KR20240070379A - Monomer composition for synthesising recycled plastic, preparation method thereof, and recycled plastic, molded product using the same - Google Patents

Abstract

The present invention provides a monomer composition for synthesizing recycled plastic that can achieve excellent color quality even though it is recovered through recycling by chemical decomposition of polycarbonate resin and has improved efficiency in the recovery process, a manufacturing method thereof, recycled plastic, and molded products using the same. It's about.

Description

Monomer composition for synthesizing recycled plastic, manufacturing method thereof, recycled plastic, and molded product using the same

The present invention provides a monomer composition for synthesizing recycled plastic that can achieve excellent color quality even though it is recovered through recycling by chemical decomposition of polycarbonate resin and has improved efficiency in the recovery process, a manufacturing method thereof, recycled plastic, and molded products using the same. It's about.

Polycarbonate is a thermoplastic polymer that has excellent properties such as excellent transparency, ductility, and relatively low manufacturing cost.

Although polycarbonate is widely used for various purposes, concerns about the environment and health have continuously been raised during waste disposal.

Currently, physical recycling methods are being implemented, but in this case, the problem of deterioration in quality occurs, so research on chemical recycling of polycarbonate is in progress.

Chemical decomposition of polycarbonate refers to the process of obtaining a monomeric aromatic diol compound (e.g., Bisphenol A (BPA)) through decomposition of polycarbonate and then using it for polymerization to obtain high purity polycarbonate. says

Representative examples of such chemical decomposition include thermal decomposition, hydrolysis, and alcohol decomposition. Among these, the most common method is alcohol decomposition using a base catalyst, but methanol decomposition has the problem of using methanol, which is harmful to the human body. In the case of ethanol, high temperature and high pressure conditions are required and the yield is not high.

In addition, although a method for decomposing alcohol using an organic catalyst is known, it has disadvantages in terms of economics.

The present invention is intended to provide a monomer composition for synthesizing recycled plastic that can achieve excellent color quality even when recovered through recycling by chemical decomposition of polycarbonate resin and has improved efficiency of the recovery process.

In addition, the present invention is to provide a method for producing the monomer composition for synthesizing recycled plastic, recycled plastic, and molded articles using the monomer composition for synthesizing recycled plastic.

In order to solve the above problem, in the present specification, it contains an aromatic diol compound, has a color coordinate b* of 1.8 or less, an APHA Color value measured by ASTM D 1209 of 30 or less, and is recovered from a polycarbonate-based resin. Provides a monomer composition for synthesizing recycled plastic.

Also in this specification, the step of depolymerizing a polycarbonate-based resin; Separating the carbonate precursor from the depolymerization reaction product; and a step of purifying the depolymerization product from which the carbonate precursor has been separated, wherein the step of purifying the depolymerization product from which the carbonate precursor has been separated includes adding a hydrophilic reducing agent to the depolymerization product from which the carbonate precursor has been separated; and adding an adsorbent to the depolymerization reaction product from which the carbonate precursor was separated, purifying it by adsorption, and then removing the adsorbent. A method for producing a monomer composition for synthesizing recycled plastic is provided.

The present specification also provides a recycled plastic comprising a reaction product of the monomer composition for synthesizing recycled plastic and a comonomer.

Also provided herein is a molded article containing the recycled plastic.

Hereinafter, the monomer composition for synthesizing recycled plastic according to specific embodiments of the invention, its manufacturing method, and recycled plastic and molded products using the same will be described in more detail.

Unless explicitly stated herein, terminology is intended to refer only to specific embodiments and is not intended to limit the invention.

As used herein, singular forms include plural forms unless phrases clearly indicate the contrary.

As used herein, the meaning of 'comprise' is to specify a specific characteristic, area, integer, step, operation, element and/or component, and to specify another specific property, area, integer, step, operation, element, component and/or group. It does not exclude the existence or addition of .

Additionally, in this specification, terms including ordinal numbers such as 'first' and 'second' are used for the purpose of distinguishing one component from another component and are not limited by the ordinal numbers. For example, within the scope of the present invention, a first component may also be referred to as a second component, and similarly, the second component may be referred to as a first component.

1. Monomer composition for recycling plastic synthesis

According to one embodiment of the invention, it contains an aromatic diol compound, has a color coordinate b* of 1.8 or less, an APHA Color value measured by ASTM D 1209 of 30 or less, and is recovered from a polycarbonate-based resin. A monomer composition for synthesizing recycled plastic may be provided.

The present inventors have found that the monomer composition for recycling plastic synthesis of the above embodiment can achieve excellent color quality for the aromatic diol compound, which is the main target of recovery, even though it is recovered through recycling by chemical decomposition of polycarbonate-based resin. The invention was completed after confirming through experiments that excellent physical properties were possible when synthesizing resin.

In particular, the monomer composition for recycling plastic synthesis of the above embodiment reduces the amount of organic solvent used in the adsorption purification process during the manufacturing process described later, and can also reduce the amount of water used in the recrystallization process, thereby increasing process efficiency and providing excellent color quality. There are technical advantages that can be implemented.

In addition, the present invention is a technology that can obtain a first composition containing an aromatic diol compound in high purity by recycling polycarbonate-based resin by chemical decomposition, and at the same time obtain a second composition containing diethyl carbonate, a high value-added by-product. It can have special advantages.

Specifically, the monomer composition for recycling plastic synthesis of the above embodiment is characterized in that it is recovered from polycarbonate-based resin. That is, as a result of recovery from polycarbonate-based resin to obtain the monomer composition for recycled plastic synthesis of the above embodiment, a monomer composition for recycled plastic synthesis containing an aromatic diol compound is obtained.

The polycarbonate-based resin includes all homopolymers or copolymers containing polycarbonate repeating units, and refers to reaction products obtained through polymerization or copolymerization of monomers including an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized if it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor. In addition, as the monomer, one type of aromatic diol compound and two or more types of carbonate precursors may be used, two or more types of aromatic diol compounds and one type of carbonate precursor may be used, or one type of other diol in addition to one type of aromatic diol compound and one type of carbonate precursor may be used. Using the above, a copolymer can be synthesized when two or more types of carbonate are contained. The homopolymer or copolymer may include low molecular weight compounds, oligomers, and polymers depending on the molecular weight range.

Additionally, the monomer composition for synthesizing recycled plastic of one 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, 1,1-bis (4-hydroxyphenyl) cyclonucleic acid (bisphenol Z), 2,2-bis (4-hydroxy-3,5-di Bromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, or mixtures of two or more thereof. Preferably, the aromatic diol compound of the monomer composition for recycling plastic synthesis of the above embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

The aromatic diol compound is characterized in that it is recovered from the polycarbonate-based resin used to recover the monomer composition for synthesizing recycled plastic. That is, as a result of recovery from polycarbonate-based resin to obtain the monomer composition for recycling plastic synthesis of the above embodiment, this means that an aromatic diol compound is also obtained. Therefore, the case where a new aromatic diol compound is added externally, separately from recovery from the polycarbonate-based resin, to produce the monomer composition for recycled plastic synthesis of the above embodiment is not included in the scope of the aromatic diol compound of the present invention.

Specifically, recovered from the polycarbonate-based resin means obtained through a depolymerization reaction of the polycarbonate-based resin. The depolymerization reaction can be performed under acidic, neutral, or basic conditions. In particular, the depolymerization reaction can be performed under basic (alkaline) conditions. In particular, the depolymerization reaction is preferably carried out in an ethanol solvent, as described later.

Meanwhile, the monomer composition for recycling plastic synthesis of the embodiment has a color coordinate b* value of 1.8 or less, or 1.65 or less, or 0.1 or more, or 1.0 or more, or 0.1 to 1.8, or 1.0 to 1.8, or 0.1 to 1.65, or 1.0. to 1.65, or 1.6 to 1.7, or 1.6 to 1.65, or 1.65 to 1.7.

In addition, the monomer composition for recycling plastic synthesis of the embodiment has a color coordinate L* of 95.5 or more, or 96 or more, or 100 or less, or 95.5 to 100, or 96 to 100, or 95.6 to 96.7, or 95.6 to 96, or 96. It may be from 96.7 to 96.7.

In addition, the monomer composition for recycling plastic synthesis of the embodiment has a color coordinate a* of -0.7 to -0.2, or -0.6 to -0.2, or -0.5 to -0.2, or -0.4 to -0.2, or -0.7 to -0.3. , or -0.6 to -0.3, or -0.5 to -0.3, or -0.4 to -0.3, or -0.7 to -0.5, or -0.6 to -0.5.

In the present invention, “color coordinates” refer to coordinates in the CIE Lab color space, which are color values specified by CIE (Commission International de l'Eclairage), and any position in the CIE color space is L*, It can be expressed as three coordinate values: a*, b*.

Here, the L* value represents brightness. If L*=0, it represents black, and if L*=100, it represents white. In addition, the a* value indicates whether the color with the corresponding color coordinate is biased toward pure red or pure green, and the b* value indicates whether the color with the corresponding color coordinate is biased toward pure yellow or pure green. It indicates which direction the color is biased towards pure blue.

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

The color coordinate b* value of the monomer composition for recycling plastic synthesis of the above embodiment excessively increases to more than 1.8, the color coordinate L* value excessively decreases to less than 95.5, or the color coordinate a* value deviates to more than -0.2 or less than -0.7. If this happens, the color characteristics of the monomer composition for synthesizing recycled plastic according to the above embodiment become poor. The example of the method for measuring the color coordinates L*, a*, and b* values of the monomer composition for recycling plastic synthesis of the above embodiment is not greatly limited, and various color characteristic measurement methods in the plastics field can be applied without limitation.

However, as an example of a method of measuring the color coordinates L*, a*, and b* values of the monomer composition for recycling plastic synthesis of the above embodiment, they can be measured in reflection mode using HunterLab UltraScan PRO Spectrophotometer equipment.

Meanwhile, the monomer composition for recycling plastic synthesis of one embodiment has an APHA Color value measured by ASTM D 1209 of 30 or less, or 29 or less, or 28 or less, or 25 or less, or 22 or less, or 0 or more, or 1 or more. , or 0 to 30, or 0 to 29, or 0 to 28, or 0 to 25, or 0 to 22, or 1 to 30, or 1 to 29, or 1 to 28, or 1 to 25, or 1 to 22 , or 22 to 28, or 22 to 25, or 25 to 28.

The example of the method for measuring the APHA Color of the monomer composition for recycling plastic synthesis of the above embodiment is not greatly limited. For example, it can be measured according to the ASTM D 1209 measurement method using HunterLab UltraScan PRO Spectrophotometer equipment.

APHA Color is a value derived from a color comparison between colorless water and a yellow PtCo solution. The closer the value is to 0, the more colorless it is, and the closer it is to 500, the more yellow it appears. Therefore, as the APHA Color of the monomer composition for synthesizing recycled plastic of the above embodiment decreases to 30 or less, it is possible to use this to achieve transparent color properties when synthesizing polycarbonate-based resin.

On the other hand, if the APHA Color of the monomer composition for recycling plastic synthesis of the above embodiment increases excessively, such as exceeding 30, there is a limitation in that it becomes difficult to synthesize a colorless and transparent polycarbonate-based resin due to yellow discoloration.

Meanwhile, the monomer composition for synthesizing recycled plastic of one embodiment may further include a hydrophilic reducing agent. The hydrophilic reducing agent is soluble in water and can be used as a bleaching agent to remove color by changing colored substances. Examples of the hydrophilic reducing agent are not greatly limited, and various conventionally known hydrophilic reducing bleaching agents can be applied without limitation, but one example is sodium dithionite (SDT).

Meanwhile, the monomer composition for recycling plastic synthesis of the above embodiment may be obtained as a by-product of diethyl carbonate. The diethyl carbonate is characterized in that it is recovered from the polycarbonate-based resin used to recover the monomer composition for recycling plastic synthesis of the above embodiment.

That is, as a result of recovery from polycarbonate-based resin to obtain the monomer composition for recycling plastic synthesis of the above embodiment, diethyl carbonate is also obtained. Therefore, the case where new diethyl carbonate is added externally, separately from recovery from polycarbonate-based resin, to produce the monomer composition for recycled plastic synthesis according to the above embodiment, is not included in the scope of diethyl carbonate of the above embodiment. .

Specifically, recovered from the polycarbonate-based resin means obtained through a depolymerization reaction of the polycarbonate-based resin. The depolymerization reaction can be performed under acidic, neutral, or basic conditions. In particular, the depolymerization reaction can be performed under basic (alkaline) conditions. In particular, the depolymerization reaction is preferably carried out in an ethanol solvent, as described later.

Since the main recovery target material in the monomer composition for recycled plastic synthesis of the embodiment is an aromatic diol compound, the diethyl carbonate can be separately separated and recovered as a by-product from the monomer composition for recycled plastic synthesis of the embodiment.

The monomer composition for synthesizing recycled plastic of one embodiment can be used as a raw material for manufacturing various recycled plastics (eg, polycarbonate (PC)), which will be described later.

The monomer composition for recycling plastic synthesis of the above embodiment may further include a small amount of other additives and solvents, and the type of specific additives or solvents is not greatly limited, and may include an aromatic diol compound recovery process by depolymerization of polycarbonate-based resin. A variety of widely used materials can be applied without limitation.

The monomer composition for synthesizing recycled plastic of the above embodiment may be obtained by the method for producing a monomer composition for synthesizing recycled plastic, which will be described later. That is, the monomer composition for recycling plastic synthesis of the above embodiment is obtained by going through various filtration, purification, washing, and drying processes to secure only the aromatic diol compound, which is the main recovery target material, in high purity after the depolymerization reaction of the polycarbonate-based resin. It applies.

2. Manufacturing method of monomer composition for recycled plastic synthesis

According to another embodiment of the invention, depolymerizing a polycarbonate-based resin; Separating the carbonate precursor from the depolymerization reaction product; and a step of purifying the depolymerization product from which the carbonate precursor has been separated, wherein the step of purifying the depolymerization product from which the carbonate precursor has been separated includes adding a hydrophilic reducing agent to the depolymerization product from which the carbonate precursor has been separated; And a step of adding an adsorbent to the depolymerization reaction product from which the carbonate precursor has been separated, purifying it by adsorption, and then removing the adsorbent.

The present inventors include a hydrophilic reducing agent input process and an adsorption purification process using an adsorbent in the process of recycling polycarbonate-based resin by chemical decomposition, as in the method of producing a monomer composition for recycling plastic synthesis in the other embodiments above. The invention was completed after confirming through experiments that excellent color quality could be realized while increasing process efficiency by reducing the amount of organic solvent used in the purification process.

Specifically, the method for producing a monomer composition for recycling plastic synthesis according to another embodiment may further include a pretreatment step of the polycarbonate-based resin before depolymerizing the polycarbonate-based resin.

The polycarbonate-based resin includes all homopolymers or copolymers containing polycarbonate repeating units, and refers to reaction products obtained through polymerization or copolymerization of monomers including an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized if it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor. In addition, as the monomer, one type of aromatic diol compound and two or more types of carbonate precursors may be used, two or more types of aromatic diol compounds and one type of carbonate precursor may be used, or one type of other diol in addition to one type of aromatic diol compound and one type of carbonate precursor may be used. Using the above, a copolymer can be synthesized when two or more types of carbonate are contained. The homopolymer or copolymer may include low molecular weight compounds, oligomers, and polymers depending on the molecular weight range.

The polycarbonate-based resin can be applied in various forms and types, such as new polycarbonate-based resin produced through synthesis, recycled polycarbonate-based resin produced through a recycling process, or polycarbonate-based resin waste.

By performing the pretreatment process for the polycarbonate-based resin, the efficiency of the process for recovering the aromatic diol compound and carbonate precursor from the polycarbonate-based resin can be increased. Examples of the pretreatment process include filtration, washing, drying, grinding, glycol decomposition, etc., and the specific method of each pretreatment process is not limited. An aromatic diol compound by depolymerization of a polycarbonate-based resin, and a carbonate precursor are used. A variety of widely used methods in the recovery process can be applied without limitation.

However, an example of the pretreatment process may include dissolving the polycarbonate-based resin in an organic solvent and then filtering it. The organic solvent may include tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to another embodiment may include the step of depolymerizing a polycarbonate-based resin.

During the depolymerization reaction of the polycarbonate-based resin, the depolymerization reaction may be performed under acidic, neutral, or basic conditions, and in particular, the depolymerization reaction may be performed under basic (alkaline) conditions. The type of the base is not greatly limited, and examples include sodium hydroxide (NaOH) or potassium hydroxide (KOH). The base is a base catalyst that acts as a catalyst, and has the advantage of being economical compared to organic catalysts mainly used under mild conditions.

During the depolymerization reaction of the polycarbonate-based resin, 0.5 mol or less, or 0.4 mol or less, or 0.3 mol or less, or 0.1 mol or more, or 0.2 mol or more, or 0.1 mol to 0.5 mol, or 0.1 mol, relative to 1 mole of the polycarbonate-based resin. It may be carried out by reacting the base in an amount of 0.4 mol to 0.4 mol, or 0.1 mol to 0.3 mol, or 0.2 mol to 0.5 mol, or 0.2 mol to 0.4 mol, or 0.2 mol to 0.3 mol. During the depolymerization reaction of the polycarbonate-based resin, if more than 0.5 mole of base is reacted relative to 1 mole of the polycarbonate-based resin, impurities increase due to the increased amount of alkali salt, which reduces the purity of the target recovered material and reduces the economic feasibility of the catalytic reaction. There is a limit to its decline.

Additionally, the depolymerization reaction of the polycarbonate-based resin may be carried out in a solvent containing ethanol. The present invention has the advantage of being able to stably obtain bisphenol A, a highly pure monomer, by decomposing polycarbonate-based resin with a solvent containing ethanol, and additionally obtaining diethyl carbonate, which has high added value, as a reaction by-product.

The content of ethanol may be 5 mole to 15 mole, or 8 mole to 13 mole, based on 1 mole of polycarbonate-based resin. Since the ethanol has good solubility in bisphenol A, ethanol within the above range must be included. If the ethanol content is excessively reduced to less than 5 moles compared to 1 mole of polycarbonate-based resin, it is difficult for the alcohol decomposition of the polycarbonate-based resin to sufficiently proceed. On the other hand, if the content of ethanol is excessively increased to more than 15 moles relative to 1 mole of polycarbonate-based resin, the economic feasibility of the process may decrease due to excessive use of alcohol.

The solvent in which the depolymerization reaction of the polycarbonate resin proceeds is, in addition to ethanol, at least one selected from the group consisting of tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, and dipropyl carbonate. It may further contain an organic solvent.

The organic solvent may include tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

More preferably, methylene chloride can be used as the organic solvent. When methylene chloride is used as an organic solvent mixed with ethanol, there is an advantage in that the dissolution characteristics of polycarbonate are improved and reactivity can be improved.

The content of the organic solvent may be 16 to 20 mol, or 16 to 18 mol, based on 1 mol of polycarbonate-based resin. Additionally, the content of the organic solvent may be 1.5 to 2 moles relative to 1 mole of ethanol. There is an advantage that the depolymerization reaction of the polymer can proceed at the required level by mixing the polycarbonate-based resin, ethanol, and the organic solvent within the above range.

Meanwhile, the temperature at which the depolymerization reaction of the polycarbonate-based resin proceeds is not greatly limited, but may be carried out, for example, at 20°C to 100°C, or 50°C to 70°C. Additionally, the depolymerization reaction of the polycarbonate-based resin may be performed for 1 hour to 30 hours, or 4 hours to 6 hours.

Specifically, the above conditions are mild process conditions compared to the existing pressurization/high temperature process, and by performing stirring under the above conditions, the process can be performed in a mild process compared to the pressurization/high temperature process, especially at temperatures between 50°C and 50°C. There is an advantage in obtaining the most efficient results in terms of reproducibility and stability when stirring at 70°C for 4 to 6 hours.

That is, the present invention provides high-purity aromatic diol compounds (e.g., There is an advantage in that bisphenol A) can be obtained and diethyl carbonate can be obtained as a by-product by using an ethanol solvent.

More specifically, the step of depolymerizing the polycarbonate-based resin includes a first step of dissolving the carbonate-based resin in an organic solvent; And a second step of adding a catalyst solution containing ethanol and a base and stirring it. In the first and second steps, the details about ethanol, organic solvent, base, and polycarbonate-based resin are the same as described above.

Additionally, the step of depolymerizing the polycarbonate-based resin may include adding an antioxidant to the reaction product containing the polycarbonate-based resin. Accordingly, since the aromatic diol compound obtained during the depolymerization reaction of the polycarbonate resin is easily oxidized under basic conditions, an antioxidant can be added to the reaction solution.

The antioxidant is at least one selected from the group consisting of sodium dithionite (Na ₂ S ₂ O ₄ , SDT), sodium metabisulfite (Na ₂ S ₂ O ₅ ), and sodium sulfite (Na ₂ SO ₃ ). It may contain compounds. That is, the antioxidants include one type of sodium dithionite (Na ₂ S ₂ O ₄ , SDT), one type of sodium metabisulfite (Na ₂ S ₂ O ₅ ), one type of sodium sulfite (Na ₂ SO ₃ ), Or it may include a mixture of two or more types thereof.

The amount of the antioxidant added is not greatly limited, but for example, it may be added in an amount of 0.05% to 4% by weight based on the weight of the polycarbonate resin. Within the above range, it has an oxidation prevention effect, is cost-effective, and the decomposition reaction rate does not decrease.

The adsorbent includes at least one type of activated carbon selected from the group consisting of plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, and waste activated carbon.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to another embodiment may further include a step of neutralizing the depolymerization product with an acid before separating the carbonate precursor from the depolymerization product.

For example, the alkaline decomposition product of polycarbonate resin includes an aromatic diol compound or a salt thereof, but the main recovery target material of the present invention is an aromatic diol compound, so in the case of the salt of the aromatic diol compound obtained by the alkaline decomposition, additional It can be converted to an aromatic diol compound through a neutralization process with acid. That is, when the depolymerization reaction of the polycarbonate-based resin is alkaline decomposition, a neutralization reaction step with acid may be performed.

The acid used during the neutralization reaction may be a strong acid, for example, hydrochloric acid (HCl). Due to the neutralization reaction using the strong acid, the pH may be satisfied at 4 or less, or less than 2, at the end of the neutralization reaction. The temperature during the neutralization reaction can be adjusted to between 25°C and 100°C.

Additionally, if necessary, after neutralizing the depolymerization product with acid, a process of removing remaining impurities through filtration or adsorption may be additionally performed. Specifically, the liquid containing the aromatic diol compound can be recovered by separating the water layer and the organic layer and filtering the organic layer through vacuum filtration.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to another embodiment may include the step of separating the carbonate precursor from the depolymerization reaction product. Accordingly, the separated carbonate precursor may include diethyl carbonate.

For example, the depolymerization product of polycarbonate-based resin includes an aromatic diol compound, or a salt thereof, and a carbonate precursor. The contents of the aromatic diol compound and the carbonate precursor include all of the contents described above in the one embodiment.

The step of separating the carbonate precursor from the depolymerization reaction product may include a step of distilling the depolymerization reaction product under reduced pressure. The examples of the reduced pressure distillation conditions are not greatly limited, but to give a specific example, after depressurizing the product of the depolymerization reaction of the polycarbonate-based resin at a pressure of 200 mbar to 300 mbar and a temperature of 20 ℃ to 30 ℃, 50 After reducing the pressure to a pressure of mbar to 150 mbar and a temperature of 25 ℃ to 35 ℃, distillation can be performed by reducing the pressure to a pressure of 10 mbar to 50 mbar and a temperature of 35 ℃ to 45 ℃. Methylene chloride (MC) can be distilled off under the conditions of reducing the pressure to 200 mbar to 300 mbar and reducing the temperature to 20 ℃ to 30 ℃. Additionally, ethanol (EtOH) can be distilled off under the conditions of the pressure of 50 mbar to 150 mbar and the temperature of 25°C to 35°C. In addition, the carbonate precursor can be separated and recovered under the conditions of reducing the pressure to a pressure of 10 mbar to 50 mbar and a temperature of 35 ℃ to 45 ℃.

The separated carbonate precursor can be recycled without a separate separation and purification process, or can be recycled through separation and purification such as conventional extraction, adsorption, and drying, if necessary. Specific purification conditions are not greatly limited, and various previously known purification techniques can be applied without limitation regarding specific purification equipment and methods.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to another embodiment may include a purification step of the depolymerization reaction product from which the carbonate precursor is separated. Through this, an aromatic diol compound, which is the main recovered material, is obtained, which corresponds to the monomer composition for synthesizing recycled plastic in one embodiment.

Specifically, the step of purifying the depolymerization reaction product from which the carbonate precursor has been separated includes adding a hydrophilic reducing agent to the depolymerization reaction product from which the carbonate precursor has been separated; And it may include the step of adding an adsorbent to the depolymerization reaction product from which the carbonate precursor was separated, purifying it by adsorption, and then removing the adsorbent.

In the purification step, the order of the hydrophilic reducing agent input step and the adsorption purification step is not particularly limited and may be performed in any order. For example, after the hydrophilic reducing agent input step, the purification step may be performed in the order of the adsorption purification step. there is. The step of adding the hydrophilic reducing agent; The adsorption purification step may be repeated at least once. Various previously known purification technologies can be applied without limitation regarding specific reducing agent input, adsorption equipment, and methods.

Meanwhile, before the step of adding a hydrophilic reducing agent to the depolymerization reaction product from which the carbonate precursor was separated, a washing step of the depolymerization reaction product from which the carbonate precursor was separated may be further included.

Specifically, in the washing step of the depolymerization reaction product from which the carbonate precursor is separated, the depolymerization reaction product from which the carbonate precursor is separated may contain an aromatic diol compound. However, since various impurities remain during the recovery process for obtaining the aromatic diol compound, washing can be performed to sufficiently remove these to secure a high purity aromatic diol compound.

Specifically, the washing step includes washing with a solvent at a temperature of 10°C to 30°C, or 20°C to 30°C; and washing with a solvent at a temperature of 40°C to 80°C, or 40°C to 60°C, or 45°C to 55°C. The temperature condition refers to the temperature inside the cleaning vessel where cleaning with a solvent is performed, and various heating devices can be applied without limitation to maintain a high temperature outside of room temperature.

The washing step may be performed first with a solvent at a temperature of 10°C to 30°C, and then with a solvent at a temperature of 40°C to 80°C. Additionally, the step of washing with a solvent at a temperature of 40°C to 80°C may be performed first, and the step of washing with a solvent at a temperature of 10°C to 30°C may be performed later.

More preferably, the washing step may be performed first with a solvent at a temperature of 10°C to 30°C, and then with a solvent washing step at a temperature of 40°C to 80°C. Accordingly, corrosion of the reactor caused by strong acid after the neutralization step can be minimized.

Washing with a solvent at a temperature of 10°C to 30°C; and washing with a solvent at a temperature of 40°C to 80°C may each be repeated at least once.

Additionally, if necessary, washing with a solvent at a temperature of 10°C to 30°C; And after performing the step of washing with a solvent at a temperature of 40°C to 80°C, a process of removing the remaining solvent through filtration may be additionally performed.

More specifically, the difference value between the temperature of the step of washing with a solvent at a temperature of 40 ℃ to 80 ℃ and the temperature of the step of washing with a solvent at a temperature of 10 ℃ to 30 ℃ may be 20 ℃ to 50 ℃. .

The difference value between the temperature of the step of washing with a solvent at a temperature of 40 ℃ to 80 ℃ and the temperature of the step of washing with a solvent at a temperature of 10 ℃ to 30 ℃ refers to the temperature of the step of washing with a solvent at a temperature of 40 ℃ to 80 ℃ It means the temperature of the washing step minus the temperature of the washing step with solvent from the temperature of 10 ℃ to 30 ℃.

If the difference value between the temperature of the step of washing with a solvent at a temperature of 40 ℃ to 80 ℃ and the temperature of the step of washing with a solvent at a temperature of 10 ℃ to 30 ℃ decreases too much to less than 20 ℃, impurities are sufficiently removed. It's difficult to do.

If the difference value between the temperature of the step of washing with a solvent at a temperature of 40 ℃ to 80 ℃ and the temperature of the step of washing with a solvent at a temperature of 10 ℃ to 30 ℃ increases excessively to exceed 50 ℃, extreme temperature conditions Harsh conditions may be created to maintain the process, which may reduce the efficiency of the process.

The solvent used in the washing step may include one of water, alcohol, and organic solvent. The organic solvent may be tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, or a mixture of two or more thereof.

The solvent used in the washing step may be used in a weight ratio of 1 part by weight to 30 parts by weight, or 1 part by weight to 10 parts by weight based on 1 part by weight of the polycarbonate resin used in the depolymerization reaction.

More specifically, the solvent in the step of washing with a solvent at a temperature of 10°C to 30°C may be an organic solvent. Preferably, methylene chloride can be used as the organic solvent. And, at this time, the organic solvent may be used in an amount of 1 part by weight or more and 10 parts by weight or less based on 1 part by weight of the polycarbonate-based resin.

Additionally, the solvent in the step of washing with a solvent at a temperature of 40°C to 80°C may be water. When the water is used, residual impurities in the form of salts can be effectively removed. And, at this time, the solvent may be used in an amount of 1 part by weight or more and 10 parts by weight or less based on 1 part by weight of the polycarbonate-based resin.

Meanwhile, before the step of adding a hydrophilic reducing agent to the depolymerization reaction product from which the carbonate precursor has been separated, a re-dissolution step of adding a mixture of an organic solvent and an aqueous solvent to the depolymerization reaction product from which the carbonate precursor has been separated may be further included. Through the step of adding a mixture of an organic solvent and an aqueous solvent to the depolymerization reaction product from which the carbonate precursor was separated, the aromatic diol compound crystals contained in the depolymerization reaction product from which the carbonate precursor was separated are redissolved in the mixture of the organic solvent and the aqueous solvent. It can be. An example of the organic solvent may be ethanol, and an example of the aqueous solvent may be water.

The order of the washing step and the re-dissolution step is not particularly limited and may be performed in any order, but for example, the purification step may be performed in the order of the re-dissolution step after the washing step. The washing step; The re-dissolution step may be repeated at least once. Regarding specific washing and dissolution equipment and methods, various previously known purification technologies can be applied without limitation.

Specifically, the mixture of the organic solvent and the aqueous solvent may include 15% to 50% by weight of the organic solvent and 50% to 85% by weight of the aqueous solvent based on the total weight of the mixture. When the aqueous solvent is reduced to less than 50% by weight based on the total weight of the mixture, there is a problem that the organic solvent is contained in a relatively excessive amount and the process cost due to the use and recovery of the organic solvent increases, thereby reducing the efficiency of the process. On the other hand, when the aqueous solvent increases to more than 85% by weight based on the total weight of the mixture, the carbonate precursor has a problem in that the solubility of the aromatic diol compound crystals contained in the separated depolymerization reaction product decreases, making it difficult for re-dissolution to proceed sufficiently.

Meanwhile, the method for producing a monomer composition for recycling plastic synthesis according to another embodiment may include adding a hydrophilic reducing agent to the depolymerization product from which the carbonate precursor is separated.

The hydrophilic reducing agent is soluble in water and can be used as a bleaching agent to remove color by changing colored substances. Accordingly, by adding the hydrophilic reducing agent, the colorless characteristic of the aromatic diol compound contained in the depolymerization reaction product from which the carbonate precursor was separated can be strengthened.

Examples of the hydrophilic reducing agent are not greatly limited, and various conventionally known hydrophilic reducing bleaching agents can be applied without limitation, but one example is sodium dithionite (SDT).

In addition, based on the weight of the depolymerization reaction product from which the carbonate precursor was separated, the amount of the hydrophilic reducing agent added is 0.1% by weight to 7% by weight, or 0.1% by weight to 6% by weight, or 0.1% by weight to 5% by weight, or 1% by weight. % to 7% by weight, or 1% to 6% by weight, or 1% to 5% by weight, or 3% to 7% by weight, or 3% to 6% by weight, or 3% to 5% by weight. , or 0.1% to 3% by weight, or 1% to 3% by weight.

The depolymerization reaction product from which the carbonate precursor is separated may include an aromatic diol compound. That is, the amount of the hydrophilic reducing agent added is 0.1% by weight to 0.1% by weight based on the weight of the aromatic diol compound contained in the depolymerization reaction product from which the carbonate precursor is separated. 7% by weight, or 0.1% to 6% by weight, or 0.1% to 5% by weight, or 1% to 7% by weight, or 1% to 6% by weight, or 1% to 5% by weight, or It can be from 3% to 7% by weight, or from 3% to 6% by weight, or from 3% to 5% by weight, or from 0.1% to 3% by weight, or from 1% to 3% by weight.

If the amount of the hydrophilic reducing agent is excessively increased, the hydrophilic agent may not be sufficiently dissolved or the color characteristic improvement effect may not be sufficiently realized due to side reactions. On the other hand, if the input amount of the hydrophilic reducing agent is reduced to an excessively small amount, it is difficult to sufficiently implement the effect of improving color characteristics by the hydrophilic reducing agent.

Meanwhile, in the step of adding an adsorbent to the depolymerization reaction product from which the carbonate precursor was separated to purify it by adsorption and then removing the adsorbent, an adsorbent may be brought into contact with the depolymerization reaction product.

Examples of the adsorbent include activated carbon, charcoal, celite, or mixtures thereof. The activated carbon is a black carbon material with micropores manufactured through a carbonization process at about 500 ℃ and an activated carbon process at about 900 ℃. The examples are not greatly limited, but for example, raw materials Depending on the type, various activated carbons such as plant-based, coal-based, petroleum-based, and waste activated carbon can be applied without limitation.

To give a more specific example, plant-based activated carbon may include coconut activated carbon, wood activated carbon, and sawdust activated carbon. In addition, coal-based activated carbon includes lignite activated carbon, bituminous activated carbon, and anthracite activated carbon. Additionally, petroleum-based activated carbon includes petroleum coke activated carbon and oil carbon activated carbon. Additionally, waste activated carbon includes synthetic resin activated carbon and pulp activated carbon.

The adsorbent may include one or more types of activated carbon selected from the group consisting of plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, and waste activated carbon. That is, the second adsorbent may include plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, waste activated carbon, or a mixture of two or more types thereof.

More specifically, the adsorbent may include one or more types of activated carbon selected from the group consisting of coconut activated carbon, lignite activated carbon, anthracite activated carbon, and bituminous activated carbon. That is, the adsorbent may include coconut activated carbon, lignite activated carbon, anthracite activated carbon, bituminous activated carbon, or a mixture of two or more types thereof.

As such, the method for producing a monomer composition for recycling plastic synthesis according to another embodiment of the present invention applies an adsorption purification process using an adsorbent during a depolymerization reaction in which polycarbonate-based resin is recycled by chemical decomposition, which is the main synthesis target material in the present invention. Not only can aromatic diol compounds be secured with high purity, but the content of impurities other than aromatic diol compounds can be significantly reduced.

The conditions for adsorption purification using the above adsorbent are not particularly limited, and various conventionally known adsorption purification conditions can be used without limitation. However, for example, the amount of adsorbent may be 40 to 60 wt% compared to the polycarbonate resin, the adsorption time may be 0.1 to 5 hours, and the adsorption method may be stirred adsorption or using a lab adsorption tower. You can.

Meanwhile, after purifying the depolymerization product from which the carbonate precursor was separated by adding an adsorbent to the depolymerization product from which the carbonate precursor was separated and then removing the adsorbent, the method may further include a recrystallization step of the depolymerization product from which the carbonate precursor was separated.

In the recrystallization step of the depolymerization reaction product from which the carbonate precursor has been separated, various impurities contained in the depolymerization reaction product from which the carbonate precursor has been separated can be sufficiently removed to secure a high-purity aromatic diol compound.

Specifically, the recrystallization step may include recrystallizing the carbonate precursor by adding a recrystallization solvent to the depolymerization product from which it was separated. Through the process of recrystallizing the depolymerization reaction product from which the carbonate precursor was separated by adding a recrystallization solvent, the aromatic diol compound or salt thereof contained in the depolymerization reaction product is crystallized by increasing the solubility, or impurities trapped between crystals are removed as much as possible from the solvent. It can be dissolved, and since the dissolved aromatic diol compound has poor solubility compared to impurities, it can be easily precipitated as aromatic diol compound crystals through the difference in solubility when the temperature is lowered. Water can be used as the recrystallization solvent.

More specifically, the recrystallization step of the depolymerization reaction product from which the carbonate precursor is separated may include adding 5 to 25 parts by weight of a recrystallization solvent based on 1 part by weight of the aromatic diol compound contained in the depolymerization reaction product. . If too little of the recrystallization solvent is used, the temperature for dissolving the aromatic diol compound contained in the depolymerization reaction product from which the carbonate precursor is separated becomes too high, which reduces process efficiency and makes it difficult to remove impurities through recrystallization. On the other hand, if an excessive amount of recrystallization solvent is used, the solubility of the aromatic diol compound contained in the depolymerization product from which the carbonate precursor was separated increases too much, resulting in a decrease in the yield of the aromatic diol compound recovered after recrystallization, and the use of a large amount of solvent causes Process efficiency may be reduced.

If necessary, after performing the recrystallization step of the depolymerization reaction product from which the carbonate precursor is separated, a process of removing remaining impurities through filtration or adsorption may be additionally performed.

Additionally, if necessary, a drying step may be further included after the recrystallization step. The remaining solvent can be removed through the drying, and specific drying conditions are not greatly limited, but drying can be performed at a temperature of, for example, 10°C to 100°C, or 10°C to 50°C. Regarding the specific drying equipment and methods used during the drying, various known drying techniques can be applied without limitation.

3. Recycled plastic

According to another embodiment of the invention, a recycled plastic containing a reaction product of the monomer composition for synthesizing recycled plastic of the above embodiment and a comonomer may be provided.

The content of the monomer composition for synthesizing recycled plastic of the one embodiment includes all of the content described above in the one embodiment and other embodiments.

Examples of the above recycled plastics are not greatly limited, and various plastics synthesized using aromatic diol compounds such as bisphenol A as monomers can be applied without limitation, and more specific examples include polycarbonate-based resins.

The polycarbonate-based resin includes all homopolymers or copolymers containing polycarbonate repeating units, and refers to reaction products obtained through polymerization or copolymerization of monomers including an aromatic diol compound and a carbonate precursor. A homopolymer can be synthesized if it contains one type of carbonate repeating unit obtained using only one type of aromatic diol compound and one type of carbonate precursor. In addition, as the monomer, one type of aromatic diol compound and two or more types of carbonate precursors may be used, two or more types of aromatic diol compounds and one type of carbonate precursor may be used, or one type of other diol in addition to one type of aromatic diol compound and one type of carbonate precursor may be used. Using the above, a copolymer can be synthesized when two or more types of carbonate are contained. The homopolymer or copolymer may include low molecular weight compounds, oligomers, and polymers depending on the molecular weight range.

More specifically, in the recycled plastic containing the reaction product of the monomer composition for recycling plastic synthesis and the comonomer of the above embodiment, a carbonate precursor may be used as the comonomer. Specific examples of the carbonate precursor include phosgene, triphosgene, diphosgene, bromophosgene, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diphenyl carbonate, ditoryl carbonate, bis(chlorophenyl) carbonate, m -Cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, or bishaloformate may be mentioned.

Examples of the monomer composition for synthesis and the reaction process of the comonomer are not greatly limited, and various previously known polycarbonate production methods can be applied without limitation.

However, as an example of the polycarbonate production method, a polycarbonate production method including the step of polymerizing a monomer composition for synthesizing recycled plastic and a composition containing a comonomer can be used. At this time, the polymerization can be performed by interfacial polymerization. During interfacial polymerization, the polymerization reaction is possible at normal pressure and low temperature, and molecular weight control is easy.

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

The solvent that can be used in the polymerization is not particularly limited as long as it is a solvent used in the polymerization of polycarbonate in the art. For example, halogenated hydrocarbons such as methylene chloride and chlorobenzene can be used.

Additionally, the polymerization can be performed in the presence of an acid binder, and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine can be used as the acid binder.

Additionally, in order to control the molecular weight of polycarbonate during the polymerization, the polymerization may be performed in the presence of a molecular weight regulator. The molecular weight regulator may be an alkylphenol having 1 to 20 carbon atoms, and specific examples thereof include p-tert-butylphenol, p-cumylphenol, decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, Examples include eicosylphenol, docosylphenol, or triacontylphenol. The molecular weight regulator may be added before the start of polymerization, during the start of polymerization, or after the start 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, based on 100 parts by weight of the aromatic diol compound, and the desired molecular weight can be obtained within this range.

In addition, in order to promote the polymerization reaction, reactions such as tertiary amine compounds such as triethylamine, tetra-n-butylammonium bromide, tetra-n-butylphosphonium bromide, quaternary ammonium compounds, quaternary phosphonium compounds, etc. Additional accelerators may be used.

4. Molded product

According to another embodiment of the invention, a molded article containing the recycled plastic of the other embodiment can be provided. The content regarding the recycled plastic includes all the content described in detail in the other embodiments.

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

Examples of the above molded products are not greatly limited, and can be applied to various molded products using plastic without limitation. Examples of the molded products include automobile parts, electrical and electronic products, communication products, household goods, building materials, optical parts, and exterior materials.

In addition to the recycled plastic of the other embodiments, the molded article may optionally contain one or more additives selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent whitening agents, ultraviolet absorbers, pigments, and dyes. may additionally be included.

As an example of a method of manufacturing the molded product, the recycled plastic and additives of the other embodiments are mixed well using a mixer, then extruded using an extruder to produce pellets, and the pellets are dried and then injected using an injection molding machine. It can be included.

According to the present invention, a monomer composition for synthesizing recycled plastic that can achieve excellent color quality even though it is recovered through recycling by chemical decomposition of polycarbonate resin and has improved efficiency in the recovery process, a manufacturing method thereof, and recycled plastic using the same, and molded articles may be provided.

The invention is explained in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited by the following examples.

<Examples, comparative examples, and reference examples: Preparation of recycled bisphenol A monomer composition>

Example 1

(1. Decomposition step) 1 mol of pretreated waste polycarbonate (PC) was dissolved in 17 mol of methylene chloride (MC) and then added to a 3L high pressure reactor along with 11 mol of ethanol (EtOH) and 0.25 mol of sodium hydroxide (NaOH). , 2.5 g (1% by weight of PC weight) of sodium dithionite (Na ₂ S ₂ O ₄ , SDT) was added and stirred at 60° C. for 6 hours to perform PC depolymerization reaction.

(2. Neutralization step) The product of the depolymerization reaction was cooled to below 30°C and then neutralized at 20 to 30°C using 0.25 mol of 10% hydrochloric acid (HCl).

(3. Distillation step) Afterwards, methylene chloride (MC) is distilled off at 250 mbar and 20°C, ethanol (EtOH) is distilled off at 80 mbar and 30°C, and the by-product is distilled under reduced pressure at 30 mbar and 40°C. Diethyl carbonate (DEC) was recovered.

(4. Washing step) Afterwards, the residue from which diethyl carbonate (DEC) was removed was first washed at 20-30°C using methylene chloride (MC), which is 1 times the mass of PC used, and vacuum filtered. The filtrate was washed a second time at 50°C using water 1 times the mass of PC used.

(5. Re-dissolution step) 15 g of ethanol and 15 g of water were added to 6 g of bisphenol A that had been washed and re-dissolved at room temperature.

(6. Reducing agent addition step) After that, 0.06 g (1% by weight based on the weight of bisphenol A) of sodium dithionite (Na ₂ S ₂ O ₄ , SDT) was added to the solution and dissolved.

(7. Adsorption step) Afterwards, 3 g of activated lignite carbon as an adsorbent was added to the solution and stirred for 10 minutes. Afterwards, the activated carbon was first removed using a sieve filter (75 ㎛), and the remaining activated carbon was secondarily removed using a syringe filter (0.45 ㎛).

(8. Recrystallization step) Afterwards, 75 g of water was slowly added while stirring to recrystallize bisphenol A, and then the solid was obtained through filtration.

(9. Drying step) Afterwards, the recycled bisphenol A monomer composition was prepared by drying in a vacuum oven at 30-50°C.

Example 2, Comparative Examples 1 to 2, Reference Examples 1 to 2

Except for changing the process conditions shown in Table 1 below, the recycled bisphenol A monomer compositions of Example 2, Comparative Examples 1 to 2, and Reference Examples 1 to 2 were prepared in the same manner as Example 1.

division 1. Decomposition step 5. Re-dissolution step 6. Reducing agent input step 7. Adsorption step 8. Recrystallization stage SDT input amount (% by weight based on PC weight) Ethanol/water input amount SDT input amount (% by weight based on bisphenol A weight) Adsorbent dosage water input Example 1 2.5g (1% by weight) 15g/15g (ethanol/water) 0.06g (1% by weight) 3g 75g Example 2 2.5g (1% by weight) 15g/15g (ethanol/water) 0.3g (5% by weight) 3g 75g Comparative Example 1 2.5g (1% by weight) 15g/15g (ethanol/water) 0g (0% by weight) 0g 75g Comparative example 2 2.5g (1% by weight) 15g/15g (ethanol/water) 0.3g (5% by weight) 0g 75g Comparative example 3 2.5g (1% by weight) 15g/15g (ethanol/water) 0g (0% by weight) 3g 75g Reference example 1 2.5g (1% by weight) 30g/0g (ethanol/water) 0g (0% by weight) 3g 180g Reference example 2 2.5g (1% by weight) 15g/15g (ethanol/water) 0.6g (10% by weight) 3g 75g

<Experimental example>

For the recycled bisphenol A monomer compositions obtained in the above Examples, Comparative Examples, and Reference Examples, the physical properties were measured by the following method, and the results are shown in Table 2.

1. APHA Color

The recycled bisphenol A monomer composition was measured according to the ASTM D 1209 measurement method using HunterLab UltraScan PRO Spectrophotometer equipment.

2. Color coordinates (L*, a*, b*)

The recycled bisphenol A monomer composition was measured in reflection mode using HunterLab UltraScan PRO Spectrophotometer equipment.

Experimental example measurement results division APHA Color L* a* b* Example 1 28 95.6 -0.3 1.7 Example 2 22 96.7 -0.6 1.6 Comparative Example 1 100 94.8 1.5 5.0 Comparative example 2 89 95.2 1.2 4.6 Comparative Example 3 34 96.1 0 2.0 Reference example 1 21 96.5 -0.2 1.3 Reference example 2 44 96.2 -0.8 3.0

As shown in Table 2, the recycled bisphenol A monomer composition obtained in Examples 1 and 2 has color coordinates L* of 95.6 to 96.7, a* of -0.6 to -0.3, and b* of 1.6 to 1.7, and APHA Color value. Measurements from Figures 22 to 28 showed excellent optical properties.

On the other hand, the recycled bisphenol A monomer composition obtained in Comparative Examples 1 to 3 had a color coordinate L* of 94.8 to 96.1, a* of 0 to 1.5, and b* of 2.0 to 5.0, and the APHA color value was also measured at 34 to 100. showed poor optical properties compared to the examples.

On the other hand, the recycled bisphenol A monomer composition obtained in Reference Example 1 showed optical properties similar to those of the Examples, but in order to achieve this, an excessive amount of water (180 g) was used in the recrystallization step as shown in Table 1. There was a problem of decline.

In addition, the recycled bisphenol A monomer composition obtained in Reference Example 2 had a color coordinate b* of 3.0 and an APHA color value of 44, showing poor optical properties compared to the examples.

Claims (20)

Contains an aromatic diol compound,
The color coordinate b* is 1.8 or less,
APHA Color value measured by ASTM D 1209 is 30 or less,
A monomer composition for synthesizing recycled plastic, characterized in that it is recovered from polycarbonate-based resin.
According to paragraph 1,
The monomer composition for synthesizing recycled plastic has a color coordinate L* of 95.5 or more.
According to paragraph 1,
The monomer composition for synthesizing recycled plastic has a color coordinate a* of -0.7 to -0.2.
According to paragraph 1,
A monomer composition for synthesizing recycled plastic, wherein the aromatic diol compound includes bisphenol A.
According to paragraph 1,
A monomer composition for recycling plastic synthesis, wherein the aromatic diol compound is recovered from a polycarbonate-based resin.
According to paragraph 1,
The monomer composition for synthesizing recycled plastic further includes a hydrophilic reducing agent.
Depolymerizing a polycarbonate-based resin;
Separating the carbonate precursor from the depolymerization reaction product; and
It includes a purification step of the depolymerization reaction product from which the carbonate precursor is separated,
The purification step of the depolymerization reaction product from which the carbonate precursor is separated is,
Adding a hydrophilic reducing agent to the depolymerization product from which the carbonate precursor was separated; and
A method for producing a monomer composition for recycling plastic synthesis, comprising: adding an adsorbent to the depolymerization product from which the carbonate precursor was separated, purifying it by adsorption, and then removing the adsorbent.
In clause 7,
A method for producing a monomer composition for recycling plastic synthesis, wherein the hydrophilic reducing agent is sodium dithionate.
In clause 7,
A method for producing a monomer composition for recycling plastic synthesis, wherein the amount of the hydrophilic reducing agent added is 0.1% to 7% by weight based on the weight of the depolymerization reaction product from which the carbonate precursor is separated.
In clause 7,
Before adding a hydrophilic reducing agent to the depolymerization product from which the carbonate precursor was separated,
A method for producing a monomer composition for recycling plastic synthesis, further comprising a re-dissolution step of adding a mixture of an organic solvent and an aqueous solvent to the depolymerization product from which the carbonate precursor is separated.
According to clause 10,
The mixture is,
A method for producing a monomer composition for synthesizing recycled plastic, comprising 15% to 50% by weight of an organic solvent and 50% to 85% by weight of an aqueous solvent based on the total weight of the mixture.
In clause 7,
The step of depolymerizing the polycarbonate-based resin is,
A method for producing a monomer composition for synthesizing recycled plastic, comprising adding an antioxidant to a reactant containing the polycarbonate resin.
According to clause 12,
The antioxidant is a method of producing a monomer composition for recycling plastic synthesis, wherein the antioxidant includes at least one compound selected from the group consisting of sodium bisulfite, sodium metabisulfite, and sodium sulfite.
In clause 7,
Before adding a hydrophilic reducing agent to the depolymerization product from which the carbonate precursor was separated,
It further includes a washing step of the depolymerization reaction product from which the carbonate precursor is separated,
The washing step includes washing with a solvent at a temperature of 10°C to 30°C; and washing with a solvent at a temperature of 40°C to 80°C.
In clause 7,
The depolymerization reaction of the polycarbonate-based resin is,
A method for producing a monomer composition for synthesizing recycled plastic, characterized in that it is carried out in a solvent containing ethanol.
In clause 7,
In the step of separating the carbonate precursor from the depolymerization reaction product,
A method for producing a monomer composition for synthesizing recycled plastic, comprising the step of vacuum distillation of the depolymerization reaction product.
In clause 7,
After purifying the depolymerization product from which the carbonate precursor was separated by adding an adsorbent to it, removing the adsorbent,
A method for producing a monomer composition for recycling plastic synthesis, further comprising a recrystallization step of the depolymerization reaction product from which the carbonate precursor is separated.
According to clause 17,
The recrystallization step of the depolymerization reaction product from which the carbonate precursor is separated,
A method for producing a monomer composition for synthesizing recycled plastic, comprising adding 5 to 25 parts by weight of a recrystallization solvent based on 1 part by weight of the aromatic diol compound contained in the depolymerization reaction product.
A recycled plastic comprising a reaction product of the monomer composition for recycling plastic synthesis of claim 1 and a comonomer.
A molded article comprising the recycled plastic of claim 19.