Separating textile waste into component materials using supercritical and subcritical fluids

Abstract

A system and process are described for separating and recycling target components in textile waste and converting various recycled components into new ready-to-use fibers or textile manufacturing. The disclosed methods enable the recovery and reuse of high-purity polymers and fibers, including synthetic materials such as polyester, nylon, spandex, acrylics, and ultra-high molecular weight polyethylene (UHMWPE), as well as natural fibers such as cotton. The target components in the textile waste are separated based on their differential extractability using supercritical or subcritical fluids.

Description

METHODS FOR SEPARATING TEXTILE WASTE INTO COMPONENT MATERIALS USING SUPERCRITICAL AND SUBCRITICAL FLUIDS, AND PRODUCTS DERIVEDTHEREFROMBACKGROUNDTechnical Field

[0001] The present disclosure relates to the field of textile recycling, and more particularly to methods for separating composite textile waste into its constituent materials using supercritical and / or subcritical fluids. The disclosed methods enable the recovery and reuse of high-purity polymers and fibers, including synthetic materials such as polyester, nylon, spandex, acrylics, and ultra-high molecular weight polyethylene (UHMWPE), as well as natural fibers such as cotton. The recovered materials may be used to produce new fibers, thereby promoting a circular economy within the textile industry.Description of the Related Art

[0002] The textile industry generates substantial waste due to the widespread use of composite materials and blends of various fibers, both synthetic and natural. Common synthetic fibers include polyester, nylon, spandex, acrylics, and ultra-high molecular weight polyethylene (UHMWPE), while natural fibers such as cotton are also prevalent. Conventional recycling methods, including mechanical shredding, thermal treatment, and chemical processing, are often inadequate for effectively separating these composites into pure and reusable components. Consequently, valuable resources are lost, and recycled materials frequently suffer from degraded quality.

[0003] Supercritical and subcritical fluids offer a promising solution to these challenges. In their supercritical state, fluids such as carbon dioxide (CO2) and water exhibit unique solvating properties that enable the selective extraction of specific materials based on their chemical characteristics. The disclosed methods exploit these properties to efficiently separate textile waste into high-purity components, including the recovery of fibers suitable for producing new textile products. By enabling the recovery of both synthetic and natural fibers from composite blends, the present disclosure addresses the complexities of modern textile blends and offers an environmentally friendly and efficient recycling method.BRIEF SUMMARY

[0004] The present disclosure provides a comprehensive method for separating textile waste into constituent polymers and fibers using supercritical and / or subcritical fluids. The method comprises the following steps:

[0005] 1) Placement of Textile Waste: a composite textile waste, including blends of synthetic fibers such as polyester, nylon, spandex, polyacrylate, and UHMWPE, together with natural fibers such as cotton, is introduced into a high-pressure extraction chamber configured to operate under supercritical and subcritical conditions.

[0006] 2) Sequential Extraction: the extractable components of the textile waste including polyester, nylon, spandex, and polyacrylate are separated from each other and from other non-extractable components using suitable extractants through a series of sequential extraction processes. The remaining non-extractable components including cotton and UHMWPE fibers are then mechanically recovered for reuse.

[0007] Polyester Extraction: supercritical methanol or subcritical water is used to selectively dissolve and extract polyester fibers.

[0008] Nylon Extraction: subcritical water is used to selectively dissolve and extract nylon fibers.

[0009] Spandex and Polyacrylate Extraction: supercritical or subcritical water is used to dissolve and extract spandex and polyacrylate fibers.

[0010] Cotton Separation: cotton fibers, which may remain undissolved, are isolated from the other components in the textile waste. The isolated cotton fibers are further processed for reuse.

[0011] UHMWPE Recovery: UHMWPE fibers, which remain undissolved due to their chemical resistance, are recovered. The recovered UHMWPE fibers are further processed for reuse.

[0012] 3) Fiber Production from Recycled Components:

[0013] Recycling Extracted Components: the extracted components, such as polyester, nylon, spandex, and polyacrylate polymers, are processed to produce new fibers.

[0014] Fiber Formation from Recovered Fibers: the recovered fibers including recovered natural fibers such as cotton fibers and recovered synthetic fibers such as UHMWPE fibers are used to produce new textile products.

[0015] The method of the present disclosure is advantageous in that it enables recovery of high-purity polymers and fibers, as well as the production of new fibers from recoveredcomponents collected through supercritical or subcritical extraction, thereby enhancing sustainability in textile manufacturing.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

[0017] FIG. 1 is a block diagram of a system for separating target components in a textile waste and producing new fibers, in accordance with some embodiments.DETAILED DESCRIPTION

[0018] In one aspect of the present disclosure, a method for separating one or more target components from textile waste is provided. The target components in the textile waste are separated based on their differential extractability using supercritical or subcritical fluids. The reclaimed (z.e., recycled) target components may be used as starting materials to produce regenerated fibers. In some embodiments, the method includes the following steps:

[0019] In step 1 , a textile waste is provided. The textile waste may include postconsumer and / or post-industrial textiles. For example, the textile waste may be wom-out clothes, end-of-life fabrics, or scraps of chemical fiber cloth. The textile waste may contain one or more target components, such as blends of synthetic fibers (e.g., polyester, nylon, spandex, polyacrylate, and UHMWPE fibers) and natural fibers such as cotton fibers. These different types of fibers are typically intimately intertwined in the textile waste. In some embodiments, in order to increase the contact between the target components of the textile waste and the extraction fluid, the textile waste is comminuted to obtain a comminuted textile waste. The comminuted textile waste may be of any particle size. In some embodiments, the comminuted textile waste has a particle size between 0.5 mm and 100 mm, for example, between 1 mm and 50 mm or between 5 mm and 20 mm.

[0020] In step 2, the textile waste is placed in a high-pressure extraction chamber configured to operate under both supercritical and subcritical conditions. The term “supercritical conditions” encompasses conditions at temperatures and pressures above the extractant’s critical temperature (Tc) and critical pressure (Pc). The term “subcritical conditions” encompassesconditions at temperatures and pressures below an extractant’s critical temperature (Tc) and critical pressure.

[0021] In step 3, a series of sequential extraction processes is performed to separate the target component using different extractants. The extractant may be a supercritical or subcritical fluid such as supercritical or subcritical carbon dioxide (CO2), supercritical or subcritical water, supercritical or subcritical methanol, or supercritical or subcritical ethanol. In some embodiments, the extraction processes are performed to sequentially extract and separate polyester, nylon, spandex, and polyacrylate from the textile waste. a. Polyester Extraction

[0022] In some embodiments, the textile waste may first be treated with supercritical methanol at a temperature around 240°C and a pressure above 80 bar, or with subcritical water at a temperature between 200°C and 374°C and a pressure above its saturation pressure. Under these conditions, supercritical or subcritical methanol selectively dissolves polyester fibers without significantly affecting the other components. The polyester is then precipitated upon cooling and depressurization, yielding high-purity polyester suitable for reuse or fiber production. b. Nylon Extraction

[0023] In some embodiments, the textile waste may subsequently be treated with subcritical water at a temperature between 200°C and 374°C and a pressure above its saturation pressure. Under these conditions, subcritical water selectively dissolves nylon fibers. The Nylon is then recovered after cooling and depressurization. c. Spandex and Polyacrylate Extraction

[0024] In some embodiments, the textile waste may subsequently be treated with supercritical water at a temperature above 374°C and a pressure above 220 bar, or with subcritical water at a temperature between 200°C and 374°C. Under these conditions, supercritical or subcritical water dissolves spandex and polyacrylate fibers. Spandex and polyacrylate are recovered in pure form after cooling and depressurization. d. Residual Cotton Separation

[0025] Cotton fibers that are not dissolved by the supercritical and subcritical extractants under the conditions used for the above synthetic fibers such as polyester, nylon, spandex, and polyacrylate fibers and remain in the textile waste may subsequently be mechanically separated and then cleaned and processed for reuse. e. Residual UHMWPE Recovery

[0026] UHMWPE fibers, due to their high chemical resistance, remain undissolved under the above extraction conditions. The textile waste containing UHMWPE fibers may be recovered and may be either mechanically processed or ground into powder form for reuse.

[0027] In step 4, the recovered target components may be further processed to produce new fibers for reuse. a. Polymer Reprocessing

[0028] In some embodiments, the extracted polymers such as polyester, nylon, spandex, or polyacrylate may undergo purification to remove any impurities. The purified polymers may subsequently be extruded to produce new fibers using conventional spinning techniques. b. Natural Fiber Reuse

[0029] The recovered cotton fibers may be cleaned to remove any impurities, carded, and spun into new yarns. c. UHMWPE Fiber Production

[0030] In some embodiments, the recovered UHMWPE powder may be dispersed in a solvent to form a slurry, which may then undergo gel-spinning to produce new fibers. The solvent may include any hydrocarbon solvent such as octane, nonane, decane, mineral oil (e.g., paraffin oil, naphthene mineral oil, or white mineral oil), kerosene, toluene, xylene, decalin, or tetraline. In some embodiments, the UHMWPE powder may be processed with supercritical CO2 to produce fine particles for fiber production.

[0031] The method of the present disclosure provides the following environmental and economic benefits, including but not limited to:

[0032] Sustainability: Separating the target components from the textile waste and using these recycled components for new fiber preparation can reduce waste and conserve resources by enabling the reuse of both synthetic and natural fibers in the textile waste.

[0033] Closed-Loop System: The supercritical and subcritical fluids used in the present disclosure are environmentally benign solvents, facilitating a closed-loop recycling process.

[0034] Quality Preservation: The recovered materials maintain properties comparable to virgin materials.

[0035] Unique Features and Advantages: The method of the present disclosure provides a comprehensive material recovery approach which allows the effective separation of a wide range of synthetic and natural fibers from composite textile waste.

[0036] Innovative Separation Technique: The present method utilizes unique solvating properties of supercritical and subcritical fluids for selective extraction of target components in the textile waste.

[0037] Production of New Fibers from Waste: The recovered target components enable production of high-quality fibers from both synthetic and natural recovered materials.

[0038] Environmental Compliance: Sustainability can be promoted by reducing reliance on virgin resources and minimizing environmental impact.

[0039] Accordingly, the present disclosure provides methods that preserve material integrity and enable high-value reuse, differentiating it significantly from prior art methods. Specifically, the methods of the present disclosure provide several advancements over prior art methods. First of all, prior art methods fail to efficiently separate and recover pure components from complex textile blends. Unlike the prior methods, the present methods effectively separate natural fibers like cotton from synthetic blends, allowing for their reuse without degradation. Second, the present method also accommodates a wide range of common synthetic fibers such as polyester, nylon, spandex, polyacrylate, and UHMWPE fibers as well as natural fibers, thereby addressing the complexities of modern textile blends. Third, by utilizing supercritical methanol and subcritical water to selectively extract polyester, the present methods allow recovery of common synthetic fibers that cannot be effectively recovered by the prior art methods. Fourth, by enabling the recovery and reuse of both synthetic and natural fibers, the present methods significantly reduce textile waste and support a truly circular economy. Fifth, the ability to produce high-quality fibers from recovered components, including natural fibers such as cotton, adds significant value and utility to the recycling process.

[0040] In another aspect, a system 100 for separating textile waste and producing new fibers from the recycled components is provided. FIG. 1 illustrates a block diagram of such a system in accordance with some embodiments. Referring to FIG. 1, the system 100 includes a high-pressure extraction chamber 110 configured to operate under both supercritical and subcritical conditions, a control system 120 for regulating the temperature and pressure of the extraction chamber 110, a fluid delivery system 130 for introducing and removing supercritical and subcritical fluids in and out of the extraction chamber 110, a purification system 140 for purifying the extracted components, including extracted polymers and residue fibers for further processes, and a fiber producing system 150 for processing the recovered materials into new fibers for reuse.

[0041] The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and / or listed in the Application Data Sheet, including but not limited to U.S. provisional patent application number 63 / 696,247, filed on September 18, 2024, incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

[0042] These and other changes can be made to the embodiments in light of the abovedetailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

CLAIMS1. A method for separating a textile waste into target components, comprising: placing the textile waste comprising a plurality of target components in an extraction chamber; subjecting the textile waste to a series of extraction processes each using an extractant under conditions specific to each target component, wherein the extractant comprises a supercritical fluid, a subcritical fluid or a mixture thereof, and wherein the conditions are supercritical or subcritical conditions; separating the target components from each other based on their chemical properties; and recovering the target components to produce recovered materials.

2. The method of claim 1, wherein the textile waste comprises blends of synthetic fibers including polyester, nylon, spandex, polyacrylate and UHMWPE fibers and natural fibers including cotton fibers.

3. The method of any one of claims 1-2, wherein the extractant comprises supercritical or subcritical carbon dioxide (CO2), supercritical or subcritical water, supercritical or subcritical methanol, or supercritical or subcritical ethanol.

4. The method of any one of claims 1-3, wherein the series of extraction processes comprises a process to extract polyester, the process comprising: subjecting the textile waste to supercritical methanol at a temperature around 240°C and a pressure above 80 bar or subcritical water at a temperature between 200°C and 374°C to selectively dissolve the polyester fibers.

5. The method of any one of claims 1-4, wherein the series of extraction processes comprises a process to extract nylon, the process comprising: subjecting the textile waste to subcritical water at a temperature between 200°C and 374°C to selectively dissolve the nylon fibers.

6. The method of any one of claims 1-5, wherein the series of extraction processes comprises a process to extract spandex and polyacrylate, the process comprising: subjecting the textile waste to supercritical water at a temperature above 374°C and a pressure above 220 bar or subcritical water at a temperature between 200°C and 374°C to selectively dissolve the spandex and polyacrylate fibers.

7. The method of any one of claims 1-6, wherein recovering the target components comprises mechanically separating the cotton fibers after the extraction of the polyester, nylon, spandex and polyacrylate fibers.

8. The method of any one of claims 1-7, wherein recovering the target components comprises recovering the UHMWPE fibers that are undissolved after the series of extraction processes by mechanically grinding the UHMWPE fibers into a UHMWPE powder.

9. The method of any one of claims 1-8, further comprising processing the recovered materials to produce new fibers suitable for textile manufacturing.

10. The method of claim 9, wherein processing the recovered materials comprises processing the recovered UHMWPE fibers to produce new UHMWPE fibers via a fiber-forming method.

11. The method of claim 10, wherein the fiber-forming method is a gel spinning method.

12. The method of any one of claims 1-11, wherein the supercritical or subcritical conditions are specifically adjusted for extracting the synthetic fibers in the textile waste.

13. The method of any one of claims 1-12, further comprising processing the UHMWPE powder using supercritical CO2 in an atomization vessel to produce fine particles for fiber production.

14. A fiber produced from a target component collected by the method of any one of claim 1-13, wherein the fiber is produced from the recycled polyester, nylon, spandex,polyacrylate, UHMWPE, or cotton and retains mechanical properties suitable for textile applications.

15. The fiber of claim 14, wherein the fiber is produced via a spinning method appropriate for the specific recovered material.

16. The fiber of claim 15, wherein the spinning method is melt spinning for producing the fiber from the recovered polyester.

17. The fiber of claim 15, wherein the spinning method is gel spinning for producing the fiber from the recovered UHMWPE.

18. A system for separating target components in a textile waste and producing new fibers, comprising: an extraction chamber configured to operate under both supercritical and subcritical conditions; a control system for regulating temperatures and pressures of the extraction chamber; a fluid delivery system for introducing and removing extractants in and out of the extraction chamber; a purification system for purifying the recovered materials comprising the extracted polymers and non-extractable fibers; and a fiber producing system for processing the recovered materials into new fibers.

19. The system of claim 18, wherein the extractants comprise supercritical or subcritical fluids.

20. The system of claim 19, wherein the extractants comprises the supercritical or subcritical carbon dioxide (CO2), supercritical or subcritical water, supercritical or subcritical methanol, or supercritical or subcritical ethanol.

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