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, filed November 18, 2022, Korean Patent Application No. 10-2023-0052249, filed April 20, 2023, Korean Patent Application No. 10-2023-0159224, filed November 16, 2023, and Korean Patent Application No. 10-2023-0159225, filed November 16, 2023, and all contents disclosed in the documents of these Korean patent applications are incorporated herein by reference.

[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 with excellent properties such as excellent transparency, flexibility, and relatively low manufacturing costs.

[0004] Although polycarbonate is widely used in a variety of applications, environmental and health concerns have been raised regarding its disposal.

[0005] Currently, physical recycling methods are being used, but this has caused problems such as a deterioration in quality, and research is being conducted into chemical recycling of polycarbonate.

[0006] Chemical decomposition of polycarbonate refers to the process of obtaining aromatic diol compounds (e.g., bisphenol A (BPA)) and carbonate compounds (e.g., diethyl carbonate), which are the monomers that make up polycarbonate, through the decomposition of polycarbonate.

[0007] Typical examples of such chemical decomposition include pyrolysis, hydrolysis, and alcoholysis. Among these, alcoholysis is the most common method. However, methanolysis has the drawback of using methanol, which is harmful to the human body, and ethanol requires high temperature and pressure conditions, resulting in 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 mentioned above, there is an increasing need to develop a method for producing industrially useful cyclic carbonates by chemically decomposing polycarbonates, taking advantage of the fact that carbonate compounds can be obtained by chemically decomposing polycarbonates. 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 high yields of high-purity cyclic carbonate compounds recovered through recycling by chemical decomposition of polycarbonate resins. [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 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.

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

[0013] Unless expressly stated otherwise herein, terminology 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 otherwise.

[0015] As used herein, the meaning of "comprising" embodies certain properties, regions, integers, steps, operations, elements and / or components, and does not exclude the presence or addition 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 to distinguish one component from another, and are not limited by the ordinal numbers. 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] As used herein, the term "substituted or unsubstituted" refers to a group selected from the group consisting of deuterium, halogen, cyano, nitro, hydroxy, carbonyl, ester, imide, amido, primary amino, carboxy, sulfonic acid, sulfonamide, phosphine oxide, alkoxy, aryloxy, alkylthioxy, arylthioxy, alkylsulfoxy, arylsulfoxy, silyl, boron, alkyl, cycloalkyl, alkenyl, aryl, aralkyl, aralkenyl, alkylaryl, alkoxysilylalkyl, arylphosphine, or heterocyclic groups containing one or more N, O, and S atoms, or a group in which two or more of the above-listed substituents are linked together. For example, a "substituent in which two or more substituents are linked together" may be a biphenyl group. In other words, a biphenyl group may be an aryl group or may be interpreted as a substituent in which two phenyl groups are linked together.

[0018] In this specification, an alkyl group is a monovalent functional group derived from an alkane, and 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. Furthermore, 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-methylbutyl, 1-ethylbutyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethylpropyl, 1,1-dimethylpropyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, 2,6-dimethylheptan-4-yl, and the like. The alkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

[0019] As used herein, an alkylene group is a divalent functional group derived from an alkane, and the above description of the alkyl group is applicable, except that it is a divalent functional group. For example, it may be linear or branched, and may be a methylene group, ethylene group, propylene group, isobutylene group, sec-butylene group, tert-butylene group, pentylene group, hexylene group, etc. The alkylene group may be substituted or unsubstituted, and if 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 consisting of two or more carbon rings or heterocyclic rings, in which adjacent rings share only two atoms.

[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 present invention, there may be provided a method for producing a recycled cyclic carbonate composition, including 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.

[0023] The present 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 a high yield by having a purity comparable to that of a newly synthesized alkylene carbonate, even though the recycled cyclic carbonate composition is recovered through recycling by chemical decomposition of a polycarbonate resin.

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

[0025] In one embodiment, the method for producing a recycled cyclic carbonate composition may include the steps of adding a polycarbonate resin to an organic solvent to prepare a mixture, and adding an alkylene glycol and a catalyst to the mixture to depolymerize the polycarbonate resin.

[0026] The term "polycarbonate-based resin" refers to any homopolymer or copolymer containing polycarbonate repeating units, collectively referring to reaction products obtained through the polymerization or copolymerization of monomers containing alkylene carbonate and carbonate precursors. A homopolymer can be synthesized when a single carbonate repeating unit is obtained using only one alkylene carbonate and one carbonate precursor. Alternatively, a copolymer can be synthesized when two or more carbonates are contained using one alkylene carbonate and two or more carbonate precursors, two or more alkylene carbonates and one carbonate precursor, or one alkylene carbonate, one carbonate precursor, and one or more diols. The homopolymer or copolymer can include low molecular weight compounds, oligomers, and polymers within a range of molecular weights.

[0027] The polycarbonate-based resin may be applied regardless of 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, i.e., 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, it has the advantage of improving the dissolving property for polycarbonate and improving the reactivity.

[0031] The weight ratio of the alkylene glycol, organic solvent, and polycarbonate resin is not particularly limited, but for example, the weight ratio of the alkylene glycol to the polycarbonate 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] The weight ratio of the organic solvent to 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 and the alkylene glycol can be 20:1 to 1:20, or 1:1 to 20:1, or 5:1 to 20:1, or 9:1 to 20:1, or 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, relative to 100 parts by weight of the polycarbonate resin. Specifically, by including a catalyst in the above content range, there is an advantage in 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 can contain an amidine cation having a fused ring. The fused ring can include a fused ring of a 7-membered ring and a 6-membered ring. The 7-membered ring refers to a ring having seven elements, and the 6-membered ring refers to a ring having six elements.

[0039] The six-membered ring may contain a C=N double bond of the amidine. The seven-membered ring may contain a CC single bond of the amidine. The overlapping portion of the seven-membered ring and the six-membered ring may contain a C=N single bond of the amidine.

[0040] More specifically, specific examples of the organic salt catalyst include salt compounds represented by the following chemical formula A.

[0041] [ka]

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

[0043] Specific examples of the organic salt catalyst represented by the formula A include, but are not limited to, compound a where R1 = R2 = R3 = hydrogen (H) in the formula A, compound b where R1 = R3 = hydrogen (H) and R2 = methyl (CH3) in the formula A, compound c where R1 = R2 = hydrogen (H) and R3 = methyl (CH3) in the formula A, compound d where R1 = R3 = hydrogen (H) and R2 = isopropyl in the formula A, and compound e where 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 and their derivative compounds. The guanidine-based compound may include all guanidine compounds and their derivative compounds.

[0045] The amidine-based compound or guanidine-based compound may have a fused ring. The fused ring may include a fused ring of another 6-membered ring. The fused ring may also include a fused ring of a 7-membered ring and a 6-membered ring. The fused ring may also include a fused ring of a 5-membered ring and a 6-membered ring. The 7-membered ring refers to a ring having seven elements, the 6-membered ring refers to a ring having six elements, and the 5-membered ring refers to a ring having five elements.

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

[0047] Specifically, the amidine compound may include an amidine compound having a fused 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 refers to a non-ionic inorganic compound having basicity, specifically, sodium hydroxide (NaOH) or potassium hydroxide (KOH), preferably sodium hydroxide (NaOH), but is not limited thereto. The use of the inorganic base catalyst has the advantage that the decomposition reaction can be carried out under mild conditions and is economical.

[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 pressure / high temperature process, and stirring under these conditions allows the process to be carried out in a milder process than the existing pressure / high temperature process. In particular, stirring at 70°C to 100°C for 1 to 12 hours has the advantage of providing 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 the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerized solution. Through the step of removing the aromatic diol compound, the organic solvent, and the 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 depolymerized solution may include the steps of crystallizing the aromatic diol compound formed by the depolymerization; and filtering the aromatic diol compound crystals.

[0058] The aromatic diol compound is recovered from the polycarbonate resin, which means that the aromatic diol compound is also recovered 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, and 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol A). Examples of aromatic diol compounds 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, and mixtures of two or more thereof. Preferably, the aromatic diol compound is 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 adding the depolymerization solution to water. When the depolymerization solution is added to water, the aromatic diol compound contained in the depolymerization solution may crystallize due to the difference in solubility. The crystallization conditions are not particularly limited, and various conventionally known crystallization conditions, methods, and equipment may be used without limitation.

[0062] Among the aromatic diol compound, alkylene glycol, and alkylene carbonate contained in the depolymerization solution, the aromatic diol compound forms crystals, while the remaining substances remain dissolved. At this time, the crystallized aromatic diol compound is removed by filtration, thereby removing the aromatic diol compound and obtaining 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 may effectively remove the aromatic diol compound contained in the depolymerization solution. The filtering conditions are not particularly limited, and various filtering conditions, methods, and equipment known in the art may be used without limitation.

[0064] The step of removing the organic solvent from the depolymerization solution may include 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, it has the advantage of improving the solubility of polycarbonate and thereby improving reactivity.

[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 removed by distillation. Other distillation conditions are not particularly limited, and various conventionally known distillation conditions, methods, and equipment 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 the 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, using methylene chloride as the organic solvent has the advantage of improving the solubility of polycarbonate and thereby improving reactivity.

[0068] Among the alkylene glycol and alkylene carbonate contained in the depolymerization solution, the alkylene glycol is relatively hydrophilic and can be dissolved in the aqueous layer, while the alkylene carbonate is dissolved in the organic solvent layer, resulting in phase separation. 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 using 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. Activated carbon is a black carbon material with micropores that is produced by carbonizing a raw material at about 500°C and then activating it at about 900°C. The activated carbon is 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 at a 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. For example, the amount of adsorbent added can be 40% to 60% by weight based on the polycarbonate resin, the adsorption time can be 0.1 to 5 hours, and the adsorption method can be stirring adsorption or a laboratory adsorption tower.

[0073] Meanwhile, the method for producing a recycled cyclic carbonate composition according to one embodiment may include recovering 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 removed by distillation. Other distillation conditions are not particularly limited, and various conventionally known distillation conditions, methods, and equipment 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. [Effects 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 INVENTION

[0079] The present invention will be described in more detail in the following examples, but 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 5 266.67 g of methylene chloride and 30 g of polycarbonate were placed in a 250 ml three-neck flask 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 added to 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 resulting filtrate was then separated into layers using water and methylene chloride to remove the aqueous layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The resulting methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate, producing 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 11 266.67 g of methylene chloride and 30 g of polycarbonate were placed in a 250 ml three-neck flask and stirred.

[0092] Thereafter, 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 added to 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 resulting filtrate was then separated into layers using water and methylene chloride to remove the aqueous layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The resulting methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate, producing 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 12 266.67 g of methylene chloride and 30 g of polycarbonate were placed in a 250 ml three-neck flask 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 added to 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 resulting filtrate was then separated into layers using water and methylene chloride to remove the aqueous layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The resulting methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate, producing 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 and preparing 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 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 and preparing a recycled cyclic carbonate composition.

[0121] (Comparative Example 3) 60 ml of methylene chloride, 30 ml of ethylene glycol, and 0.6 g of sodium hydroxide (NaOH) were placed in a 250 ml three-neck flask 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 and preparing 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 and preparing 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, 100 g of toluene was added to the depolymerization product, which was then neutralized using hydrochloric acid. The phenol was removed by distillation at 120°C and 150 psi, and then phenolic impurities were removed by charcoal treatment. The charcoal-treated material was then added to water to crystallize, and bisphenol A was removed by filtration under reduced pressure.

[0130] The resulting filtrate was then separated into layers using water and methylene chloride to remove the aqueous layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The resulting methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate, producing 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, 100 g of toluene was added to the depolymerization product, which was then neutralized using hydrochloric acid. The phenol was removed by distillation at 120°C and 150 psi, and then phenolic impurities were removed by charcoal treatment. The charcoal-treated material was then added to water to crystallize, and bisphenol A was removed by filtration under reduced pressure.

[0134] The resulting filtrate was then separated into layers using water and methylene chloride to remove the aqueous layer containing ethylene glycol and obtain a methylene chloride layer containing ethylene carbonate. The resulting methylene chloride solution was distilled at 40°C and 150 psi to remove the methylene chloride and obtain ethylene carbonate, producing 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, 100 g of toluene was added to the depolymerization product, which was then neutralized using hydrochloric acid. The phenol was removed by distillation at 120°C and 150 psi, and then phenolic impurities were removed by charcoal treatment. The charcoal-treated material was then added to water to crystallize, and bisphenol A was removed by filtration under reduced pressure.

[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, and ethylene carbonate was obtained to produce 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 a retention time of 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 Temperature: 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 using the following equation 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 rate 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 rate of 58.7% to 90.3%, which was lower than that of the Examples, and the yield of cyclic carbonate (ethylene carbonate or propylene carbonate) was 23.1% to 48.1%, which was lower than that of the Examples.

Claims

1. adding a polycarbonate-based resin to an organic solvent to prepare a mixed solution; adding alkylene glycol and a catalyst to the mixture to depolymerize the polycarbonate-based resin, thereby obtaining a depolymerized solution; removing the aromatic diol compound, the organic solvent, and the alkylene glycol from the depolymerized solution; and recovering alkylene carbonate from the depolymerized solution from which the aromatic diol compound, the organic solvent, and the alkylene glycol have been removed; the organic solvent is methylene chloride; the weight ratio of the organic solvent to the alkylene glycol is 20:1 to 1:20; A method for producing a recycled cyclic carbonate composition.

2. 2. 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.

3. 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.

4. The method for producing a recycled cyclic carbonate composition according to claim 3 , wherein the organic salt catalyst comprises an amidine salt compound.

5. The method for producing a recycled cyclic carbonate composition according to claim 4, wherein the amidine salt compound comprises a salt compound represented by the following chemical formula A: 【Chemistry 1】 (In the above chemical formula A, R 1 , R 2 , R 3 are the same or different and can each independently be hydrogen or alkyl.

6. The method for producing a recycled cyclic carbonate composition according to claim 3 , wherein the organic base catalyst comprises an amidine-based compound or a guanidine-based compound.

7. The method for producing a recycled cyclic carbonate composition according to claim 6, wherein the amidine compound comprises 1,8-diazabicyclo[5.4.0]undec-7-ene or 1,5-diazabicyclo[4.3.0]non-5-ene.

8. The method for producing a recycled cyclic carbonate composition according to claim 6, wherein the guanidine-based compound comprises 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.

9. 4. The method for producing a recycled cyclic carbonate composition according to claim 3, wherein the inorganic base catalyst comprises sodium hydroxide (NaOH) or potassium hydroxide (KOH).

10. The step of depolymerizing the polycarbonate-based resin by adding alkylene glycol and a catalyst to the mixture includes:

2. 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 24 hours.

11. 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 for producing the recycled cyclic carbonate composition of claim 1, comprising the step of: removing alkylene glycol from the depolymerized solution.

12. The step of removing the aromatic diol compound from the depolymerization solution comprises: crystallizing the aromatic diol compound formed by the depolymerization; and 12. The method for producing the recycled cyclic carbonate composition according to claim 11, further comprising: filtering the crystals of the aromatic diol compound.

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

12. The method of claim 11, comprising distilling the organic solvent.

14. The step of distilling the organic solvent comprises:

14. The method for producing a recycled cyclic carbonate composition according to claim 13, wherein the method is carried out at a temperature of from 40°C to 80°C and a pressure of from 689.5 kPa (100 psi) to 1379 kPa (200 psi).

15. The step of removing alkylene glycol from the depolymerization solution comprises:

12. The method for producing a recycled cyclic carbonate composition according to claim 11, further comprising 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.

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

12. The method for producing a recycled cyclic carbonate composition according to claim 11, further comprising the step of removing phenolic impurities derived from the aromatic diol compound formed by the depolymerization using an adsorbent.

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

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

18. The method for producing a recycled cyclic carbonate composition according to claim 17, carried out at a temperature of from 40°C to 80°C and a pressure of from 689.5 kPa (100 psi) to 1379 kPa (200 psi).

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