Monomer composition for synthesizing recycled plastic, method for preparing same, and recycled plastic and molded article using same

Abstract

The present invention relates to a monomer composition for synthesizing a recycled plastic, a method for preparing same, and a recycled plastic and a molded article using same, wherein the monomer composition comprises an aromatic diol compound, has a proportion of aromatic diol compound derivative impurities of 0.3% or less, as determined by equation 1, and a melting point of 156.4℃, and is recovered from a polycarbonate-based resin.

Description

Monomer composition for synthesizing recycled plastic, method for producing the same, and recycled plastic and molded products using the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0098842, filed July 28, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a monomer composition for synthesizing recycled plastic, which can realize high purity and excellent color quality and has improved efficiency in the recovery process even though it is recovered through recycling by chemical decomposition of polycarbonate resin, a method for producing the same, and recycled plastic and molded products using the same.

[0004] Polycarbonate is a thermoplastic polymer with excellent properties such as excellent transparency, flexibility, and relatively low manufacturing cost.

[0005] Although polycarbonate is widely used for various purposes, concerns about the environment and health when it is disposed of have been continuously raised.

[0006] Currently, physical recycling methods are being implemented, but this method is accompanied by quality degradation, so research is being conducted on chemical recycling of polycarbonate.

[0007] Chemical decomposition of polycarbonate refers to obtaining a monomeric aromatic diol compound (e.g., bisphenol A (BPA)) through decomposition of polycarbonate, and then using this again for polymerization to obtain high-purity polycarbonate.

[0008] Meanwhile, in order to purify the aromatic diol compound obtained through the decomposition of polycarbonate and secure high purity, a process of redissolving and recrystallizing in an organic solvent such as toluene has been carried out. However, there were limitations in that the types of solvents increased and they were toxic substances, requiring management.

[0009] The present invention provides a monomer composition for synthesizing recycled plastics, which can realize high purity and excellent color quality even when recovered through recycling by chemical decomposition of polycarbonate resin, and which has improved efficiency in the recovery process.

[0010] In addition, the present invention provides a method for producing the monomer composition for synthesizing recycled plastic, and a recycled plastic and a molded product using the monomer composition for synthesizing recycled plastic.

[0011] In order to solve the above problem, the present specification provides a monomer composition for synthesizing recycled plastic, which comprises an aromatic diol compound, has an aromatic diol compound derivative impurity ratio of 0.3% or less according to the following formula 1, has a melting point of 156.4°C or higher, and is characterized by being recovered from a polycarbonate resin.

[0012] [Formula 1]

[0013] Aromatic diol compound derivative impurity ratio (%) = (Aromatic diol compound derivative peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

[0014] The present specification also provides a method for producing a monomer composition for synthesizing recycled plastic, comprising the steps of: depolymerizing a polycarbonate resin; separating a carbonate compound from the depolymerization product; dissolving the depolymerization product from which the carbonate compound has been separated in a solvent containing the separated carbonate compound; and recrystallizing an aromatic diol compound from the dissolved solution.

[0015] The present specification also provides a method for producing a monomer composition for synthesizing recycled plastic, comprising the steps of: depolymerizing a polycarbonate resin; dissolving the depolymerization product in a solvent containing a carbonate compound; and recrystallizing an aromatic diol compound from the dissolved solution.

[0016] The present specification also provides a recycled plastic comprising a monomer composition for synthesizing the recycled plastic and a reaction product of a comonomer.

[0017] The present specification also provides a molded article comprising the recycled plastic.

[0018] Hereinafter, a monomer composition for synthesizing recycled plastic according to a specific embodiment of the invention, a method for producing the same, and recycled plastic and molded products using the same will be described in more detail.

[0019]

[0020] Unless explicitly stated otherwise in this specification, terminology is used only to describe specific embodiments and is not intended to limit the invention.

[0021] As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise.

[0022] The term "pH" used herein refers to the hydrogen ion concentration (pH), a numerical value indicating the degree of acidity or alkalinity of a substance. It is calculated by taking the reciprocal logarithm of the hydrogen ion dissociation concentration, and is used as a measure of the acidity and alkalinity of a substance.

[0023] In this specification, a derivative compound means a compound that has been modified from an organic compound as a parent compound, such as by introduction of a functional group, oxidation, reduction, or substitution of atoms, without significantly changing the structure and properties of the parent compound.

[0024] The term "substituted or unsubstituted" as used herein means a group which is unsubstituted or substituted with one or more substituents selected from the group consisting of deuterium; a halogen group; a cyano group; a nitro group; a hydroxy group; a carbonyl group; an ester group; an imide group; an amide group; a primary amino group; a carboxyl group; a sulfonic acid group; a sulfonamide group; a phosphine oxide group; an alkoxy group; an aryloxy group; an alkylthioxy group; an arylthioxy group; an alkylsulfoxy group; an arylsulfoxy group; a silyl group; a boron group; an alkyl group; a cycloalkyl group; an alkenyl group; an aryl group; an aralkyl group; an aralkenyl group; an alkylaryl group; an alkoxysilylalkyl group; an arylphosphine group; or a heterocyclic group containing one or more of N, O, and S atoms, or a substituted or unsubstituted group in which two or more of the above-mentioned substituents are linked.

[0025] In the present specification, an alkyl group is a monovalent functional group derived from an alkane, which may be straight or branched, and the number of carbon atoms in the straight-chain alkyl group is not particularly limited, but is preferably 1 to 20. In addition, the number of carbon atoms in the branched-chain alkyl group is 3 to 20. Specific examples of alkyl groups include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 4-methylhexyl, 5-methylhexyl, 2,6-dimethylheptan-4-yl, etc., but are not limited thereto. The alkyl group may be substituted or unsubstituted, and examples of the substituent when substituted are as described above.

[0026] In the present specification, a cycloalkyl group is a monovalent functional group derived from cycloalkane, which may be monocyclic or polycyclic, and has, but is not particularly limited to, 3 to 20 carbon atoms. According to another embodiment, the cycloalkyl group has 3 to 10 carbon atoms. Specifically, examples thereof include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, cyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethylcyclohexyl, 3,4,5-trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl, cyclooctyl, bicyclo[2,2,1]heptyl, and the like. The cycloalkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0027] In the present specification, the aryl group is a monovalent functional group derived from arene, and is not particularly limited, but preferably has 6 to 20 carbon atoms, and may be a monocyclic aryl group or a polycyclic aryl group. The monocyclic aryl group may be a phenyl group, a biphenyl group, a terphenyl group, etc., but is not limited thereto. The polycyclic aryl group may be a naphthyl group, anthracenyl group, a phenanthryl group, a pyrenyl group, a perylenyl group, a chrysenyl group, a fluorenyl group, etc., but is not limited thereto. The aryl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0028] In the present specification, a heteroaryl group includes one or more non-carbon atoms or heteroatoms, and specifically, the heteroatoms may include one or more atoms selected from the group consisting of O, N, Se, and S. The number of carbon atoms is not particularly limited, but is preferably 4 to 20 carbon atoms, and the heteroaryl group may be monocyclic or polycyclic. Examples of heterocyclic groups include thiophene group, furanyl group, pyrrole group, imidazolyl group, thiazolyl group, oxazolyl group, oxadiazolyl group, pyridyl group, bipyridyl group, pyrimidyl group, triazinyl group, triazolyl group, acridyl group, pyridazinyl group, pyrazinyl group, quinolinyl group, quinazolinyl group, quinoxalinyl group, phthalazinyl group, pyridopyrimidyl group, pyridopyrazinyl group, pyrazinopyrazinyl group, isoquinolinyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzimidazolyl group, benzothiazolyl group, benzocarbazolyl group, benzothiophene group, dibenzothiophene group, benzofuranyl group, phenanthroline group, Examples thereof include, but are not limited to, a thiazolyl group, an isoxazolyl group, an oxadiazolyl group, a thiadiazolyl group, a benzothiazolyl group, a phenothiazinyl group, an aziridyl group, an azaindolyl group, an isoindolyl group, an indazolyl group, a purine group, a pteridyl group, a beta-carbolyl group, a naphthyridine group, a tert-pyridyl group, a phenazinyl group, an imidazopyridyl group, a pyropyridyl group, an azepine group, a pyrazolyl group, and a dibenzofuranyl group. The heteroaryl group may be substituted or unsubstituted, and examples of the substituent when substituted are as described above.

[0029] In the present specification, an alkylene group is a divalent functional group derived from an alkane, and the description of the alkyl group described above may be applied to these groups except that they are divalent functional groups. For example, they may be linear or branched, and may be a methylene group, an ethylene group, a propylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, a hexylene group, etc. The alkylene group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0030] In the present specification, an arylene group is a divalent functional group derived from arene, and the description of the above-mentioned aryl group may be applied to these except that they are divalent functional groups. For example, they may be a phenylene group, a biphenylene group, a terphenylene group, a naphthalene group, a fluorenyl group, a pyrenyl group, a phenanthrenyl group, a perylene group, a tetracenyl group, an anthracenyl group, etc. The arylene group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0031] In the present specification, a cycloalkylene group is a divalent functional group derived from cycloalkane, and the description of the cycloalkyl group described above may be applied except that it is a divalent functional group. The cycloalkylene group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0032] In the present specification, the heteroarylene group has 2 to 20 carbon atoms, or 2 to 10 carbon atoms, or 6 to 20 carbon atoms. The description of the heteroaryl group described above may be applied to the arylene group containing O, N, or S as a heteroatom, except that it is a divalent functional group. The heteroarylene group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0033] As used herein, the term “including” means specifying a particular characteristic, region, integer, step, operation, element and / or component, but does not exclude the presence or addition of other particular characteristics, regions, integers, steps, operations, elements, components and / or groups.

[0034] In addition, terms including ordinal numbers, such as "first" and "second," in this specification are used to distinguish one component from another and are not limited by the ordinal numbers. For example, within the scope of the present invention, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

[0035]

[0036] 1. Monomer composition for synthesizing recycled plastics

[0037] According to one embodiment of the invention, a monomer composition for synthesizing recycled plastic can be provided, characterized in that it comprises an aromatic diol compound, has an aromatic diol compound derivative impurity ratio of 0.3% or less according to the following formula 1, has a melting point of 156.4°C or higher, and is recovered from a polycarbonate resin.

[0038] [Formula 1]

[0039] Aromatic diol compound derivative impurity ratio (%) = (Aromatic diol compound derivative peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

[0040] The inventors of the present invention have experimentally confirmed that the monomer composition for synthesizing recycled plastic of the above embodiment can realize excellent color quality of the aromatic diol compound, which is the main target of recovery, even though it is recovered through recycling by chemical decomposition of polycarbonate resin, and can secure the aromatic diol compound with high purity, thereby completing the invention.

[0041] In particular, together with the monomer composition for synthesizing recycled plastic (first composition) of the above embodiment, a monomer composition for synthesizing recycled plastic (second composition) comprising a carbonate-based compound such as a dialkyl carbonate, wherein the carbonate-based compound is recovered from a polycarbonate-based resin, can be obtained simultaneously in the method for producing a monomer composition for synthesizing recycled plastic described below.

[0042] That is, the present invention can have a technical advantage of being able to obtain a first composition including an aromatic diol compound with high purity by recycling through chemical decomposition of a polycarbonate resin, and at the same time, obtain a second composition including a carbonate compound, which is a high value-added by-product.

[0043] Specifically, the monomer composition for synthesizing recycled plastic of the above embodiment is characterized by being recovered from a polycarbonate-based resin. That is, as a result of recovering the monomer composition for synthesizing recycled plastic of the above embodiment, a monomer composition for synthesizing recycled plastic containing an aromatic diol compound is also obtained.

[0044] The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization or copolymerization reaction of a monomer including an aromatic diol compound and a carbonate compound. When it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor, a homopolymer can be synthesized. In addition, when one type of aromatic diol compound and two or more types of carbonate precursors are used as the monomer, or two or more types of aromatic diol compounds and one type of carbonate precursor are used, or one or more types of other diols are used in addition to one type of aromatic diol compound and one type of carbonate precursor, and two or more types of carbonates are contained, a copolymer can be synthesized. The above homopolymer or copolymer may include all low-molecular-weight compounds, oligomers, and polymers according to the molecular weight range.

[0045] Additionally, the monomer composition for synthesizing recycled plastic of the above embodiment may include an aromatic diol compound. Specific examples of the above aromatic diol compounds include bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, Examples thereof include 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, or a mixture of two or more thereof. Preferably, the aromatic diol compound of the monomer composition for synthesizing recycled plastic of the above embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0046] The above aromatic diol compound is characterized in that it is recovered from the polycarbonate resin used in the recovery of the monomer composition for the synthesis of recycled plastic. That is, it means that the aromatic diol compound is also obtained as a result of recovery from the polycarbonate resin to obtain the monomer composition for the synthesis of recycled plastic of the above embodiment. Therefore, in order to prepare the monomer composition for the synthesis of recycled plastic of the above embodiment, a case in which a new aromatic diol compound is added externally separately from the recovery from the polycarbonate resin is not included in the category of the aromatic diol compound of the present invention.

[0047] Specifically, "recovered from the polycarbonate resin" means obtained through a depolymerization reaction of the polycarbonate resin. The depolymerization reaction can be performed under acidic, neutral, or alkaline conditions, and in particular, the depolymerization reaction can be performed under alkaline (alkaline) conditions. In particular, the depolymerization reaction is preferably performed under alcohol, as described below.

[0048] Meanwhile, the monomer composition for synthesizing recycled plastic of the above embodiment may have an APHA Color value measured by ASTM D 1209 of 60 or less, or 50 or less, or 40 or less, or 30 or less, or 20 or less, or 10 or less, or 0 or more, or 1 or more, or 0 to 60, or 0 to 50, or 0 to 40, or 0 to 30, or 0 to 20, or 0 to 10, or 1 to 60, or 1 to 50, or 1 to 40, or 1 to 30, or 1 to 20, or 1 to 10.

[0049] The method for measuring the APHA Color of the monomer composition for synthetic recycled plastic of the above embodiment is not particularly limited, and for example, the method may be measured using a HunterLab UltraScan PRO Spectrophotometer according to the ASTM D 1209 measurement method.

[0050] APHA Color is a value obtained from a color comparison between colorless water and a yellow PtCo solution. The closer the value is to 0, the more colorless it is, and the closer it is to 500, the more yellow it is. Therefore, as the APHA Color of the monomer composition for synthesizing recycled plastic of the above embodiment is reduced to 60 or less, it is possible to implement transparent color properties when synthesizing polycarbonate resin using the same.

[0051] On the other hand, if the APHA Color of the monomer composition for synthetic recycled plastic of the above-mentioned embodiment increases excessively, such as exceeding 60, there is a limitation that it becomes difficult to synthesize a colorless and transparent polycarbonate resin due to yellowing.

[0052] Meanwhile, the monomer composition for synthesizing recycled plastic of the above embodiment may have an aromatic diol compound purity of 99.6% or more, or 99.7% or more, or 99.8% or more, or 99.9% or more, or 100% or less, or 99.6% to 100%, or 99.7% to 100%, or 99.8% to 100%, or 99.9% to 100%.

[0053] Examples of a method for measuring the purity of an aromatic diol compound in a monomer composition for synthesizing recycled plastic according to the above embodiment are not particularly limited, for example, 1 H NMR, ICP-MS analysis, HPLC analysis, UPLC analysis, etc. can be used without limitation. The specific methods, conditions, equipment, etc. of the above NMR, ICP-MS, HPLC, UPLC, etc. can be applied without limitation to various existing known contents.

[0054] In this way, the purity of the aromatic diol compound, which is the main target material for recovery, in the monomer composition for synthesizing recycled plastic of the above-described embodiment is greatly increased to 99.6% or more, thereby minimizing other impurities, thereby enabling the implementation of excellent physical properties when synthesizing polycarbonate resin using the same.

[0055] Meanwhile, the monomer composition for synthesizing recycled plastic of the above embodiment may have a melting point of 156.4° C. or higher, or 156.5° C. or higher, or 156.6° C. or higher, or 156.7° C. or higher, or 156.8° C. or higher, or 156.9° C. or higher, or 160° C. or lower, or 156.4° C. to 160° C., or 156.5° C. to 160° C., or 156.6° C. to 160° C., or 156.7° C. to 160° C., or 156.8° C. to 160° C., or 156.9° C. to 160° C. The fact that the melting point of the monomer composition for synthesizing recycled plastic increases to 156.4° C. or higher is believed to be due to the method for producing the monomer composition for synthesizing recycled plastic, which will be described later.

[0056] Examples of a method for measuring the melting point of the monomer composition for synthesizing recycled plastic according to the above embodiment are not particularly limited, and for example, the melting point can be measured using differential scanning calorimetry.

[0057] In this way, the melting point of the monomer composition for synthesizing recycled plastic of the above-described embodiment is increased to 156°C or higher, thereby minimizing other impurities, thereby enabling the implementation of excellent physical properties when synthesizing polycarbonate resin using the same.

[0058] Meanwhile, the monomer composition for synthesizing recycled plastic may further contain impurities other than aromatic diol compounds. The impurities refer to aromatic diol compound derivative compounds other than the aromatic diol compound, which is the main target material for recovery of the present invention.

[0059] The derivative of the above aromatic diol compound may include at least one compound selected from the group consisting of a monoalkyl carbonate of bisphenol A, a bisalkyl carbonate of bisphenol A, and a bisphenol A dimer. The monoalkyl carbonate of bisphenol A is a product obtained by reacting a hydroxyl group at one end of bisphenol A with a dialkyl carbonate, and specific examples thereof include, but are not particularly limited to, monoethyl carbonate of bisphenol A or monomethyl carbonate of bisphenol A. The bisethyl carbonate of bisphenol A is a product obtained by reacting both hydroxyl groups at both ends of bisphenol A with a dialkyl carbonate, and specific examples thereof include, but are not particularly limited to, bisethyl carbonate of bisphenol A or bismethyl carbonate of bisphenol A. The bisphenol A dimer is a linear or cyclic product obtained by reacting bisphenol A and bisphenol A.

[0060] That is, the derivative of the above aromatic diol compound may include one monoalkyl carbonate of bisphenol A, one bisalkyl carbonate of bisphenol A, one bisphenol A dimer, or a mixture of two thereof.

[0061] By applying the method for producing a monomer composition for synthesizing recycled plastic described below, the production of derivative impurities of aromatic diol compounds can be significantly reduced.

[0062] Specifically, the monomer composition for synthesizing recycled plastic may have an upper limit numerical range of an aromatic diol compound derivative impurity ratio according to Equation 1 of 0.3% or less, or 0.25% or less, or 0.2% or less, or 0.12% or less, or 0.1% or less, and a lower limit numerical range of 0.01% or more. The upper limit numerical range and the lower limit numerical range may be combined to satisfy a numerical range of the lower limit to the upper limit. As an example of the numerical range of the lower limit to the upper limit, the aromatic diol compound derivative impurity ratio according to Equation 1 may be 0.01% to 0.3%.

[0063] [Formula 1]

[0064] Aromatic diol compound derivative impurity ratio (%) = (Aromatic diol compound derivative peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

[0065] According to the above formula 1, the unit of the ratio of the aromatic diol compound derivative impurities is %, which is the peak area ratio measured in liquid chromatography and means area %.

[0066] In the above formula 1, the peak area of ​​the aromatic diol compound derivative measured by liquid chromatography may be the sum of the peak areas of each of one or more aromatic diol compound derivatives. For example, when the aromatic diol compound derivative is a mixture of three types of a monoalkyl carbonate of bisphenol A, a bisalkyl carbonate of bisphenol A, and a bisphenol A dimer, it means the sum of the peak areas of the monoalkyl carbonate of bisphenol A, the bisalkyl carbonate of bisphenol A, and the bisphenol A dimer, respectively.

[0067] Examples of methods for measuring the weight ratio of aromatic diol compound derivative impurities in the monomer composition for synthesizing recycled plastic according to the above embodiment are not particularly limited, and for example, high performance liquid chromatography (HPLC) analysis can be used. Specific methods, conditions, equipment, etc. of the HPLC can be applied without limitation to various contents known in the art.

[0068] However, as an example, after dissolving the recycled bisphenol A monomer composition in a methanol solvent at a concentration of 0.5 mg / mL under atmospheric pressure and 20 to 30°C conditions, solid impurities in the solution are removed using a syringe filter (0.45 μm), and then Capcell Pak C18 (4.6 mm ID x 50 mm L, 5 μm) can be measured through UPLC (ultra performance liquid chromatography) in a Waters HPLC system (e2695 separation module, 2998 PDA detector). More specifically, measurement can be performed under the following conditions: ① Column: Capcell Pak C18 (4.6 mm ID x 50 mm L, 5 μm), ② Column Temp: 40 ℃, ③ Injection volume: 10 μl, ④ Flow: Mobile phase A-Acetonitrile / TFA=100 / 0.1%, B-Water / TFA=100 / 0.1%, Gradient elution - 0 min A:B=2:8, 10 min A:B=100:0, volume=1 ml / min (total=10 min), ⑤ Detector: 275 nm.

[0069] In this way, in the monomer composition for synthesizing recycled plastic of the above embodiment, the proportion of impurities of derivatives of aromatic diol compounds other than the aromatic diol compound, which is the main target material for recovery, is greatly reduced, so that excellent physical properties can be achieved when synthesizing polycarbonate resin using this.

[0070] More specifically, the ratio of the monoalkyl carbonate of the bisphenol A and the bisalkyl carbonate of the bisphenol A according to the following formula 2 may be 0.1% or less, or 0.05% or less, or 0% or more, or 0% to 0.1%, or 0% to 0.05%.

[0071] [Formula 2]

[0072] Monoalkyl carbonate of bisphenol A, and bisalkyl carbonate ratio of bisphenol A (%) = (Monoalkyl carbonate of bisphenol A, and bisalkyl carbonate peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

[0073] In addition, the bisphenol A dimer ratio according to the following formula 3 may be 0.3% or less, or 0.2% or less, or 0.13% or less, or 0.12% or less, or 0.1% or less, or 0.09% or less, or 0.01% or more, or 0.01% to 0.3%, or 0.01% to 0.2%, or 0.01% to 0.13%, or 0.01% to 0.12%, or 0.01% to 0.1%, or 0.01% to 0.09%.

[0074] [Formula 2]

[0075] Bisphenol A dimer ratio (%) = (Bisphenol A dimer peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

[0076] Meanwhile, the monomer composition for synthesizing recycled plastic according to the above embodiment may be obtained from a carbonate compound as a byproduct. The carbonate compound includes all compounds containing a carbonate functional group (-OCOO-) and may include a carbonate compound having a linear or cyclic structure. In addition, the type of organic functional group bonded to the carbonate functional group in the carbonate compound is not particularly limited, but may include, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or a combination of two or more thereof.

[0077] More specifically, the carbonate compound may include a dialkyl carbonate or a diaryl carbonate. The dialkyl carbonate has a structure in which two alkyl groups are bonded to both ends of a carbonate functional group, and the two alkyl groups may be the same or different. Specific examples of the dialkyl carbonate are not particularly limited, but include dialkyl carbonates having 3 to 15 carbon atoms, or 3 to 13 carbon atoms, such as dimethyl carbonate or diethyl carbonate.

[0078] In addition, the above-mentioned diaryl carbonate has a structure in which two aryl groups are bonded to both terminals of a carbonate functional group, and the two aryl groups may be the same or different. Specific examples of the above-mentioned diaryl carbonate are not particularly limited, but include diaryl carbonates having 13 to 20 carbon atoms, or 13 to 15 carbon atoms, such as diphenyl carbonate.

[0079] Since the main target material for recovery in the monomer composition for synthesizing recycled plastic of the above embodiment is an aromatic diol compound, the carbonate compound can be separated and recovered as a by-product from the monomer composition for synthesizing recycled plastic of the above embodiment.

[0080] The monomer composition for synthesizing recycled plastics of the above embodiment can be used as a raw material for manufacturing various recycled plastics (e.g., polycarbonate (PC)) described below.

[0081] The monomer composition for synthesizing recycled plastic of the above embodiment may further include a small amount of other additives and solvents, and the types of specific additives or solvents are not particularly limited, and various materials widely used in the process of recovering aromatic diol compounds by depolymerization of polycarbonate resins can be applied without limitation.

[0082] The monomer composition for synthesizing recycled plastics of the above embodiment may be obtained by the method for producing a monomer composition for synthesizing recycled plastics described below. That is, the monomer composition for synthesizing recycled plastics of the above embodiment corresponds to a result obtained through various filtration, purification, washing, and drying processes to secure only the aromatic diol compound, which is the main target material for recovery, with high purity after the depolymerization reaction of the polycarbonate resin.

[0083]

[0084] 2. Method for producing a monomer composition for synthesizing recycled plastic

[0085] (1) First manufacturing method

[0086] According to another embodiment of the invention, a method for producing a monomer composition for synthesizing recycled plastic may be provided, comprising the steps of: depolymerizing a polycarbonate resin; separating a carbonate compound from the depolymerization product; dissolving the depolymerization product from which the carbonate compound has been separated in a solvent containing the separated carbonate compound; and recrystallizing an aromatic diol compound from the dissolved solution.

[0087] Specifically, the method for producing a monomer composition for synthesizing recycled plastic of the above other embodiments may include a step of depolymerizing a polycarbonate resin.

[0088] The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization or copolymerization reaction of a monomer including an aromatic diol compound and a carbonate compound. When it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor, a homopolymer can be synthesized. In addition, when one type of aromatic diol compound and two or more types of carbonate precursors are used as the monomer, or two or more types of aromatic diol compounds and one type of carbonate precursor are used, or one or more types of other diols are used in addition to one type of aromatic diol compound and one type of carbonate precursor, and two or more types of carbonates are contained, a copolymer can be synthesized. The above homopolymer or copolymer may include all low-molecular-weight compounds, oligomers, and polymers according to the molecular weight range.

[0089] The above polycarbonate resin can be applied to various forms and types, including new polycarbonate resin produced through synthesis, recycled polycarbonate resin produced through a recycling process, or polycarbonate resin waste.

[0090] However, if necessary, before carrying out the depolymerization reaction of the polycarbonate resin, a pretreatment process of the polycarbonate resin may be performed to increase the efficiency of the process of recovering aromatic diol compounds and carbonate compounds from the polycarbonate resin. Examples of the pretreatment process include washing, drying, grinding, glycol decomposition, etc., and the specific method of each pretreatment process is not limited, and various methods widely used in the process of recovering aromatic diol compounds and carbonate precursors by depolymerization of polycarbonate resins can be applied without limitation.

[0091] When the polycarbonate resin is depolymerized, the depolymerization reaction can be carried out under acidic, neutral, or alkaline conditions, and in particular, the depolymerization reaction can proceed under alkaline (alkaline) conditions. The type of the base is not particularly limited, and examples thereof include sodium hydroxide (NaOH) or potassium hydroxide (KOH). The base is a base catalyst that acts as a catalyst, and has the advantage of being economical compared to organic catalysts that are mainly used under mild conditions. More specifically, when the polycarbonate resin is depolymerized, the depolymerization reaction can proceed within a pH range of more than 8 and less than 12.

[0092] In the depolymerization reaction of the polycarbonate resin, the base may be reacted in an amount of 0.5 mol or less, or 0.4 mol or less, or 0.3 mol or less, or 0.1 mol or more, or 0.2 mol or more, or 0.1 to 0.5 mol, or 0.1 to 0.4 mol, or 0.1 to 0.3 mol, or 0.2 to 0.5 mol, or 0.2 to 0.4 mol, or 0.2 to 0.3 mol, per 1 mol of the polycarbonate resin. In the depolymerization reaction of the polycarbonate resin, if the base is reacted in an amount exceeding 0.5 mol per 1 mol of the polycarbonate resin, the amount of impurities increases due to the increased generation of alkali salts, which reduces the purity of the target recovered material and has a limitation in that the economic feasibility of the catalytic reaction decreases.

[0093] In addition, the depolymerization reaction of the polycarbonate resin can be carried out in the presence of alcohol. The present invention has the advantage of being able to stably obtain bisphenol A, a high-purity monomer, by decomposing the polycarbonate resin with alcohol, and additionally obtain a carbonate compound, such as a dialkyl carbonate, which has high added value as a reaction byproduct.

[0094] The number of hydroxyl groups in the above alcohol is not particularly limited, but may include, for example, monohydric alcohols. The monohydric alcohols are compounds having one hydroxyl group in the molecule.

[0095] In addition, the type of monovalent organic functional group bonded to the hydroxyl group in the monovalent alcohol is not particularly limited, but may include an organic functional group having 1 to 10 carbon atoms, or 1 to 6 carbon atoms, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or a combination of two or more thereof.

[0096] The alcohol may be a single compound or a mixture of two or more compounds. Specific examples of the alcohol are not particularly limited, but include, for example, ethanol, methanol, phenol, or mixtures thereof.

[0097] The content of the alcohol may be 5 to 15 moles, or 8 to 13 moles, per 1 mole of the polycarbonate resin. Since the alcohol has good solubility in bisphenol A, the alcohol within the above range must be included. If the content of the alcohol is excessively reduced to less than 5 moles per 1 mole of the polycarbonate resin, it is difficult for the alcohol decomposition of the polycarbonate resin to proceed sufficiently. On the other hand, if the content of the alcohol is excessively increased to more than 15 moles per 1 mole of the polycarbonate resin, the economic feasibility of the process may decrease due to excessive use of alcohol.

[0098] The solvent in which the depolymerization reaction of the above polycarbonate resin is carried out may include at least one organic solvent selected from the group consisting of tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate.

[0099] The organic solvent may include tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0100] More preferably, methylene chloride can be used as the organic solvent. When methylene chloride is used as the organic solvent, the solubility characteristics for polycarbonate are improved, which has the advantage of enhancing reactivity.

[0101] The content of the organic solvent may be 16 to 20 moles, or 16 to 18 moles, relative to 1 mole of the polycarbonate resin. In addition, the content of the organic solvent may be 1.5 to 2 moles relative to 1 mole of ethanol. Within the above range, there is an advantage in that the polycarbonate resin, alcohol, and organic solvent are mixed, thereby allowing a depolymerization reaction of the polymer to proceed at a required level.

[0102] Meanwhile, the temperature at which the depolymerization reaction of the polycarbonate resin is performed is not particularly limited, but may be performed at, for example, 20°C to 100°C, or 50°C to 70°C. In addition, the time at which the depolymerization reaction of the polycarbonate resin is performed may be 1 hour to 30 hours, or 4 hours to 6 hours.

[0103] Specifically, the above conditions are mild process conditions compared to the existing pressurized / high-temperature process, and by performing stirring under the above conditions, the process can be performed in a mild process compared to the pressurized / high-temperature process, and in particular, there is an advantage in that the most efficient results can be obtained in terms of reproducibility and recognizability when stirring for 4 to 6 hours at 50 to 70 °C.

[0104] That is, the present invention has the advantage of being able to obtain a high-purity aromatic diol compound (e.g., bisphenol A) under mild conditions without using a pressurized / high-temperature process by controlling the type and amount of mixed solvent and the type and content of a base catalyst even without using an organic catalyst, and of being able to obtain a carbonate-based compound such as a dialkyl carbonate as a byproduct by using alcohol as a reactant.

[0105] Meanwhile, during the depolymerization reaction of the polycarbonate resin, an antioxidant may be added to the reaction solution. By adding the antioxidant, the aromatic diol compound recovered through recycling by chemical decomposition of the polycarbonate resin can satisfy a color level equivalent to that of a commercially available reagent or reagent used for PC polymerization.

[0106] Specific examples of the above antioxidants are not particularly limited, and various antioxidants that have been widely used in the prior art can be applied without limitation. However, examples thereof include sodium hyposulfite, sodium sulfite, erythorbic acid, dibutylhydroxytoluene, butylhydroxyanisole, α-tocopherol, tocopherol acetate, L-ascorbic acid and its salts, L-ascorbic acid palmitate, L-ascorbic acid stearate, triamyl gallate, propyl gallate, or disodium ethylenediaminetetraacetate (EDTA), sodium pyrophosphate, sodium metaphosphate, or mixtures of two or more thereof.

[0107] The specific amount of the antioxidant to be added is not particularly limited, but for example, it may be added in a range of 0.1 wt% to 5 wt%, or 0.1 wt% to 1 wt%, based on the total weight of the reaction solution, at a level that does not affect the properties of the monomer composition for synthesizing recycled plastic.

[0108] Additionally, when the polycarbonate resin is depolymerized, the depolymerization reaction can be performed under a nitrogen atmosphere.

[0109] More specifically, the step of depolymerizing the polycarbonate resin may include a first step of dissolving the carbonate resin in an organic solvent; and a second step of adding and stirring a catalyst solution containing alcohol, a base, and an antioxidant. In the first and second steps, the contents of the alcohol, the organic solvent, the base, the antioxidant, and the polycarbonate resin are the same as those described above.

[0110] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the other embodiment may further include, after the step of depolymerizing the polycarbonate resin, a step of adding an acid so that the pH of the depolymerization product becomes 2 to 8. The acid may be a strong acid, and examples thereof include hydrochloric acid (HCl).

[0111] In the step of adding acid so that the pH of the depolymerization product becomes 2 to 8, the salt of the aromatic diol compound contained in the depolymerization product can be converted into an aromatic diol compound. Since the depolymerization reaction proceeds under basic conditions, the produced aromatic diol compound exists in the form of a salt through a reaction with the base, thereby having hydrophilicity. Therefore, by adding acid, the salt of the aromatic diol compound contained in the depolymerization product can be converted into an aromatic diol compound, thereby inducing hydrophobicity.

[0112] Accordingly, in the step of removing impurities by adding water after the acid addition described below, layers can be formed that are divided into a water layer containing impurities and an organic solvent layer containing aromatic diol compounds and carbonate compounds. Since the aromatic diol compounds and carbonate compounds have hydrophobicity, they can be included in the organic solvent layer among water and organic solvent, and various water-soluble impurities can be included in the water layer. Accordingly, the main product, the aromatic diol compound, and the impurities can be easily separated with just a simple process of changing the pH.

[0113] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the other embodiment may further include a step of adding water in the step of adding acid so that the pH of the depolymerization reaction product becomes 2 to 8. Through this, in the impurity removal step described below, a layer can be formed that is divided into a water layer containing impurities and an organic solvent layer containing an aromatic diol compound and a carbonate compound.

[0114] There is no significant limitation on the order of the process of adding acid and the process of adding water, and it is possible to add water after adding acid, or to add water after adding acid, or to add water and acid simultaneously.

[0115] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the other embodiment may include a step of removing impurities after adding the acid. Accordingly, the impurities may be hydrophilic substances, such as salt compounds, ionic compounds, acid compounds, etc.

[0116] As described above, after the step of adding acid so that the pH of the depolymerization product becomes 2 to 8, by performing the step of removing impurities from the depolymerization product after the addition of the acid, the depolymerization product forms layers divided into a water layer containing impurities and an organic solvent layer containing an aromatic diol compound and a carbonate compound, and the water layer containing impurities can be separated and removed therefrom.

[0117] After the acid addition, in the step of removing impurities from the depolymerization product, the aqueous layer can be separated from the organic layer, thereby removing impurities contained in the aqueous layer. The specific separation conditions for separating the aqueous layer from the organic layer are not particularly limited, and various existing purification technologies can be applied without limitation to the specific separation equipment and method. However, as an example, a drain device can be used.

[0118] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic of the other embodiment may include a step of separating a carbonate compound from the depolymerization reaction product.

[0119] The above carbonate compound includes all compounds containing a carbonate functional group (-OCOO-), and may include a carbonate compound having a linear or cyclic structure. In addition, the type of organic functional group bonded to the carbonate functional group in the carbonate compound is not particularly limited, but may include, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or a combination of two or more thereof.

[0120] More specifically, the carbonate compound may include a dialkyl carbonate or a diaryl carbonate. The dialkyl carbonate has a structure in which two alkyl groups are bonded to both ends of a carbonate functional group, and the two alkyl groups may be the same or different. Specific examples of the dialkyl carbonate are not particularly limited, but include dialkyl carbonates having 3 to 15 carbon atoms, or 3 to 13 carbon atoms, such as dimethyl carbonate or diethyl carbonate.

[0121] In addition, the above-mentioned diaryl carbonate has a structure in which two aryl groups are bonded to both terminals of a carbonate functional group, and the two aryl groups may be the same or different. Specific examples of the above-mentioned diaryl carbonate are not particularly limited, but include diaryl carbonates having 13 to 20 carbon atoms, or 13 to 15 carbon atoms, such as diphenyl carbonate.

[0122] The step of separating the carbonate compound from the above-mentioned depolymerization product may include an evaporation step of the depolymerization product. Examples of the above-mentioned evaporation conditions are not particularly limited, but as a specific example, the polycarbonate resin may be evaporated as a depolymerization product using an evaporator (e.g., a thin film evaporator).

[0123] In addition, the step of separating the carbonate compound from the depolymerization product may include a distillation step of the depolymerization product. Although the examples of the distillation conditions are not particularly limited, as a specific example, the polycarbonate resin may be pressurized under the conditions of a pressure of 200 to 300 mbar and a temperature of 20 to 30°C, and then decompressed under the conditions of a pressure of 10 to 50 mbar and a temperature of 20 to 30°C to perform low-temperature distillation.

[0124] The order in which the above evaporation step and distillation step are performed is not particularly limited, and the evaporation step and distillation step may be performed simultaneously or sequentially. That is, the evaporation step and distillation step may be performed simultaneously, the distillation step may be performed after the evaporation step, or the evaporation step may be performed after the distillation step.

[0125] The separated carbonate compounds can be recycled without a separate separation and purification process, or, if necessary, through conventional separation and purification processes such as extraction, adsorption, and drying. Specific purification conditions are not significantly limited, and various existing purification technologies can be applied without limitation to specific purification equipment and methods.

[0126] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to another embodiment may include a step of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound. Through the step of adding the solvent containing the separated carbonate-based compound to the depolymerization product from which the carbonate-based compound is separated, the aromatic diol compound crystals included in the depolymerization product from which the carbonate-based compound is separated can be redissolved in the solvent.

[0127] Through this, the solubility of the aromatic diol compound or its salt contained in the depolymerization reaction product increases, so that the crystals or impurities caught between the crystals can be dissolved with the solvent as much as possible, and since the dissolved aromatic diol compound has poor solubility compared to the impurities, when the temperature is lowered thereafter, the aromatic diol compound can be easily precipitated as crystals through the difference in solubility.

[0128] In the past, there was a limitation in that the efficiency of the process was reduced due to the use of a separate ethanol solution, but in the present invention, the efficiency of the process can be greatly improved by recycling the carbonate compound separated in the previous step and applying it as a redissolution solvent.

[0129] The solvent may contain a separated carbonate compound. The separated carbonate compound is a product obtained in the step of separating the carbonate compound from the depolymerization reaction product, and the solvent may be composed solely of the separated carbonate compound, or may be composed primarily of the separated carbonate compound with some impurities mixed in.

[0130] The step of dissolving the depolymerization reaction product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound may be performed at a temperature of 0°C to 200°C, or 50°C to 150°C, or 50°C to 120°C, or 50°C to 100°C.

[0131] The amount of the solvent containing the carbonate compound may be 10 parts by weight or more, or 40 parts by weight or more, or 90 parts by weight or more, or 100 parts by weight or more, or 200 parts by weight or less, or 10 to 200 parts by weight, or 40 to 200 parts by weight, or 90 to 200 parts by weight, or 100 to 200 parts by weight, based on 100 parts by weight of the aromatic diol compound contained in the depolymerization product from which the carbonate compound is separated. If too little of the solvent containing the carbonate compound is used, the temperature for dissolving the aromatic diol compound contained in the depolymerization product from which the carbonate compound is separated becomes too high, thereby lowering process efficiency, and as the temperature difference between the dissolution temperature and the cooling temperature increases, it is not easy to remove impurities through recrystallization. In addition, after recrystallization, the solid concentration is so high that transport or solid-liquid separation becomes very difficult, and thus, impurity removal may not be easy.

[0132] On the other hand, if a solvent containing a carbonate compound is used in an excessive amount, the solubility of the aromatic diol compound contained in the depolymerization product from which the carbonate compound is separated becomes excessively high, which reduces the yield of the aromatic diol compound recovered after recrystallization, and the process efficiency may decrease due to the use of a large amount of solvent.

[0133] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to another embodiment of the present invention may include a step of recrystallizing an aromatic diol compound from the dissolved solution. Through the recrystallization step, an aromatic diol compound can be obtained with high purity.

[0134] The concentration of the aromatic diol compound contained in the above solution may be 90 wt% or less, or 70 wt% or less, or 60 wt% or less, or 50 wt% or less, or 40 wt% or more, or 40 wt% to 90 wt%, or 40 wt% to 70 wt%, or 40 wt% to 60 wt%, or 40 wt% to 70 wt%. The concentration of the aromatic diol compound contained in the solution means the mass percentage of the aromatic diol compound relative to the mass of the entire solution.

[0135] If the concentration of the aromatic diol compound contained in the above solution increases excessively, it is difficult to remove impurities through recrystallization. On the other hand, if the concentration of the aromatic diol compound contained in the above solution decreases excessively, the yield of the aromatic diol compound recovered after recrystallization may decrease.

[0136] In the step of recrystallizing the aromatic diol compound from the above-mentioned dissolved solution, specific examples of the recrystallization method are not particularly limited, and various methods widely known as conventional recrystallization methods, such as cooling, evaporation, and flash cooling, can be applied without limitation.

[0137] However, as an example, the step of recrystallizing the aromatic diol compound from the dissolved solution may include a step of cooling the dissolved solution. The step of cooling the dissolved solution may be performed at a temperature of 0° C. to 40° C., or 5° C. to 40° C., or 5° C. to 30° C., or 5° C. to 20° C. The temperature difference between the step of dissolving the depolymerization reaction product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound; and the step of recrystallizing the aromatic diol compound from the dissolved solution may be 40° C. to 100° C., or 40° C. to 80° C., or 50° C. to 70° C.

[0138] The steps of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound; and recrystallizing the aromatic diol compound from the dissolved solution; may be repeated two or more times. That is, after the steps of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound; and recrystallizing the aromatic diol compound from the dissolved solution are performed once, the steps of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound; and recrystallizing the aromatic diol compound from the dissolved solution may be performed one or more times again. Through this, the aromatic diol compound to be recovered can have excellent color quality.

[0139] Meanwhile, the method may further include a step of separating a carbonate compound from the depolymerization product; and a step of dissolving the depolymerization product from which the carbonate compound has been separated in a solvent containing the separated carbonate compound; and a step of adding an adsorbent to the depolymerization product from which the carbonate compound has been separated to perform adsorption purification, and then removing the adsorbent.

[0140] In addition, in the step of removing the adsorbent after adding an adsorbent to the depolymerization reaction product from which the carbonate compound is separated and performing adsorption purification, the adsorbent may be brought into contact with the depolymerization reaction product.

[0141] Examples of the above adsorbent include activated carbon, charcoal, or a mixture thereof. The activated carbon is a black carbon material with micropores manufactured by subjecting raw materials to a carbonization process at approximately 500°C and an activation process at approximately 900°C. Examples are not particularly limited, but various activated carbons such as plant-based, coal-based, petroleum-based, and waste-based activated carbons can be applied without limitation depending on the type of raw material.

[0142] More specific examples include plant-based activated carbons such as palm, wood, and sawdust. Coal-based activated carbons include lignite, bituminous, and anthracite. Petroleum-based activated carbons include petroleum coke and oil carbon. Waste-based activated carbons include synthetic resin and pulp activated carbon.

[0143] The above adsorbent may include at least one type of activated carbon selected from the group consisting of plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, and waste-based activated carbon. That is, the adsorbent may include plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, waste-based activated carbon, or a mixture of two or more types thereof.

[0144] More specifically, the adsorbent may include at least one type of activated carbon selected from the group consisting of palm activated carbon, lignite activated carbon, anthracite activated carbon, and bituminous carbon activated carbon. That is, the adsorbent may include palm activated carbon, lignite activated carbon, anthracite activated carbon, bituminous carbon activated carbon, or a mixture of two or more types thereof.

[0145] The adsorption purification conditions using the above adsorbent are not particularly limited, and various adsorption purification conditions known in the art can be used without limitation. However, for example, the amount of the adsorbent added can be 40 to 60 wt% relative to the polycarbonate resin, the adsorption time can be 1 to 5 hours, and the adsorption method can be stirred adsorption or a lab-type adsorption tower.

[0146] If necessary, a step of adding a solvent to the depolymerization product from which the carbonate-based compound is separated before the step of removing the adsorbent after adding an adsorbent to the depolymerization product from which the carbonate-based compound is separated and performing adsorption purification may be further included. An example of the solvent is ethanol, and the ethanol may be added in a ratio of 1 to 20 mol, or 10 to 20 mol, or 15 to 20 mol per mol of the polycarbonate-based resin. Through the step of adding a solvent to the depolymerization product from which the carbonate-based compound is separated, the aromatic diol compound crystals included in the depolymerization product from which the carbonate-based compound is separated may be redissolved in the solvent.

[0147] Meanwhile, a step of evaporating the solvent may be further included after the step of adding a solvent to the depolymerization product from which the carbonate-based compound is separated. Examples of the evaporation conditions are not particularly limited, but a specific example may include evaporation using an evaporator (e.g., a thin film evaporator). After the evaporation step, a step of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound may be performed.

[0148] Meanwhile, after the step of adding a solvent to the depolymerization product from which the carbonate-based compound is separated, a recrystallization step of the depolymerization product from which the carbonate-based compound is separated may be further included. In the recrystallization step of the depolymerization product from which the carbonate-based compound is separated, various impurities contained in the depolymerization product from which the carbonate-based compound is separated can be sufficiently removed to secure a high-purity aromatic diol compound.

[0149] Specifically, the recrystallization step may include a step of recrystallizing by adding water to the depolymerization product from which the carbonate-based compound is separated. Through the process of recrystallizing by adding water to the depolymerization product from which the carbonate-based compound is separated, the solubility of the aromatic diol compound, or its salt, contained in the depolymerization product increases, so that impurities present in the crystals or between the crystals can be dissolved with the solvent as much as possible, and since the dissolved aromatic diol compound has poor solubility compared to the impurities, when the temperature is lowered thereafter, the aromatic diol compound can be easily precipitated as crystals due to the difference in solubility.

[0150] More specifically, in the step of recrystallizing by adding water to the depolymerization product from which the carbonate-based compound is separated, 200 to 400 moles, or 250 to 350 moles, of water may be used per 1 mole of the polycarbonate-based resin. If too little water is used, the temperature for dissolving the aromatic diol compound contained in the depolymerization product from which the carbonate-based compound is separated becomes too high, which lowers the process efficiency and makes it difficult to remove impurities through recrystallization. On the other hand, if too much water is used, the solubility of the aromatic diol compound contained in the depolymerization product from which the carbonate-based compound is separated becomes too high, which reduces the yield of the aromatic diol compound recovered after recrystallization, and the process efficiency may decrease due to the use of a large amount of solvent.

[0151] After the recrystallization step of the depolymerization product from which the carbonate-based compound is separated has been performed, a step of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound may be performed. However, if necessary, after the recrystallization step of the depolymerization product from which the carbonate-based compound is separated has been performed, a process of removing remaining impurities through filtration or adsorption may be additionally performed.

[0152] In addition, between the step of dissolving the depolymerization product from which the carbonate-based compound is separated in a solvent containing the separated carbonate-based compound and the step of recrystallizing the aromatic diol compound from the dissolved solution, a step of adding an adsorbent to the depolymerization product from which the carbonate-based compound is separated, performing adsorption purification, and then removing the adsorbent may be further included. The description of the step of adding an adsorbent to the depolymerization product from which the carbonate-based compound is separated, performing adsorption purification, and then removing the adsorbent is the same as described above.

[0153] Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the other embodiment may further include a step of washing the depolymerization product from which the carbonate compound has been separated between the step of separating the carbonate compound from the depolymerization product and the step of dissolving the depolymerization product from which the carbonate compound has been separated in a solvent containing the separated carbonate compound.

[0154] In the washing step of the depolymerization product from which the carbonate-based compound is separated, the depolymerization product from which the carbonate-based compound is separated may contain an aromatic diol compound. However, since various impurities remain during the recovery process for obtaining the aromatic diol compound, washing may be performed to sufficiently remove these impurities and secure a high-purity aromatic diol compound.

[0155] Specifically, the washing step may include a step of washing with a solvent at a temperature of 10°C or higher and 30°C or lower, or 20°C or higher and 30°C or lower. The temperature condition refers to the temperature inside the washing container where washing with the solvent is performed, and various heating devices may be applied without limitation to maintain a high temperature exceeding room temperature.

[0156] If necessary, after the step of washing with a solvent at a temperature of 10°C or higher and 30°C or lower, an additional process of removing the remaining solvent through filtration may be performed.

[0157] The solvent used in the above washing step may include one of water, alcohol, and an organic solvent. The organic solvent may be tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0158] The solvent used in the above washing step may be used in a weight ratio of 1 part by weight or more and 30 parts by weight or less, or 1 part by weight or more and 10 parts by weight or less, based on 1 part by weight of the polycarbonate resin used in the depolymerization reaction.

[0159] More specifically, the solvent in the step of washing with a solvent at a temperature of 10°C or higher and 30°C or lower may be an organic solvent. Preferably, methylene chloride may be used as the organic solvent. In this case, the organic solvent may be used in an amount of 1 part by weight or more and 10 parts by weight or less relative to 1 part by weight of the polycarbonate resin.

[0160] Meanwhile, if necessary, after the carbonate compound has undergone a recrystallization step of the separated depolymerization product, an additional process of removing remaining impurities through filtration or adsorption may be performed.

[0161] In addition, if necessary, a drying step may be further included after the recrystallization step. The drying step can remove any remaining solvent, and although the specific drying conditions are not particularly limited, drying may be performed at a temperature of, for example, 10°C to 100°C, or 50°C to 100°C. Various known drying technologies can be applied without limitation to the specific drying equipment and method used during the drying step.

[0162]

[0163] (2) Second manufacturing method

[0164] Meanwhile, according to another embodiment of the invention, a method for producing a monomer composition for synthesizing recycled plastic may be provided, comprising the steps of: depolymerizing a polycarbonate resin; dissolving the depolymerization product in a solvent containing a carbonate compound; and recrystallizing an aromatic diol compound from the dissolved solution.

[0165] For convenience, the method for producing a monomer composition for synthesizing recycled plastic of the above-described other embodiment is referred to as the first production method, and the method for producing a monomer composition for synthesizing recycled plastic of the above-described other embodiment is referred to as the second production method.

[0166] The second manufacturing method may include a step of depolymerizing the polycarbonate resin, and the contents of the step of depolymerizing the polycarbonate resin may include the same as those described above in the first manufacturing method.

[0167] Meanwhile, the second manufacturing method may further include, after the step of depolymerizing the polycarbonate resin, a step of adding acid so that the pH of the depolymerization product becomes 2 to 8; and the contents of the step of adding acid so that the pH of the depolymerization product becomes 2 to 8 may include the same as that described above in the first manufacturing method.

[0168] The second manufacturing method may include a step of removing impurities after adding the acid, and the contents of the step of removing the impurities may include the same as those described above in the first manufacturing method.

[0169] The second manufacturing method may include a step of dissolving the depolymerization product in a solvent containing a carbonate compound. The content of the depolymerization product and the carbonate compound may include the same as described above in the first manufacturing method. Through the step of adding the solvent containing the carbonate compound to the depolymerization product, the aromatic diol compound crystals included in the depolymerization product may be redissolved in the solvent.

[0170] Through this, the solubility of the aromatic diol compound or its salt contained in the depolymerization reaction product increases, so that the crystals or impurities caught between the crystals can be dissolved with the solvent as much as possible, and since the dissolved aromatic diol compound has poor solubility compared to the impurities, when the temperature is lowered thereafter, the aromatic diol compound can be easily precipitated as crystals through the difference in solubility.

[0171] The solvent may contain a carbonate compound. The solvent may be composed solely of a carbonate compound, or may be composed primarily of a carbonate compound with some impurities mixed in. The method for producing the carbonate compound is not particularly limited, and any carbonate compound obtained through a conventionally known method for producing a carbonate compound may be applied without limitation.

[0172] For example, it may be obtained from a depolymerization reaction of a polycarbonate resin, may be newly synthesized industrially, or may be obtained through a combination of a depolymerization reaction and a new synthesis.

[0173] The step of dissolving the above-mentioned depolymerization reaction product in a solvent containing the carbonate compound may be performed at a temperature of 0°C to 200°C, or 50°C to 150°C, or 50°C to 120°C, or 50°C to 100°C.

[0174] The amount of the solvent containing the carbonate compound may be 10 parts by weight or more, or 40 parts by weight or more, or 90 parts by weight or more, or 100 parts by weight or more, or 200 parts by weight or less, or 10 to 200 parts by weight, or 40 to 200 parts by weight, or 90 to 200 parts by weight, or 100 to 200 parts by weight, based on 100 parts by weight of the aromatic diol compound contained in the depolymerization product. If too little of the solvent containing the carbonate compound is used, the temperature for dissolving the aromatic diol compound contained in the depolymerization product becomes too high, thereby lowering process efficiency, and as the temperature difference between the dissolution temperature and the cooling temperature increases, it is not easy to remove impurities through recrystallization. In addition, after recrystallization, the solid concentration is too high, making transportation or solid-liquid separation very difficult, and thus impurity removal may not be easy.

[0175] On the other hand, if a solvent containing a carbonate compound is used in an excessive amount, the solubility of the aromatic diol compound contained in the depolymerization reaction product becomes excessively high, which reduces the yield of the aromatic diol compound recovered after recrystallization, and the process efficiency may decrease due to the use of a large amount of solvent.

[0176] Meanwhile, the second manufacturing method may include a step of recrystallizing an aromatic diol compound from the dissolved solution, and the contents of the step of recrystallizing an aromatic diol compound from the dissolved solution may include the same as those described above in the first manufacturing method.

[0177] Meanwhile, the second manufacturing method may repeat the steps of dissolving the depolymerization product in a solvent containing a carbonate compound; and recrystallizing the aromatic diol compound from the dissolved solution two or more times. That is, after the steps of dissolving the depolymerization product in a solvent containing a carbonate compound; and recrystallizing the aromatic diol compound from the dissolved solution are performed once, the steps of dissolving the depolymerization product in a solvent containing a carbonate compound; and recrystallizing the aromatic diol compound from the dissolved solution may be performed one or more times again. Through this, the aromatic diol compound to be recovered can have excellent color quality.

[0178] Meanwhile, the second manufacturing method may further include, between the step of depolymerizing a polycarbonate resin and the step of dissolving the depolymerization product in a solvent containing a carbonate compound, a step of adding an adsorbent to the depolymerization product, performing adsorption purification, and then removing the adsorbent. The content of the step of adding an adsorbent to the depolymerization product, performing adsorption purification, and then removing the adsorbent may include the same as that described above in the first manufacturing method.

[0179] Meanwhile, the second manufacturing method may further include, between the step of dissolving the depolymerization product in a solvent containing a carbonate compound and the step of recrystallizing the aromatic diol compound from the dissolved solution, a step of adding an adsorbent to the depolymerization product to perform adsorption purification and then removing the adsorbent. The content of the step of adding an adsorbent to the depolymerization product to perform adsorption purification and then removing the adsorbent may include the same as that described above in the first manufacturing method.

[0180] Meanwhile, the second manufacturing method may further include a washing step of the depolymerization product between the step of depolymerizing a polycarbonate resin and the step of dissolving the depolymerization product in a solvent containing a carbonate compound, and the contents of the washing step of the depolymerization product may include the same as those described above in the first manufacturing method.

[0181]

[0182] 3. Recycled plastic

[0183] According to another embodiment of the invention, a recycled plastic comprising a monomer composition for synthesizing recycled plastic and a reaction product of a comonomer of the above embodiment can be provided.

[0184] The content of the monomer composition for synthesizing recycled plastic of the above embodiment includes all of the content described above in the above embodiment.

[0185] Examples corresponding to the above recycled plastics are not particularly limited, and various plastics synthesized using aromatic diol compounds such as bisphenol A and carbonate compounds such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate as monomers can be applied without limitation, and a more specific example is polycarbonate resin.

[0186] The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization or copolymerization reaction of a monomer including an aromatic diol compound and a carbonate compound. When it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor, a homopolymer can be synthesized. In addition, when one type of aromatic diol compound and two or more types of carbonate precursors are used as the monomer, or two or more types of aromatic diol compounds and one type of carbonate precursor are used, or one or more types of other diols are used in addition to one type of aromatic diol compound and one type of carbonate precursor, and two or more types of carbonates are contained, a copolymer can be synthesized. The above homopolymer or copolymer may include all low-molecular-weight compounds, oligomers, and polymers according to the molecular weight range.

[0187] More specifically, in the recycled plastic comprising the monomer composition for synthesizing the recycled plastic of the above embodiment and the reaction product of the comonomer, a carbonate-based compound may be used as the comonomer. Specific examples of the carbonate precursor include phosgene, triphosgene, diphosgene, bromophosgene, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, or bishaloformate.

[0188] Examples of the reaction process of the monomer composition and comonomer for synthesizing the above polycarbonate resin for synthesizing recycled plastic are not particularly limited, and various polycarbonate manufacturing methods known in the art can be applied without limitation.

[0189] However, as an example of the above polycarbonate manufacturing method, a polycarbonate manufacturing method including a step of polymerizing a composition including a monomer composition for synthesizing recycled plastic and a comonomer may be used. In this case, the polymerization may be performed through interfacial polymerization, and during interfacial polymerization, the polymerization reaction can be performed at normal pressure and low temperature, and molecular weight control is easy.

[0190] The polymerization temperature may be 0°C to 40°C, and the reaction time may be 10 minutes to 5 hours. In addition, the pH during the reaction may be maintained at 9 or higher or 11 or higher.

[0191] The solvent that can be used for the above polymerization is not particularly limited as long as it is a solvent used in the polymerization of polycarbonate in the art, and for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene can be used.

[0192] In addition, the polymerization can be carried out in the presence of an acid binder, and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine can be used as the acid binder.

[0193] In addition, in order to control the molecular weight of the polycarbonate during the polymerization, polymerization can be performed in the presence of a molecular weight regulator. The molecular weight regulator can be an alkylphenol having 1 to 20 carbon atoms, and specific examples thereof include p-tert-butylphenol, p-cumylphenol, decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, or triacontylphenol. The molecular weight regulator can be added before the start of polymerization, during the start of polymerization, or after the start of polymerization. The molecular weight regulator can be used in an amount of 0.01 to 10 parts by weight, or 0.1 to 6 parts by weight, based on 100 parts by weight of the aromatic diol compound, and a desired molecular weight can be obtained within this range.

[0194] In addition, in order to promote the polymerization reaction, a reaction promoter such as a tertiary amine compound, a quaternary ammonium compound, a quaternary phosphonium compound, etc., such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, can be additionally used.

[0195]

[0196] 4. Molded products

[0197] According to another embodiment of the invention, a molded article comprising the recycled plastic of the other embodiment may be provided. The content of the recycled plastic includes all of the content described above in the other embodiment.

[0198] The above molded product may be obtained by applying various known plastic molding methods to the above recycled plastic without limitation, and examples of the molding methods include injection molding, foam injection molding, blow molding, or extrusion molding.

[0199] The above examples of molded products are not particularly limited and can be applied to a variety of molded products using plastics without limitation. Examples of molded products include automotive parts, electrical and electronic products, communication products, household goods, building materials, optical components, and exterior materials.

[0200] In addition to the recycled plastic of the other embodiments, the above-mentioned molded product may additionally include one or more additives selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent whitening agents, ultraviolet absorbers, pigments, and dyes, as needed.

[0201] As an example of a method for manufacturing the above-mentioned molded product, the method may include a step of mixing the recycled plastic and additives of the other embodiment well using a mixer, extruding them with an extruder to manufacture pellets, drying the pellets, and then injecting them with an injection molding machine.

[0202] According to the present invention, a monomer composition for synthesizing recycled plastic, which can realize high purity and excellent color quality even when recovered through recycling by chemical decomposition of polycarbonate resin and has improved efficiency in the recovery process, a method for producing the same, and recycled plastic and molded products using the same can be provided.

[0203] The invention is described in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited by the following examples.

[0204]

[0205] <Examples and Comparative Examples: Preparation of Recycled Bisphenol A Monomer Composition>

[0206] Example 1

[0207] (1. Decomposition step) 1 mol of pretreated waste polycarbonate (PC) was dissolved in 17 mol of methylene chloride (MC), and then introduced into a 3 L high-pressure reactor together with 11 mol of ethanol (EtOH) and 0.25 mol of sodium hydroxide (NaOH). Sodium hydrosulfite was introduced as an antioxidant at 0.7 wt% based on the total solution, and the atmosphere in the system was replaced with nitrogen to make it inert, and the PC depolymerization reaction was carried out by stirring at 60°C for 6 hours.

[0208] (2. pH adjustment) The product of the above depolymerization reaction was cooled to 30°C or lower, and then 10% hydrochloric acid (HCl) and water were added to the bisphenol A product to adjust the pH to 8.

[0209] (3. Layer separation) After the water layer and the methylene chloride (MC) layer were formed, the organic layer located at the bottom was recovered using the drain device at the bottom of the reactor, and the water layer located at the top was discharged and discarded.

[0210] (4. Distillation) Afterwards, the recovered methylene chloride (MC) layer was distilled at low temperature from 250 mbar, 20 to 30 ℃ to 30 mbar, 30 ℃, to separate and recover the by-product diethyl carbonate (DEC).

[0211] (5. Purification step - filtration) Afterwards, the residue from which diethyl carbonate (DEC) was removed was washed at 20 to 30°C using methylene chloride (MC) twice the mass of PC used, and bisphenol A was recovered through vacuum filtration.

[0212] (6-1. Additional purification step - re-dissolution step) 50 g of the recovered bisphenol A and 50 g of the diethyl carbonate (DEC) recovered in the distillation step 4 were mixed at room temperature, and then the temperature was raised to 80 ℃ while stirring to re-dissolve.

[0213] (6-2. Additional purification step - recrystallization step) The above solution was cooled to 20°C to recrystallize bisphenol A, and then the obtained slurry was vacuum filtered at 20°C to recover bisphenol A (BPA) crystals.

[0214] (7. Drying step) Afterwards, a recycled bisphenol A monomer composition was manufactured by drying in a 100 ℃ convection oven to recover recycled bisphenol A (BPA).

[0215]

[0216] Example 2

[0217] (1. Decomposition step) 1 mol of pretreated waste polycarbonate (PC) was dissolved in 17 mol of methylene chloride (MC), and then introduced into a 3 L high-pressure reactor together with 11 mol of ethanol (EtOH) and 0.25 mol of sodium hydroxide (NaOH). Sodium hydrosulfite was introduced as an antioxidant at 0.7 wt% based on the total solution, and the atmosphere in the system was replaced with nitrogen to make it inert, and the PC depolymerization reaction was carried out by stirring at 60°C for 6 hours.

[0218] (2. pH adjustment) The product of the above depolymerization reaction was cooled to 30°C or lower, and then 10% hydrochloric acid (HCl) and water were added to the bisphenol A product to adjust the pH to 8.

[0219] (3. Layer separation) After the water layer and the methylene chloride (MC) layer were formed, the organic layer located at the bottom was recovered using the drain device at the bottom of the reactor, and the water layer located at the top was discharged and discarded.

[0220] (4. Distillation) Afterwards, the recovered methylene chloride (MC) layer was distilled at low temperature from 250 mbar, 20 to 30 ℃ to 30 mbar, 30 ℃, to separate and recover the by-product diethyl carbonate (DEC).

[0221] (5. Purification step - filtration) Afterwards, the residue from which diethyl carbonate (DEC) was removed was washed at 20 to 30°C using methylene chloride (MC) twice the mass of PC used, and bisphenol A was recovered through vacuum filtration.

[0222] (6-1. Additional purification step - re-dissolution step) 50 g of the recovered bisphenol A and 50 g of the diethyl carbonate (DEC) recovered in the distillation step 4 were mixed at room temperature, and then the temperature was raised to 80 ℃ while stirring to re-dissolve.

[0223] (6-2. Additional purification step - recrystallization step) The above solution was cooled to 20°C to recrystallize bisphenol A, and then the obtained slurry was vacuum filtered at 20°C to recover bisphenol A (BPA) crystals.

[0224] (6-3. Additional purification step - re-dissolution step) 50 g of the recovered bisphenol A and 50 g of the diethyl carbonate (DEC) recovered in the distillation step 4 were mixed at room temperature, and then the temperature was raised to 80 ℃ while stirring to re-dissolve.

[0225] (6-4. Additional purification step - recrystallization step) The above solution was cooled to 20°C to recrystallize bisphenol A, and then the obtained slurry was vacuum filtered at 20°C to recover bisphenol A (BPA) crystals.

[0226] (7. Drying step) Afterwards, a recycled bisphenol A monomer composition was manufactured by drying in a 100 ℃ convection oven to recover recycled bisphenol A (BPA).

[0227]

[0228] Example 3

[0229] (1. Decomposition step) 1 mol of pretreated waste polycarbonate (PC) was dissolved in 17 mol of methylene chloride (MC), and then introduced into a 3 L high-pressure reactor together with 11 mol of ethanol (EtOH) and 0.25 mol of sodium hydroxide (NaOH). Sodium hydrosulfite was introduced as an antioxidant at 0.7 wt% based on the total solution, and the atmosphere in the system was replaced with nitrogen to make it inert, and the PC depolymerization reaction was carried out by stirring at 60°C for 6 hours.

[0230] (2. pH adjustment) The product of the above depolymerization reaction was cooled to 30°C or lower, and then 10% hydrochloric acid (HCl) and water were added to the bisphenol A product to adjust the pH to 8.

[0231] (3. Layer separation) After the water layer and the methylene chloride (MC) layer were formed, the organic layer located at the bottom was recovered using the drain device at the bottom of the reactor, and the water layer located at the top was discharged and discarded.

[0232] (4. Distillation) Afterwards, the recovered methylene chloride (MC) layer was distilled at low temperature from 250 mbar, 20 to 30 ℃ to 30 mbar, 30 ℃, to separate and recover the by-product diethyl carbonate (DEC).

[0233] (5. Purification step - filtration) Afterwards, the residue from which diethyl carbonate (DEC) was removed was washed once at 20 to 30°C using methylene chloride (MC) twice the amount of PC used, and vacuum filtered. The filtrate was washed a second time at 50°C using water twice the amount of PC used.

[0234] (6-1. Additional purification step - re-dissolution step) After that, bisphenol A was added to 16.6 mol of ethanol and re-dissolved.

[0235] (6-2. Additional purification step - adsorption step) Afterwards, brown activated carbon was added as an adsorbent at a ratio of 50 wt% compared to waste polycarbonate, and purified through adsorption for 3 hours, and then brown activated carbon was removed through filtration.

[0236] (6-3. Additional purification step - recrystallization step) After that, 300 mol of water was added and bisphenol A was recrystallized, and then the obtained slurry was vacuum filtered at 20 to 30°C to recover bisphenol A (BPA) crystals.

[0237] (7-1. Additional purification step - re-dissolution step) 50 g of the recovered bisphenol A and 50 g of diethyl carbonate (DEC) recovered in the distillation step 4 were mixed at room temperature, and then the temperature was raised to 80 ℃ while stirring to re-dissolve.

[0238] (7-2. Additional purification step - recrystallization step) The above solution was cooled to 20°C to recrystallize bisphenol A, and then the obtained slurry was vacuum filtered at 20°C to recover bisphenol A (BPA) crystals.

[0239] (8. Drying step) Afterwards, a recycled bisphenol A monomer composition was manufactured by drying in a 100 ℃ convection oven to recover recycled bisphenol A (BPA).

[0240]

[0241] Comparative Example 1

[0242] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that (6-1. Additional purification step - re-dissolution step) and (6-2. Additional purification step - recrystallization step) of Example 1 were not performed.

[0243]

[0244] Comparative Example 2

[0245] A recycled bisphenol A monomer composition was prepared in the same manner as in Example 3, except that (7-1. Additional purification step - re-dissolution step) and (7-2. Additional purification step - recrystallization step) of Example 3 were not performed.

[0246]

[0247] <Experimental Example>

[0248] The physical properties of the recycled bisphenol A monomer compositions obtained in the above examples and comparative examples were measured by the following methods, and the results are shown in Table 1.

[0249]

[0250] 1. BPA purity

[0251] After dissolving the recycled bisphenol A monomer composition in methanol solvent at a concentration of 0.5 mg / mL under atmospheric pressure and 20 to 30 ℃ conditions, solid impurities in the solution were removed using a syringe filter (0.45 μm), and then the purity of bisphenol A (BPA) was analyzed using UPLC (ultra performance liquid chromatography) on a Waters HPLC system using Capcell Pak C18 (inner diameter 4.6 mm, length 50 mm, particle size 5 μm). Specifically, the peak area ratio (unit: %) of bisphenol A (BPA) was measured with respect to 100% of the total UPLC peak area.

[0252] The specific UPLC measurement conditions are as follows.

[0253] ① Column: Capcell Pak C18 (4.6 mm ID 0min A:B=2:8, 10min A:B=100:0, volume=1ml / min (total=10min), ⑤ Detector: 275nm

[0254]

[0255] 2. Impurity ratio

[0256] UPLC analysis was performed using the same method as the above 1.BPA purity measurement method, and the peak area ratio (unit: %) of BPA derivatives (monoethylcarbonate of bisphenol-A (MEBPA; ethyl (4-(2-(4-hydroxyphenyl)propan-2-yl)phenyl) carbonate)], bisethylcarbonate of bisphenol-A (BEBPA; diethyl (propane-2,2-diylbis(4,1-phenylene)) bis(carbonate))], bisphenol A dimer [BPA dimer]) impurities was measured using the following formula A.

[0257] [Formula A]

[0258] BPA derivative impurity ratio (%) = (Bisphenol A derivative peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

[0259] In the above formula A, the peak area of ​​the bisphenol A derivative measured by liquid chromatography is the sum of the peak areas of MEBPA, BEBPA, and BPA dimer, respectively.

[0260]

[0261] 3. APHA Color

[0262] For the above recycled bisphenol A monomer composition, solid impurities in the solution were removed using a syringe filter (0.45 ㎛), and then measurements were made in the same manner as ASTM D1209 using a Hunterlab UltraScan PRO model device.

[0263]

[0264] 4. Melting point

[0265] For the above recycled bisphenol A monomer composition, the melting point (T) was obtained from a temperature-heat flow graph obtained at a heating rate of 10 ℃ / min in a temperature range of 0 ℃ to 180 ℃ using a differential scanning calorimeter (Device name: DSC 2920, Manufacturer: TA instrument). m ) Onset value was measured. Melting point (T m ) was obtained through peak analysis of the heating curve of the heat flow at the first temperature increase, and the average value was taken by measuring three times for each sample.

[0266]

[0267] Experimental example Measurement results Classification BPA purity (%) BPA derivative impurities (%) MEBPA and BEBPA (%) BPA dimer (%) APHA Color Melting point (℃) Example 1 99.7 5 0.25 0.05 0.23 6 156.5 Example 2 99.8 8 0.12 0 0.12 2 7 156.8 Example 3 99.9 1 0.0 9 0 0.0 9 6 156.9 Comparative example 1 98.8 2 0.9 5 0.48 0.47 133 154.8 Comparative example 2 99.5 7 0.3 5 0.21 0.14 17 156.3

[0268] As shown in Table 1 above, the recycled bisphenol A monomer compositions obtained in Examples 1 to 3 exhibited high purity of 99.75% to 99.91%, and had high melting points of 156.5°C to 156.9°C. In addition, the recycled bisphenol A monomer compositions obtained in Examples 1 to 3 were measured to have a low BPA derivative impurity ratio of 0.09% to 0.25%. On the other hand, the recycled bisphenol A monomer compositions obtained in Comparative Examples 1 to 2 had a purity of 98.82% to 99.57%, which was lower than that of the Examples, and had melting points of 154.8°C to 156.3°C, which were lower than that of the Examples. In addition, the BPA derivative impurity ratio was measured to be 0.35% to 0.95%, which was higher than that of the Examples.

Claims

1. Contains an aromatic diol compound, The ratio of aromatic diol compound derivative impurities according to the following formula 1 is 0.3% or less, The melting point is 156.4 ℃ or higher, A monomer composition for synthesizing recycled plastic, characterized by being recovered from polycarbonate resin: [Formula 1] Aromatic diol compound derivative impurity ratio (%) = (Aromatic diol compound derivative peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

2. In paragraph 1, A monomer composition for synthesizing recycled plastic, wherein the derivative of the above aromatic diol compound comprises at least one compound selected from the group consisting of monoalkyl carbonates of bisphenol A, bisalkyl carbonates of bisphenol A, and bisphenol A dimers.

3. In paragraph 2, Monomer composition for synthesizing recycled plastic, wherein the monoalkyl carbonate of bisphenol A according to the following formula 2 and the bisalkyl carbonate of bisphenol A have a ratio of 0.1% or less: [Formula 2] Monoalkyl carbonate of bisphenol A, and bisalkyl carbonate ratio of bisphenol A (%) = (Monoalkyl carbonate of bisphenol A, and bisalkyl carbonate peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

4. In paragraph 2, A monomer composition for synthesizing recycled plastic, wherein the bisphenol A dimer ratio according to the following formula 3 is 0.3% or less: [Formula 3] Bisphenol A dimer ratio (%) = (Bisphenol A dimer peak area measured by liquid chromatography / Total peak area measured by liquid chromatography) X 100.

5. In paragraph 1, The above monomer composition for synthesizing recycled plastic is a monomer composition for synthesizing recycled plastic, having an APHA Color value of 60 or less as measured by ASTM D 1209.

6. In paragraph 1, The above monomer composition for synthesizing recycled plastic is a monomer composition for synthesizing recycled plastic, wherein the aromatic diol compound purity is 99.6% or more.

7. Step of depolymerizing polycarbonate resin; A step of separating a carbonate compound from the above depolymerization reaction product; A step of dissolving the depolymerization reaction product from which the carbonate compound is separated in a solvent containing the separated carbonate compound; and A step of recrystallizing an aromatic diol compound from the above dissolved solution; A method for producing a monomer composition for synthesizing recycled plastic.

8. In paragraph 7, The step of dissolving the depolymerization reaction product from which the above carbonate compound is separated in a solvent containing the above separated carbonate compound is as follows: A method for producing a monomer composition for synthesizing recycled plastic, the method comprising: performing a process at a temperature of 0°C to 200°C.

9. In paragraph 7, In the step of dissolving the depolymerization reaction product from which the above carbonate compound is separated in a solvent containing the above separated carbonate compound, A method for producing a monomer composition for synthesizing recycled plastic, wherein the amount of the solvent containing the carbonate compound is 10 parts by weight or more relative to 100 parts by weight of the aromatic diol compound contained in the depolymerization product from which the carbonate compound is separated.

10. In paragraph 7, In the step of recrystallizing the aromatic diol compound from the above dissolved solution, A method for producing a monomer composition for synthesizing recycled plastic, wherein the concentration of an aromatic diol compound contained in the above solution is 90 wt% or less.

11. In paragraph 7, The step of recrystallizing the aromatic diol compound from the above dissolved solution is: A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of cooling the above-described dissolved solution.

12. In paragraph 7, A step of dissolving the depolymerization reaction product from which the carbonate compound is separated in a solvent containing the separated carbonate compound; and A method for producing a monomer composition for synthesizing recycled plastic, comprising repeating the step of recrystallizing an aromatic diol compound from the above-described dissolved solution at least twice.

13. In paragraph 7, A step of separating a carbonate compound from the above depolymerization reaction product; and a step of dissolving the depolymerization reaction product from which the carbonate compound has been separated in a solvent containing the separated carbonate compound; between A method for producing a monomer composition for synthesizing recycled plastic, further comprising a step of adding an adsorbent to the depolymerization reaction product from which the carbonate compound is separated, performing adsorption purification, and then removing the adsorbent.

14. In paragraph 7, The depolymerization reaction of the above polycarbonate resin is A method for producing a monomer composition for synthesizing recycled plastic, characterized in that the process is carried out under alcohol.

15. In paragraph 14, A method for producing a monomer composition for synthesizing recycled plastic, wherein the content of the alcohol is 10 to 15 moles per mole of polycarbonate resin.

16. In paragraph 7, A method for producing a monomer composition for synthesizing recycled plastic, wherein the carbonate compound comprises a dialkyl carbonate or a diaryl carbonate.

17. In paragraph 7, A step of separating a carbonate compound from the above depolymerization reaction product; and a step of dissolving the depolymerization reaction product from which the carbonate compound has been separated in a solvent containing the separated carbonate compound; between A method for producing a monomer composition for synthesizing recycled plastic, further comprising a washing step of a depolymerization reaction product from which the carbonate compound is separated.

18. Step of depolymerizing polycarbonate resin; A step of dissolving the above depolymerization reaction product in a solvent containing a carbonate compound; and A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of recrystallizing an aromatic diol compound from the above-described dissolved solution.

19. A recycled plastic comprising a monomer composition for synthesizing recycled plastic and a reaction product of a comonomer of paragraph 1.

20. A molded product containing recycled plastic of Article 19.