Low-energy-consumption rapid chemical separation method for polyester cotton fiber product

Abstract

The invention relates to the technical field of fiber product treatment, and discloses a low-energy-consumption rapid chemical separation method for polyester cotton fiber products. The method comprises the following steps: mixing and dissolving a hydrogen bond donor and a hydrogen bond acceptor to prepare a betaine-based eutectic solvent, and mixing the betaine-based eutectic solvent with alkali liquor to obtain a eutectic solvent / alkali composite system; immersing the polyester-cotton product in the deep eutectic solvent / alkali composite system for dissolution reaction, filtering after the reaction is finished, taking undissolved components in the polyester-cotton product, washing with water, and drying; according to the method, a betaine-based eutectic solvent / alkali composite system is adopted, polyester fiber components are dissolved in a mild condition within a short time, meanwhile, cotton fiber components are not damaged, the method has the advantages of being low in cost, environmentally friendly and the like, and rapid quantitative analysis of the polyester and cotton fiber components is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of fiber product processing, and in particular to a low-energy consumption rapid chemical separation method for polyester-cotton fiber products. Background Art

[0002] Polyester-cotton fiber products include polyester-cotton interwoven / blended clothing fabrics, home textile fabrics and industrial textiles. This type of fiber products has excellent performance, and can show good elasticity, wear resistance and dimensional stability in dry and humid environments, small shrinkage, strong wrinkle resistance, easy washing and quick drying, etc., which meet the market's comprehensive demand for the aesthetics, practicality and comfort of textiles, and have a large market share. For this reason, more than 14 million tons of polyester-cotton fiber-based waste textiles will need to be recycled and reused worldwide each year, which also accounts for 60% or more of the total amount of waste textiles. The key to the recycling of polyester-cotton fiber products lies in the rapid, efficient and low-energy separation of polyester and cotton fiber components, and then the components can be used at a high value.

[0003] At present, the technical methods for recycling and reusing polyester-cotton fiber products include physical methods, chemical methods, biological methods and modern spectroscopy. The physical method is relatively simple to operate, but the separation purity is not high, the efficiency is low, and the equipment and process requirements are high; the microscope observation method is to distinguish the polyester-cotton fibers by the different appearance characteristics of the fiber cross-section, and count and measure the diameter to obtain the percentage of each component of the polyester-cotton, but this method requires professional operation, is easily affected by human factors, and is relatively time-consuming; although the density gradient centrifugation method has the advantages of good separation effect, wide application range, good fiber integrity, etc., it cannot be ignored that the centrifugation time is long, the operation is complicated, and the number of sample processing is limited.

[0004] The chemical method is to separate the polyester and cotton fibers by acid or alkaline hydrolysis to cause a chemical reaction. However, it is difficult to achieve a chemical reaction of only a single component, and there are more side reactions, making it difficult to separate them completely. At the same time, the reactants are not easy to be recycled and reused. For example, the current standard GB / T 2910-2006 "Quantitative Chemical Analysis of Textiles" specifically uses sulfuric acid reagent to dissolve the cotton fiber component in polyester-cotton blended fabrics to achieve quantitative analysis of the fiber ratio. However, the standard requires the consumption of a large amount of high-concentration sulfuric acid. In actual operation, it is also found that concentrated sulfuric acid will also dissolve and etch polyester fibers to a certain extent, affecting the accuracy of the test results.

[0005] The biological method uses specific enzymes to degrade cotton or polyester fibers without affecting the other components. This method has the advantages of mild reaction conditions and environmental friendliness, but the enzyme cost is high and the reaction time is long. It is still in the research and exploration stage.

[0006] The most commonly used modern spectroscopic method for testing components is infrared spectroscopy, which uses the absorption spectrum characteristics of different chemical substances under infrared light. By comparing the infrared spectra of polyester-cotton fabric samples with known polyester-cotton standards, the composition of polyester and cotton fibers in polyester-cotton fabrics can be determined. However, infrared spectroscopy also has its drawbacks: limited sensitivity, many interference factors, complex analysis, and difficulty in rapid quantification. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a low-energy consumption rapid chemical separation method for polyester-cotton fiber products. The method adopts a betaine-based low eutectic solvent / alkali composite system to achieve the dissolution of polyester fiber components under mild conditions and in a short time without damaging the cotton fiber components. It has the advantages of low cost and green environmental protection, and realizes rapid quantitative analysis of polyester and cotton fiber components.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the method comprising the following steps: Step (1), adding a hydrogen bond donor and a hydrogen bond acceptor into a reaction bottle, stirring and dissolving, to prepare a betaine-based deep eutectic solvent; Step (2), adding alkali solution to the betaine-based low eutectic solvent and mixing to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system to undergo a dissolution reaction. After the reaction is completed, filtering is performed to obtain undissolved components in the polyester-cotton product, washing with water, and drying.

[0009] Preferably, in step (1), the hydrogen bond donor includes one of a polyol and urea, and the hydrogen bond acceptor is betaine.

[0010] Furthermore, the polyol in step (1) includes one of propylene glycol and ethylene glycol.

[0011] Furthermore, the polyol in step (1) is preferably ethylene glycol.

[0012] Preferably, in step (1), the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:2-4.

[0013] Preferably, in step (1), the stirring and dissolving operation comprises: stirring at 80° C. until completely dissolved, and then maintaining the temperature and continuing stirring for not less than 30 minutes.

[0014] Preferably, in step (2), the alkali solution is a sodium hydroxide solution with a concentration of 10 g / L to 50 g / L.

[0015] Preferably, in step (2), the mass ratio of the alkali solution to the betaine-based low eutectic solvent is 1.5:30-50.

[0016] Preferably, in step (2), the mixing conditions are: stirring at 90° C. for 25 minutes until completely dissolved.

[0017] Preferably, in step (3), the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30-50.

[0018] Preferably, in step (3), the dissolution reaction conditions are: dissolution reaction at 58-108° C. for 30-120 min.

[0019] Preferably, a polyester-cotton fiber product is processed using the low-energy rapid chemical separation method for polyester-cotton fiber products as described above.

[0020] Preferably, a low-energy rapid chemical separation method for polyester-cotton fiber products as described above is used in the rapid quantitative analysis of the components of polyester-cotton fiber products.

[0021] Compared with the prior art, the present invention has the following beneficial effects: A low eutectic solvent refers to a two-component or three-component low eutectic mixture composed of a hydrogen bond acceptor (such as a quaternary ammonium salt) and a hydrogen bond donor (such as compounds such as amides, carboxylic acids and polyols), and its freezing point is significantly lower than the melting point of the pure substances of each component. The betaine-based low eutectic solvent prepared in the present invention is prepared by mixing betaine (as a hydrogen bond acceptor) and ethylene glycol (as a hydrogen bond donor) in a certain proportion, that is, a low eutectic solvent.

[0022] Since a dense film will form on the surface of polyester after hot melt extrusion, it is difficult for high-concentration alkali to penetrate into the interior of polyester fibers and can only act on the surface of the fibers. Betaine-based low eutectic solvents can make the fibers swell and fibrillate at a certain temperature, making the originally compact fibers loose and destroying the dense film on the surface of the fibers. The alkali can then enter the amorphous region of the fibers and act on the carbonyl groups of the polyester fibers, causing the fibers to break and dissolve. Cotton fibers are polysaccharides composed of glucose units linked by β-1,4-glycosidic bonds. There are a large number of hydroxyl groups (-OH) on the cellulose molecular chain. These hydroxyl groups have a certain chemical stability in an alkaline environment. In this system, alkali ions (Na + ) will react with the hydroxyl groups on the cellulose molecular chain, but this action is mainly ion exchange or forming a relatively loose complex structure, and does not destroy the β-1,4-glycosidic bonds of the cotton fiber. The cotton fiber can still maintain its basic fiber morphology.

[0023] When the betaine-based low eutectic solvent is used alone to treat polyester-cotton fiber, since the low eutectic solvent can only act on the fiber surface, produce weak chemical reactions at the micro-nano scale, and cannot enter the dense fiber interior, even if it is reacted at 80-100°C for 12 hours, its weight loss rate is only 5%. Therefore, the effect of using the low eutectic solvent alone to dissolve the polyester fiber is not ideal; on the other hand, if the alkali solution is used alone to treat the polyester-cotton fiber, due to the high concentration of the alkali solution and the large viscosity of the solution, it can only adhere to the fiber surface and is difficult to quickly enter the polyester fiber. Within 60 minutes of reaction at 80-100°C, the weight loss rate of the polyester fiber can only reach about 20%, so the effect of using the alkali solution alone to treat the polyester-cotton product is also poor. In the present invention, when the betaine-based low eutectic solvent is used in combination with the alkali solution, the polyester component in the polyester-cotton fiber can be 100% dissolved by only treating at 98°C for 60 minutes; it can be seen that the betaine-based low eutectic solvent and the alkali solution have a synergistic effect in dissolving the polyester component in the polyester-cotton fiber product.

[0024] In view of the problem that the components of existing polyester-cotton fiber products are difficult to separate, the present invention adopts a betaine-based low eutectic solvent / alkali composite system. After systematic optimization and analysis of process parameters, the dissolution of polyester fiber components is achieved under mild conditions of 58-98°C, and the cotton fiber components are not damaged. The dissolution and separation temperature and dissolution and separation time save time compared with the current GB / T2910-2006 standard (sulfuric acid method); at the same time, the low eutectic solvent / alkali composite system adopted by the present invention also has the advantages of low cost and green environmental protection. Compared with the temperature of 170-230°C required in the literature reports on polyester dissolution, the process of the present invention requires a lower temperature, milder conditions, and better effects.

[0025] In the present invention, the polyester fiber components in the polyester-cotton fiber products can be dissolved and separated under mild conditions in a short time, the betaine-based low eutectic solvent / alkali composite system has almost no effect on the cotton fiber, and its mass loss can be controlled within 1.0%, which can realize the rapid quantitative analysis of the two fiber components of polyester and cotton, filling the technical gap of rapid quantitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram of the dissolution mechanism of the polyester component in the polyester-cotton fiber product of the present invention; Figure 2 It is a process flow chart of the low energy consumption rapid chemical separation method for polyester-cotton fiber products in the present invention; Figure 3 It is a bar graph of weight loss rate of polyester-cotton fiber products after chemical separation obtained in Example 1 and Comparative Examples 1-7 of the present invention; Figure 4 is a line graph of weight loss rate of polyester-cotton fiber products after chemical separation obtained in Examples 2-7 of the present invention; Figure 5 It is a line graph of weight loss rate of the polyester-cotton fiber products after chemical separation obtained in Example 6, Examples 8-9 and Comparative Example 8 of the present invention; Figure 6 This is a dissolution sample of the polyester-cotton fiber product obtained after chemical separation in Example 6, Examples 8-9 and Comparative Example 8 of the present invention; Figure 7 is an infrared spectrum of the polyester-cotton fiber products after chemical separation obtained in Example 6, Examples 8-9 and Comparative Example 8 of the present invention; Figure 8 It is a microscopic morphology of the polyester-cotton fiber products after chemical separation obtained in Example 6, Examples 8-9 and Comparative Example 8 of the present invention; Fig. 9 is a bar graph of the weight loss rate of the polyester-cotton fiber product after chemical separation obtained by repeating the experiment 20 times under the same parameters and conditions as Example 6 in the present invention; Fig.10 This is an infrared spectrum of the product of degradation and recovery of the polyester component in the present invention; In the figure: Figure 4 Where 1 is the weight loss rate of the polyester-cotton fiber product after the reaction; 2 is the mass of the product recovered from the degradation of the polyester component; Figure 5 3 is the dissolution rate of the polyester component; 4 is the mass of the product recovered from the degradation of the polyester component; Figure 6 , Figure 7 , Figure 8 In the figure, a is the polyester-cotton fiber product after treatment for 0 min; b is the polyester-cotton fiber product after treatment for 30 min; c is the polyester-cotton fiber product after treatment for 60 min; d is the polyester-cotton fiber product after treatment for 120 min. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0030] Example 2

[0031] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 58° C. for 60 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0032] Example 3

[0033] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 68° C. for 60 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0034] Example 4

[0035] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 78° C. for 60 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0036] Example 5

[0037] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 88° C. for 60 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0038] Example 6

[0039] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 98° C. for 60 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0040] Example 7

[0041] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 108° C. for 60 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0042] Example 8

[0043] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 98° C. for 120 min. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0044] Example 9

[0045] This embodiment discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 98° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0046] Comparative Example 1 This comparative example discloses a low-energy rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / Urea / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and urea (Urea) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / urea low eutectic solvent; Step (2), adding alkali solution to the betaine / urea low eutectic solvent under stirring conditions, stirring at 90° C. for 25 min until completely dissolved, wherein the mass ratio of alkali solution to betaine / urea low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0047] Comparative Example 2 This comparative example discloses a low-energy rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / Gly / NaOH composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and glycerol (Gly) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and then keeping the temperature and stirring for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / glycerol low eutectic solvent; Step (2), adding alkali solution to the betaine / glycerol low eutectic solvent under stirring conditions, stirring at 90° C. for 25 minutes until completely dissolved, wherein the mass ratio of alkali solution to betaine / glycerol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0048] Comparative Example 3 This comparative example discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / NaOH composite system, and the method comprises the following steps: Step (1), adding alkali solution to betaine (Bet) under stirring conditions, stirring at 90° C. for 25 minutes until completely dissolved, wherein the mass ratio of alkali solution to betaine is 1:2, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a betaine / alkali composite system; Step (2), immersing the polyester-cotton product in the betaine / alkali composite system, wherein the mass ratio of the polyester-cotton product to the betaine / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0049] Comparative Example 4 This comparative example discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Urea / NaOH composite system, and the method comprises the following steps: Step (1), adding alkali solution to urea (Urea) under stirring conditions, stirring at 90°C for 25 minutes until completely dissolved, the mass ratio of alkali solution to urea is 1:2, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50g / L, to obtain a urea / alkali composite system; Step (3), immersing the polyester-cotton product in the urea / alkali composite system, wherein the mass ratio of the polyester-cotton product to the urea / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0050] Comparative Example 5 This comparative example discloses a low-energy rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Gly / NaOH composite system, and the method comprises the following steps: Step (1), adding alkali solution to glycerol (Gly) under stirring conditions, stirring at 90° C. for 25 minutes until completely dissolved, wherein the mass ratio of alkali solution to glycerol is 1:2, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain a glycerol / alkali composite system; Step (2), immersing the polyester-cotton product in the propylene glycol / alkali composite system, wherein the mass ratio of the polyester-cotton product to the propylene glycol / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0051] Comparative Example 6 This comparative example discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is a Bet / EG composite system, and the method comprises the following steps: Step (1), adding betaine (Bet) and ethylene glycol (EG) in a molar ratio of 1:2 into a reaction bottle, stirring at 80°C until completely dissolved, and keeping the temperature to continue dissolving for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (3), immersing the polyester-cotton product in a betaine / ethylene glycol low eutectic solvent, wherein the mass ratio of the polyester-cotton product to the betaine / ethylene glycol low eutectic solvent is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0052] Comparative Example 7 This comparative example discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the composite system used is an EG / NaOH composite system, and the method comprises the following steps: Step (1), adding alkali solution to ethylene glycol (EG) under stirring conditions, stirring at 90° C. for 25 minutes until completely dissolved, wherein the mass ratio of alkali solution to ethylene glycol is 1:2, and the alkali solution is a sodium hydroxide (NaOH) solution with a concentration of 50 g / L, to obtain an ethylene glycol / alkali composite system; Step (3), immersing the polyester-cotton product in the ethylene glycol / alkali composite system, wherein the mass ratio of the polyester-cotton product to the ethylene glycol / alkali composite system is 1:30, and dissolving and reacting at 85° C. for 30 minutes. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0053] Comparative Example 8 This comparative example discloses a low-energy consumption rapid chemical separation method for polyester-cotton fiber products, the method comprising the following steps: Step (1), adding betaine and ethylene glycol in a molar ratio of 1:2 into a reaction bottle, stirring at 90° C. for 25 minutes until completely dissolved, stirring at 80° C. until completely dissolved, and keeping warm for not less than 30 minutes to obtain a clear and transparent solution, which is the synthesized betaine / ethylene glycol low eutectic solvent; Step (2), adding alkali solution to the betaine / ethylene glycol low eutectic solvent under stirring, wherein the mass ratio of the alkali solution to the betaine / ethylene glycol low eutectic solvent is 1.5:30, and the alkali solution is a sodium hydroxide solution with a concentration of 50 g / L, to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system, wherein the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30, and performing a dissolution reaction at 98° C. for 0 min. After the reaction is completed, filtering, taking the undissolved components in the polyester-cotton product, washing them thoroughly with deionized water, and drying them to constant weight.

[0054] Test example (1) If Figure 3 , Figure 4 As shown, the weight loss rates of the polyester-cotton fiber products after chemical separation obtained in Examples 1-7 and Comparative Examples 1-7 were calculated, and the specific test results are shown in Table 1: Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Weight loss rate (%) 68.35 14.0 29.2 46.6 65.0 80.5 84.7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Weight loss rate (%) 41.60 52.33 3.70 12.80 31.10 14.21 23.33 According to the test results in Table 1, it can be seen that the betaine / ethylene glycol low eutectic solvent / alkali composite system in Example 1, Example 6, and Example 7 is highly effective in degrading the polyester component in polyester-cotton. When the polyester-cotton fiber products are chemically separated, the weight loss rate can reach up to 84.7%; among them, under the conditions of the same temperature and dissolution reaction time, the weight loss rate of Example 1 is 68.35%, which is 26.75% and 16.02% higher than that of Comparative Examples 1 and 2 with different hydrogen bond acceptors and hydrogen bond donors, respectively; The weight loss rates of the composite system of Example 3 and Example 4 lacking hydrogen bond donor polyols were increased by 64.65% and 55.55% respectively; compared with the composite system of Example 5 and Example 7 lacking hydrogen bond acceptor betaine or urea, the weight loss rates were increased by 37.25% and 45.02% respectively; compared with the composite system of Example 6 lacking alkali solution, the weight loss rate was increased by 54.14%; in summary, the betaine / ethylene glycol low eutectic solvent / alkali composite system used in Example 1 has significant advantages in degrading the polyester component in polyester-cotton. The principle is: the betaine-based low eutectic solvent can swell the fiber, and at a certain temperature, it can fibrillate the fiber, making the originally compact fiber loose, destroying the dense film on the fiber surface, and then allowing the alkali solution to enter the amorphous region of the fiber, and act on the carbonyl group of the polyester fiber, causing the fiber to break and dissolve.

[0055] In Comparative Example 1, due to the use of a betaine, urea and sodium hydroxide system, compared with the best embodiment, although urea participates in the chemical reaction to a certain extent, its reaction activity with polyester is relatively weak. In this system, betaine and urea mainly promote the degradation process of polyester by jointly creating an alkaline environment with sodium hydroxide; however, the effect of this synergistic effect is not as good as the effect exhibited by the combination of betaine, ethylene glycol and sodium hydroxide; therefore, the weight loss rate in Comparative Example 1 is lower than that in the best embodiment.

[0056] In Comparative Example 2, due to the use of a betaine, glycerol and sodium hydroxide system, compared with the best embodiment, the glycerol molecule is larger and has a certain steric hindrance, making it relatively difficult to penetrate into the crystallization area, and its ability to destroy the crystallization area is not as strong as that of ethylene glycol; at the same time, due to the steric hindrance, when it synergizes with betaine and sodium hydroxide to attack the carbonyl group on polyester, the effect produced is not as good as that of the best embodiment; therefore, the weight loss rate in Comparative Example 2 is lower than that of the best embodiment.

[0057] The composite system used in Comparative Examples 3-7 can only act on the surface of the fiber when treating polyester-cotton fiber products, resulting in incomplete dissolution of the polyester fiber, so the weight loss rate is lower than that of the optimal embodiment; in summary, the weight loss rates of polyester in Comparative Examples 1-7 are all lower than those of the optimal embodiment.

[0058] According to the test results in Table 1, it can be seen from Example 2 that when the reaction temperature is 58°C during the chemical separation of the polyester-cotton fiber product, the weight loss rate of the polyester-cotton fiber product after chemical separation is 14.0%, which indicates that the reaction has begun under this condition; it can be seen from Examples 3-6 that with the gradual increase in the reaction temperature, the weight loss rate of the polyester-cotton fiber product after chemical separation increases sharply, which proves that the increase in temperature is conducive to the reaction in the positive direction and increases the reaction rate; it can be seen from Example 7 that when the reaction temperature reaches 108°C, the weight loss rate of the polyester-cotton fiber product after chemical separation is as high as 84.7%; but compared with Example 6 with a reaction temperature of 98°C, the weight loss rate of Example 7 with a reaction temperature of 108°C did not increase significantly, which indicates that when the reaction temperature is 98°C, the polyester component in the polyester-cotton fiber product has approached or reached a state of complete degradation, and therefore, the optimal reaction temperature for chemical separation of the polyester-cotton fiber product is 98°C.

[0059] (2) If Figure 5 , Figure 6 and Figure 7 As shown, the chemically separated polyester-cotton fiber products obtained in Example 6, Examples 8-9 and Comparative Example 8 were subjected to infrared spectrum test; the dissolution rate of the polyester component in the chemically separated polyester-cotton fiber products obtained in Example 6, Examples 8-9 and Comparative Example 8 was tested by filtration weighing method. The specific test results are shown in Table 2: Table 2 Example 6 Example 8 Example 9 Comparative Example 8 Dissolution rate (%) 100 100 88.2 0 According to Table 2 and Figure 4 , Figure 5 and Figure 6It can be seen from the test results that, from Comparative Example 8, when the polyester-cotton fiber product is chemically separated, when the reaction time is 0 min, the dissolution rate of the polyester component is 0%. As the reaction time is gradually extended, from Example 9, when the reaction time reaches 30 min, the polyester-cotton fiber product after chemical separation still retains the characteristic absorption peaks of the cotton fiber and polyester fiber in the original sample, which indicates that the polyester fiber is not effectively removed within the treatment time of 30 min; as the treatment time is further extended, from Example 8, when the reaction time reaches 120 min, the dissolution rate of the polyester component decreases, and only the characteristic absorption peak of the cotton fiber is shown in the polyester-cotton fiber product after chemical separation, indicating that the polyester component is completely removed, but compared with Example 6 with a reaction time of 60 min, the dissolution rate of the polyester component in Example 8 with a reaction time of 120 min is not significantly reduced, which indicates that when the reaction time is 60 min, the polyester component in the polyester-cotton fiber product has been completely degraded. This is because betaine-based low eutectic solvents can swell the fibers and fibrillate them at a certain temperature, making the originally compact fibers loose and destroying the dense film on the fiber surface, so that the alkali solution can enter the amorphous region of the fibers and act on the carbonyl groups of the polyester fibers, causing the fibers to break and dissolve. Cotton fibers are polysaccharides composed of glucose units through β-1,4-glycosidic bonds. There are a large number of hydroxyl groups (-OH) on the cellulose molecular chain. These hydroxyl groups have a certain chemical stability in an alkaline environment. In this system, alkali ions (Na + ) will react with the hydroxyl groups on the cellulose molecular chain, but this reaction is mainly ion exchange or forming a relatively loose complex structure, which does not destroy the β-1,4-glycosidic bond of the cotton fiber, and the cotton fiber can still maintain its basic fiber shape. Therefore, when chemically separating polyester-cotton fiber products, the optimal reaction time is 60 minutes.

[0060] (3) If Figure 8 As shown, the polyester-cotton fiber products after chemical separation obtained in Example 6, Examples 8-9 and Comparative Example 8 were subjected to microscopic morphology testing using a VHX-970F ultra-depth three-dimensional microscope; according to Figure 8It can be seen from the test results that from Comparative Example 8, when the reaction time is 0min for chemical separation of polyester-cotton fiber products, the polyester fiber and the cotton fiber are tightly entangled, and the polyester fiber is smooth and cylindrical; in contrast, the surface of the cotton fiber is relatively rough and flat. From Example 9, it can be seen that when the reaction time reaches 30min, the originally tightly entangled polyester fiber and cotton fiber begin to become messy and scattered; from Example 6, it can be seen that when the reaction time is 60min for chemical separation of polyester-cotton fiber products, the originally tightly entangled polyester fiber and cotton fiber become more messy and scattered, the smooth polyester fiber basically disappears, the coarse cotton fiber is retained, and the cotton fiber maintains a good shape, and there is basically no obvious cracks; from Example 8, it can be seen that when the reaction time is 120min for chemical separation of polyester-cotton fiber products, the polyester-cotton fiber is only more dispersed, the fiber surface does not change, and there are only some wrinkles. Therefore, it can be concluded that the low eutectic solvent / alkali composite system has almost no effect on cotton fibers, and the optimal reaction time for chemical separation of polyester-cotton fiber products is 60min.

[0061] (4) If Fig. 9 As shown, under the same parameters and conditions as Example 6, the experiment was repeated 20 times, and the weight loss rates of the polyester-cotton fiber products after chemical separation were calculated respectively; according to Figure 8 It can be seen from the test results that the weight data of the polyester-cotton fiber products treated with the betaine / ethylene glycol low eutectic solvent / alkali composite system obtained under multiple parallel experimental conditions all showed a high degree of consistency, indicating that the low-energy rapid chemical separation method of the polyester-cotton fiber products used in the present invention has good stability and repeatability, and can be used for quantitative analysis. It is concluded that the cotton component accounts for about 20% of the polyester-cotton fiber and the polyester component accounts for about 80%.

[0062] (5) If Fig.10 As shown, the product recovered from the degradation of the polyester component obtained in the embodiment was subjected to infrared testing; according to Fig.10 The test results show that 3063.30 cm −1 The characteristic absorption peak of carboxylic acid -OH of terephthalic acid is 1683.72 cm −1 The typical vibration peak of C=O is 1286.45 cm −1 The typical vibration peaks of CO are shown at , which are consistent with the characteristic absorption peaks of terephthalic acid reported in the literature (ACS Sustainable Chem. Eng. 2021, 9, 17174−17185). Therefore, it can be proved that when the separation method of the present invention is used to treat polyester-cotton fiber products, the degradation product of the polyester component is terephthalic acid.

[0063] 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 low energy consumption rapid chemical separation method for polyester-cotton fiber products, characterized in that: The method comprises the following steps: Step (1), adding a hydrogen bond donor and a hydrogen bond acceptor into a reaction bottle, stirring and dissolving, to prepare a betaine-based deep eutectic solvent; Step (2), adding alkali solution to the betaine-based low eutectic solvent and mixing to obtain a low eutectic solvent / alkali composite system; Step (3), immersing the polyester-cotton product in a low eutectic solvent / alkali composite system to undergo a dissolution reaction. After the reaction is completed, filtering is performed to obtain undissolved components in the polyester-cotton product, washing with water, and drying.

2. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (1), the hydrogen bond donor is ethylene glycol, and the hydrogen bond acceptor is betaine.

3. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (1), the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:2-4.

4. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (1), the stirring and dissolving operation includes: stirring at 80° C. until completely dissolved, and then maintaining the temperature and stirring for no less than 30 minutes.

5. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (2), the alkali solution is a sodium hydroxide solution with a concentration of 10 g / L to 50 g / L.

6. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (2), the mass ratio of the alkali solution to the betaine-based low eutectic solvent is 1.5:30-50.

7. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (2), the mixing condition is: stirring at 90° C. for 25 minutes until the mixture is completely dissolved.

8. A low energy consumption rapid chemical separation method for polyester-cotton fiber products according to claim 1, characterized in that: In the step (3), the mass ratio of the polyester-cotton product to the low eutectic solvent / alkali composite system is 1:30-50; and the dissolution reaction conditions are: dissolution reaction at 58-108° C. for 30-120 min.

9. A method for processing polyester-cotton fiber products using a low-energy consumption rapid chemical separation method for polyester-cotton fiber products as described in any one of claims 1 to 8.

10. Application of the low-energy rapid chemical separation method for polyester-cotton fiber products as claimed in any one of claims 1 to 8 in rapid quantitative analysis of components of polyester-cotton fiber products.

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