JP2019150775A - Surface-modified porous film and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide a surface-modified porous membrane having a high permeation flow rate, excellent fractionation characteristics, and high hydrophilicity and excellent stain resistance. A surface-modified porous film comprising a porous film and a functional polymer layer formed on the surface of the porous film, wherein the surface has a fine structure including nodes and fibrils, and has an aperture ratio of 30. Provided is a surface-modified porous membrane, characterized by having an average pore diameter of 0.05 to 0.5 μm and a variation coefficient of the average pore diameter of 0.2 to 0.6. [Selection diagram] Fig. 1

Description

  The present invention relates to a surface-modified porous membrane and a method for producing the same. By using the present invention, a porous membrane having a large permeation flow rate and excellent fractionation characteristics, and having a high hydrophilic property and excellent stain resistance can be obtained, and used in the field of water treatment and the separation and purification of foods and pharmaceuticals. It can be used for microfiltration membranes, battery separators, and the like.

  As a method for producing a porous membrane, a non-solvent induced phase separation method in which a cast solution in which a polymer as a membrane material is dissolved in a solvent is poured into a coagulating solution made of a non-solvent and a porous structure is formed by phase separation ( NIPS method), heat-induced phase separation method (TIPS method) that forms a porous structure by cooling the heated cast liquid, and a stretching method that forms a porous structure by stretching the film are known. ing. The required characteristics for the porous membrane include a large permeation flow rate and excellent fractionation characteristics, but it is difficult to achieve both of these characteristics. The reason for this is that in order to increase the permeate flow rate, it is necessary to increase the aperture ratio and the porosity inside the membrane, but the increase in aperture ratio and porosity tends to cause non-uniformity in the membrane structure, and the fractionation characteristics are It will decline. On the other hand, in order to improve the fractionation characteristics, it is necessary to increase the uniformity of the aperture ratio and the porosity, but in order to improve the uniformity, it is necessary to reduce the aperture ratio and the porosity, and the permeate flow rate decreases. End up. As described above, it has been difficult to produce a porous membrane having a large permeation flow rate and excellent fractionation characteristics by the conventional technique.

  As a method of improving the disadvantages of the conventional modification methods described above, the permeate flow rate and fractionation characteristics can be adjusted by adjusting the temperature of the casting liquid and coagulating liquid to produce a porous membrane, or adjusting the solution viscosity of the casting liquid. Patent Documents 1 and 2 describe a method for producing a compatible porous membrane. However, the improvement by these methods is limited and has not led to a full solution of the problem.

  On the other hand, as a method for modifying the surface of the porous membrane, 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 processing with plasma or corona, A method of introducing a polymerization initiating group on the surface of the film and performing graft polymerization has been proposed. 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. After blending the functional polymer with the membrane material, the method of forming the membrane on the separation porous membrane is a simple method that does not require special equipment, but in order to sufficiently coat the membrane surface with the functional polymer, the functional polymer The addition amount must be considerably increased, which tends to cause deterioration of the 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 3 and 4 describe a method for introducing a functional polymer onto a substrate surface using a nitrene insertion reaction as a method for improving the above-described drawbacks of the conventional modification methods. This method is excellent in that the functional polymer can be introduced to the substrate surface via a covalent bond by a simple method such as functional polymer coating and UV irradiation. However, because the nitrene insertion reaction is consumed not only by the reaction with the substrate at the substrate 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.

JP2013-202461A WO2014 / 054658 publication 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 having a large permeation flow rate and excellent fractionation characteristics, and having high hydrophilicity and excellent stain resistance.

  In order to achieve the above object, as a result of intensive studies by the present inventors, corona treatment and / or plasma treatment is performed on the surface of the porous membrane, and then a functional polymer layer is immobilized on the surface of the porous membrane. The inventors have found that a surface-modified porous membrane having a large opening ratio and a uniform average pore diameter and having high hydrophilicity can be produced, and the present invention has been completed.

That is, the present invention
[1] A surface-modified porous film comprising a porous film and a functional polymer layer formed on the surface of the porous film, the surface having a microstructure including nodes and fibrils, and an aperture ratio of 30 to A surface-modified porous membrane characterized by 60%, an average pore diameter of 0.05 to 0.5 μm, and an average pore diameter variation coefficient of 0.2 to 0.6.
[2] In the above [1], the functional polymer layer contains a functional unit containing a hydrophilic group and 5 to 30 mol% of a secondary amino group unit, and has a thickness of 5 to 100 nm. The surface-modified porous membrane as described.
[3] The surface-modified porous membrane according to [1] or [2], wherein the functional polymer layer is a polymer having a structure represented by the following general formula (1).

(In the formula, m and n each independently represent an integer of 1 or more, X represents a phenylene group which may have a substituent, or a group represented by an ester bond or an amide bond, and Y represents a betaine group. Represents a hydrophilic group selected from an alkoxyalkyl group, an alkoxypolyoxyethylene group, and a hydroxypolyoxyethylene group, Z represents a group represented by —O— or —N (R ₃ ) —, and A represents —O -Or -CH _2- represents a group, R ₁ , R ₂ and R ₃ each independently represent a hydrogen atom or a C ₁ -C ₆ hydrocarbon group, and R ₄ is a C ₃ -C ₆ Represents a divalent hydrocarbon group, R ₅ represents a fluorine atom, and p represents an integer of 0 to 4.)
[4] A water treatment separation membrane comprising the surface-modified porous membrane according to any one of [1] to [3].
[5] The method for producing a surface-modified porous membrane according to any one of [1] to [4], comprising at least the following two steps.
(I) A step of subjecting the porous membrane surface to corona treatment or plasma treatment.
(Ii) A functional polymer composed of a functional unit and a unit having 5 to 30 mol% of a nitrene precursor functional group is present on the porous membrane surface, and a functional polymer layer is formed on the porous membrane surface by light irradiation. Process.

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

  The surface-modified porous membrane of the present invention comprises a porous membrane and a functional polymer layer formed on the porous membrane surface. As shown in FIG. 1, the surface-modified porous membrane surface has a fine structure composed of nodes (nodes) that are aggregates of the base polymer of the porous membrane and fibrils that connect the nodes. The gap between the fibrils forms pores. Porous material excellent in fractionation characteristics in which the average pore diameter is uniform when the average value of the diameter of the node is 0.05 to 0.5 μm and the average value of the length of the fibril is 0.06 to 1.0 μm. Since it becomes a film | membrane, it is preferable. The distribution of average pore diameter can be expressed by a coefficient of variation of average pore diameter. Here, the coefficient of variation is a value obtained by dividing the standard deviation by the average value. The porous membrane of the present invention is characterized in that the coefficient of variation in average pore diameter is as small as 0.2 to 0.6. In addition, the surface modification film of the present invention is characterized in that the aperture ratio is 30 to 60%, which is much larger than that of a conventional porous film. The aperture ratio referred to in the present invention refers to the ratio of the area of pore openings per unit surface area of the membrane. A large aperture ratio is preferable because the permeate flow rate of the fluid to be treated can be increased at a low operating pressure. The aperture ratio and the average pore diameter described in the present invention are values obtained by observing the surface of the porous membrane with a scanning electron microscope and analyzing the obtained image with image processing software.

  The porous film used in the present invention preferably has a fine structure composed of nodes and fibrils. The fine structure easily damages fibrils by corona treatment or plasma treatment, and easily develops the structure of the present invention. The porous membrane substrate having such a structure is easily developed in a membrane produced by the NIPS method or the stretching method.

The material of the porous film used in the present invention is not particularly limited, but an organic polymer having a site that reacts with nitrene generated by UV irradiation of the functional polymer is preferably used.
The site that reacts with nitrene refers to carbon-hydrogen bonds or nitrogen-hydrogen bonds, and some examples of such organic polymers include polyethylene, chlorinated polyethylene, polypropylene, polyvinyl chloride, chlorinated polyvinyl chloride, Vinylidene chloride, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS, polymethyl methacrylate, cellulose acetate, cellulose, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene ether, polyether Examples include ether ketone, polycarbonate, polyacetal, polyester, polyamide, polyimide, polyurethane, epoxy resin, phenol resin, and unsaturated polyester.

  Examples of the shape of the porous membrane include a flat membrane-like porous membrane and a hollow fiber-like porous membrane, and in particular, a porous membrane used as a microfiltration membrane is preferably used in the present invention. The microfiltration membrane mentioned here is a porous membrane having a pore diameter of about 0.05 to 10 μm, and the structure in the thickness direction of the membrane may be a uniform porous structure, but reduces the transmembrane pressure difference during fluid permeation It is preferable that the dense layer on the surface and the inner support layer have an asymmetric membrane structure having different porous structures. 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 herein include polyethylene fibers, polypropylene fibers, polyester fibers, nylon fibers, polyurethane fibers, acrylic fibers, rayon fibers, organic fibers such as cotton and silk, and woven fabrics, knitted fabrics, nonwoven fabrics, and the like. Inorganic fibers such as glass fibers and metal fibers, and their woven and knitted fabrics. Some examples of composite membranes include flat membrane microfiltration membranes in which a polyester nonwoven fabric is combined with a polyvinylidene fluoride porous membrane, hollow fiber microfiltration membranes in which a polyester braid is combined with a polyvinylidene fluoride porous membrane, etc. It is done.

  A battery separator is also preferably used as the porous membrane used in the present invention. The battery separator is a porous film that isolates 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. It is.

  Examples of the material of the membrane include polyethylene, polypropylene, cellulose, aromatic polyamide, and the like, and these materials are laminated and composited by coating.

  The thickness of the porous membrane is not particularly limited as long as it has a mechanical strength that can withstand pressure loss during use, and can be selected in the range of 1 to 500 μm.

  The functional polymer layer used in the present invention is a polymer layer formed on the surface of the porous membrane, and is a functional component containing a hydrophilic group that is electrically neutral (apparently has no charge), such as alkoxy. It preferably contains a functional unit having an alkyl group, a monoalkoxypolyoxyethylene group, a polyoxyethylene group or a betaine group and 5 to 30 mol% of a secondary amino group unit. Specific examples of the alkoxyalkyl group that is a functional component 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 (no apparent charge). Specific examples of the betaine group include a sulfobetaine group, a carboxybetaine group, and a phosphobetaine group.

  In the present invention, the term “functional unit” refers to porous functions such as imparting hydrophilicity and wettability to an electrolyte solution, inhibiting protein adsorption, preventing biofouling, antithrombogenicity, biocompatibility, and antistatic properties. It is a unit for imparting to a film, and contains an electrically neutral (apparently no charge) hydrophilic group.

  In the present invention, the “secondary amino group unit” means that a unit having a 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 be crosslinked and covalently bonded. Is a unit generated when forming It is important for the secondary amino group unit to be contained in the functional polymer layer in a proportion of 5 to 30 mol% in order to exhibit the effects of the present invention. If the secondary amino group unit is less than 5 mol%, it is not preferable because the functional polymer layer is insufficiently immobilized on the surface of the porous membrane. On the other hand, if it exceeds 30 mol%, protein adsorption is suppressed. It is not preferable because biofouling is prevented and functions such as antithrombogenicity are reduced.

  In the present invention, the “functional polymer layer” refers to a polymer layer including the “functional unit” and the “secondary amino group unit” and formed on the surface of the porous membrane. 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 thickness of the functional polymer layer formed on the porous membrane surface is preferably 5 to 100 nm. If the thickness of the polymer layer is 5 nm or more, the expression of the function to be imparted is sufficient. On the other hand, if the thickness of the polymer layer is 100 nm or less, the pores of the porous membrane are not likely to be blocked, which is preferable. When the thickness of the polymer layer is 5 nm or more, functions such as imparting hydrophilicity and wettability to the electrolyte solution, inhibiting protein adsorption, preventing biofouling, antithrombogenicity, biocompatibility, antistatic properties, etc. In addition, it has excellent durability even when used for a long time under harsh conditions.

The method for producing a surface-modified porous membrane of the present invention includes at least the following two steps.
(I) A step of subjecting the porous membrane surface to corona treatment or plasma treatment.
(Ii) A functional polymer composed of a functional unit and a unit having 5 to 30 mol% of a nitrene precursor functional group is present on the porous membrane surface, and a functional polymer layer is formed on the porous membrane surface by light irradiation. Process.

The step of corona treatment or plasma treatment on the surface of the porous membrane is a step of partially cutting or embrittlement of the fibrils on the surface of the porous membrane substrate, and only in this step, the aperture ratio and average pore diameter of the porous membrane are reduced. It does not expand dramatically. The corona treatment referred to here is a surface treatment technology that modifies the surface of the porous membrane substrate by corona discharge irradiation, and high-energy electrons generated by corona discharge cut the main chain and side chains of the substrate polymer, A radical is generated, and oxygen radical and ozone react with it to introduce a polar functional group to the surface of the porous substrate. On the other hand, since corona discharge generates low-temperature plasma, it cuts fibrils on the surface of the membrane substrate. The optimum conditions for the corona treatment vary greatly depending on the material of the membrane base material, so it cannot be said unconditionally. It is preferred to treat in the range of / m ^2. On the other hand, the plasma treatment referred to in the present invention is a method in which a discharge electrode is placed inside a nozzle under atmospheric pressure, various gases are allowed to flow between the electrodes, and a plasma gas is ejected from the nozzle. ing. This method is different from the corona treatment in that the gas is continuously flowed so that the electrode is cooled, and because the sample is separated from the discharge electrode, damage to the membrane substrate is reduced. The plasma treatment conditions are the same as the corona treatment conditions, and the conditions differ depending on the material of the membrane substrate. It is good to select appropriately within the range.

  Next, the functional polymer layer is formed on the surface of the porous membrane. In this process, the functional coat layer takes in the fibrils remaining without being cut by the corona treatment or plasma treatment, and a new pore structure is formed. It is a process of forming.

  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 may be selected from dip coating, spin coating, gravure 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. . 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 light irradiation. Although it does not specifically limit about drying conditions, In order to maintain the structure of a porous membrane, it is preferable to dry for a short time at low temperature, and it is preferable to dry for about 1 to 10 minutes at room temperature-60 degreeC.

After the functional polymer is present on the surface of the porous membrane by the above method, light is irradiated. 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 >.

  The molecular weight of the functional polymer used in the present invention is preferably selected in the range of 1,000 to 1,000,000, but from the viewpoint of the viscosity and solubility during coating and the mechanical strength of the polymer layer, 5,000. A range of ˜500,000 is preferred. The functional polymer is a copolymer of a monomer constituting a functional unit and a monomer having a nitrene precursor functional group, and they may be arranged randomly 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 the monomer-derived component having a nitrene precursor functional group is low, it becomes water-soluble, but the functional unit is insoluble in water and the monomer-derived component having a nitrene precursor functional group If the ratio is high, it will not dissolve in water.

  The functional unit constituting the functional polymer of the present invention includes a functional group selected from an alkoxyalkyl group, a monoalkoxypolyoxyethylene group, a polyoxyethylene group, a sulfobetaine group, a carboxybetaine group, and a phosphobetaine group, and vinyl. A polymer of a monomer having a group can be used. Examples of the vinyl group include vinyl group, allyl group, methallyl group, isoprenyl group, methacryloxy group, methacrylamide group, acryloxy group, acrylamide group, and styryl group. A methacryloxy group, an acryloxy group, an acrylamide group, and a styryl group are preferable in terms of excellent affinity with the membrane.

  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 layer of the present invention is obtained by crosslinking a functional polymer containing a polymer of a monomer having a nitrene precursor functional group and a vinyl group by light irradiation. Can do. The nitrene precursor functional group is an azide group, specifically, aryl azides such as phenyl azide and tetrafluorophenyl azide; acyl azides 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, a styryl group, and the like, since copolymerization proceeds well when using the same type of vinyl group as the functional component. It is preferred to use the same type of vinyl group.

  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.

  The functional polymer used in the present invention is a copolymer of the above exemplified monomers, but is preferably a polymer having a structure represented by the general formula (2).

(In the formula, m and n each independently represent an integer of 1 or more, X represents a phenylene group which may have a substituent, or a group represented by an ester bond or an amide bond, and Y represents a betaine group. Represents a hydrophilic group selected from an alkoxyalkyl group, an alkoxypolyoxyethylene group, and a hydroxypolyoxyethylene group, Z represents a group represented by —O— or —N (R ₃ ) —, and A represents —O -Or -CH _2- represents a group, R ₁ , R ₂ and R ₃ each independently represent a hydrogen atom or a C ₁ -C ₆ hydrocarbon group, and R ₄ is a C ₃ -C ₆ Represents a divalent hydrocarbon group, R ₅ represents a fluorine atom, and p represents an integer of 0 to 4.)
The substituent of the phenylene group which may have a substituent represented by X is not particularly limited, but an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec -Butyl group, tert-butyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, propoxy group, isopropoxy group, etc.), halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), carboxy Examples include groups, amino groups, hydroxy groups and the like. X is preferably an ester bond.

  Examples of the hydrophilic group represented by Y include a betaine group, an alkoxyalkyl group, an alkoxypolyoxyethylene group, and a hydroxypolyoxyethylene group. In the present invention, the term “betaine” means that a portion having a positive charge and a portion having a negative charge in an ionized state are not adjacent to each other in the same group and can be dissociated into atoms having a positive charge. It means that the atoms are not bonded and are neutral as a whole (has no charge). The betaine group is not particularly limited, and examples thereof include a carboxybetaine group, a sulfobetaine group, a phosphobetaine group, and an amide betaine group. Although it does not specifically limit as an alkoxyalkyl group, 2-methoxyethyl group, 3-methoxypropyl group, 4-methoxybutyl group is illustrated. The alkoxy polyoxyethylene group is not particularly limited, and examples thereof include a methoxy polyoxyethylene group, an ethoxy polyoxyethylene group, a normal propoxy polyoxyethylene group, and an isopropoxy polyoxyethylene group. An oxyethylene group, a carboxybetaine group, a sulfobetaine group, and a phosphobetaine group are preferred.

R _{1, R 2} and is not particularly restricted but includes hydrocarbon groups _C 1 -C ₆ represented by _{R 3,} methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, sec-butyl group, tert-butyl group, cyclobutyl group, pentyl group, neopentyl group, isopentyl group, 1-methylbutyl group, 1-ethylpropyl group, cyclobutylmethyl group, cyclopentyl group, hexyl group, 1-methylpentyl group, Examples include 4-methylpentyl group, 1-ethylbutyl group, 2-ethylbutyl group, cyclohexyl group, and phenyl group.

The C _{3 to} C ₆ divalent hydrocarbon group represented by R ₄ is not particularly limited, but — (CH ₂ ) ₃ —, — (CH ₂ ) ₄ —, — (CH ₂ ) ₅ —, — Examples include (CH ₂ ) _6- , a phenylene group, and the like. If the carbon number of the divalent hydrocarbon group represented by R ₄ is 3 to 6, the glass transition temperature of the photoreactive polymer is kept low and the molecular mobility of the side chain is good. Is preferable because the nitrene produced from the above works efficiently in the reaction with the substrate and the photoreactive polymer immobilization rate on the substrate surface is improved. Further, when the carbon number of the divalent hydrocarbon group represented by R ₄ is 3 to 6, the azide group concentration in the photoreactive polymer is maintained at a high concentration, so that the number of crosslinking points increases and the substrate It is preferable because the photoreactive polymer immobilization rate on the surface is improved.

  In the functional polymer having the structure represented by the general formula (2), m and n each independently represent an integer of 1 or more. Here, the value of m / (m + n) is preferably 0.02 to 0.7, and more preferably 0.05 to 0.5. If it is this range, it is excellent at the point of coexistence of the adhesiveness to a base material, and the protein adsorption | suction suppression effect.

  The following general formula (3) included in the general formula (2)

(Wherein R ₁ , X, Y and n represent the same meaning as described above), the functional unit represented by polyethylene glycol methyl ether methacrylate, polyethylene glycol methacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol acrylate 2-hydroxyethyl methacrylate, 2-methacryloyloxyethyl phosphorylcholine, 2-acryloyloxyethyl phosphorylcholine, [2- (methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide, N-methacryloyloxyethyl-N, Functional units derived from monomers such as N-dimethylammonium-α-N-methylcarboxybetaine are exemplified, and the hydrophilicity is high and the protein adsorption inhibiting effect is excellent From polyethylene glycol methyl ether methacrylate, 2-methacryloyloxyethyl phosphorylcholine, [2- (methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide, N-methacryloyloxyethyl-N, N-dimethylammonium-α A functional unit derived from -N-methylcarboxybetaine is preferably used.

  The following general formula (4) included in the general formula (2)

(Wherein R ₂ , R ₄ , R ₅ , A, Z, m and p represent the same meaning as described above), the unit having a nitrene precursor functional group represented by 3- (4-azido Phenoxy) propyl methacrylate, 4- (4-azidophenoxy) butyl methacrylate, 5- (4-azidophenoxy) pentyl methacrylate, 6- (4-azidophenoxy) hexyl methacrylate, 3- (4-azido-2,3,5) , 6-Tetrafluorophenoxy) propyl methacrylate, 4- (4-azidophenyl) butyl methacrylate, 4- (4-azido-2,3,5,6-tetrafluorophenyl) butyl methacrylate, 3- (4-azidophenoxy) ) Propyl acrylate, 4- (4-azidophenyl) butyl acrylate, 3- (4-azidophenoxy) Lopylmethacrylamide, 3- (4-azido-2,3,5,6-tetrafluorophenoxy) propylmethacrylamide, 3- (4-azidophenoxy) propylacrylamide, 4- (4-azidophenyl) butylmethacrylamide And a unit obtained by polymerizing monomers such as 4- (4-azidophenyl) butylacrylamide. Among these, a unit obtained by polymerizing 3- (4-azidophenoxy) propyl methacrylate having a high photodegradation rate of azide is preferably used.

  The arrangement of the functional unit represented by the general formula (3) and the unit having a nitrene precursor functional group represented by the general formula (4) is not particularly limited, and may be any order of random, block, and alternating. May be.

  The functional polymer having the structure represented by the general formula (2) preferably has a number average molecular weight of 1,000 to 1,000,000, viscosity and solubility during coating, and mechanical strength of the functional polymer layer. From the viewpoint of the above, it is more preferably in the range of 10,000 to 500,000. Further, the polydispersity (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is not particularly limited, but for example, adhesion to a hydrophobic substrate. From the viewpoint of the stability of the coating film, about 1 to 5 is preferable.

  Examples of the functional polymer represented by the general formula (2) include polyethylene glycol methyl ether methacrylate / methacryloyloxypropyloxy 4-phenylazide copolymer, 2-methacryloyloxyethyl phosphorylcholine / methacryloyloxypropyloxy 4-phenylazide copolymer Polymer, 2- (N-3-sulfopropyl-N, N-dimethylammonium) ethyl methacrylate / methacryloyloxypropyloxy 4-phenylazide copolymer, 2- (N-carbomethoxy-N, N-dimethylammonium) Ethyl methacrylate / methacryloyloxypropyloxy 4-phenylazide copolymer, polyethylene glycol methyl ether methacrylate / methacryloyloxybutyl 4-phenylazide copolymer, 2 Methacryloyloxyethyl phosphorylcholine / methacryloyloxybutyl 4-phenylazide copolymer, 2- (N-3-sulfopropyl-N, N-dimethylammonium) ethyl methacrylate / methacryloyloxybutyl 4-phenylazide copolymer, 2- ( N-carbomethoxy-N, N-dimethylammonium) ethyl methacrylate / methacryloyloxybutyl 4-phenylazide copolymer and the like.

  The functional polymer used in the present invention may have a structural unit derived from another monomer without departing from the effects of the present invention. The structural units derived from other monomers are not particularly limited, but polystyrene, poly (α-methylstyrene), polyvinyl benzyl chloride, polyvinyl aniline, sodium polystyrene sulfonate, polyvinyl benzoic acid, polyvinyl phosphoric acid, polyvinyl pyridine, polydimethyl. Styrenic polymers such as aminomethylstyrene and polyvinylbenzyltrimethylammonium chloride; polyolefins such as polyethylene, polypropylene, polybutadiene, polybutene, and polyisoprene; poly (halogenated olefins) such as polyvinyl chloride, polyvinylidene chloride, and polytetrafluoroethylene; Polyvinyl esters such as polyvinyl acetate and polyvinyl propionate, and saponified polyvinyl alcohol, such as polyacrylonitrile (Meth) acrylic polymers such as polymethacrylic acid, polyperfluoroalkyl methacrylate, polyethyl acrylate, polyacrylic acid, polydimethylaminoethyl acrylate; polyacrylamide, polymethacrylamide, polydimethylaminopropyl acrylamide, And (meth) acrylamide polymers and the like.

  The functional polymer used in the present invention can be produced by a conventional method basically based on the technical level of those skilled in the art including preparation of monomer compounds and polymerization thereof. For example, the monomer used is not particularly limited, but polyethylene glycol methyl ether methacrylate, polyethylene glycol methacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol acrylate, 2-hydroxyethyl methacrylate, 2-methacryloyloxyethyl phosphorylcholine, 2-acryloyloxyethyl. It has a hydrophilic group such as phosphorylcholine, 2- (N-3-sulfopropyl-N, N-dimethylammonium) ethyl methacrylate, N-methacryloyloxyethyl-N, N-dimethylammonium-α-N-methylcarboxybetaine. A monomer, 3- (4-azidophenoxy) propyl methacrylate, 4- (4-azidophenoxy) butyl methacrylate, -(4-azidophenoxy) pentyl methacrylate, 6- (4-azidophenoxy) hexyl methacrylate, 3- (4-azido-2,3,5,6-tetrafluorophenoxy) propyl methacrylate, 4- (4-azidophenyl) ) Butyl methacrylate, 4- (4-azido-2,3,5,6-tetrafluorophenyl) butyl methacrylate, 3- (4-azidophenoxy) propyl acrylate, 4- (4-azidophenyl) butyl acrylate, 3- (4-azidophenoxy) propyl methacrylamide, 3- (4-azido-2,3,5,6-tetrafluorophenoxy) propyl methacrylamide, 3- (4-azidophenoxy) propyl acrylamide, 4- (4-azido Phenyl) butyl methacrylamide, 4- (4-azi A monomer having a nitrene precursor functional group such as dophenyl) butylacrylamide is used.

  The polymerization is not particularly limited, and examples thereof include radical polymerization, ionic polymerization, and coordination polymerization. From the viewpoint of ease of operation, radical polymerization, particularly free radical polymerization or living radical polymerization is preferably used. The polymerization initiator is not particularly limited. For example, 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide, diisopropyl peroxydicarbonate, tert-butylperoxy-2-ethylhexanoate, tert Known radical initiators such as -butyl peroxypivalate, tert-butyl peroxydiisobutyrate, persulfate or persulfate-bisulfite can be used. As a polymerization solvent, for example, a known radical polymerization solvent such as water, THF, dioxane, acetone, 2-butanone, ethyl acetate, isopropyl acetate, benzene, toluene, DMF, DMSO, methanol, ethanol, isopropanol or a mixture thereof is used. For example, it can be manufactured by diluting the monomer concentration to 0.01 to 5 mol / L and the polymerization initiator concentration to 1 to 100 mmol / L and reacting at 0 to 80 ° C. for 1 to 72 hours. . Moreover, there is no restriction | limiting in particular as a superposition | polymerization form, For example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, dispersion polymerization, precipitation polymerization is illustrated, and solution polymerization is preferably used from the simplicity of operation.

  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.

  According to the present invention, it is possible to provide a separation membrane having a large permeation flow rate and excellent fractionation characteristics, which has been difficult to realize in the past. By combining corona treatment or plasma treatment with surface modification by coating, an unprecedented pore structure was developed and high performance of the porous membrane was realized. Further, the surface modification film of the present invention has high hydrophilicity, high contamination resistance, good wettability to the electrolyte solution, imparts protein non-adsorption property, suppresses biofouling, antithrombogenicity, biocompatibility, charging Water treatment separation membranes that are durable and capable of maintaining high and stable performance for a long period of time, plasma separation membranes that require precise fractionation characteristics, and wine and sake clarification It is useful as a separation membrane, a separation membrane for fermentation / culture liquid purification, a chemical separation membrane for semiconductor production, and a battery separator for secondary batteries, and can be widely used in this application field.

It is the figure which showed the SEM image of the surface of the surface modification porous membrane of this invention. 2 is a diagram showing an SEM image of the porous membrane surface of Example 1. FIG. 4 is a diagram showing an SEM image of the porous membrane surface of Example 2. FIG. 4 is a view showing an SEM image of the porous membrane surface of Example 3. FIG. 6 is a view showing an SEM image of the porous membrane surface of Example 4. FIG. 6 is a diagram showing an SEM image of the porous membrane surface of Example 5. FIG. 6 is a view showing an SEM image of a porous membrane surface in Comparative Example 1. FIG. 6 is a view showing an SEM image of a porous membrane surface in Comparative Example 2. FIG. 6 is a view showing an SEM image of a porous membrane surface in Comparative Example 3. FIG.

  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 having an azide group content of 9 mol%)
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. Monomers and initiators 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, and dried under reduced pressure to obtain a brown syrupy PEGMA copolymer. 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%.
(Corona treatment of porous membrane)
Using a polyvinylidene fluoride (PVDF) composite membrane (MF022, composed of polyester nonwoven fabric and porous PVDF membrane, made by Rising Sun Membrane) with a nominal pore size of 0.22 μm as the porous membrane, corona treatment at a corona treatment station (made by Kasuga Denki) Discharge amount 780 W · min. / M2.

(Immobilization of functional polymer A on the porous membrane surface)
A 1.3% methanol solution of functional polymer A in a baker applicator (BAP-05, manufactured by Imoto Seisakusho) using a desktop coater (TC-1, manufactured by Mitsui Denki) on a PVDF porous membrane subjected to corona treatment 1 m / min. And dried at 40 ° C. for 2 minutes, using a conveyor type UV irradiation device (GS Yuasa, light source: high pressure mercury lamp), lamp output 4 kW, line speed 5 m / min. Was irradiated with UV (integrated light quantity 700 mJ / cm ² ) to obtain a PVDF porous membrane having a PEGMA copolymer immobilized on the membrane surface. In order to calculate the thickness of the PEGMA copolymer layer on the membrane surface, the carbonyl absorption intensity (1720 cm ⁻¹ ) derived from the PEGMA copolymer was normalized with the absorption intensity of 870 cm ⁻¹ derived from PVDF using ATR / FT-IR. As a result, the relative strength was 0.035. Further, a calibration curve was prepared by calculating the film thickness of the coat layer from the weight increase rate before and after coating and the specific surface area of the film and plotting it against the relative carbonyl strength. Using this calibration curve, the thickness of the coating layer was estimated from the carbonyl relative intensity, and the film thickness was 6 nm.
(Analysis of porous structure on membrane surface)
The surface of the surface modification film was observed using a scanning electron microscope (SU8230, manufactured by Hitachi High Technology), and an image was obtained at a magnification of 20000 times. The obtained image is shown in FIG. The obtained image was analyzed with image analysis software (WinRoof, manufactured by Mitani Corp.), and the aperture ratio and average pore diameter were calculated. The opening ratio was 46%, the average pore diameter was 0.16 μm, and the variation coefficient of the average pore diameter was 0.57. The results are summarized in Table 1.
(Measurement of water permeability)
The above surface-modified membrane was loaded on a stainless steel filter holder (effective filtration area 2.2 cm2, made by Merck Millipore), and after passing pure water at 70 kPa for 5 minutes, the amount of water permeation was measured. The water permeability is 57 ml / min. / Cm ² .
(Evaluation of protein adsorption characteristics)
The above surface-modified membrane was loaded into a stainless steel filter holder, and pure water was passed through at 70 kPa for 5 minutes. When the water permeation amount (A) at the time when 5 minutes had elapsed was measured, it was 57 ml / min. / Cm ² . After measuring the water permeation amount, the solution line (concentration: 1000 mg / mL, hereinafter abbreviated as BSA solution) in which bovine serum albumin (manufactured by Wako Pure Chemical Industries) was dissolved in pure water was passed at 70 kPa. The BSA solution was passed for 10 minutes, and the flow rate (B) was measured. The flow rate was 39 ml / min. / Cm <2>. After the flow rate measurement, the supply liquid line was switched and pure water was passed for 10 minutes. The flow rate maintenance rate, which is an index of protein adsorption characteristics, was obtained from the following formula (5).

Flow rate maintenance rate (%) = {(B) / (A)} × 100 (5)
The flow rate maintenance rate was 69%.

Example 2
(Manufacture of functional polymer, corona treatment of porous membrane, immobilization of functional polymer A on porous membrane surface)
The amount of discharge during corona treatment was 310 W · min. Except for setting to / m ² , the corona treatment was performed in the same manner as in Example 1, and the functional polymer A was used to form a coat layer on the porous film after the corona treatment. The relative value of the carbonyl absorption intensity derived from the PEGMA copolymer determined using ATR / FT-IR was 0.048, and the coating layer thickness was 8 nm.
(Analysis of porous structure on membrane surface)
The porous structure was analyzed in the same manner as in Example 1. The opening ratio was 32%, the average pore diameter was 0.28 μm, and the variation coefficient of the average pore diameter was 0.47. The results are summarized in Table 1.
(Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 48 ml / min. / Cm ² , and the flow rate maintenance rate was 69%. The results are summarized in Table 1.

Example 3
(Manufacture of functional polymer, corona treatment of porous membrane, immobilization of functional polymer A on porous membrane surface)
The amount of discharge during corona treatment is 1560 W · min. Except for setting to / m ² , the corona treatment was performed in the same manner as in Example 1, and the functional polymer A was used to form a coat layer on the porous film after the corona treatment. The relative value of the carbonyl absorption intensity derived from the PEGMA copolymer determined using ATR / FT-IR was 0.037, and the coating layer thickness was 6 nm.
(Analysis of porous structure on membrane surface)
The porous structure was analyzed in the same manner as in Example 1. The aperture ratio was 49%, the average pore diameter was 0.32 μm, and the variation coefficient of the average pore diameter was 0.52. The results are summarized in Table 1. (Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 70 ml / min. / Cm ² , and the flow rate maintenance rate was 64%. The results are summarized in Table 1.

Example 4
(Production of functional polymer B having an azide group content of 12 mol%)
A glass Schlenk flask was charged with 2- (N-3-sulfopropyl-N, N-dimethylammonium) ethyl methacrylate (Aldrich, hereinafter abbreviated as SBMA) (21 mmol) and methacryloyloxypropyloxy 4-phenylazide (10 mmol). As an initiator, 2,2′-azobisisobutyronitrile (AIBN) (0.14 mmol) was weighed. A monomer and an initiator were dissolved using 80 ml of methanol to prepare a uniform solution. Nitrogen bubbling was performed for 30 minutes to sufficiently remove oxygen in the solution with nitrogen, followed by polymerization at 60 ° C. for 8.5 hours. After completion of the polymerization, the supernatant was removed, the polymer was washed by decantation with methanol and THF to remove unreacted monomers, and dried under reduced pressure to obtain a pale yellowish white solid SBMA copolymer. 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 12 mol%.
(Corona treatment of porous membrane, immobilization of functional polymer B on the porous membrane surface)
Corona treatment was carried out in the same manner as in Example 1 except that functional polymer B was used instead of functional polymer A, and water / methanol (2/1) mixed solvent was used instead of methanol as the coating solvent. The coating layer was formed on the porous film after the corona treatment. The relative value of the carbonyl absorption intensity derived from the SBMA copolymer obtained by using ATR / FT-IR was 0.089, and the coating layer thickness was 15 nm.
(Analysis of porous structure on membrane surface)
The porous structure was analyzed in the same manner as in Example 1. The aperture ratio was 33%, the average pore diameter was 0.18 μm, and the variation coefficient of the average pore diameter was 0.48. The results are summarized in Table 1.
(Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 44 ml / min. / Cm ² , and the flow rate maintenance rate was 80%. The results are summarized in Table 1.

Example 5
(Production of functional polymer, plasma treatment of porous membrane, immobilization of functional polymer A on the porous membrane surface)
A coat layer was formed on the porous film using the functional polymer A in the same manner as in Example 1 except that the plasma treatment was performed instead of the corona treatment. For the plasma treatment of the porous membrane, an atmospheric pressure plasma apparatus (FPE20, manufactured by Fuji Machine Manufacturing Co., Ltd.) was used, and treatment was performed at a working distance of 20 mm and a line speed of 50 mm / s. The relative value of the carbonyl absorption intensity derived from the PEGMA copolymer determined using ATR / FT-IR was 0.042, and the coating layer thickness was 7 nm.
(Analysis of porous structure on membrane surface)
The porous structure was analyzed in the same manner as in Example 1. The opening ratio was 45%, the average pore diameter was 0.17 μm, and the variation coefficient of the average pore diameter was 0.56. The results are summarized in Table 1.
(Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 58 ml / min. / Cm ² , and the flow rate maintenance rate was 70%. The results are summarized in Table 1.

Comparative Example 1
(Analysis of porous structure on membrane surface)
With respect to a PVDF porous membrane (MF022, manufactured by Rising Sun Membrane) having the same nominal pore diameter of 0.22 μm as used in Example 1, the porous structure was analyzed in the same manner as in Example 1. The aperture ratio was 25%, which was small compared to the examples. The average pore diameter was 0.04 μm, and the variation coefficient of the average pore diameter was 0.58. The results are summarized in Table 1.
(Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 15 ml / min. / Cm ² , which is a low value compared to the examples. Further, the flow rate maintenance rate was 30%, which was a low value compared to the examples. The results are summarized in Table 1.

Comparative Example 2
(Corona treatment of porous membrane, analysis of porous structure on membrane surface)
A PVDF porous membrane (MF022, manufactured by Rising Sun Membrane) having the same nominal pore diameter of 0.22 μm as used in Example 1 was subjected to corona treatment in the same manner as in Example 1 to analyze the porous structure. The aperture ratio was 24%, which was small compared to the example and was almost the same as the value of Comparative Example 1 (before corona treatment). Moreover, although the average pore diameter was 0.06 μm, which was slightly larger than that of Comparative Example 1, it was much smaller than that of the Examples. The variation coefficient of the average pore diameter is 0.72, which is larger than that before the corona treatment, and it can be seen that the variation in the pore diameter is increased. The results are summarized in Table 1.
(Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 29 ml / min. Although it was larger than / cm ² and Comparative Example 1, it was smaller than the Example. Further, the flow rate maintenance rate was 45%, which was a low value compared to the examples. The results are summarized in Table 1.

Comparative Example 3
(Immobilization of functional polymer A on the porous membrane surface)
A coating layer was formed on the porous film using the functional polymer A in the same manner as in Example 1 except that the corona treatment was not performed. The relative value of the carbonyl absorption intensity derived from the PEGMA copolymer determined using ATR / FT-IR was 0.034, and the coating layer thickness was 6 nm.
(Analysis of porous structure on membrane surface)
The porous structure was analyzed in the same manner as in Example 1. The aperture ratio was 23%, which was small compared to the examples. The average pore diameter was 0.09 μm, which was larger than that of Comparative Example 1, but was smaller than that of the example. The variation coefficient of the average pore diameter is as large as 0.81, and it can be seen that the variation in the pore diameter is increased. The results are summarized in Table 1.
(Measurement of water permeability, evaluation of protein adsorption characteristics)
In the same manner as in Example 1, the water permeability was measured and the protein adsorption characteristics were evaluated. The water permeability is 18 ml / min. / Cm ^{2, which} is comparable to that of Comparative Example 1, and is smaller than that of the Example. Further, the flow rate maintenance rate was 46%, which was a low value compared to the example.

Claims (5)

A surface-modified porous membrane comprising a porous membrane and a functional polymer layer formed on the surface of the porous membrane, wherein the surface has a fine structure containing nodes and fibrils, and the opening ratio is 30 to 60%, A surface-modified porous membrane having an average pore diameter of 0.05 to 0.5 μm and an average pore diameter variation coefficient of 0.2 to 0.6. 2. The surface according to claim 1, wherein the functional polymer layer comprises a functional unit containing a hydrophilic group and 5 to 30 mol% of a secondary amino group unit, and has a thickness of 5 to 100 nm. Modified porous membrane. The surface-modified porous membrane according to claim 1 or 2, wherein the functional polymer layer is a polymer having a structure represented by the following general formula (1).

(In the formula, m and n each independently represent an integer of 1 or more, X represents a phenylene group which may have a substituent, or a group represented by an ester bond or an amide bond, and Y represents a betaine group. Represents a hydrophilic group selected from an alkoxyalkyl group, an alkoxypolyoxyethylene group, and a hydroxypolyoxyethylene group, Z represents a group represented by —O— or —N (R ₃ ) —, and A represents —O -Or -CH _2- represents a group, R ₁ , R ₂ and R ₃ each independently represent a hydrogen atom or a C ₁ -C ₆ hydrocarbon group, and R ₄ is a C ₃ -C ₆ Represents a divalent hydrocarbon group, R ₅ represents a fluorine atom, and p represents an integer of 0 to 4.) A water treatment separation membrane comprising the surface-modified porous membrane according to any one of claims 1 to 3. The method for producing a surface-modified porous membrane according to claim 1, comprising at least the following two steps.
(I) A step of subjecting the porous membrane surface to corona treatment or plasma treatment.
(Ii) A functional polymer composed of a functional unit and a unit having 5 to 30 mol% of a nitrene precursor functional group is present on the porous membrane surface, and a functional polymer layer is formed on the porous membrane surface by light irradiation. Process.

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