Aqueous ink set for inkjet recording

Abstract

An ink set for inkjet printing, the ink set comprising an ink, the ink comprising water and a pigment, and an aqueous reaction liquid comprising a dispersant, a polycarbodiimide according to Formula I, II, III or IV, or a carbodiimide according to Formula V or VI. Also included is an ink jet recording method using the ink set on a non-absorbent substrate or a low-absorbent substrate. Formula I, formula II, formula III, formula IV and formula V and formula VI

Description

Technical Field

[0001] This invention relates to a water-based ink kit for inkjet printing and an inkjet printing method. Background Technology

[0002] To improve the water and weather resistance of images obtained through inkjet printing, inks using pigments instead of dyes as colorants have been proposed. However, when printing characters or images with pigment-containing inks on low-absorption printing media such as coated paper or resin films, pigment particles often remain on the surface of the printing media after printing. These pigment particles are likely to peel off from the printing media due to rubbing against the image or water contamination of the image.

[0003] To meet these requirements, additional resins or polymers are incorporated into water-based inkjet inks as binders. In some applications, the substrate used is temperature-sensitive, thus limiting the usable drying and optionally curing temperatures. Depending on the specific application requirements, various resin technologies compatible with temperature-sensitive substrates have been disclosed in the prior art.

[0004] Latex-based approaches have been disclosed in patent documents (see WO2018 / 114314A, US 2013 / 0245157A1, and EP3275949A1), offering adhesion capabilities that meet certain physical property requirements for several applications. However, latex-based inkjet inks typically cannot simultaneously improve the water resistance and abrasion resistance of printed images on low-absorbency substrates such as corrugated cardboard or non-absorbent substrates. Furthermore, latex-based inkjet inks often form films in the nozzles of the printhead and in the ink supply source, leading to reliability issues during printing. In industrial applications, system reliability, especially jetting reliability, is crucial. Therefore, further optimized resin technologies remain needed.

[0005] In attempts to improve the abrasion resistance of such pigment ink prints, for example, JP-2011-63016-A and JP-2011-105900-A disclose methods for protecting (fixing) the surface of the print by applying a transparent post-processing fluid to the recording medium after the image has been printed.

[0006] The simplest way to apply a transparent post-processing fluid to a recording medium carrying an inkjet-printed image is to coat the entire surface with the post-processing fluid, as described in US2007 / 0282037A1.

[0007] Commercially available similar overprinting varnishes are available. In this case, the amount of post-processing fluid is significantly greater than if only the post-processing fluid were applied to the inkjet-printed image. Furthermore, the changeover time required for switching between different paper sizes is considerably longer, resulting in lower economic efficiency of the printing process.

[0008] Therefore, it is advantageous to apply post-processing liquid only to the inkjet-printed image. The most suitable technology for applying post-processing liquid to the image is inkjet, and it only requires one additional inkjet head in the printing equipment.

[0009] EP3835376A discloses an ink set for inkjet printing comprising an aqueous composition containing a carbodiimide compound and water, and an aqueous ink containing pigments and vinyl polymers.

[0010] WO2022 / 046112 discloses a crosslinking agent composition comprising linear polycarbodiimide and an aqueous crosslinking agent medium.

[0011] From the perspective of stability and operability in aqueous liquids, the polycarbodiimides disclosed in the aforementioned literature are preferably aqueous polycarbodiimide compounds. Aqueous polycarbodiimide compounds can be water-soluble or water-dispersible. Therefore, aqueous polycarbodiimide compounds include compounds containing hydrophilic groups at their end groups, such as CARBODILITE V-02 (Nisshinbo Chemical Inc.). However, such water dispersibility or water solubility can lead to reduced mechanical durability of wet-printed images.

[0012] Therefore, there remains a strong need for a post-processing solution that improves the mechanical durability of dry and wet printed images and is well-suited for printing via jet printing. Summary of the Invention

[0013] The object of the present invention is to provide a solution to the above-mentioned problems. This object has been achieved by providing an ink set having an aqueous ink and an aqueous reaction liquid, the aqueous reaction liquid comprising polycarbodiimide or carbodiimide and a dispersant as defined in claim 1.

[0014] Another embodiment of the present invention provides a printing method using the ink group of claim 1, as defined in claim 10.

[0015] Other features, elements, steps, characteristics, and advantages of the invention will become more apparent from the following detailed description of preferred embodiments. Specific embodiments of the invention are also defined in the dependent claims. Detailed Implementation

[0016] A. Ink sets for inkjet printing The ink assembly for inkjet printing according to the present invention comprises an aqueous inkjet ink and a reaction solution. The ink contains water and pigment, and the reaction solution comprises water, polycarbodiimide or carbodiimide, and a dispersant.

[0017] A.1. Reaction solution polycarbodiimide or carbodiimide As part of the ink group according to the invention, the reaction solution is used to protect inkjet printed images from dry and wet friction, scratching, water, and solvents. The reaction solution therefore comprises water, a dispersant, and a polycarbodiimide according to formula I, II, III, or IV, or a carbodiimide according to formula V or VI. Formula I Formula II Formula III Formula IV Formula V Style VI in A represents the atomic group existing between the two isocyanate groups in the diisocyanate or polyisocyanate used in the preparation of polycarbodiimide. L, L1, and L2 are independently divalent linking groups, selected from substituted and unsubstituted urethanes, substituted and unsubstituted ureas, substituted and unsubstituted 2-oxazolidinones, substituted and unsubstituted carbodiimides, substituted and unsubstituted amides, substituted and unsubstituted acylureas, and substituted and unsubstituted biurets. R1 and R3 are independently unsubstituted alkyl groups, unsubstituted alkenyl groups, unsubstituted alkynyl groups, unsubstituted aryl or heteroaryl groups, unsubstituted aralkyl groups, unsubstituted alkylaryl groups, and unsubstituted cycloalkyl groups. R2 and R4 are independently substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted aryl or heteroaryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, or substituted or unsubstituted cycloalkyl groups. n is an integer with a value of 1 or greater. Preferably, n is an integer between 2 and 10.

[0018] An example of R2 being a substituted alkyl group is the structure shown in Table 2 with CAS number 2762319-28-6, where R2 is an alkoxylated alcohol (for n = 1) or a poly(alkoxylated) alcohol (for n > 1).

[0019] In a preferred embodiment of the present invention, A is selected from isophorone, 4,4'-dicyclohexylmethane, 2,4,4'-trimethyl-1,6-hexamethylene, hexamethylene, pentamethyl, methylphenylene, xylene, m-tetramethylxylene, and diphenylmethane.

[0020] Unbound by theory, it is believed that polycarbodiimides according to formulas I, II, III, or IV, or carbodiimides according to formulas V or VI, can crosslink with resins present in inkjet inks or reaction solutions, resulting in crosslinked polymer networks. Since carbodiimides do not contain ethylene oxide moieties at both ends and are therefore insoluble or dispersible in aqueous media, the water resistance of the resulting images is significantly improved after drying.

[0021] Suitable commercially available polycarbodiimide or carbodiimide include Carbodilite E-05 from Nisshinbo Chemical according to formula VI and Desmodur X2802 from Covestro according to formula III.

[0022] Other suitable polycarbodiimides with the same end-capped R groups are listed in Table 1.

[0023] Table 1 Suitable polycarbodiimides with different end-capped R groups are listed in Table 2.

[0024] Table 2 Suitable examples of carbodiimides are listed in Table 3.

[0025] Table 3 .

[0026] dispersant The dispersant present in the reaction solution according to the invention is a compound capable of dispersing polycarbodiimides according to formula I, II, III or IV, or carbodiimides according to formula V or VI. Preferably, the dispersant is a polymeric dispersant, more preferably a nonionic polymeric dispersant. A suitable nonionic polymeric dispersant is a water-soluble copolymer selected from PPO / PEO copolymers, arylethylphenyl polyethylene glycol ethers, polycarbodiimides having isocyanate groups at their ends capped with hydrophilic groups such as epoxy alkyl groups, and fatty acid derivatives having an EO / PO moiety.

[0027] Suitable linear PPO-PEO copolymers preferably have 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 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.

[0028] 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, glucosyl, etc., can also be used to replace EO. Typical trade names include Lutensol (BASF), Plurafac (BASF), Tergitol (Dow), Etocas (Croda), Pionin (NOF), Emulsogen (Clariant), and Silco sperse (Keim Additec).

[0029] Other specific examples of water-soluble polymers that can be used in the reaction solution of the present invention include arylethylphenyl polyethylene glycol ethers, such as Lucramul DA554 from LEVACO Chemicals GmbH.

[0030] Particularly preferred are water-soluble linear copolymers based on EO and PO with an average molecular weight between 3000 g / mol and 30000 g / mol, more preferably between 4000 g / mol and 15000 g / mol, and a PPO / PEO weight ratio between 0.1 and 2.5. The average Mw (average molar mass) is determined by the number of OH groups (mg KOH / g) obtained by titration, for example using the ISO 4326 method.

[0031] The water-soluble polymer in the reaction solution of the present invention is preferably nonionic. Due to its nonionic properties, the water-soluble polymer interacts less with the cationic fixative in the pretreatment solution during the drying step of the reaction solution. Therefore, a higher gloss value is obtained.

[0032] The water-soluble polymer is present in the reaction liquid composition in an amount ranging from 1% to 40% by weight, more preferably from 2% to 35% by weight, and most preferably from 5% to 20% by weight, based on the total dry solids content of the treatment composition.

[0033] Water-soluble organic solvents For a variety of reasons, one or more water-soluble organic solvents may be present in the reaction solution from the ink assembly according to the invention. For example, adding a small amount of organic solvent may be advantageous to prevent rapid drying of the reaction solution at the nozzle of the inkjet head.

[0034] Preferred water-soluble organic solvents include polyols (e.g., ethylene glycol, glycerol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, tetraethylene glycol, triethylene 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-hydroxyethyl-pyrrolidone, N-butyl-pyrrolidone, amines (e.g., ethanolamine and 2-(dimethylamino)ethanol), and monohydric alcohols (e.g., methanol, ethanol and butanol). Other examples of solvents listed in the Swiss Category A list and therefore compatible with food packaging include: polyol alkyl ethers (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. These solvents can be used alone or in combination of two or more.

[0035] It is preferable to add an organic solvent to the reaction liquid formulation in an amount of 0.1 to 45% by weight based on the total weight of the liquid.

[0036] wax The reaction liquid contained in the ink assembly according to the invention may contain wax. Wax can improve the durability of printed images. Generally, any suitable wax can be used in the reaction liquid composition. Thus, 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 may be high-density polyethylene wax.

[0037] 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 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.

[0038] Examples of modified paraffin particles include paraffins that have been modified (e.g., via emulsification) to improve their dispersibility in water. Modified paraffins can be surface-modified, chemically modified, etc.

[0039] 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, Maryland), and Liquilube 404E from Lubrizol.

[0040] 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 melting temperature T, such as T equal to or above 90°C. Furthermore, the wax can have an average particle size in the range of 0.03 µm to 1.5 µm, more preferably 0.05 µm to 1 µm (D50) (assuming that the individual wax particles are not perfectly spherical in terms of effective diameter). If the particle size exceeds these upper limits, problems may arise with the spraying reliability of the varnish.

[0041] The wax may be present in the reaction solution in an amount ranging from 0.1 to 10% by weight, more preferably from 0.3 to 5% by weight, relative to the total weight of the reaction solution.

[0042] resin particles Examples of resin particles contained in the reaction solution include well-known resins such as urethane-based resins, acrylic resins, fluorene-based resins, polyolefin-based resins, rosin-modified resins, terpene-based resins, polyester-based resins, polyamide-based resins, epoxy-based resins, and vinyl chloride-based resins. Vinyl chloride-based resins include vinyl chloride copolymers such as vinyl chloride-vinyl acetate copolymers. These resins can be used alone or in combination of two or more.

[0043] In the aforementioned resin particles, the resin contained in the reaction solution is preferably a urethane-based resin, an acrylic resin, or a styrene-acrylic resin.

[0044] As urethane-based resins, commercially available products can be used, such as SUPER FLEX 460, 460s, 840, E-4000 (trade name, manufactured by DKS Co., Ltd.); RESAMINE D-1060, D-2020, D-4080, D-4200, D-6300, D-6455 (trade name, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.); TAKELAC WS-6021, W-512-A-6 (trade name, manufactured by Mitsui Chemicals Polyurethanes INC.); SUNCURE 2710 (trade name, manufactured by LUBRIZOL); and Permalin UA-150 (trade name, manufactured by Sanyo Chemical Industries, Ltd.).

[0045] Acrylic resins are a general term for polymers obtained by polymerizing at least one acrylic monomer, such as (meth)acrylic acid and (meth)acrylate, and examples include (meth)acrylic resins obtained from acrylic monomers, and copolymers of acrylic monomers with monomers other than acrylic monomers (e.g., vinyl-based monomers such as styrene). Acrylamide and acrylonitrile can also be used as acrylic monomers. Acrylic resins can be non-reactive or self-crosslinking. As resin emulsions using acrylic resins as raw materials, commercially available products can be used, examples of which include FK-854 (trade name, manufactured by CHIRIKA.Co., Itd.), Mowinyl 952B, 718A (trade name, manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.), Nipol LX852 and LX874 (trade name, manufactured by ZEON Corporation).

[0046] Examples of styrene-acrylic resins include poly(styrene-alkyl acrylate), poly(styrene-1,3-diene), poly(styrene-alkyl methacrylate), poly(styrene-alkyl acrylate-acrylic acid), poly(styrene-1,3-diene-acrylic acid), poly(styrene-alkyl methacrylate-acrylic acid), poly(styrene-alkyl acrylate-acrylonitrile-acrylic acid), and poly(styrene-1,3-diene-acrylonitrile-acrylic acid). Other examples include poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid), poly(styrene-butadiene-methacrylic acid), poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butyl acrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid), poly(styrene-butyl acrylate-acrylonitrile), and poly(styrene-butyl acrylate-acrylonitrile-acrylic acid). Commercially available styrene-acrylic resins include Neocryl D2101 (Covestro), Bonron PS001, and Bonron PS002 (Mitsui).

[0047] Polyolefin-based resins use olefins such as ethylene, propylene, and butene as the structural backbone, and well-known resins can be appropriately selected. Commercially available products can be used as olefin resins, examples of which include Arrowbase CB-1200 and CD-1200 (trade names, manufactured by UNITIKA LTD.).

[0048] The reaction solution preferably contains resin in an amount of 1% to 30% by weight relative to the total mass of the reaction solution. When the resin content in the reaction solution is within the aforementioned range, the effect of improving the abrasion resistance of the image tends to be more excellent. If the amount is higher than the aforementioned range, problems with the ejection of the reaction solution through the inkjet head may occur.

[0049] Polyether siloxane surfactants The reaction solution according to the invention may contain a polyether siloxane surfactant. A preferred surfactant is that according to formula V: Formula V In formula V, R1 to R9 independently represent alkyl groups having 1 to 6 atoms, preferably methyl groups, or aryl groups, preferably phenyl groups. n and m independently represent integers 0 or greater, but preferably 0 to 8. R10 to R11 independently represent hydrogen atoms or alkyl groups, preferably methyl groups. p and n preferably represent integers 0 or greater.

[0050] If m = 0 and n = 1, the structure is defined as a trisiloxane. If n and m are greater than 0, the structure is defined as a graft copolymer. The polyether units have a degree of polymerization p and a degree of polymerization q. These units can be arranged in a block or random manner. If R10 = R11, the graft contains only one type of epoxide unit. Preferably, graft A contains one or two different types of epoxide units. If graft A contains one type of epoxide, ethylene oxide is preferred. If two types of epoxides are present, ethylene oxide and propylene oxide are preferred. The spacer group m is preferably 2 or 3, prepared from vinyl or allyl-terminated polyethers, respectively.

[0051] Based on the total weight of the liquid, the preferred content of the surfactant based on polyether siloxane is 0.03% by weight or more, more preferably 0.2% by weight or more. If this content is low, the water resistance or wet rubbing resistance of the printed image will be insufficient.

[0052] In addition to compounds of formula V having a trialkylsilyl end group, similar structures may also have an alkyl end group, a substituted alkyl group, an aryl group, or a substituted alkyl group.

[0053] Typical examples of trisiloxane structures include Byk 3450, Byk 3451, Tego wet 260, Tego wet 240, Tego wet KL245, Korasilon additive PS1, and Korasilon additive PS2.

[0054] Typical examples of graft copolymer structures include Tego glide 410, Korasilon addtive PS5, and Coatosil 7607.

[0055] Another usable silicone polyether structure is shown in Formula VI, namely a silicone polyether block copolymer: Formula VI.

[0056] In Formula VI, R1 to R9 independently represent alkyl groups having 1 to 6 atoms, preferably methyl groups, or aryl groups, preferably phenyl groups. n and m independently represent integers 0 or greater, but preferably 0 to 8. R10 to R11 independently represent hydrogen atoms or alkyl groups, preferably methyl groups. p and n preferably represent integers 0 or greater.

[0057] In a typical triblock copolymer, n=0 represents a siloxane-polyether-siloxane triblock copolymer. An example of a block copolymer silicone surfactant is Byk 3420, which has an ABA structure (A=polyether, B=silicone).

[0058] Furthermore, polyether siloxane surfactants can be structures in which both polyether segments and siloxane segments exist as grafts. Examples of polyether siloxanes with siloxane grafts include Byk 3565, Byk 3566, and Byk 3568.

[0059] Polyether siloxane structures can also be designed to have better hydrolytic stability, such as the trade names Silwet HS312 and Silwet HS212 available from Momentive.

[0060] Suitable commercially available surfactants include Olfine PD-501 (Nissin Chemical Industry Co., Ltd.), Olfine PD-570 (Nissin Chemical Industry Co., Ltd.), BYK-333 (BYK Co., Ltd.), BYK-347 (BYK Co., Ltd.), and BYK-348 (BYK Co., Ltd.).

[0061] The presence of polyether siloxane surfactants in the reaction solution of this invention improves abrasion resistance (water resistance) under both dry and wet conditions. Unbound by theory, it is believed that polyether siloxanes reduce the coefficient of friction of the reaction solution coating after drying, thereby reducing the mechanical damage to the image caused by friction.

[0062] Layer thickness The coverage of the dried reaction solution coating is preferably from 0.2 g / m² to 2.5 g / m², more preferably from 0.6 to 2.0 g / m². If the coverage is less than 0.2 g / m², the resistance to dry and wet rubbing will be insufficient. If the coverage is greater than 2.5 g / m², the drying of the applied reaction solution will be slow, which will limit the printing speed.

[0063] A.2. Aqueous pretreatment solution The ink assembly according to the invention may contain an aqueous pretreatment solution to adhere to a substrate before or during inkjet printing of an image. The aqueous pretreatment solution contains water as a medium and a fixative. The aqueous medium may contain one or more water-soluble organic solvents.

[0064] Fixative The fixative present in the pretreatment solution is preferably a polyvalent metal salt, cationic polymer, or organic acid. The fixative acts to agitate, precipitate, or destabilize the ink colorants, thereby fixing them to the substrate. This results in improved image quality (reduced bleeding, reduced coalescence).

[0065] Polyvalent metal salts can be present in the pretreatment solution 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 another polyvalent metal.

[0066] 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.

[0067] In some cases, the polyvalent metal salt may be present in an amount from 1 wt% to 99 wt% relative to the total weight of the pretreatment solution. In more specific instances, the polyvalent metal salt may be present in an amount from 5 wt% to 65 wt%, more preferably from 25 wt% to 60 wt%, relative to the solid contents of the pretreatment solution. If this amount is below the lower limit, insufficient fixation of the colorant occurs, resulting in reduced image quality.

[0068] Suitable cationic polymers for use as fixatives in pretreatment solutions contain guanidine salts or fully quaternized ammonium functional groups, 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 Mws are less than 500,000, and in some respects, less than 50,000.

[0069] 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 (meth)acrylate dimethylaminoethyl ester polymers, quaternized vinylimidazolium polymers, alkylguanidine polymers, alkoxylated polyethyleneimine and mixtures thereof.

[0070] surfactants The pretreatment solution 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.

[0071] 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, 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.

[0072] resin The pretreatment solution may contain resin particles. The resin particles are preferably selected from polyurethane, polyacrylate, or wax. Examples of suitable resin particles are given in section A.1.

[0073] In a preferred embodiment of the invention, the pretreatment solution may contain a water-soluble copolymer selected from PPO / PEO copolymers, arylethylphenyl polyethylene glycol ethers, and fatty acid derivatives having EO / PO moieties. Suitable examples can be found in section A.1.

[0074] additive Pretreatment solutions may also contain biocides, waxes, thickeners, pH adjusters, and corrosion inhibitors.

[0075] The pretreatment solution may contain a thickener to increase the viscosity to the range required by the application method.

[0076] 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.

[0077] Biocides can be added to the pre-coating solution 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.

[0078] 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 .

[0079] 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.

[0080] The pretreatment solution may contain at least one pH adjuster. Suitable pH adjusters include organic amines such as triethanolamine, NaOH, KOH, NET3, NH3, HCl, HNO3, sodium acetate, and H2SO4. In a preferred embodiment, the pH of the pre-coating solution is equal to or lower than 9.

[0081] A.3. Water-based inkjet inks Aqueous inkjet inks, as part of the ink group according to the invention, used for printing at least on areas where a pretreatment solution has been applied to obtain a printed image, contain colorants such as dyes and pigments. The pigments are preferably stabilized by anionic dispersing groups. The pigments may also be further stabilized by polymeric dispersants, surfactants, or combinations thereof to achieve additional colloidal stability.

[0082] The aqueous medium of ink contains water, but may contain one or more water-soluble organic solvents. Suitable water-soluble organic solvents are described in section A.1.

[0083] In a preferred embodiment of the invention, the water-based inkjet ink comprises a resin and / or a wax. Suitable waxes are described in section A.1.

[0084] Water-based inkjet inks may also contain surfactants, wetting agents, biocides, resins, and thickeners as additives.

[0085] A.3.1. Pigments The pigments in the water-based inkjet inks according to the present invention can be black, white, cyan, magenta, yellow, red, orange, purple, blue, green, brown, or mixtures thereof. The 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.

[0086] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0087] 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 interaction between the polymeric dispersant and the dispersing groups of binders or capsules that may be included in the inkjet ink (see below).

[0088] Self-dispersible pigments are pigments that have covalently bonded anionic hydrophilic groups or salt-forming groups on their surface, which allows the pigment to be dispersed in an aqueous medium without the use of surfactants or resins.

[0089] 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.

[0090] The pigment particles in inkjet inks should be small enough to allow the ink to flow freely through the inkjet printing device, especially at the nozzle. Small particles are also desirable for achieving maximum color intensity and slowing down settling.

[0091] 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 BI90plus particle size analyzer based on the principle of dynamic light scattering.

[0092] 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] .

[0093] 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.

[0094] Suitable polymer dispersants are copolymers of two monomers, but they can contain three, four, five, or even more monomers. The properties of a polymer dispersant depend on both the properties of the monomers and their distribution in the polymer. Copolymer dispersants preferably have the following polymer composition: • Statistical polymerization of monomers (e.g., monomers A and B polymerize into ABBAABAB); • Alternating polymerization of monomers (e.g., monomers A and B polymerize to form ABABABAB); • Gradient (conical) polymerization of monomers (e.g., monomers A and B polymerize into AAABAABBABBBB); • Block copolymers (e.g., monomers A and B polymerized into AAAAABBBBBB), where the block lengths (2, 3, 4, 5 or even more) of each block are important for the dispersing ability of the polymer dispersant; • Graft copolymers (graft copolymers consist of a polymer backbone and polymer side chains attached to the backbone); and • These polymers can be in mixed forms, such as block gradient copolymers.

[0095] 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: ManufacturingConfectioner Publishing Co., 1990. pp.110-129 discloses a detailed list of non-polymer dispersants and some polymer dispersants.

[0096] The polymer dispersant preferably has a number average molecular weight Mn between 500 and 30,000, more preferably between 1,500 and 10,000.

[0097] 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.

[0098] 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.

[0099] In a preferred embodiment of the invention, the water-based ink comprises pigment encapsulated in a cross-linked polymer shell. Compared to pigment dispersed in an uncross-linked polymer, the encapsulated pigment provides printed images with improved physical properties such as water resistance and dry rubbing resistance.

[0100] Suitable encapsulating pigments are provided by Lubrizol in Diamond HSDX dispersions and by Fujifilm in RxD pigment dispersions such as APD1000 and APD400 premium dispersions.

[0101] A.3.2. Medium The water-based ink according to the present invention contains water as a medium. The water-based medium may also contain one or more water-soluble organic solvents.

[0102] 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 ink composition to be prepared or to prevent the ink from drying too quickly at the nozzle of the inkjet head. Preferred water-soluble organic solvents are listed in section A.1.

[0103] Preferably, if the ink contains two or more organic solvents, the organic solvent present in the largest quantity has a boiling point of 150°C or higher and 250°C or lower. If the boiling point is below this range, the solvent is highly volatile and may impart an unpleasant odor to the ink. When the boiling point of the solvent is above the stated range, the solvent often cannot be eliminated during the drying step and remains in the printed image, resulting in a reduction in the abrasion and scratch resistance of the printed image. Based on the total weight of the ink, this water-soluble organic solvent is preferably added to the ink composition formulation in an amount of 0.1 to 55% by weight.

[0104] A.3.3. Resin The inkjet ink composition according to the invention may contain a resin. Resin is typically added to inkjet ink formulations to achieve good adhesion of the pigment to the recording medium. The resin is preferably a polymer, and suitable resins may be acrylic-based resins, polyurethane resins, or waxes. The wax in the inkjet ink of the ink group according to the invention will improve the dry and wet abrasion resistance of the printed image.

[0105] The polyurethane resin is to be 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.

[0106] A preferred polyurethane 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.

[0107] 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.

[0108] 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. Examples of suitable polyurethane resins and their preparation are disclosed in unpublished patent application EP16196224.6.

[0109] 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.

[0110] Acrylic-based 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, for example, methacrylates, methacrylamides, and methacrylic acid. Acrylic latex polymers can be homopolymers or copolymers of acrylic monomers with another monomer, such as, for example, vinyl aromatic monomers, including but not limited to styrene, styrene-butadiene, p-chloromethylstyrene, divinylbenzene, vinylnaphthalene, and divinylnaphthalene.

[0111] Some examples of suitable acrylic latex polymer suspensions include, for example, JONCRYL 537 and JONCRYL 538 (BASF, 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); 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 XP 2741, BAYHYDROL A 2427 and BAYHYDROL A2651. (Bayer) or a combination of two or more of the above.

[0112] The inkjet ink composition according to the invention may comprise capsules. Capsules, more preferably nanocapsules, are typically incorporated into inkjet ink formulations to encapsulate colorants (US2009227711A, JP2004075759) or 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].

[0113] Based on the total weight of the ink, the resin is preferably present in the inkjet ink in an amount not exceeding 30% by weight, preferably between 5% and 25% by weight.

[0114] A.3.4. Additives The ink composition may contain surfactants. Any known surfactant may be used, but glycol surfactants and / or ethynyl alcohol surfactants and / or polysiloxane surfactants are preferred. Suitable surfactants are described in section A.2.

[0115] Biocides can be added to inks to prevent unwanted microbial growth that may occur over time. Suitable biocides are listed in section A.2.

[0116] 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 ink.

[0117] Inks may also contain defoamers, anti-corrosion additives, and wetting agents that reduce surface tension, such as 1,2-hexanediol, n-butanol, and n-pentanol.

[0118] B. Recording Method B.1. Method for applying the pretreatment solution The ink assembly according to the invention may include a pretreatment liquid. The pretreatment liquid is preferably applied to the substrate before jetting the inkjet ink. The pretreatment liquid is used to agitate, deposit, or destabilize the ink colorants, thereby fixing them to the substrate. This results in improved image quality (reduced bleeding, reduced coalescence). As part of the ink assembly according to the invention, the pretreatment liquid is suitable for application to various substrates, both absorbent and non-absorbent. A substrate is characterized as absorbent when the amount of water absorbed after a 60-second contact time is at least 10 g / m². Absorbent substrates include paper, cardboard, white-lined cardboard, corrugated cardboard, packaging cardboard, folding cardboard, wood, ceramics, stone, leather, and textiles. Non-absorbent substrates include metals, glass, polypropylene, polyvinyl chloride, PET, PMMA, polycarbonate, polyamide, polystyrene, or copolymers thereof.

[0119] The pretreatment solution is particularly suitable for coating or spraying onto paper intended for packaging applications, more preferably including packaging applications with absorbent substrates such as cardboard, paper liners, corrugated board, packaging board, folding board, and paper. The paper can be single-layer or multi-layered.

[0120] 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 web press 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 the double-sided liner after corrugation. The paper can also be paperboard for boxes and other packaging applications.

[0121] All well-known conventional methods can be used to coat or impregnate the pretreatment liquid onto the substrate. Examples of methods include air knife coating, doctor blade coating, roller coating, gravure coating, and spray coating. More preferably, the pretreatment liquid is applied by means of a spraying technique.

[0122] The pretreatment liquid 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 liquid compared to other application methods. Using the jet head, the pretreatment liquid can be applied to the area of ​​the substrate where the image is to be printed. Suitable inkjet head types for applying the pretreatment liquid include piezoelectric, continuous, thermal printhead, Memjet, valve jet, or flow-through types, as described in Section B.2.

[0123] After applying a pretreatment liquid to the substrate, the coating is preferably dried at least partially before printing an image onto the treated substrate, such as to form a pre-coated layer.

[0124] Prior to the subsequent ink jetting step of applying a colorant-containing ink to the formed pre-coated layer, 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.

[0125] In another embodiment of the invention, the pretreatment composition is essentially not dried before printing the image by means of the water-based ink jetting step.

[0126] B.2. Ink spraying and drying The water-based inkjet ink, which is part of the ink group according to the invention, is applied to a substrate. If a pretreatment liquid has been applied to the substrate, it is preferable to apply the inkjet ink to the portion thereon where the pretreatment liquid has been applied or where a pre-coated layer has been formed. The water-based inkjet ink contains a colorant, more preferably a pigment. A preferred method for applying the water-based inkjet ink is by means of an ink jetting technique.

[0127] 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. The application of voltage alters the shape of the piezoelectric ceramic transducer in the printhead, creating a void that is subsequently filled with water-based inkjet ink. When the voltage is removed again, the ceramic expands to its original shape, thereby ejecting a drop of pretreatment composition from the printhead. However, the ink ejection 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.

[0128] In a preferred embodiment, the printing system may be configured to recycle the aqueous ink prior to printing. An inkjet head particularly suitable for printing the aqueous inkjet inks of the ink group of the present invention is of the type that includes ink recycling within the head, such as the flow-through head disclosed in WO 2006 / 030235 A2 and WO 2006 / 064036 A1. This type of inkjet head is well-suited for integration into a printing system comprising: a flow-through printhead having one or more nozzles for ejecting droplets of aqueous ink onto a pretreatment liquid layer; and an ink circulation system for feeding and circulating ink through the printhead, the ink circulation system comprising an ink tank for holding ink, a supply buffer tank for receiving ink from a main tank and supplying ink to the flow-through printhead, and a return manifold for receiving ink from the flow-through printhead and returning ink to the main ink tank via a pump.

[0129] After applying water-based inkjet ink to at least a portion of a pretreatment liquid or pre-coated layer to form an image, the image is dried.

[0130] The drying step of an image can be performed by applying an airflow or by applying heat. The heating step must be performed using a heat source; examples include forced air heating, radiant heating (such as IR radiation, including NIR-, CIR-, and SWIR radiation), conductive heating, high-frequency drying, and microwave drying. Examples of heating processes include, but are not limited to, hot pressing, atmospheric pressure steaming, high-pressure steaming, and THERMOFIX. The heating process can use any heat source; for example, an infrared lamp.

[0131] B.3. Application of the reaction solution The reaction solution can be applied during or after inkjet printing of the image. Preferably, the reaction solution, which constitutes part of the ink group according to the invention, is applied to at least a portion of the image obtained by spraying the water-based inkjet ink of section A.3. The image can be at least partially dried before the reaction solution is applied.

[0132] The reactive liquid can be coated or printed onto at least a portion of an image using all well-known conventional methods. Examples of methods include air knife coating, doctor blade coating, roller coating, gravure coating, and spray coating. The advantage of coating or printing techniques is that a thick layer of reactive liquid can be obtained in a single pass through the recording medium to ensure sufficient abrasion resistance of the image.

[0133] The reaction solution is preferably applied via a jetting technique, which allows for selective application of the reaction solution onto the image. This preferred method of applying the reaction solution composition according to the image has the advantage of requiring a significantly smaller amount of reaction solution material compared to other application methods.

[0134] The nozzles suitable for spraying the reaction liquid are the same as those described in section B.1.

[0135] Finally, the applied reaction solution is dried according to one of the methods described above for drying the pretreatment solution or water-based inkjet ink.

[0136] C. Example C.1. Materials 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 is demineralized water. •PB15:3 is Hostaperm TM B4G-KR, CI Pigment Blue 15:3 Pigment from CLARIANT. •Edaplan is used for Edaplan TM 482 is an abbreviation for polymer dispersant from MUNZING CHEMIE GmbH. • Proxel is a 5% by weight aqueous solution of 1,2-benzisothiazolin-3-one. TM K is derived from YDSCHEMICALS NV. •Liquilube 404E is a 35% by weight aqueous HDPE wax dispersion from Lubrizol. •Carbodilite V-02 is a resin with carbodiimide groups, both end groups capped with polyoxyethylene groups, and manufactured by Nisshinbo Chemical. • Carbodilite E-05 is a mixture of a resin and a dispersant. The resin has carbodiimide groups and is end-capped at one or both ends with a capping agent different from polyethoxylated alcohols. The dispersant is a resin with carbodiimide groups, end-capped at both ends with polyoxyethylene groups, and manufactured by Nisshinbo. • Desmodur XP2802 is a mixture of a resin and a dispersant, the resin having carbodiimide groups and having one or both end groups capped with a capping agent different from polyethoxylated alcohols according to the structure below, the dispersant being a resin having carbodiimide groups, both end groups capped with polyoxyethylene groups, and manufactured by Covestro. Synperonic PE P105 is a block copolymer of ethylene oxide and propylene oxide, containing 50% EO, with a molecular weight of 6500, and is sourced from Croda GmbH. •Surfynol 104PG50 is a 50% by weight solution of 2,4,7,9-tetramethyl-5-decyn-4,7-diol in propylene glycol, from Evonik. •Printrite DP379 is a 30% by weight aqueous dispersion of a polyether-based polyurethane from Lubrizol. • Aquacer 530 is an aqueous dispersion containing 32% by weight oxidized HDPE wax, sourced from BYK. Kauropal K933 is a nonionic ethylene oxide mono(2-propylheptyl) ether, derived from BASF. • Tego Foamex 822 is a polyether siloxane copolymer from Evonik. •Mg(NO3)2.6H2O is magnesium nitrate hexahydrate, from Merck Group.

[0137] C.2. Evaluation Methods C.2.1. Sample Preparation Samples for image abrasion and water resistance measurements were prepared as follows: A pretreatment solution was applied to a MM Karton XLHD corrugated pad (180 g / m²) using a 4 µm spiral rod. The coated pad was then dried in an oven at 60°C for 2 minutes.

[0138] The inkjet ink was applied to the coating pad using a 10 µm spiral rod. The coated inkjet ink was then dried in an oven at 60 °C for 5 minutes. After the coated inkjet ink had dried, the reaction solution was applied to the dried inkjet ink using a 10 µm spiral rod to achieve a solids coverage of 0.75 g / m². The reaction solution was then dried in a Thermo Scientific™ Heratherm oven.

[0139] C.2.2. Water resistance The water resistance of the samples prepared according to section C.2.1 was evaluated by measuring CIELAB ΔE after wet rubbing.

[0140] Water resistance tests were performed according to ISO 105-X12 using an SDL ATLAS M238AA color fastness tester for rubbing. 0.02-0.04 ml of water was applied to the top of the sample, and the sample surface was then treated with 10 double-pass rubbings using the color fastness tester for rubbing.

[0141] The colorfastness to rubbing was measured 24 hours after the test, and the colorfastness was given as ΔE according to the Cielab color space. The lower the ΔE value, the better the water fastness.

[0142] Water resistance was evaluated according to the standards shown in Table 4. A good pretreatment composition should provide excellent (0) or good (1) levels of water resistance.

[0143] Table 4 score Water resistance 0 (Excellent) ΔE<10 1 (Good) 10 ≤ ΔE<20 2 (Medium) 20 ≤ ΔE<40 3 (Poor) ΔE ≥40 C.3. Preparation of pretreatment solution PL-1 Pretreatment solution PL-1 was prepared by mixing the components given in Table 5. Weight percentages are relative to the total weight of the pretreatment composition. Raw materials were used as supplied without any further processing.

[0144] Table 5: Composition of the pretreatment solution compound Quantity (by weight) Printrite DP 379 17.78 <![CDATA[Mg(NO3)2.6H2O]]> 11.25 Synperonic PE P105 1 Aquacer 530 8 Kauropal K933 0.04 Tego Foamex 822 0.04 1,2-Propanediol 19 1,2-Hexanediol 2.85 Deionized water 40.04 C.4. Preparation of Inkjet Ink INK-1 In the first step, by using Disperlux TM Yellow mixers combine pigment PB15:3 with dispersant Edaplan and 1,2-hexanediol and use Dynomill. TM KDL 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.

[0145] Water-based cyan ink INK-1 was prepared by diluting the corresponding concentrated pigment dispersion with other ink components according to Table 6 (expressed as a percentage by weight based on the total weight of the ink). Water was added to bring the ink to the desired pigment concentration.

[0146] Table 6: Composition of Inkjet Ink INK-1 compound Quantity (by weight) Liquilube 404E 2.86 1,2-Propanediol 36 1,2-Hexanediol 3.0 Surfynol 104PG50 0.4 Proxel K 0.2 PB15:3 3.0 Edaplan 482 1.5 Deionized water Up to 100% by weight C.5. Preparation of the reaction solution The comparative and inventive reaction solutions were prepared by mixing the ingredients given in Table 7. Weight percentages are relative to the total weight of the pretreated compositions. Raw materials were used as supplied without any further processing.

[0147] Table 7: Composition of the Comparative Reaction Solution and the Inventive Reaction Solution C.6. Example 1 The comparative ink set and the inventive ink set for inkjet printing are assembled by combining the pretreatment solution PL-1 prepared above, the inkjet ink INK-1 prepared above, and the corresponding comparative and inventive reaction solutions. Samples are prepared by coating the comparative ink set and the inventive ink set onto a recording medium as described in section C.2.1.

[0148] The water resistance of the printed image was measured as described in section C.2.2. The measured values ​​are listed in Table 8.

[0149] Table 8: Water resistance of printed images using the invented reaction solution and the comparative reaction solution reaction solution Water resistance COMP-V1 3 INV-V1 0 INV-V2 2 COMP-V2 3 INV-V3 0 INV-V4 2 The table leads to the conclusion that the group of inks, including water-based inks and reaction solutions containing carbodiimides according to Formula I or Formula II, does indeed result in printed images exhibiting improved water resistance.

Claims

1. An ink assembly for inkjet printing, the ink assembly comprising ink and an aqueous reaction solution, the ink comprising water and pigment, the aqueous reaction solution comprising a dispersant, a polycarbodiimide according to formula I, II, III or IV, or a carbodiimide according to formula V or VI. Formula I Formula II Formula III Formula IV Formula V Style VI in A represents the atomic group existing between the two isocyanate groups in the diisocyanate or polyisocyanate used in the preparation of polycarbodiimide. L, L1, and L2 are independently divalent linking groups selected from substituted and unsubstituted urethanes, substituted and unsubstituted ureas, substituted and unsubstituted 2-oxazolidinones, substituted and unsubstituted carbodiimides, substituted and unsubstituted amides, substituted and unsubstituted acylureas, and substituted and unsubstituted biurets. R1 and R3 are independently unsubstituted alkyl groups, unsubstituted alkenyl groups, unsubstituted alkynyl groups, unsubstituted aryl or heteroaryl groups, unsubstituted aralkyl groups, unsubstituted alkylaryl groups, and unsubstituted cycloalkyl groups. R2 and R4 are independently substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted aryl or heteroaryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, or substituted or unsubstituted cycloalkyl groups. n is an integer with a value of 1 or greater.

2. The ink group according to claim 1, wherein A is selected from isophorone, 4,4'-dicyclohexylmethane, 2,4,4'-trimethyl-1,6-hexamethylene, hexamethylene, pentamethylene, methylphenylene, xylene, m-tetramethylxylene and diphenylmethane.

3. The ink group according to any one of the preceding claims, wherein the dispersant is a water-soluble copolymer selected from PPO / PEO copolymers, arylethylphenyl polyethylene glycol ethers, fatty acid derivatives having an EO / PO moiety, and polycarbodiimides having an isocyanate group at its end that is capped by a hydrophilic group such as a polyepoxyalkyl group based on ethylene oxide, propylene oxide, glycidyl glycerol, or glycerol, or any hydrophilic polyether.

4. The ink group according to any one of the preceding claims, wherein the reaction solution comprises a polyether siloxane surfactant.

5. The ink group according to any one of the preceding claims, wherein the ink comprises a dispersant containing anionic groups.

6. The ink group according to any one of the preceding claims, wherein the ink comprises a pigment, the pigment being encapsulated in a crosslinked polymer shell.

7. The ink group according to any one of the preceding claims, wherein the ink comprises a water-soluble organic solvent.

8. The ink group according to any one of the preceding claims, wherein the ink further comprises resin particles, said resin being selected from resins containing polyacrylates, resins containing polyurethanes, and waxes.

9. The ink group according to any one of the preceding claims, the ink group further comprising a pretreatment liquid, the pretreatment liquid comprising a fixative selected from polyvalent salts, cationic polymers and organic acids.

10. A recording method, the recording method comprising the following steps: a) Spraying the ink as defined in claims 1 to 9 onto the recording area of ​​the substrate; and b) Optionally, the sprayed ink is at least partially dried by applying heat or an airflow to the area; and b) Adhere to at least a portion of the recording area The reaction solution as defined in claims 1 to 9; and c) Dry the aqueous reaction solution by applying heat or airflow to the recording area.

11. The recording method of claim 10, wherein the pretreatment liquid as defined in claim 9 is adhered to the substrate prior to step a).

12. The recording method according to claim 11, wherein the pretreatment liquid is adhered by a spraying method.

13. The recording method according to claims 11 and 12, wherein the liquid is at least partially dried by applying heat or an airflow to the pretreated liquid.

Images