Method for forming colored cellulosic materials

Abstract

A method for applying a colorant to a cellulosic substrate to improve the resistance of the colorant to removal from the substrate by wetting or rubbing. The method is a two-step process in which the colorant is applied to the substrate in a first step, and in which an elastomeric overcoat is applied to the substrate over the colorant in a second step. The colorant includes a pigment, thickeners and water and can be applied to the substrate in a manner similar to the application of the overcoat, i.e., by any suitable on or off-paper machine process.

We hereby claim:  
     
         1 . A method for coloring a substrate, the method comprising the steps of: 
 a) providing a cellulosic substrate;    b) applying a colorant to the substrate, the colorant including a pigment, a thickener and a solvent; and    c) applying an overcoat to the substrate over the colorant.    
     
     
         2 . The method of  claim 1  wherein the substrate is selected from the group consisting of: 
 white-top linerboard, linerboard and paper.  
 
     
     
         3 . The method of  claim 1  wherein the pigment is selected from the group consisting of a basic fiber reactive dye, an anionic fiber reactive dye, and dry coloring matter.  
     
     
         4 . The method of  claim 1  wherein the thickener is present in an amount of between 1% and 40% by weight.  
     
     
         5 . The method of  claim 4  wherein the thickener is selected from the group consisting of: natural thickeners, synthetic thickeners and combinations thereof.  
     
     
         6 . The method of  claim 5  wherein the natural thickeners are polysaccharides.  
     
     
         7 . The method of  claim 5  wherein the natural thickener is selected from the group consisting of starch, carboxymethylcellulose and combinations thereof.  
     
     
         8 . The method of  claim 7  comprising: 
 a) starch in an amount of between about 1% and 25% by weight of the colorant; and  
 b) carboxymethyl cellulose in an amount of between about 0% and 10% by 5 weight of the colorant.  
 
     
     
         9 . The method of  claim 1  wherein the pigment is present in an amount of between about 1% and 50% by weight of the colorant.  
     
     
         10 . The method of  claim 9  wherein the pigment is present in an amount of between about 1% and 30% by weight of the colorant.  
     
     
         11 . The method of  claim 1  wherein the step of applying the colorant comprises dispensing the colorant at an application rate of between about 1% to 40% by weight of the substrate.  
     
     
         12 . The method of  claim 1  wherein the overcoat is an elastomer.  
     
     
         13 . The method of  claim 12  wherein the overcoat is selected from the group consisting of polybutadienes, polyisobutylenes, polystyrenes, polyacrylates, and polyurethanes.  
     
     
         14 . The method of  claim 12  wherein the overcoat is a latex.  
     
     
         15 . The method of  claim 12  wherein the step of applying the overcoat comprises dispensing the overcoat at an application rate of between about 1% and 25% by weight of the substrate.  
     
     
         16 . The method of  claim 1  wherein the step of applying the colorant is performed in a process selected from the group consisting of off-paper machine applications or on-paper machine applications.  
     
     
         17 . The method of  claim 1  wherein the step of applying the overcoat is performed in a process selected from the group consisting of off-paper machine applications or on-paper machine applications.  
     
     
         18 . A colored substrate formed by a process comprising the steps of: 
 a) providing a cellulosic substrate;    b) applying a colorant to the substrate, the colorant including a pigment, at least one thickener selected from the group consisting of synthetic thickeners, natural thickeners and combinations thereof, and water; and    c) applying an overcoat to the substrate over the colorant, wherein the overcoat is an elastomer.    
     
     
         19 . A colored cellulosic substrate comprising: 
 a) a sheet of a cellulosic substrate;    b) a colorant applied to a surface of the substrate, the colorant including a pigment, at least one thickener selected from the group consisting of synthetic thickeners, natural thickeners and combinations thereof, and water; and    c) an overcoat applied to the surface over the colorant, wherein the overcoat is an elastomer.