Catalyst for depolymerization of polycarbonate-based resin, production method, method for depolymerizing

Abstract

The present disclosure relates to a catalyst for depolymerization of a polycarbonate-based resin comprising a compound represented by Chemical Formula 1, a method for preparing the catalyst, a method for decomposing a polycarbonate-based resin, and a method for recovering the catalyst for depolymerization of a polycarbonate-based resin.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0099505 filed in the Korean Intellectual Property Office on July 31, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0003] The present invention relates to a catalyst for depolymerization of a polycarbonate resin, a method for preparing the catalyst, a method for decomposing a polycarbonate resin, and a method for recovering the catalyst for depolymerization of a polycarbonate resin. Background Art

[0004] Polycarbonate is a plastic with high heat resistance, impact resistance and transparent optical properties, and is therefore widely used in various fields, including not only industrial products such as various optical products, electronic products, and building materials, but also daily necessities such as water bottles and tableware.

[0005] Polycarbonate is generally produced to have various colors and physical properties depending on the field of use, and therefore, a physical recycling method is not suitable, with the limitation that even recycled plastics produced therefrom show relatively large deterioration in physical properties.

[0006] The depolymerization process is a chemical recycling method that recovers polycarbonate waste as raw material bisphenol A, which is then reused in plastic production. This is a recycling method that can not only overcome the deterioration of physical properties that occurs in physical recycling, but also reduce the generation of additional bisphenol A.

[0007] Conventional depolymerization processes use acid or base catalysts in the depolymerization of polycarbonate, but acid or base catalysts have the problem of corroding equipment and require wastewater treatment and neutralization processes in the process. In addition, the disadvantage of acid or base catalysts is that the reaction is terminated by the neutralization reaction and the catalyst cannot be recovered, so it is not economical.

[0008] Therefore, it is necessary to develop a new catalyst that can replace the conventionally used acid or base catalysts. Summary of the invention

[0009] Technical issues

[0010] An object of the present disclosure is to provide a catalyst for depolymerization of a polycarbonate resin and a method for preparing the catalyst, which can recover the polycarbonate resin by chemical decomposition to ensure aromatic diol compounds at a high yield and can improve chemical decomposition reactivity and reaction efficiency.

[0011] Another object of the present disclosure is to provide a method for decomposing a polycarbonate-based resin by using a catalyst for depolymerization of a polycarbonate-based resin and a method for recovering the catalyst for depolymerization of a polycarbonate-based resin.

[0012] Technical Solution

[0013] In order to achieve the above object, a catalyst for depolymerization of a polycarbonate resin is provided herein, comprising a compound represented by the following Chemical Formula 1:

[0014] [Chemical formula 1]

[0015]

[0016] Wherein, in Chemical Formula 1, R 1 and R 2 is a straight-chain alkyl group having 1 to 3 carbon atoms.

[0017] Also provided herein is a method for preparing a catalyst for depolymerization of a polycarbonate resin, the method comprising the steps of: reacting 1-alkyl-imidazole with an alkyl halide to prepare a compound represented by the following Chemical Formula 4; and reacting the compound represented by Chemical Formula 4 with an alkali metal acetate:

[0018] [Chemical formula 4]

[0019]

[0020] In chemical formula 4, R 3 and R 4 is a straight chain alkyl group having 1 to 3 carbon atoms, and X is a halogen.

[0021] Further provided herein is a method for decomposing a polycarbonate-based resin, the method comprising subjecting the polycarbonate-based resin to a depolymerization reaction in the presence of a catalyst for depolymerization of the polycarbonate-based resin.

[0022] Also provided herein is a method for recovering a catalyst for depolymerization of a polycarbonate resin, the method comprising the following steps: subjecting a polycarbonate resin to a depolymerization reaction in the presence of the catalyst for depolymerization of the polycarbonate resin; adding water and an organic solvent to the depolymerization reaction product; separating a water layer containing the catalyst for depolymerization of the polycarbonate resin; and removing water contained in the water layer.

[0023] Hereinafter, a catalyst for depolymerization of a polycarbonate-based resin, a method for preparing the catalyst, a method for decomposing a polycarbonate-based resin, and a method for recovering the catalyst for depolymerization of a polycarbonate-based resin according to specific embodiments of the present disclosure will be described in more detail.

[0024] Unless explicitly stated herein, the technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the present invention.

[0025] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0026] It should be understood that the terms "comprises", "includes", "has", etc. are used herein to illustrate the presence of described features, regions, integers, steps, actions, elements and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, actions, elements, components and / or groups.

[0027] In addition, the terms including ordinal numbers such as "first", "second", etc. are only used for the purpose of distinguishing one component from another component and are not limited by the ordinal numbers. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, or similarly, the second component may be referred to as the first component.

[0028] As used herein, a derivative compound refers to a compound in which, when an organic compound is included as a substrate, it is changed within the limit of not significantly changing the structure and properties of the substrate such as introduction of a functional group, oxidation, reduction or substitution of atoms.

[0029] In the present disclosure, examples of the substituent are described below, but are not limited thereto.

[0030] As used herein, the term "substituted" means that other functional groups in the compound are bonded instead of hydrogen atoms, and there is no limitation on the position to be substituted as long as the position is a position where a hydrogen atom is substituted, that is, a position where a substituent can be substituted, and when two or more are substituted, the two or more substituents may be the same as or different from each other.

[0031] As used herein, the term "substituted or unsubstituted" refers to unsubstituted or substituted with one or more substituents selected from the following groups: deuterium, halogen group, cyano group, nitro group, hydroxyl group, carbonyl group, ester group, imide group, amide group, primary amino group, carboxyl group, sulfonic acid group, sulfonamide group, phosphine oxide group, alkoxy group, aryloxy group, alkylthiooxy group, arylthiooxy group, alkylsulfoxide group, arylsulfoxide group, silyl group, boron group, alkyl group, cycloalkyl group, alkenyl group, aryl group, aralkyl group, aralkenyl group; alkylaryl group; alkoxysilylalkyl group; arylphosphino group; or heterocyclic group containing at least one of N, O and S atoms, or unsubstituted or substituted with substituents connected to it by two or more substituents in the above-mentioned substituents. For example, "substituents to which two or more substituents are connected" can be biphenyl. That is, biphenyl can also be aryl, and it can be understood as a substituent to which two phenyl groups are connected.

[0032] As used herein, an alkyl group is a monovalent functional group derived from an alkane, and may be linear or branched. The number of carbon atoms of the linear alkyl group is not particularly limited, but is preferably 1 to 20. In addition, the number of carbon atoms of the branched alkyl group is 3 to 20. Specific examples of the alkyl group may include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methylbutyl, 1-ethylbutyl, 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-ethylpropyl, 1,1-dimethylpropyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, 2,6-dimethylheptan-4-yl, and the like, but are not limited thereto. The alkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are the same as described above.

[0033] As used herein, examples of halogen include fluorine, chlorine, bromine or iodine.

[0034] 1. Catalyst for depolymerization of polycarbonate resins

[0035] According to one embodiment of the present disclosure, a catalyst for depolymerization of a polycarbonate resin may be provided, comprising a compound represented by the following Chemical Formula 1:

[0036] [Chemical formula 1]

[0037]

[0038] Wherein, in Chemical Formula 1, R 1 and R 2is a straight-chain alkyl group having 1 to 3 carbon atoms.

[0039] The present inventors experimentally confirmed that a catalyst for depolymerization of a polycarbonate-based resin according to one embodiment can ensure aromatic diol compounds at high yield by recovering a polycarbonate-based resin through chemical decomposition and can improve chemical decomposition reactivity and reaction efficiency, and completed the present disclosure.

[0040] Specifically, the catalyst for depolymerization of a polycarbonate-based resin according to one embodiment may include a compound represented by Chemical Formula 1. The compound represented by Chemical Formula 1 is a salt composed of an imidazolium cation and an acetate anion, and may be used as both an acid catalyst and a base catalyst.

[0041] That is, according to one embodiment, the compound represented by Chemical Formula 1 as a catalyst for depolymerization of a polycarbonate-based resin corresponds to an ionic liquid which is a salt that maintains a liquid phase in a wide temperature range due to structural asymmetry between ions composed of cations and anions.

[0042] The acid catalyst or base catalyst conventionally used as a catalyst for depolymerization of polycarbonate resins has the following problems: it corrodes equipment and requires wastewater treatment and neutralization processes in the process, and has disadvantages: the reaction is terminated by neutralization reaction and the catalyst cannot be recovered, thus making it uneconomical.

[0043] On the other hand, the compound represented by Chemical Formula 1 is an ionic liquid, in which reactor management and replacement due to reactor corrosion are not required, a separate neutralization process is not required, and the catalyst can be recycled after recovery, whereby the compound can serve as a catalyst that is economically and environmentally superior to existing acid catalysts or base catalysts.

[0044] In addition, the catalyst for depolymerization of a polycarbonate resin according to one embodiment is an ionic liquid, which is a salt composed of cations and anions, and which simultaneously performs the functions of an acid catalyst and a base catalyst, thereby when the step of subjecting the polycarbonate resin to a depolymerization reaction in the presence of the catalyst for depolymerization of a polycarbonate resin according to one embodiment is performed, the depolymerization reactivity can be improved.

[0045] In addition, the compound represented by Chemical Formula 1 has high selective solubility and is thermally and chemically stable, making it possible to depolymerize the polycarbonate resin with high yield and high efficiency. Specifically, the catalyst for depolymerization of the polycarbonate resin according to one embodiment has high solubility in the polycarbonate resin, so that the depolymerization reaction can be fully carried out without adding any organic solvent other than the alcohol solvent. Therefore, the use of organic solvents that require a separate wastewater treatment process can be reduced, thereby increasing process efficiency.

[0046] In Chemical Formula 1, R 1 and R 2 It may be a straight chain alkyl group having 1 to 3 carbon atoms. That is, in Chemical Formula 1, R 1 and R 2 Both are straight-chain alkyl groups having 1 to 3 carbon atoms. Examples of the straight-chain alkyl group having 1 to 3 carbon atoms include methyl, ethyl and propyl.

[0047] In chemical formula 1, since R 1 and R 2 The linear alkyl group having 1 to 3 carbon atoms is satisfied and thus has a small steric effect in structure and a large basicity in chemical structure, so the depolymerization reactivity of the polycarbonate resin can be improved, the decomposition efficiency of the polycarbonate resin can be improved, and the yield of bisphenol A obtained by the decomposition of the polycarbonate resin can also be improved. In addition, when the polycarbonate resin is recovered and reused after the depolymerization reaction, it is recovered with high purity and recovery rate, so even if it is reused repeatedly many times, the depolymerization reactivity of the polycarbonate resin and the yield of bisphenol A can be maintained at a high level.

[0048] On the other hand, if R in Formula 1 1 and R 2 If at least one of the polycarbonate resins is a linear alkyl group having 4 or more carbon atoms, there may be a problem that the depolymerization reactivity of the polycarbonate resin and the yield of bisphenol A are reduced due to the large steric effect in the structure and the low basicity in the chemical structure. In addition, when the polycarbonate resin is recovered and reused after the depolymerization reaction, there is a limitation that it is difficult to maintain the depolymerization reactivity of the polycarbonate resin and the yield of bisphenol A at a sufficiently high level when repeatedly reused due to the reduction in purity and recovery rate.

[0049] Specifically, in Chemical Formula 1, R 1 and R 2 It may be a straight chain alkyl group having 1 to 2 carbon atoms. That is, in Chemical Formula 1, R 1 and R 2 Both are straight-chain alkyl groups having 1 to 2 carbon atoms. Examples of the straight-chain alkyl group having 1 to 2 carbon atoms include methyl and ethyl groups.

[0050] Furthermore, in Chemical Formula 1, R 1 and R 2 Can be different from each other. 1 and R 2 One of them can be ethyl and the other can be methyl. That is, if R 1 is ethyl, then R 2 can be methyl. Alternatively, if R 1 is ethyl, then R 2 It may be methyl.

[0051] More specifically, the compound represented by Chemical Formula 1 may be a compound represented by the following Chemical Formula 1-1.

[0052] [Chemical formula 1-1]

[0053]

[0054] On the other hand, the compound represented by Chemical Formula 1 may be a compound represented by the following Chemical Formula 2. Alternatively, the catalyst for depolymerization of a polycarbonate-based resin may include a compound represented by the following Chemical Formula 2.

[0055] [Chemical formula 2]

[0056]

[0057] In the chemical formula 2, R 1 and R 2 The contents described in the above Chemical Formula 1 are included as they are. More specifically, the compound represented by Chemical Formula 2 may be a compound represented by the following Chemical Formula 2-1.

[0058] [Chemical formula 2-1]

[0059]

[0060] That is, the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 correspond to resonance structures of each other.

[0061] That is, the compound represented by Chemical Formula 1 may be a compound represented by the following Chemical Formula 3. Alternatively, the catalyst for depolymerization of a polycarbonate-based resin may include a compound represented by the following Chemical Formula 3.

[0062] [Chemical formula 3]

[0063]

[0064] Wherein, in Chemical Formula 3, R 1 and R 2 The contents described in the above Chemical Formula 1 are included as they are. More specifically, the compound represented by Chemical Formula 3 may be a compound represented by the following Chemical Formula 3-1.

[0065] [Chemical formula 3-1]

[0066]

[0067] 2. Preparation method of catalyst for depolymerization of polycarbonate resin

[0068] According to other embodiments of the present disclosure, a method for preparing a catalyst for depolymerization of a polycarbonate resin may be provided, the method comprising the steps of: reacting 1-alkylimidazole with an alkyl halide to prepare a compound represented by the following Chemical Formula 4; and reacting the compound represented by Chemical Formula 4 with an alkali metal acetate:

[0069] [Chemical formula 4]

[0070]

[0071] In chemical formula 4, R 3 and R 4 is a straight chain alkyl group having 1 to 3 carbon atoms, and X is a halogen.

[0072] Specifically, the method for preparing the catalyst for depolymerization of a polycarbonate-based resin according to other embodiments may include the step of reacting 1-alkylimidazole with an alkyl halide to prepare a compound represented by Chemical Formula 4.

[0073] 1-Alkyl imidazole is a compound in which an alkyl group is bonded to the first nitrogen of the imidazole compound, and may be represented by Chemical Formula 7 below.

[0074] [Chemical formula 7]

[0075]

[0076] In chemical formula 7, R 3 With R in chemical formula 4 3 That is, in Chemical Formula 7, R 3 The definition includes R in the chemical formula 4 3 All definitions of .

[0077] Specifically, R 3 is a linear alkyl group having 1 to 3 carbon atoms. Examples of the linear alkyl group having 1 to 3 carbon atoms include methyl, ethyl and propyl. Specifically, in Chemical Formula 7, R 3 is a linear alkyl group having 1 to 2 carbon atoms. Examples of the linear alkyl group having 1 to 2 carbon atoms include methyl and ethyl. As a more specific example, in Chemical Formula 7, R 3 That is, examples of the compound represented by Chemical Formula 7 may include 1-methylimidazole.

[0078] On the other hand, the alkyl halide may be represented by Chemical Formula 8 below.

[0079] [Chemical formula 8]

[0080] R 4 -X

[0081] In the chemical formula 8, R4 With R in chemical formula 4 3 That is, in Chemical Formula 8, R 4 The definition includes R in the chemical formula 4 4 All definitions of .

[0082] Specifically, R 4 is a linear alkyl group having 1 to 3 carbon atoms. Examples of the linear alkyl group having 1 to 3 carbon atoms include methyl, ethyl and propyl. Specifically, in Chemical Formula 8, R 4 is a linear alkyl group having 1 to 2 carbon atoms. Examples of the linear alkyl group having 1 to 2 carbon atoms include methyl and ethyl. As a more specific example, in Chemical Formula 8, R 4 It may be an ethyl group. In addition, in Chemical Formula 8, X is a halogen, and examples of the halogen include fluorine, chlorine, bromine or iodine.

[0083] That is, examples of the compound represented by Chemical Formula 8 may include ethyl bromide or ethyl chloride.

[0084] The compound obtained by reacting 1-alkylimidazole with an alkyl halide may be represented by Chemical Formula 4 below.

[0085] [Chemical formula 4]

[0086]

[0087] In chemical formula 4, R 3 and R 4 is a straight chain alkyl group having 1 to 3 carbon atoms, and X is a halogen.

[0088] In chemical formula 4, R 3 and R 4 It may be a straight chain alkyl group having 1 to 3 carbon atoms. That is, in Chemical Formula 1, R 1 and R 2 Both are straight-chain alkyl groups having 1 to 3 carbon atoms. Examples of the straight-chain alkyl group having 1 to 3 carbon atoms include methyl, ethyl and propyl.

[0089] Specifically, in Chemical Formula 4, R 3 and R 4 It may be a straight chain alkyl group having 1 to 2 carbon atoms. That is, in Chemical Formula 4, R 3 and R 4 Both are straight-chain alkyl groups having 1 to 2 carbon atoms. Examples of the straight-chain alkyl group having 1 to 2 carbon atoms include a methyl group or an ethyl group.

[0090] Furthermore, in Chemical Formula 4, R 3 and R 4 Can be different from each other. 3 and R4 One of them can be ethyl and the other can be methyl. That is, if R 3 is ethyl, then R 4 can be methyl. Alternatively, if R 4 is ethyl, then R 3 It may be methyl.

[0091] X is a halogen, and examples of the halogen include fluorine, chlorine, bromine or iodine.

[0092] More specifically, the compound represented by Chemical Formula 4 may be a compound represented by the following Chemical Formula 4-1, or a compound represented by the following Chemical Formula 4-2.

[0093] [Chemical formula 4-1]

[0094]

[0095] [Chemical formula 4-2]

[0096]

[0097] On the other hand, the compound represented by Chemical Formula 4 may be a compound represented by Chemical Formula 5 below.

[0098] [Chemical formula 5]

[0099]

[0100] In the chemical formula 5, R 3 , R 4 and X as is includes the contents shown in the above Chemical Formula 4. More specifically, the compound represented by Chemical Formula 5 may be a compound represented by the following Chemical Formula 5-1, or a compound represented by the following Chemical Formula 5-2.

[0101] [Chemical formula 5-1]

[0102]

[0103] [Chemical formula 5-2]

[0104]

[0105] That is, the compound represented by Chemical Formula 4 and the compound represented by Chemical Formula 5 correspond to resonance structures of each other. That is, the compound represented by Chemical Formula 4 may be a compound represented by the following Chemical Formula 6.

[0106] [Chemical formula 6]

[0107]

[0108] In Chemical Formula 6, R3 , R 4 and X includes those shown in the above Chemical Formula 4. More specifically, the compound represented by Chemical Formula 6 may be a compound represented by the following Chemical Formula 6-1, or a compound represented by the following Chemical Formula 6-2.

[0109] [Chemical formula 6-1]

[0110]

[0111] [Chemical formula 6-2]

[0112]

[0113] The reaction conditions under which the reaction of 1-alkylimidazole and alkyl halide is performed are not particularly limited, but for example, the reaction can be performed at a temperature of 50° C. to 100° C. for 1 hour to 100 hours.

[0114] On the other hand, the method for preparing the catalyst for depolymerization of a polycarbonate-based resin according to other embodiments may include the step of reacting the compound represented by Chemical Formula 4 with an alkali metal acetate.

[0115] The alkali metal acetate may include potassium acetate.

[0116] The description of the compound represented by Chemical Formula 4 may include all of the above.

[0117] Examples of reaction conditions for the step of reacting the compound represented by Chemical Formula 4 with the alkali metal acetate are not particularly limited, but may be performed, for example, at room temperature (20-30° C.) in the presence of an alcohol solvent.

[0118] On the other hand, the method for preparing a catalyst for depolymerization of a polycarbonate-based resin according to other embodiments may further include a step of removing an alkali metal halide after the step of reacting the compound represented by Chemical Formula 4 with an alkali metal acetate.

[0119] When the compound represented by Chemical Formula 4 reacts with an alkali metal acetate, an alkali metal halide may be generated as a reaction byproduct. Examples of methods for removing the alkali metal halide are not particularly limited, but include, for example, a filter removal method. Examples of the alkali metal halide are not particularly limited, but include, for example, potassium chloride (KCl) or potassium bromide (KBr).

[0120] 3. Decomposition method of polycarbonate resin

[0121] According to still another embodiment of the present disclosure, there may be provided a method for decomposing a polycarbonate-based resin, the method including subjecting the polycarbonate-based resin to a depolymerization reaction in the presence of the catalyst for depolymerization of the polycarbonate-based resin according to one embodiment.

[0122] Specifically, the method for decomposing a polycarbonate-based resin may include a step of subjecting the polycarbonate-based resin to a depolymerization reaction in the presence of a catalyst for depolymerization of the polycarbonate-based resin.

[0123] The depolymerization of polycarbonate resin is carried out by esterification reaction, wherein the esterification reaction includes a method using an acid catalyst or a method using a base catalyst. The acid catalyst reaction causes the hydrogen cation to react with the oxygen of the carbonyl group of the polycarbonate, which helps the nucleophilic attack of the alcohol on the carbonyl group. In addition, the base catalyst reaction causes it to interact with the hydrogen of the hydroxyl group of the alcohol to form an alkoxy group, which helps the nucleophilic attack on the carbonyl group of the polycarbonate.

[0124] The catalyst for depolymerization of a polycarbonate resin according to one embodiment is an ionic liquid, which is a salt composed of cations and anions, and which functions as an acid catalyst and a base catalyst at the same time, whereby when the step of subjecting the polycarbonate resin to a depolymerization reaction is performed in the presence of the catalyst for depolymerization of a polycarbonate resin according to one embodiment, the depolymerization reactivity can be improved.

[0125] The content of the catalyst for depolymerization of the polycarbonate resin includes all the contents in the above one embodiment. However, based on 100 parts by weight of the polycarbonate resin, the content of the catalyst may be 5 parts by weight to 90 parts by weight, or 10 parts by weight to 88 parts by weight. By including the catalyst within the above content range, there is an advantage that the catalytic reaction can be carried out economically.

[0126] Polycarbonate resins include one or both of homopolymers and copolymers containing polycarbonate repeating units, collectively referred to as reaction products obtained by polymerization or copolymerization of monomers including aromatic diol compounds and carbonate precursors. When containing one type of carbonate repeating unit obtained by using only one aromatic diol compound and one carbonate precursor, a homopolymer can be synthesized.

[0127] In addition, when by using a kind of aromatic diol compound and two or more carbonate precursors as monomer, or use two or more aromatic diol compounds and a carbonate precursor, or when also using one or more other glycols to comprise two or more carbonates except a kind of aromatic diol compound and a carbonate precursor, can synthetic copolymer.According to molecular weight range, homopolymer or copolymer can comprise all low molecular weight compounds, oligomer and polymkeric substance.

[0128] The polycarbonate-based resin may be applied regardless of various forms and types, such as a new polycarbonate-based resin produced by synthesis, a recycled polycarbonate-based resin produced by a recycling process, or a polycarbonate-based resin waste.

[0129] However, if necessary, before the depolymerization reaction of the polycarbonate resin is carried out, a pretreatment process of the polycarbonate resin can be carried out to improve the process efficiency of recovering the aromatic diol compound and the carbonate precursor from the polycarbonate resin. Examples of the pretreatment process include washing, drying, pulverization and diol decomposition, and there is no limitation on the specific methods of the various pretreatment processes, and various methods widely used in the process of recovering the aromatic diol compound and the carbonate precursor by depolymerization of the polycarbonate resin can be applied without limitation.

[0130] In addition, the depolymerization reaction of the polycarbonate resin can be carried out in the presence of an alcohol solvent. More specifically, the alcohol can be ethanol. The advantage of the present disclosure is that the polycarbonate resin can be decomposed with a solvent including ethanol to stably obtain high-purity monomer bisphenol A, and further obtain diethyl carbonate with high added value as a reaction byproduct.

[0131] Based on 100 parts by weight of the polycarbonate resin, the content of the alcohol may be 50 parts by weight to 250 parts by weight. Since alcohol has good solubility in bisphenol A, the alcohol within the above range should be substantially contained. If the content of the alcohol is excessively reduced relative to the polycarbonate resin, the alcohol decomposition of the polycarbonate resin may not be fully carried out. On the other hand, if the content of the alcohol is excessively increased relative to the polycarbonate resin, the economic feasibility of the process may be reduced due to excessive use of the alcohol.

[0132] Conventionally, the solvent for depolymerization of polycarbonate resins uses an organic solvent such as tetrahydrofuran, toluene, dichloromethane, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate or dipropyl carbonate in addition to alcohols such as ethanol to increase the solubility of polycarbonate resins.

[0133] However, in the decomposition method of the polycarbonate resin according to other embodiments, since the catalyst for depolymerization of the polycarbonate resin according to one embodiment is used, the solubility of the catalyst in the polycarbonate resin is high, so that the depolymerization reaction can be fully carried out without adding any organic solvent other than the alcohol solvent. Therefore, the use of organic solvents that require a separate wastewater treatment process can be reduced, thereby improving process efficiency.

[0134] Meanwhile, the temperature at which the depolymerization reaction of the polycarbonate-based resin is carried out is not particularly limited, but the reaction may be carried out, for example, at 50° C. to 95° C., or 60° C. to 95° C., or 85° C. to 95° C. In addition, the depolymerization reaction of the polycarbonate-based resin may be carried out for 1 hour to 100 hours, or 1 hour to 30 hours, or 2 hours to 24 hours.

[0135] Specifically, the above conditions are mild process conditions relative to the existing pressurized / high temperature process, and by stirring under the above conditions, the process can be performed in a mild process compared to the pressurized / high temperature process. Specifically, when stirring is performed at 50° C. to 70° C. for 4 to 6 hours, there is an advantage that the most effective results can be obtained in terms of reproducibility and identifiability.

[0136] That is, the advantages of the present disclosure are that even without using an organic catalyst, the type and amount of the mixed solvent and the type and content of the alkali catalyst can be adjusted to obtain a high-purity aromatic diol compound (e.g., bisphenol A) under mild conditions without using a pressurized / high-temperature process, and diethyl carbonate can be obtained as a by-product by using an ethanol solvent.

[0137] Meanwhile, the method for decomposing a polycarbonate-based resin according to other embodiments may further include a step of obtaining an aromatic diol compound after the step of subjecting the polycarbonate-based resin to a depolymerization reaction in the presence of a catalyst for depolymerization of the polycarbonate-based resin.

[0138] Specific examples of the aromatic diol compound 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-hydroxyphenyl)butane, Preferably, the aromatic diol compound may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0139] The aromatic diol compound is characterized in that it is recovered from a polycarbonate-based resin. That is, in addition to being recovered from a polycarbonate-based resin, when a new aromatic diol compound is added from the outside, it is not included in the category of the aromatic diol compound of the present disclosure. "Recovered from a polycarbonate-based resin" means obtained by a depolymerization reaction of a polycarbonate-based resin.

[0140] The step of obtaining the aromatic diol compound may include the steps of adding water and an organic solvent to the depolymerization reaction product; separating an organic solvent layer containing the aromatic diol compound; and removing the organic solvent contained in the organic solvent layer.

[0141] In the step of adding water and an organic solvent to the depolymerization reaction product, as the organic solvent, an acetate-based solvent or an ether-based solvent may be used, and more specifically, diethyl ether may be used. As water and an organic solvent are added to the depolymerization reaction product, the depolymerization reaction product may form a layer divided into a water layer containing a catalyst and an organic solvent layer containing an aromatic diol compound.

[0142] In the step of separating the organic solvent layer containing the aromatic diol compound, the organic solvent layer may be separated from the water layer in a layer separated into a water layer containing the catalyst and an organic solvent layer containing the aromatic diol compound. There is no particular limitation on the specific separation conditions for separating the organic solvent layer from the water layer, and for the specific separation device and method, various purification techniques previously known in the art may be applied without limitation. However, as an example, a drainage device may be used.

[0143] In the step of removing the organic solvent contained in the organic solvent layer, there is no particular limitation on the specific organic solvent removal conditions, but as an example, an evaporator can be used. For a specific evaporator and method, various evaporators known in the art can be applied without limitation. However, as an example, a rotary evaporator can be used.

[0144] The aromatic diol compound obtained above can be recovered without a separate separation and purification process, or if necessary, can be recovered after undergoing separation and purification such as conventional extraction, adsorption and drying. There is no particular limitation on specific purification conditions, and for specific purification equipment and methods, various purification techniques previously known in the art can be applied without limitation.

[0145] Furthermore, if necessary, the method may further include a step of drying the obtained aromatic diol compound.

[0146] The remaining solvent may be removed by drying, and there is no particular limitation on the specific drying conditions, but for example, the drying may be performed at a temperature of 10° C. to 100° C. or 10° C. to 50° C. As for the specific drying equipment and method used in the drying process, various known drying techniques may be applied without limitation.

[0147] 4. Method for recovering catalyst for depolymerization of polycarbonate resin

[0148] According to another embodiment of the present disclosure, a method for recovering a catalyst for depolymerization of a polycarbonate resin may be provided, the method comprising the following steps: subjecting a polycarbonate resin to a depolymerization reaction in the presence of a catalyst for depolymerization of a polycarbonate resin according to one embodiment; adding water and an organic solvent to the depolymerization reaction product; separating a water layer containing the catalyst for depolymerization of a polycarbonate resin; and removing water contained in the water layer.

[0149] Specifically, the method for recovering a polycarbonate-based resin depolymerization catalyst according to another embodiment may include a step of subjecting a polycarbonate-based resin to a depolymerization reaction in the presence of the polycarbonate-based resin depolymerization catalyst according to one embodiment.

[0150] The content of the catalyst for depolymerization of the polycarbonate resin includes all the contents in the above-mentioned embodiment. In addition, the content of the step of subjecting the polycarbonate resin to a depolymerization reaction in the presence of the catalyst for depolymerization of the polycarbonate resin according to one embodiment includes all the contents in the above-mentioned method for decomposing the polycarbonate resin.

[0151] The method for recovering a catalyst for depolymerization of a polycarbonate resin according to another embodiment may include the step of adding water and an organic solvent to the depolymerization reaction product. In the step of adding water and an organic solvent to the depolymerization reaction product, as the organic solvent, an acetate solvent or an ether solvent may be used, and more specifically, diethyl ether may be used. As water and an organic solvent are added to the depolymerization reaction product, the depolymerization reaction product may form a layer divided into a water layer containing the catalyst and an organic solvent layer containing the aromatic diol compound.

[0152] The recovery method of the catalyst for depolymerization of polycarbonate resin according to other embodiments may include the step of separating the water layer containing the catalyst for depolymerization of polycarbonate resin. In the step of separating the water layer containing the catalyst for depolymerization of polycarbonate resin, the water layer may be separated from the organic solvent layer in a layer divided into the water layer containing the catalyst and the organic solvent layer containing the aromatic diol compound. There is no specific limitation on the specific separation conditions for separating the water layer from the organic solvent layer, and for the specific separation device and method, various purification techniques previously known in the art may be applied without limitation. However, as an example, a drainage device may be used.

[0153] On the other hand, the method for recovering the catalyst for depolymerization of a polycarbonate-based resin according to other embodiments may include a step of removing water contained in the water layer. Therefore, the catalyst for depolymerization of a polycarbonate-based resin contained in the water layer may be recovered.

[0154] Specifically, the step of removing the water contained in the water layer may include the step of freeze drying the water. The step of freeze drying the water may be performed at a temperature of -90°C to -70°C for 1 hour to 100 hours. The catalyst recovered by such freeze drying may have high purity even when reused multiple times in the decomposition reaction of polycarbonate, and thus the decomposition rate of polycarbonate may be maintained at a high level.

[0155] Beneficial Effects

[0156] According to the present disclosure, there can be provided: a catalyst for depolymerization of a polycarbonate resin and a method for preparing the catalyst, which can recover the polycarbonate resin by chemical decomposition to ensure a high yield of aromatic diol compounds and can improve chemical decomposition reactivity and reaction efficiency; and a method for decomposing a polycarbonate resin by using the catalyst and a method for recovering the catalyst for depolymerization of a polycarbonate resin. DETAILED DESCRIPTION

[0157] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the following examples. However, the following examples are provided for illustrative purposes only, and the scope of the present disclosure is not intended to be limited thereto.

[0158] <Synthesis Example and Comparative Synthesis Example: Preparation of Catalyst>

[0159] Synthesis Example 1

[0160] 1-Methylimidazole and ethyl bromide were added to a 20 ml vial, and stirred at 70° C. for 24 hours. When the reaction was completed according to the following Reaction Scheme 1, Compound 1 was obtained as a pale yellow liquid.

[0161] [Reaction Scheme 1]

[0162]

[0163] Compound 1 and potassium acetate were added to methanol in equal moles and stirred. KBr salt produced according to the following reaction scheme 2 was removed by a filter to obtain compound 2 (1-ethyl-3-methylimidazolium acetate ([EMIM][Ac])) as a light yellow liquid.

[0164] [Reaction Scheme 2]

[0165]

[0166] Synthesis Example 2

[0167] Compound 3 was obtained in the same manner as in Synthesis Example 1 according to the following Reaction Scheme 3, except that ethyl chloride was used instead of ethyl bromide in Synthesis Example 1.

[0168] [Reaction Scheme 3]

[0169]

[0170] Compound 3 and potassium acetate were added to methanol in equal moles and stirred. KCl salt produced according to the following reaction scheme 4 was removed by a filter to obtain compound 4 (1-ethyl-3-methylimidazolium acetate ([EMIM][Ac])) as a light yellow liquid.

[0171] [Reaction Scheme 4]

[0172]

[0173] Comparative Synthesis Example 1

[0174] Compound 5 was obtained in the same manner as in Synthesis Example 1 according to the following Reaction Scheme 5, except that 1-bromobutane was used instead of bromoethane in Synthesis Example 1.

[0175] [Reaction Scheme 5]

[0176]

[0177] Compound 5 and potassium acetate were added to methanol in equal moles and stirred. KBr salt produced according to the following reaction scheme 6 was removed by a filter to obtain compound 6 (1-n-butyl-3-methylimidazolium acetate, [BMIM][Ac]) as a light yellow liquid.

[0178] [Reaction Scheme 6]

[0179]

[0180] <Examples and Comparative Examples>

[0181] Example 1

[0182] (1) Decomposition of polycarbonate

[0183] In a 20 ml vial, polycarbonate (PC) and the catalyst [EMIM][Ac] obtained in Synthesis Example 1 or Synthesis Example 2 were added in a ratio of polycarbonate:[EMIM][Ac]=2:1 (weight ratio), and EtOH was added in an amount of 50 wt % relative to PC, and the mixture was stirred at a reaction temperature of 90° C. for 10 hours to carry out a depolymerization reaction.

[0184] (2) Obtaining bisphenol A

[0185] Water (1 to 5 equivalents) and diethyl ether are added to the solution after the depolymerization reaction is completed. At this time, the catalyst [EMIM] [Ac] is separated into a water layer, and the depolymerization reaction product, bisphenol A (BPA), is separated into a diethyl ether layer, so that the water layer and the diethyl ether layer are separated. Using a rotary evaporator, bisphenol A contained in the separated diethyl ether layer is obtained.

[0186] (3) Catalyst recovery

[0187] The aqueous layer separated in step (2) was freeze-dried at -80°C for 72 hours to remove water, and the [EMIM][Ac] catalyst was recovered.

[0188] Example 2 to Example 15, Comparative Example 1 to Comparative Example 3

[0189] (1) Decomposition of polycarbonate

[0190] The depolymerization reaction was carried out in the same manner as in (1) of Example 1, except that the depolymerization reaction conditions were changed as described in Table 1 below.

[0191] (2) Obtaining bisphenol A

[0192] Bisphenol A was obtained in the same manner as in Example 1 (2).

[0193] (3) Catalyst recovery

[0194] The catalyst was recovered in the same manner as in Example 1 (3).

[0195] <Experimental Example 1>

[0196] 1. PC decomposition

[0197] By sampling the partially decomposed reactants and 1 H NMR was used to measure the degree of decomposition of polycarbonate. 1 H NMR measures the amount of unreacted material that may be produced at regular time intervals (approximately 2 hours) during the reaction for a total of 24 hours.

[0198] 2. Yield of Bisphenol A (BPA)

[0199] The weight of BPA generated when the polycarbonate used in the reaction was 100% decomposed was measured, and the weight of the obtained BPA was measured to calculate the yield of BPA according to the following Equation 1.

[0200] [Equation 1]

[0201] Yield (%) = (W 1 / W 0 )×100(%)

[0202] Where, in Equation 1, W 0 is the mass of BPA obtained when 100% decomposed, W 1 The mass of BPA actually obtained is (80 / 89)*100=90%. Specifically, when about 100g of polycarbonate is decomposed, the mass of BPA obtained when 100% of the decomposition is theoretically 89g. If the mass of BPA actually obtained is 80g, the yield is (80 / 89)*100=90%.

[0203] [Table 1]

[0204] Measurement results of Experimental Example 1

[0205]

[0206]

[0207] As shown in Table 1, it can be confirmed that Example 3 showed 100% PC decomposition and 99.9% BPA yield, while Comparative Example 3, in which only the catalyst was changed to [BMIM][Ac] under the same reaction conditions, showed 99.5% PC decomposition and 98.8% BPA yield, which were worse than those of Example 3.

[0208] Under the same principle, when Example 11 is compared with Comparative Example 1, or Example 12 is compared with Comparative Example 2, the comparative example in which only the catalyst is changed to [BMIM][Ac] under the same reaction conditions shows inferior results to those in the examples.

[0209] <Experimental Example 2>

[0210] 1. Performance evaluation of recovered catalyst

[0211] For the [EMIM][Ac] catalyst recovered in Example 3 and the [BMIM][Ac] catalyst recovered in Comparative Example 3, polycarbonate decomposition and catalyst recovery were repeated a total of 5 times, and the following physical properties were measured for each catalyst reuse cycle to evaluate catalyst performance. For the catalyst recovered in Example 3, the process of polycarbonate decomposition and catalyst recovery was repeated in the same manner as in Example 3, and for the catalyst recovered in Comparative Example 3, the process of polycarbonate decomposition and catalyst recovery was repeated a total of 5 times in the same manner as in Comparative Example 3.

[0212] (1) PC decomposition

[0213] By sampling a portion of the reactants that have completed decomposition and 1 H NMR was used to measure the degree of decomposition of polycarbonate. 1 H NMR measures the amount of unreacted material that may be produced at regular time intervals (approximately 2 hours) during the reaction for a total of 24 hours.

[0214] (2) Yield of bisphenol A (BPA)

[0215] The weight of BPA generated when the polycarbonate used in the reaction was 100% decomposed was measured, and the weight of the obtained BPA was measured to calculate the yield of BPA according to the following Equation 1.

[0216] [Equation 1]

[0217] Yield (%) = (W 1 / W 0 )×100(%)

[0218] Where, in Equation 1, W 0 is the mass of BPA obtained when 100% decomposed, W 1 The mass of BPA actually obtained is (80 / 89)*100=90%. Specifically, when about 100g of polycarbonate is decomposed, the mass of BPA obtained when 100% of the decomposition is theoretically 89g. If the mass of BPA actually obtained is 80g, the yield is (80 / 89)*100=90%.

[0219] (3) Catalyst recovery rate

[0220] The catalyst recovery rate was calculated by dividing the weight of the catalyst recovered after the reaction by the weight of the catalyst charged before the reaction, and multiplying the resulting value by 100.

[0221] (4) Catalyst purity

[0222] The recovered catalyst was diluted with DMSO-d6 to a concentration of 10 mg / ml to prepare a sample, and an NMR spectrum detected by a 1HNMR apparatus was obtained. The area ratio of the catalyst peak in the catalyst peak and the bisphenol A (BPA) peak was measured and used as the catalyst purity.

[0223] Specifically, for [EMIM][Ac], the target peaks of the catalyst are 9.9-9.6 ppm (s, 1H) and 7.8:7.7 ppm (t, 1H); for [BMIM][Ac], the peaks are 9.6-9.5 ppm (s, 1H), 7.8:7.7 (t, 1H) ppm; and for bisphenol A (BPA), the peak is 6.67 ppm (d, 4CH), and the catalyst purity is calculated using the following equation 2.

[0224] [Equation 2]

[0225] Catalyst purity (%) = {(peak area of ​​catalyst) / 3×100} / (peak area of ​​catalyst / 3+peak area of ​​BPA / 4).

[0226] [Table 2]

[0227] Measurement results of Experimental Example 2

[0228]

[0229] As shown in Table 2, it can be confirmed that Example 3 has a high bisphenol A yield of 95.2% and a high catalyst recovery rate of 99.9% even when the catalyst was reused five times.

[0230] On the other hand, it can be confirmed that Comparative Example 3 has a bisphenol A yield of 90.14%, which is lower than that of Example 3, and a catalyst recovery rate of 98.3%, which is lower than that of Example 3, when the catalyst is reused five times.

Claims

1. A catalyst for depolymerization of a polycarbonate resin, comprising a compound represented by the following chemical formula 1: [Chemical formula 1] in, In Chemical Formula 1, R1 and R2 are linear alkyl groups having 1 to 3 carbon atoms.

2. The catalyst for depolymerization of polycarbonate resin according to claim 1, wherein: R1 and R2 are straight-chain alkyl groups having 1 to 2 carbon atoms.

3. The catalyst for depolymerization of polycarbonate resin according to claim 1, wherein: R1 and R2 are different from each other.

4. The catalyst for depolymerization of polycarbonate resin according to claim 1, wherein: One of R1 and R2 is an ethyl group, and the other is a methyl group.

5. The catalyst for depolymerization of polycarbonate resin according to claim 1, wherein: The compound represented by Chemical Formula 1 is a compound represented by the following Chemical Formula 1-1: [Chemical formula 1-1] 6. A method for preparing a catalyst for depolymerization of a polycarbonate resin, the method comprising the following steps: reacting 1-alkyl-imidazole with an alkyl halide to prepare a compound represented by the following Chemical Formula 4; The compound represented by Chemical Formula 4 is reacted with an alkali metal acetate: [Chemical formula 4] In Chemical Formula 4, R3 and R4 are linear alkyl groups having 1 to 3 carbon atoms, and X is a halogen.

7. The method for preparing a catalyst for depolymerization of polycarbonate resin according to claim 6, wherein: The 1-alkyl-imidazole is a compound represented by the following Chemical Formula 7: [Chemical formula 7] In Chemical Formula 7, R3 is the same as R3 in Chemical Formula 4.

8. The method for preparing a catalyst for depolymerization of polycarbonate resin according to claim 6, wherein: The alkyl halide is a compound represented by the following Chemical Formula 8: [Chemical formula 8] R4-X In Chemical Formula 8, R4 is the same as R3 in Chemical Formula 4, and X is a halogen.

9. The method for preparing the catalyst for depolymerization of polycarbonate resin according to claim 6, Further comprising removing the alkali metal halide after reacting the compound represented by Chemical Formula 4 with the alkali metal acetate. 10 . A method for decomposing a polycarbonate resin, comprising subjecting the polycarbonate resin to a depolymerization reaction in the presence of the catalyst for depolymerization of the polycarbonate resin according to claim 1 .

11. The method for decomposing a polycarbonate resin according to claim 10, wherein: The catalyst may be included in an amount of 5 to 90 parts by weight based on 100 parts by weight of the polycarbonate-based resin.

12. The method for decomposing a polycarbonate resin according to claim 10, wherein: The depolymerization of the polycarbonate resin is carried out in the presence of an alcohol solvent.

13. The method for decomposing a polycarbonate resin according to claim 12, wherein: The alcohol may be included in an amount of 50 to 250 parts by weight based on 100 parts by weight of the polycarbonate-based resin.

14. The method for decomposing a polycarbonate resin according to claim 12, wherein: The alcohol is ethanol.

15. The method for decomposing a polycarbonate resin according to claim 10, wherein: The depolymerization of the polycarbonate-based resin is performed at a temperature of 50° C. to 95° C. for 1 hour to 100 hours.

16. The method for decomposing a polycarbonate resin according to claim 10, The method further comprises subjecting the polycarbonate resin to a depolymerization reaction in the presence of a catalyst for depolymerization of the polycarbonate resin to obtain the aromatic diol compound.

17. The method for decomposing a polycarbonate resin according to claim 16, wherein: The aromatic diol compound obtained comprises: adding water and an organic solvent to the depolymerization reaction product; separating an organic solvent layer containing the aromatic diol compound; as well as The organic solvent contained in the organic solvent layer is removed.

18. A method for recovering a catalyst for depolymerization of a polycarbonate resin, the method comprising the following steps: Depolymerizing the polycarbonate resin in the presence of the catalyst for depolymerization of the polycarbonate resin according to claim 1; adding water and an organic solvent to the depolymerization reaction product; separating an aqueous layer containing a catalyst for depolymerization of a polycarbonate resin; and The water contained in the water layer is removed.

19. The method for recovering a catalyst for depolymerization of a polycarbonate resin according to claim 18, wherein: The removing of water contained in the water layer includes freeze-drying the water.

20. The method for recovering a catalyst for depolymerization of a polycarbonate resin according to claim 19, wherein: The freeze-drying of water is performed at a temperature of -90°C to -70°C for 1 hour to 100 hours.

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