JP2015058418A - Polymer porous membrane and method for producing polymer porous membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer porous membrane having excellent water permeability and excellent solid substance removal performance.
SOLUTION: It is obtained from resin particles containing a fluoropolymer (A) containing a vinylidene fluoride unit and an acrylic polymer (B) containing a (meth) acrylic acid ester unit in the same particle. Molecular porous membrane.
[Selection figure] None

Description

The present invention relates to a polymer porous membrane and a method for producing a polymer porous membrane.

In recent years, porous membranes have been used in various fields such as water treatment fields such as water purification and wastewater treatment, medical applications such as blood purification, food industry fields, etc., as well as charged membranes, battery separators, and fuel cells. Yes.

For example, in the field of water treatment, porous membranes have come to be used as water treatment membranes in order to replace conventional sand filtration and coagulation sedimentation processes and improve the quality of treated water. In such a water treatment field, since the amount of treated water is large, the polymer porous membrane is required to have excellent water permeability. If the water permeation performance is excellent, the membrane area can be reduced, so the water purifier becomes compact and the equipment cost can be reduced.

Further, in the water purification treatment, the membrane may be washed with an alkaline solution or the like for chemical cleaning of the membrane, and the polymer porous membrane is required to have chemical resistance. In recent years, porous membranes using fluoropolymers such as polyvinylidene fluoride resin as a highly chemical-resistant material have been studied. However, since vinylidene fluoride resin is a hydrophobic polymer, it is included in treated water during the treatment process. The problem is that solid substances and dissolved components that adhere to the membrane become difficult to remove (fouling), and it has been studied to hydrophilize the fluoropolymer to form a water treatment membrane.

Examples of hydrophobizing the hydrophobic polymer to form a water treatment membrane include, for example, hydrophilization containing a hydrolyzate decomposition product that generates a hydrophilic chemical species by a decomposition reaction and a polyvinylidene fluoride resin. A porous membrane (for example, refer to Patent Document 1), a semipermeable membrane for water treatment (for example, containing cellulose acetate and polyvinylidene fluoride, and the content ratio of polyvinylidene fluoride in all polymer components is 5 to 60% by mass (for example, , Patent Document 2) Caustic resistance comprising a homogeneous polymer blend comprising 50 to 99 weight percent of at least one polyvinylidene fluoride (PVDF) polymer or copolymer and 1 to 50 weight percent of at least one acrylic polymer. A film (see, for example, Patent Document 3), a polyvinylidene fluoride resin, an acrylic ester polymer having a main chain, and Or a porous film composed mainly of a mixture of a methacrylic acid ester-based polymer and a graft copolymer whose side chain is an ethylene oxide-based polymer and / or a propylene oxide-based polymer, A porous film having a degree of polymerization of 25 or less and the side chain contained in the graft copolymer by 55% by weight or more (for example, see Patent Document 4) is disclosed.

Japanese Patent Application Laid-Open No. 2005-296846 JP 2006-326497 A Special table 2010-526885 gazette JP 2007-723 A

As described above, various methods for forming a water treatment membrane by hydrophilizing a hydrophobic polymer have been studied. However, in Patent Document 1, for example, the hydrophilic low molecular weight compound which is a decomposition product of the hydrophilizing agent and the polyvinylidene fluoride are poorly compatible. There was a risk of spilling. In Patent Documents 2 and 3, since the compatibility between the hydrophilic polymer and polyvinylidene fluoride is poor, it is necessary to devise a blending method in order to produce a uniform film. In the meantime, the hydrophilic polymer may flow out. As described above, the conventional polymer porous membrane has various problems, and as a result, it is not sufficient in terms of both the water permeation performance and the removal performance of the substance to be separated, and there is room for improvement.

This invention is made | formed in view of the said present condition, and it aims at providing the polymeric porous membrane which is excellent in water permeability performance, and is excellent also in the removal performance of a solid substance.

The present inventors shall obtain a polymer porous membrane from resin particles containing a fluoropolymer containing a vinylidene fluoride unit and an acrylic polymer containing a (meth) acrylic ester unit in the same particle. As a result, the inventors have found that the above problem can be solved brilliantly and have reached the present invention.

That is, the present invention is characterized in that it is obtained from resin particles containing a fluoropolymer (A) containing a vinylidene fluoride unit and an acrylic polymer (B) containing a (meth) acrylic acid ester unit in the same particle. It is a polymer porous membrane.

The fluoropolymer (A) is preferably a polyvinylidene fluoride or a copolymer containing a vinylidene fluoride unit and a tetrafluoroethylene unit and / or a chlorotrifluoroethylene unit.

The acrylic polymer (B) is preferably a copolymer containing a (meth) acrylic acid ester unit and a (meth) acrylic acid monomer unit.

The (meth) acrylic acid monomer is preferably (meth) acrylic acid.

The (meth) acrylic acid monomer is preferably a hydroxyl group-containing (meth) acrylic acid ester.

The (meth) acrylic acid monomer is preferably an oxyalkylene group-containing (meth) acrylic ester.

The content ratio of the fluoropolymer (A) and the acrylic polymer (B) in the resin particles is such that the fluoropolymer (A) / acrylic polymer (B) has a mass ratio of 30/70 to 80/20. preferable.

The acrylic polymer (B) is preferably a polymer obtained by polymerizing a (meth) acrylic acid ester in the presence of a reactive emulsifier.

The polymer porous membrane is preferably used for water treatment.

The present invention also includes a step of emulsion polymerization of a monomer containing vinylidene fluoride to produce an aqueous dispersion containing particles made of fluoropolymer (A), in the presence of particles made of fluoropolymer (A) (meta ) A step of producing an aqueous dispersion containing resin particles containing a fluoropolymer (A) and an acrylic polymer (B) in the same particle by emulsion polymerization of a monomer containing an acrylate ester, It is also a method for producing a polymer porous membrane comprising a step of separating and a step of forming the resin particles into a porous membrane to obtain a polymer porous membrane.

The emulsion polymerization in the step of producing the aqueous dispersion containing the resin particles is preferably performed in the presence of a reactive emulsifier.

In the step of forming the resin particles into a porous membrane, it is preferable to obtain a porous membrane-like molded product by a non-solvent induced phase separation method and / or a thermally induced phase separation method.

Since the porous polymer membrane of the present invention has the above-described configuration, it is excellent in water permeability and solid material removal performance.
According to the method for producing a polymer porous membrane of the present invention, the polymer porous membrane can be suitably produced.

4 is a photograph of the surface of the hollow fiber membrane obtained in Example 3 observed with a scanning electron microscope.

The present invention is described in detail below.

The porous polymer membrane of the present invention is obtained from resin particles containing a fluoropolymer (A) containing a vinylidene fluoride unit and an acrylic polymer (B) containing a (meth) acrylate unit in the same particle. Is.

Since the porous polymer membrane is made of the fluoropolymer (A) having excellent durability, it is also made of the acrylic polymer (B) having excellent hydrophilicity as well as excellent durability of the membrane. Excellent anti-fouling performance.

The resin particles contain the fluoropolymer (A) and the acrylic polymer (B) in the same particle. By producing a polymer porous membrane from such resin particles, the phase between the fluoropolymer and the acrylic polymer can be compared with the case of producing a polymer porous membrane from a mixture of a fluoropolymer and an acrylic polymer. The solubility is improved, and these polymers are present more uniformly in the membrane, so that the polymer porous membrane is more excellent in terms of water permeability and solid substance removal performance. The resin particles can be produced, for example, by polymerizing a monomer containing a (meth) acrylic acid ester in the presence of particles made of the fluoropolymer (A).
In the resin particles, the fluoropolymer (A) and the acrylic polymer (B) may be chemically bonded or not bonded as long as they are present in the same particle.

The fluoropolymer (A) contains a vinylidene fluoride unit, but may contain other monomer units as long as it contains at least a vinylidene fluoride unit.

Examples of the other monomers include fluoroolefins other than vinylidene fluoride. Specifically, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro (alkyl vinyl ether) (PAVE), Perfluoroolefins represented by chemical formulas: non-perfluoroolefins such as chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), trifluoroethylene, trifluoropropylene, pentafluoropropylene, tetrafluoropropylene, hexafluoroisobutene Can be mentioned. One or more of these fluoroolefins can be used. Examples of PAVE include perfluoro (methyl vinyl ether) (PMVE), perfluoro (ethyl vinyl ether) (PEVE), perfluoro (propyl vinyl ether) (PPVE), and the like.

Also, CH ₂ = CZ ¹ (CF ₂ ) _n1 Z ² (wherein Z ¹ is H, F or Cl, Z ² is H, F or Cl, and n1 is an integer of 1 to 10). A monomer is also mentioned. Specifically, CH ₂ = CFCF ₃ , CH ₂ = CHCF ₃ , CH ₂ = CFCHF ₂ , CH ₂ = CClCF _{3 and the} like can be mentioned.

Moreover, as said other monomer, a functional group containing fluoroolefin can also be used. Examples of the functional group-containing fluoroolefin include formula (1):
CX ¹ ₂ = CX ^2- (R _f ) _m -Y ¹ (1)
Wherein Y ¹ is —OH, —COOH, —SO ₂ F, —SO ₃ M ² (M ² is a hydrogen atom, NH ₄ group or alkali metal), carboxylate, carboxyester group, epoxy group or A cyano group; X ¹ and X ² are the same or different and both are hydrogen atoms or fluorine atoms; R _f is a divalent fluorine-containing alkylene group having 1 to 40 carbon atoms or an ether bond having 1 to 40 carbon atoms. A divalent fluorine-containing alkylene group; m is an integer of 0 or 1, and the like.

Specific examples of the functional group-containing fluoroolefin include the following compounds.

Examples of the other monomers include iodine-containing monomers and, for example, perfluoro (6,6-dihydro-) described in JP-B-5-63482 and JP-A-62-212734. Periodinated vinyl ethers such as 6-iodo-3-oxa-1-hexene) and perfluoro (5-iodo-3-oxa-1-pentene) can also be used.

The fluoropolymer (A) may be a polymer composed of vinylidene fluoride units, or may be a polymer composed of one or more of vinylidene fluoride units and other monomer units. Good. Further, it may be a copolymer containing a non-fluorinated monomer unit copolymerizable with vinylidene fluoride. Examples of the non-fluorine monomer include olefins such as ethylene, propylene, and isobutylene; vinyl ethers such as ethyl vinyl ether, cyclohexyl vinyl ether, and hydroxybutyl vinyl ether; alkenyls such as allyl alcohol and allyl ether; vinyl acetate, lactic acid Examples thereof include vinyl esters such as vinyl; ethylenically unsaturated carboxylic acids such as succinic anhydride and crotonic acid.

Among these, the fluoropolymer (A) is a polyvinylidene fluoride or a copolymer containing a vinylidene fluoride unit and a tetrafluoroethylene unit and / or a chlorotrifluoroethylene unit from the viewpoint of weather resistance. It is preferable. More preferably, it is a polyvinylidene fluoride or a copolymer containing a vinylidene fluoride unit and a tetrafluoroethylene unit. Particularly preferred is a copolymer comprising vinylidene fluoride units, tetrafluoroethylene units and chlorotrifluoroethylene units.

In the copolymer consisting of the above-mentioned vinylidene fluoride unit, tetrafluoroethylene unit, and chlorotrifluoroethylene unit, the content ratio of each unit is as follows: vinylidene fluoride unit / tetrafluoroethylene unit / chlorotrifluoroethylene unit The ratio is preferably 50 to 90/5 to 45/1 to 30. More preferably, it is 60-90 / 5-25-25 / 1.

The fluoropolymer (A) can be produced, for example, by polymerizing the constituent monomer of the fluoropolymer (A) containing vinylidene fluoride according to a usual emulsion polymerization method as described later.

The acrylic polymer (B) contains a (meth) acrylate unit, but may contain other monomer units as long as it contains at least a (meth) acrylate unit.

As said (meth) acrylic acid ester, the C1-C10 alkyl ester of (meth) acrylic acid is preferable, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate (BA). , Methyl methacrylate (MMA), n-propyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, etc. it can. Of these, MMA and BA are preferred from the viewpoint of good compatibility with the fluoropolymer (A).
The (meth) acrylic acid ester does not include a hydroxyl group-containing (meth) acrylic acid ester and an oxyalkylene group-containing (meth) acrylic acid ester described later.

The acrylic polymer (B) is preferably a copolymer containing a (meth) acrylic acid ester unit and a (meth) acrylic acid monomer unit.

The (meth) acrylic acid monomer unit is a hydrophilic (meth) acrylic acid monomer unit capable of hydroxylating the fluoropolymer (A).
The term “hydrophilic (meth) acrylic acid monomer unit” in this specification refers to a (meth) acrylic acid monomer unit having a high affinity for water, and the contact angle with water is the above (meta). ) A (meth) acrylic acid monomer unit capable of producing an acrylic polymer smaller than an acrylic polymer consisting only of an acrylic ester.

As the hydrophilic (meth) acrylic acid monomer, acrylic acid and methacrylic acid are preferable.

Moreover, as a hydrophilic (meth) acrylic-acid type monomer, a hydroxyl-containing (meth) acrylic ester is also preferable. As the hydroxyl group-containing (meth) acrylic acid ester, hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA), 3-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 4 Examples include -hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 6-hydroxyhexyl acrylate, and 6-hydroxyhexyl methacrylate. Of these, HEMA and HEA are preferred from the viewpoint of good compatibility with the fluoropolymer (A).

Moreover, as a hydrophilic (meth) acrylic-acid type monomer, an oxyalkylene group containing (meth) acrylic acid ester is also preferable. As a (meth) acrylic acid ester having an oxyalkylene group, as a hydroxyl-terminated (meth) acrylate,
Polyethylene glycol mono (meth) acrylate:
_{CH 2 = CR-COO- (C} 2 H 4 O) n -H n = 2~20,
Polypropylene glycol mono (meth) acrylate:
_{CH 2 = CR-COO- (C} 3 H 6 O) n -H n = 2~20,
Polyethylene glycol-polypropylene glycol mono (meth) acrylate:
_{CH 2 = CR-COO- (C} 2 H 4 O) n - (C 3 H 6 O) m -H n = 1~20, m = 1~20,
Poly (ethylene glycol-tetramethylene glycol) mono (meth) acrylate:
_{CH 2 = CR-COO- (C} 2 H 4 O) n - (C 4 H 8 O) m -H n = 1~20, m = 1~20,
Poly (propylene glycol-tetramethylene glycol) monomethacrylate:
_{CH 2 = CR-COO- (C} 3 H 6 O) n - (C 4 H 8 O) m -H n = 1~20, m = 1~20 , and the like.
As alkyl group terminal (meth) acrylate,
Methoxypolyethylene glycol mono (meth) acrylate:
_{CH 2 = CR-COO- (C} 2 H 4 O) n -CH 3 n = 2~20,
Examples include lauroxy polyethylene glycol mono (meth) acrylate, stearoxy polyethylene glycol mono (meth) acrylate, and nonyl phenoxy polyethylene glycol mono (meth) acrylate.
Although overlapping with the above, ethoxy-diethylene glycol (meth) acrylate, methoxy-triethylene glycol (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, methoxy-polyethylene glycol (meth) acrylate, methoxydipropylene glycol ( Examples include meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxy-polyethylene glycol (meth) acrylate, and polypropylene glycol (meth) acrylate. Among these, methoxypolyethylene glycol mono (meth) acrylate is preferable from the viewpoint of having moderate hydrophilicity and low fouling properties.

Examples of other monomers in the acrylic polymer (B) include unsaturated carboxylic acid monomers.
Examples of the unsaturated carboxylic acid-based monomer include vinyl acetic acid, crotonic acid, cinnamic acid, 3-allyloxypropionic acid, 3- (2-allyloxyethoxycarbonyl) propionic acid, itaconic acid, and itaconic acid monoester. Maleic acid, maleic acid monoester, maleic anhydride, fumaric acid, fumaric acid monoester, vinyl phthalate, vinyl pyromellitic acid, undecylenic acid and the like. Among these, maleic acid, maleic acid monoester, and maleic anhydride are preferable from the viewpoint of good adhesion, thickening, and heat resistance.

In addition to the above-mentioned other monomers, other copolymerizable radical polymerizable non-fluorinated monomers may be used in combination. Examples of the other non-fluorinated monomers include vinyl ether monomers, olefin monomers, hydrolyzable silyl group-containing vinyl monomers, vinyl ester monomers, and the like.

Examples of the vinyl ether monomers include alkyl vinyl ethers and hydroxyl group-containing vinyl ethers.

Examples of the hydroxyl group-containing vinyl ethers include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2- Examples include methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, glycerol monoallyl ether, and the like.

Examples of the olefin monomer include ethylene, propylene, n-butene, isobutene, and styrene.

Examples of the hydrolyzable silyl group-containing vinyl monomer include γ-methacryloxypropyltrimethoxysilane.

Examples of the vinyl ester monomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate. And carboxylic acid vinyl esters such as vinyl benzoate and vinyl para-t-butylbenzoate.

Among these, the acrylic polymer (B) is preferably a copolymer containing a (meth) acrylic acid ester unit and a hydrophilic (meth) acrylic acid monomer unit. More preferably, it has a (meth) acrylic acid alkyl ester unit having 1 to 6 carbon atoms and a (meth) acrylic acid unit and / or a hydroxyl group-containing (meth) acrylic acid ester unit and / or an oxyalkylene group (meta ) A copolymer containing an acrylate unit, and particularly preferably a copolymer comprising an alkyl ester unit having 1 to 3 carbon atoms of (meth) acrylic acid and a (meth) acrylic acid unit.

The content ratio of each unit in the copolymer consisting of the (meth) acrylic acid alkyl ester unit having 1 to 3 carbon atoms and the (meth) acrylic acid unit is the alkyl group having 1 to 3 carbon atoms of (meth) acrylic acid. The ester unit / (meth) acrylic acid unit is preferably 55/45 to 99/1 in molar ratio. More preferably, it is 75/25 to 99/1.

The content ratio of the fluoropolymer (A) and the acrylic polymer (B) in the resin particles is such that the fluoropolymer (A) / acrylic polymer (B) has a mass ratio of 20/80 to 80/20. preferable. It is preferable that the content ratio of the fluoropolymer (A) and the acrylic polymer (B) in the resin particles is in such a range because of excellent weather resistance, water resistance, and storage stability. The content ratio of the fluoropolymer (A) and the acrylic polymer (B) in the resin particles is more preferably 35/65 to 80/20 (mass ratio), still more preferably 40/60 to 75/25. (Mass ratio).
In addition, the mass ratio of the said fluoropolymer (A) and acrylic polymer (B) represents the mass ratio in the single particle of the fluoropolymer (A) and acrylic polymer (B) which comprise a single particle.

The fluorine content of the resin particles is preferably 15 to 60% by mass. When the fluorine content of the resin particles is within such a range, the compatibility between the fluoropolymer (A) and the acrylic polymer (B) is good. More preferably, it is 15-55 mass% as a fluorine content rate of the resin particle, More preferably, it is 20-50 mass%.

The average particle size of the resin particles is preferably 50 to 500 nm. When the average particle diameter of the resin particles is in such a range, when an aqueous dispersion containing the resin particles is prepared, the aqueous dispersion does not settle or solidify even during storage. Can be prepared. More preferably, it is 80-300 nm as an average particle diameter of a resin particle, More preferably, it is 100-250 nm.

The resin particles are, for example, in accordance with a seed polymerization method in which a constituent monomer of an acrylic polymer (B) containing a (meth) acrylic acid ester is usually performed in the presence of particles made of a fluoropolymer (A), as will be described later. It can be produced by emulsion polymerization. However, here, when the emulsion polymerization is carried out in the presence of a reactive emulsifier, the polymer porous membrane prepared from the resin particles thus obtained is incorporated into the resin particles (A). This is preferable in that the elution of the emulsifier is suppressed.
Thus, it is also possible that the acrylic polymer (B) is obtained by emulsion polymerization of a constituent monomer of the acrylic polymer (B) containing a (meth) acrylic acid ester in the presence of a reactive emulsifier. This is one of the preferred embodiments of the present invention.

As described above, the porous polymer membrane of the present invention contains the fluoropolymer (A) containing a vinylidene fluoride unit and the acrylic polymer (B) containing a (meth) acrylate unit in the same particle. Although it is obtained from resin particles, as long as the resin particles are included, other resins may be included.
However, even when the polymer porous membrane of the present invention contains other resin or the like, it is preferable that the resin particles contain 40% by weight or more of the entire polymer porous membrane from the viewpoint of water permeability. , More preferably 60% by weight or more, and still more preferably 80% by weight or more.

As said other resin, a thermoplastic resin is mentioned, for example. A thermoplastic resin is a resin that deforms or flows by an external force when heated.
Examples of the thermoplastic resin include polyethylene resins, polypropylene resins, polyvinylidene fluoride resins, acrylic resins, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resins, polystyrene resins, acrylonitrile-styrene (AS) resins, Vinyl chloride resin, polyethylene terephthalate, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polyphenylene sulfide resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, and mixtures and copolymers thereof Is mentioned. Other resins miscible with these may be mixed.

The thermoplastic resin is preferably at least one selected from the group consisting of polyethylene resins, polypropylene resins, polyvinylidene fluoride resins, and acrylic resins because of its high chemical resistance.

The polyethylene resin is a resin made of an ethylene homopolymer or an ethylene copolymer. The polyethylene resin may be composed of a plurality of types of ethylene copolymers. Examples of the ethylene copolymer include a copolymer of ethylene and at least one selected from linear unsaturated hydrocarbons such as propylene, butene, and pentene.

The polypropylene resin is a resin made of a propylene homopolymer or a propylene copolymer. The polypropylene resin may be composed of a plurality of types of propylene copolymers. Examples of the propylene copolymer include a copolymer of propylene and one or more selected from linear unsaturated hydrocarbons such as ethylene, butene, and pentene.

The polyvinylidene fluoride resin is a resin made of a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer. The polyvinylidene fluoride resin may be composed of a plurality of types of vinylidene fluoride copolymers. As the vinylidene fluoride copolymer, a copolymer of vinylidene fluoride with at least one selected from hexafluoropropylene units, chlorotrifluoroethylene units, perfluorovinyl ether units, vinyl alcohol units, vinyl ester monomer units, etc. Is mentioned.
Specific examples include vinylidene fluoride / tetrafluoroethylene copolymer and vinylidene fluoride / hexafluoropropylene copolymer. From the viewpoint of mechanical strength and alkali resistance, the copolymer having a vinylidene fluoride unit is particularly preferably a vinylidene fluoride / tetrafluoroethylene copolymer.
The vinylidene fluoride / tetrafluoroethylene copolymer more preferably has a vinylidene fluoride unit / tetrafluoroethylene unit in a molar ratio of 50 to 90/50 to 10. In addition to vinylidene fluoride / tetrafluoroethylene copolymer consisting of only vinylidene fluoride units and tetrafluoroethylene units, vinylidene fluoride / tetrafluoroethylene copolymers include vinylidene fluoride units and tetrafluoroethylene units. In addition, a terpolymer having other structural units such as a hexafluoropropylene unit, a chlorotrifluoroethylene unit, a perfluorovinyl ether unit, a vinyl alcohol unit, and a vinyl ester monomer unit may be used as long as the characteristics are not impaired.
In addition, when the said vinylidene fluoride / tetrafluoroethylene copolymer further has other structural units in addition to the vinylidene fluoride units and tetrafluoroethylene units, the vinylidene fluoride units and tetrafluoroethylene units in all the structural units The total ratio is preferably 80 mol% or more, and more preferably 85 mol% or more. More preferably, it is 90 mol% or more, Most preferably, it is 97 mol% or more.

The acrylic resin is a polymer compound mainly including a polymer such as acrylic acid, methacrylic acid and derivatives thereof such as acrylamide and acrylonitrile. Particularly preferred are acrylic ester resins and methacrylic ester resins.

By using other resins as described above in combination, the film strength, water permeability, removal performance and the like can be adjusted.

From the viewpoint of hydrophilization, the improvement of mechanical strength, and the viewpoint of phase separation control, the polymer porous membrane of the present invention is further composed of polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate resin, montmorillonite, SiO ₂ , CaCO. _{3. It} may comprise an additive such as polytetrafluoroethylene.

The porous polymer membrane of the present invention preferably has a pore size of 2 nm to 2.0 μm, more preferably 5 nm to 0.5 μm. If the pore diameter is too small, the gas or liquid permeability may be insufficient, and if the pore diameter is too large, the blocking performance may be lowered, or the mechanical strength may be lowered and the glass may be easily damaged.

The pore diameter is a magnification at which pores can be clearly confirmed, and the surface of the porous polymer membrane is photographed using SEM or the like, and the pore diameter is measured. In the case of an elliptical hole, the diameter of the pore can be obtained by (a × b) ^0.5, where a is the minor axis and b is the major axis. Further, a rough pore diameter can be obtained from the fine particle rejection rate. That is, for example, a porous film that blocks 95% or more of polystyrene fine particles of 50 nm or the like is considered to have a pore diameter of 50 nm or less.

The polymer porous membrane of the present invention has a pure water permeability coefficient of 5.0 × 10 ⁻¹⁰ m ³ / m ² / s / Pa or more, for example, when it has a performance of blocking 50% or more of fine particles of 50 nm or more. It is preferably 1.0 × 10 ⁻⁹ m ³ / m ² / s / Pa or more. The upper limit of the pure water permeability coefficient is not particularly limited, but it is desirable that the value is higher as long as the desired rejection and strength are maintained.

The pure water permeation coefficient can be determined by pressurizing ion-exchanged water at a temperature of 25 ° C. to 0.01 MPa or more as necessary with a pump or nitrogen pressure, and filtering the produced hollow fiber membrane or flat membrane. Specifically, it is obtained from the following formula.
Pure water permeability coefficient [m ³ / m ² / s / Pa] = (amount of permeated water) / (membrane area) / (permeation time) / (evaluation pressure)

The polymer porous membrane of the present invention preferably has a fine particle blocking rate of 100 nm or 50 nm of 90% or more, more preferably 95% or more.

The fine particle blocking rate is obtained by the following equation after filtering a dispersion solution in which polystyrene latex fine particles having a controlled particle size are diluted to about 100 ppm with ion exchange water.
Fine particle rejection (%) = ((Evaluation stock solution absorbance) − (Transmission solution absorbance)) / (Evaluation stock solution absorbance) × 100

From the viewpoint of mechanical strength, the polymer porous membrane of the present invention preferably has a maximum point breaking strength of 0.5 MPa or more, and more preferably 0.6 MPa or more.
The maximum point breaking strength can be obtained by measuring the breaking strength of a test piece under the conditions of a distance between chucks of 50 mm and a tensile speed of 200 mm / min, and a sectional area before the tensile test as a unit measurement area. Further, the breaking strength of the test piece is measured under the conditions of a distance between chucks of 25 mm and a tensile speed of 50 mm / min, and the cross-sectional area before the tensile test can be obtained as a unit measurement area. The direction of pulling the test piece is the extrusion direction in the case of a hollow fiber membrane, and the direction of casting in the case of a flat membrane.

From the viewpoint of toughness, the polymer porous membrane of the present invention preferably has a maximum point elongation of 120% or more, and more preferably 150% or more.
The maximum point elongation is obtained from the elongation at the maximum point on the basis of the distance between the chucks of 50 mm and the tensile strength of 200 mm / min.
Further, the breaking strength of the test piece is measured under the conditions of a distance between chucks of 25 mm and a tensile speed of 50 mm / min, and it is also obtained from the elongation at the maximum point on the basis of the distance between chucks of 25 mm. The direction of pulling the test piece is the extrusion direction in the case of a hollow fiber membrane, and the direction of casting in the case of a flat membrane.

The structure of the polymer porous membrane of the present invention is not particularly limited. For example, a three-dimensional network structure in which the solid content spreads in a three-dimensional network, or a spherical structure in which a large number of spherical or nearly spherical solid components are connected directly or via a streaky solid content Etc. Moreover, you may have both these structures.

The shape of the polymer porous membrane of the present invention is preferably a flat membrane shape or a hollow fiber membrane shape.

In the case of a flat membrane shape, the polymer porous membrane of the present invention may be a composite membrane composed of a fluoropolymer layer composed of the resin particles and a porous substrate. In the case of a composite film, the surface of the porous substrate may be coated with a fluoropolymer layer made of the resin particles, or the porous substrate and the fluoropolymer layer made of the resin particles may be laminated. It may be.
Moreover, the composite film which consists of a porous base material and the resin layer which consists of resin other than the said resin particle may be sufficient. Examples of the resin forming the resin layer include the thermoplastic resins described above.

Examples of the porous substrate include polyester fibers, nylon fibers, polyurethane fibers, acrylic fibers, rayon fibers, woven fabrics, knitted fabrics, and nonwoven fabrics made of organic fibers such as cotton and silk. Moreover, the textile fabric, knitted fabric, or nonwoven fabric which consists of inorganic fibers, such as glass fiber and a metal fiber, is also mentioned. From the viewpoint of stretchability and cost, a porous substrate made of organic fibers is preferable.

The pore diameter of the surface of the porous substrate can be freely selected depending on the use, but is preferably 5 nm to 100 μm, more preferably 8 nm to 10 μm.

In the case of a flat membrane shape, the thickness of the polymer porous membrane is preferably 10 μm to 2 mm, and more preferably 30 μm to 500 μm. Even in the case of a composite membrane using the above porous substrate, the thickness of the polymer porous membrane is preferably within the above range.

The porous polymer membrane of the present invention is more preferably in the form of a hollow fiber membrane from the viewpoint of unit area and the amount of treated water per unit volume.

In the case of a hollow fiber membrane shape, the inner diameter of the hollow fiber membrane is preferably 100 μm to 10 mm, and more preferably 150 μm to 8 mm. The outer diameter of the hollow fiber membrane is preferably 120 μm to 15 mm, more preferably 200 μm to 12 mm.

In the case of a hollow fiber membrane shape, the thickness of the polymer porous membrane is preferably 20 μm to 3 mm, more preferably 50 μm to 2 mm. Moreover, although the hole diameter of the inner and outer surfaces of the hollow fiber membrane can be freely selected depending on the application, it is preferably in the range of 2 nm to 2.0 μm, more preferably 5 nm to 0.5 μm.

Next, the manufacturing method of the polymeric porous membrane of this invention is demonstrated.
In the method for producing a porous polymer membrane of the present invention, a step of producing an aqueous dispersion containing particles made of fluoropolymer (A) by emulsion polymerization of a monomer containing vinylidene fluoride, fluoropolymer (A) An aqueous dispersion containing resin particles containing a fluoropolymer (A) and an acrylic polymer (B) in the same particle by emulsion polymerization of a monomer containing (meth) acrylic acid ester in the presence of particles comprising A step of producing, a step of isolating the resin particles, and a step of forming the resin particles into a porous membrane to obtain a polymer porous membrane are performed.

The production method of the aqueous dispersion in the step of producing an aqueous dispersion containing particles composed of the fluoropolymer (A) is not particularly limited, and can be carried out by a usual emulsion polymerization method. Specifically, an aqueous dispersion containing particles comprising the fluoropolymer (A) can be produced by emulsion polymerization of a constituent monomer of the fluoropolymer (A) containing vinylidene fluoride.

In the emulsion polymerization, a polymerization initiator, an emulsifier, a chain transfer agent, and a solvent can be used, and those usually used can be used.

The aqueous dispersion containing particles made of the fluoropolymer (A) produced above is a liquid in which particles made of the fluoropolymer (A) produced by the emulsion polymerization are dispersed in an aqueous medium. Examples of the aqueous medium include an aqueous medium that can be used as a solvent in the emulsion polymerization. The aqueous dispersion may be a dispersion itself in which the particles made of the fluoropolymer (A) obtained by the emulsion polymerization are dispersed in an aqueous medium used as a solvent in the emulsion polymerization, or in the emulsion polymerization reaction. A dispersion liquid in which particles of the fluoropolymer (A) are dispersed in an aqueous medium different from the solvent used may be used.

Resin particles containing a fluoropolymer (A) and an acrylic polymer (B) in the same particle by emulsion polymerization of a monomer containing a (meth) acrylic acid ester in the presence of the particles made of the fluoropolymer (A). As a method for producing the aqueous dispersion in the step of producing an aqueous dispersion containing, a seed polymerization method that is usually performed when the resin is combined can be employed. Specifically, the fluoropolymer (A) and the acrylic are obtained by emulsion polymerization of a constituent monomer of the acrylic polymer (B) containing a (meth) acrylic acid ester unit in the presence of particles made of the fluoropolymer (A). An aqueous dispersion containing resin particles containing the polymer (B) in the same particles can be produced.

In emulsion polymerization of the constituent monomer of the acrylic polymer (B), a polymerization initiator, an emulsifier, a chain transfer agent, and a solvent can be used, and those usually used can be used. However, it is particularly preferable to use a reactive emulsifier. By carrying out the emulsion polymerization in the presence of a reactive emulsifier, the reactive emulsifier is incorporated into the resin particles, thereby suppressing the elution of the emulsifier. Thus, it is also one of the preferred embodiments of the present invention that the emulsion polymerization in the step of producing the aqueous dispersion containing the resin particles is further performed in the presence of a reactive emulsifier.

As the reactive emulsifier, a reactive emulsifier usually used in emulsion polymerization can be used, and is not particularly limited. For example, Blemmer PE-350, Blemmer PME-400, Blemmer 70PEP350B (manufactured by NOF Corporation) , NK ester M-40G, NK ester M-90G, NK ester M-230G (manufactured by Shin-Nakamura Chemical Co., Ltd.), RMA450M (manufactured by Nippon Emulsifier Co., Ltd.), Aqualon HS10, Aqualon HS20, Aqualon HS1025, Aqualon RN10, Aqualon RN20, Aqualon RN30, Aqualon RN50, Aqualon RN2025 (Daiichi Kogyo Seiyaku Co., Ltd.), NK Ester AMP-60G, NK Ester CB-1, NK Ester SA, NK Ester A-SA, Eleminol JS2, Eleminol RS 0 (manufactured by Sanyo Chemical Industries, Ltd.), LATEMUL WX (Co. Kao Corporation) and the like.

Also the formula:

The compound (2-1) shown by (In formula, n is a mixture of 10 and 11) is also mentioned.

Among these, eleminol JS2, eleminol RS30, and the compound (2-1) are preferable, and eleminol JS2 and the compound (2-1) are more preferable.

As the usage-amount of the said reactive emulsifier, it is preferable that it is 0.05-5.0 weight% with respect to 100 weight% of the structural monomer whole quantity of the acrylic polymer (B) with which it uses for emulsion polymerization. More preferably, it is 0.10 to 2.0% by weight.

The aqueous dispersion containing the resin particles produced is a liquid in which the resin particles produced by the emulsion polymerization are dispersed in an aqueous medium. Examples of the aqueous medium include an aqueous medium that can be used as a solvent in the emulsion polymerization. As the aqueous dispersion, the resin particles obtained by the emulsion polymerization may be a dispersion itself dispersed in an aqueous medium used as a solvent in the emulsion polymerization, or different from the solvent used in the emulsion polymerization reaction. A dispersion liquid in which resin particles are dispersed in an aqueous medium may be used.

In the manufacturing method of this invention, the process of isolating the said resin particle is performed.

The step of isolating the resin particles can be performed by various methods. For example, the aqueous dispersion containing the produced resin particles is frozen to be coagulated, and then sufficiently washed with a methanol solution. A method of performing vacuum drying or the like can be used.

In the production method of the present invention, a step of forming a polymer porous membrane by forming the resin particles into a porous membrane is performed.

The process of forming on the porous membrane can be produced by various methods. For example, a phase separation method, a melt extraction method, a vapor solidification method, a stretching method, an etching method, a method of forming a porous film by sintering a polymer sheet, a porous film by crushing a polymer sheet containing bubbles And a method using electrospinning.

In the melt extraction method, inorganic fine particles and an organic liquid are melt-kneaded into a mixture, extruded from a die at a temperature equal to or higher than the melting point of the resin particles, or molded by a press machine, and then solidified by cooling. In this method, a porous structure is formed by extracting fine particles.

In the vapor coagulation method, a non-solvent and / or a poor solvent which is compatible with the good solvent and does not dissolve the resin particles is formed on at least one surface of a thin film product made of a resin solution obtained by dissolving the resin particles in a good solvent. This is a method for forcibly supplying saturated steam or steam containing mist.

The method for producing the porous membrane is preferably a phase separation method because the pore size can be easily controlled. Examples of the phase separation method include a thermally induced phase separation method (TIPS) and a non-solvent induced phase separation method (NIPS).

In the case of using the thermally induced phase separation method, the present invention is carried out by a production method comprising a step of obtaining a mixture by dissolving resin particles in a poor solvent or a good solvent at a relatively high temperature, and a step of cooling and solidifying the mixture. The polymer porous membrane of the invention can be produced.

The mixture in which the resin particles are dissolved in the solvent becomes a uniform one-phase liquid when maintained at a temperature higher than the temperature called cloud point (cloud point), but phase separation occurs below the cloud point, and the resin When the particles are separated into a resin-rich phase in which particles are dissolved and a solvent-rich phase, and when the temperature is lower than the crystallization temperature, the polymer matrix is fixed and a porous film is formed.

When using a thermally induced phase separation method, it is preferable that the said mixture is 10-60 mass% with respect to the sum total of a resin particle and a solvent. More preferably, it is 15-50 mass%.

By adjusting the concentration of the resin particles to an appropriate range, the viscosity of the mixture can be adjusted to an appropriate range. If the viscosity of the mixture is not within an appropriate range, the polymer porous membrane may not be formed.

The poor solvent cannot dissolve the resin particles at 5% by mass or more at a temperature lower than 60 ° C., but it is 60 ° C. or higher and the melting point of the resin (the melting point of the resin particles, or when containing other resins, It is a solvent that can be dissolved in an amount of 5% by mass or more below the lowest melting point of any melting point of resin particles and other resins. A solvent capable of dissolving 5% by mass or more of resin particles at a temperature lower than 60 ° C. with respect to a poor solvent is referred to as a good solvent. A solvent that does not dissolve or swell resin particles up to the melting point of the resin or the boiling point of the liquid is called a non-solvent.

Examples of poor solvents include cyclohexanone, isophorone, γ-butyrolactone, methyl isoamyl ketone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, aliphatic polyhydric alcohol, propylene glycol methyl ether, propylene carbonate, diacetone alcohol, glycerol triacetate, etc. Medium chain length alkyl ketones, esters, glycol esters and organic carbonates, and mixed solvents thereof. Fluorine-containing solvents such as HFC-365, diphenyl carbonate, methyl benzoate, diethylene glycol ethyl acetate, benzophenone and the like can also be mentioned. In addition, even if it is a mixed solvent of a non-solvent and a poor solvent, the solvent which satisfy | fills the definition of the said poor solvent is a poor solvent.
When the thermally induced phase separation method is used, a poor solvent is preferable as the solvent of the mixture. However, the solvent is not limited to this, and a good solvent may be used in consideration of the phase separation behavior of the fluoropolymer.

Good solvents include fluorine-containing solvents such as HCFC-225, lower alkyl such as N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, methanol, tetrahydrofuran, tetramethylurea, and trimethyl phosphate. Examples thereof include ketones, esters, amides, and mixed solvents thereof.

Non-solvents include water, hexane, pentane, benzene, toluene, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol. , Aliphatic hydrocarbons such as methanol, ethanol, propanol, and low molecular weight polyethylene glycol, aromatic hydrocarbons, aromatic polyhydric alcohols, chlorinated hydrocarbons, other chlorinated organic liquids, and mixed solvents thereof. .

When using a thermally induced phase separation method, it is preferable that the process of obtaining a mixture is what melt | dissolves a resin particle in the solvent which is a poor solvent or a good solvent at 30-270 degreeC. The melting temperature is preferably 40 to 250 ° C. When dissolved at a relatively high temperature, the concentration of the resin particles can be increased, whereby a polymer porous membrane having high mechanical strength can be obtained. If the above concentration is too high, the porosity of the resulting polymer porous membrane will be small, and the water permeation performance may be reduced. Moreover, if the viscosity of the prepared mixture is not in an appropriate range, there is a possibility that it cannot be formed into a porous membrane.

As a method for cooling and solidifying the mixture, for example, a method of discharging the mixture from a die into a cooling bath is preferable. When the polymer porous membrane is a flat membrane, a method of casting and immersing in a cooling bath can also be mentioned as a preferable method.

The cooling liquid that can be used as a cooling bath has a temperature lower than that of the mixture, and includes, for example, a solvent that is a poor solvent or a good solvent having a temperature of 0 to 80 ° C. and a concentration of 60 to 100% by mass. Liquid can be used. The cooling liquid may be a non-solvent or a non-solvent containing a poor solvent or a good solvent.

In this method for producing a porous membrane, the concentration of the mixture, the composition of the solvent that dissolves the resin particles, and the composition of the cooling liquid constituting the cooling bath are important. By adjusting these compositions, the porous structure of the polymer porous membrane can be controlled.

For example, by changing the combination of the composition of the mixture and the composition of the cooling liquid on one side and the other side of the polymer porous membrane, the structure of one side of the polymer porous membrane and the structure of the other side are changed. It can be different.

When producing the porous membrane by a non-solvent induced phase separation method, for example, a step of dissolving a resin particle in a solvent to obtain a mixture, and a step of discharging the obtained mixture from a die into a coagulation bath containing a non-solvent It is preferable to obtain a porous membrane-like molded product by a production method comprising:

By immersing the mixture in a coagulation bath containing a non-solvent, the concentration gradient of the solvent and the non-solvent in the mixture and the coagulation bath is used as a driving force to incorporate the non-solvent into the mixture and into the coagulation bath. Elution of the solvent occurs, and as a result, non-solvent induced phase separation can occur. According to this method, a dense skin layer is first formed on the outer surface where phase separation occurs due to substitution between a solvent and a non-solvent, and the phase separation phenomenon proceeds toward the inside of the film. As a result, it is also possible to manufacture an asymmetric membrane in which the pore diameter continuously increases toward the inside of the membrane following the skin layer.

When the non-solvent induced phase separation method is used, the mixture is preferably composed of resin particles and a solvent. In addition to the resin particles and the solvent, the mixture is preferably formed of a non-solvent.

It is preferable that a resin particle is 5-60 mass% with respect to the sum total of a resin particle, a solvent, and a non-solvent (when a mixture does not contain a non-solvent, the sum of a resin particle and a solvent). More preferably, it is 10-50 mass%.
It is preferable that a non-solvent is 0.1-10 mass% with respect to the sum total of a resin particle, a solvent, and a non-solvent. More preferably, it is 0.5-8 mass%.
By adjusting the resin particle concentration to an appropriate range, the viscosity of the mixture can be adjusted to an appropriate range. If the viscosity of the mixture is not within an appropriate range, the polymer porous membrane may not be formed.

The mixture may be at room temperature or heated. For example, 10-75 degreeC is preferable.

In the non-solvent induced phase separation method, the solvent exemplified in the thermally induced phase separation method can be used as the solvent. The solvent may be a poor solvent or a good solvent, but a good solvent is preferred.
As the non-solvent, the non-solvent exemplified in the thermally induced phase separation method can be used.

The coagulation liquid that can be used as the coagulation bath is preferably solidified using a liquid containing a non-solvent, and may contain a poor solvent or a good solvent. As the non-solvent, the non-solvent exemplified in the thermally induced phase separation method can be used. For example, water can be preferably used.

In the step of forming the porous membrane, the thermally induced phase separation method and the non-solvent induced phase separation method may be used in combination.

In the non-solvent induced phase separation method and / or the thermally induced phase separation method, a porous film-like molded product can be obtained by discharging a mixture obtained by dissolving resin particles in a solvent from a die and then solidifying the mixture. As the base, for example, a slit base, a double pipe base, a triple pipe base, or the like is used.

When a hollow fiber membrane-shaped molded product is produced as a porous membrane-shaped molded product, a double-tube type die or a triple-tube type die for spinning a hollow fiber membrane is preferably used as the die.

When using the above-mentioned double tube type die, discharge the mixture from the outer tube of the double tube type die, and solidify in a coagulation bath or cooling bath while discharging hollow part forming fluid such as ion exchange water from the inner tube. By doing so, it can be set as a hollow fiber membrane-like molded product.

As the hollow portion forming fluid, gas or liquid can be usually used. In the thermally induced phase separation method, a liquid containing a poor solvent or a good solvent having a concentration of 60 to 100%, which is the same as the cooling liquid, can be preferably used, but a non-solvent or a non-solvent containing a poor solvent or a good solvent is used. It may be used. In the non-solvent induced phase separation method, the above-mentioned non-solvent is preferably used as the hollow portion forming fluid, and for example, water such as ion-exchanged water is preferable. Moreover, the non-solvent mentioned above may contain a poor solvent and a good solvent.

When the thermally induced phase separation method is used, the above-mentioned solvent is preferably used as the hollow portion forming fluid, and for example, a poor solvent such as glycerol triacetate is preferable. In addition, when a thermally induced phase separation method is used, nitrogen gas can also be used.

A hollow fiber membrane having two types of structures can also be formed by changing the composition of the hollow portion forming fluid and the cooling liquid or coagulating liquid. The hollow portion forming fluid may be supplied after cooling, but if the hollow fiber membrane is solidified only by the cooling power of the cooling bath, the hollow portion forming fluid may be supplied without cooling. .

The triple tube type die is suitable when two kinds of resin solutions are used. For example, a hollow fiber membrane can be obtained by discharging two types of mixture from an outer tube and an intermediate tube of a triple tube type die and solidifying in a coagulation bath or a cooling bath while discharging a hollow portion forming liquid from an inner tube. It can be. Also, the mixture is discharged from the outer tube of the triple tube type die, the resin solution made of resin other than resin particles is discharged from the intermediate tube, and the solidification bath or cooling bath is discharged while discharging the hollow portion forming fluid from the inner tube. It can be set as a hollow fiber membrane by solidifying in.
Examples of the resin other than the resin particles include those described above. Especially, the thermoplastic resin mentioned above is preferable and an acrylic resin is more preferable.

As described above, when a hollow fiber membrane is produced by a production method using a double tube type die or a triple tube type die, the amount of the solidification liquid or the cooling liquid may be made smaller than when a flat membrane is produced. It is preferable in that it can be performed.

When the shape of the polymer porous membrane to be produced is a hollow fiber membrane, on the outer surface or inner surface of the hollow fiber membrane obtained by the above method, a layer made of the fluoropolymer (A) or the fluoropolymer ( A resin layer made of a resin other than A) may be formed.

The fluoropolymer layer or resin layer can be formed by applying a solution or resin solution of the fluoropolymer (A) to the outer surface or inner surface of the hollow fiber membrane. As a method of applying the fluoropolymer (A) solution or resin solution to the outer surface of the hollow fiber membrane, the hollow fiber membrane is immersed in the fluoropolymer (A) solution or resin solution, or the hollow fiber membrane is coated with a fluoropolymer ( The method of dropping the solution or resin solution of A) is preferably used. As a method of applying the fluoropolymer (A) solution or resin solution to the inner surface of the hollow fiber membrane, a method of injecting the fluoropolymer (A) solution or resin solution into the hollow fiber membrane is preferably used.
As a method for controlling the coating amount of the solution or resin solution of the fluoropolymer (A), in addition to the method of controlling the coating amount itself of the solution or resin solution of the fluoropolymer (A), the porous film is made of a fluoropolymer (A ), Or after the fluoropolymer (A) solution or resin solution is applied to the porous membrane, a part of the fluoropolymer (A) solution or resin solution is scraped off, or an air knife is used. A method of using and blowing away and a method of adjusting the concentration during coating are also preferably used.

Moreover, when manufacturing a flat film-shaped molded object as a porous film-shaped molded object, it can manufacture by casting a mixture and immersing it in a cooling bath or a coagulation bath. Moreover, it can manufacture also by discharging a mixture to a cooling bath or a coagulation bath using a slit nozzle | cap | die.

Further, when the polymer porous film is a composite film made of a porous substrate, the polymer porous film is formed by a method of immersing the porous substrate in a mixture, a method of applying the mixture to at least one surface of the porous substrate, or the like. A membrane can also be obtained.

A polymer porous membrane having excellent water permeability can be obtained by the production method described above, but if the water permeability is not sufficient, the porous membrane obtained by the production method may be further stretched. .

In the step of forming the porous membrane, as a method for controlling the pore size, for example, an additive for controlling the pore size is added to the mixture to form a porous structure with resin particles, or the porous structure is After the formation, the pore diameter of the polymer porous membrane can be controlled by eluting the additive. Further, the additive may remain in the porous membrane.

In both the non-solvent induced phase separation method and the thermally induced phase separation method, the mixture may contain an additive. After forming the porous structure, the pore diameter of the polymer porous membrane can be controlled by eluting the additive. The additive may remain in the porous membrane as necessary.

Examples of additives include organic compounds and inorganic compounds. As an organic compound, it is preferable that it is what is melt | dissolved in the solvent which comprises a mixture, or what is disperse | distributed uniformly. Furthermore, a non-solvent contained in the coagulating liquid in the non-solvent induced phase separation method and a solvent dissolved in the solvent contained in the cooling liquid in the thermally induced phase separation method are preferable.

For example, as organic compounds, water-soluble polymers such as polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, and textlan, surfactants such as Tween 40 (polyoxyethylene sorbitan monopalmitate), glycerin, and saccharides Etc.

As the inorganic compound, a water-soluble compound is preferably used. For example, calcium chloride, lithium chloride, barium sulfate and the like can be mentioned.

It is also possible to control the average pore diameter of the surface by controlling the phase separation speed by the type, concentration and temperature of the non-solvent in the coagulating liquid without using an additive. In general, when the phase separation rate is high, the average pore size on the surface is small, and when the phase separation rate is low, the average pore size is large. Moreover, adding a non-solvent to the mixture is also effective for controlling the phase separation rate.

From the viewpoint of hydrophilization, phase separation control, and mechanical strength improvement, the mixture further includes polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate resin, montmorillonite, SiO ₂ , TiO ₂ , CaCO ₃ , polytetra An additive such as fluoroethylene may be contained.

Moreover, in the said manufacturing method, after obtaining the porous film-shaped molded object, the wet process may be performed to the said porous film-shaped molded object.
The wet treatment may be performed, for example, by immersing the porous membrane-shaped molded product in an alcohol such as methanol or ethanol, and then substituting it with water.
Furthermore, the polymer porous membrane obtained by the above production method may be treated with an alkali from the viewpoint of improving water permeability. Examples of the alkali include NaOH aqueous solution, KOH aqueous solution, aqueous ammonia, and amine solution. These may contain alcohols such as ethanol and methanol, and organic solvents. In particular, the alkali preferably contains an alcohol, but is not limited thereto.

The porous membrane-like molded product obtained by the above production method is suitable as a microfiltration membrane or an ultrafiltration membrane used for water treatment such as drinking water production, water purification treatment, and wastewater treatment. Since the porous membrane-like molded product obtained by the above production method has high permeability and excellent chemical resistance, it is suitable for a polymer porous membrane for water treatment.

In addition, the porous membrane-like molded product obtained by the above production method is also suitably used in the medical field, food field, battery field and the like.

In the medical field, as a membrane for blood purification for the purpose of removing blood waste products by extracorporeal circulation such as blood dialysis, blood filtration, blood filtration dialysis, etc. The obtained porous membrane-like molded product can be used.

In the food field, a porous membrane-shaped product obtained by the above production method can be used for the purpose of separating and removing yeasts used for fermentation and concentrating liquids.

In the battery field, a porous membrane obtained by the above production method as a separator for a battery or a polymer solid electrolyte base material for allowing an electrolyte to permeate but not a product produced by a battery reaction. Shaped moldings can be used.

In the method for producing a porous polymer membrane of the present invention, the porous polymer membrane of the present invention can be suitably produced as described above.

EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail about this invention, this invention is not limited only to these Examples.

[Composition of fluoropolymer by NMR (nuclear magnetic resonance)]
^{For the 1} H-NMR (nuclear magnetic resonance method) measurement, JNM-EX270 (manufactured by JEOL: 270 MHz) was used. Heavy acetone was used as the solvent.

[Pure water permeability coefficient]
The pure water permeability coefficient was determined by pressing ion-exchanged water to 0.01 MPa or more with nitrogen at a temperature of 25 ° C. and filtering with the produced hollow fiber membrane.
Pure water permeability coefficient [m ³ / m ² / s / Pa] = (amount of permeated water) / (membrane area) / (permeation time) / (evaluation pressure)

[Particle rejection rate]
The fine particle rejection was obtained by filtering a dispersion solution in which polystyrene latex fine particles (100 nm) having a controlled particle size were diluted to about 100 ppm with ion-exchanged water as an evaluation stock solution, and obtained by the following formula.
Fine particle blocking ratio [%] = ((Evaluation stock solution absorbance) − (Transmission solution absorbance)) / (Evaluation stock solution absorbance) × 100

[Maximum breaking strength]
The maximum breaking strength was determined by measuring the breaking strength of the test piece under the conditions of a distance between chucks of 50 mm and a tensile speed of 200 mm / min, and the cross-sectional area before the tensile test as a unit measurement area.

[Maximum elongation]
The maximum point elongation was obtained by measuring the breaking strength of the test piece under the conditions of a distance between chucks of 50 mm and a tensile speed of 200 mm / min, and calculating from the elongation at the maximum point based on the distance between chucks of 50 mm.

[Elastic modulus]
The elastic modulus was obtained by measuring the breaking strength of the test piece under the conditions of a distance between chucks of 50 mm and a tensile speed of 200 mm / min, and calculating from the slope of the initial linear portion in the obtained stress-elongation curve.

[IR analysis]
The measurement was performed at room temperature using a Perkin Elmer Fourier transform infrared spectrophotometer 1760X.

(Production Example 1)
In a 2 L stainless steel autoclave, 500 g of ion exchange water, formula:

(Wherein n is a mixture of 10 and 11) is charged with 0.789 g of a 38 mass% aqueous solution of compound (2-1) (concentration of compound (2-1): 600 ppm / water), and the system is filled with nitrogen gas Then, the pressure was reduced. Subsequently, a VDF / TFE / CTFE (= 74/14/12 mol%) mixed monomer was injected into the polymerization tank so that the internal pressure became 0.75 to 0.80 MPa, and the temperature was raised to 70 ° C. .

Next, a polymerization initiator solution in which 1.0 g (2000 ppm / water) of ammonium persulfate (APS) was dissolved in 4 mL of ion-exchanged water and 0.75 g (1500 ppm / water) of ethyl acetate were injected with nitrogen gas and stirred at 600 rpm. The reaction was started.

When the internal pressure began to drop as the polymerization progressed, a VDF / TFE / CTFE (= 74/14/12 mol%) mixed monomer was supplied so that the internal pressure was maintained at 0.75 to 0.80 MPa. . Two hours and five minutes after the start of polymerization, unreacted monomers were released, and the autoclave was cooled to obtain a dispersion of the fluoropolymer (Ia) having a solid content concentration of 10.6% by mass.

(Production Example 2)
An SUS autoclave with a content of 2 liters was charged with 910 g of ion-exchanged water and 0.5 g of methylcellulose, and after evacuating the tank after purging with nitrogen, 1.5 g of ethyl acetate, 1,1-difluoroethylene (VdF) ( 365 g of vinylidene fluoride) was charged and kept constant at 28 ° C. After the temperature in the tank was constant, 12 g of dinormalpropyl peroxydicarbonate was charged to start suspension polymerization. After 10 hours, the inside of the tank was depressurized to complete the reaction. The polymer slurry was dehydrated and washed with water, followed by drying at 105 ° C. for 24 hours to obtain polyvinylidene fluoride (PVdF) powder. The obtained polyvinylidene fluoride powder was 110 g and had a weight average molecular weight of 270,000.

(Synthesis Example 1)
In order to ensure the stability of seed particles during seed polymerization, 1200 g of a fluoropolymer (Ia) dispersion was charged into a 2 L four-necked flask equipped with a stirring blade, a cooling tube and a thermometer. Surfactant (manufactured by Sanyo Chemical Industries, Ltd., Eleminol JS-20) is 1% by mass with respect to the fluoropolymer solid content, and RMA-450M (manufactured by Nippon Emulsifier Co., Ltd.) is used as the fluoropolymer solid content. On the other hand, 3% by mass and 1% by mass of RS-3000 (manufactured by Nippon Emulsifier Co., Ltd.) were added to the solid content of the fluoropolymer. Warming in a water bath with stirring, the temperature in the flask was raised to 75 ° C. Separately, 87.4 / 10 / 2.6 (molar ratio) of MMA, BA and AA mixed monomer and 1% aqueous solution of APS (amount corresponding to 0.158% by mass of the mixed monomer) A mixed emulsion was prepared, and the mixed emulsion was dropped into the flask over 2 hours to polymerize. 2.5 hours after the start of polymerization, the temperature in the flask was raised to 80 ° C., held for 2 hours, cooled, neutralized with ammonia water to adjust the pH to 7, and filtered through a 300 mesh wire mesh. An aqueous dispersion of blue-white resin particles FA-1 (average particle size 200 nm) was produced.
The weight ratio of the seed particles (fluorinated polymer (Ia)) and the acrylic monomer mixture is 70:30, and the results of NMR analysis of the aqueous dispersion of the obtained resin particles FA-1 are also shown in FIG. The weight ratio of polymer was 70:30.
The obtained aqueous dispersion of resin particles FA-1 was coagulated by freezing, and then sufficiently washed with a methanol solution and then vacuum dried to isolate resin particles FA-1.

(Synthesis Example 2)
In order to ensure the stability of the seed particles during seed polymerization, 509 g of the fluoropolymer (Ia) dispersion was charged into a 2 L four-necked flask equipped with a stirring blade, a cooling tube and a thermometer. 25 g of surfactant (707SF) was added. A mixed monomer of MMA, BA and AA of 87.4 / 10 / 2.6 (mole% ratio) was placed in the dropping funnel, and dropping was started. 30 minutes after the start of dropping, the mixture was heated in a water bath, and the temperature in the flask was raised to 70 ° C. Every 30 minutes after the internal temperature reached 70 ° C., 4.15 g of APS was added in four portions. The temperature in the flask was raised to 80 ° C., kept for 2 hours, cooled, neutralized with aqueous ammonia to adjust the pH to 7, filtered through a 300 mesh wire mesh, and pale blue resin particles FA-2 ( An aqueous dispersion having an average particle size of 200 nm was obtained.
The weight ratio of the seed particles (fluorinated polymer (Ia)) and the acrylic monomer mixture is 70:30, and the results of NMR analysis of the aqueous dispersion of the obtained resin particles FA-2 are also shown in FIG. The weight ratio of polymer was 70:30.
The obtained aqueous dispersion of resin particles FA-2 was frozen to be coagulated, and then sufficiently washed with a methanol solution, followed by vacuum drying to isolate resin particles FA-2.

(Comparative Synthesis Example 1)
Acrylic emulsion polymerization was carried out except for the fluoropolymer (Ia) dispersion alone in Synthesis Example 1 to obtain an acrylic dispersion AD-1.

Example 1
The polymer solution was adjusted so that the resin particle FA-1 of Synthesis Example 1 was 18% by mass and dimethylacetamide was 82.0% by mass.
This polymer solution was applied to a glass plate using an applicator (203 μm), and immediately immersed in a water coagulation bath at 25 ° C. for 10 minutes to obtain a flat porous film. The pure water permeability coefficient was 4.23 × 10 ⁻⁹ (m ³ / m ² / s / Pa). The fine particle rejection was 92%.

(Example 2)
A flat porous membrane was obtained in the same manner as in Example 1 except that the resin particle FA-2 of Synthesis Example 2 was used instead of the resin particle FA-1 of Synthesis Example 1.
The pure water permeability coefficient of the obtained porous membrane was 1.85 × 10 ⁻⁹ (m ³ / m ² / s / Pa). The fine particle rejection was 96%.

(Comparative Example 1)
A flat porous membrane was obtained in the same manner as in Example 1 except that the polyvinylidene fluoride powder of Production Example 2 was used instead of the resin particles FA-1 of Synthesis Example 1.
The pure water permeability coefficient of the obtained porous membrane was 3.50 × 10 ⁻¹⁰ (m ³ / m ² / s / Pa). Further, the fine particle rejection was 98%.

(Example 3)
Each component was mixed at 25 ° C. to obtain a polymer solution containing 18% by mass of resin particles FA-1 obtained in Synthesis Example 1 and 82.0% by mass of dimethylacetamide. This polymer solution was discharged from a double-tube base while accompanying ion exchange water as an internal liquid, and solidified in ion exchange water. The obtained hollow fiber membrane had an outer diameter of 1.14 mm and an inner diameter of 0.83 mm. The pure water permeability coefficient, fine particle rejection rate, maximum point breaking strength, maximum point elongation, and elastic modulus were evaluated. The results are shown in Table 1. Moreover, the SEM image of the surface of the obtained hollow fiber membrane is shown in FIG. As is apparent from FIG. 1, the surface of the hollow fiber membrane obtained from the present invention is excellent because it has uniform holes.

Example 4
A hollow fiber membrane was obtained in the same manner as in Example 3 except that the resin particle FA-2 of Synthesis Example 2 was used instead of the resin particle FA-1 of Synthesis Example 1. The obtained hollow fiber membrane had an outer diameter of 0.83 mm and an inner diameter of 0.62 mm. In the same manner as in Example 3, the pure water permeability coefficient, fine particle rejection rate, maximum point breaking strength, maximum point elongation, and elastic modulus were evaluated. The results are shown in Table 1.

(Comparative Example 2)
A dispersion blend of the acrylic dispersion AD-1 obtained in Comparative Synthesis Example 1 and the fluorinated polymer (Ia) dispersion obtained in Production Example 1 was made into a dispersion blend, and almost the same composition as in Synthesis Example 1 (fluoropolymer and acrylic) A dispersion (BL-1) having a polymer weight ratio of 70:30) was produced.
The obtained dispersion BL-1 was coagulated by freezing, and then sufficiently washed with a methanol solution, followed by vacuum drying to isolate the acrylic polymer BL-1.
A hollow fiber membrane was obtained in the same manner as in Example 3 except that BL-1 was used instead of FA-1. The obtained hollow fiber membrane had an outer diameter of 0.77 mm and an inner diameter of 0.46 mm. In the same manner as in Example 1, the pure water permeability coefficient, fine particle rejection, maximum breaking strength, maximum elongation, and elastic modulus were evaluated. However, the solution before film formation was also non-uniform, and the obtained hollow fiber membrane had many pinholes, and the membrane was uneven, and measurements of pure water permeability coefficient and fine particle rejection were not performed. The results are shown in Table 1.

(Comparative Example 3)
Each component was mixed at 25 ° C. to obtain a polymer solution of 18.0% by mass of the polyvinylidene fluoride powder obtained in Production Example 2 and 82.0% by mass of dimethylacetamide. This polymer solution was discharged from a double-tube base while accompanying ion exchange water as an internal liquid, and solidified in ion exchange water. The obtained hollow fiber membrane had an outer diameter of 0.81 mm and an inner diameter of 0.74 mm. Although a water pressure of 0.1 MPaG was applied at 25 ° C., pure water did not permeate. The maximum point breaking strength was 11.0 MPa, and the maximum point elongation was 440%. The results are shown in Table 1.

Claims (12)

A polymer porous membrane obtained from resin particles containing a fluoropolymer (A) containing a vinylidene fluoride unit and an acrylic polymer (B) containing a (meth) acrylate unit in the same particle . The polymeric porous membrane according to claim 1, wherein the fluoropolymer (A) is a polyvinylidene fluoride or a copolymer containing a vinylidene fluoride unit and a tetrafluoroethylene unit and / or a chlorotrifluoroethylene unit. The porous polymer membrane according to claim 1 or 2, wherein the acrylic polymer (B) is a copolymer containing a (meth) acrylic acid ester unit and a (meth) acrylic acid monomer unit. 4. The polymer porous membrane according to claim 3, wherein the (meth) acrylic acid monomer is (meth) acrylic acid. The porous polymer membrane according to claim 3, wherein the (meth) acrylic acid monomer is a hydroxyl group-containing (meth) acrylic ester. The polymer porous membrane according to claim 3, wherein the (meth) acrylic acid monomer is an oxyalkylene group-containing (meth) acrylic ester. The content ratio of the fluoropolymer (A) and the acrylic polymer (B) in the resin particles is such that the fluoropolymer (A) / acrylic polymer (B) has a mass ratio of 30/70 to 80/20. The polymeric porous membrane in any one of -6. The polymer porous membrane according to any one of claims 1 to 7, wherein the acrylic polymer (B) is a polymer obtained by polymerizing a (meth) acrylic acid ester in the presence of a reactive emulsifier. The polymer porous membrane according to any one of claims 1 to 8, which is used for water treatment. A step of producing an aqueous dispersion containing particles made of fluoropolymer (A) by emulsion polymerization of a monomer containing vinylidene fluoride, and (meth) acrylic acid ester in the presence of particles made of fluoropolymer (A) A step of producing an aqueous dispersion containing resin particles containing the fluoropolymer (A) and the acrylic polymer (B) in the same particle by emulsion polymerization of the monomer containing, a step of isolating the resin particle, and , The step of forming the resin particles into a porous membrane to obtain a polymer porous membrane,
A method for producing a porous polymer membrane comprising: The method for producing a porous polymer membrane according to claim 10, wherein the emulsion polymerization in the step of producing the aqueous dispersion containing the resin particles is further performed in the presence of a reactive emulsifier. 12. The polymer porous membrane according to claim 10 or 11, wherein in the step of molding the resin particles into a porous membrane, a porous membrane-like molded product is obtained by a non-solvent induced phase separation method and / or a thermally induced phase separation method. Manufacturing method.