Liquid bonding agent for liquid ink

1. A liquid bonding agent for a liquid ink, the liquid bonding agent comprising:

a calcium salt;

a first wax emulsion present in an amount ranging from greater than 0% actives to about 2% actives;

an acetylenic surfactant;

a glycol; and

a balance of water;

wherein the liquid bonding agent is to be digitally printed with a thermal inkjet printhead on a substrate under the liquid ink;

wherein the liquid bonding agent excludes a pigment and a polymeric binder;

and wherein the liquid ink includes a second wax emulsion present in an amount ranging from about 0.25% actives to less than 1% actives.

2. The liquid bonding agent as defined in claim 1 wherein:

the calcium salt is present in an amount ranging from about 5 wt % to about 15 wt %;

the acetylenic surfactant is present in an amount ranging from about 0.25 wt % to about 2 wt %; and

the glycol is present in an amount ranging from about 2 wt % to about 20 wt %.

3. The liquid bonding agent as defined in claim 1 wherein the calcium salt is selected from the group consisting of calcium propionate, calcium pantothenate, calcium nitrate, and combinations thereof.

4. The liquid bonding agent as defined in claim 1 wherein:

the wax emulsion is selected from the group consisting of a low density polyethylene wax emulsion, a paraffin wax emulsion, a carnauba wax emulsion, a polytetrafluoroethylene wax emulsion, and a combination thereof; and

a melting point of a wax in the wax emulsion is one of:

less than 105° C.; or

greater than 300° C.

5. The liquid bonding agent as defined in claim 1 wherein a particle size of a wax in the wax emulsion is less than 500 nm.

6. An inkjet printing system, comprising:

a liquid bonding agent, including:

a calcium salt;

a first wax emulsion present in an amount ranging from greater than 0% actives to about 2% actives;

a first acetylenic surfactant;

a glycol; and

a balance of water;

wherein the liquid bonding agent excludes a pigment and a polymeric binder; and

a liquid ink, including:

a pigment dispersion;

a polyurethane dispersion;

a second wax emulsion present in an amount ranging from about 0.25% actives to less than 1% actives;

an ether co-solvent; and

a balance of water.

7. The inkjet printing system as defined in claim 6 wherein the liquid ink further includes a humectant, a phosphate surfactant, and a second acetylenic surfactant.

8. The inkjet printing system as defined in claim 7 wherein:

the calcium salt is present in the liquid bonding agent in an amount ranging from about 5 wt % to about 15 wt %;

the first acetylenic surfactant is present in the liquid bonding agent in an amount ranging from about 0.25 wt % to about 2 wt %;

the glycol is present in the liquid bonding agent in an amount ranging from about 2 wt % to about 20 wt %;

the pigment dispersion is present in the liquid ink in an amount ranging from about 2% actives to about 5% actives;

the polyurethane dispersion is present in the liquid ink in an amount ranging from about 1% actives to about 10% actives;

the ether co-solvent is present in the liquid ink in an amount ranging from about 2 wt % to about 12 wt %;

the humectant is present in the liquid ink in an amount ranging from about 2 wt % to about 12 wt %;

the phosphate surfactant is present in the liquid ink in an amount ranging from about 0.25 wt % to about 2 wt %; and

the second acetylenic surfactant is present in the liquid ink in an amount ranging from about 0.25 wt % to about 2 wt %.

9. The inkjet printing system as defined in claim 6 wherein:

the polyurethane dispersion is selected from the group consisting of an aromatic olyether polyurethane dispersion, an aliphatic polyether polyurethane dispersion, an aromatic polyester polyurethane dispersion, an aliphatic polyester polyurethane dispersion, an aromatic polycaprolactam polyurethane dispersion, an aliphatic polycaprolactam polyurethane dispersion, a vinyl-urethane hybrid polymer dispersion, an acrylic-urethane hybrid polymer dispersion, a dispersion of co-polymers thereof, and a combination thereof; and

the calcium salt is selected from the group consisting of calcium propionate, calcium pantothenate, calcium nitrate, and combinations thereof.

10. The inkjet printing system as defined in claim 6 wherein each of the first wax emulsion and the second wax emulsion is selected from the group consisting of a low density polyethylene wax emulsion, a paraffin wax emulsion, a carnauba wax emulsion, a polytetrafluoroethylene wax emulsion, and a combination thereof; and

a melting point of each of a wax in the first wax emulsion and a wax in the second wax emulsion is one of:

less than 105° C.; or

greater than 300° C.

11. The inkjet printing system as defined in claim 6 wherein the inkjet printing system is a thermal inkjet printing system.

12. A method for improving thermal inkjet print nozzle health and reliability, the method comprising:

incorporating from greater than 0% actives to about 2% actives of a wax emulsion in a liquid bonding agent composition, including:

a calcium salt;

an acetylenic surfactant;

a glycol; and

water;

wherein the liquid bonding agent excludes a pigment and a polymeric binder; and

incorporating from about 0.25% actives to less than 1% actives of the wax emulsion in a liquid ink, including:

a pigment dispersion;

a polyurethane dispersion;

an ether co-solvent; and

water.

13. The method as defined in claim 12 wherein thermal inkjet print nozzle health and reliability is measured by filterability, agglomerate formation, and agglomerate recoverability.