Decoloring method of waste colored polyester textile

Abstract

The invention relates to a decolorizing method of waste colored polyester textiles. The decolorizing method comprises the following steps: A, adding an organic solvent of which the solubility parameter is similar to that of polyester into a reducing agent solution to serve as a mixed decolorizing solvent; b, the waste colored polyester textiles are soaked in the mixed decolorizing solvent, solid-liquid separation is performed after decolorizing treatment, and decolorized polyester textiles and a primary decolorizing solvent are obtained; c, soaking the colored waste polyester textile into a primary decoloring solvent, and performing solid-liquid separation after decoloring treatment to obtain a decolored polyester textile and a secondary decoloring solvent; d, repeating the step C until the waste colored polyester textiles are difficult to decolorize, and at the moment, obtaining a deep-color decolorizing solvent which is repeatedly decolorized; e, drying the decolored textile to obtain a regenerated white polyester textile; and F, distilling the repeatedly decolored deep-color decoloring solvent, rectifying, and recovering to obtain the regenerated decoloring solvent. The problems of high energy consumption, low efficiency and the like of an existing decolorization process system can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of recycling waste textiles, in particular to a decolorization method for waste colored polyester textiles. Background Art

[0003] Polyester is the most widely used fiber in textiles and is also a hot spot and focus for the recycling of waste textiles. Theoretically, waste polyester textiles are more suitable for chemical depolymerization for recycling of raw materials, but polyester textiles often have heterogeneous characteristics due to their color, function, high added value, etc. For example, colored polyester products often contain dyes, pigments and other additives, which may have irreversible effects on the recycling quality of waste polyester textiles, and ultimately affect the appearance, hue, performance and cost of the recycled products, resulting in low recycling of waste colored polyester textiles. How to remove dyes from waste colored polyester textiles and give them high-value recycling effects is an important factor affecting the recycling of waste textiles.

[0004] Chinese invention patent CN118221520A discloses a system and method for chemically recovering waste PET products, wherein waste polyester with dye is transported to a flash evaporator and N,N-dimethylformamide or dimethyl sulfoxide decolorizing solvent is added for flash evaporation decolorization, and the decolorized product is crushed, melt extruded, subjected to convective alcoholysis, convective transesterification, crystallized and purified, and cyclic transesterification to prepare high-purity BHET; Chinese invention patent CN118344565A discloses a method for preparing heavy metal-free recycled polyester from waste polyester textiles, which mainly comprises decolorizing the waste polyester textiles in anisole or a mixed solvent of anisole and at least one of methanol, ethanol, ethylene glycol, and isopropanol, and removing the decolorized polyester textiles by adding a non-heavy metal catalyst and an alcoholysis agent. An alcoholysis reaction is carried out, and the obtained alcoholysis liquid is separated and purified to obtain a depolymerized regenerated monomer, and a non-heavy metal catalyst and a functional additive are added to catalyze the regenerated monomer to polymerize again to obtain a heavy metal-free regenerated polyester; Chinese invention patent CN118320857A discloses an integrated catalyst for degradation and decolorization of waste polyester and its preparation method and application, which mainly comprises mixing the integrated catalyst for degradation and decolorization of waste polyester with ethylene glycol, heating and stirring under the protection of nitrogen and a condenser, and then stopping the heating after heating, at which time the alcoholysis and decolorization are completed, recovering the catalyst and adding boiling water and stirring, and then filtering quickly, refrigerating and standing the filtrate and filtering again to obtain BHET crystals and alcoholysis liquid, drying the BHET crystals to constant weight, and recovering the alcoholysis liquid by rotary distillation.

[0005] Judging from the above disclosed technologies, the current decolorization technologies for waste colored polyester textiles mainly include: physical extraction method and oxidation-reduction method.

[0006] (1) The physical extraction method is to place the waste colored polyester textiles with dyes in a decolorization solvent system. Under the action of solvent extraction, the dye follows the movement of the decolorization solvent and is peeled off from the fiber, thereby achieving the decolorization of the waste colored polyester fabrics. At present, this method has the disadvantages of low decolorization efficiency and high cost. After decolorization once, the waste colored polyester textiles need to be recycled and reused. The solvent recovery problem is also a key issue that needs to be solved urgently.

[0007] (2) The redox method is to destroy the dye chromophore groups in waste textile fibers under oxidants, reducing agents and similar conditions, so that the dye molecules do not produce color, thereby achieving the decolorization of waste colored polyester fabrics. This method works well for some dyes, but for disperse dyes with special structures, the decolorization conditions may cause a serious decline in the performance of polyester fibers and even affect subsequent recycling. Summary of the invention

[0008] 1. Technical issues to be resolved In view of the shortcomings of the prior art, the present invention provides a decolorization method for waste colored polyester textiles, which can eliminate the influence of disperse dyes in waste colored polyester on the quality of polyester recycling products and improve many problems of the existing decolorization process system such as high energy consumption and low efficiency.

[0009] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a method for decolorizing waste colored polyester textiles, the method comprising the following steps: A. Select an organic solvent with a solubility parameter similar to that of polyester, and add a reducing agent solution to obtain a mixed decolorizing solvent; B. soaking the waste colored polyester textiles in a mixed decolorizing solvent, performing solid-liquid separation after decolorizing at a certain temperature, and obtaining decolorized polyester textiles and a primary decolorizing solvent; C. Immersing the waste colored polyester textile in a primary decolorization solvent, performing solid-liquid separation after decolorization at a certain temperature, and obtaining a decolorized polyester textile and a secondary decolorization solvent; D. Repeat step C until the waste colored polyester textile is difficult to decolorize, and a dark decolorizing solvent with repeated decolorization is obtained; E. Drying the decolorized polyester textile to obtain a regenerated white polyester textile; F. The dark decolorizing solvent that has been repeatedly decolorized is distilled and recovered to obtain a regenerated decolorizing solvent.

[0010] Preferably, in step A, the selected organic solvent having a solubility parameter close to that of polyester is tetramethyl urea, and the reducing agent solution is an aqueous solution of thiourea dioxide.

[0011] Preferably, in step A, the mass fraction of the reducing agent solution in the mixed decolorization solvent is 5-20%; the mass fraction of the reducing agent in the reducing agent solution is 10-50%.

[0012] Preferably, the color source of the waste colored polyester textiles is one or more of azo disperse dyes, anthraquinone disperse dyes and heterocyclic disperse dyes.

[0013] Preferably, in step B, the mass ratio of the waste colored polyester textile to the mixed decolorization solvent is 1:6-15; in step C, the mass ratio of the waste colored polyester textile to the primary decolorization solvent is 1:8-20.

[0014] Preferably, in step B, the decolorization temperature is 110-140° C., and the decolorization time is 5 min-30 min; in step C, the decolorization temperature is 110-140° C., and the decolorization time is 10 min-30 min.

[0015] Preferably, in step B and step C, the solid-liquid separation comprises one or more of suction filtration, centrifugal separation and reduced pressure distillation.

[0016] Preferably, in step F, the distillation recovery includes one or more of distillation, vacuum distillation, and rectification.

[0017] (III) Beneficial effects The invention provides a decolorization method for waste colored polyester textiles integrating extraction and decolorization, which can realize complete decolorization of waste colored polyester textiles, and the solvent after decolorization still has a decolorization effect, and can realize multiple decolorization. The waste liquid after multiple decolorization can be completely recovered and reused, thereby realizing efficient utilization of the decolorization solvent.

[0018] The present invention not only utilizes waste polyester textiles of a single color system, but also, based on the source of the raw materials, performs mixed bleaching treatment on waste polyester textiles of different colors, and also has a high extraction-reduction effect, thereby meeting the application requirements of the color of the regenerated fibers and avoiding the yellowing phenomenon caused by traditional bleaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The actual fabric picture of the waste blue polyester textile in Example 1 before and after the decolorization treatment; Figure 2 is the visible light absorption curve of the waste blue polyester textile in Example 1 before and after the decolorization treatment; Figure 3 The actual fabric picture of the waste red polyester textile in Example 2 before and after the decolorization treatment; Figure 4is the visible light absorption curve of the waste red polyester textile in Example 2 before and after the decolorization treatment; Figure 5 The actual fabric picture of the waste yellow polyester textile in Example 3 before and after the decolorization treatment; Figure 6 This is the visible light absorption curve of the waste yellow polyester textile in Example 3 before and after decolorization. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with examples. The protection scope of the present invention is not limited by the following examples.

[0021] In addition, it is worth mentioning that the color of the samples before and after bleaching is evaluated according to AATCC test method 110-2011, and the results are expressed as the ratio of the color absorption coefficient K to the color scattering coefficient S (K / S value). Specific operation: select a calibrated Datacolor colorimeter, use D65 light source and CIE10° viewing angle, fold the fabric to be tested twice to ensure that the color measurement makes the sample opaque, measure the K / S value of the samples before and after bleaching, measure 4 groups of each sample and take the average value, and process the test data to obtain the visible light absorption curve of the fabric. Embodiment 1:

[0022] A method for decolorizing waste colored polyester textiles comprises the following steps: A. Adding a 10% mass fraction of thiourea dioxide aqueous solution into tetramethyl urea to obtain a mixed decolorizing solvent, wherein the mass fraction of the thiourea dioxide aqueous solution in the mixed decolorizing solvent is 5%; B. Soaking the waste blue polyester textile in the mixed decolorization solvent in step A, wherein the mass ratio of the waste colored polyester textile to the mixed decolorization solvent is 1:10, the decolorization temperature is 140° C., and the decolorization time is 5 min. After the decolorization treatment is completed, solid-liquid separation is performed to obtain a decolorized polyester textile and a primary decolorization solvent; C. Soaking the waste blue polyester textile in the primary decolorization solvent in step B, wherein the mass ratio of the waste colored polyester textile to the primary decolorization solvent is 1:8, the decolorization temperature is 135° C., and the decolorization time is 15 min. After the decolorization treatment is completed, solid-liquid separation is performed to obtain a decolorized polyester textile and a secondary decolorization solvent; D. Repeat step C until the waste blue polyester textile is difficult to decolorize, and a dark decolorizing solvent with repeated decolorization is obtained; E. Drying the decolorized polyester textile to obtain a regenerated white polyester textile; F. Recover the repeatedly decolorized dark decolorizing solvent by vacuum distillation to obtain a regenerated decolorizing solvent. Embodiment 2:

[0023] A method for decolorizing waste colored polyester textiles comprises the following steps: A 50% by mass thiourea dioxide aqueous solution is added to tetramethyl urea to obtain a mixed decolorizing solvent, wherein the mass fraction of the thiourea dioxide aqueous solution in the mixed decolorizing solvent is 20%; The waste red polyester textile is immersed in the mixed decolorization solvent in step A, the mass ratio of the waste colored polyester textile to the mixed decolorization solvent is 1:15, the decolorization temperature is 110° C., the decolorization time is 30 min, and after the decolorization treatment is completed, solid-liquid separation is performed to obtain a decolorized polyester textile and a primary decolorization solvent; The waste red polyester textile is immersed in the primary decolorization solvent in step B, the mass ratio of the waste colored polyester textile to the primary decolorization solvent is 1:20, the decolorization temperature is 140° C., the decolorization time is 10 min, and after the decolorization treatment is completed, solid-liquid separation is performed to obtain a decolorized polyester textile and a secondary decolorization solvent; Repeat step C until the waste red polyester textile is difficult to decolorize, and a dark decolorizing solvent with repeated decolorization is obtained; E. Drying the decolorized polyester textile to obtain a regenerated white polyester textile; F. The dark decolorizing solvent that has been repeatedly decolorized is distilled and recovered to obtain a regenerated decolorizing solvent. Embodiment 3:

[0024] A method for decolorizing waste colored polyester textiles comprises the following steps: A. Adding a 20% mass fraction of thiourea dioxide aqueous solution into tetramethyl urea to obtain a mixed decolorizing solvent, wherein the mass fraction of the thiourea dioxide aqueous solution in the mixed decolorizing solvent is 10%; B. Soaking the waste yellow polyester textile in the mixed decolorization solvent in step A, wherein the mass ratio of the waste colored polyester textile to the mixed decolorization solvent is 1:6, the decolorization temperature is 130° C., the decolorization time is 20 min, and after the decolorization treatment is completed, solid-liquid separation is performed to obtain a decolorized polyester textile and a primary decolorization solvent; C. Soaking the waste yellow polyester textile in the primary decolorization solvent in step B, wherein the mass ratio of the waste colored polyester textile to the primary decolorization solvent is 1:12, the decolorization temperature is 110° C., and the decolorization time is 30 min. After the decolorization treatment is completed, solid-liquid separation is performed to obtain a decolorized polyester textile and a secondary decolorization solvent; D. Repeat step C until the waste yellow polyester textile is difficult to decolorize, and a dark decolorizing solvent with repeated decolorization is obtained; E. Drying the decolorized polyester textile to obtain a regenerated white polyester textile; F. Recover the repeatedly decolorized dark decolorizing solvent by distillation to obtain a regenerated decolorizing solvent.

[0025] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for decolorizing waste colored polyester textiles, characterized in that The method comprises the following steps: A. Select an organic solvent with a solubility parameter similar to that of polyester, and add a reducing agent solution to obtain a mixed decolorizing solvent; B. soaking the waste colored polyester textiles in a mixed decolorizing solvent, performing solid-liquid separation after decolorizing at a certain temperature, and obtaining decolorized polyester textiles and a primary decolorizing solvent; C. Immersing the waste colored polyester textile in a primary decolorization solvent, performing solid-liquid separation after decolorization at a certain temperature, and obtaining a decolorized polyester textile and a secondary decolorization solvent; D. Repeat step C until the waste colored polyester textile is difficult to decolorize, and a dark decolorizing solvent with repeated decolorization is obtained; E. Drying the decolorized polyester textile to obtain a regenerated white polyester textile; F. The dark decolorizing solvent that has been repeatedly decolorized is distilled and recovered to obtain a regenerated decolorizing solvent.

2. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: In step A, the organic solvent selected with a solubility parameter close to that of polyester is tetramethyl urea, and the reducing agent solution is an aqueous solution of thiourea dioxide.

3. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: In step A, the mass fraction of the reducing agent solution in the mixed decolorizing solvent is 5-20%; the mass fraction of the reducing agent in the reducing agent solution is 10-50%.

4. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: The color source of the waste colored polyester textiles is one or more of azo disperse dyes, anthraquinone disperse dyes and heterocyclic disperse dyes.

5. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: In step B, the mass ratio of the waste colored polyester textile to the mixed decolorization solvent is 1:6-15; in step C, the mass ratio of the waste colored polyester textile to the primary decolorization solvent is 1:8-20.

6. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: In step B, the decolorization temperature is 110-140° C., and the decolorization time is 5 min-30 min; in step C, the decolorization temperature is 110-140° C., and the decolorization time is 10 min-30 min.

7. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: In step B and step C, the solid-liquid separation includes one or more of suction filtration, centrifugal separation, and reduced pressure distillation.

8. The method for decolorizing waste colored polyester textiles according to claim 1, characterized in that: In step F, the distillation recovery includes one or more of distillation, vacuum distillation, and rectification.

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