JP4861128B2 - Continuous production method of 9,9-bis (4-hydroxyphenyl) fluorenes - Google Patents

Description

  The present invention relates to a method for continuously producing fluorene derivatives, particularly 9,9-bis (4-hydroxyphenyl) fluorenes useful as raw materials for optical lenses, films, optical fibers, optical disks, heat-resistant resins, engineering plastics, and the like.

In recent years, there has been a strong demand for materials having higher heat resistance, transparency, and higher refractive index than conventional products in polymers (for example, polycarbonate resins, epoxy resins, polyester resins, etc.) using bisphenols as raw materials. Yes. 9,9-bis (4-hydroxyphenyl) fluorenes, which are a kind of fluorene derivatives, are promising as polymer raw materials having excellent optical properties such as high refractive index, low birefringence, transparency and heat resistance, and are used for automobiles. Headlamp lenses, CDs, CD-ROM pickup lenses, Fresnel lenses, fθ lenses for laser printers, optical lenses such as camera lenses, projection lenses for rear projection televisions, retardation films, films such as diffusion films, plastic optical fibers, optical disk substrates It is expected as a raw material.
Examples of 9,9-bis (4-hydroxyphenyl) fluorenes include 9,9-bis (4-hydroxyphenyl) fluorene; 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9-bis (4-hydroxy-3-ethylphenyl) fluorene, 9,9-bis (3-hydroxy-6-methylphenyl) fluorene, 9,9-bis (2-hydroxy-4-methylphenyl) fluorene, 9 9,9-bis (alkylhydroxyphenyl) fluorene such as 9,9-bis (4-hydroxy-2-methylphenyl) fluorene; 9,9-bis (4-hydroxy-3,5-dimethylphenyl) fluorene, 9,9-bis (dialkylhydroxyl) such as 9-bis (4-hydroxy-3,5-di-tert-butylphenyl) fluorene Phenyl) fluorene; 9,9-bis (cycloalkylhydroxyphenyl) fluorene such as 9,9-bis (4-hydroxy-3-cyclohexylphenyl) fluorene; 9,9-bis (4-hydroxy-3-phenylphenyl) And 9,9-bis (arylhydroxyphenyl) fluorene such as fluorene.
As a method for producing these, a method is known in which a fluorenone and a phenol are subjected to a condensation reaction in the presence of a catalyst.
As a condensation reaction, a method is known in which fluorenone obtained by air oxidation of fluorene is used as a starting material, and a condensation reaction with phenol is performed using hydrogen chloride gas and mercaptopropionic acid as catalysts (Patent Documents 1 and 2). .
Patent Document 3 includes a method in which sulfuric acid having a sulfuric acid content higher than 70% is used as a catalyst used in the method for producing 9,9-bis (4-hydroxyphenyl) fluorene, and β-mercaptopropionic acid is used as a cocondensation agent. It has been.
When these reaction steps are used, the reaction product contains a mineral acid that is a water-soluble catalyst in addition to the target component, and it is necessary to remove it in a subsequent step.
Patent Document 4 proposes a method in which a sulfonic acid type cation exchange resin is used as a catalyst without using a water-soluble catalyst such as hydrochloric acid or sulfuric acid. Inventions using an ion exchange resin without using a mineral acid have been made (Patent Document 5 and Patent Document 6).
Even when such a reaction step is used, the reaction products include 9,9-bis (4-hydroxyphenyl) fluorenes, unreacted phenols and fluorenone and a cocatalyst, water produced by the reaction, and by-products. Organisms are included and some means of separation is required. As the separation means, methods such as extraction / liquid-liquid separation, distillation, and crystallization have been proposed.
In Patent Document 7, in a method for producing a fluorene derivative in which fluorenone and phenol are subjected to a condensation reaction in the presence of thiols and hydrochloric acid, an extractant is added to the resulting reaction mixture to distribute the target compound to the organic layer. A method of adding a crystallization solvent to the organic layer and crystallization separation as an inclusion compound has been proposed.
Patent Document 8 describes a method of precipitating crystals using a solvent that forms an adduct (clathrate compound) as a separation method after the synthesis of 9,9-bis (4-hydroxyphenyl) fluorene.
Patent Document 9 proposes a method using a low fatty acid alcohol and water as a separation method for the same purpose, and Patent Document 10 proposes a method using a mixed solvent of a low fatty acid alcohol and an aromatic hydrocarbon.
Patent Document 11 discloses aliphatic hydrocarbons or aromatics having 6 to 12 carbon atoms as a method for producing 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (same as biscresol fluorene, hereinafter referred to as BCF). A method of performing crystallization using a group hydrocarbon or a mixed solvent thereof has been proposed. Patent Document 12 proposes a method for crystallization using a mixed solvent containing a lower aliphatic alcohol having 1 to 3 carbon atoms and a lower aliphatic ketone having 3 to 7 carbon atoms when purifying biscresols. ing.
Even if only the reaction process is continued from the above known technology, separation of generated water, separation of cocatalyst, separation of unreacted phenols, separation of the crystallization solvent constituting the clathrate compound are necessary, and industrialization is intended. In this case, continuation including a plurality of separation steps is required. In order to recycle and reuse the useful components recovered in the separation process, it is necessary to improve the product recovery rate while suppressing impurities, but the composition of the impurities generated in each separation process and the reuse destination respectively. There is no literature mentioning the characteristics of this process, and no effective continuous production method has been proposed yet.
JP-A-62-230741 (Patent No. 1611498) Japanese Patent Laid-Open No. 10-265423 (Patent No. 3500488) Japanese Patent Application Laid-Open No. 61-103846 JP-A-5-000980 JP 45-10337 A (Patent No. 585576) JP-A-57-35533 (Patent No. 1468745) JP 2002-047227 A (Patent 3490960) JP-A-62-230741 (Patent No. 1611498) JP-A-4-41450 JP-A-4-41451 Japanese Patent Laid-Open No. 10-265423 (Patent No. 3500488) JP 10-245352 A (Patent No. 3512242)

  Therefore, the main problem to be solved by the present invention is to provide a method for continuously producing 9,9-bis (4-hydroxyphenyl) fluorenes. Another object is to provide a continuous process for producing 9,9-bis (4-hydroxyphenyl) fluorenes that provides advantages such as a large crystal grain size and excellent crystal quality.

  As a result of research, the present inventors have found a method for continuously producing 9,9-bis (4-hydroxyphenyl) fluorenes through a series of organically coupled steps, and particularly suitable for each step. It was found that the raw material basic unit and the energy basic unit can be suppressed by combining the processes so that the material is circulated.

The present invention that has solved the above problems is as follows.
[Invention of Claim 1]
The continuous manufacturing method of 9,9-bis (4-hydroxyphenyl) fluorene characterized by including the following processes.
A reaction step in which 9,9-bis (4-hydroxyphenyl) fluorenes are produced by a condensation reaction of 9-fluorenone with a phenol selected from phenol and alkylphenol in the presence of a catalyst;
A dehydration step of removing water from the reaction product obtained from the reaction step to obtain a phenol solution containing 9,9-bis (4-hydroxyphenyl) fluorenes;
A concentration step of separating phenols from the solution containing 9,9-bis (4-hydroxyphenyl) fluorenes obtained in the dehydration step and concentrating 9,9-bis (4-hydroxyphenyl) fluorenes;
A crystallization step of crystallizing 9,9-bis (4-hydroxyphenyl) fluorenes from the concentrate obtained in the concentration step;
A crystallization product separation step of separating crystals from the crystallization product obtained in the crystallization step and washing the separated crystals;
A solvent removal step of removing the solvent from the slurry containing the crystals obtained in the crystallization product separation step to produce a product;
A solvent purification step for reusing the solvent by purifying at least a part of the liquid containing the solvent obtained in the solvent removal step, the mother liquor obtained in the crystallization product separation step and the washing solution;
A phenol purification step in which at least a part of the mother liquor obtained in the crystallization product separation step and the remaining liquid from which the purification solvent is recovered in the solvent purification step is purified and supplied to the reaction step.

[Invention of Claim 2]
The 9,9-bis according to claim 1, wherein the liquid obtained in the solvent purification step is supplied to the concentration step together with a solution containing 9,9-bis (4-hydroxyphenyl) fluorenes obtained in the dehydration step. A continuous process for producing (4-hydroxyphenyl) fluorenes.

[Invention of Claim 3]
The method for continuously producing 9,9-bis (4-hydroxyphenyl) fluorenes according to claim 1, wherein a liquid containing phenols obtained in the concentration step is supplied to the reaction step.

The continuous production method of the present invention increases the production efficiency of 9,9-bis (4-hydroxyphenyl) fluorenes, and can suppress the raw material basic unit at a low cost compared with the conventional batch production method. Product purity and recovery rate equivalent to or better than the batch manufacturing method can be realized.
Incidentally, the crystal grain size obtained by the conventional batch process was about 50 μm, but the crystal grain size obtained by the continuous process was about 60 to 80 μm, about 1.2 to 1.6 times. A colorless transparent crystal having a particle size is obtained, and the crystal particle size is large.
As described above, since the crystal by the continuous process has a large crystal grain size and is not turbid, it is considered that the mother liquor is little involved in the crystal, and the purity of the crystal is high. In addition, since the amount of the mother liquor adhering to the crystal is small, it is possible to perform the crystal cleaning efficiently and continuously, thereby achieving the target product quality.

Next, the present invention will be described with reference to the drawings. First, representative examples will be shown, and then the scope of application of the present invention will be described.
<First Embodiment>
FIG. 1 is a process diagram according to a first embodiment for producing 9,9-bis (4-hydroxyphenyl) fluorenes according to the present invention.
In FIG. 1, 1 is a reaction process, 2 is a dehydration process, 3 is a concentration process, 5 is a crystallization process, 6 is a crystallization product separation process, 7 is a solvent removal process, 8 is a solvent purification process, and 9 is a phenol. Each of the purification steps is shown.

すなわち、１モルのフルオレノンに２モルのオルトクレゾールが反応し、１モルのＢＣＦと１モルの水が発生する。
反応工程１で得られた反応生成物は、目的物である９，９−ビス（４−ヒドロキシフェニル）フルオレン類のほか、未反応のフェノール類及び助触媒を含む。更に、少量の９，９−ビス（４−ヒドロキシフェニル）フルオレン類の異性体、二量体、三量体、ビスフェノール類、トリスフェノール類、クロマン化合物等の副生物を含む。
フェノール類としてオルトクレゾールを選択した場合の副生物の例として、ＢＣＦの２量体（以下ＷＢＣＦと表記する）が挙げられる。ＷＢＣＦは次のような構造で表される。

In the reaction step 1, 9-fluorenone and phenols are reacted in the presence of a catalyst to obtain a reaction product containing 9,9-bis (4-hydroxyphenyl) fluorenes. As the catalyst, a mineral acid such as hydrochloric acid or sulfuric acid or a sulfonic acid type cation exchange resin is used, and it is desirable to use a sulfonic acid type cation exchange resin. Further, if necessary, conventional thiols as cocatalysts such as mercaptocarboxylic acid (thioacetic acid, β-mercaptopropionic acid, α-mercaptopropionic acid, thioglycolic acid, thiooxalic acid, mercaptosuccinic acid, mercaptobenzoic acid, etc. ), Alkyl mercaptan (such as methyl mercaptan, ethyl mercaptan, propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, dodecyl mercaptan), aralkyl mercaptan (such as benzyl mercaptan) or a salt thereof. The usage-amount of phenols is 2-50 mol with respect to 1 mol of fluorenones, Preferably it is 6-30 mol. The reaction temperature is 30 to 150 ° C, preferably 60 to 120 ° C.
This reaction is expressed as follows when, for example, ortho-cresol is selected as the phenol.

That is, 2 mol of orthocresol reacts with 1 mol of fluorenone to generate 1 mol of BCF and 1 mol of water.
The reaction product obtained in the reaction step 1 contains unreacted phenols and a cocatalyst in addition to the target 9,9-bis (4-hydroxyphenyl) fluorenes. Furthermore, a small amount of by-products such as isomers, dimers, trimers, bisphenols, trisphenols, and chroman compounds of 9,9-bis (4-hydroxyphenyl) fluorenes are included.
An example of a by-product when ortho-cresol is selected as the phenol is BCF dimer (hereinafter referred to as WBCF). The WBCF is represented by the following structure.

The reaction product obtained in the reaction step 1 is supplied to the dehydration step 2 through the line 13. The dehydration step 2 includes a function of removing the catalyst and the like as necessary in addition to removing water generated by the reaction. That is, the dehydration process 2 may be a combined process in which acid catalyst neutralization with alkali, separation / extraction of water with an organic solvent, evaporation, distillation, and the like are appropriately combined. In the reaction step 1, it is preferable to use a sulfonic acid type cation exchange resin because neutralization is not required.
In the dehydration step 2, an aqueous phenolic solution containing a large amount of water is discharged out of the system through the line 14, and the dehydrated reaction product is supplied to the concentration step 3 through the line 15. In the concentration step 3, excess unreacted phenols are removed. Generally, an evaporator can be used for the concentration step 3, and the separated phenols are preferably condensed and then returned to the reaction step 1 through the line 16. Returning the vapor in the concentration step 3 to the reaction step 1 through the line 16 contributes to reducing the calorific value in the phenol purification step 9 described later. In the dehydration step 2 and the concentration step 3, the operation temperature needs to be 180 ° C. or lower, preferably 120 ° C. or lower in order to prevent coloring and deterioration of the final product. Therefore, these steps are operated under vacuum. Therefore, in the concentration step 3, the liquid is concentrated to such a concentration that does not cause crystals to precipitate at this operating temperature and maintains a viscosity that does not hinder transportation.

In the crystallization step 5, crystallization can be performed using an appropriate method or apparatus. For example, an indirect cooling crystallization can is used in which a refrigerant is passed through a jacket to indirectly cool the liquid.
The slurry containing the crystals obtained in the crystallization step 5 is supplied to the crystallization product separation step 6 through the line 20. In the crystallization product separation step 6, any separator that can perform solid-liquid separation may be used. As such a separator, a centrifuge or a filter is generally used. However, a filter is used because of the required power, ease of maintenance, and easy handling of the mother liquor and the cleaning liquid separately. It is desirable to use it. The use of a horizontal belt filter as the filter is particularly excellent in cleaning and filtration characteristics. The case where a horizontal belt filter is used will be described. In the crystallization product separation step 6 using a filter, it is obtained in the solvent purification step 8 to be described later as a washing liquid for the solid-liquid separated crystal and supplied through the line 28. It is desirable to use a purified solvent, and since the solvent is lost as a whole system, a new solvent may be supplied. In replenishing the solvent, the purified solvent and a new solvent may be mixed and then supplied to the crystallization product separation step 6. However, the new solvent may be used for cake washing without mixing. The mother liquid obtained by supplying the slurry to the horizontal belt filter and the washing liquid obtained by further washing the filtered crystals remaining after the mother liquid separation with the solvent are supplied to the solvent purification step 8 through the line 21 and the line 22, respectively. Is done. The washing crystals remaining after the washing liquid separation can be supplied to the solvent removal step 7 through the line 23.

  In the solvent removal step 7, the solvent contained in the washing crystal is removed, and a high-purity 9,9-bis (4-hydroxyphenyl) fluorene is obtained as a product through the line 25. In general, a heat dryer can be used to remove the solvent, and product modification due to the heating must be suppressed as much as possible. Therefore, the solvent should be selected with a boiling point as low as possible. For example, use toluene. it can. It is also effective to use a carrier gas such as nitrogen. The operation temperature is 180 ° C. or lower, preferably 120 ° C. or lower. A part of the solvent removed in the solvent removal step 7 in the case of using a heat dryer is purged out of the system through the line 36, and the rest is supplied to the solvent purification step 8 through the line 24.

Since the mother liquid passing through the line 21 and the washing liquid passing through the line 22 contain a solvent, they are collected in the solvent purification step 8. Also in the solvent purification step 8, it is necessary to operate at 180 ° C. or lower, preferably 120 ° C. or lower to prevent product coloring and quality deterioration, and it is preferable to use vacuum distillation. In order to prevent circulating accumulation of low-boiling components, a part is removed from the system through the line 27 (combustion treatment if necessary), and the rest is used as a washing liquid in the crystallization product separation step.
The remaining solution after recovering the solvent mainly contains phenols, but includes unrecovered solvent, 9,9-bis (4-hydroxyphenyl) fluorenes, unreacted fluorenone, reaction byproducts, and the like. It is. This solution is discharged from the solvent purification step 8 through the line 29 and supplied to the concentration step 3.

A part of the mother liquor in the crystallization product separation step 6 is supplied to the phenol purification step 9 through a line 31.
The phenol purification step 9 needs to be operated at 200 ° C. or lower, preferably 140 ° C. or lower in order to prevent product coloring or quality deterioration. However, since phenols (for example, cresol) have a high boiling point, vacuum distillation is used. Is desirable. The mother liquor passing through the line 31 is removed in the phenol purification step 9 by removing light components in the line 32 and heavy components (WBCF, etc.) in the line 33, and is supplied to the reaction step 1 through the line 34 as purified phenols. Is done.

<Second Embodiment>
FIG. 2 is a process diagram according to the second embodiment for producing 9,9-bis (4-hydroxyphenyl) fluorenes. The number which shows each process is the same as FIG.
The second embodiment includes processes and lines common to the first embodiment, but differs in the following points.
The steam in the concentration step 3 is sent to the phenol purification step 9 through the line 16. Further, the mother liquor and the washing solution obtained in the crystallization product separation step 6 are all sent to the solvent purification step 8. The entire amount of the remaining solution after the solvent is recovered in the solvent purification step 8 is sent to the phenol purification step 9 through the line 29, and the light component and the heavy component are separated and removed.

<Disclosure scope of the present invention>
The phenols used in the present invention are phenol or alkylphenol, and for example, 2-C _1-4 alkylphenol (such as ortho-cresol) can be preferably used.
As the reactor, a packed column of ion exchange resin can be used, and the reaction heat generated can be removed by warm water passing through a jacket by using the liquid as a down flow.
As the ion exchange resin used as the catalyst, for example, a strongly acidic sulfonic acid type cation exchange resin can be used. Other ion exchange resins that can be used are those described in the patent literature described in this specification.

Examples and comparative examples are shown below to clarify the effects of the present invention.
[Example 1]
In accordance with the process shown in FIG. 1, 9,9-bis (4-hydroxyphenyl) was prepared using 9-fluorenone as a raw material and ortho-cresol as a phenol and β-mercaptopropionic acid (hereinafter referred to as βMPA) as a co-catalyst. ) The raw material basic unit when continuously producing BCF as fluorenes was calculated using PRO / II (product name) which is a simulator of Invensys. As a simulation parameter, the annual production amount was 2000 t / y. The conversion rate of fluorenone is 99% based on the results of the reaction experiment using the sulfonic acid type ion exchange resin. However, the conversion rate of fluorenone is 95% and the BCF selectivity is 97% in consideration of operational fluctuations. And all the by-products became WBCF. The purity of the raw material ortho-cresol was 99.7 wt% (designated phenol or the like as an impurity), and the purity of the raw material toluene was 99.9 wt% (designated benzene or the like as an impurity). The raw material molar ratio was 20 for orthocresol / fluorenone and 40 for fluorenone / βMPA. The solubility curve of BCF in ortho-cresol was approximated as a logarithmic function based on the actually measured values.
As a result, each raw material unit was 0.77 kg / kg BCF for orthocresol, 0.57 kg / kg BCF for fluorenone, and 0.0022 kg / kg BCF for toluene. The utility unit was 0.4 kg / kg BCF for low pressure steam, 4.5 kg / kg BCF for medium pressure steam, and 0.5 Ton / kg BCF for cooling water. The amount of waste was 0.054 kg / kg BCF for wastewater, 0.002 kg / kg BCF for light waste, 0.02 kg / kg BCF for medium waste, and 0.27 kg / kg BCF for heavy waste. The BCF recovery rate was 90%, the BCF purity was 99.6 wt%, and the TS concentration in the product was 5.2 ppm.

[Comparative Example 1]
Using the same raw material, it was manufactured in a batch system. That is, a 2 L glass reactor equipped with a stirrer, a cooler, and a thermometer was charged with 70 g of fluorenone having a purity of 99%, 250 g of orthocresol, 0.4 g of βMPA, and 15 g of concentrated sulfuric acid and stirred at 55 ° C. for 6 hours. The reaction was carried out. As a result of confirmation by HPLC, the residual amount of fluorenone was 0.1% or less. To the obtained reaction mixture, 300 g of toluene and 80 g of water were added, and neutralized by adding a 32% aqueous sodium hydroxide solution until the pH was about 7, and then the aqueous layer was removed. The organic layer was heated to 80 ° C. and then washed 3 times with 80 g of water. After recovering 300 g of toluene from the organic layer by distillation under reduced pressure, 400 ml of a toluene-acetone mixed solvent (mixing ratio 1: 4) was added to the organic layer, and the mixture was stirred at 70 ° C. for 1 hour. Crystallization gave 140 g of the desired product, BCF. In this case, the BCF recovery rate was 89%, the BCF purity was 99.7 wt%, and the TS concentration in the product was 6.2 ppm. The crystal grain size was about 50 μm. The raw material basic unit is 0.924 kg / kg BCF for orthocresol, 0.529 kg / kg BCF for fluorenone, 0.003 kg / kg BCF for βMPA, 0.091 kg / kg BCF for 98% sulfuric acid, 1.063 kg / kg BCF for acetone, Toluene was 0.15 kg / kg BCF. The utility unit was 6.062 kg / kg BCF for steam and the amount of waste was 2.533 kg / kg BCF for waste water.

[Example 2]
According to the process shown in FIG. 2, the same calculation as in Example 1 was performed using a simulator. As a result, orthocresol was 1.30 kg / kg BCF, fluorenone was 0.96 kg / kg BCF, and toluene was 0.0025 kg / kg BCF. The utility unit was 0.4 kg / kg BCF for low pressure steam, 8.1 kg / kg BCF for medium pressure steam, and 0.8 Ton / kg BCF for cooling water. The amount of waste was 0.093 kg / kg BCF for wastewater, 0.002 kg / kg BCF for light waste, 0.02 kg / kg BCF for medium waste, and 1.15 kg / kg BCF for heavy waste. The BCF recovery rate was 54%, the BCF purity was 99.1 wt%, and the TS concentration in the product was 5.0 ppm.

Example 3
According to the process shown in FIG. 1, BCF was produced using 9-fluorenone and ortho-cresol as raw materials and βMPA as a cocatalyst, and the crystal grain size was measured. For the analysis, a Shimadzu laser diffraction flow rate distribution measuring device (SALD-2000J) was used. Water and a surfactant were used as the dispersion material. The median diameter was 74 μm, and the average particle diameter was 66 μm.

It is process drawing of 1st Embodiment for manufacturing bisphenol fluorene by this invention. It is process drawing of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reaction process, 2 ... Dehydration process, 3 ... Concentration process, 5 ... Crystallization process, 6 ... Crystallization product separation process, 7 ... Solvent removal process, 8 ... Solvent purification process, 9 ... Phenol purification process.

Claims (3)

The continuous manufacturing method of 9,9-bis (4-hydroxyphenyl) fluorene characterized by including the following processes.
A reaction step in which 9,9-bis (4-hydroxyphenyl) fluorenes are produced by a condensation reaction of 9-fluorenone with a phenol selected from phenol and alkylphenol in the presence of a catalyst. ,
A dehydration step of removing water from the reaction product obtained from the reaction step to obtain a phenol solution containing 9,9-bis (4-hydroxyphenyl) fluorenes;
A concentration step of separating phenols from the solution containing 9,9-bis (4-hydroxyphenyl) fluorenes obtained in the dehydration step and concentrating 9,9-bis (4-hydroxyphenyl) fluorenes;
A crystallization step of crystallizing 9,9-bis (4-hydroxyphenyl) fluorenes from the concentrate obtained in the concentration step;
A crystallization product separation step of separating crystals from the crystallization product obtained in the crystallization step and washing the separated crystals;
A solvent removal step of removing the solvent from the slurry containing the crystals obtained in the crystallization product separation step to produce a product;
A solvent purification step for reusing the solvent by purifying at least a part of the liquid containing the solvent obtained in the solvent removal step, the mother liquor obtained in the crystallization product separation step and the washing solution;
A phenol purification step in which at least a part of the mother liquor obtained in the crystallization product separation step and the remaining liquid from which the purification solvent is recovered in the solvent purification step is purified and supplied to the reaction step.   The 9,9-bis according to claim 1, wherein the liquid obtained in the solvent purification step is supplied to the concentration step together with a solution containing 9,9-bis (4-hydroxyphenyl) fluorenes obtained in the dehydration step. A continuous process for producing (4-hydroxyphenyl) fluorenes.   The method for continuously producing 9,9-bis (4-hydroxyphenyl) fluorenes according to claim 1, wherein a liquid containing phenols obtained in the concentration step is supplied to the reaction step.

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