Monomer composition for synthesizing recycled plastics, its manufacturing method, recycled plastics using the same, and molded articles

Abstract

The present invention relates to a monomer composition for synthesizing recycled plastics, which contains an aromatic diol compound, has an aromatic diol compound derivative impurity ratio of 10% or less according to formula 1, and has a color coordinate b* of 0.01 to 2, and is recovered from a polycarbonate resin; a method for producing the same; and recycled plastics and molded articles each using the same.

Description

[Technical Field]

[0001] Cross-citation with related applications (etc.) This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0045959, filed April 13, 2022, and Korean Patent Application No. 10-2023-0044308, filed April 4, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a monomer composition for synthesizing recycled plastics, which contains an aromatic diol compound having high purity and excellent optical properties recovered through recycling by chemical decomposition of polycarbonate resins, a method for producing the same, and recycled plastics and molded articles using the same. [Background technology]

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

[0004] Although polycarbonate is widely used for various purposes, environmental and health concerns have been raised regarding its disposal.

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

[0006] Chemical decomposition of polycarbonate refers to the process of decomposing polycarbonate to obtain its monomer, an aromatic diol compound (e.g., bisphenol A (BPA)), which is then used again in polymerization to obtain high-purity 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. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a monomer composition for synthesizing recycled plastics, which can secure aromatic diol compounds having high purity and excellent optical properties recovered through recycling by chemical decomposition of polycarbonate resins.

[0009] The present invention also provides a method for producing the monomer composition for synthesizing recycled plastics, and recycled plastics and molded articles made using the monomer composition for synthesizing recycled plastics. [Means for solving the problem]

[0010] To solve the above problems, the present specification provides a monomer composition for synthesizing recycled plastics, which contains an aromatic diol compound, has an aromatic diol compound derivative impurity ratio of 10% or less according to the following formula 1, has a color coordinate b* of 0.01 to 2, and is recovered from a polycarbonate resin. [Formula 1] Aromatic diol compound derivative impurity ratio (%) = (Aromatic diol compound derivative peak area on HPLC / Total peak area on HPLC) × 100

[0011] The present specification further provides a method for producing a monomer composition for synthesizing recycled plastics, the method including the steps of: adding polycarbonate to an organic solvent to produce a mixed solution; adding a glycol compound and an inorganic base catalyst to the mixed solution and stirring the mixture; and obtaining an aromatic diol compound formed in the stirring step.

[0012] Further provided herein is a recycled plastic comprising a reaction product of the monomer composition for synthesizing recycled plastic and a comonomer.

[0013] Further provided herein is a molded article comprising the recycled plastic.

[0014] Hereinafter, a monomer composition for synthesizing recycled plastics according to specific embodiments of the present invention, a method for producing the same, and recycled plastics and molded articles using the same will be described in more detail.

[0015] 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.

[0016] As used herein, the singular includes the plural unless the phrase clearly indicates otherwise.

[0017] As used herein, the meaning of "comprising" is to embody 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.

[0018] 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, the first component can be named the second component, and similarly, the second component can be named the first component.

[0019] 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, amide, 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 linked to two or more substituents" 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.

[0020] In this specification, the alkyl group is a monovalent functional group derived from an alkane, and may be linear or branched. The number of carbon atoms in the linear alkyl group is not particularly limited, but is preferably 1 to 20. The number of carbon atoms in the branched alkyl group is preferably 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 substituents are the same as those described above.

[0021] As used herein, the term "alkylene group" refers to a divalent functional group derived from an alkane, and the above description of the alkyl group is applicable, except that the alkyl group is a divalent functional group. Examples of the alkylene group include linear or branched groups such as methylene, ethylene, propylene, isobutylene, sec-butylene, tert-butylene, pentylene, and hexylene. The alkylene group may be substituted or unsubstituted, and if substituted, examples of the substituent are the same as those described above.

[0022] As used herein, the term "fused ring" refers to a cyclic structure in a polycyclic system consisting of two or more carbocyclic or heterocyclic rings, in which adjacent rings share only two atoms.

[0023] 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, more particularly 1 or 2."

[0024] 1. Monomer composition for synthesizing recycled plastics According to one embodiment of the present invention, there is provided a monomer composition for synthesizing recycled plastics, which comprises an aromatic diol compound, has an impurity ratio of aromatic diol compound derivatives represented by the following formula 1 of 10% or less, has a color coordinate b* of 0.01 to 2, and is recovered from a polycarbonate-based resin. [Formula 1] Aromatic diol compound derivative impurity ratio (%) = (Aromatic diol compound derivative peak area on HPLC / Total peak area on HPLC) × 100

[0025] The present inventors have confirmed through experiments that the monomer composition for synthesizing recycled plastics of one embodiment is recovered through recycling by chemical decomposition of polycarbonate-based resins, yet has the characteristics of high purity and significantly reduced impurities at the level of a newly synthesized aromatic diol compound, as well as excellent optical properties, and therefore can realize excellent properties when synthesizing polycarbonate-based resins using this monomer composition, and have completed the invention.

[0026] The present invention has the technical advantage that a highly pure composition containing an aromatic diol compound can be obtained by recycling a polycarbonate resin through chemical decomposition.

[0027] Specifically, the monomer composition for synthesizing recycled plastics according to one embodiment is characterized by being recovered from a polycarbonate-based resin. That is, as a result of recovering the monomer composition for synthesizing recycled plastics according to one embodiment from a polycarbonate-based resin, a monomer composition for synthesizing recycled plastics containing an aromatic diol compound is also obtained.

[0028] The polycarbonate-based resin includes both homopolymers and copolymers containing polycarbonate repeating units, and is a general term for reaction products obtained through the polymerization or copolymerization of monomers containing an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized when a single carbonate repeating unit is obtained using only one aromatic diol compound and one carbonate precursor. Alternatively, a copolymer can be synthesized when two or more carbonates are obtained using one aromatic diol compound and two or more carbonate precursors, two or more aromatic diol compounds and one carbonate precursor, or one aromatic diol compound, one carbonate precursor, and one or more other diols. The homopolymer or copolymer may include low molecular weight compounds, oligomers, or polymers depending on the molecular weight range.

[0029] In addition, the monomer composition for synthesizing recycled plastics according to the embodiment may include an aromatic diol compound. 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 of the monomer composition for synthesizing recycled plastics according to one embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0030] The aromatic diol compound is recovered from the polycarbonate resin used to recover the monomer composition for synthesizing recycled plastics. In other words, the aromatic diol compound is also obtained as a result of recovery from the polycarbonate resin to obtain the monomer composition for synthesizing recycled plastics of the embodiment. Therefore, when a new aromatic diol compound is added from outside, separately from the recovery from the polycarbonate resin to prepare the monomer composition for synthesizing recycled plastics of the embodiment, it is not included in the category of aromatic diol compounds of the present invention.

[0031] 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.

[0032] Specifically, the monomer composition for synthesizing recycled plastics may have an upper numerical range of the aromatic diol compound derivative impurity ratio according to Formula 1 of 10% or less, or 5% or less, or 1% or less, or 0.5% or less, or 0.43% or less, and a lower numerical range of 0.01% or more, or 0.05% or more, or 0.1% or more, or 0.15% or more, or 0.2% or more, or 0.25% or more, or 0.3% or more, or 0.35% or more, or 0.40% or more. The upper and lower numerical ranges may be combined to satisfy the range from the lower limit to the upper limit. For example, the aromatic diol compound derivative impurity ratio according to Formula 1 may be 0.01% to 10%.

[0033] According to the formula 1, the unit of the aromatic diol compound derivative impurity ratio, % means the peak area ratio on HPLC, that is, area %.

[0034] In the formula 1, the peak area of ​​the aromatic diol compound derivative on HPLC may be the sum of the peak areas of one or more aromatic diol compound derivatives. For example, when the aromatic diol compound derivative is a mixture of two types of aromatic diol compound derivatives, monohydroxyethyl-bisphenol A and bishydroxyethyl-bisphenol A, the peak area means the sum of the peak areas of monohydroxyethyl-bisphenol A and bishydroxyethyl-bisphenol A.

[0035] More specifically, the monohydroxyethyl-bisphenol A [MHE-BPA] may exhibit a peak at an HPLC retention time of 2.84 minutes, and the bishydroxyethyl-bisphenol A [BHE-BPA] may exhibit a peak at an HPLC retention time of 2.61 minutes.

[0036] The method for measuring the weight ratio of aromatic diol compound derivative impurities in the monomer composition for synthesizing recycled plastics according to an embodiment is not particularly limited, and for example, high performance liquid chromatography (HPLC) analysis can be used. The specific HPLC method, conditions, and equipment can be various known methods without limitation. However, as an example, 1 wt% of the recycled bisphenol A monomer composition can be dissolved in acetonitrile (ACN) solvent at atmospheric pressure and 20-30°C, and then measured using a UG 120 (4.6 mm 1.DX 50 mm) and a Waters HPLC system (e2695 separation module, 2998 PDA detector). More specifically, the measurement can be performed under the following 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.

[0037] As described above, in the monomer composition for synthesizing recycled plastics according to one embodiment, the ratio of impurities derived from aromatic diol compounds other than aromatic diol compounds, which are the main target substances for recovery, is significantly reduced, and excellent physical properties can be realized when synthesizing polycarbonate-based resins using the same.

[0038] Meanwhile, the monomer composition for synthesizing recycled plastics according to one embodiment may have a color coordinate b* value of 0.01 to 2, or 0.5 to 1.2, or 0.58 to 1.02. That is, the lower limit numerical range of the color coordinate b* value of the monomer composition for synthesizing recycled plastics according to one embodiment may be 0.01 or more, or 0.5 or more, or 0.58 or more, or 0.6 or more, or 0.7 or more, or 0.8 or more, or 0.9 or more, or 1.0 or more, and the upper limit numerical range may be 2 or less, or 1.2 or less, or 1.02 or less. The upper limit numerical range and the lower limit numerical range may be combined to satisfy the range from the lower limit to the upper limit.

[0039] In addition, the monomer composition for synthesizing recycled plastics according to one embodiment may have a color coordinate L* value of 94 to 99, or 95 to 98, or 96 to 98, or 96.554 to 97.207. That is, the monomer composition for synthesizing recycled plastics according to one embodiment may have a lower numerical range for the color coordinate L* value of 94 or more, or 95 or more, or 96 or more, or 96.3 or more, or 96.554 or more, or 96.6 or more, or 96.9 or more, or 97.2 or more, and an upper numerical range of 99 or less, or 98 or less, or 97.207 or less. The upper numerical range and the lower numerical range may be combined to satisfy the range from the lower limit to the upper limit.

[0040] In addition, the monomer composition for synthesizing recycled plastics according to one embodiment may have a color coordinate a* of 0.01 to 1.5, or 0.1 to 1, or 0.10 to 0.23. That is, the lower limit of the color coordinate a* value of the monomer composition for synthesizing recycled plastics according to one embodiment may be 0.01 or more, or 0.1 or more, or 0.12 or more, or 0.14 or more, or 0.16 or more, or 0.18 or more, or 0.2 or more, or 0.22 or more, and the upper limit may be 1.5 or less, or 1 or less, or 0.23 or less. The upper limit and lower limit numerical ranges may be combined to satisfy a range from the lower limit to the upper limit.

[0041] In the present invention, "color coordinates" refers to coordinates in the CIE Lab color space, which are color values ​​defined by the CIE (Commission International de l'Eclairage), and any position in the CIE color space can be expressed by three coordinate values: L*, a*, and b*.

[0042] Here, the L* value indicates brightness, with L* = 0 indicating black and L* = 100 indicating white. The a* value indicates whether the color having the color coordinates is biased toward either pure red or pure green, and the b* value indicates whether the color having the color coordinates is biased toward either pure yellow or pure blue.

[0043] Specifically, the a* value ranges from -a to +a. The maximum value of a* (a* max) indicates pure red, and the minimum value of a* (a* min) indicates pure green. The b* value ranges from -b to +b. The maximum value of b* (b* max) indicates pure yellow, and the minimum value of b* (b* min) indicates pure blue. For example, a negative b* value indicates a color that is biased toward pure blue, and a positive b* value indicates a color that is biased toward pure yellow. Comparing b*=50 and b*=80 means that b*=80 is closer to pure yellow than b*=50.

[0044] When the color coordinate b* value of the monomer composition for synthesizing recycled plastics of the embodiment increases excessively to more than 2, the color of the monomer composition for synthesizing recycled plastics of the embodiment becomes too yellowish, resulting in poor color characteristics. Also, when the color coordinate b* value of the monomer composition for synthesizing recycled plastics of the embodiment decreases excessively to less than 0.01, the color of the monomer composition for synthesizing recycled plastics of the embodiment becomes too blueish, resulting in poor color characteristics.

[0045] If the color coordinate L* value of the monomer composition for synthesizing recycled plastics of the embodiment is excessively reduced to less than 94, the color properties of the monomer composition for synthesizing recycled plastics of the embodiment will be poor.

[0046] On the other hand, if the color coordinate a* value of the monomer composition for synthesizing recycled plastics of the embodiment increases too much to exceed 1.5, the color of the monomer composition for synthesizing recycled plastics of the embodiment becomes too reddish, resulting in poor color characteristics. Also, if the color coordinate a* value of the monomer composition for synthesizing recycled plastics of the embodiment decreases too much to less than 0.01, the color of the monomer composition for synthesizing recycled plastics of the embodiment becomes too greenish, resulting in poor color characteristics.

[0047] The method for measuring the color coordinates L*, a*, and b* of the monomer composition for synthesizing recycled plastics according to the embodiment is not particularly limited, and various color characteristic measurement methods used in the plastics field may be applied without limitation.

[0048] However, as an example of a method for measuring the color coordinates L*, a*, and b* values ​​of the monomer composition for synthesizing recycled plastics according to an embodiment, the measurement can be performed in a reflection mode using a HunterLab UltraScan PRO Spectrophotometer.

[0049] Meanwhile, in the monomer composition for synthesizing recycled plastics according to one embodiment, the lower limit of the aromatic diol compound yield may be 90% or more, or 92% or more, or 93% or more, or 94% or more, or 95% or more, or 96% or more, and the upper limit may be 100% or less, or 98% or less, or 97% or less, or 96.4% or less. The upper limit and the lower limit may be combined to satisfy the range from the lower limit to the upper limit. The increase in the aromatic diol compound yield to 90% or more is believed to be due to the method for producing the monomer composition for synthesizing recycled plastics, which will be described later.

[0050] The method for measuring the aromatic diol compound yield of the monomer composition for synthesizing recycled plastics according to the embodiment is not particularly limited, and may be calculated, for example, according to the following Equation 2: [Formula 2] Yield (%) = W1 / W0 In the above formula 2, W0 is the mass of the aromatic diol compound obtained upon 100% decomposition, and W1 is the mass of the aromatic diol compound actually obtained.

[0051] In the formula 2, the mass of the aromatic diol compound can be measured by various commonly known mass measurement methods without limitation, for example, by using a balance.

[0052] As such, in the monomer composition for synthesizing recycled plastics according to one embodiment, the yield of aromatic diol compounds, which are the main target materials for recovery, is significantly increased to over 90%, thereby improving the efficiency of the recycling process for polycarbonate resins.

[0053] The monomer composition for synthesizing recycled plastics according to an embodiment can be used as a raw material for manufacturing various recycled plastics (e.g., polycarbonate (PC)) as described below.

[0054] The monomer composition for synthesizing recycled plastics according to one embodiment may further contain small amounts of other additives and solvents. The specific types of additives and solvents are not particularly limited, and various substances widely used in the process of recovering aromatic diol compounds by depolymerization of polycarbonate-based resins may be used without limitation.

[0055] The monomer composition for synthesizing recycled plastics according to one embodiment may be obtained by a method for producing a monomer composition for synthesizing recycled plastics, which will be described later. That is, the monomer composition for synthesizing recycled plastics according to one embodiment corresponds to a resultant product obtained through various filtration, purification, washing, and drying processes to obtain only aromatic diol compounds, which are the main target substances for recovery, in high purity after the depolymerization reaction of polycarbonate-based resin.

[0056] 2. Manufacturing method of monomer composition for synthesizing recycled plastics According to another embodiment of the present invention, there may be provided a method for producing a monomer composition for synthesizing recycled plastics, as described in claim 7, comprising the steps of: adding polycarbonate to an organic solvent to prepare a mixed solution; adding a glycol compound and an inorganic base catalyst to the mixed solution and stirring the mixture; and obtaining an aromatic diol compound formed in the stirring step.

[0057] Specifically, the present invention decomposes polycarbonate into glycol compounds under mild conditions, and can stably obtain bisphenol A, a highly pure monomer.

[0058] The term "polycarbonate" refers to both homopolymers and copolymers containing carbonate repeating units, and is a general term for reaction products obtained through the polymerization or copolymerization of monomers containing an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized when a single carbonate repeating unit is obtained using only one aromatic diol compound and one carbonate precursor. Alternatively, a copolymer can be synthesized when two or more carbonates are obtained using one aromatic diol compound and two or more carbonate precursors, two or more aromatic diol compounds and one carbonate precursor, or one aromatic diol compound, one carbonate precursor, and one or more other diols. The homopolymer or copolymer may be a low molecular weight compound, oligomer, or polymer, depending on the molecular weight range.

[0059] The polycarbonate may be applied in various forms and types, such as new polycarbonate produced through synthesis, recycled polycarbonate produced through a recycling process, or polycarbonate waste.

[0060] In the present invention, the glycol-based compound may include any glycol compound or a derivative thereof, and specifically, the glycol-based compound may include an alkylene glycol. Specific examples of the alkylene glycol are not particularly limited, and various known alkylene glycols can be used without limitation, but examples include ethylene glycol and propylene glycol.

[0061] Meanwhile, the organic solvent may include one or more solvents selected from the group consisting of tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate. That is, the organic solvent may include tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

[0062] Specifically, when methylene chloride is used as the organic solvent, there is an advantage in that the dissolving property for polycarbonate is improved and the reactivity can be improved.

[0063] The weight ratio of the glycol-based compound, organic solvent, and polycarbonate is not particularly limited, but for example, the weight ratio of the glycol-based compound to the polycarbonate 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, or 1:1.2 to 1:2.

[0064] The weight ratio of the organic solvent to the polycarbonate may also be from 10:1 to 1:10, or from 10:1 to 1:1, or from 10:1 to 2:1, or from 5:1 to 2:1, or from 3:1 to 2:1, or from 3:1 to 2.5:1, or from 10:1 to 5:1, or from 7:1 to 5:1, or from 7:1 to 6:1.

[0065] The weight ratio of the organic solvent to the glycol-based compound may also be 20:1 to 1:20, or 10:1 to 1:10, or 1:1 to 10:1, or 2:1 to 10:1, or 2:1 to 5:1, or 3:1 to 4:1, or 10:1 to 20:1, or 10:1 to 15:1, or 11:1 to 13:1, or 12:1 to 13:1.

[0066] Specifically, by mixing the glycol compound and the organic solvent within the above range, it is possible to carry out a desired level of depolymerization reaction of the polymer.

[0067] The inorganic base catalyst may be added in an amount of 0.1 to 10 parts by weight, or 0.1 to 5 parts by weight, or 0.1 to 1 part by weight, per 100 parts by weight of polycarbonate. Specifically, by including an inorganic base catalyst in the above content range, there is an advantage in that the catalytic reaction can be carried out economically.

[0068] The inorganic base catalyst refers to a basic non-ionic inorganic compound, specifically, sodium hydroxide (NaOH) or potassium hydroxide (KOH), preferably sodium hydroxide (NaOH), but is not limited thereto. The use of the inorganic base catalyst allows the decomposition reaction to be carried out under mild conditions, which is advantageous in terms of economy.

[0069] Meanwhile, the step of adding a glycol compound and an inorganic base catalyst to the mixed solution and stirring the mixture may involve 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, or 70°C to 90°C for 1 hour to 24 hours, or 1 hour to 12 hours, or 1 hour to 8 hours.

[0070] Specifically, the above conditions are mild process conditions compared to existing pressurized / high temperature processes, and stirring under these conditions allows the process to be carried out in a mild process compared to pressurized / high temperature processes. In particular, stirring at 70 to 90°C for 1 to 12 hours has the advantage of providing the most efficient results in terms of reproducibility and stability.

[0071] Meanwhile, the step of obtaining the aromatic diol compound formed in the stirring step may include the steps of adding the product obtained in the stirring step to a crystallization solvent to form aromatic diol compound crystals, and filtering the aromatic diol compound crystals. Specific equipment and conditions for adding the crystallization solvent to form aromatic diol compound crystals are not limited, and various recrystallization processes that have been widely used in the technical field of recovering aromatic diol compounds (bisphenol A) can be applied without limitation. One example of the crystallization solvent is water.

[0072] Furthermore, the step of filtering the aromatic diol compound crystals is not limited to specific filtering equipment or conditions, and various filtering processes that have been widely used in the technical field of recovering aromatic diol compounds (bisphenol A) can be applied without limitation. For example, vacuum filtration may be used.

[0073] 3. Recycled plastic According to another embodiment of the present invention, there may be provided a recycled plastic comprising a reaction product of the monomer composition for synthesizing recycled plastic of the above embodiment and a comonomer.

[0074] The content of the monomer composition for synthesizing recycled plastics according to the embodiment includes all of the content described above in embodiments different from the embodiment.

[0075] Examples of the recycled plastic are not particularly limited, and various plastics synthesized using an aromatic diol compound such as bisphenol A and a carbonate precursor such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate as a monomer can be used without limitation. A more specific example is a polycarbonate resin.

[0076] The polycarbonate-based resin includes both homopolymers and copolymers containing polycarbonate repeating units, and is a general term for reaction products obtained through the polymerization or copolymerization of monomers containing an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized when a single carbonate repeating unit is obtained using only one aromatic diol compound and one carbonate precursor. Alternatively, a copolymer can be synthesized when two or more carbonates are obtained using one aromatic diol compound and two or more carbonate precursors, two or more aromatic diol compounds and one carbonate precursor, or one aromatic diol compound, one carbonate precursor, and one or more other diols. The homopolymer or copolymer may include low molecular weight compounds, oligomers, or polymers depending on the molecular weight range.

[0077] More specifically, the recycled plastic may include a reaction product of the monomer composition for synthesizing recycled plastic and a comonomer, and the comonomer may be a carbonate precursor. Specific examples of the carbonate precursor include phosgene, triphosgene, diphosgene, bromophosgene, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl)carbonate, and bishaloformates.

[0078] The reaction process of the monomer composition and comonomer for synthesizing recycled plastics to synthesize the polycarbonate-based resin is not particularly limited, and various known polycarbonate manufacturing methods can be applied without limitation.

[0079] However, as an example of the method for producing polycarbonate, a method for producing polycarbonate including a step of polymerizing a composition containing a monomer composition for synthesizing recycled plastics and a comonomer may be used. In this case, the polymerization may be performed by interfacial polymerization, which allows the polymerization reaction to occur at atmospheric pressure and low temperature, and facilitates the control of molecular weight.

[0080] The polymerization temperature may be 0° C. to 40° C., and the reaction time may be 10 minutes to 5 hours. The pH during the reaction may be maintained at 9 or higher or 11 or higher.

[0081] The solvent used in the polymerization is not particularly limited as long as it is a solvent used in the art for polycarbonate polymerization. For example, halogenated hydrocarbons such as methylene chloride and chlorobenzene may be used.

[0082] The polymerization may be carried out in the presence of an acid binder, and as the acid binder, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an amine compound such as pyridine may be used.

[0083] The polymerization can be carried out in the presence of a molecular weight regulator to control the molecular weight of the polycarbonate. The molecular weight regulator can be an alkylphenol having 1 to 20 carbon atoms, and specific examples thereof include p-tert-butylphenol, p-cumylphenol, decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, or triacontylphenol. The molecular weight regulator can be added before, during, or after the initiation of polymerization. The molecular weight regulator can be used in an amount of 0.01 to 10 parts by weight, or 0.1 to 6 parts by weight, per 100 parts by weight of the aromatic diol compound. The desired molecular weight can be obtained within this range.

[0084] In addition, to accelerate the polymerization reaction, a reaction accelerator such as a tertiary amine compound, a quaternary ammonium compound, or a quaternary phosphonium compound, such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, may be additionally used.

[0085] 4. Molded products According to another embodiment of the present invention, a molded product may be provided that includes the recycled plastic of the other embodiment. The recycled plastic includes all of the above-mentioned aspects of the other embodiment.

[0086] The molded product may be obtained by applying the recycled plastic to various known plastic molding methods without limitation, and examples of the molding methods include injection molding, foam injection molding, blow molding, and extrusion molding.

[0087] The molded article is not particularly limited and can be applied to various molded articles using plastics without any limitation, such as automobile parts, electrical and electronic products, communication products, daily necessities, building materials, optical parts, exterior materials, etc.

[0088] In addition to the recycled plastic of the other embodiment, the molded article may further include, if necessary, one or more additives selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent brighteners, UV absorbers, pigments, and dyes.

[0089] An example of a method for manufacturing the molded product may include thoroughly mixing the recycled plastic of the other embodiment and an additive using a mixer, extruding the mixture using an extruder to form pellets, drying the pellets, and then injecting them into an injection molding machine. [Effects of the Invention]

[0090] According to the present invention, there are provided a monomer composition for synthesizing recycled plastics, which contains an aromatic diol compound having high purity and excellent optical properties recovered through recycling by chemical decomposition of polycarbonate resins, a method for producing the same, and recycled plastics and molded articles using the same. DETAILED DESCRIPTION OF THE INVENTION

[0091] 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.

[0092] <Example: Production of Recycled Bisphenol A Monomer Composition> Example 1 80 g of methylene chloride and 30 g of polycarbonate were placed in a 250 ml three-neck flask and stirred.

[0093] Then, 22 g of ethylene glycol and 0.05 g of sodium hydroxide (NaOH) as a catalyst were added, and the mixture was stirred at 70°C for 24 hours (mass ratio of polycarbonate:methylene chloride:ethylene glycol:sodium hydroxide = 30:80:22:0.05).

[0094] After the reaction was completed, the reaction product was poured into water, and the crystallized bisphenol A was filtered under reduced pressure to obtain bisphenol A, thereby producing a recycled bisphenol A monomer composition.

[0095] Example 2 A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that the mass ratio of polycarbonate:methylene chloride:ethylene glycol:sodium hydroxide was changed to 30:200:16:0.16.

[0096] Example 3 80 g of methylene chloride and 30 g of polycarbonate were placed in a 250 ml three-neck flask and stirred.

[0097] Then, 27 g of propylene glycol and 0.05 g of sodium hydroxide (NaOH) as a catalyst were added, and the mixture was stirred at 70°C for 24 hours (mass ratio of polycarbonate:methylene chloride:propylene glycol:sodium hydroxide = 30:80:27:0.05).

[0098] After the reaction was completed, the reaction product was poured into water, and the crystallized bisphenol A was filtered under reduced pressure to obtain bisphenol A, thereby producing a recycled bisphenol A monomer composition.

[0099] Example 4 A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that the mass ratio of polycarbonate:methylene chloride:ethylene glycol:sodium hydroxide was changed to 30:200:20:0.16.

[0100] <Comparative Example: Production of Recycled Bisphenol A Monomer Composition> Comparative Example 1 20 g of polycarbonate was placed in a 250 ml three-neck flask and stirred.

[0101] Thereafter, 22 g of ethylene glycol and 0.05 g of sodium hydroxide (NaOH) as a catalyst were added, and the mixture was stirred at 130° C. for 24 hours.

[0102] After the reaction was completed, the reaction product was poured into water, and the crystallized bisphenol A was filtered under reduced pressure to obtain bisphenol A, thereby producing a recycled bisphenol A monomer composition.

[0103] Comparative Example 2 60 ml of methylene chloride, 30 ml of methanol, and 0.6 g of sodium hydroxide (NaOH) were placed in a 250 ml three-neck flask and stirred.

[0104] Thereafter, 30 g of waste polycarbonate was added and stirred at 40°C for 5 hours.

[0105] After the reaction was completed, the reaction product was poured into water, and the crystallized bisphenol A was filtered under reduced pressure to obtain bisphenol A, thereby producing a recycled bisphenol A monomer composition.

[0106] Comparative Example 3 Toluene (60 ml), methanol (30 ml), and sodium hydroxide (NaOH) (0.6 g) were placed in a 250 ml three-neck flask and stirred.

[0107] Thereafter, 30 g of waste polycarbonate was added and stirred at 60°C for 5 hours.

[0108] After the reaction was completed, the reaction product was poured into water, and the crystallized bisphenol A was filtered under reduced pressure to obtain bisphenol A, thereby producing a recycled bisphenol A monomer composition.

[0109] <Experimental Example> The properties of the recycled bisphenol A monomer compositions or by-products obtained in the examples and comparative examples were measured by the following methods, and the results are shown in Table 1.

[0110] 1. Color coordinates (L*, a*, b*) The recycled bisphenol A monomer composition was analyzed in reflectance mode using a HunterLab UltraScan PRO Spectrophotometer instrument.

[0111] 2. Impurity ratio of BPA derivatives (MHE-BPA, BHE-BPA) A 1 wt% recycled bisphenol A monomer composition was dissolved in acetonitrile (ACN) solvent at atmospheric pressure and 20-30°C, and the purity of bisphenol A (BPA) was analyzed using a UG 120 (4.6 mm I.D.X 50 mm) and a Waters HPLC system (e2695 separation module, 2998 PDA detector).

[0112] The peak area ratio (unit: %) of BPA derivative (monohydroxyethyl-bisphenol A [MHE-BPA], bishydroxyethyl-bisphenol A [BHE-BPA]) impurities relative to 100% of the total HPLC peak area was measured according to the following formula 1. [Formula 1] BPA derivative impurity ratio (%) = (bisphenol A derivative peak area on HPLC / total peak area on HPLC) × 100 In the above formula 1, the peak area of ​​the bisphenol A derivative on HPLC is specifically as follows, and in the above formula 1, the peak area of ​​the bisphenol A derivative on HPLC is the sum of the peak areas of MHE-BPA and BHE-BPA. Monohydroxyethyl-bisphenol A [MHE-BPA]: Peak at retention time 2.84 minutes Bishydroxyethyl-bisphenol A [BHE-BPA]: Peak at retention time 2.61 minutes

[0113] Also, the HPLC measurement conditions are as follows. <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

[0114] 3. BPA Yield When the polycarbonate used in the reaction was completely decomposed, the weight of BPA generated was measured, and the obtained BPA weight was measured. The yield of BPA was calculated as shown in the following formula 2. [Formula 2] Yield (%) = W1 / W0 In the above formula 2, W0 is the mass of BPA obtained at 100% decomposition, and W1 is the actual mass of BPA obtained. Specifically, when about 100 g of polycarbonate is decomposed, theoretically, the mass of BPA obtained at 100% decomposition is 89 g. If the actual mass of BPA obtained is 80 g, the yield is 80 / 89 * 100 = 90%.

[0115]

Table 1

[0116] As shown in Table 1, the recycled bisphenol A monomer compositions obtained in Examples 1 to 4 exhibited excellent optical properties, with color coordinates L* ranging from 96.554 to 97.207, a* ranging from 0.10 to 0.23, and b* ranging from 0.58 to 1.02. Furthermore, the recycled bisphenol A monomer compositions obtained in Examples 1 to 4 exhibited low BPA derivative impurity ratios ranging from 0.05% to 0.43%. Furthermore, the recycled bisphenol A monomer compositions obtained in Examples 1 to 4 exhibited high bisphenol A yields ranging from 93.2% to 96.4%.

[0117] In contrast, the recycled bisphenol A monomer composition obtained in Comparative Example 1 had a BPA derivative impurity ratio of 22.9%, which was measured to be higher than those of the Examples.

[0118] In addition, the recycled bisphenol A monomer compositions obtained in Comparative Examples 2 and 3 exhibited color coordinates L* of 91.73 to 91.95, a* of 2.554 to 2.667, and b* of 3.457 to 3.847, showing poor optical properties compared to the Examples, and the bisphenol A yield was 85% to 86%, which was lower than that of the Examples.

Claims

1. Contains an aromatic diol compound, The aromatic diol compound derivative impurity ratio according to the following formula 1 is 10% or less, the color coordinate b* is from 0.01 to 2; A method for producing a monomer composition for synthesizing recycled plastics recovered from polycarbonate-based resins, comprising: adding polycarbonate to an organic solvent to prepare a mixture; adding a glycol compound and an inorganic base catalyst to the mixed solution and stirring the mixture; and obtaining the aromatic diol compound formed in the stirring step, the organic solvent comprises methylene chloride; the weight ratio of the organic solvent to the glycol-based compound is from 2:1 to 10:1, or from 10:1 to 20:1; Method for producing a monomer composition for synthesizing recycled plastics: [Formula 1] Aromatic diol compound derivative impurity ratio (%)=(Aromatic diol compound derivative peak area on HPLC / Total peak area on HPLC)×100.

2. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein in formula 1, the peak area of ​​the aromatic diol compound derivative on HPLC is the sum of the peak areas of one or more aromatic diol compound derivatives.

3. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the derivative of the aromatic diol compound comprises one or more compounds selected from the group consisting of monohydroxyethyl-bisphenol A and bishydroxyethyl-bisphenol A.

4. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the monomer composition for synthesizing recycled plastics has a color coordinate L* of 94 to 99.

5. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the monomer composition for synthesizing recycled plastics has a color coordinate a* of 0.01 to 1.

5.

6. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the aromatic diol compound is recovered from a polycarbonate resin used in recovering the monomer composition for synthesizing recycled plastics.

7. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the glycol-based compound includes alkylene glycol.

8. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the inorganic base catalyst is added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of polycarbonate.

9. 2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the inorganic base catalyst comprises sodium hydroxide (NaOH) or potassium hydroxide (KOH).

10. The step of adding a glycol compound and an inorganic base catalyst to the mixed solution and stirring the mixture includes:

2. The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, wherein the mixture is stirred at a temperature of 20°C to 100°C for 1 hour to 30 hours.

11. The step of obtaining the aromatic diol compound formed in the stirring step includes: adding the product obtained in the stirring step to a crystallization solvent to form aromatic diol compound crystals; The method for producing a monomer composition for synthesizing recycled plastics according to claim 1, further comprising the step of filtering the aromatic diol compound crystals.

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