Dye recycling methods

Abstract

A method for recycling dye from a dyed textile, the method comprising providing a textile coloured with a dye; adding the textile to a bath comprising a solution of ionic liquid, thereby causing the dye to strip from the textile and to disperse within said solution.

1 . A method for recycling dye from a dyed textile, the method comprising the following steps:
 providing a textile coloured with a dye;   adding the textile to a bath comprising a solution of ionic liquid, thereby causing the dye to strip from the textile and to disperse within said solution.   
     
     
         2 . The method of  claim 1 , wherein the dye is a disperse dye, an acid dye, a basic dye, a reactive dye, or a vat dye. 
     
     
         3 . The method of  claim 1 , wherein the solution of ionic liquid is a solution of protic ionic liquid. 
     
     
         4 . The method of  claim 1 , wherein the solution of ionic liquid is an aqueous ionic liquid solution, or the solution of ionic liquid comprises ionic liquid and one or more organic co-solvents. 
     
     
         5 . The method of  claim 4 , wherein the organic co-solvents are selected from ethanol, acetone, or dimethyl sulfoxide. 
     
     
         6 . A method for recycling dye from a dyed textile, the method comprising the following steps:
 providing a textile coloured with a dye, said dye being a disperse dye;   adding the textile to a bath comprising a solution of ionic liquid, thereby causing the dye to strip from the textile and to disperse within said solution, wherein said solution of ionic liquid is an aqueous solution of protic liquid.   
     
     
         7 . The method of  claim 6 , wherein the protic ionic liquid is an ammonium-based, imidazolium based, amino acid based, or an acetate based protic ionic liquid. 
     
     
         8 . The method of  claim 6 , wherein the protic ionic liquid is the reaction product of ammonium or imidazolium with hydrogen sulfate (HSO 4 ) or chloride anions. 
     
     
         9 . The method of  claim 1 , wherein the ionic liquid is an aprotic ionic liquid comprising 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylammonium metanehylsulfonate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methyl-imazodlium chloride, 1-ethyl-3-methyl-imidazolium bromide, N.N-dimethylbutylammonium acetate, or dimethylethanolammonium formate. 
     
     
         10 . The method of  claim 1 , wherein the ionic liquid is based on anions selected from: hydrogen sulfate, a carboxylate, alkylsulfonates, a halide, or amino acid-based anions; or
 cations selected from: protic or aprotic alkylammoniums, alkylimidazolium, alkylpyridinium, alkylpyrrolidinium, or choline.   
     
     
         11 . The method of  claim 1 , wherein the ionic liquid comprises 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, Butylammonium methanesulfonate, Butylammonium trifluoroacetate, N,N-dimethylbutylammonium 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 methyl sulfate, or Dimethylethanolammonium formate. 
     
     
         12 . The method of  claim 1 , 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 ]). 
     
     
         13 . The method of  claim 1 , wherein after the stripping step the stripped textile is removed from the bath. 
     
     
         14 . The method of  claim 1 , wherein the textile is added to the bath for 0.5-3 hours, before it is removed. 
     
     
         15 . The method of  claim 1 , wherein the concentration of the ionic liquid in the solution of ionic liquid in the stripping step is 95 wt % -50 wt %. 
     
     
         16 . The method of  claim 1 , further comprising heating the solution of ionic liquid to a temperature of 70° C. to 200° C. 
     
     
         17 . The method of  claim 1 , wherein the loading of dyed textile per kilogram of the solution of ionic liquid is 10 g-500 g. 
     
     
         18 . The method of  claim 1 , wherein the dyed textile is one or more dyed textile strips around 3 mm-500 mm wide. 
     
     
         19 . The method of  claim 1 , wherein the dyed textile is a synthetic textile comprising a polyester, a polycotton, an acrylic, nylon, or polyester blends, or is a natural textile comprising cellulose. 
     
     
         20 . The method of  claim 1 , further comprising cooling the solution of ionic liquid with dye dispersed therein after the stripping step to a temperature of around 10° C.-80° C. 
     
     
         21 . The method of  claim 1 , further comprising a dyeing step where the solution of ionic liquid with dye dispersed therein obtained from the stripping step is used to dye a textile, the dyeing step comprising:
 adding a textile to be dyed to the bath comprising the solution of ionic liquid and dye dispersed therein, thereby exposing the textile to the dye and dyeing the textile.   
     
     
         22 . The method of  claim 21 , wherein the loading of textile to be dyed per kilogram of the solution is 10 g-500 g. 
     
     
         23 . The method of  claim 21 , further comprising heating the textile to be dyed and the solution of ionic liquid and dye to a temperature of 40° C.-200° C. for 0.25 hours-2 hours once the textile to be dyed has been added to the bath. 
     
     
         24 . The method of  claim 23 , wherein the heating of the textile to be dyed and the solution of ionic liquid and dye comprises at least two heating steps comprising heating to a temperature of 50° C.-80° C. for 0.5 hours followed by 100° C.-180° C. for 0.5 hours once the textile to be dyed has been added to the bath. 
     
     
         25 . The method of  claim 21 , the dyeing step further comprising a hydrating step of adding water to the bath to reduce the concentration of protic ionic liquid in the aqueous solution to 70 wt %-10 wt %. 
     
     
         26 . The method of  claim 25 , further comprising a dehydration step after the dyeing step wherein heat is applied to the bath to increase the concentration of protic ionic liquid in the aqueous solution through evaporation to 95 wt %-65 wt %. 
     
     
         27 . The method of  claim 21 , wherein after the dyeing step the method further comprises a clean-up step of removing any remaining dye from the solution of ionic liquid thereby producing a cleaned solution of ionic liquid. 
     
     
         28 . The method of  claim 27 , wherein the clean-up step comprises removing any remaining dye from the solution of ionic liquid and recovering said removed dye as a solid, using an adsorbent configured to adsorb said dye. 
     
     
         29 . The method of  claim 28 , wherein the dye is recovered by heating the solution of ionic liquid with dye dispersed therein to a temperature of 20° C.-80° C., until a desired amount of the dye dispersed in the solution of ionic liquid has adsorbed into the adsorbent, thereby forming a dye-rich adsorbent comprising dye. 
     
     
         30 . The method of  claim 29 , wherein the heating in the clean-up step is for a time period of around 12-48 hours. 
     
     
         31 . The method of  claim 28 , the clean-up step further comprising washing the dye-rich adsorbent with a solvent, thereby removing dye from the dye-rich adsorbent. 
     
     
         32 . The method of  claim 31 , wherein the solvent is acetone. 
     
     
         33 . The method of  claim 28 , wherein the adsorbent is selected from an organic adsorbent. 
     
     
         34 . The method of  claim 28 , wherein the clean-up step is simultaneous to the stripping step. 
     
     
         35 . The method of  claim 28 , further comprising removing the textile from the bath after dye has been partially stripped therefrom in the stripping step and before the clean-up step, and then re-introducing said textile to the cleaned solution of ionic liquid after the clean-up step. 
     
     
         36 . The method of  claim 28 , wherein the recovered solid dye is used to dye a textile to be dyed in a water-based dyeing or ionic liquid-base dyeing process. 
     
     
         37 . The method of  claim 21 , wherein the textile to be dyed is a synthetic textile comprising a polyester. 
     
     
         38 . A method of dyeing a textile, the method comprising the steps:
 providing a textile;   adding the textile to a bath, the bath comprising a solution of ionic liquid and a dye dispersed therein obtained from the method of  claim 1 , thereby exposing the textile to the dye and dyeing the textile.   
     
     
         39 . The method of  claim 38 , wherein the loading of the textile to be dyed per kilogram of the solution is 10 g-500 g. 
     
     
         40 . The method of  claim 38  or  claim 39 , further comprising heating the textile to be dyed and the solution of ionic liquid and dye to a temperature of 40° C.-200° C. for 0.25 hours-2 hours once the textile to be dyed has been added to the bath. 
     
     
         41 . The method of  claim 40 , wherein the heating of the textile to be dyed and the solution of ionic liquid and dispersed dye comprises at least two heating steps comprising heating to a temperature of 50° C.-80° C. for 0.5 hours followed by 100° C.-180° C. for 0.5 hours once the textile to be dyed has been added to the bath. 
     
     
         42 . The method of  claim 38 , wherein the ionic liquid solution is an aqueous ionic liquid solution and the dyeing step further comprising
 a hydrating step of adding water to the bath to reduce the concentration of ionic liquid in the aqueous solution to 70 wt %-10 wt %; and optionally   a dehydration step after the dyeing step wherein heat is applied to the bath to increase the concentration of ionic liquid in the aqueous solution through evaporation to 95 wt %-65 wt %.   
     
     
         43 . A method for recycling dye from a dyed textile, the method comprising the following steps:
 providing a textile coloured with disperse dye;   adding the textile to a bath comprising an aqueous solution of protic ionic liquid, thereby causing the dye to strip from the textile and to disperse within the aqueous solution;   removing the stripped textile from the bath; and   adding a textile to be dyed to the bath comprising the aqueous solution comprising protic ionic liquid and dispersed dye, thereby exposing the textile to the dye and dyeing the textile.   
     
     
         44 . A method for recycling dye from a dyed textile, the method comprising the following steps:
 providing a natural textile material comprising cellulose coloured with a dye;   adding the textile to a bath comprising a solution of ionic liquid; and   heating the bath, thereby causing the cellulosic material to break down.   
     
     
         45 . The method of  claim 44 , wherein the heating is carried out to maintain the solution of ionic liquid in the bath at a temperature of at least 90° C. 
     
     
         46 . The method of  claim 44 , wherein the broken down cellulosic material has a solid loading of 10 g-500g per kg of the textile. 
     
     
         47 . The method of  claim 44 , further comprising removing the broken down cellulosic material from the bath and milling said broken down cellulosic material to form a dye powder for use in dyeing a textile in a subsequent dyeing process. 
     
     
         48 . The method of  claim 44 , wherein the dye powder is mixed, during or after milling, with one or more other dye powders of different pigment, thereby creating a dye powder of a desired pigment colour.