Porous membrane and method for producing porous membrane

Abstract

To provide a porous membrane possessing high porosity on both surfaces, and exhibiting superior blocking capability and superior strength.SOLUTION: A porous membrane has porosity of at least 20% on one surface, the porous membrane having an average pore diameter of 0.13 μm or less. The porous membrane contains polyketone, which is a copolymer of one or more olefins and carbon monoxide.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a porous membrane and a method for producing the same. [Background technology]

[0002] In recent years, in semiconductor manufacturing processes, biopharmaceutical manufacturing processes, etc., from the viewpoint of product reliability and yield, there is a demand for filter media that can efficiently remove impurities such as very small particles and viruses. If a filter media with a pore size smaller than the size of the object to be filtered is used, the above impurities can be removed to a certain extent. However, generally, the smaller the pore size, the greater the pressure loss in filtration and the smaller the permeation flux. Therefore, a filter media that can sufficiently filter extremely small impurities and has low pressure loss is required. In addition, since a wide variety of chemicals and organic solvents are used in the above-mentioned processes, chemical resistance is required for the filter media. When the gas and liquid to be treated are organic solvents, some filters may be used with corrosive organic solvents and may be used in high-temperature environments. In such cases, chemical resistance, chemical stability, heat resistance, etc. are often required for the filter. Currently, polyethylene porous membranes or polytetrafluoroethylene porous membranes are used as filter media that can remove minute impurities and have chemical resistance. However, polyethylene porous membranes have the problem of low heat resistance. In addition, polytetrafluoroethylene porous membranes are very expensive, and there is a problem in that it is difficult to produce filter media with pores large enough to remove minute impurities.

[0003] On the other hand, porous membranes are also used as separators, which are components for preventing contact between the anode and the cathode in lithium ion secondary batteries, electric double layer capacitors, electrolytic capacitors, etc. In recent years, the demand for heat resistance and insulation has been increasing for the separators from the viewpoint of safety and product life. Currently used separators for lithium ion secondary batteries are mainly porous membranes made of polyethylene or polypropylene. However, since polyethylene and polypropylene have poor heat resistance, separators using these resins melt, soften, and shrink at high temperatures, and there is a risk that the anode and the cathode may come into contact and cause a short circuit. In electric double layer capacitors and electrolytic capacitors, paper made of cellulose material is mainly used, but there is a problem that the life of the product is short because cellulose is decomposed or dissolved at high temperatures by an electrolyte solution developed for high temperature resistance, in which an ionic liquid such as 1-ethyl-3-methylimidazolium tetrafluoroborate is dissolved as an electrolyte in a solvent such as γ-butyrolactone.

[0004] By the way, polyketone has high mechanical properties, high melting point, organic solvent resistance and chemical resistance when it is made into fiber or film due to its high crystallinity.Therefore, the polyketone porous membrane obtained by processing polyketone into porous membrane also has heat resistance and chemical resistance.In addition, polyketone has affinity with water and various organic solvents, and raw materials carbon monoxide and olefin such as ethylene are relatively cheap, and the polymer price of polyketone may be reduced, so that the polyketone porous membrane with small pore size can be expected to be used industrially as a filter material.

[0005] A known method for producing porous membranes is the thermally induced phase separation method. In this method, a thermoplastic resin and an organic liquid are used. The organic liquid is a solvent that does not dissolve the thermoplastic resin at room temperature but dissolves it at high temperatures, i.e., a latent solvent. The thermally induced phase separation method involves mixing a thermoplastic resin and an organic liquid at high temperatures, dissolving the thermoplastic resin in the organic liquid, and then cooling the mixture to room temperature to induce phase separation. The organic liquid is then removed to produce a porous body. This method has the following advantages: (a) It becomes possible to form films even with polymers such as polyethylene that do not have suitable solvents that can dissolve them at room temperature. (b) Since the film is formed by melting at high temperature and then cooling and solidifying, crystallization is promoted during film formation, particularly when the thermoplastic resin is a crystalline resin, making it easier to obtain a high-strength film.

[0006] Due to the above advantages, the thermally induced phase separation method is widely used as a method for producing a porous membrane (see, for example, Non-Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent No. 101984059 [Patent Document 2] JP 2022-133095 A [Non-patent literature]

[0008] [Non-Patent Document 1] Plastics and Functional Polymer Materials Encyclopedia Editorial Committee, "Plastics and Functional Polymer Materials Encyclopedia," Industrial Research Institute, February 2004, pp. 672-679 [Non-Patent Document 2] Hideto Matsuyama, "Preparation of Polymer-Based Porous Membranes by Thermally Induced Phase Separation (TIPS)," Chemical Engineering, Chemical Industry Press, June 1998, pp. 45-56 [Non-Patent Document 3] Akira Takizawa, "Membrane", IPC Co., Ltd., January 1992, pp. 404-406 [Non-Patent Document 4] DRLLoyd, et.al., "Journal of Membrane Science", 64, 1991, pp. 1-11. Summary of the Invention [Problem to be solved by the invention]

[0009] According to the above Patent Document 1 (Korean Patent No. 101984059), it was known that a porous membrane was formed by a thermally induced phase separation method using polyketone. However, although the porous membrane described in Patent Document 1 is a porous membrane made of polyketone, it was not possible to obtain a porous membrane that exhibits high filtration performance by increasing the surface porosity. In addition, according to Patent Document 2 (JP Patent Publication 2022-133095 A), it was possible to increase the porosity of one surface at the expense of the strength of the membrane by extremely lowering the polymer concentration by a non-solvent induced phase separation method. However, it was not possible to increase the porosity of both surfaces of the membrane with high strength.

[0010] Therefore, an object of the present invention is to provide a porous membrane having a high porosity on both surfaces thereof and excellent blocking performance and strength, and to provide a manufacturing method for obtaining a porous membrane having a high porosity on both surfaces thereof and excellent blocking performance and strength. [Means for solving the problem]

[0011] That is, the present invention is as follows.

[0012] [1] The porosity of one surface of the porous membrane is 20% or more; The average pore size of the porous membrane is 0.13 μm or less, A porous membrane comprising a polyketone, which is a copolymer of one or more olefins and carbon monoxide.

[0013] [2] The porous membrane according to [1], characterized in that the porosity of the one surface is 30% or more.

[0014] [3] The porous membrane according to [1] or [2], wherein the other surface of the porous membrane has a porosity of 15% or more.

[0015] [4] Pure water permeability is 200 L / (m 2 The porous membrane according to any one of [1] to [3], characterized in that it has a durability of at least 1.0 hr.

[0016] [5] The porous membrane according to any one of [1] to [4], characterized in that the breaking strength is 1.0 MPa or more.

[0017] [6] The porous membrane according to any one of [1] to [5], wherein the porous membrane is in the form of a hollow fiber.

[0018] [7] The porous membrane is in the form of a hollow fiber; The porous membrane according to [3], characterized in that the one surface is an inner surface of the hollow fiber-shaped porous membrane, and the other surface is an outer surface of the hollow fiber-shaped porous membrane.

[0019] [8] A method for producing a porous membrane by a thermally induced phase separation method, comprising the steps of: The method includes melt-mixing and dissolving polyketone, which is a copolymer of one or more olefins and carbon monoxide, and an organic liquid to prepare a molten mixture, discharging the molten mixture from a nozzle and cooling and solidifying it in a coagulation bath to form a hollow fiber-shaped product, and then extracting and removing the organic liquid from the hollow fiber-shaped product to obtain a hollow fiber-shaped porous membrane, At least one of the hollow forming agent discharged from the inner nozzle of the nozzle and the external liquid discharged from the outer nozzle of the nozzle has a Hansen solubility parameter distance with respect to the polyketone of 15 MPa. 0.5 A method for producing a porous membrane, comprising using the following solvent:

[0020] [9] A method for producing a porous membrane according to [8], characterized in that a solution in which a polyketone and an organic liquid are dissolved is discharged from a double-tube or triple-tube nozzle.

[0021]

[10] Using the triple cylindrical nozzle, The method for producing a porous membrane according to [9], characterized in that one or more solvents selected from propylene carbonate, sulfolane, dimethyl phthalate, and diethyl phthalate are used as the external liquid.

[0022]

[11] A method for producing a porous membrane according to any one of [8] to

[10] , A method for producing a porous membrane, characterized in that one or more solvents selected from propylene carbonate and polyethylene glycol are used as the hollow-forming agent.

[0023]

[12] A method for producing a porous membrane according to any one of [8] to

[11] , comprising the steps of: A method for producing a porous film, wherein the viscosity of the hollow-forming agent for the porous film is 60 mPa·sec or less. Effect of the Invention

[0024] According to the present invention, it is possible to provide a porous membrane having a high porosity on both surfaces thereof, a practical blocking performance, and excellent strength, and a method for producing such a porous membrane. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a schematic diagram of a pure water permeability measuring device. [Diagram 2] FIG. 2 is a schematic diagram of a cross section of a discharge port of a triple cylindrical nozzle. [Diagram 3] FIG. 1 is a schematic diagram of an example of an apparatus for producing a hollow fiber porous membrane. [Figure 4] 1 is an electron microscope photograph of the outer surface of the hollow fiber porous membrane produced in Example 4. [Diagram 5] 1 is an electron microscope photograph of the inner surface of the hollow fiber-shaped porous membrane produced in Example 4. [Figure 6] 1 is an electron microscope photograph of the outer surface of the hollow fiber porous membrane produced in Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An embodiment of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiment.

[0027] The porous membrane and the method for producing the porous membrane of this embodiment will be described below.

[0028] <Porous membrane> The porous membrane of this embodiment is The porosity of one surface of the porous membrane is 20% or more, The average pore size of the porous membrane is 0.13 μm or less, It is characterized by comprising a polyketone which is a copolymer of one or more olefins and carbon monoxide.

[0029] The porous membrane of the present embodiment contains polyketone as the thermoplastic resin. The porous membrane may be made of only a thermoplastic resin, or may further contain other components. The polyketone in the porous membrane contains polyketone, which is a copolymer of one or more olefins and carbon monoxide. In addition, the polyketone preferably has a high affinity for various liquids, particularly water, and is highly durable against oil, and is represented by the following formula (1): [ka] A polyketone containing a repeating unit of the structure represented by the following formula (1) may be used: {In formula (1), a plurality of R's are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a phenyl group, a halogenated alkyl group having 1 to 10 carbon atoms, or an alkoxycarbonyl group having an alkyl group having 1 to 4 carbon atoms, and a plurality of R's may be bonded to each other to form an alicyclic ring.}

[0030] As described above, the porous membrane of the present embodiment includes a polyketone having a structure formed by copolymerization of one or more olefins and carbon monoxide (i.e., a copolymer of one or more olefins and carbon monoxide or a polymer having the same structure). In the synthesis of the polyketone, any type of compound can be selected as the olefin to be copolymerized with carbon monoxide depending on the purpose. Examples of the olefin include linear olefins such as ethylene, propylene, butene, hexene, octene, and decene; alkenyl aromatic compounds such as styrene and α-methylstyrene; cyclic olefins such as cyclopentene, norbornene, 5-methylnorbornene, tetracyclododecene, tricyclodecene, pentacyclopentadecene, and pentacyclohexadecene; halogenated alkenes such as vinyl chloride and vinyl fluoride; acrylic acid esters such as ethyl acrylate and methyl methacrylate; and vinyl acetate. From the viewpoint of ensuring strength, the type of olefin to be copolymerized is preferably 1 to 3 types, and more preferably 1 to 2 types.

[0031] For the porous membrane of the present invention, a polyketone terpolymer comprising repeating units represented by the following general formulas (2) and (3) may be used. -(CH2CH2-CO) x - (2) -(CH2CH(CH3)-CO) y - (3) (x and y are the mole percentages of the general formulae (2) and (3) in the polymer, respectively) In order to maintain the strength of the porous membrane, y is preferably 30 mol % or less, and more preferably 20 mol % or less.

[0032] The polyketone has a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography of preferably 5,000 or more and 5,000,000 or less, more preferably 10,000 or more and 1,000,000 or less, even more preferably 50,000 or more and 750,000 or less, and particularly preferably 100,000 or more and 500,000 or less.

[0033] Polyketones can be obtained, for example, by polymerizing carbon monoxide and olefins using palladium, nickel or the like as a catalyst.

[0034] The porous membrane of the present embodiment is a porous membrane obtained by processing the polyketone, or a porous membrane containing polyketone as a main component. Here, "containing polyketone as a main component" means that it contains 50 mass% or more of the polymer component in terms of solid content. The polymer component may be only one type, or may be a combination of polymer components of the same polymer component with multiple molecular weights.

[0035] The form of the porous membrane of this embodiment can be, for example, a form having a membrane structure of a hollow fiber membrane, and the porous membrane is preferably a hollow fiber porous membrane. Here, the hollow fiber membrane means a membrane having a hollow ring shape. By having the porous membrane have a membrane structure of a hollow fiber membrane, it is possible to increase the membrane area per unit volume of a module compared to a flat membrane. However, the above-mentioned porous membrane is not limited to a porous membrane having a hollow fiber-like membrane structure (hollow fiber-like porous membrane), and may be a membrane having other membrane structures such as a flat membrane or a tubular membrane. In this embodiment, the one surface and the other surface of the porous membrane may be arbitrarily determined, for example, in the case of a hollow fiber porous membrane, when one surface is the inner surface of the hollow fiber membrane, the other surface is the outer surface of the hollow fiber membrane. When the porous membrane is hollow fiber, it is preferable that the one surface is the inner surface of the hollow fiber porous membrane and the other surface is the outer surface of the hollow fiber porous membrane.

[0036] The porous membrane has a pure water permeability of 200 L / (m 2 ·hr) or more. More preferably, the pure water permeability is 500 L / (m 2 ·hr) or more, and more preferably, the pure water permeability is 800L / (m 2 ·hr) or more. The pure water permeability is 3400L / (m 2 ·hr) or less is preferable. When the porous membrane is a hollow fiber membrane (e.g., a hollow fiber-shaped porous membrane), the pure water permeability can be determined by pouring pure water at 25°C into a pencil-type module 1 as shown in Figure 1, and measuring the amount of water passing through the hollow portion in which the hollow fiber membrane 2 is present by external pressure filtration at a pressure of 0.1 MPa. In addition, when the porous membrane is a flat membrane, the flat membrane can be fixed in a container into which pure water can be supplied and discharged, and pure water at 25°C can be poured at a pressure of 0.1 MPa from any side of the flat membrane and the amount of water that permeates from the opposite side can be measured to determine the pure water permeation rate.

[0037] The porous membrane of this embodiment has an average pore size of 0.13 μm or less. More preferably, the average pore size is 0.12 μm or less, and more preferably, the average pore size is 0.11 μm or less. If the average pore size is 0.13 μm or less, the porous membrane has sufficient blocking performance. In addition, the average pore size of the porous membrane is preferably 0.030 μm or more, and more preferably 0.050 μm or more. The average pore size can be measured using a Liquid-liquid porometer (LLP-1100A) manufactured by Porous Material.

[0038] The porous membrane of this embodiment has a porosity of 20% or more on one surface. When the porosity of one surface is 20% or more, it has high filtration performance. When the porosity of one surface is high, the load of membrane fouling per hole with respect to the blocking matter inside the membrane is small, and it is estimated that high filtration performance can be exhibited for a long time because there are few holes that are completely blocked. The porosity of one surface of the porous membrane is more preferably 30% or more. When the porous membrane of this embodiment is a hollow fiber porous membrane, the one surface is preferably the inner surface of the hollow fiber porous membrane. In addition, the porosity of one surface is preferably 80% or less in order to prevent a decrease in strength due to the thinning of the trunk of the polymer forming the porous membrane. The porosity of one surface of the porous membrane can be measured by the following method. First, the outer and inner surfaces of the porous membrane are photographed at a magnification that allows the shapes of 10 or more holes to be confirmed. Using the photographed image, as described in International Publication No. 2001 / 53213, a transparent sheet is placed over the copy of the image, the holes are filled in black using a black pen or the like, and the transparent sheet is copied onto a blank sheet of paper, so that the holes are clearly distinguished as black and the non-porous parts as white. Then, binarization is performed by discriminant analysis using commercially available image analysis software Winroof2018 Ver4.23.1. The porosity can be calculated by determining the area occupied by the binarized image obtained in this way.

[0039] In addition, the porous membrane of this embodiment preferably has a porosity of the other surface of 15% or more. It is estimated that the surface is less likely to be completely blocked and has high filtration performance when the porosity of the other surface is 15% or more. In addition, the porosity of the other surface is more preferably 16% or more. When the porous membrane of this embodiment is a hollow fiber porous membrane, the other surface is preferably the outer surface of the hollow fiber porous membrane. High filtration performance can be achieved by increasing the porosity of both sides of the porous membrane. In addition, the porosity of the other surface is preferably 30% or less, more preferably 25% or less, in order to prevent a decrease in strength due to the thinning of the trunk of the polymer forming the porous membrane. The porosity of the other surface of the porous membrane can be measured in the same manner as the method for measuring the porosity of one surface.

[0040] The breaking strength of the porous membrane of the present embodiment is preferably 1.0 MPa or more. If the breaking strength is 1.0 MPa or more, the porous membrane has sufficient strength. From the viewpoint of strength, the breaking strength is more preferably 2.0 MPa or more, and since it is sufficient to have a practically sufficient strength, it is preferably 10 MPa or less, and more preferably 8 MPa or less. The breaking strength of the porous membrane is determined using the breaking load measured under the following conditions and the following formula. Measuring equipment: Instron type tensile testing machine (Shimadzu Corporation AGS-J 20N) Chuck distance: 2cm Pulling speed: 1cm / min

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[0041] <Method of manufacturing porous membrane> The method for producing the porous membrane of the present embodiment is characterized by producing the porous membrane by a thermally induced phase separation method.The thermally induced phase separation method is to homogeneously mix a thermoplastic resin such as polyketone with an organic liquid such as dioctyl phthalate or dibutyl phthalate in a heat-molten state, form this into a hollow fiber or flat membrane in a heat-molten state, and then immerse the formed body in a liquid (such as water) that does not dissolve the formed body components or cool in air to phase-separate the polymer layer and the solvent layer, and then immerse this in a solution to extract the solvent in the membrane, thereby producing a porous membrane.

[0042] The method for producing a porous membrane according to the present embodiment includes the steps of: A method for producing a porous membrane by a thermally induced phase separation method, comprising the steps of: The method includes melt-mixing and dissolving polyketone, which is a copolymer of one or more olefins and carbon monoxide, and an organic liquid to prepare a molten mixture, discharging the molten mixture from a nozzle and cooling and solidifying it in a coagulation bath to form a hollow fiber-shaped product, and then extracting and removing the organic liquid from the hollow fiber-shaped product to obtain a hollow fiber-shaped porous membrane, At least one of the hollow forming agent and the external liquid discharged from the outer nozzle of the nozzle has a Hansen solubility parameter distance for polyketone of 15 MPa. 0.5 The following solvents are used: According to the above-mentioned method for producing a porous membrane, it is possible to obtain a porous membrane having a high porosity on both surfaces of the membrane and excellent blocking performance and strength.

[0043] The thermoplastic resin (polyketone) used in the manufacturing method of the porous membrane (preferably hollow fiber porous membrane) of this embodiment is a resin that has elasticity and does not show plasticity at room temperature, but shows plasticity and becomes moldable when appropriately heated. Moreover, a thermoplastic resin is a resin that returns to its original elastic body when cooled and the temperature is reduced, and does not undergo chemical changes such as molecular structure during this time (for example, see "Chemical Encyclopedia 6, Condensed Edition, Edited by the Editorial Committee for the Chemical Encyclopedia, Kyoritsu Shuppan, pp. 860 and 867, 1963").

[0044] The polyketone concentration when mixing the polyketone with the organic liquid is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less. If the polyketone concentration is 10% by mass or more, the mechanical strength and porosity of the porous membrane are easily ensured, and if the polyketone concentration is 50% by mass or less, the water permeability of the porous membrane is not reduced.

[0045] The organic liquid used is preferably one that is a potential solvent for the thermoplastic resin, such as polyketone, used in this embodiment. In this embodiment, a potential solvent refers to a solvent that barely dissolves the thermoplastic resin at room temperature (25°C) but can dissolve the thermoplastic resin at temperatures higher than room temperature. The solvent only needs to be liquid at the melt mixing temperature with the thermoplastic resin, and does not necessarily need to be liquid at room temperature. The organic liquid has a Hansen solubility parameter distance for polyketone of 12 MPa or less. 0.5 More than 17.5MPa 0.5 The following range is preferable: When the distance of the Hansen solubility parameter for the polyketone is within this range, a liquid-liquid phase separation type having excellent durability can be expressed, and the membrane structure can be controlled.

[0046] Examples of the organic liquid include phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dicyclohexyl phthalate, diheptyl phthalate, dioctyl phthalate, and di(2-ethylhexyl) phthalate; sebacates such as dibutyl sebacate; adipic acids such as dioctyl adipate; trimellitic acids such as trioctyl trimellitate; benzoates such as methyl benzoate and ethyl benzoate; phosphates such as triphenyl phosphate, tributyl phosphate, and tricresyl phosphate; glycerin esters such as propylene glycol dicaprate and propylene glycol dioleate; polyethers such as polyethylene glycol; ethers such as triethylene glycol; paraffins such as liquid paraffin; ketones such as γ-butyrolactone, ethylene carbonate, propylene carbonate, cyclohexanone, acetophenone, and isophorone; and mixtures thereof. Of these, polyethylene glycol, triethylene glycol or propylene carbonate is preferred.

[0047] The mass ratio of the organic liquid in the mixture of the thermoplastic resin and the organic liquid is preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 85% by mass or less. If the mass ratio of the organic liquid is 20% by mass or more, the thermoplastic resin can be stably dissolved, and if it is 90% by mass or less, the viscosity is sufficient for producing a porous membrane, so that a porous membrane can be stably produced.

[0048] The shape of the porous membrane produced by the porous membrane and the method for producing the porous membrane of the present embodiment may be any shape, such as a flat membrane, a hollow fiber, etc. The porous membrane may be a free-standing membrane without a support, or may exist as a composite membrane having the porous membrane on a support. The support may be any shape, such as a flat membrane, a hollow fiber, etc.

[0049] The porous membrane of the present embodiment is a flat membrane in one embodiment. The flat membrane is suitable as a filter medium. The thickness of the flat membrane is not particularly limited and can be any thickness depending on the application, but may be preferably 0.1 to 1,000 μm. When the porous membrane is used as a filter medium, from the viewpoint of miniaturization of the module and the width of the effective filtration area, the thickness of the porous membrane is preferably small. The thickness of the flat membrane is measured using a microscope.

[0050] The Hansen solubility parameter distance (Ra) between a polyketone and an organic liquid or solvent can be calculated by the following formula: The following formula is a relational equation between the Hansen (three-dimensional) solubility parameter of polyketone and the Hansen (three-dimensional) solubility parameter of organic liquid or solvent, and is used to evaluate the solubility of polyketone and organic liquid or solvent. The right side of the following formula represents the solubility range of the Hansen solubility parameter three-dimensionally, and the Hansen (three-dimensional) solubility parameter of polyketone (σ dp , σ pp , σ hp ) to the Hansen (three-dimensional) solubility parameter (σ dm , σ pm , σ hm ) quantitatively represents the distance (Ra) to the target. Ra = (4 × (σ dm -σ dp ) 2 +(σ pm -σ pp ) 2 +(σ hm -σ hp ) 2 )^0.5 [In the formula, σ dm and σ dp are the dispersion terms of the organic liquid or solvent and the polyketone, respectively, and σ pm and σ pp are the dipole binding terms of the organic liquid or solvent and the polyketone, respectively, and σ hm and σ hp denote the hydrogen bonding terms of the organic liquid or solvent and the polyketone, respectively.] Hansen (three-dimensional) solubility parameters (σdp , σ pp , σ hp ) can be calculated using the following formulas (S1) to (S3) with reference to the literature (DWV Krevelen, KT Nijenhuis, Properties of Polymers: Their correlation with chemical structure; their numerical estimation and prediction from additive group contributions, Fourth ed., Elsevier BV, Amsterdam, Noord-Holland, 2008.).

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[0051] The organic liquid may be one type, or two or more types of organic liquid may be used. Here, the two or more types of organic liquid may be two or more types of organic liquids having different compounds, or may be two or more types of organic liquids having the same compound but different molecular weights, for example, two or more types of organic liquids having the same monomer structure but different weight average molecular weights due to differences in polymerization degrees. By mixing two types of organic liquids having different compatibility with a thermoplastic resin (polyketone), it becomes possible to control the membrane structure. The two types of organic liquids may be two types of organic liquids having different molecular weights, and further, the membrane structure can be adjusted by changing the mixing ratio of the two different types of organic liquids. In this embodiment, it is preferable to mix, for example, polyethylene glycols having different molecular weights while containing polyketone as the thermoplastic resin. In addition, the mixing ratio of the two types of polyethylene glycols may be adjusted. For example, when the two types of polyethylene glycols are polyethylene glycol A and B, the mixing ratio is preferably polyethylene glycol A:polyethylene glycol B=9:1 to 5:5.

[0052] When two organic liquids having different molecular weights are mixed, the ratio of the weight average molecular weight of one of the two organic liquids to the weight average molecular weight of the other organic liquid is preferably 1.0 or more and 3.5 or less. When the ratio of weight average molecular weights is within the above range, it is preferable because the compatibility with the thermoplastic resin can be adjusted and a suitable membrane structure can be obtained. In addition, when polyethylene glycol is used as the organic liquid of the polyketone, the molecular weight of the polyethylene glycol is preferably 200 or more and 600 or less. When the molecular weight of the polyethylene glycol is within the above range, it is preferable because it can express a liquid-liquid phase separation type.

[0053] In the extraction and removal of the organic liquid, a liquid suitable for extraction (extraction liquid) is used that does not dissolve or denature the thermoplastic resin used and is miscible with the organic liquid. Specifically, the extraction can be performed by contacting the porous membrane with the extraction liquid by a technique such as immersion. The extraction liquid is preferably volatile so that it can be easily removed from the porous membrane after extraction. Examples of the extraction liquid include alcohols and methylene chloride. In addition, if the organic liquid used is water-soluble, water can also be used as the extraction liquid.

[0054] The method for producing a porous membrane of this embodiment includes the steps of melt-mixing polyketone, which is a copolymer of one or more olefins and carbon monoxide, with an organic liquid to obtain a molten mixture; discharging the molten mixture containing the polyketone and the organic liquid from a nozzle (spinneret) having a tubular (e.g., double tubular or triple tubular as shown in FIG. 2) outlet to form a hollow fiber-shaped molten mixture; solidifying (e.g., cooling and solidifying) the hollow fiber-shaped molten mixture to form a hollow fiber-shaped product; and, after forming the hollow fiber-shaped product, extracting and removing the organic liquid from the hollow fiber-shaped product to produce a porous membrane (preferably a hollow fiber-shaped porous membrane).

[0055] The nozzle is preferably a double cylindrical nozzle or a triple cylindrical nozzle. Here, the triple cylindrical nozzle will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of a triple cylindrical nozzle. The triple cylindrical nozzle has portions called an inner nozzle 3, an intermediate nozzle 4, and an outer nozzle 5 in this order from the radially inner side. In the triple cylindrical nozzle, the diameter of the inner nozzle 3 is called the inner diameter a, the diameter of the intermediate nozzle 4 is called the outer diameter b, and the diameter of the outer nozzle 5 is called the outermost diameter c. A hollow-forming agent is discharged from the inner nozzle 3, a molten mixture is discharged from the intermediate nozzle 4, and an external liquid is discharged from the outer nozzle 5. Although not shown in the figure, the double cylindrical nozzle is a double cylindrical nozzle that does not have a portion corresponding to the outer nozzle of the triple cylindrical nozzle in Figure 2, and is composed of a portion corresponding to the inner nozzle and a portion corresponding to the intermediate nozzle.

[0056] Here, the hollow forming agent and one or more of the external liquids flowing around the outer periphery of the hollow fiber-shaped molten mixture have a Hansen solubility parameter distance for polyketone of 15 MPa or less. 0.5 The following solvents are used. In this case, when the free running distance, which is the distance from when the molten mixture is discharged from the nozzle to when it is immersed in the coagulation bath, is not provided (i.e., the free running distance = 0), the solubility parameter distance for polyketone in the liquid of the coagulation bath is 15 MPa. 0.5 The following solvents may be used: The Hansen solubility parameter distance for the polyketone of the hollow forming agent or the liquid (external liquid) poured on the outer periphery of the hollow fiber-shaped molten mixture is 15 MPa. 0.5 If the polyketone is made to have a high compatibility with the solvent, the polyketone will be energetically stabilized, and the phenomenon of the interface between the polymer solution and the hollow-hole forming agent or the external liquid becoming smaller can be prevented. In other words, it is possible to prevent the blocking of the dilute phase (pores) by the polymer (polyketone) thick phase after phase separation. As a result, it is possible to increase the openness of the surface. From the same viewpoint, the hollow-hole forming agent and one or more of the liquids (external liquids) poured on the outer periphery of the hollow fiber-shaped molten mixture are each set to have a Hansen solubility parameter distance for polyketone of 13 MPa or less. 0.5 More preferably, it is 12 MPa or less. 0.5 It is even more preferred that:

[0057] More preferably, the hollow forming agent is one or more solvents selected from polyethylene glycol (PEG) and propylene carbonate (PC), and the external liquid is one or more solvents selected from propylene carbonate (PC), sulfolane (SLF), dimethyl phthalate (DMP), and diethyl phthalate (DEP).

[0058] Furthermore, the viscosity of the hollow-forming agent is preferably 60 mPa·sec or less. Furthermore, the viscosity of the hollow-forming agent is more preferably 55 mPa·sec or less. When the viscosity of the hollow-forming agent is low, ie, 60 mPa·sec or less, the hollow-forming agent penetrates the polymer solution quickly, which can further suppress the phenomenon of the interface becoming smaller and enhance the effect of increasing the openness. The viscosity of the hollow-forming agent can be measured using an EMS viscometer (EMS1000, manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0059] The mixture of the thermoplastic resin such as polyketone and the organic liquid can be obtained by a mixing means commonly used in laboratory or industry, such as a Henschel mixer, a Banbury mixer, or a Plosser mixer.

[0060] FIG. 3 shows an example of a hollow fiber porous membrane manufacturing apparatus used to carry out the porous membrane manufacturing method of this embodiment. The polyketone and the organic liquid are heated by a heater 8 and melt-mixed in a melt mixer 6 using a purge gas 7. The molten mixture is then discharged from a cylindrical nozzle together with a hollow-forming agent (and optionally an external liquid), and after passing through an idle distance 9, is immersed in a coagulation bath to produce a porous membrane. EXAMPLES

[0061] Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0062] The measurement method used in this embodiment is as follows. Unless otherwise specified, all of the following measurements were performed at 25° C. Below, the evaluation methods will be explained, followed by a description of the manufacturing methods and evaluation results of the porous membranes of the examples and comparative examples.

[0063] The composition and manufacturing conditions of the membrane, as well as various performance characteristics, are shown in Table 1.

[0064] (1) Polyketone used Polyketone copolymer (CPK) manufactured by Hyosung Co., Ltd., product name "M630A"

[0065] (2) Solvents Used PC: Propylene carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) SFL: Sulfolane (FUJIFILM Wako Pure Chemical Industries, Ltd.) DMP: Dimethyl phthalate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) DEP: Diethyl phthalate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) TEG: Triethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) PEG300: Polyethylene glycol 300 (Tokyo Chemical Industry Co., Ltd.)

[0066] (3) Organic liquid used PEG300: Polyethylene glycol 300 (Tokyo Chemical Industry Co., Ltd.) PC: Propylene carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) TEG: Triethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0067] (4) Outer diameter, inner diameter and film thickness The hollow fiber membrane was cut into thin slices at 15 cm intervals vertically in the longitudinal direction of the membrane using a razor or similar tool, and the long and short inner diameters and long and short outer diameters of the cross sections were measured using a microscope, and the inner and outer diameters were calculated using the following formulas. The inner diameter was subtracted from the calculated outer diameter and the result divided by 2 was used as the membrane thickness. 20 points were measured, and the average values ​​were used as the inner diameter (mm), outer diameter (mm), and membrane thickness (mm) under those conditions.

number

number

[0068] (5) Pure water permeability (L / (m 2 hr) The hollow fiber membrane was immersed in ethanol for 24 hours, and then immersed in water for 30 minutes to moisten the hollow fiber membrane. The moist hollow fiber membrane, approximately 10 cm long, was set in a pencil-type module and one end was sealed. Then, pure water at 25°C was poured into the pencil module, and the amount of water permeating from the hollow was measured by external pressure filtration at a pressure of 0.1 MPa. A schematic diagram of the pure water permeation measurement device is shown in Figure 1. Three measurements were taken, and the average value was taken as the pure water permeation amount under each condition.

number

[0069] (6) Average pore size The average pore size was measured using a Porous Material Liquid-liquid porometer (LLP-1100A). The hollow fiber membrane was moistened using isopropyl alcohol (IPA, Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent. The moistened sample was then placed in the device and measurements were performed using Galwick (Porous Material) as a solvent.

[0070] (7) Breaking strength (MPa) The tensile strength, load and displacement at break were measured under the following conditions. Sample: Wet hollow fiber membrane prepared by method (5) Measuring equipment: Instron type tensile testing machine (Shimadzu Corporation AGS-J 20N) Chuck distance: 2cm Pulling speed: 1cm / min The breaking strength and breaking elongation were determined according to the following formulas.

number

number

number

[0071] (8) Observation of membrane structure The morphology of the membrane was observed using FE-SEM (JSF-7500F, manufactured by JEOL). When observing the cross section of the membrane, it was immersed in liquid nitrogen and fractured. After drying in a vacuum for 12 hours, osmium tetroxide was evaporated onto the surface and observation was performed. The observation of the membrane structure was performed on the porous membranes of Example 4 and Comparative Example 2.

[0072] (9) Perforation ratio of outer and inner surfaces Using the above-mentioned method for observing the membrane structure, the outer and inner surfaces of the porous membrane were photographed at a magnification that allowed the shapes of 10 or more pores to be confirmed. Using the photographed image, as described in International Publication No. 2001 / 53213, a transparent sheet was placed on top of a copy of the image, the holes were filled in black with a black pen, and the transparent sheet was copied onto a blank sheet of paper to clearly distinguish the holes as black and the non-holes as white. Then, binarization was performed using discriminant analysis using commercially available image analysis software Winroof2018 Ver4.23.1. The opening rate was calculated by calculating the area occupied by the binarized image obtained in this way.

[0073] (10) Viscosity of hollow forming agent The viscosity of the hollow-forming agent was measured using an EMS viscometer (EMS1000, manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0074] Example 1 Polyketone (M630A manufactured by Hyosung Co., Ltd.) was used as the thermoplastic resin, and propylene carbonate (PC) and polyethylene glycol 300 (PEG300) were used as the organic liquid, and mixed at 200°C for 30 minutes in a ratio of polyketone:PC:PEG300 = 20:40:40 (mass ratio). This mixture was used to mold a hollow fiber-shaped molten mixture using a melt mixer and a hollow fiber molding nozzle. A liquid in which PEG300 and PC were mixed at 70:30 (mass ratio) was used as the hollow forming agent. A double cylindrical nozzle with an outer diameter of 1.6 mm and an inner diameter of 0.60 mm was used as the hollow fiber molding nozzle. The extruded hollow fiber-shaped molten mixture was guided to a coagulation bath containing a 20% PC aqueous solution at 23°C after traveling 1.0 cm in the air, and was taken up at a speed of 19 m / min. The obtained hollow fiber-like material was immersed in ethanol for 2 days to extract and remove the organic liquid, thereby obtaining a hollow fiber-like porous membrane.

[0075] Example 2 A hollow fiber-shaped porous membrane was obtained in the same manner as in Example 1, except that a mixture of PEG300 and PC in a ratio of 40:60 (by mass) was used as the hollow-forming agent.

[0076] Example 3 A hollow fiber-shaped porous membrane was obtained in the same manner as in Example 1, except that PC was used as the hollow-hole forming agent.

[0077] Comparative Example 1 A hollow fiber-shaped porous membrane was obtained in the same manner as in Example 1, except that PEG300 was used as the hollow-hole forming agent.

[0078] Example 4 Polyketone (M630A manufactured by Hyosung Co., Ltd.) was used as the thermoplastic resin, and triethylene glycol (TEG) and polyethylene glycol 300 (PEG300) were used as the organic liquid. They were mixed at 200°C for 30 minutes in a ratio of polyketone:TEG:PEG300 = 20:40:40 (mass ratio). This mixture was used to form a hollow fiber-shaped molten mixture in a melt mixer using a triple cylindrical nozzle as shown in Figure 2. The external liquid was poured onto the outer periphery of the hollow fiber-shaped molten mixture using the triple cylindrical nozzle. PC was used as the hollow forming agent. In addition, a triple cylindrical nozzle with a maximum outer diameter of 2.0 mm, an outer diameter of 1.6 mm, and an inner diameter of 0.60 mm was used as the nozzle for forming the hollow fiber. The discharged hollow fiber-shaped molten mixture was guided to a coagulation bath filled with water at 23°C after traveling 5.0 cm in the air, and was taken up at a speed of 30 m / min. The obtained hollow fiber-like material was immersed in ethanol for 2 days to extract and remove the organic liquid, thereby obtaining a hollow fiber-like porous membrane.

[0079] Example 5 A hollow fiber porous membrane was obtained in the same manner as in Example 4, except that sulfolane (SFL) was used as the external liquid.

[0080] Example 6 A hollow fiber-shaped porous membrane was obtained in the same manner as in Example 4, except that dimethyl phthalate (DMP) was used as the external liquid.

[0081] Example 7 A hollow fiber-shaped porous membrane was obtained in the same manner as in Example 4, except that diethyl phthalate (DEP) was used as the external liquid.

[0082] Comparative Example 2 A hollow fiber porous membrane was obtained in the same manner as in Example 4, except that triethylene glycol (TEG) was used as the external liquid.

[0083] [Table 1]

[0084] From Table 1, it can be seen that the porous membranes of the Examples have higher porosity on the outer and inner surfaces and also have higher breaking strength than the porous membranes of the Comparative Examples.

[0085] Fig. 4 is an electron microscope photograph of the outer surface of the hollow fiber porous membrane produced in Example 4, and Fig. 5 is an electron microscope photograph of the inner surface of the hollow fiber porous membrane produced in Example 4. Also, Fig. 6 is an electron microscope photograph of the outer surface of the hollow fiber porous membrane produced in Comparative Example 2. Comparing Fig. 4 and Fig. 6, it can be seen that the hollow fiber porous membrane of the Example has more pores and the pores are larger than those of the hollow fiber porous membrane of the Comparative Example. [Explanation of symbols]

[0086] 1: Pencil type module 2: Hollow fiber membrane 3: Inner nozzle 4: Intermediate nozzle 5: Outer nozzle 6: Melt mixer 7: Purge gas 8: Heater 9: Empty running distance A: Inner diameter b:Outer diameter c: outermost diameter

Claims

1. The porosity of one surface of the porous membrane is 20% or more; The average pore size of the porous membrane is 0.13 μm or less, A porous membrane comprising a polyketone, which is a copolymer of one or more olefins and carbon monoxide.

2. 2. The porous membrane according to claim 1, wherein the porosity of said one surface is 30% or more.

3. 2. The porous membrane according to claim 1, wherein the other surface of the porous membrane has a porosity of 15% or more.

4. Pure water permeability is 200 L / (m ２ 2. The porous membrane according to claim 1, characterized in that the thermal expansion coefficient (SSC) is equal to or greater than 1.0 s.

5. The porous membrane according to claim 1, characterized in that the breaking strength is 1.0 MPa or more.

6. The porous membrane according to claim 1, characterized in that the porous membrane is in the form of a hollow fiber.

7. The porous membrane is in the form of a hollow fiber, 4. The porous membrane according to claim 3, wherein said one surface is an inner surface of the hollow fiber-shaped porous membrane, and said other surface is an outer surface of the hollow fiber-shaped porous membrane.

8. A method for producing a porous membrane by a thermally induced phase separation method, comprising the steps of: The method includes melt-mixing and dissolving polyketone, which is a copolymer of one or more olefins and carbon monoxide, and an organic liquid to prepare a molten mixture, discharging the molten mixture from a nozzle and cooling and solidifying it in a coagulation bath to form a hollow fiber-shaped product, and then extracting and removing the organic liquid from the hollow fiber-shaped product to obtain a hollow fiber-shaped porous membrane, At least one of the hollow forming agent discharged from the inner nozzle of the nozzle and the external liquid discharged from the outer nozzle of the nozzle has a Hansen solubility parameter distance with respect to the polyketone of 15 MPa or less. ０．５ A method for producing a porous membrane, comprising using the following solvent:

9. 9. The method for producing a porous membrane according to claim 8, wherein the solution in which the polyketone and the organic liquid are dissolved is discharged from a double-tube or triple-tube nozzle.

10. Using the triple cylindrical nozzle, The method for producing a porous membrane according to claim 9, wherein the external solution is one or more solvents selected from the group consisting of propylene carbonate, sulfolane, dimethyl phthalate, and diethyl phthalate.

11. A method for producing the porous membrane according to claim 8, comprising the steps of: A method for producing a porous membrane, characterized in that one or more solvents selected from propylene carbonate and polyethylene glycol are used as the hollow-forming agent.

12. A method for producing the porous membrane according to claim 8, comprising the steps of: A method for producing a porous membrane, characterized in that the viscosity of a hollow-forming agent for the porous membrane is 60 mPa·sec or less.

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