Method for removing colorants and / or additives from textile materials

Abstract

A method for removing colorants and / or additives from a textile material, the method comprising the step of contacting a textile material comprising a plurality of colorants and / or additives with a non-polar or polar supercritical or subcritical phase.

Description

Technical Field

[0001] This disclosure relates to a method for removing colorants and / or additives from textile materials using polar / non-polar supercritical / subcritical phases. Background Technology

[0002] Traditional methods for removing dyes from textile materials typically involve the use of harsh chemicals and the consumption of large amounts of water. More sustainable alternatives are currently being explored to minimize ecological impact and damage to the performance of textile materials. For example, WO22178704 discloses a method for extracting disperse dyes from synthetic fibers, wherein the dyed textile is contacted with supercritical CO2, thereby extracting at least a portion of the disperse dye from the textile into the supercritical fluid and forming at least partially decolorized textile.

[0003] Blended fabrics typically combine different fibers, such as cotton and polyester. These fibers have different properties and react differently to bleaching methods.

[0004] For such blended fabrics, finding a bleaching method that can effectively target and remove color without damaging individual fibers is a challenge. Some dyes used to color textiles are reversible and resistant to fading or bleaching. Decolorizing these dyes without compromising the integrity of the fabric can be difficult.

[0005] Therefore, there is a need for a decolorization technology that removes various dyes from a variety of textiles, including blended fabrics, with low water and chemical consumption and minimal or no damage to individual fibers. Summary of the Invention

[0006] The purpose of this disclosure is to provide a method for removing colorants and / or additives from textile materials (including blended fabrics) in a way that consumes little water and chemicals and causes little or no damage to individual fibers.

[0007] This disclosure is defined by the appended independent claims. Non-limiting embodiments are given by the dependent claims, drawings, and the following description.

[0008] In a first aspect, this disclosure provides a method for removing colorants and / or additives from a textile material, the method comprising the steps of: 1) contacting the textile material with a supercritical or subcritical phase, said supercritical or subcritical phase being nonpolar or polar and having a first density, wherein the method further comprises at least one of the following steps: 2a) adjusting the density of the nonpolar or subcritical phase used in step 1) to a second density different from the first density, such that the textile material is contacted with the nonpolar or subcritical phase having the second density; and / or 2b1) if the supercritical or subcritical phase used in step 1) is a nonpolar supercritical or subcritical phase, then contacting the textile material with a polar supercritical or subcritical phase; or 2b2) if the supercritical or subcritical phase used in step 1) is a polar supercritical or subcritical phase, then contacting the textile material with a nonpolar supercritical or subcritical phase.

[0009] The above methods can be batch, continuous, or semi-continuous processes. Using these methods, polar and non-polar colorants / additives can be removed from textile materials (e.g., textile waste) and extracted into a supercritical or subcritical phase with little or no damage to individual textile fibers, and with zero or very low water and chemical consumption. The polarity of the supercritical / subcritical fluid / phase can be adjusted according to the properties of the colorants / additives, allowing them to be extracted at least partially from the textile material. The conditions of the supercritical / subcritical fluid / phase (e.g., density, i.e., pressure and temperature) can be adjusted to target specific components.

[0010] This method can be used to produce high-value new raw materials from textile waste. Furthermore, this energy-efficient technology uses green solvents such as supercritical / subcritical fluids, which can be continuously recovered and reused. Finally, the method uses little or no water during the process. The extracted colorants and additives can be collected. The extraction of colorants and additives is carried out under mild pressure and temperature conditions, such as pressures of 10 to 400 bar and temperatures of 20°C to 250°C. Moreover, because supercritical / subcritical fluids / phases are used instead of water, this technology requires no drying step after treatment.

[0011] The above method can be used to remove additives and colorants from any type of textile material. For example, it can be used for blended textile materials, such as blended textile materials containing at least a first fiber type and at least a second fiber type, wherein the first fiber type is cellulose fiber and the second fiber type is non-cellulose fiber.

[0012] In step 2a), the density of the nonpolar or polar supercritical or subcritical phase used in step 1) is adjusted to a second density different from the first density, so that the textile material comes into contact with the nonpolar or polar supercritical or subcritical phase having the second density. This means that the phases used in steps 1) and 2a) can both be supercritical or both be subcritical, or the phase used in one of the above steps is a supercritical phase while the phase used in the other step is a subcritical phase.

[0013] In this article, the first density (i.e., the first pressure / temperature) and the second density (i.e., the second pressure / temperature) refer to a specific density or a smaller density range within which the first density or the second density is within ±5 kg / m³ of the specific density. 3 The density varies within a certain range. The density change between the first and second density stages is at least 30 kg / m³. 3 .

[0014] The pressure and temperature required to obtain a supercritical or subcritical phase, or the density (i.e., pressure and / or temperature) adjustment required to change from the first density to the second density, naturally depends on the type of supercritical / subcritical fluid used, such as carbon dioxide, water, methane, ethane, ethanol, or propane.

[0015] The transition between supercritical / subcritical and subcritical / supercritical phases, or between two supercritical or subcritical phases with different densities, is achieved by changing the pressure and / or temperature of the phases. Therefore, it primarily affects the density, solubility, and mass transfer of the supercritical or subcritical phase. By switching between different densities (i.e., pressure / temperature), more components can be dissolved or extracted from textile materials.

[0016] In some applications, it may not be necessary to switch / circulate between the supercritical and subcritical phases. A small density change or circulation while keeping the fluid in the supercritical or subcritical phase may be sufficient to extract additives / colorants from textile materials.

[0017] It should be understood that nonpolar supercritical or subcritical phases encompass both completely nonpolar phases and polar phases whose polarity is reduced / nonpolarity is enhanced by the addition of, for example, a nonpolar solvent to a polar phase. Similarly, polar supercritical or subcritical phases encompass both completely polar phases and nonpolar phases whose polarity is reduced / nonpolarity is enhanced by the addition of, for example, a polar solvent to a nonpolar phase.

[0018] Textile materials containing multiple colorants and / or additives and treated by the methods described above (steps 1 and 2a and / or 2b1 or 2b2) should be understood as textile materials containing two or more different types of colorants, or two or more additives, or at least one colorant and one additive. The different types of colorants / additives differ, for example, in polarity.

[0019] In one implementation, the phases used in steps 1) and 2a) can both be supercritical phases or both be subcritical phases, or the phase used in one step can be a supercritical phase while the phase used in the other step can be a subcritical phase.

[0020] The non-polar or polar supercritical or subcritical phase used in the method can have a pressure of 10 bar to 400 bar and a temperature of 20°C to 250°C.

[0021] The density difference between the first density of the phase used in step 1) and the second density of the phase used in step 2a) can be at least 30 kg / m³.

[0022] In one implementation, the method includes at least step 1) and step 2a).

[0023] In another embodiment, the method includes steps 1), 2a), and 2b1) or 2b2).

[0024] In yet another implementation, the method includes step 1) and step 2b1) or step 2b2).

[0025] At least one step (step 1), step 2a), and step 2b1 or step 2b2) in the method may be repeated once or multiple times.

[0026] The duration of each step in step 1), step 2a), and step 2b1) or step 2b2) can be at least 10 minutes.

[0027] The supercritical or subcritical phase may contain supercritical or subcritical carbon dioxide, water, methane, ethane, ethanol, or propane.

[0028] Nonpolar supercritical or subcritical phases may contain nonpolar cosolvents.

[0029] The nonpolar cosolvent can be selected from ethane, propane, dimethyl ether, aromatic hydrocarbons, alkanes, or any combination thereof.

[0030] Polar supercritical or subcritical phases may contain polar cosolvents.

[0031] The polar co-solvent can be selected from water, ethanol, acetone, methanol, dichloromethane, or any combination thereof.

[0032] Some colorants / additives are readily soluble in supercritical or subcritical phases, while others may require the addition of nonpolar or polar co-solvents to improve solubility and thus enhance extraction efficiency. Some colorants / additives are readily soluble in naturally occurring polar or nonpolar supercritical or subcritical phases.

[0033] Nonpolar or polar supercritical or subcritical phases may include any one or more of enzymes, ionic liquids, and surfactants.

[0034] The enzyme can be selected from peroxidase, laccase, azo reductase, cellulase, manganese peroxidase, horseradish peroxidase, tyrosinase, or any combination thereof.

[0035] The ionic liquid can be selected from imidazolium-based ionic liquids, phosphonium-based ionic liquids, pyridinium-based ionic liquids, ammonium-based ionic liquids, or any combination thereof.

[0036] Surfactants can be selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, or any combination thereof.

[0037] The additives may be polar additives and may be residual or permanent dispersants, fixing agents, residual antistatic agents, residual emulsifiers, residual softeners, polar ultraviolet absorbers, polar flame retardants, or any combination thereof.

[0038] The colorant can be a polar colorant, and can be a reactive dye, a mordant dye, azo dye, acid dye, basic dye, direct dye, or any combination thereof.

[0039] The colorant can be a non-polar colorant, and can be a disperse dye, an oil-soluble dye, a vat dye, a solvent dye, a hydrophobic azo dye, or any combination thereof.

[0040] The additives can be non-polar additives, and can be hydrophobic finishers, residual softeners, slip agents, antifouling agents, non-polar flame retardants, non-polar ultraviolet absorbers, or any combination thereof.

[0041] Before implementing step 1), the method may also include a pre-step: contacting a supercritical or subcritical phase with a textile material to extract any moisture, dirt, grease or sizing agent from the textile material into the supercritical or subcritical phase.

[0042] This preliminary step can be used to improve the efficiency of subsequent steps. Attached Figure Description

[0043] Figure 1This illustration schematically demonstrates a method for removing colorants or additives from textile materials.

[0044] Figure 2 The following is shown for implementation Figure 1 A system based on one implementation of the method shown.

[0045] Figure 3 To demonstrate the use of Figure 1 The diagram shows the color intensity curves before and after processing in one embodiment of the method shown.

[0046] Figure 4 It shows Figure 1 An example of the pressure cycle used in a method for removing colorants or additives from textile materials is shown. Detailed Implementation

[0047] Figure 1 A method for removing colorants and / or additives from textile material 1 is shown. Figure 2 A system for carrying out this method is shown. The textile material 1 to which the colorant and / or additives are to be removed can be placed in a pressure chamber 2, such as an autoclave.

[0048] In an optional pre-step (99), the supercritical or subcritical phase 3 is contacted with the textile material 1 for at least 10 minutes to, for example, 60 minutes, to extract any moisture / water, dirt, grease, or sizing agent from the material into the supercritical or subcritical phase. The pressure can be from 75 bar to 100 bar, and the temperature can be from 40°C to 100°C. The ratio of the supercritical or subcritical phase to the blended textile material in this step can be from 0.5:1 to 50:1 or from 5:1 to 40:1, or preferably from 10:1 to 30:1. After contacting the supercritical or subcritical phase with the textile material 1 to extract any moisture / water, dirt, grease, or sizing agent from the material, a decompression step can be performed, and all extracted water, dirt, grease, and other components such as sizing agents can be separated from the textile material and transferred to a collector 5 located outside the pressure chamber 2. Alternatively, the extracted substances can be removed by using a continuously flowing supercritical or subcritical phase through / through the textile material 1.

[0049] Subsequently, or without performing the optional pre-step 99, in step 1), the textile material 1 is contacted 100 with a non-polar or polar supercritical or subcritical phase having a first density, thereby extracting the non-polar or polar colorant and / or additive from the textile material into the non-polar or polar supercritical or subcritical phase.

[0050] After contacting the textile material with a nonpolar or polar supercritical or subcritical phase, the extracted nonpolar or polar components can be removed from the textile material by depressurizing the nonpolar or polar supercritical or subcritical phase. These components can then be transferred to a collector 5 located outside the pressure chamber 2. Alternatively, the extracted nonpolar or polar substances can be removed by using a continuously flowing supercritical or subcritical phase through / through the textile material. The removal of the extracted components can be performed before the next step of the method. Alternatively, the removal of the extracted components can be performed after two or more steps of the method or after the method is completed.

[0051] The method also includes one or more steps selected from the following: - Step 2a), wherein the pressure and / or temperature of the non-polar or polar supercritical or subcritical phase used in step 1) is adjusted to a second density different from the first density, such that the textile material 1 is in contact 100 with the non-polar or polar supercritical or subcritical phase having the second density; and / or - Step 2b1), if the supercritical or subcritical phase used in step 1) is a non-polar supercritical or subcritical phase, then the textile material 1 is brought into contact with a polar supercritical or subcritical phase 102a, or - Step 2b2), if the supercritical or subcritical phase used in step 1) is a polar supercritical or subcritical phase, then the textile material 1 is brought into contact with a non-polar supercritical or subcritical phase 102b.

[0052] Depending on the properties of the various colorants and / or additives contained in the textile material, the textile material may first come into contact with a non-polar supercritical or subcritical phase, or first come into contact with a polar supercritical or subcritical phase.

[0053] In step 2a), the density, pressure, and / or temperature of the nonpolar or polar phase used in step 1) are adjusted to a second density different from the first density, so that the textile material comes into contact with a nonpolar or polar supercritical or subcritical phase having the second density. This means that the phases used in steps 1) and 2a) can both be supercritical or both be subcritical, or the phase used in one of the above steps can be a supercritical phase while the phase used in the other step can be a subcritical phase.

[0054] In one example, the density of the nonpolar or polar supercritical or subcritical phase used in step 1) is 480 kg / m³. 3 That is, the first pressure and temperature are 200 bar and 100 °C, respectively. In step 2a), the non-polar or polar supercritical or subcritical phase has a density of 580 kg / m³. 3The second density. In one example, the second density is obtained by keeping the temperature constant and adjusting the pressure. In another example, compared to step 1), the pressure and temperature are changed simultaneously in step 2a), thus changing the density. The density change between steps 1) and 2a) can keep the supercritical phase as supercritical and the subcritical phase as subcritical. Alternatively, the density change between steps 1) and 2a) can cause the supercritical phase in step 1) to transform into the subcritical phase in step 2a), and the subcritical phase in step 1) to transform into the supercritical phase in step 2a).

[0055] In one implementation, the phases used in steps 1) and 2a) can both be supercritical phases or both be subcritical phases, or the phase used in one step can be a supercritical phase while the phase used in the other step can be a subcritical phase.

[0056] The non-polar or polar supercritical or subcritical phases used can have pressures from 10 bar to 400 bar and temperatures from 20°C to 250°C. Subcritical phases can each have a pressure of at least 10 bar and a temperature of at least 20°C. Supercritical phases can each have a pressure of at least 50 bar and a temperature of at least 40°C.

[0057] At least one of the multiple steps (i.e., step 1), step 2a), and step 2b1) or step 2b2) may be repeated once or multiple times.

[0058] When one or more of these steps are repeated, the order of the steps does not have to be the same between different loops of the method. Furthermore, the first loop of the method may include a certain number of steps, while the second and / or subsequent loops may include a subset of the steps used in the first loop, or may include more steps than were used in the first loop of the method.

[0059] By cycling through this process—that is, changing density conditions and possibly further or optionally switching between polar and nonpolar phases—the effectiveness of extracting additives and / or colorants from textile materials can be improved.

[0060] This "swing process," which involves oscillating between or repeatedly switching between different supercritical / subcritical density conditions, can improve the efficiency and selectivity of extraction methods, especially when dealing with complex mixtures of colorants and additives. This oscillating process can enhance the solubility of different components in the supercritical or subcritical phase, improve mass transfer of components from the solid (fiber) to the supercritical or subcritical phase, achieve selective extraction, and enhance extraction kinetics. This helps overcome mass transfer barriers within the sample, resulting in better extraction performance.

[0061] Textile waste may contain different types of colorants / additives, such as non-polar colorants / additives. This means that under specific pressures and temperatures, a non-polar supercritical phase may dissolve some of the non-polar colorants and additives, but not all of them. Cyclic density regulation (i.e., pressure and / or temperature) can facilitate the extraction of other types of non-polar or polar additives.

[0062] Figure 4 An example of the pressure and temperature / density cycling used in this "oscillating method" is shown, in which the textile material is first placed in an autoclave, for example, at atmospheric pressure and room temperature 50. Then, CO2 is introduced into the autoclave, and the autoclave is pressurized 51 to reach supercritical conditions / phase 52. After holding in phase 52 for a certain time, the autoclave is depressurized 53 until a different supercritical phase 54 is reached. After holding in phase 54 for a certain time, the autoclave is pressurized 55 until a different supercritical phase 56 is reached. After holding in phase 56 for a certain time, the autoclave is depressurized 57 until a subcritical phase 58 is reached. After holding in phase 58 for a certain time, the autoclave is depressurized 59 until atmospheric pressure and room temperature 60 are reached.

[0063] The duration of each step in Step 1), Step 2a), and Step 2b1) or Step 2b2) may be at least 10 minutes, at least 30 minutes, or from 10 minutes to 6 hours. The duration of each step does not include the time required to switch between different conditions used in different steps.

[0064] The time required for the phase transition depends on the current pressure / temperature and the fluid used. In one example, supercritical CO2 is used at 200 bar. To reach subcritical conditions, the pressure needs to be reduced to below approximately 70 bar. The decompression rate can be, for example, between 0.5 bar / min and 15 bar / min. A preferred decompression rate is 10 bar / min, and the most preferred rate is 5 bar / min. Under the above conditions, the time required to transition from supercritical to subcritical conditions is approximately 13 minutes.

[0065] The textile material 1 obtained by this method has at least some of the additives and / or colorants removed from it. The textile material can be weighed before and after the method to assess its efficiency. The extracted colorants and / or additives are also weighed. Furthermore, the color intensity of the textile material can be measured before and after the method to assess its efficiency. Mechanical and thermal analyses, such as DSC, can be performed to assess the effect of the method on the properties of the textile fibers. Additionally, chromatographic analysis can be used to identify the properties of all chemicals extracted by the method.

[0066] Textile material 1 can be 1 cm 2 Or larger, or 10 cm 2 Larger fragments (thickness ranging from mm to cm) are acceptable. Grinding is not required. Large textile fragments and whole garments can be processed if the textile material is contacted with a supercritical or subcritical fluid during mixing, without any pre-cutting or grinding. However, to reduce processing time, the textile material can be shredded into smaller fragments before contacting it with the supercritical or subcritical phase. Larger textile fragments yield fibers with better properties. In one embodiment, the textile material is first shredded or cut into smaller fragments, i.e., less than 10 cm, before contacting it with the supercritical or subcritical fluid. 2 Fragments. Textile materials can be textile waste with any zippers and buttons removed. Textile waste can include post-consumer and industrial waste clothing, scraps of fabric, and / or various textile or biomass materials used as raw materials.

[0067] Textile material 1 can be a blended textile material, comprising at least a first fiber type and a second fiber type, wherein the first fiber type is cellulose fiber and the second fiber type is non-cellulose fiber. Cellulose fiber can be natural or man-made cellulose fiber, selected from cotton, hemp, flax, ramie, modal, lyocell, bamboo fiber, sisal, viscose fiber, Manila hemp (abaca), kenaf, jute, or combinations thereof. Non-cellulose fiber can be polyester, wool, nylon, spandex, silk, acrylic, polypropylene, polyethylene, polyamide, modified acrylic, carbon fiber, aramid, phenolic fiber, or combinations thereof. The blended textile material to be recycled can be composed of, for example, cotton-polyester, cotton-modal, cotton-bamboo fiber, polyester-cotton-rayon, polyester-spandex, wool-cotton, polyester-viscose fiber, cotton-linen, polyester-rayon, cotton-nylon, and modal-spandex. An example of blended textile materials is 65 wt% polyester-35 wt% cotton, 80 wt% polyester-20 wt% cotton, 50 wt% polyester-50 wt% cotton, 60 wt% polyester-40 wt% cotton, 70 wt% polyester-30 wt% cotton, and 20 wt% polyester-80 wt% cotton.

[0068] Supercritical or subcritical fluids can be supercritical or subcritical carbon dioxide, water, methane, ethane, ethanol, or propane.

[0069] In this paper, supercritical fluid / phase (SCF) refers to a substance at temperatures and pressures above its critical point. At this critical point, there are no distinct liquid and gas phases, but the substance remains in a single-phase state. Supercritical fluids exhibit properties intermediate between those of gases and liquids.

[0070] In this article, subcritical fluid / phase refers to a liquid at a temperature between its atmospheric boiling point and its critical temperature. It lies below the critical point, where distinct liquid and gas phases exist. A subcritical fluid can transform from a gas to a liquid without crossing the gas-liquid boundary.

[0071] The mass ratio of the supercritical or subcritical phase to the textile material can be 0.5:1 to 50:1, or 5:1 to 40:1, or preferably 10:1 to 30:1.

[0072] This ratio indicates that a certain number of units of supercritical or subcritical phase are required to remove colorants / additives per unit weight of textile material.

[0073] Nonpolar supercritical or subcritical phases can be obtained by selecting naturally occurring supercritical fluids with properties similar to nonpolar solvents, such as carbon dioxide (CO2), ethane, n-butane, and nitrous oxide. Naturally occurring nonpolar supercritical fluids, such as CO2, can be used at pressures, for example, from 10 bar to 400 bar and temperatures, from 20°C to 250°C.

[0074] Nonpolar supercritical or subcritical phases can contain nonpolar cosolvents, such as ethane, propane, dimethyl ether, aromatic hydrocarbons, and alkanes, or combinations thereof. This enhances the nonpolarity of the supercritical phase, increases the solubility of nonpolar compounds (additives / colorants) in the nonpolar phase, reduces interference with polar compounds, and enhances mass transfer.

[0075] Polar supercritical or subcritical phases can be obtained by selecting naturally occurring supercritical fluids with properties similar to polar solvents, such as water or ethanol. They can be used at pressures from 10 bar to 400 bar and temperatures from 20°C to 300°C. To further enhance polarity, a polar co-solvent can be added; this co-solvent can be water, ethanol, acetone, methanol, dichloromethane, or any combination thereof. This increases the solubility of polar compounds in the polar phase, reduces interference with nonpolar compounds, and enhances mass transfer.

[0076] Alternatively, a nonpolar supercritical or subcritical fluid with added polar solvent can be used to reduce the nonpolarity of the nonpolar phase / enhance its polarity, and then use it as a more polar / stronger polar phase.

[0077] Alternatively, a polar supercritical or subcritical fluid with added nonpolar solvent can be used to reduce the polarity of the polar fluid / enhance its nonpolarity, and then used as a nonpolar / more nonpolar phase.

[0078] The amount of solvent in the supercritical or subcritical phase can be from 0.1 mol% to 40 mol%, or from 5 mol% to 30 mol%, or from 10 mol% to 20 mol%.

[0079] The polar or nonpolar supercritical or subcritical phase may include any one or more of enzymes, ionic liquids, and surfactants.

[0080] The enzyme can be selected from peroxidase, laccase, azo reductase, cellulase, manganese peroxidase, horseradish peroxidase, and tyrosinase.

[0081] Enzymes can be used to promote and enhance the extraction of dyes from textile fibers. Enzymes such as peroxidase and laccase catalyze the oxidation of dye molecules, leading to their degradation or polymerization. This reaction can result in the dye being extracted from the textile fibers or converted into a colorless or less noticeable form. In the case of azo reductase, this enzyme catalyzes the reduction of azo bonds present in many synthetic dyes. The textile will then be decolored, and the dye will be removed by breaking the azo bonds.

[0082] The ionic liquid can be selected from imidazolium-based ionic liquids, phosphonium-based ionic liquids, pyridinium-based ionic liquids, ammonium-based ionic liquids, or any combination thereof.

[0083] Examples of imidazole-onium ionic liquids include: 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]).

[0084] Example of an ammonium-based ionic liquid: Tetrabutylammonium bromide ([N4444]Br).

[0085] Examples of phosphoronium-based ionic liquids: trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpent ...

[0086] Examples of pyridinium-based ionic liquids include: 1-butyl-3-methylpyridine bromide ([Bmpy][Br]), 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim][PF6]), 1-octyl-3-methylimidazolium bromide ([Omim][Br]), 1-ethyl-3-methylpyridine acetate ([Empy][OAc]), 1-butyl-4-methylpyridine tetrafluoroborate ([Bmpy][BF4]), and 1-butyl-4-methylpyridine bis(trifluoromethanesulfonyl)imide ([Bmpy][NTf2]).

[0087] The amount of ionic liquid in the supercritical or subcritical phase can be from 0.05 mol% to 60 mol% or from 1 mol% to 50 mol%, preferably from 10 mol% to 40 mol%.

[0088] Ionic liquids can be used to dissolve colorants / additives, thereby promoting their extraction. Ionic liquids exhibit high solubility for a wide range of polar and nonpolar substances. They can also form complexes with colorant / dye molecules, increasing their solubility in supercritical or subcritical phases / fluids, thus further promoting extraction.

[0089] Surfactants can be selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and any combination thereof. Surfactants can assist and promote the removal of colorants / additives by increasing their solubility in the supercritical or subcritical phase. Surfactant molecules can interact with colorant / additive molecules to form mixed micelles or complexes, thereby dissolving the colorant / additive molecules in the supercritical or subcritical phase. Furthermore, surfactants can enhance the mass transfer rate between the textile material and the supercritical or subcritical phase by reducing interfacial tension and improving wetting properties. Finally, surfactants can achieve selective extraction by targeting and dissolving specific types of dyes in the textile material and preventing dye redeposition into the textile fibers. Anionic surfactants can be, for example, sodium dodecyl sulfate. Nonionic surfactants can be, for example, alkyl polyethylene glycol. Cationic surfactants can be, for example, hexadecyltrimethylammonium bromide (CTAB). Amphoteric surfactants can be, for example, amphoteric acetates.

[0090] Polar additives may be residual or permanent dispersants, color-fixing agents, residual antistatic agents, residual emulsifiers, residual softeners, polar ultraviolet absorbers, polar flame retardants, or any combination thereof.

[0091] Polar colorants can be reactive dyes, mordant dyes, azo dyes, acid dyes, basic dyes, direct dyes, or any combination thereof.

[0092] Polar colorants are relatively water-soluble, enabling them to form bonds with hydrophilic functional groups present in textile fibers. Furthermore, polar colorants may include dyes designed to dye hydrophilic or polar fibers, such as natural cellulosic fibers (e.g., cotton, rayon) or protein fibers (e.g., wool and silk).

[0093] Nonpolar colorants can be disperse dyes, oil-soluble dyes, vat dyes, solvent dyes, hydrophobic azo dyes, or any combination thereof.

[0094] Non-polar additives may be residual softeners, slip agents, antifouling agents, non-polar flame retardants, non-polar ultraviolet absorbers, or any combination thereof.

[0095] Non-polar flame retardants can be brominated or chlorinated flame retardants.

[0096] Disperse dyes do not chemically react with textile fibers (e.g., polyester or polyester-cotton blends). These dyes are applied to the textile through physical adsorption and diffusion. Reactive dyes, on the other hand, chemically bond with textile fibers (e.g., polyester-cotton blends). To remove disperse dyes from textiles only, a method including step 1) above, or possibly step 2a), should be sufficient. To remove reactive or vat dyes from textiles, the above method should include step 2b1) or step 2b2) in addition to step 1) and possibly step 2a), because simply increasing or decreasing the phase density is insufficient to extract such dyes. Phase cycling (i.e., step 1) plus step 2a) may result in a slight change in the polarity of the supercritical or subcritical phase, but this is insufficient to extract reactive or vat dyes, as these dyes require chemical reaction for removal. Therefore, to be able to extract multiple dyes and / or additives from textile materials, the method typically includes all of steps 1), 2a), and 2b1) or 2b2).

[0097] like Figure 2 As shown, the textile material 1 to be treated is introduced into a high-pressure chamber (e.g., an autoclave) 2. Carbon dioxide, water, methane, ethane, or propane, possibly mixed with a co-solvent 4 (e.g., ethanol, acetone, water, etc.), is supplied from a storage tank 3 and introduced into the autoclave 2. The pressure and temperature in the autoclave are then increased to reach a supercritical phase. The first step 101 is a pretreatment step using a supercritical or subcritical fluid (e.g., supercritical or subcritical CO2) to remove dirt, grease, and simultaneously dry the textile material 1. At the end of this pretreatment step, a depressurization step is performed, and all extracted water, dirt, grease, and other components (e.g., sizing agents) are separated from the textile material fibers 1.

[0098] The pretreatment step 101 can be performed in an intermittent, semi-continuous or continuous process within a pressure range of 10 bar to 400 bar and a temperature range of 20°C to 250°C.

[0099] In one example, 100 g of blended polyester-cotton textile waste and 3 mol% sorbitan monooleate were introduced into a 500 mL high-pressure chamber 2. The blended polyester-cotton textile waste consisted of 65 wt% polyester and 35 wt% cotton. (Sorbitan monooleate is a nonionic surfactant that can enhance the solubility of nonpolar colorants / additives, particularly disperse dyes, by forming mixed micelles or complexes with dye molecules. The hydrophobic portion of sorbitan monooleate interacts with nonpolar dyes, while the hydrophilic head group provides steric stability and dispersibility of the complex in supercritical or subcritical fluids.) CO2 was introduced into the pressure chamber at a pressurization rate of 3 bar / min until a pressure of 220 bar was reached, and the pressure chamber was also heated to 80°C. Within 40 minutes, the supercritical fluid containing the surfactant penetrated into the polyester-cotton blend and dissolved nonpolar colorants / additives such as disperse dyes. At the end of the 40-minute duration, 5 mol% ethanol is introduced into the pressure chamber using a pump, raising the temperature of the pressure chamber to 120°C and the pressure to 250 bar. The presence of the co-solvent alters the polarity of the supercritical fluid towards a more polar direction. The changes in pressure and temperature improve the solubility of the supercritical fluid for more polar components. Within 60 minutes, the supercritical fluid dissolves polar components and may also extract some non-polar components (due to the presence of surfactants). During the depressurization phase (5 bar / min), the extracted components removed from the textile material can be transferred to collector 5 located outside pressure chamber 2 and / or collected at the bottom of the high-pressure chamber.

[0100] In another example, 100 g of polyester-cotton blend waste 1, composed of 70 wt% polyester and 30 wt% cotton, was introduced into a 500 mL high-pressure chamber 2. CO2 was introduced into high-pressure chamber 2 at a pressurization rate of 3 bar / min until a pressure of 200 bar was reached, and the chamber was also heated to 100°C. Over 15 minutes, the supercritical fluid was allowed to penetrate the polyester-cotton blend and dissolve some non-polar colorants / additives, such as disperse dyes. At the end of the 15-minute duration, the pressure in high-pressure chamber 2 was reduced from 200 bar to 100 bar (at a depressurization rate of 5 bar / min) while the temperature remained constant. These conditions were maintained for 15 minutes. During this period, the supercritical fluids with different densities and solubilities dissolved different non-polar components. At the end of this 15-minute period, the pressure in the chamber was increased again to 200 bar at a pressurization rate of 5 bar / min, the temperature was raised to 120°C, and 10% methanol was introduced into the chamber using a pump. Within 40 minutes, the polar supercritical fluid preferentially extracts polar dyes. At the end of the 40-minute duration, the pressure is reduced to 60 bar at a decompression rate of 5 bar / min, while the temperature is kept constant. Within 20 minutes, the subcritical fluid dissolves the remaining polar and non-polar dyes and additives in the polyester-cotton fibers. At the end of this duration, the high-pressure chamber is decompressed at a decompression rate of 5 bar / min, and the decolorized polyester-cotton fibers are characterized.

[0101] Figure 3 The diagram shows the color intensity (K / S) curves of textile materials before and after treatment using the method described in the example immediately preceding above. The line marked X represents the polyester-cotton textile before treatment using the method described above. The line marked Y represents the polyester-cotton textile after treatment using the method described above. The color intensity (K / S) of the textiles was measured using a spectrophotometer. Color intensity quantifies the intensity / depth of color in the fiber, and more specifically measures the ratio of the absorption coefficient (K) to the scattering coefficient (S) of the fiber at a specific wavelength group.

[0102] from Figure 3 It can be seen that there is a huge difference in color intensity between the textile materials before and after treatment using the above method.

[0103] The properties of textiles can also be evaluated before and after extraction using mechanical analysis and differential scanning calorimetry (DSC) to study the morphological changes that occur in textiles after extraction.

[0104] In one specific example, CO2 is introduced into an autoclave 2, heated to 80°C and containing polyester-cotton textile waste 1 composed of 65 wt% polyester and 35 wt% cotton, at a pressurization rate of 5 bar / min until a pressure of 120 bar is reached. 5% water is added to the autoclave using a pump. A semi-continuous flow of CO2 is used while maintaining constant pressure and temperature to clean and extract grease, dirt, and moisture from the textiles. After approximately 40 minutes of semi-continuous flow, the autoclave is depressurized at a rate of 5 bar / min, and the extracted grease, dirt, and moisture are collected in a collector 5.

[0105] Subsequently, colorants and / or additives are extracted from the textile waste. Depending on the nature of the colorants / additives in the textile, the process may involve two steps. If the textile material is polyester-cotton, which is typically heterogeneous, composed of varying amounts of cotton and polyester, and may be dyed with different types of colorants and additives, then the method can be tailored to the overall properties of the colorants / additives.

[0106] The first step considers the extraction of nonpolar colorants / additives, such as water-insoluble dyes, like disperse dyes. For this step, a nonpolar supercritical or subcritical fluid is used to extract the nonpolar colorant / additive. This step can be carried out at a pressure range of 90 to 350 bar, a temperature range of 60°C to 200°C, and a duration of 10 minutes to 6 hours.

[0107] The second step involves extracting polar colorants / additives, such as water-soluble dyes, including reactive and direct dyes. For this second step, the polarity of the supercritical or subcritical fluid is altered by adding a co-solvent such as ethanol, methanol, or water, and pressure and temperature are typically adjusted during this step.

[0108] In one example, textile waste 1, consisting of 35 wt% cotton and 65 wt% polyester, is introduced into autoclave 2. CO2 is introduced into the autoclave at a pressurization rate of 1.5 bar / min until a pressure of 250 bar is reached, and the autoclave is heated to 140°C. For a duration of 60 minutes, a nonpolar supercritical fluid dissolves nonpolar colorants / additives, such as disperse dyes, from the cotton and polyester. At the end of this duration, the autoclave is depressurized at a rate of 2.5 bar / min. The extracted dye is separated in collector 5. The same reactor containing the 35 wt% cotton and 65 wt% polyester textile waste is refilled with CO2 until a pressure of 300 bar is reached and heated to 160°C, followed by the addition of 7 vol% co-solvent ethanol using a pump. The supercritical fluid dissolves polar colorants / additives, and after 55 minutes, the autoclave is depressurized at a rate of 2 bar / min. The extracted dye is recovered in collector 5, and the CO2 is recycled and recovered.

[0109] The pressure oscillation method described above can be carried out, for example, by supplying a textile material 1 (e.g., a textile material containing 50 wt% cotton and 50 wt% polyester) to an autoclave 2. CO2 is introduced into the autoclave at a pressurization rate of 2 bar / min until a pressure of 220 bar is reached, and the autoclave is heated to 120°C. During a duration of 25 minutes, a non-polar supercritical fluid partially dissolves non-polar colorants / additives, such as disperse dyes, from the polyester / cotton blend. At the end of this duration, the pressure is reduced to 60 bar at a depressurization rate of 2 bar / min, while the temperature is maintained at 120°C. During another 25 minutes, a subcritical fluid partially dissolves polar colorants / additives, such as reactive dyes and direct dyes. This oscillation between supercritical and subcritical fluids can be repeated at least twice to remove up to 91% or more of the polar and non-polar colorants / additives from the polyester / cotton waste.

[0110] In one example, a 50-50% polyester-cotton blend waste was processed. A pre-step using supercritical CO2 was first performed to extract any moisture, dirt, grease, or sizing agents from the textile material into the supercritical fluid. Subsequently, 100 g of polyester-cotton blend waste, containing polyester and cotton in varying proportions (waste, exact composition, and dyes unknown), was introduced into a 500 mL high-pressure chamber. CO2 was introduced into the high-pressure chamber at a pressurization rate of 10 bar (1 MPa) / min until a pressure of 260 bar (26 MPa) was reached, while the chamber was also heated to 135°C. Over 20 minutes, the supercritical fluid permeated the polyester-cotton blend, dissolving some of the non-polar colorants / additives (such as disperse dyes). At the end of this 20-minute duration, the pressure in the chamber was reduced from 260 bar (26 MPa) to 170 bar (17 MPa) (at a decompression rate of 5 bar (0.5 MPa) / min), while the temperature remained constant. These conditions were maintained for 20 minutes. During this period, supercritical fluids with different densities and solubilities dissolved various nonpolar components. At the end of the 20-minute period, the pressure in the pressure chamber was increased again to 320 bar (32 MPa) at a pressurization rate of 15 bar (1.5 MPa) / min, the temperature was reduced to 100°C, and 1 mol% NH3 dissolved in 20 mol% ethanol was introduced into the pressure chamber by pump. During the 20 minutes, pulsed CO2 flow circulation was used to help break some covalent bonds between the dye and the textile. The polar supercritical fluid then preferentially extracted the polar dye, while increasing the pressure to a higher level combined with a relatively moderate temperature also helped to weaken the bond between the textile and the dye. The use of 1 mol% NH3 in ethanol helped to break some ester bonds; the duration and temperature of this treatment needed to be carefully monitored to avoid damaging the fiber properties. At the end of the 20-minute period, the pressure was reduced to 55 bar (5.5 MPa) at a depressurization rate of 20 bar (2.0 MPa) / min, while the temperature remained constant. During the 20-minute period, the subcritical fluid dissolved the remaining polar and nonpolar dyes and additives from the polyester-cotton fibers. At the end of this period, the high-pressure chamber was depressurized at a rate of 5 bar (0.5 MPa) / min, and the decolorized polyester-cotton fibers were characterized online during the supercritical extraction process. Throughout the extraction process, in-situ UV monitoring connected to the high-pressure chamber was continuously performed to assess the decolorization of the textile waste by measuring the online absorbance of the extracted dyes. When no change in absorbance was detected over time, it was assumed that all dyes had been extracted at equilibrium.

[0111] After the extraction process was completed and the autoclave was opened, FTIR analysis was performed to check for the presence of potentially residual dye. The polyester-cotton waste was clearly whitish. UV-VIS spectroscopy analysis was performed after mixing the extracted dye with different co-solvents used. Disperse Red 60 was detected at 520 nm, Reactive Blue 19 at 590 nm, and Vapor Orange 7 at 450 nm. Furthermore, high-performance liquid chromatography (HPLC) was performed after this analysis to separate and identify the exact dye components, and retention times were compared with standard dye references.

[0112] Therefore, it is evident that the above methods can be used to extract a variety of dyes and / or additives from textile waste from different geographical regions of the world, which may contain mixtures of additives and dyes (from different colorant families). Disperse dyes are generally soluble in nonpolar phases, while reactive dyes can be removed under polar conditions. Vat dyes are preferably converted to their soluble form and can be dissolved using polar solvents.

Claims

1. A method for removing colorants and / or additives from textile materials, the method comprising the following steps: 1) Contacting a textile material (1) containing a variety of colorants and / or additives with a supercritical or subcritical phase (100), said supercritical or subcritical phase being nonpolar or polar and having a first density; The method further includes at least one of the following steps: 2a) Adjust the density of the nonpolar or polar supercritical or subcritical phase used in step 1) to a second density different from the first density, such that the textile material (1) is in contact (101) with the nonpolar or polar supercritical or subcritical phase having the second density; and / or 2b1) If the supercritical or subcritical phase used in step 1) is a nonpolar supercritical or subcritical phase, then the textile material is brought into contact with a polar supercritical or subcritical phase (102a); or 2b2) If the supercritical or subcritical phase used in step 1) is a polar supercritical or subcritical phase, then the textile material is brought into contact with a nonpolar supercritical or subcritical phase (102b).

2. The method according to claim 1, wherein, The phases used in steps 1) and 2a) are either supercritical or subcritical phases, or In one step, the phase used is a supercritical phase, while in the other step, the phase used is a subcritical phase.

3. The method according to claim 1 or 2, wherein, The non-polar or polar supercritical or subcritical phase used in the method has a pressure of 10 bar to 400 bar and a temperature of 20°C to 250°C.

4. The method according to any one of the preceding claims, wherein, The density difference between the first density used in step 1) and the second density used in step 2a) is at least 30 kg / m³. 3 .

5. The method according to any one of the preceding claims, wherein, The method includes at least step 1) and step 2a).

6. The method according to claim 5, wherein, The method includes steps 1), 2a), and 2b1) or 2b2).

7. The method according to any one of claims 1 to 4, wherein, The method includes step 1) and step 2b1) or step 2b2).

8. The method according to any one of the preceding claims, wherein, At least one of steps 1), 2a), and 2b1) or 2b2) is repeated once or more.

9. The method according to any one of the preceding claims, wherein, The duration of each step in step 1), step 2a), and step 2b1) or step 2b2) is at least 10 minutes.

10. The method according to any one of the preceding claims, wherein, The supercritical or subcritical phase includes supercritical or subcritical carbon dioxide, water, ethane, ethanol, or propane.

11. The method according to any one of the preceding claims, wherein, Nonpolar supercritical or subcritical phases contain nonpolar cosolvents.

12. The method according to claim 11, wherein, The nonpolar cosolvent is selected from ethane, propane, dimethyl ether, aromatic hydrocarbons, alkanes, or any combination thereof.

13. The method according to any one of the preceding claims, wherein, Polar supercritical or subcritical phases contain polar cosolvents.

14. The method according to claim 13, wherein, The polar co-solvent is selected from water, ethanol, acetone, methanol, dichloromethane, or any combination thereof.

15. The method according to any one of the preceding claims, wherein, The nonpolar or polar supercritical or subcritical phase comprises any one or more of enzymes, ionic liquids, and surfactants.

16. The method according to claim 15, wherein, The enzyme is selected from peroxidase, laccase, azo reductase, cellulase, manganese peroxidase, horseradish peroxidase, tyrosinase, or any combination thereof.

17. The method according to claim 15 or 16, wherein, The ionic liquid is selected from imidazolium-based ionic liquids, phosphorium-based ionic liquids, pyridinium-based ionic liquids, ammonium-based ionic liquids, or any combination thereof.

18. The method according to any one of claims 15 to 17, wherein, The surfactant is selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, or any combination thereof.

19. The method according to any one of the preceding claims, wherein, The additive is a polar additive and is a residual or permanent dispersant, fixing agent, residual antistatic agent, residual emulsifier, residual softener, polar ultraviolet absorber, polar flame retardant, or any combination thereof.

20. The method according to any one of the preceding claims, wherein, The colorant is a polar colorant and is a reactive dye, mordant dye, azo dye, acid dye, basic dye, direct dye, or any combination thereof.

21. The method according to any one of the preceding claims, wherein, The colorant is a non-polar colorant and is a disperse dye, oil-soluble dye, vat dye, solvent dye, hydrophobic azo dye, or any combination thereof.

22. The method according to any one of the preceding claims, wherein, The additive is a non-polar additive and is a hydrophobic finishing agent, residual softener, slip agent, antifouling agent, non-polar flame retardant, non-polar ultraviolet absorber, or any combination thereof.

23. The method according to any one of the preceding claims, prior to performing step 1), further comprises a pre-step (99): contacting a supercritical or subcritical phase with the provided textile material (101) to extract any moisture, dirt, grease or sizing agent from the textile material into the supercritical or subcritical phase.

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