JP2006052173A - Method for obtaining aromatic dihydroxy compound from waste aromatic polycarbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining a high-purity aromatic dihydroxy compound useful as a raw material, etc., for producing a polycarbonate by which a waste aromatic polycarbonate (e.g. an aromatic polycarbonate product such as a CD, a CD-ROM or a DVD which became unnecessary) is inexpensively treated in a large amount in a short degradation time. <P>SOLUTION: The method for obtaining the aromatic dihydroxy compound from the waste aromatic polycarbonate is characterized as follows. The waste aromatic polycarbonate is degraded in the presence of a halogenated hydrocarbon compound solvent and a metal hydroxide catalyst by transesterification with a 1-4C alcohol. An aqueous solution of an inorganic acid is added to neutralize the reaction mixture liquid after the degradation while keeping the liquid temperature within the range of 0-70°C. The organic solvent phase and the aqueous solution phase are separated to recover the organic solvent phase. The solid aromatic dihydroxy compound is then obtained from the recovered organic solvent phase. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for obtaining an aromatic dihydroxy compound by decomposing waste aromatic polycarbonate by a transesterification reaction with a lower alcohol. Moreover, it is related with the manufacturing method of the aromatic polycarbonate which uses the aromatic dihydroxy compound obtained by decomposition | disassembly as a manufacturing raw material of a polycarbonate.

  Aromatic polycarbonate (hereinafter sometimes abbreviated as PC) has excellent mechanical properties, electrical properties, heat resistance, cold resistance, transparency, etc., optical disks such as lenses and compact disks, and building materials. These materials are used in various applications such as automobile parts, OA equipment chassis and camera bodies, and the demand for these materials is increasing year by year. Along with the increase in demand for PCs, many of the PC products to be discarded are processed by methods such as incineration or filling in the ground. This not only accelerates the depletion of petroleum resources due to the increasing demand for PC, but also promotes the deterioration of the global environment. Therefore, it has become important to reuse (recycle) discarded plastic.

  Methods for recycling waste plastic include (1) thermal recycling that recovers waste plastic as thermal energy, (2) material recycling that mixes and processes waste plastic in a certain proportion, and (3) waste. There is chemical recycling in which plastic is chemically decomposed and returned to plastic raw materials and reused for plastic manufacturing. Of these, thermal recycling incinerates plastic to extract heat, generating carbon dioxide, essentially destroying the global environment and reducing resources. Material recycling is preferable because it consumes the least amount of resources and reduces the environmental load. However, the plastic itself cannot be denied, and there are problems that the products that can be mixed are limited, the proportion that can be mixed is small, and the amount that can be recycled is limited. On the other hand, chemical recycling decomposes plastics into raw materials, so it can be used for the production of new plastics and can be used for a wide range of applications including the original product.

  As a method for chemically recycling PC, for example, Patent Document 1 discloses a method in which PC is decomposed with phenol in the presence of an alkali catalyst to recover an aromatic dihydroxy compound and a diaryl carbonate. Patent Document 2 discloses a method for obtaining a dialkyl carbonate and an aromatic dihydroxy compound by performing a transesterification reaction in a toluene, xylene, benzene or dioxane solvent using a small amount of alkali as a catalyst. In Patent Document 3, PC is transesterified with a lower alcohol in the presence of a solvent such as an alkyl chloride, an ether or an aromatic hydrocarbon solvent and a tertiary amine as a catalyst to obtain an aromatic dihydroxy compound and a dialkyl carbonate. A method has been proposed.

  However, in the method of Patent Document 1, the separation and recovery step of the solvent and the decomposition product is complicated. In the method of Patent Document 2, after completion of the reaction, the reaction mixture is introduced into water to crystallize the aromatic dihydroxy compound, or a solvent several times the amount of the decomposition mixture is introduced to precipitate the aromatic dihydroxy compound, This is a method of washing with water, and in this method, the recovery of the used alcohol and solvent is very complicated. It is also difficult to remove the solvent used from the solid aromatic dihydroxy compound. In the method of Patent Document 3, a tertiary amine as a catalyst is used in a larger amount than an organic solvent, and even if an attempt is made to remove under reduced pressure with an evaporator or the like, the tertiary amine, dialkyl carbonate and aromatic dihydroxy compound are separated. Is very difficult. Furthermore, a terminal terminator is contained in the obtained aromatic dihydroxy compound, and it is necessary to separate the terminal terminator. In fact, when manufacturing polycarbonate, there is an inconvenience that it is difficult to adjust the molecular weight if a terminal terminator is mixed in the initial stage of the reaction.

Japanese Patent Application Laid-Open No. 06-056885 Japanese Patent Laid-Open No. 10-259151 JP 2002-212335 A

  It is an object of the present invention to process waste aromatic polycarbonate (for example, aromatic polycarbonate products such as CDs, CD-ROMs, and DVDs that are no longer needed) at low cost, with a short decomposition time, and in a large amount to be processed as a raw material for producing polycarbonate. It is to provide a method for obtaining useful high purity aromatic dihydroxy compounds.

  Another object of the present invention is to provide a method for producing a high-quality aromatic polycarbonate that can be used for CD or the like using the obtained aromatic dihydroxy compound.

  Still another object of the present invention is to provide a process for obtaining dialkyl carbonates useful for the production of aromatic polycarbonates by melt polymerization and for other industries.

  As a result of intensive studies to achieve the above object, the present inventor decomposed waste aromatic polycarbonate using an alcohol having 1 to 4 carbon atoms, a halogenated hydrocarbon compound solvent and a metal hydroxide catalyst, and after the decomposition In the operation of neutralizing the reaction mixture solution with an acid aqueous solution, the aromatic dihydroxy compound obtained is highly pure by maintaining the liquid temperature in the temperature range of 0 to 70 ° C., and this aromatic dihydroxy compound is used. The quality of the obtained aromatic polycarbonate was found to be comparable to that of an aromatic polycarbonate produced using a commercially available aromatic dihydroxy compound, and the present invention was completed.

That is, according to the present invention,
1. Waste aromatic polycarbonate is decomposed by transesterification with an alcohol having 1 to 4 carbon atoms in the presence of a halogenated hydrocarbon compound solvent and a metal hydroxide catalyst, and the temperature of the reaction mixture after decomposition is reduced to 0 to 70 ° C. An aqueous inorganic acid solution is added to neutralize the solution while keeping it in the range, and the organic solvent phase and the aqueous solution phase are separated to recover the organic solvent phase, and a solid aromatic dihydroxy compound is obtained from the recovered organic solvent phase. A process for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate characterized by

  2. 2. The method for obtaining an aromatic dihydroxy compound from the waste aromatic polycarbonate according to item 1, wherein the halogenated hydrocarbon compound is dichloromethane, dichloroethane or chloroform.

  3. The method for obtaining an aromatic dihydroxy compound from the waste aromatic polycarbonate resin according to item 1, wherein the inorganic acid aqueous solution is at least one acid aqueous solution selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid aqueous solutions.

4). A method for producing an aromatic polycarbonate, wherein the aromatic dihydroxy compound obtained by the method according to item 1 is used as a raw material for producing an aromatic polycarbonate.
Is provided.

Hereinafter, the present invention will be described in detail.
In the present invention, the waste aromatic polycarbonate to be used may be one produced by a known method such as an interfacial polymerization method or a melt polymerization method, and the molecular weight is preferably a viscosity average molecular weight of 1000 to 100,000. The shape of the waste aromatic polycarbonate is not particularly limited, such as powder, pellets, sheets, films, and molded products. For example, optical discs such as CDs, CD-Rs, DVDs, etc., which are no longer used, such as discarded ones or defective ones, are used as they are, or ones that have been removed by removing the printed film or metal film are used for disassembly. You can also. Further, the waste aromatic polycarbonate used for decomposition may be a solid obtained by removing the solvent from the solution of the polycarbonate that has not reached the target molecular weight during the production of the polycarbonate, and has not been pelletized or pelletized. Here, the viscosity average molecular weight (M) of the polycarbonate resin is obtained by inserting the specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of the polycarbonate resin in 100 ml of methylene chloride at 20 ° C. into the following equation. .
η _sp /c=[η]+0.45×[η] ² c (where [η] is the intrinsic viscosity)
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
c = 0.7

  The polycarbonate includes hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, 1,4-dihydroxynaphthalene, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) phenyl} methane, , 1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2 -Bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(3,5-dibromo- 4-hydroxy) phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propa 2,2-bis {(4-hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, , 2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2 -Bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis ( 4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9- {(4-hydroxy-3-methyl) phenyl} fluorene, α, α'-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene , Α, α'-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenylsulfone, 4,4 Single or two or more of dihydroxy compounds such as' -dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxydiphenyl ester Made from a mixture of

  In the present invention, waste aromatic polycarbonate is subjected to a decomposition reaction (depolymerization reaction) by transesterification with an alcohol having 1 to 4 carbon atoms in the presence of a halogenated hydrocarbon compound solvent and a metal hydroxide catalyst. Use of a halogenated hydrocarbon compound solvent and a metal hydroxide catalyst is preferred because the decomposition reaction of the aromatic polycarbonate by the alcohol easily proceeds.

  Examples of the alcohol having 1 to 4 carbon atoms used for the decomposition of the aromatic polycarbonate include methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol, and 2-methyl-1-propanol. (Isobutyl alcohol) and 1,1-dimethyl-1-ethanol (t-butyl alcohol). Methanol is particularly preferable. Alcohols having 5 or more carbon atoms are not preferable because the decomposition reaction is slow and separation is difficult in the purification and separation steps.

  The amount of the alcohol used is preferably 2.4 to 7 mol, more preferably 3 to 7 mol, per 1 mol of the carbonate bond of the aromatic polycarbonate. When the molar ratio is more than 7 moles, the recovery rate of the aromatic dihydroxy compound is deteriorated, and further, the separation and recovery of the unreacted alcohol may be costly. On the other hand, when the molar ratio is less than 2.4 mol, the decomposition reaction rate is slow, or the polycarbonate resin is not completely decomposed and the carbonate oligomer tends to remain, and the recovery rate of the aromatic dihydroxy compound may decrease.

  The cracking catalyst used in the present invention is a metal hydroxide. The decomposition reaction does not proceed in the absence of metal hydroxide. As the metal hydroxide, sodium hydroxide and / or potassium hydroxide can be preferably used. Sodium hydroxide is particularly preferable.

  The amount of the metal hydroxide used is preferably 0.002 to 0.4 mol with respect to 1 mol of the carbonate bond of the polycarbonate. When the amount of metal hydroxide used is less than 0.002 mol, the decomposition reaction rate is greatly reduced. When the amount is more than 0.4 mol, it is economically disadvantageous, and the decomposition of the dialkyl carbonate tends to occur.

  Usually, the metal hydroxide used in the production of the aromatic polycarbonate is purchased and used in the form of a solid or an aqueous solution. When a large amount of water is present in the reaction system, the catalyst and the generated aromatic dihydroxy compound react to form a salt, which is consumed, and the decomposition reaction becomes very slow. In addition, the yield of recoverable dialkyl carbonate decreases. In particular, when an aqueous solution of metal hydroxide is used, water tends to increase in the reaction system. There are several methods for removing water from the reaction system, such as mixing chlorinated compound organic solvent and metal hydroxide aqueous solution, azeotropically separating them with a decanter, and passing the mixture through a dehydrating agent (adsorbent). However, it can be removed by any method. The amount of water in the system (that is, in the solution subjected to the decomposition reaction) before the decomposition reaction (that is, in the solution subjected to the decomposition reaction) is preferably 2.5% by weight or less, more preferably 1% by weight or less, and 0.5% by weight or less. Is more preferable, and 0.3% by weight or less is particularly preferable.

  Specific examples of the halogenated hydrocarbon compound solvent used in the present invention include dichloromethane, chloroform, dichloroethane, trichloroethane, tetrachloroethane, dichloroethylene, etc., and at least one selected from the group consisting of dichloromethane, dichloroethane, and chloroform. Solvents are preferred, especially dichloromethane. These solvents are good solvents for polycarbonate, and are actually used as reaction solvents in the polycarbonate production process. Even if these solvents remain in the aromatic dihydroxy compound after decomposition and separation, they adversely affect polycarbonate production. There is an advantage that does not affect.

  In this invention, the usage-amount of a halogenated hydrocarbon compound solvent has the preferable range of 40 weight part-1000 weight part with respect to 100 weight part of polycarbonate resin. If the amount of the solvent is less than 40 parts by weight, the initial mixing may not be successful, the polycarbonate resin may not be sufficiently swollen or dissolved, and the time until the decomposition reaction may be prolonged. On the other hand, when the amount is more than 1000 parts by weight, the carbonate bond concentration and the catalyst concentration in the reaction system become low, the decomposition reaction rate decreases, the decomposition reaction time becomes long, and the solvent recovery cost may increase. In addition, it is preferable that a molded product such as an optical disk is pulverized to a size of about 0.1 to 2 cm in advance and the pulverized material is dissolved, because the dissolution time is shortened.

  In the decomposition reaction, the waste aromatic polycarbonate may be previously dissolved in a halogenated hydrocarbon compound solvent, or may be charged into a reactor in which the decomposition reaction is performed without dissolving all of them. When a dissolution tank is used separately from the reactor and the polycarbonate resin is dissolved in the organic solvent, impurities that do not dissolve in the organic solvent, such as additives, metal films, coating agents, fillers, etc. contained in the molded product Can be filtered off.

  In the present invention, the temperature at which the decomposition reaction is performed is preferably 30 ° C to 150 ° C. When it is less than 30 ° C., the decomposition reaction time becomes long, and the processing efficiency may be remarkably inferior. Further, if the temperature exceeds 150 ° C., a large amount of heating energy is required, and the color of the solution is easily browned during the decomposition process. It may not be possible.

  Since the aromatic dihydroxy compound produced during the decomposition reaction is easily oxidized under basic conditions, it is preferable to add an antioxidant to the reaction solution. It is also effective to reduce the oxygen concentration in the process with an inert gas.

Examples of the antioxidant include sodium bisulfite (Na ₂ S ₂ O ₅ ), sodium sulfite (Na ₂ SO ₃ ), and sodium hydrosulfite (Na ₂ S ₂ O ₄ ). These may be used alone or in combination of two or more. As for the usage-amount of antioxidant, 0.05-4.0 weight part is preferable with respect to 100 weight part of aromatic polycarbonate. If it is in the range of 0.05 to 4.0 parts by weight, it has an antioxidant effect, is advantageous in terms of cost, and is preferable because the decomposition reaction rate does not decrease.

  Nitrogen, argon etc. are mentioned as a kind of inert gas. Nitrogen is preferred because of its cost advantage.

  After decomposing the waste aromatic polycarbonate, the reaction mixture is neutralized by adding an inorganic acid aqueous solution while maintaining the liquid temperature in the range of 0 to 70 ° C. The decomposition reaction is completely stopped by neutralization. By adding an aqueous inorganic acid solution to the reaction mixture, the aromatic dihydroxy compound is dissolved in the organic solvent phase. As the inorganic acid aqueous solution, an inorganic acid aqueous solution such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid is preferably used. The amount of the inorganic acid aqueous solution to be added needs to be such that the aqueous solution phase becomes neutral to acidic, and is particularly preferably an amount such that the pH is in the neutral pH range of 6 to 8. In addition, when water is added without adding an acid, hydrolysis of a dialkyl carbonate occurs, and the aromatic dihydroxy compound reacts with a metal hydroxide to form a salt, and the yield decreases. Further, when the solvent is removed in the reaction mixture, the aromatic dihydroxy compound reacts with the metal hydroxide to form a salt, and a colored component is generated. For this reason, the process of removing a coloring component is needed and becomes a disadvantageous method.

  Moreover, the liquid temperature during neutralization operation needs to maintain 0-70 degreeC. The liquid temperature is preferably maintained at 20 to 70 ° C, more preferably 20 to 60 ° C, and still more preferably 20 to 50 ° C. When the liquid temperature exceeds 70 ° C., when the obtained aromatic dihydroxy compound is used as a raw material for producing an aromatic polycarbonate, the hue, thermal stability and the like of the obtained polycarbonate are deteriorated. On the other hand, if the liquid temperature during the neutralization operation is less than 0 ° C., solid precipitation occurs and handling becomes difficult.

  When an aqueous acid solution is added to the reaction mixture after the decomposition reaction, it is separated into an organic solvent phase and an aqueous solution phase. By using a liquid-liquid separator such as a decanter or a centrifuge, the organic solvent phase and the aqueous solution phase can be separated to obtain an organic solvent phase. If the liquid separation is insufficient, water suspended in a granular form in the organic solvent phase will affect the purity of the resulting aromatic dihydroxy compound, so the organic solvent phase can be further contacted with pure water. It is preferable to remove as much as possible. As this method, a known method such as contact with a washing tower, separation with a stirrer, liquid-liquid separator, or centrifugal separator can be used. If the solvent is removed as it is without separating the organic solvent phase and the aqueous solution phase, the aromatic dihydroxy compound reacts with the metal hydroxide to form a salt, and a colored component is generated. For this reason, the process of removing a coloring component is needed and it becomes a disadvantageous method.

  As a method for recovering the solid aromatic dihydroxy compound from the organic solvent phase, a method of separating the organic solvent, unreacted alcohol and dialkyl carbonate from the aromatic dihydroxy compound by distillation is preferably employed.

  The distillation operation is carried out under reduced pressure or atmospheric pressure, and the method may be either batch type or continuous type, but batch type is preferred for precipitation of the aromatic dihydroxy compound. Distillation requires a temperature and pressure conditions at which the organic solvent, unreacted alcohol and dialkyl carbonate can be distilled off, but in order to suppress thermal decomposition of the aromatic dihydroxy compound, the distillation temperature (distillation tank bottom temperature) is 100 ° C. or less. It is preferable to do. Alternatively, an inert gas may be flowed through the distillation tank to facilitate the distillation.

  The aromatic dihydroxy compound obtained by separation by distillation operation is a reaction between a trace amount of unreacted alcohol, dialkyl carbonate, monohydroxy compound (terminal terminator), polycarbonate-derived carbonate and metal hydroxide and an aqueous acid solution. It is preferable that these compounds be removed because they contain impurities such as neutral salts produced. In order to remove these impurities, a method of washing the aromatic dihydroxy compound with a halogenated hydrocarbon compound organic solvent and / or water is employed.

  Examples of the halogenated hydrocarbon compound organic solvent include a solvent in which the solubility of the aromatic dihydroxy compound at 25 ° C. is 20 g / L or less and the solubility of the aromatic monohydroxy compound (terminal stopper) at 25 ° C. is 50 g / L or more. Specifically, dichloromethane, chloroform, dichloroethane, trichloroethane, tetrachloroethane, dichloroethylene and the like are preferable, and dichloromethane (methylene chloride) is particularly preferably used. It is preferable to use pure water having an electric conductivity of 50 μS / cm or less.

  The washing method is a method in which a solid aromatic dihydroxy compound is transferred to a stirring tank, and an organic solvent and water are added simultaneously or separately, followed by stirring and filtering. The organic solvent and water are sprinkled simultaneously or alternately in a centrifuge. Examples include a method of removing liquid by centrifugation. Dialkyl carbonates and monohydroxy compounds are extracted into the organic solvent phase, and unreacted alcohols and salts are extracted into the aqueous phase to improve the purity of the aromatic dihydroxy compound.

  When washing with an organic solvent, the washing time for one time is preferably in the range of 1 minute to 60 minutes, and the washing temperature is preferably in the range of 5 to 40 ° C. The amount of the organic solvent used for one-time washing is preferably 50 to 1000 parts by weight, more preferably 100 to 500 parts by weight with respect to 100 parts by weight of the aromatic dihydroxy compound.

  When washing with water, the time for one washing is preferably in the range of 1 to 60 minutes, and the washing temperature is preferably in the range of 5 to 80 ° C. The amount of water used for one-time washing is preferably 50 to 1000 parts by weight, more preferably 100 to 500 parts by weight with respect to 100 parts by weight of the aromatic dihydroxy compound.

  The aromatic dihydroxy compound to be washed preferably has an average particle size (weight average particle size) of 100 to 1000 μm, more preferably 100 to 800 μm, and particularly preferably 200 to 600 μm. Use of an aromatic dihydroxy compound having an average particle diameter in the above range is preferable because it can be efficiently washed.

  The obtained solid aromatic dihydroxy compound can be reused as a raw material in the production process of an aromatic polycarbonate. As a re-use method, it can be used as it is in the melt polymerization method, and in the interfacial polymerization method, it can be dissolved in a metal hydroxide aqueous solution at a desired concentration and used for the production of an aromatic polycarbonate. . At that time, it is also preferable to use a solution obtained by heating a solution obtained by dissolving an aromatic dihydroxy compound in a metal hydroxide aqueous solution and volatilizing the remaining organic solvent.

  In addition, the aromatic dihydroxy compound obtained in the present invention and a commercially available aromatic dihydroxy compound may be used together as a raw material for producing an aromatic polycarbonate. The method for mixing the recovered aromatic dihydroxy compound and the commercially available aromatic dihydroxy compound may be any method of solids, solids and liquids, or liquids.

  On the other hand, as a method for recovering the dialkyl carbonate obtained by decomposing the waste aromatic polycarbonate, unreacted alcohol and dialkyl carbonate are recovered from the aqueous solution phase obtained by the liquid separation, and from the organic solvent phase. A method of recovering the organic solvent, unreacted alcohol and dialkyl carbonate from the evaporated fraction is preferable. Examples of the operation method include an extraction method and a distillation method, and the distillation method is preferably used.

  The recovered dialkyl carbonate can be used as a raw material for the production process of an aromatic polycarbonate by a melt polymerization method. The recovered chlorine compound organic solvent and alcohol can be reused in the decomposition reaction of the polycarbonate resin.

  Since the polycarbonate resin obtained by using the aromatic dihydroxy compound recovered by the method of the present invention as a raw material is excellent in hue and thermal stability, for example, a magneto-optical disc, various write-once discs, a digital audio disc (so-called compact disc) It can be suitably used as a material for an optical disk substrate such as an optical video disk (so-called laser disk) or a digital versatile disk (DVD), or as a material for a precision equipment container such as a silicon wafer. It is suitably employed as a substrate material.

  According to the present invention, waste aromatic polycarbonate is dissolved in an organic solvent, a metal hydroxide is used as a decomposition catalyst, decomposed by transesterification with alcohol, and an aqueous acid solution is added to the reaction mixture after decomposition. By maintaining the liquid temperature during the sum operation at 0 to 70 ° C., the obtained aromatic dihydroxy compound has a high purity, and the quality of the aromatic polycarbonate obtained using this aromatic dihydroxy compound is a commercially available aromatic dihydroxy compound. The quality of the aromatic polycarbonate produced using the dihydroxy compound is not inferior to that of the aromatic polycarbonate. Therefore, the industrial effect exhibited by the present invention is exceptional.

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these. Unless indicated otherwise, parts represent parts by weight. The evaluation was performed by the following method.
(1) Hue (b value)
Using a polycarbonate resin pellet, a 50 mm square plate having a thickness of 2 mm was molded at a cylinder temperature of 340 ° C. using an injection molding machine (manufactured by Nippon Steel Works, Ltd .: Nikko Anchor V-17-65 type). The molded plate was measured for b value using a color difference meter (manufactured by Nippon Denshoku Co., Ltd.).

(2) Thermal stability (△ E)
Test pieces (thickness 2 mm) of polycarbonate resin pellets that were not allowed to stay for 10 minutes at a cylinder temperature of 340 ° C. using an injection molding machine (manufactured by Nippon Steel Co., Ltd .: Nikko Anchor V-17-65 type) 50 mm square plate) was prepared, and the change in hue (ΔE) was measured. The change in hue was calculated using the following formula after measuring the L, a, and b values with a color difference meter (manufactured by Nippon Denshoku Co., Ltd.).
ΔE = [(L′−L) ² + (a′−a) ² + (b′−b) ² ] ^1/2
(L, a, b are not retained, L ′, a ′, b ′ are retained for 10 minutes)

(3) Purity of bisphenol A (bisphenol A purity in organic matter)
Using a Waters high performance liquid chromatograph, 0.2 mL of sample (organic matter) was added with 1 mL of acetonitrile with o-cresol added as an internal standard, dissolved, and chromatographed using acetonitrile / 0.2% acetic acid aqueous solution as a developing solvent. The purity of bisphenol A was obtained using a calibration curve prepared in advance.

(4) Moisture content Using a Karl Fischer moisture meter manufactured by Metrohm, a sample 2 g was charged and measured.

[Example 1]
In a reactor equipped with a thermometer, stirrer, reflux condenser and water bath, 4 parts of solid sodium hydroxide (20 mol% with respect to carbonate bond of aromatic polycarbonate), 80 parts of methanol (1 mol of carbonate bond of aromatic polycarbonate) 5 mol) was added and dissolved by stirring at 25 ° C. Next, 2 parts of hydrosulfite sodium as an antioxidant, 200 parts of methylene chloride, and a commercially available CD-R are cut to a size of about 2 cm square with a cutter and sonicated for 5 minutes with stirring to remove the film. 127 parts of the resin substrate (main component bisphenol A polycarbonate resin, viscosity average molecular weight 15200, containing blue pigment) was added, and stirring was continued at 25 ° C. Immediately after the addition, the resin was in a dumpling state, but as the internal temperature increased, the solid content was dissolved and completely dissolved after 10 minutes of stirring. Here, in order to measure the concentration in the system, a part of the solution was sampled and the water content was measured, and it was 0.05% by weight. Thereafter, the water bath was adjusted to bring the internal temperature to 85 ° C. Two hours after the addition of the resin, the carbonate oligomer in the reaction mixture was analyzed by ¹ H-NMR. As a result, the carbonate oligomer peak disappeared completely, and the peak area ratio of methanol / dimethyl carbonate was 1.5. Since it was confirmed that a sufficient amount of dimethyl carbonate had been produced, the water bath temperature was lowered and cooled to 40, and then 202 parts of a 0.5 mol / L hydrochloric acid aqueous solution was added and neutralized to stop the decomposition reaction. The temperature after addition of hydrochloric acid was 41 ° C. The aqueous phase was pH 7.

  The reaction mixture in which an aqueous hydrochloric acid solution was added to the separatory funnel was transferred, and separated into an organic phase and an aqueous phase. The aqueous phase contained methanol, dimethyl carbonate and methylene chloride, and these organic substances were recovered by repeated distillation. In distillation, salt such as sodium chloride was discarded together with water.

The organic phase was depressurized by an evaporator provided with a 40 ° C. water bath to remove methylene chloride, methanol and dimethyl carbonate, and 131 parts of a solid content were obtained. From the analysis result of solid content of ¹ H-NMR, bisphenol A, p-tertiary butylphenol and dimethyl carbonate were present.

  To this solid content, 200 parts of methylene chloride and 200 parts of pure water were added and stirred at 25 ° C. for 30 minutes to form a slurry. The slurry was filtered through a stainless steel filter having a pore size of 50 μm, and 100 parts of methylene chloride was washed with solid content. When the solid content was dried after washing, 108 parts of bisphenol A was obtained. The purity of bisphenol A was 99.8%, and this solid bisphenol A was white.

[Comparative Example 1]
In Example 1, after confirming that the carbonate oligomer peak had completely disappeared, 202 parts of a 0.5 mol / L hydrochloric acid aqueous solution was added at 85 ° C. without lowering the water bath temperature, and the decomposition reaction was stopped by neutralization. A solid bisphenol A was obtained by the same operation as in Example 1 except that the temperature after addition of hydrochloric acid was 87 ° C. and the aqueous phase was pH 7. The purity of bisphenol A was 99.3%.

[Reference Example 1] Production of polycarbonate resin (A) A thermometer, a stirrer, a reflux condenser, and a reactor with a circulator were charged with 650 parts of ion-exchanged water and 252 parts of a 25% aqueous sodium hydroxide solution and purchased. 170 parts of commercially available bisphenol A, 13 parts of methylene chloride, and 0.34 part of hydrosulfite were added, and the temperature was kept at 30 ° C. while circulating and dissolved in 40 minutes to prepare a bisphenol A aqueous solution.

  (B) A thermometer, a stirrer and a reactor equipped with a reflux condenser were charged with 367 parts of the aqueous bisphenol A solution prepared by the method (A), 181 parts of methylene chloride was added, and phosgene 28 was stirred at 15 to 25 ° C. .3 parts were blown in over 40 minutes. After completion of the phosgene blowing, 7.2 parts of a 48% aqueous sodium hydroxide solution and 1.55 parts of solid p-tertiary butylphenol were added and emulsified. After 10 minutes, 0.06 part of triethylamine was added, and further 28 to 33 The reaction was terminated by stirring for 1 hour at ° C. After completion of the reaction, 400 parts of methylene chloride was added to and mixed with the product, the stirring was stopped, and the aqueous phase and the organic phase were separated to obtain an organic solvent solution having a polycarbonate resin concentration of 14.5% by weight. (This operation was repeated using two reactors.)

  After adding 150 parts of water to this organic solvent solution and stirring and mixing, stirring was stopped and the aqueous phase and the organic phase were separated. To this organic phase, 200 parts of aqueous hydrochloric acid having a pH of 3 was added and mixed by stirring to extract triethylamine. Then, stirring was stopped and the aqueous phase and the organic phase were separated. Next, 200 parts of ion-exchanged water was added to the separated organic phase, and the mixture was stirred and mixed. Then, the stirring was stopped, and the aqueous phase and the organic phase were separated. This operation was repeated (four times) until the conductivity of the aqueous phase was almost the same as that of ion-exchanged water. The obtained purified polycarbonate resin solution was filtered with a filter made of SUS304 having a filtration accuracy of 1 μm.

  Next, the organic solvent solution was put together with 100 L of ion-exchanged water into a 1000 L kneader made of SUS316L with an inner wall provided with an isolation chamber having a foreign matter outlet at the bearing, and methylene chloride was evaporated at a water temperature of 42 ° C. The mixture was added to a hydrothermal treatment tank with a stirrer controlled at a water temperature of 95 ° C., and stirred and mixed for 30 minutes at a mixing ratio of 25 parts of powder and 75 parts of water. This mixture of powder and water was separated with a centrifuge to obtain a powder containing 0.5% by weight of methylene chloride and 45% by weight of water. This granular material is continuously fed at 50 kg / h (converted to polycarbonate resin) to a conductive heat receiving groove type biaxial stirring continuous dryer made of SUS316L controlled at 140 ° C. and dried under the condition of an average drying time of 3 hours. To obtain a granular material.

  Tris (2,4-di-tert-butylphenyl) phosphite is 0.01 parts by weight to 100 parts by weight of this granular material, tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphinate ) And 0.08 part by weight of stearic acid monoglyceride were added and mixed. Such a powder is melt-kneaded and extruded by a vent type twin screw extruder [TEM-50B manufactured by Toshiba Machine Co., Ltd.] with a cylinder temperature of 280 ° C. and a suction vacuum of 700 Pa using a dry vacuum pump. Obtained. The obtained pellets were molded and evaluated for hue and thermal stability. The results are shown in Table 1.

[Example 2]
In Reference Example 1 (A), a pellet was obtained by performing the same operation as in Reference Example 1 except that bisphenol A obtained in Example 1 was used instead of commercially available bisphenol A. The obtained pellets were molded and evaluated for hue and thermal stability. The results are shown in Table 1.

[Comparative Example 2]
In Reference Example 1 (A), a pellet was obtained by performing the same operation as in Reference Example 1 except that bisphenol A obtained in Comparative Example 1 was used instead of commercially available bisphenol A. The obtained pellets were molded and evaluated for hue and thermal stability. The results are shown in Table 1.

Claims (4)

  Waste aromatic polycarbonate is decomposed by transesterification with an alcohol having 1 to 4 carbon atoms in the presence of a halogenated hydrocarbon compound solvent and a metal hydroxide catalyst, and the temperature of the reaction mixture after decomposition is reduced to 0 to 70 ° C. An aqueous inorganic acid solution is added to neutralize the solution while keeping it in the range, and the organic solvent phase and the aqueous solution phase are separated to recover the organic solvent phase, and a solid aromatic dihydroxy compound is obtained from the recovered organic solvent phase. A process for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate characterized by   The method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to claim 1, wherein the halogenated hydrocarbon compound is dichloromethane, dichloroethane or chloroform.   2. The method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate resin according to claim 1, wherein the inorganic acid aqueous solution is at least one acid aqueous solution selected from the group consisting of aqueous solutions of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.   The manufacturing method of an aromatic polycarbonate which uses the aromatic dihydroxy compound obtained by the method of Claim 1 as a manufacturing raw material of an aromatic polycarbonate.