How to recycle polyester fabrics

Abstract

This invention provides a method for recycling polyester fabrics that can improve the uniformity of the intrinsic viscosity of recycled polyester. [Solution] A decolorized polyester fabric is subjected to a decolorization treatment to form a decolorized polyester fabric. The decolorized polyester fabric is mixed with a thickening agent to form an initial supply material. Liquid polymerization is performed on the initial supply material to form a liquid polymerization product. The liquid polymerization product is refluxed and mixed with the initial supply material to form an intermediate supply material. Liquid polymerization is performed on the intermediate supply material to form a final polymerization product.

Description

Technical Field

[0001] The present invention relates to a method for recycling textiles, and particularly to a method for recycling polyester textiles.

Background Art

[0002] Conventional physical (mechanical) recycling methods for waste polyester (e.g., polyethylene terephthalate (PET)) textiles improve their intrinsic viscosity (IV) by mixing with PET bottle flakes, facilitating subsequent spinning processes.

Summary of the Invention

Problems to be Solved by the Invention

[0003] If the difference in IV between recycled textiles and PET bottle flakes is too large, even when mixed in a mixer and an extruder, only macroscopic mixing occurs, and the microscopic uniformity is not good. Also, both the textile and PET bottle flakes that have undergone a heat history have a reduced IV, resulting in poor IV stability (excessive variation) of the mechanical recycling pellets of PET textiles, making it impossible to effectively control the IV quality and deteriorating subsequent spinning processability. For example, the strength of the yarn is insufficient, making yarn breakage more likely to occur.

Means for Solving the Problems

[0004] The present invention provides a method for recycling polyester textiles that can improve the uniformity of the intrinsic viscosity of recycled polyester.

[0005] The present invention provides a method for recycling polyester fabrics, comprising the following steps: A polyester fabric is decolorized to form a decolorized polyester fabric. The decolorized polyester fabric is mixed with a thickening agent to form an initial feed material. Liquid polymerization is performed on the initial feed material to form a liquid polymerization product. The liquid polymerization product is refluxed and mixed with the initial feed material to form an intermediate feed material. Liquid polymerization is performed on the intermediate feed material to form a final polymerization product.

[0006] In one embodiment of the present invention, the weight ratio of the decolorized polyester fabric to the thickening material described above is 5:95 to 80:20.

[0007] In one embodiment of the present invention, the liquid polymerization temperature is 210°C to 290°C, and the liquid polymerization pressure is 0.1 torr to 5.0 torr.

[0008] In one embodiment of the present invention, the residence time for the liquid polymerization of the decolorized polyester fabric and the thickening material described above is approximately 5 minutes to 200 minutes.

[0009] In one embodiment of the present invention, the intrinsic viscosity of the final polymerization product described above is 0.60 or higher.

[0010] In one embodiment of the present invention, the standard deviation of the intrinsic viscosity of the final polymerization product described above is less than 0.0036.

[0011] In one embodiment of the present invention, the L value of the final polymerization product described above is 70 or greater in the CIELAB color space, the a value is between -3.0 and +3.0, and the b value is between -10.0 and +10.0.

[0012] In one embodiment of the present invention, the weight ratio of the reflux rate of the liquid polymerization product described above to the amount of initial supply material supplied is 5:1 to 50:1.

[0013] In one embodiment of the present invention, the amount of the initial supply material described above is equal to the amount of the final polymerization product discharged.

[0014] In one embodiment of the present invention, the polyester fabric described above includes raw fabric, dyed fabric containing a dye, or fabric containing a surface treatment agent.

[0015] In one embodiment of the present invention, the intrinsic viscosity (IV) of the polyester fabric described above is 0.50 to 0.70.

[0016] In one embodiment of the present invention, the intrinsic viscosity of the decolorized polyester fabric described above is 0.45 to 0.65.

[0017] In one embodiment of the present invention, the L value of the decolorized polyester fabric described above is 85 or higher in the CIELAB color space, the a value is between -5.0 and +5.0, and the b value is between -15.0 and +15.0.

[0018] In one embodiment of the present invention, the decolorization treatment described above is carried out using a solvent extraction method or an aqueous solution extraction method.

[0019] In one embodiment of the present invention, the thickening material described above is PET bottle flakes, and the intrinsic viscosity of the PET bottle flakes is 0.75 to 0.95.

[0020] In one embodiment of the present invention, the thickening material described above is PET bottle flakes, wherein the L value of the PET bottle flakes as defined in the CIELAB color space is 80 or higher, the a value is between -2.0 and +2.0, and the b value is between -4.0 and +4.0. [Effects of the Invention]

[0021] As described above, the polyester fabric recycling method of the present invention involves refluxing the liquid polymerization product multiple times to repeatedly perform liquid polymerization. This not only improves the IV (intermediate temperature) and increases the uniformity of the IV, but also improves the hue expression of the final polymerization product. [Brief explanation of the drawing]

[0022] [Figure 1] It is a schematic flowchart of a method for recycling a polyester fabric according to one embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view of a liquid polymerization unit according to one embodiment of the present invention.

Mode for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are exemplary, and the disclosure of the present invention is not limited thereto.

[0024] In the present specification, a range indicated by "from one numerical value to another numerical value" is a schematic expression method for avoiding listing each numerical value within the range one by one in the specification. Therefore, the description of a specific numerical range includes any numerical value within the numerical range and a smaller numerical range defined by any numerical value within the numerical range, which is the same as if the any numerical value and the smaller numerical range are explicitly described in the specification.

[0025] FIG. 1 is a schematic flowchart of a method 100 for recycling a polyester fabric according to one embodiment of the present invention.

[0026] Referring to Figure 1, in step S1, the decolorized polyester fabric and the thickening material are first mixed, and the thickening material is dispersed almost uniformly in the decolorized polyester fabric to form the initial feed material. The weight ratio of the decolorized polyester fabric to the thickening material may be in the range of 5:95 to 80:20. For example, the weight ratio of the decolorized polyester fabric to the thickening material may be 1:4, 1:2, or 1:1. The decolorized polyester fabric may be a decolorized waste polyester fabric. For example, the waste polyester fabric is a waste PET fabric, and the decolorized waste polyester fabric is a decolorized PET fabric, but the polyester of the present invention is not limited to PET. In some embodiments, the waste PET fabric includes raw fabric, dyed fabric containing dyes, or fabric containing surface treatment agents. In some embodiments, the surface treatment agent included in the waste PET fabric includes polyurethane (PU), acrylic, thermoplastic polyester elastomer (TPEE), or a combination thereof.

[0027] In some embodiments, the intrinsic viscosity (IV) of the waste PET fabric is approximately 0.50 to 0.70. In some embodiments, due to the thermal history of the decolorization treatment, the intrinsic viscosity of the decolorized PET fabric is approximately 0.45 to 0.65. In some embodiments, the decolorized PET fabric has a hue (defined in the CIELAB color space) with an L value of 85 or higher, an a value of -5.0 to +5.0, and a b value of -15.0 to +15.0.

[0028] Decolorization treatment achieves a decolorizing effect by removing impurities such as dyes from waste polyester fabrics. Decolorization treatment can be carried out using solvent extraction or aqueous solution extraction, achieving the decolorizing effect by extracting dyes or destroying colored functional groups using solvents and aqueous solutions, respectively.

[0029] The solvents used in solvent extraction methods may include aromatic hydrocarbon solvents, alcohol ether solvents, benzyl alcohol solvents, alcohol solvents, or amide solvents. In some embodiments, aromatic hydrocarbon solvents include benzene, toluene, or xylene. In some embodiments, alcohol ether solvents include propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, or benzyl ether. In some embodiments, alcohol solvents include ethylene glycol, butanol, pentanol, or hexanol. In some embodiments, amide solvents include dimethylformamide, dimethylacetamide, or N-methylpyrrolidone. In some embodiments, the solvents mentioned above include propylene glycol monomethyl ether, benzyl ether, dimethylacetamide, dimethylformamide, ethylene glycol, N-methylpyrrolidone, or combinations thereof.

[0030] The aqueous solution used in the aqueous solution extraction method may contain alkalis, surfactants, reducing agents, oxidizing agents, or combinations thereof. In some embodiments, the aqueous solution used in the aqueous solution extraction method may contain sodium hydroxide, sodium hypochlorite, calcium hypochlorite, sodium thiosulfate, sodium hydrosulfite, thiourea dioxide, or combinations thereof.

[0031] The thickening material may be a material having a higher intrinsic viscosity than the decolorized polyester fabric. For example, the thickening material is PET bottle flakes, but the present invention is not limited thereto. In some embodiments, the intrinsic viscosity of the PET bottle flakes is about 0.75 to 0.95. In some embodiments, the PET bottle flakes have a hue with an L value of about 80 or more, an a value of about -2.0 to +2.0, and a b value of about -4.0 to +4.0.

[0032] Next, in step S2, the mixed decolorized polyester fabric and thickening material (i.e., initial feed material) are placed in an extruder and extruded to produce a molten mixture of the decolorized polyester fabric and thickening material. The extruder may be equipped with a single-screw or twin-screw, and the extrusion may be carried out at a temperature higher than room temperature. In some embodiments, the extrusion temperature is 210°C to 290°C, for example, 220°C to 250°C, 250°C to 280°C, or 240°C to 270°C. In some embodiments, the extrusion time is 0.3 minutes to 30 minutes, for example, 1 minute to 10 minutes, 10 minutes to 20 minutes, or 15 minutes to 25 minutes.

[0033] Next, in step S3, the molten mixture of the decolorized polyester fabric and the thickening material is filtered while maintaining it at the extrusion temperature, and further impurities are filtered out to produce a filtered molten mixture. The molten mixture of the decolorized polyester fabric and the thickening material can be filtered through a sieve. In some embodiments, the sieve has a mesh size of 30 μm to 120 μm (e.g., 40 μm to 100 μm or 50 μm to 80 μm), but the present invention is not limited thereto.

[0034] Next, in step S4, the filtered molten mixture is placed in a liquid polymerization unit and liquid polymerization is carried out to form a liquid polymerization product. Figure 2 is a schematic cross-sectional view of a liquid polymerization unit 200 according to one embodiment of the present invention. The liquid polymerization unit 200 may include a supply line 210, a static mixer 220, a liquid polymerization tank 230, a reflux line 240, and a discharge line 250. The supply line 210 may be connected to the inlet of the static mixer 220. The outlet of the static mixer 220 may be connected to the inlet of the liquid polymerization tank 230. The outlet of the liquid polymerization tank 230 may be connected to the input end of the reflux line 240 and the discharge line 250, and the output end of the reflux line 240 may be connected to the inlet of the static mixer 220.

[0035] The liquid polymerization unit 200 may further include a plurality of valves V1, V2, and V3. For example, valve V1 may be installed in the supply pipeline 210, valve V2 in the return pipeline 240, and valve V3 in the discharge pipeline 250, and each valve may be used to control the flow rate in each pipeline.

[0036] The filtered molten mixture can enter the liquid polymerization unit 200 via the supply pipeline 210. Next, the filtered molten mixture enters the static mixer 220 from the supply pipeline 210 for static mixing. Next, the filtered molten mixture leaves the static mixer 220 and enters the liquid polymerization tank 230 for liquid polymerization to form a liquid polymerization product. Next, the liquid polymerization product leaves the liquid polymerization tank 230 and is refluxed back to the static mixer 220 via the reflux pipeline 240, where it can be mixed with other filtered molten mixtures or liquid polymerization products to form an intermediate feed material. Alternatively, the liquid polymerization product can leave the liquid polymerization unit 200 via the discharge pipeline 250 as the final polymerization product. The weight ratio of the reflux rate of the liquid polymerization product to the static mixer 220 and the amount of filtered molten mixture supplied to the static mixer 220 may be 5:1 to 50:1, or for example, 10:1 to 40:1 or 20:1 to 30:1. The reflux mechanism via the reflux pipe 240 allows the liquid polymerization product to be refluxed to the static mixer 220 multiple times, mixed with other filtered molten mixtures or liquid polymerization products, and then fed into the liquid polymerization tank 230 multiple times for liquid polymerization. This allows for microscopically uniform mixing of the decolorized polyester fabric and the thickening material, resulting in a stable and uniform (small variation) final polymerization product IV, thereby improving the processability and quality of subsequent spinning.

[0037] The liquid polymerization tank 230 may include a sprayer 232, a retention tank 234, and a reflux pipe 236. The sprayer 232 may have a pore size of 0.01 mm to 10 mm (e.g., 0.05 mm to 5.0 mm). The filtered molten mixture and liquid polymerization product can be sprayed more uniformly into the retention tank 234 of the liquid polymerization tank 230 via the sprayer 232, and after liquid polymerization has taken place in the retention tank 234, it can be discharged through the reflux pipe 236 into the reflux pipeline 240 and the discharge pipeline 250.

[0038] During the operation of the liquid polymerization unit 200, the liquid polymerization unit 200 can be maintained at a temperature between 210°C and 290°C (e.g., 220°C to 280°C), and the liquid polymerization tank 230 can be maintained at a pressure between 0.1 torr and 5.0 torr (e.g., 0.2 torr to 3.0 torr). In some embodiments, the residence time for liquid polymerization of the decolorized polyester fabric and the thickening material is approximately 5 minutes to 200 minutes (e.g., 10 minutes to 100 minutes). In some embodiments, during the operation of the liquid polymerization unit 200, the filtered molten mixture can be continuously supplied to the liquid polymerization unit 200, and the final polymerization product can be continuously discharged from the liquid polymerization unit 200. In some embodiments, the supply rate of the filtered molten mixture is approximately equal to the discharge rate of the final polymerization product.

[0039] Next, in step S5, the final polymerization product can be cooled after being removed from the liquid polymerization unit 200. Then, in step S6, the cooled final polymerization product can be granulated to produce mechanically recycled polyester fabric pellets that can be used in subsequent applications. In some embodiments, the IV of the mechanically recycled polyester fabric pellets is 0.60 or greater, the IV standard deviation is less than 0.0036, the L value is 70 or greater, the a value is -3.0 to +3.0, and the b value is -10.0 to +10.0. The mechanically recycled polyester fabric pellets can be reused in spun, woven, and dyed and finished fabrics, thereby forming a waste fabric recycling system.

[0040] The following describes in detail, with reference to embodiments, the method for recycling the polyester fabric described above as proposed by the present invention. However, the following embodiments are not intended to limit the present invention.

[0041] <Preparation of solvent-decolorized PET fabric using solvent extraction method>

[0042] 108.7 kg of waste PET fabric was obtained, with an intrinsic viscosity of approximately 0.55, an L value of approximately 22.4, an a value of approximately 2.7, and a b value of approximately 2.8. Here, dye accounted for 8.7 kg and PET accounted for 100 kg. Next, this was cut into 3 cm squares, and then 1 m 3 The fabric was placed in a stirring tank. Next, 600 kg of dimethylacetamide (DMAc) was poured into the stirring tank, heated to 130°C, stirred for 30 minutes, and then filtered through a 1 cm filter to separate the DMAc. Next, the fabric was returned to the stirring tank, 500 kg of DMAc was poured in, heated to 130°C, stirred for 30 minutes, and then filtered again to separate the DMAc. This operation was repeated four times. Next, the fabric was dried in an oven at 120°C and 5 torr for 6 hours. After drying, the weight of the decolorized PET fabric was 96.2 kg, the intrinsic viscosity was approximately 0.48, the L value was approximately 90.1, the a value was approximately 0.9, and the b value was approximately 3.2. Using this method, 962 kg of solvent-decolorized PET fabric was produced.

[0043] <Preparation of aqueous solution-decolorized PET fabric using aqueous solution extraction method>

[0044] 108.7 kg of waste PET fabric was obtained, with an intrinsic viscosity of approximately 0.55, an L value of approximately 22.4, an a value of approximately 2.7, and a b value of approximately 2.8. Here, dye accounted for 8.7 kg and PET accounted for 100 kg. Next, this was cut into 3 cm squares, and then 2 m 3The material was placed in a stirring tank. Next, 1,000 kg of water, 5 kg of NaOH, and 3 kg of sodium thiosulfate were added to the stirring tank, and the mixture was heated to 137°C. The temperature was maintained for 30 minutes, and the tank body was maintained at a pressure of 5 bar with nitrogen gas. After that, the water was drained, and this operation was repeated once. Subsequently, 1,000 kg of water and 3 kg of calcium hypochlorite were added, and the mixture was heated to 137°C. The temperature was maintained for 30 minutes, and the tank body was maintained at a pressure of 5 bar with nitrogen gas. After that, the water was drained. Next, the fabric was dried in an oven at 120°C and 5 torr for 6 hours. The weight of the decolorized PET fabric after drying was 97.8 kg, the intrinsic viscosity was approximately 0.50, the L value was approximately 89.0, the a value was approximately 1.2, and the b value was approximately 8.4. Using this method, 978 kg of aqueous solution decolorized PET fabric was produced.

[0045] <PET bottle flakes>

[0046] Used PET bottles were obtained, the caps and labels were removed, and then they were crushed into 3 cm squares. After that, they were washed with an aqueous solution containing a surfactant, and finally washed with clean water. Finally, they were placed in an oven and dried at 105°C for 6 hours. The resulting PET bottle flakes had an intrinsic viscosity of approximately 0.81, an L value of approximately 85, an a value of approximately 0.7, and a b value of approximately 1.4.

[0047] Example 1

[0048] Referring to Figures 1 and 2 simultaneously, 200 kg of solvent-decolorized PET fabric and 800 kg of PET bottle flakes were mixed to form the initial feed material, which was then supplied to a twin-screw extruder at a flow rate of 6 kg / min. The extruder temperature was 260°C. The extruded molten PET was then filtered through a 60 μm mesh, and the filtered molten PET was placed in a liquid polymerization unit 200 to undergo liquid polymerization, forming a liquid polymerization product, such as liquid polymerized PET.

[0049] To explain in more detail, the filtered molten PET (supply rate: approximately 6 kg / min) was placed in a static mixer 220, and then mixed with liquid polymerized PET that was refluxed back into the static mixer 220 via a reflux pipe 240 (reflux rate: approximately 60 kg / min). After mixing the two fluids, the filtered molten PET and the liquid polymerized PET, in the static mixer 220, the mixture was sprayed into the retention tank 234 using a sprayer 232 with a pore size of 1.0 mm. The temperature in the retention tank 234 was 265°C and the pressure was 0.5 torr. The weight of the filtered molten PET and liquid polymerized PET retained in the retention tank 234 was approximately 150 kg. After multiple reflux and liquid polymerization cycles, the final polymerization product was discharged from the liquid polymerization tank 230 at a rate of 6 kg / min. The residence time of the filtered molten PET in the retention tank 234 was approximately 25 minutes. Subsequently, the final polymerization product was cooled and solidified to produce recycled PET pellets, and the quality of the recycled PET pellets was analyzed. The measured quality analysis results for the recycled PET pellets showed an IV of approximately 0.65, an IV standard deviation of approximately 0.0020, an L value of approximately 78, an a value of approximately 0.9, and a b value of approximately 2.8. This indicates that the IV was effectively improved, the IV distribution was highly stable, and the color was good.

[0050] Example 2

[0051] PET recycled pellets were produced using almost the same method as in Example 1, except that the main difference was the change in the supply amounts and reflux rates of the solvent-decolorized PET fabric and PET bottle flakes. The quality analysis results of the PET recycled pellets of Example 2, which were measured, are shown in Table 1.

[0052] Example 3

[0053] PET recycled pellets were produced using almost the same method as in Example 1, but the main differences were the changes in the supply amounts of solvent-decolorized PET fabric and PET bottle flakes, the reflux rate, the liquid polymerization temperature, and the liquid polymerization pressure. The quality analysis results of the PET recycled pellets of Example 3 are shown in Table 1.

[0054] Examples 4-6

[0055] Examples 4-6 were manufactured using almost the same method as Examples 1-3, except that aqueous solution decolorized PET fabric was used instead of solvent decolorized PET fabric. The quality analysis results for the measured PET recycled pellets of Examples 4-6 are shown in Table 1.

[0056] The manufacturing methods and measurement results for Examples 1 to 6 described above are summarized in Table 1 below.

[0057] [Table 1]

[0058] Comparative Example 1

[0059] PET recycled pellets were manufactured using almost the same method as in Example 1, but the main difference is that the liquid polymerization unit 200 is not equipped with a static mixer 220 and a reflux pipeline 240. In other words, the filtered molten PET in the supply pipeline 210 enters the liquid polymerization tank 230 directly and undergoes liquid polymerization, and the liquid polymerized PET that flows out of the liquid polymerization tank 230 leaves the liquid polymerization unit 200 directly through the discharge pipeline 250 and does not reflux back into the liquid polymerization tank 230 for further liquid polymerization, so the weight ratio of reflux flow rate to supply amount is 0.

[0060] Comparative Example 2

[0061] PET recycled pellets were produced using almost the same method as in Example 2, but the main difference is that the liquid polymerization unit 200 is not equipped with a static mixer 220 and a reflux pipeline 240. In other words, the filtered molten PET in the supply pipeline 210 enters the liquid polymerization tank 230 directly for liquid polymerization, and the reflux flow rate / supply weight ratio is 0.

[0062] Comparative Example 3

[0063] PET recycled pellets were produced using almost the same method as in Example 3, except that the static mixer 220 was not installed in the liquid polymerization unit 200, and the weight ratio of reflux rate / supply rate was 1.0.

[0064] Comparative Example 4

[0065] PET recycled pellets were produced using almost the same method as in Example 4, but the main difference is that the liquid polymerization unit 200 is not equipped with a static mixer 220 and a reflux pipeline 240. In other words, the filtered molten PET in the supply pipeline 210 enters the liquid polymerization tank 230 directly for liquid polymerization, and the reflux flow rate / supply weight ratio is 0.

[0066] Comparative Example 5

[0067] PET recycled pellets were produced using almost the same method as in Example 5, but the main difference is that the liquid polymerization unit 200 is not equipped with a static mixer 220 and a reflux pipeline 240. In other words, the filtered molten PET in the supply pipeline 210 enters the liquid polymerization tank 230 directly for liquid polymerization, and the reflux flow rate / supply weight ratio is 0.

[0068] Comparative Example 6

[0069] PET recycled pellets were produced using almost the same method as in Example 6, except that the static mixer 220 was not installed in the liquid polymerization unit 200, and the weight ratio of reflux rate / supply rate was 1.0.

[0070] The preparation methods and measurement results for Comparative Examples 1 to 6 described above are summarized in Table 2 below.

[0071] [Table 2]

[0072] As can be seen from the quality analysis results in Table 1, the standard deviation of IV for the PET recycled pellets in Examples 1 to 6 is all less than 0.0036, indicating high IV stability and the ability to achieve an IV of 0.60 or higher. Furthermore, the L values ​​for Examples 1 to 6 are all greater than 70, the a values ​​are all less than 2.5, and the b values ​​are all less than 8.5, indicating good hue.

[0073] As can be seen from the quality analysis results in Table 2, the standard deviation of IV for the PET recycled pellets of Comparative Examples 1 to 6 is all greater than 0.004, indicating that the IV distribution could not be stabilized and that IV could not be effectively controlled. Furthermore, the L values ​​of Examples 1 to 6 are all greater than the L values ​​of Comparative Examples 1 to 6, the a values ​​of Examples 1 to 6 are all smaller than the a values ​​of Comparative Examples 1 to 6, and the b values ​​of Examples 1 to 6 are all smaller than the b values ​​of Comparative Examples 1 to 6, indicating that the hue performance of Examples 1 to 6 is clearly superior to that of Comparative Examples 1 to 6.

[0074] As described above, the polyester fabric recycling method of the present invention involves refluxing the liquid polymerization product multiple times to repeatedly perform liquid polymerization. This not only improves the IV (vitreous intensity) and effectively stabilizes the IV distribution, thereby increasing IV uniformity, but also improves the hue expression of the recycled polyester. [Industrial applicability]

[0075] The polyester fabric recycling method of the present invention can be applied to the recycling of raw fabric, dyed fabrics containing dyes, or fabrics containing surface treatment agents, and the produced polyester fabric recycling pellets can be reused in spun, woven, and dyed / finished fabrics. [Explanation of symbols]

[0076] 100 Recycling Methods 200 Liquid polymerization units 210 Supply pipeline 220 Static Mixer 230 liquid coincidence tank 232 sprayer 234 Retention Tank 236 Recirculation Tube 240 recirculation piping 250 Discharge Pipeline S1~S6 ステップ V1, V2, V3 バルブ

Claims

1. A method for recycling polyester fabrics, The aforementioned polyester fabric is subjected to a decolorization treatment to form a decolorized polyester fabric, The decolorized polyester fabric and the thickening material are mixed to form the initial supply material, Liquid polymerization is carried out on the initial supply material to form a liquid polymerization product, The liquid polymerization product is refluxed and mixed with the initial supply material to form an intermediate supply material. Liquid polymerization is carried out on the aforementioned intermediate supply material to form the final polymerization product. A method that includes this.

2. The method according to claim 1, wherein the weight ratio of the decolorized polyester fabric to the thickening material is 5:95 to 80:

20.

3. The method according to claim 1, wherein the temperature of the liquid polymerization is 210°C to 290°C, and the pressure of the liquid polymerization is 0.1 torr to 5.0 torr.

4. The method according to claim 1, wherein the residence time for the liquid polymerization of the decolorized polyester fabric and the thickening material is approximately 5 minutes to 200 minutes.

5. The method according to claim 1, wherein the intrinsic viscosity of the final polymerization product is 0.60 or higher.

6. The method according to claim 1, wherein the standard deviation of the intrinsic viscosity of the final polymerization product is less than 0.0036.

7. The method according to claim 1, wherein the L value of the final polymerization product, as defined in the CIELAB color space, is 70 or more, the a value is -3.0 to +3.0, and the b value is -10.0 to +10.

0.

8. The method according to claim 1, wherein the weight ratio of the reflux rate of the liquid polymerization product to the amount of the initial supply material supplied is 5:1 to 50:

1.

9. The method according to claim 8, wherein the amount of the initial supply material supplied is equal to the amount of the final polymerization product discharged.

10. The method according to claim 1, wherein the polyester fabric includes a raw fabric, a dyed fabric containing a dye, or a fabric containing a surface treatment agent.

11. The method according to claim 1, wherein the intrinsic viscosity (IV) of the polyester fabric is 0.50 to 0.

70.

12. The method according to claim 1, wherein the intrinsic viscosity of the decolorized polyester fabric is 0.45 to 0.

65.

13. The method according to claim 1, wherein the L value of the decolorized polyester fabric, as defined in the CIELAB color space, is 85 or greater, the a value is -5.0 to +5.0, and the b value is -15.0 to +15.

0.

14. The method according to claim 1, wherein the decolorization treatment is performed using a solvent extraction method or an aqueous solution extraction method.

15. The method according to claim 1, wherein the thickening material is PET bottle flakes, and the intrinsic viscosity of the PET bottle flakes is 0.75 to 0.

95.

16. The method according to claim 1, wherein the thickening material is PET bottle flakes, and the L value of the PET bottle flakes as defined in the CIELAB color space is 80 or more, the a value is -2.0 to +2.0, and the b value is -4.0 to +4.0.

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