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Title:
THERMAL INKJET FLUID SET
Document Type and Number:
WIPO Patent Application WO/2022/046112
Kind Code:
A1
Abstract:
A thermal inkjet fluid set includes a fixer fluid, an inkjet ink, and a cross-linker composition. The fixer fluid includes a cationic polyurethane including a phosphonium salt, and an aqueous fixer vehicle. The inkjet ink includes a colorant, a polyurethane binder, and an aqueous ink vehicle. The cross-linker composition includes a linear polycarbodiimide and an aqueous cross-linker vehicle.

Inventors:
ZHOU ZHANG-LIN (US)
BRANDSTEIN OR (US)
ZHOU XIAOQI (US)
Application Number:
PCT/US2020/048783
Publication Date:
March 03, 2022
Filing Date:
August 31, 2020
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HEWLETT PACKARD DEVELOPMENT CO (US)
International Classes:
C09D11/30; C09D175/04; D06P1/44; D06P1/54; D06P5/30
Domestic Patent References:
WO2020046340A12020-03-05
WO2020005253A12020-01-02
Attorney, Agent or Firm:
COSTALES, Shruti et al. (US)
Download PDF:
Claims:
65

What is claimed is:

1 . A thermal inkjet fluid set, comprising: a fixer fluid, including: a cationic polyurethane including a phosphonium salt; and an aqueous fixer vehicle; and an inkjet ink, including: a colorant; a polyurethane binder; and an aqueous ink vehicle; and a cross-linker composition, including: a linear polycarbodiimide; and an aqueous cross-linker vehicle.

2. The thermal inkjet fluid set as defined in claim 1 wherein the linear polycarbodiimide has a structure: wherein:

R1 is a divalent organic group which has no reactivity toward a carbodiimide functional group;

R2 and R3 are each a monovalent organic group which has no reactivity toward the carbodiimide functional group; and n is an integer ranging from 2 to 100.

3. The thermal inkjet fluid set as defined in claim 1 wherein the linear polycarbodiimide has a weight average molecular weight ranging from about 1 ,000 Daltons to about 6,000 Daltons. 66

4. The thermal inkjet fluid set as defined in claim 1 wherein the linear polycarbodiimide has a particle size of 200 nm or less.

5. The thermal inkjet fluid set as defined in claim 1 wherein the linear polycarbodiimide is present in the cross-linker composition in an amount ranging from about 1 wt% about 10 wt%, based on a total weight of the cross-linker composition.

6. The thermal inkjet fluid set as defined in claim 1 wherein the cationic polyurethane including the phosphonium salt is present in the fixer fluid in an amount ranging from about 1 wt% to about 15 wt%, based on a total weight of the fixer fluid.

7. The thermal inkjet fluid set as defined in claim 1 wherein: the cationic polyurethane includes a polyurethane backbone with pendent side chain groups along the polyurethane backbone and end cap groups terminating the polyurethane backbone; and the pendent side chain groups and the end cap groups of the cationic polyurethane collectively include the phosphonium salt and a polyalkylene oxide.

8. The thermal inkjet fluid set as defined in claim 1 wherein the polyurethane binder includes self-cross-linked polyurethane binder particles having an acid number less than 10, a weight average molecular weight ranging greater than 50,000, and a particle size ranging from about 200 nm to about 400 nm.

9. A textile printing kit, comprising: a textile fabric; a fixer fluid, including: a cationic polyurethane including a phosphonium salt; and an aqueous fixer vehicle; and an inkjet ink, including: a colorant; a polyurethane binder; and 67 an aqueous ink vehicle; and a cross-linker composition, including: a linear polycarbodiimide; and an aqueous cross-linker vehicle.

10. The textile printing kit as defined in claim 9 wherein the textile fabric is selected from the group consisting of polyester fabrics, polyester blend fabrics, cotton fabrics, cotton blend fabrics, nylon fabrics, nylon blend fabrics, silk fabrics, silk blend fabrics, wool fabrics, wool blend fabrics, and combinations thereof.

11 . The textile printing kit as defined in claim 9 wherein the linear polycarbodiimide has a structure: wherein:

R1 is a divalent organic group which has no reactivity toward a carbodiimide functional group;

R2 and R3 are each a monovalent organic group which has no reactivity toward the carbodiimide functional group; and n is an integer ranging from 2 to 100.

12. A printing method, comprising: applying a fixer fluid to a textile fabric to form a fixer fluid layer, the fixer fluid including: a cationic polyurethane including a phosphonium salt; and an aqueous fixer vehicle; applying an inkjet ink to the textile fabric to form an ink layer on the fixer fluid layer, the inkjet ink including: a colorant; 68 a polyurethane binder; and an aqueous ink vehicle; and applying a cross-linker composition to the textile fabric to form a cross-linker layer on the ink layer, the cross-linker composition including: a linear polycarbodiimide; and an aqueous cross-linker vehicle; and exposing the textile fabric, having the fixer fluid layer, the ink layer, and the cross-linker layer thereon, to heat or electromagnetic energy irradiation. 13. The printing method as defined in claim 12 wherein the textile fabric is exposed to the electromagnetic energy irradiation for a total exposure time of 30 seconds or less.

14. The printing method as defined in claim 12 wherein the textile fabric is exposed to the heat at a temperature ranging from about 100°C to about 200°C.

15. The printing method as defined in claim 12 wherein each of the fixer fluid, the inkjet ink, and the cross-linker composition are printed via inkjet printing.

Description:
THERMAL INKJET FLUID SET

BACKGROUND

[0001] Textile printing methods often include rotary and/or flat-screen printing.

Traditional analog printing typically involves the creation of a plate or a screen, i.e. , an actual physical image from which ink is transferred to the textile. Both rotary and flat screen printing have great volume throughput capacity, but also have limitations on the maximum image size that can be printed. For large images, pattern repeats are used. Conversely, digital inkjet printing enables greater flexibility in the printing process, where images of any desirable size can be printed immediately from an electronic image without pattern repeats. Inkjet printers are gaining acceptance for digital textile printing. Inkjet printing is a non-impact printing method that utilizes electronic signals to control and direct droplets or a stream of ink to be deposited on media.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Features of examples of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear. [0003] Fig. 1 schematically illustrates an example fluid set and an example textile printing kit, each of which includes an example of a fixer fluid, an example of an inkjet ink, and an example of a cross-linker composition; [0004] Figs. 2 through 5 schematically depict different examples of the cationic polyurethane that is present in examples of the fixer fluid disclosed herein;

[0005] Fig. 6 schematically depict a cross-linking reaction between carbodiimide and carboxyl functional groups;

[0006] Fig. 7 is a flow diagram illustrating an example printing method;

[0007] Figs. 8A and 8B are schematic diagrams of different examples of a printing system disclosed herein;

[0008] Figs. 9A and 9B depict Turn-On-Energy (TOE) curves for two example cross-linking compositions and four comparative example cross-linking compositions, plotting drop weight in nanograms (ng) vs. energy in microJoules (pJ); and [0009] Fig. 10 depicts Turn-On-Energy (TOE) curves for three example crosslinking compositions and three comparative example cross-linking compositions, plotting drop weight in nanograms (ng) vs. energy in microJoules (pJ).

DETAILED DESCRIPTION

[0010] The textile market is a major industry, and printing on textiles, such as cotton, etc., has been evolving to include digital printing methods. Some digital printing methods, such as inkjet printing, enable direct to garment (or other textile) printing. In order to achieve a textile print with good wash durability, cross-linkers have been included in the inkjet ink and/or in other fluids that are printed with the inkjet ink. Some cross-linkers release undesirable byproducts, others are unstable in aqueous inkjet vehicles, and/or still others pose challenges when thermally inkjet printed (e.g., poor jettability, clogging printheads, etc.).

[0011 ] Disclosed herein is a fluid set, which includes a fixer fluid, an inkjet ink, and a cross-linking composition that is reliably jettable from a thermal inkjet printhead. The cross-linking composition includes a linear polycarbodiimide. The linear polycarbodiimide is capable of cross-linking with reactive groups on the textile fabric surface and/or with reactive groups of the polyurethane binder in the inkjet ink, and thus improves the durability of the print. Additionally, the linear polycarbodiimide exhibits excellent thermal inkjet performance. [0012] The compositions disclosed herein may include different components (e.g., cationic polyurethane polymer, polyurethane binder) which have an acid number. As used herein, the term “acid number” refers to the mass of potassium hydroxide (KOH) in milligrams that is used to neutralize one (1 ) gram of a particular substance. The test for determining the acid number of a particular substance may vary, depending on the substance. For example, to determine the acid number of a polyurethane binder, a known amount of a sample of the binder may be dispersed in water and the aqueous dispersion may be titrated with a polyelectrolyte titrant of a known concentration. In this example, a current detector for colloidal charge measurement may be used. An example of a current detector is the Mutek PCD-05 Smart Particle Charge Detector (available from BTG). The current detector measures colloidal substances in an aqueous sample by detecting the streaming potential as the sample is titrated with the polyelectrolyte titrant to the point of zero charge. An example of a suitable polyelectrolyte titrant is poly(diallyldimethylammonium chloride) (i.e., PolyDADMAC). It is to be understood that any suitable test for a particular component may be used.

[0013] Fluid Sets and Textile Printing Kits

[0014] The fixer fluid, the inkjet ink, and the cross-linker composition disclosed herein may be part of a fluid set and/or of a textile printing kit, both of which are shown schematically in Fig. 1 .

[0015] The fluid kit 10 includes i) a fixer fluid 12 including a cationic polyurethane including a phosphonium salt, and an aqueous fixer vehicle; ii) an inkjet ink 14 including a colorant, a polyurethane binder, and an aqueous ink vehicle; and iii) a cross-linker composition 16 including a linear polycarbodiimide and an aqueous crosslinker vehicle. It is to be understood that any example of the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 disclosed herein may be used in the examples of the fluid kit 10.

[0016] In one example, the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 are formulated for thermal inkjet printing, and thus the fluid set is a thermal inkjet fluid set. [0017] In any example of the fluid kit 10, the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 may be maintained in separate containers (e.g., respective reservoirs/fluid supplies of respective inkjet cartridges) or separate compartments (e.g., respective reservoirs/fluid supplies) in a single container (e.g., inkjet cartridge). [0018] The textile printing kit 20 includes i) a textile fabric 18; ii) a fixer fluid 12 including a cationic polyurethane including a phosphonium salt, and an aqueous fixer vehicle; iii) an inkjet ink 14 including a colorant, a polyurethane binder, and an aqueous ink vehicle; and iv) a cross-linker composition 16 including a linear polycarbodiimide and an aqueous cross-linker vehicle. It is to be understood that any example of the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 disclosed herein may be used in the examples of the textile printing kit 20. It is also to be understood that any example of the textile fabric 18 disclosed herein may be used in the examples of the textile printing kit 20.

[0019] Fixer Fluid

[0020] Examples of the fixer fluid 12 disclosed herein include a cationic polyurethane including a phosphonium salt and an aqueous fixer vehicle.

[0021] The cationic polyurethane may be present in the form of particles. These particles may have a D50 particle size ranging from about 20 nm to about 500 nm. The “D50” particle size is defined as the particle size at which about half of the particles are larger than the D50 particle size and about half of the other particles are smaller than the D50 particle size. In other examples, the cationic polyurethane particles have a D50 particle size ranging from about 20 nm to about 200 nm, from about 40 nm to about 400 nm, from about 60 nm to about 300 nm, or from about 100 nm to about 500 nm. As used herein, particle size with respect to the cationic polyurethane particles can be calculated using volume of the particle size normalized to a spherical shape for diameter measurement. Particle size information can also be determined and/or verified using a scanning electron microscope (SEM) [0022] The cationic polyurethane polymer structure includes a polyurethane backbone, pendant side chain groups along the polyurethane backbone, and end cap groups terminating the polyurethane backbone. The pendant side chain groups and the end cap groups collectively include aliphatic phosphonium salts and polyalkylene oxides. As discussed in more detail below, the aliphatic phosphonium salts may be pendant side chain groups and/or end cap groups, and the polyalkylene oxides may be pendant side chain groups and/or end cap groups.

[0023] Several examples of the cationic polyurethane polymer structure 21 A, 21 B, 21 C, 21 D are respectively shown in Fig. 2 through Fig. 5.

[0024] In each of the schematic structures 20A, 20B, 20C, 20D respectively shown in Fig. 2 through Fig. 5, “m” can be from 1 to 18, each “R” is independently selected from a straight-chain or branched C1 to C5 alkyl, and “X” can be any counterion suitable for the positively charged phosphorus atom of the aliphatic phosphonium salt. As other examples, m can range from 1 to 14, from 1 to 10, from 2 to 18, from 2 to 10, from 1 to 5, or from 2 to 5; each “R” is independently selected from a straight-chain or branched C2 to C5 alkyl; and “X” is Cl, Br, I, sulfonate, toluenesulfonate, trifluoromethanesulfonate, etc.

[0025] Each of the cationic polyurethane polymer structures in Fig. 2 through Fig. 5 includes several chemical moieties, such as urethane linkage groups 22 (formed by the reaction of isocyanate groups 24 with any of a number of polyols 26 that may be present). A carbon atom of an isocyanate group 24 reacts with an oxygen atom of a hydroxyl of the polyol 26 to form the urethane linkage group 22. The polyols 26 and the isocyanate groups 24 are shown schematically after polymerization. The isocyanate groups 24 are shown along the cationic polyurethane backbone, and are schematically represented by a circle with isocyanate groups on either side thereof. Other chemical moieties represented in each of Fig. 2 through Fig. 5 include the polyalkylene oxides 28 and the aliphatic phosphonium salts 30. The polyalkylene oxides 28 are shown as PEO/PPO, indicating that the polyalkylene oxide 28 can be polyethylene oxide (PEO), polypropylene oxide (PPO), or include both types of monomeric units as a hybrid polyalkylene.

[0026] The cationic polyurethane polymer structure 21 A shown in Fig. 2 includes two aliphatic phosphonium salts 30 as the end cap groups EG. In this example, the polyalkylene oxides 28 are included as a pendant side chain group PG. [0027] The cationic polyurethane polymer structure 21 B shown in Fig. 3 includes two aliphatic phosphonium salts 30 as the end cap groups EG. In this example, both polyalkylene oxides 28 and additional aliphatic phosphonium salts 30 are included as pendant side chain groups PG.

[0028] The cationic polyurethane polymer structure 21 C shown in Fig. 4 includes two polyalkylene oxides 28 as the end cap groups EG. In this example, aliphatic phosphonium salts 30 are included as pendant side chain groups PG.

[0029] The cationic polyurethane polymer structure 21 D shown in Fig. 5 includes two polyalkylene oxides 28 as the end cap groups EG. In this example, both aliphatic phosphonium salts 30 and additional polyalkylene oxides 28 are included as pendant side chain groups PG.

[0030] The cationic polyurethane polymer structures 21 A, 21 B, 21 C, and 21 D shown in Fig. 2 through Fig. 5 are not intended to depict specific polymers, but rather show examples of the types of pendent groups PG that may be present along the polyurethane backbone and/or end cap groups EG of the polyurethane backbone. It is contemplated that the cationic polyurethane polymer structures 21 A, 21 B, 21 C, and 21 D may include additional polymerized polymeric diols, polymerized isocyanates, urethane linkage groups, polyalkylene oxides, or even other moieties not shown in these examples, such as epoxides, organic acids, etc. provided by other diols. As used herein, the terms “polymerized polyols/diols” and “polymerized isocyanates” refer to the respective monomers in their polymerized states (e.g., after the monomers have bonded together to form a polyurethane chain). It is to be understood that the monomers change in certain ways during polymerizing, and do not exist as separate molecules in the polymer.

[0031 ] Examples of other types of compounds that can be used in the formation of the cationic polyurethane polymer structures 21 A, 21 B, 21 C, and 21 D include various organic acid diols, C2-C20 aliphatic diols, glycidyl-containing diols to generate epoxy functional groups, functional amine groups derived from isocyanate groups that do not form a urethane linkage group, acid groups introduced from sulfonic acid or carboxylic acid diamines, or the like. These and other types of moieties can be included. [0032] As mentioned, the cationic polyurethane may be prepared by the reaction of the isocyanate 24 and the polyol 26. As described hereinbelow, mono-alcohols may also be included in the reaction mixture, for example, to incorporate end cap groups EC. The reaction between the isocyanate 24 and the polyol 26 can also occur in the presence of a catalyst in acetone under reflux.

[0033] The isocyanate 24 may be a diisocyanate. Example diisocyanates include 2,2,4 (or 2, 4, 4)-trimethylhexane-1 ,6-diisocyanate (TMDI), hexamethylene diisocyanate (HDI), methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), and/or 1-lsocyanato-4-[(4-isocyanatocyclohexyl)methyl]cyclohexane (H12MDI), etc., or combinations thereof. Others can likewise be used alone, or in combination with these diisocyanates, or in combination with other di isocyanates.

[0034] Some examples of the polyol 26 are diols that include the aliphatic phosphonium salts. Aliphatic phosphonium salt-based diols may be desirable to incorporate the aliphatic phosphonium salts as pendant side chain groups PG in the cationic polyurethane polymer. Aliphatic phosphonium salt-based diols may be prepared following the reaction scheme in equation 1 . In this example, an alkyl phosphine (I) is reacted with a halogenated primary alcohol (II) at a high temperature, e.g., 100°C, to give a trialkylphosphonium salt-based alcohol (III).

Equation 1 where R is independently selected from a straight-chain or branched C1 to C5 alkyl; m can be from 1 to 18; and X can be any suitable counterion for the positively charged phosphorus atom, such as bromide, chloride, or iodide, sulfonate, p-toluenesulfonate, trifluoromethanesulfonate, for example.

[0035] In accordance with Equation 1 , several example trialkylphosphonium saltbased diols can be formed, as shown below:

[0036] Other polymeric diols may be used, for example, if it is not desirable to incorporate the aliphatic phosphonium salts 30 as pendent side chain groups PG. Example polymeric diols that can be used include polyether diols (or polyalkylene diols), such as polyethylene oxide diols, polypropoylene oxide diols (or a hybrid diol of polyethylene oxide and polypropylene oxide), or polytetrahydrofuran. Still other polymeric diols that can be used include polyester diols, such as polyadipic ester diol, polyisophthalic acid ester diol, polyphthalic acid ester diol; or polycarbonate diols, such as hexanediol based polycarbonate diol, pentanediol based polycarbonate diol, hybrid hexanediol and pentanediol based polycarbonate diol, etc. Combinations of polymeric diols can also be used.

[0037] In some examples, it may be desirable to incorporate the aliphatic phosphonium salts 30 as end cap groups EG in the cationic polyurethane polymer. In these examples, mono-alcohols may be prepared following the reaction scheme in equation 2.

Equation 2 where R is independently selected from a straight-chain or branched C1 to C5 alkyl; m can be from 1 to 18; and X can be any suitable counterion for the positively charged phosphorus atom, such as bromide, chloride, or iodide, sulfonate, p-toluenesulfonate, trifluoromethanesulfonate, for example.

[0038] In accordance with Equation 2, several example aliphatic phosphonium saltbased mono-alcohols can be formed, as shown below:

[0039] As mentioned, the polyalkylene oxides 28 can be included, for example, as pendant side chain groups PG and/or as end cap groups EG. The polyalkylene oxides 28 can include polyethylene oxide (PEG), polypropylene oxide (PPG), or a hybrid of both PEG and PPG, which includes both types of monomeric units as a hybrid polyalkylene. In one example, the polyalkylene oxides 28 can be grafted or copolymerized during the formation of the cationic polyurethane. This provides polyalkylene oxide 28 moieties as pendent side chain groups PG along the polyurethane backbone. In another example, the polyalkylene oxides 28 can be added after the cationic polyurethane is synthesized. In this example, the polyalkylene oxides 28 are reacted with the end isocyanate groups of the cationic polyurethane.

Either way, the polyalkylene oxide 28 moieties can have a number average molecular weight (Mn, g/mol or Daltons) from about 200 Mn to about 15,000 Mn, from about 500 Mn to about 15,000 Mn, from about 1 ,000 Mn to about 12,000 Mn, from about 2,000 Mn to about 10,000 Mn, or from about 3,000 Mn to about 8,000 Mn, which can be measured by gel permeation chromatography.

[0040] The cationic polyurethane polymer that is formed has an acid number ranging from 0 mg KOH/g to 10 mg KOH/g, or from 0 mg KOH/g to 5mg KOH/g. In one specific example, the acid number of the cationic polyurethane polymer is 0 mg KOH/g.

[0041] The cationic polyurethane polymer that is formed has an NCO/OH ratio ranging from 1 .2 to 2.2. In another example, the cationic polyurethane polymer can be prepared with an NCO/OH ratio ranging from 1 .4 to 2.0. In yet another example, the cationic polyurethane polymer can be prepared with an NCO/OH ratio from 1.6 to 1 .8. As used herein, "NCO/OH ratio" refers to the mole ratio of NCO groups to OH groups in the monomers that react to form the polymer backbone.

[0042] The weight average molecular weight (Mw, g/mol or Daltons) of the cationic polyurethane polymer (which makes up the cationic polyurethane particles) can range from about 5,000 Mw to about 500,000 Mw, from about 10,000 Mw to about 400,000 Mw, from about 20,000 Mw to about 250,000 Mw, from about 10,000 Mw to about 200,000 Mw, or from about 50,000 Mw to about 500,000 Mw, as measured by gel permeation chromatography, for example.

[0043] As mentioned, the cationic polyurethane polymer can be in form of particles. Reaction(s) may be performed to generate the cationic polyurethane polymer, and then additional processing may be performed in order to obtain cationic polyurethane particles. In one example method, a diisocyanate is reacted with a polyalkylene oxide diol in the presence of a catalyst in acetone (or another organic solvent) under reflux to generate a pre-polymer including isocyanate end groups with polyalkylene oxide side chains positioned along a polyurethane backbone. After the pre-polymer is formed, an alkyl phosphonium salt with a single hydroxyl group, such as a triphenylphosphonium- based alcohol, is reacted with the isocyanate end groups to form alkyl phosphonium salt end cap groups. In another example method, a diisocyanate is reacted with an aliphatic phosphonium salt in the form of a diol to form the pre-polymer including aliphatic phosphonium salt pendant side chain groups, and then the pre-polymer can be reacted with polyalkylene oxides associated with a single hydroxyl group to form the end cap groups. In either example, more water can be added, and the organic solvent can be removed by vacuum distillation, for example, to provide cationic polyurethane particles that are stable in water. As such, the cationic polyurethane, and particles thereof, are water dispersible.

[0044] The cationic polyurethane including the phosphonium salt is present in the fixer fluid 12 in an amount ranging from about 1 wt% to about 15 wt%, based on a total weight of the fixer fluid 12. In another example, the cationic polyurethane is present in the fixer fluid 12 in an amount ranging from about 2 wt% to about 10 wt%, based on a total weight of the fixer fluid 12. If the cationic polyurethane is incorporated into the aqueous fixer vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the cationic polyurethane.

[0045] In addition to the cationic polyurethane, the fixer fluid 12 includes an aqueous fixer vehicle. The aqueous fixer vehicle includes water and any of a cosolvent, a surfactant, an acid, or combinations thereof.

[0046] The aqueous fixer vehicle includes water. The water may be purified water or deionized water. The amount of water will depend on the other components in the fixer fluid 12. In some instances, the aqueous fixer vehicle includes water, without any other components. In other instances, the aqueous fixer vehicle includes water, a cosolvent, and one or more additives. Some suitable additives may include a surfactant, an acid, or combinations thereof.

[0047] The aqueous fixer vehicle may include co-solvent(s). In an example, the cosolvent is a water soluble or water miscible organic co-solvent. Examples of cosolvents include alcohols, amides, esters, ketones, lactones, and ethers. In additional detail, the co-solvents may include aliphatic alcohols, aromatic alcohols, diols, glycol ethers, polyglycol ethers, lactams, formamides, acetamides, glycols, and long chain alcohols. Examples of such compounds include primary aliphatic alcohols, secondary aliphatic alcohols, 1 ,2-alcohols, 1 ,3-alcohols, 1 ,5-alcohols, ethylene glycol alkyl ethers, propylene glycol alkyl ethers (e.g., DOWANOL™ TPM or DOWANOL™ TPnB (from Dow Chemical), higher homologs (C6-C12) of polyethylene glycol alkyl ethers, N-alkyl caprolactams, unsubstituted caprolactams, both substituted and unsubstituted formamides, both substituted and unsubstituted acetamides, and the like. Some specific examples include dimethyl sulfoxide, sulfolane, propylene carbonate, ethylene carbonate, 2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, and triethanolamine. Specific examples of alcohols may include ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Other alcohols, such as polyhydric alcohols or derivatives thereof, may also be used. Examples of polyhydric alcohols may include ethylene glycol, diethylene glycol, propylene glycol, 2,2-dimethyl-1 ,3-propanediol, 2-ethyl-2-(hydroxymethyl)-1 ,3-propanediol, butylene glycol, triethylene glycol, 1 ,5-pentanediol, 1 ,2-hexanediol, 1 ,2-butanediol, 1 ,2,6- hexanetriol, glycerin, trimethylolpropane, and xylitol. Examples of polyhydric alcohol derivatives may include an ethylene oxide adduct of diglycerin. Some examples of the co-solvent also function as a humectant.

[0048] The co-solvent(s) may be present in the fixer fluid 12 in an amount ranging from about 4 wt% to about 30 wt% (based on the total weight of the fixer fluid 12). In an example, the total amount of co-solvent(s) present in the fixer fluid 12 is about 10 wt% (based on the total weight of the fixer fluid 12).

[0049] When included, the surfactant in the aqueous fixer vehicle may be any nonionic or cationic surfactant.

[0050] Examples of the non-ionic surfactant may include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, alkylalkanolamide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol, and a polyoxyethylene adduct of acetylene glycol. Specific examples of the non-ionic surfactant may include polyoxyethylenenonyl phenylether, polyoxyethyleneoctyl phenylether, and polyoxyethylenedodecyl. Further examples of the non-ionic surfactant may include silicon surfactants such as a polysiloxane oxyethylene adduct; fluorine surfactants such as perfluoroalkylcarboxylate, perfluoroalkyl sulfonate, and oxyethyleneperfluoro alkylether; and biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin.

[0051 ] In some examples, the aqueous fixer vehicle may include a silicone-free alkoxylated alcohol surfactant such as, for example, TEGO® Wet 510 (Evonik Degussa) and/or a self-emulsifiable wetting agent based on acetylenic diol chemistry, such as, for example, SURFYNOL® SE-F (Evonik Degussa). Other suitable commercially available surfactants include SURFYNOL® 465 (ethoxylatedacetylenic diol), SURFYNOL® 440 (an ethoxylated low-foam wetting agent) SURFYNOL® CT- 211 (now CARBOWET® GA-211 , non-ionic, alkylphenylethoxylate and solvent free), and SURFYNOL® 104 (non-ionic wetting agent based on acetylenic diol chemistry), (all of which are from Evonik Degussa); ZONYL® FSO (a.k.a. CAPSTONE®, which is a water-soluble, ethoxylated non-ionic fluorosurfactant from DuPont); TERGITOL® TMN-3 and TERGITOL® TMN-6 (both of which are branched secondary alcohol ethoxylate, non-ionic surfactants), and TERGITOL® 15-S-3, TERGITOL® 15-S-5, and TERGITOL® 15-S-7 (each of which is a secondary alcohol ethoxylate, non-ionic surfactant) (all of the TERGITOL® surfactants are available from The Dow Chemical Company); and BYK® 345, BYK® 346, BYK® 347, BYK® 348, BYK® 349 (each of which is a silicone surfactant) (all of which are available from BYK Chemie).

[0052] Examples of the cationic surfactant include quaternary ammonium salts, such as benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetalkonium chloride, cetylpyridinium chloride, cetrimonium, cetrimide, dofanium chloride, tetraethylammonium bromide, didecyldimethylammonium chloride, domiphen bromide, alkylbenzyldimethylammonium chlorides, distearyldimethylammonium chloride, diethyl ester dimethyl ammonium chloride, dipalmitoylethyl hydroxyethylmonium methosulfate, and ACCOSOFT® 808 (methyl (1 ) tallow amidoethyl (2) tallow imidazolinium methyl sulfate available from Stepan Company). Other examples of the cationic surfactant include amine oxides, such as lauryldimethylamine oxide, myristamine oxide, cocamine oxide, stearamine oxide, and cetamine oxide.

[0053] When included in the aqueous fixer vehicle, the surfactant may be present in an amount ranging from about 0.01 wt% to about 5 wt%, based on the total weight of the fixer fluid 12. In an example, the surfactant is present in an amount ranging from about 0.05 wt% to about 3 wt%, based on the total weight of the fixer fluid 12. In another example, the surfactant is present in an amount of about 0.3 wt%, based on the total weight of the fixer fluid 12. If the surfactant is incorporated into the aqueous fixer vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the surfactant solids.

[0054] The fixer fluid 12 may also include an acid. The acid may be used, in part, to control the pH of the fixer fluid 12. The acid may be included in the fixer fluid 12 to achieve a desired pH (e.g., ranging from about 4 to less than 7) and/or to counteract any slight pH increase that may occur over time. In an example, the total amount of acid(s) in the fixer fluid 12 ranges from greater than 0 wt% to about 3 wt% (based on the total weight of the fixer fluid 12). Examples of suitable acids that may be used in the fixer fluid 12 includes diluted hydrochloric acid (10%) or succinic acid.

[0055] The fixer fluid 12 is also devoid of colorant. This means that a pigment and/or dye is not included in the fixer fluid 12.

[0056] Inkjet Ink

[0057] Examples of the inkjet ink 14 disclosed herein include a colorant, a polyurethane binder, and an aqueous ink vehicle. In some examples, the inkjet ink 14 consists of the colorant, the polyurethane binder, and the aqueous ink vehicle; and thus does not include any other components. The aqueous ink vehicle may include water, water and a co-solvent, or water, a co-solvent and one or more additives.

Example additives include a humectant, a non-ionic or an anionic surfactant, an anti- kogation agent, an anti-microbial agent, a sequestering agent, a viscosity modifier, a pH adjuster, or combinations thereof.

[0058] The colorant in the inkjet ink 14 is pigment or a dye. As used herein, the term “pigment” generally includes organic or inorganic pigment colorants, magnetic particles, aluminas, silicas, and/or other ceramics, or organo-metallics or other opaque particles. The present description primarily illustrates the use of pigment colorants, but it is to be understood that other pigments, such as organometallics, ferrites, ceramics, etc., may also be used.

[0059] In some examples, the colorant in the inkjet ink 14 is a black pigment, a cyan pigment, a yellow pigment, or a magenta pigment. In other examples, the colorant may be a white pigment, an orange pigment, a green pigment, or any other desirable color.

[0060] Specific examples of black pigment include carbon black pigments. An example of an organic black pigment includes aniline black, such as C.l. Pigment Black 1.

[0061 ] Specific examples of a cyan pigment may include C.l. Pigment Blue -1 , -2, - 3, -15, -15:1 , -15:2, -15:3, -15:4, -16, -22, and -60.

[0062] Specific examples of a yellow pigment may include C.l. Pigment Yellow -1 , - 2, -3, -12, -13, -14, -16, -17, -73, -74, -75, -83, -93, -95, -97, -98, -114, -128, -129, - 138, -151 , -154, and -180.

[0063] Specific examples of a magenta pigment may include C.l. Pigment Red -5, - 7, -12, -48, -48:1 , -57, -112, -122, -123, -146, -168, -177, -184, -202, and C.l. Pigment Violet-19.

[0064] The colorant may be a white pigment, such as titanium dioxide, or other colored inorganic pigments such as zinc oxide and iron oxide.

[0065] Suitable pigments include the following, which are available from BASF Corp.: PALIOGEN® Orange, HELIOGEN® Blue L 6901 F, HELIOGEN® Blue NBD 7010, HELIOGEN® Blue K 7090, HELIOGEN® Blue L 7101 F, PALIOGEN® Blue L 6470, HELIOGEN® Green K 8683, HELIOGEN® Green L 9140, CHROMOPHTAL® Yellow 3G, CHROMOPHTAL® Yellow GR, CHROMOPHTAL® Yellow 8G, IGRAZIN® Yellow 5GT, and IGRALITE® Rubine 4BL. The following pigments are available from Degussa Corp.: Color Black FWI, Color Black FW2, Color Black FW2V, Color Black 18, Color Black, FW200, Color Black 5150, Color Black S160, and Color Black 5170. The following black pigments are available from Cabot Corp.: REGAL® 400R, REGAL® 330R, REGAL® 660R, MOGUL® L, BLACK PEARLS® L, MONARCH® 1400, MONARCH® 1300, MONARCH® 1100, MONARCH® 1000, MONARCH® 900, MONARCH® 880, MONARCH® 800, and MONARCH® 700. The following pigments are available from Orion Engineered Carbons GMBH: PRINTEX® II, PRINTEX® V, PRINTEX® 140U, PRINTEX® 140V, PRINTEX® 35, Color Black FW200, Color Black FW2, Color Black FW2V, Color Black FW 1 , Color Black FW 18, Color Black S 160, Color Black S 170, Special Black 6, Special Black 5, Special Black 4A, and Special Black 4. The following pigment is available from DuPont: TI-PURE® R-101. The following pigments are available from Heubach: MONASTRAL® Magenta, MONASTRAL® Scarlet, MONASTRAL® Violet R, MONASTRAL® Red B, and MONASTRAL® Violet Maroon B. The following pigments are available from Clariant: DALAMAR® Yellow YT-858-D, Permanent Yellow GR, Permanent Yellow G, Permanent Yellow DHG, Permanent Yellow NCG-71 , Permanent Yellow GG, Hansa Yellow RA, Hansa Brilliant Yellow 5GX-02, Hansa Yellow-X, NOVOPERM® Yellow HR, NOVOPERM® Yellow FGL, Hansa Brilliant Yellow 10GX, Permanent Yellow G3R-01 , HOSTAPERM® Yellow H4G, HOSTAPERM® Yellow H3G, HOSTAPERM® Orange GR, HOSTAPERM® Scarlet GO, and Permanent Rubine F6B. The following pigments are available from Sun Chemical: QUINDO® Magenta, INDOFAST® Brilliant Scarlet, QUINDO® Red R6700, QUINDO® Red R6713, INDOFAST® Violet, L74-1357 Yellow, L75-1331 Yellow, L75-2577 Yellow, and LHD9303 Black. The following pigments are available from Birla Carbon: RAVEN® 7000, RAVEN® 5750, RAVEN® 5250, RAVEN® 5000 Ultra® II, RAVEN® 2000, RAVEN® 1500, RAVEN® 1250, RAVEN® 1200, RAVEN® 1190 Ultra® RAVEN® 1170, RAVEN® 1255, RAVEN® 1080, and RAVEN® 1060. The following pigments are available from Mitsubishi Chemical Corp.: No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, No. 2300, MCF-88, MA600, MA7, MA8, and MA100.

[0066] While several examples have been given herein, it is to be understood that any other pigment can be used that is useful in modifying the color of the inkjet ink 14. [0067] The pigment can be present in the inkjet ink 14 in an amount from about 0.5 wt% to about 15 wt% based on a total weight of the inkjet ink 14. In one example, the pigment can be present in an amount from about 1 wt% to about 12 wt%. In another example, the pigment can be present in an amount from about 5 wt% to about 10 wt%. If the pigment is incorporated into the aqueous ink vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the pigment solids.

[0068] When the inkjet ink 14 includes a pigment, the ink 14 may also include a dispersant that helps to disperse the pigment. The pigment(s) can be dispersed by a dispersant that is adsorbed or ionically attracted to a surface of the pigment, or the dispersant can be covalently attached to a surface of the pigment (e.g., a selfdispersed pigment). In one example, the dispersant can be an acrylic dispersant, such as a styrene (meth)acrylate dispersant, or another dispersant suitable for keeping the pigment suspended in the liquid vehicle.

[0069] In some examples, the colorant may be a dye. The dye (prior to being incorporated into the ink formulation), may be dispersed in water alone or in combination with an additional water soluble or water miscible co-solvent. It is to be understood however, that the liquid components of the dye dispersion become part of the ink vehicle in the inkjet ink 14.

[0070] The dye can be nonionic, anionic, or a mixture of nonionic and anionic dyes. The dye can be a hydrophilic anionic dye, a direct dye, a reactive dye, a polymer dye or an oil soluble dye. Specific examples of dyes that may be used include Sulforhodamine B, Acid Blue 113, Acid Blue 29, Acid Red 4, Rose Bengal, Acid Yellow 17, Acid Yellow 29, Acid Yellow 42, Acridine Yellow G, Acid Yellow 23, Acid Blue 9, Nitro Blue Tetrazolium Chloride Monohydrate or Nitro BT, Rhodamine 6G, Rhodamine 123, Rhodamine B, Rhodamine B Isocyanate, Safranine O, Azure B, and Azure B Eosinate, which are available from Sigma-Aldrich Chemical Company (St. Louis, Mo.). Examples of anionic, water-soluble dyes include Direct Yellow 132, Direct Blue 199, Magenta 377 (available from Ilford AG, Switzerland), alone or together with Acid Red 52. Examples of water-insoluble dyes include azo, xanthene, methine, polymethine, and anthraquinone dyes. Specific examples of water-insoluble dyes include ORASOL® Blue GN, ORASOL® Pink, and ORASOL® Yellow dyes available from BASF Corp. Black dyes may include Direct Black 154, Direct Black 168, Fast Black 2, Direct Black 171 , Direct Black 19, Acid Black 1 , Acid Black 191 , Mobay Black SP, and Acid Black 2. [0071] In some examples, the dye may be present in an amount ranging from about 0.5 wt% to about 15 wt% based on a total weight of the inkjet ink 14. In one example, the dye may be present in an amount ranging from about 1 wt% to about 10 wt%. In another example, the dye may be present in an amount ranging from about 5 wt% to about 10 wt%.

[0072] The inkjet ink 14 also includes the polyurethane binder. The polyurethane binder may be present in the form of particles. It is to be understood that the polyurethane binder and the corresponding binder particles present in the inkjet ink 14 are not the same as the cationic polyurethane and the corresponding cationic polyurethane particles present in the fixer fluid 12.

[0073] In the examples disclosed herein, the polyurethane binder is considered non-reactive or non-UV-reactive, because it does not include a UV reactive group. Also in the examples disclosed herein, the polyurethane binder may be self-cross- linked and may also include groups (e.g., carboxyl groups, sulfonate groups, etc.) that can cross-link with the crosslinking agent disclosed herein.

[0074] The polyurethane binder in the inkjet ink 14 may be synthesized by first reacting a diisocyanate with a polyester diol. This reaction may occur in the presence of a catalyst (e.g., dibutyl tin dilaurate, bismuth octanoate, and 1 ,4- diazabicyclo[2.2.2]octane) and in an organic solvent (e.g., methyl ethyl ketone (MEK), tetrahydrofuran (THF), ethyl acetate, acetone, or combinations thereof) under reflux. This reaction forms a pre-polymer having urethane linkages. The pre-polymer is dissolved in the organic solvent.

[0075] Some example diisocyanates include those set forth herein for the cationic polyurethane, such as hexamethylene-1 ,6-di isocyanate (HDI), 2,2,4-trimethyl- hexamethylene-diisocyanate (TDMI), 1 ,12-dodecane diisocyanate, 2,4,4-trimethyl- hexamethylene diisocyanate, 2-methyl-1 ,5-pentamethylene diisocyanate, isophorone diisocyanate (IPDI), and combinations thereof. Polyester polyols are typically made from mixtures of diols, triols, and dibasic acids or anhydrides.

[0076] During this reaction, the diisocyanate is used in excess so that additional NCO groups are available for subsequent cross-linking. [0077] The pre-polymer is then cross-linked. Cross-linking may be accomplished by adding water, and one or more diamine cross-linkers to the pre-polymer solution. [0078] With respect to the diamines that can be used in forming the polyurethane binder particles, polymerized sulfonated-diamines as well as non-ionic diamines can be used. Polymerized sulfonated-diamines can be prepared from diamines by adding sulfonate groups thereto. Non-ionic diamines can be diamines that include aliphatic groups that are not charged, such as alkyl groups, alicyclic groups, etc. A charged diamine is not used for the non-ionic diamine, if the non-ionic diamine is present. Example diamines can include various dihydrazides, alkyldihydrazides, sebacic dihydrazides, alkyldioic dihydrazides, aryl dihydrazides, e.g., terephthalic dihydrazide, organic acid dihydrazide, e.g., succinic dihydrazides, adipic acid dihydrazides, etc, oxalyl dihydrazides, azelaic dihydrazides, carbohydrazide, etc. It is noted however, that these examples may not be appropriate for use as one or the other type of diamine, but rather, this list is provided as being inclusive of the types of diamines that can be used in forming the polymerized sulfonated-diamines and/or the non-ionic diamines, and not both in every instance (though some can be used for either type of diamine).

[0079] Example diamine structures are shown below. More specific examples of diamines include 4,4'-methylenebis(2-methylcyclohexyl-amine) (DMDC), 4-methyl-1 ,3'- cyclohexanediamine (HTDA), 4,4'-Methylenebis(cyclohexylamine) (PACM), isphorone diamine (IPDA), tetramethylethylenediamine (TMDA), ethylene diamine (DEA), 1 ,4- cyclohexane diamine, 1 ,6-hexane diamine, hydrazine, adipic acid dihydrazide (AAD), carbohydrazide (CHD), and/or diethylene triamine (DETA), notably, DETA includes three amines, and thus, is a triamine. However, since it also includes 2 amines, it is considered to fall within the definition herein of “diamine,” meaning it includes two amines. Many of the diamine structures shown below can be used as the non-ionic diamine, such as the uncharged aliphatic diamines shown below. 2

1,4-cyclohexane diamine 1,6-hexane diamine hydrazine

[0080] There are also other alkyl diamines (other than 1 ,6-hexane diamine) that can be used, such as, by way of example: [0081 ] There are also other dihydrazides (other than AAD shown above) that can be used, such as, by way of example:

[0082] As an example of a carboxylated or sulfonated diamine, which in this case is an alkylamine-alkylamine-sulfonate (shown as a sulfonic acid in Formula I below, but as a sulfonate, would include a positive counterion associated with an SOs' group). While one example is shown in Formula I below, it is to be understood that other diamines may be used, including those based on structures shown above. (Formula I) where R is H or is a C1 to C10 straight-or branched-alkyl or alicyclic or combination of alkyl and alicyclic, m is 1 to 5, and n is 1 to 5. One example of such a structure, sold by Evonik Industries (USA), is A-95, which is exemplified where R is H, m is 1 , and n is 1 . Another example structure sold by Evonik Industries is VESTAMIN®, where R is H, m is 1 , and n is 2.

[0083] After the cross-linking reaction, any solvent is then removed, e.g., by vacuum distillation to afford the final polyurethane dispersion, which includes self- cross-linked polyurethane binder particles dispersed in water. More specifically, the polyurethane solution may be slowly added to water including a base with vigorous agitation, or vice versa. The mixture may be stirred and the organic solvent may be removed by distillation to form the polyurethane binder dispersion.

[0084] In an example, the acid number of the polyurethane binder particles is 30 mg KOH/g solid resin or less, or 10 mg KOH/g solid resin or less. As examples, the polyurethane binder particles may have an acid number ranging from greater than 0 mg KOH/g to 30 mg KOH/g, or from greater than 0 mg KOH/g to about 20 mg KOH/g, or from greater than 0 mg KOH/g to about 19 mg KOH/g, or from greater than 0 mg KOH/g to about 15 mg KOH/g, or from greater than 0 mg KOH/g to about 10 mg KOH/g, etc.

[0085] The average particle size of the polyurethane binder particles may range from about 200 nm to about 400 nm. In one example, this range refers to the D50 particle size. As examples, the polyurethane binder particles may have a D50 particle size ranging from about 200 nm to about 400 nm, or from about 200 nm to about 350 nm, or from about 300 nm to about 375 nm, or from about 250 nm to about 350 nm, etc.

[0086] In some examples, the polyurethane binder includes self-cross-linked polyurethane binder particles having an acid number less than 10, a weight average molecular weight ranging greater than 50,000, and a particle size ranging from about 200 nm to about 400 nm.

[0087] The polyurethane binder particles may be incorporated into the inkjet ink 14 as a polyurethane dispersion, and any liquid components of the dispersion become part of the ink vehicle. The polyurethane dispersion is added in a suitable amount so that the polyurethane binder particles are present in an active amount that is suitable for the inkjet printing architecture that is to be used. In an example, the polyurethane binder particles (which does not account for other dispersion components) are present in an amount ranging from about 0.1 wt% to about 30 wt%, based on a total weight of the inkjet ink 14. In other examples, the self-cross-linked polyurethane binder particles are present in an amount ranging from about 2 wt% to about 20 wt%, or from about 3 wt% to about 15 wt%, based on a total weight of the inkjet ink 14. In still another example, the polyurethane binder particles are present in an amount of about 5 wt% or about 12 wt%, based on a total weight of the inkjet ink 14. These percentages reflect the total polyurethane binder solids in the final inkjet ink 14.

[0088] The colorant and polyurethane binder are dispersed in an aqueous ink vehicle. The aqueous ink vehicle includes water. The water may be purified water or deionized water. The amount of water will depend on the other components in the inkjet ink 14, but will include at least 30 wt%. In some instances, water may be present in the inkjet ink 14 in an amount of at least 60 wt%. Water may be present in an amount of at most 99 wt%, for example, at most 95 wt%. In some examples, water may be present in the inkjet ink 14 in an amount ranging from about 30 wt% to about 99 wt%, for instance, from about 40 wt% to about 98 wt% or from about 50 wt% to about 95 wt%. In other examples, water may be present in an amount ranging from about 60 wt% to about 93 wt%, for instance, from about 70 wt% to about 90 wt%.

[0089] In some of the examples disclosed herein, the aqueous ink vehicle includes water, without any other components. In other instances, the aqueous ink vehicle includes water, a co-solvent, and one or more additives. Some suitable additives may include a humectant, a non-ionic or an anionic surfactant, an anti-kogation agent, an anti-microbial agent, a viscosity modifier, a pH adjuster, a sequestering agent, or combinations thereof.

[0090] Any of the co-solvents set forth herein for the fixer fluid 12 may be used in the inkjet ink 14. The amount of the co-solvent in the inkjet ink 14 may be up to 50 wt%, depending on the jetting architecture. As other example, the co-solvent(s) may range from about 1 wt% to about 30 wt%, or from about 5 wt% to about 20 wt% of the total weight of the inkjet ink 14.

[0091] The aqueous ink vehicle may include a humectant. An example of a suitable humectant is ethoxylated glycerin having the following formula: in which the total of a+b+c ranges from about 5 to about 60, or in other examples, from about 20 to about 30. An example of the ethoxylated glycerin is LIPONIC® EG-1 (LEG-1 , glycereth-26, a+b+c=26, available from Lipo Chemicals). Other examples of suitable humectants include alcohols, for example, glycols such as 2,2’-thiodiethanol, glycerol, 1 ,3-propanediol, 1 ,5-pentanediol, polyethylene glycol, ethylene glycol, diethylene glycol, propylene glycol and/or tetraethylene glycol; pyrrolidones, such as 2- pyrrolidone, N-methyl-2-pyrrolidone, and/or N-methyl-2-oxazolidinone; and/or monoalcohols, such as n-propanol and/or iso-propanol. In an example, the humectant includes a mixture of alcohols. In another example, the humectant includes a mixture of 2,2'-thiodiethanol and a glycol, such as a polyalkylene glycol.

[0092] The humectant(s) may be present in an amount ranging from about 0.2 wt% to about 5 wt% (based on the total weight of the inkjet ink 14). In an example, the humectant is present in the inkjet ink 14 in an amount of about 1 wt%, based on the total weight of the inkjet ink 14.

[0093] The surfactant in the aqueous ink vehicle may be any example of the nonionic surfactant set forth herein for the fixer fluid 12. The surfactant in the aqueous ink vehicle may also or alternatively be an anionic surfactant. Examples of the anionic surfactant may include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate ester salt of higher fatty acid ester, sulfonate of higher fatty acid ester, sulfate ester salt and sulfonate of higher alcohol ether, higher alkyl sulfosuccinate, polyoxyethylene alkylether carboxylate, polyoxyethylene alkylether sulfate, alkyl phosphate, and polyoxyethylene alkyl ether phosphate.

Specific examples of the anionic surfactant may include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, monobutylbiphenylsul fonate, and dibutylphenylphenol disulfonate.

[0094] The amount of the non-ionic and/or anionic surfactant present in the inkjet ink 14 may be any amount set forth herein for the surfactant(s) in the fixer fluid 12 (except that the amount(s) are based on the total weight of the inkjet ink 14 instead of the fixer fluid 12).

[0095] An anti-kogation agent may also be included in the vehicle of the inkjet ink 14, for example, when the inkjet ink 14 is to be applied via a thermal inkjet printhead. Anti-kogation agent(s) is/are included to assist in preventing the buildup of kogation. In some examples, the anti-kogation agent may improve the jettability of the inkjet ink 14.

[0096] Examples of suitable anti-kogation agents include oleth-3-phosphate (commercially available as CRODAFOS™ O3A or CRODAFOS™ N-3A) or dextran 500k. Other suitable examples of the anti-kogation agents include CRODAFOS™ HCE (phosphate-ester from Croda Int.), CRODAFOS® 010A (oleth-10-phosphate from Croda Int.), or DISPERSOGEN® LFH (polymeric dispersing agent with aromatic anchoring groups, acid form, anionic, from Clariant), etc. It is to be understood that any combination of the anti-kogation agents listed may be used.

[0097] The anti-kogation agent may be present in the inkjet ink 14 in an amount ranging from about 0.1 wt% to about 1 .5 wt%, based on the total weight of the inkjet ink 14. In an example, the anti-kogation agent is present in an amount of about 0.5 wt%, based on the total weight of the inkjet ink 14. If the anti-kogation agent is incorporated into the aqueous ink vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the anti-kogation agent solids.

[0098] The aqueous ink vehicle may also include anti-microbial agent(s). Antimicrobial agents are also known as biocides and/or fungicides. Examples of suitable anti-microbial agents include the NUOSEPT® (Ashland Inc.), UCARCIDE™ or KORDEK™ or ROCIMA™ (The Dow Chemical Company), PROXEL® (Arch Chemicals) series, ACTICIDE® B20 and ACTICIDE® M20 and ACTICIDE® MBL (blends of 2-methyl-4-isothiazolin-3-one (MIT), 1 ,2-benzisothiazolin-3-one (BIT) and Bronopol) (Thor Chemicals), AXIDE™ (Planet Chemical), NIPACIDE™ (Clariant), blends of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT or CMIT) and MIT under the tradename KATHON™ (The Dow Chemical Company), and combinations thereof. [0099] In an example, the total amount of anti-microbial agent(s) in the inkjet ink 14 ranges from about 0.001 wt% to about 0.05 wt% (based on the total weight of the inkjet ink 14). In another example, the total amount of anti-microbial agent(s) in the inkjet ink 14 is about 0.04 wt% (based on the total wet weight of the inkjet ink 14). If the anti-microbial agent is incorporated into the aqueous ink vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the anti-microbial agent solids.

[0100] The aqueous ink vehicle may also include chelating agent/sequestering agent. In an example, the chelating agent is selected from the group consisting of methylglycinediacetic acid, trisodium salt; 4,5-dihydroxy-1 ,3-benzenedisulfonic acid disodium salt monohydrate; ethylenediaminetetraacetic acid (EDTA); hexamethylenediamine tetra(methylene phosphonic acid), potassium salt; and combinations thereof. Methylglycinediacetic acid, trisodium salt (Na3MGDA) is commercially available as TRILON® M from BASF Corp. 4,5-dihydroxy-1 ,3- benzenedisulfonic acid disodium salt monohydrate is commercially available as TIRON™ monohydrate. Hexamethylenediamine tetra(methylene phosphonic acid), potassium salt is commercially available as DEQUEST® 2054 from Italmatch Chemicals.

[0101] When included in the inkjet ink 14, the chelating agent is present in an amount greater than 0 wt% and less than or equal to 0.5 wt% based on the total wet weight of the inkjet ink 14. In an example, the chelating agent is present in an amount ranging from about 0.05 wt% to about 0.2 wt% based on the total weight of the inkjet ink 14. If the chelating agent is incorporated into the aqueous ink vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the chelating agent solids.

[0102] Any suitable viscosity modifier may also be added to the aqueous ink vehicle. The viscosity modifier may be used to achieve suitable jetting viscosity. Some examples viscosity modifiers include LUCANT™ Hydrocarbon Synthetic Fluid (commercially available from Lubrizol), maleic anhydride styrene copolymer (MSC), olefin copolymer (OCP), polyisobutylene (PIB), polymethacrylate (PMA), pour point depressants (PPD), styrene butadiene (SBR), and combinations thereof. In an example, the viscosity modifier is added in an amount up to 5 wt% based on the total weight of the inkjet ink 14. If the viscosity modifier is incorporated into the aqueous ink vehicle in the form of a water-based dispersion, it is to be understood that these weight percentages reflect the active weight percent of the viscosity modifier solids.

[0103] The aqueous ink vehicle may also include a pH control agent. A pH adjuster may be included in the inkjet ink 14 to achieve a desired pH (e.g., 8.5) and/or to counteract any slight pH drop that may occur over time. In an example, the total amount of pH adjuster(s) in the inkjet ink 14 ranges from greater than 0 wt% to about 0.1 wt% (based on the total weight of the inkjet ink 14). In another example, the total amount of pH adjuster(s) in the inkjet ink 14 is about 0.03 wt% (based on the total weight of the inkjet ink 14).

[0104] Examples of suitable pH adjusters include metal hydroxide bases, such as potassium hydroxide (KOH), sodium hydroxide (NaOH), etc. In an example, the metal hydroxide base may be added to the inkjet ink 14 in an aqueous solution. In another example, the metal hydroxide base may be added to the inkjet ink 14 in an aqueous solution including 5 wt% of the metal hydroxide base (e.g., a 5 wt% potassium hydroxide aqueous solution).

[0105] Suitable pH ranges for examples of the inkjet ink 14 can be from pH 7 to pH 11 , from pH 7 to pH 10, from pH 7.2 to pH 10, from pH 7.5 to pH 10, from pH 8 to pH 10, 7 to pH 9, from pH 7.2 to pH 9, from pH 7.5 to pH 9, from pH 8 to pH 9, from 7 to pH 8.5, from pH 7.2 to pH 8.5, from pH 7.5 to pH 8.5, from pH 8 to pH 8.5, from 7 to pH 8, from pH 7.2 to pH 8, or from pH 7.5 to pH 8.

[0106] Cross-linking Composition

[0107] Examples of the cross-linking composition 16 disclosed herein include a linear polycarbodiimide and an aqueous cross-linker vehicle.

[0108] The linear polycarbodiimide has the structure: wherein:

R 1 is a divalent organic group which has no reactivity toward a carbodiimide functional group;

R 2 and R 3 are each a monovalent organic group which has no reactivity toward the carbodiimide functional group; and n is an integer ranging from 2 to 100.

[0109] R 1 may be any linear or cyclic hydrocarbon of - (CH 2 )m- where m ranges from 1 to 10, e.g., 2 to 8, 1 to 5, etc. R 2 and R 3 are independently selected from an alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.), an alkenyl, a cycloalkyl (e.g., cyclopentyl, cyclohexyl, etc.), a cyclo-alkenyl, or an aryl (e.g., benzyl, m-tolyl, o-tolyl, p- tolyl, etc.), each of which may be substituted with substituents which do not interfere with the carbodiimide functionality.

[0110] The linear polycarbodiimide is mono-functional because the sole reactive groups are the carbodiimide reactive groups. In other words, the linear polycarbodiimide does not include any other reactive cross-linking functional groups along its backbone chain in addition to the carbodiimide reactive groups. For example, the linear polycarbodiimide does not include a blocked isocyanate, aziridine, azetidine, epoxide, oxazoline, oxazolidine, and/or thiazolidine. While the linear polycarbodiimide may be less reactive than a multi-functional polycarbodiimide (which includes other reactive functional groups), it has surprisingly been found that the reactivity of the carbodiimide groups, e.g., with carboxyl groups of the polyurethane in the fixer fluid 12 and/or in the inkjet ink 14 and/or with reactive surface groups of the textile fabric 20, is sufficient to achieve high durability. An example of the cross-linking reaction between the carbodiimide functional group (-N=C=N-) and carboxyl group(s) of the textile fabric 18, the cationic polyurethane in the fixer fluid 12, and/or the polyurethane binder in the inkjet ink 14 is shown in Fig. 6. [0111] Moreover, unlike multi-functional polycarbodiimide, the linear polycarbodiimide has been found to be readily jettable from a thermal inkjet printhead (see the example section herein).

[0112] The linear polycarbodiimide has a weight average molecular weight (Mw, g/mol or Daltons) ranging from about 1 ,000 Daltons to about 6,000 Daltons. In another example, the weight average molecular weight of the linear polycarbodiimide ranges from about 3,000 Daltons to about 3,500 Daltons.

[0113] The linear polycarbodiimide may be in the form of particle. The average particle size of the linear polycarbodiimide particles may be 200 nm or less. In one example, this range refers to the D50 particle size. As examples, the linear polycarbodiimide may have a D50 particle size ranging from about 1 nm to about 200 nm, or from about 10 nm to about 150 nm, or from about 25 nm to about 200 nm, or from about 100 nm to about 200 nm, etc.

[0114] Some examples of the linear polycarbodiimide particles are commercially available in a water-based dispersion. Some suitable examples include PICASSIAN® XL-702 (Stahl Polymers) and CARBODILITE® V-02 (Nisshinbo Chemical Inc.). Emulsion forms of the linear polycarbodiimide may not be desirable, because the presence of dispersants may deleteriously affect the thermal inkjettability of the resulting cross-linker composition 16.

[0115] As such, the linear polycarbodiimide particles may be incorporated into the cross-linker composition 16 as a water-based dispersion, and any liquid components of the dispersion become part of the cross-linker vehicle. The linear polycarbodiimide dispersion is added in a suitable amount so that the linear polycarbodiimide particles are present in an active amount that is suitable for the inkjet printing architecture that is to be used. In an example, the linear polycarbodiimide particles (which does not account for other dispersion components) are present in an amount ranging from about 1 wt% to about 10 wt%, based on a total weight of cross-linker composition 16. In other examples, the linear polycarbodiimide particles are present in an amount ranging from about 2 wt% to about 8 wt%, or from about 3 wt% to about 6 wt%, based on a total weight of the cross-linker composition 16. These percentages reflect the total linear polycarbodiimide solids in the final cross-linker composition 16. [0116] The aqueous cross-linker vehicle includes water. The water may be purified water or deionized water. The amount of water will depend on the other components in the cross-linker, but will include at least 50 wt%. In some instances, water may be present in the cross-linker in an amount of at least 60 wt%. Water may be present in an amount of at most 99 wt%, for example, at most 95 wt%. In some examples, water may be present in the cross-linker in an amount ranging from about 30 wt% to about 99 wt%, for instance, from about 40 wt% to about 98 wt% or from about 50 wt% to about 95 wt%. In other examples, water may be present in an amount ranging from about 60 wt% to about 93 wt%, for instance, from about 70 wt% to about 90 wt%.

[0117] In some of the examples disclosed herein, the aqueous cross-linker vehicle includes water, without any other components. In other instances, the aqueous crosslinker vehicle includes water, a co-solvent, and a non-ionic surfactant. In some examples, the aqueous cross-linker vehicle may include additional additives, such as a humectant, an anti-kogation agent, an anti-microbial agent, a sequestering agent, a viscosity modifier, a pH adjuster, or combinations thereof.

[0118] The co-solvent and the non-ionic surfactant in the cross-linker composition 16 may be any example, respectively, of the co-solvent and the non-ionic surfactant set forth herein for the fixer fluid 12. The amount of the co-solvent and the non-ionic surfactant present in the cross-linker composition 16 may be any amount set forth herein, respectively, for the co-solvent(s) and the non-ionic surfactant(s) in the fixer fluid 12 (except that the amount(s) are based on the total weight of the cross-linker composition 16 instead of the fixer fluid 12).

[0119] Any of the other additives (e.g., humectant, anti-kogation agent, etc.) may be incorporated into the cross-linker composition 16 in any amount set forth herein for the respective additives in the inkjet ink 14 (except that the amount(s) are based on the total weight of the cross-linker composition 16 instead of the inkjet ink 14).

[0120] Textile Fabric

[0121] The textile fabric 18 may be selected from the group consisting of polyester fabrics, polyester blend fabrics, cotton fabrics, cotton blend fabrics, nylon fabrics, nylon blend fabrics, silk fabrics, silk blend fabrics, wool fabrics, wool blend fabrics, and combinations thereof. In a further example, the textile fabric 18 is selected from the group consisting of cotton fabrics and cotton blend fabrics.

[0122] It is to be understood that organic textile fabrics and/or inorganic textile fabrics may be used for the textile fabric 18. Some types of fabrics that can be used include various fabrics of natural and/or synthetic fibers. It is to be understood that the polyester fabrics may be a polyester coated surface. The polyester blend fabrics may be blends of polyester and other materials (e.g., cotton, linen, etc.). In another example, the textile fabric 18 may be selected from nylons (polyamides) or other synthetic fabrics.

[0123] Example natural fiber fabrics that can be used include treated or untreated natural fabric textile substrates, e.g., wool, cotton, silk, linen, jute, flax, hemp, rayon fibers, thermoplastic aliphatic polymeric fibers derived from renewable resources (e.g. cornstarch, tapioca products, sugarcanes), etc. Example synthetic fibers used in the textile fabric/substrate 18 can include polymeric fibers such as nylon fibers, polyvinyl chloride (PVC) fibers, PVC-free fibers made of polyester, polyamide, polyimide, polyacrylic, polypropylene, polyethylene, polyurethane, polystyrene, polyaramid (e.g., KEVLAR®) polytetrafluoroethylene (PTFE) (TEFLON®) (both trademarks of Chemours), fiberglass, polytrimethylene, polycarbonate, polyethylene terephthalate, polyester terephthalate, polybutylene terephthalate, or a combination thereof. In an example, natural and synthetic fibers may be combined at ratios of 1 :1 , 1 :2, 1 :3, 1 :4, 1 :5, 1 :6, 1 :7, 1 :8, 1 :9, 1 :10, 1 :11 , 1 :12, 1 :13, 1 :14, 1 :15, 1 :16, 1 :17, 1 :18, 1 :19, 1 :20, or vice versa. In some examples, the fiber can be a modified fiber from the above-listed polymers. The term “modified fiber” refers to one or both of the polymeric fiber and the fabric as a whole having undergone a chemical or physical process such as, but not limited to, copolymerization with monomers of other polymers, a chemical grafting reaction to contact a chemical functional group with one or both the polymeric fiber and a surface of the fabric, a plasma treatment, a solvent treatment, acid etching, or a biological treatment, an enzyme treatment, or antimicrobial treatment to prevent biological degradation. [0124] In addition, the textile fabric 18 can contain additives, such as a colorant (e.g., pigments, dyes, and tints), an antistatic agent, a brightening agent, a nucleating agent, an antioxidant, a UV stabilizer, a filler, and/or a lubricant, for example.

[0125] It is to be understood that the terms “textile fabric” or “fabric substrate” do not include materials commonly known as any kind of paper (even though paper can include multiple types of natural and synthetic fibers or mixtures of both types of fibers). Fabric substrates can include textiles in filament form, textiles in the form of fabric material, or textiles in the form of fabric that has been crafted into finished articles (e.g., clothing, blankets, tablecloths, napkins, towels, bedding material, curtains, carpet, handbags, shoes, banners, signs, flags, etc.). In some examples, the fabric substrate can have a woven, knitted, non-woven, or tufted fabric structure. In one example, the fabric substrate can be a woven fabric where warp yarns and weft yarns can be mutually positioned at an angle of about 90°. This woven fabric can include fabric with a plain weave structure, fabric with twill weave structure where the twill weave produces diagonal lines on a face of the fabric, or a satin weave. In another example, the fabric substrate can be a knitted fabric with a loop structure. The loop structure can be a warp-knit fabric, a weft-knit fabric, or a combination thereof. A warp-knit fabric refers to every loop in a fabric structure that can be formed from a separate yam mainly introduced in a longitudinal fabric direction. A weft-knit fabric refers to loops of one row of fabric that can be formed from the same yam. In a further example, the fabric substrate can be a non-woven fabric. For example, the non-woven fabric can be a flexible fabric that can include a plurality of fibers or filaments that are one or both bonded together and interlocked together by a chemical treatment process (e.g., a solvent treatment), a mechanical treatment process (e.g., embossing), a thermal treatment process, or a combination of multiple processes.

[0126] In one example, the textile fabric 18 can have a basis weight ranging from 10 gsm to 500 gsm. In another example, the textile fabric 18 can have a basis weight ranging from 50 gsm to 400 gsm. In other examples, the textile fabric 18 can have a basis weight ranging from 100 gsm to 300 gsm, from 75 gsm to 250 gsm, from 125 gsm to 300 gsm, or from 150 gsm to 350 gsm. [0127] Printing Method and System

[0128] Fig. 7 depicts an example of the printing method 100. The method 100 includes applying a fixer fluid 12 to a textile fabric 18 to form a fixer fluid layer, the fixer fluid 12 including a cationic polyurethane including a phosphonium salt and an aqueous fixer vehicle (reference numeral 102); applying an inkjet ink 14 to the textile fabric 18 to form an ink layer on the fixer fluid layer, the inkjet ink 14 including a colorant, a polyurethane binder, and an aqueous ink vehicle (reference numeral 104); applying a cross-linker composition 16 to the textile fabric 18 to form a cross-linker composition layer on the ink layer, the cross-linker composition 16 including a linear polycarbodiimide and an aqueous cross-linker vehicle (reference numeral 106); and exposing the textile fabric 18, having the fixer fluid layer, the ink layer, and the crosslinker composition layer thereon, to heat or electromagnetic energy irradiation (reference numeral 108).

[0129] It is to be understood that any example of the fixer fluid 12 may be used in the examples of the method 100. In some examples, the fixer fluid 12 may be applied digitally using inkjet technology. Any suitable inkjet applicator, such as a thermal inkjet cartridge/printhead, a piezoelectric cartridge/printhead, or a continuous inkjet cartridge/printhead, may eject the fixer fluid 12 in a single pass or in multiple passes. As an example of single pass printing, the cartridge(s) of an inkjet printer deposit the desired amount of the fixer fluid 12 during the same pass of the cartridge(s) across the textile fabric 18. In other examples, the cartridge(s) of an inkjet printer deposit the desired amount of the fixer fluid 12 over several passes of the cartridge(s) across the textile fabric 18.

[0130] It is also to be understood that any example of the inkjet ink 14 may be used in the examples of the method 100. The inkjet ink 14 may be ejected onto the textile fabric 18 using inkjet technology. Any of the inkjet applicators may eject the inkjet ink 14 in a single pass or in multiple passes (as described herein).

[0131] Further, it is to be understood that any example of the cross-linker composition 16 may be used in the examples of the method 100. The cross-linker composition 16 may also be ejected onto the textile fabric 18 using inkjet technology. Any of the inkjet applicators may eject the cross-linker composition 16 in a single pass or in multiple passes (as described herein).

[0132] In the example method 100, the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 are printed onto the previously applied layer while it is wet. Wet on wet printing may be desirable because less fluid/ink/composition may be applied during this process, because it is desirable for the polyurethane(s) to interact with the polycarbodiimide, and because the printing workflow may be simplified without the additional drying. In an example of wet on wet printing, the inkjet ink 14 is printed onto the printed fixer fluid 12 (e.g., the fixer fluid layer) within a period of time ranging from about 0.01 second to about 30 seconds after the fixer fluid 12 is printed, and the cross-linker composition 16 is printed onto the printed inkjet ink (e.g., the ink layer) within a period of time ranging from about 0.01 second to about 30 seconds after the inkjet ink 14 is printed. In further examples, the inkjet ink 14 is printed onto the previously applied fixer fluid 12 and/or the cross-linker composition 16 is printed onto the previously applied inkjet ink 14 within a period of time ranging from about 0.1 second to about 20 seconds; or from about 0.2 second to about 10 seconds; or from about 0.2 second to about 5 seconds. Wet on wet printing may be accomplished in a single pass, or each fluid 12/ink 14/composition 16 may be deposited in multiple passes.

[0133] In any of the examples of the method, the amount of the cross-linker composition 16 and the inkjet ink 14 applied to the textile fabric 18 may be such that the polycarbodiimide and the polyurethane binder particles are present at a weight ratio ranging from 1 :1 to 1 :9.

[0134] In examples of the method 100, the desired amount of the fixer fluid 12, of the inkjet ink 14, and of the cross-linker composition 16 are deposited in a single pass or in multiple passes, and then curing occurs (via heat or electromagnetic radiation exposure). In these examples, the application of the fixer fluid 12 occurs prior to the application of the inkjet ink 14, the application of the inkjet ink 14 occurs prior to the application of the cross-linker composition 16, and the application of all the fluids 12, 14, 16 occurs prior to the exposure. [0135] The exposure to heat or electromagnetic energy irradiation may cure the fixer fluid layer, the ink layer, and the cross-linker composition layer to generate the print. In an example of the method 100, the exposure to heat or electromagnetic energy irradiation generates enough heat and/or energy to initiate the cross-linking reaction(s). Suitable temperatures may range from about 80°C to about 200°C. In another example, the temperature ranges from about 100°C to about 200°C or from about 100°C to about 180°C. The heat or energy exposure time may range from about 10 seconds to about 15 minutes, depending, in part, upon the temperature used. In one example, curing is achieved by heating the layers to a temperature of 150°C for about 3 minutes. In another example, curing is achieved by exposing the layers to UV light for about 30 seconds.

[0136] Any heat source or electromagnetic radiation source may be used in the method 100. The heat source or electromagnetic radiation source can provide enough energy to initiate the cross-linking reaction(s). The heat source may be a clam shell press, an oven, and iron, or any other suitable heat source. The electromagnetic radiation source may be selected from the group consisting of an ultraviolet (UV) or infrared (IR) light emitting diode (LED), a UV or IR lamp, and a UV or IR laser. In one example, the UV light source is a light emitting diode that emits emission wavelengths ranging from about 365 nm to about 400 nm.

[0137] When electromagnetic energy irradiation is used, intermittent electromagnetic radiation source on events and electromagnetic radiation source off events may be used. During electromagnetic radiation source on events, the electromagnetic radiation source is turned on, and during electromagnetic radiation source off events, the electromagnetic radiation source is turned off. The intermittent on and off events can effectively heat the layers without overheating the textile fabric 18. The electromagnetic radiation source on events may range from about 0.1 second to about 5 seconds. In some instances, the total exposure time is 30 seconds or less. As such, in these instances, the number of electromagnetic radiation source on events will depend upon the duration of each on event and the desired total exposure time. For example, when each electromagnetic radiation source on event is 1 second long, a total of thirty electromagnetic radiation source on events may take place so that the total exposure time is 30 seconds. For another example, a single on event may be 2.5 seconds or 5 seconds. The electromagnetic radiation source off events may be long enough to allow the textile fabric 18 to cool in between on events.

[0138] When exposed to heating, the carbodiimide reactive groups can cross-link to carboxyl groups of the cationic polyurethane and/or the polyurethane binder and/or the textile fabric 18 to form cross-linking between polymer strands. These cross-linked polyurethane stands form a durable structure between the layers and the textile fabric 18. These cross-linked strands can also trap the pigments from the inkjet ink 14. The cationic polyurethane in the fixer fluid 12 can also interact with the pigment and/or the polyurethane binder in the inkjet ink 14 to fix the components to the textile fabric 18. The interactions of the polyurethanes and the pigment helps fix the pigment and improve the optical density, and also improve the durability of the resulting print.

[0139] Referring now to Figs. 8A and 8B, schematic diagrams of two different printing systems 40, 40’ including inkjet applicators 42, 44, 45 or 42’, 44’, 45’ and a heat or electromagnetic radiation source 46.

[0140] The example system 40 shown in Fig. 8A illustrates a system for single pass printing and selective curing, and the example system 40’ shown in Fig. 8B illustrates a system for multiple pass printing and single or multiple pass selective curing.

[0141] In the example system 40 shown in Fig. 8A, the textile fabric/ fabric substrate 18 is transported through the printing system 40 along the path shown by the arrow 48. In this example, pagewide applicators 42, 44, 45 (i.e. , each including a series of printheads extending the width of the textile fabric 18) are in fixed positions relative to the textile fabric 18. When the textile fabric 18 is moved relative to the pagewide applicator 42, the fixer fluid 12 is inkjet printed directly onto the textile fabric 18. When the textile fabric 18 is moved relative to the pagewide applicator 44, a single color or multiple colors of the inkjet ink 14 is/are inkjet printed directly onto the textile fabric 18. When the textile fabric 18 is moved relative to the pagewide applicator 45, the cross-linker composition 16 is/are inkjet printed directly onto the textile fabric 18. The color(s), amount(s), and/or arrangement of the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 that are applied depend upon the digital image from which the print 50 is being generated. [0142] In this example, after the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 are dispensed, the heat or electromagnetic radiation source 46 is operated to expose the textile fabric 18 to heat/energy for a desirable time period. In this single pass printing system 40, printing and selective curing are each performed as the textile fabric 18 is within proximity of the respective printer component.

[0143] The single pass printing and selective curing performed using the printing system 40 results in the printed article 50 on the textile fabric 18.

[0144] In the example system 40’ shown in Fig. 8B, the textile fabric/ fabric substrate 18 may be transported through the printing system 40’ along the path shown by the arrow 48’. In this example, the inkjet applicators 42’, 44’, 45’ are attached to a carriage (not shown) or other mechanism that moves the inkjet applicators 42’, 44’, 45’ relative to the textile fabric 18 in the path shown by the arrow 52. When the inkjet applicator 42’ is activated and moved relative to the textile fabric 18, the fixer fluid 12 is inkjet printed directly onto textile fabric 18. When the inkjet applicator 44’ is activated and moved relative to the textile fabric 18, a single color or multiple colors of the inkjet ink 14 is/are inkjet printed directly onto textile fabric 18. When the inkjet applicator 45’ is activated and moved relative to the textile fabric 18, the cross-linker composition 16 is inkjet printed directly onto textile fabric 18. The color(s), amount(s), and/or arrangement of the fixer fluid 12, the inkjet ink 14, and the cross-linker composition 16 that are applied depend upon the digital image from which the print 50 is being generated. In this example, the total desired amount of fixer fluid 12, inkjet ink 14, and cross-linker composition 16 that is dispensed takes place over multiple passes of each of the inkjet applicators 42’, 44’, 45’.

[0145] Exposure to the heat/energy occurs after the multiple printing passes. In this example, the heat or electromagnetic radiation source 46’ is attached to a carriage (not shown) or other mechanism that moves the heat or electromagnetic radiation source 46’ relative to the textile fabric 18 in the path shown by the arrow 52. The multiple pass printing and single or multiple pass selective curing performed using the printing system 40’ results in the printed article 50 on the textile fabric 18. [0146] To further illustrate the present disclosure, examples are given herein. It is to be understood that these examples are provided for illustrative purposes and are not to be construed as limiting the scope of the present disclosure.

EXAMPLES

[0147] Example 1

[0148] Two example cross-linker compositions (Ex. CC1 and Ex. CC2) were prepared. These examples included different water-based dispersions of linear polycarbodiimides. Four comparative cross-linker compositions (Comp. Ex. CC3 - Comp. Ex. CC6) were also prepared. These examples included different water-based dispersions of multi-functional polycarbodiimides or an emulsion of a linear polycarbodiimide. The formulations for the example and the comparative example cross-linker fluid are shown in Tables 1 and 2 respectively.

TABLE 1 - Example Cross-linker Compositions

‘represents the solid polycarbodiimide amount TABLE 2 - Comp. Example Cross-linker Compositions

‘represents the solid polycarbodiimide amount

[0149] The jettability performance of each of the example and comparative example cross-linker compositions was tested. The cross-linker compositions were printed using a thermal inkjet printer. The jettability performance was evaluated for missing nozzles, drop weight, drop velocity, decel performance, and turn on energy performance.

[0150] For the missing nozzles test, a small amount of dye was added to each cross-linker composition so that it was visible when printed. A test print was printed to make sure all of the nozzles of the printer were firing properly, which was followed by a diagnostic pattern showing the health of each nozzle. The nozzles remained unfired for about 1 second, and then the diagnostic pattern was printed again. The percentage of missing nozzles after the idle time was recorded, and the results are shown in Table 3.

[0151 ] Both the drop weight and the drop velocity of the cross-linker compositions were monitored. The average drop weight of 2,000 drops fired at a firing frequency of 30 KHz was calculated.

[0152] The term “decel,” as referred to herein, refers to a decrease in the drop velocity over time (e.g., 6 seconds) of droplets fired from an inkjet printhead. A large decrease in drop velocity (e.g., a decrease in drop velocity of greater than 0.5 m/s) can lead to poor image quality, which can be observed, for example, by the color difference between the print samples from continuously firing nozzles and the print samples from non-continuously firing nozzles. In contrast, fluids that do not experience decel (i.e. , no decrease in drop velocity) or experience an acceptable decel (e.g., a decrease in drop velocity of 0.5 m/s or less) will continue to generate quality printed images. In order to determine decel performance, each of the example and comparative example cross-linking compositions were filled into a thermal inkjet print head and the drop velocity vs. firing time over 6 seconds was collected. The results of the decel performance tests for each cross-linking composition are also shown in Table 3.

[0153] The term “Turn-On Energy (TOE) curve,” as used herein, refers to the drop weight of the cross-linker composition (or other fluid) as a function of firing energy. An inkjet fluid with good jettability performance also has a good TOE curve, where the fluid drop weight rapidly increases (with increased firing energy) to reach a designed drop weight for the pen architecture used; and then a steady drop weight is maintained when the firing energy exceeds the TOE. In other words, a sharp TOE curve may be correlated with good jettability performance. In contrast, an inkjet fluid with a poor TOE curve may show a slow increase in drop weight (with increased firing energy) and/or may never reach the designed drop weight for the pen architecture. A poor TOE curve may be correlated with poor jettability performance. The TOE curves for the example cross-linker compositions and the comparative cross-linker compositions are shown in Figs. 9A and 9B. As depicted and noted in Table 3 below, each of the example cross-linker compositions exhibited a good TOE curve, indicating good jettability via thermal inkjet printheads. In comparison, each of the comparative example cross-linker compositions has a worse TOE curve. TABLE 3 - Printing Performance

[0154] The results shown in Table 3 indicate that the example cross-linker compositions 1 and 2 have excellent printability, especially in terms of % missing nozzles, decel, and turn on energy.

[0155] Example 2

[0156] PICASSIAN® XL-702 (water-based dispersion of linear polycarbodiimide, Stahl Polymers) was selected to prepare three additional examples of the cross-linker composition (Ex. CC7, Ex. CC8, and Ex. CC9). The formulations are shown in Table 4. PICASSIAN® XL- 732 (water-based dispersion of multi-functional polycarbodiimide, Stahl Polymers) was selected to prepare three additional comparative examples of the cross-linker composition (Comp. Ex. CC10, Comp. Ex. CC11 , and Comp. Ex. CC12). The formulations are shown in Table 5. TABLE 4 - Example Cross-linker Compositions

‘represents the solid polycarbodiimide amount

TABLE 5 - Comp. Example Cross-linker Compositions

‘represents the solid polycarbodiimide amount

[0157] The jettability performance of each of the example and comparative example cross-linker compositions was tested. The cross-linker compositions were printed using a thermal inkjet printer. The jettability performance was evaluated for missing nozzles, drop weight, drop velocity, decel performance, and turn on energy performance as described in Example 1 . The results are shown in Table 6, and the TOE curves are shown in Fig. 10. As depicted and noted in Table 6 below, each of the example cross-linker compositions exhibited a good TOE curve, indicating good jettability via thermal inkjet printheads. In comparison, each of the comparative example cross-linker compositions has a worse TOE curve.

TABLE 6 - Printing Performance

[0158] The results shown in Table 6 indicate that the example cross-linker compositions 7-9 have excellent printability, especially in terms of % missing nozzles, decel, and turn on energy. In contrast, the comparative cross-linker compositions IQ- 12 were not jettable or had poor jettability.

[0159] The example cross-linker compositions (Ex. CC7 - Ex. CC9) and the comparative example cross-linker compositions (Comp. Ex. CC10 - Comp. CC12) were printed on different textile fabrics without a fixer fluid, with an example fixer fluid, and with cyan, magenta, yellow, and black inks.

[0160] The fixer fluid (Ex. FF) included a cationic polyurethane as described herein, which was prepared as follows:

[0161] First, 2-hydroxyethyltributylphosphonium chloride was prepared (as the phosphonium salt). A 500 ml 4-necked flask equipped with a mechanical stirrer, a thermometer, a dropping funnel, and a condenser was sufficiently purged with nitrogen, and about 150.0 g of tri-n-butylphosphine was added. At 80°C, about 62.7 g of 2-chloroethanol was added dropwise over 30 minutes, and the solution turned into white and cloudy. Then, the solution was continued to heat to 100°C for 2 days under nitrogen and stirring. The reaction solution was an extremely viscous colorless and transparent liquid. The presence of unreacted trialklphopshine was tested using carbon disulphide, but trialkylphosphine was not detected. The solution was concentrated using an evaporator and then dried with a vacuum pump to give about

206.4 g of a colorless and transparent viscous liquid.

[0162] The 2-hydroxyethyltributylphosphonium chloride was then used in the preparation of the cationic polyurethane. About 24.9 g of YMER™ N-120 (from Perstorp, molecular weight 1000), about 25.2 g of isophorone disisocyanate (IPDI), and about 64 g of acetone were mixed in a 500 ml of 4-neck round bottom flask. A mechanical stirrer with glass rod and a polytetrafluoroethylene (PTFE) blade was attached. A condenser was attached. The flask was immersed in a constant temperature bath at 75°C. The system was kept under a drying tube. Three drops of bismuth catalyst (REAXIS™ C3203) was added to initiate the polymerization.

Polymerization was continued for 3 hours at 75°C. About 0.5 g of pre-polymer was withdrawn for final % NCO titration. The measured NCO value was 14.75%. The theoretical % NCO should be 14.81 %.

[0163] About 49.9 g of the 2-hydroxylethyltributylphosphonium chloride (3, TBPHECI) in 20 ml of acetone was added to the pre-polymer over 10 minutes. After 60 minutes, the polymerization temperature was reduced to 50°C and then about

259.4 g of deionized (DI) water was added over 20 minutes. The solution became milky and white color and the milky dispersion was continued to stir for overnight at room temperature. The cationic polyurethane dispersion was filtered through 400 mesh stainless sieve. Acetone was removed with rotorvap at 50°C (added 2 drops (20 mg) BYK-011 de-foaming agent to control foaming). The final cationic polyurethane dispersion was filtered through fiber glass filter paper.

[0164] The fixer fluid formulation is shown in Table 7. TABLE 7 - Fixer Fluid

‘represents the solid cationic polyurethane amount “represents the solid surfactant amount

[0165] Each of the cyan, magenta, yellow, and black inks (Ex. Ink C, Ex. Ink M, Ex. Ink Y, and Ex. Ink K) included a polyurethane binder as described herein, which was prepared as follows:

[0166] About 72.6 g of polyester polyol (Stephanol PC-1015-55), and about 20.6 g of isophorone diisocyanate (IPDI) in about 80 g of acetone were mixed in a 500 ml 4- neck round bottom flask. A mechanical stirrer with glass rod and PTFE blade was attached. A condenser was attached. The flask was immersed in a constant temperature bath at 75°C. The system was kept under a drying tube. 3 drops of dibutyltin dilaurate (DBTDL) was added to initiate the polymerization. Polymerization was continued for 6 hours at 75°C.

[0167] The polymerization temperature was reduced to 50°C. About 3.8 g of 2,2,4 (or 2, 4, 4)-trimethylhexane-1 ,6-diamine (TMD), about 5.9 g of sodium aminoalklysulphonate (A-95, 50% in water) and about 14.8 g of deionized water were mixed in a beaker until TMD and A-95 were completely dissolved. The TMD and A-95 solution was added to the pre-polymer solution at 50°C with vigorous stirring over 5 minutes. The solution became viscous and slight hazy. Stirring was continued for about 30 minutes at 50°C. Then, about 201 .7 g of cold deionized water was added to polymer mixture in a 4-neck round bottom flask over 10 minutes with good agitation to form the non-UV-reactive polyurethane binder A dispersion. The agitation was continued for 60 minutes at 50°C. The non-UV-reactive polyurethane binder A dispersion was filtered through 400 mesh stainless sieve. Acetone was removed with rotorvap at 50°C (added 2 drops (20mg) BYK-011 de-foaming agent to control foaming). The final non-UV-reactive polyurethane binder A dispersion was filtered through fiber glass filter paper.

[0168] The ink formulations are shown in Table 8.

TABLE 8 - Inks

‘represents the solid pigment amount

“represents the solid polyurethane binder amount

[0169] Several different prints were prepared with different combinations of the example inks (Ex. Ink C, M, Y or K) and one of the example cross-linker compositions (Ex. CC7 - Ex. CC9) or one of the comparative cross-linker compositions (Comp. Ex. CC10 - Comp. Ex. CC12). Some of the prints were prepared without the fixer fluid (Ex. FF) and some were prepared with the Ex. FF.

[0170] The textile fabrics were T-shirt media: Pakistan roll #1 (50:50 cotton/polyester blend, 175 GSM, knit) (PR#1 ) and Pakistan roll # 4 (100% cotton, 150 GSM, knit) (PR#4). [0171] When used, the fixer fluid (Ex. FF) was thermally inkjet printed on the textile fabric at 1.5 dpp (drop per pixel). The inkjet inks were thermally inkjet printed on the textile fabric at 3 dpp and the example and comparative example cross-linker compositions were thermally inkjet printed on the textile fabric at 1.5 dpp.

[0172] All prints were exposed to heating or irradiation conditions. For thermal heating, a heat press alone was used, and the prints were exposed to 150°C for 3 minutes. For irradiation, a 395 nm light emitting diode (Hereaus lamp) was used. When operated at 50% power, the light source emitted 6.62 W/cm 2 . 0.5 second pulses were used, and the curing time varied.

[0173] The prints were washed 5 times in a Kenmore 90 Series Washer (Model 110.289 227 91 ) with warm water (at about 40°C) and detergent. Each print was allowed to air dry between each wash.

[0174] All of the prints were analyzed for optical density. The initial optical density (initial OD) of each print (after heating or irradiation) was measured. Then, the prints were washed 5 times in a Kenmore 90 Series Washer (Model 110.289227 91 ) with warm water (at about 40°C) and detergent. Each print was allowed to air dry between each wash. Then, the optical density (OD after 5 washes) of each print was measured. A smaller change in optical density indicates that the color of the print has less fading.

[0175] All of the prints were also analyzed for washfastness. The L*a*b* values of a color (e.g., cyan, magenta, yellow, black) before and after the 5 washes were measured. L* is lightness, a* is the color channel for color opponents green-red, and b* is the color channel for color opponents blue-yellow. The color change was then calculated using both the CIEDE1976 color-difference formula (AE CMC) and the CIEDE2000 color-difference formula (AE 2000).

[0176] The CIEDE1976 color-difference formula is based on the CIELAB color space. Given a pair of color values in CIELAB space L*i ,a*i,b*i and L* 2 ,a* 2 ,b* 2 , the CIEDE1976 color difference between them is as follows: [0177] The CIEDE2000 color-difference formula is based on the CIELAB color space. Given a pair of color values in CIELAB space L*-, ,a*i,b*i and L* 2 ,a* 2 ,b* 2 , the CIEDE2000 color difference between them is as follows:

It is noted that AE 00 is the commonly accepted notation for CIEDE2000. With either calculation, a smaller change in AE indicates that the print is more durable.

[0178] Results for Prints without Fixer Fluid and with Thermal Curing

[0179] Several prints were generated on PR #1 and PR #4 with the example inks and with either the example cross-linker compositions or the comparative example cross-linker compositions, and without any of the fixer fluid. The thermal curing conditions were used. The optical density and washfastness results are shown in Table 9. The prints are identified by the ink and cross-linker composition that were used.

TABLE 9

[0180] The results in Table 9 show that the example and comparative example cyan, magenta, and yellow prints (Ex. and Comp, prints 7A-24A and 7B-24B) had excellent durability. The example cyan prints (Ex. prints 7A-9A) on PR #1 generally performed better than the Comp, cyan prints 10A-12A in terms of washfastness. The results in Table 9 also show that the black prints (Ex. and Comp, prints 1A-6A and I B- 66) had mediocre durability when cured with thermal conditions.

[0181] Results for Prints with Fixer Fluid and with Thermal Curing

[0182] Several black and cyan prints were generated on PR #1 and PR #4 with the fixer fluid, the example black or cyan ink, and either the example cross-linker compositions or the comparative example cross-linker compositions. The thermal curing conditions were used. The optical density and washfastness results are shown in Table 10. The prints are identified by the fixer fluid, ink, and cross-linker composition that were used.

TABLE 10

[0183] The results in Table 10 show that the example and comparative example cyan prints (Ex. and Comp, prints 30A-34A and prints 30B-34B formed with fixer fluid had good to excellent durability, and better durability than the prints that were formed without the fixer fluid (see Table 9). The results in Table 10 also show that the Ex. black prints 25A, 26A, 25B, and 26B had mediocre durability. These results indicate that the thermal curing conditions may not be desirable for the black ink.

[0184] Results for Prints without Fixer Fluid and with Irradiation Curing

[0185] Several prints were generated on PR #1 and PR #4 with the example inks and with either the example cross-linker compositions or the comparative example cross-linker compositions, and without any of the fixer fluid. The irradiation curing conditions were used for these prints. The optical density and washfastness results are shown in Table 11 . The prints are identified by the ink and cross-linker composition that were used.

TABLE 11

[0186] The results in Table 11 show that all of the example prints (Ex. prints 35A- 37A, 41A-43A, 47A-49A, 53A-55A and 35B-37B, 41 B-43B, 47B-49B, 53B-55B) had good to excellent durability, even without the fixer fluid. In particular, the black prints (35A-37A and 35B-37B) generally had better durability than the black prints exposed to thermal curing conditions.

[0187] Results for Prints with Fixer Fluid and with Irradiation Curing [0188] Several black and cyan prints were generated on PR #1 and PR #4 with the fixer fluid, the example black or cyan ink, and either the example cross-linker compositions or the comparative example cross-linker compositions. The irradiation curing conditions were used. The optical density and washfastness results are shown in Table 12. The prints are identified by the fixer fluid, ink, and cross-linker composition that were used.

TABLE 12

[0189] The results in Table 12 show that the example black and cyan prints (Ex. prints 59A, 60A, 59B, 60B, 64A, 65A, 64B, and 65B) had good to excellent durability, and generally better durability than the comparative example black and cyan prints (Comp. Ex. prints 61A-63A, 66A-68A, 61 B-63B, and 66B-68B).

[0190] Overall, the results in these examples illustrate that the example cross-linker compositions are readily printable using thermal inkjet printheads, while the comparative cross-linker compositions experience complications. Additionally, the results in these examples illustrate that the example cross-linker compositions generate more durable prints than the comparative cross-linker compositions, that heating conditions are suitable for generating yellow and magenta prints, and that irradiation conditions are more suitable for generating cyan and black prints.

[0191] It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range, as if the value(s) or sub- range(s) within the stated range were explicitly recited. For example, a range from about 1 wt% to about 15 wt%, should be interpreted to include not only the explicitly recited limits of from about 1 wt% to about 15 wt%, but also to include individual values, such as about 1 .15 wt%, about 2.5 wt%, 4.0 wt%, 6.77 wt%, 8.85 wt%, 9 wt%, 12.33 wt%, 14 wt%, etc., and sub-ranges, such as from about 2 wt% to about 5.65 wt%, from about 3 wt% to about 7 wt% from about 4.35 wt% to about 8.95 wt%, etc. Furthermore, when “about” is utilized to describe a value, this is meant to encompass minor variations (up to +/- 10%) from the stated value.

[0192] Reference throughout the specification to “one example”, “another example”, “an example”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the example is included in at least one example described herein, and may or may not be present in other examples. In addition, it is to be understood that the described elements for any example may be combined in any suitable manner in the various examples unless the context clearly dictates otherwise.

[0193] In describing and claiming the examples disclosed herein, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0194] While several examples have been described in detail, it is to be understood that the disclosed examples may be modified. Therefore, the foregoing description is to be considered non-limiting.