Cationic modified self-dispersing pigment dispersions and inkjet inks thereof
View Patent ↗This invention pertains to aqueous inkjet inks containing self-dispersing pigments. The self-dispersing pigments are modified with multivalent cations.
1. An aqueous pigment dispersion comprising:
a self-dispersing pigment having at least one type of hydrophilic functional group bonded onto a surface of the self-dispersing pigment, said at least one type of hydrophilic functional group comprising a carboxyl group; and
a multivalent cation selected from the group consisting of Mg 2+ , Ca 2+ , Cu 2+ , Al 3+ , Fe 3+ , and mixtures thereof, wherein said multivalent cation is adsorbed onto said self-dispersing pigment via ionic bonds between the multivalent cation and surface acid group on the self-dispersing pigment displacing monovalent cation(s) associating with the carboxyl group on the surface of the self-dispersing pigment, the displaced monovalent cation(s) are removed from the pigment dispersion.
2. The pigment dispersion of claim 1 , wherein said multivalent cation is present at a level of at least 2 ppm.
3. The pigment dispersion of claim 1 , wherein said multivalent cation is Mg 2+ .
4. The pigment dispersion of claim 1 , wherein said multivalent cation is Cu 2+ .
5. The pigment dispersion of claim 1 , wherein said multivalent cation is Ca 2+ .
6. The pigment dispersion of claim 1 , wherein said multivalent cation is Al 3+ .
7. A process for making an aqueous inkjet ink comprising the step of:
(a) preparing an aqueous vehicle;
(b) adding the aqueous vehicle to an aqueous pigment dispersion, wherein said pigment dispersion comprising a self-dispersing pigment having at least one type of hydrophilic functional group bonded onto a surface of said self-dispersing pigment, said at least one type of hydrophilic functional group comprising a carboxyl group; and a multivalent cation selected from the group consisting of Mg 2+ , Ca 2+ , Cu 2+ , Al 3+ , Fe 3+ , and mixtures thereof, wherein said cation is adsorbed onto said self-dispersing pigment via ionic bonds between the cation and surface acid group on said self-dispersing pigment displacing monovalent cation(s) associating with the carboxyl group on the surface of the self-dispersing pigment; and
(c) removing the monovalent cation(s) displaced by the multivalent cation.
8. The process of claim 7 , wherein said multivalent cation is present at a level of at least 2 ppm.
9. The process of claim 7 , wherein said multivalent cation is Mg 2+ .
10. The process of claim 7 , wherein said multivalent cation is Cu 2+ .
11. The process of claim 7 , wherein said multivalent cation is Ca 2+ .
12. The process of claim 7 , wherein said multivalent cation is Al 3+ .
13. An inkjet ink comprising an aqueous vehicle and an aqueous pigment dispersion, wherein said pigment dispersion comprising a self-dispersing pigment having at least one type of hydrophilic functional group bonded onto a surface of said self-dispersing pigment, said at least one type of hydrophilic functional group comprising a carboxyl group; and a multivalent cation selected from the group consisting of Mg 2+ , Ca 2+ , Cu 2+ , Al 3+ , Fe 3+ , and mixtures thereof, wherein said multivalent cation is adsorbed onto said self-dispersing pigment via ionic bonds between the multivalent cation and surface acid group on said self-dispersing pigment displacing monovalent cation(s) associating with the carboxyl group on the surface of the self-dispersing pigment, the displaced monovalent cation(s) are removed from the pigment dispersion.
14. The ink of claim 13 , wherein said multivalent cation is present at a level of at least 2 ppm.
15. The ink of claim 13 , wherein said multivalent cation is Mg 2+ .
16. The ink of claim 13 , wherein said multivalent cation is Cu 2+ .
17. The ink of claim 13 , wherein said multivalent cation is Ca 2+ .
18. The ink of claim 13 , wherein said multivalent cation is Al 3+ .