Ion exchange membrane container and method for storing ion exchange membrane

Abstract

Provided is an ion exchange membrane container in which an ion exchange membrane in a saturated water-containing state is packaged in a sheet having an oxygen permeability of 30 cc / (m2d∙atm) or less and water vapor permeability of 0.8 g / (m2∙d) or less.

Description

Ion exchange membrane container and method for storing ion exchange membrane

[0001] The present invention relates to an ion exchange membrane container that contains an ion exchange membrane, and a method for storing an ion exchange membrane.

[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 of this expansion and contraction also easily causes the membrane to break. Therefore, it is preferable to store ion exchange membranes in the presence of sufficient water. Furthermore, when ion exchange membranes are formed solely from ion exchange resins, they often have low strength and are subject to significant morphological changes due to swelling when immersed in a liquid, making them unsuitable for practical use. For this reason, ion exchange membranes are preferably formed by supporting ion exchange resins on substrates that have a predetermined strength, do not undergo morphological changes due to swelling, and do not impair the ion exchange capacity specific to ion exchange resins (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 membranes of Patent Document 3 are stored in a dry state after being produced.

[0005] JP 2009-96923 A JP 2016-22454 A WO 2007-029723 A

[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. However, it has also been found that the resin gradually deteriorates during storage, and that prolonged storage leads to a decrease in membrane strength. Furthermore, it has been found that in ion exchange membranes having an ion exchange resin supported on a substrate, resin deterioration progresses more rapidly 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 these circumstances, and aims to provide a method for preventing the deterioration of the physical strength of an ion exchange membrane during storage.

[0007] As a result of intensive research to solve the above-mentioned problems, the inventors 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 also found that the decrease in physical strength of ion exchange membranes during storage can be suppressed by storing the ion exchange membrane in a state where oxygen is blocked, thereby completing the present invention.

[0008] That is, the present invention is as follows: [1] An ion exchange membrane in a saturated water-containing state has an oxygen permeability of 30 cc / (m ２ [2] An ion exchange membrane container characterized in that the container is wrapped with a sheet having a water vapor permeability of 0.01 to 0.8 g / (m ２ [1] The ion exchange membrane container according to the above [1], characterized in that the ion exchange membrane is a membrane in which an ion exchange resin is fixed to a polyolefin substrate. [3] The ion exchange membrane container according to the above [1] or [2], characterized in that the ion exchange membrane is a membrane in which an ion exchange resin is fixed to a polyolefin substrate. [4] The ion exchange membrane container according to the above [3], characterized in that the polyolefin substrate is a polyethylene substrate. [5] The ion exchange membrane container according to the above [4], characterized in that the polyethylene substrate is a polyethylene porous film substrate.

[0009] [6] The ion exchange membrane container according to any one of [3] to [5] above, wherein the ion exchange resin is a cross-linked polystyrene-based ion exchange resin. [7] The ion exchange membrane container according to any one of [1] to [6] above, wherein the saturated water content of the ion exchange membrane in a saturated water-containing state is 15 to 55 mass %. [8] The ion exchange membrane container according to any one of [1] to [7] above, wherein the weight of water in the ion exchange membrane container is 1.1 to 200 times the saturated water content of the ion exchange membrane. [9] The ion exchange membrane container according to any one of [1] to [8] above, wherein the water in the ion exchange membrane container is an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60 M.

[10] The ion exchange membrane container according to [9] above, wherein the aqueous solution contains a neutral salt of an acid or base in an amount of 0.1 to 15 molar equivalents.

[0010]

[11] The ion exchange membrane in a saturated water state is subjected to an oxygen permeability test with a water content of 30 cc / (m ２ 1. A method for storing an ion exchange membrane, characterized in that the membrane is wrapped in a sheet having a temperature of 0.5 to 1.5°C (d atm) or less and stored.

[0011] According to the ion exchange membrane container 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.

[0012] The ion exchange membrane container of the present invention has an ion exchange membrane in a saturated water-containing state with an oxygen permeability of 30 cc / (m ２ It is characterized by being packaged in a sheet of less than 10 ...

[0013] The ion exchange membrane container of the present invention is a container in which the ion exchange membrane in a saturated water-containing state is placed in a state where the oxygen permeability is 30 cc / (m ２ The strength of the ion exchange membrane can be prevented from decreasing during storage by an inexpensive and simple method such as wrapping (sealing) the membrane with a sheet having a pressure of 0.5 MPa or less (0.5 MPa).

[0014] When an ion exchange membrane is stored in a water-containing state, it is believed that, as described above, 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 inclusion of water causes the ion exchange membrane to swell, which increases the oxygen permeation and diffusion rate in the membrane, resulting in significant resin degradation. More specifically, when the ion exchange membrane is in a dry state, the membrane is not swollen and oxygen cannot penetrate into the membrane, so oxidation does not progress easily. However, in a water-containing state, the membrane is swollen, allowing oxygen to penetrate into the membrane and reach the oxidation point, and oxidative degradation progresses. When this state becomes saturated with water, the membrane swells to the maximum with water, making it most susceptible to oxygen penetration, and oxidative degradation progresses rapidly. Therefore, measures against oxidation are required, and in the present invention, a membrane with an oxygen permeability of 30 cc / (m ２ By wrapping the ion exchange membrane in a sheet with a temperature of 0.5°C or less (0.5°C / 100°F), this oxidation can be prevented, and deterioration of the strength of the ion exchange membrane can be prevented.

[0015] The sheet (packaging sheet) for packaging the ion exchange membrane in the ion exchange membrane container of the present invention has an oxygen permeability of 30 cc / (m ２ There are no particular limitations as long as the oxygen permeability is 25 cc / (m 2 · d · atm) or less, but from the viewpoint of effectively blocking oxygen and further suppressing oxidative deterioration, it is preferable that the oxygen permeability is 25 cc / (m 2 · d · atm) or less. ２ · d · atm) or less is preferable, and 10 cc / (m ２ · d · atm) or less is more preferable, and 1 cc / (m ２ · d · atm) or less is more preferable, and 0.5 cc / (m ２ The lower the oxygen permeability, the better. The lower limit is, for example, 0.01 cc / (m ２ The oxygen permeability of the packaging sheet is measured for the sheet in a dry state in accordance with JIS-K7126-2.

[0016] The ion exchange membrane container of the present invention accommodates (packages) an ion exchange membrane in a saturated water-containing state. The saturated water content of the ion exchange membrane in a saturated water-containing state is, for example, 15 to 55 mass %, preferably about 20 to 50 mass %, and more preferably 25 to 45 mass %. 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

[0017] In the ion exchange membrane container of the present invention, water is present in the container so that the ion exchange membrane is at least saturated with water, thereby suppressing deterioration in strength of the ion exchange membrane due to expansion and contraction caused by drying.

[0018] The weight of water in the ion exchange membrane container is the amount required to at least saturate the ion exchange membrane, 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 a water amount 1.1 times or more the saturated water content, the surface of the ion exchange membrane is sufficiently covered with a layer of water, allowing oxygen to dissolve in the water and then penetrate the membrane to the oxidation point, thereby mitigating the progression of active oxidation. In other words, in this case, the oxygen barrier sheet's oxygen blocking effect and the water surface layer's oxygen penetration suppression effect combine to achieve a significant oxidation degradation suppression effect. On the other hand, if the amount of water in the package exceeds 200 times the saturated water content, it may cause difficulties in transportation and other usage concerns, so it is preferable not to increase the weight of water in the container more than necessary.

[0019] The weight of water in the ion exchange membrane container is calculated using the following formula: Weight of the ion exchange membrane container - (dry weight of the ion exchange membrane + weight of the packaging sheet)

[0020] The ratio (multiplication factor) of the weight of water 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)

[0021] Furthermore, the water in the ion exchange membrane container of the present invention may be an aqueous solution to which an acid or a base has been added. For example, an aqueous solution containing an acid or a base at a concentration of 0.005 to 0.60 M (hereinafter, sometimes referred to as an acid solution and a base solution, respectively) is preferred. The acid or base reacts with an active reaction intermediate generated in an oxidation reaction or the like, thereby suppressing the degradation reaction and more effectively preventing the deterioration of the strength of the ion exchange membrane. From the viewpoint of further suppressing oxidative degradation, the concentration of the acid or base in the aqueous solution in the ion exchange membrane container is more preferably 0.008 to 0.55 M, and even more preferably 0.010 to 0.50 M.

[0022] The acid or base concentration of the aqueous solution in the ion exchange membrane container can be measured by potentiometric titration using an aqueous sodium hydroxide solution or sulfuric acid solution of known concentration.

[0023] 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 oxidative degradation inhibitory effect even in small amounts are preferred, and inorganic strong acids that accumulate less in the membrane are more preferred. Specifically, hydrochloric acid, sulfuric acid, and nitric acid are preferably used. Examples of bases 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 oxidative degradation inhibitory effect even in small amounts are preferred, and inorganic strong bases that accumulate less in the membrane are more preferred. Specifically, sodium hydroxide and potassium hydroxide are preferably used.

[0024] 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 cation exchange membrane retains a base solution due to its affinity with the ion exchange group. ＋ 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.

[0025] In the present invention, the aqueous solution in the ion exchange membrane container preferably contains a neutral salt. When an ion exchange membrane retains an acid or a base, dimensional changes tend to occur, but the coexistence of a neutral salt can suppress such dimensional changes.

[0026] That is, a certain amount of water is bound around the ion exchange group 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.

[0027] To prevent the strength from decreasing, it is necessary for the ion exchange membrane to have an acid or a base around it, and for the counter ion to be H ＋ YaOH － 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 ＋ YaOH － By not making the ion exchange membrane too thick, 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.

[0028] 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.

[0029] The packaging sheet has a water vapor permeability of 0.8 g / (m ２ d) or less, and 0.5 g / (m ２ d) or less, and more preferably 0.3 g / (m ２ The lower the water vapor permeability, the better. The lower limit is, for example, 0.01 g / (m ２ The water vapor transmission rate of the packaging sheet is measured for a dry sheet in accordance with JIS Z0208 (cup method).

[0030] It should be noted that Patent Document 3 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 different in technical significance from the present invention. In relation to this technical significance, the present invention requires suppressing 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 membrane with the lowest water vapor permeability has a water vapor permeability of 1 g / (m ２ Regarding d), in the present invention, it is preferable that the water vapor permeability is even lower than this.

[0031] Specifically, the packaging sheet is not particularly limited as long as it satisfies the above conditions, but examples include metal-vapor-deposited plastic sheets having a layer of metal such as aluminum vapor-deposited on a resin film such as polyethylene, polypropylene, polyethylene terephthalate, etc.; inorganic oxide-vapor-deposited plastic sheets having a layer of inorganic oxide such as silica or alumina vapor-deposited; metal-laminated plastic sheets having a layer of metal such as aluminum; and low-oxygen-permeable polymer-laminated plastic sheets having a layer of polymer with low oxygen permeability.

[0032] The packaging sheet preferably 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.

[0033] The ion exchange membrane of the present invention can be used as an electrodialysis membrane used in salt production and desalination processes in the food industry, an electrolyte membrane for fuel cells, or a diffusion dialysis membrane used for acid recovery from metal ion-containing acids generated in the steel industry, etc.

[0034] 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 having a substrate.

[0035] (Substrate) The substrate functions as a reinforcing material for the ion exchange membrane. As the material of the substrate, those conventionally used as substrates for ion exchange membranes can be used without any limitation. For example, polyolefin, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyester, polyvinyl alcohol, polyamide, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfone, polyphenylene sulfide, polyimide, polyetherimide, polyamide, polyamideimide, polycarbonate, polyacrylate, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polychlorotrifluoroethylene and copolymers thereof can be mentioned. Among these, polyolefin is preferable as the substrate, since it is excellent in alkali resistance, strength, heat resistance, processability, cost, etc., and polyethylene substrate is particularly preferable. 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.

[0036] Although polyolefin substrates have high performance as substrates as described above, they tend to be susceptible to oxidative degradation during storage, and among polyolefin substrates, the deterioration tends to be particularly pronounced in polyethylene substrates. In the present invention, even in polyolefin substrates that are susceptible to oxidative degradation, oxidative degradation can be suppressed, and thus a decrease in strength can be suppressed.

[0037] 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 membrane 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 units of an α-olefin such as propylene, butene, pentene, hexene, or octene.

[0038] 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.

[0039] The film 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.

[0040] 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 membrane damage or deterioration due to peeling between the resin and the substrate. Furthermore, the membrane tends to lack dimensional stability and have reduced mechanical strength. On the other hand, if the porosity is too small, the amount of ion exchange resin per unit volume decreases, preventing sufficient ion exchange capacity from being exhibited, which can result in high membrane resistance.

[0041] (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.

[0042] 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.

[0043] Among these, the resin forming the skeleton is preferably a crosslinked styrene-based resin mainly 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, vinylbenzyltrimethylamine, chloromethylstyrene, bromomethylstyrene, and iodomethylstyrene.

[0044] The crosslinkable polymerizable monomer is used to densify the ion exchange resin and improve swelling resistance and membrane strength, and is not particularly limited, and examples thereof include divinyl compounds such as divinylbenzene, divinyl sulfone, butadiene, chloroprene, divinylbiphenyl, trivinylbenzenes, triacrylates, divinylnaphthalene, diallylamine, divinylpyridine, and diacrylates. Generally, the content of such crosslinkable polymerizable monomer in the raw material composition is preferably 0.1 to 50% by weight, more preferably 0.5 to 35% by weight.

[0045] The ion exchange groups contained in the ion exchange resin may be appropriately determined depending on the intended use. For example, sulfonic acid groups or carboxylic acid groups can be used in the case of cation exchange membranes, and quaternary ammonium bases or pyridinium bases can be used in the case of anion exchange membranes. Counterions of the ion exchange groups can be, for example, metal ions such as hydrogen ions or sodium ions in the case of cation exchange membranes, or hydroxide ions, halogen ions, or bicarbonate ions in the case of anion exchange membranes.

[0046] (Method for Producing 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 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 obtain an ion exchange resin. The conditions of this thermal polymerization are thought to affect the susceptibility of the ion exchange membrane to oxidative degradation.

[0047] As a method for storing the ion exchange membrane of the present invention, the ion exchange membrane in a saturated water-containing state is stored in a container with an oxygen permeability of 30 cc / (m ２ The present invention is characterized in that the ion exchange membrane is stored in a package with a sheet having a pressure of 0.5 MPa or less (d atm). That is, the ion exchange membrane is stored as the ion exchange membrane container of the present invention. This makes it possible to prevent the strength of the ion exchange membrane from decreasing during storage by an inexpensive and simple means. The packaging sheet, ion exchange membrane, etc. are the same as those described for the ion exchange membrane container of the present invention, and therefore a description thereof will be omitted.

[0048] Examples of the present invention are shown below. Various properties of the packaging sheet and ion exchange membrane were measured by the following methods.

[0049] (1) Measurement of oxygen permeability of packaging sheet A dry sheet was measured using a coulometric oxygen permeability measuring device (OX-TRAN2 / 22L manufactured by MOCON Corporation) in accordance with JIS-K7126-2. The gas conditions used were a temperature of 23°C, humidity of 50% RH, and oxygen concentration of 100%.

[0050] (2) Measurement of Water Vapor Permeability of Packaging Sheets Dry sheets were measured in accordance with JIS Z0208 (cup method) under the following temperature and humidity conditions: temperature 40°C, humidity 90% RH.

[0051] (3) 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, and then thoroughly rinsed with ion-exchanged water. Then, without drying the membrane, the burst strength was measured using a Mullen burst tester (manufactured by Toyo Seiki Seisakusho, Ltd.) in accordance with JIS-P8112.

[0052] (4) Calculation of moisture content of ion exchange membrane The moisture on the surface of the ion exchange membrane was wiped off with tissue paper, and the mass of the membrane when wet (W １ Furthermore, the weight after drying under reduced pressure at 60°C for 5 hours was measured. １ Based on the above measured values, the water content of the ion exchange membrane was calculated using the following formula:

[0053] Moisture content = 100 x (W １ -D １ ) / D １ [%]

[0054] (5) Calculation of saturated water content of ion exchange membrane The ion exchange membrane was immersed in a 1 mol / L-NaCl aqueous solution for 4 hours or more and then thoroughly washed with ion exchange water. After that, the water on the surface was wiped off with tissue paper, and the mass of the wet membrane (W ２ Furthermore, the weight after drying under reduced pressure at 60°C for 5 hours was measured. ２ Based on the above measured values, the saturated water content of the ion exchange membrane was calculated using the following formula:

[0055] Saturated water content = 100 x (W ２ -D ２ ) / D ２ [%]

[0056] (6) Measurement of the amount of water in the ion exchange membrane container The weight (Ag) of the entire container was measured. Subsequently, the dimensions of all the ion exchange membranes in the container were measured, and the total area (Bm ２ The dimensions of all sheets in the container were measured, and the total area (cm ２) was calculated. Subsequently, the ion exchange membrane and the sheet were cut into 20 cm x 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.

[0057] Moisture content = A-(D×B / 0.06+E×C / 0.06) [g]

[0058] 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 by the following formula.

[0059] Moisture content / saturated water content = {A-(D×B / 0.06+E×C / 0.06)} / (D×B / 0.06×F / 100)

[0060] <Production Example 1: Cation exchange membrane> A polymerizable composition was prepared by mixing the following components according to the formulation: Styrene 73.5 parts by mass p-chloromethylstyrene 16.5 parts by mass Acrylonitrile 10.0 parts by mass Tributyl acetylcitrate 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

[0061] 500g of this polymerizable composition is placed in a 1000mL glass container, and a porous film made of high molecular weight polyethylene with a thickness of 130 μm and a porosity of 50% is immersed therein as a substrate film, and the voids of the film are filled with the polymer composition.The porous substrate film filled with the above-mentioned polymer composition is taken out, and a polyester film with a thickness of 188 μm is used as a release material to cover both sides of the porous substrate film, and then, under a nitrogen pressure of 0.4MPa, the temperature is raised from 20 ° C to 50 ° C over 20 minutes, then the temperature is raised from 50 ° C to 110 ° C over 60 minutes, and the temperature is raised from 110 ° C to 130 ° C over 80 minutes, and the temperature is maintained at 130 ° C for 180 minutes, and the polymer composition is then heated.

[0062] 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 in 90% sulfuric acid, 60% sulfuric acid, and ion-exchanged water, successively, and further immersed 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.

[0063] <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

[0064] 500g of this polymerizable composition is placed in a 1000mL glass container, and a porous film made of high molecular weight polyethylene with a thickness of 130 μm and a porosity of 50% is immersed therein as a substrate film, and the voids of the film are filled with the polymer composition.The porous substrate film filled with the above-mentioned polymer composition is taken out, and a polyester film with a thickness of 188 μm is used as a release material to cover both sides of the porous substrate film, and then, under a nitrogen pressure of 0.4MPa, the temperature is raised from 20 ° C to 50 ° C over 20 minutes, then the temperature is raised from 50 ° C to 110 ° C over 60 minutes, and the temperature is raised from 110 ° C to 130 ° C over 80 minutes, and the temperature is maintained at 130 ° C for 180 minutes, and the polymer composition is then heated.

[0065] The resulting membrane was immersed in a mixture of 15 parts by mass of a 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. The resulting ion exchange membrane had a burst strength of 0.46 MPa and a saturated water content of 26.8% by mass.

[0066] Example 1: Oxygen permeability of 0.02 cc / (m ２ · d · atm), water vapor permeability is 0.1 g / (m ２d) A gas barrier sheet (total thickness 70 μm) having a polyethylene terephthalate layer vapor-deposited with alumina was folded, and two of the remaining three sides were heat-sealed to form a bag. The above cation exchange membrane was cut into a 5 cm x 15 cm piece, and three cut pieces were stacked and placed in a bag. 60.0 g of ion exchange water (50.5 times the saturated water content of the ion exchange membrane) was added to the bag to saturated the ion exchange membrane. The remaining side was heat-sealed to form an ion exchange membrane container.

[0067] The prepared container was stored in a dryer set at 40°C for 90 days and then opened. The moisture content inside the container was 60.0 g, and the ion exchange membrane removed from the container had a burst strength of 0.46 MPa, maintaining its strength.

[0068] Furthermore, when the prepared container was stored in a dryer set at 60°C for 90 days and then opened, the water content in the container was 56.7g, and the ion exchange membrane removed had a burst strength of 0.48MPa. When the container was opened after 180 days of storage, the water content in the container was 47.1g, and the ion exchange membrane removed had a burst strength of 0.49MPa. The results are shown in Table 1.

[0069] Example 2: Oxygen permeability of 0.11 cc / (m ２ · d · atm), water vapor permeability is 0.1 g / (m ２ ・d) A container was prepared in the same manner as in Example 1, except that a gas barrier sheet (total thickness 66 μm) consisting of an OPP layer of about 20 μm, a PE layer of about 20 μm, an aluminum foil layer of 7 μm, and a PE layer of about 20 μm was used.

[0070] The prepared container was stored in a dryer set at 40°C for 90 days and then opened. The moisture content inside the container was 60.0 g, and the ion exchange membrane removed had a burst strength of 0.49 MPa, maintaining its strength.

[0071] Furthermore, when the prepared container was stored in a dryer set at 60°C for 90 days and then opened, the water content in the container was 60.0 g and the rupture strength of the removed ion exchange membrane was 0.49 MPa. When the container was opened after 180 days of storage, the water content in the container was 59.9 g and the rupture strength of the removed ion exchange membrane was 0.45 MPa. The above results are also shown in Table 1.

[0072] Example 3: Oxygen permeability of 6.0 cc / (m ２ d atm), and water vapor permeability is 8.2 g / (m ２ A container was produced in the same manner as in Example 1, except that a gas barrier sheet (total thickness 70 μm) having a PVDC-coated nylon layer (d) was used.

[0073] The prepared container was stored in a dryer set at 40°C for 90 days and then opened. The moisture content inside the container was 53.4 g, and the ion exchange membrane removed had a burst strength of 0.42 MPa, maintaining its strength.

[0074] Furthermore, when the prepared container was stored in a dryer set at 60°C for 90 days and then opened, the water content inside the container was 19.9 g and the rupture strength of the removed ion exchange membrane was 0.24 MPa. When the container was opened after 180 days of storage, the inside of the container was dry and the rupture strength of the removed ion exchange membrane was 0.02 MPa. The above results are also shown in Table 1.

[0075] Example 4: Hiryu N-10 manufactured by SB Packs Co., Ltd. (total thickness 75 μm, composition: 15 μm polynylon / 60 μm PE, oxygen permeability 24.0 cc / (m ２ · d · atm), water vapor permeability 10.0 g / (m ２ A container was produced in the same manner as in Example 1, except that d)) was used.

[0076] The prepared container was stored in a dryer set at 40°C for 90 days and then opened. The amount of water in the container was 51.0 g, and the ion exchange membrane removed had a burst strength of 0.40 MPa, maintaining its strength.

[0077] Furthermore, when the prepared container was stored in a dryer set at 60°C for 90 days and then opened, the moisture content inside the container was 3.0 g, and the ion exchange membrane removed had a burst strength of 0.15 MPa. When the container was opened after 180 days of storage, the inside of the container was dry, and the ion exchange membrane removed had a burst strength of 0.01 MPa. The above results are also shown in Table 1.

[0078] Example 5 A container was produced in the same manner as in Example 2, except that 0.36 g of water (1.3 times the saturated water content of the ion exchange membrane) was placed in the bag.

[0079] The produced container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.44 MPa, which was maintained.

[0080] Furthermore, when the prepared container was stored in a dryer set at 60°C for 90 days and then opened, the rupture strength of the ion exchange membrane taken out was 0.45 MPa. When the container was opened after 180 days of storage, the rupture strength of the ion exchange membrane taken out was 0.45 MPa. The above results are also shown in Table 1.

[0081] Example 6 A container was produced in the same manner as in Example 3, except that 0.36 g of water (1.3 times the saturated water content of the ion exchange membrane) was placed in the bag.

[0082] The produced container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.39 MPa, which was maintained at the same strength. The results are also shown in Table 1.

[0083] Example 7: Oxygen permeability of 0.11 cc / (m ２ · d · atm), water vapor permeability is 0.1 g / (m ２A gas barrier sheet (total thickness 66 μm) consisting of an approximately 20 μm OPP layer, an approximately 20 μm PE layer, a 7 μm aluminum foil layer, and an approximately 20 μm PE layer (d) was folded, and two of the remaining three sides were heat-sealed to form a bag. The above cation exchange membrane was cut into 5 cm x 15 cm pieces, and three sheets were immersed in 250 mL of 0.01 M sulfuric acid. The three immersed membranes were then placed in a bag. 0.36 g of 0.01 M sulfuric acid (1.3 times the saturated water content of the ion exchange membrane) was added to the bag to saturated the ion exchange membrane. The remaining side was heat-sealed to form an ion exchange membrane container.

[0084] The produced container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.46 MPa, which was maintained at the same strength.

[0085] Furthermore, when the produced container was stored in a dryer set at 60° C. for 90 days and then opened, the ion exchange membrane taken out had a burst strength of 0.45 MPa. The above results are also shown in Table 1.

[0086] Example 8 A container was produced in the same manner as in Example 7, except that a mixed aqueous solution of 0.05 M sulfuric acid and 0.05 M sodium chloride was used as the aqueous solution.

[0087] The produced container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.45 MPa, which was maintained at the same strength.

[0088] Furthermore, when the produced container was stored in a dryer set at 60° C. for 90 days and then opened, the ion exchange membrane taken out had a burst strength of 0.45 MPa. The above results are also shown in Table 1.

[0089] Example 9: A sheet was prepared using Hiryu N-10 (total thickness 75 μm, composition: 15 μm polynylon / 60 μm PE, oxygen permeability 24.0 cc / (m ２ · d · atm), water vapor permeability 10.0 g / (m ２A container was prepared in the same manner as in Example 7, except that d)) was used, a mixed aqueous solution of 0.1 M hydrogen chloride and 0.1 M sodium chloride was used as the aqueous solution, and 60.0 g (50.5 times the saturated water content of the ion exchange membrane) was placed in the bag.

[0090] The produced container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.43 MPa, which was maintained.

[0091] <Comparative Example 1> Oxygen permeability is 2300 cc / (m ２ · d · atm), water vapor permeability is 25 g / (m ２ d) A container was produced in the same manner as in Example 1, except that a polyethylene sheet having a thickness of 45 μm was used.

[0092] The prepared container was stored in a dryer set at 40°C for 90 days and then opened. The moisture content inside the container was 29.1 g, and the ion exchange membrane that was removed had a burst strength of 0.02 MPa, a significant decrease in strength.

[0093] Furthermore, when the prepared container was stored in a dryer set at 60° C. for 90 days and then opened, the inside of the container was found to be dry, and the ion exchange membrane taken out had a burst strength of 0.01 MPa or less. The results are also shown in Table 1.

[0094] <Comparative Example 2> Oxygen permeability 94 cc / (m ２ · d · atm), water vapor permeability is 0.3 g / (m ２ A container was produced in the same manner as in Example 1, except that a gas barrier sheet having an alumina-deposited PET layer with a total thickness of 134 μm was used as d).

[0095] The prepared container was stored in a dryer set at 40°C for 90 days and then opened. The moisture content inside the container was 60.0 g, and the ion exchange membrane removed had a burst strength of 0.22 MPa, indicating a decrease in strength.

[0096] Furthermore, when the prepared container was stored in a dryer set at 60° C. for 90 days and then opened, the water content in the container was 57.0 g, and the ion exchange membrane taken out had a burst strength of 0.17 MPa. The above results are also shown in Table 1.

[0097] Reference Example 1: The same polyethylene sheet as in Comparative Example 1 was folded, and two of the remaining three sides were heat-sealed to form a bag. The above ion exchange membrane was cut into a 5 cm x 15 cm piece, and vacuum-dried at 60°C for 5 hours to reduce the moisture content to 0%. Three sheets of the membrane were stacked and placed in a bag. The remaining side was heat-sealed without adding water to the bag, and an ion exchange membrane container in which the membrane was not saturated with moisture was produced.

[0098] The prepared container was stored in a dryer set at 60° C. for 90 days and then opened. The container was found to be dry, and the ion exchange membrane removed from the container had a burst strength of 0.45 MPa after being immersed in water for 24 hours. The results are also shown in Table 1.

[0099]

[0100] Example 10 A container was produced in the same manner as in Example 1, except that the anion exchange membrane was used as the ion exchange membrane.

[0101] The prepared container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.43 Pa. The prepared container was also stored in a dryer set at 60° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.43 MPa. The results are shown in Table 2.

[0102] Example 11 A container was produced in the same manner as in Example 2, except that the anion exchange membrane was used as the ion exchange membrane.

[0103] When the prepared container was stored in a dryer set at 40°C for 90 days and then opened, the rupture strength of the removed ion exchange membrane was 0.43 Pa. Furthermore, when the prepared container was stored in a dryer set at 60°C for 90 days and then opened, the rupture strength of the removed ion exchange membrane was 0.43 MPa. The results are also shown in Table 2. Example 12 A container was prepared in the same manner as in Example 7, except that the anion exchange membrane was used as the ion exchange membrane, a mixed aqueous solution of 0.5 M sodium hydroxide and 1.0 M sodium chloride was used as the aqueous solution, and 60.0 g (50.5 times the saturated water content of the ion exchange membrane) was placed in the bag.

[0104] The prepared container was stored in a dryer set at 40° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.43 MPa. The prepared container was also stored in a dryer set at 60° C. for 90 days and then opened, and the ion exchange membrane taken out had a burst strength of 0.43 MPa. The above results are also shown in Table 2.

[0105]

[0106] The ion exchange membrane container 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. The ion exchange membrane in a saturated water state has an oxygen permeability of 30 cc / (m ２ 1. An ion exchange membrane container characterized by being wrapped with a sheet having a capacity of 0.1 .d.atm or less.

2. The water vapor permeability of the sheet is 0.8 g / (m ２ d) or less. The ion exchange membrane container according to claim 1, wherein:

3. The ion exchange membrane container according to claim 1 or 2, wherein the ion exchange membrane is a membrane in which an ion exchange resin is fixed to a polyolefin substrate.

4. The ion exchange membrane container according to claim 3, wherein the polyolefin substrate is a polyethylene substrate.

5. The ion exchange membrane container according to claim 4, wherein the polyethylene substrate is a polyethylene porous film substrate.

6. The ion exchange membrane container according to claim 3, wherein the ion exchange resin is a cross-linked polystyrene-based ion exchange resin.

7. The ion exchange membrane container according to claim 1 or 2, wherein the saturated water content of the ion exchange membrane in the saturated water state is 15 to 55 mass %.

8. The ion exchange membrane container according to claim 1 or 2, wherein the weight of water in the ion exchange membrane container is 1.1 to 200 times the saturated water content of the ion exchange membrane.

9. The ion exchange membrane container according to claim 1 or 2, wherein the water in the ion exchange membrane container is an aqueous solution containing an acid or base at a concentration of 0.005 to 0.60M.

10. The ion exchange membrane container according to claim 9, wherein the aqueous solution contains 0.1 to 15 molar equivalents of a neutral salt of an acid or base.

11. A saturated water-containing ion exchange membrane with an oxygen permeability of 30 cc / (m ２ 1. A method for storing an ion exchange membrane, comprising packaging the membrane in a sheet having a temperature of not higher than 100°C (d atm) and storing the membrane.

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