Process and plant for removing dyes from waste textiles

Abstract

In a process for removing dyes from a waste textile material, including at least 50% by weight of polyester fibers, a batch of said textile material in an extraction chamber is extracted with a solvent that is circulated through the textile and the extraction chamber; said solution comprising solvent and extracted material is used as a solvent to extract dye from another batch of textile material, and in that said steps of extraction are repeated, until the amount of extracted material in said solution comprising solvent and extracted material reach a concentration whereby further dye extraction is impaired.

1 . A process for removing dyes from a textile material wherein said textile material includes at least 50% by weight, of polyester that is dyed, said process comprising the following steps:
 a) providing a batch of said textile material in an extraction chamber;   b) extracting said batch of said textile material with a solvent to provide a solution comprising solvent and extracted material, said extracted material including at least a dye, wherein said textile material is kept in a still condition and said solvent is circulated through said textile material textiles and said extraction chamber;   c) removing said solution of solvent and extracted material from said textile material; and   d) using said solution comprising solvent and extracted material obtained in said step b) and/or said step c) is used as a solvent to extract dye from another batch of said textile material, and in that   repeating said steps b) and c) for a preset number of cycles or until an amount of extracted material in said solution comprising solvent and extracted material reaches a concentration whereby further dye extraction is impaired.   
     
     
         2 . The process according to  claim 1 , wherein at least part of said polyester is dyed with at least one disperse dye or dope-dyed, said textile material is a waste textile material selected from the group consisting of fibers, fiber tufts, filaments, yarns, fabrics, clippings of fabrics, garments, clippings of garments and mixtures thereof, and said textile material is pressed in said extraction chamber or in a basket housed in said extraction chamber. 
     
     
         3 . The process according to  claim 1 , wherein said step c) includes a step of separating said solution comprising solvent and extracted material from said textile by centrifuging, wherein said step c) is carried out in a centrifuge, and said extraction chamber is configured to operate as centrifuge. 
     
     
         4 . The process according to  claim 3 , wherein, after said step c), solvent is fed to the centrifugated textile material present in said centrifuge and a washing step of said textile material is carried out in said centrifuge to remove dyes from said centrifugated textile material. 
     
     
         5 . The process according to  claim 1 , wherein said extraction chamber is a first extraction chamber, and wherein said textile material, after a first said extraction step b), is fed from said first extraction chamber to a first centrifuge for a first removal step c), from said first centrifuge to a second extraction chamber for a second extraction step b) and from said second extraction chamber to a second centrifuge for a second removal step c),
 whereby said first and second extraction steps b) and removal steps c) are carried out in two different extraction chambers and two different centrifuges, respectively.   
     
     
         6 . The process according to  claim 5 , wherein the solvent removed from said second extraction chamber and/or said second centrifuge, is fed to said first extraction chamber. 
     
     
         7 . The process according to  claim 1 , wherein said steps b) and c) are repeated more than twice in more than two extraction chambers and centrifuges, and wherein the solvent removed from any said extraction chamber except a first said extraction chamber, is fed to a previous extraction chamber such that said removed solvent used in said step b) is in the form of a solution comprising solvent and an extracted material, said extracted material including at least a dye. 
     
     
         8 . The process according to  claim 1 , wherein said solvent comprises DMF or DMAC or a mixture of DMF or DMAC with alkali water, or mixtures thereof and the temperature of said solvent or said solution comprising solvent and extracted material in said extraction chamber, is in the range of 80° C. to 140° C. 
     
     
         9 . The process according to  claim 1 , wherein a bath ratio textile/solvent (kg/liters) is in a range of 1/3 to 1/20. 
     
     
         10 . The process according to  claim 1 , wherein said step c) is carried out in a centrifuge at a g-force in the range of from 250 to 5000 for a time in the range of from 0.5 to 10 minutes. 
     
     
         11 . The process according to  claim 1 , wherein said textile material comprises polyester fibers and further comprises at least a polyurethane material; said textile material comprising at least 90% by weight of said polyester fibers and at most 10% by weight of polyurethane fibers, wherein at least part of said polyester fibers is dyed with at least one disperse dye, said solvent is DMF, and the temperature of said solvent or said solution comprising solvent and extracted material in said extraction chamber is in the range of from 85° C. to 105° C. 
     
     
         12 . The process according to  claim 1 , wherein said textile material comprises polyester fibers and further comprises at least cellulosic cotton fibers, said textile material comprising at least 50%, by weight of said polyester fibers and at most 50%, by weight of said cellulosic cotton fibers, wherein at least part of said polyester fibers is dyed with at least one disperse dye and wherein at least part of said cellulosic cotton fibers is dyed with at least a dye selected from the group consisting of vat dyes, reactive dyes, pigments, direct dyes and sulfur dyes, wherein said solvent is a mixture of DMF and water comprising at least one base, and wherein the temperature of said solvent or said solution comprising solvent and extracted material in said extraction chamber and optionally in said washing step is in a range of 85° C. to 110° C. 
     
     
         13 . The process according to  claim 1 , wherein said textile material comprises polyester fibers and further comprises at least elastane and cotton fibers,
 wherein said textile material comprises at least 50% by weight of said polyester fibers and at most 50% by weight of said cotton fibers and elastane fibers, wherein at least part of said polyester fibers is dyed with at least one disperse dye and wherein at least part of said cotton fibers is dyed with at least a dye selected from the group consisting of vat dyes, reactive dyes, pigments, direct dyes and sulfur dyes, wherein said solvent is a mixture of DMF and water comprising a base and at least one reducing agent, wherein the temperature of said solvent or said solution comprising solvent and extracted material in said extraction chamber and is in a range of 95° C. to 105° C.   
     
     
         14 . The process process according to  claim 1 , wherein said solution obtained in said step b) and/or in said step c) is used as the solvent to extract dye from another batch of textile material, and in that said steps b) and c) are repeated using said solution as said solvent up to 40 times. 
     
     
         15 . An apparatus for removing dyes from a textile material in a process according to  claim 1 , said apparatus comprising:
 at least one said extraction chamber ( 2 ) configured to treat said textile material with said solvent,   a pump (P) adapted to circulate said solvent through said extraction chamber ( 2 ) and said waste textile material,   at least a centrifuge ( 3 ) for separating said solution comprising solvent and extracted material from said textile material,   at least one fresh solvent storage tank ( 6 ), and   at least one distillation device ( 5 ),   wherein said at least one fresh solvent storage tank ( 6 ) is configured to feed said fresh solvent to said extraction chamber ( 2 ), and configured to receive said solvent from said distillation device ( 5 ), and   said distillation device ( 5 ) is configured to receive said solution comprising solvent and extracted material from said extraction chamber ( 2 ) and/or from said centrifuge ( 3 ), to separate said extracted material from said solvent.   
     
     
         16 . The apparatus according to  claim 15 , wherein said apparatus comprises:
 a plurality of said extraction chambers ( 2   a - 2   d ) and a plurality of said centrifuges ( 3   a - 3   d ), wherein said extraction chambers ( 2   a - 2   d ) and said centrifuges ( 3   a - 3   d ) are arranged in a series; and   means for feeding said textile material along said series of extraction chambers ( 2   a - 2   d ) and centrifuges ( 3   a - 3   d ) to provide a flow of said textile material textiles, wherein at least one said centrifuge ( 3 ) is connected, directly or indirectly, with one said extraction chamber ( 2 ) upstream with respect to the flow of said textile material and is connected to a further said extraction chamber ( 2 ) downstream with respect to said flow of said textile material.   
     
     
         17 . The apparatus according to  claim 15 , wherein each said extraction chamber is connected to a previous extraction chamber with solvent feeding means configured to feed said solution comprising solvent and extracted material exiting from each extraction chamber to said previous extraction chamber and wherein only a last extraction chamber of said extraction chambers of said series is connected to said fresh solvent storage tank, said fresh solvent storage tank configured to feed said solvent to said last extraction chamber only. 
     
     
         18 . The apparatus according to  claim 15 , further comprising at least one storage tank ( 7   a - 7   d ), configured to receive said textile material from said extraction chamber ( 2 ) and to feed said textile material to said centrifuge ( 3 ),
 wherein said extraction chamber ( 2 ) is configured to operate as said centrifuge.   
     
     
         19 . An apparatus for removing dyes from a textile, comprising:
 at least one extraction chamber ( 2 ) configured to treat a waste textile material with a solvent,   a pump (P) for circulating said solvent through said extraction chamber ( 2 ) and said waste textile material,   at least a centrifuge ( 3 ) for separating a solution comprising said solvent and extracted material from said textile material, and   at least one fresh solvent storage tank ( 6 ) and at least one distillation device ( 5 ), wherein said at least one fresh solvent storage tank ( 6 ) is configured to feed fresh solvent to said   at least one extraction chamber ( 2 ) and configured to receive said solvent from said at least one distillation device ( 5 ),   wherein said at least one distillation device ( 5 ) is configured to receive said solution comprising said solvent and said extracted material from said extraction chamber ( 2 ) and/or said centrifuge ( 3 ), to separate said extracted material from said solvent;   said apparatus further comprising at least one storage tank ( 7   a - 7   d ), configured to receive said waste textile material from said extraction chamber ( 2 ) and to feed said textile material to said centrifuge ( 3 ).   
     
     
         20 . The apparatus according to  claim 19 , wherein said extraction chamber ( 2 ) is configured to operate as said centrifuge ( 3 ).