Patent Description:
In recent years, inkjet techniques have been increasingly utilized for industrial printing applications such as displays, posters, bulletin boards, packaging, textile, etc.. In such applications durability such as light fastness, water resistance, and wear resistance are important requirements of the printed images and pigment based inks therefore have been developed.

Inks, such as solvent-based inkjet inks using an organic solvent as a vehicle and ultraviolet curable inkjet inks including a polymerisable monomer as a main component have been used widely in industrial applications.

However, the solvent-based inkjet inks are not environmentally preferable because the solvent of the ink is evaporated in the air upon drying. The ultraviolet curable inkjet inks have limited application fields because they may have skin sensitizing properties depending on the monomer used and an expensive ultraviolet irradiation apparatus is required to be incorporated to the main body of a printer.

In view of such background, there have been developed pigment based aqueous inks for inkjet recording capable of being directly used for printing on porous and non-porous substrates and which give less environmental load. These inks are characterized by the presence of a resin which binds the pigments and prevents rubbing off the images from the substrate leading to an improved solvent and scratch resistance.

Especially, on non-porous substrates aqueous based pigment inks tend to give low image quality due to the slow evacuation of the aqueous ink carrier leading to migration of colorants, known as intercolor bleeding, coalescence, etc.. On porous substrates such as paper, cardboard and textile fabrics, colorants also tend to migrate before the aqueous carrier is completely absorbed by the porous material. A lot of these substrate materials have a negative zeta-potential in water with a pH range around <NUM>. As most colorants in aqueous inkjet inks carry a negative charge, hardly any fixing of these colorants on the negatively charged substrate material occurs before the ink carrier is evacuated.

Therefore, ink-jet recording media for aqueous ink jet inks such as paper, plastic film or textile fabric are provided with an ink-jet receiving layer provided thereon.

This layer is formed from an ink-jet receiving agent which is mostly a water soluble resin such as polyvinyl alcohol, polyvinyl pyrrolidone and the like and any of various additives, in order to prevent bleeding and coalescence caused by the water based ink or improve ink absorbing property. Image quality problems occur because bleeding and coalescence arises due to insufficient adsorption of the pigment ink into the ink-jet receiving layer.

Moreover, there is a problem that a printed image made by jetting aqueous ink jet inks has poor waterproof characteristics. The most popular method to improve the waterproof characteristics is a method wherein an ink-jet receiving agent is used which includes an aqueous cationic resin such as a poly(diallyldimethylammonium chloride) in addition to the aforementioned resin in the ink. Waterproof characteristics can be improved by fixing of the pigment of the aqueous ink due to the electrostatic bonding between an anionic group of the pigment in the ink and a cationic group of the water-soluble cationic resin. However, since the water-soluble cationic resin itself tends to be easily dissolved in water, the effect for improving waterproof characteristics was insufficient. Furthermore, these polymers do not crosslink with each other nor form a film, leading to poor physical properties of the printed image.

<CIT> discloses a fixer fluid to be used for making an ink-receiving layer and comprising a liquid vehicle, a surfactant, and a cationic polymer. The cationic polymer can be selected from the group of quaternized polyamines, dicyandiamide polycations, diallyldimethyl ammonium chloride copolymers, quaternized dimethylaminoethyl(meth)acrylate polymers, quaternized vinylimidazol polymers, alkyl guanidine polymers, alkoxylated polyethylene imines,.

<CIT> discloses an aqueous pigment composition for printing on a porous substrate such as textile which guarantees an improved washing fastness and rubbing resistance of the images on the fabric. The aqueous composition comprises pigment particles containing a urethane resin obtained by reacting polyester polyols with polyols comprising an ionic or non-ionic group and polyisocyanate.

<CIT> discloses an ink-jet receiving agent including a cationic polyurethane resin aqueous dispersion. The resin provides excellent waterproof characteristics on a coating which is formed after removing water from the dispersion. The cationic functional groups are obtained by using <NUM>-(dimethylamino)-<NUM>,<NUM>-propanediol during the synthesis of the polyurethane polymer. This diol comprises a secondary OH-group which shows a very limited reactivity, limiting the length of the polymer chains and hence reducing the physical properties of the resin such as adhesion, scratch resistance, solvent and water resistance. Furthermore, the method of preparing these cationic polyurethanes as disclosed in <CIT> is laborious.

As described above, there is great need for the development of an aqueous pigmented inkjet ink which lead to excellent image quality (high colour density, low coalescence and low inter-colour bleeding), preferably without the need of a pretreatment, does show long shelf life stability and which provides printed images showing excellent physical properties (adhesion, waterproof characteristics and wear resistance).

It is an objection of the invention to provide a solution for the above stated problems. The object has been achieved by incorporating an aqueous pigment dispersion as defined in claim <NUM> into an aqueous inkjet ink.

According to another aspect, the present invention includes an aqueous inkjet ink according to claim <NUM>.

According to another aspect, the present invention includes an inkjet recording method. This method is defined in claim <NUM>.

Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention. Specific embodiments of the invention are also defined in the dependent claims.

The aqueous pigment dispersion according to the invention is prepared by dispersing pigments in an aqueous medium with a dispersing agent having the general formula I
<CHM>
wherein.

R<NUM> represents an unsubstituted alkyl group, comprising at least <NUM> carbon atoms, more preferably at least <NUM> carbon atoms and most preferably at least <NUM> carbon atoms. In a particularly preferred embodiment, R<NUM> represents an unsubstituted alkyl group comprising at least <NUM> carbon atoms. In another preferred embodiment, R<NUM> is selected from the group consisting of a hydrogen and a substituted or unsubstituted alkyl group, a hydrogen and a C1 to C6 unsubstituted alkyl group being more preferred, a hydrogen being the most preferred. In a further preferred embodiment, L represents a divalent linking group comprising <NUM> to <NUM> carbon atoms, <NUM> to <NUM> carbon atoms being more preferred. In another preferred embodiment, R<NUM>, R<NUM> and R<NUM> independently represent a substituted or unsubstituted alkyl group, a C1 to C6 unsubstituted alkyl group being more preferred, a methyl, an ethyl and a propyl group being the most preferred.

Typical dispersing agents, according to general formula I are given in Table <NUM> without being limited thereto.

The pigment of the dispersion according to the invention can be any pigment but is preferably a colored pigment. Examples include, but are not limited to, carbon black, and colored pigments such as anthraquinones, phthalocyanine, blues, phthalocyanine greens, diazos, monoazos, pyranthrones, perylenes, heterocyclic yellows, quinacridones, diketo-pyrrolo-pyrrolo pigments and (thio)indigoids. Representative examples of phthalocyanine blues include copper phthalocyanine blue and derivatives thereof (Pigment Blue <NUM>). Representative examples of quinacridones include Pigment Orange <NUM>, Pigment Orange <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Violet <NUM> and Pigment Violet <NUM>. Representative examples of anthraquinones include Pigment Red <NUM>, Pigment Red <NUM> (Perlnone Red), Pigment Red <NUM> (Brominated Pyrathrone Red) and Pigment Red <NUM> (Pyranthrone Red). Representative examples of perylenes include Pigment Red <NUM> (Vermillion), Pigment Red <NUM> (Scarlet), Pigment Red <NUM> (Maroon), Pigment Red <NUM> (Red), Pigment Violet, Pigment Red <NUM> (Yellow Shade Red) and Pigment Red <NUM>. Representative examples of thioindigoids include Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Red <NUM>, Pigment Violet <NUM>, and Pigment Violet <NUM>. Representative examples of heterocyclic yellow include Pigment Yellow <NUM> and Pigment Yellow <NUM>.

More preferably the pigment is selected from the groups of quinacridones and diketo-pyrolo-pyrrolo pigments. Particularly preferred pigments are selected from the group consisting of Pigment Red <NUM>, Pigment Violet <NUM> and mixed crystals of the above particular pigments. A commercially available example is Cinquasia Magenta RT-<NUM>-D from Ciba Speciality Chemicals. Examples of other suitable colored pigments are described in <NPL>).

Particularly useful for printing on dark textile is an aqueous inkjet ink containing the dispersion of the invention having a white pigment as pigment. The preferred pigment is titanium dioxide. Titanium dioxide (TIO<NUM>) pigment useful in the present invention may be in the rutile or anatase crystalline form. Processes for making TiO<NUM> are described in greater detail in "<NPL>), the relevant disclosure of which is incorporated by reference herein for all purposes as if fully setforth.

The titanium dioxide particles can have a wide variety of average particle sizes of about <NUM> micron or less. For applications demanding high hiding or decorative printing applications, the titanium dioxide particles preferably have an average size of less than about I µm. Preferably, the particles have an average size of from about <NUM> to about <NUM>, more preferably from about <NUM> to about <NUM>, and still more preferably from about <NUM> to about <NUM>.

For applications demanding white colour with some degree of transparency, the pigment preference is "nano" titanium dioxide. "Nano" titanium dioxide particles typically have an average size ranging from about <NUM> to about <NUM>, preferably from about <NUM> to about <NUM>, and more preferably from about <NUM> to about <NUM>. An ink comprising nano titanium dioxide can provide improved chroma and transparency, while still retaining good resistance to light fade and appropriate hue angle. A commercially available example of an uncoated nano grade of titanium oxide is P-<NUM>, available from Degussa (Parsippany N.

In addition, unique advantages may be realized with multiple particle sizes, such as opaqueness and UV protection. These multiple sizes can be achieved by adding both a pigmentary and a nano grade of TIO<NUM>.

The titanium dioxide pigment may also bear one or more metal oxide surface coatings. These coatings may be applied using techniques known by those skilled in the art. Examples of metal oxide coatings include silica, alumina, aluminasilica, boria and zirconia, among others. These coatings can provide improved properties including reducing the photoreactivity of the titanium dioxide. Commercial examples of such coated titanium dioxides include R700 (alumina-coated, available from E. DuPont deNemours, Wilmington Del. ), RDI-S (alumina-coated, available from Kemira Industrial Chemicals, Helsinki, Finland), R706 (available from DuPont, Wilmington Del. ) and W-<NUM> (a silica alumina treated nano grade titanium dioxide from Tayco Corporation, Osaka Japan). Other suitable white pigments are given by Table <NUM> in [<NUM>] of <CIT>. The white pigment is preferably a pigment with a refractive index greater than <NUM>. The white pigments may be employed singly or in combination. Preferably titanium dioxide is used as pigment with a refractive index greater than <NUM>. Suitable titanium dioxide pigments are those disclosed in [<NUM>] and in [<NUM>] of <CIT>.

In the pigment dispersion, it is desirable that the average particle diameter of the pigment particles be in the range of <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>, most preferably in the range of <NUM> to <NUM>. When the average particle diameter of the pigment particles is <NUM> or less, the problems concerning the reliability such as clogging of the nozzle and the storage stability of the ink composition can be effectively minimized. When the average particle diameter of the pigment particles is <NUM> or more, the advantages of the pigments for use in the present invention, ie. , excellent light resistance and water resistance can be effectively exhibited, and aggregation of pigment particles can be prevented.

The pigment to dispersing agent ratio (by wt. ) is preferably, from about <NUM> to about <NUM>, more preferably, from about <NUM> to about <NUM> and most preferably from about <NUM> to about <NUM>.

For dispersing the pigments, a variety of dispersion apparatus, for example, a ball mill, sand mill, roll mill, colloid mill, ultrasonic homogenizer, and high-pressure homogenizer can be employed. Using any of the abovementioned dispersion apparatus, a pigment and water serving as a solvent are mixed and dispersed, with the addition thereto of the dispersing agent as described above thereby obtaining the pigment dispersion of the invention. The whole amount or partial amount of the dispersing agent is preferably added during the dispersing step.

The pigment dispersion may contain up to <NUM> (wt. )% pigment, but will generally be in the range of approximately <NUM> to <NUM>(wt. )%, preferably <NUM> to <NUM> (wt. )%, more preferably from <NUM> to <NUM> (wt.

It is preferable that the dispersed pigment be contained in the aqueous ink composition is up to <NUM>% pigment by weight, but will generally be in the range of approximately <NUM> to <NUM>%, preferably approximately <NUM> to <NUM>%. by weight of the total ink composition. When the amount ratio of the pigment is <NUM> wt. % or more, sufficient saturation and image density can be obtained. When the amount ratio of the pigment is <NUM> wt. % or less, a decrease in color value can be prevented and the nozzles of a print head can be prevented from being clogged.

The aqueous ink jet ink composition comprising the pigment dispersion according to the invention may further comprise a resin, particles such as latex binders, polymeric capsules or polyethylene waxes. The resin can be selected from the group of acrylic based resins, urethane-modified polyester resins and polyurethane resins.

Polyurethane resin is to be incorporated in the ink formulation as a dispersion and may be selected from the group consisting of aliphatic polyurethane dispersions, aromatic polyurethane dispersions, anionic polyurethane dispersions, non-ionic polyurethane dispersions, aliphatic polyester polyurethane dispersions, aliphatic polycarbonate polyurethane dispersions, aliphatic acrylic modified polyurethane dispersions, aromatic polyester polyurethane dispersions, aromatic polycarbonate polyurethane dispersions, aromatic acrylic modified polyurethane dispersions, for example, or a combination of two or more of the above.

A preferred urethane resin to be used as dispersion in the ink of the invention is a polyester resin including a structural unit containing a urethane bond. Among such resins, a water-soluble or water-dispersible urethane-modified polyester resin is preferred. It is preferable that the urethane-modified polyester resin include at least one structural unit derived from a hydroxyl group-containing polyester resin (polyester polyol) and at least one structural unit derived from an organic polyisocyanate.

Furthermore, the hydroxyl group-containing polyester resin is a resin formed by an esterification reaction or transesterification reaction between at least one polybasic acid component and at least one polyhydric alcohol component.

Other preferred resins are the ones having a cationic group. Polymeric cationic polymers contain either guanidinium or fully quaternized ammonium functionalities, such as quaternized polyamine copolymers. Classes of cationic polymers that can be used include, but are not limited to, quaternized polyamines, dicyandiamide polycations, diallyldimethyl ammonium chloride copolymers, quaternized dimethylaminoethyl(meth)acrylate polymers, quaternized vinylimidazol polymers, alkyl guanidine polymers, alkoxylated polyethylene imines, and mixtures thereof. It is to be understood that one or more polycations may be used, and that any desirable combination of the polycations can be used. One or more ions of the cationic polyelectrolytes may be ion-exchanged for a nitrate, acetate, mesylate, or other ion.

Preferred cationic resins are polyurethane resins which have a cationic group incorporated in it. Suitable examples are: cationic polyurethane resins including a structural unit having a cationic amino group as disclosed by <CIT>, cationic polyurethane resins having a quaternized ammonium group in the backbone of the polymer as disclosed by <CIT>, cationic polyester urethane resins obtained by reacting polyester polyols, polyols with a cationic group and polyisocyanate as disclosed in <CIT>, cationic polyurethane resins obtained by using <NUM>-(dimethylamino)-<NUM>,<NUM>-propanediol during the synthesis of the polyurethane polymer as disclosed in <CIT>.

A particular preferred cationic polyester urethane resin to be included in the ink of the invention is a polyurethane resin obtainable by reacting a polyester polyol, a polyether diol, a polyol containing a cationic group and a polyisocyanate. Examples of suitable polyurethane resins and their preparations are disclosed in the unpublished patent application <CIT> and are obtained by reacting polyester polyols, a polyether diol, a polyol containing a quaternary N-atom or amino group and a polyisocyanate. Other examples of suitable polyurethane resins and their preparations are disclosed in the unpublished patent application <CIT> obtained by reacting polyester polyols, a diol containing a quaternary N-atom or tertiary amino group in a side chain from the carbon chain linking the <NUM> hydroxyl groups of the diol and a polyisocyanate.

Some examples of suitable polyurethane dispersions are NEOREZ R-<NUM>, NEOREZ R-<NUM>, and NEOREZ R-<NUM> (DSM NeoResins); BAYHYDROL UH <NUM>, BAYHYDROL UH XP <NUM>, BAYHYDROL UH XP <NUM>, and BAYHYDROL UA XP <NUM> (Bayer Material Science); DAOTAN VTW <NUM>/35WA, DAOTAN VTW <NUM>/36WA, DAOTAN VTW <NUM>/36WA, DAOTAN VTW <NUM>/42WA, DAOTAN VTW <NUM>/36WA (Cytec Engineered Materials Inc. , Anaheim CA); and SANCURE <NUM>, SANCURE <NUM>, SANCURE <NUM> (Lubrizol Corporation), for example, or a combination of two or more of the above.

Acrylic based resins include polymers of acrylic monomers, polymers of methacrylic monomers, and copolymers of the aforementioned monomers with other monomers. These resins are present as a suspension of particles (latex) having an average diameter of about <NUM> to about <NUM>. The acrylic latex polymer is formed from acrylic monomers or methacrylic monomer residues. Examples of monomers of the acrylic latex polymer include, by way of illustration, acrylic monomers, such as, for example, acrylate esters, acrylamides, and acrylic acids, and methacrylic monomers, such as, for example, methacrylate esters, methacrylamides, and methacrylic acids. The acrylic latex polymer may be a homopolymer or copolymer of an acrylic monomer and another monomer such as, for example, a vinyl aromatic monomer including, but not limited to, styrene, styrene butadiene, p-chloromethylstyrene, divinyl benzene, vinyl naphthalene and divinylnaphthalene.

Some examples of suitable acrylic latex polymer suspensions are, JONCRYL <NUM> and JONCRYL <NUM> (BASF Corporation, Port ArthurTX); CARBOSET GA-<NUM>, CARBOSET CR-<NUM>, CARBOSET CR-<NUM>, CARBOSET CR-<NUM>, CARBOSET CR-<NUM>, CARBOSET CR-<NUM>, CARBOSET CR-<NUM>, and CARBOSET GA-<NUM> (Lubrizol Corporation, Rancho Santa Margarita CA); NEOCRYL A-<NUM>, NEOCRYL A-<NUM>, NEOCRYL A-<NUM>, NEOCRYL A-<NUM>, NEOCRYL XK-<NUM>, and NEOCRYL XK-<NUM> (DSM NeoResins, Sluisweg, The Netherlands); and BAYHYDROL AH XP <NUM>, BAYHYDROL AH XP <NUM>, BAYHYDROL A <NUM>, and BAYHYDROL A2651 (Bayer Material Science, Baytown TX), for example, or a combination of two or more of the above.

Besides resin and latices, polymeric capsules can be advantageously incorporated in the ink comprising the pigment dispersion of the invention. Useful polymeric capsules are the microcapsules disclosed in <CIT> and the nanocapsules disclosed in <CIT>. Preferably nanocapsules can be used which comprise a core having reactive chemistry which may be thermally reactive chemistry activatable directly by heat or indirectly using an optothermal converting agent. These nanocapsules are described in [<NUM>-<NUM>] of <CIT>. In the latter, for example an infrared absorbing dye converts the infrared light of an infrared laser or infrared LEDs into heat.

More preferably, nanocapsules having a shell surrounding a core, the shell comprising cationic dispersing groups as disclosed in the application <CIT> can be used. The presence of cationic groups improve the compatibility of the nanocapsules with the pigment dispersion particles in the aqueous ink. Preferably the cationic dispersing groups are selected from the group consisting of protonated amines, protonated nitrogen containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfoniums and phosphoniums. The core may comprise chemical reactants which are capable of forming a reaction product upon application of heat and/or light, preferably the chemical reactant is a thermally reactive crosslinker, more preferably a blocked isocyanate. The capsules described in [<NUM>-<NUM>] of <CIT> are particularly suited to be combined with the pigment dispersion of the invention in an aqueous ink jet ink.

The concentration of the resin in the ink jet ink according to the invention is at least <NUM> (wt. )% and preferably lower than <NUM> (wt. )%, more preferably between <NUM> and <NUM> (wt.

The aqueous ink jet ink comprising the dispersion of the invention may contain, besides water as a solvent, also a water-soluble organic solvent. Examples of water-soluble organic solvents include polyhydric alcohols such as diethylene glycol, triethylene glycol, dipropylene glycol, <NUM>,<NUM>-propanediol, <NUM>,<NUM>-butanediol, <NUM>,<NUM>-butanediol, <NUM>,<NUM>-dimethyl-<NUM>, <NUM>-propanediol, <NUM>-methyl-<NUM>, <NUM>-propanediol, <NUM>,<NUM>-pentanediol, <NUM>,<NUM>-pentanediol, <NUM>,<NUM>-pentanediol,<NUM>,<NUM>-hexanediol, <NUM>-ethyl-<NUM>, <NUM>-hexanediol, <NUM>,<NUM>-hexanediol and <NUM>,<NUM>-hexanediol, polyhydric alcohol alkyl ethers such as dipropylene glycol n-propyl ether, tripropylene glycol methyl ether, tripropylene glycol n-propyl ether, propylene glycol phenyl ether, triethylene glycol methyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, diethylene glycol n-hexyl ether and ethylene glycol phenyl ether, and nitrogen-containing heterocyclic compounds such as <NUM>-pyrrolidone and N-methylpyrrolidone.

Other preferred water soluble organic solvents include ethylene glycol, propylene glycol, <NUM>,<NUM>-butanediol, <NUM>,<NUM>-butanediol, <NUM>-methyl-<NUM>, <NUM>-pentanediol, dipropylene glycol monomethyl ether, propylene glycol n-butyl ether, propylene glycol t-butyl ether, diethylene glycol methyl ether, ethylene glycol n-propyl ether and ethylene glycol n-butyl ether.

The content of the water-soluble organic solvent, in the aqueous ink jet ink is preferably less than <NUM> wt. If the content exceeds <NUM>% by mass, the ink loses its water based, hence more green character.

In the aqueous ink of the present invention, a surfactant may be added in order to ensure wettability onto the substrate. The amount of the surfactant added is preferably <NUM> wt. % to <NUM> wt. % as an active component in the ink.

If the amount added is below <NUM>% by mass, wettability onto the substrate is not sufficient and causes degradation in image quality and in adhesion to the substrate. The surfactant that can be used is not particularly limited as long as it satisfies the above limitation.

While any of an amphoteric surfactant, a non-ionic surfactant, and a cationic surfactant can be used, non-ionic surfactants such as polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkyl amide, a polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester and an ethylene oxide adduct of acetylene alcohol are preferably used in terms of a relationship between dispersing stability and image quality. In addition, a fluorine-based surfactant and a silicon-based surfactant can be used in combination (or singly) depending on formulation.

Suitable surfactants are siloxane based surfactants such as Tego Twin <NUM> from Evonik Industries, Tegowet <NUM> from Evonik industries, Hydropalat WE3220 from BASF, silane based surfactants such as Silwet HS312 from Momentive and fluor containing surfactants such as: Thetawet FS8150 from Neochem GMBH, Capstone FS3100 from Dupont, Tivida FL2500 from Merck and surfactants from the Dynol, Envirogem & Surfynol series from Air products.

Printing methods using aqueous inkjet inks comprising the pigment dispersion of the invention include at least the steps of: a) applying the aqueous inkjet ink containing the dispersed particles of the invention by means of an inkjet technique onto a substrate; and b) applying heat and/or radiation to dry the jetted ink.

The aqueous ink jet ink according to the present invention is suitable to be jetted on different substrates, porous and non-porous ones. Porous substrates include paper, card board, white lined chipboard, corrugated board, packaging board, wood, ceramics, stone, leather and textile fabrics. Non-porous substrates include metal, synthetic leather, glass, polypropylene, polyvinylchloride, PET, PMMA, polycarbonate, polyamide, polystyrene or co-polymers thereof.

Suitable textile fabrics can be made of one type of fibre or blended fibre of two or more selected from the group consisting of cotton, hemp, rayon fibre, acetate fibre, silk, nylon fibre, and polyester fibre. The fabric may be in any form, for example, a woven, knitted, or nonwoven form of the above-mentioned fibres.

The aqueous inkjet ink according to the invention is jetted onto a substrate. The substrate can be pre-treated by applying a pre-treatment liquid. This is particularly useful on textile fabrics as substrate.

The pre-treatment liquid typically containing a flocculant may be applied to the substrate by spraying, coating, pad printing or jetting using an ink jet head or valve jet head. These last means of applying a pre-treatment liquid have the advantage that the amount of required pre-treatment liquid is substantially lower than with the other application methods. By means of an ink jet head, it is possible to apply the pre-treatment liquid onto areas of the substrate or textile fabric where the image should be printed.

Substrates and textile fabrics to which a pre-treatment liquid has been applied may be dried before applying the aqueous ink according to the invention. After drying, the pre-treated textile may optionally undergo a heat treatment, before the subsequent ink jetting step with ink. Examples of the heating process include, but are not limited to, heat press, atmospheric steaming, high-pressure steaming and THERMOFIX. Any heat source can be used for the heating process; for example, an infrared ray lamp can be employed.

A preferred ink jet head for the jetting of the ink according to the invention is a piezoelectric ink jet head. Piezoelectric inkjet jetting is based on the movement of a piezoelectric ceramic transducer when a voltage is applied thereto. The application of a voltage changes the shape of the piezoelectric ceramic transducer in the print head creating a void, which is then filled with ink. When the voltage is again removed, the ceramic expands to its original shape, ejecting a drop of ink from the ink jet head. However, the jetting of the ink according to the present invention is not restricted to piezoelectric inkjet printing. Other inkjet print heads can be used and include various types, such as a continuous type, a thermal print head type and a valve jet type.

After the ink jetting step, the printed substrate is dried. The drying step can be performed at the air or by using heat sources; examples include equipment for forced-air heating, radiation heating such as IR-radiation, including NIR- and CIR radiation, conduction heating, high-frequency drying, and microwave drying. The drying step is carried at a temperature preferably below <NUM>, more preferably below <NUM>, most preferably below <NUM>.

After the drying step, heat can also be applied to the dried substrate. This is particularly useful with textile fabrics as substrate and when the resin in the aqueous ink jet ink according to the invention comprises a resin as a latex or a capsule. The heat treatment is preferably at <NUM> to <NUM>, more preferably <NUM> to <NUM>. Heating at <NUM> or higher enables the flow of the latex or enables a thermally reactive crosslinker in the core of a capsule to be fixed to the fibres of the fabric.

The viscosity of the inks was measured at <NUM> using a "Robotic Viscometer Type VISCObot" from CAMBRIDGE APPLIED SYSTEMS.

The particle size of the pigment particles in an ink was measured on a ZetasizerTM Nano-S (Malvern Instruments, Goffin Meyvis).

Ink stability was evaluated numerically and visually. If the relative viscosity of the ink increases more than <NUM>% after being stored for <NUM> week at <NUM> the ink is called unstable. If the ink solidifies or if phase separation can be seen, the ink is called unstable.

Test images were printed with a Fujifilm Dimatix DMP-<NUM> using disposable Standard Dimatix <NUM> pL cartridges that were filled with the ink jet inks of the examples. Prints were done using the Standard Tickle <NUM> waveform and cartridge settings. After printing on a fabric, the ensemble was dried for <NUM> at <NUM> and a dry crock test is done according to ISO105-X12. Coloration of the white rubbing cloth is evaluated based on the ΔE from Cielab measurements as shown in Table <NUM>.

All materials used in the following examples were readily available from standard sources such as Sigma-Aldrich (Belgium) and Acros (Belgium) unless otherwise specified. The water used was demineralised water.

In an Erlenmeyer of <NUM> the following compounds were weighed:
<NUM> of Vylon <NUM>, <NUM> of Ymer N120, and <NUM> of acetone. The Ymer N120 was preheated in an oven at <NUM>, in order to obtain a liquid which can be easily handled. The mixture weighed in the Erlenmeyer was stirred using a magnetic stirrer and heated to <NUM>. A clear solution was obtained and cooled to room temperature which will be later on used in the reaction. In a <NUM> <NUM> necked round bottom flask equipped with a coiled condenser and stirrer, <NUM> of Genocure MDEA was added. The prepared polyol solution (Vylon <NUM> + Ymer N120) was added to Genocure MDEA present in the <NUM> <NUM> necked round bottom flask. <NUM> of DBTL was diluted in <NUM> of acetone and also added to the polyol mixture. Then the reactor was heated to <NUM> during appr. <NUM> minutes, allowing the Genocure MDEA to dissolve homogenously. Subsequently <NUM> of IPDI was added dropwise via an addition funnel with pressure equalization arm during <NUM> minutes. The amount isocyanate added was an excess towards the hydroxyl amount, ie. NCO/OH = <NUM>). The reaction was allowed to take place during <NUM> hours at <NUM>. The isocyanato terminated pre-polymer and free IPDI which was available in excess was then further reacted using a diol as chain extender. As diol <NUM> of <NUM> BD was used. The reaction mixture was cooled to <NUM>, in order to avoid evaporation of acetone. The reaction mixture was then allowed to react overnight during <NUM> hours at <NUM> s in order to reach full conversion.

From the solution <NUM> (<NUM>% solids) was weighed in a stainless steel vessel and <NUM> of acetic acid was added to acidify the amine groups from the Genocure MDEA present in the polyurethane resin. Subsequently the water based dispersion was made using Disperlux equipment adding water during high shear mixing. Under stirring at <NUM> RPM using a <NUM> diameter dissolver stirrer <NUM> of water was added during <NUM> minutes to the <NUM> of acidified PU solution. The acetone in the obtained dispersion was evaporated on a rotary evaporator. In order to avoid foaming the evaporation was started at a lower vacuum. The evaporation was stopped when also water was evaporated at a pressure of <NUM> mbars and a <NUM> heating bath. Based on the weight the concentration was corrected by adding water to <NUM>%. The exact solid content was determined by drying <NUM> of solution on an aluminum dish at <NUM> during <NUM> minutes. The solid content obtained was <NUM> %. The pH measured <NUM>. Particle size measurement using Zetasizer: <NUM>.

<NUM> (<NUM> mol) (<NUM>-acrylamidopropyl)trimethylammonium chloride is dissolved in <NUM> isopropanol. <NUM> (<NUM> mol) dodecyl amine and <NUM> (<NUM> mol) triethyl amine were added and the mixture was heated to <NUM> for <NUM> hours. The solvent was removed under reduced pressure. DISP-<NUM> was used as pigment dispersant without further purification.

<NUM> of Chromofine Magenta <NUM> was added to a solution of <NUM> DISP-<NUM> in <NUM> water. <NUM> <NUM> yttrium stabilized zirconia beads ("high wear resistant zirconia grinding media" from TOSOH Co. ) was added and the pigment was milled for <NUM> days on a roll mill. The zirconia beads were removed by filtration and the dispersion was filtered over a <NUM> filter. The dispersion MAG-<NUM> had an average particle size of <NUM>.

The magenta pigment dispersion, described above, was used for the formulation of a cationic magenta ink MAGINK-<NUM> as displayed in Table <NUM>. All weight percentages are based on the total weight of the inkjet ink.

All components were mixed and stirred for <NUM> minutes. The ink MAGINK-<NUM> was filtered over a <NUM> micron filter. The viscosity at <NUM> was <NUM> mPas.

A solid area of MAGINK-<NUM> was printed on an untreated cotton (SUBST-<NUM>) and on a mixed fiber (SUBST-<NUM>) fabrics, using a DimatixTM DMP2831 system, equipped with a standard DimatixTM <NUM> pl print head. The ink was jetted at <NUM>, using a firing frequency of <NUM>, a firing voltage of <NUM> V and a standard waveform. All nozzles printed smoothly.

The printed image was dried and given a thermal treatment at <NUM> for <NUM> minutes. The dry crock fastness was measured on both the cotton and mixed fibre. On both fabrics a score of <NUM> to <NUM> was obtained, showing that the inventive ink MAGINK-<NUM> has an acceptable crock performance on both cotton and mixed fibre fabrics. (ΔE = <NUM> on SUBST-<NUM> and ΔE = <NUM> on SUBST-<NUM>).

Claim 1:
An aqueous pigment dispersion, comprising at least one dispersing agent having the general formula I.
<CHM>
wherein
R<NUM> is selected from the group consisting of a hydrogen, an unsubstituted alkyl group, an unsubstituted alkenyl group, an unsubstituted alkynyl group, an unsubstituted aralkyl group, an unsubstituted alkaryl group and an unsubstituted (hetero)aryl group
L represents a divalent linking group comprising <NUM> to <NUM> carbon atoms
R<NUM>, R<NUM> and R<NUM> are independently selected from the group consisting of an unsubstituted alkyl group, an unsubstituted alkenyl group, an unsubstituted alkynyl group, an unsubstituted aralkyl group, an unsubstituted alkaryl group and an unsubstituted (hetero)aryl group
Any of R<NUM>, R<NUM> , R<NUM> , R<NUM> and L may represent the necessary atoms to form a five to eight membered ring
R<NUM> represents an unsubstituted alkyl group comprising at least <NUM> carbon atoms X- represents an anion to compensate the positive charge of the ammonium group.