Forward osmosis membrane element and method for producing porous film

Abstract

To provide a forward osmosis membrane element which has a high permeation flux and a low salt back diffusion coefficient, even when the thickness of a forward osmosis membrane is small.SOLUTION: A forward osmosis membrane element includes a plurality of membrane leaves, and a pipe around which the plurality of membrane leaves are wound. The membrane leaves have at least one internal flow channel bent toward a second opening from a first opening. The pipe has a first through hole communicating with the first opening, a second through hole communicating with the second opening, and at least one blocking wall for blocking the internal space. The membrane leaf has a forward osmosis membrane. The forward osmosis membrane includes a polyether ketone-based polymer layer, and a base material layer laminated on at least one main surface of the polyether ketone-based polymer layer. The polyether ketone-based polymer layer is composed of a polyether ketone-based polymer having a sulfonic acid group or its salt. The thickness of the polyether ketone-based polymer is 0.1 μm to 5 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to porous membranes and methods for making porous membranes. [Background technology]

[0002] Semipermeable membranes are useful for selectively separating a specific component from a liquid or gas mixture. Semipermeable membranes are suitable for producing high-purity water or for separating a specific solute from a solution. Reverse osmosis and forward osmosis are known membrane separation methods that utilize semipermeable membranes.

[0003] In reverse osmosis, the reverse osmosis membrane is exposed to high pressure. Therefore, composite semipermeable membranes are mainly used as reverse osmosis membranes to obtain high strength. A composite semipermeable membrane is composed of a porous support (e.g., nonwoven fabric), a porous polymer layer (e.g., polysulfone layer), and a semipermeable membrane laminated in this order.

[0004] In forward osmosis, water moves from a low-salt feed solution (e.g., freshwater) to a high-salt draw solution (e.g., seawater) driven by the osmotic pressure generated between aqueous solutions of different solute concentrations separated by a forward osmosis membrane. Therefore, forward osmosis does not require the high pressure or membrane strength required to overcome the osmotic pressure required in reverse osmosis. Therefore, forward osmosis is expected to offer advantages such as excellent energy conservation and the ability to simplify the osmosis membrane structure.

[0005] Patent Document 1 discloses a spiral-wound forward osmosis membrane element (hereinafter also referred to as "forward osmosis membrane element"). The spiral-wound forward osmosis membrane element includes a membrane leaf, a central tube, and multiple blocking walls. The membrane leaf has multiple internal flow paths arranged in parallel, each bending from a first opening toward a second opening. The membrane leaf is wrapped around the central tube. The central tube has an inlet at one end and an outlet at the other end. The central tube has a supply hole communicating with the first opening and a recovery hole communicating with the second opening. The multiple blocking walls are provided within the central tube so as to be located between the supply hole and the recovery hole for each of the multiple internal flow paths. Of the multiple blocking walls, a terminal blocking wall closest to the outlet blocks the interior of the central tube, and at least one blocking wall other than the terminal blocking wall has a through-hole formed therein. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-23985 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the thickness of the forward osmosis membrane in the forward osmosis membrane element disclosed in Patent Document 1 is relatively thick, typically about 10 μm. To further improve the permeate amount in a small space, there is a demand for a forward osmosis membrane element that has a high permeation flux and a low salt back diffusion coefficient even when the forward osmosis membrane is thin (for example, thickness: 1.5 μm or less).

[0008] The embodiments of the present disclosure have been made in view of the above, and an object of the present disclosure is to provide a forward osmosis membrane element and a forward osmosis module that have a high permeation flux and a low salt back diffusion coefficient even when the forward osmosis membrane is thin. [Means for solving the problem]

[0009] The means for solving the above problems include the following embodiments. <1> The forward osmosis membrane element of the first embodiment comprises: a plurality of membrane leaves; a tube wrapped with the plurality of membrane leaves; Equipped with the membrane leaf has at least one internal flow path that curves from the first opening to the second opening; The tube at least one first through hole communicating with the first opening; at least one second through hole communicating with the second opening; at least one blocking wall that is disposed between the first through hole and the second through hole for each of the internal flow paths and blocks off an internal space; the membrane leaf has a forward osmosis membrane; The forward osmosis membrane is a polyether ketone polymer layer; a base layer laminated on at least one main surface of the polyether ketone polymer layer; Including, the polyether ketone polymer layer is made of a polyether ketone polymer having a sulfonic acid group or a salt thereof, In the forward osmosis membrane element, the polyether ketone polymer layer has a thickness of 0.1 μm to 5 μm.

[0010] Polyetherketone polymers generally have a low salt back-diffusion coefficient and a low permeation flux. In the first embodiment, the thickness of the polyetherketone polymer layer is 0.1 μm to 5 μm. As a result, the forward osmosis membrane element of the first embodiment has a high permeation flux and a low salt back-diffusion coefficient even though the forward osmosis membrane is thin.

[0011] <2> The forward osmosis membrane element of the second embodiment is The polyether ketone polymer has a structural unit represented by the following formula (A) or a structural unit represented by the following formula (B): <1> 1. The forward osmosis membrane element according to claim 1.

[0012] [ka]

[0013] [In formula (A) and formula (B), R 1 ~R 10 are each independently H, Cl, F, CF3 or C m H 2m+1 (m represents an integer from 1 to 10.) R 1 ~R 10 may be present in two or more aromatic rings. m H 2m+1 If there are two or more C m H 2m+1 may be the same or different. 1 ~A 6 are each independently a direct bond, -CH2-, -C(CH3)2-, -C(CF3)2-, -O-, or -CO-. 1 ~A 3 At least one of X is -CO-. 1 ~X 5 are each independently H, Cl, F, CF3, a sulfonic acid group, or a salt of a sulfonic acid group, and X 1 ~X 5 At least one of X is a sulfonic acid group or a salt of a sulfonic acid group. 1 ~X 5 may be present in two or more in an aromatic ring, and when two or more sulfonic acid groups are present in one aromatic ring, the respective sulfonic acid groups may be the same or different. i, j, k, and l each independently represent 0 or 1.]

[0014] In a polyether ketone polymer comprising structural units represented by formula (A) or (B), the main chain skeleton is formed by aromatic rings, and polar groups (i.e., sulfonic acid groups or salts of sulfonic acid groups) are arranged in side chains. As a result, the forward osmosis membrane element of the second embodiment can form a free-standing membrane even if it is thin.

[0015] <3> The forward osmosis membrane element of the third embodiment is The polyether ketone polymer is a polymer having a structural unit represented by the following formula (AB1) or the following formula (AB2): <2> 1. The forward osmosis membrane element according to claim 1.

[0016] [ka]

[0017] (In formula (AB1), n ​​and m represent a copolymerization ratio on a molar basis, and m / n is 2 / 8 to 8 / 2.) In formula (AB2), p and q represent a copolymerization ratio on a molar basis, and q / p is 2 / 8 to 8 / 2.

[0018] A forward osmosis membrane made of a polymer having a structural unit represented by formula (AB1) or formula (AB2) has a large free volume due to the presence of a methyl group (CH3) and a polar group (i.e., a sulfonic acid group or a salt of a sulfonic acid group) in the side chain, and as a result, the forward osmosis membrane element of the third embodiment can have a high water permeation flux.

[0019] <4> The forward osmosis membrane element of the fourth aspect is The polyether ketone polymer layer is a laminate. <2> or <3> 1. The forward osmosis membrane element according to claim 1.

[0020] The forward osmosis membrane element of the fourth embodiment has a higher permeation flux than the single-layer configuration.

[0021] <5> The forward osmosis membrane element of the fifth aspect is the polyetherketone-based polymer layer includes a first layer and a second layer laminated on at least one main surface of the first layer, the first layer contains a polymer having a structural unit represented by formula (AB1), the second layer contains a polymer having a structural unit represented by formula (AB2), <3> 1. The forward osmosis membrane element according to claim 1.

[0022] In the polymer consisting of structural units represented by formula (AB1) or formula (AB2), the main chain skeleton is formed by aromatic rings, and polar groups (sulfonic acid groups or salts of sulfonic acid groups) are optimally arranged on side chains. As a result, the forward osmosis membrane element of the fifth embodiment has a higher permeation flux than a single-layer configuration.

[0023] <6> The forward osmosis membrane element of the sixth aspect is n in formula (AB1) is 28 mol % to 45 mol %, p in formula (AB2) is 45 mol % to 55 mol %. <5> 1. The forward osmosis membrane element according to claim 1.

[0024] In the sixth embodiment, the proportion of polar groups (i.e., sulfonic acid groups or salts of sulfonic acid groups) in the second layer is higher than the proportion of polar groups in the first layer. This allows the first layer to lower the salt back-diffusion coefficient of the forward osmosis membrane element, and the second layer to increase the permeation flux of the forward osmosis membrane element. As a result, the forward osmosis membrane element of the sixth embodiment can have a higher permeation flux and a lower salt back-diffusion coefficient than a single layer, even with the same thickness.

[0025] <7> The forward osmosis membrane element of the seventh aspect is The substrate layer comprises a nonwoven fabric or a woven fabric. <1> ~ <6> The forward osmosis membrane element according to any one of the above items.

[0026] In the seventh embodiment, the nonwoven fabric or woven fabric functions as a reinforcing material. This makes the polyetherketone polymer layer less susceptible to damage by high water pressure than when the base material layer does not include a nonwoven fabric or woven fabric. As a result, the forward osmosis membrane element of the seventh embodiment is less susceptible to damage when high water pressure is applied.

[0027] <8> The forward osmosis membrane module of the eighth aspect is The aforementioned <1> ~ <7> a forward osmosis membrane element according to any one of the above items; and a pressure vessel in which the forward osmosis membrane element is installed.

[0028] By loading multiple forward osmosis membrane elements into a pressure vessel, it is possible to connect multiple forward osmosis membrane elements. As a result, the forward osmosis membrane module of the eighth embodiment can compensate for the water permeability required for the actual amount of water to be treated by installing multiple elements. [Effects of the Invention]

[0029] According to the embodiments of the present disclosure, a forward osmosis membrane element and a forward osmosis module are provided that have a high permeation flux and a low salt back diffusion coefficient even when the forward osmosis membrane has a thin thickness. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a cross-sectional view of a forward osmosis module according to this embodiment. [Figure 2] FIG. 2 is a perspective view of the laminate before being wound around a tube in this embodiment. [Figure 3] FIG. 3 is a cross-sectional view of a forward osmosis membrane element in this embodiment, in which a laminate is wound around a tube. [Figure 4] FIG. 4 is a diagram showing the flow of liquid in the internal flow channels of the tubes and membrane leaves of this embodiment. [Figure 5] FIG. 5 is a schematic diagram of an apparatus used to evaluate the separation performance of a forward osmosis membrane in the examples. [Figure 6] FIG. 6 is a diagram illustrating a method for manufacturing a forward osmosis membrane element according to an embodiment. [Figure 7] FIG. 7 is a diagram illustrating a method for manufacturing a forward osmosis membrane element according to an embodiment. [Figure 8] FIG. 8 is a diagram illustrating a manufacturing method for a forward osmosis membrane element of the embodiment. [Figure 9] FIG. 9 is a diagram illustrating a manufacturing method for a forward osmosis membrane element of the embodiment. [Figure 10] FIG. 10 is a diagram illustrating a manufacturing method for a forward osmosis membrane element according to an embodiment. [Figure 11] FIG. 11 is a diagram illustrating a manufacturing method for a forward osmosis membrane element according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] In the present disclosure, the symbol "to" indicating a range of values ​​is used to mean that the values ​​before and after it are included as the lower limit and upper limit. In the present disclosure, in the numerical ranges described in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In the present disclosure, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, it means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0032] Hereinafter, a forward osmosis membrane element and a forward osmosis module according to an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0033] (1) Implementation form The forward osmosis module 100 according to this embodiment is cylindrical. As shown in Fig. 1, the forward osmosis module 100 includes a forward osmosis membrane element 1 and a pressure vessel 2. The forward osmosis membrane element 1 is installed in the pressure vessel 2.

[0034] (1.1) Pressure vessel The pressure vessel 2 has a cylindrical body 21, a first lid 22, a second lid 23, a first pipe 24, a second pipe 25, a first sealant 26, and a second sealant 27. The first lid 22 is attached to one axial end of the cylindrical body 21. The second lid 23 is attached to the other axial end of the cylindrical body 21.

[0035] The forward osmosis membrane element 1 includes a tube 3. The tube 3 of the forward osmosis membrane element 1 is attached to the center of each of the first lid 22 and the second lid 23. A first tube 24 is attached to a position offset from the center of the first lid 22. A second tube 25 is attached to a position offset from the center of the second lid 23.

[0036] A first sealant 26 is interposed in the gap between each of the first lid 22 and the second lid 23 and the tube 3 of the forward osmosis membrane element 1. A second sealant 27 is interposed in the gap between the cylindrical body 21 and the tube 3 of the forward osmosis membrane element 1. The first sealant 26 is, for example, an O-ring. The second sealant 27 is, for example, a V-packing.

[0037] The pressure vessel 2 may be any known pressure vessel.

[0038] In this embodiment, the forward osmosis membrane module 100 is supplied with a first fluid to be concentrated and a second fluid to be diluted. The osmotic pressure of the second fluid is higher than that of the first fluid. The tube 3 has an inlet M3A at one end and an outlet M3B at the other end. The first fluid is supplied to the inlet M3A of the tube 3 of the forward osmosis membrane element 1, passes through the interior of the forward osmosis membrane element 1, and flows through the pressure vessel 2. The first fluid is concentrated by passing through the interior of the forward osmosis membrane element 1. The concentrated first fluid is discharged from the outlet M3B. The second fluid is supplied from the second tube 25 to the interior of the pressure vessel 2. The second fluid supplied to the interior of the pressure vessel 2 passes through the forward osmosis membrane element 1, flows toward the first tube 24, and is discharged from the first tube 24. The second fluid is diluted by passing through the forward osmosis membrane element 1. The flow directions of the first fluid and the second fluid are opposite to each other.

[0039] The first fluid and the second fluid are not particularly limited as long as they have different osmotic pressures. For example, the first fluid may be an aqueous solution with a relatively low ion concentration, and the second fluid may be an aqueous solution with a high ion concentration. Examples of the first fluid include ultrapure water, pure water, ion-exchanged water, river water, groundwater (e.g., hard water or soft water), mine drainage, industrial drainage, sewage, tap water, fruit juice, and brewed products (e.g., sake, vinegar, soy sauce, etc.). Examples of the second fluid include seawater, concentrated seawater (i.e., brine), salt lake water, hot spring water, acid water with a pH of 6 or less, alkaline water with a pH of 8 or more, and salt solutions (concentration: 0.5 M or more).

[0040] (1.2) Forward osmosis membrane element The forward osmosis membrane element 1 includes a tube 3 and a laminate 4. The laminate 4 is wound around the tube 3.

[0041] As shown in Fig. 2, the tube 3 is a cylindrical object. The tube 3 has a plurality of through holes H3 formed along the axial direction. The plurality of through holes H3 are arranged to form a first row and a second row. As shown in Fig. 3, the through holes H3 constituting the first row face each other, and the through holes H3 constituting the second row face each other. The material of the tube 3 is not particularly limited, and examples thereof include metal, resin, and ceramics.

[0042] As shown in Fig. 2, the laminate 4 has a configuration in which membrane leaves 40 and outer flow path members 41 are alternately stacked. The membrane leaf 40 is formed by overlapping forward osmosis membranes 42 on both sides of an inner flow path member 43. The membrane leaf 40 is envelope-shaped. As shown in Fig. 3, the membrane leaf 40 is wound around the tube 3. That is, the forward osmosis membrane element 1 is a spiral-type element.

[0043] The inner flow path member 43 is a net. The inner flow path member 43 forms a first fluid flow path P43 (see FIG. 3) for flowing a first fluid between the forward osmosis membranes 42. The outer flow path member 41 is a net. The outer flow path member 41 forms a second fluid flow path P41 (see FIG. 3) for flowing a second fluid between the membrane leaves 40. Examples of materials for the outer flow path member 41 and the inner flow path member 43 include resins. Examples of resins include polyolefins (e.g., polyethylene, polypropylene, etc.), polyester, polyketone, and polyhydric fluorides (e.g., polyvinylidene fluoride, polynaphthalate fluoride, etc.).

[0044] The forward osmosis membrane 42 is a membrane that allows the solvent to pass through but does not allow the solute to pass through. Details of the forward osmosis membrane 42 will be described later.

[0045] As shown in FIG. 2, for example, a single continuous forward osmosis membrane 42 is folded in half, and an outer flow path member 41 is sandwiched between the forward osmosis membranes 42. The membrane leaf 40 is obtained by joining two such formed forward osmosis membranes 42 together at three sides with an inner flow path member 43 sandwiched therebetween. An adhesive is used for this joining. For example, an extended portion of one of the inner flow path members 43 is directly wrapped around the tube 3, and both ends are sealed with an adhesive to form a cylindrical flow path P3 (see FIG. 3) facing the outer peripheral surface of the tube 3. Examples of adhesives include urethane resin, acrylic resin, epoxy resin, and silicone resin. From the viewpoints of adhesive strength, viscosity, drying time, and workability, it is preferable that the adhesive contains a urethane resin.

[0046] The inside of the tube 3 and the inside of the membrane leaf 40 will be described in detail with reference to Figure 4. Figure 4 is a cross-sectional view that schematically shows the flow of liquid inside the tube 3 and inside the membrane leaf 40. For simplicity, only one membrane leaf 40 is shown. As shown in the figure, liquid flows inside the tube 3 and inside the membrane leaf 40 from the inlet M3A to the outlet M3B.

[0047] In the membrane leaf 40, a space is partitioned by a joint region R42A. The joint region R42A is a region where three sides of two forward osmosis membranes 42 are joined together. This forms an internal flow path P42. The joint region R42A is formed with an adhesive. The internal flow path P42 is divided into an upstream side and a downstream side by the joint region R42B. The joint region R42B is a region where the two forward osmosis membranes 42 are joined together. The joint region R42B is formed with an adhesive. The joint region R42A and the joint region R42B form the internal flow path P42 as a flow path bent in a U shape from the first opening P42A to the second opening P42B.

[0048] The joint portion R42A and the joint portion R42B extend toward the outer peripheral surface of the pipe 3 and divide the cylindrical flow path P3, thereby isolating the first opening P42A and the second opening P42B from each other.

[0049] The plurality of through holes H3 includes a plurality of first through holes H3A and a plurality of second through holes H3B. The first through holes H3A communicate with the internal flow path P42 via a first opening P42A and the cylindrical flow path P3. The second through holes H3B communicate with the second opening P42B via the cylindrical flow path P3.

[0050] As shown in Fig. 4, the pipe 3 is provided with a blocking wall 30 that divides the interior of the pipe 3 in the axial direction. The blocking wall 30 is located between the plurality of first through holes H3A and the plurality of second through holes H3B. The blocking wall 30 completely blocks the interior space of the pipe 3. No through holes are formed in the blocking wall 30.

[0051] (1.3) Flow of the first liquid and the second liquid Next, the flow of the first liquid to be concentrated inside the tube 3 and in the internal flow path P42 of the membrane leaf 40 will be described with reference to FIG.

[0052] The arrows in FIG. 4 schematically show the flow of a first liquid through the forward osmosis membrane element 1. The first liquid supplied to the forward osmosis membrane module 1 flows into the inlet M3A of the pipe 3. The first liquid that flows into the inlet M3A passes through the first through-hole H3A and the tubular flow path P3, enters the upstream internal flow path P42 from the first opening P42A, and flows through the internal flow path P42. A second liquid (the liquid to be diluted) supplied from the pipe 25 (see FIG. 1) flows outside the membrane leaf 40. The first liquid and the second liquid flow on both sides of the forward osmosis membrane 42 of the membrane leaf 40. Therefore, a portion of the first liquid flowing through the internal flow path P42 of the membrane leaf 40 moves to the outside of the membrane leaf 40 through the forward osmosis membrane 42 by osmosis. Then, the first liquid that does not move from the internal flow path P42 upstream of the membrane leaf 40 to the outside of the membrane leaf 40 exits the second opening P42B, returns to the inside of the tube 3 via the cylindrical flow path P3 and the second through hole H3B, and flows out from the outlet M3B.

[0053] (1.4) Forward osmosis membrane The forward osmosis membrane 42 includes a polyetherketone-based polymer layer and a substrate layer laminated on at least one main surface of the polyetherketone-based polymer layer.

[0054] The forward osmosis membrane 42 may have a two-layer structure or a three-layer structure. The two-layer forward osmosis membrane 42 includes a polyetherketone-based polymer layer and a base material layer laminated on one main surface of the polyetherketone-based polymer layer. The three-layer forward osmosis membrane 42 includes a SPEK layer and base material layers laminated on both main surfaces of the polyetherketone-based polymer layer.

[0055] The thickness of the polyetherketone polymer layer is 0.1 μm to 5 μm. From the viewpoint of the strength of the forward osmosis membrane 42, the thickness of the polyetherketone polymer layer is preferably 0.3 μm or more, and more preferably 0.5 μm or more. From the viewpoint of water permeability, the thickness of the polyetherketone polymer layer is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 0.7 μm or less. The method for measuring the thickness of the polyetherketone polymer layer is the same as the method described in the Examples.

[0056] The substrate layer preferably contains a nonwoven fabric or a woven fabric. The nonwoven fabric or the woven fabric functions as a reinforcing material. This makes the polyether ketone polymer layer less susceptible to damage by high water pressure than when the substrate layer does not contain a nonwoven fabric or a woven fabric. As a result, the forward osmosis membrane element 1 is less susceptible to damage when high water pressure is applied.

[0057] The material of the nonwoven fabric and woven fabric is not particularly limited as long as it is a resin. Examples of resins include polyolefins (e.g., polyethylene, polypropylene, etc.), polyester, polyketone, and polyhydric fluorides (e.g., polyvinylidene fluoride, polynaphthalate fluoride, etc.). The nonwoven fabric preferably contains polyester.

[0058] The polyether ketone polymer layer is made of a polyether ketone polymer having a sulfonic acid group or a salt thereof.

[0059] The term "polyether ketone polymer" refers to a polymer containing an ether bond (-O-) and a ketone bond (-CO-) in the constituent repeating unit. The term "salt of a sulfonic acid group" refers to a salt compound in which the hydrogen atom of the sulfonic acid group is replaced with a salt. The salt is not particularly limited, and examples thereof include salts of Group 1 elements (e.g., lithium, sodium, potassium, etc.), Group 2 elements (e.g., calcium, magnesium, barium, etc.), and ammonium salts.

[0060] The polyetherketone polymer may be a copolymer, such as a block copolymer, a random copolymer, an alternating copolymer, or a graft copolymer.

[0061] The polyether ketone polymer preferably has a structural unit represented by the following formula (A) (hereinafter also referred to as "structural unit (A)") or a structural unit represented by the following formula (B) (hereinafter also referred to as "structural unit (B)").

[0062] [ka]

[0063] In formula (A) and formula (B), R 1 ~R 10 are each independently H, Cl, F, CF3 or C m H 2m+1 (m represents an integer from 1 to 10.) R 1 ~R 10 may be present in two or more aromatic rings. m H 2m+1 If there are two or more C m H 2m+1 may be the same or different. 1 ~A 6 are each independently a direct bond, -CH2-, -C(CH3)2-, -C(CF3)2-, -O-, or -CO-. 1 ~A 3 At least one of X is -CO-. 1 ~X 5 are each independently H, Cl, F, CF3, a sulfonic acid group, or a salt of a sulfonic acid group, and X 1 ~X 5 At least one of X is a sulfonic acid group or a salt of a sulfonic acid group. 1 ~X 5 may be present in two or more in an aromatic ring, and when two or more sulfonic acid groups are present in one aromatic ring, the respective sulfonic acid groups may be the same or different. i, j, k, and l each independently represent 0 or 1.

[0064] The polyetherketone polymer has the structural unit (A) or the structural unit (B), and in the polyetherketone polymer composed of the structural unit (A) or the structural unit (B), the main chain skeleton is formed by aromatic rings, and polar groups (i.e., sulfonic acid groups or sulfonic acid groups) are arranged in side chains. As a result, the forward osmosis membrane element 1 can form a free-standing membrane even if it is thin.

[0065] The content of sulfonic acid groups or salts of sulfonic acid groups in the polyether ketone polymer is preferably 8 mol% to 70 mol%, more preferably 10 mol% to 50 mol%, and even more preferably 25 mol% to 30 mol%, based on all structural units contained in the polyether ketone polymer.

[0066] The structural unit (A) may be a structural unit (A-1) represented by the following formula (A-1), a structural unit (A-2) represented by the following formula (A-2), or a structural unit (A-3) represented by the following formula (A-3).

[0067] [ka]

[0068] The structural unit (B) may be a structural unit (B-1) represented by the following formula (B-1), a structural unit (B-2) represented by the following formula (B-2), or a structural unit (B-3) represented by the following formula (B-3).

[0069] [ka]

[0070] The polyether ketone polymer layer preferably contains a polymer having a structural unit represented by the following formula (AB1) (hereinafter also referred to as "polymer (AB1)") or a polymer having a structural unit represented by the following formula (AB2) (hereinafter also referred to as "polymer (AB2)").

[0071] [ka]

[0072] In formula (AB1), n ​​and m represent a copolymerization ratio on a molar basis, and m / n is 2 / 8 to 8 / 2. m is represented by the following formula (i). n is represented by the following formula (ii). In formula (AB2), p and q represent a copolymerization ratio on a molar basis, and q / p is 2 / 8 to 8 / 2. p is represented by the following formula (iii). q is represented by the following formula (iv). Formula (i) :n(mol%)=(n / (m+n))×100 Formula (ii) :m(mol%)=(m / (m+n))×100 Formula (iii): p(mol%)=(p / (p+q))×100 Formula (iv): q (mol%) = (q / (p+q)) × 100

[0073] The polyetherketone polymer layer contains polymer (AB1) or polymer (AB2), and the free volume is increased due to the presence of methyl groups (CH3) and polar groups (i.e., sulfonic acid groups or salts of sulfonic acid groups) in the side chains, resulting in a high water permeation flux through the forward osmosis membrane element 1.

[0074] The polyetherketone-based polymer layer may have a single-layer structure or a laminate structure of at least two layers (i.e., a laminate). From the viewpoint of economic efficiency, the polyetherketone-based polymer layer is preferably a single-layer structure or a two-layer structure.

[0075] The polyether ketone polymer layer is preferably a laminate, which allows the forward osmosis membrane element 1 to have a higher permeation flux than a single-layer structure.

[0076] The polyetherketone-based polymer layer preferably includes a first layer and a second layer laminated on at least one main surface of the first layer. The first layer includes a polymer having a structural unit represented by formula (AB1). The second layer includes a polymer having a structural unit represented by formula (AB2). In a polymer composed of structural units represented by formula (AB1) or formula (AB2), the main chain skeleton is formed by aromatic rings, and polar groups (sulfonic acid groups or salts of sulfonic acid groups) are optimally arranged on side chains. As a result, the forward osmosis membrane element 1 has a higher permeation flux than a single-layer configuration.

[0077] The first layer may be made of a polymer having a structural unit represented by formula (AB1), and the second layer may be made of a polymer having a structural unit represented by formula (AB2).

[0078] When the polyether ketone-based polymer layer includes a first layer and a second layer, n in formula (AB1) is preferably 28 mol% to 45 mol%, and p in formula (AB2) is preferably 45 mol% to 55 mol%. This results in a higher proportion of polar groups (i.e., sulfonic acid groups or salts of sulfonic acid groups) in the second layer than in the first layer. This allows the first layer to reduce the salt back-diffusion coefficient of the forward osmosis membrane element 1, and the second layer to increase the permeation flux of the forward osmosis membrane element 1. As a result, the forward osmosis membrane element 1 can have a higher permeation flux and a lower salt back-diffusion coefficient for the same thickness compared to a single layer.

[0079] (1.5) Action and Effect As described with reference to FIGS. 1 to 4, the forward osmosis membrane element 1 includes multiple membrane leaves 40 and a tube 3. The membrane leaf 40 has an internal flow path P42 that bends from a first opening P42A toward a second opening P42B. The tube 3 has multiple first through-holes H3A, multiple second through-holes H3B, and a blocking wall 30. The membrane leaf 40 has a forward osmosis membrane 42. The forward osmosis membrane 42 includes a polyetherketone-based polymer layer and a substrate layer. The polyetherketone-based polymer layer is made of a polyetherketone-based polymer having a sulfonic acid group or a salt thereof. The polyetherketone-based polymer layer has a thickness of 0.01 μm to 5 μm. As a result, the forward osmosis membrane element 1 has a high permeation flux and a low salt back diffusion coefficient even when the forward osmosis membrane is thin.

[0080] As described with reference to FIGS. 1 to 4, the forward osmosis membrane module 100 includes a forward osmosis membrane element 1 and a pressure vessel 2 in which the forward osmosis membrane element 1 is installed. This allows multiple forward osmosis membrane elements to be connected by loading the forward osmosis membrane module 100 into a pressure vessel, and as a result, the forward osmosis membrane module 100 can compensate for the water permeability required for the actual amount of treated water by installing multiple modules.

[0081] (2) Variations In this embodiment, the membrane leaf 40 has one internal flow path P42, but the present disclosure is not limited thereto. The membrane leaf 40 may have multiple internal flow paths P42. In this case, the tube 3 has multiple blocking walls 30, one for each internal flow path P42. In this embodiment, the number of each of the first through holes H3A and the second through holes H3B is plural, but the present disclosure is not limited to this. The number of at least one of the first through holes H3A and the second through holes H3B may be one. In this embodiment, the number of the blocking wall 30 is one, but the present disclosure is not limited to this. The number of the blocking wall 30 may be plural. In this embodiment, the substrate layer 43 is laminated on one main surface of the forward osmosis membrane 42, but the present disclosure is not limited to this. The substrate layer 43 may be laminated on both main surfaces of the forward osmosis membrane 42. In this embodiment, one inner flow path member 43 is interposed between adjacent forward osmosis membranes 42, but the present disclosure is not limited to this. Multiple inner flow path members 43 may be interposed between adjacent forward osmosis membranes 42. In this embodiment, the flow direction of the first fluid and the flow direction of the second fluid are opposite to each other, but the present disclosure is not limited to this. The flow direction of the first fluid and the flow direction of the second fluid may be the same. [Example]

[0082] The present disclosure will be explained in more detail below based on examples, but the present disclosure is not limited to these examples in any way.

[0083] [1] Abbreviation The abbreviations used in this example are as follows:

[0084] [1.1] Solvent DMSO: dimethyl sulfoxide NMP: N-methyl-2-pyrrolidone DMF: N,N-dimethylformamide

[0085] [1.2] Aromatic polyether components DFBP: 4,4'-difluorobenzophenone DSDFBP: 5,5'-carbonylbis(sodium 2-fluorobenzenesulfonate) BPA: 4,4'-(2,2-propanediyl)diphenol TMBPF: 3,3',5,5'-tetramethyl-4,4'-dihydroxydiphenylmethane

[0086] [2]Measurement method [2.1] Film thickness measurement method Measurements were carried out using a Nikon Digimicro MH-15M device (contact film thickness measurement device: minimum reading: 0.01 μm) using the following method. After the varnish was applied to the substrate and dried (i.e., at the stage of the "substrate / coated film" laminate), a portion was cut out as a sample for thickness measurement. The thickness of the sample for measurement (hereinafter referred to as "thickness A") was measured using the above device. Next, the film at the measurement location was peeled off from the substrate, and the thickness of the substrate at that location (hereinafter also referred to as "thickness B") was measured. From the above results, the film thickness was calculated using the following formula (1). Formula (1): Film thickness = Thickness A - Thickness B Measurements were taken at five or more locations, and the average value was taken as the membrane thickness. In the case of a semipermeable membrane with a laminated structure of two or more layers, the above procedure was repeated for each layer. The membrane thickness of each layer was determined from the difference between the respective measured values.

[0087] [2.2] Water flux (Jw) and salt back diffusion coefficient (SRSF) An apparatus 500 shown in FIG. 5 was prepared. The apparatus 500 included a feed solution tank 501, a flow path 502, a pump 503, a draw solution tank 511, a flow path 512, a pump 513, and a forward osmosis membrane element container 521. The feed solution tank 501 was placed on a balance 504. The draw solution tank 511 was equipped with an electrical conductivity meter 515. At the start of the evaluation, the feed solution tank 501 contained 5,000 g of Milli-Q water as a feed solution FS (Feed Solution). The electrical conductivity of Milli-Q water was 50 μS / cm or less. The draw solution tank 511 contained 10,000 g of an aqueous ammonium sulfate solution (molarity: 0.6 mol / L) as a draw solution DS (Draw Solution). The feed solution in the feed solution tank 501 was pumped through the flow path 502 at a rate of 0.6 L / min by the use of a pump 503. The draw solution in the draw solution tank 511 flows through a flow path 512 at a rate of 0.6 L / min using a pump 513. The feed solution flowing through the flow path 502 and the draw solution flowing through the flow path 512 are in contact with each other through a forward osmosis membrane element 522 inside a forward osmosis membrane element container 521. The effective membrane area of ​​the forward osmosis membrane element 522 is 0.3 m 2 A portion of the feed solution moves to the draw solution through the forward osmosis membrane element 522. A portion of the salt (ammonium sulfate) in the draw solution moves (backflows) to the feed solution through the forward osmosis membrane element 522. The forward osmosis membrane elements of Examples 1 to 5 were used as the forward osmosis membrane element 522.

[0088] [2.2.1] Water permeation flux (Jw) The weight loss of the feed solution was measured every minute using the balance 504, and the weight loss per unit time per unit area of ​​the forward osmosis membrane was calculated as the water permeation flux (L / (m 2 The allowable water permeation flux (Jw) was 15.0 (L / (m 2 ·h)) is the above.

[0089] [2.2.2] Salt Reverse Diffusion Coefficient (SRSF) The change in the electrical conductivity of the draw solution was measured every minute using the electrical conductivity meter 515, and this was converted into the change in weight of the draw solution. The change in weight per unit time and per unit area of ​​the forward osmosis membrane was calculated as the salt permeation rate (g / (m 2 The SRSF (g / L) was calculated by dividing this value by the water permeation flux (Jw). An acceptable salt back diffusion coefficient (SRSF) is 0.10 (g / L) or less.

[0090] [3] Preparation [3.1] Resin [3.1.1] Synthesis Example 1 A five-neck reactor equipped with a nitrogen inlet tube, thermometer, reflux condenser, and stirrer was prepared. Raw material (AB1-1) was weighed into the five-neck reactor. Raw material (AB1-1) consisted of 40.2 g (0.095 mol) of DSDFBP, 62.2 g (0.285 mol) of DFBP, 86.8 g (0.380 mol) of BPA, and 65.7 g (0.475 mol) of potassium carbonate. 756.2 g of DMSO and 302.1 g of toluene were mixed to obtain solvent (AB1-1). Solvent (AB1-1) was added to raw material (AB1-1), stirred under a nitrogen atmosphere, and heated at 130°C for 12 hours. The resulting water was removed from the system, and the toluene was then distilled off.

[0091] The reaction was continued for 12 hours at 160°C to obtain a viscous polymer solution. The resulting solution was diluted with 570g of toluene and then poured into 2400g of methanol. The precipitated polymer powder was filtered, washed, and then dried at 150°C for 4 hours to obtain 160.6g of polyether ketone powder (hereinafter also referred to as "resin (AB1-1)").

[0092] Resin (AB1-1) had a structural unit represented by the following formula (AB1): n in formula (AB1) of resin (AB1-1) was 25 mol %.

[0093] [ka]

[0094] [3.1.2] Synthesis Example 2 Except for changing the raw material (AB1-1) to the raw material (AB1-2) and changing the solvent (AB1-1) to the solvent (AB1-2), the same procedure as in Synthesis Example 1 was carried out to obtain 160.2 g of polymer powder (hereinafter also referred to as "resin (AB1-2)"). The raw material (AB1-2) consisted of 48.1 g (0.114 mol) of DSDFBP, 58.0 g (0.265 mol) of DFBP, 86.8 g (0.380 mol) of BPA, and 65.7 g (0.475 mol) of potassium carbonate. The solvent (AB1-2) consisted of 756.2 g of DMSO and 302.1 g of toluene.

[0095] Resin (AB1-2) had a structural unit represented by the above formula (AB1). n in formula (AB1) of resin (AB1-2) was 30 mol %.

[0096] [3.1.3] Synthesis Example 3 Except for changing the raw material (AB1-1) to the raw material (AB1-3) and changing the solvent (AB1-1) to the solvent (AB1-3), the same procedure as in Synthesis Example 1 was carried out to obtain 159.8 g of polymer powder (hereinafter also referred to as "resin (AB1-3)"). The raw material (AB1-3) consists of 64.2 g (0.152 mol) of DSDFBP, 49.8 g (0.228 mol) of DFBP, 86.8 g (0.380 mol) of BPA, and 65.7 g (0.475 mol) of potassium carbonate. The solvent (AB1-3) consisted of 756.2 g of DMSO and 302.1 g of toluene.

[0097] Resin (AB1-3) had a structural unit represented by the above formula (AB1). n in formula (AB1) of resin (AB1-3) was 40 mol %.

[0098] [3.1.4] Synthesis Example 4 A five-neck reactor equipped with a nitrogen inlet tube, thermometer, reflux condenser, and stirrer was prepared. Raw material (AB2-1) was weighed into the five-neck reactor. Raw material (AB2-1) consisted of 40.1 g (0.095 mol) of DSDFBP, 62.2 g (0.285 mol) of DFBP, 97.4 g (0.380 mol) of TMBPF, and 65.7 g (0.475 mol) of potassium carbonate. DSDFBP was obtained by the method described in Synthesis Example 1 of JP 2014-533 A. Solvent (AB2-1) was obtained by mixing 783.4 g of DMSO and 261.1 g of toluene. Solvent (AB2-1) was added to raw material (AB2-1), stirred under a nitrogen atmosphere, and heated at 130°C for 12 hours. The resulting water was removed from the system, and the toluene was then distilled off.

[0099] The reaction was continued for 12 hours at 160°C to obtain a viscous polymer solution. The resulting solution was diluted with 570g of toluene and then poured into 2400g of methanol. The precipitated polymer powder was filtered, washed, and dried at 150°C for 4 hours to obtain 171.6g (yield 95%) of polyether ketone powder (hereinafter also referred to as "resin (AB2-1)").

[0100] Resin (AB2-1) had a structural unit represented by the following formula (AB2): p in formula (AB2) of resin (AB2-1) was 25 mol %.

[0101] [ka]

[0102] [3.1.5] Synthesis Example 5 A polymer powder (174.6 g, hereinafter also referred to as "resin (AB2-2)") was obtained in the same manner as in Synthesis Example 4, except that raw material (AB2-1) was changed to raw material (AB2-2) and solvent (AB2-1) was changed to solvent (AB2-2). The raw material (AB2-2) consists of 80.2 g (0.190 mol) of DSDFBP, 41.5 g (0.190 mol) of DFBP, 97.4 g (0.380 mol) of TMBPF, and 65.7 g (0.475 mol) of potassium carbonate. The solvent (AB2-2) consisted of 876.4 g of DMSO and 292.1 g of toluene.

[0103] Resin (AB2-2) had a structural unit represented by the above formula (AB2). p in formula (AB2) of resin (AB2-2) was 50 mol %.

[0104] [3.1.6] Synthesis Example 6 Except for changing the raw material (AB2-1) to the raw material (AB2-3) and changing the solvent (AB2-1) to the solvent (AB2-3), the same procedure as in Synthesis Example 4 was carried out to obtain 173.6 g of polymer powder (hereinafter also referred to as "resin AB2-3"). The raw material (AB2-3) consists of 96.3 g (0.228 mol) of DSDFBP, 33.2 g (0.152 mol) of DFBP, 97.4 g (0.380 mol) of TMBPF, and 65.7 g (0.475 mol) of potassium carbonate. The solvent (AB2-3) consisted of 907.5 g of DMSO and 302.5 g of toluene.

[0105] Resin (AB2-3) had a structural unit represented by the above formula (AB2). p in formula (AB2) of resin (AB2-3) was 60 mol %.

[0106] The contents of structural units containing sulfonic acid groups (hereinafter also referred to as "sulfonic acid units") in the synthesized resins (AB1-1) to (AB2-3) are shown in Table 1. The sulfonic acid unit contents in the resins (AB1-1) to (AB1-3) refer to n in formula (AB1). The sulfonic acid unit contents in the resins (AB2-1) to (AB2-3) refer to p in formula (AB2).

[0107] [Table 1]

[0108] [3.2] Polyether ketone polymer layer [3.2.1] SPEK membrane 1 A varnish was prepared by dissolving the resin (AB1-3) produced in Synthesis Example 3 in a mixed solvent. The mixed solvent consisted of DMF and toluene. This varnish was cast onto a release PET (polyethylene terephthalate) substrate so that the dry film thickness would be 1 μm or less, and dried at 110°C for 3 minutes. This was peeled off from the PET substrate to obtain SPEK film 1 (i.e., a polyether ketone polymer layer). SPEK film 1 consisted of a resin (AB1-3) film. The dry film thickness of SPEK film 1 was 1.0 μm.

[0109] [3.2.2] SPEK membrane 2 The resin (AB1-1) produced in Synthesis Example 1 was dissolved in a mixed solvent to prepare a varnish. The mixed solvent consisted of DMF and toluene. This varnish was cast onto a release PET substrate and dried at 110°C for 3 minutes to obtain a resin (AB1-1) film. Thereafter, the resin (AB2-2) produced in Synthesis Example 5 was dissolved in a methyl cellosolve solvent to prepare a varnish. This varnish was cast onto the resin (AB1-1) film and dried at 160°C for 3 minutes to form a resin (AB2-2) film. This was peeled off from the PET substrate to obtain a SPEK film 2 (i.e., a polyether ketone polymer layer). The SPEK film 2 was formed by laminating a resin (AB1-1) film and a resin (AB2-2) film in this order. The dry film thickness of the SPEK film 2 was 1 μm or less. The thickness of the resin (AB1-1) film was 0.05 μm. The thickness of the resin (AB2-2) film was 0.5 μm.

[0110] [3.2.3] SPEK membrane 3 The resin (AB1-1) produced in Synthesis Example 1 was dissolved in a mixed solvent to prepare a varnish. The mixed solvent consisted of DMF and toluene. This varnish was cast onto the release PET substrate and dried at 110°C for 3 minutes to obtain a resin (AB1-1) film. Thereafter, the resin (AB2-3) produced in Synthesis Example 6 was dissolved in a methyl cellosolve solvent to prepare a varnish. This varnish was cast onto the resin (AB1-1) film and dried at 160°C for 3 minutes to form a resin (AB2-3) film. This was peeled off from the PET substrate to obtain a SPEK film 3 (i.e., a polyether ketone polymer layer). The SPEK film 3 was formed by laminating a resin (AB1-1) film and a resin (AB2-3) film in this order. The dry film thickness of the SPEK film 3 was 1 μm or less. The thickness of the resin (AB1-1) film was 0.05 μm. The thickness of the resin (AB2-3) film was 0.5 μm.

[0111] [3.2.4] SPEK membrane 4 The resin (AB1-2) produced in Synthesis Example 2 was dissolved in a mixed solvent to prepare a varnish. The mixed solvent consisted of DMF and toluene. This varnish was cast onto the release PET substrate and dried at 110°C for 3 minutes to obtain a resin (AB1-2) film. Thereafter, the resin (AB2-2) produced in Synthesis Example 5 was dissolved in a methyl cellosolve solvent to prepare a varnish. This varnish was cast onto the resin (AB1-2) film and dried at 160°C for 3 minutes to form a resin (AB2-2) film. This was peeled off from the PET substrate to obtain a SPEK film 4 (i.e., a polyether ketone polymer layer). The SPEK film 4 was formed by laminating a resin (AB1-2) film and a resin (AB2-2) film in this order. The dry film thickness of the SPEK film 4 was 1 μm or less. The thickness of the resin (AB1-2) film was 0.05 μm. The thickness of the resin (AB2-2) film was 0.5 μm.

[0112] [3.2.5] SPEK membrane 5 The resin (AB2-1) produced in Synthesis Example 4 was dissolved in a mixed solvent to prepare a varnish. The mixed solvent consisted of DMF and toluene. This varnish was cast onto the release PET substrate and dried at 110°C for 3 minutes to obtain a resin (AB2-1) film. Thereafter, the resin (AB2-2) produced in Synthesis Example 5 was dissolved in a methyl cellosolve solvent to prepare a varnish. This varnish was cast onto the resin (AB2-1) film and dried at 160°C for 3 minutes to form a resin (AB2-2) film. This was peeled off from the PET substrate to obtain a SPEK film 5 (i.e., a polyether ketone polymer layer). The SPEK film 5 was formed by laminating a resin (AB2-1) film and a resin (AB2-2) film in this order. The dry film thickness of the SPEK film 5 was 1 μm or less. The thickness of the resin (AB2-1) film was 0.05 μm. The thickness of the resin (AB2-2) film was 0.5 μm.

[0113] [Table 2]

[0114] [4] Examples and Comparative Examples [4.1] Example 1 [4.1.1] How to make a forward osmosis membrane A nonwoven fabric was prepared as the base material layer 422. As shown in Fig. 6, both main surfaces of the SPEK membrane 1 (polyether ketone polymer layer 421) were sandwiched between two base material layers 422 to produce a forward osmosis membrane 42.

[0115] A resin net having a mesh structure that does not impede water permeability was prepared as the outer flow path member 41. As shown in Fig. 7, the outer flow path member 41 was placed on the forward osmosis membrane 42. The size of the outer flow path member 41 was approximately half the size of the forward osmosis membrane 42. As shown in Fig. 8, the forward osmosis membrane 42 was folded in half, thereby sandwiching the outer flow path member 41 between the forward osmosis membrane 42, thereby obtaining a stack 400.

[0116] A tube 3 was prepared for wrapping the forward osmosis membrane 42. The tube 3 has a cylindrical structure. The tube 3 has a blocking wall 30 inside at the center in the axial direction. The tube 3 has a plurality of through holes H3 along the axial direction. The plurality of through holes H3 includes a plurality of first through holes H3A and a plurality of second through holes H3B. The plurality of first through holes H3A are located on the inlet M3A side of the blocking wall 30 in the axial direction. The plurality of second through holes H3B are located on the outlet M3B side of the blocking wall 30 in the axial direction.

[0117] [4.1.2] Preparation for forward osmosis membrane element Both axial ends of the pipe 3 were fixed to a fixed shaft. A resin net having a mesh structure that did not impede water permeability was prepared as the inner flow path member 43. The inner flow path member 43 was unwound from its roll shape and the ends were fixed with adhesive tape, and the inner flow path member 43 was lightly pulled in the unwinding direction, so that the inner flow path member 43 was in a state of being under tension.

[0118] [4.1.3] Fabrication of forward osmosis membrane element The stack 400 was placed on the inner flow path member 43 fixed to the pipe 3 (FIG. 9). Next, an adhesive was used to apply adhesive to the three edges and the center of the stack 400, as shown in FIG. 10. This formed an adhesive layer R42AU that would become the bonding site R42A and an adhesive layer R42BU that would become the bonding site R42B. Two inner flow path members 43 of the same size as the laminate 400 were placed on the laminate 400 with the adhesive applied. In addition, adhesive was used to apply adhesive to three sides at the end and the center of the inner flow path member 43, similar to the adhesive layers R42AU and R42BU.

[0119] Subsequently, the second stack 400 was placed at a position shifted by a predetermined distance (the distance obtained by dividing the circumference of the pipe 3 by the number of stacks 400). Thereafter, the lamination work was continued in the same manner in the order of the inner flow path member 43 and the stack 400, and the stack was layered as shown in FIG.

[0120] After the stacking was completed, the stacked body 400 and the inner flow path member 43 were wound around the tube 3 as a rotation axis under tension, thereby producing a forward osmosis membrane element as shown in Figures 1 to 4.

[0121] [4.2] Example 2 A forward osmosis membrane element as shown in FIGS. 1 to 4 was produced in the same manner as in Example 1, except that SPEK membrane 1 was changed to SPEK membrane 2.

[0122] [4.3] Example 3 A forward osmosis membrane element as shown in FIGS. 1 to 4 was produced in the same manner as in Example 1, except that SPEK membrane 1 was changed to SPEK membrane 2.

[0123] [4.4] Example 4 A forward osmosis membrane element as shown in FIGS. 1 to 4 was produced in the same manner as in Example 1, except that the SPEK membrane 1 was changed to the SPEK membrane 4.

[0124] [4.5] Example 5 A forward osmosis membrane element as shown in FIGS. 1 to 4 was produced in the same manner as in Example 1, except that the SPEK membrane 1 was changed to the SPEK membrane 5.

[0125] The water permeability of the forward osmosis membrane elements 1 of Examples 1 to 5 was evaluated using the device shown in Figure 5. The results are shown in Table 3.

[0126] [Table 3]

[0127] The thickness of the SPEK layer in Examples 1 to 5 was in the range of 0.1 μm to 5 μm. As a result, the water permeation flux (Jw) of the SPEK layer in Examples 1 to 5 was 15.0 (L / (m 2·h) or more. The salt back diffusion coefficients (SRSF) of the SPEK layers in Examples 1 to 5 were 0.10 (g / L) or less. These results demonstrate that the forward osmosis membrane elements 1 in Examples 1 to 5 are "forward osmosis membrane elements having a high permeation flux and a low salt back diffusion coefficient even when the forward osmosis membrane is thin."

Claims

1. a plurality of membrane leaves; a tube wrapped with the plurality of membrane leaves; Equipped with the membrane leaf has at least one internal flow path that curves from the first opening to the second opening; The tube at least one first through hole communicating with the first opening; at least one second through hole communicating with the second opening; at least one blocking wall that is disposed between the first through hole and the second through hole for each of the internal flow paths and blocks off an internal space; the membrane leaf has a forward osmosis membrane; The forward osmosis membrane is a polyether ketone polymer layer; a base layer laminated on at least one main surface of the polyether ketone polymer layer; Including, the polyether ketone polymer layer is made of a polyether ketone polymer having a sulfonic acid group or a salt thereof, A forward osmosis membrane element, wherein the polyether ketone polymer layer has a thickness of 0.1 μm to 5 μm.

2. The forward osmosis membrane element according to claim 1 , wherein the polyether ketone polymer has a structural unit represented by the following formula (A) or a structural unit represented by the following formula (B): 【Chemical 1】 [In formula (A) and formula (B), R １ ~R １０ are each independently H, Cl, F, or CF ３ or C ｍ H ２ｍ＋１ (m represents an integer of 1 to 10). １ ~R １０ may be present in two or more aromatic rings. ｍ H ２ｍ＋１ If there are two or more C ｍ H ２ｍ＋１ may be the same or different. １ ~A ６ are each independently a direct bond, —CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -O- or -CO-. １ ~A ３ At least one of X is —CO—. １ ~X ５ are each independently H, Cl, F, or CF ３ , a sulfonic acid group or a salt of a sulfonic acid group, and X １ ~X ５ At least one of X is a sulfonic acid group or a salt of a sulfonic acid group. １ ~X ５ may be present in two or more in an aromatic ring, and when two or more sulfonic acid groups are present in one aromatic ring, the respective sulfonic acid groups may be the same or different. i, j, k, and l each independently represent 0 or 1.]

3. The forward osmosis membrane element according to claim 2 , wherein the polyether ketone polymer is a polymer having a structural unit represented by the following formula (AB1) or the following formula (AB2): 【Chemistry 2】 (In formula (AB1), n ​​and m represent a copolymerization ratio on a molar basis, and m / n is 2 / 8 to 8 / 2. In formula (AB2), p and q represent a copolymerization ratio on a molar basis, and q / p is 2 / 8 to 8 / 2.

4. The forward osmosis membrane element according to claim 2 or 3, wherein the polyether ketone polymer layer is a laminate.

5. the polyetherketone-based polymer layer includes a first layer and a second layer laminated on at least one main surface of the first layer, the first layer contains a polymer having a structural unit represented by formula (AB1), The forward osmosis membrane element according to claim 3 , wherein the second layer comprises a polymer having a structural unit represented by formula (AB2):

6. n in formula (AB1) is 28 mol % to 45 mol %, The forward osmosis membrane element according to claim 5, wherein p in formula (AB2) is 45 mol % to 55 mol %.

7. The forward osmosis membrane element according to claim 1 , wherein the substrate layer comprises a nonwoven fabric or a woven fabric.

8. A forward osmosis membrane module comprising: the forward osmosis membrane element according to any one of claims 1 to 7; and a pressure vessel in which the forward osmosis membrane element is installed.

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