Manufacturing method of bisphenol A and polycarbonate resin

Abstract

To provide a method for producing bisphenol A that can efficiently remove a coloring component derived from a polycarbonate resin and can produce bisphenol A having excellent color tone.SOLUTION: A method for producing bisphenol A includes: a step G for mixing a crude solution A obtained by a step A of decomposing a polycarbonate resin (PC) with part of a mother liquor D obtained by a step D out of steps B-E, in which bisphenol A (BPA) is produced by dehydration condensation of acetone and phenol, to obtain a liquid mixture G; a step H for obtaining a solution H1 containing bisphenol A, obtained by treating the liquid mixture G under alkaline conditions to decompose the bisphenol A and then re-bonding the same, or a solution H2 containing a decomposition product, obtained by treating the liquid mixture G under alkaline conditions to decompose the bisphenol A; and a step I for feeding the solution H1 or solution H2 obtained in the step H to the step B.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Plastic is produced in large quantities not only in Japan but all over the world because it is easy to use, durable, and inexpensive. Since most of this plastic is used as "disposable," some of it is not properly disposed of and ends up in the environment. Specifically, plastic waste flows from rivers into the ocean, where it is degraded by waves and ultraviolet rays and becomes 5 mm or smaller. Such small plastic waste is called microplastics. Animals and fish mistakenly ingest these microplastics. In this way, plastic waste has a huge impact on ecosystems, and in recent years, it has become a problem around the world as marine plastics. 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] One method for recycling polycarbonate resin is chemical recycling, in which polycarbonate resin is chemically decomposed back to bisphenol A for reuse. Chemical recycling of polycarbonate resin is important as one of the means to solve the marine plastic problem. Polycarbonate resin can be decomposed by various methods such as hydrolysis and alcoholysis, and the resulting bisphenol A can be recovered by crystallization, etc.

[0004] It is also known that bisphenol A obtained by decomposing polycarbonate resin can be incorporated into the general bisphenol A production process described below and purified together to obtain high-purity bisphenol A. [General manufacturing process of bisphenol A] Step 1: A step of reacting acetone with phenol in the presence of an acid catalyst to obtain a reaction liquid containing bisphenol A. Step 2: A step of obtaining a concentrated liquid by distilling and separating the reaction liquid obtained in step 1 Step 3: A step of crystallizing and recovering the concentrated liquid obtained in step 2 to obtain adduct crystals and mother liquor. Step 4: Producing 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 a decomposition product obtained by thermally or chemically decomposing waste plastics is supplied to a concentrated liquid or mother liquor obtained in the general bisphenol A production process described above (Patent Document 1).

[0006] Also, a method is known in which waste polycarbonate is decomposed into isopropenylphenol and the like, and the decomposed product is supplied to step 1 (reaction step) of the general production process of bisphenol A (Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2005-112781 A [Patent Document 2] JP 2006-36668 A Summary of the Invention [Problem to be solved by the invention]

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

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

[0010] Also, as described above, it is possible to supply bisphenol A obtained by decomposing polycarbonate resin to a general bisphenol A manufacturing process 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 polycarbonate resin is alcoholyzed with cyclohexanol, and a heavy fraction that is not distilled out is obtained after distillation under reduced pressure. Thereafter, the heavy fraction that is not distilled out is mixed with a mother liquor obtained by crystallization in a general bisphenol A manufacturing process, and further mixed with a reaction product containing bisphenol A obtained by a condensation reaction in a general bisphenol A manufacturing process, and concentrated. It is described that the obtained concentrated liquid is crystallized, solid-liquid separation is performed to obtain bisphenol A-phenol adduct crystals, and phenol is distilled out from the obtained adduct crystals to obtain high-purity bisphenol A. However, although the obtained bisphenol A is highly pure, there is a problem that its color tone is deteriorated due to the influence of coloring components contained in the heavy fraction that is not distilled out.

[0011] Also, a method of decomposing polycarbonate resin with an alkali to decompose it to isopropenylphenol is possible. For example, according to Example 1 of Patent Document 2, decomposition to isopropenylphenol is performed by a known method, and the obtained decomposition liquid is supplied to a BPA synthesis process in which bisphenol A is synthesized. It is described that a synthetic liquid containing bisphenol A obtained by the BPA synthesis process is supplied to a concentration process in a bisphenol A production process, and high-purity bisphenol A is obtained by a conventional method. However, the isopropenylphenol is a very unstable chemical species, and there was a problem that isopropenylphenol condenses with various components before the decomposition liquid is supplied to a bisphenol A synthesis process in which bisphenol A is synthesized in the bisphenol production process. There was also a problem that the color tone of the obtained bisphenol A was deteriorated due to the condensed components.

[0012] As described above, conventional chemical recycling of polycarbonate resin requires the removal of colored components derived from the polycarbonate resin and the improvement of the color tone of the resulting bisphenol A, and further improvements were required.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing bisphenol A, which can efficiently remove colored components derived from polycarbonate resin and produce bisphenol A having a good color tone. Another object of the present invention is to provide a method for producing polycarbonate resin using the obtained bisphenol. [Means for solving the problem]

[0014] As a result of intensive research to solve the above problems, the present inventors have found a method for producing bisphenol A by decomposing a polycarbonate resin using phenol, distilling off a portion of the phenol after the decomposition to obtain a crude solution containing low-purity bisphenol A, mixing this crude solution with a mother liquor obtained in a bisphenol A production process, and then subjecting the mixture to alkaline decomposition and recombination or alkaline hydrolysis, and recycling the resulting reaction liquid to the bisphenol A production process. They have also found a method for producing a polycarbonate resin using the obtained bisphenol A.

[0015] That is, the present invention relates to the following inventions. <1> A method for producing bisphenol A, comprising the following steps A to I: Step A: A step of decomposing polycarbonate resin to obtain a crude solution A containing bisphenol A. 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 liquid C obtained in step C to obtain a slurry liquid, and subjecting the slurry liquid to solid-liquid separation to obtain a mother liquid 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 with 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 mixture G under alkaline conditions that decompose bisphenol A and then recombining the mixture, or a solution H2 containing a decomposition product obtained by treating the mixture G under alkaline conditions that decompose bisphenol A. Step I: A step of supplying the solution H1 or solution H2 obtained in step H to the dehydration condensation in step B. <2> In the step C, a part of phenol is distilled off from the reaction solution B to obtain a concentrated solution C. <1> A method for producing bisphenol A according to the above. <3> In the step H, when the mixed liquid G is treated under conditions for decomposing bisphenol A, a decomposition rate of bisphenol A in the mixed liquid G is 30 mol % or more. <1> or <2> A method for producing bisphenol A according to the above. <4> The step H comprises a step of performing distillation after or while treating the mixed solution G under alkaline conditions that decompose bisphenol A, recovering a fraction h containing a decomposition product, and removing a residue. <1> from <3> 3. A method for producing bisphenol A according to claim 1 , <5> The step H is a step of obtaining the solution H1, and includes an alkaline decomposition / distillation step of treating the mixed liquid G under alkaline conditions that decompose bisphenol A while performing distillation to obtain a fraction h1 containing decomposition products phenol and isopropenylphenol, and a recombination step of recombining the phenol and isopropenylphenol contained in the fraction h1 to produce bisphenol A. <1> from <4> 3. A method for producing bisphenol A according to claim 1 , <6> The fraction h1 contains 1.0 mass % or more of isopropenylphenol. <5> A method for producing bisphenol A according to the above. <7> The solution H1 contains 1 mass % or more of bisphenol A. <5> or <6> A method for producing bisphenol A according to the above. <8> The step H is a step of obtaining the solution H2, and includes an alkaline 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 an acetone fraction and / or a phenol fraction from the reaction solution h2 obtained in the alkaline hydrolysis step and removing a residue. <1> from <4> 3. A method for producing bisphenol A according to claim 1 , <9> The reaction liquid h2 contains 0.1 mass % or more of acetone. <8> A method for producing bisphenol A according to the above. <10> The method uses phenol to decompose the polycarbonate resin in the step A. <1> from <9> 3. A method for producing bisphenol A according to claim 1 , <11> In the step A, a polycarbonate resin is decomposed in the presence of phenol, and then a part of the phenol is distilled off to obtain the crude solution A. <10> A method for producing bisphenol A according to the above. <12> The crude solution A contains less than 90% by mass of bisphenol A. <1> from <11> 3. A method for producing bisphenol A according to claim 1 , <13> The step A is a step of decomposing the polycarbonate resin in the presence of a catalyst selected from the group consisting of an alkali metal hydroxide, an alkali metal carbonate, an alkylamine, and an acid to obtain the crude solution A. <1> from <12> 3. A method for producing bisphenol A according to claim 1 , <14> The above <1> from <13> 13. A method for producing a polycarbonate resin, comprising the steps of: producing a polycarbonate resin by using bisphenol A obtained by the method for producing bisphenol A according to any one of claims 1 to 22. Effect of the Invention

[0016] According to the present invention, there is provided a method for producing bisphenol A, which can efficiently remove colored components derived from polycarbonate resin and produce bisphenol A having good color tone. Furthermore, there is provided a method for producing polycarbonate resin using the obtained bisphenol. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a flow diagram showing an example of a method for producing bisphenol A according to the present invention. [Diagram 2] FIG. 1 is a flow chart showing an example of step A of the method for producing bisphenol A of the present invention. [Diagram 3] FIG. 1 is a flow chart showing an example of step A of the method for producing bisphenol A of the present invention. [Figure 4] FIG. 1 is a flow diagram showing an example of a method for producing bisphenol A according to the present invention. [Diagram 5] FIG. 2 is a flow chart showing an example of step H of the method for producing bisphenol A of the present invention. [Figure 6] FIG. 2 is a flow chart showing an example of step H of the method for producing bisphenol A of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The following is a detailed description of an embodiment of the present invention, but the description of the constituent elements described below is one example of an embodiment of the present invention, and the present invention is not limited to the following description as long as it does not deviate from the gist of the present invention. Note that when the expression "~" is used in this specification, it is used as an expression including the numerical values ​​or physical property values ​​before and after it.

[0019] <Bisphenol manufacturing method> The present invention relates to a method for producing bisphenol A comprising the following steps A to I (hereinafter, sometimes referred to as "the method for producing bisphenol A of the present invention"). Step A: A step of decomposing polycarbonate resin to obtain a crude solution A containing bisphenol A. 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 liquid C obtained in step C to obtain a slurry liquid, and subjecting the slurry liquid to solid-liquid separation to obtain a mother liquid 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 with 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 mixture G under alkaline conditions that decompose bisphenol A and then recombining the mixture, or a solution H2 containing a decomposition product obtained by treating the mixture G under alkaline conditions that decompose bisphenol A. Step I: A step of supplying the solution H1 or solution H2 obtained in step H to the dehydration condensation in step B.

[0020] FIG. 1 shows a process flow diagram of the method for producing bisphenol A of the present invention. As shown in FIG. 1, one of the features of bisphenol A of the present invention is that the crude solution A obtained by decomposing polycarbonate resin is mixed with the mother liquor D obtained in the production of bisphenol A, and after performing treatment such as decomposition and recombination in step H, it is returned to the step (step B) for producing bisphenol A. The reaction liquid obtained by decomposing waste plastics containing polycarbonate resin may contain stabilizers derived from the decomposed polycarbonate resin, resins other than polycarbonate resin, sebum, dust, foreign matter, etc. Conventionally, such reaction liquid has been supplied to a step in the general production process of bisphenol A in which acetone and phenol are reacted in the presence of an acid catalyst to obtain a reaction liquid containing bisphenol A, a step in which the reaction liquid containing bisphenol A is distilled and separated to obtain a concentrated liquid, and a step in which the concentrated liquid is crystallized and recovered to obtain an adduct crystal and a mother liquor, which may significantly contaminate the production process of bisphenol A and impair the quality of the produced bisphenol A.

[0021] On the other hand, some bisphenol A manufacturing processes incorporate a process for recycling mother liquor. The mother liquor that is recycled to the process for producing bisphenol A by dehydration condensation of acetone and phenol is treated to recover useful components in the mother liquor and reduce impurities before being recycled to the process.

[0022] The crude solution A obtained in step A usually contains, in addition to bisphenol A, heavy component impurities derived from decomposition products of polycarbonate resins and whose structure has not yet been fully 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 necessarily be removed by the same purification method as the production method of bisphenol A. Therefore, when using crude solution A in a general bisphenol A production process, if the step of supplying crude solution A is not appropriate, the purity of the obtained bisphenol A may decrease or the color tone may decrease. The present inventors have discovered that useful components in the mother liquor can be recovered and impurities can be decomposed or removed in crude solution A obtained by decomposing polycarbonate resin under treatment conditions for recovering useful components in the mother liquor and reducing impurities, and further discovered that bisphenol A with excellent color tone can be obtained in high purity by incorporating crude solution A in the step of circulating the mother liquor among the various steps of the bisphenol A production process.

[0023] That is, by mixing crude solution A with mother liquid D and carrying out step H including treatment under alkaline conditions for decomposing bisphenol A, not only bisphenol A in crude solution A but also remaining incomplete decomposition products of polycarbonate resin are decomposed, and the cause of coloring is removed, and then the treated solution is returned to step B, whereby bisphenol A with excellent color tone can be obtained in step E. Furthermore, since the incomplete decomposition products remaining in crude solution A are also decomposed in step H, there is no need to carry out an excessive purification operation in step A, and step A can also be simplified.

[0024] Next, each step of the method for producing bisphenol A will be described.

[0025] [Process A] Step A is a step of obtaining a crude solution A containing bisphenol A by decomposing a polycarbonate resin.

[0026] (Polycarbonate resin (PC)) The polycarbonate resin used in step A includes a polycarbonate resin containing repeating units derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane).

[0027] In addition, the polycarbonate resin may be not only a single polycarbonate resin 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 compositions containing a resin other than the polycarbonate resin include polycarbonate / polyester copolymers, polycarbonate / polyester alloys, polycarbonate / polyarylate copolymers, and polycarbonate / polyarylate alloys. When using a composition containing a resin other than the polycarbonate resin, it is preferable that the main component is polycarbonate resin (the composition contains 50% by mass or more of polycarbonate resin).

[0028] Moreover, the polycarbonate resin may be a mixture of two or more different polycarbonate resins.

[0029] From the viewpoint of chemical recycling, the polycarbonate resin is preferably polycarbonate resin contained in waste plastics. Polycarbonate resin is molded and used in various molded products such as optical components such as headlamps and optical recording media such as optical disks. As waste plastics containing polycarbonate resin, scraps, defective products, used molded products, etc., generated when molding polycarbonate resin into these molded products can be used.

[0030] The waste plastic may be used after washing, crushing, pulverization, etc., as appropriate. Methods for crushing the waste plastic include coarse crushing using a jaw crusher or a rotary crusher to crush to 20 cm or less, medium crushing using a rotary crusher, cone crusher, or mill to crush to 1 cm or less, and crushing using a mill to crush to 1 mm or less, and the like, as long as the size is small enough to be fed to the decomposition tank. In addition, 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 fed to the decomposition tank. In addition, the parts formed of components other than polycarbonate resin, such as other resins of copolymers and polymer alloys, and the layers on the front and back of optical disks, may be removed in advance before use.

[0031] (Method of decomposing polycarbonate resin) The polycarbonate resin can be decomposed by a known method. For example, the polycarbonate resin is decomposed by heating the polycarbonate resin in a solvent to obtain a crude solution A containing bisphenol A.

[0032] Among these, it is preferable to use phenol for decomposing the polycarbonate resin because the dissolution rate of the polycarbonate resin is high, that is, the polycarbonate resin is preferably decomposed in a solvent containing phenol.

[0033] The phenol-containing solvent may contain a solvent other than phenol, but preferably contains phenol as a main component. For example, the mass of phenol in the phenol-containing solvent is preferably 50 mass% or more, and can be appropriately set to 65 mass% or more, 80 mass% or more, 85 mass% or more, 90 mass% or more, etc., depending on the types of other solvents and catalysts.

[0034] In addition, since the decomposition rate of the polycarbonate resin is improved and the polycarbonate resin can be decomposed under mild conditions (for example, normal pressure, about 60 to 150°C) compared with the case where phenol is used alone as a solvent, the phenol-containing solvent is preferably a mixed solvent containing phenol and any solvent selected from the group consisting of water, monohydric alcohols, and dihydric alcohols, and more preferably a mixed solvent containing phenol and water or a mixed solvent containing phenol and a monohydric alcohol. As the monohydric alcohol, a linear alcohol having 1 to 5 carbon atoms, such as methanol, ethanol, or n-butanol, is preferred.

[0035] 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.

[0036] The alkali metal hydroxide is preferably sodium hydroxide or potassium hydroxide, and the alkali metal carbonate is preferably sodium carbonate or potassium carbonate.

[0037] Alkylamine is a compound in which at least one hydrogen atom of ammonia is replaced with an alkyl group. Examples of alkylamine include methylamine, ethylamine, propylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, etc. The alkylamine is preferably a secondary amine or a tertiary amine, and more preferably a tertiary amine.

[0038] The boiling point of the alkylamine is preferably 200° C. or lower, more preferably 160° C. or lower. The lower limit is preferably 10° C. or higher, more preferably 30° C. or higher. If the alkylamine has such a boiling point, it can be removed from the system together with the solvent when a part of the solvent is distilled off by reduced pressure distillation or the like.

[0039] The acid is preferably any one selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, and sulfonic acid. Examples of the sulfonic acid include alkylsulfonic acids such as methanesulfonic acid, and aromatic sulfonic acids such as toluenesulfonic acid.

[0040] The molar ratio of the catalyst to 1 mole of the repeating unit of the polycarbonate resin ((mass [g] of the catalyst used / molecular weight [g / mol] of the catalyst) / (mass [g] of the polycarbonate resin used / molecular weight of the repeating unit [g / mol])) is preferably 0.0001 or more, more preferably 0.0005 or more, and even more preferably 0.0007 or more. If the amount of catalyst used relative to the polycarbonate resin is small, the decomposition speed tends to be slow, the decomposition time tends to be long, and the efficiency tends to deteriorate. In addition, the molar ratio of the catalyst to 1 mole of the repeating unit of the polycarbonate resin is preferably 1 mole or less, more preferably 0.9 or less, and even more preferably 0.8 or less. If the amount of catalyst used relative to the polycarbonate resin used is large, the production efficiency tends to decrease.

[0041] Furthermore, if the crude solution A contains light components, the light components may remain in the solutions H1 and H2 obtained in step H, which may deteriorate the quality of the bisphenol A obtained in step E, such as the color tone. In order to obtain a crude solution A from which light components have been sufficiently removed, it is preferable to obtain a crude solution A by decomposing a polycarbonate resin in the presence of phenol in step A and then partially distilling off the phenol. The light components are components with a lower boiling point than phenol. For example, when a mixed solvent of phenol and water is used, or when an alkylamine or the like is used as a catalyst, the light components are water, alkylamine, and the like. When a mixed solvent of phenol and monohydric alcohol is used, the light components are monohydric alcohol, dialkyl carbonate produced as a by-product together with bisphenol A, and the like.

[0042] (crude solution A) Crude solution A is a composition containing bisphenol A and being liquid at the temperature conditions for step G. Crude solution A may be solid at a temperature lower than the temperature conditions for step G. Since crude solution A obtained in step A is usually transferred to a reaction apparatus in which step G is carried out at 40° C. or higher, crude solution A is a composition containing bisphenol A and being liquid at 40° C. or higher.

[0043] The content of bisphenol A contained in the crude solution A containing bisphenol A obtained in step A (mass of bisphenol A / mass of crude solution A×100(%)) is preferably less than 90% by mass, and is more preferably 85% by mass or less, 80% by mass or less, 70% by mass or less, and 60% by mass or less in that order. In the method for producing bisphenol A of the present invention, even if the crude solution A contains impurities of heavy components such as incomplete decomposition products of polycarbonate resin (multimers such as dimers and trimers of bisphenol A), it is possible to decompose or remove them in step H, so there is no need to purify the crude solution A excessively. In addition, if the content of bisphenol A is too high, the viscosity of the crude solution A increases, making it difficult to transport the crude solution A to mix it with the mother liquor D obtained in step D, or to mix it uniformly with the mother liquor D obtained in step D. In addition, if the content of bisphenol A is too high, when the mixed solution G is treated under alkaline conditions that decompose bisphenol A in step H (after alkaline decomposition), the concentration of isopropenylphenol produced by the alkaline decomposition in step H increases and self-condenses to form a by-product, resulting in a significant decrease in the production rate of bisphenol A in the recombination. In addition, the content of bisphenol A contained in the crude solution A is preferably 10% by mass or more, and the larger the value, the more preferable it is in the order of 20% by mass or more, 30% by mass or more, and 40% by mass or more. If the content of bisphenol A is too low, the amount of bisphenol A produced is reduced, which is economically undesirable.

[0044] 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 below the lower limit, bisphenol A in the crude solution A precipitates to form a slurry liquid, which makes it difficult to transfer the liquid.

[0045] Crude solution A may contain heavy components such as incomplete decomposition products of polycarbonate resin (multimers such as dimers and trimers of bisphenol A), but if the amount of heavy components is too large, carbon dioxide is generated in step H, causing pressure fluctuations and complicating reaction control, so the content of heavy components in crude solution A is preferably 5% by mass or less, and more preferably 1% by mass or less. Crude solution A may be thoroughly washed.

[0046] A specific example of step A will be described below with reference to FIGS.

[0047] [Process A1] Step A1 shown in Fig. 2 includes a PC decomposition step in which a polycarbonate resin is decomposed in the presence of a phenol-containing solvent and a catalyst to obtain a reaction liquid a1 containing bisphenol A, and a concentration step a1 in which the reaction liquid a1 obtained in the PC decomposition step is distilled to remove a part of the phenol. In step A1, a catalyst that can be removed in the concentration step a1 is usually used. An example of such a catalyst is an alkylamine.

[0048] (PC decomposition process) The reaction temperature is usually 60 to 150° C., preferably 70° C. or higher, more preferably 75° C. or higher, and even more preferably 80° C. or higher. 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 solvent used in decomposing the polycarbonate resin. The pressure of the PC decomposition reaction is preferably 1 kPa to 1 MPa, and more preferably 5 kPa to 0.5 MPa.

[0049] There is no particular limitation on the reaction method of the decomposition reaction of polycarbonate resin, and it may be a continuous type or a batch type. For example, in the case of a batch type, the reaction time is appropriately selected according to the concentration of polycarbonate resin, reaction temperature, reaction pressure, etc., but if the reaction time is long, the generated bisphenol A tends to decompose, so it is preferably 30 hours or less, and more preferably 25 hours or less, 20 hours or less, 15 hours or less, 10 hours or less, and 5 hours or less in that order, with the smaller the value, the more preferable. In addition, if the reaction time is short, the decomposition reaction may not proceed sufficiently, so it is preferably 0.1 hours or more, more preferably 0.5 hours or more, and even more preferably 1 hour or more.

[0050] (concentration step a1) In the concentration step a1, the reaction solution a1 is distilled to distill off a part of phenol. As described above, the obtained solution may contain heavy components such as incomplete decomposition products of polycarbonate resin (multimers such as dimers and trimers of bisphenol A), but these heavy components can also be decomposed or removed in step H, so the obtained solution can be used as it is as crude solution A. For example, the distillation can be performed at a temperature of 50 to 200°C and a pressure of 0.1 kPa to 150 kPa. In addition, light components such as alkylamines that have a boiling point lower than that of phenol are also distilled off in the concentration step a1.

[0051] [Process A2] The step A2 shown in FIG. 3 includes a PC decomposition step in which polycarbonate resin is decomposed in the presence of a phenol-containing solvent and catalyst to obtain a reaction liquid a1 containing bisphenol A, a neutralization step in which the reaction liquid a1 obtained in the PC decomposition step is neutralized to obtain an organic phase a2 containing bisphenol A, and a concentration step a2 in which the organic phase a2 obtained in the neutralization step is distilled to distill off a part of the phenol. In the step A2, the reaction liquid a1 is neutralized to remove the catalyst and the like, and then the solvent is distilled off. In the 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, and any one selected from the group consisting of an alkali metal hydroxide, an alkali metal carbonate, an alkylamine, and an acid can be used as the catalyst.

[0052] (PC decomposition process) The PC decomposition step can be carried out in the same manner as in step A1.

[0053] (neutralization process) In the neutralization step, the reaction liquid a1 obtained in the PC decomposition step is neutralized to obtain an organic phase a2 containing bisphenol A. When an alkali metal hydroxide, an alkali metal carbonate, or an alkylamine is used as a catalyst, the neutralization is performed by mixing an acid such as hydrochloric acid, sulfuric acid, or phosphoric acid with the reaction liquid a1. When an acid is used as a catalyst, the neutralization is performed by mixing a base such as sodium carbonate or sodium hydroxide with the reaction liquid a1. The neutralization is preferably performed by adjusting the amount of the acid or base to be mixed so that the pH of the reaction liquid a1 is 7.5 to 10 (preferably pH 8.0 to 9.5). After mixing the reaction liquid a1 with an acid or base depending on the catalyst used, the oil-water separation is performed, and the aqueous phase is removed to obtain an organic phase a2 containing bisphenol A.

[0054] (concentration step a2) In the concentration step a2, the organic phase a2 obtained in the neutralization step is distilled to distill off a part of the phenol. The obtained solution may contain heavy components such as incomplete decomposition products of the polycarbonate resin (multimers such as dimers and trimers of bisphenol A), but these heavy components can also be decomposed or removed in step H, so the obtained solution can be used as it is as crude solution A. For example, the distillation can be performed at a temperature of 50 to 200°C and a pressure of 0.1 Pa to 150 kPa.

[0055] [Process B] In step B, acetone and phenol are subjected to dehydration condensation in the presence of an acid catalyst to obtain a reaction liquid B containing bisphenol A.

[0056] (acetone) The raw material acetone can be used without any particular limitation as long as it is industrially available. For example, acetone may be newly supplied from outside the system, or unreacted acetone distilled off in step C described below may be circulated to be used as acetone in step B, or a mixture of these may be used.

[0057] (Phenol) The raw material phenol can be used without any particular limitation as long as it is industrially available. For example, phenol may be newly supplied from outside the system, or unreacted phenol distilled off in step C described below or phenol contained in the solution after step G may be recycled to be used as phenol in step B, or these may be mixed and used.

[0058] (acid catalyst) As the acid catalyst, an acidic substance is used, and mineral acids such as hydrochloric acid and sulfuric acid, strong acid cation exchange resins, solid acids such as polysiloxanes, etc. can be used. In view of corrosion of the equipment, separation of the catalyst after the reaction, catalytic activity, etc., strong acid cation exchange resins such as sulfonic acid type are usually used, and acid cation exchange resins of styrene-divinylbenzene copolymer type in which sulfonic acid groups are introduced into about 2 to 16% of the total number of benzene rings can be used. The average particle size is usually 0.2 to 2 mm, preferably 0.4 to 1.5 mm. In addition, for the purpose of improving the selectivity and conversion rate, it is preferable to add a sulfur-containing amine compound as a promoter during the reaction or to support the acid catalyst, and an example of a suitable acid catalyst in the step B is a strong acid cation exchange resin partially modified with a sulfur-containing amine compound.

[0059] (Acetone to Phenol Molar Ratio) There is no particular restriction on the molar ratio of the raw materials phenol and acetone, but it is preferable to use phenol in excess of the stoichiometric amount, and 3 to 30 moles, preferably 5 to 20 moles, of phenol are used per mole of acetone. If the amount of phenol used per mole of acetone is less than 3 moles, the selectivity of bisphenol A decreases, and if it is more than 30 moles, problems such as a decrease in reaction rate and an increase in the size of the apparatus occur.

[0060] The condensation reaction of acetone and phenol can be carried out by a known method. The condensation reaction of phenol and acetone is not particularly limited to a reaction method, but 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, the amount of the acid catalyst used is usually 20 to 100% by weight based on the raw material mixture, and the reaction time is usually 0.5 to 5 hours, although it varies depending on the reaction temperature and reaction pressure. 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 to which a co-catalyst is fixed, and reacted.

[0061] The reaction temperature is usually 40 to 130° C., preferably 40 to 90° C. A reaction temperature lower than 40° C. is undesirable since the reaction liquid may solidify, and a high temperature exceeding 130° C. may cause the acidic group of the acidic cation exchange resin, which is the reaction catalyst, to be detached from the catalyst and mixed into bisphenol A, causing decomposition of bisphenol A, or may cause the catalyst to be decomposed by the high temperature, shortening the catalyst life. The reaction pressure is usually normal pressure to 600 kPa (absolute pressure).

[0062] [Process C] Step C is a step of distilling off unreacted acetone and water from the reaction liquid B obtained in step B to obtain a concentrated liquid C. The reaction liquid B obtained in step B contains the produced bisphenol A, unreacted acetone, phenol, by-product water, isomers of bisphenol A, etc. In step C, the reaction liquid B is subjected to a method such as reduced pressure distillation to remove light components including unreacted acetone and water from the reaction liquid B to the outside of the system, thereby obtaining a concentrated liquid C containing bisphenol A and phenol.

[0063] In step C, it is preferable to distill off acetone, water, and a part of phenol from the reaction solution B obtained in step B to obtain a concentrated solution C. By distilling off a part of the phenol, a concentrated solution C from which acetone and water have been thoroughly removed can be obtained.

[0064] For example, the reaction liquid B obtained in step B is transferred to a distillation column, and water, unreacted acetone, and a part of phenol are removed from the top of the column, and then the reaction product is extracted from the bottom of the column, thereby obtaining a concentrated liquid C to be used in step D. The obtained concentrated liquid C is subjected to step D. The distilled acetone may be recycled to step B. The distilled phenol may be recycled to step B or used as a washing solvent for bisphenol A in step E.

[0065] 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. It is preferable that the acetone and water in the concentrated liquid C are each removed to usually 0.1% by weight or less. This reduces the solubility of the adduct crystals during the crystallization operation, improving the crystal yield. The concentration of bisphenol A in the concentrated liquid C is preferably 20 to 50% by weight. If the concentration of bisphenol A is less than 20% by weight, the yield will be low, and if it is more than 50% by weight, the viscosity of the concentrated liquid C will increase, making transportation difficult.

[0066] [Process D] Step D is a step of crystallizing the concentrated liquid C obtained in step 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.

[0067] In step 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 adjusted to usually 60 to 100°C, preferably 70 to 90°C, and transferred to a crystallizer. The transferred concentrated liquid C is cooled from 60 to 100°C (preferably 70 to 90°C) to 40 to 70°C in the crystallizer, whereby the adduct crystals are precipitated to form a slurry liquid. Next, the slurry liquid in which the adduct crystals are dispersed is subjected to solid-liquid separation to obtain a mother liquid D and a cake d. The obtained mother liquid D contains unprecipitated bisphenol A and phenol. The cake d is mainly composed of adduct crystals.

[0068] The solid-liquid separation can be carried out by a known means such as filtration or centrifugation. For example, solid-liquid separation can be carried out using a horizontal belt filter, a rotary vacuum filter, a rotary pressure filter, a centrifugal filtration separator, a centrifugal sedimentation separator, a hybrid type centrifugal separator thereof (screen ball decanter), or the like.

[0069] [Process E] Step E is a step of purifying the cake d obtained in step D to obtain bisphenol A. The method of purifying the cake d is not particularly limited, and may be a method of removing phenol from a molten liquid obtained by heating and melting the cake d, or a method of crystallization using a hydrocarbon solvent such as toluene, and the like, whereby phenol is separated from the cake d obtained in step D to recover bisphenol A.

[0070] As a method for removing phenol from the cake d, a method is usually adopted in which the cake d is heated and melted at 100 to 160°C, and most of the phenol is removed from the obtained molten liquid, for example, by using a distillation apparatus, a thin film evaporator, a flash evaporator, or the like. In addition, in order to remove a trace amount of phenol remaining in the molten liquid, a method is also adopted in which, after the above operation, the remaining phenol is further removed by steam stripping or the like to purify bisphenol A. This method is described, for example, in JP-A-63-132850 and JP-A-2-28126.

[0071] The high-purity bisphenol A obtained in the above-mentioned manner in a molten state is sent to a pelletizer or a flaker, where it becomes solid prills or flakes and becomes the product bisphenol A. The obtained bisphenol A can also be transferred to the next process in a molten state without being solidified, as in the case of supplying it to the production of polycarbonate resin by a melting method.

[0072] [Process F] The step F is a step of circulating a part of the mother liquor D obtained in the step D and supplying it to the dehydration condensation in the step B. A part of the mother liquor D obtained by solid-liquid separation is supplied to a condensation reaction apparatus in which step B is performed via a pipe connected to the condensation reaction apparatus, and is subjected to step B. In addition, all or a part of the remaining mother liquor D obtained by solid-liquid separation is supplied to an apparatus in which step G is performed via a pipe connected to the apparatus, and is subjected to step G.

[0073] [Process G] Step G is a step of obtaining a mixed solution G by mixing the crude solution A obtained in step A with a part of the mother liquor D obtained in step D.

[0074] The mixed solution G may be prepared by mixing the crude solution A and the mother liquor D before transferring them to a reaction tower in which step H is carried out, or the crude solution A and the mother liquor D may be transferred to reaction towers in which step H is carried out, and the mixed solution G may be prepared in the reaction towers.

[0075] Regarding the mixing ratio of crude solution A to mother liquor D, if the amount of crude solution A is too large, the amount of components that cannot be decomposed in step H increases, and the crude solution A may be easily solidified or the piping for transferring the crude solution A from the reaction tank in step H may be easily clogged. Therefore, the mass ratio of crude solution A to mother liquor D (mass of crude solution A / mass of mother liquor D) is preferably 10 or less, and can be appropriately determined to be 5 or less, 2 or less, 1 or less, etc., depending on the content of bisphenol A in crude solution A, etc. There is no particular upper limit to the mass ratio of crude solution A to mother liquor D, but it can be appropriately determined to be, for example, 0.0001 or more, 0.0001 or more, 0.001 or more, 0.01 or more, 0.1 or more, etc., depending on the viewpoint of recycling and the content of bisphenol A in crude solution A, etc.

[0076] Furthermore, step G may be a step of mixing the crude solution A obtained in step A with a part of the mother liquor D obtained in step D, and distilling the mixture to obtain a mixed liquid G (see FIG. 4). For example, the crude solution A and the mother liquor D can be transferred to a distillation column, where the crude solution A and the mother liquor D are mixed, and a part of the phenol is further distilled off to prepare the mixed liquid G. The distillation can be carried out at a temperature of 100 to 250° C. and a pressure of 1 kPa to 100 kPa.

[0077] [Process H] Step H is a step of treating the mixed solution G under alkaline conditions that decompose bisphenol A and then recombining to obtain a solution H1 containing bisphenol A, or a solution H2 containing a decomposition product obtained by treating the mixed solution G under alkaline conditions that decompose bisphenol A.

[0078] Examples of the basic catalyst include hydroxides, oxides, carbonates, and various phenol salts of alkali metals such as sodium and potassium, and hydroxides, oxides, carbonates, and various phenol salts of alkaline earth metals such as calcium and magnesium. Among these, sodium hydroxide or potassium hydroxide is preferred.

[0079] In step H, distillation is usually carried out after or while treating the mixed solution G under alkaline conditions that decompose bisphenol A, to recover a fraction h containing decomposition products, and to remove a residue. The amount of the residue to be removed is appropriately adjusted depending on the amount of the mixed solution G provided to step H.

[0080] In step H, the decomposition rate of bisphenol A in the mixed solution G when the mixed solution G is treated under conditions for decomposing bisphenol A 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 are not decomposed do not evaporate and remain in the residue. If the decomposition rate is too low, the components that do not evaporate and remain in the residue increase. This component becomes waste, which is not preferable. The decomposition rate of bisphenol A in the mixed solution G can be calculated as the amount of decomposition product contained in fraction h relative to the amount of bisphenol A in the mixed solution G (moles of decomposition product / moles of bisphenol A in the mixed solution G×100(%)). For example, in step H1 described later, it can be calculated as the amount of isopropenylphenol contained in fraction h1 relative to the amount of bisphenol A in the mixed solution G.

[0081] A specific example of step H will be described below with reference to FIGS.

[0082] [Process H1] Step H1 shown in FIG. 5 is an example of a process for obtaining a solution H1 containing bisphenol A by treating the mixture G under alkaline conditions that decompose bisphenol A and then recombining the mixture. Step H1 includes an alkaline decomposition and distillation process in which distillation is performed while treating the mixture G under alkaline conditions that decompose bisphenol A to obtain a fraction h1 containing decomposition products phenol and isopropenylphenol, and a recombination process in which phenol and isopropenylphenol are recombined to generate bisphenol A. Since isopropenylphenol generated by decomposing bisphenol A has high reactivity, it will become a condensation product other than bisphenol A if it is not recombined quickly. As in step H1, by treating the mixture G under alkaline conditions that decompose bisphenol A and performing distillation while decomposing bisphenol A, the generated isopropenylphenol is quickly evaporated and supplied to the recombination process, so that the side reaction of isopropenylphenol can be suppressed.

[0083] (Alkaline decomposition and distillation process) The alkaline decomposition and distillation process can be carried out, for example, by a reactive distillation apparatus having a reaction tank at the bottom and a distillation column at the top. The mixed liquid G obtained in step G and the basic catalyst are transferred to the reaction tank at the bottom and heated to decompose the bisphenol A contained in the mixed liquid G into phenol and isopropenylphenol. At this time, incomplete decomposition products of polycarbonate resin (polymers such as dimers and trimers of bisphenol A) and isomers of bisphenol A (2,4-bisphenol) are also decomposed into phenol and isopropenylphenol. In addition, impurities such as chroman compounds undergo a heavy reaction and are converted into high boiling point substances (compounds with a boiling point higher than that of bisphenol A). In order to efficiently decompose bisphenol A and the like into phenol and isopropenylphenol, the water content of the mixed liquid G is usually adjusted to 0.01% by mass or less.

[0084] The temperature of the alkaline decomposition / distillation (i.e., the temperature of the reaction vessel) is preferably 180° C. or higher, and more preferably 200° C. or higher, and is preferably 350° C. or lower, and more preferably 300° C. or lower. The alkaline decomposition and distillation are usually carried out under conditions in which the pressure inside the column is from 0.6 kPa to normal pressure, and preferably from 13 to 20 kPa.

[0085] Phenol and isopropenylphenol produced by the decomposition are evaporated, 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 ratio of phenol to isopropenylphenol is set to a predetermined ratio. In addition, the reaction liquid that does not evaporate and remains in the reaction tank is concentrated with high boiling point substances and substances that cause coloring of bisphenol A. The residue is removed by withdrawing this reaction liquid from the bottom of the reaction tower.

[0086] Fraction h1 preferably contains 1.0 mass% or more of isopropenylphenol. If the content of isopropenylphenol in fraction h1 is less than 1.0 mass%, the amount of bisphenol A recovered after recombination will be small. Fraction h1 preferably contains 50 mass% or less of isopropenylphenol, more preferably 30 mass% or less. If the content of isopropenylphenol is too high, it will turn into a condensate other than bisphenol A.

[0087] Fraction h1 preferably comprises isopropenylphenol and phenol, and the phenol content in fraction h1 is preferably 99% by mass or less, more preferably 50% by mass or more, and even more preferably 70% by mass or more.

[0088] (Recombination process) In the recombination step, phenol and isopropenylphenol are recombined by contacting them with an acid catalyst to produce bisphenol A. As a result, phenol and isopropenylphenol are condensed to produce bisphenol A, and a solution H1 containing bisphenol A is obtained. As the acid catalyst for the recombination, a sulfonic acid type strongly acidic cation exchange resin is preferable, and the recombination can be carried out, for example, in a reaction apparatus filled with a sulfonic acid type strongly acidic cation exchange resin.

[0089] The reaction temperature is usually 45 to 130° C., and preferably 50 to 100° C. The contact time with the acid catalyst is usually 5 to 200 minutes, and preferably 15 to 120 minutes.

[0090] The obtained solution H1 preferably contains 1.0 mass% or more of bisphenol A. If the content of bisphenol A in solution H1 is less than 1.0 mass%, components other than bisphenol A are generated in large amounts, and the amount of impurities contained in bisphenol A increases, tending to deteriorate the quality of bisphenol A obtained in step E. Moreover, solution H1 preferably contains 50 mass% or less of bisphenol A, and more preferably contains 40 mass% or less of bisphenol A. 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 was performed to the reaction apparatus where step B is performed is likely to become clogged.

[0091] Step H1 may also include a step of decomposing the residue (the reaction liquid remaining in the reaction tank without evaporating) with an acid catalyst. This decomposes the substances that were not decomposed in the alkali decomposition and distillation steps, and phenol is produced. For example, the residue is decomposed at 150 to 300°C in the presence of an acid catalyst, and then the resulting reaction liquid h1b containing phenol is distilled (temperature 150 to 300°C, pressure 0.1 kPa to 10 kPa) to recover phenol, which can also be returned to step B. Examples of the acid catalyst used in this step include aromatic sulfonic acids such as p-toluenesulfonic acid. In addition, since the residue is basic, the amount of the acid catalyst to be mixed is controlled so that the residue can be decomposed under acidic conditions.

[0092] [Process H2] Step H2 shown in Fig. 6 is an example of a process for treating the mixed solution G under alkaline conditions for decomposing bisphenol A to obtain a solution H2 containing decomposition products. Step H2 includes an alkaline hydrolysis process for 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 process for recovering acetone and / or phenol in the reaction solution h2 obtained in the alkaline hydrolysis process and removing the residue. Such step H2 is preferable because it can efficiently separate water, a basic catalyst, acetone, phenol, and residue contained in the reaction solution h2.

[0093] (Alkaline hydrolysis process) In the alkaline hydrolysis step, for example, the mixed solution G obtained in step G, a basic catalyst, and water are transferred to a reactor and heated to decompose the bisphenol A contained in the mixed solution G into acetone and phenol. At this time, incomplete decomposition products of polycarbonate resin (multimers such as bisphenol A dimers and trimers) and bisphenol A isomers (2,4-bisphenol) are also decomposed into phenol and acetone. In addition, impurities such as chroman compounds undergo a heavy reaction and are converted into high boiling point substances (compounds with a boiling point higher than that of bisphenol A). As a result, a reaction solution h2 containing acetone, phenol, impurities, etc. is obtained.

[0094] If the amount of water supplied to the reaction device together with the mixed solution G is too large, the decomposition efficiency decreases, and if it is too small, the amount of components that cannot be decomposed increases, tending to significantly decrease the rate of alkaline hydrolysis. The mass ratio of water to the mixed solution G (mass of water / mass of the mixed solution G) is preferably 1 or more, more preferably 1.5 or more. Also, it is preferably 300 or less, more preferably 100 or less.

[0095] The temperature of the hydrolysis is preferably 180° C. or higher, more preferably 200° C. or higher, and more preferably 350° C. or lower, more preferably 300° C. or lower. The pressure of the hydrolysis is usually the vapor pressure at that temperature.

[0096] The reaction liquid h2 preferably contains 0.1% by mass or more of acetone. If the content of acetone in the reaction liquid h2 is less than 1.0% by mass, it becomes difficult to properly recover the acetone. Moreover, the reaction liquid h2 preferably contains 30% by mass or less of acetone, and more preferably contains 20% by mass or less. This is because if the content of acetone is too high, acetone will self-condense and the recovery rate will decrease.

[0097] (Acetone / phenol recovery process) In the acetone-phenol recovery process, first, the reaction liquid H2 obtained in the alkaline hydrolysis process is neutralized and distilled to recover acetone. Phenol and impurities are concentrated in the reaction liquid H2a that remains without evaporating. Next, the phenol in the reaction liquid H2a is extracted with a solvent to obtain an organic phase H2b containing phenol, and the organic phase H2b is then distilled to recover phenol. In addition, impurities can be removed by removing the residue remaining after the distillation of phenol. The recovered acetone and phenol are each sent to step B as solution H2.

[0098] Specifically, the reaction liquid h2 is neutralized and transferred to an acetone recovery distillation tower, where acetone is distilled at a temperature of 30 to 200°C and a pressure of 0.1 to 100 kPa, and the acetone is extracted from the top of the tower. The reaction liquid h2a (tower bottom liquid) in the distillation tower is transferred to a solvent extraction device.

[0099] The reaction liquid H2a is treated with a water-immiscible organic solvent in a solvent extraction apparatus to obtain an organic phase H2b containing phenol and an aqueous phase, which are then extracted separately. Examples of the water-immiscible organic solvent include ethers such as tert-butyl methyl ether, tert-amyl ethyl ether, and diisopropyl ether; ketones such as methyl ethyl ketone and methyl isobutyl ketone; and acetates such as propyl acetate, butyl acetate, pentyl acetate, and hexyl acetate.

[0100] The organic phase h2b containing the extracted phenol is transferred to a phenol recovery distillation column, where the phenol is distilled at a temperature of 100 to 300°C and a pressure of 0.1 to 10 kPa, and the phenol is extracted from the top of the column. The residue (column bottom liquid) remaining in the phenol recovery distillation column is extracted from the bottom of the column.

[0101] In addition, the acetone / phenol recovery step may involve distilling acetone from the reaction liquid h2, neutralizing the reaction liquid remaining after extraction, and distilling the phenol to recover acetone and phenol separately.

[0102] [Process I] Step I is a step of supplying the solution H1 or solution H2 obtained in step H to the dehydration condensation in step B. For example, piping may be provided to connect the reaction vessel in which the recombination reaction is carried out, the acetone recovery distillation column, and the phenol recovery distillation column to the condensation reaction vessel in which step B is carried out, and the solution H1 extracted from the reaction vessel in which the recombination reaction is carried out, the acetone extracted from the acetone recovery distillation column, and the phenol extracted from the phenol recovery distillation column can be supplied to step B via this piping.

[0103] <Uses of bisphenol> Bisphenol A obtained by the method for producing bisphenol A of the present invention (hereinafter, may be referred to as "bisphenol A of the present invention") can be used as a constituent, curing agent, additive, or precursor thereof for various thermoplastic resins such as polyether resins, polyester resins, polyarylate resins, polycarbonate resins, polyurethane resins, and acrylic resins, and various thermosetting resins such as epoxy resins, unsaturated polyester resins, phenolic resins, polybenzoxazine resins, and cyanate resins, which are used for various applications such as optical materials, recording materials, insulating materials, transparent materials, electronic materials, adhesive materials, and heat-resistant materials. It is also useful as an additive for color developers and anti-fading agents for thermal recording materials, bactericides, and antibacterial and antifungal agents.

[0104] Among these, since it can provide good mechanical properties, 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. It is also preferably used as a color developer, and more preferably used in combination with a leuco dye and a discoloration temperature regulator.

[0105] <Production method of polycarbonate resin> The present invention also relates to a method for producing a polycarbonate resin using bisphenol A obtained by the method for producing bisphenol A of the present invention (hereinafter, sometimes referred to as the "method for producing a polycarbonate resin of the present invention").

[0106] The polycarbonate resin obtained by the method for producing a polycarbonate resin of the present invention can be produced by, for example, a method of subjecting bisphenol A of the present invention and a carbonate diester such as diphenyl carbonate to an ester exchange reaction in the presence of an alkali metal compound and / or an alkaline earth metal compound. The ester exchange reaction can be carried out by appropriately selecting a known method, but an example in which bisphenol A of the present invention and diphenyl carbonate are used as raw materials will be described below.

[0107] In the above-mentioned method for producing a polycarbonate resin, it is preferable to use an excess amount of diphenyl carbonate relative to the bisphenol A of the present invention. The amount of diphenyl carbonate used relative to the bisphenol A is preferably large in terms of the number of terminal hydroxyl groups in the produced polycarbonate resin and excellent thermal stability of the polymer, and is preferably small in terms of the high transesterification reaction rate and ease of producing a polycarbonate resin of the desired molecular weight. For these reasons, the amount of diphenyl carbonate used relative to 1 mole of bisphenol is usually 1.001 moles or more, preferably 1.002 moles or more, and usually 1.3 moles or less, preferably 1.2 moles or less.

[0108] As for the method of supplying the raw materials, bisphenol A and diphenyl carbonate of the present invention can be supplied in a solid state, but it is preferable to melt one or both of them and supply them in a liquid state.

[0109] When producing a polycarbonate resin by the transesterification reaction of diphenyl carbonate and bisphenol A, a transesterification catalyst is usually used. In the above-mentioned method for producing a polycarbonate resin, it is preferable to use an alkali metal compound and / or an alkaline earth metal compound as the transesterification catalyst. These may be used alone or in any combination and ratio of two or more kinds. For practical purposes, it is desirable to use an alkali metal compound.

[0110] The amount of catalyst used per mole 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 usually 100 μmol or less, preferably 50 μmol or less, more preferably 20 μmol or less. When the amount of catalyst used is within the above range, it is easy to obtain the polymerization activity required to produce a polycarbonate resin having a desired molecular weight, and it is easy to obtain a polycarbonate resin that is excellent in polymer hue, does not undergo excessive polymer branching, and has excellent fluidity during molding.

[0111] In producing a polycarbonate resin by the above method, it is preferred to continuously feed both of the above raw materials to a raw material mixing tank, and then continuously feed the resulting mixture and the transesterification catalyst to a polymerization tank.

[0112] In the production of polycarbonate resins by the transesterification method, usually, both raw materials are fed into a raw material mixing tank, stirred uniformly, and then fed into a polymerization tank to which a catalyst is added, thereby producing a polymer. EXAMPLES

[0113] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0114] [Raw materials and reagents] The polycarbonate resin used was "NOVAREX (registered trademark) M7027BF" manufactured by Mitsubishi Chemical Engineering Plastics Corporation. Phenol, toluene, sodium hydroxide, potassium hydroxide, hydrochloric acid, acetonitrile, and cesium carbonate were obtained from Fujifilm Wako Pure Chemical Industries, Ltd. Diphenyl carbonate used was a product of Mitsubishi Chemical Corporation.

[0115] [Preparation of cation exchange resin] Cation exchange resin A: Diaion (registered trademark) SK104, which was 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 cation exchange resin was obtained according to Example 1 described in Patent Document WO2012-108385.

[0116] [analysis] The confirmation of the production of bisphenol A, its purity, and the quantification of undecomposed polycarbonate resin and components thought 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: Shimadzu LC-2010A, Waters 5μm 150mm×4.6mmID Method: Low pressure gradient method ·Analysis temperature: 40℃ ·Eluent composition: Solution A: Acetonitrile Solution B: 85% phosphoric acid:water = 1mL:999mL solution At 0 min of analysis time, the eluent composition was A:B = 35:65 (volume ratio, same below), and from 0 to 5 min of analysis time the eluent composition was A:B = 35:65, and then gradually changed to A:B = 90:10 from 5 to 40 min of analysis time. ·Flow rate: 0.85mL / min Detection wavelength: 280nm

[0117] Dimethyl carbonate was analyzed by gas chromatography according to the following procedure and conditions. Equipment: Shimadzu GC-2014 Agilent DB-1 0.530mm×30m 1.5μm Detection method: FID Vaporizer temperature: 230℃ Detector temperature: 300℃ From 0 to 5 minutes of analysis time, the column temperature was kept at 50°C, from 5 to 30 minutes of analysis time, the column temperature was gradually increased to 280°C, and from 30 to 40 minutes of analysis time, the column temperature was maintained at 280°C. Quantitative method: Internal standard method using biphenyl as an internal standard

[0118] [Viscosity average molecular weight (Mv)] The viscosity average molecular weight (Mv) was determined 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, and calculating the viscosity average molecular weight (Mv) using the following formula. ηsp / C=[η](1+0.28ηsp) [η]=1.23×10 -4 Mv 0.83

[0119] [Melted color of bisphenol] The melt color of bisphenol was measured by placing 1g of bisphenol A and 19g of diphenyl carbonate in a test tube "P-24" (2mmφ×200mm) manufactured by Nippon Denshi Rika Glass Co., Ltd., melting it at 174℃ for 30 minutes, and measuring the Hazen color number using "OME7700" manufactured by Nippon Denshoku Industries Co., Ltd. The Hazen color number of bisphenol A was calculated by multiplying the obtained Hazen color number by the dilution rate with diphenyl carbonate.

[0120] [pH measurement] 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 of the flask.

[0121] <Example 1> [Process A-1] (PC decomposition process) In a jacketed separable flask equipped with a Dimroth condenser, stirring blade, and thermometer, polycarbonate resin (80 g, since the repeating unit of polycarbonate resin is 254 g / mol, 80 g ÷ 254 g / mol = 0.315 mol), water (30 g), phenol (250 g), and 25% by mass aqueous sodium hydroxide solution (320 g) were placed at room temperature under a nitrogen atmosphere. The reaction liquid was in the form of a slurry.

[0122] Thereafter, 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 a reaction liquid a1 (homogeneous solution).

[0123] (neutralization process) Toluene (200 g) was added to the obtained reaction liquid a1, and then 35% by mass hydrochloric acid was added until the aqueous phase reached pH 8.6, whereupon carbon dioxide gas was generated.

[0124] After that, the stirring was stopped to separate the oil and water, and the aqueous phase was extracted from the flask to obtain an organic phase a2. When the composition of a portion of the obtained organic phase a2 was confirmed by high performance liquid chromatography, the production of bisphenol A was confirmed.

[0125] (concentration step a2) The obtained organic phase a2 was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distillation tube, and a pressure regulator, and while monitoring the amount of distillation, the internal temperature was gradually raised to 180°C, and the internal pressure was gradually lowered from normal pressure to 10 kPa, and a portion of the water, toluene, and phenol was distilled off to obtain an organic phase a2-2.

[0126] The obtained organic phase a2-2 was restored in pressure with nitrogen, and the internal temperature was slowly lowered to 30° C. to obtain a slurry a3. The obtained slurry a3 was filtered to obtain recycled bisphenol A (20 g).

[0127] The time required to obtain recycled bisphenol A was 9 hours.

[0128] When the composition of a portion of the obtained recycled bisphenol A was confirmed by high performance liquid chromatography, it was found to contain 66.4 mass% bisphenol A. In addition, it contained 0.3 mass% of undecomposed polycarbonate resin and components thought to be stabilizers, calculated as bisphenol A.

[0129] [Process B-1a] ~ [Process D-1a], [Process F-1a] Mother liquor D was obtained according to Example 1 described in Patent Document JP-A-2005-220071. The composition of the obtained mother liquor D was 83 mass % of phenol, 10 mass % of bisphenol A, and 7 mass % of other components.

[0130] [Process G-1a] The mother liquid D (100 g) and the recycled bisphenol A (20 g) obtained in step A-1 were placed in a distillation apparatus equipped with a thermometer, stirring blade, distillation tube, oil bath, and pressure regulator. The temperature was then gradually increased to 180° C., and the internal pressure was gradually decreased from normal pressure to 10 kPa while monitoring the distillation amount, and phenol (19 g) was distilled off to obtain a mixed liquid G. The pressure was then restored with nitrogen. The amount of bisphenol A contained in the mixed liquid G was 23 g (100 g × 10.0 mass % + 20 g × 66.4 mass % = 23 g).

[0131] [Process H-1a] (Alkaline decomposition and distillation process) A 25% by mass aqueous solution of sodium hydroxide (0.4 g) was added to the mixed liquid G, and full vacuum was applied. The temperature of the oil bath was then raised to 230°C, and fraction h1 (80 g) was obtained. When the composition of a portion of the obtained fraction h1 was confirmed by high performance liquid chromatography, it was found to contain 93% by mass of phenol and 7% by mass of isopropenylphenol. The decomposition rate of bisphenol A in the alkaline decomposition and distillation process was 41% (80 g x 7% by mass ÷ 134 g / mol ÷ 23 g x 228 g / mol x 100% = 41%). The obtained residue was discarded.

[0132] (Recombination process) Cation exchange resin A (1 g) was placed in a round-bottom flask equipped with a stirring blade, a distillation tube, and a water bath. The obtained fraction h1 (80 g) was quickly placed in this round-bottom flask and reacted at 70°C for 2 hours. After that, the mixture was decanted to remove the cation exchange resin A, and solution H1 was obtained. When the composition of a portion of the obtained solution H1 was confirmed by high performance liquid chromatography, it was found to contain 11 mass% bisphenol A.

[0133] [Process I-1a], [Process B-1b] The solution H1 (20 g), the mother liquor D (170 g), phenol (2 g) as a reagent, acetone (8 g) as a reagent, and 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 for 5 hours at 70° C. Thereafter, the cation exchange resin B was removed by decantation to obtain reaction solution B.

[0134] [Process C-1b] The entire amount of the obtained reaction liquid 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 monitoring the amount of distillation, the internal temperature was gradually raised to 180°C, and the internal pressure was gradually lowered from normal pressure to 10 kPa. Unreacted acetone, water, and a portion of the phenol were distilled off to obtain a concentrated liquid C.

[0135] [Process D-1b] The pressure of the obtained concentrated liquid C was restored with nitrogen, and the internal temperature was slowly lowered to 30° C. to obtain a slurry liquid. The obtained slurry liquid was filtered to obtain a cake d (11 g).

[0136] [Process E-1b] The obtained cake d (11 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 five times with 50 g of desalted water to obtain an organic phase e2.

[0137] 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.

[0138] The obtained cake e4 was dried by a rotary evaporator to obtain bisphenol A (4.1 g). The Hazen color number of the obtained bisphenol A was APHA 20. In addition, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8 mass%. Furthermore, undecomposed polycarbonate resin and components thought to be stabilizers were below the detection limit.

[0139] <Example 2> [Process A-2] (PC decomposition process) In a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer, polycarbonate resin (80 g, 0.315 mol), water (30 g), phenol (240 g), and triethylamine (10 g) were placed at room temperature under a nitrogen atmosphere. The reaction liquid was in the form of a slurry.

[0140] Thereafter, the internal temperature was raised to 80° C., and the reaction was continued for 5 hours while maintaining the temperature at 80° C., thereby obtaining a reaction liquid a1 (homogeneous solution). During the reaction, the generation of carbon dioxide was confirmed.

[0141] A portion of the resulting reaction solution a1 was taken out, and its composition was confirmed by high performance liquid chromatography, revealing that bisphenol A was produced at 19.6% by mass. The weight of reaction solution a1 was 80 g + 30 g + 240 g + 10 g = 360 g, and the amount of bisphenol produced was 19.6% by mass × 360 g ÷ 228.29 g / mol = 0.309 mol, and the reaction rate was 0.309 mol ÷ 0.315 mol × 100 = 98%.

[0142] (concentration step a1) The obtained reaction liquid a1 was transferred to a distillation apparatus equipped with a thermometer, a stirring blade, a distillation tube, and a pressure regulator, and while monitoring the amount of distillation, the internal temperature was gradually raised to 180°C, and the internal pressure was gradually lowered from normal pressure to 10 kPa, whereby water, triethylamine, and a portion of the phenol were distilled off to obtain recycled bisphenol A (260 g).

[0143] The time required to obtain recycled bisphenol A was 7 hours.

[0144] When the composition of a portion of the obtained recycled bisphenol A was confirmed by high performance liquid chromatography, it was found to contain 27.0% by mass of bisphenol A. In addition, it contained 0.4% by mass, calculated as bisphenol A, of undecomposed polycarbonate resin and components thought to be stabilizers.

[0145] [Process B-2a] ~ [Process H-2a], [Process B-2b] ~ [Process E-2b] Bisphenol A (4.5 g) was obtained in the same manner as in [Steps B-1a] to [Step H-1a] and [Steps B-1b] to [Step E-1b] of Example 1, except that the recycled bisphenol A (50 g) obtained in step A-2 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 18. Furthermore, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass. Furthermore, undecomposed polycarbonate resin and components thought to be stabilizers were below the detection limit.

[0146] <Example 3> [Process A-3] (PC decomposition process) Polycarbonate resin (80 g, 0.31 mol), phenol (240 g), methanol (23 g, 0.72 mol, molar ratio to the number of moles of carbonate ester repeating units in polycarbonate resin: 0.72 mol÷0.31 mol=2.3), and triethylamine (15 g, 15 g÷101 g / mol=0.15 mol, molar ratio to the number of moles of carbonate ester repeating units in polycarbonate resin: 0.15 mol÷0.31 mol=0.48) were placed in a jacketed separable flask equipped with a Dimroth condenser, a stirring blade, and a thermometer under a nitrogen atmosphere at room temperature (amount of liquid: 80 g+240 g+23 g+15 g=358 g).

[0147] Thereafter, the internal temperature was raised to 85° C. Undissolved polycarbonate resin was observed in the reaction liquid when it reached 85° C. The reaction was continued for 4 hours while maintaining the temperature at 85° C., and a homogeneous reaction liquid a1 was obtained.

[0148] A portion of the resulting reaction solution a1 was subjected to high performance liquid chromatography to confirm the composition, and it was found that bisphenol A was produced in an amount of 19.5 mass% (19.5÷100×358 g÷228 g / mol÷0.31 mol=99 mol%). Furthermore, when a portion of the obtained reaction liquid a1 was subjected to gas chromatography to confirm the 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.

[0149] (concentration step a1) The obtained reaction liquid a1 was transferred to a distillation apparatus equipped with a thermometer, stirring blades, a distillation tube, and a pressure regulator, and while monitoring the amount of distillation, the internal temperature was gradually raised to 180°C, and the internal pressure was gradually lowered from normal pressure to 100 hPa, whereby methanol, dimethyl carbonate, and a portion of the phenol were distilled off to obtain recycled bisphenol A (262 g).

[0150] The time required to obtain recycled bisphenol A was 7 hours.

[0151] When the composition of a portion of the obtained recycled bisphenol A was confirmed by high performance liquid chromatography, it was found to contain 27.1% by mass of bisphenol A. In addition, it contained 0.4% by mass, calculated as bisphenol A, of undecomposed polycarbonate resin and components thought to be stabilizers.

[0152] [Process B-3a] ~ [Process H-3a], [Process B-3b] ~ [Process E-3b] Bisphenol A (4.7 g) was obtained in the same manner as in [Steps B-1a] to [Step H-1a] and [Steps B-1b] to [Step E-1b] of Example 1, except that the 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. Furthermore, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8% by mass. Furthermore, undecomposed polycarbonate resin and components thought to be stabilizers were below the detection limit.

[0153] <Comparative Example 1> An organic phase a2-2 was obtained in the same manner as in the PC decomposition step, neutralization step, and concentration step a2 in Step A of Example 1.

[0154] The obtained organic phase a2-2 was washed five times with 50 g of desalted 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 in a rotary evaporator to obtain bisphenol A (35 g).

[0155] The time required to obtain bisphenol A was 17 hours.

[0156] The composition was confirmed by high performance liquid chromatography, and the purity of bisphenol A was 99.8% by mass. In addition, undecomposed polycarbonate resin and components thought to be stabilizers were contained in an amount of 0.1% by mass calculated as bisphenol A.

[0157] When the bisphenol A obtained in Examples 1 to 3 was compared with that obtained in Comparative Example 1, the purity of bisphenol A was equivalent. In addition, as a result of visual evaluation, the color tone of the bisphenol 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, 0.1 mass % of components thought to be undecomposed products and stabilizers of the polycarbonate resin remained, calculated as bisphenol A, whereas in the bisphenol A obtained in Examples 1 to 3, no components thought to be undecomposed products and stabilizers of the polycarbonate resin were detected, and it is considered that the undecomposed products and stabilizers of the polycarbonate resin deteriorate the color tone of the bisphenol A.

[0158] <Comparative Example 2> The mother liquor D (170 g), phenol (2 g) as a reagent, acetone (8 g) as a reagent, and 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. After that, the cation exchange resin B was removed by decantation to obtain reaction liquid B.

[0159] The entire amount of the obtained reaction liquid 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 monitoring the amount of distillation, 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 the phenol. The pressure was then restored with nitrogen to obtain a concentrated liquid C (170 g).

[0160] The obtained concentrated liquid 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 liquid. The internal temperature was slowly lowered to 30° C. to obtain a slurry (crystallization step). The obtained slurry was filtered to obtain a cake d (15 g).

[0161] 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 five times with 50 g of desalted water to obtain an organic phase e2.

[0162] 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.

[0163] The obtained cake e4 was dried by a rotary evaporator to obtain bisphenol A (6 g). The Hazen color number of the obtained bisphenol A was APHA 89. In addition, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.5 mass%.

[0164] The amount of undecomposed polycarbonate resin and components thought to be stabilizers was 0.08% by mass.

[0165] In Examples 1 to 3 and Comparative Example 2, the liquid to be mixed with recycled bisphenol A (recycled BPA), 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 undecomposed matter of polycarbonate resin (PC) and the components thought to be stabilizers are summarized in Table 1. From Table 1, it can be seen that by mixing recycled bisphenol A with mother liquid D, performing step H, and returning to step B, the Hazen color number of bisphenol A obtained in step E is improved, and the components thought to be undecomposed matter of polycarbonate resin and the stabilizers are at the lower detection limit. It is considered that the components thought to be undecomposed matter of polycarbonate resin and the stabilizers are removed together with the bottom residue obtained in step H.

[0166] [Table 1]

[0167] <Example 4> [Process G-4a] The mother liquor D (18 g) obtained in step E-1a of Example 1 and the recycled bisphenol A (16 g) 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.

[0168] [Process H-4a] (Alkaline hydrolysis process) Water (64 g) and sodium hydroxide (2 g) were further added to the autoclave, and nitrogen was circulated to replace the air, and the autoclave was made airtight. The electric furnace was set to 250°C, the autoclave was set, and the internal temperature was heated to 250°C. After reaching 250°C, it was confirmed that the internal pressure was 3.7 MPa, and the reaction was carried out for 2 hours. Thereafter, the autoclave was removed from the electric furnace and immersed in a washbasin containing ice water for 1 hour. Thereafter, the autoclave was opened and transferred to an Erlenmeyer flask, and reaction liquid h2 was obtained. A portion of reaction liquid h2 was extracted and its composition was confirmed by gas chromatography, which confirmed that it contained 1.3 mass% acetone.

[0169] (Acetone / phenol recovery process) After neutralizing the reaction liquid h2 by adding 2.0 g of sulfuric acid, it was fed to a distillation apparatus equipped with a thermometer, stirring blade, rectification column, and water bath. Recycled acetone (0.9 g) and bottoms were obtained as the initial distillate by heating under normal pressure.

[0170] The entire amount of the resulting bottoms was transferred to a full jacket separable flask equipped with a thermometer, stirring blade, and cooling tube, diisopropyl ether was added, and oil-water separation was performed at 50°C, and the aqueous phase was removed to obtain organic phase H2B. The obtained organic phase H2B was supplied to a simple distillation apparatus equipped with a thermometer and stirring blade. The temperature was increased under normal pressure to distill and recover diisopropyl ether, and then the pressure was reduced to obtain recycled phenol (20 g).

[0171] [Process B-4b] The mother liquid D (170 g) obtained in step E-1a of 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 distillation tube, and a water bath, and reacted at 70° C. for 5 hours. Thereafter, the reaction liquid B was obtained by decantation to remove the cation exchange resin B.

[0172] [Process C-4b] The entire amount of the obtained reaction liquid 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 monitoring the amount of distillation, the internal temperature was gradually raised to 180°C, and the internal pressure was gradually lowered from normal pressure to 10 kPa. Unreacted acetone, water, and a portion of the phenol were distilled off to obtain a concentrated liquid C.

[0173] [Process D-4b] The pressure of the obtained concentrated liquid C was restored with nitrogen, and the internal temperature was slowly lowered to 30° C. to obtain a slurry. The obtained slurry was filtered to obtain a cake d (10 g).

[0174] [Process E-4b] The obtained cake d (10 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 five times with 50 g of desalted water to obtain an organic phase e2.

[0175] 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.

[0176] The obtained cake e4 was dried by a rotary evaporator to obtain bisphenol A (3.2 g). The Hazen color number of the obtained bisphenol A was APHA 22. In addition, when the composition was confirmed by high performance liquid chromatography, the purity of bisphenol A was 99.8 mass%.

[0177] Furthermore, undecomposed polycarbonate resin and components thought to be stabilizers were below the detection limit.

[0178] <Comparative Example 3> In a round-bottom flask equipped with a Dimroth condenser, stirring blade, and thermometer, polycarbonate resin (80 g; the repeating unit of polycarbonate resin is 254 g / mol, so 80 g ÷ 254 g / mol = 0.315 mol) and sodium hydroxide (50 g) were placed at room temperature under a nitrogen atmosphere. The mixture was then immersed in an oil bath at 230°C to decompose. After 2 hours, the heating was stopped and the mixture was immersed in an oil bath at 80°C to cool. The mother liquor D was added to the obtained solid, but it could not be dissolved at all, so it was abandoned from proceeding with the process any further.

[0179] <Example 5> In a 45 mL glass reaction vessel equipped with a stirrer and a distillation tube, bisphenol A obtained in Examples 1 to 3 was mixed to obtain 10.00 g (0.04 mol) of bisphenol A, 9.95 g (0.05 mol) of diphenyl carbonate, and 18 μL of an aqueous solution of 400 ppm by mass of cesium carbonate were placed. The glass reaction vessel was depressurized to about 100 Pa, and then the operation of returning the pressure 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.

[0180] The stirrer rotation speed was set to 100 revolutions per minute, and the pressure in the reaction tank was reduced from 101.3 kPa to 13.3 kPa absolute pressure over a period of 40 minutes while distilling off phenol produced as a by-product in the oligomerization reaction of bisphenol A and diphenyl carbonate in the reaction tank.

[0181] The pressure inside the reaction vessel was then maintained at 13.3 kPa, and the transesterification reaction was carried out for 80 minutes while further distilling off phenol.

[0182] Thereafter, the temperature outside the reaction vessel was raised to 290° C., and the pressure inside the reaction vessel was reduced from 13.3 kPa to 399 Pa in absolute pressure over a period of 40 minutes, and the distilled phenol was removed outside the system.

[0183] Thereafter, the absolute pressure of the reaction vessel was reduced to 30 Pa, and the polycondensation reaction was carried out. When the agitator of the reaction vessel reached a predetermined stirring power, the polycondensation reaction was terminated. The time from raising the temperature to 290°C to completing the polymerization was 120 minutes.

[0184] Next, the reactor was pressurized to 101.3 kPa absolute pressure with nitrogen, and then the gauge pressure was increased to 0.2 MPa, and the polycarbonate resin was extracted from the reactor to obtain a polycarbonate resin having a viscosity average molecular weight (Mv) of 26,500. [Industrial Applicability]

[0185] According to the present invention, bisphenol A can be produced from polycarbonate resin contained in waste plastics, etc., and the obtained bisphenol A can be used as a raw material, a curing agent, an additive, etc. for resins such as polycarbonate resins, and is therefore industrially useful.

Claims

1. A method for producing bisphenol A comprising the following steps A to I: Step A: A step of decomposing a polycarbonate resin in a solvent containing phenol to obtain a crude solution A containing bisphenol A and phenol. 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 liquid C obtained in step C to obtain a slurry liquid, and subjecting the slurry liquid to solid-liquid separation to obtain a mother liquid 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 with 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 mixture G under alkaline conditions that decompose bisphenol A and then recombining the mixture, or a solution H2 containing a decomposition product obtained by treating the mixture G under alkaline conditions that decompose bisphenol A. Step I: A step of supplying the solution H1 or solution H2 obtained in step H to the dehydration condensation in step B.

2. 2. The method for producing bisphenol A according to claim 1, further comprising the step of distilling off a part of phenol from the reaction solution B to obtain a concentrated solution C in the step C.

3. 3. The method for producing bisphenol A according to claim 1, wherein in the step H, when the mixed solution G is treated under conditions for decomposing bisphenol A, a decomposition rate of bisphenol A in the mixed solution G is 30 mol % or more.

4. 4. The method for producing bisphenol A according to claim 1, wherein the step H comprises a step of performing distillation after or while treating the mixed solution G under alkaline conditions that decompose bisphenol A, recovering a fraction h containing decomposition products, and removing a residue.

5. The step H is a step of obtaining the solution H1, an alkaline decomposition / distillation step in which the mixed liquid G is treated with distillation under alkaline conditions that decompose bisphenol A to obtain a fraction h1 containing phenol and isopropenylphenol as decomposition products; 5. The method for producing bisphenol A according to claim 1, further comprising a recombination step of recombining the phenol and isopropenylphenol contained in the fraction h1 to produce bisphenol A.

6. The method for producing bisphenol A according to claim 5, wherein the fraction h1 contains 1.0 mass% or more of isopropenylphenol.

7. The method for producing bisphenol A according to claim 5 or 6, wherein the solution H1 contains bisphenol A in an amount of 1 mass % or more.

8. The step H is a step of obtaining the solution H2, an alkaline hydrolysis step in which the mixed solution G is treated under alkaline conditions to hydrolyze bisphenol A, thereby obtaining a reaction solution h2 containing acetone and phenol; 5. The method for producing bisphenol A according to claim 1, further comprising: an acetone / phenol recovery step of recovering an acetone fraction and / or a phenol fraction from the reaction liquid h2 obtained in the alkaline hydrolysis step, and removing a residue.

9. The method for producing bisphenol A according to claim 8, wherein the reaction liquid h2 contains 0.1 mass% or more of acetone.

10. 10. The method for producing bisphenol A according to claim 1, wherein in the step A, a polycarbonate resin is decomposed in the presence of phenol, and then a part of the phenol is distilled off to obtain the crude solution A.

11. The method for producing bisphenol A according to any one of claims 1 to 10, wherein the content of bisphenol A in the crude solution A is less than 90 mass%.

12. 12. The method for producing bisphenol A according to claim 1, wherein the step A is a step of obtaining the crude solution A by decomposing the polycarbonate resin in the presence of a catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines and acids.

13. A method for producing a polycarbonate resin, comprising producing a polycarbonate resin by using bisphenol A obtained by the method for producing bisphenol A according to any one of claims 1 to 12.

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