JP2016013544A - Porous membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous membrane which is hardly clogged by a fouling substance and which is high in filtration efficiency.SOLUTION: The surface of a resin porous substrate is irradiated with an ionization radiation to create radicals, and the created radicals and chemical compounds containing bases reactive with the radicals are graft-polymerized, to prepare a fluid treatment resin porous film, in which molecular chains existing in a surface part have graft chains, in which the graft ratio is 0.1 to 5%, in which the contact angle of water is 80° or less, and in which the resin porous substrate is a fluororesin containing porous substrate.

Description

  The present invention relates to a resin porous membrane for fluid treatment.

  In recent years, there has been an increasing demand for porous membranes that remove fine particles from a fluid, for example, a solution, and process the solution. Main applications include water treatment such as seawater desalination, water and sewage treatment, and medical applications such as plasma fractionation and biopharmaceutical preparations when administered to the human body. There are uses for removing pathogens such as viruses and pathogenic proteins that may be present.

  When the liquid to be treated is separated by the porous membrane as described above, the clogging of the membrane by the fouling substance becomes a problem. In order to suppress the adhesion of such a fouling substance to the film, a graft chain having a non-affinity with the fouling substance is introduced into the porous film. For example, in Patent Document 1, in the treatment of an aqueous solution, a hydrophobic monomer such as a protein is obtained by grafting a vinyl monomer having a hydroxyl group, an anion exchange group or a cation exchange group to a base material and hydrophilizing the base material. It prevents fouling substances from adhering to the film.

JP 2009-183804 A

  In a porous membrane for solution treatment, (1) high membrane strength, (2) fouling resistance, and (3) high filtration efficiency are required.

  However, when a graft chain having a non-affinity with a fouling substance is introduced as in the prior art, (2) fouling resistance can be obtained, but the graft chain is also introduced into the pore portion of the porous membrane, resulting in a small pore diameter. Thus, the filtration resistance increases, and (3) it is difficult to obtain high filtration efficiency.

  Thus, it is difficult to obtain a porous film satisfying all of the above (1) to (3). In particular, since (2) and (3) are in a trade-off relationship, it is difficult to achieve both.

  Accordingly, an object of the present invention is to provide a porous membrane that is less likely to be clogged with a fouling substance and that has high filtration efficiency.

  As a result of intensive studies, the present inventors segregated graft chains on the surface portion of the porous membrane substrate by using low-energy ionizing radiation, without degrading the strength of the substrate of (1), It was found that (2) fouling resistance and (3) high filtration efficiency can be achieved at the same time.

  That is, according to the gist of the present invention, there is provided a resin porous membrane for fluid treatment, wherein the molecular chain present on the surface portion of the porous substrate has a graft chain.

  According to the present invention, by introducing a graft chain to the surface of a resin porous substrate, it becomes possible to provide a porous membrane that is less likely to be clogged with a fouling substance and that has excellent filtration efficiency. .

  The porous membrane of the present invention is used for fluid treatment. “Fluid treatment” means a treatment for removing impurities from a fluid containing impurities. Here, the fluid may be either gas or liquid. Examples of the gas include organic gas and air. Examples of the liquid include solutions, suspensions, emulsions, and dispersions. . The impurity may be present as a solid or may be dissolved as a solute.

  The porous membrane of the present invention is characterized in that the molecular chain present on the surface portion of the resin porous substrate has a graft chain.

  The porous film of the present invention is produced, for example, by irradiating the surface of a resin porous substrate with ionizing radiation to generate radicals, and then graft-polymerizing the generated radicals and a compound containing a radical and a reactive group. can do. Specifically, it is manufactured as follows.

  First, a resin porous substrate (hereinafter also simply referred to as “resin substrate”) is prepared.

  The material that forms the resin substrate is a resin that can generate radicals upon irradiation with ionizing radiation, for example, a compound that undergoes a radiation chemical reaction upon irradiation with ionizing radiation and a hydrogen atom or fluorine atom is eliminated, or ionizing radiation. The resin is not particularly limited as long as it is a resin formed from a compound whose main chain / side chain is cleaved by irradiation. For example, a fluororesin and a non-fluorine resin can be used. Since the resistance to light, heat, chemicals and the like is higher, it is preferable to use a fluororesin. The molecular weight of the resin substrate may be any molecular weight that can maintain the material properties according to the application, and may be reduced by irradiation with ionizing radiation for introducing a graft chain onto the surface. .

  Examples of the fluororesin include, for example, ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), perfluoroalkoxy copolymer (PFA), ethylene. -Chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-hexafluoropropylene copolymer (VdF-HFP) , Vinylidene fluoride-tetrafluoroethylene copolymer (VdF-TFE), vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer (VdF-TFE-HFP), and other fluorine-based trees In addition to the fluorine rubber, etc., these blends resins, polymer alloy, or a hybrid material of layer-by-layer.

  Examples of the non-fluorine resin include polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyolefin such as cycloolefin resin, modified polyolefin, and polyvinyl chloride. Acrylic resins such as vinyl chloride resin, polyvinylidene chloride, polystyrene, polyamide, polyimide, polyamideimide, polycarbonate, poly- (4-methylpentene-1), ionomer, polymethyl methacrylate (PMMA), acrylic-styrene copolymer Polymer (AS resin), ethylene-tetrafluoroethylene copolymer (ETFE), butadiene-styrene copolymer, ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), polybutylene terf Polyesters such as acrylate (PBT) and polycyclohexane terephthalate (PCT), polyether, polyether ketone (PEK), polyether ether ketone (PEEK), polyether imide, polyacetal (POM), polyphenylene oxide, modified polyphenylene oxide, Polyarylate, aromatic polyester (liquid crystal polymer), styrene resin, polyurethane resin, chlorinated polyethylene resin, epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester, silicone resin, polyurethane, etc. Examples thereof include copolymers, blends, polymer alloys, and layer-by-layer hybrid materials.

  The kind of material of the resin base material can be appropriately selected according to the solution to be treated.

  In a preferred embodiment, the material forming the resin base material is a vinylidene fluoride resin.

  The vinylidene fluoride-based resin is a resin made of polyvinylidene fluoride or a copolymer having a vinylidene fluoride unit.

  The weight average molecular weight of polyvinylidene fluoride is preferably 30,000 to 2,000,000, and more preferably 50,000 to 1,000,000 from the viewpoint of mechanical strength and processability of the resin base material.

  Examples of the copolymer having a vinylidene fluoride unit include a vinylidene fluoride / tetrafluoroethylene copolymer and a vinylidene fluoride / hexafluoropropylene copolymer. From the viewpoint of mechanical strength and alkali resistance, the copolymer having a vinylidene fluoride unit is particularly preferably a vinylidene fluoride / tetrafluoroethylene copolymer.

  From the viewpoint of film formability and alkali resistance, the vinylidene fluoride / tetrafluoroethylene copolymer has a molar ratio of vinylidene fluoride units and tetrafluoroethylene units (vinylidene fluoride units / tetrafluoroethylene units) of 50 to 99 / It is preferable that it is 50-1. As such a polymer, for example, NEOFRON VT series manufactured by Daikin Industries, Ltd. may be mentioned. The vinylidene fluoride / tetrafluoroethylene copolymer preferably has a vinylidene fluoride unit / tetrafluoroethylene unit in a molar ratio of 50 to 95/50 to 5, more preferably 50 to 90/50 to 10. Further preferred. In addition to vinylidene fluoride / tetrafluoroethylene copolymer consisting only of vinylidene fluoride units and tetrafluoroethylene units, vinylidene fluoride / tetrafluoroethylene copolymers include vinylidene fluoride units and tetrafluoroethylene units. In addition, a ternary or higher copolymer having a hexafluoropropylene unit, a chlorotrifluoroethylene unit, a perfluorovinyl ether unit or the like may be used as long as the characteristics are not impaired.

  The weight average molecular weight of the copolymer having a vinylidene fluoride unit varies depending on the use of the resin porous membrane, but is preferably 10,000 or more from the viewpoint of mechanical strength and film formability. More preferably, it is 30000-200000, More preferably, it is 50000-1 million, Most preferably, it is 100000-800000. The weight average molecular weight can be determined by gel permeation chromatography (GPC).

  The resin base material used in the present invention may contain only a vinylidene fluoride resin and a copolymer having a vinylidene fluoride unit as a polymer, or a vinylidene fluoride resin and a vinylidene fluoride unit as a polymer. It may contain the copolymer which has, and resin other than these.

  Examples of resins other than vinylidene fluoride resins and copolymers having vinylidene fluoride units include polyethylene resins, polypropylene resins, acrylic resins, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resins, polystyrene resins, Acrylonitrile-styrene (AS) resin, vinyl chloride resin, polyethylene terephthalate, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polyphenylene sulfide resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, And mixtures and copolymers thereof. Other resins miscible with these may be mixed.

  As the resin other than the vinylidene fluoride resin and the copolymer having a vinylidene fluoride unit, at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, and an acrylic resin is preferable.

  Next, the resin substrate is irradiated with ionizing radiation. By irradiating the resin base material with ionizing radiation, in the resin base material, for example, a hydrogen atom or a fluorine atom is eliminated from the compound forming the resin base material, or the main chain of the compound forming the resin base material And / or a side chain is cut | disconnected by a radiation chemical reaction, and a radical is produced | generated. This radical is graft-polymerized with a graft monomer having a radical-reactive group.

  The ionizing radiation is not particularly limited as long as it can generate radicals when irradiated onto a resin substrate, and for example, an electron beam, X-ray, γ-ray, neutron beam, ion, or the like can be used. An electron beam is preferable because the penetration depth (range) of ionizing radiation is easy and radicals are easily generated in the resin.

  The absorbed dose of the ionizing radiation to be irradiated is appropriately selected according to the amount of graft chains to be introduced, the graft depth, the material of the resin base material, etc., for example, 0.1 to 1000 kGy, preferably 1 to 300 kGy, More preferably 1-100 kGy, even more preferably 1-50 kGy, even more preferably 1-20 kGy, for example 1-15 kGy, 1-10 kGy. By setting the absorbed dose to 1000 kGy or less, deterioration of the resin base material can be suppressed to a minimum, and a decrease in the strength of the porous film can be suppressed. In addition, by setting the absorbed dose to 0.1 kGy or more, a sufficient amount of radicals for graft polymerization can be generated. The irradiation amount to the resin substrate can be measured with a Faraday cup, a scintillation detector, or a semiconductor detector, and more preferably, for example, a cellulose triacetate (CTA) dosimeter or a radiochromic film dose It can be measured by an absorption dosimeter using a meter.

  When an electron beam is used, the electron energy of the electron beam applied to the substrate using an electron accelerator is the energy on the substrate surface, preferably 5 keV to 100 keV, more preferably 10 keV to 80 keV, and even more preferably 30 keV to 70 keV, even more preferably 40 keV to 70 keV. By setting the energy of electrons on the substrate surface to 100 keV or less, the electron beam is absorbed substantially only near the surface of the resin substrate, and the number of electron beams penetrating into the resin substrate is reduced. Deterioration of the resin base material due to the wire can be suppressed. Furthermore, since the absorption of the electron beam inside the resin not involved in the graft polymerization is small and the amount of the electron beam passing through the resin base material is small, the energy absorption efficiency can be improved. On the other hand, by setting the energy of electrons on the substrate surface to 5 keV or more, radicals sufficient for graft polymerization can be generated on the resin substrate surface. That is, the graft polymerization can be said to be a surface graft reaction because the graft reaction occurs only on the surface portion of the resin substrate.

  When an electron beam from an electron accelerator is used, if the space between the electron gun and the substrate is a vacuum environment, the electron energy corresponds to the acceleration voltage, and the acceleration voltage is preferably 5 to 100 kV, more preferably 10 to 10 kV. It may be 80 kV, more preferably 30 to 70 kV, and even more preferably 40 to 70 kV.

  On the other hand, in the case of an electron accelerator that has an irradiation window for extraction to the atmosphere between the electron gun and the base material, the electron energy is attenuated when passing through the irradiation window even in vacuum irradiation. Therefore, the acceleration voltage needs to be higher according to the attenuation of the energy of electrons. Of course, when passing through a nitrogen stream, it is also necessary to increase the energy in consideration of the energy that attenuates according to the density and distance in the stream to the sample.

When an electron beam is used, the irradiation dose of electrons applied to the substrate is 0.01 μC / cm ^{2 to} 10 mC / cm ² , preferably 0.1 μC / cm ^{2 to} 500 μC / cm ² , more preferably 1 μC / cm ² ~100μC / cm ^2, for example, 2μC / cm ^2. By setting the irradiation dose in such a range, radicals can be generated efficiently.

Irradiation of ionizing radiation to the resin substrate is preferably performed in an atmosphere substantially free of oxygen from the viewpoint of suppressing the pair annihilation of the generated radical, for example, an oxygen concentration of 1000 ppm or less, more preferably 500 ppm, Even more preferably, it is performed under an atmosphere of 100 ppm or less. For example, the irradiation with ionizing radiation is performed in a vacuum or in an inert gas atmosphere, for example, in a nitrogen or argon atmosphere. Note that the vacuum need not be a complete vacuum, but may be substantially a vacuum, for example, a low vacuum of about 10 ³ Pa or a high vacuum of about 10 ⁻² Pa. In another embodiment, the irradiation with ionizing radiation may be performed in the atmosphere in order to obtain peroxide radicals, and oxygen may be supplied after radical generation. In addition, in order to prevent radical inactivation generated in the resin base material of the present invention, the resin base material after irradiation is preferably stored at a low temperature below the glass transition temperature of the polymer constituting the resin, Storage in a vacuum or inert atmosphere is more preferred.

  The penetration depth of the ionizing radiation is 0.1 to 50%, preferably 1 to 30%, more preferably 1 to 20%, and still more preferably 1 to 5% of the thickness of the resin base material. Preferably, the penetration depth is 0.1 μm or more. For example, the penetration depth of the ionizing radiation is 0.1 to 40 μm, preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm, for example 0.5 to 5 μm from the surface of the resin substrate. May be.

  The penetration depth of ionizing radiation means the depth at which the resin substrate absorbs the energy of ionizing radiation. The penetration depth of ionizing radiation is substantially the same as the region where graft polymerization occurs, but the surface of the sample slightly swells due to the graft reaction. It can be deeper than the penetration depth of ionizing radiation. The depth of the graft chain can be determined by analyzing the cross-section of the molded product after graft polymerization by EDX (Energy dispersive X-ray) analysis using a scanning electron microscope (SEM), EPMA (Electron Probe Microanalyser) analysis, etc. Can be measured. The depth at which the graft chain exists can also be measured with a microscopic FT-IR, a Raman microscope, or the like.

  The depth at which the graft chain is present in the molded product after the graft reaction can also be measured by positron lifetime measurement. The positron lifetime obtained by measuring the time from the generation of a positron to the pair annihilation with the electron is correlated with the amorphous free volume of the polymer and the size of the vacancies in the crystal. As the grafting, the amorphous free volume in the substrate decreases, and the positron lifetime also decreases. From this, the depth at which the graft chain exists can be measured by positron lifetime measurement. In the positron lifetime measurement, generally, gamma rays and annihilation gamma rays emitted at the time of β + decay are detected by different scintillation detectors, and the frequency of positrons annihilated at a certain time is counted from the difference in incident time. The positron lifetime can be determined by analyzing the attenuation curve thus obtained. For example, in the “Free volume study of the functionalized fluorinated polymer” by T. Oka published at The 2nd Japan-China Joint Workshop on Positron Science (JWPS2013), an example of styrene grafted on a fluororesin is introduced. Also in the present invention, the presence of graft chains can be measured by this method.

  Next, the radical in the resin substrate generated by irradiation with ionizing radiation and a compound as a monomer (hereinafter also referred to as “graft monomer”) are graft-polymerized.

  The graft monomer has a radical and a reactive group. The group reactive with the radical is not particularly limited, and examples thereof include a group having an ethylenic double bond and an oxygen-containing cyclic group (for example, glycidyl group, oxetanyl group), and derivatives thereof.

［式中、Ｒ^ｂは、結合、−Ｏ−、−ＣＯ−または−ＯＣ（Ｏ）−であり、
Ｒ^ｃは、水素原子、フッ素原子、あるいはフッ素原子により置換されていてもよい炭素数１〜１０のアルキル基（好ましくは、炭素数１〜３のアルキル基、より好ましくはメチル基）、ラクタム基（好ましくは、β-ラクタム、γ-ラクタムまたはδ-ラクタム基、より好ましくはγ-ラクタム基）またはフェニル基を表し、好ましくは、メチル基または水素原子である。］
で表される基である。 Preferred radicals and reactive groups are represented by the following formula:

Wherein R ^b is a bond, —O—, —CO— or —OC (O) —,
R ^c is a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 10 carbon atoms which may be substituted with a fluorine atom (preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group), a lactam group. (Preferably β-lactam, γ-lactam or δ-lactam group, more preferably γ-lactam group) or a phenyl group, preferably a methyl group or a hydrogen atom. ]
It is group represented by these.

［式中、Ｒ^ｃは、上記と同意義である。］
で表される基である。 More preferred radicals and groups reactive with radicals are:

[Wherein R ^c has the same meaning as described above. ]
It is group represented by these.

  More preferred radical-reactive groups are acryloyl or methacryloyl groups.

  The surface graft polymerization is carried out by bringing a graft monomer into contact with a radical in a resin substrate generated by irradiating with ionizing radiation. The contact between the radical in the resin substrate and the graft monomer may be performed by, for example, immersing the resin substrate in a solution of the graft monomer, dropping or coating the graft monomer on the resin substrate, or in the presence of a gaseous monomer. This is done by placing a resin substrate. Even when the wettability between the surface of the resin substrate and the graft monomer is low, a method of immersing the resin substrate in a solution of the graft monomer is preferable because the resin substrate can be contacted uniformly and reliably.

  Although the reaction temperature of the said graft polymerization is not specifically limited, For example, it is room temperature (for example, 20 degreeC) -100 degreeC, Preferably it is 30-80 degreeC, More preferably, it is 30-60 degreeC.

  Although the reaction time of the said surface graft polymerization is not specifically limited, For example, it is 30 minutes-32 hours, Preferably it is 1-12 hours, More preferably, it is 2-6 hours.

  In addition, as described above, the graft polymerization can be performed by bringing the resin base material and the graft monomer into contact with each other after irradiation with ionizing radiation, but is not limited thereto, and the resin base material and the resin base material simultaneously with the ionizing radiation irradiation. A graft monomer may be contacted. For example, ionizing radiation may be irradiated in a state where the resin substrate is immersed in a solution of the graft monomer or in an atmosphere in which a gaseous graft monomer is present. Alternatively, the resin base material and the graft monomer may be brought into contact with each other in advance and irradiated with ionizing radiation. For example, the graft monomer may be present on the resin substrate by dropping or coating, or the resin substrate may be immersed in the graft monomer so that the resin substrate is impregnated with the graft monomer and irradiated with ionizing radiation. It is preferable to immerse the resin substrate in the graft monomer, impregnate the resin substrate with the graft monomer, and irradiate with ionizing radiation.

  As for the resin porous membrane manufactured as mentioned above, the molecular chain which exists in the surface part of a resin porous base material has a graft chain.

  The “graft chain” means a side chain bonded in a branched manner to the main chain of the polymer constituting the resin substrate, and is not limited by the production method. That is, the graft chain includes, for example, a chain introduced into the main chain of the polymer constituting the resin substrate by other methods in addition to the graft chain formed by the above graft polymerization.

  In a preferred embodiment, the “graft chain” is a branched chain that is branched with respect to the polymer main chain of the resin base material, and can be obtained by covalently bonding the graft monomer to the polymer main chain by irradiation with ionizing radiation. .

  The graft chain may be cationic, anionic or nonionic, but is preferably nonionic. By being nonionic, adhesion of a charged fouling substance can be suppressed.

  Although it does not specifically limit as said cationic graft chain, What has a cation exchange group is mentioned. The cation exchange group is not particularly limited as long as it is a cation exchangeable group, and examples thereof include an acid group and an alcoholic hydroxyl group. The acid group may form a salt. Although it does not specifically limit as a cation exchange group, At least 1 type chosen from the group which consists of a sulfonic acid group which is an acid group, a phosphoric acid group, a carboxyl group, and an alcoholic hydroxyl group is mentioned.

  The graft chain having a cation exchange group can be introduced, for example, by graft polymerization of a compound having a cation exchange group onto a resin substrate. Examples of the compound having a cation exchange group include radical polymerizable groups such as 2-acrylamido-2-methylpropanesulfonic acid, methallylsulfonic acid, 2-sulfopropyl (meth) acrylate, styrenesulfonic acid, and sulfonic acid groups. A compound having a radical polymerizable group such as 2- (meth) acryloyloxyethyl acid phosphate and a phosphate group; a compound having a radical polymerizable group such as (meth) acrylic acid and a carboxyl group; 2-hydroxyethyl Examples thereof include compounds having a radical polymerizable group and an alcoholic hydroxyl group such as (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and p-hydroxystyrene.

Although it does not specifically limit as said anionic graft chain, What has an anion exchange group is mentioned. The anion exchange group is not particularly limited as long as it is an anion exchangeable group. A diethylamino group (DEA, Et ₂ N-), a quaternary ammonium group (Q, R ₃ N ⁺ -), a quaternary aminoethyl group (QAE). , R ₃ N ⁺ — (CH ₂ ) ₂ —), diethylaminoethyl group (DEAE, Et ₂ N— (CH ₂ ) ₂ —), diethylaminopropyl (DEAP, Et ₂ N— (CH ₂ ) ₃ —) group, etc. Is mentioned. In the formula, R is not particularly limited, but may be the same or different, and preferably represents a hydrocarbon group such as an alkyl group, a phenyl group, or an aralkyl group.

  The graft chain having an anion exchange group can be introduced, for example, by graft polymerization of a compound having an anion exchange group onto a resin substrate. Examples of the compound having an anion exchange group include ester-based monomers such as acrylic acid aminoalkyl esters such as dimethylaminoethyl acrylate and diethylaminoethyl acrylate, and methacrylic acid aminoalkyl esters such as dimethylaminoethyl methacrylate and diethylaminomethyl methacrylate. Is mentioned.

  The nonionic graft chain is not particularly limited, and examples thereof include those having a portion capable of hydrogen bonding with a water molecule.

The nonionic graft chain can be introduced, for example, by graft polymerization of a compound having a nonionic group onto a resin substrate. The nonionic group is preferably a group that does not contain an acidic group. Nonionic groups are specifically represented by the formula:
CH ₃ (C _n H _2n O) _m −
[Wherein, n is an integer of 1 to 5 independently for each unit enclosed in parentheses with m, and m is an integer of 1 to 100. ]
And is preferably a polyethylene glycol group or a polypropylene glycol group. Examples of the compound having a nonionic group include N-vinyl-2-pyrrolidone, acrylamide, 2-methoxyethyl acrylate, methacrylic acid (3-oxabutan-1-yl), (2-ethoxyethyl) vinyl ether, (2 -Methoxyethyl) vinyl ether and the like, polyethers, specifically, polyethylene glycol methyl ether methacrylate, polypropylene glycol methyl ether methacrylate and the like, and derivatives thereof.

  In one embodiment, in addition to the organic monomer described above, a compound capable of forming an inorganic network structure by a sol-gelation reaction, for example, a metal alkoxide may be added. By adding such a compound, the chemical resistance of the substrate can be further improved. In particular, it is preferable to add a hydrolyzable metal alkoxide and / or a composite oxide from the viewpoint of achieving both chemical resistance against chemicals such as sulfuric acid and water and hydrophilicity (= chemical solution permeability).

As the hydrolyzable metal alkoxide, the following formula:
(R ¹¹ ) _n M (OR ¹² ) _m
[Where:
R ¹¹ represents a methacryloxy group, an acryloxy group, a vinyl group-containing organic group, or an epoxy group-containing organic group,
R ¹² represents an alkyl group, an alkoxyalkyl group, or an aryl group,
M represents silicon (Si), titanium (Ti), aluminum (Al), zirconium (Zr),
m is 2 to 5 (preferably 3 or 4), n is 0 to 2 (preferably 0 or 1), and m + n is 3 to 5 (preferably 4). ]
The compound represented by these is mentioned.

  Examples of the composite oxide include silica / alumina, silica / alumina based synthetic zeolite, silica / alumina based natural zeolite, aluminum phosphate, aluminum phosphate based synthetic zeolite, and Si—Al—P based synthetic zeolite (SAPO). Can do.

  Preferably the depth at which the graft chain is present is 0.1 to 50% of the thickness of the resin substrate, preferably 1 to 30%, more preferably 1 to 20%, and even more preferably 1 to 5%. Good. That is, the graft chain does not exist over the entire thickness of the resin substrate, but exists in a region from the surface to a predetermined depth. Therefore, it can be said that such a graft chain is a surface graft chain. Preferably, the depth at which the graft chain exists is 0.1 μm or more. For example, the graft chain may be at least 0.1 μm deep, at most 40 μm deep, preferably at least 0.1 deep, and at most 20 μm deep, more preferably at least deep from the surface of the resin substrate. It may be present up to 0.1, up to a depth of 10 μm, for example at least up to a depth of 0.5, up to a maximum of 5 μm.

  The depth at which the surface graft chain is present in the resin substrate can be measured, for example, by observing the cross section of the resin substrate with a scanning electron microscope. More specifically, it can be measured by conducting elemental analysis with EPMA or EDX.

  Moreover, the graft ratio of the resin base material manufactured as mentioned above can be 0.1 to 5.0%, preferably 1 to 3%, more preferably 1.0 to 2.0%. The upper limit is preferably 4.0%, more preferably 3.0%, even more preferably 2.5%, even more preferably 2.0%, and the lower limit is preferably 0.3%, more preferably 0.5%, for example 0.8% or 1.0%. By setting the graft ratio to 0.1% or more, high fouling resistance can be achieved. Moreover, high water permeability can be achieved by making the graft ratio 5.0% or less.

“Graft ratio” means the ratio of graft chains introduced to the resin substrate. Specifically, the graft ratio (Dg) can be calculated by the following formula by measuring the weight change of the resin base material before and after the graft polymerization reaction.
Graft ratio: Dg [%] = (W ₁ −W ₀ ) / W ₀ × 100
[Wherein W ₀ is the weight of the resin base material before graft polymerization, and W ₁ is the weight of the resin base material after graft polymerization. ]

  The graft ratio can also be calculated by thermogravimetric analysis (TG). Specifically, the resin base material having a graft chain is measured by changing the temperature of the resin base material according to a certain program (heating or cooling), and measuring the change in the weight of the resin base material. Can be calculated. The thermogravimetric measurement can be performed, for example, using a TGA measuring instrument manufactured by Rigaku or Shimadzu Corporation.

  In the resin porous membrane of the present invention, the graft chain is unevenly distributed on the surface (or the vicinity of the surface) of the resin base material, and is not substantially present in the deep part of the resin base material. That is, since fewer graft chains are introduced into the pores of the porous membrane, an increase in filtration resistance due to grafting can be suppressed. In addition, since a sufficient amount of graft chains are introduced on the surface of the resin base material, the fouling substance adhesion preventing effect can be sufficiently exhibited.

  In one embodiment, the graft chain in the porous resin membrane of the present invention is a residue of the graft monomer. That is, the graft chain has a functional group that the graft monomer has.

  Therefore, the present invention also provides a porous resin membrane characterized in that the molecular chain present at least on the surface portion of the resin substrate has a graft chain, and the graft chain is a residue of a graft monomer.

であり得る。 Here, the “residue of the graft monomer” means a portion derived from the graft monomer after the graft monomer containing a radical and a reactive group is bonded to the resin substrate. For example, when the graft monomer is a compound represented by R—OC (O) —CH═CH ₂ (R represents an arbitrary group), the residue of the graft monomer is

It can be.

  The thickness of the resin porous membrane of the present invention is not particularly limited and can be appropriately selected depending on the solution to be treated. For example, the thickness is 10 μm to 3 mm, preferably 10 μm to 1 mm, more preferably 20 to 500 μm. It is.

  The shape of the resin porous membrane is not particularly limited, and can be, for example, a film shape, a hollow fiber membrane, or the like.

  In one aspect, the resin porous membrane of the present invention is used for treatment of an aqueous solution.

  In this embodiment, the resin substrate is preferably formed from a fluorine-containing resin, more preferably polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride. -It is formed from at least one fluorine-containing resin selected from tetrafluoroethylene-hexafluoropropylene copolymers, and more preferably formed from polyvinylidene fluoride.

  In this embodiment, the porous resin membrane is preferably made hydrophilic. By making it hydrophilic, fouling by a hydrophobic substance such as a protein can be suppressed.

  In a preferred embodiment, the graft chain has a nonionic hydrophilic group.

  When the porous membrane is used for the treatment of the aqueous solution, it is preferable to make the porous membrane hydrophilic, for example, Patent Document 1 performs hydrophilicity by introducing an ionic graft chain. However, such a graft chain is effective for a fouling substance having no charge, but it attracts a fouling substance having a reverse charge, and the adhesion prevention effect of the fouling substance cannot be sufficiently exhibited. There is. By introducing a graft chain having a nonionic hydrophilic group into a resin base material, adhesion of a fouling substance having such a charge can be suppressed.

  The nonionic hydrophilic group is not particularly limited, and may be, for example, a group having a moiety capable of hydrogen bonding with a water molecule.

  In a preferred embodiment, the graft chain having a nonionic hydrophilic group is a residue of a compound (graft monomer) containing a nonionic hydrophilic group and a radical reactive group.

  Examples of the graft monomer are not particularly limited. For example, N-vinyl-2-pyrrolidone, acrylamide, 2-methoxyethyl acrylate, methacrylic acid (3-oxabutan-1-yl), (2-ethoxyethyl) Polyethers such as vinyl ether and (2-methoxyethyl) vinyl ether, specifically, polyethylene glycol, polypropylene glycol, and the like, and derivatives thereof are mentioned.

  When the resin porous membrane is for treatment of an aqueous solution, the thickness of the resin substrate is preferably 10 μm to 1 mm, and more preferably 20 to 500 μm.

  Moreover, it is preferable that a graft chain exists from the resin base material surface to the depth of 0.1-20 micrometers, and it is more preferable to exist to the depth of 0.1-10 micrometers. Preferably the depth at which the graft chain is present is 0.1 to 50% of the thickness of the resin substrate, preferably 1 to 30%, more preferably 1 to 20%, and even more preferably 1 to 5%. Good. Preferably, the depth at which the graft chain exists is 0.1 μm or more. For example, the graft chain may be present from the surface of the resin substrate to a depth of 0.1 to 40 μm, preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm, for example 0.5 to 5 μm. .

  The depth at which the graft chain is present in the resin substrate can be measured, for example, by observing the cross section of the resin substrate with a scanning electron microscope. More specifically, it can be measured by conducting elemental analysis with EPMA or EDX.

  When the resin porous membrane is used for treatment of an aqueous solution, the ionizing radiation in the graft reaction is preferably an electron beam. Moreover, 5-100 keV is preferable and the acceleration energy in the sample surface at the time of irradiation has more preferable 30-70 keV. The absorbed dose is preferably 1 to 100 kGy, more preferably 1 to 50 kGy, still more preferably 1 to 25 kGy, still more preferably 1 to 15 kGy, for example 1 to 10 kGy.

  When the resin porous membrane is used for treatment of an aqueous solution, the contact angle of water on the surface is preferably 80 ° or less, more preferably 75 ° or less, and further preferably 70 ° or less. By having such a contact angle of water, higher fouling resistance can be achieved.

  In the present invention, the contact angle can be measured by a static method using water as the contact liquid. For example, when the resin porous membrane is a hollow fiber porous membrane, the hollow fiber porous membrane wet with water is fixed on a glass plate, and after wiping off the water on the surface of the hollow fiber porous membrane, 2 μL of water droplets are added. Dripping. When a tangent line is drawn on the curved surface of the liquid from the part where the solid (hollow fiber porous membrane), liquid (water) and gas (generally air) are in contact, the angle formed by this tangent and the solid surface is contacted It is a corner value.

The resin porous membrane for treating an aqueous solution of the present invention has a water permeability of preferably 10 to 10,000 L / m ² · h · atm, more preferably 100 to 10,000 L / m ² · h · atm. is there.

  The average pore diameter in the treatment resin porous membrane of the aqueous solution of the present invention is preferably 5 to 500 nm, more preferably 5 to 300 nm, and still more preferably 10 to 200 nm. That is, the porous resin membrane of the present invention can be used as an ultrafiltration membrane or a microfiltration membrane.

The average pore diameter can be measured by a bubble point method. For example, when the resin porous membrane is a hollow fiber porous membrane, when one end of the hollow fiber porous membrane is closed and then immersed in ethanol, and the other end is pressurized with nitrogen gas, the porous hollow fiber membrane Can be calculated as follows using the pressure (p) at which the bubble of nitrogen gas begins to come out. Assuming that the maximum pore diameter is d and the surface tension at the interface between ethanol and air is γ,
d = Cγ / p
Here, when the immersion liquid is ethanol, Cγ = 0.632 (kg / cm), and the maximum pore diameter d (μm) is obtained by substituting p (kg / cm ² ) into the above equation. be able to.

The porosity of the water treatment resin porous membrane of the present invention is 20 to 90%, preferably 25 to 85%, more preferably 30 to 70%. From the viewpoint of increasing the filtration rate, the porosity is preferably 20% or more. Moreover, it is preferable that it is 90% or less from the point which maintains the reliability of fine particle removal, and maintains the intensity | strength of a porous film. Here, the porosity is defined by the following equation.
Porosity (%) = (1-resin weight / (resin density × volume)) × 100

  The porous membrane for aqueous solution treatment of the present invention as described above can impart chemical resistance, heat resistance, oil resistance and the like in addition to hydrophilicity by appropriately selecting the base material and the graft chain. Therefore, it can be used for the treatment of various aqueous solutions. The treatment of the aqueous solution is not particularly limited, but is included in preparations such as seawater desalination, water treatment such as water and sewage treatment, water treatment of radioactive substance-containing water; plasma fractionation preparations, biopharmaceuticals, etc. Examples include treatment for removing viruses and pathogenic proteins that may be present; treatment of chemicals, for example, treatment for removing impurities in sulfuric acid-per-water used for cleaning silicon wafers, and the like. Preferably, the aqueous solution treatment porous membrane of the present invention is a water treatment porous membrane.

  In another aspect, the resin porous membrane of the present invention can be used for treating an organic solvent solution.

  In this embodiment, the resin base material is preferably formed of a fluorine-containing resin having high chemical resistance, although it depends on the type of the organic solvent solution.

  Preferred fluororesins are polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer and perfluoroalkoxy copolymer, and polytetrafluoroethylene is more preferred.

  The type of graft chain is appropriately selected according to the type of organic solvent in the organic solvent solution and the type of fouling substance.

  In another aspect, the resin porous membrane of the present invention can be used for gas treatment.

  Although it does not specifically limit as a process of gas, For example, highly purified organic solvent and an air filter are mentioned.

  The type of the resin substrate and the type of graft chain are appropriately selected according to the type of gas and the type of fouling substance.

Production Example 1
16.0% by weight of polyvinylidene fluoride, 79.0% by weight of solvent N, N-dimethylacetamide) and 5% by weight of a film-forming auxiliary (lithium chloride) are mixed and mixed at 50 ° C. overnight using a rotor. The raw material was obtained. The obtained mixed raw material was put into a hollow fiber membrane production apparatus, discharged from a double tube cap to a water tank at 25 ° C., and wound up at a speed of 10 m / min to obtain a porous membrane. The operation of immersing the porous membrane in water at 25 ° C. for 1 hour was repeated four times to extract and remove the solvent, thereby obtaining a hollow fiber membrane-shaped porous membrane.

Example 1
The polyvinylidene fluoride porous membrane prepared in Production Example 1 was immersed in an aqueous solution of 50% by volume polyethylene glycol methacrylate (PEGMA) (average molecular weight = 300) to impregnate the porous membrane with PEGMA. The porous film was placed in an electron beam irradiation chamber of an ultra-low energy electron beam EB-ENGINE (manufactured by Hamamatsu Photonics) and replaced with nitrogen gas, and then the surface of the porous film was irradiated with an electron beam of 8 kGy (irradiation condition: irradiation voltage). 60 kV, irradiation intensity 10 μA, sweep speed 10 cm / s, sample-irradiation window distance 15 mm). After irradiating an electron beam on one side, the hollow fiber membrane was turned over and the other was irradiated with an electron beam with the same irradiation dose. After the electron beam irradiation, the porous membrane was washed in a 50% by volume acetone / isopropanol solution, and then washed with water to obtain a polyvinylidene fluoride porous membrane grafted with PEGMA.

Example 2
A porous film of Example 2 was obtained in the same manner as in Example 1 except that the irradiation dose was 4 kGy (irradiation voltage 60 kV, irradiation intensity 5 μA, sweep rate 10 cm / s).

Example 3
A porous film of Example 3 was obtained in the same manner as in Example 1 except that the irradiation dose was 2 kGy (irradiation voltage 60 kV, irradiation intensity 5 μA, sweep rate 20 cm / s).

Test example 1
(Contact angle)
About the porous film obtained by manufacture example 1 and Examples 1-3, the initial contact angle of water was measured. Specifically, the initial static contact angle was 2 μL of water using a contact angle measuring device.

(Measurement of water permeability)
For the porous membranes obtained in Production Example 1 and Examples 1 to 3, the water permeability of pure water (unit of water permeability: L / () was determined by an internal pressure test under the conditions of 25 ° C. and inter-membrane differential pressure of 50 kPa. m ² · hr · atm)).

(Thermogravimetry)
The graft ratio of the porous membranes obtained in Examples 1 to 3 was measured by thermogravimetry using a differential thermobalance (TG-DTA).

(Anti-fouling test)
About the porous membrane obtained by manufacture example 1 and Examples 1-3, the fouling test of one hollow fiber membrane was done using the external pressure type water permeability measuring apparatus. BSA (bovine serum albumin: Wako Pure Chemical Industries, Ltd.) aqueous solution (1000 ppm, pH 7.0) was used as the supply liquid. One hollow fiber membrane is set in the external pressure type water permeability measuring device, the permeation pressure is adjusted to 0.5 atm, and at the same time the pure water is supplied under the conditions of a temperature of 25 ° C. and a flow rate of 15 mL / min. Flowed for more than 30 minutes. Thereafter, the feed liquid was switched to a BSA aqueous solution and allowed to flow under conditions of a temperature of 25 ° C. and a flow rate of 15 mL / min, and the water permeation amount after 30 minutes and 2 hours elapsed was compared with the initial value. Evaluation was performed according to the following criteria.
◎: Water permeability after 2 hours has been kept at 50% or more compared to the initial value ○: Water permeability after 30 minutes has been kept at 50% or more compared to the initial value ×: Water permeability after 30 minutes has passed 50% or less compared to the initial stage

The results are summarized in the following table.

  From the above results, it was confirmed that the surface of the porous membrane was grafted by irradiating the surface of the porous membrane with an electron beam. It was also confirmed that the contact angle was reduced and the surface of the porous membrane was made hydrophilic. Furthermore, it was confirmed that a sufficient amount of water permeability could be secured and that the fouling resistance was also excellent. From this, the surface of the porous membrane is sufficiently grafted, and good fouling resistance is obtained. On the other hand, the grafting does not progress so much in the porous membrane, particularly in the pores, and a sufficient amount of water permeability is obtained. It is thought that it was secured.

  The porous membrane of the present invention can be used for the treatment of various fluids.

Claims (7)

  A resin porous membrane for fluid treatment, wherein the molecular chain present on the surface portion of the resin porous substrate has a graft chain, and the graft ratio is 0.1 to 5%.   The resin porous membrane according to claim 1, which is used for liquid treatment.   The resin porous film according to claim 1 or 2, wherein a water contact angle is 80 ° or less.   The resin porous membrane according to claim 1 or 2, wherein the resin porous substrate is a fluororesin porous substrate.   The resin porous membrane according to claim 2 or 3, which is used for aqueous solution treatment.   The resin porous membrane according to claim 2 or 3, which is used for organic solvent solution treatment.   The surface of the resin porous substrate is irradiated with ionizing radiation to generate radicals, and is obtained by graft polymerization of the generated radical and a compound containing a radical and a reactive group. A resin porous membrane according to any one of the above.