Aromatic polyether production method

Abstract

To provide a method for producing an aromatic polyether that enables simple and efficient removal of a solvent and an alkali metal halide from the reaction mixture of the aromatic polyether, and reduces a residual solvent and an inorganic salt contained in the aromatic polyether to or below a specified level.SOLUTION: A method for producing an aromatic polyether, comprising: a reaction step of obtaining the aromatic polyether by reacting a raw material mixture in the presence of a reaction solvent; and a washing step of washing the aromatic polyether obtained in the reaction step using a washing solvent that dissolves both the reaction solvent and an alkali metal halide generated in the reaction step.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aromatic polyether. Specifically, the present invention relates to a process for producing aromatic polyethers, which process includes a post-treatment step of the aromatic polyether reaction mixture. [Background technology]

[0002] Aromatic polyethers have excellent heat resistance and mechanical strength, and are used as metal replacement materials. In recent years, their applications have expanded to include automobiles, aircraft, and the medical field. Polyether ether ketone (PEEK) resin, a representative aromatic polyether, is produced in the presence of carbonate from hydroquinone and halogenated diphenyl ketone as the main components. During this process, metal halides and other by-products are produced simultaneously with the production of PEEK, so the reaction mixture contains the raw material carbonate and the by-product metal halides. The reaction mixture is typically treated by cooling and solidifying the mixture using a belt cooler or similar device, followed by mechanical pulverization and subsequent purification using organic solvents, water, and other materials (Non-Patent Document 1). Furthermore, Patent Documents 1 and 2 describe a method of forming particles by directly pouring a high-temperature reaction liquid into water. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-331239 [Patent Document 2] Chinese Patent Application Publication No. 113388103 [Non-patent literature]

[0004] [Non-Patent Document 1] Process Economic Program Report No.86D, HIGH TEMPRATURE POLYMER, SRI INTERNATIONAL (October 1989) Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have noticed that a problem with these conventional purification methods is that washing with an organic solvent is repeated, followed by further repeated washing with an aqueous solvent, resulting in a large number of repeated washing / filtration cycles in total. They have also noticed that washing with an organic solvent followed by water washing may result in poor extraction efficiency of inorganic salts, and that it is usually difficult to reduce the amount of inorganic salts contained in aromatic polyethers to several hundred ppm or less.

[0006] One method for reducing the amount of inorganic salts contained in aromatic polyethers is washing with water under high pressure (British Patent Application Publication No. 2412915), but this method requires a pressure vessel. Another method is to reduce inorganic salts using a mixed solvent of water and a water-soluble aprotic solvent, such as sulfolane or dimethyl sulfoxide, which has a boiling point of 100°C or higher (Japanese Patent No. 5534815). However, this method has the drawback of requiring complicated processing to recover and reuse the aprotic solvent from the mixed solution of water and a water-soluble aprotic solvent, which has a boiling point of 100°C or higher. For example, methods of recovery and reuse include distillation and extraction with low-boiling-point solvents. However, distillation requires the water to be removed by evaporation first, followed by distillation of the solvent, which results in high energy costs. Furthermore, extraction with low-boiling-point solvents requires the use of a new extraction solvent and an additional extraction step, which makes it complicated.

[0007] One object of the present invention is to provide a method for producing an aromatic polyether, which can simply and efficiently remove solvents, alkali metal halides, and the like from a reaction mixture of an aromatic polyether, thereby reducing the residual solvent and inorganic salts contained in the aromatic polyether to a predetermined amount or less. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that by using a specific solvent system, it is possible to simply and efficiently remove solvents, alkali metal halides, and the like from a reaction mixture of an aromatic polyether, and to reduce the residual solvent and inorganic salts contained in the aromatic polyether to a predetermined amount or less, thereby completing the present invention. According to the present invention, the following resin compositions and the like can be provided. 1. A reaction step of reacting a raw material mixture in the presence of a reaction solvent to obtain an aromatic polyether; a washing step of washing the aromatic polyether obtained in the reaction step with a washing solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step; A method for producing an aromatic polyether, comprising: 2. The method for producing an aromatic polyether according to 1 above, wherein the washing solvent is a mixed solvent of water and an organic solvent having a boiling point of less than 100°C at normal pressure. 3. The method for producing an aromatic polyether according to 2 above, wherein the mass ratio of the organic solvent to the water in the washing solvent ([mass of organic solvent] / [mass of water]) is 10 / 90 to 90 / 10. 4. The method for producing an aromatic polyether according to 2 or 3 above, wherein the organic solvent is acetone. 5. Median diameter D of the aromatic polyether obtained in the reaction step 50 5. The method for producing an aromatic polyether according to any one of 1 to 4 above, wherein the particle size is 1 to 1000 μm. 6. The method for producing an aromatic polyether according to any one of 1 to 5 above, wherein the washing step comprises an acid washing step using an acidic aqueous solution and a step of diluting the acid, in this order, and the washing solvent is used in at least one of these steps. 7. The acid washing step preparing a mixture comprising an aromatic polyether and an acidic aqueous solution; agitating the mixture; and recovering the aromatic polyether from the mixture, The pH of the mixture in the stirring step is 1.0 to 6.0, the temperature of the mixture is 0 to 84°C, and the stirring time is 10 to 120 minutes; and 7. The method for producing an aromatic polyether according to 6 above, wherein the preparation step, the stirring step, and the recovery step are repeated in this order 1 to 5 times. 8. The step of diluting the acid comprises: preparing a mixture comprising an aromatic polyether and water; agitating the mixture; and recovering the aromatic polyether from the mixture, The temperature of the mixture in the stirring step is 0 to 84°C, and the stirring time is 10 to 120 minutes, and 8. The method for producing an aromatic polyether according to 6 or 7 above, wherein the preparation step, the stirring step, and the recovery step are repeated in this order 1 to 7 times. 9. The method further comprises, before the acid washing step, an organic solvent washing step using an organic solvent; The organic solvent washing step preparing a mixture comprising an aromatic polyether and an organic solvent; agitating the mixture; and recovering the aromatic polyether from the mixture, a mass ratio of the aromatic polyether to the organic solvent in the mixture ([mass of the aromatic polyether] / [mass of the organic solvent]) of 1 / 20 to 1 / 3; The stirring time in the stirring step is 10 to 120 minutes, and 9. The method for producing an aromatic polyether according to any one of 6 to 8 above, wherein the preparation step, the stirring step, and the recovery step are repeated in this order 1 to 7 times. 10. The method for producing an aromatic polyether according to any one of 1 to 9 above, wherein the reaction solvent contains diphenyl sulfone, and the content of diphenyl sulfone in the aromatic polyether after the washing step is 1 to 1000 ppm. 11. The method for producing an aromatic polyether according to any one of 1 to 10 above, wherein the reaction solvent contains diphenyl sulfone, and the content of diphenyl sulfone in the aromatic polyether after the washing step is 1 to 100 ppm. 12. The method for producing an aromatic polyether according to any one of 1 to 11 above, wherein the content of alkali metal halide in the aromatic polyether after the washing step is 1 to 500 ppm. 13. A method for purifying an aromatic polyether, comprising washing the aromatic polyether with a washing solvent that dissolves both the reaction solvent used in the synthesis of the aromatic polyether and an alkali metal halide. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for producing an aromatic polyether, which can simply and efficiently remove solvents, alkali metal halides, and the like from a reaction mixture of an aromatic polyether, thereby reducing the residual solvent and inorganic salts contained in the aromatic polyether to a predetermined amount or less. DETAILED DESCRIPTION OF THE INVENTION

[0010] The process for producing an aromatic polyether of the present invention will be described in detail below. In this specification, "x to y" represents a numerical range of "not less than x and not more than y." The upper and lower limits of the numerical ranges can be combined in any way. Furthermore, among the individual embodiments of the aspects of the present invention described below, it is possible to combine two or more embodiments that are not mutually contradictory, and an embodiment that combines two or more embodiments is also an embodiment of an aspect of the present invention.

[0011] 1. Aromatic polyether manufacturing method A method for producing an aromatic polyether according to one embodiment of the present invention (hereinafter also referred to as "a production method according to one embodiment of the present invention" or "the production method of the present invention") comprises: a reaction step of reacting a raw material mixture in the presence of a reaction solvent to obtain an aromatic polyether; a washing step of washing the aromatic polyether obtained in the reaction step with a washing solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step; Includes. According to the production method of this embodiment, the solvent, alkali metal halide, etc. can be simply and efficiently removed from the reaction mixture of the aromatic polyether, and the residual solvent and inorganic salt contained in the aromatic polyether can be reduced to a predetermined amount or less.

[0012] In this specification, the term "aromatic polyether" may refer to an aromatic polyether as a compound (the aromatic polyether itself without impurities), as well as a composition containing a residual solvent, an inorganic salt, and an aromatic polyether.

[0013] As used herein, "dissolve" means that the mixed system forms a single phase.

[0014] For example, when a washing solvent "dissolves" a reaction solvent, it means that at least a part of the washing solvent and at least a part of the reaction solvent are compatible with each other. This includes both cases where the washing solvent and the reaction solvent are phase-separated (dissolution) and cases where they are not phase-separated (mixture).

[0015] In one embodiment, the wash solvent is a solvent in which the solubility of the reaction solvent at 55°C is 5.0 g / L or more, 5.5 g / L or more, 6.0 g / L or more, or 6.5 g / L or more.

[0016] Furthermore, when the washing solvent "dissolves" the alkali metal halide, it means that at least a portion of the alkali metal halide is dispersed in the washing solvent to form a homogeneous system (solution).

[0017] In one embodiment, the wash solvent is a solvent in which the solubility of alkali metal halides at 55°C is 1.0 g / L or more, 1.2 g / L or more, 1.5 g / L or more, or 2.0 g / L or more.

[0018] The washing solvent may dissolve alkali metal halides other than the alkali metal halides produced in the reaction step.

[0019] In one embodiment, the aromatic polyether obtained by the production method of the present invention has a total content of residual solvents and inorganic salts of less than 1.0%, less than 0.5%, less than 0.1%, less than 0.05%, or less than 0.02%, or is substantially free of residual solvents and inorganic salts. The term "substantially free" means that the aromatic polyether does not contain any residual solvents or inorganic salts, or that the residual solvents and inorganic salts are present as unavoidable impurities.

[0020] In this specification, examples of "simple and efficient" include a small number of washings in the washing step and a small amount of washing liquid used.

[0021] The reason why such an effect is obtained is not entirely clear, but the following is thought to be the reason. In conventional methods, a first stage of washing is carried out using a washing solvent that dissolves the reaction solvent in the washing step, and then a second stage of washing is carried out using a washing solvent that dissolves the alkali metal halide. In such cases, the efficiency of the second cleaning step may decrease due to the residue of the first cleaning solvent. The same applies when the first cleaning step is performed using a cleaning solvent that dissolves an alkali metal halide, and then the second cleaning step is performed using a cleaning solvent that dissolves the reaction solvent.

[0022] On the other hand, in the production method of the present invention, by using a washing solvent in the washing step that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step, washing does not need to be performed in two separate stages, and the number of washings can be reduced, which is expected to reduce the amount of washing liquid used. Furthermore, since the influence of remaining washing solvent on subsequent washings can be eliminated, more efficient washing is possible, and as a result, the number of washings can be reduced, which is expected to reduce the amount of washing liquid used.

[0023] In one embodiment, the production method of the present invention includes, after the washing step, a further processing step such as another washing step, a grinding step, or a drying step. Depending on the state of the obtained aromatic polyether and the desired properties, additional treatments such as washing, pulverization, or drying may be carried out.

[0024] (aromatic polyether) The aromatic polyether produced by the production method according to one aspect of the present invention contains a structural unit represented by the following formula (1). [ka] [In formula (1), A includes one or more structural units selected from the group consisting of structural units represented by the following formulas (A1) to (A3). [ka] (In formula (A1), X A1 represents -C(=O)- or -S(=O)2-. In formula (A2), X A2 and X A3 each independently represents -C(=O)- or -S(=O)2-. In formula (A3), R A represents a cyano group. B includes one or more structural units selected from the group consisting of structural units represented by the following formulas (B1) to (B3). [ka] (In formula (B1), R B represents a hydrogen atom or a phenyl group. n is an integer of 0 to 2. When n is 0, the oxygen atom is directly bonded to the adjacent unit structure. When n is 1, B is directly bonded to the adjacent structural unit. When n is 2, of the two Bs, the B that is farthest from A is directly bonded to the adjacent unit structure.

[0025] When two or more structural units represented by formulae (A1) to (A3) are present, the two or more structural units represented by formulae (A1) to (A3) may be the same or different. When two or more structural units represented by formulae (B1) to (B3) are present, the two or more structural units represented by formulae (B1) to (B3) may be the same or different.

[0026] In the formulae (A1) to (A3) and (B1) to (B2), the bond crossing the skeleton constituting the benzene ring means that the bond is made to a bondable position among the carbon atoms constituting the benzene ring. In formula (B3), the bond that crosses the skeleton that constitutes the naphthalene ring means that the bond is made to a bondable position among the carbon atoms that constitute the naphthalene ring.

[0027] For example, formula (A1) includes all of the following structures: [ka]

[0028] In one embodiment, A in formula (1) is a structure represented by formula (A1) or formula (A3). In one embodiment, X in formula (A1) A1 is -C(=O)-.

[0029] In one embodiment, A in formula (1) is a structure represented by the following formula (A1-1): [ka]

[0030] In one embodiment, B in formula (1) is a structure represented by formula (B1) or formula (B2). In one embodiment, R in formula (B1) B is a hydrogen atom.

[0031] In one embodiment, the aromatic polyether contained in the mixed liquid contains a structural unit represented by the following formula (1-1). [ka]

[0032] In one embodiment, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 99% by mass or more, 99.5% by mass or more, or substantially 100% by mass of the aromatic polyether are structural units represented by formula (1).

[0033] In one embodiment, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 99% by mass or more, 99.5% by mass or more, or substantially 100% by mass of the aromatic polyether are structural units represented by formula (1-1).

[0034] In one embodiment, in the aromatic polyether containing the structural unit represented by formula (1), the molar ratio of the structural unit represented by A to the structural unit represented by B (structural unit represented by A:structural unit represented by B) is 47.5:52.5 to 52.5:47.5, 48.0:52.0 to 52.0:48.0, 48.5:51.5 to 51.5:48.5, 49.0:51.0 to 51.0:49.0, or 49.5:50.5 to 50.5:49.5. The number of moles of the structural unit represented by A may be larger than, smaller than, or the same as the number of moles of the structural unit represented by B.

[0035] In one embodiment, the aromatic polyether has a Cl (chlorine) atom or an F (fluorine) atom at the end of the main chain. In one embodiment of the aromatic polyether, the structural unit represented by A is located at one or more ends of the main chain. In this case, the end structure bonded to the structural unit may be a halogen atom. The halogen atom may be, for example, a chlorine atom (Cl) or a fluorine atom (F).

[0036] In an aromatic polyether according to one embodiment, a terminal structure is bonded to the structural unit represented by B and is arranged at one or more ends of the main chain. The terminal structure may be, for example, a hydrogen atom (H) or the like (when the terminal structure is a hydrogen atom (H), a hydroxyl group is formed together with the oxygen atom (O) in the structural unit). The terminal structure of the aromatic polyether may be, for example, a structure in which the above-mentioned chlorine atom (Cl), fluorine atom (F), or hydroxyl group is replaced with a hydrogen atom (H), etc. The terminal structure may have a structure other than those exemplified above. For example, the terminal structure may have a structure derived from a reaction terminator.

[0037] The method for producing the aromatic polyether is not particularly limited, and for example, the aromatic polyether can be produced by polymerizing a monomer containing a structural unit represented by A and a monomer containing a structural unit represented by B.

[0038] Examples of the monomer containing the structural unit represented by A include halogenated diphenyl ketone, halogenated benzonitrile, and halogenated diphenyl sulfone. Examples of halogenated diphenyl ketones include 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, and the like. Examples of halogenated benzonitriles include 2,6-difluorobenzonitrile, 2,6-dichlorobenzonitrile, and the like. Examples of halogenated diphenyl sulfones include 4,4'-difluorodiphenyl sulfone and 4,4'-dichlorodiphenyl sulfone. 4,4'-Difluorobenzophenone and 4,4'-dichlorobenzophenone can be easily synthesized and are also commercially available.

[0039] Examples of the monomer containing the structural unit represented by B include hydroquinone and biphenol. Hydroquinone is easily synthesized and is also commercially available.

[0040] In one embodiment, the aromatic polyether after the washing step has a reaction solvent content of 1 ppm to 1000 ppm, 1 ppm to 100 ppm, or 10 ppm to 1000 ppm, or is substantially free of the reaction solvent. The term "substantially free" means that the aromatic polyether does not contain any reaction solvent at all, or that the reaction solvent is mixed in as an unavoidable impurity. The content of the reaction solvent can be measured by the method described in the Examples.

[0041] In one embodiment, the lower limit of the reaction solvent content in the aromatic polyether after the washing step may be, for example, 1 ppm, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 50 ppm, or 100 ppm.

[0042] In one embodiment, the upper limit of the reaction solvent content in the aromatic polyether after the washing step may be, for example, 1000 ppm, 500 ppm, 200 ppm, or 100 ppm. When the content of the reaction solvent in the aromatic polyether after the washing step is 1000 ppm or less, gas generation during molding or use of the resin containing the aromatic polyether is easily suppressed.

[0043] In one embodiment, the aromatic polyether after the washing step has an alkali metal halide content of 1 ppm to 500 ppm in terms of alkali metal atoms, or is substantially free of reaction solvent. The term "substantially free" means that the aromatic polyether does not contain any alkali metal halide at all, or that the alkali metal halide is present as an unavoidable impurity. The content of alkali metal halide can be measured as the content of alkali metal atoms by the method described in the Examples.

[0044] The alkali metal atom may be, but is not limited to, an alkali metal atom derived from a base used in synthesizing the aromatic polyether. The alkali metal atom may be a free component as a simple substance, or may be a free component as a compound with other atoms, an ion, etc. The content of the alkali metal atom is the ratio to the total amount of the aromatic polyether and the free component.

[0045] In one embodiment, the lower limit of the alkali metal halide content in the aromatic polyether after the washing step may be, for example, 1 ppm, 5 ppm, 10 ppm, 20 ppm, 50 ppm, or 100 ppm in terms of alkali metal atoms.

[0046] In one embodiment, the upper limit of the alkali metal halide content in the aromatic polyether after the washing step may be, for example, 500 ppm, 400 ppm, 300 ppm, or 200 ppm in terms of alkali metal atoms. When the content of alkali metal halides in the aromatic polyether after the washing step is 500 ppm or less in terms of alkali metal atoms, the thermal stability of the resin containing the aromatic polyether is likely to be improved.

[0047] [Reaction process] The reaction step is a step in which the raw material mixture is reacted in the presence of a reaction solvent to obtain an aromatic polyether. In one embodiment, the reacting step is a step of reacting a halogenated diphenyl ketone with hydroquinone in the presence of a reaction solvent to obtain an aromatic polyether.

[0048] (raw material mixture) The raw material mixture is not particularly limited as long as it contains raw materials necessary for reacting in the presence of a reaction solvent to obtain an aromatic polyether. For example, in addition to the raw materials, the raw material mixture may contain additives that are commonly used in reactions to obtain an aromatic polyether. Examples of additives include catalysts such as bases.

[0049] In one embodiment, the raw material mixture includes a halogenated diphenyl ketone and hydroquinone.

[0050] The form of the raw material mixture may be, for example, powder, but is not limited to this.

[0051] In this specification, the term "powder" refers to an aggregate of multiple fine solids. The powder has a particle size of 100 nm to 3 mm as a guide. The shape of the powder is not important and can be selected appropriately. The powder raw material mixture may be prepared by mixing raw materials and optional additives, pulverizing the mixture as necessary, and drying the mixture.

[0052] (halogenated diphenyl ketones) The halogenated diphenyl ketone is a monomer for polymerizing an aromatic polyether, and corresponds to the structural unit represented by the above formula (A1-1). Halogenated diphenyl ketones are easily synthesized and are also commercially available. Examples of halogenated diphenyl ketones include 4,4'-difluorobenzophenone and 4,4'-dichlorobenzophenone.

[0053] (hydroquinone) Hydroquinone is a monomer for polymerizing aromatic polyethers and corresponds to the structural unit represented by the above formula (B1). Hydroquinone can be easily synthesized and is also commercially available.

[0054] (Reaction solvent) As the reaction solvent, for example, an aprotic polar solvent can be used. Examples of aprotic polar solvents include N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dipropylacetamide, N,N-dimethylbenzoic acid amide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-isobutyl-2-pyrrolidone, Nn-propyl-2-pyrrolidone, Nn-butyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-methyl-3-methyl-2-pyrrolidone, Examples of such sulfones include N-ethyl-3-methyl-2-pyrrolidone, N-methyl-3,4,5-trimethyl-2-pyrrolidone, N-methyl-2-piperidone, N-ethyl-2-piperidone, N-isopropyl-2-piperidone, N-methyl-6-methyl-2-piperidone, N-methyl-3-ethylpiperidone, dimethyl sulfoxide, diethyl sulfoxide, 1-methyl-1-oxosulfolane, 1-ethyl-1-oxosulfolane, 1-phenyl-1-oxosulfolane, N,N'-dimethylimidazolidinone, and diphenyl sulfone.

[0055] In one embodiment, a halogenated diphenyl ketone and hydroquinone are reacted with stirring in diphenyl sulfone in the presence of potassium carbonate to provide an aromatic polyether.

[0056] (potassium carbonate) The potassium carbonate preferably has a purity of 99% by mass or more and a water content of 0.01% by mass or less. Such potassium carbonate is also commercially available. Potassium carbonate may be of general-purpose reagent grade, general industrial grade, or fine particle grade. Average particle size of potassium carbonate (D 50 The average particle size (D) is preferably 1000 μm or less, 800 μm or less, 500 μm or less, 300 μm or less, 100 μm or less, or even 50 μm or less. 50 The lower limit of ) can be, for example, 0.1 μm or more, 0.5 μm or more, or 1 μm or more. The average particle size of potassium carbonate (D 50 ) is a value measured by the following method. (Average particle size of potassium carbonate (D 50 ) Measurement method) Using a CAMSIZER manufactured by Microtrack Bell, particle size distribution is measured by the dry method. The sample (potassium carbonate) is dropped into the measurement section using a vibrating feeder, and the particles are photographed with a camera to measure the particle diameter. When processing the observed image, the average particle diameter (D 50 ) is calculated.

[0057] The reaction step can be carried out in an inert gas atmosphere, which is not particularly limited and includes, for example, nitrogen, argon gas, etc.

[0058] The reaction of the raw material mixture can be carried out under heating. The reaction temperature can usually be in the range of 150 to 380° C. The reaction time can usually be 0.1 to 10 hours.

[0059] In one embodiment, the raw material mixture is heated to 150° C. or higher and then maintained at that temperature. In one embodiment, the raw material mixture is heated to 150° C. or higher, and then the heating and temperature holding are repeated multiple times. In each of the above embodiments, the temperature may be increased at a rate of 10°C / min or less after the temperature has been increased to 150°C or higher. This allows the rate-determining step in the reaction of the raw material mixture to proceed smoothly, and makes it easier to obtain an aromatic polyether having a high molecular weight.

[0060] The reaction of the raw material mixture may be, for example, (i) a step of increasing the temperature to 180 to 220°C and maintaining the increased temperature for 0.5 to 2 hours; (ii) raising the temperature to 230 to 270°C and maintaining the temperature for 0.5 to 2 hours; and (iii) A step of increasing the temperature to 280 to 320°C and maintaining the increased temperature for 1 to 8 hours may be included.

[0061] The temperature increase in (i) to (iii) can be carried out at a rate of, for example, 10°C / min or less, 5°C / min or less, or 3°C / min or less. The temperature increase in (i) to (iii) is preferably, for example, 0.1 to 10°C / min or less, which allows the rate-determining step in the reaction of the raw material mixture to proceed smoothly, and makes it easier to obtain a high molecular weight aromatic polyether.

[0062] In one embodiment, the reaction of the raw material mixture can include at least one step selected from the group consisting of the above-mentioned steps (i) to (iii). When two or three steps are included, they are preferably performed in order from the lowest temperature to the highest. Between two or three steps, the raw material mixture can be heated.

[0063] In one embodiment, the reaction of the raw material mixture is carried out under conditions in which the maximum temperature of the raw material mixture is 280 to 320°C, more preferably higher than 290°C and 320°C or lower.

[0064] The aromatic polyether obtained in the reaction step contains a reaction solvent, an alkali metal halide, etc., and is sometimes referred to as a "reaction mixture" or a "raw aromatic polyether" in this specification.

[0065] The particle size of the aromatic polyether (reaction mixture) obtained in the reaction step is preferably 10 to 1000 μm, for example, 20 to 300 μm, from the viewpoint of ease of washing and handling. In this specification, when the term "particle size" is simply mentioned, it means the average particle size.

[0066] Median diameter D of the aromatic polyether obtained in the reaction process 50 is preferably 1000 μm or less, for example, 500 μm or less, 250 μm or less, 100 μm or less, or 50 μm or less.

[0067] Median diameter D of the aromatic polyether obtained in the reaction process 50is preferably 1 to 1000 μm, for example, 5 to 250 μm or 10 to 50 μm.

[0068] Median diameter D of the aromatic polyether obtained in the reaction process 90 is preferably 3000 μm or less, for example, 2000 μm or less, 1000 μm or less, 500 μm or less, 250 μm or less, or 100 μm or less.

[0069] Median diameter D of the aromatic polyether obtained in the reaction process 90 is preferably 10 to 3000 μm, for example, 20 to 2000 μm, or 50 to 100 μm.

[0070] The particle size and median diameter of the aromatic polyether obtained in the reaction step can be adjusted to fall within the above ranges by appropriately adjusting the composition of the raw material mixture and reaction solvent, reaction conditions, and the like.

[0071] The particle size of the aromatic polyether obtained in the reaction step can be measured using a laser diffraction particle size distribution measuring device. As the laser diffraction particle size distribution measuring device, for example, LMS-3000 manufactured by Seishin Enterprise Co., Ltd. can be used. Measurement of particle size (average particle size) and particle size distribution (median diameter D 50 and median diameter D 90 Measurement of the dispersion property is carried out using a wet dispersion unit (Hydro MV) under the following conditions. <Measurement conditions> Particle refractive index: 1.6 Particle absorption rate: 0.1 ·Dispersion medium: water Dispersant: Neutral detergent

[0072] After the reaction of the raw material mixture is completed, the resulting aromatic polyether is subjected to a washing step. After the reaction of the raw material mixture is completed, the resulting aromatic polyether can be directly subjected to a washing step. If necessary, prior to the washing step, the aromatic polyether can be separated, washed or purified according to known methods.

[0073] [Cleaning process] The washing step is a step in which the aromatic polyether (reaction mixture) obtained in the reaction step is washed with a washing solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step.

[0074] In the washing step, washing may be carried out once, washing may be carried out multiple times using one type of washing solvent, or washing may be carried out in combination with two or more types of washing solvents.

[0075] (Washing solvent) As a washing solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step, a single solvent or a mixed solvent can be used.

[0076] Specific examples of the single solvent include glycols and ionic liquids. These solvents may be used alone, but this does not exclude the use of two or more of them in combination.

[0077] The mixed solvent can be prepared, for example, by appropriately mixing an organic solvent and water, but is not limited to these, as long as it is a mixed solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step.

[0078] Examples of organic solvents include alcohols such as ethanol, methanol, n-propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol; carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as γ-butyrolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; and sulfoxides such as dimethyl sulfoxide. Examples of suitable organic solvents include oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; nitrogen-containing solvents such as acetonitrile, nitromethane, and N-methyl-2-pyrrolidone; esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, and phosphate triesters; glymes such as diglyme, triglyme, and tetraglyme; ketones such as acetone, diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone; sulfones such as sulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propane sultone, 4-butane sultone, and naphtha sultone. Among these, acetone is preferred as the organic solvent. These organic solvents may be used alone or in combination of two or more.

[0079] The organic solvent is preferably a water-soluble organic solvent having a boiling point of less than 100°C at atmospheric pressure, from the viewpoint of ease of solvent recovery. When a water-soluble organic solvent having a boiling point of less than 100°C at atmospheric pressure is used, water and the organic solvent can be easily separated even by simple distillation purification. In this specification, atmospheric pressure means standard atmospheric pressure (1 atm = 101325 Pa). The boiling point of the organic solvent at atmospheric pressure is more preferably lower than the boiling point of water at atmospheric pressure, for example, 99°C or lower, 98°C or lower, 95°C or lower, 90°C or lower, 85°C or lower, 80°C or lower, 75°C or lower, 70°C or lower, or 65°C or lower.

[0080] The boiling point of an organic solvent at normal pressure is usually above room temperature. In this specification, "room temperature" means 25°C.

[0081] Specific examples of the mixed solvent include a mixed solvent of acetone / water, a mixed solvent of methyl ethyl ketone (MEK) / water, a mixed solvent of alcohol / water, and a mixed solvent of water and an organic solvent that is miscible with water.

[0082] The washing solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step is preferably a mixed solvent of an organic solvent and water, more preferably a mixed solvent of acetone / water or a mixed solvent of MEK / water, and even more preferably a mixed solvent of acetone / water.

[0083] When washing is performed using a mixed solvent, the solvent, alkali metal halides, and the like can be removed more simply and efficiently from the reaction mixture of the aromatic polyether, and the residual solvent and inorganic salts contained in the aromatic polyether can be reduced to a predetermined amount or less. The reason why such an effect is obtained is not entirely clear, but it is thought that, compared with washing with only an acidic aqueous solution in the acid washing step or washing with only water in the water washing step, the washing liquid can be immersed deep into the aromatic polyether containing inorganic salts, and the inorganic salts can be removed more efficiently.

[0084] In one embodiment, the mass ratio of the organic solvent to water in the washing solvent ([mass of organic solvent] / [mass of water]) is 10 / 90 to 90 / 10.

[0085] In one embodiment, the lower limit of the mass ratio of the organic solvent to water in the washing solvent may be, for example, 10 / 90, 15 / 85, or 20 / 80.

[0086] In one embodiment, the upper limit of the mass ratio of the organic solvent to water in the washing solvent may be, for example, 90 / 10, 85 / 15, or 80 / 20.

[0087] When the mass ratio of the organic solvent to water in the washing solvent is within the above range, both the reaction solvent (diphenyl sulfone, etc.) and the inorganic salt can be dissolved, resulting in excellent washing efficiency.

[0088] The washing step can be carried out at a temperature depending on the type of solvent remaining in the aromatic polyether obtained in the reaction step. When washing is carried out at a high temperature, the solubility of the reaction solvent and alkali metal halide tends to increase, and more efficient washing can be expected. The temperature in the cleaning step is usually set to a temperature below the boiling point of the cleaning solvent. For example, in the case of an acetone / water mixed solvent (mass ratio 1:1), the cleaning step is usually carried out at 64°C or below, which is the boiling point of the acetone / water mixed solvent (mass ratio 1:1).

[0089] If necessary, the washing step may be carried out under pressure, which allows the washing step to be carried out at a temperature equal to or higher than the boiling point of the washing solvent at normal pressure.

[0090] In one embodiment, the washing step includes an acid washing step using an acidic aqueous solution and a step of diluting the acid, in this order, and a washing solvent is used in at least one of these steps.

[0091] (acid washing process) The acid washing step is a step in which the aromatic polyether obtained in the reaction step or the preceding washing step (for example, the organic solvent washing step described below) is washed with an acidic aqueous solution.

[0092] The method for washing with an acidic aqueous solution is not particularly limited, and examples thereof include a method in which an aromatic polyether is added to water, and an acid is mixed therein while stirring to prepare a mixture containing the aromatic polyether and an acidic aqueous solution, and the mixture is stirred for a predetermined time, and then the aromatic polyether is recovered from the mixture.

[0093] The acid used in the acidic aqueous solution is not particularly limited, and examples thereof include oxalic acid, hydrochloric acid, acetic acid, and phosphoric acid. The acids may be used alone or in combination of two or more.

[0094] The concentration of the acid in the acidic aqueous solution is not particularly limited and can be set appropriately, for example, at 0.001N or more and 5N or less.

[0095] When a washing solvent is used in the acid washing step, an acid can be mixed with the washing solvent to form an acidic aqueous solution, which can be used for washing.

[0096] As a method for recovering the aromatic polyether from the mixture, for example, a method of recovering the aromatic polyether as a solid by filtration can be mentioned.

[0097] In one embodiment, the acid wash step comprises: preparing a mixture comprising an aromatic polyether and an acidic aqueous solution; agitating the mixture; and recovering the aromatic polyether from the mixture, in this order.

[0098] In one embodiment, the pH of the mixture in the stirring step of the acid washing step is 1.0 to 6.0. In one embodiment, the lower limit of the pH of the mixture in the stirring step of the acid washing step may be, for example, 1.0, 1.5, 2.0, or 2.5. In one embodiment, the upper limit of the pH of the mixture in the stirring step of the acid washing step may be, for example, 6.0, 5.5, 5.0, 4.5, or 4.0.

[0099] If the pH of the mixture in the stirring step of the acid washing step is equal to or higher than the lower limit, the cleaning ability of the step is improved and corrosion is more easily prevented regardless of the material of the container.If the pH of the mixture in the stirring step of the acid washing step is equal to or lower than the upper limit, cleaning can be more effective. Therefore, the pH of the mixture in the stirring step of the acid washing step is preferably within the above range.

[0100] In one embodiment, the temperature of the mixture in the stirring step of the acid washing step is 0 to 84°C. In one embodiment, the lower limit of the temperature of the mixture in the stirring step of the acid washing step may be, for example, 0°C, 10°C, 20°C, 30°C, 40°C, or 50°C. In one embodiment, the upper limit of the temperature of the mixture in the stirring step of the acid washing step may be, for example, 84°C, 80°C, 70°C, 60°C, or 55°C.

[0101] If the temperature of the mixture in the stirring step of the acid washing step is within the above range, the liquid components in the mixture are less likely to solidify and vaporize, which is preferable.

[0102] In one embodiment, the stirring time in the stirring step of the acid washing step is 10 to 120 minutes. In one embodiment, the lower limit of the stirring time in the stirring step of the acid washing step may be, for example, 10 minutes, 15 minutes, or 20 minutes. In one embodiment, the upper limit of the stirring time in the stirring step of the acid washing step may be, for example, 120 minutes, 100 minutes, 80 minutes, 50 minutes, or 30 minutes.

[0103] If the stirring time in the stirring step of the acid washing step is equal to or longer than the lower limit, the washing can be more effectively achieved. If the stirring time in the stirring step of the acid washing step is equal to or shorter than the upper limit, the washing efficiency (particularly the time efficiency) can be improved. Therefore, the stirring time in the stirring step of the acid washing step is preferably within the above range.

[0104] In one embodiment, the acid washing step involves repeating the preparation step, the stirring step, and the recovery step in this order 1 to 5 times, 2 to 4 times, or 2 to 3 times.

[0105] (Process for diluting the acid) The acid dilution step is a step of diluting the acid contained in the aromatic polyether obtained in the acid washing step. In this specification, diluting the acid may also be referred to as a "water wash" or a "mixed solvent wash."

[0106] The method for diluting the acid is not particularly limited, and examples thereof include a method in which an aromatic polyether is added to water and stirred to prepare a mixture containing the aromatic polyether and water, and the aromatic polyether is recovered from the mixture.

[0107] When a washing solvent is used in the step of diluting the acid, the washing solvent may be mixed with water and used for washing. When the washing solvent is a mixed solvent containing water, it may be used as is for washing in the step of diluting the acid. For example, the aromatic polyether can be added to a mixed solvent of a washing solvent and water (or a washing solvent containing water) and stirred to prepare a mixture containing the aromatic polyether, the washing solvent, and water, and the aromatic polyether can be recovered from the mixture.

[0108] As a method for recovering the aromatic polyether from the mixture, for example, a method of recovering the aromatic polyether as a solid by filtration can be mentioned.

[0109] In one embodiment, the step of diluting the acid comprises: preparing a mixture comprising an aromatic polyether and water; agitating the mixture; and recovering the aromatic polyether from the mixture, in this order.

[0110] In one embodiment, the temperature of the mixture in the stirring step of diluting the acid is 0 to 84°C. In one embodiment, the lower limit of the temperature of the mixture in the stirring step of the acid washing step may be, for example, 0°C, 10°C, 20°C, 30°C, 40°C, or 50°C. In one embodiment, the upper limit of the temperature of the mixture in the stirring step of the acid washing step may be, for example, 84°C, 80°C, 70°C, 60°C, or 55°C.

[0111] In one embodiment, the stirring time in the stirring step of the step of diluting the acid is 10 to 120 minutes. In one embodiment, the lower limit of the stirring time in the stirring step of the acid washing step may be, for example, 10 minutes, 15 minutes, or 20 minutes. In one embodiment, the upper limit of the stirring time in the stirring step of the acid washing step may be, for example, 120 minutes, 100 minutes, 80 minutes, 50 minutes, or 30 minutes.

[0112] In one embodiment, the step of diluting the acid involves repeating the preparation step, the stirring step, and the recovery step in this order 1 to 7 times, 2 to 6 times, 2 to 5 times, or 2 to 4 times.

[0113] (Organic solvent washing process) The organic solvent washing step is a step of washing the aromatic polyether obtained in the reaction step with an organic solvent.

[0114] The method for washing using an organic solvent is not particularly limited, and examples thereof include a method in which the aromatic polyether is introduced into an organic solvent and stirred to prepare a mixture containing the aromatic polyether and the organic solvent, and the aromatic polyether is recovered from the mixture.

[0115] As a method for recovering the aromatic polyether from the mixture, for example, a method of recovering the aromatic polyether as a solid by filtration can be mentioned.

[0116] Examples of organic solvents used in the organic solvent washing step include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as γ-butyrolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; and oxalates such as 1,3-dioxolane and 4-methyl-1,3-dioxolane. Examples of suitable organic solvents include solanes; nitrogen-containing solvents such as acetonitrile, nitromethane, and N-methyl-2-pyrrolidone; esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, and phosphate triesters; glymes such as diglyme, triglyme, and tetraglyme; ketones such as acetone, diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone; sulfones such as sulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propane sultone, 4-butane sultone, and naphtha sultone. Among these, acetone is preferably used as the organic solvent. These organic solvents may be used alone or in combination of two or more.

[0117] In one embodiment, the organic solvent washing step comprises: preparing a mixture comprising an aromatic polyether and an organic solvent; agitating the mixture; and recovering the aromatic polyether from the mixture, in this order.

[0118] In one embodiment, the mass ratio of the aromatic polyether to the organic solvent ([mass of aromatic polyether] / [mass of organic solvent]) in the mixture containing the aromatic polyether and the organic solvent is 1 / 20 to 1 / 3.

[0119] In one embodiment, the lower limit of the mass ratio of the aromatic polyether to the organic solvent in the mixture ([mass of aromatic polyether] / [mass of organic solvent]) may be, for example, 1 / 15, 1 / 10, or 1 / 8. In one embodiment, the upper limit of the mass ratio of the aromatic polyether to the organic solvent in the mixture ([mass of aromatic polyether] / [mass of organic solvent]) may be, for example, 10 / 31, 1 / 4, or 1 / 5.

[0120] In one embodiment, the stirring time in the stirring step is 10 to 120 minutes, or 10 to 60 minutes. In one embodiment, the lower limit of the stirring time in the stirring step of the organic solvent washing step may be, for example, 10 minutes, 15 minutes, or 20 minutes. In one embodiment, the upper limit of the stirring time in the stirring step of the organic solvent washing step may be, for example, 120 minutes, 100 minutes, 80 minutes, 50 minutes, or 30 minutes.

[0121] When the stirring time in the stirring step of the organic solvent washing step is equal to or longer than the lower limit, washing is more effectively achieved. When the stirring time in the stirring step of the organic solvent washing step is equal to or shorter than the upper limit, washing efficiency (particularly time efficiency) can be improved. Therefore, the stirring time in the stirring step of the organic solvent washing step is preferably within the above range.

[0122] In one embodiment, the organic solvent washing step involves repeating the preparation step, the stirring step, and the recovery step in this order 1 to 7 times, 2 to 6 times, or 2 to 4 times. In the organic solvent washing step, the preparation step, the stirring step, and the recovery step may be repeated until a sufficient washing effect is obtained.

[0123] [Drying process] The aromatic polyether obtained in the washing step or the step of diluting the acid may be further subjected to a drying treatment.

[0124] As the drying means, for example, a known dryer, a thermo-hygrostat, or the like can be used. The drying method is not particularly limited, but a vibration dryer, hot air dryer, vacuum dryer, flash dryer, etc. can be used.

[0125] Drying can be carried out at a temperature depending on the type of solvent remaining in the aromatic polyether, for example, at a temperature equal to or higher than the boiling point of the remaining solvent. The drying temperature can be selected from, for example, 50 to 250° C., 80 to 200° C., or 100 to 180° C. Alternatively, the drying can be carried out by drying under reduced pressure (vacuum drying) using a vacuum pump or the like. The drying time is not particularly limited, but can be, for example, 1 minute or more, 10 minutes or more, 30 minutes or more, 1 hour or more, etc. The upper limit of the drying time is not particularly limited, but can be, for example, 24 hours or less, 12 hours or less, 6 hours or less, etc.

[0126] It is not necessary to completely remove the solvent from the aromatic polyether, but at least a portion of the solvent may be removed, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more of the solvent in the aromatic polyether may be removed.

[0127] Furthermore, a filtration step may be added before drying to remove the solvent. By adding the filtration step, the amount of solvent to be removed can be reduced, and an aromatic polyether from which the solvent has been efficiently removed can be obtained with reduced environmental impact by shortening the process time, the drying time, and the capacity of the dryer.

[0128] The method for producing an aromatic polyether according to one embodiment of the present invention may employ steps, methods, conditions, and the like that are commonly used in the field of aromatic polyethers, as long as the effects of the present invention are not impaired.

[0129] 2. Purification method of aromatic polyether A method for purifying an aromatic polyether according to one embodiment of the present invention (hereinafter also referred to as "a purification method according to one embodiment of the present invention" or "the purification method of the present invention") comprises washing an aromatic polyether with a washing solvent that dissolves both the reaction solvent used in the synthesis of the aromatic polyether and an alkali metal halide. According to the purification method of this embodiment, solvents, alkali metal halides, and the like can be simply and efficiently removed from the aromatic polyether, and the residual solvents and inorganic salts contained in the aromatic polyether can be reduced to predetermined amounts or less.

[0130] The aromatic polyether, reaction solvent, alkali metal halide, and washing solvent are the same as those described in the method for producing an aromatic polyether according to one embodiment of the present invention. [Example]

[0131] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0132] Comparison Example 1 1. Synthesis of aromatic polyethers Nitrogen gas was circulated through a 240 L reactor equipped with a stirrer, thermometer, nitrogen inlet tube, and a water collection vessel connected to a condenser. 149.08 kg of diphenyl sulfone was added stepwise, and the temperature was raised to 160°C. Once melting was confirmed, 45.70 kg (182 mol) of 4,4'-dichlorobenzophenone, 18.96 kg (172 mol) of hydroquinone, and 27.37 kg (198 mol) of potassium carbonate (AGC, fine powder) were added in that order, and the reaction was carried out under the following temperature control.

[0133] <Temperature control> (1) Heat the temperature from 160°C to 200°C over 90 minutes (2) Hold at 200°C for 1 hour (3) Heat the temperature from 200°C to 250°C over 90 minutes (4) Hold at 250°C for 1 hour (5) Heat the temperature from 250°C to 300°C over 150 minutes (6) Hold at 300°C for 5 hours After the reaction was completed, the product was pulverized in a blender to obtain a powdery raw material aromatic polyether (reaction mixture).

[0134] 2. Purification of aromatic polyethers <Organic solvent (acetone) cleaning process> A SUS mug was charged with 835 mL (660 g) of acetone, and 100 g of the powdery raw material aromatic polyether (reaction mixture) obtained in "1. Synthesis of aromatic polyether" above was added while stirring, and the mixture was stirred for 20 minutes to obtain a mixture. The obtained mixture was then filtered (Kiriyama Manufacturing Co., Ltd. "5B", which was also used in the subsequent filtration steps) to obtain a solid (washed with acetone). This solid was washed with acetone four more times (a total of five times) to obtain a solid.

[0135] <Acid (oxalic acid) cleaning process> The solid obtained in the organic solvent (acetone) washing step was added to 1000 mL of hot water at 80°C, and oxalic acid was added while stirring to adjust the pH to 4.0, followed by stirring for 20 minutes to obtain a mixture. The resulting mixture was filtered to obtain a solid (oxalic acid washing). The oxalic acid wash was repeated once more on this solid (for a total of two washes).

[0136] <Process for diluting the acid> The solid obtained in the acid (oxalic acid) washing step was added to 1000 mL of hot water at 80°C and stirred for 20 minutes to obtain a mixture. The obtained mixture was filtered to obtain a solid (water washing). This solid was washed with water three more times (a total of four times) to obtain a solid, which was then dried in a dryer at 180°C for five hours.

[0137] The total number of washings was 11 (5 times with acetone, 2 times with oxalic acid, and 4 times with water), and the total amount of washing solution used was 10,175 mL.

[0138] 3. Evaluation of aromatic polyethers The diphenyl sulfone content and potassium atom (K) content of the obtained aromatic polyether were evaluated by the following methods. The results are shown in Table 1.

[0139] (1) Diphenyl sulfone content (residual DPS) Diphenyl sulfone was extracted from the obtained aromatic polyether into a solvent by the following pretreatment, and the solid matter was separated by filtration. The diphenyl sulfone content of the solvent was measured by GC analysis. The results are shown in Table 1. The quantitative values ​​were determined based on a calibration curve prepared from references of known concentrations, and the calibration curve solution was set to the same concentration as the sample solution. In Table 1, the notation "<100" means that the residual DPS was below the detection limit (100 ppm or less). <Pretreatment conditions> Approximately 1 g of the granules was placed in a 200 mL round-bottom flask with a ground stopper, and 100 mL of cyclohexanone and boiling stones were added. The mixture was heated to reflux using a mantle heater for 1 hour to extract the diphenyl sulfone into cyclohexanone. The mixture was then allowed to cool to room temperature and filtered using a 0.45 μm pore size polypropylene syringe filter (GL Sciences, non-aqueous) to remove solids. The resulting cyclohexanone solution was subjected to the following GC analysis. <Measurement conditions> Gas chromatograph: 8890 Gas chromatograph (Agilent Technologies, Inc.) Column: DB-HeavyWAX (length 30 m x film thickness 0.25 μm x inner diameter 0.25 mm) Inlet temperature: 250℃ Oven temperature: 250℃ (20 min) Flow rate: 1.0mL / min Split ratio: 40:1 Sample injection volume: 1.0 μL Detector: FID Detector temperature: 250℃

[0140] (2) Potassium atom (K) content (residual K) The aromatic polyether was dissolved under the following pretreatment conditions, and the potassium atom content was measured by ICP emission spectrometry. The quantitative values ​​were determined based on a calibration curve prepared from references of known concentrations, and the calibration curve solution had the same hydrochloric acid concentration as the sample solution. <Pretreatment conditions> 0.1 to 1 g of sample was placed on a platinum dish, and concentrated sulfuric acid was added thereto and heated to carbonize it, and then it was placed in an electric furnace and incinerated at 550°C for 12 hours. Hydrochloric acid was added to the sample, and the sample was heated. After cooling, the sample was made up to a constant volume with ultrapure water. <Measurement conditions> ICP emission spectrometer: Agilent Technologies 5100 ·K measurement wavelength: 766.491nm

[0141] Comparative Example 2 1. Synthesis of aromatic polyethers In the same manner as in Comparative Example 1, a powdery raw material aromatic polyether (reaction mixture) was obtained.

[0142] 2. Purification of aromatic polyethers <Organic solvent (acetone) cleaning process> A SUS mug was charged with 1000 mL (790 g) of acetone, and 250 g of the powdery raw material aromatic polyether (reaction mixture) obtained in "1. Synthesis of aromatic polyether" above was added while stirring, and the mixture was stirred for 20 minutes to obtain a mixture. The mixture was then filtered (using a "5B" filter manufactured by Kiriyama Seisakusho Co., Ltd., which was also used for the subsequent filtration steps) to obtain a solid (washed with acetone). This solid was washed with acetone four more times (a total of five times) to obtain a solid.

[0143] <Acid (oxalic acid) cleaning process> The solid obtained in the organic solvent (acetone) washing step was added to 1000 mL of hot water at 80°C, and oxalic acid was added while stirring to adjust the pH to 2.7, followed by stirring for 20 minutes to obtain a mixture. The resulting mixture was filtered to obtain a solid (oxalic acid washing). The oxalic acid wash was repeated two more times on this solid (for a total of three washes).

[0144] <Process for diluting the acid> The solid obtained in the acid (oxalic acid) washing step was added to 1000 mL of hot water at 80°C and stirred for 20 minutes to obtain a mixture. The obtained mixture was filtered to obtain a solid (water washing). This solid was washed with water three more times (a total of four times) to obtain a solid, which was then dried in a dryer at 180°C for five hours.

[0145] The total number of washings was 12 (5 times with acetone, 3 times with oxalic acid, and 4 times with water), and the total amount of washing solution used was 12,000 mL.

[0146] 3. Evaluation of aromatic polyethers The diphenyl sulfone content and potassium atom (K) content of the obtained aromatic polyether were evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0147] Example 1 1. Synthesis of aromatic polyethers In the same manner as in Comparative Example 1, a powdery raw material aromatic polyether (reaction mixture) was obtained.

[0148] 2. Purification of aromatic polyethers <Organic solvent (acetone) cleaning process> Acetone washing was carried out in the same manner as in Comparative Example 1, except that in the <organic solvent (acetone) washing step> of Comparative Example 1, the number of times of washing was changed to one, to obtain a solid.

[0149] <Acid (oxalic acid) cleaning process> The solid obtained in the organic solvent (acetone) washing step was added to a water / acetone mixed solution (500 mL of water, 500 mL of acetone) at 55°C, and oxalic acid was added while stirring to adjust the pH to 4.0, followed by stirring for 20 minutes to obtain a mixture. The resulting mixture was filtered to obtain a solid (washed with oxalic acid). This oxalic acid wash was repeated once more (for a total of two washes).

[0150] <Process for diluting the acid> The solid obtained in the acid (oxalic acid) washing step was added to a water / acetone mixed solution (500 mL of water, 500 mL of acetone) at 55°C and stirred for 20 minutes to obtain a mixture. The obtained mixture was filtered to obtain a solid (mixed solvent washing). This solid was washed with the mixed solvent three more times (a total of four times) to obtain a solid, which was then dried in a dryer at 180°C for five hours.

[0151] The total number of washings was seven (one acetone wash, two oxalic acid washes, and four mixed solvent washes), and the total amount of washing solution used was 6835 mL.

[0152] 3. Evaluation of aromatic polyethers The diphenyl sulfone content and potassium atom (K) content of the obtained aromatic polyether were evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0153] Example 2 1. Synthesis of aromatic polyethers In the same manner as in Comparative Example 1, a powdery raw material aromatic polyether (reaction mixture) was obtained.

[0154] 2. Purification of aromatic polyethers <Organic solvent (acetone) cleaning process> Acetone washing was carried out in the same manner as in Comparative Example 2, except that in the <organic solvent (acetone) washing step> of Comparative Example 2, the number of times of washing was changed to one, to obtain a solid.

[0155] <Acid (oxalic acid) cleaning process> In the <Acid (oxalic acid) washing step> of Comparative Example 2, oxalic acid washing was carried out in the same manner as in Comparative Example 2, except that a water / acetone mixed solution (1000 mL of water, 1000 mL of acetone) at 55°C was used instead of 1000 mL of hot water at 80°C, to obtain a solid (oxalic acid washing). This oxalic acid wash was repeated two more times (for a total of three washes).

[0156] <Process for diluting the acid> Washing was carried out in the same manner as in Comparative Example 2 to obtain a solid (mixed solvent washing), except that in the <step of diluting the acid> of Comparative Example 2, a water / acetone mixed solution (1000 mL of water, 1000 mL of acetone) at 55°C was used instead of 1000 mL of hot water at 80°C. This solid was washed with the mixed solvent once more (a total of two times) to obtain a solid, which was then dried in a dryer at 180°C for 5 hours.

[0157] The total number of washings was six (one acetone wash, three oxalic acid washes, and two mixed solvent washes), and the total amount of washing solution used was 11,000 mL.

[0158] 3. Evaluation of aromatic polyethers The diphenyl sulfone content and potassium atom (K) content of the obtained aromatic polyether were evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0159] [Table 1]

[0160] From Table 1, it can be seen that the method for producing an aromatic polyether in Example 1 was able to reduce the residual DPS and residual K with fewer washings and with a reduced amount of washing liquid used (i.e., simply and efficiently) compared to the method for producing an aromatic polyether in Comparative Example 1.

[0161] Similarly, Table 1 shows that the aromatic polyether production method of Example 2 was able to reduce residual DPS and residual K with fewer washings and with a reduced amount of washing liquid used (i.e., simply and efficiently) compared to the aromatic polyether production method of Comparative Example 2.

Claims

1. a reaction step of reacting the raw material mixture in the presence of a reaction solvent to obtain an aromatic polyether; a washing step of washing the aromatic polyether obtained in the reaction step with a washing solvent that dissolves both the reaction solvent and the alkali metal halide produced in the reaction step; A method for producing an aromatic polyether, comprising:

2. 2. The method for producing an aromatic polyether according to claim 1, wherein the washing solvent is a mixed solvent of water and an organic solvent having a boiling point of less than 100° C. at atmospheric pressure.

3. 3. The method for producing an aromatic polyether according to claim 2, wherein a mass ratio of the organic solvent to the water in the washing solvent ([mass of organic solvent] / [mass of water]) is 10 / 90 to 90 / 10.

4. The method for producing an aromatic polyether according to claim 2 or 3, wherein the organic solvent is acetone.

5. The median diameter D of the aromatic polyether obtained in the reaction step ５０ The method for producing an aromatic polyether according to any one of claims 1 to 3, wherein the average particle diameter is 1 to 1000 µm.

6. The method for producing an aromatic polyether according to any one of claims 1 to 3, wherein the washing step includes an acid washing step using an acidic aqueous solution and a step of diluting the acid, in this order, and the washing solvent is used in at least one of these steps.

7. The acid washing step preparing a mixture comprising an aromatic polyether and an acidic aqueous solution; agitating the mixture; and recovering the aromatic polyether from the mixture, The pH of the mixture in the stirring step is 1.0 to 6.0, the temperature of the mixture is 0 to 84°C, and the stirring time is 10 to 120 minutes; and The method for producing an aromatic polyether according to claim 6, wherein the preparation step, the stirring step, and the recovery step are repeated in this order 1 to 5 times.

8. diluting the acid preparing a mixture comprising an aromatic polyether and water; agitating the mixture; and recovering the aromatic polyether from the mixture, The temperature of the mixture in the stirring step is 0 to 84°C, and the stirring time is 10 to 120 minutes; and The method for producing an aromatic polyether according to claim 6, wherein the preparation step, the stirring step, and the recovery step are repeated in this order 1 to 7 times.

9. The method further comprises an organic solvent washing step using an organic solvent before the acid washing step, The organic solvent washing step preparing a mixture comprising an aromatic polyether and an organic solvent; agitating the mixture; and recovering the aromatic polyether from the mixture, a mass ratio of the aromatic polyether to the organic solvent in the mixture ([mass of the aromatic polyether] / [mass of the organic solvent]) is 1 / 20 to 1 / 3; The stirring time in the stirring step is 10 to 120 minutes, and The method for producing an aromatic polyether according to claim 6, wherein the preparation step, the stirring step, and the recovery step are repeated in this order 1 to 7 times.

10. The method for producing an aromatic polyether according to any one of claims 1 to 3, wherein the reaction solvent contains diphenyl sulfone, and the content of diphenyl sulfone in the aromatic polyether after the washing step is 1 to 1000 ppm.

11. 4. The method for producing an aromatic polyether according to claim 1, wherein the reaction solvent contains diphenyl sulfone, and the content of diphenyl sulfone in the aromatic polyether after the washing step is 1 to 100 ppm.

12. The method for producing an aromatic polyether according to any one of claims 1 to 3, wherein the content of alkali metal halide in the aromatic polyether after the washing step is 1 to 500 ppm.

13. A method for purifying an aromatic polyether, comprising washing the aromatic polyether with a washing solvent capable of dissolving both a reaction solvent used in the synthesis of the aromatic polyether and an alkali metal halide.

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