Polyester fabric recovery method

Abstract

The invention provides a polyester fabric recycling method. The polyester fabric recycling method comprises the following steps. A polyester fabric including polyethylene terephthalate and a dye is provided. The dye is removed from the polyester fabric through an extraction technology, and the extraction technology comprises the steps that ethylene glycol serves as an extraction solvent, the polyester fabric is soaked in the extraction solvent, and extraction is conducted at the temperature of 80 DEG C to 180 DEG C. A depolymerization process is performed comprising depolymerizing the extracted polyester fabric with a chemical depolymerization liquid to obtain a product comprising ethylene terephthalate (BHET), where the chemical depolymerization liquid is ethylene glycol. And performing a purification process to remove impurities from the product obtained by the depolymerization process to obtain purified ethylene glycol terephthalate. And carrying out a solvent recovery process, namely collecting waste liquid generated in the extraction process and the depolymerization process, and recovering ethylene glycol in the waste liquid through a distillation separation system.

Description

Technical Field

[0001] The present invention relates to a method for recycling fabrics, and in particular to a method for recycling polyester fabrics. Background Art

[0002] The recycling method of waste polyester fabric (PET fabric) is usually to depolymerize the polyester fabric with a chemical depolymerization liquid to obtain products including ethylene terephthalate (Bis (2-HydroxyEthyl Terephthalate, BHET), and then polymerize bis(2-HydroxyEthyl Terephthalate) to obtain recycled polyester fabric (r-PET). Waste polyester fabric is usually dyed and other treatments for use as clothing. In order to obtain high-quality recycled polyester fabric (r-PET) from these dyed waste polyester fabrics, impurities (such as dyes, etc.) in the polyester fabric must be removed before and / or after the depolymerization reaction to obtain purer bis(2-HydroxyEthyl Terephthalate), and then polymerized and regenerated. Therefore, how to recycle polyester fabric in an efficient way is an issue that needs to be improved. Summary of the invention

[0003] The invention is directed to a polyester fabric recycling method, which has a simplified process and can reduce production costs.

[0004] According to an embodiment of the present invention, a method for recycling polyester fabric includes the following steps. A polyester fabric is provided, which includes polyethylene terephthalate and a dye. An extraction process is performed to remove the dye from the polyester fabric, the extraction process includes using ethylene glycol as an extraction solvent, immersing the polyester fabric in the extraction solvent, and extracting at a temperature of 80°C to 180°C. A depolymerization process is performed, including depolymerizing the extracted polyester fabric using a chemical depolymerization liquid to obtain a product including ethylene terephthalate, wherein the chemical depolymerization liquid is ethylene glycol. A purification process is performed to remove impurities from the product obtained by the depolymerization process to obtain purified ethylene terephthalate. A solvent recovery process is performed, including concentrating the waste liquid generated by the extraction process and the depolymerization process, and recovering the ethylene glycol in the waste liquid through a distillation separation system.

[0005] In the polyester fabric recycling method according to an embodiment of the present invention, in the above extraction process, the polyester fabric is subjected to 1 to 10 extraction steps, and the polyester fabric is immersed in a new extraction solvent in each extraction step.

[0006] In the polyester fabric recycling method according to the embodiment of the present invention, the duration of each extraction step is between 20 minutes and 1 hour.

[0007] In the polyester fabric recycling method according to an embodiment of the present invention, in each of the extraction steps, the weight ratio of the extraction solvent to the polyester fabric is 5 to 10.

[0008] In the polyester fabric recycling method according to the embodiment of the present invention, the depolymerization process is performed at a temperature of 190°C to 240°C.

[0009] In the polyester fabric recycling method according to the embodiment of the present invention, the weight of the chemical depolymerization liquid accounts for 30 wt % to 80 wt % of the total weight of the chemical depolymerization liquid and the extracted polyester fabric.

[0010] In the polyester fabric recycling method according to the embodiment of the present invention, the depolymerization process is performed in an environment containing a catalyst, and the catalyst includes an organic metal or an ionic liquid.

[0011] In the polyester fabric recycling method according to an embodiment of the present invention, the weight of the catalyst accounts for 0.3 wt % to 8 wt % of the total weight of the chemical depolymerization liquid and the extracted polyester fabric.

[0012] In the polyester fabric recycling method according to the embodiment of the present invention, the depolymerization process lasts for 1 to 6 hours.

[0013] In the polyester fabric recycling method according to the embodiment of the present invention, in the above-mentioned solvent recovery process, the recovery rate of ethylene glycol is greater than 98% by weight.

[0014] Based on the above, the polyester fabric recycling method of the present invention can simplify the process and obtain r-PET with good color quality and yield by using ethylene glycol as the extraction solvent and chemical depolymerization liquid. In addition, the polyester fabric recycling method of the present invention can effectively use a single distillation separation system to recover the extraction solvent and the chemical depolymerization liquid, which can not only reduce the loss of solvent, but also reduce the cost of equipment and operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] none DETAILED DESCRIPTION

[0016] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are illustrative only, and the present invention is not limited thereto.

[0017] In this article, the range expressed by "a value to another value" is a summary expression method to avoid listing all the values ​​in the range one by one in the specification. Therefore, the description of a specific numerical range covers any value in the numerical range and a smaller numerical range defined by any value in the numerical range, just as the arbitrary value and the smaller numerical range are written in the description text of the specification.

[0018] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. The following embodiments will further explain the relevant technical content of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0019] The following is a detailed description of a polyester fabric recycling method according to an embodiment of the present invention.

[0020] First, a polyester fabric is provided, which includes polyethylene terephthalate (PET) and a dye. In some embodiments, the polyethylene terephthalate accounts for more than 80% by weight of the polyester fabric, but the present invention is not limited thereto. In some embodiments, the dye accounts for more than 0.1% by weight of the polyester fabric, but the present invention is not limited thereto.

[0021] Then, an extraction process is performed to remove the dye from the polyester fabric. The extraction process, for example, includes using ethylene glycol as an extraction solvent, immersing the polyester fabric in the extraction solvent, and performing the extraction at a temperature of 80° C. to 180° C.

[0022] In some embodiments, during the extraction process, the polyester fabric may be subjected to multiple extraction steps, for example, 1 to 10 times, 3 to 6 times or other suitable times, and the polyester fabric is immersed in a new extraction solvent in each extraction step.

[0023] In some embodiments, the duration of each extraction step is between 20 minutes and 1 hour, but the present invention is not limited thereto.

[0024] In some embodiments, in each extraction step, the weight ratio of the extraction solvent to the polyester fabric is 5 to 10, so that efficient extraction can be achieved while taking into account energy consumption and operating costs, but the present invention is not limited thereto.

[0025] Next, a depolymerization process is performed, which includes depolymerizing the extracted polyester fabric using a chemical depolymerization liquid to obtain a product including ethylene terephthalate (BHET), wherein the chemical depolymerization liquid is ethylene glycol. Since the extraction solvent and the chemical depolymerization liquid are the same, both are ethylene glycol, the polyester fabric after the extraction process in this embodiment can be directly subjected to the depolymerization process without having to undergo a drying process to remove the extraction solvent before the depolymerization process is performed, thereby simplifying the process steps and preventing the extraction solvent from being lost during the drying process.

[0026] In some embodiments, the products obtained from the depolymerization process also include oligomers.

[0027] In some embodiments, the chemical depolymerization liquid accounts for 30 wt % to 80 wt %, preferably 40 wt % to 70 wt %, of the total weight of the chemical depolymerization liquid and the extracted polyester fabric, but the present invention is not limited thereto.

[0028] In some embodiments, the depolymerization process is carried out in an environment containing a catalyst to increase the reaction rate. The catalyst may include an organic metal or an ionic liquid. The organic metal includes, for example, zinc acetate, organic titanium, organic antimony, organic aluminum or other suitable organic metals. The ionic liquid is, for example, at least one selected from the group consisting of 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6), 1-butyl-3-methylimidazolium tetrachlorozincate (BMI2ZnCl4), 1-butyl-3-methylimidazolium tetrachloroironate (BMI2FeCl4), 1-butyl-3-methylimidazolium tetrachlorocobaltate (BMI2CoCl4), and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF4), but the present invention is not limited thereto. In some embodiments, the ionic liquid may be grafted onto a granular substrate to facilitate recovery of the ionic liquid. The particulate substrate may include carbon, silicon, iron, nickel, cobalt or other suitable substrate.

[0029] In some embodiments, the catalyst accounts for 0.3 wt % to 8 wt % of the total weight of the chemical depolymerization solution and the extracted polyester fabric, preferably 1.0 wt % to 5.0 wt %, but the present invention is not limited thereto.

[0030] In some embodiments, the depolymerization process lasts from 1 hour to 6 hours, preferably from 2 hours to 4 hours, but the present invention is not limited thereto.

[0031] Afterwards, a purification process is performed to remove impurities from the product obtained by the depolymerization process to obtain purified ethylene terephthalate. For example, the purification process may include dissolving the product obtained by the depolymerization process in water, and then cooling the product to crystallize ethylene terephthalate and filtering the crystals.

[0032] In some embodiments, the purification process may further include using diatomaceous earth, activated carbon, acid clay, etc. to adsorb impurities in the product obtained from the depolymerization process.

[0033] In some embodiments, the purification process may further include drying the ethylene terephthalate obtained by filtration by hot air, microwave or infrared ray.

[0034] Then, the purified polyethylene terephthalate can be subjected to a polymerization process to form regenerated polyethylene terephthalate. The regenerated polyethylene terephthalate obtained by the recovery method of this embodiment has good hue quality, for example, an L value between 55 and 65, an a value between -1 and +1, and a b value between -5 and 5, but the present invention is not limited thereto. The above-mentioned L value, a value, and b value refer to the CIE Lab color space commonly used in the industry, where the L value represents brightness, the a value represents green-red value, and the b value represents blue-yellow value.

[0035] In some embodiments, the polymerized recycled polyethylene terephthalate can be pelletized by a single-screw pelletizer or a twin-screw pelletizer to form recycled polyester pellets.

[0036] In addition, a solvent recovery process can be performed after the extraction process and the depolymerization process. The solvent recovery process includes collecting the waste liquid generated by the extraction process and the depolymerization process, and recovering the ethylene glycol in the waste liquid through a distillation separation system. Since both the extraction solvent and the chemical depolymerization liquid use ethylene glycol, the ethylene glycol can be separated and recycled through a single distillation separation system without the need to distill the extraction solvent and the chemical depolymerization liquid separately. In this way, the equipment cost can be reduced and the operation procedures for solvent recovery can be reduced.

[0037] In some embodiments, in the solvent recovery process, the recovery rate of ethylene glycol is greater than 98% by weight, and the ethylene glycol can be effectively recovered and reused, thereby reducing the leakage rate of ethylene glycol (ie, the leakage rate of ethylene glycol is less than 2% by weight).

[0038] In some embodiments, the distillation separation system includes a dehydration tower and an ethylene glycol purification tower.

[0039] The following experimental examples are used to explain the polyester fabric recycling method of the present invention in detail. However, the following experimental examples are not intended to limit the present invention.

[0040] Example 1

[0041] 106 g of PET textile (including about 100.2 g of PET and about 5.8 g of impurities such as dyes) was placed in a 1 L beaker, and 500 g of ethylene glycol (EG) (extraction solvent) was added and the temperature was raised to 135° C. and maintained for 30 minutes for extraction. The liquid was then filtered out using a funnel with a pore size of 1 mm. The wet PET textile contained about 50 g of EG. The wet PET textile was placed in a 1 L beaker again, and 450 g of EG (extraction solvent) was added and the temperature was raised to 135° C. and maintained for 30 minutes, and the process was repeated twice. That is, the PET textile was subjected to a total of 4 extraction steps.

[0042] After 4 extractions, the wet PET textile weighs about 149.9 grams, including about 99.8 grams of PET textile, about 50 grams of EG and about 0.1 grams of impurities such as dyes. The wet PET textile is placed in a 1L reaction device (including a heating bag, stirring and condensing components), and 350 grams of EG (chemical depolymerization liquid) and 1 gram of zinc acetate (catalyst) are added. The temperature is raised to 198°C and maintained for 4 hours to perform a depolymerization process to depolymerize PET into a BHET crude product.

[0043] The crude BHET product was cooled to 15°C to crystallize BHET, and then filtered to obtain 200 g of BHET filter cake. 200 g of BHET filter cake was placed in a 1L beaker, 200 g of water was added, and the temperature was raised to 90°C to dissolve BHET, and then 5 g of activated carbon was added and stirred for 1 hour, and then impurities such as activated carbon were filtered out with a 0.1 μm filter paper, and then the filtrate was cooled from 90°C to 5°C to crystallize BHET, and then filtered with a 1 μm filter paper to obtain a BHET filter cake, and then dried at 75°C and 100 torr to obtain about 120 g of purified BHET.

[0044] 120 g of purified BHET was polymerized to obtain about 88.7 g of recycled PET (r-PET) and 31.3 g of EG and oligomers and other byproducts. The yield of r-PET = 88.7 g / 100.2 g = 88.5%, the color quality L = 60.4, a = 0.2, b = 1.2.

[0045] The waste liquid obtained from the extraction process and the depolymerization process was recovered by distillation, and the recovery rate of EG = 2,167 g / 2,200 g = 98.5%, with a total loss of about 33 g of EG.

[0046] Example 2 to Example 6

[0047] The process methods of Examples 2 to 6 are similar to those of Example 1, except that the process conditions of Examples 2 to 6 (including extraction temperature, extraction time, depolymerization temperature, and depolymerization time) are as shown in Table 1, and L, a, b and yield of r-PET obtained in Examples 2 to 6 and the total leakage rate of the extraction solvent and the chemical depolymerization liquid are recorded in Table 1.

[0048] Table 1

[0049]

[0050] Comparative Example 1

[0051] 106 grams of PET textile (including about 100.2 grams of PET and about 5.8 grams of impurities such as dyes) were placed in a 1L beaker, and 500 grams of xylene (extraction solvent) was added and the temperature was raised to 135°C and maintained for 30 minutes for extraction. Then the liquid was filtered out with a funnel with a pore size of 1 mm. The wet PET textile contained 50 grams of xylene, and the wet PET textile was placed in a 1L beaker again, 450 grams of xylene (extraction solvent) was added and the temperature was raised to 135°C and maintained for 30 minutes, and the process was repeated twice. That is, the PET textile was subjected to 4 extraction steps in total.

[0052] After four extractions, a total of about 149.5 grams of wet PET textile (including about 99.4 grams of PET textile, about 50 grams of xylene and about 0.1 grams of impurities such as dyes) must be dried (at 100 torr, 120°C) to remove xylene, and about 99.5 grams of dry PET textile (including about 99.2 grams of PET, 0.2 grams of xylene and 0.1 grams of impurities such as dyes) are obtained, and about 50 grams of xylene is collected by condensation at 5°C.

[0053] The above 99.5 g of dry PET textile was placed in a 1 L reaction device (including a heating bag, stirring and condensing components), and 400 g of EG (chemical depolymerization liquid) and 1 g of zinc acetate (catalyst) were added. The temperature was raised to 198° C. and maintained for 4 hours to perform a depolymerization reaction to depolymerize PET into a crude BHET product.

[0054] The crude BHET product was cooled to 15°C to crystallize BHET, and then 200 g of BHET filter cake was filtered out. 200 g of BHET filter cake was placed in a 1L beaker, 200 g of water was added, and the temperature was raised to 90°C to dissolve BHET, and then 5 g of activated carbon was added and stirred for 1 hour, and then impurities such as activated carbon were filtered out with 0.1 μm filter paper, and the filtrate was cooled from 90°C to 5°C to crystallize BHET, and then filtered with 1 μm filter paper to obtain BHET filter cake, and then dried at 75°C and 100 torr to obtain about 115.0 g of purified BHET.

[0055] 115.0 g of purified BHET was polymerized to obtain 86.3 g of recycled PET (r-PET) and 28.7 g of byproducts such as EG and oligomers. The yield of r-PET = 86.3 g / 100.2 g = 86.1%, the color quality L = 60.7, a = 0.1, b = 3.2.

[0056] Recovery of the extraction solvent: About 1,631 grams of the extraction solvent were recovered by distillation. Adding the 50 grams of extraction solvent collected by the aforementioned drying procedure, a total of 1,681 grams of xylene were collected, and the xylene yield = 1,681 / 1,850 = 90.9%. 169 grams of xylene solvent were lost, and the loss rate was 9.1%.

[0057] Recovery of chemical depolymerization liquid: 394 g of EG was recovered from the waste liquid of the depolymerization process by distillation, and the recovery rate of EG = 394 g / 400 g = 98.5%. 6 g of EG solvent was lost, and the loss rate was 1.5%.

[0058] The total loss of the extraction solvent and the chemical depolymerization liquid was 175 grams, and the total loss rate was 7.8%.

[0059] Comparative Examples 2 to 6

[0060] Comparative Examples 2 to 6 are similar to the process methods of Comparative Example 1, except that the process conditions of Comparative Examples 2 to 6 (including extraction solvent, extraction temperature, extraction time, depolymerization temperature, and depolymerization time) are shown in Table 2, and L, a, b and yield of r-PET obtained in Comparative Examples 2 to 6 and the leakage rates of the extraction solvent and the chemical depolymerization liquid are recorded in Table 2.

[0061] Table 2

[0062]

[0063] It can be seen from Table 1 and Table 2 that since the extraction solvent and the chemical depolymerization liquid of Examples 1 to 6 are both ethylene glycol, compared with Comparative Examples 1 to 6, the drying process of removing the extraction solvent before the depolymerization process can be omitted and r-PET with good color quality and yield can still be obtained. It can be seen that Examples 1 to 6 can simplify and improve the process, and can avoid the loss of the extraction solvent in the drying process. Therefore, the total loss rate of the extraction solvent and the chemical depolymerization liquid of Examples 1 to 6 is much lower than that of Comparative Examples 1 to 6.

[0064] In addition, the extraction solvent and the chemical depolymerization liquid of Examples 1 to 6 can be recovered in a single distillation separation system. Compared with Comparative Example 2 which requires at least two distillation separation systems to recover the extraction solvent and the chemical depolymerization liquid respectively, Examples 1 to 6 can reduce equipment costs and operating costs and simplify the recovery process.

[0065] In summary, the polyester fabric recycling method of the present invention can simplify the process and obtain r-PET with good color quality and yield by using ethylene glycol as the extraction solvent and chemical depolymerization liquid. In addition, the polyester fabric recycling method of the present invention can effectively utilize a single distillation separation system to recover the extraction solvent and the chemical depolymerization liquid, which can not only reduce the loss of solvent, but also reduce the cost of equipment and operation.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling polyester fabric, characterized in that: include: Providing a polyester fabric, the polyester fabric comprising polyethylene terephthalate and a dye; Performing an extraction process to remove the dye from the polyester fabric, the extraction process comprising using ethylene glycol as an extraction solvent, immersing the polyester fabric in the extraction solvent, and performing extraction at a temperature of 80° C. to 180° C.; Performing a depolymerization process, including depolymerizing the extracted polyester fabric using a chemical depolymerization liquid to obtain a product including ethylene terephthalate, wherein the chemical depolymerization liquid is ethylene glycol; Performing a purification process to remove impurities from the product obtained by the depolymerization process to obtain purified ethylene terephthalate; and The solvent recovery process includes collecting the waste liquid generated by the extraction process and the depolymerization process, and recovering the ethylene glycol in the waste liquid through a distillation separation system.

2. The method for recycling polyester fabric according to claim 1, characterized in that: In the extraction process, the polyester fabric is subjected to 1 to 10 extraction steps, and the polyester fabric is immersed in a new extraction solvent in each extraction step.

3. The method for recycling polyester fabric according to claim 2, characterized in that: Each extraction step lasts between 20 minutes and 1 hour.

4. The method for recycling polyester fabric according to claim 2, characterized in that: In each extraction step, the weight ratio of the extraction solvent to the polyester fabric is 5 to 10.

5. The method for recycling polyester fabric according to claim 1, characterized in that: The depolymerization process is carried out at a temperature of 190°C to 240°C.

6. The method for recycling polyester fabric according to claim 1, characterized in that: The weight of the chemical depolymerization liquid accounts for 30 wt % to 80 wt % of the total weight of the chemical depolymerization liquid and the extracted polyester fabric.

7. The method for recycling polyester fabric according to claim 1, characterized in that: The depolymerization process is carried out in an environment containing a catalyst, and the catalyst includes an organic metal or an ionic liquid.

8. The method for recycling polyester fabric according to claim 7, characterized in that: The weight of the catalyst accounts for 0.3 wt % to 8 wt % of the total weight of the chemical depolymerization liquid and the extracted polyester fabric.

9. The method for recycling polyester fabric according to claim 1, characterized in that: The depolymerization process takes between 1 hour and 6 hours.

10. The method for recycling polyester fabric according to claim 1, characterized in that: In the solvent recovery process, the recovery rate of ethylene glycol is greater than 98 weight %.

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