Inkjet inks containing crosslinked polyurethanes

Abstract

Inkjet inks are described that have, as a principal component, a crosslinked polyurethane dispersoid binder additive. These inks can be used for printing on different media, and are particularly suitable for printing on paper.

1 . An inkjet ink composition comprising an aqueous vehicle having stably dispersed therein a pigment and a crosslinked polyurethane dispersoid, wherein the ink comprises the crosslinked polyurethane dispersoid is an amount of more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the ink, and wherein the amount of crosslinking in the crosslinked polyurethane is greater than about 1% and less than about 50% (THF insolubles test).  
     
     
         2 . The inkjet ink composition of  claim 1 , wherein the crosslinking in the crosslinked polyurethane is greater than about 4% and less than about 50%.  
     
     
         3 . The inkjet ink composition of  claim 1 , having a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm, and a viscosity is in the range of about 1 cP to about 30 cP at 25° C.  
     
     
         4 . The inkjet ink composition of  claim 1 , wherein the crosslinked polyurethane has incorporated therein hydrophilic functionality to the extent required to maintain a stable dispersion of the polymer in the aqueous vehicle.  
     
     
         5 . The inkjet ink composition of  claim 4 , wherein the hydrophilic functionality of the crosslinked polyurethane is derived from anionic substituents.  
     
     
         6 . An inkjet ink set comprising at least three differently colored inkjet inks, wherein at least one of the inks is an inkjet ink composition comprising an aqueous vehicle having stably dispersed therein a pigment colorant and a crosslinked polyurethane dispersoid, wherein the ink comprises the crosslinked polyurethane dispersoid is an amount of more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the ink, and wherein the amount of crosslinking in the crosslinked polyurethane is greater than about 1% and less than about 50% (THF insolubles test).  
     
     
         7 . The inkjet ink set of  claim 6 , wherein ink set comprises: 
 (a) a first colored ink comprising a first aqueous vehicle having stably dispersed therein a first pigment colorant and a first crosslinked polyurethane dispersoid, wherein the first crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the first ink, and wherein the amount of crosslinking in the first crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%;    (b) a second colored ink comprising a second aqueous vehicle having stably dispersed therein a second pigment colorant and a second crosslinked polyurethane dispersoid, wherein the second crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the second ink, and wherein the amount of crosslinking in the second crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%; and    (c) a third colored ink comprising a third aqueous vehicle having stably dispersed therein a third pigment colorant and a third crosslinked polyurethane dispersoid, wherein the third crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the third ink, and wherein the amount of crosslinking in the third crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%.    
     
     
         8 . The inkjet ink set of  claim 7 , wherein the first colored ink is a cyan ink, the second colored ink is a magenta ink and the third colored ink is a yellow ink.  
     
     
         9 . The inkjet ink set of  claim 7 , further comprising (d) a fourth colored ink comprising a fourth aqueous vehicle having stably dispersed therein a fourth pigment colorant and a fourth crosslinked polyurethane dispersoid, wherein the fourth crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the fourth ink, and wherein the amount of crosslinking in the fourth crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%.  
     
     
         10 . The inkjet ink set of  claim 9 , wherein the first colored ink is a cyan ink, the second colored ink is a magenta ink, the third colored ink is a yellow ink and the fourth colored ink is a black ink.  
     
     
         11 . A method for inkjet printing onto a substrate, comprising the steps of: 
 (a) providing an inkjet printer that is responsive to digital data signals;    (b) loading the printer with a substrate to be printed;    (c) loading the printer with an inkjet ink composition inkjet ink composition comprising an aqueous vehicle having stably dispersed therein a pigment and a crosslinked polyurethane dispersoid, wherein the ink comprises the crosslinked polyurethane dispersoid is an amount of more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the ink, and wherein the amount of crosslinking in the crosslinked polyurethane is greater than about 1% and less than about 50% (THF insolubles test); and    (d) printing onto the substrate using the ink in response to the digital data signals.    
     
     
         12 . The method of  claim 11 , wherein the printer is loaded with an inkjet ink set comprising at least three differently colored inkjet inks, wherein at least one of the inks is an inkjet ink composition comprising an aqueous vehicle having stably dispersed therein a pigment colorant and a crosslinked polyurethane dispersoid, wherein the ink comprises the crosslinked polyurethane dispersoid is an amount of more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the ink, and wherein the amount of crosslinking in the crosslinked polyurethane is greater than about 1% and less than about 50% (THF insolubles test).  
     
     
         13 . The method of  claim 12 , wherein ink set comprises: 
 (a) a first colored ink comprising a first aqueous vehicle having stably dispersed therein a first pigment colorant and a first crosslinked polyurethane dispersoid, wherein the first crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the first ink, and wherein the amount of crosslinking in the first crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%;    (b) a second colored ink comprising a second aqueous vehicle having stably dispersed therein a second pigment colorant and a second crosslinked polyurethane dispersoid, wherein the second crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the second ink, and wherein the amount of crosslinking in the second crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%; and    (c) a third colored ink comprising a third aqueous vehicle having stably dispersed therein a third pigment colorant and a third crosslinked polyurethane dispersoid, wherein the third crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the third ink, and wherein the amount of crosslinking in the third crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%.    
     
     
         14 . The method of  claim 13 , wherein the first colored ink is a cyan ink, the second colored ink is a magenta ink and the third colored ink is a yellow ink.  
     
     
         15 . The method of  claim 13 , further comprising (d) a fourth colored ink comprising a fourth aqueous vehicle having stably dispersed therein a fourth pigment colorant and a fourth crosslinked polyurethane dispersoid, wherein the fourth crosslinked polyurethane dispersoid is more than about 0.5% to about 30% by weight (solids basis), based on the total weight of the fourth ink, and wherein the amount of crosslinking in the fourth crosslinked polyurethane dispersoid is greater than about 1% and less than about 50%.  
     
     
         16 . The method of  claim 15 , wherein the first colored ink is a cyan ink, the second colored ink is a magenta ink, the third colored ink is a yellow ink and the fourth colored ink is a black ink.  
     
     
         17 . The method of  claim 11 , wherein the substrate is a paper.