KR20250035948A - Preparation method of monomer composition for synthesising recycled plastic, and monomer composition for synthesising recycled plastic, recycled plastic, molded product using the same - Google Patents

Abstract

The present invention relates to a method for producing a monomer composition for synthesizing recycled plastics, which recovers an aromatic diol compound through recycling by chemical decomposition of a polycarbonate resin and purifies the recovered aromatic diol compound at a high yield, and a monomer composition for synthesizing recycled plastics, recycled plastics, and molded articles using the same.

Description

Method for producing a monomer composition for synthesizing recycled plastic, and a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded product using the same {PREPARATION METHOD OF MONOMER COMPOSITION FOR SYNTHESISING RECYCLED PLASTIC, AND MONOMER COMPOSITION FOR SYNTHESISING RECYCLED PLASTIC, RECYCLED PLASTIC, MOLDED PRODUCT USING THE SAME}

The present invention relates to a method for producing a monomer composition for synthesizing recycled plastic recovered through recycling by chemical decomposition of polycarbonate resin, and to a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded product using the same.

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

Although polycarbonate is widely used for a variety of purposes, concerns about the environment and health when disposed of have been continuously raised.

Currently, physical recycling methods are being implemented, but there is a problem that quality deterioration occurs, so research is being conducted on chemical recycling of polycarbonate.

Chemical decomposition of polycarbonate refers to the process of obtaining an aromatic diol compound (e.g., bisphenol A (BPA)) as a monomer through decomposition of polycarbonate, which is then used for polymerization to obtain high-purity polycarbonate.

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 in the case of methanol decomposition, there is a problem that methanol, which is harmful to the human body, is used, and in the case of ethanol, high temperature and high pressure conditions are required and there is a problem that the yield is not high.

In addition, although a method of alcohol decomposition using an organic catalyst is known, it has economic disadvantages.

The present invention provides a method for producing a monomer composition for synthesizing recycled plastic containing an aromatic diol compound having high yield and excellent optical properties recovered through recycling by chemical decomposition of a polycarbonate resin, and a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded product using the same.

In order to solve the above problem, the present specification provides a method for producing a monomer composition for synthesizing recycled plastic, comprising the steps of: preparing a mixed solution by adding a polycarbonate resin to an organic solvent; adding a glycol compound and a catalyst to the mixed solution and stirring it; washing an aromatic diol compound obtained in the stirring step; dissolving the washed aromatic diol compound in a solvent; adding an adsorbent to the solution obtained in the dissolving step to perform adsorption purification; and obtaining the aromatic diol compound, wherein the organic solvent includes an aliphatic compound.

The present specification also provides a monomer composition for synthesizing recycled plastic, comprising an aromatic diol compound obtained in the method for producing the monomer composition for synthesizing recycled plastic.

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

The present specification also provides a molded article comprising the recycled plastic.

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

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

As used herein, the singular forms include the plural forms as well, unless the phrases clearly indicate the opposite.

The term "including" as used herein means specifying a particular characteristic, region, integer, step, operation, element, and/or component, but does not exclude the presence or addition of any other particular characteristic, region, integer, step, operation, element, component, and/or group.

In addition, terms including ordinal numbers such as 'first' and 'second' in this specification 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, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

The term "substituted or unsubstituted" as used herein means a group which is unsubstituted or substituted with one or more substituents selected from the group consisting of deuterium; a halogen group; a cyano group; a nitro group; a hydroxy group; a carbonyl group; an ester group; an imide group; an amide group; a primary amino group; a carboxyl group; a sulfonic acid group; a sulfonamide group; a phosphine oxide group; an alkoxy group; an aryloxy group; an alkylthioxy group; an arylthioxy group; an alkylsulfoxy group; an arylsulfoxy group; a silyl group; a boron group; an alkyl group; a cycloalkyl group; an alkenyl group; an aryl group; an aralkyl group; an aralkenyl group; an alkylaryl group; an alkoxysilylalkyl group; an arylphosphine group; or a heterocyclic group containing at least one of N, O and S atoms, or a substituted or unsubstituted group in which two or more of the above-mentioned substituents are linked. For example, a "substituent having two or more substituents connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group, or may be interpreted as a substituent having two phenyl groups connected.

In the present specification, an alkyl group is a monovalent functional group derived from an alkane, which may be straight-chain or branched, and the number of carbon atoms in the straight-chain alkyl group is not particularly limited, but is preferably 1 to 20. In addition, the number of carbon atoms in the branched-chain alkyl group is 3 to 20. Specific examples of alkyl groups include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, 4-methylhexyl, Examples thereof include, but are not limited to, 5-methylhexyl, 2,6-dimethylheptan-4-yl, etc. The alkyl group may be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

In the present specification, an alkylene group is a divalent functional group derived from an alkane, and the description of the above-mentioned alkyl group can be applied to these except that they are divalent functional groups. For example, they can be linear or branched, and can be a methylene group, an ethylene group, a propylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, a hexylene group, etc. The above-mentioned alkylene group can be substituted or unsubstituted, and when substituted, examples of the substituent are as described above.

In this specification, a fused ring refers to a ring structure in a polycyclic system composed of two or more carbon rings or hetero rings, in which each adjacent ring shares only two atoms.

Throughout this specification, "one or more" means, for example, "1, 2, 3, 4 or 5, in particular 1, 2, 3 or 4, more particularly 1, 2 or 3, even more particularly 1 or 2."

According to one embodiment of the invention, a method for producing a monomer composition for synthesizing recycled plastic is provided, comprising: a step of preparing a mixed solution by adding a polycarbonate resin to an organic solvent; a step of adding a glycol compound and a catalyst to the mixed solution and stirring it; a step of washing an aromatic diol compound obtained in the stirring step; a step of dissolving the washed aromatic diol compound in a solvent; a step of performing adsorption purification by adding an adsorbent to the solution obtained in the dissolving step; and a step of obtaining the aromatic diol compound, wherein the organic solvent includes an aliphatic compound.

Specifically, the present invention can stably obtain an aromatic diol compound, specifically bisphenol A, which is a high-purity monomer, by decomposing a polycarbonate resin into a glycol compound under mild conditions.

The method for producing a monomer composition for synthesizing recycled plastic according to the above embodiment may include a step of producing a mixture by adding a polycarbonate resin to an organic solvent, and a step of adding a glycol compound and a catalyst to the mixture and stirring.

That is, after the step of preparing a mixture by adding a polycarbonate resin to an organic solvent is first performed, the step of adding a glycol compound and a catalyst to the mixture and stirring can be performed sequentially. Accordingly, the dissolution characteristics of the polycarbonate resin in the organic solvent can be improved, thereby enhancing the depolymerization reactivity.

The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization reaction or a copolymerization reaction of a monomer including an alkylene carbonate and a carbonate precursor. When one carbonate repeating unit obtained by using only one alkylene carbonate and one carbonate precursor is contained, a homopolymer can be synthesized. In addition, when one alkylene carbonate and two or more carbonate precursors are used as the monomer, or two or more alkylene carbonates and one carbonate precursor are used, or one or more other diols are used in addition to one alkylene carbonate and one carbonate precursor, so that two or more carbonates are contained, a copolymer can be synthesized. The homopolymer or copolymer can include all low-molecular-weight compounds, oligomers, and polymers according to the molecular weight range.

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

However, if necessary, before performing a depolymerization reaction of the polycarbonate resin, a pretreatment process of the polycarbonate resin may be performed to increase the efficiency of the process of recovering an aromatic diol compound and a carbonate precursor from the polycarbonate resin. Examples of the pretreatment process include washing, drying, pulverization, glycol decomposition, etc., and the specific method of each pretreatment process is not limited, and various methods widely used in the process of recovering an aromatic diol compound and a carbonate precursor by depolymerization of a polycarbonate resin can be applied without limitation.

In the present invention, the glycol compound may include all glycol compounds or derivative compounds thereof, and specifically, the glycol compound may include alkylene glycol. Specific examples of the alkylene glycol are not particularly limited, and various existing known alkylene glycols may be used without limitation, but examples include ethylene glycol or propylene glycol.

Meanwhile, the organic solvent may include an aliphatic compound. The aliphatic compound refers to a chain-like or cyclic non-aromatic carbon compound. The aliphatic compound may include at least one compound selected from the group consisting of a halogenated chain-like aliphatic compound, a heterocyclic aliphatic compound, and a chain-like aliphatic carbonate compound. That is, the aliphatic compound may include a halogenated chain-like aliphatic compound, a heterocyclic aliphatic compound, a chain-like aliphatic carbonate compound, or a mixture of two or more thereof.

The above halogenated chain-type aliphatic compound refers to a substance in which at least one hydrogen atom contained in the chain-type aliphatic compound is replaced with a halogen. Examples of the halogen include fluorine, chlorine, bromine, or iodine. Specifically, examples of the halogenated chain-type aliphatic compound are not particularly limited, but include, for example, methylene chloride or chloroform.

The above heterocyclic aliphatic compound refers to a cyclic aliphatic compound containing a hetero atom such as oxygen or nitrogen. Specifically, examples of the above heterocyclic aliphatic compound are not particularly limited, but include, for example, tetrahydrofuran.

The above chain-type aliphatic carbonate compound refers to a chain-type aliphatic compound having a carbonate functional group. Specifically, examples of the chain-type aliphatic carbonate compound are not particularly limited, but include, for example, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, or dipropyl carbonate.

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

More specifically, the aliphatic compound may include methylene chloride. When methylene chloride is used as the organic solvent, there is an advantage in that the solubility characteristics for polycarbonate are improved, thereby enhancing the reactivity.

With respect to 100 parts by weight of the organic solvent, the weight ratio of the glycol compound may be 1 part by weight to 20 parts by weight, or 10 parts by weight to 20 parts by weight, or 10 parts by weight to 15 parts by weight, or 13 parts by weight to 15 parts by weight. There is an advantage in that a depolymerization reaction of the polymer can proceed at a required level by mixing the glycol compound and the organic solvent within the above range.

If the weight ratio of the glycol compound is excessively reduced to less than 1 part by weight relative to 100 parts by weight of the above organic solvent, technical problems such as a slow reaction rate and a long reaction time may occur.

On the other hand, if the weight ratio of the glycol compound is excessively increased to more than 20 parts by weight with respect to 100 parts by weight of the organic solvent, a technical problem may occur in which polycarbonate is precipitated at the initial stage of the reaction or a side reaction occurs due to this, resulting in an increase in impurities.

Meanwhile, with respect to 100 parts by weight of the organic solvent, the weight ratio of the polycarbonate resin may be 1 part by weight to 50 parts by weight, or 10 parts by weight to 50 parts by weight, or 20 parts by weight to 30 parts by weight.

The above 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 3 parts by weight, relative to 100 parts by weight of the polycarbonate resin. Specifically, by including the catalyst in the above content range, there is an advantage in that an economical catalytic reaction can be performed.

The catalyst may include one catalyst selected from the group consisting of an ionic liquid catalyst, an organic base catalyst, and an inorganic base catalyst. That is, the catalyst may include an ionic liquid catalyst, an organic base catalyst, an inorganic base catalyst, or a mixture of two or more thereof.

The above ionic liquid catalyst may exist in the form of a salt including an organic cation and an organic anion, and specifically may include an amidine-based salt compound. The amidine-based salt compound may include an amidine-based cation and an imidazole-based anion. The amidine-based cation may include both an amidine cation and a derivative cation thereof. The imidazole-based cation may include both an imidazole anion and a derivative anion thereof.

Specifically, the amidine-based salt compound may include an amidine-based cation having a fused ring. The fused ring may include a 7-membered ring and a fused ring between 6-membered rings. The 7-membered ring means a case where there are 7 elements forming the ring, and the 6-membered ring means a case where there are 6 elements forming the ring, respectively.

The above six-membered ring may contain a C=N double bond of amidine. The above seven-membered ring may contain a C-C single bond of amidine. And, the C-N single bond of amidine may be contained in the part where the seven-membered ring and the six-membered ring overlap.

More specifically, a specific example of the ionic liquid catalyst may include a salt compound represented by the following chemical formula A.

[Chemical formula A]

In the above chemical formula A, R ₁ , R ₂ , and R ₃ are the same or different from each other, and can each independently be hydrogen or alkyl.

Specific examples of the ionic liquid catalyst represented by the above chemical formula A include, but are not limited to, compound a wherein in the above chemical formula A, R ₁ = R ₂ = R ₃ = hydrogen (H), compound b wherein in the above chemical formula A, R ₁ = R ₃ = hydrogen (H), R ₂ = methyl (CH ₃ ), compound c wherein in _the above chemical formula A, R ₁ = R ₂ = hydrogen (H), R ₃ = methyl (CH 3 ), compound d wherein in _{the above chemical formula A, R 1 = R 3 = hydrogen} (H), R ₂ = isopropyl, or compound e wherein in the above chemical formula A, R ₁ = R ₂ = hydrogen (H), R 3 = isopropyl.

Meanwhile, the organic base catalyst refers to a nonionic organic compound having basicity, and specifically, may include an amidine compound or a guanidine compound. The amidine compound may include all amidine compounds or derivative compounds thereof. The guanidine compound may include all guanidine compounds or derivative compounds thereof.

The above amidine compound or guanidine compound may have a fused ring. The fused ring may include a 6-membered ring and a fused ring between 6-membered rings. In addition, the fused ring may include a 7-membered ring and a fused ring between 6-membered rings. In addition, the fused ring may include a 5-membered ring and a fused ring between 6-membered rings. The 7-membered ring means a case where the ring has 7 elements, the 6-membered ring means a case where the ring has 6 elements, and the 5-membered ring means a case where the ring has 5 elements, respectively.

The above 6-membered ring may contain a C=N double bond of amidine or guanidine. The above 5-membered ring or 7-membered ring may contain a C-C single bond of amidine or a C-N single bond of guanidine. In addition, the C-N single bond of amidine or guanidine may be contained in the part where the two rings overlap.

Specifically, the amidine compound may include an amidine compound having a bonded ring.

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

Additionally, the guanidine compound may include a guanidine compound having a bonded ring.

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

Meanwhile, the inorganic base catalyst refers to a nonionic inorganic compound having basicity, and specifically, may be sodium hydroxide (NaOH) or potassium hydroxide (KOH), preferably sodium hydroxide (NaOH), but is not limited thereto. By using the inorganic base catalyst, the decomposition reaction can proceed under mild conditions, and there is an advantage of economic feasibility.

Meanwhile, the step of adding a glycol compound and a catalyst to the mixture and stirring may be 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 30 hours, or 1 hour to 25 hours, or 1 hour to 24 hours.

Specifically, the above conditions are mild process conditions compared to the existing pressurized/high temperature process, and by performing stirring under the above conditions, the process can be performed in a mild process compared to the pressurized/high temperature process, and there is an advantage in that the most efficient results can be obtained, particularly in terms of reproducibility and stability.

Meanwhile, the method for manufacturing a monomer composition for synthesizing recycled plastic according to the above embodiment may further include, after the step of adding a glycol-based compound and a catalyst to the mixed solution and stirring, a step of neutralizing the product of the stirring step with an acid. For example, the alkaline decomposition product of a polycarbonate-based resin includes an aromatic diol compound or a salt thereof, but since the main target material for recovery of the present invention is an aromatic diol compound, in the case of a salt of an aromatic diol compound obtained by the alkaline decomposition, it may be converted into an aromatic diol compound through an additional neutralization process with an acid. That is, when the depolymerization reaction of the polycarbonate-based resin is an alkaline decomposition, a step of neutralizing the product with an acid may be performed.

The acid used in the neutralization reaction may be a strong acid, and for example, hydrochloric acid (HCl) may be mentioned. The concentration of the acid is not particularly limited, but may be, for example, 0.1% to 10%. Due to the neutralization reaction by the strong acid, the pH may be satisfied to be 4 or less or less than 2 at the end of the neutralization reaction. The temperature during the neutralization reaction may be controlled to be 25°C or more and 100°C or less.

In addition, if necessary, after the acid neutralization reaction step of the above-mentioned depolymerization reaction product is performed, a process of removing remaining impurities through filtration or adsorption may be additionally performed. Specifically, the aqueous layer and the organic layer may be separated, and the organic layer may be filtered through vacuum filtration to recover a liquid containing an aromatic diol compound.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the above embodiment may include a step of washing the aromatic diol compound obtained in the stirring step.

Since various impurities remain during the recovery process for obtaining the above aromatic diol compound, washing can be performed to sufficiently remove these impurities and secure a high-purity aromatic diol compound.

Specifically, the washing step may include a step of washing with a solvent at a temperature of 10° C. to 30° C., or 20° C. to 30° C. The temperature condition refers to the temperature inside the washing container where washing with the solvent is performed, and various heating devices may be applied without limitation to maintain a high temperature exceeding room temperature.

If necessary, after the step of washing with a solvent at a temperature of 10°C to 30°C, an additional process of removing the remaining solvent through filtration may be performed.

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

The solvent used in the above washing step can be used in a weight ratio of 1 part by weight or more and 30 parts by weight or less, or 1 part by weight or more and 10 parts by weight or less, 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 may be used as the organic solvent. In this case, the organic solvent may be used in an amount of 1 part by weight or more and 10 parts by weight or less relative to 1 part by weight of the polycarbonate resin.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the above embodiment may include a step of dissolving the aromatic diol compound obtained in the stirring step in a solvent.

In the step of dissolving the washed aromatic diol compound in the solvent, the weight ratio of the solvent may be 100 parts by weight to 500 parts by weight, or 100 parts by weight to 200 parts by weight, or 100 parts by weight to 150 parts by weight, or 150 parts by weight to 200 parts by weight, with respect to 100 parts by weight of the aromatic diol compound. If too little of the solvent is used, the temperature for dissolving the aromatic diol compound becomes too high, which deteriorates the process efficiency, and as the temperature difference between the dissolution temperature and the cooling temperature increases, it is not easy to remove impurities through recrystallization.

On the other hand, if the solvent is used in excessive amounts, the solubility of the aromatic diol compound becomes excessively high, which reduces the yield of the aromatic diol compound recovered after recrystallization, and the process efficiency may decrease due to the use of a large amount of solvent.

Through the step of dissolving the washed aromatic diol compound in a solvent, the aromatic diol compound crystals can be redissolved in the solvent.

Through this, the impurities caught between the aromatic diol compound crystals can be dissolved into the solvent as much as possible, and since the dissolved aromatic diol compound has poor solubility compared to the impurities, when the temperature is lowered thereafter, it can be easily precipitated as aromatic diol compound crystals through the difference in solubility.

The solvent may include ethanol.

Meanwhile, the method for manufacturing a monomer composition for synthesizing recycled plastic according to the above-described embodiment may include a step of adding an adsorbent to the solution obtained in the dissolution step and performing adsorption purification. In the step of adding an adsorbent to the solution obtained in the dissolution step and performing adsorption purification, the adsorbent may be brought into contact with the solution obtained in the dissolution step.

Examples of the above adsorbent include activated carbon, charcoal, or a mixture thereof. The activated carbon is a black carbon material having micropores manufactured by subjecting a raw material to a carbonization process at about 500° C. and an activation process at about 900° C. Examples thereof are not particularly limited, but for example, depending on the type of raw material, various activated carbons such as plant-based, coal-based, petroleum-based, and waste-based activated carbons can be applied without limitation.

More specific examples include plant-based activated carbons such as palm activated carbon, wood activated carbon, and sawdust activated carbon. In addition, coal-based activated carbons include lignite activated carbon, bituminous carbon activated carbon, and anthracite activated carbon. In addition, petroleum-based activated carbons include petroleum coke activated carbon and oil carbon activated carbon. In addition, waste-based activated carbons include synthetic resin activated carbon and pulp activated carbon.

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

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

The conditions for adsorption purification using the above adsorbent are not particularly limited, and various adsorption purification conditions known in the art can be used without limitation. However, for example, the adsorbent can be added in an amount of 20 to 60 parts by weight, or 25 to 50 parts by weight, relative to 100 parts by weight of the polycarbonate resin. By minimizing the amount of the adsorbent added in this way, the aromatic diol compound to be recovered can have excellent color quality, and the aromatic diol compound can be secured with high purity.

Additionally, the adsorption time can be 1 to 5 hours, and the adsorption method can be stirred adsorption or a lab-use adsorption tower.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the above-described embodiment may include a step of obtaining the aromatic diol compound. The step of obtaining the aromatic diol compound may include a step of forming an aromatic diol compound crystal by introducing a crystallization solvent; and a step of filtering the aromatic diol compound crystal.

Specifically, through the step of forming an aromatic diol compound crystal by introducing the crystallization solvent, the impurities caught between the aromatic diol compound crystals can be dissolved as much as possible with the solvent, and since the dissolved aromatic diol compound has low solubility compared to the impurities, when the temperature is lowered thereafter, the aromatic diol compound can be easily precipitated as crystals through the difference in solubility.

There are no specific limitations on the specific equipment and conditions for introducing the above crystallization solvent and forming the aromatic diol compound crystals, and various recrystallization processes that have been widely used in the field of technology for recovering conventional aromatic diol compounds (bisphenol A) can be applied without limitation. As an example of the above crystallization solvent, water can be used.

If the water is used in an excessively small amount, the temperature for dissolving the aromatic diol compound becomes too high, which reduces process efficiency and makes it difficult to remove impurities through recrystallization. On the other hand, if the water is used in an excessive amount, the solubility of the aromatic diol compound becomes excessively high, which reduces the yield of the aromatic diol compound recovered after recrystallization and may reduce process efficiency due to the use of a large amount of solvent.

In addition, in the step of filtering the above-mentioned aromatic diol compound crystals, specific filtration equipment and conditions are not limited, and various filtration processes that have been widely used in the conventional field of technology for recovering aromatic diol compounds (bisphenol A) can be applied without limitation. As an example of the above-mentioned filtration, reduced pressure filtration can be used.

Meanwhile, the method for producing a monomer composition for synthesizing recycled plastic according to the above embodiment may further include a drying step after the step of obtaining the aromatic diol compound. The residual solvent can be removed through the drying, and the specific drying conditions are not particularly limited, but for example, the drying may be performed at a temperature of 10° C. to 100° C., or 10° C. to 50° C. With regard to the specific drying equipment and method used during the drying, various known drying technologies can be applied without limitation.

According to another embodiment of the invention, a monomer composition for synthesizing recycled plastic can be provided, which comprises an aromatic diol compound obtained in the method for producing a monomer composition for synthesizing recycled plastic of the above embodiment.

The monomer composition for synthesizing recycled plastic of the other embodiment may be obtained by the method for producing the monomer composition for synthesizing recycled plastic of the one embodiment. The content of the method for producing the monomer composition for synthesizing recycled plastic of the other embodiment includes all of the contents described above in the one embodiment.

That is, the monomer composition for synthesizing recycled plastic of the above-mentioned other embodiments corresponds to a result obtained through various filtration, purification, washing, and drying processes to secure only the aromatic diol compound, which is the main recovery target material, with high purity after the depolymerization reaction of the polycarbonate resin.

In addition, specific examples of the aromatic diol compounds include bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ketone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, Examples thereof include 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3-chlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, or mixtures of two or more thereof. Preferably, the aromatic diol compound of the monomer composition for synthesizing recycled plastic of the above embodiment may be 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

The aromatic diol compound is characterized in that it is obtained in the method for producing a monomer composition for synthesizing recycled plastic of the above embodiment. That is, the aromatic diol compound is characterized in that it is recovered from the polycarbonate resin used for recovering the monomer composition for synthesizing recycled plastic. Therefore, in order to produce the monomer composition for synthesizing recycled plastic of the other embodiment, a case in which a new aromatic diol compound is added externally separately from recovery from the polycarbonate resin is not included in the category of the aromatic diol compound of the present invention.

Specifically, the fact that it was recovered from the polycarbonate resin means that it was obtained through a depolymerization reaction of the polycarbonate resin. The depolymerization reaction can be performed under acidic, neutral, or alkaline conditions, and in particular, the depolymerization reaction can be performed under alkaline (alkaline) conditions. In particular, the depolymerization reaction is preferably performed under an ethanol solvent as described below.

According to another embodiment of the invention, a recycled plastic comprising a reaction product of a monomer composition for synthesizing recycled plastic and a comonomer of the other embodiment can be provided.

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

The examples corresponding to the above recycled plastics are not particularly limited, and various plastics synthesized using aromatic diol compounds such as bisphenol A and carbonate precursors such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate as monomers can be applied without limitation, and a more specific example is a polycarbonate resin.

The above polycarbonate resin includes both a homopolymer and a copolymer containing a polycarbonate repeating unit, and collectively refers to a reaction product obtained through a polymerization reaction or a copolymerization reaction of a monomer including an aromatic diol compound and a carbonate precursor. When one carbonate repeating unit obtained by using only one aromatic diol compound and one carbonate precursor is contained, a homopolymer can be synthesized. In addition, when one aromatic diol compound and two or more carbonate precursors are used as the monomer, or two or more aromatic diol compounds and one carbonate precursor are used, or one or more other diols are used in addition to one aromatic diol compound and one carbonate precursor, and two or more carbonates are contained, a copolymer can be synthesized. The homopolymer or copolymer can include all low-molecular-weight compounds, oligomers, and polymers according to the molecular weight range.

More specifically, in the recycled plastic including the monomer composition for synthesizing the recycled plastic of the above embodiment and the reaction product of the comonomer, a carbonate precursor can 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, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate or bishaloformate.

Examples of the reaction process of the monomer composition and comonomer for synthesizing the above polycarbonate resin for recycling plastic synthesis are not particularly limited, and various polycarbonate manufacturing methods known in the art can be applied without limitation.

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

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

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

In addition, 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.

In addition, in order to control the molecular weight of the polycarbonate during the polymerization, polymerization can be performed in the presence of a molecular weight regulator. 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 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, relative to 100 parts by weight of the aromatic diol compound, and a desired molecular weight can be obtained within this range.

In addition, in order to promote the polymerization reaction, a reaction promoter such as a tertiary amine compound, a quaternary ammonium compound, a quaternary phosphonium compound, etc., such as triethylamine, tetra-n-butylammonium bromide, or tetra-n-butylphosphonium bromide, can be additionally used.

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

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

The above examples of molded products are not particularly limited, and can be applied to various molded products using plastic without limitation. Examples of the above 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 above molded product may additionally contain one or more additives selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, optical whitening agents, ultraviolet absorbers, pigments, and dyes, as needed.

As an example of a method for manufacturing the above-mentioned molded product, the method may include a step of mixing the recycled plastic and additives of the other embodiment well using a mixer, extruding them with an extruder to manufacture pellets, drying the pellets, and then injecting them with an injection molding machine.

According to the present invention, a method for producing a monomer composition for synthesizing recycled plastic containing an aromatic diol compound having high purity and excellent optical properties recovered through recycling by chemical decomposition of a polycarbonate resin, and a monomer composition for synthesizing recycled plastic, recycled plastic, and a molded product using the same can be provided.

The invention is described in more detail in the following examples. However, the following examples are only intended to illustrate the present invention, and the content of the present invention is not limited by the following examples.

<Examples and Comparative Examples: Preparation of Recycled Bisphenol A Monomer Composition>

Example 1

(1. Decomposition step) 1600 g of methylene chloride and 400 g of polycarbonate (PC) were added to a 2L high-pressure reactor and stirred. Then, 220 g of ethylene glycol and 2.25 g of sodium hydroxide (NaOH) as a catalyst were added and stirred at 80°C for 24 hours to carry out the PC depolymerization reaction.

(2. Neutralization step) The product of the above depolymerization reaction was cooled to 30°C or lower, and then the product containing bisphenol A was placed in 3,000 g of a 10% hydrochloric acid (HCl) aqueous solution and neutralized at 20 to 30°C. Thereafter, bisphenol A was recovered by filtering using vacuum filtration.

(3. Purification-Washing Step) Afterwards, it was washed at 20 to 30°C using methylene chloride (MC) 1 times the mass of PC used, and vacuum filtered.

(4-1. Purification stage - re-dissolution stage) 560 g of ethanol was added to the 280 g of bisphenol A recovered above and re-dissolved.

(4-2. Purification stage - Adsorption stage) After that, brown activated carbon was added as an adsorbent at a ratio of 50 wt% compared to polycarbonate, and purified through adsorption for 3 hours, and then the brown activated carbon was removed through filtration.

(4-3. Purification step-recrystallization step) After that, 750 g of water was added and bisphenol A was recrystallized, and then the obtained slurry was vacuum filtered at 20 to 30°C to recover bisphenol A (BPA) crystals.

(5. Drying step) Afterwards, a recycled bisphenol A monomer composition was manufactured by recovering recycled bisphenol A (BPA) by vacuum drying in a 40°C convection oven.

Example 2

In the above Example 1 (4-1. Purification step - re-dissolution step), a recycled bisphenol A monomer composition was manufactured in the same manner as in Example 1, except that ethanol was changed to 280 g.

Example 3

In the above Example 1 (4-1. Purification step - re-dissolution step), ethanol was changed to 280 g, and in the (4-2. Purification step - adsorption step), brown activated carbon was added as an adsorbent at a ratio of 25 wt% relative to polycarbonate and purified through adsorption for 1 hour, except that a recycled bisphenol A monomer composition was manufactured in the same manner as in Example 1.

Example 4

A recycled bisphenol A monomer composition was manufactured in the same manner as in Example 1, except that in (4-2. Purification step-adsorption step) of Example 1, brown activated carbon was added as an adsorbent at a ratio of 25 wt% relative to polycarbonate and purified through adsorption for 1 hour.

Comparative Example 1

A recycled bisphenol A monomer composition was prepared in the same manner as in Example 1, except that phenol was used instead of methylene chloride in Example 1.

Comparative Example 2

A recycled bisphenol A monomer composition was manufactured in the same manner as in Example 1, except that (4-2. Purification step-adsorption step) of Example 1 was not performed.

<Experimental example>

The physical properties of the recycled bisphenol A monomer compositions obtained in the above examples and comparative examples were measured by the following methods, and the results are shown in Table 1.

1. Polycarbonate decomposition

The degree of polycarbonate decomposition was confirmed by HPLC measurement of a portion of the decomposed reactant. Specifically, HPLC measurement of the reactant was performed at regular time intervals (approximately 1 hour) after the start of the reaction.

2. BPA yield

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

[Formula 1]

Yield (%) = (W ₁ /W ₀ ) * 100

In the above equation 1, W ₀ is the mass of BPA obtained at 100% decomposition, and W ₁ is the mass of BPA actually obtained. Specifically, when about 100 g of polycarbonate is decomposed, the mass of BPA theoretically obtained at 100% decomposition is 89 g. If the mass of BPA actually obtained is 80 g, the yield is 80/89 * 100 = 90%.

Experimental example measurement results division PC Disassembly (%) BPA yield (%) Example 1 93.1% 78.2% Example 2 92.7% 79.4% Example 3 92.3% 78.7% Example 4 93.4% 76.9% Comparative Example 1 83.7% 64.8% Comparative Example 2 78.9% 65.3%

As shown in Table 1 above, it was confirmed that both PC decomposition and BPA yield were improved in Examples 1 to 4 compared to the Comparative Examples. Specifically, it was confirmed that Examples 1 to 4 showed PC decomposition of 92.3% to 93.4% and BPA yield of 76.9% to 79.4%, while Comparative Examples 1 to 2 showed PC decomposition of 78.9% to 83.7% and BPA yield of 64.8% to 65.3%.

Claims (18)

A step of preparing a mixed solution by adding a polycarbonate resin to an organic solvent;
A step of adding a glycol compound and a catalyst to the above mixture and stirring;
A step of washing the aromatic diol compound obtained in the above stirring step;
A step of dissolving the washed aromatic diol compound in a solvent;
A step of adding an adsorbent to the solution obtained in the above dissolution step and performing adsorption purification; and
A step of obtaining the above aromatic diol compound; comprising;
A method for producing a monomer composition for synthesizing recycled plastic, wherein the organic solvent comprises an aliphatic compound.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the aliphatic compound comprises at least one compound selected from the group consisting of a halogenated chain-type aliphatic compound, a heterocyclic aliphatic compound, and a chain-type aliphatic carbonate compound.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the aliphatic compound comprises methylene chloride.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the weight ratio of a glycol-based compound is 1 to 20 parts by weight with respect to 100 parts by weight of the organic solvent.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the adsorbent comprises at least one activated carbon selected from the group consisting of plant-based activated carbon, coal-based activated carbon, petroleum-based activated carbon, and waste-based activated carbon.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the adsorbent is added in an amount of 20 to 60 parts by weight per 100 parts by weight of polycarbonate resin.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the catalyst comprises one catalyst selected from the group consisting of an ionic liquid catalyst, an organic base catalyst, and an inorganic base catalyst.
In the first paragraph,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the glycol compound comprises an alkylene glycol.
In the first paragraph,
The step of adding a glycol compound and a catalyst to the above mixture and stirring it is as follows.
A method for producing a monomer composition for synthesizing recycled plastic, the method comprising stirring the composition at 20°C to 100°C for 1 to 30 hours.
In the first paragraph,
In the step of dissolving the above washed aromatic diol compound in a solvent,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the weight ratio of the solvent is 100 to 500 parts by weight with respect to 100 parts by weight of the aromatic diol compound.
In the first paragraph,
In the step of dissolving the washed diol compound in a solvent,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the solvent comprises ethanol.
In the first paragraph,
The step of obtaining the above aromatic diol compound is:
A step of forming an aromatic diol compound crystal by introducing a crystallization solvent; and
A method for producing a monomer composition for synthesizing recycled plastic, comprising: a step of filtering the aromatic diol compound crystals.
In Article 12,
A method for producing a monomer composition for synthesizing recycled plastic, wherein the crystallization solvent comprises water.
In the first paragraph,
After adding a glycol compound and a catalyst to the above mixture and stirring,
A method for producing a monomer composition for synthesizing recycled plastic, further comprising a neutralization reaction step of the product of the stirring step using an acid.
In the first paragraph,
The step of washing the aromatic diol compound obtained in the above stirring step is:
A method for producing a monomer composition for synthesizing recycled plastic, comprising a step of washing with a solvent at a temperature of 10° C. to 30° C.
A monomer composition for synthesizing recycled plastic, comprising an aromatic diol compound obtained in the method for producing a monomer composition for synthesizing recycled plastic of claim 1.
A recycled plastic comprising a monomer composition for synthesizing recycled plastic and a reaction product of a comonomer of claim 16.
A molded article comprising recycled plastic of Article 17.