Two-component decolorizing agent for polyester textiles and pretreatment method for recycling polyester textiles

Abstract

The invention belongs to the technical field of textile decolorization treatment, and particularly relates to a two-component decolorizer for polyester textiles and a pretreatment method for recycling polyester textiles. The two-component decolorizer comprises component I and component II in a mass ratio of 1:2.2-3, component I comprises sodium hydroxide solution and sodium borohydride, and component II comprises sodium metabisulfite and sodium sulfite. Sodium borohydride is reacted with sodium metabisulfite and sodium sulfite in a strongly alkaline environment to generate a strongly reducing intermediate product for removing organic dye molecules from the textiles. The two-component decolorizer is suitable for decolorizing and recycling polyester textiles.

Description

Technical Field

[0001] The invention belongs to the technical field of textile decolorization treatment, and particularly relates to a two-component decolorizer for polyester textiles and a pretreatment method for recycling polyester textiles. Background Art

[0002] Every year, a large number of dyed textiles with a full range of varieties and bright colors are recycled and reused. A very important step in recycling is to bleach the textiles to remove the dyes on the fabrics to prevent chemical dyes from affecting subsequent processing.

[0003] Existing methods for textile decolorization include physical, chemical, and biological methods. Physical methods utilize special organic solvents or surfactants with an affinity for dye molecules to dissolve them from the dye. Chemical methods use oxidants or reducing agents to decolorize the dye molecules. Biological methods primarily utilize various enzymes to catalyze the decolorization of dye molecules. Currently, chemical methods are the most common decolorization method due to their simplicity and low cost.

[0004] For example, commonly used chemical reagents in the prior art include hydrosulfite, thiourea dioxide, hydrogen peroxide, and sodium hypochlorite. However, these chemical reagents also have many limitations and problems. For example, hydrosulfite is chemically active and easily decomposes under hot and humid conditions and can spontaneously explode under extreme conditions. The production equipment control cost is high, and due to its rapid reaction, it is prone to incomplete decolorization. Sodium hypochlorite easily produces chlorine during use, which is extremely harmful to the environment, workers, and equipment. Hydrogen peroxide has poor stability and only moderate decolorization effect. Therefore, it is particularly important to develop a new decolorization reagent that is stable in nature, has good decolorization effect, and is safe and environmentally friendly. Summary of the Invention

[0005] In response to the problems existing in the existing polyester textile decolorizing reagents mentioned in the above-mentioned prior art, the present invention provides a two-component decolorizing agent for polyester textiles and a pretreatment method for polyester textile recycling. Sodium borohydride is used to react with sodium metabisulfite and sodium sulfite in a strong alkaline environment to produce a highly reducing intermediate product to remove organic dye molecules on the textiles. Compared with the existing decolorizing reagents, the decolorizing effect is better, the reaction conditions are mild, and the pollution is small.

[0006] First, the present invention provides a two-component decolorizing agent for polyester textiles, comprising component I and component II in a mass ratio of 1:(2.2-3), wherein component I comprises a sodium hydroxide solution and sodium borohydride, the pH value of the sodium hydroxide solution in component I is 13-14, the mass ratio of the sodium borohydride to the sodium hydroxide solution is (1-2):1000, and component II comprises sodium metabisulfite and sodium sulfite.

[0007] Furthermore, the mass ratio of sodium metabisulfite to sodium sulfite in the component II is 100:(1-3).

[0008] The present invention also provides a recycling pretreatment method for polyester textiles, comprising the following steps:

[0009] Step 1: Steam the polyester textiles to be recycled in water, then take them out and dry them;

[0010] Step 2: Place the dried polyester textile in a kettle containing the peregal O solution to soak it;

[0011] Step 3: Add component I of the two-component decolorizer to the polyester textile soaked in step 2, stir and mix, then heat to the reaction temperature. After the reaction temperature stabilizes, add component II. Keep stirring during the addition process. The amount of component I in the two-component decolorizer is 1% to 2% of the mass of the polyester textile. Then heat and stir to react and decolorize.

[0012] Step 4: The decolorized polyester textile is washed and drained, and then ethylene glycol and a catalyst are added thereto for alcoholysis reaction. After the reaction, the mixture is recrystallized and the product is collected.

[0013] Furthermore, in the step 1, the polyester textile is steamed at a temperature of 90 to 100° C. and for a time of 15 to 30 minutes.

[0014] Furthermore, in the step 2, the concentration of the peregal O solution is 0.2-0.4 g / L, the mass ratio of the amount of peregal O added to the amount of polyester textile added is (1-2):100; and the immersion time is 10-15 min.

[0015] Furthermore, in step 3, the reaction temperature is 90-100° C., and the decolorization reaction time is 5-15 minutes.

[0016] Furthermore, the step four includes the following steps: mixing ethylene glycol and a catalyst in proportion and heating to boiling, then adding the polyester textile and stirring for reaction; filtering and collecting the mixed liquid after the polyester textile is dissolved, adding a magnetic decantation to separate the catalyst, washing with hot water to remove impurities, and then refrigerating and recrystallizing at low temperature to obtain a polyester monomer.

[0017] Furthermore, the added amount of the catalyst is 0.8-1% of the weight of the polyester textile, and the added amount of the ethylene glycol is 200-250% of the weight of the polyester textile.

[0018] Furthermore, the catalyst is zinc acetate.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention adopts a two-component decolorizing agent, which uses sodium borohydride and sodium metabisulfite to react to generate a highly reducing intermediate product S2O4 2- By adding sodium sulfite to increase the reaction activity and reaction intensity, it can quickly destroy dye molecules with azo and anthraquinone structures, decolorizing polyester textiles in 5 to 15 minutes without producing new decolorization products, greatly improving the decolorization efficiency of polyester textiles. At the same time, due to its two-component formula, component I and component II are stored separately before use, and only react when mixed. Compared with other decolorizers, it is easy to store and can be prepared and used immediately. The reaction process is mild and does not produce toxic or harmful gases.

[0021] 2. In the present invention, a two-component decolorizing agent is used in the pretreatment of polyester textile recycling. After the polyester textile is first decolorized, the waste polyester textile is dissolved by an alcoholysis process and then purified and recycled. At the same time, through the dual action of the two-component decolorizing agent and the catalyst, the decolorization rate of the polyester textile can be maintained at more than 95%, and the recovery rate of polyester can reach more than 90%, which can greatly improve the recycling rate of polyester textiles.

[0022] 3. The method of the present application is used to decolorize and recycle waste polyester textiles, and chemical reactions are used to destroy the molecular structure of organic dyes in polyester textiles. Without generating new colored substances, it can ensure that the polyester monomers recovered after decolorization of the polyester textiles have good whiteness, so that the recovered products do not need to be bleached or decolorized again and can be reproduced and reused. DETAILED DESCRIPTION

[0023] The following examples illustrate the present invention. These examples are intended to illustrate the present invention only and are not intended to limit its scope. Experimental methods not specified in the examples are based on conventional conditions. The amounts of reagents used in the examples are illustrative only and should be adjusted by those skilled in the art based on actual circumstances. Unless otherwise specified, the reagents are commercially available. The polyester textiles used in this invention were obtained from Zhejiang Furun Recycling Resources Co., Ltd.

[0024] Example 1

[0025] First, this embodiment provides a two-component decolorizing agent for polyester textiles, comprising component I and component II. Component I comprises sodium hydroxide solution and sodium borohydride, while component II comprises sodium metabisulfite and sodium sulfite. Specifically, the preparation comprises: adding 1.5g of sodium borohydride to 1000g of sodium hydroxide solution with a pH of 13, and mixing thoroughly to form component I. Then, adding 2600g of sodium metabisulfite and 2.6g of sodium sulfite to form component II. During use, components I and II are sequentially added to the polyester textile.

[0026] This embodiment also provides a pretreatment method for recycling polyester textiles, which uses the above-mentioned two-component decolorizing agent to treat the polyester textiles to be recycled, and specifically includes the following steps:

[0027] Step 1: Steam the polyester textiles to be recycled in water, then take them out and dry them;

[0028] Specifically, 100 kg of polyester textiles to be recycled are weighed and placed in a heating kettle. Water is added and heated to 90°C, where it is steamed for 20 minutes to remove impurities and break down the protective oil layer on the surface. After steaming, the polyester textiles are removed and drained.

[0029] Step 2: Place the dried polyester textile in a kettle containing the peregal O solution to soak it;

[0030] Specifically, the polyester textile treated in step 1 was transferred to a stirred tank, 500 L of a 0.2 g / L peregal O solution with a pH of 4 was added thereto, and the polyester textile was immersed for 10 minutes after stirring. The peregal O solution used in this embodiment was purchased from Peregal O-15 produced by Nantong Yixun Chemical Co., Ltd.

[0031] Step 3: Add component I of the two-component decolorizing agent to the polyester textile soaked in step 2, stir and mix, then heat to the reaction temperature. After the reaction temperature stabilizes, add component II, stirring and reacting during the addition process. The amount of component I in the two-component decolorizing agent is 1% of the mass of the polyester textile, and then heat and stir to react and decolorize;

[0032] Specifically, after the above-prepared two-component decolorizing agent component I and component II are mixed evenly, component I is first poured into a stirring kettle and stirring and heating is started. After the temperature reaches 90°C, component II is added to the stirring kettle and the stirring reaction is maintained for 5 minutes for decolorization.

[0033] Step 4: The decolorized polyester textile is washed and drained, and then ethylene glycol and a catalyst are added thereto for alcoholysis reaction. After the reaction, the mixture is recrystallized and the product is collected.

[0034] Specifically, the polyester textile treated in step 3 is rinsed several times with hot water, drained, and then chopped in an alcoholysis kettle. 1 kg of catalyst is added to 220 L of ethylene glycol, mixed, and heated to boiling. The boiling ethylene glycol-catalyst mixture is then added to the alcoholysis kettle, stirred, and allowed to react until the polyester textile is completely dissolved. After dissolution, the filtrate is quickly filtered and collected. The catalyst is separated from the filtrate by magnetic decantation, and the filtrate is washed with boiling water to remove impurities. Finally, the filtrate is cooled and recrystallized at 4°C to obtain recovered polyester monomer.

[0035] Example 2

[0036] This example differs from Example 1 in that the pH of the sodium hydroxide solution in Component I of the two-component decolorizer is 14. Specifically, 1000 g of sodium hydroxide solution with a pH of 14 was added to 1.5 g of sodium borohydride and mixed uniformly to form Component I. 2600 g of sodium metabisulfite and 2.6 g of sodium sulfite were then mixed uniformly to form Component II. Components I and II were then added sequentially to the polyester textile. Other experimental procedures and parameters were consistent with those in Example 1.

[0037] Example 3

[0038] The difference between this embodiment and embodiment 1 is that the amount of component I in the two-component decolorizing agent used is 2% of the mass of the polyester textile, and the other experimental steps and experimental parameters are the same as those in embodiment 1.

[0039] In practice, 50 kg of polyester textiles to be recycled are weighed and placed in a heating kettle. Water is added and heated to 90°C, where it is steamed for 20 minutes to remove impurities and break down the protective oil layer on the surface. After steaming, the polyester textiles are removed and drained.

[0040] The polyester textile treated in step 1 was transferred to a stirred tank, 500 L of 0.2 g / L peregal O solution was added thereto, and the polyester textile was soaked for 10 minutes after stirring and mixing.

[0041] After mixing the above-prepared two-component decolorizing agent component I and component II respectively, first pour component I into the stirring kettle and start stirring and heating. After the temperature reaches 90°C, add component II into the stirring kettle and keep stirring for 5 minutes to decolorize.

[0042] Rinse the polyester textile treated in step 3 several times with hot water, drain thoroughly, and then place it in an alcoholysis kettle and shred it. Add 1 kg of the catalyst to 220 L of ethylene glycol, mix thoroughly, and heat to boiling. Add the boiling ethylene glycol-catalyst mixture to the alcoholysis kettle and stir to maintain the reaction until the polyester textile is completely dissolved. After dissolution, quickly filter and collect the filtrate. Separate the catalyst from the filtrate by magnetic decantation, and wash the filtrate with boiling water to remove impurities. Finally, cool the filtrate at 4°C and recrystallize to recover the polyester monomer.

[0043] Example 4

[0044] This example differs from Example 1 in that the mass ratio of sodium metabisulfite to sodium sulfite in Component II of the two-component decolorizer is 100:2. Other experimental steps and parameters are consistent with those of Example 1. Specifically, Component I is prepared by adding 1.5g of sodium borohydride to 1000g of sodium hydroxide solution with a pH of 13 and mixing them evenly. Component II is then prepared by mixing 2600g of sodium metabisulfite and 5.2g of sodium sulfite evenly. Components I and II are then added sequentially to polyester textiles.

[0045] Example 5

[0046] This example differs from Example 1 in that the mass ratio of Component I to Component II in the two-component decolorizer is 1:3. Other experimental steps and parameters are consistent with Example 1. Specifically, Component I is prepared by adding 1.5 g of sodium borohydride to 1000 g of sodium hydroxide solution with a pH of 13 and mixing thoroughly. Component II is then prepared by mixing 3000 g of sodium metabisulfite and 3 g of sodium sulfite. Components I and II are then added sequentially to polyester textiles.

[0047] Example 6

[0048] This example differs from Example 1 in that the mass ratio of Component I to Component II in the two-component decolorizer is 1:2.2. Other experimental steps and parameters are consistent with Example 1. Specifically, Component I is prepared by adding 1.5 g of sodium borohydride to 1000 g of sodium hydroxide solution with a pH of 13 and mixing them evenly. Component II is then prepared by mixing 2200 g of sodium metabisulfite and 2.2 g of sodium sulfite evenly. Components I and II are then added sequentially to polyester textiles.

[0049] Comparative Example 1

[0050] This comparative example differs from Example 1 in that the pH of the sodium hydroxide solution in Component I is 12. Other experimental steps and parameters are consistent with those in Example 1. Specifically, Component I is prepared by adding 1.5 g of sodium borohydride to 1000 g of sodium hydroxide solution with a pH of 12 and mixing thoroughly. Component II is then prepared by mixing 2600 g of sodium metabisulfite and 2.6 g of sodium sulfite. Components I and II are then added sequentially to the polyester textile.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 1 is that the amount of component I in the two-component decolorizing agent used is 3% of the mass of the polyester textile, and the other experimental steps and experimental parameters are the same as those in Example 1.

[0053] In practice, 33 kg of polyester textiles to be recycled were weighed and placed in a heating kettle. Water was added and heated to 90°C, where the polyester textiles were steamed for 20 minutes to remove impurities and break down the protective oil layer on the surface. After steaming, the polyester textiles were removed and drained.

[0054] The polyester textile treated in step 1 was transferred to a stirred tank, 500 L of 0.2 g / L peregal O solution was added thereto, and the polyester textile was soaked for 10 minutes after stirring and mixing.

[0055] After mixing the above-prepared two-component decolorizing agent component I and component II respectively, first pour component I into the stirring kettle and start stirring and heating. After the temperature reaches 90°C, add component II into the stirring kettle and keep stirring for 5 minutes to decolorize.

[0056] Rinse the polyester textile treated in step 3 several times with hot water, drain thoroughly, and then place it in an alcoholysis kettle and shred it. Add 1 kg of the catalyst to 220 L of ethylene glycol, mix thoroughly, and heat to boiling. Add the boiling ethylene glycol-catalyst mixture to the alcoholysis kettle and stir to maintain the reaction until the polyester textile is completely dissolved. After dissolution, quickly filter and collect the filtrate. Separate the catalyst from the filtrate by magnetic decantation, and wash the filtrate with boiling water to remove impurities. Finally, cool the filtrate at 4°C and recrystallize to recover the polyester monomer.

[0057] Comparative Example 3

[0058] This comparative example differs from Example 1 in that sodium sulfite is omitted from Component II of the two-component decolorizer. All other experimental steps and parameters are consistent with those of Example 1. Specifically, Component I is prepared by adding 1.5 g of sodium borohydride to 1000 g of a sodium hydroxide solution with a pH of 13, followed by mixing. Component II is then prepared by adding 2600 g of sodium metabisulfite. Components I and II are then added sequentially to the polyester textile.

[0059] Comparative Example 4

[0060] This comparative example differs from Example 1 in that the mass ratio of Component I to Component II in the two-component decolorizer is 1:3.5. Other experimental steps and parameters are consistent with Example 1. Specifically, Component I is prepared by adding 1.5 g of sodium borohydride to 1000 g of sodium hydroxide solution with a pH of 13 and mixing thoroughly. Component II is then prepared by mixing 3500 g of sodium metabisulfite and 3.5 g of sodium sulfite. Components I and II are then added sequentially to the polyester textile.

[0061] Comparative Example 5

[0062] This comparative example differs from Example 1 in that the mass ratio of Component I to Component II in the two-component decolorizer is 1:2. Other experimental steps and parameters are consistent with those in Example 1. Specifically, Component I is prepared by adding 1.5 g of sodium borohydride to 1000 g of sodium hydroxide solution with a pH of 13 and mixing thoroughly. Component II is then prepared by mixing 2000 g of sodium metabisulfite and 2 g of sodium sulfite. Components I and II are then added sequentially to the polyester textile.

[0063] Comparative Example 6

[0064] This comparative example differs from Example 1 in that the mass ratio of sodium borohydride to sodium hydroxide solution in Component I of the two-component decolorizer is 0.5:1000. Other experimental steps and parameters are consistent with those in Example 1. Specifically, Component I is prepared by adding 0.5g of sodium borohydride to 1000g of sodium hydroxide solution with a pH of 13, and mixing thoroughly. Component II is then prepared by mixing 2600g of sodium metabisulfite and 2.6g of sodium sulfite. Components I and II are then added sequentially to the polyester textile.

[0065] Comparative Example 7

[0066] The difference between this comparative example and Example 1 is that step 3 in the preparation method is different. Specifically, the two-component decolorizing agent prepared above is mixed evenly and then poured into a stirring kettle. Stirring and heating are started, and the temperature is heated to 90° C. for 5 minutes to decolorize.

[0067] The preparation methods and application environment parameters of the two-component decolorizing agents prepared in the above examples and comparative examples are statistically shown in Table 1 below.

[0068] The polyester textiles treated in the above examples and comparative examples were tested for their decolorization rate and color difference after decolorization. The test results are shown in Table 2 below. 65 The K / S value of polyester textiles before and after bleaching was measured under light source and 10° viewing angle. Each group of samples was measured 5 times and the average value was taken. The bleaching rate was calculated according to the following formula:

[0069]

[0070] in is the K / S value of polyester textiles before bleaching, It is the K / S value of polyester textile after bleaching.

[0071] Strength retention rate test method: Test the breaking strength of polyester textiles before and after bleaching in accordance with the breaking strength test method for textiles in GB / T 3923.1-2013, and calculate the strength retention rate according to the following formula:

[0072]

[0073] Where F1 is the breaking strength value of polyester textile after bleaching, and F2 is the breaking strength value of polyester textile before bleaching.

[0074] The color value test is expressed using the L*a*b color system, where L * Indicates the brightness of the product, a * and b * Indicates the red-green and yellow-blue states of textiles. In the present invention, a colorimeter (CR-300 type) is used to test the color value.

[0075] Table 1: Statistical table of experimental parameters of embodiments and comparative examples

[0076]

[0077] Table 2: Statistical table of experimental results of examples and comparative examples

[0078]

[0079] Experimental results analysis:

[0080] From the analysis of the above experimental results, it can be seen that the decolorization rate of the treated product can reach more than 95% by using the two-component decolorizing agent provided by the present invention to treat waste polyester textiles, and the strong retention rate can also be maintained at about 95% or even higher, indicating that this method can effectively remove the color on polyester textiles without affecting the structure of the polyester material, and is very suitable for the decolorization treatment of polyester textiles. At the same time, after the polyester textiles are recycled and pre-treated, the color value of the recycled polyester textiles is checked after decolorization. * The brightness of the product after pretreatment is higher, and a * and b * Both values ​​are close to 0, indicating that the decolorized polyester textile is nearly white. Finally, when recovering polyester monomer after pretreatment, the loss rate of the polyester textile pretreated using the embodiment of the present invention was calculated to be approximately 3.9%, meeting the product recycling requirements.

[0081] In Comparative Example 1, when the pH value of sodium hydroxide in component I was changed, the decolorization effect of the polyester textile was reduced, with the decolorization rate dropping to about 90%. The color value of the polyester textile after decolorization also decreased significantly compared with that of the embodiment. This is because when the alkalinity is increased, the reaction between sodium borohydride and sodium metabisulfite is promoted in the forward direction, thereby producing more decolorization intermediates.

[0082] In Comparative Example 2, increasing the amount of Component I resulted in enhanced decolorization of polyester textiles. However, the strength retention of the decolorized polyester textile decreased, indicating that excessive alkalinity and the use of sodium borohydride can damage the polyester structure. Furthermore, calculations showed that the loss rate of polyester textiles after pretreatment reached approximately 9%, making this method unsuitable for recycling polyester textiles.

[0083] Comparative Example 3 does not add sodium sulfite. From the experimental results, its decolorization effect is significantly weaker than the technical solution of the embodiment of the present invention under the same action time. The reason is that the addition of sodium sulfite can significantly increase the reaction rate of sodium borohydride and sodium metabisulfite, accelerating the reaction towards the forward direction.

[0084] In Comparative Examples 4-5, the decolorization efficiency of the two-component decolorizer was significantly reduced after changing the ratio of Component I and Component II. This is because increasing the proportion of Component II increases its degree of hydrolysis, thereby reducing the reaction efficiency. Furthermore, when the proportion of Component I is high, the decolorization efficiency of anthraquinone dyes is significantly reduced, thereby reducing the overall decolorization effect.

[0085] In Comparative Example 7, when the order of adding Components I and II was changed, the experimental results showed that the decolorization effect also decreased. This is because adding Component I to the polyester textile first allows the strong reactivity of the sodium borohydride in Component I to decolorize the dye first. The subsequent addition of sodium metabisulfite and sodium sulfite not only reacts with the sodium borohydride to produce stronger decolorization intermediates, but also has a certain removal effect on anthraquinone dyes, further enhancing the decolorization effect.

[0086] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be viewed as exemplary and non-restrictive in all respects. Furthermore, it should be understood that although this specification is described in terms of implementation methods, it does not encompass only one technical solution. This narrative is provided for clarity only, and those skilled in the art should consider the specification as a whole. The technical solutions in the embodiments may also be appropriately combined to form other implementation methods that are understandable to those skilled in the art.

Claims

1. A recycling pretreatment method for polyester textiles, characterized in that: The following steps are involved: Step 1: Steam the polyester textiles to be recycled in water, then take them out and dry them; Step 2: Place the dried polyester textile in a kettle containing the peregal O solution to soak it; Step 3: Add a two-component decolorizing agent to the soaked polyester textile, and heat and stir to react and decolorize; Step 4: The decolorized polyester textile is washed and drained, and then ethylene glycol and a catalyst are added thereto for alcoholysis reaction. After the reaction, the mixture is recrystallized and the product is collected; The two-component decolorizing agent in step 3 includes component I and component II in a mass ratio of 1:2.2-3, wherein component I includes sodium hydroxide solution and sodium borohydride, the pH value of the sodium hydroxide solution is 13-14, and the mass ratio of the sodium borohydride to the sodium hydroxide solution is 1-2:1000; the component II includes sodium metabisulfite and sodium sulfite, and the mass ratio of the sodium metabisulfite to the sodium sulfite is 100:1-3; The step three comprises the following steps: first adding component I of the two-component decolorizing agent to the polyester textile soaked in step two, stirring and mixing, and then heating to the reaction temperature; after the reaction temperature stabilizes, adding component II, and maintaining stirring during the addition process; the amount of component I used is 1% to 2% of the mass of the polyester textile; the reaction temperature is 90 to 100° C., and the decolorization reaction time is 5 to 15 minutes.

2. The method for recycling and pretreating polyester textiles according to claim 1, characterized in that: In the step 1, the polyester textile is steamed at a temperature of 90 to 100° C. for a time of 15 to 30 minutes.

3. The method for recycling and pretreating polyester textiles according to claim 2, characterized in that: In the second step, the concentration of the peregal O solution is 0.2-0.4 g / L, the mass ratio of the peregal O to the polyester textile addition is 1-2:100, and the immersion time is 10-15 min.

4. The method for recycling and pretreating polyester textiles according to claim 1, wherein: The fourth step comprises the following steps: mixing ethylene glycol and a catalyst in proportion and heating to boiling, then adding the polyester textile and stirring for reaction; filtering and collecting the mixed solution after the polyester textile is dissolved, separating the catalyst by magnetic decantation, washing with hot water to remove impurities, and then refrigerating and recrystallizing at low temperature to obtain a polyester monomer.

5. The method for recycling and pretreating polyester textiles according to claim 4, characterized in that: The catalyst is zinc acetate, the added amount of the catalyst is 0.8-1% of the weight of the polyester textile, and the added amount of the ethylene glycol is 200-250% of the weight of the polyester textile.

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