Dye discharge inkjet ink compositions

Abstract

A dye discharge composition exhibiting extended shelf life and/or pot life and high suitability for inkjet printing on dyed substrates, is disclosed. The composition comprises a reducing agent such as, for example, a sulfur-based reducing agent, and a chelating agent, such as a sodium salt of a polyamino carboxylic acid chelating agent. Use of the dye discharge composition in combination with a translucent colored composition and an optional opaque underbase composition, for forming an image on a dyed substrate is also disclosed. Processes for inkjet printing of an image on a dyed surface using the dye discharge composition, kits for use in such processes or an ink formulation containing same are also disclosed.

What is claimed is: 
     
         1 . A process of inkjet printing an image directly on a surface of a dyed substrate, comprising:
 providing a dye discharge composition that comprises a sulfur-based reducing agent, a chelating agent and a first carrier, and having a pH that ranges from 3 to 6.5;   providing at least one a colored ink composition which comprises a colorant, a dispersing agent and a second carrier, wherein said colored ink composition congeals or coagulates upon contacting said dye discharge composition;   forming the image on the substrate by digitally applying said dye discharge composition and said colored ink composition concurrently and/or sequentially and/or concomitantly using a separate printhead for each of said dye discharge composition and said colored ink composition; and   heating at least a portion of the surface having the image printed thereon to a temperature that ranges from 130° C. to 180° C., thereby discharging a dye in the dyed substrate and curing the image on the surface.   
     
     
         2 . The process of  claim 1 , further comprising, prior to said providing said dye discharge composition:
 combining a pre-determined amount of said sulfur-based reducing agent and a pre-determined amount of a chelating agent, with in a pre-determined amount of said first carrier, thereby providing stock solution A;   providing stock solution B which comprises a humectant and/or a surface tension modifying agent and/or a surface active agent, dissolved in said first carrier;   mixing said stock solution A with said stock solution B to thereby obtain said dye discharge composition.   
     
     
         3 . The process of  claim 2 , wherein said mixing is effected at a 1:1 volume ratio. 
     
     
         4 . The process of  claim 1 , wherein said first carrier and said second carrier are each an aqueous carrier. 
     
     
         5 . The process of  claim 1 , wherein a concentration of said sulfur-based reducing agent in said dye discharge composition ranges from 300 mM to 700 mM. 
     
     
         6 . The process of  claim 1 , wherein said chelating agent is a polyamino carboxylic acid chelating agent. 
     
     
         7 . The process of  claim 6 , wherein a concentration of said chelating agent in said dye discharge composition ranges from 300 mM to 700 mM. 
     
     
         8 . The process of  claim 1 , wherein a molar ratio of said reducing agent to said chelating agent in said dye discharge composition ranges from 0.8 to 1.2. 
     
     
         9 . The process of  claim 1 , wherein said pH is 6.3. 
     
     
         10 . The process of  claim 1 , wherein said stock solution B further comprising a colorant which is impervious to said reducing agent. 
     
     
         11 . The process of  claim 1 , wherein said at least one a colored ink composition is a translucent colored ink composition. 
     
     
         12 . The process of  claim 1 , wherein said at least one a colored ink composition an opaque white ink composition. 
     
     
         13 . The process of  claim 12 , wherein said opaque white ink composition comprises a plurality of metal oxide particles. 
     
     
         14 . A kit comprising a packaging material and the dye discharge composition of  claim 2  packaged therein. 
     
     
         15 . The kit of  claim 14 , wherein said pre-determined amount of said sulfur-based reducing agent in dry form, and said pre-determined amount of said chelating agent in dry form, and optionally said pre-determined amount of said first carrier, are each packaged individually within the kit. 
     
     
         16 . The kit of  claim 14 , wherein said pre-determined amount of said sulfur-based reducing agent in dry form, and said pre-determined amount of said chelating agent dissolved in said pre-determined amount of said first carrier, are each packaged individually within the kit. 
     
     
         17 . The kit of  claim 14 , further comprising instructions to combine said pre-determined amount of said sulfur-based reducing agent with said pre-determined amount of said chelating agent, and with said pre-determined amount of said first carrier. 
     
     
         18 . The kit of  claim 14 , further comprising said stock solution B, packaged individually within the kit. 
     
     
         19 . The kit of  claim 18 , further comprising instructions to mix one part of said stock solution A with one part of said stock solution B to thereby obtain said dye discharge composition. 
     
     
         20 . The kit of  claim 14 , further comprising said at least one colored ink composition packaged individually within the kit.