Decoloring method of waste polyester fabric

Abstract

The invention discloses a decolorization method of waste polyester fabrics, which adopts a nonionic high-molecular polymer solvent as a decolorization medium, and realizes repeated decolorization of the solvent and efficient decolorization of the waste polyester fabrics through'decolorization-adsorption-recovery '. The decolorization rate is stabilized at 98% or above, disperse dyes in various colors can be deeply removed, the structural integrity of the decolored polyester fibers is good, only the crystallinity is slightly reduced, and follow-up recycling is not affected; the solvent can be recycled for more than 5 times, so that the environmental burden and the production cost are greatly reduced, and the method is suitable for waste polyester fabrics with different sources and colors and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of textile fiber decolorization and dye recovery, and specifically to a method for decolorizing waste polyester fabrics. Background Technology

[0002] Polyester is the world's most produced fiber, accounting for 57% of total fiber production. Its main component is polyethylene terephthalate (PET), and it is widely used in clothing, home textiles, and industrial fields. Every year, a large amount of waste polyester fabrics are discarded, most of which are disposed of through incineration or landfill, resulting not only in resource waste but also pollution of soil, water, and the atmosphere. Currently, the main methods for recycling waste polyester fabrics include physical recycling and chemical recycling.

[0003] Physical recycling primarily relies on mechanical processing, using steps such as cutting and melting to reprocess waste polyester fabrics into fibers or granules. Chemical recycling mainly uses hydrolysis, glycolysis, and methanololysis to depolymerize polyester waste into monomers or oligomers for reuse. Regardless of the recycling method, the influence of dyes, chemical auxiliaries, and finishing agents present in waste polyester fabrics cannot be ignored. The presence of these chemicals reduces the quality of the recycled products and limits their reuse. Therefore, removing dyes from polyester fibers plays a positive role in promoting the recycling process of waste polyester fabrics.

[0004] Existing decolorization methods have many drawbacks: traditional oxidation methods easily damage fiber structure, leading to a decrease in fabric strength, and wastewater treatment is difficult; reduction methods are incomplete, the reducing agents have poor stability, and storage and use requirements are stringent; emerging enzymatic decolorization methods are inefficient and time-consuming; ozone decolorization equipment is costly and energy-intensive; photocatalytic decolorization is limited by light conditions and affects fiber performance; supercritical fluid decolorization requires high temperature and pressure conditions, and has high equipment requirements; some organic solvents used in existing solvent extraction decolorization methods are volatile, highly toxic, and pollute the environment. Therefore, developing an efficient, environmentally friendly, low-cost decolorization method for waste polyester fabrics that can maintain fiber performance has become an urgent need for the sustainable development of the textile industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a method for decolorizing waste polyester fabrics. By using a non-ionic polymer solvent as the decolorizing medium, the method achieves repeated solvent decolorization and efficient decolorization of waste laundry fabrics through "decolorization-adsorption-recovery".

[0006] To solve the above-mentioned technical problems, this invention discloses a method for decolorizing waste polyester fabrics, comprising the following steps:

[0007] Step (1): Add waste polyester fabric to solvent, heat to decolorize, and after solid-liquid separation, obtain decolorized fabric and colored solution respectively;

[0008] Step (2): Add activated carbon to the colored solution for adsorption, and obtain a colorless solvent after solid-liquid separation;

[0009] Step (3): Replace the solvent in step (1) with the colorless solvent and repeat the operations of steps (1) and (2).

[0010] Preferably, in step (1), the solvent is polyethylene glycol (PEG, Mn=400Da, boiling point>250℃), ethylene glycol (EG, boiling point 197.3℃), diethylene glycol (DEG, boiling point 245℃), benzyl alcohol (BA, boiling point 205℃), n-octanol (n-Octanol, boiling point 195.2℃), isooctanol (i-Octanol, boiling point 183-185℃), or benzoic acid. Methyl ester (MB, boiling point 199.6℃), ethyl benzoate (EB, boiling point 212.6℃), γ-valerol (GVL, boiling point 207-208℃), propylene carbonate (PC, boiling point 242℃), N,N-dimethylformamide (DMF, boiling point 153℃), N,N-dimethylacetamide (DMAc, boiling point 166.1℃), dimethyl sulfoxide (DMSO, boiling point 189℃), dipropylene glycol Dimethyl ether (DPGDME, boiling point 175-178℃), diethylene glycol butyl ether (DEGBE, boiling point 230-231℃), polyethylene glycol diglycidyl ether (PEGDGE, boiling point >250℃), polypropylene glycol diglycidyl ether (PPGDGE, boiling point >250℃), and isosorbide dimethyl ether (DMI, boiling point 228-230℃), preferably polyethylene glycol (PEG, Mn... =400Da, boiling point >250℃), ethylene glycol (EG, boiling point 197.3℃), diethylene glycol (DEG, boiling point 245℃), benzyl alcohol (BA, boiling point 205℃), n-octanol (n-Octanol, boiling point 195.2℃), isooctanol (i-Octanol, boiling point 183-185℃), with polyethylene glycol (PEG, Mn=400Da, boiling point >250℃) being the most preferred.

[0011] Preferably, in step (1), the mass-to-volume ratio of the waste polyester fabric to the solvent is 1:20~1:30 g / mL, and more preferably 1:25 g / mL.

[0012] Preferably, in step (1), the heating and decolorization temperature is 80℃~200℃, preferably 160℃; the heating and decolorization time is 10 minutes~80 minutes, preferably 60 minutes.

[0013] Preferably, in step (2), the mass-to-volume ratio of the activated carbon to the colored solvent is 0.01~0.1g / 5mL, and more preferably 1:25g / mL.

[0014] Preferably, in step (2), the adsorption temperature is 80℃~180℃, more preferably 150℃; the adsorption time is 1 hour~3 hours, more preferably 2 hours.

[0015] Preferably, the repeated steps (1) and (2) are repeated at least five times. Furthermore, in each operation, the decolorization rate of the waste polyester fabric is above 99%.

[0016] Preferably, the waste polyester fabric is decolorized, and then washed and dried to obtain the final product.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] First, this invention uses a non-ionic polymer to decolorize waste polyester fabrics. Disperse dyes are deeply removed through solvent swelling and extraction, achieving a stable decolorization rate of over 99%, while largely preserving the fiber structure and mechanical properties, with only a slight decrease in crystallinity. The solvent can be recycled after adsorption by activated carbon, significantly reducing costs and environmental burden. It is suitable for waste polyester fabrics of different sources and colors, balancing environmental protection and cost control requirements, and providing technical support for large-scale industrial application.

[0019] Secondly, the non-ionic polymer used in this invention decolorizes waste polyester fabrics with a small amount and short decolorization time, which greatly improves the decolorization efficiency of waste polyester fabrics. Attached Figure Description

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0021] Figure 1 This is a schematic diagram of the process for decolorizing waste polyester fabrics according to the present invention.

[0022] Figure 2 The image shows scanning electron microscope (SEM) images of the polyester fabric before and after decolorization in Example 2. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] In the following examples, the decolorization rate of the polyester fabric was calculated using the following formula:

[0025]

[0026] In the formula E cs (%) represents the decolorization rate of polyester fabric, (K / S)1 represents the arithmetic mean of the K / S values ​​of the polyester fabric at the maximum absorption wavelength before decolorization; (K / S)2 represents the arithmetic mean of the K / S values ​​of the polyester fabric at the maximum absorption wavelength after decolorization.

[0027] Example 1: Optimization of decolorizing solvent for waste polyester fabrics

[0028] 5 mL of high-boiling-point solvents (polyethylene glycol (PEG-400), ethylene glycol, diethylene glycol, benzyl alcohol, n-octanol, and isooctanol) were selected respectively, and 0.2 g of waste polyester fabric (1 cm × 1 cm) was added to each. The fabrics were decolorized at constant temperatures of 110℃, 120℃, 130℃, 140℃, 150℃, and 160℃ for 60 min. After decolorization, the fabrics were removed, and the residual solvent on the surface was cleaned with ethanol. After washing with water, the fabrics were dried. The K / S value of the fabrics before and after decolorization was measured using a colorimeter (Datacolor850), and the decolorization rate was calculated.

[0029] Table 1 shows the decolorization effects of waste polyester fabrics under different solvents and temperatures. The experimental results indicate that the decolorization rate of each solvent increases with increasing temperature, and tends to stabilize at 150℃~160℃. Among them, polyethylene glycol PEG-400 showed the best decolorization effect at 160℃, with no obvious color characteristics on the fabric surface and a decolorization rate of 99%.

[0030] Table 1. Decolorization effect of polyester fabrics under different solvents and temperatures

[0031]

[0032] Example 2: Optimization of solvent dosage for decolorizing waste polyester fabrics

[0033] Measure 5 mL of polyethylene glycol (PEG-400) and add 0.05 g, 0.10 g, 0.15 g, and 0.20 g of dyed polyester fabric respectively. Decolorize at 160℃ for 60 min and calculate the decolorization rate according to the post-treatment and detection method in Example 1.

[0034] Table 2 shows the decolorization effect of waste polyester fabrics at different fabric-to-solvent ratios (g / mL). The experimental results show that the smaller the fabric-to-solvent ratio (g / mL), the higher the decolorization rate. Considering both decolorization efficiency and solvent consumption, the optimal fabric-to-solvent ratio is 0.2 g fabric to 5 mL solvent.

[0035] Table 2. Decolorization effect of polyester fabrics under different ratios of additives to solvents (g / mL)

[0036]

[0037] Example 3: Optimization of Decolorization Time Parameters for Waste Polyester Fabrics

[0038] Measure 5 mL of polyethylene glycol PEG-400 and add 0.20 g of dyed polyester fabric. Decolorize at 160℃ for 15 min, 30 min, 45 min, 60 min, and 75 min respectively. Calculate the decolorization rate according to the post-treatment and detection method in Example 1.

[0039] The decolorization effect of polyester fabrics at different times is shown in Table 3. The experimental results show that the decolorization rate increases with the extension of decolorization time.

[0040] Table 3. Decolorization effect of polyester fabrics at different times

[0041]

[0042] Example 4: Comparison of decolorization effects on waste polyester fabrics of various colors

[0043] Eight different colors of waste polyester fabrics (black, medium khaki, army green, navy blue, maroon, dark purple, fruit green, and pink) were selected. 0.2 g of each was taken and 5 mL of polyethylene glycol PEG-400 was added. The fabrics were decolorized at 160℃ for 60 min. The decolorization rate was calculated according to the post-treatment and detection method in Example 1.

[0044] The decolorization effect is shown in Table 4. The experimental results show that the decolorization rate of the eight waste polyester fabrics is above 96%, of which black, maroon, and dark purple have a decolorization rate of 99%, and medium khaki, army green, navy blue, fruit green, and pink have a decolorization rate of 98%.

[0045] Table 4. Decolorization effect of waste polyester fabrics of different colors

[0046]

[0047] Example 5: Decolorizing solvent recovery and recycling

[0048] Measure 5 mL of polyethylene glycol PEG-400, add 0.20 g of waste polyester fabric, and decolorize at 160℃ for 60 min. Collect the decolorized mixed solution. Take 5 mL of this solution, add 0.02 g of activated carbon powder, and adsorb at 150℃ for 2 h. Separate the activated carbon and filtrate by vacuum filtration to obtain the recovered solvent.

[0049] The recovered solvent was used to repeat the above decolorization process for 5 cycles. After each cycle, the decolorization rate was tested according to the method in Example 1. The decolorization rates during the cycle are shown in Table 5. The experimental results show that the decolorization rate of the fabric remained above 99% throughout the 5 cycles, proving that the solvent recovery cycle is feasible.

[0050] Table 5 Decolorization effect during solvent recycling process

[0051]

[0052] This invention provides a method for decolorizing waste polyester fabrics. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for decolorizing waste polyester fabrics, characterized in that, Includes the following steps: Step (1): Add waste polyester fabric to solvent, heat to decolorize, and after solid-liquid separation, obtain decolorized fabric and colored solution respectively; Step (2): Add activated carbon to the colored solution for adsorption, and obtain a colorless solvent after solid-liquid separation; Step (3): Replace the solvent in step (1) with the colorless solvent and repeat the operations of steps (1) and (2).

2. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, In step (1), the solvent is any one of polyethylene glycol, ethylene glycol, diethylene glycol, benzyl alcohol, n-octanol, isooctanol, methyl benzoate, ethyl benzoate, γ-valerolactone, propylene carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dipropylene glycol dimethyl ether, diethylene glycol butyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and isosorbide dimethyl ether.

3. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of the waste polyester fabric to the solvent is 1:20~1:30 g / mL.

4. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, In step (1), the temperature for heating and decolorizing is 80℃~200℃, and the heating and decolorizing time is 10 minutes~80 minutes.

5. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, In step (2), the mass-to-volume ratio of the activated carbon to the colored solvent is 0.01~0.1g / 5mL.

6. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, In step (2), the adsorption temperature is 80℃~180℃ and the adsorption time is 1 hour~3 hours.

7. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, In step (1), the solvent is polyethylene glycol; the mass-to-volume ratio of the waste polyester fabric to the solvent is 1:25 g / mL; the heating decolorization temperature is 160°C; and the heating decolorization time is 60 minutes. In step (2), the mass-to-volume ratio of the activated carbon to the colored solvent is 0.02 g / 5 mL; the adsorption temperature is 150°C; and the adsorption time is 2 hours.

8. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, The repeated steps (1) and (2) are repeated at least five times.

9. The method for decolorizing waste polyester fabrics according to claim 8, characterized in that, In each operation, the decolorization rate of the waste polyester fabric was over 99%.

10. The method for decolorizing waste polyester fabrics according to claim 1, characterized in that, After the waste polyester fabric described in step (1) is decolorized, the fabric is washed and dried to obtain the final product.

Images