A method for separating components of waste polyester-cotton blended fabrics by solvent light treatment coupled with mechanical external force.

Abstract

This invention belongs to the field of textile resource recycling technology, and particularly relates to a method for separating components of waste cotton-polyester blended fabrics using a solvent-based light treatment coupled with mechanical force. The method includes the following steps: S1, adding the waste cotton-polyester blended fabric to a swelling solution, soaking it at 20-60℃ for 15-60 minutes, centrifuging after the reaction, and then drying to obtain the swollen cotton-polyester blended fabric; the solute concentration of the swelling solution is 1-5%; S2, mechanically pulverizing the swollen cotton-polyester blended fabric to obtain pulverized blended micropowder; S3, performing sieving separation, collecting the undersize material to obtain the cotton component, and collecting the oversize material to obtain the polyester component. This invention, through a solvent-based light treatment coupled with mechanical force opening and refining separation process, facilitates the efficient recycling of cotton-polyester components from waste fabrics. The obtained components have high purity, intact fiber structure, significantly improved crystallinity and polymerization degree, and good fiber quality.

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 waste polyester-cotton blended fabrics by solvent light treatment coupled with mechanical external force. Background Technology

[0002] With economic development and people's pursuit of "fast fashion," the demand and production of textiles have grown rapidly, while their lifespan has shortened dramatically. This has led to a year-on-year increase in the amount of waste textiles, making the textile industry the world's second-largest polluter after the petroleum industry. The proportion of blended fabrics in waste textiles is increasing, with polyester-cotton blends being the most common, reaching an annual stock of approximately 4.1 million tons. The recycling of waste textiles has become a major problem urgently needing to be solved and has significant practical implications.

[0003] The efficient separation of polyester and cotton fiber components in waste textiles is the key to the high-value recycling of waste polyester-cotton blended textiles. Generally speaking, there are two main approaches to recycling waste polyester-cotton blended textiles: (1) Direct recycling without separating the components, with incineration and landfill being the main treatment methods; however, landfilling waste textiles will cause serious harm to soil and water resources, while incineration will produce a large amount of toxic and harmful substances, polluting the atmosphere; (2) Based on the differences in the chemical properties of polyester and cotton fibers, such as hydrothermal separation, alcoholysis, hydrolysis, and enzymatic hydrolysis, cotton fibers or polyester fibers can be recycled separately. The recycled chemical fibers can be recovered through melting and spinning and used to produce new products. Cotton fibers, which are mainly composed of cellulose, are easily damaged to a certain extent after mechanical or chemical treatment, and their microstructure, such as crystallinity and degree of polymerization, will change, resulting in low quality of recycled fibers, such as a decrease in breaking strength; therefore, they can only be used as low-value textiles, such as carpets, fillings, and non-woven products. Furthermore, cotton fiber recycling often requires dissolving polyester or undergoing a dissolution-regeneration process, which consumes large amounts of organic solvents or ionic liquids, easily causing environmental pollution. Moreover, the cost of this process may exceed the value of the recycled fibers. In short, most existing methods struggle to achieve complete separation of polyester and cotton fibers, resulting in low purity recycled fibers. Furthermore, the quality of the recovered polyester-cotton fibers is poor, with severely damaged fiber structures, thus significantly limiting the added value of recycled polyester-cotton blended fabrics.

[0004] Therefore, it is of great significance to find a separation method that can effectively separate polyester and cotton fibers while improving their fiber quality for waste cotton-polyester blended fabrics. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a method for separating components of waste polyester-cotton blended fabrics using a solvent-based light treatment coupled with mechanical force. This invention, through a solvent-based light treatment coupled with mechanical force for opening and refining, facilitates the efficient recycling and reuse of polyester-cotton components in waste polyester-cotton blended fabrics. The resulting components exhibit high purity, intact fiber structure, significantly improved crystallinity and polymerization degree, and superior fiber quality.

[0006] To achieve the above objectives, the present invention is specifically implemented through the following technical solutions:

[0007] This invention provides a method for separating components of waste polyester-cotton blended fabrics using solvent light treatment coupled with mechanical external force, comprising the following steps:

[0008] S1. Add waste cotton-polyester blended fabric to a swelling solution and soak it at 20-60°C for 15-60 minutes. After the reaction is complete, centrifuge to remove excess solvent and then dry to obtain the swollen cotton-polyester blended fabric. The swelling solution is selected from one of inorganic acid aqueous solution, organic acid aqueous solution, inorganic alkali aqueous solution and organic alkali aqueous solution, and the mass concentration of the solute in the swelling solution is 1-5%.

[0009] S2. The swollen cotton-polyester blended fabric is lightly pulverized by mechanical external force to obtain pulverized blended micro powder.

[0010] S3. The pulverized blended micro powder is sieved and separated, the undersize material is collected to obtain the cotton component, and the oversize material is collected to obtain the polyester component.

[0011] Furthermore, the mass concentration of the solute in the swelling solution is 5%.

[0012] Furthermore, in step S1, the sample is soaked at 60°C for 30–60 minutes.

[0013] Further, in step S1, the solid-liquid mass ratio of the cotton-polyester blended fabric to the swelling solution is 1:5 to 30.

[0014] Further, in step S1, the inorganic acid is selected from hydrochloric acid, sulfuric acid, carbonic acid, or phosphoric acid; the organic acid is selected from tartaric acid, oxalic acid, malic acid, citric acid, or ascorbic acid; the inorganic base is selected from sodium hydroxide, lithium hydroxide, potassium hydroxide, copper hydroxide, calcium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, or sodium thiosulfate; and the organic base is selected from choline chloride, betaine, 1,8-diazabicyclo[5.4.0]undec-7-ene, triethanolamine, or triethylenediamine.

[0015] Furthermore, the swelling solution is selected from an aqueous solution of an inorganic base, wherein the inorganic base is selected from sodium hydroxide, potassium hydroxide, copper hydroxide, or calcium hydroxide.

[0016] Further, in step S2, the mechanical external force crushing is selected from wet ball mills, planetary ball mills, cryogenic ball mills, mortar and pestle grinders, disc grinders, centrifugal grinders, or rotary grinders; wherein: when using a wet ball mill, planetary ball mill, or cryogenic ball mill, the ball-to-material ratio is 1:20-40, the mass ratio of the swollen cotton-polyester blended fabric to the ball milling media is 1:10-20, the rotation speed is 200-400 rpm, the grinding time is 10-60 min, and the ball milling media is deionized water; when using a mortar and pestle grinder, there is no ball milling media, and the grinding time is 10-60 min; when using a disc grinder, centrifugal grinder, or rotary grinder, there is no ball milling media, the rotation speed is 6000-12000 rpm, and the grinding time is 1-10 min.

[0017] Furthermore, the mechanical external force crushing is selected from ultracentrifugal grinding.

[0018] Furthermore, the cotton-polyester blended fabric is selected from CVC55 / 45, CVC60 / 40, CVC70 / 30, CVC80 / 20, TC65 / 35, TC65 / 35, TC50 / 50, TC60 / 40 or TC80 / 20.

[0019] The advantages and positive effects of this invention are as follows:

[0020] This invention first uses a low-acidity, alkaline swelling solution to gently treat waste cotton-polyester blended fabrics under mild conditions. This process swells the fibers and alters the surface properties of the two fibers to varying degrees, thus increasing their differences without dissolving or degrading them. Then, a weak mechanical force is applied to disrupt the intermolecular forces within the fibers, causing peeling or slippage between the fiber crystal planes. The cotton fibers break into short fibers, while the polyester fibers become entangled to some extent. Macroscopically, this results in a difference in size between the two fibers, achieving efficient separation of cotton and polyester. Finally, sieving is used to separate and recycle the components of the waste cotton-polyester blended fabric. This two-step gentle treatment process preserves the structural integrity of the original cotton and polyester fibers to the greatest extent possible, resulting in fibers with high crystallinity and polymerization degree, high breaking strength, and significantly improved fiber quality. Furthermore, the yield and purity of each recovered component are greatly improved, effectively enhancing the recycling efficiency of waste cotton-polyester blended fabrics, demonstrating good economic benefits and application value. Attached Figure Description

[0021] 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.

[0022] Figure 1 These are scanning electron microscope (SEM) images of cross-sections of cotton fibers and cotton fibers swollen after being lightly treated with solvent, as described in an embodiment of the present invention.

[0023] Figure 2 The images show the microstructures of the original cotton and polyester fibers in the waste polyester-cotton blended fabric of this invention, after being lightly swollen by solvent treatment and after being separated by solvent treatment coupled with mechanical external force. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] This invention provides a method for separating components of waste polyester-cotton blended fabrics using solvent light treatment coupled with mechanical external force, comprising the following steps:

[0030] S1. Solvent light treatment: The waste cotton-polyester blended fabric is added to the swelling solution and soaked at 20-60℃ for 15-60 minutes. After the reaction, the excess solvent is removed by centrifugation, and then the fabric is dried to obtain the swollen cotton-polyester blended fabric. The swelling solution is selected from one of inorganic acid aqueous solution, organic acid aqueous solution, inorganic alkali aqueous solution, and organic alkali aqueous solution. The mass concentration of the solute (inorganic acid, inorganic acid, inorganic alkali, or organic alkali) in the swelling solution is 1-5% (wt).

[0031] S2. Mechanical external force treatment: The swollen cotton-polyester blended fabric is lightly crushed by mechanical external force to obtain crushed blended micro powder.

[0032] S3. Screening and separating different fiber components: The pulverized blended micro powder is screened and separated, the undersize material is collected to obtain the cotton component, and the oversize material is collected to obtain the polyester component.

[0033] This invention uses a low-acidity or low-alkalinity swelling solution to lightly treat waste polyester-cotton blended fabrics under mild conditions, causing the fibers to swell without dissolving or degrading them. The low acid or alkali concentration only changes the surface properties of the fabric fibers. Based on the difference in swelling coefficients between cotton and polyester fibers, the surface properties of the two fibers change to different degrees, thereby increasing the difference between the two different fibers. Figure 1 The image shows scanning electron microscope (SEM) images of cross-sections of cotton fibers and cotton fibers swollen after light solvent treatment (Cotton-KOH). The images show that the light solvent treatment increases the crimp, diameter, and surface roughness of the cotton fibers, but the fiber structure remains intact, while the polyester fibers show no significant changes. Figure 2Taking a 5% (wt) KOH alkaline solution treatment as an example, the microstructure of cotton fibers (Cotton) and polyester fibers (PET) after untreated processing, light solvent treatment (Cotton-KOH and PET-KOH) followed by swelling, and mechanical crushing is shown. Under the action of relatively weak mechanical force, the intermolecular interaction forces of the fiber fibers are destroyed, causing the fiber crystal planes to peel or slip, thereby ensuring the selective crushing and directional control of the size of cotton and polyester fibers, achieving efficient separation of cotton and polyester. That is, cotton fibers break into short fibers, and polyester fibers are entangled to a certain extent, resulting in a certain size difference between the two. Finally, through sieving, the cotton fibers are outside the screen and the polyester fibers are inside the screen, realizing the separation and recycling of various components of waste cotton-polyester blended fabrics. Through the two-step gentle processing of this invention, the structural integrity of the original cotton and polyester fibers is preserved to the greatest extent, resulting in fibers with high crystallinity and polymerization degree, high breaking strength, and significantly improved fiber quality. Moreover, the yield and purity of each recycled component are greatly improved, effectively enhancing the recycling efficiency of waste polyester-cotton blended fabrics, and demonstrating good economic benefits and application value.

[0034] Preferably, the mass concentration of the solute in the swelling solution is 2.5-5% (wt), more preferably 5%.

[0035] Preferably, in step S1, the soaking treatment is carried out at 40-60°C for 30-60 minutes, more preferably, the soaking treatment is carried out at 60°C for 30 minutes.

[0036] Optionally, in step S1, the solid-liquid mass ratio of the cotton-polyester blended fabric to the swelling solution is 1:5 to 30. The solid-liquid mass ratio of the waste cotton-polyester blended fabric to the swelling solution has little impact on the component separation and recovery, and can be selected according to actual needs.

[0037] Optionally, in step S1, the inorganic acid aqueous solution includes aqueous solutions prepared from hydrochloric acid, sulfuric acid, carbonic acid, or phosphoric acid; the organic acid aqueous solution includes aqueous solutions prepared from tartaric acid, oxalic acid, malic acid, citric acid, or ascorbic acid; the inorganic base aqueous solution includes aqueous solutions prepared from sodium hydroxide, lithium hydroxide, potassium hydroxide, copper hydroxide, calcium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, or sodium thiosulfate; and the organic base aqueous solution includes aqueous solutions prepared from choline chloride, betaine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triethanolamine, or triethylenediamine.

[0038] Preferably, the inorganic acid is selected from hydrochloric acid or phosphoric acid, the organic acid is selected from tartaric acid, the inorganic base is selected from sodium hydroxide, potassium hydroxide, copper hydroxide, or calcium hydroxide, and the organic base is selected from choline chloride or betaine. More preferably, the swelling solution is selected from an aqueous solution of an inorganic base, and the inorganic base is selected from sodium hydroxide or calcium hydroxide.

[0039] Optionally, in step S1, centrifugation at 800g for 10 minutes can effectively separate the swollen cotton-polyester blended fabric and recover the swollen solution, with a solution recovery rate greater than 98%. Moreover, when the recovered swollen solution is used to pretreat waste cotton-polyester blended fabric again, the swelling properties of the fibers show no significant difference.

[0040] Optionally, in step S2, the mechanical external force crushing method and the corresponding crushing instrument used include, but are not limited to: 1) High-energy ball milling: including wet ball mills, planetary ball mills, cryogenic ball mills, etc., to process waste fabrics into fragments with a length of less than 2cm, and crush them into small flake particles of 100-500μm. The crystallinity of cotton component first decreases and then increases, while the polymerization degree of polyester component will decrease slightly; 2) Grinding and shearing crushing: including hammer mills, mortar and pestle grinders, jaw mills, knife-type mixing grinders, disc mills, etc., to process waste fabrics into fragments with a length of less than 4cm, and crush them into small flake particles of 200-600μm. The crystallinity of both polyester and cotton will decrease to some extent; 3) Solid shearing crushing: including ultracentrifugal grinders, rotary grinders, cutting grinders, etc., to process waste fabrics into fragments with a length of less than 5cm, and crush them into fine short fibers of 400-1200μm, preserving the chemical structure of cotton and polyester without destroying crystallinity and polymerization degree.

[0041] In a preferred embodiment, the mechanical external force pulverization method includes wet ball mills, planetary ball mills, cryogenic ball mills, mortar and pestle grinders, disc grinders, centrifugal grinders, rotary grinders, etc. When using a wet ball mill, planetary ball mill, or cryogenic ball mill, the ball-to-material ratio is 1:20–40, the mass ratio of the swollen cotton-polyester blended fabric to the grinding media is 1:10–20, the rotation speed is 200–400 rpm, and the grinding time is 10–60 min. The grinding media in the wet ball mill is deionized water. When using a mortar and pestle grinder, no grinding media is used, and the grinding time is 10–60 min. When using a disc grinder, centrifugal grinder, or rotary grinder, no grinding media is used, the rotation speed is 6000–12000 rpm, and the grinding time is 1–10 min. The ball-milled sample is directly sieved.

[0042] It should be noted that in the mechanical crushing step, the waste polyester-cotton blended fabric needs to be processed into smaller fragments before being fed into the crushing instrument to prevent problems such as entanglement with the blades. Furthermore, the crushing method can be performed using conventional procedures in the field or according to the instrument's instruction manual; this invention does not impose any special limitations on this. For example, in a wet ball mill, a suitable ball-to-material ratio and solid-liquid ratio need to be selected, and the sample after wet grinding needs to be dried; in a cryogenic ball mill, the swollen fabric, after being lightly treated with solvent, is frozen with liquid nitrogen before being cut and crushed; in an ultracentrifuge, the swollen fabric can be directly used for sieving without any further treatment after cutting and crushing.

[0043] In step S3, the sieve used for sieving and separation is determined based on the size of the blended micropowder obtained from the pulverization. Specifically, the product size can be preliminarily determined by microscopic examination. In a preferred embodiment, a wet ball mill uses a sieve size of 50-100 mesh, a cryogenic grinder uses a sieve size of 20-60 mesh, and an ultracentrifugal grinder uses a sieve size of 12-40 mesh.

[0044] In the recycling method of the present invention, the cotton-polyester blended fabric includes CVC55 / 45, CVC60 / 40, CVC70 / 30, CVC80 / 20, TC65 / 35, TC65 / 35, TC50 / 50, TC60 / 40 or TC80 / 20, etc., without limitation on color and fiber fineness. The cotton-polyester blended fabric can be fibers, yarns and fabrics. The fibers mainly include some mixed yarns and severely damaged fabric yarns from factories. The yarns are mainly some cotton-polyester blended yarns. The fabrics include blended cotton-polyester fabrics such as denim, plain weave, corduroy and varnish.

[0045] 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.

[0046] Example 1: Establishment of a method for separating and recycling components of waste polyester-cotton blended fabrics

[0047] By comparing the effects of different recovery methods on fiber purity, degree of polymerization, and crystallinity, a separation and recovery method coupling solvent light treatment with mechanical external force was established. The cotton-polyester blended fabric used in this embodiment is TC50 / 50.

[0048] Experimental Group 1: A method of pretreatment with alkaline solution swelling coupled with mechanical external force crushing, including the following steps:

[0049] Waste cotton-polyester blended fabric was made into 5×5cm pieces and added to a 5% sodium hydroxide solution at a solid-liquid mass ratio of 1:20. The mixture was treated at 60℃ for 30 minutes. After the reaction, the fabric was centrifuged at 800g for 10 minutes to remove excess solvent. The fabric was then dried to obtain the swollen cotton-polyester blended fabric with a swelling coefficient of 45.2%. The swelling coefficient was calculated using the following formula:

[0050] Polyester / cotton swelling coefficient: X1=(m0-m1) / m0; where, X1—polyester / cotton swelling coefficient, %; m0—original polyester / cotton blended fabric, g; m1—polyester / cotton blended fabric after solvent light treatment and centrifugation, g;

[0051] The swollen cotton-polyester blended fabric was treated with zirconia balls as milling media at a ball-to-material ratio of 1:30 and processed in a wet ball mill at 400 rpm for 1 hour to obtain pulverized blended powder for later use.

[0052] The ball-milled cotton-polyester powder was sieved through 40-mesh, 60-mesh, and 80-mesh screens. Most of the polyester component remained in the screen, and the cotton component was collected after sieving.

[0053] Experimental Group 2: The method of acid solution swelling pretreatment coupled with mechanical external force crushing was adopted. The difference from Experimental Group 1 is that the 5% sodium hydroxide solution was replaced with 5% hydrochloric acid solution. The swelling coefficient of cotton-polyester blended fabric was 40.7%.

[0054] Experimental Group 3: The method of organic solvent swelling pretreatment coupled with mechanical external force crushing was adopted. The difference from Experimental Group 1 is that the 5% sodium hydroxide solution was replaced with ethanol solution. The swelling coefficient of cotton-polyester blended fabric was 25.4%.

[0055] Experimental Group 4: The method of pretreatment with pure aqueous solution coupled with mechanical external force crushing was adopted. The difference from Experimental Group 1 is that the 5% sodium hydroxide solution was replaced with pure aqueous solution. The swelling coefficient of cotton-polyester blended fabric was 34.8%.

[0056] Experimental Group 5: A high-concentration acid solution was used for acid hydrolysis separation. The difference from Experimental Group 1 was that the 5% sodium hydroxide solution was replaced with a 10% sulfuric acid solution. The swelling coefficient of the cotton-polyester blended fabric was 34.2%.

[0057] Experimental Group 6: This group employed a high-mechanical-force crushing and separation method. The difference from Experimental Group 1 was that it bypassed the solvent treatment step, directly separating waste cotton-polyester blended fabrics mechanically. It should be noted that the separated powder was analyzed using an electron microscope to determine the particle size of the cotton and polyester fibers. Under the microscope, cotton appeared as flaky particles with small pores, while polyester appeared as smooth, irregular particles larger than cotton. Most of the polyester-cotton aggregates were larger than the individual cotton-polyester components and were considered inseparable. Based on the particle size statistics, a suitable sieve was selected for sieving. The waste blended textiles separated by wet grinding had a polyester purity of 45.3% and a cotton fiber purity of 57.5%. Without solvent treatment, the purity of the polyester and cotton components was poor, making effective separation of the components impossible.

[0058] The properties of the polyester and cotton components recovered from the above experimental groups were measured, and the corresponding results are shown in Table 1. These include:

[0059] 1) Determination of fiber separation purity:

[0060] The recovered polyester component was reacted with 73% sulfuric acid at 50°C for 1 hour. Undissolved polyester components were separated by filtration. The mixture was washed repeatedly with dilute ammonia until neutral. The purity of the polyester fiber was calculated using the following formula. The sieved cotton component was then mixed with phenol / tetrachloroethane (mass fraction 6:4) and heated at 45°C with stirring for 10 minutes. Undissolved cotton components were separated by filtration. The purity of the polyester fiber was calculated using the following formula:

[0061] Polyester / cotton purity: X2=(m2-m3) / m2; where, X2—purity of polyester or cotton component, %; m2—mass of raw material taken for mechanical separation, g; m3—mass of residual solids after solvent dissolution, g.

[0062] 2) Degree of polymerization determination:

[0063] 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".

[0064]

[0065]

[0066] DP 0.905 =0.75[η];

[0067] In the formula: η r[η] is the relative viscosity (mL / g); [η] is the intrinsic viscosity of the sample in the copper ethylenediamine solution (mL / g); K' is an empirical constant, which is 0.056 for the cellulose-copper ethylenediamine system; ρ is the concentration of the sample in the solvent (g / mL); DP is the average degree of polymerization of the sample.

[0068] 3) Crystallinity determination:

[0069] 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 was obtained by comparing the background intensity at 2θ = 18° with the peak height at 2θ = 22.8°.

[0070] 4) Fracture strength determination:

[0071] 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 20mm, the tensile speed is 10mm / min, and each sample is tested at least 15 times. The average value is then calculated using software to determine the final breaking strength.

[0072] Table 1 Results of fiber performance testing for each experimental group

[0073]

[0074] Table 1 shows that compared to acid-base aqueous solution pretreatment, the purity of the separated polyester and cotton fibers is very low in organic solvent and water systems. This indicates that acid-base aqueous solutions can promote the swelling of blended textile fibers, facilitating the separation of the two components through mechanical grinding. The cotton fibers separated by acid hydrolysis in high-concentration acid solution (experimental group 5) exhibit significantly reduced crystallinity, degree of polymerization, and breaking strength. The cotton fibers separated by light treatment with low-concentration solvent have higher breaking strength, preserving the integrity of the fiber structure to the greatest extent. The purity of polyester and cotton fibers separated solely by wet grinding is significantly reduced, indicating that without light solvent treatment, the purity of cotton and polyester is poor, making effective separation of the components impossible.

[0075] Example 2: Optimization of solvent light treatment conditions

[0076] 1. Optimization of solute types in solvent light treatment

[0077] Some inorganic acids, organic acids, organic bases, and inorganic bases were used to swell cotton-polyester blended fabrics. The inorganic bases were selected from metal cations. The acid and alkaline solutes were all prepared into 5% solutions. The solutions were soaked at 60℃ for 30 min at a solid-liquid mass ratio of 1:20. After the reaction, the fabrics were centrifuged at 800g for 10 min to remove excess solvent. The fabrics were then dried to obtain the swelled cotton-polyester blended fabrics. The swelling coefficients of the fabrics after swelling with each solute are shown in Table 2.

[0078] Table 2. Results of the determination of the swelling properties of polyester-cotton blended fabrics by different solvents.

[0079]

[0080] As shown in Table 2, inorganic alkalis have a larger swelling coefficient for cotton-polyester blended fabrics compared to inorganic acids, organic acids, and organic alkalis, making them more conducive to fiber swelling in blended textiles. This alkali swelling pretreatment facilitates the effective separation of the components. Compared to organic alkalis, inorganic alkalis have a larger swelling coefficient for cotton fibers, with the best effect achieved by light treatment with sodium hydroxide, resulting in a swelling coefficient of 45.2% for cotton fibers.

[0081] 2. Optimization of solvent pretreatment time and temperature

[0082] Based on the data in Table 2, cotton-polyester blended fabrics were swelled using 5% NaOH at a solid-liquid mass ratio of 1:20. The fabrics were soaked for different times at different temperatures to discuss the effects of time and temperature on the swelling of the cotton-polyester fibers. After the reaction, the fabrics were centrifuged at 800g for 10 minutes to remove excess solvent. The results of the fabric swelling coefficient determination are shown in Table 3.

[0083] Table 3. Results of the determination of the swelling properties of polyester-cotton blended fabrics by solvents with different swelling times and temperatures.

[0084]

[0085]

[0086] As can be seen from Table 3, high temperature and increased treatment time promote the swelling of cotton-polyester blended fabrics. Treatment at 60℃ for 30 min, 45 min, and 60 min can all achieve about 45% swelling. Considering the overall cost, treatment at 60 min for 30 min can maximize swelling.

[0087] 3. Optimization of the concentration of the swelling solution in solvent light treatment

[0088] Different concentrations of sodium hydroxide solutions were used to swell polyester-cotton blended fabrics. The solutions were prepared at a solid-liquid mass ratio of 1:20 and immersed at 60℃ for 30 minutes. After the reaction, the fabrics were centrifuged at 800g for 10 minutes to remove excess solvent. Mechanical treatment was performed as in Example 1. The swelling coefficient and fiber properties of the cotton fabrics after treatment with different concentrations of sodium hydroxide are shown in Table 4.

[0089] Table 4. Results of the determination of the swelling properties of polyester-cotton blended fabrics with different solvent concentrations.

[0090]

[0091] As can be seen from Table 4, the swelling coefficient of blended fabrics increases proportionally with the increase of sodium hydroxide solution concentration, and the fiber separation purity increases. However, with the increase of solvent concentration, the crystallinity, polymerization degree and breaking strength of the fibers decrease significantly. Considering the effects on swelling performance and fiber structure, 5% sodium hydroxide swelling can achieve the optimal separation concentration.

[0092] Example 3: Optimization of Mechanical External Force Handling Method

[0093] The materials were pulverized using various methods including wet ball milling, planetary ball milling, cryogenic ball milling, mortar and pestle grinding, disc grinding, ultracentrifugal grinding, and rotary grinding. When using a wet ball mill, planetary ball mill, or cryogenic ball mill, the ball-to-material ratio was 1:30, the mass ratio of the swollen cotton-polyester blended fabric to the grinding media was 1:20, the rotation speed was 200 rpm, the grinding time was 10 min, and the grinding media was deionized water. When using a mortar and pestle grinding, no grinding media was used, and the grinding time was 10 min. When using a disc grinding, ultracentrifugal grinding, or rotary grinding, no grinding media was used, the rotation speed was 10000 rpm, and the grinding time was 10 min. The pretreatment swelling method was the same as in Example 1, and the solvent light treatment step involved pretreatment with a 5% sodium hydroxide solution, soaking at 60°C for 30 min.

[0094] Table 5. Results of the determination of separation purity of polyester-cotton blended fabrics under different mechanical external force treatments.

[0095]

[0096]

[0097] After waste blended textiles are processed by different mechanical forces, the purity of cotton and polyester fibers varies. Among them, the ultracentrifugal milling machine separates and recovers cotton fibers with a purity of 87.3% and polyester fibers with a purity of 89.2%, achieving the best separation effect.

[0098] 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 waste polyester-cotton blended fabrics using solvent light treatment coupled with mechanical external force, characterized in that, Includes the following steps: S1. Add waste cotton-polyester blended fabric to the swelling solution, soak it at 20-60℃ for 15-60 minutes, centrifuge to remove excess solvent after the reaction, and then dry to obtain the swollen cotton-polyester blended fabric. The swelling solution is selected from an aqueous solution of an inorganic alkali, and the inorganic alkali is selected from sodium hydroxide, potassium hydroxide, copper hydroxide or calcium hydroxide, and the mass concentration of the inorganic alkali in the swelling solution is 1-5%. S2. The swollen cotton-polyester blended fabric is mechanically crushed to obtain crushed blended micro powder. S3. The pulverized blended micro powder is sieved and separated, the undersize material is collected to obtain the cotton component, and the oversize material is collected to obtain the polyester component.

2. The method for separating waste polyester-cotton blended fabric components by solvent light treatment coupled with mechanical external force according to claim 1, characterized in that, The inorganic base in the swelling solution has a mass concentration of 5%.

3. The method for separating waste polyester-cotton blended fabric components by solvent light treatment coupled with mechanical external force according to claim 1, characterized in that, In step S1, the sample is soaked at 60°C for 30–60 minutes.

4. The method for separating waste polyester-cotton blended fabric components by solvent light treatment coupled with mechanical external force according to claim 1, characterized in that, In step S1, the solid-liquid mass ratio of the cotton-polyester blended fabric to the swelling solution is 1:5 to 30.

5. The method for separating waste polyester-cotton blended fabric components by solvent light treatment coupled with mechanical external force according to claim 1, characterized in that, In step S2, the mechanical external force crushing is selected from wet ball mills, planetary ball mills, cryogenic ball mills, mortar and pestle grinders, disc grinders, ultracentrifugal grinders, or rotary grinders; wherein: When using a wet ball mill, planetary ball mill, or cryogenic ball mill for pulverization, the ball-to-material ratio is 1:20 to 40, the mass ratio of the swollen cotton-polyester blended fabric to the ball milling media is 1:10 to 20, the rotation speed is 200 to 400 rpm, the grinding time is 10 to 60 min, and the ball milling media is deionized water. When using a mortar and pestle grinder to pulverize, without ball milling media, the grinding time is 10 to 60 minutes. When using a disc mill, ultracentrifugal mill, or rotary mill for pulverization, without ball milling media, the rotation speed is 6000–12000 rpm, and the grinding time is 1–10 min.

6. The method for separating waste polyester-cotton blended fabric components by solvent light treatment coupled with mechanical external force according to claim 5, characterized in that, The mechanical external force crushing is selected from ultracentrifugal grinding.

7. The method for separating waste polyester-cotton blended fabric components by solvent light treatment coupled with mechanical external force according to claim 1, characterized in that, The cotton-polyester blended fabric is selected from CVC55 / 45, CVC60 / 40, CVC70 / 30, CVC80 / 20, TC65 / 35, TC65 / 35, TC50 / 50, TC60 / 40 or TC80 / 20.

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