JP2009185250A - Manufacturing method of isolated polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an isolated polymer which can be employed to manufacture an electrolyte polymer that is almost free from a remaining solvent to be highly pure as well as an electrolyte film that is excellent for use in an electrochemical device, a fuel cell, and a direct alcohol type fuel cell. <P>SOLUTION: It has been found that a sulfonated aromatic polyether is dissolved in a water/acetone base mixed solvent, and further, the polyether exhibits excellent solubility in the mixed solvent at a specific amount of the sulfonate group introduced in the polymer and a specific rate of the components in the mixed solvent, and forms a polymer solution that is homogeneous and has a low viscosity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an isolated polymer, and can be applied to the production of a high purity electrolyte polymer with little residual solvent and the efficient production of an electrolyte membrane. The electrolyte membrane is excellent for electrochemical devices, particularly for fuel cells, and more specifically for direct alcohol fuel cells.

  As global environmental protection activities become more active, so-called greenhouse gas and NOx emission prevention is strongly screamed. In order to reduce the total emission amount of these gases, it is considered that practical application of a fuel cell system for automobiles is very effective.

  A polymer electrolyte fuel cell (PEFC), which is a type of electrochemical device using a polymer electrolyte membrane, has excellent features such as low temperature operation, high output density, and low environmental impact. . Among them, PEFC, which is a methanol fuel, can be supplied as a liquid fuel in the same manner as gasoline, and thus is considered promising as a power source for electric vehicles and a power source for portable devices.

When using methanol as a fuel, PEFC is divided into a reformed methanol type that uses a reformer to convert methanol into a hydrogen-based gas, and a direct methanol type that uses methanol directly without using a reformer (DMFC, It is divided into two types, Direct Methanol Polymer Fuel Cell). Since DMFC does not require a reformer, it has great advantages such as being able to reduce weight, and its practical use is expected.

  However, when an electrolyte membrane for DMFC is a perfluoroalkylsulfonic acid membrane that is an electrolyte membrane for PEFC using conventional hydrogen as a fuel, such as a Nafion (registered trademark) membrane manufactured by Du Pont, Since methanol permeates the membrane, there is a problem that the electromotive force decreases. Furthermore, these electrolyte membranes also have an economic problem that they are very expensive.

As means for solving the above problem, Patent Document 1 proposes an electrolyte membrane in which a porous base material such as polyimide, crosslinked polyethylene, etc., which is inexpensive and hardly deformed by external force, is filled with a polymer having proton conductivity. Has been made. However, since the electrolyte membrane includes a step of subjecting the base material to plasma irradiation and graft polymerization of the polymer, there is a problem of an increase in manufacturing equipment cost. In addition, the durability when continuously operating as a fuel cell was not sufficient.

Further, Patent Document 2 discloses an electrolyte membrane formed by filling pores of a porous substrate that does not substantially swell with an organic solvent containing methanol and water with a first polymer having proton conductivity. An electrolyte membrane has been proposed in which the first polymer is a polymer derived from 2-acrylamido-2-methylpropanoic acid. However, the durability of the electrolyte membrane described in this patent document is still insufficient.
JP 2002-83612 A International Publication No. 03/075386 Pamphlet

Among hydrocarbon-based electrolytes, a polymer in which an ion exchange group such as a sulfonic acid group is introduced into an aromatic polyether is known as a polymer excellent in oxidation resistance and heat resistance. For example, sulfonated polyether ketone (Patent Document 3), sulfonated polyethersulfone (Patent Document 4) and the like have been proposed.
Japanese National Patent Publication No. 11-502249 Japanese Patent Laid-Open No. 10-45913

  However, since aromatic polyethers as described above are insoluble in common low-boiling solvents, high-boiling polar aprotic solvents are commonly used, and as a result, polymers are isolated and purified and formed into electrolyte membranes. There was a problem of poor workability and productivity in the film process. The object of the present invention is to solve these problems, that is, to provide a method for producing a purified resin and an electrolyte membrane excellent in workability and productivity by using a low boiling point, low toxicity and inexpensive solvent. is there.

  The present inventors have intensively studied to solve the above problems. First, it was found that introduction of a sulfone group into an aromatic polyether increases the hydrophilicity, but it is difficult to completely dissolve in water. Therefore, when extensively searching for a mixed system of water and a low-boiling organic solvent, the water / acetone mixed solvent dissolves the sulfonated aromatic polyether, and further, at a specific sulfone group introduction amount and a specific mixing ratio. It has been found that a polymer solution having good solubility and a uniform and low viscosity can be obtained.

  By using the mixed solvent, it was found that the sulfonated aromatic polyether can be easily isolated and purified, and a high-purity electrolyte membrane can be easily formed, and the present invention has been completed.

  Hereinafter, the present invention will be described in detail.

（式中、Ｘ、Ｙは独立に芳香族の二価の基を表し、繰返し数ｎは１〜１００の整数である。） <Sulfonated aromatic polyether>
In the sulfonated aromatic polyether used in the present invention, the main component of the main chain is composed of an aromatic ring, at least a part of the bonds between the aromatic rings is an ether bond, and a sulfonic acid group is part of the aromatic ring. A polymer having a structure bonded directly or via a spacer.
Sulfonated aromatic polyethersulfone having an ether bond (—O—) and a sulfone group (—SO ₂ —) at the bond between aromatic rings, an ether bond (—O—), and a ketone group (—CO—) A sulfonated aromatic polyether ketone having the following formula is preferably used.
A preferred sulfonated aromatic polyether skeleton structure has a molecular structural unit represented by Formula 1.

(In the formula, X and Y independently represent an aromatic divalent group, and the repeating number n is an integer of 1 to 100.)

  A typical method for producing the sulfonated aromatic polyether is condensation polymerization of a diol that forms the structural unit X and a compound that has two leaving groups that form the structural unit Y. The leaving group at this time is a functional group that can be eliminated by a nucleophilic substitution reaction with a hydroxyl group, a halogen group such as a chloro group, a bromo group, or an iodo group, a p-toluenesulfonyloxy group, a methanesulfonyloxy group, Examples thereof include sulfonic acid ester groups such as trifluoromethanesulfonyloxy group.

  Representative examples of the structural units X and Y include 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 2-phenyl-1,4-phenylene, 2-phenoxy-1,4-phenylene, 1 , 4-naphthylene, 2,3-naphthylene, 1,5-naphthylene, 2,6-naphthylene, 2,7-naphthylene, biphenyl-4,4′-diyl, biphenyl-3,3′-diyl, biphenyl-3 , 4′-diyl, 3,3′-diphenylbiphenyl-4,4′-diyl, 3,3′-diphenoxybiphenyl-4,4′-diyl, 2,2′-diphenylpropane-4,4′- Diyl, diphenyl ether-4,4′-diyl, diphenylsulfone-4,4′-diyl, benzophenone-4,4′-diyl and the like can be mentioned.

In the present invention, at least one of the structural units X and Y includes a sulfonic acid group —SO ₃ M. Here, M means hydrogen, a metal atom or quaternary ammonium. When M is a metal atom, it is preferably an alkali metal atom or an alkaline earth metal atom because the oxidation reaction is not promoted even if it is easily exchanged with a hydrogen atom and remains. As a bonding mode of the sulfonic acid group, a structure bonded to an aromatic ring directly or via an alkyl group can be used.

  The concentration of the ion exchange group in the aromatic polyether is preferably 1.5 to 5.0 mmol / g because the higher the concentration, the better the conductivity, while the lower the concentration, the better the water resistance and durability. 2.0 to 4.0 mmol / g is more preferable, and 2.2 to 3.5 mmol / g is more preferable.

（式中、ＭはＨ，Ｎａ，Ｋ，Ｌｉ，ＮＨ₄の中から１つまたは複数を選択できる基を表し、ｎは０〜２、ｍは０〜２の正数を表す。）
As the sulfonated aromatic polyether used in the present invention, a sulfonated aromatic polyethersulfone having a structural unit of the following formula 2 of 60% by weight or more can be particularly preferably used.

(In the formula, M represents a group capable of selecting one or more of H, Na, K, Li, and NH ₄ , n represents 0 to 2, and m represents a positive number of 0 to 2.)

  The average number of sulfonic acid groups in the structural unit is preferably 1 to 4, more preferably 1.5 to 3. As a method for introducing a sulfonic acid group, introduction at a monomer stage, that is, a method in which a sulfonic acid group-containing monomer is prepared in advance and used as a polymerization raw material, and a sulfonic acid group is introduced into an aromatic ring by a sulfonation reaction after polymerization. There is a way. Any method may be used, but introduction at the monomer stage is preferable because the control of the sulfonic acid group content is easy.

<Water / acetone mixed solvent>
In the present invention, the weight ratio of the water / acetone mixed solvent used as the solvent for the sulfonated aromatic polyether is 95/5 to 30/70, preferably 90/10 to 40/60. By setting the mixing ratio within this range, a sulfonated aromatic polyether solution having a uniform and low viscosity can be prepared.

  Since water and acetone, which are constituent components, have a low boiling point, compared with general-purpose polar aprotic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, dimethylimidazolidinone, ethylene carbonate, propylene carbonate, etc. Solvent removal from the polymer is very easy.

  In some cases, components other than water / acetone, for example, other solvents, catalysts, curing agents, initiators, surfactants, stabilizers and the like may be contained in small amounts. The allowable content of these components is 50 parts by weight or less, preferably 30 parts by weight or less, more preferably 20 parts by weight or less, based on 100 parts by weight of the water / acetone mixed solvent.

<Polymer isolation step>
The polymer isolation step in the present invention means a step of obtaining a high purity sulfonated aromatic polyether by removing the solvent from the solution of the sulfonated aromatic polyether. Specifically, the following three steps (1) to (3) may be mentioned and will be described in detail below.

(1) A step of mixing a precipitant with a sulfonated aromatic polyether solution to precipitate a polymer, drying the precipitated polymer and removing the solvent. The synthesis reaction of the sulfonated aromatic polyether is usually carried out in a solution, The reaction solution immediately after the synthesis contains a solvent, catalyst, residual raw material, by-product and the like in addition to the sulfonated aromatic polyether. In order to isolate the sulfonated aromatic polyether, usually, a precipitating agent is added to the reaction solution to aggregate and precipitate the polymer, and the precipitated polymer is dried to obtain an isolated polymer. By repeating this process several times, a high-purity sulfonated aromatic polyether can be obtained.

  In the conventional method using a general-purpose polar aprotic solvent, although the catalyst, the remaining raw material, and the by-product can be removed, the polar aprotic solvent easily remains in the polymer because of its high boiling point. On the other hand, since a low boiling point water / acetone mixed solvent is used in the present invention, the solvent can be completely removed even under mild drying conditions.

As the precipitant used in this case, various organic solvents and water that do not dissolve the sulfonated aromatic polyether are used. As the organic solvent, those having a boiling point of 150 ° C. or less among various aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, ester solvents, ketone solvents, alcohol solvents and ether solvents are preferably used. More preferably, the boiling point is 130 ° C. or lower.
Specific examples of organic solvents that can be used as the precipitating agent include pentane, hexane, cyclohexane, heptane, octane, ethyl acetate, propyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropyl alcohol, butanol, tetrahydrofuran Hexane, cyclohexane, ethyl acetate, acetone, methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, and tetrahydrofuran are preferably used, and acetone, methyl ethyl ketone, methanol, ethanol, isopropyl alcohol are more preferable. Used. These solvents can also be used as a mixed solvent of two or more components.

  The concentration of the sulfonated aromatic polyether solution used in this step is preferably 2% to 50% by weight, more preferably 4% to 30% by weight. Further, the mixing weight ratio of the solvent / precipitating agent to be used is preferably 50/50 to 5/95, and more preferably 30/70 to 10/90. As a mixing method, either a method of adding a precipitant into a stirred sulfonated aromatic polyether solution or a method of adding a sulfonated aromatic polyether solution into a stirred precipitant may be used.

  The polymer precipitate formed by mixing with the precipitating agent is separated from the liquid by decantation or filtration, and the solvent and the precipitating agent can be removed by heating at normal temperature or under reduced pressure at room temperature or heating.

(2) Step of obtaining an electrolyte membrane by evaporating a solvent under normal pressure or reduced pressure after forming a sulfonated aromatic polyether solution A typical method for preparing an electrolyte membrane of sulfonated aromatic polyether is a polymer In this method, a solution is formed into a film using a coater or the like, and the solvent is evaporated under normal pressure or reduced pressure to obtain a film. Usually used polar aprotic solvents have a high boiling point, so that it takes a long time to obtain an electrolyte film, and the solvent tends to remain in the electrolyte membrane. In the present invention, since a low boiling point water / acetone mixed solvent is used, the evaporation rate is high and the productivity is excellent. In addition, a high-purity sulfonated aromatic polyether electrolyte membrane can be obtained with little residual solvent in the film.

  Moreover, in this invention, it can be set as a high concentration and low-viscosity solution by adjusting the mixing ratio of water / acetone according to the composition of the sulfonated aromatic polyether. Accordingly, the variable range of the thickness of the electrolyte membrane is wide and the thickness can be easily controlled.

  The formed film is dried under normal pressure or reduced pressure, and the solvent is evaporated by heating as necessary. Since the low boiling point acetone volatilizes mainly in the initial drying process, the volatilization rate is sufficiently fast even at normal pressure and room temperature. Since water is mainly volatilized in the latter stage of drying, heating and / or decompression may be performed as necessary to promote evaporation.

(3) A step of impregnating a porous substrate with a sulfonated aromatic polyether solution and performing a crosslinking treatment as necessary, and then removing the solvent by drying or washing with water to obtain an electrolyte membrane. Even when a composite film filled with a group polyether is prepared, removal of the solvent is facilitated by using a water / acetone mixed solvent. In addition, since the solution viscosity is low, the polymer concentration can be increased as compared with a normal polar aprotic solvent, and the filling amount into the porous substrate can be increased. In addition, organic polymer porous substrates are often not practically usable because they easily dissolve or swell in polar aprotic solvents. On the other hand, since the water / acetone mixed solvent does not attack the engineering plastic polymer frequently used as the porous substrate, these porous substrates can be used freely.

  When the residual solvent is removed by washing with water instead of drying, wastewater treatment may be necessary because the COD of the wastewater is increased by the solvent extracted into water. If a water / acetone mixed solvent is used, the COD component itself is small and removal is very easy.

  Depending on the composition of the sulfonated aromatic polyether used, water-soluble components gradually elute into water during use as an electrolyte membrane, and the durability of the electrolyte membrane may be poor. In such a case, a crosslinking treatment may be performed to insolubilize the water, followed by drying or washing with water.

  The form of the isolated polymer is determined by the above-mentioned isolation process. In the case of (1), it is indeterminate (powder, granule, pellet, rubber, etc.), and (2) and (3) are films. . In the following section, step (3) will be described in more detail.

<Porous substrate>
The porous substrate used in the polymer isolation step (3) is preferably a material that does not substantially swell with respect to methanol and water. It is desirable that there is little.

  Although the area increase rate varies depending on the immersion time and temperature, the porous substrate used in the present invention has an area increase rate of 20% at the maximum when immersed in pure water at 25 ° C. for 1 hour compared to the time of drying. The following is preferable.

  Further, the porous substrate is preferably one having heat resistance against the temperature at which the fuel cell is operated, and one that does not easily extend even when an external force is applied.

  Examples of the material having such a property include inorganic materials such as glass or ceramics such as alumina or silica. For organic materials, polyimide, polyamideimide, polyetherimide, polyethersulfone, polyetherketone, polyphenylene ether, polyphenylene sulfide, and other aromatic polymers and polyolefins are crosslinked or stretched by applying radiation or a crosslinking agent. And the like, which are difficult to be deformed such as extending with respect to an external force. These materials may be used alone or in combination by stacking two or more of them.

  Among these porous substrates, aromatic polymers such as stretched polyolefins, crosslinked polyolefins, stretched polyolefins, polyimides, polyamideimides, and polyethersulfones have good workability in the filling process, and the substrate is available. It is preferable also from the point of easiness.

  The porosity of the porous substrate used in the present invention is preferably from 5 to 95%, more preferably from 20 to 80%, since the conductivity of the electrolyte membrane is improved when the membrane strength is maintained within the range where the membrane strength is maintained. is there.

  Moreover, it is preferable that an average hole diameter exists in the range of 0.001-100 micrometers, More preferably, it is the range of 0.01-10 micrometers. The average pore diameter can be obtained by a method such as a gas adsorption pore distribution meter, a mercury porosimeter, or an electron micrograph.

  Furthermore, the thicker the substrate, the better the film strength, but the thinner the film, the smaller the film resistance, and the more preferable is 200 μm or less. More preferably, it is 1-150 micrometers, More preferably, it is 5-100 micrometers.

<Crosslinking treatment>
In the present invention, for the purpose of improving the durability of the sulfonated aromatic polyether filled in the porous substrate, a crosslinking treatment can be performed as necessary. Examples of the crosslinking method include a method in which a reactive group is introduced into a sulfonated aromatic polyether molecule in advance, and the porous substrate is filled with heat and then light.

  At this time, a low molecular compound such as a crosslinking agent, a curing agent, a curing accelerator, a catalyst, an initiator, or a surfactant can also be used in order to efficiently perform the crosslinking reaction. These compounds may be added in advance to the sulfonated aromatic polyether solution.

  For example, when photoinitiated polymerization with vinyl groups is used for crosslinking, a sulfonated aromatic polyether having a vinyl group in the molecule is prepared in advance, and a solution containing a low molecular weight vinyl compound or a photoinitiator is porous. What is necessary is just to impregnate a base material and to irradiate an ultraviolet-ray and to carry out photocrosslinking.

  The concentration of the sulfonated aromatic polyether solution impregnated into the porous substrate is preferably 10 to 90% by mass, and more preferably 20 to 70% by mass. As the solvent used in this case, the water / acetone mixed solvent already described is used.

  Further, for the purpose of facilitating the impregnation operation, hydrophilic treatment of the porous substrate, addition of a surfactant to the polymer precursor solution, or ultrasonic irradiation during the impregnation can be performed.

<Removal of solvent>
Acetone contained in the prepared electrolyte membrane can be easily removed by drying or washing with water. Since acetone has a low boiling point, it can be easily removed even at room temperature, but a normal drying device such as a hot air dryer or a drying furnace can also be used to increase the drying efficiency. It can also be easily removed by washing with water without going through a drying step. Acetone extracted into water may be appropriately drained according to the concentration in water.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, the scope of the present invention is not limited by these examples. Moreover, the part in an Example and a comparative example shall mean a mass part unless there is particular notice.

Example 1 Synthesis and purification of sulfonated aromatic polyethersulfone (1)
In a 500 mL four-necked flask equipped with a stirrer, a Dean Stark apparatus, and a thermometer, 10.69 g of 4,4′-biphenol (hereinafter abbreviated as BP), 4.54 g of dichlorodiphenyl sulfone (hereinafter abbreviated as DCDPS), 17.59 g of sulfonated dichlorodiphenylsulfone (hereinafter abbreviated as S-DCDPS), 9.67 g of potassium carbonate, 42.4 g of N-methylpyrrolidone (hereinafter abbreviated as NMP) and 106.14 g of toluene were charged. The flask was immersed in an oil bath and stirred at a bath temperature of 140 ° C. for 4 hours. During this time, the water separated by the Dean Stark apparatus was appropriately removed. Next, the bath temperature was raised to 190 ° C. over about 30 minutes, and toluene was distilled off from the reaction solution. The mixture was reacted at a bath temperature of 190 ° C. for 4 hours to obtain a terminal hydroxy aromatic polyether solution.

To this solution, 113.42 g of NMP and 1.26 g of acetic acid were added and mixed. The solution was allowed to stand overnight, the precipitate was filtered, and the solution was transferred into a 1 L beaker. While stirring vigorously with a stirrer, 518 g of isopropanol (hereinafter abbreviated as IPA) was added dropwise little by little to precipitate the resin. After the entire amount of IPA was added, the mixture was further stirred for 2 hours. This slurry was suction filtered and then vacuum dried to obtain 27.3 g of a crude product of sulfonated aromatic polyethersulfone having a sulfonation degree of 70%.
The crude product was dissolved in a water / acetone mixed solvent (weight ratio 1/1) to obtain a polymer solution having a concentration of 15% by weight, and this was stirred into a 20-fold amount of IPA / water mixture (weight ratio 5/1). The polymer was precipitated by dropwise addition below. The precipitate was filtered and then vacuum dried at 50 ° C. for 2 hours to obtain a purified product of aromatic polyethersulfone. When residual solvents (acetone and IPA) were quantified using gas chromatography, they were all 0.1% or less.

(Comparative Example 1) Synthesis and purification of sulfonated aromatic polyethersulfone (2)
The crude product of sulfonated aromatic polyethersulfone having a sulfonation degree of 70% obtained by the same method as in Example 1 was dissolved in NMP to give a polymer solution having a concentration of 15% by weight, and this was dissolved in 20 times the amount of IPA. Was added dropwise with stirring to precipitate the polymer. The precipitate was filtered and then vacuum dried at 50 ° C. for 2 hours to obtain a purified product of sulfonated aromatic polyethersulfone. When residual solvents (acetone and IPA) were quantified using gas chromatography, it was found that although IPA was 0.1% or less, it contained 3.2% of NMP.

(Example 2) Synthesis and purification of sulfonated aromatic polyethersulfone (3)
A 500 mL four-necked flask equipped with a stirrer, Dean-Stark apparatus, and thermometer was charged with 10.69 g of BP, 25.13 g of S-DCDPS, 9.67 g of potassium carbonate, 42.4 g of NMP, and 106.14 g of toluene. The reaction and isolation were conducted under the same conditions as in Example 1 to obtain 35.7 g of a crude product of a sulfonated aromatic polyethersulfone having a sulfonation degree of 100%.
This crude product was dissolved in a water / acetone mixed solvent (weight ratio 50/50) to form a polymer solution having a concentration of 15% by weight, and this was dropped into 20 times the amount of IPA with stirring to precipitate the polymer. . The precipitate was filtered and then vacuum dried at 50 ° C. for 2 hours to obtain a purified product of aromatic polyethersulfone. When residual solvents (acetone and IPA) were quantified using gas chromatography, they were all 0.1% or less.

(Comparative Example 2) Synthesis and purification of sulfonated aromatic polyethersulfone (4)
A crude product of a sulfonated aromatic polyethersulfone having a sulfonation degree of 100% obtained by the same method as in Example 2 was dissolved in NMP to obtain a polymer solution having a concentration of 15% by weight. Was added dropwise with stirring to precipitate the polymer. The precipitate was filtered and then vacuum dried at 50 ° C. for 2 hours to obtain a purified product of aromatic polyethersulfone. When residual solvents (NMP and IPA) were quantified using gas chromatography, it was found that although IPA was 0.1% or less, it contained 3.4% of NMP.

(Example 3) Solubility test of sulfonated aromatic polyethersulfone (1)
A sulfonated aromatic polyethersulfone having a sulfonation degree of 70% obtained in Example 1 and a sulfonated aromatic polyethersulfone having a sulfonation degree of 100% obtained in Example 2 in a water / acetone mixed solvent. The solubility was examined. The polymer concentration was 20% by weight, and the weight ratio of water / acetone was changed to 100/0, 85/15, 75/15, 65/35, 50/50, 25/75. All the polymers were not fluid in the gel state at a weight ratio of 100/0 and insoluble at 25/75. A weight ratio of 85/15 to 50/50 gave a soluble and low viscosity solution.

(Example 4) Solubility test of sulfonated aromatic polyethersulfone (2)
The solubility of the sulfonated aromatic polyethersulfone having a sulfonation degree of 100% obtained in Example 2 in a water / acetone mixed solvent (weight ratio 50/50), NMP, and dimethylacetamide was examined. The polymer concentration was 40% by weight, and after heating and dissolving in three kinds of solvents, the polymer was allowed to stand for several days, and then its properties were observed. A precipitate was formed in the dimethylacetamide solution, indicating that the solubility was insufficient. The water / acetone mixed solvent and NMP were uniform solutions, but the water / acetone mixed solvent had a lower viscosity.

(Example 5) Preparation of solvent cast film (1)
The purified aromatic polyethersulfone obtained in Example 1 was dissolved in a water / acetone mixed solvent (weight ratio 50/50) to obtain a solution having a concentration of 20% by weight. 10 g of this solution was poured into a petri dish (area 144 cm ² ) having a smooth bottom, and left at room temperature for 1 day to volatilize the solvent. Furthermore, it heat-processed for 30 minutes at 120 degreeC, and obtained the cast film about 120 micrometers thick. When the amount of residual solvent in the film was quantified by gas chromatography, it was 0.1% or less for both water and acetone.

(Comparative Example 3) Preparation of solvent cast film (2)
A cast film was obtained in the same manner as in Example 5 except that NMP was used as the solvent instead of the water / acetone mixed solvent. The amount of residual solvent in the film was quantified by gas chromatography and found to contain 2.8% NMP.

(Synthesis Example) Synthesis of terminal vinyl type sulfonated aromatic polyethersulfone (1)
20.0 g of a purified product of sulfonated aromatic polyether sulfone synthesized in Example 1, 40 g of NMP, and 0.75 g of 85% KOH were charged, and the resin was dissolved by stirring in an oil bath at 80 ° C. for 30 minutes. . The oil bath was set to 60 ° C., and 2.3 g of chloromethylstyrene was charged and reacted for 7 hours. The base number determined from titration with a 0.1 mol / liter HCl aqueous solution was 0.013 meq. It became a constant value at / g, and the reaction was judged to be complete.
To this solution, 55.6 g of NMP and 0.15 g of acetic acid were added and mixed. The resin was isolated and purified from this solution in the same manner as in Example 1 to obtain 17.8 g of a terminal vinyl type sulfonated aromatic polyethersulfone powder. The vinyl group concentration calculated from the 1 H-NMR spectrum was 0.393 meq. / G.

(Example 6) Preparation of composite membrane by production method of isolated polymer of the present invention 5 g of terminal vinyl-type sulfonated aromatic polyether sulfone obtained in the synthesis example and 0 for N-phenylmaleimide (hereinafter abbreviated as PMI) .34 g, 0.15 g of 2-hydroxy-2-methyl-1-phenylpropan-1-one and 10 g of a water / acetone mixed solvent (weight ratio 70/30) were mixed and heated to obtain a homogeneous solution.
A porous substrate (crosslinked polyethylene film, size 6 cm × 6 cm, thickness 16 μm, porosity 38%) was immersed in this solution, and the porous film was sufficiently impregnated with the solution. This membrane was sandwiched between PET films, and the impregnating solution was sufficiently scraped off, followed by polymerization by irradiation with ultraviolet rays for 4 minutes with a high-pressure mercury lamp. The cured film was peeled off from the PET film and dried with an electric fan for 1 minute, and then the obtained electrolyte film was immersed in 20 g of a 1 mol / liter HCl aqueous solution overnight. When the solvent extracted into the aqueous HCl solution was quantitatively determined by gas chromatography, the content of acetone was 20 ppm or less.

(Comparative Example 6) Preparation of composite membrane not using the present invention A composite membrane was prepared in the same manner as in Example 6 except that NMP was used as a solvent instead of the water / acetone mixed solvent, and the membrane was dried. In the same manner, immersion in a 1 mol / liter HCl aqueous solution was also performed. When the solvent extracted into the aqueous HCl solution was quantified by gas chromatography, it was found to contain 730 ppm of NMP.

As is clear from the above results, by using the water / acetone mixed solvent as the solvent of the method of the present invention, that is, the sulfonated aromatic polyether, the polymer can be easily isolated and the sulfonated fragrance having high purity can be obtained. Group polyethers are obtained. Moreover, if this isolation method is utilized for the manufacturing process of an electrolyte membrane, a high purity electrolyte membrane which does not contain a residual solvent can be manufactured by a simple process.

The present invention is a method for isolating a sulfonated aromatic polyether useful as an electrolyte resin, the polymer obtained by this method, for example, as an electrolyte resin film, electrochemical device elements such as fuel cells and various sensors, Applicable to the use of separation membrane for electrolysis.

Claims (7)

A method for producing an isolated polymer, wherein a water / acetone mixed solvent is used as a solvent in the step of isolating the polymer by removing the solvent from the sulfonated aromatic polyether solution. The method for producing an isolated polymer according to claim 1, wherein the mass ratio of the water / acetone mixed solvent is 95/5 to 30/70. The method for producing an isolated polymer according to claim 1 or 2, wherein the sulfonated aromatic polyether is a sulfonated aromatic polyethersulfone or a sulfonated aromatic polyetherketone. The isolated polymer manufacturing method according to any one of claims 1 to 3, wherein the sulfonated aromatic polyether is a sulfonated aromatic polyethersulfone having 60% by mass or more of the structural unit represented by the formula.

(In the formula, M represents a group capable of selecting one or more of H, Na, K, Li, and NH ₄ , n represents 0 to 2, and m represents a positive number of 0 to 2.)   The isolation according to any one of claims 1 to 4, wherein the polymer is isolated in the pores of the porous substrate after the porous substrate is impregnated with the sulfonated aromatic polyether solution. Polymer production method.   The film-like polymer is isolated by evaporating the solvent under normal pressure or reduced pressure after the sulfonated aromatic polyether solution is made into a liquid film. Isolated polymer production method. The method for producing an isolated polymer according to any one of claims 1 to 4, wherein the polymer isolation step comprises precipitating a polymer by mixing a precipitant in the sulfonated aromatic polyether solution.