Method for producing recycled cyclic carbonate composition

Abstract

The present invention relates to a method for producing a recycled cyclic carbonate composition, comprising the steps of: adding a polycarbonate resin to an organic solvent to produce a mixed solution; adding an alkylene glycol and a catalyst to the mixed solution to depolymerize the polycarbonate resin; removing an aromatic diol compound, an organic solvent, and an alkylene glycol from the depolymerized solution; and recovering an alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0155347 dated November 18, 2022, Korean Patent Application No. 10-2023-0052249 dated April 20, 2023, Korean Patent Application No. 10-2023-0159224 dated November 16, 2023, and Korean Patent Application No. 10-2023-0159225 dated November 16, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated by reference into this specification.

[0002] The present invention relates to a method for producing a recycled cyclic carbonate composition recovered through recycling by chemical decomposition of a polycarbonate resin. [Background technology]

[0003] Polycarbonate is a thermoplastic polymer, a plastic having excellent properties such as excellent transparency, flexibility and relatively low manufacturing costs.

[0004] Polycarbonate is widely used for a variety of purposes, but environmental and health concerns have been raised regarding its disposal.

[0005] Currently, physical recycling methods are being used, but this has caused problems with the quality degradation, and research is being conducted into chemical recycling of polycarbonate.

[0006] The chemical decomposition of polycarbonate refers to obtaining aromatic diol compounds (eg, bisphenol A (BPA)) and carbonate compounds (eg, diethyl carbonate), which are monomers constituting polycarbonate, through the decomposition of polycarbonate.

[0007] Representative examples of such chemical decomposition include pyrolysis, hydrolysis, and alcoholysis. Among these, alcoholysis is the most common method, but methanolysis has the problem of using methanol, which is harmful to the human body, and ethanol requires high temperature and pressure conditions and has a low yield.

[0008] Meanwhile, cyclic carbonates such as ethylene carbonate are useful as solvents for polymers and synthetic fuels for carbonate esters, and can also be used as liquid electrolyte organic solvents for electric vehicle batteries. Conventional ethylene carbonate has been produced through industrial synthesis using ethylene oxide and carbon dioxide, but there is a demand for the development of more environmentally friendly methods.

[0009] Therefore, as described above, there is an increasing need to develop a method for producing industrially useful cyclic carbonates by chemically decomposing polycarbonate, taking advantage of the fact that carbonate compounds can be obtained by chemically decomposing polycarbonate. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a method for producing a recycled cyclic carbonate composition, which can ensure a high yield of a high-purity cyclic carbonate compound recovered through recycling by chemical decomposition of a polycarbonate resin. [Means for solving the problem]

[0011] In order to solve the above problems, the present specification provides a method for producing a recycled cyclic carbonate composition, including the steps of: adding a polycarbonate-based resin to an organic solvent to produce a mixed solution; adding an alkylene glycol and a catalyst to the mixed solution to depolymerize the polycarbonate-based resin; removing an aromatic diol compound, an organic solvent, and an alkylene glycol from the depolymerized solution; and recovering an alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

[0012] The process for producing a recycled cyclic carbonate composition according to a specific embodiment of the invention will now be described in more detail.

[0013] Unless otherwise expressly stated herein, the terminology used is for the purpose of referring to particular embodiments only and is not intended to be limiting of the invention.

[0014] As used herein, the singular forms include the plural forms unless the context clearly indicates to the contrary.

[0015] As used herein, the meaning of "comprising" refers to the inclusion of certain properties, regions, integers, steps, operations, elements, components and / or components, and does not exclude the presence or inclusion of other certain properties, regions, integers, steps, operations, elements, components and / or groups.

[0016] In this specification, terms including ordinal numbers such as "first" and "second" are used for the purpose of distinguishing one component from another component, and are not limited by the ordinal number. For example, within the scope of the present invention, a first component may be named a second component, and similarly, a second component may be named a first component.

[0017] The term "substituted or unsubstituted" as used herein means that the group is selected from the group consisting of deuterium, halogen, cyano, nitro, hydroxy, carbonyl, ester, imide, amide, primary amino, carboxy, sulfonic acid, sulfonamide, phosphine oxide, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfoxy, arylsulfoxy, silyl, boron, alkyl, cycloalkyl, alkenyl, aryl, aralkyl, aralkenyl, alkylaryl, alkoxysilylalkyl, arylphosphine, or heterocyclic groups containing one or more of N, O, and S atoms, or that the group is selected from the group consisting of a ...

[0018] In this specification, an alkyl group is a monovalent functional group derived from an alkane, which may be linear or branched, and the number of carbon atoms in the linear alkyl group is not particularly limited, but is preferably 1 to 20. In addition, the number of carbon atoms in the branched alkyl group is 3 to 20. Specific examples of alkyl groups include, but are not limited to, 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, 5-methylhexyl, 2,6-dimethylheptan-4-yl, and the like. The alkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0019] In this specification, an alkylene group is a divalent functional group derived from an alkane, and the above description of the alkyl group can be applied except that it is a divalent functional group. For example, it may be a straight-chain or branched type, and may be a methylene group, an ethylene group, a propylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, a hexylene group, etc. The alkylene group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0020] As used herein, the term "fused ring" refers to a cyclic structure in a polycyclic system composed of two or more carbocyclic or heterocyclic rings, in which adjacent rings share only two atoms with each other.

[0021] Throughout this specification "one or more" means, for example, "1, 2, 3, 4 or 5, particularly 1, 2, 3 or 4, more particularly 1, 2 or 3, even more particularly 1 or 2."

[0022] According to one embodiment of the invention, there may be provided a method for producing a recycled cyclic carbonate composition, the method including: adding a polycarbonate-based resin to an organic solvent to produce a mixed solution; adding an alkylene glycol and a catalyst to the mixed solution to depolymerize the polycarbonate-based resin; removing an aromatic diol compound, an organic solvent, and an alkylene glycol from the depolymerized solution; and recovering an alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

[0023] The inventors have confirmed through experiments that the method for producing a recycled cyclic carbonate composition according to one embodiment of the present invention can achieve excellent physical properties and can be obtained in high yields by having high purity comparable to that of a newly synthesized alkylene carbonate, even though the polycarbonate resin is recovered through recycling by chemical decomposition. This led to the completion of the invention.

[0024] Specifically, the present invention makes it possible to stably obtain alkylene carbonate, which is a monomer with high purity, by decomposing polycarbonate into alkylene glycol under mild conditions.

[0025] The method for producing a recycled cyclic carbonate composition according to one embodiment may include the steps of adding a polycarbonate-based resin to an organic solvent to produce a mixed solution, and adding an alkylene glycol and a catalyst to the mixed solution to depolymerize the polycarbonate-based resin.

[0026] The polycarbonate-based resin includes all homopolymers or copolymers containing polycarbonate repeating units, and is a collective term for reaction products obtained through polymerization or copolymerization of monomers including alkylene carbonate and carbonate precursor. When one type of carbonate repeating unit is contained, obtained by using only one type of alkylene carbonate and one type of carbonate precursor, a homopolymer can be synthesized. In addition, when one type of alkylene carbonate and two or more types of carbonate precursors are used as the monomer, or when two or more types of alkylene carbonate and one type of carbonate precursor are used, or when two or more types of carbonates are contained by using one type of alkylene carbonate and one type of carbonate precursor and one or more other diols, a copolymer can be synthesized. The homopolymer or copolymer can include all low molecular weight compounds, oligomers, and polymers according to the molecular weight range.

[0027] The polycarbonate-based resin may be used regardless of its various forms and types, such as new polycarbonate produced through synthesis, recycled polycarbonate produced through a recycling process, or polycarbonate waste.

[0028] In the present invention, the specific examples of the alkylene glycol are not particularly limited, and various conventionally known alkylene glycols can be used without limitation. Examples include ethylene glycol and propylene glycol.

[0029] Meanwhile, the organic solvent may include one or more solvents selected from the group consisting of tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate. That is, the organic solvent may include tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0030] Specifically, when methylene chloride is used as the organic solvent, there is an advantage that the dissolving property for polycarbonate is improved, and the reactivity can be improved.

[0031] The weight ratio of the alkylene glycol, the organic solvent, and the polycarbonate-based resin is not particularly limited, but for example, the weight ratio between the alkylene glycol and the polycarbonate-based resin may be 10:1 to 1:10, or 1:1 to 1:10, or 1:1 to 1:5, or 1:1 to 1:2, or 1:1.1 to 1:2.

[0032] In addition, the weight ratio between the organic solvent and the polycarbonate resin may be 10:1 to 1:10, or 10:1 to 1:1, or 10:1 to 2:1, or 10:1 to 5:1, or 10:1 to 6:1, or 10:1 to 7:1, or 10:1 to 8:1, or 9:1 to 8:1.

[0033] Also, the weight ratio between the organic solvent:alkylene glycol can be from 20:1 to 1:20, or from 1:1 to 20:1, or from 5:1 to 20:1, or from 9:1 to 20:1, or from 9:1 to 17:1.

[0034] Specifically, by mixing the alkylene glycol and the organic solvent within the above range, it is possible to advantageously carry out a desired level of depolymerization reaction of the polymer.

[0035] The catalyst may be added in an amount of 0.1 to 10 parts by weight, or 0.1 to 5 parts by weight, per 100 parts by weight of the polycarbonate resin. Specifically, by including a catalyst in the above content range, there is an advantage that an economical catalytic reaction can be carried out.

[0036] The catalyst may include one catalyst selected from the group consisting of an organic salt catalyst, an organic base catalyst, and an inorganic base catalyst, i.e., the catalyst may include an organic salt compound, an organic base compound, an inorganic base compound, or a mixture of two or more of these.

[0037] The organic salt catalyst may be in the form of a salt containing an organic cation and an organic anion, and may specifically include an amidine-based salt compound. The amidine-based salt compound may include an amidine-based cation and an imidazole-based anion. The amidine-based cation may include an amidine cation or any of its derivative cations. The imidazole-based cation may include an imidazole anion or any of its derivative anions.

[0038] Specifically, the amidine salt compound may contain an amidine cation having a condensed ring. The condensed ring may contain a condensed ring of a 7-membered ring and a 6-membered ring. The 7-membered ring refers to a ring having 7 elements, and the 6-membered ring refers to a ring having 6 elements.

[0039] The six-membered ring may contain a C=N double bond of an amidine. The seven-membered ring may contain a CC single bond of an amidine. And, the portion where the seven-membered ring and the six-membered ring overlap may contain a CN single bond of an amidine.

[0040] More specifically, a specific example of the organic salt catalyst is a salt compound represented by the following chemical formula A.

[0041] [ka]

[0042] In the formula A, R1, R2, and R3 may be the same or different, and each independently may be hydrogen or alkyl.

[0043] Specific examples of the organic salt catalyst represented by the formula A include, but are not limited to, compound a in which R1=R2=R3=hydrogen (H) in the formula A, compound b in which R1=R3=hydrogen (H) and R2=methyl (CH3) in the formula A, compound c in which R1=R2=hydrogen (H) and R3=methyl (CH3) in the formula A, compound d in which R1=R3=hydrogen (H) and R2=isopropyl in the formula A, and compound e in which R1=R2=hydrogen (H) and R3=isopropyl in the formula A.

[0044] Meanwhile, the organic base catalyst refers to a non-ionic organic compound having basicity, and specifically, may include an amidine-based compound or a guanidine-based compound. The amidine-based compound may include all amidine compounds or derivative compounds thereof. The guanidine-based compound may include all guanidine compounds or derivative compounds thereof.

[0045] The amidine-based compound or guanidine-based compound may have a condensed ring. The condensed ring may include a condensed ring of a 6-membered ring and another 6-membered ring. The condensed ring may include a condensed ring of a 7-membered ring and another 6-membered ring. The condensed ring may include a condensed ring of a 5-membered ring and another 6-membered ring. The 7-membered ring means a ring having 7 elements, the 6-membered ring means a ring having 6 elements, and the 5-membered ring means a ring having 5 elements.

[0046] The six-membered ring may contain a C=N double bond of amidine or guanidine. The five-membered or seven-membered ring may contain a CC single bond of amidine or a CN single bond of guanidine. And the overlapping portion of the two rings may contain a CN single bond of amidine or guanidine.

[0047] Specifically, the amidine compound may include an amidine compound having a condensed ring.

[0048] Specific examples of the amidine compound include, but are not limited to, 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene.

[0049] The guanidine-based compound may include a guanidine-based compound having a condensed ring.

[0050] Specific examples of the guanidine-based compound include, but are not limited to, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyrimidine, and 1-methyl-1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyrimidine.

[0051] Meanwhile, the inorganic base catalyst means a non-ionic inorganic compound having basicity, specifically, sodium hydroxide (NaOH) or potassium hydroxide (KOH), preferably sodium hydroxide (NaOH), but is not limited thereto. By using the inorganic base catalyst, the decomposition reaction can be carried out under mild conditions, which is advantageous in terms of economy.

[0052] Meanwhile, the step of adding alkylene glycol and a catalyst to the mixed solution to depolymerize the polycarbonate resin may be performed by stirring at 20°C to 100°C, or 50°C to 100°C, or 60°C to 100°C, or 70°C to 100°C for 1 hour to 24 hours, or 1 hour to 12 hours, or 1 hour to 8 hours.

[0053] Specifically, the above conditions are milder process conditions than the existing pressurized / high temperature process, and stirring under the above conditions allows the process to be carried out in a milder process than the pressurized / high temperature process. In particular, stirring at 70°C to 100°C for 1 to 12 hours has the advantage of being able to obtain the most efficient results in terms of reproducibility and stability.

[0054] Meanwhile, the method for producing a recycled cyclic carbonate composition according to one embodiment may include removing an aromatic diol compound, an organic solvent, and an alkylene glycol from the depolymerized solution. Through the step of removing an aromatic diol compound, an organic solvent, and an alkylene glycol from the depolymerized solution, the organic solvent, the alkylene glycol, and the aromatic diol compound are all separated, and the remaining alkylene carbonate may be obtained as a main product.

[0055] The step of removing the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerized solution may include the steps of: removing the aromatic diol compound from the depolymerized solution; removing the organic solvent from the depolymerized solution; and removing the alkylene glycol from the depolymerized solution.

[0056] The order of the steps of removing the aromatic diol compound from the depolymerized solution; removing the organic solvent from the depolymerized solution; and removing the alkylene glycol from the depolymerized solution is not particularly limited, but for example, the steps may be performed in the order of: removing the aromatic diol compound from the depolymerized solution; removing the organic solvent from the depolymerized solution; and removing the alkylene glycol from the depolymerized solution.

[0057] More specifically, the step of removing the aromatic diol compound from the depolymerization solution may include a step of crystallizing the aromatic diol compound formed by the depolymerization; and a step of filtering the crystals of the aromatic diol compound.

[0058] The aromatic diol compound is characterized by being recovered from the polycarbonate resin, which means that the aromatic diol compound is also obtained as a result of recovery from the polycarbonate resin in order to obtain the recycled cyclic carbonate composition of the embodiment.

[0059] Specifically, the term "recovered from a polycarbonate-based resin" means that the polycarbonate-based resin is obtained through a depolymerization reaction. The depolymerization reaction may be carried out under acidic, neutral, or basic conditions, and particularly under basic (alkaline) conditions. In particular, the depolymerization reaction is preferably carried out in the presence of a glycol-based compound, as described below.

[0060] 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 A), and bis(4-hydroxyphenyl)cyclohexane (bisphenol B). Examples of the aromatic diol compound include bisphenol Z), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 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 of these. Preferably, the aromatic diol compound may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0061] The step of crystallizing the aromatic diol compound formed by the depolymerization can be performed by pouring the depolymerization solution into water. When the depolymerization solution is poured into water, the aromatic diol compound contained in the depolymerization solution can be crystallized due to the difference in solubility. The crystallization conditions are not particularly limited, and various conventionally known crystallization conditions, methods, and equipment can be applied without limitation.

[0062] Among the aromatic diol compound, alkylene glycol and alkylene carbonate contained in the depolymerization solution, the aromatic diol compound forms crystals, and the remaining substances can remain dissolved. At this time, the crystallized aromatic diol compound can be removed through filtration to remove the aromatic diol compound and obtain the alkylene carbonate.

[0063] In the step of filtering the crystals of the aromatic diol compound, the crystallized aromatic diol compound may be filtered under reduced pressure. This allows the aromatic diol compound contained in the depolymerization solution to be effectively removed. The filtering conditions are not particularly limited, and various filtering conditions, methods, and equipments known in the art may be used without any restrictions.

[0064] The step of removing the organic solvent from the depolymerization solution may include a step of distilling the organic solvent. The organic solvent may include one or more solvents selected from the group consisting of tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate. That is, the organic solvent may include tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof. Specifically, when methylene chloride is used as the organic solvent, there is an advantage that the dissolving property for polycarbonate is improved, and the reactivity can be improved.

[0065] The distillation temperature is adjusted to a temperature lower than the boiling point of the alkylene carbonate and higher than the boiling point of the organic solvent, so that the alkylene carbonate remains without being distilled and the organic solvent is distilled and removed. The distillation conditions are not particularly limited, and various distillation conditions, methods, and equipments known in the art can be applied without limitation.

[0066] Specifically, the step of distilling the organic solvent can be carried out at a temperature of 40°C to 80°C, or 40°C to 70°C, or 40°C to 60°C, or 40°C to 50°C, and a pressure of 100 psi to 200 psi, or 120 psi to 180 psi, or 140 psi to 160 psi.

[0067] The step of removing alkylene glycol from the depolymerization solution may include adding the depolymerization solution to a solution separated into an aqueous layer and an organic solvent layer, and removing the alkylene glycol dissolved in the aqueous layer. The organic solvent may include one or more solvents selected from the group consisting of tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate. That is, the organic solvent may include tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof. Specifically, when methylene chloride is used as the organic solvent, there is an advantage that the dissolving property for polycarbonate is improved, thereby improving reactivity.

[0068] Among the alkylene glycol and alkylene carbonate contained in the depolymerization solution, the alkylene glycol has relatively strong hydrophilicity and can be dissolved in the aqueous layer, and the alkylene carbonate can be dissolved in the organic solvent layer and separated into layers. At this time, the separated aqueous layer is removed to obtain the organic solvent layer, and the alkylene glycol is removed to obtain the alkylene carbonate.

[0069] Meanwhile, the step of removing the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerized solution may further include the step of removing phenolic impurities derived from the aromatic diol compound formed by the depolymerization with an adsorbent. The phenolic impurities may include one or more compounds selected from the group consisting of monohydroxyethyl-bisphenol A, bishydroxyethyl-bisphenol A, and tris(4-hydroxyphenyl)ethane.

[0070] Examples of the adsorbent include activated carbon, charcoal, celite, or a mixture thereof. The activated carbon is a black carbon material having fine pores produced by subjecting a raw material to a carbonization process at about 500°C and an activated carbon process at about 900°C. Examples are not particularly limited, and various activated carbons such as plant-based, coal-based, petroleum-based, and waste-based activated carbons can be used without limitation depending on the type of raw material.

[0071] By applying the adsorption purification process using an adsorbent, not only can the alkylene carbonate, which is the main synthetic target substance of the present invention, be secured in high purity, but also the content of other impurities can be significantly reduced.

[0072] The adsorption purification conditions using the adsorbent are not particularly limited, and various conventionally known adsorption purification conditions can be used without limitation. However, for example, the amount of the adsorbent added can be 40% by weight to 60% by weight based on the polycarbonate resin, the adsorption time can be 0.1 hours to 5 hours, and the adsorption method can be stirring adsorption or a lab adsorption tower.

[0073] Meanwhile, the method for producing a recycled cyclic carbonate composition according to one embodiment may include recovering an alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

[0074] The step of recovering the alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed may include distilling the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

[0075] In the step of distilling the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed, the organic solvent remaining in the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed may be removed through distillation.

[0076] The distillation temperature is adjusted to a temperature lower than the boiling point of the alkylene carbonate and higher than the boiling point of the organic solvent, so that the alkylene carbonate remains without being distilled and the organic solvent is distilled and removed. The distillation conditions are not particularly limited, and various distillation conditions, methods, and equipments known in the art can be applied without limitation.

[0077] Specifically, the step of distilling the organic solvent can be carried out at a temperature of 40°C to 80°C, or 40°C to 70°C, or 40°C to 60°C, or 40°C to 50°C, and a pressure of 100 psi to 200 psi, or 120 psi to 180 psi, or 140 psi to 160 psi. Effect of the Invention

[0078] According to the present invention, there can be provided a method for producing a recycled cyclic carbonate composition containing a high-purity, high-yield alkylene carbonate recovered through recycling by chemical decomposition of a polycarbonate resin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] The present invention will be described in more detail with reference to the following examples, however, the following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0080] <Example> (Examples 1 to 5) Into a 250 ml three-neck flask, 266.67 g of methylene chloride and 30 g of polycarbonate were placed and stirred.

[0081] Thereafter, 21.83 g of ethylene glycol and 1.245 g of a catalyst shown in Table 1 below were added, and the mixture was stirred at 100° C. for 3 hours to carry out a depolymerization reaction.

[0082] After the depolymerization reaction was completed, the depolymerization reaction product was poured into water to crystallize bisphenol A, which was then filtered under reduced pressure to remove bisphenol A. The resulting filtrate was then distilled at 40°C and 150 psi to remove methylene chloride, and then treated with charcoal to remove phenolic impurities.

[0083] The filtrate was then separated into layers using water and methylene chloride to remove the water layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate to produce a recycled cyclic carbonate composition.

[0084] [Table 1]

[0085] -Compound a: 20 ml of the following chemical formula A, where R1 = R2 = R3 = hydrogen (H) 0.6 g of imidazole and 1.5 g of 1,8-diazabicyclo(5,4,0)undec-7-ene were placed in a vial and stirred at room temperature for 5 hours to obtain compound a.

[0086] -Compound b: In the following chemical formula A, R1 = R3 = hydrogen (H), R2 = methyl (CH3) 0.8 g of 2-methyl-1H-imidazole and 1.5 g of 1,8-diazabicyclo(5,4,0)undec-7-ene were placed in a 20 ml vial and stirred at room temperature for 5 hours to obtain compound b.

[0087] -Compound c: In the following chemical formula A, R1 = R2 = hydrogen (H), R3 = methyl (CH3) 0.8 g of 4-methyl-1H-imidazole and 1.5 g of 1,8-diazabicyclo(5,4,0)undec-7-ene were placed in a 20 ml vial and stirred at room temperature for 5 hours to obtain compound c.

[0088] Compound d: In the following chemical formula A, R1 = R3 = hydrogen (H), R2 = isopropyl 1.1 g of 2-isopropyl-1H-imidazole and 1.5 g of 1,8-diazabicyclo(5,4,0)undec-7-ene were placed in a 20 ml vial and stirred at room temperature for 5 hours to obtain compound d.

[0089] Compound e: In the following chemical formula A, R1 = R2 = hydrogen (H), R3 = isopropyl 1.1 g of 4-isopropyl-1H-imidazole and 1.5 g of 1,8-diazabicyclo(5,4,0)undec-7-ene were placed in a 20 ml vial and stirred at room temperature for 5 hours to obtain compound e.

[0090] [ka]

[0091] (Examples 6 to 11) Into a 250 ml three-neck flask, 266.67 g of methylene chloride and 30 g of polycarbonate were placed and stirred.

[0092] Then, 21.83 g of ethylene glycol and 0.783 g of a catalyst shown in Table 2 below were added and a depolymerization reaction was carried out at 100° C. for 3 hours.

[0093] After the depolymerization reaction was completed, the depolymerization reaction product was poured into water to crystallize bisphenol A, which was then filtered under reduced pressure to remove bisphenol A. The resulting filtrate was then distilled at 40°C and 150 psi to remove methylene chloride, and then treated with charcoal to remove phenolic impurities.

[0094] The filtrate was then separated into layers using water and methylene chloride to remove the water layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate to produce a recycled cyclic carbonate composition.

[0095] [Table 2]

[0096] - Compound 1: 1,5,7-triazabicyclo[4.4.0]dec-5-ene

[0097] [ka]

[0098] Compound 2: 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene

[0099] [ka]

[0100] - Compound 3: 1,8-diazabicyclo[5.4.0]undec-7-ene

[0101] [ka]

[0102] - Compound 4: 1,5-diazabicyclo[4.3.0]non-5-ene

[0103] [ka]

[0104] -Compound 5: 1,2,3,5,6,7-Hexahydroimidazo[1,2-a]pyrimidine

[0105] [ka]

[0106] - Compound 6: 1-Methyl-1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyrimidine

[0107] [ka]

[0108] Example 12 Into a 250 ml three-neck flask, 266.67 g of methylene chloride and 30 g of polycarbonate were placed and stirred.

[0109] Thereafter, 21.83 g of ethylene glycol and 0.225 g of sodium hydroxide (NaOH) as a catalyst were added, and a depolymerization reaction was carried out at 100° C. for 3 hours.

[0110] After the depolymerization reaction was completed, the depolymerization reaction product was poured into water to crystallize bisphenol A, which was then filtered under reduced pressure to remove bisphenol A. The resulting filtrate was then distilled at 40°C and 150 psi to remove methylene chloride, and then treated with charcoal to remove phenolic impurities.

[0111] The filtrate was then separated into layers using water and methylene chloride to remove the water layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate to produce a recycled cyclic carbonate composition.

[0112] Example 13 A recycled cyclic carbonate composition was produced in the same manner as in Example 12, except that 16.37 g of ethylene glycol was used.

[0113] Example 14 A recycled cyclic carbonate composition was produced by obtaining propylene carbonate in the same manner as in Example 12, except that 26.76 g of propylene glycol was used instead of 21.83 g of ethylene glycol.

[0114] Example 15 A recycled cyclic carbonate composition was produced by obtaining propylene carbonate in the same manner as in Example 12, except that 20.07 g of propylene glycol was used instead of 21.83 g of ethylene glycol.

[0115] <Comparative Example> Comparative Example 1 Into a 250 ml three-neck flask, 60 ml of methylene chloride, 30 ml of ethylene glycol, and 1.5 g of the compound a as a catalyst were placed and stirred.

[0116] Thereafter, 30 g of waste polycarbonate was added and stirred at 40° C. for 5 hours.

[0117] After the reaction was completed, ethylene glycol was separated by distillation, and toluene was added to separate bisphenol A, thereby obtaining ethylene carbonate to prepare a recycled cyclic carbonate composition.

[0118] Comparative Example 2 Into a 250 ml three-neck flask, 60 ml of toluene, 30 ml of ethylene glycol, and 1.5 g of the above compound 1 as a catalyst were placed and stirred.

[0119] Thereafter, 30 g of waste polycarbonate was added and stirred at 80° C. for 36 hours.

[0120] After the reaction was completed, ethylene glycol was separated by distillation, and toluene was added to separate bisphenol A, thereby obtaining ethylene carbonate to prepare a recycled cyclic carbonate composition.

[0121] Comparative Example 3 Into a 250 ml three-neck flask, 60 ml of methylene chloride, 30 ml of ethylene glycol, and 0.6 g of sodium hydroxide (NaOH) were placed and stirred.

[0122] Thereafter, 30 g of waste polycarbonate was added and stirred at 40° C. for 5 hours.

[0123] After the reaction was completed, ethylene glycol was separated by distillation, and toluene was added to separate bisphenol A, thereby obtaining ethylene carbonate to prepare a recycled cyclic carbonate composition.

[0124] Comparative Example 4 Toluene (60 ml), ethylene glycol (30 ml), and sodium hydroxide (NaOH) (0.6 g) were placed in a 250 ml three-neck flask and stirred.

[0125] Thereafter, 30 g of waste polycarbonate was added and stirred at 60° C. for 5 hours.

[0126] After the reaction was completed, ethylene glycol was separated by distillation, and toluene was added to separate bisphenol A, thereby obtaining ethylene carbonate to prepare a recycled cyclic carbonate composition.

[0127] Comparative Example 5 120 g of phenol and 40 g of polycarbonate were placed in a 250 ml three-neck flask and stirred.

[0128] Thereafter, 17.5 g of ethylene glycol and 1.245 g of the compound a as a catalyst were added, and the mixture was stirred at 80° C. for 5 hours to carry out a depolymerization reaction.

[0129] After the depolymerization reaction was completed, 100g of toluene was added to the depolymerization reaction product, which was then neutralized using hydrochloric acid and distilled at 120℃ and 150 psi to remove phenol, followed by charcoal treatment to remove phenolic impurities. The charcoal-treated material was then added to water to crystallize, and filtered under reduced pressure to remove bisphenol A.

[0130] The filtrate was then separated into layers using water and methylene chloride to remove the water layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate to produce a recycled cyclic carbonate composition.

[0131] Comparative Example 6 120 g of phenol and 40 g of polycarbonate were placed in a 250 ml three-neck flask and stirred.

[0132] Then, 17.5 g of ethylene glycol and 0.783 g of the compound 1 as a catalyst were added, and the mixture was stirred at 80° C. for 5 hours to carry out a depolymerization reaction.

[0133] After the depolymerization reaction was completed, 100g of toluene was added to the depolymerization reaction product, which was then neutralized using hydrochloric acid and distilled at 120℃ and 150 psi to remove phenol, followed by charcoal treatment to remove phenolic impurities. The charcoal-treated material was then added to water to crystallize, and filtered under reduced pressure to remove bisphenol A.

[0134] The filtrate was then separated into layers using water and methylene chloride to remove the water layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate to produce a recycled cyclic carbonate composition.

[0135] Comparative Example 7 120 g of phenol and 40 g of polycarbonate were placed in a 500 ml three-neck flask and stirred.

[0136] Thereafter, 17.5 g of ethylene glycol and 1 g of sodium hydroxide (NaOH) as a catalyst were added, and a depolymerization reaction was carried out at 80° C. for 5 hours.

[0137] After the depolymerization reaction was completed, 100g of toluene was added to the depolymerization reaction product, which was then neutralized using hydrochloric acid and distilled at 120℃ and 150 psi to remove phenol, followed by charcoal treatment to remove phenolic impurities. The charcoal-treated material was then added to water to crystallize, and filtered under reduced pressure to remove bisphenol A.

[0138] Thereafter, the obtained filtrate was subjected to liquid separation using water and methylene chloride to remove the aqueous layer containing ethylene glycol, and a methylene chloride layer containing ethylene carbonate was obtained. The obtained methylene chloride solution was distilled at 40 °C and 150 psi to remove methylene chloride, obtaining ethylene carbonate and producing a recycled cyclic carbonate composition.

[0139] <Experimental Example> For the recycled cyclic carbonate compositions obtained in the above Examples and Comparative Examples, physical properties were measured by the following method, and the results are shown in Table 3.

[0140] 1. Degree of decomposition of polycarbonate (%) 1 ml of the depolymerization reaction product obtained in the production process of the recycled cyclic carbonate composition was collected as a sample and subjected to high performance liquid chromatography (HPLC) analysis under the following conditions. The peak area ratio of bisphenol A (unit: %) was measured by the following formula 1 with respect to 100% of the total HPLC peak area.

[0141] [Formula 1] Degree of decomposition of polycarbonate (%) = (Area of bisphenol A on HPLC / Total peak area on HPLC) × 100 In formula 1 above, the bisphenol A peak on HPLC corresponds to the peak at retention time 3.159 minutes, and the HPLC measurement conditions are as follows.

[0142] <HPLC Conditions> (1) Column: UG 120 (4.6 mm I.D X 50 mm) (2) Column Temp: 40 °C (3) Injection volume: 10 μl (4) Flow: THF: ACN: water = 15: 15: 70, volume = 1.23 ml / min (total = 10 min) (5) Detector: 245 nm

[0143] 2. Yield The weight of the cyclic carbonate (ethylene carbonate or propylene carbonate) produced when the polycarbonate used in the reaction was 100% decomposed was measured, and the weight of the resulting cyclic carbonate (ethylene carbonate or propylene carbonate) was measured, and the yield of the cyclic carbonate (ethylene carbonate or propylene carbonate) was calculated according to the following formula 2.

[0144] [Formula 2] Yield(%)=W1 / W0 In the above formula 2, W0 is the mass of the cyclic carbonate (ethylene carbonate or propylene carbonate) obtained upon 100% decomposition, and W1 is the mass of the cyclic carbonate (ethylene carbonate or propylene carbonate) actually obtained.

[0145] [Table 3]

[0146] Measurement results of experimental example As shown in Table 3, the recycled cyclic carbonate compositions obtained in Examples 1 to 15 exhibited a polycarbonate decomposition degree of 92.2% to 96.7%, and the yield of cyclic carbonate (ethylene carbonate or propylene carbonate) was 52.4% to 65.8%.

[0147] On the other hand, the recycled cyclic carbonate compositions obtained in Comparative Examples 1 to 7 showed a polycarbonate decomposition degree of 58.7% to 90.3%, which was reduced compared to the Examples, and the yield of cyclic carbonate (ethylene carbonate or propylene carbonate) was 23.1% to 48.1%, which was reduced compared to the Examples.

Claims

1. adding a polycarbonate-based resin to an organic solvent to prepare a mixture; adding an alkylene glycol and a catalyst to the mixture to depolymerize the polycarbonate-based resin; removing the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerization solution; and recovering an alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

2. The method for producing a recycled cyclic carbonate composition according to claim 1, wherein the organic solvent comprises one or more solvents selected from the group consisting of tetrahydrofuran, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and dipropyl carbonate.

3. 2. The method for producing a recycled cyclic carbonate composition according to claim 1, wherein the weight ratio of the organic solvent to the alkylene glycol is from 20:1 to 1:

20.

4. The method for producing a recycled cyclic carbonate composition according to claim 1, wherein the catalyst is added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the polycarbonate resin.

5. 2. The method for producing a recycled cyclic carbonate composition according to claim 1, wherein the catalyst comprises one catalyst selected from the group consisting of an organic salt catalyst, an organic base catalyst, and an inorganic base catalyst.

6. The method for producing a recycled cyclic carbonate composition according to claim 5, wherein the organic salt catalyst comprises an amidine-based salt compound.

7. The method for producing a recycled cyclic carbonate composition according to claim 6, wherein the amidine salt compound comprises a salt compound represented by the following chemical formula A: 【Chemistry 9】 (In the above formula A, R 1 , R 2 , R 3 are the same or different and can each independently be hydrogen or alkyl.

8. The method for producing a recycled cyclic carbonate composition according to claim 5, wherein the organic base catalyst comprises an amidine-based compound or a guanidine-based compound.

9. The method for producing a recycled cyclic carbonate composition according to claim 8, wherein the amidine compound comprises 1,8-diazabicyclo[5.4.0]undec-7-ene or 1,5-diazabicyclo[4.3.0]non-5-ene.

10. The method for producing a recycled cyclic carbonate composition according to claim 8, wherein the guanidine-based compound includes 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyrimidine, or 1-methyl-1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyrimidine.

11. 6. The method of claim 5, wherein the inorganic base catalyst comprises sodium hydroxide (NaOH) or potassium hydroxide (KOH).

12. The step of depolymerizing the polycarbonate-based resin by adding an alkylene glycol and a catalyst to the mixture includes: The method for producing a recycled cyclic carbonate composition according to claim 1, wherein the mixture is stirred at 20°C to 100°C for 1 hour to 30 hours.

13. The step of removing the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerization solution includes: removing the aromatic diol compound from the depolymerization solution; removing the organic solvent from the depolymerization solution; and 2. The method of claim 1, further comprising the step of: removing alkylene glycol from the depolymerized solution.

14. The step of removing the aromatic diol compound from the depolymerization solution comprises: crystallizing the aromatic diol compound formed by the depolymerization; and 14. The method for producing the recycled cyclic carbonate composition of claim 13, comprising: filtering the crystals of the aromatic diol compound.

15. The step of removing the organic solvent from the depolymerization solution comprises:

14. A method for producing the recycled cyclic carbonate composition of claim 13, comprising the step of distilling the organic solvent.

16. The step of distilling the organic solvent comprises:

16. The method of claim 15, wherein the method is carried out at a temperature of from 40° C. to 80° C. and a pressure of from 100 psi to 200 psi.

17. The step of removing alkylene glycol from the depolymerization solution comprises: The method for producing a recycled cyclic carbonate composition according to claim 13, further comprising the step of adding the depolymerization solution to a solution separated into an aqueous layer and an organic solvent layer, and removing alkylene glycol dissolved in the aqueous layer.

18. The step of removing the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerization solution includes:

14. The method for producing a recycled cyclic carbonate composition according to claim 13, further comprising the step of removing phenolic impurities derived from the aromatic diol compound formed by the depolymerization with an adsorbent.

19. The step of recovering an alkylene carbonate from the depolymerization solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed includes:

2. The method for producing the recycled cyclic carbonate composition according to claim 1, further comprising the step of distilling the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed.

20. The step of distilling the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed includes:

20. The method of claim 19, wherein the process is carried out at a temperature of from 40° C. to 80° C. and a pressure of from 100 psi to 200 psi.

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