WO2021090919A1

WO2021090919A1 - Ion exchange membrane, manufacturing method of ion exchange membrane, and ion exchange membrane cell

Info

Publication number: WO2021090919A1
Application number: PCT/JP2020/041559
Authority: WO
Inventors: 充比嘉
Original assignee: 国立大学法人山口大学
Priority date: 2019-11-06
Filing date: 2020-11-06
Publication date: 2021-05-14

Abstract

The present invention addresses the problem of providing an ion exchange membrane through which ions permeate easier than through a conventional profile membrane, which has a small pressure loss in a flow path, and in which clogging due to dirt can be reduced.　An ion exchange membrane having a concavo-convex shape has a flat portion near the end, and the curved protrusions and curved depressions created by the bending of the ion exchange membrane itself are the convex and concave portions in the concavo-convex shape of the ion exchange membrane, respectively.

Description

Ion exchange membrane, manufacturing method of ion exchange membrane and ion exchange membrane cell

The present invention relates to an ion exchange membrane having an uneven shape, a method for producing the ion exchange membrane, and an ion exchange membrane cell using the ion exchange membrane.

In recent years, promotion of the use of renewable energy has been required. As one of the renewable energies, there is a technology for converting the salinity difference energy (SGE) existing between two salt waters having different salinities such as seawater and river water into electric power. This SGE has the advantages of high operating rate and small installation area compared to solar power generation and wind power generation, and can also be used as a base load power source. Power generation using SGE includes osmotic power generation (PRO) using a semipermeable membrane and reverse electrodialysis (RED: Reverse Electro-Dialysis) power generation using an ion exchange membrane, but seawater level salt water is used. In some cases, it is said that RED power generation is superior to PRO. For RED power generation, a cation exchange membrane (CEM: Cation Exchange Membrane) and an anion exchange membrane (AEM: Anion Exchange Membrane) are used. CEM has the property of selectively permeating cations and AEM has the property of selectively permeating anions. First, electrodialysis (ED: Electro-Dialysis), which is the original technology of RED, will be described. This ED uses a stack in which hundreds of pairs of cells are stacked between two electrodes, with a pair of cells composed of CEM, a high-concentration side flow path, an AEM, and a low-concentration side flow path. When salt water such as seawater is supplied to this stack and a DC voltage is applied to the electrodes, cations move to the cathode side and anions move to the anode side, but cations pass through CEM but not AEM, and anions. Can pass through AEM but not CEM, so concentrated salt water and desalted water can be obtained in this device. This is the principle of ED (Fig. 1). On the other hand, RED power generation is the reverse process of this ED, and electric power can be obtained by adding high-salt water and low-salt water to this stack (Fig. 2). In other words, RED power generation is a technology that directly converts SGE into DC power. The voltage generated by the RED power generation is proportional to the natural logarithm of the concentration ratio between the high concentration side to which the high salt concentration water is supplied and the low concentration side to which the low salt concentration water is supplied. Also, in RED power generation, a stack consisting of a cell composed of CEM, a high-concentration side flow path, an AEM, and a low-concentration side flow path is used as a pair, and hundreds of pairs of these are stacked between two electrodes. The resistance of the cell is the total resistance of CEM, high-concentration side flow path, AEM, and low-concentration side flow path. Among them, the one with the highest electrical resistance is the low-concentration side flow path with low salt concentration. .. If the height of the low-concentration side flow path, that is, the distance between CEM and AEM is narrowed, the electrical resistance of the low-concentration side flow path decreases. However, if this interval is narrowed, the flow path will be blocked by the membrane contaminants contained in the low-concentration side salt water, and the output will drop significantly.The pressure to supply the low-concentration side salt water to the stack will increase, and the pump energy will increase. There is a problem that the net generated power obtained by subtracting the pump power from the RED output decreases.

In the ED and RED power generation devices, as shown in FIG. 3, a pair of cells composed of a CEM, a high-concentration side flow path, an AEM, and a low-concentration side flow path is used as a pair, and hundreds of pairs are placed between the two electrodes. The stacked stack is the main component. Conventionally, as shown in FIG. 4, this cell is composed of a high-concentration side flow path spacer and a low-concentration side flow path spacer between CEM and AEM, and each spacer is made of a rubber-like gasket and a spacer net. There is. While high-salt water and low-salt water flow from the upstream side through the water guide holes opened in each membrane, a part of them flows from the notch (distribution hole) opened in the gasket to the predetermined spacer net and the downstream side. It flows into the water guide hole. By doing so, the structure is such that high-concentration salt water and low-concentration salt water are uniformly supplied to each of thousands of pairs of channels. FIG. 5 shows a side view of the flow in the cell. Here, the case of RED will be described. In this figure, high-concentration and low-concentration salt water flows from left to right. Cations and anions are diffused from the high concentration side to the low concentration side due to the concentration gradient, but as shown in FIG. 5, the spacer network is non-conductive and does not allow ions to pass through. In), the diffusion is inhibited and the effective film area where the ions diffuse is reduced, so that the electric resistance of the low-concentration side flow path is higher than that of the salt solution alone. In addition, since the spacer net is made of hydrophobic polymer material such as polyethylene (PE) and polypropylene (PP), fumin and inorganic particles contained in low salt concentration water (treated sewage water, river water, etc.) adhere to it. It is easy to aggregate. Therefore, in particular, as the distance between the CEM and the AEM in this flow path becomes narrower, these aggregate and reduce the flow of water, which leads to a significant decrease in output. Therefore, in the conventional cell, it is difficult to narrow the distance between the CEM and the AEM in the low concentration side flow path (see Patent Document 1).

Therefore, as one method for solving the above problem, a method using a conductive spacer has been proposed (Fig. 6). The conductive spacer is obtained by imparting cation exchange ability and anion exchange ability to the spacer itself, and as shown in FIG. 6, the electric resistance of the low concentration side flow path is increased because the effective membrane area where ions are diffused increases. Is reduced. Further, since the spacer is ionic and hydrophilic, it is difficult for dirt substances to adhere to the spacer. Methods for producing the conductive spacer include a method of cutting out an ion exchange membrane and a method of irradiating a non-conductive spacer such as PE with an electron beam and grafting a charged monomer to impart an ion exchange ability. However, in each case, the mechanical strength of the spacer portion is low, the production cost is high, and it is difficult to increase the area (see Patent Document 2).

Further, as another method for solving the above problem, a method using a profile film has been proposed (Non-Patent Documents 1 to 3). The difference between the profile membrane and the conductive spacer is that the conductive spacer is different from the ion exchange membrane and the spacer, but the profile membrane is made of the same material by integrating the spacer with the membrane. 7 and 8 show a schematic view of the profile film. In the case of a profile film, the effective film area may be larger than that of the conventional cell, but ions do not flow in the part shown by the dotted line in FIG. 7 (cations cannot pass through the AEM part, and the anion is also the CEM part. The electrical resistance cannot be smaller than that of the conductive spacer. In addition, structures with the same material but different thicknesses (structures with different thicknesses between the convex part and other parts) are deformed because the dimensional changes due to swelling between the parts with different thicknesses when the ion exchange membrane is immersed in salt water are different. It is prone to bursting and rupture, it is difficult to increase the area, and it is expensive. FIG. 8 shows an example in which a profile film is produced from a heterogeneous ion exchange membrane formed by kneading ion exchange resin powder into a binder resin (PVC or the like). As described above, in the case of the conventional profile film, the first problem is that the film surface is covered by the upper surface of the convex portion, and the flow of the solution is slowed at the upper surface portion and the root portion of the convex portion. Prone to cause adhesion. The second problem is that since this film has a structure that rises in a columnar shape from a flat film, when the entire film swells, there is a difference in the degree of swelling between the convex part and the flat film part, and the convex part is supported. Since the structure is not reinforced by the body, deterioration (cracks) is likely to occur in the convex portion, and stress concentration is particularly likely to occur at the root, and the structure is easily damaged. The third problem is that the plane of the top of the convex part (columnar part, etc.) of the cation exchange membrane (CEM) covers the membrane surface of the opposite anion exchange membrane, so that the effective membrane area through which the ion flow passes seems to be. The smaller the value, the higher the resistance, and the lower the processing efficiency in the ED and the generated power in the RED. The fourth problem is that the flat membrane ion exchange membrane is thickened with convex portions, so that the average thickness of the membrane is thicker than that of the flat membrane ion exchange membrane, and the average electrical resistance of the entire membrane is high. That is. The fifth problem was that the presence of the protrusions reduced the cross-sectional area of the flow path, resulting in a loss of power due to the high pressure required to supply the same amount of solution.

Japanese Unexamined Patent Publication No. 2014-14776 Japanese Unexamined Patent Publication No. 2006-175408

An object of the present invention is to provide an ion exchange membrane in which ions can easily permeate the membrane as compared with a conventional profile membrane, pressure loss in the flow path is small, and clogging due to dirt can be reduced. Further, in addition to the above, it is an object of the present invention to provide an ion exchange membrane with less deformation and breakage. Another object of the present invention is to provide an ion exchange membrane cell in which ions easily permeate the membrane, pressure loss in the flow path is small, clogging due to dirt is small, and deformation and breakage of the ion exchange membrane are small.

The present inventor has started to study an ion exchange membrane that can widen the effective membrane area through which ions permeate and suppress the adhesion of stains in a salt solution when used in, for example, an ED or RED power generation device. The present inventor has focused on the shape of the ion exchange membrane and its manufacturing method, and found that an ion exchange membrane having the desired characteristics can be obtained by bending the ion exchange membrane itself to form irregularities. I found it. Conventionally, when forming irregularities on an ion exchange membrane, the film thickness of the convex portion is naturally increased, and the ion exchange membrane itself is bent, for example, to form peaks and valleys, and this curved portion is bent to form a convex portion. It was not considered to be used as a recess. Because when assembling a cell with an ion exchange membrane, the ends of the membrane must be flat to seal with a gasket. However, even if the projected areas of the uneven portion and the flat portion are the same, there is a large difference in the surface area. Therefore, continuously forming the uneven portion and the flat portion with one film is local to the film. It was considered impossible to generate a large strain. Therefore, by using an ion exchanger made of a plastic polymer, an ion exchange membrane having a suitable uneven shape that solves the above-mentioned problems was obtained. Further, by using a plastic support and, in some cases, further using an ion exchanger of a plastic polymer, an ion exchange membrane having a suitable uneven shape that solves the above-mentioned problems was obtained. The ion exchange membrane having this shape can be obtained by a simple method of pressing a flat ion exchange membrane or a precursor membrane of the ion exchange membrane using a mold. Further, according to this method, since the above characteristics are obtained by the shape of the unevenness, the material conventionally used for the ion exchange membrane can be used. The ion exchange membrane thus obtained is suitable for use in ED and RED power generation, but is not limited to these as the intended use. The present invention is thus completed.

That is, the present invention is specified by the following matters.
(1) An ion exchange membrane having a concavo-convex shape, which has a flat portion near the end, and a convex portion and a concave portion due to bending of the ion exchange membrane itself are convex in the concavo-convex shape of the ion exchange membrane, respectively. An ion exchange membrane that is a portion and a recess.
(2) The ion exchange membrane is composed of at least the support and the ion exchange layers provided on both sides or one side of the support, and the ion exchange membrane is formed on the convex and concave portions due to the bending of the support. The ion exchange membrane according to (1) above, which is an ion exchange membrane in which convex portions and concave portions are formed respectively.
(3) The ion exchange membrane according to (1) or (2) above, wherein the end face in the longitudinal direction of the convex portion adjacent to the flat portion near the end is a surface inclined from the upper end toward the adjacent flat portion. ..
(4) The convex portion and the concave portion extend linearly, the concave portion is flat, and the convex portion has a surface in which both end faces in the longitudinal direction are inclined from the upper end toward the flat portion near the end of the ion exchange membrane. The ion exchange membrane according to any one of (1) to (3) above.
(5) A method for producing an ion exchange membrane having a concavo-convex shape, which comprises any one of the following steps (i) to (iii).
(I) A step of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and bending the film;
(Ii) A step of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and bending the film, and then cross-linking the polymer;
(Iii) A step of forming irregularities on the film by pressing a film of a plastic polymer having no charged groups against a mold having irregularities and bending the film, and then introducing charged groups;
(6) A method for producing an ion exchange membrane having an uneven shape composed of at least a support and an ion exchange layer, which comprises the following steps (A) or (B).
(A) A step of forming irregularities on the support by pressing a plastic support provided on both sides or one side with a plastic polymer layer having a charged group against a mold having irregularities and bending the support;
(B) The plastic support is pressed against a mold having irregularities and bent to form irregularities on the support, and after the irregularities are formed, a polymer layer having a charged group on both sides or one side of the support is formed. Setting process;
(7) An ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and at least one of the cation exchange membrane and the anion exchange membrane has an uneven shape. The ion exchange membrane having the concavo-convex shape has a flat portion near the end, and the convex portion and the concave portion due to the bending of the ion exchange membrane itself are the convex portion in the concavo-convex shape of the ion exchange membrane, respectively. An ion exchange membrane cell that becomes a concave portion and the convex portion is arranged so as to face the other ion exchange membrane.
(8) The ion exchange membrane cell according to (7) above, wherein the convex portion of the ion exchange membrane having an uneven shape is arranged so as to be in contact with the other ion exchange membrane.
(9) Both the cation exchange membrane and the anion exchange membrane are ion exchange membranes having a concavo-convex shape, and a part of the convex portion of the cation exchange membrane and a part of the convex portion of the anion exchange membrane are formed. The ion exchange membrane cell according to (8) above, which is arranged so as to be in contact with each other.
(10) At least one of the ion exchange membranes having a concavo-convex shape is composed of at least a support and ion exchange layers provided on both sides or one side of the support, and the convex and concave portions due to the bending of the support. The ion exchange membrane cell according to any one of (7) to (9) above, which is an ion exchange membrane in which convex portions and concave portions of the ion exchange membrane are formed.
Alternatively, the present invention is specified by the following matters.
(1) An ion exchange membrane having a concavo-convex shape, which has a flat portion near the end, and a convex portion and a concave portion due to bending of the ion exchange membrane itself are convex in the concavo-convex shape of the ion exchange membrane, respectively. An ion exchange membrane that is a portion and a recess.
(2) The ion exchange membrane according to (1) above, wherein the end face in the longitudinal direction of the convex portion adjacent to the flat portion near the end is a surface inclined from the upper end toward the adjacent flat portion.
(3) The convex portion and the concave portion extend linearly, the concave portion is flat, and the convex portion has a surface in which both end faces in the longitudinal direction are inclined from the upper end toward the flat portion near the end of the ion exchange membrane. The ion exchange membrane according to (1) or (2) above.
(4) A method for producing an ion exchange membrane having a concavo-convex shape, which comprises a step of forming concavities and convexities on the film by pressing a film of a plastic polymer having a charged group against a mold on which the concavities and convexities are formed and bending the film. Alternatively, a method for producing an ion exchange membrane, which comprises a step of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and bending the film, and then cross-linking the polymer.
(5) An ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and at least one of the cation exchange membrane and the anion exchange membrane has an uneven shape. The ion exchange membrane having the concavo-convex shape has a flat portion near the end, and the convex portion and the concave portion due to the bending of the ion exchange membrane itself are the convex portion in the concavo-convex shape of the ion exchange membrane, respectively. An ion exchange membrane cell which is a concave portion and is arranged so that the convex portion is in contact with the other ion exchange membrane.
(6) Both the cation exchange membrane and the anion exchange membrane are ion exchange membranes having a concavo-convex shape, and a part of the convex portion of the cation exchange membrane and a part of the convex portion of the anion exchange membrane are formed. The ion exchange membrane cell according to (5) above, which is arranged so as to be in contact with each other.
Alternatively, the present invention is specified by the following matters.
(1) An ion exchange membrane having a concavo-convex shape, the ion exchange membrane is composed of at least a support and ion exchange layers provided on both sides or one side of the support, and has a flat portion in the vicinity of the end. , An ion exchange membrane in which convex portions and concave portions of the ion exchange membrane are formed in the convex and concave portions due to the bending of the support, respectively.
(2) The ion exchange membrane according to (1) above, wherein the end face in the longitudinal direction of the convex portion adjacent to the flat portion near the end is a surface inclined from the upper end toward the adjacent flat portion.
(3) The convex portion and the concave portion extend linearly, the concave portion is flat, and the convex portion has a surface in which both end faces in the longitudinal direction are inclined from the upper end toward the flat portion near the end of the ion exchange membrane. The ion exchange membrane according to (1) or (2) above.
(4) A method for producing an ion exchange membrane having an uneven shape composed of at least a support and an ion exchange layer, which comprises the following steps (A) or (B).
(A) A step of forming irregularities on the support by pressing a plastic support provided on both sides or one side with a plastic polymer layer having a charged group against a mold having irregularities and bending the support; (B). A step of forming irregularities on the support by pressing a plastic support against a mold having irregularities and bending the support, and then providing a polymer layer having a charged group on both sides or one side of the support after the irregularities are formed;
(5) An ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and at least one of the cation exchange membrane and the anion exchange membrane has an uneven shape. The ion exchange membrane having the uneven shape is composed of at least the support and the ion exchange layers provided on both sides or one side of the support, has a flat portion in the vicinity of the end, and is convex due to the bending of the support. An ion exchange membrane cell in which convex portions and concave portions of the ion exchange membrane are formed in the curved portion and the concave portion, respectively, and the convex portions are arranged so as to be in contact with the other ion exchange membrane.
(6) Both the cation exchange membrane and the anion exchange membrane are ion exchange membranes having a concavo-convex shape, and a part of the convex portion of the cation exchange membrane and a part of the convex portion of the anion exchange membrane are formed. The ion exchange membrane cell according to (5) above, which is arranged so as to be in contact with each other.

In the ion exchange membrane of the present invention, ions easily permeate the membrane, there is little pressure loss in the flow path, and clogging due to dirt can be reduced. In addition, deformation and breakage of the film can be reduced. In the ion exchange membrane cell of the present invention, ions easily permeate the membrane, there is little pressure loss in the flow path, there is little clogging due to dirt, and there is little deformation or breakage of the ion exchange membrane.

FIG. 1 is an explanatory diagram of the principle of electrodialysis (ED). FIG. 2 is an explanatory diagram of the principle of reverse electrodialysis (RED). FIG. 3 is a diagram showing the state of cells and stacks in the ED and RED power generation devices. FIG. 4 is a diagram showing a conventional RED cell. FIG. 5 is a schematic diagram showing a state of water flow, ion diffusion, and adhesion of contaminants when the cell shown in FIG. 1 is used. FIG. 6 is a schematic view showing a state of water flow, ion diffusion, and adhesion of contaminants when a conventional conductive spacer is used for the RED cell. FIG. 7 is a schematic view showing a state of water flow, ion diffusion, and adhesion of contaminants when a conventional profile film is used for the RED cell. FIG. 8 is a schematic view showing the structure of a conventional profile film. FIG. 9A is a schematic view showing a cross section of an embodiment of a convex portion and a concave portion of the ion exchange membrane of the present invention. FIG. 9B is a schematic view showing a cross section of an embodiment of a convex portion and a concave portion of a support according to the present invention. FIG. 9C is a schematic view showing a cross section of an embodiment of a convex portion and a concave portion of the ion exchange membrane of the present invention. FIG. 10 is a diagram showing an embodiment of the convex shape in the ion exchange membrane of the present invention. 10 (a) and 10 (c) are views showing the shape of the convex portion, and FIGS. 10 (b) and 10 (d) are views showing a state in which the convex portion is formed on the ion exchange membrane. FIG. 11 is a diagram showing an embodiment of the unevenness forming method in the manufacturing method of the present invention. FIG. 12 is a schematic view showing an embodiment of the structure of the ion exchange membrane cell of the present invention. FIG. 13 is a schematic view showing an embodiment of the structure of the ion exchange membrane cell of the present invention. FIG. 14 is a schematic view showing an embodiment of the structure of the ion exchange membrane cell of the present invention. FIG. 15 is a photograph of a model showing an embodiment of the uneven shape of the ion exchange membrane of the present invention. FIG. 16 is a schematic view showing a state of water flow, ion diffusion, and adhesion of contaminants in the ion exchange membrane cell according to the embodiment of the present invention. FIG. 17 is a schematic view showing an embodiment of the structure of the ion exchange membrane cell of the present invention. The upper figure shows each ion exchange membrane and the gasket, the interrupted figure shows the integrated state, and the lower figure shows how each ion exchange membrane is incorporated into the gasket. Is. FIG. 18 is a reaction formula of PVA-b-PSSS. FIG. 19 is a photograph of an aluminum mold used in the examples. FIG. 20 is a diagram showing measurement positions of the height of the convex portion, the width of the lower end portion of the convex portion, and the film thickness. 21 is a cross-sectional photograph of the film obtained in Examples 1 to 3, FIG. 21 (a) is Example 1, FIG. 21 (b) is Example 2, and FIG. 21 (c) is Example 3. It is a photograph. 22 is a photograph of the film obtained in Example 4, FIG. 22 (a) is a cross section, FIG. 21 (b) is a photograph of the front surface, and FIG. 22 (c) is a photograph of the back surface. FIG. 23 is a photograph of a cross section of the film obtained in Example 5, FIG. 23 (a) is a photograph of a cross section, FIG. 23 (b) is a photograph of the front surface, and FIG. 23 (c) is a photograph of the back surface. FIG. 24 is a photograph of the film obtained in Example 6, FIG. 24 (a) is a cross section, FIG. 24 (b) is a photograph of the front surface, and FIG. 24 (c) is a photograph of the back surface. FIG. 25 is a diagram showing a membrane potential measuring device used in Examples and Comparative Examples. FIG. 26 is a photograph of the film obtained in Example 2 taken from the front surface (the side on which the convex portion is formed). FIG. 27 is a photograph of the film obtained in Example 5 taken from the front surface (the side on which the convex portion is formed). FIG. 28 is a diagram showing the uneven shape of the ion exchange membrane of Example 7 (the lattice in the figure represents 10 mm on a side and is described for the purpose of explaining the dimensions). FIG. 29 is a photograph of the anion exchange membrane (PF-A) of Example 7. FIG. 30 is a photograph of the cation exchange membrane (PF-C) of Example 7. FIG. 31 is a photograph of a part of the anion exchange membrane (PF-A) of Example 7. FIG. 32 is a photograph of a part of the cation exchange membrane (PF-C) of Example 7. FIG. 33 is a diagram showing dimensional measurement points of the ion exchange membrane of Example 7. FIG. 34 is a photograph of the anion exchange membrane (FAS-50) of Comparative Example 8 on the left side and a photograph of the cation exchange membrane (FKS-50) of Comparative Example 8 on the right side. FIG. 35 is a diagram showing the structure of the RED stack of Example 7 on the left side and a diagram showing the structure of the RED stack of Comparative Example 8 on the right side. FIG. 36 is a photograph of the seawater side spacer (S) on the left side and a photograph of the river water side spacer (R) on the right side. FIG. 37 is a photograph of the river water side spacer (R') for the PF membrane. FIG. 38 is a diagram showing an apparatus for which power generation characteristics have been evaluated. FIG. 39 is a diagram showing an equivalent circuit of the device of FIG. 38. FIG. 40 is a graph showing the relationship between the voltage and the current of Example 7 and the relationship between the current and the power generation output. FIG. 41 is a measurement result of the power generation characteristic evaluation of Example 7. FIG. 42 is a graph showing the relationship between the voltage and the current of Comparative Example 8 and the relationship between the current and the power generation output. FIG. 43 is a measurement result of the power generation characteristic evaluation of Comparative Example 8.

The ion exchange membrane of the present invention is an ion exchange membrane having a concavo-convex shape, has a flat portion in the vicinity of the end, and the convex portion and the concave portion due to the bending of the ion exchange membrane itself are the ion exchange membrane, respectively. It is characterized in that it has a convex portion and a concave portion in the concave-convex shape of. The ion exchange membrane in the present invention is not particularly limited as long as it has an ion exchange ability, and may be a cation (cation) exchange membrane or an anion (anion) exchange membrane. In the present invention, the ion exchange membrane itself is bent, and the bending forms irregularities on the ion exchange membrane. The expressions relating to bending such as "bending", "bending", and "bending" used in the present invention in the present specification are bending (that is, bent state) and bending (that is, bending state without forming a clear corner). including. The convex portion of the ion exchange membrane is a portion where a convex shape is formed by the bending of the ion exchange membrane, and the concave portion of the ion exchange membrane is a concave shape formed by the bending of the ion exchange membrane. It is a part. As long as the convex shape or the concave shape is formed by the bending of the ion exchange membrane, the shapes of the convex portion and the concave portion are not particularly limited. The embodiment of the ion exchange membrane of the present invention is an ion exchange membrane having an uneven shape, which is composed of at least a support and ion exchange layers provided on both sides or one side of the support, and has a flat portion in the vicinity of the end. The convex and concave portions due to the bending of the support include an ion exchange membrane in which the convex and concave portions of the ion exchange membrane are formed, respectively. The ion exchange layer in the present invention is not particularly limited as long as it has an ion exchange ability, and may be a cation (cation) exchange layer or an anion (anion) exchange layer. In the present invention, the support has a function of improving the shape maintaining characteristics and / or strength of the ion exchange membrane as compared with the case where the ion exchange membrane is composed of only the ion exchange layer, and the support in the present invention allows ions to pass through. The support is not particularly limited, and examples thereof include a polymer net, a non-woven fabric, and a porous support. In the present invention, the support itself constituting the ion exchange membrane is bent, and the bending forms irregularities on the ion exchange membrane. That is, the convex and concave portions due to the bending of the ion exchange membrane itself having the support are the convex and concave portions in the concave-convex shape of the ion exchange membrane, respectively. The convex portion of the support is a portion where a convex shape is formed by the bending of the support, and the concave portion of the support is a portion where the concave shape is formed by the bending of the support. is there. As long as the convex or concave shape is formed by the bending of the support, the shapes of the convex and concave portions are not particularly limited.

Explaining with reference to the figure, for example, FIG. 9A is a schematic view of the ion exchange membrane IEM, which is an embodiment of the ion exchange membrane of the present invention, viewed from the side surface (thickness direction), and is an extension direction of the convex portion. It is a schematic diagram of the cross section perpendicular to the longitudinal direction. Assuming that the upper side is the front surface of the ion exchange membrane IEM and the lower side is the back surface of the ion exchange membrane IEM, in FIG. 9A (a), the ion exchange membrane IEM bends from the flat portion to the front side at the curved portion A and the back surface at the curved portion B. It bends to the side, bends in the flat direction at the curved portion C, and bends to the front side at the curved portion D. By repeating this, the convex curved portion IEM1 formed by the curved portions A to C and the concave curved portion IEM2 formed by the curved portions C to D and formed between the convex portions and the convex curved portions are formed. Alternately formed, the convex portion IEM1 becomes a convex portion of the ion exchange membrane, and the concave portion IEM2 becomes a concave portion of the ion exchange membrane. FIG. 9A (a) shows an example in which the shape of the concave portion (concave portion) is flat, and FIG. 9A (b) shows that the shape of the concave portion (concave portion) is opposite to the convex portion (convex portion). This is an example of a protruding shape (concave portion IEM2'). Further, FIG. 9A (c) shows an example in which the shape of the convex portion (convex portion) is trapezoidal (convex portion IEM1'). In FIG. 9A, the curved portion of the ion exchange membrane IEM is bent, but as described above, the curved portion of the ion exchange membrane IEM may be curved, and the curved portion between the curved portion is curved. You may. When the concave portion of the ion exchange membrane IEM protrudes to the opposite side of the convex portion, the spacer network of the high salt concentration side flow path becomes unnecessary in the cell using this membrane, but this is related to the mechanical strength of the entire cell. Suitable for cells with a relatively small area. Explaining the support in the present invention with reference to FIG. 9B, for example, FIG. 9B is a schematic view of the support S viewed from the side surface (thickness direction), and has a cross section perpendicular to the longitudinal direction, which is an extension direction of the convex portion. It is a schematic diagram of. Assuming that the upper side is the front surface of the support and the lower side is the back surface of the support, in FIG. 9B (a), the support bends from the flat portion to the front side at the curved portion a, and bends to the back surface side at the curved portion b. It bends in the flat direction at c, and bends toward the front side at the curved portion d. By repeating this, the convex curved portion S1 formed by the curved portions a to c and the concave curved portion S2 formed by the curved portions c to d and formed between the convex curved portion and the convex curved portion are formed. It is formed alternately. FIG. 9B (a) shows an example in which the shape of the concave portion is flat, and FIG. 9B (b) shows an example in which the shape of the concave portion protrudes to the opposite side of the convex portion (concave). Song part S2'). Further, FIG. 9B (c) shows an example in which the shape of the convex curved portion is trapezoidal (convex curved portion S1'). In FIG. 9B, the curved portion of the support S is bent, but as described above, the curved portion of the support S may be curved, or the curved portion between the curved portions may be curved. Good. When the concave portion of the support S protrudes to the opposite side of the convex portion, the spacer network of the seawater side flow path becomes unnecessary in the cell using this membrane, but this is related to the mechanical strength of the entire cell. Suitable for cells with a relatively small area.

Since the ion exchange membrane of the present invention is provided with ion exchange layers on both sides or one side of a support having a convex portion and a concave portion, it has a concave-convex shape reflecting the convex shape and the concave shape of the support. Explaining with reference to the figure, for example, FIG. 9C is a schematic view of the ion exchange membrane IEM viewed from the side surface (thickness direction), and is a schematic view of a cross section perpendicular to the longitudinal direction which is an extension direction of the convex portion. Assuming that the upper side is the front surface of the ion exchange membrane IEM and the lower side is the back surface of the ion exchange membrane IEM, the ion exchange membrane IEM shown in FIG. 9C (a) has ion exchange provided on both sides of the bent support S and the support S. It is composed of layer IE. In the ion exchange membrane IEM of FIG. 9C (a), the ion exchange membrane IEM bends from the flat portion to the front side at the curved portion A, bends to the back surface side at the curved portion B, bends in the flat direction at the curved portion C, and bends at the curved portion D. It is bent to the front side. By repeating this, the convex portion IEM1 of the ion exchange membrane IEM formed by the curved portions A to C and the ion exchange membrane IEM formed by the curved portions C to D and formed between the convex portion and the convex portion. The recesses IEM2 of the above are alternately formed. Since the curved portions A to D of the ion exchange membrane IEM correspond to the curved portions a to d of the support S, the convex and concave portions of the support S correspond to the convex portions of the ion exchange membrane IEM, respectively. The convex and concave portions of the support S are the convex and concave portions of the ion exchange membrane IEM, respectively. As described above, in the ion exchange membrane IEM, the convex portion and the concave portion of the ion exchange membrane IEM are formed on the convex portion and the concave portion of the support S, respectively. Therefore, the convex portion and the concave portion of the ion exchange membrane IEM have the same shape as the convex portion and the concave portion of the support S, respectively. FIG. 9C (b) is an example of an ion exchange membrane IEM in which the ion exchange layer IE is provided on one side of the bent support S. FIG. 9C (c) shows an example in which the shape of the convex portion is trapezoidal. In FIG. 9C, the curved portion of the ion exchange membrane IEM is bent, but as described above, the curved portion of the ion exchange membrane IEM may be curved, and the curved portion between the curved portion is curved. You may. When the concave portion of the ion exchange membrane IEM protrudes to the opposite side of the convex portion, the spacer network of the seawater side flow path becomes unnecessary in the cell using this membrane, but this is compared from the relationship of the mechanical strength of the entire cell. Suitable for cells with a small area.

Since the ion exchange membrane of the present invention has an uneven shape, the surface area of the membrane becomes large. Further, when the ion exchange membrane of the present invention is used for an ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, the upper end of the convex portion is a convex portion, a concave portion or a concave portion of the other ion exchange membrane. By arranging so as to be in contact with the flat portion, the distance between the two ion exchange membranes can be fixed without using a spacer, and the flow path between the two ion exchange membranes can be secured. In this case, since ions do not flow in the portion where the cation exchange membrane and the anion exchange membrane are in contact, it is preferable that the area where the two ion exchange membranes are in contact is small. That is, it is preferable that the area of the upper end of the convex portion is small. When the ion exchange membrane of the present invention has an ion exchange membrane or a support, the curved corner of the support can be the upper end of the convex portion. Therefore, when the corner is bent, curved, or a flat portion is provided at the upper end. Regardless of the case, it is easy to narrow the width of the upper end of the convex portion. Therefore, when used in an ion exchange membrane cell, the area of the contact portion of both ion exchange membranes through which ions do not flow can be narrowed, so that the effective membrane area through which ions permeate can be increased. The width of the upper end of the convex portion is preferably 50% or less, more preferably 30% or less, and further preferably 20% or less of the width of the lower end. The width of the upper end of the convex portion is the width of the upper end in the cross section perpendicular to the longitudinal direction of the convex portion, and the width of the lower end of the convex portion is the boundary between the convex portion and the concave portion in the cross section perpendicular to the longitudinal direction of the convex portion. The width a at the position of. Here, for example, in the ion exchange membranes of FIGS. 9A and 9C, the distance between the curved portion A and the curved portion C in the figure is the width a of the lower end of the convex portion. When the upper end of the convex portion is curved, the width of the upper end means the width of contact when the upper end is brought into contact with another ion exchange membrane. Further, in the ion exchange membrane having an uneven shape, when the convex portion rises in a columnar shape, dirt such as organic substances and inorganic particles in the fluid easily adheres to the root of the convex portion, and this adhesion narrows the flow path and flows the fluid. To prevent. When the ion exchange membrane of the present invention has an ion exchange membrane or a support, the support is bent to form a slope of the convex portion, so that a gently inclined convex portion is likely to be formed. Therefore, it is possible to prevent the adhesion of dirt in the fluid and widen the flow path. The convex portion of the ion exchange membrane of the present invention preferably has an angle formed by both slopes at the upper end of 10 to 140 °, more preferably 30 to 120 °, and even more preferably 60 to 120 °. The angle formed by both slopes at the upper end means the angle formed by the left and right surfaces at the upper end in a cross section perpendicular to the longitudinal direction of the convex portion. When the upper end is curved and does not form a clear corner, or when the convex part has a width such as when the shape is trapezoidal, the angle formed by both slopes at the upper end is an extension of the left and right surfaces. The angle at the intersection of the lines. The difference between the rising angles (inclination angles) of both slopes at the lower end of the convex portion is preferably 0 to 15 °. The thickness of the ion exchange membrane of the present invention is preferably 5 to 1000 μm, more preferably 10 to 200 μm, from the viewpoint of suppressing an increase in resistance while maintaining strength suitable for use. Explaining with reference to FIG. 9A (d) or FIG. 9B (d), θ1 is the angle formed by both slopes at the upper end, and θ2 and θ3 are the rising angles (tilt angles) of both slopes at the lower end of the convex portion. .. In FIG. 9B (d), the description of the support embedded inside the ion exchange layer is omitted in order to make the display of the angle easy to understand. The protrusions and recesses of the ion exchange membrane of the present invention are preferably extended in a straight line or a curved line. When the convex portion and the concave portion are extended in a curved shape such as a linear shape, a curved shape, or an arc shape, when the ion exchange membrane of the present invention is used for the ion exchange membrane cell, the flowing fluid and the ion exchange membrane The resistance of the flow path can be reduced while increasing the contact area. The linear or curved extension means that the convex portion and the concave portion are provided so as to extend in a linear or curved shape, and the ion exchange membrane may not be connected from the vicinity of one end to the vicinity of the other end. Good. For example, convex portions having a predetermined length may be lined up from the vicinity of one end to the vicinity of the other end. The ion exchange membrane of the present invention is flat near the edge of the membrane for attachment to the cell. The vicinity of the end refers to a region required for attaching the ion exchange membrane to the cell from the end of the ion exchange membrane, and refers to a region in contact with the frame when fixed with a frame such as a gasket, for example. Further, in the ion exchange membrane of the present invention, it is preferable that the end surface in the longitudinal direction of the convex portion adjacent to the flat portion near the end is a surface inclined from the upper end toward the adjacent flat portion. When the recess is not flat, it is preferable that the end face of the recess also has the above shape. With such a shape, even if there is a large difference in surface area and projected area between the uneven portion and the flat portion, the strain of the film is dispersed by forming a relatively gently inclined surface, and the flatness near the edge of the film is formed. It is possible to maintain a convex structure that continues to the part. The end face of the convex portion in the longitudinal direction may be flat, recessed in a direction opposite to the longitudinal direction of the convex portion, or raised in the longitudinal direction of the convex portion. Further, the curved portion at the boundary between the end face and the surface sandwiching the end face may be bent or curved. The shape of the end face of the convex portion other than the convex portion adjacent to the flat portion near the end is not particularly limited, but the convex portion and the concave portion are linearly extended, the concave portion is flat, and the convex portion is longitudinal. It is preferable that both end faces in the direction are inclined from the upper end toward the flat portion near the end of the ion exchange membrane. In the ion exchange membrane of the present invention, since the ion exchange membrane itself is bent to form irregularities, it is not necessary to make the film thickness of the convex portion thicker than the film thickness of the concave portion, and the film thickness of the ion exchange membrane can be made substantially constant. .. Therefore, it is possible to prevent the difference in dimensional change due to swelling due to the difference in film thickness without increasing the average electrical resistance of the film, and it is possible to prevent the ion exchange membrane from being deformed or broken. In particular, it is possible to prevent cracks and breakage at the base of the convex portion due to the difference in swelling. 10 (a) to 10 (d) are views showing one embodiment of the shape of the convex portion in the present invention, in which both end faces in the longitudinal direction are inclined from the upper end toward the flat portion. The upper view of FIG. 10A is a view of the convex portion viewed from above, and the lower figure is a view of the convex portion viewed from the side. In the convex portion of FIG. 10A, the end face in the longitudinal direction is flat. FIG. 10 (b) is a diagram showing a part of the ion exchange membrane forming the convex portion of FIG. 10 (a), and shows the periphery of the water inlet into which the solution is introduced. The left figure of FIG. 10B is a view of the convex portion viewed from above, and the right figure is a view of the convex portion viewed from the longitudinal direction. FIG. 10 (c) shows an example in which the convex portion is raised in the longitudinal direction, and the vicinity of the center of the end face is extended so as to project to the vicinity of the edge of the film. FIG. 10 (d) is a diagram showing a part of the ion exchange membrane forming the convex portion of FIG. 10 (c), and the figure on the right is a view of the convex portion viewed from the side (direction perpendicular to the longitudinal direction). .. One convex portion of these shapes may extend from the vicinity of one end of the ion exchange membrane to the vicinity of the other end, and a plurality of convex portions of these shapes may extend from the vicinity of one end to the vicinity of the other end. May be lined up. Further, if the width of the upper end of the concave portion is smaller than the width of the lower end of the convex portion, the number of places where the convex portion contacts increases when used for an ion exchange membrane cell, so that the high salt concentration side flow path and the low flow path are low. The strength of the structure is increased by the combination of membranes with respect to the pressure difference between the flow paths on the salt concentration side, while the cross-sectional area of the flow path is reduced. From these facts, assuming that the width of the upper end of the recess is b, the width b of the upper end of the recess is preferably more than 0 and 3 × a or less, more preferably more than 0 and 2 × a or less, and more than 0 and 1. It is more preferable that the value is xa or less. The width a of the lower end of the convex portion is as defined above, and the width of the upper end of the concave portion is the width at the boundary between the convex portion and the concave portion in the cross section perpendicular to the longitudinal direction of the concave portion. When the recess is flat, it is the width of the flat portion. For example, in the ion exchange membrane of FIG. 9, the distance between the curved portion C and the curved portion D is b. The case where b is 0 is a case where the convex portions are continuous and the concave portions are the corners of the slopes of the convex portions and the slopes of the convex portions adjacent to each other. Further, the ion exchange membrane having the support of the present invention is excellent in film strength because the support is arranged along the shape of the convex portion and the concave portion. Therefore, it is possible to prevent the ion exchange membrane from being deformed or damaged even when it is also used as a spacer. In particular, it is possible to prevent cracks at the base of the convex portion and damage to the upper end that tends to occur when the width of the upper end of the convex portion is narrow.

The method for producing the ion exchange membrane of the present invention is not particularly limited, and for example, a step of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and bending the film (i). ), Or a method including a step (ii) of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and then cross-linking the polymer. It can be mentioned as a preferable method. Alternatively, a method including a step (iii) of forming irregularities on the film by pressing a film of a plastic polymer having no charged groups against a mold having irregularities and then introducing a charged group is preferable. It can be mentioned as a method. The method for forming the unevenness on the film in the above step is not particularly limited as long as it is a method of pressing the film against the mold on which the unevenness is formed and bending the film. Can be mentioned. FIG. 11 is a diagram showing one embodiment of the unevenness forming method, in which the film is bent between the lower die and the upper die and heat-pressed to form the unevenness. Then, by taking out the film from the mold, a film having irregularities is obtained. In the above step, an ion exchange membrane in which a convex portion and a concave portion become a convex portion and a concave portion by pressing a plastic polymer film having a charged group to be an ion exchange layer against a mold having irregularities and bending the film. Can be manufactured. Further, the ion exchange membrane of the present invention may be obtained by forming irregularities on a film of a plastic polymer having a charged group and then cross-linking the film, if necessary. The plastic polymer membrane having no charged group in the step (iii) is a membrane that cannot be substantially used as an ion exchange membrane as it is, and does not mean only a membrane containing no charged group at all. .. In step (iii), irregularities are formed on the film of such a plastic polymer having no charged group, and then an ion exchange action is imparted by introducing a charged group to obtain an ion exchange membrane. If necessary, cross-linking may be performed before the introduction of the charged group or after the introduction of the charged group. Plasticity refers to the property that a solid is deformed by applying an external force, and even if the force is removed, it does not return to its original state. The plastic polymer in the present invention includes a polymer having plasticity at room temperature and a polymer having thermoplasticity that softens by heating to facilitate molding and becomes hard again when cooled. That is, the plastic polymer in the present invention (including the case where the plastic polymer is a support and the case where the plastic polymer has a support) has a property of being deformed by applying an external force and not returning to the original state even if the force is removed. (If it has a support, it has the above-mentioned characteristics together with the support), and includes a polymer having plasticity at room temperature and a polymer having thermoplasticity that softens by heating to facilitate molding and becomes hard again when cooled. ..

When a polymer having a site capable of chemical cross-linking is used as a plastic polymer having a charged group, it is cross-linked by heat or light irradiation after forming an uneven shape, or in the case of a polymer having a hydroxyl group such as polyvinyl alcohol. Can be chemically crosslinked by immersing it in a solution containing a crosslinking agent such as glutaaldehyde (GA) or ethylene glycol diglycidyl ether. In the case of no cross-linking, the film resistance becomes low, and if cross-linking is performed after forming irregularities, the film resistance tends to be higher than that of non-cross-linking, but the film water content is low, the ion selectivity is high, and the mechanical strength is high. Also improves. The method for producing a film of a plastic polymer having a charged group in the above step is not particularly limited. For example, a plastic polymer having a charged group is cast on a substrate to prepare a film. A method such as producing a film by applying the film to the film and drying the film and then peeling the film from the substrate can be mentioned.

The method for producing the ion exchange membrane having the support of the present invention is not particularly limited, and for example, a method including the following steps (A) or (B) can be mentioned as a suitable method.
(A) A step of forming irregularities on the support by pressing a plastic support provided on both sides or one side with a plastic polymer layer having a charged group against a mold having irregularities and bending the support; (B). A step of forming irregularities on the support by pressing a plastic support against a mold having irregularities and bending the support, and then providing a polymer layer having a charged group on both sides or one side of the support after the irregularities are formed;
The method of forming the unevenness on the support in the step (A) or (B) is not particularly limited as long as it is a method of pressing the support against the mold on which the unevenness is formed and bending the support, and examples thereof include a pressing method. A hot pressing method in which heat is applied during pressing can be mentioned. FIG. 11 is a diagram showing an example of the unevenness forming method, in which the support in the step (A) or (B) is sandwiched between the lower mold and the upper mold and heat-pressed to bend the support to form the unevenness. There is. Then, by taking out the support from the mold, a support having irregularities is obtained. The term "plasticity" refers to a property in which a solid is deformed by applying an external force and does not return to its original state even when the force is removed. The plastic support and the plastic polymer in the present invention are a support having plasticity at room temperature and a polymer having plasticity at room temperature. Includes polymers as well as thermoplastic supports and polymers that soften when heated and become easier to mold and harden again when cooled. Each of the steps (A) and (B) will be further described below.

[When step (A) is included]
A plastic support provided with a plastic polymer layer having a charged group on both sides or one side in advance is pressed against a mold having irregularities and bent to form irregularities on the support. According to this method, by bending the polymer layer to be the ion exchange layer and the support integrally, an ion exchange membrane in which convex portions and concave portions are formed in the convex portions and concave portions of the support can be manufactured. .. After forming irregularities on a support provided with a polymer layer having a charged group on both sides or one side, the polymer layer may be crosslinked, if necessary, to obtain the ion exchange membrane of the present invention.
[When step (B) is included]
The prepared plastic support is pressed against a mold having irregularities and bent to form irregularities on the support, and after the irregularities are formed, a polymer layer having a charged group is provided on both sides or one side of the support. .. According to this method, by providing the polymer layer in accordance with the shape of the support on the support on which the unevenness is formed, the ions in which the convex and concave portions are formed on the convex and concave portions of the support. Exchange membranes can be manufactured. In the step (B), after forming irregularities on the support, a polymer layer having a charged group may be formed, and the polymer layer may be crosslinked as necessary to obtain the ion exchange membrane of the present invention.

When an ion exchange membrane having a support is provided with ion exchange layers on both sides of the support, an ion exchange membrane having higher film strength can be obtained. When the ion exchange layer is provided on one side of the support, the ion exchange layer can be made thin (for example, 5 to 50 μm), and an ion exchange membrane having low membrane resistance can be obtained. The support is not particularly limited as long as it does not obstruct the passage of ions that have passed through the ion exchange layer, and examples thereof include a thermoplastic porous film, a net, a woven fabric, and a non-woven fabric. In addition, when the ion exchange layer is provided on both sides of the support, for example, when the support is impregnated with a polymer, the ion exchange layer is formed in the support, or the support is an ion exchange layer. Including the case where it is embedded in. The method for producing the support provided with the polymer layer having a charged group in the step (A) is not particularly limited, and for example, it can be produced by impregnating or applying a polymer having a charged group to the thermoplastic support. As the production method, for example, a transfer method or the like in which a polymer is poured on a cast plate (for example, PET or the like) to form a polymer layer, a support is placed on the cast plate in a half-dried state, and the support is completely dried and then peeled off from the cast plate. Can be mentioned. Further, a method of coating or impregnating a support with a monomer having a charged group to polymerize, a method of introducing a charged group after coating or impregnating a polymer having no charged group on the support, and the like can be mentioned. it can. Cross-linking may be performed before or after the introduction of the charged group, or after the unevenness is formed. The method of providing the polymer layer having a charged group on the support on which the unevenness is formed in the step (B) is not particularly limited, and for example, a charged group for impregnating the support having the unevenness with the polymer having a charged group is used. Examples thereof include applying a polymer having a charge. Further, a method of introducing a charged group after forming irregularities on a support provided with a plastic polymer layer into which a charged group can be introduced, and applying a polymer having no charged group to the support on which the irregularities are formed. Alternatively, a method of introducing a charged group after impregnation, a method of applying or impregnating a polymer having no charged group to the support before forming the unevenness, and introducing a charged group into the polymer after forming the unevenness, etc. Can be mentioned. It may be crosslinked before or after the introduction of the charged group. The polymer having no charged group in the steps (A) and (B) is a polymer that cannot be substantially used as an ion exchange membrane as it is, and does not mean only a polymer containing no charged group at all. Absent. Table 1 shows some examples of the steps (A) and (B) of the production method of the present invention. The charged layer in Table 1 is a polymer layer having a charged group, and the uncharged polymer layer is a polymer layer having no charged group. However, the specific steps (A) and (B) are not limited to this.

The plastic polymer having a charged group is not particularly limited as long as it can form an ion exchange layer, but the polymer having an anion exchange ability has a weight containing a cation group (positively charged group) in the molecular chain. Examples thereof include a cationic polymer that is a coalescence, and the cation group may be contained in any of a main chain, a side chain, and a terminal. Examples of the cation group include an ammonium group, an iminium group, a sulfonium group, and a phosphonium group. In addition, a polymer containing a functional group, such as an amino group or an imino group, which can be partially converted into an ammonium group or an iminium group in water, is also included in the cationic polymer of the present invention. Among these, an ammonium group is preferable from the viewpoint of being easily available industrially. As the ammonium group, any of a primary ammonium group (ammonium group), a secondary ammonium group (alkylammonium group, etc.), a tertiary ammonium group (dialkylammonium group, etc.) and a quaternary ammonium group (trialkylammonium group, etc.) can be used. Although it can be used, a quaternary ammonium group (trialkylammonium group or the like) is more preferable. The cationic polymer may contain only one type of cationic group, or may contain a plurality of types of cationic groups. The counter anion of the cation group is not particularly limited, and examples thereof include halide ion, hydroxide ion, phosphate ion, and carboxylic acid ion. Among these, a halide ion is preferable, and a chloride ion is more preferable from the viewpoint of easy availability. The cationic polymer may contain only one type of counter anion, or may contain a plurality of types of counter anion. The cationic polymer used in the present invention may be a polymer consisting of only structural units containing a cationic group, or a weight composed of both a structural unit containing a cationic group and a structural unit not containing a cationic group. It may be coalesced. Moreover, it is preferable that these polymers have crosslinkability. The cationic polymer may consist of only one type of polymer, or may contain a plurality of types of polymers. Further, it may be a mixture of a polymer containing these cationic groups and a polymer containing no cationic group. Examples of the polymer having a cation exchange ability include an anionic polymer which is a polymer containing an anion group (loading electric group) in the molecular chain, and the anion group is a main chain, a side chain and a terminal. It may be included in any of the above. Examples of the anion group include a sulfonate group, a carboxylate group, and a phosphonate group. Further, a polymer containing a functional group, such as a sulfonic acid group, a carboxyl group, and a phosphonic acid group, which can be partially converted into a sulfonate group, a carboxylate group, and a phosphonate group in water, is also anionic in the present invention. Included in the polymer. Among these, a sulfonate group is preferable because it has a large ion dissociation constant. The anionic polymer may contain only one kind of anionic group or may contain a plurality of kinds of anionic groups. Further, the counter anion of the anion group is not particularly limited, and hydrogen ions, alkali metal ions, and the like are exemplified. Of these, alkali metal ions are preferable because there are few problems with equipment corrosion. The anionic polymer may contain only one type of counter cation or may contain a plurality of types of counter cations. The anionic polymer used in the present invention may be a polymer consisting of only structural units containing an anionic group, or a weight composed of both a structural unit containing an anionic group and a structural unit not containing an anionic group. It may be coalesced. Moreover, it is preferable that these polymers have crosslinkability. The anionic polymer may consist of only one type of polymer or may contain a plurality of types of polymers. Further, it may be a mixture of a polymer containing these anion groups and a polymer containing no anion groups. The polymer having no charged group is not particularly limited as long as it can introduce a charged group later. For example, as a polymer having a functional group into which a cation exchange group can be introduced, a polymer obtained by polymerizing styrene, vinyltoluene or the like as a monomer having an aromatic ring into which a sulfonic acid group is easily introduced, or a carboxylic acid group. Alternatively, a polymer obtained by polymerizing an acrylic acid ester, a methacrylate ester, an acrylonitrile, or the like can be used as a monomer having a nitrile group. These polymerizable monomers may be mixed with a crosslinkable monomer or a swelling solvent and used as a polymerizable mixture. Examples of the crosslinkable monomer that can be used in the present invention include the monomers listed below. For example, a monomer capable of introducing a crosslinked structure, that is, a monomer having at least two vinyl groups, specific examples thereof include divinylbenzene (DVB), trivinylbenzene, divinyltoluene, divinylnaphthalene, ethylene glycol dimethacrylate and the like. .. Further, as a polymer having a functional group into which an anion exchange group can be introduced, chloromethylstyrene is generally used as the monomer thereof, but styrene, vinyltorene, vinylxylene, α-methylstyrene, and acenaphthylene. , Vinyl naphthalene, α-halogenated styrene, etc., α, β, β'-trihalogenated styrene, chlorostyrene, vinylpyridine, methylvinylpyridine, ethylvinylpyridine, vinylpyrrolidone, vinylcarbazole, vinylimidazole, aminostyrene, alkyl A polymer obtained by polymerizing monomers such as aminostyrene, trialkylaminostyrene, acrylic acid amide, acrylamide, and oxium can be used. Further, polyvinyl alcohol can also be used as a polymer having no charged group. An ion exchange membrane (charged sheet) used for the ion exchange membrane of the present invention having no support, a plastic polymer membrane (uncharged sheet) into which a charged group can be introduced, and an ion of the present invention having a support. An ion exchange membrane (charged sheet) provided with a support used for the exchange membrane and a plastic polymer membrane (uncharged sheet) into which a charged group provided with a support can be introduced are used when forming the membrane. Depending on the type of monomer, it may be necessary to cross-link in advance. It is not necessary to recrosslink the membrane that has already been crosslinked.

The ion exchange membrane cell of the present invention is an ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and at least one of the cation exchange membrane and the anion exchange membrane has a concave-convex shape. The ion exchange membrane having a concavo-convex shape has a flat portion in the vicinity of the end, and the convex portion and the concave portion due to the bending of the ion exchange membrane itself are each of the ion exchange membrane. It becomes a convex portion and a concave portion in the concave-convex shape, and the convex portion is arranged so as to face the other ion exchange membrane. At least a part of the convex portion of the ion exchange membrane having an uneven shape may be arranged so as to be in contact with the other ion exchange membrane, or the convex portion may be arranged so as not to be in contact with the other ion exchange membrane. One embodiment of the ion exchange membrane cell of the present invention is an ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and at least of the cation exchange membrane and the anion exchange membrane. One is an ion exchange membrane having a concavo-convex shape, and the ion exchange membrane having the concavo-convex shape has a curved shape of the ion exchange membrane itself, and the convex portion and the concave portion of the ion exchange membrane are described above. It is a film having convex portions and concave portions in the concave-convex shape of the ion exchange membrane, and is characterized in that the convex portions of the ion exchange membrane having the concave-convex shape are arranged so as to be in contact with the other ion exchange membrane. The ion exchange membrane having an uneven shape is composed of at least a support and ion exchange layers provided on both sides or one side of the support, has a flat portion in the vicinity of the end, and has a convex portion due to bending of the support. The ion exchange membrane may have convex and concave portions of the ion exchange membrane formed on the concave portion. The ion exchange membrane in the ion exchange membrane cell of the present invention is preferably the ion exchange membrane of the present invention. Further, the ion exchange membrane cell of the present invention is an ion exchange membrane in which both the cation exchange membrane and the anion exchange membrane have a concavo-convex shape, and a part of the convex portion of the cation exchange membrane and the anion exchange membrane. It is preferable that the film is arranged so as to be in contact with a part of the convex portion of the. The upper figure of FIG. 12 is an example of an embodiment in which a cation exchange membrane having a concavo-convex shape and an anion exchange membrane having a concavo-convex shape are arranged so that the convex portions face each other. This is an example in which the portion is arranged so as to be in contact with the concave portion of the other membrane. In FIG. 12, the heights of the convex portions of both ion exchange membranes are the same, but the height of one convex portion may be higher than that of the other. The distance between the two ion exchange membranes may be, for example, in the range of 15 to 1000 μm, preferably 25 to 300 μm. Similarly, the height of the convex portion may be in the range of, for example, 15 to 1000 μm, preferably 25 to 300 μm. In the lower part of FIG. 12, the cation exchange membrane having an uneven shape and the anion exchange membrane having an uneven shape are arranged so that the convex portions face each other, and the convex portions and the convex portions of both ion exchange membranes are arranged. This is an example of contact. In this case, even when a film having the same height of the convex portion is used, the height of the convex portion of the film may be half the height of the above because the distance between the films is twice the above. In the present specification, the upper end of the convex portion extending linearly or curvedly is also referred to as a ridge (the ridge may have a width), but the ridges of the two ion exchange membranes are overlapped so as to coincide with each other. Alternatively, the ridges may be overlapped so as to intersect with each other. The lower figure of FIG. 12 is an example in which the ridges are overlapped so as to intersect with each other. Further, FIGS. 13 and 14 show the extending direction of the convex portion of the cation exchange membrane and the extending direction of the convex portion of the anion exchange membrane so that the ridges intersect when the two ion exchange membranes are overlapped. This is an example of an embodiment in which a convex portion is formed by shifting (changing the angle in the extension direction). In FIGS. 13 and 14, the convex portion is formed so that the direction of inclination of one ion exchange membrane (CEM) and the direction of inclination of the other ion exchange membrane (AEM) are opposite to each other. By doing so, the ridges can be crossed. FIG. 15 is a photograph of a model for clearly showing the uneven shape of the ion exchange membrane used in FIGS. 12 to 14. In these models, the uneven structure is expressed larger than it actually is in order to make the structure easier to understand. The actual uneven structure is small, and many uneven structures are lined up in one cell according to the size. In FIGS. 13 and 14, both ion exchange membranes are fixed by sandwiching a gasket which is a frame body in which the portion corresponding to the uneven shape portion of the ion exchange membrane is hollowed out. The portion of the ion exchange membrane in contact with the four frames of the gasket, that is, the vicinity of the end of the ion exchange membrane in the present invention is flat. When assembled into a cell, the solution is supplied between the two ion exchange membranes through the distribution openings (circular openings near the upper and lower ends in the figure) formed in the ion exchange membrane. FIG. 13 shows a case where the distribution portion is also maintained at a constant interval by the concavo-convex structure of the ion exchange membrane, and FIG. 14 shows a case where the film spacing at the distribution portion is maintained at a constant level by using a conventional net spacer. The former has the advantage that the pressure loss of the distribution section is lower, but due to manufacturing complexity, a conventional net spacer may be used for the distribution section. FIG. 16 is a diagram schematically showing the flow of the salt solution and ions in the cell of FIG. 13, and the salt solution is supplied to the cell from the extending direction (extending direction) of the convex portion. When the ridges are overlapped so as to intersect with each other, the two ion exchange membranes are fixed at each point where the ridges intersect. Therefore, the area of contact between the cation exchange membrane and the anion exchange membrane is reduced, so that the effective membrane area through which ions permeate can be increased. In addition, since there are no extra spacers or convex structures that obstruct the flow of water, the flow of the salt solution between the two ion exchange membranes is smooth, and hydrophobic parts such as non-conductive spacers to which dirt substances easily adhere are formed. Since there is no convex structure that obstructs the flow of dirty substances, there is little clogging of the flow path due to the adhesion of dirty substances. From these facts, even if the height of the flow path (here, the distance between the cation exchange membrane and the anion exchange membrane) is narrowed, the possibility of adhering pollutants is low, so this width can be narrowed and the effective membrane can be narrowed. The synergistic effect with the increase in area makes it possible to significantly reduce the electrical resistance in the flow path. Further, in particular, when the cation exchange membrane having a concavo-convex shape and the anion exchange membrane having a concavo-convex shape are arranged so that the convex portions face each other so that the convex portions and the convex portions of both ion exchange membranes are in contact with each other. Since the flow path cross-sectional area can be made larger than that of the conventional profile membrane, an increase in pressure loss can be suppressed, so that the required pump energy can be reduced. This structure has high strength and is easy to increase the area, so that a cell can be manufactured at low cost. The angle formed by the ridges of the cation exchange membrane and the anion exchange membrane is not particularly limited, but if this angle is large, the number of contacts between the cation exchange membrane and the anion exchange membrane increases, so the strength against the pressure difference between the flow paths increases. On the other hand, the distance through which the solution flows becomes longer, so that the liquid feeding resistance in the flow path becomes higher. From these viewpoints, this angle is preferably 1 to 45 °, more preferably 2 to 15 °. Further, when there is a gap into which the net spacer can be inserted between the ion exchange membrane having the uneven shape and the ion exchange membrane facing each other, the net spacer may be inserted between the two ion exchange membranes. Even in this case, the ion exchange membrane of the present invention can easily narrow the width of the upper end of the convex portion and narrow the contact area with the net unit through which ions do not flow, so that the effective film area through which ions permeate is increased. Since it is possible to easily form a convex portion having a gentle slope, it is possible to prevent the adhesion of dirt in the fluid and widen the flow path. The ion exchange membrane cell of the present invention is an ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and both the cation exchange membrane and the anion exchange membrane are linear or curved. It is an ion exchange membrane having convex portions and concave portions extending in a shape, and is an ion exchange membrane arranged in contact with each other so that the convex portions of the cation exchange membrane and the convex portions of the anion exchange membrane intersect. It may be a cell. Further, the ion exchange membrane in the ion exchange membrane cell is an ion exchange membrane having a concavo-convex shape, and the ion exchange membrane itself has a curved shape. It is preferable that the ion exchange membrane has a convex portion and a concave portion in the concave-convex shape of the ion exchange membrane, respectively. Further, the ion exchange membrane in the ion exchange membrane cell is an ion exchange membrane having an uneven shape, and the ion exchange membrane is composed of at least a support and an ion exchange layer provided on both sides or one side of the support. It is preferable that the ion exchange membrane has a flat portion in the vicinity of the end, and the convex portion and the concave portion of the ion exchange membrane are formed in the convex portion and the concave portion due to the bending of the support, respectively. Since the ion exchange membrane cell of the present invention has the above characteristics, it is suitable as a cell for RED power generation. Since the difference in film thickness between the convex portion and the other portion is small in the ion exchange membrane of the present invention, it is possible to prevent a difference in swelling due to a difference in location (difference in film thickness) in the film. Therefore, the ion exchange membrane and the ion exchange membrane cell of the present invention swell even when a wide range of salt concentration (ion concentration) and a salt concentration difference (ion concentration difference) between two solutions in contact with the membrane are large. It can be used because it can prevent deformation and damage due to. For example, a solution with a low salt concentration has a conductivity of 0.05 to 50 mS / cm, and a solution with a higher salt concentration has a conductivity more than twice that of a solution with a low salt concentration. Furthermore, it can be used for the ion exchange membrane cell of the present invention at a rate of 20 times or more, and the maximum conductivity can be used within a range in which the dissolution of salt does not reach a saturated state. The conductivity of river water is in the range of about 0.1 to 0.25 mS / cm, and the conductivity of seawater is about 50 mS / cm. When used for RED power generation, in the cell shown in FIG. 16, a conventional net spacer is used for the high-concentration side flow path, but a biconvex film having a convex structure on the high-concentration side may also be used. However, since the electrical resistance on the high concentration side is not originally high, it is desirable to use a conventional net spacer on the high concentration side to maintain sufficient strength of the cell from the viewpoint of cost and strength. At this time, it is preferable that the CEM and AEM are supported by the net spacer on the high concentration side by slightly increasing the pressure on the low concentration side as compared with the high concentration side. This is because, if it is reversed, a strong force is applied to the point where the CEM and the AEM are in point contact, so that the convex portion may be partially deformed or damaged. However, even if this part is partially deformed or damaged, it does not pose a big problem as long as the film is not damaged. In the conventional cell structure in which a spacer is provided between the flat films, it is not positively performed to give a pressure difference because it usually leads to troubles such as liquid leakage. Conventionally, cells are disassembled and washed to remove contaminants. However, this is laborious and costly, and may lead to damage to the membrane and spacer members. As described above, this technology makes it difficult for contaminants to accumulate, and even if they do, they can be easily removed by physical cleaning such as backwashing or chemical cleaning such as injection of acid, alkali, or chlorine. It can be washed without disassembly. In this case, since it is not necessary to disassemble the cell, it is possible to form an integrated cell in which the cation exchange membrane and the anion exchange membrane are joined to the gasket by sandwiching the gasket. In the case of the integrated cell, liquid leakage from the low salt concentration side flow path such as fresh water is eliminated, so that high current efficiency can be obtained in the case of ED, and high energy conversion rate can be obtained in the case of RED. On top of that, the number of parts in the cell is halved, which has the advantage of lower cost. FIG. 17 is a diagram showing an embodiment of the ion exchange membrane cell of the present invention, which is an example of an integrated cell. Here, for example, a gasket is placed on the front surface of an anion exchange membrane (PF-AEM) having a concavo-convex shape on the upper left side of the drawing, and then a cation exchange membrane (PF-CEM) having a concavo-convex shape on the right side is placed. This is an example in which the film is placed so as to face the PF-AEM in the orientation on the drawing (the figure on the right side is a view seen from the back surface). "PF" is an abbreviation for profile. In the integrated half cell of FIG. 17 (a part of the cell is referred to as a half cell; the same applies hereinafter), as shown in the middle figure, the convex portion of the cation exchange membrane and the convex portion of the anion exchange membrane are one point or two. They are stacked so that they are in contact with each other at points, and each is joined to a gasket between the two ion exchange membranes. The lower figure shows a cross-sectional view of incorporating PF-AEM and PF-CEM into a gasket. A gasket is placed on one ion exchange membrane, and the other ion exchange membrane is placed on top of the gasket to join them. To produce an integrated half-cell. In each of the above drawings, there is a part that exaggerates the magnitude relationship.

The polymers and ion exchange membranes used in Examples and Comparative Examples were prepared as follows.
1. 1. PVA-based block copolymer (PVA-b-PSSS)
2. Commercially available cation exchange membrane C-CEM: Fumasep (R) FKS-50 (Fumatech BWT GmbH, Germany)
3. 3. Commercially available anion exchange membrane C-AEM: Fumasep (R) FAS-50 (Fumatech BWT GmbH, Germany)
4. Polyvinyl alcohol (PVA) (manufactured by Wako Pure Chemical Industries, Ltd.)

(Synthesis of PVA-b-PSSS)
To a separable flask, add a predetermined amount of PVA having a thiol group at one end (provided by Kuraray Co., Ltd.), a monomer having a cation exchange group (official name: Tosoh SSS), and deionized water as a solvent, and under nitrogen conditions. The raw material was completely dissolved by heating and stirring at 90 ° C. for 30 minutes. Then, 0.99 wt% V-50 (2,2'-azobis (2-methylpropionamidine) dihydrochloride) aqueous solution was sequentially added dropwise to the reaction solution, and polymerization was carried out at 90 ° C. for one and a half hours. After one and a half hours, the sequential addition of the initiator was stopped and additional polymerization was carried out at 90 ° C. for another 2 hours. After completion of the polymerization, the reaction solution was added to a large amount of acetone to precipitate and precipitate the polymer (PVA-b-PSSS). The precipitated precipitate was collected and dried under reduced pressure. The reaction formula of PVA-b-PSSS is shown in FIG.
(Preparation of membrane using PVA-b-PSSS)
PVA-b-PSSS was weighed, placed in a 500 mL Erlenmeyer flask, and ion-exchanged water was added so that the polymer concentration was 3.3 wt%. The polymer was dissolved while stirring these Erlenmeyer flasks at 90 ° C., and then the solution was poured onto an acrylic plate at 50 ° C. and cast molding was performed to obtain a PVA-b-PSSS film.

[Examples 1 to 3]
The PVA-b-PSSS film, C-CEM and C-AEM are placed on the aluminum mold shown in FIG. 19 and hot-pressed with an electric iron set to a predetermined temperature shown in Table 2 on the film. An uneven shape was formed, and ion exchange membranes of Examples 1 to 3 were obtained. The obtained ion exchange membranes of Examples 1 to 3 are abbreviated as PVA-PFCEM, C-PFCEM, and C-PFAEM, respectively. In Example 1, after forming an uneven shape on the PVA-b-PSSS film, the film was heat-treated at 140 ° C. for 30 minutes and _{immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours for post-crosslinking, and then immersed in a 0.5 M NaCl aqueous solution. The aluminum mold has 5 V-shaped grooves with depths of 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm carved at equal intervals, but this time 0.5 mm was used. .. The obtained film having the uneven shape is photographed with an optical microscope (VHX-1000 manufactured by KEYENCE CORPORATION), and the morphology of the uneven structure is observed, and the height of the convex portion, the width of the lower end portion of the convex portion, and the flatness are observed. The film thickness of the part was measured. Here, the height of the convex portion, the width of the lower end portion of the convex portion, and the measurement position of the film thickness are shown in FIG. A cross-sectional photograph of the film is shown in FIG. 21, and Table 3 shows the film thickness, the height of the convex portion, and the width of the lower end portion of the convex portion measured from this photograph. 21 (a) is a photograph of Example 1, (b) is a photograph of Example 2, and FIG. 21 (c) is a photograph of Example 3.

[Comparative Examples 1 to 4]
Table 4 shows the film materials used in Comparative Examples 1 to 4.

In Comparative Example 1, PVA was weighed and placed in a 500 mL Erlenmeyer flask, and ion-exchanged water was added so that the polymer concentration was 5.0 wt%. The polymer was dissolved while stirring these Erlenmeyer flasks at 90 ° C., and then the solution was poured onto an acrylic plate at 50 ° C. to perform cast molding. The obtained membrane was heat-treated at 120 ° C. for 30 minutes and _{immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours. Then, it was immersed in a 0.5M NaCl aqueous solution to obtain a film of Comparative Example 1. In Comparative Example 2, the PVA-b-PSSS membrane was heat-treated at 140 ° C. for 30 minutes and _{immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours for post-crosslinking, and then immersed in a 0.5 M NaCl aqueous solution. In Comparative Example 3, a commercially available cation exchange membrane, C-CEM, was used as it was, and in Comparative Example 4, a commercially available anion exchange membrane, C-AEM, was used as it was. The membranes of Comparative Examples 1 to 4 were all flat membranes.

(Measurement of membrane potential)
The membrane potential was measured using the apparatus shown in FIG. 25. The prepared film was sandwiched between holders and set between two cells. Since the effective film area of this holder is 30φ, a concave-convex shape is formed so as to fit in the effective film area. As an example, an image of Example 2 is shown in FIG. As shown in this figure, the four convex portions of Examples 1 to 3 were formed to have a length of 22 to 26 mm, and the concave (convex) spacing was 5 mm, which is equal to the distance between the centers of adjacent grooves of the mold. 0.1M NaCl and 0.5M NaCl aqueous solutions were placed in the two cells, respectively. The potential was measured with a voltmeter (kaise, KT-2008) using a salt bridge containing 3 M KCl at a measurement temperature of 25 ° C. Table 5 shows the theoretical generation potentials under this condition (when the activity coefficient of NaCl 0.1M is 0.770 and the activity coefficient of NaCl 0.5M is 0.687), and the examples and comparative examples are shown. The membrane potential is shown in Table 6.

The membrane potential of Comparative Example 1 is -4.15 mV, which is because the theoretical potential of the uncharged membrane under this condition is -7.97 mV, so that the membrane of Comparative Example 1 has a charged group. It means that you have almost no. Since the potential of Comparative Example 2 was 33.8 mV, it was found that this membrane had a sufficient function as a cation exchange membrane, and the PVA-based block copolymer (PVA-b-PSSS) synthesized this time was synthesized. Has a cation exchange group. The membrane potential values of Comparative Example 3 and Comparative Example 4 are 38.7 mV and −34.2 mV, respectively, and have extremely high ion selectivity. Further, Comparative Example 2 has high performance as a cation exchange membrane, though not as much as Comparative Example 3 which is a commercially available ion exchange membrane. Since the membrane potential of Example 1 was 32.9 mV, which was almost the same as that of Comparative Example 2, it can be said that the process of forming the uneven structure had no effect on the performance of the PVA-based cation exchange membrane. Since the membrane potentials of Examples 2 and 3 are 38.5 mV and -34.1 mV, these membranes function as cation exchange membranes and anion exchange membranes, respectively, and these membrane potentials Compared to the potentials generated under these conditions in ideal cation exchange membranes and anion exchange membranes, 38.4 mV and -38.4 mV, these membranes have high counterion selectivity. In particular, Example 2 has high performance as a cation exchange membrane. Further, since this value is almost the same as the membrane potential values of Comparative Examples 3 and 4, 38.7 mV and -34.2 mV, the uneven structure forming process does not affect the performance of the commercially available ion exchange membrane. It can be said that. Therefore, since the performance of the ion exchange membrane itself is not impaired by the uneven shape, when it is used for an ion exchange membrane cell, the effect of improving the characteristics based on the uneven shape can be obtained.

The polymers and supports used in Examples 4 to 6 and Comparative Examples 5 to 7 were prepared as follows.
(polymer)
1. 1. Polyvinyl alcohol (PVA) (manufactured by Wako Pure Chemical Industries, Ltd.)
2. Sulfonated Polyether Sulfone (SPECS)
(Support)
1. 1. Polyester non-woven fabric Thickness: 41 μm
2. Support with nylon nanofibers sprayed on PET substrate Thickness: 220 μm

(Synthesis of PVA-b-PSSS)
The PVA-based block copolymers used in Comparative Examples and Examples were synthesized in the same manner as in Example 1.
(Formation of uneven shape of the film)
To form the uneven shape on the film, the target film was placed on the aluminum mold shown in FIG. 19 and heat-pressed with an electric iron set to a predetermined temperature to form the uneven shape on the film. The aluminum mold has 5 V-shaped grooves with depths of 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm carved at equal intervals, but this time 0.5 mm was used. ..

[Example 4]
In Example 4, a 16 wt% PVA-b-PSSS aqueous solution was applied onto the PET film, the polyester non-woven fabric was immediately placed, dried at 50 ° C., and the PET film was peeled off after drying. Then, after forming a concavo-convex structure on this film at 220 ° C. by the heat pressing method shown above, heat treatment was performed at 140 ° C. for 30 minutes. Then, _{it was immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours for chemical cross-linking. Then, it was immersed in a 0.5 M NaCl aqueous solution to obtain a membrane of Example 4 (PVA-PFCEM: double-sided impregnated membrane).

[Example 5]
In Example 5, a DMSO solution prepared by dissolving 10 g of SPES in 47 mL of dimethyl sulfoxide (DMSO) was applied by a brush on a support in which nylon nanofibers were sprayed on a PET substrate, and dried at 75 ° C. Then, after forming a concavo-convex structure on this film at 140 ° C. by the heat pressing method shown above, the film was immersed in a 0.5 M NaCl aqueous solution to obtain the film of Example 5 (aromatic PFCEM: double-sided impregnated film). ..

[Example 6]
In Example 6, after applying a 16 wt% PVA-b-PSSS aqueous solution on a PET film, a support sprayed with nylon nanofibers on a PET substrate is placed on the PET film, dried at 50 ° C., and dried. The PET film on the lower rear side was peeled off. Then, after forming a concavo-convex structure on this film at 220 ° C. by the heat pressing method shown above, heat treatment was performed at 140 ° C. for 30 minutes. Then, _{it was immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours for chemical cross-linking. Then, it was immersed in a 0.5M NaCl aqueous solution to obtain the film of Example 6 (PVA-PFCEM: single-sided film).

[Comparative Example 5]
The PVA was weighed and placed in a 500 mL Erlenmeyer flask, and ion-exchanged water was added so that the polymer concentration was 5.0 wt%. The polymer was dissolved while stirring these Erlenmeyer flasks at 90 ° C., and then the solution was poured onto an acrylic plate at 50 ° C. to perform cast molding. The obtained membrane was heat-treated at 120 ° C. for 30 minutes and _{immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours. Then, it was immersed in a 0.5M NaCl aqueous solution to obtain a film (PVA uncharged flat film) of Comparative Example 5.

[Comparative Example 6]
PVA-b-PSSS was weighed, placed in a 500 mL Erlenmeyer flask, and ion-exchanged water was added so that the polymer concentration was 3.3 wt%. The polymer was dissolved while stirring these Erlenmeyer flasks at 90 ° C., and then the solution was poured onto an acrylic plate at 50 ° C. to perform cast molding. The obtained membrane was heat-treated at 140 ° C. for 30 minutes and _{immersed in a 2M Na 2} SO ₄ aqueous solution at 25 ° C. for 2 hours. This membrane was immersed in a 0.05 vol% GA aqueous solution under acidic conditions for 6 hours. Then, it was immersed in a 0.5M NaCl aqueous solution to obtain a membrane of Comparative Example 6 (a cation exchange flat membrane using PVA-b-PSSS).

[Comparative Example 7]
10 g of SPECS was dissolved in 47 mL of dimethyl sulfoxide (DMZO). Then, this solution was cast on a PET film and dried at 75 ° C. to form a film to obtain a film of Comparative Example 7 (aromatic CEM flat film).

(Observation of membrane structure with an optical microscope)
The films obtained in Examples 4 to 6 were photographed with an optical microscope (manufactured by KEYENCE, VHX-1000) to observe the morphology of the uneven structure, and the height of the convex portion, the width of the lower end portion of the convex portion, and the flatness. The film thickness of the part was measured. Here, the height of the convex portion, the width of the lower end portion of the convex portion, and the measurement position of the film thickness are shown in FIG. Cross-sectional photographs of the film are shown in FIGS. 22 to 24, and Table 7 shows the height of the convex portion, the width of the lower end of the convex portion, and the film thickness measured from this photograph. The film thickness in Example 5 is the thickness of the concave portion (flat portion), and the thickness of the convex portion is 81 μm. The film thickness in Example 6 is the thickness of the base material (support), and a charged layer of 23 μm is present on the film thickness. Images of the front and back surfaces of the film were also taken. The photographs are shown in FIGS. 22 to 24. Here, the surface means a surface coated with the polymer. 22 (a) is a cross-sectional view of the film obtained in Example 4, FIG. 22 (b) is the surface of the film obtained in Example 4, and FIG. 22 (c) is obtained in Example 4. It is the back surface of the film. FIG. 23 (a) is a cross-sectional view of the film obtained in Example 5, FIG. 23 (b) is the surface of the film obtained in Example 5, and FIG. 23 (c) is obtained in Example 5. It is the back surface of the film. FIG. 24 (a) is a cross-sectional view of the film obtained in Example 6, FIG. 24 (b) is the surface of the film obtained in Example 6, and FIG. 24 (c) is obtained in Example 6. It is the back surface of the film. In Example 4, it can be determined that there is a charged polymer coated on both the front surface and the back surface. That is, this film has a charged polymer on the front surface and the back surface almost uniformly. On the other hand, in Example 6, the front surface is clearly smooth and the polymer layer is present, whereas the base material (PET base material) is visible on the back surface. Also in the cross-sectional photograph, a polymer layer (thickness 23 μm calculated from the image) is present on the base material. From this, Example 6 is an ion exchange membrane having an asymmetric uneven structure in which a charged polymer layer is present only on one side surface of the membrane. Further, in Example 5, there is a charged polymer on the front surface, and there is a portion where the support can be seen on the back surface, but the charged polymer is present. This is different from Example 6, and since the charged polymer was applied using a brush, it is considered that the charged polymer penetrated to the inside and reached the back surface.

(Measurement of membrane potential measurement)
The membrane potential was measured using the apparatus shown in FIG. 25. The prepared film was sandwiched between holders and set between two cells. Since the effective film area of this holder is 30φ, a concave-convex shape is formed so as to fit in the effective film area. As an example, an image of Example 5 is shown in FIG. As shown in this figure, from Examples 4 to 6, the six convex portions were formed with a length of 11 to 26 mm, and the concave (convex) spacing was formed at 5 mm, which is equal to the distance between the centers of adjacent grooves. 0.1M NaCl and 0.5M NaCl aqueous solutions were placed in the two cells, respectively. The potential was measured with a voltmeter (kaise, KT-2008) using a salt bridge containing 3 M KCl at a measurement temperature of 25 ° C. Table 8 shows the theoretical generation potentials under this condition (when the activity coefficient of NaCl 0.1M is 0.770 and the activity coefficient of NaCl 0.5M is 0.687), and the examples and comparative examples are shown. The membrane potential is shown in Table 9.

The membrane potential of Comparative Example 5 is -4.15 mV, but since the potential of the uncharged film under this condition is -7.97 mV, Comparative Example 5 has almost no charged group. Means that. The potential of Comparative Example 6 was 33.8 mV, and it was found from this that this membrane had a sufficient function as a cation exchange membrane. From this, the PVA-based block copolymer synthesized this time has a cation exchange group. It shows that it has. Further, since Comparative Example 7 shows 38.4 mV, it can be seen that the membrane of Comparative Example 7 prepared from the sulfonated polyether sulfone this time has high performance as a cation exchange membrane. On the other hand, the membrane potential of Example 4 is 28.1 mV, which is almost the same as that of Comparative Example 6. Further, since Example 5 has a voltage of 35.9 mV, which is not significantly different from that of Comparative Example 7, it can be said that the process of forming the uneven structure does not affect the performance of the cation exchange membrane. Therefore, since the performance of the ion exchange membrane itself is not impaired by the uneven shape, when it is used for an ion exchange membrane cell, the effect of improving the characteristics based on the uneven shape can be obtained. The membrane potential of Example 6 is 23.4 mV, and although it has the function of a cation exchange membrane, it shows a slightly lower value than that of Comparative Example 6. This is because Example 6 has an asymmetric structure and the base material is as thick as 200 μm, so that the concentration polarization in the support causes the ion exchange membrane surface to be higher than the salt concentration of the bulk (0.5 M NaCl aqueous solution this time). It is probable that the concentration became low. Therefore, it is considered preferable to use a support having a small concentration polarization (thin support layer and large aperture ratio).

[Example 7]
(Formation of uneven shape of the film)
^{Fumasep (R)} FAS-50 (Fumatech BWT GmbH, Germany) is used as an anion exchange membrane for forming an uneven shape, and ^{Fumasep (R)} FKS-50 (Fumatech BWT GmbH, Germany) is used as a cation exchange membrane. used. With the dimensions shown in FIG. 28, the FAS-50 is hot-pressed to form a concavo-convex shape with 53 protrusions at 3 degrees tilted to the left when viewed from the convex side in the direction perpendicular to the horizontal side (side with a length of 70 mm) of the film. This film was used as the concavo-convex structure anion exchange membrane (PF-A) of Example 7. Similarly, the FKS-50 is provided with a concave-convex shape having 53 convex lines at an inclination of 3 degrees to the left side when viewed from the convex side in the direction perpendicular to the horizontal side (side with a length of 70 mm) of the film. The concave-convex structure cation exchange membrane (PF-C) of the example was used. The convex portions in FIG. 28 are not drawn with the actual number of convex portions for the sake of clarity. FIG. 29 shows an overall photograph of PF-A, and FIG. 30 shows an overall photograph of PF-C. In addition, FIG. 31 shows a surface photograph of a part of PF-A. The front side of FIG. 31 is a flat portion near the edge of the ion exchange membrane, and the back side thereof is a convex portion. The scale is placed down for easy identification of the dimensions. Also, in order to show that the back side of the convex part is concave, the photograph was taken with air bubbles in it, and since there are air bubbles on the back side of the convex part, the back side of the convex part is clearly concave. You can see that it is. Similarly, a photograph of PF-C is shown in FIG. From these photographs and using a film thickness gauge, the width of the lower end of the convex portion (A portion in FIG. 33), the width of the flat portion between the convex portions (B portion in FIG. 33), and the height of the convex portion. (Convex height in FIG. 33) and film thickness (film thickness in FIG. 33) were measured. The results are shown in Table 10.

[Comparative Example 8]
In Comparative Example 8, Fumasep (registered trademark) FAS-50 (manufactured by Fumatech, Germany) was used as it was as the anion exchange membrane, and Fumasep (registered trademark) FKS-50 (manufactured by Fumatech, Germany) was used as the cation exchange membrane. I used it as it was. The entire photograph of FAS-50 is shown on the left side of FIG. 34, and the entire photograph of FKS-50 is shown on the right side of FIG. 34.

(Making a RED stack)
As shown in the figure on the left side of FIG. 35, a 200 μm-thick seawater-side spacer (S) and a 200 μm-thick PF (profile) membrane river water-side spacer (R') are alternately used for PF-C and PF- of Example 7. A RED stack of Example 7 was prepared by arranging them between A and sandwiching them between a plurality of pairs, an electrode portion having a silver electrode and an electrode portion having silver silver chloride. The convex portions of PF-C and PF-A were arranged so as to face each other on the river water side. In this stack, PF-C and PF-A were opposed to each other so that their ridges were tilted in opposite directions with respect to the vertical direction. Since the inclination of each ridge with respect to the vertical direction was 3 degrees, the angle formed by each ridge was 6 degrees. As a comparative example, as shown in the figure on the right side of FIG. 35, a 200 μm-thick seawater-side spacer (S) and a 200 μm-thick river water-side spacer (R) are alternately placed between FAS-50 and FKS-50 of Comparative Example 8. The RED stack of Comparative Example 8 was prepared in the same manner. In both Example 7 and Comparative Example 8, Neosepta (registered trademark) AMX (manufactured by Astom Co., Ltd.) is used at one end on the electrode side, and Neosepta (registered trademark) CMX (Astom Co., Ltd.) is used at the other end. Made) was used. The photographs of the seawater side spacer (S), the river water side spacer (R), and the river water side spacer (R') for the PF membrane used are shown in FIGS. 36 and 37. The left side of FIG. 36 is a photograph of the seawater side spacer (S), which has a thickness of 200 μm and has a mesh attached to the entire surface. The right side of FIG. 36 is a photograph of the river water side spacer (R) used for the RED stack of Comparative Example 8, which has a thickness of 200 μm and has a mesh attached to the entire surface. FIG. 37 is a photograph of the river water side spacer (R') for the PF film used for the RED stack of Example 7, the thickness is 200 μm, and there is no mesh in the effective film area portion of the PF film. Table 11 shows the specifications of the RED stacks of Example 7 and Comparative Example 8.

The RED stacks of Example 7 and Comparative Example 8 produced were evaluated for power generation characteristics using the apparatus shown in FIG. 38. The equivalent circuit of this device is shown in FIG. By changing the value of the load resistance of the device while flowing simulated seawater and simulated river water vertically from bottom to top in this stack, and measuring the voltage and current, the RED stack is opened when the load resistance is infinite. As the voltage can be measured and the resistance value is decreased, the current value increases and the voltage value decreases. The internal resistance of the stack is calculated from the slope of this current-voltage curve. The salt solutions used in this measurement are shown in Table 12.

FIG. 40 shows the voltage-current curve of Example 7 and the value of the power generation output at each current, and FIG. 42 shows the voltage-current curve of Comparative Example 8 and the value of the power generation output at each current. The white circles in the graph indicate the voltage value, and the black circles indicate the power generation output value. 41 and 43 show each measured value. Table 13 shows the results of calculating the stack resistance and the maximum output density of Example 7 and Comparative Example 8 from these graphs. The output density was determined by dividing the output by the total film area (0.03 m ^2). The open circuit voltage of Example 7 and Comparative Example 8 is the same, but the stack resistance obtained from the voltage-current curve is 11.3 Ω in Comparative Example 8 and 7.85 Ω in Example 7. It showed a value lower than 30%. Further, the maximum output density of Comparative Example 8 was 1.00 W / m ² , whereas that of Example 7 was 1.44 W / m ^2, which was 44% higher.

Table 14 shows the pressure difference between the inlet side and the outlet side (atmospheric pressure) of the simulated seawater side and the simulated river water side in the evaluation device shown in FIG. 38 in Example 7 and Comparative Example 8. On the simulated river water side, the pressure in Example 7 was 17% lower than that in Comparative Example 8, and on the simulated seawater side, the value was 19% lower. The membrane of Example 7 was stored in 0.5 M NaCl and measured 5 times with the salt solution of Table 12 in about 1 month. FIGS. 29 and 30 are photographs taken after 3 months or more have passed since the film was stored, but the film was not warped or broken. Similarly, no warpage or breakage occurred in the films of the other examples. As described above, the ion exchange membrane of the present invention did not show deformation or breakage due to swelling even when the salt concentration was wide and the difference in salt concentration between the two solutions in contact with the membrane was large.

In the ion exchange membrane and the ion exchange membrane cell of the present invention, the effective membrane area through which ions permeate can be widened, the average electrical resistance of the membrane is small, the electrical resistance of the flow path is low, and the pressure loss in the flow path is low. , It is possible to reduce clogging due to pressure loss and dirt in the flow path. In addition, the cross-sectional area of the flow path can be made large, and the deformation and breakage of the membrane can be reduced. Therefore, it can be suitably used in various fields in which an ion exchange membrane is used, and in particular, it can be suitably used for electrodialysis (ED), reverse electrodialysis (RED) power generation, hydrogen production combining RED power generation and water electrolysis, and the like.

IEM ion exchange membrane IE ion exchange layer IEM1 convex part (convex part)
IEM2 recess (concave part)
S support S1, S1'convex curved part S2, S2' concave curved part a, b, c, d curved part A, B, C, D curved part

Claims

An ion exchange membrane having a concavo-convex shape, which has a flat portion near the end, and the convex and concave portions due to the bending of the ion exchange membrane itself are the convex and concave portions in the concavo-convex shape of the ion exchange membrane, respectively. Ion exchange membrane.
The ion exchange membrane is composed of at least a support and an ion exchange layer provided on both sides or one side of the support, and the convex portion and the concave portion due to the bending of the support are formed with the convex portion of the ion exchange membrane. The ion exchange membrane according to claim 1, which is an ion exchange membrane in which recesses are formed.
The ion exchange membrane according to claim 1 or 2, wherein the end face in the longitudinal direction of the convex portion adjacent to the flat portion near the end is a surface inclined from the upper end toward the adjacent flat portion.
The convex portion and the concave portion extend linearly, and the concave portion is flat, and the convex portion has a surface in which both end faces in the longitudinal direction are inclined from the upper end toward the flat portion near the end of the ion exchange membrane. The ion exchange membrane according to any one of claims 1 to 3.
A method for producing an ion exchange membrane having an uneven shape, which comprises any one of the following steps (i) to (iii).
(I) A step of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and bending the film;
(Ii) A step of forming irregularities on the film by pressing a film of a plastic polymer having a charged group against a mold having irregularities and bending the film, and then cross-linking the polymer;
(Iii) A step of forming irregularities on the film by pressing a film of a plastic polymer having no charged groups against a mold having irregularities and bending the film, and then introducing charged groups;
A method for producing an ion exchange membrane having an uneven shape composed of at least a support and an ion exchange layer, which comprises the following steps (A) or (B).
(A) A step of forming irregularities on the support by pressing a plastic support provided on both sides or one side with a plastic polymer layer having a charged group against a mold having irregularities and bending the support;
(B) The plastic support is pressed against a mold having irregularities and bent to form irregularities on the support, and after the irregularities are formed, a polymer layer having a charged group on both sides or one side of the support is formed. Setting process;
An ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged so as to face each other, and at least one of the cation exchange membrane and the anion exchange membrane is an ion exchange membrane having a concavo-convex shape. The ion exchange membrane having an uneven shape has a flat portion near the end, and the convex portion and the concave portion due to the bending of the ion exchange membrane itself become the convex portion and the concave portion in the uneven shape of the ion exchange membrane, respectively. An ion exchange membrane cell in which the convex portion is arranged so as to face the other ion exchange membrane.
The ion exchange membrane cell according to claim 7, wherein the convex portion of the ion exchange membrane having an uneven shape is arranged so as to be in contact with the other ion exchange membrane.
Both the cation exchange membrane and the anion exchange membrane are ion exchange membranes having a concavo-convex shape, so that a part of the convex portion of the cation exchange membrane and a part of the convex portion of the anion exchange membrane are in contact with each other. The ion exchange membrane cell according to claim 8, which is arranged.
At least one of the ion exchange membranes having a concavo-convex shape is composed of a support and ion exchange layers provided on both sides or one side of the support, and the convex and concave portions due to the bending of the support are formed with the above. The ion exchange membrane cell according to any one of claims 7 to 9, which is an ion exchange membrane in which convex portions and concave portions of the ion exchange membrane are formed, respectively.