Pigmented phase change inks containing low molecular weight pigment dispersants
View Patent ↗An ink comprising an ink vehicle; pigment particles; and a dispersant; wherein the dispersant stabilizes the pigment particles; and wherein the dispersant is a compound of the formula or a mixture thereof, wherein R and R′ are independently selected from alkyl, arylalkyl, or alkylaryl with from about 18 to about 60 carbon atoms and wherein m is an integer of from about 1 to about 30.
1. An ink comprising:
an ink vehicle;
pigment particles; and
a dispersant;
wherein the dispersant stabilizes the pigment particles; and
wherein the dispersant comprises a mixture of compounds of the formula
wherein each n is an integer of from 20 to 46 and m is an integer of from 1 to 14.
2. The ink of claim 1 , wherein the ink vehicle is selected from the group consisting of microcrystalline waxes, polyethylene waxes, ester waxes, long chain acids with at least 30 carbons, fatty acids, fatty amides, ethylene/propylene copolymers, urethane derivatives of oxidized synthetic or petroleum waxes, n-paraffinic hydrocarbons, branched paraffinic hydrocarbons, naphthenic hydrocarbons, highly branched hydrocarbons, ethoxylated alcohols, linear alcohols, hydrocarbon-based waxes, modified maleic anhydride hydrocarbon adducts of polyolefins prepared by graft copolymerization, mixtures of monoamides, diamides, triamides and tetraamides, and mixtures thereof.
3. The ink of claim 1 , wherein the ink composition is solid at a temperature below 40° C. and has a viscosity of from 1 to 20 centipoise at a jetting temperature of the ink.
4. The ink of claim 1 , wherein the ink vehicle is present in an amount of from 25% to 99.5% by weight of the ink.
5. The ink of claim 1 , wherein the dispersant is present in an amount of from 0.1 to 25 percent by weight.
6. The ink of claim 1 , wherein the dispersant is present in an amount of from 1 to 5 percent by weight.
7. The ink of claim 1 , wherein the pigment particles are selected from the various classes of pigment compounds consisting of cyan, yellow, magenta, and black pigment particles.
8. The ink of claim 1 , wherein the pigment particles have an average particle size from 50 to 200 nanometers.
9. The ink of claim 1 , wherein the ink composition shows Newtonian behaviour, passes at least three successive freeze thaw cycles, and does not show any settling for at least 14 days at a temperature of 115 to 130° C.
10. The ink of claim 1 , wherein the ink composition does not show any particle size growth for at least 7 days at a temperature of 115 to 130° C.
11. The ink according to claim 1 , wherein the ink composition gives prints with uniform optical density after being aged in the printer at a temperature of 100 to 120° C. for 10 days.
12. A process which comprises:
(1) incorporating into an ink jet printing apparatus a phase change ink comprising (a) an ink vehicle, (b) pigment particles and (c) a dispersant, wherein the dispersant stabilizes the pigment particles and
wherein the dispersant comprises a mixture of compounds of the formula
wherein each n is an integer of from 20 to 46 and m is an integer of from 1 to 14;
(2) melting the ink; and
(3) causing droplets of the melted ink to be ejected at a temperature of 100 to 150° C. in an imagewise pattern onto a substrate.