Composite separation membrane and method for manufacturing the same

Abstract

The present invention aims to provide a composite separation membrane having excellent resistance to organic solvents, which can be stably separated even in an organic solvent, and a method for easily producing the same. The composite separation membrane of the present invention is characterized by having a support membrane containing a modified polyphenylene ether having a sulfonic acid group and / or a sulfuric acid group, and a polar group, and a separation function layer containing a crosslinked cationic polymer, the separation function layer being formed on the support membrane.

Description

Technical Field

[0001] The present invention relates to a composite separation membrane capable of stable separation even in organic solvents and a method for easily manufacturing the composite separation membrane. Background Technology

[0002] In many industries, including chemical, pharmaceutical, and petrochemical, separation operations using organic solvents are essential, with distillation being the most common method. While distillation is a highly reliable technique, its high energy consumption and significant carbon dioxide emissions pose significant social challenges.

[0003] On the other hand, membrane separation operations have the following advantages compared to distillation: since there is no phase change, the energy required for separation can be significantly reduced. Furthermore, because it is a heat-free process, it is also suitable for purifying substances that are easily degraded by heat. Therefore, membrane technology is applied in a wide range of industries for applications such as seawater desalination, drinking water treatment, wastewater treatment, and blood purification.

[0004] In traditional membrane separation, water has been the primary medium. However, membrane separation that can be performed in organic solvent systems could potentially expand its application scope significantly.

[0005] The technique of separating, purifying, and concentrating molecules of different sizes (from several Å to several nm) using organic solvents as a medium through membranes is called organic solvent nanofiltration (OSN) or organic solvent reverse osmosis (OSRO). As a subject of this technology, in the case of separation membranes for organic polymer systems, pore size changes and performance degradation over time due to membrane swelling caused by organic solvents can be cited as examples. Therefore, there is a need to seek nanofiltration and reverse osmosis membranes that can stably perform high-precision molecular fractionation over a long period.

[0006] From the perspective of balancing excellent molecular hierarchical structure and high permeation flow rate, composite membrane structures are suitable for the separation membranes used in OSN or OSRO. A common method involves selecting a solvent-resistant porous membrane as the support membrane and forming a three-dimensionally cross-linked polymer film on the support membrane as the separation functional layer. Techniques for forming the separation functional layer include interfacial polymerization, coating, and layer-by-layer (LbL) polymer adsorption. These methods are suitable for forming films with pore sizes of several Å and few defects. LbL, in particular, can be easily formed into a separation layer by contacting the membrane surface with an aqueous solution of a polymeric electrolyte, thus making it a promising candidate for the separation layer of composite membranes in OSN or OSRO. An LbL adsorption layer with excellent permeation selectivity and long-term stability in organic solvent systems is required.

[0007] As a raw material for the support membrane in polymer composite membranes, it needs to be easy to fabricate and resistant to various organic solvents. Furthermore, separation processes in pharmaceuticals and fine chemicals often require treatment with solvents containing high concentrations of acids and alkalis, thus resistance to acid and alkali corrosion is desirable. Previous solvent-resistant membrane materials have included crosslinks of amorphous polymers such as polyimide and polybenzimidazole. Membranes containing semi-crystalline polymers such as polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) have also been studied. However, from the perspective of acid and alkali resistance to hydrolysis, polyimide and polybenzimidazole sometimes have insufficient performance. While semi-crystalline polymers such as PEEK and PPS exhibit excellent hydrolysis resistance, they are only soluble in a very limited number of solvents, such as sulfuric acid, or are completely insoluble, making membrane fabrication sometimes difficult.

[0008] Separation membranes formed using polyphenylene oxide (PPO) or its derivatives are known to possess excellent mechanical strength, as well as resistance to alkalis and acids. Furthermore, although PPO is an amorphous polymer, it exhibits resistance to N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), which are aprotic polar solvents. Therefore, it is considered to have excellent potential as a membrane raw material for filtration processes using these pure solvents as media, and further, for filtration processes using organic solvents containing alkalis or acids.

[0009] As an example of a composite membrane using LbL, the inventors sulfonated the surface of a PPO membrane with sulfuric acid to obtain an anionic membrane surface, and then adsorbed and crosslinked the separation functional layer of cationic polyvinyl alcohol, thereby developing a composite membrane that exhibits excellent permeation selectivity in nanofiltration or reverse osmosis separation (Patent Document 1).

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent No. 7226569 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] As mentioned above, composite separation membranes that use PPO membranes as support membranes and exhibit excellent permeation selectivity have been developed.

[0015] However, it is believed that if the resistance of composite separation membranes to organic solvents is further improved, the application areas will be greatly expanded.

[0016] Therefore, the object of the present invention is to provide a composite separation membrane with excellent resistance to organic solvents and capable of stable separation even in organic solvents, as well as a method for easily manufacturing the composite separation membrane.

[0017] Methods for solving problems

[0018] The inventors conducted repeated and in-depth research to solve the aforementioned problems. Their findings revealed that, in an asymmetric membrane with a separation functional layer formed on a support membrane, the resistance to organic solvents is significantly improved by introducing sulfonic acid / sulfuric acid groups and polar groups into the support membrane, thus completing this invention.

[0019] The present invention is illustrated below.

[0020] [1] A composite separation membrane, characterized in that it comprises a support membrane containing modified polyphenylene ether and a separation functional layer containing a crosslinked cationic polymer.

[0021] The modified polyphenylene ether described above has sulfonic acid groups and / or sulfate groups, as well as polar groups.

[0022] The aforementioned separation functional layer is formed on the aforementioned support membrane.

[0023] [2] According to the composite separation membrane described in [1] above, the sulfonic acid group and / or the sulfuric acid group and the polar group are introduced into the benzene ring of the modified polyphenylene ether via a linking group.

[0024] [3] According to the composite separation membrane described in [2] above, the benzene ring of the modified polyphenylene ether has a sulfomethyl group.

[0025] [4] The composite separation membrane described in any one of [1] to [3] above, wherein the polar group is one or more polar groups selected from hydroxyl, ether, sulfonyl and amino.

[0026] [5] The composite separation membrane described in any one of [1] to [4] above, wherein the cationic polymer is a cationic polyvinyl alcohol copolymer containing structural units having quaternary ammonium cationic groups.

[0027] [6] The composite separation membrane described in any one of [1] to [4] above, wherein the cationic polymer is one or more polyamines selected from polyethyleneimine, polyethyleneamine and polyallylamine.

[0028] [7] A method for manufacturing a composite separation membrane, characterized in that it comprises:

[0029] The process of obtaining a support film using polyphenylene ether;

[0030] The process of introducing sulfonic acid groups and / or sulfuric acid groups into the support film by contacting the support film with a sulfonating agent;

[0031] The process of contacting the support film, which has been infused with the above-mentioned sulfonic acid groups and / or the above-mentioned sulfuric acid groups, with an aqueous solution containing a cationic polymer to form a cationic polymer layer on the support film.

[0032] The process of crosslinking the cationic polymer in the above-mentioned cationic polymer layer; and

[0033] The process of introducing polar groups into the polyphenylene ether in the support film.

[0034] [8] According to the method described in [7] above, the sulfonic acid group is introduced onto the halogenated methyl group by contacting the support film of the polyphenylene ether containing a halogenated methyl group introduced onto the benzene ring with an aqueous solution containing sulfite as the sulfonating agent.

[0035] [9] According to the method described in [7] above, the polar group is introduced by reacting the above-mentioned polyphenylene ether with a halomethyl group introduced on the benzene ring with the monoethanolamine shown in the following formula (IV).

[0036] [Chemical Formula 1]

[0037]

[0038] [In the formula, R] 21 Indicates H or C 1-6 alkyl.]

[0039]

[10] An application of a composite separation membrane, characterized in that it is used to treat a liquid by passing it through the composite separation membrane.

[0040] The aforementioned composite separation membrane comprises a support membrane containing modified polyphenylene ether and a separation functional layer containing a cross-linked cationic polymer.

[0041] The modified polyphenylene ether described above has sulfonic acid groups and / or sulfate groups, as well as polar groups.

[0042] The aforementioned separation functional layer is formed on the aforementioned support membrane.

[0043]

[11] According to the use described in

[10] above, the liquid being treated contains an organic solvent.

[0044]

[12] According to the use described in

[10] or

[11] above, wherein the sulfonic acid group and / or the sulfate group, as well as the polar group, are introduced into the benzene ring of the modified polyphenylene ether via a linking group.

[0045]

[13] According to the use described in

[12] above, wherein the benzene ring of the modified polyphenylene ether has a sulfomethyl group.

[0046]

[14] According to any of the uses described in

[10] to

[13] above, wherein the polar group is one or more polar groups selected from hydroxyl, ether, sulfonyl and amino.

[0047]

[15] According to any one of the uses described in

[10] to

[14] above, wherein the cationic polymer is a cationic polyvinyl alcohol copolymer containing structural units having quaternary ammonium cationic groups.

[0048]

[16] According to any of the uses described in

[10] to

[14] above, wherein the cationic polymer is one or more polyamines selected from polyethyleneimine, polyethyleneamine and polyallylamine.

[0049] Invention Effects

[0050] The composite separation membrane of the present invention exhibits excellent durability against organic solvents. Furthermore, since the support membrane of the composite separation membrane of the present invention contains modified polyphenylene ether, it also exhibits excellent acid and alkali resistance. Therefore, the composite separation membrane of the present invention can be applied not only to filtration and reverse osmosis separation in water systems, but also to filtration and reverse osmosis separation in organic solvent systems, making it highly advantageous industrially. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the manufacturing process of the composite separation membrane of the present invention and the composition of the membrane in each process.

[0052] Figure 2 (1) is a graph showing the relationship between reaction temperature and sulfur elemental yield when the reaction time is fixed at 30 minutes and a phase transfer catalyst (TBAB) is used and when a phase transfer catalyst (TBAB) is not used. Figure 2(2) is a graph showing the relationship between reaction temperature and bromine content when the reaction time is fixed at 30 minutes and a phase transfer catalyst (TBAB) is used and when a phase transfer catalyst (TBAB) is not used. Figure 2 (3) is a graph showing the relationship between reaction time and sulfur content (left axis) and bromine content (right axis) when the reaction temperature is fixed at 98°C and no phase transfer catalyst (TBAB) is used.

[0053] Figure 3 (1) is the result of infrared absorption spectroscopy analysis of BrPPO membrane with bromomethyl groups, sulfonated support membrane A, and support membrane without separation functional layer and with MEA introduced after sulfonation. Figure 3 (2) is 1000cm -1 Enlarged images of the front and back. Detailed Implementation

[0054] Hereinafter, the manufacturing method of the composite separation membrane of the present invention will be described for each step, but the present invention is not limited to the specific examples described below. It should be noted that, in this disclosure, "sulfonic acid group and / or sulfuric acid group" means "one or more groups selected from sulfonic acid group and sulfuric acid group", sometimes simply referred to as "sulfonic acid group / sulfic acid group".

[0055] 1. Film-making process

[0056] In this process, polyphenylene ether is used to obtain the support film. Hereinafter, polyphenylene ether will be abbreviated as "PPO". PPO is a polymer having the following unit structure (I), for example, widely used polymers having the following unit structure (I) 1 Poly(2,6-dimethyl-1,4-phenyl ether). Furthermore, considering the ease of introducing sulfonic acid groups, as a raw material, the following unit structures having substituted halomethyl groups can be used (I... 2 ) of PPO.

[0057] [Chemical Formula 2]

[0058]

[0059] [In the formula, X represents a halogenated group selected from chlorine, bromine, and iodine, with bromine being preferred due to its high desorption capacity, low cost, and excellent processability.]

[0060] There are no particular limitations on the physical properties of the raw material PPO; it is sufficient to synthesize the desired PPO or select appropriate PPO products. For example, from the viewpoint of imparting sufficient viscosity to the film-forming solution to ensure good coatability, fiberability, and film strength, the weight-average molecular weight of PPO is preferably 5,000 or higher. Furthermore, from the viewpoint of processability such as solubility, the weight-average molecular weight of PPO is preferably 500,000 or lower. As mentioned above, a weight-average molecular weight of 10,000 or higher is preferred, and furthermore, 400,000 or lower is more desirable.

[0061] PPO can also be used as a raw material, specifically PPO with methyl or halomethyl groups introduced onto the benzene ring. The benzyl cation is conjugated with the benzene ring and is stable, while PPO with methyl or halomethyl groups introduced onto the benzene ring exhibits high reactivity. For example, poly(2,6-dimethyl-1,4-phenylene ether) is commercially available.

[0062] The halogen group can be easily introduced into the methyl group that is substituted on the benzene ring of PPO. As the halogen group, one or more halogen groups selected from chlorine, bromine and iodine can be used, and bromine, which has high desiccation ability, low compound cost and excellent processability, is preferred.

[0063] The methyl group substituted on the benzene ring of PPO can be halogenated using conventional methods. For example, a halogenating agent can be added to a solution of PPO containing a methyl group. Solvents such as dichloromethane, chloroform, and carbon tetrachloride are suitable; halogenated aromatic hydrocarbons such as chlorobenzene are suitable; and aromatic hydrocarbons such as benzene and toluene are suitable. These solvents have low halogen solubility, which helps to suppress the concentration of halogens in the reaction system, thus favoring halogenation at the benzyl position. On the other hand, it is known that halogenation of the benzene ring is preferred when using polar solvents such as acetonitrile. However, even when using the solvents described above, the benzene ring may be directly halogenated except at the benzyl position. From a processability point of view, halogenated aromatic hydrocarbon solvents such as chlorobenzene are preferred.

[0064] As halogenating agents, N-halosuccinimides such as N-bromosuccinimide and halogen elements can be used.

[0065] The halogenation conditions can be adjusted appropriately. For example, it is preferable to react at a temperature above 110°C for at least 3 hours under an inert atmosphere such as argon or nitrogen. The higher the reaction temperature, the higher the selectivity for halogenation at the benzyl position. However, from the viewpoint of suppressing side reactions, it is preferable to carry out the halogenation reaction at a temperature above 115°C and below 135°C.

[0066] After the reaction is complete, the halogenated PPO can be purified using conventional methods. For example, a poor solvent can be added to the reaction solution to precipitate the halogenated PPO, followed by filtration, washing with the poor solvent, and drying. Alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone, can be used as poor solvents. Methanol is the simplest and therefore preferred.

[0067] In this disclosure, the degree of halogenation at the benzyl position of PPO can be determined, for example, by nuclear magnetic resonance (NMR) using deuterated chloroform as a solvent. Examples of the chemical structures of halogenated PPO are shown below. Halogenated PPO may also comprise unit structures without a halogenated group, i.e., R... 1 ~R 8 The unit structure consists entirely of hydrogen atoms. Various unit structures can be generated depending on the degree of halogenation of the benzene ring and the benzyl group. In NMR, the presence ratio of each unit structure can be determined based on characteristic peaks. Detailed unit structures can also be identified, for example, using heteronuclear single quantum coherence (HSQC).

[0068] [Chemical Formula 3]

[0069]

[0070] [In the formula,]

[0071] R 1 ~R 8 Independently representing a halogenated group or H,

[0072] R 1 and R 2 This indicates a halogenated group on the benzene ring.

[0073] R 3 ~R 8 Indicates a halogroup at the benzyl position.

[0074] i is an integer greater than or equal to 1 and less than or equal to k, where i represents the i-th structure among the k number of unit structures identified by NMR.

[0075] n i [This represents the mole fraction of the i-th structure in each of the k unit structures, i.e., a number greater than 0 and less than 1.]

[0076] In this invention, the degree of halogenation D is defined as the average number of halogen atoms substituted at the benzyl position in each unit structure. Hal , represented by the following formula (1). For example, in the case of PPO with two methyl groups at positions 2 and 6 in the unit structure, since the number of hydrogens at the benzyl positions that can undergo substitution is 6, D HalValues ​​above 0 and below 6.0 are acceptable. However, to the knowledge of the inventors, in most cases, one hydrogen atom of each methyl group is substituted with a halogroup, but it is also possible for a certain number of methyl groups to have two hydrogen atoms substituted with halogroups. On the other hand, cases where three hydrogen atoms of each methyl group are substituted with halogroups have not been observed.

[0077] [Mathematical Expression 1]

[0078]

[0079] [In the formula, N] i_BzHal n represents the number of halogenated groups at the benzyl position in each unit structure of equation (II) above. i [This represents the mole fraction of each structural unit in equation (II) above.]

[0080] The average number of halogenated groups substituted on the benzene ring of each unit structure is represented by the following equation (2).

[0081] [Mathematical Expression 2]

[0082]

[0083] [In the formula, N] i_ArHal n represents the number of halogenated groups that are substituted on the benzene ring in each unit structure of equation (II) above. i [This represents the mole fraction of each structural unit in equation (II) above.]

[0084] The degree of halogenation D at the benzyl site mentioned above Hal Preferably, it is between 0.5 and 2.0. If D Hal If the degree of halogenation D is above 0.5, it can be said that the methyl group on the benzene ring of PPO is sufficiently halogenated, making it susceptible to attack by nucleophiles (described later). As a result, the hydrophilicity and solvent resistance of modified PPO are reliably improved. On the other hand, if the degree of halogenation D... Hal If the value is below 2.0, then excessive use of halogenating agents is not required, which is economical. In addition, side reactions such as cross-linking reactions in the reaction can be effectively suppressed.

[0085] In this disclosure, the degree of halogenation D of the benzene ring is... Hal2 There are no particular restrictions, but it is preferred to be above 0 and below 1.0. If D Hal2 If the value is below 1.0, the degree of halogenation D at the benzylic position can be suppressed. Hal The reduction is relatively small, and it is economical as it does not require excessive use of halogenating agents. Furthermore, it more reliably ensures the solvent resistance of modified PPO. Additionally, it can be said that D... Hal2 The lower the value, the better, but in reality, it is above 0. It should be noted that, depending on the reaction conditions, unit structures that cause both halogenation of the benzene ring and halogenation of the benzyl group can also exist.

[0086] In this process, a support film is manufactured from raw material PPO. As mentioned above, unsubstituted PPO, PPO with a methyl group on the benzene ring such as 2,6-dimethyl-1,4-phenyl ether, or PPO with a halomethyl group on the benzene ring can be used as the raw material. PPO with introduced sulfonic acid / sulfate groups is preferred over using PPO as the raw material. The introduction of sulfonic acid / sulfate groups reduces the solubility of PPO, potentially making film formation difficult. Furthermore, by introducing sulfonic acid / sulfate groups after film formation, more sulfonic acid / sulfate groups can be introduced onto the surface of the support film, thereby increasing the adsorption efficiency of the cationic polymer.

[0087] There are no particular restrictions on the shape of the support membrane; for example, it can be a flat membrane or a hollow fiber membrane.

[0088] Support membranes can be manufactured, for example, by coating a solution of raw material PPO onto a substrate such as nonwoven fabric or a filter using a doctor blade and then drying it. As for the solvent used to dissolve the raw material PPO, there are no particular limitations as long as it can dissolve the raw material PPO well; for example, amide solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide, which are water-soluble organic solvents, can be used. Furthermore, for use as a separation membrane, the support membrane needs to be porous with interconnected pores; therefore, water-soluble pore-forming materials can be added to the raw material PPO solution. Examples of pore-forming materials include polyethylene glycol, glycerol, polypropylene glycol, nonionic surfactants, and ionic surfactants.

[0089] There are no particular limitations on the substrate as long as it has excellent solvent resistance and can effectively support the support membrane. For example, nonwoven fabrics made from raw materials with excellent solvent resistance, such as polyethylene terephthalate, polyethylene, polypropylene, and polyphenylene sulfide (PPS), are suitable as substrate raw materials. PPS is preferred because it has excellent solvent resistance and resistance to alkalis and acids. After coating the substrate with a PPO solution, it is immersed in a coagulation bath containing a non-solvent such as water, thereby obtaining the support membrane. Alternatively, in the case of manufacturing hollow fiber membranes, the PPO solution is extruded from a double-cylinder nozzle along with the inner liquid and immersed in a coagulation bath. The substrate can be peeled off from the support membrane after its formation or used directly as part of a composite separation membrane.

[0090] In the above-mentioned membrane-forming process, the PPO concentration of the raw material PPO solution, the discharge temperature, the temperature and composition of the coagulation bath, and the transport speed of the support membrane can be appropriately set based on well-known principles. Furthermore, the porosity of the support membrane can be adjusted by the concentration of the pore-forming agent in the raw material PPO solution.

[0091] After the reaction, conventional post-treatment can be performed. For example, by thoroughly washing the support membrane with water, not only the solvent but also the pore-forming agent can be removed, thus making the support membrane porous.

[0092] 2. Sulfonic acid / sulfate group introduction process

[0093] In this process, the support film prepared in step 1 above is brought into contact with a sulfonating agent to introduce sulfonic acid groups (-SO3H) and / or sulfate groups (-OSO3H). It should be noted that, in this disclosure, the sulfonic acid groups / sulfuric acid groups contain ionized -SO3 groups. - / -OSO3 - SO3 as their salt - M + / -OSO3 - M + (In the formula, M represents Na) + K + (Metal ions, etc.). Additionally, the introduction of sulfonic acid / sulfuric acid groups is sometimes referred to as "sulfonation." In this process, a negative charge is specifically imparted by sulfonating the surface of the support film. Figure 1 ).

[0094] There are no particular limitations on the conditions for introducing sulfonic acid groups into at least the surface of the support film. For example, by immersing the support film obtained in step 1 above in an aqueous solution of a nucleophilic sulfonating agent such as sulfite as a sulfonating agent, it is possible, as shown in the following reaction formula, to utilize S in particular. N 2. Mechanism: The halogroup of the halomethyl group is replaced with a sulfonic acid group. In this case, it is believed that the sulfonic acid group is preferentially introduced to the outer surface of the support membrane, but the inner surface of the membrane, i.e., the surface of the pores, may also be sulfonated. However, since it is believed that the PPO inside the support membrane is substantially unsulfonated or almost unsulfonated, the membrane surface can be sulfonated without reducing the overall mechanical strength of the support membrane. Furthermore, it is believed that the sulfonic acid group is mainly introduced through the use of sulfite, but the possibility of introducing sulfate groups cannot be ruled out.

[0095] [Chemical Formula 4]

[0096]

[0097] Sodium sulfite or potassium sulfite can be used as sulfites. The concentration of the aqueous sulfite solution can be set to 5% by mass or more, preferably 10% by mass or more. The reaction temperature is preferably room temperature to less than 100°C. There is a tendency that the sulfonation reaction is accelerated the higher the reaction temperature. The reaction time can be selected by appropriate combination with the reaction temperature. In addition, adding an appropriate amount of phase transfer catalyst to the reaction solution also accelerates the sulfonation reaction on the surface of the supported film, and is therefore preferred. There are no particular limitations on the phase transfer catalyst, and examples include quaternary ammonium salts, phosphonium salts, polyethylene glycol, crown ethers, etc., with tetrabutylammonium bromide (TBAB) being preferred for example.

[0098] When sulfuric acid, fuming sulfuric acid, chlorosulfuric acid, sulfur trioxide, etc., are used as sulfonating agents, it is believed that the benzene ring of PPO is mainly directly sulfonated, but the benzyl group may also be sulfonated. Additionally, it is believed that when using PPO with hydroxyl or hydroxymethyl substitutions on the benzene ring as the raw material PPO, a sulfuric acid group is introduced into the benzyl group. An example of the structural unit of sulfonated modified PPO is shown below.

[0099] [Chemical Formula 5]

[0100]

[0101] [In the formula,]

[0102] R 11 ~R 14 Independently representing a sulfonic acid group, a sulfate group, or H,

[0103] R 11 and / or R 12 This indicates whether the group on the benzene ring is a sulfonic acid group or a sulfate group.

[0104] R 13 and / or R 14 Indicates a sulfonic acid group or a sulfate group at the benzyl position.

[0105] R 11 ~R 14 [One or more of the following are sulfonic acid groups or sulfate groups.]

[0106] After the reaction, typical post-processing can be performed. For example, the sulfonating agent can be removed by thoroughly washing the sulfonated support film with water. It should be noted that the support film is essentially composed of sulfonated modified PPO. Composed of sulfonated modified PPO means that although it may contain undesirable residual components or undesirable mixed components such as solvents, pore-forming agents, and sulfonating agents, the support film does not intentionally contain any components other than sulfonated modified PPO.

[0107] The thickness of the support film is preferably 10 μm or more and 100 μm or less. If the thickness of the support film is 10 μm or more, mechanical strength can be sufficiently ensured, and the formation of defects can be suppressed more reliably. On the other hand, if the thickness of the support film is 100 μm or less, the transmission resistance can be sufficiently reduced.

[0108] 3. Formation process of separating functional layers

[0109] In this process, the sulfonated support film manufactured in step 2 above is contacted with an aqueous solution containing a cationic polymer, forming a cationic polymer layer on the sulfonated support film that functions as a separation layer. The support film manufactured in the previous step, at least on which the surface is sulfonated, has a strongly negatively charged surface due to the sulfonic acid / sulfate groups, and is also highly hydrophilic. Therefore, by contacting this sulfonated support film with an aqueous solution containing a cationic polymer, a cationic polymer layer that functions as a separation layer can be well formed on the sulfonated support film. Figure 1 ).

[0110] As a cationic polymer, there are no particular limitations on any polymer that has cationic groups and can be adsorbed onto the surface of a support film having at least anionic sulfonic acid / sulfuric acid groups on its surface to form a layer, through ion exchange reactions and electrostatic bonding. Examples include polyethyleneimine, polyallylamine, polyethyleneamine, and cationic polyvinyl alcohol. From the viewpoint of forming chemically stable and defect-free films and obtaining high permeability selectivity in organic solvent systems, cationic polyvinyl alcohol containing quaternary ammonium groups is particularly preferred.

[0111] The concentration of the cationic polymer aqueous solution can be appropriately adjusted within a range that allows for the good formation of a cationic polymer layer on the support film; for example, it can be adjusted to 0.01% by mass or more but less than 1% by mass. It is also preferable to adjust the ionic strength by adding an inorganic salt to the aqueous solution according to the charge density and ion dissociation degree of the cationic polymer.

[0112] The conditions for forming the cationic polymer layer can be adjusted appropriately; for example, the support membrane can be impregnated in an aqueous solution of the cationic polymer. There are no particular restrictions on the impregnation temperature; room temperature can be used to allow the cationic polymer to adsorb onto the support membrane surface via ion exchange and electrostatic bonding. The impregnation time can also be adjusted appropriately, for example, it can be set to more than 1 minute and less than 10 hours.

[0113] After forming a cationic polymer layer on the support film, the formation of any anionic polymer layer, betaine polymer layer and cationic polymer layer can be further carried out multiple times and layer by layer by the known layer-by-layer adsorption method (LbL method).

[0114] When the support membrane is immersed in an aqueous solution of a cationic polymer, it is assumed that the cationic polymer in the aqueous solution adsorbs onto the sulfonic acid / sulfate groups, which are anionic groups, present on the surface of the support membrane, through ion exchange reactions and electrostatic bonding. Therefore, after the cationic polymer layer is formed, the support membrane with the cationic polymer layer on its surface can be lifted out of the aqueous solution. The support membrane with the cationic polymer layer can be cleaned with water or dried.

[0115] The thickness of the cationic polymer layer can be appropriately adjusted, for example, it can be set to 1 nm or more and 100 nm or less. Preferably, this thickness is 5 nm or more, more preferably 10 nm or more, and further preferably 50 nm or less, more preferably 30 nm or less. It should be noted that the cationic polymer layer should be formed through ion exchange reaction and electrostatic bonding, and there is no particular need to confirm its formation. However, if necessary, the adsorption amount of the cationic polymer can be calculated based on the concentration difference of the cationic polymer in the aqueous solution before and after immersing the support membrane in the cationic polymer aqueous solution.

[0116] 4. Crosslinking process of cationic polymers

[0117] In this process, the cationic polymer in the cationic polymer layer formed on the support film is cross-linked, thereby making the cationic polymer insoluble. Furthermore, the cationic polymer layer is fixed to the support film. Figure 1 ).

[0118] There are no particular restrictions on the crosslinking agents used to crosslink cationic polymers, as long as they can react with two or more active groups of cationic polymers, such as amino and hydroxyl groups, to achieve intramolecular or intermolecular crosslinking. Examples include aldehyde-type crosslinking agents such as glutaraldehyde, formaldehyde, glyoxal, and succinaldehyde; epoxy-type crosslinking agents with two or more epoxy groups; and N-hydroxymethyl-type crosslinking agents such as dihydroxymethylurea, trihydroxymethyl melamine, dihydroxymethyl ethyl urea, hexahydroxymethyl melamine, and dihydroxymethyl propylene urea. Glutaraldehyde is a suitable candidate for crosslinking.

[0119] The crosslinking conditions for cationic polymers can be adjusted appropriately. For example, a composite membrane consisting of a support membrane and a cationic polymer layer can be impregnated in a crosslinking agent solution. The solvent for the crosslinking agent solution can be selected appropriately depending on the crosslinking agent used; for example, water can be used. The concentration of the crosslinking agent solution can be adjusted appropriately, for example, it can be set to 0.1% by mass or more and 10% by mass or less. There are no particular restrictions on the impregnation temperature; it can be adjusted appropriately depending on the crosslinking agent used, for example, within a range of 20°C or higher and below the boiling point of the solvent. Alternatively, crosslinking can be carried out under reflux conditions with the solvent. The crosslinking time can also be adjusted appropriately, for example, it can be set to 30 minutes or more and 50 hours or less.

[0120] It should be noted that step 4, namely the crosslinking of the cationic polymer, can be performed after step 3, which describes the formation of the functional separation layer, or simultaneously with step 3. When performing steps 3 and 4 simultaneously, the crosslinking agent is mixed into the cationic polymer aqueous solution described in step 3, and the reaction temperature and reaction time are adjusted to ensure that the formation and crosslinking of the cationic polymer layer on the support membrane occur simultaneously. Alternatively, a rinsing process using pure water or the like can be inserted between step 3 and step 4.

[0121] 5. The process of introducing polar groups

[0122] In this process, in addition to sulfonic acid / sulfuric acid groups, polar groups are further introduced into the sulfonated modified PPO in the support film. Simply sulfonating PPO is insufficient to introduce sulfonic acid / sulfuric acid groups to a degree that sufficiently improves the solvent resistance of PPO. Therefore, according to the present invention, by further introducing polar groups on top of the sulfonic acid / sulfuric acid groups, the overall solvent resistance of PPO can be further improved. Figure 1 ).

[0123] Step 5 can be performed after step 2, which introduces sulfonic acid / sulfuric acid groups. That is, by introducing polar groups after sulfonating PPO in the support film, the solvent resistance of PPO can be improved without hindering the introduction of sulfonic acid / sulfuric acid groups.

[0124] In addition, this step 5 can be performed not only after the crosslinking step 4 of the cationic polymer, but also between the sulfonic acid / sulfuric acid group introduction step 2 and the separation functional layer formation step 3, or between the separation functional layer formation step 3 and the cationic polymer crosslinking step 4. That is, a cationic polymer layer can be formed on the support membrane after introducing polar groups in addition to sulfonic acid / sulfuric acid groups; or a hydrophilic group can be introduced into the support membrane after forming a cationic polymer layer on the sulfonated support membrane to further crosslink the cationic polymer; or a polar group can be introduced into the support membrane after crosslinking the cationic polymer layer on the support membrane.

[0125] Polar groups are those that possess a lone pair of electrons or are polarized within the group, thus imparting insolubility and resistance to nonpolar and low-polarity organic solvents. As polar groups, there are no particular restrictions on any group that possesses this effect, except for sulfonic acid and sulfate groups. Examples include: monovalent polar groups such as hydroxyl, -NH2, and carboxyl groups; ether groups (-O-), thioether groups (-S-), sulfinyl groups (-S(=O)-), sulfonyl groups (-S(=O)2-), carbonyl groups, and -NR groups. 9 - (where R is in the formula) 9 Indicates H or C 1-6 Alkyl groups, or other divalent polar groups, preferably selected from hydroxyl, ether, sulfonyl, and -NR groups. 9 - One or more polar groups are included. For example, a monovalent polar group can be covalently bonded to the unit structure of the modified polyphenylene ether directly or indirectly via a linking group, and a divalent polar group can crosslink two unit structures within a molecule of the modified polyphenylene ether, either alone or via a linking group described later, or crosslink two molecules in between. It should be noted that, for convenience, sulfonic acid groups / sulfuric acid groups are not included in the polar groups in this disclosure.

[0126] Polar groups and sulfonic acid / sulfate groups can be bonded to the benzene ring of PPO via linking groups. Linking groups increase the steric freedom of polar groups or facilitate the introduction of polar groups into PPO. There are no particular limitations on the linking group as long as it performs the above-mentioned effects; for example, C... 1-6 Alkylene, divalent C 6-12 Aromatic hydrocarbon groups, ester groups (-OC (=O)- or -C (=O)-O-), amide groups (-NH-C (=O)- or -C (=O)-NH-), urea groups (-NH-C (=O)-NH-), thiourea groups (-NH-C (=S)-NH-), and groups formed by linking two or more but less than five of these groups.

[0127] Polar groups can be introduced into modified PPO using conventional methods. For example, for modified PPO containing halomethyl groups, it is preferable to introduce polar groups by immersing the modified PPO in a solution containing a nucleophile containing polar groups, thereby using the nucleophile to replace the halogen at the unsulfonated residual benzyl position in the support film, thus imparting resistance to organic solvents. Examples of nucleophiles for introducing polar groups include amines, phenolates, and sulfinates. As amines, monofunctional amines, difunctional amines, polyfunctional amines, etc., can be used. Preferably, from the viewpoint of sufficient penetration into the interior of the film and improved resistance to organic solvents, monofunctional amines with small molecular weights are preferred, and monoethanolamines represented by the following formula (IV) are preferred.

[0128] [Chemical Formula 6]

[0129]

[0130] [In the formula, R] 21 Indicates H or C 1-6 alkyl.]

[0131] For example, modified PPO with halomethyl groups reacts with monoethanolamine (IV) as shown in the following formula. This polymer structure is rich in hydrogen bonds, thus exhibiting excellent hydrophilicity and extremely high resistance to organic solvents. Furthermore, it also demonstrates good resistance under acidic and alkaline conditions.

[0132] [Chemical Formula 7]

[0133]

[0134] As a phenolate, the preferred option is a substance that, for difunctional or trifunctional phenols, converts the phenolic hydroxyl groups into highly nucleophilic phenolate ions in an organic solvent with added alkali, thereby inducing substitution and cross-linking reactions at the benzyl group. The phenol can be selected from resorcinol, hydroquinone, phloroglucinol, bisphenols, etc. From the viewpoint of improving permeability to the membrane interior and the reactivity of cross-linking, hydroquinone and phloroglucinol are particularly preferred. As a alkali, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as potassium carbonate are preferred. Since phenols are easily oxidized in air, the reaction is preferably carried out in an inert gas such as nitrogen or argon. For example, when using hydroquinone, a cross-linking structure as shown in the following formula can be formed between the benzene groups of modified PPO. This structure exhibits excellent resistance to acid and alkali conditions. It should be noted that cross-linking is considered to be mainly intermolecular cross-linking, but intramolecular cross-linking is also possible.

[0135] [Chemical Formula 8]

[0136]

[0137] Sodium hydroxymethanesulfinate is preferred as the sulfinate. It is known that hydroxymethanesulfinate reacts to form sulfone bonds while releasing formaldehyde between two benzyl halogenated compounds. Specifically, as shown in the following reaction formula, a membrane structure resistant to organic solvents can be obtained by crosslinking the benzyl groups of modified PPO through sulfone bonds. Since sulfone bonds are electron-withdrawing functional groups, the electron density of the main chain benzene ring of the PPO membrane highly crosslinked with sulfinate is significantly reduced. As a result, in addition to resistance to acid and alkali conditions, it is expected to improve resistance to oxidizing conditions such as free radicals. It should be noted that crosslinking is considered to be mainly intermolecular crosslinking, but intramolecular crosslinking is also possible.

[0138] [Chemical Formula 9]

[0139]

[0140] The concentration of the nucleophile in the reaction of the aforementioned amine, phenolate, or sulfinate with the modified PPO support membrane can be appropriately adjusted, for example, set to 1% by mass or more and 10% by mass or less. Regarding the solvent, from the viewpoint of maximizing reaction efficiency and ensuring good permeability into the membrane bulk, it is preferable to choose an organic solvent other than water that does not dissolve the modified PPO. For example, alcoholic solvents such as methanol and ethanol; nitrile solvents such as acetonitrile; sulfoxide solvents such as dimethyl sulfoxide; and mixtures thereof can be used. Reaction conditions such as reaction temperature and reaction time can be appropriately set based on the reactivity of the nucleophile.

[0141] The composite separation membrane of the present invention is characterized in that it is an asymmetric membrane with an asymmetric structure, the asymmetric structure having a support membrane comprising a modified polyphenylene ether and a separation functional layer comprising a crosslinked cationic polymer, wherein the modified polyphenylene ether has sulfonic acid groups / sulfuric acid groups and polar groups, and the separation functional layer is formed on the support membrane.

[0142] The composite separation membrane of this invention exhibits high separation performance, particularly through its separation functional layer, for microorganisms, insoluble particles, insoluble substances such as polymers, larger solutes such as amino acids, monovalent ions, polyvalent ions, cations, anions, and neutral substances. The pore size and porosity of the composite separation membrane can be adjusted according to the substances to be separated, and can be adjusted by factors such as the concentration of the PPO solution, the amount of PPO solution coated on the substrate, the unit area weight of the substrate, the pore size of the substrate, and the amount of pore-forming agent.

[0143] To separate the target substance from the treated liquid, the treated liquid is passed through the composite separation membrane of the present invention. In addition to sulfonic acid / sulfuric acid groups, the composite separation membrane of the present invention also has polar groups, thus exhibiting excellent resistance to organic solvents and can also be used for treating liquids containing organic solvents. Therefore, it is suitable for use as a liquid treatment membrane, a gas treatment membrane, etc., and particularly suitable for use as a precision filtration membrane, ultrafiltration membrane, nanofiltration membrane, osmosis membrane, reverse osmosis membrane, gas separation membrane, etc.

[0144] The composite separation membrane of this invention exhibits excellent resistance to organic solvents, thus enabling the treatment of liquids containing organic solvents. There are no particular limitations on the organic solvents that can be contained in the liquid being treated; examples include: alcohol solvents such as methanol, ethanol, 2-propanol, cyclohexanol, and propylene glycol monoethyl ether; polyol solvents such as ethylene glycol, propylene glycol, and glycerol; ether solvents such as diethyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane, and diethylene glycol dimethyl ether; organic acid solvents such as formic acid and acetic acid; nitrile solvents such as acetonitrile; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate and ethyl lactate; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aromatic hydrocarbon solvents such as benzene, toluene, and chlorobenzene; halogenated hydrocarbon solvents such as dichloroethane, chloroform, and carbon tetrachloride; amide solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and sulfoxide solvents such as dimethyl sulfoxide.

[0145] This application claims the benefit of priority based on Japanese Patent Application No. 2024-000080, filed January 4, 2024. The entire contents of the description of Japanese Patent Application No. 2024-000080, filed January 4, 2024, are incorporated herein by reference.

[0146] [Example]

[0147] The present invention will be described in more detail below with examples, but the present invention is of course not limited to the following examples. It can also be implemented by appropriate modifications within the scope of the above and following spirit, and these are all included in the technical scope of the present invention.

[0148] Example 1

[0149] (1) Synthesis of brominated polyphenylene ether

[0150] [Chemical Formula 10]

[0151]

[0152] 40 g of poly(2,6-dimethyl-1,4-phenylene ether) (manufactured by Sigma Aldrich, “181781”) was packed into a 500 mL four-necked flask equipped with a reflux tube, nitrogen inlet, and stirrer blades. 240 mL of chlorobenzene was added, and the solution was dissolved under nitrogen purging. When a homogeneous and transparent solution was obtained, 107 g of N-bromosuccinimide and 2.0 g of azobisisobutyronitrile (AIB) as a free radical initiator were added. Under vigorous stirring, the temperature of the reaction solution was raised to 120 °C using an oil bath while monitoring the heating rate. The reaction was carried out at 120 °C for 6.5 hours. After cooling the reaction solution, 2 L of methanol was added, and the precipitated flake polymer was finely pulverized using a mixer. The polymer was then thoroughly washed while continuously replenishing the methanol. Finally, the polymer was vacuum dried at 60 °C to obtain powdered brominated polyphenylene ether (BrPPO).

[0153] NMR analysis of the obtained BrPPO showed that the degree of bromination at the benzyl position was 1.46 and the degree of bromination at the benzene ring was 0.22.

[0154] (2) Fabrication of BrPPO membrane

[0155] [Chemical Formula 11]

[0156]

[0157] N-methyl-2-pyrrolidone and polyethylene glycol (PEG400) with a molecular weight of 400 were added to BrPPO and mixed and dissolved at 60°C for 6 hours to prepare a film-forming stock solution with a BrPPO concentration of 30% by mass.

[0158] The obtained film-forming solution was degassed under reduced pressure and then coated onto a 300 mm wide and 120 μm thick polyphenylene sulfide (PPS) nonwoven fabric using a doctor blade. The film was then solidified in a water bath at 25°C for 10 minutes. After thorough washing with water, the solidified membrane was air-dried to obtain the BrPPO membrane. The membrane was then cut into circles with a diameter of 48 mm.

[0159] The resulting membrane was immersed in a 13% (w / w) sodium sulfite aqueous solution at 98°C for 30 minutes. After the reaction was complete, the membrane was thoroughly washed with water. Hereinafter, the membrane in this state will be referred to as supported membrane A.

[0160] The elemental composition of the membrane surface was evaluated using XPS, and the sulfur ratio was found to be 1.6%.

[0161] (3) Formation of the separated functional layer

[0162] A cationic polyvinyl alcohol (CPVA) having the following structural units was synthesized by completely saponifying a copolymer of diallyl dimethylammonium chloride and vinyl acetate. The weight-average molecular weight of CPVA was 64,000, and the molar fraction of the cationic monomer was 1.5 mol%.

[0163] [Chemical Formula 12]

[0164]

[0165] CPVA was dissolved in pure water to prepare an aqueous solution with a concentration of 1000 mg / L. This solution was then brought into contact with the outer surface of the supporting membrane A at room temperature for 20 minutes to form a CPVA adsorption layer. Next, the supporting membrane A was immersed in a 1% (w / w) glutaraldehyde aqueous solution, and the CPVA adsorption layer was crosslinked at 80°C for 24 hours. Finally, the resulting membrane was thoroughly washed with water to obtain composite membrane B.

[0166] (4) Introduction of polar groups

[0167] Composite membrane B was immersed in a 3 vol% methanol solution of monoethanolamine (MEA) at room temperature for 24 hours, replacing the remaining unsulfonated benzyl bromine in the supporting membrane A with MEA. After the reaction was completed, the resulting membrane was washed with methanol to obtain composite membrane C.

[0168] It should be noted that, in order to confirm the introduction of the polar group MEA, MEA was introduced into the sulfonated support film A, which had not formed a separation functional layer, under the same conditions to create a support film with introduced MEA.

[0169] Example 2

[0170] In Example 1 (2), the sulfonation reaction time was changed from 30 minutes to 5 minutes. Otherwise, the operation was the same as in Example 1, and support film A, composite film B, and composite film C were obtained. The sulfur ratio of support film A was 1.1%, which was slightly reduced due to the reduction in sulfonation reaction time.

[0171] Example 3

[0172] In Example 1 (2), 0.15 M of tetrabutylammonium bromide (TBAB) was added to a 10% by mass sodium sulfite aqueous solution, and the reaction temperature was changed from 98°C to 80°C. Otherwise, the same procedure as in Example 1 was followed to obtain support film A, composite film B, and composite film C. The sulfur ratio of support film A was 4.3%, and the sulfonation efficiency was improved by using a phase transfer catalyst.

[0173] Example 4

[0174] In Example 1 (4), a 2% by mass acetonitrile / dimethyl sulfoxide mixed solution of hydroquinone (HQ) was used instead of a 3% by mass methanol solution of MEA as a nucleophile, and potassium carbonate in an equimolar amount relative to the phenolic hydroxyl group of HQ was added. The composite membrane B was immersed at 60°C for 24 hours under a nitrogen atmosphere. Otherwise, the operation was the same as in Example 1, and support membrane A, composite membrane B and composite membrane C were obtained.

[0175] Example 5

[0176] In Example 1 (4), a 2% by mass acetonitrile / dimethyl sulfoxide mixed solution of phloroglucinol (PG) was used instead of a 3% by mass methanol solution of MEA as a nucleophile, and potassium carbonate was added in an equimolar amount relative to the phenolic hydroxyl group of PG. The composite membrane B was immersed at 60°C for 24 hours under a nitrogen atmosphere. Otherwise, the operation was the same as in Example 1, and support membrane A, composite membrane B and composite membrane C were obtained.

[0177] Example 6

[0178] In Example 1 (4), a 2% by mass methanol solution and a dimethyl sulfoxide solution of sodium hydroxymethanesulfinate (HMS-Na) were used as nucleophiles instead of a 3% by mass methanol solution of MEA. The composite membrane was immersed in the methanol solution and the dimethyl sulfoxide solution for 12 hours each at 40°C. Otherwise, the operation was the same as in Example 1, and a composite membrane C was obtained by cross-linking the benzyl groups of the support membrane A, the composite membrane B and the BrPPO membrane through sulfonyl groups (-SO2-).

[0179] Example 7

[0180] In Example 1 (3), polyethyleneimine (PEI, "EPOMIN (registered trademark) P-1000", manufactured by Nippon Shokubai Co., Ltd., molecular weight: 70,000) was used as a cationic polymer. An aqueous solution was prepared in 0.5M NaCl aqueous solution to make the PEI concentration 1000 mg / L. After pH adjustment, it was brought into contact with the surface of support film A for 20 minutes and then crosslinked by immersion in 0.3% by mass GA aqueous solution at room temperature for 1 hour. Otherwise, the operation was the same as in Example 1 to obtain support film A, composite film B and composite film C.

[0181] Example 8

[0182] In Example 1 (3), polyallylamine (PAA, “PAA-HCl-10L” manufactured by NITTOBO MEDICAL, molecular weight: 100,000) was used as a cationic polymer. An aqueous solution was prepared in 0.5M NaCl aqueous solution to make the PAA concentration 1000 mg / L. After pH adjustment, it was brought into contact with the surface of support film A for 20 minutes and then crosslinked by immersion in 0.3% by mass GA aqueous solution at room temperature for 1 hour. Otherwise, the operation was the same as in Example 1 to obtain support film A, composite film B and composite film C.

[0183] Comparative Example 1

[0184] The sulfonation of the support membrane of Example 1 (2) was not carried out. Otherwise, the same operation was performed to try to make composite membranes B and C.

[0185] Comparative Example 2

[0186] Composite membrane B was prepared by operating in the same manner as in Examples 1 (1) to (3).

[0187] Experimental Example 1: Elemental Composition

[0188] The elemental composition of the BrPPO film of Example 1, the sulfonated support film A, and the support film without a separation functional layer but which underwent sulfonation and MEA introduction were analyzed by X-ray photoelectron spectroscopy (XPS). The apparatus and measurement conditions used in the XPS analysis are described below.

[0189] Device: K-Alpha+ (Thermo Fisher Scientific)

[0190] Excitation of X-rays: Monochromatic Al Kα rays

[0191] X-ray output power: 12kV, 2.5mA

[0192] Photoelectron escape angle: 90°

[0193] Spot size: approximately 200 μm φ

[0194] Energy: 50eV

[0195] Step size: 0.1eV

[0196] The analytical results, along with the calculated elemental composition of the BrPPO membrane, are presented in Table 1. It should be noted that these calculated values ​​are based on the NMR analysis results of the BrPPO membrane, showing a degree of bromination of 1.46 at the benzyl site and 0.22 at the benzene ring.

[0197] [Table 1]

[0198]

[0199] As shown in Table 1, after sulfonation with sodium sulfite, the ratio of bromine decreased slightly, while the ratio of sulfur, sodium, and oxygen increased, suggesting the introduction of sulfonic acid groups.

[0200] Furthermore, after immersing the sulfonated support membrane A in a strongly alkaline MEA / methanol solution for 24 hours, XPS analysis showed a significant decrease in the bromine ratio and an increase in the nitrogen content from the MEA. The sulfur ratio remained almost unchanged, suggesting that the sulfonic acid groups were introduced into the MEA without being removed and were almost entirely maintained.

[0201] Furthermore, the relationship between reaction temperature and sulfur and bromine elemental ratios is shown when the reaction time is fixed at 30 minutes and with and without a phase transfer catalyst (TBAB). Figure 2 (1) and Figure 2 (2) The relationship between reaction time and sulfur fraction (left axis) and bromine fraction (right axis) with the reaction temperature fixed at 98°C and without the use of a phase transfer catalyst (TBAB) is shown in the figure. Figure 2 (3).

[0202] like Figure 2 As shown in (1) and (2), it is clear that the use of a phase transfer catalyst promotes the substitution reaction of the bromo group of bromomethyl group to the sulfonic acid group. Furthermore, according to... Figure 2 (3) It can be seen that as the reaction proceeds, the bromine group is replaced by the sulfonic acid group.

[0203] Experimental Example 2: Infrared Absorption Spectroscopy Analysis

[0204] Infrared absorption spectroscopy under the following conditions was used to analyze BrPPO membranes with bromomethyl groups, sulfonated support membrane A, and support membranes that had not formed a separation functional layer but had undergone sulfonation and MEA introduction. The results are presented below. Figure 3 .

[0205] Device: “Cary670FTIR”, manufactured by Agilent Technologies

[0206] Accessory: "Single-reflective GeATR accessory Foundation Thunder Dome" manufactured by Spectra-Tech.

[0207] Angle of incidence: 45°

[0208] Resolution: 4cm -1

[0209] Total number of times: 64

[0210] like Figure 3 As shown in (1), in the support membrane in which MEA was introduced, at 2800–3000 cm⁻¹ -1 and 3400cm -1 Peaks were detected nearby. These peaks are believed to originate from the methylene and hydroxyl groups of MEA, respectively.

[0211] In addition, such as Figure 3 As shown in (2), a peak originating from -SO3H was identified in support film A, compared to the BrPPO film. Shoulder peaks, also believed to originate from -SO3H, were also identified in the sulfonated MEA-introduced support film. Peaks attributed to the CN bonds of MEA were also found to be repetitive.

[0212] Test Example 3: Organic Solvent Resistance Test

[0213] The sulfonated BrPPO membrane of Example 1 (2) and the composite membrane C of Example 1 (4) were cut into 1 cm squares and immersed in water or various organic solvents shown in Table 2 for 24 hours at room temperature or heated to 100°C on a hot plate to evaluate the solvent resistance of the membranes. For solvents with a boiling point less than 100°C, the evaluation was performed at a temperature 10°C lower than the boiling point. The results are shown in Table 2. In the table, "NS" indicates completely insoluble, "PS" indicates soluble at high temperature, and "GS" indicates soluble at room temperature.

[0214] [Table 2]

[0215]

[0216] As shown in Table 2, the polyphenylene ether film with bromomethyl groups is insoluble in highly polar organic solvents, but it dissolves at room temperature in three organic solvents with similar Hansen solubility parameters, such as toluene and chlorobenzene.

[0217] In contrast, the composite film C of the present invention, which has a layer of cross-linked cationic polymer and polar groups, showed insolubility in all the solvents tested.

[0218] Therefore, it is clear that the composite film of the present invention exhibits sufficient durability against organic solvents.

[0219] Experimental Example 4: Separation Experiment of Water System Using Sulfonated BrPPO Membrane (Support Membrane A)

[0220] The separation performance of each supporting membrane A after being fully wetted with water and the composite membrane B before the introduction of polar groups in an aqueous system was evaluated using a cross-flow flat membrane evaluation device comprising a stainless steel pressure vessel, a water supply tank and a pump.

[0221] The permeability of pure water is determined by L. pIndicates. L p The permeation test of the membrane sample was conducted using pure water at a pressure of 15 bar, and the following formula was used to calculate the result.

[0222] L p [L / (m)] 2 [·h·bar)] = Permeate pure water volume [L] / (Membrane area [m²]) 2 [×Sampling time [h]×Measurement pressure [bar]]

[0223] Regarding the rejection rate of sodium chloride (NaCl), an aqueous solution with a concentration of 1500 mg / L was prepared and supplied at a temperature of 25°C and a pressure of 15 bar for 1 hour. The conductivity of the permeate water and the supply water was measured using a conductivity meter ("CM-25R" manufactured by DKK-TOA). The conductivity was calculated using the following formula.

[0224] NaCl rejection rate [%] = (1 - permeate water conductivity [μS / cm] / supply aqueous solution conductivity [μS / m]) × 100

[0225] The neutral molecular rejection rate of the aqueous system was evaluated using sucrose (manufactured by NACALAI TESQUE, molecular weight 342.3). A 200 mg / L sucrose aqueous solution was supplied to the aforementioned cross-flow flat membrane evaluation device at 25°C and 15 bar for 1 hour. Permeate water from the membrane was then collected, and the concentrations of the feed solution and permeate were determined using an ON-LINE TOC-VCSH analyzer (manufactured by Shimadzu Corporation). The sucrose rejection rate was calculated using the following formula.

[0226] Sucrose retention rate [%] = 100 × [1 - (permeate concentration) / (feed solution concentration)]

[0227] [Table 3]

[0228]

[0229] In Table 3, the support membrane of Comparative Example 1 was not sulfonated, and the data for support membrane A of Comparative Example 1 are for the unsulfonated support membrane. The unsulfonated support membrane had excellent pure water permeability, but it could not prevent the permeation of NaCl at all. Based on these experimental results, the sucrose rejection rate of the support membrane of Comparative Example 1 was not determined.

[0230] Furthermore, the composite membrane B of Comparative Example 1 exhibited very high pure water permeability, but it could barely prevent the permeation of NaCl and sucrose. This was attributed to the lack of sulfonation of the supporting membrane, resulting in poor adhesion between the supporting membrane and the crosslinked cationic polymer, causing the crosslinked cationic polymer to separate from the supporting membrane.

[0231] In contrast, the composite membrane B of Examples 1-8 exhibits excellent molecular retention capacity.

[0232] It should be noted that the reason for the high pure water permeability of composite membrane B in Examples 3, 7, and 8 is that: because a phase transfer catalyst was used to sulfonate the supporting membrane A in Example 3, a large number of sulfonic acid groups were introduced; and because cationic polymers without vinyl alcohol units were used in Examples 7 and 8, the composite membranes have high hydrophilicity. Correspondingly, the molecular rejection rate is relatively low.

[0233] The reason why the pure water permeability and molecular rejection rate of Comparative Example 2 are the same as those of the Example is that no polar groups, which are a feature of the present invention, were introduced at the time of composite membrane B.

[0234] Test Example 5: Permeability Test of Organic Solvent System for Composite Membranes

[0235] Acetonitrile, N-methyl-2-pyrrolidone, and toluene were used as organic solvents. Membrane samples fully wetted with each organic solvent were loaded into stainless steel pressure-resistant containers sealed with FFKM sealing material. The organic solvents were transferred from 500 mL HPLC screw-top vials to the pressure-resistant containers using an HPLC preparative pump for permeability evaluation. Initially, each pure solvent was supplied at a pressure of 15 bar, and the permeability L was calculated using the following formula. p .

[0236] L p [L / (m)] 2 [·h·bar)] = Permeate flow rate [L] / Membrane area [m²] 2 [Sampling time [h] / Measurement pressure [bar]]

[0237] As a marker for separation tests in organic solvent systems, polypropylene glycol (PPG1000) with a molecular weight of 1000 (Fujifilm Kazuko) was used. A 400 mg / L PPG1000 solution was supplied at 25°C and 15 bar. After stabilization for 6 hours, the permeate from the membrane was collected. Peak analysis of PPG1000 in both the supply and permeate was performed using high-performance liquid chromatography (HPLC) equipped with a Corona electrofogging detector. The rejection rate of PPG1000 was determined based on the area ratio of the molecular weight components at the peaks before and after permeation. For sample solutions used in separation tests with toluene as solvent, the toluene was completely evaporated once, an equal volume of ethanol was added, and the mixture was stirred thoroughly before HPLC evaluation.

[0238] Retention rate [%] = 100 × [1 - (peak area of ​​molecular weight component at the peak of the permeate) / (peak area of ​​molecular weight component at the peak of the supply solution)]

[0239] The HPLC determination conditions are shown below.

[0240] Device: Thermo Fisher Scientific Vanquish

[0241] Column: Waters BEH C18 2.1×150mm

[0242] Mobile phase: A. Ultrapure water, B. Acetonitrile

[0243] 0~15min - 5%B in A

[0244] 15–20 min - 60% B in A

[0245] 20-25 min - 100% B

[0246] Flow rate: 0.25 mL / min

[0247] Column temperature: 40℃

[0248] Injection volume: 5μL

[0249] Detection: Electro-fog detector (CAD)

[0250] Drying tube temperature: 35℃

[0251] [Table 4]

[0252]

[0253] As shown in Table 4, the molecular retention capacity of the composite separation membrane in Comparative Example 1 was insufficient. This was attributed to the fact that the supporting membrane was not sulfonated, resulting in the failure to adsorb cationic polymers and the inadequate formation of the separation functional layer. In other words, the membrane in Comparative Example 1 was essentially equivalent to a solvent-resistant supporting membrane of modified PPO. Due to the monoethanolamine, the membrane became highly polar, thus enabling filtration in organic solvents, albeit insufficiently, but exhibiting separation performance.

[0254] The composite membrane B of Comparative Example 2, which did not have polar groups introduced, swelled or dissolved in the three organic solvents tested, thus indicating that it did not function as a separation membrane at all in organic solvent systems.

[0255] In contrast, according to the present invention, on the support membrane A of the embodiment in which sulfonic acid groups are introduced via methylene to polyphenylene ether, a cationic polymer layer that functions as a separation functional layer can be effectively formed, and it exhibits high insolubility in organic solvents, thus showing excellent separation performance in both aqueous and organic solvent systems.

Claims

1. A composite separation membrane, characterized in that, It has a support membrane containing modified polyphenylene ether and a separation functional layer containing a crosslinked cationic polymer. The modified polyphenylene ether has sulfonic acid groups and / or sulfate groups, as well as polar groups. The separation functional layer is formed on the support membrane.

2. The composite separation membrane according to claim 1, wherein, The sulfonic acid group and / or the sulfuric acid group, as well as the polar group, are introduced into the benzene ring of the modified polyphenylene ether via a linking group.

3. The composite separation membrane according to claim 2, wherein, The modified polyphenylene ether has a sulfonyl group on its benzene ring.

4. The composite separation membrane according to claim 1, wherein, The polar group is selected from one or more polar groups selected from hydroxyl, ether, sulfonyl and amino.

5. The composite separation membrane according to claim 1, wherein, The cationic polymer is a cationic polyvinyl alcohol copolymer containing structural units having quaternary ammonium cationic groups.

6. The composite separation membrane according to claim 1, wherein, The cationic polymer is one or more polyamines selected from polyethyleneimine, polyethyleneamine, and polyallylamine.

7. A method for manufacturing a composite separation membrane, characterized in that, include: The process of obtaining a support film using polyphenylene ether; The process of introducing sulfonic acid groups and / or sulfuric acid groups into the support film by contacting the support film with a sulfonating agent; The process of contacting the support membrane incorporating the sulfonic acid groups and / or the sulfuric acid groups with an aqueous solution containing a cationic polymer to form a cationic polymer layer on the support membrane; The process of crosslinking the cationic polymer in the cationic polymer layer; and The process of introducing polar groups into the polyphenylene ether in the support film.

8. The method according to claim 7, wherein, The sulfonic acid group is introduced onto the halogenated methyl group by contacting a support film containing a polyphenylene ether with a halogenated methyl group introduced onto the phenyl ring with an aqueous solution containing sulfite as the sulfonating agent.

9. The method according to claim 7, wherein, The polar group is introduced by reacting the polyphenylene ether with a halomethyl group introduced onto the benzene ring with a monoethanolamine of formula (IV). In the formula, R 21 Indicates H or C 1-6 alkyl.

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