Method for producing bisphenol A and method for producing polycarbonate resin

Abstract

Provided is a method which is for producing bisphenol A and by which a colored component derived from a polycarbonate resin can be efficiently removed, and bisphenol A having a favorable color tone can be produced.　A method for producing bisphenol A according to the present invention involves: obtaining a solution H1 or a solution H2 from a crude solution A, which is obtained by decomposing a polycarbonate resin (PC) and distilling a solvent in step A, and from part of a mother liquid D, which is obtained in step D among steps B to E for producing bisphenol A (BPA) through the dehydration condensation of acetone and phenol; and supplying the obtained solution H1 or solution H2 to step B or step C. The solution H1 is a solution that contains BPA obtained by decomposing the BPA contained in the crude solution A and the mother liquid D into phenol and isopropenylphenol and then re-bonding the phenol and the isopropenylphenol, and the solution H2 is a solution that contains phenol obtained by decomposing BPA contained in the crude solution A and the mother liquid D into phenol and acetone.

Description

Technical Field

[0001] The present invention relates to a method for producing bisphenol A. Furthermore, the present invention relates to a method for producing a polycarbonate resin using bisphenol A obtained by the method for producing bisphenol A.

Background Art

[0002] Plastics are lightweight, durable, and inexpensive, and are therefore mass-produced not only in Japan but also around the world. Since many of these plastics are used as "disposable", some are not properly processed and flow into the environment. Specifically, plastic waste flows from rivers into the sea, where it deteriorates due to waves and ultraviolet rays and becomes less than 5 mm in size. Such small plastic waste is called microplastic. This microplastic is accidentally ingested by animals and fish. Thus, plastic waste has a great impact on the ecosystem and has been regarded as a problem around the world in recent years as the marine plastic problem. Polycarbonate resin, which is used in a wide range of fields due to its transparency, mechanical properties, flame retardancy, dimensional stability, and electrical properties, is no exception.

[0003] As one of the methods for recycling polycarbonate resin, chemical recycling is known in which polycarbonate resin is chemically decomposed back to bisphenol and reused. Chemical recycling of polycarbonate resin is important as one of the solutions to the marine plastic problem. Polycarbonate resin can be decomposed by various methods such as hydrolysis and alcoholysis, and the produced bisphenol A can be recovered by crystallization or the like.

[0004] It is also known that bisphenol A obtained by decomposing polycarbonate resin is incorporated into the following general production process of bisphenol A and purified together to obtain high-purity bisphenol A. [General Production Process of Bisphenol A] Step 1: Reacting acetone and phenol in the presence of an acidic catalyst to obtain a reaction solution containing bisphenol A Step 2: Separating the reaction solution obtained in Step 1 by distillation to obtain a concentrated solution Step 3: Crystallizing and recovering the concentrated solution obtained in Step 2 to obtain adduct crystals and mother liquor Step 4: Manufacturing bisphenol A from the adduct crystals

[0005] For example, a method is known in which a crude solution containing low-purity bisphenol A recovered from decomposition products obtained by thermally decomposing or chemically decomposing waste plastics is supplied to the concentrated solution or mother liquor obtained in the above general manufacturing process of bisphenol A (Patent Document 1).

[0006] Also, a method is known in which waste polycarbonate is decomposed to isopropenylphenol or the like and supplied to Step 1 (reaction step) of the above general manufacturing process of bisphenol A (Patent Document 2).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Bisphenol A is also used as a raw material for optical materials such as optical polycarbonate resins. Since optical materials are required to have excellent color tone (transparency), bisphenol A as the raw material is also required to have an excellent color tone.

[0009] However, in the method of crystallizing after hydrolyzing or alcoholyzing a polycarbonate resin, even if it is bisphenol A with high purity, if a small amount of coloring components derived from the polycarbonate resin remains, it may be insufficient as a raw material for optical materials that require excellent color tone (transparency). In addition, in the method of independently performing the decomposition of the polycarbonate resin to the purification of bisphenol A, in order to increase the purity of bisphenol A, the number of steps increases, the equipment becomes complicated, and the size becomes large, which is not preferable from the viewpoints of cost and energy.

[0010] Also, as described above, it is also possible to supply bisphenol A obtained by decomposing a polycarbonate resin to a general manufacturing process of bisphenol A and purify them together to obtain high-purity bisphenol A. For example, according to Example 1 of Patent Document 1, first, a compact disk made of a polycarbonate resin is alcoholyzed with cyclohexanol, and a heavy fraction that does not distill out obtained after distilling off under reduced pressure is obtained. Then, the non-distilling heavy fraction is mixed with the mother liquor obtained by crystallization in a normal manufacturing process of bisphenol A, and further mixed with a reaction product containing bisphenol A obtained by a condensation reaction in a normal manufacturing process of bisphenol A, and concentrated. After crystallizing the obtained concentrated solution, solid-liquid separation is performed to obtain bisphenol A-phenol adduct crystals, and by distilling off phenol from the obtained adduct crystals, it is described that high-purity bisphenol A can be obtained. However, although the obtained bisphenol A has high purity, there is a problem that its color tone deteriorates due to the influence of coloring components contained in the non-distilling heavy fraction.

[0011] In addition, it is also possible to decompose the polycarbonate resin by alkaline decomposition until isopropenylphenol is obtained. For example, according to Example 1 of Patent Document 2, by a known method, it is decomposed until isopropenylphenol is obtained, and the obtained decomposition liquid is supplied to a BPA synthesis step for synthesizing bisphenol A. It is described that the synthesis liquid containing bisphenol A obtained by the BPA synthesis step is supplied to the concentration step of the bisphenol A production process, and high-purity bisphenol A can be obtained by a conventional method. However, the isopropenylphenol is a very unstable chemical species, and there is a problem that the isopropenylphenol condenses with various components before the decomposition liquid is supplied to the bisphenol A synthesis step for synthesizing bisphenol A in the bisphenol production process. In addition, there is also a problem that the color tone of the obtained bisphenol A deteriorates due to the condensed components.

[0012] As described above, the chemical recycling of the conventional polycarbonate resin requires a long time for purifying the recycled bisphenol A, and it is necessary to remove the coloring components derived from the polycarbonate resin and improve the color tone of the obtained bisphenol A, and further improvement has been demanded.

[0013] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for producing bisphenol A that can efficiently remove the coloring components derived from the polycarbonate resin and produce bisphenol A with a good color tone. Furthermore, an object is to provide a method for producing a polycarbonate resin using the obtained bisphenol.

Means for Solving the Problems

[0014] As a result of intensive studies to solve the above problems, the inventors of the present invention decomposed a polycarbonate resin using phenol, distilled off a part of the phenol after the decomposition, obtained a crude solution containing low-purity bisphenol A, and mixed this crude solution with the mother liquor obtained in the production process of bisphenol A. After that, a method for producing bisphenol A was found by performing treatments such as under conditions for decomposing bisphenol A and circulating the obtained reaction solution to the production process of bisphenol A. In addition, a method for producing a polycarbonate resin using the obtained bisphenol A was found. That is, the present invention relates to the following inventions.

[0015] <1> A method for producing bisphenol A having the following steps A to F, step H, and step I. Step A: A step of decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and distilling off the solvent from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass Step B: A step of dehydrating and condensing acetone and phenol in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A Step C: A step of distilling off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C Step D: A step of crystallizing the concentrated solution C obtained in step C to obtain a slurry solution, and performing solid-liquid separation on the slurry solution to obtain a mother liquor D and a cake d Step E: A step of purifying the cake d obtained in step D to obtain bisphenol A Step F: A step of circulating a part of the mother liquor D obtained in step D and supplying it to step B Step H: A step of obtaining a solution H1 or a solution H2 from the crude solution A and a part of the mother liquor D Here, the solution H1 is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. The solution H2 is a solution containing phenol obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under the conditions for decomposing bisphenol A. Step I: A step of supplying the solution H1 or the solution H2 obtained in step H to step B and / or step C <2> A method for producing bisphenol A having the following steps A to I. Step A: A step of decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and distilling off the solvent from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass. Step B: A step of subjecting acetone and phenol to dehydration condensation in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A. Step C: A step of distilling off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C. Step D: A step of crystallizing the concentrated solution C obtained in step C to obtain a slurry solution, and subjecting the slurry solution to solid-liquid separation to obtain a mother liquor D and a cake d. Step E: A step of purifying the cake d obtained in step D to obtain bisphenol A. Step F: A step of circulating a part of the mother liquor D obtained in step D and supplying it to the dehydration condensation in step B. Step G: A step of mixing the crude solution A obtained in step A and a part of the mother liquor D obtained in step D to obtain a mixture G. Step H: A step of obtaining a solution H1 containing bisphenol A obtained by treating the mixture G under the conditions for decomposing bisphenol A and then recombining it, or a solution H2 containing decomposition products obtained by treating the mixture G under the conditions for decomposing bisphenol A. Step I: A step of supplying the solution H1 or the solution H2 obtained in step H to step B and / or step C. <3> The method for producing bisphenol A according to <1> or <2>, wherein the crude solution A and a part of the mother liquor D are mixed, and the obtained mixture G is supplied to the apparatus for decomposing bisphenol A in step H. <4> The method for producing bisphenol A according to <1> or <2>, wherein a part of the crude solution A and a part of the mother liquor D are respectively supplied to an apparatus for decomposing bisphenol A in the step H, and a decomposition reaction is carried out while adjusting a mixed solution G in the apparatus. <5> The method for producing bisphenol A according to any one of <1> to <4>, wherein in the step C, a part of phenol is further distilled off from the reaction solution B to obtain a concentrated solution C. <6> The method for producing bisphenol A according to any one of <2> to <5>, wherein the decomposition rate of bisphenol A in the mixed solution G when the mixed solution G is treated under conditions for decomposing bisphenol A in the step H is 30 mol% or more. <7> The method for producing bisphenol A according to any one of <1> to <6>, wherein the conditions for decomposing bisphenol A are any selected from the group consisting of alkaline conditions, acidic conditions, and supercritical water conditions. <8> The method for producing bisphenol A according to any one of <2> to <7>, wherein after treating the mixed solution G under conditions for decomposing bisphenol A, or while treating, distillation is carried out to recover a fraction h containing decomposition products and remove residues. <9> The step H is a step of obtaining the solution H1. A decomposition and distillation step of carrying out distillation while treating the mixed solution G under alkaline conditions for decomposing bisphenol A, recovering a fraction h1 containing phenol and isopropenylphenol as decomposition products, and removing residues; The method for producing bisphenol A according to any one of <2> to <8>, which has a recombination step of recombining phenol and isopropenylphenol contained in the fraction h1 to produce bisphenol A. <10> The method for producing bisphenol A according to <9>, wherein the fraction h1 contains 1.0% by mass or more of isopropenylphenol. <11> The method for producing bisphenol A according to <9> or <10>, wherein the solution H1 contains 1% by mass or more of bisphenol A. <12> The method for producing bisphenol A according to any one of <9> to <11>, wherein the residue is treated in the presence of an acid catalyst and then distilled to recover the phenol fraction h1b. <13> The step H is a step of obtaining the solution H2, An alkali hydrolysis step of treating the mixture G under alkaline conditions for hydrolyzing bisphenol A to obtain a reaction solution h2 containing acetone and phenol, The method for producing bisphenol A according to any one of <2> to <8>, having an acetone-phenol recovery step of recovering the acetone fraction and / or the phenol fraction from the reaction solution h2 obtained in the alkali hydrolysis step and removing the residue. <14> The method for producing bisphenol A according to <13>, wherein the solution H2 contains 0.1% by mass or more of acetone. <15> The method for producing bisphenol A according to any one of <1> to <14>, wherein the solvent used in the step A is phenol. <16> The step A is a step of decomposing the polycarbonate resin in the presence of any catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines, and acids to obtain the crude solution A. The method for producing bisphenol A according to any one of <1> to <15>. <17> The method for producing bisphenol A according to any one of <1> to <16>, wherein the content of bisphenol A in the crude solution A is 10% by mass or more. <18> The method for producing bisphenol A according to <17>, wherein the content of bisphenol A in the crude solution A is 20% by mass or more.

[0016] <19> A method for producing bisphenol A having the following steps B to F, step H, and step I. Step B: A step of dehydrating and condensing acetone and phenol in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A Step C: A step of distilling off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C Process D: A process of crystallizing the concentrated liquid C obtained in Process C to obtain a slurry liquid, and subjecting the slurry liquid to solid-liquid separation to obtain a mother liquor D and a cake d Process E: A process of purifying the cake d obtained in Process D to obtain bisphenol A Process F: A process of circulating a part of the mother liquor D obtained in Process D and supplying it to Process B Process H: A process of obtaining a solution H1 or a solution H2 from the crude solution A and a part of the mother liquor D Here, the crude solution A is obtained by decomposing a polycarbonate resin in a solvent to obtain a reaction liquid a1 containing bisphenol A, and then distilling off the solvent from the obtained reaction liquid a1. The content of bisphenol A in the crude solution A is less than 90% by mass. The solution H1 is a solution containing bisphenol A obtained by decomposing the bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under the conditions for decomposing bisphenol A, and then recombining the phenol and isopropenylphenol. The solution H2 is a solution containing phenol obtained by decomposing the bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under the conditions for decomposing bisphenol A. Process I: A process of supplying the solution H1 or the solution H2 obtained in Process H to Process B and / or Process C <20> The method for producing bisphenol A according to <19>, wherein the crude solution A and a part of the mother liquor D are mixed, and the obtained mixed liquid G is supplied to the apparatus for decomposing bisphenol A in Process H. <21> The method for producing bisphenol A according to <19>, wherein the crude solution A and a part of the mother liquor D are respectively supplied to the apparatus for decomposing bisphenol A in Process H, and a decomposition reaction is carried out while adjusting a mixed liquid G obtained by mixing the crude solution A and a part of the mother liquor D in the apparatus. <22> A method for producing a polycarbonate resin, which uses bisphenol A obtained by the method for producing bisphenol A according to any one of <1> to <21> to produce a polycarbonate resin.

Advantages of the Invention

[0017] According to the present invention, there is provided a method for producing bisphenol A, which can efficiently remove coloring components derived from polycarbonate resin and produce bisphenol A with good color tone. Further, there is provided a method for producing a polycarbonate resin using the obtained bisphenol A.

Brief Description of the Drawings

[0018]

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Embodiments for Carrying Out the Invention

[0019] The embodiments of the present invention will be described in detail below. However, the description of the constituent elements described below is an example of an embodiment of the present invention, and the present invention is not limited to the description content below unless it exceeds the gist thereof. In the present specification, when the expression "~" is used, it shall be used as an expression including the numerical values or physical property values before and after it.

[0020] <Method for producing bisphenol A> The present invention relates to a method for producing bisphenol A having the following steps A to F, step H, and step I (hereinafter, may be described as "the method for producing bisphenol A of the present invention").

[0021] Step A: A step of decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and distilling off the solvent from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass

[0022] Step B: A step of subjecting acetone and phenol to dehydration condensation in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A

[0023] Step C: A step of distilling off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C

[0024] Step D: A step of crystallizing the concentrated solution C obtained in step C to obtain a slurry solution, and performing solid-liquid separation on the slurry solution to obtain a mother liquor D and a cake d Step E: A step of purifying the cake d obtained in step D to obtain bisphenol A

[0025] Step F: A step of circulating a part of the mother liquor D obtained in step D and supplying it to step B

[0026] Step H: Any one of the following steps (I) to (III) (I) A step of obtaining a solution H1 or a solution H2 from the crude solution A and a part of the mother liquor D Here, the solution H1 in (I) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under conditions for decomposing bisphenol A and then recombining phenol and isopropenylphenol. Further, the solution H2 in (I) is a solution obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under conditions for decomposing bisphenol A. (II) A step of subjecting a part of the mother liquor D to isomerization treatment and crystallization / solid-liquid separation treatment to obtain solution H1 or solution H2 from the obtained mother liquor S2a and the crude solution A Here, the solution H1 in (II) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the mother liquor S2a and the crude solution A into phenol and isopropenylphenol under conditions for decomposing bisphenol A and then recombining phenol and isopropenylphenol. Further, the solution H2 in (II) is a solution obtained by decomposing bisphenol A contained in the mother liquor S2a and the crude solution A into phenol and acetone under conditions for decomposing bisphenol A. (III) A step of subjecting a solution S3b containing the solution S3a after isomerization treatment of the mother liquor D and the crude solution A to crystallization / solid-liquid separation treatment to obtain solution H1 or solution H2 from the obtained mother liquor S2b Here, the solution H1 in (III) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the mother liquor S2b into phenol and isopropenylphenol under conditions for decomposing bisphenol A and then recombining phenol and isopropenylphenol. Further, the solution H2 in (III) is a solution obtained by decomposing bisphenol A contained in the mother liquor S2b into phenol and acetone under conditions for decomposing bisphenol A.

[0027] Step I: A step of supplying the solution H1 or solution H2 obtained in step H to step B and / or step C

[0028] Fig. 1 shows an example of a flow chart of the method for producing bisphenol A according to the present invention. As shown in Fig. 1, bisphenol A produced by the decomposition of the polycarbonate resin is subjected to step H or step f2. When treating the crude solution A and the mother liquor D in step H, the crude solution A and the mother liquor D are supplied to the apparatus for performing the decomposition in step H through path P1 or P2 in Fig. 1. When treating the crude solution A and the mother liquor S2a in step H, the crude solution A and the mother liquor S2a are supplied to the apparatus for performing the decomposition in step H through path P3 or P4 in Fig. 1. When treating the mother liquor S2b in step H, the crude solution A and the mother liquor D are supplied to the apparatus for performing the decomposition in step H through path P5 in Fig. 1.

[0029] The solution H1 obtained in step H is subjected to step B (path P11 in Fig. 1) and / or step C (path P12 in Fig. 1) via step I. Further, the solution H2 obtained in step H is subjected to step B (path P21 in Fig. 1) and / or step C (path P22 in Fig. 1).

[0030] Fig. 2 shows an example of a flow chart of the method for producing bisphenol A according to the present invention. The method for producing bisphenol A shown in Fig. 2 has the following steps A to I, and is an example of mixing and treating a part of the crude solution A and the mother liquor D. Step A: A step of decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and distilling off the solvent from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass Step B: A step of subjecting acetone and phenol to dehydration condensation in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A Step C: A step of distilling off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C Step D: A step of crystallizing the concentrated solution C obtained in step C to obtain a slurry solution, and performing solid-liquid separation on the slurry solution to obtain a mother liquor D and a cake d Step E: A step of purifying the cake d obtained in step D to obtain bisphenol A Step F: A step of circulating a part of the mother liquor D obtained in step D and supplying it to step B Step G: A step of obtaining a mixture G by mixing the crude solution A obtained in Step A and a part of the mother liquor D obtained in Step D Step H: A step of obtaining a solution H1 containing bisphenol A obtained by treating the mixture G under conditions for decomposing bisphenol A and then recombining it, or a solution H2 containing decomposition products obtained by treating the mixture G under conditions for decomposing bisphenol A Step I: A step of supplying the solution H1 or the solution H2 obtained in Step H to Step B and / or Step C

[0031] One of the features of the method for producing bisphenol A of the present invention shown in Fig. 2 is that the crude solution A obtained by decomposing a polycarbonate resin is mixed with the mother liquor D obtained in the production of bisphenol A, and after performing treatments such as decomposition and recombination in Step H, it is returned to the step of producing bisphenol A (Step B) and / or the step of concentrating the reaction solution B (Step C). The reaction solution obtained by decomposing waste plastic containing a polycarbonate resin may contain a stabilizer derived from the decomposed polycarbonate resin, resins other than the polycarbonate resin, sebum, dust, foreign substances, etc. Conventionally, such a reaction solution has been supplied to the step of reacting acetone and phenol in the presence of an acidic catalyst in a general bisphenol A production process to obtain a reaction solution containing bisphenol A, the step of distilling and separating the reaction solution containing bisphenol A to obtain a concentrated solution, and the step of crystallizing and recovering the concentrated solution to obtain an adduct crystal and a mother liquor, which may significantly contaminate the bisphenol A production process and deteriorate the quality of the produced bisphenol A.

[0032] On the other hand, in some bisphenol A production processes, a step of circulating the mother liquor is incorporated. The mother liquor circulated to the step of dehydrating and condensing acetone and phenol to produce bisphenol A is subjected to treatments for recovering useful components in the mother liquor and reducing impurities before being circulated to the step.

[0033] The crude solution A obtained in Process A usually contains, in addition to bisphenol A, impurities of heavy components derived from decomposition products of polycarbonate resin, whose structures have not yet been well analyzed. The heavy components are components with a boiling point higher than that of phenol. These heavy-component impurities are different from the impurities by-produced in the production of bisphenol A and cannot always be removed by the same purification method as the production method of bisphenol A. Therefore, when the crude solution A is used in a general bisphenol A production process, if the step of supplying the crude solution A is not appropriate, the purity of the obtained bisphenol A may decrease or the color tone may deteriorate. The inventors of the present invention have found that under treatment conditions for recovering useful components in the mother liquor and reducing impurities, the useful components in the crude solution A obtained by decomposing polycarbonate resin can be recovered, and the impurities can be decomposed and removed. Furthermore, among the steps of the bisphenol A production process, it has been found that by incorporating the crude solution A into the step of circulating the mother liquor, bisphenol A with excellent color tone can be obtained with high purity. That is, by mixing the crude solution A with the mother liquor D and performing Step H including treatment under conditions for decomposing bisphenol A, not only bisphenol A in the crude solution A but also incomplete decomposition products of the remaining polycarbonate resin (such as multimers such as dimers and trimers of bisphenol A) are decomposed, and after removing the coloring cause, the treatment solution is returned to Step B and / or Step C, so that bisphenol A with excellent color tone can be obtained in the purification Step E.

[0034] Moreover, one of the features of the method for producing bisphenol A of the present invention is to prepare a crude solution A having a bisphenol content of less than 90% by mass in Process A. In Step H, not only bisphenol A in the crude solution A but also the remaining incomplete decomposition products are decomposed, so there is no need to perform an excessive purification operation in Process A, and Process A can also be simplified. If the content of bisphenol A is too high, the viscosity of the crude solution A becomes high, making it difficult to transfer the crude solution A for mixing with the mother liquor D obtained in Process D, or difficult to mix uniformly with the mother liquor D obtained in Process D. Also, if the content of bisphenol A is too low, the amount of bisphenol A produced decreases, which is not economically preferable.

[0035] Next, each step of the method for producing bisphenol A of the present invention will be described.

[0036] [Step A] In Step A, a polycarbonate resin is decomposed in a solvent to obtain a reaction solution a1 containing bisphenol A, and the solvent is distilled off from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass.

[0037] (Polycarbonate resin (PC)) The polycarbonate resin used in Step A includes a polycarbonate resin containing a repeating unit derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane).

[0038] In addition, the polycarbonate resin may be not only a polycarbonate resin alone containing a repeating unit derived from bisphenol A, but also a composition containing a resin other than the polycarbonate resin such as a copolymer or a polymer alloy. Examples of the composition containing a resin other than the polycarbonate resin include a polycarbonate / polyester copolymer, a polycarbonate / polyester alloy, a polycarbonate / polyarylate copolymer, a polycarbonate / polyarylate alloy, and the like. When using a composition containing a resin other than the polycarbonate resin, it is preferable that the polycarbonate resin is the main component (the composition contains 50% by mass or more of the polycarbonate resin).

[0039] In addition, two or more different polycarbonate resins may be mixed and used.

[0040] From the perspective of chemical recycling, polycarbonate resin is preferably the polycarbonate resin contained in waste plastics. Polycarbonate resin is used by being formed into various molded products such as optical members such as headlamps and optical recording media such as optical discs. As waste plastics containing polycarbonate resin, edge materials, defective products, used molded products, etc. when molding polycarbonate resin into these molded products can be used.

[0041] Waste plastics may be appropriately washed, crushed, pulverized, etc. and then used. As a method for crushing waste plastics, there are coarse crushing using a jaw crusher or a gyratory crusher to crush to 20 cm or less, medium crushing using a gyratory crusher, a cone crusher, or a mill to crush to 1 cm or less, and pulverization using a mill to crush to 1 mm or less, etc. It is sufficient if it can be made small enough to be supplied to the decomposition tank. Also, when the waste plastic is a thin plastic such as a CD or DVD, it can be cut using a shredder or the like and supplied to the decomposition tank. Further, other resins such as copolymers and polymer alloys, and parts formed of components other than polycarbonate resin such as the surface and back layers of optical discs may be removed in advance and then used.

[0042] (Decomposition of Polycarbonate Resin) As a method for decomposing polycarbonate resin, known methods can be used. For example, by heating the polycarbonate resin in a solvent, the polycarbonate resin is decomposed to obtain a reaction solution a1 containing bisphenol A.

[0043] Among them, since the dissolution rate of polycarbonate resin is fast, it is preferable to use phenol for the decomposition of polycarbonate resin. That is, it is preferable to decompose the polycarbonate resin in a solvent containing phenol.

[0044] The solvent containing phenol may contain solvents other than phenol, but preferably has phenol as the main component. For example, in the solvent containing phenol, the mass of phenol is preferably 50% by mass or more, and can be appropriately set to 65% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, etc. according to the types of other solvents and catalysts.

[0045] In addition, compared with the case of using phenol alone as the solvent, the decomposition rate of the polycarbonate resin is improved, and the polycarbonate resin can be decomposed even under mild conditions (for example, normal pressure, about 60 to 150 °C). Therefore, the solvent containing phenol is preferably a mixed solvent containing any solvent selected from the group consisting of water, monohydric alcohols, and dihydric alcohols and phenol, and more preferably a mixed solvent containing phenol and water or a mixed solvent containing phenol and a monohydric alcohol. As the monohydric alcohol, linear alcohols having 1 to 5 carbon atoms such as methanol, ethanol, and n-butanol are preferred.

[0046] In addition, for the decomposition of the polycarbonate resin, it is preferable to use a catalyst, and it is preferable to use any catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines, and acids.

[0047] As the alkali metal hydroxide, sodium hydroxide or potassium hydroxide is preferred. As the alkali metal carbonate, sodium carbonate or potassium carbonate is preferred.

[0048] Alkylamine is a compound in which at least one hydrogen atom of ammonia is substituted with an alkyl group. Examples of alkylamines include methylamine, ethylamine, propylamine, dimethylamine, diethylamine, trimethylamine, and triethylamine. The alkylamine is preferably a secondary amine or a tertiary amine, and more preferably a tertiary amine.

[0049] Further, the boiling point of the alkylamine is preferably 200 °C or lower, more preferably 160 °C or lower. Further, the lower limit is preferably 10 °C or higher, more preferably 30 °C or higher. With such a boiling point, when a part of the solvent is distilled off by vacuum distillation or the like, it can be removed out of the system together.

[0050] As the acid, any one selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid and sulfonic acid is preferable. Examples of the sulfonic acid include alkylsulfonic acids such as methanesulfonic acid, and aromatic sulfonic acids such as toluenesulfonic acid.

[0051] The molar ratio of the catalyst to 1 mol of the repeating unit of the polycarbonate resin ((mass of the catalyst used [g] / molecular weight of the catalyst [g / mol]) / (mass of the polycarbonate resin used [g] / molecular weight of the repeating unit [g / mol])) is preferably 0.0001 or more, more preferably 0.0005 or more, and still more preferably 0.0007 or more. When the amount of the catalyst used with respect to the polycarbonate resin is small, the decomposition rate becomes slow, the decomposition time becomes long, and the efficiency tends to deteriorate. Further, the molar ratio of the catalyst to 1 mol of the repeating unit of the polycarbonate resin is preferably 1 mol or less, more preferably 0.9 mol or less, and still more preferably 0.8 mol or less. When the amount of the catalyst used with respect to the polycarbonate resin used is large, the production efficiency tends to decrease.

[0052] (Removal of the solvent) In Step A, after decomposing the polycarbonate resin, the solvent is distilled off from the obtained reaction solution a1. The solvent can be distilled off by distillation. Further, it is not necessary to completely distill off the solvent in the reaction solution a1 by distillation, and the amount of the solvent to be distilled off is appropriately determined according to the content of the target bisphenol A, the components contained in the reaction solution a1, and the like.

[0053] When using a solvent containing phenol, in order to efficiently supply bisphenol A obtained by decomposing the polycarbonate resin to Step G or Step H, etc., after decomposing the polycarbonate resin in the presence of phenol, it is preferable to distill off a part of the phenol. If light components are contained in the crude solution A, there is a risk that the light components will remain in the solution H1 or solution H2 obtained in Step H, and the quality of bisphenol A obtained in Step E will deteriorate. In Step A, after decomposing the polycarbonate resin in the presence of phenol and then distilling off a part of the phenol, a crude solution A in which light components are firmly removed can be obtained. The light components mean components having a lower boiling point than phenol. For example, when using a mixed solvent of phenol and water or an alkylamine as a catalyst, water, alkylamine, etc. become light components. Also, when using a mixed solvent of phenol and a monohydric alcohol, the monohydric alcohol, dialkyl carbonate by-produced together with bisphenol A, etc. become light components.

[0054] (Crude solution A) The crude solution A is a composition containing bisphenol A at a ratio of less than 90% by mass and being liquid under the temperature conditions for use in Step G or Step H. The crude solution A may be solid at a temperature lower than the temperature conditions for use in Step G or Step H. Usually, since the crude solution A obtained in Step A is transferred to the apparatus where Step G or Step H is carried out at 40°C or higher, the crude solution A is a composition containing bisphenol A and being liquid at 40°C or higher.

[0055] The content of bisphenol A contained in the crude solution A containing bisphenol A obtained in Project A (mass of bisphenol A / mass of crude solution A × 100 (%)) is less than 90% by mass. Preferably, it is 85% by mass or less, and more preferably in the order of 80% by mass or less, 70% by mass or less, and 60% by mass or less as the numerical value is lower. As described above, in the method for producing bisphenol A of the present invention, even when the crude solution A contains impurities of heavy components such as incomplete decomposition products of polycarbonate resin (polymers such as dimers and trimers of bisphenol A), decomposition and removal can be performed in Step H, so it is not necessary to purify the crude solution A excessively. Also, if the content of bisphenol A is too high, the viscosity of the crude solution A will increase, making it difficult to transfer the crude solution A or making it difficult to mix uniformly with the mother liquor D obtained in Step D. Further, if the content of bisphenol A is too high, when rebinding phenol and isopropenylphenol generated by decomposing bisphenol A in Step H, the concentration of isopropenylphenol generated by the decomposition treatment such as alkaline decomposition in Step H becomes high and self-condenses to form by-products, and the production rate of bisphenol A in the rebinding significantly decreases.

[0056] Also, the content of bisphenol A contained in the crude solution A is preferably 10% by mass or more, and more preferably in the order of 20% by mass or more, 30% by mass or more, and 40% by mass or more as the numerical value is larger. If the content of bisphenol A is too small, the amount of bisphenol A produced will be small, which is not economically preferable.

[0057] The crude solution A may contain phenol in addition to bisphenol A. The content of phenol contained in the crude solution A is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more. If the content of phenol is too small, bisphenol A in the crude solution A may precipitate to form a slurry, making it difficult to feed the solution.

[0058] Further, the crude solution A may contain heavy components such as incomplete decomposition products of the polycarbonate resin (polymers such as dimers and trimers of bisphenol A), etc. However, if there are too many heavy components, carbon dioxide will be generated in step H, causing pressure fluctuations and making reaction control complex. Therefore, the content of the heavy components contained in the crude solution A is preferably 5% by mass or less, and more preferably 1% by mass or less. Note that the crude solution A may be sufficiently washed.

[0059] Hereinafter, specific examples of step A will be described based on FIGS. 3 and 4.

[0060] [Step A1] Step A1 shown in FIG. 3 includes a PC decomposition step of decomposing a polycarbonate resin in the presence of a solvent containing phenol and a catalyst to obtain a reaction solution a1 containing bisphenol A, and a concentration step a1 of distilling the reaction solution a1 obtained in the PC decomposition step to distill off a part of the phenol. In step A1, usually, a catalyst that can be distilled off in the concentration step a1 is used. Examples of such a catalyst include alkylamine and the like.

[0061] (PC decomposition step) The reaction temperature is usually 60 to 150°C. Preferably it is 70°C or higher, more preferably 75°C or higher, and even more preferably 80°C or higher. Also, the upper limit of the reaction temperature can be appropriately set to 130°C or lower, 120°C or lower, 110°C or lower, 100°C or lower, 95°C or lower, etc., depending on the type of the solvent used for the decomposition of the polycarbonate resin. Also, the pressure of the PC decomposition reaction is preferably 1 kPa to 50 MPa, and more preferably 5 kPa to 10 MPa.

[0062] There is no particular limitation on the reaction method of the decomposition reaction of the polycarbonate resin, and it may be a continuous method or a batch method. For example, in the case of the batch method, the reaction time is appropriately selected according to the concentration of the polycarbonate resin, the reaction temperature, the reaction pressure, etc. However, when it is long, the generated bisphenol A tends to decompose, so it is preferably 30 hours or less, and more preferably in the order of 25 hours or less, 20 hours or less, 15 hours or less, 10 hours or less, 5 hours or less as the numerical value becomes smaller. In addition, when the reaction time is short, the decomposition reaction may not proceed sufficiently, so it is preferably 0.1 hour or more, more preferably 0.5 hour or more, and still more preferably 1 hour or more.

[0063] (Concentration step a1) In the concentration step a1, the reaction solution a1 is distilled to distill off a part of phenol. The obtained solution may contain heavy components such as incomplete decomposition products of the polycarbonate resin (polymers such as dimers and trimers of bisphenol A), etc. However, since these heavy components can also be decomposed or removed in step H, the obtained solution can be directly used as the crude solution A. For example, the distillation can be carried out at a temperature of 50 to 200 °C and a pressure of 0.1 kPa to 150 kPa. In addition, light components with a lower boiling point than phenol, such as alkylamine, are also distilled off in the concentration step a1.

[0064] [Step A2] Step A2 shown in Figure 4 includes a PC decomposition step of decomposing the polycarbonate resin in the presence of a solvent containing phenol and a catalyst to obtain a reaction solution a1 containing bisphenol A, a neutralization step of neutralizing the reaction solution a1 obtained in the PC decomposition step to obtain an organic phase a2 containing bisphenol A, and a concentration step a2 of distilling the organic phase a2 obtained in the neutralization step to distill off a part of phenol. In step A2, after the reaction solution a1 is neutralized and the catalyst etc. are removed, the solvent is distilled off. In step A2, since the catalyst can be removed in the neutralization step, a catalyst with a high boiling point such as an alkali metal hydroxide can also be used. As the catalyst, for example, any one selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines and acids can be used.

[0065] (PC decomposition process) The PC decomposition process can be carried out in the same manner as process A1.

[0066] (Neutralization process) In the neutralization process, the reaction solution a1 obtained in the PC decomposition process is neutralized to obtain an organic phase a2 containing bisphenol A. Neutralization is carried out by mixing an acid such as hydrochloric acid, sulfuric acid, or phosphoric acid into the reaction solution a1 when using a base such as an alkali metal hydroxide, an alkali metal carbonate, or an alkylamine as a catalyst. Also, when using an acid as a catalyst, neutralization is carried out by mixing a base such as sodium carbonate or sodium hydroxide into the reaction solution a1. It is preferable to carry out neutralization by adjusting the amount of the acid or base to be mixed so that the pH of the reaction solution a1 becomes 7.5 to 10 (preferably pH 8.0 to 9.5). After mixing an acid or a base according to the catalyst used into the reaction solution a1, oil-water separation is performed, and the aqueous phase is removed, whereby an organic phase a2 containing bisphenol A can be obtained.

[0067] (Concentration process a2) In the concentration process a2, the organic phase a2 obtained in the neutralization process is distilled to distill off a part of phenol. The obtained solution may contain incomplete decomposition products of the polycarbonate resin (such as dimers and trimers of bisphenol A and other polymers) and heavy impurities having a higher boiling point than phenol. However, since these incomplete decomposition products and impurities can also be decomposed or removed in process H, the obtained solution can be used as the crude solution A as it is. For example, distillation can be carried out at a temperature of 50 to 200 °C and a pressure of 0.1 kPa to 150 kPa.

[0068] In addition, even when using a catalyst having a high boiling point such as an alkali metal hydroxide, when decomposing bisphenol A under alkaline conditions in process H, the crude solution A may be obtained in the same manner as in process A1 without neutralization.

[0069] [Process B] Process B is a process in which acetone and phenol are subjected to dehydration condensation in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A.

[0070] (Acetone) The raw material acetone can be used without particular limitation as long as it is industrially available. For example, acetone may be newly supplied from outside the system, or the unreacted acetone distilled off in Step C described later may be circulated and used as the acetone in Step B, or these may be mixed and used.

[0071] (Phenol) The raw material phenol can be used without particular limitation as long as it is industrially available. For example, phenol may be newly supplied from outside the system, or the unreacted phenol distilled off in Step C described later or the phenol contained in the solution after Step G may be circulated and used as the phenol in Step B, or these may be mixed and used.

[0072] (Acid catalyst) As the acid catalyst, an acidic substance is used, and mineral acids such as hydrochloric acid and sulfuric acid, solid acids such as strongly acidic cation exchange resins and polysiloxanes can be used. From the viewpoints of corrosion of the apparatus, separation of the catalyst after the reaction, catalyst activity, etc., usually, a strongly acidic cation exchange resin such as a sulfonic acid type is used, and a styrene-divinylbenzene copolymer type acidic cation exchange resin having a sulfonic acid group introduced to about 2 to 16% of the total number of benzene rings can be used. Its average particle size is usually 0.2 to 2 mm, preferably 0.4 to 1.5 mm. Further, for the purpose of improving the selectivity and conversion rate, it is preferable to add a sulfur-containing amine compound as a cocatalyst during the reaction or support it on the acid catalyst. A suitable acid catalyst in Step B includes a strongly acidic cation exchange resin partially modified with a sulfur-containing amine compound.

[0073] (Molar ratio of acetone to phenol) There is no particular limitation on the molar ratio of the raw material phenol to acetone, but it is preferable to use phenol in an amount in excess of the stoichiometric amount. Usually, 3 to 30 moles, preferably 5 to 20 moles of phenol are used per mole of acetone. When the amount of phenol used per mole of acetone is less than 3 moles, the selectivity of bisphenol A decreases. When it is more than 30 moles, problems such as a decrease in the reaction rate and an increase in the size of the apparatus occur.

[0074] For the condensation reaction of acetone and phenol, known methods can be used. The condensation reaction of phenol and acetone is not particularly limited in the reaction method, but it is usually carried out by a fixed-bed flow method or a suspension-bed batch method. In the case of the fixed-bed flow method, the liquid hourly space velocity of the raw material mixture supplied to the reactor is usually 0.2 to 50 / hour. In the case of the suspension-bed batch method, although it varies depending on the reaction temperature and reaction pressure, the amount of acid catalyst used is usually 20 to 100% by mass based on the raw material mixture, and the reaction time is usually 0.5 to 5 hours. Among them, it is preferable to use a fixed-bed continuous reaction method in which phenol and acetone are continuously supplied to a condensation reaction apparatus filled with an acidic cation exchange resin immobilized with a cocatalyst and reacted.

[0075] The reaction temperature is usually 40 to 130°C, preferably 40 to 90°C. If the reaction temperature is less than 40°C, the reaction solution may solidify, which is not preferable. Also, at a high temperature exceeding 130°C, the acidic groups of the acidic cation exchange resin, which is the reaction catalyst, may desorb from the catalyst and mix into bisphenol A, causing bisphenol A to decompose, or the catalyst may decompose at a high temperature, reducing the catalyst life. The reaction pressure is usually from atmospheric pressure to 600 kPa (absolute pressure).

[0076] [Step C] Step C is a step of obtaining concentrated liquid C by distilling off unreacted acetone and water from reaction liquid B obtained in Step B. Reaction liquid B obtained in Step B contains generated bisphenol A, unreacted acetone, phenol, by-produced water, isomers of bisphenol A, and the like. In Step C, by removing light components including unreacted acetone and water from reaction liquid B by a method such as vacuum distillation, concentrated liquid C containing bisphenol A and phenol is obtained.

[0077] Also, in Step C, it is preferable to distill off acetone, water, and a part of phenol from reaction liquid B obtained in Step B to obtain concentrated liquid C. By distilling off a part of phenol, concentrated liquid C in which acetone and water are firmly removed is obtained.

[0078] For example, reaction liquid B obtained in Step B is transferred to a distillation column, water, unreacted acetone, and a part of phenol are removed from the top of the column, and then the reaction product is withdrawn from the bottom of the column, whereby concentrated liquid C used in Step D can be obtained. The obtained concentrated liquid C is subjected to Step D. Also, the distilled-off acetone may be circulated to Step B. The distilled-off phenol may be circulated to Step B or used as a washing solvent for bisphenol A in Step E.

[0079] The distillation is preferably carried out at a reaction temperature of 50 to 150°C and a pressure of 0.0065 to 0.040 MPa. Acetone and water in concentrated liquid C are each preferably removed to 0.1% by mass or less. Thereby, the solubility of adduct crystals during the crystallization operation is reduced, and the crystal yield is improved. Also, the concentration of bisphenol A in concentrated liquid C is preferably 20 to 50% by mass. When the concentration of bisphenol A is less than 20% by mass, the yield is low, and when it is more than 50% by mass, the viscosity of concentrated liquid C becomes high and transportation becomes difficult.

[0080] [Step D] Step D is a step of crystallizing concentrated liquid C obtained in Step C to obtain a slurry liquid, and subjecting the slurry liquid to solid-liquid separation to obtain mother liquid D and cake d.

[0081] In Process D, first, the concentrated liquid C is crystallized to precipitate an adduct crystal of bisphenol A and phenol. For example, the concentrated liquid C is usually adjusted to 60 to 100°C, preferably 70 to 90°C, and then transferred to a crystallization apparatus. The transferred concentrated liquid C is cooled in the crystallization apparatus from 60 to 100°C (preferably 70 to 90°C) to 40 to 70°C, thereby precipitating adduct crystals to form a slurry liquid. Next, the slurry liquid in which the adduct crystals are dispersed is subjected to solid-liquid separation to obtain mother liquid D and cake d, respectively. The obtained mother liquid D contains un-precipitated bisphenol A and phenol. Also, cake d mainly consists of adduct crystals.

[0082] Solid-liquid separation can be performed by known means such as filtration and centrifugation. For example, horizontal belt filters, rotary vacuum filters, rotary pressure filters, batch filters, centrifugal filtration separators, centrifugal sedimentation separators, hybrid centrifugal separators (screen bowl decanters), etc. can be used for solid-liquid separation.

[0083] [Process E] Process E is a process of purifying the cake d obtained in Process D to obtain bisphenol A. The purification method of cake d is not particularly limited. Methods such as removing phenol from the molten liquid obtained by heating and melting cake d, or crystallizing using a hydrocarbon solvent such as toluene are used to separate phenol from the cake d obtained in Process D and recover bisphenol A.

[0084] As a method for removing phenol from cake d, usually, cake d is heated and melted at 100 to 160°C, and most of the phenol is removed from the obtained melt by using, for example, a distillation apparatus, a thin-film evaporator, a flash evaporator, etc. In addition, in order to remove trace amounts of phenol remaining in the melt, after performing the above operations, the remaining phenol is further removed by steam stripping or the like to purify bisphenol A. This method is described in, for example, Japanese Patent Laid-Open No. 63-132850, Japanese Patent Laid-Open No. 2-28126, etc.

[0085] The high-purity molten bisphenol A obtained as described above is sent to a granulation tower or a flaker and becomes solid prills or flakes to be the product bisphenol A. Also, the obtained bisphenol A can be transferred to the next process in a molten state without being made solid, as in the case of being used for the production of polycarbonate resin by the melt method.

[0086] [Process F] Process F is a process of circulating a part of mother liquor D obtained in Process D and supplying it to the dehydration condensation in Process B. A part of mother liquor D obtained by solid-liquid separation is supplied to the condensation reaction apparatus through a pipe connected to the condensation reaction apparatus in which Process B is performed and is used in Process B. Also, all or part of the remaining mother liquor D obtained by solid-liquid separation is supplied through a pipe connected to the apparatus in which Process G or Process H is performed and is used in Process G or Process H.

[0087] [Process G] Process G is a process of mixing the crude solution A obtained in Process A and a part of mother liquor D obtained in Process D to obtain a mixed solution G.

[0088] The mixed solution G may be prepared by mixing the crude solution A and the mother liquor D before transferring it to the reaction tower where Process H is performed, or the crude solution A and the mother liquor D may be transferred to the reaction tower (apparatus) where Process H is performed respectively and prepared in the reaction tower.

[0089] Step G is a step performed when treating a mixed solution G containing a crude solution A and a mother liquor D in step H. As shown by path P2 in Fig. 1, the crude solution A and the mother liquor D can be premixed and then the obtained mixed solution G can be supplied to the apparatus for decomposing bisphenol A in step H. Also, as shown by path P1 in Fig. 1, the crude solution A and a part of the mother liquor D obtained in step D can be respectively supplied to the apparatus for decomposing bisphenol A in step H, and while mixing the crude solution A and a part of the mother liquor in the reaction tower, the decomposition in step H may be carried out.

[0090] If the mixing ratio of the crude solution A and the mother liquor D is such that the crude solution A is too much, the components that cannot be decomposed in step H will increase, making it easier to solidify and the pipes for transferring from the reaction tank where step H is carried out are likely to be blocked. Therefore, the mass ratio of the crude solution A to the mother liquor D (mass of the crude solution A / mass of the mother liquor D) is preferably 10 or less, and can be appropriately determined, such as 5 or less, 2 or less, 1 or less, etc., according to the content of bisphenol A in the crude solution A. The lower limit of the mass ratio of the crude solution A to the mother liquor D is not particularly limited, but can be appropriately determined, such as 0.0001 or more, 0.0001 or more, 0.001 or more, 0.01 or more, 0.1 or more, etc., according to the content of bisphenol A in the crude solution A.

[0091] The content of bisphenol A in the mixed solution G is preferably 0.1 mass% or more. If the content of bisphenol A is too much, bisphenol A will precipitate and the pipes will be blocked, which is not preferable. Also, if the content of bisphenol A is too little, the amount of isopropenylphenol or acetone obtained by decomposition will be reduced, which is not preferable.

[0092] Also, step G may be a step of mixing a part of the crude solution A obtained in step A and the mother liquor D obtained in step D and performing distillation to obtain the mixed solution G (see Fig. 5). For example, by transferring the crude solution A and the mother liquor D to a distillation column, the crude solution A and the mother liquor D can be mixed, and a part of phenol can be distilled off to prepare the mixed solution G. The distillation can be carried out at a temperature of 100 to 250°C and a pressure of 1 kPa to 100 kPa.

[0093] A part of mother liquor D may be used in step H after undergoing treatments such as isomerization, concentration, crystallization, and solid-liquid separation. For example, as shown in FIG. 1, a step f1 of isomerizing the reaction by-products in mother liquor D obtained in step D, or a step f2 of subjecting solution S3 containing solution S3a after isomerization treatment in step f1 to crystallization and solid-liquid separation may be performed.

[0094] [Step f1] Step f1 is a step of isomerizing the reaction by-products in mother liquor D obtained in step D. The composition of mother liquor D obtained in step D usually contains 65 - 85% by mass of phenol, 1 - 20% by mass of bisphenol A, and 1 - 15% by mass of by-products such as 2,4-bisphenol A. Mother liquor D contains a large amount of impurities such as isomers of bisphenol A (2,4-bisphenol A). By isomerization treatment, the isomers of bisphenol A are converted to bisphenol A (2,2-bisphenol A). Solution S3a after isomerization treatment contains approximately 15 - 20% by mass of bisphenol A and approximately 5 - 10% by mass of by-products such as 2,4-bisphenol A. A part of solution S3a after isomerization treatment is withdrawn to prevent the accumulation of impurities and sent to step f2. Also, a part of solution S3a after isomerization treatment may be recycled to at least one of step B, step C, and step D.

[0095] For the isomerization treatment, usually, a sulfonic acid type cation exchange resin is used as a catalyst. In the case of a fixed bed flow method with a reaction temperature of about 50 - 100°C and a continuous pushing flow method, the liquid hourly space velocity (LHSV) is carried out at about 0.2 - 50 / h.

[0096] [Step f2] Step f2 is a step of subjecting solution S3 containing solution S3a after isomerization treatment in step f1 to crystallization and solid-liquid separation. Solution S3 is solution S3a (routes P3 and P4 in FIG. 1), or solution S3b (route P5 in FIG. 1) containing solution S3a and crude solution A. As solution S3a, the liquid after isomerization treatment in step f1 may be used as it is, or it may be a concentrated liquid obtained by removing a part of phenol from the liquid after isomerization treatment in step f1. As solution S3b, the liquid containing solution S3a and crude solution A may be used as it is, or it may be a concentrated liquid obtained by removing a part of phenol from the liquid containing solution S3a and crude solution A. The concentration of bisphenol A in the concentrated liquid is about 20 to 50% by mass. The concentration operation can be carried out by a distillation column or the like, and is carried out in the range of a pressure of about 5.3 to 40 kPa and a temperature of about 70 to 140°C. Further, the evaporated phenol may be reused as a washing liquid for washing the cake of the adduct crystals after solid-liquid separation.

[0097] By cooling solution S3a, adduct crystals (adduct crystals) of bisphenol A and phenol are crystallized to obtain a slurry liquid. Solution S3a may be precooled to near the freezing point by a heat exchanger using warm water as a refrigerant before being supplied to the crystallization apparatus, and then supplied to the crystallization apparatus. Next, by subjecting the slurry liquid in which adduct crystals have crystallized to solid-liquid separation, a cake of adduct crystals and mother liquor S2a (routes P3 and P4 in FIG. 1) can be obtained respectively. Solid-liquid separation can be carried out by a known method in the same manner as in step D.

[0098] Similarly, in the case of solution S3b, after cooling solution S3b to obtain a slurry liquid and then subjecting the slurry liquid to solid-liquid separation, a cake of adduct crystals and mother liquor S2b (route P5 in FIG. 1) can be obtained respectively.

[0099] The obtained mother liquor S2a and mother liquor S2b are subjected to step H. The cake of adduct crystals is melted and then recycled to step C and / or step D.

[0100] Steps f1 and f2 are pre-treatment steps that are carried out when treating mother liquor S2a and crude solution A in step H, or when treating mother liquor S2b. As shown in path P4 of FIG. 1, mother liquor S2a obtained by performing steps f1 and f2 on mother liquor D and crude solution A can be pre-mixed and then supplied to an apparatus for decomposing bisphenol A in step H. Also, as shown in path P3 of FIG. 1, mother liquor S2a obtained by performing steps f1 and f2 on mother liquor D and crude solution A can be respectively supplied to an apparatus for decomposing bisphenol A in step H, and the decomposition in step H may be carried out while mixing crude solution A and mother liquor S2a in the reaction tower. Further, mother liquor S2a and crude solution A may be separately treated in step H without mixing. Also, as shown in path P5 of FIG. 1, S3a after isomerization treatment of mother liquor D in step f1 and crude solution A are mixed, and mother liquor S2b after performing step f2 can be supplied to an apparatus for decomposing bisphenol A in step H.

[0101] [Step H] Step H is any one of the following (I) to (III).

[0102] (I) A step of obtaining solution H1 or solution H2 from a part of the crude solution A and the mother liquor D Here, solution H1 in (I) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under the conditions for decomposing bisphenol A and then recombining phenol and isopropenylphenol. Also, solution H2 in (I) is a solution obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under the conditions for decomposing bisphenol A.

[0103] (II) A step of subjecting a part of the mother liquor D to isomerization treatment and crystallization / solid-liquid separation treatment, and obtaining solution H1 or solution H2 from the obtained mother liquor S2a and the crude solution A Here, the solution H1 in (II) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the mother liquor S2a and the crude solution A into phenol and isopropenylphenol under conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. Further, the solution H2 in (II) is a solution obtained by decomposing bisphenol A contained in the mother liquor S2a and the crude solution A into phenol and acetone under conditions for decomposing bisphenol A.

[0104] (III) A step of subjecting a solution S3b containing the solution S3a after isomerization treatment of the mother liquor D and the crude solution A to crystallization and solid-liquid separation treatment to obtain solution H1 or solution H2 from the obtained mother liquor S2b Here, the solution H1 in (III) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the mother liquor S2b into phenol and isopropenylphenol under conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. Further, the solution H2 in (III) is a solution obtained by decomposing bisphenol A contained in the mother liquor S2b into phenol and acetone under conditions for decomposing bisphenol A.

[0105] Hereinafter, taking the case of obtaining solution H1 or solution H2 from the mixture G containing the crude solution A and the mother liquor D (Figure 2) as an example, step H will be described in more detail.

[0106] Step H is a step of obtaining solution H1 containing bisphenol A obtained by treating the mixture G under conditions for decomposing bisphenol A and then recombining, or solution H2 containing decomposition products obtained by treating the mixture G under conditions for decomposing bisphenol A.

[0107] Further, in step H, usually, after treating the mixture G under conditions for decomposing bisphenol A, or while treating, distillation is performed to recover a fraction h containing decomposition products and remove the residue. The amount of the residue to be removed is appropriately adjusted according to the amount of the mixture G subjected to step H.

[0108] In Step H, when treating the mixture G under conditions for decomposing bisphenol A, the decomposition rate of bisphenol A in the mixture G is preferably 20 mol% or more, more preferably 30 mol% or more. As described above, in Step H, the decomposition product is evaporated by distillation. At this time, the components that have not been decomposed remain in the residue without evaporating. If the decomposition rate is too low, the components remaining in the residue without evaporating increase. Since this component becomes waste, it is not preferable. The decomposition rate of bisphenol A in the mixture G can be determined as the amount of the decomposition product contained in the fraction h with respect to the amount of bisphenol A in the mixture G (number of moles of the decomposition product / number of moles of bisphenol A in the mixture G × 100 (%)). For example, in Step H1 described later, it can be determined as the amount of isopropenylphenol contained in the fraction h1 with respect to the amount of bisphenol A in the mixture G.

[0109] The conditions for decomposing bisphenol A are any selected from the group consisting of alkaline conditions for alkaline decomposition of bisphenol A in the presence of a basic catalyst, acidic conditions for acid decomposition of bisphenol A in the presence of an acid catalyst, and supercritical water conditions for decomposing bisphenol A in supercritical water.

[0110] Examples of the basic catalyst that can be used when alkaline decomposing bisphenol A under alkaline conditions include hydroxides, oxides, carbonates of alkali metals such as sodium and potassium, various phenol salts, hydroxides, oxides, carbonates of alkaline earth metals such as calcium and magnesium, and various phenol salts. Among them, sodium hydroxide or potassium hydroxide is preferable.

[0111] Examples of the acid catalyst that can be used when acid decomposing bisphenol A under acidic conditions include alkylsulfonic acids such as methanesulfonic acid, aromatic sulfonic acids such as toluenesulfonic acid, phenolsulfonic acid, and cresolsulfonic acid, inorganic acids such as sulfuric acid, hydrogen chloride, phosphoric acid, nitric acid, and phosphinic acid, titanium oxide, zirconium oxide, acidic alumina, etc. Among them, sulfonic acid is preferable, aromatic sulfonic acid is more preferable, and toluenesulfonic acid is even more preferable.

[0112] "Supercritical water" used for the supercritical water decomposition of bisphenol A refers to water in a state above the critical point of water (374°C, 218 atm).

[0113] Hereinafter, the case of treating the mixed solution G under alkaline conditions, acidic conditions, and supercritical water conditions will be specifically described with reference to FIGS. 6 to 9.

[0114] (i) Alkaline decomposition Step H1 shown in FIG. 6, step H1a shown in FIG. 7, and step H2 shown in FIG. 8 have a step of alkaline decomposing bisphenol A in the mixed solution G in the presence of a basic catalyst.

[0115] [Step H1] Step H1 shown in FIG. 6 is an example of a step of obtaining a solution H1 containing bisphenol A obtained by recombining after treating the mixed solution G under conditions for decomposing bisphenol A. Step H1 includes an alkaline decomposition and distillation step of performing distillation while treating the mixed solution G under alkaline conditions for decomposing bisphenol A to obtain a fraction h1 containing phenol and isopropenylphenol as decomposition products, and a recombination step of recombining phenol and isopropenylphenol contained in the fraction h1 to generate bisphenol A. Since the reaction activity of isopropenylphenol generated by decomposing bisphenol A is high, if it is not rapidly recombined, it will form condensates other than bisphenol A. By treating the mixed solution G under alkaline conditions for decomposing bisphenol A and performing distillation while decomposing bisphenol A as in step H1, the generated isopropenylphenol rapidly evaporates and is supplied to the recombination step, so that side reactions of isopropenylphenol can be suppressed.

[0116] (Alkaline decomposition and distillation step) The alkali decomposition and distillation process can be carried out, for example, using a reactive distillation apparatus having a reaction tank at the bottom and a distillation column at the top. The mixed liquid G and the basic catalyst are transferred to the reaction tank at the bottom and heated to decompose bisphenol A contained in the mixed liquid G into phenol and isopropenylphenol. At this time, incomplete decomposition products of the polycarbonate resin (polymers such as dimers and trimers of bisphenol A) and isomers of bisphenol A (2,4-bisphenol), etc. are also decomposed into phenol and isopropenylphenol. In addition, impurities such as chroman compounds undergo a heavyweight reaction and are converted into high-boiling point substances (compounds having a boiling point higher than that of bisphenol A). In order to efficiently decompose bisphenol A etc. into phenol and isopropenylphenol, the water content of the mixed liquid G is usually adjusted to 0.01 mass% or less.

[0117] The temperature of the alkali decomposition and distillation (i.e., the temperature of the reaction tank) is preferably carried out at 180 °C or higher, more preferably at 200 °C or higher. Also, it is preferably carried out at 350 °C or lower, preferably at 300 °C or lower. In addition, the alkali decomposition and distillation is usually carried out at a pressure in the tower of 0.6 kPa to normal pressure, and can preferably be carried out under the conditions of 13 to 20 kPa.

[0118] The phenol and isopropenylphenol generated by the decomposition evaporate, are withdrawn from the top of the reaction tower, recovered as fraction h1, and transferred to the reaction tank where the recombination step is carried out. At this time, phenol may be supplied to the reaction tank where the recombination step is carried out together with fraction h1 so that the phenol and isopropenylphenol are in a predetermined ratio. Also, in the reaction liquid remaining in the reaction tank without evaporating, high-boiling point substances and substances that cause coloring of bisphenol A are concentrated. By withdrawing this reaction liquid from the bottom of the reaction tower, the residue is removed.

[0119] The fraction h1 preferably contains 1.0 mass% or more of isopropenylphenol. If the content of isopropenylphenol in the fraction h1 is less than 1.0 mass%, the recovery amount of bisphenol A after recombination will decrease. Further, the fraction h1 preferably contains 50 mass% or less of isopropenylphenol, more preferably 30 mass% or less. This is because if the content of isopropenylphenol is too high, it will react to form condensates other than bisphenol A.

[0120] Moreover, the fraction h1 preferably consists of isopropenylphenol and phenol, and the content of phenol in the fraction h1 is preferably 99 mass% or less. Also, it is preferably 50 mass% or more, and more preferably 70 mass% or more.

[0121] (Recombination step) In the recombination step, phenol and isopropenylphenol are brought into contact with an acid catalyst to be recombined to produce bisphenol A. As a result, phenol and isopropenylphenol condense to form bisphenol A, and a solution H1 containing bisphenol A is obtained. As the acid catalyst for recombination, a sulfonic acid type strongly acidic cation exchange resin is preferred, and the recombination can be carried out, for example, in a reaction apparatus filled with a sulfonic acid type strongly acidic cation exchange resin.

[0122] The reaction temperature is generally 45 to 130°C, preferably 50 to 100°C. Also, the contact time with the acid catalyst is generally 5 to 200 minutes, preferably 15 to 120 minutes.

[0123] The resulting solution H1 preferably contains 1.0% by mass or more of bisphenol A. If the content of bisphenol A in solution H1 is less than 1.0% by mass, more components other than bisphenol A are generated, increasing the impurities contained in bisphenol A, and the quality of bisphenol A obtained in step E tends to deteriorate. Further, solution H1 preferably contains 50% by mass or less of bisphenol A, more preferably 40% by mass or less. This is because if the content of bisphenol A is too high, the generated bisphenol A precipitates, and the piping for transferring solution H1 from the reaction tank where recombination is performed to the reactor for performing step B and / or step C is likely to be blocked.

[0124] Further, step H1 may have a step of decomposing the residue (the reaction solution remaining in the reaction tank without evaporation) with an acid catalyst. Thereby, those not decomposed in the alkali decomposition / distillation step are decomposed to generate phenol. For example, as in step H1a shown in FIG. 7, after decomposing the residue at 150 to 300° C. in the presence of an acid catalyst, the resulting reaction solution h1b containing phenol is distilled (temperature 150 to 300° C., pressure 0.1 kPa to 10 kPa) to recover phenol, and this phenol can also be returned to step B and / or step C. Examples of the acid catalyst at this time include aromatic sulfonic acids such as p-toluenesulfonic acid. Further, since the residue is basic, the amount of the acid catalyst mixed to decompose the residue under acidic conditions is controlled.

[0125] [Step H2] The step H2 shown in FIG. 8 is an example of a step of obtaining a solution H2 containing a decomposition product obtained by treating the mixed solution G under conditions for decomposing bisphenol A. Step H2 includes an alkali hydrolysis step of treating the mixed solution G under alkaline conditions for hydrolyzing bisphenol A to obtain a reaction solution h2 containing acetone and phenol, and an acetone / phenol recovery step of recovering acetone and / or phenol in the reaction solution h2 obtained in the alkali hydrolysis step and removing the residue. Such step H2 is preferable because it can efficiently separate the water, basic catalyst, acetone, phenol, and residue contained in the reaction solution h2.

[0126] (Alkaline hydrolysis step) In the alkaline hydrolysis step, for example, the mixture G, the basic catalyst, and water are transferred to a reaction apparatus and heated to decompose bisphenol A contained in the mixture G into acetone and phenol. At this time, incomplete decomposition products of the polycarbonate resin (polymers such as dimers and trimers of bisphenol A) and isomers of bisphenol A (2,4-bisphenol), etc. are also decomposed into phenol and acetone. In addition, impurities such as chroman compounds undergo a heavyweight reaction and are converted into high-boiling point substances (compounds having a boiling point higher than that of bisphenol A). Thereby, a reaction solution h2 containing acetone, phenol, impurities, etc. is obtained.

[0127] If the amount of water supplied to the reaction apparatus together with the mixture G is too large, the decomposition efficiency will decrease. If it is too small, the components that cannot be decomposed will increase, and the alkaline hydrolysis rate will tend to decrease significantly. The mass ratio of water to the mixture G (mass of water / mass of mixture G) is preferably 1 or more, more preferably 1.5 or more. Also, it is preferably 300 or less, more preferably 100 or less.

[0128] The hydrolysis temperature is preferably 180 °C or higher, more preferably 200 °C or higher. Also, it is preferably 350 °C or lower, more preferably 300 °C or lower. Also, the hydrolysis pressure is usually the vapor pressure at that temperature.

[0129] The reaction solution h2 preferably contains 0.1 mass% or more of acetone. If the acetone content in the reaction solution h2 is less than 1.0 mass%, it becomes difficult to appropriately recover acetone. Also, the reaction solution h2 preferably contains 30 mass% or less of acetone, more preferably 20 mass% or less. This is because if the acetone content is too high, acetone will self-condense and the acetone recovery rate will decrease.

[0130] (Acetone·Phenol Recovery Step) In the acetone - phenol recovery process, first, the reaction solution h2 obtained in the alkali hydrolysis process is neutralized and distilled to recover acetone. In the reaction solution h2a that remains without evaporation, phenol, impurities, etc. are concentrated. Next, the phenol in the reaction solution h2a is subjected to solvent extraction to obtain an organic phase h2b containing phenol, and then the organic phase h2b is distilled to recover phenol. Also, impurities can be removed by removing the residue remaining after the distillation of phenol. The recovered acetone and phenol are respectively used as solution H2 and supplied to process B and / or process C.

[0131] Specifically, the reaction solution h2 is neutralized and transferred to an acetone recovery distillation column, and acetone is distilled under the conditions of a temperature of 30 - 200°C and a pressure of 0.1 - 100 kPa, and the acetone is withdrawn from the top of the column. Also, the reaction solution h2a (bottom liquid) in the distillation column is transferred to a solvent extraction device.

[0132] The reaction solution h2a is treated with a water - immiscible organic solvent in a solvent extraction device to obtain an organic phase h2b containing phenol and an aqueous phase, and these are withdrawn separately. Examples of the water - immiscible organic solvent include ethers such as tert - butyl methyl ether, tert - amyl ethyl ether, diisopropyl ether; ketones such as methyl ethyl ketone, methyl isobutyl ketone; and acetate esters such as propyl acetate, butyl acetate, pentyl acetate, hexyl acetate.

[0133] The withdrawn organic phase h2b containing phenol is transferred to a phenol recovery distillation column, and phenol is distilled under the conditions of a temperature of 100 - 300°C and a pressure of 0.1 - 10 kPa, and the phenol is withdrawn from the top of the column. Also, the residue (bottom liquid) remaining in the phenol recovery distillation column is withdrawn from the bottom of the column.

[0134] Also, in the acetone - phenol recovery process, acetone can be distilled from the reaction solution h2, the remaining reaction solution after extraction can be neutralized, and then phenol can be distilled to recover acetone and phenol respectively.

[0135] (ii) Acid decomposition Step H3 shown in Fig. 9 is to treat the mixture G under acidic conditions for decomposing bisphenol A. In step H3, a solution H2 containing decomposition products obtained by treating the mixture G under conditions for decomposing bisphenol A is obtained.

[0136] [Step H3] Step H3 shown in Fig. 9 includes an acid decomposition step of treating the mixture G under acidic conditions for decomposing bisphenol A to obtain a reaction solution h3 containing phenol, and a phenol recovery step of distilling the reaction solution h3 obtained in the acid decomposition step to recover a fraction containing phenol and removing residues. Such step H3 is preferable because it can improve the recovery rate of phenol. The temperature of the acid decomposition is preferably carried out at 100°C or higher, more preferably at 150°C or higher. Also, it is preferably carried out at 300°C or lower, more preferably at 250°C or lower. Further, the pressure of the acid decomposition can be set to 0.1 - 10 kPa. The distillation of the reaction solution h3 obtained in the acid decomposition step can be carried out at a temperature of 150 - 300°C and a pressure of 0.1 - 10 kPa.

[0137] (iii) Supercritical water decomposition Step H4 shown in Fig. 10 is to treat the mixture G under supercritical water conditions for decomposing bisphenol A. By using supercritical water, bisphenol A can be decomposed into phenol and acetone.

[0138] [Step H4] Step H4 shown in Fig. 10 includes a supercritical water decomposition step of treating the mixture G under supercritical water conditions for decomposing bisphenol A to obtain a reaction solution h4 containing phenol, and a phenol recovery step of distilling the reaction solution h4 obtained in the supercritical water decomposition step to recover a fraction containing phenol and removing residues. Such step H4 is preferable because it can be decomposed without using a catalyst. In the supercritical water decomposition step, the mixture G and water are added into the reaction device, and by setting the temperature and pressure above the critical point of water to make water in a supercritical state, bisphenol A can be decomposed in supercritical water. Specifically, it can be set at a temperature of 300 - 700°C, preferably 350 - 500°C. The distillation of the reaction solution h4 obtained in the supercritical water decomposition process can be carried out at a temperature of 150 to 300 °C and a pressure of 0.1 to 10 kPa.

[0139] [Process I] Process I is a process of supplying the solution H1 or the solution H2 obtained in Process H to Process B and / or Process C. For example, a pipe connecting a reaction apparatus where a recombination reaction is carried out, an acetone recovery distillation column, a phenol recovery distillation column, and a condensation reaction apparatus where Process B is carried out is provided, and the solution H1 withdrawn from the reaction apparatus where the recombination reaction is carried out, the acetone withdrawn from the acetone recovery distillation column, and the phenol withdrawn from the phenol recovery distillation column can be supplied to Process B through this pipe.

[0140] In addition, a pipe connecting a reaction apparatus where a recombination reaction is carried out, an acetone recovery distillation column, a phenol recovery distillation column, and a distillation column where Process C is carried out is provided, and the solution H1 withdrawn from the reaction apparatus where the recombination reaction is carried out, the acetone withdrawn from the acetone recovery distillation column, and the phenol withdrawn from the phenol recovery distillation column can be supplied to Process C through this pipe.

[0141] Note that the crude solution A and the mother liquor D may be separately supplied to the apparatus for carrying out Process H for treatment, or may be separately treated in Process H without mixing the crude solution A and the mother liquor D. Further, (II) is the same as the method for obtaining the solution H1 or the solution H2 in (I) except that the mother liquor S2a and the crude solution A are used. (III) is the same as the method for obtaining the solution H1 or the solution H2 in (I) except that the mother liquor S2b is used.

[0142] <Method for producing second bisphenol A> The present invention relates to a method for producing bisphenol A having the following Processes B to F, Process H, and Process I (hereinafter, may be described as "method for producing second bisphenol A"). Process B: A process of subjecting acetone and phenol to dehydration condensation in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A Process C: A process of distilling off unreacted acetone and water from the reaction solution B obtained in Process B to obtain a concentrated solution C Process D: A process of crystallizing the concentrated solution C obtained in Process C to obtain a slurry solution, and subjecting the slurry solution to solid-liquid separation to obtain a mother liquor D and a cake d Process E: A process of purifying the cake d obtained in Process D to obtain bisphenol A Process F: A process of circulating a part of the mother liquor D obtained in Process D and supplying it to Process B Process H: Any one of the following steps (I) to (III) (I) A process of obtaining a solution H1 or a solution H2 from the crude solution A and a part of the mother liquor D Here, the crude solution A in (I) is obtained by decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then distilling off the solvent from the obtained reaction solution a1. The content of bisphenol A in the crude solution A is less than 90% by mass. Further, the solution H1 in (I) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. Also, the solution H2 in (I) is a solution obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under conditions for decomposing bisphenol A (II) A process of subjecting a part of the mother liquor D to isomerization treatment and crystallization / solid-liquid separation treatment, and obtaining a solution H1 or a solution H2 from the obtained mother liquor S2a and the crude solution A Here, the crude solution A of (II) is obtained by decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then distilling off the solvent from the obtained reaction solution a1. The content of bisphenol A in the crude solution A is less than 90% by mass. Further, the solution H1 of (II) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the mother liquor S2a and the crude solution A into phenol and isopropenylphenol under conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. Also, the solution H2 of (II) is a solution obtained by decomposing bisphenol A contained in the mother liquor S2a and the crude solution A into phenol and acetone under conditions for decomposing bisphenol A. (III) A step of subjecting a solution S3b containing the solution S3a after isomerization treatment of the mother liquor D and the crude solution A to crystallization and solid-liquid separation treatment to obtain the solution H1 or the solution H2 from the obtained mother liquor S2b Here, the crude solution A of (III) is obtained by decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then distilling off the solvent from the obtained reaction solution a1. The content of bisphenol A in the crude solution A is less than 90% by mass. Further, the solution H1 of (III) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the mother liquor S2b into phenol and isopropenylphenol under conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. Also, the solution H2 of (III) is a solution obtained by decomposing bisphenol A contained in the mother liquor S2b into phenol and acetone under conditions for decomposing bisphenol A. Step I: A step of supplying the solution H1 or the solution H2 obtained in Step H to Step B and / or Step C

[0143] The method for producing the second bisphenol A is the same as the method for producing bisphenol A of the present invention, except that the production of the crude solution A may be carried out in a different separate facility that is not integrated with the facility in which Steps B to F, Step H, and Step I are performed. In the method for producing the second bisphenol A, the crude solution A can be produced in the same manner as in Step A of the method for producing bisphenol A of the present invention. Steps B to F, Step H, and Step I of the method for producing the second bisphenol A are the same as Steps B to F, Step H, and Step I of the method for producing bisphenol A of the present invention.

[0144] The crude solution A and a part of the mother liquor D can be mixed to carry out Step H. At this time, the crude solution A and a part of the mother liquor D may be mixed in advance, and the obtained mixed liquid G may be supplied to the apparatus for decomposing bisphenol A in Step H. The mixed liquid G may be appropriately concentrated and then supplied to Step H. Alternatively, the crude solution A and a part of the mother liquor D may be respectively supplied to the apparatus for decomposing bisphenol A in Step H, and the decomposition reaction may be carried out while adjusting the mixed liquid G in the apparatus. The mixing ratio and the like of the crude solution A and a part of the mother liquor D are the same as in Step G of the method for producing bisphenol A of the present invention. Further, the crude solution A and the mother liquor D may be separately treated in Step H without mixing.

[0145] Also, a part of the mother liquor D may be used in Step H after being subjected to treatments such as isomerization, concentration, and crystallization / solid-liquid separation. For example, a step f1 of isomerizing the reaction by-products in the mother liquor D obtained in Step D or a step f2 of subjecting the solution S3 containing the solution S3a after isomerization treatment in Step f1 to crystallization and solid-liquid separation may be carried out. By Step f1 and Step f2, mother liquor S2a and mother liquor S2b can be obtained. Step f1 and Step f2 are the same as in the method for producing bisphenol A of the present invention. In (II) and (III), Step G and Step H can be carried out in the same manner as in (I) using this mother liquor S2a and mother liquor S2b.

[0146] <Use of Bisphenol A> The bisphenol A obtained by the method for producing bisphenol A of the present invention or the method for producing secondary bisphenol A (hereinafter sometimes referred to as "the bisphenol A of the present invention") can be used as a component, curing agent, additive or precursor thereof, etc. of various thermoplastic resins such as polyether resin, polyester resin, polyarylate resin, polycarbonate resin, polyurethane resin, acrylic resin, etc. and various thermosetting resins such as epoxy resin, unsaturated polyester resin, phenol resin, polybenzoxazine resin, cyanate resin, etc. used in various applications such as optical materials, recording materials, insulating materials, transparent materials, electronic materials, adhesive materials, heat-resistant materials, etc. Further, it is also useful as an additive such as a developer, a fading inhibitor, a bactericide, a fungicide and a mold inhibitor for heat-sensitive recording materials and the like.

[0147] Among these, since good mechanical properties can be imparted, it is preferably used as a raw material (monomer) for thermoplastic resins and thermosetting resins, and more preferably used as a raw material for polycarbonate resins and epoxy resins. Further, it is also preferably used as a developer, and more preferably used in combination with a leuco dye and a discoloration temperature adjuster.

[0148] <Method for Producing Polycarbonate Resin> The present invention also relates to a method for producing a polycarbonate resin (hereinafter sometimes referred to as "the method for producing a polycarbonate resin of the present invention") for producing a polycarbonate resin using the bisphenol A obtained by the method for producing bisphenol A of the present invention or the method for producing secondary bisphenol A.

[0149] The polycarbonate resin obtained by the method for producing a polycarbonate resin of the present invention can be produced, for example, by a method of subjecting the bisphenol A of the present invention and a carbonic acid diester such as diphenyl carbonate to a transesterification reaction in the presence of an alkali metal compound and / or an alkaline earth metal compound. The above transesterification reaction can be carried out by appropriately selecting a known method. An example using the bisphenol A of the present invention and diphenyl carbonate as raw materials will be described below.

[0150] In the method for producing the above polycarbonate resin, it is preferable to use an excessive amount of diphenyl carbonate with respect to the bisphenol A of the present invention. The amount of diphenyl carbonate used with respect to the bisphenol A is preferably large in that the produced polycarbonate resin has few terminal hydroxyl groups and excellent thermal stability of the polymer, and is preferably small in that the transesterification reaction rate is high and it is easy to produce a polycarbonate resin having a desired molecular weight. From these facts, the amount of diphenyl carbonate used per 1 mol of bisphenol is usually 1.001 mol or more, preferably 1.002 mol or more, and is usually 1.3 mol or less, preferably 1.2 mol or less.

[0151] As a method for supplying the raw materials, the bisphenol A and diphenyl carbonate of the present invention can be supplied as solids, but it is preferable to supply one or both of them in a molten state in a liquid state.

[0152] When producing a polycarbonate resin by a transesterification reaction between diphenyl carbonate and bisphenol A, a transesterification catalyst is usually used. In the method for producing the above polycarbonate resin, it is preferable to use an alkali metal compound and / or an alkaline earth metal compound as this transesterification catalyst. These may be used alone, or two or more kinds may be used in combination in any combination and ratio. Practically, it is desirable to use an alkali metal compound.

[0153] The amount of catalyst used per 1 mol of bisphenol A or diphenyl carbonate is usually 0.05 μmol or more, preferably 0.08 μmol or more, more preferably 0.10 μmol or more, and is usually 100 μmol or less, preferably 50 μmol or less, more preferably 20 μmol or less. When the amount of the catalyst used is within the above range, it is easy to obtain the polymerization activity necessary for producing a polycarbonate resin having a desired molecular weight, and it is easy to obtain a polycarbonate resin having excellent polymer hue, no excessive branching of the polymer, and excellent fluidity during molding.

[0154] In order to produce a polycarbonate resin by the above method, it is preferable to continuously supply both of the above raw materials to a raw material mixing tank and continuously supply the obtained mixture and a transesterification catalyst to a polymerization tank.

[0155] In the production of a polycarbonate resin by the transesterification method, usually, both raw materials supplied to the raw material mixing tank are uniformly stirred and then supplied to a polymerization tank to which a catalyst is added, and a polymer is produced.

Examples

[0156] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0157] [Raw Materials and Reagents] As the polycarbonate resin, polycarbonate resin "NOVAREX (registered trademark) M7027BF" of Mitsubishi Chemical Engineering Plastics Corporation was used. As phenol, toluene, sodium hydroxide, potassium hydroxide, hydrochloric acid, acetonitrile, and cesium carbonate, reagents of Fujifilm Wako Pure Chemical Corporation were used. As diphenyl carbonate, a product of Mitsubishi Chemical Corporation was used.

[0158] [Preparation of Cation Exchange Resin] Cation exchange resin A: Diaion (registered trademark) SK104 completely substituted with phenol was obtained according to Reference Example 1 described in Patent Document JP-A-2012-201619. Cation exchange resin B: A 2-(2-mercaptoethyl)pyridine-modified strong acid type cation exchange resin was obtained according to Example 1 described in Patent Document WO2012-108385.

[0159] [Analysis] Confirmation of the production of bisphenol A, quantification of its purity, undecomposed substances of the polycarbonate resin, and components considered to be stabilizers (components other than phenol and bisphenol A) were performed by high performance liquid chromatography according to the following procedures and conditions. · Equipment: LC-2010A manufactured by Shimadzu Corporation, 5μm 150mm×4.6mm ID manufactured by Waters · Method: Low pressure gradient method · Analysis temperature: 40°C · Eluent composition: Solution A Acetonitrile Solution B Solution of 85% phosphoric acid: water = 1 mL: 999 mL At the analysis time of 0 minutes, Solution A: Solution B = 35:65 (volume ratio, the same below). After the eluent composition was set to Solution A: Solution B = 35:65 from the analysis time of 0 to 5 minutes, it was gradually changed to Solution A: Solution B = 90:10 from the analysis time of 5 to 40 minutes. · Flow rate: 0.85 mL / min · Detection wavelength: 280 nm

[0160] Analysis of dimethyl carbonate was performed by gas chromatography according to the following procedures and conditions. · Equipment: GC-2014 manufactured by Shimadzu Corporation Agilent DB-1 0.530mm×30m 1.5μm · Detection method: FID · Vaporization chamber temperature: 230°C · Detector temperature: 300°C · From the analysis time of 0 to 5 minutes, the column temperature was maintained at 50°C. From the analysis time of 5 to 30 minutes, the column temperature was gradually increased to 280°C. From the analysis time of 30 to 40 minutes, the column temperature was maintained at 280°C. · Quantification method: Internal standard method using biphenyl as the internal standard

[0161] [Viscosity average molecular weight (Mv)] The viscosity average molecular weight (Mv) was calculated by dissolving the polycarbonate resin in methylene chloride (concentration 6.0 g / L), measuring the specific viscosity (ηsp) at 20°C using an Ubbelohde viscometer tube, and using the following formula. ηsp / C = [η](1 + 0.28ηsp) [η]=1.23×10 -4 Mv 0.83

[0162] [Melt color of bisphenol] The melt color of bisphenol was measured by putting 1 g of bisphenol A and 19 g of diphenyl carbonate into a test tube "P-24" (2 mm φ × 200 mm) manufactured by Nippon Denshikagaku Glass Co., Ltd., melting at 174 °C for 30 minutes, and using "OME7700" manufactured by Nippon Denshoku Industries Co., Ltd. to measure the Hazen color number. The Hazen color number of bisphenol A was calculated by multiplying the obtained Hazen color number by the dilution rate with diphenyl carbonate.

[0163] [Measurement of pH] The pH was measured using a pH meter "pH METER ES-73" manufactured by Horiba, Ltd. on the aqueous phase at 25 °C taken out from the flask.

[0164] [Example 1] [Step A-1] [PC decomposition step] Into a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer, under a nitrogen atmosphere, polycarbonate resin (80 g, since the repeating unit of the polycarbonate resin is 254 g / mol, 80 g ÷ 254 g / mol = 0.315 mol), water (30 g), phenol (250 g), and a 25 mass% aqueous sodium hydroxide solution (320 g) were put at room temperature. The reaction solution was in a slurry state.

[0165] Thereafter, the internal temperature was raised to 80 °C and reacted for 5 hours while maintaining 80 °C to obtain a reaction solution a1 (a homogeneous solution).

[0166] [Neutralization step] After adding toluene (200 g) to the obtained reaction solution a1, when 35 mass% hydrochloric acid was added until the aqueous phase reached pH 8.6, carbon dioxide gas was generated.

[0167] Thereafter, stirring was stopped to allow oil-water separation, and the aqueous phase was withdrawn from the flask to obtain organic phase a2. When a part of the obtained organic phase a2 was analyzed for its composition by high performance liquid chromatography, the formation of bisphenol A was confirmed.

[0168] (Concentration step a2) The obtained organic phase a2 was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distillate pipe, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off part of the water, toluene, and phenol to obtain organic phase a2-2.

[0169] The obtained organic phase a2-2 was repressurized with nitrogen, and the internal temperature was slowly lowered to 30 °C to obtain slurry a3. The obtained slurry a3 was filtered to obtain recycled bisphenol A (20 g) (crude solution A).

[0170] The time required to obtain recycled bisphenol A (crude solution A) was 9 hours.

[0171] Incidentally, when a part of the obtained recycled bisphenol A was analyzed for its composition by high performance liquid chromatography, it was found to contain 66.4% by mass of bisphenol A. Further, components considered to be undegraded products of the polycarbonate resin and stabilizers were contained in an amount of 0.3% by mass in terms of bisphenol A.

[0172] [Step B-1a] to [Step D-1a], [Step F-1a] According to Example 1 described in Patent Document JP-A-2005-220071, mother liquor D was obtained. The composition of the obtained mother liquor D was 83% by mass of phenol, 10% by mass of bisphenol A, and 7% by mass of other components.

[0173] [Step G-1a] The mother liquor D (100 g) and the recycled bisphenol A (20 g) (crude solution A) obtained in Step A-1 were placed in a distillation apparatus equipped with a thermometer, a stirring blade, a distillate pipe, an oil bath, and a pressure regulator. Next, the temperature was gradually raised to 180°C, and while observing the distillate amount, the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off phenol (19 g) to obtain a mixed solution G. Thereafter, the pressure was restored with nitrogen. The bisphenol A contained in the mixed solution G was 23 g (100 g × 10.0 mass% + 20 g × 66.4 mass% = 23 g).

[0174] [Step H-1a] (Alkaline decomposition and distillation step) To the mixed solution G, an aqueous sodium hydroxide solution (0.4 g) of 25 mass% was added, and a full vacuum was applied. Thereafter, the temperature of the oil bath was raised to 230°C to obtain a distillate h1 (80 g). When a part of the obtained distillate h1 was analyzed by high performance liquid chromatography, it was found that it contained 93 mass% of phenol and 7 mass% of isopropenylphenol. The decomposition rate of bisphenol A in the alkaline decomposition and distillation step was 41% (80 g × 7 mass% ÷ 134 g / mol ÷ 23 g × 228 g / mol × 100% = 41%). The obtained still residue was discarded.

[0175] (Recombination step) The cation exchange resin A (1 g) was placed in a round-bottom flask equipped with a stirring blade, a distillate pipe, and a water bath. The obtained distillate h1 (80 g) was quickly added to this round-bottom flask and reacted at 70°C for 2 hours. Thereafter, decantation was performed to remove the cation exchange resin A to obtain a solution H1. When a part of the obtained solution H1 was analyzed by high performance liquid chromatography, it was found that it contained 11 mass% of bisphenol A.

[0176] [Step I-1a], [Step B-1b] The above solution H1 (20 g), the above mother liquor D (170 g), the reagent phenol (2 g), the reagent acetone (8 g), and the cation exchange resin B (2 g) were placed in a round-bottom flask equipped with a stirring blade, a distilling tube, and a water bath, and reacted at 70 °C for 5 hours. Thereafter, decantation was performed to remove the cation exchange resin B, and a reaction solution B was obtained.

[0177] [Step C-1b] The entire amount of the obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distilling tube, an oil bath, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off unreacted acetone, water, and a part of phenol, and a concentrated solution C was obtained.

[0178] [Step D-1b] The obtained concentrated solution C was repressurized with nitrogen, and the internal temperature was slowly decreased to 30 °C to obtain a slurry solution. The obtained slurry solution was filtered to obtain a cake d (11 g).

[0179] [Step E-1b] The obtained cake d (11 g) and toluene (60 g) were placed in a separable flask equipped with a distilling tube and a stirring blade, and dissolved at 80 °C to obtain an organic phase e1. The obtained organic phase e1 was washed 5 times with 50 g of demineralized water to obtain an organic phase e2.

[0180] The obtained organic phase e2 was cooled to 10 °C to obtain a slurry e3. The obtained slurry e3 was filtered to obtain a cake e4.

[0181] The obtained cake e4 was dried with a rotary evaporator to obtain bisphenol A (4.1 g). The Hazen color number of the obtained bisphenol A was APHA 20. Further, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass. In addition, the undecomposed product of the polycarbonate resin and the component considered to be a stabilizer were below the detection limit.

[0182] [Example 2] [Step A-2] (PC decomposition process) Into a jacketed separable flask equipped with a Dimroth condenser, stirring blade, and thermometer, 80 g (0.315 mol) of polycarbonate resin, 30 g of water, 240 g of phenol, and 10 g of triethylamine were placed at room temperature under a nitrogen atmosphere. The reaction solution was in a slurry state.

[0183] Subsequently, the internal temperature was raised to 80 °C, and the reaction was carried out for 5 hours while maintaining the temperature at 80 °C to obtain reaction solution a1 (a homogeneous solution). During the reaction, the generation of carbon dioxide was confirmed.

[0184] When a part of the obtained reaction solution a1 was taken out and its composition was confirmed by high-performance liquid chromatography, the production of bisphenol A was 19.6% by mass. The mass of reaction solution a1 was 80 g + 30 g + 240 g + 10 g = 360 g, and the generated bisphenol was 19.6% by mass × 360 g ÷ 228.29 g / mol = 0.309 mol. The reaction rate was 0.309 mol ÷ 0.315 mol × 100 = 98%.

[0185] (Concentration process a1) The obtained reaction solution a1 was transferred to a distillation apparatus equipped with a thermometer, stirring blade, distillate tube, and pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off a part of water, triethylamine, and phenol to obtain recycled bisphenol A (260 g).

[0186] The time required to obtain recycled bisphenol A was 7 hours.

[0187] When a part of the obtained recycled bisphenol A was taken out and its composition was confirmed by high-performance liquid chromatography, bisphenol A was contained at 27.0% by mass. Also, components considered to be undegraded polycarbonate resin and stabilizers were contained at 0.4% by mass in terms of bisphenol A.

[0188] [Process B-2a] to [Process H-2a], [Process B-2b] to [Process E-2b] Instead of the recycled bisphenol A (20 g) obtained in Step A-1 of Example 1, 50 g of the recycled bisphenol A obtained in Step A-2 was used, and bisphenol A (4.5 g) was obtained in the same manner as in [Step B-1a] to [Step H-1a] and [Step B-1b] to [Step E-1b] of Example 1. The Hazen color number of the obtained bisphenol A was APHA 18. When the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass. In addition, the undegraded product of the polycarbonate resin and the components considered to be stabilizers were below the detection limit.

[0189] <Example 3> [Step A-3] (PC Degradation Step) Into a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer, under a nitrogen atmosphere, polycarbonate resin (80 g, 0.31 mol), phenol (240 g), methanol (23 g, 0.72 mol, molar ratio 0.72 mol÷0.31 mol = 2.3 with respect to the number of moles of carbonate ester of the repeating unit in the polycarbonate resin), and triethylamine (15 g, 15 g÷101 g / mol = 0.15 mol, molar ratio 0.15 mol÷0.31 mol = 0.48 with respect to the number of moles of carbonate ester of the repeating unit in the polycarbonate resin) were placed at room temperature (the liquid volume was 80 g + 240 g + 23 g + 15 g = 358 g).

[0190] Thereafter, the internal temperature was raised to 85°C. Undissolved polycarbonate resin was observed in the reaction solution when 85°C was reached. While maintaining 85°C, the reaction was carried out for 4 hours to obtain a uniform reaction solution a1.

[0191] When a part of the obtained reaction solution a1 was confirmed for its composition by high performance liquid chromatography, it was confirmed that bisphenol A was produced at 19.5% by mass (19.5÷100×358 g÷228 g / mol÷0.31 mol = 99 mol%). Also, when a part of the obtained reaction solution a1 was analyzed by gas chromatography to confirm its composition, it was confirmed that 6.5 mass% of dimethyl carbonate (6.5÷100×358 g÷90 g / mol÷0.31 mol = 83 mol%) was produced.

[0192] (Concentration step a1) The obtained reaction solution a1 was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distillate pipe, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off a part of methanol, dimethyl carbonate, and phenol to obtain recycled bisphenol A (262 g).

[0193] The time required to obtain recycled bisphenol A was 7 hours.

[0194] In addition, when a part of the obtained recycled bisphenol A was analyzed by high performance liquid chromatography to confirm its composition, it was found that it contained 27.1 mass% of bisphenol A. Also, components considered to be undegraded products of the polycarbonate resin and stabilizers were contained in an amount equivalent to 0.4 mass% in terms of bisphenol A.

[0195] [Step B-3a] to [Step H-3a], [Step B-3b] to [Step E-3b] Bisphenol A (4.7 g) was obtained in the same manner as in [Step B-1a] to [Step H-1a], [Step B-1b] to [Step E-1b] of Example 1, except that recycled bisphenol A (50 g) obtained in Step A-3 was used instead of the recycled bisphenol A (20 g) obtained in Step A-1 of Example 1. The Hazen color number of the obtained bisphenol A was APHA 15. Also, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8 mass%. In addition, components considered to be undegraded products of the polycarbonate resin and stabilizers were below the detection limit.

[0196] [Comparative Example 1] In the same manner as in the PC decomposition step, neutralization step, and concentration step a2 of Step A in Example 1, an organic phase a2-2 was obtained.

[0197] The obtained organic phase a2-2 was washed 5 times with 50 g of deionized water to obtain an organic phase a2-3. The obtained organic phase a2-3 was cooled to 20 °C to obtain a slurry. The obtained slurry was filtered to obtain a cake. The obtained cake was dried with a rotary evaporator to obtain bisphenol A (35 g).

[0198] The time required to obtain bisphenol A was 17 hours.

[0199] When the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass. Also, components considered to be undegraded products of the polycarbonate resin and stabilizers were contained at 0.1% by mass in terms of bisphenol A.

[0200] When comparing the bisphenol A obtained in Examples 1 to 3 and Comparative Example 1, the purity of bisphenol A was equivalent. Also, as a result of visual evaluation, the color tone of the phenol A obtained in Examples 1 to 3 was good (colorless and transparent) compared to Comparative Example 1. In the bisphenol A obtained in Comparative Example 1, components considered to be undegraded products of the polycarbonate resin and stabilizers remained at 0.1% by mass in terms of bisphenol A, whereas in the bisphenol A obtained in Examples 1 to 3, components considered to be undegraded products of the polycarbonate resin and stabilizers were not detected, and it is thought that the undegraded products of the polycarbonate resin and stabilizers deteriorated the color tone of bisphenol A.

[0201] <Comparative Example 2> The mother liquor D (170 g), the reagent phenol (2 g), the reagent acetone (8 g), and the cation exchange resin B (2 g) were placed in a round bottom flask equipped with a stirring blade, a distillation tube, and a water bath, and reacted at 70 °C for 5 hours. Then, decantation was performed to remove the cation exchange resin B, and a reaction solution B was obtained.

[0202] The entire amount of the obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distillation tube, an oil bath, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off unreacted acetone, water, and a part of phenol. The pressure was restored with nitrogen to obtain a concentrated solution C (170 g).

[0203] The obtained concentrated solution C (170 g) and the recycled bisphenol A (50 g) obtained in Step A-3 of Example 3 were placed in a round-bottom flask equipped with a stirring blade, a distillation tube, and a water bath, and heated to 80 °C to obtain a mixed solution. The internal temperature was slowly decreased to 30 °C to obtain a slurry (crystallization step). The obtained slurry was filtered to obtain a cake d (15 g).

[0204] The obtained cake d (15 g) and toluene (60 g) were placed in a separable flask equipped with a stirring blade, a distillation tube, and a stirring blade, and dissolved at 80 °C to obtain an organic phase e1. The obtained organic phase e1 was washed 5 times with 50 g of demineralized water to obtain an organic phase e2.

[0205] The obtained organic phase e2 was cooled to 10 °C to obtain a slurry e3. The obtained slurry e3 was filtered to obtain a cake e4.

[0206] The obtained cake e4 was dried with a rotary evaporator to obtain bisphenol A (6 g). The Hazen color number of the obtained bisphenol A was APHA89. Also, when the composition was confirmed by high-performance liquid chromatography, the purity of bisphenol A was 99.5% by mass.

[0207] In addition, the undegraded product of the polycarbonate resin and the component considered to be a stabilizer were 0.08% by mass.

[0208] In Examples 1 to 3 and Comparative Example 2, the liquid for mixing recycled bisphenol A (recycled BPA, crude solution A), the treatment after mixing with recycled bisphenol A (recycled BPA), the Hazen color number of the obtained bisphenol A (BPA), the purity of bisphenol A (BPA), the undegraded product of polycarbonate resin (PC), and the components considered to be stabilizers are summarized in Table 1. From Table 1, it can be seen that by mixing recycled bisphenol A with mother liquor D, performing Step H, and returning to Step B, the Hazen color number of the bisphenol A obtained in Step E is improved, and the undegraded product of polycarbonate resin and the components considered to be stabilizers are below the detection limit. It is considered that the undegraded product of polycarbonate resin and the components considered to be stabilizers were removed together with the kettle residue obtained in Step H.

[0209]

Table 1

[0210] <Example 4> [Step G-4a] 18 g of mother liquor D obtained in Example 1 and 16 g of recycled bisphenol A obtained in Step A-3 of Example 3 were placed in an autoclave equipped with a pressure gauge, a thermocouple, and a stirring blade to obtain a mixed liquid G.

[0211] [Step H-4a] (Alkaline hydrolysis step) Further, 64 g of water and 2 g of sodium hydroxide were added to the autoclave, nitrogen was passed through for substitution, and the autoclave was made airtight. The electric furnace was set to 250 °C, the autoclave was set, and it was heated until the internal temperature reached 250 °C. After reaching 250 °C, it was confirmed that the internal pressure became 3.7 MPa, and the reaction was carried out for 2 hours. Then, the autoclave was removed from the electric furnace and immersed in a washbasin filled with ice water for 1 hour. Then, the autoclave was opened and transferred to an Erlenmeyer flask to obtain a reaction solution h2. A part of the reaction solution h2 was taken out, and when the composition was confirmed by gas chromatography, 1.3 mass% of acetone was confirmed.

[0212] (Acetone-Phenol Recovery Process) 2.0 g of sulfuric acid was added to the reaction solution h2 for neutralization, and then it was fed into a distillation apparatus equipped with a thermometer, a stirring blade, a rectifying column, and a water bath. Under normal pressure, recycled acetone (0.9 g) and the residue in the kettle (reaction solution h2a) were obtained as the initial distillate upon heating.

[0213] The obtained residue in the kettle was completely transferred to a full-jacket separable flask equipped with a thermometer, a stirring blade, and a condenser tube. Diisopropyl ether was added, and phase separation was carried out at 50 °C to remove the aqueous phase, obtaining an organic phase h2b. The obtained organic phase h2b was fed into a simple distillation apparatus equipped with a thermometer and a stirring blade. Under normal pressure, after raising the temperature to distill and recover diisopropyl ether, the pressure was reduced to obtain recycled phenol (20 g).

[0214] [Process B-4b] The mother liquor D (170 g) obtained in Example 1, the recycled phenol (2 g), the recycled acetone (0.9 g), reagent acetone (8.1 g), and cation exchange resin B (2 g) were placed in a round-bottom flask equipped with a stirring blade, a distilling tube, and a water bath, and reacted at 70 °C for 5 hours. Then, decantation was carried out to remove the cation exchange resin B, obtaining a reaction solution B.

[0215] [Process C-4b] The entire amount of the obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distilling tube, an oil bath, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually reduced from normal pressure to 10 kPa to distill off a part of the unreacted acetone, water, and phenol, obtaining a concentrated solution C.

[0216] [Process D-4b] The obtained concentrated solution C was repressurized with nitrogen, and the internal temperature was slowly decreased to 30 °C to obtain a slurry. The obtained slurry was filtered to obtain a cake d (10 g).

[0217] [Process E-4b] The obtained cake d (10 g) and toluene (60 g) were placed in a separable flask equipped with a distillation tube and a stirring blade, and dissolved at 80 °C to obtain an organic phase e1. The obtained organic phase e1 was washed 5 times with 50 g of deionized water to obtain an organic phase e2.

[0218] The obtained organic phase e2 was cooled to 10 °C to obtain a slurry e3. The obtained slurry e3 was filtered to obtain a cake e4.

[0219] The obtained cake e4 was dried with a rotary evaporator to obtain bisphenol A (3.2 g). The Hazen color number of the obtained bisphenol A was APHA 22. Also, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass.

[0220] In addition, undecomposed products of the polycarbonate resin and components considered to be stabilizers were below the detection limit.

[0221] <Example 5> [Step G-5a], [Step H-5a] Recycled bisphenol (1.2 g) obtained in Step A-1 of Example 1, mother liquor D (1.3 g) obtained in Step D-1a of Example 1, and distilled water (3 g) were placed in a reaction tube made of SUS316. Then, after making it airtight, the reaction tube was heated to 400 °C in an electric furnace and decomposed for 1 hour. Then, the reaction tube was removed from the electric furnace and allowed to cool at room temperature. After being sufficiently cooled, the reaction tube was opened to obtain a reaction solution h4.

[0222] This operation was repeated 10 times to obtain a reaction solution h4 (52 g).

[0223] The obtained reaction solution h4 was supplied to a simple distillation apparatus equipped with a stirrer and a thermometer. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa. After distilling off light-boiling components and water, phenol was distilled off to obtain recycled phenol (16 g).

[0224] [Step I-5a], [Step B-5b] The mother liquor D (170 g), the recycled phenol (2 g), and the reagent acetone (9 g) were placed in a round-bottom flask equipped with a stirring blade, a distilling tube, and a water bath, along with the cation exchange resin B (2 g), and reacted at 70°C for 5 hours. Thereafter, decantation was performed to remove the cation exchange resin B, obtaining the reaction solution B.

[0225] [Step C-5b] The entire amount of the obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distilling tube, an oil bath, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually increased to 180°C, and the internal pressure was gradually decreased from normal pressure to 10 kPa to distill off unreacted acetone, water, and a part of phenol, obtaining the concentrated solution C.

[0226] [Step D-5b] The obtained concentrated solution C was repressurized with nitrogen, and the internal temperature was slowly decreased to 30°C to obtain a slurry. The obtained slurry was filtered to obtain the cake d (9 g).

[0227] [Step E-5b] The obtained cake d (9 g) and toluene (60 g) were placed in a separable flask equipped with a distilling tube and a stirring blade, and dissolved at 80°C to obtain the organic phase e1. The obtained organic phase e1 was washed 5 times with 50 g of demineralized water to obtain the organic phase e2.

[0228] The obtained organic phase e2 was cooled to 10°C to obtain the slurry e3. The obtained slurry e3 was filtered to obtain the cake e4.

[0229] The obtained cake e4 was dried with a rotary evaporator to obtain bisphenol A (2.8 g). The Hazen color number of the obtained bisphenol A was APHA 18. Also, when the composition was confirmed by high performance liquid chromatography, the bisphenol A purity was 99.8% by mass. In addition, the undecomposed product of the polycarbonate resin and the component considered to be a stabilizer were below the detection limit.

[0230] [Example 6] [Process G-6a], [Process H-6a] Into a round-bottomed flask equipped with a stirring blade, Dimroth condenser tube, and thermometer, recycled bisphenol A (30 g) obtained in Step A-2 of Example 2, mother liquor D (30 g) obtained in Step D-1a of Example 1, and p-toluenesulfonic acid (0.1 g) were placed. The round-bottomed flask was immersed in an oil bath at 200 °C and decomposed for 3 hours. Then, the pressure was gradually reduced to obtain recycled phenol (35 g).

[0231] [Process I-6a], [Process B-6b] The mother liquor D (170 g), the recycled phenol (2 g), and reagent acetone (9 g) were placed into a round-bottomed flask equipped with a stirring blade, a distilling tube, and a water bath, along with cation exchange resin B (2 g), and reacted at 70 °C for 5 hours. Then, decantation was performed to remove the cation exchange resin B, obtaining reaction solution B.

[0232] [Process C-6b] The entire amount of the obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distilling tube, an oil bath, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off unreacted acetone, water, and a part of phenol, obtaining concentrated solution C.

[0233] [Process D-6b] The obtained concentrated solution C was repressurized with nitrogen, and the internal temperature was slowly decreased to 30 °C to obtain a slurry solution. The obtained slurry solution was filtered to obtain cake d (13 g).

[0234] [Process E-6b] The obtained cake d (13 g) and toluene (60 g) were placed into a separable flask equipped with a distilling tube and a stirring blade, and dissolved at 80 °C to obtain organic phase e1. The obtained organic phase e1 was washed 5 times with 50 g of deionized water to obtain organic phase e2.

[0235] The obtained organic phase e2 was cooled to 10 °C to obtain slurry e3. The obtained slurry e3 was filtered to obtain cake e4.

[0236] The obtained cake e4 was dried with a rotary evaporator to obtain bisphenol A (3.1 g). The Hazen color number of the obtained bisphenol A was APHA 15. Also, when the composition was confirmed by high performance liquid chromatography, the bisphenol A purity was 99.8% by mass. In addition, undecomposed substances of the polycarbonate resin and components considered to be stabilizers were below the detection limit.

[0237] <Example 7> [Step H-7a] 1 g of p-toluenesulfonic acid was added to the distillation apparatus containing the kettle residue discarded in Example 1, decomposed at 190 °C for 2 hours, and then 5 g of recycled phenol was distilled off under full vacuum.

[0238] [Step I-7a], [Step B-7b] The mother liquor D (170 g), the recycled phenol (2 g), reagent acetone (9 g), and cation exchange resin B (2 g) were placed in a round bottom flask equipped with a stirring blade, a distilling tube, and a water bath, and reacted at 70 °C for 5 hours. Then, decantation was performed to remove cation exchange resin B, and reaction solution B was obtained.

[0239] [Step C-7b] The entire amount of the obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distilling tube, an oil bath, and a pressure regulator. While observing the distillate amount, the internal temperature was gradually raised to 180 °C, and the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off unreacted acetone, water, and a part of phenol, and concentrated liquid C was obtained.

[0240] [Step D-7b] The obtained concentrated liquid C was repressurized with nitrogen, the internal temperature was slowly lowered to 30 °C, and a slurry was obtained. The obtained slurry was filtered to obtain cake d (13 g).

[0241] [Step E-7b] The obtained cake d (13 g) and toluene (60 g) were placed in a separable flask equipped with a distillation tube and a stirring blade, and dissolved at 80 °C to obtain an organic phase e1. The obtained organic phase e1 was washed 5 times with 50 g of deionized water to obtain an organic phase e2.

[0242] The obtained organic phase e2 was cooled to 10 °C to obtain a slurry e3. The obtained slurry e3 was filtered to obtain a cake e4.

[0243] The obtained cake e4 was dried with a rotary evaporator to obtain bisphenol A (2.7 g). The Hazen color number of the obtained bisphenol A was APHA 14. Also, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass. In addition, the undecomposed product of the polycarbonate resin and the component considered to be a stabilizer were below the detection limit.

[0244] In Examples 1 and 4 to 6, the decomposition method of bisphenol A in Step H, the Hazen color number of the obtained bisphenol A, the purity of bisphenol A, the undecomposed product of the polycarbonate resin, and the component considered to be a stabilizer were summarized in Table 2. From Table 2, it can be seen that regardless of whether the decomposition method of bisphenol A in Step H is alkali decomposition, alkali hydrolysis, supercritical water decomposition, or acid decomposition, the Hazen color number of the obtained bisphenol A is improved, and the undecomposed product of the polycarbonate resin and the component considered to be a stabilizer are below the detection limit.

[0245]

Table 2

[0246] <Example 8> A 45-mL glass reaction vessel equipped with a stirrer and a distillation tube was charged with 10.00 g (0.04 mol of bisphenol A), 9.95 g (0.05 mol) of diphenyl carbonate, and 18 μL of a 400 ppm aqueous cesium carbonate solution, which were obtained in Examples 5 to 7. The glass reaction vessel was evacuated to about 100 Pa, and then the operation of repressurizing to atmospheric pressure with nitrogen was repeated three times to replace the inside of the reaction vessel with nitrogen. Thereafter, the reaction vessel was immersed in an oil bath at 220 °C to dissolve the contents.

[0247] The rotation speed of the stirrer was set at 100 revolutions per minute, and while distilling off the phenol by-produced by the oligomerization reaction of bisphenol A and diphenyl carbonate in the reaction vessel, the pressure in the reaction vessel was reduced from 101.3 kPa to 13.3 kPa in absolute pressure over 40 minutes.

[0248] Subsequently, the pressure in the reaction vessel was maintained at 13.3 kPa, and a transesterification reaction was carried out for 80 minutes while further distilling off the phenol.

[0249] Thereafter, the external temperature of the reaction vessel was raised to 290 °C, and the pressure in the reaction vessel was reduced from 13.3 kPa to 399 Pa in absolute pressure over 40 minutes to remove the distilled phenol out of the system.

[0250] Thereafter, the absolute pressure of the reaction vessel was reduced to 30 Pa, and a polycondensation reaction was carried out. When the stirrer of the reaction vessel reached a predetermined stirring power, the polycondensation reaction was terminated. The time from raising the temperature to 290 °C until the polymerization was completed was 120 minutes.

[0251] Next, after the reaction vessel was repressurized to 101.3 kPa in absolute pressure with nitrogen, the pressure was increased to 0.2 MPa in gauge pressure, and the polycarbonate resin was withdrawn from the reaction vessel to obtain a polycarbonate resin. The viscosity-average molecular weight (Mv) of the obtained polycarbonate resin was 26,500.

[0252] <Example 9> In the same manner as in Example 1, mother liquor D and recycled bisphenol A (crude solution A) were obtained. The obtained mother liquor D (100 g) was placed in a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer and kept at 80°C. Further, the obtained recycled bisphenol A (20 g) was placed in an eggplant-shaped flask and immersed in an oil bath at 120°C to be melted. When the melted recycled bisphenol A was put into the jacketed separable flask using a glass funnel with an inner diameter of 5 mm, it could be supplied without clogging, and a homogeneous solution was obtained. The obtained homogeneous solution was placed in a distillation apparatus equipped with a thermometer, a stirring blade, a distillate tube, an oil bath, and a pressure regulator. Next, the temperature was gradually raised to 180°C, and while observing the distillate amount, the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off phenol (19 g) to obtain a mixed solution G. Thereafter, the pressure was restored with nitrogen. The amount of bisphenol A contained in the mixed solution G was 23 g (100 g × 10.0 mass% + 20 g × 66.4 mass% = 23 g).

[0253] (Alkaline decomposition and distillation step) To the mixed solution G, an aqueous sodium hydroxide solution (0.4 g) of 25 mass% was added, and full vacuum was applied. Thereafter, the temperature of the oil bath was raised to 230°C to obtain a fraction h1 (80 g). When a part of the obtained fraction h1 was analyzed for its composition by high performance liquid chromatography, it was found that it contained 93 mass% of phenol and 7 mass% of isopropenylphenol. The decomposition rate of bisphenol A in the alkaline decomposition and distillation step was 41% (80 g × 7 mass% ÷ 134 g / mol ÷ 23 g × 228 g / mol × 100% = 41%). The obtained still residue was discarded.

[0254] <Comparative Example 3> Mother liquor D was obtained in the same manner as in Example 1. Bisphenol A was obtained in the same manner as in Comparative Example 1. The mother liquor D (100 g) was placed in a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer, and kept at 80 °C. Further, the bisphenol A (20 g) was placed in an eggplant-shaped flask and immersed in an oil bath at 120 °C. However, since the purity of bisphenol A was high, it could not be melted. Therefore, the bisphenol A could not be supplied to a distillation apparatus equipped with a thermometer, a stirring blade, a distillate tube, an oil bath, and a pressure regulator using a glass funnel with an inner diameter of 5 mm.

[0255] <Comparative Example 4> Mother liquor D was obtained in the same manner as in Example 1. Bisphenol A was obtained in the same manner as in Comparative Example 1. The mother liquor D (100 g) was placed in a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer. Further, the obtained bisphenol A (20 g) was placed in an eggplant-shaped flask and immersed in an oil bath at 180 °C to be melted. The melted bisphenol A was placed in the jacketed separable flask using a glass funnel with an inner diameter of 5 mm and could be supplied without clogging, obtaining a homogeneous solution. The obtained homogeneous solution was significantly colored reddish-brown because of its high melting temperature. The obtained homogeneous solution was placed in a distillation apparatus equipped with a thermometer, a stirring blade, a distillate tube, an oil bath, and a pressure regulator. Next, the temperature was gradually raised to 180 °C, and while observing the distillate amount, the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off phenol (19 g) to obtain a mixed liquid G. Then, the pressure was restored with nitrogen. The amount of bisphenol A contained in the mixed liquid G was 30 g (100 g × 10.0 mass% + 20 g × 99.8 mass% = 30 g).

[0256] (Alkaline decomposition and distillation step) To the mixed solution G, 25% by mass aqueous sodium hydroxide solution (0.6 g) was added, and a full vacuum was applied. Then, the temperature of the oil bath was raised to 230 °C to obtain a fraction h1 (50 g). When a part of the obtained fraction h1 was analyzed for its composition by high performance liquid chromatography, it was found to contain 97% by mass of phenol and 3% by mass of isopropenylphenol. The decomposition rate of bisphenol A in the alkali decomposition and distillation step was 14% (80 g × 3% by mass ÷ 134 g / mol ÷ 30 g × 228 g / mol × 100% = 14%). The obtained residue in the kettle was discarded.

[0257] In Example 9, Comparative Example 3, and Comparative Example 4, the bisphenol A purity of recycled bisphenol A (content of BPA in the crude solution A), the melting temperature of recycled bisphenol A, the supply feasibility through a glass funnel with an inner diameter of 5 mm, and the decomposition rate of bisphenol A in the alkali decomposition and distillation step are summarized in Table 3. From Table 3, it can be seen that when the bisphenol A purity of recycled bisphenol A is high, recycled bisphenol A cannot be supplied at a low melting temperature. It can also be seen that when the melting temperature is increased to supply recycled bisphenol A, the color tone deteriorates significantly and the quality changes, resulting in a decrease in the decomposition rate of bisphenol A in the alkali decomposition and distillation step.

[0258]

Table 3

[0259] <Comparative Example 5> Into a 200 mL autoclave equipped with an induction stirring blade, a pressure gauge, and a thermometer, 30 g of polycarbonate resin (30 g ÷ 254 g / mol = 0.12 mol), 100 g of phenol, and 1 g of sodium carbonate were placed. After three nitrogen replacements, the autoclave was installed in an electric furnace and reacted at an internal temperature of 250 °C for 3 hours. After the reaction, the autoclave was immersed in ice water to return the internal pressure to normal pressure and obtain a reaction solution. The obtained reaction solution was put into a distillation apparatus equipped with a thermometer, a stirring blade, a distillate pipe, an oil bath, and a pressure regulator. Next, the temperature was gradually raised to 180 °C, and while observing the distillate amount, the internal pressure was gradually lowered from normal pressure to 10 kPa to distill off phenol (100 g) to obtain a concentrated solution.

[0260] (Alkaline decomposition and distillation step) The inside of the distillation apparatus was brought to full vacuum. Then, the temperature of the oil bath was raised to 230 °C to obtain a fraction h1 (5 g). When a part of the obtained fraction h1 was analyzed by high performance liquid chromatography, it was found to be almost phenol, and isopropenylphenol was not detected.

Industrial applicability

[0261] According to the present invention, bisphenol A can be produced from a polycarbonate resin contained in waste plastics or the like, and the obtained bisphenol A is industrially useful because it can be used as a raw material, a curing agent, an additive, etc. for resins such as polycarbonate resins.

Claims

1. A method for producing bisphenol A having the following steps A to F, step H, and step I. Step A: Decompose a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and distill off the solvent from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass. Step B: Dehydration-condense acetone and phenol in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A. Step C: Distill off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C. Step D: Crystallize the concentrated solution C obtained in step C to obtain a slurry solution, and perform solid-liquid separation on the slurry solution to obtain a mother liquor D and a cake d. Step E: Purify the cake d obtained in step D to obtain bisphenol A. Step F: Circulate a part of the mother liquor D obtained in step D and supply it to step B. Step H: Obtain a solution H1 or a solution H2 from the crude solution A and a part of the mother liquor D. Here, the solution H1 is a solution containing bisphenol A obtained by decomposing the bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under the conditions for decomposing bisphenol A, and then recombining the phenol and isopropenylphenol. The solution H2 is a solution containing phenol obtained by decomposing the bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under the conditions for decomposing bisphenol A. Step I: Supply the solution H1 or the solution H2 obtained in step H to step B and / or step C.

2. A method for producing bisphenol A having the following steps A to I. Step A: Decompose a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and distill off the solvent from the obtained reaction solution a1 to obtain a crude solution A having a bisphenol A content of less than 90% by mass. Step B: Dehydration-condense acetone and phenol in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A. Step C: Distill off unreacted acetone and water from the reaction solution B obtained in step B to obtain a concentrated solution C. Step D: Crystallize the concentrated solution C obtained in step C to obtain a slurry solution, and perform solid-liquid separation on the slurry solution to obtain a mother liquor D and a cake d. Step E: Purify the cake d obtained in step D to obtain bisphenol A. Step F: A step of circulating a part of the mother liquor D obtained in Step D and supplying it to the dehydration condensation in Step B Step G: A step of mixing the crude solution A obtained in Step A and a part of the mother liquor D obtained in Step D to obtain a mixed solution G Step H: A step of obtaining a solution H1 containing bisphenol A obtained by treating the mixed solution G under conditions for decomposing bisphenol A and then recombining it, or a solution H2 containing decomposition products obtained by treating the mixed solution G under conditions for decomposing bisphenol A Step I: A step of supplying the solution H1 or solution H2 obtained in Step H to Step B and / or Step C

3. The method for producing bisphenol A according to claim 1 or 2, wherein the crude solution A and a part of the mother liquor D are mixed, and the obtained mixed solution G is supplied to the apparatus for decomposing bisphenol A in Step H

4. The method for producing bisphenol A according to claim 1 or 2, wherein the crude solution A and a part of the mother liquor D are respectively supplied to the apparatus for decomposing bisphenol A in Step H, and the decomposition reaction is carried out while adjusting the mixed solution G in the apparatus

5. The method for producing bisphenol A according to any one of claims 1 to 4, wherein in Step C, further, a part of phenol is distilled off from the reaction solution B to obtain a concentrated solution C

6. The method for producing bisphenol A according to any one of claims 2 to 5, wherein in Step H, when the mixed solution G is treated under conditions for decomposing bisphenol A, the decomposition rate of bisphenol A in the mixed solution G is 30 mol% or more

7. The method for producing bisphenol A according to any one of claims 1 to 6, wherein the conditions for decomposing bisphenol A are any selected from the group consisting of alkaline conditions, acidic conditions, and supercritical water conditions

8. The method for producing bisphenol A according to any one of claims 2 to 7, wherein after or while treating the mixed solution G under conditions for decomposing bisphenol A, distillation is carried out to recover a fraction h containing decomposition products and remove residues

9. Step H is a step of obtaining the solution H1, a decomposition and distillation step of carrying out distillation while treating the mixed solution G under alkaline conditions for decomposing bisphenol A, recovering a fraction h1 containing phenol and isopropenylphenol as decomposition products, and removing residues A method for producing bisphenol A according to any one of claims 2 to 8, comprising a recombination step of recombining phenol and isopropenylphenol contained in the fraction h1 to produce bisphenol A.

10. The method for producing bisphenol A according to claim 9, wherein the fraction h1 contains 1.0% by mass or more of isopropenylphenol.

11. The method for producing bisphenol A according to claim 9 or 10, wherein the solution H1 contains 1% by mass or more of bisphenol A.

12. The method for producing bisphenol A according to any one of claims 9 to 11, wherein the residue is treated in the presence of an acid catalyst and then distilled to recover a fraction h1b of phenol.

13. The step H is a step of obtaining the solution H2, An alkali hydrolysis step of treating the mixture G under alkaline conditions for hydrolyzing bisphenol A to obtain a reaction solution h2 containing acetone and phenol, A method for producing bisphenol A according to any one of claims 2 to 8, comprising an acetone / phenol recovery step of recovering a fraction of acetone and / or a fraction of phenol from the reaction solution h2 obtained in the alkali hydrolysis step and removing the residue.

14. The method for producing bisphenol A according to claim 13, wherein the solution H2 contains 0.1% by mass or more of acetone.

15. The method for producing bisphenol A according to any one of claims 1 to 14, wherein the solvent used in the step A is phenol.

16. The step A is a step of decomposing the polycarbonate resin in the presence of any catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines, and acids to obtain the crude solution A. The method for producing bisphenol A according to any one of claims 1 to 15.

17. The method for producing bisphenol A according to any one of claims 1 to 16, wherein the content of bisphenol A in the crude solution A is 10% by mass or more.

18. The method for producing bisphenol A according to claim 17, wherein the content of bisphenol A in the crude solution A is 20% by mass or more.

19. A method for producing bisphenol A having the following steps B to F, step H, and step I. Step B: A step of subjecting acetone and phenol to dehydration condensation in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A Process C: A process of distilling off unreacted acetone and water from the reaction solution B obtained in Process B to obtain a concentrated solution C Process D: A process of crystallizing the concentrated solution C obtained in Process C to obtain a slurry solution, and subjecting the slurry solution to solid-liquid separation to obtain a mother liquor D and a cake d Process E: A process of purifying the cake d obtained in Process D to obtain bisphenol A Process F: A process of circulating a part of the mother liquor D obtained in Process D and supplying it to Process B Process H: A process of obtaining a solution H1 or a solution H2 from the crude solution A and a part of the mother liquor D Here, the crude solution A is obtained by decomposing a polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then distilling off the solvent from the obtained reaction solution a1. The content of bisphenol A in the crude solution A is less than 90% by mass. The solution H1 is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under the conditions for decomposing bisphenol A, and then recombining phenol and isopropenylphenol. The solution H2 is a solution containing phenol obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under the conditions for decomposing bisphenol A. Process I: A process of supplying the solution H1 or the solution H2 obtained in Process H to Process B and / or Process C

20. The method for producing bisphenol A according to claim 19, wherein the crude solution A and a part of the mother liquor D are mixed, and the obtained mixed solution G is supplied to the apparatus for decomposing bisphenol A in Process H.

21. The method for producing bisphenol A according to claim 19, wherein the crude solution A and a part of the mother liquor D are respectively supplied to the apparatus for decomposing bisphenol A in Process H, and a decomposition reaction is carried out while adjusting a mixed solution G obtained by mixing the crude solution A and a part of the mother liquor D in the apparatus.

22. A method for producing a polycarbonate resin, which uses bisphenol A obtained by the method for producing bisphenol A according to any one of claims 1 to 21 to produce a polycarbonate resin.

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