TWI820160B - 9,9-bis(4-hydroxyphenyl)-2,3-benzofluorene crystal - Google Patents

Abstract

An object of the present invention is to provide a 9,9-bis (4-hydroxyphenyl) -2,3-benzofluorene crystal having a specific melting point, and not being an inclusion body or having a remaining organic solvent content of 1% by weight or less. As a means for solving the object, it has been found that by crystallizing a 9,9-bis (4-hydroxyphenyl)- 2,3-benzofluorene having a chemical structure represented by the following formula (1) by using a specific solvent, the obtained crystal does not become an inclusion body, and has a remaining organic solvent content of 1% by weight or less.

Description

9,9-bis(4-hydroxyphenyl)-2,3-benzofluoride crystal

The present invention relates to a crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen and a method for producing the crystal. The aforementioned 9,9-bis(4-hydroxyphenyl)-2, The melting point of the crystal of 3-benzofluoride is 182 to 187°C as measured by differential scanning calorimetry, and the crystal is not an inclusion compound (also known as a clathrate compound) or the content of residual organic solvents It is less than 1% by weight.

In the past, a group of compounds with a fluorine skeleton such as 9,9-bis(4-hydroxyphenyl)fluoride have been used as raw materials for thermoplastic synthetic resins such as polycarbonate resin and epoxy resins because of their excellent heat resistance and optical properties. Such as thermosetting resin raw materials, antioxidant raw materials, thermal recording material raw materials, photoresist raw materials, etc. Among them, resins produced from 9,9-bis(4-hydroxyphenyl)-2,3-benzoquinone having a chemical structure represented by the following formula (1) are attracting particular attention because of their excellent optical properties (for example, Patent Document 1, etc.).

As for the production method of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquinone represented by the above formula (1), it is known that 2,3-benzo-9-benzoquinone and A method in which phenol is condensed in a dimethyl carbonate solvent in the presence of 3-mercaptopropionic acid and methanesulfonic acid, and the precipitated crystals are separated and dried (Patent Document 1). However, the crystals obtained by this method are in 9 , an inclusion crystal containing dimethyl carbonate included in 9-bis(4-hydroxyphenyl)-2,3-benzofluoride.

In addition, a method is known in which acetone is added to a reaction mixture containing 9,9-bis(4-hydroxyphenyl)-2,3-benzofen, the precipitated crystals are separated, and then recrystallization is carried out using acetone (Patent Document 2), but the obtained crystal is an inclusion crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin and acetone.

For conventional inclusion crystals of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquine, the temperature at which the solvent belonging to the guest compound is released is above the melting point of the crystal. When the temperature is raised in order to remove the included solvent, the crystals melt. Therefore, a method for obtaining solvent-free crystals is not yet known.

It is known that a group of compounds having a fluorine skeleton such as 9,9-bis(4-hydroxyphenyl)benzoate forms inclusion compounds with the reaction solvent and the solvent used for purification. On the other hand, in order to remove the included solvent, it is necessary to remove the included solvent. It takes a lot of time to operate at high temperature, so it is difficult to apply it on an industrial scale. In addition, it is also known that compounds with a fluorine skeleton containing a solvent are used as raw materials for manufacturing epoxy resins, polyesters, etc., and for other uses. There are problems in industrial use (Patent Document 3).

[Prior technical literature] [Patent Document]

Patent Document 1: Japanese Patent Application Publication No. 2017-036249

Patent Document 2: International Publication No. 2015/147115

Patent Document 3: Japanese Patent Application Publication No. 10-245352

The present invention was made in view of the above background, and its object is to provide a crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen and a method for producing the crystal. The aforementioned 9,9 - The crystal of bis(4-hydroxyphenyl)-2,3-benzofen has a specific melting point, and the crystal is not a clathrate, or the content of the residual organic solvent in the crystal is 1% by weight or less.

The present inventors conducted careful examinations to solve the above-mentioned problems and found that 9,9-bis(4-hydroxyphenyl)-2,3-benzene having a specific melting point can be obtained by crystallizing using a specific solvent. The present invention is completed by finding a crystal that is not a clathrate, or the content of the remaining organic solvent in the crystal is 1% by weight or less.

The present invention is described below.

1. A crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen, with a melting point of 182 to 187°C as measured by differential scanning calorimetry.

2. The crystal as described in 1., which is not an inclusion compound.

3. The crystal as described in 1. or 2., the content of residual organic solvent is less than 1% by weight.

4. A method for producing a crystal according to any one of 1. to 3., including the step of crystallizing using a mixed solvent of methanol and water.

5. The manufacturing method as described in 4., further comprising the step of drying the crystals obtained by crystallization at a temperature above 45°C and below the melting point.

According to the present invention, a crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen and a method for producing the crystal can be provided. The crystal has a specific melting point, and the crystal is not an inclusion. The content of the substance or its residual organic solvent is less than 1% by weight.

In the case where a compound such as an organic solvent is included in 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin, when the inclusion compound is reacted with (meth)acrylic acid, for example, There may be a problem that the included organic solvent and other compounds hinder the reaction and make the reaction impossible. Furthermore, when the clathrate is melted and used as a resin raw material, in addition to the vapor originating from the "compounds such as included organic solvents" generated during the melting, it is necessary to remove from the reaction device, as well as The quality of the target resin is reduced due to residual organic solvents and other compounds. In addition, depending on the flash point and ignition point of compounds such as organic solvents included, there may be disaster prevention concerns during the transportation and storage of the inclusion compounds.

As mentioned above, there is no known so-called "crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin, which has a specific melting point and does not contain compounds such as organic solvents" , or the content of residual organic solvent is less than 1% by weight." Furthermore, regarding conventional methods for removing organic solvents from inclusion crystals, only methods such as melting and removing the crystals are known, which are difficult to implement industrially or are very costly.

That is, "a novel crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin, which has a specific melting point, and which does not contain compounds such as organic solvents, or other "The content of the residual organic solvent is 1% by weight or less" and the provision of its production method is very useful for industrial use such as resin raw materials.

Figure 1 is a graph showing a differential scanning calorimetry (DSC) curve of the crystal obtained in the synthesis example (crystal of the present invention).

Figure 2 is a graph showing a differential scanning calorimetry (DSC) curve of the crystal obtained in Example 1 (crystal of the present invention).

Figure 3 is a graph showing a differential scanning calorimetry (DSC) curve of the crystal obtained in Comparative Example 1.

Figure 4 is a graph showing a differential scanning calorimetry (DSC) curve of the crystal obtained in Comparative Example 2.

The present invention will be described in detail below.

The 9,9-bis(4-hydroxyphenyl)-2,3-benzoquine of the present invention is a compound represented by the following formula (1).

<About synthesis method>

The synthesis method of 9,9-bis(4-hydroxyphenyl)-2,3-benzofluoride of the present invention is not particularly limited, and the well-known 9,9-bis(4-hydroxyphenyl)-2,3-benzofluoride, etc. can be used. A method for producing a compound with a fluorine skeleton can be obtained, for example, by reacting phenol and 2,3-benzo-9-quinone as raw materials in the presence of an acid catalyst as shown in the following reaction formula. .

Explain the reaction between phenol and 2,3-benzo-9-quinone shown in the above reaction formula.

The molar ratio of phenol to 2,3-benzo-9-quinone is not particularly limited as long as it is above the theoretical value (2.0). Usually, it is in the range of 2 to 20 times the molar amount, preferably 3 to 10 times the molar volume.

The catalyst used is not particularly limited, and a well-known acid catalyst can be used. Specific acid catalyst systems include, for example, hydrochloric acid, hydrogen chloride gas, inorganic acids such as 60 to 98% sulfuric acid and 85% phosphoric acid; p-toluenesulfonic acid, methanesulfonic acid, oxalic acid, formic acid, trichloroacetic acid or trifluoroacetic acid, etc. Organic acids; solid acids such as heteropoly acid (heteropoly acid), etc. Hydrogen chloride gas is preferred. The appropriate amount of acid catalyst used will vary depending on the reaction conditions. For example, in the case of hydrogen chloride gas, it is better to replace the air in the reaction system with an inactive gas such as nitrogen and then blow in hydrogen chloride. gas, and set the hydrogen chloride gas concentration in the gas phase in the reaction vessel to 75 to 100% by volume, so that the hydrogen chloride concentration in the reaction solution becomes a saturated concentration. In the case of 35% hydrochloric acid, the range of 5 to 70 parts by weight is used relative to 100 parts by weight of phenol, preferably the range of 10 to 40 parts by weight is used, and the range of 20 to 30 parts by weight is more preferably used.

During the reaction, an acid catalyst and a catalyst accelerator may also be used simultaneously if necessary. For example, when hydrogen chloride gas is used as a catalyst, the reaction rate can be accelerated by using mercaptans as a catalyst accelerator. Examples of such thiols include alkyl mercaptans and mercaptocarboxylic acids, preferably alkyl mercaptans having 1 to 12 carbon atoms and mercaptocarboxylic acids having 1 to 12 carbon atoms. Examples thereof include: methyl group Mercaptans, ethyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, etc. and alkali metal salts such as sodium salts thereof, thioacetic acid, β-mercaptopropionic acid, etc. Moreover, these can be used individually or in combination of 2 or more types. The amount of thiols used as a catalyst accelerator is usually in the range of 1 to 30 mol%, preferably 2 to 10 mol%, relative to the raw material 2,3-benzo-9-quinone. range.

During the reaction, the reaction solvent may not be used, or it may be used for reasons such as improved operability and reaction speed during industrial production. The reaction solvent is not particularly limited as long as it does not distill out from the reactor at the reaction temperature and is inactive for the reaction. Examples include aromatic hydrocarbons such as toluene and xylene; methanol, ethanol, Lower aliphatic alcohols such as 1-propanol and 2-propanol; organic solvents such as saturated aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, and water or mixtures thereof. Among these, aromatic hydrocarbons are preferably used.

The reaction temperature varies depending on the type of raw material phenol and acid catalyst. When hydrogen chloride gas is used as the acid catalyst, the reaction temperature is usually in the range of 10 to 60°C, preferably in the range of 25 to 50°C. The reaction pressure is usually carried out under normal pressure. It can also be carried out under increased pressure or reduced pressure according to the boiling point of the organic solvent that can be used and so that the reaction temperature is within the aforementioned range.

The reaction time varies depending on the type of raw material phenol, acid catalyst, reaction temperature, etc., but usually ends in about 1 to 30 hours.

The end point of the reaction can be confirmed by liquid chromatography or gas chromatography analysis. Preferably, the time point when it is confirmed that the unreacted 2,3-benzo-9-quinone has disappeared and the target substance no longer increases is set as the end point of the reaction.

During the reaction, the method of adding the reaction raw materials is not particularly limited, and it can be carried out according to a known method for producing compounds having a fluorine skeleton such as 9,9-bis(4-hydroxyphenyl)fluoride. In a preferred embodiment, for example, a predetermined amount of phenol, acid catalyst, and optional catalyst accelerator and reaction solvent are added to the reaction vessel, and the temperature is raised to the predetermined reaction while stirring under a nitrogen stream. After reaching the temperature, add 2,3-benzo-9-quinone one by one to it.

<About post-reaction processing>

After the reaction is completed, known post-processing methods can be applied. For example, in order to neutralize the acid catalyst, an alkali aqueous solution such as sodium hydroxide aqueous solution or ammonia aqueous solution is added to the reaction completion liquid to neutralize the acid catalyst. The neutralized reaction mixture is allowed to stand, and if necessary, a solvent for separating from water is added to separate and remove the water layer. If necessary, perform the operation of "add distilled water to the obtained oil layer, stir and wash with water, and then separate and remove the water layer" once or repeat it multiple times to remove the neutralizing salt and remove the remaining phenol from the obtained oil layer. Removed by distillation under reduced pressure. A solvent such as an aromatic hydrocarbon is added to the obtained residue to prepare a uniform solution, and the crystals precipitated by cooling are separated to obtain crude crystals. This crude crystal and the aforementioned residue can be transformed into a 9,9-bis(4-hydroxyphenyl)-2,3-benzoquine by undergoing the crystallization step of the present invention, which has a specific melting point and does not include The content of the compound or its residual organic solvent is less than 1% by weight.

<About crystallization steps>

The manufacturing method of the present invention includes the step of crystallizing using a mixed solvent of methanol and water. Among them, the methanol that can be used is not particularly limited, and generally commercially available methanol can be used, or any of special grade, first grade, and industrial use can be used. In addition, the water that can be used is not particularly limited, and for example, tap water, distilled water, ion exchange water, natural water, etc. can be suitably used.

The mixing ratio (weight ratio) of methanol and water is preferably methanol:water=0.4 to 2.0:1.0. If the content ratio of water is lowered than the mixing ratio (weight ratio) of methanol and water, the target 9,9-bis(4-hydroxyphenyl)-2,3-benzofluoride will remain. The amount of methanol will increase. In addition, when the crude crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin used for crystallization is an inclusion compound, compared with the mixing ratio (weight ratio) of methanol and water, if When the water content ratio becomes higher, 9,9-bis(4-hydroxyphenyl)-2,3- is included in the solvent used for the reaction and post-reaction treatment (for example, aromatic hydrocarbon solvents such as toluene). Benzoic acid will increase, so it is not good. Among them, the mixing ratio (weight ratio) of methanol and water is preferably 1.0 to 1.8:1.0, and further preferably 1.4 to 1.6:1.0.

Used relative to 100 parts by weight of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin contained in the residue obtained from the post-treatment step of the reaction or the crude crystal used in the crystallization step The mixed solvent amount of methanol and water is preferably 250 to 1000 parts by weight, more preferably 300 to 700 parts by weight, and even more preferably 400 to 600 parts by weight, especially 450 to 550 parts by weight. . When the amount of the mixed solvent of methanol and water is large, the amount of crystals obtained decreases. When the amount of the mixed solvent of methanol and water is small, the purity of the target product decreases, which is undesirable.

Furthermore, in the crystallization step of the present invention, if a solvent other than methanol and water is used, a 9,9-bis(4-hydroxyphenyl)-2,3-benzoquinone will not be obtained, which has It is not preferable because it has a specific melting point, is not a clathrate, or has a residual organic solvent content of 1% by weight or less.

In the crystallization step of the present invention, a mixed solvent of methanol and water can be added to the treated residue or crude crystal after the reaction to achieve the above mixing ratio (weight ratio) of methanol and water, and the mixture can be placed under normal pressure or The mixed solvent is heated under pressure until it is equal to or lower than the boiling point of the mixed solvent so that it is completely dissolved to form a uniform solution, and then cooled to obtain precipitated crystals. When the solution is heated to form a uniform solution and then cooled, it is cooled to 0 to 40°C, preferably 10 to 35°C, at a rate of 5 to 15°C/hour, preferably 8 to 12°C/hour. , more preferably between 20 and 30°C, and the precipitated crystals are preferably separated by filtration or the like.

In addition, methanol can also be added to the treated residue or crude crystal after the reaction to be completely dissolved to prepare a uniform solution, and the mixture ratio (weight ratio) of methanol and water can be obtained with stirring. Water was added dropwise to obtain precipitated crystals. At this time, it is preferable to maintain a temperature of 60°C or higher during crystallization. It is more preferable to maintain the temperature at the same temperature for at least 1 hour or more after the crystallization starts, and then separate the precipitated crystals. Furthermore, when cooling further, it is preferable to perform cooling at the above-mentioned speed.

<About drying steps>

By performing the drying step, the solvent (methanol, water) used in the crystallization step of the present invention can be removed. The drying step of the present invention can be carried out at a temperature of 45°C or higher and lower than the melting point of the crystals obtained in the crystallization step, preferably 70°C or higher, more preferably 90°C or higher, and particularly 120°C or higher. good. In addition, depending on other conditions, etc., the crystal color may be deteriorated by heat, so the temperature is preferably 150°C or lower, and more preferably 130°C or lower. At a temperature lower than 45°C, the solvent (methanol, water) used in the crystallization step cannot be removed, or even if it can be removed, it takes a lot of time, which is undesirable.

The drying step may be carried out under normal pressure or under reduced pressure. However, when carried out industrially, the solvent (methanol) used in the crystallization step can be removed more efficiently when carried out under reduced pressure. , water), so it is also suitable. In addition, the drying step is preferably carried out in a gas atmosphere of inert gas such as nitrogen.

<Crystal of the present invention>

The melting point of the crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen of the present invention is in the range of 182°C to 187°C as measured by differential scanning calorimetry. Among them, the lower limit of the melting point measured by differential scanning calorimetry is preferably 183°C or higher, and particularly preferably 184°C or higher. Furthermore, the upper limit value may be 186°C or lower.

Furthermore, the crystal of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen of the present invention is not a inclusion compound, that is, it is a crystal that does not include compounds such as organic solvents. In the present invention, the so-called crystals that do not contain compounds such as organic solvents are preferably crystals with a residual organic solvent content of 1% by weight or less, more preferably 0.5% by weight or less. The content of crystals is more preferably 0.3% by weight or less, and particularly preferably 0.1% by weight or less.

(Example)

The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

The analysis method is described below.

<Analysis method> 1. Powder X-ray diffraction (XRD)

About 100 mg of crystals were filled into the sample filling portion of the glass test plate, and measured under the following conditions using a powder X-ray diffraction device (manufactured by Rigaku Co., Ltd.: SmartLab).

X-ray source: CuKα

Scan axis: 2θ/θ

Mode: Continuous

Measuring range: 2θ=5° to 70°

Step: 0.01°

Speed measurement time: 2θ=2°/minute

IS：1/2

RS:20.00mm

Output: 40kV-30mA

2. Differential scanning calorimetry (DSC)

5 mg of crystals were weighed into an aluminum pan, and measured using a differential scanning calorimeter (DSC-60 manufactured by Shimadzu Corporation) under the following operating conditions using alumina as a control.

(Operating conditions)

Heating rate: 10℃/min

Measuring temperature range: 30 to 260℃

Measuring gas environment: open, nitrogen 50mL/min

3. Differential thermal/thermogravimetric analysis (DTG)

8 mg of crystals were weighed into an aluminum pot and measured under the following operating conditions using a differential heat/thermogravimetric analyzer (manufactured by Shimadzu Corporation: DTG-60A).

(Operating conditions)

Heating rate: 10℃/min

Measuring temperature range: 30 to 300℃

Measuring gas environment: open, nitrogen 50mL/min

4. Hue (APHA)

The crystal was dissolved in methanol to obtain a 10% by weight solution, and the following measuring device was calibrated with methanol, and then the dissolved color of the 10% by weight solution was measured.

Measuring machine: TZ6000 manufactured by Nippon Denshoku Industries Co., Ltd.

<Synthesis example>

Synthesis of 9,9-bis(4-hydroxyphenyl)-2,3-benzoquin

A 1-liter four-necked flask equipped with a thermometer, a stirrer, and a cooling tube was replaced with nitrogen, 119 g (1.2 mol) of phenol was added, hydrogen chloride gas was blown in, and the flask was replaced with hydrogen chloride gas. Then, 13g of 15% sodium methylmercaptide aqueous solution was added dropwise, and then 145g of 2,3-benzo-9-quinone (0.63 mole), 119g of phenol (1.2 mole) and 58g of toluene were added dropwise over 1 hour. The mixture was stirred at the reaction temperature of 40°C for 3 hours. The disappearance of the raw materials was confirmed by liquid chromatography analysis, and the reaction was considered to be completed. An aqueous sodium hydroxide solution was added to the reaction mixture for neutralization, and 60 g of toluene was added and allowed to stand, and then the aqueous layer was removed. Repeat the operation of "add distilled water to the obtained oil layer and stir, let it stand and remove the water layer" twice to remove the neutralizing salt, and remove the remaining phenol by distillation under reduced pressure. To this distillation residue, 1009 g of toluene was added to prepare a uniform solution, and the solution was cooled to precipitate crystals. Then, the mixture was cooled to 25° C., and the precipitated crystals were filtered out.

The obtained crystal was dried at 90°C under reduced pressure of 1.2 kPa for 2 hours, and the result measured by headspace gas chromatography (hereinafter referred to as "HS-GC analysis") was that it contained 4% by weight toluene. Furthermore, it was dried at 120°C for 3 hours under reduced pressure of 1.2 kPa, but the toluene content did not change. In addition, from the results of DTG analysis, a weight loss of 2.0% was confirmed at temperatures above the melting point. The differential scanning calorimetry (DSC) curve of the obtained crystal is shown in Figure 1.

Appearance white crystal

Hue 47(APHA)

Purity 98.7% (high-speed liquid chromatography)

Melting point: 144℃ (differential scanning calorimetry)

<Example 1>

70g of the white crystals obtained in the above "Synthesis Example" were heated and dissolved in 210g of methanol to prepare a solution. The solution was stirred for 30 minutes while maintaining a temperature of 60°C or above and below the boiling point (64.7°C). Add 135g of distilled water dropwise. After the dropwise addition, precipitation of crystals was immediately confirmed, and then the mixture was kept at the same temperature for 1 hour, then cooled to 25°C at a rate of 10°C every 1 hour, and the precipitated crystals were filtered out. The temperature of the obtained white crystal was gradually raised to 120°C under reduced pressure of 1.2 kPa, and then dried under reduced pressure at 120°C for 3 hours. According to the HS-GC analysis method, it was confirmed that the residual methanol was 0.5% by weight or less, so the drying under reduced pressure was completed, and the target substance 9,9-bis(4-hydroxyphenyl)-2,3-, which was not a clathrate, was obtained. 64g of benzofen crystals.

The obtained crystal was measured by the HS-GC analysis method. As a result, it was confirmed that the remaining organic solvents were 460 ppm of toluene and 290 ppm of methanol. Therefore, it was confirmed that the obtained crystal was not a clathrate. In addition, from the results of DTG analysis, no weight loss was confirmed at temperatures above the melting point. The differential scanning calorimetry (DSC) curve of the obtained crystal is shown in Figure 2 .

Appearance white crystal

Hue 14(APHA)

Purity 99.1% (high-speed liquid chromatography)

Melting point: 185℃ (differential scanning calorimetry)

9,9-bis(4-hydroxyphenyl)-2 obtained from the above "Example 1" has a specific melting point of the present invention, is not a clathrate, and has a residual organic solvent content of 1% by weight or less. , 3-benzofluoride crystals were subjected to powder X-ray diffraction (XRD), and the main peaks (those with relative intensity exceeding 5%) are listed in Table 1.

<Comparative example 1>

Referring to Example 20 of the above-mentioned "Patent Document 1", 9,9-bis(4-hydroxyphenyl)-2,3-benzoquine was synthesized.

Substitute nitrogen into a 1-liter four-necked flask equipped with a thermometer, stirrer, and cooling tube, and add 10.5g (0.046 mole) of 2,3-benzo-9-quinone, 21.5g (0.228 mole) of phenol, and 6.6 toluene. g, dissolve it by raising the temperature to 40°C, add 0.17g of 3-mercaptopropionic acid, add 5.9g of methanesulfonic acid dropwise over 30 minutes, and stir at 60°C for 1 hour. 69.9 g of toluene and 43.7 g of water were added to the reaction solution, and the organic layer was washed, and then washed and separated three times with 43.7 g of saturated brine. Then, 8.1 g of dimethyl carbonate was added, the temperature was raised to 80°C, and then the mixture was gradually cooled to 25°C to precipitate crystals, and then stirred at 25°C for 1 hour. The precipitated crystals were filtered, and the obtained white crystals were slowly heated to 120°C under reduced pressure of 1.2 kPa, dried under reduced pressure at 120°C for 1 hour, and the amount of remaining organic solvent was measured by ¹ H-NMR analysis. Furthermore, drying was continued at 120°C for 3 hours under reduced pressure of 1.2 kPa, but the amount of organic solvent contained in the crystal did not change.

Appearance white crystal

Purity 97.4% (high-speed liquid chromatography)

Melting point: 170℃ (differential scanning calorimetry)

The obtained crystal was subjected to DTG analysis, and it was confirmed that there was a 4.2% weight loss at a temperature above the melting point. In addition, it was confirmed by ¹ H-NMR measurement that the obtained crystal contained 1 mole of dimethyl carbonate based on 5 moles of the compound. From this, it can be seen that this is substantially the same as the "crystal containing 1 mole of dimethyl carbonate with respect to 4.9 moles of the compound" described in Example 20 of "Patent Document 1". The differential scanning calorimetry (DSC) curve of the obtained crystal is shown in Figure 3 .

<Comparative example 2>

In a test tube equipped with a stirrer, 2 g of the dried crystals of the synthesis example and 2 g of acetone were put in, and dissolved at 50°C. While maintaining the internal temperature at 50°C, 7 g of water was slowly added dropwise. Then, after stirring briefly, crystals precipitated. Thereafter, after cooling to 25°C, the crystals were filtered out. The obtained crystal was heated to 100°C under reduced pressure of 1.2 kPa, and dried under reduced pressure for 3 hours to obtain 1.64 g of crystal. Furthermore, drying was performed at 120° C. for 3 hours under reduced pressure of 1.2 kPa, but the amount of organic solvent contained in the crystal did not change. The organic solvent remaining in the obtained crystal was measured by the HS-GC analysis method and found to contain 4200 ppm of toluene and 62100 ppm of acetone. In addition, the results of DTG analysis confirmed a 3.5% weight loss at temperatures above the melting point.

Melting point: 139℃ (differential scanning calorimetry)

The differential scanning calorimetry (DSC) curve of the obtained crystal is shown in Figure 4.

<Comparative Example 3>

Referring to Comparative Example 1 of the above-mentioned "Patent Document 1", 9,9-bis(4-hydroxyphenyl)-2,3-benzoquine was synthesized.

Substitute nitrogen into a 1-liter four-necked flask equipped with a thermometer, stirrer, and cooling tube, and add 10.5g (0.046 mole) of 2,3-benzo-9-quinone, 21.5g (0.228 mole) of phenol, and 6.6 toluene. g, the temperature was raised to 40°C and dissolved. After adding 0.17g of 3-mercaptopropionic acid, 4.5g of sulfuric acid was added dropwise over 30 minutes under stirring, and the reaction was carried out at 60°C for 1 hour. Then, 69.9 g of toluene and 43.7 g of water were added to the reaction liquid, stirred, and left to stand, and then the water layer was separated and removed. Furthermore, the washing operation of "adding 43.7 g of saturated salt water to the obtained organic layer, stirring, leaving it to stand, and then separating and removing the aqueous layer" was repeated three times. Thereafter, the organic layer was slowly cooled to 5° C., and stirring was continued for another 5 hours, but no crystals were precipitated. Further, stirring was continued at room temperature for 15 hours, but no crystals precipitated.

Claims (5)

A crystalline form of 9,9-bis(4-hydroxyphenyl)-2,3-benzofen, with a melting point of 182 to 187°C as measured by differential scanning calorimetry. For example, if the crystal is described in item 1 of the patent application, the crystal is not an inclusion compound. For example, in the crystals described in Item 1 or 2 of the patent application, the content of residual organic solvent is less than 1% by weight. A method for manufacturing the crystals described in any one of items 1 to 3 of the patent application scope, including using a mixed solvent of methanol and water in a weight ratio of methanol:water=0.4 to 2.0:1.0 Perform the crystallization step. The manufacturing method described in item 4 of the patent application further includes the step of drying the crystals obtained by crystallization at a temperature above 45°C and below the melting point.

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