Catalyst for depolymerization of polycarbonate-based resin, method for preparing same, method for decomposing polycarbonate-based resin using same, and method for recovering catalyst for depolymerization of polycarbonate-based resin

Abstract

The present invention relates to: a catalyst for depolymerization of a polycarbonate-based resin, comprising a compound represented by chemical formula 1; a method for preparing same; a method for decomposing a polycarbonate-based resin using same; and a method for recovering the catalyst for depolymerization of a polycarbonate-based resin.

Description

Catalyst for depolymerization of polycarbonate resin, method for producing same, method for decomposing polycarbonate resin using same, and method for recovering catalyst for depolymerization of polycarbonate resin

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

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0099505, filed July 31, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a catalyst for depolymerizing a polycarbonate resin, a method for producing the same, a method for decomposing a polycarbonate resin using the same, and a method for recovering a catalyst for depolymerizing a polycarbonate resin.

[0004] Polycarbonate is a plastic that is used in a wide range of fields, including industrial products such as various optical products, electronic products, and building materials, as well as daily necessities such as water bottles and tableware, due to its high heat resistance, impact resistance, and transparent optical properties.

[0005] Polycarbonate is often produced with a variety of colors and properties depending on the application, making physical recycling methods inappropriate. Furthermore, the recycled plastic produced through this process also suffers from a relatively large deterioration in its properties.

[0006] The depolymerization process is a chemical recycling method that recovers polycarbonate waste as the raw material, bisphenol A, and then reuses it in plastic production. It is a recycling method that can overcome the deterioration of physical properties that occurs in physical recycling and reduce the production of additional bisphenol A.

[0007] Conventional depolymerization processes utilize acid or base catalysts for polycarbonate depolymerization. However, these catalysts corrode equipment and require wastewater treatment and neutralization within the process. Furthermore, acid or base catalysts are uneconomical because the neutralization reaction terminates the reaction and makes it impossible to recover the catalyst.

[0008] Accordingly, there is a need to develop a new catalyst that can replace the acid or base catalysts that have been used in the past.

[0009] The present invention provides a catalyst for depolymerization of polycarbonate resin and a method for producing the same, which can secure an aromatic diol compound in a high yield through recycling by chemical decomposition of polycarbonate resin and improve chemical decomposition reactivity and reaction efficiency.

[0010] In addition, the present invention provides a method for decomposing a polycarbonate resin using the above-described catalyst for depolymerizing a polycarbonate resin, and a method for recovering a catalyst for depolymerizing a polycarbonate resin.

[0011] In order to solve the above problem, the present specification provides a catalyst for depolymerizing a polycarbonate resin, comprising a compound represented by the following chemical formula 1.

[0012] [Chemical Formula 1]

[0013]

[0014] In the above chemical formula 1, R1 and R2 are straight-chain alkyl having 1 to 3 carbon atoms.

[0015] The present specification also provides a method for producing a catalyst for depolymerizing a polycarbonate resin, comprising the steps of: reacting 1-alkyl-imidazole and an alkyl halide to produce a compound represented by the following chemical formula 4; and reacting the compound represented by the above chemical formula 4 with an alkali metal acetate.

[0016] [Chemical Formula 4]

[0017]

[0018] In the above chemical formula 4, R3 and R4 are straight-chain alkyl having 1 to 3 carbon atoms, and X is halogen.

[0019] The present specification also provides a method for decomposing a polycarbonate resin, comprising a step of depolymerizing the polycarbonate resin in the presence of a catalyst for depolymerizing the polycarbonate resin.

[0020] The present specification also provides a method for recovering a catalyst for depolymerizing a polycarbonate resin, comprising: a step of depolymerizing a polycarbonate resin in the presence of the catalyst for depolymerizing the polycarbonate resin; a step of adding water and an organic solvent to the depolymerization product; a step of separating an aqueous layer containing the catalyst for depolymerizing the polycarbonate resin; and a step of removing water contained in the aqueous layer.

[0021] Hereinafter, a catalyst for depolymerizing a polycarbonate resin according to a specific embodiment of the invention, a method for producing the same, a method for decomposing a polycarbonate resin using the same, and a method for recovering a catalyst for depolymerizing a polycarbonate resin will be described in more detail.

[0022]

[0023] Unless explicitly stated otherwise in this specification, terminology is used only to describe specific embodiments and is not intended to limit the invention.

[0024] As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In this specification, examples of substituents are described below, but are not limited thereto.

[0029] In this specification, the term "substitution" means that another functional group is bonded instead of a hydrogen atom in a compound, and the position of substitution is not limited as long as it is a position where a hydrogen atom is substituted, i.e., a position where a substituent can be substituted, and when two or more are substituted, the two or more substituents may be the same or different from each other.

[0030] 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. For example, a "substituent having two or more substituents connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group, or may be interpreted as a substituent having two phenyl groups connected.

[0031] 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, 2-methylpentyl, 4-methylhexyl, Examples thereof include, but are not limited to, 5-methylhexyl, 2,6-dimethylheptan-4-yl, etc. The alkyl group may be substituted or unsubstituted, and examples of the substituent when substituted are as described above.

[0032] In this specification, examples of halogen include fluorine, chlorine, bromine or iodine.

[0033]

[0034] 1. Catalyst for depolymerization of polycarbonate resins

[0035] According to one embodiment of the invention, a catalyst for depolymerizing a polycarbonate resin can be provided, comprising a compound represented by the following chemical formula 1.

[0036] [Chemical Formula 1]

[0037]

[0038] In the above chemical formula 1, R1 and R2 are straight-chain alkyl having 1 to 3 carbon atoms.

[0039] The inventors of the present invention have experimentally confirmed that the catalyst for depolymerization of a polycarbonate resin according to the above-described embodiment can secure an aromatic diol compound in a high yield through recycling by chemical decomposition of a polycarbonate resin, and can improve chemical decomposition reactivity and reaction efficiency, thereby completing the invention.

[0040] Specifically, the catalyst for depolymerizing a polycarbonate resin of the above embodiment may include a compound represented by the above chemical formula 1. The compound represented by the above chemical formula 1 is a salt composed of an imidazolium cation and an acetate anion, and can simultaneously function as an acid catalyst and a base catalyst.

[0041] That is, the compound represented by chemical formula 1, which is a catalyst for depolymerizing a polycarbonate resin of the above-described embodiment, corresponds to an ionic liquid, which is a salt that maintains a liquid phase over a wide temperature range due to structural asymmetry between ions composed of cations and anions.

[0042] Acid catalysts or base catalysts previously used as catalysts for depolymerization of polycarbonate resins have the problem of corroding equipment and requiring wastewater treatment and neutralization processes within the process, and have the disadvantage of being uneconomical because the reaction is terminated through the neutralization reaction and the catalyst cannot be recovered.

[0043] On the other hand, the compound represented by the above chemical formula 1 is an ionic liquid, so there is no need for reactor management or replacement due to reactor corrosion, and since a separate neutralization process is not required, the catalyst can be recovered and recycled, so it can act as a catalyst that is economically and environmentally superior to existing acid catalysts or base catalysts.

[0044] In addition, the catalyst for depolymerizing a polycarbonate-based resin of the above embodiment is an ionic liquid that is a salt composed of cations and anions and simultaneously functions as an acid catalyst and a base catalyst, so that when a step of depolymerizing a polycarbonate-based resin is performed in the presence of the catalyst for depolymerizing a polycarbonate-based resin of the above embodiment, the depolymerization reactivity can be improved.

[0045] In addition, the compound represented by the above chemical formula 1 has high selective solubility and is thermally and chemically stable, enabling high-yield and high-efficiency depolymerization of polycarbonate resins. Specifically, the catalyst for depolymerization of polycarbonate resins of the above embodiment has high solubility in polycarbonate resins, allowing the depolymerization reaction to proceed sufficiently without the addition of any organic solvent other than alcohol. Accordingly, the use of organic solvents requiring a separate wastewater treatment process can be reduced, thereby increasing process efficiency.

[0046] In the above chemical formula 1, R1 and R2 may be straight-chain alkyl having 1 to 3 carbon atoms. That is, in the above chemical formula 1, both R1 and R2 are straight-chain alkyl having 1 to 3 carbon atoms. Examples of the straight-chain alkyl having 1 to 3 carbon atoms include methyl, ethyl, and propyl.

[0047] In the above chemical formula 1, since R1 and R2 satisfy a straight-chain alkyl having 1 to 3 carbon atoms, the depolymerization reactivity of the polycarbonate resin is improved due to the structurally small steric effect and chemically large basicity, so that the decomposition efficiency of the polycarbonate resin can be increased, 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 that even if it is repeatedly reused multiple 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 at least one of R1 and R2 in the above chemical formula 1 is a straight-chain alkyl having 4 or more carbon atoms, the depolymerization reactivity of the polycarbonate resin or the yield of bisphenol A may decrease due to the structurally large steric effect and chemically low basicity. In addition, if the polycarbonate resin is recovered and reused after the depolymerization reaction, there is a limitation in 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 decrease in purity and recovery rate.

[0049] Specifically, in the above chemical formula 1, R1 and R2 may be straight-chain alkyl having 1 to 2 carbon atoms. That is, in the above chemical formula 1, both R1 and R2 are straight-chain alkyl having 1 to 2 carbon atoms. Examples of the straight-chain alkyl having 1 to 2 carbon atoms include methyl and ethyl.

[0050] In addition, in the above chemical formula 1, R1 and R2 may be different from each other. One of R1 and R2 may be ethyl, and the other may be methyl. That is, if R1 is ethyl, R2 is It can be methyl. Also, if R1 is ethyl, R2 can be methyl.

[0051] More specifically, the compound represented by the above chemical formula 1 may be a compound represented by the following chemical formula 1-1.

[0052] [Chemical Formula 1-1]

[0053]

[0054] Meanwhile, the compound represented by the above chemical formula 1 may be represented by a compound represented by the following chemical formula 2. Alternatively, the catalyst for depolymerizing the polycarbonate resin may include a compound represented by the following chemical formula 2.

[0055] [Chemical Formula 2]

[0056]

[0057] In the above chemical formula 2, R1 and R2 include the contents described above in the above chemical formula 1. More specifically, the compound represented by the above 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 the above chemical formula 1 and the compound represented by the above chemical formula 2 correspond to each other's resonance structure.

[0061] That is, the compound represented by the above chemical formula 1 may be represented by a compound represented by the following chemical formula 3. Alternatively, the catalyst for depolymerizing the polycarbonate resin may include a compound represented by the following chemical formula 3.

[0062] [Chemical Formula 3]

[0063]

[0064] In the above chemical formula 3, R1 and R2 include the contents described above in the above chemical formula 1. More specifically, the compound represented by the above chemical formula 3 may be a compound represented by the following chemical formula 3-1.

[0065] [Chemical Formula 3-1]

[0066] .

[0067]

[0068] 2. Method for manufacturing a catalyst for depolymerization of polycarbonate resins

[0069] According to another embodiment of the invention, a method for producing a catalyst for depolymerizing a polycarbonate resin may be provided, comprising: a step of reacting 1-alkyl-imidazole and an alkyl halide to produce a compound represented by the following chemical formula 4; and a step of reacting the compound represented by the chemical formula 4 with an alkali metal acetate.

[0070] [Chemical Formula 4]

[0071]

[0072] In the above chemical formula 4, R3 and R4 are straight-chain alkyl having 1 to 3 carbon atoms, and X is halogen.

[0073] Specifically, the method for producing a catalyst for depolymerizing a polycarbonate resin of the above other embodiments may include a step of reacting 1-alkyl-imidazole and an alkyl halide to produce a compound represented by the following chemical formula 4.

[0074] The above 1-alkyl-imidazole is a compound in which alkyl is bonded to the 1st nitrogen of the imidazole compound, and can be represented by the following chemical formula 7.

[0075] [Chemical Formula 7]

[0076]

[0077] In the above chemical formula 7, R3 is the same as R3 in the above chemical formula 4. That is, in the above chemical formula 7, the description of R3 includes all descriptions of R3 in the above chemical formula 4.

[0078] Specifically, R3 is a straight-chain alkyl having 1 to 3 carbon atoms. Examples of the straight-chain alkyl having 1 to 3 carbon atoms include methyl, ethyl, and propyl. Specifically, in the above chemical formula 7, R3 is a straight-chain alkyl having 1 to 2 carbon atoms. Examples of the above straight-chain alkyl having 1 to 2 carbon atoms include methyl and ethyl. As a more specific example, in the above chemical formula 7, R3 may be methyl. That is, an example of a compound represented by the above chemical formula 7 may be 1-methyl-imidazole.

[0079] Meanwhile, the alkyl halide can be represented by the following chemical formula 8.

[0080] [Chemical Formula 8]

[0081] R4-X

[0082] In the above chemical formula 8, R4 is the same as R3 of the above chemical formula 4. That is, in the above chemical formula 8, the description of R4 includes all descriptions of R4 of the above chemical formula 4.

[0083] Specifically, R4 is a straight-chain alkyl having 1 to 3 carbon atoms. Examples of the straight-chain alkyl having 1 to 3 carbon atoms include methyl, ethyl, and propyl. Specifically, in the above chemical formula 8, R4 is a straight-chain alkyl having 1 to 2 carbon atoms. Examples of the above straight-chain alkyl having 1 to 2 carbon atoms include methyl and ethyl. As a more specific example, in the above chemical formula 8, R4 may be ethyl. In addition, in the above chemical formula 8, X is a halogen, and examples of the halogen include fluorine, chlorine, bromine, and iodine.

[0084] That is, examples of the compound represented by the above chemical formula 8 include ethyl bromide or ethyl chloride.

[0085] The compound obtained by reacting 1-alkyl-imidazole and alkyl halide can be represented by the following chemical formula 4.

[0086] [Chemical Formula 4]

[0087]

[0088] In the above chemical formula 4, R3 and R4 are straight-chain alkyl having 1 to 3 carbon atoms, and X is halogen.

[0089] In the above chemical formula 4, R3 and R4 may be straight-chain alkyl having 1 to 3 carbon atoms. That is, in the above chemical formula 1, both R1 and R2 are straight-chain alkyl having 1 to 3 carbon atoms. Examples of the straight-chain alkyl having 1 to 3 carbon atoms include methyl, ethyl, and propyl.

[0090] Specifically, in the above chemical formula 4, R3 and R4 may be straight-chain alkyl having 1 to 2 carbon atoms. That is, in the above chemical formula 4, both R3 and R4 are straight-chain alkyl having 1 to 2 carbon atoms. Examples of the above straight-chain alkyl having 1 to 2 carbon atoms include methyl and ethyl.

[0091] In addition, in the above chemical formula 4, R3 and R4 may be different from each other. One of R3 and R4 may be ethyl, and the other may be methyl. That is, if R3 is ethyl, R4 is It can be methyl. Also, if R4 is ethyl, R3 can be methyl.

[0092] X is a halogen, examples of halogens include fluorine, chlorine, bromine, or iodine.

[0093] More specifically, the compound represented by the above 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.

[0094] [Chemical Formula 4-1]

[0095]

[0096] [Chemical Formula 4-2]

[0097]

[0098] Meanwhile, the compound represented by the above chemical formula 4 can be represented by a compound represented by the following chemical formula 5.

[0099] [Chemical Formula 5]

[0100]

[0101] In the above chemical formula 5, R3, R4 and X include the contents described above in the above chemical formula 4. More specifically, the compound represented by the above 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.

[0102] [Chemical Formula 5-1]

[0103]

[0104] [Chemical Formula 5-2]

[0105]

[0106] That is, the compound represented by the above chemical formula 4 and the compound represented by the above chemical formula 5 correspond to resonance structures with each other. That is, the compound represented by the above chemical formula 4 can be represented by the compound represented by the following chemical formula 6.

[0107] [Chemical Formula 6]

[0108]

[0109] In the above chemical formula 6, R3, R4 and X include the contents described above in the above chemical formula 4. More specifically, the compound represented by the above 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.

[0110] [Chemical Formula 6-1]

[0111]

[0112] [Chemical Formula 6-2]

[0113]

[0114] The reaction conditions under which the above 1-alkyl-imidazole and alkyl halide reaction proceeds are not particularly limited, but for example, the reaction may proceed at a temperature of 50°C to 100°C for 1 hour to 100 hours.

[0115] Meanwhile, the method for producing a catalyst for depolymerizing a polycarbonate resin of the other embodiment may include a step of reacting a compound represented by the above chemical formula 4 with an alkali metal acetate.

[0116] The above alkali metal acetate may include potassium acetate.

[0117] The description of the compound represented by the above chemical formula 4 may include all of the above-described contents.

[0118] The reaction conditions for the step of reacting the compound represented by the above chemical formula 4 with an alkali metal acetate are not particularly limited, but for example, the reaction may be carried out in an alcohol solvent at room temperature (20 to 30°C).

[0119] Meanwhile, the method for manufacturing a catalyst for depolymerizing a polycarbonate resin of the other embodiment may further include a step of removing an alkali metal halide after the step of reacting the compound represented by the above chemical formula 4 with an alkali metal acetate.

[0120] When reacting the compound represented by the above chemical formula 4 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).

[0121]

[0122] 3. Method for decomposing polycarbonate resin

[0123] According to another embodiment of the invention, a method for decomposing a polycarbonate resin can be provided, comprising a step of depolymerizing a polycarbonate resin in the presence of a catalyst for depolymerizing a polycarbonate resin of the above embodiment.

[0124] Specifically, the method for decomposing a polycarbonate resin of the above other embodiments may include a step of depolymerizing the polycarbonate resin in the presence of a catalyst for depolymerizing the polycarbonate resin.

[0125] The depolymerization of the above polycarbonate resin proceeds through an esterification reaction, and the esterification reaction can be carried out using an acid catalyst or a base catalyst. The acid catalyst reacts with a hydrogen cation to the oxygen of the carbonyl group of the polycarbonate, thereby facilitating a nucleophilic attack of the alcohol on the carbonyl group. In addition, the base catalyst reacts with the hydrogen of the hydroxyl group of the alcohol to form an alkoxy group, thereby facilitating a nucleophilic attack on the carbonyl group of the polycarbonate.

[0126] The catalyst for depolymerizing a polycarbonate resin of the above embodiment is an ionic liquid that is a salt composed of cations and anions, and thus simultaneously functions as an acid catalyst and a base catalyst. Therefore, when a step of depolymerizing a polycarbonate resin is performed in the presence of the catalyst for depolymerizing a polycarbonate resin of the above embodiment, the depolymerization reactivity can be improved.

[0127] The content of the catalyst for depolymerization of the above polycarbonate resin includes all of the content described above in the above embodiment. However, the content of the catalyst may be 5 to 90 parts by weight, or 10 to 88 parts by weight, based on 100 parts by weight of the polycarbonate resin. By including a catalyst in the above content range, there is an advantage in that an economical catalytic reaction can be performed.

[0128] 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 precursor. When one carbonate repeating unit is contained using only one aromatic diol compound and one carbonate precursor, a homopolymer can be synthesized. In addition, a copolymer can be synthesized when two or more carbonates are contained by using one aromatic diol compound and two or more carbonate precursors as the monomer, or using two or more aromatic diol compounds and one carbonate precursor, or using one or more other diols in addition to one aromatic diol compound and one carbonate precursor. The homopolymer or copolymer can include all low molecular weight compounds, oligomers, and polymers according to the molecular weight range.

[0129] 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.

[0130] However, if necessary, before performing a 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 an aromatic diol compound and a carbonate precursor 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 an aromatic diol compound and a carbonate precursor by depolymerization of a polycarbonate resin can be applied without limitation.

[0131] In addition, the depolymerization reaction of the polycarbonate resin may be carried out in an alcohol solvent. More specifically, the alcohol may be ethanol. The present invention has the advantage of stably obtaining bisphenol A, a high-purity monomer, by decomposing the polycarbonate resin in a solvent including ethanol, and additionally obtaining diethyl carbonate, which has high added value, as a reaction byproduct.

[0132] The alcohol content may be 50 to 250 parts by weight based on 100 parts by weight of the polycarbonate resin. Since the alcohol has good solubility in bisphenol A, the alcohol within the above range must be included. If the alcohol content is excessively reduced compared to the polycarbonate resin, it is difficult for the alcohol decomposition of the polycarbonate resin to proceed sufficiently. On the other hand, if the alcohol content is excessively increased compared to the polycarbonate resin, the economic feasibility of the process may decrease due to excessive use of alcohol.

[0133] In the past, in addition to alcohols such as ethanol, solvents in which the depolymerization reaction of the polycarbonate resin proceeded were organic solvents such as tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, or dipropyl carbonate, to increase the solubility of the polycarbonate resin.

[0134] However, in the method for decomposing a polycarbonate resin according to the other embodiment, since the catalyst for depolymerizing a polycarbonate resin according to the one embodiment is used, the solubility of the catalyst in the polycarbonate resin is high, so that the depolymerization reaction can proceed sufficiently without adding any organic solvent other than an alcohol solvent. Accordingly, the use of an organic solvent requiring a separate wastewater treatment process can be reduced, thereby increasing the efficiency of the process.

[0135] 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, 50°C to 95°C, or 60°C to 95°C, or 85°C to 95°C. In addition, the time at which the depolymerization reaction of the polycarbonate resin is performed may be 1 hour to 100 hours, or 1 hour to 30 hours, or 2 hours to 24 hours.

[0136] 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.

[0137] 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 diethyl carbonate as a byproduct by using an ethanol solvent.

[0138] Meanwhile, the method for decomposing a polycarbonate resin of the other embodiment may further include a step of obtaining an aromatic diol compound after the step of depolymerizing the polycarbonate resin in the presence of a catalyst for depolymerizing the polycarbonate resin.

[0139] 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 may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0140] The above aromatic diol compound is characterized by being recovered from the polycarbonate resin. In other words, cases where a new aromatic diol compound is added externally separately from recovery from the polycarbonate resin are not included in the category of aromatic diol compounds of the present invention. Recovering from the polycarbonate resin means that it is obtained through a depolymerization reaction of the polycarbonate resin.

[0141] The step of obtaining the above aromatic diol compound may include a step of adding water and an organic solvent to a depolymerization reaction product; a step of separating an organic solvent layer containing the aromatic diol compound; and a step of removing the organic solvent contained in the organic solvent layer.

[0142] In the step of adding water and an organic solvent to the above-described depolymerization product, an acetate-based solvent or an ether-based solvent may be used as the organic solvent, and more specifically, diethyl ether may be used. By adding water and an organic solvent to the above-described depolymerization product, the above-described depolymerization product may form layers divided into a water layer containing a catalyst and an organic solvent layer containing an aromatic diol compound.

[0143] In the step of separating the organic solvent layer containing the aromatic diol compound, the organic solvent layer can be separated from the aqueous layer in layers divided into a water layer containing a catalyst and an organic solvent layer containing the aromatic diol compound. The specific separation conditions for separating the organic solvent layer from the aqueous layer are not particularly limited, and various conventionally known purification technologies can be applied without limitation to specific separation equipment and methods. However, as an example, a drain device can be used.

[0144] While the specific conditions for removing the organic solvent contained in the organic solvent layer are not particularly limited, an evaporation device may be used, for example. Various existing evaporation technologies can be applied without limitation to specific evaporation equipment and methods. However, a rotary evaporator, for example, may be used.

[0145] The aromatic diol compound obtained above 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.

[0146] Additionally, if necessary, a drying step may be further included for the obtained aromatic diol compound. The drying process can remove any remaining solvent, and while specific drying conditions are not particularly limited, drying may be performed at a temperature of, for example, 10°C to 100°C, or 10°C to 50°C. Various known drying technologies can be applied without limitation to the specific drying equipment and method used during the drying process.

[0147]

[0148] 4. Recovery method of catalyst for depolymerization of polycarbonate resin

[0149] According to another embodiment of the invention, a method for recovering a catalyst for depolymerizing a polycarbonate resin may be provided, comprising: a step of depolymerizing a polycarbonate resin in the presence of a catalyst for depolymerizing a polycarbonate resin of the above embodiment; a step of adding water and an organic solvent to the depolymerization product; a step of separating an aqueous layer containing the catalyst for depolymerizing a polycarbonate resin; and a step of removing water contained in the aqueous layer.

[0150] Specifically, the method for recovering a catalyst for depolymerizing a polycarbonate resin of the other embodiment may include a step of depolymerizing a polycarbonate resin in the presence of the catalyst for depolymerizing a polycarbonate resin of the one embodiment.

[0151] The content of the above polycarbonate resin depolymerization catalyst includes all of the content described above in the above embodiment. In addition, the content of the step of depolymerizing the polycarbonate resin in the presence of the polycarbonate resin depolymerization catalyst of the above embodiment includes all of the content described above in the method for decomposing a polycarbonate resin of the other embodiment.

[0152] The method for recovering a catalyst for depolymerizing a polycarbonate resin of the above-described other embodiment may include a step of adding water and an organic solvent to the depolymerization product. In the step of adding water and an organic solvent to the depolymerization product, the organic solvent may be an acetate solvent or an ether solvent, and more specifically, diethyl ether may be used. By adding water and an organic solvent to the depolymerization product, the depolymerization product may form a layer divided into a water layer containing a catalyst and an organic solvent layer containing an aromatic diol compound.

[0153] The method for recovering a catalyst for depolymerizing a polycarbonate resin of another embodiment of the present invention may include a step of separating an aqueous layer containing a catalyst for depolymerizing a polycarbonate resin. In the step of separating the aqueous layer containing the catalyst for depolymerizing a polycarbonate resin, the aqueous layer may be separated from the organic solvent layer in layers divided into an aqueous layer containing the catalyst and an organic solvent layer containing an aromatic diol compound. Specific separation conditions for separating the aqueous layer from the organic solvent layer are not particularly limited, and various conventionally known purification technologies may be applied without limitation to specific separation equipment and methods. However, for example, a drain device may be used.

[0154] Meanwhile, the method for recovering a polycarbonate resin depolymerization catalyst of the above-described other embodiment may include a step of removing water contained in the water layer. Through this, the polycarbonate resin depolymerization catalyst contained in the water layer can be recovered.

[0155] Specifically, the step of removing water contained in the water layer may include a 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 to 100 hours. The catalyst recovered through such freeze-drying can have a high purity even when reused multiple times in the polycarbonate decomposition reaction, thereby maintaining a high decomposition rate of the polycarbonate.

[0156] According to the present invention, a catalyst for depolymerization of polycarbonate resin, which can secure an aromatic diol compound at a high yield through recycling by chemical decomposition of polycarbonate resin and improve chemical decomposition reactivity and reaction efficiency, a method for producing the same, a method for decomposing polycarbonate resin using the same, and a method for recovering a catalyst for depolymerization of polycarbonate resin can be provided.

[0157]

[0158] 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.

[0159]

[0160] <Synthetic examples and comparative synthetic examples: Preparation of catalysts>

[0161] Synthesis Example 1

[0162] 1-methyl imidazole 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, a pale yellow liquid, was obtained.

[0163] [Reaction Formula 1]

[0164]

[0165] The above compound 1 and potassium acetate were added to methanol in equal molar amounts and stirred. The KBr salt produced according to the following reaction scheme 2 was removed by filtering, and compound 2 (1-ethyl-3-methylimidazolium acetate ([EMIM][Ac])) as a pale yellow liquid was obtained.

[0166] [Reaction Formula 2]

[0167]

[0168] Synthesis Example 2

[0169] Compound 3 was obtained according to the following reaction scheme 3 in the same manner as in Synthesis Example 1, except that ethyl chloride was used instead of ethyl bromide in Synthesis Example 1.

[0170] [Reaction Formula 3]

[0171]

[0172] The above compound 3 and potassium acetate were added to methanol in equal molar amounts and stirred. The KCl salt produced according to the following reaction scheme 4 was removed by filtering, and compound 4 (1-ethyl-3-methylimidazolium acetate ([EMIM][Ac])) as a pale yellow liquid was obtained.

[0173] [Reaction Formula 4]

[0174]

[0175]

[0176] Comparative synthesis example 1

[0177] Compound 5 was obtained according to the following reaction scheme 5 in the same manner as in Synthesis Example 1, except that 1-n-butyl bromide was used instead of ethyl bromide in Synthesis Example 1.

[0178] [Reaction Formula 5]

[0179] The above compound 5 and potassium acetate were added to methanol in equal molar amounts and stirred. The KBr salt produced according to the following reaction scheme 6 was removed by filtering, and compound 6 (1-n-butyl-3-methylimidazolium acetate, [BMIM][Ac]) as a pale yellow liquid was obtained.

[0180] [Reaction Formula 6]

[0181]

[0182]

[0183] <Examples and Comparative Examples>

[0184] Example 1

[0185] (1) Polycarbonate decomposition

[0186] Polycarbonate (PC) and the catalyst [EMIM][Ac] obtained in Synthesis Example 1 or Synthesis Example 2 were added to a 20 ml vial in a weight ratio of Polycarbonate:[EMIM][Ac] = 2:1, and EtOH was added in an amount of 50 wt% relative to PC, and the depolymerization reaction was carried out while stirring at a reaction temperature of 90°C for a reaction time of 10 hours.

[0187] (2) Obtaining bisphenol A

[0188] Water (1-5 equivalents) and diethyl ether were added to the solution after the depolymerization reaction was completed. At this time, the catalyst [EMIM][Ac] separated into the water layer, and the depolymerization reaction product, bisphenol A (BPA), separated into the diethyl ether layer. The water layer and the diethyl ether layer were separated. Bisphenol A contained in the separated diethyl ether layer was obtained using a rotary evaporator.

[0189] (3) Catalyst recovery

[0190] The water layer separated in the above step (2) was freeze-dried at a temperature of -80°C for 72 hours to remove water and recover the [EMIM][Ac] catalyst.

[0191]

[0192] Examples 2 to 15, Comparative Examples 1 to 3

[0193] (1) Polycarbonate decomposition

[0194] The depolymerization reaction was carried out in the same manner as (1) of Example 1, except that the depolymerization reaction conditions were changed as described in Table 1 below.

[0195] (2) Obtaining bisphenol A

[0196] Bisphenol A was obtained using the same method as (2) of Example 1 above.

[0197] (3) Catalyst recovery

[0198] The catalyst was recovered using the same method as (3) of Example 1 above.

[0199]

[0200] <Experimental Example 1>

[0201] 1. Disassemble the PC

[0202] The degree of decomposition of polycarbonate was measured by sampling a portion of the decomposed reactant. 1 It was confirmed through H NMR measurement. Specifically, the amount of unreacted products that could be generated during the reaction process for a total of 24 hours was measured at regular time intervals (approximately 2 hours) after the start of the reaction. 1 Measured by H NMR.

[0203]

[0204] 2. Bisphenol A (BPA) yield

[0205] The weight of BPA produced when the polycarbonate used in the reaction was 100% decomposed was measured, and the weight of BPA obtained was measured to calculate the yield of BPA as shown in Equation 1 below.

[0206] [Formula 1]

[0207] Yield (%) = (W1 / W0)X 100(%)

[0208] In the above equation 1, W0 is the mass of BPA obtained upon 100% decomposition, and W1 is the mass of BPA actually obtained. Specifically, when about 100 g of polycarbonate is decomposed, the mass of BPA theoretically obtained upon 100% decomposition is 89 g. If the mass of BPA actually obtained is 80 g, the yield is (80 / 89) * 100 = 90%.

[0209]

[0210] Experimental Example 1 Measurement Results Classification Catalyst Solvent PC: Catalyst: Solvent (Weight Ratio) Reaction Temperature (℃) Reaction Time (hr) PC Decomposition (%) BPA Yield (%) Example 1 [EMIM][Ac]EtOH2:1:1 90 10 10 0 9 6.5 Example 2 [EMIM][Ac]EtOH2:1:2 90 10 10 0 9 8.6 Example 3 [EMIM][Ac]EtOH2:1:3 90 10 10 0 9 9.9 Example 4 [EMIM][Ac]EtOH2:1:4 90 10 10 0 9 9.9 Example 5 [EMIM][Ac]EtOH2:1:5 90 10 10 0 9 9.9 Example 6 [EMIM][Ac]EtOH2:0.2:3 90 10 8 3.7 9 6.4 Example 7[EMIM][Ac]EtOH2:0.5:3901091.090.1Example 8[EMIM][Ac]EtOH2:1.25:3901010099.9Example 9[EMIM][Ac]EtOH2:1.5:3901010099.9Example 10[EMIM][Ac]EtOH2:1.75:3901010099.9Example 11[EMIM][Ac]EtOH2:1:390219.799.8Example 12[EMIM][Ac]EtOH2:1:390610096.9Example 13[EMIM][Ac]EtOH2:1:3901410099.9Example 14[EMIM][Ac]EtOH2:1:3901810099.9Example 15[EMIM][Ac]EtOH2:1:3902410099.9Comparative Example 1[BMIM][Ac]EtOH2:1:390212.514.6Comparative Example 2[BMIM][Ac]EtOH2:1:390694.496.9Comparative Example 3[BMIM][Ac]EtOH2:1:3901099.598.8

[0211] As shown in Table 1 above, 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 inferior to Example 3.

[0212] By the same principle, when comparing Example 11 with Comparative Example 1, or Example 12 with Comparative Example 2, the comparative example in which only the catalyst was changed to [BMIM][Ac] under the same reaction conditions showed worse results than the example.

[0213]

[0214] <Experimental Example 2>

[0215] 1. Performance evaluation of recovered catalyst

[0216] 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 number of catalyst reuses to evaluate the catalyst performance. The process of repeating the polycarbonate decomposition and catalyst recovery a total of 5 times was repeated in the same manner as in Example 3 for the catalyst recovered in Example 3, and in the same manner as in Comparative Example 3 for the catalyst recovered in Comparative Example 3.

[0217]

[0218] (1) PC disassembly

[0219] The degree of decomposition of polycarbonate was measured by sampling a portion of the decomposed reactant. 1 It was confirmed through H NMR measurement. Specifically, the amount of unreacted products that could be generated during the reaction process for a total of 24 hours was measured at regular time intervals (approximately 2 hours) after the start of the reaction. 1 Measured by H NMR.

[0220]

[0221] (2) Bisphenol A (BPA) yield

[0222] The weight of BPA produced when the polycarbonate used in the reaction was 100% decomposed was measured, and the weight of BPA obtained was measured to calculate the yield of BPA as shown in Equation 1 below.

[0223] [Formula 1]

[0224] Yield (%) = (W1 / W0)X 100(%)

[0225] In the above equation 1, W0 is the mass of BPA obtained upon 100% decomposition, and W1 is the mass of BPA actually obtained. Specifically, when about 100 g of polycarbonate is decomposed, the mass of BPA theoretically obtained upon 100% decomposition is 89 g. If the mass of BPA actually obtained is 80 g, the yield is (80 / 89) * 100 = 90%.

[0226]

[0227] (3) Catalyst recovery rate

[0228] The catalyst recovery rate was calculated by dividing the weight of the catalyst recovered after the reaction by the weight of the catalyst introduced before the reaction and multiplying the result by 100.

[0229]

[0230] (4) Catalyst purity

[0231] A sample was prepared by diluting the recovered catalyst with DMSO-d6 to a concentration of 10 mg / ml, and the NMR spectrum detected through 1H NMR equipment was obtained. The area ratio of the catalyst peak among the catalyst peak and bisphenol A (BPA) peak was measured, and this was used as the catalyst purity.

[0232] Specifically, the catalyst was targeted at peaks at 9.9 to 9.6 ppm (s, 1H) and 7.8:7.7 ppm (t, 1H) for [EMIM][Ac], 9.6 to 9.5 ppm (s, 1H), 7.8:7.7 (t, 1H) ppm for [BMIM][Ac], and 6.67 ppm (d, 4CH) for bisphenol A (BPA), and the catalyst purity was obtained through calculation of Equation 2 below.

[0233] [Formula 2]

[0234] Catalyst purity (%) = {(catalyst peak area) / 3 X 100} / (catalyst peak area / 3 + BPA peak area / 4).

[0235]

[0236] Experimental Example 2 Measurement Results Classification Number of Reuses PC Decomposition (%) BPA Yield (%) Catalyst Recovery Rate (%) Catalyst Purity (%) Example 3 110097.6 10099 210096.699.999 310096.299.999 410096.399.999 510095.299.999 Comparative Example 3 199.595.0899.799 210093.2699.798 310088.9899.398 410090.1699.5995 10090.1498.399

[0237] As shown in Table 2 above, Example 3 showed that even when the catalyst was reused five times, the bisphenol A yield was as high as 95.2%, and the catalyst recovery rate was also maintained as high as 99.9%.

[0238] On the other hand, in Comparative Example 3, when the catalyst was reused 5 times, the bisphenol A yield decreased to 90.14% compared to Example 3, and the catalyst recovery rate decreased to 98.3% compared to Example 3.

Claims

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

2. In paragraph 1, A catalyst for depolymerization of polycarbonate resin, wherein R1 and R2 are straight-chain alkyl groups having 1 to 2 carbon atoms.

3. In paragraph 1, The above R1 and R2 are different catalysts for depolymerization of polycarbonate resin.

4. In paragraph 1, A catalyst for depolymerization of a polycarbonate resin, wherein one of the above R1 and R2 is ethyl and the other is methyl.

5. In paragraph 1, The compound represented by the above chemical formula 1 is a catalyst for depolymerization of polycarbonate resin, which is a compound represented by the following chemical formula 1-1: [Chemical Formula 1-1] . 6.1-A step of reacting an alkyl-imidazole and an alkyl halide to produce a compound represented by the following chemical formula 4; and A method for producing a catalyst for depolymerization of a polycarbonate resin, comprising the step of reacting a compound represented by the above chemical formula 4 with an alkali metal acetate: [Chemical Formula 4] In the above chemical formula 4, R3 and R4 are straight-chain alkyl having 1 to 3 carbon atoms, and X is halogen.

7. In paragraph 6, The above 1-alkyl-imidazole is a compound represented by the following chemical formula 7, a method for producing a catalyst for depolymerization of polycarbonate resin: [Chemical Formula 7] In the above chemical formula 7, R3 is the same as R3 in the above chemical formula 4.

8. In paragraph 6, The above alkyl halide is a compound represented by the following chemical formula 8, and a method for producing a catalyst for depolymerization of polycarbonate resin: [Chemical Formula 8] R4-X In the above chemical formula 8, R4 is the same as R3 of the above chemical formula 4, and X is halogen.

9. In paragraph 6, After the step of reacting the compound represented by the above chemical formula 4 with an alkali metal acetate, A method for producing a catalyst for depolymerization of a polycarbonate resin, further comprising a step of removing an alkali metal halide.

10. A method for decomposing a polycarbonate resin, comprising a step of depolymerizing the polycarbonate resin in the presence of a catalyst for depolymerizing the polycarbonate resin of claim 1.

11. In paragraph 10, A method for decomposing a polycarbonate resin, wherein the catalyst content is 5 to 90 parts by weight based on 100 parts by weight of the polycarbonate resin.

12. In paragraph 10, The step of depolymerizing the above polycarbonate resin is: A method for decomposing a polycarbonate resin, which is carried out in an alcohol solvent.

13. In paragraph 12, A method for decomposing a polycarbonate resin, wherein the alcohol content is 50 to 250 parts by weight based on 100 parts by weight of the polycarbonate resin.

14. In paragraph 12, A method for decomposing polycarbonate resin, wherein the alcohol is ethanol.

15. In paragraph 10, The step of depolymerizing the above polycarbonate resin is: A method for decomposing a polycarbonate resin, the method comprising: performing the decomposition at a temperature of 50°C to 95°C for 1 to 100 hours.

16. In paragraph 10, After the step of depolymerizing the polycarbonate resin in the presence of the above polycarbonate resin depolymerization catalyst, A method for decomposing a polycarbonate resin, further comprising a step of obtaining an aromatic diol compound.

17. In paragraph 16, The step of obtaining the above aromatic diol compound is: A step of adding water and an organic solvent to the depolymerization reaction product; A step of separating an organic solvent layer containing an aromatic diol compound; and A method for decomposing a polycarbonate resin, comprising: a step of removing an organic solvent contained in the organic solvent layer.

18. A step of depolymerizing a polycarbonate resin in the presence of a catalyst for depolymerizing a polycarbonate resin of the first clause; A step of adding water and an organic solvent to the above depolymerization reaction product; A step of separating a water layer containing a catalyst for depolymerizing a polycarbonate resin; and A method for recovering a catalyst for depolymerization of a polycarbonate resin, comprising a step of removing water contained in the above water layer.

19. In paragraph 18, The step of removing water contained in the above water layer is: A method for recovering a catalyst for depolymerization of a polycarbonate resin, comprising a step of freeze-drying water.

20. In paragraph 19, The step of freeze-drying the water is as follows: A method for recovering a catalyst for depolymerization of polycarbonate resin, the method comprising: performing the process at a temperature of -90°C to -70°C for 1 to 100 hours.

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