Separation membrane and method of manufacturing separation membrane, and separation method

Abstract

To provide a separation membrane capable of improving water permeability by irradiating a light-responsive cross-linked polyamide with ultraviolet light.SOLUTION: A separation membrane comprises a porous support and a separation functional layer including cross-linked polyamide, and the cross-linked polyamide is light-responsive. The cross-linked polyamide of the separation membrane has an azobenzene skeleton. A method of manufacturing the separation membrane includes the processes of: obtaining a mixed liquid including water and an amine component; and causing polymerization reaction on the amine component in the mixed liquid sticking on the porous support after bringing the mixed liquid into contact with the porous support so as to obtain the separation membrane. The amine component includes the azobenzene skeleton and light-responsive molecules having an amino group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a separation membrane, a method for producing a separation membrane, and a separation method. [Background technology]

[0002] With advances in water treatment technology, separation membranes, such as reverse osmosis and nanofiltration (NF) membranes (hereafter referred to as "NF membranes"), are playing important roles in a wide range of fields, including seawater desalination, industrial water purification, and food applications. NF membranes, among others, have a separation mechanism similar to that of reverse osmosis membranes, but their relatively loose membrane structure allows for high permeation flux at lower operating pressures. They are particularly effective at removing divalent ions, such as sulfate ions, as well as hardness and scale components. NF membranes are typically made of cross-linked polyamides produced by interfacial polymerization, and consist of a porous support and a separation functional layer made of cross-linked polyamide.

[0003] The development of NF membranes is actively underway. For example, in Patent Document 1, a cross-linked polyamide is produced using a mixture of two specific types of polyfunctional amine compounds. This allows the SO4 2- , Mg 2+ , Ca 2+ However, there is still room for improvement in terms of permeability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-277298 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above circumstances, and its main object is to provide a separation membrane such as an NF membrane whose water permeability can be improved by producing a photoresponsive crosslinked polyamide and irradiating it with ultraviolet light. [Means for solving the problem]

[0006] The separation membrane of the first invention is a separation membrane comprising a porous support and a separation functional layer containing a crosslinked polyamide, wherein the crosslinked polyamide has photoresponsiveness. The separation membrane of the second invention is characterized in that, in the invention described in claim 1, the crosslinked polyamide has an azobenzene skeleton. The separation membrane of the third invention is the invention described in claim 2, characterized in that the azobenzene skeleton has a trans structure. A method for producing a separation membrane according to a fourth aspect of the present invention includes the steps of obtaining a mixed solution containing water and an amine component, bringing the mixed solution into contact with a porous support, and then polymerizing the amine component in the mixed solution that has adhered to the porous support to obtain a separation membrane, wherein the amine component contains a photoresponsive molecule having an azobenzene skeleton and an amino group. The method for producing a separation membrane of the fifth invention is characterized in that, in the invention described in claim 4, it includes a step of heating the mixed liquid after the step of obtaining the mixed liquid and before the step of obtaining the separation membrane by the polymerization reaction. The method for producing a separation membrane of the sixth invention is characterized in that, in the invention described in claim 4 or 5, the mass ratio of the amine component containing the photoresponsive molecule to the total weight of the amine components is 5 mass% or more and 80 mass% or less. The separation method of the seventh invention is characterized by including a step of supplying a material to be treated to a separation membrane described in any one of claims 1 to 3, irradiating the separation membrane with ultraviolet light, and then separating highly permeable substances in the material to be treated from other substances by allowing them to pass through. [Effects of the Invention]

[0007] According to the first aspect of the present invention, the separation membrane contains a photoresponsive crosslinked polyamide, and thus, by irradiating the crosslinked polyamide with ultraviolet light, a change in free volume is imparted to the crosslinked polyamide, thereby increasing the water permeability of the separation membrane. According to the second invention, the crosslinked polyamide can be endowed with photoresponsiveness by virtue of having an azobenzene skeleton. According to the third invention, the azobenzene skeleton of the crosslinked polyamide has a trans structure, and can be converted to a cis structure by irradiation with ultraviolet light. According to the fourth invention, a mixture containing water and an amine component of a photoresponsive molecule having an azobenzene skeleton and an amino group can be obtained, and a separation membrane containing a crosslinked polyamide having an azobenzene skeleton can be produced by a polymerization reaction. According to the fifth invention, a step of heating the mixed solution before the polymerization reaction is included, so that the amine component consisting of the photoresponsive molecule having an azobenzene skeleton has a trans structure and can undergo the polymerization reaction while maintaining that structure. According to the sixth invention, since the mass ratio of the amine component containing the photoresponsive molecule is 5 mass% or more and 80 mass% or less, the crosslinked polyamide undergoes a change in free volume upon irradiation with light, thereby improving the water permeability without reducing the salt rejection ability of the separation membrane. According to the seventh invention, the separation membrane according to the first to third inventions is irradiated with ultraviolet light to cause a change in free volume, and then highly permeable substances (e.g., water) in the object to be treated are allowed to pass through, thereby improving the water permeability. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating the cross-sectional structure of the separation membrane according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram of the cross-flow permeability test device used to evaluate permeability and salt rejection rate. [Figure 3] FIG. 3 shows the evaluation results of the water permeability and salt rejection rate of MgSO4 of the membrane prepared with azodianiline:piperazine=0.25:0.75. [Figure 4]FIG. 4 shows the evaluation results of the water permeability and salt rejection rate of MgSO4 of the membrane prepared with azodianiline:piperazine=0.50:0.50. [Figure 5] FIG. 5 shows the evaluation results of the water permeability and salt rejection rate of MgSO4 of the membrane prepared with azodianiline:piperazine=0.75:0.25. [Figure 6] FIG. 6 shows the evaluation results of the water permeability and salt rejection rate of MgSO4 of the membrane prepared with azodianiline:piperazine=0:1. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described.

[0010] 1. Structure of the separation membrane The separation membrane according to the first embodiment of the present invention includes a porous support having a porous layer and a separation functional layer covering at least a part of the surface of the porous support. Specific examples of the separation membrane of this embodiment include, but are not limited to, reverse osmosis membranes and NF membranes for liquid separation.

[0011] 1 is a diagram illustrating the cross-sectional structure of a separation membrane according to the first embodiment. Separation membrane 1 has a separation function layer 3 laminated on one surface of a porous support 2. In this example, separation membrane 1 is a laminate made up of porous support 2 and separation function layer 3.

[0012] (Porous support) The porous support 2 is provided to provide mechanical strength to the separation function layer 3. The porous support 2 does not necessarily have to have substantial separation performance. A known porous support for an NF membrane can be used as the porous support 2. The material of the porous support 2 is not particularly limited. Examples include polysulfone, polyarylethersulfone such as polyethersulfone, polyimide, and polyvinylidene fluoride. However, porous supports made of polysulfone or polyarylethersulfone are preferred because of their chemical, mechanical, and thermal stability. The thickness of such a porous support is not particularly limited as long as it can maintain the strength and shape of the separation function layer 3 it supports; however, it typically has a thickness of 5 μm to 250 μm, preferably 100 μm to 250 μm.

[0013] The porous support 2 may have either a symmetrical or asymmetrical structure, but can have an asymmetrical structure in order to achieve both the supporting function of the thin film and liquid permeability.

[0014] The porous support 2 has fine pores from the front surface to the back surface. The average pore size of the side of the porous support 2 on which the separation function layer 3 is formed is preferably 100 nm or less. The porous support 2 may be reinforced by a backing such as a woven fabric or nonwoven fabric. For example, an ultrafiltration membrane can be used as the porous support 2.

[0015] (separation functional layer) The thickness of the separation functional layer 3 is preferably 5 nm to 100 nm, more preferably 5 nm to 50 nm. If the thickness of the separation functional layer 3 is 5 nm or more, salt removal is possible. If the thickness of the separation functional layer 3 is 100 nm or less, a practical water permeation flux can be obtained when a crosslinked polyamide is used in the separation functional layer.

[0016] The material of the separation functional layer 3 can be any known crosslinked polyamide as an active layer having separation selectivity, including crosslinked polyamides that are photoresponsive to ultraviolet light. Crosslinked polyamides having an azobenzene skeleton can be used as the crosslinked polyamides that are photoresponsive to ultraviolet light. The azobenzene skeleton is preferably in the trans form.

[0017] When a crosslinked polyamide has an azobenzene skeleton, irradiating it with ultraviolet light causes the azobenzene skeleton to undergo a photoisomerization reaction, converting from a trans isomer to a cis isomer. Photoresponsiveness refers to this property of responding to light. Photoresponsiveness is the property of instantly changing the molecular structure from a trans isomer to a cis isomer in a reversible and continuous manner upon irradiation with light. This photoresponsive property is also called photoisomerization. Crosslinked polyamides with an azobenzene skeleton undergo large reversible molecular movements upon photoisomerization.

[0018] The photoresponsive crosslinked polyamide is not limited to one having an azobenzene skeleton, and may have any other structure as long as its structure changes in response to light.

[0019] 2. Separation membrane raw materials Next, each raw material used in the method for producing the separation membrane will be described. (Polyamide separation functional layer) The polyamide in the separation functional layer is an aromatic polyamide and is crosslinked. Crosslinked polyamides can be formed by a crosslinking polymerization reaction between an amine compound as a monomer and a dicarboxylic acid as a monomer. In the case of crosslinked polyamides having an azobenzene skeleton, the amine compound includes a monomer having an azobenzene skeleton and an amine group and having photoresponsive properties, i.e., a photoresponsive molecule, and may be a mixture with other amine components that do not have an azobenzene skeleton.

[0020] Examples of amine compounds having an azobenzene skeleton, i.e., aromatic amine compounds A having an azo group, include 4-phenylazo-m-phenylenediamine monohydrochloride, Bismarck Brown, 4,4'-azodianiline, 2,4-diaminoazobenzene, etc. Among these, 4,4'-azodianiline is preferred from the viewpoint of high photoresponsiveness.

[0021] Amine compounds having an azobenzene skeleton, such as 4,4'-azodianiline, undergo photoisomerization and thermal isomerization reactions as shown in the following formulas.

[0022] [ka]

[0023] Other examples of the amine compound B that does not have an azobenzene skeleton include piperazine (PIP), 2-methylpiperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine. Of these, piperazine is preferably used from the viewpoint of improving the rejection rate of scale components, but aromatic amine compounds such as m-phenylenediamine may also be used.

[0024] As the crosslinking agent, for example, an organic solvent solution containing an acid chloride component such as trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, or biphenyldicarboxylic acid chloride can be used.

[0025] (Porous support) The porous support may be made of polysulfone, polyethersulfone, cellulose acetate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, etc. Polysulfone and polyethersulfone are suitable for the porous support because of their high chemical, mechanical, and thermal stability.

[0026] 3. Separation membrane manufacturing method A method for producing the separation membrane will now be described. A method for producing a separation membrane according to a second embodiment of the present invention includes the steps of obtaining a mixture containing water and an amine component, bringing the mixture into contact with a porous support, and then polymerizing the amine component in the mixture that has adhered to the porous support to obtain a separation membrane, wherein the amine component contains a photoresponsive molecule having an azobenzene skeleton and an amino group.

[0027] (Two types of amines with and without azobenzene skeleton) The step of obtaining the mixed solution may involve, for example, mixing water with an amine component containing an amine compound. The mixed solution may contain an alcohol component such as isopropyl alcohol (IPA). In the method for producing a separation membrane according to the second embodiment of the present invention, the amine compound is obtained by mixing an amine compound A having an azobenzene skeleton with an amine compound B not having an azobenzene skeleton. The amine compound A having an azobenzene skeleton may be at least one selected from the aromatic amine compounds described in paragraph

[0020] . Furthermore, the amine compound B not having an azobenzene skeleton may be at least one selected from the amine compounds described in paragraph

[0023] .

[0028] The mixing of water and the amine component, or the mixing of water, the amine component, and the alcohol can be carried out by a known method, for example, by using a magnetic stirrer or an ultrasonic stirrer.

[0029] In the mixed solution, the total weight of the amine compound mixture, which is a mixture of amine compound A having an azobenzene skeleton and amine compound B not having an azobenzene skeleton, is preferably in the range of 0.1 to 2.0% by weight based on the weight of the mixed solution from the viewpoint of polymerization reaction. From the viewpoint of photoresponsiveness and water permeability, when the total weight of amine compound A having an azobenzene skeleton and amine compound B not having an azobenzene skeleton (weight of A+B) is taken as 100%, the weight of amine compound A having an azobenzene skeleton is preferably in the range of 5 to 80% by weight, more preferably in the range of 15 to 80% by weight, and even more preferably in the range of 25 to 75% by weight.

[0030] (Heat treatment of the mixed liquid) It is desirable to heat and stir the mixture of water and an amine component, or the mixture of water, an amine component, and an alcohol, while shielding from light. Shielding from light is intended to prevent the azobenzene skeleton of the amine component from isomerizing from a trans form to a cis form (photoisomerization). Heating and stirring is particularly effective for dissolving amine compounds that are poorly soluble in water, and also because heating promotes isomerization (thermal isomerization) of the azobenzene skeleton from a cis form to a trans form. The heating temperature is 40°C or higher, preferably 50°C or higher, from the viewpoints of dissolution and promotion of thermal isomerization. The upper limit of the temperature is the temperature at which the amine component does not decompose.

[0031] (Cross-linking reaction, preparation of separation membrane) In the process of obtaining a separation membrane, the mixed solution obtained as described above is brought into contact with a porous support 2, and then the aromatic amine in the mixed solution that has adhered to the porous support 2 can be subjected to a crosslinking reaction.

[0032] The mixed solution is applied to the porous support 2 to allow it to soak in water, after which excess mixed solution is removed. A solution containing a cross-linking agent is then applied, causing an interfacial polymerization reaction to form cross-links, and the solution is then removed. After removing the solution, the porous support 2 may be heated to increase the degree of cross-linking. In this way, a separation functional layer 1 is formed. The separation membrane 1 can then be produced by drying at room temperature or by heating, followed by washing with distilled water.

[0033] As described in paragraph

[0024] , the crosslinking agent may be, for example, an organic solvent solution containing an acid chloride component such as trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, or biphenyldicarboxylic acid chloride.

[0034] In the step of applying the mixed liquid to the porous support 2, a bar coater can be used to apply the mixed liquid uniformly. As long as the mixed liquid can be applied uniformly, other known devices may be used instead of the bar coater.

[0035] 4. Use of separation membranes Next, a method for using the separation membrane will be described. (Raw water supply) A separation method according to a third embodiment of the present invention, which uses the separation membrane according to the first embodiment, includes the steps of supplying the material to be treated, irradiating the separation membrane with ultraviolet light, and then separating highly permeable substances in the material to be treated from other substances by allowing them to pass through.

[0036] Examples of materials to be treated include SO4 2- , Mg 2+ , Ca 2+ Examples of highly permeable substances in the object to be treated include the water component of an aqueous solution. In this case, the other substances correspond to the solutes of divalent ions.

[0037] The aqueous solution containing the divalent ions is then supplied to the separation membrane as raw water under pressure using a pump. As the raw water flows over the surface of the separation membrane, some of the highly permeable water components pass through the membrane. The resulting permeate has a lower solute concentration (divalent ion concentration) than the raw water. Meanwhile, the solutes (divalent ions) in the water flowing through the raw water flow path are concentrated.

[0038] (Ultraviolet light irradiation) In the separation method using the separation membrane according to the present embodiment, the separation membrane can be irradiated with ultraviolet light before the water component of the raw water is passed through the separation membrane. That is, after the separation membrane is irradiated with ultraviolet light, the highly permeable substance (water) in the treatment object containing divalent ions can be passed through the membrane.

[0039] The separation membrane according to the present embodiment contains a photoresponsive crosslinked polyamide, and when irradiated with ultraviolet light, the azobenzene structure in the crosslinked polyamide changes from a trans isomer to a cis isomer, thereby increasing the free volume of the crosslinked polyamide and increasing the flow rate of water passing through the polyamide separation functional layer.

[0040] The water permeation may be carried out while irradiating the polyamide separating functional layer with ultraviolet light, in which case the free volume can be continuously increased during separation of the water component. [Example]

[0041] Examples will be described below.

[0042] <Separation membrane production> [Example 1] (Porous support) The porous support was an ultrafiltration membrane (manufactured by SYNDER, model number LX), which was washed as follows.

[0043] First, 20% IPA and 80% ultrapure Milli-Q water (Millipore, registered trademark Milli-Q) (hereinafter referred to as "Milli-Q water") were weighed out and mixed in a wide-mouth bottle by shaking. Next, this solution was placed in a Tupperware container, and a porous support (ultrafiltration membrane) cut into a 6 cm x 6 cm piece was immersed in the solution by shaking at 70 rpm using a rotary shaker (AS ONE, model number SK-O180-S). The porous support was then removed, lightly rinsed with Milli-Q water, and immersed in a Tupperware container filled with Milli-Q water. The porous support was then immersed in the solution by rotary shaking at 70 rpm for 24 hours to wash the porous support.

[0044] (Polyamide separation functional layer) Next, an amine aqueous solution was prepared. 4,4'-azodianiline was used as the amine compound A (amine monomer, a photoresponsive molecule) having an azobenzene skeleton, and piperazine (PIP) was used as the amine compound B without an azobenzene skeleton. The amine aqueous solution was prepared by dissolving 0.05% by mass of 4,4'-azodianiline, 0.15% by mass of piperazine (total of 0.2% by mass of the amine compounds), and 50% by mass of IPA in Milli-Q water. In Example 1, the mass ratio of 4,4'-azodianiline to piperazine was 4,4'-Azodianiline:Piperazine=0.25:0.75 It was.

[0045] The amine aqueous solution was prepared by heating and stirring at 70°C for 1 hour in the dark. 4,4'-Azodianiline is difficult to dissolve, and heating promotes isomerization from cis to trans, resulting in the polymerization of 4,4'-azodianiline in the trans form. The acid chloride solution was prepared by weighing out 1,3,5-benzenetricarbonyl chloride (TMC) to a concentration of 0.15% by mass and dissolving it in n-hexane. Because TMC is prone to deterioration due to reaction with water in the air, it was transferred to a separate bottle before use.

[0046] The porous support was then rinsed on both sides with Milli-Q water and attached to a frame. The water was gently removed with an air blower, and the porous support was quickly immersed in an amine aqueous solution to prevent excessive drying. The support was then immersed for 2 minutes. An air duster was then used to gently remove the surface water. The acid chloride solution was then poured onto the support, and the support was immersed for 15 seconds. The solution was then removed while the porous support was still standing. Once the separation membrane was confirmed to be completely dry, the support was heat-treated at 100°C for 10 minutes in a thermo-hygrostat (manufactured by Isuzu Motors, model number ANS-113S) while the frame was still standing, producing a separation membrane.

[0047] [Example 2] In Example 2, the amine aqueous solution contained 0.1 mass% of 4,4'-azodianiline and 0.1 mass% of piperazine (the total amount of the amine compounds was 0.2 mass%), and the mass ratio of 4,4'-azodianiline to piperazine was 4,4'-Azodianiline:Piperazine=0.50:0.50 The other conditions are the same as in Example 1 except that:

[0048] [Example 3] In Reference Example 1, the aqueous amine solution contained 0.15% by mass of 4,4'-azodianiline and 0.05% by mass of piperazine (the total amount of the amine compounds was 0.2% by mass), and the mass ratio of 4,4'-azodianiline to piperazine was 4,4'-Azodianiline:Piperazine=0.75:0.25 The other conditions are the same as in Example 1 except that:

[0049] [Comparative Example 1] In Comparative Example 1, the amine aqueous solution contained 0 mass% of 4,4'-azodianiline and 0.2 mass% of piperazine (the total amount of amine compounds was 0.2 mass%), and the mass ratio of 4,4'-azodianiline to piperazine was 4,4'-Azodianiline:piperazine=0:1 The other conditions are the same as in Example 1 except that:

[0050] <Evaluation of permeability and salt rejection rate> (Permeability testing equipment) The water permeability and salt rejection rate of each separation membrane were evaluated using a cross-flow water permeability tester shown in Figure 2. A stainless steel cell (membrane effective area 8.0 cm) was used. 2 The separation membrane was set in a separator, and feed water was supplied to the membrane cell using a plunger pump (Nippon Seimitsu Kagaku, model NPL-120). Milli-Q water was used as the feed water for the water permeability test. 0.05% by mass of aqueous NaCl, MgSO4, and Na2SO4 solutions were used to measure salt rejection. The temperature in the laboratory was 25°C, and the pressure was adjusted to 0.750 MPa using a back pressure valve. A magnetic stirrer was used in the cell to mitigate concentration polarization, and the stirring speed was set to 800 rpm. Water permeability and salt rejection were calculated using the following equations. TIFF2025180701000003.tif42127The amount of permeated liquid was measured by weight, and the solute concentration was calculated from the electrical conductivity using an electrical conductivity meter (Horiba, Ltd., model number B-771).

[0051] (Azo group isomerization procedure) To isomerize the azo groups contained in the prepared membrane from trans to cis, the membrane was immersed in Milli-Q water and irradiated with 365 nm ultraviolet light for 1 hour at room temperature (25°C) using a UV lamp (Analytik Jena, model UVL-56) in the dark. On the other hand, to isomerize from cis to trans, the membrane was immersed in Milli-Q water and heated at 60°C for 16 hours in a vacuum sample dryer (Miyamoto Riken Kogyo, model RA-155S).

[0052] (Permeability test results) The evaluation results of the water permeability and salt rejection rate of each separation membrane are shown in Tables 1 to 4 and Figs. 3 to 6.

[0053] Table 1 shows the results of the water permeability and salt rejection of the separation membranes of Example 1, Table 2 shows the results of Example 2, Table 3 shows the results of Example 3, and Table 4 shows the results of Comparative Example 1. Tables 1 to 3 show (1) the test results "after polymerization," (2) the test results "after the first ultraviolet light irradiation" after ultraviolet light irradiation, (3) the test results "after the first heating at 60°C" after heating at 60°C, (4) the test results "after the second ultraviolet light irradiation" after ultraviolet light irradiation again, and finally (5) the test results "after the second heating at 60°C" after heating at 60°C. Table 4 shows (1) the test results "after polymerization," (2) the test results "after ultraviolet light irradiation" after ultraviolet light irradiation, and (3) the test results "after the first heating at 60°C" after heating at 60°C.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4]

[0058] 3, 4, and 5 are bar graphs showing the water permeability (left vertical axis) and salt rejection rate of MgSO4 (right vertical axis) for Examples 1, 2, and 3, respectively. The horizontal axes correspond, from left to right, to (1) "after polymerization," (2) "after first UV light irradiation," (3) "after first heating at 60°C," (4) "after second UV light irradiation," and (5) "after second heating at 60°C." FIG. 6 is a bar graph showing the water permeability (left vertical axis) and salt rejection rate of MgSO4 (right vertical axis) for Comparative Example 1. The horizontal axes correspond, from left to right, to (1) "after polymerization," (2) "after UV light irradiation," and (3) "after first heating at 60°C."

[0059] The results in Tables 1-3 and Figures 3-5 show that the salt rejection rate of MgSO4 for separation membranes with a photoresponsive crosslinked polyamide separation functional layer remained above 90% without significant change when irradiated with UV light and then heated. However, it was found that the water permeability increased significantly when irradiated with UV light and decreased when heated. It is believed that the azobenzene structure in the polyamide isomerized from trans to cis isomer upon UV light irradiation, widening the distance between polymer chains and increasing the free volume, which reduced the density of the polyamide and improved water permeability. Furthermore, the decrease in water permeability upon heating is thought to be due to the re-isomerization of the azobenzene structure in the polyamide from cis to trans isomer upon heating, returning the polyamide polymer structure to a denser state.

[0060] This change in water permeability due to light and heat showed reversible behavior. This is thought to be due to the reversible isomerization from trans to cis isomers and from cis to trans isomers. It was found that the photoresponsiveness of the polyamide separation membrane is reversible due to light and heat.

[0061] On the other hand, the results of Table 4 and Figure 6 show that the separation membrane made from 100% piperazine without 4,4'-azodianiline shows almost no change in water permeability when irradiated with ultraviolet light or heated, and does not exhibit photoresponsiveness or thermoresponsiveness.

[0062] In Examples 1 and 2, after polymerization and before irradiation with UV light, the water permeation rate was higher than in Comparative Example 1 (100% piperazine), and the water permeation rate increased further when UV light was irradiated. In Example 3, after polymerization and before UV light irradiation, the water permeation rate was lower than in Comparative Example 1, but when UV light was irradiated, the water permeation rate increased and exceeded the value of Comparative Example 1. From the above, it can be said that high water permeability can be achieved by a separation membrane having a photoresponsive polyamide separation function layer. [Explanation of symbols]

[0063] 1 Separation membrane 2 Porous support 3 Separation functional layer

Claims

1. A separation membrane comprising a porous support and a separation functional layer containing a crosslinked polyamide, A separation membrane, wherein the crosslinked polyamide has photoresponsiveness.

2. The separation membrane according to claim 1, wherein the crosslinked polyamide has an azobenzene skeleton.

3. The separation membrane according to claim 2, wherein the azobenzene skeleton has a trans structure.

4. obtaining a mixed liquid containing water and an amine component; and a step of bringing the mixed solution into contact with a porous support, and then polymerizing the amine component in the mixed solution that has adhered to the porous support to obtain a separation membrane, A method for producing a separation membrane, wherein the amine component contains a photoresponsive molecule having an azobenzene skeleton and an amino group.

5. The method for producing a separation membrane according to claim 4 , further comprising the step of heating the mixture after the step of obtaining the mixture and before the step of obtaining the separation membrane by polymerization reaction.

6. 6. The method for producing a separation membrane according to claim 4, wherein a mass ratio of the amine component containing the photoresponsive molecule to the total weight of the amine components is 5 mass % or more and 80 mass % or less.

7. A separation method comprising the steps of supplying a material to be treated to the separation membrane according to any one of claims 1 to 3, irradiating the separation membrane with ultraviolet light, and then separating highly permeable substances in the material to be treated from other substances by passing them through.

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