Recycled raw material and method for preparing same

Abstract

The present invention relates to: a method for preparing a recycled raw material, which comprises a step of depolymerizing reaction raw materials comprising a main raw material and an auxiliary raw material, wherein the main raw material includes waste polyester, and the auxiliary raw material includes one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl) isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl] terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl] benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl) terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester); and a recycled raw material prepared by the method.

Description

Recycled raw material and method of manufacturing the same

[0001] The present invention relates to a method for manufacturing a recycled raw material capable of producing a high-purity recycled raw material with a high yield by reusing by-products generated in a separation and purification process as auxiliary raw materials, and to the recycled raw material obtained thereby.

[0002] Due to international environmental regulations, interest in sustainable packaging is on the rise. In line with this trend, active research is being conducted globally on manufacturing technologies for recycled raw materials (monomers) used in the production of recycled resins. Consequently, the recycling market continuously demands high-purity recycled raw materials to enhance the quality of recycled resins. Therefore, technology is required to manufacture recycled raw materials with a purity level comparable to that of virgin resins in order to achieve quality equivalent to that of virgin resins.

[0003] Examples of the above-mentioned recycled raw materials include recycled bis(2-hydroxyethyl)terephthalate (r-BHET). The above-mentioned r-BHET can be obtained by chemically depolymerizing waste polyester, and depolymerization reactions such as glycolysis, hydrolysis, methanolysis, and aminolysis are applied to the chemical depolymerization.

[0004] In order to improve the quality (purity) of the aforementioned r-BHET, various separation and purification processes are performed during the chemical depolymerization process. When these separation and purification processes are carried out, solvents used in the process and by-products are generated. At this time, while the solvent is recovered and reused, the by-products are considered impurities and discarded, acting as a limiting factor in improving the manufacturing cost of recycled raw materials.

[0005] [Prior Art Literature]

[0006] [Patent Literature]

[0007] (Patent Document 1) Republic of Korea Published Patent No. 2022-0138819

[0008]

[0009] The inventors have confirmed that in the manufacture of recycled raw materials, by reusing by-products generated during the separation and purification process as auxiliary raw materials, it is possible to achieve high purity of the recycled raw materials while improving the manufacturing cost of the recycled raw materials.

[0010] Therefore, the objective of the present invention is to provide a method for manufacturing a recycled raw material having high purity in an economical and high-yield manner, and to provide the recycled raw material manufactured through said method.

[0011] In addition, another objective of the present invention is to provide a raw material composition for depolymerization that can be efficiently used in the manufacture of the above-mentioned recycled raw material.

[0012] To solve the above problem, the present invention provides a method for manufacturing a recycled raw material comprising the step of depolymerizing a reaction raw material including a main raw material and an auxiliary raw material, wherein the main raw material comprises waste polyester, and the auxiliary raw material comprises one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

[0013] In addition, the present invention provides a recycled raw material produced from the method for producing the recycled raw material.

[0014] In addition, the present invention provides a raw material composition for depolymerization comprising an auxiliary raw material comprising one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

[0015] The method for manufacturing recycled raw materials according to the present invention can reduce the manufacturing cost of recycled raw materials and significantly reduce the amount of process waste generated at the end, because by-products inevitably generated in the polymerization process of polyester, the polymerization process of recycled polyester, and / or the depolymerization process of waste polyester are reused as auxiliary raw materials for manufacturing recycled raw materials rather than being treated as process waste.

[0016] Therefore, the present invention can provide high-purity recycled raw materials (e.g., r-BHET) with a high yield, while being more economical and environmentally friendly.

[0017] The present invention will be described in detail below. Hereinafter, the present invention is not limited to the contents described below, but can be modified in various forms as long as the essence of the invention is not altered.

[0018] In this specification, the use of the word “comprising” is intended to specify certain characteristics, regions, steps, processes, elements, and / or components, and unless specifically stated otherwise, it does not exclude the presence or addition of other characteristics, regions, steps, processes, elements, and / or components.

[0019] In this specification, terms such as "first," "second," etc. are used to describe various components, and said components are not limited to said terms. These terms are used for the purpose of distinguishing one component from another.

[0020] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification may be understood to be modified by the term "about" in all cases unless otherwise specified.

[0021] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0022]

[0023] Various by-products are generated during the polymerization process of polyester (or recycled polyester) or the depolymerization process of waste polyester. Since these by-products reduce the purity of the desired final product, they are removed through various separation and purification processes. The by-products removed through these processes are treated as process waste and are subject to incineration. As such, the generation of by-products, which are process waste, is unavoidable in polymerization or depolymerization processes; this leads to increased manufacturing costs and reduced yields of recycled raw materials, and furthermore, may result in insufficient environmental regeneration effects.

[0024] Accordingly, the present invention aims to achieve a reduction in manufacturing costs and an increase in yield of recycled raw materials, and to enhance eco-friendliness, by manufacturing recycled raw materials using by-products that inevitably occur. In particular, the present invention has technical significance in that it is possible to manufacture high-purity recycled raw materials even when using by-products with relatively high impurity content, such as metals and dyes.

[0025] Specifically, the present invention relates to a recycled raw material, a method for manufacturing the same, and a raw material composition for depolymerization used in the manufacture of the recycled raw material, and is described as follows.

[0026]

[0027] Method for manufacturing recycled raw materials

[0028] A method for manufacturing a recycled raw material according to the present invention comprises the step of depolymerizing a reaction raw material comprising a main raw material and an auxiliary raw material, wherein the main raw material comprises waste polyester, and the auxiliary raw material comprises one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

[0029] The main raw material included in the above reaction raw material is the primary raw material subject to decomposition through a depolymerization reaction. Such main raw material includes waste polyester.

[0030] The waste polyester included in the above main raw material may be a polyester product discarded after use or a discarded polyester resin. Specifically, the waste polyester may be various waste polyester products containing polyester, such as bottles, textiles, films, cases, boxes, partitions, shelves, protective panels, packaging, building materials, and interior and exterior materials.

[0031] The waste polyester may undergo a pretreatment process to increase depolymerization efficiency. Specifically, the waste polyester may be obtained through a pretreatment process in which heterogeneous components (components different from polyester), metals, and other foreign substances mixed in various waste polyester products are removed, washed, and then ground using a grinder. As a result of undergoing the pretreatment process, the waste polyester may have a flake form, a scrap form, a powder form, or a fiber form.

[0032] The above main raw material further comprises a decomposition compound that participates in the depolymerization reaction. Specifically, the depolymerization of the above reaction raw material may be carried out by reactions such as glycolysis, hydrolysis, methanolysis, or aminolysis, and according to each of the above reactions, the above main raw material further comprises a decomposition compound that decomposes the polymer chains of the waste polyester. For example, the above depolymerization may be carried out through a glycolysis reaction in which the polymer chains of the waste polyester are decomposed by a glycol-based compound, and accordingly, the above main raw material may further comprise a glycol-based compound as a decomposition compound, such as ethylene glycol, propylene glycol, diethylene glycol, or a combination thereof.

[0033] The auxiliary raw material included in the above reaction raw material is an auxiliary raw material that promotes the depolymerization reaction. Specifically, the auxiliary raw material may include monomers or oligomers with a molecular weight smaller than that of the main raw material to promote the ester exchange reaction in the depolymerization reaction. The auxiliary raw material has the characteristics of having a high metal content compared to the main raw material and a dark color due to the inclusion of dyes, etc. These auxiliary ingredients include one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

[0034] Specifically, according to the present invention, the auxiliary raw material is a by-product obtained (or derived) from one or more processes among the depolymerization process of waste polyester, the polymerization process of polyester, and the polymerization process of recycled polyester, and comprises one or more of the above compounds. As the auxiliary raw material comprises one or more of the above compounds, the depolymerization reaction efficiency of the waste polyester included in the main raw material is improved, thereby increasing the yield of the recycled raw material. Furthermore, by reusing the above compounds which are by-products, the manufacturing cost of the recycled raw material can be reduced, and at the same time, the amount of process waste generated finally can be significantly reduced.

[0035] The above depolymerization process of waste polyester may refer to a process of producing recycled raw materials by decomposing waste polyester products through reactions such as glycolysis, hydrolysis, methanolysis, or aminolysis. The above polymerization process of polyester may refer to a process of producing polyester through a polymerization reaction of virgin raw materials (e.g., an esterification reaction / ester exchange reaction and / or condensation reaction in which a diol component and a dicarboxylic acid component are applied). The polymerization process of the above-mentioned recycled polyester may refer to a process for manufacturing recycled polyester through a polymerization reaction of recycled raw materials (e.g., an esterification reaction / ester exchange reaction and / or condensation reaction involving a recycled diol component or a recycled dicarboxylic acid component), or a polymerization reaction of recycled raw materials and virgin raw materials (e.g., an esterification reaction / ester exchange reaction and / or condensation reaction involving a recycled diol component and a dicarboxylic acid component, or a diol component and a recycled dicarboxylic acid component).

[0036] According to the present invention, the depolymerization process of the waste polyester, the polymerization process of the polyester, and the polymerization process of the recycled polyester, in which the auxiliary raw material is obtained, may each include one or more processes among a centrifugation process, a distillation process, a crystallization process, and a decolorization process. Specifically, the auxiliary raw material may be obtained from one or more processes among a centrifugation process, a distillation process, a crystallization process, or a decolorization process included in the depolymerization process of the waste polyester. Additionally, the auxiliary raw material may be obtained from one or more processes among a centrifugation process, a distillation process, a crystallization process, or a decolorization process included in the polymerization process of the polyester. Furthermore, the auxiliary raw material may be obtained from one or more processes among a centrifugation process, a distillation process, a crystallization process, or a decolorization process included in the polymerization process of the recycled polyester.

[0037] Each of the above centrifugation process, distillation process, crystallization process, and decolorization process is not particularly limited as long as it is a process typically performed to remove impurities from a substance (target substance) generated during the process. Specifically, the above centrifugation process may be a process that removes particulate impurities or high-density impurities from the target substance using centrifugal force. Additionally, the above distillation process may be a process that removes unreacted substances or liquid impurities from the target substance through vacuum distillation and / or thin-film distillation. The above crystallization process may be a process that separates heterogeneous components contained in the target substance by cooling and crystallizing the target substance. The above decolorization process may be a process that removes dye (pigment) components contained in the target substance by filtration, adsorbent treatment, or solvent treatment of the target substance.

[0038] According to the present invention, when the auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the compound may be 1 to 30% (meaning that, based on the total weight of the auxiliary raw material, the content of one or more compounds selected from the group consisting of MHET, BHEI, DEG-ester-1, DEG-ester-2, HA-ester, and ME-ester included in the auxiliary raw material is 1 to 30% by weight). Specifically, when the auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the one or more compounds may be 3 to 30%, 5 to 29.5%, 10 to 29%, 15 to 28.5%, 20 to 28%, 23 to 27.5%, or 25 to 27%.

[0039] In addition, when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer may be 0.1 to 85% (meaning that the content of the oligomer included in the auxiliary raw material is 0.1 to 85% by weight based on the total weight of the auxiliary raw material). Specifically, when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer may be 1 to 83%, 5 to 80%, 7 to 75%, 10 to 70%, 12 to 65%, 15 to 60%, or 20 to 55%. The above oligomer refers to a dimer, trimer, or tetramer having a molecular weight of 2,000 g / mol or less (e.g., 500 to 1,000 g / mol).

[0040] In addition, the above auxiliary raw material may not contain metal or may contain metal. Specifically, the above auxiliary raw material may contain metal in an amount of 500 to 50,000 ppm based on the total weight of the above auxiliary raw material. More specifically, the content of the metal included in the above auxiliary raw material may be 600 to 40,000 ppm, 700 to 30,000 ppm, 800 to 20,000 ppm, 900 to 15,000 ppm, 1,000 to 10,000 ppm, 1,500 to 7,000 ppm, or 3,000 to 5,500 ppm based on the total weight of the above auxiliary raw material.

[0041] As the content of each of the compound, oligomer, and metal included in the above auxiliary raw material is within the above range, it is possible to achieve a reduction in manufacturing cost and a high yield of recycled raw materials.

[0042] According to the present invention, the auxiliary raw material may have a yellowness index (YID) of 20 or more. Specifically, the yellowness index (YID) of the auxiliary raw material may be 22 or more, 24 or more, 26 or more, 28 or more, 30 or more, 35 or more, 40 or more, 50 or more, 60 or more, 80 or more, 100 or more, 120 or more, or 150 or more (e.g., 20 to 180, 25 to 175, 30 to 130, 35 to 100, 40 to 80, or 40 to 70).

[0043] Meanwhile, the content of the main raw material (specifically, waste polyester) included in the above reaction raw material is not particularly limited, but may be 45 to 99.9 weight% based on the total weight of the main raw material and the auxiliary raw material. Specifically, the content of the main raw material may be 46 to 99 weight%, 47 to 95 weight%, 48 to 90 weight%, 49 to 85 weight%, 50 to 83 weight%, 50 to 80 weight%, or 50 to 75 weight%.

[0044] In addition, the content of the auxiliary raw material (specifically, one or more compounds) included in the reaction raw material is not particularly limited, but may be 0.1 to 55 weight% based on the total weight of the main raw material and the auxiliary raw material. Specifically, the content of the auxiliary raw material may be 1 to 54 weight%, 5 to 53 weight%, 10 to 52 weight%, 15 to 51 weight%, 17 to 50 weight%, 20 to 50 weight%, or 25 to 50 weight%.

[0045] As the content of each of the main raw material and the auxiliary raw material included in the above reaction raw material is within the above range, the yield of recycled raw material can be maximized while the amount of process waste can be minimized.

[0046] According to the present invention, the step of depolymerizing the reaction raw material may mean a step of chemically decomposing waste polyester contained in the main raw material to produce a recycled raw material. Specifically, the depolymerizing step may include a step (S-1) of obtaining a product by chemically depolymerizing the main raw material (specifically, waste polyester) contained in the reaction raw material; and a step (S-2) of obtaining a purified product (recycled raw material) by passing the product through one or more purification processes among a filtration process, a distillation process, a crystallization process, and a solid-liquid separation process.

[0047] The chemical depolymerization of the above S-1 step can be carried out through reactions such as glycolysis, hydrolysis, methanolysis, or aminolysis, and preferably can be carried out by a glycolysis reaction using a glycolic compound (e.g., ethylene glycol, propylene glycol, diethylene glycol, or a combination thereof) as the decomposition compound.

[0048] The conditions for chemically depolymerizing the main raw material through the glycolysis reaction are not particularly limited, but may be performed at 160 to 200 ℃ (specifically, 175 to 200 ℃, or 185 to 195 ℃) for 1 to 4 hours (specifically, 2 to 4 hours, or 3 to 4 hours). As chemical depolymerization is performed under the above conditions, the decomposition of the main raw material is carried out smoothly, and the generation of by-products, which are process waste, can be minimized.

[0049] The purification process of the above S-2 step is a process for removing impurities, such as insoluble impurities, unreacted residues, and by-products, from the product obtained through the above S-1 step, and can be performed using commonly known methods. Specifically, the filtration process can be performed using a commonly known filter, ion exchange resin, or adsorbent. Additionally, the distillation process can be performed through commonly known thin-film distillation and / or vacuum distillation. Furthermore, the crystallization process can be performed using a commonly known crystallizer. Additionally, the solid-liquid separation process can be performed through commonly known centrifugation, flotation, pressurized separation, filter separation, or sedimentation separation.

[0050] The present invention can significantly reduce the manufacturing cost of recycled raw materials by manufacturing recycled raw materials through a step of depolymerizing the reaction raw materials. Specifically, according to the present invention, the method for manufacturing recycled raw materials may have a raw material unit price reduction rate (%) according to Formula 1 below of 5% or more. Specifically, the raw material unit price reduction rate (%) may be 7% or more, 10% or more, 12% or more, 13% or more, 15% or more, 16% or more, or 17% or more (e.g., 5 to 20%, 6 to 19%, 8 to 18%, or 10 to 17.5%).

[0051] [Equation 1]

[0052] Raw material unit price reduction rate (%) = {(Y ref - Y com ) / Y ref} × 100

[0053] In the above Equation 1,

[0054] Y ref is the yield of regenerated bis-2-hydroxyethyl terephthalate (r-BHET) obtained through the depolymerization of reaction raw materials not containing the above auxiliary raw materials, and

[0055] Y comis the yield of regenerated bis-2-hydroxyethyl terephthalate (r-BHET) produced (derived) from the main raw material among the regenerated bis-2-hydroxyethyl terephthalate (r-BHET) obtained through the depolymerization of the reaction raw material containing the above auxiliary raw material.

[0056]

[0057] Renewable materials

[0058] The recycled raw material according to the present invention is manufactured from the method for manufacturing the recycled raw material described above. Specifically, the recycled raw material is manufactured through a step of depolymerizing the reaction raw material described above, thereby enabling it to be manufactured with high purity and high yield.

[0059] According to the present invention, the recycled raw material may include recycled bis(2-hydroxyethyl)terephthalate (r-BHET). Specifically, the recycled raw material may be recycled bis(2-hydroxyethyl)terephthalate (r-BHET). The recycled bis(2-hydroxyethyl)terephthalate (r-BHET) is a recycled monomer produced (derived) from waste polyester included in the main raw material described above, and may have the same structure as virgin bis(2-hydroxyethyl)terephthalate (BHET).

[0060] The above-mentioned regenerated raw material may have high purity, such that when analyzed by high-performance liquid chromatography (HPLC), the peak area ratio (%) of the regenerated bis(2-hydroxyethyl)terephthalate (r-BHET) is 90% or more. Specifically, when the above-mentioned regenerated raw material is analyzed by high-performance liquid chromatography (HPLC), the peak area ratio (%) of the r-BHET may be 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more (e.g., 90 to 99.9%, 92 to 99.8%, or 94 to 99.5%). The above r-BHET peak area ratio refers to the ratio (Area%) of the r-BHET peak area to the total peak area obtained by analyzing the above-mentioned regenerated raw material using high-performance liquid chromatography (HPLC).

[0061] In addition, when the above-mentioned recycled raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester) is 5% or less, 4% or less, 3% or less, 2% or less, 1.8% or more, or 1.6% or less (e.g., 0 to 5%, greater than 0 to It may be 5%, 0.1 to 4.5%, 0.5 to 4%, 0.8 to 2.5%, or 1 to 1.6%.

[0062] In addition, when the above-mentioned recycled raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer (e.g., a dimer, trimer, and / or tetramer with a molecular weight of 2,000 g / mol or less) may be 0.3% or less, 0.27% or less, 0.25% or less, 0.23% or less, 0.2% or less, 0.18% or less, 0.15% or less, 0.11% or less, or 0.1% or less (e.g., 0 to 0.3%, 0 to 0.23%, 0 to 0.17%, 0.01 to 0.14%, or 0.01 to 0.1%).

[0063] According to the present invention, the recycled raw material may have a yellowness index (YID) of less than 10. Specifically, the yellowness index (YID) of the recycled raw material may be 9.9 or less, 9.5 or less, 9.3 or less, 9 or less, 8.9 or less, 8.7 or less, 8.5 or less, 8 or less, 7.5 or less, 7 or less, 6.5 or less, 6 or less, 5.5 or less, 5 or less, or 4.5 or less (e.g., greater than 0 to less than 10, 0.5 to 9, 1 to 7.5, 1.5 to 5, or 2 to 4.5).

[0064] In addition, the recycled raw material may not contain metal or may contain metal. Specifically, the recycled raw material may contain less than 10 ppm of metal based on the total weight of the recycled raw material. More specifically, the content of the metal contained in the recycled raw material may be 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, or 5 ppm or less based on the total weight of the recycled raw material (e.g., less than 0 to 10 ppm, 0 to 8 ppm, 0.1 to 6 ppm, or 1 to 5 ppm).

[0065] Since these recycled raw materials exhibit high purity, they can be utilized in various industrial fields, and specifically, they can be used as polymerization raw materials for the manufacture of recycled polyester resins.

[0066]

[0067] Raw material composition for depolymerization

[0068] The raw material composition for depolymerization according to the present invention is a raw material composition used for depolymerizing waste polyester, and comprises an auxiliary raw material comprising one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

[0069] Specifically, according to the present invention, the auxiliary raw material is a by-product obtained (or derived) from one or more processes among the depolymerization process of waste polyester, the polymerization process of polyester, and the polymerization process of recycled polyester, and comprises one or more of the above compounds, and the raw material composition for depolymerization may be made of such auxiliary raw material. The description of the depolymerization process and the polymerization process is the same as described above, so a detailed description thereof is omitted.

[0070] The above-mentioned raw material composition for depolymerization may have a standardized formulation. Specifically, the above-mentioned raw material composition for depolymerization may have a flake formulation with a width of 15 mm or less and a length of 15 mm or less.

[0071] According to the present invention, when the auxiliary raw material included in the raw material composition for depolymerization is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the compound may be 1 to 30% (meaning that, based on the total weight of the auxiliary raw material, the content of one or more compounds selected from the group consisting of MHET, BHEI, DEG-ester-1, DEG-ester-2, HA-ester, and ME-ester included in the auxiliary raw material is 1 to 30% by weight). Specifically, when the auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the one or more compounds may be 3 to 30%, 5 to 29.5%, 10 to 29%, 15 to 28.5%, 20 to 28%, 23 to 27.5%, or 25 to 27%.

[0072] In addition, when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer may be 0.1 to 85% (meaning that the content of the oligomer included in the auxiliary raw material is 0.1 to 85% by weight based on the total weight of the auxiliary raw material). Specifically, when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer may be 1 to 83%, 5 to 80%, 7 to 75%, 10 to 70%, 12 to 65%, 15 to 60%, or 20 to 55%. The above oligomer refers to a dimer, trimer, or tetramer having a molecular weight of 2,000 g / mol or less (e.g., 500 to 1,000 g / mol).

[0073] In addition, the above auxiliary raw material may not contain metal or may contain metal. Specifically, the above auxiliary raw material may contain metal in an amount of 500 to 50,000 ppm based on the total weight of the above auxiliary raw material. More specifically, the content of metal included in the above auxiliary raw material may be 600 to 40,000 ppm, 700 to 30,000 ppm, 800 to 20,000 ppm, 900 to 15,000 ppm, 1,000 to 10,000 ppm, 1,500 to 7,000 ppm, or 3,000 to 5,500 ppm based on the total weight of the above auxiliary raw material.

[0074] In addition, the above auxiliary raw material may have a yellowness index (YID) of 20 or higher. Specifically, the yellowness index (YID) of the above auxiliary raw material may be 22 or higher, 24 or higher, 26 or higher, 28 or higher, 30 or higher, 35 or higher, 40 or higher, 50 or higher, 60 or higher, 80 or higher, 100 or higher, 120 or higher, or 150 or higher (e.g., 20 to 180, 25 to 175, 30 to 130, 35 to 100, 40 to 80, or 40 to 70).

[0075]

[0076] The present invention will be explained in more detail through the following examples. However, the following examples are merely illustrative of the present invention and do not limit the scope of the present invention.

[0077]

[0078] [Preparation Example 1]

[0079] A flake-type auxiliary ingredient was prepared by formulating the product obtained from the centrifugation process (centrifugation decanting) during the depolymerization process of waste polyester bottles subjected to a glycolysis reaction.

[0080]

[0081] [Preparation Example 2]

[0082] A flake-type auxiliary material was prepared by formulating the product obtained from the thin film distillation process (thin film distillation bottom) during the depolymerization process of waste polyester textiles to which a glycolysis reaction was applied.

[0083]

[0084] [Preparation Example 3]

[0085] A flake-type auxiliary material was prepared by formulating the product obtained from the thin film distillation process (thin film distillation bottom) during the depolymerization process of waste polyester film to which a glycolysis reaction was applied.

[0086]

[0087] [Preparation Example 4]

[0088] A flake-type auxiliary ingredient was prepared by formulating the product obtained from the crystallization process during the depolymerization process of waste polyester bottles subjected to a glycolysis reaction (dissolved product in the crystallization mother liquor).

[0089]

[0090] [Preparation Example 5]

[0091] A flake-type auxiliary ingredient was prepared by formulating the product obtained from the esterification process during the polymerization process of a polyester in which a dicarboxylic acid and a diol are reacted.

[0092]

[0093] [Test Example 1]

[0094] The following tests were conducted on the auxiliary raw materials (raw material compositions for depolymerization) prepared in each of the above Preparation Examples 1 to 5, and the results are shown in Tables 1 to 4 below.

[0095]

[0096] (1) High-performance liquid chromatography (HPLC)

[0097] 0.01 g of the sample was diluted in 20 ml of methanol and analyzed by high-performance liquid chromatography (HPLC) (Model: Waters e2695, Column: C18 (4.6 x 250 mm), 5 μm, UV Detector: 242 nm, Injection volume: 10 μL, Eluent (Gradient) A: H2O+H3PO4, B: Acetonitrile). Subsequently, the percentage of the peak area of ​​each of the following components within the total peak area of ​​the HPLC was determined.

[0098] - MHET: Monohydroxyethyl terephthalate

[0099] - TPA: Terephthalic acid

[0100] - BHET: Bis(2-hydroxyethyl)terephthalate

[0101] - BHEI: Bis(2-hydroxyethyl)isophthalate

[0102] - DEG-ester-1: 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate

[0103] - DEG-ester-2: Bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate

[0104] - Me-ester: 2-hydroxyethylmethyl terephthalate

[0105] - HA-ester: 2-hydroxyethyl(2-acetoxyethyl)terephthalate

[0106] - Dimer: BHET dimer

[0107] - Trimer: BHET trimer

[0108]

[0109] (2) Color (L, a, b) and Yellowness Index (YID)

[0110] 20 g of ethylene glycol and 20 g of the sample were each dissolved by heat treatment in an oven at 170°C for 1 hour. Subsequently, the two solutions were mixed, and the color (L, a, b) and yellowness index (molten color, YID) of the resulting mixture were measured. Specifically, for the mixture, transmission data was obtained using Illuminant D65 with Hunterlab’s Color Flex EZ at an observer angle of 2°, and the color and yellowness index were calculated using a color analysis device within the software.

[0111]

[0112] (3) Metal content

[0113] Approximately 0.3 g of the sample was pretreated with microwave and diluted with ultrapure water, and then the metal content was analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) (detection limit 5 ppm).

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123] Referring to Tables 1 to 4 above, it can be seen that the auxiliary materials prepared in Preparation Examples 1 to 5 each contain useful compounds such as BHET and TPA, and contain metal at an appropriate level.

[0124]

[0125] [Example 1]

[0126] 700 g of waste polyester scrap, 300 g of auxiliary material (1) of Preparation Example 1, and 2,500 g of ethylene glycol as reaction raw materials, and 0.35 g of anhydrous zinc acetate as a catalyst were all introduced together into a stainless steel (SUS) reactor, and the internal temperature of the reactor was raised to 195 ℃ and depolymerization was carried out for 4 hours to obtain a product.

[0127] Next, residual insoluble solid impurities in the obtained product were removed through a mesh filter, and the impurity-removed mixture was transferred to a 10 L distillation apparatus and vacuum distillation was performed at 130 °C to remove (recover) unreacted ethylene glycol.

[0128] The reaction product from which the unreacted ethylene glycol had been removed was thin-film distilled in a thin-film distiller (VTA’s VKL70-4S) at 220 °C and 0.08 Torr to obtain crude-BHET from which oligomers of dimer or higher were removed.

[0129] Afterwards, the above crude-BHET and distilled water were added to a 20 L adsorption tank and dissolved at a temperature of 70 ℃, then 2.6 g of activated carbon was added and stirred for 30 minutes, followed by filtration to proceed with adsorption-crystallization.

[0130] After transferring the solution obtained through the above filtration to an evaporation-type crystallizer, the evaporation conditions (pressure control) were adjusted to maintain a uniform temperature throughout, and crystallization was carried out by cooling to room temperature.

[0131] 1,220 g of recycled raw material containing r-BHET was obtained by separating the r-BHET crystals obtained through the above crystallization and the mother liquor through pressurized filtration.

[0132]

[0133] [Example 2]

[0134] 1,207 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 800 g of waste polyester scrap, 200 g of auxiliary raw material (2) of Preparation Example 2 and 2,500 g of ethylene glycol were applied as reaction raw materials to carry out depolymerization.

[0135]

[0136] [Example 3]

[0137] 1,254 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 500 g of waste polyester scrap, 500 g of auxiliary raw material (3) of Preparation Example 3 and 2,500 g of ethylene glycol were applied as reaction raw materials to carry out depolymerization.

[0138]

[0139] [Example 4]

[0140] 1,240 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 700 g of waste polyester scrap, 300 g of auxiliary raw material (4) of Preparation Example 4 and 2,500 g of ethylene glycol were applied as reaction raw materials to carry out depolymerization.

[0141]

[0142] [Example 5]

[0143] 1,197 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 700 g of waste polyester scrap, 300 g of auxiliary raw material (5) of Preparation Example 5 and 2,500 g of ethylene glycol were applied as reaction raw materials to carry out depolymerization.

[0144]

[0145] [Example 6]

[0146] 1,098 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 400 g of waste polyester scrap, 600 g of auxiliary raw material (2) of Preparation Example 2, and 2,500 g of ethylene glycol were applied as reaction raw materials to carry out depolymerization.

[0147]

[0148] [Example 7]

[0149] 1,084 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 300 g of waste polyester scrap, 700 g of auxiliary raw material (5) of Preparation Example 3 and 2,500 g of ethylene glycol were applied as reaction raw materials to carry out depolymerization.

[0150]

[0151] [Comparative Example 1]

[0152] 1,177 g of recycled raw material containing r-BHET was obtained by following the same process as in Example 1, except that 1,000 g of waste polyester scrap and 2,500 g of ethylene glycol were applied as reaction raw materials (without adding auxiliary raw material (1) of Preparation Example 1) and depolymerization was carried out.

[0153]

[0154] [Test Example 2]

[0155] The same test as in Test Example 1 was conducted on the recycled raw materials prepared in Examples 1 to 7 and Comparative Example 1, respectively, and the results are shown in Tables 5 to 8 below.

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165] Referring to Tables 5 to 8 above, it can be confirmed that the recycled raw materials of Examples 1 to 7, which are produced by introducing by-products obtained from a depolymerization process or a polymerization process as auxiliary raw materials into the depolymerization process of waste polyester, have high purity and yield of r-BHET, a useful compound.

[0166] In particular, when the content of auxiliary materials included in the reaction raw materials is controlled to less than 60 weight% as in Examples 1 to 5, it can be confirmed that the color characteristics of the recycled raw materials are excellent and the raw material unit cost reduction rate is 5% or more, thereby reducing the manufacturing cost.

Claims

1. A step of depolymerizing reaction raw materials including main raw materials and auxiliary raw materials, and The above main raw material includes waste polyester, and A method for manufacturing a recycled raw material, wherein the above auxiliary raw material comprises one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

2. In Paragraph 1, A method for manufacturing recycled raw materials, wherein the above auxiliary raw materials are obtained from one or more processes among the depolymerization process of waste polyester, the polymerization process of polyester, and the polymerization process of recycled polyester.

3. In Paragraph 2, A method for manufacturing recycled raw materials, wherein the depolymerization process of the waste polyester, the polymerization process of the polyester, and the polymerization process of the recycled polyester each include one or more processes among a centrifugation process, a distillation process, a crystallization process, and a decolorization process.

4. In Paragraph 1, A method for manufacturing a recycled raw material, wherein the content of the auxiliary raw material included in the reaction raw material is 0.1 to 55 weight% based on the total weight of the main raw material and the auxiliary raw material.

5. In Paragraph 1, A method for manufacturing recycled raw materials having a raw material unit cost reduction rate (%) of 5% or more according to Formula 1 below: [Equation 1] Raw material unit price reduction rate (%) = {(Y ref - Y com ) / Y ref } × 100 In the above Equation 1, Y ref is the yield of regenerated bis-2-hydroxyethyl terephthalate (r-BHET) obtained through the depolymerization of reaction raw materials not containing the above auxiliary raw materials, and Y com is the yield of regenerated bis-2-hydroxyethyl terephthalate (r-BHET) produced from the main raw material among the regenerated bis-2-hydroxyethyl terephthalate (r-BHET) obtained through the depolymerization of the reaction raw material containing the above auxiliary raw material.

6. In Paragraph 1, A method for producing a recycled raw material, wherein when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer is 0.1 to 85%.

7. In Paragraph 1, A method for manufacturing a recycled raw material, wherein when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the compound is 1 to 30%.

8. In Paragraph 1, A method for manufacturing a recycled raw material, wherein the above auxiliary raw material contains metal in an amount of 500 to 50,000 ppm based on the total weight of the above auxiliary raw material.

9. In Paragraph 1, A method for manufacturing recycled raw materials in which the yellowness index (YID) of the above auxiliary raw materials is 20 or higher.

10. Recycled raw material produced from a method for producing recycled raw material according to any one of claims 1 to 9.

11. In Paragraph 10, The above-mentioned recycled raw material includes recycled bis(2-hydroxyethyl)terephthalate (r-BHET), and A recycled raw material having a peak area ratio (%) of 90% or more of the recycled bis(2-hydroxyethyl)terephthalate (r-BHET) when the recycled raw material is analyzed by high-performance liquid chromatography (HPLC).

12. In Paragraph 10, Recycled raw material having a yellowness index (YID) of less than 10.

13. In Paragraph 10, A recycled material containing less than 10 ppm of metal based on the total weight of the recycled material.

14. A raw material composition for depolymerization comprising an auxiliary raw material comprising one or more compounds selected from the group consisting of monohydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl)isophthalate (BHEI), 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), 2-hydroxyethyl(2-acetoxyethyl)terephthalate (HA-ester), and 2-hydroxyethylmethyl terephthalate (ME-ester).

15. In Paragraph 14, The above auxiliary raw material is obtained in one or more processes among the depolymerization process of waste polyester, the polymerization process of polyester, and the polymerization process of recycled polyester, and A raw material composition for depolymerization having a flake formulation.

16. In Paragraph 14, A raw material composition for depolymerization, wherein the above auxiliary raw material contains 500 to 50,000 ppm of metal based on the total weight of the above auxiliary raw material.

17. In Paragraph 14, A raw material composition for depolymerization in which the yellowness index (YID) of the above auxiliary raw material is 20 or higher.

18. In Paragraph 14, A raw material composition for depolymerization, wherein when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the oligomer is 0.1 to 85%.

19. In Paragraph 14, A raw material composition for depolymerization, wherein when the above auxiliary raw material is analyzed by high-performance liquid chromatography (HPLC), the total peak area ratio (%) of the compound is 1 to 30%.

Images