Ion exchange membrane cell and gasket

Abstract

To provide an ion exchange membrane cell which can widen an area of a membrane effective for ion permeation, is excellent in shape retention, and can suppress external leakage and internal leakage of a liquid.SOLUTION: There is provided an ion exchange membrane cell where 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, wherein the projection is arranged so as to face the other ion exchange membrane, a gasket is arranged between the ion exchange membrane having the uneven shape and the other ion exchange membrane that the projection faces, the gasket includes a frame body having thickness larger than the height of the projection of the ion exchange membrane having the uneven shape, an opening surrounded by the frame body and a reinforcement member which is provided in the opening and connects different sides of the frame body, and the projection of the ion exchange membrane having the uneven shape is inserted into the opening of the frame body, and has a reinforcement member arranged between the other ion exchange membrane facing the projection and the projection.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to an ion exchange membrane cell and a gasket. [Background technology]

[0002] In electrodialysis (ED) and reverse electrodialysis (RED), as shown in FIG. 1, a cation exchange membrane (CEM), a high salt concentration side (concentration side) flow path spacer, an anion exchange membrane (AEM), and a low concentration side (demineralization side) flow path spacer are paired to form a cell, and a stack is used in which hundreds of pairs are placed between two electrodes. In this cell, a spacer network is arranged between the CEM and AEM, and between the AEM and CEM, to keep the inter-membrane distance between the ion exchange membranes constant and allow the solution to flow. This spacer network keeps the inter-membrane distance constant (see FIG. 2 and Patent Document 1), and the solution flows between them. However, this flow path spacer uses a hydrophobic, insulating net such as PP or PE, which causes problems such as increased electrical resistance of the flow path, increased pressure loss of the flow path, and increased fouling of the flow path.

[0003] In order to solve these problems, the present inventors proposed to use a profile CEM (PF-CEM) and a profile AEM (PF-AEM) in which a concave-convex structure is formed on the membrane as shown in FIG. 3 (see Patent Document 2). With this structure, the inter-membrane distance can be kept constant without using a spacer net in the high salt concentration side (concentration side) flow path, and a solution can be passed between the opposing PF-CEM and PF-AEM. FIG. 4 shows an example of a stack (left side) made using the above PF-CEM and PF-AEM, and a stack (right side) made using flat membrane CEM and AEM for comparison. In the right side of FIG. 4, a spacer net (mesh) is present in all the flow paths in the stack using flat membranes, but in the stack in the left side of FIG. 4 using PF-CEM and PF-AEM, there is no spacer net (mesh) in the flow path where the convex parts of the PF-CEM and PF-AEM face each other. This structure not only provides low membrane resistance, but also provides advantages such as reduced electrical resistance of the flow path, reduced pressure loss in the flow path, and improved contamination resistance of the flow path.

[0004] In this way, in the spacers in the stacks produced using the above PF-CEM and PF-AEM, there is no spacer network within the effective membrane area. However, when the area of ​​the stack becomes large, that is, when the area of ​​the ion exchange membrane and the spacer becomes large, the spacers become distorted when constructing the stack, and it becomes difficult to stack a large number of spacers by aligning the positions of the gaskets on the horizontal and vertical edges of each spacer. Furthermore, since the stack may be disassembled and cleaned periodically, not just at the time of initial construction, it is necessary to assemble and build the stack each time with very high technical skill and effort. In addition, the movement of the assembled stack, shaking due to earthquakes, and the pressure of the liquid passing through it may cause the gaskets on the edges to shift, resulting in external leakage of the liquid outside the stack and internal leakage of the liquid between the high concentration side flow path and the low concentration side flow path. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 6-277458 [Patent Document 2] International Publication WO2021 / 090919 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an ion exchange membrane cell that can increase the area of ​​the membrane effective for ion permeation, has excellent shape retention, and is capable of preventing external and internal leakage of liquid. [Means for solving the problem]

[0007] The present inventors have conducted research to solve the above problems, and have found that the above problems can be solved by producing an ion exchange membrane cell using a gasket that is completely different in technical concept and shape from the spacers that have been used conventionally. This can also be applied to other ion exchange membranes invented by the present inventors as described in Patent Document 1.

[0008] That is, the present invention is specified by the following items. (1) An ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged opposite each other, and which satisfies the following (i) to (iv). (i) at least one of the cation exchange membrane and the anion exchange membrane is an ion exchange membrane having an uneven shape; (ii) the convex portions of the ion exchange membrane having the concave-convex shape are disposed so as to face the other ion exchange membrane; (iii) a gasket is disposed between the ion exchange membrane having the uneven shape and another ion exchange membrane opposite to the convex portion of the ion exchange membrane having the uneven shape, the gasket including a frame having a thickness greater than the height of the convex portion of the ion exchange membrane having the uneven shape, an opening surrounded by the frame, and a reinforcing member provided in the opening and connecting different sides of the frame; and (iv) a convex portion of the ion exchange membrane having a concave-convex shape is inserted into the opening of the frame, and the reinforcing member is disposed between the convex portion and the other ion exchange membrane facing the convex portion; (2) An ion exchange membrane cell according to (1) above, further satisfying the following (v). (v) an ion exchange membrane having a concave-convex shape has flat portions near the ends, and convex and concave portions due to bending of the ion exchange membrane itself become convex and concave portions in the concave-convex shape of the ion exchange membrane, respectively, the convex and concave portions extend linearly or curvedly, the concave portions are flat, the convex portions have a top and a side in the longitudinal direction, and the side is inclined from the top toward the concave portions; (3) An ion exchange membrane cell according to the above (2), wherein the ion exchange membrane having an uneven shape is at least composed of a support and an ion exchange layer provided on one or both sides of the support, and the convex and concave portions of the ion exchange membrane are formed in the convex and concave portions caused by the curvature of the support itself. (4) An ion exchange membrane cell according to (1) or (2) above, wherein the recesses of the ion exchange membrane having an uneven shape include a first recess adjacent to the protrusion in the short direction along the longitudinal direction of the protrusion and a second recess between the longitudinal end face of the other protrusion facing the longitudinal end face of the protrusion, the protrusion having a top and a side in the longitudinal direction, and the side face being inclined from the top toward the first recess. (5) An ion exchange membrane cell according to (1) or (2) above, wherein the longitudinal end faces of the convex portions of the ion exchange membrane having an uneven shape form a surface that is inclined from the upper end toward the flat portion near the adjacent end. (6) An ion exchange membrane cell according to (4) above, in which the convex portions and the second concave portions of the ion exchange membrane having an uneven shape are arranged alternately in the longitudinal direction from the vicinity of one end of the ion exchange membrane to the vicinity of the other end. (7) The ion exchange membrane of (6) above, in which an uneven shape is formed such that, between adjacent convex portions in the short side direction of the convex portions of the ion exchange membrane having an uneven shape, an end of one convex portion is not positioned in the short side direction of at least one end in the longitudinal direction of the other convex portion. (8) An ion exchange membrane cell according to (1) or (2), in which both the cation exchange membrane and the anion exchange membrane have an uneven shape, and a reinforcing member is disposed between the convex portions of the cation exchange membrane and the convex portions of the anion exchange membrane. (9) A gasket for a stack for electrodialysis or reverse electrodialysis comprising a frame, an opening surrounded by the frame, and a reinforcing member provided at the opening and connecting different sides of the frame, wherein the thickness of the reinforcing member is 60% or less of the thickness of the frame, and the opening ratio of the opening is 80 to 99%. Effect of the Invention

[0009] The ion exchange membrane cell of the present invention can provide an ion exchange membrane cell that can increase the area of ​​the membrane effective for ion permeation and has excellent shape retention. In addition, the use of the gasket of the present invention can provide an ion exchange membrane cell that can increase the area of ​​the membrane effective for ion permeation, has excellent shape retention, and can prevent external and internal leakage of liquid. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a conventional ion exchange membrane cell. [Diagram 2] FIG. 2 is a diagram showing the relationship between the spacer and the ion exchange membrane of a conventional ion exchange membrane cell. [Diagram 3] FIG. 3 is a diagram showing an embodiment of an ion exchange membrane having a concave-convex shape. [Figure 4] FIG. 4 is a diagram showing a conventional stack. [Diagram 5] FIG. 5 is a schematic diagram showing a cross section of one embodiment of a preferred ion exchange membrane of the present invention. [Figure 6] Fig. 6 is a diagram showing one embodiment of the shape of the convex portions in a preferred ion exchange membrane of the present invention, in which Fig. 6(a) and (c) are diagrams showing the shape of the convex portions, and Fig. 6(b) and (d) are diagrams showing the state in which the convex portions are formed on the ion exchange membrane. [Figure 7] FIG. 7 is a diagram showing an embodiment of the concave-convex shape of the present invention. [Figure 8] FIG. 8 is a diagram showing an embodiment of the concave-convex shape of the present invention. [Figure 9] FIG. 9 is a diagram showing an embodiment of the concave-convex shape of the present invention. [Figure 10] FIG. 10 is a diagram showing an embodiment of the uneven shape of the present invention. [Figure 11] FIG. 11 is a diagram showing an embodiment of the concave-convex shape of the present invention. [Figure 12] FIG. 12 is a diagram showing an embodiment of the uneven shape of the present invention. [Figure 13] FIG. 13 is a cross-sectional view showing one embodiment of the ion exchange membrane cell of the present invention. [Figure 14] FIG. 14 is a cross-sectional view showing one embodiment of a gasket of the present invention (the portion of the reinforcing member that extends into the frame is shown embedded in the frame). [Figure 15] FIG. 15 is a cross-sectional view showing a conventional spacer. [Figure 16] FIG. 16 is a cross-sectional view showing one embodiment of a gasket of the present invention (the portion of the reinforcing member that extends into the frame is shown embedded in the frame). [Figure 17] FIG. 17 is a diagram showing one embodiment of a preferred ion exchange membrane of the present invention. [Figure 18] FIG. 18 is a diagram showing one embodiment of a preferred ion exchange membrane of the present invention. [Figure 19] FIG. 19 is a schematic diagram showing one embodiment of the structure of an ion exchange membrane cell of the present invention. [Figure 20] FIG. 20 is a schematic diagram showing one embodiment of the structure of the ion exchange membrane cell of the present invention. [Figure 21] 21 is a schematic diagram showing one embodiment of the structure of the ion exchange membrane cell of the present invention. The upper figure shows each ion exchange membrane and a gasket, the middle figure shows a state where they are integrated, and the lower figure shows how each ion exchange membrane is incorporated into the gasket. [Figure 22]FIG. 22 is a photograph of the aluminum mold used in Preparation Example 1. [Figure 23] FIG. 23 is a diagram showing the uneven shape of the ion exchange membrane of Preparation Example 1 (the grid in the figure has a side of 10 mm, and is shown for the purpose of explaining the dimensions). [Figure 24] FIG. 24 is a photograph of PF-A and PF-C obtained in Preparation Example 1. [Diagram 25] FIG. 25 is a cross-sectional photograph of a portion of PF-A and PF-C obtained in Preparation Example 1, where FIG. 25(a) is a cross-sectional photograph of a portion of PF-A and FIG. 25(b) is a cross-sectional photograph of a portion of PF-C. [Figure 26] FIG. 26 is a diagram showing the dimensional measurement points and measurement results of PF-A and PF-C obtained in Preparation Example 1. [Figure 27] FIG. 27 is a diagram showing the mold used in Production Example 2. As shown in FIG. [Figure 28] FIG. 28 is a diagram showing the mold used in Production Example 2. As shown in FIG. [Figure 29] FIG. 29 is a photograph of the CT-2 film on which projections and recesses were formed using the mold shown in FIG. 27 of Preparation Example 2. [Diagram 30] FIG. 30 is a photograph of an AT-2 film on which projections and recesses were formed using the mold shown in FIG. [Diagram 31] FIG. 31 is a photograph of the CT-2 film in which projections and recesses were formed using the mold shown in FIG. [Diagram 32] FIG. 32 is a photograph of an AT-2 film on which projections and recesses were formed using the mold shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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 opposite each other, in which (i) at least one of the cation exchange membrane and the anion exchange membrane is an ion exchange membrane having an uneven shape, (ii) a convex portion of the ion exchange membrane having an uneven shape is arranged to face the other ion exchange membrane, (iii) a gasket is arranged between the ion exchange membrane having an uneven shape and the other ion exchange membrane facing the convex portion of the ion exchange membrane having an uneven shape, and the gasket includes a frame having a thickness greater than the height of the convex portion of the ion exchange membrane having an uneven shape, an opening surrounded by the frame, and a reinforcing member provided in the opening and connecting different sides of the frame, and (iv) the convex portion of the ion exchange membrane having an uneven shape is inserted into the opening of the frame, and the reinforcing member is arranged between the convex portion and the other ion exchange membrane facing the other ion exchange membrane. The ion exchange membrane having an uneven shape in the ion exchange membrane cell of the present invention is not particularly limited as long as it is an ion exchange membrane having an uneven shape, but (v) an ion exchange membrane having a flat portion near an end, in which a convex curved portion and a concave curved portion due to curvature of the ion exchange membrane itself become a convex portion and a concave portion, respectively, in the uneven shape of the ion exchange membrane, the convex portion and the concave portion extend in a straight line or curved line, the concave portion is flat, the convex portion has a top and a side surface in the longitudinal direction, and the side surface is inclined from the top toward the concave portion is preferred.

[0012] In the present invention, the ion exchange membrane is preferably curved, and the curve forms unevenness in the ion exchange membrane. In the present specification, expressions related to bending, such as "bend", "bent", and "bend", include bending (i.e., a bent state) and curvature (i.e., a bent state without forming a clear corner). The convex curved portion of the ion exchange membrane is a portion in which a convex shape is formed by bending the ion exchange membrane, and the concave curved portion of the ion exchange membrane is a portion in which a flat concave shape is formed by bending the ion exchange membrane. The shape of the convex curved portion is not particularly limited as long as a convex shape or a flat concave shape is formed by bending the ion exchange membrane. The embodiment of the ion exchange membrane in the present invention includes an ion exchange membrane having an uneven shape and not having a support, and an ion exchange membrane having an uneven shape, which is at least composed of a support and an ion exchange layer provided on both sides or one side of the support, has a flat portion near the end, and the convex portion and the concave portion of the ion exchange membrane are formed at the convex curved portion and the concave portion caused by bending the support itself, respectively. Here, "ion exchange layers provided on both sides or one side of a support" refers to a state in which the support is entirely or partially embedded in the ion exchange layer, and when the support is entirely embedded, it is provided on both sides, and when the support is partially embedded, it is provided on one side. Examples of ion exchange membranes include homogeneous membranes, including membranes that have been subjected to graft polymerization by irradiation with electron beams or the like. In addition, it may be an ion exchange membrane that is a heterogeneous membrane in which an ion exchange resin is contained within the membrane and does not have a curve in the membrane itself, but has an uneven shape. In the following, homogeneous membranes that have better properties than practical ones will be mainly exemplified as ion exchange membranes having an uneven shape.

[0013] The ion exchange layer in the present invention is not particularly limited as long as it is a layer having 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 retention property and / or strength of the ion exchange membrane compared to the case where it is composed of only the ion exchange layer, and the support in the present invention is not particularly limited as long as it is a support through which ions can pass when the ion exchange layer is formed, and for example, a porous body can be mentioned, and the porous body also includes forms such as woven fabric and nonwoven fabric. As the material of the support, a polymer material can be preferably mentioned. As the support, a mechanical strength is required more than that of the polymer layer having a charged group, and it is preferable that it is excellent in tensile strength and shear strength. In a preferred embodiment in the present invention, the support itself constituting the ion exchange membrane is curved, and the curve forms unevenness in the ion exchange membrane. That is, the convex curved portion and the concave curved portion due to the curve of the ion exchange membrane itself having the support become the convex portion and the concave portion in the uneven shape of the ion exchange membrane, respectively. The convex curved portion of the support is a portion in which a convex shape is formed by bending the support, and the concave curved portion of the support is a portion in which a flat concave shape is formed by bending the support. The shape of the convex curved portion is not particularly limited as long as a convex shape or a flat concave shape is formed by bending the support.

[0014] 5(A)(a) and (c) are schematic diagrams of an ion exchange membrane IEM, which is one embodiment of the ion exchange membrane of the present invention, viewed from the side (thickness direction), and are schematic diagrams of a cross section perpendicular to the extension direction of the convex curved portion (hereinafter, the "extension direction" is also referred to as the "longitudinal direction" or "extension direction"). If the upper side is the front side of the ion exchange membrane IEM and the lower side is the back side of the ion exchange membrane IEM, in FIG. 5(A)(a), the ion exchange membrane IEM bends from the flat portion toward the front side at curved portion A, bends toward the back side at curved portion B, bends toward the flat direction at curved portion C, and bends toward the front side at curved portion D. By repeating this, a convex curved portion IEM1 formed by curved portions A to C and a concave curved portion IEM2 formed by curved portions C to D and formed between the convex curved portions are alternately formed, and the convex curved portion IEM1 becomes the convex portion of the ion exchange membrane, and the concave curved portion IEM2 becomes the concave portion of the ion exchange membrane. The concave curved portion (concave portion) in FIG. 5(A)(a) has a flat shape. Also, FIG. 5(A)(c) shows an example in which the convex curved portion (convex portion) has a trapezoidal shape (convex curved portion IEM1'). In FIG. 5(A)(a) and (c), 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, or the portion between the curved portions may be curved.

[0015] The support in the ion exchange membrane having a support is described with reference to FIG. 5(A). For example, FIG. 5(A) is a schematic diagram of a support S (IE is replaced with S) viewed from the side (thickness direction), and is a schematic diagram of a cross section perpendicular to the longitudinal direction, which is the extension direction of the convex curved portion. If the upper side is the front side of the support and the lower side is the back side of the support, in FIG. 5(A)(a), the support bends from the flat portion to the front side at curved portion a (A is replaced with a), bends to the back side at curved portion b (B is replaced with b), bends in the flat direction at curved portion c (C is replaced with c), and bends to the front side at curved portion d (D is replaced with d). By repeating this, a convex curved portion S1 (IEM1 is replaced with S1) formed by curved portions a to c and a concave curved portion S2 (IEM2 is replaced with S2) formed by curved portions c to d and formed between the convex curved portions are alternately formed. The shape of the concave curved portion in FIG. 9(A)(a) is flat. Also, FIG. 5(A)(c) is an example in which the shape of the convex curved portion is trapezoidal (convex curved portion S1' (IEM1' is replaced with S1')). In FIG. 5(A)(a) and (c), the curved portion of the support S is bent, but as described above, the curved portion of the support S may be curved, and the portion between the curved portions may be curved. Here, when the concave curved portion (recess) is "flat" regardless of the presence or absence of a support, it also includes the case where the curve occurs due to unintended deformation during film production or under the conditions of film storage or use. The same applies to the flat portion near the end described later.

[0016] The ion exchange membrane having a support of a preferred embodiment of the present invention has an ion exchange layer on both sides or one side of the support having a convex curved portion and a concave curved portion, and therefore has an uneven shape reflecting the convex and concave shapes of the support. Explaining with reference to the drawing, for example, FIG. 5(B) is a schematic diagram of the ion exchange membrane IEM seen from the side (thickness direction), and is a schematic diagram of a cross section perpendicular to the longitudinal direction which is the extension direction of the convex portion. If the upper side is the front side of the ion exchange membrane IEM and the lower side is the back side of the ion exchange membrane IEM, the ion exchange membrane IEM of FIG. 5(B)(a) is composed of a curved support S and an ion exchange layer IE provided on both sides of the support S. In the ion exchange membrane IEM of FIG. 5(B)(a), the ion exchange membrane IEM is curved from the flat portion to the front side at the curved portion A, curved to the back side at the curved portion B, curved in the flat direction at the curved portion C, and curved to the front side at the curved portion D. By repeating this, convex portions IEM1 of the ion exchange membrane IEM formed by the curved portions A to C and flat concave portions IEM2 of the ion exchange membrane IEM formed by the curved portions C to D and formed between the convex portions are alternately formed. The curved portions A to D of the ion exchange membrane IEM correspond to the curved portions a to d of the support S, respectively, so that the convex curved portions and concave curved portions of the support S correspond to the convex portions and concave portions of the ion exchange membrane IEM, respectively, and the convex curved portions and concave curved portions of the support S become the convex portions and concave portions of the ion exchange membrane IEM, respectively. In this way, in the ion exchange membrane IEM, the convex portions and concave portions of the ion exchange membrane IEM are formed at the convex curved portions and concave curved portions of the support S, respectively. Therefore, the convex portions and concave portions of the ion exchange membrane IEM have the same shapes as the convex curved portions and concave curved portions of the support S, respectively.

[0017] FIG. 5(B)(c) is an example in which the shape of the convex portion is trapezoidal. In FIG. 5(B), 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 portion between the curved portions may be curved. In the ion exchange membrane of the present invention, the concave portion between the convex portions is flat, so that stagnation is unlikely to occur in the concave portion, adhesion is unlikely to occur, and output is unlikely to decrease. FIG. 5(A)(b) is a reference example in which the shape of the concave portion (concave portion) protrudes to the opposite side of the convex portion (convex portion) (concave portion IEM2'). In this case, unlike the ion exchange membrane of the present invention in which the concave portion is flat, stagnation is likely to occur between the convex portions (concave portion) and adhesion is likely to occur. In addition, in the case of RED power generation, the ion concentration of the low concentration side solution increases and the electrical resistance of the solution decreases, but on the other hand, the concentration difference between the high concentration side solution and the low concentration side solution decreases, so the generated voltage decreases, which causes a decrease in output. In the case of ED, stagnation causes local desalting in that area, resulting in a decrease in salt concentration, which results in an increase in electrical resistance, and Joule heat causes the membrane to burn, and in some cases, the membrane to break. FIG. 5(A)(b), which is an explanation assuming that FIG. 5(A) is a support, is a reference example in which the shape of the concave curved part of the support protrudes to the opposite side of the convex curved part (concave curved part S2' (IEM2' is replaced with S2')). When an ion exchange layer is formed on such a support, the above problems arise, unlike the ion exchange membrane of the present invention in which the concave part is flat. The same is true when only the convex parts are arranged. FIG. 5(B)(b) is a reference example of an ion exchange membrane IEM in which an ion exchange layer IE is provided on one side of a curved support S.

[0018] The width of the upper end of the convex portion of the ion exchange membrane in the present invention is preferably 50% or less of the width of the lower end, more preferably 30% or less, and even more preferably 20% or less. The width of the upper end of the convex portion is the width of the upper end in a cross section perpendicular to the longitudinal direction of the convex portion, and the width of the lower end of the convex portion is the width a at the boundary position between the convex portion and the concave portion in a cross section perpendicular to the longitudinal direction of the convex portion. Here, for example, in the ion exchange membrane of FIG. 5(A) and FIG. 5(B), 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 refers to the width of contact when the upper end is brought into contact with another ion exchange membrane, a gasket, or the like. As described above, the ion exchange membrane in the present invention is easy to narrow the width of the upper end of the convex portion, so that when used in a cell, the cross-sectional area of ​​the effective flow path portion through which the solution flows can be widened. In addition, in an ion exchange membrane having an uneven shape, when the convex portion rises in a columnar shape, dirt such as organic matter and inorganic particles in the fluid is likely to adhere to the base of the convex portion, and this adhesion narrows the flow path and hinders the flow of the fluid. In the ion exchange membrane of the present invention, when the ion exchange membrane or support is included, the support is bent to form the slope of the convex portion, so that the convex portion with a gentle slope is easily formed. Therefore, since adhesion of dirt in the fluid can be prevented, the flow path can be widened, and the advantage of the cell that is less likely to be clogged due to pressure loss and dirt in the flow path can be provided. In the convex portion of the ion exchange membrane of the present invention, the angle formed by both slopes at the upper end is preferably 10 to 176°, more preferably 30 to 150°, and even more preferably 60 to 120°. In the present specification, the expression "P to Q" means P or more and Q or less, including P and Q. The angle formed by both slopes at the upper end refers to the angle formed by the left and right faces (side faces) at the upper end in a cross section perpendicular to the longitudinal direction of the convex portion. In other words, it is the angle at which the left and right faces intersect at the line segment (ridge) of the top of the convexity, which passes through the line segment (longitudinal direction of the convexity) indicating the start of bending of the left and right faces toward the front side with respect to the flat part or the face near the end of the ion exchange membrane. Here, the start of bending can be also called the rising start point of the convexity, and refers to the position of the boundary between the convexity and the concaveity that are aligned parallel to each other in the longitudinal direction.The line segment indicating the beginning of the bend is a line segment that transitions from the vicinity of the end of the ion exchange membrane or the upper surface of the flat part of the recess to the slope of the convex part, and the position of the line segment in the longitudinal cross section of the uneven shape (shown as a dot in the figure) is found by drawing a straight line extending from the vicinity of the end or the upper surface of the flat part of the recess in parallel to the upper surface. When the upper end is curved and does not form a clear corner, or when the shape of the convex part has width such as a trapezoid, the angle formed by both slopes at the upper end refers to the angle at the position where the left and right faces intersect at the top of the convex part, and when there is a flat part at the top, refers to the angle at the center position of the line segment indicating the flat part as viewed from the side.

[0019] The angle (inclination angle) of both slopes at the lower end of the convex portion is preferably 2 to 85°, 15 to 75°, or 30 to 60°, and the difference between the inclination angles of both slopes is preferably 0 to 15°. The angle (inclination angle) of both slopes at the lower end of the convex portion refers to the angle between the line segment at the lower end connecting both lower ends of the convex portion and the side surface (inclined surface) of the convex portion in a cross section perpendicular to the longitudinal direction of the convex portion. When the position of the lower end of the convex portion is unclear, such as when the membrane is curved, the position of the lower end may be a position where the height of the slope is 10% higher than the thickness of the flat portion as the rising part of the slope gradually rises. The thickness of the ion exchange membrane in 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 a strength suitable for use. Explaining with reference to Fig. 5(A)(d) or Fig. 5(B)(d), θ1 is the angle between the two slopes at the upper end, and θ2 and θ3 are the angles (tilt angles) of the rise of the two slopes at the lower end of the convex portion. Note that in Fig. 5(B)(d), the support embedded inside the ion exchange layer is omitted in order to make the display of the angles easier to understand.

[0020] The convex and concave portions of the ion exchange membrane of the present invention are extended in a linear or curved shape. In another embodiment, at least the convex portions of the convex and concave portions may be extended in a linear or curved shape. When the convex and concave portions are extended in a linear or curved shape such as a curved shape or an arc shape, when the ion exchange membrane of the present invention is used in the ion exchange membrane cell, the flow resistance of the flow path can be reduced while increasing the contact area between the flowing fluid and the ion exchange membrane. The term "extending in a linear or curved shape" means that the convex and concave portions are provided in a linear or curved shape, and may or may not be connected from the vicinity of one end of the ion exchange membrane to the vicinity of the other end. For example, a plurality of convex portions of a predetermined length may be arranged in the longitudinal direction from the vicinity of one end to the vicinity of the other end, that is, two or more. The ion exchange membrane of the present invention is preferably flat near the end of the membrane in order to attach it 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 for example, when the ion exchange membrane is fixed with a frame such as a gasket, the region is the region that the frame can contact. This region is called the flat portion near the end. Convexities and concaves are formed inside this flat portion. In other words, the vicinity of the end can be said to be a region along the edge of the ion exchange membrane outside the part closest to the end of the convex portion closest to each end of the ion exchange membrane (the end side of the ion exchange membrane). In the present invention, this region is preferably flat. In addition, when there is no other convex portion between the longitudinal side surface of the convex portion and the end vicinity, and when there is no other convex portion between the longitudinal end face and the end vicinity, the side surface and the area between the end face and the end vicinity are also flat. When there is no other convex portion between the longitudinal side surface of the convex portion and the end vicinity, the side surface of the convex portion is also called the side surface adjacent to the end vicinity, and when there is no other convex portion between the longitudinal end face of the convex portion and the end vicinity, the end surface of the convex portion is also called the end surface adjacent to the end vicinity.

[0021] In the present invention, a recess adjacent to a convex in the short direction along the longitudinal side of the convex is called a first recess. In addition, in the present invention, when a recess is formed between the longitudinal end face of one convex and the longitudinal end face of the other convex facing it, this recess is called a second recess. Here, facing includes not only the case where the end faces face each other directly in the longitudinal direction, but also the case where they face each other while being shifted in an oblique direction, and the case where they face each other in the short direction of the convex. In addition, in the ion exchange membrane of the present invention, it is preferable that the longitudinal end face of the convex adjacent to the flat part near the end forms a surface that slopes from the upper end toward the adjacent flat part. By making such a shape, even if there is a large difference in the surface area and projected area between the uneven part and the flat part, the relatively gentle slope forms a surface that distributes the distortion of the membrane and maintains a convex structure that continues to the flat part near the end of the membrane. The longitudinal end face of the convex may be flat, may be recessed in the opposite direction to the longitudinal direction of the convex, or may be raised in the longitudinal direction of the convex. In addition, the curved portion at the boundary between the end face and the longitudinal side faces sandwiching the end face may be bent or curved. The shape of the end faces of the other convex parts other than the convex parts adjacent to the flat part near the end is not particularly limited, but it is preferable that the convex parts and the concave parts are linearly extended, the concave parts are flat, and both longitudinal end faces of the convex parts form surfaces that are inclined from the upper end toward the flat part near the end of the ion exchange membrane. This makes it possible to average out distortion and strain caused by the difference between the projected area and the surface area of ​​the ion exchange membrane. In addition, stagnation is unlikely to occur between the convex parts (concave parts), so that adhesion is unlikely to occur. Furthermore, problems such as a decrease in power generation output and processing efficiency and insufficient strength are unlikely to occur.

[0022] In the ion exchange membrane of the present invention, the left and right side surfaces in the longitudinal direction of the convex portion are inclined from the upper end toward a flat concave portion (first concave portion) adjacent to the convex portion in parallel thereto, or the end face in the longitudinal direction of the convex portion is inclined from the upper end toward a flat concave portion (second concave portion) between the flat portion near the end face adjacent to the end face in the longitudinal direction of the convex portion or the end face in the longitudinal direction of the other convex portion facing the convex portion. In the ion exchange membrane of the present invention, in addition to the concave portion between the convex portions being flat, if the side surface of the convex portion is inclined from the upper end toward the adjacent concave portion, the membrane surface area is increased when used in a cell, promoting the flow of ions, and the liquid easily flows over the convex portion into the flat concave portion, which can be called the adjacent lane, and ion stagnation is reduced, thereby reducing a local increase in the concentration of the solution, which causes a decrease in the generated voltage in the case of RED power generation, and a local decrease in the salt concentration, which causes membrane burning or membrane destruction in the case of ED. In addition, by reducing stagnation, adhesion of fouling substances can also be prevented. Furthermore, it is less likely to be distorted than an ion exchange membrane having a rectangular (U-shaped) convex portion. This is because such a rectangular membrane is more likely to be distorted due to the large difference between its surface area and projected area. In addition, it is preferable that the side surface adjacent to the end of the ion exchange membrane of the convex portion is also inclined toward the end. Alternatively, in the ion exchange membrane of the present invention, in addition to the concave portion between the convex portions being flat, if the end face in the longitudinal direction of the convex portion is inclined from its upper end toward the flat portion near the end adjacent to the end face or the second concave portion, when used in a cell as described above, the membrane surface area is increased to promote the flow of ions, and the liquid easily flows over the convex portion into the concave portion, which can be called the next lane, and the local increase in the concentration of the solution in the case of RED power generation and the local decrease in the salt concentration in the case of ED can be reduced. In addition, by reducing stagnation, it is also possible to prevent adhesion of fouling substances. Furthermore, it is less likely to be distorted than an ion exchange membrane having a rectangular (U-shaped) convex portion as described above.In the ion exchange membrane of the present invention, in addition to the concave portions between the convex portions being flat, it is preferable that the side surface of the convex portion is inclined from the upper end toward the adjacent first concave portion, and that the longitudinal end face of the convex portion forms a surface that is inclined from the upper end toward the flat portion near the end to which the end face is adjacent, or toward the second concave portion.

[0023] 6(a) to 6(d) are diagrams showing an 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 diagram of FIG. 6(a) is a diagram of the convex portion seen from above, and the lower diagram is a diagram of the convex portion seen from the side. In the convex portion in FIG. 6(a), the end faces in the longitudinal direction are flat. FIG. 6(b) is a diagram showing a part of the ion exchange membrane in which the convex portion in FIG. 6(a) is formed, showing the periphery of the water guide port through which the solution is introduced. The left diagram of FIG. 6(b) is a diagram of the convex portion seen from above, and the right diagram is a diagram of the convex portion seen from the longitudinal direction. FIG. 6(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 spreads so as to overhang the vicinity of the end of the membrane. FIG. 6(d) is a diagram showing a part of the ion exchange membrane in which the convex portion in FIG. 6(c) is formed, and the right diagram is a diagram of the convex portion seen from the side (perpendicular to the longitudinal direction). A single convex portion of these shapes may be extended from near one end of the ion exchange membrane to near the other end, or multiple convex portions of these shapes may be arranged from near one end to near the other end. In addition, if the width of the recess is smaller than the width of the lower end of the convex portion, when used in an ion exchange membrane cell, the number of places where the convex portions come into contact increases, so that the strength of the structure formed by the combination of the membranes against the pressure difference between the high salt concentration side flow path and the low salt concentration side flow path between the flow paths increases, while the cross-sectional area of ​​the flow path decreases. For these reasons, when the width of the recess is b, the width b of the recess is preferably greater than 0 and 3×a or less, more preferably greater than 0 and 2×a or less, and even more preferably greater than 0 and 1×a or less. The width a of the lower end of the convex portion is as defined above, and the width of the recess is the width at the boundary between the convex portion and the recess in a cross section perpendicular to the longitudinal direction of the recess, and is the width of the flat portion. For example, in the ion exchange membrane of FIG. 5, the distance between the curved portion C and the curved portion D is b. When b is 0, the convex portions are continuous and the concave portions form the corners between the inclined surfaces of adjacent convex portions. Furthermore, the ion exchange membrane having the support of the present invention has excellent membrane strength because the support is arranged along the shapes of the convex portions and the concave portions. Therefore, even when the support is used to function as a spacer, the ion exchange membrane can be prevented from being deformed or damaged. In particular, cracks at the base of the convex portions and damage to the upper ends that is likely to occur when the width of the upper ends of the convex portions is narrow can be prevented.

[0024] 7 to 12 show examples of the embodiment of the uneven shape of the ion exchange membrane of the present invention. FIG. 7 shows an example in which the convex portion extends linearly from the vicinity of one end of the ion exchange membrane to the vicinity of the other end, and both longitudinal end faces of the convex portion form a surface inclined from the upper end toward the flat portion near the adjacent end. FIGS. 8 to 10 and 12 show examples in which a plurality of convex portions are arranged in a line in the longitudinal direction from the vicinity of one end of the ion exchange membrane to the vicinity of the other end, and FIG. 11 shows an example in which the convex portion extends linearly from the vicinity of one end of the ion exchange membrane to the vicinity of the other end. In these examples, the longitudinal end of the convex portion forms a surface inclined toward the flat portion when adjacent to the flat portion near the end of the ion exchange membrane, and forms a surface inclined toward the concave portion when adjacent to the concave portion between the convex portions adjacent in the longitudinal direction. By providing a plurality of convex portions in the longitudinal direction, the shape of the convex portion can be retained, and The strength of the membrane can be increased, and the strength of the membrane can be further increased by making the end of each convex part an inclined surface. In addition, a part of the solution flows a short distance without going over the mountain of the convex part, so that the pressure loss is reduced. FIG. 8 shows an example in which each convex part is arranged in a straight line at the same angle in the longitudinal direction, and FIG. 9 shows an example in which each convex part is arranged at a different angle in the longitudinal direction. FIG. 10 shows an example in which an uneven shape is formed between adjacent convex parts in the lateral direction of the convex parts so that the end of one convex part in the longitudinal direction is not arranged in the lateral direction of the end of the longitudinal direction of the other convex part, that is, in the direction approximately perpendicular to the longitudinal direction of the end part. In this figure, the end part on the flat part side near the end of adjacent convex parts in the lateral direction is alternately shown protruding toward the end of the membrane and receding from the flat part near the end into the inner side of the membrane surface. Since the concave portions between adjacent convex portions in the longitudinal direction are staggered in the transverse direction and are not aligned in a straight line, that is, the concave portions and the convex portions are aligned alternately, the membrane strength against deformation of the entire membrane is increased even if pressure is concentrated across multiple convex portions in the transverse direction of the convex portions, and the difference in the surface area and projected area between the flat portion and the convex portion is further reduced, so that the distortion can be reduced. Therefore, it contributes to stabilizing the operation of the reverse electrodialysis power generation and electrodialysis device using the membrane. As a modification of FIG. 10, the transverse direction of either one of the end portions of the convex portion closest to the flat portion near one end of the membrane in the longitudinal direction and the end portion of the convex portion closest to the flat portion near the other end opposite the flat portion near the one end is aligned in the same position as part or all of the end portions of the convex portions of the other lane, and the above-mentioned distortion reduction effect is obtained. Fig. 11 shows an example in which the convex portions extend linearly from the vicinity of one end of the ion exchange membrane to the vicinity of the other end, but the length of the convex portions is changed to change the distance between the longitudinal end of the convex portion and the end of the ion exchange membrane, and the convex portions close to the end and the convex portions farther from the end are arranged alternately. In this case, the difference in the surface area and projected area between the flat portion near the end and the convex portions is further reduced, so that distortion can be reduced. Fig. 12 shows an example in which the convex portions are not arranged in a straight line in the longitudinal direction, but are arranged so that one of the positions of adjacent convex portions in the longitudinal direction is shifted in the lateral direction, and further the ends of adjacent convex portions in the longitudinal direction are adjacent to each other in the lateral direction.

[0025] In the ion exchange membrane of the present invention, the ion exchange membrane itself is curved to form unevenness, so that it is not necessary to make the film thickness of the convex parts thicker than the film thickness of the concave parts, and the film thickness of the ion exchange membrane can be made almost constant. Therefore, it is possible to prevent the difference in dimensional change due to swelling caused by the difference in film thickness without increasing the average electrical resistance of the membrane, and to prevent deformation and damage of the ion exchange membrane. In particular, it is possible to prevent cracks and damage at the base of the convex parts due to the difference in swelling. Here, the film thickness being almost constant does not exclude the provision of some thickness difference between one or more of the three parts between the flat part and the convex part near the end, between the convex part and the flat concave part, and between the flat part and the flat concave part near the end of the ion exchange membrane. Rather, it is preferable that the film thickness difference is provided at these parts. Here, the flat concave part includes not only the above-mentioned first concave part which is a flat concave part between the convex parts when the cross section of the membrane in the longitudinal direction of the linear or curved convex parts is viewed, but also the above-mentioned second concave part which is a flat concave part that may be provided between the convex parts in the longitudinal direction when a plurality of convex parts are extended at a predetermined interval in the longitudinal direction. The film thickness does not simply remain almost completely uniform as it bends, but for example, the film thickness of the flat portion of the ion exchange membrane, i.e., the film thickness near the ends of the membrane and the flat portion of the recess, may have thin or thick portions in the film thickness of both sloping faces in the short direction at the upper end of the protrusion and the inclined faces at the end in the long direction, or on either of the both sloping faces or the inclined faces (hereinafter referred to as the "film thickness of the protrusion"). The film thickness of the ion exchange membrane may continuously become thinner or thicker from the rising start point of the protrusion of the ion exchange membrane toward the top of both sloping faces at the upper end of the protrusion. Conversely, when the film thickness of the protrusion becomes thicker, the film thickness of the recess may become somewhat thinner.

[0026] Among the three regions, when the thickness of one region is 100%, the ratio of the thickness of the other region is preferably 30 to 95%, more preferably 50 to 95%, and even more preferably 80 to 95%. The lower limit of the thinner thickness is determined from the mechanical strength of the membrane. In order to make the thickness of the ion exchange membrane different depending on the region, the ion exchange membrane of the present invention has a feature that it can reduce distortion and increase the surface area even if the projected area is almost the same compared to a membrane with a flat entire surface. When forming the unevenness of the ion exchange membrane described later, it is preferable to provide a difference in thickness so that the thickness of both slopes at the upper end of the convex portion and the inclined surface of the end portion in the longitudinal direction is thinner than the flat portion of the ion exchange membrane by the above-mentioned ratio even if only partially. This is because the structure is stable when viewed as a whole membrane, and the average electrical resistance of the membrane is in the direction of decreasing. It should be noted that even if there is a thicker portion in addition to a thinner portion in the thickness of the convex portion near the end or the flat portion of the concave portion, it is within the scope of this technical idea. In addition, when the support has the plasticity described below and is formed with unevenness before film formation, the film thickness may be made to differ between the three types of parts of the support itself in the above ratio, and as a result, even if a difference in film thickness occurs in one or more of the three types of parts after film formation, the film will have the same characteristics.

[0027] In the ion exchange membrane cell of the present invention, the convex portion of the ion exchange membrane having a concave-convex shape is arranged so as to face the other ion exchange membrane. Furthermore, in the ion exchange membrane cell of the present invention, a gasket is arranged between the ion exchange membrane having a concave-convex shape and the other ion exchange membrane facing it, and the gasket includes a frame having a thickness greater than the height of the convex portion of the ion exchange membrane having a concave-convex shape, an opening surrounded by the frame, and a reinforcing member provided in the opening and connecting different sides of the frame, and the convex portion is inserted into the opening of the frame, and the reinforcing member is arranged between the convex portion and the other ion exchange membrane facing it. Figure 13 is a cross-sectional view showing one embodiment of the ion exchange membrane cell of the present invention. In the ion exchange membrane cell of Figure 13, both of the facing ion exchange membranes are ion exchange membranes having a concave-convex shape, and the respective convex portions face each other. Furthermore, different sides of the frame of the gasket, i.e., the left and right sides in Figure 13, are connected by a reinforcing member. The frame of the gasket is arranged so as to be sandwiched between a flat portion near the end of the CEM and a flat portion near the end of the AEM, the convex portion of the cation exchange membrane (CEM) and the convex portion of the anion exchange membrane (AEM) are inserted into the opening of the gasket, and the reinforcing member is arranged between the convex portion of the CEM and the convex portion of the AEM. Both the convex portion of the CEM and the convex portion of the AEM may be in contact with the reinforcing member, or either one of the convex portion of the CEM and the convex portion of the AEM may be in contact with the reinforcing member, or both the convex portion of the CEM and the convex portion of the AEM may not be in contact with the reinforcing member. In addition, the ion exchange membrane cell of FIG. 13 is an example in which both the CEM and the AEM are ion exchange membranes having an uneven shape, but either one of the CEM and the AEM may be an ion exchange membrane having an uneven shape, and the other may be a flat ion exchange membrane. FIG. 14 is a top view of the gasket used in the ion exchange membrane cell of FIG. 13 (however, the structure of the distribution portion and the like is omitted). The gasket in Fig. 14 has a rectangular shape when viewed from above, a frame is formed along the outer periphery, and an opening is provided inside that is surrounded by the frame. The reinforcing member provided in the opening is a thread-like member with a small diameter, and this reinforcing member connects different sides of the frame, i.e., between the left side and right side as viewed from above in Fig. 14, and between the upper side and lower side.

[0028] In the ion exchange membrane cell of the present invention, the cation exchange membrane and the anion exchange membrane are arranged opposite to each other, and at least one of the ion exchange membranes has an uneven shape, and the convex portion is arranged so as to face the other ion exchange membrane, so that the interval between the two ion exchange membranes can be fixed and a flow path between the two ion exchange membranes can be secured. Therefore, a spacer for keeping the intermembrane distance between the cation exchange membrane and the anion exchange membrane constant is not necessarily required as in the conventional technology. FIG. 15 is a cross-sectional view showing the structure of a conventional spacer, in which a mesh having the same thickness as the gasket is provided at the opening, and this mesh maintains a constant intermembrane distance (i.e., the distance of the mesh thickness) between the cation exchange membrane and the anion exchange membrane over the entire surface of the ion exchange membrane cell. The reinforcing member of the gasket in the present invention is not for maintaining the intermembrane distance between the cation exchange membrane and the anion exchange membrane constant, but for maintaining the shape of the frame body, so that the thickness of the reinforcing member does not need to be the same as the thickness of the frame body as in the conventional technology, and furthermore, it does not need to be densely provided as in the conventional technology, so that the opening ratio of the opening can be increased. In the present invention, the height of the convex portion of the ion exchange membrane in the "frame having a thickness greater than the height of the convex portion of the ion exchange membrane" refers to the height of one of the convex portions when only one of the cation exchange membrane and the anion exchange membrane has an uneven shape, and refers to the total height of both convex portions when both the cation exchange membrane and the anion exchange membrane have an uneven shape. In addition, the height of the convex portion of each ion exchange membrane refers to the height of the highest convex portion when convex portions of different heights are mixed in one ion exchange membrane. In the ion exchange membrane cell of the present invention, the intermembrane distance between the ion exchange membrane having an uneven shape and the ion exchange membrane facing the convex portion can be, for example, 15 to 3000 μm, 25 to 3000 μm, etc. when only one of the ion exchange membranes has an uneven shape, and can be, for example, 30 to 3000 μm, 50 to 3000 μm, etc. when both ion exchange membranes have an uneven shape. Therefore, the thickness of the frame of the gasket in the present invention can be, for example, 15 to 3000 μm, 25 to 3000 μm, 30 to 3000 μm, 50 to 3000 μm, and the like.The height of the projections of the ion exchange membrane having an uneven shape in the present invention may be, for example, 15 to 1000 μm, or 25 to 300 μm.

[0029] The reinforcing member in the present invention is not particularly limited in terms of its material, shape, etc., but is preferably a material that does not undergo physical changes such as swelling due to salt water or chemical changes such as decomposition over a long period of time. In addition, examples of the shape include filaments with a circular or polygonal cross-sectional shape. Examples of the reinforcing member in the present invention include polyolefin-based members such as polyethylene (PE) and polypropylene (PP), polyester, polystyrene, nylon, polyvinylidene fluoride (fluorocarbon), glass fibers such as glass fibers, aramid fibers, and continuous inorganic fiber members composed of silicon carbide. Among these materials, polyolefin-based members that can be fixed by melting the intersections of intersecting filaments are preferred. The method of connecting different sides of the frame with the reinforcing member is not particularly limited, and examples include methods such as embedding, bonding, and tying the ends of the reinforcing member into the frame. In addition, the reinforcing members may be arranged so that the opening is in a checkerboard pattern or a mesh pattern of various shapes when viewed from above, or may be arranged so that the reinforcing members do not cross each other. The thickness of the reinforcing member (diameter when the cross-sectional shape is circular) is preferably small, and the density of the reinforcing member at the opening is low and the opening rate of the opening is high, because the electrical resistance of the flow path and the water flow resistance (pressure loss) of the flow path are low. On the other hand, the strength of the gasket to maintain the shape of the frame is increased when the thickness of the reinforcing member is large and the density of the reinforcing member at the opening is high and the opening rate of the opening is low. In consideration of these points, the thickness of the reinforcing member is preferably 10 to 200 μm, more preferably 20 to 150 μm, more preferably 30 to 130 μm, and even more preferably 50 to 110 μm. The interval between the reinforcing members is preferably 5 to 50 mm, more preferably 10 to 40 mm, and even more preferably 20 to 35 mm. If the interval between the reinforcing members is too narrow, the electrical resistance of the flow path and the water flow resistance of the flow path may increase, and if it is too wide, the strength may decrease. The opening ratio of the openings is preferably 80 to 99%, more preferably 85 to 98%, more preferably 90 to 97%, and even more preferably 92 to 96%. The thickness of the frame of the gasket is preferably 100 to 700 μm, more preferably 150 to 500 μm, and even more preferably 200 to 400 μm.The mesh (reinforcing mesh) formed by the reinforcing member has a larger opening rate than the mesh of the conventional spacer, so clogging due to adhesion of dirt can be reduced. If the thickness of the frame of the spacer is too thin, the pressure loss may increase, and if it is too thick, the electrical resistance of the flow path may increase. In addition, from the viewpoint of smoothing the flow of the salt solution between both ion exchange membranes and reducing the electrical resistance of the flow path, the ratio of the thickness of the reinforcing member to the thickness of the frame is preferably 60% or less, more preferably 55% or less, more preferably 50% or less, more preferably 30% or less, and even more preferably 20% or less. The lower limit of the ratio of the thickness of the reinforcing member to the thickness of the frame is preferably about 5%. The opening rate of the opening refers to the ratio of the area of ​​the part (opening) where the reinforcing member is not present to the area of ​​the entire opening when viewed from above. Since pressure during assembly and use of the ion exchange membrane cell is applied toward the outside of the gasket, if the tension of the reinforcing member is low, the shape retention of the frame will be poor, and if it is too high, the shape retention of the frame will also be poor and the bonding with the frame will also be poor. Therefore, when using PE or PP, which have low extensibility, as the filaments, it is desirable to use a tension that makes the threads almost straight when the frame is in a specified shape. When connecting the filaments to the frame in a checkerboard pattern as the reinforcing member, the crossing angle of the warp and weft threads is desirably a right angle from the standpoint of shape retention of the frame, but they may also have an angle of 20° to 80° in the opposite directions to the direction of liquid flow.

[0030] The gasket of the present invention may have a through hole through which the salt solution passes and a liquid passage part through which the salt solution passes between the ion exchange membranes, in addition to the frame and the reinforcing member. For example, the gasket of the present invention may have a mesh of the reinforcing member in a checkerboard pattern or various other shapes embedded in the frame, and then the through hole and the liquid passage part may be formed. The material of the frame is not particularly limited, and for example, thermoplastic elastomers such as polystyrene, polyolefin, polyester, and fluororubber, CR rubber, etc. may be used. The outer shape of the gasket formed by the frame is not particularly limited, and may be a shape that matches the shape of the ion exchange membrane to be used, and the shape of the opening is not particularly limited, and may be any shape that allows the part of the ion exchange membrane to be used with the convex part formed therein to be inserted. Note that FIG. 16 shows an example of a gasket of the present invention in which a conventional mesh is used for the liquid passage part and the reinforcing member of the present invention is used for the opening. The gasket of the present invention is a gasket comprising a frame, an opening surrounded by the frame, and a reinforcing member provided at the opening and connecting different sides of the frame, and the ratio of the thickness of the reinforcing member to the thickness of the frame is preferably 60% or less, more preferably 55% or less, more preferably 50% or less, more preferably 30% or less, and even more preferably 20% or less, and the lower limit is preferably about 5%. The opening ratio of the gasket of the present invention is preferably 80 to 99%, more preferably 85 to 98%, more preferably 90 to 97%, and even more preferably 92 to 96%. The gasket of the present invention can be suitably used as a gasket for a stack for electrodialysis or reverse electrodialysis.

[0031] In the ion exchange membrane cell of the present invention, an ion exchange membrane having an uneven shape is used, so that the surface area of ​​the membrane is large. Therefore, the surface area of ​​the membrane effective for ion permeation can be increased. In addition, even when the ion exchange membrane contacts the reinforcing member, the convex portion contacts, so that the area of ​​the contact portion where ions do not flow can be narrowed, and the surface area of ​​the membrane effective for ion permeation can be increased. Furthermore, in the ion exchange membrane of a preferred embodiment of the present invention, when the ion exchange membrane or the support member is included, the curved corner of the support member can be the upper end of the convex portion, so that the width of the upper end of the convex portion can be easily narrowed regardless of whether the corner is bent or curved, or whether a flat portion is provided at the upper end. In the ion exchange membrane of a preferred embodiment of the present invention, the width of the upper end of the convex portion can be narrowed and the area of ​​the upper end can be reduced, so that even when the convex portion of the ion exchange membrane contacts the reinforcing member, the area of ​​the contact portion where ions do not flow can be narrowed, and the surface area of ​​the membrane effective for ion permeation can be increased. In the ion exchange membrane cell of the present invention, when both of the opposing ion exchange membranes are ion exchange membranes having an uneven shape, and the upper ends of the convex parts of both ion exchange membranes are in contact with the reinforcing member or the distance between the upper ends of the convex parts and the reinforcing member is very close, the convex parts of both ion exchange membranes support each other via the reinforcing member, and a flow path between both ion exchange membranes can be secured. Even if only one of the ion exchange membranes has an uneven shape, the ion exchange membrane of the present invention is less likely to deform or break, so that the distance between both ion exchange membranes can be secured. The ion exchange membrane of the present invention can particularly prevent cracks at the base of the convex parts and breakage at the upper ends, which are likely to occur when the width of the upper ends of the convex parts is narrow.

[0032] The ion exchange membrane cell of the present invention is suitable as a cell for RED power generation and ED power generation. In particular, the ion exchange membrane of the preferred embodiment of the present invention has a small difference in film thickness between the convex portion and other portions, so that it is possible to prevent differences in swelling due to differences in locations (differences in film thickness) in the membrane. Therefore, the ion exchange membrane cell using the ion exchange membrane of the present invention is less likely to be deformed or damaged due to swelling of the ion exchange membrane even in a wide range of salt concentrations and when the salt concentration difference between two solutions with which the membrane is in contact is large. Therefore, the ion exchange membrane cell of the present invention can be used not only for solutions with low salt concentrations (ion concentrations), but also for solutions with, for example, electrical conductivity of 0.05 mS / cm or more, or 0.1 mS / cm or more. The ion exchange membrane cell of the present invention can be used for any solution in which the dissolution of salt does not reach a saturated state, so that the maximum electrical conductivity of the solution that can be used is less than the electrical conductivity when the dissolution of salt is saturated. Furthermore, the ion exchange membrane cell of the present invention can be used even when the conductivity of the solution on the lower concentration side is 0.05 to 50 mS / cm and the conductivity of the solution on the higher concentration side is 2 times or more, 20 times or more, 50 times or more, or 600 times or more than that of the solution on the lower concentration side, between which the membrane is in contact. There is no particular upper limit to the conductivity of the solution on the higher concentration side as long as the dissolution of the salt does not reach a saturated state, and examples of the upper limit include 4000 times or less, 1000 times or less, or 700 times or less than that of the solution on the lower concentration side. The ion exchange membrane cell of the present invention can be used for a solution having a TDS (total dissolved solid) of 10 ppm (0.001%) or more, or 20 ppm (0.002%) or more. In the case where the membrane is in contact with two solutions having different salt concentrations, the TDS of the solution on the lower concentration side is 10 ppm (0.001%) to 35,000 ppm (3.5%), and the TDS of the solution on the higher concentration side is 2 times or more, 20 times or more, 50 times or more, or 100 times or more than the solution on the lower concentration side. The conductivity of the solution on the higher concentration side can be, for example, 10 to 200 mS / cm, and the TDS can be, for example, 7000 ppm (0.7%) to 200000 ppm (20%). 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 as a cell for RED power generation, for example, a solution with a low salt concentration can be a solution with a conductivity of 0.05 to 50 mS / cm, and a solution with a high salt concentration can be a solution with a conductivity of 10 to 200 mS / cm.

[0033] The distance (intermembrane distance) between the cation exchange membrane and the anion exchange membrane in the ion exchange membrane cell of the present invention, particularly from the viewpoint of the electrical resistance and pressure loss of the flow path of the low concentration solution, can be, for example, more than 15 μm and 3000 μm or more than 25 μm and 3000 μm, when only one of the ion exchange membranes has an uneven shape, and can be, for example, more than 30 μm and 3000 μm or more than 50 μm and 3000 μm, when both ion exchange membranes have an uneven shape. The height of the convex part of the ion exchange membrane having an uneven shape can be, for example, 15 to 1000 μm or 25 to 300 μm. When both ion exchange membranes have an uneven shape, the height of the convex part of both ion exchange membranes does not necessarily have to be the same. The height of the convex part of one ion exchange membrane may be higher than the height of the convex part of the other ion exchange membrane.

[0034] In the present specification, the upper end of the convex portion extending in a straight or curved shape is also referred to as a ridge (the ridge may have a width), but the ridges of both ion exchange membranes may be overlapped so that they coincide with each other, or so that they intersect. Figures 17 and 18 are examples of ridges intersecting. In the present invention, the ridges intersect with each other when the ridges of the cation exchange membrane and the anion exchange membrane are arranged opposite to each other, and the ridges of both ion exchange membranes appear to intersect when viewed from above the ion exchange membranes. Figures 17 and 18 omit the illustration of the reinforcing member in order to show the relative positions of the ion exchange membranes, but the reinforcing member is arranged between the convex portions of each ion exchange membrane. Figures 19 and 20 are examples of an embodiment in which the extension direction of the convex portion of the cation exchange membrane and the extension direction of the convex portion of the anion exchange membrane are shifted (the angle of the extension direction is changed) so that the ridges intersect when the two ion exchange membranes are overlapped. In Figs. 19 and 20, the convex parts are formed so that the direction of inclination of one ion exchange membrane (CEM) is opposite to the direction of inclination of the other ion exchange membrane (AEM). This allows the ridges to cross each other. In Figs. 19 and 20, the part corresponding to the uneven shape part of the ion exchange membrane is a hollowed-out opening, and both ion exchange membranes are fixed by sandwiching a gasket having a reinforcing member that connects different sides of the frame at the opening. The part of the ion exchange membrane that contacts the frame on all four sides of the gasket, that is, the vicinity of the edge of the ion exchange membrane in the present invention, is flat. When assembled into a cell, the solution is supplied between both ion exchange membranes from the distribution part openings (circular openings near the upper end and the lower end in the figure) formed in the gasket. Fig. 19 shows a case where the distribution part also maintains a constant gap by the uneven structure of the ion exchange membrane, and Fig. 20 shows a case where the distribution part maintains a constant membrane gap by using a reinforcing mesh. The former has the advantage of lowering the pressure loss in the distribution section, but due to the complexity of manufacturing, a conventional mesh spacer may be used in the distribution section.

[0035] In the ion exchange membrane cell of the present invention, the contact area between the cation exchange membrane and the anion exchange membrane, or between each ion exchange membrane and the reinforcing member of the gasket, is reduced, so that the effective membrane area through which ions pass can be increased. In addition, the flow of the salt solution between the two ion exchange membranes is smooth, and since there is no convex structure that impedes the flow of contaminants, clogging of the flow path due to adhesion of contaminants is reduced. Furthermore, the liquid easily flows over the convex part and into the flat concave part, which can be called the adjacent lane. Since such a flow of the liquid occurs between both the cation exchange membrane and the anion exchange membrane, stagnation of the ions is reduced, and therefore it is possible to reduce a local increase in the concentration of the solution, which causes a decrease in the generated voltage in the case of RED power generation, and a local decrease in the salt concentration, which causes membrane burning and membrane destruction in the case of ED power generation. From these points of view, 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 adhesion of contaminants is reduced, so that the width can be narrowed, and the electrical resistance in the flow path can be appropriately reduced significantly by the synergistic effect of the increase in the effective membrane area. In particular, when a cation exchange membrane with a concave-convex shape and an anion exchange membrane with a concave-convex shape are arranged so that the convex parts face each other, the cross-sectional area of ​​the flow path can be made larger than that of a conventional profiled membrane, which prevents an increase in pressure loss and reduces the required pump energy. This structure is strong and can be easily made large, making it possible to manufacture cells at low cost.

[0036] The angle that the edge of each ion exchange membrane makes with the flow direction of the solution is not particularly limited. Here, the flow direction of the solution is as follows. When a stack (cell) of ion exchange membranes is constructed as described below, a pair of ion exchange membranes are arranged parallel to each other with their protruding parts facing each other. The solution flows from the inlet to the outlet through a flow path of the solution that is formed when the membranes are sandwiched between a gasket (frame) that seals the vicinity of the edge of each membrane. At this time, the solution flows from the inlet to the outlet along two parallel sides of the gasket that face each other across the flow path. The direction parallel to these sides is the flow direction of the solution. The flow direction of the solution is shown diagrammatically by arrows in the gasket diagram of FIG. 19. If the angle between the edge of the ion exchange membrane and the flow direction of the solution becomes large, the distance the solution flows becomes long, and the liquid transfer resistance in the flow path becomes high. The angle between the edge of the ion exchange membrane and the flow direction of the solution is preferably 0 to 45° (0° is parallel to the flow direction of the solution), more preferably 0 to 30°, 0 to 15°, or 1 to 9°. In addition, when both the cation exchange membrane and the anion exchange membrane are ion exchange membranes having an uneven shape, the preferred range of the angle between the edges of both ion exchange membranes is 0 to 90°, more preferably 0 to 45°, 2 to 30°, 2 to 18°, or 2 to 15°. Here, the angle between the edges of both ion exchange membranes refers to the intersection angle between edges that intersect on different planes. In addition, it is preferable that the surfaces of both ion exchange membranes facing each other are parallel to each other, and each ion exchange membrane is provided so that the line segment that bisects the angle between the respective facing edges coincides with the flow direction of the solution. In this way, by arranging the edges of the ion exchange membranes so that they are line-symmetric when they are parallel to each other, it is possible to reduce the number of molds required for manufacturing the ion exchange membrane to one type.

[0037] When used for RED power generation, it is desirable to use a conventional mesh spacer in the high-concentration side flow path to maintain sufficient cell strength in terms of cost, strength, etc. In addition, it is preferable to make the pressure on the low-concentration side slightly higher than that on the high-concentration side so that the CEM and AEM are supported by the mesh spacer on the high-concentration side. This is because if the pressure is reversed, the convex parts of the CEM and AEM may be partially deformed or damaged. However, even if this part is partially deformed, it is not a major problem as long as the membrane is not damaged. In conventional cell structures with spacers between flat membranes, creating a pressure difference is not usually done actively because it can lead to problems such as liquid leakage. Conventional cells are disassembled and cleaned to remove contaminants. However, this is labor-intensive and costly, and may lead to damage to the membrane and spacer materials. With this technology, contaminants are less likely to accumulate as described above, and even if they do accumulate, they can be easily removed by physical cleaning such as backwashing or chemical cleaning such as acid, alkali, or chlorine injection, making it possible to clean the cells without disassembly. In this case, since there is no need to disassemble the cell, it is possible to make an integrated cell in which the cation exchange membrane and the anion exchange membrane are joined to the gasket through a gasket. With an integrated cell, there is no leakage from the low-salt-concentration side flow path such as fresh water, so a high current efficiency can be obtained in the case of ED, and a high energy conversion rate can be obtained in the case of RED. In addition, the number of parts in the cell is halved, which has the advantage of lowering costs.

[0038] FIG. 21 is a diagram showing one embodiment of the ion exchange membrane cell of the present invention, which is an example of an integrated cell. In this example, the gasket of the present invention is placed on the front surface of the anion exchange membrane (PF-AEM) having a concave-convex shape shown on the left side of the upper part of the figure, and then the cation exchange membrane (PF-CEM) having a concave-convex shape shown on the right side is placed so as to face the PF-AEM while keeping the orientation as shown in the figure (the figure on the right side is a view from the back side). "PF" is an abbreviation of profile. In the integrated half cell of FIG. 21 (a part of a cell is called a half cell. The same applies below), as shown in the figure in the middle part (the illustration of the reinforcing member is omitted), the convex parts of the cation exchange membrane and the convex parts of the anion exchange membrane are arranged so as to intersect at one or more points, and each is joined to the gasket of the present invention between the two ion exchange membranes. The lower figure shows a cross section of the PF-AEM and PF-CEM being incorporated into the gasket of the present invention, in which the gasket of the present invention is placed on one ion exchange membrane, and the other ion exchange membrane is placed on top of the gasket and joined to produce an integrated half cell. In each of the figures described above, some parts are drawn in an exaggerated manner to express the relationship in size.

[0039] One embodiment of the method for producing an ion exchange membrane having a concave-convex shape in the present invention includes any one of the following steps: (i) forming concave-convex shapes on a plastic polymer film having a charged group by pressing the film against a mold having concave-convex shapes and a flat concave shape, and bending the film; (ii) forming concave-convex shapes on a plastic polymer film having a charged group by pressing the film against a mold having concave-convex shapes and a flat concave shape, and then crosslinking the polymer; and (iii) forming concave-convex shapes on a plastic polymer film having no charged group by pressing the film against a mold having concave-convex shapes and a flat concave shape, and then introducing a charged group. In the above-mentioned production method, by using a concave-convex shape mold in which the portions corresponding to the edge vicinity and concave portion of the ion exchange membrane are flat, an ion exchange membrane having a concave-convex shape, which has a flat portion near the edge, and in which the convex curved portion and the concave curved portion due to the bending of the ion exchange membrane itself are the convex portion and the flat concave portion in the concave-convex shape of the ion exchange membrane, respectively, can be produced. The above-mentioned production method is suitable as a method for producing an ion exchange membrane for use in ion exchange of a solution having an electrical conductivity of 0.05 mS / cm or more.

[0040] The method for producing the ion exchange membrane of the present invention is not particularly limited, but the above-mentioned production method is suitable as the method for producing the ion exchange membrane of the present invention. The method for forming the unevenness on the membrane in the above-mentioned production method is not particularly limited as long as the membrane is pressed against a mold with unevenness and bent, and for example, a pressing method can be mentioned, and a hot pressing method in which heat is applied during pressing can be mentioned. For example, the membrane can be bent to form unevenness by sandwiching the membrane between a lower mold and an upper mold and hot pressing. Then, the membrane is removed from the mold to obtain a membrane with unevenness. In the above-mentioned process, the membrane of a plastic polymer having a charged group that will become an ion exchange layer is pressed against a mold with unevenness to bend it, thereby producing an ion exchange membrane in which the convex curved portion and the concave curved portion become a convex portion and a concave portion. In addition, after forming unevenness on a membrane of a plastic polymer having a charged group, the membrane may be crosslinked as necessary to obtain an ion exchange membrane. Alternatively, the ion exchange membrane may be obtained by forming unevenness on a plastic polymer having a charged group that has already been crosslinked. In step (iii), the membrane of the plastic polymer having no charged groups means a membrane that cannot be substantially used as an ion exchange membrane as it is, and does not mean only a membrane that does not contain any charged groups. In step (iii), unevenness is formed in such a membrane of the plastic polymer having no charged groups, and then charged groups are introduced to impart an ion exchange function to form an ion exchange membrane. Crosslinking may be performed before or after the introduction of the charged groups, as necessary. The step of forming unevenness in the crosslinked polymer layer, i.e., the crosslinked membrane, has the following three advantages. First, a commercially available crosslinked ion exchange membrane can be used as is. Second, by inserting an unevenness formation step after the conventional manufacturing step of a flat ion exchange membrane, the existing manufacturing line requires less modification, and production efficiency is good. Third, when unevenness is formed in a non-crosslinked polymer layer, the polymer layer may be immersed in water, in which case it may be difficult to match the dimensions of the unevenness formed in the mold to the design value depending on the swelling state of the polymer layer, but since the crosslinked membrane is difficult to swell, the difference between the design dimension and the actual size is small. This process results in an ion exchange membrane in which convex and concave portions are formed due to bending in a flat membrane of a crosslinked, plastic polymer having charged groups.

[0041] Plasticity refers to the property of applying an external force to a solid to deform it and not returning to its original shape even when the force is removed. The plastic polymer in the present invention includes polymers that have plasticity at room temperature and polymers that have thermoplasticity, which soften when heated to make it easier to mold and harden again when cooled. That is, the plastic polymer in the present invention (including the case where the plastic polymer is a support or has a support) is a polymer that has the property of being deformed when an external force is applied and not returning to its original shape even when the force is removed (if a support is used, it has the above-mentioned properties together with the support), and includes polymers that have plasticity at room temperature and polymers that have thermoplasticity, which soften when heated to make it easier to mold and harden again when cooled.

[0042] When a polymer having a site capable of chemical crosslinking is used as the plastic polymer having a charged group, it is possible to crosslink the polymer by heat or light irradiation after forming the uneven shape, or to chemically crosslink the polymer by immersing it in a solution containing a crosslinking agent such as glutaraldehyde (GA) or ethylene glycol diglycidyl ether in the case of a polymer having a hydroxyl group such as polyvinyl alcohol. In the case of no crosslinking, the membrane resistance is low, and when crosslinking is performed after forming the unevenness, the membrane resistance tends to be higher than that of the non-crosslinking case, but the membrane water content is low, the ion selectivity is high, and the mechanical strength is also improved. The method of producing the membrane of the plastic polymer having a charged group in the above process is not particularly limited, but examples of the method include casting the plastic polymer having a charged group to produce a film, applying the plastic polymer having a charged group to a substrate, drying it, and then peeling it off from the substrate to produce a film.

[0043] One embodiment of the method for producing an ion exchange membrane in the present invention includes: (a) a step of pressing a plastic support having a plastic polymer layer having a charged group on both sides or one side thereof against a mold having unevenness and flat recesses to form unevenness on the support, or a step of pressing a plastic support having a plastic polymer layer not having a charged group on both sides or one side thereof against a mold having unevenness to form unevenness on the support, and then introducing a charged group; or (b) a step of pressing a plastic support against a mold having unevenness and flat recesses to form unevenness on the support, and then providing a polymer layer having a charged group on both sides or one side of the support after forming the unevenness, a step of providing a plastic polymer layer not having a charged group on one side or both sides of the plastic support, introducing a charged group, and then forming unevenness; or a step of providing a plastic polymer layer not having a charged group on one side or both sides of the plastic support, forming unevenness, and then introducing a charged group. In the above-mentioned manufacturing method, by using an uneven mold in which the portions near the edges and corresponding to the recesses of the ion exchange membrane are flat, it is possible to manufacture an ion exchange membrane having an uneven shape, which is composed of at least a support and an ion exchange layer provided on both sides or one side of the support, and in which convex portions and flat recesses of the ion exchange membrane are formed at the convex curved portions and concave curved portions caused by the bending of the support, respectively.

[0044] The above-mentioned manufacturing method is suitable as a manufacturing method of an ion exchange membrane for use in ion exchange of a solution having an electric conductivity of 0.05 mS / cm or more. The method of manufacturing an ion exchange membrane having a support in the present invention is not particularly limited, but the above-mentioned manufacturing method is suitable as a manufacturing method of an ion exchange membrane having a support in the present invention. The method of forming the unevenness on the support in the above-mentioned (a) or (b) step is not particularly limited as long as it is a method of pressing the support against a mold in which the unevenness is formed and bending it, and examples thereof include a pressing method, and examples of which include a hot pressing method in which heat is applied during pressing. For example, the support in the step (a) or (b) can be bent to form unevenness by sandwiching the support between a lower mold and an upper mold and hot pressing it. Thereafter, the support having the unevenness formed thereon is obtained by removing the support from the mold. Plasticity refers to the property of applying an external force to a solid to deform it and not returning to its original state even when the force is removed, and the plastic support and plastic polymer in the present invention include a support and polymer having plasticity at room temperature, and a support and polymer having thermoplasticity that softens and becomes easy to mold when heated and hardens again when cooled. Each of steps (a) and (b) will be further explained below.

[0045] [Including step (a)] A plastic support having a plastic polymer layer having a charged group on both sides or one side in advance is pressed against a mold having unevenness and a flat concave portion to form unevenness on the support. Alternatively, a plastic support having a plastic polymer layer having no charged group on both sides or one side is pressed against a mold having unevenness and a flat concave portion to form unevenness on the support, and then a charged group is introduced. According to this method, an ion exchange membrane having a convex portion and a concave portion formed on the convex curved portion and the concave curved portion of the support can be manufactured by bending the polymer layer to be an ion exchange layer as a unit with the support. In addition, after forming unevenness on the support or introducing a charged group, the polymer layer may be crosslinked as necessary to obtain the ion exchange membrane of the present invention. The advantages of the step of crosslinking the polymer layer and then forming unevenness are the same as the three advantages described above, and an ion exchange membrane having a convex portion and a concave portion formed by bending a flat support having a plastic polymer layer having a charged group and crosslinked on both sides or one side is obtained by this step. An example of a method for producing an ion exchange membrane having such an uneven shape is a method for producing an ion exchange membrane in which a plastic polymer layer having charged groups is provided on both sides or one side of a plastic support, the polymer layer is crosslinked, and then the support is pressed against a mold in which unevenness is formed and the concave portions are flat, thereby bending the support to form unevenness. [Including step (b)] The prepared plastic support is pressed against a mold in which unevenness is formed and the concave portion is flat to bend the support, and then unevenness is formed on the support, and a polymer layer having a charged group is provided on both sides or one side of the support after the unevenness is formed. Alternatively, a plastic polymer layer not having a charged group is provided on one or both sides of the plastic support, and a charged group is introduced, or unevenness is formed, or a plastic polymer layer not having a charged group is provided on one or both sides of the plastic support, and unevenness is formed, and then a charged group is introduced. According to this method, the polymer layer is provided on the support on which unevenness is formed, in accordance with the shape of the support, thereby producing an ion exchange membrane in which convex portions and concave portions are formed on the convex curved portion and concave curved portion of the support. In the step (b), after unevenness is formed on the support, a polymer layer having a charged group is formed, and this polymer layer may be crosslinked as necessary to obtain the ion exchange membrane of the present invention.

[0046] In the case of an ion exchange membrane having a support, when an ion exchange layer is provided on both sides of the support, an ion exchange membrane with higher membrane strength can be obtained. When an 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 with low membrane resistance can be obtained. The support is not particularly limited as long as it does not prevent the passage of ions that have permeated the ion exchange layer, and examples thereof include thermoplastic porous films, nets, woven fabrics, nonwoven fabrics, etc. In addition, when an ion exchange layer is provided on both sides of the support, it also includes a case where an ion exchange layer is formed in the support or a case where the support is embedded in the ion exchange layer, for example, when the support is impregnated with a polymer.

[0047] The method for producing the support provided with the polymer layer having a charged group in the step (a) is not particularly limited, but for example, it can be produced by impregnating or coating a thermoplastic support with a polymer having a charged group. Examples of the production method include a transfer method in which a polymer is poured onto a cast plate (e.g., PET, etc.) to form a polymer layer, a support is placed on top in a half-dried state, and the support is peeled off from the cast plate after it has completely dried. Other examples include a method in which a monomer having a charged group is applied or impregnated into a support and polymerized, and a method in which a polymer not having a charged group is applied or impregnated into a support and then a charged group is introduced. Crosslinking may be performed before or after introducing a charged group, or after forming unevenness. The method for producing the support provided with the polymer layer not having a charged group is not particularly limited, but for example, it can be produced by impregnating or coating a thermoplastic support with a polymer not having a charged group.

[0048] The method of providing a polymer layer having a charged group on the support having the unevenness in the step (b) is not particularly limited, but examples thereof include impregnating the support having the unevenness with a polymer having a charged group, coating the support having the unevenness with a polymer having a charged group, etc. In addition, examples thereof include a method of introducing a charged group after forming unevenness on a support provided with a plastic polymer layer capable of introducing a charged group, a method of coating or impregnating a polymer having no charged group on a support having the unevenness formed thereon and then introducing a charged group, a method of coating or impregnating a polymer having no charged group on a support before the unevenness is formed, and introducing a charged group into the polymer after the unevenness is formed, etc. In addition, the method of providing a plastic polymer layer having no charged group on one or both sides of a plastic support is not particularly limited, but examples thereof include a method of impregnating or coating a polymer having no charged group on a thermoplastic support. Crosslinking may be performed before or after the charged group is introduced. The polymer having no charged groups in steps (a) and (b) refers to a polymer that cannot be substantially used as an ion exchange membrane as it is, and does not mean only a polymer having no charged groups at all. Some examples of steps (a) and (b) of the production method of the present invention are shown in Table 1. In Table 1, the charged layer refers to a polymer layer having charged groups, and the uncharged polymer layer refers to a polymer layer having no charged groups. However, the specific steps (a) and (b) are not limited to these.

[0049] [Table 1]

[0050] One embodiment of the method for producing an ion exchange membrane having a concave-convex shape in the present invention includes any one of the steps of: (A) pressing a plastic polymer membrane having no charged groups against a mold having concaves and convexes and a flat concave portion to form concaves and convexes in the membrane, and then introducing charged groups; (B) providing a polymer layer having no charged groups on both or one side of a plastic support, introducing charged groups into the polymer layer to form a plastic support having a plastic polymer layer having charged groups on both or one side, and pressing the support against a mold having concaves and convexes and a flat concave portion to bend the support, thereby forming concaves and convexes on the support; and (C) pressing a plastic support against a mold having concaves and convexes and a flat concave portion to form concaves and convexes on the support, providing a polymer layer having no charged groups on both or one side of the support after the formation of the concaves and convexes, and introducing charged groups into the polymer layer to provide a polymer layer having charged groups on both or one side of the support. The step (A) corresponds to the step (iii), the step (B) corresponds to the step (a) where a charged group is introduced, and the step (C) corresponds to the step (b) where a charged group is introduced. The manufacturing method can manufacture an ion exchange membrane having an uneven shape, which has a flat portion near the end, and in which the convex curved portion and the concave curved portion caused by the bending of the ion exchange membrane itself are respectively the convex portion and the concave portion in the uneven shape of the ion exchange membrane, and an ion exchange membrane which is at least composed of a support and an ion exchange layer provided on both sides or one side of the support, and in which the convex portion and the concave portion of the ion exchange membrane are respectively formed on the convex curved portion and the concave curved portion caused by the bending of the support (hereinafter, these are also collectively referred to as "an ion exchange membrane having an uneven shape"). The manufacturing method is suitable as a manufacturing method for an ion exchange membrane having an uneven shape.

[0051] As described above, the unevenness of the ion exchange membrane can be formed not only on the ion exchange membrane but also on the so-called precursor during the manufacturing process of the ion exchange membrane. Here, the precursor refers to (I) a plastic support, (II) a film of a plastic polymer that does not have a charged group before and after crosslinking, (III) a film of a plastic polymer that has a charged group before crosslinking, and (IV) the above-mentioned (II) and (III) films that include a plastic support, and the precursor film refers to the above-mentioned (II) to (IV). 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 can be a cationic polymer that is a polymer containing a cationic group (positively charged group) in the molecular chain, and the cationic group may be contained in any of the main chain, side chain, and terminal.

[0052] Examples of the cationic group include an ammonium group, an iminium group, a sulfonium group, and a phosphonium group. In addition, polymers containing functional groups, such as an amino group or an imino group, a part of which can be converted to an ammonium group or an iminium group in water, are also included in the cationic polymer of the present invention. Among these, an ammonium group is preferred from the viewpoint of industrial availability. 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, but a quaternary ammonium group (trialkylammonium group, etc.) is more preferred. The cationic polymer may contain only one type of cationic group, or may contain multiple types of cationic groups. In addition, the counter anion of the cationic group is not particularly limited, and examples thereof include a halide ion, a hydroxide ion, a phosphate ion, and a carboxylate ion. Among these, a halide ion is preferred from the viewpoint of availability, and a chloride ion is more preferred. The cationic polymer may contain only one type of counter anion, or may contain multiple types of counter anions. The cationic polymer used in the present invention may be a polymer consisting of only a structural unit containing a cationic group, or may be a polymer consisting of both a structural unit containing a cationic group and a structural unit not containing a cationic group. In addition, it is preferable that these polymers have crosslinking properties. The cationic polymer may be a polymer consisting of only one type of polymer, or may contain multiple types of polymers. In addition, it may be a mixture of these polymers containing a cationic group and polymers not containing a cationic group.

[0053] Examples of polymers having cation exchange capacity include anionic polymers, which are polymers containing anionic groups (negatively charged groups) in the molecular chain, and the anionic groups may be contained in any of the main chain, side chain, and terminal. Examples of the anionic groups include sulfonate groups, carboxylate groups, and phosphonate groups. Polymers containing functional groups, such as sulfonic acid groups, carboxyl groups, and phosphonic acid groups, a part of which can be converted to sulfonate groups, carboxylate groups, and phosphonate groups in water, are also included in the anionic polymers of the present invention. Among these, sulfonate groups are preferred in terms of their large ionic dissociation constant. Anionic polymers may contain only one type of anionic group, or may contain multiple types of anionic groups. In addition, the counter anion of the anionic group is not particularly limited, and examples include hydrogen ions and alkali metal ions. Among these, alkali metal ions are preferred in terms of less corrosion problems of equipment. Anionic polymers may contain only one type of counter cation, or may contain multiple 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 may be a polymer consisting of both structural units containing an anionic group and structural units not containing an anionic group. In addition, it is preferable that these polymers have crosslinking properties. The anionic polymer may be one consisting of only one type of polymer, or may contain multiple types of polymers. In addition, it may be a mixture of these polymers containing an anionic group and polymers not containing an anionic group.

[0054] The polymer without a charged group is not particularly limited as long as a charged group can be introduced later. For example, as a polymer having a functional group to which a cation exchange group can be introduced, a polymer obtained by polymerizing styrene, vinyltoluene, etc. as a monomer having an aromatic ring to which a sulfonic acid group is easily introduced, and a polymer obtained by polymerizing acrylic acid ester, methacrylic acid ester, acrylonitrile, etc. as a monomer having a carboxylic acid group or a nitrile group can be used. These polymerizable monomers may be mixed with a crosslinkable monomer or a swelling solvent to be used as a polymerizable mixture. Examples of crosslinkable monomers 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, one having at least two vinyl groups, is specifically exemplified by divinylbenzene (DVB), trivinylbenzene, divinyltoluene, divinylnaphthalene, ethylene glycol dimethacrylate, etc. As a polymer having a functional group to which an anion exchange group can be introduced, chloromethylstyrene is generally used as the monomer, but polymers obtained by polymerizing monomers such as styrene, vinyltoluene, vinylxylene, α-methylstyrene, acenaphthylene, vinylnaphthalene, α-halogenated styrene, α,β,β'-trihalogenated styrene, chlorostyrene, vinylpyridine, methylvinylpyridine, ethylvinylpyridine, vinylpyrrolidone, vinylcarbazole, vinylimidazole, aminostyrene, alkylaminostyrene, trialkylaminostyrene, acrylic acid amide, acrylamide, oxinium, etc. Furthermore, polyvinyl alcohol can also be used as a polymer having no charged group. In addition, the ion exchange membrane (charged sheet) and the membrane (uncharged sheet) of a plastic polymer to which a charged group can be introduced, which are used in the ion exchange membrane of the present invention having no support, and the ion exchange membrane (charged sheet) and the membrane (uncharged sheet) of a plastic polymer to which a charged group can be introduced, which are used in the ion exchange membrane of the present invention having a support, which are provided with a support, may need to be crosslinked in advance depending on the type of monomer used in forming the membrane. The membrane that has already been crosslinked may also be crosslinked again.

[0055] A preferred example of the preparation of an ion exchange membrane having a concave-convex shape to be used in the ion exchange membrane cell of the present invention is shown below, but the ion exchange membrane having a concave-convex shape to be used in the ion exchange membrane cell of the present invention is not limited to this preparation example.

[0056] [Preparation Example 1] As the anion exchange membrane (AEM) and cation exchange membrane (CEM) used in Preparation Example 1, an AEM developed membrane (AEM-1, Astom Corporation) with a polyolefin film substrate and a CEM developed membrane (CEM-1, Astom Corporation) with a polyolefin film substrate were used. AEM-1 is a precursor membrane prepared by crosslinking a polyolefin support with chloromethylstyrene monomers and divinylbenzene monomers, which is then quaternized to form an anion exchange membrane. CEM-1 is a precursor membrane prepared by crosslinking a polyolefin support with styrene monomers and divinylbenzene monomers, which is then sulfonated to form a cation exchange membrane.

[0057] (Formation of uneven film shape) The sample membranes of CEM-1 and AEM-1 were placed on the aluminum mold shown in Fig. 22 and hot-pressed with an electric iron set to a prescribed temperature to form a textured structure on the membrane. AEM-1 was hot-pressed at 200°C for 30 seconds, and CEM-1 was hot-pressed at 100°C for 10 seconds. The hot-pressed AEM-1 and CEM-1 were punched out with a Thomson punching die to obtain the textured anion-exchange membrane (PF-A) and textured cation-exchange membrane (PF-C) of Preparation Example 1 with the dimensions shown in Fig. 23.

[0058] Figure 24 shows an example of an overall photograph of PF-A and PF-C from Preparation Example 1. Figure 25 shows an example of a surface photograph of part of PF-A. The front of the photograph is the convex part, and the back is the flat part, and in order to show that the back of the convex part is concave, the photograph was taken with air bubbles inserted, and it is clear from this photograph that the back of the convex part is concave. From this photograph, the convex part (part A), flat part (part B), convex part height, and film thickness were measured and are shown in Figure 26. The CEM-1 used has a membrane charge density of 0.86 mol / dm 3 , membrane resistance is 0.18Ωcm2 The transference number was 0.94, the water content was 0.37, the ion exchange capacity was 2.42 meq / g, and the membrane thickness was 36 μm. The AEM-1 used had a membrane charge density of 0.98 mol / dm 3 , membrane resistance is 1.25Ωcm 2 The transport number was 0.98, the water content was 0.29, the ion exchange capacity was 1.03 meq / g, and the membrane thickness was 36 μm.

[0059] [Preparation Example 2] (Ion exchange membrane used) Flat membranes AT-2 (Astrom Corporation) and CT-2 (Astrom Corporation) were used as the anion exchange membrane (AEM) and cation exchange membrane (CEM) in Preparation Example 2, respectively. The preparation methods for AT-2 and CT-2 were similar to those for AEM-1 and CEM-1 used in Preparation Example 1, with some exceptions. The CT-2 used had a membrane charge density of 0.43 mol / dm 3 , membrane resistance is 0.21Ωcm 2 The transference number was 0.94, the membrane thickness was 34 μm, and the membrane charge density of the AT-2 used was 0.7 mol / dm 3 , membrane resistance is 0.28Ωcm 2 The transference number was 0.99, and the film thickness was 34 μm.

[0060] (Formation of uneven film shape) The flat AT-2 and CT-2 films were placed on a metal mold, and processed in a high-frequency fusion device to form irregularities in the AT-2 and CT-2 films. High-frequency fusion is a process in which high-frequency dielectric heating, a type of radio wave, is applied to electrical insulators such as plastic materials, films, and sheets, causing collisions, vibrations, and friction at the molecular level inside the material, which then generates self-heating and fuses the film. The metal mold on which the flat AT-2 and CT-2 films were placed was placed in the device, and the flat AT-2 and CT-2 films were pressed against the metal mold to form irregularities. A schematic diagram and dimensions of the metal mold are shown in Figures 27 and 28.

[0061] After the hot pressing by high-frequency dielectric heating treatment, both films were subjected to Thomson processing using a hydraulic die-cutting machine to punch out the outer frame, flow path holes, and holes for inserting the bamboo skewers for positioning. In this way, the ion exchange membrane of Preparation Example 2 was produced. The CT-2 membrane and the AT-2 membrane in which the unevenness was formed using the mold shown in FIG. 27 are shown in FIG. 29 and FIG. 30, respectively, and the CT-2 membrane and the AT-2 membrane in which the unevenness was formed using the mold shown in FIG. 28 are shown in FIG. 31 and FIG. 32, respectively. The uneven shape (FIG. 29 and FIG. 30) obtained using the mold shown in FIG. 27 is a shape in which the convex portion extends from the vicinity of one end of the ion exchange membrane to the vicinity of the other end, and has only the first concave portion. The uneven shape (FIG. 31 and FIG. 32) obtained using the mold shown in FIG. 28 is a shape in which the convex portion extends in a row in the longitudinal direction from the vicinity of one end of the ion exchange membrane to the vicinity of the other end, and has the first concave portion and the second concave portion. [Industrial Applicability]

[0062] The ion exchange membrane cell of the present invention can increase the surface area of ​​the membrane effective for ion permeation, appropriately reduce the electrical resistance and adhesion of deposits in the flow path between the membranes, and further increase the mechanical strength of the membrane itself. In addition, the cell can appropriately reduce the electrical resistance and adhesion of deposits in the solution flow path between the opposing cation exchange membrane and anion exchange membrane. Therefore, the cell can be suitably used in various fields that utilize ion exchange membranes, and can be particularly suitably used in electrodialysis (ED), reverse electrodialysis (RED) power generation, and hydrogen production that combines RED power generation and water electrolysis. The RED uses high-concentration salt-containing water with an electric conductivity of 10 to 200 mS / cm, such as seawater, brine (natural brine, artificial brine), Na-salt-containing industrial wastewater, high-concentration discharge water from seawater desalination facilities, hot spring water, etc., and low-concentration salt-containing water with an electric conductivity of 0.05 to 50 mS / cm, such as freshwater, river water, sewage treatment water, industrial water, hot spring water, etc., so that the difference in concentration of the salt-containing water used is large, but the ion exchange membrane cell of the present invention can be suitably used. The ED can be applied to the desalination and concentration of seawater, brine, and sewage treatment water, the treatment of sewage, wastewater from industrial and industrial waste treatment facilities, and the desalination of food and pharmaceutical raw materials. [Explanation of symbols]

[0063] IEM Ion Exchange Membrane IE Ion Exchange Layer IEM1, IEM1' Convex part (convex curved part) IEM2, IEM2' Concave (concave curve) S support A, B, C, D track section

Claims

1. An ion exchange membrane cell in which a cation exchange membrane and an anion exchange membrane are arranged facing each other, and which satisfies the following (i) to (iv): (i) at least one of the cation exchange membrane and the anion exchange membrane is an ion exchange membrane having an uneven shape; (ii) the convex portions of the ion exchange membrane having the concave-convex shape are arranged so as to face the other ion exchange membrane; (iii) a gasket is disposed between the ion exchange membrane having the uneven shape and another ion exchange membrane opposite to the convex portions of the ion exchange membrane having the uneven shape, and the gasket includes a frame having a thickness greater than the height of the convex portions of the ion exchange membrane having the uneven shape, an opening surrounded by the frame, and a reinforcing member provided in the opening and connecting different sides of the frame; and (iv) the convex portion of the ion exchange membrane having the concave-convex shape is inserted into the opening of the frame, and the reinforcing member is disposed between the convex portion and the other ion exchange membrane facing the convex portion;

2. 2. The ion exchange membrane cell according to claim 1, wherein the ion exchange membrane having a concave-convex shape is at least composed of a support and an ion exchange layer provided on one or both sides of the support, and the convex and concave portions of the ion exchange membrane are formed in the convex and concave portions caused by the curvature of the support itself.

3. 3. The ion exchange membrane cell according to claim 1, wherein both the cation exchange membrane and the anion exchange membrane are ion exchange membranes having an uneven shape, and a reinforcing member is disposed between the convex portions of the cation exchange membrane and the convex portions of the anion exchange membrane.

4. A gasket for an electrodialysis or reverse electrodialysis stack comprising a frame, an opening surrounded by the frame, and a reinforcing member provided in the opening and connecting different sides of the frame, wherein the thickness of the reinforcing member is 60% or less of the thickness of the frame, and the opening ratio of the opening is 80 to 99%.

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