A low-damage separation and recovery method for waste polyester and nylon blended fabric

Abstract

This invention relates to a low-damage separation and recycling method for waste polyester and nylon blended fabrics. The method includes mixing the waste polyester and nylon blended fabric with a dissolving solution to undergo a dissolution reaction, yielding insoluble matter and a filtrate. The dissolving solution comprises calcium chloride, ethanol, water, and a compounded surfactant. The insoluble matter is treated to obtain recycled polyester, and a poor solvent is added to the filtrate to obtain recycled nylon. This invention introduces a compounded surfactant into the calcium chloride-ethanol-water nylon dissolution system, achieving a synergistic mechanism of wetting, complexation, and dispersion, thereby improving the dissolution rate and reducing the use of calcium chloride. The resulting recycled polyester exhibits a crystallinity change ≤3% and a breaking strength retention rate ≥98%; the recycled nylon retains a relative viscosity ≥95%, and both the recycled polyester and recycled nylon products have a purity ≥98.5%.

Description

Technical Field

[0001] This invention relates to the field of waste blended fabric technology, specifically to a low-damage separation and recycling method for waste polyester and nylon blended fabrics. Background Technology

[0002] Polyester (polyethylene terephthalate, PET) and nylon (polyamide, PA) blended fabrics combine the excellent properties of polyester (crispness, wrinkle resistance, and dimensional stability) with nylon (abrasion resistance, high elasticity, and soft hand feel), and are widely used in outdoor sportswear, high-end home textiles, and industrial filtration textiles. With the annual increase in textile consumption, the annual volume of waste polyester-nylon blended fabrics is enormous. Due to the significant differences in the chemical structures of the two components and their tightly interwoven yarns, achieving efficient, low-fiber-damage, and high-purity simultaneous separation and recycling of both components has long been a difficult technical challenge in the field of textile solid waste resource utilization.

[0003] Existing mainstream recycling technologies all have significant drawbacks: high-temperature hydrolysis processes using strong acids and alkalis severely damage the molecular chain matrix structure of polyester and nylon fibers, resulting in a significant decrease in the mechanical properties of the regenerated fibers, making them unsuitable for respinning into high-end fabrics; single organic solvent dissolution methods have poor component selectivity, high solvent volatility, and are flammable and explosive, posing a high risk of environmental pollution; enzymatic hydrolysis methods can only degrade natural fibers and have no effect on PET and PA synthetic fibers, limiting their industrial application. Some studies, such as the "Research on Dissolution Recycling Process of Waste Nylon 6," use a solvent system composed of calcium chloride dihydrate, anhydrous ethanol, and deionized water (CEW) to dissolve and recover polyamide from waste nylon 6 yarn, but this study did not evaluate the purity of the product and had low processing efficiency.

[0004] It is necessary to provide a more efficient recovery method with higher product purity based on the CEW system. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a low-damage separation and recycling method for waste polyester and nylon blended fabrics, comprising: Waste polyester and nylon blended fabric is mixed with a dissolving solution to carry out a dissolution reaction, resulting in insoluble matter and filtrate. The dissolving solution includes calcium chloride, ethanol, water and compound surfactant. Recycled polyester is obtained by treating the insoluble matter, and recycled nylon is obtained by adding a poor solvent to the filtrate.

[0006] Furthermore, the mass ratio of calcium chloride, ethanol, and water in the solution is 8-12:60-70:18-22; The amount of the compound surfactant added is 0.05%-0.5% of the total mass of calcium chloride, ethanol and water.

[0007] Furthermore, the compound surfactant is composed of Tween-80 and alkyl glycosides mixed in a mass ratio of 1-3:1.

[0008] Furthermore, the dissolution reaction is carried out at a temperature of 60-65℃ and a stirring rate of 100-150 r / min for 50-80 min.

[0009] Furthermore, the solid-liquid ratio of the waste polyester and nylon blended fabric and the dissolving solution is 1:10-20.

[0010] Furthermore, the volume of the undesirable solvent is 2-8 times the volume of the filtrate.

[0011] Further, the obtained recycled nylon includes, After adding a poor solvent to the filtrate, solid-liquid separation is performed to obtain recycled nylon and waste liquid; The waste liquid was pre-concentrated and then distilled to obtain a mixed fraction of ethanol and water, as well as an aqueous solution of calcium chloride.

[0012] Furthermore, the pre-concentration is carried out using a nanofiltration membrane with a molecular weight cutoff of 1200 Da at a pressure of 0.3-0.5 MPa; The mixed fraction of ethanol and water, along with the calcium chloride aqueous solution, is processed and prepared into a new solution for use in the next batch of dissolution reactions.

[0013] Furthermore, the process of obtaining recycled polyester by treating insoluble substances includes washing and drying, wherein the drying temperature is 80-90°C.

[0014] The present invention also provides recycled polyester and recycled nylon obtained by the above-mentioned low-damage separation and recycling method for waste polyester and nylon blended fabrics.

[0015] Compared with the prior art, the beneficial effects of the present invention include: 1. By introducing a compound surfactant into the calcium chloride-ethanol-water nylon dissolution system, the triple synergistic mechanism of wetting, complexation, and dispersion improves the dissolution rate and reduces the amount of calcium chloride used.

[0016] 2. The crystallinity change of recycled polyester is ≤3%, and the breaking strength retention rate is ≥98%; the relative viscosity retention rate of recycled nylon is ≥95%, and the product purity of both recycled polyester and recycled nylon is ≥98.5%.

[0017] 3. Both calcium chloride and compound surfactants are low-toxic industrial raw materials. No strong acids, strong alkalis, or heavy metal salts are used in the entire process. Waste liquid treatment is simple, and the environmental advantages are outstanding.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0019] To more clearly illustrate the technical solution of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0020] Figure 1 This is a flowchart of the low-damage separation and recycling method for waste polyester and nylon blended fabrics of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] Nylon molecules contain a large number of amide groups (-CONH-), resulting in strong intermolecular hydrogen bonding. Calcium chloride dissociates into Ca when dissolved in an ethanol-water system. 2+ Cl - ;Ca 2+It has a strong coordination binding ability to the carbonyl oxygen in the amide group, which can disrupt the hydrogen bond network between nylon molecules and achieve nylon dissolution. Adding Tween-80 and alkyl glycosides to the dissolution system, Tween-80, a long-chain polyoxyethylene nonionic surfactant, can significantly reduce the liquid-solid interfacial tension between hydrophobic polyester / nylon fabrics and the solvent, and increase the solvent penetration rate; alkyl polyglycosides are green and biodegradable nonionic surfactants, with a large number of hydroxyl groups carried by the glucose ring in the molecule, which can form hydrogen bonds with the amide groups on the nylon surface for pre-adsorption, forming an additive enrichment layer at the nylon-solvent interface.

[0025] The enhancing mechanism of Tween-80 and alkyl glycosides is as follows: (i) Wetting synergy: Tween-80 rapidly reduces interfacial tension, and APG is directionally adsorbed on the surface of nylon fibers, synergistically promoting the rapid penetration of solvent into the interfiber gaps inside the fabric. (ii) Complexation synergy: APG pre-adsorption stretches the conformation of nylon amide groups, reducing Ca²⁺. + The steric hindrance of coordination with carbonyl oxygen accelerates the formation of calcium-amide coordination complexes and significantly improves the dissolution rate; (iii) Dispersion and synergy: The long chain of Tween-80 polyoxyethylene provides steric stabilization to the dissolved nylon molecular chain, preventing the premature aggregation and precipitation of nylon oligomers and ensuring the uniformity and stability of the dissolved system.

[0026] Accordingly, the present invention provides a low-damage separation and recycling method for waste polyester and nylon blended fabrics. Waste polyester and nylon blended fabric is mixed with a dissolving solution to carry out a dissolution reaction, resulting in insoluble matter and filtrate. The dissolving solution includes calcium chloride, ethanol, water and compound surfactant. Recycled polyester is obtained by treating the insoluble matter, and recycled nylon is obtained by adding a poor solvent to the filtrate.

[0027] In some preferred embodiments, the mass ratio of calcium chloride, ethanol and water in the solution is 8-12:60-70:18-22; The amount of the compound surfactant added is 0.05%-0.5% of the total mass of calcium chloride, ethanol and water.

[0028] In some preferred embodiments, the compound surfactant is composed of Tween-80 and alkyl glycosides mixed in a mass ratio of 1-3:1.

[0029] In some preferred embodiments, the dissolution reaction is carried out at a temperature of 60-65°C and a stirring rate of 100-150 r / min for 50-80 min.

[0030] This invention limits the dissolution reaction to a temperature of 60-65℃, which is lower than the atmospheric boiling point of ethanol (78.3℃). Combined with a reflux condenser, ethanol volatilization can be completely suppressed. At the same time, this temperature range will not damage the PET molecular chain or cause the polyester to plasticize and swell, and the polyester crystalline structure and mechanical properties will be fully preserved.

[0031] After the dissolution reaction is complete, the product is first cooled to 30-40℃ before solid-liquid separation is performed to obtain insoluble matter and filtrate. This avoids the large amount of ethanol volatilization caused by high-temperature filtration and prevents material loss due to premature flocculation and precipitation of nylon molecular chains at high temperatures.

[0032] In some preferred embodiments, the solid-liquid ratio of the waste polyester and nylon blended fabric to the dissolving liquid is 1:10-20.

[0033] In some preferred embodiments, the volume of the undesirable solvent is 2-8 times the volume of the filtrate.

[0034] In some preferred embodiments, obtaining recycled nylon includes, After adding a poor solvent to the filtrate, solid-liquid separation is performed to obtain recycled nylon and waste liquid; The waste liquid was pre-concentrated and then distilled to obtain a mixed fraction of ethanol and water, as well as an aqueous solution of calcium chloride.

[0035] In some preferred embodiments, the pre-concentration is carried out using a nanofiltration membrane with a molecular weight cutoff of 1200 Da at a pressure of 0.3-0.5 MPa; The mixed fraction of ethanol and water, along with the calcium chloride aqueous solution, is processed and prepared into a new solution for use in the next batch of dissolution reactions.

[0036] Wastewater containing nylon flocs formed by adding unsuitable solvents is first pre-concentrated through a nanofiltration membrane with a molecular weight cutoff of 1200 Da, with the operating pressure controlled at 0.3-0.5 MPa. Calcium chloride forms hydrated ion clusters in an ethanol-water mixed solvent. The ion dynamics diameter is larger than the pore size of the nanofiltration membrane. Combined with the Donnan repulsion effect of the charged nanofiltration membrane on divalent cations, the membrane retains calcium chloride at a stable rate of 50%-60%. Pre-concentration can remove a large amount of free water from the wastewater, reducing the energy consumption and treatment time of subsequent distillation.

[0037] After pre-concentration, the mixture is distilled at atmospheric pressure at 75-85℃, and the ethanol-water mixed fraction is collected in sections at 74-82℃. The salting-out effect keeps the ethanol content of the fraction stable at 90%-94%. Concentrated calcium chloride aqueous solution is collected at the bottom, and the mass concentration of calcium chloride is controlled to ≤50% to prevent salt crystallization and clogging of the equipment.

[0038] The mass fraction of each component in the ethanol-water fraction and the calcium chloride aqueous solution at the bottom of the vessel are tested separately. Anhydrous ethanol with a purity of 99.5% or higher, deionized water, and solid calcium chloride are added as needed. The total water content of the system is monitored online. If the water content exceeds 12%, excess water is removed by distillation. The mixture is then adjusted to be completely consistent with the initial ratio and returned to the dissolution process for recycling.

[0039] In some preferred embodiments, the treatment of insoluble materials to obtain recycled polyester includes washing and drying, wherein the drying temperature is 80-90°C.

[0040] Through numerous experiments, the present invention has determined the optimal parameters for the dissolution reaction, as shown in Table 1.

[0041] Table 1

[0042] Test Standards and Testing Methods Nylon solubility: calculated based on the difference in fiber dry weight before and after the reaction, combined with the nylon solid content in the mother liquor; Purity of recycled polyester fiber and recycled nylon raw materials: determined according to GB / T 2910.4-2022 "Quantitative chemical analysis of textiles - Part 4: Mixtures of certain protein fibers and certain other fibers (hypochlorite method)"; Retention rate of breaking strength of recycled polyester: determined according to GB / T 3916-2013 "Breaking strength and elongation at break of single yarn in packaged textile fiber". Relative viscosity of recycled nylon: determined according to GB / T 1632.1-2024 "Determination of viscosity of polymer dilute solutions using capillary viscometer - Part 1: General rules". The sample was dried at 105℃ to constant weight, with 96% sulfuric acid as solvent, and kept at a constant temperature of 25℃. The sample concentration was 0.01 g / mL. Each group of samples was tested in parallel for 3 times and the arithmetic mean was taken. Solvent single-cycle recovery rate: calculated through material balance of the entire process; Ethanol content in fractions: detected by gas chromatography, FID detector, PEG-20M capillary column.

[0043] The present invention will be further described in detail below through specific embodiments. It should be noted that 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 shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0044] Example 1 A low-damage separation and recycling method for waste polyester / nylon blended fabrics, such as... Figure 1 As shown, it includes the following steps: S1. Raw material pretreatment: Select waste polyester and nylon 6 blended fabric, in which the mass ratio of polyester and nylon 6 is 65% and 35% respectively. Manually sort and remove metal zippers and elastic band accessories. After dust removal and impurity removal, dry at room temperature to obtain pretreated fabric for use.

[0045] S2. Dissolution Reaction: Add 10.0g of calcium chloride to 20.0g of deionized water, stir to dissolve, and cool to room temperature; then add 0.15g of a compound surfactant composed of Tween-80 and alkyl glycosides in a mass ratio of 2:1, stir evenly, and then add 69.85g of anhydrous ethanol. Stir at room temperature until the system is completely clear to obtain a solution. The components in the solution are: calcium chloride 10wt%, anhydrous ethanol 69.85wt%, deionized water 20wt%, and compound surfactant 0.15wt%. Mix 5.00g of pretreated fabric with 80g of solution and transfer to a three-necked reaction flask equipped with a reflux condenser; maintain the system temperature at 60℃ using an oil bath, stir at 120r / min, and react at this temperature for 60min; the system should not boil at atmospheric pressure, and there should be no obvious ethanol reflux droplets in the condenser.

[0046] S3. Purification: After the dissolution reaction is complete, the product is naturally cooled to 35℃. Vacuum filtration is used to separate the insoluble matter and filtrate. The insoluble matter is washed three times with deionized water at 35℃. The wastewater from washing is combined with the filtrate to obtain a mixed solution with a total volume of 88mL. After washing, the insoluble matter is dried at 60℃ to constant weight to obtain 3.24g of recycled polyester. 264mL of deionized water is added to the mixed solution, and the mixture is allowed to stand at room temperature for 30min to precipitate the nylon. Filtration is used to obtain the waste liquid and insoluble matter. The insoluble matter is washed with water and dried to obtain 1.72g of recycled nylon.

[0047] S4. Solvent Closed-Loop Recovery: Waste liquid is pre-concentrated through a nanofiltration membrane with a molecular weight cutoff of 1200 Da, operating at a pressure of 0.3 MPa. The membrane has a calcium chloride rejection rate of 55% (calibrated by conductivity standard curve R). 2 =0.999); the mixed permeate and membrane concentrate were transferred to an atmospheric distillation apparatus and distilled at a constant temperature of 78℃. 45.5g of the fraction distilled at 74-82℃ was collected, and gas chromatography analysis showed an ethanol content of 92.5%. A concentrated calcium chloride aqueous solution with a CaCl2 mass concentration of 50% was obtained at the bottom of the still. The content of each component in the fraction and the bottom liquid was analyzed, and the total water content of the system was within the acceptable range. Anhydrous ethanol and solid calcium chloride were added as needed to prepare 80g of the standard solution for the next batch of dissolution reaction. The solvent recovery rate for this batch in a single cycle was 95.8%.

[0048] The test results show that the purity of recycled polyester is 99.5%, and the breaking strength retention rate is 99.2%; the crystallinity of virgin polyester is 38.5%, and the crystallinity of recycled polyester is 36.4%, with a difference of only 2.1%. The purity of recycled nylon is 99.3%; the relative viscosity of virgin PA6 is 2.45, and the relative viscosity of recycled nylon is 2.33, with a viscosity retention rate of 95.1%, and no hydrolytic chain breakage of the molecular chains.

[0049] Example 2 The difference from Example 1 is that the same mass of the compound surfactant in S2 is composed of Tween-80 and alkyl glycosides mixed in a mass ratio of 1:1.

[0050] The test results showed that the nylon solubility was 94.2%; the purity of recycled polyester was 99.1% and the strength retention rate was 98.8%; the purity of recycled nylon was 99.0% and the relative viscosity retention rate was 94.7%; and the solvent single-cycle recovery rate was 95.2%.

[0051] Example 3 The difference compared to Example 1 is that the amount of solution used in S2 is 50g, and the temperature is raised to 80°C.

[0052] The test results showed that the nylon was completely dissolved; the recycled polyester had a purity of 99.2% and a strength retention rate of 98.8%; the recycled nylon had a purity of 99.0% and a relative viscosity retention rate of 95.0%; and the solvent single-cycle recovery rate was 94.8%.

[0053] The overall dissolution effect was similar to that of Example 1, which also shows that appropriately increasing the reaction temperature can reduce the solid-liquid ratio, reduce the amount of solvent added at one time, and reduce production costs.

[0054] Example 4 Following the method in Example 1, the solvent was recycled. After solvent recovery was completed for each batch, the components were tested. During the operation of each batch, materials were replenished according to the corresponding concentration to maintain the standard ratio. Five production batches were run continuously. The test data for each batch are shown in Table 2.

[0055] Table 2

[0056] It can be seen that after five consecutive cycles, all indicators still meet the industrial raw material standards, proving that the entire process has excellent long-term operational stability.

[0057] Comparative Example 1 The difference compared to Example 1 is that the solution of S2 does not contain a compound surfactant.

[0058] The results showed that when the reaction was carried out at 60°C for 60 min, the nylon dissolution rate was only 82.3%, and a large amount of undissolved nylon flocculent material was attached to the surface of the polyester fiber, reducing the purity of the recycled polyester to 94.5%. When the reaction was extended to 90 min, the nylon dissolution rate only increased to 88.7%, which was far lower than the 98.5% in Example 1.

[0059] Comparative Example 2 The difference from Example 1 is that Tween-80 is used instead of the compound surfactant in S2.

[0060] The results showed that the nylon dissolution rate was 89.5% after 60 minutes, and the purity of the recycled polyester was 96.8%; the dissolution effect was far inferior to that in Example 1. This is attributed to the coordination-assisted adsorption of alkyl glycosides, which improved the degradation efficiency.

[0061] Comparative Example 3 The difference from Example 1 is that in S2, the compound surfactant is replaced with an alkyl glycoside.

[0062] The results showed that the nylon dissolution rate was 87.2% after 60 minutes, and the purity of the recycled polyester was 96.1%; the dissolution effect was far inferior to that of Example 1. This also demonstrates that a single alkyl glycoside cannot achieve efficient wetting and penetration, and proves the synergistic effect of Tween-80 and alkyl glycoside.

[0063] Comparative Example 4 The difference from Example 1 is that the solution consists of 15.0g calcium chloride, 65.0g anhydrous ethanol, and 20.0g deionized water.

[0064] The results showed that after reacting at 60℃ for 60 min, the nylon dissolution rate was 94.8%; the purity of the recycled polyester was 97.5%, and the tensile strength retention rate was only 96.8%.

[0065] Example 1 reduced the amount of calcium chloride used by 33% compared to Comparative Example 4, while achieving higher nylon solubility and less damage to polyester fibers. Introducing a compound surfactant significantly reduced the use of calcium chloride, resulting in higher-quality recycled fiber materials.

[0066] Comparative Example 5 Compared with Example 1, the difference is that the reaction temperature is 25°C and the time is extended to 90 min.

[0067] The results show that the nylon dissolution rate is only 18%, which is insufficient for effective industrial separation; this also indicates that the solution needs to be at a suitable temperature to provide sufficient dissolution kinetics.

[0068] Comparative Example 6 The difference compared to Example 1 is that the reaction temperature is 85°C.

[0069] The results showed that ethanol boiled violently, and the reflux load was extremely high; polyester fibers underwent solvent-induced plasticization, and the retention rate of the breaking strength of recycled polyester dropped to 86.3%, with a purity of 95.2%; high temperature would severely damage polyester fibers.

[0070] Comparative Example 7 The difference from Example 1 is that in S4, nanofiltration membrane pre-concentration is not used, and the ethanol fraction is directly recovered by distillation at atmospheric pressure at 78°C.

[0071] The results showed that the distillation time was 1.7 times that of Example 1, and the steam energy consumption increased by 65%; the ethanol content of the fraction was only 86.3%, and a large amount of anhydrous ethanol needed to be added to adjust the solvent; this confirmed that nanofiltration pre-concentration is a key process to reduce energy consumption and increase fraction concentration.

[0072] Comparative Example 8 The difference compared to Example 1 is that in S4, anhydrous ethanol and calcium chloride are directly added to the flocculated waste liquid for the next batch of dissolution reaction.

[0073] The results showed that after three consecutive cycles, the internal moisture content of the solvent accumulated to 16.8%, the nylon solubility dropped to 76.5%, and the purity of the recycled polyester decreased to 90.8%. This demonstrates that the distillation and dehydration, precise formulation, and closed-loop process of this invention are necessary conditions for long-term stable production.

[0074] Comparative Example 9 The difference compared to Example 1 is that the proportion of compound surfactant in the solution in S2 is 1 wt%.

[0075] The results showed that the nylon solubility was 94.5% after reacting at 60℃ for 60 min; excessive additives co-precipitated with nylon during the nylon flocculation stage, reducing the purity of the recycled nylon to 96.2% and the relative viscosity retention rate to only 91.8%; confirming that there is an optimal upper limit range for the amount of surfactant added, and excessive amounts deteriorate the product quality.

[0076] Overall, the separation and recovery method based on this invention uses common industrial equipment: a stirred reactor, a reflux condenser, a vacuum filtration device, a nanofiltration membrane module, and an atmospheric distillation kettle. Equipment procurement and maintenance costs are low, and the operation process is simple and safe. The raw materials—calcium chloride, anhydrous ethanol, Tween-80, and alkyl polysaccharides—are all readily available domestic industrial commodities with ample supply and low procurement costs. The amount of compound surfactant added is extremely low, and its impact on overall production costs is negligible.

[0077] This method is applicable to all specifications of polyester-nylon blended woven and knitted waste fabrics. The purity and mechanical properties of the separated recycled polyester and recycled nylon raw materials meet the raw material standards of the textile spinning and modified engineering plastics industries. They can be directly utilized at high value without additional refining. The solvent can be recycled in a closed loop for a long time, and the waste liquid discharge is extremely low. It has both significant environmental and economic benefits and has the value for large-scale industrial promotion.

[0078] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A low-damage separation and recycling method for waste polyester and nylon blended fabrics, characterized in that, include, Waste polyester and nylon blended fabric is mixed with a dissolving solution to carry out a dissolution reaction, resulting in insoluble matter and filtrate. The dissolving solution includes calcium chloride, ethanol, water and compound surfactant. Recycled polyester is obtained by treating the insoluble matter, and recycled nylon is obtained by adding a poor solvent to the filtrate.

2. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The mass ratio of calcium chloride, ethanol and water in the solution is 8-12:60-70:18-22; The amount of the compound surfactant added is 0.05%-0.5% of the total mass of calcium chloride, ethanol and water.

3. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The compound surfactant is composed of Tween-80 and alkyl glycosides mixed in a mass ratio of 1-3:

1.

4. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The dissolution reaction was carried out at a temperature of 60-65℃ and a stirring rate of 100-150 r / min for 50-80 min.

5. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The solid-liquid ratio of the waste polyester and nylon blended fabric and the dissolving solution is 1:10-20.

6. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The volume of the undesirable solvent is 2-8 times the volume of the filtrate.

7. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The obtained recycled nylon includes, After adding a poor solvent to the filtrate, solid-liquid separation is performed to obtain recycled nylon and waste liquid; The waste liquid was pre-concentrated and then distilled to obtain a mixed fraction of ethanol and water, as well as an aqueous solution of calcium chloride.

8. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 7, characterized in that, The pre-concentration is carried out using a nanofiltration membrane with a molecular weight cutoff of 1200 Da at a pressure of 0.3-0.5 MPa. The mixed fraction of ethanol and water, along with the calcium chloride aqueous solution, is processed and prepared into a new solution for use in the next batch of dissolution reactions.

9. The method for low-damage separation and recycling of waste polyester and nylon blended fabrics according to claim 1, characterized in that, The process of obtaining recycled polyester by treating insoluble substances includes washing and drying, wherein the drying temperature is 80-90°C.

10. Recycled polyester and recycled nylon obtained by the low-damage separation and recycling method for waste polyester and nylon blended fabrics as described in any one of claims 1-9.

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