Method and apparatus for dyeing cellulosic textile substrates with a leuco-state dye

Abstract

An apparatus for dyeing a cellulosic textile substrate with reduced indigo dye in a leuco-state in an inert atmosphere substantially isolated from oxidizing substances. A plurality of applicator faces that each apply a portion of the total dye application. The first foam applicator is spaced from the entrance of the chamber to allow air entrapped in the interstices of the substrate to escape. The applicators are spaced from each other to allow collapse of the foam and dispersion of the dye applied in the previous applicator before the substrate reaches the next applicator. Similarly, the exit is spaced from the last applicator to allow the foam to collapse and the dye to disperse prior to exiting the apparatus and entering the atmosphere in which oxidization of the dye occurs.

1 . An apparatus for dyeing a traveling cellulosic textile substrate with a dye in leuco-state applied in a foam condition, comprising: 
 a housing having an interior chamber sealed from atmospheric air and through which said substrate travels from an entrance having a seal through which said substrate enters said chamber to an exit having a seal through which said substrate exists said chamber;    a supply of inert gas communicating with said chamber to provide an inert environment therein;    at least one foam applicator having an applicator face in said chamber and extending across the width of said substrate for applying foam containing said dye in leuco-state to said substrate in said chamber; and    a source of foam containing said leuco-state dye in the absence of any significant amount of oxygen, said foam generator communicating with said applicator for supplying said foamed leuco-state dye to said applicator.    
   
   
       2 . The apparatus of  claim 1 , characterized further in that said foam contains a small controlled amount of oxygen.  
   
   
       3 . The apparatus of  claim 1 , characterized further in that said supply of inert gas is under pressure to provide a pressurized inert environment in said chamber.  
   
   
       4 . The apparatus of  claim 1  characterized further in that said at least one applicator is spaced from said entrance to provide a free reach of said substrate in which air trapped in the interstices of said substrate is allowed to escape.  
   
   
       5 . The apparatus of  claim 1  characterized further in that said at least one applicator is spaced from said exit to allow foam on the substrate to collapse and deposit the leuco-state dye on said substrate before the substrate exits said chamber and is exposed to air.  
   
   
       6 . The apparatus of  claim 3  characterized further in that said at least one applicator is spaced from said exit to allow foam on the substrate to collapse and deposit the leuco-state dye onto said substrate before the substrate exits said chamber and is exposed to air.  
   
   
       7 . The apparatus of  claim 1  characterized in that said at least one applicator comprises a plurality of applicators disposed with spaces therebetween to allow foam to at least partially collapse and said leuco-state dye to at least partially deposit on said substrate before having foam applied by the following applicator.  
   
   
       8 . The applicator of  claim 7  characterized further by hold-down elements between said applicators for engaging said substrate to displace the substrate between applicators to maintain said substrate in foam receiving engagement with said applicator faces.  
   
   
       9 . The apparatus of  claim 1  characterized further in that said at least one applicator is parabolically shaped for uniform distribution of foam across the width of said substrate.  
   
   
       10 . The apparatus of  claim 7  characterized further in that said at least one applicator comprises a plurality of said parabolically shaped applicators disposed with spaces therebetween to allow foam to at least partially collapse and said leuco-state dye to at least partially deposit on said substrate before having foam applied by the following applicator.  
   
   
       11 . The applicator of  claim 10  characterized further by hold-down elements between said applicators for engaging said substrate to displace the substrate between applicators to maintain said substrate in foam receiving engagement with said applicators.  
   
   
       12 . The apparatus of  claim 1  characterized further in that said inert gas comprises nitrogen and said foam generator generates a foam primarily of nitrogen containing said leuco-state dye with said nitrogen contributing to the nitrogen contained in said chamber when said foam collapses.  
   
   
       13 . The apparatus of  claim 1  characterized in that said textile substrate is woven denim fabric and said leuco-state dye is indigo dye applied at a weight as little as approximately 10% to 15% of the weight of the fabric.  
   
   
       14 . The apparatus of  claim 1  characterized in that said housing has an openable cover sealingly mounted thereon, said hold-down elements are mounted on a frame movable for movement away from said spaces when said cover is open.  
   
   
       15 . The apparatus of  claim 11  characterized in that said hold-down elements are idler rollers under which said substrate travels.