A method for separating polyester-cotton blended fibers using water and an organic solvent

Abstract

The application provides a method for separating polyester-cotton blended fibers by using water and an organic solvent, which comprises the following steps: firstly, opening and crushing recycled polyester-cotton cloth; then, putting the crushed polyester-cotton fiber powder into water, fully stirring and ultrasonic dispersing; further, adding an organic solvent which is incompatible with water and has affinity with polyester; stirring, oscillating and standing for stratification; separating the water phase and the organic phase; and finally, filtering and drying to obtain polyester and cotton staple dry products. The application adopts the method of opening and crushing polyester-cotton fibers into staple fibers, and separating polyester staple fibers and cotton staple fibers by using the difference in the affinity of water and specific organic solvent to polyester and cotton fibers. The application utilizes the good affinity of water to cotton and the good affinity of the selected organic solvent to polyester, and the complete incompatibility of the organic solvent to water. Through the mixing and separation process of the two solvents, polyester and cotton are pulled into their respective phases, and the separation of the two fibers is realized. The method is simple, effective, low in production cost and easy for large-scale production.

Description

Technical Field

[0001] This application belongs to the field of textile fiber recycling technology, and in particular relates to a method for separating polyester-cotton blended fibers using water and organic solvents. Background Technology

[0002] In the recycling and high-value utilization of waste textiles, the separation of polyester (polyethylene terephthalate, PET) and cotton fiber blends (referred to as "polyester-cotton") is an important issue in polyester-cotton recycling and reuse, and has always been a technical challenge in textile recycling and reuse. Because polyester, as a synthetic fiber, is chemically inert and hydrophobic, while cotton, as a natural cellulose fiber, is hydrophilic and acid-base sensitive, their physicochemical properties are drastically different. This leads to a general contradiction between efficiency, environmental protection, and economic viability in existing separation technologies.

[0003] Currently, there are two main categories of technologies for separating polyester and cotton fibers: chemical methods and physical methods. Chemical methods primarily involve chemical depolymerization, transforming one fiber into a soluble substance, or selective dissolution using appropriate solvents to achieve separation of polyester and cotton fibers. While chemical methods can achieve relatively thorough separation and recycling, they also have several drawbacks. These include the use of potentially harmful chemicals or the need for large quantities of expensive solvents. Furthermore, the depolymerization and dissolution processes generally require high temperatures and are complex, leading to high costs.

[0004] Existing methods mainly utilize the suspension properties of both fibers for separation. For example, Chinese invention patent CN 118321312 A describes a process where fibers are first opened and broken to obtain polyester-cotton fiber bundles, resulting in bundled fibers. These bundled fibers are then dispersed in an air flotation sedimentation solution. Gas is continuously introduced into the bottom of the solution, forming rising bubbles. A portion of the bundled fibers adheres to these bubbles and floats to the surface, forming a floating fiber component, while the other portion sinks to the bottom. The sinking fiber component is then dispersed in the air flotation sedimentation solution for further sedimentation. This process is repeated 2-3 times to achieve separation of the polyester and cotton fibers. However, this separation process relies on the differences in suspension properties. Because bubbles can vary in size and fiber lengths, their adsorption on bubbles is difficult to standardize, leading to numerous instances where separation is challenging. Furthermore, this method defines "bundled fibers" as a state where a large number of fibers are mixed together but remain independent strands. This method is completely ineffective for cases where polyester and cotton are interwoven. Chinese invention patent CN118477883 A also proposes a method of first treating polyester-cotton fabric with a swelling solution, then mechanically pulverizing it, and finally sieving the resulting blended micro-powder to separate the cotton component from the undersize and the polyester component from the oversize. This method suffers from problems such as the separation effect being sensitive to the swelling solvent composition, the solvent composition being relatively complex, the overall process being difficult to control, and the separation purity being difficult to exceed 90%. Existing technology also discloses a method of separating polyester-cotton fibers using potassium carbonate aqueous solutions of different densities. Since polyester density is generally 1.38 g / cm³, while cotton fiber density is typically 1.54 g / cm³, the sedimentation rates of the two fibers in the potassium carbonate aqueous solution system will differ. By using different sedimentation conditions, separation of polyester and cotton fibers can be achieved. However, the separation effect of this method is greatly affected by fiber length and surface physicochemical characteristics, and the optimal polyester fiber purity is only 62%, far from meeting application requirements. The products obtained by this method are severely affected in the later reuse process. For example, the PET fiber is mixed with a small amount of cotton fiber, which has a great negative impact on the later degradation and polymerization of PET.

[0005] In summary, current chemical separation methods are relatively thorough, but require a large number of chemical processes and have shortcomings in terms of hazards and energy consumption; while currently reported physical methods are generally more energy-efficient, but have long cycles, use too many additives, and still have the problem of poor separation effect. Summary of the Invention

[0006] This invention addresses the aforementioned problems, aiming to comprehensively solve the energy consumption, efficiency, and effectiveness issues in polyester-cotton separation. This invention belongs to the category of physical separation methods; therefore, compared to chemical methods, it features a simpler process and lower energy consumption. Based on initial opening and crushing, it uses highly differential solvents—water and specific organic solvents—to separate the crushed polyester staple fibers from the cotton staple fibers. The process involves first dispersing the opened and crushed fibers in water, and then adding an organic solvent that is incompatible with water but has good affinity for polyester.

[0007] To achieve the above objectives, the present invention provides a method for separating polyester-cotton blended fibers using water and organic solvents, comprising the following steps: S1. The recycled polyester-cotton fabric is washed, dried, opened and crushed to obtain polyester-cotton fiber powder. S2. The pulverized polyester-cotton fiber powder is added sequentially to water and an organic solvent that is incompatible with water but compatible with polyester, and stirred and / or ultrasonically vibrated separately to obtain a mixture. S3. Let the above mixture stand until the aqueous phase and organic phase separate into layers; S4. Separate the aqueous phase and the organic phase, filter and dry them respectively to obtain dry polyester staple fiber and cotton staple fiber.

[0008] In any embodiment, step S2 first involves placing the pulverized polyester-cotton fiber powder into water, stirring and / or using ultrasonic vibration to disperse it, thereby obtaining a polyester-cotton dispersion of free short fibers; then, an organic solvent that is incompatible with water but compatible with polyester is added to the polyester-cotton dispersion, and the mixture is stirred and / or used ultrasonic vibration to ensure that the aqueous phase and the organic solvent phase are fully mixed and in contact, thereby obtaining a mixed solution.

[0009] In any embodiment, step S2 first involves placing the pulverized polyester-cotton fiber powder into an organic solvent that is incompatible with water but compatible with polyester, and then dispersing it by stirring and / or ultrasonic vibration to obtain a polyester-cotton dispersion of free short fibers; then adding water to the polyester-cotton dispersion, and stirring and / or ultrasonic vibration to ensure that the aqueous phase and the organic solvent phase are fully mixed and in contact to obtain a mixed solution.

[0010] In any embodiment, the solubility parameter of the organic solvent is below 21 MPa. 1 / 2 .

[0011] In any embodiment, the polyester-cotton fabric is pulverized to 50-300 mesh. Preferably, it is 80-200 mesh.

[0012] In any embodiment, the ultrasonic frequency is 20-100Hz and the duration is 1-120 min.

[0013] In any embodiment, the solid-liquid mass ratio of water to polyester-cotton fiber powder is 0.1-30:100. Preferably, it is 0.1-10:100.

[0014] In any embodiment, the volume ratio of the water to the organic solvent is 100:20-200.

[0015] In any embodiment, the stirring and / or ultrasonic oscillation for 1-60 minutes ensures that the aqueous phase and the organic solvent phase are fully mixed and in contact.

[0016] In any embodiment, the organic solvent includes, but is not limited to, one or more mixed solvents selected from cyclohexane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, ethyl acetate, butyl acetate, isoamyl acetate, dimethyl carbonate, limonene, γ-valerolactone, ethyl lactate, terpinene (α-terpinene), cyclopentylmethyl ether, methyltetrahydrofuran, isoalkanes (such as D80 solvent oil), cyclomethylhexane (MCH), and perfluorocarbon cycloethers (fluorocarbon solvents). The most readily available local organic solvent can be selected, and good results can be obtained from all of these.

[0017] In any embodiment, the organic solvent is selected from one or more mixed solvents selected from ethyl lactate, limonene, and dimethyl carbonate. This takes into account the factors of being environmentally friendly and non-toxic.

[0018] The beneficial effects of this application are: This invention utilizes a physical separation method. First, recycled polyester-cotton fabric is opened and pulverized. The pulverized polyester-cotton fiber powder is placed in water, thoroughly stirred, and ultrasonically dispersed. Then, an organic solvent that is immiscible with water but has an affinity for polyester is added. The mixture is stirred and shaken to ensure thorough mixing and contact between the aqueous and organic solvent phases. The mixture is allowed to settle and separate into layers. The aqueous and organic phases are then separated. The mixture is filtered and dried to obtain dry polyester and cotton staple fibers. This invention first opens and pulverizes the polyester-cotton fibers into short fibers, then utilizes the difference in affinity between water and a specific organic solvent for polyester and cotton fibers to separate the polyester and cotton staple fibers. The principle of this invention is based on the excellent affinity between water and cotton, while the selected organic solvent has a good affinity for polyester and is completely immiscible with water. Through the mixing and separation process of the two solvents, their affinity for their respective components is utilized to pull polyester and cotton into their respective phases, achieving the separation of the two fibers. This is a process similar to but distinct from solvent extraction. It utilizes the significant differences in the surface affinity of the solvent for the components of the solid particles to be separated, achieving separation through liquid-liquid phase transfer. This method is simple, effective, low-cost, environmentally friendly, and easy to scale up. However, this method has not yet been seen in the separation of polyester and cotton. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for separating polyester-cotton blended fibers using water and organic solvents according to this application; Figure 2 Photograph of polyester-cotton fibers in water without added organic solvents; Figure 3 These are photographs showing the separation of the aqueous and organic phases after the addition of organic solvents. Figure 4 This is a photograph taken after the organic phase and aqueous phase have been separated. Figure 5 Infrared spectra of the separated samples for testing; Figure 6 This is a diagram showing the separation effect of 40-mesh polyester-cotton fibers in Comparative Example 1 sample; Figure 7 The image shows the separation effect of 10-mesh polyester-cotton fibers in the comparative example 2 sample. Detailed Implementation

[0020] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the method for separating polyester-cotton blended fibers using water and organic solvents according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0021] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0023] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0024] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0025] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0026] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0027] In one embodiment of this application, a method for separating polyester-cotton blended fibers using water and organic solvents is proposed, comprising the following steps: S1. The recycled polyester-cotton fabric is washed, dried, opened and crushed to obtain polyester-cotton fiber powder. S2. The pulverized polyester-cotton fiber powder is added sequentially to water and an organic solvent that is incompatible with water but compatible with polyester, and stirred and / or ultrasonically vibrated separately to obtain a mixture. S3. Let the above mixture stand until the aqueous phase and organic phase separate into layers; S4. Separate the aqueous phase and the organic phase, filter and dry them respectively to obtain dry polyester staple fiber and cotton staple fiber.

[0028] Because cotton fibers contain a large number of hydroxyl and carboxyl groups on their surface, they have excellent hydrophilicity and will spontaneously enter the aqueous phase. Polyester, on the other hand, is a hydrophobic polymer with weak affinity for water and will spontaneously enter the organic solvent phase, thus achieving the separation of polyester fibers from cotton fibers.

[0029] In some embodiments, step S2 first involves placing the pulverized polyester-cotton fiber powder into water, stirring and / or using ultrasonic vibration to disperse it, thereby obtaining a polyester-cotton dispersion of free short fibers; then, an organic solvent that is incompatible with water but compatible with polyester is added to the polyester-cotton dispersion, and the mixture is stirred and / or used ultrasonic vibration to ensure that the aqueous phase and the organic solvent phase are fully mixed and contacted to obtain a mixed solution.

[0030] In some embodiments, step S2 involves first placing the pulverized polyester-cotton fiber powder into water, stirring and / or using ultrasonic vibration to disperse it, thereby obtaining a polyester-cotton dispersion of free short fibers; then adding a mixed solvent of an organic solvent that is incompatible with water but compatible with polyester to the polyester-cotton dispersion, stirring and / or using ultrasonic vibration to ensure that the aqueous phase and the organic solvent phase are fully mixed and in contact, thereby obtaining a mixed solution.

[0031] In some embodiments, step S2 first involves placing the pulverized polyester-cotton fiber powder into an organic solvent that is incompatible with water but compatible with polyester, and then dispersing it by stirring and / or ultrasonic vibration to obtain a polyester-cotton dispersion of free short fibers; then adding water to the polyester-cotton dispersion, and stirring and / or ultrasonic vibration to fully mix and contact the aqueous phase and the organic solvent phase to obtain a mixed solution.

[0032] In some embodiments, step S2 first involves placing the pulverized polyester-cotton fiber powder into a mixed solvent of an organic solvent that is incompatible with water but compatible with polyester, and then dispersing it by stirring and / or ultrasonic vibration to obtain a polyester-cotton dispersion of free short fibers; then adding water to the polyester-cotton dispersion, and stirring and / or ultrasonic vibration to ensure that the aqueous phase and the organic solvent phase are fully mixed and in contact to obtain a mixed solution.

[0033] Stirring can improve the ultrasonic dispersion effect, especially for cases with high fiber content, where stirring and ultrasonication need to be performed simultaneously.

[0034] In some embodiments, the solubility parameter of the organic solvent is less than 21 MPa. 1 / 2 .

[0035] In some embodiments, the polyester-cotton fabric is pulverized to 50-300 mesh. Preferably, it is 80-200 mesh. If the mesh number is too small, the polyester-cotton fibers are prone to entanglement, making them difficult to separate and resulting in poor separation.

[0036] In some embodiments, the ultrasonic frequency is 20-100Hz and the duration is 1-120 min. Generally, the smaller the mesh size and the larger the particles, the lower the ultrasonic frequency is, thus separating the polyester-cotton fibers.

[0037] Preferred grades include: Coarse powder (50-80 mesh): Fibers are longer and have higher entanglement. Low-frequency, high-penetration ultrasound (20-35kHz) is used for 2-10 minutes. The micro-jets and shock waves generated by the cavitation bubble collapse of low-frequency ultrasound penetrate deep into the fiber bundle and disintegrate the entanglement knots. Medium powder (80-150 mesh): Fibers are of moderate length. Medium-frequency, balanced ultrasound (35-60kHz) is used for 2-10 minutes, balancing dispersion and anti-entanglement. Fine powder (150-300 mesh): Fibers have been fully unbuckled. High-frequency, fine ultrasound (60-100kHz) is used for 2-10 minutes, utilizing the fine vibration of high-frequency ultrasound to prevent the microfibers from re-aggregating.

[0038] In some embodiments, the solid-liquid mass ratio of water to polyester / cotton fiber powder is 0.1-30:100. A more preferred ratio is 0.1-10:100. Excessive solid-liquid concentration hinders separation and results in poor separation performance.

[0039]

[0040] In some embodiments, the volume ratio of water to organic solvent is 100:20-200.

[0041] In some embodiments, the stirring and / or ultrasonic vibration for 1-60 minutes ensures that the aqueous phase and the organic solvent phase are fully mixed and in contact. In some embodiments, the organic solvent is one or more mixed solvents such as cyclohexane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, ethyl acetate, butyl acetate, isoamyl acetate, dimethyl carbonate, limonene, γ-valerolactone, ethyl lactate, terpinene, cyclopentylmethyl ether, methyltetrahydrofuran, isoalkanes (such as D80 solvent oil), cyclomethylhexane, perfluorocarbon cycloethers (fluorocarbon solvents), etc. The most readily available organic solvent locally can be selected to achieve good results.

[0042] In some embodiments, the organic solvent is selected from one or more mixed solvents selected from ethyl lactate, limonene, and dimethyl carbonate. This takes into account the factors of being environmentally friendly and non-toxic.

[0043] Organic solvents are solvents that are immiscible with water, meaning that water has very low solubility in them; they are hydrophobic solvents. Structurally, these solvents are predominantly nonpolar, and their solubility parameter δ is generally below 21 MPa. 1 / 2 The δ of water is 47.9 MPa. 1 / 2 The greater the difference in δ value between an organic solvent and water, the stronger its hydrophobicity. Organic solvents that meet these conditions include (but are not limited to): cyclohexane: δ = 16.8 MPa 1 / 2 Toluene: δ=18.2 MPa1 / 2 o-Xylene: δ=18.4 MPa 1 / 2 m-Xylene: δ=18.2 MPa 1 / 2 p-Xylene: δ=18.0 MPa 1 / 2 Dichloromethane: δ=19.8 MPa 1 / 2 Chloroform: δ=19.0 MPa 1 / 2 Carbon tetrachloride: δ=17.6 MPa 1 / 2 1,2-Dichloroethane: δ=20.1 MPa 1 / 2 1,1,1-Trichloroethane: δ=15.8 MPa 1 / 2 Ethyl acetate: δ = 18.2 MPa 1 / 2 Butyl acetate: δ=17.4 MPa 1 / 2 Isoamyl acetate: δ=17.0 MPa 1 / 2 Dimethyl carbonate δ=18.0 MPa 1 / 2 ; Limonene (D-limonene) δ=17.2 MPa 1 / 2 γ-valerol δ=19.7 MPa 1 / 2 Ethyl lactate δ=18.4MPa 1 / 2 Terpinene δ=17.4 MPa 1 / 2 ; Cyclopentyl methyl ether (CPME) δ=17.6 MPa 1 / 2 Methyltetrahydrofuran δ=18.2MPa 1 / 2 Isoparaffins (such as D80 solvent oil) δ=15.5~16.5 MPa 1 / 2 ; Cyclomethylhexane δ=16.8 MPa 1 / 2 Perfluorocarbon cyclic ethers (fluorocarbon solvents) δ≈12.0 MPa 1 / 2 .

[0044] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0045] Example 1 Take 1 gram (100 mesh) of loosened and crushed polyester-cotton (40% polyester, 60% cotton) fiber powder, disperse it in 200 ml of water, stir and sonicate (50 kHz) for 5 minutes; add 100 ml of toluene solvent, stir, shake, and let stand until the layers separate; separate the organic layer from the water layer, with cotton staple fiber in the aqueous phase and polyester staple fiber in the organic phase, separate the aqueous phase from the organic phase, filter them separately, and dry them to obtain polyester staple fiber powder and cotton fiber powder.

[0046] Example 2 Take 1 gram (100 mesh) of loosened and crushed polyester-cotton (60% polyester, 40% cotton) fiber powder, disperse it in 200 ml of water, stir and sonicate for 5 minutes; add 150 ml of toluene solvent, stir, shake, and let stand to separate the layers; separate the organic layer from the water layer, with cotton staple fiber in the aqueous phase and polyester staple fiber in the organic phase, separate the aqueous phase from the organic phase, filter them separately, and dry them to obtain polyester staple fiber powder and cotton fiber powder.

[0047] Example 3 Take 1 gram (100 mesh) of loosened and crushed polyester-cotton (60% polyester, 40% cotton) fiber powder, disperse it in 200 ml of water, stir and sonicate for 5 minutes; add 100 ml of chloroform solvent, stir, shake, and let stand to separate the layers; separate the organic layer from the water layer, with cotton staple fiber in the aqueous phase and polyester staple fiber in the organic phase, separate the aqueous phase from the organic phase, filter them separately, and dry them to obtain polyester staple fiber powder and cotton fiber powder.

[0048] Example 4 Take 1 gram (100 mesh) of loosened and crushed polyester-cotton (60% polyester, 40% cotton) fiber powder, disperse it in 200 ml of water, stir and sonicate for 5 minutes; add 100 ml of cyclohexanone solvent, stir, shake, and let stand to separate the layers; separate the organic layer from the water layer, with cotton staple fiber in the aqueous phase and polyester staple fiber in the organic phase, separate the aqueous phase from the organic phase, filter them separately, and dry them to obtain polyester staple fiber powder and cotton fiber powder.

[0049] Comparative Example 1 Take 1 gram (40 mesh) of loosened and crushed polyester-cotton (40% polyester, 60% cotton) fiber powder, and follow the same procedure as in Example 1. Fiber particles that are too large are difficult to separate effectively. Figure 6 ).

[0050] Comparative Example 2 Take 1 gram (10 mesh) of loosened and crushed polyester-cotton (40% polyester, 60% cotton) fiber powder, and follow the same procedure as in Example 1. Fiber particles that are too large are difficult to separate effectively. Figure 7 ).

[0051] Figure 2 Image of polyester-cotton fibers in water (without added organic solvents); Figure 3 Images showing the separation of the aqueous and organic phases after the addition of organic solvents; Figure 4 Photographs showing the separation of the organic and aqueous phases; the left side shows the organic phase (polyester dispersion), and the right side shows the aqueous phase (cotton fiber dispersion). Figure 5 Infrared spectroscopy was performed on the separated samples. The resulting infrared spectra are as follows: (The black aqueous sample is cotton fiber, and no obvious polyester component was observed in its infrared spectrum at the 1713 cm⁻¹ ester carbonyl stretching characteristic peak and the 722 cm⁻¹ out-of-plane bending absorption of the para-benzene ring CH; the red organic sample is polyester fiber, and no obvious cotton fiber component was observed in its infrared spectrum at the 3300-3400 cm⁻¹ OH stretching absorption peak).

[0052] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for separating polyester-cotton blended fibers using water and organic solvents, characterized in that, Includes the following steps: S1. The recycled polyester-cotton fabric is washed, dried, opened and crushed to obtain polyester-cotton fiber powder of 80-300 mesh. S2. Place the polyester-cotton fiber powder obtained in step S1 into water and disperse it by ultrasonic vibration to obtain a polyester-cotton dispersion of free short fibers; then add an organic solvent that is incompatible with water but compatible with polyester to the polyester-cotton dispersion, stir and vibrate ultrasonically to fully mix and contact the aqueous phase and the organic solvent phase to obtain a mixture; wherein, the solvent in the mixture consists of only water and the organic solvent. S3. Let the above mixture stand until the aqueous phase and organic phase separate into layers; S4. Separate the aqueous phase and the organic phase, filter and dry them respectively to obtain dry polyester staple fiber and cotton staple fiber; The solubility parameter of the organic solvent is less than 21 MPa. 1 / 2 The organic solvent is selected from one or more of the following solvents: cyclohexanone, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, and 1,1,1-trichloroethane.

2. The method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1, characterized in that, Step S2 can also involve first placing the pulverized polyester-cotton fiber powder into an organic solvent that is incompatible with water but compatible with polyester, and then dispersing it by ultrasonic vibration to obtain a polyester-cotton dispersion of free short fibers; then adding water to the polyester-cotton dispersion, stirring and ultrasonic vibration to fully mix and contact the aqueous phase and the organic solvent phase to obtain a mixed liquid.

3. A method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1 or 2, characterized in that, The stirring and ultrasonic treatment are performed as follows: the ultrasonic frequency is 20-100 kHz, and the duration is 1-120 min; when the polyester-cotton fiber powder is 50-80 mesh, the ultrasonic frequency is 20-35 kHz, and the ultrasonic oscillation time is 2-10 min; when the polyester-cotton fiber powder is 80-150 mesh, the ultrasonic frequency is 35-60 kHz, and the ultrasonic oscillation time is 2-10 min; when the polyester-cotton fiber powder is 150-300 mesh, the ultrasonic frequency is 60-100 kHz, and the ultrasonic oscillation time is 2-10 min.

4. A method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1 or 2, characterized in that, The organic solvent is selected from one or more of the following solvents: chloroform, carbon tetrachloride, dichloromethane, dichloroethane, and trichloroethane, and the density of each solvent is greater than that of water.

5. A method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1 or 2, characterized in that, The organic solvent is selected from one or more of the following solvents: chloroform, carbon tetrachloride, and dichloromethane, and all of them have a density greater than that of water and are non-flammable.

6. A method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1 or 2, characterized in that, The solid-liquid mass ratio of water to polyester-cotton fiber powder is 0.1-10:100; when the polyester-cotton fiber powder is 50-80 mesh and has a cotton content ≥60%, the solid-liquid mass ratio of fiber powder to water is 0.2:100~0.6:100; when the polyester-cotton fiber powder is 50-80 mesh and has a polyester content ≥60%, the solid-liquid mass ratio of fiber powder to water is 0.5:100~1.0:100; when the polyester-cotton fiber powder is 80-150 mesh and has a cotton content ≥60%, the solid-liquid mass ratio of fiber powder to water is 1:100 ~ 5:100; when the polyester-cotton fiber powder is 80-150 mesh and has a polyester content ≥60%, the solid-liquid mass ratio of fiber powder to water is 0.5:100 ~ 3:100; when the polyester-cotton fiber powder is 150-300 mesh and the cotton content is ≥60%, the solid-liquid mass ratio of the fiber powder to water is 0.5:100 ~ 2:100; when the polyester-cotton fiber powder is 150-300 mesh and the polyester content is ≥60%, the solid-liquid mass ratio of the fiber powder to water is 0.1:100 ~ 1:

100.

7. A method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1 or 2, characterized in that, The volume ratio of water to organic solvent is 100:20-200.

8. A method for separating polyester-cotton blended fibers using water and organic solvents according to claim 1 or 2, characterized in that, The stirring and ultrasonic vibration for 1-60 minutes ensure that the aqueous phase and the organic solvent phase are fully mixed and in contact.

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