JP2008238134A - Ion exchange filter and manufacturing method thereof - Google Patents

Abstract

An ion exchange filter having excellent durability and high performance of removing ion components contained in a gas, and a production method capable of easily producing the ion exchange filter. Moreover, the nonwoven fabric useful also as a reinforcement body for ion exchange membranes and a filter for liquid processing is provided.
An ion-exchange filter comprising a nonwoven fabric containing fibers containing a fluorine-based ion exchange polymer, wherein the proportion of the fluorine-based ion exchange polymer is 95% by mass or more of the nonwoven fabric (100% by mass); A method for producing an ion-exchange filter produced by an electrospinning method using a spinning stock solution containing a fluorine-based ion exchange polymer and a solvent.
[Selection] Figure 1

Description

  The present invention relates to an ion exchange filter, a production method thereof, and a nonwoven fabric used for the ion exchange filter and the like.

  An ion exchange filter is known as a filter for removing ion components contained in gas. The filter removes an ionic component contained in, for example, a fuel gas (hydrogen gas, etc.) and an oxidant gas (air, oxygen gas, etc.) supplied to the polymer electrolyte fuel cell, and the fuel is produced by the ionic component. It is used as a filter for suppressing an increase in electric resistance of a solid polymer electrolyte membrane of a battery.

The following filters have been proposed as ion exchange filters.
(1) A filter comprising ion-exchange fibers obtained by introducing ion-exchange groups into polystyrene of a multi-core sea-island composite fiber in which polypropylene is an island component and polystyrene is a sea component (Non-patent Document 1).
(2) An ion exchange filter in which an ion exchange polymer is applied to the surface of a base filter made of polyolefin or the like (Patent Document 1).

However, the filter of (1) is composed of a fiber in which the sea component of the fiber introduces an ion exchange group into polystyrene, so that the fiber is rigid and brittle and has poor durability.
The filter of (2) has a flexible base material filter and excellent durability, but has a low ion component removal performance because the ratio of the ion exchange polymer contained in the filter is small.

Moreover, the nonwoven fabric used for this filter is used also for other uses, such as a reinforcement body for ion exchange membranes, and a liquid filtration processing filter.
Examples of conventional ion exchange membrane reinforcements include nonwoven fabrics, woven fabrics, porous bodies, and the like containing polymers that do not contain ion exchange groups such as polytetrafluoroethylene, polyethylene, polypropylene, and polyimide. However, since the reinforcing body has no ion exchange group, the resistance of the ion exchange membrane is increased.

Examples of the conventional liquid processing filter include a filter made of an ion exchange fiber based on polystyrene, a filter in which an ion exchange polymer is coated on the surface of a base material filter made of polyolefin, and the like. However, the liquid processing filter is inferior in durability or lacks ion exchange performance.
Supervised by Satoshi Takeuchi, “Properties of porous materials and their applied technologies”, Fuji Techno System, March 1999, p. 747 JP 2001-137717 A

  The present invention provides an ion exchange filter having excellent durability and high performance for removing ion components contained in a gas, and a production method capable of easily producing the ion exchange filter. Moreover, the nonwoven fabric useful also as a reinforcement body for ion exchange membranes and a filter for liquid processing is provided.

  The ion exchange filter of the present invention is made of a nonwoven fabric containing fibers containing a fluorine-based ion exchange polymer, and the proportion of the fluorine-based ion exchange polymer is 95% by mass or more of the nonwoven fabric (100% by mass). Features.

The ion exchange capacity of the fluorine ion exchange polymer is preferably 1.1 to 1.8 meq / g dry resin.
The fluorine-based ion exchange polymer is preferably a copolymer having a repeating unit based on tetrafluoroethylene and a repeating unit represented by the following formula (1).

  However, X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1.

  The manufacturing method of the ion exchange filter of this invention consists of a nonwoven fabric containing the fiber containing a fluorine-type ion exchange polymer, The ratio of the said fluorine-type ion exchange polymer is 95 mass% or more in a nonwoven fabric (100 mass%). A method for producing an ion exchange filter, wherein the nonwoven fabric is produced by an electrospinning method using a spinning stock solution containing the fluorine ion exchange polymer and a solvent.

The nonwoven fabric of this invention contains the fiber containing a fluorine-type ion exchange polymer and a polyalkylene oxide, and the ratio of the said polyalkylene oxide is 0.00 of the sum total (100 mass%) of a fluorine-type ion exchange polymer and a polyalkylene oxide. It is 01-5 mass%.
The polyalkylene oxide is preferably polyethylene oxide.
The polyethylene oxide preferably has a weight average molecular weight of 100,000 to 10,000,000.

The ion exchange filter of the present invention is excellent in durability and has a high ability to remove ion components contained in gas.
According to the method for producing an ion exchange filter of the present invention, it is possible to easily produce an ion exchange filter having excellent durability and high performance of removing ion components contained in a gas.
The nonwoven fabric of the present invention is useful as a filter for liquid treatment that has a low resistance and a strong ion exchange membrane from which an ion exchange membrane can be obtained; excellent durability and removal performance of ion components contained in the liquid. .

  In this specification, a compound represented by the formula (2) is referred to as a compound (2). The same applies to compounds represented by other formulas.

(Ion exchange filter)
The ion exchange filter of this invention consists of a nonwoven fabric containing the fiber containing a fluorine-type ion exchange polymer.

Examples of the fluorine ion exchange polymer include perfluorocarbon polymers having a sulfonic acid group (hereinafter referred to as sulfonic acid type perfluorocarbon polymer).
The sulfonic acid type perfluorocarbon polymer is selected from the group consisting of perfluoroolefins (tetrafluoroethylene (hereinafter referred to as TFE), hexafluoropropylene, etc.), chlorotrifluoroethylene, and perfluoro (alkyl vinyl ether). A copolymer having a repeating unit based on one or more types and a repeating unit having a sulfonic acid group is preferred, and a copolymer H having a repeating unit based on TFE and a repeating unit represented by the following formula (1) Is particularly preferred.

  However, X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1.

Copolymer H after obtaining a precursor polymer F by polymerizing a monomer mixture containing a compound having a TFE and -SO 2 _F group, a sulfonic acid group -SO 2 _F groups in the precursor polymer F Can be obtained by converting to Conversion of the —SO ₂ F group into a sulfonic acid group is performed by hydrolysis and acidification treatment.

As the compound having a —SO ₂ F group, the compound (2) is preferable.
_{CF 2 = CF- (OCF 2 CFX} ) m -O p - (CF 2) n -SO 2 F ··· (2).
However, X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1.

As the compound (2), compounds (21) to (24) are preferable.
CF ₂ = CFO (CF ₂ ) _q SO ₂ F (21),
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _r SO ₂ F (22),
CF ₂ = CF (CF ₂ ) _s SO ₂ F (23),
_{CF 2 = CF (OCF 2 CF} (CF 3)) t O (CF 2) 2 SO 2 F ··· (24).
However, q is an integer of 1-8, r is an integer of 1-8, s is an integer of 1-8, and t is an integer of 1-5.

  The ion exchange capacity of the fluorinated ion exchange polymer is preferably 1.0 to 1.8 meq / g dry resin, more preferably 1.1 to 1.5 meq / g dry resin. If the ion exchange capacity is 1.1 meq / g dry resin or more, the ion component removal performance is sufficiently high. When the ion exchange capacity is 1.8 meq / g dry resin or less, a decrease in strength of the fiber containing the fluorine-based ion exchange polymer can be suppressed.

  The proportion of the fluorine-based ion exchange polymer is 95% by mass or more, preferably 99% by mass or more, in the nonwoven fabric (100% by mass). When the ratio of the fluorine-based ion exchange polymer is 95% by mass or more, the ion component removal performance is sufficiently high.

The fiber may contain other components as long as the ratio of the fluorine-based ion exchange polymer in the nonwoven fabric is 95% by mass or more.
The nonwoven fabric may contain other fibers as long as the ratio of the fluorine-based ion exchange polymer in the nonwoven fabric is 95% by mass or more.

The thickness of the nonwoven fabric is preferably 10 μm or more, and more preferably 20 μm or more. In addition, the thickness of the nonwoven fabric is preferably 100 μm or less, and more preferably 60 μm or less. If the thickness of the nonwoven fabric is 10 μm or more, the strength of the ion exchange filter is sufficiently high. When the thickness of the nonwoven fabric is 100 μm or less, the pressure loss of the ion exchange filter is sufficiently small.
The thickness of the non-woven fabric is measured from a cross-sectional photomicrograph and is the maximum value.

The basis weight of the nonwoven fabric is preferably 5 g / m ² or more, and more preferably 10 g / m ² or more. Also, the basis weight of the nonwoven fabric is preferably 70 g / ^{m 2} or less, 40 g / ^{m 2} or less is more preferable. If the fabric weight of a nonwoven fabric is 5 g / m < ² > or more, the intensity | strength of an ion exchange filter will become high enough. When the basis weight of the nonwoven fabric is 70 g / m ² or less, the pressure loss of the ion exchange filter is sufficiently small.
The weight per unit area of the nonwoven fabric was 25 ° C., a polyethylene terephthalate (hereinafter referred to as PET) film with an adhesive was pressed against the nonwoven fabric, the nonwoven fabric was transferred to the film, the area of the transferred nonwoven fabric, The basis weight (g / m ² ) of the nonwoven fabric is determined from the mass increase.

The porosity of the nonwoven fabric is preferably 66% or more, and more preferably 70% or more. Further, the porosity of the nonwoven fabric is preferably 95% or less, and more preferably 90% or less. When the porosity of the nonwoven fabric is 66% or more, the pressure loss of the ion exchange filter is sufficiently small. If the porosity of the nonwoven fabric is 95% or less, the strength of the ion-exchange filter is sufficiently high.
The porosity of the nonwoven fabric is calculated from the following formula.
Porosity (%) = 100−A × 100 / (B × C).
However, A is a fabric weight (g / m < ² >) of a nonwoven fabric, B is the density (g / m < ³ >) of the fluorine-type ion exchange polymer which is a material of a nonwoven fabric, C is the thickness (( m).

  The ion exchange filter of the present invention may be laminated on a substrate filter. Examples of the substrate filter include woven fabric, non-woven fabric, and porous material. Examples of the material for the base filter include polyolefin, polyfluoroolefin, polyolefin-polyfluoroolefin copolymer, polyester, polyamide, polyamideimide, polyimide, polysulfone, polyethersulfone, polyarylene, and polyphenylene sulfide.

(Method for producing ion-exchange filter)
In this invention, the nonwoven fabric which comprises an ion exchange filter is manufactured by the electrospinning method.
The electrospinning method is a method of spinning fibers electrically by applying a high voltage to the spinning dope.

The electrospinning method has the following characteristics.
(I) Compared with other methods, it can be manufactured with a simple apparatus.
Known methods for producing nonwoven fabrics include meltblown, spunbond, and papermaking methods, all of which require large-scale nonwoven fabric production equipment, and separate fiber production equipment is required to prepare the raw material fibers. The device cost is high.
(Ii) An ultrafine fiber aggregate is obtained.
Manufacturing a non-woven fabric composed of ultrafine fibers using a normal non-woven fabric facility is severe in terms of conditions and has many limitations such as the viscosity of the raw material and stretchability. On the other hand, since the electrospinning method is a spinning method using a solution, volume shrinkage occurs in the drying process, and since the raw material itself has a low viscosity, molding with an ultrafine nozzle is possible. Easy to get fiber.
(Iii) The fiber assembly is usually obtained as a nonwoven fabric in which fibers are combined.
In the electrospinning method, since solidification from a solution and spinning by stretching occur simultaneously or sequentially, the fiber assembly is obtained as a nonwoven fabric in which fibers are bonded to each other.
FIG. 1 is a schematic configuration diagram illustrating an example of a nonwoven fabric manufacturing apparatus using an electrospinning method. The nonwoven fabric manufacturing apparatus 10 applies a high voltage between the syringe 12 filled with the spinning dope, the rotatable drum 16 disposed so as to face the needle 14 of the syringe 12, and the needle 14 and the drum 16. And a syringe pump (not shown) for discharging the spinning solution from the syringe at a constant flow rate by moving the plunger portion of the syringe 12 at a constant speed in the discharge direction.

  First, the spinning solution is filled into the syringe 12. While rotating the drum 16, a high voltage is applied between the needle 14 and the drum 16 by the high voltage power source 18. The syringe pump is operated, and the spinning solution is discharged from the needle 14 at the tip of the syringe 12 at a constant speed. When a voltage is applied to the tip of the needle 14 and the electrostatic attractive force exceeds the surface tension of the spinning stock solution, the spinning stock solution is deformed into a conical shape called Taylor cone at the tip of the needle 14, and the tip of the cone Stretched. The stretched spinning dope is refined by electrostatic repulsion of the positively charged spinning dope. The solvent instantly evaporates from the refined spinning dope, and ultrafine fibers are formed. Positively charged fibers adhere to the negatively charged drum 16. As the fibers gradually accumulate on the rotating drum 16, a fluorine-based nonwoven fabric is formed on the drum 16.

The spinning dope is a solution or dispersion containing a fluorinated ion exchange polymer and a solvent.
Examples of the solvent include a mixed solvent containing an organic solvent having a hydroxyl group and water.
The organic solvent having a hydroxyl group is preferably an organic solvent having 1 to 4 carbon atoms in the main chain. For example, methanol, ethanol, n-propanol, isopropanol, 2-methoxyethanol, n-butanol, 2-methyl-1- Examples include propanol, tert-butanol, and 2-ethoxyethanol.

  The proportion of water is preferably 10% by mass or more, more preferably 20% by mass or more, in the mixed solvent (100% by mass). Moreover, 99 mass% or less is preferable and the ratio of water is more preferable 80 mass%. If the ratio of water is 10% by mass or more, fibers are easily formed. If the ratio of water is 99% by mass or less, it is easy to adjust the viscosity of the spinning dope.

  The proportion of the fluorine-based ion exchange polymer is preferably 20% by mass or more, and more preferably 25% by mass or more in the spinning dope (100% by mass). Further, the proportion of the fluorinated ion exchange polymer is preferably 40% by mass or less, and more preferably 35% by mass or less. If the ratio of the fluorinated ion exchange polymer is within this range, fibers are easily formed.

The spinning dope preferably contains a polyalkylene oxide from the viewpoint that fibers can be stably formed.
As the polyalkylene oxide, polyethylene oxide (hereinafter referred to as PEO) is preferable.

The molecular weight of PEO is preferably 100,000 or more, and more preferably 200,000 or more. The molecular weight of PEO is preferably 10 million or less, more preferably 8 million or less, and further preferably 5 million or less. If the molecular weight of PEO is within this range, fibers can be formed stably.
The molecular weight of PEO is the weight average molecular weight Mw as measured by GPC (gel permeation chromatography).

  The proportion of the polyalkylene oxide is preferably 0.02% by mass or more and more preferably 0.05% by mass or more in the spinning dope (100% by mass). The proportion of polyalkylene oxide is preferably 5% by mass or less, and more preferably 2% by mass or less. If the ratio of the polyalkylene oxide is within this range, fibers can be formed stably.

The viscosity of the spinning dope is preferably 100 mPa · s or more, and more preferably 200 mPa · s or more. The viscosity is preferably 5000 mPa · s or less, and more preferably 2500 mPa · s or less. If the viscosity of the spinning dope is in this range, fibers are easily formed.
The viscosity of the spinning dope is measured at 25 ° C. using a TV-20 viscometer (manufactured by Toki Sangyo Co., Ltd.) equipped with a cone plate type (rotor code: 01, rotor No .: 1 ° 34′XR24).

  The discharge amount of the spinning dope is preferably 0.5 mL / hour or more, and more preferably 1 mL / hour or more. Further, the discharge amount of the spinning dope is preferably 20 mL / hour or less, more preferably 10 mL / hour. If the discharge rate of the spinning dope is 0.5 mL / hour or more, the needle 14 is hardly clogged and the fibers are not easily cut. If the discharge rate of the spinning solution is 20 mL / hour or less, fine fibers can be formed.

  The inner diameter of the tip of the needle 14 is preferably 0.05 mm or more, and more preferably 0.1 mm or more. The inner diameter is preferably 2 mm or less, and more preferably 1 mm or less. If the inner diameter of the tip of the needle 14 is 0.05 mm or more, the needle 14 is not easily clogged. If the inner diameter of the tip of the needle 14 is 2 mm or less, fine fibers can be formed.

  The distance from the tip of the needle 14 to the drum 16 is preferably 3 cm or more, and more preferably 5 cm or more. The distance is preferably 30 cm or less, and more preferably 20 cm or less. If the distance is 3 cm or more, discharge can be suppressed. If the distance is 30 cm or less, fibers are easily formed.

The voltage applied between the needle 14 and the drum 16 is preferably 3 kV or more, and more preferably 10 kV or more. The applied voltage is preferably 50 kV or less, and more preferably 30 kV or less.
If the voltage is 3 kV or more, fibers are easily formed. If the voltage is 50 kV or less, the discharge can be suppressed.

(Solid polymer fuel cell)
The ion exchange filter of the present invention is suitable as a filter for removing ion components contained in fuel gas (hydrogen gas, etc.) and oxidant gas (air, oxygen gas, etc.) supplied to a polymer electrolyte fuel cell. It is.
Examples of the polymer electrolyte fuel cell include a hydrogen / oxygen fuel cell and a direct methanol fuel cell (DMFC).

  In the ion exchange filter of the present invention described above, the nonwoven fabric constituting the filter is high in flexibility compared to a conventional multicore sea-island type composite fiber in which an ion exchange group is introduced into polystyrene as a sea component. Since the fiber containing the fluorine ion exchange polymer is included, the durability is excellent even when the proportion of the fluorine ion exchange polymer is 95% by mass or more in the nonwoven fabric (100% by mass). Moreover, since the ratio of a fluorine-type ion exchange polymer is 95 mass% or more among nonwoven fabrics (100 mass%), ion exchange performance is high and the removal performance of the ion component contained in gas is high.

  Moreover, in the manufacturing method of the ion exchange filter of this invention demonstrated above, the nonwoven fabric which comprises this filter is manufactured by the electrospinning method using the spinning stock solution containing a fluorine-type ion exchange polymer and a solvent. Therefore, it is possible to easily manufacture an ion exchange filter that is excellent in durability and has high performance of removing ion components contained in the gas.

<Nonwoven fabric>
The nonwoven fabric of this invention contains the fiber containing a fluorine-type ion exchange polymer and a polyalkylene oxide.

Examples of the fluorine-based ion exchange polymer include the same fluorine-based ion exchange polymers as those used for the above-described ion-exchange filter.
The ratio of the fluorine-based ion exchange polymer is 95 to 99.99% by mass or more in the total (100% by mass) of the fluorine-based ion exchange polymer and the polyalkylene oxide.

PEO is preferable as the polyalkylene oxide.
The molecular weight of PEO is preferably 100,000 or more, and more preferably 200,000 or more. The molecular weight of PEO is preferably 10 million or less, more preferably 8 million or less, and further preferably 5 million or less.

The ratio of the polyalkylene oxide is 0.01 to 5% by mass in the total (100% by mass) of the fluorine-based ion exchange polymer and the polyalkylene oxide.
The nonwoven fabric of the present invention can be produced by the above-described electrospinning method.

(Ion exchange membrane reinforcement)
The nonwoven fabric of this invention is suitable as a reinforcement body for ion exchange membranes.
The ion exchange membrane reinforced with the reinforcing body can be produced by the following method.
(I) A method in which the reinforcing body is impregnated with an ion exchange polymer solution and then dried.
(Ii) A method in which a reinforcing body is sandwiched between two ion exchange membranes and heat-pressed.

(Filter for liquid processing)
The nonwoven fabric of the present invention can be used not only as a gas processing filter but also as a liquid processing filter.
By using the liquid processing filter, cations in the liquid can be removed. The liquid processing filter is particularly useful when the water discharged from the fuel cell is reused.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Examples 1-3, 5, and 7 are examples, and examples 4 and 6 are comparative examples.

(Ion exchange capacity)
The ion exchange capacity of the copolymer was determined by the following method.
0.7 g of the precursor polymer F was accurately weighed and put into a test tube with a cap, and 5 mL of a 0.7N NaOH aqueous methanol solution was measured with a whole pipette and put into a test tube containing a sample. After sealing, it was kept in a constant temperature bath at 60 ° C. for 16 hours, and the whole amount was taken out into a beaker and titrated with 0.1N HCl using phenolphthalein as an indicator to obtain the ion exchange capacity.

(Viscosity of spinning dope)
The viscosity of the spinning dope is measured at 25 ° C. using a TV-20 viscometer (manufactured by Toki Sangyo Co., Ltd.) equipped with a cone plate type (rotor code: 01, rotor No .: 1 ° 34′XR24). The viscosity when the shear rate was 1 / second was determined.
(Fiber diameter of fiber)
The cross section of the nonwoven fabric was observed with a laser microscope, and the fiber diameter of the fibers that appeared on the cross section of the nonwoven fabric was measured.

(Thickness of nonwoven fabric)
The cross section of the nonwoven fabric was observed with a laser microscope, and the thickness of the thickest part was measured.

(Amount of non-woven fabric)
The basis weight of the nonwoven fabric was determined by pressing a PET film with an adhesive on the nonwoven fabric at 25 ° C., transferring the nonwoven fabric to the film, and determining the basis weight of the nonwoven fabric from the area of the transferred nonwoven fabric and the increase in mass of the PET film ( g / m ² ).

(Porosity of nonwoven fabric)
The porosity of the nonwoven fabric was calculated from the following formula.
Porosity (%) = 100−A × 100 / (B × C).
However, A is the fabric weight (g / m < ² >) of a nonwoven fabric, B is the density (g / m < ³ >) of the copolymer H which is a material of a nonwoven fabric, C is the thickness (m of a nonwoven fabric) ).

(Ion component removal performance)
The ion exchange filter was cut into a disk shape having a diameter of 10 cm and accommodated in a filter holder. The holder was placed between the compressor supplying the cathode side air and the fuel cell, so that the cathode side air was supplied to the fuel cell after passing through the filter.
The temperature of the fuel cell was kept at 80 ° C., and air that passed through the filter was supplied to the cathode and hydrogen was supplied to the anode at 1.5 atm. The terminal voltage at a current density of 1 A / cm ² was measured. The fuel cell was kept at a temperature of 80 ° C. and continuously operated at a current density of 0.2 A / cm ² . After 1000 hours, the terminal voltage at a current density of 1 A / cm ² was measured. From the comparison between the initial terminal voltage and the terminal voltage after 1000 hours, the ion component removal performance was evaluated.

The fuel battery cell was produced as follows.
A copolymer comprising a repeating unit based on TFE and a repeating unit represented by the following formula (14-1) (ion exchange capacity: 1.1 meq / g dry resin) and platinum-supported carbon. / Platinum-supported carbon = 1/3 mass ratio, and a coating solution containing ethanol as a solvent is coated on a carbon cloth by a die coating method, dried and 10 μm thick, and a platinum-supported amount of 0.5 mg / cm ² A gas diffusion electrode in which the gas diffusion electrode layer was formed was prepared.

Between the two gas diffusion electrodes, from a copolymer (ion exchange capacity: 1.1 meq / g dry resin) comprising a repeating unit based on TFE and a repeating unit represented by formula (14-1) A solid polymer electrolyte membrane (thickness: 50 μm) was sandwiched and pressed using a flat plate press to produce a membrane electrode assembly.
A titanium current collector is disposed outside the membrane electrode assembly, a polytetrafluoroethylene gas supply chamber is disposed outside the membrane electrode assembly, and a heater is disposed outside the titanium current collector to assemble a fuel cell having an effective membrane area of 25 cm ² . .

[Example 1]
Precursor polymer F1 powder (ion exchange capacity: 1.1 meq / g dry resin) consisting of a repeating unit based on TFE and a repeating unit based on compound (24-1) is mixed with 10% by weight of potassium hydroxide. Hydrolysis treatment was carried out in an aqueous solution containing 20000 g of an aqueous solution and 5000 g of methanol, followed by washing with water.
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) 2 SO 2 F ··· (24-1).

  The hydrolyzed copolymer powder was immersed in 20 L of 1.5 mol / L sulfuric acid at room temperature for 0.5 hours and then drained. This operation was repeated a total of 7 times for acidification treatment. After washing again with water and drying, a powder of copolymer H1 composed of a repeating unit based on TFE and a repeating unit represented by formula (14-1) (ion exchange capacity: 1.1 meq / g dried) Resin) 4960 g was obtained.

A mixed solvent of ethanol / water (ethanol / water = 60/40 mass ratio) is added to the copolymer H1 powder, the solid content concentration is adjusted to 30 mass%, and the mixture is stirred at 105 ° C. for 4 hours using an autoclave. A liquid composition A in which the copolymer H1 was dispersed in a mixed solvent was obtained.
0.05 g of PEO (molecular weight: 200,000) was added to 9.95 g of the liquid composition A, and the mixture was stirred at room temperature to obtain a spinning dope A. The viscosity of the spinning dope A was measured. The results are shown in Table 1.

A non-woven fabric production apparatus (manufactured by Iuchi Seisakusho Co., Ltd.) was prepared by electrospinning. A stainless syringe needle of 30 G (inner diameter: 0.13 mm, outer diameter: 0.3 mm, length: 2 cm) was attached to the tip of a disposable syringe with a capacity of 10 mL.
Using the nonwoven fabric production apparatus and the spinning dope A, electrospinning was performed under the conditions of a distance from the tip of the needle to the drum: 10.0 cm, an applied voltage: 20 kV, and a discharge amount: 5 mL / hour. A nonwoven fabric A composed of fibers having a fiber diameter of 0.3 to 1.5 μm was obtained on the drum.

The thickness, basis weight, and porosity of the nonwoven fabric A were measured. The results are shown in Table 1. The density of the copolymer H1 at 25 ° C. was 2 g / cm ³ .
The ratio of PEO contained in the nonwoven fabric A was 1.6% by mass in the total (100% by mass) of the copolymer H1 and PEO.
Moreover, the nonwoven fabric A was used as an ion exchange filter, and the initial terminal voltage of the fuel cell and the terminal voltage after 1000 hours were measured. The results are shown in Table 1. The terminal voltage hardly changed.

[Example 2]
0.01 g of PEO (molecular weight: 1,000,000) was added to 9.99 g of the liquid composition A, and the mixture was stirred at room temperature to obtain a spinning dope B. The viscosity of the spinning dope B was measured. The results are shown in Table 1.
A nonwoven fabric B composed of fibers having a fiber diameter of 0.5 to 3.0 μm was obtained in the same manner as in Example 1 except that the spinning stock solution B was used instead of the spinning stock solution A.

The thickness, basis weight, and porosity of the nonwoven fabric B were measured. The results are shown in Table 1.
The ratio of PEO contained in the nonwoven fabric B was 0.3% by mass in the total (100% by mass) of the copolymer H1 and PEO.
Moreover, the nonwoven fabric B was used as an ion exchange filter, and the initial terminal voltage of the fuel cell and the terminal voltage after 1000 hours were measured. The results are shown in Table 1. The terminal voltage hardly changed.

[Example 3]
Instead of copolymer H1, copolymer H2 (ion exchange capacity: 1.3 meq / g dry resin) consisting of a repeating unit based on TFE and a repeating unit represented by formula (14-1) is used. A liquid composition C was obtained in the same manner as in Example 1 except that.

A spinning dope C was obtained in the same manner as in Example 1 except that the liquid composition C was used instead of the liquid composition A. The viscosity of the spinning dope C was measured. The results are shown in Table 1.
A nonwoven fabric C composed of fibers having a fiber diameter of 0.6 to 4.0 μm was obtained in the same manner as in Example 1 except that the spinning stock solution C was used instead of the spinning stock solution A.

The thickness, basis weight, and porosity of the nonwoven fabric C were measured. The results are shown in Table 1. The density of copolymer H2 at 25 ° C. was 2 g / cm ³ .
Moreover, the nonwoven fabric C was used as an ion exchange filter, and the initial terminal voltage of the fuel cell and the terminal voltage after 1000 hours were measured. The results are shown in Table 1. The terminal voltage hardly changed.

[Example 4]
Without using an ion exchange filter (by supplying air directly to the cathode without passing through the filter), the initial terminal voltage of the fuel cell and the terminal voltage after 1000 hours were measured. The results are shown in Table 1. A decrease in terminal voltage was observed.

[Example 5]
The liquid composition A of Example 1 was applied onto a substrate and dried to obtain an ion exchange membrane having a thickness of 10 μm by a casting method. The nonwoven fabric B of Example 2 was sandwiched between two ion exchange membranes and heated and pressed at 130 ° C. to obtain a reinforced ion exchange membrane having a thickness of 25 μm.
The dimensions of the ion exchange membrane at 25 ° C. and 50% relative humidity were measured. Subsequently, the dimension after being immersed in 90 degreeC warm water for 2 hours was measured. The dimensional change rate was 15%, which was about ½ of the dimensional change rate (30%) of the unreinforced ion exchange membrane.
In addition, proton conductivity at 80 ° C. and 50% relative humidity was measured. The proton conductivity was measured at a voltage of 10 kHz AC and 1 V under the constant temperature and humidity conditions by a well-known four-terminal method by closely contacting a substrate having four-terminal electrodes arranged at 5 mm intervals on a 5 mm wide film. The proton conductivity was 0.048 S / cm, which was almost equivalent to the proton conductivity (0.05 S / cm) of an unreinforced ion exchange membrane. The results are shown in Table 2.

[Example 6]
A polytetrafluoroethylene porous membrane having a porosity of 80% and a thickness of 15 μm was impregnated with the liquid composition A and dried to obtain a reinforced ion exchange membrane having a thickness of 25 μm.
The dimensions of the ion exchange membrane at 25 ° C. and 50% relative humidity were measured. Subsequently, the dimension after being immersed in 90 degreeC warm water for 2 hours was measured. The dimensional change rate was 10%, which was about 1/3 of the dimensional change rate (30%) of the unreinforced ion exchange membrane.
However, when the proton conductivity at 80 ° C. and 50% relative humidity was measured, it was 0.03 S / cm, and a significant decrease was observed. The results are shown in Table 2.

[Example 7]
The nonwoven fabric A of Example 1 was used as an ion-exchangeable water treatment filter, and water discharged from the fuel cell was treated and reused as water used for humidification. The initial terminal voltage and the terminal voltage after 1000 hours were measured. The terminal voltage hardly changed.

  INDUSTRIAL APPLICABILITY The ion-exchange filter of the present invention is useful as a filter for removing ion components contained in fuel gas (hydrogen gas etc.) and oxidant gas (air, oxygen gas etc.) supplied to the polymer electrolyte fuel cell. It is. The nonwoven fabric of the present invention is also useful as an ion exchange membrane reinforcement and a liquid processing filter.

It is a schematic block diagram which shows an example of the nonwoven fabric manufacturing apparatus by an electrospinning method.

Explanation of symbols

  10 Nonwoven fabric manufacturing equipment

Claims (7)

It consists of a nonwoven fabric containing fibers containing a fluorine-based ion exchange polymer,
The ion exchange filter whose ratio of the said fluorine-type ion exchange polymer is 95 mass% or more among nonwoven fabrics (100 mass%).   The ion exchange filter according to claim 1, wherein the ion exchange capacity of the fluorine-based ion exchange polymer is 1.1 to 1.8 meq / g dry resin. The ion exchange filter according to claim 1 or 2, wherein the fluorine-based ion exchange polymer is a copolymer having a repeating unit based on tetrafluoroethylene and a repeating unit represented by the following formula (1).

However, X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1. A method for producing an ion-exchange filter comprising a nonwoven fabric containing fibers containing a fluorine-based ion exchange polymer, wherein the ratio of the fluorine-based ion exchange polymer is 95% by mass or more of the nonwoven fabric (100% by mass),
A method for producing an ion exchange filter, wherein the nonwoven fabric is produced by an electrospinning method using a spinning stock solution containing the fluorine-based ion exchange polymer and a solvent. A fiber comprising a fluorinated ion exchange polymer and a polyalkylene oxide;
The nonwoven fabric whose ratio of the said polyalkylene oxide is 0.01-5 mass% among the sum total (100 mass%) of a fluorine-type ion exchange polymer and a polyalkylene oxide.   The nonwoven fabric according to claim 5, wherein the polyalkylene oxide is polyethylene oxide.   The nonwoven fabric according to claim 6, wherein the polyethylene oxide has a weight average molecular weight of 100,000 to 10,000,000.

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