Water-based inkjet inks containing polyurethane polymers

Abstract

The present disclosure relates to an aqueous inkjet ink containing a pigment as a colorant, a polymeric dispersant, a polyurethane binder, and an aqueous vehicle. The ink exhibits improved properties for printing on low-absorbent and non-absorbent substrates.

Description

[Technical field]

[0001] The present disclosure relates to an aqueous ink containing an aqueous vehicle, a pigment, a polymeric dispersant for dispersing the pigment, and a polyurethane polymer as a binder. The aqueous vehicle includes an organic solvent having a boiling point of 230° C. or less at ambient atmospheric pressure. [Background technology]

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63 / 289,346, filed December 14, 2021.

[0003] Inkjet printing is a non-impact digital printing process in which droplets of ink are deposited on a substrate, such as paper, to form a desired image. For full-color printing, inkjet printers are typically equipped with an ink set that includes cyan, magenta, yellow, and an additional black ink (CMYK), with black ink being the most common ink. For transparent substrates, such as clear plastic, a white ink is generally required to enhance the color image. In this case, the ink set typically includes CMYKW inks.

[0004] Inkjet printing is becoming more important in markets outside of traditional desktop printing for small / home offices. Digital printing methods have gained popularity in textile, commercial and packaging printing, offering several potential advantages over traditional printing methods such as screen printing, offset printing, flexography and gravure printing. Inkjet digital printing may eliminate the setup costs associated with screen and plate manufacturing, allowing for cost-effective short run production. The expansion of inkjet in these new applications has created a need to print directly onto low-absorbency substrates such as coated paper, coated corrugated board, and folding carton, as well as non-absorbent plastic substrates such as vinyl, polystyrene, and polypropylene boards, and flexible polypropylene, polyester, nylon, and polyethylene films. Compared to plain paper and specialty inkjet papers, low-absorbency and non-absorbent substrates have little or no ink penetration, resulting in slower drying, poorer image quality, and prints sticking together before use. These disadvantages are particularly exacerbated when printing at high speeds. Aiming to address these issues, low-boiling water-soluble organic solvents can be formulated into the ink to improve the volatility and drying speed of water-based inks. However, fast-volatilizing water-based inks tend to face jettability issues. This is especially problematic when the ink is jetted after the printhead has been left idle or uncapped for an extended period of time, resulting in partial blockage of the printhead nozzles as a result of fast drying and solidification of the ink. Furthermore, inks for commercial and packaging printing applications on low-absorbency and non-absorbency substrates are typically formulated with polymer binders to reduce the solvent load and achieve faster drying speeds and durability requirements such as resistance to smearing and smearing. Inks with polymer binders tend to film and clog around the nozzles, further reducing jetting reliability. On the other hand, if the solidified pigment-polymer based inks can be easily redissolved or redispersed in the bulk ink, the process of ink priming or flushing can restore clogged nozzles, allowing for reliable jetting.

[0005] US Patent No. 8,636,839 discloses an inkjet ink capable of realizing high scratch resistance and marker resistance of an image, as well as excellent ink ejection stability. This ink contains a polyurethane polymer having an acid value in the range of 20 mgKOH / g to 100 mgKOH / g, and includes units derived from a polyisocyanate, a polyol, a compound having a carboxy group, and a compound having a sulfo group. This document does not teach the combination of the polyurethane polymer with a specific water-soluble organic solvent.

[0006] There is a need for inkjet inks that can provide faster drying and image durability on low-absorbency and non-absorbency substrates while having good redispersion properties for reliable jetting performance. The present disclosure meets this need by providing ink compositions having a combination of a specific polyurethane binder and a solvent having a boiling point of 230° C. or less at ambient atmospheric pressure. Summary of the Invention [Means for solving the problem]

[0007] One embodiment provides an aqueous inkjet ink containing an aqueous vehicle, a pigment, and a polyurethane binder; the pigment is stabilized by a polymeric dispersant selected from the group consisting of polyurethane polymers, acrylic polymers, hydrolyzed styrene maleic anhydride copolymers, and mixtures thereof; the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH number of 28 to 800, a second polydiol having carboxyl groups neutralized with a tertiary amine, a third polydiol or diamine having sulfonic acid groups neutralized with an alkali, and at least one triol and / or one polyamine, or mixtures thereof; and the aqueous vehicle comprises one or more water-soluble organic solvents having a boiling point below 230° C. at ambient atmospheric pressure.

[0008] Another embodiment provides that the polymeric dispersant is a polyurethane polymer.

[0009] Another embodiment provides that the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH number of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one triol.

[0010] Another embodiment provides that the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH number of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one polyamine.

[0011] Another embodiment provides that the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH number of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a diamine having sulfonic acid groups neutralized with an alkali, and at least one triol and one polyamine.

[0012] Another embodiment provides that the polymeric dispersant is an acrylic polymer.

[0013] Yet another embodiment provides that the polymeric dispersant is a hydrolyzed styrene maleic anhydride (SMA) copolymer.

[0014] These and other features and advantages of the present embodiments will be more readily understood by those of ordinary skill in the art upon reading the following detailed description. Certain features of the disclosed embodiments that are, for clarity, described above and below as separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosed embodiments that are described in the context of a single embodiment may also be provided separately or in any subcombination. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Unless otherwise stated or defined, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0016] Unless otherwise stated, all percentages, parts, ratios, etc. are by weight.

[0017] When an amount, concentration, or other value or parameter is given as a range, preferred range, or list of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed from any pairing of any upper range limit or preferred value with any lower range limit or preferred value, whether or not the ranges are separately disclosed. When a range of numerical values ​​is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range.

[0018] When the term "about" is used to describe a value or an end point of a range, the disclosure should be understood to include the specific value or end point referred to.

[0019] As used herein, the term "dispersion" means a two-phase system in which one phase consists of fine particles (often in the colloidal size range) distributed throughout a bulk material, the particles being the dispersed or internal phase and the bulk material being the continuous or external phase.

[0020] As used herein, the term "dispersant" refers to a surfactant added to a suspension medium to promote uniform and maximum separation of very fine solid particles, often of colloidal size. In the case of pigments, the dispersant is most often a polymeric dispersant, and the dispersant and pigment are usually combined using a dispersing device.

[0021] As used herein, the term "aqueous vehicle" refers to water or a mixture of water and at least one water-soluble or partially water-soluble (ie, methyl ethyl ketone) organic solvent (co-solvent).

[0022] As used herein, the term "substantially" means to a great extent, almost entirely.

[0023] As used herein, the term "dynes / cm" refers to dynes per centimeter, a surface tension unit.

[0024] As used herein, the term "cP" means centipoise, a unit of viscosity.

[0025] Except only as expressly stated, the materials, methods, and examples herein are illustrative only and not intended to be limiting.

[0026] Additionally, singular references may include plurals (e.g., "a" and "an" may refer to one or to more than one) unless the context clearly indicates otherwise.

[0027] Ink set The term "ink set" refers to all the individual inks or other fluids that an inkjet printer has in stock for jetting. A white ink used to print an image after printing colored inks or before printing colored inks is considered part of the ink set.

[0028] In one preferred embodiment, the ink set comprises at least two different color inkjet inks, at least one of which is a white pigment-based inkjet ink as described above.

[0029] In another preferred embodiment, the ink set comprises at least four different colour inkjet inks, at least one being a cyan inkjet ink, at least one being a magenta inkjet ink, at least one being a yellow inkjet ink and at least one being a white inkjet ink.

[0030] In addition to the color inkjet inks just described, it is also preferred to include a black inkjet ink in the ink set.

[0031] In addition to the CMYKW inks listed above, the ink set may contain additional inks of different colors as well as different strength versions of the CMYKW and other inks.

[0032] For example, an ink set of the present invention may include a full strength version and a "light" version of one or more of the inks in the ink set.

[0033] Further colors of the inkjet ink set may include, for example, orange, violet, green, red and / or blue.

[0034] The preferred inks of the ink set are pigment-based inks.

[0035] Pigments The colorants used to print color images can be dyes or pigments. Dyes include disperse dyes, reactive dyes, acid dyes, etc. As used herein, the term "pigment" refers to an insoluble colorant that requires being dispersed in a dispersant and processed under dispersing conditions in the presence of the dispersant. Pigment-based inks are preferred.

[0036] Suitable pigments for use are those generally well known in the art for aqueous inkjet inks. The selected pigment may be used in dry or wet form. For example, pigments are usually manufactured in aqueous media and the resulting pigment is obtained as a water-moistened presscake. In presscake form, the pigment does not agglomerate to the same extent that it does in dry form. Thus, pigments in the form of water-moistened presscake do not require as much mixing energy to deagglomerate in the premixing process as pigments in dry form. Representative commercially available dry pigments are listed in U.S. Pat. No. 5,085,698.

[0037] Some examples of pigments having colorant properties useful in inkjet inks include, but are not limited to, the following: cyan pigments Pigment Blue 15:3 and Pigment Blue 15:4, magenta pigments Pigment Red 122 and Pigment Red 202, yellow pigments Pigment Yellow 14, Pigment Yellow 74, Pigment Yellow 95, Pigment Yellow 110, Pigment Yellow 114, Pigment Yellow 128, and Pigment Yellow 155, Pigment Orange 5, Pigment Orange 34, Pigment Orange 43, Pigment Orange 62, Pigment Red 17, Pigment Red 49:2, Pigment Yellow 59:3, Pigment Yellow ... The pigments in the range of red pigments Pigment Red 112, Pigment Red 149, Pigment Red 177, Pigment Red 178, Pigment Red 188, Pigment Red 254, Pigment Red 184, Pigment Red 264 and Pigment Red PV 19, the green pigments Pigment Green 1, Pigment Green 2, Pigment Green 7 and Pigment Green 36, the blue pigments Pigment Blue 60, Pigment Violet 3, Pigment Violet 19, Pigment Violet 23, Pigment Violet 32, Pigment Violet 36 and Pigment Violet 38, and the black pigment Carbon Black. The pigment names and abbreviations used herein are the "CI" designation for pigments established by the Society of Dyers and Colourists, Bradford, Yorkshire, UK, and published in The Color Index, Third Edition, 1971.

[0038] Examples of white materials include, but are not limited to, white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide. In addition to such white inorganic pigments, white organic pigments such as white hollow resin particles and polymer particles can also be used. A preferred pigment for aqueous pigment-based white inks is titanium dioxide. Useful titanium dioxide (TiO2) pigments can be in rutile or anatase crystalline form. It is generally made by either the chloride process or the sulfate process. In the chloride process, TiCl4 is oxidized to TiO2 particles. In the sulfate process, sulfuric acid and titanium-containing ores are dissolved, and the resulting solution undergoes a series of steps to produce TiO2. Both the sulfate and chloride processes are described in detail in "The Pigment Handbook", Vol. 1, 2nd Ed., John Wiley & Sons, NY (1988), the relevant disclosures of which are incorporated herein by reference for all purposes as if fully set forth.

[0039] The titanium dioxide particles can have a variety of average particle sizes up to about 1 micron depending on the desired end use of the ink. For applications requiring high hiding or decorative printing applications, the titanium dioxide particles preferably have an average size of less than about 1 micron (1000 nanometers). Preferably, the particles have an average size of about 50 to about 950 nanometers, more preferably about 75 to about 750 nanometers, and even more preferably about 100 to about 500 nanometers. These titanium dioxide particles are commonly referred to as pigmentary TiO2.

[0040] For applications requiring a white color with some degree of transparency, "nano" titanium dioxide is preferred as a pigment. "Nano" titanium dioxide particles typically have an average size ranging from about 10 to about 200 nanometers, preferably from about 20 to about 150 nanometers, and more preferably from about 35 to about 75 nanometers. Inks containing nano titanium dioxide can improve saturation and transparency while still maintaining good resistance to fading from light and suitable hue angles. A commercially available example of uncoated nano-grade titanium dioxide is P-25 available from Degussa, Parsippany NJ.

[0041] The titanium dioxide pigment may be substantially pure titanium dioxide or may include other metal oxides such as silica, alumina and zirconia. The other metal oxides may be incorporated into the pigment particles, for example, by co-oxidizing or co-precipitating the titanium compound with other metal compounds. When co-oxidized or co-precipitated metals are present, they are preferably present in an amount of from about 0.1% to about 20% by weight, more preferably from about 0.5% to about 5% by weight, and even more preferably from about 0.5% to about 1.5% by weight, as metal oxides, based on the total weight of the titanium dioxide pigment.

[0042] Titanium dioxide pigments can also have one or more metal oxide surface coatings. These coatings can be applied using techniques known to those skilled in the art. Examples of metal oxide coatings include silica, alumina, alumina-silica, boria, and zirconia, among others. Such coatings can be optionally present in an amount of about 0.1% to about 10% by weight, preferably about 0.5% to about 3% by weight, based on the total weight of the titanium dioxide pigment. These coatings can provide improved properties, such as reducing the photoreactivity of titanium dioxide. Commercial examples of such coated titanium dioxide include R700 (alumina coated, available from Chemours, Wilmington Del.), RDI-S (alumina coated, available from Kemira Industrial Chemicals, Helsinki, Finland), R706 (available from Chemours, Wilmington Del.) and W-6042 (silica-alumina treated nano-grade titanium dioxide from Tayco Corporation, Osaka, Japan).

[0043] Titanium dioxide pigments may also have one or more organic surface coatings, such as, for example, carboxylic acids, silanes, siloxanes, and hydrocarbon waxes and their reaction products with the titanium dioxide surface. The amount of organic surface coating, if present, generally ranges from about 0.01% to about 6% by weight, preferably from about 0.1% to about 3% by weight, more preferably from about 0.5% to about 1.5% by weight, and even more preferably about 1% by weight, based on the total weight of the pigment.

[0044] Polymer Dispersants Traditionally, pigments are stabilized by dispersants, such as polymeric dispersants or surfactants, to produce a stable dispersion of the pigment in the vehicle. More recently, however, so-called "self-dispersing" or "self-dispersing" pigments (hereinafter "SDPs") have been developed. As the name suggests, SDPs are dispersible in water without dispersants.

[0045] Polymeric dispersants for non-self-dispersing pigments can be random or structured polymers. Typically, acrylic polymeric dispersants are copolymers of hydrophobic and hydrophilic monomers. Some examples of hydrophobic monomers used are methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, 2-phenylethyl methacrylate and the corresponding acrylates. Examples of hydrophilic monomers are, for example, methacrylic acid, acrylic acid, dimethylaminoethyl (meth)acrylate and their salts. Also, quaternary salts of dimethylaminoethyl (meth)acrylate can be used. "Random polymer" means a polymer in which the molecules of each monomer are randomly arranged in the polymer backbone. For references of suitable random polymeric dispersants, see U.S. Pat. No. 4,597,794. "Structured polymer" means a polymer with a block, branched, graft or star structure. Examples of structured polymers include AB or BAB block copolymers such as those disclosed in U.S. Pat. No. 5,085,698, ABC block copolymers such as those disclosed in EP 0556649, and graft polymers such as those disclosed in U.S. Pat. No. 5,231,131. Other polymeric dispersants that can be used are described, for example, in U.S. Pat. Nos. 6,117,921, 6,262,152, 6,306,994 and 6,433,117.

[0046] "Random polymers" also include polyurethanes. Particularly useful are the polyurethane dispersants disclosed in US Patent Publication No. 2012 / 0214939, which are crosslinked after dispersing the pigment to form the pigment dispersion, the relevant disclosure of which is incorporated by reference for all purposes as if fully set forth herein.

[0047] Another suitable type of polymeric dispersant is a styrene maleic anhydride (SMA) copolymer. A "styrene maleic anhydride copolymer" or "SMA copolymer" is a polymer formed from styrene, maleic anhydride monomer, and optionally one or more additional comonomers. The copolymer can have a molar ratio of styrene / maleic anhydride repeat units of 0.2 to 5, preferably 0.5 to 2. The dispersant is usually in the form of a hydrolyzed solution of the SMA copolymer. The hydrolyzed solution preferably comprises the SMA copolymer dissolved in an aqueous alkaline solution. The aqueous alkaline solution is useful for hydrolyzing the SMA copolymer because the SMA copolymer is poorly soluble in water. The hydroxyl ions of the alkaline solution hydrolyze or react with the carbonyl carbon on the anhydride ring, cleaving the carbon-oxygen single bond. The reaction opens the anhydride ring and forms a monoacid group. The aqueous alkaline solution used to dissolve the SMA copolymer is preferably prepared from ammonium hydroxide, sodium hydroxide, potassium hydroxide, or an organic amine. Hydrolyzed SMA copolymer solutions suitable for the present invention include those available from Polyscope Polymers under the tradename XIRAN® SL.

[0048] Colored Pigment Dispersions Colored pigment dispersions stabilized by added polymeric dispersants can be prepared by methods known in the art. It is generally desirable to have the stabilized pigment in a concentrated form. The stabilized pigment is prepared by first premixing the selected pigment with the polymeric dispersant in an aqueous carrier medium (such as water and optionally a water-miscible solvent) and then dispersing or deflocculating the pigment. The premixing step is generally carried out in an agitated mixing vessel, with high speed dispersers (HSDs) being particularly suitable for the mixing step. Cowels-type blades mounted on the HSDs, operating at 500 rpm to 4000 rpm, more typically 2000 rpm to 3500 rpm, provide optimal shear to achieve the desired mixing. Sufficient mixing is usually achieved after 15 to 120 minutes of mixing under the above conditions. The subsequent dispersion step can be accomplished in a two-roll mill, media mill, horizontal mini mill, ball mill, attritor, or by passing the mixture through multiple nozzles in a liquid jet interaction chamber at a liquid pressure of at least 5,000 psi to produce a uniform dispersion of pigment particles in an aqueous carrier medium (microfluidizer). Alternatively, the concentrate can be prepared by dry grinding the polymeric dispersant and pigment under pressure. The media for the media mill is selected from commonly available media such as zirconia, YTZ, and nylon. These various dispersion processes are well known in the art in a general sense, as exemplified in U.S. Pat. Nos. 5,022,592, 5,026,427, 5,310,778, 5,891,231, 5,976,232, and U.S. Patent Publication No. 20030089277. The disclosures of each of these publications are incorporated herein by reference for all purposes as if fully set forth. Preferably, by a two roll mill, a media mill and forcing the mixture through multiple nozzles in a liquid jet interaction chamber at a liquid pressure of at least 5,000 psi.

[0049] After the milling process is complete, the color pigment concentrate can be "let down" into an aqueous system. "Let down" refers to the dilution of the concentrate by mixing or dispersion, the intensity of the mixing / dispersion is usually determined by trial and error using traditional methodologies and often depends on the combination of polymeric dispersant, solvent and pigment.

[0050] The useful particle size range after dispersion is typically about 0.005 micrometers to about 15 micrometers. Typically, the pigment particle size should be in the range of about 0.005 micrometers to about 5 micrometers, especially about 0.005 micrometers to about 1 micrometer. The average particle size as measured by dynamic light scattering is less than about 500 nm, typically less than about 300 nm.

[0051] White pigment dispersion One or more dispersants described in the colored pigments are also used to stabilize the titanium dioxide. It is generally desirable to make the stabilized TiO2 pigment in the form of a concentrated slurry. The TiO2 slurry is generally carried out in a mixing vessel that is stirred, with a high speed disperser (HSD) being particularly suitable for the mixing step. A Cowels type blade mounted on the HSD, operating at 500 rpm to 4000 rpm, more typically 2000 rpm to 3500 rpm, provides optimal shear to achieve the desired mixing. Sufficient mixing is usually achieved after 15 to 600 minutes of mixing under the above conditions. The amount of titanium dioxide present in the slurry composition is preferably about 35% to about 80% by weight based on the total weight of the slurry, more preferably about 50% to about 75% by weight based on the total weight of the slurry. The titanium dioxide preferably has a 50% average particle size (hereinafter referred to as "D50") in the range of 50 to 500 nm, more preferably in the range of 150 to 350 nm. Titanium dioxide having a D50 within these ranges enables the printed film to exhibit sufficient opacity of the image, which allows for the formation of high quality images.

[0052] In the case of colored pigments, the ink may contain up to about 30% by weight of pigment, preferably about 0.1 to about 25% by weight, and more preferably about 0.25 to about 10% by weight, based on the total weight of the ink. When an inorganic pigment such as a TiO2 pigment is selected, the ink will tend to contain a higher weight percentage of pigment than a comparable ink using a colored pigment, possibly as much as about 75%, since inorganic pigments generally have a higher specific gravity than organic pigments.

[0053] Post-modification of polymeric dispersants after formation of pigment dispersion The polymeric dispersant that disperses the pigment may be crosslinked after the pigment dispersion is prepared to form a crosslinked pigment dispersion before it is included in the inkjet ink. The crosslinkable polymeric dispersant is a polymer substituted with a crosslinkable moiety selected from the group consisting of acetoacetoxy, acid, amine, epoxy, hydroxyl, blocked isocyanate, and mixtures thereof. The crosslinker is selected from the group consisting of acetoacetoxy, acid, amine, anhydride, epoxy, hydroxyl, isocyanate, blocked isocyanate, and mixtures thereof. In the crosslinking step, the crosslinking is performed by adding a crosslinker to the pigment dispersion after dispersing the pigment and heating the mixture at an elevated temperature for several hours. After the crosslinking step, excess polymer can be removed by a purification process such as ultrafiltration. Specific examples of crosslinking moiety / crosslinker pairs are hydroxyl / isocyanate and acid / epoxy.

[0054] Ink binder Binders are polymeric compounds or mixtures of polymeric compounds that are added to the ink formulation. Binders can impart properties to the final printed material, such as providing greater durability to the printed material. Typical polymers used as binders in inkjet inks include polyurethane dispersions and solutions, acrylic, styrene acrylic, styrene butadiene, styrene butadiene acrylonitrile, neoprene, ethylene acrylic acid, ethylene vinyl acetate emulsions, latex, and other polymers. Binders can be in solution or stabilized as emulsions by having ionic substituents such as carboxylic acids, sulfur-containing acids, amine groups, and other similar ionic groups. Typically, binders are non-reactive to colorants, unlike the aforementioned polymeric dispersants. Binders are typically added to the ink during the final formulation stage, not during the preparation of the pigment dispersion.

[0055] In the present disclosure, the ink binder is an aqueous polyurethane dispersion, more specifically, a branched polyurethane colloidal particle that is stabilized with carboxyl and sulfonic acid functional groups in both acid and neutralized ionic forms in an aqueous solution. Inkjet inks containing branched polyurethane polymers have been found to have excellent redispersibility in water upon drying while maintaining good water resistance performance of the printed image. The amount of polyurethane polymer typically ranges from about 0.05% to about 20% by weight based on the total weight of the ink. More typically, the amount ranges from about 1% to about 12% by weight based on the total weight of the ink.

[0056] The branched polyurethane colloid particles stabilized with carboxyl and sulfonic acid functional groups in both acid and neutralized ionic forms are derived from isocyanate, isocyanate-reactive compounds with carboxy and / or carboxylate (carboxy / carboxylate) substituents, isocyanate-reactive compounds with sulfonic acid and / or sulfonate (sulfonic acid / sulfonate) substituents, and isocyanate-reactive compounds without ionic or ionizable substituents. To introduce branching points for polymer chain growth, the isocyanate can be a mixture of diisocyanates and polyisocyanates with three or more isocyanate groups; the isocyanate-reactive compounds without ionic or ionizable substituents can be a mixture of compounds with two isocyanate-reactive groups and compounds with three or more isocyanate-reactive groups. In one embodiment, the polyurethane polymer is derived from a diisocyanate, a first polydiol having an OH number of 28 to 800, a second polydiol having carboxyl groups neutralized with a tertiary amine, a third polydiol or diamine having sulfonic acid groups neutralized with an alkali, or at least one triol or one polyamine, or mixtures thereof.

[0057] Suitable diisocyanates are those which contain either aromatic, cycloaliphatic, or aliphatic groups attached to the isocyanate group. Mixtures of these compounds may also be used. Examples of suitable diisocyanates include 1,6-hexamethylene diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate; 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate); bis-(4-isocyanatocyclohexyl)-methane; 1,3- and 1,4-bis-(isocyanatomethyl)-cyclohexane; 1-isocyanato-2-isocyanato-4-isocyanato-1,4-isocyanato-2,5-diisocyanato-1,6-diisocyanate; Examples of suitable diisocyanates include tetramethylcyclopentane, 2,4'-diisocyanato-dicyclohexylmethane, bis-(4-isocyanato-3-methyl-cyclohexyl)-methane, α,α,α',α'-tetramethyl-1,3- and / or 1,4-xylylene diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, and 2,4- and / or 2,6-hexahydrotoluylene diisocyanate. Among these, from the viewpoint of preventing yellowing, aliphatic diisocyanates, specifically isophorone diisocyanate and 1,6-hexamethylene diisocyanate, are preferably used.

[0058] To produce branched polyurethanes, additional isocyanates containing three or more isocyanates, or polymeric isocyanates may be used. Triisocyanates include 1,6-hexamethylene diisocyanate trimer and isophorone diisocyanate trimer. To avoid gelling of the polymer during the manufacturing stage, the number of moles of isocyanate from the polymeric isocyanate is typically less than 25%, preferably less than 20%, of the number of moles of diisocyanate.

[0059] Examples of second and third polydiols or diamines for use in the present invention include isocyanate-reactive compounds having ionic and / or ionizable substituents that constitute hydrophilic segments in polyurethane polymers that can stabilize polyurethane particles in the aqueous phase. These compounds usually contain one or two, more preferably two, isocyanate-reactive groups, such as hydroxy or amino groups, and at least one ionic and / or ionizable group that may be a carboxyl / carboxylate and / or sulfonic acid / sulfonate group. In the present disclosure, both the isocyanate-reactive compound having a carboxy / carboxylate group that is the second polydiol and the isocyanate-reactive compound having a sulfonic acid / ionic sulfonate group that is the third polydiol or diamine are used to prepare polyurethane polymers. The mole % of ionic and ionizable groups in polyurethane binders is measured by the acid number (AN). AN is expressed in milligrams of potassium hydroxide required to neutralize 1 gram (g) of polyurethane polymer, as known to those skilled in the art. To improve ink redispersibility and stabilize the polyurethane particles in water while maintaining water fastness after drying, the total AN from both carboxy / carboxylate and sulfonic acid / sulfonate groups ranges from 8 to 65, more preferably from 10 to 55, and most preferably from 15 to 50. The ratio of carboxy / carboxylate AN to sulfonic acid / sulfonate AN typically ranges from 6:1 to 1:1, more preferably from 5:1 to 2:1, and most preferably from 4:1 to 2.5:1.

[0060] Examples of second polydiols are hydroxycarboxylic acids corresponding to the formula (HO)xQ(COOH)y, where Q represents a linear or branched hydrocarbon radical containing 1 to 12 carbon atoms, x is 1 or 2 (preferably 2) and y is 1 to 3 (preferably 1 or 2). Particularly preferred acids are those of the above formula where x is 2 and y is 1. These dihydroxyalkanoic acids are described in U.S. Pat. No. 3,412,054, the disclosure of which is incorporated herein by reference for all purposes as if fully set forth. Particularly preferred dihydroxyalkanoic acids are α,α-dimethylolalkanoic acids, represented by the following structural formula:

[0061] [ka]

[0062] (wherein Q' is hydrogen or C1-C8 alkyl.) The most preferred compound is α,α-dimethylolpropionic acid, ie, the compound in the above formula where Q' is methyl.

[0063] Suitable third polydiols and diamines containing sulfonic acid / sulfuric acid groups are hydroxysulfonic acids or aminosulfonic acids / sulfonates having one or two isocyanate-reactive hydroxy or amino groups and at least one sulfonic acid / sulfonate group. Examples include, but are not limited to, 2-(bis(2-hydroxyethyl)amino)ethanesulfonic acid, sodium 2-[(2-aminoethyl)amino]ethanesulfonate, 2-(2-aminoethylamino)ethanesulfonic acid, 3-[(2-aminoethyl)amino]propanesulfonic acid, polypropylene glycol diamine sulfopropylated sodium salt, taurine, sodium 3-aminopropane-1-sulfonate, 6-amino-1-hexanesulfonic acid, and 2-(methylamino)ethanesulfonic acid.

[0064] To stabilize the polyurethane particles in the aqueous phase, neutralizing agents for the carboxy and sulfonic acid groups are required to form carboxylate and sulfonate ion groups. Examples of neutralizing agents for converting the acid groups to anionic salt groups include alkali metal cations (K + , Li + , Na + ), trialkyl-substituted tertiary amines such as triethylamine, tripropylamine, dimethylcyclohexylamine, dimethylethylamine, and 4-methylmorpholine oxide, substituted amines such as diethylethanolamine, diethanolmethylamine. The conversion may be carried out after polymer synthesis or before polymer synthesis at the monomer stage. The molar ratio of neutralizing agent to acid groups is preferably in the range of 50% to 100%, more preferably at least 60%.

[0065] Suitable first polydiols are compounds having two hydroxy groups, including low molecular weight monomers and polymeric diols having a molecular weight of about 100 to about 4000 or a hydroxyl value ranging from 28 to 800. Examples of low molecular weight diols include 1,3-propanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, hydroquinone bis(2-hydroxyethyl)ether, and bisphenol A. Examples of polymeric diols include polyesters, polyethers, polycarbonates, polyacetals, poly(meth)acrylates, polyamides, or mixed polymers, such as polyester-polycarbonates in which both ester and carbonate bonds are present in the same polymer, as well as polyether-polycarbonates in which both ether and carbonate bonds are present in the same polymer. Typical polymeric diols have a number average molecular weight ranging from about 250 to about 3000, preferably from about 600 to about 2000. Any combination of these diols can also be used.

[0066] A branched polyurethane structure is obtained by mixing a compound having trihydroxy (triol) or higher functional groups (polyol), commonly known in polyurethane chemistry, such as trimethylolpropane and polyether triols, e.g., Arcol® polyether triol, with a first polydiol compound. To avoid gelation during the polyurethane manufacturing process, the number of moles of hydroxy from the triol and polyol must be less than 30%, preferably less than 25%, and most preferably less than 20% of the number of moles of hydroxy from the diol compound.

[0067] Suitable compounds with amino groups are typically diamine or polyamine chain extenders. Common examples include 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis-(4-amino-cyclohexyl)-methane, bis-(4-amino-3-methylcyclohexyl)-methane, 1,6-diaminohexane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or mixtures thereof. The degree of branching of polyurethane can be adjusted by the amount of polyamine and the ratio of polyamine to diamine when using a mixture.

[0068] Branched polyurethane refers to polyurethanes with a non-linear chain structure with three or more polymer chains attached at one point. Suitable branched polyurethane particles stabilized by both carboxy / carboxylate and sulfonic acid / sulfonate groups are typically synthesized from isocyanates, isocyanate-reactive compounds with ionic / ionizable substituents, and isocyanate-reactive compounds without ionic / ionizable substituents, as described above. The means of achieving polyurethane branching usually depends on at least one of three compounds having three or more reactive sites. If only one or two reactive sites are available on each reactive compound, only linear polyurethanes are produced. Examples of branching techniques include, but are not limited to, the following: (a) the isocyanate has at least three isocyanate groups, such as polyisocyanate trimers including, for example, 1,6-hexamethylene diisocyanate trimer and isophorone diisocyanate trimer; (b) the isocyanate-reactive compound has at least three reactive groups, such as triols and polyamines. Examples of triols include trimethylolpropane and polyether triols, such as Arcol® polyether triol. Examples of polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and the like; (c) Any combination of the above methods (a) and (b).

[0069] The degree of branching of the polyurethane to achieve a balanced performance between the desired properties, especially the redispersibility and water resistance of the ink, can vary over a wide range. To avoid gelation or excessive branching in the process of polyurethane production, the number of moles of isocyanate from the polymeric isocyanate is typically less than 25%, preferably less than 20%, of the number of moles of diisocyanate. Also, the number of moles of hydroxy from the triol and polyol should be less than 30%, preferably less than 25%, and most preferably less than 20% of the number of moles of hydroxy from the diol compound.

[0070] Based on the teachings described herein, one of ordinary skill in the art can, by routine experimentation, determine the degree of branching required for a particular type of polyurethane to yield an effective inkjet ink.

[0071] Ink Vehicle The pigmented inks of the present disclosure include an ink vehicle, also known as an aqueous carrier medium, typically an aqueous ink vehicle.

[0072] An ink vehicle is a liquid carrier (or medium) for the aqueous dispersion and optional additives. The term "aqueous ink vehicle" refers to an ink vehicle consisting of water or a mixture of water and one or more organic, water-soluble vehicle components, commonly referred to as co-solvents or humectants. Selection of an appropriate mixture depends on the requirements of the specific application, such as the desired surface tension and viscosity, stability with the selected pigment dispersion and ink binder, drying time of the inkjet ink, and the type of medium on which the ink will be printed.

[0073] Examples of water-soluble organic solvents and humectants include alcohols, ketones, keto-alcohols, ethers and others such as thiodiglycol, sulfolane, 2-pyrrolidine, 1,3-dimethyl-2-imidazolidinone and caprolactam; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trimethylene glycol, butylene glycol and hexylene glycol; addition polymers of oxyethylene or oxypropylene such as polyethylene glycol and polypropylene glycol; triols such as glycerol and 1,2,6-hexanetriol; lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether; lower dialkyl ethers of polyhydric alcohols such as diethylene glycol dimethyl or diethyl ether; urea and substituted ureas.

[0074] In the present disclosure, the ink vehicle was made to dry quickly by including a solvent with a boiling point of 230° C. or less at ambient atmospheric pressure. One skilled in the art can make an appropriate selection based on the disclosure herein. Such solvents typically include, but are not limited to, alkanediol and glycol ether types. Typical alkanediol-based solvents with a boiling point of 230° C. or less include, but are not limited to, methylpentanediol, ethylene glycol, 1,2-hexanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 3-methoxy-3-methyl-1-butanol. Exemplary glycol ether solvents having a boiling point of 230° C. or less include, but are not limited to, propylene glycol methyl ether, dipropylene glycol dimethyl ether, propylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, dipropylene glycol n-propyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-propyl ether, tripropylene glycol n-butyl ether, propylene glycol methyl ether acetate, and dipropylene glycol methyl ether acetate.

[0075] The amount of glycol ether(s) and alkanediol(s) added typically ranges from 1% to 30% by weight, more typically from 2% to 20% by weight, based on the total weight of the ink.

[0076] The sum of all solvents excluding water, surfactants, biocides, and buffers is typically less than 45% by weight based on the total weight of the ink, more typically less than 35% by weight based on the total weight of the ink, and most typically less than 30% by weight based on the total weight of the ink.

[0077] Surfactants Surfactants are usually added to the ink to adjust the surface tension and wetting properties. Suitable surfactants include ethoxylated acetylenic diols (e.g., Surfynol® series available from Evonik), ethoxylated alkyl primary alcohols (e.g., Neodol® series available from Shell) and secondary alcohols (e.g., Tergitol® series available from Dow Chemical), sulfosuccinates (e.g., Aerosol® series available from Cytec), organosilicones (e.g., DYNOL™, TEGO® Wet series available from Evonik), and fluorosurfactants (e.g., CAPSTONE™ series available from Chemours). Surfactants are typically used in amounts up to about 3% by weight, more typically up to 2% by weight, based on the total weight of the ink.

[0078] Other components, additives, may be incorporated into the ink-jet ink to the extent that such other components do not interfere with the stability and jettability of the ink-jet ink, which can be readily determined by one of ordinary skill in the art through routine experimentation.

[0079] The inclusion of a sealing (or chelating) agent such as ethylenediaminetetraacetic acid, iminodiacetic acid, ethylenediamine-di(o-hydroxyphenylacetic acid), nitrilotriacetic acid, dihydroxyethylglycine, trans-1,2-cyclohexanediaminetetraacetic acid, diethylenetriamine-N,N,N',N'',N''-pentaacetic acid and glycoletherdiamine-N,N,N',N'-tetraacetic acid and salts thereof may be beneficial, for example, to remove the deleterious effects of heavy metal impurities. Biocides may be used to inhibit the growth of microorganisms.

[0080] Ink characteristics Jet velocity, separation length of droplets, droplet size, and stream stability are highly influenced by the surface tension and viscosity of the ink. Typically, pigmented inkjet inks have a surface tension ranging from about 20 dynes / cm to about 45 dynes / cm at 25° C. Viscosity can be as high as 30 cP at 25° C., but is typically much lower, more typically less than 10 cP at 25° C. The ink has physical properties that are compatible with a wide range of ejection conditions, i.e., driving frequencies of piezo elements or ejection conditions of thermal heads in drop-on-demand or continuous devices, and nozzle shapes and sizes. The ink must have excellent storage stability over time so as not to clog to any significant extent in the inkjet device. Additionally, the ink must not corrode parts of the inkjet printing device and must be essentially odorless and non-toxic. The preferred pH of the ink ranges from about 6.5 to about 8.5.

[0081] Base material The ink of the present disclosure can be printed on any substrate without limitation. The ink of the present disclosure is most advantageous for printing on low-absorbency and non-absorbency media. Low-absorbency media typically include coated paper, coated corrugated board, coated carton, and folding carton, which have low surface porosity due to calendaring and / or application of one or more layers of hydrophobic coating layers. Non-absorbency substrates typically refer to plastic substrates such as acrylic, polyvinyl chloride, polycarbonate, polyethylene terephthalate, and polyolefin panels or films with various thicknesses and flexibilities. All substrates may be subjected to common surface treatments such as primer treatment and corona treatment before printing to improve the fixation and adhesion performance of the ink.

[0082] printing The method relates to digitally printing substrates that have low or no ink absorption. Typically, it comprises the following steps: (1) providing an inkjet printer responsive to digital data signals; (2) loading the substrate to be printed into the printer; (3) loading the inks or ink-jet ink sets described above into the printer in any order in response to digital data signals; and (4) printing, in response to digital data signals, onto a substrate using the white inkjet ink followed by an inkjet ink or inkjet ink set.

[0083] White ink can be printed first as a background image followed by the colored inks, or the colored inks can be printed first and then covered with white ink for reverse printing. Drying between the colored inks or between the white and colored inks is optional.

[0084] Printing can be performed with any inkjet printer equipped to handle and print low-absorbency and non-absorbency substrates. Films printed with pigmented inks are dried at elevated temperatures after printing. Drying temperatures range depending on the printer and dryer design and line speed, but should not be too high so as to damage the integrity of the printed film. Typically drying temperatures are below 120°C, preferably below 100°C, more preferably below 95°C. EXAMPLES

[0085] The invention is further illustrated, but not limited, by the following examples in which parts and percentages are by weight unless otherwise noted.

[0086] Ingredients and Abbreviations DMPA = Dimethylolpropionic acid EDA = ethylenediamine IPDI = Isophorone diisocyanate TEA = triethylamine DETA = diethylenetriamine MEK = methyl ethyl ketone TMP = Trimethylolpropane DMEA = Dimethylethanolamine CHDM = 1,4-cyclohexanedimethanol DBTL = dibutyltin dilaurate

[0087] Unless otherwise stated, the above mentioned chemicals were obtained from Aldrich (Milwaukee, WI) or other similar research chemical suppliers. Terathane® T650 - a polyether polyol from Invista, Wilmington, Del. Vestamin® A95 - a 50% solids solution of sodium 2-[(2-aminoethyl)amino]ethanesulfonate in water from Evonik, Essen, Germany Eternacoll® UC-100 and UH-200 - polycarbonate polyols from UBE industries (Tokyo, Japan) Surfynol® 440 and 420 - non-ionic surfactants from Evonik, Essen, Germany TEGO™ Wet 280 - a silicone surfactant from Evonik, Essen, Germany

[0088] Cyan Pigment Dispersion A cyan dispersion was prepared using the procedure disclosed in U.S. Patent Application Publication No. 2012 / 0214939, the disclosure of which is incorporated by reference for all purposes as if fully set forth. Cyan TRB2 pigment was used and the dispersant was crosslinked after dispersing the pigment.

[0089] Ink Polyurethane Binder Comp.PU-1 To a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, stirrer, and nitrogen gas line was added 15.8 g CHDM, 104.7 g Terathane T650, 4.0 g TMP, and 118 g acetone. The contents were heated to 40° C. and mixed well. 120 g IPDI was then added to the flask via the addition funnel over 5 minutes at 40° C., and the remaining IPDI was rinsed into the flask from the addition funnel with 2 g acetone.

[0090] The flask temperature was increased to 50°C and held for 240 minutes, then 15.8g DMPA was added to the flask via the addition funnel, followed by 11g TEA, which was then rinsed with 2g acetone. The flask temperature was then increased again to 50°C and held at 50°C until the NCO% was 2.0% or less.

[0091] At a temperature of 50° C., 570 g of deionized (DI) water was added over 10 minutes, followed by 38 g of an aqueous solution of EDA (as a 10% solution in water) over 5 minutes via an addition funnel. The mixture was held at 50° C. for 1 hour and then cooled to room temperature.

[0092] Acetone (about 122.0 g) was removed under vacuum to give a final dispersion of polyurethane at about 30.0% solids by weight.

[0093] Comp.PU-2 To a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, stirrer, and nitrogen gas line was added 824 g of Eternacoll UC-100 and 835 g of acetone. The contents were heated to 40° C. and mixed well. 202 g of IPDI was then added to the flask via the addition funnel over a period of 5 minutes at 40° C., and the remaining IPDI was rinsed from the addition funnel into the flask with 10 g of acetone.

[0094] The flask temperature was increased to 50°C and held for 120 minutes, then 104g of DMPA was added to the flask via the addition funnel, followed by 70g of TEA, which was then rinsed with 10g of acetone. The flask temperature was then increased again to 50°C and held at 50°C until the NCO% was 1.5% or less.

[0095] At a temperature of 50° C., 2750 g of deionized (DI) water was added over 10 minutes, followed by 35.5 g of an aqueous solution of EDA (as a 6.25% solution in water) over 5 minutes via an addition funnel. The mixture was held at 50° C. for 1 hour and then cooled to room temperature.

[0096] Acetone (about 855.0 g) was removed under vacuum to give a final dispersion of polyurethane at about 30.0% solids by weight.

[0097] Comp.PU-3 To a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, stirrer, and nitrogen gas line was added 824 g of Eternacoll UC-100 and 835 g of acetone. The contents were heated to 40° C. and mixed well. 202 g of IPDI was then added to the flask via the addition funnel over a period of 5 minutes at 40° C., and the remaining IPDI was rinsed from the addition funnel into the flask with 10 g of acetone.

[0098] The flask temperature was increased to 50°C and held for 120 minutes, then 104g of DMPA was added to the flask via the addition funnel, followed by 70g of TEA, which was then rinsed with 10g of acetone. The flask temperature was then increased again to 50°C and held at 50°C until the NCO% was 1.5% or less.

[0099] At a temperature of 50° C., 2750 g of deionized (DI) water was added over 10 minutes, followed by 35.5 g of an aqueous solution of EDA (as a 6.25% solution in water) over 5 minutes via an addition funnel. The mixture was held at 50° C. for 1 hour and then cooled to room temperature.

[0100] Acetone (about 855.0 g) was removed under vacuum to give a final dispersion of polyurethane at about 30.0% solids by weight.

[0101] PU-1 of the present invention To a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, stirrer, and nitrogen gas line was added 31 g CHDM, 204 g Terathane T650, 8 g TMP, 10.5 g TEA, and 225 g acetone. The contents were heated to 40° C. and mixed well. 234 g IPDI was then added to the flask via the addition funnel over 5 minutes at 40° C., and the remaining IPDI was rinsed into the flask from the addition funnel with 10 g acetone.

[0102] The flask temperature was increased to 50°C and held for 300 minutes, then 31 g of DMPA was added to the flask via the addition funnel, followed by 10.5 g of TEA, which was then rinsed with 10 g of acetone. The flask temperature was then increased again to 50°C and held at 50°C until the NCO% was 2.2% or less.

[0103] In a separate container, an aqueous taurine solution was prepared by dissolving 25.5 g of taurine in 25.4 g of 45 wt % KOH solution and 51 g of deionized (DI) water.

[0104] At a temperature of 50° C., 1084 g of deionized (DI) water was added over 10 minutes, followed by 102 g of the aqueous taurine solution prepared above via an addition funnel over 5 minutes. The mixture was held at 50° C. for 1 hour and then cooled to room temperature.

[0105] Acetone (about 245.0 g) was removed under vacuum to give a final dispersion of polyurethane at about 30.0% solids by weight.

[0106] PU-2 of the present invention To a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, stirrer, and nitrogen gas line was added 31 g CHDM, 204 g Terathane T650, 8 g TMP, 10.5 g TEA, and 225 g acetone. The contents were heated to 40° C. and mixed well. 234 g IPDI was then added to the flask via the addition funnel over 5 minutes at 40° C., and the remaining IPDI was rinsed into the flask from the addition funnel with 10 g acetone.

[0107] The flask temperature was increased to 50°C and held for 300 minutes, then 31 g of DMPA was added to the flask via the addition funnel, followed by 10.5 g of TEA, which was then rinsed with 10 g of acetone. The flask temperature was then increased again to 50°C and held at 50°C until the NCO% was 2.2% or less.

[0108] At a temperature of 50° C., 1084 g of deionized (DI) water was added over 10 minutes, followed by 43 g of the Vestamin A95 solution prepared above via an addition funnel over 5 minutes. The mixture was held at 50° C. for 1 hour and then cooled to room temperature.

[0109] Acetone (about 245.0 g) was removed under vacuum to give a final dispersion of polyurethane at about 30.0% solids by weight.

[0110] PU-3 of the present invention (D201308-322) To a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, stirrer, and nitrogen gas line was added 280 g Eternacoll UC-100, 4 g TMP, 10 g TEA, and 287 g acetone. The contents were heated to 40° C. and mixed well. 162 g IPDI was then added to the flask via the addition funnel over 5 minutes at 40° C., and the remaining IPDI was rinsed into the flask from the addition funnel with 10 g acetone.

[0111] The flask temperature was increased to 50°C and held for 120 minutes, then 35g of DMPA was added to the flask via the addition funnel, followed by 13.5g of TEA, which was then rinsed with 10g of acetone. The flask temperature was then increased again to 50°C and held at 50°C until the NCO% was 1.4% or less.

[0112] At a temperature of 50° C., 28 g of the Vestamin A95 solution was added via an addition funnel over 5 minutes, followed by 950 g of deionized (DI) water over 10 minutes, followed by 28 g of an aqueous DETA solution (as a 10% solution in water) over 5 minutes via an addition funnel. The mixture was held at 50° C. for 1 hour and then cooled to room temperature.

[0113] Acetone (about 307.0 g) was removed under vacuum to give a final dispersion of polyurethane at about 35.0% solids by weight.

[0114] All other inventive PUD-type polymers, PU-4 through PU-9, were made using a process similar to the preparation of inventive PU-3, with the ingredients listed in Table 1 below.

[0115] [Table 1]

[0116] Ink Formulation The inks used in the examples were made according to standard procedures in the inkjet technology field. Component amounts are in weight % of the final ink. Polymer binders and colorants are shown on a solids basis. As an example of ink preparation, an ink vehicle was prepared and added to the aqueous ink binder with stirring. After stirring until a homogeneous mixture was obtained, the solution was added to the pigment dispersion and mixed again until homogeneous. Three cyan ink formulations A, B, and C were prepared using different combinations of solvents and surfactants. Various comparative and final inks using the PU of the present invention were made from these three ink formulations. The compositions of all inks tested are shown in Tables 2-6 below.

[0117] [Table 2]

[0118] [Table 3]

[0119] [Table 4]

[0120] [Table 5]

[0121] [Table 6]

[0122] Ink redispersibility test Ink redispersibility was evaluated by first placing a drop of ink with a manual single channel pipette onto a glass slide backed Bytac VF-81 film. The Bytac VF-81 film is manufactured by Saint-Gobair Performance Plastics, Poestenkill, NY, and is a vinyl film backed FEP film with a pressure sensitive adhesive on the back. The non-wetting film of Bytac was chosen so that the ink drop size and surface area would be constant for all tests. In this test, the ink drop weight was kept at approximately 40 mg and the drop size was approximately 5 mm in diameter. The ink drop was dried at 50°C for 20 minutes, after which the glass slide with the dried ink was immediately immersed in 50 ml of deionized water. After 30 minutes of immersion, the ink redispersibility rating was determined as follows: 1. The ink is completely dissolved and there are no or very few particles 2. There are some particles or some small solid masses present 3. There are a significant number of solid masses 4. Ink dries as an undissolved mass

[0123] Dry and water resistance test Mylar MLBT, a transparent PET film from DuPont Taijing Film, was coated with Ink Formulations A Series and Ink Formulations B Series from Tables 4 and 5 using a Gardco film applicator rod with wire size 5.0 (Paul N. Gardner Inc., Florida, USA) to form coatings with dry thicknesses that varied from 10 to 15 microns depending on solids content and viscosity. All the above ink coatings were dried in a 65°C convection oven for 3 minutes. Ink Formulations C Series from Table 6 were applied to Styrex® polystyrene panel substrates using the same process except the ink was subsequently dried in a 90°C convection oven for 2 minutes.

[0124] The degree of drying of the ink formulations A series was evaluated by smearing the ink with a cotton swab. If the ink smeared more than 50% without resistance, it was rated as poor. If the ink smeared less than about 30%, it was rated as good.

[0125] The waterfastness of Ink Formulation B and Ink Formulation C series was evaluated by smearing the ink with light pressure using a water-soaked paper towel. The waterfastness rating was determined using the following criteria: 1. The ink was completely intact 2. Although there was a slight discoloration, the ink was still intact. 3. The ink has rubbed off and the color has transferred. 4. The ink has rubbed off and there is a large amount of color transfer, and the base material is visible. 5. The ink has been completely removed

[0126] The ink redispersibility and drying degree of the inks of the ink formulation A series and the ink formulation B series are summarized in Table 7 below. Although Comp.InkA-1 and Comp.Ink-2, which contain glycerol as the ink solvent, had better ink redispersibility compared to InkB-1 and InkB-2, both inks had poor drying properties. Even after one week of storage at room temperature, the inks were still not dry. Ink B-1 and Ink B-2, which do not contain glycerol, had excellent drying properties immediately after oven drying.

[0127] [Table 7]

[0128] The ink redispersibility and water resistance of the ink formulation B series are summarized below in Table 8. Comp.Ink B-1 and Comp.Ink B-2, which contain Comp.PU-1 and Comp.PU-2, which do not have sulfonate functionality, had poor ink redispersibility, while Inks B-3, B-4, B-5, B-6, and B-7 of the present invention all had improved redispersibility and excellent water resistance.

[0129] [Table 8]

[0130] The redispersibility and water resistance of the C series of ink formulations are summarized below in Table 9. Comp.InkC-1, which contains unbranched Comp.PU-3 as the binder, resulted in good ink redispersibility but poor water resistance.

[0131] [Table 9]

Claims

1. 1. An aqueous inkjet ink comprising an aqueous vehicle, a pigment, and a polyurethane binder; the pigment is stabilized by a polymeric dispersant selected from the group consisting of polyurethane polymers, acrylic polymers, hydrolyzed styrene maleic anhydride copolymers, and mixtures thereof; The polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH number of 28 to 800, a second polydiol having carboxyl groups neutralized with a tertiary amine, a third polydiol or diamine having sulfonic acid groups neutralized with an alkali, and at least one triol and / or one polyamine, or a mixture thereof; An aqueous inkjet ink, wherein the aqueous vehicle comprises one or more water-soluble organic solvents having a boiling point below 230° C. at ambient atmospheric pressure.

2. The aqueous inkjet ink of claim 1 , wherein the polymeric dispersant is a polyurethane polymer.

3. 3. The aqueous ink-jet ink according to claim 2, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one triol.

4. 3. The aqueous ink-jet ink according to claim 2, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one polyamine.

5. 3. The aqueous ink-jet ink according to claim 2, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a diamine having sulfonic acid groups neutralized with an alkali, and at least one triol and one polyamine.

6. The aqueous inkjet ink of claim 1 , wherein the polymeric dispersant is an acrylic polymer.

7. 7. The aqueous ink-jet ink according to claim 6, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one triol.

8. 7. The aqueous ink-jet ink according to claim 6, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one polyamine.

9. 7. The aqueous ink-jet ink according to claim 6, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a diamine having sulfonic acid groups neutralized with an alkali, and at least one triol and one polyamine.

10. The aqueous ink-jet ink of claim 1 , wherein the polymeric dispersant is a hydrolyzed styrene maleic anhydride copolymer.

11. 11. The aqueous ink-jet ink according to claim 10, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one triol.

12. 11. The aqueous ink-jet ink according to claim 10, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a third polydiol having sulfonic acid groups neutralized with an alkali, and at least one polyamine.

13. 11. The aqueous ink-jet ink according to claim 10, wherein the polyurethane binder comprises units derived from a diisocyanate, a first polydiol having an OH value of 28 to 800, a second polydiol having COOH groups neutralized with a tertiary amine, a diamine having sulfonic acid groups neutralized with an alkali, and at least one triol and one polyamine.