KR102425247B1 - Eco-friendly depolymerization method of polymers containing ester functional groups - Google Patents

Abstract

[화학식 1]The present invention relates to a method of depolymerizing a polymer containing an ester functional group, and more particularly, by adding a compound represented by the following formula (1) as an additive, depolymerization is possible even at a lower temperature, and the yield of the target product can be increased It relates to a method for depolymerizing a polymer containing an ester functional group and a composition therefor.

[Formula 1]

Description

Eco-friendly depolymerization method of polymers containing ester functional groups

The present invention relates to an environmentally friendly depolymerization method of a polymer containing an ester functional group.

More specifically, in decomposing by adding a polyalcohol such as glycol to a raw material in a pulverized form of a polymer containing an ester functional group in a polymerized form, an exchange esterification reaction catalyst, for example, a metal cation of Group 1A, Group 2A, or Group 2B A metal salt catalyst or an organic compound catalyst is used in which the counter-ion is composed of an organic anion such as carbonic acid, bicarbonate, alkoxide, acetate, etc., and at least one alkyl group is connected to the aromatic ring through a linker, and the linker is at least It relates to depolymerizing a polymer containing an ester functional group by adding a compound characterized by having at least one oxygen to obtain a polyalcohol addition monomer.

Plastic is an inexpensive and durable material, and has the advantage of being convenient for molding and processing, so it is used in the production of various products. Due to these advantages, the consumption of plastics in industry and life has increased dramatically over the decades. However, as plastic waste that is not properly managed is left in the environment, it causes environmental pollution, or microplastics decomposed into small pieces float around the ecosystem, accumulate in living things, and eventually enter the human body again through fine dust, drinking water, and food. is being caused Moreover, more than 50% of these plastics are used for single-use, single-use, disposable applications such as packaging, agricultural films, disposable consumer products, etc. or as short-term products that are discarded within one year of manufacture.

Most of the discarded plastics are randomly discharged to designated landfills or natural habitats that are difficult to purify naturally, so the seriousness of the environmental pollution problem is increasing day by day. Even biodegradable or biodegradable plastics can persist for decades, depending on local environmental factors such as level of UV exposure, temperature, and the presence of degrading microorganisms.

In order to solve these problems, from the chemical degradation of existing petroleum-based plastics to the physical regeneration and reprocessing of plastics, including the development of new plastic materials with a short decomposition cycle in the natural state, to minimize the accumulation of plastics or reduce the environmental impact. Several studies are in progress.

Polymers containing ester functional groups can be monomerized through depolymerization, and various chemical reaction pathways have been developed. The monomers generated through decomposition can theoretically have properties equivalent to those of raw materials used for initial polymer synthesis. Depolymerization pathways that are industrially applied to recycle polyester include hydrolysis, glycolysis, methanolysis, ammonolysis, and the like. Various chemical depolymerization methods are widely used, ranging from complex processes utilizing only specific advantages.

More specifically, the method for preparing depolymerization of a polymer containing the ester functional groups listed above is known. In the case of hydrolysis, it is known that decomposition can proceed through various reaction pathways in the presence of acid, base, and metal salt catalysts. In the case of an acid-catalyzed reaction, a very high concentration of sulfuric acid solution is required to obtain a high reaction yield, so economical problems due to design, operation, and post-treatment of the process are pointed out as disadvantages. When a base and metal salt catalyst is applied, it is inefficient because the decomposition reaction rate is very slow, the product purity is low, and the catalyst recovery becomes difficult.

The methanolysis process is one of the processes widely applied to actual commercial processes not only in global chemical companies but also in small and medium-sized plastics industries. However, since methanol is used as a reaction solvent, severe reaction conditions of high temperature and high pressure are required, and accordingly, a high investment cost may be required because the design cost of the device and additional unit processes for recovery of reactants and product purification are essential. In order to perform efficient methanolysis, an exchange esterification catalyst is required. Catalysts commonly used for depolymerization of polymers containing ester functional groups include metals such as zinc acetate, magnesium acetate, cobalt acetate, and lead dioxide as cations. things that have been done can be exemplified. However, metals constituting the catalyst may remain in the obtained depolymerization product, and depending on the purpose and use of the material to be repolymerized, the type and amount of the catalyst may be adjusted to minimize harm to the human body or the effect on product quality. and constraints that must be considered along with economics.

Although hydrolysis and methanolysis processes are utilized in many fields, both reactions have limited quality and yield of products produced during decomposition of polyester resins, long decomposition reaction times, and as decomposition products, terephthalic acid (TPA) or Since only one type of dimethyl terephthalate (DMT) is produced as the main product and other types of terephthalate compounds are treated as by-product impurities. This may be requested.

Glycolysis is a depolymerization reaction in which glycol is added as a reactant. The most common example of glycolysis is a process for preparing bis(2-hydroxyethyl) terephthalate (BHET) by adding an excess of ethylene glycol (EG), one of the monomer raw materials. Since EG, which is a part of PET raw material, is used as a reactant, thermodynamic miscibility with the reaction product is high, and it can be used by changing the existing polymerization process with a small investment in equipment, and the raw material can be directly applied to production without additional chemical treatment. There is this. Glycolysis is generally carried out under the reflux condition of glycol, the reactant, because the rate of decomposition from oligomers to monomers is slow and the product distribution is wide even in reaction equilibrium. may exist, and a high-cost purification process may be necessary to separate the final product, the monomer, from the reactant in high yield and high purity. The reaction catalyst used is generally zinc acetate or lithium acetate. These metal salt catalysts may not be completely removed during the refining process and may remain in the product, and even a small amount may contain metals that are harmful to the human body. The reprocessing of the material of the product is difficult to utilize. In addition, although glycolysis proceeds at a high temperature, the recovery and purification process of the product generally follows a low-temperature recrystallization method, so energy consumption is high and the cost and efficiency of the heat source supply method of the production process are low. There is a problem.

In carrying out the above-described glycolysis reaction, if the depolymerization reaction rate can be increased at a low temperature and an eco-friendly catalyst system with low toxicity can be applied, not only efficient and economical operation, but also a polymer containing an ester functional group discharged in large quantities is used. Therefore, it is expected that it can be efficiently used in the manufacture of eco-friendly raw materials without restrictions on product quality or use.

In the present invention, in decomposing the polymer containing the ester functional group, the prepared monomer can be adjusted to correspond to the initial raw material produced before polymerization or in an existing petrochemical process or to have a very low impurity content. In addition, the waste polymer resin discharged after consumption can be used as a raw material for depolymerization, and the monomer produced therefrom can also be reintroduced into the same process without an additional pre-treatment process based on glycolysis, which can contribute to achieving a plastic recycling economy An object of the present invention is to provide a method for preparing a high-quality regenerated monomer.

In addition, it is intended to provide a depolymerization method that can significantly reduce energy consumption because depolymerization is possible under a reaction condition that is much lower than the existing high temperature reaction condition.

In addition, the present invention enables eco-friendly reaction materials, reaction routes and system configurations compared to existing processes, and facilitates the purification process of products depolymerized from polymer resins containing ester functional groups, making it economical and efficient compared to other reaction technologies. It is intended to provide a manufacturing method.

In order to solve the above problems, the present invention is (1) at least one polyhydric alcohol; (2) an exchange esterification reaction catalyst; (3) a method of depolymerizing a polymer containing an ester functional group, characterized in that the polymer containing the ester functional group is decomposed by contacting a mixture containing the compound represented by the following Chemical Formula 1 with the polymer containing the ester functional group provides

[화학식 1]

[Formula 1]

In Formula 1,

The substituent R ₁ is any one selected from hydrogen, a hydroxyl group, an aldehyde group, a carboxyl group, a C ₁ -C ₆ alkyl group, a C ₄ -C ₆ cycloalkyl group, and a C ₆ -C ₁₂ aryl group,

Wherein n is an integer from 0 to 5, and when n is 2 or more, R ₁ are the same or different,

The substituent R ₂ is a C ₁ -C ₁₀ alkyl group,

Wherein m is an integer of any one of 1 to 6, and when m is 2 or more, -OR ₂ is the same or different.

In one embodiment of the present invention, the exchange esterification reaction catalyst may include at least one selected from metal salts of Group 1A, Group 2A, and Group 2B metals.

In one embodiment of the present invention, the counter-ion of the metal salt may be composed of an organic anion selected from carbonic acid, bicarbonate, alkoxide, and acetate.

In one embodiment of the present invention, the exchange esterification reaction catalyst may include at least one non-metallic organic compound catalyst composed of an organic material.

In one embodiment of the present invention, the polyhydric alcohol is ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5 - in pentanediol, 1,6-hexanediol, 1,7-octanediol, 1,9-nonanediol, neopentyl glycol, 1,4-cyclohexanediol, isosorbide and 1,4-cyclohexane dimethanol It may be one or more selected.

In one embodiment of the present invention, the compound represented by Formula 1 is methoxy benzene, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, 1,2,3 -Trimethoxybenzene, 1,2,4-trimethoxybenzene, 1,3,5-trimethoxybenzene, 1,2,3,4-tetramethoxybenzene, 1,2,3,5-tetra Methoxybenzene, 1,2,4,5-tetramethoxybenzene, 2-methoxyphenol, 1,3-dimethoxy-2-hydroxybenzene, 4-hydroxy-3,5-dimethoxybenzoic acid , 3- (4-hydroxy-3,5-dimethoxyphenyl) prop-2-enal, 4-hydroxy-3,5-dimethoxybenzaldehyde, 4-hydroxy-3,5-dimethoxy Acetophenone, 3-(4-hydroxy-3,5-dimethoxyphenylprop-2-enoic acid, 4-enyl-2,6-dimethoxyphenol, 4-hydroxy-3-methoxybenzalde Hyde, 3-hydroxy-4-methoxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-4-methoxy Benzaldehyde, 3,4-dihydroxybenzaldehyde, 1-methoxy-4-[(E)-prop-1-enyl]benzene, 1-bromo-4-methoxybenzene, 2-tert -Butyl-4-methoxyphenol, ethoxybenzene, phenol, 1,3,5-trichloro-2-methoxybenzene, 1,3,5-tribromo-2-methoxybenzene, 4- (pro P-2-en-1-yl)phenol, 1-methoxy-4 (prop-2-en-1-yl)benzene, 5-(prop-2-en-1-yl)-2H-1 From the group consisting of ,3-benzodioxole, 4-methoxy-2-[(E)-prop-1-yl]phenol, 2-methoxy-4-(prop-1-en-yl)phenol It may be one or more selected.

In one embodiment of the present invention, the polymer including the ester functional group is polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polyglycolide or polyglycolic acid (PGA), polylactic acid (PLA), poly Caprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co- 3-hydroxyvalerate) (PHBV), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), may be at least one selected from the group consisting of Vectran.

The present invention also provides a composition for polymer depolymerization containing an ester functional group, comprising (1) one or more polyhydric alcohols, (2) an exchange esterification reaction catalyst, and (3) a compound represented by Formula 1 above. The metal salt catalyst may be at least one selected from metal salts of Group 1A, Group 2A, and Group 2B.

In addition, the amount of the polyhydric alcohol contained in the composition is a ratio of 1 to 50 moles per mole of the repeating unit of the polymer to be depolymerized, and the amount of the exchange esterification reaction catalyst is 0.001 to 1 of the moles per mole of the repeating unit of the polymer to be depolymerized. Formula 1 The addition amount of the compound represented by can be made to be a ratio of 0.001 to 50 moles per mole of the repeating unit of the polymer to be depolymerized.

In addition, the present invention provides a method for purifying a glycol addition monomer obtained by the depolymerization method according to the present invention.

The purification method includes the steps of (1) separating the compound represented by Formula 1 from the depolymerization reaction product by using gas-liquid separation or liquid-liquid extraction; (2) after step (1), a solid separation step of separating a solid material containing a polymer including an unreacted ester functional group; (3) after the solid separation of step (2), a recovery step of recrystallizing and recovering the glycol addition monomer; includes.

In one embodiment of the present invention, in the purification method, the solid material containing the unreacted ester functional group can be separated using physical filtration, and the step of separating the oligomer before recrystallization of the glycol addition monomer in step (3). can be performed first.

According to the present invention, it is possible to produce a glycol addition monomer (eg, bis(2-hydroxyethyl)terephthalate), which is a raw material for polymer resynthesis, in high yield and with high purity from a polymer containing an ester functional group before manufacture or for polymer resynthesis. In addition, high-purity bis(2-hydroxyethyl)terephthalate (bis(2-hydroxyethyl)terephthalate, BHET) can be usefully used for the large-scale production of regenerated monomers.

According to the present invention, by applying a reaction system composed of eco-friendly materials and a reaction condition that is relaxed compared to the existing reaction conditions, and applying it to the production of a glycolysis-based depolymerization monomer, the reactivity to the decomposition of the polymer containing the ester functional group and the desired monomer Selectivity can be secured at the same time, and thermodynamic phase separation methods such as liquid-liquid extraction or gas-liquid separation can all be effectively applied to most of the materials including catalysts after the reaction, so recovery is easy and the impurity content in the decomposition product is reduced. can be significantly lowered.

In addition, the present invention can obtain a glycol addition monomer of high yield and high purity even at a lower temperature and atmospheric pressure compared to the glycolysis process reported in the existing prior literature.

In addition, the selection of catalysts that can be applied to the technology according to the present invention can be very diverse, and it is possible to produce products that are harmless to the human body because they have low toxicity and inexpensive catalysts can also be used compared to conventionally used commercial catalysts (eg, zinc acetate). In addition, it is possible to produce environmentally friendly and economical products.

Even when the monomer depolymerized by the technique according to the present invention is reused as a raw material for plastics or resin products by polymerization, the quality and use are not limited, so a perfect chemical recycling technology can be realized.

1 is a ¹ H NMR spectrum of BHET obtained from PET depolymerization according to a comparative example of the present invention.
FIG. 2 is a ¹ H NMR spectrum of a sample obtained by repeatedly washing BHET obtained from PET depolymerization according to a comparative example of the present invention several times with water.
3 is a ¹ H NMR spectrum of BHET obtained from PET depolymerization according to an embodiment of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is those well known and commonly used in the art.

Throughout this specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

The depolymerization method of a polymer containing an ester functional group according to the present invention uses one or more polyhydric alcohols as a raw material for the glycolysis reaction, and a conventional catalyst such as zinc acetate may be used as a reaction catalyst, but groups 1A and 2A Alternatively, salts composed of an organic anion such as carbonic acid, bicarbonate, alkoxide, or acetate in which a Group 2B metal cation and a counter-ion are organic anions may also be used as catalysts. may be

In addition, the present invention is to convert a polymer raw material containing an ester functional group into a glycol addition monomer by adding a compound in which at least one alkyl group is connected to the aromatic ring represented by the following formula 1 through a linker having at least one oxygen as an additive. It is possible to significantly lower the activation energy of the depolymerization reaction for Therefore, it is easy to secure economic feasibility and control impurities by reuse and recovery of materials. Accordingly, the present invention is characterized in that it is possible to maintain high reactivity of depolymerization at a low temperature, as well as improve the purity, yield, and reaction selectivity of the depolymerization monomer.

[화학식 1]

[Formula 1]

In Formula 1,

The substituent R ₁ is any one selected from hydrogen, a hydroxyl group, an aldehyde group, a carboxyl group, a C ₁ -C ₆ alkyl group, a C ₄ -C ₆ cycloalkyl group, and a C ₆ -C ₁₂ aryl group,

Wherein n is an integer from 0 to 5, and when n is 2 or more, R ₁ are the same or different,

The substituent R ₂ is a C ₁ -C ₁₀ alkyl group,

Wherein m is an integer of any one of 1 to 6, and when m is 2 or more, -OR ₂ is the same or different.

The depolymerization method of a polymer containing an ester functional group according to the present invention has a simple process, high yield and easy purity management of the product, and the process is eco-friendly and economical efficiency can be easily secured because a low-cost catalyst can be used. It may be a technology with high application value in chemical and environmental industries.

The method of the present invention is useful for depolymerization of polymers containing ester functional groups, wherein the polymer containing ester functional groups is used alone or in the form of mixed waste plastics, such as polyethylene, high density polyethylene, low density polyethylene, polypropylene or a combination thereof. It may be in a mixed form with a polymer containing a functional group. Other polymers to be mixed with the polymer containing the ester functional group listed as examples above are merely examples and are not limited to those listed above.

In addition, the polymer including the ester functional group may be a polymer formed by condensation polymerization of dicarboxylic acid and dialcohol, wherein the dicarboxylic acid is terephthalic acid, naphthalene dicarboxylic acid, diphenyldicarboxylic acid, diphenyl ether dicarboxyl. Acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, trimellitic acid, pyro mellitic acid and combinations thereof, and the dialcohol is ethylene glycol, trimethylene glycol, 1,2-propanediol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, decamethylene glycol, dodecamethylene glycol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, di(tetramethylene) glycol, tri(tetra methylene) glycol, polytetramethylene glycol, pentaerythritol, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, and combinations thereof.

For example, the polymer containing the ester functional group is polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polyglycolide or polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), Polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) ) (PHBV), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), Vectran, and combinations thereof.

The most common example of the polymer including the ester functional group is polyethylene terephthalate, wherein the starting materials for preparing the polymer are terephthalic acid or a derivative thereof, and ethylene glycol.

The polymer including the ester functional group used in the present invention may be in a state containing various impurities, not in a pure state. For example, in addition to a polymer containing an ester functional group, a mixture of debris including, but not limited to, bottle caps, adhesives, paper, residual liquid, dust, or a combination thereof may be used as a raw material for depolymerization.

The method of depolymerizing a polymer including an ester functional group according to the present invention may contain the polymer including the ester functional group in an amount of about 0.1 mass% to about 70 mass% of the reaction raw material. If less than 0.1 mass % is initially added, it may be difficult to secure economic feasibility, and if more than 70 mass % is added, mass transfer may be restricted and the rate of reaction may be significantly lowered.

The polyhydric alcohol for glycolysis depolymerization of the polymer containing the ester functional group is a compound having at least two alcohol functional groups, and more specifically, includes a compound having two or more hydroxyl groups, such as a secondary straight-chain alcohol. It is not particularly limited thereto.

The polyhydric alcohol may be used in a ratio range of 1 to 50 moles per mole of the repeating unit of the polymer.

Examples of polyhydric alcohols having at least two alcohol functional groups according to the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl- 1,5-pentanediol, 1,6-hexanediol, 1,7-octanediol, 1,9-nonanediol, neopentyl glycol, 1,4-cyclohexanediol, isosorbide and 1,4-cyclohexane It may be at least one selected from the group consisting of dimethanol and the like.

As an example of the exchange esterification reaction catalyst according to the present invention, a catalyst in the form of an organic material that does not include a metal may be used. Non-limiting examples of the organic type catalyst include linear amines (eg, ethylenediamine, diethylenetriamine, tris(2-aminoethyl)amine, tetraethylenepentamine) and amides (eg, acetamide). , guanidine (eg triazabicyclodecene), imidazole (eg 2-ethyl-4-methylimidazole), urea (eg urea, 1,1-dimethylurea, 1,3- dimethyl urea), aromatic amines (eg, benzenedimethanamine), and cycloalkyl amines (eg, cyclohexylmethylamine, dimethylcyclohexylamine).

As another example of the catalyst according to the present invention, a salt composed of a group 1A, 2A, or 2B metal cation and an anion selected from carbonic acid, bicarbonate, alkoxide or acetate as a counter-ion may be used as the catalyst.

Group 1A ions used as the catalyst include lithium (Li ⁺ ), sodium (Na ⁺ ), potassium (K ⁺ ), group 2A metal magnesium (Mg ²⁺ ), calcium (Ca ²⁺ ), and group 2B metal zinc (Zn ²⁺ ) and the like, but is not particularly limited.

The amount of the catalyst may be used in a ratio of 0.001 to 1 moles per mole of the repeating unit of the polymer, preferably 0.01 to 0.1 moles per mole of the repeating unit of the polymer.

The compound represented by Formula 1 is used as an additive in the depolymerization reaction in order to increase the depolymerization reactivity of a polymer including an ester functional group and to increase the selectivity of a useful product.

As an example, the substituent R ₂ may be a C ₁ ~ C ₁₀ alkyl group, preferably a C ₁ ~ C ₆ alkyl group, more preferably a C ₁ ~ C ₃ alkyl group.

Examples of the compound represented by Formula 1 as an additive include methoxy benzene, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, 1,2,3-trimethoxybenzene , 1,2,4-trimethoxybenzene, 1,3,5-trimethoxybenzene, 1,2,3,4-tetramethoxybenzene, 1,2,3,5-tetramethoxybenzene, 1 , 2,4,5-tetramethoxybenzene, 2-methoxyphenol, 1,3-dimethoxy-2-hydroxybenzene, 4-hydroxy-3,5-dimethoxybenzoic acid, 3- (4 -Hydroxy-3,5-dimethoxyphenyl) prop-2-enal, 4-hydroxy-3,5-dimethoxybenzaldehyde, 4-hydroxy-3,5-dimethoxyacetophenone, 3- (4-hydroxy-3,5-dimethoxyphenyl) prop-2-enoic acid, 4-enyl-2,6-dimethoxyphenol, 4-hydroxy-3-methoxybenzaldehyde, 3- Hydroxy-4-methoxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3,4-dihydroxybenzaldehyde, 1-methoxy-4-[(E)-prop-1-enyl]benzene, 1-bromo-4-methoxybenzene, 2-tert-butyl-4 -Methoxyphenol, ethoxybenzene, phenol, 1,3,5-trichloro-2-methoxybenzene, 1,3,5-tribromo-2-methoxybenzene, 4- (prop-2- En-1-yl)phenol, 1-methoxy-4 (prop-2-en-1-yl)benzene, 5-(prop-2-en-1-yl)-2H-1,3-benzo There may be naturally occurring or synthetic compounds such as dioxol, 4-methoxy-2-[(E)-prop-1-enyl]phenol and 2-methoxy-4-(prop-1-enyl)phenol. may be, but is not particularly limited.

The amount of the additive may be used in a ratio of 0.001 to 50 moles per mole of the repeating unit of the polymer, preferably 0.1 to 10 moles per mole of the repeating unit of the polymer.

The method for depolymerizing a polymer according to the present disclosure provides a rapid method for depolymerizing a polymer comprising an ester functional group in the range of 100°C to 200°C, preferably 130°C to 160°C. As a result, the depolymerization method of a polymer including an ester functional group provided herein can proceed at a lower temperature than the conventional method, thereby saving energy, and the used catalyst and additives can be recovered and reused through a separate recovery process. it is economical

In addition, the depolymerization method of the polymer of the present invention may be performed at atmospheric pressure, but may also be performed in a pressurized form depending on the vapor pressure of the added additive or reactant.

In the method described herein, the depolymerization reaction time may vary depending on the amount of polymer used, but may be carried out according to the reaction time of 0.5 to 12 hours. In order to minimize the yield of by-products, the reaction time is 0.5 to 4 hours. This may be desirable.

After the reaction, a process of separating and removing unreacted polymer materials from the reaction mixture by filtration may be additionally performed.

The depolymerization of a polymer including an ester functional group according to the present invention is depolymerized using a polyhydric alcohol, and may correspond to a kind of glycolytic depolymerization reaction.

A method for purifying a glycol addition monomer obtained according to the depolymerization method according to the present invention comprises the steps of (1) separating a compound represented by the following formula (1) as an additive from a depolymerization reaction product by gas-liquid separation or liquid-liquid extraction;

[화학식 1]

[Formula 1]

In Formula 1,

The substituent R ₁ is any one selected from hydrogen, a hydroxyl group, an aldehyde group, a carboxyl group, a C ₁ -C ₆ alkyl group, a C ₄ -C ₆ cycloalkyl group, and a C ₆ -C ₁₂ aryl group,

Wherein n is an integer from 0 to 5, and when n is 2 or more, R ₁ are the same or different,

The substituent R ₂ is a C ₁ -C ₁₀ alkyl group,

Wherein m is an integer of any one of 1 to 6, and when m is 2 or more, -OR ₂ is the same or different.

(2) after step (1), a solid separation step of separating a solid material containing a polymer including an unreacted ester functional group; (3) after the separation of the solid in step (2), a recovery step of recrystallizing and recovering the glycol addition monomer; may include.

The gas-liquid separation of the additive may be performed separately from the reaction, or may be continuously performed after the reaction is completed. For example, while maintaining the state of condensing the vaporized additive using a condenser maintained at a low temperature installed in advance and refluxing it into the reactor, the temperature is increased or maintained after the reaction is completed, but the flow path of the condensed and refluxed additive is directed outside the reactor rather than inside the reactor. It can be changed and separated.

In the liquid-liquid extraction method, water is added to separate the target product for recovery and purification. When water is added, a phase separation boundary occurs clearly, and when only the organic layer is separated at a low temperature, most additives can be physically separated. Additives that may remain in the aqueous solution after separation have very limited solubility when the water content is increased or the temperature is lowered, and thus most can be separated and recovered. Most of the product can be recovered through crystallization, and trace amounts of additives that may remain in the purified target product can be easily and completely removed by heating and drying at 50 to 150° C., preferably by heating and drying under vacuum.

The gas-liquid phase separation for the recovery of the additive according to the method described herein separates the step of raising the temperature of the reactor above the reaction temperature after the reaction so that some or all of the additive can be vaporized or volatilized to separate the additive to the outside by distilling it including methods. For the separation of additives by liquid-liquid extraction, it may be most economical to use water, but hydrophilic substances that can induce a thermodynamically unstable phase with the additives may be used, which may be glycols or diols used as reactants. have.

The solid material containing the polymer containing the unreacted ester functional group can be removed before or after the completion of the reaction through various physical methods such as precipitation, filtration, coagulation, floating, and compression after the depolymerization reaction, and can be reintroduced to the depolymerization have. In the case of the removal method using filtration, a filter having micropores having a size less than or equal to the particle size of the unreacted polymer may be used, and pressurization or pressure reduction may be performed in parallel to increase the flow rate of the filtrate.

The glycol-added monomer recovery method through the recrystallization process is more preferably performed after removing the unreacted material according to the reaction, and the temperature above room temperature, for example, in the range of 60°C to 120°C, preferably in the range of 90°C to 110°C. It may be carried out after adding the step of separating the oligomer by filtration using water at the corresponding temperature or a solvent necessary for crystallization of the desired product. The filtrate may be recovered as a product through a recrystallization process by maintaining it at a low temperature, and physical separation and recrystallization may be repeated to control the concentration of impurities in the product. The step of separating the oligomer before recrystallization of the glycol addition monomer in step (3) may be performed first.

On the other hand, in configuring the reaction system according to the depolymerization method according to the present invention, a non-metallic catalyst is used, or a Group 1A or 2A metal cation and a counter-ion are organic anions such as carbonic acid, bicarbonate, alkoxide or acetate. When the constituted metal salt is used as a catalyst, product toxicity due to residual metal components is low and impurity concentration management can be much easier.

Hereinafter, details of the process of the present invention will be described through Examples, Comparative Examples and Experimental Examples. This is a representative example related to the present invention, and it is to be understood that this alone cannot limit the scope of application of the present invention.

Raw material 1 (single layer PET flake raw material)

As a polymer material containing an ester functional group, a plastic chip having an area of 1 cm ² or less and a thickness (single layer) of 0.3 mm or less was prepared as a raw material by cutting a bottle of polyethylene terephthalate material discharged after use.

Raw material 2 (composite layer PET flake raw material)

As a polymer material containing an ester functional group, a plastic chip having an area of 1 cm ² or less and a thickness of 0.8 to 1.2 mm (composed of 10 or more multilayers) is used as a raw material by cutting a bottle of polyethylene terephthalate material discharged after use. prepared.

Raw material 3 (colored PET film)

As a polymer material containing an ester functional group, a plastic piece having an area of 1 cm ² or less and a thickness of 0.1 mm or less was prepared as a raw material by cutting the colored label paper of a polyethylene terephthalate material bottle discharged after use.

Raw material 4 (colored polyester fiber)

As a polymer material containing an ester functional group, the polyester cloth discharged after use was cut to prepare waste fiber pieces having an area of 1 cm ² or less and a thickness of 1 mm or less as raw materials.

Comparative Example 1

About 10 g of the polymer raw material prepared according to raw material 1 was quantified as a raw material for the reaction. About 38.75 g of ethylene glycol, a dihydric alcohol polar solvent, (12 moles per mole of polymer repeating unit) was added to a 3-neck flask, equipped with a reflux condenser at atmospheric pressure, and stirred using a heated magnetic stirrer. The temperature reached 177°C. When 10 g of the polymer raw material was added, the temperature was continuously increased and the mixture was stirred simultaneously. When the reaction mixture reached 197 °C or reflux temperature, about 0.457 g of zinc acetate catalyst (0.04 mol per mole of polymer repeating unit) was added to initiate the catalytic reaction, and stirring was continued for 2 hours, but the reaction temperature was within the range of ±0.5 °C. The reaction was carried out using a condenser with one end exposed to atmospheric pressure while maintaining it constant. After the reaction, unreacted substances in the product were separated and quantified through filtration, and the decomposed monomers, dimers, side reactants such as mono(hydroxyethyl) terephthalate (MHET) and oligomers were calibrated as standard samples by high-performance liquid chromatography (HPLC, reversed-phase C18). The concentration was quantified using a column (250 mm, 5 micron), UV detector (λ=254 nm). As a mobile phase for HPLC analysis, a mixed solution having a volume ratio of methanol:water of 70:30 was used while maintaining a constant flow rate of 0.7 ml/min.

Comparative Example 2

Glycolysis depolymerization was carried out and evaluated in the same manner as in Comparative Example 1, except that about 0.204 g (0.04 mol per mole of polymer repeating unit) was used as a catalyst, potassium acetate (CH ₃ COOK).

Comparative Example 3

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 1, except that about 0.171 g (0.04 mol per mole of polymer repeating unit) was used as a catalyst for sodium acetate (CH ₃ COONa).

Comparative Example 4

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 1, except that the reaction temperature was maintained at 153°C.

Comparative Example 5

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 2, except that the reaction temperature was maintained at 153°C.

Comparative Example 6

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 3, except that the reaction temperature was maintained at 153°C.

Example 1

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 4, except that about 22.51 g (4 moles per mole of the polymer repeating unit) of methoxybenzene was additionally added.

Example 2

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 5, except that about 22.51 g of methoxybenzene (4 moles per mole of polymer repeating unit) was additionally added.

Example 3

Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 6, except that about 22.51 g (4 moles per mole of polymer repeating unit) of methoxybenzene was additionally added.

Example 4

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 3, except that Raw Material 2 was used as the polymer raw material.

Example 5

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 3, except that raw material 3 was used as a polymer raw material.

Example 6

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 3, except that Raw Material 4 was used as the polymer raw material.

Example 7

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 3 except that the reaction temperature was maintained at 130° C., but the experiment was repeated so that the reaction proceeded for a total of 3 or 6 hours, and the resulting reactants were Each was quantified.

Example 8

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 7, except that the reaction temperature was maintained at 135°C.

Example 9

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 7, except that the reaction temperature was maintained at 140°C.

Example 10

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 7, except that the reaction temperature was maintained at 145°C.

Example 11

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 7, except that the reaction temperature was maintained at 150°C.

Example 12

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 2, except that the repeated experiment was performed by changing the additional amount of methoxybenzene from 0 g to 39.4 g (7 moles per mole of polymer repeating unit). .

Example 13

Glycolysis depolymerization was performed and evaluated in the same manner as in Example 3, except that the repeated experiment was performed by changing the additional amount of methoxybenzene from 0 g to 39.4 g (7 moles per mole of polymer repeating unit). .

Example 14

Glycolysis depolymerization was carried out in the same manner as in Example 2, except that a repeated experiment was performed by changing the input amount of potassium acetate (CH ₃ COOK) as a catalyst from 0 g to 1.0 g (0.20 mol per mole of polymer repeating unit). was carried out and evaluated.

Example 15

Glycolysis depolymerization was carried out in the same manner as in Example 3, except that repeated experiments were performed by changing the amount of sodium acetate (CH ₃ COONa) as a catalyst from 0 g to 1.0 g (0.23 mol per mole of polymer repeating unit). was carried out and evaluated.

Example 16

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 2, except that about 28.75 g of 1,2-dimethoxybenzene (4 moles per mole of polymer repeating unit) was added instead of methoxybenzene.

Example 17

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 2, except that about 28.75 g of 1,4-dimethoxybenzene (4 moles per mole of polymer repeating unit) was added instead of methoxybenzene.

Example 18

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 2, except that about 35.00 g of 1,3,5-trimethoxybenzene (4 moles per mole of polymer repeating unit) was added instead of methoxybenzene. .

Example 19

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 2, except that about 25.43 g of phenetol (ethyl phenyl ether) (4 moles per mole of polymer repeating unit) was added instead of methoxybenzene.

Example 20

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 2, except that about 25.84 g of guaiacol (2-methoxyphenol) (4 moles per mole of polymer repeating unit) was added instead of methoxybenzene. .

Comparative Example 7

Glycolysis depolymerization was performed and evaluated in the same manner as in Example 2, except that about 23.76 g of 1-methoxycyclohexane (4 moles per mole of polymer repeating unit) was added instead of methoxybenzene.

Example 21

About 0.110 g of sodium carbonate (Na ₂ CO ₃ ) as a catalyst (0.02 mol per mole of repeating polymer), about 32.30 g of ethylene glycol (10 moles per mole of repeating polymer), and about 16.88 g of methoxybenzene (repeat polymer) Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 1, except that 3 moles per mole) was used.

Example 22

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 21, except that about 0.144 g (0.02 mol per mole of polymer repeating unit) was used as a catalyst for potassium carbonate (K ₂ CO ₃ ).

Example 23

Depolymerization of glycolysis was carried out and evaluated in the same manner as in Example 21, except that about 0.087 g (0.02 mol per mole of polymer repeating unit) was used as a catalyst for sodium bicarbonate (NaHCO ₃ ).

Example 24

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 21, except that about 0.104 g (0.02 mol per mole of polymer repeating unit) was used as a catalyst for potassium carbonate (KHCO ₃ ).

Example 25

Glycolysis depolymerization was performed and evaluated in the same manner as in Example 21, except that about 0.088 g (0.02 mol per mole of polymer repeating unit) was used as a catalyst for magnesium carbonate (MgCO ₃ ).

Example 26

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 21, except that about 0.073 g (0.02 mol per mole of polymer repeating unit) was used as a catalyst, potassium methoxy potassium (CH ₃ OK).

Example 27

In the same manner as in Example 21, except that about 0.145 g (0.02 moles per mole of polymer repeating unit) was used as a catalyst, triazabicyclodecene (1.5,7-triazabicyclo[4.4.0]dec-5-ene, TBD) was used. Glycolysis depolymerization was carried out and evaluated.

[Calculation formula]

The unreacted substances obtained according to Comparative Examples 1 to 7 and Examples 1 to 27 were quantified by the gravimetric method, and the reactants were quantified through HPLC analysis, and the conversion and product yield were calculated by the following formulas.

Polymer depolymerization conversion by depolymerization (%) =

(Initial input high molecular weight - unreacted high molecular weight) / (Initial input high molecular weight) × 100

Yield of monomer obtained by depolymerization (%) =

(No. of moles of BHET obtained)/(No. of moles of terephthalate units in the input polymer structure) × 100

Yield of dimer obtained by depolymerization (%) =

(No. of moles of dimer obtained)/(No. of moles of terephthalate unit in the input polymer structure) × 100

Yield (%) of by-product (MHET) obtained by depolymerization =

(No. of moles of MHET obtained)/(No. of moles of terephthalate units in the input polymer structure) × 100

Comparative Example 8

About 5 g of the polymer raw material prepared according to Raw Material 1, about 0.5 g of zinc acetate as a catalyst (0.088 mol per mole of polymer repeating unit), and about 20 g of ethylene glycol (12.4 mol per mole of polymer repeating unit) were used. Glycolysis depolymerization was carried out and evaluated by the same method as in Example 1. In order to purify the glycol addition monomer obtained through this, after the reaction was completed, the product and 400 mL distilled water were mixed in a 500 mL round flask, and then stirred continuously for about 1 hour within a range of 90 to 95°C. After the reaction, oligomers in the mixture were removed through filter paper (Whatman, pore diameter: 3 micron) placed in a filter by a vacuum pump. The filtrate obtained primarily was filtered again through the same filter to separate and remove recrystallized oligomers and solids. The obtained filtrate was crystallized through storage for at least 16 hours in a low-temperature bath maintained at 4°C or less, and after collecting the precipitate through a vacuum filter, the obtained white powder was dried in an oven maintained at about 80°C for 6 hours. It was quantified with glycol addition monomers.

In order to check the residual content of metals in the purified monomer, about 0.1 g of the purified monomer was dissolved in HNO ₃ and pretreated by acid treatment, and then inductively coupled plasma-atomic emission spectrometry (ICP-AES, model name: Thermo Fisher Scientific iCAP 6500Duo) and It was measured using inductively coupled plasma-mass spectrometry (ICP-MS, model name: Thermo Fisher Scientific X Series), and the measurement results are shown in Table 8.

In order to confirm the structural characteristics of the purified monomer, about 0.1 g of the purified monomer was prepared by diluting it in DMSO ^- d6 solvent ^. The obtained NMR spectrum is shown in FIG. 1 .

Comparative Example 9

An additional purification method was performed in order to reduce the metal residual amount in the glycol addition monomer obtained according to Comparative Example 8. After adding about 100 mL of distilled water in a 250 mL flask, the white powder finally obtained through the process of Comparative Example 8 was stirred for about 1 hour using a magnetic stirrer, and after completion, the same vacuum used in the process of Comparative Example 8 A filter was used to recover the further washed precipitate. The above washing process was repeated until the metal content of the recovered monomer was not detected by ICP-MS, and the finally obtained precipitate was dried in an oven maintained at about 80° C. for 6 hours, corresponding to the glycol addition monomer. A white powder was obtained. Again, as in Comparative Example 8, the structural characteristics of the monomer were analyzed through ¹ H-NMR, which is shown in FIG. 2 .

Example 28

About 5 g of the polymer raw material prepared according to Raw Material 1, about 0.5 g of potassium acetate (CH ₃ COOK) as a catalyst (0.196 mol per mole of polymer repeating unit), and about 20 g of ethylene glycol (12.4 mol per mole of polymer repeating unit), Glycolysis depolymerization was performed and evaluated in the same manner as in Comparative Example 1, except that about 10 g of methoxybenzene (3.56 moles per mole of polymer repeating unit) was used. A glycol addition monomer was obtained through the same process as in Comparative Example 8, except that in purifying the glycol addition monomer obtained through the process of recovering the additive, a drying process to remove moisture without performing an additional purification process The white powder obtained from was quantified as a glycol addition monomer product. According to the same analysis method as in Comparative Example 8, the structural characteristics of the monomer were analyzed through the residual content of metal and ¹ H-NMR, and the results are shown in FIG. 3 .

Example 29

Glycolysis depolymerization was carried out and evaluated in the same manner as in Example 28, except that about 0.5 g (0.234 mol per mole of polymer repeating unit) was added instead of potassium acetate as a catalyst for sodium acetate (CH ₃ COONa).

[Comparison of Reaction Characteristics of Depolymerization Using Metal Salt as Catalyst]

division used
catalytic
type Polymer (PET) repeating unit
moles of compound added per mole Conversion rate (%) transference number(%) EG additive catalyst BHET Dimer MHET Comparative Example 1 Zn(OAc) ₂ 12 0 0.04 100.0 90.06 4.69 0.37 Comparative Example 2 KOAc 12 0 0.04 100.0 83.52 4.06 2.36 Comparative Example 3 NaOAc 12 0 0.04 100.0 84.46 4.29 3.92 EG: ethylene glycol, BHET: bis(2-hydroxyethyl) terephthalate,
Dimer: dimer of BHET, MHET: mono(hydroxyethyl) terephthalate,
Zn(OAc) ₂ : zinc acetate, NaOAc : sodium acetate, KOAc : potassium acetate

Referring to Table 1, in order to compare and explain the effects of Examples of the present invention, the depolymerization performance of polyethylene terephthalate by adding a zinc acetate catalyst most commonly used in the glycolysis reaction was previously described in Comparative Example 1. The reaction was carried out according to the method. In addition, the depolymerization reactions performed by adding the same amount of moles added in Comparative Example 1 by selecting catalysts that can be modified and combined according to an example of the present invention as alkali acetate salts are shown in Comparative Examples 2 and 3. An experiment was conducted under the same conditions to compare and discriminate the depolymerization reaction performance with Comparative Example 1, and Table 1 shows the comparison results obtained by quantitative analysis of each reaction product after 2 hours of reaction. In both reactions, ethylene glycol was used for the addition reaction, and the reaction was performed at a reflux temperature (197° C.).

As previously reported in a number of patents and non-patent literature, when zinc acetate was applied as a catalyst (Comparative Example 1), all polyethylene terephthalate was converted in only two hours reaction, and BHET was obtained in a high yield of up to 90%. On the other hand, high reactivity was observed in the depolymerization of polyethylene terephthalate, which was carried out under the same reaction conditions but using an acetate salt having an alkali cation as potassium instead as a catalyst, but low selectivity of the monomer BHET was observed. The relatively low yield of BHET may affect productivity, and may cause various economic and environmental problems, such as the burden of the purification process for separating low-value by-products, and treatment of by-products.

[PET Glycolysis under Low Temperature Conditions]

When a glycolysis reaction route is selected to perform depolymerization of a polymer containing an ester functional group, as shown in the depolymerization reaction conditions of Comparative Examples 1 to 3 above, as an addition reactant of the exchange esterification reaction It is common to carry out the reaction at the boiling point of ethylene glycol (197° C.) or higher. Even if an excessive amount of catalyst is used or a very dilute concentration of a polymer raw material is applied to the reaction, if the reaction temperature is lowered, the reactivity becomes very low or the rate of side reaction is relatively increased because the reaction does not have sufficient activation energy to secure the desired product. Can not. On the other hand, in the case of a manufacturing process requiring a high reaction temperature, a method of applying fuel or a utility for supplying a heat source for the reaction may be limited, and an investment in equipment and excessive cost may be required for process operation. Therefore, the design of the low-temperature glycolysis depolymerization reaction capable of providing high reactivity and high yield can provide a decisive means for securing the economic feasibility of the process.

Most of the prior literatures that have performed depolymerization of polymers containing ester functional groups along the glycolysis reaction route suggest reaction conditions corresponding to high temperatures of ethylene glycol (197° C.) or higher, and are simply single or specific components. It is known that it is very difficult to lower the reaction activation energy even if a catalyst composed of only a catalyst or a composite material applied by mixing the same is added. In particular, practical examples of a reaction system capable of significantly lowering the reaction temperature while maintaining equivalent performance have not been reported.

In the present invention, as a means to overcome this, a compound having at least one oxygen among the bonding functional groups between the aromatic ring and the alkyl group is added as an additive to significantly lower the activation energy of the catalytic reaction, and from this, the temperature is higher than that of the general glycolysis reaction. An attempt is made to suggest a new reaction route through which depolymerization of a polymer containing an ester functional group can proceed in a low-temperature region lowered by 40°C or higher. From this, since decomposition can occur at high temperatures, organic compounds that are difficult to maintain performance or recovery can be difficult, or metal salts composed of cations of Group 1A or 2A metals, which are low in harmfulness to the human body, can be applied as catalysts. We would like to present an implementation method for the colic reaction.

In order to specifically explain the effect on the low-temperature glycolysis reaction according to the present invention, Table 2 shows the results of the glycolysis reaction carried out at low temperature (153° C.) with the same composition as in the previous comparative example. In order to explain the characteristics of the low-temperature glycolysis reaction according to the present invention, the reaction results for each catalyst system in which all conditions were identical except for the presence or absence of additives were divided into Comparative Examples and Examples. In Comparative Example 4, a depolymerization reaction was performed using zinc acetate as a catalyst, in Comparative Examples 5 and 6, a depolymerization reaction was performed using potassium acetate and sodium acetate as catalysts, and in Example 1, a zinc acetate catalyst was used. However, the depolymerization reaction was performed by adding methoxy benzene (anisole), a compound corresponding to Chemical Formula 1, as an additive. Examples 2 and 3 were tested in the same manner as in Example 1, except that potassium acetate or sodium acetate was used as a catalyst, respectively.

Methoxy benzene used as the additive is extracted as a natural product, but it can also be industrially synthesized in large quantities, so it is used as a raw material or precursor for perfume or perfume production, and has very low toxicity compared to other aromatic compounds.

The polyethylene terephthalate bottle-derived raw material used in Comparative Examples and Examples has an amorphous structure and a raw material having a large unit area with a thickness of 0.3 mm or less is input to the reaction, so from the initial stage of depolymerization, additives, catalysts and reactants A high effective contact area can be maintained. On the other hand, raw materials for depolymerization having different geometries, such as polymer polymerization degree, properties, and material thickness, may affect mass transfer and reaction rate changes, and may have a significant impact on the yield and performance of the final depolymerization target product. Examples 4, 5 and 6 are polymers of waste resin prepared with an area of 1 cm ² or less by pulverizing a multi-layered PET bottle, PET colored label paper, and polyester fiber among waste plastics that can be discharged from daily life. After quantification as a raw material, depolymerization was carried out for each, and depolymerization was performed under the same method and reaction conditions as in Example 3 using raw material 1.

division used
catalytic
type polymer
Raw material Polymer (PET) repeating unit
moles of compound added per mole conversion rate
(%) transference number
(%) EG additive catalyst BHET Dimer MHET Comparative Example 4 Zn(OAc) ₂ Raw material 1 12 0 0.04 9.41 3.53 0.06 0.11 Comparative Example 5 KOAc Raw material 1 12 0 0.04 13.92 6.06 0.00 1.19 Comparative Example 6 NaOAc Raw material 1 12 0 0.04 14.06 5.18 0.00 1.37 Example 1 Zn(OAc) ₂ Raw material 1 12 4 0.04 100.0 82.47 4.60 1.19 Example 2 KOAc Raw material 1 12 4 0.04 100.0 86.50 4.89 1.77 Example 3 NaOAc Raw material 1 12 4 0.04 100.0 86.91 4.98 1.82 Example 4 NaOAc Raw material 2 12 4 0.04 99.53 82.50 4.43 1.78 Example 5 NaOAc Raw material 3 12 4 0.04 100.0 77.63 1.87 2.01 Example 6 NaOAc Raw material 4 12 4 0.04 100.0 88.33 5.26 1.03 EG: ethylene glycol, BHET: bis(2-hydroxyethyl) terephthalate,
Dimer: dimer of BHET, MHET: mono(hydroxyethyl) terephthalate,
Zn(OAc) ₂ : zinc acetate, NaOAc : sodium acetate, KOAc : potassium acetate

Referring to Table 2, which is a performance comparison result of low-temperature PET glycolysis, as shown in Table 1 above, in Comparative Example 1, in which zinc acetate was applied as a catalyst and a high temperature of 197° C. was applied, most of PET was decomposed, but the same According to the result of Comparative Example 4 in which depolymerization was performed at low temperature (153° C.) with the composition of the reaction mixture, the conversion rate was less than 10%, and the reactivity was extremely poor. In addition, a relatively high ratio of by-products compared to the desired product was obtained.

In Comparative Example 5 and Comparative Example 6, the reaction was carried out in a similar manner using a metal salt containing an alkali metal cation instead of zinc acetate, more specifically, potassium acetate and sodium acetate as catalysts. Compared with Comparative Example 4, it can be seen that the conversion rate was slightly increased, but the reactivity was not significantly improved. At the same time, the amount of by-products was greatly increased, and higher BHET selectivity was observed when zinc acetate was used (Comparative Examples 1 and 4).

The reaction result of Example 1 is that low-temperature (153° C.) glycolysis was performed using zinc acetate by adding only methoxy benzene to the composition of the reactant of Comparative Example 3. Comparing the depolymerization results according to Comparative Example 4 and Example 1, it can be seen that the addition of the additive according to the present invention has a very dramatic effect on the change in the depolymerization performance.

Although Example 1 was a low-temperature reaction with a temperature of 40° C. or higher, a BHET yield of 82.5% was obtained within 2 hours, and when the depolymerization reaction time was continued for 3 hours or more, a BHET yield of 85% to 90% was obtained.

A more dramatic effect was observed when the catalyst was changed to an alkaline acetic acid catalyst. For example, the results of the glycolysis reaction (Examples 2 and 3) conducted at low temperature (153° C.) in the presence of additives with potassium acetate and sodium acetate as catalysts were compared with the high-temperature reaction (Comparative Example 2 and Comparative Example). 3) and low-temperature glycolysis without additives (Comparative Examples 5 and 6).

In the case of Example 2, in which low-temperature glycolysis was performed by adding only methoxy benzene to the composition of the reactant of Comparative Example 5, it can be seen that, similar to the catalyst system described above, very dramatic depolymerization reaction characteristics are outstanding. When depolymerization was performed by adding methoxy benzene to a reaction system to which a catalyst containing alkali metal was applied, high reactivity was observed in which all raw PET materials were completely decomposed within 2 hours despite keeping the reaction temperature as low as 153 ° C. It can be seen that the selectivity of BHET is also greatly improved. Methoxy benzene for catalyst systems containing other modified types of catalysts effective for high-temperature glycolysis at 197°C, such as other salt type catalysts containing alkali metals or non-metal organic type catalysts such as guanidine type catalysts. A dramatic reaction effect was observed in the low-temperature glycolysis reaction below 153° C. performed with the addition of addition, and similar or improved performance was also observed.

On the other hand, when comparing the depolymerization reaction results of Examples 4 to 6 in which polymer raw materials with different properties were used under the same conditions, the intrinsic viscosity (IV ~ 0.65) is low, so the restriction of mass transfer during the depolymerization process is low. It was found that in Example 6 using the expected polyester fiber as a raw material, BHET in a higher yield was obtained compared to other cases in which PET flake was used as a raw material (IV=0.74). In the case of Example 4 using a multi-layered piece of PET as a raw material, the BHET yield was observed to be rather low at 82.5% with only 2 hours of reaction.

On the other hand, in the case of Example 5, in which a thin colored PET film, which is not expected to be significantly affected by mass transfer, was used as a raw material, high initial reactivity was observed, but the yield was observed as low as 80% or less. In this case, the yield did not improve even when left in the reaction conditions for a long time, and it can be expected that the low BHET yield is due to the content of impurities such as pigments.

[Temperature Range of Low-Temperature Depolymerization Reaction]

In the following embodiments, the composition of the reactants effective for the low-temperature glycolysis reaction is maintained, and from this, the reaction or depolymerization performance at a low temperature is to be described in an effective range. Therefore, the following examples include specific examples in which the reaction conditions other than temperature are kept the same in order to determine the qualitative and quantitative reaction characteristics of the depolymerization reaction, but the temperature is changed to observe the depolymerization performance.

Depolymerization reaction including the experimental results to have the same reactant composition as in Example 3, but at different reaction temperatures (catalyst: sodium acetate (NaOAc), compound usage per mole of polymer repeating unit: catalyst 0.04 moles, anisole 4 moles) , EG 12 mol) were summarized in Table 3.

division reaction temperature
(℃) reaction time
(h) conversion rate
(%) transference number(%) BHET Dimer MHET Example 7 130 3 17.50 9.70 0.06 0.60 6 33.68 23.79 0.35 1.36 Example 8 135 3 25.10 20.96 0.38 0.88 6 53.03 43.04 1.32 1.81 Example 9 140 3 50.82 42.18 1.33 1.35 6 91.85 72.22 3.71 2.19 Example 10 145 3 75.44 63.50 3.08 1.64 6 99.72 79.51 4.46 2.59 Example 11 150 3 100.0 84.10 4.84 2.10 6 100.0 84.10 4.83 3.23 BHET: bis(2-hydroxyethyl) terephthalate, Dimer: dimer of BHET,
MHET: mono(hydroxyethyl) terephthalate, NaOAc: sodium acetate
NaOAc: sodium acetate,

As can be seen in the case of adding methoxy benzene to follow an example of the composition of the reactant according to the present invention (Table 3), as a result of low-temperature glycolysis using PET as a raw material, a clear and effective reaction characteristic at 130 ° C. or higher was expressed, and a very dramatic effect with a conversion rate close to 100% was observed when exposed to a reaction for a long time (6 hours) at 145° C. or higher.

On the other hand, Example 3, in which depolymerization was performed at a temperature of 153 ° C., showed high reactivity, but when the reaction was performed at a low temperature, rather low selectivity for the desired product was observed, which indicates that the already produced desired product was This is because the yield of MHET continues to increase by the side reaction pathway when continuously exposed to the reaction temperature. Therefore, it may be desirable to improve the production yield of the final target product by optimizing not only the temperature but also the reaction time in order to completely decompose the mass of the polymer and prevent the side reaction rate from proceeding.

[Performance evaluation of depolymerization reaction according to the amount of additives]

In the following embodiments, the composition and reaction conditions of the reactants effective for the low-temperature glycolysis reaction are maintained, but it is intended to explain the effective range in which the additive effect is expressed. The following examples include specific examples in which the depolymerization performance is observed by changing the amount of additives while maintaining the same reaction conditions in order to determine the characteristics of the depolymerization reaction.

The depolymerization reaction ( Reaction temperature: 153° C., reaction time: 2 hours, additive: anisole) was observed and the results are summarized in Table 4.

used
catalytic
type division Polymer (PET) repeating unit
moles of compound added per mole conversion rate
(%) transference number(%) EG additive catalyst BHET Dimer MHET KOAc Comparative Example 5 12 0 0.04 13.92 6.06 0.00 1.19 Example 12 12 One 0.04 32.05 24.06 0.35 2.06 12 2 0.04 91.47 76.83 3.70 2.18 12 3 0.04 99.72 83.65 4.56 1.85 12 4 0.04 100.0 86.50 4.89 1.77 12 5 0.04 100.0 85.22 4.81 1.69 12 7 0.04 100.0 83.19 5.39 1.69 NaOAc Comparative Example 6 12 0 0.04 14.07 5.19 0.00 1.37 Example 13 12 One 0.04 33.44 26.30 0.41 1.05 12 2 0.04 75.49 63.85 2.50 1.20 12 3 0.04 99.73 84.30 4.39 1.11 12 4 0.04 100.0 86.91 4.98 1.82 12 5 0.04 100.0 85.96 4.58 0.92 12 7 0.04 100.0 82.55 4.68 0.85 EG: ethylene glycol, BHET: bis(2-hydroxyethyl) terephthalate,
Dimer: dimer of BHET, MHET: mono(hydroxyethyl) terephthalate,
NaOAc: sodium acetate, KOAc: potassium acetate

In Comparative Examples 5 and 6 using a metal salt containing an alkali metal cation as a catalyst, but not adding an additive corresponding to Chemical Formula 1 according to the present invention, very poor glycolysis reaction performance was observed, but the additive (me Looking at the results of Examples 12 and 13 in which even a small amount of toxybenzene) was added, it can be seen that not only the increase in reactivity but also the selectivity of BHET produced according to the glycolysis reaction of PET was greatly improved. In particular, it can be seen that when the amount of the additive added to the applied polymer raw material is increased to more than 3 molar ratio, almost all of the polymer is decomposed only after two hours of reaction, and a high value is maintained in the selectivity of the target product.

On the other hand, when the temperature of the additive used is lowered to 100° C. or less, phase separation occurs from the excess ethylene glycol used as a reactant, and even if excess water is added to purify the target product, only a very limited concentration of the additive is the purpose Since the product remains in the dissolved aqueous solution, it can be easily recovered. Therefore, the additive can be easily separated by liquid-liquid extraction, but rather, at the end of the reaction, the reaction temperature is raised to the boiling point of the additive, and then some or all of the additive condensed through the condenser is separated into an external flow. The separation method may be more advantageous in terms of efficiency. Although the additive according to the present invention is a compound that does not directly participate in the reaction, it has a characteristic similar to that of the catalyst because it has a distinct effect of lowering the activation energy of the reaction, but does not directly improve the reactivity in the absence of metal salts or other catalysts. Therefore, it can be seen that the characteristics such as a cocatalyst are expressed.

[Performance evaluation of depolymerization reaction according to the amount of catalyst]

In the following embodiments, while maintaining the composition and reaction conditions of the reactants effective for the low-temperature glycolysis reaction, it is intended to explain the effect of controlling the amount of catalyst added. In the following example, the reaction conditions are kept the same (reaction temperature: 153°C, reaction time: 2 hours, additive: anisole) in order to determine the characteristics of the depolymerization reaction, but the depolymerization performance is observed by changing the amount of catalyst added. Includes specific examples of implementation.

division used
catalytic
type Polymer (PET) repeating unit
moles of compound added per mole Conversion rate (%) transference number(%) EG additive catalyst BHET Dimer MHET Example 14 KOAc 12 4 0.00 3.53 0.01 0.00 0.00 12 4 0.01 27.21 20.51 0.45 0.17 12 4 0.02 81.00 67.49 3.06 0.36 12 4 0.03 95.68 80.32 4.26 0.51 12 4 0.04 100.0 86.50 4.89 1.06 12 4 0.05 100.0 84.68 4.50 1.07 12 4 0.06 100.0 82.91 4.38 1.28 12 4 0.08 100.0 83.73 4.63 1.98 12 4 0.10 100.0 80.89 4.24 2.55 12 4 0.20 100.0 80.12 4.32 3.16 Example 15 NaOAc 12 4 0.00 3.53 0.01 0.00 0.00 12 4 0.01 24.24 17.67 0.44 0.31 12 4 0.02 92.52 74.97 3.60 0.41 12 4 0.03 99.85 83.93 4.40 0.65 12 4 0.04 100.0 85.58 4.54 1.03 12 4 0.05 100.0 86.13 4.58 1.24 12 4 0.06 100.0 83.48 4.62 2.68 12 4 0.08 100.0 84.16 4.63 2.94 12 4 0.10 100.0 82.38 4.53 4.62 12 4 0.23 100.0 80.39 4.37 4.89 EG: ethylene glycol, BHET: bis(2-hydroxyethyl) terephthalate,
Dimer: dimer of BHET, MHET: mono(hydroxyethyl) terephthalate,
NaOAc: sodium acetate, KOAc: potassium acetate

Table 5 shows the results of depolymerization in order to observe the effect of the reaction by controlling the amount of the metal salt containing the alkali metal cation used as a catalyst in carrying out the PET glycolysis reaction. When the amount of the catalyst added in a trace amount of 0.01 mole or less compared to the repeating unit of the polymer raw material, the reactivity was observed to be significantly lowered, but the selectivity of the target product, BHET, was observed to be higher. This is considered to be because the increase in the addition amount of the catalyst has a greater effect on the increase of the side reaction rate.

On the other hand, when the amount of catalyst was added in excess of 0.01 mol relative to the repeating unit of the polymer raw material, most of the applied PET was decomposed due to high reactivity, and when it was added in excess of 0.03, complete decomposition occurred. In the ratio range where the amount of catalyst exceeds 0.03 for complete decomposition, but less than 0.10 mole, a slight change in selectivity or yield for the target product (BHET) was observed depending on the amount of catalyst, but the catalyst was used in excess of 0.10 mole or more When the yield of by-products increased, it was confirmed that the yield of BHET was somewhat lowered. It is possible to maintain and control the reaction performance according to the input amount of the catalyst in a relatively wide range, and even when reusing some catalysts after the completion of the reaction, it is necessary to replenish only the part of the catalyst that is considered lost without determining the exact amount. Flexibility can also be expected to be secured.

[Performance evaluation of depolymerization reaction according to the type of additive]

In the following embodiments, while maintaining the composition and reaction conditions of the reactants effective for the low-temperature glycolysis reaction, it is intended to explain the effect of the reaction when some or all of the additives according to the present invention are modified. In order to determine the characteristics of the depolymerization reaction, the reaction conditions are maintained the same (reaction temperature 153° C., reaction time 2 hours, catalyst: KOAc), but when using a compound containing oxygen among the bonding functional groups between the aromatic ring and the alkyl group Specific examples of observing the depolymerization performance by varying the number of functional group bonds or adding a modified form of the additive are included.

division used
of additives
type Polymer (PET) repeating unit
moles of compound added per mole Conversion rate (%) transference number(%) EG additive catalyst BHET Dimer MHET Comparative Example 5 - 12 0 0.04 13.92 6.06 0.00 1.19 Example 2 Anisole 12 4 0.04 100.00 86.50 4.89 1.77 Example 16 1,2-DMB 12 4 0.04 69.76 58.38 2.19 1.43 Example 17 1,4-DMB 12 4 0.04 70.18 57.35 2.62 1.56 Example 18 1,3,5-TMB 12 4 0.04 96.09 65.13 3.58 1.53 Example 19 phenetole 12 4 0.04 41.63 36.57 0.69 2.46 Example 20 Guaiacol 12 4 0.04 62.68 57.33 2.20 1.42 Comparative Example 7 1-MCH 12 4 0.04 6.87 4.63 0.00 0.68 Anisole: methoxy benzene, 1,2- or 1,4-DMB: 1,2- or 1,4-dimethoxybenzene, 1,3,5-TMB: 1,3,5-trimethoxybenzene, Guaiacol: 2-methoxyphenol,
Phenetole: ethoxy benezene, 1-MCH: 1-methoxycyclohexane,
BHET: bis(2-hydroxyethyl) terephthalate, Dimer: dimer of BHET,
MHET: mono(hydroxyethyl) terephthalate, KOAc: potassium acetate

Results of Comparative Example 5, in which PET glycolysis was performed without adding an additive, and Example 2 and Examples 16 to 20, in which a compound containing at least one oxygen among the bonding functional groups between the aromatic ring and the alkyl group was added By comparing the results, it can be seen that although there is some difference in performance, the effect of adding the additive according to the present invention is remarkably observed. According to the performance results of depolymerization according to Examples 16 to 18, which represent examples of modified additives, it was observed that when m in Formula 1 is increased to 2 or more, the reactivity and selectivity of the target product are somewhat lowered. Examples 19 and 20 are examples according to depolymerization carried out by adding a modified additive to which the number of carbon atoms of the alkyl group bonded by oxygen is not one or to which a functional group other than the alkyl functional group can be further bonded. According to the depolymerization results of Examples 18 and 19, some deviations were observed in the reactivity and the yield of BHET, but it was found that the effect according to the present invention was similarly observed. Comparative Example 7 has a structure similar to that of the additive according to the present invention, but the central functional group of the compound is in a different form (at least one alkyl group is connected through a linker, and the linker has at least one oxygen but has a central functional group The depolymerization performance was evaluated by substituting an additive for a saturated cycloalkane-based functional group having the same number of carbon atoms instead of an aromatic ring. Reactivity and BHET selectivity were observed to be lower than those of Comparative Example 5 in which no additive was added.

In a specific embodiment of the present invention, the additive to be added was evaluated based on the same number of moles, but if the form of the binding functional group is changed, the interaction with the raw material and the additive may appear differently, and the performance by adjusting the form or amount of the additive added to the reactant You can even compensate for this inadequacy.

[Evaluation of depolymerization reaction performance of catalysts containing alkali metals or alkaline earth metals]

In the following embodiments, the composition and reaction conditions of the reactants effective for the low-temperature glycolysis reaction are maintained (reaction temperature 153° C., reaction time 2 hours), but the type of catalyst according to the present invention is partially or entirely modified and used. This is to explain the effect of the reaction when In order to determine the characteristics of the depolymerization reaction, the reaction conditions are kept the same, and a metal salt containing an alkali metal or alkaline earth metal cation is used as a catalyst as a catalyst, but the counter ion is transformed into another form such as carbonic acid, bicarbonate, alkoxide, or the metal is Specific examples of observing the change in depolymerization performance according to the application of an organic compound catalyst not included are included.

division used
catalytic
type Polymer (PET) repeating unit
moles of compound added per mole Conversion rate (%) transference number(%) EG additive catalyst BHET Dimer MHET Example 21 Na ₂ CO ₃ 10 3 0.02 90.58 74.78 4.27 2.38 Example 22 K ₂ CO ₃ 10 3 0.02 90.74 74.86 4.23 2.24 Example 23 NaHCO ₃ 10 3 0.02 40.41 33.98 1.04 1.66 Example 24 KHCO ₃ 10 3 0.02 37.21 30.87 0.78 1.36 Example 25 MgCO ₃ 10 3 0.02 64.47 53.86 2.54 0.55 Example 26 CH ₃ OK 10 3 0.02 49.01 41.48 1.43 1.40 Example 27 TBD 10 3 0.02 99.00 81.81 5.28 2.18 BHET: bis(2-hydroxyethyl) terephthalate, Dimer: dimer of BHET,
MHET: mono(hydroxyethyl) terephthalate, TBD: 1,5,7-triazabicyclodec-5-ene

The additive according to the present invention was added, but the amount of all the compounds added compared to the polymer was limited, so that the difference in performance for each catalyst was conspicuously evaluated in the kinetic limited regime. Table 7 shows the results of depolymerization at a low temperature (153° C.) with different catalysts. When various modified catalysts or organic compound catalysts in which alkali metal exists as a cation and a different counterion form are used, but the reaction is carried out at a low temperature below the boiling point of ethylene glycol without adding the additive according to the present invention, additives according to a similar method Like the performance results of Comparative Examples 4 to 6 in which the reaction was performed without adding , mostly poor reactivity and very limited BHET yield were observed.

In the case of Examples 21 and 22, in which a metal salt catalyst composed of a cation as a Group 1A metal and an anion as a carbonate ion was used, high reactivity and high monomer yield were observed similarly to the case where a catalyst composed of an anion was applied. . On the other hand, relatively low reaction performance was observed in Examples 23 and 24 having the same number of moles of bicarbonate as an anion. In the case of the glycolysis reaction carried out by replacing the metal carbonate catalyst composed of a Group 2A metal cation under the same conditions (Example 25), higher reactivity and higher monomer yield than the alkali metal salt catalyst having a bicarbonate as an anion was observed. On the other hand, when the same conditions are applied and triazabicyclodecene, an organic compound catalyst containing no metal, is applied as a catalyst with the same number of moles, the conversion rate of the reaction is 99.0% or more, and the yield of BHET is 81.8% or more. A reaction was observed.

As can be seen from the results of the depolymerization reaction using the exchange esterification catalyst of various modified types, when the additive (compound represented by Formula 1) according to the present invention is added, the polymer containing an ester functional group at low temperature (153° C.) It can be seen that the lycolysis reactivity can be greatly improved, and it is possible to obtain BHET in high yield below the boiling point of ethylene glycol.

[Purification and analysis of glycol addition monomers produced after depolymerization]

The following embodiments are intended to explain the characteristics of the purity of BHET obtained from the purification process after the depolymerization reaction of a polymer containing an ester functional group is performed in the method of the present invention. This process may include a separation method to recover the additive. As described in the above specific examples, when additives are added, it is possible to perform a high-performance glycolysis reaction in a low temperature region below 153°C, and it is possible to introduce a catalyst system that is difficult to use in a high temperature region above 197°C, which is a can bring advantages. For example, the scope of the catalytic reaction that exhibits optimal performance in the low-temperature region can be extended to alkali metal salts, and organic compounds that can be decomposed at high temperatures can be applied as a catalyst without loss, so that purification or material recovery can be easy. In addition, as it does not require the use of catalysts containing harmful metals such as zinc, lead and other heavy metals, which are mainly used in existing commercial processes, it is used as a recycling technology to manufacture raw materials for high-quality eco-friendly materials or to create a perfect recycling economy for waste plastics. value can be expected.

In the purification process, the molar composition of the compound presented in the present invention was maintained the same, but zinc acetate was used as a catalyst at high temperature (197° C.) (Comparative Examples 8 and 9) and an acetate salt of a Group 1A metal was used as a catalyst. Specific examples carried out to evaluate the yield and purity of glycol addition monomers obtained using (Examples 28 and 29) are included.

Analysis items
division residual metal amount
(mg/kg) Comparative Example 8 3.4 Comparative Example 9 ND Example 28 ND Example 29 ND ND: not detected

Table 8 shows ICP-MS and ICP-AES analysis methods with a detection limit of 1 ppm or more for BHET obtained through primary recrystallization after obtaining a product according to the glycolysis reaction route of PET. It is the result of analysis.

In the case of BHET, which was purified after the reaction using zinc acetate, the amount of residual metal was partially detected. Zinc used as a catalyst is classified as an important mineral for the human body, but it is classified as a toxic metal that can cause digestive disorders when a large dose or continuous exposure to the human body through the use of products such as beverage containers. Zinc remaining in plastic is discharged to nature as waste, accumulated in animals and plants, and then various side effects can occur through an indirect route where it can be absorbed again into the human body. Therefore, a low-temperature depolymerization reaction technology based on a non-toxic metal catalyst that can replace it can be advantageous in terms of commercial viability of products as well as reduction of environmental pollution.

Therefore, when a group 1A or 2A metal salt is used as a catalyst instead of a zinc metal salt, an alkali metal salt catalyst having the same number of moles as in Comparative Example 8 of Table 8 was added and prepared according to Example 28 (or Example 29) As the amount of residual metal in the final product is not detected, the metal can be efficiently separated and removed during the refining process, and the metal ion itself constituting the catalyst is an essential electrolyte in the human body and has the advantage of being less harmful than zinc. The reason for the low residual amount of Group 1A or Group 2A metal is that the catalyst is easily dissociated due to its relatively high degree of ionization during the purification process, so it remains in the BHET product recovered in the solid phase during recrystallization and physical filtration or in aqueous solution. This is because the amount of metal that does not elute is very rare.

Structural characteristics of the purified glycol-added monomer were confirmed by ¹ H-NMR, and analyzed by diluting the monomer concentration to 6.25% in DMSO- d ₆ by weight. The measured specific spectra are shown in FIGS. 1 to 3 .

¹ H-NMR of the high-temperature glycolysis-based monomer obtained by purification by the method of Comparative Example 8 is as follows.

¹ H-NMR (500 MHz, DMSO- d ₆ ) δ (ppm): 8.12 ( s , 4H), 4.99 ( br s , 2H), 4.33 ( t , 4H), 3.73 ( t , 4H)

If ethylene glycol is referred to a number of prior literatures on the NMR spectrum of the monomer of BHET obtained from the glycolysis of PET, the characteristic peak due to the hydrogen of the hydroxyl group, which is the most terminal group, is adjacent at 4.95 ppm. A peak in the form of a quartet, which is split into a triplet by a group hydrogen, and characterized by a hydrogen bonded to a carbon adjacent to a hydroxyl group ( c in FIGS. 2 to 3 ) near 3.73 ppm is generally reported in the literature. However, looking at the ¹ H-NMR spectrum of the BHET monomer obtained after simple purification according to the method of Comparative Example 8, a broad single peak was observed around 4.99 ppm, and a triplet was observed around 3.27 ppm. As shown in Table 8, it can be inferred that the zinc acetate catalyst, which is an impurity remaining in BHET, caused interference.

According to the method of Comparative Example 9, the characteristic peaks of the ¹ H NMR spectrum measured again after obtaining a monomer of BHET in which a metal is no longer detected within the detection limit in ICP by repeatedly performing the washing process using distilled water additionally are As follows.

¹ H-NMR (500 MHz, DMSO- d ₆ ) δ (ppm): 8.12 ( s , 4H), 4.97 ( t , 2H), 4.33 ( t , 4H), 3.73 ( q , 4H)

A broad single peak at around 4.99 ppm observed in the high-temperature glycolysis-based monomer obtained by purification by the method of Comparative Example 8 was separated and observed as a triplet at around 4.97 ppm, and not a triplet peak at around 3.73 ppm, but a quartet was observed as

Next, glycolysis was performed by the method of Example 28 (using potassium acetate), the product was purified, and then ¹ H- Structural analysis was performed through NMR, and the observed characteristic peaks are as follows.

¹ H-NMR (500 MHz, DMSO- d ₆ ) δ (ppm): 8.12 ( s , 4H), 4.95 ( t , 2H), 4.33 ( t , 4H), 3.73 ( q , 4H)

Almost the same ¹ H-NMR spectrum was obtained for BHET (the same procedure and method as in Example 28 applied), which was reacted and purified by the method of Example 29 (using sodium acetate) and recovered.

As the structural characteristics of the monomer with zinc metal remaining and the high-purity monomer are distinguished by these Comparative Examples and Examples, when the catalyst system prepared according to the present invention is used, the obtained BHET can be obtained with high purity even through a simple purification process. Therefore, it can be seen that efficient purification is possible and it is advantageous in terms of productivity and economy.

As described above in detail specific parts of the present invention, it will be clear to those skilled in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. . Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims (12)

In the depolymerization method of a polymer containing an ester functional group
(1) one or more polyhydric alcohols
(2) Exchange esterification reaction catalyst
(3) a compound represented by the following formula (1)
A method of depolymerizing a polymer containing an ester functional group, characterized in that the polymer containing the ester functional group is depolymerized by contacting the mixture containing the ester functional group with the polymer containing the ester functional group.

[Formula 1]
In Formula 1,
The substituent R ₁ is any one selected from hydrogen, a hydroxyl group, an aldehyde group, a carboxyl group, a C ₁ -C ₆ alkyl group, a C ₄ -C ₆ cycloalkyl group, and a C ₆ -C ₁₂ aryl group,
Wherein n is an integer from 0 to 5, and when n is 2 or more, R ₁ are the same or different,
The substituent R ₂ is a C ₁ -C ₁₀ alkyl group,
Wherein m is an integer of any one of 1 to 6, and when m is 2 or more, -OR ₂ is the same or different.
According to claim 1,
The depolymerization method of a polymer including an ester functional group, characterized in that the catalyst for the exchange esterification reaction is at least one selected from a metal-free organic compound catalyst or a metal salt of a group 1A, 2A, or 2B metal.
3. The method of claim 2,
The depolymerization method of a polymer comprising an ester functional group, wherein the metal salt is an organic anion selected from carbonic acid, bicarbonate, alkoxide, and acetate, wherein the counter-ion is an organic anion.
According to claim 1,
The polyhydric alcohol is ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexane Ester functional group, characterized in that at least one selected from diol, 1,7-octanediol, 1,9-nonanediol, neopentyl glycol, 1,4-cyclohexanediol, isosorbide and 1,4-cyclohexane dimethanol A depolymerization method of a polymer comprising a.
According to claim 1,
The compound represented by Formula 1 is methoxy benzene, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, 1,2,3-trimethoxybenzene, 1,2 ,4-trimethoxybenzene, 1,3,5-trimethoxybenzene, 1,2,3,4-tetramethoxybenzene, 1,2,3,5-tetramethoxybenzene, 1,2,4 ,5-tetramethoxybenzene, 2-methoxyphenol, 1,3-dimethoxy-2-hydroxybenzene, 4-hydroxy-3,5-dimethoxybenzoic acid, 3- (4-hydroxy- 3,5-dimethoxyphenyl) prop-2-enal, 4-hydroxy-3,5-dimethoxybenzaldehyde, 4-hydroxy-3,5-dimethoxyacetophenone, 3-(4-hydro Roxy-3,5-dimethoxyphenylprop-2-enoic acid, 4-enyl-2,6-dimethoxyphenol, 4-hydroxy-3-methoxybenzaldehyde, 3-hydroxy-4- Methoxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3,4-di Hydroxybenzaldehyde, 1-methoxy-4-[(E)-prop-1-enyl]benzene, 1-bromo-4-methoxybenzene, 2-tert-butyl-4-methoxyphenol, Ethoxybenzene, phenol, 1,3,5-trichloro-2-methoxybenzene, 1,3,5-tribromo-2-methoxybenzene, 4- (prop-2-en-1-yl ) Phenol, 1-methoxy-4 (prop-2-en-1-yl) benzene, 5- (prop-2-en-1-yl) -2H-1,3-benzodioxole, 4- Ester functional group, characterized in that at least one selected from the group consisting of methoxy-2-[(E)-prop-1-yl]phenol and 2-methoxy-4-(prop-1-en-yl)phenol A depolymerization method of a polymer comprising a.
According to claim 1,
Polymers containing an ester functional group include polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polyglycolide or polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyal Canoate (PHA), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) , polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN) and at least one selected from the group consisting of Vectran. A method of depolymerizing a polymer comprising an ester functional group.
A composition for polymer depolymerization comprising an ester functional group, comprising:
(1) one or more polyhydric alcohols;
(2) an exchange esterification reaction catalyst and
(3) a compound represented by the following formula (1)
A composition for polymer depolymerization comprising an ester functional group, characterized in that it comprises a.

[Formula 1]
In Formula 1,
The substituent R ₁ is any one selected from hydrogen, a hydroxyl group, an aldehyde group, a carboxyl group, a C ₁ -C ₆ alkyl group, a C ₄ -C ₆ cycloalkyl group, and a C ₆ -C ₁₂ aryl group,
Wherein n is an integer from 0 to 5, and when n is 2 or more, R ₁ are the same or different,
The substituent R ₂ is a C ₁ -C ₁₀ alkyl group,
Wherein m is an integer of any one of 1 to 6, and when m is 2 or more, -OR ₂ is the same or different.
8. The method of claim 7,
The catalyst for the exchange esterification reaction is a polymer depolymerization composition comprising an ester functional group, characterized in that at least one selected from a metal-free organic compound catalyst or a metal salt of Group 1A, Group 2A, and Group 2B.
8. The method of claim 7,
The amount of polyhydric alcohol contained in the composition is a ratio of 1 to 50 moles per mole of the repeating unit of the polymer to be depolymerized, and the amount of the exchange esterification reaction catalyst is the ratio of moles of 0.001 to 1 per mole of the repeating unit of the polymer to be depolymerized. A composition for polymer depolymerization comprising an ester functional group, characterized in that the amount of the compound to be used is mixed so as to have a ratio of 0.001 to 50 moles per mole of the repeating unit of the polymer to be depolymerized.
In the method for purifying a glycol addition monomer obtained by the depolymerization of a polymer containing an ester functional group according to the depolymerization method of any one of claims 1 to 6,
(1) separating the compound represented by the following formula (1) from the depolymerization reaction product by gas-liquid separation or liquid-liquid extraction;

[Formula 1]
In Formula 1,
The substituent R ₁ is any one selected from hydrogen, a hydroxyl group, an aldehyde group, a carboxyl group, a C ₁ -C ₆ alkyl group, a C ₄ -C ₆ cycloalkyl group, and a C ₆ -C ₁₂ aryl group,
Wherein n is an integer from 0 to 5, and when n is 2 or more, R ₁ are the same or different,
The substituent R ₂ is a C ₁ -C ₁₀ alkyl group,
Wherein m is an integer of any one of 1 to 6, and when m is 2 or more, -OR ₂ is the same or different.
(2) after step (1), a solid separation step of separating a solid material containing a polymer including an unreacted ester functional group;
(3) after separation of the solid in step (2), a recovery step of recrystallizing and recovering the glycol addition monomer; a method for purifying a glycol addition monomer obtained by depolymerization of a polymer containing an ester functional group, characterized in that it includes: .
11. The method of claim 10,
A method for purifying a glycol addition monomer obtained by depolymerization of a polymer containing an ester functional group, characterized in that the solid material containing the unreacted ester functional group is separated using physical filtration.
11. The method of claim 10,
A method for purifying a glycol addition monomer obtained by depolymerization of a polymer containing an ester functional group, characterized in that the step of separating the oligomer before recrystallization of the glycol addition monomer in step (3) is performed first.

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