Method for producing high-purity aromatic diol

Abstract

To provide a method for preparing a high-purity aromatic diol.SOLUTION: There is provided a method for producing a high-purity aromatic diol represented by the formula (1), which comprises a step of dissolving a crude composition containing an aromatic diol represented by the formula (1) [wherein, Ar1 and Ar2 each individually represents a divalent aromatic group] in a mixed solvent of an organic solvent (A), an organic solvent (B) different from the organic solvent (A) and water and a step of crystallizing the obtained solution, wherein the organic solvent (B) is an alcohol, the sulfur atom content contained in the crude composition containing the aromatic diol represented by the formula (1) is 200 ppm or more and the sulfur atom content contained in the high-purity aromatic diol represented by the formula (1) is less than 200 ppm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a high-purity aromatic diol. [Background technology]

[0002] Aromatic diols having an ester group in the molecule are used as structural units of various resins, including polyesters (Patent Documents 1 and 2). In particular, in recent years, it has been reported that the cured products of thermosetting resin compositions obtained by mixing aromatic diols with epoxy resins have excellent thermal conductivity (Patent Document 3), and they are expected to be used in applications such as encapsulants for semiconductor devices and heat dissipation insulating materials such as heat dissipation insulating substrates and sheets.

[0003] As a method for producing an aromatic diol having an ester group in the molecule, there have been proposed a method for producing 4-hydroxyphenyl 4-hydroxybenzoate by reacting p-hydroxybenzoic acid with hydroquinone using an esterification catalyst in a reaction solvent in which the reactants are substantially dispersed (Patent Document 4), and a method for producing a diphenol compound characterized by a step of dehydration condensation of 6-hydroxy-2-naphthoic acid with hydroquinone in the presence of sulfuric acid and phosphoric acid (Patent Document 5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-049733 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-113511 [Patent Document 3] Patent Publication No. 2021-183683 [Patent Document 4] Japanese Patent Application Publication No. 63-022540 [Patent Document 5] Japanese Patent Application Laid-Open No. 2012-201603 Summary of the Invention [Problem to be solved by the invention]

[0005] However, diols produced by such esterification contain residual esterification catalysts such as sulfuric acid, and therefore, for use as polymer materials, diols of higher purity are required. [Means for solving the problem]

[0006] In view of the above problems, the present inventors have conducted extensive research and have found that by dissolving a crude composition containing an aromatic diol in a specific mixed solvent and then crystallizing the resulting composition, it is possible to easily remove the catalyst, unreacted raw materials, and the like while suppressing side reactions during purification, thereby enabling the preparation of a high-purity aromatic diol, which has led to the completion of the present invention.

[0007] That is, the present invention includes the following preferred embodiments. [1] Formula (1) [ka] [In the formula, Ar1 and Ar2 each represent a divalent aromatic group.] a step of dissolving a crude composition containing an aromatic diol represented by the formula (I) in a mixed solvent of an organic solvent (A), an organic solvent (B) different from the organic solvent (A), and water; A step of crystallizing the obtained solution A method for producing a high-purity aromatic diol represented by formula (1), comprising: The organic solvent (B) is an alcohol, The method, wherein the content of sulfur atoms contained in the crude composition containing the aromatic diol represented by formula (1) is 200 ppm or more, and the content of sulfur atoms contained in the high-purity aromatic diol represented by formula (1) is less than 200 ppm. [2] Ar1 and Ar2 are each independently represented by the formulas (I) to (III) [ka] [In the formula, "-*" indicates the bonding position of the aromatic group] The method according to [1], wherein the aromatic group is selected from aromatic groups represented by the formula: [3] The method according to [2], wherein Ar1 and Ar2 are both aromatic groups represented by formula (I). [4] A crude composition containing an aromatic diol represented by formula (1) is reacted with an aromatic diol represented by formula (2) in an organic solvent (A) in the presence of a sulfur-containing acid catalyst. [ka] and a compound represented by formula (3) [ka] The method according to any one of [1] to [3], wherein the compound is obtained by reacting a compound represented by the formula: [5] The method according to [4], wherein the sulfur-containing acid catalyst is at least one selected from the group consisting of sulfuric acid, sulfurous acid, dimethyl sulfate, diethyl sulfate, chlorosulfonic acid, fluorosulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. [6] The method according to any one of [1] to [5], wherein the organic solvent (B) is one or more alcohols selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, 2-butanol, 2-ethyl-2-propanol, and 2-ethoxyethanol. [7] The method according to [6], wherein the organic solvent (B) is methanol. [8] The method according to any one of [1] to [7], wherein the organic solvent (A) is at least one selected from the group consisting of toluene, xylene, anisole, mesitylene, and 4-methyltetrahydropyran. [9] The method according to [8], wherein the organic solvent (A) is toluene.

[10] The method according to any one of [1] to [9], wherein the content of the organic solvent (A) in the mixed solvent is 4 to 22 mass %.

[11] The method according to any one of [1] to

[10] , wherein the content of the organic solvent (B) in the mixed solvent is 40 to 80 mass %.

[12] The method according to any one of [1] to

[11] , wherein the content of water in the mixed solvent is 10 to 45 mass %.

[13] The method according to any one of [1] to

[12] , wherein 100 parts by mass of the aromatic diol represented by formula (1) in the crude composition is dissolved in 300 to 3,000 parts by mass of a mixed solvent.

[14] The method according to any one of [1] to

[13] , wherein the solution temperature in the dissolving step is 50 to 65°C. [Effects of the Invention]

[0008] According to the present invention, a high-purity aromatic diol represented by formula (1) can be obtained which has a low content of sulfur atoms derived from the sulfur-containing acid catalyst used in synthesizing the target aromatic diol. DETAILED DESCRIPTION OF THE INVENTION

[0009] The production method of the present invention relates to a method for producing a high-purity aromatic diol represented by formula (1), comprising the steps of dissolving a crude composition containing an aromatic diol represented by formula (1) in a mixed solvent of an organic solvent (A), an organic solvent (B) different from the organic solvent (A), and water, and crystallizing the obtained solution. [ka] [In the formula, Ar1 and Ar2 each represent a divalent aromatic group.]

[0010] In formula (1), Ar1 and Ar2 are each independently selected from the aromatic groups represented by formulae (I) to (III). [ka] [In the formula, "-*" indicates the bonding position of the aromatic group.]

[0011] An example of the aromatic diol represented by formula (1) is a compound represented by the following formula (1)-1 (hereinafter referred to as HQ-POB) in which both Ar1 and Ar2 are aromatic groups of formula (I). [ka]

[0012] Examples of aromatic diols represented by formula (1) include compounds in which Ar1 is an aromatic group of formula (II) and Ar2 is an aromatic group of formula (I), that is, compounds represented by the following formula (1)-2. [ka]

[0013] In the present invention, the crude composition containing the aromatic diol represented by formula (1) refers to a composition containing impurities such as reaction raw materials, catalysts, and reaction by-products in addition to the target aromatic diol represented by formula (1), and is a composition having a sulfur atom content of 200 ppm or more. In one embodiment, the sulfur atom content is 5000 ppm or more, and in another embodiment, 2000 ppm or more. The sulfur atom content is usually 10000 ppm or less. Furthermore, the high-purity aromatic diol represented by formula (1) refers to an aromatic diol represented by formula (1) having a sulfur atom content of less than 200 ppm. The sulfur atom content in the high-purity aromatic diol is preferably 500 ppm or less, more preferably 300 ppm or less, and even more preferably 200 ppm or less. In the high-purity aromatic diol according to the present invention, the sulfur atom content is usually 1 ppm or more.

[0014] In this specification, a crude composition containing HQ-POB is also simply referred to as "crude HQ-POB."

[0015] The crude composition containing the aromatic diol represented by formula (1) used in the present invention is preferably one obtained by reacting a compound represented by formula (2) with a compound represented by formula (3) in an organic solvent (A) in the presence of a sulfur-containing acid catalyst. Alternatively, a commercially available crude composition containing the aromatic diol represented by formula (1) having a sulfur atom content of 200 ppm or more may be used. Note that Ar1 and Ar2 in formulas (2) and (3) are the same aromatic groups as Ar1 and Ar2 in formula (1). [ka] [ka]

[0016] In the method for obtaining a crude composition containing an aromatic diol represented by the above formula (1), the sulfur-containing acid catalyst refers to an acid catalyst containing a sulfur atom in the molecule, and examples thereof include one or more selected from the group consisting of sulfuric acid, sulfurous acid, dimethyl sulfate, diethyl sulfate, chlorosulfonic acid, fluorosulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid, with sulfuric acid being preferred in terms of its excellent reactivity.

[0017] In the method for obtaining a crude composition containing an aromatic diol represented by the above formula (1), the organic solvent (A) may be at least one selected from the group consisting of toluene, xylene, anisole, mesitylene, and 4-methyltetrahydropyran, and toluene is preferred in terms of its excellent reactivity.

[0018] In the method for obtaining a crude composition containing an aromatic diol represented by the formula (1), the amount of the organic solvent (A) used is 0.5 times or more by mass, preferably 1 to 20 times by mass, and more preferably 5 to 15 times by mass relative to the amount of the compound represented by the formula (2).

[0019] The reaction temperature of the compound represented by formula (2) and the compound represented by formula (3) is usually 50 to 150° C., preferably 80 to 120° C., and more preferably 100 to 110° C. If the temperature is lower than 50° C., the reaction will not proceed, and if the temperature is higher than 150° C., the reaction will plateau, resulting in a loss of energy and the risk of side reactions occurring.

[0020] The reaction time is usually from several minutes to 30 hours, and can be appropriately selected from the range of preferably 1 to 20 hours, more preferably 4 to 18 hours, and particularly preferably 8 to 15 hours.

[0021] The reaction is preferably carried out under an atmosphere of an inert gas such as nitrogen or helium.

[0022] The reaction solution containing the aromatic diol obtained by the reaction is subjected to solid-liquid separation by a conventional means such as filtration, and a crude composition containing the aromatic diol used in the present invention is recovered. After solid-liquid separation, it is preferable to wash the crystals by pouring fresh solvent onto the solid on the filter cloth or filter paper and then subjecting it to solid-liquid separation again.

[0023] The crude composition containing the aromatic diol represented by formula (1) thus obtained is subjected to the production method of the present invention.

[0024] In the production method of the present invention, first, in the dissolution step, a crude composition containing an aromatic diol represented by formula (1) is dissolved in a mixed solvent of an organic solvent (A), an organic solvent (B) different from the organic solvent (A), and water.

[0025] The organic solvent (B) used in the present invention may be one or more alcohols selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, 2-butanol, 2-ethyl-2-propanol, 2-ethylhexanol, and 2-ethoxyethanol. Among these, methanol is preferred because of its excellent purification efficiency.

[0026] The organic solvent (A) used in the present invention may be at least one selected from the group consisting of toluene, xylene, anisole, mesitylene, and 4-methyltetrahydropyran. Among these, toluene is preferred because of its excellent purification efficiency.

[0027] As the organic solvent (A), the reaction solvent that has not been completely separated during filtration or the like in the method for obtaining a crude composition containing the aromatic diol represented by the formula (1) may be used as is in the dissolving step of the production method of the present invention.

[0028] In the mixed solvent of organic solvent (A), organic solvent (B) different from organic solvent (A), and water used in the present invention, the content of organic solvent (A) is preferably 4 to 22 mass%, more preferably 5 to 20 mass%, and even more preferably 6 to 18 mass%.

[0029] In the mixed solvent of organic solvent (A), organic solvent (B) different from organic solvent (A), and water used in the present invention, the content of organic solvent (B) is preferably 40 to 80 mass%, more preferably 45 to 75 mass%, and even more preferably 50 to 70 mass%.

[0030] In the mixed solvent of the organic solvent (A), the organic solvent (B) different from the organic solvent (A), and water used in the present invention, the water content is preferably 10 to 45 mass%, more preferably 13 to 42 mass%, and even more preferably 15 to 40 mass%.

[0031] When the contents of the components constituting the mixed solvent are within the above ranges, there is a tendency that the catalyst, unreacted raw materials, etc. can be easily removed while side reactions during purification are suppressed.

[0032] In the production method of the present invention, the amount of the mixed solvent is preferably 300 to 3,000 parts by mass, more preferably 500 to 2,500 parts by mass, and even more preferably 700 to 2,000 parts by mass, per 100 parts by mass of the aromatic diol represented by formula (1) in the crude composition. If the amount of the mixed solvent is below the lower limit, the efficiency of removing raw materials, catalysts, by-products, etc. tends to decrease, making it difficult to obtain high-purity crystals. If the amount of the mixed solvent is above the upper limit, the yield tends to decrease significantly.

[0033] The temperature of the solution in the dissolving step is not particularly limited as it differs depending on the types and mixing ratio of the organic solvents (A) and (B) used, but is preferably 10 to 100°C, more preferably 30 to 80°C, and even more preferably 50 to 65°C.

[0034] The dissolving step is carried out until the crude composition of the aromatic diol represented by formula (1) is completely dissolved in the mixed solvent.

[0035] If necessary, before dissolving the crude composition of the aromatic diol represented by formula (1), washing with an aqueous medium may be performed to remove water-soluble compounds contained in the crude composition, and after dissolving the crude composition of the aromatic diol represented by formula (1), filtration may be performed to remove insoluble foreign matter, or adsorbent treatment with activated carbon or the like may be performed to remove coloring substances, metals, and the like.

[0036] The solution in which the crude composition of the aromatic diol represented by formula (1) is dissolved is then subjected to a crystallization step.

[0037] The crystallization step is carried out at a temperature of preferably 0 to 30°C, more preferably 3 to 20°C, and even more preferably 5 to 10°C while stirring.

[0038] If the crystallization temperature is below the lower limit, the solubility of the raw materials, catalyst, by-products, etc. will decrease, making it difficult to obtain high-purity crystals. If the crystallization temperature is above the upper limit, the yield will tend to decrease significantly.

[0039] The aromatic diol crystallized in the crystallization step is separated and recovered from the solution by conventional means such as centrifugation, filtration with a filter press, etc. The recovered aromatic diol crystals are washed with cold water, hot water, an aqueous alcohol solution, etc., as necessary, and then dried.

[0040] The high purity aromatic diol thus obtained is suitable for use as a raw material for preparing various polymers.

[0041] The content of sulfur atoms contained in the high-purity aromatic diol obtained by the method of the present invention is less than 200 ppm. The content of sulfur atoms is preferably less than 180 ppm, more preferably less than 150 ppm, and even more preferably less than 100 ppm. The content of sulfur atoms contained in the high-purity aromatic diol obtained by the method of the present invention is usually 1 ppm or more, and in other cases 50 ppm or more. Such sulfur atoms are derived from sulfuric acid, p-toluenesulfonic acid, or the like used as a sulfur-containing acid catalyst during the synthesis of the aromatic diol represented by formula (1).

[0042] The content of sulfur atoms is measured by oxidative decomposition-coulometric titration method. [Example]

[0043] The present invention will be described in detail below with reference to examples, but these examples are not intended to limit the scope of the present invention. The target aromatic diol represented by formula (1) was analyzed by the following method.

[0044] [High-Performance Liquid Chromatography (HPLC)]: (Measurement of the purity of aromatic diols) Instrument: Waters Alliance 2690 / 2996 Column model number: L-Column Fluid volume: 1.0mL / min Solvent ratio: H2O (pH 2.3) / MeOH = 60 / 40 (20 min) → 15 min → 10 / 90 → 1 min → 5 / 95 (9 min), gradient analysis Wavelength: 229nm Column temperature: 40℃

[0045] [Gas Chromatography (GC)]: (Measurement of Toluene and Methanol Content in Aromatic Diols) Equipment: Shimadzu Corporation GC-2014 (G-2) Column model number: TC-WAX 0.32mm x 30m 0.25μm Injection volume: 1.0μL Oven temperature: 300°C Internal standard: n-propylbenzene Carrier gas: Helium Detector: FID

[0046] [Oxidative decomposition - coulometric titration]: (Measurement of sulfur atom content in aromatic diols) Instrument: Mitsubishi Chemical Analytech TOX-2100H Temperature: 900℃ Gases used: oxygen, argon

[0047] [Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP)]: (Measurement of the sodium and potassium atom content in aromatic diols) Instrument: Thermo Scientific iCAP 6000 Sample introduction: Direct High frequency power: 1250W Plasma gas flow rate: 13.0L / min Nebulizer gas flow rate: 0.22L / min

[0048] <Yield measurement> The yield was determined by the following formula: Yield (%) = 100 - elution rate of HQ-POB into mother wash and washing liquor

[0049] Reference Example 1 (Preparation of crude HQ-POB (1)) A 1L four-neck flask equipped with a stirrer, a sample tube, and a temperature sensor was charged with 63g (0.46mol) of 4-hydroxybenzoic acid, 50g (0.46mol) of hydroquinone, 630g of toluene, and 2g (0.02mol) of concentrated sulfuric acid as a reaction catalyst, followed by nitrogen substitution. The suspension was heated while stirring and refluxed for 10 hours while dehydrating. After the reaction, the mixture was cooled to room temperature and separated into solid and liquid to obtain 200g of solid.

[0050] The obtained solid was quantitatively analyzed by HPLC, GC, oxidative decomposition-coulometric titration, and ICP (the solid contained 85 g of HQ-POB and 115 g of toluene). The results are shown in Table 1.

[0051] [Example 1] A 1-L four-neck flask equipped with a stirrer and a temperature sensor was charged with 200 g of the solid obtained in Reference Example 1, 529 g of methanol (620 parts by mass relative to 100 parts by mass of HQ-POB contained in the solid), and 227 g of ion-exchanged water (270 parts by mass relative to 100 parts by mass of HQ-POB contained in the solid), and the mixture was heated to 60°C under a nitrogen stream. After dissolution was confirmed at this temperature, the mixture was filtered to remove foreign matter. After removal, the mixed solvent was cooled to 5°C. After cooling, solid-liquid separation was performed to obtain 120 g of solid. The obtained HQ-POB crystals were dried at 80°C for 15 hours to obtain 72 g of HQ-POB. Quantitative analysis was performed using HPLC, GC, oxidative decomposition-coulometric titration, and ICP. The results are shown in Table 1.

[0052] [Examples 2 to 3] An aromatic diol was obtained in the same manner as in Example 1, except that the mixed solvent was changed to the solvent composition shown in Table 1. The obtained aromatic diol was quantitatively analyzed by HPLC, GC, oxidative decomposition-coulometric titration, and ICP. The results are shown in Table 1.

[0053] Reference Example 2 (Preparation of crude HQ-POB (2)) The solid obtained in the same manner as in Reference Example 1 was dried under reduced pressure for 5 hours. Quantitative analysis was carried out by HPLC, GC, oxidative decomposition-coulometric titration, and ICP. The results are shown in Table 1.

[0054] [Comparative Examples 1 to 2] An aromatic diol was obtained in the same manner as in Example 1, except that the 200 g of the solid obtained in Reference Example 1 was changed to 85 g of the solid obtained in Reference Example 2, and the mixed solvent was changed to the solvent shown in Table 1. The obtained aromatic diol was quantitatively analyzed by HPLC, GC, oxidative decomposition-coulometric titration, and ICP. The results are shown in Table 1.

[0055] [Comparative Examples 3 to 4] The same procedure as in Example 1 was carried out except that 200 g of the solid obtained in Reference Example 1 was changed to 85 g of the solid obtained in Reference Example 2 and the mixed solvent was changed to the solvent composition shown in Table 1. However, since the aromatic diol did not dissolve, purification by crystallization could not be carried out.

[0056] As shown in Table 1, Examples 1 to 3 of the present invention, in which recrystallization was carried out using a mixed solvent of organic solvent (A), organic solvent (B) different from organic solvent (A), and water, were able to significantly reduce the sulfur atom content compared to Comparative Examples 1 and 2. [Table 1]

Claims

1. Formula (1) 【Chemistry 1】 [In the formula, Ar １ and Ar ２ each represents a divalent aromatic group. a step of dissolving a crude composition containing an aromatic diol represented by the formula (I) in a mixed solvent of an organic solvent (A), an organic solvent (B) different from the organic solvent (A), and water; and A step of crystallizing the obtained solution A method for producing a high-purity aromatic diol represented by formula (1), comprising: the organic solvent (B) is an alcohol; The method of claim 1, wherein the crude composition containing the aromatic diol represented by formula (1) has a sulfur atom content of 200 ppm or more, and the high-purity aromatic diol represented by formula (1) has a sulfur atom content of less than 200 ppm.

2. Ar １ and Ar ２ are each independently of one another represented by the formulas (I) to (III) 【Chemistry 2】 [In the formula, "-*" indicates the bonding position of the aromatic group] The method of claim 1, wherein the aromatic group is selected from aromatic groups represented by the formula:

3. Ar １ and Ar ２ and are both aromatic groups represented by formula (I).

4. The crude composition containing the aromatic diol represented by formula (1) is reacted with an aromatic diol represented by formula (2) in an organic solvent (A) in the presence of a sulfur-containing acid catalyst. 【Transformation 3】 and a compound represented by formula (3) 【Chemistry 4】 The method according to claim 1, wherein the compound is obtained by reacting a compound represented by the formula:

5. The method according to claim 4, wherein the sulfur-containing acid catalyst is at least one selected from the group consisting of sulfuric acid, sulfurous acid, dimethyl sulfate, diethyl sulfate, chlorosulfonic acid, fluorosulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.

6. 2. The method according to claim 1, wherein the organic solvent (B) is one or more alcohols selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, 2-butanol, 2-ethyl-2-propanol, and 2-ethoxyethanol.

7. The method of claim 6, wherein the organic solvent (B) is methanol.

8. 2. The method according to claim 1, wherein the organic solvent (A) is at least one selected from the group consisting of toluene, xylene, anisole, mesitylene, and 4-methyltetrahydropyran.

9. 9. The method of claim 8, wherein the organic solvent (A) is toluene.

10. The method according to claim 1, wherein the content of the organic solvent (A) in the mixed solvent is 4 to 22 mass%.

11. The method according to claim 1, wherein the content of the organic solvent (B) in the mixed solvent is 40 to 80 mass%.

12. The method according to claim 1, wherein the content of water in the mixed solvent is 10 to 45% by mass.

13. The method according to claim 1, wherein the aromatic diol represented by formula (1) in the crude composition is dissolved in 300 to 3,000 parts by mass of a mixed solvent relative to 100 parts by mass of the aromatic diol.

14. The method according to claim 1, wherein the solution temperature in the dissolving step is 50 to 65°C.

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