Method for separating components of cotton-polyester blended fabric based on eutectic system

Abstract

The invention relates to a method for separating components of a cotton-polyester blended fabric based on a eutectic system, which comprises the following steps: (S1) soaking the cotton-polyester blended fabric in the eutectic system to obtain a swollen cotton-polyester blended fabric; (S2) carrying out freezing treatment on the swollen cotton and polyester blended fabric to obtain a frozen cotton and polyester blended fabric; (S3) carrying out crushing treatment on the frozen cotton-polyester blended fabric to obtain a crushed cotton-polyester blended fabric; and (S4) the crushed cotton-polyester blended fabric is screened and separated, undersize products and oversize products are collected, the undersize products are cotton components, and the oversize products are polyester components. According to the separation process for adjusting the aggregation state structure of the cotton fibers through the eutectic system and coupling the ice crystals to increase brittleness, a new solution is provided for sustainable recycling of the cotton-polyester blended textiles, and the progress of a waste textile separation technology is promoted.

Description

Technical Field

[0001] This invention relates to the field of textile resource recycling technology, and in particular to a method for separating components of cotton-polyester blended fabrics based on a eutectic system. Background Technology

[0002] Most everyday clothing is made of blended textiles. However, blended textiles have complex compositions, and the different components of the fibers have significantly different properties, making separation difficult. This has become a major bottleneck in the recycling of waste textiles. For example, patent CN115197468A discloses a method for recycling waste nylon and its blended fabrics, but this method can only extract nylon from multi-component fiber blended fabrics and cannot recover other components. Patent CN118791777A discloses a method for separating and regenerating waste polyester-nylon-cotton blended textiles. This method uses solvents, co-solvents, and diols, and the subsequent solvent removal step is cumbersome. Furthermore, this method requires the reaction to be carried out in a high-pressure reactor at high temperature and high pressure in the presence of a catalyst, making the process cumbersome and costly.

[0003] Therefore, developing novel separation methods that combine environmental friendliness and functionality is a core challenge for improving the quality of recycled fibers and expanding their high-value applications. Given the structural differences in cotton-polyester blended fabrics, finding a method that can effectively and precisely control the aggregated structure of cotton cellulose fibers while simultaneously separating the cotton and polyester components is of great significance. Summary of the Invention

[0004] To address the problems in the existing technology, this invention provides a method for separating components of cotton-polyester blended fabrics based on a eutectic system. This invention utilizes a separation process that adjusts the aggregated structure of cotton fibers through a eutectic system, achieving efficient recycling and reuse of both polyester and cotton components. This provides a new solution for the sustainable recycling of cotton-polyester blended textiles and promotes advancements in waste textile separation technology.

[0005] This invention provides a method for separating components of cotton-polyester blended fabrics based on a eutectic system, comprising the following steps: (S1) The cotton-polyester blended fabric is immersed in a eutectic system to obtain a swollen cotton-polyester blended fabric. (S2) The swollen cotton-polyester blended fabric is subjected to a freeze treatment to obtain a frozen cotton-polyester blended fabric. (S3) The frozen cotton-polyester blended fabric is pulverized to obtain pulverized cotton-polyester blended fabric. (S4) The pulverized cotton-polyester blended fabric is sieved and separated to collect the undersize and oversize, wherein the undersize is the cotton component and the oversize is the polyester component.

[0006] Deep eutectic systems can effectively dissociate the original intramolecular / intermolecular hydrogen bond network of cellulose molecules through competitive hydrogen bond interactions with hydroxyl groups on the molecular chain. During this process, the disassembly and reassembly of the cellulose supramolecular structure is achieved through dynamic hydrogen bond recombination. Therefore, deep eutectic solvents can selectively induce swelling and decrystallization of cotton cellulose in cotton-polyester blends, with the degree of swelling and decrystallization being jointly regulated by the fiber microstructure, chemical composition, and solution environment. Under the coupled action of external stress and temperature fields, precise control can be achieved over the fracture and fragmentation methods and sizes of cotton and polyester fibers. The deep eutectic system (or "deep eutectic solvent") in this invention is a binary or multi-component eutectic mixture comprising hydrogen bond donors and acceptors, with a melting point far lower than that of the individual pure components. The anions (such as Cl-) of the deep eutectic solvent (DES) are... - Polar groups (such as carboxyl or hydroxyl groups) can form competitive hydrogen bonds with hydroxyl groups on the cellulose molecular chain, thereby disrupting the highly ordered intermolecular / intramolecular hydrogen bond network of cellulose, leading to fiber swelling or partial dissolution.

[0007] In some embodiments, the cotton component in the cotton-polyester blended fabric has a mass percentage of 40-60%, for example, 40%, 45%, 50%, 55%, 60%, or any value therebetween; and the polyester component in the cotton-polyester blended fabric has a mass percentage of 60-40%, for example, 60%, 55%, 50%, 45%, 40%, or any value therebetween.

[0008] In some embodiments, the cotton-polyester blended fabric is selected from TC50 / 50, that is, the cotton component and the polyester component each account for 50wt%.

[0009] In some embodiments, the eutectic system includes a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). The hydrogen bond donor is selected from a mixture of an alcohol solvent, a carboxylic acid solvent, and water; the hydrogen bond acceptor is selected from quaternary ammonium compounds, alkaloid compounds, or inorganic salt compounds. The molecular configuration (coordination) of the hydrogen bond acceptor and the type of hydrogen bond donor (such as HBD containing a strong electron-withdrawing group) in the above-mentioned eutectic system significantly affect its degree of disruption and selectivity to the cellulose hydrogen bond network. The above-mentioned eutectic solvent system exhibits good separation effect on cotton-polyester blended fabric components.

[0010] In some embodiments, the alcohol solvent is selected from ethylene glycol. In some embodiments, the carboxylic acid solvent is selected from formic acid or lactic acid.

[0011] In some embodiments, the quaternary ammonium salt compound is selected from choline chloride. In some embodiments, the alkaloid compound is selected from betaine. In some embodiments, the inorganic salt compound is selected from one or more of zinc chloride and potassium carbonate. In some embodiments, the inorganic salt compound is selected from zinc chloride. Because Zn 2+ As strong Lewis acids, choline chloride targets the hydroxyl groups of cellulose through coordination, weakening its intramolecular hydrogen bond network and significantly increasing the swelling rate of cotton fibers, thereby increasing their size difference with polyester. In contrast, choline chloride and betaine, lacking metal coordination ability, mainly interact with hydrogen bonds formed with cotton fibers, resulting in lower swelling efficiency for cotton fibers and thus a decrease in the purity of recycled cotton and polyester fibers.

[0012] In some embodiments, the hydrogen bond donor is selected from one or more of ethylene glycol, formic acid, and lactic acid in a mixture with water. In some embodiments, the hydrogen bond donor is selected from formic acid and water. In some embodiments, the hydrogen bond acceptor is selected from one or more of choline chloride, betaine, zinc chloride, or potassium carbonate. In some embodiments, the hydrogen bond acceptor is selected from zinc chloride.

[0013] In some embodiments, the eutectic system is selected from choline chloride, formic acid, and water.

[0014] In some embodiments, the eutectic system is selected from betaine, lactic acid, and water.

[0015] In some embodiments, the eutectic system is selected from betaine, formic acid, and water.

[0016] In some embodiments, the eutectic system is selected from zinc chloride, ethylene glycol, and water.

[0017] In some embodiments, the eutectic system is selected from zinc chloride, formic acid, and water.

[0018] In some embodiments, the eutectic system is selected from zinc chloride, lactic acid, and water.

[0019] In some embodiments, the eutectic system is selected from potassium carbonate, ethylene glycol, and water.

[0020] In some embodiments, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is (1~10):(5~20); for example, it is 1:(5~20), 5:(5~20), 10:(5~20), (1~10):5, (1~10):10, (1~10):15, (1~10):20, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any value between them.

[0021] In some embodiments, the molar ratio of the alcohol solvent or carboxylic acid solvent to water in the hydrogen bond donor is 1:(1~10), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any value between them.

[0022] In some embodiments, the molar ratio of hydrogen bond acceptor, alcohol solvent or carboxylic acid solvent and water in the eutectic system is (1~10):3:(5~20), for example 1:3:(5~20), 3:3:(5~20), 5:3:(5~20), 7:3:(5~20), 9:3:(5~20), 10:3:(5~20), (1~10):3:5, (1~10):3:7, (1~10):3:9, (1~10):3:10, 1:3:10, 2:3:10, 5:3:10, 10:3:10, 2:3:5, 2:3:15 or any value between them.

[0023] In some embodiments, the method for preparing the eutectic system includes reacting the hydrogen bond acceptor and the hydrogen bond donor.

[0024] In some embodiments, the reaction temperature is 50 to 130 °C; for example, 50 °C, 70 °C, 90 °C, 110 °C, 130 °C or any value between them.

[0025] In some implementations, the reaction time is 1-24 hours, for example, 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 24 hours or any value between them.

[0026] In some embodiments, in step (S1), the mass ratio of the cotton-polyester blended fabric to the eutectic system is 1:5 to 30; for example, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30 or any value between them.

[0027] In some embodiments, the immersion treatment temperature is 40°C to 80°C; for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value between them.

[0028] In some implementations, the pretreatment time is 40 to 80 minutes, for example, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, 80 minutes or any value between them.

[0029] In some embodiments, step (S2) of the freezing process includes placing the swollen cotton-polyester blended fabric in liquid nitrogen for freezing treatment. Through freezing treatment, water molecules in the swollen cotton-polyester blended fabric will form ice crystals at the freezing point temperature, thereby increasing the brittleness of the ice crystals and further improving the separation effect.

[0030] In some embodiments, the freezing temperature is -76°C to -40°C, for example -76°C, -70°C, -60°C, -50°C, -40°C or any value between them.

[0031] In some embodiments, in step (S3), the particle size of the pulverized cotton-polyester blended fabric is 150-495 μm, for example, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 495 μm or any value between them. The cotton component in the pulverized cotton-polyester blended fabric has a particle size of 150-390 μm; for example, 150 μm, 170 μm, 190 μm, 210 μm, 230 μm, 250 μm, 270 μm, 290 μm, 310 μm, 330 μm, 350 μm, 370 μm, 390 μm or any value between them, preferably 150-250 μm. The polyester component in the pulverized cotton-polyester blended fabric has a particle size of 289-495 μm; for example, 300 μm, 320 μm, 340 μm, 360 μm, 380 μm, 400 μm, 420 μm, 440 μm, 460 μm, 480 μm, 495 μm or any value between them, preferably 300-495 μm.

[0032] In some embodiments, the pulverizing temperature is -40 to -10°C, for example -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, or any value between them.

[0033] In some embodiments, in step (S3), the pulverization is performed by mechanical external force. Mechanical pulverization allows for precise control over the breaking mode and size of cotton and polyester fibers.

[0034] In some embodiments, the grinding is performed using one or more of a centrifugal grinder, an ultracentrifugal grinder, or a rotary grinder.

[0035] In some implementations, when pulverizing using a disc mill, ultracentrifugal mill, or rotary mill, there is no ball milling media, and the rotation speed is 6000 to 12000 rpm, for example, 6000 rpm, 8000 rpm, 10000 rpm, 12000 rpm, or any value between them.

[0036] In some embodiments, the grinding time is 1 to 20 min, for example, 1 min, 3 min, 5 min, 7 min, 9 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min or any value between them.

[0037] In some embodiments, the mesh size of the sieve used for sieving in step (3) is 40-80 mesh. In some embodiments, the mesh size of the sieve used for sieving in step (3) is 50-60 mesh. In some embodiments, the mesh size of the sieve used for sieving in step (3) is 60 mesh. The components are effectively separated through sieving. While ensuring high separation efficiency, the integrity of the cotton structure is preserved to the maximum extent, achieving closed-loop recycling of all components of waste blended fabrics.

[0038] The present invention has the following beneficial effects: This invention focuses on the controllable dissociation and reconstruction of the hydrogen bond network and aggregated structure of cotton cellulose fibers. By adjusting the aggregated structure of cotton fibers through a eutectic system, it significantly increases the difference in physicochemical properties between cotton and polyester fibers in cotton-polyester blended fabrics, and innovatively develops a new method for separating cotton and polyester components through "structure regulation-property differentiation-physical separation". This invention selects a eutectic system to separate cotton and polyester components, causing the cotton cellulose in the cotton-polyester blended fabric to swell and decrystallize. After swelling, the water molecules inside the cellulose will form ice crystals at freezing point, further affecting the multilevel structure and mechanical properties of the cellulose fibers.

[0039] Furthermore, mechanical pulverization allows for precise control over the breaking patterns and dimensions of cotton and polyester fibers, while sieving effectively separates the components. This ensures high separation efficiency while maximizing the preservation of the cotton's structural integrity, enabling closed-loop recycling of all components from waste blended fabrics. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 The images show the microstructure of cotton fibers after treatment with the eutectic system of experimental group 1, experimental group 2 and control group 1 in this invention. Figure 2 Infrared spectra of cotton fibers after treatment with the eutectic system in experimental groups 1, 4, 7 and control group 1.

[0042] Figure 3 X-ray diffraction patterns of cotton fibers treated with the eutectic system in experimental groups 1, 4, 7 and control group 1. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0044] Based on the information contained herein, various changes to the precise description of the invention can be readily made by those skilled in the art without departing from the spirit and scope of the appended claims. It should be understood that the scope of the invention is not limited to the defined processes, properties, or components, as these embodiments and other descriptions are merely illustrative of specific aspects of the invention. In fact, various modifications to embodiments of the invention that will be apparent to those skilled in the art or related fields are covered within the scope of the appended claims.

[0045] To better understand the invention and not to limit its scope, all figures and other numerical values ​​used in this invention to indicate amounts, percentages, or other quantities should, in all cases, be understood to be modified by the word "approximately." Therefore, unless specifically stated otherwise, the numerical parameters listed in the specification and appended claims are approximate values ​​and may vary depending on the desired properties being sought. Each numerical parameter should at least be considered as obtained based on reported significant figures and through conventional rounding methods.

[0046] Additionally, it should be noted that, unless otherwise defined, the scientific and technical terms used in the context of this invention should have the meanings commonly understood by those skilled in the art. The terms "comprising," "including," "containing," "having," and similar words are non-limiting, allowing for the addition of other steps and components that do not affect the result. The term "and / or" should be considered as a specific disclosure of each of the two specified features or components, with or without the other. For example, "A and / or B" would be considered to include (i) A, (ii) B, and (iii) A and B.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will now be described in detail.

[0048] The present invention will be further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to the conditions recommended by the manufacturer.

[0049] Example: Establishment of a method for separating and recycling components of waste polyester-cotton blended fabrics

[0050] By comparing the separation purity and other effects of cotton fibers treated with different eutectic systems, a method for separating and recycling waste polyester-cotton blended fabrics was established. In this embodiment, the cotton-polyester blended fabrics used in the experimental and control groups were TC50 / 50.

[0051] The eutectic solvent used in this embodiment was prepared by reacting the hydrogen bond donor and the hydrogen bond acceptor at 50-130°C for 1-24 hours.

[0052] Experimental Group 1: A method for separating cotton-polyester blended fabric components by controlling the aggregated structure of cotton fibers using a eutectic system, including the following steps: Waste cotton-polyester blended fabric was made into 5×5cm pieces and added to a ZnCl2 (hydrogen bond acceptor)-formic acid (hydrogen bond donor)-water (molar ratio 2:3:10) system at a solid-liquid mass ratio of 1:20. The mixture was soaked at 60 ℃ for 60 min. After soaking, the fabric was centrifuged at 800 g for 5 min to separate the solid and liquid phases, yielding the swollen cotton-polyester blended fabric. The morphology of the cotton fibers in the swollen cotton-polyester blended fabric is shown below. Figure 1 As shown, the eutectic system promotes fiber swelling. The infrared spectrum of the cotton component in the swollen cotton-polyester blended fabric is shown below. Figure 2 As shown. The XRD pattern of the cotton component in the swollen cotton-polyester blended fabric is shown in the figure. Figure 3 As shown.

[0053] The swollen cotton-polyester blended fabric is placed in liquid nitrogen for freezing treatment. Water molecules in the cotton-polyester blended fabric will form ice crystals at the freezing point temperature (i.e., -76 ℃ ~ -40 ℃), resulting in frozen cotton-polyester blended fabric.

[0054] At a low temperature (i.e. -20℃), the frozen cotton-polyester blended fabric was placed in an ultracentrifugal grinder for pulverization at a speed of 1000 rpm for 2 min to obtain the pulverized cotton-polyester blended fabric for later use. The particle size of the pulverized cotton-polyester blended fabric was statistically analyzed using an electron microscope, as shown in Table 1. Under the microscope, the cotton component appeared as flaky particles with small pores on the surface, while the polyester component appeared as smooth, irregular particles larger than the cotton particles. Most of the cotton-polyester aggregates were larger than the individual cotton-polyester components and were considered as non-separable parts. Based on the particle size statistics, a suitable sieve was selected for sieving.

[0055] The pulverized cotton-polyester blended fabric was sieved using a 60-mesh sieve. Most of the polyester component remained in the sieve, and the cotton component was collected after sieving.

[0056] Experimental Group 2: The difference from Experimental Group 1 is that ZnCl2-formic acid-water was replaced with ZnCl2-lactic acid-water. The morphology of cotton fibers in the swollen cotton-polyester blended fabric is as follows: Figure 1 As shown.

[0057] Experimental Group 3: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with ZnCl2-ethylene glycol-water.

[0058] Experimental Group 4: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with choline chloride-formic acid-water. The infrared spectrum of the cotton component in the swollen cotton-polyester blended fabric is shown below. Figure 2 As shown. The XRD pattern of the cotton component in the swollen cotton-polyester blended fabric is shown in the figure. Figure 3 As shown.

[0059] Experimental Group 5: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with choline chloride-lactic acid-water.

[0060] Experimental Group 6: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with choline chloride-ethylene glycol-water.

[0061] Experimental Group 7: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with betaine-formic acid-water. The infrared spectrum of the cotton component in the swollen cotton-polyester blended fabric is shown below. Figure 2 As shown. The XRD pattern of the cotton component in the swollen cotton-polyester blended fabric is shown in the figure. Figure 3 As shown.

[0062] Experimental Group 8: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with betaine-lactic acid-water.

[0063] Experimental Group 9: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with betaine-ethylene glycol-water.

[0064] Experimental Group 10: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with potassium carbonate-formic acid-water.

[0065] Experimental Group 11: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with potassium carbonate-lactic acid-water.

[0066] Experimental Group 12: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with potassium carbonate-ethylene glycol-water.

[0067] Experimental Group 13: The difference from Experimental Group 1 is that ZnCl2-formic acid-water (molar ratio 2:3:10) is replaced with ZnCl2-formic acid-water (molar ratio 1:3:10).

[0068] Experimental Group 14: The difference from Experimental Group 1 is that ZnCl2-formic acid-water (molar ratio 2:3:10) is replaced with ZnCl2-formic acid-water (molar ratio 5:3:10).

[0069] Experimental Group 15: The difference from Experimental Group 1 is that ZnCl2-formic acid-water (molar ratio 2:3:10) is replaced with ZnCl2-formic acid-water (molar ratio 10:3:10).

[0070] Experimental Group 16: The difference from Experimental Group 1 is that ZnCl2-formic acid-water (molar ratio 2:3:10) is replaced with ZnCl2-formic acid-water (molar ratio 2:3:5).

[0071] Experimental Group 17: The difference from Experimental Group 1 is that ZnCl2-formic acid-water (molar ratio 2:3:10) is replaced with ZnCl2-formic acid-water (molar ratio 2:3:15).

[0072] Experimental Group 18: The only difference from Experimental Group 1 is that the soaking temperature is 40℃.

[0073] Experimental Group 19: The only difference from Experimental Group 1 is that the soaking temperature is 80℃.

[0074] Experimental group 20-21 changed the mechanical crushing process

[0075] The only difference between experimental group 20 and experimental group 21 is that experimental groups 20 and 21 were pulverized using a disc mill or a rotary mill, respectively, without ball milling media, at a speed of 10,000 rpm, and for a grinding time of 2 min.

[0076] Experimental Group 22: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with ZnCl2-formic acid.

[0077] Experimental Group 23: The difference from Experimental Group 1 is that ZnCl2-formic acid-water is replaced with ZnCl2-oxalic acid-water.

[0078] Control group 1: The difference from experimental group 1 is that ZnCl2-formic acid-water was replaced with water. The morphology of cotton fibers in the cotton-polyester blended fabric after water treatment is as follows... Figure 1 As shown, water has no effect on the cotton components and does not promote the swelling of cotton fibers. The infrared spectrum of the cotton component in the swollen cotton-polyester blended fabric is shown below. Figure 2 As shown. The XRD pattern of the cotton component in the swollen cotton-polyester blended fabric is shown in the figure. Figure 3 As shown.

[0079] Table 1

[0080] In Table 1, DP50 represents the average particle size.

[0081] The purity of the cotton components recovered from the above experimental groups and control groups was determined according to the following method, and the corresponding determination results are shown in Table 2.

[0082] Method for determining the recovery rate of cotton components: The recovered cotton components are washed with water, dried, and weighed as m1.

[0083] The recovery rate of the cotton component is calculated using the following formula: X1 = m1 / m0; Wherein, X1—cotton component recovery rate, %; m0—mass of cotton in waste cotton-polyester blended fabric, g; m1—mass of solids after washing and drying of the separated and recovered cotton component, g.

[0084] Methods for determining the purity of cotton components: The recovered cotton component was mixed with phenol / tetrachloroethane (mass fraction 6:4) and heated at 45 °C for 10 min with stirring. The undissolved cotton component was then separated by filtration.

[0085] The purity of the cotton component is calculated using the following formula: X2 = (m2 - m3) / m2; Wherein, X2—purity of cotton component, %; m2—mass of raw material taken for mechanical separation, g; m3—mass of residual solids after solvent dissolution, g.

[0086] Table 2 Results of cotton component performance testing in experimental and control groups

[0087] In Table 2, the molar ratio of each component in the eutectic system refers to the molar ratio of hydrogen bond acceptor, hydrogen bond donor, and water.

[0088] As shown in Table 2, the purity of cotton fibers mechanically separated from waste blended textiles after water treatment (i.e., control group 1) was 51.5%, indicating poor purity of the cotton component and hindering effective separation of the components. The purity of polyester and cotton fibers separated by the ZnCl2-based DES system was higher than that obtained by betaine and choline chloride treatment. This is because Zn... 2+ As strong Lewis acids, choline chloride targets the hydroxyl groups of cellulose through coordination, weakening its intramolecular hydrogen bond network and significantly increasing the swelling rate of cotton fibers, thereby increasing their size difference with polyester. In contrast, choline chloride and betaine, lacking metal coordination ability, mainly interact with hydrogen bonds formed with cotton fibers, resulting in lower swelling efficiency for cotton fibers and thus a decrease in the purity of recycled cotton and polyester fibers.

[0089] According to Experimental Group 1 and Experimental Groups 20-21, the purity of cotton and polyester fibers varies after waste blended textiles are crushed by different mechanical forces. Among them, the ultracentrifugal grinder (i.e., Experimental Group 1) has the best separation effect.

[0090] Application Example 1

[0091] The swelling coefficient and fiber properties of the swollen cotton-polyester blended fabrics obtained from the experimental group and the control group were determined according to the following methods, and the corresponding test results are shown in Table 3.

[0092] 1) Degree of polymerization determination: The JWC-32C Ubbelohde viscometer was used to determine the average degree of polymerization of cotton cellulose according to GB / T1548—2016 "Determination of intrinsic viscosity in copper ethylenediamine (CED) solution for pulp".

[0093]

[0094] In the formula: η r The relative viscosity is (mL / g); in this application, [η] is the intrinsic viscosity of the sample in the copper ethylenediamine solution (mL / g); K' is an empirical constant, for the cellulose-copper ethylenediamine system, K'=0.056; ρ is the concentration of the sample in the solvent (g / mL); DP is the average degree of polymerization of the sample. η0 is the solvent viscosity, in millipascal-seconds (mPa·s).

[0095] 2) Crystallinity determination: X-ray diffraction (XRD) was used to obtain spectra, which were then analyzed using MDI Jade 6.0. The crystallinity index (CI) was calculated by comparing the minimum intensity before the maximum diffraction peak with the height of the main diffraction peak. For cellulose, this is done by using 2θ = 18... ° The background intensity at that location is related to 2θ = 22.8. ° The peak heights at each location were compared to obtain the results.

[0096] Table 3 shows the results of the determination of the swelling properties of polyester-cotton blended fabrics.

[0097] As shown in Table 3, the cotton fibers treated with water (i.e., control group 1) exhibited the lowest degree of swelling, resulting in the worst recovery rate and purity of the cotton components, making effective separation of the components impossible. The cotton fibers separated by the eutectic system showed a slight decrease in crystallinity and degree of polymerization, indicating that the separation process preserved the structural integrity of the cotton fibers to the greatest extent possible.

[0098] Application Example 2: The process of low-temperature treatment making cotton fibers brittle.

[0099] The mechanical properties of cotton and polyester fibers in the frozen cotton-polyester blended fabrics obtained from the experimental and control groups were determined as follows, and the corresponding test results are shown in Table 4.

[0100] Fracture strength determination: The YG004 electronic single-fiber tensile testing machine is used to test the mechanical properties of fibers. Stress-strain tests are performed on samples at 25℃ and 60% relative humidity. The sample length is 20 mm, the tensile speed is 10 mm / min, and each sample is tested at least 15 times. The average value is then calculated using software analysis to determine the final breaking strength.

[0101] Table 4. Results of the determination of mechanical properties of cotton-polyester blended fabrics by different solvents.

[0102] As can be seen from Table 4, the eutectic system makes cotton fibers brittle, thereby achieving efficient separation of cotton and polyester fibers.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for separating components of cotton-polyester blended fabrics based on a eutectic system, comprising the following steps: (S1) The cotton-polyester blended fabric is immersed in a eutectic system to obtain a swollen cotton-polyester blended fabric. (S2) The swollen cotton-polyester blended fabric is subjected to a freeze treatment to obtain a frozen cotton-polyester blended fabric. (S3) The frozen cotton-polyester blended fabric is pulverized to obtain pulverized cotton-polyester blended fabric. (S4) The pulverized cotton-polyester blended fabric is sieved and separated to collect the undersize and oversize, wherein the undersize is the cotton component and the oversize is the polyester component.

2. The separation method according to claim 1, characterized in that, The cotton-polyester blended fabric has a cotton component mass percentage of 40-60% and a polyester component mass percentage of 60-40%.

3. The separation method according to claim 1 or 2, characterized in that, The eutectic system includes hydrogen bond donors and hydrogen bond acceptors. The hydrogen bond donor is selected from a mixture of an alcohol solvent, a carboxylic acid solvent, and water; preferably, the alcohol solvent is selected from ethylene glycol; the carboxylic acid solvent is selected from formic acid or lactic acid. The hydrogen bond acceptor is selected from quaternary ammonium compounds, alkaloid compounds, or inorganic salt compounds; Preferably, the quaternary ammonium salt compound is selected from choline chloride; The alkaloid compound is selected from betaine; The inorganic salt compound is selected from one or more of zinc chloride and potassium carbonate, preferably zinc chloride.

4. The separation method according to claim 3, characterized in that, The eutectic system is selected from choline chloride, formic acid, and water; the eutectic system is selected from betaine, lactic acid, and water. And / or, the eutectic system is selected from betaine, formic acid and water; And / or, the eutectic system is selected from zinc chloride, ethylene glycol, and water; And / or, the eutectic system is selected from zinc chloride, formic acid, and water; And / or, the eutectic system is selected from zinc chloride, lactic acid, and water; And / or, the eutectic system is selected from potassium carbonate, ethylene glycol and water.

5. The separation method according to claim 3 or 4, characterized in that, The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is (1~10):(5~20); Preferably, in the hydrogen bond donor, the molar ratio of the alcohol solvent or carboxylic acid solvent to water is 1:(1~10). Preferably, in the eutectic system, the molar ratio of hydrogen bond acceptor, alcohol solvent or carboxylic acid solvent and water is (1~10):3:(5~20).

6. The separation method according to any one of claims 3-5, characterized in that, The method for preparing the eutectic system includes: reacting the hydrogen bond acceptor and the hydrogen bond donor; Preferably, the reaction temperature is 50 ~ 130 °C; And / or, the reaction time is 1-24 h.

7. The separation method according to claim 1 or 2, characterized in that, In step (S1), the mass ratio of the cotton-polyester blended fabric to the eutectic system is 1:5~30; Preferably, the soaking temperature is 40℃~80℃; And / or, the soaking treatment time is 40~80 minutes.

8. The separation method according to claim 1, characterized in that, In step (S2), the freezing process includes: placing the swollen cotton-polyester blended fabric in liquid nitrogen for freezing treatment; Preferably, the freezing temperature is -76 ℃ to -40 ℃.

9. The separation method according to claim 1, characterized in that, In step (S3), the particle size of the pulverized cotton-polyester blended fabric is 150-495 μm; wherein, the particle size of the cotton component in the pulverized cotton-polyester blended fabric is 150-390 μm, preferably 150-250 μm; and the particle size of the polyester component in the pulverized cotton-polyester blended fabric is 280-495 μm, preferably 300-495 μm. Preferably, the pulverization temperature is -40 to -10°C; Preferably, the crushing is mechanical crushing. Preferably, the grinding instrument is selected from any one or more of a disc grinder, an ultracentrifugal grinder, or a rotary grinder; Preferably, the pulverizing speed is 6000~12000 rpm, and the pulverizing time is 1~20 min.

10. The separation method according to claim 1, characterized in that, In step (S4), the mesh size of the sieve used for sieving and separation is 40-80 mesh, preferably 50-60 mesh, and more preferably 60 mesh.

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