Chemical compounds and methods for removing dye

Abstract

Chemical compounds and methods for removing dye from polyester fibers, in particular poly(ethylene terephthalate) (“PET”) fibers, is disclosed. The compounds and methods are particularly useful for removing dye from panel fabric made from recycled PET fibers. The method involves contacting the PET with a dye removal compound in a sealable vessel. The contents of the vessel are agitated and heated to achieve an increase in pressure and temperature. Following a cooling down period, the PET is removed and rinsed with water. The dye removal compound includes an aqueous solution of at least one leveling agent.

1 . A method for removing dye from polyester comprising: 
 a) contacting the polyester with a dye removal composition comprising an aqueous solution of at least one leveling agent to form a mixture;    b) heating the mixture until it reaches an elevated temperature and a pressure higher than the equilibrium pressure of the dye removal composition at the elevated temperature;    c) maintaining the mixture at the elevated temperature and pressure for a time interval sufficient to at least partially remove dye from the polyester;    d) cooling the mixture;    e) separating the polyester from the mixture; and    f) removing any residual dye removal composition from the polyester.    
     
     
         2 . The method of  claim 1  wherein the dye removal composition further comprises at least one chemical selected from the group consisting of scouring agents, wetting agents and leveling carriers.  
     
     
         3 . The method of  claim 1  wherein the leveling agent is selected from the group consisting of anionic leveling agents, nonionic leveling agents and mixtures thereof.  
     
     
         4 . The method of  claim 3  wherein the leveling agent is selected from the group consisting of alkyl polyglycol ether, isopropyl alcohol, n-butyl phthalimide, nonyl phenol ethoxylate and combinations thereof.  
     
     
         5 . The method of  claim 2  wherein the scouring agent or wetting agent is nonionic.  
     
     
         6 . The method of  claim 5  wherein the nonionic scouring agent or wetting agent is selected from the group consisting of polyoxyethene ethers.  
     
     
         7 . The method of  claim 2  wherein the leveling carrier comprises a nonionic leveling carrier.  
     
     
         8 . The method of  claim 7  wherein the nonionic leveling carrier comprises alkyl phthalimide.  
     
     
         9 . The method of  claim 2  wherein the dye removal composition comprises isopropyl alcohol, n-butyl phthalimide, nonyl phenol ethoxylate, propylene glycol ether and combinations thereof.  
     
     
         10 . The method of  claim 1  wherein the dye removal composition comprises an aqueous solution of about 0.5 wt % to about 8.0 wt % of leveling agent, based on the total dye removal composition.  
     
     
         11 . The method of  claim 10  wherein the dye removal composition comprises an aqueous solution of about 2.0 wt % to about 8.0 wt %/o of leveling agent, based on the total dye removal composition.  
     
     
         12 . The method of  claim 11  wherein the dye removal composition comprises an aqueous solution of about 4.0 wt % to about 8.0 wt % leveling agent, based on the total dye removal composition.  
     
     
         13 . The method of  claim 1  wherein the mixture is agitated for about 120 minutes during one or more of the contacting, heating or maintaining steps.  
     
     
         14 . The method of  claim 1  wherein the mixture is maintained at a pressure of about 28 psi to about 39 psi.  
     
     
         15 . The method of  claim 14  wherein the mixture is maintained at a pressure of about 33 psi.  
     
     
         16 . The method of  claim 1  wherein the mixture is heated to a temperature of from about 135° C. to about 145° C.  
     
     
         17 . The method of  claim 16  wherein the mixture is maintained at the elevated temperature about 140° C.  
     
     
         18 . The method of  claim 1  wherein the mixture is maintained at the elevated temperature for a period of about 30 minutes to about 60 minutes.  
     
     
         19 . The method of  claim 18  wherein the mixture is maintained at the elevated temperature for about 45 minutes.  
     
     
         20 . The method of  claim 1  wherein the mixture is cooled over a period of about 20 minutes to about 40 minutes.  
     
     
         21 . The method of  claim 1  wherein the mixture is cooled to a temperature of about 20° C. to about 50° C.  
     
     
         22 . The method of  claim 21  wherein the mixture is cooled to a temperature of about 30° C.  
     
     
         23 . The method of  claim 1  wherein the polyester comprises polyester obtained from panel fabric.  
     
     
         24 . The method of  claim 23  wherein the panel fabric has been garnetted into loose fibers.  
     
     
         25 . The method of  claim 1  wherein the method is carried out in a sealable vessel.  
     
     
         26 . The method of  claim 1  wherein the method is carried out as a batch process.  
     
     
         27 . The method of  claim 1  wherein the polyester comprises poly(ethylene terephthalate) (“PET”).  
     
     
         28 . A method for removing dye from PET comprising: 
 a) contacting the PET with a dye removal composition comprising an aqueous solution of one or more of propylene glycol ether, isopropyl alcohol, n-butyl phthalimide and nonyl phenol ethoxylatein to form a mixture;    b) heating the mixture for about 120 minutes;    c) maintaining the temperature of the mixture at about 140° C. and the pressure at about 33 psi for a time sufficient to at least partially remove dye from the PET;    d) cooling the mixture to 30° C. over a period of about 20 minutes to 40 minutes;    e) separating the PET from the mixture; and    f) rinsing the PET with water.    
     
     
         29 . A composition for removing dye from polyester comprising an aqueous solution of about 2.0 wt % to about 8.0 wt % of at least one leveling agent, based on the total composition.  
     
     
         30 . The composition of  claim 29  wherein the composition comprises an aqueous solution of about 4.0 wt % to about 8.0 wt % of leveling agent, based on the total composition.  
     
     
         31 . The composition of  claim 29  further comprising at least one chemical selected from the group consisting of scouring agents, wetting agents and leveling carriers.  
     
     
         32 . The composition of  claim 29  further comprising at least one leveling agent selected from the group consisting of anionic leveling agents, nonionic leveling agents and mixtures thereof.  
     
     
         33 . The composition of  claim 32  wherein the leveling agent is selected from the group consisting of alkyl polyglycol ether, isopropyl alcohol, n-butyl phthalimide and nonyl phenol ethoxylate.  
     
     
         34 . The composition of  claim 31  wherein the scouring agent or wetting agent is nonionic.  
     
     
         35 . The composition of  claim 34  wherein the nonionic scouring agent or wetting agent is selected from the group consisting of polyoxyethene ethers.  
     
     
         36 . The composition of  claim 31  wherein the leveling carrier comprises a nonionic leveling carrier.  
     
     
         37 . The composition of  claim 36  wherein the nonionic leveling carrier comprises alkyl phthalimide.  
     
     
         38 . The composition of  claim 31  wherein the composition comprises isopropyl alcohol, n-butyl phthalimide, nonyl phenol ethoxylate, and propylene glycol ether.  
     
     
         39 . The composition of  claim 29  wherein the polyester comprises PET.  
     
     
         40 . A device for removing dye from polyester, comprising: 
 a sealable vessel; and    a dye removal composition disposed therein, the dye removal composition comprising an aqueous solution of about 2.0 wt % to about 8.0 wt % of at least one leveling agent, based on the total dye removal composition.    
     
     
         41 . The device of  claim 40 , wherein the dye removal composition comprises an aqueous solution of about 4.0 wt % to about 8.0 wt % leveling agent.  
     
     
         42 . The device of  claim 40  wherein the dye removal composition further comprises at least one chemical selected from the group consisting of scouring agents, wetting agents and leveling carriers.  
     
     
         43 . The device of  claim 40  wherein the dye removal composition comprises at least one leveling agent selected from the group consisting of anionic leveling agents, nonionic leveling agents and mixtures thereof.  
     
     
         44 . The device of  claim 43  wherein the dye removal composition comprises at least one leveling agent selected from the group consisting of alkyl polyglycol ether, isopropyl alcohol, n-butyl phthalimide and nonyl phenol ethoxylate.  
     
     
         45 . The device of  claim 42  wherein the scouring agent or wetting agent is nonionic.  
     
     
         46 . The device of  claim 45  wherein the nonionic scouring agent or wetting agent is selected from the group consisting of polyoxyethene ethers.  
     
     
         47 . The device of  claim 42  wherein the leveling carrier comprises a nonionic leveling carrier.  
     
     
         48 . The device of  claim 47  wherein the nonionic leveling carrier comprises alkyl phthalimide.  
     
     
         49 . The device of  claim 40  wherein the dye removal composition comprises one or more of isopropyl alcohol, n-butyl phthalimide, nonyl phenol ethoxylate and propylene glycol ether.  
     
     
         50 . The device of  claim 40  wherein the polyester comprises PET.  
     
     
         51 . A method for recycling panel fabric comprising polyester, the method comprising: 
 a) removing from the fabric any structural elements;    b) removing dye from the fabric using the method of  claim 1;     c) recovering the polyester;    d) melting the polyester;    e) pelletizing the melted polyester; and    f) extruding the resulting pellets into full-length fiber.    
     
     
         52 . The method of  claim 51  wherein the contacting takes place in a sealable vessel and the residual dye removal composition is removed by rinsing with water.  
     
     
         53 . The method of  claim 51  wherein the dye removal composition further comprises at least one chemical selected from the group consisting of scouring agents, wetting agents and leveling carriers.  
     
     
         54 . The method of  claim 53  wherein the dye removal composition comprises isopropyl alcohol, n-butyl phthalimide, nonyl phenol ethoxylate, and propylene glycol ether.  
     
     
         55 . The method of  claim 51  wherein the polyester comprises PET.