JP7183618B2 - Method for producing purified electrolyte polymer - Google Patents

Description

The present invention relates to a method for producing purified electrolyte polymers.

Examples of electrochemical devices using polymer electrolyte membranes as ion conductors include water electrolysis devices, electrochemical hydrogen compression devices, and polymer electrolyte fuel cells. Polymer electrolyte fuel cells, in particular, are expected to find wide-ranging applications as power sources for relatively small-scale distributed power generation facilities, power generators for mobile bodies such as automobiles and ships, small mobile devices, and portable devices.

Polymer electrolyte membranes used for these are membranes obtained by forming electrolyte polymers, and have high proton conductivity as cation exchange membranes and are chemically, thermally, electrochemically and mechanically sufficiently stable. must be something. Nafion (registered trademark) (manufactured by DuPont), which is a perfluorosulfonic acid-based polymer, has been widely used as an electrolyte polymer. On the other hand, the development of hydrocarbon-based electrolyte polymers has been active in recent years as an electrolyte polymer that can replace expensive Nafion.

In the process of synthesizing a perfluoro-based electrolyte polymer, impurities such as unreacted monomers, low-molecular-weight oligomers, excessive polymerization initiators, emulsifiers, alkali metals used in the hydrolysis treatment, and the like are generated. In addition, water-soluble inorganic salts such as sodium chloride and potassium chloride, unreacted monomers, and low-molecular-weight oligomers are produced as impurities in the process of synthesizing the hydrocarbon-based electrolyte polymer. These impurities in the electrolyte polymer adversely affect the moldability when the electrolyte polymer is processed into an electrolyte membrane or the like, and when the electrolyte membrane is used in a fuel cell, pores are formed inside the membrane during power generation. It is necessary to eliminate it as much as possible because it becomes a factor that occurs. Therefore, methods have been proposed for removing ionic and nonionic impurities from electrolyte polymers using various methods such as ultrafiltration, purification using ion exchange resins, and reprecipitation. For example, Patent Document 1 describes a method of purifying a perfluoro-based electrolyte polymer by ultrafiltration or ion exchange resin. Further, Patent Document 2 describes a method of extruding a hydrocarbon-based electrolyte polymer into water in the form of strands for purification.

JP 2013-245237 A JP 2007-39525 A

However, conventional methods have problems with processability when purifying large amounts of electrolytic polymers in-line. For example, the method described in Patent Document 1 requires a long time for purification. Further, in the method described in Patent Document 2, there is a high possibility that the highly elastic electrolyte polymer will wrap around the stirring blades in the water, and the process will be interrupted.

SUMMARY OF THE INVENTION In view of the background of such prior art, the present invention aims to provide a method for producing an electrolyte polymer having excellent processability, including a refinement step of the electrolyte polymer. (In this specification, an electrolytic polymer purified by removing a certain amount of impurities generated during polymerization is particularly referred to as "purified electrolytic polymer.")

The present invention employs the following means in order to solve such problems. That is, the present invention includes an extrusion step of extruding a polymerization solution of an electrolyte polymer into a poor solvent in which the solubility of the electrolyte polymer is lower than that of the solvent of the polymerization solution and which is miscible with the solvent of the polymerization solution in the form of strands; A method for producing a purified electrolyte polymer, comprising continuously in-line cutting a chopped strand-like electrolyte polymer to obtain a chopped strand-like electrolyte polymer.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the refined electrolyte polymer excellent in process passability can be provided.

[Extrusion process]
The extrusion step is a step of extruding the polymerization solution of the electrolyte polymer into strands into a poor solvent in which the electrolyte polymer is less soluble than the solvent of the polymerization solution and miscible with the solvent of the polymerization solution.

Here, the electrolyte polymer refers to a polymer containing an ionic group, and the electrolyte polymer solution refers to a solution obtained by dissolving or dispersing the electrolyte polymer in a solvent. Typical electrolyte polymers include ionic group-containing perfluoro-based polymers (hereinafter sometimes referred to as "perfluoro-based polymers") and ionic group-containing hydrocarbon-based polymers (hereinafter referred to as "hydrocarbon-based polymers"). ), and the present invention can be applied to any of these.

Perfluoro-based polymer means a polymer in which most or all of the hydrogen atoms of alkyl groups and/or alkylene groups in the polymer are substituted with fluorine atoms, typically alkyl groups and/or alkylene groups in the polymer. It is a polymer in which 85% or more of the hydrogen atoms in the groups are replaced with fluorine atoms. Representative examples of perfluoro-based polymers include commercially available products such as Nafion (registered trademark) (manufactured by DuPont), Flemion (registered trademark) (manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark) (manufactured by Asahi Kasei Corporation). can be done. The structure of these perfluoro-based polymers can be represented by the following general formula (N1). However, the perfluoro-based polymer used in the present invention is not limited to these.

(In general formula (N1), n1 and n2 each independently represent a natural number. k1 and k2 each independently represent an integer of 0 to 5.)
Further, the hydrocarbon-based polymer means that most or all of the hydrogen atoms of the alkyl groups and/or alkylene groups in the polymer remain unsubstituted by halogen groups and/or halogenated alkyl groups, Typically, it is a polymer in which the ratio of the number of hydrogen atoms to the number of halogen groups and/or halogenated alkyl groups of alkyl groups and/or alkylene groups in the polymer is 5 or more.

Perfluoro-based polymers are extremely expensive and have the problem of large gas crossover. A polymer is preferred, and an aromatic hydrocarbon-based electrolyte polymer having an aromatic ring in its main chain is particularly preferred. In this case, the aromatic ring may contain not only a hydrocarbon-based aromatic ring but also a heterocyclic ring. In addition, the aromatic ring unit and a part of the aliphatic unit may constitute the polymer. Aromatic units include hydrocarbon groups such as alkyl groups, alkoxy groups and aromatic groups, halogen groups, nitro groups, cyano groups, amino groups, halogenated alkyl groups, carboxyl groups, phosphonic acid groups, hydroxyl groups and the like. It may have a substituent.

Specific examples of aromatic hydrocarbon polymers include polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, polyarylene ketone, and polyether ketone. , polybenzoxazole, polybenzthiazole, polybenzimidazole, aromatic polyamide, polyimide, polyetherimide, and polyimidesulfone. Polysulfone, polyether sulfone, polyether ketone, etc., as used herein are generic names for polymers having sulfone bonds, ether bonds, and ketone bonds in their molecular chains, and do not limit specific polymer structures. .

Among these aromatic hydrocarbon polymers, polysulfone, polyether sulfone, polyphenylene oxide, polyarylene ether polymer, polyphenylene sulfide sulfone, polyarylene ketone, polyether ketone, polyarylenephosphine phosphine, polyetherphosphine phosphine Such polymers are preferable in terms of mechanical strength, physical durability, processability and hydrolysis resistance due to their rigid polymer structures, but they are difficult to purify due to the occurrence of stringiness and the like during purification. By applying the method of the present invention, even a rigid polymer structure can be easily purified, which is preferable.

The ionic group of the electrolyte polymer is preferably a negatively charged atomic group and preferably has proton exchange ability. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, a phosphoric acid group and a carboxylic acid group are preferably used. Among them, it is more preferable to have at least a sulfonic acid group, a sulfonimide group or a sulfuric acid group from the viewpoint of high proton conductivity, and it is most preferable to have at least a sulfonic acid group from the viewpoint of raw material cost.

Here, in the present specification, the term "ionic group" includes the case of forming a salt. Examples of cations that form such salts include arbitrary metal cations, NR ₄ ⁺ (where R is an arbitrary organic group), and the like. Specific examples of preferred metal cations include cations such as Li, Na, K, Rb, Cs, Mg, Ca, Pt, Rh, Ru, Ir, and Pd.

The molecular weight of the electrolyte polymer is preferably 50,000 or more, more preferably 100,000 or more, in terms of polystyrene equivalent weight average molecular weight. When the average molecular weight is 50,000 or more, the viscosity becomes high and stringiness or the like tends to occur during purification, so that the merit of adopting the production method of the present invention increases.

The solvent for the electrolyte polymer in the polymerization solution to be subjected to the extrusion step is not particularly limited as long as it can dissolve or disperse the electrolyte polymer. In the case of perfluoro-based polymers, at least one solvent selected from water, lower alcohols such as 1-propyl alcohol, isopropyl alcohol, ethanol and methanol, and lower fluoroalcohols such as hexafluoroisopropyl alcohol can be used. In the case of hydrocarbon-based polymers, alkyl halides such as chloroform, aromatic halides such as o-dichlorobenzene and 1-chloronaphthalene, N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, and N-methyl-ε -N-alkylcaprolactams such as caprolactam, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, dimethylsulfoxide, dimethylsulfone, tetramethylene At least one solvent selected from polar solvents such as sulfone can be used. Among these, N-methyl-2-pyrrolidone is particularly preferred in terms of solubility, handleability and cost.

The concentration of the electrolyte polymer in the polymerization solution to be subjected to the extrusion step is preferably 5% by weight or more and 30% by weight or less. If the concentration of the electrolyte polymer is less than 5% by weight, a large amount of solvent is required for purification, which may result in high process costs. If it exceeds 30% by weight, solvent exchange may not be carried out smoothly, and purification efficiency may deteriorate. Therefore, after completion of the polymerization reaction, the electrolyte polymer concentration in the polymerization solution can be adjusted as required.

The term "polymerization solution" is intended mainly for the solution immediately after the completion of the polymerization reaction of the electrolyte polymer. However, any substantially unpurified solution is included in the "polymerization solution."

In the present invention, the polymerization solution of the electrolyte polymer is formed into strands (continuous rods) in a poor solvent in which the solubility of the electrolyte polymer is lower than that of the solvent of the polymerization solution and which is miscible with the solvent of the polymerization solution. Subject to extrusion process. By extruding in the form of strands, the contact area between the poor solvent and the electrolyte polymer is increased, and the purification efficiency of impurities is improved.

The poor solvent is not particularly limited as long as the electrolyte polymer has lower solubility than the solvent of the polymerization solution and is miscible with the solvent of the polymerization solution. Specific examples include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diacetone alcohol, t-butanol, 1-propyl alcohol, isopropyl alcohol, ethanol, methanol, ethylene glycol, 2-methoxyethanol, hexafluoroisopropyl alcohol, ethyl acetate, tetrahydrofuran, acetonitrile, toluene, dipropyl ether, It is preferable that the main component is at least one solvent selected from diethylene glycol dimethyl ether and the like. In particular, when the electrolyte polymer is a perfluoro polymer, diethylene glycol dimethyl ether is preferred, and when the electrolyte polymer is a hydrocarbon polymer, a solvent containing acetone or isopropyl alcohol as a main component is preferred. In addition, "contained as a main component" means that the weight ratio of the poor solvent is the largest, and it is more preferable that the poor solvent contains 50 wt % or more of these liquids.

As the poor solvent, for the purpose of improving purification efficiency, a liquid in which impurities generated by a polymerization reaction or the like are dissolved may be used. It is preferable to use one containing a soluble liquid (hereinafter referred to as "refining aid"). Such a purification aid is preferably miscible with the solvent that is the main component of the poor solvent and the solvent of the polymerization solution. Specifically, water for the purpose of removing water-soluble inorganic salts, unreacted monomer and a good solvent for electrolytic polymers for the purpose of removing low-molecular-weight oligomers, and acid solutions such as sulfuric acid, hydrochloric acid, acetic acid, fluorosulfuric acid, amino acids, and citric acid for the purpose of removing metal impurities. Furthermore, it is more preferable that the poor solvent contains two or more kinds of water, a good solvent for the electrolyte polymer, and an acid solution, since a plurality of kinds of impurities can be removed simultaneously.

The ratio of the purification aid in the poor solvent should be adjusted according to the type and concentration of the electrolyte polymer contained in the polymerization solution, the amount of impurities in the polymerization solution, the solvent of the main component, etc. In this case, it is preferably 1% by weight or more and 20% by weight or less of the poor solvent, and in the case of a hydrocarbon-based polymer, it is preferably 5% by weight or more and 50% by weight or less of the poor solvent. If the amount of the purification aid is too small, the impurities in the electrolyte polymer will not be sufficiently dissolved in the poor solvent, and the purification efficiency may deteriorate. If the amount of the purification aid is too large, the electrolyte polymer may be severely swollen by the purification aid, and processability such as a solid-liquid separation step may be deteriorated.

The total amount of the poor solvent to be used is preferably 3 times or more and 30 times or less with respect to the total amount of the electrolyte polymer solution to be purified. If the total amount of the poor solvent is less than 3 times, the purification efficiency may deteriorate, and if it is more than 30 times, there is a concern that the process cost will increase.

The temperature of the poor solvent is not particularly limited, but is preferably 10° C. or higher and 50° C. or lower, and 20° C., from the viewpoint of purification efficiency, stability of the poor solvent composition, processability such as solid-liquid separation step, and the like. More preferably, the temperature is 30°C or less.

[Cutting process]
Next, the strand-shaped electrolyte polymer extruded into the poor solvent in the extrusion process is subjected to a cutting process of mechanically cutting into chopped strands (discontinuous rods). Since the electrolytic polymer after the extrusion step is swollen in contact with the poor solvent, passing through the separation step described below is improved by passing through the cutting step.

The mechanical cutting method is not particularly limited as long as it can be cut in-line, but an in-line high-shear mixer, crushing pump, or the like is preferably used. Alternatively, shear can be applied using an in-line mixer such as a static mixer, an in-line homomixer, or a homomic line flow. Alternatively, a rotary pump such as a gear pump or vane pump may be used to cut the electrolyte polymer when the poor solvent and strand-like electrolyte polymer pass through the gap between the rotating teeth and the casing.

The breaking stress of the strand electrolyte polymer when cut is preferably 8000 N/m ² or more, more preferably 10000 N/m ² or more. If the breaking stress is less than 8000 N/m ² , the electrolyte polymer will be in an extremely soft state, which may deteriorate the process passability of the solid-liquid separation process described later. Moreover, the breaking stress of the strand electrolyte polymer when cut is preferably 60000 N/m ² or less, more preferably 40000 N/m ² or less. A breaking stress of more than 60,000 N/m ² means that the electrolyte polymer is not swollen by the poor solvent, and in this case, purification efficiency may deteriorate.

Since the electrolyte polymer that has come into contact with the poor solvent during the extrusion process takes time to exchange the solvent, it may be extremely soft immediately after the extrusion process. Therefore, the time from the start of the extrusion process, i.e., the moment the extruded electrolyte polymer comes into contact with the poor solvent, to the time when the electrolyte polymer is cut into chopped strands in the cutting process is set to 2 seconds or longer, whereby the solvent exchange progresses and the electrolyte polymer is cut. It may become moderately hard and easy to cut. From this point of view, it is more preferable that the time from the start of the extrusion process to cutting is 5 seconds or longer.

The chopped strand electrolyte polymer cut by the above cutting step preferably has a length of 5 mm or more and 100 mm or less. If the length of the chopped strand electrolyte polymer is more than 100 mm, it may become entangled with the stirring blades in the solvent exchange process described later, or may clog when being extracted from the reactor, resulting in poor processability. If the length of the chopped strand-like electrolyte polymer is less than 5 mm, the electrolyte polymer becomes porridge-like, which may deteriorate the process passability of the solid-liquid separation process described later.

In addition, the strand diameter of the chopped strand electrolyte polymer can be determined by the hole diameter of the electrolyte polymer outlet. If the strand diameter is too large, the poor solvent and the purification aid cannot sufficiently penetrate into the interior and impurities cannot be sufficiently extracted. Therefore, the strand diameter is preferably 10 mm or less, more preferably 5 mm or less.

Taking overall consideration of the refining efficiency of the electrolyte polymer and the ability to pass subsequent processes, the aspect ratio of the chopped strand-like electrolyte polymer is preferably 5 or more and 60 or less.

[Solvent exchange step]
After the cutting step, a solvent exchange step may be provided for promoting solvent exchange between the solvent of the polymerization solution contained in the chopped strand electrolyte polymer and the poor solvent while the chopped strand electrolyte polymer is held in the poor solvent. preferable. The solvent exchange step can be a step of mixing the poor solvent and the chopped strand electrolyte polymer by stirring or the like. Alternatively, a step of circulating a mixture of the chopped strand electrolyte polymer and the poor solvent through a long pipe may be employed. The time for the solvent exchange step can be appropriately selected depending on the size of the chopped strand electrolyte polymer and the like, but is preferably 20 minutes or more and 200 minutes or less.

[Solid-liquid separation step]
After the cutting step and optionally after the solvent exchange step, it is preferable to provide a solid-liquid separation step for solid-liquid separation of the chopped strand electrolyte polymer and the poor solvent. As a method for separating the chopped strand electrolyte polymer, a known solid-liquid separation method, for example, a decantation method in which the chopped strand electrolyte polymer is naturally precipitated and then the supernatant of the poor solvent is extracted, a cylinder type, a decanter type, or the like. A centrifugal separation method using a centrifuge, vacuum filtration using a Nutsche or the like, pressure filtration using a filter press, or the like can be used. In the present invention, it is preferable to use a centrifugal separation method from the viewpoint of productivity and solid-liquid separation efficiency.

[Washing process]
A washing step may be performed to further remove impurities in the chopped strand electrolyte polymer by adding a poor solvent again to the chopped strand electrolyte polymer separated in the solid-liquid separation step. As the poor solvent added in the washing step, the same poor solvent as the poor solvent described in the extrusion step can be used.

The solid-liquid separation step and the washing step described above may be repeated multiple times.

[Drying process]
After the solid-liquid separation step, a drying step may be performed to remove the poor solvent contained in the chopped strand electrolyte polymer. As a drying method, a known drying method can be used. Specific examples include hot air drying, vacuum drying, infrared drying, superheated steam drying, and microwave drying.

The amount of impurities in the purified electrolyte polymer obtained by the production method of the present invention can be estimated by standing the purified electrolyte polymer in hot water and then measuring the conductivity of the supernatant. The conductivity of the supernatant is preferably 50 μS/cm ⁻¹ or less, more preferably 30 μS/cm ⁻¹ or less. When the conductivity of the supernatant is 50 μS/cm ⁻¹ or less, impurities such as water-soluble inorganic salts, ionic residual monomers, and low-molecular-weight components in the electrolyte polymer are reduced. The deterioration of moldability during processing is reduced. In addition, for example, when used as a fuel cell, impurities are less likely to be extracted and removed by the water generated during power generation, causing voids to form inside the membrane. In addition, in this specification, the conductivity measurement of the supernatant liquid shall be performed by the method as described in an Example.

[Polymer electrolyte membrane]
The chopped strand-shaped purified electrolyte polymer thus produced can be dissolved again in an organic solvent in which the purified electrolyte polymer can be dissolved to obtain a polymer electrolyte composition, that is, a purified electrolyte polymer solution for film formation. can.

A polymer electrolyte membrane can be obtained by forming the polymer electrolyte composition into a membrane. The method for forming the film is not particularly limited, but preferably the polymer electrolyte composition is cast on a support such as a polyethylene terephthalate film, a polyimide film, or a glass substrate, and then heated. A method of removing the organic solvent by the method of is exemplified.

As a method for casting the polymer electrolyte composition on the support, a known method can be used, but it is preferable to cast a solution having a constant concentration so as to have a constant thickness. For example, a doctor blade, an applicator, a bar coater, etc., can be used to force the solution into spaces with a certain gap to make the casting thickness constant, or a slit die can be used to supply the polymer electrolyte composition at a constant rate. and a method of transferring a certain amount of the polymer electrolyte composition onto a support using a gravure roll.

In addition, when forming into a film, the polymer electrolyte composition is compounded with a microporous membrane, woven fabric, non-woven fabric, mesh, etc. for the purpose of improving mechanical strength, thermal stability, processability, etc. is also possible.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these. The measurement conditions for each physical property are as follows.

(1) Number Average Molecular Weight and Weight Average Molecular Weight The number average molecular weight and weight average molecular weight of the polymer electrolyte (A) were measured by the GPC method. Tosoh HLC-8022GPC as an integrated device of an ultraviolet detector and a differential refractometer, and two Tosoh TSK gel SuperHM-H (inner diameter 6.0 mm, length 15 cm) as GPC columns, N-methyl-2 -Pyrrolidone solvent (N-methyl-2-pyrrolidone solvent containing 10 mmol/L of lithium bromide) was measured at a sample concentration of 0.1 wt%, a flow rate of 0.2 mL/min, and a temperature of 40°C, and converted to standard polystyrene. A number average molecular weight and a weight average molecular weight were obtained.

(2) Yield About 2 g of the electrolyte polymer solution (polymerization solution) before purification was taken, and the weight was taken as W1. The separated electrolyte polymer solution was dried under reduced pressure at 250° C. for 1 hour, and the weight after drying was defined as W2. The weight of the electrolyte polymer solution (polymerization solution) actually subjected to purification was W3, and the weight of the purified electrolyte polymer obtained by purification was W4, and the yield was determined by the following formula.

Yield (%) = W1/W2/W3 x W4 x 100
(3) Conductivity measurement of supernatant liquid 1 g of electrolyte polymer to be tested and 100 g of pure water with conductivity of 0.1 μS / cm ⁻¹ or less are placed in a polypropylene container and placed in a constant temperature bath at a temperature of 90 ° C. ± 5 ° C. for 8 hours. left undisturbed. The supernatant was separated, and the conductivity of the supernatant was measured using a conductivity meter (CyberScan CON400, manufactured by Eutech Instruments).

(4) Ion Exchange Capacity The ion exchange capacity of the polymer electrolyte membrane was measured by the neutralization titration method as follows. The measurement was performed 3 times and the average value was taken.
(i) After wiping off moisture on the surface of the film-like sample which had undergone proton substitution and was sufficiently washed with pure water, it was vacuum-dried at 100° C. for 12 hours or longer to determine the dry weight.
(ii) 50 mL of a 5 wt % sodium sulfate aqueous solution was added to the film sample, and the sample was allowed to stand for 12 hours for ion exchange.
(iii) A 0.01 mol/L sodium hydroxide aqueous solution was used to titrate the resulting sulfuric acid. As an indicator, 0.1 w/v % of a commercially available phenolphthalein solution for titration was added, and the end point was defined as a light reddish purple color.
(iv) The ion exchange capacity was determined by the following formula.

Ion exchange capacity (meq/g) = [concentration of sodium hydroxide aqueous solution (mmol/ml) x drop amount (ml)]/dry weight of membrane sample (g)
(5) Film thickness The film thickness of the polymer electrolyte membrane was measured using Mitutoyo ID-C112 type set in Mitutoyo granite comparator stand BSG-20.

(6) Measurement of Hydrogen Permeability Hydrogen gas was supplied to one side of the polymer electrolyte membrane to be tested, and the other side was evacuated to create a pressure difference to permeate the hydrogen gas. After the hydrogen gas reached a steady state, the evacuation was stopped, and the hydrogen gas that permeated the electrolyte membrane during the time t was stored in the metering tube. The stored gas was quantified with a thermal conductivity detector, and the permeability P for hydrogen gas was obtained from the following equation.

Q=P×(p _h −p _l )/A×t
Here, Q is the hydrogen gas permeation amount (cm ³ ), P is the hydrogen gas permeability, _ph is the hydrogen gas high pressure side, _pl is the hydrogen gas low pressure side pressure = 0, and A is the hydrogen gas in the electrolyte membrane. permeation area (cm ² ), t represents the time (permeation time) (s) for storing the permeation gas.

The measurement conditions are as follows.

Apparatus: Differential pressure type gas permeability measurement system manufactured by GTR Tech Co., Ltd. Measurement temperature: 80°C
Humidity: 90%
Test gas: mixed gas of dry hydrogen and water vapor Hydrogen gas partial pressure: 44 cmHg
Gas permeation area: ^15.2cm2
Measurement n number: 2
[Synthesis Example 1] Synthesis of block copolymer b1 (Synthesis of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane (K-DHBP) represented by the following general formula (G1))

495 g of 4,4'-dihydroxybenzophenone, 1340 g of ethylene glycol, 969 g of trimethyl orthoformate and 5 g of p-toluenesulfonic acid monohydrate were placed in a 5000 mL flask equipped with a stirrer, thermometer and distillation tube and dissolved. After that, the mixture was heated and stirred at 78 to 82°C for 2 hours. Further, the internal temperature was gradually raised to 120° C., and the mixture was heated until distillation of methyl formate, methanol and trimethyl orthoformate stopped completely. After cooling the reaction solution to room temperature, the reaction solution was diluted with ethyl acetate, and the organic layer was washed with 1000 mL of a 5% potassium carbonate aqueous solution to separate the layers, and the solvent was distilled off. 800 mL of dichloromethane was added to the residue to precipitate crystals, which were filtered and dried to obtain 520 g of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane.

(Synthesis of disodium 3,3'-disulfonate-4,4'-difluorobenzophenone represented by the following general formula (G2))

1091 g of 4,4'-difluorobenzophenone (Aldrich Reagent) was reacted in 1500 mL of fuming sulfuric acid (50% SO3) (Wako Pure Chemical Reagent) at 100°C for 10 hours. After that, it was gradually poured into a large amount of water, neutralized with NaOH, and then 2000 g of salt was added to precipitate the compound. The resulting precipitate was filtered off and recrystallized with an isopropyl alcohol aqueous solution to obtain disodium 3,3'-disulfonate-4,4'-difluorobenzophenone represented by the general formula (G2).

(Synthesis of oligomer a1' containing no ionic group represented by the following general formula (G3))
165.9 g of potassium carbonate (Aldrich's reagent), 258.0 g of K-DHBP and 203.0 g of 4,4'-difluorobenzophenone (Aldrich's reagent) were placed in a 10000 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap. After dehydration at 160° C. in 3000 mL of N-methyl-2-pyrrolidone (NMP) and 1000 mL of toluene, the temperature was raised to remove toluene, followed by polymerization at 180° C. for 1 hour. Purification was performed by reprecipitation with a large amount of methanol to obtain oligomer a1 (terminal hydroxyl group) containing no ionic group. The number average molecular weight was 10,000.

A 5000 mL three-necked flask equipped with a stirrer, a nitrogen introduction tube, and a Dean-Stark trap is charged with 11.0 g of potassium carbonate (Aldrich reagent) and 200.0 g of the oligomer a1 (terminal hydroxyl group) containing no ionic group, and nitrogen is added. After substitution, dehydration was carried out at 100° C. in 1000 mL of NMP and 300 mL of cyclohexane, and the temperature was raised to remove cyclohexane. Purification was performed by reprecipitation with a large amount of isopropyl alcohol to obtain an ionic group-free oligomer a1' (terminal fluoro group) represented by the following formula (G3). The number average molecular weight was 11,000, and the number average molecular weight of oligomer a1' containing no ionic group was found to be 10,400, a value obtained by subtracting the linker site (molecular weight 630).

(Synthesis of oligomer a2 containing an ionic group represented by the following general formula (G4))
276.0 g of potassium carbonate (Aldrich's reagent), 129.0 g of K-DHBP and 93.0 g of 4,4'-biphenol (BP, Aldrich's reagent) were added to a 10000 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap. , disodium 3,3'-disulfonate-4,4'-difluorobenzophenone 393.0 g and 18-crown-6, 179.0 g (Wako Pure Chemical Reagent). After dehydration at 170° C., the temperature was raised to remove toluene, and polymerization was carried out at 180° C. for 1 hour. Purification was performed by reprecipitation with a large amount of isopropyl alcohol to obtain an oligomer a2 (terminal hydroxyl group) containing an ionic group represented by the following formula (G4). The number average molecular weight was 16,000.

(In formula (G4), M represents Na or K.)
(Synthesis of oligomer a2 as segment (A1) containing ionic group, oligomer a1 as segment (A2) not containing ionic group, block polymer b1 containing hexafluorobenzene as linker site)
16.8 g of potassium carbonate (Aldrich's reagent) and 480 g of oligomer a2 containing an ionic group (terminal hydroxyl group) were placed in a 5000 mL three-necked flask equipped with a stirrer, a nitrogen inlet tube, and a Dean-Stark trap. After dehydration at 100° C. in 3000 mL of NMP and 900 mL of cyclohexane, the temperature was raised to remove cyclohexane. 330 g of oligomer a1′ (terminal fluoro group) containing no ionic group was added, reacted at 105° C. for 24 hours, and then diluted with 1470 mL of NMP to obtain block polymer b1 solution. The weight average molecular weight of block polymer b1 was 360,000.

[Synthesis Example 2] Synthesis of block copolymer b2 (Synthesis of oligomer a3 containing no ionic group represented by the following formula (G5))
49.97 g of 2,6-dichlorobenzonitrile (DCBN, Aldrich's reagent), 54.99 g of 4,4'-biphenol (Aldrich's reagent), 46.94 g of potassium carbonate (Aldrich's reagent), 750 mL of N-methyl-2-pyrrolidone, 150 mL of toluene was placed in a 1000 mL side-arm flask equipped with a nitrogen inlet tube, a stirring blade, a Dean-Stark trap, and a thermometer, and heated in an oil bath under nitrogen while stirring. After azeotropic dehydration with toluene was carried out at 140° C., all toluene was distilled off. After that, the temperature was raised to 200° C. and heated for 15 hours. 200 mL of NMP and 4.85 g of decafluorobiphenyl (Wako Pure Chemical Reagent) were added to another 1000 mL branched flask equipped with a nitrogen inlet tube, a stirring blade, a cooling reflux tube, and a thermometer. Heated to 110° C. in a bath. A reaction solution of DCBN and BP was added thereto over 2 hours with stirring using a dropping funnel, and after the addition was completed, the mixture was further stirred for 2 hours. After the reaction solution was cooled to room temperature, it was poured into 3000 mL of pure water to solidify the oligomer. After the water-washed oligomer was separated by filtration and dried under reduced pressure, it was washed twice with 3000 mL of acetone to remove excess decafluorobiphenyl. The oligomer was again filtered off and dried under reduced pressure to obtain an oligomer a3 containing no ionic group. The number average molecular weight was 13,880.

(Synthesis of oligomer a4 containing an ionic group represented by the following formula (G6))
250.0 g of sodium 4,4'-dichlorodiphenylsulfone-3,3'-disulfonate (SDCDPS, Aldrich's reagent), 97.04 g of BP (Aldrich's reagent), 66.23 g of sodium carbonate (Aldrich's reagent), 650 mL of NMP, and 150 mL of toluene , a nitrogen inlet tube, a stirring blade, a Dean-Stark trap, and a 2000 mL branched flask equipped with a thermometer, and heated under a nitrogen stream while stirring in an oil bath. After azeotropic dehydration with toluene was carried out at 140° C., all toluene was distilled off. After that, the temperature was raised to 200° C. and heated for 16 hours. Subsequently, 500 mL of NMP was added, and the mixture was cooled to room temperature while stirring. The obtained solution was suction-filtered through a glass filter to obtain a yellow transparent solution. The resulting solution was added dropwise to 3 L of acetone to solidify the oligomer. The oligomer was further washed with acetone three times, filtered and dried under reduced pressure to obtain oligomer a4 containing an ionic group. The number average molecular weight was 25,560.

(Synthesis of oligomer a4 as segment containing ionic group, oligomer a3 as segment containing no ionic group, block polymer b2 containing decafluorobiphenyl as linker site)
225.0 g of the above oligomer a4 containing an ionic group, 123.0 g of the oligomer a3 not containing an ionic group, 1.4 g of sodium carbonate (Aldrich reagent), NMP 2000 mL, a nitrogen introduction tube, a stirring blade, Dean Stark The mixture was placed in a 5000 mL branched flask equipped with a trap and a thermometer, stirred in an oil bath at 50°C under a nitrogen stream to dissolve, then heated to 110°C and reacted for 10 hours to obtain a block copolymer b2 solution. The weight average molecular weight of block polymer b2 was 330,000.

[Synthesis Example 3] Synthesis of ionic group-containing perfluoro polymer b3 (Synthesis of ionic group-containing perfluoro polymer b3 represented by the following formula (G7))
150 g of a 20% by weight aqueous solution of CF3(CF2)6CO2NH4 and 2850 g of pure water were charged into a 6000 ml stainless steel stirring autoclave, and the autoclave was sufficiently vacuumed and replaced with nitrogen. After the autoclave was sufficiently evacuated, tetrafluoroethylene (hereinafter sometimes abbreviated as TFE) gas was introduced to a gauge pressure of 0.2 MPa, and the temperature was raised to 50°C. Thereafter, 180 g of CF ₂ =CFOCF ₂ CF ₂ SO ₂ F was injected, and TFE gas was introduced to increase the gauge pressure to 0.7 MPa. Subsequently, 30 g of a 5% ammonium persulfate aqueous solution was injected to initiate polymerization.

In order to replenish the TFE consumed by the polymerization, TFE gas was continuously supplied to keep the pressure of the autoclave at 0.7 MPa. Further, an amount of CF ₂ =CFOCF ₂ CF ₂ SO ₂ F corresponding to 0.65 times the mass ratio of TFE supplied was continuously supplied to continue the polymerization.

When the supplied TFE reached 780 g, the pressure in the autoclave was released to stop the polymerization. After cooling to room temperature, 4450 g of a slightly cloudy ionic group-containing perfluoro polymer aqueous dispersion containing about 28% by mass of the ionic group-containing perfluoro polymer containing SO ₂ F was obtained.

780 g of 48% by weight KOH and 2820 g of pure water were added to 4200 g of the obtained ionic group-containing perfluoro polymer aqueous dispersion, and the mixture was reacted at 80° C. for 20 hours to obtain an ionic group-containing perfluoro polymer b3. 9480 g of an aqueous dispersion of

[Example 1]
Using a mixed solvent of 6000 g of isopropyl alcohol, 2000 g of NMP and 2000 g of water as a poor solvent, 1000 g of the block polymer b1 solution obtained in Synthesis Example 1 was purified.

A poor solvent is passed through the extruding part shown in FIG. (extrusion process). After providing a pipe having a length through which the poor solvent can pass 5 seconds after the discharge, a cutting portion was provided. A homomic line flow LF-100 manufactured by Primix Co., Ltd. was used for the cutting section, and the strand electrolyte polymer was cut at 3000 rpm to obtain a chopped strand electrolyte polymer having a length of 20 mm and a diameter of 3 mm (cutting step). The chopped strand electrolyte polymer and the poor solvent were mixed by stirring in a 50 L reaction vessel for 1 hour (solvent exchange step), extracted from the reaction vessel, and subjected to solid-liquid separation by small basket type centrifugation (solid-liquid separation step). Then, it was washed with a mixed solvent of 8000 g of isopropyl alcohol and 2000 g of water (washing step). After repeating the solid-liquid separation step and washing step three times, vacuum drying was performed at 100° C. and 1.0×10 ⁻³ MPa for 48 hours (drying step) to obtain a purified electrolyte polymer.

The processability was good, and the yield was 85%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 22 μS/cm ⁻¹ .

20 g of the resulting purified electrolyte polymer was dissolved in 80 g of N-methyl-1-pyrrolidone, filtered under pressure using a glass fiber filter, cast on a polyethylene terephthalate film using an applicator, and coated at 150° C. for 1 hour. After drying for an hour, an electrolyte membrane was obtained. After being immersed in a 10% by weight sulfuric acid aqueous solution at 50° C. for 24 hours for proton substitution, it was thoroughly washed by being immersed in a large excess amount of pure water for 24 hours to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.8×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 2]
A chopped strand-like electrolyte polymer having a length of 20 mm and a diameter of 1 mm was obtained in the same manner as in Example 1, except that the diameter of the electrolyte polymer discharge port was changed to 1 mm. The processability was good, and the yield was 80%. For the electrolyte polymer obtained, the conductivity of the supernatant was 18 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.6×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 3]
A chopped strand-like electrolyte polymer having a length of 20 mm and a diameter of 10 mm was obtained in the same manner as in Example 1, except that the diameter of the electrolyte polymer discharge port was changed to 10 mm. The processability was good, and the yield was 86%. For the electrolyte polymer obtained, the conductivity of the supernatant was 36 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.9×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 4]
A chopped strand-like electrolyte polymer having a length of 5 mm and a diameter of 3 mm was obtained in the same manner as in Example 1, except that the rotation speed of the homomic line flow manufactured by Primix Co., Ltd. was changed to 8000 rpm. The yield was 72% because clogging occurred in the filter cloth during the solid-liquid separation step. The conductivity of the supernatant was 16 μS/cm ⁻¹ for the resulting purified electrolyte polymer.

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.6×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 5]
A chopped strand-like electrolyte polymer having a length of 30 mm and a diameter of 3 mm was obtained in the same manner as in Example 1, except that a Nikuni wet crusher Sancutta C125H was used for the cutting portion. The processability was good, and the yield was 86%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 20 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.7×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 6]
A chopped strand electrolyte polymer having a length of 20 mm and a diameter of 3 mm was obtained in the same manner as in Example 1, except that a pipe having a length through which the poor solvent passed over 3 seconds was provided between the extruded portion and the cut portion. . The processability was good, and the yield was 84%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 24 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.8×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 7]
A chopped strand electrolyte polymer having a length of 20 mm and a diameter of 3 mm was obtained in the same manner as in Example 1 except that a mixed solvent of 8000 g of isopropyl alcohol and 2000 g of water was used as a poor solvent. The processability was good, and the yield was 82%. The conductivity of the supernatant was 49 μS/cm ⁻¹ for the resulting purified electrolyte polymer.

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 2.1×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 8]
A chopped strand electrolyte having a length of 20 mm and a diameter of 3 mm was prepared in the same manner as in Example 1, except that a mixed solvent of 7000 g of isopropyl alcohol, 1000 g of NMP, and 2000 g of water was used as a poor solvent, and the block copolymer b2 synthesized in Synthesis Example 2 was purified. A polymer was obtained. The processability was good, and the yield was 81%. For the purified electrolyte polymer obtained, the conductivity of the supernatant was 29 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 2.8×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 9]
A chopped strand-like electrolyte polymer having a length of 30 mm and a diameter of 3 mm was obtained in the same manner as in Example 8, except that a wet crusher Sancutta C125H manufactured by Nikuni Co., Ltd. was used for the cutting portion. The processability was good, and the yield was 82%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 27 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 2.9×10 ⁻¹⁰ kmol/s/m ² /kPa.

[Example 10]
In the same manner as in Example 1, except that a mixed solvent of 9500 g of diethylene glycol dimethyl ether and 500 g of water was used as a poor solvent, and 1000 g of the ionic group-containing perfluoro polymer b3 aqueous dispersion synthesized in Synthesis Example 3 was purified. , a chopped strand-like electrolyte polymer with a diameter of 3 mm was obtained. The processability was good, and the yield was 76%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 24 μS/cm ⁻¹ .

20 g of the resulting purified electrolyte polymer, 40 g of water, and 40 g of isopropyl alcohol were placed in a stainless steel stirring autoclave and dispersed. After pressure filtration using a glass fiber filter, the mixture was applied by casting onto a glass substrate using an applicator and dried at 150° C. for 1 hour to obtain an electrolyte membrane. After being immersed in a 10% by weight sulfuric acid aqueous solution at 50° C. for 24 hours for proton substitution and deprotection reaction, it was thoroughly washed by being immersed in a large excess amount of pure water for 24 hours to obtain a polymer electrolyte membrane with a thickness of 15 μm. . The hydrogen permeability of the obtained polymer electrolyte membrane was 1.4×10 ⁻⁹ kmol/s/m ² /kPa.

[Example 11]
A chopped strand electrolyte polymer having a length of 30 mm and a diameter of 3 mm was obtained in the same manner as in Example 10, except that a Nikuni wet crusher Sancutta C125H was used for the cutting part. The processability was good, and the yield was 78%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 25 μS/cm ⁻¹ .

In the same manner as in Example 10, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 15 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.6×10 ⁻⁹ kmol/s/m ² /kPa.

[Example 12]
A chopped strand-like electrolyte polymer having a length of 20 mm and a diameter of 3 mm was prepared in the same manner as in Example 1, except that a pipe having a length through which the poor solvent passed over 0.5 seconds was provided between the extrusion part and the cutting part. Obtained. Clogging occurred in the homomic line flow and the yield was 53%. For the resulting purified electrolyte polymer, the conductivity of the supernatant was 27 μS/cm ⁻¹ .

In the same manner as in Example 1, it was processed into a membrane to obtain a polymer electrolyte membrane with a thickness of 10 μm. The hydrogen permeability of the obtained polymer electrolyte membrane was 1.8×10 ⁻¹⁰ kmol/s/m ² /k.

Claims (9)

an extrusion step of extruding a polymerization solution of an electrolyte polymer into a poor solvent in which the electrolyte polymer has a lower solubility than the solvent of the polymerization solution and is miscible with the solvent of the polymerization solution in the form of strands; The step of mechanically cutting the electrolyte polymer into chopped strand-like electrolyte polymers is continuously performed in-line , and impurities contained in the polymerization solution of the electrolyte polymer can be dissolved in the poor solvent. A method for producing a purified electrolyte polymer, comprising : After the cutting step, a solvent exchange step of promoting solvent exchange between the poor solvent and the solvent of the polymerization solution contained in the chopped strand electrolyte polymer while the chopped strand electrolyte polymer is held in the poor solvent. The method for producing a purified electrolyte polymer according to claim 1, having 3. The method for producing a purified electrolyte polymer according to claim 1, further comprising a solid-liquid separation step of solid-liquid separating said chopped strand electrolyte polymer and said poor solvent. 4. The method for producing a purified electrolyte polymer according to any one of claims 1 to 3, wherein the time from the start of the extrusion step to the cutting in the cutting step is 2 seconds or longer. 5. The method for producing a purified electrolyte polymer according to any one of claims 1 to 4, wherein the chopped strand-like electrolyte after the cutting step has an aspect ratio of 5 or more and 60 or less. 6. The method for producing a purified electrolyte polymer according to any one of claims 1 to 5, wherein the strand electrolyte polymer has a breaking stress of 8000 N/m ² or more and 60000 N/m ² or less when cut in the cutting step. The method for producing a purified electrolyte polymer according to any one of claims 1 to 6 , wherein the electrolyte polymer is a hydrocarbon-based electrolyte polymer. The method for producing a purified electrolyte polymer according to any one of claims 1 to 7 , wherein the electrolyte polymer has a molecular weight of 50,000 or more. Production of a polymer electrolyte membrane by forming a polymer electrolyte composition by dissolving the purified electrolyte polymer obtained by the method for producing a purified electrolyte polymer according to any one of claims 1 to 8 in a good solvent for the electrolyte polymer. Method.