass ratio of 80/20 was used instead of ethanol. A fibril-like fluorocarbon polymer-containing ion-exchanger polymer dispersion comprising a fibril-like fluorocarbon polymer and a perfluorocarbon polymer having a sulfonic acid group, which was 10% of the total mass, was obtained.

Using this ion-exchanger polymer dispersion, a 30-μm ion-exchange membrane containing 2.7% by mass of a reinforcing material composed of a fibrillar fluorocarbon polymer was formed in the same manner as in Example 1. When the obtained fibril-containing ion exchange membrane was evaluated in the same manner as in Example 1, the fiber diameter was 1 μm.
The fibril numbers below were 90% of the total fibril numbers. When the specific resistance and tear strength of this ion exchange membrane were measured, the specific resistance was 4 Ω · cm and the tear strength was 2N.
/ Mm.

Example 4 (Example) Copolymer A was hydrolyzed and acidified, and the solution dispersed in ethanol to a concentration of 9% by mass was concentrated to give a solid content of 11%. ．
It was 6% by mass. 11 g of the obtained dispersion liquid and PTFE dispersion (trade name: AFLON ADI, manufactured by Asahi Glass Co., Ltd.)
After mixing with 0.25g, Homijinisa (trade name:
Polytron homogenizer Model K, manufactured by Kinematica Co., Ltd.) is dispersed at a rotation speed of 25,000 RPM for 10 minutes to impart a shearing force to the PTFE dispersion to promote fibrillation, and to have a fibril-like fluorocarbon polymer and a sulfonic acid group. A fibril-like fluorocarbon polymer-containing ion-exchanger polymer dispersion containing a perfluorocarbon polymer was obtained.

Using this ion-exchanger polymer dispersion, an ion-exchange membrane was formed in the same manner as in Example 1. When the specific resistance and tear strength of the obtained fibril-containing ion exchange membrane were measured, the specific resistance was 4 Ω · cm and the tear strength was 3 N / mm.

Example 5 (Comparative Example) Copolymer A and PTFE
An ion-exchanger polymer dispersion having a solid content concentration of 10% of the total weight of the dispersion was obtained in the same manner as in Example 1 except that pellets containing only the copolymer A were obtained instead of the pellets containing It was

This ion-exchanger polymer dispersion liquid was used as a coating liquid and coated with a die coater to form an ion-exchange membrane having a thickness of 30 μm. When the specific resistance and tear strength of this ion exchange membrane were measured, the specific resistance was 4 Ω · cm. The tear strength was 0.5 N / mm.

Example 6 (Comparative Example) Polymerized units based on tetrafluoroethylene and CF ₂ ═CF—OCF ₂ CF (C
9730 g of a copolymer powder consisting of polymerized units based on F ₃ ) O (CF ₂ ) ₂ SO ₂ F (ion exchange capacity 1.1 meq / g dry resin) and PTFE powder (trade name: Fluon CD-1, 270 g of Asahi Glass Co., Ltd., and 2
9500 g of pellets were obtained by axial extrusion molding. The obtained pellets were formed into a film by a uniaxial extruder, and even the thinnest film had a thickness of 150 μm, and there were holes when it was attempted to make it thinner.

[0053]

By using the ion-exchanger polymer dispersion of the present invention, an ion-exchange membrane having a uniform and thin thickness and high tear strength can be obtained. When the ion exchange membrane obtained using the ion-exchanger polymer dispersion of the present invention is used as an electrolyte membrane of a polymer electrolyte fuel cell, for example, a polymer electrolyte fuel cell having excellent output characteristics and excellent durability is obtained. To be

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Claims (8)

[Claims] 1. An ion-exchanger polymer dispersion, wherein an ion-exchanger polymer having a sulfonic acid group and a fibrillar fluorocarbon polymer are dispersed in a dispersion medium. 2. The ion-exchanger polymer dispersion according to claim 1, wherein the fibril-like fluorocarbon polymer is a polytetrafluoroethylene or a copolymer containing 95 mol% or more of polymerized units based on tetrafluoroethylene. 3. The ion-exchanger polymer dispersion liquid according to claim 1, wherein the fibril-like fluorocarbon polymer is contained in an amount of 0.5 to 15% by mass based on the total mass of the solid content of the dispersion liquid. 4. The ion-exchanger polymer dispersion liquid according to claim 1, wherein the ion-exchanger polymer is a fluoropolymer having a sulfonic acid group. 5. The fluorinated polymer having a sulfonic acid group comprises a polymer unit based on tetrafluoroethylene and CF _{2
= CF (OCF 2 CFX) m} -O p - (CF 2) n SO
Polymerized units based on ₃ H (wherein X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, and n is
Is an integer of 0 to 12, p is 0 or 1, and n is 0.
In case of, p is also 0. 5. The ion-exchanger polymer dispersion according to claim 4, which is a copolymer consisting of 6. The method for producing an ion-exchanger polymer dispersion according to claim 4, wherein the fluoropolymer having a sulfonic acid group precursor group and the fibrillizable fluorocarbon polymer are 150 A mixing step of mixing at a temperature not less than ℃ and not more than the melting point of the fibrillizable fluorocarbon polymer, a fibrillation step of fibrillating the fibrillizable fluorocarbon polymer, and a sulfonic acid precursor group sulfonic acid An acid-forming step of converting to a group to obtain a fluoropolymer having a sulfonic acid group, and dispersing the fibrillated fluorocarbon polymer and the fluoropolymer having a sulfonic acid group in a dispersion medium And a dispersion step for allowing the dispersion of the ion exchanger polymer to be produced. 7. The method for producing an ion-exchanger polymer dispersion according to claim 6, wherein in the dispersion step, the temperature of the dispersion medium is maintained in the temperature range from room temperature to 270 ° C. 8. A method for producing an ion-exchanger polymer dispersion according to any one of claims 1 to 5, comprising a solution or dispersion of a polymer having a sulfonic acid group and a fibrillizable fluorocarbon polymer. An ion exchanger comprising a step of mixing a dispersion liquid and a step of applying a shearing force to the mixed liquid obtained in the step to fibrillate the fibrillizable fluorocarbon polymer. Method for producing polymer dispersion.