Composition based on water-dissipatable polyurethane
View Patent ↗A composition comprising water-dissipatable polyurethane, water, colorant, a water-miscible organic solvent and a water-immiscible organic solvent. The compositions are useful as inks for ink jet printers.
1. An ink jet printing ink composition comprising water, water-miscible organic solvent, water-immiscible organic solvent, a colorant which is soluble in the water-immiscible solvent, and a water-dissipatable polyurethane having a weight average molecular weight less than 25,000, which is obtained from the reaction of:
(a) at least one diisocyanate; and
(b) at least one compound having one or two isocyanate reactive groups;
wherein the mole ratio of isocyanate groups to isocyanate-reactive groups is about 1:1.
2. A composition according to claim 1 wherein the colorant is soluble in the polyurethane.
3. A composition according to claim 1 wherein the water-immiscible organic solvent is benzyl alcohol.
4. A composition according to claim 1 comprising:
(a) from 0.5 to 50 parts of a water-dissipatable polyurethane having a weight average molecular weight less than 25,000;
(b) from 0.1 to 20 parts of colorant;
(c) from 40 to 90 parts of water;
(d) from 2 to 30 parts of a water-immiscible organic solvent; and
(e) from 2 to 60 parts of a water-miscible organic solvent;
wherein all parts are by weight relative to the total of (a)+(b)+(c)+(d)+(e).
5. A composition according to claim 1 wherein the polyurethane has a weight average molecular weight from 1,000 to 15,000.
6. A composition according to claim 1 having a viscosity less than 20 cp at 20° C.
7. A composition according to claim 1 which has been filtered through a filter having a mean pore size below 10 μm.
8. A process for printing an image on a substrate comprising applying thereto a composition according to claim 1 by means of an ink jet printer.
9. An ink jet printer cartridge containing a composition according to claim 1 .
10. An ink jet printing ink composition comprising water, water-miscible solvent, water-immiscible organic solvent, colorant which is soluble in the water-immiscible organic solvent and water-dissipatable polyurethane having a weight average molecular weight less than 25,000.