Method of inkjet printing
An inkjet printing method uses an aqueous inkjet ink composition having a non-crosslinked, crosslinkable polyurethane having an acid number of 20-40 and is derived from an aromatic diisocyanate; and a diol mixture of D 1 and D 2 diols, and optionally including D 3 diol, D 4 diol, or both D 3 and D 4 diols. D 1 has a C 3 to C 7 aliphatic group and a pendant carboxy group or neutralized carboxy group. D 2 has a chain of repeating C 2 to C 6 alkylene oxide groups. D 3 is an alkoxylated bisphenol A or aliphatic cyclic diol, present at least 5 mol %. D 4 is a hydroxy-terminated polybutadiene having a molecular weight of at least 1000 and is present in an amount of 0.1-5 mol %. The ink composition also contains a dispersed pigment colorant; a humectant or organic co-solvent, and optionally, a crosslinking agent.
1. A method for inkjet printing, comprising:
inkjet printing an aqueous inkjet ink composition onto a substrate to provide an inkjet printed image, wherein the aqueous inkjet ink composition has a viscosity of at least 1 centipoise and up to and including 100 centipoise at 25° C., and comprises:
(a) an aqueous solvent medium,
(b) a non-crosslinked, crosslinkable polyurethane having an acid number of at least 20 and up to and including 40, and a glass transition temperature (T g ) of up to and including 40° C.,
the non-crosslinked crosslinkable polyurethane derived from:
1) an aromatic diisocyanate; and
2) a diol mixture of at least D 1 , D 2 , and D 3 diols, and optionally including a D 4 diol,
wherein:
the D 1 diol comprises a C 3 to C 7 aliphatic group between two hydroxy groups, and at least one pendant carboxy group or pendant neutralized carboxy group,
the D 2 diol comprises a chain of one or more repeating C 2 to C 6 alkylene oxide groups and has a weight average molecular weight of at least 250 and up to and including 3,000,
the D 3 diol is an alkoxylated bisphenol A or an aliphatic cyclic diol that is present in an amount of at least 5 mol %, based on the total molar amount of the D 1 through D 4 diols in the diol mixture, and
the D 4 diol is a hydroxy-terminated polybutadiene having a weight average molecular weight of at least 1000, and when present, is present in an amount of at least 0.1 mol % and up to and including 5 mol %, based on the total molar amount of the D 1 through D 4 diols in the diol mixture;
(c) a dispersed pigment colorant;
(d) a humectant or organic co-solvent, and
(e) optionally, a crosslinking agent.
2. The method of claim 1 , further comprising treating the inkjet printed image with heat.
3. The method of claim 1 , further comprising treating the inkjet printed image with both heat and pressure.
4. The method of claim 1 , wherein the substrate is a textile material.
5. The method of claim 1 , comprising providing a black, cyan, yellow, or magenta inkjet printed image using the aqueous inkjet ink composition.
6. The method of claim 1 , comprising using two or more aqueous inkjet ink compositions, to provide a multi-colored inkjet printed image on the substrate.
7. The method of claim 1 , wherein the diol mixture further comprises the D 4 diol.
8. The method of claim 1 , wherein the aqueous inkjet ink composition further comprises the crosslinking agent that is a melamine formaldehyde resin, carbodiimide, glyoxal, urea resin, or phenolic resin.
9. The method of claim 1 , wherein the non-crosslinked, crosslinkable polyurethane is present in an amount of at least 2 weight % and up to and including 15 weight %, based on the total wet weight of the inkjet ink composition.
10. The method of claim 1 , wherein the humectant or organic co-solvent is present in the aqueous inkjet ink composition in an amount of at least 0.5 weight % and up to and including 35 weight %, based on the total wet weight of the aqueous inkjet ink composition.
11. The method of claim 1 , wherein the non-crosslinked, crosslinkable polyurethane has an acid number of at least 25 and up to and including 35, a glass transition temperature (T g ) of at least 10° C. and including 40° C., and a weight average molecular weight of at least 20,000 and up to and including 150,000.
12. The method of claim 1 , wherein the D 1 diol comprises a repeating C 3 to C 5 aliphatic group between the two hydroxy groups.
13. The method of claim 1 , wherein the D 2 diol comprises a chain of repeating C 3 or C 4 alkylene oxide groups and has a weight average molecular weight of at least 250 and up to and including 1,000.
14. The method of claim 1 , wherein the D 3 diol comprises an alkoxylated bisphenol A.
15. The method of claim 1 , wherein the D 3 diol is present in an amount of at least 5 mol % and up to and including 30 mol %, based on the total molar amount of the D 1 through D 4 diols in the diol mixture.
16. The method of claim 1 , wherein the D 3 diol is present in an amount of at least 8 mol % and up to and including 25 mol %, based on the total molar amount of the D 1 through D 4 diols in the diol mixture.
17. The method of claim 7 , wherein the D 4 diol has a weight average molecular weight of at least 1,000 and up to and including 7,000.
18. The method of claim 7 , wherein the D 4 diol is present in the diol mixture in an amount of at least 0.2 mol % and up to and including 2 mol %, based on the total molar amount of the D 1 through D 4 diols in the diol mixture.