Dye recycling methods

Abstract

1. A method for recycling dye from dyed textiles, the method comprising: providing a textile colored with a dye; and adding the textile to a bath containing a solution of an ionic liquid, thereby stripping the dye from the textile and dispersing it within the solution.

Description

[Technical field]

[0001] The present invention relates to methods for recycling dye from dyed textiles, including methods for stripping dye from dyed textiles for reuse in dyeing processes, and methods for dyeing using recycled dye obtained from the methods disclosed herein. [Background technology]

[0002] The global textile industry is large and supplies textile products to many industries, such as the clothing and furniture industries. In addition to forming textiles from fibers, filaments, yarns and threads, the process of dyeing the formed textiles constitutes a large part of the textile industry. Textile manufacturers obtain large amounts of unused synthetic dyes for use in coloring their fabrics.

[0003] There is growing awareness of the large amount of waste generated by the textile industry, and there is a demand for sustainable materials and sustainable solutions to manufacture new materials and recycle waste. Millions of tons of waste textiles and clothing produced each year remain unsold because supply exceeds demand or the products are no longer considered fashionable. Little attention has been paid to dye recycling technologies to reduce the demand for unused synthetic dyes within the textile industry, but providing an effective way to recycle dyes would be an attractive proposition from both a sustainability and economic perspective.

[0004] Dye recycling technology will provide the textile industry with an opportunity to recover and utilize dyes trapped in textile waste (fabric scraps) and unused and unwanted dead stock in textile facilities. It will also provide unique economic advantages to textile manufacturers as they can i) buy less unused synthetic dyes and ii) reuse less dyed or dye-free (bleached) fabrics (stripped fabrics) or sell it for upcycling purposes since dye-free fabrics are highly desired by textile recyclers for upcycling applications.

[0005] The present disclosure provides a method that allows for the use of dyed waste textiles as a feedstock in a dyeing process. The disclosed method allows for the use of dyes extracted from textiles to dye textiles, reducing the need to use virgin dyes in the dyeing process. The disclosed method is a sustainable dyeing solution. Summary of the Invention

[0006] In a first aspect of the invention, there is provided a method for recycling dye from dyed textiles, the method comprising the steps of: providing a textile coloured with a dye; and adding the textile to a bath comprising a solution of an ionic liquid, thereby stripping the dye from the textile and dispersing it within the solution.

[0007] Optionally, the dye is a disperse dye, an acid dye, a basic dye, a reactive dye, a vat dye. Preferably, the dye is a disperse dye.

[0008] Optionally, the solution of ionic liquid is an aqueous solution of a protic ionic liquid. Preferably, the solution of ionic liquid is an aqueous solution of a protic ionic liquid and the dyed textile is colored with a disperse dye.

[0009] Optionally, the solution of ionic liquid is an aqueous ionic liquid solution (i.e., ionic liquid mixed with water as a co-solvent) or the solution of ionic liquid comprises ionic liquid and one or more organic co-solvents. Optionally, the organic co-solvent used is selected from ethanol, acetone, or dimethylsulfoxide, preferably the co-solvent used is selected from ethanol and acetone. That is, the solution of ionic liquid is formed using the aforementioned co-solvents (water, ethanol, acetone, or dimethylsulfoxide) in combination with ionic liquid, thereby forming a solution when mixed together.

[0010] Optionally, the ionic liquid solution is a protic ionic liquid, which is an ammonium-, imidazolium-, amino acid-, or acetate-based protic ionic liquid. Preferably, the cation is an alkylammonium or mixture thereof, preferably a protic alkylammonium, although aprotic alkylammonium can also be used when the ionic liquid is not a protic ionic liquid.

[0011] Optionally, the ionic liquid solution is a protic ionic liquid that is the reaction product of ammonium or imidazolium with hydrogen sulfate (HSO4) or a chloride anion, such as dimethylbutylammonium hydrogen sulfate, 1-methylimidazolium hydrogen sulfate, triethylammonium hydrogen sulfate, or 1-methylimidazolium chloride.

[0012] Optionally, the ionic liquid is an aprotic ionic liquid comprising 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylammonium methane hirsulfonate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methyl-imazolium chloride, 1-ethyl-3-methyl-imidazolium bromide, N-N-dimethylbutylammonium acetate, or dimethylethanolammonium formate. Preferably, the cation comprises a protic alkylammonium, protic methylimidazolium, protic pyridinium, aprotic tetraalkylammonium, or aprotic dialkylimidazolium ion.

[0013] Optionally, the ionic liquid is a carboxylate, including branched and / or halogenated carboxylates, such as hydrogen sulfate, trifluoroacetate, for example acetate, formate or propionate, alkyl sulfates, such as ethyl sulfate or methyl sulfate, alkyl sulfonates, such as methanesulfonate or ethanesulfonate, halides, such as chlorides, bromides or fluorides, dicyanamide, trifluoromethylsulfonate, thiocyanate, bi(trifluoromethylsulfonyl)imide, trifluoromethylsulfonate, tetrafluoroborate, heptane, tetrafluoroborate ... or based on a cation selected from protic or aprotic alkylammonium, for example alkylammonium such as N,N-dimethylbutylammonium, triethylammonium, tetraethylammonium, butylammonium, dimethylethanolammonium, alkylimidazolium, such as 1-methylimidazolium, 1-ethyl,3-methylimidazolium, alkylpyridinium, or alkylpyrrolidinium, choline.

[0014] Optionally, the ionic liquid is N,N-dimethylbutylammonium hydrogen sulfate, 1-methylimidazolium chloride, 1-methylimidazolium bromide, triethylammonium hydrogen sulfate, 1-ethyl,3-methylimidazolium ethyl sulfate, 1-ethyl,3-methylimidazolium methyl sulfate, N,N-dimethylbutylammonium methanesulfonate, 1-butyl,3-methylimidazolium bi(trifluoromethylsulfonyl)imide, choline hydrogen sulfate, choline chloride, 1-methylimidazolium ethyl Examples of suitable fluorinated alkyl ammonium salts include 1-ethyl,3-methylimidazolium chloride, 1-ethyl,3-methylimidazolium bromide, 1-butyl,3-methylimidazolium chloride, 1-methylimidazolium hydrogen sulfate, 1-methylimidazolium methanesulfonate, 1-methylimidazolium methylsulfate, or dimethylethanolammonium formate.

[0015] Preferably, the ionic liquid is triethylammonium hydrogen sulfate ([TEA][HSO4]), N,N-dimethyl-N-butylammonium hydrogen sulfate ([DMBA][HSO4]), 1-methylimidazolium hydrogen sulfate ([HMIM][HSO4]), I-butylimidazolium hydrogen sulfate ([HBIM][HSO4]), or 1-ethyl,3-methylimidazolium ethyl sulfate ([Emim][EthSO4]).

[0016] Optionally, after the stripping step, the stripped textile is removed from the bath.

[0017] Optionally, the textile is added to the bath for 0.5 to 3 hours, preferably 0.75 to 1.5 hours, before it is removed. Most preferably, the textile is added to the bath for 0.75 to 1 hour before it is removed.

[0018] Optionally, the concentration of ionic liquid in the solution (which may be called an ionic liquid solution or a solution of ionic liquid) in the stripping step is 95 wt% to 65 wt%, preferably 80 wt% to 70 wt%.

[0019] Optionally, the method further comprises heating the protic ionic solution (the solution of ionic liquid) to a temperature between 70° C. and 200° C., preferably between 100° C. and 200° C., more preferably between 140° C. and 160° C. Most preferably, the method further comprises heating the ionic solution to a temperature of about 150° C.

[0020] Optionally, the loading of dyed textile per kilogram of ionic liquid solution is from 10 g to 500 g, preferably from 50 g to 300 g, more preferably from 100 g to 250 g.

[0021] Optionally, the dyed textile is one or more dyed textile strips having a width of about 3 mm to 500 mm, preferably about 5 mm to 70 mm, more preferably about 10 mm to 40 mm, such as 20 mm. Advantageously, it has been found that the use of textiles of these sizes improves dye stripping efficiency.

[0022] Optionally, the dyed textile is a synthetic textile comprising polyester, such as polyethylene terephthalate (PET), polycotton, acrylic, nylon, or polyester blends, or a natural textile comprising cellulose, such as cotton, linen, viscose, or lyocell.

[0023] Optionally, the method further comprises cooling the solution of ionic liquid with dispersed dye after the stripping step to a temperature of about 10° C. to 80° C., preferably at or near room temperature.

[0024] Optionally, the method further comprises a dyeing step of dyeing a textile using the solution of ionic liquid with dye dispersed therein obtained from the stripping step, the dyeing step comprising adding the textile to be dyed to a bath comprising the solution of ionic liquid and dye dispersed therein, thereby exposing the textile to the dye and dyeing the textile.

[0025] Optionally, the loading of textile to be dyed per kilogram of solution is from 10 g to 500 g, preferably from 50 g to 300 g, more preferably from 100 g to 250 g.

[0026] Optionally, once the textile to be dyed has been added to the bath, the dyeing step further comprises a heating step comprising heating the textile to be dyed and the solution of the protic ionic liquid in which the dye is dispersed to 40°C to 200°C for 0.25 hours to 4 hours, preferably 40°C to 200°C for 0.25 hours to 2 hours. Preferably, the heating step comprises heating the textile to be dyed and the solution of the protic ionic liquid in which the dye is dispersed to 60°C to 150°C for 0.5 hours to 1 hour. Most preferably, the dyeing heating step is a two-stage preheating step comprising heating the solution of the protic ionic liquid in which the dye is dispersed to 50°C to 80°C (preferably 70°C) for 0.5 hours, followed by heating to 100°C to 180°C (preferably 150°C) for 0.5 hours.

[0027] Optionally, when the solution of ionic liquid is an aqueous ionic liquid solution, the dyeing step further comprises a hydration step in which water is added to the bath to reduce the concentration of the protic ionic liquid in the aqueous solution to between 70 wt% and 10 wt%, preferably between 65 wt% and 20 wt%, more preferably between 60 wt% and 40 wt%.

[0028] Optionally, when the solution of ionic liquid is an aqueous ionic liquid solution, the method further comprises a dehydration step after the dyeing step, in which heat is applied to the bath to increase the concentration of the protic ionic liquid in the aqueous solution by evaporation to 95 wt% to 65 wt%, preferably 80 wt% to 70 wt%.

[0029] Optionally, the method further comprises a purification step after the dyeing step, which comprises removing any residual dye from the solution. The purification step reduces the amount of dye in the ionic liquid solution, thereby forming a "purified ionic liquid solution" which may be substantially dye-free, i.e., completely dye-purified. Preferably, the purification step comprises removing residual dye by an adsorption process, such as by using an activated carbon column or by using an adsorbent.

[0030] Optionally, the purification step includes removing any residual dye from the solution in the ionic liquid and recovering the removed dye as a solid using an adsorbent.

[0031] Optionally, the dye is recovered by heating the solution of ionic liquid in which the dye is dispersed to a temperature between 20° C. and 80° C., preferably between 40° C. and 60° C., until a desired amount of the dye dispersed in the solution of ionic liquid is adsorbed onto the adsorbent, thereby forming a dye-rich adsorbent containing the dye. Optionally, the heating in the purification step is for a period of about 12 to 48 hours, preferably 24 hours.

[0032] Optionally, the purifying step further comprises washing the dye-rich adsorbent with a solvent, thereby removing the dye from the dye-rich adsorbent. Preferably, the solvent used to wash the dye-rich adsorbent is acetone.

[0033] Optionally, the adsorbent is selected from organic adsorbents, such as activated carbon adsorbents, or commercially available activated carbon and polymeric adsorbents, such as Amberlite XAD-4.

[0034] Optionally, the purification step is performed simultaneously with the stripping step, i.e., the adsorbent is added to and present in the bath during the stripping step.

[0035] Optionally, the method further comprises removing the textile from the bath after the dye has been partially stripped from the textile in the stripping step and before the purifying step (i.e., removing the dye-stripped textile from the bath before the purifying step is performed), and then reintroducing the textile to a purified solution of ionic liquid after the purifying step and using the washed solution of ionic liquid as the ionic liquid solution to recycle the dye from the textile using the methods disclosed herein.

[0036] Optionally, the recovered solid dye is used to dye textiles dyed with a water-based or ionic liquid-based dyeing process.

[0037] Optionally, the textile to be dyed is a synthetic textile including polyester such as polyethylene terephthalate (PET), acrylic, nylon, or polyester blends such as polycotton, or a natural textile including cellulose such as cotton, viscose, or lyocell.

[0038] According to a second aspect of the present invention, there is provided a method of dyeing a textile, the method comprising the steps of providing a textile and adding the textile to a bath comprising a solution of ionic liquid obtained from the dye recycling process disclosed herein and a dye dispersed therein, thereby exposing the textile to the dye and dyeing the textile.

[0039] According to a third aspect of the invention there is provided a method for recycling dye from dyed textiles comprising the steps of providing a textile coloured with a disperse dye, adding the textile to a bath comprising an aqueous solution of a protic ionic liquid, whereby the dye is stripped from the textile and dispersed in the aqueous solution, removing the stripped textile from the bath, and adding a textile to be dyed to a bath comprising an aqueous solution comprising a protic ionic liquid and a disperse dye, whereby the textile is exposed to the dye and dyed.

[0040] The optional and preferred features described in relation to the first aspect may be applied to equivalent effect as optional and preferred features of the second and third aspects. The optional features may be applied to the first, second and third aspects independently and in any combination.

[0041] According to a fourth aspect of the present invention there is provided a method for recycling dye from dyed textiles, the method comprising the steps of providing a natural textile material comprising cellulose coloured with a dye, adding the textile to a bath comprising a solution of an ionic liquid, and heating the bath, thereby decomposing the cellulosic material.

[0042] Optionally, heating is performed to maintain the aqueous solution of ionic liquid in the bath at a temperature of at least 90°C, preferably at least 150°C, more preferably between 90°C and 300°C, and most preferably between 150°C and 200°C.

[0043] Optionally, the degraded cellulosic material has a solids loading of from 10 g to 500 g / kg of textile, preferably from 50 g to 250 g / kg of textile.

[0044] Optionally, the method further includes removing the degraded cellulosic material from the bath and grinding the degraded cellulosic material to form a dye powder for use in dyeing textiles in a subsequent dyeing process. Preferably, the recovered powder is suitable for dyeing (and may be used as part of this method) textiles that are to be dyed, such as synthetic rich textiles, such as textiles that include polyester or nylon.

[0045] Optionally, the dye powder is mixed with one or more other dye powders of different pigments during or after milling, thereby creating a dye powder of a desired pigment color.

[0046] Optional preferred features described in relation to the first aspect may be applied as optional preferred features of the fourth aspect to similar effect. Optional features from the first aspect may be applied to the fourth aspect independently and in any combination.

[0047] According to a fifth aspect, there is provided a method for recycling dye from dyed textiles, the method comprising the steps of providing a textile coloured with a dye, the dye being a disperse dye, and adding the textile to a bath comprising a solution of an ionic liquid, whereby the dye is stripped from the textile and dispersed within the solution, the solution of ionic liquid being an aqueous solution of a protic liquid.

[0048] Optional preferred features described in relation to the first aspect may be applied as optional preferred features of the fifth aspect to similar effect (these optional preferred features of the first aspect are not already present as limitations of the fifth aspect in its broadest sense). Optional features from the first aspect may be applied to the fifth aspect independently and in any combination.

[0049] These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0050] [Figure 1a] FIG. 1 shows UV-vis spectra of polyester textiles that have been dye stripped using the methods disclosed herein using different bath times. [Figure 1b] FIG. 1b shows an image of the dye-stripped polyester textile from FIG. 1a. [Diagram 2] FIG. 1 shows UV-vis spectra of aqueous solutions of protic ionic liquids after being used to strip polyester textiles using the methods disclosed herein at various bath times. [Diagram 3] FIG. 1 shows UV-vis spectra of aqueous solutions of protic ionic liquids with various concentrations of protic ionic liquid (IL) after being used to strip polyester textiles using the methods disclosed herein. [Figure 4a] FIG. 1 shows UV-vis spectra of aqueous solutions of protic ionic liquids after being used to strip polyester textiles using the methods disclosed herein at various bath temperatures. [Figure 4b] FIG. 1 shows UV-vis spectra of polyester textiles that have been dye-stripped using the methods disclosed herein at various bath temperatures. [Diagram 5] FIG. 1 shows the UV-vis spectra of polyester textiles that have been dye-stripped using the methods disclosed herein with various textile solids loadings used in the bath, and compares these spectra to the UV-vis spectrum of the original dyed polyester textile. [Figure 6] FIG. 1 shows the UV-vis spectra of dye-stripped polyester textiles using the methods disclosed herein with various textile piece sizes and compares these spectra to the UV-vis spectrum of the original dyed polyester textile. [Figure 7a] FIG. 1 shows the UV-vis spectrum of an acrylic textile that has been dye-stripped using the methods disclosed herein and compares the spectrum to the UV-vis spectrum of the original brown dyed acrylic. [Figure 7b] Figure 7a shows an image of the dye-stripped textile from the UV-vis spectrum shown in Figure 7a compared to the original brown dyed acrylic. [Figure 8a] FIG. 1 shows the UV-vis spectra of polyester textiles dyed using the dyeing method disclosed herein with pink recycled disperse dye obtained from the method disclosed herein at varying concentrations of protic ionic liquid in the extracted dye solution, and compares these spectra to the UV-vis spectrum of the original pink dyed polyester textile. [Figure 8b] FIG. 8b shows K / S values ​​based on the results shown in FIG. 8a. [Figure 9a] FIG. 1 shows the UV-vis spectra of polyester textiles dyed using the dyeing method disclosed herein with red recycled disperse dye obtained from the method disclosed herein at varying concentrations of protic ionic liquid in the extracted dye solution, and compares these spectra with the UV-vis spectrum of the original dyed polyester textile. [Figure 9b] FIG. 9b shows K / S values ​​based on the results shown in FIG. 9a. [Figure 10] FIG. 1 shows the K / S values ​​of different colored textiles before and after dye stripping using the methods disclosed herein. [Figure 11a] FIG. 1 shows dilution-adjusted UV-vis spectra for the original and purified dye extraction solutions (ionic liquid solutions containing disperse dyes that have been subjected to the purification process disclosed herein) of the first purification experiment. [Figure 11b]FIG. 14 shows dilution-adjusted UV-vis spectra for the original and purified dye extraction solutions (ionic liquid solutions containing disperse dyes that have been subjected to the purification process disclosed herein) of the second purification experiment. [Figure 12a] FIG. 1 illustrates the effect of K / S value reduction resulting from an exemplary multi-stage purification according to the methods described herein. [Figure 12b] FIG. 1 shows the decrease in K / S value at strongest color intensity (620 nm) over a full cycle of an exemplary multi-step purification according to the method described herein. [Figure 13a] FIG. 1 shows sorbent recovered solid dye recovered using the methods disclosed herein. [Figure 13b] FIG. 1 shows K / S values ​​of dyed textile materials and textile materials dyed with solid dyes recovered using the methods disclosed herein. [Figure 14a] FIG. 1 shows the absorbance of a solution of ionic liquid with dye (at the peak wavelength of the visible spectrum) during a simultaneous stripping and dye recovery / purification process using methods of the type disclosed herein. [Figure 14b] FIG. 1 shows the absorbance of a solution of ionic liquid with dye (at the peak wavelength of the visible spectrum) during a simultaneous stripping and dye recovery / purification process using methods of the type disclosed herein. [Figure 15a] FIG. 1 shows the reduction in K / S value of blue pre-consumer PET textile using the dye recycling method disclosed herein with ionic liquids containing different co-solvents (indicated co-solvents, all 20 wt%). [Figure 15b] FIG. 1 shows the reduction in K / S value of blue pre-consumer PET textile using the dye recycling method disclosed herein with various concentrations of ionic liquid aqueous solutions. [Figure 16a] FIG. 1 shows the K / S values ​​of a blue pre-consumer PET textile before and after being subjected to a dye recycling method of the type disclosed herein, in which a solution of ionic liquid is formed using water and ethanol as co-solvents. [Figure 16b] FIG. 1 shows the K / S values ​​of a blue pre-consumer PET textile before and after being subjected to a dye recycling method of the type disclosed herein, in which a solution of ionic liquid is formed using water and acetone as co-solvents. [Figure 17a] FIG. 1 shows the K / S values ​​of undyed and nylon dyed fabrics using cellulosic colorant powder obtained from the method disclosed herein using a) water as dye bath and b) ionic liquid solution as dye bath. [Figure 17b] FIG. 1 shows the K / S values ​​of undyed and freshly dyed polyester using cellulose colorant powder obtained from the method disclosed herein using a) water as the dye bath and b) ionic liquid solution as the dye bath. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Described herein are methods that can be used to reclaim dye from dyed textiles, i.e., stripping the dye from the textile to a partial or substantially complete extent so that the dye can be used as a replacement for unused dye in the dyeing process. The methods described herein can be used with textiles dyed with disperse, acid, basic, reactive, and vat dyes. Also described herein are methods that can be used to dye textiles using dye stripped from textiles according to the methods disclosed herein as part of a recycling process. The methods described herein relate to stripping dyed textiles (including dyed yarns made from fibers), but are equally applicable to single dyed yarns or fibers. Also described herein are methods that can be used to break down cellulose-rich textile fibers into colored powders, which can be used as dyes for dyeing new textile fabrics or starting materials for pigments.

[0052] The method is based on the use of low-cost, readily available ionic liquids (e.g., protic ionic liquids) to strip dye from dyed waste textiles to produce decolorized textiles suitable for reuse, as well as to separate the dye for use in downstream dyeing processes.

[0053] Below is an example of a method according to the present disclosure that involves recycling dye from textiles dyed with disperse dyes and using protic ionic liquids.

[0054] Thus, there is provided a method for recycling dye from dyed textiles, comprising the steps of: A method is described herein that includes providing a textile colored with a disperse dye, adding the textile to a bath containing an aqueous solution of a protic ionic liquid, thereby causing a stripping step (forming an aqueous solution of a protic ionic liquid dye dispersion) in which the dye in the dyed textile is stripped from the textile and dispersed (i.e., dissolved) in the aqueous solution, and optionally removing the stripped textile from the bath after the stripping step.

[0055] Recycling of dyes in the present method relates to stripping (extracting) dyes from dyed textiles so that the dyes from the textiles can be reused in another disperse dye process. Advantageously, the protic ionic liquids used according to this method have been found to be effective in stripping dyes from textiles without substantially decomposing the dyes. When the textile to be dyed is added to the bath, the action of the aqueous solution of the protic ionic liquid penetrates the fibers of the textile, swelling them and stripping the disperse dyes therefrom. Once stripped from the textile, the dyes form a dispersion in the aqueous solution in the bath. The bath containing the aqueous solution and the dye dispersion is then suitable for use in dyeing textiles in another dye process. The stripped textiles may advantageously be dyed in another color using a different dye process or may be used for other applications such as upcycling.

[0056] Particularly useful protic ionic liquids are ammonium-, imidazolium-, amino acid-, or acetate-based protic ionic liquids, such as the reaction product of ammonium or imidazolium with hydrogen sulfate (HSO4) or a chloride anion, such as dimethylbutylammonium hydrogen sulfate, 1-methylimidazolium hydrogen sulfate, triethylammonium hydrogen sulfate, or 1-methylimidazolium chloride.

[0057] The method can be practiced with textiles dyed with other dyes, including but not limited to acid, basic, reactive or vat dyes, and therefore the following can be read in the context of other dyes as well as disperse dyes.

[0058] The method may be carried out using alternative ionic liquids to the aqueous solution of the protic ionic liquid. Ionic liquids that may be used alternatively include: hydrogen sulfate, carboxylates, including branched and / or halogenated carboxylates such as trifluoroacetate, alkyl sulfates such as ethyl sulfate or methyl sulfate, alkyl sulfonates such as methanesulfonate or ethanesulfonate, halides such as chlorides, bromides or fluorides, dicyanamides, trifluoromethylsulfonates, thiocyanates, bi(trifluoromethylsulfonyl)imides, trifluoromethylsulfonates, tetrafluoroborates, hexafluorosulfonates, tetrafluorobor ... an anion selected from fluorophosphate, or an amino acid-based anion such as lysinate, serinate or alginate; or a cation selected from protic or aprotic alkylammonium, for example, alkylammonium such as N,N-dimethylbutylammonium, triethylammonium, tetraethylammonium, butylammonium, dimethylethanolammonium, 1-methylimidazolium, 1-ethyl,3-methylimidazolium, alkylpyridinium, alkylpyrrolidinium, or choline.

[0059] Preferably, the ionic liquid is N,N-dimethylbutylammonium hydrogen sulfate, 1-methylimidazolium chloride, 1-methylimidazolium bromide, triethylammonium hydrogen sulfate, 1-ethyl,3-methylimidazolium ethyl sulfate, 1-ethyl,3-methylimidazolium methyl sulfate, N,N-dimethylbutylammonium methanesulfonate, 1-butyl,3-methylimidazolium bi(trifluoromethylsulfonyl)imide, choline hydrogen sulfate, choline chloride, 1-methylimidazolium ethyl sulfate. The imidazolium chloride, 1-ethyl,3-methylimidazolium bromide, 1-butyl,3-methylimidazolium chloride, 1-methylimidazolium hydrogen sulfate, 1-methylimidazolium methanesulfonate, 1-methylimidazolium methylsulfate, or dimethylethanolammonium formate.

[0060] Preferably, the ionic liquid is triethylammonium hydrogen sulfate ([TEA][HSO4]), N,N-dimethyl-N-butylammonium hydrogen sulfate ([DMBA][HSO4]), 1-methylimidazolium hydrogen sulfate ([HMIM][HSO4]), I-butylimidazolium hydrogen sulfate ([HBIM][HSO4]), or 1-ethyl,3-methylimidazolium ethyl sulfate ([Emim][EthSO4]).

[0061] Ionic liquids can be prepared by methods known to those skilled in the art or can be obtained commercially. For example, ionic liquids can be made from simple alkyl amines such as triethylamine and sulfuric acid in a one-step synthesis, for example as described in George et al., (2015) "Design of low-cost ionic liquids for lignocellulosic biomass treatment" Green Chemistry 17:1728-173.

[0062] The textile may be added to the bath for 0.5 to 3 hours, preferably 0.75 to 1.5 hours, before being removed. For example, the textile may be added for 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3 hours before being removed. That is, the textile from which the dye is stripped in the stripping step has these residence times in the bath (time in contact with the aqueous solution of the protic ionic liquid) before being removed from the bath. Preferably, the textile is added to the bath for 0.75 to 1 hour before being removed. Advantageously, adding the textile to the bath for these amounts of time balances the dye stripping efficiency (amount of dye stripped from the textile) and the decomposition of the stripped dye.

[0063] The concentration of the protic ionic liquid in the aqueous solution in the stripping step may be 95wt% to 50wt%, preferably 85wt% to 65wt%, more preferably 80wt% to 70wt%. For example, the concentration of the protic ionic liquid in the aqueous solution in the stripping step may be 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt% or 95wt%. Advantageously, it has been found that providing the protic ionic liquid with these concentrations improves the dye stripping efficiency.

[0064] The method may further comprise heating the protic ion solution to a temperature of from 100° C. to 200° C., preferably from 140° C. to 160° C. Most preferably, the method further comprises heating the protic ion solution to a temperature of about 150° C. Advantageously, heating to these temperatures has been found to provide improved dye stripping efficiency while substantially avoiding dye decomposition.

[0065] The loading of dyed textile per kilogram of aqueous solution added in the stripping step can be from 10g to 500g (10g textile per kilogram of aqueous solution to 500g textile per kilogram of aqueous solution), preferably from 50g to 300g, more preferably from 100g to 250g, for example 50g, 60g, 70g, 80g, 90g, 100g, 120g, 130g, 140g, 150g, 160g, 170g, 180g, 190g, 200g, 210g, 220g, 230g, 240g or 250g.

[0066] The dyed textile may be one or more dyed textile strips (e.g. resulting from a roll of textile or garment) having a width of about 3 mm to 500 mm, preferably about 5 mm to 70 mm, more preferably 10 mm to 40 mm (e.g. 20 mm). The strips may be of various lengths and thicknesses. Advantageously, it has been found that the use of textiles of these sizes improves the efficiency of dye stripping.

[0067] The dyed textiles may be synthetic textiles including polyesters such as polyethylene terephthalate (PET), polycotton or acrylic, nylon, polyester blends, or natural textiles including cellulose such as cotton, viscose or lyocell.

[0068] The method may include a cooling step in which the aqueous solution containing the disperse dye after the stripping step is cooled to a temperature of about 10° C. to 80° C., preferably to a temperature near room temperature (about 21° C.). Cooling after the stripping step advantageously reduces any decomposition of the dye in the aqueous solution.

[0069] The method may further comprise a dyeing step of dyeing a textile using the aqueous solution comprising a disperse dye obtained from the stripping step, the dyeing step comprising adding the textile to be dyed to a bath comprising an aqueous solution of a protic ionic liquid and a disperse dye, thereby exposing the textile to the dye and dyeing the textile. Optionally, additional dye may be added to the ionic liquid solution comprising the dye to achieve a particular shade of color.

[0070] Advantageously, the stripping step followed by the dyeing step provides a closed loop method of recycling disperse dyes, where the disperse dyes are stripped (extracted) from textiles, such as waste textile products, and then used to dye new textile products. When added to a bath for the dyeing step, the aqueous solution penetrates the fibers of the textile to be dyed, causing the dye dispersions to diffuse into the fibers where they remain due to hydrogen bonding and van der Waals forces. Surprisingly, it has been found that protic ionic liquids act as both an effective stripping agent during the stripping step and an effective dispersing agent during the dyeing step.

[0071] The loading of textile to be dyed per kilogram of solution may be from 50g to 500g, preferably from 50g to 300g, more preferably from 100g to 250g, for example 50g, 60g, 70g, 80g, 90g, 100g, 120g, 130g, 140g, 150g, 160g, 170g, 180g, 190g, 200g, 210g, 220g, 230g, 240g or 250g. Preferably, the loading of textile for the dyeing process allows the dyeing process to use up substantially all of the dye available for dyeing dispersed in the solution.

[0072] With the textile being dyed in the bath, the dyeing process may further comprise a dyeing heating step in which the aqueous solution of the protic ionic liquid and the disperse dye is heated to 40°C to 200°C, preferably 60°C to 150°C for 0.25 to 2 hours, preferably 0.5 to 1 hour. Preferably, the dyeing heating step is a two-stage preheating step comprising heating the aqueous solution of the protic ionic liquid and the disperse dye to 50°C to 80°C (preferably 70°C) for 0.5 hours followed by heating to 100°C to 180°C (preferably 150°C) for 0.5 hours. The heating step has been found to improve dyeing efficiency whilst substantially avoiding degradation of the dye.

[0073] The dyeing process may further include a hydration step in which water is added to the bath to reduce the concentration of the protic ionic liquid in the aqueous solution to 65wt% to 10wt%, preferably 60wt% to 40wt%. For example, the concentration of the protic ionic liquid in the aqueous solution in the stripping step may be diluted to 65wt%, 60wt%, 55wt%, 50wt%, 45wt%, 40wt%, 35wt%, 30wt%, 25wt%, 20wt%. This concentration of the protic ionic liquid in the aqueous solution excludes any amount of disperse dye. The dye is diluted during the hydration step. It has been found that increasing the water concentration in the aqueous solution within this amount advantageously improves the dyeing efficiency (taking into account the hydrophobicity of the disperse dye) without diluting the disperse dye to an amount that is ineffective for the purpose of the dyeing process.

[0074] The method may include a purification step after the dyeing step, which comprises removing residual disperse dye from the solution. Preferably, the purification step comprises removing residual disperse dye from the solution using an activated carbon column process. Due to the high solubility of the dye in aqueous solutions of protic ionic liquids, some dye may remain in solution after the dyeing step. The optional purification step advantageously removes substantially all of the dye from the solution so that the solution can be used in a later stripping step as disclosed herein. Such a purification step is not necessary if it is known that the color of the dye stripped from the textile in the later stripping step is the same as the color of the dye remaining in the solution.

[0075] The method further comprises a dehydration step after the dyeing step, where heat is applied to the bath to increase the concentration of the protic ionic liquid in the aqueous solution by evaporation to 95 wt% to 65 wt%, preferably 80 wt% to 70 wt%. For example, the concentration of the protic ionic liquid in the aqueous solution in the stripping step can be 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt% or 95 wt%. The dehydration step advantageously allows recycling of the protic ionic liquid in the aqueous solution for use in further extraction / stripping processes. These hydration and dehydration steps have been found to provide a balance between improved dyeing efficiency and energy consumption.

[0076] The textile to be dyed may be a synthetic textile including polyester such as polyethylene terephthalate (PET), polycotton, acrylic, nylon, or polyester blends. Preferably, the synthetic textile includes hydrophobic fibers. The textile to be dyed may be or include a natural textile including cellulose such as cotton, viscose, or lyocell.

[0077] A method of dyeing a textile is described herein, the method comprising the steps of providing a textile and adding the textile to a bath, the bath comprising an aqueous solution of a protic ionic liquid and a disperse dye resulting from the stripping method disclosed herein, thereby exposing the textile to the dye and dyeing the textile.

[0078] Any preferred feature described with respect to any dyeing step for the method of recycling dye from dyed textiles described herein may be applied as any preferred feature for the method of dyeing textiles described herein.

[0079] A method is provided for recycling dye from dyed textiles in combination with the recycling method comprising stripping dye from the dyed textile and dyeing the textile as described herein, the method comprising the steps of providing a textile colored with a disperse dye, adding the textile to a bath comprising an aqueous solution of a protic ionic liquid, thereby stripping the dye from the textile and dispersing it in the aqueous solution, removing the stripped textile from the bath, and adding the textile to be dyed to a bath comprising an aqueous solution comprising a protic ionic liquid and a disperse dye, thereby exposing the textile to the dye and dyeing the textile, optionally in order.

[0080] Also described herein is a method for recycling dye from dyed textiles, the method comprising providing a natural textile material comprising cellulose colored with a dye, adding the textile to a bath comprising a solution of an ionic liquid, and heating the bath together with the textile, thereby decomposing the cellulose material. The term "decomposition" refers to a yarn in which the textile is at least partially decomposed into smaller pieces. Can a particular degree of how the textile is decomposed (e.g., particle size, etc.) be defined?

[0081] Heating of the contents of the bath is conducted to maintain the solution of ionic liquid at a temperature of at least 90°C, preferably at least 150°C, more preferably between 90°C and 300°C, and most preferably between 150°C and 200°C.

[0082] The method optionally includes removing the degraded cellulosic material from the bath once the cellulosic textile is at least partially degraded and grinding it to form a dye powder for use in dyeing the textile in a subsequent dyeing process. Optionally, the degraded cellulosic material removed from the bath is dried before grinding occurs.

[0083] Once the dye powder is obtained, it can be mixed with one or more other dye powders of different pigments, either before or after the milling process, thereby creating a dye powder of the desired pigment color.

[0084] Throughout the description and claims of this specification, the words "comprise" and "contain," as well as variations of these words, such as, for example, "comprising" and "comprises," mean "including but not limited to" and are not intended to (and do not) exclude other elements.

[0085] It will be understood that modifications to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Each feature disclosed in this specification, unless expressly stated otherwise, may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only one example of a generic series of equivalent or similar features.

[0086] All of the features disclosed herein may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Similarly, features described in non-essential combinations may be used separately (not in combination).

[0087] It will be appreciated that many of the features described above, particularly the preferred embodiments, are inventive in their own right and not as part of embodiments of the present invention, and independent protection may be sought for these features in addition to, or in place of, any presently claimed invention.

[0088] Reference is now made to the following examples which illustrate, but are not limiting of, the invention. EXAMPLES

[0089] Preparation of aqueous protic ionic liquid solutions N,N,N-Dimethylbutylamine (101.19 g, 1 mol) was added to a 500 mL round bottom flask and cooled in an ice bath. 200 mL of 5 M H2SO4 (1 mol) was added dropwise using an addition funnel with stirring. The reaction was allowed to proceed for at least 5 h with continuous stirring. Excess water was removed using a rotary evaporator. The ionic liquid was recovered as a clear viscous liquid. The water content of the ionic liquid was adjusted to 20 wt% using a Volumetric Karl Fisher Titrator (V20 Mettler-Toledo).

[0090] Characterization method Reflectance spectroscopy (Ultraviolet-Visible Spectroscopy (or UV-vis)) was used to determine the % reflectance of the textile. From the UV-vis spectrum, the K / S value was calculated to measure the % color loss relative to the original fabric and therefore determine the extent of stripping and dyeing (stripping efficiency can be tested). The K / S value represents the color depth / intensity (also called color strength) of the material, the higher the value the higher the intensity and vice versa. The K / S value is calculated based on the following formula:

[0091]

number

[0092] where K is absorbance, S is scattering, and R min is the minimum reflectance value (maximum absorbance) at the characteristic wavelength λ of all colors, for example for red dyed polyester λ=517 nm.

[0093] Absorption spectroscopy (UV-vis spectroscopy) was used to measure the concentration of disperse dyes in aqueous solutions of protic ionic liquids. To characterize the protic ionic liquid + dye aqueous solutions, dilutions of the protic ionic liquid + dye solutions were performed using ethanol as a solvent due to the insolubility of disperse dyes in water. The dye concentration in the aqueous solution is directly proportional to the measured absorbance. From the UV-vis absorbance spectrum, a higher absorbance indicates more dye dispersed in the aqueous solution and vice versa for a lower absorbance.

[0094] The color density of the fabric samples and the absorbance of aqueous solutions of the protic ionic liquids were analyzed using a Shimadzu UV-1800 UV spectrophotometer. First, background spectra were acquired from an empty sample holder. Spectra were acquired from 200 to 900 nm with a data interval of 1 nm.

[0095] The water content of the protic ionic liquid solutions before and after the hydration step (dilution step) was measured in triplicate using a Karl Fisher volumetric Titrator (Mettler-Toledo) and the average concentration was calculated accordingly.

[0096] Results and Discussion Dye extraction of disperse dyes from textiles using aqueous protic ion solutions as ionic liquids The extraction time (i.e., residence time of the dyed textile in the bath) was tested to determine its effect on dye stripping. A bath of aqueous solution containing 80 wt% of protic ionic liquid (N,N,N-dimethylbutylammonium hydrogen sulfate), prepared according to the method disclosed herein, was used. The temperature of the bath for the stripping step was fixed at 150°C. The original dyed textile added to the bath was a real post-consumer red 100% polyester obtained from a charity shop. Figure 1a shows the UV-vis reflectance spectra of the decolorized (stripped) textile at different times with a solids loading of 100g per kg of solution (g of textile per kg of aqueous solution). From the UV-vis spectra shown in Figure 1a, the K / S value was calculated to measure the % color loss relative to the original fabric, as shown in Table 1 below.

[0097] A color reduction of 51% was achieved at 30 min, further reducing to 66% at 45 min and 79% at 60 min, as shown in Table 1. At 90 min stripping time, the color reduction reached 96%, and further increasing the treatment time to 120 min resulted in a reduction of 98%, and the fabric appeared substantially decolorized, as seen in Figure 1b.

[0098] [Table 1]

[0099] Since this process is a dye recycling process, one objective is to obtain satisfactory dye removal while preserving the dye from degradation in the aqueous solution of the protic ionic liquid so that the dye can be reused. The state and concentration of the dye in the aqueous solution were monitored simultaneously with the data shown in Figure 1a and Table 1 to examine the effect of stripping time on the dye concentration (and dye degradation) to ensure that a balance was maintained between the dye extraction efficiency and the stability and state of the dye dispersed in the dye bath after stripping. Figure 2 shows the UV-vis absorbance spectrum of a bath containing an aqueous solution of the protic ionic liquid and the dye.

[0100] Figure 2 shows that the dye absorbance (which directly correlates to the dye concentration) was highest at 30 minutes and began to decrease at longer times suggesting that the dye began to decompose. After 90 minutes, the concentration of the dye in the aqueous solution decreased (and therefore the red color in the solution began to fade).

[0101] In a separate test from the above, the effect of various concentrations of protic ionic liquid in the aqueous solution was tested for its impact on dye extraction efficiency (shown in Figure 3). Figure 3 shows the UV-vis absorbance spectrum of a bath containing an aqueous solution of protic ionic liquid and dye after a stripping step was carried out according to the methods disclosed herein under the following conditions: the bath was heated to a temperature of 150°C, the dyed PET textile was held in the bath for 30 minutes, and a solids loading of 50 g of textile per kg of aqueous N,N,N-dimethylbutylammonium hydrogen sulfate solution (prepared using the methods disclosed herein).

[0102] FIG. 3 shows how changing the concentration of protic ionic liquid in the aqueous solution affects the extraction efficiency. Reducing the concentration of protic ionic liquid in the aqueous solution from 80 wt% to 70 wt% reduces the absorbance level (proportional to the dye concentration in the aqueous solution and then the dye stripped from the textile) by approximately 50%. The absorbance level, and therefore the dye concentration, decreases when the concentration is reduced to 50 wt%. It is understood that the concentration of the protic ionic liquid affects the extent to which it swells the fibers in the textile and thus the efficiency of stripping the dye from the textile.

[0103] The effect of bath temperature on the dye stripping efficiency of the present method was tested. The data shown in Figures 4a and 4b was obtained by carrying out the method described herein using an aqueous solution of protic ionic liquid with a protic ionic liquid concentration of 80 wt%. The bath was heated to various temperatures (170°C, 150°C, and 120°C), the textile was held in the bath for 30 minutes, and the solids loading of the textile was 50 g of textile per kg of aqueous solution of protic ionic liquid. The textile used was 100% post-consumer polyester.

[0104] As shown in Figure 4a, a surprising optimum absorbance was found at 150° C. Operating the process at a lower temperature of 120° C. did not extract the same amount of dye as at 150° C., and operating the process at 170° C. gave a low absorbance spectrum indicating the decomposition of the dye.

[0105] Figure 4b shows the reflectance of the stripped textile after 40 minutes in the bath versus the reflectance of the original fabric. Both fabrics extracted at 150°C and 170°C showed similar levels of color loss in the textile.

[0106] The effect of textile solids loading on the dye stripping efficiency in the present method was tested. The data shown in FIG. 5 was obtained by performing UV-vis reflectance spectroscopy on a textile subjected to the method described herein using an aqueous solution of protic ionic liquid having a protic ionic liquid concentration of 80 wt%, the bath was heated to 150° C. and the textile was held in the bath for 45 minutes. The textile tested was a red 100% polyester textile. FIG. 5 shows the effect of solids loading on the dye extraction efficiency as a function of solids loading. From the UV-vis spectra shown in FIG. 5, the K / S value was calculated to measure the % color loss relative to the original fabric, as shown in Table 2 below. It was found that increasing the solids loading from 7% (70 g textile per kg aqueous protic ionic liquid) to 21% (210 g textile per kg aqueous protic ionic liquid) caused a very slight decrease in the dye extraction efficiency, decreasing the color loss from 79% to 71%, respectively (see Table 2).

[0107] Operating the processes disclosed herein at higher solids loadings is important from an economic standpoint since it allows for more dye to be recycled.

[0108] The effect of textile sizing on the dye stripping efficiency in the present process was also examined. The data shown in Figure 6 was obtained by performing UV-vis reflectance spectroscopy on textiles of various sizes subjected to the process described herein using an aqueous solution of N,N,N-dimethylbutylammonium hydrogen sulfate (80 wt% N,N,N-dimethylbutylammonium hydrogen sulfate), the bath was heated to 150°C, the solids loading of the textile was 21% m, and the textile was held in the bath for 30 minutes. The textile tested was a red 100% polyester textile, and the physical size of the dyed polyester textile was a whole piece (4 x 4 cm 2size) and the same dyed polyester textile cut into yarns (strips) approximately 0.5 cm wide. From the UV-vis spectra shown in Figure 6, the K / S values ​​were calculated to measure the % color loss relative to the original fabric, as shown in Table 2 below.

[0109] Figure 6 and Table 2 show that the use of polyester yarns / strips results in a significant improvement in color reduction from 77% to 98% for the entire fabric piece. This indicates the advantageous extraction capabilities of the protic ionic liquid used, which can achieve high extraction by increasing the surface area of ​​exposure while maintaining the stability of the dye dispersion in the bath for later use as a dye bath.

[0110] [Table 2]

[0111] The dye recycling method of the present disclosure was carried out with a dyed acrylic textile dyed with a disperse dye. Figure 7a shows the UV-vis reflectance spectrum of a brown post-consumer acrylic textile before and after dye stripping using the method disclosed herein, and Figure 7b shows images of the same acrylic textile before (right) and after (left) dye stripping. An aqueous solution of protic ionic liquid with a concentration of 80 wt% of protic ionic liquid was used as the bath, and the bath was set at a temperature of 150°C, where the acrylic textile was held for 30 minutes. The solids loading of acrylic used was 100g of textile per kg of aqueous solution of protic ionic liquid. From the UV-vis spectrum shown in Figure 7a, the K / S value was calculated to measure the % color reduction with respect to the original fabric, as shown in Table 3 below. The amount of dye stripping achieved was very high, with a color reduction of 92%.

[0112] [Table 3]

[0113] Dyeing with recycled dyes The recycled dye solution (i.e., an aqueous solution of protic ionic liquid having dye dispersed therein, which may also be described as an "extracted dye solution" or "stripped dye solution") obtained from the methods disclosed herein was used in a dyebath to color virgin PET-based textiles using the methods disclosed herein.

[0114] The dyeing process consisted of adding the textile to the extracted dye solution in the bath and heating to 70°C for 30 minutes, followed by heating the dye bath to 150°C for an additional 30 minutes. The dyed textile was then removed from the bath. UV-vis reflectance spectroscopy was then performed on the dyed textile. Using this method, a fresh piece of 100% PET white polyester textile was dyed using the red dye solution extracted from 100% polyester and the extracted dye solution from 100% pink polyester textile described in connection with Figures 1a and 1b, the solution comprising an aqueous solution of N,N,N-dimethylbutylammonium hydrogen sulfate (80 wt% N,N,N-dimethylbutylammonium hydrogen sulfate). The dyeing process was carried out using both extracted dye solutions and both solutions were diluted with water to vary the concentration of protic ionic liquid in the aqueous solution to test the effect on dyeing efficiency.

[0115] The white polyester was obtained from a T-shirt purchased from Highstreet retailer H&M, approximately 6×7cm 2 The solid loading used in the dyeing experiments was 100 g per kg of aqueous solution of protic ionic liquid.

[0116] Four concentrations of aqueous solutions containing protic ionic liquid were tested: 80 wt% (which did not require dilution of the extracted dye solution in any case), 60 wt%, 40 wt% and 20 wt% (these latter three concentrations required dilution of the extracted dye solution with water). The diluted solutions were prepared by diluting the extracted dye solutions (both of which originally contained an aqueous solution of protic ionic liquid at a concentration of 80 wt%) with water. This process reduces the dye concentration in the dye bath medium by a factor of 1.03, 2 and 4 for the 60, 40 and 20 wt% protic ionic liquid solutions, respectively (dilution factors are shown in Table 4 below).

[0117] [Table 4]

[0118] Figure 8a shows the UV-vis reflectance spectrum of the dyed fabric using the extracted pink dye solution as well as the spectrum of the original pink polyester fabric from which the dye was extracted, and Figure 8b shows the corresponding calculated K / S ratio. After the extraction process, the extracted dye solution was used for dyeing as is (i.e., 80 wt% with protic ionic liquid), and the lowest K / S was 1.6. When the protic ionic liquid content in the solution dye bath was reduced from 80 wt% to 60 wt%, the K / S ratio increased to 3.7 (dye concentration dilution factor 1.03), which is 55% higher compared to dyeing with 20 wt% water. Further increasing the water concentration by using 40 wt% protic ionic liquid slightly decreased the K / S ratio compared to the fabric dyed with 60 wt%. However, the K / S was still higher compared to the fabric dyed with 80 wt% IL without dilution. Further increase in water concentration resulted in a decrease in the K / S value, which was relatively close to that of the fabric dyed with 80 wt% protic ionic liquid in solution. It is important to note that even though the K / S value of the dyed fabric decreased after 60 wt% protic ionic liquid, the dyeing efficiency was still very high, considering the fact that the dye concentration in the bath was diluted by 2 and 4 times in the 40 wt% and 20 wt% protic ionic liquid dye baths, respectively. Figure 9a shows the UV-vis reflectance spectrum of the dyed fabric using the extracted red dye solution, as well as the spectrum of the original red polyester fabric from which the dye was extracted, and Figure 9b shows the corresponding calculated K / S ratio. The results shown in Figures 9a and 9b follow the same trend as those in Figures 8a and 8b.

[0119] Recycling dyes from textiles using other ionic liquid solutions Figure 10 shows the K / S ratios of different colored textiles, namely nylon, acrylic, polyester, polycotton, and polyester / spandex, before and after dye extraction using the method of the present disclosure, using an ionic liquid solution of 80 wt% N,N-dimethylbutylammonium hydrogen sulfate for 30-45 minutes at 150° C. The color reduction in these materials ranged from 92% to 44%.

[0120] Purification of aqueous solutions of ionic liquids containing stripped dyes The stripped dye-containing aqueous solution resulting from the methods disclosed herein (i.e., an aqueous solution of ionic liquid with dye dispersed therein, which may also be described as an "extracted dye solution" or "stripped dye solution") may be "washed" using an adsorbent to remove the dissolved dye and thus color from the solution. In this manner, residual color can be advantageously removed from the ionic liquid solution, and the same ionic liquid solution can then be washed and reused between different colored textile waste batches.

[0121] An exemplary purification method involves adding the adsorbent material to the stripped dye solution in a glass screw-top jar and heating to 45° C. with magnetic stirring for up to 24 hours. The mixture is then filtered through filter paper under vacuum to separate the adsorbent (which is rich in dye and is hereafter referred to as the “dye-rich absorbent”) and recover the “cleaned” dye solution. Commercially available adsorbent material, AmberLite™, was used to purify the ionic liquid dye bath. The ratio of AmberLite™ to dye solution was 1:10 (by weight).

[0122] The solid loading used in both extraction experiments was 100 g per kg of ionic liquid solution.

[0123] 1. The first purification experiment was carried out on a 6 x 7 cm 2 An extracted dye solution obtained by extracting pre-consumer light blue virgin PET cut into rectangular pieces of 1000 μm was used. The ionic liquid solution used contained 80 wt% N,N,dimethylbutylammonium hydrogen sulfate and 20 wt% water.

[0124] 2. In the second purification experiment, a sample of approximately 1×1 cm 2An extracted dye solution obtained by extracting pre-consumer dark blue recycled PET cut into rectangular pieces was used. The ionic liquid solution used contained 80 wt% 1-ethyl,3-methylimidazolium ethyl sulfate and 20 wt% dimethyl sulfoxide.

[0125] Figures 11a and 11b show the dilution-adjusted UV-vis absorbance spectra of the original and purified dye extract solutions for the first and second purification experiments, respectively. Similar levels of dye removal from the extracted dye solutions were observed in both experiments, ranging from 71% to 74%, demonstrating that purification of the dye-rich ionic liquid was achieved and that the solution can be purified and reused between different colored textile waste batches.

[0126] Recycling of ionic liquid solutions for the extraction of dyes in multiple stages, with purification steps between stages The decolorized solid textile waste material resulting from the dye recycling method of the type disclosed herein can be separated from the ionic liquid solution by filtration, and the resulting dye-rich dye solution (stripped dye solution or dye dispersed in ionic liquid solution / solution of ionic liquid containing dye) can be "purified" using the sorbent material using the purification method described herein. After purification, the washed ionic liquid solution can be recovered and used to re-extract the decolorized material once extracted. The washing and reuse of the dye solution may be repeated multiple times (e.g., two, three, four times, etc.) such that the textile waste material is extracted several times using the same ionic liquid solution. Using this method, it has been found that high color removal can be achieved by washing and reusing the ionic liquid solution to extract the same batch of textile waste multiple times. An example illustrating this approach of washing and reusing the ionic liquid solution is described below, and the results are shown in Figures 12a and 12b.

[0127] The textile waste material used was approximately 1 x 1 cm 2The dye samples were pre-consumer PET cut into rectangular pieces of 1:10 wt / wt. All extractions were carried out at 150 °C for 30 min with a solids loading of 1:10 wt / wt. The ionic liquid solutions used contained 80 wt% 1-ethyl,3-methylimidazolium ethyl sulfate and 20 wt% dimethyl sulfoxide. The clean-up method consisted of adding the sorbent material at a solids loading of 1:10 wt / wt to the extracted dye solution in a glass screw-top jar and heating to 45 °C for 24 h with magnetic stirring. The mixture was filtered under vacuum through filter paper to separate the sorbent and recover the washed ionic liquid solution for recycling.

[0128] Figure 12a shows the K / S ratio (determined from UV-vis reflectance spectra) of the starting fabric and the fabric extracted after 1-4 cycles. Figure 12b shows the corresponding decrease in the K / S ratio at the strongest color intensity (620 nm) over all four cycles. Increasing the number of cycles increases the decolorization of the starting material, with 93% color removal being achieved after four cycles. In absolute terms, the color removal decreases with each cycle, starting at 40% in cycle 1 and ending at 5% in cycle 4. It was therefore found that ionic liquid solutions can be effectively reused to re-extract textile waste materials after purification, and multiple extraction cycles can be used to increase the degree of decolorization using reused ionic liquid solutions.

[0129] Recovery of dyes from stripped dye solutions using adsorbents. After purifying the stripped dye solution using the purification methods disclosed herein (i.e., using an adsorbent material to wash the stripped dye solution), the dye-rich adsorbent can be recovered by vacuum filtration through filter paper in a standard laboratory setting, the adsorbed dye can be desorbed using an organic solvent (e.g., acetone) and then removed by evaporation, and the extracted dye can be recovered as a solid. This recovered solid dye can then be redissolved in fresh ionic liquid and used to dye virgin materials. In other words, after removing the dye from the stripped dye solution using purification methods of the type disclosed herein, the dye can be advantageously recovered from the adsorbent and then reused for dyeing. An example of this approach for using the extracted / recovered solid dye is described below.

[0130] The textile waste material used was approximately 1 x 1 cm 2The dye-rich sorbent was pre-consumer PET cut into rectangular pieces of 1000 µm. All extractions were performed at 150 °C for 30 min with a solids loading of 1:10 wt / wt. The ionic liquid solution used contained 80 wt% 1-ethyl,3-methylimidazolium ethyl sulfate and 20 wt% dimethyl sulfoxide. The clean-up method consisted of adding a commercial sorbent material, AmberLite XAD-4 (a non-ionic polymeric sorbent), with a solids loading of 1:10 wt / wt, to the extracted dye solution (stripped dye solution) in a glass screw-top jar and heating to 45 °C for 24 h with magnetic stirring. The Amberlite XAD-4 was washed with water and acetone before use and then air-dried before use. The mixture was filtered under vacuum through filter paper and a Büchner funnel to separate the dye-rich sorbent and recover the "washed" dye solution. The sorbent was washed four times with deionized water to remove residual ionic liquid. The dye in the dye-rich absorbent was then desorbed from the adsorbent by adding 50 mL of acetone and shaking for 1 h, and the dye-rich acetone was recovered by filtering through filter paper. A total of four desorption cycles were performed using fresh acetone each time, and the dye-rich acetone obtained from each cycle was then added together. Rotary evaporation was used to remove the acetone from the dye-rich solution (recovered from the four desorption cycles), and the dye was recovered as a solid material.

[0131] The recovered solid dye was added to a fresh ionic liquid solution containing 60 wt% 1-ethyl,3-methylimidazolium ethyl sulfate and 40 wt% water. The resulting dye-rich solution was used to dye virgin uncolored PET fabric at 150° C. for 30 min at a solids loading of 1:10 wt / wt using the dyeing method disclosed herein (i.e., an aqueous solution of ionic liquid with dispersed dye).

[0132] Figure 13a shows the dye recovered as a solid material at the bottom of the round bottom flask. Figure 13b shows the K / S ratios (determined from UV-vis reflectance spectra) of the starting material from which the dye was extracted and the material dyed using both ionic liquid solutions. Thus, using the methods disclosed herein, it is possible to recover the extracted dye as a solid material and then use it to successfully dye new materials. The recovered dye can be used to advantageously dye virgin textile materials to very similar color intensities as the starting materials, exhibiting similar K / S ratios across the visible spectrum.

[0133] Simultaneous ionic liquid purification and dye recovery Dye recycling methods of the type disclosed herein can be used to strip dyes from textiles in the presence of an adsorbent (added to the ionic liquid solution). It has been found that the extracted dye adsorbs onto the adsorbent material during extraction of the dye from the textile, advantageously increasing the extent of decolorization by maintaining a high concentration gradient in the extraction medium (ionic liquid solution). An example of a simultaneous ionic liquid purification and dye recovery approach is given, where dye 2 pre-consumer PET material was extracted / recycled using the methods disclosed herein, and the material was removed from a 6×7 cm 2 The textile material was cut into rectangular pieces of 1:5 wt / wt. Two different commercial adsorbent materials, activated carbon and AmberLite XAD-4, were used at solid loadings of 1:5 wt / wt and 2:5 wt / wt, respectively, with respect to the ionic liquid solution. Extraction was carried out using N,N-dimethylbutylammonium hydrogen sulfate at a solid loading of 1:10 wt / wt of the textile material for various durations and at various temperatures.

[0134] Figures 14a and 14b show the absorbance of the resulting dye-rich ionic liquid solution at peak wavelengths in the visible spectrum. It can be seen that the addition of the adsorbent material to the extraction medium improves color removal, reaching near quantitative levels after 60 minutes at 150°C for 60 minutes. The successful adsorption of the dye to the adsorbent material during extraction can be seen through the significant decrease in absorbance of the dye-rich IL solution at characteristic wavelengths.

[0135] Ionic Liquid Performance The dye extraction / stripping performance of several different ionic liquid solutions in the dye recycling method disclosed herein was compared with dyed pre-consumer PET textiles. The ionic liquids compared are N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), 1-ethyl,3-methylimidazolium chloride ([emim]Cl), 1-ethyl,3-methylimidazolium bromide ([emim]Br), 1-methylimidazolium chloride ([Hmim]Cl), 1-ethyl,3-methylimidazolium ethyl sulfate ([emim][EtSO4]), 1-ethyl,3-methylimidazolium methyl sulfonate ([emim][MeSO3]), and dimethylethanolammonium formate ([DMEta][HCOO]). As disclosed herein, the method disclosed herein is not limited to use with these ionic liquid solutions, and other ionic liquid solutions may be used.

[0136] Figure 15a shows the reduction in the K / S ratio of blue pre-consumer PET using several ionic liquids with different co-solvents (co-solvents are shown, all 20 wt%). All extractions were performed at 150 °C for 30 and 60 min with a solids loading of 1:10 wt / wt. The largest difference in performance between the ionic liquids concerned the extraction kinetics, with large differences in extraction at 30 min (50-93%) but relatively small differences after 60 min (78-92%).

[0137] Figure 15b shows the reduction in the K / S ratio of blue pre-consumer PET using several ionic liquids with different water contents. All extractions were performed at 120 °C for 120 min with a solids loading of 1:10 wt / wt.

[0138] Use of organic solvents as co-solvents The ionic liquid solutions used in the methods disclosed herein, for example, N,N-dimethylbutylammonium hydrogen sulfate, may be used with an organic co-solvent.

[0139] The following example uses N,N-dimethylbutylammonium hydrogen sulfate as an ionic liquid solution to extract dyes from pre-consumer PET textiles. The co-solvents used were ethanol and acetone, and the results are compared to water as the co-solvent.

[0140] Figure 16a shows the reduction in the K / S ratio for blue pre-consumer PET extracted for 30 and 60 minutes at 150 °C with a solids loading of 1:10 wt / wt using water and ethanol as co-solvents. Replacement of water with ethanol as the co-solvent has been found to improve the extraction / stripping performance, as seen by faster kinetics of extraction due to increased solubility of the dye in a non-aqueous environment. Extraction was found to be complete after 30 minutes when using ethanol as the co-solvent, whereas the use of water as the co-solvent significantly increases extraction from 30 to 60 minutes.

[0141] Figure 16b shows the decrease in the K / S ratio for blue pre-consumer PET extracted with water and acetone as co-solvents at a solids loading of 1:10 wt / wt for 30 and 60 min at 140° C. Using acetone as a co-solvent can potentially improve the dye extraction performance with higher decolorization than water and ethanol co-solvents.

[0142] Therefore, the extraction performance can be improved in terms of decolorization rate and dye stability by using an organic solvent as a co-solvent on top of water. However, the use of organic solvents increases safety concerns in the process and reduces the environmental qualifications of the process.

[0143] Disintegration of cellulosic textiles Another route to recycle dyes from textile waste fibers considers the disintegration of textile fibers, particularly cellulosic textiles such as linen, hemp, viscose, lyocell, cotton, etc., into ionic liquid solutions. It has been found that when cellulose-rich textiles as dyed textiles in the methods disclosed herein are heated to temperatures >90°C, or more preferably >120°C, the fibers begin to disintegrate into smaller fragments and eventually into colored powder form while the dye from the textile is dispersed in the ionic liquid solution. The colored powder can then be separated from the ionic liquid, thoroughly washed with water, and dried. The colored powder can then be mechanically ground into finer particles and used as a dye to dye a new piece of textile fiber, particularly synthetic textiles where dyeing is achieved by entrapment of the dye in the swollen fibers under heat. The dye bath can be either a conventional water-based dye bath or an ionic liquid-based dye bath.

[0144] In the following examples, the dye recycling method disclosed herein was carried out using dyed post-consumer 100% linen cellulosic fabric. The dyed post-consumer linen fabric was cut and immersed in an ionic liquid solution of 80 wt% N,N dimethylbutylammonium hydrogen sulfate at 150°C for 45 minutes. The conditions were such that the fabric was disintegrated into colored powder while some of the dye was stripped into the ionic liquid solution. The colored powder was then separated from the ionic liquid, washed thoroughly with water, and dried. The colored powder was then crushed into finer particles using a pestle. The colored powder was then used as a dye to dye 100% nylon fabric at 120°C for 60 minutes with a dye concentration of 10% owf (on weight fabric; 10g dye powder / 100g fabric). Dyeing in this process can be done conventionally using a water bath or ionic liquid as the dyeing medium. The dyed nylon fabric was then washed thoroughly with water and a commercial detergent (Ariel™ 3-1 wash pod). Figure 17a shows the K / S values ​​of undyed nylon fabric and nylon dyed fabric using cellulosic coloring powder using a) water as dye bath and b) ionic liquid solution as dye bath. Both dye baths were used without the addition of auxiliary chemicals and undyed nylon fabric was used without applying any pretreatment step.

[0145] Another example is shown in Figure 17b, where 100% cotton denim was used that was immersed in an ionic liquid solution of 80 wt% N,N-dimethylbutylammonium hydrogen sulfate at 150°C for 60 minutes. This cotton powder was used as the dye (5% owf) to dye polyester fabric at 150°C for 45 minutes. Figure 17b shows the K / S ratio of undyed and freshly dyed polyester using a) water as dye bath and b) ionic liquid solution as dye bath. Undyed nylon fabric was used without the addition of auxiliary chemicals and without applying a pre-treatment step.

Claims

1. 1. A method for recycling dye from dyed textiles, comprising the steps of: Providing a textile colored with a dye; adding the textile to a bath containing a solution of an ionic liquid, thereby stripping the dye from the textile and dispersing it within the solution; wherein the concentration of the ionic liquid in the solution of ionic liquid in the stripping step is 95 wt % to 50 wt %.

2. 2. The method according to claim 1, wherein the dye is a disperse dye, an acid dye, a basic dye, a reactive dye, a vat dye, preferably the dye is a disperse dye.

3. 3. The method according to claim 1 or 2, wherein the solution of ionic liquid is a solution of a protic ionic liquid, preferably an aqueous solution of a protic ionic liquid.

4. 3. The method of claim 1 or 2, wherein the solution of ionic liquid is an aqueous ionic liquid solution or the solution of ionic liquid comprises an ionic liquid and one or more organic co-solvents which may be selected from ethanol, acetone, or dimethylsulfoxide.

5. The method of claim 1, wherein the dye is a disperse dye and the solution of the ionic liquid is an aqueous solution of a protic liquid.

6. The protic ionic liquid is (a) an ammonium-based, imidazolium-based, amino acid-based, or acetate-based protic ionic liquid; or (b) The method according to claim 3 or 5, wherein the anion is a reaction product of ammonium or imidazolium with hydrogen sulfate (HSO 4 ) or a chloride anion, such as dimethylbutylammonium hydrogen sulfate, 1-methylimidazolium hydrogen sulfate, triethylammonium hydrogen sulfate or 1-methylimidazolium chloride.

7. (a) the ionic liquid is an aprotic ionic liquid comprising 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylammonium methanehirsulfonate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methyl-imazolium chloride, 1-ethyl-3-methyl-imidazolium bromide, N.N-dimethylbutylammonium acetate, or dimethylethanolammonium formate; (b) an anion selected from carboxylates, including branched and / or halogenated carboxylates, such as hydrogen sulfate, trifluoroacetate, for example acetate, formate or propionate, alkyl sulfates, such as ethyl sulfate or methyl sulfate, alkyl sulfonates, such as methanesulfonate or ethanesulfonate, halides, such as chloride, bromide or fluoride, dicyanamide, trifluoromethylsulfonate, thiocyanate, bi(trifluoromethylsulfonyl)imide, trifluoromethylsulfonate, tetrafluoroborate, hexafluorophosphate, or amino acid-based anions, such as lysinate, serinate or alginate; or Cations selected from protic or aprotic alkylammoniums, for example, alkylammoniums such as N,N-dimethylbutylammonium, triethylammonium, tetraethylammonium, butylammonium, and dimethylethanolammonium, alkylimidazoliums such as 1-methylimidazolium, 1-ethyl,3-methylimidazolium, alkylpyridinium, and alkylpyrrolidinium, and choline. Based on; (c) The ionic liquid is selected from the group consisting of N,N-dimethylbutylammonium hydrogen sulfate, 1-methylimidazolium chloride, 1-methylimidazolium bromide, triethylammonium hydrogen sulfate, 1-ethyl,3-methylimidazolium ethyl sulfate, 1-ethyl,3-methylimidazolium methyl sulfate, N,N-dimethylbutylammonium methanesulfonate, 1-butyl,3-methylimidazolium bi(trifluoromethylsulfonyl)imide, choline hydrogen sulfate, choline chloride, 1-methylimidazolium ethyl sulfate. ammonium formate, butyl ammonium methanesulfonate, butyl ammonium trifluoroacetate, N,N-dimethylbutyl ammonium trifluoroacetate, choline hydrogen sulfate, 1-ethyl,3-methylimidazolium chloride, 1-ethyl,3-methylimidazolium bromide, 1-butyl,3-methylimidazolium chloride, 1-methylimidazolium hydrogen sulfate, 1-methylimidazolium methanesulfonate, 1-methylimidazolium methylsulfonate, or dimethylethanolammonium formate; or (d) The method of claim 1, 2 or 4, wherein the ionic liquid is triethylammonium hydrogen sulfate ([TEA][HSO 4 ]), N,N dimethyl-N-butylammonium hydrogen sulfate ([DMBA][HSO 4 ]), 1-methylimidazolium hydrogen sulfate ([HMIM][HSO 4 ]), I butylimidazolium hydrogen sulfate ([HBIM][HSO 4 ]), or 1-ethyl,3-methylimidazolium ethyl sulfate ([Emim][EthSO 4 ]).

8. (a) after the stripping step, the stripped textile is removed from the bath; (b) the textile is added to the bath for 0.5 to 3 hours, preferably 0.75 to 1.5 hours, before being removed; (c) the concentration of the ionic liquid in the ionic liquid solution in the stripping step is 85 wt % to 65 wt %, preferably 80 wt % to 70 wt %; (d) further comprising heating the solution of ionic liquid to a temperature of from 70° C. to 200° C., preferably from 100° C. to 200° C., or more preferably from 140° C. to 160° C. or from 70° C. to 120° C.; (e) the loading of dyed textile per kilogram of the ionic liquid solution is from 10 g to 500 g, preferably from 50 g to 300 g, more preferably from 100 g to 250 g; (f) the dyed textile is one or more dyed textile strips having a width of about 3 mm to 500 mm, preferably about 5 mm to 70 mm, more preferably about 10 mm to 40 mm; (g) the dyed textile is a synthetic textile comprising polyester such as polyethylene terephthalate (PET), polycotton, acrylic, nylon, or polyester blends, or a natural textile comprising cellulose such as cotton, linen, viscose, or lyocell; and / or 8. The method according to any one of claims 1 to 7, further comprising (h) cooling the solution of ionic liquid having dispersed dye therein after the stripping step to a temperature of about 10°C to 80°C, preferably to about room temperature.

9. The method further includes a dyeing step of dyeing a textile using the solution of the ionic liquid having a dye dispersed therein obtained from the stripping step, the dyeing step comprising: adding a textile to be dyed to a bath comprising a solution of an ionic liquid and a dye dispersed therein, thereby exposing the textile to the dye and dyeing the textile; (a) the loading of the textile to be dyed per kilogram of the solution may be from 10 g to 500 g, preferably from 50 g to 300 g, more preferably from 100 g to 250 g; (b) may further comprise heating the textile to be dyed and the solution of ionic liquid and dye to a temperature of from 40° C. to 200° C. for 0.25 hours to 2 hours after the textile to be dyed is added to the bath, wherein the heating of the textile to be dyed and the solution of ionic liquid and dye may comprise at least two heating steps including heating to a temperature of from 50° C. to 80° C. for 0.5 hours after the textile to be dyed is added to the bath, followed by heating to a temperature of from 100° C. to 180° C. for 0.5 hours; and / or 9. The method according to any one of claims 1 to 8, wherein the dyeing step may further comprise a hydration step in which water is added to the bath to reduce the concentration of the protic ionic liquid in the aqueous solution to 70 wt % to 10 wt %, preferably 65 wt % to 20 wt %, more preferably 60 wt % to 40 wt %, and wherein after the dyeing step, a dehydration step in which heat is applied to the bath to increase the concentration of the protic ionic liquid in the aqueous solution by evaporation to 95 wt % to 65 wt %, preferably 80 wt % to 70 wt %.

10. 10. The method of claim 9, further comprising a purification step after the dyeing step of removing residual dye from the ionic liquid solution, thereby producing a washed solution of ionic liquid, said purification step preferably comprising removing residual dye by an adsorption process, such as by using an activated carbon column process or by using an adsorbent.

11. the purification step comprising removing any residual dye from the ionic liquid solution and recovering the removed dye as a solid, preferably as a powder, using an adsorbent configured to adsorb the dye; In this case, the dye may be recovered by heating the solution of the ionic liquid in which the dye is dispersed to a temperature of 20° C. to 80° C., preferably 40° C. to 60° C., until a desired amount of the dye dispersed in the solution of the ionic liquid is adsorbed onto the adsorbent, thereby forming a dye-rich adsorbent containing the dye; The method of claim 10, further wherein the heating in the purification step may be for a period of about 12 to 48 hours, preferably 24 hours.

12. (a) the purifying step further comprises washing the dye-rich adsorbent with a solvent, thereby removing dye from the dye-rich adsorbent, wherein the solvent may be acetone; (b) the adsorbent is selected from organic adsorbents, such as activated carbon adsorbents, or polymeric adsorbents, such as commercially available activated carbon; (c) the purifying step is simultaneous with the stripping step, or after the dye has been partially stripped from the textile in the stripping step, removing the textile from the bath before the purifying step, and then reintroducing the textile into the washed solution of ionic liquid after the purifying step and using the purified solution of ionic liquid as the solution of ionic liquid to recycle the dye from the textile using the method of any one of claims 1 to 11; and / or 12. The method of claim 11, wherein (d) the recovered solid dye is used to dye a textile dyed with a water-based dyeing process or an ionic liquid-based dyeing process.

13. 13. A method according to any one of claims 9 to 12, wherein the textile to be dyed is a synthetic textile comprising polyester such as polyethylene terephthalate (PET), acrylic, nylon or a polyester blend such as polycotton, or a natural textile comprising cellulose such as cotton, viscose or lyocell.

14. 1. A method for dyeing a textile, comprising the steps of: Providing a textile; adding said textile to a bath comprising a solution of an ionic liquid obtained from the method according to any one of claims 1 to 8 and a dye dispersed therein, thereby exposing said textile to said dye and dyeing said textile; A method comprising: (a) a loading of the textile to be dyed per kilogram of the solution is from 10 g to 500 g, preferably from 50 g to 300 g, more preferably from 100 g to 250 g; (b) further comprising heating the textile to be dyed and the solution of ionic liquid and dye to a temperature of from 40° C. to 200° C. for 0.25 hours to 2 hours after the textile to be dyed is added to the bath, wherein the heating of the textile to be dyed and the solution of ionic liquid and disperse dye after the textile to be dyed is added to the bath may comprise at least two heating steps including heating to a temperature of from 50° C. to 80° C. for 0.5 hours, followed by heating to a temperature of from 100° C. to 180° C. for 0.5 hours; and / or 15. The method according to claim 14, wherein the ionic liquid solution is an aqueous ionic liquid solution, and the dyeing step further comprises a hydration step of adding water to the bath to reduce the concentration of ionic liquid in the aqueous solution to 70 wt % to 10 wt %, preferably 65 wt % to 20 wt %, more preferably 60 wt % to 40 wt %, and may further comprise a dehydration step after the dyeing step of applying heat to the bath to increase the concentration of ionic liquid in the aqueous solution by evaporation to 95 wt % to 65 wt %, preferably 80 wt % to 70 wt %.

16. 1. A method for recycling dye from dyed textiles, comprising the steps of: Providing a textile colored with a disperse dye; adding the textile to a bath containing an aqueous solution of a protic ionic liquid, thereby stripping the dye from the textile and dispersing it in the aqueous solution; removing the stripped textile from the bath; adding a textile to be dyed to the bath containing the aqueous solution comprising a protic ionic liquid and a disperse dye, thereby exposing the textile to the dye and dyeing the textile; A method comprising:

17. 1. A method for recycling dye from dyed textiles, comprising the steps of: Providing a natural textile material comprising cellulose colored with a dye; adding the textile to a bath containing a solution of an ionic liquid; heating the bath, thereby decomposing cellulosic material; A method comprising:

18. The method of claim 17, wherein the heating is performed to maintain a solution of the ionic liquid in the bath at a temperature of at least 90° C., preferably at least 150° C., more preferably from 90° C. to 300° C., and most preferably from 150° C. to 200° C.; (b) the degraded cellulosic material has a solids loading of from 10 g to 500 g / kg of the textile, preferably from 50 g to 250 g / kg of the textile; (c) removing the degraded cellulosic material from the bath and grinding the degraded cellulosic material to form a dye powder for use in dyeing textiles in a subsequent dyeing process; and / or 20. The method of claim 17, wherein (d) the dye powder is mixed with one or more other dye powders of different pigments during or after milling, thereby producing a dye powder of a desired pigment color.

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