Method for depolymerization of polycarbonate resin, reaction tank treatment method, reaction tank post-treatment method, and method for producing polycarbonate resin

Abstract

To provide a depolymerization method and a reaction tank treatment method that achieve high depolymerization effect with reduced facility limitations through the use of a specific dihydroxy compound.SOLUTION: A method for depolymerization of a polycarbonate resin, the polycarbonate resin comprises a structural unit (a) derived from a dihydroxy compound having a specific site, the method using a compound (A) containing an alicyclic dihydroxy compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for depolymerizing a polycarbonate resin, a method for treating a reactor, a method for post-treatment of a reactor, and a method for producing a polycarbonate resin. [Background technology]

[0002] In recent years, concerns have arisen that increased carbon dioxide emissions and accumulation can lead to global warming, resulting in climate change, and there is a demand for the development of polycarbonates made from plant-derived monomers that are carbon-neutral even when disposed of after use. Among these, polycarbonate resins made from isosorbide (hereinafter sometimes abbreviated as ISB) obtained from biomass resources as a monomer component are known. It has been proposed that, after resin production, the polycarbonate remaining in the reactor be depolymerized using a diol monomer and then discharged from the reactor. In particular, to enhance the depolymerization effect, i.e., the depolymerization rate, it is known that a carbonic acid diester is preferably used in combination with a dihydroxy compound represented by a linear alkylene group or an ether bond (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-94029 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as disclosed in Patent Document 1, the depolymerization method for a dihydroxy compound alone represented by a linear alkylene group or an ether bond requires heating the dihydroxy compound at a temperature above its boiling point. This requires equipment that can withstand pressurized conditions, and since the dihydroxy compound is classified as a hazardous material under the Fire Service Act, there is a high risk of ignition and fire. Furthermore, when used in large quantities, there are storage volume restrictions, which imposes equipment constraints. Furthermore, in a depolymerization method that also uses a carbonate diester, which has a high depolymerization effect, the highly flexible linear dihydroxy compound reacts with the carbonate diester, resulting in a portion of the compound becoming cyclic and not contributing to depolymerization. Furthermore, when polycarbonate is produced using isosorbide again, contamination can cause color deterioration, deterioration of physical properties, and delayed polymerization rate, which can lead to reduced yields and a deterioration in polycarbonate quality.

[0005] An object of the present invention is to provide a depolymerization method and a reaction vessel treatment method which use a specific dihydroxy compound and which have few restrictions on equipment and have a high depolymerization effect, and to provide a method for producing a polycarbonate resin which has little coloration and high transparency after the reaction vessel treatment method is carried out. [Means for solving the problem]

[0006] Means for Solving the Problems The present inventors have conducted extensive research to solve the above problems, and as a result have found that depolymerization easily proceeds when a specific dihydroxy compound is used in a polycarbonate resin having a specific structural unit, and have arrived at the present invention.

[0007] The above-mentioned problems of the present invention can be solved by the following means. That is, the gist of the present invention lies in the following [1] to [8].

[0008] [1] A method for depolymerizing a polycarbonate resin, comprising: The polycarbonate resin contains a structural unit (a) derived from a dihydroxy compound having a moiety represented by the following formula (1): A method for depolymerizing a polycarbonate resin using a compound (A) containing an alicyclic dihydroxy compound.

[0009] [ka]

[0010] (However, this does not include the case where the moiety represented by the above formula (1) is part of -CH2-OH.)

[0011] [2] The method for depolymerizing a polycarbonate resin according to [1], wherein the structural unit (a) is a structural unit represented by the following formula (2):

[0012] [ka]

[0013] [3] The method for depolymerizing a polycarbonate resin according to [1] or [2], wherein the alicyclic dihydroxy compound is a compound represented by the following formula (3) and / or the following formula (4):

[0014] [ka]

[0015] [ka]

[0016] [4] The method for depolymerizing a polycarbonate resin according to any one of [1] to [3], wherein the compound (A) further contains a carbonic acid diester.

[0017] [5] A reaction tank treatment method, comprising: a step of producing the polycarbonate resin; and a depolymerization step, after the step of producing the polycarbonate resin, of depolymerizing the polycarbonate resin contained on the inner wall surface of the reaction tank by the depolymerization method according to any one of [1] to [4].

[0018] [6] The method for treating a reaction vessel according to [5], wherein in the depolymerization step, the temperature is 185°C to 320°C and the inside of the reaction vessel is maintained under an inert gas atmosphere.

[0019] [7] A method for post-treatment of a reactor, comprising contacting an aromatic hydroxy compound with the reactor after carrying out the method for treating a reactor according to [5] or [6].

[0020] [8] A method for producing a polycarbonate resin, comprising the step of producing the polycarbonate resin by transesterification after the reaction vessel post-treatment method according to [7]. [Effects of the Invention]

[0021] According to the present invention, by using a specific dihydroxy compound, it is possible to provide a depolymerization method and a reactor treatment method which have few restrictions on equipment and have a high depolymerization effect, and further, after carrying out the reactor treatment method, it is possible to produce a polycarbonate resin which is less colored and has high transparency. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described in detail below, but the present invention is not limited to the following description and can be practiced with any modifications within the scope of the gist of the present invention. In this specification, when "to" is used with a numerical value or physical property value between the two sides, the values ​​before and after the "to" are used to include the values ​​before and after the "to." Furthermore, numerical values ​​or physical values ​​described as upper and lower limits, other than those described as "greater than" or "less than," are used to include the values. Furthermore, unless otherwise specified, "%" means "% by mass." Furthermore, "parts by weight" and "parts by mass," and "% by weight" and "% by mass" are essentially synonymous.

[0023] In the present disclosure, the term "polycarbonate resin" refers to a polymer in which the structural units constituting the polymer include not only carbonate bonds but also moieties linked by ester bonds.

[0024] The term "structural unit" refers to a partial structure constituting a resin, and refers to a specific partial structure contained in a repeating structural unit. For example, in the case of a polycarbonate resin, it refers to a partial structure sandwiched between adjacent linking groups in the resin, or a partial structure sandwiched between a polymerization reactive group present at the terminal portion of a polymer and a linking group adjacent to the polymerization reactive group. More specifically, in the case of a polycarbonate resin, a carbonyl group is the linking group, and a partial structure sandwiched between adjacent carbonyl groups is referred to as a structural unit. In this specification, the mass ratio of each structural unit in the resin is calculated assuming that the total mass of all structural units and linking groups is 100 mass %.

[0025] The following describes in detail the embodiments of the present invention. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to the following content as long as it does not exceed the gist of the present invention.

[0026] <Polycarbonate resin> The polycarbonate resin in the present invention contains a structural unit (a) derived from a dihydroxy compound having a moiety represented by the following formula (1). In this specification, unless otherwise specified, the term "polycarbonate resin" refers to both the polycarbonate resin to be depolymerized in the depolymerization method of the present invention and the polycarbonate resin produced after treating a reaction vessel by the depolymerization.

[0027] [ka]

[0028] Dihydroxy compounds having a moiety represented by formula (1) include isosorbide (ISB), isomannide, and isoidet, which are stereoisomers. These may be used alone or in combination of two or more. Among these, isosorbide, which is obtained by dehydration condensation of sorbitol, which is produced from various starches that are abundant and easily available as plant-derived resources, is most preferred in terms of availability, ease of production, and the properties of the resulting molded products (e.g., heat resistance, impact resistance, surface hardness). Furthermore, isosorbide is preferably used from the viewpoint of carbon neutrality.

[0029] The structural unit (a) is preferably a structural unit represented by the following formula (2).

[0030] [ka]

[0031] The mass ratio of the structural unit (a) in the polycarbonate resin of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more, based on 100% by mass of all structural units constituting the polycarbonate resin. At or above the lower limit, the solidification temperature of the resulting polycarbonate resin can be set to room temperature or higher, and melting of the pellets can be prevented when the polycarbonate resin is pelletized and handled. Furthermore, the mass ratio of the structural unit (a) is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. At or below the upper limit, the water absorption rate of the polycarbonate resin can be suppressed.

[0032] Furthermore, examples of dihydroxy compounds having a moiety represented by formula (1) that can be used include spiroglycol (also known as 3,9-bis(1,1-dimethyl-2-hydroxyethyl-2,4,8,10-tetraoxaspiro[5,5]undecane) and dioxane glycol (also known as 2-(1,1-dimethyl-2-hydroxyethyl)-5-ethyl-5-hydroxymethyl-1,3-dioxane). Of these, spiroglycol is more preferred. Furthermore, the structural unit (a) derived from a dihydroxy compound having a moiety represented by formula (1) is preferably a structural unit represented by formula (5) below.

[0033] [ka]

[0034] As the structural unit (a) in the polycarbonate resin, a dihydroxy compound having one type of moiety represented by the formula (1) may be used, or two or more types of dihydroxy compounds having moieties represented by the formula (1) may be used.

[0035] (Structural unit (b)) From the viewpoint of a balance between optical properties, heat resistance, mechanical properties, etc., the polycarbonate resin in the present invention preferably contains a structural unit (b) in addition to the structural unit (a). Examples of dihydroxy compounds that form the structural unit (b) include aliphatic dihydroxy compounds, alicyclic dihydroxy compounds, ether-containing dihydroxy compounds, aromatic-containing dihydroxy compounds, and diester compounds. Among these, from the viewpoints of weather resistance and moist heat resistance, alicyclic dihydroxy compounds are preferred.

[0036] Examples of aliphatic dihydroxy compounds include the following dihydroxy compounds: linear aliphatic dihydroxy compounds such as ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol; and branched aliphatic dihydroxy compounds such as 1,3-butanediol, 1,2-butanediol, neopentyl glycol, and hexylene glycol. Of these, 1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol are preferred.

[0037] Examples of alicyclic dihydroxy compounds include the following dihydroxy compounds: dihydroxy compounds which are primary alcohols of alicyclic hydrocarbons, exemplified by 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 2,6-decalindimethanol, 1,5-decalindimethanol, 2,3-decalindimethanol, 2,3-norbornane dimethanol, 2,5-norbornane dimethanol, 1,3-adamantanedimethanol, and dihydroxy compounds derived from terpene compounds such as limonene; and dihydroxy compounds which are secondary or tertiary alcohols of alicyclic hydrocarbons, exemplified by 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,3-adamantanediol, hydrogenated bisphenol A, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. Among these, tricyclodecane dimethanol and 1,4-cyclohexane dimethanol are more preferred. Furthermore, the structural unit (b) derived from an alicyclic dihydroxy compound is preferably a structural unit represented by the following formula (6) or (7).

[0038] [ka]

[0039] [ka]

[0040] Examples of the ether-containing dihydroxy compound include oxyalkylene glycols and dihydroxy compounds containing an acetal ring. Examples of the oxyalkylene glycol include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0041] Examples of aromatic-containing dihydroxy compounds that can be used include the following dihydroxy compounds: 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 2,2-bis(4-hydroxy-(3-phenyl)phenyl)propane, 2,2-bis(4-hydroxy-(3,5-diphenyl)phenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, bis(4-hydroxyphenyl)propane, )methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 1,1-bis(4-hydroxyphenyl)decane, bis(4-hydroxy-3-nitrophenyl)methane, 3,3-bis(4-hydroxyphenyl)pentane, 1,3- ...diphenylmethane, 1,1-bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4- Bis(2-(4-hydroxyphenyl)-2-propyl)benzene, 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone, 2,4'-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxy-3-methylphenyl)sulfide, bis(4-hydroxyphenyl)disulfide, 4, Aromatic bisphenol compounds such as 4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dichlorodiphenyl ether; dihydroxy compounds having an ether group bonded to an aromatic group such as 2,2-bis(4-(2-hydroxyethoxy)phenyl)propane, 2,2-bis(4-(2-hydroxypropoxy)phenyl)propane, 1,3-bis(2-hydroxyethoxy)benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, and bis(4-(2-hydroxyethoxy)phenyl)sulfone;9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxypropoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxypropoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene Dihydroxy compounds having a fluorene ring, such as 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, and 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene;

[0042] Examples of diester compounds include the following dicarboxylic acids: aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; and aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. These dicarboxylic acid components can be used as raw materials for polyester carbonate resins as dicarboxylic acids themselves, but depending on the production method, dicarboxylic acid esters such as methyl esters and phenyl esters, or dicarboxylic acid derivatives such as dicarboxylic acid halides can also be used as raw materials.

[0043] The mass ratio of the structural unit (b) in the polycarbonate resin of the present invention is preferably 5% by mass or more, more preferably 12% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of all structural units constituting the polycarbonate resin. If the mass ratio is above the above lower limit, the water absorption rate of the resulting polycarbonate resin can be suppressed. Furthermore, the mass ratio of the structural unit (b) is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. If the mass ratio is below the above upper limit, the solidification temperature of the polycarbonate resin can be set to room temperature or higher, and melting of the pellets can be prevented when the polycarbonate resin is formed into pellets and handled.

[0044] (Structural unit (c)) From the viewpoint of a balance between optical properties, heat resistance, mechanical properties, etc., the polycarbonate resin in the present invention preferably contains a structural unit (c) in addition to the structural unit (a). The structural unit (c) is preferably a structural unit represented by the following formula (8) and / or a structural unit represented by the following formula (9). Hereinafter, such a structural unit may be referred to as an "oligofluorene structural unit."

[0045] [ka]

[0046] [ka]

[0047] In equations (8) and (9), R 1 ~R 3 R each independently represents a direct bond or a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms. 4 ~R 9 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, a substituted or unsubstituted acyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 2 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 2 to 10 carbon atoms, a sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, a nitro group, or a cyano group, provided that R 4 ~R 9 may be the same or different, and R 4 ~R 9 At least two adjacent groups among these may be bonded to each other to form a ring. From the viewpoint that the fluorene rings in the polymer are likely to be oriented perpendicular to the main chain direction and that stronger reverse wavelength dispersion is exhibited, it is preferable that the polycarbonate resin in the present invention contains a structural unit represented by formula (8).

[0048] R 1 and R 2As R, for example, the following alkylene groups can be used. Specific examples include linear alkylene groups such as methylene, ethylene, n-propylene, and n-butylene; and branched alkylene groups such as methylmethylene, dimethylmethylene, ethylmethylene, propylmethylene, (1-methylethyl)methylene, 1-methylethylene, 2-methylethylene, 1-ethylethylene, 2-ethylethylene, 1-methylpropylene, 2-methylpropylene, 1,1-dimethylethylene, 2,2-dimethylpropylene, and 3-methylpropylene. 1 and R 2 The positions of the branched chains in R are indicated by numbers assigned so that the carbon on the fluorene ring side is at position 1. From the viewpoint that the fluorene rings in the polymer tend to be oriented perpendicular to the main chain direction and exhibit stronger reverse wavelength dispersion, 1 and R 2 is preferably an ethylene group.

[0049] R 1 and R 2 The selection of R may be related to the expression of the reverse dispersion wavelength dependency. Polycarbonate resins exhibit the strongest reverse dispersion wavelength dependency when the fluorene rings are oriented perpendicular to the main chain direction (stretching direction). In order to bring the orientation state of the fluorene rings closer to this state and to express a strong reverse dispersion wavelength dependency, it is necessary to select R in which the main chain of the alkylene group has 2 to 3 carbon atoms. 1 and R 2 It is preferable to use the following. When the carbon number is 1, unexpectedly, the reverse dispersion wavelength dependency may not be exhibited. This is thought to be because, for example, steric hindrance of the carbonate group and / or ester group, which are the linking groups of the oligofluorene structural unit, fixes the orientation of the fluorene ring in a direction that is not perpendicular to the main chain direction. On the other hand, when the carbon number is too large, the fixation of the orientation of the fluorene ring becomes weak, which may result in insufficient reverse dispersion wavelength dependency. Furthermore, the heat resistance of the polycarbonate resin may be reduced.

[0050] R 3As R, for example, the following alkylene groups can be used. Specific examples include linear alkylene groups such as methylene, ethylene, n-propylene, and n-butylene; and branched alkylene groups such as methylmethylene, dimethylmethylene, ethylmethylene, propylmethylene, (1-methylethyl)methylene, 1-methylethylene, 2-methylethylene, 1-ethylethylene, 2-ethylethylene, 1-methylpropylene, 2-methylpropylene, 1,1-dimethylethylene, 2,2-dimethylpropylene, and 3-methylpropylene. 3 The alkylene group preferably has 1 to 2 carbon atoms on the main chain, and more preferably has 1 carbon atom. When the number of carbon atoms on the main chain is too large, R 1 and R 2 As in the case of (1), the fixation of the fluorene rings is weakened, which may result in a decrease in the wavelength dependence of the reverse dispersion, an increase in the photoelastic coefficient, a decrease in heat resistance, etc. On the other hand, the fewer the number of carbon atoms on the main chain, the better the optical properties and heat resistance, but if the 9-positions of two fluorene rings are directly connected, the thermal stability may be deteriorated.

[0051] R 1 ~R 3 Examples of the substituent in include a halogen atom (specifically, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom); an alkoxy group having 1 to 10 carbon atoms such as a methoxy group or an ethoxy group; an acyl group having 1 to 10 carbon atoms such as an acetyl group or a benzoyl group; an acylamino group having 1 to 10 carbon atoms such as an acetamido group or a benzoylamido group; a nitro group; a cyano group; and an aryl group having 6 to 10 carbon atoms such as a phenyl group or a naphthyl group. One to three hydrogen atoms in the aryl group may be substituted with the above-mentioned halogen atom, alkoxy group, acyl group, acylamino group, nitro group, cyano group, etc.

[0052] R 4 ~R 9The substituted or unsubstituted alkyl group in may be, for example, the following alkyl groups. Specific examples include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, and n-decyl; branched alkyl groups such as isopropyl, 2-methylpropyl, 2,2-dimethylpropyl, and 2-ethylhexyl; and cyclic alkyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, and cyclooctyl. The number of carbon atoms in the alkyl group is preferably 4 or less, and more preferably 2 or less. When the number of carbon atoms is within this range, steric hindrance between fluorene rings is unlikely to occur, making it easier to obtain the desired optical properties derived from the fluorene rings. Examples of substituents for the alkyl group include R 1 ~R 3 Examples of the substituents include those described above for the group.

[0053] R 4 ~R 9 As the substituted or unsubstituted aryl group in the above, for example, the following aryl groups can be used. Specific examples include aryl groups such as phenyl, 1-naphthyl, and 2-naphthyl; and heteroaryl groups such as 2-pyridyl, 2-thienyl, and 2-furyl. The number of carbon atoms in the aryl group is preferably 8 or less, and more preferably 7 or less. When the number of carbon atoms is within this range, steric hindrance between the fluorene rings is unlikely to occur, making it easier to obtain the desired optical properties derived from the fluorene rings. As the substituent of the aryl group, R 1 ~R 3 Examples of the substituents include those described above for the group.

[0054] R 4 ~R 9As the substituted or unsubstituted acyl group in the above, for example, the following acyl groups can be used. Specific examples include aliphatic acyl groups such as formyl, acetyl, propionyl, 2-methylpropionyl, 2,2-dimethylpropionyl, and 2-ethylhexanoyl; and aromatic acyl groups such as benzoyl, 1-naphthylcarbonyl, 2-naphthylcarbonyl, and 2-furylcarbonyl. The number of carbon atoms in the acyl group is preferably 4 or less, and more preferably 2 or less. When the number of carbon atoms is within this range, steric hindrance between the fluorene rings is unlikely to occur, making it easy to obtain the desired optical properties derived from the fluorene rings. As the substituent of the acyl group, R 1 ~R 3 Examples of the substituents include those described above for the group.

[0055] R 4 ~R 9 As the substituted or unsubstituted alkoxy group or aryloxy group in the above, for example, the following can be used. Specific examples include a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, a trifluoromethoxy group, and a phenoxy group. The number of carbon atoms in the alkoxy group or aryloxy group is preferably 4 or less, and more preferably 2 or less. When the number of carbon atoms is within this range, steric hindrance between the fluorene rings is unlikely to occur, making it easier to obtain the desired optical properties derived from the fluorene ring. As the substituent of the alkoxy group or aryloxy group, R 1 ~R 3 Examples of the substituents include those described above for the group.

[0056] R 4 ~R 9The substituted or unsubstituted amino group in the formula (I) can be, for example, the following amino groups. Specific examples include amino groups; aliphatic amino groups such as N-methylamino, N,N-dimethylamino, N-ethylamino, N,N-diethylamino, N,N-methylethylamino, N-propylamino, N,N-dipropylamino, N-isopropylamino, and N,N-diisopropylamino; aromatic amino groups such as N-phenylamino and N,N-diphenylamino; acylamino groups such as formamide, acetamide, decanoylamide, benzoylamide, and chloroacetamide; and alkoxycarbonylamino groups such as benzyloxycarbonylamino and tert-butyloxycarbonylamino. The amino group is preferably an N,N-dimethylamino, N-ethylamino, or N,N-diethylamino group, with an N,N-dimethylamino group being more preferred. In this case, the amino group does not have a highly acidic proton and has a small molecular weight, so the fluorene ratio can be increased, thereby improving thermal stability and reducing the amount of monomers containing oligofluorene structural units used.

[0057] R 4 ~R 9 The following can be used as the substituted or unsubstituted vinyl or ethynyl group in the above formula (1). Specific examples include vinyl, 2-methylvinyl, 2,2-dimethylvinyl, 2-phenylvinyl, 2-acetylvinyl, ethynyl, methylethynyl, tert-butylethynyl, phenylethynyl, acetylethynyl, and trimethylsilylethynyl groups. The vinyl or ethynyl group preferably has four or fewer carbon atoms. When the carbon number is within this range, steric hindrance between fluorene rings is unlikely to occur, making it easier to obtain desired optical properties derived from the fluorene rings. Furthermore, the longer the conjugated system of the fluorene ring, the easier it is to obtain stronger reverse dispersion wavelength dependency.

[0058] R 4 ~R 9As the sulfur atom having a substituent in the above, for example, the following sulfur-containing groups can be used. arylsulfonyl groups such as a phenylsulfonyl group and a p-tolylsulfonyl group; alkylsulfonyl groups such as a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, and an isopropylsulfinyl group; arylsulfinyl groups such as a phenylsulfinyl group and a p-tolylsulfinyl group; alkylthio groups such as a methylthio group and an ethylthio group; arylthio groups such as a phenylthio group and a p-tolylthio group; alkoxysulfonyl groups such as a methoxysulfonyl group and an ethoxysulfonyl group; aryloxysulfonyl groups such as a phenoxysulfonyl group; an aminosulfonyl group; alkylsulfonyl groups such as an N-methylaminosulfonyl group, an N-ethylaminosulfonyl group, an N-tert-butylaminosulfonyl group, an N,N-dimethylaminosulfonyl group, and an N,N-diethylaminosulfonyl group; and arylaminosulfonyl groups such as an N-phenylaminosulfonyl group and an N,N-diphenylaminosulfonyl group. The sulfo group may form a salt with lithium, sodium, potassium, magnesium, ammonium, etc. As the sulfur-containing group, a methylsulfinyl group, an ethylsulfinyl group, or a phenylsulfinyl group is preferred, and a methylsulfinyl group is more preferred. In this case, the sulfur-containing group does not have a proton with high acidity and has a small molecular weight, so the fluorene ratio can be increased. Therefore, in addition to improving thermal stability, the amount of monomers having oligofluorene structural units used can be reduced.

[0059] R 4 ~R 9 As the silicon atom having a substituent in the above, for example, the following silyl groups can be used. Specific examples include trialkylsilyl groups such as trimethylsilyl and triethylsilyl; and trialkoxysilyl groups such as trimethoxysilyl and triethoxysilyl. Trialkylsilyl groups are preferred because they are superior in stability and ease of handling.

[0060] Also, R 4 ~R 9 In the formula (I), examples of the halogen atom that can be used include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, it is preferable to use a fluorine atom, a chlorine atom, or a bromine atom, and more preferably a chlorine atom or a bromine atom, from the viewpoints that they are relatively easy to introduce and have an electron-withdrawing property that tends to increase the reactivity of the 9-position of the fluorene.

[0061] R 4 ~R 9 Specific examples of the ring formed by bonding at least two adjacent groups include the substituted fluorene structures shown in the following group [I]. In the following group [I], the wavy line indicates the position from the 9-position of the fluorene structure to R 1 and R 2 Or R 2 and R 3 This indicates that the bond leading to

[0062] [ka]

[0063] In the present invention, from the viewpoint of being able to adjust the wavelength dispersion of the polycarbonate resin to a desired range and improving mechanical properties, the content of the structural unit (c) relative to the total amount (100% by mass) of all structural units and linking groups constituting the polycarbonate resin is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 7% by mass or more. Furthermore, from the viewpoint of being able to reduce the photoelastic coefficient of the polycarbonate resin and to expect improved retardation expression, and further being able to reduce the proportion of the structural unit (c) in the resin, the scope of molecular design is broadened, and improvements when modifications of the resin are required are easily made, the content of the structural unit (c) is preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. Specifically, the linking group is a carbonate group or an ester group present at the end of each structural unit. The content of the structural unit (c) is the total content of the structural unit represented by formula (8) and the structural unit represented by formula (9), and when only one of the structural units is contained, the content of the other is 0.

[0064] The method for adjusting the ratio of oligofluorene structural unit in the polycarbonate resin of the present invention can be, for example, copolymerizing the monomer having oligofluorene structural unit with other monomer, or blending the resin containing oligofluorene structural unit with other resin.The method for copolymerizing the monomer having oligofluorene structural unit with other monomer is preferred, because it can precisely control the content of oligofluorene structural unit, obtain high transparency, and obtain uniform properties on the entire surface of the film.

[0065] The polycarbonate resin in the present invention may be used singly or in combination of two or more kinds.

[0066] (carbonate diester) The polycarbonate resin of the present invention can be obtained by polycondensing a dihydroxy compound containing the specific dihydroxy compound described above and a carbonic acid diester as raw materials through an ester exchange reaction. The carbonic acid diester used is typically one represented by the following formula (10). These carbonic acid diesters may be used alone or in combination of two or more.

[0067] [ka]

[0068] (In formula (10), R 10 and R 11 are each an aliphatic hydrocarbon group having 1 to 18 carbon atoms which may have a substituent, or an aromatic hydrocarbon group which may have a substituent, and R 10 and R 11 may be the same or different.)

[0069] R 10 and R 11 is preferably a substituted or unsubstituted aromatic hydrocarbon group, more preferably an unsubstituted aromatic hydrocarbon group. Examples of the substituent on the aliphatic hydrocarbon group include an ester group, an ether group, an amide group, and a halogen atom, and examples of the substituent on the aromatic hydrocarbon group include alkyl groups such as a methyl group and an ethyl group.

[0070] Examples of the carbonic acid diester represented by the formula (10) include diphenyl carbonate (hereinafter sometimes abbreviated as DPC), substituted diphenyl carbonates such as ditolyl carbonate, and dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-tert-butyl carbonate, with diphenyl carbonate and substituted diphenyl carbonate being preferred, and diphenyl carbonate being particularly preferred.

[0071] The carbonate diester may contain impurities such as chloride ions, and these impurities may inhibit the polymerization reaction or deteriorate the hue of the resulting resin. Therefore, it is preferable to use a diester that has been purified by distillation or the like, as necessary.

[0072] The polycarbonate resin of the present invention can be synthesized by a process of polycondensation by transesterification using as raw materials a dihydroxy compound forming at least the structural unit represented by structural unit (a) and a carbonate diester. More specifically, the polycarbonate resin can be obtained by removing from the system, during polycondensation, the monohydroxy compound and other by-products produced in the transesterification reaction.

[0073] <Manufacturing method of polycarbonate resin> Hereinafter, a method for producing a polycarbonate resin, which is the target of depolymerization by the depolymerization method of the present invention, and a method for producing a polycarbonate resin after treating the reaction vessel with the depolymerization method of the present invention will be described.

[0074] The transesterification reaction proceeds in the presence of a transesterification catalyst (hereinafter, the transesterification catalyst will be referred to as a "polymerization catalyst"). The type of polymerization catalyst can have a significant effect on the reaction rate of the transesterification reaction and the quality of the resulting polycarbonate resin.

[0075] The polymerization catalyst is not particularly limited as long as it can provide a polycarbonate resin that satisfies the desired transparency, color tone, heat resistance, weather resistance, and mechanical properties. Examples of polymerization catalysts that can be used include metal compounds of Group I or Group II (hereinafter simply referred to as "Group 1" and "Group 2") in the long-form periodic table, as well as basic compounds such as basic boron compounds, basic phosphorus compounds, basic ammonium compounds, and amine compounds. Among these, Group 1 metal compounds and / or Group 2 metal compounds are preferred.

[0076] Examples of Group 1 metal compounds include the following compounds: sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, cesium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium acetate, potassium acetate, lithium acetate, cesium acetate, sodium stearate, potassium stearate, lithium stearate, cesium stearate, sodium borohydride, potassium borohydride, lithium borohydride, cesium borohydride, sodium phenylborohydride, and boron phenylide. Examples of the Group 1 metal compound include potassium, lithium boron phenylide, cesium boron phenylide, sodium benzoate, potassium benzoate, lithium benzoate, cesium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, dilithium hydrogen phosphate, dicesium hydrogen phosphate, disodium phenylphosphate, dipotassium phenylphosphate, dilithium phenylphosphate, dicesium phenylphosphate, alcoholates and phenolates of sodium, potassium, lithium and cesium, and disodium salt, dipotassium salt, dilithium salt and dicesium salt of bisphenol A. As the Group 1 metal compound, lithium compounds are preferred from the viewpoints of polymerization activity and the color tone of the resulting polycarbonate resin.

[0077] Examples of Group 2 metal compounds include the following compounds: calcium hydroxide, barium hydroxide, magnesium hydroxide, strontium hydroxide, calcium hydrogen carbonate, barium hydrogen carbonate, magnesium hydrogen carbonate, strontium hydrogen carbonate, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium acetate, barium acetate, magnesium acetate, strontium acetate, calcium stearate, barium stearate, magnesium stearate, and strontium stearate. As the Group 2 metal compound, magnesium compounds, calcium compounds, or barium compounds are preferred, and from the viewpoints of polymerization activity and the color tone of the resulting polycarbonate resin, barium compounds, magnesium compounds, and / or calcium compounds are more preferred, and calcium compounds are most preferred.

[0078] Although it is possible to use a basic compound such as a basic boron compound, a basic phosphorus compound, a basic ammonium compound, or an amine compound in combination with the Group 1 metal compound and / or Group 2 metal compound, it is more preferable to use only a Group 1 metal compound and / or a Group 2 metal compound, and most preferably, from the viewpoint of the color tone of the resulting polycarbonate resin, to use only a Group 2 metal compound.

[0079] The amount of the polymerization catalyst used is preferably 0.5 μmol or more, more preferably 1.0 μmol or more, and particularly preferably 1.5 μmol or more per mole of all dihydroxy compounds used in the reaction, and is preferably 300 μmol or less, more preferably 200 μmol or less, and particularly preferably 100 μmol or less per mole of all dihydroxy compounds used in the reaction.

[0080] By adjusting the amount of polymerization catalyst used within the above-mentioned range, the polymerization rate can be increased, making it possible to obtain a polycarbonate resin with a desired molecular weight without necessarily increasing the polymerization temperature, thereby suppressing deterioration in the color tone of the polycarbonate resin. Furthermore, it is possible to prevent unreacted raw materials from volatilizing during the polymerization, which would cause the molar ratio of the dihydroxy compound and the carbonate diester to be disrupted, thereby more reliably obtaining a resin with a desired molecular weight and copolymerization ratio. Furthermore, it is possible to suppress the occurrence of side reactions, thereby further preventing deterioration in the color tone of the polycarbonate resin or discoloration during molding.

[0081] The polycondensation of a dihydroxy compound and a carbonate diester is carried out in multiple stages using multiple reactors in the presence of the above-mentioned catalyst. The reaction may be carried out in a batchwise manner, a continuous manner, or a combination of a batchwise manner and a continuous manner, but it is preferable to adopt a continuous manner, which allows the production of a polycarbonate resin with less thermal history and is therefore excellent in productivity.

[0082] The dihydroxy compound and carbonate diester raw materials are preferably melted separately or uniformly mixed prior to the transesterification reaction. The melting or mixing temperature is typically 80°C or higher, preferably 90°C or higher, and typically 200°C or lower, preferably 150°C or lower, and particularly preferably 120°C or lower. In this case, the dissolution rate can be increased, the solubility can be sufficiently improved, and problems such as solidification can be sufficiently avoided. Furthermore, in this case, thermal degradation of the dihydroxy compound can be sufficiently suppressed, and the quality, typified by the color tone, of the resulting polycarbonate resin can be further improved.

[0083] From the viewpoint of controlling the polymerization rate and the quality of the resulting polycarbonate resin, it is important to appropriately select the jacket temperature, internal temperature, and pressure in the reaction system according to the reaction stage. Specifically, it is preferable to obtain a prepolymer at a relatively low temperature and low vacuum in the early stage of the polycondensation reaction, and to increase the molecular weight to a predetermined value at a relatively high temperature and high vacuum in the later stage of the reaction. In this case, distillation of unreacted monomers is suppressed, and it becomes easier to adjust the molar ratio of the dihydroxy compound to the carbonate diester to the desired ratio. As a result, a decrease in the polymerization rate can be suppressed. Furthermore, it becomes possible to more reliably obtain a polymer with the desired molecular weight and terminal groups.

[0084] Adjusting the temperature of the polycondensation reaction can improve productivity and prevent the product from being subjected to increased heat history. Furthermore, it is possible to further prevent volatilization of the monomer and decomposition and discoloration of the polycarbonate resin. Specifically, the following reaction conditions can be adopted for the first-stage reaction. The maximum internal temperature of the polymerization reactor is set within the range of usually 160 to 230°C, preferably 170 to 220°C, and more preferably 180 to 210°C. The pressure of the polymerization reactor (hereinafter, "pressure" refers to absolute pressure) is set within the range of usually 1 to 110 kPa, preferably 5 to 50 kPa, and more preferably 7 to 30 kPa. The reaction time is set within the range of usually 0.1 to 10 hours, preferably 1 to 5 hours. The first-stage reaction is preferably carried out while distilling off the by-product monohydroxy compound from the reaction system.

[0085] From the second stage onwards, it is preferable to gradually reduce the pressure of the reaction system from the pressure of the first stage, and ultimately reduce the pressure (absolute pressure) of the reaction system to 1 kPa or less while continuously removing the generated monohydroxy compound from the reaction system. The maximum internal temperature of the polymerization reactor in the final stage is set within the range of usually 200 to 265°C, preferably 210 to 250°C, and particularly preferably 215 to 245°C. The reaction time in the final stage is usually 0.1 to 20 hours, preferably 0.5 to 15 hours.

[0086] It is preferable that the polycarbonate resin contains as little foreign matter as possible. In order to remove foreign matter such as discoloration and gel from the polycarbonate resin obtained by melt polycondensation, it is preferable to perform filtration using a filter. In particular, it is preferable to remove residual monomers, by-product phenol, etc. by devolatilization under reduced pressure, and to mix additives such as a heat stabilizer and a mold release agent, by melt-extruding the polycarbonate resin using a vented twin-screw extruder and then filtering it using a filter.

[0087] The filter can be in any known form, such as a candle type, pleated type, or leaf disc type. The filter mesh size, in terms of 99% filtration accuracy, is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 20 μm or less. When it is particularly important to reduce foreign matter, the filter mesh size is preferably 10 μm or less. However, smaller mesh sizes increase pressure loss in the filter, potentially leading to filter damage or deterioration of the polycarbonate resin due to shear heating. Therefore, in terms of 99% filtration accuracy, the filter mesh size is preferably 1 μm or more. The filter mesh size referred to here is determined in accordance with ISO 16889.

[0088] The polycarbonate resin filtered through the filter is discharged from a die head in the form of strands, cooled and solidified, and pelletized using a rotary cutter or the like. However, when stranding or pelletizing the polycarbonate resin, which comes into direct contact with the outside air, it is desirable to carry out this process in a clean room that is preferably Class 7, more preferably Class 6, as defined in JIS B 9920-1 (2019), in order to prevent the inclusion of foreign matter from the outside air.

[0089] During pelletization, cooling methods such as air cooling or water cooling are preferably used. The air used during air cooling should be freed of foreign matter using a HEPA filter or similar to prevent re-adhesion of the airborne foreign matter. When using water cooling, it is desirable to remove metals from the water using an ion-exchange polycarbonate resin or similar, and then use water from which foreign matter has been removed using a water filter. The mesh size of the water filter used is preferably 10 to 0.45 μm, providing a filtration accuracy of 99% removal.

[0090] In the method for producing the polycarbonate resin of the present invention, after polymerization as described above, the polycarbonate resin can usually be cooled and solidified, and then pelletized using a rotary cutter, etc. The pelletization method is not limited, and examples thereof include a method in which the polycarbonate resin is withdrawn in a molten state from the final polymerization reactor and cooled and solidified in the form of strands to be pelletized, a method in which the polycarbonate resin is fed in a molten state from the final polymerization reactor to a single-screw or twin-screw extruder, melt-extruded, and then cooled and solidified to be pelletized, and a method in which the polycarbonate resin is withdrawn in a molten state from the final polymerization reactor, cooled and solidified in the form of strands to be pelletized, and then fed again to a single-screw or twin-screw extruder, melt-extruded, and then cooled and solidified to be pelletized.

[0091] <Various additives> The polycarbonate resin of the present invention may be blended with additives such as catalyst deactivators, antioxidants, heat stabilizers, neutralizing agents, light stabilizers, mold release agents, colorants, antistatic agents, lubricants, plasticizers, compatibilizers, flame retardants, fillers, etc. The additives may also be mixed using a tumbler, super mixer, floater, V-type blender, Nauta mixer, Banbury mixer, extruder, etc.

[0092] (Catalyst deactivator) The color tone and thermal stability of the polycarbonate resin of the present invention can be improved by adding an acidic compound to neutralize and deactivate the catalyst used in the polymerization reaction. The acidic compound used as a catalyst deactivator may be a compound having a carboxylic acid group, a phosphoric acid group, or a sulfonic acid group, or an ester thereof. It is particularly preferable to use a phosphorus-based compound containing a partial structure represented by the following formula (11) or (12).

[0093] [ka]

[0094] [ka]

[0095] Examples of the phosphorus-based compound represented by the formula (11) or (12) include phosphoric acid, phosphonic acids, hypophosphorous acid, polyphosphoric acid, phosphonate esters, acidic phosphate esters, etc. Among the above, phosphonic acids and phosphonate esters are more effective in deactivating the catalyst and inhibiting coloration, and phosphonic acid (phosphorous acid), which is a phosphonic acid, is particularly preferred.

[0096] Examples of the phosphonic acids include phosphonic acid (phosphorous acid), methylphosphonic acid, ethylphosphonic acid, vinylphosphonic acid, decylphosphonic acid, phenylphosphonic acid, benzylphosphonic acid, aminomethylphosphonic acid, methylenediphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, 4-methoxyphenylphosphonic acid, nitrilotris(methylenephosphonic acid), and propylphosphonic anhydride.

[0097] Examples of the phosphonate esters include dimethyl phosphonate, diethyl phosphonate, bis(2-ethylhexyl) phosphonate, dilauryl phosphonate, dioleyl phosphonate, diphenyl phosphonate, dibenzyl phosphonate, dimethyl methylphosphonate, diphenyl methylphosphonate, diethyl ethylphosphonate, diethyl benzylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, dipropyl phenylphosphonate, diethyl (methoxymethyl)phosphonate, diethyl vinylphosphonate, hydroxymethyl diethyl phosphonate, dimethyl (2-hydroxyethyl)phosphonate, diethyl p-methylbenzylphosphonate, diethyl phosphonoacetic acid, ethyl diethylphosphonoacetate, tert-butyl diethylphosphonoacetate, diethyl (4-chlorobenzyl)phosphonate, diethyl cyanophosphonate, diethyl cyanomethylphosphonate, diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, diethyl phosphonoacetaldehyde diethyl acetal, and diethyl (methylthiomethyl)phosphonate.

[0098] Examples of the acidic phosphate ester include phosphate diesters such as dimethyl phosphate, diethyl phosphate, divinyl phosphate, dipropyl phosphate, dibutyl phosphate, bis(butoxyethyl) phosphate, bis(2-ethylhexyl) phosphate, diisotridecyl phosphate, dioleyl phosphate, distearyl phosphate, diphenyl phosphate, and dibenzyl phosphate, or mixtures of diesters and monoesters, diethyl chlorophosphate, and zinc stearyl phosphate.

[0099] These may be used alone or in any combination and ratio of two or more.

[0100] In the present invention, if the amount of the phosphorus-based compound added to the polycarbonate resin is too small, the effects of catalyst deactivation and coloration prevention will be insufficient, while if the amount is too large, the resin will actually become colored, especially in durability tests under high temperature and high humidity. The amount of the phosphorus-based compound added corresponds to the amount of catalyst used in the polymerization reaction. The amount of phosphorus atoms in the phosphorus-based compound is preferably 0.5 to 5 times the mol, more preferably 0.7 to 4 times the mol, and particularly preferably 0.8 to 3 times the mol, per 1 mol of the metal catalyst used in the polymerization reaction.

[0101] (heat stabilizer) The polycarbonate resin of the present invention may contain a heat stabilizer, if necessary, to prevent a decrease in molecular weight or deterioration in color during melt processing, etc. Examples of such heat stabilizers include commonly known hindered phenol-based heat stabilizers and / or phosphorus-based heat stabilizers.

[0102] Examples of the hindered phenol compounds include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4-methoxyphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,5-di-tert-butylhydroquinone, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, 2-tert-butyl-6-(3'-tert-butyl-5'-methyl ... 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(6-cyclohexyl-4-methylphenol), 2,2'-ethylidene-bis-(2,4-di-tert-butylphenol), pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and the like can be used. Among these, it is preferable to use pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, and 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

[0103] As the phosphorus-based compound, for example, phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid, and esters thereof shown below can be used, but phosphorus-based compounds other than these compounds can also be used. For example, triphenyl phosphite, tris(nonylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecyl phosphite, didecyl monophenyl phosphite, dioctyl monophenyl phosphite, diisopropyl monophenyl phosphite, monobutyl diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, 2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite Examples of suitable stabilizers include bis(nonylphenyl)pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tributyl phosphate, triethyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenyl monoorthoxenyl phosphate, dibutyl phosphate, dioctyl phosphate, diisopropyl phosphate, tetrakis(2,4-di-tert-butylphenyl) 4,4'-biphenylenediphosphinate, dimethyl benzenephosphonate, diethyl benzenephosphonate, and dipropyl benzenephosphonate. Among these, tris(2,4-di-tert-butylphenyl)phosphite and bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite are preferred. These heat stabilizers may be used alone or in combination of two or more.

[0104] Such a heat stabilizer may be added to the reaction liquid during melt polymerization, or may be added to the resin using an extruder and kneaded. When a film is produced by melt extrusion, the heat stabilizer or the like may be added to the extruder to produce a film, or the heat stabilizer or the like may be added to the resin in advance using an extruder and formed into pellets or the like before use.

[0105] The amount of these heat stabilizers added is preferably 0.0001 parts by mass or more, more preferably 0.0005 parts by mass or more, and even more preferably 0.001 parts by mass or more, and is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and even more preferably 0.3 parts by mass or less, based on 100 parts by mass of polycarbonate resin.

[0106] (light stabilizer) Examples of light stabilizers include 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2,2'-methylenebis(4-cumyl-6-benzotriazolephenyl), and 2,2'-p-phenylenebis(1,3-benzoxazin-4-one).

[0107] These light stabilizers may be used alone or in combination of two or more. The amount of such light stabilizer to be added is preferably 0.01 to 2 parts by mass, based on 100 parts by mass of polycarbonate resin. A bluing agent can be added to the polycarbonate resin of the present invention to counteract the yellowish color due to the polymer or ultraviolet absorber. Any bluing agent that is used for polycarbonate resins can be used without any particular problems. In general, anthraquinone dyes are easily available and are therefore preferred.

[0108] Specific examples of bluing agents include Solvent Violet 13 (CA No. (Color Index No.) 60725), Solvent Violet 31 (CA No. 68210), Solvent Violet 33 (CA No. 60725), Solvent Blue 94 (CA No. 61500), Solvent Violet 36 (CA No. 68210), Solvent Blue 97 (Bayer's "Macrolex Violet RR"), and Solvent Blue 45 (CA No. 61110).

[0109] These bluing agents may be used alone or in combination of two or more. These bluing agents are usually used in an amount of 0.1 × 10 -4 ~2×10 -4 It is blended in a ratio of parts by mass.

[0110] <Physical properties of polycarbonate resin> (molecular weight) The molecular weight of the polycarbonate resin in the present invention is preferably 5,000 or more, more preferably 10,000 or more, in terms of polystyrene equivalent number average molecular weight (hereinafter sometimes abbreviated as Mn). Also, it is preferably 40,000 or less, more preferably 30,000 or less. When the molecular weight is within the above range, the polycarbonate resin can be easily produced with good yield.

[0111] (Plate YI) After treating the reactor using the depolymerization method of the present invention, the polycarbonate resin produced using the reactor is characterized by low coloration and high transparency. The plate YI of a 3 mm-thick molded product of the polycarbonate resin produced in this manner is preferably 3.0 or less, more preferably 1.5 or less. A plate YI within the above range is advantageous in fields requiring high transparency and good color tone. Furthermore, in the field of adhesive technology in which resins are directly colored, color can be adjusted without being affected by the color of the resin itself. Plate YI is measured by the method described below.

[0112] <Depolymerization method> The depolymerization method of the present invention uses a compound (A) containing an alicyclic dihydroxy compound. The depolymerization of the polycarbonate resin in the present invention proceeds with the alicyclic dihydroxy compound, resulting in the production of polycarbonate oligomers with lower molecular weights. In the description of the present invention, the term "equipment" refers to reaction vessels (also called reactors), piping connecting the reaction vessels, valves, liquid transfer pumps, by-product distillation lines, and the like.

[0113] (alicyclic dihydroxy compounds) Examples of the alicyclic dihydroxy compound used in the depolymerization include dihydroxy compounds which are primary alcohols of alicyclic hydrocarbons, exemplified by 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 2,6-decalindimethanol, 1,5-decalindimethanol, 2,3-decalindimethanol, 2,3-norbornane dimethanol, 2,5-norbornane dimethanol, 1,3-adamantanedimethanol, and dihydroxy compounds derived from terpene compounds such as limonene; and dihydroxy compounds which are secondary or tertiary alcohols of alicyclic hydrocarbons, exemplified by 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,3-adamantanediol, hydrogenated bisphenol A, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. Among these, 1,4-cyclohexanedimethanol and tricyclodecane dimethanol are preferred, and 1,4-cyclohexanedimethanol is more preferred. Specific examples of suitable compounds include alicyclic dihydroxy compounds represented by the following formula (3) and / or formula (4). In this case, when separating phenol (boiling point: about 182°C), a by-product generated in the production of polycarbonate resin, in a distillation column, it is preferable that the boiling point difference between 1,4-cyclohexanedimethanol (boiling point: about 284°C) and phenol (boiling point: about 182°C), which is a by-product generated in the production of polycarbonate resin, is large. The boiling point difference is preferably 50°C or more, more preferably 75°C or more. These alicyclic dihydroxy compounds may be used alone or in combination of two or more.

[0114] [ka]

[0115] [ka]

[0116] In depolymerization methods using a dihydroxy compound alone represented by a linear alkylene group or an ether bond, the dihydroxy compound must be heated to a temperature above its boiling point for depolymerization, necessitating equipment capable of withstanding pressurized conditions. Furthermore, because the dihydroxy compound is classified as a hazardous material under the Fire Service Act, there is a high risk of ignition and fire. Furthermore, when used in large quantities, storage capacity is limited, resulting in equipment limitations. Furthermore, in depolymerization methods using a dihydroxy compound represented by a linear alkylene group or an ether bond in combination with a carbonate diester, the highly flexible linear dihydroxy compound may react with the carbonate diester, resulting in a partial cyclic structure that does not contribute to depolymerization. Furthermore, when polycarbonate is produced using isosorbide again, contamination can cause color deterioration, deterioration of physical properties, and delayed polymerization rate, potentially resulting in reduced yield and deterioration of polycarbonate quality.

[0117] In the depolymerization method using a dihydroxy compound having an aromatic structure, there are concerns about a decrease in yield and a decrease in weather resistance due to contamination, similar to the above-mentioned dihydroxy compound represented by a linear alkylene group or an ether bond, and there is a risk of inviting a serious deterioration in quality.

[0118] In contrast, the depolymerization method of the present invention uses a non-hazardous alicyclic dihydroxy compound, which poses a low risk of ignition or fire and is free of equipment limitations, allowing for the storage and use of large quantities of alicyclic dihydroxy compounds. Furthermore, because alicyclic dihydroxy compounds are rigid, they do not react with a carbonate diester to form a ring, as do highly flexible linear dihydroxy compounds, and therefore contribute fully to depolymerization. Even when polycarbonate is produced again using isosorbide, the molecular weight of the polycarbonate remaining in the reaction vessel is sufficiently reduced, so that the effects of contamination, such as deterioration in color tone, deterioration in physical properties, and delayed polymerization rate, can be minimized, allowing for the production of high-quality polycarbonate resin with good yield.

[0119] (carbonate diester) The use of a carbonate diester can enhance the depolymerization effect, so it is preferable to use a carbonate diester in combination with an alicyclic dihydroxy compound as compound (A). Preferred examples of the carbonate diester contained in compound (A) are the same as those described above for the "carbonate diester" used as a raw material for polycarbonate resin. These carbonate diesters may be used alone or in combination of two or more.

[0120] The mass ratio of the alicyclic dihydroxy compound to the carbonic acid diester is preferably 100:0 to 0:100, more preferably 90:10 to 10:90, and even more preferably 80:20 to 20:80. Within the above upper and lower limit ranges, depolymerization proceeds efficiently.

[0121] (Depolymerization temperature) The depolymerization temperature in the present invention is preferably 185°C or higher, more preferably 192°C or higher, and particularly preferably 200°C or higher. At temperatures above the lower limit of the above temperature range, the alicyclic dihydroxy compound dissolves the polycarbonate resin, and depolymerization proceeds easily. Furthermore, the depolymerization temperature is preferably 320°C or lower, more preferably 300°C or lower, and particularly preferably 280°C or lower. At temperatures below the upper limit of the above temperature range, volatilization of the alicyclic dihydroxy compound is prevented, and depolymerization proceeds efficiently.

[0122] (depolymerization time) The depolymerization time in each reactor is preferably 30 minutes or more, more preferably 60 minutes or more, and particularly preferably 90 minutes or more. If the time is equal to or longer than the above lower limit, the polycarbonate resin can be sufficiently depolymerized.

[0123] <Reaction tank treatment method> The reaction vessel treatment method of the present invention includes a step of producing a polycarbonate resin and, after the polycarbonate resin is produced, a depolymerization step of depolymerizing the polycarbonate resin contained on the inner wall surface of the reaction vessel by the above-mentioned depolymerization method. Specifically, after the polymerization reaction of the polycarbonate resin is terminated, a mixed solution of an alicyclic dihydroxy compound and a carbonate diester is brought into contact with the polycarbonate resin remaining in the equipment, and depolymerization is carried out while stirring at a predetermined internal temperature and for a predetermined time while maintaining the internal pressure of each reactor at atmospheric pressure, thereby reducing the molecular weight of the polycarbonate resin. More specifically, a mixture of an alicyclic dihydroxy compound and a carbonate diester is melted in a raw material preparation tank under an inert gas atmosphere and supplied to a first vertical stirred reaction vessel without adding a polymerization catalyst. Under the above-mentioned conditions, the mixed solution from the first vertical stirred reactor is brought into contact with the residual resin and then sent to the next second vertical stirred reactor, so that depolymerization is carried out sequentially from the first vertical stirred reactor to the fourth horizontal stirred reactor, and finally the polycarbonate oligomer is extracted from the fourth horizontal stirred reactor.

[0124] <Reactor post-treatment method> After the reaction vessel treatment method is performed and before the polycarbonate resin is produced, it is preferable to contact the reaction vessel with an aromatic hydroxy compound, which can prevent the molar ratio of the dihydroxy compound to the carbonate diester from deviating from the intended amount of raw materials charged, thereby preventing a polycarbonate having the desired molecular weight from being obtained.

[0125] From the viewpoint of eliminating concerns about contamination, it is preferable that the compound constituting compound (A) such as an alicyclic dihydroxy compound used in the depolymerization method of the present invention is the same type as the monomer constituting the polycarbonate resin to be produced later.

[0126] Specifically, after carrying out the above-mentioned reaction vessel treatment method, the polycarbonate oligomer remaining in the equipment is washed with an aromatic hydroxy compound (hereinafter, a liquid containing an aromatic hydroxy compound may be referred to as a washing liquid.) As the aromatic hydroxy compound, an aromatic monohydroxy compound is preferred. During washing, it is preferable to wash the upper part of the reaction vessel and the distillation line for by-products by heating the reaction vessel to a temperature equal to or higher than the boiling point of at least one compound contained in the washing solution and refluxing the compound while maintaining a slight reduced pressure. If washing is insufficient, oligomers, raw materials, etc. will remain in the upper part of the reaction vessel and the distillation line together with the by-products, and these will often be modified and discolored by heat history, and will be mixed into the reaction liquid during the next polycarbonate production, causing discoloration. In particular, the reaction vessels and distillation lines that are best washed by refluxing the washing solution are those in which the polycarbonate has a high degree of polymerization and therefore generates little monohydroxy compounds as by-products. As the aromatic hydroxy compound, it is preferable to use phenol, which has a relatively low boiling point and is easy to reflux, and is a by-product of transesterification during polycarbonate production. Washing may be performed once to remove any residual resin, but it may also be repeated multiple times.

[0127] <Manufacturing method of polycarbonate resin> In the method for producing a polycarbonate resin of the present invention, after the above-mentioned reaction vessel post-treatment method is carried out, the above-mentioned polycarbonate resin is produced by transesterification.

[0128] (molecular weight) The molecular weight of the polycarbonate resin after depolymerization, expressed as a polystyrene-equivalent number average molecular weight (hereinafter sometimes abbreviated as Mn), is preferably less than 1500, more preferably 1000 or less, and particularly preferably 750 or less. The depolymerization rate of the polycarbonate resin is preferably 94.0% or more, more preferably 95.0% or more, and particularly preferably 96.0% or more. If the Mn of the polycarbonate after depolymerization is 1500 or more or the depolymerization rate is less than 94.0%, the resin will stick to the walls of the reaction vessel, and oxides will be generated due to long-term thermal history. Furthermore, since the polycarbonate remains in the reaction vessel even after the reaction vessel post-treatment process, there is a risk that the color tone of the polycarbonate produced will deteriorate. [Example]

[0129] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded.

[0130] <Evaluation method> In the following, the physical properties of the polycarbonate resin and polycarbonate oligomer were evaluated by the following methods. (1) Number average molecular weight (Mn), depolymerization rate (%) Measurement was performed using gel permeation chromatography (GPC) under the following conditions. Approximately 0.1 g of sample was dissolved in 2 mL of chloroform, and the solution was filtered through a 0.2 μm disk filter. GPC measurement was also performed using standard polystyrene as a calibration curve, and the polystyrene-equivalent number average molecular weight (Mn) and depolymerization rate (%) were calculated. Pump: LC-20AD (Shimadzu Corporation) Degasser: DGU-20A5 (Shimadzu Corporation) Column oven: CTO-20AC (Shimadzu Corporation) Detector: Differential refractive index detector RID-20A (Shimadzu Corporation) Column: PLgel 10 μm Guard (Agilent), PLgel 10 μm MIXED-B (Agilent) Standard polystyrene: (molecular weight: 589 (Mw / Mn≦1.19), 2550 (Mw / Mn≦1.03), 10200 (Mw / Mn≦1.02), 37900 (Mw / Mn≦1.01), 96400 (Mw / Mn≦1.01), 427000 (Mw / Mn≦1.02), 1090000 (Mw / Mn≦1.08) (manufactured by Tosoh Corporation) Oven temperature: 40℃ Eluent: Chloroform ·Flow rate: 1mL / min ·Injection volume: 10μL

[0131] Depolymerization rate (%)=100-(Resin Mn after depolymerization / Resin Mn before depolymerization)×100 A low depolymerization rate can lead to a decrease in yield due to factors such as a deterioration in the physical properties of the polycarbonate resin produced next and a delay in the polymerization rate. Therefore, a depolymerization rate of 94.0% or higher was considered to be excellent.

[0132] (2) Polycarbonate resin molding The polycarbonate resin pellets were vacuum dried for 8 hours or more at 90°C. The dried polycarbonate resin pellets were fed into an injection molding machine (J75EII model, manufactured by The Japan Steel Works, Ltd.), and a molded product measuring 60 mm square and 3 mm thick was obtained under the conditions of a final cylinder temperature of 240°C and a molding cycle of 23 seconds.

[0133] (3) Hue measurement Using a colorimeter (ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.), the tristimulus values ​​of the color of the above-mentioned molded product were measured using the Illuminant C transmission method, and the yellow index (YI) value was calculated using the following formula as an index of yellow discoloration. Yellow index (YI) = 100 × (1.28X - 1.06Z) / Y

[0134] <Production Example 1: Production of Polycarbonate Resin A> The abbreviations of the raw material monomer compounds used in Production Example 1 and the manufacturers thereof are as follows: (raw material monomer) ISB: Isosorbide (manufactured by Rocket Fleuret) CHDM: 1,4-cyclohexanedimethanol (SK Chemicals) DPC: Diphenyl carbonate (Mitsubishi Chemical Corporation)

[0135] (heat stabilizer) Irganox 1010: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (BASF) AS2112: Tris(2,4-di-tert-butylphenyl) phosphite (Adeka Corporation) (mold release agent) E-275: Ethylene glycol distearate (NOF Corporation)

[0136] Polycarbonate resin polymerization was carried out under a nitrogen atmosphere using a continuous polymerization system equipped with a distillation process, which consisted of three vertical stirred reactors, one horizontal stirred reactor, and a twin-screw extruder with a vacuum vent, connected in this order. Specifically, ISB, CHDM, and DPC were melted in raw material preparation tanks and continuously fed to the first vertical stirred reactor in molar ratios of ISB / CHDM / DPC = 0.700 / 0.300 / 1.010 and ISB / CHDM / DPC = 58.8 / 24.9 / 16.5 (mass%). At the same time, an aqueous solution of calcium acetate monohydrate was added as a polymerization catalyst in an amount of 1.5 μmol per mole of total hydroxy compounds to the first vertical stirred reactor. The temperature, pressure, and residence time of each reactor were approximately: first vertical stirred reactor: 190°C, 25 kPa, 90 minutes; second vertical stirred reactor: 195°C, 10 kPa, 45 minutes; third vertical stirred reactor: 210°C, 3 kPa, 45 minutes; and fourth horizontal stirred reactor: 225°C, 0.5 kPa, 90 minutes. The polymerization product was extracted from the fourth horizontal stirred reactor and fed in a molten state to a twin-screw extruder (TEX30α, L / D = 42, manufactured by The Japan Steel Works, Ltd.) equipped with a vacuum vent at three locations. Water was continuously injected into the molten resin just before the second vent at a ratio of approximately 2000 ppm by mass, performing so-called water injection devolatilization. Next, just before the third vent, 0.1 parts by weight of Irganox 1010 (manufactured by BASF Japan Ltd., pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) as a heat stabilizer, 0.05 parts by weight of Adekastab 2112 (manufactured by ADEKA Corporation, tris(2,4-di-tert-butylphenyl)phosphite), and 0.3 parts by weight of Unistar E-275 (manufactured by NOF Corporation) as a mold release agent were continuously added per 100 parts by weight of the polycarbonate copolymer. Low molecular weight substances such as phenol were devolatilized under reduced pressure at each vent equipped in the twin-screw extruder, and the mixture was then pelletized using a pelletizer to obtain polycarbonate resin A.

[0137] <Production Example 2: Production of Polycarbonate Resin B> The abbreviations of the raw material monomer compounds used in Production Example 2 and the manufacturers thereof are as follows: (raw material monomer) ISB: Isosorbide (manufactured by Rocket Fleuret) SPG: Spiroglycol (Mitsubishi Gas Chemical Company, Inc.) BPFM: bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane (compound of formula (13), synthesized by the method described in JP 2015-25111 A)

[0138] [ka]

[0139] DPC: Diphenyl carbonate (Mitsubishi Chemical Corporation)

[0140] (heat stabilizer) Irganox 1010: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (BASF)

[0141] Polycarbonate resin polymerization was carried out under a nitrogen atmosphere using the same continuous polymerization equipment as in Production Example 1. Specifically, the components were continuously fed into a first vertical stirred reactor at flow rates of SPG / ISB / BPFM / DPC = 0.266 / 0.734 / 0.126 / 0.874 (molar ratio), SPG / ISB / BPFM / DPC = 30.0 / 39.5 / 21.4 / 9.1% by mass. Simultaneously, an aqueous solution of calcium acetate monohydrate, serving as a polymerization catalyst, was fed into the first vertical stirred reactor in an amount such that 12 μmol of calcium acetate monohydrate was added per mole of the total dihydroxy compounds. The internal temperature, internal pressure, and residence time of each reactor were as follows: first vertical stirred reactor: 195°C, 27 kPa, 90 minutes; second vertical stirred reactor: 205°C, 20 kPa, 90 minutes; third vertical stirred reactor: 220°C, 10 kPa, 60 minutes; and fourth horizontal stirred reactor: 235°C, 0.1 to 1.0 kPa, 120 minutes. The polymerization reaction product was extracted from the fourth horizontal stirred reactor and fed in a molten state to a twin-screw extruder. Just before the second vent, 2000 ppm by weight of water was added to the molten resin and water injection devolatilization was carried out, and just before the third vent, 0.1 parts by weight of Irganox 1010 was continuously added per 100 parts by weight of polycarbonate resin, and low molecular weight substances such as phenol were devolatilized under reduced pressure at each vent equipped in the twin-screw extruder, followed by pelletization using a pelletizer to obtain polycarbonate resin B.

[0142] <Compounds used for depolymerization> The abbreviations and manufacturers of the compounds used in the following Examples and Comparative Examples are as follows: DPC: Diphenyl carbonate (Mitsubishi Chemical Corporation) CHDM: 1,4-cyclohexanedimethanol (SK Chemicals) TCDDM: Tricyclodecane dimethanol (OQ Chemicals) TEG: Triethylene glycol (Tokyo Chemical Industry Co., Ltd.) EG: Ethylene glycol (Tokyo Chemical Industry Co., Ltd.) BPA: Bisphenol A (Mitsubishi Chemical Corporation) PhOH: Phenol (Fujifilm Wako Pure Chemical Industries, Ltd.) SPG: Spiroglycol (Mitsubishi Gas Chemical Company, Inc.)

[0143] Example 1 2 g of polycarbonate resin A obtained in Production Example 1, 5.6 g of DPC, and 2.4 g of CHDM were placed in a test tube, and the tube was placed in an oil bath heated to 240°C and depolymerized for 2 hours under a nitrogen atmosphere to obtain an oligomer sample. The obtained oligomer sample and polycarbonate resin A were evaluated according to the above-mentioned evaluation method (1), and the results are shown in Table 1.

[0144] <Example 2> Depolymerization was carried out in the same manner as in Example 1 except that 6.4 g of DPC and 1.6 g of CHDM were used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0145] Example 3 After producing polycarbonate resin A in Production Example 1, 240 kg of DPC and 60 kg of CHDM were melted in a raw material preparation tank under a nitrogen atmosphere and fed to the first vertical stirred reactor without adding a polymerization catalyst, and the polycarbonate resin remaining in each reactor and piping was depolymerized. While maintaining the internal pressure of each reactor at approximately atmospheric pressure and stirring, the internal temperatures of the first vertical stirred reactor, second vertical stirred reactor, third vertical stirred reactor, and fourth horizontal stirred reactor were set to 200°C, 200°C, 220°C, and 240°C, respectively, and the depolymerization time was 120 minutes for each. Polycarbonate oligomer was discharged from the fourth horizontal stirred reactor to the outside of the reactors.

[0146] Next, 400 kg of molten phenol was supplied to the first vertical stirred reactor under a nitrogen atmosphere to wash away any polycarbonate oligomer remaining in each reactor and piping. While stirring each reactor, the internal temperature was set to 180°C, the internal pressure to 80-95 kPa, and the washing time was set to 120 minutes. Phenol was extracted from the fourth horizontal stirred reactor to obtain a phenol sample C. Polycarbonate was then produced in the same manner as in Production Example 1 to obtain a polycarbonate resin D. The resulting phenol sample C was evaluated according to the aforementioned evaluation method (1), and the polycarbonate resin D was evaluated according to the aforementioned evaluation methods (2) and (3). The results are shown in Table 1.

[0147] Example 4 Depolymerization was carried out in the same manner as in Example 1, except that DPC was not used and only 8.0 g of CHDM was used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0148] <Example 5> Depolymerization was carried out in the same manner as in Example 1 except that 4.0 g of DPC and 4.0 g of CHDM were used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0149] Example 6 Depolymerization was carried out in the same manner as in Example 1 except that 0.8 g of DPC and 7.2 g of CHDM were used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0150] Example 7 2 g of polycarbonate resin B obtained in Production Example 2, 5.6 g of DPC, and 2.4 g of TCDDM were placed in a test tube, and the tube was placed in an oil bath heated to 240°C and depolymerized for 2 hours under a nitrogen atmosphere to obtain an oligomer sample. The obtained oligomer sample and polycarbonate resin B were evaluated according to the above-mentioned evaluation method (1), and the results are shown in Table 1.

[0151] Example 8 After producing polycarbonate resin B in Production Example 2, depolymerization of the polycarbonate resin was carried out in the same manner as in Example 3, except that 210 kg of DPC and 90 kg of CHDM were melted in a raw material preparation tank under a nitrogen atmosphere, and the polycarbonate oligomer was discharged from the fourth horizontal stirred reactor. Subsequently, the polycarbonate oligomer was washed in the same manner as in Example 3, and phenol was discharged from the fourth horizontal stirred reactor to obtain phenol sample E. Polycarbonate was then produced in the same manner as in Production Example 2, and polycarbonate resin F was obtained. The obtained phenol sample E was evaluated according to the above-mentioned evaluation method (1), and polycarbonate resin F was evaluated according to the above-mentioned evaluation methods (2) and (3). The results are shown in Table 1.

[0152] Example 9 Depolymerization was carried out in the same manner as in Example 7 except that 6.4 g of DPC and 1.6 g of CHDM were used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0153] <Comparative Example 1> Depolymerization was carried out in the same manner as in Example 1 except that 8.0 g of DPC alone was used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0154] <Comparative Example 2> Depolymerization was carried out in the same manner as in Example 1 except that 4.0 g of DPC and 4.0 g of TEG were used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0155] <Comparative Example 3> 2 g of polycarbonate resin A obtained in Production Example 1 and 8.0 g of EG were placed in a test tube, which was then placed in an oil bath heated to 180°C and depolymerized for 2 hours under a nitrogen atmosphere. However, the polycarbonate resin did not dissolve in the EG and fused to the test tube, making it impossible to obtain a sample.

[0156] <Comparative Example 4> Depolymerization was carried out in the same manner as in Comparative Example 3 except that the oil bath temperature was heated to 240°C. However, EG volatilized and the polycarbonate resin fused to the test tube, making it impossible to obtain a sample.

[0157] <Comparative Example 5> Depolymerization was carried out in the same manner as in Example 1 except that 8.0 g of BPA alone was used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0158] <Comparative Example 6> Depolymerization was carried out in the same manner as in Comparative Example 3 except that 8.0 g of PhOH alone was used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0159] <Comparative Example 7> Depolymerization was carried out in the same manner as in Comparative Example 6 except that the oil bath temperature was heated to 240°C. However, the PhOH evaporated and the polycarbonate resin fused to the test tube, making it impossible to obtain a sample.

[0160] <Comparative Example 8> Depolymerization was carried out in the same manner as in Example 1 except that 8.0 g of SPG alone was used, and an oligomer sample was obtained and evaluated in the same manner. The results are shown in Table 1.

[0161] [Table 1]

[0162] As can be seen from Table 1, by depolymerizing a polycarbonate resin using compound (A) containing an alicyclic dihydroxy compound, it is possible to sufficiently reduce the molecular weight, and the specific polycarbonate resin subsequently produced has little coloration and high transparency, making it an effective method that can be used to produce a polycarbonate resin with a high yield.

Claims

1. A method for depolymerizing a polycarbonate resin, comprising: The polycarbonate resin contains a structural unit (a) derived from a dihydroxy compound having a moiety represented by the following formula (1): A method for depolymerizing a polycarbonate resin using a compound (A) containing an alicyclic dihydroxy compound. 【Chemical 1】 (However, the moiety represented by the above formula (1) is -CH ２ -Except when it is part of O-H.)

2. 2. The method for depolymerizing a polycarbonate resin according to claim 1, wherein the structural unit (a) is a structural unit represented by the following formula (2): 【Chemistry 2】

3. 3. The method for depolymerizing a polycarbonate resin according to claim 1 or 2, wherein the alicyclic dihydroxy compound is a compound represented by the following formula (3) and / or the following formula (4): 【Chemistry 3】 【Chemistry 4】

4. 3. The method for depolymerizing a polycarbonate resin according to claim 1 or 2, wherein the compound (A) further contains a carbonate diester.

5. 3. A reaction tank treatment method, comprising: a step of producing a polycarbonate resin; and a depolymerization step, subsequent to the step of producing the polycarbonate resin, of depolymerizing the polycarbonate resin contained on an inner wall surface of the reaction tank by the depolymerization method according to claim 1 or 2.

6. 6. The reaction tank treatment method according to claim 5, wherein, in the depolymerization step, the temperature is 185°C to 320°C and the inside of the reaction tank is maintained under an inert gas atmosphere.

7. A method for post-treatment of a reactor, comprising contacting the reactor with an aromatic hydroxy compound after carrying out the method for treating a reactor according to claim 5 .

8. A method for producing a polycarbonate resin, comprising the step of producing the polycarbonate resin by transesterification after the reaction vessel post-treatment method according to claim 7.

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