Porous membranes and their manufacturing methods

Abstract

A porous membrane comprising a blend of a matrix polymer and poly(2-methoxyethyl acrylate) and having a porous structure. A method for manufacturing a porous membrane comprising: a step of preparing a membrane-forming solution comprising a matrix polymer, poly(2-methoxyethyl acrylate) and a solvent; and a step of using the membrane-forming solution to precipitate the porous membrane by phase separation.

Description

Technical Field

[0001] This invention relates to porous membranes and methods for their preparation. Background Technology

[0002] Membrane treatment technologies exist that separate solutes such as polymers dissolved in liquids or contaminants contained in liquids using porous membranes. Examples of water treatment technologies utilizing membrane treatment include water purification, wastewater treatment, seawater desalination, and industrial water treatment. Besides water treatment, examples include the treatment of samples containing biomolecules.

[0003] Currently, water treatment facilities using membrane technology are rapidly becoming larger in scale, and the application of membrane technology on a larger scale is considered to have a promising future.

[0004] On the other hand, due to long-term use, membranes become fouled, resulting in deterioration of membrane performance (fouling). Fouling increases energy consumption in membrane treatment and further increases the cost of cleaning and replacement, becoming a major problem in membrane treatment technology.

[0005] Therefore, the development of fouling-inhibiting membranes (low-fouling membranes) is gaining momentum. For example, as a technique for physically or chemically immobilizing a polymer with fouling-inhibiting (low-fouling) properties onto a porous membrane surface, examples include (a) physical adhesion (e.g., Non-Patent Literature 1), (b) grafting using ultraviolet light or plasma (e.g., Non-Patent Literature 2), and (c) ATRP: a method based on atom transfer radical polymerization (e.g., Non-Patent Literature 3) has been proposed.

[0006] In addition, as a membrane fabrication technique that contains low-fouling polymers in the membrane feedstock, (d) phase separation induced membrane fabrication has been proposed (e.g., non-patent literature 4).

[0007] Non-patent literature 1: K. Akamatsue et al., Ind. Eng. Chem. Res., 50 (2011) 12281-12284

[0008] Non-patent literature 2: K. Akamatsue et al., Sep. Purif. Technol., 204 (2018) 298-303. Non-patent literature 3: YC Chiang et al., J. Membr. Sci., 339 (2009) 151-159. Non-patent literature 4: GV Dizone et al., J. Membr. Sci., 550 (2018) 45-58. Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] As a technique for physically or chemically immobilizing low-fouling polymers onto porous membranes, (a) physical attachment techniques offer many simple methods, but the modified polymers are prone to peeling off. Additionally, (b) grafting using ultraviolet light or plasma, and (c) ATRP-based methods, offer high membrane stability but require multiple modification steps and lack practicality.

[0011] In addition, although the (d) phase separation induced film formation has studied the mixing of various polymers, most of them use high-priced polymers, which raises the issue of cost.

[0012] In view of the above problems, the object of the present invention is to provide a porous membrane that can be manufactured inexpensively and easily and has high dirt resistance, and a method thereof.

[0013] Methods for solving problems

[0014] The means to solve the above problems include the following methods.

[0015] <1> A porous membrane comprising a blend of a matrix polymer and poly(2-methoxyethyl acrylate) having a porous structure.

[0016] <2> like <1> The porous membrane is an asymmetric porous structure in which the porosity increases as the pore size increases from one surface side of the porous membrane to the other surface side.

[0017] <3> like <1> or <2> The porous membrane wherein the matrix polymer is one or more polymers selected from the group consisting of polyvinylidene fluoride, polysulfone, polyethersulfone, polyvinyl chloride, polyacrylonitrile, cellulose acetate and polyamide.

[0018] <4> A method for manufacturing a porous membrane, comprising:

[0019] The process of preparing a film-forming solution containing a matrix polymer, poly(2-methoxyethyl acrylate), and a solvent; and

[0020] The process of using the membrane-forming solution to precipitate a porous membrane via phase separation.

[0021] <5> like <4> In the method for manufacturing the porous membrane, the matrix polymer is one or more polymers selected from the group consisting of polyvinylidene fluoride, polysulfone, polyethersulfone, polyvinyl chloride, polyacrylonitrile, cellulose acetate and polyamide.

[0022] <6> like <4> or <5> The method for manufacturing the porous membrane, wherein the phase separation method is a non-solvent-induced phase separation method.

[0023] The effects of the invention

[0024] According to the present invention, a porous membrane that is inexpensive and easy to manufacture and has high dirt resistance, and a method thereof are provided. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating an example of a method for manufacturing the porous membrane of the present invention.

[0026] Figure 2 This is a graph showing the FT-IR (ATR) spectrum of the surface of the porous membranes manufactured in the examples and comparative examples.

[0027] Figure 3 These are FE-SEM images showing the surface of the porous membranes manufactured in the embodiments and comparative examples.

[0028] Figure 4 These are FE-SEM images showing cross-sections of the porous membranes manufactured in the embodiments and comparative examples.

[0029] Figure 5 It is a graph showing the relationship between the pure water permeability coefficient and the membrane thickness relative to the PMEA mixing ratio.

[0030] Figure 6 This is a graph representing the experimental results of bovine serum albumin (BSA). Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0032] In addition, the numerical range indicated by “~” in this specification refers to the range including the values ​​recorded before and after “~” as the lower and upper limits.

[0033] Furthermore, the term "process" in this specification is not limited to independent processes. Even when it cannot be clearly distinguished from other processes, it is included in this terminology as long as the intended purpose of the process is achieved.

[0034] In this invention, poly(2-methoxyethyl acrylate) may be referred to as "MEA polymer" or "PMEA".

[0035] The inventors discovered that prior to the invention of the porous membrane of the present invention, MEA polymers, which were developed with an eye toward biomaterials, could be modified by plasma graft polymerization to produce porous membranes with excellent fouling inhibition.

[0036] However, plasma graft polymerization suffers from complex modification processes and difficulty in scaling up. Therefore, repeated studies were conducted on a simpler method for manufacturing porous membranes with excellent fouling resistance. It was found that by using a membrane-forming solution in which the matrix polymer and poly(2-methoxyethyl acrylate) are dissolved in a specific good solvent, and by using a phase separation-induced membrane-forming method, inexpensive and simple porous membranes with high fouling resistance can be manufactured.

[0037] <Porous membrane>

[0038] The porous membrane of the present invention is a porous membrane containing a blend polymer comprising a matrix polymer and poly(2-methoxyethyl acrylate) and having a porous structure.

[0039] The matrix polymer constitutes the largest proportion (by mass%) of the porous membrane of the present invention and serves as the matrix of the porous membrane. There are no particular limitations on the matrix polymer, as long as it can form a porous membrane as a blend with the MEA polymer. Examples of matrix polymers include polyvinylidene fluoride, polysulfone, polyethersulfone, polyvinyl chloride, polyacrylonitrile, cellulose acetate, and polyamide. The porous membrane may contain one or more matrix polymers. From the viewpoints of membrane formation properties, compatibility with the MEA polymer, membrane strength, and availability, polyvinylidene fluoride (PVDF) is preferred as the matrix polymer.

[0040] PVDF has excellent membrane-forming properties and excellent mechanical and chemical durability, making it suitable as a material for the porous membrane of this invention.

[0041] As PVDF, homopolymers or copolymers of PVDF can be used. Examples of copolymers include polyvinylidene fluoride-hexafluoropropylene copolymer and polyvinylidene fluoride-chlorotrifluoroethylene copolymer.

[0042] There is no particular limitation on the molecular weight of PVDF; for example, polymers with a weight-average molecular weight of 10,000 to 10 million can be used.

[0043] The content (mass%) of the matrix polymer in the porous membrane of the present invention also depends on the type of matrix polymer. For example, when using PVDF, from the viewpoint of membrane formation properties and membrane strength, it can be 55-95% by mass or 65-85% by mass.

[0044] (Poly(2-methoxyethyl acrylate))

[0045] Poly(2-methoxyethyl acrylate) (hereinafter referred to as MEA polymer) is a polymer formed by polymerizing 2-methoxyethyl acrylate.

[0046] MEA polymers are inexpensive materials and are readily available on the market. MEA polymers can be homopolymers of 2-methoxyethyl acrylate or copolymers of 2-methoxyethyl acrylate with other monomers.

[0047] There are no particular limitations on the molecular weight of MEA polymers; for example, MEA polymers with a weight-average molecular weight of 10,000 to 5 million can be used.

[0048] The content (mass%) of MEA polymer in the porous membrane of the present invention also depends on the type of matrix polymer, but from the viewpoint of membrane formation properties, membrane strength, etc., it is, for example, 5 to 45% by mass, or 15 to 35% by mass.

[0049] (Other ingredients)

[0050] The porous membrane according to the present invention may contain components other than the matrix polymer and MEA polymer (other components) within a range that does not significantly impair fouling resistance.

[0051] Other components include polymers and additives other than the matrix polymer and MEA polymer.

[0052] Other components, such as hydrophilic substances used for pore size control, include ethylene glycol, diethylene glycol, tetraethylene glycol, polyethylene glycol, polyvinylpyrrolidone, glycerin, etc., which may contain one or more of these.

[0053] (Porous structure)

[0054] The shape, size, distribution, and morphology of the pores in the porous membrane of the present invention are not particularly limited. Depending on the application of the porous membrane, for example, when used as a separation membrane, an asymmetric porous membrane with an asymmetric porous structure in which the porosity increases as the average pore size increases from one surface side to the other is preferred. An asymmetric porous membrane is typically a porous membrane with a sponge-like porous structure on one surface side and a dense porous structure with small pores on the other surface side. By utilizing the dense layer as a separation surface, it can be used as a precision filtration membrane, ultrafiltration membrane, nanofiltration membrane, or reverse osmosis membrane.

[0055] There is no particular limitation on the pore size; for asymmetric porous membranes, one surface side has a pore size of 1–1000 μm, and the other surface side has a pore size of 0.001–50 μm. Furthermore, the pore size is determined by observing each surface of the porous membrane using a field emission scanning electron microscope (FE-SEM), measuring the maximum diameter of 50 randomly selected pores, and calculating the pore size using a number average.

[0056] Furthermore, the porosity of the porous membrane of the present invention is not particularly limited. However, when the porous membrane of the present invention is an asymmetric porous membrane, the porosity of the dense layer, which functions as a separation surface, and the support layer, which functions as a support on the opposite side of the dense layer, varies considerably. Therefore, the porosity cannot be generalized; for example, the average porosity of the membrane as a whole can range from 25% to 85%.

[0057] (film thickness)

[0058] The thickness of the porous membrane involved in this invention is not particularly limited. However, if the membrane is too thin, it is prone to breakage during manufacturing, membrane setup, or use; if it is too thick, the solution cannot pass through, potentially leading to increased power consumption. The thickness of the porous membrane involved in this invention can be selected according to the intended use of the membrane, for example, from 10 μm to 1.0 mm. Furthermore, the membrane thickness is calculated as the average of the thicknesses measured at five randomly selected locations.

[0059] <Methods for manufacturing porous membranes>

[0060] The method for manufacturing the porous membrane of the present invention includes the step of preparing a membrane-forming solution containing a matrix polymer, poly(2-methoxyethyl acrylate) and a solvent.

[0061] The process of using the above-mentioned membrane-forming solution to precipitate a porous membrane via phase separation.

[0062] (The process of preparing the film-forming solution)

[0063] First, prepare a film-forming solution containing a matrix polymer, poly(2-methoxyethyl acrylate), and a solvent.

[0064] The above-mentioned materials can be used as the matrix polymer and poly(2-methoxyethyl acrylate) to serve as the membrane material.

[0065] There are no particular restrictions on the solvent, as long as it can dissolve both the base polymer and poly(2-methoxyethyl acrylate). For example, when using PVDF as the base polymer, the solvent is not limited due to the excellent physical and chemical durability of PVDF. However, since both PVDF and PMEA are good solvents for dissolution, N-methyl-2-pyrrolidone (NMP) is preferred.

[0066] In addition, when using polymers other than PVDF as the matrix polymer, a good solvent can be selected based on Hansen's solubility parameters.

[0067] Other solvents besides NMP include, for example, dimethylacetamide.

[0068] The solution may contain the above-mentioned "other components" as components other than the matrix polymer and poly(2-methoxyethyl acrylate).

[0069] A higher mixing ratio of MEA polymers in the membrane-forming solution results in a higher proportion of MEA polymers in the membrane, making it easier to create porous membranes with high water permeability. However, if the proportion of the matrix polymer decreases, the membrane strength decreases. Furthermore, if the total polymer concentration in the membrane-forming solution is too low, the membrane strength decreases; if it is too high, it becomes a porous membrane with low permeability.

[0070] Therefore, the mass ratio of the matrix polymer to the MEA polymer in the film-forming solution (matrix polymer:MEA polymer) is preferably 30:1 to 1:1, more preferably 5:1 to 2:1.

[0071] Furthermore, the content of the matrix polymer in the film-forming solution is, for example, 10 to 30% by mass, preferably 15 to 25% by mass. Additionally, the content of the MEA polymer in the film-forming solution is, for example, 1 to 10% by mass, preferably 3 to 8% by mass.

[0072] (The process of precipitating porous membranes via phase separation)

[0073] Using the above-mentioned membrane-forming solution, a porous membrane is precipitated by phase separation.

[0074] Phase separation is a membrane fabrication technique used to create asymmetric membranes; for example, the following methods can be cited.

[0075] (A) Non-solvent Induced Phase Separation (NIPS)

[0076] NIPS is a method that induces phase separation through the interdiffusion of solutions in non-solvent (solvent: soluble, polymer: insoluble).

[0077] (B) Thermally Induced Phase Separation (TIPS)

[0078] TIPS is a method that induces phase separation by heating or cooling the cast solution.

[0079] (C) Vapor Induced Phase Separation (VIPS)

[0080] VIPS is a method that induces phase separation by bringing the casting liquid into contact with water vapor in a humidity-controlled space.

[0081] In the method for manufacturing the porous membrane of the present invention, any of the methods of NIPS, TIPS, or VIPS can be used as the phase separation method. Here, an example of NIPS will be described. Figure 1An example of a method for manufacturing the porous membrane of the present invention using NIPS is shown.

[0082] like Figure 1 As shown in (A) and (B), firstly, a film-forming solution (casting solution) 14, composed of a matrix polymer (membrane material polymer), MEA polymer, solvent (good solvent), additives, etc., is thinly spread (cast) on a flat surface such as a glass plate 10 using a coating machine 12.

[0083] If the thin film 16 formed on the glass plate 10 is left in this state for a certain period of time (about several seconds to several minutes), only the evaporation of the good solvent on the surface will occur, the polymer concentration on the surface will increase, and it will become a state of covering the film.

[0084] Next, as Figure 1 As shown in (C), the film 16 and the glass plate 10 are immersed together in a coagulation liquid (poor solvent) in one go from this state. The poor solvent enters from the surface of the film and becomes mixed with the good solvent, thereby reducing the solubility of the polymer and solidifying (phase separation induced).

[0085] Furthermore, the detachment of good solvents towards poor solvents can create through-pores in the cured polymer. On the surface side, the polymer concentration increases during the drying process, and curing occurs all at once on the surface, forming a dense layer. The interior cures slowly, thus creating a sponge-like porous asymmetric film. And, as... Figure 1 As shown in (D), the whitened porous membrane 20 can be recovered after a few minutes.

[0086] In this invention, when porous membranes are deposited using NIPS, the method is not limited to the one described above. For example, they can be mass-produced by continuously casting them onto a roll of nonwoven fabric, allowing them to penetrate and be wound in a poor solvent.

[0087] Furthermore, the unsuitable solvent for precipitating the porous membrane of the present invention can be selected based on the type of matrix polymer and the type of good solvent. For example, when using PVDF as the matrix polymer and NMP as the good solvent, water can be used as the unsuitable solvent.

[0088] The above method allows for the inexpensive and easy manufacture of porous membranes with excellent low-fouling properties (low-fouling membranes).

[0089] The application of the porous membrane of the present invention is not particularly limited. For example, by using it in water treatment, it can effectively suppress fouling, which not only reduces membrane manufacturing costs but also significantly reduces operating costs and membrane exchange costs.

[0090] [Example]

[0091] The following examples illustrate the porous membrane and its manufacturing method according to the present invention in more detail. However, these examples do not limit the present invention.

[0092] (Reagents)

[0093] The reagents used in the examples are as follows.

[0094] Poly(vinylidene fluoride) [PVDF] (Solef (registered trademark) 6010., SOLVAY., Mw: 300,000-320,000 [Da] powder)

[0095] ·1-Methyl-2-pyrrolidone (NMP) (Wako Premium, Fujifilm Wako Pure Chemicals Co., Ltd.)

[0096] • Deionized water (DI-water, pure water) (Elix Essential5 (UV), Millipore).

[0097] 2-Methoxyethyl Acrylate (MEA) (Wako Grade I, Fujifilm Wako Pure Chemicals Co., Ltd.)

[0098] ·2,2'-Azobis(isobtyronitrile)[AIBN] (Wako Premium, Fujifilm Wako Pure Chemicals Co., Ltd.)

[0099] ·1,4-Dioxane (Special Grade Reagent, Fujifilm and Koichi Pure Chemicals Co., Ltd.)

[0100] Tetrahydrofuran (THF) (Special Grade Reagent, Fujifilm and Koichi Chemicals Co., Ltd.)

[0101] Hexane (Special Grade Reagent, Fujifilm, and Koichi Chemicals Co., Ltd.)

[0102] • Acetylated bovine serum albumin (BSA) (pH 5.2, SIGMA-ALDRICH)

[0103] <Preparation of Membrane Materials>

[0104] The matrix polymer used is commercially available polyvinylidene fluoride (PVDF).

[0105] Poly(2-methoxyethyl acrylate) (PMEA) is synthesized through the following steps.

[0106] 20 g of distilled MEA monomer and 100 g of 1,4-dioxane were placed in a gaiwan-shaped flask and bubbled with nitrogen for 30 min. After bubbling, 0.08 g of AIBN and a small stirrer were added, and free radical polymerization was carried out at a polymerization temperature of 75 °C and a polymerization time of 24 h.

[0107] After the free radical polymerization is complete, the polymerized solution is poured into a beaker containing 500 mL of hexane, causing the polymer, which is insoluble in hexane, to precipitate. At this point, the mixed solution is generally turbid, but because there is a white precipitate with a high polymerization amount at the bottom of the beaker, this precipitate is obtained as the target polymer.

[0108] A turbid solution containing hexane and 1,4-dioxane, excluding the precipitate (polymer), was prepared by completely dissolving the polymer in 10 mL of THF. If no solution was dissolved in 10 mL, 10 mL was added each time. Hexane containing 15 times the amount of THF required to dissolve the polymer was added to the solution, and the polymer was precipitated again. This process was repeated a total of 3 times to obtain the MEA polymer (PMEA).

[0109] <Fabrication of Porous Membranes>

[0110] (Preparation of the film-forming solution)

[0111] As shown in Table 1, the PVDF:PMEA mixing ratio was set to 15:0, 15:1, 15:3, 15:5, and 15:7. N-methyl-2-pyrrolidone (NMP) was used as the solvent, and the mixture was stirred at 70°C for 1 to 4 hours to prepare the film-forming solution (casting solution).

[0112] [Table 1]

[0113]

[0114] (Membrane fabrication using phase separation method)

[0115] After the prepared casting solution was naturally cooled to room temperature, it was spread on a glass plate, and the gaps with a thickness of 200 μm were spread thinly and evenly.

[0116] After 30 seconds, the porous membrane (PMEA0~PMEA7) is precipitated by immersing it together with the glass plate in a non-solvent (pure water) through phase separation.

[0117] [evaluate]

[0118] <FT-IR analysis>

[0119] The surface spectroscopy of the fabricated membrane was measured by FT-IR (ATR) to confirm the presence of PMEA on the membrane surface. Figure 2The figure shows the FT-IR (Fourier Transform Infrared) spectra of the membrane surface for each membrane. In the membranes mixed with PMEA (PMEA1, 3, 5, 7), the FT-IR spectra at 1740 cm⁻¹ are also shown. -1 A C=O peak, characteristic of PMEA, was confirmed nearby.

[0120] Furthermore, it was confirmed that the ratio of the C=O peak intensity of PMEA to that of PVDF increases with the increase of the PMEA / PVDF mixing ratio. Therefore, it is demonstrated that increasing the PMEA / PVDF blending ratio contributes to an increase in the proportion of PMEA present on the membrane surface.

[0121] <FE-SEM Observation>

[0122] The structure of the membrane surface and membrane cross-section was observed using FE-SEM. Figure 3 These are FE-SEM images showing the surface of each film (the side opposite to the glass substrate during casting). Figure 4 These are FE-SEM images showing the cross-sections of each membrane.

[0123] Both films are asymmetric porous structures with different porous structures on one surface side (opposite to the glass substrate during casting) and the other surface side. Additionally, as... Figure 4 It can be observed that the porosity of the membrane mixed with PMEA is larger compared to the membrane without PMEA.

[0124] <Pure Water Through Experiment>

[0125] The flow rate was set to 2 L / min, the supply temperature to 25 °C, and a pure water permeation test was conducted in a cross-flow manner to determine the pure water permeation coefficient (Lp) and compare the water permeability performance of the membranes. Furthermore, five random measurements were taken on the membrane surface using a micrometer, and the average value was used as the membrane thickness for evaluation.

[0126] Figure 5 This is a graph showing the relationship between the pure water permeation coefficient Lp and the membrane thickness relative to the PMEA mixing ratio. A higher Lp indicates lower membrane resistance, allowing water to permeate under lower pressure, thus facilitating membrane separation. It can be seen that mixing PMEA significantly improves the membrane's water permeability. Furthermore, PMEA3 exhibits the highest pure water permeation coefficient Lp, while PMEA5 and PMEA7 show decreased Lp. It is speculated that this is not due to an increased proportion of PMEA blends, but rather to a higher total polymer content (blended polymer content).

[0127] Furthermore, the membrane thickness did not differ significantly, indicating that the membrane thickness of the PMEA-mixed membrane was not reduced, meaning the membrane strength was not decreased, and it could maintain high water permeability. By mixing PMEA, it can be assumed that the internal structure of the membrane changes (…). Figure 4 This significantly affected the increase in the pure water permeability coefficient.

[0128] <Bovine serum albumin (BSA) through testing>

[0129] After calculating the pure water permeability coefficient, the flux was adjusted at 10-minute intervals (the permeate collection time was approximately 5 minutes) using a 4×10⁻⁶ frequency. -6 [m 3 m -2 s -1 The total time was measured at a constant rate of 30 min.

[0130] After permeation with pure water, BSA was prepared in a manner where the entire supply solution was BSA1000 [ppm], and a total of 180 [min] of BSA permeation tests were conducted. In the BSA permeation tests, the permeate and pure water permeation tests were both sampled at 10 [min] intervals of 5 [min].

[0131] In addition, to determine the rejection rate, the supply solution was collected in vials at 30-minute intervals. The BSA concentration was determined using a pre-fabricated BSA detection line with a TOC-V (manufactured by Shimadzu Corporation). Although permeate was collected every 30 minutes, insufficient permeate could be collected in the vials under low-throughput conditions. Therefore, it was diluted with pure water, and the concentration was corrected by multiplying the dilution factor by the TOC measurement result. The apparent rejection rate, calculated from the supply solution concentration and permeate concentration obtained from the TOC measurement, was calculated using the following formula.

[0132] R obs =(1-C p / C b )

[0133] R obs Apparent Restriction Rate

[0134] C p Permeate concentration (mol / m³) 3 )

[0135] C b Supply solution concentration (mol / m³) 3 )

[0136] Figure 6 This is a graph showing the BSA permeation test results. After the test began, by replacing the pure water with a 1000ppm BSA aqueous solution, it was observed that the permeability of the membrane without PMEA mixture decreased sharply, indicating poor low-fouling performance. On the other hand, the membranes mixed with PMEA, especially PMEA 3, 5, and 7, although showing a slight decrease in permeability, remained almost constant until the end of the test, indicating excellent low-fouling performance. Furthermore, it was found that as the proportion of PMEA blend increases, the low-fouling performance improves.

[0137] As mentioned above, by blending PMEA, changes in the internal structure of the membrane and improvements in water permeability can be observed. Furthermore, increasing the PMEA / PVDF blend ratio helps to ensure a high concentration of PMEA on the membrane surface. Therefore, PMEA-blended PVDF porous membranes can be expected to inhibit fouling.

[0138] Industrial availability

[0139] The porous membrane of this invention can suppress fouling in various applications, and in addition to water treatment, it can also open up new applications such as protein fractionation. It is considered to have particularly excellent low fouling properties compared to protein-based or polysaccharide-based substances.

[0140] The publication of Japanese Patent Application No. 2020-159864, filed on September 24, 2020, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein, as well as the specific and individually described details of each document, patent application, and technical standard, are similarly incorporated herein by reference.

Claims

1. A porous membrane comprising a blend of a matrix polymer and poly(2-methoxyethyl acrylate) and having a porous structure; The mass ratio of the matrix polymer to poly(2-methoxyethyl acrylate) is 5:1 to 2:1; and The matrix polymer is selected from one or more polymers selected from polyvinylidene fluoride, polysulfone, polyethersulfone, polyvinyl chloride, polyacrylonitrile, cellulose acetate and polyamide.

2. The porous membrane according to claim 1, wherein, The porous structure is an asymmetric porous structure in which the porosity increases as the pore size increases from one surface side of the porous membrane to the other surface side.

3. A method for manufacturing a porous membrane, comprising: The process of preparing a film-forming solution containing a matrix polymer, poly(2-methoxyethyl acrylate) and a solvent; The mass ratio of the matrix polymer to poly(2-methoxyethyl acrylate) is 5:1 to 2:1; and the matrix polymer is one or more polymers selected from polyvinylidene fluoride, polysulfone, polyethersulfone, polyvinyl chloride, polyacrylonitrile, cellulose acetate, and polyamide; and The process of using the membrane-forming solution to precipitate a porous membrane via phase separation.

4. The method for manufacturing a porous membrane according to claim 3, wherein, The phase separation method is a solvent-inducible phase separation method.

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