Recycled polyester resin and preparation method therefor

Abstract

The present invention relates to a recycled polyester resin comprising recycled dimethyl terephthalate prepared using waste polyester, and a preparation method therefor. Specifically, according to an embodiment of the present invention, the recycled polyester resin comprises: a repeating unit derived from a glycol component; and a repeating unit derived from recycled dimethyl terephthalate (rDMT), and satisfies a crystallized area value of 20% or more calculated according to equation 1 for a crystallized region and an amorphous region that are obtained by separating, by an individual peak fitting method, crystal diffraction peaks appearing at a two-theta value of 0° to 50° in an X-ray diffraction (XRD) analysis, thereby exhibiting excellent properties of crystallinity as well as color, such as color-b and color-L, melting point (Tm), melting enthalpy, and heat deflection temperature.

Description

Regenerated polyester resin and method for producing the same

[0001] The present invention relates to a recycled polyester resin comprising recycled dimethyl terephthalate manufactured using waste polyester, and a method for manufacturing the same.

[0002]

[0003] Polyester boasts excellent mechanical strength, heat resistance, transparency, and gas barrier properties, making it widely used in beverage containers, packaging films, audio and video films, and industrial materials such as medical fibers and tire cords. In particular, polyester sheets and boards, with their excellent transparency and mechanical strength, are widely used in cases, boxes, partitions, shelves, panels, packaging, building materials, and interior and exterior finishes.

[0004] Accordingly, plastic waste, such as polyester, is being generated globally at an unmanageable rate each year. Recently, countries around the world have been establishing regulations and measures for the recycling of waste plastic resources, including waste polyester. Physical and chemical methods are used to recycle waste polyester. Physical recycling methods are not widely used due to their inability to guarantee purity, while chemical recycling methods depolymerize waste polyester by breaking its ester bonds. These reactions include glycolysis, hydrolysis, methanolysis, and aminolysis.

[0005] Recently, research is being conducted to improve the quality of polyester products manufactured using recycled raw materials, not just the simple recycling of waste polyester. For example, there have been attempts to recycle waste polyethylene terephthalate (PET) through glycolysis and use the recycled raw materials produced through this process to manufacture recycled polyester resins other than PET. However, this reaction involves excessive amounts of glycol and long reaction times, resulting in large amounts of byproducts and low purity. Furthermore, when PET is recycled through methanolysis and the recycled raw materials produced through this process are used to manufacture recycled polyester resins other than PET, the physical properties of the final resin and the products manufactured using it are significantly degraded, resulting in lower quality.

[0006] Therefore, research is ongoing on recycled polyester resins and products manufactured using them, which have excellent quality and minimize the generation of byproducts by not using excessive alcohol or glycol in the process of recycling waste polyester, while not deteriorating the properties of the final resin manufactured using them and the products manufactured using them.

[0007] For example, Korean Patent Publication No. 2011-0080260 discloses a method for chemically regenerating polyester, which is easy to manufacture fine fiber yarn, functional yarn, etc., by depolymerizing waste polyester and ethylene glycol to produce an oligomer solution, contacting the oligomer solution with an ion exchange resin to remove a catalyst in the oligomer solution, then passing the oligomer solution from which the catalyst has been removed through a decolorizing agent to remove colored substances such as a coloring agent in the oligomer solution, and then performing condensation polymerization.

[0008] [Prior Art Literature]

[0009] (Patent Document 1) Korean Patent Publication No. 2011-0080260

[0010]

[0011] Accordingly, the present invention aims to provide a recycled polyester resin and a method for producing the same, which can minimize the generation of by-products in a process of depolymerizing waste polyester and can produce high-purity recycled dimethyl terephthalate with excellent processability, and which has excellent physical properties by including the recycled dimethyl terephthalate.

[0012]

[0013] A recycled polyester resin according to one embodiment of the present invention comprises a repeating unit derived from a glycol component and a repeating unit derived from recycled dimethyl terephthalate (rDMT), and a crystallized area value calculated according to Equation 1 below for a crystallized region and an amorphous region obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis by an individual peak fitting method is 20% or more.

[0014] [Formula 1]

[0015]

[0016] A method for producing recycled dimethyl terephthalate according to another embodiment of the present invention comprises the steps of depolymerizing waste polyester to obtain a depolymerized composition; and the step of crystallizing the produced depolymerized composition.

[0017] According to another embodiment of the present invention, a method for producing a recycled polyester resin comprises the steps of: depolymerizing waste polyester to produce recycled dimethyl terephthalate (rDMT); mixing the rDMT with a glycol component and subjecting it to an esterification reaction to produce recycled bis(4-hydroxybutyl) terephthalate (rBHBT); and subjecting the rBHBT to a condensation polymerization reaction to produce a recycled polyester resin, wherein the recycled polyester resin has a crystallized area value of 20% or more calculated according to Equation 1 for a crystallized region and an amorphous region obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis by an individual peak fitting method.

[0018]

[0019] According to one embodiment of the present invention, a recycled polyester resin comprises a repeating unit derived from a glycol component and a repeating unit derived from recycled dimethyl terephthalate (rDMT), and a crystallized area value calculated according to Equation 1 for a crystallized region and an amorphous region obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis by an individual peak fitting method is 20% or more, so that the resin has excellent crystallinity as well as properties such as colors such as color-b and color-L, melting point (Tm), melting enthalpy, and heat distortion temperature.

[0020] More specifically, the above-mentioned recycled polyester resin includes recycled dimethyl terephthalate (rDMT) having excellent color, purity, and crystallinity, and thus has excellent properties such as color, melting point (Tm), melting enthalpy, and heat distortion temperature, as well as excellent crystallinity.

[0021] Typically, recycled dimethyl terephthalate (rDMT), manufactured from waste polyester, has low purity due to impurities arising from side reactions with reagents used in the depolymerization process. Attempts to improve purity through processes such as fractional distillation have been made, but these methods are inefficient and prohibit commercial application due to high process costs. Furthermore, there are limitations to improving purity.

[0022] The method for producing recycled dimethyl terephthalate of the present invention comprises crystallizing a depolymerized composition produced by depolymerizing waste polyester at a low temperature, separating the slurry produced through the crystallization into solids and liquids, drying and washing the resulting product, and then purifying the resulting product, thereby providing rDMT having excellent color, purity, and crystallinity. More specifically, the method for producing rDMT has a low content of ethylene glycol byproducts that may be generated as side reactions in the process or terephthalate derivatives such as methyl hydrogen terephthalate (MHT) other than the desired DMT, thereby improving color characteristics and purity, and improving quality when used as a raw material for various polymers. In addition, the method for producing rDMT has excellent processability because it can produce high-purity rDMT, and is environmentally friendly because it has a low content of ethylene glycol byproducts that may have an environmental impact.

[0023] Accordingly, the above-mentioned recycled polyester resin is manufactured using rDMT having excellent purity, crystallinity and color properties, and thus has excellent crystallinity as well as properties such as color, melting point (Tm), melting enthalpy and heat distortion temperature such as color-b and color-L, and therefore a product composed solely of the recycled polyester resin without mixing with commercially available polyester resins also has excellent quality.

[0024]

[0025] Figure 1 shows X-ray diffraction (XRD) analysis of the recycled polyester (rPBT) resins manufactured in Example 1 and Comparative Examples 1, 2, 5, and 6.

[0026] Figures 2 to 6 show peaks separated by deconvolution of the X-ray diffraction peaks of the recycled polyester (rPBT) resins manufactured in Comparative Example 1, Example 1, Comparative Example 2, Comparative Example 5, and Comparative Example 6, respectively, using the individual peak fitting method.

[0027]

[0028] The present invention is described in detail below. The present invention is not limited to the details disclosed below and may be modified in various ways without altering the spirit of the invention.

[0029] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0030] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood to be modified by the term “about” in all cases unless otherwise specified.

[0031] In this specification, the terms "first," "second," etc. are used to describe various components, and the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0032] As used herein, a unit or group "derived from" a specific component refers to a portion of a final product resulting from a chemical reaction, such as a polymerization reaction, in which the component is modified or combined with other components during the reaction process. For example, a chain comprising a polymer may contain units or groups derived from one or more monomers.

[0033]

[0034] Regenerated polyester resin

[0035] A recycled polyester resin according to one embodiment of the present invention comprises a repeating unit derived from a glycol component and a repeating unit derived from recycled dimethyl terephthalate (rDMT), and a crystallized area value calculated according to Equation 1 below for a crystallized region and an amorphous region obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis by an individual peak fitting method is 20% or more.

[0036] [Formula 1]

[0037]

[0038] The above-mentioned regenerated polyester resin may include repeating units derived from one or more glycol components and repeating units derived from one or more acid components.

[0039] The above-mentioned recycled polyester resin may be a homopolymer or a copolymer resin. As a specific example, the above-mentioned recycled polyester resin may be a polybutylene terephthalate (PBT) resin, which is a homopolymer resin comprising 1,4-butanediol as a constituent glycol component and recycled dimethyl terephthalate as an acid component. As another example, the above-mentioned recycled polyester resin may be a copolymer resin comprising 1,4-butanediol and an additional glycol as constituent glycol components, and recycled dimethyl terephthalate and an additional acid as acid components. The above-mentioned additional glycol and acid components may be additionally added in the esterification reaction step and / or the condensation polymerization reaction step, which will be described in detail in the method for producing a recycled polyester resin below.

[0040] According to one embodiment of the present invention, the regenerated polyester resin comprises a repeating unit derived from a glycol component.

[0041] The above glycol components are 1,3-propanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymer of ethylene oxide and tetrahydrofuran, ethylene oxide addition polypropylene glycol, polycarbonate diol, polyneopentyl glycol, It may include at least one selected from the group consisting of poly-3-methylpentanediol and poly-1,5-pentanediol.

[0042] The above-mentioned recycled dimethyl terephthalate may be manufactured by depolymerizing waste polyester. Alternatively, the above-mentioned recycled dimethyl terephthalate may be manufactured by secondary depolymerizing recycled bis(2-hydroxyethyl) terephthalate (rBHET), which is manufactured by primary depolymerizing waste polyester. The method for manufacturing recycled dimethyl terephthalate will be described in detail below.

[0043] Conventionally, recycled terephthalate manufactured from waste polyester has poor physical properties such as color characteristics and low purity, making it difficult to use it alone as a raw material for polyester resin as an acid component. However, a recycled polyester resin according to an embodiment of the present invention is manufactured using the recycled terephthalate, and thus can secure sufficient physical properties even if the content of recycled terephthalate is increased compared to the conventional method, thereby having excellent quality. Therefore, a recycled polyester resin according to an embodiment of the present invention may contain the recycled terephthalate alone, or may contain it together with another acid component to improve physical properties, etc.

[0044] The above acid component may include at least one selected from the group consisting of adipic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid.

[0045] The purity of the above-mentioned recycled dimethyl terephthalate may be 90% or higher. For example, the purity of the above-mentioned recycled dimethyl terephthalate may be measured by measuring the area of ​​a peak using high-performance liquid chromatography (UPLC) and then calculating the fraction (%) relative to the total peak area, and may be 91% or higher, 93% or higher, 95% or higher, 97% or higher, 98% or higher, 99% or higher, 99.5% or higher, or 99.9% or higher.

[0046] Specifically, 0.01 g of a sample is diluted in 20 mL of a mixture of methanol and 0.3% distilled aqueous phosphoric acid solution, and the area of ​​the peak is measured using high-performance liquid chromatography (UPLC), and the fraction (%) relative to the total peak area is calculated to determine the purity, components produced by side reactions, components produced other than the target DMT, and their contents. At this time, the dilution can be performed depending on the mobile phase and flow rate.

[0047] In addition, the recycled dimethyl terephthalate may have an APHA color value of 120 or less. For example, the recycled dimethyl terephthalate may be dissolved in a dimethylformamide solvent at a concentration of 10 wt% according to ASTM-D1209, placed in an analysis container with a quartz material and a light path length of 10 mm, and then measured in the transmittance mode of a colorimeter, and may be 105 or less, 100 or less, 93 or less, 90 or less, 85 or less, 65 or less, or 55 or less. APHA (American Public Health Association) is a colorimetric indicator that indicates the degree of contamination of a liquid, and a lower value indicates a closer color to pure water (colorless). Since the recycled dimethyl terephthalate has an APHA color value that satisfies the above range, it has high purity and a low degree of contamination by impurities, etc., and thus has excellent quality.

[0048] According to one embodiment of the present invention, the regenerated polyester resin has a crystallized area value of 20% or more calculated according to Equation 1 below for a crystallized region and an amorphous region obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis using an individual peak fitting method.

[0049] [Formula 1]

[0050]

[0051] Here, the crystallized area value (%) means the area of ​​the total area measured during X-ray diffraction (XRD) analysis of the polyester resin, i.e., the percentage (%) of the crystallized area area with respect to the sum of the areas of the crystallized area and the amorphous area. The area of ​​each area, which is the basis for calculating the crystallized area value (%) according to the present invention, is obtained by separating the peaks measured during X-ray diffraction (XRD) analysis of the polyester resin at 2θ values ​​of 0° to 50° using an individual peak fitting method, and can be calculated as an integral value for each crystallized area or amorphous area. Since the crystalline components are regularly arranged in a three-dimensional space, scattering caused by X-rays striking the diffraction surface occurs in a certain direction, and accordingly, the diffraction peak of the crystallized area appears as a high and narrow peak. However, since the amorphous components are irregularly arranged and scatter in various directions, the peak of the amorphous area is gently formed over a wide 2θ area (see FIGS. 2 to 6).

[0052] The larger the crystallized area value according to the above equation 1, and more specifically, the larger the ratio of each crystallized area separated by the individual peak fitting method, the better the crystallinity of the resin. In addition, the mechanical strength, heat resistance, chemical resistance, and other physical properties of the resin can also be improved. However, as the crystallinity increases, the adhesive strength decreases at temperatures lower than the melting point (Tm), which may limit the use of the resin. Therefore, it is important to control the physical properties within an appropriate range.

[0053] For example, for the above-mentioned recycled polyester resin, the crystallized area value calculated according to Equation 1 may be 20.5% or more, 21% or more, 21.5% or more, 22% or more, 22.5% or more, 23% or more, 25% or more, 26% or more, 27% or more, 29% or more, 30% or more, 31% or more, 33% or more, or 33.5% or more. Since the crystallized area value according to Equation 1 of the above-mentioned recycled polyester resin satisfies the above range, it has excellent crystallinity, and at the same time, it also has desirable properties such as mechanical properties, heat resistance, chemical resistance, and adhesive strength, so that it is easy to apply to various purposes.

[0054] The XRD analysis according to the above formula 1 may be a Wide Angle X-Ray Diffraction (WAXD) analysis, and may be performed by taking a picture of a WAXD plate using a SmartLab type X-ray diffraction device from Rigaku. When analyzing the WAXD, correction data that has been corrected for polarization factor, absorption factor, and air scattering may be used for the measurement data, and X-ray diffraction (XRD) analysis deconvolution and amorphous component region curve separation may be performed, and the crystallized area value (crystallized area value, %) calculated according to the above formula 1 may be calculated using the integral value for the crystallized region crystal diffraction peak and the amorphous region scattering intensity at 2θ values ​​of 0° to 50°.

[0055] Additionally, the above-mentioned regenerated polyester resin may have a difference in crystallized area value according to the following equation 2 that is negative.

[0056] [Formula 2]

[0057] Difference in crystallized area values ​​= Ca1- Ca2

[0058] In the above equation 2,

[0059] Ca1 is the unit-excluding value of the crystallized area calculated according to Equation 1 for a polyester resin containing repeating units derived from dimethyl terephthalate (virgin DMT),

[0060] Ca2 is the unit-deducted value of the crystallized area calculated according to Equation 1 for a recycled polyester resin containing repeating units derived from recycled dimethyl terephthalate (rDMT).

[0061] Specifically, the above Ca1 is a numerical value excluding the unit from the crystallized area value calculated according to the above formula 1 for a polyester resin containing repeating units derived from commercially available dimethyl terephthalate, not recycled dimethyl terephthalate manufactured from waste polyester. For example, the above Ca1 may be 20 or more, 20.5 or more, 21 or more, 21.5 or more, or 22 or more.

[0062] The above Ca2 is a numerical value excluding the unit from the crystallized area value calculated according to the above formula 1 for a recycled polyester resin containing repeating units derived from recycled dimethyl terephthalate manufactured from waste polyester. For example, the above Ca2 may be 20.5 or more, 21 or more, 21.5 or more, 22 or more, 22.5 or more, 23 or more, 25 or more, 25.5 or more, 27 or more, 29 or more, 30 or more, 31.5 or more, 32 or more, or 33.5 or more, as described above.

[0063] The difference in the crystallized area value according to the above formula 2 may be -0.5 or less, -1 or less, -2 or less, -3 or less, -4 or less, -5 or less, -6 or less, -7 or less, -8 or less, -9.5 or less, -10 or less, -11 or less, or -12 or less. Since the difference in the crystallized area value according to the above formula 2 satisfies the above range, it has superior crystallinity compared to a polyester resin containing commercially available dimethyl terephthalate rather than recycled dimethyl terephthalate.

[0064] In addition, the recycled polyester resin may have a total content (mol%) of ethylene glycol residues and diethylene glycol residues of 5 mol% or less based on the total mole number of residues of the glycol component. Specifically, the recycled polyester resin may include ethylene glycol residues, and more specifically, may include ethylene glycol residues and diethylene glycol residues. For example, the recycled polyester resin may include 3.5 mol% or less, 2.5 mol% or less, 2 mol% or less, 1.8 mol% or less, or 1.5 mol% or less of ethylene glycol residues and diethylene glycol residues based on the total mole number of residues of the glycol component, and may include 0.01 mol% or more, 0.02 mol% or more, 0.03 mol% or more, 0.05 mol% or more, or 0.1 mol% or more.

[0065] The above-mentioned recycled polyester resin may have an intrinsic viscosity at 35°C of 0.5 dL / g to 1.5 dL / g. For example, the above-mentioned recycled polyester resin may have an intrinsic viscosity at 35°C of 0.55 dL / g to 1.35 dL / g, 0.65 dL / g to 1.3 dL / g, 0.7 dL / g to 1.2 dL / g, 0.72 dL / g to 1.14 dL / g, 0.55 dL / g to 1.1 dL / g, or 0.6 dL / g to 0.7 dL / g.

[0066] The above-mentioned recycled polyester resin may have a color-b of 12 or less. For example, the color-b of the above-mentioned recycled polyester resin may be 10 or less, 9 or less, 8.5 or less, 8.1 or less, 7.5 or less, or 7 or less, and may be greater than 0, 1 or more, 2 or more, 2.5 or more, or 3 or more.

[0067] The above-mentioned recycled polyester resin may have a color-L of 70 or more. For example, the color-L of the above-mentioned recycled polyester resin may be 72 or more, 75 or more, 78 or more, 80 or more, 81 or more, 82 or more, or 83 or more.

[0068] The above color characteristics are a color system established by the International Standard Color Measurement Organization (CIE (Commission International d'Eclairage), and color is expressed by indicating color as L (brightness), a (complementary color from green to red), and b (complementary color from yellow to blue), and can be measured using a colorimeter.

[0069] In addition, the above-described recycled polyester resin may have a melting point of 210°C or higher, and a melting enthalpy (△Hm) of 38 J / g or higher, as measured in a second scan using a differential scanning calorimeter. For example, the melting point may be 215°C or higher, 218°C or higher, 220°C or higher, 222°C or higher, or 225°C or higher, and may be 300°C or lower, 280°C or lower, 260°C or lower, or 240°C or lower, and the melting enthalpy may be 39.5 J / g or higher, 40 J / g or higher, 40.5 J / g or higher, 41 J / g or higher, 41.3 J / g or higher, 42 J / g or higher, 42.5 J / g or higher, 43 J / g or higher, 43.2 J / g or higher, or 43.5 J / g or higher.

[0070] Specifically, the melting enthalpy can be measured by drying the recycled polyester resin under reduced pressure at 50°C for 15 hours, melting it at 260°C, rapidly cooling it to 30°C, and then scanning it at a heating rate of 10°C / min using a differential scanning calorimeter. At this time, the melting enthalpy can be measured using the 1st scan or the 2nd scan using the differential scanning calorimeter, and in the present specification, it is measured using the 2nd scan.

[0071] In the heat flow curve obtained by scanning, the first endothermic temperature is the glass transition temperature (Tg), the exothermic temperature measured after the glass transition temperature (Tg) is the crystallization temperature (Tc), and the endothermic temperature measured after the crystallization temperature (Tc) is the melting point (Tm). In addition, the integral at the melting point (Tm) was calculated as the melting enthalpy (△Hm).

[0072] Additionally, the recycled polyester resin may have a heat deflection temperature (HDT) of 90°C or higher, measured at a low load of 0.48 MPa according to ASTM D648. For example, the heat deflection temperature may be 92°C or higher, 94.5°C or higher, 95°C or higher, 96°C or higher, 98°C or higher, 98.4°C or higher, 99°C or higher, 99.3°C or higher, 99.5°C or higher, 100°C or higher, or 101°C or higher.

[0073]

[0074] Method for producing recycled dimethyl terephthalate

[0075] A method for producing recycled dimethyl terephthalate according to another embodiment of the present invention comprises the steps of depolymerizing waste polyester to obtain a depolymerized composition; and the step of crystallizing the produced depolymerized composition.

[0076] The waste polyester may be a pulverized or melted waste polyester product. For example, the waste polyester may be a pulverized polyester product that has been recovered and separated after use through consumption, or may be a pelletized product (PCR, post-consumer recycled material), or may be polyester waste (PIR, post-industrial recycled material), such as defective products or scraps that may be generated in processes such as forming polyester films, fibers, containers, etc., but is not limited thereto. As a specific example, the waste polyester may be waste polyethylene terephthalate (waste PET).

[0077] In addition, the waste polyester can be cut or crushed into sizes of 1 mm to 30 mm, 2 mm to 25 mm, or 3 mm to 20 mm to improve process efficiency in the depolymerization step, and can be washed and dried to be manufactured into recycled polyester chips and used.

[0078] For example, the waste polyester may have an intrinsic viscosity (IV) of greater than 0.3 dl / g, greater than 0.35 dl / g, greater than 0.4 dl / g, or greater than 0.45 dl / g, and less than or equal to 1.1 dl / g, less than or equal to 1.0 dl / g, or less than or equal to 0.9 dl / g.

[0079] A method for producing recycled dimethyl terephthalate according to another embodiment of the present invention comprises a step of depolymerizing waste polyester to obtain a depolymerized composition.

[0080] The above depolymerization may include alcoholysis. Specifically, the alcoholysis may be performed using alcohol, more specifically, monoalcohol or glycol. Additionally, the depolymerization may include glycolysis. Specifically, the glycolysis may be performed using ethylene glycol.

[0081] Additionally, the depolymerization may be performed at a temperature of 80°C to 240°C. For example, the depolymerization may be performed at a temperature of 85°C to 235°C, 90°C to 225°C, or 90°C to 220°C.

[0082] According to one embodiment of the present invention, the depolymerization may be performed in one step, or in two steps of primary depolymerization and secondary depolymerization.

[0083] As a specific example, the depolymerization may be performed by alcoholysis of waste polyester, and may be performed by first depolymerizing waste polyester to produce recycled bis(2-hydroxyethyl) terephthalate (rBHET), and then secondarily depolymerizing the rBHET. More specifically, the first depolymerization may be depolymerization through glycolysis using ethylene glycol, and the second depolymerization may be depolymerization through alcoholysis using alcohol.

[0084] For example, the waste polyester and methanol are introduced into the first high-pressure reactor, an alcoholysis catalyst is added, and alcoholysis can be performed while maintaining the seal by fastening all connecting parts of the first high-pressure reactor.

[0085] As another example, the waste polyester, ethylene glycol, and zinc acetate anhydride may be introduced into a stainless steel reactor and subjected to primary depolymerization through glycolysis to obtain solid rBHET. Thereafter, the solid rBHET and methanol may be introduced into a first high-pressure reactor, an alcoholysis catalyst may be added, and then all of the connecting parts of the first high-pressure reactor may be fastened to maintain a sealed state, and secondary depolymerization through alcoholysis may be performed to obtain solid rDMT.

[0086] The alcoholysis can be carried out at a temperature of 80°C to 240°C and a pressure of 2 bar to 60 bar for 2 to 5 hours. For example, the alcoholysis can be carried out at a temperature of 80°C to 235°C, 85°C to 230°C or 90°C to 230°C and a pressure of 2 bar to 60 bar, 3 bar to 60 bar, 4 bar to 60 bar, 3 bar to 20 bar, 3 bar to 15 bar, 35 bar to 60 bar, 40 bar to 60 bar or 50 bar to 60 bar for 2.5 to 5 hours, 2.5 to 4 hours or 3 to 5 hours.

[0087] An alcoholysis catalyst may be added during the above alcoholysis. The alcoholysis can be performed smoothly even as a non-catalytic reaction without the use of an alcoholysis catalyst, making it environmentally friendly. In particular, when the content of insoluble metals in waste polyester is high, a non-catalytic reaction may be advantageous for the efficient treatment and removal of impurities. Furthermore, an alcoholysis catalyst may be added from an energy perspective, which can enhance reactivity and thus processability.

[0088] The above alcohol decomposition catalyst may be a metal acetate salt, an alkali metal salt, or a hydroxy salt.

[0089] More specifically, the alcohol decomposition catalyst is Li+ , Na + , K + or Cs + Alkali metal ions, Be 2+ , Mg 2+ , Ca 2+ or Ba 2+ Alkaline earth metal ions, NH 4+ or NR 4+ Ammonium ion of (R is alkyl), and Zn 2+ One or more cations selected from the group consisting of; and OH - , OR - (R is alkyl), HCO3 - , CO3 2- , benzoate ion (C7H5O2 - ), may include at least one anion selected from the group consisting of 4-alkoxycarbonylbenzoate ion, acetate ion, and terephthalate ion. The R may be an alkyl having 1 to 10 carbon atoms or an alkyl having 1 to 5 carbon atoms.

[0090] For example, the above alcoholysis catalyst is Zn(OAC)2, Co(OAc)2, Mn(OAc)2, Mg(OAc)2, Ca(OAc)2, Ba(OAc)2, LiOAc, NaOAc, KOAc, Zn(OAC)2·2H2O, Co(OAc)2·4H2O, Pb(OAc)2, Mn(OAc)2·4H2O, Mg(OAc)2·4H2O, Pd(OAc)2, It may include at least one selected from the group consisting of Ti(OBu)4, Ti(OiPr)4, GeO2, Al(OiPr)3, Na2CO3, K2CO3, dibutyltin(IV) oxide, tin octoate, titanium phosphate, and terephthalic acid.

[0091] The amount of the alcoholysis catalyst to be added may be 10 ppm to 10,000 ppm relative to the total weight of the waste polyester. For example, when the first stage of depolymerization is performed, the amount of the alcoholysis catalyst to be added may be 10 ppm to 9,000 ppm, 50 ppm to 8,000 ppm, 100 ppm to 6,000 ppm, 250 ppm to 3,500 ppm, 300 ppm to 2,000 ppm, 500 ppm to 1,500 ppm, or 600 ppm to 1,200 ppm relative to the total weight of the waste polyester.

[0092] In addition, the amount of the alcoholysis catalyst may be 10 ppm to 10,000 ppm based on the total weight of the rBHET. For example, when two-stage depolymerization is performed and the depolymerization for the alcoholysis reaction is a secondary depolymerization, the amount of the alcoholysis catalyst based on the intermediate product manufactured through the first depolymerization, specifically, the total weight of the rBHET, may be 10 ppm to 9,000 ppm, 50 ppm to 8,000 ppm, 100 ppm to 6,000 ppm, 250 ppm to 3,500 ppm, 300 ppm to 2,000 ppm, or 300 ppm to 1,500 ppm.

[0093] Additionally, the glycolysis may be performed at 160°C to 240°C. For example, the glycolysis may be performed by raising the temperature inside the reactor to 170°C to 220°C, 175°C to 210°C, or 185°C to 200°C.

[0094] A method for producing regenerated dimethyl terephthalate according to another embodiment of the present invention includes a step of crystallizing the produced depolymerization composition.

[0095] The crystallization step may be performed by cooling the depolymerization composition to 25°C to 60°C and stirring at a low speed of 10 rpm to 30 rpm for 1 to 6 hours or leaving it alone. For example, the crystallization step may be performed by stirring the depolymerization composition at a low speed of 10 rpm to 25 rpm or 10 rpm to 20 rpm for 1 to 5 hours or 2 to 4 hours at a temperature of 25°C to 55°C, 30°C to 60°C, or 40°C to 55°C.

[0096] More specifically, by performing a crystallization step according to the above conditions after depolymerization is completed, a depolymerized composition in the form of a slurry can be obtained. As a specific example, by performing a crystallization step according to the above conditions after depolymerization is completed through alcoholysis, a slurry-form depolymerized composition can be obtained. The slurry-form depolymerized composition may include solid-phase recycled dimethyl terephthalate (rDMT), an excess of unreacted methanol, a small amount of liquid-phase dissolved recycled dimethyl terephthalate (rDMT), ethylene glycol derivatives, polyester oligomers, methanol-terminated oligomers, etc. produced as side reactions.

[0097] At this time, the depolymerization composition obtained through the crystallization step may include ethylene glycol derivatives generated as a side reaction or terephthalic acid and terephthalate derivatives generated in addition to the desired DMT or BHET, and the components and contents of each of these can be analyzed using high-performance liquid chromatography (UPLC).

[0098] Additionally, after the depolymerization is completed, the components introduced for depolymerization can be recovered through layer separation or fractional distillation. As a specific example, methanol introduced for alcoholysis or ethylene glycol introduced for glycolysis can be recovered through layer separation or fractional distillation.

[0099] Additionally, in the above depolymerization step, an ethylene glycol derivative as a by-product may be produced.

[0100] The content of the ethylene glycol derivative may be 5 wt% or less relative to the total weight of the recycled dimethyl terephthalate. For example, the ethylene glycol derivative may include ethylene glycol and diethylene glycol, and the content of the ethylene glycol derivative relative to the total weight of the recycled dimethyl terephthalate may be 4 wt% or less, 3.5 wt% or less, 3 wt% or less, 2.5 wt% or less, or 2 wt% or less, and may be 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, or 0.5 wt% or more.

[0101] Additionally, in the above depolymerization step, by-products such as terephthalic acid and terephthalate derivatives can be produced.

[0102] The above terephthalate derivatives do not include dimethyl terephthalate, but include dimethyl isophthalate (DMI), methyl hydrogen terephthalate (MHT), 1-(2-hydroxyethyl)-4-methyl terephthalate (HEMT), ethylmethyl terephthalate (EMT), mono(hydroxylethyl) terephthalate (MHET), 2-hydroxyethyl [2-(2-hydroxyethoxy)ethyl] terephthalate (HEHDET), and bis[2-(2-hydroxyethoxy)ethyl] terephthalate (Bis[2-(2-hydroxyethoxy)ethyl] terephthalate; It may be at least one selected from the group consisting of, but is not limited to, BDHET.

[0103] At this time, the content of the terephthalic acid and terephthalate derivatives may be 10 wt% or less relative to the total weight of the regenerated dimethyl terephthalate. For example, the content of the terephthalic acid and terephthalate derivatives may be 9 wt% or less, 8 wt% or less, 6.5 wt% or less, 5 wt% or less, 3 wt% or less, 1.5 wt% or less, or 1 wt% or less relative to the total weight of the regenerated dimethyl terephthalate.

[0104] In addition, the rDMT finally manufactured through the depolymerization may include an inorganic compound. For example, the rDMT finally manufactured may include one or more inorganic compounds selected from the group consisting of antimony-containing compounds, germanium-containing compounds, titanium-containing compounds, zinc-containing compounds, cobalt-containing compounds, tin-containing compounds, aluminum-containing compounds, magnesium, sodium salts, potassium salts, phosphorus-containing compounds, and sulfur-containing compounds. The inorganic compound may be derived from waste polyester, and may be an additional component added during the depolymerization process. The content of the inorganic compound may be 10 ppm to 500 ppm, 30 ppm to 400 ppm, 50 ppm to 350 ppm, or 100 ppm to 300 ppm based on the total weight of the rDMT.

[0105] According to one embodiment of the present invention, the method for producing the regenerated dimethyl terephthalate may additionally include at least one step selected from the group consisting of a solid-liquid separation step, a drying step, a washing step, and a purification step.

[0106] For example, after the crystallization step, a washing step and a purification step may be performed, and after the crystallization step, a solid-liquid separation step, a washing step and a purification step may be performed.

[0107] More specifically, after the crystallization step, the solid-liquid separation step, the drying step, the washing step, and the purification step may be sequentially performed. As a specific example, the depolymerized composition obtained through the crystallization step may be subjected to solid-liquid separation, followed by drying and washing to obtain rDMT in the form of a wet cake. The washed rDMT in the form of a wet cake may be purified to obtain rDMT in a solid phase.

[0108] The solid-liquid separation can be performed using a centrifuge. Specifically, the solid-liquid separation can separate the solid rDMT or rBHET contained in the depolymerization composition from the liquid components introduced in the depolymerization, such as ethylene glycol and methanol. Specifically, the solid-liquid separation can be performed using a centrifuge at 1,000 rpm to 4,000 rpm, 1,500 rpm to 3,500 rpm, or 2,000 rpm to 3,000 rpm.

[0109] The drying step may be performed at a temperature of 85°C to 130°C. For example, the temperature at which the drying step is performed may be 90°C to 120°C, 95°C to 110°C, or 95°C to 105°C.

[0110] The washing may be performed three or more times using a mixture of alcohol and / or water, a protic solvent such as isopropanol or acetic acid, or an aprotic solvent such as acetone, dichloromethane, chloroform, tetrahydrofuran (THF), or toluene. The washing effectively removes residual pigments or yellow impurities generated by pigment decomposition during hydrolysis, thereby improving color characteristics.

[0111] The purification step may be performed by fractional distillation at a temperature of 170°C to 240°C and a reduced pressure of 100 torr or less. For example, the purification step may be performed by fractional distillation at a temperature of 175°C to 235°C, 180°C to 225°C, or 190°C to 220°C and a reduced pressure of 100 torr or less, 80 torr or less, or 60 torr or less. In addition, the purification step may additionally include a step of cooling to room temperature after the fractional distillation.

[0112]

[0113] Method for producing recycled polyester resin

[0114] According to another embodiment of the present invention, a method for producing a recycled polyester resin comprises the steps of: depolymerizing waste polyester to produce recycled dimethyl terephthalate (rDMT); mixing the rDMT with a glycol component and subjecting it to an esterification reaction to produce recycled bis(4-hydroxybutyl) terephthalate (rBHBT); and subjecting the rBHBT to a condensation polymerization reaction to produce a recycled polyester resin, wherein the recycled polyester resin has a crystallized area value of 20% or more calculated according to Equation 1 for a crystallized region and an amorphous region obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis by an individual peak fitting method.

[0115] The step of depolymerizing the above waste polyester to produce recycled dimethyl terephthalate is as described above.

[0116] The description of the above glycol component is as described above, and the rDMT forms a residue of bis(4-hydroxybutyl)terephthalate (rBHBT) or an oligomer thereof through an esterification reaction with glycol. More specifically, the rBHBT and its oligomers can form a polymer chain of the polyester resin to be finally manufactured.

[0117] The above esterification reaction may be performed at 165°C or higher, 170°C or higher, 180°C or higher, or 190°C or higher, and may be performed at 225°C or lower, 220°C or lower, 215°C or lower, 210°C or lower, or 205°C or lower. For example, the esterification reaction may be performed at a temperature of 170°C or higher to facilitate smooth removal of methanol, which is a by-product, and may be performed at a temperature 10°C lower than the boiling point of the glycol to be substituted to reduce loss of the glycol. As a specific example, the esterification reaction of 1,4-butanediol and rDMT may be performed at 170°C to 220°C.

[0118] In addition, the above esterification reaction is at 0 kg / cm compared to atmospheric pressure. 2 10 kg / cm 2 (0 mmHg to 7355.6 mmHg), 0 kg / cm 2 5 kg / cm 2 (0 to 3677.8 mmHg) or 0 kg / cm 2 2.0 kg / cm 2 (0 to 1471.1 mmHg). In addition, the esterification reaction can be performed for 1 hour to 24 hours, 1 hour to 10 hours, or 1 hour to 6 hours.

[0119] The polycondensation reaction may be performed at a temperature of 150°C to 300°C, 200°C to 290°C, 240°C to 280°C, or 260°C to 280°C. In addition, the polycondensation reaction may be performed under reduced pressure conditions of 0.01 mmHg to 600 mmHg, 0.05 mmHg to 300 mmHg, or 0.1 mmHg to 100 mmHg. In addition, the polycondensation reaction may be performed for a necessary time until a desired intrinsic viscosity is reached, and may be performed for, for example, 1 hour to 24 hours, 1 hour to 10 hours, or 1 hour to 4 hours. When the process conditions of the polycondensation reaction satisfy the above range, it may be advantageous to remove glycol, a by-product of the polycondensation reaction, from the system.

[0120] At the beginning of the polycondensation reaction, the stirring speed is set to high, and as the polycondensation reaction progresses, the stirring force becomes weak due to the increase in the viscosity of the reactants, or the temperature of the reactants rises above the set temperature, the stirring speed can be appropriately adjusted accordingly.

[0121] Additionally, a glycol component or an acid component may be additionally added in the esterification reaction step and / or the condensation polymerization reaction step.

[0122] The above glycol components are 1,3-propanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymer of ethylene oxide and tetrahydrofuran, ethylene oxide addition polypropylene glycol, polycarbonate diol, polyneopentyl glycol, It may include at least one selected from the group consisting of poly-3-methylpentanediol and poly-1,5-pentanediol.

[0123] The above acid component may include at least one selected from the group consisting of adipic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid.

[0124] Additionally, a catalyst and / or stabilizer may be additionally added in the esterification reaction and the condensation polymerization reaction.

[0125] For example, the esterification reaction catalyst may be a methylate of sodium or magnesium; an acetate, borate, fatty acid salt, or carbonate of Zn, Cd, Mn, Co, Ca, or Ba; a metal Mg; an oxide of Pb, Zn, Sb, Ge, or Ti; or the like.

[0126] In addition, the polycondensation reaction catalyst may be, for example, a titanium-based catalyst such as tetraethyl titanate, acetyltripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, polybutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, lactate titanate, triethanolamine titanate, acetyl acetonate titanate, ethyl acetoacetic ester titanate, isostearyl titanate, titanium dioxide, titanium dioxide / silicon dioxide copolymer, titanium dioxide / zirconium dioxide copolymer, etc.; a germanium-based catalyst such as germanium dioxide and copolymers using the same; or a tin-based catalyst such as monobutyl tin oxide, dibutyl tin oxide, monobutyl hydroxy tin oxide, etc.

[0127] Additionally, the stabilizer may be a phosphorus compound such as phosphoric acid, trimethyl phosphate, or triethyl phosphate, but is not limited thereto.

[0128] A method for producing a polyester resin according to another embodiment of the present invention may further include a step of conducting a solid-state polymerization reaction. For example, the solid-state polymerization may be performed after the condensation polymerization reaction step, and may be performed at a temperature of 190°C to 230°C, under vacuum conditions of 0.2 torr to 2.0 torr, or under a nitrogen atmosphere.

[0129]

[0130] The above contents are explained in more detail with the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited to these examples.

[0131]

[0132] Manufacturing of recycled dimethyl terephthalate (rDMT)

[0133] Manufacturing Example 1

[0134] 120 g of waste polyethylene terephthalate (waste PET) and 400 g of methanol were charged into a first high-pressure reactor with a capacity of 1 L, and 120 mg of Zn(OAC)2·2H2O (1,000 ppm based on the total weight of the waste PET) was added as an alcoholysis catalyst.

[0135] Afterwards, all the connecting parts of the first high-pressure reactor were fastened and sealed, and the temperature was raised to 220°C over 1 hour. While maintaining the temperature of 220°C and the pressure of 58 bar, depolymerization through alcoholysis was performed by stirring for 3 hours. After the alcoholysis was completed, it was cooled to room temperature, and crystallization was performed by low-speed stirring at 10 to 20 rpm for 2 hours, and a slurry-type alcoholysis composition was obtained. At this time, the alcoholysis composition included solid-phase recycled dimethyl terephthalate (rDMT), an excess of unreacted methanol, and an ethylene glycol derivative produced as a side reaction.

[0136] Thereafter, the alcoholysis composition was placed in a centrifuge to perform solid-liquid separation, dried in an oven at 100°C, and washed with methanol. This process was repeated three or more times to obtain rDMT in the form of a wet cake. The washed rDMT in the form of a wet cake was subjected to fractional distillation at a temperature of 205°C under a reduced pressure condition of 100 torr or less, and cooled to room temperature to obtain additionally purified solid rDMT. At this time, the components and contents of ethylene glycol derivatives produced as a side reaction or terephthalic acid and terephthalate derivatives produced in addition to the target DMT were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0137] Afterwards, the above-mentioned solid rDMT was filtered, and the remaining filtrate was poured into a separate flask, and an excess of unreacted methanol and ethylene glycol (EG) produced as a side reaction were recovered using a fractional distillation device.

[0138]

[0139] Manufacturing Example 2

[0140] 1,000 g of waste polyethylene terephthalate (waste PET), 4,000 g of ethylene glycol, and 3.5 g of zinc acetate anhydride were placed in a stainless steel (SUS) reactor, and the internal temperature of the reactor was raised to 196°C to perform primary depolymerization through glycolysis for 4 hours.

[0141] Thereafter, the first depolymerization composition was cooled to 30°C and stirred at 10 to 20 rpm for 2 hours to proceed with crystallization, and as a result, a slurry containing regenerated bis(2-hydroxyethyl) terephthalate (rBHET) and an excess of ethylene glycol (EG) was obtained.

[0142] Thereafter, the slurry was placed in a centrifuge to perform solid-liquid separation, washed twice with distilled water, and the residual solvent was removed using an oven at 80°C to obtain about 1,000 g of solid rBHET. At this time, the components and contents of the terephthalic acid and terephthalate derivatives produced in addition to the ethylene glycol derivatives produced as a side reaction or the desired bis(2-hydroxyethyl) terephthalate (rBHET) were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0143] Afterwards, the above-mentioned solid rBHET was filtered, and the remaining filtrate was poured into a separate flask, and an excess of unreacted ethylene glycol (EG) was recovered using a fractional distillation device.

[0144] Afterwards, 150 g of the solid rBHET and 400 g of methanol were introduced into the first high-pressure reactor with a capacity of 1 L, and 45 mg of Zn(OAC)2·2H2O (300 ppm relative to the total weight of the rBHET) was added as an alcoholysis catalyst.

[0145] Thereafter, all the connecting parts of the first high-pressure reactor were fastened and sealed, and the temperature was raised to 90°C over 1 hour. The secondary depolymerization through alcoholysis was performed by stirring for 5 hours while maintaining the temperature at 90°C and the pressure at 3 bar. After the alcoholysis was completed, the secondary depolymerization composition was cooled to room temperature and left for 4 hours to obtain a slurry-type secondary depolymerization composition. At this time, the secondary depolymerization composition contained solid-phase regenerated dimethyl terephthalate (rDMT), an excess of unreacted methanol, and an ethylene glycol derivative produced as a side reaction.

[0146] Thereafter, the secondary depolymerization composition was placed in a centrifuge to perform solid-liquid separation, dried in an oven at 100°C, and washed with methanol. This process was repeated three or more times to obtain rDMT in the form of a wet cake. The washed rDMT in the form of a wet cake was subjected to fractional distillation at a temperature of 205°C and a reduced pressure of 100 torr or less, and cooled to room temperature to obtain additionally purified solid rDMT. At this time, the components and contents of ethylene glycol derivatives produced as a side reaction or terephthalic acid and terephthalate derivatives produced other than the target DMT were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0147] Afterwards, the above-mentioned solid rDMT was filtered, and the remaining filtrate was poured into a separate flask, and an excess of unreacted methanol and ethylene glycol (EG) produced as a side reaction were recovered using a fractional distillation device.

[0148]

[0149] Manufacturing Example 3

[0150] 1,000 g of waste polyethylene terephthalate (waste PET), 4,000 g of ethylene glycol, and 3.5 g of zinc acetate anhydride were placed in a stainless steel (SUS) reactor, and the internal temperature of the reactor was raised to 196°C to perform primary depolymerization through glycolysis for 4 hours.

[0151] Thereafter, the first depolymerization composition was cooled to 30°C and stirred at 10 to 20 rpm for 2 hours to proceed with crystallization, and as a result, a slurry containing regenerated bis(2-hydroxyethyl) terephthalate (rBHET) and an excess of ethylene glycol (EG) was obtained.

[0152] Thereafter, the slurry was placed in a centrifuge to perform solid-liquid separation, washed twice with distilled water, and the residual solvent was removed using an oven at 80°C to obtain about 1,000 g of solid rBHET. At this time, the components and contents of the terephthalic acid and terephthalate derivatives produced in addition to the ethylene glycol derivatives produced as a side reaction or the desired bis(2-hydroxyethyl) terephthalate (rBHET) were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0153] Afterwards, the above-mentioned solid rBHET was filtered, and the remaining filtrate was poured into a separate flask, and an excess of unreacted ethylene glycol (EG) was recovered using a fractional distillation device.

[0154] Afterwards, 150 g of the solid rBHET and 400 g of methanol were introduced into the first high-pressure reactor with a capacity of 1 L, and 45 mg of Zn(OAC)2·2H2O (300 ppm relative to the total weight of the waste rBHET) was added as an alcoholysis catalyst.

[0155] Thereafter, all the connecting parts of the first high-pressure reactor were fastened and sealed, and the temperature was raised to 220°C over 1 hour. The secondary depolymerization through alcoholysis was performed by stirring for 3 hours while maintaining the temperature of 220°C and the pressure of 58 bar. After the alcoholysis was completed, the mixture was cooled to room temperature and left for 3 hours to obtain a slurry-type secondary depolymerization composition. At this time, the secondary depolymerization composition contained solid-phase recycled dimethyl terephthalate (rDMT), an excess of unreacted methanol, and an ethylene glycol derivative produced as a side reaction.

[0156] Thereafter, the secondary depolymerization composition was placed in a centrifuge to perform solid-liquid separation, and dried in a 100°C oven to obtain solid rDMT. At this time, the components and contents of terephthalic acid and terephthalate derivatives produced in addition to the ethylene glycol derivatives produced as side reactions or the desired DMT were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0157] Afterwards, the above-mentioned solid rDMT was filtered, and the remaining filtrate was poured into a separate flask, and an excess of unreacted methanol and ethylene glycol (EG) produced as a side reaction were recovered using a fractional distillation device.

[0158]

[0159] Manufacturing Example 4

[0160] 1,000 g of waste polyethylene terephthalate (waste PET), 4,000 g of ethylene glycol, and 3.5 g of zinc acetate anhydride were placed in a stainless steel (SUS) reactor, and the internal temperature of the reactor was raised to 196°C to perform primary depolymerization through glycolysis for 4 hours.

[0161] Thereafter, the first depolymerization composition was cooled to 30°C and stirred at 10 to 20 rpm for 2 hours to proceed with crystallization, and as a result, a slurry containing regenerated bis(2-hydroxyethyl) terephthalate (rBHET) and an excess of ethylene glycol (EG) was obtained.

[0162] Thereafter, the slurry was placed in a centrifuge to perform solid-liquid separation, washed twice with distilled water, and the residual solvent was removed using an oven at 80°C to obtain about 1,000 g of solid rBHET. At this time, the components and contents of the terephthalic acid and terephthalate derivatives produced in addition to the ethylene glycol derivatives produced as a side reaction or the desired bis(2-hydroxyethyl) terephthalate (rBHET) were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0163] Afterwards, 150 g of the solid rBHET and 400 g of methanol were introduced into the first high-pressure reactor with a capacity of 1 L, and 150 mg of Zn(OAC)2·2H2O (1,000 ppm relative to the total weight of the rBHET) was added as an alcohol decomposition catalyst.

[0164] Thereafter, all the connecting parts of the first high-pressure reactor were fastened and sealed, and the temperature was raised to 220°C over 1 hour. The secondary depolymerization through alcoholysis was performed by stirring for 3 hours while maintaining the temperature of 220°C and the pressure of 58 bar. After the alcoholysis was completed, the mixture was cooled to room temperature and left for 3 hours to obtain a slurry-type secondary depolymerization composition. At this time, the secondary depolymerization composition contained solid-phase recycled dimethyl terephthalate (rDMT), an excess of unreacted methanol, and an ethylene glycol derivative produced as a side reaction.

[0165] Thereafter, for the secondary depolymerization composition, first fractional distillation was performed under the conditions of 60°C and 500 mmHg, second fractional distillation was performed under the conditions of 170°C and 300 mmHg, and third fractional distillation was performed under the conditions of 200°C and 60 mmHg to obtain solid rDMT. At this time, the components and contents of ethylene glycol derivatives produced as side reactions or terephthalic acid and terephthalate derivatives produced other than the target DMT were analyzed using high-performance liquid chromatography (UPLC) (see Table 2 below).

[0166] Afterwards, the above-mentioned solid rDMT was filtered, and the remaining filtrate was poured into a separate flask, and an excess of unreacted methanol and ethylene glycol (EG) produced as a side reaction were recovered using a fractional distillation device.

[0167]

[0168] Experimental Example 1-1: High-Performance Liquid Chromatography (UPLC)

[0169] Using high-performance liquid chromatography (UPLC), the purity of rDMT obtained in Manufacturing Examples 1 to 4 and rBHET obtained in Manufacturing Example 2 was calculated, and the components and contents of ethylene glycol derivatives produced as side reactions or terephthalic acid or terephthalate derivatives produced other than the desired DMT or BHET were analyzed.

[0170] Specifically, 0.01 g of the sample was diluted in 20 mL of a mixture of methanol and 0.3% distilled aqueous phosphoric acid solution according to the mobile phase and flow rate in Table 1 below, and the peak area was measured using high-performance liquid chromatography (Manufacturer: Water, Model: ACQUITY UPLC H-Class Systems), and the fraction (%) with respect to the total peak area was calculated to measure purity, components produced by side reactions, and components produced other than the target DMT and their contents. At this time, commercially available DMT (Manufacturer: SK Chemicals, Model: SKYDMT) was also listed in Table 2 as a control.

[0171]

[0172]

[0173] Experimental Example 1-2: APHA Color Values

[0174] The APHA (American Public Health Association) color value was measured for the rDMT obtained in the above Manufacturing Examples 1 to 4 and the rBHET obtained in the above Manufacturing Example 2 according to ASTM-D1209. Specifically, the rDMT and the rBHET were dissolved in a dimethylformamide solvent at a concentration of 10 wt% according to ASTM-D1209, placed in an analysis container made of quartz and having a light path length of 10 mm, and then the APHA color value was measured using the transmittance mode of a colorimeter (model name: ColorEye7000A).

[0175]

[0176]

[0177] As shown in Table 2 above, the rDMT of Manufacturing Examples 1 and 2 manufactured according to one embodiment of the present invention had a high purity of 95% or more and excellent transparency with an APHA color value of 85 or less. In particular, Manufacturing Examples 1 and 2 had low contents of ethylene glycol and diethylene glycol, so they had excellent purity and crystallinity, and had low contents of terephthalate derivatives such as methyl hydrogen terephthalate (MHT) in addition to the target DMT, so they are suitable for use as raw materials for various polymers.

[0178] In addition, Manufacturing Example 3, which did not perform the washing process using methanol, had a low purity of less than 90%, and Manufacturing Example 4, which performed the conventional fractional distillation process, had an APHA color value of 125, which was very low in transparency, and the purity was also very low at about 68%.

[0179]

[0180] Manufacturing of recycled polyester resin

[0181] Example 1

[0182] Step (1): Preparation of regenerated bis(4-hydroxybutyl)terephthalate (rBHBT) through transesterification reaction

[0183] A 1 L transesterification reactor, which was connected to a water-coolable condenser and a column, was charged with 3,068 g of 1,4-butanediol (BD) as a diol component, 4,407 g of rDMT prepared in Preparation Example 1 as an acid component, and 2 g of tetrabutyl titanate (TBT) as a transesterification catalyst. Nitrogen was flowed to adjust the pressure inside the reactor to 0.1 kg / cm2, and the temperature was increased to 200°C while maintaining this pressure, and the transesterification reaction was performed while maintaining 200°C. At this time, while the transesterification reaction was proceeding, methanol as a by-product was discharged through the column and condenser, and the transesterification reaction was performed until the discharge of methanol stopped, thereby obtaining a transesterification reaction composition including rBHBT and its oligomers. After the transesterification reaction was completed, the nitrogen inside the pressurized reactor was discharged to the outside to lower the pressure of the reactor to normal pressure.

[0184] Step (2): Production of recycled polyester resin through polycondensation reaction

[0185] The transesterification reaction composition obtained in the above step (1) was introduced into a polycondensation reactor. The pressure of the reactor was reduced from atmospheric pressure to 5.0 Torr (absolute pressure: 5 mmHg) over 30 minutes, and at the same time, the temperature of the reactor was increased to 245°C over 1 hour. Thereafter, the pressure of the reactor was maintained at 1.0 Torr (absolute pressure: 1.0 mmHg) or less to proceed with the polycondensation reaction. At this time, the stirring speed was set to high in the early stage of the polycondensation reaction, and as the polycondensation reaction progressed, the stirring speed was appropriately adjusted when the by-product glycol component escaped from the reactor, the stirring force weakened due to the increase in the viscosity of the mixture in the reactor, or the temperature of the mixture rose above the set temperature. The polycondensation reaction was proceeded until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 1.14 dl / g. When the intrinsic viscosity of the mixture within the reactor reached a desired level, the mixture was discharged outside the reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 mg to 14 mg, thereby obtaining 5,000 g of recycled polyester (rPBT) resin.

[0186]

[0187] Example 2

[0188] Except that in the above step (1), rDMT manufactured in Manufacturing Example 2 was used instead of rDMT manufactured in Manufacturing Example 1, an ester exchange reaction was carried out in the same manner as in Example 1, and in the above step (2), polycondensation was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 0.98 dl / g, thereby obtaining 5,000 g of a recycled polyester (rPBT) resin.

[0189]

[0190] Example 3

[0191] In the above step (2), condensation polymerization was performed in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 0.72 dl / g, thereby obtaining 5,000 g of recycled polyester (rPBT) resin.

[0192]

[0193] Comparative Example 1

[0194] Except that commercially available DMT (manufacturer: SK Chemicals, model name: SKYDMT) was used instead of the rDMT manufactured in Manufacturing Example 1 in the above step (1), the ester exchange reaction was carried out in the same manner as in Example 1, and in the above step (2), polycondensation was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 1.11 dl / g, thereby obtaining 5,000 g of general polyester (PBT) resin.

[0195]

[0196] Comparative Example 2

[0197] Except that in the above step (1), rDMT manufactured in Manufacturing Example 3 was used instead of rDMT manufactured in Manufacturing Example 1, an ester exchange reaction was carried out in the same manner as in Example 1, and in the above step (2), polycondensation was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 1.1 dl / g, thereby obtaining 5,000 g of a recycled polyester (rPBT) resin.

[0198]

[0199] Comparative Example 3

[0200] Except that in the above step (1), rDMT manufactured in Manufacturing Example 4 was used instead of rDMT manufactured in Manufacturing Example 1, an ester exchange reaction was carried out in the same manner as in Example 1, and in the above step (2), polycondensation was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 0.9 dl / g, thereby obtaining 5,000 g of a recycled polyester (rPBT) resin.

[0201]

[0202] Comparative Example 4

[0203] An ester exchange reaction was carried out in the same manner as in Example 1 except that 2,836 g of 1,4-butanediol (BD) was used as the diol component in the above step (1), and 2,852 g of rDMT manufactured in Preparation Example 4 and 1,600 g of rBHET manufactured in Preparation Example 2 were used as the acid component, and in the above step (2), condensation polymerization was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 0.83 dl / g, thereby obtaining 5,000 g of a recycled polyester (rPBT) resin.

[0204]

[0205] Comparative Example 5

[0206] An ester exchange reaction was carried out in the same manner as in Example 1 except that 1,783 g of 1,4-butanediol (BD) was used as a diol component in the above step (1) and 6,287 g of rBHET manufactured in Preparation Example 2 was used as an acid component. In the above step (2), condensation polymerization was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 0.81 dl / g, thereby obtaining 5,000 g of a recycled polyester (rPBT) resin.

[0207]

[0208] Comparative Example 6

[0209] An ester exchange reaction was carried out in the same manner as in Example 1 except that 1,286 g of 1,4-butanediol (BD) was used as a diol component in the above step (1) and 7,257 g of rBHET manufactured in Preparation Example 2 was used as an acid component. In the above step (2), condensation polymerization was carried out in the same manner as in Example 1 until the intrinsic viscosity (IV) in the reactor became 0.78 dl / g, thereby obtaining 5,000 g of a recycled polyester (rPBT) resin.

[0210]

[0211] Experimental Example 2-1: WAXD (Wide Angle X-Ray Diffraction) Analysis

[0212] For the recycled polyester (rPBT) resins manufactured in Examples 1 to 3 and Comparative Examples 1, 2, 5, and 6, WAXD plate photographs were taken using a SmartLab type X-ray diffraction apparatus from Rigaku. At this time, the photographing conditions were set as follows.

[0213] - X-ray generator: 3kW (Cu target)

[0214] - Theta-Theta goniometer with horizontal sample mounting

[0215] - Detector: D / teX Ultra250

[0216] - Application Software: PDXL

[0217] - ICDD Database PDF-2

[0218] When analyzing WAXD, correction data that corrected polarization factor, absorption factor, and air scattering were used for the measured data. From the WAXD pattern derived from X-ray diffraction (XRD) analysis, deconvolution was performed by single line fitting using the Fundamental parameter (FP) approach of the fitting program (Bruker TOPAS), and the crystallized region peak and the amorphous region peak at 2θ values ​​of 0° to 50° were separated, and the area and area ratio of each peak were calculated (see Figs. 2 to 6). The crystallized area value (%) was calculated for the area of ​​each peak according to the following Equation 1.

[0219] [Formula 1]

[0220]

[0221] Fig. 1 shows X-ray diffraction (XRD) analysis of the recycled polyester (rPBT) resins manufactured in Example 1 and Comparative Examples 1, 2, 5, and 6. As shown in Fig. 1, the recycled polyester resin manufactured in Example 1 exhibited strong diffraction peaks due to crystals at angles (2θ, Braggs angles) of 9, 15.9, 17.2, 20.6, 23.4, and 25.1. These correspond to diffraction planes (001), (011), (010), (110), (100), and (111), and correspond to the α crystal form of PBT. However, the recycled polyester resins manufactured in Comparative Examples 2, 5, and 6 had low crystallinity because the positions of the peak angles corresponding to each diffraction plane shifted or the areas of the peaks decreased.

[0222]

[0223] Experimental Example 2-2: color-b and color-L

[0224] For the recycled polyester (rPBT) resins manufactured in Examples 1 to 3 and Comparative Examples 1 to 6, the color-b value and color-L value, which are color characteristics, were measured using a colorimeter.

[0225] Specifically, the recycled polyester resin was manufactured into a specimen with a width of 30 mm, a length of 30 mm, and a thickness of 6 mm using a hot press, and transmission data was obtained with Illuminant D65 at an observer angle of 2°, and this was processed using a color analysis device within the Grams / 32 software to measure the color-b value and color-L value of Hunter Lab.

[0226]

[0227] Experimental Example 2-3: Intrinsic Viscosity

[0228] The recycled polyester (rPBT) resins manufactured in Examples 1 to 3 and Comparative Examples 1 to 6 were dissolved in orthochlorophenol (OCP) at 150°C at a concentration of 0.12%, and then the intrinsic viscosity was measured using a Ubbelrod viscometer in a constant temperature bath at 35°C. Specifically, the temperature of the viscosity tube was maintained at 35°C, and the time it took for the solvent to pass through a specific internal section of the viscosity tube (efflux time) and the time it took for the solution to pass through were measured to obtain the specific viscosity, which was then used to calculate the intrinsic viscosity.

[0229]

[0230] Experimental Example 2-4: Tm and △Hm

[0231] For the recycled polyester (rPBT) resins manufactured in Examples 1 to 3 and Comparative Examples 1 to 6, the melting point (Tm) and melting enthalpy (△Hm) were calculated using a differential scanning calorimeter (DSC, TA Instruments).

[0232] Specifically, the above-mentioned recycled polyester resin was dried under reduced pressure at 50°C for 15 hours, melted at 260°C, rapidly cooled to 30°C, and measured by scanning at a heating rate of 10°C / min using a differential scanning calorimeter. At this time, the melting enthalpy can be measured by using the 1st scan or the 2nd scan using the differential scanning calorimeter, and in this experimental example, it was measured by using the 2nd scan.

[0233] In the heat flow curve obtained by scanning, the first endothermic temperature is the glass transition temperature (Tg), the exothermic temperature measured after the glass transition temperature (Tg) is the crystallization temperature (Tc), and the endothermic temperature measured after the crystallization temperature (Tc) is the melting point (Tm). In addition, the integral at the melting point (Tm) was calculated as the melting enthalpy (△Hm).

[0234]

[0235] Experimental Example 2-5: Heat Deflection Temperature (HDT)

[0236] For the recycled polyester (rPBT) resins manufactured in Examples 1 to 3 and Comparative Examples 1 to 6, specimens were prepared according to ASTM D648, and the heat distortion temperature was measured at a low load of 0.48 MPa using a 6M-2 model tester from Toyoseiki.

[0237]

[0238] Experimental Example 2-6: 1 H-NMR

[0239] The recycled polyester (rPBT) resins manufactured in Examples 1 to 3 and Comparative Examples 1 to 6 were each dissolved in CDCl3 solvent at a concentration of 3 mg / mL and then analyzed at 25°C using a nuclear magnetic resonance device (JEOL, 600 MHz FT-NMR). 1 H-NMR spectrum was obtained. 1 The total content (mol%) of ethylene glycol residues and diethylene glycol residues was calculated based on the total mole number of residues derived from all glycols (EG, DEG, TEG, BD, etc.) by analyzing the H-NMR spectrum.

[0240]

[0241]

[0242] As shown in Table 3 above, the recycled polyester resins of Examples 1 to 3 were manufactured using rDMT having excellent purity, crystallinity, and color characteristics, and thus had excellent crystallinity as well as characteristics such as color, melting point (Tm), melting enthalpy, and heat distortion temperature, such as color-b and color-L.

[0243] More specifically, the recycled polyester resins of Examples 1 to 3 had excellent crystallinity, with a difference in the crystallized area value according to Equation 1 of 5.8 or more when compared to Comparative Example 1 using commercially available dimethyl terephthalate rather than recycled dimethyl terephthalate, while satisfying a crystallized area value according to Equation 1 of 20% or more. In addition, the recycled polyester resins of Examples 1 to 3 had excellent purity and crystallinity, since the total content of ethylene glycol residues and diethylene glycol residues was 5 mol% or less based on the total molar number of all glycols and derivatives thereof.

[0244] In addition, the recycled polyester resins of Comparative Examples 2 to 4, which used rDMT having a purity of less than 90% as an acid component alone or together with rBHET, and Comparative Examples 5 to 6, which used rBHET alone, had crystallized area values ​​according to Equation 1 of 20% or less, which was lower in crystallinity than Comparative Example 1, which used commercially available dimethyl terephthalate rather than recycled dimethyl terephthalate. In addition, the recycled polyester resins of Comparative Examples 2 to 6 also had lower color characteristics such as color-b and color-L, and characteristics such as melting point (Tm), melting enthalpy, and heat distortion temperature.

Claims

Containing repeating units derived from glycol components and repeating units derived from recycled dimethyl terephthalate (rDMT), A recycled polyester resin having a crystallized area value of 20% or more calculated according to Equation 1 below for crystallized and non-crystallized regions obtained by separating crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis using an individual peak fitting method: [Formula 1] 　 In the first paragraph, A recycled polyester resin having a negative difference in crystallized area value according to the following formula 2: [Formula 2] Difference in crystallized area values ​​= Ca1- Ca2 In the above equation 2, Ca1 is a value excluding the unit from the crystallized area value calculated according to the above formula 1 for a polyester resin containing repeating units derived from dimethyl terephthalate, Ca2 is the unit-deducted value of the crystallized area calculated according to Equation 1 for a recycled polyester resin containing repeating units derived from recycled dimethyl terephthalate (rDMT). 　 In the second paragraph, A recycled polyester resin, wherein the difference in the crystallized area value according to the above formula 2 is -0.5 or less. 　 In the first paragraph, A recycled polyester resin having a total content (mol%) of ethylene glycol residues and diethylene glycol residues of 5 mol% or less based on the total mole number of residues of the glycol component. 　 In the first paragraph, The above recycled dimethyl terephthalate is, The purity is over 90%, Recycled polyester resin having an APHA color value of 120 or less. 　 In the first paragraph, The above-mentioned recycled dimethyl terephthalate is a recycled polyester resin manufactured by depolymerizing waste polyester. 　 In the first paragraph, The above-mentioned recycled dimethyl terephthalate is a recycled polyester resin manufactured by secondary depolymerization of recycled bis(2-hydroxyethyl) terephthalate (rBHET) manufactured by primary depolymerization of waste polyester. 　 In the first paragraph, The above recycled polyester resin is, The intrinsic viscosity at 35℃ is 0.5 dL / g to 1.5 dL / g, color-b is less than or equal to 12, Regenerated polyester resin with color-L of 70 or higher. 　 In the first paragraph, A recycled polyester resin having a melting point of 210°C or higher and a melting enthalpy (△Hm) of 38 J / g or higher as measured in a second scan using a differential scanning calorimeter. 　 In the first paragraph, A recycled polyester resin having a heat deflection temperature (HDT) of 90°C or higher, measured at a low load of 0.48 MPa according to ASTM D648. 　 A step of depolymerizing waste polyester to obtain a depolymerized composition; and A method for producing recycled dimethyl terephthalate, comprising a step of crystallizing the above-mentioned depolymerization composition. 　 In paragraph 11, The above crystallization step is, A method for producing regenerated dimethyl terephthalate, which is performed by cooling the above-mentioned depolymerization composition to 25°C to 60°C and stirring it at a low speed of 10 rpm to 30 rpm for 1 hour to 6 hours or leaving it alone. 　 In paragraph 11, A method for producing regenerated dimethyl terephthalate, further comprising at least one step selected from the group consisting of a solid-liquid separation step, a drying step, a washing step, and a purification step. 　 In paragraph 13, A method for producing regenerated dimethyl terephthalate, wherein after the crystallization step, the solid-liquid separation step, the drying step, the washing step, and the purification step are performed sequentially. 　 In paragraph 13, A method for producing regenerated dimethyl terephthalate, wherein the above purification step is performed by fractional distillation under conditions of a temperature of 170°C to 240°C and a reduced pressure of 100 torr or less. 　 In paragraph 11, In the above depolymerization step, an ethylene glycol derivative as a by-product is generated, A method for producing recycled dimethyl terephthalate, wherein the content of the ethylene glycol derivative is 5 wt% or less based on the total weight of the recycled dimethyl terephthalate. 　 In paragraph 11, In the above depolymerization step, by-products such as terephthalic acid and terephthalate derivatives are produced, The above terephthalate derivative does not contain dimethyl terephthalate, A method for producing recycled dimethyl terephthalate, wherein the content of the terephthalic acid and terephthalate derivatives is 10 wt% or less based on the total weight of the recycled dimethyl terephthalate. 　 A step of depolymerizing waste polyester to produce recycled dimethyl terephthalate (rDMT); A step of mixing the above rDMT with a glycol component and performing an esterification reaction to produce regenerated bis(4-hydroxybutyl)terephthalate (rBHBT); and It includes a step of manufacturing a regenerated polyester resin by subjecting the above rBHBT to a condensation polymerization reaction, The above-mentioned recycled polyester resin has a crystallized area value of 20% or more calculated according to the following equation 1 for the crystallized region and the non-crystallized region obtained by separating the crystal diffraction peaks appearing at 2θ values ​​of 0° to 50° during X-ray diffraction (XRD) analysis by individual peak fitting: [Formula 1] 　 In paragraph 18, A method for producing a regenerated polyester resin, wherein a glycol component or an acid component is additionally added in the esterification reaction step and / or the condensation polymerization reaction step. 　 In paragraph 19, The above glycol components are 1,3-propanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymer of ethylene oxide and tetrahydrofuran, ethylene oxide addition polypropylene glycol, polycarbonate diol, polyneopentyl glycol, Containing at least one selected from the group consisting of poly-3-methylpentanediol and poly-1,5-pentanediol, A method for producing a regenerated polyester resin, wherein the acid component comprises at least one selected from the group consisting of adipic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid.

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