CN-122013472-A - Method for decoloring supercritical mixed fluid

Abstract

The invention belongs to the field of resource utilization of waste textiles, and discloses a method for decoloring supercritical mixed fluid. The method comprises the steps of S1, placing pretreated textiles to be decolorized in a reaction kettle for vacuum treatment, S2, adding a decolorizing agent into the reaction kettle subjected to vacuum treatment, introducing supercritical mixed fluid, pressurizing and heating the reaction kettle to enable the supercritical mixed fluid to circularly flow in the reaction kettle subjected to pressurizing and heating so as to decolorize the textiles to be decolorized, S3, after the textiles to be decolorized are decolorized in the reaction kettle, depressurizing the reaction kettle to separate dyes removed from the textiles to be decolorized from the supercritical mixed fluid, wherein the supercritical mixed fluid is supercritical CO 2 -N 2 mixed fluid. The invention provides an environment-friendly decoloring technology which can give consideration to the nonpolar and polar dye removal effect and is suitable for complex vamps, and provides technical support for efficient and high-quality recovery of waste textiles.

Inventors

• XU JINTAI
• XU XUECHAO
• Wen Jieyun
• Sheng Enen

Assignees

• 信泰(福建)科技有限公司

Dates

Publication Date

20260512

Application Date

20260109

Claims (10)

1. 1. A method for decolorizing a supercritical mixed fluid, the method comprising the steps of: s1, placing the pretreated textile to be decolorized in a reaction kettle for vacuum treatment; s2, adding a decoloring agent into the reaction kettle subjected to vacuum treatment, introducing a supercritical mixed fluid, and pressurizing and heating the reaction kettle to enable the supercritical mixed fluid to circularly flow in the reaction kettle subjected to pressurizing and heating, so as to decolor the textile to be decolored; S3, after the textile to be decolorized is decolorized in the reaction kettle, depressurizing the reaction kettle to separate the dye removed from the textile to be decolorized from the supercritical mixed fluid; The supercritical mixed fluid is supercritical CO 2 -N 2 mixed fluid.
2. 2. The method according to claim 1, wherein in step S1, the pretreatment is performed by sequentially subjecting the textile to be decolorized to a crushing, washing and drying process, and the drying temperature is 60-80 ℃.
3. 3. The method according to claim 1, characterized in that in step S1 the water content of the pretreated textile to be decolorized is lower than 1%.
4. 4. The method according to claim 1, wherein in the step S2, the decoloring agent is at least one of dimethylformamide and dimethyl sulfoxide, and the mass ratio of the decoloring agent to the pretreated textile to be decolored is 5-15%.
5. 5. The method according to claim 1, wherein in step S2, the mass ratio of N 2 to CO 2 in the supercritical mixed fluid is 5% -15%.
6. 6. The method according to claim 1, wherein in step S2, the pressure of the reaction kettle after pressurization is 10-30 MPa, and the temperature of the reaction kettle after temperature rise is 80-120 ℃.
7. 7. The method according to claim 1, wherein in step S2, the supercritical mixed fluid is circulated in the reaction vessel at a flow rate of 20-40L/h for a period of 1-4 h.
8. 8. The method according to claim 1, wherein in step S3, the pressure in the reaction vessel is reduced to normal pressure in a stepwise manner while controlling the temperature change.
9. 9. The method of claim 8, wherein the staged depressurization comprises at least a first stage of maintaining the reactor temperature at 80-100 ℃ and reducing the reactor pressure to 10 MPa at a rate of 2-4 MPa/min and a second stage of reducing the reactor temperature from the reactor temperature of the first stage to 60-80 ℃ at a rate of 1-2 ℃/min and reducing the 10 MPa pressure to atmospheric pressure at the end of the first stage at a rate of 1 MPa/min.
10. 10. The method according to claim 1, wherein in step S3, the separated supercritical fluid mixture is purified and recycled.

Description

Method for decoloring supercritical mixed fluid Technical Field The invention belongs to the field of resource utilization of waste textiles, and particularly relates to a method for decoloring supercritical mixed fluid. Background In the field of sports shoes and running shoes, polyester fabrics (including mesh fabrics, knitted fabrics and composite fabrics) have become core substrates for current vamp manufacturing by virtue of light weight, high wear resistance and excellent air permeability. However, recycling of resources and reduction of carbon emission become core guide of the development of manufacturing industry, so that recycling of waste vamps is a key measure for reducing pollution of solid wastes and is a necessary choice for reducing raw material consumption in industry. However, in the actual recycling process, the decolorization treatment of various vamps has become a key point to be solved urgently. The vamp of different batches and different colors are mixed together, and the residual dye not only can lead to uneven color of the regenerated polyester material, but also can influence the chemical stability and mechanical property of the regenerated material. The current decolorizing method is mainly divided into two major categories, namely physical decolorizing and chemical decolorizing, and is respectively aimed at directly decolorizing the recovered fabric or carrying out decolorizing treatment on the monomer and intermediate products after depolymerizing the recovered fabric. The physical method mainly comprises two modes of adsorption and dissolution, namely, the adsorption method has mild operation conditions, limited adsorption capacity, frequent replacement of the adsorbent after saturation is needed to influence continuous treatment efficiency, and the solvent dissolution method has mature technology and wide applicability, generally depends on high-temperature and high-pressure equipment, and is easy to cause secondary pollution due to solvent residues. The chemical method mainly comprises oxidation/reduction, and damages the dye structure through a strong oxidant or a reducing agent, and although the process is mature, the physical properties of the fiber can be damaged in the decoloring process, and toxic byproducts are generated. In general, traditional physical and chemical decolorization methods still have obvious limitations in terms of environmental friendliness and process cleanliness, and are difficult to meet the development requirements of the current green cycle. In this context, supercritical carbon dioxide fluid decolorization technology has shown great potential as an emerging high-efficiency environmental-friendly process. The technology utilizes the excellent penetration and extraction capacity of supercritical carbon dioxide to dye, can realize high-efficiency decolorization without using water and strong-reactivity chemical auxiliary agents, and provides a more sustainable technical path for fabric recovery. However, the decolorization of waste textile dyes still faces multiple difficulties that the types of the waste textile dyes are extremely complex, reactive dyes, acid dyes and other dyes with stronger polarity are often remained besides disperse dyes, the disperse dyes and polyester fibers are tightly combined through Van der Waals force, hydrogen bonds and even chemical bonds, the fibers are high in crystallinity and compact in structure, the dyes are difficult to separate and permeate due to lack of active groups acting on the dyes, a barrier layer is formed on the surfaces of the fibers by polymer byproducts, the contact reaction of a decolorizing agent and the dyes is further limited, the effects of traditional reduction cleaning, oxidation stripping and other methods on the dyes in the fibers are limited, the fibers can be damaged or the decolorization is not thorough, the decolorization process is complicated due to the difference of dyeing properties of different fibers if the waste textiles are blended materials, various fiber characteristics are needed, and the decolorization unevenness or fiber damage are easy to be caused. Disclosure of Invention Aiming at the problems in the prior art, the invention provides a method for decoloring supercritical mixed fluid, which uses supercritical CO 2-N2 mixed fluid as a decoloring medium to optimize the polarity suitability and dissolution characteristic of the mixed fluid, so that the fluid not only maintains the high-efficiency extraction capacity of nonpolar disperse dyes, but also can show remarkable removal effect on polar dyes such as reactive dyes, acid dyes and the like, and improves the suitability of the technology to waste textiles with complex components and various dyes. The aim of the invention is achieved by the following technical scheme: the invention provides a method for decoloring supercritical mixed fluid, which comprises the following steps: s1, placing the pretreated textile to be deco