JP2017047411A - Hollow porous film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow porous film having high water-permeable performance.SOLUTION: There is provided a porous film containing a film formation polymer (A) and an amphiphatic copolymer (B) comprising a hydrophobic monomer (b1) and a hydrophilic monomer (b2), in which the peak intensity ratio of FT-IR on a porous film surface is 0.4 or higher and 10 or lower, and which is a hollow fiber-shaped porous film in which a surface aperture ratio of the film surface is 20% or higher and 50% or lower.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hollow porous membrane having high water permeability and surface hydrophilicity.

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

As a porous film excellent in hydrophilicity, a porous film in which the surface of a porous substrate is subjected to a hydrophilic treatment with a copolymer composed of a hydrophilic monomer and a hydrophobic monomer is known.
For example, a porous film including a hydrophobic film-forming polymer such as polyvinylidene fluoride and a random copolymer composed of a hydrophilic monomer and a hydrophobic monomer has been proposed (for example, Patent Document 1). In addition, a porous film formed from a polymer obtained by polymerizing a monomer composition containing a film-forming polymer, a (meth) acrylic acid ester macromonomer, and other monomers has been proposed (for example, patents). Reference 2).

JP 2006-239680 A International Publication No. WO2014 / 142231

  However, the porous membrane described in Patent Document 1 has a problem of low water permeability and membrane surface hydrophilicity. In addition, the porous membrane described in Patent Document 2 has a problem that water permeability is not sufficient.

  An object of the present invention is to provide a hollow fiber-like porous membrane having high water permeability and surface hydrophilicity.

The present invention has the following aspects.
[1] A hollow porous membrane comprising a film-forming polymer (A) and an amphiphilic copolymer (B) comprising a hydrophobic monomer (b1) and a hydrophilic monomer (b2),
FT-IR peak intensity ratio (peak intensity appearing at 1726 to 1730 cm ⁻¹ / peak intensity appearing at 1398 to 1402 cm ⁻¹⁾ on the surface of the hollow porous membrane is 0.4 or more and 10 or less, and A hollow porous membrane having a surface porosity of 20% to 50% on the membrane surface.
[2] The hollow porous membrane according to [1], wherein the film-forming polymer (A) is polyvinylidene fluoride.
[3] The hollow porous membrane according to [1] or [2], wherein the hydrophilic monomer (b2) is a (meth) acrylic monomer.
[4] The hollow porous membrane according to any one of [1] to [3], wherein the main component of the amphiphilic copolymer (B) is a graft copolymer.
[5] The hollow shape according to any one of [1] to [4], wherein the amphiphilic copolymer (B) contains 5 to 99 wt% of the hydrophobic monomer (b1) unit. Porous membrane.

  The present invention makes it possible to provide a hollow porous membrane having high water permeability and surface hydrophilicity. Further, according to the present invention, it can be expected that the hydrophilization step is omitted in commercialization.

It is an example of the peak intensity ratio of FT-IR of the porous membrane surface in this invention.

Hereinafter, this description will be described in detail.
<Hollow porous membrane>
In the present invention, the hollow porous membrane is a hollow porous membrane containing a film-forming polymer (A) and an amphiphilic copolymer (B) comprising a hydrophobic monomer (b1) and a hydrophilic monomer (b2). The film has the following characteristics (1) and (2). Thereby, high water permeability and surface hydrophilicity can be expressed.
(1) FT-IR peak intensity ratio (peak intensity appearing at 1726 to 1730 cm ⁻¹ / peak intensity appearing at 1398 to 1402 cm ⁻¹ ) on the surface of the porous film is 0.4 to 10 (2) Film Surface porosity of the surface is 20% or more and 50% or less

The hollow porous membrane has an FT-IR peak intensity ratio (from 1726 to 1730 cm ⁻¹⁾ on the surface of the porous membrane from the viewpoint of pore connectivity, hydrophilicity and fouling resistance of the porous membrane. (Intensity / peak intensity appearing at 1398 to 1402 cm ⁻¹ ) is preferably 0.4 or more and 10 or less, more preferably 0.45 or more and 8 or less, and 0.5 or more and 7 or less. Particularly preferred.
Furthermore, from the viewpoint of water permeability and strength of the porous membrane, the surface porosity of the membrane surface is preferably 20% or more and 50% or less, and more preferably 25% or more and 45% or less.

[FT-IR peak intensity ratio]
The peak intensity ratio of FT-IR in the present invention is a value obtained by an infrared total reflection absorption spectrum method (ATR method).
The analysis was performed on the surface of the porous membrane which was immersed in an 80% ethanol aqueous solution at 60 ° C. for 4 hours and washed. As shown in FIG. 1, the film-forming polymer to the position of 1726~1730cm ^-1 (A
The peak derived from the film-forming polymer (A) and the amphiphilic copolymer (B) at the position of 1398 to 1402 cm ⁻¹ was used for the calculation of the intensity ratio. This peak intensity ratio is a value indicating the amount of the amphiphilic copolymer (B) present on the surface of the porous membrane after washing.

[Surface open area ratio]
The surface area ratio in the present invention is a value obtained as a result of image analysis by Image Pro on the film surface observed with a scanning electron microscope (manufactured by JEOL Ltd., product name: JSM-6340F).

<Film-forming polymer (A)>
In the present invention, the film-forming polymer (A) is for maintaining the structure of a hollow porous film (hereinafter also referred to as a porous film). The composition of the film-forming polymer (A) can be selected according to the characteristics required for the porous film. For example, when chemical resistance, oxidation deterioration resistance and heat resistance are required as the film-forming polymer (A), polyvinylidene fluoride (PVDF), PVDF-co-hexafluoropropylene (HFP), ethylene-co -Chlorotrifluoroethylene (ECTFE), polyvinyl fluoride, polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyethylene, polypropylene, polystyrene, polystyrene derivatives, polyamide, polyurethane, polycarbonate, polysulfone, polyethersulfone and cellulose Acetate is mentioned.
Further, from the viewpoint of promoting non-solvent phase separation, the film-forming polymer (A) is preferably a polymer that can be dissolved in a solvent described later and does not dissolve in pure water. Among the aforementioned polymers, PVDF is preferable from the viewpoint of compatibility with the amphiphilic copolymer (B) described later and the solvent (I) described later.

  The film-forming polymer (A) preferably has a mass average molecular weight (hereinafter referred to as “Mw”) of 100,000 to 2,000,000 from the viewpoint of the mechanical strength of the porous film and the solubility in a solvent. 300,000 to 1,500,000 are more preferred.

The content of the film-forming polymer (A) in the porous film is based on the total amount of 100 wt% of the film-forming polymer (A) and the amphiphilic copolymer (B) from the viewpoint of porosity and hydrophilicity. 20 to 95 wt% is preferable, and 40 to 80 wt% is more preferable.
In the present invention, “high hydrophilicity” means that the contact angle with respect to pure water is 75 ° or less.

In the hollow porous membrane of the present invention, the thickness is preferably 10 μm or more and 1,000 μm or less, and more preferably 30 μm or more and 800 μm or less from the viewpoint of stretchability, durability, and production cost.
Further, the outer diameter of the hollow porous membrane is preferably 20 to 2,000 μm, more preferably 40 to 1,500 μm from the viewpoint of yarn breakage suppression and flatness suppression.

<Solvent (I)>
Examples of the solvent (I) include hydrocarbons such as toluene; diethyl ether, tetrahydrofuran and the like in terms of solubility and ease of handling of the film-forming polymer (A) and the amphiphilic copolymer (B) described later. Ethers; halogenated hydrocarbons such as dichloromethane and chloroform; ketones such as acetone; alcohols such as methanol; nitriles such as acetonitrile; vinyl esters such as ethyl acetate; carbonates such as ethylene carbonate; and supercritical carbon dioxide. Among these, tetrahydrofuran (THF), dimethylformamide (DMF), dimethyl are preferred in terms of solubility and ease of handling of the film-forming polymer (A), the polymer (B) and the polymer (C) containing vinylpyrrolidone units. Acetamide (DMAc), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP) are preferred. Solvent (II) can be used individually or in combination of 2 or more types.

<Amphiphilic copolymer (B)>
In the present invention, the amphiphilic copolymer (B) is obtained by polymerizing a monomer composition containing a hydrophobic monomer (b1) and a hydrophilic monomer (b2).
The number average molecular weight (hereinafter referred to as “Mn”) of the amphiphilic copolymer (B) is 1,000 to 5,000,000 in terms of tensile strength, tensile elongation, bending strength and thermal stability. It is preferable that it is 5,000 or more and 300,000 or less.
In the amphiphilic copolymer (B), from the viewpoint of easy incorporation into the film-forming polymer (A), the content of the hydrophobic monomer (b1) unit is preferably 5 wt% or more and 99 wt% or less, and 20 wt%. It is more preferably 98 wt% or less and particularly preferably 40 wt% or more and 95 wt% or less.
This is because the molecular entanglement with the film-forming polymer (A) is increased, thereby forming a communication structure in the porous film.

  In the amphiphilic copolymer (B), the content of the hydrophilic monomer (b2) unit is preferably 1 wt% or more and 95 wt% or less, more preferably 2 wt% or more and 80 wt% or less, from the viewpoint of openness. % To 60 wt% is particularly preferable.

  Examples of the method for producing the polymer (B) include a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these, the solution polymerization method is preferable from the viewpoint of polymerization reactivity of the hydrophobic monomer (b1) and the hydrophilic monomer (b2).

  From the viewpoint of imparting surface hydrophilicity to the hollow porous membrane, the amphiphilic copolymer (B) is a graft copolymer having a structure having a hydrophilic chain in the main chain and a hydrophobic chain in the side chain. preferable. This can be presumed to be because the entanglement between the molecules of the hydrophobic chain of the amphiphilic copolymer (B) and the film-forming polymer (A), which is also hydrophobic, becomes strong.

<Solvent (II)>
Examples of the solvent (II) used when the amphiphilic copolymer (B) is produced by a solution polymerization method include hydrocarbons such as toluene; ethers such as diethyl ether and tetrahydrofuran; dichloromethane, chloroform and the like. Examples include halogenated hydrocarbons; ketones such as acetone; alcohols such as methanol; nitriles such as acetonitrile; vinyl esters such as ethyl acetate; carbonates such as ethylene carbonate; and supercritical carbon dioxide. Among these, tetrahydrofuran (THF), dimethylformamide (DMF), dimethyl are preferred in terms of solubility and ease of handling of the film-forming polymer (A), the polymer (B) and the polymer (C) containing vinylpyrrolidone units. Acetamide (DMAc), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP) are preferred. Solvent (II) can be used individually or in combination of 2 or more types.

[Hydrophobic monomer (b1)]
In the present invention, the hydrophobic monomer (b1) forms an amphiphilic copolymer. Here, the term “hydrophobic” means that the segment is insoluble or non-dispersible in water.
Among the hydrophobic monomers (b1), examples of useful ethylenically unsaturated monomers include, but are not limited to: styrene, hydrophobic derivatives of styrene, conjugated dienes, acrylic acid C1-30 linear, cyclic, or branched alkyl and aryl esters, methacrylic acid C1-30 linear, cyclic, or branched alkyl and aryl esters, olefins, fluorine-containing monomers, and silicon-containing monomers .
Useful methacrylic monomers are preferred from the standpoint of availability and the balance of mechanical properties of the resulting copolymer.
From the viewpoint of molecular entanglement with the film-forming polymer (A) and solubility in a solvent, the number average molecular weight of the hydrophobic block (hereinafter referred to as “Mn”) is preferably 500 or more and 120,000 or less, Is more preferably 5,000 or more and 80,000 or less.

Examples of useful methacrylic monomers from the viewpoint of easy availability and mechanical property balance of the resulting copolymer include, but are not limited to, the following: methyl methacrylate, methacrylic acid n-butyl, lauryl methacrylate, dodecyl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate, methacrylic acid, Blemmer PME-100, Blemmer PME -200 and Bremmer PME-400.
Among these, when the film-forming polymer (A) is PVDF, methyl methacrylate is particularly preferable from the viewpoint of good compatibility with PVDF.

<Solvent (III)>
Examples of the solvent (III) used for obtaining the above-mentioned hydrophobic monomer (b1) by solution polymerization include hydrocarbons such as toluene; ethers such as diethyl ether and tetrahydrofuran; halogenated carbonization such as dichloromethane and chloroform. Examples include hydrogen; ketones such as acetone; alcohols such as methanol; nitriles such as acetonitrile; vinyl esters such as ethyl acetate; carbonates such as ethylene carbonate; and supercritical carbon dioxide. These can be used alone or in combination of two or more.

[Hydrophilic monomer (b2)]
In the present invention, the hydrophilic monomer (b2) forms an amphiphilic copolymer.
Here, the term “hydrophilic” means that the segment is water soluble or water dispersible or generally capable of absorbing and / or transmitting water.
Among the hydrophilic monomers (b2), useful ethylenically unsaturated monomers include, but are not limited to: acrylic acid, methacrylic acid, and salts of methacrylic acid and acrylic acid Esters, anhydrides and amides; dicarboxylic anhydrides; carboxyethyl acrylate; hydrophilic derivatives of acrylates; hydrophilic derivatives of styrene;
From the viewpoint of easy availability and the balance of mechanical properties of the copolymer obtained, useful hydrophilic derivatives of acrylates are preferred. Examples of useful acrylic monomers include, but are not limited to, the following from the viewpoint of easy availability and the balance of mechanical properties of the resulting copolymer: methyl acrylate, acrylic acid n-butyl, lauryl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, acrylic acid.
Further, from the viewpoint of hydrophilicity and solubility in a solvent, the Mn of the hydrophilic block is preferably 1,000 to 160,000, more preferably 5,000 to 60,000.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to this.

(FT-IR measurement method)
The peak intensity ratio of FT-IR was measured by an infrared total reflection absorption spectrum method (ATR method) using Varian UMA600. The measurement was performed on the surface of the porous membrane which was immersed in an 80% ethanol aqueous solution at 60 ° C. for 4 hours and washed.

(Surface open area measurement method)
The surface open area ratio and the average surface pore diameter are values calculated by image analysis using Image Pro for the film surface observed with a scanning electron microscope (manufactured by JEOL Ltd., product name: JSM-6340F).

(Water permeability measurement method)
One end of the porous membrane was potted with a urethane resin (Nippon Polyurethane Co., Ltd., Coronate 4403, Nippon Run 4221), and inserted into the hose connected to the pressure tank from the side not potted. A pressure of 100 kPa and 10 kPa was applied to the pressure tank, and the amount of water coming out from the potting side was measured. The water permeability was calculated by dividing the amount of water by the effective membrane area, measurement time, and measurement pressure.

(Measurement method of Mn, Mw / Mn)
Mn and Mw / Mn of the amphiphilic copolymer (B) were determined under the following conditions using GPC (“HLC-8220” (trade name) manufactured by Tosoh Corporation).
Column: TSK GUARD COLUMN SUPER HZ-L (4.6 × 35 mm) and two TSK-GEL SUPER HZM-N (6.0 × 150 mm) connected in series Eluent: Chloroform, DMF or THF
Measurement temperature: 40 ° C
Flow rate: 0.6 mL / min In addition, Mw and Mn are polymethyl methacrylate (Mp (peak top molecular weight) 141,500, 55,600, 10,290, and 1,590) manufactured by Polymer Laboratories). It was obtained using a calibration curve prepared using

(Synthesis Example 1; Synthesis of Cobalt Chain Transfer Agent CoBF-1)
In a reactor equipped with a stirrer, 1.00 g of cobalt acetate (II) tetrahydrate (manufactured by Wako Pure Chemical Industries, Ltd., Wako Special Grade), diphenylglyoxime (manufactured by Tokyo Chemical Industry Co., Ltd.) under a nitrogen atmosphere. , EP grade) 1.93 g and 80 ml of diethyl ether (special grade, manufactured by Kanto Chemical Co., Ltd.) previously deoxygenated by nitrogen bubbling were added and stirred at room temperature for 30 minutes. Next, 10 ml of boron trifluoride diethyl ether complex (manufactured by Tokyo Chemical Industry Co., Ltd., EP grade) was added, and the mixture was further stirred for 6 hours. The mixture was filtered, and the solid was washed with diethyl ether (manufactured by Kanto Chemical Co., Ltd., special grade) and dried in vacuo for 15 hours to obtain 2.12 g of a cobalt chain transfer agent CoBF-1 as a reddish brown solid.

(Synthesis Example 2; Synthesis of Dispersant 1)
In a reactor equipped with a stirrer, a condenser tube and a thermometer, 61.6 wt% of 17% potassium hydroxide aqueous solution, 19.1 wt% of methyl methacrylate (trade name: Acryester M manufactured by Mitsubishi Rayon Co., Ltd.) and Charged 19.3 wt% of deionized water. Subsequently, the liquid in the reaction apparatus was stirred at room temperature, and after confirming an exothermic peak, it was further stirred for 4 hours. Thereafter, the reaction solution in the reaction apparatus was cooled to room temperature to obtain a potassium methacrylate aqueous solution.
Next, in a polymerization apparatus equipped with a stirrer, a condenser tube and a thermometer, deionized water 900 wt%, 42% aqueous 2-sulfoethyl sodium methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester SEM-Na) ) 70 wt%, potassium methacrylate aqueous solution 16 wt% and methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) 7 wt% were added and stirred. The temperature was raised to. In the mixture, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-50) as a polymerization initiator was added in an amount of 0.053 wt%. The temperature was raised to 60 ° C. After the introduction of the polymerization initiator, 1.4 wt% of methyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester M) was added in 15 portions every 15 minutes. Thereafter, the liquid in the polymerization apparatus was kept at 60 ° C. for 6 hours while stirring, and then cooled to room temperature, whereby Dispersant 1 having a solid content of 8% was obtained as a transparent aqueous solution.

(Synthesis Example 3; Synthesis of hydrophobic monomer (b1))
In a flask with a condenser tube, methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) 100 wt%, deionized water 150 wt%, sodium sulfate 1.39 wt%, dispersant 1, 1.53 wt%, CoBF −1, 0.00075 wt% was charged. In a state where the liquid in the flask was heated to 70 ° C., CoBF-1 was dissolved, and the inner wt% was replaced with nitrogen by nitrogen bubbling. Subsequently, after adding AIBN and 1 mass%, it hold | maintained for 6 hours in the state which maintained internal temperature at 70 degreeC, and superposition | polymerization was completed. Thereafter, the polymerization reaction product was cooled to room temperature and further filtered to recover the polymer. The obtained polymer was washed with water and then vacuum-dried at 50 ° C. overnight to obtain a hydrophobic monomer (b1). Mn of the hydrophobic monomer (b1) was 7,000, and Mw / Mn was 3.0. The introduction rate of the terminal double bond of the hydrophobic monomer (b1) was almost 100%. In the hydrophobic monomer (b1), R in the formula (1) was a methyl group.

(Synthesis Example 4; Synthesis of Amphiphilic Copolymer (B-1))
In a flask with a condenser tube, methyl methacrylate (Mitsubishi Rayon Co., Ltd.) (65 wt%) as a hydrophobic monomer, HEA (2-hydroxyethyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) as a hydrophilic monomer (b2), First, a monomer composition containing 35 wt% and DMAc (N, N-dimethylacetamide, manufactured by Wako Pure Chemical Industries, Ltd., Wako Special Grade) 150 wt% as a solvent was added, and the inner wt% was replaced with nitrogen by nitrogen bubbling. did. Next, after heating the monomer composition and maintaining the internal temperature at 70 ° C., AIBN 0.1 wt% (Wako Pure Chemical Industries, Ltd., Wako Special Grade) was added to the monomer composition as a radical polymerization initiator, It was held for 4 hours, then heated to 80 ° C. and held for 30 minutes to complete the polymerization, and a polymerization reaction product was obtained. Thereafter, the polymerization reaction product was cooled to room temperature and reprecipitated with deionized water. The polymer precipitated by reprecipitation was collected and dried under vacuum overnight at 50 ° C. and 50 mmHg (6.67 kPa) or less to obtain an amphiphilic copolymer (B-1) (PMMA-) as a graft copolymer. g-PHEA) was obtained. The yield of the obtained amphiphilic copolymer (B-1) was almost 100%. Mn of the amphiphilic copolymer (B-1) was 71,000, and Mw / Mn was 3.0.

(Synthesis Example 5; Synthesis of Amphiphilic Copolymer (B′-1))
Hydrophobic monomer (b1) methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) 50 wt%, hydrophilic monomer (b2) HEA (2-hydroxyethyl acrylate (Wako Pure Chemical Industries, Ltd.) Manufactured by Wako No. 1)) 50 wt%, toluene (manufactured by Wako Pure Chemical Industries, Ltd., reagent special grade) 150 wt%, amphiphilic copolymer (B′-1) (PMMA-r) which is a random copolymer -PHEA). Mn of the amphiphilic copolymer (B′-1) was 89,000, and Mw / Mn was 6.8.

(Synthesis Example 6; Synthesis of Amphiphilic Copolymer (B′-2))
Methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) 70 wt% as the hydrophobic monomer (b1), and HEMA (2-hydroxyethyl methacrylate (Mitsubishi Rayon Co., Ltd.) as the hydrophilic monomer (b2) ) An amphiphilic copolymer (B′-2) (PMMA-r-HEMA), which is a random copolymer, was obtained in the same manner as in Synthesis Example 5 except that 30 wt% was used. The Mn of B′-1) was 105,000, and Mw / Mn was 3.0.

(Synthesis Example 7; Synthesis of Amphiphilic Copolymer (B′-3))
Synthesis except that 70 wt% of the hydrophobic monomer (b1) (methyl methacrylate) and 30 wt% of HEA (2-hydroxyethyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd., Wako First Grade)) as the hydrophilic monomer (b2) are used. In the same manner as in Example 4, an amphiphilic copolymer (B′-3) (PMMA-g-HEMA), which is a graft copolymer, was obtained. Mn of the amphiphilic copolymer (B′-3) was 20,000, and Mw / Mn was 1.7.

(Synthesis Example 8; Synthesis of Amphiphilic Copolymer (B-2))
Methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) 50 wt% as the hydrophobic monomer (b1), and HEMA (2-hydroxyethyl methacrylate (Mitsubishi Rayon Co., Ltd.) as the hydrophilic monomer (b2) ) An amphiphilic copolymer (B′-2) (PMMA-r-HEMA), which is a random copolymer, was obtained in the same manner as in Synthesis Example 5 except that 50 wt% was used. The Mn of B′-1) was 260,000, and Mw / Mn was 4.2.

(Synthesis Example 9; Synthesis of Amphiphilic Copolymer (B′-4))
Methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M) 50 wt% as the hydrophobic monomer (b1), and HEMA (2-hydroxyethyl methacrylate (Mitsubishi Rayon Co., Ltd.) as the hydrophilic monomer (b2) ) An amphiphilic copolymer (B′-2) (PMMA-r-HEMA), which is a random copolymer, was obtained in the same manner as in Synthesis Example 5 except that 50 wt% was used. The Mn of B′-1) was 129,000 and Mw / Mn was 3.2.

The abbreviations in the table indicate the following compounds.
MMA: Methyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acryester M)
HEA: 2-hydroxyethyl acrylate (Wako Pure Chemical Industries, Ltd., Wako first grade)
HEMA: 2-hydroxyethyl methacrylate (Mitsubishi Rayon Co., Ltd., trade name: Acrylic ester HOMA)
PME-400 (Nippon Yushi Co., Ltd., Bremer PME-400 (trade name))

[Example 1]
15 wt% of Kynar 761A (manufactured by Arkema, PVDF homopolymer, trade name, Mw = 550,000) as the film-forming polymer (A), and the copolymer (B-1) as the amphiphilic copolymer (B) A polymer solution containing 10 wt% and 75 wt% NMP (manufactured by Kanto Chemical Co., Ltd., special grade) as a solvent is applied on a braided string while being heated to 75 ° C., immersed in pure water at room temperature, and hollow A porous membrane was prepared.
About the obtained hollow porous membrane, FT-IR, the surface opening rate, the surface average pore diameter, and the water permeation amount were measured. The results are shown in Table 1.

[Example 2]
A hollow porous membrane was produced in the same manner as in Example 1 except that the copolymer (B-2) was used as the amphiphilic copolymer (B).
About the obtained hollow porous membrane, FT-IR, the surface opening rate, the surface average pore diameter, and the water permeation amount were measured. The results are shown in Table 1.

[Comparative Example 1]
A hollow porous membrane was produced in the same manner as in Example 1 except that the copolymer (B′-1) was used as the amphiphilic copolymer (B).
About the obtained hollow porous membrane, FT-IR, the surface opening rate, the surface average pore diameter, and the water permeation amount were measured. The results are shown in Table 1.

[Comparative Example 2]
A hollow porous membrane was produced in the same manner as in Example 1 except that the copolymer (B′-2) was used as the amphiphilic copolymer (B).
About the obtained hollow porous membrane, FT-IR, the surface opening rate, the surface average pore diameter, and the water permeation amount were measured. The results are shown in Table 1.

[Comparative Example 3]
A hollow porous membrane was produced in the same manner as in Example 1 except that the copolymer (B′-3) was used as the amphiphilic copolymer (B).
About the obtained hollow porous membrane, FT-IR, the surface opening rate, the surface average pore diameter, and the water permeation amount were measured. The results are shown in Table 1.

[Comparative Example 4]
A hollow porous membrane was produced in the same manner as in Example 1 except that the copolymer (B′-4) was used as the amphiphilic copolymer (B).
About the obtained hollow porous membrane, FT-IR, the surface opening rate, the surface average pore diameter, and the water permeation amount were measured. The results are shown in Table 1.

From Table 1, the porous FT-IR peak intensity ratio of the porous membrane surface (the intensity of the peak appearing in the intensity peak / 1398~1402cm ^-1 appearing in 1726~1730cm ^-1) is 0.4 to 10 Examples 1 and 2 which are membranes and have a surface porosity of 20% or more and 50% or less exhibited high water permeability at both measurement pressures of 100 kPa and 10 kPa. Even at 3 to 30 kPa, which is the actual use pressure of the porous membrane, Examples 1 and 2 showed sufficient water permeability.
On the other hand, Comparative Examples 1, 2 and 4 where the peak intensity ratio is outside the range, and Comparative Example 3 where the surface porosity is outside the range have a low water permeability at a measurement pressure of 100 kPa and 10 kPa, particularly 10 kPa. The water permeability in was low.

Claims (5)

A hollow porous membrane comprising a film-forming polymer (A) and an amphiphilic copolymer (B) comprising a hydrophobic monomer (b1) and a hydrophilic monomer (b2),
FT-IR peak intensity ratio (peak intensity appearing at 1726 to 1730 cm ⁻¹ / peak intensity appearing at 1398 to 1402 cm ⁻¹⁾ on the porous film surface is 0.4 to 10 A hollow porous membrane having a surface porosity of 20% or more and 50% or less.   The hollow porous membrane according to claim 1, wherein the film-forming polymer (A) is polyvinylidene fluoride.   The hollow porous membrane according to claim 1 or 2, wherein the hydrophilic monomer (b2) is a (meth) acrylic monomer.   The hollow porous membrane according to any one of claims 1 to 3, wherein a main component of the amphiphilic copolymer (B) is a graft copolymer.   The hollow porous membrane according to any one of claims 1 to 4, wherein the hydrophobic monomer (b1) unit is 5 wt% or more and 99 wt% or less.