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JP-7855690-B2 - Method for producing polycarbonate, method for recovering dihydroxy compounds, and apparatus for producing polycarbonate

JP7855690B2JP 7855690 B2JP7855690 B2JP 7855690B2JP-7855690-B2

Inventors

  • 林 文範

Assignees

  • 旭化成株式会社

Dates

Publication Date
20260508
Application Date
20230612
Priority Date
20220613

Claims (13)

  1. A polymerization step in which a dihydroxy compound and diaryl carbonate, or a prepolymer thereof, is polymerized in a polymerization reactor, A washing step in which exhaust vapor containing hydroxyaryl compounds, diaryl carbonates, and dihydroxy compounds discharged from the polymerization reactor in the polymerization step is brought into contact with a washing solution in a scrubber, The process includes a condensation step for condensing the exhaust steam that has been cleaned by the cleaning step, At least a portion of the bottom liquid of the scrubber in the washing step is supplied to the polymerization reactor. A method for manufacturing polycarbonate.
  2. The method for producing polycarbonate according to claim 1, wherein at least a portion of the condensate of the exhaust vapor from the condensation step is used as the cleaning solution in the cleaning step.
  3. The method for producing polycarbonate according to claim 2, wherein the mass ratio of the condensate from the condensation step to the cleaning step supplied as a cleaning solution is 0.1 or more and 1 or less with respect to the amount of discharged steam at the inlet of the cleaning step.
  4. The method for producing polycarbonate according to claim 1, wherein the bottom liquid of the scrubber in the washing step is supplied to the washing step as the washing liquid.
  5. The method for producing polycarbonate according to claim 4, wherein the mass ratio of the liquid supplied to the washing process as the washing liquid from the bottom liquid of the scrubber in the washing process is 0.1 or more and 10 or less with respect to the amount of discharged steam at the inlet of the washing process.
  6. The method for producing polycarbonate according to claim 1, wherein the diaryl carbonate content in the bottom liquid of the scrubber during the washing step is 20% to 90% by mass.
  7. The method for producing polycarbonate according to any one of claims 1 to 6, wherein the scrubber in the washing step comprises irregular fillers.
  8. A method for producing polycarbonate according to any one of claims 1 to 6, wherein, in the washing step, droplets containing airborne particles are separated by a demister.
  9. A method for producing polycarbonate according to claim 8, wherein the void ratio of the demister is 95 vol% to 99 vol%.
  10. The method for producing polycarbonate according to claim 1, wherein the dihydroxy compound comprises bisphenol A.
  11. The method for producing a polycarbonate according to claim 10, wherein the diaryl carbonate includes diphenyl carbonate .
  12. A washing step in which exhaust vapor containing hydroxyaryl compounds, diaryl carbonates, and dihydroxy compounds discharged from a polymerization reactor that polymerizes dihydroxy compounds and diaryl carbonates, or prepolymers thereof, is brought into contact with a washing solution in a scrubber, The process includes a condensation step for condensing the exhaust steam that has been cleaned by the cleaning step, A method for recovering dihydroxy compounds.
  13. A polymerization reactor for polymerizing dihydroxy compounds and diaryl carbonates, or prepolymers thereof, A scrubber that brings the exhaust vapor containing hydroxyaryl compounds, diaryl carbonates, and dihydroxy compounds discharged from the polymerization reactor into contact with a washing liquid, A condenser for condensing the exhaust steam washed by the scrubber, A supply channel for supplying at least a portion of the bottom liquid of the scrubber to the polymerization reactor, A manufacturing apparatus for polycarbonate containing [a specific substance].

Description

This invention relates to a method for producing polycarbonate, a method for recovering dihydroxy compounds, and an apparatus for producing polycarbonate. Polycarbonate, leveraging its advantages such as transparency, heat resistance, and mechanical strength, is widely used as an engineering plastic in fields such as electrical and electronic components, automotive parts, optical recording media, and lenses. The typical methods for producing polycarbonate are the transesterification method or the melting method. In these methods, a dihydroxy compound, such as bisphenol A (BPA), is transesterified with a diaryl carbonate, such as diphenyl carbonate (DPC), and polymerization proceeds by removing the by-product hydroxyaryl compound from the system. In the production of polycarbonate, a method using a polymerization reactor with a condenser has been proposed, for example, as shown in Patent Document 1. This method reduces manufacturing costs and effectively utilizes resources by condensing and recovering the monohydroxy compounds produced as by-products in the condenser. Japanese Patent Publication No. 2012-214801 Figure 1 is a schematic diagram of a polycarbonate manufacturing apparatus.Figure 2 is a schematic diagram of a polycarbonate manufacturing apparatus according to another embodiment.Figure 3 is a schematic diagram of the polycarbonate manufacturing apparatus used in the comparative experiment. The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention, and the present invention is not limited to this embodiment. The present invention can be implemented with appropriate modifications within the scope of its gist. In this specification, for example, the notation of a numerical range such as "1 to 100" includes both the lower limit "1" and the upper limit "100". The same applies to other numerical range notations. [Method for manufacturing polycarbonate] The method for manufacturing polycarbonate according to this embodiment is as follows: A polymerization step in which a dihydroxy compound and diaryl carbonate, or a prepolymer thereof, is polymerized in a polymerization reactor, A washing step in which exhaust vapor containing hydroxyaryl compounds, diaryl carbonates, and dihydroxy compounds discharged from the polymerization reactor in the polymerization step is brought into contact with a washing solution in a scrubber, The process includes a condensation step for condensing the exhaust steam that has been cleaned by the cleaning step, At least a portion of the bottom liquid from the scrubber in the washing step is supplied to the polymerization reactor. According to this embodiment, it is possible to provide a method for producing polycarbonate, a method for recovering dihydroxy compounds, and an apparatus for producing polycarbonate, which can recover dihydroxy compounds from the vapor discharged from the polymerization reactor and reduce the amount of loss. In this embodiment, during the washing process, dihydroxy compounds in the exhaust vapor discharged from the polymerization reactor can be recovered by contacting the exhaust vapor with a washing solution in a scrubber. The bottom liquid of the scrubber contains relatively high-boiling-point compounds such as diaryl carbonates and dihydroxy compounds contained in the exhaust vapor. Therefore, by supplying at least a portion of the bottom liquid of the scrubber to the polymerization reactor, the recovered diaryl carbonates and dihydroxy compounds can be reused in polymerization, thereby reducing the amount of dihydroxy compound lost. <Polycarbonate Manufacturing Equipment> The apparatus used in the method for manufacturing polycarbonate according to this embodiment will be described. Figure 1 is a schematic diagram of a polycarbonate manufacturing apparatus. The polycarbonate manufacturing apparatus includes a polymerization reactor 1, a scrubber 2, a condenser 3, and a supply line 4. Polymerization reactor 1 polymerizes dihydroxy compounds and diaryl carbonates, or prepolymers thereof. Polymerization reactor 1 may be a large-area polymerization reactor for evaporating hydroxyaryl compounds and the like generated as the polymerization reaction progresses. Examples of polymerization reactors include thin-film polymerization reactors, centrifugal thin-film evaporation polymerization reactors, surface-renewal twin-screw kneading polymerization reactors, twin-screw horizontal stirring polymerization reactors, wet-wall polymerization reactors, porous plate polymerization reactors that polymerize while free-falling, polymerization reactors that allow polymer to melt and fall along a support to proceed with polymerization, and porous plate polymerization reactors with wires. These polymerization reactors may be used individually or in combination. The polymerization process using the polymerization reactor may be