KR101011878B1 - Manufacturing method of bisphenol A - Google Patents

Abstract

A method for producing bisphenol A in which a slurry formed by crystallization of an adduct of bisphenol A and phenol from a reaction mixture of phenol and acetone is separated from a solid liquid, and then phenol is removed from a solid component. A phenol slurry solution of bisphenol A contained in a crystalline state was introduced onto a horizontal circulation belt filter in an inert gas stream heated under reduced pressure to form an adduct layer of crystalline bisphenol A and phenol on the filter, through the filter. After separating the mother liquid contained in the said adduct layer to make the content rate of an adduct layer into 30 weight% or less, the adduct layer is isolate | separated by the self weight from a filter phase. According to the production method of the present invention, crystals of bisphenol A and phenol adducts can be stably and continuously separated from the mother liquor, and high purity crystals can be efficiently recovered.

Description

Production method of bisphenol A {PROCESS FOR PRODUCING BISPHENOL A}

The present invention relates to a method for producing bisphenol A [2,2-bis (4-hydroxyphenyl) propane], and more particularly, to a method for separating an adduct of bisphenol A and phenol A in the above production method. .

Bisphenol A is known to be an important compound as a raw material for engineering plastics such as polycarbonate resins, polyallylate resins, or epoxy resins, and in recent years, the demand tends to increase.

This bisphenol A is produced by condensation of excess phenol and acetone in the presence of an acidic catalyst and optionally a sulfur compound to be used.

As a method for extracting bisphenol A from the reaction mixture, a method of separating bisphenol A directly into the crude crystalline phase and a liquid mixture after removing acetone and water from the reaction mixture are concentrated and cooled to precipitate an adduct of bisphenol A and phenol. Separation methods are known.

The method of separating the crude crystalline phase directly from the former reaction mixture has a drawback in that bisphenol A has to be washed several times with microcrystalline, resulting in high loss.

For this reason, in the present state, the method of precipitating and separating the adduct of the latter bisphenol A and phenol is mainly used. In this case, crystallization of the bisphenol A and the phenol adduct is carried out, and crystal separation from the mother liquor is carried out by a known solid liquid separation method using filtration or a centrifugal separator (for example, JP-A-1982-77637, See Japanese Patent Laid-Open No. 1993-331088, Japanese Patent Laid-Open No. 1988-275539, and Japanese Patent Laid-Open No. 1994-306002.

In the solid liquid separation method, a suction belt filter, a tray filter, a drum filter and the like can be used as the separation by the filtration method (see, for example, Japanese Patent Laid-Open No. 1995-25798, page 3). In order to prevent the loss due to the mesh size of the filter medium or to increase the purity, it is necessary to make the surface area small (see, for example, Japanese Patent Laid-Open No. 1993-331088).

In the separation by such a filtration method, it is difficult to sufficiently remove the mother liquid and the like contained between the crystals due to the high content of the liquid, and there is also a risk of containing the mother liquid in large crystals. It becomes difficult to get out or the blockage of the filter medium occurs, which causes a significant decrease in the treatment efficiency.

The method of using a centrifuge is preferable in that the content of the liquid between the crystals is lowered to obtain a drier adduct. However, since the centrifugal load is applied, the crystals are crushed and the substitution efficiency of the mother liquor and the washing liquid is higher than that of the filtration method. Worse Therefore, when processing a large amount of products, it is generally necessary to repeat the cleaning using a plurality of devices in order to increase the purity, which leads to an increase in the number of devices or an extension of the operating time, which is not economically desirable.

In addition, in order to obtain bisphenol A having excellent color and high purity and high quality, a method of crystallizing and separating the adducts of bisphenol A and phenol, then melting in a low oxygen atmosphere and dephenolizing is known (for example, Japanese Patent Laid-Open No. 1993-32577, page 1, Japanese Patent Laid-Open No. 1993-39238, Japanese Patent Laid-Open No. 1994-25044, and Japanese Patent Laid-Open No. 1994-25045.

Summary of the Invention

The present invention is directed to recovering bisphenol A and phenol from the reaction mother liquor with high purity when taking out bisphenol A from the reaction mixture in the above-described situation.

As a result of earnestly examining the manufacturing method of bisphenol A which has the said subject, in the method of depositing and separating the adduct of bisphenol A and a phenol, the inventors used the suction type horizontal endless belt filter for solid-liquid separation. By introducing a heated inert gas stream and operating the belt filter under specific conditions, it was found that the adducts of bisphenol A and phenol can be recovered continuously, stably, efficiently and with high purity.

That is, this invention provides the manufacturing method of the following bisphenol A.

1. Bisphenol which precipitates an adduct of bisphenol A and phenol from a phenol solution of bisphenol A obtained by reacting phenol and acetone in the presence of an acid catalyst and removes phenol from the solid component after solid liquid separation of the resulting slurry. In the manufacturing method of A,

(1) A phenol slurry solution of bisphenol A containing an adduct of bisphenol A and phenol in a crystalline state was introduced onto a horizontal circulating belt filter in an inert gas stream heated under reduced pressure to form bisphenol A and phenol in a crystalline state on the filter. To form an adduct layer of

(2) The content of the additive layer is 30% by weight or less by separating the mother liquid contained in the additive layer through the filter,

(3) A method for producing bisphenol A, wherein the adduct layer is separated from the filter phase by its own weight.

2. The method for producing bisphenol A of 1 described above, wherein the heated inert gas is 80 ° C. or less of nitrogen gas, and the oxygen concentration in the nitrogen gas is 5000 ppm or less.

3. The method for producing bisphenol A according to the above 1, wherein the content of the adduct layer is 30% by weight or less by adjusting the pressure reduction degree and the belt speed of the horizontal circulation belt filter.

4. The process for producing bisphenol A of 1 above, wherein the adduct layer is cleaned with a cleaning liquid before the adduct layer is separated by its own weight from the horizontal circulation belt filter.

In the manufacturing method of bisphenol A of this invention, (A) reaction process of a phenol and acetone, (B) low boiling point material removal process in by-product water and unreacted raw material, (C) concentration process of bisphenol A, (D) crystal precipitation Bisphenol through solid liquid separation step, (D ') phenol adduct dissolution, crystal precipitation and solid liquid separation step, (E) heating melting step, (F) dephenol step of bisphenol A, and (G) granulation step A is prepared.

In the present invention, the belt filter is operated under specific conditions by using a horizontal circulation belt filter in the solid liquid separation in the above-mentioned steps (D) and (D ').

As mentioned above, in order to obtain bisphenol A which is excellent in color, high purity, and high quality, a method of crystallizing and separating an adduct of bisphenol A and a phenol, and then melting and dephenolizing in a low oxygen atmosphere is known.

However, even if the adduct of bisphenol A and phenol is melt | dissolved in a low oxygen atmosphere after crystal precipitation separation, and dephenol is removed, the influence of oxygen contained in the adduct of bisphenol A and phenol cannot be excluded.

In the present invention, in the solid liquid separation of the steps (D) and (D '), a low-oxygen atmosphere heated under reduced pressure in a slurry solution containing bisphenol A and an phenol adduct in a crystalline state using a horizontal circulation belt filter. By introducing an inert gas, a higher quality bisphenol is obtained because oxygen contained in the adduct is effectively removed.

Next, each process in the manufacturing method of bisphenol A is demonstrated.

(A) reaction process

In this reaction process, excess phenol and acetone are condensed in the presence of an acidic catalyst to produce bisphenol A. An acid type ion exchange resin can be used as said acidic catalyst. Although it does not restrict | limit especially as this acid type ion exchange resin, Although what is conventionally used as a catalyst of bisphenol A can be used, A sulfonic acid type cation exchange resin is suitable especially from a catalyst activity viewpoint.

The sulfonic acid type cation exchange resin is preferably a strong acid cation exchange resin having a sulfonic acid group, and is not particularly limited. Examples thereof include sulfonated styrene-divinylbenzene copolymers, sulfonated crosslinked styrene polymers, phenolformaldehyde-sulfonic acid resins, Benzeneformaldehyde-sulfonic acid resin and the like. These may be used independently, respectively and may be used in combination of 2 or more type.

In this step, mercaptans are usually used together as a cocatalyst like the acid type ion exchange resin. The mercaptans refer to a compound having an SH group in a free form in the molecule, and examples thereof include alkyl mercaptans and alkyl mercaptans having at least one substituent such as a carboxyl group, an amino group, and a hydroxyl group, such as mercapto carboxylic acid and amino. Alkane thiol, mercapto alcohol, etc. can be used. Examples of such mercaptans include alkyl mercaptans such as methyl mercaptan, ethyl mercaptan, n-butyl mercaptan and n-octyl mercaptan, thiocarboxylic acids such as thioglycolic acid and β-mercaptopropionic acid, and 2-aminoethanes. Although aminocapane thiols, such as a thiol, mercapto alcohols, such as mercaptoethanol, etc. are mentioned, Among these, alkyl mercaptan is especially preferable from a viewpoint of an effect as a promoter. In addition, these mercaptans may be used independently and may be used in combination of 2 or more type.

These mercaptans can also be immobilized on the acid type ion exchange resin to function as a cocatalyst.

The amount of the mercaptans used is generally selected in the range of 0.1 to 20 mol%, preferably 1 to 10 mol% with respect to acetone as a raw material.

The use ratio of phenol and acetone is not particularly limited, but the amount of unreacted acetone is preferably as small as possible from the viewpoint of ease of purification and economical efficiency of the resulting bisphenol A, and therefore, phenol is stoichiometric. It is advantageous to use in excess of the amount. Usually, 3 to 30 moles, preferably 5 to 15 moles of phenol are used per mole of acetone. In addition, in the preparation of this bisphenol A, a reaction solvent is generally not required except when the reaction liquid is too high in viscosity, or reacted at a low temperature where solidification is difficult to operate.

The condensation reaction of phenol and acetone is preferably either batch or continuous, but a phenol, acetone, and mercaptans (if the mercaptans are not immobilized on the acid type ion exchange resin) in a reaction column filled with an acidic ion exchange resin are continuously used. It is advantageous to use a fixed bed-type continuous reaction method which is fed and reacted. At this time, one reaction tower may be used, or two or more reaction towers may be arranged in series. However, industrially, two or more reaction towers filled with an acidic ion exchange resin are connected in series to provide a fixed bed multistage continuous operation. It is particularly advantageous to employ the reaction system.

The reaction conditions in this fixed bed type continuous reaction system are demonstrated.

First, the acetone / phenol molar ratio is usually selected in the range of 1/30 to 1/3, preferably 1/15 to 1/5. When this molar ratio is smaller than 1/30, there exists a possibility that reaction rate may become slow too much, and when larger than 1/3, generation | occurrence | production of an impurity will increase and the selectivity of bisphenol A will fall. On the other hand, when the mercaptans are not immobilized on the acid type ion exchange resin, the mercaptans / acetone molar ratio is usually selected in the range of 0.1 / 100 to 20/100, preferably 1/100 to 10/100. When this molar ratio is smaller than 0.1 / 100, there is a possibility that the effect of improving the reaction rate and the selectivity of bisphenol A may not be sufficiently exhibited. If the molar ratio is larger than 20/100, the improvement of the effect is not much recognized compared to the amount.

In addition, the reaction temperature is usually selected in the range of 40 to 150 ° C, preferably 60 to 110 ° C. If the temperature is less than 40 ° C, the viscosity of the reaction solution is very high in that the reaction rate is slow, and there is a risk of solidification in some cases, and if it exceeds 150 ° C, the reaction control becomes difficult, and bisphenol A (p, p ' Since the selectivity of -isomer decreases, the acid type ion exchange resin of a catalyst may decompose | disassemble or deteriorate. In addition, the LHSV (liquid space velocity per hour) of the raw material mixture is usually selected in the range of 0.2 to 30 hour ^-1 , preferably 0.5 to 10 ^{-1 -1} .

(B) Low boiling point material removal process

In the low boiling point material removal step, the reaction mixture containing bisphenol A obtained in the reaction step of the step (A) is substantially free of acid type ion exchange resin, that is, in the case of a batch reaction method, the catalyst is filtered by filtration or the like. In the case of a fixed bed type continuous reaction system, the low boiling point substance removal process is performed as it is.

In this step, usually, first, by vacuum distillation using a distillation column, low-boiling substances such as unreacted acetone, by-product water and alkyl mercaptan are removed.

This vacuum distillation is generally performed at the pressure of 6.5-80 kPa and the temperature of 70-180 degreeC. At this time, the unreacted phenol is azeotrope and a part of it is removed from the tower top of the distillation column together with the low boiling point material. In this distillation, in order to prevent the thermal decomposition of bisphenol A, it is preferable that the temperature of the heating source to be used shall be 190 degrees C or less. In addition, generally, SUS304, SUS316, and SUS316L are used as a material of an apparatus.

(C) concentration process

Bisphenol A, phenol, etc. are contained in the bottom liquid from which the low boiling point component was removed from the reaction mixture, and phenol is evaporated and removed by vacuum distillation, and bisphenol A is concentrated. Although it does not restrict | limit especially about this concentration condition, Usually, it implements on the conditions of the temperature of about 100-170 degreeC, and a pressure of 5-70 kPa. If this temperature is lower than 100 DEG C, high vacuum is required, and if higher than 170 DEG C, it is not preferable because excess heat needs to be removed in the next crystal precipitation step. The concentration of bisphenol A in the concentrate is preferably in the range of 20 to 50% by weight, more preferably 20 to 40% by weight. If this concentration is less than 20% by weight, the recovery of bisphenol A is low, and if it is more than 50% by weight, the slurry transfer after crystal precipitation may be difficult.

(D) Crystal Precipitation and Solid Liquid Separation Process

In the crystal precipitation and solid liquid separation step, crystallization and separation of 1: 1 adducts of bisphenol A and phenol (hereinafter sometimes referred to as phenol adducts) are performed from the concentrate obtained in the concentration step of step (C). It is a process.

In this step, the concentrate is first cooled to about 40 to 70 ° C, and the phenol adduct is crystallized to obtain a slurry. The cooling at this time may be performed using an external heat exchanger, or may be performed by a vacuum cooling crystal precipitation method in which water is added to the concentrate and cooled using latent heat of evaporation of water under reduced pressure. In this vacuum cooling crystal precipitation method, about 3 to 20 weight% of water is added to the said concentrated liquid, and a crystal precipitation process is given on the conditions of normal temperature 40-70 degreeC and pressure 4-16 kPa. If the added amount of water is less than 3% by weight, the heat removal capacity is not sufficient. If the amount of water is more than 20% by weight, the dissolution loss of bisphenol A becomes large, which is not preferable. In such crystal precipitation operation, when the crystal precipitation temperature is less than 40 ° C., there is a risk of increasing the viscosity and solidification of the crystal precipitation liquid, and when it exceeds 70 ° C., the dissolution loss of bisphenol A becomes large, which is not preferable.

In the present invention, next, the slurry containing the phenol adducts which have been crystallized is introduced into a horizontal circulation belt filter (simply referred to as a belt filter) in an inert gas stream heated under reduced pressure to crystallize on the filter. The adduct layer of bisphenol A and phenol of a state is formed.

The horizontal circulation belt filter supports a filter cloth with a porous circulation conveyor, runs on a vacuum box, feeds a slurry from one end, filters it, and washes the cake. The solid content is separated by its own weight. As the filter cloth of the horizontal circulation belt filter, a porous sheet made of polypropylene, polyester, nylon, polytetrafluoroethylene, cotton cloth, abrasion, or the like is used.

The use of the horizontal circulation belt filter is advantageous because the filtration is continuously performed and the filtration can be performed without applying great gravity.

At this time, it is preferable to make the average particle diameter of the bisphenol A and a phenol adduct of a crystalline state into 0.05-1 mm. If the average particle diameter is less than 0.05 mm, separation of the phenol adduct crystal from the mother liquor becomes difficult, and clogging of the filter medium occurs, leading to a decrease in treatment efficiency. If it is larger than 1 mm, there is a risk of containing the mother liquor in the crystal.

As an inert gas, nitrogen gas is normally used, and the oxygen concentration in nitrogen gas is 5000 ppm or less, Preferably it is 3000 ppm or less.

By separating the mother liquid contained in the adduct layer through a belt filter, the content of the adduct layer is 30% by weight or less, preferably 2.5% or less. In order to spontaneously fall to its own weight in the form of a solid when separated from the belt filter, the content of the additive layer needs to be 30% by weight or less, and the content of the additive deposited on the filter is lower. The load becomes smaller.

By filtering under reduced pressure, the mother liquor can be separated from the phenol adduct crystal, and the content of the adduct layer can be lowered. However, if the pressure is too strong, micronization due to crushing of the crystals may occur in some cases, which may cause clogging of the filter cloth and may cause problems, which is not preferable. Preferred degrees of decompression are from 60 to 95 kPa.

Moreover, since the content rate of the said additive layer is influenced by the advancing speed (belt speed) of a belt filter, the content rate of an additive layer can be 30 weight% or less by adjusting the pressure reduction degree and belt speed of a horizontal circulation belt filter.

The thickness of the adduct layer is not limited if the content of the deposited phenol adduct of 30% by weight or less is produced on the belt filter. However, if the thickness is too thick, the weight per unit area increases, which is unfavorable. .

In addition, before separating the bisphenol A and the phenol adduct layer from the horizontal circulation belt filter by its own weight, a washing solution is added to the adduct layer in order to remove as much as possible impurities and trace amounts of the acid catalyst contained in the adduct layer. It is preferable to spray and wash. As the washing liquid, phenol, water, a water-phenol mixed liquid, or a liquid in which bisphenol A is dissolved therein is used.

The thickness of the adduct layer and the time to be sucked under reduced pressure may be controlled by a belt speed. The slower the belt speed, the thicker the deposited phenol adduct, but can be exposed under reduced pressure for a longer time.

In order to hold the slurry containing the phenol adduct which crystallized out at the time of filtration, it is necessary to be 80 degrees C or less, and since the coagulation | solidification of a mother liquid and a washing | cleaning liquid may occur, the temperature of the atmosphere containing a filter is 30-80. It is important to maintain the temperature at 35 ° C, preferably 35 to 50 ° C.

The separated mother liquor may be recycled directly or in part to a reactor, or may be recycled to crystallization raw material by isomerizing part or all of it.

It is effective to repeat this (D) crystal precipitation and solid liquid separation process in order to obtain a high purity product. That is, after crystal precipitation, the dissolution of the following (D ′) phenol adduct and the crystal precipitation / solid liquid separation process are repeated one or more times with respect to the phenol adduct obtained by solid liquid separation, followed by (E) heating melting step. Move to.

(D ') dissolution of phenol adduct, crystal precipitation and solid liquid separation process

The phenol adduct which precipitated and isolate | separated the crystal | crystallization in the process (D) is melt | dissolved using a phenol containing solution. The phenol-containing solution used in this step is not particularly limited, for example, the recovered phenol obtained in the concentration step of step (C), the crystallization and solid liquid separation step in step (D), and a phenol adduct washing liquid, As a thing produced in the process after this (D ') process, the mother liquid in the solid-liquid separation of the phenol adduct of the crystal precipitation, the cleaning liquid of the said phenol adduct, etc. are mentioned.

In this step, the phenol-containing solution is added to the phenol adduct crystal obtained in the step (D), heated to about 80 to 110 ° C, and the solvent is dissolved by heating the phenol adduct. A bisphenol A containing solution is prepared. The bisphenol A-containing solution thus prepared has a low viscosity and relatively easy handling even at a relatively low temperature, and is suitable for filtration with a filter.

Thus, from the bisphenol A containing solution, the phenol adduct is crystal-crystallized and solid-liquid separation, Furthermore, the said phenol adduct is melt | dissolved using a phenol containing solution, and operation (D) of crystal precipitation and solid-liquid separation is performed. Repeat at least once.

(E) heating melting process

The heat melting step is a step of heating and melting a phenol adduct which has been precipitated and separated in the step (D) or (D ′). In this step, when the phenol adduct is heated and melted at about 100 to 160 ° C, a liquid mixture is obtained.

(F) Dephenol Process

The dephenol step is a step of recovering bisphenol A in a molten state by evaporating and removing phenol from the phenol adduct heated and melted in step (E) by vacuum distillation. The vacuum distillation is generally carried out under conditions of a pressure of 1.3 to 13.3 kPa and a temperature of 150 to 190 ° C. Residual phenol can be further removed by steam stripping.

(G) granulation process

In the granulation step, bisphenol A in the dissolved state obtained in the above (G) step is dropped into a droplet by a granulation device such as a spray dryer, and cooled and solidified to obtain a product. The droplets are formed by spraying, spraying or the like and are cooled by nitrogen, air or the like.

A feature of the method for producing bisphenol A of the present invention is to introduce a heated inert gas stream using a suction belt filter in the solid liquid separation of the steps (D) and (D ') to introduce a mother liquor through the filter. After separation, the phenol adducts are separated by their own weight, whereby the adducts of bisphenol A and phenol can be recovered stably, continuously and efficiently with high purity.

Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these examples.

Example 1

The reactor charged with the cation exchange resin was continuously fed while maintaining the temperature at 75 ° C. at a rate of 49.7 t / hr phenol, 3.7 t / hr acetone and 0.25 t / hr ethyl mercaptan. The reaction mixture was sent to a low boiling point material removal process to remove unreacted acetone, the main component of low boiling point material. Next, a part of bisphenol A and unreacted phenol was evaporated and removed in the concentration step, and the concentration was adjusted so that the concentration of bisphenol A was 30% by weight. Water was added to this bisphenol A concentrate, and cooling crystal | crystallization precipitated on 45 degreeC conditions under stirring, and the adduct (addition product) of bisphenol A and phenol was crystal-crystallized. A slurry solution of the adduct maintained at a liquid temperature of 45 ° C. was collected in a casing under a nitrogen gas stream of 60 ° C. containing 1200 ppm of oxygen, and a filter cloth made of propylene (Daiwa Boseki Kampa) moving at a running speed of 2 m / min. The adjuvant crystals of bisphenol A and phenol and the mother liquor were separated over 15 seconds under a reduced pressure of 55 kPa under Niwa Boseki Co., Ltd., aeration 70CCS). The adduct crystals separated from the mother liquor formed a layer 82 mm thick. After the adhered mother liquor was liquefied, washing was performed twice with phenol (wash ratio 0.75) for about 10 seconds, followed by dehydration and drying, followed by dropping to its own weight from the return stage of the horizontal circulation belt filter to obtain a wet adduct. It was 24.5 weight% when the content rate of the said wet adduct was measured. The substitution rate of the mother liquor was 98.7%, as determined from the isomer content by liquid chromatography. The obtained adduct was melted, and Hazen color number was measured at 175 ° C. for 20 minutes. As a result, it was APHA5.

In addition, CCS of air permeability is abbreviation of cc / cm <^2> / sec, and shows the amount of air (cc) which passes a filter cloth per unit area (1 cm) in unit time (1 second).

Preparation Example 1

After continuously producing the bisphenol A concentrate by the above-mentioned steps (A) to (C), an adduct (adduct) of bisphenol A and phenol was obtained.

First, in the step (A), the reactor was continuously supplied with 600 g of cation exchange resin, while the temperature was maintained at 75 ° C. at a rate of 4600 g / h phenol, 280 g / h acetone, and 16 g / h ethyl mercaptan. did. The reaction mixture was sent to a low boiling point material removal process (B) to remove low boiling point material in which unreacted acetone was the main component, thereby obtaining a reaction product having 4,640 g / hr of bisphenol A and unreacted phenol as the main component. Next, in the step (C), part of the phenol was removed from the reaction product under conditions of 165 ° C and 53.3 kPa (400 Torr), and the concentration was adjusted so that the concentration of bisphenol A was 30% by weight. Water was added to this bisphenol A concentrate, and cooling crystal | crystallization precipitated on 45 degreeC conditions under stirring, and the adduct (addition product) of bisphenol A and phenol was crystal-crystallized.

Reference Example 1

A slurry of bisphenol A and phenol adduct obtained in Production Example 1 was made of propylene under a reduced pressure of 55 kPa at a liquid temperature of 45 ° C. under a nitrogen atmosphere of 45 ° C. containing 1200 ppm of oxygen (Daiwa Boseki Co., Ltd.). , ACC 70CCS) was poured into Nutsche, and crystals of the adducts of bisphenol A and phenol were separated from the mother liquor. Washing phenol (amount of about 0.75 times the wet solid content) was poured into the adduct crystal separated from the mother liquor, and then suction was continued for about 15 seconds. The adduct was in the form of a solid having a thickness of 64 mm, a sheath was placed in the solid, and a light impact was taken out to extract the solid content of the adduct. The content rate of the obtained adduct was measured and found to be 25.2%. In addition, the substitution rate of the mother liquid was 99.1% as a result of the liquid chromatography finding the isomer content. The obtained adduct was melted, and the Hazen color number was measured at 175 ° C for 20 minutes. As a result, it was APHA5.

It can be seen that Example 1 can be reproduced using the nutche as described above.

Reference Example 2

Filtration was attempted at the reduced pressure in Reference Example 1 at atmospheric pressure, but the mother liquor was separated into two layers with the mother liquor remaining on the filter, so that the adduct and the mother liquor could not be separated.

Reference Example 3

Instead of the nucleus used in Reference Example 1, the same procedure as in Example 1 was carried out except that a nucleus having an inner diameter of 1/2 was used. The thickness of the obtained solid content was 15 mm, the content rate of solid content was 38 weight%, and the substitution rate was 95.5%.

Reference Example 4

After the slurry was treated under reduced pressure using the same apparatus as in Reference Example 1, the solid was compressed to squeeze the mother liquor contained therein. Some samples were taken out and the content rate was examined, and it was 15 weight%. Thereafter, after pouring the washing phenol, suction was continued for about 15 seconds. The thickness of solid content was 55 mm, the content rate of solid content was 21 weight%, and the substitution rate was 84%.

From this, it can be seen that if the solid content becomes too hard, the washing liquid does not penetrate into the adduct crystal for a short time, and the adherent mother liquid is not sufficiently removed.

According to the method for producing bisphenol A of the present invention, in the solid liquid separation in the steps (D) and (D '), crystals of the adducts of bisphenol A and phenol can be stably and continuously separated from the mother liquor, and crystals of high purity Can be efficiently recovered.

Therefore, this invention contributes to the stable operation of the manufacturing apparatus of bisphenol A, and can manufacture bisphenol A of high purity efficiently.

Claims (4)

Of bisphenol A which crystallizes an adduct of bisphenol A and phenol from a phenol solution of bisphenol A obtained by reacting phenol and acetone in the presence of an acid catalyst and removes phenol from the solid component after solid liquid separation of the resulting slurry. In the manufacturing method, (1) A phenol slurry solution of bisphenol A containing bisphenol A and an adduct of phenol in a crystalline state is introduced on a horizontal endless belt filter in an inert gas stream heated under reduced pressure to thereby form a crystalline state on the filter. To form an adduct layer of bisphenol A and phenol, (2) The content of the additive layer is 30% by weight or less by separating the mother liquid contained in the additive layer through the filter, (3) A method for producing bisphenol A, wherein the adduct layer is separated from the filter phase by its own weight. The method of claim 1, The heated inert gas is 80 degrees C or less nitrogen gas, and the oxygen concentration in the said nitrogen gas is 5000 ppm or less, The manufacturing method of bisphenol A characterized by the above-mentioned. The method of claim 1, The content rate of an addition layer is 30 weight% or less by adjusting the pressure reduction degree and belt speed of a horizontal circulation belt filter, The manufacturing method of bisphenol A characterized by the above-mentioned. The method of claim 1, A method for producing bisphenol A, wherein the adduct layer is washed with a cleaning liquid before the adduct layer is separated from the horizontal circulation belt filter by its own weight.