JP6524806B2 - Method of manufacturing porous membrane - Google Patents

Description

  The present invention relates to a method of producing a porous membrane.

  Porous membranes are used in various fields such as drinking water production, water purification treatment, water treatment fields such as wastewater treatment. In recent years, in addition to the performance of a membrane such as high fractionation performance and hydrophilicity, simplification of the manufacturing process is desired.

  As a porous membrane, Patent Document 1 proposes a polymer membrane containing a hydrophobic matrix polymer such as polyvinylidene fluoride and an amphiphilic block copolymer. However, since the block copolymer used in Patent Document 1 is produced by a controlled radical polymerization method such as nitroxide-mediated polymerization (NMP), it is necessary to remove the monomer after polymerization, which is advantageous in cost. Absent. Also, the film consists only of block copolymer and PVDF resin, and includes purification steps by precipitation or evaporation to obtain a pure block copolymer. In addition, as in Non-Patent Document 1, a method is proposed in which a porous membrane is obtained after polymerizing a monomer in situ using a solution in which PVDF is previously dissolved. However, in the case of using a reactive monomer having a medium to high molecular weight monomer such as a PMMA macromonomer, the viscosity in the system is excessively increased prior to polymerization, resulting in a problem that dissolution takes time. Further, since the PVDF is dissolved in advance, only a small amount of the macromonomer can be dissolved, the reaction rate with other comonomers does not increase, and there is a problem which is not suitable particularly for copolymerization and the like.

Japanese Patent Application Publication No. 2012-506772

Journal of Materials Chemistry, 2012, 22, 9131.

  An object of the present invention is to provide a porous membrane obtained by using a polymer composition easily obtained by conventional radical polymerization which does not include purification steps such as precipitation and evaporation, and a method for producing the same.

The said subject is solved by the following this invention [1]-[5].
[1] A monomer composition containing a methacrylic acid ester macromonomer (b1) (hereinafter referred to as "macromonomer (b1)") represented by the following formula (1) and another monomer (b2) is polymerized in a solvent Preparing a polymer solution (C) containing a polymer (B) obtained by the step of dissolving the film forming polymer (A) in the polymer solution (C) to prepare a solution (D) for preparing a porous film A method for producing a porous membrane comprising a solution (D) for preparing a porous membrane, a step of immersing in a coagulating solution to obtain a precursor, and a washing step of partially or completely removing the polymer (B) from the precursor by washing. .

In formula (1), R and R ^{1 to} R ⁿ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and n is an integer of 2 or more and 10,000 or less. is there.
[2] The porous membrane according to [1], wherein the membrane-forming polymer (A) is a fluorine-containing polymer.
[3] The method for producing a porous membrane according to any one of [1] to [3], wherein the other monomer (b2) is (meth) acrylic acid or (meth) acrylate.
[4] The ratio of the other monomer (b2) to the total 100% by mass of the polymer (B) contained in the porous membrane is 100 to 100% by mass in total of the methacrylic acid ester macromonomer (b1) and the other monomer (b2) The manufacturing method of the porous membrane in any one of [1]-[3] which contains the polymer (B) which is%.
[5] The method for producing a porous membrane according to any one of claims 1 to 4, wherein the cleaning step is performed using hot water at 60 ° C. to 100 ° C.

  According to the production method of the present invention, a porous film can be obtained using a polymer composition easily obtained by conventional radical polymerization which does not include purification steps such as precipitation and evaporation.

  In addition, the porous membrane obtained by the method for producing a porous membrane of the present invention is not limited to the use in the water treatment field, and is also suitable as a porous membrane used for a support of an electrolyte solution, particularly lithium A support swollen with a lithium ion electrolyte of an ion battery is preferred.

<Film-forming polymer (A)>
The film-forming polymer (A) is one of the components for the porous film preparation solution (D) and the porous film of the present invention.

  The film-forming polymer (A) is for maintaining the structure of the porous film obtained from the solution (D) for preparing a porous film of the present invention, and according to the characteristics required of the porous film The composition of A) can be selected.

When chemical resistance, oxidation degradation resistance and heat resistance are required as the film-forming polymer (A), for example, polyvinylidene fluoride (PVDF), PVDF-co-hexafluoropropylene (HFP), ethylene-co- Fluorinated polymers such as chlorotrifluoroethylene (ECTFE), polyvinyl fluoride, polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyethylene, polypropylene, polystyrene, polystyrene derivatives, polyamide, polyurethane, polycarbonate, polysulfone, poly Ether sulfone and cellulose acetate are mentioned. Among these, polyvinylidene fluoride (PVDF), PVDF-co-hexafluoropropylene (HFP), ethylene-co-chlorotrifluoroethylene (ECTFE) in terms of chemical resistance and oxidative degradation resistance of the porous membrane. Fluorine-containing polymers such as polyvinyl fluoride and polytetrafluoroethylene (PTFE) are preferred. Among these, PVDF is preferred in terms of resistance to oxidative degradation and mechanical durability of the porous membrane.
The film-forming polymer (A) can be used alone or in combination of two or more.

  The film-forming polymer (A) is preferably a polymer that can be dissolved in the below-mentioned solvent (ii) and not dissolved in pure water.

  Among the aforementioned polymers, PVDF is preferred from the viewpoints of compatibility with the solvent (ii) described later, chemical resistance and heat resistance.

  As a film formation polymer (A), a mass mean molecular weight (henceforth "Mw") 100,000-2,000,000 are preferable. When the Mw is 100,000 or more, the mechanical strength of the porous membrane of the present invention tends to be good, and when the Mw is 2,000,000 or less, the solubility in the solvent (b) is good. Tend to be The lower limit value of Mw is more preferably 300,000 or more, and the upper limit value of Mw is more preferably 1,500,000 or less.

  In addition, when using what has said Mw as a film formation polymer (A), what has different Mw can be mixed and it can be set as the film formation polymer (A) which has predetermined Mw.

<Macromonomer (b1)>
The macromonomer (b1) is one of the components of the polymerization liquid (C) of the present invention, the solution (D) for preparing a porous membrane, and the polymer (B) contained in the porous membrane.

  The macromonomer (b1) is a monomer represented by the formula (1), in which a radically polymerizable group having an unsaturated double bond is added to one end of a polymethacrylic acid ester segment.

In Formula (1), R and R ^{1 to} R ⁿ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group. The alkyl group, the cycloalkyl group, the aryl group or the heterocyclic group can have a substituent.

As an alkyl group of R or R ^{< 1 >} -R ^<n>, a C1-C20 branched or linear alkyl group is mentioned, for example. Specific examples of the alkyl group of R or R ^{1 to} R ⁿ include a methyl group, an ethyl group, an n-propyl group and an i-propyl group.

As a cycloalkyl group of R or R ^{< 1 >} -R ^<n>, a C3-C20 cycloalkyl group is mentioned, for example. Specific examples of the cycloalkyl group of R or R ^{1 to} R ⁿ include cyclopropyl group, cyclobutyl group and adamantyl group.

As an aryl group of R or R ^{< 1 >} -R ^<n>, a C6-C18 aryl group is mentioned, for example. Specific examples of the aryl group of R or R ^{1 to} R ⁿ include a phenyl group and a naphthyl group.

As a heterocyclic group of R or R ^{< 1 >} -R ^<n>, a C5-C18 heterocyclic group is mentioned, for example. Specific examples of the heterocyclic group of R or R ^{1 to} R ⁿ include γ-lactone group and ε-caprolactone group.

The substituent of R or R ^{1 to} R ⁿ is, independently of each other, an alkyl group, an aryl group, a carboxyl group, an alkoxycarbonyl group (—COOR ′), a carbamoyl group (—CONR′R ′ ′), a cyano group, A group selected from the group consisting of a hydroxyl group, an amino group, an amido group (-NR'R ''), a halogen, an allyl group, an epoxy group, an alkoxy group (-OR ') or a group exhibiting hydrophilicity or ionicity It can be mentioned. In addition, R 'or R''is respectively independently the same group as R except the heterocyclic group.

As an alkoxycarbonyl group of the substituent of R or R ^{< 1 >} -R ^<n> , a methoxycarbonyl group is mentioned, for example.

As a carbamoyl group of the substituent of R or R ^{< 1 >} -R ^<n> , N- methyl carbamoyl group and N, N- dimethyl carbamoyl group are mentioned, for example.

As an amido group of the substituent of R or R ^{< 1 >} -R ^<n> , a dimethyl amido group is mentioned, for example.

As a halogen of the substituent of R or R ^{< 1 >} -R ^<n> , a fluorine, chlorine, a bromine, and an iodine are mentioned, for example.

As an alkoxy group of the substituent of R or R ^{< 1 >} -R ^<n> , a C1-C12 alkoxy group is mentioned, for example, A methoxy group is mentioned as a specific example.

As a group which shows hydrophilicity or ionicity of a substituent of R or R ^{1 to} R ⁿ , for example, alkali salts of carboxyl group or alkali salts of sulfoxyl group, poly (alkylene oxide) such as polyethylene oxide group, polypropylene oxide group, etc. And cationic substituents such as quaternary ammonium bases.

n represents the degree of polymerization and is an integer of 2 or more and 10,000 or less. More preferably, it is 3 or more and 1,000 or less.
As R, a methyl group, an ethyl group, an n-propyl group or an i-propyl group is preferable from the viewpoint of the availability of the macromonomer (b1) and the solubility of the resulting polymer (B) in the solvent (ii). And methyl groups are more preferred.

  The end group of the macromonomer (b1) is the end group of a polymer obtained by known radical polymerization. Similarly, examples thereof include, but are not limited to, an alkyl group derived from a hydrogen atom and a radical polymerization initiator, a hydroxyl group, a thiol group and the like.

  The macromonomer (b1) has an effect of acting as a chain transfer agent in radical polymerization of a monomer mixture containing the macromonomer (b1). Therefore, when radically polymerizing a monomer composition containing the macromonomer (b1) and the other monomer (b2) described later, at least one selected from a block copolymer and a graft copolymer without using a metal catalyst or a sulfur compound Since the polymer (B) having a species can be obtained, the obtained polymer (B) is suitable in that it is used for a molded article, a water treatment membrane or the like in which the content of impurities such as metal is required to be small.

In addition, by using the macromonomer (b1), it is possible to obtain a polymer containing at least one selected from a block copolymer and a graft copolymer relatively inexpensively than conventional controlled radical polymerization. It is. Examples of controlled radical polymerization include reversible addition fragmentation chain transfer polymerization (RAFT), atom transfer radical polymerization (ATRP), nitroxide mediated polymerization (NMP), and living radical polymerization (TERP) having organic tellurium as a growth terminal. Can be mentioned. These controlled radical polymerizations are characterized by having a controlled molecular weight and a narrow molecular weight distribution.

  In the present invention, the macromonomer means a polymer compound having a polymerizable functional group, and is also referred to as a macromer.

  As a radically polymerizable monomer used as a raw material for comprising the polymethacrylic acid ester segment in macromonomer (b1), for example, from the solubility of polymer (B) in the solvent (b), for example, methyl methacrylate, methacrylic acid Ethyl, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, isoamyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate, dodecyl methacrylate, methacrylic acid Stearyl, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxy methacrylate , 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, Plaxel FM (trade name, manufactured by Daicel Chemical Industries, Ltd .; caprolactone addition monomer), methoxyethyl methacrylate, methacryl Ethoxyethyl methacrylate, normal butoxyethyl methacrylate, isobutoxyethyl methacrylate, t-butoxyethyl methacrylate, phenoxyethyl methacrylate, nonyl phenoxyethyl methacrylate, 3-methoxybutyl methacrylate, Blemmer PME-100 (trade name, Japan Fats and oils Co., Ltd., methoxy polyethylene glycol methacrylate (the chain of ethylene glycol is 2), Blenmer PME-200 (trade name, Nippon Oil and Fats Co., Ltd.) Methoxy polyethylene glycol methacrylate (in which the chain of ethylene glycol is 4), Blemmer PME-400 (trade name, Nippon Oil and Fats Co., Ltd., methoxy polyethylene glycol methacrylate (in which the chain of ethylene glycol is 9)), Blemmer 50 POEP -800 B (trade name, Nippon Oil and Fats Co., Ltd., Octoxy polyethylene glycol-polypropylene glycol-methacrylate (the chain of ethylene glycol is 8 and the chain of propylene glycol is 6)) and Blenmer 20 ANEP-600 (trade name) Nippon Oil and Fats Co., Ltd., nonyl phenoxy (ethylene glycol-polypropylene glycol) monoacrylate). These can be used alone or in combination of two or more.

  Among them, methyl methacrylate, n-butyl methacrylate, and methacrylic acid from the viewpoint of the availability of the radically polymerizable monomer as the raw material and the solubility of the obtained polymer (B) in the solvent (ii). Lauryl, dodecyl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate, methacrylic acid, Blemmer PME-100, Blenmer PME-200 and Blemmer PME- 400 is preferred. In addition, as a radically polymerizable monomer to be a raw material, methyl methacrylate, n-butyl methacrylate, lauryl methacrylate, dodecyl methacrylate, methacrylic, in terms of good compatibility with the film-forming polymer (A), particularly PVDF. More preferred are 2-ethylhexyl acid, 2-hydroxyethyl methacrylate, Blemmer PME-100, Blemmer PME-200 and Blemmer PME-400, and more preferred is methyl methacrylate.

  The number average molecular weight (hereinafter referred to as "Mn") of the macromonomer (b1) is 1,000 or more and 1,000,000 in view of the mechanical properties of the polymer (B) to be obtained and the solubility in the solvent (b). The following are preferred. The lower limit value of Mn is more preferably 3,000 or more, further preferably 4,000 or more. As for the upper limit value of Mn, 60,000 or less is more preferable, and 50,000 or less is still more preferable.

  The molecular weight distribution (hereinafter referred to as "Mw / Mn") of the macromonomer (b1) is 1.5 or more and 5.0 or less from the viewpoint of the mechanical properties of the polymer (B) to be obtained and the solubility in the solvent (b). Is preferred.

  In the present invention, the macromonomer (b1) can be used alone or in combination of two or more.

  As a method for producing the macromonomer (b1), for example, a method of producing it using a cobalt chain transfer agent (for example, US Pat. No. 4,680,352), α-substituted non-e.g. A method of using a saturated compound as a chain transfer agent (for example, WO 88/04, 304), a method of chemically bonding a polymerizable group (for example, JP-A 60-133, 007, US Pat. (US Pat. No. 5,147,952) and a thermal decomposition method (for example, JP-A-11-240,854). Among these, the method of producing using a cobalt chain transfer agent is preferable from the viewpoint that the macromonomer (b1) can be efficiently produced.

  Examples of the method for producing the macromonomer (b1) include aqueous dispersion polymerization methods such as bulk polymerization method, solution polymerization method, suspension polymerization method, and emulsion polymerization method. Among these, solution polymerization and aqueous dispersion polymerization are preferable from the viewpoint of simplification of the recovery step of the macromonomer (b1).

  Examples of the solvent (b) used when obtaining the macromonomer (b1) by solution polymerization include hydrocarbons such as toluene; ethers such as diethyl ether and tetrahydrofuran; halogenated hydrocarbons such as dichloromethane and chloroform; acetone Ketones; alcohols such as methanol; nitriles such as acetonitrile; vinyl esters such as ethyl acetate; carbonates such as ethylene carbonate; and supercritical carbon dioxide. These can be used alone or in combination of two or more.

<Other monomer (b2)>
The other monomer (b2) is one of the raw materials for forming the polymer (B) contained in the polymerization liquid (C), the solution (D) for preparing a porous membrane, and the porous membrane of the present invention.

As other monomers (b2), for example, monomers similar to radically polymerizable monomers as a raw material for constituting a polymethacrylic acid ester segment in macromonomer (b1), methyl acrylate, ethyl acrylate, acracrylic acid n-propyl, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, isoamyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, dodecyl acrylate, stearyl acrylate, acrylic acid Phenyl, benzyl acrylate, glycidyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate Acrylic acid 4-hydroxybutyl, acrylic acid polyethylene glycol, acrylic acid polypropylene glycol, Plaxel FA (Daicel Chemical Industries, Ltd .; caprolactone addition monomer), methoxyethyl acrylate, ethoxyethyl acrylate, normal butoxyethyl acrylate, Isobutoxyethyl acrylate, tert-butoxyethyl acrylate, phenoxyethyl acrylate, nonyl phenoxyethyl acrylate, 3-methoxybutyl acrylate, Brenmer AME-100, 200 (Nippon Oil Co., Ltd.), Blenmer 50 AOEP-800B Acrylic acid, fumaric acid, maleic anhydride, itaconic acid, itaconic acid, bicyclo [2.2.1] -5-heptene-2,3-dicarboxylic acid anhydride, N-phenylmaleimide, N -Shi Lohexyl maleimide, N-t-butyl maleimide, vinyl caprate, vinyl laurate, vinyl stearate, vinyl trifluoroacetate, butadiene, isoprene, 4-methyl-1,3-pentadiene, 1,3-pentadiene styrene, o -Methylstyrene, m-methylstyrene, p-methylstyrene, o, p-dimethylstyrene, N-methylol methacrylamide, butoxy methacrylamide, acrylamide, N-methylol acrylamide, butoxy acrylamide, dimethylaminoethyl (meth) acrylate, dimethyl Aminoethyl (meth) acrylate methyl chloride salt, dimethylaminoethyl (meth) acrylate benzyl chloride salt, diethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) a Crylate methyl chloride salts, diethylaminoethyl (meth) acrylate benzyl chloride salts, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane and vinyltrimethoxysilane can be mentioned.
Among these, (meth) acrylic acid or (meth) acrylate is preferable in view of the copolymerizability with the macromonomer (b1).

<Monomer composition>
In the present invention, the monomer composition contains macromonomer (b1) and other monomers (b2).

The content of the macromonomer (b1) is preferably 5 to 99 parts by mass with respect to 100 parts by mass of the total amount of the macromonomer (b1) and the other monomers (b2) in the monomer composition. When the content of the macromonomer (b1) is 5 parts by mass or more, the film forming polymer (A) is added to the obtained polymerization liquid (C) to prepare the solution (D) for preparing a porous film In the case of 99 parts by mass or less, the contact angle of the porous membrane of the present invention to pure water tends to be 90 ° or less. The lower limit value of the content of the macromonomer (b1) is more preferably 20 parts by mass or more, further preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more. 98 mass parts or less are more preferable, and, as for the upper limit of content of a macromonomer (b1), 95 mass parts or less are still more preferable.

<Polymer (B)>
The polymer (B) is one of the components of the polymerization liquid (C) of the present invention, the solution (D) for preparing a porous membrane, and the porous membrane.

The polymer (B) is obtained by polymerizing a monomer composition containing the macromonomer (b1) and the other monomer (b2), and is a block copolymer of the macromonomer (b1) and the other monomer (b2), and It is comprised by at least 1 sort (s) chosen from the graft copolymer of the other monomer (b2) which has a macromonomer (b1) unit in a side chain.

  In the present invention, a polymer having only the macromonomer (b1) unit in the polymer (B), a polymer having only the other monomer (b2) unit, an unreacted macromonomer (b1) and an unreacted other monomer ( It can contain at least one selected from b2).

  The Mn of the polymer (B) is 1,000 or more and 5,000,000 or less in view of the thermal stability of the polymer (B) and the mechanical strength of the obtained porous membrane and the hydrophilicity of the outer surface of the porous membrane. preferable. The lower limit value of Mn of the polymer (B) is more preferably 2,000 or more, and still more preferably 5,000 or more. The upper limit value of Mn of the polymer (B) is more preferably 300,000 or less.

  The polymer (B) can be used alone or in combination of two or more polymers having different composition ratios, chain distribution or molecular weight.

  As a method of producing the polymer (B), a solution polymerization method can be mentioned.

  As a solvent (ii) used when manufacturing a polymer (B) by a solution polymerization method, for example, acetone, dimethylformamide (DMF), dimethylacetamide (DMAc) are used in view of dissolving the film forming polymer (A). Dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), hexamethyl phosphate triamide (HMPA), tetramethyl urea (TMU), triethyl phosphate (TEP) and trimethyl phosphate (TMP). Among these, acetone, DMF, DMAc, DMSO and NMP are preferable in view of the solubility of the film-forming polymer (A) and the polymer (B) and the ease of handling. The solvents (b) can be used alone or in combination of two or more.

  When producing the polymer (B), a chain transfer agent such as mercaptan, hydrogen, α-methylstyrene dimer, terpenoid can be used to control the molecular weight of the polymer (B).

  A radical polymerization initiator can be used in obtaining the polymer (B).

As a radical polymerization initiator, an organic peroxide and an azo compound are mentioned, for example.

  Specific examples of organic peroxides include 2,4-dichlorobenzoyl peroxide, t-butylperoxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, octanoyl Peroxide, t-butylperoxy-2-ethylhexanoate, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide and Di-t-butyl peroxide is mentioned.

  Specific examples of the azo compound include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-azobis (2,4-) And dimethyl-4-methoxyvaleronitrile).

  As a radical polymerization initiator, benzoyl peroxide, AIBN, 2,2′-azobis (2,4-dimethylvaleronitrile) and 2, and 2, from the viewpoint of easy availability and having a half-life temperature suitable for polymerization conditions. 2'-Azobis (2,4-dimethyl-4-methoxyvaleronitrile) is preferred. These can be used alone or in combination of two or more.

  The addition amount of the radical polymerization initiator is preferably 0.0001 parts by mass to 10 parts by mass with respect to 100 parts by mass of the other monomer (b2).

  As a polymerization temperature for obtaining a polymer (B), the boiling point of the solvent to be used and the use temperature range of a radical polymerization initiator are suitable, for example -100-250 degreeC is preferable. The lower limit value of the polymerization temperature is more preferably 0 ° C. or more, and the upper limit value is more preferably 200 ° C. or less.

<Polymerization solution (C)>
The polymerization liquid (C) of the present invention is a solution containing a polymer (B) obtained by polymerizing a monomer composition containing a macromonomer (b1) and another monomer (b2) in a solvent (ii) . By preparing a solution (D) for preparation of a porous membrane described later using the polymerization liquid (C) of the present invention, a porous membrane can be obtained without including complicated steps such as reprecipitation and evaporation. it can.

<Solution for preparation of porous membrane (D)>
The porous film preparation solution (D) of the present invention is obtained by dissolving the film-forming polymer (A) in the polymerization liquid (C) containing the polymer (B). The macromonomer (b1) and other monomers contained in the polymer (B) are obtained by dissolving the film-forming polymer (A) in the polymerization liquid (C) by obtaining the solution (D) for porous membrane preparation of the present invention. The reaction rate of (b2) is good, and it becomes possible to obtain a porous membrane by a simpler method than conventional. Incidentally, the solution (D) for preparing a porous film is uniform, even if a part of the film-forming polymer (A) or the polymer (B) is dispersed without being dissolved in the polymerization solution (C). It may be in a dispersed state as long as it can maintain its sex.
When the porous film preparation solution (D) is obtained, the film forming polymer (A) can be dissolved in the polymerization solution (C) while heating the solvent (b) if it is not higher than the boiling point of the solvent (b). . Moreover, the polymerization liquid (C) can be cooled as needed.

The content of the film-forming polymer (A) in the porous film preparation solution (D) of the present invention is 100 parts by mass of the total amount of the film-forming polymer (A), the polymer (B) and the solvent (B). The amount is preferably 5 to 40 parts by mass. When the content of the film-forming polymer (A) is 5 parts by mass or more, the porous film tends to be formed. In addition, when the content of the film-forming polymer (A) is 30 parts by mass or less, it tends to be easily soluble in the polymerization solution.
8 mass parts or more are more preferable, and, as for the lower limit of content of a film formation polymer (A), 10 mass parts or more are still more preferable. 30 mass parts or less are more preferable, 25 mass parts or less are still more preferable, and 20 mass parts or less are especially preferable.
The content of the polymer (B) in the porous membrane preparation solution (D) of the present invention is 1 part per 100 parts by mass of the total of the film-forming polymer (A), the polymer (B) and the solvent (B). -30 mass parts are preferable. The content of the polymer (B) tends to be a porous membrane at 1 part by mass or more. When the content of the polymer (B) is 30 parts by mass or less, dissolution of the polymer (A) in the polymerization liquid (C) tends to be easy.

  2 mass parts or more are more preferable, and, as for the lower limit of polymer (B) content, 5 mass parts or more are still more preferable. The upper limit of the content of the film-forming polymer (A) is more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

<Porous membrane>
In the polymer (B) contained in the porous membrane of the present invention, the ratio of the other monomer (b2) to the total 100% by mass of the methacrylic acid ester macromonomer (b1) and the other monomer (b2) is 51 to 100. It contains the polymer (B) which is% by mass.
In the porous membrane obtained, the proportion of the other monomer (b2) to the total 100% by mass of the methacrylate macromonomer (b1) in the polymer (B) and the other monomer (b2) is 51% by mass or more The pore size tends to be larger than that of the conventional method, and the polymer (B) can be contained in the porous membrane even when the method for manufacturing the porous membrane described later is used at 100% by mass or less.

The upper limit of the ratio of the other monomer (b2) to the total 100% by mass of the methacrylic acid ester macromonomer (b1) and the other monomer (b2) in the polymer (B) contained in the porous membrane of the present invention is 99 % By mass is more preferable, and 95% by mass is even more preferable. The lower limit of the ratio of the other monomer (b2) to the total 100% by mass of the methacrylic acid ester macromonomer (b1) and the other monomer (b2) in the polymer (B) contained in the porous membrane of the present invention is 60 mass% is more preferable, and 70 mass% is further preferable.

<Method of producing porous membrane>
The following method is mentioned as an example as a manufacturing method of the porous membrane of the present invention.
First, as described above, the porous film preparation solution (D) obtained by dissolving the film forming polymer (A) in the polymerization solution (C) containing the polymer (B) is immersed in the coagulation solution to coagulate it. To obtain a porous membrane precursor. Thereafter, the solvent (ii) remaining in the porous membrane precursor and part or all of the polymer (B) are washed and removed, and the porous membrane precursor after washing is dried to obtain the porous membrane of the present invention Get
From the viewpoint of controlling the pore size of the membrane, a 0 to 50% by mass aqueous solution of the solvent (ii) is preferable as the coagulating solution used when obtaining the porous membrane precursor.

  The temperature of the coagulating solution is preferably 10 ° C. or more and 90 ° C. or less. If the temperature of the coagulating liquid is 10 ° C. or higher, the water permeability of the porous membrane of the present invention tends to be improved, and if it is 90 ° C. or lower, the mechanical strength of the porous membrane of the present invention tends not to be impaired.

  The obtained porous membrane precursor is preferably removed from the solvent (ii) by immersion in hot water at 40 to 100 ° C. and washing. If the temperature of the hot water is 40 ° C. or higher, a high cleaning effect on the porous film precursor tends to be obtained, and if the temperature of the hot water is 100 ° C. or lower, the porous film precursor tends to be difficult to fuse. It is in.

  The porous membrane precursor after washing is preferably dried at 60 ° C. or more and 120 ° C. or less for 1 minute or more and 24 hours or less. If the drying temperature of the porous membrane precursor after washing is 60 ° C. or higher, the drying process time may be short and the production cost can be suppressed, which is preferable in industrial production. In addition, if the drying temperature of the porous film precursor after washing is 120 ° C. or lower, the porous film precursor tends not to be excessively shrunk in the drying step, and micro cracks are generated on the outer surface of the film. There is a tendency not to happen and it is preferable.

  The average pore diameter of the pores in the porous membrane is preferably 1 nm or more and 1200 nm or less from the viewpoint of removal of bacteria and viruses, purification of a protein or enzyme, or use in fresh water applications. If the average pore size of the pores is 1200 nm or less, it tends to be possible to remove bacteria, viruses and suspended substances in the upper water, and if it is 1 nm or more, there is a tendency that high water permeation pressure is not required when treating water. It is in.

  The average pore diameter of the pores in the porous membrane of the present invention can be determined by using a scanning electron microscope (product name: JSM-7400, manufactured by Nippon Denshi Co., Ltd.) to narrow the outer surface portion of the porous membrane of the present invention. The average pore diameter obtained by measuring the longest diameter of the pores.

  The porous membrane of the present invention can have an outer surface having a contact angle to pure water of 90 ° or less. The contact angle on the outer surface of the porous membrane is an index that indicates the hydrophilicity of the outer surface of the porous membrane. As the contact angle of the outer surface of the porous membrane of the present invention is smaller, the outer surface of the porous membrane has higher hydrophilicity, and the porous membrane can be expected to have high water permeability.

  By setting the contact angle of the outer surface of the porous membrane to pure water to 90 ° or less, the permeability of the porous membrane of the present invention can be improved.

  As a method of reducing the contact angle of the outer surface of the porous membrane to pure water, for example, hydrophilic functional groups such as macromonomer (b1) as the polymer (B) and hydroxyl group or carboxyl group as the other monomer (b2) Included are methods of obtaining a porous membrane using a copolymer with a monomer having a group. By obtaining a porous membrane using the above-mentioned copolymer, it is possible to obtain an outer surface of the porous membrane in which a polymer segment having a hydrophilic functional group is efficiently localized.

  The upper limit value of the contact angle with pure water of the outer surface of the porous membrane is more preferably 86 ° or less. In addition, the lower limit value of the contact angle to pure water of the outer surface of the porous membrane is preferably as low as possible, and generally is 1 ° or more. The lower limit value of the contact angle to the pure water of the outer surface of the porous membrane varies depending on the type of the polymer (A) used, but when using PVDF as the polymer (A), 20 ° or more is generally is there.

  Examples of the form of the porous membrane of the present invention include flat membranes and hollow fiber membranes.

  When the porous membrane is a flat membrane, the thickness is preferably 10 to 1,000 μm. If it is 10 μm or more, it has high stretchability and tends to be satisfactory in durability, and if it is 1,000 μm or less, it tends to be able to be produced at low cost. When a porous membrane is a flat membrane, 20 micrometers or more are more preferable, and, as for the lower limit of thickness, 30 micrometers or more are still more preferable. 900 micrometers or less are more preferable, and, as for the upper limit of thickness, 800 micrometers or less are still more preferable.

  When the porous membrane of the present invention is a flat membrane, examples of the internal structure of the membrane include a sloped structure in which the size of the pores decreases in a specific direction in the cross section of the membrane or a structure having homogeneous pores.

  When the porous membrane of the present invention is a flat membrane, the membrane may have a macrovoid or spherulite structure.

  When the shape of the porous membrane of the present invention is a hollow fiber membrane, the outer diameter of the hollow fiber membrane is preferably 20 to 2,000 μm. When the outer diameter of the porous membrane is 20 μm or more, yarn breakage tends to be difficult to occur during film formation. In addition, when the outer diameter of the hollow fiber membrane is 2,000 μm or less, the hollow shape can be easily maintained, and in particular, it tends to be difficult to be flattened even when an external pressure is applied. The lower limit value of the outer diameter of the hollow fiber membrane is more preferably 30 μm or more, and still more preferably 40 μm or more. The upper limit of the outer diameter of the hollow fiber membrane is more preferably 1,800 μm or less, and still more preferably 1,500 μm or less.

  When the shape of the porous membrane of the present invention is a hollow fiber membrane, the thickness of the hollow fiber membrane is preferably 5 to 500 μm. If the thickness of the hollow fiber membrane is 5 μm or more, yarn breakage tends to be difficult to occur during membrane formation, and if it is 500 μm or less, the hollow shape tends to be easily maintained. 10 micrometers or more are preferable and, as for the lower limit of the thickness of a hollow fiber membrane, 15 micrometers or more are still more preferable. The upper limit of the thickness of the hollow fiber membrane is more preferably 480 μm or less, and still more preferably 450 μm or less.

  Hereinafter, the present invention will be described in more detail by way of examples. In the following, the composition and structure of the macromonomer (b1) and the polymer, the Mw of the polymer and the macromonomer (b1) and the Mn and Mw / Mn of the polymer were evaluated by the following methods.

Moreover, "part" and "%" respectively show "mass part" and "mass%" below.
-Composition and structure of macromonomer (b1), polymer (B) and polymer (B ') The composition and structure of macromonomer (b1), polymer (B) and polymer (B') are shown by 1H-NMR (Nippon Electron ( , Inc., product name: JNM-EX270).
The composition of macromonomer (b1) and other monomer (b2) in polymer (B) and polymer (B ') can be referred to the spectrum database (SDBS) of organic compounds provided by National Institute of Advanced Industrial Science and Technology Calculated to

(2) Mw of film-forming polymer (A)
The Mw of the film-forming polymer (A) was determined under the following conditions using GPC (manufactured by Tosoh Corporation, “HLC-8020” (trade name)).
· Column: TSK GUARD COLUMN α (7.8 mm × 40 mm) and three TSK-GEL α-M (7.8 × 300 mm) connected in series · Eluent: DMF 20 mM LiBr solution · Measurement temperature: 40 ° C
Flow rate: 0.1 mL / min Mw is a polystyrene standard (Mp (peak top molecular weight) manufactured by Tosoh Corp.) 76, 969, 900, 2, 110,000, 1, 260,000, 775,000 , 355,000, 186,000, 19, 500, 1, 050 and 9 types of styrene monomers (M = 104) manufactured by NS Styrene Monomer Co., Ltd. were obtained using calibration curves.

(3) Mn and Mw / Mn of macromonomer (b1), polymer (B) and polymer (B ')
The Mn and Mw / Mn of the macromonomer (b1), the polymer (B) and the polymer (B ′) are measured under the following conditions using GPC (manufactured by Tosoh Corp., “HLC-8220” (trade name)) I asked.
-Column: TSK GUARD COLUMN SUPER H-L (4.6 x 35 mm) and two TSK-GEL SUPER HZM-H (4.6 x 150 mm) are connected in series-Eluent: DMF 0.01 M LiCl solution- Measurement temperature: 40 ° C
Flow rate: 0.6 mL / min Mw is a polystyrene standard (Mp (peak top molecular weight) manufactured by Tosoh Corp.) of 6,200,000, 2,800,000, 1,110,000 and 707,000. , 35, 4,000, 189,000, 98, 900, 37, 200, 9, 830, 5, 870, 870, and 500).

(4) Contact Angle The contact angle of the porous membrane to pure water was measured by the following method.

The porous membrane test piece was placed on the sample table of a contact angle measurement device (manufactured by Kruss, product name: DSA-10). Then, the drop of pure water (Wako Pure Chemical Industries, Ltd., LC / MS) drop (10 μl) was dropped on the outer surface of the sample for contact angle measurement, and the state of the drop 3 seconds after the drop was attached to the device Photographed using a CCD camera. The contact angle of the water drop of the obtained photograph was determined by automatic measurement with an image processing program incorporated in the contact angle measurement device.

(5) Average Pore Size Select an arbitrary 500 μm × 500 μm range on the outer surface of the porous membrane in 5 or more places, measure the pore size for 30 randomly selected pores present in them, and The mean value was taken as the mean pore size.

Synthesis Example 1 Synthesis of Cobalt Chain Transfer Agent CoBF-1 In a reactor equipped with a stirrer, under a nitrogen atmosphere, cobalt acetate (II) tetrahydrate (Wako Pure Chemical Industries, Ltd. Wako special grade) Add 1.00 g, 1.93 g of diphenylglyoxime (manufactured by Tokyo Kasei Kogyo Co., Ltd., EP grade) and 80 ml of diethyl ether (specially manufactured by Kanto Chemical Co., Ltd., special grade) deoxygenated beforehand by bubbling nitrogen and stirring at room temperature for 30 minutes did. Subsequently, 10 ml of boron trifluoride diethyl ether complex (manufactured by Tokyo Kasei Kogyo Co., Ltd., EP grade) was added, and the mixture was further stirred for 6 hours. The mixture was filtered, and the solid was washed with diethyl ether (special grade, manufactured by Kanto Chemical Co., Ltd.) and vacuum dried for 15 hours to obtain 2.12 g of cobalt chain transfer agent CoBF-1 which is a reddish brown solid.

Synthesis Example 2 Synthesis of Dispersant 1 In a reaction apparatus equipped with a stirrer, a condenser and a thermometer, 61.6 parts of a 17% aqueous potassium hydroxide solution, methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name) A: 19.1 parts of Acryester M) and 19.3 parts of deionized water were charged. Then, the solution in the reactor was stirred at room temperature, and after confirming the exothermic peak, the solution was further stirred for 4 hours. Thereafter, the reaction solution in the reactor was cooled to room temperature to obtain an aqueous potassium methacrylate solution.

  Next, 900 parts of deionized water, 42% sodium 2-sulfoethyl methacrylate aqueous solution (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester SEM-Na) in a polymerization apparatus equipped with a stirrer, a condenser and a thermometer. 70 parts, 16 parts of the above aqueous solution of potassium methacrylate and 7 parts of methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) are added and stirred, and the inside of the polymerization apparatus is replaced with nitrogen at 50 ° C. The temperature rose to Into it, 0.053 parts of 2,2'-azobis (2-methylpropionamidine) dihydrochloride (Wako Pure Chemical Industries, Ltd., trade name: V-50) is added as a polymerization initiator, and further The temperature was raised to 60 ° C. After charging of the polymerization initiator, 1.4 parts of methyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester M) was dividedly added a total of five times every 15 minutes. Thereafter, the liquid in the polymerization apparatus was kept at 60 ° C. for 6 hours while being stirred, and then cooled to room temperature to obtain Dispersant 1 having a solid content of 8% which is a transparent aqueous solution.

Synthesis Example 3 Synthesis of Macromonomer (b1-1) In a flask equipped with a condenser, 100 parts of methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M), 150 parts of deionized water, sodium sulfate 1 .39 parts, 1.53 parts of Dispersant 1, and 0.00125 parts of CoBF-1 were charged. While the solution in the flask was heated to 70 ° C., CoBF-1 was dissolved, and the interior was purged with nitrogen by nitrogen bubbling. Then, 1 part by mass of AIBN was added, and the mixture was maintained for 6 hours while maintaining the internal temperature at 70 ° C. to complete the polymerization. After this, the polymerization reaction product was cooled to room temperature and filtered to recover the polymer. The polymer obtained was washed with water and vacuum dried at 50 ° C. overnight to obtain a macromonomer (b1-1). The Mn of the macromonomer (b1-1) was 13,000, and the Mw / Mn was 2.3. The introduction rate of the terminal double bond of the macromonomer (b1-1) was approximately 100%. In the macromonomer (b1-1), R in the formula (1) was a methyl group.

Synthesis Example 4 Synthesis of Macromonomer (b1-2) In a flask equipped with a condenser, 100 parts of methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M), 150 parts of deionized water, sodium sulfate 1 Then, .39 parts, 1.53 parts of Dispersant 1, and 4.0045 parts of CoBF-1 were charged. While the solution in the flask was heated to 70 ° C., CoBF-1 was dissolved, and the interior was purged with nitrogen by nitrogen bubbling. Then, 1 part by mass of AIBN was added, and the mixture was maintained for 6 hours while maintaining the internal temperature at 70 ° C. to complete the polymerization. After this, the polymerization reaction product was cooled to room temperature and filtered to recover the polymer. The polymer obtained was washed with water and vacuum dried at 50 ° C. overnight to obtain a macromonomer (b1-1). The Mn of the macromonomer (b1-2) was 40,000, and the Mw / Mn was 2.3. The introduction rate of the terminal double bond of the macromonomer (b1-2) was approximately 100%. In the macromonomer (b1-2), R in the formula (1) was a methyl group.

Synthesis Example 5 Synthesis of Polymer (B-1) In a flask equipped with a condenser, 50 parts of macromonomer (b1-1), 2-hydroxyethyl acrylate as another monomer (b2) (manufactured by Wako Pure Chemical Industries, Ltd.) , Wako first grade, HEA) 50 parts and solvent (ii) N, N-dimethylacetamide (Wako Pure Chemical Industries, Ltd., reagent special grade, D
MAc) A monomer composition containing 300 parts was charged, and the interior was purged with nitrogen by nitrogen bubbling. Next, while the monomer composition was heated and the internal temperature was kept at 70 ° C., 0.1 part of AIBN (Wako Pure Chemical Industries, Wako special grade) as a radical polymerization initiator was added to the monomer composition Thereafter, the temperature was maintained for 4 hours, and then the temperature was raised to 80 ° C. and maintained for 30 minutes to complete the polymerization to obtain a polymerization solution (C-1). Thereafter, the obtained polymerization solution (C-1) was cooled to room temperature to obtain a polymer (B-1) in the polymerization solution (C-1). Mn of polymer (B-1) contained in the polymerization liquid (C-1) obtained by GPC measurement was 51,000, and Mw / Mn was 3.0. The content of the macromonomer (b1) in the polymer (B-1) determined by 1 H-NMR was 50%. In addition, the content of the other monomer (b2) was 50%. The evaluation results are shown in Table 1.

Synthesis Example 6 to Synthesis Example 10 Synthesis of Polymers (B-2) to (B-6) A polymer (B-B) was prepared in the same manner as in Synthesis Example 5 except that the monomer composition was changed to the ratio shown in Table 1. 2) to (B-6) were obtained. The evaluation results of the polymers (B-2) to (B-6) are shown in Table 1.

Synthesis Example 11 Synthesis of Polymer (B′-1) 100 parts of the polymerization solution (C-1) obtained in Synthesis Example 5 is extracted, dissolved in 400 parts of DMAc and diluted, and then re-diluted in a large amount of deionized water It precipitated. The polymer precipitated by reprecipitation was recovered, and dried overnight with a hot air dryer at 75 ° C. to obtain a polymer (B′-1). The yield of the polymer (B′-1) was 94%. The Mn of the polymer (B′-1) obtained by GPC measurement was 62,000, and the Mw / Mn was 2.6. The content of the macromonomer (b1) in the polymer (B-1) determined by 1 H-NMR was 65%. In addition, the content of the other monomer (b2) was 35%. The evaluation results are shown in Table 1.

Synthesis Example 12 to Synthesis Example 16 Synthesis of Polymers (B′-2) to (B′-6) The same as in Synthesis Example 9 except that the polymerization solutions used in Table 1 were used. Polymers (B'-2) to (B'-6) were obtained by the method. The evaluation results of the polymers (B'-2) to (B'-6) are shown in Table 1.

Synthesis Example 17
In a flask equipped with a condenser, 16.2 parts of Kynar 761A as a film-forming polymer, 8.2 parts of a macromonomer (b1-2), and N, N-dimethylacetamide (Wako Pure Chemical Industries, Ltd., reagent) as a solvent (ii) A monomer composition containing 72.4 parts of a special grade, DMAc) was charged, and the inside of the flask was heated to 70 ° C. and held for 2 hours to dissolve Kynar 761A and the macromonomer (b1-2) in DMAc. Once the flask is cooled to 30 ° C., 4.2 parts of 2-hydroxyethyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd., Wako grade, HEA) as the other monomer (b2) is introduced into the flask and nitrogen bubbling is performed. The inside was replaced with nitrogen by Next, 0.011 part (Wako Pure Chemical Industries, Ltd., Wako special grade) of AIBN as a radical polymerization initiator was added to the monomer composition while heating the monomer composition and keeping the internal temperature at 70 ° C. Thereafter, the temperature was maintained for 4 hours, and then the temperature was raised to 80 ° C. and maintained for 30 minutes to complete the polymerization to obtain a polymerization solution (C-7). Thereafter, the obtained polymerization solution (C-7) was cooled to room temperature to obtain a polymer (B'-7) in the polymerization solution (C-7). Although the molecular weight measurement of the polymer (B'-7) contained in a superposition | polymerization liquid (C-7) was tried by GPC measurement, since it was a mixture with Kynar 761A simultaneously contained, it was not able to measure. The content of the macromonomer (b1) in the polymer (B-1) determined by 1 H-NMR was 50%. In addition, the content of the other monomer (b2) was 50%. The evaluation results are shown in Table 1.

The abbreviations in the table indicate the following compounds.
HEA: 2-hydroxyethyl acrylate (Wako Pure Chemical Industries, Wako first grade)
DMAc: N, N-dimethylacetamide (Wako Pure Chemical Industries, Ltd., reagent special grade)

Example 1
A polymerization solution (C-) containing 5.1 parts of Kynar 761A (Arkema Co., Ltd., PVDF homopolymer, trade name, Mw = 550,000) as the film-forming polymer (A), and the polymer (B-1) as the polymer (B) 1) 2.25 parts and 21.45 parts of DMAc (Wako Pure Chemical Industries, Ltd. Wako special grade) as solvent (ii) are blended in a glass container, and film formation is carried out by stirring with a stirrer at 50 ° C for 10 hours The solution was prepared.
The obtained film forming solution was allowed to stand for one day at room temperature, and then coated using a bar coater to a thickness of 125 μm on a glass substrate to obtain a coated film laminate. The coating stack was immersed in a room temperature coagulation bath containing 40 parts deionized water and 60 parts DMAc.

  After the coated film laminate is left in the coagulating bath for 5 minutes, the coagulated product of the coated film is peeled off from the glass substrate, and the coagulated product of the coated film is washed with hot water of 80 ° C. for 5 minutes to remove DMAc and form a flat film. The porous membrane of The obtained flat membrane-shaped porous membrane was dried at room temperature for 20 hours to obtain a porous membrane test piece having a thickness of 100 μm. The contact angle to water of the outer surface of the porous membrane test piece was 76.3 °, and the average pore diameter was 300 nm. The evaluation results are shown in Table 2.

The abbreviations in the table indicate the following compounds.
Kynar 761A: PVDF homopolymer (manufactured by Arkema, trade name, Mw = 550,000)
DMAc: N, N-dimethylacetamide (Wako Pure Chemical Industries, Ltd., Wako class 1)

[Examples 2 to 8]
The porous membrane test piece was obtained like Example 1 except using what is shown in Table 2 as a film forming liquid and a coagulation bath. The evaluation results are shown in Table 2.

Comparative Examples 1 to 9
The porous membrane test piece was obtained like Example 1 except using what is shown in Table 2 as a film forming liquid and a coagulation bath. The evaluation results are shown in Table 2.

  In Comparative Example 1, since (B'-1) was used instead of the polymerization liquid (C-1) containing the polymer (B-1), the step of reprecipitation is necessary, and the obtained porous membrane outer surface The contact angle with pure water of 76.9 ° was not able to obtain a highly hydrophilic membrane as compared with Example 1. The average pore size was smaller than that of Example 1 at 220 nm.

  In Comparative Example 2, since (B'-2) was used instead of the polymerization solution (C-2) containing the polymer (B-2), a step of reprecipitation is required, and the obtained porous membrane outer surface The contact angle to pure water of 79.9 ° was not able to obtain a highly hydrophilic membrane as compared with Example 2. The average pore size was reduced to 100 nm as compared with Example 2.

  In Comparative Example 3, since (B'-3) was used instead of the polymerization liquid (C-3) containing the polymer (B-3), a step of reprecipitation is required, and the obtained porous membrane outer surface The contact angle with pure water of 97.8 ° was not able to obtain a highly hydrophilic membrane as compared with Example 3. The average pore size was reduced to 1,000 nm as compared with Example 3.

  In Comparative Example 4, since (B'-3) was used instead of the polymerization liquid (C-3) containing the polymer (B-3), a re-precipitation step was necessary, and the obtained porous membrane outer surface The contact angle with pure water of 66.6 ° was not able to obtain a highly hydrophilic membrane as compared with Example 4. The average pore size was reduced to 200 nm as compared with Example 4.

  In Comparative Example 5, since (B'-4) was used instead of the polymerization liquid (C-4) containing the polymer (B-4), a re-precipitation step was necessary, and the obtained porous membrane outer surface The contact angle with pure water of 57.5 ° was not able to obtain a highly hydrophilic membrane as compared with Example 5. The average pore size was 230 nm, which was smaller than that of Example 5.

  In Comparative Example 6, since (B'-4) was used instead of the polymerization liquid (C-4) containing the polymer (B-4), a re-precipitation step was necessary, and the obtained porous membrane outer surface The contact angle to pure water of 77.6 ° was not able to obtain a highly hydrophilic membrane as compared with Example 6. The average pore size was reduced to 250 nm as compared to Example 6.

  In Comparative Example 7, since (B'-5) was used instead of the polymerization solution (C-5) containing the polymer (B-5), a re-precipitation step was necessary, and the obtained porous membrane outer surface The contact angle with pure water of 57.1 ° was not able to obtain a highly hydrophilic membrane as compared with Example 7. The average pore size was reduced to 280 nm as compared with Example 6.

  In Comparative Example 8, since (B'-6) was used instead of the polymerization liquid (C-6) containing the polymer (B-6), a re-precipitation step was necessary, and the obtained porous membrane outer surface The contact angle with pure water of 61.3 ° was not able to obtain a highly hydrophilic membrane as compared with Example 8. The average pore size was reduced to 100 nm as compared with Example 8.

  In Comparative Example 9, since polymerization was performed in a state where Kynar 761A having a high molecular weight was mixed in the polymerization liquid (C-7), the polymerization did not proceed sufficiently, and a porous test piece was prepared directly from (C-7). As a result, it was not possible to obtain a highly hydrophilic membrane as compared to Example 2 in which the contact angle of the outer surface of the obtained porous membrane with pure water was 80.2 °. In addition, no pores were observed on the surface of the porous membrane.

Claims (5)

A monomer composition comprising a methacrylic acid ester macromonomer (b1) (hereinafter referred to as "macromonomer (b1)") represented by the following formula (1) and another monomer (b2) is polymerized in a solvent (b) Preparing a polymerization solution (C) containing a polymer (B) obtained by
Step of dissolving the film-forming polymer (A) in the polymerization solution (C) to prepare a solution (D) for preparing a porous film The solution (D) for preparing a porous film is dipped in a coagulation solution to obtain a precursor The process of obtaining
And a method of producing a porous membrane including a washing step of partially or completely removing the polymer (B) from the precursor by washing.
In formula (1), R and R ^{1 to} R ⁿ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and n is an integer of 2 or more and 10,000 or less. is there. Z is an end group of a polymer obtained by radical polymerization or a hydrogen atom. The method for producing a porous membrane according to claim 1, wherein the membrane-forming polymer (A) is a fluorine-containing polymer. The method for producing a porous membrane according to any one of claims 1 and 2, wherein the other monomer (b2) is (meth) acrylic acid or (meth) acrylate. In the polymer (B) contained in the porous membrane, the proportion of the other monomer (b2) is 51 to 100% by mass with respect to 100% by mass in total of the methacrylic acid ester macromonomer (b1) and the other monomer (b2) The manufacturing method of the porous membrane in any one of the Claims 1-3 containing a certain polymer (B). The cleaning step, the manufacturing method of the porous membrane according to any one of 請 Motomeko 1 to claim 4 carried out using 60 ° C. to 100 ° C. hot water.