Method for producing porous film made of polyketone

Abstract

To provide a method for producing a porous film made of polyketone, which enables realization of a liquid-liquid phase-separated structure excellent in durability, etc. and controlling the film structure thereof by choosing the most appropriate solvent in a heat-induced phase separation method by using a polyketone having high organic solvent resistance.SOLUTION: Provided is a method for producing a porous film made of polyketone by using a polyketone and at least one solvent, where the solvent has a solubility parameter (Ra) in a range of 12 MPa0.5 to 17.5 MPa0.5 and the porous film is produced by a heat-induced phase separation method.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a porous polyketone membrane. [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 process, chemical resistance is required for the filter media. Some filters may be corrosive when the gas and liquid to be treated are organic solvents, and may also 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 carbon monoxide and ethylene, which are raw materials, are relatively inexpensive, and the polymer price of polyketone may become cheaper, 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 a porous membrane 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 is a method in which a thermoplastic resin and an organic liquid are kneaded at high temperatures to dissolve the thermoplastic resin in the organic liquid, and then the mixture is cooled to room temperature to induce phase separation, and the organic liquid is 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, making it easier to obtain a high-strength film, particularly when the thermoplastic resin is a crystalline resin.

[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 [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] It was known from the above Patent Document 1 (Korean Patent No. 101984059) that a porous membrane was produced by a thermally induced phase separation method using polyketone. However, the membrane produced by the above method was a porous membrane made of polyketone, but there was no suggestion regarding the selection of a solvent, and the adjustment of the membrane performance was limited.

[0010] The present invention aims to provide a manufacturing method that allows for the selection of an optimal solvent in a thermally induced phase separation method using a polyketone having high organic solvent resistance, thereby realizing a liquid-liquid phase separation type membrane that is excellent in terms of durability, etc., and enabling control of the membrane structure. [Means for solving the problem]

[0011] That is, the present invention is as follows. [1] A method for producing a porous polyketone membrane using a polyketone and at least one solvent, comprising the steps of: The solvent has a solubility parameter (Ra) of 12 MPa. 0.5 More than 17.5MPa 0.5 The range is as follows: A method for producing a porous polyketone membrane, comprising producing the porous membrane by a thermally induced phase separation method.

[0012] [2] The method for producing the polyketone porous membrane according to [1], characterized in that two or more types of solvents are used.

[0013] [3] The method for producing a polyketone porous membrane according to [2], wherein the two or more solvents have the same monomer structure and differ in weight-average molecular weight due to differences in the degree of polymerization.

[0014] [4] The method for producing a polyketone porous membrane according to any one of [1] to [3], characterized in that the solvent is two types of solvent, and the ratio of the weight average molecular weight of one of the two solvents to the weight average molecular weight of the other solvent is between 1.0 or more and 3.5 or less.

[0015] [5] A method for producing a porous polyketone membrane according to [2] or [3], characterized in that a mixing ratio of the two or more types of solvents is adjusted.

[0016] [6] The method for producing a porous polyketone membrane according to [1], wherein the solvent is polyethylene glycol or dipropyl phthalate (DPrP).

[0017] [7] The method for producing a polyketone porous membrane according to [6], characterized in that the solvent is polyethylene glycol.

[0018] [8] The method for producing a polyketone porous membrane according to [7], characterized in that the solvent is polyethylene glycol with a weight average molecular weight of 200 or more and 600 or less.

[0019] [9] A method for producing a polyketone porous membrane according to any one of [1] to [8], characterized in that the concentration of the polyketone when mixing the polyketone with the solvent is 20% by mass or more and 50% by mass or less. Effect of the Invention

[0020] According to the method for producing a porous membrane of the present invention, various membrane structures of a liquid-liquid phase separation type can be obtained by a thermally induced phase separation method using polyketones having high resistance to organic solvents and chemicals. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a phase diagram of the two solvents of Example 2. [Diagram 2] 1 is a cross-sectional SEM image of the flat membrane produced in Example 2. [Diagram 3] FIG. 11 is a phase diagram of Example 3. [Figure 4] 1 is a cross-sectional SEM image of the flat membrane produced in Example 4. [Diagram 5] 1 is a cross-sectional SEM image of the flat membrane produced in Example 5. [Figure 6]1 is a cross-sectional SEM image of the flat membrane produced in Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] An embodiment of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiment.

[0023] The method for producing a porous membrane according to the present embodiment includes the steps of: A method for producing a porous polyketone membrane using a polyketone and at least one solvent, comprising the steps of: The solvent has a solubility parameter (Ra) of 12 MPa. 0.5 More than 17.5MPa 0.5 The range is as follows: The method is characterized in that the porous membrane is produced by a thermally induced phase separation method. The above-mentioned method for producing a porous membrane makes it possible to realize a liquid-liquid phase separation type membrane having excellent durability and to control the membrane structure.

[0024] The thermally induced phase separation method involves heating and melting a thermoplastic resin such as polyketone and mixing it homogeneously with a solvent such as dioctyl phthalate or dibutyl phthalate, molding this in the heated and melted state into a hollow fiber or flat membrane, and then immersing the molded body in a liquid (such as water) that does not dissolve the molded body components or cooling in air to cause phase separation into a polymer layer and a solvent layer. The membrane is then immersed in a solution to extract the solvent and the like from the membrane, producing a porous membrane.

[0025] The porous film obtained by the manufacturing method of this embodiment will be described below.

[0026] The porous membrane obtained by the manufacturing method of the present embodiment contains a thermoplastic resin. The porous membrane may be made of only a thermoplastic resin, or may further contain other components.

[0027] The porous membrane obtained by the manufacturing method of this embodiment uses polyketone as the thermoplastic resin. The polyketone in the porous membrane is preferably one that has high affinity for various liquids, especially water, and high durability 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.}

[0028] Such a polyketone is preferably a polyketone having a structure formed by copolymerization of an olefin and carbon monoxide (i.e., a copolymer of an olefin and carbon monoxide or a polymer having the same structure). In the synthesis of a 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.

[0029] In 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.

[0030] 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.

[0031] Polyketones can be obtained, for example, by polymerizing carbon monoxide and olefins using palladium, nickel or the like as a catalyst.

[0032] The porous membrane produced by the production method 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.

[0033] The porous membrane manufactured by the manufacturing method of this embodiment has a pore size of 1.0 μm or less on one surface of the porous membrane, and more preferably 0.5 μm or less. When the pore size of one surface of the porous membrane is 1.0 μm or less, the porous membrane can have sufficient blocking performance. The pore size is measured by image analysis of images observed using FE-SEM.

[0034] The thermoplastic resin used in the manufacturing method of the porous membrane (preferably a 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. Furthermore, when cooled and cooled, the thermoplastic resin returns to its original elastic body, and during this time no chemical changes occur in the molecular structure or the like (see, for example, "Chemical Encyclopedia 6, Condensed Edition, Edited by the Editorial Committee for the Chemical Encyclopedia, Kyoritsu Shuppan, pp. 860 and 867, 1963").

[0035] The thermoplastic resin in this embodiment is preferably a polyketone as described above.

[0036] The concentration of the polyketone when mixing the polyketone with the solvent is preferably 20% by mass or more and 50% by mass or less, more preferably 25% by mass or more and 45% by mass or less. If it is 20% by mass or more, the mechanical strength and porosity of the porous membrane are easily ensured, and if it is 50% by mass or less, the water permeability of the porous membrane is not reduced.

[0037] The solvent to be used in this embodiment is a latent solvent for the thermoplastic resin used in this embodiment. In this embodiment, the latent solvent refers to a solvent that hardly dissolves the thermoplastic resin at room temperature (25° C.) but can dissolve the thermoplastic resin at a temperature higher than room temperature. It is sufficient that the solvent is liquid at the melt-kneading temperature with the thermoplastic resin, and it is not necessarily liquid at room temperature.

[0038] Examples of the solvent 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; 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 and dipropyl phthalate (DPrP) are preferred.

[0039] The mass ratio of the solvent in the mixture of the thermoplastic resin and the solvent is preferably 10% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 60% by mass or less. If the mass ratio of the solvent is 10% by mass or more, the thermoplastic resin can be stably dissolved, and if it is 70% by mass or less, the viscosity is sufficient for producing a porous membrane, so that a porous membrane can be stably produced.

[0040] The shape of the porous membrane 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.

[0041] In one embodiment, the porous membrane of the present invention is a flat membrane. 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.

[0042] In the present invention, when evaluating the structure of the porous membrane, a simple method for producing a flat membrane was carried out as follows. A hot stage was used to heat the thermoplastic resin and the solvent to form a homogeneous solution, which was then cooled to produce a flat membrane. The cooling method may be, for example, immersion in a water bath at 10°C or 50°C for rapid cooling, or cooling at a controlled constant cooling rate. The solvent is then extracted with a solvent such as alcohol to obtain a porous membrane.

[0043] As another method for producing a flat membrane, the following method can be carried out. A thermoplastic resin and a solvent are placed in a temperature-controlled tank or the like, degassed, and then the thermoplastic resin and the solvent are cast onto a preheated stainless steel plate to which a Teflon film of a specified thickness and size is attached. The plate is then immersed in a water bath, and the solvent mixed with the thermoplastic resin is extracted with a solvent such as alcohol to obtain a porous membrane.

[0044] In this embodiment, polyketone is used as the thermoplastic resin, and a solvent having a solubility parameter (Ra) of 12 MPa is used. 0.5 More than 17.5MPa 0.5 Use a solvent with a solubility parameter (Ra) of 12 MPa or less. 0.5 If the solubility parameter (Ra) is 17.5 MPa or more, the membrane structure has excellent water permeability and strength because the spherulite structure due to solid-liquid phase separation does not appear due to liquid-liquid phase separation. 0.5When the temperature is lower than 100° C., the polyketone can be dissolved by heating to a high temperature, and thermally induced phase separation can be exhibited. In the present invention, the solvent having the solubility parameter (Ra) in the above range is preferably polyethylene glycol or dipropyl phthalate.

[0045] The solubility parameter (Ra) is calculated by the following formula. The following formula is a relational formula between the three-dimensional solubility parameter of polyketone and the three-dimensional solubility parameter of a solvent, and is used to evaluate the solubility of polyketone and a solvent. The right side of the formula below represents the solubility range of the Hansen solubility parameter three-dimensionally, and the three-dimensional solubility parameter of polyketone (σ dp , σ pp , σ hp ) to obtain the 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 solvent and polyketone, respectively, and σ pm and σ pp are the dipole binding terms of the solvent and polyketone, respectively, and σ hm and σ hp denote the hydrogen bond terms of the solvent and polyketone, respectively.] Three-dimensional solubility parameters (σ dp , σ pp , σ hp) was 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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[0046] The solvent may be one type, or two or more types of solvents may be used. Here, the two or more types of solvents may be two or more types of solvents with different compounds, or two or more types of solvents with the same compound but different molecular weights, for example, two or more types of solvents with the same monomer structure but different weight average molecular weights due to differences in polymerization degrees. By mixing two types of solvents with different compatibility with a thermoplastic resin (polyketone), it becomes possible to control the membrane structure. The two types of solvents may be two types of solvents with different molecular weights, and further, the membrane structure can be adjusted by changing the mixing ratio of the two different types of solvents. In this embodiment, it is preferable to mix, for example, polyethylene glycols with different molecular weights while using 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. When two types of solvents with different molecular weights are mixed, the ratio of the weight average molecular weight of one of the two solvents to the weight average molecular weight of the other solvent 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 film structure can be obtained. In addition, when polyethylene glycol is used as the solvent for polyketone, the molecular weight of polyethylene glycol is preferably 200 or more and 600 or less. When the molecular weight of polyethylene glycol is within the above range, it is preferable because it can express a liquid-liquid phase separation type.

[0047] In the extraction and removal of the solvent, a liquid suitable for extraction (extraction liquid) is used that does not dissolve or denature the thermoplastic resin used and is miscible with the solvent. 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 solvent used is water-soluble, water can also be used as the extraction liquid. EXAMPLES

[0048] 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.

[0049] The measurement method used in this embodiment is as follows.

[0050] 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 examples.

[0051] Tables 1 and 2 show the composition and manufacturing conditions of the membrane, as well as various performance characteristics.

[0052] (1) Polyketone used Polyketone homopolymer (HPK) Asahi Kasei Corporation Polyketone copolymer (CPK) manufactured by Hyosung Co., Ltd., product name "M630A"

[0053] (2) Solvent Screening Polyketone and each solvent were placed in a test tube and heated to 250°C in an oil bath. The heated solution was quenched with liquid nitrogen to solidify, and then cut into small pieces. The cut samples were heated on a hot stage (LK-600PH, Linkam) and then cooled to 25°C at a cooling rate of 10°C / min. During cooling, the cloud point and crystallization behavior were observed under an optical microscope (BX50, Olympus) to determine whether solid-liquid phase separation (SL) or liquid-liquid phase separation (LL) had occurred.

[0054] (3) Preparation of phase diagram The polyketone and the solvent were heated on a hot stage (LK-600PH Hotstage, Linkam, Surrey, UK) and cooled at 10 °C / min. During cooling, the solution was observed under an optical microscope (Olympus BX50), and the temperature at which the solution started to become cloudy was defined as the cloud point. The sample was heated at 20° C. / min using a DSC (DSC-8500, PerkinElmer, USA), held for 2 minutes, and then cooled at 10° C. / min. The starting temperature of the exothermic peak was taken as the crystallization temperature.

[0055] (4) Flat membrane manufacturing method 1 A homogeneous solution was formed by heating the polyketone and the solvent using a hot stage (LK-600PH Hotstage, Linkam, Surrey, UK), and then cooled to produce a flat membrane. The temperature was lowered at a cooling rate of 10°C / min or 50°C / min, or the membrane was immersed in a water bath at 10°C or 50°C for rapid cooling. The solvent was then extracted with ethanol to obtain a porous membrane.

[0056] (5) Flat membrane manufacturing method 2 Polyketone and a solvent were placed in a temperature-controlled tank and degassed, then cast onto a preheated stainless steel plate with a size of 15 x 15 cm and a Teflon film of 200 μm thickness attached, and then immersed in a water bath at 10° C. The solvent was extracted with ethanol to obtain a porous membrane.

[0057] (6) Membrane structure The morphology of the film was observed using a FE-SEM (JEOL, JSF-7500F). When observing the cross section of the film, it was immersed in liquid nitrogen and fractured. After drying in a vacuum for 12 hours, cesium tetroxide was evaporated onto the surface and observation was performed.

[0058] Example 1 In the above solvent screening, the solubility and phase separation behavior of the polyketone homopolymer and polyketone copolymer were confirmed for the 26 types of solvents in Table 1 and the 5 types of mixed solvents in Table 2. Tables 1 and 2 show the results of the solvent screening in Example 1 and the calculation results of the solubility parameters. In Table 1, as described above, "SL" indicates solid-liquid phase separation, and "LL" indicates liquid-liquid phase separation. In addition, in Tables 1 and 2 below, σ dp is the dispersion term of polyketone, σ pp is the dipole bond term of polyketone, σ hpis the hydrogen bond term of polyketone, and σ dm is the dispersion term of the solvent, σ pm is the dipole binding term of the solvent, σ hm is the hydrogen bonding term of the solvent and Ra is the solubility parameter. Three-dimensional solubility parameters (σ dp , σ pp , σ hp ) was 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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[0059] [Table 1]

[0060] *1 HPK: Polyketone homopolymer (manufactured by Asahi Kasei Corporation) *2 CPK: Polyketone copolymer (manufactured by Hyosung, product name "M630A") *3 PC: Propylene carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *4 SFL: Sulfolane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *5 CPL: Caprolactam (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *6 DMSO2: Dimethylsulfone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *7 DMP: Dimethyl phthalate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *8 DEP: Diethyl phthalate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) *9 DPrP: Dipropyl phthalate (Tokyo Chemical Industry Co., Ltd.) *10 DPC: Diphenyl carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *11 TEG: Triethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *12 DEG: Diethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *13 DBS: Dibutyl sebacate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *14 GTA: Glycerol triacetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *15 TEC: Triethyl citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *16 ATEC: Acetyl triethyl citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *17 ATBC: Acetyl tributyl citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *18 DIBA: Diisobutyl adipate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *19 PEG300: Polyethylene glycol 300 (Tokyo Chemical Industry Co., Ltd.) *20 PEG400: Polyethylene glycol 400 (Tokyo Chemical Industry Co., Ltd.) *21 PEG600: Polyethylene glycol 600 (Tokyo Chemical Industry Co., Ltd.) *22 PEG200: Polyethylene glycol 200 (Tokyo Chemical Industry Co., Ltd.) *23 DPM: Diphenylmethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *24 EG: Ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *25 Glycerol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0061] [Table 2]

[0062] From Tables 1 and 2, the solubility parameter (Ra) of the solvent is 12 MPa. 0.5 More than 17.5MPa 0.5 It can be seen that liquid-liquid phase separation occurs between the following:

[0063] Example 2 A phase diagram (Figure 1) was created using polyketone copolymer and PEG300 or DPrP as the solvent. In order to evaluate the membrane structure, flat membranes were produced using 25 mass% polyketone copolymer at the following cooling rates based on the above-mentioned flat membrane production method 1. Figure 2 shows a cross-sectional view of the produced flat membrane. In Figures 1 and 2, (a) is the CPK / PEG300 system, and (b) is the CPK / DPrP system. The numbers after a and b represent the cooling rates described below. 1: Rapid cooling in a 10℃ water bath 2: Rapid cooling in a 50℃ water bath 3: Cool at 50℃ / min 4: Cooling at 10℃ / min

[0064] As shown in Figure 1, PEG and DPrP can express liquid-liquid phase separation regions. When the cross-sectional structure was examined (shown in Figure 2), the spherulite structure seen in solid-liquid phase separation was not observed in either (a) or (b), and it was confirmed that a liquid-liquid phase separation structure was expressed.

[0065] Example 3 A phase diagram was created as shown in Figure 3 using a polyketone homopolymer in the same manner as in Example 1. It can be seen that the liquid-liquid phase separation region can be controlled by mixing two types of PEG.

[0066] Example 4 Using a polyketone homopolymer with a concentration of 25% by mass, PEG200 alone was used as a solvent, or PEG200 and PEG300, PEG200 and PEG400, or PEG200 and PEG600 were mixed according to the flat membrane production method 1, and a flat membrane was produced at the following cooling rates. The two types of PEG were mixed at PEG200:PEG300=9:1, PEG200:PEG400=9:1, and PEG200:PEG600=9:1. In FIG. 4, a is PEG200 alone, b is PEG200 / PEG300, c is PEG200 / PEG400, and d is PEG200 / PEG600. The numbers after a, b, c, and d represent the cooling rates below. 1: Rapid cooling in a 10℃ water bath 2: Rapid cooling in a 50℃ water bath 3: Cool at 50℃ / min 4: Cooling at 10℃ / min

[0067] When the cross-sectional structure was examined (shown in Figure 4), a spherulitic structure similar to that seen in solid-liquid phase separation was confirmed in PEG200 alone, but it was confirmed that a liquid-liquid phase separation structure was expressed by mixing PEG200 with PEG300, PEG400, or PEG600.

[0068] Example 5 Using a polyketone homopolymer with a concentration of 25% by mass, a flat membrane was produced using PEG200 and PEG300 as solvents at the following cooling rates based on the flat membrane production method 1. The two types of PEG were mixed in ratios of PEG200:PEG300=10:0, 9:1, 8:2, and 6:4, and flat membranes were produced at the following cooling rates. Note that a is PEG200:PEG300=10:0, b is PEG200:PEG300=9:1, c is PEG200:PEG300=8:2, and d is PEG200:PEG300=6:4. The numbers after a, b, c, and d represent the cooling rates below. 1: Rapid cooling in a 10℃ water bath 2: Rapid cooling in a 50℃ water bath 3: Cool at 50℃ / min 4: Cooling at 10℃ / min

[0069] When the cross-sectional structure was examined (shown in Figure 5), it was confirmed that the liquid-liquid phase separation structure could be controlled by adjusting the mixing ratio of two types of polyethylene glycol (PEG).

[0070] Example 6 Using polyketone copolymer and PEG300 as a solvent, the polyketone copolymer concentrations were set to 25 mass%, 30 mass%, 40 mass%, and 50 mass%, and flat membranes were produced by quenching in a 10°C water bath based on flat membrane production method 1. As shown in Figure 6, the higher the concentration of polyketone copolymer, the smaller the pores and the denser the structure.

Claims

1. A method for producing a porous polyketone membrane using a polyketone and at least one solvent, comprising the steps of: The solvent has a solubility parameter (Ra) of 12 MPa. ０．５ More than 17.5MPa ０．５ The range is as follows: A method for producing a porous polyketone membrane, comprising producing the porous membrane by a thermally induced phase separation method.

2. The method for producing a polyketone porous membrane according to claim 1, characterized in that two or more types of solvents are used.

3. The method for producing a polyketone porous membrane according to claim 2 , wherein the two or more solvents have the same monomer structure and different weight average molecular weights due to differences in polymerization degrees.

4. The method for producing a polyketone porous membrane according to claim 1, characterized in that the solvent is two types of solvent, and the ratio of the weight average molecular weight of one of the two solvents to the weight average molecular weight of the other solvent is between 1.0 and 3.

5.

5. The method for producing a polyketone porous membrane according to claim 2 , characterized in that a mixing ratio of the two or more types of solvents is adjusted.

6. 2. The method for producing a polyketone porous membrane according to claim 1, wherein the solvent is polyethylene glycol or dipropyl phthalate.

7. The method for producing a polyketone porous membrane according to claim 6, wherein the solvent is polyethylene glycol.

8. The method for producing a polyketone porous membrane according to claim 7, wherein the solvent is polyethylene glycol having a weight average molecular weight of 200 or more and 600 or less.

9. 2. The method for producing a polyketone porous membrane according to claim 1, wherein the concentration of the polyketone when mixing the polyketone with the solvent is 20% by mass or more and 50% by mass or less.

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