Process for removing colorants and / or additives from a textile material

Abstract

A process for removing colorants and / or additives from a textile material, the process comprising steps of bringing textile material comprising multiple colorants and / or additives in contact with a supercritical or subcritical phase being non-polar or polar.

Description

[0001] PROCESS FOR REMOVING COLORANTS AND / OR ADDITIVES FROM A TEXTILE MATERIAL

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a process for removing colorants and / or additives from a textile material using polar / non-polar supercritical / subcritical phase.

[0004] BACKGROUND ART

[0005] Traditional methods of removing dyes from textile material often involve harsh chemicals and use of large quantities of water. More sustainable alternatives are currently being explored to minimize the ecological impact and damage of the properties of the textile material. In for example WO22178704 is shown a way of extracting disperse dyes from synthetic fibers wherein the dyed textile is contacted with a supercritical CO2, thereby extracting at least a portion of the disperse dye from the textile into the supercritical fluid and forming an at least partially decolorized textile.

[0006] Blended textiles often combine different fibers, such as cotton and polyester. These fibers have distinct properties and react differently to color removal methods.

[0007] For such blended textiles there is a challenge in finding a decolorizing process that effectively targets the color without damaging the individual fibers. Some dyes used in textile coloring are resilient and resistant to fading or bleaching. Decoloring these dyes without compromising the fabric’s integrity can be difficult.

[0008] There is a need for techniques for decoloring all kind of textiles, including blended textiles, from all kind of dyes with low water and chemical consumption, with little or no damaging of the individual fibers

[0009] SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to provide a process for removing colorants and / or additives from a textile material, including blended textiles, with low water and chemical consumption, with little or no damaging of the individual fibers The invention is defined by the appended independent patent claims. Non-limiting embodiments emerge from the dependent claims, the appended drawings, and the following description.

[0011] According to a first aspect there is provided a process for removing colorants and / or additives from a textile material, the process comprising a step of: 1 ) bringing a textile material in contact with a supercritical or subcritical phase being non-polar 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 non-polar or polar supercritical or subcritical phase used in step 1 ) to a second density, different from the first density, such that the textile material is brought in contact with a non-polar or polar supercritical or subcritical phase with said second density, and / or 2b1 ) if the supercritical or subcritical phase used in step 1 ) is a non-polar supercritical or subcritical phase, bringing the textile material in contact 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, bringing the textile material in contact with a non-polar supercritical or subcritical phase.

[0012] The described process can be a batch, continuous or semi-continuous mode process. With the above described process both polar and non-polar colors / additives can be removed from the textile material, such as textile waste, and extracted into the supercritical or subcritical phase without or a with a low degree of damaged individual textile fibres, with no / low water and chemical consumption. The polarity of the supercritical / subcritical fluid / phase may be adjusted to the nature of the colorants / additives, such that these can be, at least partially, extracted from the textile material. Conditions of the supercritical / subcritical fluid / phase, such as density, i.e. pressure and temperature, may be adjusted in order to target specific components.

[0013] This process may be used to generate new raw materials with high value out of textile waste. Moreover, this energy efficient technology uses green solvents such as supercritical / subcritical fluids, which may be recycled and reused continuously. Finally, no / little water is used during the process. The extracted colorants and additives may be collected. The extraction of colorants and additives is carried out at mild conditions of pressure and temperature, such as at a pressure of 10-400 bar and at a temperature of 20-250 °C. Moreover, this technology does not require any drying step after the treatment since a supercritical / subcritical fluid / phase is used instead of water.

[0014] The above describe process can be used to remove additives and colorants from any type of textile material. It can for example be used on blended textile materials, such as a blended textile material comprising at least a first fibre type being cellulosic fibres and at least a second fibre type being non-cellulosic fibres.

[0015] In step 2a) the density 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 is brought in contact with a non-polar or polar supercritical or subcritical phase with the second density. This means that the phase used in step 1 ) and in step 2a) may both be supercritical phases or both be subcritical phases, or the phase used in one of the steps may be a supercritical phase and the phase used in the other step may be a subcritical phase.

[0016] With a first density, i.e. first pressure / temperature, and a second density, i.e. second pressure / temperature, is here meant a specific density, or a smaller density range in which the first density or second density is varied from a specific density ± 5 kg / m3A change in density between the first and second density stage is at least 30 kg / m3.

[0017] What pressures and temperatures used to obtain a supercritical or subcritical phase, or what adjustment of density, i.e. pressure and / or temperature, needed to go from the first density to the second density is naturally dependent on what supercritical or subcritical fluid is used, e.g. carbon dioxide, water, methane, ethane, ethanol, or propane.

[0018] A change between supercritical / subcritical phase or subcritical / supercritical phase or between two supercritical or subcritical phase conditions with different densities is made by changing the pressure and / or temperature of the phase, thereby mainly affecting the density, solvation power and mass transfer of the supercritical / subcritical phase. By changing between different densities, i.e. pressures / temperatures, more components may be possible to dissolve / extract from the textile material.

[0019] In some applications, it is not necessary to change / cycle from supercritical to subcritical phase or vice versa but a smaller change / cycle of density keeping the fluid in the supercritical or subcritical phase might be enough to extract additives / colorants from the textile.

[0020] It is to be understood that a non-polar supercritical or subcritical phase covers fully non-polar phases and polar phases made less polar / more non-polar by adding for example a non-polar solvent in the polar phase. Similarly, a polar supercritical or subcritical phase covers fully polar phases and non-polar phases made less non- polar / more polar by adding for example a polar solvent in the non-polar phase.

[0021] The textile material comprising multiple colorants and / or additives and that is treated in the process described above (in step 1 and step 2a and / or step 2b1 or 2b2) is understood to be a textile comprising 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 differing for example in polarity.

[0022] In one embodiment, the phases used in step 1) and in step 2a) may both be supercritical phases or both be subcritical phases, or the phase used in one of the steps may be a supercritical phase and the phase used in the other step may be a subcritical phase.

[0023] The non-polar or polar supercritical or subcritical phase used in the process may have a pressure of 10-400 bar and a temperature of 20-250 °C.

[0024] The difference in density between the first density of the phase used in step 1 ) and the second density of the phase used in step 2a) may be at least 30 kg / m3

[0025] In one embodiment, the process comprises at least step 1 ) and step 2a).

[0026] In another embodiment the process comprises step 1 ), step 2a) and step 2b1 ) or step 2b2).

[0027] In yet an embodiment the process comprises step 1 ) and step 2b1 ) or step 2b2).

[0028] At least one of the process steps, step 1 ), 2a) and 2b1 ) or 2b2), may be repeated one or more times.

[0029] The duration of each step 1), 2a) and 2b1) or 2b2) may be at least 10 minutes.

[0030] The supercritical or subcritical phase may comprise supercritical or subcritical carbon dioxide, water, methane, ethane, ethanol, or propane. The non-polar supercritical or subcritical phase may comprise a non-polar co-solvent.

[0031] The non-polar co-solvent may be selected from ethane, propane, dimethyl ether, aromatic hydrocarbons, alkanes or any combination thereof.

[0032] The polar supercritical or subcritical phase may comprise a polar co-solvent.

[0033] The polar co-solvent may be selected from water, ethanol, acetone, methanol, dichloromethane, or any combination thereof.

[0034] Some colorant / additives are easily soluble into the supercritical or subcritical phase, while others can require the additions of non-polar or polar co-solvents to enhance the solubility and therefore the extraction. Some colorant / additives are easily soluble into the naturally polar / non-polar supercritical or subcritical phase.

[0035] The polar or non-polar supercritical or subcritical phase may comprise anyone or more of enzyme(s), ionic liquid(s) and surfactant(s).

[0036] The enzyme may be selected from peroxidases, laccases, azoreductases, cellulases, manganese peroxidases, horseradish peroxidases, tyrosinases or any combination thereof.

[0037] The ionic liquid may be selected from midazolium-based ionic liquids, phosphonium- based ionic liquids, pyridinium-based ionic liquids, ammonium-based ionic liquids or any combination thereof.

[0038] The surfactant may be selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants or any combination thereof.

[0039] The additive may be a polar additive and may be a residual or permanent dispersing agent, a fixative, a residual antistatic agent, a residual emulsifier, a residual softener, a polar UV absorber, a polar flame retardant or any combination thereof.

[0040] The colorant may be a polar colorant and may be a reactive dye, a mordant dye, an azoic dye, an acid dye, a basic dye, a direct dye, or any combination thereof.

[0041] The colorant may be a non-polar colorant and may be a disperse dye, an oil-soluble dye, a vat dye, a solvent dye, and a hydrophobic azo dye or any combination thereof. The additive may be a non-polar additive and may be a hydrophobic finisher, a residual softener, a slip agent, an anti-soiling agent, a non-polar flame retardant, a non-polar UV absorber or any combination thereof.

[0042] The process described may further comprise a pre-step before performing step 1 ) of bringing a supercritical or subcritical phase in contact with the textile material to extract any moisture, dirt, grease or sizing agent from the material into the supercritical or subcritical phase

[0043] This pre-step may be used in order to increase the efficiency of the preceding steps.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Fig. 1 schematically illustrates a process for removing colorants or additives from textile material.

[0046] Fig. 2 illustrates a system for performing an embodiment of the process shown in Fig. 1.

[0047] Fig. 3 is a graph showing color strength before and after treatment with an embodiment of the process in Fig. 1 .

[0048] Fig. 4 illustrates an example of pressure cycling used in the process for removing colorants or additives from textile material shown in Fig. 1

[0049] DETAILED DESCRIPTION

[0050] In Fig. 1 is illustrated a process for removing colorants and / or additives from a textile 1 material and in Fig. 2 is illustrated a system for performing such a process. A textile material 1 from which colorants and / or additives are to be removed may be provided in a pressure cell 2, e.g. an autoclave.

[0051] In an optional pre-step 99, a supercritical or subcritical phase 3 is brought into contact with the textile material 1 for at least 10 minutes to e.g. 60 minutes to extract any moisture / water, dirt, grease or sizing agent from the material into the supercritical or subcritical phase. The pressure may be 75 bar to 100 bar and the temperature may be 40 to 100 °C. A ratio of supercritical or subcritical phase to blended textile in this step may be 0.5: 1 to 50: 1 , or 5: 1 to 40: 1 , or preferably 10:1 to 30: 1 . After bringing the supercritical or subcritical phase in contact with the textile material 1 to extract any moisture / water, dirt, grease or sizing agent from the material, a depressurization step may be performed, and all the extracted water, dirt, grease and other components such as sizing agents may be separated from the textile material and transferred to a trap 5 located outside the pressure cell 2. Alternatively, the extracted substances are removed by using a continues flow of supercritical / subcritical phase through / passing the textile material 1 .

[0052] Thereafter, or without the optional pre-step 99, the textile material 1 is brought 100 in a step 1 ) in contact with a supercritical or subcritical phase being non-polar or polar and having a first density, thereby extracting non-polar or polar colorant(s) and / or additive(s) from the textile material into the non-polar or polar supercritical or subcritical phase.

[0053] After bringing the textile material in contact with the non-polar or polar supercritical or subcritical phase, the extracted non-polar or polar components may be removed by depressurizing the non-polar or polar supercritical or subcritical phase to remove the extracted non-polar or polar components from the textile material, which may be transferred to a trap 5 located outside the pressure cell 2. Alternatively, the extracted non-polar or polar substances may be removed by using a continuous flow of supercritical / subcritical phase through / passing the blended textile material. Such removal of extracted components may take place before the next step of the process is performed. Alternatively, the removal of extracted components is performed after two or more of the process steps have been performed or the end of the process.

[0054] The process in addition comprises one or more steps selected from:

[0055] - a step 2a) in which the pressure and / or temperature of the non-polar or polar supercritical of subcritical phase used in step 1) is adjusted 100 to a second density, different from the first density, such that the textile material 1 is brought in contact with a non-polar or polar supercritical or subcritical phase with the second density, and / or

[0056] - a step 2b1 ) if the supercritical of subcritical phase used in step 1 ) is a non-polar supercritical or subcritical phase of bringing 102a the textile material 1 in contact with a polar supercritical or subcritical phase, or

[0057] - a step 2b2) if the supercritical of subcritical phase used in step 1) is a polar supercritical or subcritical phase of bringing 102b the textile material in contact with a non-polar supercritical or subcritical phase. Depending on the nature of the multiple colorants and / or additives comprised in the textile material, the textile material may first be brought in contact with a non-polar supercritical / subcritical phase or a polar supercritical / subcritical phase.

[0058] In step 2a) the density, pressure and / or temperature, of the non-polar or polar phase used in step 1 ) is adjusted to a second density, different from the first density, such that the textile material is brought in contact with a non-polar or polar supercritical or subcritical phase with the second density. This means that the phase used in step 1 ) and in step 2a) may both be supercritical phases or both be subcritical phases, or the phase used in one of the steps may be a supercritical phase and the phase used in the other step may be a subcritical phase.

[0059] In one example the non-polar or polar supercritical or subcritical phase used in step 1 ) has a density of 480 kg / m3, i.e. a first pressure and temperature of 200 bar and 100 °C, respectively. In step 2a) the non-polar or polar supercritical or subcritical phase has a second density that is 580 kg / m3. In one example the second density is obtained by keeping the temperature unchanged and adjusting the pressure. In one example, both the pressure and temperature are changed in step 2a) as compared to in step 1 ) to change the density. Density changes between step 1 ) and 2a) could be such that the supercritical phase is still a supercritical phase and the subcritical phase is still a subcritical phase. Alternatively, density changes between step 1 ) and 2a) could be such that a supercritical phase in step 1 ) is turned into a subcritical phase in step 2a) and a subcritical phase in step 1 ) is turned into a supercritical phase in step 2a).

[0060] In one embodiment, the phases used in step 1 ) and in step 2a) may both be supercritical phases or both be subcritical phases, or the phase used in one of the steps may be a supercritical phase and the phase used in the other step may be a subcritical phase.

[0061] The non-polar or polar supercritical or subcritical phase used may have a pressure of 10-400 bar and a temperature of 20-250 °C. The subcritical phase may have a pressure and temperature of at least 10 bar and 20 °C, respectively. The supercritical phase may have a pressure and temperature of at least 50 bar and 40 °C respectively.

[0062] At least one of the process steps, step 1 ), 2a) and 2b1 ) or 2b2), may be repeated one or more times. When repeating one or more of these steps, the order of the steps is not necessarily the same between different cycles of the process. Further, a first cycle of the process may comprise a certain number of the steps, while a second and / or further cycle of the process may comprise a sub-selection of the steps used in the first cycle or more steps than used in the first cycle of the process.

[0063] By such cycling, i.e. altering the density condition and possibly also or alternatively altering between polar and non-polar phases may increase the extraction of additives and / or colorants from the textile material.

[0064] This “swing process”, i.e. swinging between different supercritical / subcritical density conditions or swinging between supercritical / subcritical density conditions can be used to improve the efficiency and selectivity of the extraction process, particularly when dealing with a complex mix of colorants and additives. This swing process may enhance the solubility of different components in the supercritical or subcritical phase, improve the mass transfer of components from the solid (fibers) to the supercritical or subcritical phase, allow a selective extraction, enhance the extraction kinetic which help overcome the mass transfer barrier within the sample leading to a better extraction.

[0065] In textile wastes, there might be different types of e.g. non-polar colorants / additives, which mean that at a certain pressure and temperature, a non-polar supercritical phase might dissolve some of the non-polar colorants and additives but not all of them. Cycling the density, i.e. pressure and / or temperature, may help to extract other type of additives that can be polar or non-polar.

[0066] In Fig. 4 is illustrated an example of pressure and temperature / density cycling used in such a “swing process”. The process starts with providing the textile material in e.g. an autoclave in atmospheric pressure and room temperature 50. Thereafter, e.g. CO2 is entered into the autoclave and the autoclave pressurized 51 such that supercritical conditions / phase is reached 52. After a certain time in this phase 52, the autoclave is depressurized 53 until a different supercritical phase 54 is reached. After a certain time in this phase 54, the autoclave is pressurized 55 until a different supercritical phase 56 is reached. After a certain time in this phase 56, the autoclave is depressurized 57 until a subcritical phase 58 is reached. After a certain time in this phase 58, the autoclave is depressurized 59 until atmospheric pressure and room temperature 60 is reached. The duration of each step 1 ), 2a) and 2b1 ) or 2b2) may be at least 10 minutes, at least 30 minutes, or 10 minutes to 6 hours. The time stayed in each step does not include the time it takes to change between the different conditions used in the different steps.

[0067] The time it takes to change between phases 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 need to be lowered to below about 70 bars. The depressurization rate may e.g. be between 0.5 bar and 15 bar / min. The preferred depressurization rate may be 10 bar / min and the most preferred one may be 5 bar / min. Under such conditions, the time it takes to change from supercritical to subcritical conditions is then about 13 min.

[0068] This process leaves a textile material 1 from which at least portion of additives and / or colorants have been removed. The textile may be weighted before and after the process has been performed in order to assess the efficiency of the process. The extracted colorants and / or additives are also weighted. Moreover, the color strength of the textile may be measured before and after the process in order to assess the efficiency of the process. Mechanical and thermal analysis such as DSC may be performed in order to assess the impact of the process on the properties of the textile fibers. Moreover, chromatography analysis might be used in order to identify the nature of all the chemicals extracted during the process.

[0069] The textile material 1 may be in pieces of 1 cm2or larger or 10 cm2or larger (with a thickness ranging from mm to cm). There is no need for shredding. If the textile is contacted with the supercritical / subcritical fluid during mixing, large textile pieces, and full garments can be treated without any pre-cutting or shredding. The textile could, however, be shredded into smaller pieces before being contacted with the supercritical or subcritical fluid to reduce the treatment time. Larger pieces of the textile may result in fibres with better properties. In one embodiment, the textile is first shredded or cut into smaller pieces, i.e. smaller than 10 cm2before being contacted with the supercritical or subcritical fluid. The textile could be textile waste from which any zips and buttons have been removed. The textile waste may include post-consumer and industrial waste garments, scrap fabric and / or various textile of biomass material as a raw feed material. The textile material 1 may be a blended textile material comprising at least a first fibre type being cellulosic fibres and at least a second fibre type being non-cellulosic fibres. The cellulosic fibres may be natural or man-made cellulosic fibres selected from cotton, hemp, linen, ramie, modal, lyocell, bamboo, sisal, viscose, abaca, kenaf, jute or combinations thereof. The non-cellulosic fibres may be polyester, wool, nylon, elastane, silk, acrylic, polypropylene, polyethylene, polyamide, modacrylic, carbon fiber, aramid, novoloid, or combinations thereof. The textile blends to be recovered could for example be composed of cotton-polyester, cotton modal, cotton-bamboo, polyester-cotton-rayon, polyester-spandex, wool-cotton, polyester viscose, cottonlinen, polyester-rayon, cotton-nylon and modal spandex. An example of textile blend 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, 20 wt.% polyester-wt. 80% cotton..

[0070] The supercritical or subcritical fluid may be supercritical or subcritical carbon dioxide, water, methane, ethane, ethanol, or propane.

[0071] With supercritical fluid / phase (SCF) is meant a substance at a temperature and pressure above its critical point. At this critical point, distinct liquid and gas phases do not exist, but the substance remains in a single-phase state. SCFs exhibit properties between those of a gas and a liquid.

[0072] With subcritical fluid / phase is here meant a liquid at temperatures between the atmospheric boiling point and the critical temperature. It lies below the critical point, where distinct liquid and gas phases exist. Subcritical fluids can transition from a gas to a liquid without crossing the vapor-liquid boundary.

[0073] The supercritical or subcritical phase and the textile material may be present in a mass ratio between 0.5: 1 to 50: 1 , or 5: 1 to 40: 1 , or preferably 10: 1 to 30: 1 .

[0074] This ratio indicates that for every unit of weight of textile, a certain number of units of supercritical or subcritical phase is needed to obtain removal of colorants / additives.

[0075] The non-polar supercritical / subcritical phase may be obtained by choosing a supercritical fluid that naturally has properties similar to non-polar solvents, such as carbon dioxide (CO2), ethane, N-buthane, nitrous oxide. A naturally non-polar supercritical fluid such as CO2 may e.g. be used at a pressure of 10-400 bar and a temperature of 20-250 °C.

[0076] The non-polar supercritical or subcritical phase may comprise a non-polar co-solvent, e.g. ethane, propane, dimethyl ether, aromatic hydrocarbons, and alkanes or combinations thereof. Thereby, the non-polarity of the supercritical phase can be enhanced, improving the solubility of non-polar compounds (additives / colorants) in the non-polar phase, reducing the interference with polar compounds, and enhance the mass transfer.

[0077] The polar supercritical or subcritical phase may be obtained by choosing a supercritical fluid, which naturally has properties similar to polar solvents, such as water of ethanol. This may be used at a pressure of 10-400 bar and a temperature of 20-300 °C. To further enhance the polarity, a polar co-solvent, which may be water, ethanol, acetone, methanol, dichloromethane, or any combination thereof may be added, thereby improving the solubility of polar compounds in the polar phase, reducing the interference with non-polar compounds, and enhance the mass transfer.

[0078] Alternatively, a non-polar supercritical / subcritical fluid may be used with added polar solvent to make the non-polar phase less non-polar / more polar and then used as the polar / more polar phase.

[0079] Alternatively, a polar supercritical / subcritical fluid may be used with added non-polar solvent to make the polar fluid less polar / more non-polar and then used as the non- polar / more non-polar phase.

[0080] The amount of co-solvent in the supercritical / subcritical phase may be 0.1 -40 mol%, or 5-30 mol%, or 10-20 mol%.

[0081] The polar or non-polar supercritical or subcritical phase may comprise anyone or more of enzyme(s), ionic liquid(s) and surfactant(s).

[0082] The enzyme(s) may be selected from peroxidases, laccases, azoreductases, cellulases, manganese peroxidases, horseradish peroxidases and tyrosinases.

[0083] Enzymes may be used to facilitate and enhance the extraction of colorants from the textile fibers. Enzymes such as peroxidases and laccases catalyze the oxidation of dye molecules, leading to their degradation or polymerization. This reaction can lead to the dyes extraction from the textile fibers or their conversion into colorless or less visible forms. In the case where an azeroductase is used, this enzyme catalyzes the reduction of azo bonds present in many synthetic dyes. The textile will then be decolorized, and the dyes removed by breaking the azo bonds.

[0084] The ionic liquid may be selected from midazolium-based ionic I iquids, phosphonium- based ionic liquids, pyridinium-based ionic liquids, ammonium-based ionic liquids or any combination thereof.

[0085] Examples of imidazolium-based ionic liquids: 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and 1- ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]).

[0086] Examples of ammonium-based ionic liquids: tetrabutylammonium bromide ([N4444]Br).

[0087] Examples of phosphonium-based ionic liquids: Trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate ([P6, 6,6, 14][TMP][TMP]), Trihexyl(tetradecyl)phosphonium tosylate ([P6,6,6,14][Tos]), Tetrabutylphosphonium bromide ([P4,4,4,4][Br])

[0088] Examples of pyridinium-based ionic liquids: 1-Butyl-3-methylpyridinium bromide ([Bmpy][Br]), 1-Octyl-3-methylimidazolium hexafluorophosphate ([0mim][PF6]) and 1- Octyl-3-methylimidazolium bromide ([Omim][Br]), 1-Ethyl-3-methylpyridinium acetate ([Empy][OAc]), 1-Butyl-4-methylpyridinium tetrafluoroborate ([Bmpy][BF4]), 1 -Butyl-4- methylpyridinium bis(trifluoromethylsulfonyl)imide ([Bmpy][NTf2]).

[0089] The amount of ionic liquid in the supercritical / subcritical phase may be 0.05-60 mol%, or 1-50 mol%, or preferably 10-40 mol%.

[0090] Ionic liquids may be used to solubilize the colorants / additives and facilitate therefore their extraction. Ionic liquids have high solubilizing power of a wide range of polar and non-polar substances. Ionic liquids may also form complexes with colorant / dye molecules, which can enhance their solubility in supercritical or subcritical phases / fluids and therefore their extraction

[0091] The surfactant may be selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants and any combination thereof. Surfactants can be used to assist and facilitate the removal of colorants / additives by improving their solubility in supercritical or subcritical phases. The surfactant molecules can interact with the colorant / additive molecules, forming mixed micelles or complexes that can solubilize the colorant / additive molecule in the supercritical orsubcritical phase. Moreover, surfactants can enhance the mass transfer rate between the textile and the supercritical / subcritical phase by reducing the interfacial tension and increasing the wetting properties. Finally, surfactants can enable selective extraction and prevent the re-deposition of dyes into the textile fibers by targeting and dissolving certain types of dyes from the textile. Anionic surfactants may be e.g. sodium dodecyl sulfate. Nonionic surfactant may be e.g. alkyl polyethylene glycol. Cationic surfactants may be e.g. cetyltrimethylammonium bromide (CTAB)). Amphoteric surfactants may be e.g. amphoacetates.

[0092] The polar additive may be a residual or permanent dispersing agent, a fixative, a residual antistatic agent, a residual emulsifier, a residual softener, a polar UV absorber, a polar flame retardant or any combination thereof.

[0093] The polar colorant may be a reactive dye, a mordant dye, an azoic dye, an acid dye, a basic dye, a direct dye or any combination thereof.

[0094] Polar colorants have a relatively water-soluble characteristic, allowing them to form bonds with the hydrophilic functional groups present in textile fibers. Also, polar colorants might include dyes designed for dyeing hydrophilic or polar fibers such natural cellulosic fibers (such as cotton, rayon) or protein fibers such as wool and silk.

[0095] The non-polar colorant may be a disperse dye, an oil-soluble dye, a vat dye, a solvent dye, and a hydrophobic azo dye or any combination thereof.

[0096] The non-polar additive may be a residual softener, a slip agent, an anti-soiling agent, a non-polar flame retardant, a non-polar UV absorber or any combination thereof.

[0097] A non-polar flame retardant may be brominated or chlorinated flame retardant.

[0098] Disperse dyes do not chemically react with textile fibres such as polyester or polycotton fibers. These dyes are applied through a physical adsorption and diffusion into the textile. Reactive dyes on the other hand are bound to the textile fibres such as polycotton fibers chemically. To remove only disperse dyes from a textile, a method comprising step 1) or possibly also step 2a) described above might be enough. To remove reactive dyes or VAT dyes from a textile, the method should in addition to step 1 ) and possibly also step 2a) comprise step 2b1 ) or step 2b2). This, as just an increase or decrease of phase density is not enough to extract such dyes. A phase cycling, i.e. step 1 ) plus step 2a) may result in a slight change of polarity of the supercritical or subcritical phase but this is not enough to extract reactive or VAT dyes, which require a chemical reaction. Therefore, in order to be able to extract a plurality of dyes and / or additives from a textile material most often all steps 1 ), 2a) and 2b1) / 2b2) may be included in the method.

[0099] Illustrated in Fig. 2, in a high-pressure cell, e.g. an autoclave, 2, the textile material 1 to be treated is introduced. Carbon dioxide or water, methane, ethane or propane is supplied from tank 3, possibly mixed with a co-solvent 4 (e.g. ethanol, acetone, water, etc) and introduced in the autoclave 2. The pressure and temperature in the tank is then increased in order to reach a supercritical phase. The first step 101 is a pretreatment step using supercritical / subcritical fluid, such as supercritical / subcritical CO2, in order to remove dirt, grease and also dry the textile material 1 . At the end of this pre-treatment step, a depressurization step is performed, and all the extracted water, dirt, grease and other components such as sizing agents are separated from the textile material fibers 1 .

[0100] This pre-treatment step 101 can be performed in batch, semi-continuous or continuous mode at a pressure range between 10 and 400 bar and temperature between 20 to 250 °C.

[0101] In one example a 500 mL high-pressure cell 2, 100 g of blended polycotton textile waste 1 with a composition of 65 wt.% polyester - 35 wt.% cotton and 3 mol% of sorbitan monooleate was introduced. (Sorbitan monooleate is a non-ionic surfactant, which can enhance the solubility of non-polar colorants / additives and specially disperse dyes by forming mixed micelles or complexes with the dye molecule. The hydrophobic part of sorbitan monooleate interact with the non-polar dye while the hydrophilic head-group provides steric stabilisation and dispersibility of the complex in the supercritical or subcritical fluid.) CO2 is introduced into the high pressure-cell with a pressurization rate of 3 bar / min until reaching a pressure of 220 bar and the cell is also heated up to 80 °C. For 40 minutes, the supercritical fluid containing the surfactant penetrates within the blend of polycotton and dissolves non-polar colorants / additives such as disperse dyes. At the end of this 40 min duration, 5 mol% of ethanol is introduced with a pump to the cell, temperature of the cell increased to 120°C and pressure to 250 bar. The presence of the co-solvent modifies the polarity of the supercritical fluid towards a more polar behavior. The change of the pressure and temperature improve the solvation properties of supercritical fluids toward more polar components. For 60 min, the supercritical fluid dissolves the polar components, might also extract some non-polar components (because of the presence of the surfactant). During a depressurization phase (5 bar / min) the extracted components removed from the textile material, may be transferred to a trap 5 located outside the pressure cell 2 and / or be collected at the bottom of the high-pressure cell.

[0102] In another example, in a 500 mL high-pressure cell 2, 100 g of blended polycotton textile waste 1 with a composition of 70 wt.% polyester - 30 wt.% cotton is introduced. CO2 is introduced to the high pressure-cell 2 with a pressurization rate of 3 bar / min until reaching a pressure of 200 bar and the cell is also heated up to 100 °C. For 15 minutes, the supercritical fluid is allowed to penetrate within the blend of polycotton and dissolves part of the non-polar colorants / additives such as disperse dye. At the end of this 15 min duration, the pressure in the cell 2 is reduced from 200 bar to 100 bar (depressurization rate of 5 bar / min), while the temperature remains constant. Those conditions are maintained for 15 min. During this period the supercritical fluid with a different density and solvation power will dissolve different non-polar components. At the end of these 15 min, the pressure of the cell is increased again to 200 bar with a pressurization rate of 5 bar / min, the temperature increases to 120 °C, and 10% of methanol is introduced to the cell with a pump. During 40 min, the polar supercritical fluid will extract preferable the polar dyes. At the end of this 40 min duration, the pressure is decreased to 60 bar with a depressurization rate of 5 bar / min, while the temperature remains constant. For 20 min, the subcritical fluid will dissolve the remaining polar and non-polar dyes and additives from the polycotton fibers. At the end of this duration, the high-pressure cell is depressurized with a depressurization rate of 5 bar / min and the discolored polycotton fiber is characterized.

[0103] In Fig. 3 is shown a graph of color strength of the textile material (K / S) before and after the treatment with the process described in the example immediately above. The line marked X shows the polycotton textile before treatment with the above process. The line marked Y shows the polycotton textile after treatment with the above process. The color strength of the textile (K / S) is measured by a spectrophotometer. The color strength quantify, the intensity / depth of color in the fibers, measures more specifically the absorption coefficient (K) to the scattering coefficient (S) of the fibers in particular set of wavelengths.

[0104] As can be seen from the graph in Fig. 3, there is a big difference between the color strength of the textile material before and after the treatment with the above process.

[0105] The properties of the textiles may also be assessed before and after the extraction through mechanical and analysis and differential scanning calorimetry (DSC) to investigate the morphological change occurring in the textiles after the extraction.

[0106] In one specific example, in a high-pressure autoclave 2 heated to 80°C and containing waste polycotton 1 , composed of 65 wt.% polyester - 35 wt.% cotton, CO2 is introduced with a pressurization rate of 5 bar / min until reaching a pressure of 120 bar. 5% of water is added to the autoclave using a pump. A semi-continuous flow of CO2, while maintaining the pressure and temperature constant, is used in order to clean and extract grease, dirt and moisture from the textile. After about 40 min 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 trap 5.

[0107] Thereafter, colorants and / or additives are extracted from the textile waste. This process may comprise two steps according to the nature of colorants / additives in the textile. If the textile material is polycotton, which often is heterogeneous and composed of different amounts of cotton and polyester, and possibly also dyed with different types of colorants and with different types of additives, the process can be adjusted to the global nature of colorants / additives.

[0108] The first step considers the extraction of non-polar colorants / additives, such as waterinsoluble dyes, e.g. disperse dyes. For this step, a non-polar supercritical / subcritical fluid is used in order to extract the non-polar colorants / additives. This step can be performed at a pressure range of 90 to 350 bar and temperature of 60 to 200 °C and for a duration from 10 min to 6 h.

[0109] The second step considers the extraction of polar colorants / additives such as water- soluble dyes, e.g. reactive and direct dyes. For this second step, the polarity of the supercritical / subcritical fluid is changed by adding a co-solvent such ethanol, methanol, or water and often during this step the pressure and temperature are also modified. In one example, in an autoclave 2, 35 wt.% cotton - 65 wt.% polyester textile waste 1 is introduced. CO2 is introduced to the autoclave with a pressurization rate of 1 .5 bar / min until reaching a pressure of 250 bar and the autoclave is heated up to 140 °C. For a duration of 60 min, the non-polar supercritical fluid dissolves the non-polar colorant / additive, such as disperse dye, from the polycotton. At the end of this duration, the autoclave is depressurized at a rate of 2.5 bar / min. The extracted dyes are separated in the trap 5. The same reactor containing 35 wt.% cotton - 65 wt.% polyester textile waste is filled again with CO2 until reaching a pressure of 300 bar and heated up to 160°, and 7 v% of the co-solvent ethanol is added with a pump. The supercritical fluid dissolves the polar colorant / additive and after 55 min, the autoclave is depressurized at a rate of 2 bar / min, the extracted dyes are recovered in the trap 5 and the CO2 is recycled and recovered.

[0110] A pressure swing process, as discussed above, may for example be performed by providing a textile material 1 , such as e.g. a textile material comprising a 50 wt.% cotton - 50 wt.% polyester, in an autoclave 2. CO2 is introduced to the autoclave with a pressurization rate of 2 bar / min until reaching a pressure of 220 bar and the autoclave is heated up to 120 °C. For a duration of 25 min, the non-polar supercritical fluid dissolves partially the non-polar colorant / additive such as disperse dye from the polycotton. At the end of this duration, the pressure is reduced to 60 bar with a depressurization rate of 2 bar / min and the temperature is maintained at 120°C. For 25 min, the subcritical fluid dissolves partially the polar colorants / additives such as reactive dyes and direct dyes. This swing between supercritical and subcritical fluid may be repeated at least two times in order to remove the polar and non-polar colorants / additives from the polycotton wastes up to more than 91%.

[0111] In one example a 50-50% blend of poly cotton textile waste was treated. A pre-step was performed using supercritical CO2 to extract any moisture, dirt, grease or sizing agent from the material into the supercritical fluid. Thereafter, in a 500 mL high- pressure cell , 100 g of blended polycotton textile waste with blends of different compositions of polyester and cotton (waste, unknown exact composition and dyes) was introduced. CO2 was introduced to the high pressure-cell with a pressurization rate of 10 bar (1 MPa) / min until reaching a pressure of 260 bar (26 MPa) and the cell was also heated up to 135 °C. For 20 minutes, the supercritical fluid was allowed to penetrate within the blend of polycotton and dissolve part of the non-polar colorants / additives such as disperse dye. At the end of this 20 min duration, the pressure in the cell was reduced from 260 bar (26 MPa) to 170 bar (17 MPa) (depressurization rate of 5 bar (0.5 MPa) / min), while the temperature remained constant. Those conditions were maintained for 20 min. During this period the supercritical fluid with a different density and solvation power dissolved different nonpolar components. At the end of these 20 min, the pressure of the cell was increased again to 320 bar (32 MPa) with a pressurization rate of 15 bar (1.5 MPa) / min, the temperature decreased to 100 °C, and 1 mol% of NH3 in 20 mol% of ethanol was introduced into the cell with a pump. During 20 min, a pulsed CO2 flow cycle was used in order to help break some of the covalent bonding of the dyes with the textile. The polar supercritical fluid then extract preferably the polar dyes but also the increase to a higher pressure in combination with a relative medium temperature helps to weaken the bounding between the textile and dyes. The use of 1 mol% of NH3 in ethanol helps to break some ester bounds, where the duration and the temperature of this treatment needs to be carefully monitored in order not to damage the properties of the fibres. At the end of this 20 min duration, the pressure was decreased to 55 bar (5.5 MPa) with a depressurization rate of 20 bar (2.0 MPa) / min, while the temperature remained constant. For 20 min, the subcritical fluid dissolved the remaining polar and non-polar dyes and additives from the polycotton fibres. At the end of this duration, the high- pressure cell was depressurized with a depressurization rate of 5 bar (0.5 MPa) / min and the discolored poly cotton fibre was characterized online during the supercritical extraction. During the whole extraction process, an in-situ UV monitoring connected to the high pressure cell was performed continuously to assess the discoloration of the textile waste through the online absorbance measurement of extracted dyes. When no change in the absorbance was detected overtime, it was assumed that all the dyes had been extracted at equilibrium.

[0112] At the end of this extraction process and once the high pressure vessel was opened, FTIR analysis was performed to check the presence of potential residual dyes. It can also be seen clearly that the polycotton wastes showed a white off-color. The extracted dyes mixed with the different co-solvent used were analysed through LIV-VIS spectroscopy and disperse red 60 was detected at a wavelength of 520 nm, reactive bleu 19 was detected at 590 nm and Vat Orange7 was detected at 450 nm. Moreover, this analysis was followed with a high-performance liquid chromatography to separate and identify the exact dye components. A retention time comparison with standard dye reference was performed.

[0113] Hence, it is clear that the methods described above can be used to extract a plurality of dyes and / or additives from textile waste coming from different geographical areas in the world and that might contain a mix of additives and dyes (from different families of colorants). Disperse dyes are in general soluble in a non-polar phase, while the reactive dyes, may be removed in polar conditions. VAT dyes are preferably converted into their soluble form and can be dissolved using a polar solvent.

Claims

CLAIMS1 . A process for removing colorants and / or additives from a textile material, the process comprising a step of:1 ) bringing textile material (1) comprising multiple colorants and / or additives in contact with a supercritical or subcritical phase being non-polar or polar and having a first density (100), wherein the method further comprises at least one of the following steps:2a) adjusting (101 ) the density of the non-polar or polar supercritical or subcritical phase in step 1 ) to a second density, different from the first density, such that the textile material (1) is brought in contact with a non-polar or polar supercritical or subcritical phase with said second density, and / or2b1 ) if the supercritical or subcritical phase used in step 1 ) is a non-polar supercritical or subcritical phase bringing (102a) the textile material in contact with a polar supercritical or subcritical phase, or2b2) if the supercritical or subcritical phase used in step 1 ) is a polar supercritical or subcritical phase bringing (102b) the textile material in contact with a non-polar supercritical or subcritical phase.

2. The process of claim 1 , wherein the phases used in step 1 ) and in step 2a) are both supercritical phases or both subcritical phases, or the phase used in one of the steps is a supercritical phase and the phase used in the other step is a subcritical phase.

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

4. The process of any of the preceding claims, wherein a difference in density between the first density used in step 1 ) and the second density of the phase used in step 2a) is at least 30 kg / m35. The process of any of the preceding claims, wherein the process comprises at least step 1 ) and step 2a).

6. The process of claim 5, wherein the process comprises step 1 ), step 2a) and step 2b1 ) or step 2b2).

7. The process of any of claims 1 -4, wherein the process comprises step 1 ) and step 2b1 ) or step 2b2).

8. The process of any of the preceding claims wherein at least one of the process steps, step 1 ), 2a) and 2b1) or 2b2), is repeated one or more times.

9. The process of any of the preceding claims, wherein the duration of each step 1 ), 2), 2a), 2b1 ) and 2b2) is at least 10 minutes.

10. The process of any of the preceding claims, wherein the supercritical or subcritical phase comprises supercritical or subcritical carbon dioxide, water, methane, ethane, ethanol, or propane.11 . The process of any of the preceding claims, wherein the non-polar supercritical or subcritical phase comprises a non-polar co-solvent.

12. The process of claim 11 , wherein the non-polar co-solvent is selected from ethane, propane, dimethyl ether, aromatic hydrocarbons, alkanes or any combination thereof.

13. The process of any of the preceding claims, wherein the polar supercritical or subcritical phase comprises a polar co-solvent.

14. The process of claim 13, wherein the polar co-solvent is selected from water, ethanol, acetone, methanol, dichloromethane, or any combination thereof.

15. The process of any of the preceding claims, wherein the polar or non-polar supercritical or subcritical phase comprises anyone or more of enzyme(s), ionic liquid(s) and surfactant(s).

16. The process of claim 15, wherein the enzyme is selected from peroxidases, laccases, azoreductases, cellulases, manganese peroxidases, horseradish peroxidases, tyrosinases or any combination thereof.

17. The process of claim 15 or 16, wherein the ionic liquid is selected from imidazolium-based ionic liquids, phosphonium-based ionic liquids, pyridinium-based ionic liquids, ammonium-based ionic liquids or any combination thereof.

18. The process of any of claims 15-17, wherein the surfactant is selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants or any combination thereof.

19. The process of any of the preceding claims, wherein the additive is a polar additive and is a residual or permanent dispersing agent, a fixative, a residual antistatic agent, a residual emulsifier, a residual softener, a polar UV absorber, a polar flame retardant or any combination thereof.

20. The process of any of the preceding claims, wherein the colorant is a polar colorant and is a reactive dye, a mordant dye, an azoic dye, an acid dye, a basic dye, a direct dye, or any combination thereof.21 . The process of any of the preceding claims wherein the colorant is a non-polar colorant and is a disperse dye, an oil-soluble dye, a vat dye, a solvent dye, and a hydrophobic azo dye or any combination thereof.

22. The process of any of the preceding claims, wherein the additive is a non-polar additive and is a hydrophobic finisher, a residual softener, a slip agent, an anti-soiling agent, a non-polar flame retardant, a non-polar UV absorber or any combination thereof.

23. The process of any of the preceding claims further comprising a pre-step (99) before performing step 1 ) of bringing a supercritical or subcritical phase in contact withthe provided textile material (101 ) to extract any moisture, dirt, grease or sizing agent from the material into the supercritical or subcritical phase.

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