JP2019147879A - Surface-modified porous film - Google Patents

Abstract

To provide a surface-modified porous film having a strong hydrophilic coating layer formed by a simple operation and having fouling resistance imparted thereto and to provide a method for producing the surface-modified porous film.SOLUTION: In one or more embodiments, the present invention relates to a surface-modified porous film which comprises: a porous film composed of a modacrylic copolymer including a constitutional unit derived from an acrylonitrile, a constitutional unit derived from a halogen-containing monomer and a constitutional unit derived from a vinyl monomer having an ionic substituent; and a coating layer composed of an amphoteric ion-containing copolymer produced by copolymerizing a monomer having an ionic substituent included in the modacrylic copolymer and an ion group having an opposite charge with a monomer having an amphoteric ion group and which has the porous film and the coating layer bonded through an ionic bond. In one or more embodiments of the present invention, the surface-modified porous film is produced by immersing a porous film composed of a modacrylic copolymer in an aqueous solution of an amphoteric ion-containing copolymer.SELECTED DRAWING: None

Description

  The present invention relates to a surface-modified porous membrane that can be used for liquid treatment such as water treatment and a method for producing the same, and more particularly to a surface-modified porous membrane having a hydrophilic coating layer and a method for producing the same.

  Many water treatment methods for removing impurities contained in river water and industrial water have been developed. The membrane filtration method which is one of these methods is used in many fields such as a cartridge for a water purifier and a membrane unit for waste water treatment. Various types of filter media used in the membrane filtration method have been developed, such as ceramics, inorganics, and polymers. Among them, the polymer-based porous film has features such that a film having a stable quality can be continuously produced in large quantities and the pore diameter of the film can be controlled relatively freely by adjusting the film forming conditions.

  For polymer-based porous membranes, it is required to improve properties such as membrane strength, water permeation rate, rejection rate of components to be filtered, and fouling resistance. Among them, the fouling resistance is a particularly important factor for determining the performance of the porous membrane. When the membrane is fouled by contaminants, the flow rate is reduced and the initial performance cannot be maintained. Further, when fouling progresses, it is necessary to stop the operation and perform cleaning in order to recover the performance, leading to an increase in operation cost.

  One of the important factors determining this fouling property is surface electrification. The presence of surface charges increases hydrophilicity and improves fouling resistance. On the other hand, a foulant having a charge distribution is adsorbed on the film surface by electrostatic attraction, so that a foulant having an opposite charge is not always a good result. As a solution to this problem, various techniques for introducing a charge-neutral hydrophilic substituent have been studied so far.

  For example, Patent Document 1 discloses a hydrophilic membrane in which polyvinyl alcohol is coated on the surface of a porous membrane made of polytetrafluoroethylene and crosslinked with glutaraldehyde.

  Patent Document 2 discloses a hydrophilic property in which a polyvinylidene fluoride film is coated with a vinyl copolymer of a monomer having a polyethylene glycol structure and a monomer having an azide structure and then irradiated with ultraviolet rays to nitrene-crosslink the coating layer. A membrane is disclosed.

JP 2017-80674 A International Publication No. 2017/170210

  In the techniques disclosed in Patent Documents 1 and 2, a hydrophilic film with improved fouling resistance can be obtained by applying a hydrophilic polymer coating to a hydrophobic fluorine-based porous film. However, in these methods, it is necessary to perform a crosslinking treatment in order to prevent the hydrophilic polymer coated on the porous membrane surface from falling off. For this reason, there existed a problem that a complicated crosslinking process was required after film forming. In addition, there is no direct interaction between the membrane and the coating layer.

  In order to solve the above-mentioned conventional problems, the present invention forms a strong hydrophilic coating layer on the surface of the porous film by a simple operation, and imparts anti-fouling resistance to the surface-modified porous film and a method for producing the same I will provide a.

  In one or more embodiments, the present invention is a surface-modified porous membrane comprising a porous membrane composed of a modacrylic copolymer and a coating layer disposed on the surface of the porous membrane, The modacrylic copolymer includes a structural unit derived from acrylonitrile, a structural unit derived from a halogen-containing monomer, and a structural unit derived from a vinyl monomer having an ionic substituent, and the coating layer is included in the modacrylic copolymer. And a zwitterion-containing copolymer obtained by copolymerization of a monomer having an ionic group opposite to the ionic substituent and the zwitterionic group, and the porous membrane and the coating layer are connected via an ionic bond. The present invention relates to a surface-modified porous membrane characterized by being bonded.

  The modacrylic copolymer is composed of 15 to 85 parts by mass of an acrylonitrile-derived structural unit, and vinyl halide and vinylidene halide when the total structural unit constituting the copolymer is 100 parts by mass. 14.5 parts by mass or more and 84.5 parts by mass or less of a structural unit derived from one or more halogen-containing monomers selected from the group, and 0.5 to 10 parts by mass of a structural unit derived from a vinyl monomer having an ionic substituent. It is preferable to contain not more than part by mass. The modacrylic copolymer is composed of 35 to 65 parts by mass of an acrylonitrile-derived structural unit when the total structural unit constituting the modacrylic copolymer is 100 parts by mass, vinyl halide and vinylidene halide. More preferably, the halogen-containing monomer selected from the group contains 34.5 parts by mass or more and 64.5 parts by mass or less, and the vinyl monomer-containing structural unit having an ionic substituent contains 0.5 parts by mass or more and 10 parts by mass or less. .

  The ionic substituent in the vinyl monomer having an ionic substituent constituting the modacrylic copolymer is preferably a strong electrolysis type substituent. The ionic substituent in the vinyl monomer having an ionic substituent constituting the modacrylic copolymer is more preferably a sulfonic acid group.

  The halogen-containing monomer is preferably at least one selected from the group consisting of vinyl chloride and vinylidene chloride.

  The amphoteric ion-containing copolymer is a monomer having an ionic group having a charge opposite to that of the ionic substituent contained in the modacrylic copolymer when the total constitutional unit constituting the copolymer is 100 parts by mass. It is preferable to contain 20 parts by mass or more and 80 parts by mass or less of a monomer having a zwitterionic group in an amount of 20 parts by mass or more and 80 parts by mass or less.

  The monomer having an zwitterionic group is preferably at least one selected from the group consisting of a sulfobetaine monomer, a carboxybetaine monomer, and a phosphobetaine monomer.

  The ionic group having a charge opposite to that of the ionic substituent contained in the modacrylic copolymer is preferably a strong electrolysis type ionic group, more preferably an ammonium group.

  The porous membrane preferably has one shape selected from the group consisting of a hollow fiber shape, a flat membrane shape, a spiral shape, a pleated shape and a tubular shape.

  In one or more embodiments, the present invention provides a method for producing the above surface-modified porous membrane, wherein a modacrylic copolymer solution obtained by dissolving a modacrylic copolymer in a good solvent is used as a modacrylic copolymer. A step of obtaining a porous membrane by solidifying it in contact with a non-solvent, and immersing the porous membrane in an aqueous solution of an amphoteric ion-containing copolymer, and the porous membrane on the surface of the porous membrane Including a step of forming an ion-bonded coating layer, wherein the modacrylic copolymer includes a structural unit derived from acrylonitrile, a structural unit derived from a halogen-containing monomer, and a structural unit derived from a vinyl monomer having an ionic substituent, The zwitterion-containing copolymer includes a monomer having an ionic group having a charge opposite to that of the ionic substituent contained in the modacrylic copolymer, and a monomer having a zwitterionic group. The method for producing a surface modified porous membrane, which is a copolymer.

  According to one or more embodiments of the present invention, there is provided a surface-modified porous membrane imparted with fouling resistance by forming a strong hydrophilic coating layer on the surface of the porous membrane by a simple operation. In addition, according to the production method of one or more embodiments of the present invention, a surface-modified porous membrane having a strong hydrophilic coating layer formed on the surface of the porous membrane and imparting fouling resistance can be easily produced. can do.

FIG. 1 is a graph showing the relationship between the immersion time of the SBMA-MTAC copolymer (amphoteric ion-containing copolymer) of Production Example 1 in an aqueous solution and the adsorption amount of the SBMA-MTAC copolymer on the surface of the porous membrane. is there. FIG. 2 is a graph showing zeta potentials on the surface of the surface-modified porous membrane of Example 1 and the surface of the porous membrane of Reference Example 1. FIG. 3 is a confocal laser scanning micrograph in which the adhesion state of lysozyme to the porous surface was observed using FITC-lysozyme. (A) is a porous film of Reference Example 1, and (b) is Example 1. This is a result of the surface-modified porous membrane. FIG. 4 is a graph showing the relative fluorescence intensity analyzed by ImageJ after observing the adhesion state of lysozyme to the surface of the porous film using FITC-lysozyme using a confocal laser scanning microscope. FIG. 5 is a graph showing the relationship between the elapsed time and the flux when a 50 ppm lysozyme solution is passed through for 60 minutes. 6A and 6B are confocal laser scanning micrographs observing the surface of the surface-modified porous film, where FIG. 6A is the surface-modified porous film of Example 1, and FIG. 6B is the example after the ethanol solution treatment. (C) is the surface-modified porous membrane of Example 1 after the NaCl treatment, (d) is the surface-modified porous membrane of Example 1 after the NaOH aqueous solution treatment, (e ) Is the result of the surface-modified porous membrane of Example 1 after SDS treatment. FIG. 7 is a graph showing the relative fluorescence intensity obtained by observing the surface of the surface-modified porous film with a confocal laser scanning microscope and analyzing with ImageJ.

  The inventors diligently studied to easily form a strong hydrophilic coating layer and impart fouling resistance in a polymer-based porous film. As a result, a porous film is formed with a modacrylic copolymer including a structural unit derived from acrylonitrile, a structural unit derived from a halogen-containing monomer, and a structural unit derived from a vinyl monomer having an ionic substituent, and the modacrylic copolymer By forming a coating layer with a monomer having an ionic group opposite in charge to an ionic substituent contained therein and a zwitterion-containing copolymer obtained by copolymerization of a monomer having a zwitterionic group, the porous membrane and the above It has been found that the coating layer can be bonded through ionic bonds to easily form a strong hydrophilic coating layer and impart fouling resistance. Specifically, by immersing the porous membrane in an aqueous solution of the amphoteric ion-containing copolymer, a reinforced hydrophilic coating layer ion-bonded to the porous membrane can be easily formed on the surface of the porous membrane. It is formed.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to these embodiments.

  In one or more embodiments of the present invention, the “porous membrane” has a structure in which a plurality of micropores are connected to each other, and these micropores are connected to each other. It means a membrane through which gas or liquid can pass. In one or more embodiments of the present invention, the internal structure of the porous membrane can be confirmed by observing the cross section of the porous membrane with a scanning electron microscope.

  In one or more embodiments of the present invention, the porous membrane comprises a structural unit derived from acrylonitrile, a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl halide and vinylidene halide, and ions. It is composed of a modacrylic copolymer containing a structural unit derived from a vinyl monomer having a functional substituent. That is, in one or more embodiments of the present invention, the porous film is a copolymer of acrylonitrile, a halogen-containing monomer selected from the group consisting of vinyl halide and vinylidene halide, and a vinyl monomer having an ionic substituent. It is composed of a modified modacrylic copolymer. In the present specification, unless otherwise indicated, the halogen-containing monomer means one or more halogen-containing monomers selected from the group consisting of vinyl halides and vinylidene halides.

  In one or more embodiments of the present invention, when the modacrylic copolymer is 100 parts by mass of all structural units constituting the modacrylic copolymer, the acrylonitrile-derived structural unit is 15 parts by mass or more and 85 parts by mass. Hereinafter, from 14.5 parts by weight to 84.5 parts by weight of a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl halide and vinylidene halide, and derived from a vinyl monomer having an ionic substituent It is preferable that 0.5 mass part or more and 10 mass parts or less are included. The modacrylic copolymer is composed of 35 to 65 parts by mass of an acrylonitrile-derived structural unit when the total structural unit constituting the modacrylic copolymer is 100 parts by mass, vinyl halide and vinylidene halide. More preferably, the halogen-containing monomer selected from the group contains 34.5 parts by mass or more and 64.5 parts by mass or less, and the vinyl monomer-containing structural unit having an ionic substituent contains 0.5 parts by mass or more and 10 parts by mass or less. .

  In one or more embodiments of the present invention, the modacrylic copolymer has a structural unit derived from a vinyl monomer having an ionic substituent when the total structural unit constituting the modacrylic copolymer is 100 parts by mass. , Preferably 0.5 to 5 parts by mass, more preferably 0.5 to 3 parts by mass.

  In the modacrylic copolymer, if the content of the structural unit derived from acrylonitrile and the content of the structural unit derived from the halogen-containing monomer is within the above-described ranges, a film excellent in chemical resistance and fouling resistance can be obtained. . In the modacrylic copolymer, when the content of the vinyl monomer having an ionic substituent is in the above-described range, the ionic bond between the porous film and the coating layer is improved.

  The halogen-containing monomer is not particularly limited, and examples thereof include vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, vinyl iodide, and vinylidene iodide. These may be used alone or in combination of two or more.

  The vinyl monomer having an ionic substituent is not particularly limited, and vinyl monomers having various ionic substituents can be used. The ionic substituent may be an anionic substituent or a cationic substituent. Although it does not specifically limit as said anionic substituent, For example, a strong electrolysis type anionic substituent, a weak electrolysis type anionic substituent, etc. are mentioned. The strong electrolysis type anionic substituent is not particularly limited, and examples thereof include a sulfonic acid group. The weakly electrolytic anionic substituent is not particularly limited, and examples thereof include a carboxylic acid group and a phosphoric acid group. Although it does not specifically limit as said cationic substituent, For example, a strong electrolysis type cationic substituent, a weak electrolysis type cationic substituent, etc. are mentioned. Although it does not specifically limit as said strong electrolysis type cationic substituent, For example, onium groups, such as an ammonium group, a phosphonium group, and a sulfonium group, etc. are mentioned. The weakly electrolytic type anionic substituent is not particularly limited, and examples thereof include a primary to tertiary amino group, a pyridyl group, and an imino group.

  The vinyl monomer having a strong electrolysis type anionic substituent is not particularly limited, and examples thereof include allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid, and 2-methyl. -1,3, -butadiene-1-sulfonic acid and salts thereof.

  The weakly electrolytic vinyl monomer having an anionic substituent is not particularly limited, and examples thereof include carboxylic acid group-containing vinyl monomers such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, vinylphosphonic acid, (meth) Examples thereof include phosphoric acid group-containing vinyl monomers such as acryloyloxyalkyl (C1-4) phosphoric acid, and salts thereof. In this specification, (meth) acryloyl means methacryloyl and / or acryloyl.

  In the vinyl monomer having a strong electrolysis type anionic substituent and the vinyl monomer having a weak electrolysis type anionic substituent exemplified above, when the anionic substituent exists as a salt, these anionic substituents are completely It may be neutralized, or may be neutralized to any degree of neutralization. Examples of counter ions in these salts include ammonium ions, monoalkylammonium ions, dialkylammonium ions, trialkylammonium ions, hydroxyalkylammonium ions, alkali metal ions, alkaline earth metal ions, and the like. In the monoalkylammonium ion, dialkylammonium ion, trialkylammonium ion and hydroxyalkylammonium ion, the carbon number of the alkyl group is not particularly limited, but may be, for example, 1 to 6, and the alkyl group is, for example, A methyl group, an ethyl group, etc. are mentioned. Although it does not specifically limit as a trialkylammonium ion, For example, a trimethylammonium ion, a triethylammonium ion, etc. are mentioned.

  The strong electrolysis type vinyl monomer having a cationic substituent is not particularly limited. For example, vinyl compounds having an ammonium group such as trimethylvinylammonium and salts thereof, diallyl such as dimethyldiallylammonium chloride and diethyldiallylammonium chloride. Examples include type quaternary ammonium and salts thereof.

  The weakly electrolytic vinyl monomer having a cationic substituent is not particularly limited, and examples thereof include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, and diisopropylaminoethyl. (Meth) acrylate, dibutylaminoethyl (meth) acrylate, diisobutylaminoethyl (meth) acrylate, di-t-butylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, dipropylamino Propyl (meth) acrylamide, diisopropylaminopropyl (meth) acrylamide, dibutylaminopropyl (meth) acrylamide, diisobutylaminopropyl ( And (meth) acrylic acid ester or (meth) acrylamide having a dialkylamino group such as acrylamide or di-t-butylaminopropyl (meth) acrylamide; styrene having a dialkylamino group such as dimethylaminostyrene or dimethylaminomethylstyrene; Examples thereof include vinylpyridines such as 2- or 4-vinylpyridine; N-vinyl heterocyclic compounds such as N-vinylimidazole and salts thereof. In the present specification, (meth) acrylate means methacrylate and / or acrylate, (meth) acrylamide means methacrylamide and / or acrylamide, and (meth) acrylic acid means methacrylic acid and / or Or it means acrylic acid.

  In the vinyl monomer having a strong electrolysis type cationic substituent and the vinyl monomer having a weak electrolysis type cationic substituent exemplified above, the cationic substituent may be completely neutralized, and any You may neutralize to the degree of neutralization. Counter ions in these salts include halide ions such as chloride ion and bromide ion, halogen oxoacid ions such as hypochlorite ion and chlorite ion, borate ion, carbonate ion, nitrate ion, phosphate Examples include ions, oxo acid ions such as sulfate ions and chromate ions, and various complex ions.

  In the vinyl monomer having an ionic substituent, from the viewpoint of ionic bonding, the ionic substituent is preferably a strong electrolysis type ionic substituent, and more preferably a sulfonic acid group. One vinyl monomer having the ionic substituent may be used alone, or two or more vinyl monomers may be used in combination.

  In addition to the above monomers, the modacrylic copolymer may be appropriately copolymerized with one or more other monomers as long as the effects of the present invention are not impaired. When all the structural units constituting the modacrylic copolymer are 100 parts by mass, the content of structural units derived from other monomers is preferably 20 parts by mass or less, more preferably 10 parts by mass or less.

  The modacrylic copolymer is not particularly limited, but the weight average molecular weight (also referred to as mass average molecular weight) measured by the GPC method is preferably 30,000 to 150,000, and more preferably 50,000 to 100,000. More preferred. If the molecular weight is too low, the strength of the resulting porous membrane may be reduced. On the other hand, if it is too high, the viscosity at the time of film formation becomes too high, and the processing may be difficult.

  The zwitterion-containing copolymer is a zwitterion-containing copolymer obtained by copolymerizing a monomer having an ionic group opposite to the ionic substituent contained in the modacrylic copolymer and a monomer having a zwitterionic group. It is configured. The amphoteric ion-containing copolymer has a structural unit derived from a monomer having an ionic group opposite in charge to the ionic substituent contained in the modacrylic copolymer, so that the porous membrane and the coating layer have an ionic bond. And a firm coating layer is easily formed. Moreover, since the zwitterion-containing copolymer has a structural unit derived from a monomer having a zwitterionic group, a hydrophilic coating layer having a substantially neutral charge is formed, and the fouling resistance is improved.

  From the viewpoint of improving the ionic bond between the porous membrane and the coating layer, the zwitterion-containing copolymer has a content of 100 mass parts in all of the structural units constituting the copolymer. It is preferable to contain 10 parts by mass or more and 70 parts by mass or less of a monomer having an ionic group having a charge opposite to that of the ionic substituent, and 30 parts by mass or more and 90 parts by mass or less of a monomer having an zwitterionic group. More preferably, the monomer having an ionic group opposite to the ionic substituent contained in the modacrylic copolymer is 20 parts by mass or more and 50 parts by mass or less, and the monomer having an zwitterionic group is 50 parts by mass or more and 80 parts by mass. Contains up to parts.

  The monomer having a zwitterionic group is not particularly limited as long as it is a compound having a cationic group and an anionic group in the molecule. From the viewpoint of excellent hydrophilicity, for example, it is preferable to use one or more selected from the group consisting of a sulfobetaine monomer, a carboxybetaine monomer, and a phosphobetaine monomer. For example, a betaine monomer having a (meth) acryloyl group can be used. . As the betaine monomer having a (meth) acryloyl group, for example, a betaine monomer represented by the following general formula (1) can be used.

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a sulfobetaine group represented by the following general formula (2) or a carboxybetaine group represented by the general formula (3). Or it is a phosphobetaine group represented by General formula (4).

In the general formulas (2) to (4), R ³ and R ⁴ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, or carbon of an alkyl group. A (meth) acryloyloxyalkyl group having 1 to 4; a and b are each independently an integer of 1 to 8, preferably an integer of 2 to 6, more preferably 2 to 2; It is an integer of 4. In the general formula (4), R ⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group. As a C1-C4 hydroxyalkyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group etc. are mentioned, for example. Examples of the (meth) acryloyloxyalkyl group having 1 to 4 carbon atoms in the alkyl group include, for example, (meth) acryloyloxymethyl group, (meth) acryloyloxyethyl group, (meth) acryloyloxypropyl group, (meth) And acryloyloxybutyl group. R ³ , R ⁴ and R ⁵ are preferably each independently a methyl group.

  The sulfobetaine monomer having the (meth) acryloyl group is not particularly limited. For example, (2- (methacryloyloxy) ethyl) dimethyl- (3-sulfopropyl) ammonium, 3- (methacryloylamino) propyl] dimethyl ( 3-sulfopropyl) ammonium, 3-((3-acryloyloxymethyl) dimethylammonio) ethane-1-sulfonate, and the like.

  The carboxybetaine monomer having the (meth) acryloyl group is not particularly limited. For example, (2- (methacryloyloxy) ethyl) dimethyl- (3-carboxylatopropyl) ammonium, N- (methacryloyloxyethyl-N, N-methacryloyloxyethyl-N, N-dimethylammonium-α-N-methylcarboxybetaine, N-methacryloyloxyethyl-N, N-diethylammonium-α-N-methylcarboxybetaine and the like can be mentioned.

  The phosphobetaine monomer having the (meth) acryloyl group is not particularly limited, and examples thereof include 2-methacryloyloxyethyl phosphorylcholine, 2- (methacryloylyloxy) ethyl-2- (trimethylammonio) ethyl phosphate, and the like. .

  One of the monomers having the zwitterionic group may be used alone, or two or more may be used in combination.

  The monomer having an ionic group opposite in charge to the ionic substituent contained in the modacrylic copolymer (hereinafter, also referred to as “ionic monomer”) is not particularly limited. For example, a monomer having a cationic group It may be a monomer having an anionic group. Although it does not specifically limit as said cation group, For example, a strong electrolysis type cation group, a weak electrolysis type cation group, etc. are mentioned. The strong electrolysis type cationic group is not particularly limited, and examples thereof include an onium group such as an ammonium group, a phosphonium group, and a sulfonium group. The weakly electrolytic cation group is not particularly limited, and examples thereof include a primary to tertiary amino group, a pyridyl group, and an imino group. Although it does not specifically limit as said anion group, For example, a strong electrolysis type anion group, a weak electrolysis type anion group, etc. are mentioned. Although it does not specifically limit as said strong electrolysis type anion group, For example, a sulfonic acid group etc. are mentioned. The weakly electrolyzed anionic group is not particularly limited, and examples thereof include a carboxylic acid group and a phosphoric acid group.

  Specific examples of the ionic monomer include acrylic acid, methacrylic acid, itaconic acid, 3-vinylpropionic acid, vinylsulfonic acid, 2-sulfoethyl (meth) acrylate, 3-sulfopropyl (meth) acrylate, 2-acrylamide- 2-methylpropanesulfonic acid, styrenesulfonic acid, salts thereof; allylamine, 2-dimethylaminoethyl (meth) acrylate, salts thereof; 3-trimethylammoniumpropyl (meth) acrylate, 3-trimethylammoniumpropyl (meth) acrylamide N, N, N-trimethyl-N- (2-hydroxy-3-methacryloyloxypropyl) ammonium chloride, 2- (methacryloyloxy) ethyltrimethylammonium chloride (methacryloylcholine chloride), Methylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, diisopropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate, diisobutylaminoethyl (meth) acrylate, dit -Butylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, dipropylaminopropyl (meth) acrylamide, diisopropylaminopropyl (meth) acrylamide, dibutylaminopropyl (meth) acrylamide, diisobutyl Dialkylamino such as aminopropyl (meth) acrylamide and di-t-butylaminopropyl (meth) acrylamide (Meth) acrylic acid ester or (meth) acrylamide having styrene; styrene having a dialkylamino group such as dimethylaminostyrene and dimethylaminomethylstyrene; vinylpyridine such as 2- or 4-vinylpyridine; N such as N-vinylimidazole -Vinyl heterocyclic compounds and salts thereof.

  In the ionic monomer, from the viewpoint of ionic bonding, the ionic group is preferably a strong electrolysis type ionic group, and more preferably a (quaternary) ammonium group. One ionic monomer may be used alone, or two or more ionic monomers may be used in combination.

  The zwitterion-containing copolymer comprises a monomer composition containing the ionic monomer and a monomer having a zwitterionic group at a predetermined ratio, in the presence of a polymerization initiator, and an inert gas such as nitrogen, carbon dioxide, helium, or argon. It can be easily obtained by radical polymerization in an atmosphere. For example, the radical polymerization can be performed by appropriately setting conditions by known methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. The obtained zwitterion-containing copolymer can be purified by a general purification method such as a reprecipitation method, a dialysis method, or an ultrafiltration method.

  In one or more embodiments of the present invention, although not particularly limited, the surface-modified porous membrane contains zwitterions on the surface of the porous membrane obtained by processing a modacrylic copolymer by any method. It can be produced by coating a copolymer and forming a coating layer ion-bonded to the porous membrane on the surface of the porous membrane.

  First, a modacrylic copolymer is processed to produce a porous film. Examples of the method for forming the porous membrane include a thermally induced phase separation method, a non-solvent induced phase separation method, and a stretching method. Among them, the non-solvent induced phase separation method is preferable from the viewpoint of simple manufacturing process and low cost.

  In one or more embodiments of the present invention, when forming a porous membrane by a non-solvent induced phase separation method, a modacrylic copolymer is made into a solution using a good solvent and then brought into contact with a non-solvent. A porous membrane is produced by solidification.

  The good solvent is not particularly limited as long as it can dissolve the modacrylic copolymer, and examples thereof include ketones such as acetone, methyl ethyl ketone and diethyl ketone, sulfoxides such as dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. Illustrated.

  The concentration of the modacrylic copolymer solution may be appropriately selected according to the target porous pore size and water permeability, and is not limited, but is preferably 5% by mass to 30% by mass, more preferably It is 10 mass% or more and 20 mass% or less. If the concentration is too low, the processability during film formation cannot be maintained, and the strength of the resulting porous film may be insufficient. If it is too high, the viscosity of the solution becomes too high and processing may become difficult.

  In preparing a modacrylic copolymer solution, various film forming aids such as a pore opening agent, a lubricant and a stabilizer may be used in combination with a good solvent. Examples of the pore opening agent include water-soluble polymers such as polyethylene glycol and polyvinyl pyrrolidone. As these water-soluble polymers, those having an arbitrary molecular weight can be used according to the pore size and water permeability of the target porous membrane. For example, if it is polyethylene glycol, a thing with a polymerization degree of about 100-5000 is used suitably. The amount of these film-forming aids can be arbitrarily adjusted according to the intended physical properties as long as film-forming is possible.

  As the non-solvent during film formation, a solvent that does not dissolve the modacrylic copolymer and is miscible with a good solvent is used. For example, when dimethylsulfoxide and dimethylformamide are used as good solvents, water, alcohols such as methanol and ethanol, and polar solvents such as acetonitrile can be used as non-solvents. Among these, water is preferably used from the viewpoints of economy and safety. These non-solvents may be used individually by 1 type, and may be used in combination of 2 or more type. It is also possible to use a mixed solvent in which a good solvent capable of dissolving a modacrylic copolymer is mixed with these non-solvents. For example, a mixed solvent of dimethyl sulfoxide and water can be used as the non-solvent. When using a mixed solvent, generally, the lower the ratio of the non-solvent, the smaller the pore size of the porous membrane. As a result, it is possible to obtain a porous membrane having a high rejection rate of the substance to be treated, although the water permeability performance is lowered. Therefore, the concentration of the mixed solvent can be arbitrarily selected according to the desired physical properties of the porous membrane.

  Although the said porous membrane is not specifically limited, For example, it is preferable that thickness is 0.01-1 mm, More preferably, it is 0.05-0.5 mm. If the thickness is too thin, defects such as cracks may occur, and the filtration performance may be reduced. If the thickness is too thick, the water permeability may be reduced.

  The shape of the porous membrane is not limited. For example, any shape such as a hollow fiber shape, a flat membrane shape, a spiral shape, a pleated shape, a tubular shape, or the like can be selected. Among these, a hollow fiber shape is preferable from the viewpoint of easy production, low cost, and use at low pressure.

  Next, the amphoteric ion-containing copolymer is coated on the surface of the porous film to form a coating layer ion-bonded to the porous film on the surface of the porous film. The method for coating the surface of the porous membrane with the zwitterion-containing copolymer is not particularly limited, and examples thereof include applying an aqueous solution of the zwitterion-containing copolymer. Coating methods include dipping, spin coating using spinner, spray coating, roll coating, screen printing, blade coater, die coater, calendar coater, meniscus coater, bar coater, roll coater, comma roll coater, gravure coater, screen coater. And a slit die coater. Among them, the dipping method is preferable from the viewpoint of simplicity. Although the temperature at the time of immersion is not specifically limited, For example, it is preferable to carry out at room temperature (20 ± 5 degreeC) from a viewpoint of simplicity. The coating film thickness is not particularly limited, but usually, the thickness of the coating layer after drying may be adjusted to 0.1 to 100 μm, and adjusted to 2.0 to 50 μm. May be.

  The surface-modified porous membrane can be suitably used for water treatment for removing impurities contained in river water or industrial water. In particular, it can be suitably used for water treatment for removing impurities contained in river water and industrial water having a low electrolyte concentration. For example, it can be used as a filter medium for a cartridge for a water purifier or a membrane unit for wastewater treatment.

  Hereinafter, the present invention will be described in detail based on examples. In addition, this invention is not limited only to these Examples.

(Production Example 1)
In the flask, 15.7 mL of pure water, 3.07 g (11.0 mmol) of (2- (methacryloyloxy) ethyl) dimethyl- (3-sulfopropyl) ammonium (hereinafter referred to as SBMA), and 0.98 g ( 4.7 mmol) of (2- (methacryloyloxy) ethyl) trimethylammonium chloride salt (hereinafter referred to as MTAC) was added, and then bubbled under a nitrogen stream for 30 minutes to remove oxygen. Thereto was added potassium peroxodisulfate as a polymerization initiator, and the mixture was stirred at 30 ° C. for 3 hours to carry out a polymerization reaction. Thereafter, the reaction solution was dialyzed with ultrapure water using a dialysis tube (Fisherbrand, MWCO = 6000-8000 Da) to remove unreacted monomers and oligomers. Finally, the obtained copolymer was lyophilized and separated to obtain 0.92 g of SBMA-MTAC copolymer. The molar ratio of SBMA and MTAC was confirmed by NMR spectrum using heavy water as a solvent using a nuclear magnetic resonance apparatus (“ECZ400” manufactured by JEOL Ltd.). As a result, SMBA: MTAC = 68: 32.

(Production Example 2)
The experiment was performed in the same manner as in Production Example 1 except that 15.5 mL of pure water, 2.29 g of SBMA, and 1.70 g of MTAC were used. As a result, 0.68 g of SBMA-MTAC copolymer having a molar ratio of SBMA and MTAC of 43:57 was obtained.

(Production Example 3)
The experiment was performed in the same manner as in Production Example 1 except that 15.3 mL of pure water, 1.45 g of SBMA, and 2.53 g of MTAC were used. As a result, 0.85 g of SBMA-MTAC copolymer having a molar ratio of SBMA to MTAC of 25:75 was obtained.

(Examples 1-8)
<Preparation of porous membrane>
Modacrylic copolymer (weight average molecular weight) comprising 47.0 parts by mass of a structural unit derived from a vinyl chloride monomer, 51.0 parts by mass of a structural unit derived from acrylonitrile, and 2.0 parts by mass of a structural unit derived from sodium styrenesulfonate 113000) and 40 g of polyethylene glycol 200 as a pore-opening agent were dissolved in 45 g of dimethyl sulfoxide to obtain a modacrylic copolymer solution. The obtained modacrylic copolymer solution was applied onto a glass plate using a film applicator, and then developed into a 60% by mass dimethyl sulfoxide aqueous solution to obtain a porous membrane (thickness 114 μm).
<Preparation of coating layer>
The SBMA-MTAC copolymers obtained in Production Examples 1 to 3 were dissolved in pure water and adjusted to predetermined concentrations as shown in Table 1 below. The porous film obtained above was immersed in an aqueous solution of SBMA-MTAC copolymer for 180 minutes at room temperature (20 ± 5 ° C.) to form a coating layer composed of the SBMA-MTAC copolymer. Thereafter, it was washed with pure water to obtain a surface-modified porous membrane having a coating layer disposed on the surface of the porous membrane. While the SBMA-MTAC copolymer is immersed in an aqueous solution, the amount of SBMA-MTAC copolymer adhering to the surface of the porous membrane (adsorption amount) is quantitatively determined by the quartz crystal microbalance method as described below. The final adhesion amount is shown in Table 1 below. Further, FIG. 1 shows the relationship between the immersion time of the SBMA-MTAC copolymer of Production Example 1 in the aqueous solution and the adsorption amount of the SBMA-MTAC copolymer on the surface of the porous membrane.

(Reference Example 1)
A porous membrane (thickness: 114 μm) was obtained in the same manner as in Example 1 except that no coating layer was produced.

(Quartz crystal microbalance method)
Quartz crystal microbalance with dissipation monitoring (QCM-D, Q-Sense E1, manufactured by Meiwa Forsys) ). The piezoelectric crystal sensor (QSX301, manufactured by Q-sense) had a basic resonance frequency of 5 Hz and a diameter of 14 mm. The SBMA-MTAC copolymer adjusted to 1% by mass with a dimethylacetamide (DMAC) solution was spin-coated at 3000 rpm for 1 minute at room temperature and dried at 80 ° C. for 20 minutes. Next, the sensor was attached to the QCM-D and stabilized by flowing pure water at a rate of 5 μL / min for 30 minutes to obtain a baseline. Next, an aqueous solution of SBMA-MTAC copolymer was flowed. The adsorption amount of the SBMA-MTAC copolymer was calculated by the following formula. In the following formula, Δm is the adsorption amount (ng / cm ² ) of the SBMA-MTAC copolymer, C is a mass sensitivity constant (17.7 ng / cm ² · Hz when f is 4.95 Hz), Δf is a frequency change amount, and n is an overtone order (n = 7).
Δm = −CΔf / n

As can be seen from FIG. 1, 120 nm / cm ² of SBMA-MTAC copolymer was adsorbed on the surface of the porous membrane within 1 minute after immersion of the SBMA-MTAC copolymer in an aqueous solution, and after about 200 minutes, 160 ng / Cm ² .

  The zeta potentials of the surface-modified porous membrane of Example 1 and the porous membrane of Reference Example 1 were measured as follows, and the results are shown in FIG.

(Measurement of zeta potential)
The surface zeta potential of the porous membrane was measured using a zeta potential measuring device for solid surface analysis (“SuePASS” manufactured by Anton Paar). Specifically, it was measured in 10 mM KCl solution under different pH conditions from pH 3 to pH 6.

  As can be seen from FIG. 2, the zeta potential of the surface modified porous film of Example 1 was close to 0 as compared with the porous film of Reference Example 1 before the surface modification. While the porous membrane of Reference Example 1 has a negative potential derived from a sulfonic acid group, the surface-modified porous membrane of Example 1 has a coating layer composed of an amphoteric ion-containing copolymer. It is presumed that the potential has become more neutral.

  Further, with respect to the surface-modified porous membrane of Example 1 and the porous membrane of Reference Example 1, the adsorption amount of bovine serum albumin (BSA) was measured as follows, and the results are shown in Table 2 below.

(Adsorption amount of bovine serum albumin (BSA))
The amount of bovine serum albumin (BSA) adsorbed on the porous membrane was measured using FITC-BSA (manufactured by Wako Pure Chemical Industries, Ltd.). A porous membrane sample (about 0.5 × 3 cm ² ) was immersed in a phosphate buffer solution (PBS, pH 7.4) containing 20 ppm FITC-BSA, and a constant temperature shake incubator (Bio Shaker (registered trademark)). (BR-43FL, manufactured by Taitec Co., Ltd.) was shaken at a temperature of 25 ° C. and a shaking number of 100 rpm for 19 hours. Thereafter, the porous membrane sample was washed twice with PBS to remove FITC-BSA which was weakly adhered. Next, it observed using the confocal laser scanning microscope (CLSM, Olympus "FV1000D"), and analyzed the fluorescence intensity by ImageJ.

  As can be seen from Table 2, compared with the porous membrane of Reference Example 1, the surface-modified porous membrane of Example 1 has a lower BSA adsorption amount, so that the foulant adhesion amount is expected to be reduced.

  Further, the surface-modified porous membrane of Example 1 and the porous membrane of Reference Example 1 were measured using FOTC-Lysozyme (manufactured by Wako Pure Chemical Industries, Ltd.) in which the amount of adsorption to lysozyme was fluorescently labeled as described below. The results are shown in FIG. 3 and FIG.

(Adsorption amount to lysozyme)
The amount of lysozyme adsorbed on the porous membrane was measured using FITC-lysozyme (manufactured by Wako Pure Chemical Industries, Ltd.). A porous membrane sample (about 0.5 × 3 cm ² ) was immersed in a phosphate buffer solution (PBS, pH 7.4) containing 20 ppm FITC-BSA, and a constant temperature shake incubator (Bio Shaker (registered trademark)). (BR-43FL, manufactured by Taitec Co., Ltd.) was shaken at a temperature of 25 ° C. and a shaking number of 100 rpm for 19 hours. Thereafter, the porous membrane sample was washed twice with PBS to remove weakly attached FITC-lysozyme. Next, it observed using the confocal laser scanning microscope (CLSM, Olympus "FV1000D"), the fluorescence intensity was analyzed by ImageJ, and the relative fluorescence intensity with respect to the control example was computed. As a control example, a porous material produced in the same manner as in Reference Example 1 except that a modacrylic copolymer comprising 49.0 parts by mass of a structural unit derived from a vinyl chloride monomer and 51.0 parts by mass of a structural unit derived from acrylonitrile was used. A membrane was used.

  As can be seen from the fluorescence photograph in FIG. 3, (a) the fluorescence was strongly observed in the case of the porous film of Reference Example 1, whereas (b) the surface-modified porous film of Example 1 was almost fluorescent. It was not observed and it was found that the amount of lysozyme adsorbed was small. This was also evident from the results of relative fluorescence intensity in FIG.

  Further, the fouling resistance of the surface-modified porous membrane of Example 1 and the porous membrane of Reference Example 1 was measured as follows, and the results are shown in FIG.

(Fouling resistance)
Fouling resistance was measured using lysozyme (mass average molecular weight 14000, isoelectric point 11.00 to 11.35). A cross flow sail having an effective area of the membrane of 8.07 cm ² was used, and stabilized by flowing ultrapure water with a water pressure of 0.1 MPa (1 atm). Next, ultrapure water was passed for 10 minutes at a flow rate of 80 L / m · h. Next, a 50 ppm lysozyme solution was passed through for 60 minutes, and the flux was measured.

  As can be seen from FIG. 5, the flow rate of the porous membrane of Reference Example 1 decreases immediately after passing the lysozyme solution, whereas the flow rate of the porous membrane of Example 1 even after about 60 minutes has passed after passing the lysozyme solution. High fouling resistance with almost no change in bundle. The surface-modified porous membrane of Example 1 has a zeta potential close to neutrality by having a coating layer composed of an amphoteric ion-containing copolymer, and thus the amount of adsorption to protein is low. It had high fouling resistance.

  The stability of the surface-modified porous membrane of Example 1, that is, the robustness of the coating layer was measured as follows, and the results are shown in FIGS.

(Strength of coating layer)
Samples of the surface-modified porous membrane of Example 1 (about 0.5 × 3 cm ² ) were respectively mixed with ethanol solution (ethanol / water, volume ratio of 7/3), 0.1M NaCl, NaOH aqueous solution (pH 11.0). ) And 0.01 MSDS for 6 hours, followed by observation using a confocal laser scanning microscope (CLSM, “FV1000D” manufactured by Olympus), the fluorescence intensity was analyzed by ImageJ, and the relative fluorescence intensity relative to the control example was determined. Calculated. As a control example, a porous material produced in the same manner as in Reference Example 1 except that a modacrylic copolymer comprising 49.0 parts by mass of a structural unit derived from a vinyl chloride monomer and 51.0 parts by mass of a structural unit derived from acrylonitrile was used. A membrane was used.

  As can be seen from FIGS. 6 and 7, the fluorescence intensity of the surface-modified porous membrane of Example 1 after (b) ethanol solution treatment, (c) NaCl treatment, (d) NaOH aqueous solution treatment, and (e) SDS treatment. (A) The surface-modified porous membrane of the example was excellent in stability, almost unchanged from the fluorescence intensity of the surface-modified porous membrane of the example 1 that was not subjected to any treatment. That is, in the surface-modified porous membrane of the example, the coating layer was firmly bonded to the porous membrane.

  The porous membrane which concerns on one or more embodiment of this invention can be used suitably for the water treatment which removes the impurity contained in river water or industrial water.

Claims (12)

A surface-modified porous membrane comprising a porous membrane composed of a modacrylic copolymer and a coating layer disposed on the surface of the porous membrane,
The modacrylic copolymer includes a structural unit derived from acrylonitrile, a structural unit derived from a halogen-containing monomer, and a structural unit derived from a vinyl monomer having an ionic substituent,
The coating layer is composed of a monomer having an ionic group opposite to the ionic substituent contained in the modacrylic copolymer, and a zwitterion-containing copolymer obtained by copolymerizing a monomer having a zwitterionic group,
The surface-modified porous membrane, wherein the porous membrane and the coating layer are bonded through ionic bonds.   The modacrylic copolymer is composed of 15 to 85 parts by mass of an acrylonitrile-derived structural unit, and vinyl halide and vinylidene halide when the total structural unit constituting the copolymer is 100 parts by mass. 14.5 parts by mass or more and 84.5 parts by mass or less of a structural unit derived from one or more halogen-containing monomers selected from the group, and 0.5 to 10 parts by mass of a structural unit derived from a vinyl monomer having an ionic substituent. The surface-modified porous membrane according to claim 1, comprising not more than part by mass.   The modacrylic copolymer is composed of 35 to 65 parts by mass of an acrylonitrile-derived structural unit when the total structural unit constituting the modacrylic copolymer is 100 parts by mass, vinyl halide and vinylidene halide. The halogen-containing monomer selected from the group is 34.5 parts by mass or more and 64.5 parts by mass or less, and the structural unit derived from a vinyl monomer having an ionic substituent is 0.5 parts by mass or more and 10 parts by mass or less. 2. The surface-modified porous membrane according to 2.   The surface-modified porous according to any one of claims 1 to 3, wherein the ionic substituent in the vinyl monomer having an ionic substituent constituting the modacrylic copolymer is a strong electrolysis type substituent. film.   The surface-modified porous membrane according to any one of claims 1 to 4, wherein the ionic substituent in the vinyl monomer having an ionic substituent constituting the modacrylic copolymer is a sulfonic acid group.   The surface-modified porous membrane according to any one of claims 1 to 5, wherein the halogen-containing monomer is at least one selected from the group consisting of vinyl chloride and vinylidene chloride.   The amphoteric ion-containing copolymer is a monomer having an ionic group having a charge opposite to that of the ionic substituent contained in the modacrylic copolymer when the total constitutional unit constituting the copolymer is 100 parts by mass. The surface-modified porous membrane according to any one of claims 1 to 6, comprising 20 to 80 parts by mass of a monomer having a zwitterionic group and 20 to 80 parts by mass of a monomer having an zwitterionic group.   The surface-modified porous membrane according to any one of claims 1 to 7, wherein the monomer having an zwitterionic group is at least one selected from the group consisting of a sulfobetaine monomer, a carboxybetaine monomer, and a phosphobetaine monomer.   The surface-modified porous membrane according to any one of claims 1 to 8, wherein an ionic group having a charge opposite to the ionic substituent contained in the modacrylic copolymer is a strong electrolysis type ionic group.   The surface-modified porous membrane according to any one of claims 1 to 9, wherein an ionic group having an opposite charge to the ionic substituent contained in the modacrylic copolymer is an ammonium group.   The surface-modified porous according to any one of claims 1 to 10, wherein the porous membrane has one shape selected from the group consisting of a hollow fiber shape, a flat membrane shape, a spiral shape, a pleated shape, and a tubular shape. Membrane. It is a manufacturing method of the surface modification porous membrane according to any one of claims 1 to 11,
A step of obtaining a porous film by coagulating a modacrylic copolymer solution obtained by dissolving a modacrylic copolymer in a good solvent in contact with a non-solvent of the modacrylic copolymer; and
Immersing the porous membrane in an aqueous solution of an amphoteric ion-containing copolymer to form a coating layer ionically bonded to the porous membrane on the surface of the porous membrane;
The modacrylic copolymer includes a structural unit derived from acrylonitrile, a structural unit derived from a halogen-containing monomer, and a structural unit derived from a vinyl monomer having an ionic substituent,
The zwitterion-containing copolymer is a copolymer of a monomer having an ionic group opposite to the ionic substituent contained in the modacrylic copolymer and a monomer having a zwitterionic group. A method for producing a surface-modified porous membrane.