Ink fluid set for printing on offset media

Abstract

To provide more stable and reliable pre-treatment compositions producing higher quality print images on print media surfaces.SOLUTION: An inkjet printing fluid set comprises: a) an aqueous pretreatment composition comprising an ink-aggregating agent, an ink-nonaggregating polymer and a surfactant, where the ink-aggregating agent is one or more components selected from cationic polymers, multivalent metal salts and mixtures thereof; and b) an aqueous inkjet ink comprising a cross-linked polymeric pigment dispersion and an aqueous vehicle, where the cross-linked pigment dispersion is made by dispersing the pigment with a polymeric dispersant and then reacting the dispersion with a cross-linking agent. The ink-nonaggregating polymer is a urethane and cellulosic structure based non-ionic water-soluble polymer, or non-ionic waterborne polyurethane dispersion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This application claims priority under 35 U.S.C. § 119 from U.S. Provisional Patent Application No. 62 / 599994, filed December 18, 2017.

[0002] The present disclosure relates to a fluid ink set containing an aqueous pretreatment composition and an aqueous inkjet ink, the fluid ink set being particularly suitable for printing on offset coated media. [Background technology]

[0003] Inkjet printing is a non-impact 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 typically use an ink set containing cyan, magenta, and yellow inks (CMY). Typically, the ink set also includes a black ink (CMYK), with black ink being the most common ink. However, due to the media's limited ink absorption and surface hydrophobicity, aqueous inkjet inks have traditionally not been suitable for printing on offset-coated media. The hydrophobic coating on offset-coated media is typically a mixture of polymer resins and additives such as kaolinite, calcium carbonate, bentonite, and talc. The coating formulation imparts specific qualities to the paper, such as weight, surface gloss, smoothness, and low surface porosity. The resulting low porosity means fewer access channels for the ink vehicle, which results in a greater reliance on ink drying by evaporation. Furthermore, the hydrophobic nature of the coating layer reduces the wetting and spreading of aqueous inks during printing, which can subsequently result in ink droplets puddling on the media surface. When printing aqueous inks directly onto offset media, the combined effects of less dot spreading and slower drying result in more image defects. The most obvious defects include uneven colorant deposition on these media. These uneven colorant deposition defects are variously known as mottling, coalescence, framing, or square-effect edges. Another equally unacceptable effect of the hydrophobicity and low porosity of offset media is increased ink drying time, which increases the time for adjacent colors to mix, resulting in intercolor bleed, where one color diffuses into its neighbor.

[0004] One common solution to overcome these problems is to treat offset-coated media with a primer or pretreatment liquid before printing. Another solution is to incorporate a primer into the paper manufacturing process to make the paper more compatible with inkjet inks. Most primers are designed to instantly precipitate or coalesce ink droplets through electrostatic interactions, fixing them in place and preventing multiple ink droplets from coalescing. However, this instantaneous fixing of ink droplets usually reduces dot gain during printing. As a result, if the ink is printed at low resolution or if the ink droplets are misaligned, the printed image tends to exhibit white areas or white streaks due to insufficient droplet spreading. Summary of the Invention [Problem to be solved by the invention]

[0005] There remains a need for more stable and reliable pretreatment compositions that produce higher quality printed images on print media surfaces. The present disclosure meets this need by providing ink fluid sets having pretreatment compositions that include an ink flocculant and an ink de-flocculating polymer. [Means for solving the problem]

[0006] One embodiment provides an inkjet printing fluid set comprising: (a) an aqueous pretreatment composition comprising an ink flocculating agent, an ink anti-flocculating polymer, and a surfactant, wherein the ink flocculating agent is one or more components selected from a cationic polymer, a polyvalent metal salt, an organic acid, and a mixture thereof; and (b) an aqueous inkjet ink comprising a crosslinked polymer pigment dispersion and an aqueous vehicle, wherein the crosslinked pigment dispersion is produced by dispersing the pigment with a polymer dispersant and then reacting the crosslinked pigment dispersion with a crosslinker.

[0007] One embodiment provides that the surfactant is selected from the group consisting of cationic, nonionic and amphoteric surfactants.

[0008] One embodiment provides that the ink de-agglomerating polymer is an aqueous polyurethane dispersion.

[0009] One embodiment provides that the cationic polymer is derived from the polymerization of diallyldialkylammonium monomers.

[0010] One embodiment provides that the polyvalent metal salt is a salt of a metal selected from the group consisting of Ca, Ba, Ru, Co, Zn and Ga, and mixtures thereof.

[0011] One embodiment provides that the polyvalent metal salt is a Ca salt.

[0012] One embodiment provides that the fluid set is used for printing onto a substrate that is offset coated media.

[0013] One embodiment provides that the fluid set is used for printing on a substrate that is offset coated cardboard.

[0014] One embodiment provides that the cationic polymer is a polyalkylamine polymer.

[0015] One embodiment provides that the cationic polymers are epichlorohydrin-amine polymers and copolymers derived from epichlorohydrin.

[0016] Yet another embodiment provides that the cationic polymer is derived from the polymerization of quaternized vinylpyridine.

[0017] These and other features and advantages of the present embodiments will be 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 INVENTION

[0018] 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.

[0019] Unless otherwise specified, all percentages, parts, ratios, etc. are by weight.

[0020] When an amount, concentration, or other value or parameter is given as a range, preferred range, or list of upper 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 specified, the range is intended to include the endpoints thereof, and all integers and fractions within the range.

[0021] When the term "about" is used to describe a value or an endpoint of a range, the disclosure should be understood to include the specific value or endpoint referred to.

[0022] As used herein, the term "dispersion" refers to 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 inner phase, and the bulk material being the continuous or outer phase.

[0023] 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 dispersing equipment.

[0024] As used herein, the term "aqueous vehicle" means water or a mixture of water and at least one water-soluble or partially water-soluble (i.e., methyl ethyl ketone) organic solvent (co-solvent).

[0025] As used herein, the term "substantially" means to a great extent, almost entirely.

[0026] As used herein, the term "dynes / cm" means dynes per centimeter, a surface tension unit.

[0027] As used herein, the term "cP" refers to the viscosity unit centipoise.

[0028] Except only as expressly stated, the materials, methods, and examples herein are illustrative only and not intended to be limiting.

[0029] Additionally, unless the context clearly indicates otherwise, references in the singular may also include the plural (for example, "a" and "an" may refer to one or to more than one).

[0030] Ink anti-agglomeration polymer The pretreatment solution contains a compatible polymeric binder that does not "crack out" or "disintegrate" with the fixer and does not agglomerate with the ink. Such polymeric binders are called "ink-nonagglomerating polymers." Some suitable compatible ink-nonagglomerating polymeric binders include, for example, nonionic water-soluble polymers based on acrylic, urethane, polyester, polyamide, polyvinyl, polyether, polyamine, and cellulose structures or dispersion polymers such as acrylic latexes, polyurethane dispersions, vinyl acetate copolymer latexes, polyester and polyamide dispersions. These polymers can be produced by any known process, including, but not limited to, free radical, group transfer, ionic, RAFT, condensation, and other types of polymerization.

[0031] Ink-non-agglomerating polymers can be formed by incorporating non-ionic stabilizers into the polymer, either chemically bonded or physically absorbed. Examples of non-ionic reactive components include ethylene oxide derivatives, acrylamide, hydroxyethyl-substituted monomers, vinylpyrrolidone, ethyleneimine, and the like. Incorporation can occur during the polymerization process or after the polymerization process to prepare the latex polymer. In the case of ethylene oxide non-ionic components, substitution is sufficient to impart non-ionic stability (-CH2-CHO-). n The nonionic latex polymer may take the form of incorporating a glycol having a unit. For example, a polyurethane may have an alkyl polyethylene glycol incorporated into the nonionic polyurethane. The nonionic component may be the major component in the nonionic latex polymer, as long as its properties meet the stability test described above.

[0032] Nonionic latex polymers can also have ionic components incorporated into the polymer. For example, polyurethane ionic components, such as acids, can be used in the polyurethane reaction; a specific example of an acid is dimethylolpropionic acid. For acylamide and hydroxyethyl-substituted nonionic latex polymers, the ion source can be from (meth)acrylic acid. There is a limit to the amount of ionic component in the nonionic latex polymer due to the possibility of complexation between the ionic component and the ink flocculant, which can lead to instability of the nonionic latex polymer / multivalent cationic solution. A balance of the nonionic and ionic components must result in a stable solution, as described above.

[0033] When present, the ink deagglomerating polymer is advantageously used at a level of at least about 0.3%, typically at least about 0.6%, based on the total weight of the ink. The upper limit is determined by the viscosity of the pretreatment liquid or other physical limitations. In more typical embodiments, no more than about 25%, and most typically no more than about 20%, of the ink deagglomerating polymer is present in the pretreatment composition, based on the total weight of the pretreatment liquid.

[0034] Ink flocculant The pretreatment solution contains an ink flocculating agent that "precipitates" or "disintegrates" with the colorant or other components in the ink. Some suitable ink flocculating agents include cationic polymers and copolymers, polyvalent metal salts, and organic acids.

[0035] Cationic polymers and copolymers in pretreatment compositions attract and anchor oppositely charged anionic pigment dispersions and anionic binder molecules to substrates. Cationic groups have a greater variety of molecular structures than any other group. Such cationic resins can incorporate charged groups either on the main polymer backbone or as pendant groups on the polymer chain, and typically contain quaternary ammonium groups, resulting in a formal positive charge regardless of pH level. Cationic polymers containing sulfonium or phosphonium groups have also been synthesized. For applications that achieve cationic properties in acidic media, weak electrolyte versions are used; these are based on polyamines containing primary, secondary, or tertiary amino groups or mixtures thereof. Preparation techniques often encompass polymerization by chain-growth and step-growth mechanisms in simple aqueous solutions and as water-in-oil emulsions, as well as modification of existing polymers.

[0036] Cationic polymers for use in the pretreatment coating include, but are not limited to, polymers and copolymers of diallyldialkylammonium monomers such as diallyldimethylammonium chloride (such as polydiallyldimethylammonium chloride (PDADMAC)); polymers and copolymers of cationic acrylates and acrylamides such as polyacryloxyethyldimethylammonium chloride or polyacrylamidoethyldimethylammonium chloride; polymers and copolymers of quaternized vinylpyridines such as polymethylvinylpyridine chloride; polymers and copolymers of polyalkylamines and quaternary ammonium; linear and branched polyethyleneimines; polyvinylamines; and epihalohydrin-amine polymers, polymers and copolymers derived from epichlorohydrin such as FLOQUAT® FL2650 from SNF Inc., France, and KYMENE® 557LX polymer from Ashland Inc., Wilmington, Del. Comonomers in such systems can be configured to modify the flexibility, hydrophobicity, or mechanical properties of the polymer molecule. Additionally, reactive and / or self-condensing monomers may be included to enhance adhesion to the substrate.

[0037] There are also naturally occurring polymers that have inherent cationic properties, or the polymers can be modified to yield cationic polyelectrolytes. The most prominent of these is chitosan. Other examples include cationic starch, cationic polymer-modified kraft lignin, and cationic grafted amylopectin, guar gum, and polysaccharides.

[0038] "Multivalent" refers to two or more oxidation states, and for the element "Z", typically Z 2+ , Z 3+ , Z 4+ For simplicity, multivalent cations are referred to herein as Z xThe multivalent cations are substantially soluble in the aqueous pretreatment solution and preferably exist (in solution) in a substantially ionized state so that they are free and in a form that can interact with the textile when the textile is exposed to the pretreatment solution.

[0039] Z x Examples of polyvalent cations include, but are not limited to, multivalent cations of the following elements: Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr, V, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Au, Zn, Al, Ga, In, Sb, Bi, Ge, Sn, and Pb. In another embodiment, the multivalent cation comprises at least one of Ca, Ba, Ru, Co, Zn, and Ga. In yet another embodiment, the multivalent cation comprises at least one of Ca, Ba, Ru, Co, Zn, and Ga. Preferably, the multivalent cation is Ca.

[0040] Z x can be incorporated into the pretreatment solution by adding it in the form of a salt or by adding it in the form of an alkali, which can be used as a base in adjusting the pH of the pretreatment solution.

[0041] The relevant anionic material can be selected from any common anionic material, particularly halides, nitrates, and sulfates. The form of the anion is selected so that the multivalent cations are soluble in the pretreatment aqueous solution. The multivalent cation salts can be used in their hydrated form. One or more multivalent cation salts can be used in the pretreatment solution.

[0042] For Ca, the preferred polyvalent cation salts are calcium chloride, calcium nitrate, calcium nitrate hydrate and mixtures thereof.

[0043] The organic acid used as the flocculating agent lowers the pH of the ink, coagulating the pigment dispersion and other ink components, thereby causing the ink droplets to precipitate. Specific examples of acids include polyacrylic acid, acetic acid, glycolic acid, malonic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidonecarboxylic acid, pyronecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid, nicotinic acid, and derivatives of these compounds. Polyacrylic acid and acetic acid are particularly preferred.

[0044] Pretreatment Composition The ink de-agglomerating polymer is combined with an ink flocculant to form a pretreatment solution. The ink de-agglomerating polymer / ink flocculant solution thus formed must be stable as a solution or stable emulsion to allow for processing of the coated medium. If the ink de-agglomerating polymer gels or its emulsion precipitates in the presence of an ink flocculant, such as a polyvalent cation salt solution, it cannot be used as a pretreatment additive. A screening test to determine whether an ink de-agglomerating polymer is stable in the presence of an ink flocculant is to mix 10% by weight of the polymer (dry basis) with 15% by weight of calcium nitrate tetrahydrate and observe whether the solution / emulsion is stable. Stability is observed at 10 minutes and 24 hours at ambient temperature (approximately 25°C). The ink de-agglomerating polymer components must provide a stable ink de-agglomerating polymer / polyvalent cation solution / emulsion mixture.

[0045] Some suitable compatible ink-deagglomerating polymeric binders include, for example, nonionic water-soluble polymers based on acrylic, urethane, polyester, polyamide, polyvinyl, polyether, polyamine, and cellulosic structures or dispersion polymers including acrylic latexes, polyurethane dispersions, vinyl acetate copolymer latexes, polyester, and polyamide dispersions. These polymers can be made by any known process, including, but not limited to, free radical, group transfer, ionic, RAFT, condensation, and other types of polymerization.

[0046] Ink-non-agglomerating polymers can be formed by incorporating non-ionic stabilizers into the polymer, either chemically bonded or physically absorbed. Examples of non-ionic reactive components include ethylene oxide derivatives, acrylamide, hydroxyethyl-substituted monomers, vinylpyrrolidone, ethyleneimine, and the like. Incorporation can occur during the polymerization process or after the polymerization process to prepare the latex polymer. In the case of ethylene oxide non-ionic components, substitution is sufficient to provide non-ionic stability (-CH2-CHO-). n The nonionic latex polymer may take the form of incorporating a glycol having a unit. For example, a polyurethane may have an alkyl polyethylene glycol incorporated into the nonionic polyurethane. The nonionic component may be the major component in the nonionic latex polymer, as long as its properties meet the stability test described above.

[0047] Nonionic latex polymers can also have ionic components incorporated into the polymer. For example, for polyurethanes, an ionic component such as an acid can be used in the polyurethane reaction; a specific example of an acid is dimethylolpropionic acid. For acylamide and hydroxyethyl-substituted nonionic latex polymers, the ion source can be from (meth)acrylic acid. There is a limit to the amount of ionic component in the nonionic latex polymer due to the possibility of complexation of the ionic component with the ink flocculant, which can lead to instability of the nonionic latex polymer / multivalent cation solution. A balance of the nonionic and ionic components must result in a stable solution, as described above.

[0048] When present, the ink deagglomerating polymer is advantageously used at a level of at least about 0.3%, typically at least about 0.6%, based on the total weight of the ink. The upper limit is determined by the viscosity of the pretreatment liquid or other physical limitations. In more typical embodiments, no more than about 25%, and most typically no more than about 20%, of the ink deagglomerating polymer is present in the pretreatment composition, based on the total weight of the pretreatment liquid.

[0049] Other optional components in the pretreatment solution can include, but are not limited to, humectants and biocides. Biocides prevent microbial decomposition. Their selection and use are widely known in the art. Suitable humectants are the same as those suitable for use in the color inkjet inks, which are described in more detail below.

[0050] The solution should contain sufficient ink aggregating agent content and other ingredients to achieve sufficient ink aggregating agent penetration and / or coating of the substrate. Typically, the pretreatment contains at least about 0.5 wt. % ink aggregating agent, with amounts up to the solubility limit of the particular ink aggregating agent being used being used. Preferably, the pretreatment contains about 1 wt. % to about 30 wt. % ink aggregating agent. The combined total weight of the ink de-agglomerating polymer and ink aggregating agent can be up to about 45 wt. %.

[0051] The pretreatment composition may further comprise a surfactant. Some suitable surfactants include those that are miscible with the amphoteric polymer, i.e., those that do not form precipitates or aggregates when mixed. Some useful surfactants include cationic, nonionic, and amphoteric surfactants. Some suitable cationic surfactants include, for example, quaternized ammonium or pyridinium surfactants, such as dodecyltrimethylammonium chloride, cetyltrimethylammonium bromide, and cetyltrimethylpyridinium chloride. Some suitable nonionic surfactants include ethoxylated acetylenic diols (e.g., Air Products' Surfynol® series), ethoxylated primary alcohols (e.g., Shell's Neodol® series) and secondary alcohols (e.g., Union Carbide's Tergitol® series), Pluronic® block copolymer surfactants, sulfosuccinates (e.g., Cytec's Aerosol® series), organosilicones (e.g., Witco's Silwet® series), and fluorosurfactants (e.g., DuPont's Zonyl® series). Amphoteric surfactants that are cationic within a specific pH range can also be used. In this case, the pH of the liquid composition must be adjusted below the isoelectric point of the surfactant. Some examples of useful zwitterionic surfactants include N,N-dimethyl-N-tetradecylamine oxide (NTAO), N,N-dimethyl-N-hexadecylamine oxide (NHAO), and related amine oxide compounds. Another example is N-dodecyl-N,N-dimethylglycine. Further examples include phosphates, phosphites, phosphonates, lecithin, and phosphonate esters (such as phosphomyelin). The surfactant can be used in an amount of typically about 0.1 to about 10%, more typically about 0.5 to about 5%, based on the total weight of the pretreatment solution.

[0052] Ink Water-Based Vehicle Selection of an appropriate aqueous vehicle mixture depends on the requirements of the particular application, such as the desired surface tension and viscosity, the selected colorant, the drying time of the ink, and the type of substrate onto which the ink will be printed. Representative examples of water-soluble organic solvents that can be utilized in the present disclosure are those disclosed in U.S. Pat. No. 5,085,698.

[0053] When a mixture of water and a water-soluble solvent is used, the aqueous vehicle typically comprises about 30% to about 95% water, with the remaining balance (i.e., about 70% to about 5%) being the water-soluble solvent. The compositions of the present disclosure may comprise about 60% to about 95% water, based on the total weight of the aqueous vehicle.

[0054] The amount of aqueous vehicle in the ink typically ranges from about 70% to about 99.8%, more typically from about 80% to about 99.8%, based on the total weight of the ink.

[0055] The surfactant may typically be used in an amount of about 0.01% to about 5%, particularly about 0.2% to about 2%, based on the total weight of the ink.

[0056] pigment As used herein, the term "pigment" refers to an insoluble colorant that must be dispersed by a dispersant and processed under dispersing conditions in the presence of the dispersant. Colorants also include dispersed dyes. The dispersion process results in a stable dispersed pigment.

[0057] The selected pigment can be used in dry or wet form. For example, pigments are typically manufactured in aqueous media, resulting in a water-wet presscake. In presscake form, the pigment does not agglomerate to the same extent as it does in dry form. Therefore, water-wet presscake pigments 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.

[0058] Some examples of pigments having color properties useful in inkjet inks include cyan pigments such as Pigment Blue 15:3 and Pigment Blue 15:4; magenta pigments such as Pigment Red 122 and Pigment Red 202; yellow pigments such as Pigment Yellow 14, Pigment Yellow 95, Pigment Yellow 110, Pigment Yellow 114, Pigment Yellow 128, and Pigment Yellow 155; yellow pigments such as Pigment Orange 5, Pigment Orange 34, Pigment Orange 43, Pigment Orange 62, Pigment Red 17, Pigment Red 49:2, Pigment Red 112, Pigment These include red pigments such as Red 149, Pigment Red 177, Pigment Red 178, Pigment Red 188, Pigment Red 255, and Pigment Red 264; green pigments such as Pigment Green 1, Pigment Green 2, Pigment Green 7, and Pigment Green 36; blue pigments such as Pigment Blue 60, Pigment Violet 3, Pigment Violet 19, Pigment Violet 23, Pigment Violet 32, Pigment Violet 36, and Pigment Violet 38; white pigments such as TiO and ZnO; and the black pigment carbon black. The pigment names and abbreviations used herein are the "CI" designations for pigments established by the Society of Dyers and Colourists, Bradford, Yorkshire, UK, and published in The Color Index, Third Edition, 1971.

[0059] The pigments of the present disclosure can also be self-dispersing (or self-dispersing) pigments. The term self-dispersing pigment (or "SDP") refers to pigment particles whose surfaces have been chemically modified with groups that impart hydrophilic dispersibility, allowing the pigment to be stably dispersed in an aqueous vehicle without a separate dispersant. "Stably dispersed" means that the pigment is finely divided, uniformly distributed, and resistant to particle growth and agglomeration.

[0060] SDPs can be prepared by grafting functional groups or molecules containing functional groups onto the surface of the pigment, by physical treatment (such as vacuum plasma) or chemical treatment (e.g., oxidation with ozone, hypochlorous acid, etc.). Single or multiple types of hydrophilic functional groups can be attached to a single pigment particle. The hydrophilic groups are carboxylate or sulfonate groups, which impart a negative charge to the SDP when dispersed in an aqueous vehicle. The carboxylate or sulfonate groups are usually accompanied by monovalent and / or divalent cationic counterions. Methods for preparing SDPs are well known and can be found, for example, in U.S. Pat. Nos. 5,554,739 and 6,852,156, which are incorporated herein by reference as if fully set forth.

[0061] The SDP can be black, such as based on carbon black, or can be a colored pigment. Examples of pigments with color properties useful in inkjet inks include Pigment Blue 15:3 and Pigment Blue 15:4 (for cyan); Pigment Red 122 and Pigment Red 202 (for magenta); Pigment Yellow 14, Pigment Yellow 74, Pigment Yellow 95, Pigment Yellow 110, Pigment Yellow 114, Pigment Yellow 128, and Pigment Yellow 155 (for yellow); 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 62, Pigment Red 17, Pigment Red 49:2, Pigment Yellow 59:4, Pigment Yellow 62, Pigment Red 17, Pigment Red 49:2, Pigment Yellow 6 ... Examples of suitable pigments include Pigment Red 112, Pigment Red 149, Pigment Red 177, Pigment Red 178, Pigment Red 188, Pigment Red 255, and Pigment Red 264 (for red); Pigment Green 1, Pigment Green 2, Pigment Green 7, and Pigment Green 36264 (for green); Pigment Blue 60, Pigment Violet 3, Pigment Violet 19, Pigment Violet 23, Pigment Violet 32, Pigment Violet 36, and Pigment Violet 38 (for blue); and carbon black. However, some of these pigments may not be suitable for preparation as SDPs. Colorants are represented herein by their "CI" designation.

[0062] The SDPs of the present disclosure can have a degree of functionalization, where the density of anionic groups is less than about 3.5 μmol per square meter (3.5 μmol / m) of pigment surface. 2 ), more particularly about 3.0 μmol / m 2 It is less than about 1.8 μmol / m 2 less than, more particularly about 1.5 μmol / m 2 A degree of functionalization of less than 100 may be appropriate and may be preferred for certain specific types of SDPs.

[0063] 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; particularly 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.

[0064] The amount of pigment present in the ink is typically in the range of about 0.1% to about 25% by weight, more typically in the range of about 0.5% to about 10% by weight, based on the total weight of the ink. If an inorganic pigment is selected, the ink will tend to contain a higher weight percentage of pigment than in a comparable ink using an organic pigment, since inorganic pigments generally have a higher density than organic pigments.

[0065] Polymeric dispersants for dispersed pigments Polymeric dispersants for non-self-dispersing pigments can be random or structured polymers. Typically, polymeric dispersants are copolymers of hydrophobic and hydrophilic monomers. "Random polymer" refers to a polymer in which the molecules of each monomer are randomly arranged in the polymer backbone. For references to suitable random polymeric dispersants, see U.S. Pat. No. 4,597,794. "Structured polymer" refers to 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 0 556 649; 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, which are incorporated herein by reference as if fully set forth.

[0066] "Random polymer" also includes polyurethanes. Particularly useful are the polyurethane dispersants disclosed in U.S. Patent Application Publication No. 2012 / 0214939, in which the polyurethane dispersant is crosslinked after dispersing the pigment to form the pigment dispersion.

[0067] Ink polymer binder A binder is a polymeric compound or mixture of polymeric compounds added to an ink formulation. Binders can impart properties to printed materials, such as greater durability. Typical polymers used as binders in inkjet inks include polyurethane dispersions and solutions, acrylics, styrene-acrylics, styrene-butadiene, styrene-butadiene-acrylonitrile, neoprene, ethylene-acrylic acid, ethylene-vinyl acetate emulsions, latexes, and the like. Binders can be in solution or stabilized as emulsions by containing ionic substituents such as carboxylic acids, sulfur-containing acids, amine groups, and other similar ionic groups. Co-stabilizers of nonionic nature, such as those containing polyethylene oxide, can also be present. Alternatively, binders can be stabilized by external surfactants. Binders can be used alone or in combination with other binders. Typically, the binder is a polyurethane. Binders are typically present in the ink in an amount of at least 0.2% by weight, based on the total weight of the ink.

[0068] Typically, the binder is non-reactive with the colorant, unlike the polyurethane dispersants mentioned above. The binder is typically added to the ink during the final formulation stage, rather than during the preparation of the pigment dispersion.

[0069] Other ink additives Other ingredients, additives, may be incorporated into the ink-jet ink to the extent that such other ingredients do not interfere with the stability and jettability of the ink-jet ink, which can be readily determined by one skilled in the art through routine experimentation.

[0070] Typically, surfactants are added to inks to adjust surface tension and wetting properties. Suitable surfactants include those disclosed above in the vehicle section. Typically, surfactants are used in amounts up to about 3 wt %, more typically up to 1 wt %, based on the total weight of the ink.

[0071] The inclusion of a capping (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 can be beneficial, for example, in removing the deleterious effects of heavy metal impurities.

[0072] Polymers can be added to inks to improve durability or other properties. The polymers can be soluble in the vehicle or in dispersed form and can be ionic or nonionic. Soluble polymers include linear homopolymers and copolymers or block polymers. They can also be structured polymers, including graft or branched polymers, stars, and dendrimers. Dispersed polymers can include, for example, latexes and hydrosols. The polymers can be made by any well-known process, including, but not limited to, free radical, group transfer, ionic, condensation, and other types of polymerization. The polymers can be made by solution, emulsion, or suspension polymerization processes. Typical classes of polymer additives include anionic acrylic, styrene-acrylic, and polyurethane polymers.

[0073] If the polymer is present, its concentration is typically about 0.01% to about 10% by weight based on the total weight of the ink, with the upper limit determined by ink viscosity or other physical limitations.

[0074] Ink set The term "ink set" refers to all the individual inks or other liquids that an inkjet printer is equipped with and jets. Typically, an ink set includes at least three differently colored inks. For example, cyan (C), magenta (M), and yellow (Y) inks form a CMY ink set. More typically, an ink set includes at least four differently colored inks, for example, by adding a black (K) ink to a CMY ink set to form a CMYK ink set. The magenta, yellow, and cyan inks of an ink set are typically aqueous inks and may include dyes, pigments, or combinations thereof as colorants. Such other inks are generally known to those skilled in the art.

[0075] In addition to the typical CMYK inks, the ink set may further include one or more "gamut-enhancing" inks, including differently colored inks such as orange, green, red, and / or blue inks, and combinations of high- and low-intensity color inks such as light cyan and light magenta. Such other inks are known in the general sense to those skilled in the art.

[0076] A typical ink set includes magenta, yellow, cyan, and black inks, where the black ink is an ink according to the present disclosure that includes an aqueous vehicle and a self-dispersed carbon black pigment. In particular, the colorant in each of the magenta, yellow, and cyan inks is a dye.

[0077] Ink characteristics Jet velocity, droplet separation length, droplet size, and stream stability are greatly affected 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., the drive frequency of piezoelectric elements or the ejection conditions of thermal heads in drop-on-demand or continuous devices, as well as nozzle shapes and sizes. The ink should have excellent storage stability over long periods of time so as not to significantly clog in the inkjet device. Furthermore, the ink should not corrode parts of the inkjet printing device it comes into contact with and should be essentially odorless and non-toxic.

[0078] Although not limited to any particular viscosity range or printhead, the ink fluid sets of the present invention are particularly suited for lower viscosity applications, such as those required by thermal printheads. As such, the viscosity of the inks of the present invention at 25° C. can be less than about 7 cP, typically less than about 5 cP, and more typically less than about 3.5 cP. Thermal inkjet actuators rely on instantaneous heating / bubble formation to expel ink droplets, and this mechanism of droplet formation generally requires lower viscosity inks.

[0079] Base material The inks of the present disclosure can be printed on common print substrates such as paper and textiles. The ink fluid sets of the present disclosure are most advantageous for printing on low-porosity media such as offset coated media and coated media.

[0080] Offset coated and coated media are generally known to have poor receptivity to aqueous inkjet inks. These papers have low surface porosity due to the calendaring and / or application of one or more hydrophobic coating layers. Such surface smoothing procedures and coatings provide papers that can withstand the high viscosity of conventional printing pastes and / or accept hydrophobic toner particles. However, the resulting low porosity reduces the ink vehicle's access channels, resulting in a greater reliance on evaporation for ink drying. Furthermore, the hydrophobic nature of the coating layer reduces the wetting and spreading of aqueous inks during printing, which can subsequently cause ink droplets to puddle on the media surface. When printing aqueous inks directly onto offset media, the combined effects of poorer dot spreading and slower drying lead to more image defects. The most obvious defect involves uneven colorant deposition on these media. These uneven colorant deposition defects are variously known as mottling, coalescence, framing, or square-effect edges. Another equally unacceptable consequence of the hydrophobicity and low porosity of offset media is increased ink drying time, which increases the time for adjacent colors to mix, resulting in intercolor bleed, where one color diffuses into its neighbor. Such image defects can be mitigated by applying a chemical precoating or pretreatment, often colorless, that interacts with the wet ink droplets to immobilize the colorant. Chemical immobilization can effectively resolve the image defect of uneven coloration or migration of colorant in intercolor bleed. [Example]

[0081] The invention is further illustrated, but not limited, by the following examples in which parts and percentages are by weight unless otherwise noted.

[0082] Ingredients and Abbreviations DBTL = dibutyltin dilaurate DMPA = dimethylolpropionic acid IPDI = Isophorone diisocyanate Terathane® 650—a polyether diol from Invista (Wilmington, Del.). PrintRite® DP375 - Lubrizol (Wickliffe, OH) ink non-flocculant polymer, polyurethane dispersion. FLOQUAT® FL2650—Ink-flocculating cationic polymer from SNF Inc., France. Surfynol® 440—A nonionic surfactant from Air Products (Allentown, PA). Capstone® FS35—a nonionic fluorosurfactant from Chemours Company (Wilmington, DE).

[0083] Unless otherwise stated, the above chemicals were obtained from Aldrich (Milwaukee, Wis.) or other similar research chemical suppliers.

[0084] Dispersants Terathane® 650 (300 g), DMPA (180 g), sulfolane (876 g), and DBTL (0.12 g) were added to a dry, alkali- and acid-free flask equipped with an addition funnel, condenser, and stirrer under a nitrogen atmosphere. The resulting mixture was heated to 60°C and thoroughly mixed. IDPI (438 g) was added to the mixture via an addition funnel attached to the flask, and any remaining IDPI in the addition funnel was then rinsed into the flask with sulfolane (15 g). The temperature of the reaction mixture was increased to 85°C and maintained at 85°C until the isocyanate content was 0.8% or less. The temperature was then cooled to 60°C and maintained at 60°C. morpholine (30 g) was added via the addition funnel over 5 minutes, and any remaining morpholine in the addition funnel was then rinsed into the flask with sulfolane (5 g). After the temperature was held at 60°C for 1 hour, an aqueous solution of KOH (1755g, 3 wt%) was added via an addition funnel over 10 minutes, followed by deionized water (207g). The mixture was held at 60°C for 1 hour and cooled to room temperature to give a polyurethane dispersion with 25% solids.

[0085] pigment dispersion Crosslinked cyan, magenta, and yellow pigment dispersions were prepared using the pigments listed in Table 1 below and the dispersants prepared above according to the methods described in U.S. Patent Application Publication No. 20140045975, which is incorporated herein by reference as if fully set forth.

[0086] [Table 1]

[0087] Inkjet ink Ink-C and Ink-Y were prepared using crosslinked dispersions XL-C and XL-Y in a standard inkjet vehicle containing 2-pyrrolidone, glycol, and surfactants.

[0088] [Table 2]

[0089] Pretreatment Solution Pretreatment solutions were prepared using calcium nitrate salt as the ink flocculant and Printrite® DP375 as the ink de-flocculating polymer and are listed in Table 3 below.

[0090] [Table 3]

[0091] A pretreatment solution using the cationic polymer FLQUART® FL2650 as the ink flocculant was prepared and is listed in Table 4 below.

[0092] [Table 4]

[0093] Coating of pretreatment solution, printing and image quality evaluation Two offset media were selected for the study: Oji "Newage Blanc" matte art paper supplied by Oji Paper Company, Tokyo, Japan, and UPM Finesse glossy paper supplied by UPM-Kymmene Corp., Helsinki, Finland. One newspaper media was also selected: Holmen PLUS72 supplied by Holmen AB, Sverige, Sweden. The ink was applied at 2 to 10 grams per square meter using a Pamarco hand ink proofer from Pamarco Global Graphics, Roselle, NJ. 2 The pretreatment solution was applied to the selected media at wet coating weights ranging from 1000 to 10000. After the coating was applied, the media was allowed to dry at room temperature for at least 24 hours before printing.

[0094] Two patterns were printed on the specified media with and without pre-coating using a Ricoh Ipsio GX e5500#4442 printer equipped with a GelSprinter GX e5550N (Raster) printer driver to obtain first and second solid print areas of 7 cm x 3.5 cm in cyan and green. Ink-C and Ink-Y were used for this test.

[0095] Print quality was quantitatively evaluated using a DuPont Appearance Analyzer (DAA) mottle evaluation method. Details of this method are described in U.S. Patent No. 6,438,256. The DAA analysis yields three different mottle measurements: the DuPont Appearance Value (DAV2), the DuPont Mottle Measurement (DMM), and the DuPont Mottle Value (DMV). The DAV2 is calculated directly by dividing the standard deviation of the image's gray levels by the mean grayscale value, and is most sensitive to fine or short-distance mottle. The DMM value calculation was adjusted to incorporate both fine-scale and large-scale mottle / non-uniformity, while the DMV is a further refinement for measurements that are reproducible even with slight differences in light and dark. Both the DMM and DMV calculations were optimized to match visual and mottle assessments. For samples with mottle values ​​below 30, DMV is most suitable for repeatable measurements, especially with inter-instrument reproducibility; otherwise, DMV and DMM should be considered essentially the same. Therefore, only DMM data was recorded. Lower DMM values ​​indicate less mottle and better image quality. DAA instruments typically analyze over an area of ​​1.99 x 2.66 inches. Unfortunately, most prints have significant banding, and only a small area of ​​interest (0.35 x 2.15 inches in area) was characterized. The DMM data areas for the cyan and green color blocks are summarized in Table 5 below.

[0096] [Table 5]

[0097] DMM data shows ink non-agglomeration. TM It shows that the inventive examples in which the DP375 polymer and surfactant were present had better image quality than the comparative examples in which the polymer and surfactant were not present.

[0098] The pretreatment solutions Comparative B, Example B, and Example C were coated onto Holmen PLUS 72 newspaper media supplied by Holmen AB, Sverige, Sweden, using the same coating process as described above for coating selected offset media. The pretreated and unpretreated Holmen PLUS 72 papers were then printed using a laboratory printing system. Ink-C was jetted from a fixed Kyocera (Kyoto, Japan) KJ4B printhead onto the paper, which was held on a rotating cylinder below. A 5 cm x 2 cm solid color block was printed at a setting of 600 x 600 dpi to evaluate color and image quality. Optical density (OD) values ​​were measured using an X-Rite densitometer. Image quality (IQ) was determined by observing the number of white streaks along the print direction.

[0099] The OD data and image assessment for Holmen PLUS72 are summarized in Table 6 below.

[0100] [Table 6]

[0101] Prints on all coating solutions had higher OD than prints on uncoated paper. However, Comparative B solution produced numerous white streaks as a result of poor ink penetration and spreading due to ink coagulation. Inventive Examples B and C surprisingly showed improved ink coverage without white streaks while maintaining high OD.

[0102] The pretreatment solutions Comparative Example C, Example D, Example E, Example F, and Example G were coated onto offset media UPM Fine glossy paper using the same coating process described above. Solid blocks of images were then printed with Ink-C using a Kyocera printhead printing system. Optical density (OD) values ​​were measured using an X-Rite densitometer. The IQ of the solid blocks was evaluated by rating the image graininess from 1 to 3. 3 was the best, with no visible grain; 2 showed moderate graininess; and 1 was the worst, with a patchy image and many white streaks. Images with separate, uncoalesced ink droplets were also printed by firing only 5% of the nozzles. The diameter of a single ink droplet was recorded to measure the ink droplet spreading and penetration on the media.

[0103] [Table 7]

[0104] The inventive examples demonstrated improved image quality, as shown in the graininess evaluation data in Table 7. Ink drop size measurements also showed improved spreading and wetting with the inventive examples.

Claims

1. (a) an aqueous pretreatment composition comprising an ink flocculant, an ink de-flocculating polymer, and a surfactant, wherein the ink flocculating agent is selected from a cationic polymer and a mixture of a cationic polymer and a multivalent metal salt; and (b) An aqueous inkjet ink comprising a crosslinked polymer pigment dispersion and an aqueous vehicle, wherein the crosslinked polymer pigment dispersion is produced by dispersing the pigment with a polymer dispersant and then reacting the resulting dispersion with a crosslinking agent. wherein the cationic polymer is derived from the polymerization of diallyldialkylammonium monomers and the ink de-flocculating polymer is a non-ionic aqueous polyurethane dispersion.

2. 2. The liquid set of claim 1, wherein the surfactant is selected from the group consisting of cationic, nonionic, and amphoteric surfactants.

3. The fluid set of claim 2 , wherein the ink non-agglomerating polymer is an aqueous polyurethane dispersion.

4. 2. The liquid set according to claim 1, wherein the polyvalent metal salt is a salt of a metal selected from the group consisting of Ca, Mg, Ba, Ru, Co, Zn, and Ga, and mixtures thereof.

5. The liquid set according to claim 4 , wherein the polyvalent metal salt is a Ca salt.

6. 6. The fluid set of claim 5 for use in printing on a substrate that is offset coated media.

7. (a) an aqueous pretreatment composition comprising an ink flocculant, an ink de-flocculating polymer, and a surfactant, wherein the ink flocculating agent is selected from a cationic polymer and a mixture of a cationic polymer and a multivalent metal salt; and (b) An aqueous inkjet ink comprising a crosslinked polymer pigment dispersion and an aqueous vehicle, wherein the crosslinked polymer pigment dispersion is produced by dispersing the pigment with a polymer dispersant and then reacting the resulting dispersion with a crosslinking agent. wherein the cationic polymers are epichlorohydrin-amine polymers and copolymers derived from epichlorohydrin, and the ink de-flocculating polymer is a non-ionic water-soluble polymer based on urethane and cellulose structures, or a non-ionic aqueous polyurethane dispersion.

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