Efficient recycling method for waste polyester fabrics

Abstract

To provide a chemical recycling method for waste PET fabrics, which effectively solves the problems of high cost and poor quality in the conventional technology.SOLUTION: The disclosure provides a chemical recycling method for polyester fabrics, which includes the following steps. The polyester fabric is subjected to extraction using a composite solvent and then filtration to obtain a decolored polyester fabric. The composite solvent contains alcohol ether and phenyl ether, and the decolored polyester fabric contains the composite solvent. Ethylene glycol is subsequently added to the decolored polyester fabric to depolymerize into ethylene terephthalate monomers.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an efficient recycling method for textiles, and particularly to an efficient chemical recycling method for waste polyester textiles.

Background Art

[0002] In conventional polyester textile recycling methods, in the pretreatment process, usually, first, the waste PET textile is decolorized to achieve a decolorization effect, a solvent is used to extract dyes, and then the decolorized PET textile is dried to remove the solvent. Then, the dried PET textile is chemically recycled. In the pretreatment process, the textile drying process requires heating to evaporate the solvent, and the evaporated solvent is concentrated and recovered. This process has drawbacks including (1) the residual solvent in the textile must be less than 1.0% to avoid affecting PET depolymerization, (2) drying requires equipment and energy consumption, and (3) the solvent recovery process causes solvent leakage.

[0003] After decolorization, the PET textile is depolymerized with EG (ethylene glycol) to obtain BHET monomer (bis(2-hydroxyethyl) terephthalate) products and purified to obtain clean BHET monomers, which is generally called the "BHET monomer chemical recycling process". In the conventional BHET monomer chemical recycling process, the depolymerization is carried out at 190°C to 240°C. The drawbacks of this process include (1) high temperature, (2) long depolymerization time, (3) low selectivity, and (4) yellowish hue of BHET.

[0004] Based on the above, the conventional pretreatment process and BHET monomer chemical recycling process have problems such as high cost and poor quality. Therefore, the development of an efficient recycling method for waste PET textiles to solve the problems of high cost and poor quality in the prior art is an important issue that currently requires research.

Summary of the Invention

[0005] The present invention provides a chemical recycling method for waste PET fabrics, which efficiently solves the problems of high cost and poor quality in the prior art. [Problem to be solved by the invention]

[0006] The chemical recycling method of polyester fabric according to the present invention includes: carrying out extraction of polyester fabric with a composite solvent, carrying out filtration to obtain a bleached polyester fabric, the composite solvent including alcohol ether and phenyl ether, and the bleached polyester fabric including the composite solvent, and then adding ethylene glycol to the bleached polyester fabric for depolymerization into ethylene terephthalate monomer.

[0007] In one embodiment of the invention, the alcohol ether comprises ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, or combinations thereof. The phenyl ether comprises anisole, phenethyl ether, phenyl propyl ether, phenyl butyl ether, methyl anisole, methyl phenethyl ether, methyl phenyl propyl ether, methyl phenyl butyl ether, or combinations thereof.

[0008] In one embodiment of the present invention, the weight ratio of the composite solvent to the polyester fabric is 3:10 to 10:10.

[0009] In one embodiment of the invention, the extraction is carried out at a temperature between 110°C and 150°C.

[0010] In one embodiment of the present invention, the extraction time ranges from 10 minutes to 60 minutes.

[0011] In one embodiment of the present invention, the extraction is carried out 2 to 6 times.

[0012] In one embodiment of the present invention, the weight ratio of alcohol ether to phenyl ether in the composite solvent is 1:9 to 9:1.

[0013] In one embodiment of the present invention, the weight ratio of ethylene glycol to the bleached polyester fabric is 2:1 to 6:1.

[0014] In one embodiment of the invention, the catalyst for depolymerization comprises an organometallic and an ionic liquid, where the organometallic comprises zinc acetate, organotitanium acetate, organoantimony acetate, or organoaluminum acetate.

[0015] In one embodiment of the present invention, the weight ratio of catalyst for depolymerization to bleached polyester fabric is 0.5:100 to 10:100.

[0016] In one embodiment of the present invention, the depolymerization temperature is 140°C to 190°C.

[0017] In one embodiment of the present invention, the depolymerization time is 1.5 hours to 5 hours.

[0018] In one embodiment of the invention, the ionic liquid comprises 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF4). Effect of the Invention

[0019] Based on the above, the present invention provides a chemical recycling method for polyester fabrics, in which a composite solvent (alcohol ether and phenyl ether) is used as a solvent for pretreatment of waste PET fabrics, and the composite solvent is used as a co-solvent for depolymerization in the BHET monomer chemical recycling process. The composite solvent has the functions of a solvent for pretreatment extraction and a co-solvent for depolymerization. Therefore, the problems of high cost and poor quality in the prior art can be effectively solved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, embodiments of the present invention will be described in detail, but these embodiments are merely examples and the present invention is not limited to these.

[0021] In this specification, ranges expressed as "one value to another value" are general expressions to avoid listing every value within the range in the specification. Thus, the recitation of a particular numerical range covers any value within that numerical range, and smaller ranges defined by any value within that numerical range, as well as the recitation of any numerical value and smaller numerical ranges herein.

[0022] The chemical recycling method of polyester fabric according to the present invention includes: extracting polyester fabric with a composite solvent and filtering to obtain a bleached polyester fabric; the composite solvent includes alcohol ether and phenyl ether, and the bleached polyester fabric includes the composite solvent; and then adding ethylene glycol to the bleached polyester fabric for depolymerization into ethylene terephthalate monomer.

[0023] In the present invention, a composite solvent is used for the extraction of polyester fabrics. The polyester fabric is, for example, a waste polyester fabric that may include waste clothing, scraps from textile factories, or defective products. The PET content of the waste polyester fabric is, for example, more than 90% by weight, and impurities such as dyes and adhesives are less than 10% by weight. The composite solvent includes an alcohol ether and a phenyl ether. The alcohol ether may include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, or a combination thereof. The phenyl ether includes anisole, phenethyl ether, phenylpropyl ether, phenylbutyl ether, methylanisole, methylphenethyl ether, methylphenylpropyl ether, methylbutyl ether, or a combination thereof, but the present invention is not limited thereto. More specifically, the weight ratio of the alcohol ether to the phenyl ether is, for example, 1:9 to 9:1, and preferably 2:8 to 8:2. The weight ratio of the composite solvent to the polyester fabric is, for example, 3:10 to 10:10, and preferably 4:10 to 9:10. In terms of the execution conditions of the extraction, the extraction temperature is, for example, 110°C to 150°C, and preferably 120°C to 140°C. The extraction time is, for example, 10 minutes to 60 minutes, and preferably 20 minutes to 40 minutes. The number of extractions is, for example, 2 to 6 times, and preferably 3 to 5 times.

[0024] In this embodiment, a polyester fabric is extracted using a composite solvent and filtered to obtain a decolorized polyester fabric. The decolorized polyester fabric contains the composite solvent. After decolorization, it is not necessary to dry the fabric, and it is subsequently depolymerized into crude ethylene terephthalate monomers with ethylene glycol. More specifically, the weight ratio of ethylene glycol to the decolorized polyester fabric is, for example, 2:1 to 6:1, and 3:1 to 4:1 is preferable. The depolymerization catalyst may contain an organometal and an ionic liquid. The organometal may contain zinc acetate, organic titanium, organic antimony, or organic aluminum. The ionic liquid may contain 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF4). In terms of the depolymerization execution conditions, the weight ratio of the depolymerization catalyst to the decolorized polyester fabric is, for example, 0.5:100 to 10:100, and 1:100 to 5:100 is preferable. The depolymerization temperature is, for example, 140°C to 190°C, and 150°C to 180°C is preferable. The depolymerization time is, for example, 1.5 hours to 5 hours, and 2 hours to 4 hours is preferable.

[0025] In this embodiment, the selectivity of the ethylene terephthalate monomer is, for example, 90% or more. The crude ethylene terephthalate monomer product undergoes purification procedures such as activated carbon adsorption of impurities, crystallization, filtration, and drying. Next, the purified ethylene terephthalate monomer is polymerized into r-PET. The quality of r-PET is L>62%, a±1.0, b±2.0.

[0026] The chemical recycling method of the polyester fabric according to the present invention will be described in detail below with experimental examples. However, the following experimental examples are not intended to limit the present invention. Experimental Example

[0027] To prove that the chemical recycling method of the polyester fabric according to the present invention achieves both separation and decolorization and effectively overcomes the problems of high cost and poor quality in the prior art, the following experimental examples are provided.

[0028] Example 1 103 g of waste PET fabric (L=22.5%, a=4.4, b=5.6) was obtained, of which impurities such as dyes accounted for 3 g and PET material accounted for 100 g.

[0029] (1) Pretreatment process: The waste PET fabric was placed in a 1L three-neck glass flask, 600g of composite solvent A (ethylene glycol ethyl ether / ethylene glycol butyl ether / propylene glycol methyl ether / anisole / methyl phenylene ether=2 / 1 / 3 / 2 / 2, weight ratio) was added, heated to 128°C and maintained at the temperature for 0.5 hours, then filtered with a suction flask to separate the fabric from composite solvent A. This was the first extraction procedure. The filtered wet base fabric (175g) contained 101g of fabric (including dyes, etc.) and 74g of composite solvent. The wet-based fabric was then returned to the three-neck glass flask, 526g of composite solvent was added, heated to 128℃ and maintained at the temperature for 0.5 hours, and then filtered to separate the fabric from the composite solvent, which was the second extraction procedure. The third extraction procedure was the same as the second extraction procedure. After the third extraction of the waste PET fabric, L=85.4%, a=1.7, b=2.3, the result was a wet-based decolorized fabric (174g, composite solvent / fabric=74 / 100). The composite solvent (alcohol ether+phenyl ether) was used as the co-solvent for PET depolymerization in the BHET monomer chemical recycling process. Therefore, drying was not required before entering the PET depolymerization process.

[0030] (2) BHET monomer chemical recycling process: The wet base fabric was placed in a three-neck glass flask, then 26g of composite solvent, 300g of ethylene glycol (EG), and 1g of zinc acetate as catalyst were added. After heating to 150℃ and maintaining for 2.5h, PET was depolymerized to crude BHET, with PET conversion=100%, selectivity to BHET monomer (m-BHET) of 90.4%, and selectivity to by-products such as BHET oligomers (dimers or trimers or higher, o-BHET) of 10.6%. The temperature of the crude was reduced from 150°C to 18°C ​​for crystallization of BHET monomer, then filtered through a 5μm filter to obtain wet-based BHET monomer filter cake, then the wet-based BHET filter cake was placed in a 1L three-neck glass flask, 518g of purified water was added, stirred and heated to 90°C for 0.5h, then filtered through a 1μm filter to remove BHET oligomers. 1g of powdered activated carbon was added to the 90°C filtrate to adsorb impurities, filtered through a 0.5μm filter, the filtrate was cooled from 90°C to 5°C for crystallization of BHET monomer, then filtered through a 1μm filter to obtain BHET monomer crystals, then dried with hot air at 70°C. The BHET moisture content is lower than 1% and easy to repolymerize.

[0031] (3) Repolymerization process: Polycondensation reaction of BHET was carried out to obtain r-PET with color quality L=66.4%, a=1.1, b=1.7.

[0032] When the composite solvent is used as the extraction solvent for pretreatment and the co-solvent for depolymerization, the fabric pretreatment process does not require drying, and there is no need to invest in drying equipment in the production line, saving energy consumption of 30-150 cal / g fabric. In the depolymerization unit, the depolymerization temperature can be lowered and the selectivity is high, so the production line has the advantages of low energy consumption and high productivity. In terms of quality, the recycled r-PET has the advantages of high selectivity and low color quality. Examples 2 to 6

[0033] After the pretreatment of the PET fabric, the formulation and dosage of the composite solvent, the type and amount of the depolymerization catalyst, the amount of depolymerization EG added, and the depolymerization temperature were changed (see Table 1). The rest were the same as in Example 1. The recycling rate and color quality of the r-PET are shown in Table 1.

[0034] The composite solvent formulation is as follows: In Example 2, composite solvent B was used: (ethylene glycol ethyl ether / ethylene glycol phenyl ether / propylene glycol methyl ether / anisole / methyl phenyl ether=1 / 2 / 3 / 2 / 2, weight ratio). In Example 3, composite solvent C was used: (ethylene glycol butyl ether / propylene glycol methyl ether / propylene glycol phenyl ether / phenylene ether / methyl anisole=3 / 2 / 1 / 2 / 2, weight ratio). In Example 4, composite solvent D was used: (ethylene glycol ethyl ether / propylene glycol ethyl ether / phenylene ether / methyl phenylene ether=3 / 3 / 2 / 2, weight ratio). In Example 5, composite solvent E was used: (ethylene glycol ethyl ether / ethylene glycol propyl ether / propylene glycol propyl ether / phenyl butyl ether / methyl phenyl propyl ether=2 / 1 / 3 / 2 / 2, weight ratio). Example 6 used composite solvent F: (ethylene glycol methyl ether / ethylene glycol ethyl ether / propylene glycol butyl ether / phenyl propyl ether / methyl phenyl butyl ether=2 / 1 / 3 / 2 / 2, weight ratio).

[0035] As shown in Table 1, Examples 1 to 6 using the chemical recycling method for polyester fabrics of the present invention have the advantages of high selectivity of BHET monomer (higher than 90.0%), L / a / b of recycled r-PET=62% or more / ±1.0 / ±2.0, and good color. In addition, the fabric pretreatment process does not require drying, so there is no need to invest in drying equipment in the production line, and no drying energy is consumed, which has the advantages of energy saving and cost reduction.

[0036] [Table 1] JPEG2025079766000002.jpg108166

[0037] Comparative Example 1 103 g of waste PET fabric (L=22.5%, a=4.4, b=5.6) was obtained, of which impurities such as dyes accounted for 3 g and PET material accounted for 100 g.

[0038] (1) Pretreatment process: The waste PET fabric was placed in a 1 L three-neck glass flask, poured with 600 g of o-xylene, heated to 128°C and maintained at that temperature for 0.5 h, then filtered with a suction flask to separate the fabric from the o-xylene. In the first extraction step, the filtered wet base fabric (164 g) contained 101 g of fabric (including dyes, etc.) and 63 g of o-xylene. The wet-based textile was returned to the three-necked glass flask, 537 g of o-xylene was added, heated to 128°C and maintained at this temperature for 0.5 hours, and then filtered to separate the textile from o-xylene, which was the second extraction procedure. The third extraction procedure was the same as the second extraction procedure. After the third extraction of the waste PET textile, L=86.1%, a=1.9, b=2.1, the wet-based decolorized textile (169 g, xylene / textile=69 / 100) was dried in a dryer, and the o-xylene of the textile was reduced to 0.5 g / 100 g textile, facilitating the subsequent chemical recycling process of BHET monomer. In the drying process, the wet-based decolorized textile was heated at 125°C. The o-xylene was evaporated by heat and separated from the textile. Then, the vaporized o-xylene was evaporated to recover 58.1 g of o-xylene. The o-xylene loss rate was 10.9 g / 100 g fabric.

[0039] (2) BHET monomer chemical recycling process: The dried fabric was placed in a three-neck glass flask, 400 g of ethylene glycol (EG) and 1 g of zinc acetate as catalyst were added, and the flask was heated to 195°C for 4 hours to depolymerize the PET to crude BHET monomer product with a conversion of PET=100%, a selectivity for BHET monomer (m-BHET) of 79.2%, and a selectivity for by-products such as BHET oligomers (dimers or trimers and higher, o-BHET) of 20.8%. The temperature of the crude was reduced from 195°C to 18°C ​​to crystallize the BHET monomer, then filtered through a 5μm filter to obtain a wet-based BHET monomer filter cake, then the wet-based BHET filter cake was placed in a 1L three-neck glass flask, 518g of pure water was added, stirred and heated to 90°C and maintained for 0.5 hours, then filtered through a 1μm filter to remove BHET oligomers, 1g of powdered activated carbon was added to the 90°C filtrate to adsorb impurities, filtered through a 0.5μm filter, then the filtrate was cooled from 90°C to 5°C to crystallize the BHET monomer, then filtered through a 1μm filter to obtain the BHET monomer crystals, then dried with hot air at 70°C. The BHET moisture content is lower than 1%, which makes it easy to repolymerize.

[0040] (3) Repolymerization process: Polycondensation reaction of BHET was carried out to obtain r-PET with color quality L=60.4%, a=1.9, b=3.7.

[0041] The results of the test using xylene as the extraction solvent for pretreatment and the co-solvent for depolymerization are shown in Table 2. The BHET monomer selectivity was low (79.2%), and the recycled r-PET had L / a / b=60.4% / 1.9 / 3.7 and poor color. In addition, the textile pretreatment process required drying, which required investment in drying equipment on the production line, used 55 cal / g textile, and the loss rate of recovered o-xylene=0.019 g / g textile.

[0042] The yield and color of r-PET in Comparative Examples 2 to 6 are shown in Table 2. The explanation is as follows:

[0043] Comparative Example 2 The fabric was not dried in the pretreatment step, otherwise it was the same as Comparative Example 1. The BHET monomer selectivity was low (76.4%), and the recycled r-PET had L / a / b=61.4% / 2.4 / 4.2 and poor color.

[0044] Comparative Example 3 The depolymerization temperature of the BHET monomer chemical recycling process was changed to 150°C, and the rest was the same as in Comparative Example 1. The BHET monomer selectivity was low (45.8%), and the recycled r-PET had L / a / b = 60.8% / 1.5 / 3.4, having the drawback of poor hue. In addition, the fabric pretreatment process required drying, and it was necessary to invest in drying equipment in the production line. 55 cal / g of fabric was used, and the loss rate of the recovered o-xylene was 0.019 g / g of fabric.

[0045] Comparative Example 4 EG in the BHET monomer chemical recycling process was reduced from 400 g to 300 g, and 100 g of anisole was added for depolymerization. The rest was the same as in Comparative Example 3. The selectivity of the BHET monomer was high (90.3%), and the recycled r-PET had L / a / b = 64.1% / 1.0 / 1.7. Although it had a good hue, the fabric pretreatment process required drying, and it was necessary to invest in drying equipment in the production line. It consumed 55 cal / g of fabric energy, and the loss rate of the recovered o-xylene was 0.019 g / g of fabric.

[0046] Comparative Example 5 The extraction solvent / fabric was 1,000 / 103 g, the extraction temperature was 140°C, the extraction time was 60 minutes, the number of extraction times was 6 times, the catalyst was 2 g, and the depolymerization temperature was 150°C. The rest was the same as in Comparative Example 3. The BHET monomer had a low selectivity (86.7%), and the recycled r-PET had L / a / b = 63.7% / 1.1 / 1.5, and the hue was good.

[0047] Comparative Example 6 Ethylene glycol was used instead of o-xylene as the extraction solvent, and 100 g of anisole was added during depolymerization. The rest was the same as in Comparative Example 2. The BHET monomer had a high selectivity (91.4%), but the recycled r-PET had L / a / b = 55.4% / 2.5 / 6.1, having the drawback of poor hue.

[0048]

Table 2

[0049] The chemical recycling method for polyester fabrics of the present invention mainly uses a composite solvent to extract dyes from waste PET fabrics to decolorize the fabrics. The decolorized PET fabrics contain the composite solvent. After the decolorization of the PET fabrics containing the composite solvent, ethylene glycol is directly added to depolymerize it into ethylene glycol terephthalate monomer. During the entire process, the PET fabrics do not need to be dried, and the depolymerization has the characteristics of low temperature and high BHET selectivity, and has the advantages of low process cost.

[0050] The composite solvent (alcohol ether and phenyl ether) of the present invention can effectively decolorize waste PET fabrics and accelerate the depolymerization of PET to BHET at the same time. The principle is that ether has affinity with PET structure. Moreover, alcohol ether is more compatible with EG segment monomer in PET structure, which gives them more advantage in decolorization and depolymerization function.

[0051] The waste PET fabric contains impurities such as dyes and surface treatment agents. In this embodiment, a composite solvent (alcohol ether and phenyl ether) is used to extract the dyes and other impurities to achieve the purification effect such as decolorization. The decolorized PET fabric does not need to be dried and is then depolymerized into BHET monomer with ethylene glycol. Compared with the prior art, the PET fabric does not need to be dried and has high depolymerization efficiency, high BHET selectivity, and low hue because the composite solvent plays the role of both extraction solvent and co-solvent for depolymerization. The composite solvent is a solvent for decolorization and depolymerization at the same time. The decolorized PET fabric containing the composite solvent is depolymerized into BHET monomer in the presence of EG and catalyst, which is beneficial for cost reduction and quality improvement. In addition, the composite solvent used in the present invention also has the advantage of being environmentally friendly.

[0052] In summary, the present invention provides a method for chemical recycling of polyester fabrics, in which a composite solvent (alcohol ether and phenyl ether) is used as a solvent for pretreatment of waste PET fabrics, and the composite solvent is used as a co-solvent for the depolymerization step of BHET monomer chemical recycling. The composite solvent has the functions of a solvent for pretreatment extraction and a co-solvent for depolymerization. In this way, after using the composite solvent to decolorize the waste PET fabrics, they can be directly put into the depolymerization step without drying, which reduces the cost. The composite solvent remaining in the PET fabrics is also a co-solvent for depolymerization. PET depolymerization in the presence of a co-solvent has the advantages of low-temperature depolymerization, high BHET selectivity, and good color. Therefore, the quality can be improved. [Industrial Applicability]

[0053] The chemical recycling method for polyester fabrics of the present invention can be applied to the polyester fabric recycling industry.

Claims

1. carrying out extraction of the polyester fabric with a composite solvent comprising an alcohol ether and a phenyl ether, and carrying out filtration to obtain a bleached polyester fabric, the bleached polyester fabric comprising the composite solvent; adding ethylene glycol to said bleached polyester fabric to depolymerize it into ethylene terephthalate monomer; Including, Chemical recycling methods for polyester fabrics.

2. the alcohol ether comprises ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, or a combination thereof; The phenyl ether comprises anisole, phenethyl ether, phenyl propyl ether, phenyl butyl ether, methyl anisole, methyl phenethyl ether, methyl phenyl propyl ether, methyl phenyl butyl ether, or a combination thereof; A method for chemically recycling the polyester fabric according to claim 1.

3. The weight ratio of the composite solvent to the polyester fabric is 3:10 to 10:10; A method for chemically recycling the polyester fabric according to claim 1.

4. The extraction is carried out at a temperature between 110°C and 150°C. A method for chemically recycling the polyester fabric according to claim 1.

5. The extraction time ranges from 10 minutes to 60 minutes. A method for chemically recycling the polyester fabric according to claim 1.

6. The extraction is carried out 2 to 6 times. A method for chemically recycling the polyester fabric according to claim 1.

7. In the composite solvent, the weight ratio of the alcohol ether to the phenyl ether is 1:9 to 9:1; A method for chemically recycling the polyester fabric according to claim 1.

8. the weight ratio of said ethylene glycol to said bleached polyester fabric is from 2:1 to 6:1; A method for chemically recycling the polyester fabric according to claim 1.

9. The catalyst for depolymerization comprises an organometallic and an ionic liquid, the organometallic comprising zinc acetate, organotitanium acetate, organoantimony acetate, or organoaluminum acetate; A method for chemically recycling the polyester fabric according to claim 1.

10. the weight ratio of the catalyst for depolymerization to the bleached polyester fabric is 0.5:100 to 10:100; A method for chemically recycling the polyester fabric according to claim 9.

11. The temperature of depolymerization is 140°C to 190°C. A method for chemically recycling the polyester fabric according to claim 1.

12. The depolymerization time is 1.5 hours to 5 hours. A method for chemically recycling the polyester fabric according to claim 1.

13. The ionic liquid includes 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF4). A method for chemically recycling the polyester fabric according to claim 9.

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