Pretreatment composition for inkjet printing

Abstract

A pretreatment composition for inkjet printing comprises water, a water-soluble polyvalent metal salt, a wax, a nonionic dispersant, and resin particles stabilized by nonionic groups or nonionic or amphiphilic compounds. A fluid kit comprising the pretreatment composition and water-based inkjet ink is suitable for printing liners for corrugated packaging, folding cardboard, or corrugated cardboard.

Description

Technical Field

[0001] This invention relates to pre-coating compositions suitable for inkjet recording, and more specifically for inkjet printing on liners used in corrugated packaging, folding boards, and corrugated cardboard. Background Technology

[0002] The field of digital pre-printing for liners used in corrugated packaging and corrugated cardboard is growing rapidly. Pre-printing with a primer or pre-coating improves the image quality of images printed on the pre-coating. The possibility of applying a pre-coating only to the portion that will carry the image reduces the consumption of pre-coating.

[0003] Inkjet printing is a growing field of printing for corrugated packaging liners and corrugated cardboard. In printing for corrugated cardboard liners, flexographic or offset printing is typically used to apply a pre-coating or primer.

[0004] To obtain high-quality images, a pre-coating is a composition that can receive ink and retain colorants in the ink to a greater extent than a substrate without pre-coating. In particular, the pre-coating can hold colorants at or near the surface of the substrate, thereby improving the optical density and color gamut of the printed image compared to a porous substrate without pre-coating.

[0005] WO 2018 / 017089 describes a sprayable pre-coating for corrugated cardboard or boxboard packaging as packaging material. The pre-coating composition contains a polyvalent metal salt, wax, dispersant, latex, and water. The latex contains monomers such as styrene, 1,3-butadiene, acrylonitrile, or combinations thereof. The ability to fix colored pigments to the substrate remains moderate, resulting in images that are easily rubbed off the substrate.

[0006] WO2019 / 013785 describes a treatment composition for packaging liners comprising a fixative, a wax, and a latex. The latex is stabilized by anionic groups (e.g., anionic groups derived from carboxyl groups). The image quality of images obtained by spraying water-based inks onto the treatment composition still faces the problems of mottling and poor ink spreading of water-based inks, which result in uneven color density in solid areas of the printed image.

[0007] There is still a need for a pretreatment composition that produces inkjet-printed images with acceptable image quality and exhibits increased resistance to wiping the image off the pad surface. Summary of the Invention

[0008] The object of the present invention is to provide a solution to the above-mentioned problems. This object has been achieved by providing a pretreatment composition as described in the present invention.

[0009] Another embodiment of the present invention provides a fluid kit containing water-based inkjet ink and a pretreatment composition according to the present invention.

[0010] Another embodiment of the present invention provides a printing method using the pretreatment composition of the present invention as described in the present invention.

[0011] Other features, elements, steps, characteristics, and advantages of the invention will become more apparent from the following detailed description of preferred embodiments of the invention. Attached Figure Description

[0012] Figure 1: A pattern used for inkjet printing during the evaluation of image quality and physical properties of an image obtained with the pretreatment composition. The pattern contains solid areas and negative text of varying sizes, ranging from 1 pt to 16 pt. Detailed Implementation

[0013] A. Fluid kit containing pretreatment composition and water-based inkjet ink

[0014] A. 1. Pretreatment composition

[0015] A.1.1. Resin particles

[0016] The pretreatment composition according to the invention comprises resin particles dispersed in an aqueous medium of the composition. The resin is selected from poly(urethane) and its copolymers, acrylic resins and their copolymers, poly(ester) and its copolymers, poly(styrene) and its copolymers, poly(vinylamide) and its copolymers, poly(vinyl alcohol) derivatives and their copolymers, poly(acetal) and its copolymers, poly(ether) and its copolymers, poly(vinyl ether) and its copolymers, polyvinyl (ester) and its copolymers, poly(imide) and its copolymers, poly(imide) and its copolymers, polycarbonate and its copolymers, poly(vinyl chloride) and its copolymers, poly(amic acid) and its copolymers, poly(sugar) and its derivatives, and cellulose and its derivatives. The resin particles are stabilized by nonionic groups or nonionic or amphiphilic compounds. Nonionic groups should be understood as groups covalently linked to the resin particles.

[0017] To ensure compatibility with fixatives such as polyvalent metal salts or cationic polymers in the pretreatment composition, the resin particles are preferably nonionic and sterically stable.

[0018] This spatial stabilization to obtain an aqueous resin particle dispersion is preferably achieved by covalently linking oligomeric or polymeric groups to the resin particles. Nonionic surfactants can also provide nonionically stabilized resin particle dispersions. If the surfactant is not fixed to the resin particles, poorer water resistance will be obtained. Therefore, the resin particle dispersion is preferably stabilized by nonionic water-soluble groups or polymeric segments covalently linked to the resin particles.

[0019] Resin particle dispersions can be prepared in various ways, such as emulsion copolymerization of acrylic copolymers, solvent methods and subsequent high-shear dispersion for the synthesis of polyurethane dispersions, and Perutz dispersion techniques (e.g., dissolving the polymer in a water-immiscible solvent such as ethyl acetate, dispersing the polymer solution in water and evaporating the water-immiscible solvent).

[0020] For poly(urethane) dispersions, nonionic stabilization can be achieved by using polyether diols in the preparation of the poly(urethane) resin. Preferred polyether diols used in this invention are Ymer N180, Ymer N120, Ymer N90, or Tegomer D3403, i.e., α-[2,2-bis(hydroxymethyl)butyl]-ω-methoxy-poly(oxy-1,2)-ethylenedimethyl. These diols can be prepared from trimethylolpropaneoxetane (TMPO). Possible synthetic procedures are described in Fock, J.; Möhring, V., Polyether-1,2- and -1,3-diols as macromonomers for the synthesis of graft copolymers, 1. Synthesis and characterization of the macromonomers. Die Makromolekulare Chemie 1990, 191 (12), 3045-3057. Generally, other polyether 1,2- or 1,3-diols can also be used.

[0021] The advantage of using 1,2- or 1,3-diols of polyethers is that the side chains of such polyethers provide additional steric stabilization. α,ω-dihydroxy-terminated polyepoxides can also be used, but they are more difficult to orient themselves toward the aqueous phase compared to diols in which both hydroxyl groups are located on one side of the polyether and form graft copolymers during copolymerization.

[0022] Monohydroxy-terminated polyethers can also be used, but block copolymers are provided during copolymerization. Generally, graft copolymers are preferred to achieve steric stabilization with the polyepoxide chains. The polyepoxide segments preferably have a high ethylene glycol content to provide water solubility, especially when the pretreated composition contains a high water content.

[0023] Ymer, a trade name from Perstorp, is a diol based on ethylene oxide and offers good water solubility. These diol telomers are suitable structural units for polycondensation polymerization and the preparation of polyether-grafted polyurethanes, polyesters, or polycarbonates.

[0024] For addition polymerization, such as the preparation of polyacrylates, graft copolymers with polyether side chains can be prepared using monomethacrylate or monoacrylate-terminated polyethers. Examples of suitable macromonomers for addition polymerization include polyethylene glycol monomethacrylate (CAS Registry No. 25736-86-1), polyethylene glycol monoacrylate (CAS Registry No. 26403-58-7), polyethylene glycol monomethyl ether monomethacrylate (CAS Registry No. 26915-72-0), polyethylene glycol methyl ether acrylate (CAS Registry No. 32171-39-4), monomethoxy polyethylene glycol monoglycidyl methacrylate (CAS Registry No. 152952-46-0), α-[2-hydroxy-3-[(1-oxo-2-propenyl)oxy]propyl]-ω-methoxy-poly(oxy-1,2-ethylenediyl) (52656-37-8), and α-(3-carboxyl-1-oxo-2-propenyl-1-yl)-ω-methoxy-poly(oxy-1,2-ethylenediyl). (CAS Registry No. 62884-81-50 or α,α'-(1,4-dioxo-2-butene-1,4-diyl)bis[ω-methoxy-poly(oxy-1,2-ethylenediyl) (CAS Registry No. 164659-91-0).

[0025] Monofunctional ethylene oxide-functional polyethers are also suitable for preparing polyether-grafted polymers via ring-opening polymerization or for use in polymer modification reactions, such as polyethylene glycol monoglycidyl ether (CAS Registry No. 27252-81-90) or α-[(3-methyl-3-oxetyl)methyl]-ω-hydroxy-poly(oxy-1,2-ethylenedimethyl) (CAS Registry No. 84032-51-9).

[0026] Polyether graft copolymers can also be obtained via the reaction of amine-terminated polyethers. Suitable graft copolymers can be obtained by reacting glycidyl or maleic anhydride functional polymers with amine-terminated polyethers. Typical amine-terminated polyethers include, for example, amine poly(ethylene glycol) methyl ether (CAS Registry No. 80506-64-5) and polyethylene glycol 2-aminoethyl ether (CAS Registry No. 32130-27-1).

[0027] Nonionic stabilization of resin particles can also be achieved by incorporating polysaccharides or sugar derivatives such as 2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl D-mannopyranoside (CAS Registry No. 132153-56-1) or α-D-glucopyranoside 6-O-[2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl]-α-D-glucopyranoside (CAS Registry No. 1448612-64-3).

[0028] Spatial stabilization can also be achieved by adding nonionic or amphiphilic compounds such as hydrophilic polymers like polyvinyl alcohol copolymers, cellulose derivatives, dextrin derivatives, or other polysaccharides. Such stabilization is well known for polymer dispersions or emulsions based on vinyl acetate copolymers or homopolymers.

[0029] The preferred resin particle dispersion incorporated into the pretreated composition according to the invention is based on a polyurethane particle dispersion. In polyurethane synthesis, different polyols can be used to obtain suitable physical, mechanical, or optical properties, such as adhesion to the substrate, water resistance, solvent resistance, weather resistance, scratch resistance, gloss, or opacity, etc. Commonly used polyols include: polyether polyols, polyester polyols, polycarbonate polyols, polyamide polyols, polyacrylate polyols, and polyolefin polyols. In addition to polymeric polyols, low molar mass diols and diols with an affinity for the aqueous phase, such as dimethylolpropionic acid, can also be used. For good compatibility with polyvalent salts, water-soluble polyether diols are preferred.

[0030] The desired polyurethane resin (PU) can be obtained by reacting different polyols with diisocyanates, modified isocyanates, or polyisocyanates. Suitable diisocyanates include: isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 2,4,4'-trimethyl-1,6-hexamethylene diisocyanate (TMDI), hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), toluene diisocyanate (TDI), xylene diisocyanate (XDI), and diphenylmethane diisocyanate (MDI). Typically, such PUs are prepared in organic solvents such as acetone or MEK, dispersed in water by adding water under high shear and subsequently evaporating the organic solvent.

[0031] The amount of resin particles in the pre-coating composition is between 1% and 50% by weight, preferably between 5% and 45% by weight, and more preferably between 20% and 40% by weight, relative to the total solid contents of the pre-coating composition. If the pre-coating composition is applied via a spraying technique, amounts exceeding these values ​​will negatively impact the spraying reliability of the pre-coating composition.

[0032] Suitable commercially available PU dispersions include, for example, Vondic 2220 and Vondic 1980NE supplied by Toyobo; Printrite DP375 and Printrite PD379 supplied by Lubrizol; Esacote PU3511 supplied by Lamberti; Neorez R9340 available from DSM; and 2019WTT001-3 available from BASF.

[0033] A.1.2. Nonionic Dispersants

[0034] The pretreatment composition of the present invention further comprises a nonionic dispersant, preferably a nonionic polymeric dispersant.

[0035] Suitable nonionic dispersants include polymeric dispersants, nonionic surfactants, and segmented polymers such as grafted, block, star-branched, comb-shaped, or gradient copolymers. These polymeric dispersants preferably have an amphiphilic structure having at least one segment that is soluble, dispersible, or compatible in an aqueous medium. The medium is not necessarily water, but can also be a mixture with other solvents. In water-based inkjet inks, other water-soluble solvents such as propylene glycol, glycerin, dipropylene glycol monomethyl ether, and 2-hydroxyethylpyrrolidone can be added. At least one segment or portion of the polymeric dispersant should be compatible with the solvent medium of the ink.

[0036] Examples of nonionic surfactants suitable as nonionic dispersants include: alkyl ethoxylates, alkyl aryl ethoxylates, alkyl alkoxylates based on copolymers of ethylene oxide, butane oxide, and / or propylene oxide, tristyryl alkoxylates, and alkylphenol alkoxylates. Most conventional alkoxylated surfactants prepared using different epoxide units are based on EO (ethylene oxide) and PO (propylene oxide), but can also be based on ethylene oxide and butane oxide (BO) or ethylene oxide and styrene oxide (SO). The hydrophilicity of the hydrophilic segment can be altered by changing the number of EO units, but other hydrophilic epoxide units, such as those based on glycidyl, other ethylene oxides, glycerol, glucosinolates, etc., can be used instead of EO. Typical trade names include Lutensol (BASF), Plurafac (BASF), Lucramul (Levaco Chemicals), Tergitol (Dow), Etocas (Croda), Pionin (NOF), Emulsogen (Clariant), and Silco sperse (Keim Additec).

[0037] The hydrophobic portion of a nonionic surfactant can be based on alkyl, aryl, or alkylaryl groups, but it can also be based on more hydrophobic polymer segments, such as polyethers (e.g., polypropylene oxide, polybutane oxide), polyesters (e.g., polycaprolactone), polyacrylates (e.g., PMMA), polystyrene, polyethylene esters, polyethylene ethers, polyurethanes, polyureas, and polyamides.

[0038] Suitable polymer dispersants are amphiphilic dispersants with polymeric or oligomeric hydrophobic segments. They are also known as segmented copolymers. Typical examples include diblock or triblock copolymers based on EO and PO. Typical trade names include Pluronic RPE or Pluronic PE, available from BASF, and Synperonic from Croda. In the case of triblock copolymers, the outer blocks have a different polarity than the middle blocks. The most polar block can be located on the outer side, but it can also be located in the middle as an intermediate block. In addition to diblock and triblock copolymers, multiblock copolymers can also be used.

[0039] Particularly preferred are copolymers based on EO and PO, with an average molecular weight between 3000 g / mol and 10000 g / mol, more preferably between 4000 g / mol and 8500 g / mol, and a PPO / PEO weight ratio between 0.3 and 2.5. Pre-coated compositions of copolymers having these molecular weight ranges and PPO / PEO weight ratios exhibit even better storage stability and image quality. The average Mw (average molar mass) is determined by the number of OH groups (mgKOH / g) obtained by titration, for example using the ISO 4326 method.

[0040] The nonionic dispersant is present in the pretreatment composition in an amount greater than 0% by weight to 40% by weight, more preferably in an amount from 2% by weight to 35% by weight, and most preferably in an amount from 5% by weight to 30% by weight, based on the total dry solids content of the treatment composition.

[0041] The nonionic dispersant is preferably selected from trialkylaryl polyethylene glycol alkyl acrylate and polydimethylsiloxane-co-polyethylene glycol methacrylate. In another aspect of the invention, the dispersant may be a block copolymer-based dispersant.

[0042] Suitable nonionic dispersants include SILCO SPERSE™ HLD-6, available from Silcona GmbH 8 Co., KG (Stromberg, Germany). SILCO SPERSE™ HLD-6 is a nonionic, slightly yellow polymeric dispersant with groups that have high pigment affinity.

[0043] A.1.3. Wax

[0044] The pretreatment composition according to the invention comprises a wax. The wax can improve ink durability during corrugation. Generally, any suitable wax can be used in the pretreatment composition. Therefore, the wax can be polyethylene wax, petroleum wax, paraffin wax, carnauba wax, polypropylene wax, crystalline wax and microcrystalline wax, amide wax (oleamide, stearamide, erucamide, cycloamide, etc.) and combinations thereof. In one aspect of the invention, the wax can be a high-density polyethylene wax. In another aspect, the wax can be a micronized polypropylene wax, such as Mju:Wax 4810 available from Cerona GmbH.

[0045] In one aspect of the invention, the wax may be a polyethylene wax or a modified paraffin wax. Examples of polyethylene waxes include high-density polyethylene (HDPE) wax with a density in the range of about 0.93 g / mL to about 0.97 g / mL. HDPE typically has a higher density than low-density polyethylene (LDPE), at least in part due to the lower degree of molecular branching in HDPE. Examples of modified paraffin wax particles include paraffin waxes that have been modified (e.g., via emulsification) to improve their solubility in water. Modified paraffin waxes may be surface-modified, chemically modified, etc. Some specific examples of waxes that can be used include those from the JONCRYL wax series (such as JONCRYL Wax 22, JONCRYL Wax 26, and JONCRYL Wax 120, available from BASF Corp.), those from the AQUACER series (such as AQUACER 498, AQUACER 501, AQUACER 505, AQUACER 513, AQUACER 530, AQUACER 531, AQUACER 535, AQUACER 537, AQUACER 539, and AQUACER 552, available from BYK-Gardner (Columbia, NY), and Liquilube 404E from Lubrizol. Waxes may also be selected, or otherwise, from water-dispersible waxes available from Micro Powders, Inc. (Talleytown, NY).

[0046] The wax can have i) a high melting temperature T and / or ii) a small average particle size. In one example, the wax can have a high T, such as a T equal to or higher than about 100°C. In another example, the wax's T can be in the range of about 100°C to about 150°C. In yet another example, the wax's T can be in the range of about 110°C to about 135°C. Furthermore, the wax can have an average particle size in the range of 0.03µm to 15µm (assuming that the individual wax particles are not perfectly spherical in terms of effective diameter). In yet another example, the wax particles can have an average particle size of 0.05µm to 10µm, more preferably 0.09µm to 0.50µm (D50). The particle size of the wax can be measured by various techniques, such as dynamic light scattering. If the particle size exceeds these upper limits, spraying reliability issues may arise with the pre-coated composition.

[0047] The wax may be present in the pretreatment composition in an amount ranging from 5 to 25% by weight, more preferably from 10 to 20% by weight, relative to the total solid weight of the pretreatment composition.

[0048] A.1.4. Fixative

[0049] The fixative present in the pretreatment composition is preferably a polyvalent metal salt or a cationic polymer.

[0050] Polyvalent metal salts can be present in pretreatment compositions to improve inkjet printing quality. Typically, the polyvalent metal salt can be any water-soluble polyvalent metal salt. In specific examples, the polyvalent metal salt may include calcium chloride (CaCl2), magnesium chloride (MgCl2), magnesium sulfate (MgSO4), aluminum chloride (AlCl3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), magnesium acetate (Mg(CH3COO)2), zinc acetate (Zn(CH3COO)2), calcium propionate (Ca(C2H5COO)2), or combinations thereof. In a particular example, the polyvalent metal salt may be calcium chloride. In further examples, the polyvalent metal salt may include a metal cation selected from calcium, copper, nickel, magnesium, zinc, barium, iron, aluminum, chromium, or other polyvalent metals.

[0051] Polyvalent metal salts can also contain anions. In some instances, the anion can be fluoride, chloride, iodide, bromide, nitrate, chlorate, sulfate, acetate, or RCOO. -The anion can be a hydrogen atom or any low-molecular-weight hydrocarbon chain, such as C1 to C12. In a more specific example, the anion can be a carboxylate derived from a saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms or a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms. Examples of saturated aliphatic monocarboxylic acids having 1 to 6 carbon atoms can include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, neovaleric acid, and / or hexanoic acid. The cation salt can also be a mixture of two or more different cation salts.

[0052] In some cases, the polyvalent metal salt may be present in an amount from 1% to 99% by weight relative to the total weight of the pretreatment composition. In more specific examples, the polyvalent metal salt may be present in an amount from 5% to 65% by weight, more preferably from 25% to 60% by weight, relative to the solid contents of the pretreatment composition. If this amount is below the lower limit, insufficient fixation of the colorant will result in reduced image quality.

[0053] Suitable cationic polymers for use as fixatives in pretreatment compositions contain guanidine salts or fully quaternized ammonium functionalities, such as quaternized polyamine copolymers. Typically, the weight-average molecular weight (Mw) of the cationic polymer allows for a viscosity of less than 25 cP at 25°C, as measured on a Brookfield viscometer. Typical Mw is less than 500,000, and in some respects, less than 50,000.

[0054] Suitable classes of cationic polymers that may be used include, but are not limited to, quaternized polyamines, dicyandiamide polycations, diallyl dimethyl ammonium chloride copolymers, quaternized dimethylaminoethyl (meth)acrylate polymers, quaternized vinylimidazolium polymers, alkylguanidine polymers, alkoxylated polyethyleneimine and mixtures thereof.

[0055] A.1.5. Medium

[0056] The aqueous pretreatment composition according to the present invention comprises water as a medium. The aqueous medium may comprise one or more water-soluble organic solvents.

[0057] The one or more organic solvents may be added for a variety of reasons. For example, it may be advantageous to add a small amount of organic solvent to improve the solubility of the compound in the pretreated composition to be prepared, to obtain better penetration in porous substrates, or to prevent rapid drying of the pretreated composition at the nozzle of the inkjet head. Preferred water-soluble organic solvents include polyols (e.g., ethylene glycol, glycerol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, tetraethylene glycol). ,threeEthylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,5-pentanediol, 1,2-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 3-methyl-1,3-butanediol and 2-methyl-1,3-propanediol), N-hydroxyethylpyrrolidone, N-butylpyrrolidone, amines (e.g., ethanol) The wetting agent is preferably added to the pre-coating composition formulation in an amount of 0.1 to 25% by weight based on the total weight of the liquid. Alkyl ethers of polyols (e.g., diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether), 2,2'-thiodiethanol, amides such as N,N-dimethylformamide, heterocyclic compounds such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and acetonitrile.

[0058] A.1.6. Additives

[0059] The pretreatment composition may contain surfactants. Any known surfactant can be used, but glycol surfactants and / or ethynyl alcohol surfactants and / or polysiloxane surfactants are preferred. The use of ethynyl glycol surfactants and / or ethynyl alcohol surfactants and / or polysiloxane surfactants will improve drying properties during printing to allow for high-speed printing.

[0060] The acetylenic diol surfactant and / or acetylenol surfactant are preferably selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol, and alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol. These are available from Nissin Chemical Industry, for example, under the Olfine (registered trademark) E series such as Olfine E1010, or from Evonik (formerly Air Products (GB)) under Surfynol (registered trademark) 104, Surfynol 465, and Surfynol 61.

[0061] Biocides can be added to the pre-coating composition to prevent unwanted microbial growth that may occur over time. Biocides can be used alone or in combination. Suitable biocides for use in the inkjet inks of this invention include sodium dehydroacetate, 2-phenoxyethanol, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate, and 1,2-benzisothiazolin-3-one and their salts.

[0062] The preferred biocide is Proxel, which is available from ARCH UK BIOCIDES. TM GXL and Proxel TM Ultra 5 and Bronidox available from COGNIS TM .

[0063] The biocides are preferably added to the aqueous medium in an amount of 0.001 to 3% by weight, more preferably 0.01 to 1.0% by weight, each based on the total weight of the liquid.

[0064] The pre-coating composition may also contain at least one thickener for viscosity adjustment in the liquid. Suitable thickeners include urea or urea derivatives, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, derived chitin, derived starch, carrageenan, amylopectin, protein, poly(styrene sulfonic acid), poly(styrene-co-maleic anhydride), poly(alkyl vinyl ether-co-maleic anhydride), polyacrylamide, partially hydrolyzed polyacrylamide, poly(acrylic acid), poly(vinyl alcohol), partially hydrolyzed poly(vinyl acetate), poly(hydroxyethyl acrylate), poly(methyl vinyl ether), polyvinylpyrrolidone, poly(2-vinylpyridine), poly(4-vinylpyridine), and poly(diallyl dimethyl ammonium chloride).

[0065] Based on the liquid level, the thickener is preferably added in an amount of 0.01 to 20% by weight, more preferably 0.1 to 10% by weight.

[0066] The pre-coating composition may also contain a photothermal conversion agent, which can be any suitable compound that absorbs within the wavelength range emitted by the infrared light source. The photothermal conversion agent is preferably an infrared dye, as this allows for easy handling into a liquid. Suitable examples of infrared dyes are disclosed in

[0179] of WO2015158649.

[0067] Based on the total weight of the liquid, the one or more photothermal conversion agents are preferably present in the range of 0.1 to 10% by weight.

[0068] The pre-coating composition may also contain pigments. Pre-coating compositions containing white pigments are particularly suitable for printing on dark or transparent substrates. Preferred pigments for water-based pre-coating composition inks are titanium dioxide. The titanium dioxide (TiO2) pigment used in this invention can be in rutile or anatase crystalline form. The method for preparing TiO2 is described in more detail in "The Pigment Handbook", Volume I, 2nd Edition, John Wiley & Sons, NY (1988), the relevant disclosure of which is incorporated herein by reference for all purposes as if fully explained.

[0069] Titanium dioxide particles can have a wide range of average particle sizes, from about 1 micrometer to less, depending on the desired end-use application of the pre-coated composition. For applications requiring high opacity or decorative printing applications, titanium dioxide particles preferably have an average size of less than about 1 μm. Preferably, the average particle size is from about 50 to about 950 nm, more preferably from about 75 to about 750 nm, and even more preferably from about 100 to about 500 nm.

[0070] For applications requiring a certain degree of transparency in white, the pigment is preferably "nano" titanium dioxide. The average size of "nano" titanium dioxide particles is typically in the range of about 10 to about 200 nm, preferably about 20 to about 150 nm, and more preferably about 35 to about 75 nm. Inks containing nano titanium dioxide provide improved chroma and transparency while still maintaining good resistance to light fading and a suitable hue angle. A commercially available example of uncoated nano-sized titanium dioxide is P-25, available from Degussa (Parsipani, New Jersey).

[0071] Furthermore, utilizing multiple particle sizes can achieve unique advantages, such as opacity and UV protection. These multiple sizes can be achieved by adding both pigment-grade and nano-grade TiO2.

[0072] Titanium dioxide is preferably incorporated into the pretreatment formulation via a slurry concentrate composition. Based on the total slurry weight, the amount of titanium dioxide present in the slurry composition is preferably from about 15% to about 80% by weight.

[0073] Titanium dioxide pigments may 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, aluminosilicate, boron oxide, and zirconium oxide. These coatings can provide improved properties, including reduced photoreactivity of titanium dioxide. Metal oxide coatings of alumina, aluminosilicate, boron oxide, and zirconium oxide result in a positively charged surface on the TiO2 pigment and are therefore particularly suitable for use in combination with polyvalent metal salts in the pretreatment compositions of the present invention, as no additional surface treatment of the pigment is required.

[0074] Commercially available examples of such coated titanium dioxide include R700 (coated with alumina, available from EI DuPont de Nemours (Wilmington, Delaware)), RDI-S (coated with alumina, available from Kemira Industrial Chemicals (Helsinki, Finland)), R706 (available from DuPont (Wilmington, Delaware)), and W-6042 (nanoscale titanium dioxide treated with silica and alumina, from Tayco Corporation (Osaka, Japan)).

[0075] The pre-coating composition may contain at least one pH adjuster. Suitable pH adjusters include organic amines such as triethanolamine, NaOH, KOH, NET3, NH3, HCl, HNO3, and H2SO4. In a preferred embodiment, the pH of the pre-coating composition is equal to or lower than 9.

[0076] Water-based inkjet ink

[0077] Aqueous inkjet inks used for printing on areas where a pretreated composition has been applied to obtain a printed image contain colorants such as dyes and pigments. Pigments are preferably stabilized by anionic dispersing groups. Pigments may also be further stabilized by polymeric dispersants, surfactants, or combinations thereof to achieve additional colloidal stability. Aqueous media contain water but may contain one or more water-soluble organic solvents. Suitable organic solvents are described in § A.1.5.

[0078] In a preferred embodiment of the invention, the aqueous inkjet ink comprises a resin and / or a wax. Suitable waxes are described in § A.1.3.

[0079] Water-based inkjet inks may also contain surfactants, wetting agents, biocides, resins, and thickeners as additives. Suitable additives are described in § A.1.6.

[0080] A.2.1. Pigments

[0081] Pigments can be black, white, cyan, magenta, yellow, red, orange, purple, blue, green, brown, or mixtures thereof. Colored pigments can be selected from those disclosed in HERBST, Willy et al., Industrial Organic Pigments, Production, Properties, Applications. 3rd ed. Wiley - VCH, 2004. ISBN 3527305769.

[0082] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0083] Pigment particles are dispersed in an aqueous medium using polymeric dispersants, surfactants, or combinations thereof. Self-dispersing pigments may also be used. The latter prevents the polymeric dispersant from interacting with the dispersing groups of binders or capsules that may be contained in the inkjet ink (see below).

[0084] Self-dispersible pigments are pigments with covalently bonded anionic hydrophilic groups or salt-forming groups on their surface, which allow the pigments to be dispersed in aqueous media without the use of surfactants or resins.

[0085] Techniques for preparing self-dispersible pigments are well known. For example, EP1220879A discloses a pigment suitable for inkjet inks, which is linked to a) at least one sterically hindered group and b) at least one organic ionic group and at least one amphiphilic counterion, wherein the amphiphilic counterion has an opposite charge to the organic ionic group. EP906371A also discloses suitable surface-modified colored pigments having linked hydrophilic organic groups containing one or more ionic or ionizable groups. Suitable commercially available self-dispersible colored pigments include, for example, CAB-O-JET from CABOT. TM Inkjet colorant.

[0086] The pigment particles in inkjet inks should be small enough to allow the ink to flow freely through the inkjet printing apparatus, especially at the jet nozzles. Small particles are also desirable for achieving maximum color intensity and slowing down settling.

[0087] The average pigment particle size is preferably between 0.050 and 1 μm, more preferably between 0.070 and 0.300 μm, and particularly preferably between 0.080 and 0.200 μm. Most preferably, the number-average pigment particle size is not greater than 0.150 μm. The average particle size of the pigment particles is measured using a Brookhaven Instruments Particle Sizer BI90plus based on the principle of dynamic light scattering. However, for white pigment inkjet inks, the number-average particle diameter of the white pigment is the same as described in § A.1.6.

[0088] Suitable white pigments are given in Table 2 of WO 2008 / 074548

[0116] . The white pigments are preferably pigments with a refractive index greater than 1.60. The white pigments can be used alone or in combination. Titanium dioxide is preferably used as a pigment with a refractive index greater than 1.60. Suitable titanium dioxide pigments are those disclosed in WO 2008 / 074548

[0117] and

[0118] .

[0089] Special colorants can also be used, such as fluorescent pigments for special effects on clothing, and metallic pigments for printing a luxurious silver and gold look on textiles.

[0090] Suitable polymer dispersants are copolymers of two monomers, but they can contain three, four, five, or even more monomers. The properties of the polymer dispersant depend on the properties of the monomers and their distribution in the polymer. Copolymer dispersants preferably have the following polymer composition:

[0091] Statistical polymerization of monomers (e.g., monomers A and B polymerize to form ABBAABAB);

[0092] Alternating polymerization of monomers (e.g., monomers A and B polymerize to form ABABABAB);

[0093] Gradient (gradual) polymerization of monomers (e.g., monomers A and B polymerize to form AAABAABBABBB);

[0094] Block copolymers (e.g., monomers A and B polymerized into AAAAABBBBBB), where the block length of each block (2, 3, 4, 5 or even more) is important for the dispersing ability of the polymer dispersant;

[0095] Graft copolymers (graft copolymers consist of a polymer backbone and polymer side chains attached to the backbone); and

[0096] These polymers can be mixed forms, such as block gradient copolymers.

[0097] Suitable dispersants include DISPERBYK, which is available from BYK CHEMIE. TM Dispersant, JONCRYL, available from JOHNSONPOLYMERS TM Dispersant and SOLSPERSE available from ZENECA TM Dispersants. MC CUTCHEON. Functional Materials, North American Edition. Glen Rock, NJ: Manufacturing Confectioner Publishing Co., 1990. pp. 110-129 discloses a detailed list of non-polymer dispersants and some polymer dispersants.

[0098] The polymer dispersant preferably has a number average molecular weight Mn between 500 and 30,000, more preferably between 1,500 and 10,000.

[0099] The polymer dispersant preferably has a weight-average molecular weight Mw of less than 100,000, more preferably less than 50,000, and most preferably less than 30,000.

[0100] The pigment is preferably present in an amount ranging from 0.01 to 15% by weight, more preferably from 0.05 to 10% by weight, and most preferably from 0.1 to 5% by weight, each based on the total weight of the inkjet ink. For white inkjet ink, the white pigment is preferably present in an amount ranging from 3% to 40% by weight, more preferably from 5% to 35% by weight of the inkjet ink. An amount less than 3% by weight cannot obtain sufficient hiding power.

[0101] A.2.2. Resin

[0102] The inkjet ink composition according to the present invention may contain a resin suspension. Resin is typically added to inkjet ink formulations to achieve good adhesion of the pigment to the substrate. The resin is a polymer, and suitable resins may be acrylic resins, urethane-modified polyester resins, or waxes.

[0103] The polyurethane resin is incorporated into the ink formulation as a dispersion and may be selected from, for example, aliphatic polyurethane dispersions, aromatic polyurethane dispersions, anionic polyurethane dispersions, nonionic 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, or combinations of two or more of the above.

[0104] A preferred urethane resin for use as a dispersion in the inks of the present invention is a polyester resin comprising structural units containing urethane bonds. Among such resins, water-soluble or water-dispersible urethane-modified polyester resins are preferred. Preferably, the urethane-modified polyester resin comprises at least one structural unit derived from a polyester resin (polyester polyol) containing hydroxyl groups and at least one structural unit derived from an organic polyisocyanate.

[0105] In addition, the polyester resin containing hydroxyl groups is a resin formed by esterification or transesterification between at least one polyacid component and at least one polyol component.

[0106] The preferred polyurethane resin to be included in the ink of the present invention is a polyurethane resin obtained by reacting a polyester polyol, a polyether glycol, a polyol containing an anionic group, and a polyisocyanate. A particularly preferred polyurethane resin is a polyurethane resin obtained by reacting a polyester polyol, a polyether glycol, a polyol containing an anionic group, and a polyisocyanate, wherein the polyester polyol is obtained by reacting an aromatic polycarboxylic acid with a polyol. Suitable polyurethane resins and examples of their preparation are disclosed in unpublished patent application EP16196224.6.

[0107] Some examples of suitable polyurethane dispersions include, for example, NEOREZ R-989, NEOREZ R-2005, and NEOREZ R-4000 (DSM NeoResins); BAYHYDROL UH 2606, BAYHYDROL UH XP 2719, BAYHYDROL UH XP2648, and BAYHYDROL UA XP 2631 (Bayer Material Science); DAOTAN VTW 1262 / 35WA, DAOTAN VTW 1265 / 36WA, DAOTAN VTW 1267 / 36WA, DAOTAN VTW 6421 / 42WA, and DAOTAN VTW6462 / 36WA (Cytec Engineered Materials Inc., Anaheim, CA); and SANCURE 2715, SANCURE 20041, and SANCURE 2725 (Lubrizol Corporation), or combinations of two or more of the above.

[0108] Acrylic resins include polymers of acrylic monomers, polymers of methacrylic monomers, and copolymers of the above monomers with other monomers. These resins exist as suspensions of particles with an average diameter of about 30 nm to about 300 nm. Acrylic latex polymers are formed from acrylic monomers or methacrylic monomer residues. Examples of monomers for acrylic latex polymers, as illustrated, include acrylic monomers such as acrylates, acrylamides, and acrylic acid, and methacrylic monomers such as methacrylates, methacrylamides, and methacrylic acid. Acrylic latex polymers can be homopolymers or copolymers of acrylic monomers with another monomer, such as vinyl aromatic monomers, including but not limited to styrene, styrene-butadiene, p-chloromethylstyrene, divinylbenzene, vinylnaphthalene, and divinylnaphthalene.

[0109] Some examples of suitable acrylic latex polymer suspensions include, for example, JONCRYL 537 and JONCRYL 538 (BASF Corporation, Port ArthurTX); CARBOSET GA-2111, CARBOSET CR-728, CARBOSET CR-785, CARBOSET CR-761, CARBOSET CR-763, CARBOSET CR-765, CARBOSET CR-715 and CARBOSET GA-4028 (Lubrizol Corporation); NEOCRYL A-1110, NEOCRYL A-1131, NEOCRYL A-2091, NEOCRYL A-1127, NEOCRYL XK-96 and NEOCRYL XK-14 (DSM); and BAYHYDROL AH XP 2754, BAYHYDROL AH XP 2741, BAYHYDROL A 2427 and BAYHYDROL A2651 (Bayer) or a combination of two or more of the above.

[0110] The resin concentration in the inkjet ink according to the present invention is at least 1% by weight and preferably less than 30% by weight, more preferably less than 20% by weight.

[0111] The inkjet ink compositions according to the invention may comprise capsules. Capsules, more preferably nanocapsules, are typically incorporated into inkjet ink formulations to encapsulate colorants (US2009227711A, JP2004075759) or to encapsulate crosslinkable reactive components. Particularly useful are the nanocapsules disclosed in WO2015158649 [0037-0110]: said nanocapsules have a polymer shell surrounding a core containing a reactive chemical substance. Shell materials include polyurea, polyurethane, polyester, polycarbonate, polyamide, melamine-based polymers, and mixtures thereof, with polyurea and polyurethane being particularly preferred. Other particularly useful nanocapsules are disclosed in WO2016165970 [0051-0138]: said nanocapsules are self-dispersible and contain dispersive groups covalently coupled to the shell polymer. The nanocapsules in WO2015158649 [0037-0110] and WO2016165970 [0051-0138] contain a core of reactive chemicals capable of forming reaction products upon application of heat and / or light, thereby allowing for the processing of a wide range of substrates. Other suitable reactive chemicals are those activated upon radiation, as described in WO2015158649 [0068-0110].

[0112] Based on the total weight of the ink, the nanocapsules are preferably present in the inkjet ink in an amount not exceeding 30% by weight, preferably between 5% and 25% by weight.

[0113] B. Inkjet recording method

[0114] B.1. Method for applying the pretreatment composition

[0115] The pretreatment compositions according to the present invention are suitable for treating various substrates: porous and non-porous substrates. Porous substrates include paper, paperboard, pulp-lined corrugated cardboard, corrugated cardboard, packaging cardboard, folding cardboard, wood, ceramics, stone, leather, and textiles. Non-porous substrates include metals, glass, polypropylene, polyvinyl chloride, PET, PMMA, polycarbonate, polyamide, polystyrene, or copolymers thereof.

[0116] The pretreatment composition is particularly suitable for spraying onto paper intended for packaging applications. The paper can be single-layer or multi-layered.

[0117] The paper can be brown kraft paper, white-top paper, or bleached paperboard. It can be made from chemical fibers, wood fibers, or recycled fibers. As an example, the paper can be a liner intended for printing on a page-wide webpress and converting into corrugated boxes. In this regard, the liner can be used as a double-sided liner and can be converted directly in the corrugating machine or laminated onto a double-sided liner after corrugation. The paper can also be paperboard for boxes and other packaging applications.

[0118] All well-known conventional methods can be used to coat or impregnate the pretreatment composition onto the substrate. Examples of methods include air knife coating, doctor blade coating, roller coating, gravure coating, and spray coating. More preferably, the pretreatment composition is applied by means of a spraying technique.

[0119] The pretreatment composition is then applied using an inkjet head or a valve jet head. This method of applying the pretreatment composition according to the image has the advantage of requiring a significantly smaller amount of pretreatment composition compared to other application methods. Using a jet head, the pretreatment composition can be applied to the area of ​​the substrate where the image will be printed. Suitable inkjet head types for applying the pretreatment composition include piezoelectric, continuous, thermal printhead, Memjet, or valve jet types.

[0120] After applying the pretreatment composition to the substrate, the coating is preferably dried at least partially before printing an image onto the treated substrate.

[0121] Prior to the subsequent ink jetting step with colorant-containing ink, the substrate to which the pretreated composition has been applied can be dried and optionally heat-treated. Examples of heating processes include, but are not limited to, hot pressing, atmospheric pressure steaming, high pressure steaming, and THERMOFIX. Any heat source can be used for the heating process; for example, an infrared lamp.

[0122] In another preferred embodiment of the invention, the pretreatment composition is essentially not dried before the image is printed by means of the water-based ink jetting step.

[0123] Ink spraying and drying

[0124] After applying a pretreatment composition to a substrate, the aqueous inkjet ink according to the invention is applied to the substrate, preferably to the portion on which the pretreatment composition has already been applied. The inkjet ink contains a colorant, more preferably a pigment. A preferred method for applying the aqueous inkjet ink is by means of an ink jetting technique.

[0125] The preferred inkjet head for a pretreatment composition printing system is a piezoelectric inkjet head. Piezoelectric inkjet printing is based on the movement of a piezoelectric ceramic transducer when a voltage is applied to it. The application of voltage alters the shape of the piezoelectric ceramic transducer in the printhead, creating a void that is then filled by the pretreatment composition. When the voltage is removed again, the ceramic expands back to its original shape, thereby ejecting droplets of the pretreatment composition from the inkjet head. However, the ejection of the pretreatment composition according to the invention is not limited to piezoelectric inkjet printing. Other inkjet printheads can be used and include various types such as continuous type, thermal printhead type, Memjet type head, and valve jet type.

[0126] C. Example

[0127] C.1. Materials

[0128] Unless otherwise stated, all materials used in the following examples are readily available from standard sources such as Aldrich Chemical Co. (Belgium) and Acros (Belgium). The water used was demineralized water.

[0129] PB15:3 is Hostaperm TM B4G-KR, CI Pigment Blue 15:3 Pigment from CLARIANT.

[0130] Edaplan is Edaplan TM 482 is an abbreviation for polymer dispersant from MUNZING CHEMIE GmbH.

[0131] Proxel is a 5% by weight aqueous solution of 1,2-benzisothiazolin-3-one. Proxel... TM K is derived from YDSCHEMICALS NV.

[0132] Liquilube 404E is a 35% by weight HDPE wax water dispersion from Lubrizol.

[0133] Surfynol 104PG50 is a 50% by weight solution of 2,4,7,9-tetramethyl-5-decyn-4,7-diol in propylene glycol, from Evonik.

[0134] Printrite DP379 is a 30% by weight aqueous dispersion of a polyether-based polyurethane from Lubrizol.

[0135] Styron HPX94 is a 54% by weight aqueous dispersion of poly(styrene-butadiene) from Styron Europe.

[0136] Aquacer 530 is an aqueous dispersion containing 32% by weight of oxidized HDPE wax, sourced from BYK.

[0137] Aquacer 531 is an aqueous dispersion containing 45% by weight of modified PE wax, sourced from BYK.

[0138] Synperonic PE P105 is a PEO / PPO copolymer dispersant with an average Mw of 6500 g / mol and a PPO / PEO weight ratio of approximately 1.00, sourced from Croda.

[0139] Tergitol 15-S-15 is a 100% secondary alcohol ethoxylate dispersant from Dow.

[0140] Emulsogen TS200 is a 100% tristyrene-phenol-polyethylene glycol ether dispersant from Clariant.

[0141] Pluronic L44 is a 100% PEO / PPO copolymer dispersant with an average Mw of 2200 g / mol and a PPO / PEO weight ratio of approximately 1.50, sourced from BASF.

[0142] Pluronic L68 is a 100% PEO / PPO copolymer dispersant with an average Mw of 8750 g / mol and a PPO / PEO weight ratio of approximately 0.25, sourced from BASF.

[0143] Kauropal K933 is a nonionic ethylene oxide mono(2-propylheptyl) ether, derived from BASF.

[0144] Tego Foamex 822 is a polyether siloxane copolymer from Evonik.

[0145] C.2. Evaluation Methods

[0146] C.2.1. Image Quality

[0147] The pretreatment composition was applied to the coated corrugated liner XLHD MMX-Liner HD (180g / m²) from MM Karton using a 4μm spiral rod. 2 Apply the coating to the pad and dry it in an oven at 60°C for 2 minutes.

[0148] After drying the pretreatment composition, the coated pad was printed using an ImageXpert JetXpert with electronics driven by a GIS printhead equipped with a FujiFilm Dimatix Samba printhead (Samba G3L) at 32°C and a firing frequency of 7.8 kHz, employing water-based cyan pigment at droplet volumes between 5.4 and 6.5 pL. The printed image was then dried in an oven at 60°C for 2 minutes. The pattern of the printed material is shown in Figure 1.

[0149] The image quality of printed materials is evaluated by visually analyzing the following three properties: 1) ink spread; 2) ink fixation; and 3) image sharpness.

[0150] Ink Spread: The ink should completely cover the solid areas in the printed image. White lines in solid areas indicate insufficient ink spread. Solid areas are visually inspected and evaluated using a score from 0 (excellent ink spread, complete coverage) to 3 (poor ink spread, more than 20 white lines visible in solid areas).

[0151] Ink Fixing: The ink should evenly and tightly cover the solid areas in the printed image. Uneven patterns in the solid areas indicate insufficient ink fixing. Ink fixing is evaluated by visually inspecting the solid areas and assigning a score from 0 (excellent ink fixing, even coverage) to 3 (poor ink fixing, strong unevenness can be observed).

[0152] Image sharpness: Fine text should be readable. The disappearance of negative text indicates insufficient image sharpness. Image sharpness is evaluated by visually inspecting the negative text and assigning a score from 0 (excellent image sharpness, 6 pt clearly readable) to 3 (poor image sharpness, 16 pt partially or completely covered by ink).

[0153] C.2.2. Water resistance

[0154] The water resistance of printed materials was evaluated by measuring CIELAB ΔE after a water resistance test.

[0155] Water resistance was evaluated by wiping the solid area with a damp cotton swab 10 times. The ΔE of the image was calculated by comparing the CIELAB E values ​​of the solid area of ​​the printed image before and after wet wiping.

[0156] Water resistance should be evaluated according to the criteria shown in Table 1. A good pretreatment composition should provide an acceptable level of water resistance.

[0157] Table 1

[0158] Score Water resistance 0 (Excellent) ΔE<10 1 (Good) 10 ≤ ΔE<20 2 (Medium) 20 ≤ ΔE<40 3 (Poor) ΔE>=40

[0159] C.3. Preparation of the pretreatment composition

[0160] The pretreatment composition is prepared by mixing the ingredients given in Table 2. Weight percentages are relative to the total weight of the pretreatment composition. Raw materials are used as is without any further processing.

[0161] Table 2

[0162]

[0163] A white, opaque liquid was obtained. All of the above pre-coated compositions exhibited good storage stability and showed a stable particle size distribution after aging at 60°C for 1 week.

[0164] The pre-coating composition containing the PPO / PEO copolymer was prepared by mixing the ingredients given in Table 3. Weight percentages are relative to the total weight of the pre-treated composition. The raw materials were used as is without any further processing.

[0165] Table 3

[0166]

[0167] A white, opaque liquid was obtained. All of the above pre-coated compositions exhibited good storage stability and showed a stable particle size distribution after aging at 60°C for 1 week.

[0168] C.4. Preparation of water-based inkjet inks

[0169] In the first step, by using Disperlux TM Yellow mixers mix pigment PB15:3 with dispersant Edaplan and use Dynomill. TMKDL and 0.04mm yttrium-stabilized zirconium beads YTZ TM Concentrated aqueous pigment dispersions are prepared by milling with grinding media (available from TOSOH Corp.). After milling, the dispersions are separated from the beads. The concentrated aqueous pigment dispersions are used as the base for preparing inkjet inks.

[0170] Water-based cyan ink is prepared by diluting the corresponding concentrated pigment dispersion with other ink components according to Table 4 (expressed as a percentage by weight based on the total weight of the ink). Water is added to achieve the desired pigment concentration.

[0171] Table 4

[0172] Components Quantity (by weight) PB15:3 3.0 Edaplan 1.5 Proxel 0.2 1,2-Hexanediol 3.00 Surfynol 104PG50 0.4 Propylene glycol 36.00 Liquilube 404 E 2.86 water 53.04

[0173] The properties of different pretreatment compositions are listed in Tables 5 and 6.

[0174] Table 5

[0175] Pretreatment composition No primer COMP-PC INV-PC1 INV-PC2 INV-PC3 Ink spreading 1 2 0 0 1 Ink Fixing 3 3 0 0 0 Image clarity 0 0 0 0 0 Water resistance 0 2 2 1 2

[0176] As shown in Table 5, the pre-coating composition combining polyether-based polyurethane resin particle dispersion, wax, polyvalent salt, and nonionic dispersant significantly improved image quality in terms of ink spreading and ink setting. Compared to the comparative example, the physical properties of the printed material did not show any negative impact.

[0177] Table 6

[0178] Primer liquid INV-PC4 INV-PC5 INV-PC6 INV-PC7 Ink spreading 0 1 0 1 Ink Fixing 0 0 0 0 Image clarity 0 0 0 0

[0179] As can be seen from Table 6, if the pretreatment composition contains a PPO / PEO block copolymer with Mw between 4000 g / mol and 8500 g / mol and a PPO / PEO weight ratio between 0.3 and 2.5, even better image quality will be obtained than with PPO / PEO block copolymers outside this range.

Claims

1. A pretreatment composition for inkjet printing, the pretreatment composition comprising water, a water-soluble polyvalent metal salt comprising 1% to 99% by weight of the total weight of the pretreatment composition, a wax comprising 5% to 25% by weight of the total solids of the pretreatment composition, a nonionic dispersant comprising 2% to 35% by weight of the total dry solids of the pretreatment composition, and resin particles comprising 1% to 50% by weight of the total solids of the pretreatment composition, wherein the resin is selected from polyurethanes and copolymers thereof, acrylic resins and copolymers thereof, polyesters and copolymers thereof, polystyrene and copolymers thereof, polyvinylamide and copolymers thereof, polyvinyl alcohol derivatives and copolymers thereof, polyacetals and copolymers thereof, polyethers and copolymers thereof, polyimides and copolymers thereof, polyvinyl chloride and copolymers thereof, polyvinylidene chloride and copolymers thereof, polyamic acid and copolymers thereof, polysaccharides and derivatives thereof, wherein the resin particles are stabilized by nonionic groups or nonionic or amphiphilic compounds, and the nonionic dispersant is a PPO / PEO copolymer or an arylethylphenyl polyethylene glycol ether.

2. The pretreatment composition according to claim 1, wherein the polyester is selected from polyvinyl esters and their copolymers, polycarbonates and their copolymers, the polyether is polyvinyl ether or its copolymer, the polyimide is polyimide or its copolymer, and the polysaccharide is cellulose or its copolymer.

3. The pretreatment composition according to claim 1, wherein the nonionic group is selected from grafted polyethylene glycol, cellulose, dextran, sugar derivatives and grafted polyvinyl alcohol.

4. The pretreatment composition according to claim 1, wherein the nonionic or amphiphilic compound is selected from polyvinyl alcohol copolymers and polysaccharide derivatives.

5. The pretreatment composition according to claim 3, wherein the nonionic or amphiphilic compound is selected from polyvinyl alcohol copolymers and polysaccharide derivatives.

6. The pretreatment composition according to claim 4, wherein the polysaccharide derivative is selected from cellulose derivatives, dextran derivatives, and cyclodextrin.

7. The pretreatment composition according to claim 5, wherein the polysaccharide derivative is selected from cellulose derivatives, dextran derivatives, and cyclodextrin.

8. The pretreatment composition according to claim 1, wherein the nonionic dispersant is a PPO / PEO copolymer having an average Mw of 4000 g / mol to 8500 g / mol and a PPO / PEO weight ratio of 0.3 to 3.

0.

9. The pretreatment composition according to claim 1, wherein the pretreatment composition further comprises a pigment.

10. A fluid kit comprising an aqueous pretreatment composition as defined in claim 1 and an aqueous ink comprising a colorant.

11. The fluid kit of claim 10, wherein the water-based ink comprises a resin selected from acrylic resins, urethane resins, and wax.

12. A fluid kit comprising an aqueous pretreatment composition as defined in claim 8 and an aqueous ink comprising a colorant.

13. The fluid kit of claim 12, wherein the water-based ink comprises a resin selected from acrylic resins, urethane resins, and wax.

14. A printing method comprising the steps of: a) applying a pretreatment composition as defined in claim 1 to a substrate; and b) spraying water-based inkjet ink containing colorant onto the applied pretreatment composition; and c) optionally, at least partially, drying the applied pretreatment composition; d) Apply heat to dry the applied pretreatment composition and the sprayed water-based inkjet ink.

15. The printing method of claim 14, wherein the pretreatment composition is applied via a jetting technique.

16. The printing method of claim 14, wherein the substrate is a liner for corrugated packaging, folding cardboard, or corrugated cardboard.

17. The printing method according to claim 14, wherein the water-based inkjet ink comprises pigments and waxes as colorants.

18. A printed pad or corrugated cardboard that can be obtained by the printing method as defined in claim 14.

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