AQUEOUS INKJET INKS WITH IONICALLY STABILIZED DISPERSIONS AND POLYURETHANE INK ADDITIVES
First Claim
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1. An aqueous pigmented ink jet ink comprising a polyurethane, an aqueous pigment dispersion in an aqueous vehicle, wherein:
- the aqueous pigment dispersion comprises an polymeric ionic dispersant and pigment where(a) the polymeric ionic dispersant is physically adsorbed to the pigment,(b) the polymeric ionic dispersant stably disperses the pigment in the aqueous vehicle,(c) the average particle size of the dispersion is less than about 300 nm, and(d) when three drops of the ink is added to about 1.5 g of an aqueous salt solution of about 0.20 molar salt, the pigment precipitates out of the aqueous salt solution when observed 24 hours after the addition; and
wherein the polyurethane is selected from the group consisting essentially ofa). an urea terminated polyurethane where the weight fraction of the urea-terminated polyurethane part of the polyurethane is at least 2 wt % to the urethane resin; and
b). a crosslinked polyurethane in the amount in the in jet ink of more than about 0.5% to about 30% by weight based on the total weight of the aqueous ink, and wherein the amount of crosslinking in the crosslinked polyurethane is greater than about 1% and less than about 50% as determined by the THF insolubles test.
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Abstract
Inks that contain ionically stabilized dispersions and selected polyurethane ink additives are described. These ionically stabilized dispersions are obtained from polymeric dispersants where the hydrophilic components are minimized. These stabilized dispersions can be utilized to prepare ink jet inks which when printed result in improved optical density, chroma, gloss and especially distinctness of image. The stability of the ionically stabilized dispersions are sufficient for ink jet inks. The polyurethane ink additives are chosen from polyurethanes which are urea terminated or crosslinked.
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16 Claims
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1. An aqueous pigmented ink jet ink comprising a polyurethane, an aqueous pigment dispersion in an aqueous vehicle, wherein:
- the aqueous pigment dispersion comprises an polymeric ionic dispersant and pigment where
(a) the polymeric ionic dispersant is physically adsorbed to the pigment, (b) the polymeric ionic dispersant stably disperses the pigment in the aqueous vehicle, (c) the average particle size of the dispersion is less than about 300 nm, and (d) when three drops of the ink is added to about 1.5 g of an aqueous salt solution of about 0.20 molar salt, the pigment precipitates out of the aqueous salt solution when observed 24 hours after the addition; and wherein the polyurethane is selected from the group consisting essentially of a). an urea terminated polyurethane where the weight fraction of the urea-terminated polyurethane part of the polyurethane is at least 2 wt % to the urethane resin; and b). a crosslinked polyurethane in the amount in the in jet ink of more than about 0.5% to about 30% by weight based on the total weight of the aqueous ink, and wherein the amount of crosslinking in the crosslinked polyurethane is greater than about 1% and less than about 50% as determined by the THF insolubles test. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- the aqueous pigment dispersion comprises an polymeric ionic dispersant and pigment where
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