BACKGROUND

In addition to home and office usage, inkjet technology has been expanded to high-speed, commercial and industrial 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. Some commercial and industrial inkjet printers utilize fixed printheads and a moving substrate web in order to achieve high speed printing. Current inkjet printing technology involves forcing the ink drops through small nozzles by thermal ejection, piezoelectric pressure or oscillation onto the surface of the media. This technology has become a popular way of recording images on various media surfaces (e.g., paper), for a number of reasons, including, low printer noise, capability of high-speed recording and multi-color recording.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIG. 1 is a diagram illustrating an example of a method for improving durability of prints created with an example of the inkjet ink composition disclosed herein;

FIG. 2 is a diagram illustrating an example of a method for improving durability of prints created with another example of the inkjet ink composition disclosed herein;

FIG. 3 is an enlarged, cutaway, cross sectional, perspective semi-schematic illustration of an example of a print cartridge including an example of the inkjet ink composition disclosed herein;

FIGS. 4A, 4B, 4C and 4D depict images of a comparative ink (FIGS. 4A and 4C) and of an example of the inkjet ink composition disclosed herein (FIGS. 4B and 4D) printed on brochure media (FIGS. 4A and 4B) and on photo media (FIGS. 4C and 4D) after being exposed to scratch and smudge testing performed at different time periods after printing (0, 2, or 4 minutes); and

FIGS. 5A and 5B depict images of another example of the inkjet ink composition disclosed herein printed on brochure media (FIG. 5A) and on photo media (FIG. 5B) after being exposed to scratch and smudge testing performed at different time periods after printing (0, 2, or 4 minutes).

DETAILED DESCRIPTION

Examples of the inkjet ink compositions disclosed herein exhibit desirable durability performance on a variety of different types of media. With many inkjet inks, it is difficult to simultaneously achieve desirable durability on porous, uncoated media, coated media, and photo paper. This is due, in part, to the interaction of the ink of the particular type of media. For example, ink is to be maintained on the surface of coated media, but is to penetrate into porous, uncoated media, and the different ink/media interactions can render it difficult to develop one ink that is suitable for different media types.

Durability performance may be measured in terms of the abrasion resistance of a printed image. Abrasion resistance may be measured in terms of smudge resistance and/or scratch resistance. The term “smudge resistance,” as referred to herein means the ability of a printed image to remain un-smeared when subjected to a smudge test. The smudge test may be performed manually by applying pressure across a print in a single motion. The term “scratch resistance,” as referred to herein means the ability of a printed image to remain un-smeared when subjected to a scratch test. The scratch test may also be performed manually by pressure across a print in a single motion. In an example, the tool used to perform the scratch test may be harder than the tool used to perform the smudge test. When the test are performed using a human hand, the finger may be used to perform the smudge test and the nail or nail bed of a finger may be used to perform the scratch test.

Examples of the inkjet ink composition disclosed herein achieve desirable durability performance on different types of media through a combination of specific organic solvent packages and from about 0.25 wt % to about 2 wt % (with respect to the weight of the inkjet ink composition) of a specific polyurethane binder having a specific molecular weight.

It has been unexpectedly discovered that the amount of the polyurethane may be reduced to an amount ranging from about 0.25 wt % to about 2 wt % without significantly affecting durability performance. Reducing the amount of the polyurethane in the inkjet ink compositions may improve its print stability performance by reducing the total solids content of the inkjet ink compositions (which may reduce clogging, plugging, etc. of printer nozzles).

Still further, it has also been unexpectedly discovered that the number average molecular weight of the polyurethane can be increased (to at least 10,000) with chain extenders to improve durability performance without resulting in print performance degradation caused by the polyurethane. In some instances, the use of a chain extender can lead to runaway reactions, and in such instances, the resulting polyurethane may degrade the performance of the ink to the point that the ink is not printable. However, it has been found that the ink disclosed herein, which includes the specific polyurethane of the specific molecular weight, exhibits desirable print performance and generates desirable prints.

In addition, the ink compositions disclosed herein may be suitable for use with any inkjet printing system. For example, the ink composition may be printed with a thermal inkjet printer having a drop frequency ranging from about 2 kHz to about 18 kHz. For another example, the ink composition may be printed with a high speed inkjet printer having a drop frequency ranging from about 24 kHz to about 36 kHz.

Inkjet Ink Composition with Polyurethane of Formula I

In some examples, the inkjet ink composition comprises: a colorant; an organic solvent package, including: from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; at least 50 wt % water with respect to the weight of the inkjet ink composition; and from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of a polyurethane binder having a general structure of Formula I:

[Image Omitted]

and

for Formula I:

- each Y is —(C═O)NHW¹N(C═O)OR²or —(C═O)NH(CH₂)_mSi(R⁴)₃;
- each X is O, S or NR³;
- each R¹is C₁-C₂₀alkyl, C₆-C₄₀aryl, polyester, polycarbonate, polyamide or polyurethane, each substituted by one or more hydrophilic groups;
- each R²is C₁-C₂₀alkyl, C₃-C₂₀substituted alkyl, C₆-C₄₀aryl or C₉-C₄₀substituted aryl;
- each R³is H, C₁-C₂₀alkyl, C₃-C₂₀substituted alkyl, C₆-C₄₀aryl or C₉-C₄₀substituted aryl;
- each R⁴is independently H, C₁-C₂₀alkyl, C₃-C₂₀substituted alkyl, C₆-C₄₀aryl, C₉-C₄₀substituted aryl or OR⁵;
- each R⁵is independently H, C₁-C₂₀alkyl or C₆-C₄₀aryl;
- each W¹is independently C₄-C₂₀alkyl, C₄-C₂₀substituted alkyl, C₆-C₂₀cycloalkyl, C₆-C₂₀substituted cycloalkyl, C₆-C₄₀aryl or C₉-C₄₀substituted aryl;
- each W²is C₁-C₂₀alkyl or C₂-C₂₀substituted alkyl;
- m is an integer from 1 to 15; and
- n is an integer from 1 to 200;
  
  and wherein a chain extender is present between at least some neighboring isocyanates in Formula I such that a number average molecular weight of the polyurethane binder ranges from about 10,000 to about 25,000.

The branched polyurethane of Formula I can be prepared by a ring opening reaction of poly-uretdiones. The poly-uretdione may be reacted with a reagent R¹XH (where R¹and X are as defined), which provides a branched polyurethane product. In an example, R¹XH contains a hydroxyl group. The reaction is typically carried out at temperatures ranging from about 25° C. and about 150° C. A suitable solvent for this reaction is an aprotic solvent, such as acetone, diethyl ether, ethyl acetate, N-methyl pyrrolidone, nitromethane, acetonitrile, pyridine, methylene chloride, benzene, hexane and tetraglyme (i.e., tetraethylene glycol dimethyl ether).

In an example, the poly-uretdione is an alternating uretdione-carbamate adduct that contains an isocyanate and a diol. Suitable isocyanates may be diisocyanates, which may be may be selected from the group consisting of 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI), 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI), dodecane diisocyanate (C₁₂DI), 1,5-naphthalene diisocyanate (NDI), m-tetramethylene xylylene diisocyanate (TMXDI), 1,4-benzene diisocyanate, trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene diisocyanate.

In some examples, the poly-uretdione may be reacted with a diol-diacid adduct and a polycarbonate diol. The diol-diacid adduct may be formed from biphenyl dianhydride, a sulfolane solvent, and a polycarbonate diol, or from 1,2,4,5 tetracarboxyl benzene dianhydride (pyromellitic dianhydride, or PMDA), a sulfolane solvent, and tetraethylene glycol. In other examples, the poly-uretdione may be reacted with PMDA. Any of these reactions may take place in the solvents noted above, and may the reaction mixture may also include metal complex used in uretdione crosslinked powder coatings.

In an example, the chain extender is a primary monoamino compound, a secondary monoamino compound, a primary diamino compound, a secondary diamino compound, or combinations thereof. In another example, the chain extender is a triamino compound or a tetraamino compound. In an example, the chain extender is a mixture of primary and/or secondary monoamino compound and a primary and/or secondary diamino compound, where at least one of the components carries sulfonic acid and/or carboxyl groups.

Examples of the monoamino compounds include aliphatic and/or alicyclic primary and/or secondary monoamines (such as ethylamine, diethylamine, the isomeric propyl- and butyl-amines), higher linear-aliphatic monoamines and cycloaliphatic monoamines (such as cyclohexylamine). Further examples of the monoamino compounds are amino alcohols, i.e., compounds that contain amino and hydroxyl groups in a molecule, such as, for example, ethanolamine, N-methylethanolamine, diethanolamine and 2-propanolamine. Further examples of the monoamino compounds are those monoamino compounds that additionally carry sulfonic acid and/or carboxyl groups, such as, for example, taurine, glycine or alanine. Some specific examples of the monoamino compounds include diethylamine, ethanolamine or diethanolamine.

Examples of the diamino compounds include 1,2-ethanediamine (i.e., ethylene diamine), propylene diamine, butylene diamine, cyclohexylene diamine, 2-methyl piperazine, phenylene diamine, toluene diamine, xylylene diamine, m-xylene diamine, isophorone diamine, 1,6-hexamethylenediamine, 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane (isophoronediamine), 3,3-dinitrobenzidine, 4,4′-diaminodiphenyl methane, piperazine, and 1,4-diaminocyclohexane or bis-(4-aminocyclohexyl)-methane. Other suitable examples include adipic acid dihydrazide, hydrazine, or hydrazine hydrate. Still other suitable examples include acetone azine, substituted hydrazines such as, for example, dimethyl hydrazine, 1,6-hexamethylene-bis-hydrazine, carbodihydrazine, dihydrazides of dicarboxylic acids and sulphonic acids such as oxalic acid dihydrazide, isophthalic acid dihydrazide, hydrazides made by reacting lactones with hydrazine such as gamma hydroxylbutyric hydrazide, bis-semi-carbazide, and bis-hydrazide carbonic esters of glycols. Still other examples of the diamino compounds include amino alcohols, i.e., compounds that contain amino and hydroxyl groups in a molecule, such as, for example, 1,3-diamino-2-propanol, N-(2-hydroxyethyl)-ethylenediamine or N,N-bis(2-hydroxyethyl)-ethylenediamine. Yet further examples of the diamino compounds are those diamino compounds that additionally carry sulfonate and/or carboxylate groups, such as, for example, the sodium or potassium salts of N-(2-aminoethyl)-2-am inoethanesulfonic acid, of N-(3-aminopropyl)-2-aminoethanesulfonic acid, of N-(3-aminopropyl)-3-aminopropanesulfonic acid, of N-(2-aminoethyl)-3-aminopropanesulfonic acid or of the analogous carboxylic acids. Some specific examples of the diamino compounds Include 1,2-ethanediamine, 1,6-hexamethylenediamine, 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane (isophoronediamine), piperazine, N-(2-hydroxyethyl)-ethylenediamine, N,N-bis(2-hydroxyethyl)-ethylenediamine, the sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid or the sodium salt of N-(2-aminoethyl)-2-aminoethanecarboxylic acid.

It is to be understood that polyamines, such as diethylenetriamine, can also be used instead of a diamino compound.

Examples of suitable triamines include diethylene triamine, tris (2-aminoethyl) amine, and adducts of diethylene triamine with acrylate or its hydrolyzed products, and an example of a suitable tetraamine is triethylene tetramine.

The chain extender may be added during the formation of the polyurethane (i.e., for Formula I, during the ring opening of the polyuretdione). The total amount of chain extender that is added depends upon the desired molecular weight of the polyurethane. In some examples, the number average (M_N) molecular weight of the polyurethane binder ranges from about 10,000 to about 25,000. In other examples, the number average (M_N) molecular weight of the polyurethane binder ranges from about 12,000 to about 25,000. To achieve the desired molecular weight, the total amount of chain-extender material employed may be such that the ratio of active amine functional groups in the chain-extender to NCO groups in the pre-polymer component (e.g., polyuretdione) ranges from 2:1 to 3:1.

Any of the previously mentioned chain-extenders may also be used as a capping agent, and may be added when it is desirable to terminate the polymerization. The amount of the capping agent employed should be approximately equivalent to the unreacted isocyanate groups in the prepolymer. The ratio of active hydrogens from amine groups in the chain terminator to isocyanate groups in the prepolymer are in the range from about 1.0:1 to about 1.2:1, or from about 1.0:1.1 to about 1.1:1, or from about 1.0:1.05 to about 1.1:1, on an equivalent basis.

In the final polyurethane copolymer binder, the acid number of the polyurethane copolymer binder ranges from 50 to 100.

In these examples, the inkjet ink composition may include additional components. An example of an additional component that may be included in the inkjet ink composition includes an additive selected from the group consisting of a surfactant, a biocide, a pH adjuster, and combinations thereof.

In other examples, the inkjet ink composition consists of: the colorant; the organic solvent package including: from about 1 wt % to about 12 wt %, with respect to the weight of the inkjet ink composition, of the first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of the second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; at least 50 wt % water with respect to the weight of the inkjet ink composition; and from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of the polyurethane binder having the general structure of Formula I. In these examples, the inkjet ink composition includes no other components.

In still other examples, the inkjet ink composition consists of: the colorant; the organic solvent package including: from about 1 wt % to about 12 wt %, with respect to the weight of the inkjet ink composition, of the first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of the second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; at least 50 wt % water with respect to the weight of the inkjet ink composition; from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of the polyurethane binder having the general structure of Formula I; and the additive selected from the group consisting of the surfactant, the biocide, the pH adjuster, and combinations thereof. In these examples, the inkjet ink composition includes no other components.

As mentioned above, desirable durability performance may be achieved through the combination of the organic solvent package and from about 0.25 wt % to about 2 wt % (with respect to the weight of the inkjet ink composition) of the polyurethane binder.

In this example of the inkjet ink composition, the organic solvent package includes from about 1 wt % to about 12 wt %, with respect to the weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof. In an example of the inkjet ink composition, the organic solvent package consists of the first solvent and the second solvent.

In some examples, the first solvent has 1 or 2 free hydroxyl groups and 0 to 3 glycol units. It is to be understood that the first solvent may include multiple solvents as long as each solvent included in the combination has 1 or 2 free hydroxyl groups and 0 to 3 glycol units. In an example, the first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units is selected from the group consisting of tripropylene glycol, tripropylene glycol methyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monoethyl ether, triethylene glycol, triethylene glycol monobutyl ether, triethylene glycol monomethyl ether, diethylene glycol, diethylene glycol butyl ether, ethylene glycol, ethylene glycol butyl ether, ethylene glycol phenyl ether, 3-methyl-1,3-butanediol, 2-ethyl-2-hydroxymethyl-1,3,-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, and a combination thereof. In another example, the first solvent is selected from the group consisting of tripropylene glycol methyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monoethyl ether, triethylene glycol monomethyl ether, ethylene glycol phenyl ether, 3-methyl-1,3-butanediol, 2-ethyl-2-hydroxymethyl-1,3,-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, and a combination thereof.

In other examples, the first solvent may have 1 or 2 free hydroxyl groups and 1 to 3 glycol units. In another example, the first solvent has 1 or 2 free hydroxyl groups and 1 to 3 glycol units and is selected from the group consisting of tripropylene glycol, tripropylene glycol methyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monoethyl ether, triethylene glycol, triethylene glycol monobutyl ether, triethylene glycol monomethyl ether, diethylene glycol, diethylene glycol butyl ether, ethylene glycol, ethylene glycol butyl ether, ethylene glycol phenyl ether, and a combination thereof.

The first solvent is present in this example of the ink composition in an amount ranging from about 1 wt % to about 12 wt %, with respect to the weight of the inkjet ink composition. In an example, the first solvent is present in the ink composition in an amount ranging from about 1 wt % to about 8 wt %, with respect to the weight of the inkjet ink composition. In another example, the first solvent is present in the ink composition in an amount ranging from about 2.5 wt % to about 6.5 wt %, with respect to the weight of the inkjet ink composition. In still another example, the first solvent is present in the ink composition in an amount of about 5 wt %.

The second solvent is selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof. In an example, the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone.

The second solvent is present in this example of the ink composition in an amount ranging from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition. In an example, the second solvent is present in the ink composition in an amount of about 19 wt %.

In an example of this inkjet ink composition, the first solvent is present in the ink composition in an amount of about 5 wt %, and the second solvent is present in the ink composition in an amount of about 19 wt %. In some examples of this inkjet ink composition: the first solvent is 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 19 wt %; or the first solvent is 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and the second solvent is a combination of 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 11 wt % and glycerol present in an amount of about 8 wt %; or the first solvent is 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and the second solvent is a combination of 2-pyrrolidone present in an amount of about 11 wt % and glycerol present in an amount of about 8 wt %; or the first solvent is a combination of 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and 2-ethyl-2-hydroxymethyl-1,3-propanediol present in an amount of about 4 wt % and the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 15 wt %; or the first solvent is tripropylene glycol methyl ether present in an amount of about 8 wt % and the second solvent is glycerol present in an amount of about 16 wt %; or the first solvent is 2-methyl-1,3-propanediol present in an amount of about 5 wt % and the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 19 wt %; or the first solvent is 2-ethyl-2-hydroxymethyl-1,3-propanediol present in an amount of about 5 wt % and the second solvent is a combination of 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 11 wt % and 2-pyrrolidone present in an amount of about 8 wt %.

The polyurethane binder of Formula I is present in example(s) of the inkjet ink composition in an amount ranging from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition. In an example, the polyurethane binder is present in the inkjet ink composition in an amount ranging from about 0.25 wt % to about 0.85 wt %. In another example, the polyurethane binder is present in the inkjet ink composition in an amount of about 0.85 wt %. In still another example, the polyurethane binder is present in the inkjet ink composition in an amount of about 0.25 wt %.

The inkjet ink composition including the polyurethane of Formula I may be any color, such as black, cyan, magenta, yellow, etc. As such, the inkjet ink composition includes a colorant. The colorant may be a self-dispersed pigment, a polymer dispersed pigment, a dye, or a combination thereof.

As used herein, “pigment” may generally include organic or inorganic pigment colorants, magnetic particles, aluminas, silicas, and/or other ceramics, organo-metallics, metallic particulates, or other opaque particles that introduce color to the inkjet ink composition. In an example, the pigment is selected from the group consisting of organic pigment colorants, inorganic pigment colorants, organo-metallics, and metallic particulates. The pigment may be any color, including, as examples, a cyan pigment, a magenta pigment, a yellow pigment, a black pigment, a violet pigment, a green pigment, a brown pigment, an orange pigment, a purple pigment, a white pigment, a metallic pigment (e.g., a gold pigment, a bronze pigment, a silver pigment, or a bronze pigment), a pearlescent pigment, or combinations thereof.

Examples of suitable blue or cyan organic pigments include C.I. Pigment Blue 1, C.I. Pigment Blue 2, C.I. Pigment Blue 3, C.I. Pigment Blue 15, Pigment Blue 15:3, C.I. Pigment Blue 15:34, C.I. Pigment Blue 15:4, C.I. Pigment Blue 16, C.I. Pigment Blue 18, C.I. Pigment Blue 22, C.I. Pigment Blue 25, C.I. Pigment Blue 60, C.I. Pigment Blue 65, C.I. Pigment Blue 66, C.I. Vat Blue 4, and C.I. Vat Blue 60.

Examples of suitable magenta, red, or violet organic pigments include C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 4, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 8, C.I. Pigment Red 9, C.I. Pigment Red 10, C.I. Pigment Red 11, C.I. Pigment Red 12, C.I. Pigment Red 14, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 17, C.I. Pigment Red 18, C.I. Pigment Red 19, C.I. Pigment Red 21, C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 30, C.I. Pigment Red 31, C.I. Pigment Red 32, C.I. Pigment Red 37, C.I. Pigment Red 38, C.I. Pigment Red 40, C.I. Pigment Red 41, C.I. Pigment Red 42, C.I. Pigment Red 48(Ca), C.I. Pigment Red 48(Mn), C.I. Pigment Red 57(Ca), C.I. Pigment Red 57:1, C.I. Pigment Red 88, C.I. Pigment Red 112, C.I. Pigment Red 114, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 149, C.I. Pigment Red 150, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I. Pigment Red 170, C.I. Pigment Red 171, C.I. Pigment Red 175, C.I. Pigment Red 176, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 179, C.I. Pigment Red 184, C.I. Pigment Red 185, C.I. Pigment Red 187, C.I. Pigment Red 202, C.I. Pigment Red 209, C.I. Pigment Red 219, C.I. Pigment Red 224, C.I. Pigment Red 245, C.I. Pigment Red 286, C.I. Pigment Violet 19, C.I. Pigment Violet 23, C.I. Pigment Violet 32, C.I. Pigment Violet 33, C.I. Pigment Violet 36, C.I. Pigment Violet 38, C.I. Pigment Violet 43, and C.I. Pigment Violet 50.

Examples of suitable yellow organic pigments include C.I. Pigment Yellow 1, C.I. Pigment Yellow 2, C.I. Pigment Yellow 3, C.I. Pigment Yellow 4, C.I. Pigment Yellow 5, C.I. Pigment Yellow 6, C.I. Pigment Yellow 7, C.I. Pigment Yellow 10, C.I. Pigment Yellow 11, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 16, C.I. Pigment Yellow 17, C.I. Pigment Yellow 24, C.I. Pigment Yellow 34, C.I. Pigment Yellow 35, C.I. Pigment Yellow 37, C.I. Pigment Yellow 53, C.I. Pigment Yellow 55, C.I. Pigment Yellow 65, C.I. Pigment Yellow 73, C.I. Pigment Yellow 74, C.I. Pigment Yellow 75, C.I. Pigment Yellow 77, C.I. Pigment Yellow 81, C.I. Pigment Yellow 83, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 95, C.I. Pigment Yellow 97, C.I. Pigment Yellow 98, C.I. Pigment Yellow 99, C.I. Pigment Yellow 108, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 113, C.I. Pigment Yellow 114, C.I. Pigment Yellow 117, C.I. Pigment Yellow 120, C.I. Pigment Yellow 122, C.I. Pigment Yellow 124, C.I. Pigment Yellow 128, C.I. Pigment Yellow 129, C.I. Pigment Yellow 133, C.I. Pigment Yellow 138, C.I. Pigment Yellow 139, C.I. Pigment Yellow 147, C.I. Pigment Yellow 151, C.I. Pigment Yellow 153, C.I. Pigment Yellow 154, C.I. Pigment Yellow 167, C.I. Pigment Yellow 172, C.I. Pigment Yellow 180, and C.I. Pigment Yellow 185.

Carbon black may be a suitable inorganic black pigment. Examples of carbon black pigments include those manufactured by Mitsubishi Chemical Corporation, Japan (such as, e.g., carbon black No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, and No. 2200B); various carbon black pigments of the RAVEN® series manufactured by Columbian Chemicals Company, Marietta, Ga., (such as, e.g., RAVEN® 5750, RAVEN® 5250, RAVEN® 5000, RAVEN® 3500, RAVEN® 1255, and RAVEN® 700); various carbon black pigments of the REGAL® series, the MOGUL® series, or the MONARCH® series manufactured by Cabot Corporation, Boston, Mass., (such as, e.g., REGAL® 400R, REGAL® 330R, REGAL® 660R, MOGUL® E, MOGUL® L, AND ELFTEX® 410); and various black pigments manufactured by Evonik Degussa Orion Corporation, Parsippany, N.J., (such as, e.g., Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, PRINTEX® 35, PRINTEX® U, PRINTEX® V, PRINTEX® 140U, Special Black 5, Special Black 4A, and Special Black 4). An example of an organic black pigment includes aniline black, such as C.I. Pigment Black 1.

Some examples of green organic pigments include C.I. Pigment Green 1, C.I. Pigment Green 2, C.I. Pigment Green 4, C.I. Pigment Green 7, C.I. Pigment Green 8, C.I. Pigment Green 10, C.I. Pigment Green 36, and C.I. Pigment Green 45.

Examples of brown organic pigments include C.I. Pigment Brown 1, C.I. Pigment Brown 5, C.I. Pigment Brown 22, C.I. Pigment Brown 23, C.I. Pigment Brown 25, C.I. Pigment Brown 41, and C.I. Pigment Brown 42.

Some examples of orange organic pigments include C.I. Pigment Orange 1, C.I. Pigment Orange 2, C.I. Pigment Orange 5, C.I. Pigment Orange 7, C.I. Pigment Orange 13, C.I. Pigment Orange 15, C.I. Pigment Orange 16, C.I. Pigment Orange 17, C.I. Pigment Orange 19, C.I. Pigment Orange 24, C.I. Pigment Orange 34, C.I. Pigment Orange 36, C.I. Pigment Orange 38, C.I. Pigment Orange 40, C.I. Pigment Orange 43, and C.I. Pigment Orange 66.

A suitable metallic pigment includes a metal selected from the group consisting of gold, silver, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, aluminum, and alloys of any of these metals. These metals may be used alone or in combination with two or more metals or metal alloys. Some examples of metallic pigments include STANDART® RO100, STANDART® RO200, and DORADO® gold-bronze pigments (available from Eckart Effect Pigments, Wesel, Germany).

The average particle size of the pigments may range anywhere from about 50 nm to about 200 nm. In an example, the average particle size ranges from about 80 nm to about 150 nm.

As mentioned above, in some examples, the colorant may be a polymer dispersed pigment. When the colorant may be a polymer dispersed pigment, the polymer dispersant may be present in inkjet ink composition in an amount ranging from about 0.1 wt % to about 5 wt % of a total weight of the inkjet ink composition.

In an example, the colorant is an anionically dispersed pigment. In an example, the anionically dispersed pigment is a dispersion including water, the pigment, and an anionic polymer that disperses the pigment (i.e., the anionic polymeric dispersant). In an example, the pigment dispersion may also include, for example, a co-solvent, such as 2-pyrrolidone. The pigment dispersion may be prepared or purchased, and the other components of the inkjet ink composition (e.g., the polyurethane, the organic solvent, etc.) may be mixed with the pigment dispersion to form the inkjet ink composition.

In other examples, the colorant may be a self-dispersing pigment. As used herein, the term “self-dispersing pigment” refers to a pigment having water-solubilizing groups on the pigment surface. The self-dispersing pigment can be dispersed in water without the polymer dispersant. In an example, the self-dispersing pigment is obtained by carrying out surface modification treatments, such as an acid/base treatment, a coupling agent treatment, a polymer graft treatment, a plasma treatment, an oxidation/reduction treatment, an ozone and light (e.g., light and ultra-violet radiation) treatment, on a pigment. Examples of the self-dispersion type pigment may include, in addition to the above described surface modified pigment, commercially available self-dispersion pigments such as CAB-O-JET®-200, CAB-O-JET®-300, CAB-O-JET®-400, IJX-157, IJX-253, IJX-266, IJX-273, IJX-444, IJX-55, CAB-O-JET®-250C, CAB-O-JET®-260M, CAB-O-JET®-270Y, CAB-O-JET®-450C, CAB-O-JET®-465M, CAB-O-JET®-470Y, and CAB-O-JET®-480M manufactured by Cabot Corporation, and Microjet Black CWI, and CW-2 manufactured by Orient Chemical Industries Co., Ltd.

Still other examples of the colorant include self-dispersed carbon blacks and polymer dispersed pigments commercially available from E.I. du Pont de Nemours and Co. (Wilmington, Del.) and Sensient Technologies Corporation (Milwaukee, Wis.).

In another example, the colorant is a dye. Examples of dyes include a hydrophilic anionic dye, a direct dye, a cationic dye, a reactive dye, a polymer dye and an oil soluble dye, and a fluorescent dye.

In this example of the inkjet ink composition, the colorant may be present in the inkjet ink composition in an amount ranging from about 0.5 wt % to about 14 wt %, with respect to the weight of the inkjet ink composition. In another example, the colorant is present in an amount ranging from about 0.5 wt % to about 8 wt %, with respect to the weight of the inkjet ink composition. In still another example, the colorant is present in an amount ranging from about 2 wt % to about 7 wt %, with respect to the weight of the inkjet ink composition. In still another example, the colorant is present in an amount ranging from about 3 wt % to about 5 wt %, with respect to the weight of the inkjet ink composition. In yet another example, the colorant is present in an amount ranging of about 4.4 wt %, with respect to the weight of the inkjet ink composition.

As mentioned above, the inkjet ink composition may also include an additive selected from the group consisting of a surfactant, a biocide, a pH adjuster, and combinations thereof.

When the inkjet ink composition includes surfactant(s), the surfactant(s) may be present in an amount ranging from about 0.01 wt % to about 2 wt % (with respect to the weight of the inkjet ink composition). In an example, the surfactant is present in the inkjet ink composition in an amount of about 0.01 wt %, with respect to the weight of the inkjet ink composition. In another example, the surfactant is present in the inkjet ink composition in an amount of about 0.1 wt %, with respect to the weight of the inkjet ink composition. In still another example, the surfactant is present in the inkjet ink composition in an amount of about 1.1 wt %, with respect to the weight of the inkjet ink composition.

The surfactant may include anionic and/or non-ionic surfactants. 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, monobutylbiphenylsulfonate, and dibutylphenylphenol disulfonate. 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.

In some examples, the inkjet ink composition may include a silicone-free alkoxylated alcohol surfactant such as, for example, TEGO® Wet 510 (EvonikTegoChemie GmbH) and/or a self-emulsifiable wetting agent based on acetylenic diol chemistry, such as, for example, SURFYNOL® SE-F (Air Products and Chemicals, Inc.). In another example, the surfactant may be BYK-3410 (butanedioic acid, 2-sulfo-, 1,4-bis(2-ethylhexyl) ester, sodium salt available form BYK Additives & Instruments). 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 Air Products and Chemicals, Inc.); 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 Co.); and SURFADONE™ LP-100 (N-octyl-2-pyrrolidone, a low-foaming, nonionic rapid wetting agent with an HLB of 6, available from Ashland Inc.).

This example of the inkjet ink composition may also include biocide(s). In an example, the total amount of biocide(s) in the inkjet ink composition ranges from about 0.1 wt % to about 0.5 wt % (with respect to the weight of the inkjet ink composition). In another example, the total amount of biocide(s) in the inkjet ink composition is about 0.27 wt % (with respect to the weight of the inkjet ink composition).

Examples of suitable biocides include the NUOSEPT® (Ashland Inc.), UCARCIDE™ or KORDEK™ (Dow Chemical Co.), PROXEL® (Arch Chemicals) series, ACTICIDE® B20 and ACTICIDE® M20 (Thor Chemicals), and combinations thereof.

The inkjet ink composition including the polyurethane of Formula I may have a pH ranging from about 7 to about 10, and pH adjuster(s) may be added to the inkjet ink composition 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 composition ranges from greater than 0 wt % to about 0.1 wt % (with respect to the weight of the inkjet ink composition). In another example, the total amount of pH adjuster(s) in the inkjet ink composition is about 0.03 wt % (with respect to the weight of the inkjet ink composition).

Examples of suitable pH adjusters include metal hydroxide bases, such as sodium hydroxide (NaOH), potassium hydroxide (KOH), etc.

The balance of this inkjet ink composition is water. The inkjet ink composition includes at least 50 wt % water, with respect to the weight of the inkjet ink composition. In an example, the inkjet ink composition includes at least 60 wt % water, with respect to the weight of the inkjet ink composition. In another example, the inkjet ink composition includes at least 65 wt % water, with respect to the weight of the inkjet ink composition. In still another example, the inkjet ink composition includes water in an amount ranging from about 50 wt % to about 90 wt %, with respect to the weight of the inkjet ink composition. In an example, the water may be deionized water or purified water.

Referring now to FIG. 1, a method 100 for improving durability of prints created with the example of the inkjet ink composition is depicted. One example of the method 100 comprises: incorporating from about 0.25 wt % to about 2 wt %, with respect to a weight of the inkjet ink composition, of the polyurethane of Formula I into a liquid ink; wherein the liquid ink includes: a colorant; an organic solvent package including: from about 1 wt % to about 12 wt %, with respect to the weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; and at least 50 wt % water with respect to the weight of the inkjet ink composition (reference numeral 102).

As shown at reference numeral 102, the method 100 includes incorporating from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of the polyurethane of Formula I into the liquid ink. The polyurethane may be as previously described with respect to Formula I. Further, the polyurethane of Formula I may be incorporated into the inkjet ink composition in any of the amounts previously described.

In this example of the method 100, the liquid ink includes: the colorant; the organic solvent package including: from about 1 wt % to about 12 wt %, with respect to the weight of the inkjet ink composition, of the first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of the second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; and at least 50 wt % water with respect to the weight of the inkjet ink composition. The liquid ink components and there amounts may be as previously described.

Inkjet Ink Composition with Polyurethane of Formula II

In some other examples, the inkjet ink composition comprises: a colorant; an organic solvent package including from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; at least 50 wt % water with respect to the weight of the inkjet ink composition; and from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of a polyurethane binder having a general structure of Formula II:

OCNQ¹_nQ²_mQ³_pR¹—NCO (II),

where the terminal isocyanate groups are capped with a capping agent; and for Formula II:

- each Q¹, Q²and Q³is independently:

[Image Omitted]

provided that Q¹, Q²and Q³contain at least one Formula III, one Formula IV and one Formula V groups;

each R¹is C₁-C₂₀alkylene, C₃-C₂₀substituted alkylene, C₃-C₁₀cycloalkylene, C₃-C₂₀substituted cycloalkylene, C₆-C₄₀arylene or C₉-C₄₀substituted arylene from a diisocyanate;

each R²is independently C₃-C₂₀substituted alkylene, C₃-C₂₀substituted cycloalkylene or C₉-C₄₀substituted arylene;

each R³is independently C₉-C₂₀alkylene, C₂alkylene substituted by C₁-C₁₀alkyl, C₉-C₂₀alkylene substituted by C₁-C₁₀alkyl or C₆-C₁₅aryl, C₉-C₄₀arylene, C₉-C₄₀arylene substituted by C₁-C₁₀alkyl or C₆-C₂₀aryl, or —(R⁵—O—R⁶—O—R⁵)—; or HO—R³—OH is a diol incorporating polyether, polyester, polycarbonate, polycarbonate-co-polyester or acrylic;

each R⁴is independently a C₁-C₇alkyl, a C₃-C₂₀alkyl substituted by C₁-C₄₀alkyl or a C₆-C₁₅aryl, a C₆-C₄₀aryl or a C₉-C₄₀aryl substituted by C₁-C₁₀alkyl or a C₆-C₁₅aryl, C₁-C₇alkylene, C₃-C₂₀alkylene substituted by C₁-C₁₀alkyl or C₆-C₁₅aryl, C₆-C₄₀arylene, C₉-C₄₀arylene substituted by C₁-C₁₀alkyl or C₆-C₂₀aryl, provided that the backbone atoms on R⁴forming a chain linking the two oxygen atoms in Formula V are less than 8;

n, m and p are integers from 1 to 200;

the capping agent is R⁷R⁸NH;

each R⁷is C₁-C₂₀alkyl;

each R⁸is C₁-C₂₀alkyl;

R⁷and R⁸are taken together with the nitrogen atom to form a cyclic amine or a substituted cyclic amine with an O or S atom replacing a C atom on said cyclic amine;

each R⁶is independently C₄-C₂₀alkyl, C₄-C₂₀alkyl substituted by C₁-C₁₀alkyl or C₆-C₁₅aryl, C₉-C₄₀aryl, C₉-C₄₀aryl substituted by C₁-C₁₀alkyl or C₆-C₂₀aryl;

each R⁵is independently C₁-C₁₀alkyl, C₄-C₂₀alkyl substituted by C₁-C₁₀alkyl or C₆-C₁₅aryl; and

q is an integer from 1 to 20;

and wherein a chain extender is present between at least some neighboring isocyanates in Formula II such that a number average molecular weight of the polyurethane binder ranges from about 10,000 to about 25,000.

In the examples disclosed herein, the isocyanate is a diisocyanate. Suitable diisocyanates may be selected from the group consisting of 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI), 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI), dodecane diisocyanate (C₁₂DI), 1,5-naphthalene diisocyanate (NDI), m-tetramethylene xylylene diisocyanate (TMXDI), 1,4-benzene diisocyanate, trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene diisocyanate.

Any suitable method that reacts the isocyanate with the compounds of Formulas III, IV, and V, as well as the chain-extender, may be used to form the polyurethane copolymer of Formula II. Different diols may be used to form each of the monomers with Formulas III, IV and V. For example, R², R³, R⁴groups in Formulas III, IV, and V may come from respective diols.

Some examples of a first diol, which includes a hydrophilic stabilizing group and ultimately forms part of the monomer with Formula (III), include dimethylol acetic acid, 2,2′-dimethylol butanoic acid, 2,2′-dimethylol propionic acid (DMPA), and 2,2′-dimethylol butyric acid.

Some examples of a second diol, which has less than 8 atoms in the backbone chain between two hydroxyl group and ultimately forms part of the monomer with Formula (V), include 1,2-propanediol, 1,3-propanediol, ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentane diol, and combinations thereof.

When included, examples of a third diol have a hydrophobic segment and ultimately form part of the monomer with Formula (IV). Some examples of this third diol have the formula OH—R—OH, wherein R is selected from the group consisting of a polyether, a polyester, a polycarbonate, a polycarbonate-co-polyester, and an acrylic. Other examples of the third diol have the formula OH—R⁴—OH. R⁴may be any of the examples previously given, such as a C₁-C₇alkyl, or a C₆-C₄₀aryl, or a C₉-C₄₀aryl substituted by C₁-C₁₀alkyl.

Alternatively, a polyol can be used in place of, or in combination with the diols mentioned above. In such cases, these polyols may be triols, such as trimethylol propane or 1,2,6-hexane triol.

Any of the chain extenders previously described for Formula I may be used in this example of the polyurethane binder.

The total amount of chain extender that is added depends upon the desired molecular weight of the polyurethane. In some examples, the number average (M_N) molecular weight of the polyurethane binder ranges from about 10,000 to about 25,000. In other examples, the number average (M_N) molecular weight of the polyurethane binder ranges from about 12,000 to about 25,000. To achieve the desired molecular weight, the total amount of chain-extender material employed may be such that the ratio of active amine functional groups in the chain-extender to NCO groups in the pre-polymer component ranges from 2:1 to 3:1.

In the final polyurethane copolymer binder of Formula II, the mole percentage of the second diol is at least 30% of a total mole percentage of diol monomers in the polyurethane copolymer binder. The acid number of the polyurethane copolymer binder ranges from 50 to 100, and the number average (M_n) molecular weight of the polyurethane copolymer binder ranges from about 10,000 to about 25,000. In another example, the M_nof the polyurethane copolymer binder ranges from about 12,000 to about 25,000 or from about 12,000 to about 20,000.

In other examples, the inkjet ink composition consists of: the colorant; the organic solvent package including: from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; at least 50 wt % water with respect to the weight of the inkjet ink composition; and from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of the polyurethane binder having the general structure of Formula II. In these examples, the inkjet ink composition includes no other components.

In still other examples, the inkjet ink composition consists of: the colorant; the organic solvent package including: from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of the polyurethane binder having the general structure of Formula II; and the additive selected from the group consisting of the surfactant, the biocide, the pH adjuster, and combinations thereof. In these examples, the inkjet ink composition includes no other components.

In this example of the inkjet ink composition, the organic solvent package includes from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of the first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of the second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof. In an example, a weight ratio of the first solvent to the second solvent ranges from 0.25 to 0.8. In another example of the inkjet ink composition, this organic solvent package consists of the first solvent and the second solvent.

As mentioned above, in some examples, the weight ratio of the first solvent to the second solvent in the examples of the inkjet ink composition including the polyurethane of Formula II ranges from 0.25 (1:4) to 0.8 (1:1.25). As specific examples, the weight ratio of total first solvent(s): total second solvent(s) may be 5:19 (0.26), 9:15 (0.6), or 1:2 (0.5). In these examples, the weight percent of each of the first solvent(s) and the second solvent(s) may be any suitable weight percent within this example of the inkjet ink composition, as long the weight ratio of first solvent(s) to second solvent(s) falls within the range presented herein. As an example, the first solvent(s) may be present in this example of the ink composition in an amount ranging from about 5 wt % to about 9 wt %, and the second solvent(s) may be present in this example of the ink composition in an amount ranging from about 15 wt % to about 19 wt %.

In some examples of this inkjet ink composition: the first solvent is 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 19 wt % (weight ratio=0.26); or the first solvent is 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and the second solvent is a combination of 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 11 wt % and glycerol present in an amount of about 8 wt % (weight ratio=0.26); or the first solvent is 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and the second solvent is a combination of 2-pyrrolidone present in an amount of about 11 wt % and glycerol present in an amount of about 8 wt % (weight ratio=0.26); or the first solvent is a combination of 2-ethyl-1,3-hexanediol present in an amount of about 5 wt % and 2-ethyl-2-hydroxymethyl-1,3-propanediol present in an amount of about 4 wt % and the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 15 wt % (weight ratio=0.6); or the first solvent is tripropylene glycol methyl ether present in an amount of about 8 wt % and the second solvent is glycerol present in an amount of about 16 wt % (weight ratio=0.5); or the first solvent is 2-methyl-1,3-propanediol present in an amount of about 5 wt % and the second solvent is 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 19 wt % (weight ratio=0.26); or the first solvent is 2-ethyl-2-hydroxymethyl-1,3-propanediol present in an amount of about 5 wt % and the second solvent is a combination of 1-(2-hydroxyethyl)-2-pyrrolidinone present in an amount of about 11 wt % and 2-pyrrolidone present in an amount of about 8 wt % (weight ratio=0.26).

The polyurethane binder of Formula II is present in example(s) of the inkjet ink composition in an amount ranging from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition. In an example, this polyurethane binder is present in the inkjet ink composition in an amount ranging from about 0.25 wt % to about 0.85 wt %. In another example, this polyurethane binder is present in the inkjet ink composition in an amount of about 0.85 wt %. In still another example, this polyurethane binder is present in the inkjet ink composition in an amount of about 0.25 wt %.

The inkjet ink composition including the polyurethane of Formula II may be any color, such as black, cyan, magenta, yellow, etc., and thus includes a colorant. In this example inkjet ink composition, any of the colorants disclosed herein for the inkjet ink composition containing the polyurethane of Formula I may be used in any of the amounts disclosed herein for the inkjet ink composition containing the polyurethane of Formula I.

The inkjet ink composition including the polyurethane of Formula II may also include an additive selected from the group consisting of a surfactant, a biocide, a pH adjuster, and combinations thereof. Any of the example additives may be used in any of the amounts disclosed herein for the inkjet ink composition containing the polyurethane of Formula I.

The inkjet ink composition including the polyurethane of Formula II may have a pH ranging from about 7 to about 10, and pH adjuster(s) may be added to the inkjet ink composition 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 composition ranges from greater than 0 wt % to about 0.1 wt % (with respect to the weight of the inkjet ink composition). In another example, the total amount of pH adjuster(s) in the inkjet ink composition is about 0.03 wt % (with respect to the weight of the inkjet ink composition). Examples of suitable pH adjusters include metal hydroxide bases, such as sodium hydroxide (NaOH), potassium hydroxide (KOH), etc.

Referring now to FIG. 2, a method 200 for improving durability of prints created with the example of the inkjet ink composition is depicted. One example of the method 200 comprises: incorporating from about 0.25 wt % to about 2 wt %, with respect to a weight of the inkjet ink composition, of the polyurethane of Formula II into a liquid ink; wherein the liquid ink includes: a colorant; an organic solvent package including: from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; and at least 50 wt % water with respect to the weight of the inkjet ink composition (reference numeral 202).

As shown at reference numeral 202, the method 200 includes incorporating from about 0.25 wt % to about 2 wt %, with respect to the weight of the inkjet ink composition, of the polyurethane of Formula II into the liquid ink. The polyurethane may be as previously described with respect to Formula II. Further, the polyurethane of Formula II may be incorporated into the inkjet ink composition in any of the amounts previously described.

In this example of the method 200, the liquid ink includes: the colorant; the organic solvent package including: from about 1 wt % to about 12 wt %, with respect to a weight of the inkjet ink composition, of a first solvent having 1 or 2 free hydroxyl groups and 0 to 3 glycol units; and from about 0.5 wt % to about 25 wt %, with respect to the weight of the inkjet ink composition, of a second solvent selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidinone, 2-pyrrolidone, glycerol, and combinations thereof; and at least 50 wt % water with respect to the weight of the inkjet ink composition. The liquid ink components and there amounts may be as previously described.

Referring now to FIG. 3, a print cartridge 10 is generally and schematically depicted. It is to be understood that the print cartridge 10 may include additional components (some of which are described herein) and that some of the components described herein may be removed and/or modified. Furthermore, components of the print cartridge 10 depicted in FIG. 3 may not be drawn to scale and thus, the print cartridge 10 may have a different size and/or configuration other than as shown therein.

In an example, the print cartridge 10 comprises a fluid reservoir 14; a fluid ejector 16 in fluid communication with the fluid reservoir 14; a nozzle 18 in fluid communication with the fluid ejector 16; an inkjet ink composition 20 present in the fluid reservoir 14; and an orifice 26 of the nozzle 18, through which the inkjet ink composition 20 is ejected.

In one example, the inkjet ink composition 20 is the inkjet ink composition disclosed herein that includes the polyurethane of Formula I and its corresponding organic solvent package. In another example, the inkjet ink composition 20 is the inkjet ink composition disclosed herein that includes the polyurethane of Formula II and its corresponding organic solvent package.

The print cartridge 10 includes a housing 12 (which may include one or more layers of different materials) that is operatively connected to the reservoir 14 that contains an example of the inkjet ink composition 20 disclosed herein. A fluid path/ink channel 24 connects the reservoir 14 to a fluid ejector 16. In a thermal inkjet print cartridge, the fluid ejector 16 is a heating element that creates heat to vaporize the inkjet ink composition 20, which creates a bubble that expands to push the inkjet ink composition 20 (in the form of drops 22) out of an orifice 26 of a nozzle 18 that is aligned with the fluid ejector 16. While a single fluid ejector 16 and nozzle 18 is shown, it is to be understood that a single print cartridge 10 may include multiple (e.g., 400 or some other desirable number) fluid ejectors 16 and nozzles 18. While not shown, it is to be understood that the print cartridge 10 includes an integrated circuit that routes signals (e.g., from a processor that is capable of running suitable computer readable instructions) to the desirable fluid ejector(s)16 and nozzle(s) 18 for firing ink drops 22 therefrom to produce images on a desirable medium.

To further illustrate the present disclosure, examples are given herein. It is to be understood these examples are provided for illustrative purposes and are not to be construed as limiting the scope of the present disclosure.

EXAMPLES
Example 1

An example of the inkjet ink composition was prepared, and a comparative inkjet ink composition was also prepared. The example inkjet ink composition and the comparative inkjet ink composition each included a self-dispersed carbon black pigment as the colorant, 2-ethyl-1,3-hexanediol as the first solvent, and 1-(2-hydroxyethyl)-2-pyrrolidone as the second solvent. The example inkjet ink composition included a polyurethane with the general structure of Formula II having a number average molecular weight of 11,000. The comparative inkjet ink composition included a comparative linear polyurethane having a number average molecular weight of 5,500 (formed without chain extenders). The example inkjet ink composition and the comparative inkjet ink composition each had the same general formulation except for the polyurethane included therein. The general formulations of the example inkjet ink composition and the comparative inkjet ink composition are shown in Table 1, with the wt % of each component that was used.

TABLE 1

Example
Comp.

inkjet ink 1
inkjet ink

Ingredient
Specific Component
(wt %)
(wt %)

Colorant
Self-dispersed carbon
4.4
4.4

black pigment

Polyurethane
Formula II
1.7
0

Comparative polyurethane
0
1.7

First solvent
2-ethyl-1,3-hexanediol
5
5

Second solvent
1-(2-hydroxyethyl)-2-
19
19

pyrrolidone

Surfactant
BYK-3410
1
1

SURFYNOL ® 104
0.05
0.05

SURFADONE ® LP100
0.05
0.05

Biocide
ACTICIDE ® B20
0.20
0.20

ACTICIDE ® M20
0.07
0.07

Deionized Water

Balance
Balance

The example inkjet ink composition and the comparative inkjet ink composition were each tested for durability. The example inkjet ink composition and the comparative inkjet ink composition were each used to create example and comparative prints on brochure media (HP® Inkjet Glossy Brochure Paper available from Hewlett-Packard, Co., California) and on photo media (HP® Advanced Glossy Photo Paper available from Hewlett-Packard, Co., California) using an ink flux of 56 ng/300^th(printed using a HP® Cartridge 940 in an OFFICEJET® Pro 8000 inkjet printer available from Hewlett-Packard, Co., California). Two of these prints were tested for abrasion resistance by scratch testing. In this example, the scratch test was performed manually by applying pressure to the print using the back (i.e., the nail bed) of an index (i.e., pointer) finger. The nail bed was pressed against the print and moved from the lower left corner to the upper right corner in a single motion. Two other of these prints were tested for abrasion resistance by smudge testing. In this example, the smudge test was performed by manually applying pressure to the print using a thumb pressed against the print and moved from the lower left corner to the upper right corner in a single motion. For each of the scratch and smudge tests, the results were recorded for the same print at different times, where, at 0 minutes, the tests were performed immediately after printing, at time 2 minutes, the tests were performed two minutes after printing, and at time 4 minutes, the tests were performed four minutes after printing.

The results of the scratch testing and smudge testing for the prints created on brochure media with the comparative inkjet ink composition are shown in FIG. 4A. The results of the scratch testing and smudge testing for the prints created on brochure media with the example inkjet ink composition are shown in FIG. 4B. The results of the scratch testing and smudge testing for the prints created on photo media with the comparative inkjet ink composition are shown in FIG. 4C, and the results of the scratch testing and smudge testing for the prints created on photo media with the example inkjet ink composition are shown in FIG. 4D. In each of FIGS. 4A through 4D, the results of the scratch testing are shown in the top row, and the results of the smudge testing are shown in the bottom row. Also in each of FIGS. 4A through 4D, the results for tests performed immediately after printing (t=0 minutes) are shown in the left column, the results for tests performed two minutes after printing (t=2 minutes) are shown in the middle column, and the results for tests performed four minutes after printing (t=4 minutes) are shown in the right column. After four minutes, no further changes were observed, and so the tests were stopped.

Comparing FIGS. 4A and 4B, using the example inkjet ink composition improved the durability of the prints on brochure media, most notably when tested four minutes after printing. Comparing FIGS. 4C and 4D, using the example inkjet ink composition significantly improved the durability of the prints on photo media, immediately after printing, two minutes after printing, and four minutes after printing.

Example 2

Four additional examples of the inkjet ink composition were prepared. Each of the additional example inkjet ink composition included a self-dispersed carbon black pigment as the colorant and a polyurethane with the general structure of Formula II (M_N=11,000). For one of the additional example inkjet ink compositions, 2-ethyl-1,3-hexanediol was the first solvent, and a combination of 1-(2-hydroxyethyl)-2-pyrrolidone and glycerol was the second solvent. For another of the additional example inkjet ink compositions, 2-ethyl-1,3-hexanediol was the first solvent, and a combination of 2-pyrrolidone and glycerol was the second solvent. For another of the additional example inkjet ink compositions, a combination of 2-ethyl-1,3-hexanediol and 2-ethyl-2-hydroxymethyl-1,3-propanediol was the first solvent, and 1-(2-hydroxyethyl)-2-pyrrolidone was the second solvent. For another of the additional example inkjet ink compositions, tripropylene glycol methyl ether was the first solvent, and glycerol was the second solvent. All four of the example inkjet ink compositions had the same general formulation except for the organic solvent package (i.e., the first and second solvents). The general formulation of the four additional example inkjet ink compositions is shown in Table 2, with the wt % of each component that was used.

TABLE 2

Example
Example
Example
Example

inkjet ink 2
inkjet ink 3
inkjet ink 4
inkjet ink 5

Ingredient
Specific Component
(wt %)
(wt %)
(wt %)
(wt %)

Colorant
Self-dispersed carbon
4.4
4.4
4.4
4.4

black pigment

First solvent
2-ethyl-1,3-hexanediol
5
5
5
0

2-ethyl-2-hydroxymethyl-
0
0
4
0

1,3-propanediol

Tripropylene glycol
0
0
0
8

methyl ether

Second
1-(2-hydroxyethyl)-2-
11
0
15
0

solvent
pyrrolidone

2-pyrrolidone
0
11
0
0

Glycerol
8
8
0
16

Polyurethane
Formula II
1.7
1.7
1.7
1.7

Surfactant
SURFYNOL ® 104
0.05
0.05
0.05
0.05

SURFADONE ™ LP-100
0.05
0.05
0.05
0.05

Biocide
ACTICIDE ® B20
0.20
0.20
0.20
0.20

ACTICIDE ® M20
0.07
0.07
0.07
0.07

Deionized

Balance
Balance
Balance
Balance

Water

The durability of prints created on brochure media (HP® Inkjet Glossy Brochure Paper available from Hewlett-Packard, Co., California) and photo media (HP® Advanced Glossy Photo Paper available from Hewlett-Packard, Co., California) using an ink flux of 56 ng/300^th(printed using a HP® Cartridge 940 in an OFFICEJET® Pro 8000 inkjet printer available from Hewlett-Packard, Co., California) with the additional example inkjet ink compositions was tested. The durability of these prints was comparable to the durability of prints created with the example inkjet ink composition in Example 1. The durability of the prints created with the additional example inkjet ink compositions in this Example was also improved as compared to the durability of prints created with the comparative inkjet ink composition in Example 1. This indicates that the organic solvent package, which may include different examples of the first and second solvent disclosed herein, can play a significant role in improved durability performance on both brochure and photo media.

Example 3

Twelve additional examples of the inkjet ink composition were prepared. Each of the additional example inkjet ink compositions included a self-dispersed carbon black pigment as the colorant, a combination of 2-ethyl-1, 3-hexanediol and 2-ethyl-2-hydroxymethyl-1,3-propanediol as the first solvent, 1-(2-hydroxyethyl)-2-pyrrolidone as the second solvent, and a polyurethane with the general structure of Formula II (M_N=11,000). Each example inkjet ink composition had the same general formulation except for the amount of the polyurethane. The amount of the polyurethane in example inkjet ink compositions (e.g., inkjet inks 6 through 17) was, respectively, 2 wt %, 1.5 wt %, 1.3 wt %, 1.1 wt %, 1 wt %, 0.85 wt %, 0.75 wt %, 0.65 wt %, 0.55 wt %, 0.45 wt %, 0.35 wt %, and 0.25 wt %. The general formulation of the example inkjet ink compositions is shown in Table 3, with the wt % of each component that was used.

TABLE 3

Amount

Ingredient
Specific Component
(wt %)

Colorant
Self-dispersed carbon black
4.4

pigment

Polyurethane
Formula II
0.25-2

First solvent
2-ethyl-1,3-hexanediol
5

2-ethyl-2-hydroxymethyl-
4

1,3-propanediol

Second solvent
1-(2-hydroxyethyl)-2-
15

pyrrolidone

Surfactant
BYK-3410
0.1

Biocide
ACTICIDE ® B20
0.20

ACTICIDE ® M20
0.07

Water

Balance

FIG. 5A shows the results of scratch testing and smudge testing for prints created on brochure media with example inkjet ink 17 (including 0.25 wt % of a polyurethane with the general structure of Formula II (M_N=11,000)). FIG. 5B shows the results of scratch testing and smudge testing for prints created on photo media with the example inkjet ink 17. In each of FIGS. 5A and 5B, the results of the scratch testing are shown in the top row, and the results of the smudge testing are shown in the bottom row. Also in each of FIGS. 5A and 5B, the results for the prints tested immediately after printing (t=0 minutes) are shown in the left column, the results for the prints tested two minutes after printing (t=2 minutes) are shown in the middle column, and the results for the prints tested four minutes after printing (t=4 minutes) are shown in the right column. After four minutes, no further change was observed, and so the tests were stopped.

As shown in FIG. 5A, using example inkjet ink 17 created prints with durability on brochure media that was comparable to the durability of prints created with example inkjet ink 1, and that was improved as compared to the durability of prints created with the comp. inkjet ink. As shown in FIG. 5B, using example inkjet ink 17 created prints with durability on photo media that was comparable to the durability of prints created with example inkjet ink 1, and that was improved as compared to the durability of prints created with the comp. inkjet ink.

These results indicate that the amount of the polyurethane may be reduced (e.g., to 0.25 wt %) without significantly affecting durability performance.

It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from about 1 wt % to about 12 wt % should be interpreted to include not only the explicitly recited limits of from about 1 wt % to about 12 wt %, but also to include individual values, such as 1.01 wt %, 1.8 wt %, 5.0 wt %, 7.05 wt %, 10.785 wt %, etc., and sub-ranges, such as from about 1.1 wt % to about 10.95 wt %, from about 1.5 wt % to about 11.5 wt %, from about 2.5 wt % to about 8.0 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.

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.

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

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.