Decoloring method of polyester fabric

Abstract

The invention discloses a decoloring method of a polyester fabric, which has the advantages that the use amount of a solvent is low, and the color of the decolored fabric is stable. The polyester fabric is subjected to a first extraction treatment using a recovery solvent to move a first portion of the dye in the polyester fabric into the recovery solvent. And carrying out first filtering treatment on the recovered solvent and the polyester fabric to obtain the treated polyester fabric. The treated polyester fabric is subjected to a second extraction treatment using a fresh solvent to move a second portion of the dye in the treated polyester fabric to the fresh solvent. And carrying out second filtration treatment to obtain the decolorized polyester fabric and the recovered solvent.

Description

Technical Field

[0001] The invention relates to a method for decolorizing fabric, and in particular to a method for decolorizing polyester fabric. Background Art

[0002] Polyester fabrics (e.g., polyethylene terephthalate (PET) fabrics) usually contain impurities such as dyes attached thereto. Generally, the impurities such as dyes must be removed with a suitable solvent before the decolorized polyester fabrics can be effectively separated and purified, and the polyester and fiber materials in the polyester fabrics can be recovered.

[0003] Currently, in the process of removing impurities such as dyes, 3 to 6 extractions are required with a solvent / polyester fabric weight ratio of 5 to 10. In other words, the amount of solvent used may be as much as 15 to 60 times the weight of the fabric, resulting in a very large amount of solvent that needs to be purified before it can be reused. In addition, the decolorized polyester fabric obtained after the above extraction process still has a color cast, for example, a blue fabric still has a blue color after decolorization, and so on.

[0004] US7,959,807B2 proposes a method for removing dyes from PET fabrics. Although this method can remove the dyes, the treated PET fabrics also have color deviation, and the amount of solvent used is as much as 24 times the weight of the fabric, so the cost of solvent recovery is very high.

[0005] TW I481762B proposes a method for removing dyes from recycled PET fabrics, which uses solvent vapor gas to extract dyes. Although it can improve the efficiency of dye extraction, there is still a color shift phenomenon. At the same time, the use of solvent vapor to extract dyes will result in excessively high energy consumption costs. Summary of the invention

[0006] The invention provides a decolorization method for polyester fabrics, which has the advantages of low solvent usage, stable fabric color after decolorization, and can reduce the decolorization cost of the polyester fabrics and alleviate the color deviation phenomenon.

[0007] The decolorization method of polyester fabric of the present invention comprises the following steps: performing a first extraction treatment on the polyester fabric using a recovery solvent so that a first part of the dye in the polyester fabric is transferred to the recovery solvent; performing a first filtering treatment on the recovery solvent and the polyester fabric to obtain a treated polyester fabric; performing a second extraction treatment on the treated polyester fabric using a fresh solvent so that a second part of the dye in the treated polyester fabric is transferred to the fresh solvent; and performing a second filtering treatment to obtain a decolorized polyester fabric and a recovery solvent.

[0008] In one embodiment of the present invention, the recovered solvent includes fresh solvent and dye, and the dye accounts for 0.1 wt % to 10 wt % based on the total weight of the recovered solvent.

[0009] In one embodiment of the present invention, in the first extraction process, the weight ratio of the recovered solvent to the polyester fabric is 4:1 to 50:1.

[0010] In one embodiment of the present invention, the weight ratio of the fresh solvent to the treated polyester fabric is 4:1 to 50:1.

[0011] In one embodiment of the present invention, the fresh solvent includes an aromatic hydrocarbon solvent, an alcohol ether solvent, a benzyl alcohol solvent, an alcohol solvent or an amide solvent.

[0012] In one embodiment of the present invention, the fresh solvent includes benzene, toluene, xylene, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, butanol, pentanol, hexanol, dimethylformamide, dimethylacetamide or a combination thereof.

[0013] In one embodiment of the present invention, based on the total weight of the dye, the total amount of the first part and the second part removed is 90 wt % to 99.9 wt %.

[0014] In one embodiment of the present invention, the CIELAB color of the bleached polyester fabric is defined as an L value of 80 or more, an a value of -3.0 to +3.0, and a b value of -6.0 to +6.0.

[0015] In one embodiment of the present invention, the method further comprises repeating the cycle of the first extraction process and the first filtration process 1 to 7 times before the second extraction process.

[0016] In one embodiment of the present invention, the method further comprises repeating the cycle of the second extraction process and the second filtration process 1 to 3 times after the second filtration process.

[0017] Based on the above, the present invention provides a decolorization method for polyester fabric, which uses a recovered solvent to perform a front-end extraction treatment on the polyester fabric, which can reduce the color deviation of the decolorized polyester fabric produced, and at the same time can greatly reduce the use of fresh solvent and the amount of recovered solvent produced, thereby reducing the cost required for decolorization of the polyester fabric.

[0018] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The figure is a schematic flow chart of a polyester fabric decolorization method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] 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.

[0021] 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.

[0022] Figure 1 The figure is a schematic flow chart of a polyester fabric decolorization method according to an embodiment of the present invention.

[0023] Please refer to Figure 1 In step S1, first, a first extraction treatment is performed on the polyester fabric using a recovery solvent to move a first portion of the dye in the polyester fabric into the recovery solvent.

[0024] In some embodiments, the recovered solvent includes a fresh solvent and a dye, and the dye is 0.1wt% to 10wt%, such as 2wt%, 6wt% or 8wt%, based on the total weight of the recovered solvent. For example, the recovered solvent can be a solvent containing a dye produced after the polyester fabric or the treated polyester fabric is subjected to an extraction treatment and a filtration treatment using a fresh solvent. Since the recovered solvent has a lower dye concentration, it can also be used for the first extraction treatment of other batches of polyester fabrics.

[0025] In some embodiments, the polyester fabric comprises a bleached polyester fabric and a dye, wherein the bleached polyester fabric may comprise polyester and fiber. In some embodiments, the polyester in the bleached polyester fabric is polyethylene terephthalate (PET). In some embodiments, the fiber in the bleached polyester fabric comprises cotton fiber. In some embodiments, the total weight of the polyester fabric is 100 parts by weight, and the content of the dye in the polyester fabric is, for example, 0.1 to 10 parts by weight, for example, 3 parts by weight, 5 parts by weight or 9 parts by weight. For example, the polyester fabric may be a product obtained by dyeing and finishing an undyed polyester fabric.

[0026] In some embodiments, the weight ratio of the recovery solvent to the polyester fabric for the first extraction process is 4: 1 to 50: 1. In certain embodiments, the weight ratio of the recovery solvent to the polyester fabric for the first extraction process is 5: 1 to 20: 1, such as 6: 1, 10: 1 or 15: 1.

[0027] In some embodiments, the first extraction treatment includes placing the polyester fabric in a recovery solvent and then heating the polyester fabric and the recovery solvent to a treatment temperature. In some embodiments, the treatment temperature of the first extraction treatment is higher than the glass transition temperature (Tg) of the polyester in the polyester fabric and lower than the melting point of the polyester. In some embodiments, the treatment temperature of the first extraction treatment is 80°C to 160°C. In some embodiments, the treatment temperature of the first extraction treatment is 100°C to 150°C, such as 120°C, 130°C or 140°C. In some embodiments, the treatment time of the first extraction treatment is 0.5 hours to 5 hours. In some embodiments, the treatment time of the first extraction treatment is 1 hour to 3 hours, such as 1.5 hours, 2 hours or 2.5 hours. In some embodiments, the treatment pressure of the first extraction treatment is 1.0 bar to 2.0 bar. In certain embodiments, when the boiling point of the recovery solvent is lower than the glass transition temperature of the polyester in the polyester fabric, the treatment pressure of the first extraction treatment may be greater than 1.0 bar.

[0028] Next, the recovered solvent and the polyester fabric are subjected to a first filtration treatment to obtain a treated polyester fabric and a filtered solvent to be purified, wherein the treated polyester fabric may include the decolorized polyester fabric to be produced later and the remaining dye, and the remaining dye is the dye remaining after the first portion of the dye is removed. In some embodiments, the first filtration treatment uses a mesh to filter to separate the solvent to be purified from the treated polyester fabric. In some embodiments, the mesh has an aperture of 0.1 mm to 1.0 mm, such as 0.3 mm, 0.5 mm or 0.7 mm. In some embodiments, after the first extraction treatment and before the first filtration treatment, a cooling treatment may be performed first, such as reducing the temperature to between 25° C. and 80° C., and then the treated polyester fabric and the solvent to be purified are separated.

[0029] In certain embodiments, solvent to be purified includes pure solvent and dye.Solvent to be purified can have higher dye concentration, is therefore not suitable for being used for extraction again.In certain embodiments, the dye concentration in the solvent to be purified is greater than the dye concentration of the recovery solvent.In certain embodiments, the gross weight of solvent to be purified is 100 weight parts, and the content of the dye in the solvent to be purified is about 1.0 weight part to 30 weight parts, for example 12 weight parts, 18 weight parts or 24 weight parts.In certain embodiments, solvent to be purified is distilled or evaporated to be pure solvent with the solvent purification in the solvent to be purified.In certain embodiments, pure solvent can be used as fresh solvent.

[0030] Please continue to refer to Figure 1In the optional step S2, step S1 may be repeated m times. In other words, after completing step S1, step S2 may be skipped and step S3 may be performed directly; or, after completing step S1, step S1 may be repeated m times, and then step S3 may be performed. In some embodiments, m may be 1 to 7, that is, step S1 may be repeated 11 times, 2 times, 3 times, 4 times, 5 times, 6 times, or 7 times, but the present invention is not limited thereto.

[0031] Next, in step S3, the treated polyester fabric may be subjected to a second extraction treatment using a fresh solvent to transfer a second portion of the dye in the treated polyester fabric to the fresh solvent. In some embodiments, the second extraction treatment includes placing the treated polyester fabric in a fresh solvent, and then heating the treated polyester fabric and the fresh solvent to a treatment temperature that is higher than the glass transition temperature of the polyester in the polyester fabric and lower than the melting point of the polyester.

[0032] In some embodiments, in the second extraction process, the weight ratio of fresh solvent to treated polyester fabric is 4:1 to 50:1. In certain embodiments, in the second extraction process, the weight ratio of fresh solvent to treated polyester fabric is 5:1 to 20:1. In some embodiments, the treatment temperature of the second extraction process is 80°C to 160°C. In some embodiments, the treatment temperature of the second extraction process is 100°C to 150°C. In some embodiments, the treatment time of the second extraction process is 0.5 to 5 hours. In some embodiments, the treatment time of the second extraction process is 1 to 3 hours.

[0033] In some embodiments, the fresh solvent comprises an aromatic hydrocarbon solvent, an alcohol ether solvent, a benzyl alcohol solvent, an alcohol solvent or an amide solvent. In some embodiments, the aromatic hydrocarbon solvent comprises benzene, toluene or xylene. In some embodiments, the alcohol ether solvent comprises propylene glycol monomethyl ether, ethylene glycol monobutyl ether or diethylene glycol monobutyl ether. In some embodiments, the alcohol solvent comprises butanol, amyl alcohol or hexanol. In some embodiments, the amide solvent comprises dimethylformamide or dimethylacetamide. In some embodiments, the fresh solvent comprises benzene, toluene, xylene, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, butanol, amyl alcohol, hexanol, dimethylformamide, dimethylacetamide or a combination thereof.

[0034] Then, after the second extraction treatment, a second filtration treatment is performed to obtain a decolorized polyester fabric and a recovered solvent, wherein the recovered solvent can be used for the aforementioned first extraction treatment. In some embodiments, the decolorized polyester fabric may include a trace amount of dye, and the trace amount of dye is the dye remaining after the first part and the second part of the dye are removed. In some embodiments, with the total weight of the dye in the polyester fabric being 100 parts by weight, the total amount of the first part removed by the first extraction treatment and the second part removed by the second extraction treatment is, for example, 90 parts by weight to 99.9 parts by weight, such as 92 parts by weight, 95 parts by weight, or 98 parts by weight.

[0035] In some embodiments, the second filtration treatment uses a mesh to filter to separate the recovered solvent from the decolorized polyester fabric. In some embodiments, the mesh has a pore size of 0.1 mm to 1.0 mm, such as 0.3 mm, 0.5 mm or 0.7 mm. In some embodiments, after the second extraction treatment, the decolorized polyester fabric and the recovered solvent are cooled, for example, to a temperature between 25° C. and 80° C., and then the second filtration treatment is performed.

[0036] Next, in the optional step S4, step S3 may be repeated n times. In other words, after completing step S3, step S4 may be skipped; or, after completing step S3, step S3 may be repeated n times. In some embodiments, n may be 1 to 3, that is, step S3 may be repeated 1, 2, or 3 times, but the present invention is not limited thereto.

[0037] In some embodiments, the decolorization method of polyester fabric further comprises drying the decolorized polyester fabric to remove the residual solvent on the decolorized polyester fabric. For example, the decolorized polyester fabric can be placed in an oven set at a temperature of 80° C. to 160° C. and left to stand for 1 hour to 24 hours for drying. In some embodiments, the decolorized polyester fabric after drying is white and has a CIELAB color definition of L value greater than 80, a value of -3.0 to +3.0, and b value of -6.0 to +6.0.

[0038] The following examples are used to describe the decolorization method of polyester fabrics according to the present invention in detail. However, the following examples are not intended to limit the present invention.

[0039] Example 1

[0040] Please also refer to Figure 1First, step S1 is performed using propylene glycol monomethyl ether recovery solvent and PET fabric to obtain treated PET fabric, wherein the weight ratio of propylene glycol monomethyl ether recovery solvent to PET fabric is 6:1, the treatment temperature of the first extraction treatment is 120° C., the treatment time of the first extraction treatment is 0.5 hour, the treatment pressure of the first extraction treatment is 1.0 bar, the first filtration treatment uses a sieve with a pore size of 0.5 mm, the propylene glycol monomethyl ether recovery solvent contains about 0.5wt% of dye, and the PET fabric contains about 8wt% of dye.

[0041] Then, step S1 is repeated twice in step S2. Then, step S3 is performed using fresh propylene glycol monomethyl ether solvent and the treated PET fabric to produce decolorized PET fabric and propylene glycol monomethyl ether recovery solvent, wherein the weight ratio of fresh propylene glycol monomethyl ether solvent to the treated PET fabric is 6:1, the treatment temperature of the second extraction treatment is 120° C., the treatment time of the second extraction treatment is 0.5 hours, the treatment pressure of the second extraction treatment is 1.0 bar, and the second filtration treatment uses a sieve with a pore size of 0.5 mm.

[0042] Then, step S4 is skipped. Since the second extraction treatment is performed once in total, in Example 1, the total amount of fresh solvent used is only about 6 times the weight of the PET fabric, so the total amount of propylene glycol monomethyl ether recovered solvent produced is about 6 times the weight of the PET fabric, which can be used as a recovered solvent for other batches of PET fabrics when performing the first extraction treatment of step S1. In addition, since the first extraction treatment is performed three times in total, the amount of recovered solvent that can be reused in Example 1 is as much as 18 times the weight of the PET fabric, which greatly improves the reuse rate of the recovered solvent, thereby reducing the amount of solvent to be purified in the overall decolorization process, thereby reducing the purification energy consumption and purification cost of the solvent.

[0043] Next, the decolorized polyester fabric was placed in an oven at 105°C for 2 hours for drying. Afterwards, the CIELAB color definition of the decolorized polyester fabric was measured to be L value 82, a value 1.1, and b value 2.4. The color of the fabric after decolorization was stable, and the color deviation was reduced. The total amount of dye removed was about 99.4wt%.

[0044] Example 2

[0045] The main differences between the treatment procedure of Example 2 and the treatment procedure of Example 1 are: step S1 is repeated once in step S2; step S3 is repeated once in step S4; the treatment temperature of the first extraction treatment and the second extraction treatment is 130°C; and the treatment pressure of the first extraction treatment and the second extraction treatment is 1.8 bar.

[0046] Since the second extraction treatment is performed twice in total, in Example 2, the total amount of fresh solvent used is about 12 times the weight of the PET fabric, so the total amount of propylene glycol monomethyl ether recovered solvent produced is about 12 times the weight of the PET fabric, which can be used as a recovered solvent for other batches of PET fabrics when performing the first extraction treatment in step S1. In addition, since the first extraction treatment is performed twice in total, the amount of recovered solvent that can be reused in Example 2 is about 12 times the weight of the PET fabric, which can also improve the reuse rate of the recovered solvent, thereby reducing the amount of solvent to be purified in the overall decolorization process, thereby reducing the purification energy consumption and purification cost of the solvent.

[0047] After drying the decolorized polyester fabric, the CIELAB color definition of the decolorized polyester fabric produced in Example 2 was measured to be L value 83, a value 1.8, and b value 2.7. The color of the fabric after decolorization was stable, and the color deviation was reduced. The total amount of dye removed was about 99.6wt%.

[0048] Example 3

[0049] The processing procedure of the third embodiment differs from the processing procedure of the first embodiment mainly in that: in step S2, step S1 is repeated once; and in step S4, step S3 is repeated once.

[0050] Since the second extraction treatment is performed twice in total, in Example 3, the total amount of fresh solvent used is about 12 times the weight of the PET fabric, so the weight of the propylene glycol monomethyl ether recovery solvent produced is about 12 times the weight of the PET fabric, which can be used as a recovery solvent for other batches of PET fabrics when performing the first extraction treatment in step S1. In addition, since the first extraction treatment is performed twice in total, the amount of recovery solvent that can be reused in Example 3 is about 12 times the weight of the PET fabric, which can also improve the reuse rate of the recovery solvent, thereby reducing the amount of solvent to be purified in the overall decolorization process, thereby reducing the purification energy consumption and purification cost of the solvent.

[0051] After drying the decolorized polyester fabric, the CIELAB color definition of the decolorized polyester fabric produced in Example 3 was measured to be L value 84, a value 1.5, b value 2.4, and the color of the fabric after decolorization was stable, and the color deviation was reduced. The total amount of dye removed was about 99.5wt%.

[0052] Example 4

[0053] The propylene glycol monomethyl ether was replaced by xylene, and the rest was the same as in Example 1. The CIELAB color definition of the decolorized polyester fabric was measured to be L value 82, a value 1.2, and b value 2.5. The color of the fabric after decolorization was stable, and the color deviation was reduced. The total amount of dye removed was about 99.4wt%.

[0054] Example 5

[0055] The propylene glycol monomethyl ether was replaced by xylene, and the rest was the same as in Example 3. The CIELAB color definition of the decolorized polyester fabric was measured to be L value 83, a value 1.6, and b value 2.5. The color of the fabric after decolorization was stable, and the color deviation was reduced. The total amount of dye removed was about 99.6wt%.

[0056] Example 6

[0057] Dimethylacetamide was used to replace propylene glycol monomethyl ether, and the rest was the same as in Example 3. The CIELAB color definition of the decolorized polyester fabric was measured to be L value 85, a value 1.4, and b value 2.3. The color of the fabric after decolorization was stable, and the color deviation was reduced. The total amount of dye removed was about 99.7wt%.

[0058] Comparative Example 1

[0059] The processing procedure of Comparative Example 1 is different from that of Example 1 mainly in that: Step S1 and Step S2 are skipped; and Step S3 is repeated three times in Step S4.

[0060] Since the second extraction treatment was performed four times in total, in Comparative Example 1, the total amount of fresh solvent used was as much as 24 times the weight of the PET fabric, so the total weight of the propylene glycol monomethyl ether recovered solvent produced was about 24 times the weight of the PET fabric. Since the overall decolorization process of Comparative Example 1 did not reuse the recovered solvent, the recovered solvent must be purified by distillation or evaporation before it can be reused. In other words, the propylene glycol monomethyl ether recovered solvent of Comparative Example 1 is the propylene glycol monomethyl ether solvent to be purified. In this way, the amount of solvent to be purified in the overall decolorization process will be greatly increased, resulting in an increase in the energy consumption and purification cost of the solvent.

[0061] After drying the decolorized polyester fabric, the CIELAB color definition of the decolorized polyester fabric produced in Comparative Example 1 was measured to be 87 for L value, 2.1 for a value, and 6.1 for b value. Since the fabric itself has red and yellow dyes, the color of the fabric is still reddish (high a value) and yellowish (high b value) after continuous decolorization with fresh solvent. The total amount of dye removed is about 99.6wt%.

[0062] Comparative Example 2

[0063] The processing procedure of Comparative Example 2 is different from that of Example 2 mainly in that: Step S1 and Step S2 are skipped; and Step S3 is repeated three times in Step S4.

[0064] Since the second extraction treatment was performed four times in total, the total amount of fresh solvent used in Comparative Example 2 was as much as 24 times the weight of the PET fabric, so the total weight of the propylene glycol monomethyl ether recovered solvent produced was about 24 times the weight of the PET fabric. Since the overall decolorization process of Comparative Example 2 did not reuse the recovered solvent, the recovered solvent must be purified by distillation or evaporation before it can be reused, which greatly increases the amount of solvent to be purified in the overall decolorization process, resulting in an increase in the energy consumption and purification cost of the solvent.

[0065] After drying the decolorized polyester fabric, the CIELAB color definition of the decolorized polyester fabric produced in Comparative Example 2 was measured to be 88 for L value, 3.8 for a value, and 6.8 for b value. Since the fabric itself has red and yellow dyes, the color of the fabric is still reddish (high a value) and yellowish (high b value) after continuous decolorization with fresh solvent. The total amount of dye removed is about 99.7wt%.

[0066] Comparative Example 3

[0067] The processing procedure of Comparative Example 3 is different from that of Example 3 mainly in that step S1 and step S2 are skipped.

[0068] Since the second extraction treatment was performed twice in total, the total amount of fresh solvent used was about 12 times the weight of the PET fabric in Comparative Example 3, so the total weight of the propylene glycol monomethyl ether recovered solvent produced was about 12 times the weight of the PET fabric. Since the overall decolorization process of Comparative Example 3 did not reuse the recovered solvent, the recovered solvent must be purified by distillation or evaporation before it can be reused, which will also increase the amount of solvent to be purified in the overall decolorization process, resulting in an increase in the purification energy consumption and purification cost of the solvent.

[0069] After drying the decolorized polyester fabric, the CIELAB color definition of the decolorized polyester fabric produced in Comparative Example 3 was measured to be 75 for L value, 3.2 for a value, and 6.3 for b value. Due to incomplete removal of the dye, the decolorization was incomplete, and the decolorized polyester fabric had obvious dye residue. The total amount of dye removed was about 98.7 wt%.

[0070] Comparative Example 4

[0071] The propylene glycol monomethyl ether was replaced by xylene, and the rest was the same as in Comparative Example 1. The CIELAB color definition of the decolorized polyester fabric produced in Comparative Example 4 was measured to be L value 86, a value 2.3, and b value 6.4. Because the fabric itself has red and yellow dyes, the color of the fabric is still reddish (a value is high) and yellowish (b value is high) after continuous decolorization with fresh solvent. The total amount of dye removed is about 99.5wt%.

[0072] Comparative Example 5

[0073] The propylene glycol monomethyl ether was replaced by xylene, and the rest was the same as in Comparative Example 3. The CIELAB color definition of the decolorized polyester fabric produced in Comparative Example 5 was measured to be 74 for L value, 3.5 for a value, and 6.4 for b value. Due to incomplete removal of the dye, the decolorization was incomplete, and the decolorized polyester fabric had obvious dye residue. The total amount of dye removed was about 98.4wt%.

[0074] Comparative Example 6

[0075] Dimethylacetamide was used to replace propylene glycol monomethyl ether, and the rest was the same as in Comparative Example 3. The CIELAB color definition of the decolorized polyester fabric produced in Comparative Example 6 was measured to be 75 for L value, 3.1 for a value, and 6.0 for b value. Due to incomplete removal of the dye, the decolorization was incomplete, and the decolorized polyester fabric had obvious dye residue. The total amount of dye removed was about 98.8wt%.

[0076] The preparation methods and test results of the above-mentioned Examples 1 to 6 and Comparative Examples 1 to 6 are summarized in the following Table 1.

[0077] [Table 1]

[0078]

[0079]

[0080]

[0081] Comparing Example 1 with Comparative Example 1, it can be seen that the total number of extraction treatments is four times. However, since only the fourth extraction treatment of Example 1 uses fresh solvent, the amount of recovered solvent produced is significantly less than that of Comparative Example 1, and the color deviation is also better than that of Comparative Example 1. Comparing Example 2 with Comparative Example 2, it can be seen that even at a higher extraction temperature and extraction pressure, Example 2, which uses a recovered solvent to perform two first extraction treatments, can not only reduce the amount of recovered solvent, but also significantly improve the color deviation phenomenon. In addition, comparing Example 3 with Comparative Example 3, it can be seen that both use fresh solvent to perform two second extraction treatments, so the amount of recovered solvent produced is similar. However, since Example 3 also first uses a recovered solvent to perform two first extraction treatments, its color performance is significantly improved compared with Comparative Example 3. In addition, the total amount of dye removed from Examples 1 to 3 is similar to that of Comparative Examples 1 and 2, indicating that using a recovered solvent to perform the first extraction treatment first does not affect the overall dye removal effect.

[0082] In addition, it can be seen from Examples 4 to 6 that using xylene or dimethylacetamide as a solvent can also achieve the effect of stabilizing the color of the fabric after bleaching and reducing the color deviation. As for Comparative Examples 4 to 6, using xylene or dimethylacetamide as a solvent still cannot improve the reddish, yellowish, and incomplete bleaching of the fabric after bleaching in Comparative Example 1 or Comparative Example 3.

[0083] As can be seen from Table 1 above, in Examples 1 to 6, the recycled solvent is used to perform the first extraction treatment of the polyester fabric in the front step S1, and only the fresh solvent is used in the second extraction treatment in the back step S3, so the amount of the recovered solvent produced and the amount of the solvent to be purified can be significantly reduced. In addition, since the recycled solvent used in the first extraction treatment can be a mixture of the recycled solvents produced by multiple batches of the second extraction treatment, the problem of color deviation of the decolorized polyester fabric produced due to the dye contained in the recycled solvent being too single can be avoided, so that the CIELAB color definition of the decolorized polyester fabric finally obtained can be in the range of L value of more than 80, a value of -3.0 to +3.0, and b value of -6.0 to +6.0.

[0084] In summary, the present invention provides a method for decolorizing polyester fabrics. By using a recycled solvent to perform a first extraction treatment on the polyester fabrics, the color deviation of the decolorized polyester fabrics produced can be reduced, thereby improving the quality of the recycled decolorized polyester fabrics. At the same time, the amount of fresh solvent used, the amount of recycled solvent produced, and the amount of solvent to be purified can all be greatly reduced, thereby reducing the cost required for decolorizing the polyester fabrics.

[0085] 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 decolorizing polyester fabric, characterized in that: include: Performing a first extraction treatment on the polyester fabric using a recovery solvent so that a first portion of the dye in the polyester fabric is transferred to the recovery solvent; subjecting the recovered solvent and the polyester fabric to a first filtering treatment to obtain a treated polyester fabric; subjecting the treated polyester fabric to a second extraction treatment using a fresh solvent so that a second portion of the dye in the treated polyester fabric moves into the fresh solvent; as well as A second filtration treatment is performed to obtain the decolorized polyester fabric and the recovered solvent.

2. The method according to claim 1, characterized in that The recovered solvent comprises the fresh solvent and the dye, and based on the total weight of the recovered solvent, the dye accounts for 0.1 wt % to 10 wt %.

3. The method according to claim 1, characterized in that In the first extraction process, a weight ratio of the recovery solvent to the polyester fabric is 4:1 to 50:

1.

4. The method according to claim 1, characterized in that: The weight ratio of the fresh solvent to the treated polyester fabric is 4:1 to 50:

1.

5. The method according to claim 1, characterized in that The fresh solvent includes an aromatic hydrocarbon solvent, an alcohol ether solvent, an alcohol solvent or an amide solvent.

6. The method according to claim 1, characterized in that The fresh solvent includes benzene, toluene, xylene, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, butanol, pentanol, hexanol, dimethylformamide, dimethylacetamide or a combination thereof.

7. The method according to claim 1, characterized in that Based on the total weight of the dye, the total amount of the first part and the second part removed is 90 wt % to 99.9 wt %.

8. The method according to claim 1, characterized in that: The CIELAB color of the bleached polyester fabric is defined as an L value of 80 or more, an a value of -3.0 to +3.0, and a b value of -6.0 to +6.

0.

9. The method according to claim 1, characterized in that: The method further includes repeating the first extraction process and the first filtration process for 1 to 7 times before the second extraction process.

10. The method according to claim 1, characterized in that The method further includes repeating the second extraction process and the second filtration process for 1 to 3 times after the second filtration process.

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