JP2018130671A - Surface-modified porous film and manufacturing method of the same - Google Patents

Abstract

[Problem] The present invention provides a surface-modified porous membrane that is provided with a function by simply introducing a functional polymer layer onto the surface of the porous membrane. [Solution] The surface-modified porous membrane is characterized in that the nitrogen gas permeation rate at a transmembrane pressure difference of 70 kPa is 4.1 x 103 to 6.8 x 103 mL/cm2/min, and the ratio of the pure water permeation rate to the nitrogen gas permeation rate (pure water permeation rate/nitrogen gas permeation rate) at a transmembrane pressure difference of 70 KPa is 6.0 x 10-3 to 8.0 x 10-3. [Selected Figures] None

Description

  The present invention relates to a surface-modified porous membrane and a method for producing the same.

The modification method of the surface of the porous membrane includes a method of coating a functional polymer on the membrane surface, a method of forming a porous membrane after blending the functional polymer with the membrane material, a method of treating with plasma or corona, and a membrane surface. There has been proposed a method of introducing a polymerization initiating group into a graft polymerization and the like.
The method of coating the functional polymer is simple and widely used, but the coated functional polymer is easily peeled off from the porous membrane, and it has been difficult to stably maintain the function for a long period of time. The method of blending a membrane material with a functional polymer and then forming it into a porous membrane is a simple method that does not require special equipment, but in order to sufficiently coat the membrane surface with a functional polymer, a functional polymer is added. The amount must be considerably increased, which tends to cause deterioration of mechanical properties and chemical resistance of the film, and further increases the cost due to the addition of a large amount of functional polymer. On the other hand, methods using plasma treatment or corona treatment require a large-scale apparatus, and have a drawback that the substrate is easily damaged during the treatment. The method of introducing a polymerization initiating group on the surface and performing graft polymerization is an excellent modification method because it has excellent long-term stability and there is no damage to the base material. The disadvantage is that it requires a simple introduction reaction.

  Patent Documents 1 and 2 describe a method for introducing a functional polymer onto a substrate surface using a nitrene insertion reaction as a method for improving the drawbacks of the conventional modification method. This method is excellent in that it can be introduced onto the surface of a substrate through a functional polymer covalent bond by a simple method such as coating of a functional polymer and UV irradiation. However, because the nitrene insertion reaction is consumed not only by the reaction with the base material at the base material interface but also by the internal crosslinking of the functional polymer, there are many functional polymers introduced and immobilized. However, there was a case where the function did not appear. In addition, when coating on the surface of the porous membrane, the pores are clogged with the functional polymer and fixed, so that there is a drawback that the air permeability and water permeability as the porous membrane are lowered.

Japanese Patent Publication No. 3-505979 JP 2010-59346 A

  An object of the present invention is to produce and provide a surface-modified porous membrane that has a function by simply introducing a functional polymer layer on the surface of the porous membrane.

  In order to achieve the above object, as a result of intensive studies by the present inventors, selecting a hydrophilic unit containing a hydrophilic group in the functional polymer layer, a secondary amino group unit that is a crosslinking point at a specific ratio And that a functional polymer layer is formed on the surface of the porous membrane and treated with a basic oxidizing agent to provide high functionality to the surface-modified porous membrane, thereby completing the present invention. It came.

That is, the present invention provides a surface-modified porous membrane that satisfies the following [1] to [9] and a method for producing the same.
[1] A surface-modified porous membrane having a nitrogen gas permeation amount of 4.1 × 10 ^{3 to} 6.8 × 10 ³ mL / cm ² / min at a transmembrane pressure difference of 70 kPa, and a transmembrane difference The surface is characterized in that the ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) at a pressure of 70 KPa is 6.0 × 10 ^{−3 to} 8.0 × 10 ^−3. Modified porous membrane.
[2] The surface-modified porous membrane is composed of a porous membrane and a functional polymer layer formed on the membrane surface, and the functional polymer layer is bonded to the porous membrane surface via a covalent bond. The surface-modified porous membrane according to [1].
[3] The functional polymer layer is a polymer of a monomer having a hydrophilic group selected from an alkoxyalkyl group, a monoalkoxypolyoxyethylene group, a polyoxyethylene group or a betaine group and a polymerizable vinyl group. It consists of a functional unit and a secondary amino group unit which is a polymer having a secondary amino group as a crosslinking point, and the secondary amino group unit is 5 to 30 mol%, [1] Alternatively, the surface-modified porous membrane according to [2].
[4] The surface-modified porous film according to any one of [1] to [3], wherein the porous film is made of a resin having a carbon-hydrogen bond and a carbon-fluorine bond.
[5] in the Fourier transform infrared spectroscopy in attenuated total reflection method, the absorption ratio of 1,170Cm ^-1 and ^{1,070cm -1 (1,170cm -1 / 1,070cm -1} ) is 1.0 to 2 The surface-modified porous membrane according to any one of [1] to [4], which is 0.0.
[6] The surface-modified porous membrane according to any one of [1] to [5], wherein the material of the porous membrane is polyvinylidene fluoride. The functional polymer layer is formed on the surface of the porous membrane via a covalent bond by ultraviolet irradiation, and the product of the basic oxidant concentration and the treatment time is 20,000 to 100 in the basic oxidant aqueous solution. The method for producing a surface-modified porous membrane according to any one of [1] to [6], wherein the surface-modified porous membrane is immersed so as to be 1,000 ((mg / L) · h).
[8] The method for producing a surface-modified porous film according to [7], wherein the functional polymer is composed of a functional unit and a unit having 5 to 30 mol% of a nitrene precursor functional group. . [9] The method for producing a surface-modified porous membrane according to [7] or [8], wherein the basic oxidizing agent aqueous solution is a sodium hypochlorite aqueous solution.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

The surface-modified porous membrane of the present invention has a nitrogen gas permeation amount of 4.1 × 10 ^{3 to} 6.8 × 10 ³ mL / cm ² / min at a transmembrane differential pressure of 70 kPa and a transmembrane differential pressure of 70 kPa. The ratio of the pure water permeation amount and the nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) is 6.0 × 10 ^{−3 to} 8.0 × 10 ⁻³ .

  The nitrogen gas permeation amount depends on the porous membrane structure such as the porosity of the porous membrane, pore blockage, and pore diameter, and does not depend on the polarity of the material. In the present invention, by measuring the nitrogen gas permeation amount at the same pressure, it can be used as an index of pore clogging.

  The nitrogen gas permeation amount can be obtained by passing pure water by dead end filtration, flowing nitrogen gas at a transmembrane pressure difference of 70 kPa, and measuring the nitrogen flow rate after the outlet pressure becomes constant.

A general porous membrane having an average pore diameter of 0.2 μm has a nitrogen gas permeation amount of 4.0 × 10 ³ mL / cm ² / min at a transmembrane pressure difference of 70 kPa, and the surface-modified porous membrane in the present invention is The nitrogen gas permeation amount at a transmembrane pressure difference of 70 kPa is 4.1 × 10 ^{3 to} 6.8 × 10 ³ mL / cm ² / min, which indicates that the pores are not blocked by the functional polymer layer.

  The permeated water amount of pure water can be obtained by passing pure water through dead-end filtration under a transmembrane pressure of 70 kPa and measuring the permeated water amount after the outlet pressure becomes constant.

A general porous membrane having an average pore diameter of 0.2 μm has a permeate amount of 21 mL / cm ² / min at a transmembrane differential pressure of 70 kPa, and the surface-modified porous membrane of the present invention has a permeate amount of water at a transmembrane differential pressure of 70 kPa. Is 25 to 55 mL / cm ² / min, indicating that the water permeability is improved by the functional polymer layer.

In general, in the membrane separation activated sludge method, the membrane is clogged by so-called fouling, where micro solids, microbial-derived biofilms, colloids, organic matter, inorganic substances, etc. are deposited on the membrane. Rises. Membrane cleaning is performed to eliminate clogging, and the timing of cleaning is based on the time when the transmembrane pressure difference reaches 70 kPa. That is, the surface-modified porous membrane of the present invention has a ratio of the permeated water amount to the nitrogen gas permeating amount (pure water permeating water amount / nitrogen) even in a state where clogging occurs at an intermembrane differential pressure of 70 kPa. Gas permeation amount) of 6.0 × 10 ^{−3 to} 8.0 × 10 ⁻³ indicates that water permeability is improved without causing clogging of the pores.

  The surface-modified porous membrane of the present invention comprises a porous membrane and a functional polymer layer formed on the membrane surface, and the functional polymer layer is bonded to the porous membrane surface via a covalent bond. Preferably there is.

  Examples of the shape of the porous membrane include a flat membrane-like porous membrane and a hollow fiber-like porous membrane.

  The porous membrane having the above-mentioned shape is mainly used as a microfiltration membrane or an ultrafiltration membrane. The microfiltration membrane mentioned here is a porous membrane having a pore diameter of about 0.05 to 10 μm, and the material is polyethylene, polypropylene, polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene. Polyacrylonitrile, polycarbonate, polysulfone, cellulose acetate and the like are used. On the other hand, the ultrafiltration membrane is a porous membrane having a pore size of about 2 to 50 nm, and the material is polyethylene, polyacrylonitrile, polyvinyl chloride, polyvinyl chloride-polyacrylonitrile copolymer, polysulfone, polyethersulfone, Polyvinylidene fluoride, aromatic polyamide, polyimide, cellulose acetate and the like are used.

In many cases, microfiltration membranes have a uniform porous structure, whereas ultrafiltration membranes have an asymmetric membrane structure in which the porous structure differs between the dense layer on the surface and the inner support layer. Yes. Furthermore, a composite film in which two or more kinds of materials are combined may be used. As the composite membrane, a membrane in which a porous layer, which is a separation functional layer, and a base material for reinforcing the composite layer is preferably used. Examples of the base material used for reinforcement include polyester fibers, nylon fibers, polyurethane fibers, acrylic fibers, rayon fibers, cotton, silk and other organic fibers and their woven fabrics, knitted fabrics, non-woven fabrics, glass fibers, metal fibers, etc. And inorganic fibers such as those and their woven and knitted fabrics.
Some examples of composite membranes include flat membrane ultrafiltration membranes that combine polyethersulfone porous membranes with polyester nonwoven fabrics, and flat membrane-like microfiltration membranes that combine polyvinylidene fluoride porous membranes with polyester nonwoven fabrics. And a hollow fiber microfiltration membrane in which a polyester braid is combined with a polyvinylidene fluoride porous membrane.

  A battery separator is also preferably used as the porous membrane used in the present invention. The battery separator is a porous film that separates the positive electrode and the negative electrode in the battery and retains the electrolytic solution to ensure ionic conductivity between the positive electrode and the negative electrode, and has a pore diameter of about 0.05 to 1 μm. is there.

  As the material for the porous membrane of the present invention, those that are preferably used have a carbon-hydrogen bond that forms a secondary amino group that becomes a crosslinking point upon irradiation of the functional polymer with ultraviolet rays, and are chemically stable. Examples of the resin having a carbon-fluorine bond include polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene / ethylene copolymer, chlorotrifluoroethylene / ethylene copolymer, and particularly preferably polyvinylidene fluoride. It is done. Lamination of these materials and compounding by coating are also included in the scope of the present invention.

  The thickness of the porous film is not particularly limited as long as light reaches the inside, and can be selected in the range of 1 to 500 μm.

  As the functional polymer layer used in the present invention, a polymer of a monomer having a hydrophilic group selected from an alkoxyalkyl group, a monoalkoxypolyoxyethylene group, a polyoxyethylene group or a betaine group and a polymerizable vinyl group And a secondary amino group unit that is a polymer having a secondary amino group that is a crosslinking point, and the secondary amino group unit is used in an amount of 5 to 30 mol%.

  By forming the functional polymer layer on the surface of the porous membrane, various functions derived from the functional unit can be immobilized and introduced on the surface of the porous membrane.

  The functional unit of the functional polymer layer is a porous membrane that has functions such as imparting hydrophilicity and wettability to the electrolyte solution, inhibiting protein adsorption, preventing biofouling, antithrombogenicity, biocompatibility, and antistatic properties. It contains a hydrophilic group which is electrically neutral (apparently has no charge).

  The secondary amino group unit of the functional polymer layer is a secondary amino group in which the nitrene precursor functional group generates nitrene by light irradiation, and the nitrene is inserted into a carbon-hydrogen bond or a nitrogen-hydrogen bond to form a crosslinking point. Is a unit to form. It is important that the secondary amino group unit is contained in the functional polymer layer in an amount of 5 to 30 mol% in order to exhibit the effects of the present invention. When the secondary amino group unit is contained in the functional polymer layer in an amount of 5 to 30 mol%, the functional polymer layer can be used without inhibiting functions such as protein adsorption suppression, biofouling prevention, and antithrombogenicity. Immobilization to the porous membrane surface can be performed sufficiently.

  The functional unit constituting the functional polymer of the present invention is polymerized with a hydrophilic group selected from an alkoxyalkyl group, a monoalkoxypolyoxyethylene group, a polyoxyethylene group, a sulfobetaine group, a carboxybetaine group or a phosphobetaine group. It is a polymer of a monomer having a functional vinyl group.

  Specific examples of the alkoxyalkyl group that is a hydrophilic group include a methoxyethyl group, a methoxypropyl group, a methoxybutyl group, and an ethoxyethyl group.

  Specific examples of the monoalkoxypolyoxyethylene group include 2- (2-methoxyethoxy) ethyl group, 2- (2-ethoxyethoxy) ethyl group, 2- {2- (2-methoxyethoxy) ethoxy} ethyl. Group, methoxypolyoxyethylene group, ethoxypolyoxyethylene group and the like. Specific examples of the polyoxyethylene group include 2- (2-hydroxyethoxy) ethyl group, 2- {2- (2-hydroxyethoxy) And ethoxy} ethyl group, ω-hydroxypolyoxyethylene group and the like.

  A betaine group has a positively charged portion and a negatively charged portion in an ionized state at non-adjacent positions in the same group, and a dissociable hydrogen atom is bonded to a positively charged atom. In general, it refers to a group that is electrically neutral (has no charge) as a whole. Specific examples of the betaine group include a sulfobetaine group, a carboxybetaine group, and a phosphobetaine group.

  Examples of the vinyl group include a methacryloxy group, a methacrylamide group, an acryloxy group, an acrylamide group, a styryl group, and the like, but in terms of excellent mechanical strength of the polymer and an affinity with a polymer porous membrane. A methacryloxy group and an acryloxy group are preferred.

  Specific examples of the monomer include methoxyethyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylamide, methoxyethyl acrylamide, 2-methoxyethoxystyrene, 2- (2-methoxyethoxy) ethyl methacrylate, 2- (2-methoxyethoxy) Ethyl acrylate, 2- (2-methoxyethoxy) ethyl methacrylamide, 2- (2-methoxyethoxy) ethyl acrylamide, 2- (2-methoxyethoxy) ethoxystyrene, polyethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether acrylate, polyethylene Glycol methyl ether methacrylamide, polyethylene glycol methyl ether acrylamide, polyethylene glycol ethyl ether Methacrylate, polyethylene glycol ethyl ether acrylate, polyethylene glycol ethyl ether methacrylamide, polyethylene glycol ethyl ether acrylamide, 2- (2-hydroxyethoxy) ethyl methacrylate, 2- (2-hydroxyethoxy) ethyl acrylate, 2- (2-hydroxy Ethoxy) ethyl methacrylamide, 2- (2-hydroxyethoxy) ethyl acrylamide, 2- (2-hydroxyethoxy) ethoxy styrene, polyethylene glycol monomethacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylamide, polyethylene glycol monoacrylamide, N -Methacryloyl-L-histidine, 2-methacryloyloxyethyl Suhorirukorin, 2- (N-3- sulfopropyl -N, N-dimethylammonium) ethyl methacrylate, 2-(N-carbomethoxy -N, N-dimethylammonium) ethyl methacrylate.

  The secondary amino group unit constituting the functional polymer of the present invention is obtained by covalently bonding a polymer of a monomer having a nitrene precursor functional group and a vinyl group to a porous surface. The nitrene precursor functional group is an azide group, specifically, an aryl azide such as phenyl azide and tetrafluorophenyl azide; an acyl azide such as benzoyl azidomethyl benzoyl azide; Although sulfonyl azides, such as benzene sulfonyl azide, are mentioned, Preferably an aryl azide is used. Examples of the vinyl group include a methacryloxy group, a methacrylamide group, an acryloxy group, an acrylamide group, and a styryl group. In the case of a polymer of a monomer having a methacryloxy group or an acryloxy group as a functional unit, A methacryloxy group and an acryloxy group are preferable from the viewpoint of enhancing the polymerizability.

Specific examples of the monomer include methacryloyloxypropyloxy 4-phenylazide, acryloyloxypropyloxy 4-phenylazide, methacrylamidepropyloxy 4-phenylazide, acrylamidopropyloxy 4-phenylazide, methacryloyloxyethyloxy 4-phenyl Azide, acryloyloxyethyloxy 4-phenylazide, methacrylamidoethyloxy 4-phenylazide, acrylamidoethyloxy 4-phenylazide, methacryloyloxyethyloxycarboxy 4-phenylazide, acryloyloxyethyloxycarboxy 4-phenylazide, methacrylamide Ethyloxycarboxy 4-phenylazide, acrylamide ethyloxycarboxy 4-phenylazide, Tacryloyloxyethyl 4-phenylazide, acryloyloxyethyl 4-phenylazide, methacrylamidoethyl 4-phenylazide, acrylamidoethyl 4-phenylazide, methacryloyloxypropyl 4-phenylazide, acryloyloxypropyl 4-phenylazide, methacrylamide Propyl 4-phenylazide, acrylamidopropyl 4-phenylazide, methacryloyloxybutyl 4-phenylazide, acryloyloxybutyl 4-phenylazide, methacrylamidobutyl 4-phenylazide, acrylamidobutyl 4-phenylazide, methacryloyloxyethyloxycarboxy 2 , 3,5,6-tetrafluoro-4-phenylazide, acryloyloxyethyloxycarboxy 2,3 , 6-tetrafluoro-4-phenyl azide, methacrylamidoethyloxycarboxy 2,3,5,6-tetrafluoro-4-phenyl azide, acrylamidoethyloxycarboxy 2,3,5,6-tetrafluoro-4-phenyl Azide, methacryloyloxypropyloxy 2,3,5,6-tetrafluoro-4-phenylazide, acryloyloxypropyloxy 2,3,5,6-tetrafluoro-4-phenylazide, methacrylamidepropyloxy 2,3 5,6-tetrafluoro-4-phenyl azide, acrylamidopropyloxy 2,3,5,6-tetrafluoro-4-phenyl azide, methacrylamide 4-phenyl azide, acrylamide 4-phenyl azide, methacrylamide 2,3 5,6-tetrafluoro Examples include rho-4-phenyl azide, acrylamide 2,3,5,6-tetrafluoro-4-phenyl azide and the like.

  In the present invention, it is necessary to synthesize a copolymer so that the unit having the nitrene precursor functional group is contained in the functional polymer in an amount of 5 to 30 mol%.

  When the copolymerization of the monomer constituting the functional unit and the monomer having a nitrene precursor functional group is good, the monomer charge ratio is such that the monomer having a nitrene precursor functional group is 5 to 30 mol% in the total monomers. The polymerization may be performed in On the other hand, when the copolymerization property of the monomer having a nitrene precursor functional group is low, it is necessary to charge an excessive amount of the monomer having a nitrene precursor functional group. It should be noted that other monomers may be copolymerized without departing from the effects of the present invention. There are no particular restrictions on the polymerization, and radical polymerization or ionic polymerization may be used, and any method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, dispersion polymerization, and precipitation polymerization may be used. Absent. From the viewpoint of ease of operation, radical polymerization, particularly free radical polymerization is preferably used.

  The molecular weight of the functional polymer is preferably in the range of 1,000 to 1,000,000, and preferably in the range of 5,000 to 500,000 from the viewpoints of viscosity and solubility during coating and mechanical strength of the polymer layer. The functional polymer is a copolymer of a functional unit and a unit having a nitrene precursor functional group, but they may be arranged at random or in a block form. The functional polymer is soluble in water, but may be water-soluble or water-insoluble. For example, when the functional unit is water-soluble and the proportion of units having a nitrene precursor functional group is low, the functional unit is water-soluble, but when the proportion of units having a nitrene precursor functional group is high, it does not dissolve in water.

Porous film used for the surface modification porous membrane of the present invention, in the Fourier transform infrared spectroscopy in attenuated total reflection method, the absorption ratio of the porous membrane surface of 1,170Cm ^-1 and 1,070cm ^-1 (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is preferably 0.5 to 1.0. The absorption at 1,170 cm ^{−1 is} the absorption derived from the carbon-fluorine bond, and the absorption at 1,070 cm ⁻¹ is the absorption derived from the carbon-hydrogen bond bending vibration, so that the functional polymer layer is efficiently used as a porous film. In order to form it, it is preferable that many carbon-hydrogen bonds exist on the surface. Within the range of the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 porous membrane surface ^{(1,170cm -1} / 1,070cm -1) is 0.5 to 1.0 carbon - fluorine bonds Since the chemical stability is maintained and the surface carbon-hydrogen bonds are sufficiently present, the functional polymer layer can be fixed evenly, which is preferable.

Surface modified porous membrane of the present invention, in the Fourier transform infrared spectroscopy in attenuated total reflection method, the absorption ratio of 1,170Cm ^-1 and 1,070cm ^{-1 (1,170cm -1} / 1,070cm ^-1 ) Is 1.0 to 2.0. The 1,170 cm ⁻¹ absorption includes an absorption peak of carbon-oxygen bonds derived from the functional polymer layer in addition to absorption derived from carbon-fluorine bonds. By performing the surface modification treatment, 1,170 cm ⁻¹ absorption is increased as compared with that before the surface modification, which means that the functional polymer layer is immobilized on the porous film. In the Fourier transform infrared spectroscopy in attenuated total reflection method, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface modification porous membrane ^{(1,170cm -1} / 1,070cm -1) is 1. If it is 0 to 2.0, excessive formation on the porous film by the functional polymer layer is suppressed, that is, the pores are maintained, and there is a sufficient amount of the functional polymer layer. Functions such as water permeability and antifouling properties are effectively expressed.

  In the method for producing a surface-modified porous membrane of the present invention, a functional polymer is present on the surface of the porous membrane, a functional polymer layer is formed on the porous membrane surface via a covalent bond by ultraviolet irradiation, and then basic oxidation is performed. It is characterized in that it is immersed in the aqueous solution of the agent so that the product of the basic oxidant concentration and the treatment time is 20,000 to 100,000 ((mg / L) · h).

  The formation of an excess functional polymer layer causes the air permeability and water permeability, which are the original functions of the porous membrane, to decrease, but in the present invention, the excess functional polymer layer once fixed is used as a basic oxidizing agent. By treating with clogging, it is possible to eliminate clogging while maintaining the functional polymer layer.

  That is, in the present invention, the “basic oxidizing agent” is a pore regenerating agent for closed pores formed by an excess functional polymer layer. Commonly known basic oxidants include halogen oxo acids and their metal salts. Examples of halogen oxoacids include hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hypobromous acid, hypoiodous acid, and the like, and metal salts thereof include sodium hypochlorite, hypochlorous acid, and the like. Examples include calcium chlorate, sodium chlorite, and potassium chlorite. Among them, sodium hypochlorite having high oxidizing power is preferable.

  The method for allowing the functional polymer to be present on the surface of the porous membrane is not particularly limited, and a method of coating the porous membrane as it is or after diluting with a solvent can be used. The coating method is not particularly limited, and can be selected from dip coating, spin coating, gravure coating, roll coating, bar coating, die coating, knife coating, etc. according to the shape of the porous film and the viscosity of the functional polymer (solution) to be coated. Just do it. When the functional polymer is diluted with a solvent and used for coating, it is preferable to remove the solvent by drying or the like before ultraviolet irradiation.

The functional polymer is allowed to exist on the surface of the porous membrane by the above method and then irradiated with ultraviolet light. The light needs to be light having a wavelength that allows the photoreactive group to be used to generate nitrene. When an azide group is used as the photoreactive group, the light is irradiated with ultraviolet rays having a wavelength of 10 to 400 nm, preferably 250 to 380 nm. . Although the intensity | strength of the ultraviolet-ray to irradiate is not specifically limited, It can select suitably in the range of 1-1000 mW / cm < ² >.

  In the present invention, the treatment capacity of the basic oxidant is indicated by the product of the basic oxidant concentration and the treatment time, and is preferably in the range of 20,000 to 100,000 ((mg / L) · h). The functional polymer layer directly bonded to the polymer porous membrane is also removed by controlling the treatment capacity with the basic oxidant within the range of 20,000 to 100,000 ((mg / L) · h). Since only the excess functional polymer layer can be removed appropriately, pore clogging can be eliminated, surface modification effect is effectively expressed, high permeated water amount, high antifouling surface modification It becomes a porous membrane.

  The basic oxidant concentration is preferably 2,000 to 10,000 (mg / L). When the basic oxidant concentration is controlled within the range of 2,000 to 10,000 (mg / L), it does not adversely affect the functional polymer layer directly bonded to the porous membrane and is chemically stable. This condition is preferable because it can be provided as a membrane and can be reduced to a processing time that does not affect productivity and is advantageous in terms of cost.

  According to the present invention, a functional polymer layer is simply introduced on the surface of the porous membrane to give various functions to the porous membrane, such as hydrophilicity and wettability to the electrolyte solution, protein adsorption inhibition, biofau Prevention of ring generation, antithrombotic properties, biocompatibility, antistatic properties and the like can be imparted. In particular, by controlling the unit having the functional group of nitrene precursor of the functional polymer to a specific range and forming the functional polymer layer on the porous film, the functional polymer layer is treated with a basic oxidant to express a high function. be able to. Such characteristics are particularly useful in water treatment separation membranes and battery separators that require durability capable of maintaining high functionality for a long period of time, and can be widely used in this application field.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
(Production of functional polymer A)
In a glass Schlenk flask, polyethylene glycol monomethyl ether methacrylate (manufactured by Aldrich, number average molecular weight 300, hereinafter abbreviated as PEGMA) (18 mmol) and methacryloyloxypropyloxy-4-phenylazide (2 mmol), 2,2 ′ as an initiator -Azobisisobutyronitrile (AIBN) (0.09 mmol) was weighed. A monomer and an initiator were dissolved using 25 mL of THF to prepare a uniform solution. After sufficiently removing oxygen in the solution with nitrogen, polymerization was carried out at 60 ° C. for 8 hours. After completion of the polymerization, unreacted monomers were removed by reprecipitation using hexane, followed by drying under reduced pressure to obtain a brown syrupy polymer. The obtained polymer had a number average molecular weight of 72,000, a weight average molecular weight of 253,000, and an azide group content of 9 mol%.
(Production of surface-modified porous membrane A-1)
A PVDF composite membrane (MV020 manufactured by Microdyne Nadia) having a nominal pore diameter of 0.2 μm using a polyester nonwoven fabric as a porous membrane as a base material is cut into a 3.5 cm square, and a 1.3 wt% methanol solution of functional polymer A For 5 minutes. Then, it was made to dry at room temperature in nitrogen atmosphere, and the ultraviolet irradiation (100mW / cm < ² >) was then performed for 1 minute using LED (the product made from an ITEC system; main wavelength 365nm). Then, it wash | cleaned by irradiating an ultrasonic wave for 1 minute each in ultrapure water and methanol, and obtained the surface coat porous membrane. Next, the surface-coated porous film was immersed in 200 mL of a 6,000 mg / L sodium hypochlorite aqueous solution for 8 hours. In this case, the treatment capacity with the basic oxidizing agent is 48,000 ((mg / L) · h). Then, the surface modification porous membrane A-1 which removed the excess functional polymer was obtained by irradiating an ultrasonic wave with ultrapure water for 1 minute.
(Membrane surface composition)
In the Fourier transform infrared spectroscopy in attenuated total reflection method, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1,170Cm ⁻¹ / 1,070 cm ⁻¹ ) was 0.53. Absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface modification porous membrane A-1 after treatment with sodium hypochlorite solution ^{(1,170cm -1} / 1,070cm -1) 1.72 Met.
(Measurement of permeate volume and nitrogen flow rate)
Under a transmembrane pressure difference of 70 kPa, pure water was passed through dead-end filtration, and the amount of permeated water after the outlet pressure became constant was measured and found to be 45 mL / cm ² / min. Thereafter, nitrogen gas was flowed at a transmembrane pressure difference of 70 kPa, and the nitrogen flow rate after the outlet pressure became constant was measured and found to be 6.0 × 10 ³ mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 7.4 × 10 ⁻³ .

(Pressure change when passing protein solution)
A 1,000 mg / L aqueous solution of bovine serum albumin was prepared, and after the surface-modified porous membrane A-1 was loaded into the membrane holder, the membrane inlet pressure from the beginning of the passage was measured by passing the solution at 100 mL / min for 5 minutes. The rise was measured. The increase in pressure was as small as 6 kPa, and it was considered that the increase in pressure was also suppressed because the adsorption of protein to the membrane was suppressed.

Example 2
(Production of surface-modified porous membrane A-2)
Surface-modified porous membrane A-2 was obtained in the same manner as in Example 1 except that the treatment conditions with the sodium hypochlorite aqueous solution were changed to 3,000 mg / L for 16 hours. In this case, the treatment capacity with the basic oxidizing agent is 48,000 ((mg / L) · h).
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane A-2 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 1.79.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane A-2 by the same operation as in Example 1 revealed that the permeated water amount was 46 mL / cm ² / min and the nitrogen flow rate was 6.0 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 7.7 × 10 ⁻³ .

(Pressure change when passing protein solution)
When the pressure change when the protein solution was passed through the surface-modified porous membrane A-2 was measured in the same manner as in Example 1, the increase in pressure was as small as 4 kPa, and the protein adsorption to the membrane was suppressed. It is thought that the pressure rise was also suppressed.

Example 3
(Production of surface-modified porous membrane A-3)
Surface-modified porous membrane A-3 was obtained in the same manner as in Example 1 except that the functional polymer A solution was changed to a 2.0 wt% methanol solution.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane A-2 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 1.55.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane A-3 by the same operation as in Example 1 revealed that the permeated water amount was 37 mL / cm ² / min and the nitrogen flow rate was 5.6 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount to nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 6.7 × 10 ⁻³ .

(Pressure change when passing protein solution)
When the pressure change during the passage of the protein solution of the surface-modified porous membrane A-3 was measured by the same operation as in Example 1, the increase in pressure was as small as 9 kPa, and the adsorption of protein to the membrane was suppressed. It is thought that the pressure rise was also suppressed.

Example 4
(Production of surface-modified porous membrane A-4)
Surface-modified porous membrane A-4 was obtained in the same manner as in Example 1 except that the treatment time with the aqueous sodium hypochlorite solution was changed to 12 hours. In this case, the treatment capacity with the basic oxidizing agent is 72,000 ((mg / L) · h).
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption at 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane A-4 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 1.79.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the amount of permeated water and the nitrogen flow rate of the surface-modified porous membrane A-4 was measured in the same manner as in Example 1. As a result, the permeated water amount was 46 mL / cm ² / min, and the nitrogen flow rate was 5.9 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 7.8 × 10 ⁻³ .

(Pressure change when passing protein solution)
When the pressure change when the protein solution was passed through the surface-modified porous membrane A-4 was measured in the same manner as in Example 1, the pressure increase was as small as 4 kPa, and the adsorption of the protein to the membrane was suppressed. It is thought that the pressure rise was also suppressed.

Example 5
(Production of functional polymer B)
To a glass Schlenk flask, sulfobetaine (manufactured by Wako Pure Chemicals, number average molecular weight 279, hereinafter abbreviated as SBMA) (21 mmol) and methacryloyloxypropyloxy-4-phenylazide (10 mmol), 2,2′- Azobisisobutyronitrile (AIBN) (0.14 mmol) was weighed. After adding 80 mL of methanol, oxygen in the solution was sufficiently removed with nitrogen, followed by polymerization at 60 ° C. for 8.5 hours. After completion of the polymerization, the polymerization solution was removed, the precipitated polymer was washed with a methanol / THF mixed solvent, and dried under reduced pressure to obtain a light yellowish white solid polymer. The obtained polymer had a number average molecular weight of 72,000, a weight average molecular weight of 137,000, and an azide group content of 11 mol%.

(Production of surface-modified porous membrane B-1)
Except having changed into the functional polymer B, operation similar to Example 1 was performed and surface modified porous membrane B-1 was obtained.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane B-1 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 1.84.
(Measurement of permeate volume and nitrogen flow rate)
When the measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane B-1 was measured in the same manner as in Example 1, the permeated water amount was 47 mL / cm ² / min, and the nitrogen flow rate was 6.1 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 7.8 × 10 ⁻³ .

(Pressure change when passing protein solution)
When the pressure change during the passage of the protein solution of the surface-modified porous membrane B-1 through the same operation as in Example 1 was measured, the increase in pressure was as small as 3 kPa, and the adsorption of protein to the membrane was suppressed. It is thought that the pressure rise was also suppressed.

Example 6
(Production of functional polymer C)
In a glass Schlenk flask, SBMA (10 mmol) and methacryloyloxypropyloxy-4-phenylazide (10 mmol) and 2,2′-azobisisobutyronitrile (AIBN) (0.09 mmol) as an initiator were weighed. . After adding 60 mL of methanol, oxygen in the solution was sufficiently removed with nitrogen, followed by polymerization at 60 ° C. for 6.5 hours. After completion of the polymerization, the polymerization solution was removed, the precipitated polymer was washed with a methanol / THF mixed solvent, and dried under reduced pressure to obtain a light yellowish white solid polymer. The obtained polymer had a number average molecular weight of 59,000, a weight average molecular weight of 105,000, and an azide group content of 20 mol%.
(Production of surface-modified porous membrane C-1)
Except having changed into the functional polymer C, operation similar to Example 1 was performed and the surface modification porous membrane C-1 was obtained.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane C-1 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 1.77.
(Measurement of permeate volume and nitrogen flow rate)
When the measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane C-1 was measured by the same operation as in Example 1, the permeated water amount was 43 mL / cm ² / min, and the nitrogen flow rate was 5.6 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 7.6 × 10 ⁻³ .

(Pressure change when passing protein solution)
When the pressure change when the protein solution was passed through the surface-modified porous membrane C-1 was measured in the same manner as in Example 1, the increase in pressure was as small as 5 kPa, and protein adsorption to the membrane was suppressed. It is thought that the pressure rise was also suppressed.

Example 7
(Production of functional polymer D)
Carboxybetaine (manufactured by Osaka Organic Chemical Industry, number average molecular weight 233, hereinafter abbreviated as CBMA) (125 mmol) and methacryloyloxypropyloxy-4-phenylazide (31 mmol) and 2,2′- Azobis (2,4-dimethylvaleronitrile) (ADVN) (0.70 mmol) was weighed. After adding 700 mL of ethanol, oxygen in the solution was sufficiently removed with nitrogen, and polymerization was performed at 60 ° C. for 8 hours. After completion of the polymerization, the solvent was distilled off, the precipitated polymer was washed with 2-propanol and methanol / THF mixed solvent, and dried under reduced pressure to obtain a light yellowish white solid polymer. The obtained polymer had a number average molecular weight of 33,000, a weight average molecular weight of 49,000, and an azide group content of 10 mol%.
(Production of surface-modified porous membrane D-1)
Except having changed to the functional polymer D, operation similar to Example 1 was performed and the surface modification porous membrane D-1 was obtained.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane D-1 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 1.81.
(Measurement of permeate volume and nitrogen flow rate)
When the measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane D-1 was measured in the same manner as in Example 1, the permeated water amount was 50 mL / cm ² / min, and the nitrogen flow rate was 6.4 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 7.7 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the pressure change when the protein solution was passed through the surface-modified porous membrane D-1 was measured in the same manner as in Example 1, the increase in pressure was as small as 4 kPa, and protein adsorption to the membrane was suppressed. It is thought that the pressure rise was also suppressed.

Comparative Example 1
(Membrane surface composition)
When the surface composition of the PVDF composite membrane (MV020 manufactured by Microdyne Nadia) having a nominal pore diameter of 0.2 μm based on the polyester nonwoven fabric used in Example 1 was measured without surface treatment, it was 1,170 cm ^−1. the absorption ratio of ^{1,070cm -1 (1,170cm -1 / 1,070cm -1} ) was 0.53.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the MV020 permeate flow rate and nitrogen flow rate was measured in the same manner as in Example 1. The permeate flow rate was 21 mL / cm ² / min, and the nitrogen flow rate was 4.0 × 10 ³ mL / cm ² / min. there were. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 5.2 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the change in pressure during the passage of the MV020 protein solution was measured in the same manner as in Example 1, the increase in pressure was as large as 77 kPa, and it is considered that biofouling occurred due to the protein adsorbed to the membrane.

Comparative Example 2
(Production of surface-modified porous membrane a-1)
Surface-coated porous membrane a-1 was obtained in the same manner as in Example 1 except that the treatment with the aqueous sodium hypochlorite solution was not performed.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous membrane surface ^{(1,170cm -1} / 1,070cm -1) Was 0.53.
(Measurement of permeate volume and nitrogen flow rate)
When the measurement of the permeated water amount and the nitrogen flow rate of the surface-coated porous membrane a-1 was measured in the same manner as in Example 1, the permeated water amount was 18 mL / cm ² / min, and the nitrogen flow rate was 3.9 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 4.7 × 10 ⁻³ . Since the amount of permeated water is low, it is considered that clogging of pores due to the functional polymer layer has occurred.
(Pressure change when passing protein solution)
When the change in pressure during the passage of the protein solution of the surface-coated porous membrane a-1 was measured by the same operation as in Example 1, the pressure increase was as large as 43 kPa, and biofouling due to the protein adsorbed on the membrane was observed. It is thought that it occurred.

Comparative Example 3
(Production of surface-modified porous membrane a-2)
A surface-coated porous membrane a-2 was obtained in the same manner as in Example 1 except that the treatment time with the aqueous sodium hypochlorite solution was 1 hour. In this case, the treatment capacity with the basic oxidizing agent is 6,000 ((mg / L) · h).
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption at 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane a-2 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 0.77.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane a-2 by the same operation as in Example 1, the permeated water amount was 19 mL / cm ² / min, and the nitrogen flow rate was 3.9 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 4.9 × 10 ⁻³ . Since the treatment capacity of the sodium hypochlorite aqueous solution was low, the amount of permeated water was low, and it is considered that clogging of pores due to the functional polymer A occurred.
(Pressure change when passing protein solution)
When the change in pressure during passage of the protein solution of the surface-modified porous membrane a-2 was measured by the same operation as in Example 1, the increase in pressure was as large as 44 kPa, and biofouling due to protein adsorption to the membrane was observed. It is thought that it occurred.

Comparative Example 4
(Production of surface-modified porous membrane a-3)
A surface-coated porous membrane a-2 was obtained in the same manner as in Example 1 except that the treatment time with the aqueous sodium hypochlorite solution was 20 hours. In this case, the treatment capacity with the basic oxidizing agent is 120,000 ((mg / L) · h).
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.53, and absorption at 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane a-3 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 0.51.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane a-3 by the same operation as in Example 1 revealed that the permeated water amount was 57 mL / cm ² / min and the nitrogen flow rate was 6.9 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 8.3 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the pressure change at the time of passing the protein solution of the surface-modified porous membrane a-3 was measured by the same operation as in Example 1, the pressure increase was as large as 68 kPa. The treatment capacity of sodium hypochlorite aqueous solution is large, and the functional polymer layer directly bonded to the polymer porous membrane has also been removed, so the surface modification effect has diminished and biofouling has occurred. It is done.

Comparative Example 5
(Manufacture of functional polymer E)
In a glass Schlenk flask, polyethylene glycol monomethyl ether methacrylate (manufactured by Aldrich, number average molecular weight 300, hereinafter abbreviated as PEGMA) (12 mmol) and methacryloyloxypropyloxy-4-phenylazide (0.25 mmol), 2′-azobisisobutyronitrile (AIBN) (0.06 mmol) was weighed. Monomers and initiators were dissolved using 16 mL of THF to prepare a uniform solution. After sufficiently removing oxygen in the solution with nitrogen, polymerization was carried out at 60 ° C. for 8 hours. After completion of the polymerization, unreacted monomers were removed by reprecipitation using hexane, followed by drying under reduced pressure to obtain a brown syrupy polymer. The obtained polymer had a number average molecular weight of 67,000, a weight average molecular weight of 203,000, and an azide group content of 2 mol%.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.56, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane e-1 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 0.94.
(Measurement of permeate volume and nitrogen flow rate)
When the measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane e-1 was measured by the same operation as in Example 1, the permeated water amount was 21 mL / cm ² / min, and the nitrogen flow rate was 3.9 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 5.5 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the change in pressure during passage of the protein solution of the surface-modified porous membrane e-1 was measured by the same operation as in Example 1, the pressure increase was as large as 57 kPa. Since there are few secondary amino group units used as a crosslinking point, the surface modification effect is thin and it is considered that biofouling occurred.

Comparative Example 6
(Production of functional polymer F)
In a glass Schlenk flask, polyethylene glycol monomethyl ether methacrylate (Aldrich, number average molecular weight 300, hereinafter abbreviated as PEGMA) (20 mmol) and methacryloyloxypropyloxy-4-phenylazide (10 mmol), 2,2 ′ as an initiator -Azobisisobutyronitrile (AIBN) (0.14 mmol) was weighed. Monomers and initiators were dissolved using 38 mL of THF to prepare a uniform solution. After sufficiently removing oxygen in the solution with nitrogen, polymerization was carried out at 60 ° C. for 8 hours. After completion of the polymerization, unreacted monomers were removed by reprecipitation using hexane, followed by drying under reduced pressure to obtain a brown syrupy polymer. The obtained polymer had a number average molecular weight of 82,000, a weight average molecular weight of 290,000, and an azide group content of 34 mol%.
(Membrane surface composition)
Measurement of the membrane surface composition in the same manner as in Example 1, the absorption ratio of 1,170Cm ^-1 and 1,070Cm ^-1 surface coat the porous film surface before treatment with aqueous sodium hypochlorite solution (1 , 170 cm ⁻¹ / 1,070 cm ⁻¹ ) is 0.49, and absorption of 1,170 cm ⁻¹ and 1,070 cm ⁻¹ of the surface-modified porous membrane f-1 after treatment with an aqueous sodium hypochlorite solution The ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 0.87.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the permeated water amount and the nitrogen flow rate of the surface-modified porous membrane f-1 by the same operation as in Example 1 revealed that the permeated water amount was 22 mL / cm ² / min and the nitrogen flow rate was 3.8 × 10 ^3. mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 5.8 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the pressure change when the protein solution of the surface-modified porous membrane f-1 was passed through the same operation as in Example 1, the pressure increase was as large as 54 kPa. It is considered that biofouling occurred because the secondary amino group unit serving as a cross-linking point was large and the pores were clogged, and the hydrophilic unit was also cross-linked, so that the surface modification effect was diminished.

Comparative Example 7
(Membrane surface composition)
When the surface composition of a PVDF composite membrane (MF022 manufactured by Rising Sun Membrane) using a polyester nonwoven fabric as a porous membrane as a base material was measured without surface treatment, 1,170 cm ⁻¹ and 1 , the absorption ratio of ^{070cm -1 (1,170cm -1 / 1,070cm -1} ) was 0.51.
(Measurement of permeate volume and nitrogen flow rate)
Measurement of the MF022 permeate flow rate and nitrogen flow rate was carried out in the same manner as in Example 1. The permeate flow rate was 14 mL / cm ² / min, and the nitrogen flow rate was 3.0 × 10 ³ mL / cm ² / min. there were. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 4.6 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the pressure change during the passage of the protein solution of MF022 was measured by the same operation as in Example 1, the pressure increase was as large as 93 kPa, and it is considered that biofouling occurred due to the protein adsorbed to the membrane.

Comparative Example 8
(Membrane surface composition)
When the surface composition of the PVDF composite membrane (Toray MF membrane) having a nominal pore size of 0.08 μm using a polyester nonwoven fabric as the porous membrane was measured without surface treatment, 1,170 cm ⁻¹ and 1,070 cm ^-1 absorption ratio (1,170 cm ⁻¹ / 1,070 cm ⁻¹ ) was 0.55.
(Measurement of permeate volume and nitrogen flow rate)
When the measurement of the permeated water amount and the nitrogen flow rate of the MF membrane was measured by the same operation as in Example 1, the permeated water amount was 30 mL / cm ² / min, and the nitrogen flow rate was 3.0 × 10 ³ mL / cm ² / min. Met. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 10.0 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the pressure change during the passage of the protein solution through the MF membrane was measured by the same operation as in Example 1, the pressure increase was as large as 87 kPa, and it is considered that biofouling occurred due to the protein adsorbed to the membrane.

Comparative Example 9
(Membrane surface composition)
When a PVDF composite membrane (VO.2 manufactured by Cinder Filtration) having a nominal pore diameter of 0.2 μm using a polyester nonwoven fabric as a base material as a porous membrane was measured without surface treatment, the membrane surface composition was 1,170 cm ^−. absorption ratio of ¹ and ^{1,070cm -1 (1,170cm -1 / 1,070cm -1} ) was 1.79.
(Measurement of permeate volume and nitrogen flow rate)
In the same manner as in Example 1, VO. As a result of measuring the amount of permeated water and nitrogen flow rate of 2, the amount of permeated water was 20 mL / cm ² / min, and the nitrogen flow rate was 3.8 × 10 ³ mL / cm ² / min. The ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) was 5.4 × 10 ⁻³ .
(Pressure change when passing protein solution)
When the change in pressure during the passage of the protein solution through the MF membrane was measured by the same operation as in Example 1, the pressure increase was as large as 90 kPa, and it is considered that biofouling occurred due to the protein adsorbed to the membrane.

Claims (9)

The surface-modified porous membrane has a nitrogen gas permeation amount of 4.1 × 10 ^{3 to} 6.8 × 10 ³ mL / cm ² / min at a transmembrane pressure difference of 70 kPa, and a transmembrane pressure difference of 70 kPa. Surface-modified porous material, characterized in that the ratio of pure water permeation amount and nitrogen gas permeation amount (pure water permeation amount / nitrogen gas permeation amount) is 6.0 × 10 ^{−3 to} 8.0 × 10 ⁻³ film. The surface-modified porous membrane comprises a porous membrane and a functional polymer layer formed on the membrane surface, and the functional polymer layer is bonded to the porous membrane surface via a covalent bond. Item 2. The surface-modified porous membrane according to Item 1. The functional polymer layer is a polymer of a hydrophilic monomer having a hydrophilic group selected from an alkoxyalkyl group, a monoalkoxypolyoxyethylene group, a polyoxyethylene group or a betaine group and a polymerizable vinyl group. It is composed of a certain functional unit and a secondary amino group unit which is a polymer having a secondary amino group which is a crosslinking point, and the secondary amino group unit is 5 to 30 mol%, 2. The surface-modified porous membrane according to 2. The surface-modified porous film according to claim 1, wherein the porous film is made of a resin having a carbon-hydrogen bond and a carbon-fluorine bond. In the Fourier transform infrared spectroscopy in attenuated total reflection method, the absorption ratio of 1,170Cm ^-1 and ^{1,070cm -1 (1,170cm -1 / 1,070cm -1} ) is in the 1.0 to 2.0 The surface-modified porous membrane according to any one of claims 1 to 4, wherein the surface-modified porous membrane is provided. The surface-modified porous membrane according to any one of claims 1 to 5, wherein the material of the porous membrane is polyvinylidene fluoride. After the functional polymer is present on the porous membrane surface and a functional polymer layer is formed on the porous membrane surface via a covalent bond by UV irradiation, the basic oxidant concentration and treatment time in the basic oxidizer aqueous solution The method for producing a surface-modified porous membrane according to any one of claims 1 to 6, wherein the product is immersed so that the product of 20,000 to 100,000 ((mg / L) · h). The method for producing a surface-modified porous membrane according to claim 7, wherein the functional polymer is composed of a functional unit and a unit having 5 to 30 mol% of a nitrene precursor functional group. The method for producing a surface-modified porous membrane according to claim 7 or 8, wherein the basic oxidizing agent aqueous solution is a sodium hypochlorite aqueous solution.