Methods for manufacturing bisphenol A and polycarbonate resin

Abstract

Provided: A method for manufacturing bisphenol A capable of efficiently removing coloring components derived from polycarbonate resin and producing bisphenol A with good color tone. In the bisphenol A manufacturing method of the present invention, a crude solution A obtained by decomposing polycarbonate resin (PC) in step A and removing the solvent by distillation, and a portion of a mother liquor D obtained in step D of steps B to E (where bisphenol A (BPA) is manufactured by dehydration condensation of acetone and phenol), are used to obtain solution H1 or solution H2. Solution H1 or solution H2 is supplied to step B or step C. Solution H1 is a solution containing BPA obtained by decomposing BPA contained in crude solution A and mother liquor D into phenol and isopropenylphenol, and then recombinating the phenol and isopropenylphenol. Solution H2 is a solution containing phenol obtained by decomposing BPA contained in crude solution A and mother liquor D into phenol and acetone.

Description

Technical Field

[0001] This invention relates to a method for manufacturing bisphenol A. Furthermore, it also relates to a method for manufacturing a polycarbonate resin of bisphenol A obtained using the aforementioned method for manufacturing bisphenol A. Background Technology

[0002] Plastics are lightweight, durable, and inexpensive, leading to their mass production not only in Japan but worldwide. Most plastics are used in a "single-use" form, and therefore, without proper disposal, they end up in the environment. Specifically, plastic waste flows into the ocean from rivers, where it deteriorates to less than 5mm due to waves, ultraviolet radiation, and other factors. Such small pieces of plastic waste are called microplastics. These microplastics can be ingested by animals and fish. Therefore, plastic waste has a serious impact on ecosystems, and in recent years, marine plastic pollution has become a global problem. Polycarbonate resin, used in various fields due to its transparency, mechanical properties, flame retardancy, dimensional stability, and electrical properties, is no exception.

[0003] Chemical recycling is one method for recycling polycarbonate resin, involving the chemical decomposition of polycarbonate resin to restore it to bisphenol A (BPA) for reuse. Chemical recycling of polycarbonate resin is crucial as a solution to the marine plastics problem. Polycarbonate resin can be decomposed using various methods such as hydrolysis and alcoholysis, and the generated BPA can be recovered through crystallization.

[0004] In addition, there is a known method for purifying high-purity bisphenol A by adding bisphenol A obtained from the decomposition of polycarbonate resin to the general bisphenol A manufacturing process described below.

[0005] [The typical manufacturing process of bisphenol A]

[0006] Step 1: The process of reacting acetone and phenol in the presence of an acidic catalyst to obtain a reaction solution containing bisphenol A.

[0007] Step 2: The process of distilling and separating the reaction solution obtained in Step 1 to obtain a concentrated solution.

[0008] Step 3: The process of crystallizing / recovering the concentrate obtained in Step 2 to obtain adduct crystals and mother liquor.

[0009] Step 4: The process of producing bisphenol A by crystallizing the adduct.

[0010] For example, there is a known method for supplying a crude solution containing low-purity bisphenol A, recovered from the decomposition products obtained by thermal or chemical decomposition of waste plastics, to the concentrate or mother liquor obtained in the above-mentioned general bisphenol A manufacturing process (Patent Document 1).

[0011] In addition, there is a known method for decomposing waste polycarbonate into isopropylphenol and supplying it to step 1 (reaction step) of the general bisphenol A manufacturing process (Patent Document 2).

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: Japanese Patent Application Publication No. 2005-112781

[0015] Patent Document 2: Japanese Patent Application Publication No. 2006-36668 Summary of the Invention

[0016] The problem the invention aims to solve

[0017] There are also areas where bisphenol A is used as a raw material for optical materials such as optical polycarbonate resins. Optical materials require excellent hue (transparency), therefore, bisphenol A, as a raw material for them, also requires excellent hue.

[0018] However, in methods involving the hydrolysis and alcoholysis of polycarbonate resin followed by crystallization, even with high-purity bisphenol A, if a small amount of coloring components derived from the polycarbonate resin remains, there may be insufficient raw materials for optical materials requiring excellent color tone (transparency). Furthermore, methods that independently proceed from the decomposition of polycarbonate resin to the purification of bisphenol A often involve increased steps or more complex and larger equipment to improve bisphenol A purity, making them less desirable from a cost and energy perspective.

[0019] Alternatively, as described above, bisphenol A obtained from the decomposition of polycarbonate resin can be supplied to a general bisphenol A manufacturing process and purified together to obtain high-purity bisphenol A. For example, according to Example 1 of Patent Document 1, the following steps are described: First, a compression pan formed from polycarbonate resin is alcoholyzed with cyclohexanol to obtain a non-distilled heavy component after vacuum distillation. Then, the aforementioned non-distilled heavy component is mixed with the mother liquor obtained by crystallization in a general bisphenol A manufacturing process, and then mixed with the reaction product containing bisphenol A obtained by condensation reaction in a general bisphenol A manufacturing process, and concentrated. After crystallization of the obtained concentrate, solid-liquid separation is performed to obtain bisphenol A-phenol adduct crystals. Phenol is removed from the obtained adduct crystals by distillation, thereby obtaining high-purity bisphenol A. However, although the obtained bisphenol A is of high purity, its color is degraded due to the influence of coloring components contained in the non-distilled heavy component.

[0020] Alternatively, it is also feasible to use alkaline hydrolysis of polycarbonate resin to decompose it into isopropenylphenol. For example, according to Example 1 of Patent Document 2, the following is described: isopropenylphenol is decomposed using a known method, and the resulting decomposition solution is supplied to the BPA synthesis step of bisphenol A synthesis. The synthesis solution containing bisphenol A obtained through the BPA synthesis step is supplied to the concentration step of the bisphenol A manufacturing step, and high-purity bisphenol A is obtained using conventional methods. However, isopropenylphenol is a very unstable chemical, and there is a problem that isopropenylphenol condenses with various components before the aforementioned decomposition solution is supplied to the bisphenol A synthesis step of the bisphenol manufacturing step. Furthermore, there is a problem that the color of the obtained bisphenol A deteriorates due to the condensed components.

[0021] In the past, the chemical recycling of polycarbonate resins required a long time to purify the recycled bisphenol A, necessitating the removal of coloring components from the polycarbonate resin and the improvement of the hue of the resulting bisphenol A, thus requiring further improvements.

[0022] The present invention was made in view of the following circumstances, and aims to provide a method for manufacturing bisphenol A that can efficiently remove coloring components derived from polycarbonate resin and produce bisphenol A with good color tone. Furthermore, the object is to provide a method for manufacturing a polycarbonate resin using the aforementioned bisphenol.

[0023] Solution for solving the problem

[0024] In order to solve the above-mentioned problems, the inventors conducted in-depth research and discovered the following method: Polycarbonate resin is decomposed using phenol; after decomposition, a portion of the phenol is removed by distillation to obtain a crude solution containing low-purity bisphenol A; this crude solution is mixed with the mother liquor obtained in the bisphenol A manufacturing process; and then treated under conditions for decomposing bisphenol A. The resulting reaction solution is then recycled in the bisphenol A manufacturing process to produce bisphenol A. Furthermore, a method for manufacturing polycarbonate resin using the aforementioned bisphenol A was discovered.

[0025] That is, the present invention relates to the following invention.

[0026] <1> A method for manufacturing bisphenol A, comprising the following steps A to F, H, and I.

[0027] Step A: Decompose polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A. Remove the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass.

[0028] Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A.

[0029] Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C.

[0030] Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d.

[0031] Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A.

[0032] Process F: A portion of the mother liquor D obtained in process D is recycled and supplied to process B.

[0033] Step H: The step of obtaining solution H1 or solution H2 from a portion of the aforementioned mother liquor D and the aforementioned crude solution A.

[0034] Here, solution H1 is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then combining phenol and isopropenylphenol.

[0035] The aforementioned solution H2 is a phenol-containing solution obtained by decomposing the bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and acetone under the condition of decomposing bisphenol A.

[0036] Step I: Supply solution H1 or solution H2 obtained in step H to steps B and / or C.

[0037] <2> A method for manufacturing bisphenol A, comprising the following steps A to I.

[0038] Step A: Decompose polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A. Remove the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass.

[0039] Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A.

[0040] Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C.

[0041] Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d.

[0042] Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A.

[0043] Process F: A portion of the mother liquor D obtained in process D is recycled and supplied to the dehydration and condensation process in process B.

[0044] Process G: The process of mixing the crude solution A obtained in process A and a portion of the mother liquor D obtained in process D to obtain the mixture G.

[0045] Step H: A step of obtaining a solution H1 containing bisphenol A obtained by treating the aforementioned mixture G under conditions of bisphenol A decomposition followed by recombination, or a solution H2 containing decomposition products obtained by treating the aforementioned mixture G under conditions of bisphenol A decomposition.

[0046] Step I: Supply solution H1 or solution H2 obtained in step H to steps B and / or C.

[0047] <3> According to the foregoing <1> or <2> The method for manufacturing bisphenol A includes mixing a portion of the aforementioned mother liquor D with the aforementioned crude solution A, and supplying the resulting mixture G to an apparatus for decomposing bisphenol A in the aforementioned step H.

[0048] <4> According to the foregoing <1> or <2> The method for manufacturing bisphenol A includes supplying a portion of the aforementioned mother liquor D and the aforementioned crude solution A to an apparatus for decomposing bisphenol A in the aforementioned step H, wherein the decomposition reaction is carried out in the aforementioned apparatus while preparing a mixed solution G.

[0049] <5> According to the foregoing <1> ~ <4> In any one of the methods for manufacturing bisphenol A, in the aforementioned step C, a portion of the phenol is further removed by distillation from the aforementioned reaction solution B to obtain a concentrated solution C.

[0050] <6> According to the foregoing <2> ~ <5> In any one of the methods for manufacturing bisphenol A, wherein, in the aforementioned step H, when the aforementioned mixture G is treated under conditions that decompose bisphenol A, the decomposition rate of bisphenol A in the aforementioned mixture G is 30 mol% or more.

[0051] <7> According to the foregoing <1> ~ <6> The method for manufacturing bisphenol A according to any one of the following, wherein the conditions for decomposing the aforementioned bisphenol A are selected from any group consisting of alkaline conditions, acidic conditions, and supercritical water conditions.

[0052] <8> According to the foregoing <2> ~ <7> In any one of the methods for manufacturing bisphenol A, the aforementioned mixture G is treated under conditions that decompose bisphenol A, or distilled while being treated, to recover the fraction h containing the decomposition products and remove the residue.

[0053] <9> According to the foregoing <2> ~ <8> The method for manufacturing bisphenol A according to any one of the following, wherein the aforementioned step H is the step of obtaining the aforementioned solution H1, which comprises:

[0054] In the decomposition / distillation process, the aforementioned mixture G is treated under alkaline conditions for the decomposition of bisphenol A while distillation is performed to recover the fraction h1 containing phenol and isopropenylphenol as decomposition products, and the residue is removed; and

[0055] In the next step, the phenol and isopropylphenol contained in the aforementioned fraction h1 are recombined to generate bisphenol A.

[0056] <10> According to the foregoing <9> The method for manufacturing bisphenol A, wherein the aforementioned fraction h1 contains more than 1.0% by mass of isopropenylphenol.

[0057] <11> According to the foregoing <9> or <10> The method for manufacturing bisphenol A, wherein the aforementioned solution H1 contains more than 1% by mass of bisphenol A.

[0058] <12> According to the foregoing <9> ~ <11> In any one of the methods for manufacturing bisphenol A, after treating the aforementioned residue in the presence of an acid catalyst, distillation is performed to recover the phenol fraction h1b.

[0059] <13> According to the foregoing <2> ~ <8> The method for manufacturing bisphenol A according to any one of the following, wherein the aforementioned step H is the step of obtaining the aforementioned solution H2, which comprises:

[0060] In the alkaline hydrolysis process, the aforementioned mixture G is treated under alkaline conditions for hydrolyzing bisphenol A to obtain a reaction solution h2 containing acetone and phenol; and

[0061] The acetone / phenol recovery process recovers the acetone fraction and / or phenol fraction from the reaction solution h2 obtained in the aforementioned alkaline hydrolysis process, and removes the residue.

[0062] <14> According to the foregoing <13> The method for manufacturing bisphenol A, wherein the aforementioned solution H2 contains more than 0.1% by mass of acetone.

[0063] <15> According to the foregoing <1> ~ <14> The method for manufacturing bisphenol A according to any one of the above-mentioned steps A, wherein the solvent used in the aforementioned step A is phenol.

[0064] <16> According to the foregoing <1> ~ <15> The method for manufacturing bisphenol A according to any one of the following, wherein step A is a step of decomposing the aforementioned polycarbonate resin in the presence of any catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines and acids to obtain the aforementioned crude solution A.

[0065] <17> According to the foregoing <1> ~ <16> In any one of the methods for manufacturing bisphenol A, the content of bisphenol A in the aforementioned crude solution A is 10% by mass or more.

[0066] <18> According to the foregoing <17> In the method for manufacturing bisphenol A, the content of bisphenol A in the aforementioned crude solution A is 20% by mass or more.

[0067] <19> A method for manufacturing bisphenol A, comprising the following steps B to F, H, and I.

[0068] Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A.

[0069] Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C.

[0070] Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d.

[0071] Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A.

[0072] Process F: A process that recycles a portion of the mother liquor D obtained in process D and supplies it to process B. Process H: A process that obtains solution H1 or solution H2 from a portion of the aforementioned mother liquor D and crude solution A.

[0073] In this process, crude solution A is obtained by decomposing polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, followed by distillation to remove the solvent from the obtained reaction solution a1.

[0074] The content of bisphenol A in the aforementioned crude solution A is less than 90% by mass.

[0075] The aforementioned solution H1 is a solution containing bisphenol A obtained by decomposing the bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombining the phenol and isopropenylphenol.

[0076] The aforementioned solution H2 is a phenol-containing solution obtained by decomposing the bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and acetone under the condition of decomposing bisphenol A.

[0077] Step I: Supply solution H1 or solution H2 obtained in step H to steps B and / or C.

[0078] <20> According to the foregoing <19> The method for manufacturing bisphenol A includes mixing a portion of the aforementioned mother liquor D with the aforementioned crude solution A, and supplying the resulting mixture G to an apparatus for decomposing bisphenol A in the aforementioned step H.

[0079] <21> According to the foregoing <19> The method for manufacturing bisphenol A includes supplying a portion of the aforementioned mother liquor D and the aforementioned crude solution A to an apparatus for decomposing bisphenol A in the aforementioned step H. In the aforementioned apparatus, a decomposition reaction is carried out while preparing a mixture G containing a portion of the aforementioned mother liquor D and the aforementioned crude solution A.

[0080] <22> A method for manufacturing a polycarbonate resin, wherein the resin is used in accordance with the aforementioned... <1> ~ <21> Bisphenol A obtained by any one of the methods for manufacturing bisphenol A is used to manufacture polycarbonate resin.

[0081] The effects of the invention

[0082] This invention provides a method for manufacturing bisphenol A that can efficiently remove coloring components derived from polycarbonate resin and produce bisphenol A with good color tone. Furthermore, it provides a method for manufacturing polycarbonate resin using the aforementioned bisphenol A. Attached Figure Description

[0083] Figure 1 A flowchart illustrating an example of a method for manufacturing bisphenol A according to the present invention.

[0084] Figure 2 A flowchart illustrating an example of a method for manufacturing bisphenol A according to the present invention.

[0085] Figure 3 A flowchart illustrating an example of step A in the method for manufacturing bisphenol A according to the present invention.

[0086] Figure 4 A flowchart illustrating an example of step A in the method for manufacturing bisphenol A according to the present invention.

[0087] Figure 5 A flowchart illustrating an example of a method for manufacturing bisphenol A according to the present invention.

[0088] Figure 6 A flowchart illustrating an example of step H in the method for manufacturing bisphenol A according to the present invention.

[0089] Figure 7 A flowchart illustrating an example of step H in the method for manufacturing bisphenol A according to the present invention.

[0090] Figure 8 A flowchart illustrating an example of step H in the method for manufacturing bisphenol A according to the present invention.

[0091] Figure 9 A flowchart illustrating an example of step H in the method for manufacturing bisphenol A according to the present invention.

[0092] Figure 10A flowchart illustrating an example of step H in the method for manufacturing bisphenol A according to the present invention. Detailed Implementation

[0093] The embodiments of the present invention will be described in detail below. However, the description of the constituent elements described below is only one example of the embodiments of the present invention, and the present invention is not limited to the contents described below as long as it does not deviate from its gist. It should be noted that when the expression "~" is used in this specification, it is used to describe the numerical values ​​or physical property values ​​before and after it.

[0094] <Method for manufacturing bisphenol A>

[0095] This invention relates to a method for manufacturing bisphenol A having the following steps A to F, H, and I (hereinafter sometimes referred to as "the method for manufacturing bisphenol A of the present invention").

[0096] Step A: Decompose polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A. Remove the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass.

[0097] Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A.

[0098] Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C.

[0099] Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d.

[0100] Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A.

[0101] Process F: A process that recycles a portion of the mother liquor D obtained in process D and supplies it to process B. Process H: Any of the processes (I) to (III) below.

[0102] (I) The process of obtaining solution H1 or solution H2 from a portion of the aforementioned mother liquor D and the aforementioned crude solution A

[0103] Here, solution H1 in (I) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombining phenol and isopropenylphenol. Additionally, solution H2 in (I) is a solution obtained by decomposing bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and acetone under conditions of bisphenol A decomposition.

[0104] (II) A portion of the aforementioned mother liquor D undergoes isomerization and crystallization / solid-liquid separation treatment, from which solution H1 or solution H2 is obtained from the resulting mother liquor S2a and the aforementioned crude solution A.

[0105] Here, solution H1 in (II) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the aforementioned mother liquor S2a and the aforementioned crude solution A into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombinizing phenol and isopropenylphenol. Similarly, solution H2 in (II) is a solution obtained by decomposing bisphenol A contained in the aforementioned mother liquor S2a and the aforementioned crude solution A into phenol and acetone under conditions of bisphenol A decomposition.

[0106] (III) A process of performing crystallization / solid-liquid separation treatment on solution S3a, which contains the aforementioned mother liquor D after isomerization treatment, and the aforementioned crude solution A, to obtain solution H1 or solution H2 from the obtained mother liquor S2b.

[0107] Here, solution H1 in (III) is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the aforementioned mother liquor S2b into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombinizing phenol and isopropenylphenol. Similarly, solution H2 in (III) is a solution obtained by decomposing bisphenol A contained in the aforementioned mother liquor S2b into phenol and acetone under conditions of bisphenol A decomposition.

[0108] Step I: Supply solution H1 or solution H2 obtained in step H to steps B and / or C.

[0109] Figure 1 An example flowchart of a method for manufacturing bisphenol A according to the present invention is shown. For example... Figure 1 As shown, bisphenol A, generated from the decomposition of polycarbonate resin, is supplied to process H or process f2. When crude solution A and mother liquor D are processed in process H, crude solution A and mother liquor D are... Figure 1 The path P1 or P2 supplies the equipment for decomposition in process H. When crude solution A and mother liquor S2a are processed through process H, crude solution A and mother liquor S2a pass through... Figure 1 The path P3 or P4 supplies the equipment for decomposition in process H. When the mother liquor S2b is processed through process H, the crude solution A and mother liquor D pass through... Figure 1 Path P5 is supplied to the device for decomposing process H.

[0110] Solution H1 obtained in process H is supplied to process B via process I. Figure 1 Path P11) and / or process C ( Figure 1 The path is P12). Additionally, the solution H2 obtained in process H is supplied to process B (…). Figure 1Path P21) and / or process C ( Figure 1 Path P22).

[0111] Figure 2 An example flowchart of a method for manufacturing bisphenol A according to the present invention is shown. Figure 2 The method for manufacturing bisphenol A shown is an example of mixing a portion of the aforementioned mother liquor D and the aforementioned crude solution A and processing them, with steps A to I described below.

[0112] Step A: Decompose polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A. Remove the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass.

[0113] Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A.

[0114] Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C.

[0115] Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d.

[0116] Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A.

[0117] Process F: A portion of the mother liquor D obtained in process D is recycled and supplied to process B.

[0118] Process G: A process that combines the crude solution A obtained in process A with a portion of the mother liquor D obtained in process D to obtain a mixed solution G.

[0119] Step H: A step of obtaining a solution H1 containing bisphenol A obtained by treating the aforementioned mixture G under conditions of bisphenol A decomposition followed by recombination, or a solution H2 containing decomposition products obtained by treating the aforementioned mixture G under conditions of bisphenol A decomposition.

[0120] Step I: Supply solution H1 or solution H2 obtained in step H to steps B and / or C.

[0121] Figure 2One feature of the bisphenol A manufacturing method of the present invention is that a crude solution A obtained by decomposing polycarbonate resin is mixed with a mother liquor D obtained by manufacturing bisphenol A. After decomposition and recombination in step H, the mixture is returned to the step of generating bisphenol A (step B) and / or the step of concentrating the reaction solution B (step C). The reaction solution obtained by decomposing waste plastics containing polycarbonate resin sometimes contains stabilizers derived from the decomposed polycarbonate resin, resins other than polycarbonate resin, sebum, dust, foreign matter, etc. Conventionally, supplying such a reaction solution to the general bisphenol A manufacturing process—specifically, the steps of reacting acetone and phenol in the presence of an acidic catalyst to obtain a reaction solution containing bisphenol A, the steps of distilling and separating the reaction solution containing bisphenol A to obtain a concentrated solution, and the steps of crystallizing / recovering the concentrated solution to obtain adduct crystals and mother liquor—may significantly contaminate the bisphenol A manufacturing process and impair the quality of the manufactured bisphenol A.

[0122] On the other hand, the manufacturing process of bisphenol A includes a step for recycling the mother liquor. Before recycling the mother liquor in the process of dehydrating and condensing acetone and phenol to produce bisphenol A, a treatment is performed to recover useful components or reduce impurities from the mother liquor.

[0123] Typically, the crude solution A obtained in step A contains, in addition to bisphenol A, heavy components derived from the decomposition of polycarbonate resin, whose structures have not been fully analyzed. These heavy components are those with boiling points higher than phenol. These heavy impurities differ from the impurities byproducts in the manufacture of bisphenol A and are not limited to those that can be removed using the same purification methods as those used in the manufacture of bisphenol A. Therefore, in a typical bisphenol A manufacturing process, if the process for supplying crude solution A is inappropriate, the purity or color of the resulting bisphenol A may decrease. The inventors have discovered that by using treatment conditions for recovering useful components from the mother liquor or for reducing impurities, useful components in the crude solution A obtained from the decomposition of polycarbonate resin can be recovered, or impurities can be decomposed and removed. Furthermore, it has been discovered that by incorporating crude solution A into the process of circulating the mother liquor in each step of the bisphenol A manufacturing process, bisphenol A with excellent color can be obtained with high purity. That is, by performing step H, which includes mixing crude solution A with mother liquor D and treating it under conditions that decompose bisphenol A, not only is bisphenol A in crude solution A decomposed, but also the incomplete decomposition products of residual polycarbonate resin (dimers, trimers, and other polymers of bisphenol A) are decomposed. Alternatively, after removing the cause of coloring, the treated solution can be returned to step B and / or step C, thereby obtaining bisphenol A with excellent color in purification step E.

[0124] Furthermore, one characteristic of the bisphenol A manufacturing method of the present invention is that, in step A, a crude solution A with a bisphenol content of less than 90% by mass is prepared. In step H, not only bisphenol A in the crude solution A but also residual incomplete decomposition products are decomposed, thus eliminating the need for excessive purification operations in step A and simplifying the process. When the bisphenol A content is too high, the viscosity of the crude solution A increases, making it difficult to transport the crude solution A for mixing with the mother liquor D obtained in step D, or making it difficult to mix it uniformly with the mother liquor D obtained in step D. Conversely, when the bisphenol A content is too low, the amount of bisphenol A produced decreases, which is economically undesirable.

[0125] Next, each step of the method for manufacturing bisphenol A according to the present invention will be described.

[0126] [Process A]

[0127] Step A is a process of decomposing polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and removing the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass.

[0128] (Polycarbonate resin (PC))

[0129] The polycarbonate resin used in process A comprises a polycarbonate resin containing repeating units derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane).

[0130] Furthermore, polycarbonate resins can be used not only as a single resin containing repeating units derived from bisphenol A, but also as compositions containing resins other than polycarbonate resin, such as copolymers and polymer alloys. Examples of compositions containing resins other than polycarbonate resin include polycarbonate / polyester copolymers, polycarbonate / polyester alloys, polycarbonate / polyaryl copolymers, and polycarbonate / polyaryl alloys. When using compositions containing resins other than polycarbonate resin, those with polycarbonate resin as the main component (containing 50% by mass or more of polycarbonate resin in the composition) are preferred.

[0131] In addition, two or more different polycarbonate resins can be mixed together.

[0132] From a chemical recycling perspective, polycarbonate resin is preferably polycarbonate resin contained in waste plastics. Polycarbonate resin is used to mold various products, such as optical components like headlamps and optical recording media like optical discs. Waste plastics containing polycarbonate resin can include residues, defective products, and used products from the molding process of polycarbonate resin into these products.

[0133] Waste plastics can be used after appropriate washing, crushing, and pulverizing. Methods for crushing waste plastics include using jaw crushers and rotary crushers to crush them into coarse pieces (less than 20cm), using rotary crushers, cone crushers, and mills to crush them into medium pieces (less than 1cm), and using mills to pulverize them into pieces (less than 1mm), reducing the size to a size suitable for feeding into the decomposition tank. Additionally, when the waste plastic is thin plastic like that used in CDs and DVDs, it can be cut and fed into the decomposition tank using a shredder. Furthermore, components other than polycarbonate resin, such as those found in the surface and inner layers of optical discs, can be removed before use.

[0134] (Decomposition of polycarbonate resin)

[0135] As a method for decomposing polycarbonate resin, known methods can be used. For example, by heating the polycarbonate resin in a solvent, the polycarbonate resin is decomposed to obtain a reaction solution a1 containing bisphenol A.

[0136] Polycarbonate resin dissolves quickly, therefore phenol is preferably used to decompose it. That is, it is preferable to decompose the polycarbonate resin in a solvent containing phenol.

[0137] The solvent containing phenol may also contain solvents other than phenol, but phenol is preferred as the main component. For example, it is preferred that the phenol content in the solvent containing phenol is 50% by mass or more, and depending on the type of other solvents, catalysts, etc., it can be appropriately set to 65% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, etc.

[0138] Furthermore, compared to using phenol alone as a solvent, the decomposition rate of polycarbonate resin can be increased, and polycarbonate resin can be decomposed even under mild conditions (e.g., normal pressure, around 60–150°C). Therefore, the solvent containing phenol is preferably a mixed solvent containing any solvent selected from the group consisting of water, monohydric alcohols, and dihydric alcohols, and phenol. More preferably, it is a mixed solvent containing phenol and water or a mixed solvent containing phenol and monohydric alcohols. As a monohydric alcohol, methanol, ethanol, n-butanol, or other straight-chain alcohols with 1 to 5 carbon atoms are preferred.

[0139] In addition, a catalyst is preferably used in the decomposition of polycarbonate resin, and any catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines and acids is preferred.

[0140] Sodium hydroxide or potassium hydroxide is preferred as an alkali metal hydroxide. Additionally, sodium carbonate or potassium carbonate is preferred as an alkali metal carbonate.

[0141] Alkylamines are compounds formed by substituting at least one hydrogen atom of an amine with an alkyl group. Examples of alkylamines include methylamine, ethylamine, propylamine, dimethylamine, diethylamine, trimethylamine, and triethylamine. Alkylamines are preferably secondary or tertiary amines, and more preferably tertiary amines.

[0142] Furthermore, the boiling point of the alkylamine is preferably below 200°C, more preferably below 160°C. Additionally, its lower limit is preferably above 10°C, more preferably above 30°C. With such a boiling point, when a portion of the solvent is removed by distillation using methods such as vacuum distillation, it can be removed along with the alkylamine and removed from the system.

[0143] As an acid, it is preferably any one of the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, and sulfonic acid. Examples of sulfonic acids include alkyl sulfonic acids such as methanesulfonic acid and aromatic sulfonic acids such as toluenesulfonic acid.

[0144] The molar ratio of catalyst to 1 mole of repeating unit of polycarbonate resin ((mass of catalyst used [g] / molecular weight of catalyst [g / mol]) / (mass of polycarbonate resin used [g] / molecular weight of repeating unit [g / mol])) is preferably 0.0001 or more, more preferably 0.0005 or more, and even more preferably 0.0007 or more. When the amount of catalyst used relative to the polycarbonate resin is small, the decomposition rate slows down, the decomposition time becomes longer, and the efficiency tends to deteriorate. Furthermore, the molar ratio of catalyst to 1 mole of repeating unit of polycarbonate resin is preferably 1 mole or less, more preferably 0.9 or less, and even more preferably 0.8 or less. When the amount of catalyst used relative to the polycarbonate resin is large, the manufacturing efficiency tends to decrease.

[0145] (Removal of solvent by distillation)

[0146] In step A, after the polycarbonate resin is decomposed, the solvent is removed from the resulting reaction solution a1 by distillation. Solvent removal can be performed by distillation. Alternatively, it is not necessary to completely remove the solvent from the reaction solution a1 by distillation; the amount of solvent removed by distillation is appropriately determined based on the content of the target bisphenol A and the components contained in the reaction solution a1.

[0147] When using a solvent containing phenol, in order to efficiently supply bisphenol A obtained from the decomposition of polycarbonate resin to steps G or H, it is preferable to partially remove the phenol by distillation after decomposing the polycarbonate resin in the presence of phenol. If light components are present in crude solution A, these light components may remain in solutions H1 and H2 obtained in step H, raising concerns about a decrease in the quality of bisphenol A obtained in step E. In step A, by partially removing the phenol by distillation after decomposing the polycarbonate resin in the presence of phenol, crude solution A with sufficient removal of light components can be obtained. It should be noted that light components refer to components with a boiling point lower than phenol. For example, when using a mixed solvent of phenol and water, or alkylamines as catalysts, water and alkylamines are considered light components. Furthermore, when using a mixed solvent of phenol and a monohydric alcohol, the monohydric alcohol and dialkyl carbonates produced as a byproduct with bisphenol A are considered light components.

[0148] (Crude solution A)

[0149] Crude solution A is a composition containing less than 90% by mass of bisphenol A and is liquid at the temperature conditions supplied to process G or process H. Crude solution A may also be solid at a temperature lower than the temperature conditions supplied to process G or process H. Typically, crude solution A obtained in process A is supplied to the apparatus performing process G or process H at a temperature of 40°C or higher, therefore crude solution A is a composition containing bisphenol A and is liquid at a temperature of 40°C or higher.

[0150] The bisphenol A content (mass of bisphenol A / mass of crude solution A × 100%) in the crude solution A obtained in step A is less than 90% by mass. Preferably, it is 85% by mass or less, and the lower the value, the more preferred, in the order of 80% by mass or less, 70% by mass or less, and 60% by mass or less. As described above, in the bisphenol A manufacturing method of the present invention, even if the crude solution A contains heavy components such as incomplete decomposition products of polycarbonate resin (dimers, trimers, and other polymers of bisphenol A), these impurities can be decomposed and removed in step H, thus eliminating the need for excessive purification of the crude solution A. Furthermore, if the bisphenol A content is too high, the viscosity of the crude solution A increases, making it difficult to transport or uniformly mix with the mother liquor D obtained in step D. In addition, when the content of bisphenol A is too high, when phenol and isopropenylphenol generated by the decomposition of bisphenol A in step H recombine, the concentration of isopropenylphenol generated by the alkaline hydrolysis and other decomposition treatments in step H increases, and it will self-condense into a byproduct, thus significantly reducing the formation rate of bisphenol A in the recombination.

[0151] Furthermore, the content of bisphenol A in the crude solution A is preferably 10% by mass or more, with higher values ​​being preferred 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 will be reduced, which is therefore not economically desirable.

[0152] In addition to bisphenol A, crude solution A may also contain phenol. The phenol content in 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 phenol content is too low, bisphenol A in crude solution A will precipitate into a slurry, making delivery difficult.

[0153] Furthermore, crude solution A may contain heavy components such as incomplete decomposition products of polycarbonate resin (dimers, trimers, and other polymers of bisphenol A). However, if there are too many heavy components, carbon dioxide will be generated in process H, causing pressure fluctuations and raising concerns about the complexity of reaction control. Therefore, the content of heavy components in crude solution A is preferably 5% by mass or less, more preferably 1% by mass or less. It should be noted that crude solution A can also be thoroughly washed.

[0154] The following is based on Figure 3 and Figure 4 A specific example of process A will be provided.

[0155] [Process A1]

[0156] Figure 3 The illustrated process A1 comprises: a PC decomposition process in which polycarbonate resin is decomposed in the presence of a solvent containing phenol and a catalyst to obtain a reaction solution a1 containing bisphenol A; and a concentration process a1 in which the reaction solution a1 obtained in the PC decomposition process is distilled to remove a portion of the phenol. In process A1, a catalyst that can be removed by distillation in the concentration process a1 is typically used. Examples of such catalysts include alkylamines.

[0157] (PC disassembly process)

[0158] The reaction temperature is typically 60–150°C. Preferably, it is 70°C or higher, more preferably 75°C or higher, and even more preferably 80°C or higher. Furthermore, the upper limit of the reaction temperature can be appropriately set to below 130°C, below 120°C, below 110°C, below 100°C, below 95°C, etc., depending on the type of solvent used in the decomposition of the polycarbonate resin. Additionally, the pressure for the PC decomposition reaction is preferably 1 kPa–50 MPa, more preferably 5 kPa–10 MPa.

[0159] The reaction mode for the decomposition reaction of polycarbonate resin is not particularly limited; it can be continuous or batch. For example, in the batch reaction, the reaction time is appropriately selected based on the concentration of polycarbonate resin, reaction temperature, and reaction pressure. However, when the reaction time is longer, the generated bisphenol A tends to decompose. Therefore, a reaction time of 30 hours or less is preferred, followed by 25 hours or less, 20 hours or less, 15 hours or less, 10 hours or less, and 5 hours or less, with smaller values ​​being more preferred. In addition, when the reaction time is short, the decomposition reaction may not proceed sufficiently. Therefore, a reaction time of 0.1 hours or more is preferred, 0.5 hours or more is more preferred, and 1 hour or more is even more preferred.

[0160] (Concentration process a1)

[0161] In the concentration step a1, the reaction solution a1 is distilled to remove a portion of the phenol. As mentioned above, the resulting solution may contain heavy components such as incomplete decomposition products of polycarbonate resin (dimers, trimers, and other polymers of bisphenol A), but these heavy components can also be decomposed and removed in step H, so the resulting solution can be directly used as crude solution A. For example, distillation can be carried out at a temperature of 50–200°C and a pressure of 0.1 kPa–150 kPa. In addition, light components such as alkylamines, which have a lower boiling point than phenol, are also removed by distillation in the concentration step a1.

[0162] [Process A2]

[0163] Figure 4 The illustrated step A2 comprises: a PC decomposition step in which polycarbonate resin is decomposed in the presence of a solvent containing phenol and a catalyst to obtain a reaction solution a1 containing bisphenol A; a neutralization step in which the reaction solution 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 remove a portion of the phenol. In step A2, after neutralizing the reaction solution a1 and removing the catalyst, the solvent is removed by distillation. In step A2, the catalyst can be removed by the neutralization step, so a catalyst with a high boiling point, such as an alkali metal hydroxide, can also be used. As a catalyst, for example, any one selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines, and acids can be used.

[0164] (PC disassembly process)

[0165] The PC decomposition process can be performed in the same way as process A1.

[0166] (Neutralization process)

[0167] In the neutralization process, the reaction solution a1 obtained from the PC decomposition process is neutralized to obtain an organic phase a2 containing bisphenol A. For neutralization, when using a base such as an alkali metal hydroxide, alkali metal carbonate, or alkylamine as a catalyst, it is carried out by mixing an acid such as hydrochloric acid, sulfuric acid, or phosphoric acid into the reaction solution a1. Alternatively, when using an acid as a catalyst, it is carried out by mixing a base such as sodium carbonate or sodium hydroxide into the reaction solution a1. For neutralization, it is preferable to adjust the amount of mixed acid or base so that the pH of the reaction solution a1 is 7.5–10 (preferably pH 8.0–9.5). After mixing the acid or base with the reaction solution a1 according to the catalyst used, oil and water are separated, and the aqueous phase is removed, thereby obtaining the organic phase a2 containing bisphenol A.

[0168] (Concentration process a2)

[0169] In concentration step a2, the organic phase a2 obtained in the neutralization step is distilled to remove a portion of the phenol. The resulting solution may contain incomplete decomposition products of polycarbonate resin (dimers, trimers, and other polymers of bisphenol A) and heavy impurities with boiling points higher than phenol. However, these incomplete decomposition products and impurities can be decomposed and removed in step H, so the resulting solution can be directly used as crude solution A. For example, distillation can be carried out at a temperature of 50–200°C and a pressure of 0.1 kPa–150 kPa.

[0170] It should be noted that when using catalysts with high boiling points such as alkali metal hydroxides, in step H, when bisphenol A is decomposed under alkaline conditions, neutralization can be omitted, and crude solution A can be obtained in the same way as in step A1.

[0171] [Process B]

[0172] Step B is a process in which acetone and phenol are dehydrated and condensed in the presence of an acid catalyst to obtain a reaction solution B containing bisphenol A.

[0173] (acetone)

[0174] Acetone, as the raw material, can be used without particular restrictions as long as it is industrially available. For example, new acetone can be supplied from outside the system, or unreacted acetone removed by distillation in step C can be recycled as acetone for step B, or these can be used in combination.

[0175] (phenol)

[0176] Phenol, as a raw material, can be used without particular restrictions as long as it is industrially available. For example, new phenol can be supplied from outside the system, or unreacted phenol removed by distillation in step C and phenol contained in the solution after step G can be recycled as phenol for step B, or they can be used in combination.

[0177] (Acid catalyst)

[0178] As an acid catalyst, acidic substances are used, such as hydrochloric acid, sulfuric acid, and other mineral acids, strong acidic cation exchange resins, and solid acids such as polysiloxanes. Considering factors such as corrosion of the apparatus, separation of the catalyst after the reaction, and catalytic activity, strong acidic cation exchange resins such as sulfonic acid type are typically used. For example, styrene-divinylbenzene copolymer acidic cation exchange resins, in which approximately 2-16% of the total benzene rings are introduced with sulfonic acid groups, can be used. Their average particle size is typically 0.2-2 mm, preferably 0.4-1.5 mm. Furthermore, to improve selectivity and conversion, it is preferable to add a sulfur-containing amine compound as a co-catalyst during the reaction, or to load it onto the acid catalyst. A preferred acid catalyst in step B is a strong acidic cation exchange resin partially modified with a sulfur-containing amine compound.

[0179] (Molar ratio of acetone to phenol)

[0180] There are no particular restrictions on the molar ratio of phenol to acetone. An excess of phenol compared to the stoichiometric amount can be used. 3 to 30 moles of phenol can be used relative to 1 mole of acetone, preferably 5 to 20 moles. When the amount of phenol used relative to 1 mole of acetone is less than 3 moles, the selectivity of bisphenol A decreases; when it is greater than 30 moles, problems such as reduced reaction rate and increased equipment size will occur.

[0181] The condensation reaction of acetone and phenol can be carried out using known methods. There are no particular restrictions on the reaction mode; typically, it is conducted in a fixed-bed flow mode or a suspended-bed batch mode. In the case of a fixed-bed flow mode, the liquid hourly space velocity (LHSV) of the feed mixture supplied to the reactor is typically 0.2–50 L / h. In the case of a suspended-bed batch mode, depending on the reaction temperature and pressure, the amount of acid catalyst used relative to the feed mixture is typically 20–100% by mass, and the reaction time is typically 0.5–5 hours. Preferably, a fixed-bed continuous reaction mode is used, in which phenol and acetone are continuously supplied to a condensation reaction apparatus filled with an acidic cation exchange resin immobilized with a catalyst to allow the reaction to proceed.

[0182] The reaction temperature is typically 40–130°C, preferably 40–90°C. Temperatures below 40°C may cause the reaction solution to solidify, and are therefore not preferred. Furthermore, at temperatures above 130°C, the acidic groups of the acidic cation exchange resin acting as a catalyst may detach from the catalyst and mix with bisphenol A, causing bisphenol A decomposition; alternatively, the catalyst may decompose at high temperatures, reducing its lifespan. The reaction pressure is typically atmospheric pressure to 600 kPa (absolute pressure).

[0183] [Process C]

[0184] Step C involves removing unreacted acetone and water from reaction solution B obtained in step B by distillation, yielding concentrated solution C. Reaction solution B in step B contains generated bisphenol A, unreacted acetone, phenol, byproduct water, and isomers of bisphenol A. In step C, by performing vacuum distillation or other methods on reaction solution B, the light components containing unreacted acetone and water are removed from the system, thus obtaining concentrated solution C containing bisphenol A and phenol.

[0185] In addition, in step C, it is preferable to remove a portion of the acetone, water, and phenol from the reaction solution B obtained in step B by distillation to obtain concentrated solution C. By removing a portion of the phenol by distillation, concentrated solution C in which acetone and water are sufficiently removed can be obtained.

[0186] For example, by feeding the reaction solution B obtained in step B to a distillation column, removing water, unreacted acetone, and a portion of the phenol from the top of the column, and then extracting the reaction product from the bottom, concentrated solution C used in step D can be obtained. The resulting concentrated solution C is supplied to step D. Alternatively, the acetone removed by distillation can be recycled in step B. The phenol removed by distillation can be recycled in step B or used as a cleaning solvent for bisphenol A in step E.

[0187] Distillation is preferably carried out at a reaction temperature of 50–150°C and a pressure of 0.0065–0.040 MPa. Acetone and water in concentrate C are typically removed to a concentration of less than 0.1% by mass. This reduces the solubility of the addition crystals during the crystallization process and increases the crystallization yield. Furthermore, the concentration of bisphenol A in concentrate C is preferably 20–50% by mass. When the concentration of bisphenol A is less than 20% by mass, the yield decreases; conversely, when it is greater than 50% by mass, the viscosity of concentrate C increases, making transportation difficult.

[0188] [Process D]

[0189] Step D involves crystallizing the concentrated liquid C obtained in step C to obtain a slurry, and then separating the solid and liquid components of the slurry to obtain mother liquor D and filter cake d.

[0190] In step D, firstly, the adducts of bisphenol A and phenol are crystallized (addition crystallization) by crystallizing the concentrate C. For example, the concentrate C is typically adjusted to 60–100°C, preferably 70–90°C, and then fed to a crystallization apparatus. In the crystallization apparatus, the concentrate C is cooled from 60–100°C (preferably 70–90°C) to 40–70°C, thereby causing addition crystallization to precipitate as a slurry. Then, the slurry containing the dispersed addition crystals is subjected to solid-liquid separation to obtain mother liquor D and filter cake d, respectively. The obtained mother liquor D contains unprecipitated bisphenol A and phenol. Furthermore, the filter cake d contains addition crystals as the main component.

[0191] Solid-liquid separation can be achieved through known methods such as filtration and centrifugation. For example, horizontal belt filters, rotary vacuum filters, rotary pressure filters, intermittent filters, centrifugal filter separators, centrifugal sedimentation separators, and hybrid centrifugal separators (Screen Bowl Centrifuges) can be used for solid-liquid separation.

[0192] [Process E]

[0193] Step E is the process of purifying the filter cake d obtained in step D to obtain bisphenol A. There are no particular restrictions on the purification method of filter cake d. It can be achieved by removing phenol from the molten liquid in which filter cake d is heated and melted, or by crystallization using hydrocarbon solvents such as toluene, thereby separating phenol from the filter cake d obtained in step D and recovering bisphenol A.

[0194] As a method for removing phenol from filter cake d, the filter cake d is usually heated and melted to 100-160°C, and most of the phenol is removed from the resulting melt using, for example, a distillation apparatus, a thin-film evaporator, or a flash evaporator. Alternatively, to remove trace amounts of residual phenol from the melt, the following method can be used: after performing the above operation, the residual phenol is further removed by steam stripping or the like, thus purifying bisphenol A. This method is described, for example, in Japanese Patent Application Publication No. 63-132850 and Japanese Patent Application Publication No. 2-28126.

[0195] The high-purity, molten bisphenol A obtained as described above is fed to a granulation tower and a flaker to produce solid granules and tablets, thus becoming the finished bisphenol A product. Alternatively, as in the case where the obtained bisphenol A is used in the manufacture of polycarbonate resin based on a melt process, it can be directly fed to the next process in a molten state without being made into a solid.

[0196] [Process F]

[0197] Process F is a process that recycles a portion of the mother liquor D obtained in process D and supplies it to process B.

[0198] A portion of the mother liquor D obtained through solid-liquid separation is supplied to the condensation reaction apparatus via piping connected to the apparatus for process B, thereby supplying process B. Additionally, all or a portion of the remaining mother liquor D obtained through solid-liquid separation is supplied to process G or process H via piping connected to the apparatus for process G or process H.

[0199] [Process G]

[0200] Process G is a process that combines the crude solution A obtained in process A with a portion of the mother liquor D obtained in process D to obtain a mixed solution G.

[0201] Mixture G can be prepared by mixing crude solution A and mother liquor D before being transported to the reaction tower for process H; alternatively, crude solution A and mother liquor D can be transported separately to the reaction tower (device) for process H and prepared within the reaction tower.

[0202] Process G is performed in process H when a mixture G containing crude solution A and mother liquor D is processed. For example... Figure 1 As shown in path P2, the crude solution A and mother liquor D can be mixed beforehand, and the resulting mixture G can be supplied to the apparatus for the decomposition of bisphenol A in step H. Additionally, as... Figure 1 As shown in path P1, crude solution A and a portion of mother liquor D obtained in process D can also be supplied to the apparatus for decomposing bisphenol A in process H, while the crude solution A and a portion of the mother liquor are mixed in the reaction tower, and the decomposition in process H is carried out simultaneously.

[0203] Regarding the mixing ratio of crude solution A and mother liquor D, if there is too much crude solution A, the amount of undecomposed components in process H increases, which may cause the solution to solidify more easily or the piping from the reaction tank in process H to become more prone to blockage. 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. Depending on the bisphenol A content in crude solution A, it can be appropriately determined to be 5 or less, 2 or less, 1 or less, etc. There is no particular limitation on the lower limit of the mass ratio of crude solution A to mother liquor D. Depending on the bisphenol A content in crude solution A, 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.

[0204] The content of bisphenol A in mixture G is preferably 0.1% by mass or more. Excessive bisphenol A content will cause bisphenol A to precipitate and pipes to become clogged, so this is not preferred. Conversely, insufficient bisphenol A content will result in a smaller amount of isopropenylphenol or acetone obtained from decomposition, which is also not preferred.

[0205] Alternatively, process G can also be a part of the crude solution A obtained in process A and the mother liquor D obtained in process D, and then distilled to obtain the mixture G (see process G). Figure 5 For example, a mixture G can be prepared by feeding crude solution A and mother liquor D into a distillation column, mixing crude solution A and mother liquor D, and then distilling away a portion of the phenol.

[0206] Distillation can be carried out at temperatures of 100–250℃ and pressures of 1 kPa–100 kPa.

[0207] A portion of the mother liquor D can be reused in process H after undergoing isomerization, concentration, and crystallization / solid-liquid separation. For example, ... Figure 1As shown, step f1 can be performed to isomerize the reaction byproducts in the mother liquor D obtained in step D, and step f2 can be performed to crystallize and separate the solid and liquid in solution S3 containing solution S3a that has undergone isomerization treatment in step f1.

[0208] [Process f1]

[0209] Step f1 is a process of isomerizing the reaction byproducts in the mother liquor D obtained in step D. The mother liquor D obtained in step D typically contains 65-85% by mass of phenol, 1-20% by mass of bisphenol A, and 1-15% by mass of byproducts such as 2,4-bisphenol A. Mother liquor D contains a large amount of impurities such as the isomer of bisphenol A (2,4-bisphenol A). Through isomerization, the isomer of bisphenol A is converted to bisphenol A (2,2-bisphenol A). The isomerized solution S3a contains approximately 15-20% by mass of bisphenol A and approximately 5-10% by mass of byproducts such as 2,4-bisphenol A. To prevent the accumulation of impurities, a portion of the isomerized solution S3a is extracted and sent to step f2. Alternatively, a portion of the isomerized solution S3a can be recycled to at least one of steps B, C, and D.

[0210] In the isomerization process, sulfonic acid-type cation exchange resin is usually used as a catalyst. The reaction is carried out at a reaction temperature of about 50 to 100°C in a continuous and flushing fixed bed flow mode with a liquid hourly space velocity (LHSV) of about 0.2 to 50 / h.

[0211] [Process f2]

[0212] Step f2 is a process of crystallization and solid-liquid separation of solution S3, which contains solution S3a after isomerization treatment in step f1. Solution S3 contains solution S3a ( Figure 1 Paths P3 and P4), or solution S3b containing solution S3a and crude solution A. Figure 1 (Path P5). Solution S3a can be the liquid that underwent isomerization treatment in step f1 directly, or it can be a concentrated solution obtained by removing a portion of the phenol from the liquid that underwent isomerization treatment in step f1. Solution S3b can be the liquid containing solution S3a and crude solution A directly, or it can be a concentrated solution obtained by removing a portion of the phenol from the liquid containing solution S3a and crude solution A. The concentration of bisphenol A in the concentrated liquid is approximately 20–50% by mass. The concentration operation can be carried out using a distillation column, etc., at a pressure of approximately 5.3–40 kPa and a temperature of approximately 70–140 °C. In addition, the evaporated phenol can be reused as a washing liquid for washing the filter cake of addition crystallization from solid-liquid separation.

[0213] By cooling solution S3a, the adducts of bisphenol A and phenol crystallize (addition crystallization) to obtain a slurry. Solution S3a can be pre-cooled to near its freezing point by a heat exchanger using warm water as a refrigerant before being supplied to the crystallization device. Then, the slurry that has undergone addition crystallization is subjected to solid-liquid separation to obtain the addition crystallized filter cake and mother liquor S2a. Figure 1 (Paths P3 and P4). Solid-liquid separation can be carried out using the same known methods as process D.

[0214] The same applies to solution S3b. After cooling solution S3b to obtain a slurry, the slurry is subjected to solid-liquid separation, thereby obtaining the addition crystallized filter cake and mother liquor S2b respectively. Figure 1 Path P5).

[0215] The resulting mother liquors S2a and S2b are supplied to process H. The filter cake from the addition crystallization is then recycled to process C and / or process D after melting.

[0216] Processes f1 and f2 are pretreatment processes performed in process H, where mother liquor S2a and crude solution A are processed, or where mother liquor S2b is processed. For example... Figure 1 As shown in path P4, the mother liquor S2a obtained from processes f1 and f2 of mother liquor D, and the crude solution A can be mixed beforehand and supplied to the apparatus for the decomposition of bisphenol A in process H. Additionally, as... Figure 1 As shown in path P3, the mother liquor S2a obtained from steps f1 and f2 of mother liquor D, and the crude solution A, can also be fed separately to the apparatus for the decomposition of bisphenol A in step H. The crude solution A and mother liquor S2a are mixed in the reaction tower while the decomposition in step H is carried out. Alternatively, the mother liquor S2a and crude solution A can be processed separately through step H without mixing. Furthermore, as... Figure 1 As shown in path P5, S3a, which is isomerizes mother liquor D through step f1, can be mixed with crude solution A, and mother liquor S2b, which has undergone step f2, can be supplied to the apparatus for decomposing bisphenol A in step H.

[0217] [Process H]

[0218] Process H is any one of (I) to (III) below.

[0219] (I) The process of obtaining solution H1 or solution H2 from a portion of the aforementioned mother liquor D and the aforementioned crude solution A

[0220] Here, solution H1 in (I) is a solution of bisphenol A obtained by decomposing bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and isopropenylphenol under the conditions of bisphenol A decomposition, and then recombining phenol and isopropenylphenol. Furthermore, solution H2 in (I) is a solution obtained by decomposing bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and acetone under the conditions of bisphenol A decomposition.

[0221] (II) A portion of the aforementioned mother liquor D undergoes isomerization and crystallization / solid-liquid separation treatment to obtain solution H1 or solution H2 from the resulting mother liquor S2a and the aforementioned crude solution A.

[0222] Here, solution H1 in (II) is a solution containing bisphenol A obtained by decomposing the bisphenol A contained in the aforementioned mother liquor S2a and the aforementioned crude solution A into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombinizing the phenol and isopropenylphenol. Similarly, solution H2 in (II) is a solution obtained by decomposing the bisphenol A contained in the aforementioned mother liquor S2a and the aforementioned crude solution A into phenol and acetone under conditions of bisphenol A decomposition.

[0223] (III) A process of performing crystallization / solid-liquid separation treatment on solution S3a, which contains the aforementioned mother liquor D after isomerization treatment, and the aforementioned crude solution A, to obtain solution H1 or solution H2 from the obtained mother liquor S2b.

[0224] Here, solution H1 in (III) is a solution containing bisphenol A obtained by decomposing bisphenol A in the aforementioned mother liquor S2b into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombinizing the phenol and isopropenylphenol. Similarly, solution H2 in (III) is a solution obtained by decomposing bisphenol A in the aforementioned mother liquor S2b into phenol and acetone under conditions of bisphenol A decomposition.

[0225] The following describes the case where solution H1 or solution H2 is obtained from a mixture G containing crude solution A and mother liquor D. Figure 2 Taking (e.g.) as an example, we will explain process H in more detail.

[0226] Step H is a step to obtain a solution H1 containing bisphenol A by recombination after treating a mixture G under conditions of bisphenol A decomposition, or a solution H2 containing decomposition products by treating a mixture G under conditions of bisphenol A decomposition.

[0227] In addition, in step H, the aforementioned mixture G is typically treated under conditions that decompose bisphenol A, or distilled simultaneously during treatment to recover the fraction h containing the decomposition products and remove the residue. The amount of residue removed is adjusted appropriately based on the amount of mixture G supplied to step H.

[0228] In step H, when the mixture G is treated under conditions that decompose bisphenol A, the decomposition rate of bisphenol A in the mixture G is preferably 20 mol% or more, more preferably 30 mol% or more. As described above, in step H, the decomposition products are evaporated by distillation. At this time, the undecomposed components 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 will increase. These components are waste and are therefore not preferred. It should be noted that the decomposition rate of bisphenol A in the mixture G can be calculated as the amount of decomposition products contained in fraction h relative to the amount of bisphenol A in the mixture G (moles of decomposition products / moles of bisphenol A in the mixture 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 mixture G.

[0229] The conditions for the decomposition of bisphenol A are any conditions selected from the group consisting of alkaline conditions for alkaline hydrolysis of bisphenol A in the presence of an alkaline catalyst, acidic conditions for acid decomposition of bisphenol A in the presence of an acid catalyst, and supercritical water conditions for the decomposition of bisphenol A in supercritical water.

[0230] Examples of alkaline catalysts that can be used for the alkaline hydrolysis of bisphenol A under alkaline conditions include hydroxides, oxides, carbonates, and various phenolates of alkali metals such as sodium and potassium, as well as hydroxides, oxides, carbonates, and various phenolates of alkaline earth metals such as calcium and magnesium. Among these, sodium hydroxide or potassium hydroxide is preferred.

[0231] Examples of acid catalysts that can be used for the acid decomposition of bisphenol A under acidic conditions include alkyl sulfonic acids such as methanesulfonic acid, aromatic sulfonic acids such as toluenesulfonic acid, phenolsulfonic acid, and cresolsulfonic acid, inorganic acids such as sulfuric acid, hydrogen chloride, phosphoric acid, nitric acid, and hypophosphoric acid, as well as titanium dioxide, zirconium oxide, and acidic alumina. Among these, sulfonic acids are preferred, aromatic sulfonic acids are more preferred, and toluenesulfonic acid is even more preferred.

[0232] The "supercritical water" used in the supercritical hydrolysis of bisphenol A is water in a state above the critical point (374°C, 218 atm).

[0233] The following is based on Figures 6-9 The treatment of mixture G under alkaline, acidic, and supercritical water conditions will be explained in detail.

[0234] (i) Alkaline hydrolysis

[0235] Figure 6 The process H1 shown Figure 7 The process H1a shown is Figure 8 The step H2 shown includes a step of alkaline hydrolysis of bisphenol A in mixture G in the presence of an alkaline catalyst.

[0236] [Process H1]

[0237] Figure 6 The illustrated step H1 is an example of a process for obtaining a solution H1 containing bisphenol A by treating a mixture G under conditions that decompose bisphenol A and then recombining it. Step H1 includes: an alkaline hydrolysis / distillation step that treats the mixture G under alkaline conditions that decompose bisphenol A while distilling to obtain a fraction h1 containing phenol and isopropenylphenol as decomposition products; and a recombining step that recombines the phenol and isopropenylphenol contained in fraction h1 to generate bisphenol A. Isopropenylphenol, generated by decomposing bisphenol A, is highly reactive, and therefore will be converted into a condensate other than bisphenol A if recombining is not carried out quickly. As in step H1, by treating the mixture G under alkaline conditions that decompose bisphenol A and distilling while decomposing bisphenol A, the isopropenylphenol generated is rapidly evaporated and supplied to the recombining step, thus suppressing the side reactions of isopropenylphenol.

[0238] (Alkali hydrolysis / distillation process)

[0239] The alkaline hydrolysis / distillation process can be carried out, for example, in a reactive distillation apparatus with a reaction tank at the bottom and a distillation column at the top. The mixture G and an alkaline catalyst are fed into the reaction tank at the bottom and heated, thereby decomposing bisphenol A contained in the mixture G into phenol and isopropenylphenol. At this time, incomplete decomposition products of the polycarbonate resin (dimers, trimers, and other polymers of bisphenol A), and isomers of bisphenol A (2,4-bisphenol) are also decomposed into phenol and isopropenylphenol. Additionally, impurities such as chromane compounds undergo a re-oxidation reaction, transforming into high-boiling-point substances (compounds with boiling points higher than bisphenol A). It should be noted that, in order to efficiently decompose bisphenol A and other substances into phenol and isopropenylphenol, the water content of the mixture G is typically adjusted to below 0.01% by mass.

[0240] Preferably, the alkaline hydrolysis / distillation temperature (i.e., the temperature of the reaction vessel) is 180°C or higher, more preferably 200°C or higher. Furthermore, it is preferable to perform the process at 350°C or lower, and even more preferably 300°C or lower.

[0241] In addition, alkaline hydrolysis / distillation is carried out in the column at a pressure of 0.6 kPa to atmospheric pressure, preferably at 13 to 20 kPa.

[0242] The phenol and isopropenylphenol produced by decomposition are evaporated and extracted from the top of the reaction tower as fraction h1, which is then transported to the reaction tank for the recombination process. At this point, phenol can be fed together with fraction h1 to the reaction tank for the recombination process to ensure that the phenol and isopropenylphenol are in a specified ratio. Additionally, the reaction liquid remaining in the reaction tank without evaporation contains concentrated high-boiling-point substances, which are the cause of the coloring of bisphenol A. This reaction liquid is extracted from the bottom of the reaction tower to remove the residue.

[0243] Fraction h1 preferably contains 1.0% by mass or more of isopropenylphenol. When the content of isopropenylphenol in fraction h1 is less than 1.0% by mass, the recovery of bisphenol A after recombination decreases. Furthermore, fraction h1 preferably contains 50% by mass or less of isopropenylphenol, more preferably 30% by mass or less. This is because excessive isopropenylphenol will convert into condensates other than bisphenol A.

[0244] Furthermore, fraction h1 is preferably composed of isopropenylphenol and phenol, and the phenol content in fraction h1 is preferably 99% by mass or less. More preferably, it is 50% by mass or more, and even more preferably 70% by mass or more.

[0245] (Further combine with the process)

[0246] In the recombination process, phenol and isopropenylphenol are recombinated with an acid catalyst to generate bisphenol A. Phenol and isopropenylphenol condense to form bisphenol A, yielding a solution H1 containing bisphenol A. A sulfonic acid-type strongly acidic cation exchange resin is preferred as the acid catalyst for recombination, and the recombination can be carried out, for example, in a reaction apparatus filled with a sulfonic acid-type strongly acidic cation exchange resin.

[0247] The reaction temperature is typically 45–130°C, preferably 50–100°C. Additionally, the contact time with the acid catalyst is typically 5–200 minutes, preferably 15–120 minutes.

[0248] The resulting solution H1 preferably contains 1.0% by mass or more of bisphenol A. If the bisphenol A content in solution H1 is less than 1.0% by mass, a large amount of components other than bisphenol A will be generated, increasing the impurities contained in the bisphenol A and tending to degrade the quality of the bisphenol A obtained in step E. Furthermore, solution H1 preferably contains 50% by mass or less of bisphenol A, more preferably 40% by mass or less. This is because if the bisphenol A content is too high, the generated bisphenol A will precipitate, making the piping that transports solution H1 from the recombination reaction tank to the reaction apparatus for step B and / or step C prone to clogging.

[0249] Alternatively, process H1 may include a step of using an acid catalyst to decompose the residue (the reaction liquid that remains in the reaction tank without evaporation). In this way, the components not decomposed in the alkaline hydrolysis / distillation process are decomposed to produce phenol. For example, as... Figure 7In step H1a, after decomposing the residue at 150–300°C in the presence of an acid catalyst, the reaction solution h1b containing the obtained phenol is distilled (temperature 150–300°C, pressure 0.1 kPa–10 kPa) to recover the phenol, which can then be returned to step B and / or step C. Aromatic sulfonic acids such as p-toluenesulfonic acid can be used as the acid catalyst in this process. Furthermore, since the residue is alkaline, the amount of acid catalyst mixed in to decompose the residue under acidic conditions can be controlled.

[0250] [Process H2]

[0251] Figure 8 The illustrated step H2 is an example of a process for obtaining a solution H2 containing decomposition products by treating a mixture G under conditions of bisphenol A decomposition. Step H2 includes an alkaline hydrolysis step of treating the mixture G under alkaline conditions of bisphenol A hydrolysis to obtain a reaction solution h2 containing acetone and phenol; and an acetone / phenol recovery step of recovering acetone and / or phenol from the reaction solution h2 obtained in the alkaline hydrolysis step and removing residues. Such a step H2 can efficiently separate water, alkaline catalyst, acetone, phenol, and residues contained in the reaction solution h2, and is therefore preferred.

[0252] (Alkaline hydrolysis process)

[0253] In the alkaline hydrolysis process, for example, by feeding a mixture G, an alkaline catalyst, and water into a reaction apparatus and heating it, bisphenol A contained in the mixture G can be decomposed into acetone and phenol. At this time, incomplete decomposition products of polycarbonate resin (dimers, trimers, and other polymers of bisphenol A), isomers of bisphenol A (2,4-bisphenol), etc., also decompose into phenol and acetone. Furthermore, impurities such as chromane compounds undergo a rehydration reaction, transforming into high-boiling-point substances (compounds with boiling points higher than bisphenol A). Thus, a reaction solution h2 containing acetone, phenol, impurities, etc., is obtained.

[0254] If too much water is supplied to the reaction apparatus along with the mixture G, the decomposition efficiency will decrease; if too little water is supplied, the number of undecomposed components will increase, and the alkaline hydrolysis rate tends to decrease significantly. The mass ratio of water to the mixture G (mass of water / mass of mixture G) is preferably 1 or more, more preferably 1.5 or more. Furthermore, it is preferably 300 or less, more preferably 100 or less.

[0255] The hydrolysis temperature is preferably above 180°C, more preferably above 200°C. Furthermore, it is preferably below 350°C, more preferably below 300°C. Additionally, the hydrolysis pressure is typically the vapor pressure at that temperature.

[0256] The reaction solution h2 preferably contains 0.1% by mass or more of acetone. When the acetone content in the reaction solution h2 is less than 1.0% by mass, it is difficult to properly recover the acetone. Furthermore, the reaction solution h2 preferably contains 30% by mass or less of acetone, more preferably 20% by mass or less. This is because when the acetone content is too high, acetone self-condenses, reducing the acetone recovery rate.

[0257] (Acetone / phenol recovery process)

[0258] In the acetone / phenol recovery process, firstly, the reaction solution h2 obtained from the alkaline hydrolysis process is neutralized and distilled to recover acetone. The remaining reaction solution h2a, which does not evaporate, contains concentrated phenol and impurities. Then, the phenol in reaction solution h2a is extracted with a solvent to obtain an organic phase h2b containing phenol. This organic phase h2b is then distilled to recover the phenol. Additionally, impurities are removed by removing the residue remaining after phenol distillation. The recovered acetone and phenol are supplied as solution H2 to processes B and / or C, respectively.

[0259] Specifically, the reaction solution h2 is neutralized and then fed to an acetone recovery distillation column, where acetone is distilled at a temperature of 30–200°C and a pressure of 0.1–100 kPa, and acetone is extracted from the top of the column. Meanwhile, the reaction solution h2a (bottom liquid) in the distillation column is fed to a solvent extraction unit.

[0260] By treating the reaction solution h2a with an immiscible organic solvent in a solvent extraction apparatus, an organic phase h2b containing phenol and an aqueous phase can be obtained, and they can be extracted separately. Examples of immiscible organic solvents 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, amyl acetate, and hexyl acetate.

[0261] The organic phase h2b containing the extracted phenol is fed to a phenol recovery distillation column, where the phenol is distilled at a temperature of 100–300 °C and a pressure of 0.1–10 kPa, and the phenol is extracted from the top of the column. Additionally, the residue remaining in the phenol recovery distillation column (bottom liquid) is extracted from the bottom of the column.

[0262] Alternatively, in the acetone / phenol recovery process, acetone can be distilled from the reaction solution h2, the residual reaction solution after extraction can be neutralized, and phenol can be distilled to recover acetone and phenol respectively.

[0263] (ii)Acid decomposition

[0264] Figure 9 The step H3 shown is a process of treating mixture G under acidic conditions that decompose bisphenol A. In step H3, mixture G is treated under conditions that decompose bisphenol A to obtain a solution H2 containing the decomposition products.

[0265] [Process H3]

[0266] Figure 9 The illustrated process H3 includes an acid decomposition process that treats a mixture G under acidic conditions to decompose bisphenol A, yielding a reaction solution h3 containing phenol; and a phenol recovery process that distills the reaction solution h3 obtained in the acid decomposition process, recovers the fraction containing phenol, and removes the residue. Such a process H3 can improve the phenol recovery rate and is therefore preferred.

[0267] The acid decomposition temperature is preferably 100°C or higher, more preferably 150°C or higher. It is also preferably carried out at 300°C or lower, more preferably 250°C or lower. The acid decomposition pressure can be set to 0.1–10 kPa. The distillation of the reaction solution h3 obtained in the acid decomposition process can be carried out at a temperature of 150–300°C and a pressure of 0.1–10 kPa.

[0268] (iii) Supercritical hydrolysis

[0269] Figure 10 The step H4 shown is a process of treating mixture G under supercritical water conditions to decompose bisphenol A. By using supercritical water, bisphenol A can be decomposed into phenol and acetone.

[0270] [Process H4]

[0271] Figure 10 The illustrated process H4 includes a supercritical hydrolysis process that treats the mixture G under supercritical water conditions for decomposing bisphenol A to obtain a reaction solution h4 containing phenol; and a phenol recovery process that distills the reaction solution h4 obtained in the supercritical hydrolysis process, recovers the fraction containing phenol, and removes residue. Such a process H4 can perform decomposition without the use of a catalyst, and is therefore preferred.

[0272] In the supercritical hydrolysis process, a mixture G and water are added to the reaction apparatus, and the temperature and pressure are set above the critical point of water to make the water supercritical, thereby decomposing bisphenol A in supercritical water. Specifically, the temperature can be set to 300–700°C, preferably 350–500°C.

[0273] The distillation of the reaction solution h4 obtained in the supercritical hydrolysis process can be carried out at a temperature of 150–300 °C and a pressure of 0.1–10 kPa.

[0274] [Process I]

[0275] Process I is the process of supplying solution H1 or solution H2 obtained from process H to process B and / or process C.

[0276] For example, by providing piping connecting the reaction apparatus for the recombination reaction, the acetone recovery distillation column, the phenol recovery distillation column, and the condensation reaction apparatus for step B, the solution H1 extracted from the reaction apparatus for the recombination reaction, 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 these piping.

[0277] Additionally, a piping system can be installed connecting the recombination reaction apparatus, the acetone recovery distillation column, the phenol recovery distillation column, and the distillation column for process C. Through this piping, solution H1 extracted from the recombination reaction apparatus, acetone extracted from the acetone recovery distillation column, and phenol extracted from the phenol recovery distillation column can be supplied to process C.

[0278] It should be noted that the crude solution A and the mother liquor D can be supplied separately to the apparatus for process H, or they can be processed separately in process H without mixing them. Furthermore, in (II), except for the use of mother liquor S2a and crude solution A, the method for obtaining solution H1 or solution H2 is the same as in (I). In (III), except for the use of mother liquor S2b, the method for obtaining solution H1 or solution H2 is the same as in (I).

[0279] <Method for manufacturing second bisphenol A>

[0280] This invention relates to a method for manufacturing bisphenol A having the following steps B to F, H, and I (hereinafter sometimes referred to as "a second method for manufacturing bisphenol A").

[0281] Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A.

[0282] Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C.

[0283] Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d.

[0284] Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A.

[0285] Process F: A process that recycles a portion of the mother liquor D obtained in process D and supplies it to process B. Process H: Any of the processes (I) to (III) below.

[0286] (I) The process of obtaining solution H1 or solution H2 from a portion of the aforementioned mother liquor D and crude solution A.

[0287] Here, (I) crude solution A is obtained by decomposing polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then removing the solvent from the obtained reaction solution a1 by distillation. The content of bisphenol A in crude solution A is less than 90% by mass. Furthermore, (I) solution H1 is obtained by decomposing the bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombining the phenol and isopropenylphenol to obtain a solution containing bisphenol A. Furthermore, (I) solution H2 is obtained by decomposing the bisphenol A contained in the aforementioned crude solution A and the aforementioned mother liquor D into phenol and acetone under conditions of bisphenol A decomposition.

[0288] (II) A portion of the aforementioned mother liquor D undergoes isomerization and crystallization / solid-liquid separation treatment to obtain solution H1 or solution H2 from the resulting mother liquor S2a and crude solution A.

[0289] Here, (II) crude solution A is obtained by decomposing polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then removing the solvent from the obtained reaction solution a1 by distillation. The content of bisphenol A in crude solution A is less than 90% by mass. Furthermore, (II) solution H1 is obtained by decomposing the bisphenol A contained in the aforementioned mother liquor S2a and the aforementioned crude solution A into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombinizing the phenol and isopropenylphenol to obtain a solution containing bisphenol A. Furthermore, (II) solution H2 is obtained by decomposing the bisphenol A contained in the aforementioned mother liquor S2a and the aforementioned crude solution A into phenol and acetone under conditions of bisphenol A decomposition.

[0290] (III) A process of crystallization / solid-liquid separation is performed on solution S3a, which contains the isomerized solution D, and crude solution A, to obtain solution H1 or solution H2 from the obtained mother liquor S2b.

[0291] Here, (III) crude solution A is obtained by decomposing polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A, and then distilling off the solvent from the obtained reaction solution a1. The content of bisphenol A in crude solution A is less than 90% by mass. Furthermore, (III) solution H1 is obtained by decomposing the bisphenol A contained in the aforementioned mother liquor S2b into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then recombinizing the phenol and isopropenylphenol to obtain a solution containing bisphenol A. Furthermore, (III) solution H2 is obtained by decomposing the bisphenol A contained in the aforementioned mother liquor S2b into phenol and acetone under conditions of bisphenol A decomposition.

[0292] Step I: Supply solution H1 or solution H2 obtained in step H to steps B and / or C.

[0293] The second method for manufacturing bisphenol A is identical to the method for manufacturing bisphenol A of the present invention, except that the crude solution A is manufactured using separate equipment instead of combined equipment for steps B to F, H, and I. In the second method for manufacturing bisphenol A, the crude solution A can be manufactured in the same manner as step A of the method for manufacturing bisphenol A of the present invention. Steps B to F, H, and I of the second method for manufacturing bisphenol A are identical to steps B to F, H, and I of the method for manufacturing bisphenol A of the present invention.

[0294] A portion of the mother liquor D can be mixed with the crude solution A and proceeded to step H. Alternatively, a portion of the mother liquor D and the crude solution A can be pre-mixed, and the resulting mixture G can be supplied to the apparatus for the decomposition of bisphenol A in step H. The mixture G can also be supplied to step H after appropriate concentration. Alternatively, a portion of the mother liquor D and the crude solution A can be supplied separately to the apparatus for the decomposition of bisphenol A in step H, and the decomposition reaction can be carried out while the mixture G is being prepared within the apparatus. The mixing ratio of the portion of the mother liquor D and the crude solution A is the same as in step G of the bisphenol A manufacturing method of the present invention. Alternatively, the crude solution A and the mother liquor D can be processed separately in step H without mixing.

[0295] Additionally, a portion of the mother liquor D can be used in step H after undergoing isomerization, concentration, and crystallization / solid-liquid separation. For example, step f1 can be performed to isomerize the reaction byproducts in the mother liquor D obtained in step D, and step f2 can be performed to crystallize and separate the solution S3 containing the solution S3a after isomerization in step f1. Through steps f1 and f2, mother liquor S2a and mother liquor S2b can be obtained. Steps f1 and f2 are the same as the method for manufacturing bisphenol A of the present invention. In (II) and (III), the mother liquor S2a and mother liquor S2b can be used to perform steps G and H in the same way as in (I).

[0296] <Uses of Bisphenol A>

[0297] Bisphenol A obtained by the method of manufacturing bisphenol A of the present invention or the second method of manufacturing bisphenol A (hereinafter sometimes referred to as "bisphenol A of the present invention") can be used as a component, curing agent, additive, or precursor of various thermoplastic resins such as polyether resins, polyester resins, polyarylate resins, polycarbonate resins, polyurethane resins, and acrylic resins, as well as various thermosetting resins such as epoxy resins, unsaturated polyester resins, phenolic resins, polybenzoxazine resins, and cyanate ester resins, used in various applications such as optical materials, recording materials, insulating materials, transparent materials, electronic materials, adhesive materials, and heat-resistant materials. Furthermore, it is also useful as an additive such as a color developer, anti-fading agent, bactericide, and antibacterial and antifungal agent for heat-sensitive recording materials.

[0298] Of these, in order to impart good mechanical properties, they are preferably used as raw materials (monomers) for thermoplastic resins and thermosetting resins, and more preferably as raw materials for polycarbonate resins and epoxy resins. In addition, they are also preferably used as color developers, and are particularly preferred to be used in combination with leuco dyes and color-changing temperature regulators.

[0299] <Manufacturing Method of Polycarbonate Resin>

[0300] Furthermore, the present invention relates to a method for manufacturing polycarbonate resin using bisphenol A obtained by the bisphenol A manufacturing method of the present invention or a second bisphenol A manufacturing method (hereinafter sometimes referred to as "the method for manufacturing polycarbonate resin of the present invention").

[0301] The polycarbonate resin obtained by the method for manufacturing polycarbonate resin of the present invention can be manufactured, for example, by a transesterification reaction of bisphenol A and diphenyl carbonate, etc., in the presence of an alkali metal compound and / or an alkaline earth metal compound. The transesterification reaction can be carried out by a known method. Hereinafter, an example using bisphenol A and diphenyl carbonate of the present invention as raw materials will be described.

[0302] In the above-described method for manufacturing polycarbonate resin, diphenyl carbonate is preferably used in excess relative to bisphenol A of the present invention. From the perspective of producing a polycarbonate resin with fewer terminal hydroxyl groups and excellent polymer thermal stability, the amount of diphenyl carbonate used relative to bisphenol A is preferably higher. Furthermore, from the perspective of a fast transesterification reaction rate and ease of manufacturing polycarbonate resin with the desired molecular weight, the amount of diphenyl carbonate used relative to bisphenol A is preferably lower. Therefore, the amount of diphenyl carbonate used per mole of bisphenol A is typically 1.001 moles or more, preferably 1.002 moles or more, and typically 1.3 moles or less, preferably 1.2 moles or less.

[0303] As a method of supplying raw materials, bisphenol A and diphenyl carbonate of the present invention can be supplied in solid form, or preferably one or both can be melted and supplied in liquid form.

[0304] In the production of polycarbonate resin via the transesterification reaction of diphenyl carbonate and bisphenol A, a transesterification catalyst is typically used. In the aforementioned method for producing polycarbonate resin, alkali metal compounds and / or alkaline earth metal compounds are preferably used as the transesterification catalyst. One type can be used, or two or more can be used in any combination and ratio. Practically, the use of alkali metal compounds is desirable.

[0305] The amount of catalyst used relative to 1 mole of bisphenol A or diphenyl carbonate is typically 0.05 μmol or more, preferably 0.08 μmol or more, more preferably 0.10 μmol or more, and typically 100 μmol or less, preferably 50 μmol or less, more preferably 20 μmol or less. By keeping the amount of catalyst used within the above range, it is easy to obtain the polymerization activity necessary for producing polycarbonate resin with the desired molecular weight, and the polymer has excellent color. In addition, excessive polymer branching does not occur, and it is easy to obtain polycarbonate resin with excellent flowability during molding.

[0306] In order to manufacture polycarbonate resin by the above method, it is preferable to continuously supply the two raw materials to the raw material mixing tank, and continuously supply the resulting mixture and transesterification catalyst to the polymerization tank.

[0307] In the manufacture of polycarbonate resin based on transesterification, two raw materials are typically supplied to a raw material mixing tank and then uniformly stirred before being supplied to a polymerization tank containing a catalyst to produce a polymer.

[0308] Example

[0309] The present invention will be further described in detail below through examples and comparative examples, but the present invention is not limited to the following examples as long as it does not exceed its spirit.

[0310] [Raw Materials and Reagents]

[0311] The polycarbonate resin used is "NOVAREX (registered trademark) M7027BF" polycarbonate resin from Mitsubishi Chemical Engineering Plastics Co., Ltd.

[0312] Phenol, toluene, sodium hydroxide, potassium hydroxide, hydrochloric acid, acetonitrile, and cesium carbonate were used in the reagents from Fujifilm and Koichi Chemical Co., Ltd.

[0313] Diphenyl carbonate is a product manufactured by Mitsubishi Chemical Company.

[0314] [Preparation of cation exchange resins]

[0315] Cation exchange resin A: According to Reference Example 1 described in Japanese Patent Application Publication No. 2012-201619, Diaion (registered trademark) SK104, which is completely substituted with phenol, was obtained.

[0316] 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.

[0317] [analyze]

[0318] The formation and purity of bisphenol A, the quantification of components considered as undecomposed polycarbonate resins and stabilizers (components other than phenol and bisphenol A) were determined using high-performance liquid chromatography (HPLC) under the following steps and conditions.

[0319] • Apparatus: Shimadzu LC-2010A, Waters 5μm 150mm×4.6mm ID

[0320] Method: Low-pressure gradient method

[0321] • Analysis temperature: 40℃

[0322] • Elution buffer composition:

[0323] A liquid acetonitrile

[0324] Solution B is an 85% phosphoric acid:water solution with a ratio of 1 mL:999 mL.

[0325] When the analysis time is 0 minutes, the ratio of solution A to solution B is 35:65 (volume ratio, the same below). When the analysis time is 0 to 5 minutes, the eluent composition is adjusted to solution A to solution B = 35:65. Then, when the analysis time is 5 to 40 minutes, the ratio of solution A to solution B is gradually adjusted to 90:10.

[0326] • Flow rate: 0.85 mL / min

[0327] • Detection wavelength: 280nm

[0328] The analysis of dimethyl carbonate was performed using gas chromatography, following the steps and conditions below.

[0329] • Device: GC-2014 manufactured by Shimadzu Corporation

[0330] Agilent DB-1 0.530mm×30m 1.5μm

[0331] • Detection method: FID

[0332] • Vaporization chamber temperature: 230℃

[0333] • Detector temperature: 300℃

[0334] • During the analysis time of 0 to 5 minutes, maintain the column temperature at 50°C. During the analysis time of 5 to 30 minutes, slowly increase the column temperature to 280°C. During the analysis time of 30 to 40 minutes, maintain the column temperature at 280°C.

[0335] • Quantitative method: Internal standard method using biphenyl as an internal standard

[0336] [Viscosity-average molecular weight (Mv)]

[0337] For viscosity-average molecular weight (Mv), polycarbonate resin is dissolved in dichloromethane (concentration 6.0 g / L), and the specific viscosity (ηsp) at 20°C is measured using an Ubbelohde viscometer. The viscosity-average molecular weight (Mv) is then calculated using the following formula.

[0338] ηsp / C=[η](1+0.28ηsp)

[0339] [η] = 1.23 × 10 -4 Mv 0.83

[0340] [The melting color of bisphenol]

[0341] Regarding the melting color of bisphenol, test tube "P-24" was prepared at Nippon Electric Chemical Nitrogen Co., Ltd. 1g of bisphenol A and 19g of diphenyl carbonate were added to the mixture and melted at 174°C for 30 minutes. The Hazen color number was determined using an OME7700 instrument manufactured by Nippon Denshoku Kogyo Co., Ltd. The Hazen color number of bisphenol A was calculated by multiplying the obtained Hazen color number by the dilution rate based on diphenyl carbonate.

[0342] [pH Measurement]

[0343] pH was measured using a pH meter “pH METER ES-73” from Horiba Manufacturing Co., Ltd., on an aqueous phase taken from a flask at 25°C.

[0344] <Example 1>

[0345] [Process A-1]

[0346] (PC disassembly process)

[0347] In a jacketed, detachable flask equipped with a Demrod cooling tube, stirring blades, and a thermometer, polycarbonate resin (80 g, the repeating unit of polycarbonate resin is 254 g / mol, therefore 80 g ÷ 254 g / mol = 0.315 mol), water (30 g), phenol (250 g), and a 25% by mass sodium hydroxide aqueous solution (320 g) were added under a nitrogen atmosphere at room temperature. The reaction solution was in slurry form.

[0348] Then, the internal temperature was raised to 80°C and maintained at 80°C for 5 hours to obtain reaction solution a1 (homogeneous solution).

[0349] (Neutralization process)

[0350] After adding toluene (200g) to the obtained reaction solution a1, 35% hydrochloric acid was added until the aqueous phase reached pH 8.6, resulting in the generation of carbon dioxide gas.

[0351] Afterwards, stirring was stopped, and oil-water separation was performed. The aqueous phase was extracted from the flask to obtain organic phase a2. The composition of a portion of the obtained organic phase a2 was confirmed by high-performance liquid chromatography, and the results confirmed the formation of bisphenol A.

[0352] (Concentration process a2)

[0353] The obtained organic phase a2 was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C, and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to distill off some of the water, toluene, and phenol, thus obtaining organic phase a2-2.

[0354] The obtained organic phase a2-2 was pressurized with nitrogen gas, and the internal temperature was slowly reduced to 30°C to obtain slurry a3. The obtained slurry a3 was filtered to obtain recycled bisphenol A (20g) (crude solution A).

[0355] The time required to obtain recycled bisphenol A (crude solution A) is 9 hours.

[0356] It should be noted that the composition of the recycled bisphenol A fraction obtained was confirmed by high-performance liquid chromatography, and the results showed that it contained 66.4% by mass of bisphenol A. In addition, converted to bisphenol A, it contained 0.3% by mass of components considered as undecomposed polycarbonate resin and stabilizer.

[0357] [Process B-1a]~[Process D-1a]、[Process F-1a]

[0358] Mother liquor D was obtained according to Example 1 described in Japanese Patent Application Publication No. 2005-220071.

[0359] The resulting mother liquor D consisted of 83% by mass of phenol, 10% by mass of bisphenol A, and 7% by mass of other components.

[0360] [Process G-1a]

[0361] The aforementioned mother liquor D (100g) and the recycled bisphenol A (20g) obtained in step A-1 (crude solution A) were added to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath, and pressure regulator. The temperature was then slowly raised to 180°C, and while observing the distillate volume, the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to remove phenol (19g) by distillation, yielding a mixture G. Afterward, the mixture was repressurized with nitrogen.

[0362] The mixture G contains 23g of bisphenol A (100g × 10.0% by mass + 20g × 66.4% by mass = 23g).

[0363] [Process H-1a]

[0364] (Alkali hydrolysis / distillation process)

[0365] Add 0.4 g of 25% (w / w) sodium hydroxide aqueous solution to mixture G and set to full vacuum. Then, raise the oil bath temperature to 230°C to obtain fraction h1 (80 g). The composition of a portion of fraction h1 was confirmed by high-performance liquid chromatography (HPLC), revealing it to contain 93% (w / w) phenol and 7% (w / w) isopropenylphenol. The decomposition rate of bisphenol A in the alkaline hydrolysis / distillation process was 41% (80 g × 7% (w / w) ÷ 134 g / mol ÷ 23 g × 228 g / mol × 100% = 41%). It should be noted that the resulting bottom liquid was discarded.

[0366] (Further combine with the process)

[0367] Cation exchange resin A (1 g) was added to a round-bottom flask equipped with a stirring blade, a distillation tube, and a water bath. The resulting fraction h1 (80 g) was then rapidly added to the flask, and the mixture was reacted at 70°C for 2 hours. Subsequently, to remove cation exchange resin A, decantation was performed to obtain solution H1. The composition of a portion of solution H1 was confirmed by high-performance liquid chromatography (HPLC), revealing the presence of 11% by mass of bisphenol A.

[0368] [Process I-1a], [Process B-1b]

[0369] The aforementioned solution H1 (20g), the aforementioned mother liquor D (170g), reagent phenol (2g), reagent acetone (8g), and cation exchange resin B (2g) were added to a round-bottom flask equipped with a stirring blade, a distillation tube, and a water bath, and reacted at 70°C for 5 hours. Afterwards, to remove cation exchange resin B, the mixture was decanted to obtain reaction solution B.

[0370] [Process C-1b]

[0371] The obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. A portion of the unreacted acetone, water and phenol were removed by distillation to obtain concentrated solution C.

[0372] [Process D-1b]

[0373] The concentrated liquid C was pressurized with nitrogen gas to slowly cool the internal temperature to 30°C, resulting in a slurry. The slurry was then filtered to obtain filter cake d (11g).

[0374] [Process E-1b]

[0375] The obtained filter cake d (11 g) and toluene (60 g) were added to a detachable flask equipped with a distillation tube and stirring blades, and dissolved at 80 °C to obtain organic phase e1. Organic phase e1 was washed five times with 50 g of deionized water to obtain organic phase e2.

[0376] The obtained organic phase e2 is cooled to 10℃ to obtain slurry e3. The slurry e3 is filtered to obtain filter cake e4.

[0377] The resulting filter cake (e4) was dried using a rotary evaporator to obtain bisphenol A (4.1 g). The Hazen color number of the obtained bisphenol A was APHA20. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0378] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0379] <Example 2>

[0380] [Process A-2]

[0381] (PC disassembly process)

[0382] In a jacketed, detachable flask equipped with a Demrod cooling tube, stirring blades, and a thermometer, polycarbonate resin (80 g, 0.315 mol), water (30 g), phenol (240 g), and triethylamine (10 g) were added at room temperature under a nitrogen atmosphere. The reaction solution was in slurry form.

[0383] The internal temperature was then raised to 80°C and maintained at 80°C for 5 hours to obtain reaction solution a1 (a homogeneous solution). During the reaction, the generation of carbon dioxide was confirmed.

[0384] A portion of the obtained reaction solution a1 was taken out and its composition was confirmed by high-performance liquid chromatography (HPLC). The result showed that bisphenol A was generated at 19.6% by mass. The mass of reaction solution a1 was 80g + 30g + 240g + 10g = 360g. The amount of bisphenol A generated was 19.6% by mass × 360g ÷ 228.29g / mol = 0.309 mol, and the reaction rate was 0.309 mol ÷ 0.315 mol × 100 = 98%.

[0385] (Concentration process a1)

[0386] The obtained reaction solution a1 was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to distill off some of the water, triethylamine, and phenol, yielding recycled bisphenol A (260 g).

[0387] The time required to obtain recycled bisphenol A is 7 hours.

[0388] It should be noted that the composition of the recycled bisphenol A fraction obtained was confirmed by high performance liquid chromatography, and the results showed that it contained 27.0% by mass of bisphenol A. In addition, converted to bisphenol A, it contained 0.4% by mass of components considered as undecomposed polycarbonate resin and stabilizer.

[0389] [Process B-2a]~[Process H-2a], [Process B-2b]~[Process E-2b]

[0390] The recycled bisphenol A (50g) obtained in step A-2 was used instead of the recycled bisphenol A (20g) obtained in step A-1 of Example 1. Otherwise, bisphenol A (4.5g) was obtained in the same manner as in steps B-1a to H-1a and B-1b to E-1b of Example 1.

[0391] The Hazen color number of the obtained bisphenol A was APHA18. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0392] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0393] <Example 3>

[0394] [Process A-3]

[0395] (PC disassembly process)

[0396] In a jacketed, detachable flask equipped with a Dimro cooling tube, stirring blades, and a thermometer, polycarbonate resin (80 g, 0.31 mol), phenol (240 g), methanol (23 g, 0.72 mol, with a molar ratio of 0.72 mol ÷ 0.31 mol = 2.3 relative to the number of repeating units of carbonate in the polycarbonate resin), and triethylamine (15 g, 15 g ÷ 101 g / mol = 0.15 mol, with a molar ratio of 0.15 mol ÷ 0.31 mol = 0.48 relative to the number of repeating units of carbonate in the polycarbonate resin) were added at room temperature under a nitrogen atmosphere (liquid volume: 80 g + 240 g + 23 g + 15 g = 358 g).

[0397] The internal temperature was then raised to 85°C. Undissolved polycarbonate resin components were observed in the reaction solution at 85°C. The reaction was maintained at 85°C for 4 hours to obtain a homogeneous reaction solution a1.

[0398] The composition of a portion of the obtained reaction solution a1 was confirmed by high performance liquid chromatography, and the result confirmed that the generated bisphenol A was 19.5% by mass (19.5 ÷ 100 × 358 g ÷ 228 g / mol ÷ 0.31 mol = 99 mol%).

[0399] In addition, the composition of a portion of the obtained reaction solution a1 was confirmed by gas chromatography, and the results confirmed that the generated dimethyl carbonate was 6.5% by mass (6.5 ÷ 100 × 358 g ÷ 90 g / mol ÷ 0.31 mol = 83 mol%).

[0400] (Concentration process a1)

[0401] The obtained reaction solution a1 was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to distill off a portion of methanol, dimethyl carbonate, and phenol, yielding recycled bisphenol A (262 g).

[0402] The time required to obtain recycled bisphenol A is 7 hours.

[0403] It should be noted that the composition of the recycled bisphenol A fraction obtained was confirmed by high performance liquid chromatography, and the results showed that it contained 27.1% by mass of bisphenol A. In addition, converted to bisphenol A, it contained 0.4% by mass of components considered as undecomposed polycarbonate resin and stabilizer.

[0404] [Process B-3a]~[Process H-3a], [Process B-3b]~[Process E-3b]

[0405] The recycled bisphenol A (50g) obtained in step A-3 was used instead of the recycled bisphenol A (20g) obtained in step A-1 of Example 1. Otherwise, bisphenol A (4.7g) was obtained in the same manner as in steps B-1a to H-1a and B-1b to E-1b of Example 1.

[0406] The Hazen color number of the obtained bisphenol A was APHA15. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0407] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0408] <Comparative Example 1>

[0409] Similar to the PC decomposition, neutralization, and concentration steps a2 in step A of Example 1, organic phase a2-2 is obtained.

[0410] Organic phase a2-2 was washed five times with 50g of deionized water to obtain organic phase a2-3. Organic phase a2-3 was cooled to 20℃ to obtain a slurry. The slurry was filtered to obtain a filter cake. The filter cake was dried using a rotary evaporator to obtain bisphenol A (35g).

[0411] The time required to obtain bisphenol A is 17 hours.

[0412] The composition was confirmed by high performance liquid chromatography, and the purity of bisphenol A was 99.8% by mass. In addition, based on bisphenol A, it contains 0.1% by mass of components considered as undecomposed polycarbonate resin and stabilizer.

[0413] Comparing the bisphenol A obtained in Examples 1-3 with that obtained in Comparative Example 1, the purity of the bisphenol A was found to be equivalent. Furthermore, visual evaluation showed that the bisphenol A obtained in Examples 1-3 had a better color tone (colorless and transparent) compared to Comparative Example 1. In the bisphenol A obtained in Comparative Example 1, 0.1% by mass of components considered as undecomposed polycarbonate resin and stabilizers were found, based on bisphenol A conversion. In contrast, no components considered as undecomposed polycarbonate resin and stabilizers were detected in the bisphenol A obtained in Examples 1-3. It is believed that the undecomposed polycarbonate resin and stabilizers degraded the color tone of the bisphenol A.

[0414] <Comparative Example 2>

[0415] The aforementioned mother liquor D (170g), reagent phenol (2g), reagent acetone (8g), and cation exchange resin B (2g) were added to a round-bottom flask equipped with a stirring blade, a distillation tube, and a water bath, and reacted at 70°C for 5 hours. Afterwards, to remove cation exchange resin B, the mixture was decanted to obtain reaction solution B.

[0416] The obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. A portion of the unreacted acetone, water and phenol were removed by distillation. The solution was then repressurized with nitrogen to obtain concentrated solution C (170 g).

[0417] The obtained concentrated solution C (170g) and the recycled bisphenol A (50g) obtained in step A-3 of Example 3 were added to a round-bottom flask equipped with stirring blades, a distillation tube, and a water bath, and heated to 80°C to obtain a mixture. The internal temperature was then slowly lowered to 30°C to obtain a slurry (crystallization step). The obtained slurry was filtered to obtain filter cake d (15g).

[0418] The obtained filter cake d (15g) and toluene (60g) were added to a detachable flask equipped with stirring blades, a distillation tube, and stirring blades, and dissolved at 80°C to obtain organic phase e1. Organic phase e1 was washed five times with 50g of deionized water to obtain organic phase e2.

[0419] The obtained organic phase e2 is cooled to 10℃ to obtain slurry e3. The slurry e3 is filtered to obtain filter cake e4.

[0420] The resulting filter cake (e4) was dried using a rotary evaporator to obtain bisphenol A (6 g). The Hazen color number of the obtained bisphenol A was APHA89. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.5% by mass.

[0421] It should be noted that the component considered as undecomposed polycarbonate resin and stabilizer is 0.08% by mass.

[0422] Regarding Examples 1-3 and Comparative Example 2, the treatment of the liquid after mixing recycled bisphenol A (recycled BPA, crude solution A) with recycled bisphenol A (recycled BPA), the Hazen color number of the obtained bisphenol A (BPA), the purity of bisphenol A (BPA), the undecomposed polycarbonate resin (PC) components, and the components considered as stabilizers are summarized in Table 1. According to Table 1, by mixing recycled bisphenol A with mother liquor D, proceeding to step H, and returning to step B, the Hazen color number of the bisphenol A obtained in step E is improved, and the undecomposed polycarbonate resin and stabilizer components are considered as detection limits. It can be considered that the undecomposed polycarbonate resin and stabilizer components are removed along with the bottom liquid obtained in step H.

[0423] [Table 1]

[0424]

[0425] <Example 4>

[0426] [Process G-4a]

[0427] The mother liquor D (18g) obtained in Example 1 and the recycled bisphenol A (16g) obtained in step A-3 of Example 3 were added to a high-pressure reactor equipped with a pressure gauge, thermocouple and stirring blades to obtain a mixture G.

[0428] [Process H-4a]

[0429] (Alkaline hydrolysis process)

[0430] Water (64g) and sodium hydroxide (2g) were added to the autoclave, and nitrogen gas was purged to ensure an airtight seal. The electric furnace was set to 250℃, and the autoclave was placed on top, heated until the internal temperature reached 250℃. After reaching 250℃, the internal pressure was confirmed to be 3.7MPa, and the reaction was allowed to proceed for 2 hours. Afterward, the autoclave was removed from the electric furnace and immersed in a basin of ice water for 1 hour. Then, the autoclave was opened and transferred to an Erlenmeyer flask to obtain reaction solution h2.

[0431] A portion of the reaction solution h2 was extracted and its composition was confirmed by gas chromatography, which showed that acetone was 1.3% by mass.

[0432] (Acetone / phenol recovery process)

[0433] After neutralizing the reaction solution h2 with 2.0 g of sulfuric acid, the solution is fed into a distillation apparatus equipped with a thermometer, stirring blades, a distillation column, and a water bath. Under atmospheric pressure, the initial fraction obtained by heating yields recycled acetone (0.9 g) and the bottom liquid (reaction solution h2a).

[0434] The obtained bottom liquid was transferred to a fully jacketed, detachable flask equipped with a thermometer, stirring blades, and cooling pipes. Diisopropyl ether was added, and the mixture was subjected to oil-water separation at 50°C to remove the aqueous phase, yielding the organic phase h2b. The obtained organic phase h2b was then fed into a single distillation apparatus equipped with a thermometer and stirring blades. Under normal pressure, the temperature was increased to distill off and recover the diisopropyl ether, followed by depressurization to obtain recycled phenol (20g).

[0435] [Process B-4b]

[0436] The mother liquor D (170g) obtained in Example 1, the aforementioned recycled phenol (2g), the aforementioned recycled acetone (0.9g), reagent acetone (8.1g), and cation exchange resin B (2g) were added to a round-bottom flask equipped with a stirring blade, a distillation tube, and a water bath, and reacted at 70°C for 5 hours. Afterwards, to remove cation exchange resin B, the mixture was decanted to obtain reaction solution B.

[0437] [Process C-4b]

[0438] The obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. A portion of the unreacted acetone, water and phenol were removed by distillation to obtain concentrated solution C.

[0439] [Process D-4b]

[0440] The concentrated liquid C was repressurized with nitrogen gas to slowly cool the internal temperature to 30°C, resulting in a slurry. The slurry was filtered to obtain filter cake d (10g).

[0441] [Process E-4b]

[0442] The obtained filter cake d (10g) and toluene (60g) were added to a detachable flask equipped with a distillation tube and stirring blades, and dissolved at 80°C to obtain organic phase e1. Organic phase e1 was washed five times with 50g of deionized water to obtain organic phase e2.

[0443] The obtained organic phase e2 is cooled to 10℃ to obtain slurry e3. The slurry e3 is filtered to obtain filter cake e4.

[0444] The resulting filter cake (e4) was dried using a rotary evaporator to obtain bisphenol A (3.2 g). The Hazen color number of the obtained bisphenol A was APHA22. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0445] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0446] <Example 5>

[0447] [Process G-5a], [Process H-5a]

[0448] In a reaction tube made of SUS316 stainless steel, 1.2 g of recycled bisphenol obtained in step A-1 of Example 1, 1.3 g of mother liquor D obtained in step D-1a of Example 1, and 3 g of distilled water were added. After sealing, the reaction tube was heated to 400°C using an electric furnace for 1 hour for decomposition. The reaction tube was then removed from the furnace and allowed to cool naturally at room temperature. After sufficient cooling, the reaction tube was opened to obtain reaction solution h4.

[0449] Repeat this operation 10 times to obtain reaction solution h4 (52g).

[0450] The obtained reaction solution h4 was supplied to a single distillation apparatus equipped with a stir bar and a thermometer. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. After removing the light boiling components and water by distillation, phenol was distilled off to obtain recycled phenol (16 g).

[0451] [Process I-5a], [Process B-5b]

[0452] The aforementioned mother liquor D (170g), the aforementioned recycled phenol (2g), reagent acetone (9g), and cation exchange resin B (2g) were added to a round-bottom flask equipped with a stirrer, distillation tube, and water bath, and reacted at 70°C for 5 hours. Afterwards, to remove cation exchange resin B, the mixture was decanted to obtain reaction solution B.

[0453] [Process C-5b]

[0454] The obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. A portion of the unreacted acetone, water and phenol were distilled off to obtain concentrated solution C.

[0455] [Process D-5b]

[0456] The concentrated liquid C was repressurized with nitrogen gas to slowly cool the internal temperature to 30°C, resulting in a slurry. The slurry was filtered to obtain filter cake d (9g).

[0457] [Process E-5b]

[0458] The obtained filter cake d (9g) and toluene (60g) were added to a detachable flask equipped with a distillation tube and stirring blades, and dissolved at 80°C to obtain organic phase e1. Organic phase e1 was washed five times with 50g of deionized water to obtain organic phase e2.

[0459] The obtained organic phase e2 is cooled to 10℃ to obtain slurry e3. The slurry e3 is filtered to obtain filter cake e4.

[0460] The resulting filter cake (e4) was dried using a rotary evaporator to obtain bisphenol A (2.8 g). The Hazen color number of the obtained bisphenol A was APHA18. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0461] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0462] <Example 6>

[0463] [Process G-6a], [Process H-6a]

[0464] In a round-bottom flask equipped with a stirring blade, a Dimro cooling tube, and a thermometer, 30 g of recycled bisphenol A obtained in step A-2 of Example 2, 30 g of mother liquor D obtained in step D-1a of Example 1, and 0.1 g of p-toluenesulfonic acid were added. The round-bottom flask was then immersed in an oil bath at 200°C for 3 hours to allow decomposition. Afterward, the pressure was slowly reduced to obtain 35 g of recycled phenol.

[0465] [Process I-6a], [Process B-6b]

[0466] The aforementioned mother liquor D (170g), the aforementioned recycled phenol (2g), reagent acetone (9g), and cation exchange resin B (2g) were added to a round-bottom flask equipped with a stirrer, distillation tube, and water bath, and reacted at 70°C for 5 hours. Afterwards, to remove cation exchange resin B, the mixture was decanted to obtain reaction solution B.

[0467] [Process C-6b]

[0468] The obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. A portion of the unreacted acetone, water and phenol were distilled off to obtain concentrated solution C.

[0469] [Process D-6b]

[0470] The concentrated liquid C was repressurized with nitrogen gas to slowly cool the internal temperature to 30°C, resulting in a slurry. The slurry was then filtered to obtain a filter cake d (13g).

[0471] [Process E-6b]

[0472] The obtained filter cake d (13g) and toluene (60g) were added to a detachable flask equipped with a distillation tube and stirring blades, and dissolved at 80°C to obtain organic phase e1. Organic phase e1 was washed five times with 50g of deionized water to obtain organic phase e2.

[0473] The obtained organic phase e2 is cooled to 10℃ to obtain slurry e3. The slurry e3 is filtered to obtain filter cake e4.

[0474] The resulting filter cake (e4) was dried using a rotary evaporator to obtain bisphenol A (3.1 g). The Hazen color number of the obtained bisphenol A was APHA15. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0475] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0476] <Example 7>

[0477] [Process H-7a]

[0478] In a distillation apparatus containing the waste bottom liquid from Example 1, 1g of p-toluenesulfonic acid was added and decomposed at 190°C for 2 hours. Then, 5g of recycled phenol was distilled out under full vacuum.

[0479] [Process I-7a], [Process B-7b]

[0480] The aforementioned mother liquor D (170g), the aforementioned recycled phenol (2g), reagent acetone (9g), and cation exchange resin B (2g) were added to a round-bottom flask equipped with a stirrer, distillation tube, and water bath, and reacted at 70°C for 5 hours. Afterwards, to remove cation exchange resin B, the mixture was decanted to obtain reaction solution B.

[0481] [Process C-7b]

[0482] The obtained reaction solution B was transferred to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath and pressure regulator. While observing the distillation amount, the internal temperature was slowly raised to 180°C and the internal pressure was slowly reduced from atmospheric pressure to 10 kPa. A portion of the unreacted acetone, water and phenol were removed by distillation to obtain concentrated solution C.

[0483] [Process D-7b]

[0484] The concentrated liquid C was repressurized with nitrogen gas to slowly cool the internal temperature to 30°C, resulting in a slurry. The slurry was filtered to obtain filter cake d (13g).

[0485] [Process E-7b]

[0486] The obtained filter cake d (13g) and toluene (60g) were added to a detachable flask equipped with a distillation tube and stirring blades, and dissolved at 80°C to obtain organic phase e1. Organic phase e1 was washed five times with 50g of deionized water to obtain organic phase e2.

[0487] The obtained organic phase e2 is cooled to 10℃ to obtain slurry e3. The slurry e3 is filtered to obtain filter cake e4.

[0488] The resulting filter cake (e4) was dried using a rotary evaporator to obtain bisphenol A (2.7 g). The Hazen color number of the obtained bisphenol A was APHA14. Furthermore, the composition was confirmed by high-performance liquid chromatography, and the purity of bisphenol A was found to be 99.8% by mass.

[0489] It should be noted that components considered as undecomposed polycarbonate resins and stabilizers are below the detection limit.

[0490] Table 2 summarizes the decomposition methods of bisphenol A in step H of Examples 1, 4-6, the Hazen color number of the obtained bisphenol A, the purity of bisphenol A, the components considered as undecomposed polycarbonate resin, and the components of the stabilizer. According to Table 2, in step H, the Hazen color number of the obtained bisphenol A was improved under alkaline hydrolysis, alkaline hydrolysis, supercritical hydrolysis, and acid decomposition. The components considered as undecomposed polycarbonate resin and the components of the stabilizer were all below the detection limit.

[0491] [Table 2]

[0492]

[0493] <Example 8>

[0494] In a 45 mL glass reaction vessel equipped with a stirrer and distillation tube, bisphenol A obtained in Examples 5-7 was mixed with 10.00 g (0.04 mol of bisphenol A), 9.95 g (0.05 mol) of diphenyl carbonate, and 18 μL of a 400 ppm aqueous solution of cesium carbonate. The glass reaction vessel was depressurized to approximately 100 Pa, and then repressurized to atmospheric pressure using nitrogen, repeated three times to replace the interior of the reaction vessel with nitrogen. Afterward, the reaction vessel was immersed in an oil bath at 220°C to dissolve the contents.

[0495] Set the mixer speed to 100 times per minute, while distilling away the phenol byproduct of the oligomerization reaction of bisphenol A and diphenyl carbonate in the reaction tank, and reduce the pressure in the reaction tank from 101.3 kPa to 13.3 kPa using an absolute pressure gauge over 40 minutes.

[0496] Then, the pressure in the reaction vessel was maintained at 13.3 kPa, and the phenol was further removed by distillation while the transesterification reaction was carried out for 80 minutes.

[0497] Then, the external temperature of the reaction tank was raised to 290°C, and the pressure inside the reaction tank was reduced from 13.3 kPa to 399 Pa using an absolute pressure gauge over 40 minutes to remove the distilled phenol from the system.

[0498] Next, the absolute pressure in the reaction tank was reduced to 30 Pa to carry out the polycondensation reaction. The polycondensation reaction was terminated when the agitator in the reaction tank reached the pre-set stirring power. The time from heating to 290°C to the end of polymerization was 120 minutes.

[0499] Then, the reaction tank was pressurized with nitrogen to 101.3 kPa (absolute pressure), and then further pressurized to 0.2 MPa (gauge pressure). Polycarbonate resin was extracted from the reaction tank to obtain polycarbonate resin. The viscosity-average molecular weight (Mv) of the obtained polycarbonate resin was 26,500.

[0500] <Example 9>

[0501] Similar to Example 1, mother liquor D and recycled bisphenol A (crude solution A) were obtained. The obtained mother liquor D (100g) was added to a jacketed, detachable flask equipped with a Demrod cooling tube, stirring blades, and a thermometer, and kept at 80°C. Separately, the obtained recycled bisphenol A (20g) was added to a pear-shaped flask and immersed in an oil bath at 120°C to melt it. The molten recycled bisphenol A was added to the aforementioned jacketed, detachable flask using a 5mm inner diameter glass funnel, resulting in a clog-free supply and a homogeneous solution. The resulting homogeneous solution was then added to a distillation apparatus equipped with a thermometer, stirring blades, a distillation tube, an oil bath, and a pressure regulator.

[0502] Then, the temperature was slowly raised to 180°C, and while observing the distillation rate, the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to remove phenol (19 g) by distillation, yielding mixture G. Afterwards, the mixture was repressurized with nitrogen.

[0503] The mixture G contains 23g of bisphenol A (100g × 10.0% by mass + 20g × 66.4% by mass = 23g).

[0504] (Alkali hydrolysis / distillation process)

[0505] Add 0.4 g of 25% (w / w) sodium hydroxide aqueous solution to mixture G and set to full vacuum. Then, raise the oil bath temperature to 230°C to obtain fraction h1 (80 g). The composition of a portion of fraction h1 was confirmed by high-performance liquid chromatography (HPLC), revealing it to contain 93% (w / w) phenol and 7% (w / w) isopropenylphenol. The decomposition rate of bisphenol A in the alkaline hydrolysis / distillation process was 41% (80 g × 7% (w / w) ÷ 134 g / mol ÷ 23 g × 228 g / mol × 100% = 41%). It should be noted that the resulting bottom liquid was discarded.

[0506] <Comparative Example 3>

[0507] Mother liquor D was obtained in the same manner as in Example 1. Bisphenol A was obtained in the same manner as in Comparative Example 1. The aforementioned mother liquor D (100g) was added to a jacketed, detachable flask equipped with a Demrod cooling tube, stirring blades, and a thermometer, and kept at an temperature of 80°C. Meanwhile, the aforementioned bisphenol A (20g) was added to a pear-shaped flask and immersed in an oil bath at 120°C, but due to the high purity of bisphenol A, it failed to melt. Therefore, it was impossible to use a 5mm inner diameter glass funnel to supply the aforementioned bisphenol A to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath, and pressure regulator.

[0508] <Comparative Example 4>

[0509] Mother liquor D was obtained in the same manner as in Example 1. Bisphenol A was obtained in the same manner as in Comparative Example 1. The aforementioned mother liquor D (100g) was added to a jacketed detachable flask equipped with a Demrod cooling tube, stirring blades, and a thermometer. Separately, the obtained bisphenol A (20g) was added to a pear-shaped flask and immersed in an oil bath at 180°C to melt it. The molten bisphenol A was added to the aforementioned jacketed detachable flask using a glass funnel with an inner diameter of 5mm, resulting in a clog-free supply and a homogeneous solution. The resulting homogeneous solution had a high melting temperature and therefore exhibited a significant reddish-brown color.

[0510] The resulting homogeneous solution is added to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath, and pressure regulator.

[0511] Then, the temperature was slowly raised to 180°C, and while observing the distillation rate, the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to remove phenol (19 g) by distillation, yielding mixture G. Afterwards, the mixture was repressurized with nitrogen.

[0512] The mixture G contains 30g of bisphenol A (100g × 10.0% by mass + 20g × 99.8% by mass = 30g).

[0513] (Alkali hydrolysis / distillation process)

[0514] Add 0.6 g of 25% (w / w) sodium hydroxide aqueous solution to mixture G and set to full vacuum. Then, raise the oil bath temperature to 230°C to obtain fraction h1 (50 g). The composition of a portion of fraction h1 was confirmed by high-performance liquid chromatography (HPLC), revealing it to contain 97% (w / w) phenol and 3% (w / w) isopropenylphenol. The decomposition rate of bisphenol A in the alkaline hydrolysis / distillation process was 14% (80 g × 3% (w / w) ÷ 134 g / mol ÷ 30 g × 228 g / mol × 100% = 14%). It should be noted that the resulting bottom liquid was discarded.

[0515] In Examples 9, 3, and 4, the purity of recycled bisphenol A (the BPA content in crude solution A), the melting temperature of recycled bisphenol A, whether it could be supplied using a glass funnel with an inner diameter of 5 mm, and the decomposition rate of bisphenol A in the alkaline hydrolysis / distillation process are summarized in Table 3. Table 3 shows that when the purity of recycled bisphenol A is high, it is impossible to supply recycled bisphenol A at low melting temperatures. It was also found that if the melting temperature is increased to supply recycled bisphenol A, the color tone deteriorates and changes, thus reducing the decomposition rate of bisphenol A in the alkaline hydrolysis / distillation process.

[0516] [Table 3]

[0517]

[0518] <Comparative Example 5>

[0519] 30g of polycarbonate resin (30g ÷ 254g / mol = 0.12 mol), 100g of phenol, and 1g of sodium carbonate were added to a 200mL autoclave equipped with induction stirring blades, a pressure gauge, and a thermometer. After three nitrogen purgings, the autoclave was placed in an electric furnace and reacted at an internal temperature of 250℃ for 3 hours. After the reaction, the autoclave was immersed in ice water to restore the internal pressure to atmospheric pressure, yielding the reaction solution.

[0520] The resulting reaction solution is added to a distillation apparatus equipped with a thermometer, stirring blades, distillation tube, oil bath, and pressure regulator.

[0521] Then, the temperature was slowly raised to 180°C, and while observing the distillation rate, the internal pressure was slowly reduced from atmospheric pressure to 10 kPa to remove phenol (100 g) by distillation, resulting in a concentrated solution.

[0522] (Alkali hydrolysis / distillation process)

[0523] The distillation apparatus was set to full vacuum. Then, the oil bath temperature was raised to 230°C, yielding fraction h1 (5g). The composition of a portion of fraction h1 was confirmed by high-performance liquid chromatography (HPLC), revealing it to be almost entirely phenol, with no detectable isopropenylphenol.

[0524] Industrial availability

[0525] This invention enables the production of bisphenol A from polycarbonate resin contained in waste plastics, etc. The obtained bisphenol A can be used as a raw material, curing agent, additive, etc. for resins such as polycarbonate resin, and is therefore useful in industry.

Claims

1. A method for manufacturing bisphenol A, comprising the following steps A to F, step H, and step I, Step A: Decompose polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A. Remove the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass. Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A. Step C: From the reaction solution B obtained in step B, unreacted acetone and water are removed by distillation to obtain concentrated solution C. Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d. Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A. Process F: A portion of the mother liquor D obtained in process D is recycled and supplied to process B. Step H: The step of obtaining solution H1 or solution H2 from a portion of the mother liquor D and the crude solution A. in, Solution H1 is a solution containing bisphenol A obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and isopropenylphenol under conditions of bisphenol A decomposition, and then combining phenol and isopropenylphenol. Solution H2 is a phenol-containing solution obtained by decomposing bisphenol A contained in the crude solution A and the mother liquor D into phenol and acetone under conditions of bisphenol A decomposition. Step I: Supplying the solution H1 or solution H2 obtained in step H to steps B and / or C.

2. A method for manufacturing bisphenol A, comprising the following steps A to I, Step A: Decompose polycarbonate resin in a solvent to obtain a reaction solution a1 containing bisphenol A. Remove the solvent from the obtained reaction solution a1 by distillation to obtain a crude solution A with a bisphenol A content of less than 90% by mass. Step B: In the presence of an acid catalyst, acetone and phenol are dehydrated and condensed to obtain reaction solution B containing bisphenol A. Step C: Unreacted acetone and water are removed from the reaction solution B obtained in Step B by distillation to obtain concentrated solution C. Step D: The concentrated liquid C obtained in step C is crystallized to obtain a slurry. The slurry is then subjected to solid-liquid separation to obtain mother liquor D and filter cake d. Step E: The process of purifying the filter cake d obtained in step D to obtain bisphenol A. Process F: A portion of the mother liquor D obtained in process D is recycled and supplied to the dehydration and condensation process in process B. Process G: A process that mixes the crude solution A obtained in process A with a portion of the mother liquor D obtained in process 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 conditions of bisphenol A decomposition followed by recombination, or a solution H2 containing decomposition products obtained by treating the mixture G under conditions of bisphenol A decomposition. Step I: Supplying the solution H1 or solution H2 obtained in step H to steps B and / or C.

3. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, A portion of the mother liquor D is mixed with the crude solution A, and the resulting mixture G is supplied to the apparatus for the decomposition of bisphenol A in step H.

4. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, A portion of the mother liquor D and the crude solution A are respectively supplied to the apparatus for the decomposition of bisphenol A in step H, and the decomposition reaction is carried out in the apparatus while the mixture G is being prepared.

5. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, In step C, a portion of the phenol is further removed by distillation from the reaction solution B to obtain concentrated solution C.

6. The method for manufacturing bisphenol A according to claim 2, wherein, In step H, when the mixture G is treated under conditions that decompose bisphenol A, the decomposition rate of bisphenol A in the mixture G is 30 mol% or more.

7. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, The conditions for decomposing the bisphenol A are any one of the group consisting of alkaline conditions, acidic conditions, and supercritical water conditions.

8. The method for manufacturing bisphenol A according to claim 2, wherein, After treating the mixture G under conditions that decompose bisphenol A, or while treating, distillation is performed to recover the fraction h containing the decomposition products and remove the residue.

9. The method for manufacturing bisphenol A according to claim 2, wherein, The process H is the process of obtaining the solution H1, which has the following characteristics: In the decomposition / distillation process, the mixture G is treated under alkaline conditions for decomposing bisphenol A while distillation is performed to recover the fraction h1 containing phenol and isopropenylphenol as decomposition products, and the residue is removed. and In the next step, the phenol and isopropylphenol contained in the fraction h1 are recombined to generate bisphenol A.

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

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

12. The method for manufacturing bisphenol A according to claim 9 or 10, wherein, After treating the residue in the presence of an acid catalyst, distillation is performed to recover the phenol fraction h1b.

13. The method for manufacturing bisphenol A according to claim 2, wherein, The process H is the process of obtaining the solution H2, which has the following characteristics: In the alkaline hydrolysis step, the mixture G is treated under alkaline conditions for hydrolyzing bisphenol A to obtain a reaction solution h2 containing acetone and phenol; and The acetone / phenol recovery process recovers the acetone fraction and / or phenol fraction from the reaction solution h2 obtained in the alkaline hydrolysis process, and removes the residue.

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

15. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, The solvent used in step A is phenol.

16. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, Step A is a step in which the polycarbonate resin is decomposed in the presence of any catalyst selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkylamines and acids to obtain the crude solution A.

17. The method for manufacturing bisphenol A according to claim 1 or 2, wherein, The crude solution A contains 10% by mass or more of bisphenol A.

18. The method for manufacturing bisphenol A according to claim 17, wherein, The crude solution A contains 20% by mass or more of bisphenol A.

19. A method for manufacturing a polycarbonate resin, wherein, The manufacturing method includes: Bisphenol A is manufactured according to the method for manufacturing bisphenol A according to any one of claims 1 to 18; The bisphenol A is used to manufacture polycarbonate resins.

Images