JP2014200702A - Porous polymer membrane and method for producing porous polymer membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous polymer membrane that is excellent in water permeability and alkali resistance and has excellent mechanical strength and elongation characteristic.SOLUTION: The porous polymer membrane includes a fluoropolymer (A) having a vinylidene fluoride unit and a tetrafluoroethylene unit and a rubber (B).

Description

The present invention relates to a polymer porous membrane and a method for producing a polymer porous membrane. More specifically, the present invention relates to a polymer porous membrane suitable as a microfiltration membrane or an ultrafiltration membrane used for water treatment and a method for producing the same.

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 such as water purification treatment and wastewater treatment, porous membranes are used 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 water permeability of the porous membrane is required to be excellent. 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 porous membrane is required to have chemical resistance. In recent years, porous films using fluoropolymers such as polyvinylidene fluoride resins as materials with high chemical resistance have been studied (see, for example, Patent Documents 1 to 14). However, conventional porous membranes are not sufficient in terms of water permeability and have room for improvement.

JP 2009-203584 A Japanese National Patent Publication No. 10-512194 JP 63-248405 A JP-A-63-248406 JP 58-98105 A International Publication No. 2003/106545 Pamphlet JP 2003-138422 A JP 2003-236351 A Japanese Patent Laid-Open No. 3-38228 JP-A-3-38227 JP 2005-522316 A Japanese Patent Laid-Open No. 61-4504 Japanese Examined Patent Publication No. 63-11370 JP 2007-167839 A

The present invention provides a polymer porous membrane having excellent water permeability and alkali resistance and having excellent mechanical strength and elongation characteristics.

The porous polymer membrane of the present invention is characterized by comprising a fluoropolymer (A) having a vinylidene fluoride unit and a tetrafluoroethylene unit and a rubber (B).

From the viewpoint of compatibility with the fluoropolymer, the rubber (B) is preferably fluororubber.

The porous polymer membrane of the present invention is preferably composed of a fluoropolymer (A) having a vinylidene fluoride unit / tetrafluoroethylene unit in a molar ratio of 50 to 90/50 to 10 and a rubber (B).

In the porous polymer membrane of the present invention, the ratio (O / F) of the O element content on the surface to the F element content measured by XPS (X-ray photoelectron spectroscopy) is 0 from the viewpoint of improving hydrophilicity. It is preferably 0.050 or more and less than 0.150. It is also preferable that the ratio of the C—F bond on the surface to the C—H bond (C—F / C—H) measured by XPS (X-ray photoelectron spectroscopy) is greater than 0.50.

The fluoropolymer (A) preferably further has a unit represented by the following formula (1) (hereinafter also referred to as a unit of the formula (1)).
—CHX ¹ —CX ² (OR) — (1)
(In the formula, ^one of X ¹ and X ² is a hydrogen atom and the other is a fluorine atom, and R is either a hydrogen atom or an alkyl group having 1 to 8 carbon atoms).
Here, R in the formula (1) is preferably hydrogen, a methyl group or an ethyl group.

The method for producing a polymer porous membrane of the present invention is formed into a porous membrane shape at least with respect to a mixture of a fluoropolymer (A) having a vinylidene fluoride unit and a tetrafluoroethylene unit and a rubber (B). It is characterized by performing a process of

In the method for producing a porous polymer membrane of the present invention, a molded product having a porous membrane shape is obtained by a non-solvent induced phase separation method and / or a thermally induced phase separation method in the step of forming the porous membrane shape. Is preferred.

In the method for producing a porous polymer membrane of the present invention, it is preferable to further perform a step of performing an alkali treatment in the presence of water and / or an alcohol having 1 to 8 carbon atoms.
Here, the alcohol is preferably ethanol or methanol.

In the method for producing a porous polymer membrane of the present invention, the fluoropolymer (A) preferably has a vinylidene fluoride unit / tetrafluoroethylene unit in a molar ratio of 50 to 90/50 to 10.

The polymer porous membrane is preferably a hollow fiber membrane. The polymer porous membrane is preferably used for water treatment.

The hollow fiber membrane of the present invention is characterized by comprising the polymer porous membrane of the present invention.

Since the porous polymer membrane of the present invention has the above-described configuration, it has excellent water permeability and alkali resistance, as well as excellent mechanical strength and elongation characteristics.
According to the method for producing a polymer porous membrane of the present invention, the polymer porous membrane can be suitably produced.

The present invention is described in detail below.
The porous polymer membrane of the present invention comprises a fluoropolymer (A) having a vinylidene fluoride (VdF) unit and a tetrafluoroethylene (TFE) unit and a rubber (B).
In the present specification, the fluoropolymer (A) is a substance that does not have rubber elasticity, and the rubber (B) is a substance that has rubber elasticity.

The fluoropolymer (A) has VdF units and TFE units. Since the fluoropolymer (A) has VdF units and TFE units, the polymer porous membrane of the present invention is excellent in alkali resistance, and the mechanical strength is hardly lowered by alkali treatment.
For example, when a porous membrane made of polyvinylidene fluoride is used, a decrease in elongation retention and a decrease in breaking stress may occur in the tensile test of the polymer porous membrane due to alkali treatment. This is probably because a dehydrofluorination reaction occurs in polyvinylidene fluoride, a double bond is generated, and the film becomes brittle. Moreover, brown coloring is also seen in the film due to the formation of double bonds. In the fluoropolymer (A), the dehydrofluorination reaction caused by the alkali treatment is suppressed by incorporating the TFE unit, the coloring of the porous film caused by the double bond is suppressed, and the long-term use is also possible.

Since the porous polymer membrane of the present invention is composed of the fluoropolymer (A) having excellent water permeability and alkali resistance, the polymer porous membrane is excellent in permeability of treatment liquid such as water, and has tensile strength, bending strength, etc. Excellent mechanical strength and excellent elongation characteristics. For example, the elongation performance is remarkably excellent even when compared with a polymer porous membrane made of polyvinylidene fluoride. In addition, the polymer porous membrane of the present invention has a high fine particle rejection rate, and even fine particles having a diameter of about 50 nm can be fractionated by controlling the film forming conditions.

In the fluoropolymer (A), the molar ratio of VdF units / TFE units is preferably 50 to 90/50 to 10, and more preferably 50 to 85/50 to 15.
This is because when the TFE unit is 10 mol% or more, the dehydrofluorination reaction caused by the alkali treatment is easily suppressed, and when the TFE unit is 15 mol% or more, the alkali resistance is drastically improved. In addition, when the TFE unit is 50 mol% or more, the solubility in a solvent is lowered and it becomes difficult to form a film.

In the porous polymer membrane of the present invention, the ratio (O / F) of the O element content on the surface to the F element content measured by XPS (X-ray photoelectron spectroscopy) is 0 from the viewpoint of improving hydrophilicity. It is preferably 0.050 or more and less than 0.150.
When the ratio (O / F) is 0.150 or more, the strength of the porous polymer membrane is reduced, whereas by setting the ratio (O / F) to less than 0.150, excellent strength can be obtained. Can be secured.
In addition, the preferable minimum of the said ratio (O / F) is 0.050. When the ratio (O / F) is less than 0.050, the unit of the formula (1) is small, and the water permeability of the polymer porous membrane may be inferior.

Here, the ratio (O / F) can be calculated by the following method using a value obtained by XPS (X-ray photoelectron spectroscopy) measurement.
Ratio (O / F) = A / B
A: Peak area value of O element B: Peak area value of F element

Further, the porous polymer membrane has a ratio of C—F bonds to C—H bonds on the surface (C—F / C—H) measured by XPS (X-ray photoelectron spectroscopy) from 0.50. It is preferably large and more preferably larger than 0.65.
When the ratio (C—F / C—H) is 0.50 or less, the mechanical strength of the polymer porous membrane becomes insufficient, and the color may be changed to brown.
In addition, the preferable upper limit of the said ratio (C-F / C-H) is 2.0, and a more preferable upper limit is 1.4. When the ratio (C / F / C—H) is increased, the hydrophobicity of the surface of the polymer porous membrane is increased, and when the ratio (C / F / C—H) is greater than 2.0, the hydrophobicity of the membrane surface is increased. Depending on the nature, water permeability may be inferior.

The ratio (C−F / C−H) can be calculated by the following method using a value obtained by XPS (X-ray photoelectron spectroscopy) measurement.
Ratio (C−F / C−H) = a / b
a: Peak area value of bond energy (292.4 eV) between atoms derived from C—F bond b: Peak area value of bond energy (286.0 and 287.8 eV) between atoms derived from C—H bond

The fluoropolymer (A) preferably further has a unit represented by the following formula (1) (unit of formula (1)).
—CHX ¹ —CX ² (OR) — (1)
(In the formula, ^one of X ¹ and X ² is a hydrogen atom and the other is a fluorine atom, and R is either a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.)
When the said fluoropolymer (A) has the said Formula (1) unit, the polymeric porous membrane of this invention will be excellent by water permeability.

R in the above formula (1) may be either a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, but is preferably a hydrogen atom, a methyl group or an ethyl group. In this case, the water permeability of the polymer porous membrane is greatly improved.
Moreover, when the said fluoropolymer (A) has two or more units of said Formula (1), R of each unit may be the same and may differ.
Hereinafter, in the present specification, the fluoropolymer (A) having the unit of the formula (1) is also referred to as a fluoropolymer (A1).

The fluoropolymer (A) may also comprise another constituent unit such as a hexafluoropropylene unit, a chlorotrifluoroethylene unit, a perfluorovinyl ether unit or the like as long as the characteristics are not impaired.
Among these, the fluoropolymer (A) is particularly preferably a fluoropolymer consisting only of VdF units and TFE units.

Although the weight average molecular weight of the said fluoropolymer (A) changes with uses of the polymeric porous membrane of this invention, it is preferable that it is 10,000 or more from a viewpoint of mechanical strength and film-forming property. More preferably, it is 50000-1 million, More preferably, it is 100000-900000. The weight average molecular weight can be determined by gel permeation chromatography (GPC).

The rubber (B) is made of a polymer having rubber elasticity. The rubber (B) may be composed of one kind of polymer or may be composed of two or more kinds of polymers.
By including the rubber (B) in addition to the fluoropolymer (A), the polymer porous membrane of the present invention is further excellent in mechanical strength, particularly tensile strength and breaking strength, and elongation properties. Can be.

Examples of the rubber (B) include fluorine rubber, acrylic rubber, and silicone rubber. Among these, fluororubber is preferable from the viewpoint of heat resistance and chemical resistance.

The fluororubber usually comprises a polymer having a fluorine atom bonded to a carbon atom constituting the main chain and having rubber elasticity. The fluororubber may be composed of one kind of polymer or may be composed of two or more kinds of polymers.

The fluororubber is composed of vinylidene fluoride (VdF) / hexafluoropropylene (HFP) copolymer, VdF / HFP / tetrafluoroethylene (TFE) copolymer, TFE / propylene copolymer, TFE / propylene / VdF copolymer. Copolymer, ethylene / HFP copolymer, ethylene / HFP / VdF copolymer, ethylene / HFP / TFE copolymer, VdF / TFE / perfluoro (alkyl vinyl ether) (PAVE) copolymer, and VdF / chlorotri It is preferably at least one selected from the group consisting of fluoroethylene (CTFE) copolymers.

The fluororubber (hereinafter also referred to as “VdF-based fluororubber”) made of a copolymer containing the vinylidene fluoride (VdF) unit will be described. The VdF-based fluororubber is a fluororubber containing at least polymerized units derived from vinylidene fluoride.

The copolymer containing a VdF unit is preferably a copolymer containing a VdF unit and a copolymer unit derived from a fluorine-containing ethylenic monomer (excluding the VdF unit). The copolymer containing a VdF unit preferably further contains a copolymer unit derived from a monomer copolymerizable with VdF and a fluorine-containing ethylenic monomer.

The copolymer containing VdF units preferably contains 30 to 85 mol% of VdF units and 70 to 15 mol% of copolymerized units derived from a fluorine-containing ethylenic monomer, and 30 to 80 mol% of VdF. More preferably, it contains a unit and a copolymer unit derived from 70 to 20 mol% of a fluorine-containing ethylenic monomer. The copolymerized unit derived from the monomer copolymerizable with VdF and the fluorine-containing ethylenic monomer is 0 to 10 with respect to the total amount of the VdF unit and the copolymerized unit derived from the fluorine-containing ethylenic monomer. It is preferable that it is mol%.

Examples of the fluorine-containing ethylenic monomer include TFE, CTFE, trifluoroethylene, HFP, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, perfluoro (alkyl vinyl ether) (hereinafter, And fluorine-containing monomers such as vinyl fluoride. Among these, at least one selected from the group consisting of TFE, HFP and PAVE is preferable.

As the PAVE, the general formula (2):
^{_{CF 2 = CFO (CF 2 CFY}} 1 O) p - (CF 2 CF 2 CF 2 O) q -R f (2)
(Wherein, ^{Y 1} represents F or CF _3, ^{R f} represents an integer of .p 0-5 representing a perfluoroalkyl group having 1 to 5 carbon atoms, q is an integer of 0-5. ) And general formula (3):
CFX = CXOCF ₂ OR ¹ (3)
(Wherein X is the same or different and represents H, F, or CF ₃ , and R ¹ is a linear or branched fluoroalkyl group having 1 to 6 carbon atoms, or 5 or 5 carbon atoms) It is preferably at least one selected from the group consisting of 6 cyclic fluoroalkyl groups.

R ¹ in the general formula (3) may be a fluoroalkyl group containing 1 to 2 atoms of at least one selected from the group consisting of H, Cl, Br and I.

The PAVE is preferably perfluoro (methyl vinyl ether) or perfluoro (propyl vinyl ether), and more preferably perfluoro (methyl vinyl ether). These can be used alone or in any combination.

Examples of the monomer copolymerizable with VdF and the fluorine-containing ethylenic monomer include ethylene, propylene, and alkyl vinyl ether.

Specific examples of such a copolymer containing VdF units include a VdF / HFP copolymer, a VdF / HFP / TFE copolymer, a VdF / CTFE copolymer, a VdF / CTFE / TFE copolymer, and a VdF. Preferred are one or more of / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, VdF / HFP / TFE / PAVE copolymer, and the like. Among these copolymers containing VdF units, VdF / HFP copolymers and VdF / HFP / TFE copolymers are particularly preferred from the viewpoints of heat resistance, compression set, workability, and cost.

The VdF / HFP copolymer preferably has a VdF / HFP molar ratio of 45 to 85/55 to 15, more preferably 50 to 80/50 to 20, and still more preferably 60 to 80/40. ~ 20.

As the VdF / HFP / TFE copolymer, a VdF / HFP / TFE molar ratio of 30 to 80/10 to 35/10 to 35 is preferable.

The VdF / PAVE copolymer preferably has a VdF / PAVE molar ratio of 65 to 90/10 to 35.

As the VdF / TFE / PAVE copolymer, a VdF / TFE / PAVE molar ratio of 40 to 80/3 to 40/15 to 35 is preferable.

As the VdF / HFP / PAVE copolymer, a VdF / HFP / PAVE molar ratio of 65 to 90/3 to 25/3 to 25 is preferable.

The VdF / HFP / TFE / PAVE copolymer preferably has a VdF / HFP / TFE / PAVE molar ratio of 40 to 90/0 to 25/0 to 40/3 to 35, more preferably 40 to 80. / 3 to 25/3 to 40/3 to 25.

It is also preferable that the fluororubber is made of a copolymer containing a copolymer unit derived from a monomer that provides a crosslinking site. Examples of the monomer that gives a crosslinking site include perfluoro (6,6-dihydro-6-iodo-3-oxa-1-) described in JP-B-5-63482 and JP-A-7-316234. Hexene) and iodine-containing monomers such as perfluoro (5-iodo-3-oxa-1-pentene), bromine-containing monomers described in JP-A-4-505341, JP-A-4-505345, Examples include cyano group-containing monomers, carboxyl group-containing monomers, and alkoxycarbonyl group-containing monomers as described in JP-T-5-500070.

The fluororubber is preferably a fluororubber having an iodine atom or a bromine atom at the end of the main chain. Fluororubber having iodine atom or bromine atom at the main chain end is produced by adding a radical initiator in the presence of a halogen compound in an aqueous medium in the absence of oxygen and performing emulsion polymerization of the monomer. it can. Representative examples of the halogen compound used include, for example, the general formula:
R ² I _x Br _y
(In the formula, x and y are each an integer of 0 to 2 and satisfy 1 ≦ x + y ≦ 2, and R ² is a saturated or unsaturated fluorohydrocarbon group having 1 to 16 carbon atoms, carbon A saturated or unsaturated chlorofluorohydrocarbon group having 1 to 16 carbon atoms, a hydrocarbon group having 1 to 3 carbon atoms, or a cyclic hydrocarbon group having 3 to 10 carbon atoms that may be substituted with an iodine atom or a bromine atom And these may contain an oxygen atom).

Examples of the halogen compound include 1,3-diiodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloro. Perfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2- Diiodoethane, 1,3-diiodo-n-propane, CF ₂ Br ₂ , BrCF ₂ CF ₂ Br,
CF ₃ CFBrCF ₂ Br, CFClBr ₂ , BrCF ₂ CFClBr,
CFBrClCFClBr, BrCF ₂ CF ₂ CF ₂ Br, BrCF ₂ CFBrOCF ₃ , 1-bromo-2-iodoperfluoroethane, 1-bromo- ₃ -iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2- Bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, diiodomonobromo of benzene Substituents and (2-iodoethyl) and (2-bromoethyl) substituents of benzene and the like can be mentioned, and these compounds may be used alone or in combination with each other.

Among these, it is preferable to use 1,4-diiodoperfluorobutane or diiodomethane from the viewpoints of polymerization reactivity, crosslinking reactivity, availability, and the like.

The rubber (B) preferably has a Mooney viscosity (ML _{1 + 10} (100 ° C.)) of 5 to 140, more preferably ₁₀ to 120, and preferably 20 to 100 from the viewpoint of good processability. More preferably.

The rubber (B) may be crosslinked or uncrosslinked, but is preferably uncrosslinked from the viewpoint of the elongation characteristics of the polymer porous membrane.

The polymer porous membrane of the present invention is composed entirely of the fluoropolymer (A) and the rubber (B) even if a part thereof is composed of the fluoropolymer (A) and the rubber (B). It may be.
The polymer porous membrane may be composed of a fluoropolymer (A) containing a fluoropolymer (A1) and a rubber (B), and the surface thereof is composed of the fluoropolymer (A1) and the rubber (B It is preferable that it consists of.
This is because in this case, the polymer porous membrane is extremely excellent in water permeability.

As will be described later, the porous polymer membrane of the present invention may be subjected to a specific alkali treatment step from the viewpoint of improving hydrophilicity.

When a part of the polymer porous membrane is made of the fluoropolymer (A1), the ratio of the fluoropolymer (A1) to the whole fluoropolymer (A) is 0.01 to 99% by weight. preferable.

The polymer porous membrane of the present invention may be substantially composed of only the fluoropolymer (A) and the rubber (B). In addition to the fluoropolymer (A) and the rubber (B), Furthermore, another resin may be included.

In the porous polymer membrane of the present invention, the composition ratio of the fluoropolymer (A) and the rubber (B) is preferably 40:60 to 99: 1 (weight ratio). When the composition ratio of the fluoropolymer (A) and the rubber (B) is within such a range, it is possible to exhibit water permeability, alkali resistance, mechanical strength, and elongation properties at a higher level. The composition ratio of the fluoropolymer (A) and the rubber (B) is more preferably 60:40 to 99: 1, and still more preferably 70:30 to 98: 2.

However, even when the polymer porous membrane of the present invention contains other resins, the fluoropolymer (A) and the rubber (B) are added to the entire polymer porous membrane from the viewpoint of mechanical strength and alkali resistance. It is preferably contained in an amount of not less than wt%, more preferably not less than 60 wt%, and still more preferably not less than 80 wt%.

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 resin, polypropylene resin, polyvinylidene fluoride resin, acrylic resin, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resin, polystyrene resin, acrylonitrile-styrene (AS) resin, and chloride. Vinyl 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. Can be 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-based resin is a resin made of a polyethylene homopolymer or a polyethylene copolymer. The polyethylene resin may be composed of a plurality of types of polyethylene copolymers. Examples of the polyethylene copolymer include a copolymer of ethylene and one or more selected from linear unsaturated hydrocarbons such as propylene, butene and pentene.

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

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, blocking performance, etc. 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, polymethyl methacrylate resin, montmorillonite, SiO ₂ , CaCO ₃ , poly It may contain an additive such as tetrafluoroethylene.

The porous polymer membrane of the present invention preferably has a pore size of 2 nm to 1.0 μm, and 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 measured by taking a photograph of the surface of the porous polymer membrane at a magnification at which the pores can be clearly confirmed using an SEM or the like, and measuring the diameter of the pores. 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.

From the viewpoint of water permeability, the polymer porous membrane of the present invention preferably has a water static contact angle of 100 ° or less, more preferably 95 ° or less. When the static contact angle of water on the membrane surface is in such a range, it can be said that the membrane surface is hydrophilic, and the water permeability of the membrane can be further improved.
The static contact angle of water on the surface of the membrane is such that the average pore diameter of the outermost surface is 0.01 to 0.1 μm, and the polymer porous membrane in a sufficiently dried state is measured using a contact angle meter. It is a value measured using pure water as a measurement solvent at 25 ° C.

The polymer porous membrane of the present invention has a pure water permeability coefficient of 1.0 × 10 ⁻¹⁰ m ³ / m ² / s / Pa or more, for example, when it has the performance of blocking 95% or more of 100 nm fine particles. It is preferably 2.0 × 10 ⁻¹⁰ 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 permeability coefficient can be determined by pressurizing ion-exchanged water to 0.01 MPa or more with a pump or nitrogen at a temperature of 25 ° C., and filtering the produced porous polymer membrane. Specifically, it is a value obtained from the following formula.
Pure water permeability coefficient = (permeated water amount) / (membrane area) / (permeation time) / (evaluation pressure)

The polymer porous membrane of the present invention preferably has a fine particle rejection of 100 nm or 80 nm of 90% or more, more preferably 95% or more.
The fine particle blocking rate is a value obtained by filtering a dispersion solution obtained by diluting polystyrene latex fine particles having a controlled particle size to about 100 ppm with ion-exchanged water as an evaluation stock solution, and calculating the following formula.
Fine particle rejection (%) = {((Evaluation stock solution absorbance) − (Transmission solution absorbance)) / (Evaluation stock solution absorbance)} × 100

When the polymer porous membrane of the present invention is a flat membrane, from the viewpoint of mechanical strength, the maximum point breaking strength of the membrane is preferably 0.5 MPa or more, more preferably 0.6 MPa or more. .
The maximum point breaking strength is a value obtained by measuring the breaking strength of a test piece under the conditions of a distance between chucks of 20 mm and a tensile speed of 20 mm / min and using a cross-sectional area before a tensile test as a unit measurement area.

When the polymer porous membrane of the present invention is a hollow fiber membrane, from the viewpoint of mechanical strength, the maximum point breaking strength of the membrane is preferably 1.0 MPa or more, more preferably 2.0 MPa or more. preferable.
The maximum breaking strength is a value 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 using the cross-sectional area before the tensile test as a unit measurement area.

When the porous polymer membrane of the present invention is a flat membrane, the maximum point elongation of the membrane is preferably 120% or more, and more preferably 150% or more from the viewpoint of mechanical strength.
The maximum point elongation is a value obtained by measuring the breaking strength of a test piece under the conditions of a distance between chucks of 20 mm and a tensile speed of 20 mm / min, and from the elongation of the maximum point with reference to 20 mm between the chucks.

When the polymer porous membrane of the present invention is a hollow fiber membrane, the maximum point elongation of the membrane is preferably 120% or more, and more preferably 150% or more from the viewpoint of mechanical strength.
The maximum point elongation is a value 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 based on the elongation at the maximum point with reference to 50 mm between the chucks.

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

When the polymer porous membrane of the present invention is a flat membrane, the thickness of the polymer porous membrane is preferably 10 μm to 1 mm, and more preferably 30 μm to 500 μm.

When the polymer porous membrane of the present invention is a hollow fiber membrane, the inner diameter of the hollow fiber membrane is preferably 100 μm to 10 mm, 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.
The film thickness of the porous polymer membrane of the present invention 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 1.0 μm, more preferably 5 nm to 0.5 μm.

The polymer porous membrane of the present invention 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. Moreover, in the ultrapure water production field, it can also be used as a charged porous membrane for enhancing ion exclusion and increasing the purity of the obtained pure water. The polymer porous membrane of the present invention is preferably a polymer porous membrane for water treatment because of its high permeation performance of the treatment liquid.

The porous polymer membrane of the present invention is also suitably used in the medical field, food field, battery field and the like.

In the medical field, the membrane of the present invention is used as a blood purification membrane for the purpose of removing blood waste, particularly blood dialysis to substitute for renal function, blood filtration, blood filtration dialysis, etc. A molecular porous membrane can be used.

In the food field, the polymer porous membrane of the present invention can be used for the purpose of separating and removing yeasts used for fermentation and concentrating liquids.

In the battery field, the polymer porous membrane of the present invention can be used as a separator for a battery so that the electrolytic solution can permeate but a product generated by a battery reaction cannot permeate, or as a base material of a polymer solid electrolyte. it can.

The polymer porous membrane of the present invention can of course be used as it is as a porous membrane for the above-mentioned applications, but it is integrated with other porous substrates and porous resin members made of other resins. (Composite membrane) may be used.
Here, examples of the other resin include the thermoplastic resins described above.

Specifically, for example, when used as a flat membrane, the surface of the porous substrate may be coated with the polymer porous membrane of the present invention, or the porous substrate and the polymer porous membrane of the present invention may be used. It may be a laminate of layers made of a porous film. Further, a porous substrate, a layer made of the polymer porous membrane of the present invention, and the porous resin member may be laminated in any order.
Also, when used in a hollow fiber membrane, a porous coating layer made of the above-mentioned other resin is formed on the surface (inner surface and / or outer surface) of the porous polymer membrane of the present invention which is a hollow fiber membrane. May be integrated.

Examples of the porous substrate include woven fabrics, knitted fabrics, and nonwoven fabrics made of organic fibers such as polyester fibers, nylon fibers, polyurethane fibers, acrylic fibers, rayon fibers, 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 on the surface of the porous substrate can be freely selected depending on the application, but is preferably 5 nm to 1.0 μm, more preferably 8 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, at least a mixture of a fluoropolymer (A) having a vinylidene fluoride unit and a tetrafluoroethylene unit and a rubber (B) is formed into a porous membrane shape. The process to do is performed.

First, a method for producing a fluoropolymer (A) having a vinylidene fluoride unit and a tetrafluoroethylene unit will be described.
The fluoropolymer (A) can be produced by a conventionally known method. For example, it can be produced by a polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization or the like, but it is preferably produced by emulsion polymerization or suspension polymerization in terms of industrial implementation.

In the above polymerization, a polymerization initiator, a surfactant, a chain transfer agent, and a solvent can be used, and conventionally known ones can be used.

The solvent may be appropriately determined depending on the polymerization method, and examples thereof include water, a mixed solvent of water and alcohol, and a fluorine-containing solvent.

As said polymerization initiator, an oil-soluble radical polymerization initiator, a water-soluble radical polymerization initiator, etc. can be used, for example.

As the surfactant, a known surfactant can be used. For example, a nonionic surfactant, an anionic surfactant, a cationic surfactant, or the like can be used. Among these, a fluorine-containing anionic surfactant is preferable, and ether-bonded oxygen may be contained (that is, an oxygen atom may be inserted between carbon atoms). A linear or branched fluorine-containing anionic surfactant having 4 to 20 carbon atoms is more preferred.

Examples of the chain transfer agent include hydrocarbons such as ethane, isopentane, n-hexane and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetates such as ethyl acetate and butyl acetate; Examples include alcohols such as methanol and ethanol; mercaptans such as methyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride. The amount added may vary depending on the size of the chain transfer constant of the compound used, but is usually used in the range of 0.001 to 10% by mass with respect to the polymerization solvent.

It does not specifically limit as polymerization temperature, It may be 0-100 degreeC. The polymerization pressure is appropriately determined according to other polymerization conditions such as the type, amount and vapor pressure of the solvent to be used, the polymerization temperature, etc., but may usually be 0 to 9.8 MPaG.

Although the said fluoropolymer (A) can be manufactured by such a method, the said fluoropolymer (A) may be a commercial item.
Examples of commercially available products of the fluoropolymer (A) include Neoflon VT50, VP50, VT100, VP100, VP101, and VP100X manufactured by Daikin Industries, Ltd.

The fluoropolymer (A) preferably has a vinylidene fluoride unit / tetrafluoroethylene unit in a molar ratio of 50 to 90/50 to 10.
If the amount of VdF units is too small, it is difficult to dissolve in a solvent, which may make it difficult to obtain a polymer porous membrane. Further, when the TFE unit is 10 mol% or more, when an alkali treatment step described later is performed, a dehydrofluorination reaction and an alcohol addition reaction occur moderately, and there are few double bonds in the resulting polymer porous membrane. Thus, deterioration of the film can be suppressed.
Furthermore, in the fluoropolymer (A), when the TFE unit is 15 mol% or more, the above-described effect becomes more remarkable. Therefore, the molar ratio of VdF unit / TFE unit is more preferably 60 to 85/40 to 15.

In this production method, the mixture of the fluoropolymer (A) and the rubber (B), or the mixture of the fluoropolymer (A), another resin and the rubber (B) (hereinafter referred to as the raw material mixture together) In other words, a step of forming a porous film is performed.
Examples of the other resin include resins other than the fluoropolymer (A) that can be contained in the porous polymer membrane of the present invention described above.
In addition, it is preferable that the compounding ratio of fluoropolymer (A) and rubber (B) in the said raw material mixture is 40: 60-99: 1 (weight ratio). When the blending ratio of the fluoropolymer (A) and the rubber (B) is within such a range, a polymer porous membrane that exhibits water permeability, alkali resistance, mechanical strength, and elongation characteristics at a higher level is obtained. Is possible. The compounding ratio of the fluoropolymer (A) and the rubber (B) is more preferably 60:40 to 99: 1, and still more preferably 70:30 to 98: 2.

The step of forming the porous film can be performed by various methods, for example, a phase separation method, a melt extraction method, a vapor coagulation method, a stretching method, an etching method, and a porous material obtained by sintering a polymer sheet. A forming method such as a method for forming a porous film, a method for obtaining a porous film by crushing a polymer sheet containing bubbles, and a method using electrospinning can be used.

In the melt extraction method, inorganic fine particles and an organic liquid are melt-kneaded into a raw material mixture, extruded from a die at a temperature equal to or higher than the melting point of the fluoropolymer (A), or molded by a press or the like, and then cooled and solidified. Then, a porous structure is formed by extracting an organic liquid and inorganic fine particles.

The vapor coagulation method includes a saturated vapor or mist of a poor solvent that is compatible with the good solvent and does not dissolve the raw material mixture, on at least one surface of a thin film-like product made of a mixture solution obtained by dissolving the raw material mixture in a good solvent. This is a method for forcibly supplying steam.

The molding method 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).
Since a three-dimensional network structure is relatively easy to produce, a porous membrane produced by a non-solvent induced phase separation method has a high mechanical strength and is suitably used for producing a membrane having an asymmetric structure. Porous membranes produced by thermally induced phase separation tend to have excellent water permeability due to the relatively easy formation of a spherical structure, and also increase the concentration of the raw material mixture in the mixture solution during film formation. The mechanical strength can be improved. It is preferable to select a film formation method in consideration of these.

When using the thermally induced phase separation method, a step of dissolving the raw material mixture in a solvent that is a poor solvent or a good solvent at a relatively high temperature to obtain a solution of the raw material mixture, and a step of cooling and solidifying the mixture solution By passing, a porous film-like molded product can be obtained.

The mixture solution in which the raw material mixture is 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, The polymer matrix is fixed when a raw material mixture rich phase and a solvent rich phase are separated into two phases and the temperature is lower than the crystallization temperature, and a porous film is formed.

When using a thermally induced phase separation method, it is preferable that the said mixture solution is 10-60 weight% of raw material mixtures with respect to the sum total of a raw material mixture and a solvent. More preferably, it is 15 to 50% by weight.
By adjusting the concentration of the raw material mixture to an appropriate range, the viscosity of the mixture solution can be adjusted to an appropriate range. If the viscosity of the mixture solution is not within an appropriate range, there is a possibility that it cannot be formed into a porous membrane.

The poor solvent cannot dissolve the raw material mixture at 5% by weight or more at a temperature lower than 60 ° C., but it contains 60 ° C. or higher and the melting point of the resin (the melting point of the fluoropolymer (A) or other resin). Means a solvent that can be dissolved by 5% by weight or less below the melting point of the melting point of the fluoropolymer (A) and other resins, whichever is lower. A solvent capable of dissolving 5% by weight or more of the raw material mixture at a temperature lower than 60 ° C. with respect to the poor solvent is referred to as a good solvent. A solvent that does not dissolve or swell the raw material mixture up to the melting point of the resin or the boiling point of the liquid is called a non-solvent.

In the case of the above raw material mixture, examples of the poor solvent include cyclohexanone, isophorone, γ-butyrolactone, methyl isoamyl ketone, dimethyl phthalate, diethyl phthalate, propylene glycol methyl ether, propylene carbonate, diacetone alcohol, and glycerol triacetate. Examples include chain alkyl ketones, esters, glycol esters, organic carbonates, and the like, and mixed solvents thereof. Diphenyl carbonate, methyl benzoate, diethylene glycol ethyl acetate, benzophenone, and the like are also included. 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 solution. However, the solvent is not limited to this, and a good solvent may be used in consideration of the phase separation behavior of the raw material mixture.

Examples of good solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, trimethyl phosphate, and other lower alkyl ketones, esters, amides, and the like. A solvent is mentioned.

Non-solvents include, for example, water, hexane, pentane, benzene, toluene, methanol, ethanol, propanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol. , Pentanediol, hexanediol, low molecular weight polyethylene glycol and other aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic polyhydric alcohols, aromatic polyhydric alcohols, chlorinated hydrocarbons, or other chlorinated organic liquids and the like A mixed solvent etc. are mentioned.

When the thermally induced phase separation method is used, in the step of obtaining the mixture solution, it is preferable to dissolve the raw material mixture in a solvent that is a poor solvent or a good solvent at 20 to 220 ° C. More preferably, it is 30-200 degreeC. When dissolved at a relatively high temperature, the concentration of the raw material mixture can be increased, whereby high mechanical strength can be imparted to the polymer porous membrane produced through the subsequent steps.
When the said density | concentration is too high, the porosity of the polymer porous membrane obtained may become small, and there exists a possibility that water permeability performance may fall. Further, if the viscosity of the prepared mixture solution is not within an appropriate range, there is a possibility that it cannot be formed into a porous film-like molded product.

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

The cooling liquid that can be used as the cooling bath has a temperature lower than that of the mixture solution. For example, the solvent is a poor solvent or a good solvent having a temperature of 5 to 50 ° C. and a concentration of 60 to 100% by weight. Can be used. The cooling liquid may be a non-solvent or a non-solvent containing a poor solvent or a good solvent.

In the step of obtaining the porous film-like molded product, the concentration of the mixture solution, the composition of the solvent for dissolving the raw material mixture, and the composition of the cooling liquid constituting the cooling bath are important. By adjusting these compositions, it is also possible to control the porous structure of the polymer porous membrane that is completed through a subsequent process.

For example, by changing the combination of the composition of the mixture solution and the composition of the cooling liquid on one side and the other side of the porous membrane-shaped molded product, the structure of one side of the polymer porous membrane, The structure of the other surface can be different.

In the case of producing by a non-solvent induced phase separation method, the raw material mixture is dissolved in a solvent to obtain a mixture solution, and the solution is discharged from a base into a coagulation bath containing a non-solvent, thereby obtaining a porous material. A film-like molded product can be obtained.

By immersing the mixture solution in a coagulation bath containing a non-solvent, non-solvent-induced phase separation can be caused by using the mixture solution, the solvent in the coagulation bath, and the concentration gradient of the non-solvent as a driving force. it can. 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 membrane with the passage of time. 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 solution is preferably composed of a raw material mixture and a solvent. In addition to the raw material mixture and the solvent, the above-mentioned mixture solution further includes a non-solvent.
It is preferable that a raw material mixture is 5-35 weight% with respect to the sum total of a raw material mixture, a solvent, and a nonsolvent (when a nonsolvent is not included, the total of a raw material mixture and a solvent). More preferably, it is 10 to 25% by weight.
It is preferable that a non-solvent is 0.1-10 weight% with respect to the sum total of a raw material mixture, a solvent, and a nonsolvent. More preferably, it is 0.5 to 8% by weight.
By adjusting the concentration of the raw material mixture to an appropriate range, the viscosity of the mixture solution can be adjusted to an appropriate range. If the viscosity of the mixture solution is not within an appropriate range, there is a possibility that it cannot be formed into a porous membrane.

The mixture solution may be at room temperature or heated. For example, 10-35 degreeC is preferable.

In the non-solvent induced phase separation method, the method of obtaining the above mixture solution includes kneading all the raw material mixtures in advance and then dissolving them in a solvent to obtain a mixture solution. A method of obtaining a mixture solution by dissolving in a solvent together with the raw materials of the above, or a method of obtaining a mixture solution by previously kneading a part of the raw material mixture and then dissolving the kneaded material in a solution in which the remaining raw materials are dissolved. Examples thereof include a method of dissolving the raw material mixture in a solvent, a method of mixing each solution obtained by dissolving a part of the raw material mixture or each component of the raw material mixture in the solvent, and obtaining a mixture solution.
In addition, when each component of a raw material mixture is melt | dissolved in a solvent, the solvent which melt | dissolves each component may be the same kind of solvent, and a different kind of solvent may be sufficient as it.
In addition, when the mixture solution contains a non-solvent in addition to the raw material mixture and the solvent, the timing and method of adding the non-solvent in the step of obtaining the mixture solution are not particularly limited.
Among these, from the viewpoint of ease of preparation of the mixture solution, the step of obtaining the mixture solution in the non-solvent induced phase separation method is the step of obtaining the mixture solution by dissolving all the raw material mixtures in the solvent, or the raw material mixture Particularly preferred is a step of dissolving each of the above components in a solvent and mixing the resulting solutions and a non-solvent to obtain a mixture solution.

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 suitably used as the non-solvent.

In the step of obtaining the porous membrane-like molded product, 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 membrane-like molded product can be obtained by discharging a mixture solution obtained by dissolving a raw material mixture in a solvent from a die and then solidifying the mixture solution. . As the base, for example, a slit base, a double pipe base, a triple pipe base, or the like is used.

In the case of producing a hollow fiber membrane shaped product as the porous membrane shaped product, as the die, for example, a double tube die or a triple tube die for spinning a hollow fiber membrane is preferably used.

When using a double-tube base, discharge the mixture solution from the outer pipe of the double-tube base, and solidify in a coagulation bath or cooling bath while discharging hollow part forming fluid such as ion exchange water from the inner pipe. 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% by weight similar to 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. 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.

By changing the composition of the hollow portion forming fluid and the cooling liquid or coagulating liquid, it is possible to form a hollow fiber membrane-shaped molded article having two types of structures. The hollow portion forming fluid may be supplied after cooling. However, if the hollow fiber membrane-shaped molded article is sufficient to be solidified only by the cooling power of the cooling bath, the hollow portion forming fluid is supplied without cooling. May be.

The triple tube type die is suitable when two types of resin solutions are used. For example, by discharging two types of mixture solution from the outer tube and the intermediate tube of the triple tube type die, and solidifying in a coagulation bath or cooling bath while discharging the hollow portion forming liquid from the inner tube, the hollow fiber A film-like molded product can be obtained. In addition, the mixture solution is discharged from the outer tube of the triple tube type die, the resin solution made of resin other than fluoropolymer is discharged from the intermediate tube, and the solidification bath or cooling is performed while discharging the hollow portion forming fluid from the inner tube. By solidifying in a bath, a hollow fiber membrane shaped product can be obtained.

As described above, when a hollow fiber membrane shaped product is formed by a manufacturing method using a double tube type die or a triple tube type die, the amount of solidified liquid or cooling liquid is more than that when a flat membrane is produced. This is preferable in that it can be reduced.

When the polymer porous membrane to be produced is a hollow fiber membrane, a layer made of the fluoropolymer (A) or other than the fluoropolymer (A) on the outer surface or inner surface of the molded product obtained by the method described above A resin layer made of the above resin may be formed.
When a resin layer made of a resin other than the fluoropolymer (A) is formed, the resin layer made of another resin is integrated on the surface of the polymer porous film made of the fluoropolymer (A) and the rubber (B). A hollow fiber membrane can be obtained.

The resin layer can be formed by applying a solution of fluoropolymer (A) or a resin solution to the outer surface or inner surface of a hollow fiber membrane-shaped molded product. Examples of the method for applying the fluoropolymer (A) solution or the resin solution include a method in which a hollow fiber membrane-shaped molded product is crushed in the solution, or the solution is dropped onto the hollow fiber membrane-shaped molded product. Preferably used. As a method of applying the above solution to the inner surface of the hollow fiber membrane shaped product, a method of injecting the solution into the hollow fiber membrane shaped product is preferably used.
As a method for controlling the coating amount of the solution, in addition to the method for controlling the coating amount of the solution itself, the porous membrane is immersed in the solution, or after the solution is applied to the porous membrane, A method in which a part is scraped off or blown off using an air knife is also preferably used.

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

Further, when producing a composite membrane in which a porous substrate or the like is integrated as the polymer porous membrane of the present invention, a method of immersing the porous substrate in a mixture solution, on at least one surface of the porous substrate You may perform the process of apply | coating a mixture solution.

Further, after obtaining a porous membrane-like molded product, the molded product may be further stretched. Thereby, the water permeation performance and mechanical strength of the polymer porous membrane can be further improved.
In addition, when performing the alkali treatment process mentioned later, you may perform an extending | stretching process after performing an alkali treatment process.

In this step, as a method for controlling the pore size of the porous membrane-shaped molded product, for example, an additive for controlling the pore size is added to the mixture solution, and the porous membrane-shaped molded product is molded or porous. A method of controlling the pore diameter by eluting the additive after molding the film-like molded product can be employed. Moreover, you may make an additive remain in a porous film-shaped molded object as needed from a viewpoint of a hydrophilic improvement or a mechanical strength improvement.

Examples of the additive include organic compounds and inorganic compounds. As an organic compound, it is preferable that it is what melt | dissolves in the solvent which comprises a mixture solution. Further, it is preferable that the non-solvent induced phase separation method dissolves in the non-solvent contained in the coagulating liquid, and the thermally induced phase separation method dissolves in the solvent contained in the cooling liquid.

Examples of the organic compound include water-soluble polymers such as polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, polyethylene imine, polyacrylic acid, and textlan, surfactants, glycerin, and saccharides.

As the inorganic compound, a water-soluble compound is preferably used, and examples thereof include calcium chloride, lithium chloride, and barium sulfate.

As a method of controlling the pore size of the porous membrane-shaped molded product without using additives, a method of controlling the average pore size of the surface by controlling the phase separation rate according to the type, concentration and temperature of the non-solvent in the coagulation liquid is adopted. It is also possible to do. 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 solution is also effective for controlling the phase separation rate.

From the viewpoint of hydrophilization, mechanical strength improvement, and phase separation control, the above mixture solution is further added with additives such as polyvinylpyrrolidone, polymethyl methacrylate resin, montmorillonite, SiO ₂ , CaCO ₃ , PTFE and the like. May be included.

By passing through such a process, in the manufacturing method of the polymeric porous membrane of this invention, the porous polymeric membrane which consists of said fluoropolymer (A) and rubber | gum (B) can be manufactured.

In the method for producing a porous polymer membrane of the present invention, a step of performing an alkali treatment may be further performed.
Here, the step of performing the alkali treatment may be performed after the step of forming the raw material mixture into a porous film or before the step of forming into a porous film.

In the step of performing the alkali treatment (hereinafter also referred to as an alkali treatment step), the porous film-like molding is performed on an alkali treatment solution in which a solid or liquid alkali is dissolved in water and / or an alcohol having 1 to 8 carbon atoms. It is carried out by bringing the alkaline treatment solution into contact with the porous membrane-shaped molded article, for example, by immersing the product, or applying the alkali-treated solution to the porous membrane-shaped molded article.

Examples of the alkali include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali carbonates such as potassium carbonate, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, and alkali metals. Alternatively, alkaline earth metal alkoxides, organic amines such as trimethylamine, triethylamine, and the like can be given.

Although it will not specifically limit as said alcohol if it is C1-C8 alcohol, Ethanol or methanol is preferable.

The alkali concentration of the alkali treatment solution is not particularly limited. For example, when sodium hydroxide is used as the alkali, an alkali treatment solution of 0.01 to 8N may be used.

When the alkali treatment solution contains both water and the alcohol, the volume ratio between them is arbitrary, but is preferably about 30 to 70/70 to 30, for example.

In this step, when the molded article of the porous membrane is immersed in the alkaline treatment solution, the immersion time and the immersion temperature are not particularly limited, but are usually immersed in a solution at 5 to 70 ° C. for about several minutes to several days. Just do it.

In the method for producing a porous polymer membrane of the present invention, a wet treatment may be performed on the molded product of the porous membrane prior to the alkali treatment step. In particular, when the molded product of the porous film or the raw material mixture to be subjected to alkali treatment is difficult to wet, the wet treatment makes it easy to wet the alkali treatment solution.
The wet treatment may be performed, for example, by immersing an alkali treatment target in an alcohol such as methanol or ethanol and then substituting it with water.

Moreover, after the alkali treatment step, the alkali treatment solution may be replaced with water as necessary.

In the method for producing a porous polymer membrane of the present invention, as described above, after performing the step of subjecting the raw material mixture to the alkali treatment by the method described above, the step of forming the porous membrane is performed. Also good.
Furthermore, after performing the process which performs an alkali treatment with the method mentioned above with respect to a raw material mixture, the process shape | molded in the shape of a porous film may be performed, and an alkali treatment process may be performed again after that.

In the method for producing a porous polymer membrane of the present invention, through the alkali treatment step, a part of the VdF unit of the fluoropolymer (A) is dehydrated and added with water or alcohol. (1) A polymer porous membrane comprising a fluoropolymer (A) substituted with a unit and containing the fluoropolymer (A1) and a rubber (B) can be obtained. And since the number of double bonds in the fluoropolymer (A) is small, the solvent solubility is not impaired and the film-forming property is excellent, and deterioration after film formation hardly occurs, so that it is excellent as a polymer porous film. Become.

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.
In the following examples, a polymer porous membrane was prepared and evaluated by the following method.

[Maximum breaking strength]
The maximum breaking strength was measured according to JIS K6301 using an autograph (manufactured by SHIMADZU). When the sample was a porous flat membrane, the breaking strength of the test piece was measured under the conditions of a distance between chucks of 20 mm and a tensile speed of 20 mm / min, and the cross-sectional area before the tensile test was obtained as a unit measurement area. When the sample was a hollow fiber membrane, the breaking strength of the test piece was measured 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 was determined as a unit measurement area.

[Maximum elongation]
The maximum point elongation was measured using an autograph (manufactured by SHIMADZU) according to JIS K6301. When the sample was a porous flat membrane, the breaking strength of the test piece was measured under the conditions of a distance between chucks of 20 mm and a tensile speed of 20 mm / min, and obtained from the elongation at the maximum point with reference to 20 mm between the chucks. When the sample was a hollow fiber membrane, the breaking strength of the test piece was measured under the conditions of a distance between chucks of 50 mm and a tensile speed of 200 mm / min, and obtained from the elongation at the maximum point based on the distance between chucks of 50 mm.

[Alkali treatment]
The alkali treatment in the following examples / comparative examples was performed under the following conditions.
Alkali treatment: The polymer porous membrane was immersed in an aqueous solution (alkali treatment solution) of 1N NaOH in ethanol / water (50/50% by volume) for 24 hours.

[Surface measurement by XPS (X-ray photoelectron spectroscopy)]
The surface of the polymer porous membrane (and the porous membrane-like molded product) was measured by XPS (X-ray photoelectron spectroscopy) by the following method.
For the measurement, ESCA3400 (manufactured by SHIMADZU) was used. Measurement was performed under the conditions of using a MgKα ray (1253.6 eV) as a radiation source and a measurement area diameter of about 3 mm and a detection depth of about 7 nm (photoelectron extraction angle 90 °).

[Static contact angle of water on membrane surface]
A porous polymer membrane having an average pore diameter of 0.01 to 0.1 μm on the outermost surface was prepared, and the static contact angle of water (25 ° C.) in a state where the porous polymer membrane was sufficiently dried Was measured using DropMaster 701 (manufactured by Kyowa Interface Science Co., Ltd.) using pure water as a measurement solvent.

[Example 1]
In the screw tube, 2.88 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 0.72 g of fluoro rubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), Crosslinking aid (UA-1100) 0.36 g, photoinitiator (IRGACURE184 36 mg, IRGACURE369 36 mg), photosensitizer (DETX) 36 mg, tween 40 0.36 g, dimethylacetamide 15.68 g were mixed at 25 ° C. to obtain a polymer solution. It was.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was prepared using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.70 MPa and the maximum point elongation was 225%.
Further, the ratio (O / F) on the surface of the molded article measured by XPS was 0.119, and the ratio (C—F / C—H) was 0.67. The static contact angle of water was 92.0 °.
The ratio (O / F) on the surface of the molded article measured by XPS after alkali treatment after subjecting the obtained polymer porous membrane to alkali treatment was 0.106, and the ratio (C−F / C—H) was 0.50. The static contact angle of water was 89.5 °.

[Example 2]
In the screw tube, 2.88 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 0.72 g of fluoro rubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), A polymer solution was prepared by mixing 0.36 g of tween 40 and 16.04 g of dimethylacetamide at 25 ° C.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was produced using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.60 MPa and the maximum point elongation was 161%. The static contact angle of water was 79.0 °.

Example 3
In the screw tube, 3.42 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 0.18 g of fluoro rubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), A polymer solution was prepared by mixing 0.36 g of tween 40 and 16.06 g of dimethylacetamide at 25 ° C.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
A tensile test piece was prepared using a dumbbell No. 6 mold and subjected to a tensile test. The maximum point breaking strength was 1.49 MPa and the maximum point elongation was 214%.
Further, the ratio (O / F) on the surface of the molded article measured by XPS was 0.106, and the ratio (C—F / C—H) was 0.60. The static contact angle of water was 89.1 °.
The ratio (O / F) on the surface of the molded article measured by XPS after alkali treatment after subjecting the obtained polymer porous membrane to alkali treatment was 0.124, and the ratio (C−F / C—H) was 0.84. The static contact angle of water was 83.7 °.

Example 4
In a screw tube, 2.52 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 1.08 g of fluoro rubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), A polymer solution was prepared by mixing 0.36 g of tween 40 and 16.06 g of dimethylacetamide at 25 ° C.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was produced using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.98 MPa and the maximum point elongation was 216%.

Example 5
To the screw tube, 3.24 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 0.36 g of fluoro rubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), A polymer solution was prepared by mixing 0.36 g of tween 40 and 16.06 g of dimethylacetamide at 25 ° C.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was prepared using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 1.15 MPa and the maximum point elongation was 129%.

Example 6
In the screw tube, 1.80 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 1.80 g of fluoro rubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), A polymer solution was prepared by mixing 0.36 g of tween 40 and 16.06 g of dimethylacetamide at 25 ° C.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was produced using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.61 MPa and the maximum point elongation was 144%.

[Comparative Example 1]
In a screw tube, fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) 3.60 g, cross-linking aid (UA-1100) 0.36 g, photoinitiator (IRGACURE 184 36 mg, IRGACURE 369 36 mg), 36 mg of photosensitizer (DETX), 0.36 g of tween 40, and 15.57 g of dimethylacetamide were mixed at 25 ° C. to obtain a polymer solution.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was prepared using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.53 MPa and the maximum point elongation was 94%.
Further, the ratio (O / F) on the surface of the molded article measured by XPS was 0.050, and the ratio (C—F / C—H) was 0.99. The static contact angle of water was 96.3 °.
The ratio (O / F) on the molded product surface measured by XPS after alkali treatment after subjecting the obtained polymer porous membrane to alkali treatment was 0.116, and the ratio (C−F / C—H) was 0.58. The static contact angle of water was 93.9 °.

[Comparative Example 2]
In a screw tube, 3.60 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]), 0.36 g of tween 40, and 16.04 g of dimethylacetamide were mixed at 25 ° C. to obtain a polymer solution.
The obtained polymer solution was applied onto a glass plate using an applicator (250 μm) and immediately immersed in a water coagulation bath at 25 ° C. for 1 minute to obtain a flat polymer porous membrane.
When a tensile test piece was produced using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.61 MPa and the maximum point elongation was 113%.

[Comparative Example 3]
In a screw tube, 2.88 g of polyvinylidene fluoride, 0.72 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), 0.36 g of tween 40, 16.04 g of dimethylacetamide were mixed at 25 ° C. A polymer solution was obtained.
The obtained polymer solution was coated on a glass plate using an applicator (250 μm), and immediately immersed in a water coagulation bath at 25 ° C. for 5 minutes to obtain a flat polymer porous membrane.
A tensile test piece was prepared using a dumbbell No. 6 mold and subjected to a tensile test. The maximum point breaking strength was 0.90 MPa and the maximum point elongation was 74%.
Further, the ratio (O / F) on the surface of the molded article measured by XPS was 0.127, and the ratio (C—F / C—H) was 0.74. The static contact angle of water was 91.3 °.
The ratio (O / F) on the surface of the molded article measured by XPS after alkali treatment after subjecting the obtained polymer porous membrane to alkali treatment was 0.097, and the ratio (C−F / C—H) was 0.66. The static contact angle of water was 106.9 °.

[Comparative Example 4]
The screw tube was mixed with 3.60 g of polyvinylidene fluoride, 0.36 g of tween 40, and 16.04 g of dimethylacetamide at 25 ° C. to obtain a polymer solution.
The obtained polymer solution was coated on a glass plate using an applicator (250 μm), and immediately immersed in a water coagulation bath at 25 ° C. for 5 minutes to obtain a flat polymer porous membrane.
When a tensile test piece was produced using a dumbbell No. 6 mold and a tensile test was performed, the maximum point breaking strength was 0.96 MPa and the maximum point elongation was 59%.
Further, the ratio (O / F) on the surface of the molded article measured by XPS was 0.044, and the ratio (C—F / C—H) was 0.96. The static contact angle of water was 93.1 °.
The ratio (O / F) on the surface of the molded article measured by XPS after alkali treatment after subjecting the obtained polymer porous membrane to alkali treatment was 0.109, and the ratio (C−F / C—H) was 0.64. The static contact angle of water was 112.7 °.

Example 7
16.2 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 1.8 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), dimethylformamide 78. 9 g, tween 40 2.4 g, and crosslinking aid (TAIC) 0.75 g were mixed at 25 ° C. to obtain a polymer solution. 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 0.90 mm and an inner diameter of 0.76 mm. The pure water permeability coefficient at 25 ° C. was 1.2 × 10 ⁻¹⁰ [m ³ / m ² / Pa / s], and the blocking rate of 80 nm polystyrene fine particles was 98% or more. The maximum point breaking strength was 2.1 MPa, and the maximum point elongation was 530%.

Example 8
14.4 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 3.6 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), dimethylformamide 78. 9 g, tween 40 2.4 g, and crosslinking aid (TAIC) 0.75 g were mixed at 25 ° C. to obtain a polymer solution. 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 0.84 mm and an inner diameter of 0.72 mm. The pure water permeability coefficient at 25 ° C. was 1.4 × 10 ⁻¹⁰ [m ³ / m ² / Pa / s], and the blocking rate of 80 nm polystyrene fine particles was 98% or more. The maximum point breaking strength was 2.9 MPa, and the maximum point elongation was 590%.

Example 9
13.5 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 1.5 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), dimethylformamide 65. 8 g, 2.0 g of tween 40, 0.84 g of Pluronic, and 0.62 g of a crosslinking aid (TAIC) were mixed at 25 ° C. to obtain a polymer solution. 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 0.85 mm and an inner diameter of 0.64 mm. The pure water permeability coefficient at 25 ° C. was 1.1 × 10 ⁻⁹ [m ³ / m ² / Pa / s], and the blocking rate of 80 nm polystyrene fine particles was 98% or more. The maximum point breaking strength was 1.4 MPa, and the maximum point elongation was 310%.

Example 10
16.2 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 1.8 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), crosslinking aid ( UA-1100) 0.90 g, photoinitiator (IRGACURE184 180 mg, IRGACURE369 180 mg), dimethylformamide 78.4 g and tween 40 2.4 g were mixed at 25 ° C. to obtain a polymer solution. 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 0.92 mm and an inner diameter of 0.70 mm. The pure water permeability coefficient at 25 ° C. was 5.0 × 10 ⁻¹⁰ [m ³ / m ² / Pa / s], and the blocking rate of 100 nm polystyrene fine particles was 54%. The maximum point breaking strength was 1.6 MPa, and the maximum point elongation was 450%.

Example 11
14.4 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 3.6 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), crosslinking aid ( UA-1100) 0.90 g, photoinitiator (IRGACURE184 180 mg, IRGACURE369 180 mg), dimethylformamide 78.4 g and tween 40 2.4 g were mixed at 25 ° C. to obtain a polymer solution. 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 0.94 mm and an inner diameter of 0.76 mm. The pure water permeability coefficient at 25 ° C. was 4.4 × 10 ⁻¹⁰ [m ³ / m ² / Pa / s], and the blocking rate of 100 nm polystyrene fine particles was 41%. The maximum point breaking strength was 1.6 MPa, and the maximum point elongation was 540%.

Example 12
14.4 g of fluoropolymer (vinylidene fluoride / tetrafluoroethylene = 80/20 [molar ratio]) and 3.6 g of fluororubber (vinylidene fluoride / hexafluoropropylene = 78/22 [molar ratio]), crosslinking aid ( (UA-1100) 0.90 g, dimethylformamide 78.7 g, and tween 40 2.4 g were mixed at 25 ° C. to obtain a polymer solution. 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 0.90 mm and an inner diameter of 0.74 mm. The pure water permeability coefficient at 25 ° C. was 4.5 × 10 ⁻¹⁰ [m ³ / m ² / Pa / s], and the blocking rate of 100 nm polystyrene fine particles was 93%. The maximum point breaking strength was 2.0 MPa, and the maximum point elongation was 460%.

The polymer porous membrane of the present invention can be used for various applications, and is particularly suitable for water treatment applications.

Claims (14)

A polymer porous membrane comprising a fluoropolymer (A) having a vinylidene fluoride unit and a tetrafluoroethylene unit and a rubber (B). 2. The porous polymer membrane according to claim 1, wherein the rubber (B) is fluororubber. The porous polymer membrane according to claim 1 or 2, wherein the vinylidene fluoride unit / tetrafluoroethylene unit is in a molar ratio of 50 to 90/50 to 10. 4. The ratio (O / F) of the O element content on the surface to the F element content measured by XPS (X-ray photoelectron spectroscopy) is 0.050 or more and less than 0.150. Polymer porous membrane. The ratio of C—F bonds to C—H bonds (C—F / C—H) on the surface as measured by XPS (X-ray photoelectron spectroscopy) is greater than 0.50. The polymeric porous membrane as described. The polymeric porous membrane according to claim 1, wherein the fluoropolymer (A) has a unit represented by the following formula (1).
—CHX ¹ —CX ² (OR) — (1)
(In the formula, ^one of X ¹ and X ² is a hydrogen atom and the other is a fluorine atom, and R is either a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.) The polymer porous membrane according to claim 6, wherein R in the formula (1) is hydrogen, a methyl group or an ethyl group. The polymer porous membrane according to claim 1, which is a hollow fiber membrane. 9. The polymer porous membrane according to claim 1, which is used for water treatment. A method for producing a porous polymer membrane according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9.
At least for the mixture of the fluoropolymer (A) having vinylidene fluoride units and tetrafluoroethylene units and the rubber (B),
A method for producing a polymer porous membrane, comprising performing a step of forming a porous membrane. The method for producing a porous polymer membrane according to claim 10, wherein in the step of forming 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. Furthermore, the manufacturing method of the polymeric porous membrane of Claim 10 or 11 which performs the process of performing an alkali treatment in presence of water and / or C1-C8 alcohol. The method for producing a porous polymer membrane according to claim 12, wherein the alcohol is ethanol or methanol. A hollow fiber membrane comprising the polymer porous membrane according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9.