JP2008248013A - Method for recovering solvent and method for preparing aromatic polyether - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which prevents reduction of thermal efficiency or occlusion of heat exchanger which are caused by deposition of byproduct salts inside the heat exchanger and is capable of continuously recovering a solvent for a long time from a solution which contains a reaction solvent and a purification solvent and is produced at preparation of an aromatic polyether, and a method for preparing the aromatic polyether using the method. <P>SOLUTION: In the method for recovering the solvent from the solution containing the reaction solvent, water and at least one solvent having a boiling point lower than that of the reaction solvent, the solution is produced when preparing the aromatic polyether by carrying out polycondesation of a bivalent phenolic compound and a dihalogenodiphenyl compound in the presence of the reaction solvent and an alkali metal compound. The method comprises a step of adjusting the water content in the solution to ≥15 mass% by distilling the solution using a first evaporator and a step of recovering the reaction solvent by distilling the obtained solution using a second evaporator. The method is used in the method for preparing the aromatic polyether. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solvent recovery method, and more particularly, to a reaction solvent used in producing an aromatic polyether and a purification solvent recovery method used for purification of the aromatic polyether. The present invention also relates to a method for producing an aromatic polyether using the solvent recovery method.

  Aromatic polyether is useful as a polymer compound excellent in heat resistance, impact resistance, transparency and the like. Such an aromatic polyether can be produced by subjecting a biphenol compound and a dihalogenated biphenyl compound to a condensation reaction in the presence of a base and a reaction solvent (for example, Patent Document 1).

  Patent Document 2 discloses a method for producing an aromatic polyether by condensation reaction of a biphenol compound and a dihalogenated biphenyl compound in the presence of a base and diphenylsulfone as a reaction solvent, from the condensation reaction mixture as a by-product. It is described that after removing the salt and separating the aromatic polyether and diphenylsulfone, the diphenylsulfone is washed with water and the remaining water is removed to recover and reuse the diphenylsulfone. Then, as a specific means for separating the aromatic polyether and diphenylsulfone, the reaction mixture from which the by-product salt has been removed is a low boiling point solvent that dissolves diphenylsulfone but does not dissolve aromatic polyether or its A method for extracting diphenylsulfone by washing with a purified solvent comprising a mixture is disclosed.

Here, in the method for producing the aromatic polyether, a diphenylsulfone-containing solution obtained by washing with a purification solvent is separated into diphenylsulfone and a low-boiling solvent or a mixture thereof by distillation operation, and these are again obtained. It can be used as a reaction solvent and a purification solvent, respectively. However, in the diphenylsulfone-containing solution, a part of the by-product salt that is a reactive product of the hydrogen halide eliminated by the condensation reaction and the base remains, and the by-product salt is used for evaporation. It may be deposited in the heat exchanger of the heat exchanger, reducing the heat efficiency or closing the heat exchanger. Therefore, it is necessary to open the equipment frequently for cleaning, resulting in a decrease in productivity. It was.
JP-A-53-97094 JP 2004-315564 A

  The present invention has been made in view of such circumstances, and its purpose is to recover a solvent by distillation from a solution containing a reaction solvent and a purified solvent, which is generated when an aromatic polyether is produced. A method capable of suppressing a decrease in thermal efficiency and blockage of a heat exchanger caused by precipitation of by-product salts in a heat exchanger used for heating, and recovering the solvent continuously for a longer period of time and the method It is to provide a method for producing the aromatic polyether used.

  The present inventor collects a solvent by distillation from a solution containing a reaction solvent, one or more solvents having a boiling point lower than that of the reaction solvent, and water obtained when producing an aromatic polyether. In this case, first, a fraction mainly containing one or more solvents having a boiling point lower than that of the reaction solvent is removed from the solution, and the water concentration in the solution is adjusted to such an extent that precipitation of by-product salts is sufficiently suppressed. After the increase, it was found that the above problem was solved by a method of distilling the solution and recovering the reaction solvent. That is, the present invention is as follows.

  The present invention relates to a method for recovering a solvent from a solution obtained when polycondensation of a dihydric phenol compound and a dihalogenodiphenyl compound in the presence of a reaction solvent and an alkali metal compound to produce an aromatic polyether, The solution contains a reaction solvent, one or more solvents having a boiling point lower than that of the reaction solvent, and water, and the solution is distilled using a first evaporator, whereby water in the solution is distilled. A first distillation step in which the concentration is 15% by mass or more, and a second distillation step in which the reaction solvent is recovered by distilling the solution obtained in the first distillation step using a second evaporator. It is a recovery method of the solvent containing.

  Here, the reaction solvent is preferably diphenyl sulfone. Examples of the one or more solvents having a boiling point lower than that of the reaction solvent include low-boiling solvents such as methanol, ethanol, isopropanol, acetone or methyl ethyl ketone, and mixtures thereof.

  The present invention also provides a hydrogen halide desorbed by the polycondensation reaction by polycondensation of a dihydric phenol compound and a dihalogenodiphenyl compound in the presence of a reaction solvent and an alkali metal compound, and the alkali metal compound. A polycondensation step for obtaining a reaction mixture containing a by-product salt, a reaction solvent, and an aromatic polyether, and at least a part of the by-product salt using water from the obtained reaction mixture. After removing the reaction solvent, a purification step of removing the reaction solvent using one or more solvents having a boiling point lower than that of the reaction solvent, a reaction solvent obtained in the purification step, and a boiling point of 1 lower than that of the reaction solvent. A solvent recovery step of recovering the solvent by distillation from a solution containing at least a seed solvent and water, wherein the recovery of the solvent in the solvent recovery step is It is carried out by a method of recovering a solvent according to either provide a process for producing an aromatic polyether.

  In the method for producing an aromatic polyether of the present invention, the solvent recovered in the solvent recovery step can be preferably used as the reaction solvent and / or one or more solvents having a boiling point lower than that of the reaction solvent.

  According to the present invention, a solvent is recovered by distillation from a solution containing a reaction solvent, one or more solvents having a boiling point lower than that of the reaction solvent, and water generated when an aromatic polyether is produced. In this case, it is possible to continuously recover the solvent for a longer period of time by suppressing a decrease in thermal efficiency and blockage of the heat exchanger due to precipitation of by-product salts in the heat exchanger used for heating, Contributes to improved productivity.

<Recovery method of solvent>
The method for recovering a solvent of the present invention comprises a solvent obtained by distillation from a solution containing a reaction solvent, one or more solvents having a boiling point lower than that of the reaction solvent, and water, which are obtained when an aromatic polyether is produced. It is related with the method of collect | recovering. Here, the method for producing an aromatic polyether to which the solvent recovery method of the present invention is applied is obtained by polycondensing a dihydric phenol compound and a dihalogenodiphenyl compound in the presence of a reaction solvent and an alkali metal compound. Although it is performed and is not particularly limited as long as it is a method capable of obtaining a solution for solvent recovery having the above composition, for example, a method for producing an aromatic polyether shown below Can be mentioned as suitable.

  In the method for producing an aromatic polyether according to the present invention, first, a dihydric phenol compound and a dihalogenodiphenyl compound are polycondensed in the presence of a reaction solvent and an alkali metal compound, and desorbed by the polycondensation reaction. A reaction mixture containing a by-product salt which is a reaction product of hydrogen halide and the alkali metal compound, a reaction solvent, and an aromatic polyether is obtained. Examples of the reaction solvent include sulfoxide solvents such as dimethyl sulfoxide and hexamethylene sulfoxide, amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-vinyl- Pyrrolidone solvents such as 2-pyrrolidone, piperidone solvents such as N-methyl-2-piperidone, 2-imidazolinone solvents such as 1,3-dimethyl-2-imidazolidinone, diphenyl compounds such as diphenyl ether and diphenyl sulfone And halogen solvents such as methylene chloride, chloroform, dichloroethane, tetrachloroethane, and trichloroethylene, lactone solvents such as γ-butyrolactone, sulfolane solvents such as sulfolane, and mixtures of two or more of these. Of these, diphenyl compounds such as diphenylsulfone are preferably used.

  Examples of the dihydric phenol compound include hydroquinone, catechol, resorcin, and 4,4′-biphenol, as well as 2,2-bis (4-hydroxyphenyl) methane and 2,2-bis (4-hydroxyphenyl). Ethane, bis (4-hydroxyphenyl) alkanes such as 2,2-bis (4-hydroxyphenyl) propane, dihydroxydiphenyl sulfones such as 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenyl ether, etc. Dihydroxydiphenyl ethers, wherein at least one of the hydrogens in the benzene ring is a lower alkyl group such as a methyl group, an ethyl group, or a propyl group, a lower alkoxy group such as a methoxy group, an ethoxy group, or a propyloxy group, chlorine, bromine, fluorine, etc. Substituted with halogen, these 2 Like mixtures of more. In particular, hydroquinone, 4,4′-biphenol, 2,2-bis (4-hydroxyphenyl) propane, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfone, and the like are preferable because of price and availability. Used.

  Examples of the dihalogenodiphenyl compound include dihalogenodiphenyl compounds having a sulfone group, such as dihalogenodiphenylsulfones such as 4,4′-dichlorodiphenylsulfone, 4,4′-difluorodiphenylsulfone, 1,4-bis ( Bis (halogenophenylsulfonyl) benzenes such as 4-chlorophenylsulfonyl) benzene, 1,4-bis (4-fluorophenylsulfonyl) benzene, 1,4-bis (4-chlorophenylsulfonyl) biphenyl, 1,4- Examples thereof include bis (halogenophenylsulfonyl) biphenyls such as bis (4-fluorophenylsulfonyl) biphenyl, and mixtures of two or more thereof. Among them, dihalogenodiphenyl sulfones such as 4,4′-dichlorodiphenyl sulfone and 4,4′-difluorodiphenyl sulfone are preferably used because they are easily available.

  Examples of the alkali metal compound include alkali metal carbonates, alkali metal hydroxides, alkali metal hydrides, alkali metal alkoxides, and the like. Of these, alkali metal carbonates such as potassium carbonate and sodium carbonate are preferred, and anhydrous alkali metal carbonates such as anhydrous potassium carbonate and anhydrous sodium carbonate are particularly preferably used.

  The reaction product obtained by the reaction is a mixture containing a by-product salt which is a reaction product of hydrogen halide and base released by the condensation reaction, a reaction solvent, and an aromatic polyether. The by-product salt is, for example, potassium chloride when potassium carbonate is used as the alkali metal compound.

  The dihalogenodiphenyl compound is usually used in an equimolar amount with respect to the alkali metal compound and the dihydric phenol compound of the reaction solvent. In order to adjust the molecular weight, the dihydric phenol compound can be used from an equimolar amount to a slight excess amount or a small amount. Similarly, in order to adjust the molecular weight, a small amount of a monohalogenodiphenyl compound or a monohydric phenol compound can be added to the polymerization solution. The polycondensation reaction temperature is preferably 140 to 340 ° C. When the polycondensation is performed at a temperature higher than 340 ° C., the decomposition reaction of the product polymer proceeds, so that there is a tendency that a high-purity aromatic polyether cannot be obtained. There is a tendency that a polymer cannot be obtained.

  In the subsequent step, after removing at least a part of the by-product salt from the obtained reaction mixture using water, the reaction solvent is removed using one or more solvents having a boiling point lower than that of the reaction solvent, Aromatic polyether is purified. More specifically, first, a mixture of an aromatic polyether, a by-product salt and a reaction solvent is cooled and solidified, and then pulverized. Next, the pulverized product is washed with water to remove by-product salts. Thereafter, the reaction solvent is removed from the reaction product from which the by-product salt has been removed by extracting the reaction solvent using one or more solvents having a boiling point lower than that of the reaction solvent (hereinafter also referred to as a purification solvent).

  The one or more solvents having a boiling point lower than that of the reaction solvent are preferably solvents that dissolve the reaction solvent but do not dissolve the aromatic polyether. Examples of such solvents include methanol, ethanol, isopropanol, Examples thereof include a low boiling point solvent such as acetone or methyl ethyl ketone, and a mixture thereof.

  By the said refinement | purification process, the solution containing the reaction solvent, 1 or more types of solvent whose boiling point is lower than this reaction solvent, and water will generate | occur | produce. As described above, in a typical example of the method for producing an aromatic polyether according to the present invention, a step of washing a mixed pulverized product of an aromatic polyether, a by-product salt and a reaction solvent is provided. Although the raw salt has been removed, it cannot be completely removed, and the solution contains a small amount of by-product salt. The by-product salt in the solution was a factor causing a decrease in thermal efficiency and a blockage of the heat exchanger. In addition, the said solution typically contains 10-13 mass% water.

  The solvent recovery method of the present invention includes, for example, a reaction solvent obtained when an aromatic polyether is produced using the method as described above, one or more solvents having a boiling point lower than the reaction solvent, water, Is a method for recovering a solvent from a solution containing a solution by distillation, wherein the solution is distilled using a first evaporator, so that the concentration of water in the solution is 15% by mass or more. And a second distillation step of recovering the reaction solvent by distilling the solution obtained in the first distillation step using a second evaporator. Hereinafter, each step will be described in detail with reference to FIG. FIG. 1 is a schematic view showing an example of an apparatus suitably used in the solvent recovery method of the present invention.

  First, in the first distillation step, the solution is supplied to the first evaporator 101 through the pipe 102 and distilled, so that the concentration of water in the solution is 15% by mass or more. Here, in the apparatus of FIG. 1, a wet wall evaporator integrated with a heat exchanger is used as the first evaporator, but the invention is not limited to this. Alternatively, a part of the solution remaining in the first evaporator 101 may be circulated and supplied to the first evaporator 101 through the pipe 102.

  The distillate 113 distilled by distillation is removed through the pipe 103. The distillation amount of the distillate 113 in this step is not particularly limited as long as the concentration of water in the solution remaining in the first evaporator 101 is 15% by mass or more. The concentration of water in the solution remaining in the first evaporator 101 after the first distillation is preferably 16% by mass or more, more preferably 17% by mass or more, and further preferably 18% by mass or more. By setting the water concentration to 15% by mass or more, problems such as a decrease in thermal efficiency and blockage of the heat exchanger due to precipitation of by-product salts in the heat exchanger in the second distillation step of the next step are effectively obtained. It is suppressed. The temperature of the solution during distillation is appropriately changed according to the type of solvent to be distilled. Further, the pressure at the time of distillation is not particularly limited, and the distillation may be performed under any pressure of reduced pressure, normal pressure, or increased pressure.

  The distillate 113 is a solvent mainly composed of one or more solvents having a boiling point lower than that of the reaction solvent, and may contain a small amount of water, but preferably does not substantially contain the reaction solvent. When diphenylsulfone is used as the reaction solvent and one or more solvents having a boiling point lower than that of the reaction solvent are used, such as a low-boiling solvent or a mixture thereof as described above, the boiling point of diphenylsulfone is the same as that of these solvents. Since it is very high in comparison (boiling point of diphenylsulfone 379 ° C.), it may be said that there is almost no possibility that the reaction solvent is mixed into the distillate 113. Such a distillate 113 can be used again as a purification solvent as it is or after being appropriately treated.

  Next, after the distilled solution remaining in the first evaporator 101 is transferred to the distillation column 106 through the pipe 110 using the supply pump 104, the distillation column 106 and the multi-tube heat exchanger 107 are formed. The reaction solvent is recovered by distillation using a second evaporator (second distillation step). In the distillation in this step, the solution supplied into the distillation column 106 is circulated and supplied to the distillation column 106 via the piping 111 and the piping 112 using the circulation pump 108. At this time, the solution is heated by the multi-tube heat exchanger 107. The distillate 114 distilled is taken out from the top of the distillation column 106. Since the solution after the first distillation transferred from the first evaporator 101 contains 15% by mass or more of moisture, the solution in the multi-tube heat exchanger 107 when distilling using the second evaporator is used. By-product salt precipitation is greatly suppressed, and as a result, the problem of a decrease in the heat efficiency of the heat exchanger and the blockage of the heat exchanger are greatly improved.

  The second distillation in this step is typically performed to such an extent that the solution remaining in the distillation column 106 does not substantially contain solvent components other than the reaction solvent. The temperature of the solution during distillation is usually in the range of 125 to 200 ° C. When the temperature is lower than 125 ° C., the reaction solvent such as diphenylsulfone is solidified and loses fluidity. When the temperature is higher than 200 ° C., the collected reaction solvent tends to be remarkably colored. Further, the pressure during distillation is not particularly limited, and may be performed under any pressure of reduced pressure, normal pressure, or increased pressure. The solvent 115 remaining after distillation is discharged from the bottom of the column through the piping 111 and the piping 109 using the circulation pump 108. The solvent 115 remaining after distillation can be reused as a reaction solvent. When the recovered reaction solvent is reused, it may be used as it is as the reaction solvent, but it is preferably used after being washed with water. The distillate 114 distilled by distillation in this step can be reused as a purification solvent, preferably after rectification.

The series of distillation operations for solvent recovery can be performed continuously.
<Method for producing aromatic polyether>
The method for producing an aromatic polyether of the present invention utilizes the above-mentioned solvent recovery method. Specifically, a dihydric phenol compound and a dihalogenodiphenyl compound are polycondensed in the presence of a reaction solvent and an alkali metal compound, and the hydrogen halide desorbed by the polycondensation reaction and the alkali metal compound A polycondensation step for obtaining a reaction mixture containing a by-product salt as a reaction product, a reaction solvent and an aromatic polyether, and at least a part of the by-product salt from the resulting reaction mixture using water. After the removal, a purification step of removing the reaction solvent using one or more solvents having a boiling point lower than that of the reaction solvent, a reaction solvent obtained in the purification step, and one or more types of boiling points lower than the reaction solvent A solvent recovery step of recovering the solvent by distillation from a solution containing the solvent and water, wherein the recovery of the solvent in the solvent recovery step is the solvent described above It is characterized in that performed by the recovery process.

  The polycondensation step, purification step and solvent recovery step are as described above. In the method for producing an aromatic polyether of the present invention, the solvent recovered in the solvent recovery step can be suitably used as the reaction solvent and / or one or more solvents (purification solvents) having a boiling point lower than that of the reaction solvent. . That is, as the reaction solvent in the polycondensation step, the reaction solvent recovered in the second distillation step (the solvent remaining after the second distillation) can be used, and one or more solvents having a lower boiling point than the reaction solvent in the purification step As the (purification solvent), the distillate obtained in the first distillation step and / or the second distillation step can be used after being subjected to treatment such as rectification as necessary.

  The aromatic polyether obtained by the production method of the present invention can be made into a resin having excellent transparency by drying as necessary. In addition, a desired molded product can be obtained by an injection molding machine, an extrusion molding machine, or the like. When molding with a molding machine, reactive fiber coupling agents such as glass fiber such as milled glass fiber and chopped glass fiber, inorganic filler, silane coupling agent, titanate coupling agent, borane coupling agent, Higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, lubricants such as fluorocarbon surfactants, mold release improvers such as fluororesins and metal soaps, nucleating agents, antioxidants, stabilizers, plasticizers, lubricants, Coloring agents, coloring agents, ultraviolet absorbers, antistatic agents, lubricants, flame retardants, and the like may be added. However, it is preferable not to use additives that reduce transparency such as glass fibers, inorganic fillers, and colorants for applications requiring transparency such as glass substitute materials.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
(Polycondensation reaction)
Diphenyl sulfone is used as a reaction solvent, a polycondensation tank is charged with a 180 ° C. diphenyl sulfone solution in which 4,4′-dihydroxydiphenyl sulfone and 4,4′-dichlorodiphenyl sulfone as monomers are dissolved, and anhydrous potassium carbonate is added. did. Thereafter, the temperature was gradually raised to 290 ° C., and the reaction was carried out at the same temperature for a certain time. After completion of the reaction, the reaction solution was cooled to room temperature, solidified, and finely pulverized. The obtained aromatic polyether, a by-product salt (KCl) produced by neutralization reaction of potassium carbonate and hydrogen halide, and a powdery mixture of diphenyl sulfone are washed with warm water to remove the above-mentioned by-product salt. did. Next, the mixture after removing the by-product salt was extracted using a mixed solvent of acetone and methanol, which is a low boiling point solvent, to obtain a diphenyl sulfone solution (A) containing the low boiling point solvent. Table 1 shows the composition of the obtained diphenylsulfone solution (A).

(Recovery of solvent)
The reaction solvent and the purified solvent were recovered from the diphenylsulfone solution (A) using the apparatus shown in FIG. First, the diphenylsulfone solution (A) is continuously supplied to the first evaporator 101 at 25 ° C. through the pipe 102 and distilled (first distillation), and the low boiling point solvent (B) distilled from the pipe 103 is used. The diphenylsulfone solution (C) from which a part of the low boiling point solvent was distilled off from the bottom of the evaporator was continuously transferred to the distillation column 106 through the pipe 110 using the supply pump 104. The distillation amount of the low boiling point solvent (B) in the first distillation is approximately 54% by mass of the total amount of solvents (methanol, acetone and water) other than diphenyl sulfone in the supplied diphenyl sulfone solution (A). did. The temperature of the solution in the first evaporator 101 during distillation was 59 to 64 ° C. Moreover, the gas temperature of the low boiling point solvent (B) to distill and the temperature of the diphenyl sulfone solution (C) at the time of transfer were 59-64 degreeC. Table 2 summarizes the average supply flow rate (average distillate flow rate) of the diphenylsulfone solution (A), the low boiling point solvent (B) and the diphenylsulfone solution (C), and the composition of each solution. The concentration of water in the diphenylsulfone solution (C) was 18.3% by mass.

  Further, the diphenylsulfone solution (C) continuously supplied to the distillation tower 106 is distilled (second distillation), the low boiling point solvent (D) is distilled off from the top of the distillation tower 106, and diphenylsulfone ( E) was continuously extracted and collected. The distillation was performed while circulating the solution through the distillation tower 106 and the pipes 111 and 112 using the circulation pump 108, and heated so that the outlet temperature of the heat exchanger 107 of the circulating solution was 145 ° C. The gas temperature of the low boiling point solvent (D) to be distilled was 115 ° C. Table 2 summarizes the average distillation flow rate (average withdrawal flow rate) of the low boiling point solvent (D) and diphenylsulfone (E) and the composition of each solution.

The heat transfer coefficient of the heat exchanger 107 at the start of distillation in the above series of distillation operations was about 500 W / m ² K. Due to the continuous operation, the heat efficiency of the heat exchanger gradually decreased, and after about 120 days, the heat transfer coefficient became about 250 W / m ² K, so it was judged that open cleaning was necessary.

<Comparative Example 1>
Using the apparatus shown in FIG. 2, the diphenylsulfone solution (A) is continuously supplied to the distillation column 202 through the pipe 201 to be distilled, and the low boiling point solvent (F) (in FIG. 2) from the top of the distillation column 202 is distilled. 208) was distilled off, and diphenylsulfone (G) (209 in FIG. 2) was continuously extracted from the bottom of the column and recovered. The distillation was performed by circulating the solution through the distillation column 202 and the pipes 203 and 204 using the circulation pump 206, and heated so that the outlet temperature of the heat exchanger 205 of the circulating solution was 145 ° C. The gas temperature of the low boiling point solvent (F) to be distilled was 115 ° C. Table 3 summarizes the average distillation flow rate (average withdrawal flow rate) of the low boiling point solvent (F) and diphenylsulfone (G) and the composition of each solution.

The heat transfer coefficient of the heat exchanger 205 at the start of distillation in the above series of distillation operations was about 500 W / m ² K. Due to the continuous operation, the heat efficiency of the heat exchanger gradually decreased, and after about 50 days, the heat transfer coefficient became about 250 W / m ² K, so it was judged that open cleaning was necessary.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is the schematic which shows an example of the apparatus used suitably in the solvent collection | recovery method of this invention. 2 is a schematic view showing an apparatus used for solvent recovery in Comparative Example 1. FIG.

Explanation of symbols

  101 First evaporator, 102, 103, 109, 110, 111, 112 piping, 104 feed pump, 106 distillation tower, 107 multi-tube heat exchanger, 108 circulation pump, 113, 114 distillate, 115 after distillation Residual solvent.

Claims (4)

In the method of recovering a solvent from a solution obtained when polycondensation of a dihydric phenol compound and a dihalogenodiphenyl compound in the presence of a reaction solvent and an alkali metal compound to produce an aromatic polyether,
The solution contains the reaction solvent, one or more solvents having a boiling point lower than that of the reaction solvent, and water.
A first distillation step in which the solution is distilled using a first evaporator so that the concentration of water in the solution is 15% by mass or more;
A second distillation step of recovering the reaction solvent by distilling the solution obtained by the first distillation step using a second evaporator;
The recovery method of the solvent containing this.   The method for recovering a solvent according to claim 1, wherein the reaction solvent is diphenylsulfone. It is a reaction product of a hydrogen halide desorbed by the polycondensation reaction by polycondensation of a dihydric phenol compound and a dihalogenodiphenyl compound in the presence of a reaction solvent and an alkali metal compound and the alkali metal compound. A polycondensation step for obtaining a reaction mixture comprising a by-product salt, a reaction solvent, and an aromatic polyether;
From the obtained reaction mixture, after removing at least a part of the by-product salt using water, a purification step of removing the reaction solvent using one or more solvents having a boiling point lower than that of the reaction solvent;
A solvent recovery step of recovering the solvent by distillation from a solution containing the reaction solvent obtained in the purification step, one or more solvents having a boiling point lower than the reaction solvent, and water;
A process for producing an aromatic polyether comprising:
The method for producing an aromatic polyether, wherein the solvent is recovered in the solvent recovery step by the method according to claim 1.   The method for producing an aromatic polyether according to claim 3, wherein the solvent recovered in the solvent recovery step is used as the reaction solvent and / or one or more solvents having a boiling point lower than that of the reaction solvent.

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