JP2006045371A - 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, by treating a waste aromatic polycarbonate (including an aromatic polycarbonate product, such as a CD, a CD-ROM, and a DVD, which becomes useless) at a low cost in a large amount. <P>SOLUTION: This method for obtaining the aromatic dihydroxy compound from the waste aromatic polycarbonate comprises dissolving the waste aromatic polycarbonate in an organic solvent, filtering the organic solvent solution of the waste aromatic polycarbonate, and subjecting the aromatic polycarbonate in the solution to decomposition reaction by transesterification reaction in the presence of a 1-4C alcohol and a metal hydroxide. <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 solve these problems, the present inventors have dissolved waste aromatic polycarbonate in an organic solvent, used a metal hydroxide as a decomposition catalyst, decomposed by an ester exchange reaction with alcohol, In the method of obtaining the aromatic dihydroxy compound, if there are many insoluble foreign matters in the organic solvent solution of the waste aromatic polycarbonate, a side reaction may occur during the decomposition reaction of the polycarbonate, or the purity of the obtained aromatic dihydroxy compound is lowered. When this low-purity aromatic dihydroxy compound is used as a raw material for polycarbonate production, it can be seen that the amount of foreign matter in the resulting aromatic polycarbonate is greater than when a commercially available aromatic dihydroxy compound is used. As a result of various studies, the organic solvent solution of the waste aromatic polycarbonate was filtered. Its Using the filtrate, leading to the present invention found that the above object can be achieved Te.

That is, according to the present invention,
1. Dissolving the waste aromatic polycarbonate in an organic solvent, filtering the organic solvent solution of the waste aromatic polycarbonate, and esterifying the aromatic polycarbonate in the filtrate in the presence of an alcohol having 1 to 4 carbon atoms and a metal hydroxide. A method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate, characterized by causing a decomposition reaction by an exchange reaction.

  2. 2. The method for obtaining an aromatic dihydroxy compound from the waste aromatic polycarbonate according to item 1, wherein the organic solvent is a halogenated hydrocarbon compound.

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

  4). A method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to item 1 above, wherein an organic solvent solution of waste aromatic polycarbonate is filtered with a filter having a pore size of 1 to 10 μm.

  5. A method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to item 1 above, wherein an organic solvent solution of waste aromatic polycarbonate is filtered with a filter having a pore size of 20 μm or more and then filtered with a filter having a pore size of 1 to 10 μm.

6). 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, first, the waste aromatic polycarbonate resin is dissolved in an organic solvent, and the organic solvent solution of the waste aromatic polycarbonate is filtered.

  As the organic solvent, a solvent having an aromatic polycarbonate resin solubility at 25 ° C. of 50 g / L or more is preferable. Specifically, halogenated hydrocarbon compound solvents such as dichloromethane, chloroform, dichloroethane, trichloroethane, tetrachloroethane, and dichloroethylene Dichloromethane, dichloroethane or chloroform is more preferable, and dichloromethane (methylene chloride) is particularly preferably used. These solvents are good solvents for aromatic polycarbonate resins and are used as reaction solvents in the production process of aromatic polycarbonate resins. Even if these organic solvents remain in the aromatic dihydroxy compounds obtained by decomposition, these solvents are used. There is an advantage that does not adversely affect the production of the aromatic polycarbonate resin.

  The amount of the organic solvent used is preferably in the range of 400 to 1000 parts by weight with respect to 100 parts by weight of the waste aromatic polycarbonate resin. If the amount of the organic solvent used is less than 400 parts by weight, the aromatic polycarbonate resin may not be sufficiently dissolved to increase the insoluble content, and the yield of the aromatic dihydroxy compound may decrease. If the amount exceeds 1000 parts by weight, the decomposition reaction rate decreases. However, the decomposition reaction time may be increased, 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.

  Examples of the method for filtering the organic solvent solution of the waste aromatic polycarbonate include a method using a filter, a centrifuge, and the like.

The filter preferably includes a filter having a pore size of 1 to 100 μm, more preferably 1 to 50 μm, still more preferably 1 to 20 μm, and particularly preferably 1 to 10 μm. It is industrially preferable to install a filter in a line that uses a pump to pump a tank that performs a decomposition reaction from a tank that stores an organic solvent solution. Use of a filter having a pore size in this range is preferable because the filtration time is short, and foreign matters such as a printed film, a metal film, a UV cured film, an additive, and a filler to be filtered hardly flow out together with the filtrate. The filter material is preferably made of a resin such as PET, nylon or cellulose, or a metal such as ceramic or stainless steel.
Moreover, the differential pressure during filtration is preferably 0.01 to 0.5 MPa, particularly preferably 0.1 to 0.4 MPa.

  Moreover, 1-50 mm is preferable and, as for the hole diameter of the metal spin-drying | dehydration part (basket part), 5-20 mm is especially preferable. The material of the filtration filter attached to the metal dehydration part is preferably made of a resin such as cotton, PET, or nylon, and the pore size of the filtration filter is preferably 5 to 100 μm. Filtration is preferably performed using a centrifuge under conditions of a centrifugal force of 100 to 1000 G, more preferably a centrifugal force of 200 to 700 G.

  The organic solvent solution of waste aromatic polycarbonate is filtered by the above-described method, but it is finally desirable to filter with a filter having a pore diameter of 1 to 10 μm, preferably 1 to 5 μm. Further, a method of filtering with a filter having a pore size of 1 to 10 μm, preferably 1 to 5 μm after filtering with a filter having a pore size of 20 μm or more, preferably 20 to 100 μm is desirable. Further, the amount of insoluble foreign matter of 10 μm or more after filtration is preferably 0.02 parts by weight or less, particularly preferably 0.01 parts by weight or less, relative to 100 parts by weight of the polycarbonate resin.

  Foreign matter contained in the waste aromatic polycarbonate resin is removed by filtration. In particular, when a waste optical disk is used, a printed film, a metal film, a UV cured film, and the like are provided on the surface of the optical disk, and it is important to remove these foreign substances. If these foreign substances are present, a side reaction occurs in the decomposition reaction of the aromatic polycarbonate resin, resulting in a decrease in the purity of the aromatic dihydroxy compound, and the resulting aromatic dihydroxy compound is used in the production process of the aromatic polycarbonate resin. The resulting aromatic polycarbonate resin is inferior in hue and thermal stability is reduced, and the amount of foreign matter in the aromatic polycarbonate resin is increased, so that it cannot be used for applications such as optical disk substrates that dislike fine foreign matter.

  Next, the filtrate obtained by filtering the organic solvent solution of the waste aromatic polycarbonate is subjected to a decomposition reaction (dissolution) of the aromatic polycarbonate in the filtrate by transesterification in the presence of an alcohol having 1 to 4 carbon atoms and a metal hydroxide. Polymerization reaction). Use of a metal hydroxide as a catalyst is preferable because the decomposition reaction easily proceeds at a low temperature.

  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. As a method for removing water in the reaction system, there are several methods such as a method in which an organic solvent and a metal hydroxide aqueous solution are azeotropically separated by a decanter, and a method in which the mixed solution is passed 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.

  In the present invention, the temperature at which the decomposition reaction is performed is preferably 30 ° C to 90 ° C. When it is less than 30 ° C., the decomposition reaction time becomes long, and the processing efficiency may be remarkably inferior. If the temperature exceeds 90 ° C., a large amount of heating energy is required, and the color of the solution tends to turn brown during the decomposition treatment, and a high-quality aromatic dihydroxy compound may not be obtained.

  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 reactor with an inert gas such as nitrogen.

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.

  The aromatic dihydroxy compound obtained by subjecting the aromatic polycarbonate in the filtrate to a decomposition reaction (depolymerization reaction) by transesterification in the presence of an alcohol having 1 to 4 carbon atoms and a metal hydroxide is obtained by the following method. It is preferable to recover and wash as a solid aromatic dihydroxy compound.

  As a method for recovering the solid aromatic dihydroxy compound, an aqueous acid solution is added to the reaction solution after the decomposition reaction, the organic solvent phase and the aqueous solution phase are separated, and a solid solution is obtained by distillation from the obtained organic solvent phase. A method for recovering the aromatic dihydroxy compound is preferably employed.

  By adding an acid aqueous solution to the reaction solution after the decomposition reaction, the aromatic dihydroxy compound is dissolved in the organic solvent phase. As the acid aqueous solution, an aqueous solution of an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid is preferably used. The amount of the acid aqueous solution to be added needs to be such that the aqueous solution phase is neutral to acidic, and is particularly preferably such that the pH is in the neutral pH range of 6 to 8. When water is added without adding an acid, hydrolysis of the dialkyl carbonate occurs, and the aromatic dihydroxy compound reacts with the metal hydroxide to form a salt, thereby reducing the yield of the aromatic dihydroxy compound. When the solvent is removed from the reaction solution after the decomposition reaction, 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.

  When an aqueous acid solution is added to the reaction solution 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 is mixed in the next step and affects the purity of the resulting aromatic dihydroxy compound. It is preferable to contact and 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 aromatic polycarbonate, unreacted alcohol and dialkyl carbonate are recovered from the aqueous solution phase obtained by the liquid separation and evaporated from the organic solvent phase. A method of recovering the organic solvent, the unreacted alcohol and the dialkyl carbonate from the fraction obtained 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, by using the filtrate obtained by filtering the waste polycarbonate resin solution for the decomposition reaction, a high-quality aromatic dihydroxy compound can be obtained by a method in which the decomposition time is short and the energy cost is not high. The aromatic dihydroxy compound can be reused as a raw material for producing an aromatic polycarbonate. Therefore, the industrial effect produced 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) Amount of foreign matter of 0.5 μm or more in aromatic polycarbonate pellet 1 g of aromatic polycarbonate pellet was dissolved in 100 ml of methylene chloride, and 0.5 μm was measured with a fine particle measuring device (He-Ne laser light scattering method manufactured by Hyac Royco). The number of fine particles was measured.

[Example 1]
100 parts of a commercially available compact disc and 600 parts of methylene chloride were added to the stirring tank and stirred for 6 hours. The compact disc membrane was dispersed in a methylene chloride solution of polycarbonate. This solution was passed through a filtration device (manufactured by Nippon Pole Co., Ltd.) equipped with a stainless steel filter having a pore size of 5 μm to remove the compact disc film (printing, UV curable resin, aluminum film, etc.).

  To a thermometer, a stirrer, a reflux condenser, and a reactor with a water bath, 4 parts of solid sodium hydroxide (20 mol% with respect to the carbonate bond of the aromatic polycarbonate), 80 parts of methanol (1 mol of the carbonate bond of the aromatic polycarbonate) 5 mol), 894 parts of filtrate (methylene chloride solution of polycarbonate) and 2 parts of hydrosulfite sodium as an antioxidant were added and stirred. Here, when a part of the solution in the system was sampled and the water content was measured, it was 0.05% by weight. Thereafter, the water bath was adjusted to bring the internal temperature to 40 ° C.

After 4 hours from the start of the reaction (inner temperature reached 40 ° C.), the carbonate oligomer in the reaction mixture was analyzed by ¹ H-NMR. As a result, it completely disappeared and the peak area ratio of methanol / dimethyl carbonate was 1 Since it was confirmed that the theoretical amount of dimethyl carbonate was formed, 202 parts of 0.5 mol / L hydrochloric acid aqueous solution was added to stop the decomposition reaction.

  The reaction mixture was transferred to a separatory funnel and separated into 949 parts of an organic phase and 233 parts of 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 with an evaporator provided with a water bath at 40 ° C. to remove methylene chloride, methanol and dimethyl carbonate to obtain 133 parts of a solid content. Distillation was further repeated from the fraction to separate methylene chloride, methanol and dimethyl carbonate. From the analysis result of solid content of ¹ H-NMR, bisphenol A, p-tertiary butylphenol and dimethyl carbonate were present. Although no blue pigment was observed, the solid was slightly bluish.

  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 over the solid content. When the solid content was dried after washing, 107 parts of bisphenol A was obtained, and its purity was 99.8%.

  The organic phase of the filtrate after washing was bluish, and p-tertiary butylphenol, dimethyl carbonate and bisphenol A were present in the organic phase, and dimethyl carbonate and methanol were present in the aqueous phase. Methylene chloride and dimethyl carbonate were recovered from the organic phase by distillation, and dimethyl carbonate and methanol were recovered from the aqueous phase by distillation.

[Example 2]
In Example 1, a solid bisphenol A was obtained by performing the same operation as in Example 1 except that a filter with a stainless steel filter with a pore size of 8 μm was used instead of the filter with a stainless steel filter with a pore size of 5 μm. It was. The purity of bisphenol A was 99.8%.

[Example 3]
In Example 1, after filtering with a PET back filter with a pore size of 40 μm instead of a filtration device with a stainless steel filter with a pore size of 5 μm, a filtration device with a stainless steel filter with a pore size of 8 μm was used. The same operation as in Example 1 was performed to obtain solid bisphenol A. The purity of bisphenol A was 99.8%.

[Comparative Example 1]
Example 1 was the same as Example 1 except that the solution in which the membrane of the compact disc was dispersed in a methylene chloride solution of polycarbonate was used as it was for the decomposition reaction without using a filtration device equipped with a stainless steel filter having a pore size of 5 μm. Thus, solid bisphenol A was obtained. 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 through a filter made of SUS304 having a pore size 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.

  0.01 parts by weight of tris (2,4-di-tert-butylphenyl) phosphite and 4,4′-biphenylenediphosphosphinic acid tetrakis (2,4-di-tert- Butylphenyl) and 0.018 parts 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 used to evaluate the amount of foreign matter, hue (b value), and thermal stability (ΔE). The results are shown in Table 1.

[Example 4]
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 used to evaluate the amount of foreign matter, hue (b value), and thermal stability (ΔE). The results are shown in Table 1.

[Example 5]
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 2 was used instead of commercially available bisphenol A. The obtained pellets were used to evaluate the amount of foreign matter, hue (b value), and thermal stability (ΔE). The results are shown in Table 1.

[Example 6]
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 3 was used instead of commercially available bisphenol A. The obtained pellets were used to evaluate the amount of foreign matter, hue (b value), and thermal stability (ΔE). 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 used to evaluate the amount of foreign matter, hue (b value), and thermal stability (ΔE). The results are shown in Table 1.

Claims (6)

  Dissolving the waste aromatic polycarbonate in an organic solvent, filtering the organic solvent solution of the waste aromatic polycarbonate, and esterifying the aromatic polycarbonate in the filtrate in the presence of an alcohol having 1 to 4 carbon atoms and a metal hydroxide. A method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate, which comprises causing a decomposition reaction by an exchange reaction.   The method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to claim 1, wherein the organic solvent is a halogenated hydrocarbon compound.   The method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to claim 1, wherein the organic solvent is dichloromethane, dichloroethane or chloroform.   The method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to claim 1, wherein the organic solvent solution of the waste aromatic polycarbonate is filtered with a filter having a pore size of 1 to 10 µm.   The method for obtaining an aromatic dihydroxy compound from waste aromatic polycarbonate according to claim 1, wherein the organic solvent solution of waste aromatic polycarbonate is filtered with a filter having a pore size of 20 µm or more and then filtered with a filter having a pore size of 1 to 10 µm.   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.