Ion exchange membrane storage body and method for storing ion exchange membrane

Abstract

To provide a method capable of suppressing deterioration of physical strength of an ion exchange membrane during storage.SOLUTION: An ion-exchange membrane in a saturated water-containing state is housed in a storage member, and the ion-exchange membrane is stored as an ion-exchange membrane storage body holding an aqueous solution containing acid or base with a concentration of 0.005 to 0. 60M.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ion exchange membrane storage body in which an ion exchange membrane is housed in a storage member, and a method for storing an ion exchange membrane. [Background technology]

[0002] Ion exchange membranes are used industrially in many fields, including as electrodialysis membranes used in salt production and desalination processes in the food industry, as electrolyte membranes in fuel cells, and as diffusion dialysis membranes used to recover acid from acids containing metal ions generated in the steel industry.

[0003] When such ion exchange membranes are stored in a dry state, they become brittle and prone to breakage. Furthermore, when the moisture in the membrane is lost due to drying, the membrane shrinks significantly, and when it is again exposed to an aqueous solution, it expands significantly. The stress caused by this expansion and contraction also easily causes the membrane to break. For this reason, it is preferable to store ion exchange membranes in the presence of sufficient water. Furthermore, when an ion exchange membrane is formed solely from an ion exchange resin, it is often not suitable for practical use due to its low strength and large morphological changes caused by swelling when immersed in a liquid for use. For this reason, ion exchange membranes are preferably formed by supporting an ion exchange resin on a substrate that has a predetermined strength, does not change morphologically due to swelling, and does not impair the ion exchange ability specific to the ion exchange resin (see, for example, Patent Documents 1 and 2).

[0004] There are also ion exchange membranes that do not have a substrate (see Patent Document 3), and the ion exchange membrane of Patent Document 3 is stored in a dry state after being produced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-96923 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-22454 [Patent Document 3] WO2007-029723 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] As described above, it has been found that storing an ion exchange membrane in a hydrated state can prevent the membrane from losing strength or breaking due to drying, but on the other hand, the resin gradually deteriorates during storage, and the membrane loses strength over a long period of storage. Furthermore, it has been found that in an ion exchange membrane having a structure in which an ion exchange resin is supported on a substrate, resin deterioration progresses more in the substrate portion, and this deterioration occurs more significantly when a specific substrate is used. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method capable of suppressing the decrease in physical strength of an ion exchange membrane during storage. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the inventors have discovered that the cause of the decrease in physical strength of ion exchange membranes in a hydrated state during storage is the effect of oxidation of the ion exchange membrane. They have also found that the decrease in physical strength of ion exchange membranes during storage can be suppressed by storing the ion exchange membrane while retaining an aqueous solution containing a predetermined concentration of acid or base, and have thus completed the present invention.

[0008] That is, the present invention is as follows. [1] An ion exchange membrane storage body in which an ion exchange membrane in a saturated water state is stored in a storage member, An ion exchange membrane storage body, wherein the ion exchange membrane holds an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60M. [2] The ion exchange membrane storage body according to [1] above, wherein the aqueous solution held in the ion exchange membrane contains a neutral salt. [3] The ion exchange membrane storage body according to [2] above, wherein the neutral salt is contained in an amount of 0.1 to 15 molar equivalents of an acid or a base.

[0009] [4] The ion exchange membrane storage body according to any one of [1] to [3] above, characterized in that the ion exchange membrane is a cation exchange membrane and the aqueous solution held in the cation exchange membrane is an aqueous solution containing an acid. [5] H of the counter ion of the cation exchange group of the cation exchange membrane + The ion exchange membrane storage body according to [4] above, characterized in that the ratio of is 30 mol % or less. [6] The ion exchange membrane storage body according to [1] or [2] above, characterized in that the ion exchange membrane is an anion exchange membrane and the aqueous solution retained in the anion exchange membrane is an aqueous solution containing a base. [7] OH of the counter ion of the anion exchange group of the anion exchange membrane - The ion exchange membrane storage body according to [6] above, characterized in that the ratio of is 30 mol % or less.

[0010] [8] The ion exchange membrane storage body according to any one of [1] to [7] above, wherein the saturated water content of the ion exchange membrane in a saturated water-containing state is 15 to 55 mass %. [9] The ion exchange membrane storage body according to any one of [1] to [8] above, wherein the ion exchange membrane is a membrane in which an ion exchange resin is fixed to a polyolefin substrate.

[10] The ion exchange membrane storage body according to [9] above, wherein the polyolefin substrate is a polyethylene substrate.

[11] The ion exchange membrane storage body according to

[10] above, wherein the polyethylene substrate is a polyethylene porous film substrate.

[12] The ion exchange membrane storage body according to [9], wherein the ion exchange resin is a cross-linked polystyrene-based ion exchange resin.

[0011]

[13] The ion exchange membrane storage body according to any one of [1] to

[12] above, wherein the storage member is a sheet, and the ion exchange membrane is in the form of an ion exchange membrane container wrapped in the sheet.

[14] The oxygen permeability of the sheet is 30 cc / (m 2 The ion exchange membrane storage body according to

[13] above, characterized in that the temperature is 100°C or less (100°F).

[15] The ion exchange membrane storage body according to

[13] or

[14] , wherein the weight of the aqueous solution in the ion exchange membrane storage body is 1.1 to 200 times the saturated water content of the ion exchange membrane.

[16] The ion exchange membrane storage body according to any one of [1] to

[12] above, characterized in that the storage member is a dialysis stack component and the ion exchange membrane is incorporated into the dialysis stack component to form a dialysis stack.

[0012]

[17] A method for storing an ion exchange membrane, comprising storing an ion exchange membrane that is saturated with water and holds an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60 M in a storage member.

[18] The method for storing an ion exchange membrane according to the above

[17] , characterized in that the ion exchange membrane in a water-containing state is immersed in an aqueous solution containing an acid or a base, and then stored in a storage member.

[19] The method for storing an ion exchange membrane according to

[17] above, wherein the storage member is a sheet, and the ion exchange membrane is stored in the form of an ion exchange membrane container wrapped in the sheet.

[20] The oxygen permeability of the sheet is 30 cc / (m 2 The method for storing an ion exchange membrane according to

[19] above, characterized in that the temperature is 500°C or less (d·atm).

[21] The method for storing an ion exchange membrane according to

[17] above, wherein the storage member is a dialysis stack component and is incorporated into the dialysis stack component and stored in the form of a dialysis stack.

[22] A method for storing an ion exchange membrane according to the above

[21] , characterized in that the ion exchange membrane in a water-containing state is incorporated into the dialysis stack component and then brought into contact with an aqueous solution containing an acid or a base. [Effects of the Invention]

[0013] According to the ion exchange membrane storage body and the method for storing an ion exchange membrane of the present invention, it is possible to suppress a decrease in the physical strength of the ion exchange membrane during storage. DETAILED DESCRIPTION OF THE INVENTION

[0014] The ion exchange membrane storage body of the present invention is characterized in that an ion exchange membrane in a saturated water-containing state is contained in a storage member, and the ion exchange membrane holds an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60 M.

[0015] When an ion exchange membrane is stored in a hydrated state, as described above, it is believed that oxidative degradation of the resin is accelerated, resulting in a decrease in the strength of the ion exchange membrane. That is, it is presumed that the incorporation of water causes the ion exchange membrane to swell, which increases the oxygen permeation and diffusion rate through the membrane, resulting in significant resin degradation. More specifically, when the ion exchange membrane is dry, the membrane is not swollen and oxygen cannot penetrate the membrane, so oxidation is unlikely to progress. However, in a hydrated state, the membrane is swollen, allowing oxygen to penetrate the membrane and reach the oxidation point, resulting in oxidative degradation. When this state becomes saturated with water, the membrane swells to the maximum extent, making it most susceptible to oxygen penetration, and oxidative degradation progresses rapidly. Therefore, measures against oxidation are necessary, and in the present invention, an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60 M is retained in the ion exchange membrane, whereby an active reaction intermediate generated in an autoxidation reaction or the like reacts with the acid or base, thereby suppressing the oxidation reaction and preventing deterioration of the strength of the ion exchange membrane. In this way, the present invention can suppress deterioration of the strength of the ion exchange membrane during storage in an inexpensive and simple manner.

[0016] As described above, the ion exchange membrane of the present invention is not particularly limited as long as it holds an aqueous solution containing an acid or a base at a concentration of 0.005 to 0.60 M (hereinafter, these may be referred to as an acid solution and a base solution, respectively). However, in order to further suppress oxidative deterioration, the concentration of the solution containing an acid or a base held by the ion exchange membrane is preferably 0.008 to 0.55 M, more preferably 0.010 to 0.50 M, and even more preferably 0.015 to 0.30 M.

[0017] The acid or base concentration of the aqueous solution retained in the ion exchange membrane can be measured by potentiometric titration using an aqueous sodium hydroxide solution or sulfuric acid of known concentration.

[0018] Examples of acids include strong inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, strong organic acids such as benzenesulfonic acid, and weak acids such as acetic acid, citric acid, and ascorbic acid. Strong acids that have a high oxidation degradation suppression effect even in small amounts are preferred, and strong inorganic acids that accumulate less in the membrane are more preferred. Specifically, hydrochloric acid, sulfuric acid, and nitric acid can be preferably used. Examples of the base include strong inorganic bases such as sodium hydroxide and potassium hydroxide, strong organic bases such as tetraalkylammonium hydroxide, and weak bases such as sodium carbonate and sodium bicarbonate. Strong bases that have a high oxidation degradation suppression effect even in small amounts are preferred, and strong inorganic bases that accumulate less in the film are more preferred. Specifically, sodium hydroxide and potassium hydroxide can be preferably used.

[0019] Although any solution may be retained in the ion exchange membrane, it is preferable to retain an acid solution when the ion exchange membrane is a cation exchange membrane, and a base solution when the ion exchange membrane is an anion exchange membrane. This is because the affinity with the ion exchange group is such that in the case of a cation exchange membrane, H + In the case of anion exchange membranes, OH - This is because the oxygen can more easily penetrate into the interior of the membrane, which makes it possible to more effectively suppress oxidative degradation of the ion exchange membrane.

[0020] In the present invention, the aqueous solution held by the ion exchange membrane preferably contains a neutral salt. When an acid or base is held in the ion exchange membrane, dimensional changes tend to occur, but the coexistence of a neutral salt can suppress such dimensional changes.

[0021] In other words, a certain amount of water is bound around the ion exchange groups of the ion exchange membrane. Even with the same ion exchange group, the amount of bound water changes when the counter ion changes. For example, when a cation exchange membrane is immersed in an acid solution, the counter ion changes to H + This increases the amount of bound water. As the amount of bound water increases, the ion exchange membrane absorbs more water, causing the membrane to stretch and undergo dimensional changes. The ion exchange membranes used in dialysis have openings formed to allow the liquid to pass through. If the membrane stretches after the openings are formed and before lamination, the openings will not be aligned properly, making lamination difficult. Furthermore, if the membrane stretches after lamination, it may break or interfere with its surroundings, causing damage.

[0022] Therefore, if the ion exchange membrane is a cation exchange membrane, the counter ions of the cation exchange groups are H + On the other hand, when the ion exchange membrane is an anion exchange membrane, the proportion of OH of the counter ion of the anion exchange group is preferably 30 mol % or less, more preferably 25 mol % or less, and even more preferably 15 mol % or less. - The proportion of is preferably 30 mol % or less, more preferably 25 mol % or less, and even more preferably 15 mol % or less. In order to suppress the decrease in strength, it is necessary for an acid or a base to be present around the ion exchange membrane, and the counter ion is H + OH - Therefore, it is not important to add a certain amount of neutral salt to the acid or base to convert the counter ions of the exchange groups into H + OH - By not increasing the temperature, it is possible to suppress a decrease in strength and a change in dimension. The change in dimension of the ion exchange membrane is preferably 1.0% or less, more preferably 0.6% or less, and even more preferably 0.4% or less.

[0023] The neutral salt is not limited as long as it contains an anion or cation that can be ion-exchanged as a counter ion of the ion exchange membrane as described above, and specific examples thereof include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, sodium sulfate, potassium sulfate, and lithium sulfate. The content of the neutral salt is preferably 0.1 to 15 molar equivalents of the acid or base, more preferably 0.3 to 12 molar equivalents, and even more preferably 0.5 to 6 molar equivalents.

[0024] Examples of storage materials used in the present invention include sheets (packaging sheets) and dialysis stack components. That is, the ion exchange membrane storage body of the present invention can take the form of an ion exchange membrane container in which the ion exchange membrane is packaged in a sheet, or the form of a dialysis stack in which the ion exchange membrane is incorporated into a dialysis stack component.

[0025] The packaging sheet is not particularly limited as long as it can package the ion exchange membrane, but in order to further suppress oxidative deterioration, it is preferable that the packaging sheet has an oxygen permeability of 30 cc / (m 2 ·d·atm) or less, and oxygen permeability is 25cc / (m 2 ·d·atm) or less is more preferable, and 10cc / (m 2 ·d·atm) or less is more preferable, and 1cc / (m 2 ·d·atm) or less is particularly preferable, and 0.5cc / (m 2 The lower the oxygen permeability, the better. The lower limit is, for example, 0.01 cc / (m 2 ·d·atm). The oxygen permeability of the packaging sheet is measured in accordance with JIS-K7126-2 for the sheet in a dry state.

[0026] The packaging sheet also has a water vapor permeability of 0.8g / (m) so that the ion exchange membrane can reliably retain moisture during storage. 2 ·d) or less, and 0.5g / (m 2·d) or less is more preferable, and 0.3 g / (m 2 The lower the water vapor permeability, the better. The lower limit is, for example, 0.01 g / (m 2 ·d). The water vapor permeability of the packaging sheet is measured for the sheet in a dry state in accordance with JIS Z0208 (cup method).

[0027] It should be noted that Patent Document 3 above describes packaging an ion exchange membrane using a packaging sheet material with low water vapor permeability, but the invention of Patent Document 3 is intended to prevent swelling due to moisture absorption even when a dried ion exchange membrane is stored for a long period of time, and is therefore technically different from the present invention. In relation to this technical significance, in the present invention, it is necessary to suppress the loss of moisture from the environment inside the container, which contains a lot of water, and it is preferable to more strictly prevent water vapor permeation. For example, in the examples of Patent Document 3, even the one with the lowest water vapor permeability has a water vapor permeability of 1 g / (m 2 d), but in the present invention, it is preferable that the water vapor permeability is even lower than this.

[0028] The packaging sheet preferably also has ultraviolet-shielding properties to prevent deterioration of the ion-exchange membrane due to ultraviolet rays during outdoor storage. In particular, the packaging sheet preferably has a transmittance of 3% or less, more preferably 0.1% or less, at the wavelength showing the maximum transmittance of ultraviolet rays in the wavelength range of 290 nm to 400 nm.

[0029] Specifically, examples of packaging sheets include resin films such as polyethylene, polypropylene, and polyethylene terephthalate, metal-vapor-deposited plastic sheets having a layer of a metal such as aluminum vapor-deposited on one of these, inorganic oxide-vapor-deposited plastic sheets having a layer of an inorganic oxide such as silica or alumina vapor-deposited on one of these, metal-laminated plastic sheets having a layer of a metal such as aluminum, and low-oxygen-permeable polymer-laminated plastic sheets having a layer of a polymer with low oxygen permeability.

[0030] The dialysis stack components are made up of gaskets, frames, etc., and the ion exchange membranes are incorporated to form the dialysis stack. The dialysis stack, together with the anode and cathode electrode plates, forms an electrodialysis cell.

[0031] The ion exchange membrane of the ion exchange membrane storage body of the present invention is saturated with water. This makes it possible to suppress deterioration in strength of the ion exchange membrane due to expansion and contraction caused by drying. The saturated water content of the ion exchange membrane in the saturated water state is, for example, 15 to 55 mass%, preferably about 20 to 50 mass%, and more preferably 25 to 45 mass%.

[0032] When the ion exchange membrane storage body is in the form of an ion exchange membrane container, the weight of the aqueous solution in the ion exchange membrane container is an amount sufficient to at least saturate the ion exchange membrane with water, preferably 1.1 to 200 times the saturated water content of the ion exchange membrane, more preferably 1.3 to 150 times, even more preferably 2 to 90 times, and particularly preferably 5 to 60 times. By using an aqueous solution volume 1.1 times or more the saturated water content, the surface of the ion exchange membrane is sufficiently covered with a layer of water, which allows oxygen to dissolve in the water and then penetrate the membrane to the oxidation point, thereby mitigating the progress of active oxidation. In other words, in this case, the oxygen barrier sheet provides an oxygen blocking effect, the water surface layer provides an oxygen penetration suppression effect, and the acid or base solution provides an oxidation suppression effect, resulting in a more significant oxidation degradation suppression effect. On the other hand, if the amount of aqueous solution in the container exceeds 200 times the saturated water content, it may cause concerns about use, such as difficulty in transportation, and therefore it is preferable not to increase the weight of the aqueous solution in the container more than necessary.

[0033] The weight of the aqueous solution in the ion exchange membrane container is calculated by the following formula. Weight of ion exchange membrane container - (dry weight of ion exchange membrane + weight of packaging sheet)

[0034] The ratio of the weight of the aqueous solution in the ion exchange membrane container to the saturated water content of the ion exchange membrane is calculated by the following formula. Weight of water in the ion exchange membrane container / (dry weight of ion exchange membrane × saturated water content) The saturated water content can be calculated using the following formula. (Wet weight of ion exchange membrane - Dry weight of ion exchange membrane) / Dry weight of ion exchange membrane

[0035] Next, the ion exchange membrane in the ion exchange membrane storage body of the present invention will be described. The ion exchange membrane of the present invention can be used as an electrodialysis membrane used in salt production, desalination processes in the food industry, etc., an electrolyte membrane for a fuel cell, or a diffusion dialysis membrane used for acid recovery from an acid containing metal ions generated in the steel industry, etc.

[0036] The ion exchange membrane of the present invention generally has a structure in which an ion exchange resin is fixed (held) on a specific substrate. The present inventors have discovered that the decrease in strength of ion exchange membranes during storage is caused by oxidative degradation, which is thought to be mainly due to degradation of the substrate. Therefore, the present invention is particularly effective for ion exchange membranes that include a substrate.

[0037] (base material) The substrate functions as a reinforcing material for the ion exchange membrane. Materials conventionally used as substrates for ion exchange membranes can be used without any limitations. Examples include polyolefin, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyester, polyvinyl alcohol, polyamide, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfone, polyphenylene sulfide, polyimide, polyetherimide, polyamideimide, polycarbonate, polyacrylate, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polychlorotrifluoroethylene, and copolymers thereof. Among these, polyolefin substrates are preferred because they are superior in alkali resistance, strength, heat resistance, processability, cost, etc., and polyethylene substrates are particularly preferred. Specific preferred examples of polyolefins include homopolymers and copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, and 5-methyl-1-heptene.

[0038] Although polyolefin substrates have high performance as substrates as described above, they tend to be easily oxidized and deteriorated during storage. In the present invention, even in polyolefin substrates that are prone to oxidative deterioration, oxidative deterioration can be suppressed, and thus a decrease in strength can be suppressed. Among polyolefin substrates, polyethylene substrates are preferred because they have good chemical resistance and a slow oxidation rate due to the absence of tertiary carbon.

[0039] The polyethylene constituting the substrate may be any known polyethylene, such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, or ultra-high molecular weight polyethylene. From the viewpoint of mechanical properties such as film strength and dimensional stability, high-density polyethylene or ultra-high molecular weight polyethylene is particularly preferred. Furthermore, by using a blend of the above polyethylenes, it is possible to adjust the concentration characteristics and mechanical properties. Furthermore, these polyethylenes may be copolymers (linear copolymerized polyethylenes) containing ethylene units and α-olefin units such as propylene, butene, pentene, hexene, or octene.

[0040] Examples of the form of the substrate include woven fabric, nonwoven fabric, porous film, etc. Porous film substrates tend to be easily deteriorated by oxidation due to their large surface area, but in the present invention, even in porous film substrates that are prone to oxidative deterioration, oxidative deterioration can be suppressed, and thus a decrease in strength can be suppressed.

[0041] The thickness of the substrate is, for example, 5 μm to 1000 μm, preferably 10 μm to 500 μm, and more preferably 20 μm to 200 μm. If the thickness is too small, the mechanical strength decreases, and if the thickness is greater than necessary, the electrical resistance tends to increase.

[0042] The porosity of the substrate is, for example, 25% to 95%, preferably 30% to 90%, and more preferably 35% to 85%. If the porosity is higher than necessary, the amount of ion exchange resin per unit volume increases, and in practical use, the swelling and shrinkage of the ion exchange resin can easily cause peeling between the resin and the substrate, resulting in membrane damage and deterioration. Furthermore, the membrane tends to lack dimensional stability and have reduced mechanical strength. On the other hand, if the porosity is too low, the amount of ion exchange resin per unit volume decreases, preventing sufficient ion exchange capacity from being exhibited, potentially resulting in high membrane resistance.

[0043] (ion exchange resin) The ion exchange resin fixed to the substrate may be a cation exchange resin, an anion exchange resin, or an amphoteric ion exchange resin.

[0044] Examples of resins that form the skeleton of ion exchange resins include polymers obtained by polymerizing monomers having ethylenically unsaturated double bonds, such as vinyl, styrene, and acrylic monomers, and copolymers thereof; and hydrocarbon resins such as polymers containing an aromatic ring in the main chain, such as polysulfone, polyphenylene sulfide, polyether ketone, polyether ether ketone, polyetherimide, polyphenylene oxide, polyethersulfone, and polybenzimidazole.

[0045] Among these, the resin forming the skeleton is preferably a crosslinked styrene-based resin primarily composed of a styrene-based monomer in terms of heat resistance, chemical resistance, strength, etc. Examples of raw material compositions (styrene-based resin-forming compositions) for forming this crosslinked styrene-based resin (cured product) include compositions containing a styrene-based monomer, a crosslinkable polymerizable monomer (e.g., divinylbenzene), and a polymerization initiator (e.g., organic peroxide). Examples of styrene-based monomers include styrene, vinyltoluene, ethylvinylbenzene, vinylpyridine, vinylimidazole, styrenesulfonic acid, vinylbenzylamine, vinylbenzyldimethylamine, vinylbenzyltrimethylammonium halide, chloromethylstyrene, bromomethylstyrene, iodomethylstyrene, etc.

[0046] The crosslinkable polymerizable monomer is used to densify the ion exchange resin and to improve swelling prevention properties, membrane strength, etc., and is not particularly limited, but examples thereof include divinyl compounds such as divinylbenzene, divinyl sulfone, butadiene, chloroprene, divinylbiphenyl, trivinylbenzenes, triacrylates, divinylnaphthalene, diallylamine, divinylpyridine, and diacrylates. In general, the content of such crosslinkable polymerizable monomers in the raw material composition is preferably 0.1 to 50% by weight, more preferably 0.5 to 35% by weight.

[0047] The ion exchange groups contained in the ion exchange resin may be appropriately determined depending on the intended application. For example, sulfonic acid groups or carboxylic acid groups may be used in the case of cation exchange membranes, and quaternary ammonium bases or pyridinium bases may be used in the case of anion exchange membranes. Counterions of the ion exchange groups may be, for example, hydrogen ions or sodium ions in the case of cation exchange membranes, and hydroxide ions, halogen ions, or bicarbonate ions in the case of anion exchange membranes.

[0048] (Method of manufacturing ion exchange membrane) The ion exchange membrane is produced, for example, by applying the above-described ion exchange resin-forming composition to a substrate, curing the composition by thermal polymerization to produce an ion exchange resin precursor, and then introducing ion exchange groups into the ion exchange resin precursor. Alternatively, a composition containing a polymerizable monomer having an ion exchange group may be used and cured by thermal polymerization to produce an ion exchange resin. The conditions of this thermal polymerization are thought to affect the susceptibility of the ion exchange membrane to oxidative degradation.

[0049] The method for storing an ion exchange membrane of the present invention is characterized in that an ion exchange membrane that is saturated with water and retains an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60 M is stored in a storage member. That is, the ion exchange membrane is stored as the ion exchange membrane storage body of the present invention. For example, an ion exchange membrane in a dry or hydrated state (preferably saturated with water) can be immersed in an aqueous solution containing an acid or base and then stored in a storage member. This makes it possible to prevent a decrease in the strength of the ion exchange membrane during storage in an inexpensive and simple manner. The components, such as the packaging sheet, dialysis stack, and ion exchange membrane, are the same as those described for the ion exchange membrane storage body of the present invention, and therefore their description will be omitted. [Example]

[0050] Examples of the present invention are shown below. Various properties of the ion exchange membrane and packaging sheet were measured by the following methods.

[0051] (1) Burst strength of ion exchange membrane The ion exchange membrane was immersed in a 0.5 mol / L NaCl aqueous solution for 4 hours or more, thoroughly rinsed with ion exchange water, and then, without drying, the burst strength was measured in accordance with JIS-P8112 using a Mullen burst tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.).

[0052] (2) Counterion H of the cation exchange membrane + conversion rate The cation exchange membrane was immersed in a 1 mol / L NaCl aqueous solution for 4 hours or more, and the liberated hydrogen ions were quantified (Amol) using a potentiometric titrator (AT-710, Kyoto Electronics Manufacturing Co., Ltd.) with a sodium hydroxide aqueous solution. Next, the same cation exchange membrane was immersed in a 1 mol / L HCl aqueous solution for more than 10 hours and then thoroughly washed with ion-exchanged water. After washing, the ion exchange membrane was immersed in a 1 mol / L NaCl aqueous solution to replace the counter ions of the ion exchange groups from hydrogen ions to sodium ions. The liberated hydrogen ions were quantified using a potentiometric titrator with a sodium hydroxide aqueous solution (B mol). Based on the above measurements, the counter ions H of the cation exchange membrane were + The conversion rate was calculated using the following formula.

[0053] Counterion H + conversion rate=A / B×100[%]

[0054] (3) Counterion OH of the anion exchange membrane - conversion rate The anion exchange membrane was immersed in a 1 mol / L NaCl aqueous solution for 4 hours or more, and the liberated hydroxide ions were quantified (Amol) using sulfuric acid with a potentiometric titrator (AT-710, Kyoto Electronics Manufacturing Co., Ltd.). Next, the same anion exchange membrane was immersed in a 1 mol / L NaOH aqueous solution for more than 10 hours and then thoroughly washed with ion-exchanged water. After washing, the ion exchange membrane was immersed in a 1 mol / L NaCl aqueous solution to replace the counter ions of the ion exchange groups from hydroxide ions to chloride ions, and the liberated hydroxide ions were quantified using a potentiometric titrator with sulfuric acid (B mol). Based on the above measurements, the counter ions OH of the anion exchange membrane were - The conversion rate was calculated using the following formula.

[0055] Counterion OH - conversion rate=A / B×100[%]

[0056] (4) Water content of ion exchange membrane The moisture on the surface of the ion exchange membrane was wiped off with tissue paper, and the wet mass of the membrane (W1g) was measured. Furthermore, the membrane was dried under reduced pressure at 60°C for 5 hours, and the dry weight (D1g) was measured. Based on these measurements, the moisture content of the ion exchange membrane was calculated using the following formula:

[0057] Moisture content = 100×(W1-D1) / D1[%]

[0058] (5) Saturation water content of ion exchange membrane The ion exchange membrane was immersed in a 1 mol / L NaCl aqueous solution for at least 4 hours and then thoroughly rinsed with ion exchange water. The surface moisture was then wiped off with tissue paper, and the wet weight of the membrane (W2g) was measured. The membrane was then dried under reduced pressure at 60°C for 5 hours, and its dry weight (D2g) was measured. Based on the above measurements, the saturated water content of the ion exchange membrane was calculated using the following formula:

[0059] Saturated moisture content = 100×(W2-D2) / D2[%]

[0060] (6) Dimensional changes of ion exchange membranes due to immersion in liquid The ion exchange membrane was immersed in ion exchange water for 4 hours or more and thoroughly rinsed with ion exchange water. The surface moisture was then wiped off with tissue paper, and the lengths of the four sides were measured. The average length of the two longitudinal sides was designated A mm, and the average length of the two lateral sides was designated B mm. After immersion in various liquids, the ion exchange membrane was immersed in ion exchange water for 4 hours or more and thoroughly rinsed with ion exchange water. The surface moisture was then wiped off with tissue paper, and the lengths of the four sides were measured. The average length of the two longitudinal sides was designated C mm, and the average length of the two lateral sides was designated D mm. Based on the above measured values, the dimensional change of the ion exchange membrane due to liquid immersion was calculated using the following formula.

[0061] Dimensional change = 100 × {(CA) / A + (DB) / B} / 2 [%]

[0062] (7) Measurement of the amount of aqueous solution retained in the container The weight (Ag) of the entire container was measured. Then, the dimensions of all the ion exchange membranes in the container were measured, and the total area (Bm 2 ) was calculated. In addition, the dimensions of all sheets in the container were measured, and the total area (cm 2 ) was calculated. Next, the ion exchange membrane and the sheet were cut into 20 cm × 30 cm pieces and dried under reduced pressure at 60 ° C for 5 hours, and the dry weights (Dg, Eg) of the ion exchange membrane and the sheet were measured. Based on the above measured values, the amount of water in the container was calculated using the following formula.

[0063] Moisture content=A-(D×B / 0.06+E×C / 0.06)[g]

[0064] The ratio (multiple) of the amount of water in the container to the amount of water in the ion exchange membrane in a saturated water content state (saturated water content) was calculated from the saturated water content F (%) of the ion exchange membrane using the following formula.

[0065] Moisture content / saturated water content={A-(D×B / 0.06+E×C / 0.06)} / (D×B / 0.06×F / 100)

[0066] (8) Acid concentration of the aqueous solution held by the ion exchange membrane (the aqueous solution in the container) A mL of the solution was measured, and ion-exchanged water was added to bring the total volume to 200 mL. The acid content was quantified using a potentiometric titrator with a 0.10 mol / L sodium hydroxide solution (B mol). Based on the measured values, the acid concentration in the solution was calculated using the following formula:

[0067] Acid concentration=B / (A / 1000)[mol / L]

[0068] (9) Base concentration of the aqueous solution held by the ion exchange membrane (the aqueous solution in the container) A mL of the solution was measured, and ion-exchanged water was added to bring the total volume to 200 mL. The base component was quantified (B mol) using a potentiometric titrator with a 0.05 mol / L sulfuric acid solution. Based on the measured values, the base concentration in the solution was calculated using the following formula:

[0069] Base concentration = B / (A / 1000) [mol / L]

[0070] (10) Sodium chloride concentration of the aqueous solution held by the ion exchange membrane (aqueous solution in the container) A mL of the solution was measured, and the chloride ion content was quantified using a potentiometric titrator with a 0.10 mol / L silver nitrate solution (B mol). Furthermore, C mL of the solution was measured again, and the acid content was quantified using a potentiometric titrator with a 0.10 mol / L sodium hydroxide solution (D mol). Based on the above measurements, the sodium chloride concentration in the aqueous solution containing hydrogen chloride was calculated using the following formula:

[0071] Sodium chloride concentration = B / (A / 1000) - D / (C / 1000) [mol / L] In addition, the sodium chloride concentration in the aqueous solution containing no hydrogen chloride was calculated using the following formula.

[0072] Sodium chloride concentration = B / (A / 1000) [mol / L]

[0073] (11) Measurement of oxygen permeability of packaging sheets The dry sheet was measured for oxygen permeability using a coulometric oxygen permeability measuring device (OX-TRAN2 / 22L manufactured by MOCON) in accordance with JIS-K7126-2. The gas conditions used were temperature: 23°C, humidity: 50% RH, and oxygen concentration: 100%.

[0074] (12) Measurement of water vapor permeability of packaging sheets The dry sheet was measured in accordance with JIS Z0208 (cup method) under the temperature and humidity conditions of 40°C and 90% RH.

[0075] <Production Example 1: Cation Exchange Membrane> A polymerizable composition was prepared by mixing the components according to the following formulation. Styrene 73.5 parts by mass p-chloromethylstyrene 16.5 parts by mass Acrylonitrile 10.0 parts by mass Acetyl tributyl citrate 2.5 parts by mass Styrene oxide 2.9 parts by mass Trigonox B (di-t-butyl peroxide, manufactured by Kayaku Nouryon Co., Ltd.) 1.9 parts by mass

[0076] 500 g of this polymerizable composition was placed in a 1000 mL glass container, and a porous film made of high molecular weight polyethylene with a thickness of 130 μm and a porosity of 50% was immersed as a substrate film to fill the voids in the film with the polymer composition. The porous substrate film filled with the above polymer composition was removed, and both sides of the porous substrate film were covered with a 188 μm thick polyester film as a release agent.Then, under a nitrogen pressure of 0.4 MPa, the temperature was raised from 20°C to 50°C over 20 minutes, then from 50°C to 110°C over 60 minutes, and then from 110°C to 130°C over 80 minutes.The temperature was then maintained at 130°C for 180 minutes, and the film was subjected to thermal polymerization.

[0077] The resulting membrane was immersed in a 1:1 (weight ratio) mixture of 98% concentrated sulfuric acid and chlorosulfonic acid with a purity of 90% or higher at 40°C for 60 minutes. The membrane was then immersed sequentially in 90% sulfuric acid, 60% sulfuric acid, and ion-exchanged water, and then in a 4 mol / L NaOH aqueous solution for 12 hours. The resulting ion-exchange membrane had a burst strength of 0.50 MPa and a saturated water content of 42.6% by mass.

[0078] <Production Example 2: Anion Exchange Membrane> A polymerizable composition was prepared by mixing the components according to the following formulation. p-Chloromethylstyrene 86.0 parts by mass Divinylbenzene (purity 57%) 14.0 parts by mass Styrene oxide 4.0 parts by mass Trigonox B 4.0 parts by mass

[0079] 500 g of this polymerizable composition was placed in a 1000 mL glass container, and a porous film made of high molecular weight polyethylene with a thickness of 130 μm and a porosity of 50% was immersed as a substrate film to fill the voids in the film with the polymer composition. The porous substrate film filled with the above polymer composition was removed, and both sides of the porous substrate film were covered with a 188 μm thick polyester film as a release agent.Then, under a nitrogen pressure of 0.4 MPa, the temperature was raised from 20°C to 50°C over 20 minutes, then from 50°C to 110°C over 60 minutes, and then from 110°C to 130°C over 80 minutes.The temperature was then maintained at 130°C for 180 minutes, and the film was subjected to thermal polymerization.

[0080] The resulting membrane was immersed in a mixture of 15 parts by mass of 30% aqueous trimethylamine solution, 52.5 parts by mass of water, and 22.5 parts by mass of acetone at 30°C for 16 hours and then washed with water to obtain a quaternary ammonium anion exchange membrane with chloride ions as counter ions. The resulting ion exchange membrane had a burst strength of 0.46 MPa and a saturated water content of 26.8% by mass.

[0081] Example 1 The cation exchange membrane was cut into three pieces measuring 5 cm x 15 cm and immersed in 250 mL of a mixed aqueous solution of 0.01 M hydrogen chloride and 0.1 M sodium chloride. The dimensional change of the cation exchange membrane from before immersion was 0.09%, and the change of the counter ion H + The conversion rate was 8%. Three immersed membranes were stacked and placed on a PP sheet (oxygen permeability 150cc / (m 2 ·d·atm), water vapor permeability 0.9g / (m 2 d)) was packaged together with 20 g of the above mixed aqueous solution after immersion to prepare a saturated water-containing ion exchange membrane storage body (ion exchange membrane container). The aqueous solution in the storage body had a hydrogen chloride concentration of 0.009 M and a sodium chloride concentration of 0.101 M, and 20 g was retained (16.8 times the saturated water content of the ion exchange membrane).

[0082] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane taken out had a burst strength of 0.40 MPa. The results are shown in Table 1.

[0083] <Example 2> A storage body was prepared in the same manner as in Example 1, except that 21 mL of a mixed aqueous solution of 0.05 M hydrogen chloride and 0.05 M sodium chloride was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was 0.11%, and the change of the counter ion H + The conversion rate was 22%, and the hydrogen chloride concentration of the aqueous solution in the storage body was 0.026M and the sodium chloride concentration was 0.074M.

[0084] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.41 MPa. The above results are also shown in Table 1.

[0085] Example 3 A storage body was prepared in the same manner as in Example 1, except that 250 mL of a mixed aqueous solution of 0.1 M hydrogen chloride and 1.0 M sodium chloride was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was 0.07%, and the change of the counter ion H +The conversion rate was 5%, and the hydrogen chloride concentration of the aqueous solution in the storage body was 0.10M and the sodium chloride concentration was 1.00M.

[0086] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.45 MPa. The above results are also shown in Table 1.

[0087] Example 4 A storage body was prepared in the same manner as in Example 1, except that 25 mL of 0.05 M hydrochloric acid was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was large, at 0.55%. + The conversion rate was 35%, and the hydrogen chloride concentration of the aqueous solution in the storage body was 0.018 M and the sodium chloride concentration was 0.033 M. In this example, the neutral salt sodium chloride was not added to the aqueous solution for immersion, but the counter ions sodium ions expelled from the ion exchange membrane reacted with hydrogen chloride to produce sodium chloride (the same applies to Examples 5 to 7).

[0088] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.42 MPa. The results are also shown in Table 1. <Example 5> A storage body was prepared in the same manner as in Example 1, except that 25 mL of 0.03 M hydrochloric acid was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was 0.30%, and the H + The conversion rate was 25%, and the hydrogen chloride concentration of the aqueous solution in the storage body was 0.007M and the sodium chloride concentration was 0.023M.

[0089] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.37 MPa. The above results are also shown in Table 1. Example 6 A storage body was prepared in the same manner as in Example 1, except that 25 mL of 0.5 M hydrochloric acid was used as the immersion solution. The dimensional change of the cation exchange membrane before immersion was as extremely large as 1.22%, and the change was due to the presence of counter ions H + The conversion rate was 83%, and the hydrogen chloride concentration of the aqueous solution in the storage body was 0.42M and the sodium chloride concentration was 0.08M.

[0090] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.47 MPa. The results are also shown in Table 1. Example 7 A storage body was prepared in the same manner as in Example 1, except that 250 mL of 0.1 M hydrochloric acid was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was large at 0.69%, and the change was due to the counter ion H + The conversion rate was 84%, and the hydrogen chloride concentration of the aqueous solution in the storage body was 0.092M and the sodium chloride concentration was 0.008M.

[0091] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.46 MPa. The results are also shown in Table 1. Example 8 A storage body was prepared in the same manner as in Example 1, except that 100 mL of a 0.50 M aqueous sodium hydroxide solution was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was 0.03%, and the change of the counter ion H + The conversion rate was 0%, and the sodium hydroxide concentration of the aqueous solution in the storage body was 0.50M.

[0092] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.42 MPa. The results are also shown in Table 1.

[0093] Example 9 A storage body was prepared in the same manner as in Example 1, except that 250 mL of a mixed aqueous solution of 0.1 M citric acid and 0.2 M sodium chloride was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was 0.38%, and the change of the counter ion H + The conversion rate was 8%, and the citric acid concentration of the aqueous solution in the storage body was 0.099M and the sodium chloride concentration was 0.21M.

[0094] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane taken out had a burst strength of 0.36 MPa. The above results are also shown in Table 1.

[0095] Example 10 As a packaging sheet, the oxygen permeability is 0.11cc / (m 2 ·d·atm), water vapor permeability is 0.1g / (m 2 ·d) A storage body was prepared in the same manner as in Example 1, except that a gas barrier sheet consisting of an OPP layer of approximately 20 μm, a PE layer of approximately 20 μm, an aluminum foil layer of 7 μm, and a PE layer of approximately 20 μm was used.

[0096] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.47 MPa. The results are also shown in Table 1.

[0097] Example 11 A storage body was prepared in the same manner as in Example 10, except that the amount of aqueous solution held in the storage body was 1.5 g (1.3 times the saturated water content of the ion exchange membrane).

[0098] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.47 MPa. The results are also shown in Table 1.

[0099] Example 12 As a packaging sheet, the oxygen permeability is 0.11cc / (m 2·d·atm), water vapor permeability is 0.1g / (m 2 ·d) A storage body was prepared in the same manner as in Example 8, except that a gas barrier sheet consisting of an OPP layer of approximately 20 μm, a PE layer of approximately 20 μm, an aluminum foil layer of 7 μm, and a PE layer of approximately 20 μm was used.

[0100] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.47 MPa. The results are also shown in Table 1.

[0101] <Comparative Example 1> A storage body was prepared in the same manner as in Example 1, except that ion-exchanged water was used as the immersion solution.

[0102] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 7 days, the ion exchange membrane had a burst strength of 0.08 MPa. The above results are also shown in Table 1.

[0103] <Comparative Example 2> A storage body was prepared in the same manner as in Example 1, except that 250 mL of a mixed aqueous solution of 0.005 M hydrogen chloride and 0.005 M sodium chloride was used as the immersion solution. The dimensional change of the cation exchange membrane from before immersion was 0.27%, and the change of the counter ion H + The conversion rate was 15%, and the hydrogen chloride concentration in the stored material was 0.002M and the sodium chloride concentration was 0.010M.

[0104] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 7 days, the ion exchange membrane had a burst strength of 0.05 MPa. The above results are also shown in Table 1.

[0105] [Table 1]

[0106] Example 13 A storage body was prepared in the same manner as in Example 1, except that the anion exchange membrane was used as the ion exchange membrane and 250 mL of 0.5 M hydrochloric acid was used as the immersion solution. The dimensional change of the anion exchange membrane from before immersion was 0.00%, and the OH of the counter ion - The conversion rate was 0%, the hydrogen chloride concentration of the aqueous solution in the storage body was 0.5M, the sodium chloride concentration was 0M, and the volume of the aqueous solution was 26.7 times the saturated water content of the ion exchange membrane.

[0107] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane taken out had a burst strength of 0.43 MPa. The results are shown in Table 2.

[0108] Example 14 A storage body was prepared in the same manner as in Example 13, except that 250 mL of a mixed aqueous solution of 0.1 M sodium hydroxide and 0.1 M sodium chloride was used as the immersion solution. The dimensional change of the anion exchange membrane from before immersion was 0.23%, and the OH of the counter ion - The conversion rate was 4%, and the sodium hydroxide concentration of the aqueous solution in the storage body was 0.10M and the sodium chloride concentration was 0.10M.

[0109] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane taken out had a burst strength of 0.43 MPa. The above results are also shown in Table 2.

[0110] Example 15 A storage body was prepared in the same manner as in Example 13, except that 250 mL of a mixed aqueous solution of 0.01 M sodium hydroxide and 0.01 M sodium chloride was used as the immersion solution. The dimensional change of the anion exchange membrane from before immersion was 0.21%, and the OH of the counter ion - The conversion rate was 6%, and the sodium hydroxide concentration of the aqueous solution in the storage body was 0.009M and the sodium chloride concentration was 0.011M.

[0111] The prepared storage body was stored in a dryer set at 80°C, and when it was opened after 35 days, the ion exchange membrane had a burst strength of 0.40 MPa. The above results are also shown in Table 2.

[0112] [Table 2]

[0113] Example 16 Effective current area: 25 dm 2 77 of the above cation exchange membranes and 75 of the above anion exchange membranes were stacked alternately with gasket spacers. 70 L of 0.03 M hydrochloric acid was passed through the stack for 2 hours, allowing sufficient contact between the membrane and the liquid to achieve a saturated water-containing state. The solution was then drained by gravity, and all liquid inlets and outlets were sealed to create a storage container. The hydrogen chloride concentration of the aqueous solution remaining in the storage container was 0.14 M, and the sodium chloride concentration was 0.16 M.

[0114] The prepared storage body was stored at room temperature, and after one year the stack was disassembled and the ion exchange membranes were removed. The rupture strength of the removed cation exchange membrane was 0.46 MPa, and the rupture strength of the anion exchange membrane was 0.39 MPa. [Industrial Applicability]

[0115] The ion exchange membrane storage body and the method for storing an ion exchange membrane of the present invention are effective in maintaining the performance of the produced ion exchange membrane, and are therefore industrially useful.

Claims

1. An ion exchange membrane storage body in which an ion exchange membrane in a saturated water-containing state is stored in a storage member, The ion exchange membrane storage body is characterized in that the ion exchange membrane holds an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60M.

2. 2. The ion exchange membrane storage body according to claim 1, wherein the aqueous solution held in the ion exchange membrane contains a neutral salt.

3. 3. The ion exchange membrane storage body according to claim 2, wherein the neutral salt is contained in an amount of 0.1 to 15 molar equivalents of an acid or a base.

4. 3. The ion exchange membrane storage body according to claim 1, wherein the ion exchange membrane is a cation exchange membrane, and the aqueous solution held in the cation exchange membrane is an aqueous solution containing an acid.

5. H of the counter ion of the cation exchange group of the cation exchange membrane ＋ 5. The ion exchange membrane storage body according to claim 4, wherein the ratio of is 30 mol % or less.

6. 3. The ion exchange membrane storage body according to claim 1, wherein the ion exchange membrane is an anion exchange membrane, and the aqueous solution held in the anion exchange membrane is an aqueous solution containing a base.

7. The anion exchange membrane has an OH group as a counter ion of the anion exchange group. － 7. The ion exchange membrane storage body according to claim 6, wherein the ratio of is 30 mol % or less.

8. 3. The ion exchange membrane storage body according to claim 1, wherein the saturated water content of the ion exchange membrane in the saturated water-containing state is 15 to 55 mass %.

9. 3. The ion exchange membrane storage body according to claim 1, wherein the ion exchange membrane is a membrane in which an ion exchange resin is fixed to a polyolefin substrate.

10. The ion exchange membrane storage body according to claim 9, characterized in that the polyolefin substrate is a polyethylene substrate.

11. The ion exchange membrane storage body according to claim 10, characterized in that the polyethylene substrate is a polyethylene porous film substrate.

12. 10. The ion exchange membrane storage body according to claim 9, wherein the ion exchange resin is a cross-linked polystyrene-based ion exchange resin.

13. 3. The ion exchange membrane storage body according to claim 1, wherein the storage member is a sheet, and the ion exchange membrane is in the form of an ion exchange membrane container wrapped in the sheet.

14. The oxygen permeability of the sheet is 30 cc / (m ２ 14. The ion exchange membrane storage body according to claim 13, characterized in that the storage temperature is 100°C or less (.d.atm).

15. 14. The ion exchange membrane storage body according to claim 13, wherein the weight of the aqueous solution in the ion exchange membrane container is 1.1 to 200 times the saturated water content of the ion exchange membrane.

16. 3. The ion exchange membrane storage body according to claim 1, wherein the storage member is a dialysis stack component, and the ion exchange membrane is incorporated into the dialysis stack component to form a dialysis stack.

17. A method for storing an ion exchange membrane, comprising storing the ion exchange membrane in a storage member, the ion exchange membrane being saturated with water and holding an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60 M.

18. 18. The method for storing an ion exchange membrane according to claim 17, wherein the ion exchange membrane in a water-containing state is immersed in an aqueous solution containing an acid or a base, and then stored in a storage member.

19. 18. The method for storing an ion exchange membrane according to claim 17, wherein the storage member is a sheet, and the ion exchange membrane is wrapped in the sheet and stored in the form of an ion exchange membrane container.

20. The oxygen permeability of the sheet is 30 cc / (m ２ 20. The method for storing an ion exchange membrane according to claim 19, wherein the temperature is 100°C or less (.d.atm).

21. 18. The method for storing an ion exchange membrane according to claim 17, wherein the storage member is a dialysis stack component, and the storage member is incorporated into the dialysis stack component and stored in the form of a dialysis stack.

22. 22. The method for storing an ion exchange membrane according to claim 21, wherein the ion exchange membrane in a water-containing state is brought into contact with an aqueous solution containing an acid or a base after being incorporated into a dialysis stack component.

Images