Colorant Removal from Polymeric Fibers

Abstract

Novel organic compositions for removing dyes from the surface of polymeric fibers are disclosed. The method for dye removal from the surface of fibers includes contacting the fibers with a non-aqueous ester stripping composition preferably containing at least one cyclic ester and optionally containing a surfactant, an alcohol, or both. The process of the present invention is especially useful for removing color from dyed polyamide fibers as part of a recycling process for such materials.

1 . A process for removing colorants from surface-dyed polyamide fibers comprising: 
 (a) contacting said fibers with an organic solvent stripping composition containing at least one cyclic ester at an elevated temperature; and    (b) separating the fibers from at least a portion of the solvent stripping composition containing dissolved dye.    
   
   
       2 . The process of  claim 1  wherein the solvent stripping composition containing at least one cyclic ester is ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof.  
   
   
       3 . The process of  claim 1  wherein the solvent stripping composition further contains an alcohol from the group of C.sub.7 to C.sub.12 alcohols, or mixtures thereof, in addition to at least one cyclic ester.  
   
   
       4 . The process of  claim 1  wherein the solvent stripping composition is present in an amount of at least about 200% by weight of the polyamide fibers.  
   
   
       5 . The process of  claim 2  wherein the solvent stripping composition is propylene carbonate.  
   
   
       6 . The process of  claim 1  wherein the solvent stripping composition is substantially non-reactive with the dyes.  
   
   
       7 . The process of  claim 1  wherein the solvent stripping composition further comprises a surfactant.  
   
   
       8 . The process of  claim 5  wherein the contacting is conducted at a temperature between about 130 degrees Celsius and about 220 degrees Celsius.  
   
   
       9 . The process of  claim 1  wherein the stripping composition contains decomposition products of poly(ethylene terephthalate) formed by heating poly(ethylene terephthalate) in the presence of a cyclic ester to a temperature above about 215 degrees Celsius.  
   
   
       10 . The process of  claim 1  wherein the stripping composition contains poly(ethylene terephthalate).  
   
   
       11 . A process for removing colorants from the surface of a polyamide material comprising: 
 (a) contacting the polyamide material with a first ester stripping composition at a temperature up to about the boiling temperature of the first ester stripping composition but without substantial dissolution or degradation of the polyamide material;    (b) separating the polyamide material from at least a portion of the first ester stripping composition; and    (c) contacting the polyamide material with a second ester stripping composition at a temperature up to about the boiling temperature of the second stripping composition.    
   
   
       12 . The process of  claim 11  wherein in step (a) the first ester stripping composition is composed exclusively of ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof.  
   
   
       13 . The process of  claim 11  wherein in step (c) the second ester stripping composition is composed exclusively of ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof.  
   
   
       14 . The process of  claim 12  wherein the first ester stripping composition is present in an amount of at least about 200% by weight of the polyamide material.  
   
   
       15 . The process of  claim 11  wherein in step (a) the first ester stripping composition contains a cyclic ester and decomposition products of poly (ethylene terephthalate) formed by heating poly(ethylene terephthalate) in the presence of a cyclic ester to a temperature above about 215 degrees Celsius.  
   
   
       16 . The process of  claim 13  wherein the second ester stripping composition is composed exclusively of propylene carbonate.  
   
   
       17 . The process of  claim 11  wherein in step (a) the first ester stripping composition further comprises a surfactant.  
   
   
       18 . The process of  claim 11  wherein in step (a) the polyamide material is contacted with the first ester stripping composition at a temperature between about 130 degrees Celsius and about 200 degrees Celsius.  
   
   
       19 . The process of  claim 11  wherein in step (a) the first ester stripping composition contains propylene carbonate and the methyl ester of soybean oil.  
   
   
       20 . The process of  claim 11  wherein in step (c) the second ester stripping composition contains a cyclic ester and decomposition products of poly(ethylene terephthalate) formed by heating poly(ethylene terephthalate) in the presence of a cyclic ester to a temperature above about 215 degrees Celsius.  
   
   
       21 . The process of  claim 11  wherein in step (a) the first ester stripping composition contains poly(ethylene terephthalate).  
   
   
       22 . A process for removing a colorant from the surface of polyamide material comprising: 
 (a) contacting the polyamide material with an ester composition under conditions sufficient to promote substantial release of the colorant from the surface of the polyamide material into the ester composition; and    (b) separating the polyamide material from at least a portion of the ester composition containing released colorant through centrifugation, sedimentation, filtration, or combinations thereof.    
   
   
       23 . The process of  claim 22  wherein in step (a) the ester composition contains ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof.  
   
   
       24 . The process of  claim 23  wherein in step (a) the ester composition further contains one or more C.sub.7 to C.sub.12 alcohols.  
   
   
       25 . The process of  claim 22  wherein the ester composition is present in an amount of at least about 400% by weight of the polyamide.  
   
   
       26 . The process of  claim 23  wherein the ester composition further contains decomposition products of poly(ethylene terephthalate) formed by heating poly(ethylene terephthalate) in the presence of propylene carbonate to a temperature above about 215 degrees Celsius.  
   
   
       27 . The process of  claim 22  wherein the ester composition further contains a methyl ester of a vegetable oil.  
   
   
       28 . The process of  claim 22  wherein in step (a) the contacting is conducted at a temperature up to the boiling temperature of the ester composition.  
   
   
       29 . The process of  claim 22  further comprising: 
 (a) cooling the ester composition containing released colorant to precipitate the released colorant from the ester composition; and    (b) separating the precipitated colorant from the ester composition through centrifugation, sedimentation, filtration, or combinations thereof.    
   
   
       30 . A process for recycling colored polyamide fibers from post consumer carpet comprising: 
 (a) separating polyamide face fibers from carpet backing by shearing, cutting with a hot wire, cutting with a laser, or other means;    (b) contacting said face fibers with an organic ester composition containing at least one cyclic ester under conditions sufficient to substantially remove the colorant from the surface of the polyamide fibers without substantial dissolution or degradation of the polyamide; and    (c) separating the polyamide fibers from at least a portion of the ester composition containing colorant.    
   
   
       31 . The process of  claim 30  wherein in step (b) the contacting is carried out at a temperature of between about 130 degrees Celsius and about 220 degrees Celsius.  
   
   
       32 . The process of  claim 30  wherein in step (b) the ester composition containing at least one cyclic ester contains propylene carbonate and the decomposition products of poly(ethylene terephthalate) formed by heating poly (ethylene terephthalate) in the presence of propylene carbonate to a temperature above about 215 degrees Celsius.