Fluid set for inkjet printing

Abstract

A fluid set for inkjet printing, which comprises a fluid and an aqueous inkjet ink, the fluid having a compound functionalized with at least two functional groups selected from primary amines or secondary amines, the aqueous inkjet ink comprising a colorant and polymer particles, the polymer particles comprising an oligomer or a polymer, the oligomer or polymer comprising at least three repeating units functionalized with functional groups selected from 1,3-diketones, 0-ketoaldehydes and 1,3-dialdehydes, provided that the active methylene is functionalized with at least one hydrogen. The fluid is preferably a pretreatment liquid or an overcoat liquid.

Description

Technical Field

[0001] The present invention relates to a fluid set comprising a resin-based aqueous inkjet ink. Background Art

[0002] As an alternative to UV-curable technology, the importance of aqueous inkjet technology in industrial applications on non-absorbent substrates has increased rapidly, especially in applications where the toxicology of monomers, photoinitiators, and degradation products formed during curing is of concern.

[0003] Indoor decoration is a typical technical field where odors and volatiles have to be avoided. Resin-based aqueous inkjet technology avoids these problems by design because they are entirely polymer-based. In the prior art, several methods for designing resin-based inks have been disclosed. Most inks are latex-based, for example in WO2018077624A. However, latex-based inks often encounter inkjet reliability problems, which are related to spontaneous film formation at the inkjet head nozzles or colloidal chemical instability due to the interaction between the latex and the pigment dispersion. Therefore, an encapsulation-based method using a core-shell system has been disclosed, where the shell avoids premature film formation.

[0004] Encapsulation-based techniques using the core-shell systems disclosed in WO2015158654A and EP293337A avoid film formation at the nozzles of the inkjet head, but generally require high activation temperatures, making the technique suitable for temperature-resistant applications (such as fabric printing), but not suitable for printing on temperature-sensitive substrates (such as poly(olefins)).

[0005] The compatibility problem with temperature-sensitive substrates has been solved by inks comprising encapsulated polymer β-ketoesters or amides as disclosed in patent application WO2021 / 122411. The reliability of inkjet systems for industrial applications is of utmost importance, including the chemical stability of the ink components. Encapsulated β-ketoesters still have a risk of hydrolysis during long-term storage. Therefore, there is still a need to further optimize the chemical stability of the encapsulated polymers. It has now been found that encapsulated polymers functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes exhibit excellent physical properties while being completely stable against hydrolysis by design. Summary of the Invention

[0006] The object of the present invention is to provide a solution to the above problems. This object is achieved by providing a fluid set as defined in claim 1.

[0007] Another embodiment of the present invention is to provide a printing method using the fluid set of claim 1 as defined in claim 14.

[0008] Other features, elements, steps, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention. Specific embodiments of the present invention are also defined in the dependent claims. Detailed Description

[0009] A. Fluid set according to the present invention

[0010] The fluid set according to the present invention comprises:

[0011] a) a fluid comprising a compound functionalized with at least two functional groups selected from primary amines and secondary amines.

[0012] b) an aqueous inkjet ink comprising a colorant and polymer particles, the polymer particles comprising an oligomer or polymer, the oligomer or polymer comprising at least three repeating units functionalized with a functional group selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes, provided that the active methylene is functionalized with at least one hydrogen.

[0013] The fluid can be 1) a primer or pretreatment liquid that is applied before the aqueous inkjet ink of the fluid set is ejected; 2) an overcoat that is applied after the aqueous inkjet ink of the fluid set is ejected; 3) an inkjet ink that is ejected together with the aqueous inkjet ink of the fluid set and comprises a colorant.

[0014] A.1. Aqueous inkjet ink according to the present invention

[0015] A.1.1. Polymer Particles

[0016] The aqueous inkjet ink of the fluid set according to the present invention comprises a colorant and polymer particles, the polymer particles comprising an oligomer or polymer having at least 3 repeating units comprising a functional group selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes, provided that the active methylene is functionalized with at least one hydrogen.

[0017] Preferably, the oligomer or polymer having at least 3 repeating units comprising a functional group selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes can be obtained by polymerization of monomers according to general formula I

[0018]

[0019] where

[0020] R1 - R3 are independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, and substituted or unsubstituted aryl or heteroaryl,

[0021] The condition is that one of R1 - R3 is functionalized with a functional group selected from acrylate, methacrylate, acrylamide, methacrylamide, styrene, vinyl ether, vinyl ester, itaconate, fumarate, maleate, and maleimide, and the monomer according to general formula I is a monofunctional monomer.

[0022] Either of R1 and R3 may represent an atom necessary for forming a five - to eight - membered ring.

[0023] In a preferred embodiment, R1 and R3 are selected from substituted or unsubstituted alkyl and substituted or unsubstituted aryl, more preferably unsubstituted alkyl or aryl, and most preferably C1 - C4 alkyl. In a particularly preferred embodiment, at least one of R1 and R3 represents an alkyl, more preferably methyl.

[0024] In a particularly preferred embodiment, R2 is functionalized with a functional group selected from acrylate, methacrylate, acrylamide, methacrylamide, styrene, vinyl ether, vinyl ester, itaconate, fumarate, maleate, and maleimide, more preferably acrylate, methacrylate, acrylamide, methacrylamide, and styrene groups, and most preferably acrylamide, methacrylamide, and styrene groups.

[0025] Typical monomers functionalized with a functional group selected from 1,3 - diones, β - ketoaldehydes, and 1,3 - dialdehydes are given in Table 1, but are not limited thereto.

[0026] Table 1

[0027]

[0028]

[0029] In a preferred embodiment, the oligomer or polymer contains at least three repeating units functionalized with a functional group selected from 1,3 - diones, β - ketoaldehydes, and 1,3 - dialdehydes, and the oligomer or polymer contains at least 7 functional groups, more preferably at least 10, and most preferably at least 15 functional groups.

[0030] The oligomer or polymer according to the present invention preferably has a weight - average molecular weight of at least 2000, more preferably 4000, and most preferably between 6000 - 30000.

[0031] The polymer according to the present invention may be a homopolymer or a copolymer of different repeating units.

[0032] The oligomers or polymers according to the invention can be prepared by addition polymerization, polycondensation and ring-opening polymerization of ethylenically unsaturated monomers, with addition polymerization being particularly preferred. In the most preferred embodiment, radical polymerization of ethylenically unsaturated monomers is used to prepare the resins according to the invention. In another embodiment of the invention, the molecular weight of the resins according to the invention is controlled using RAFT reagents, ATRP, nitroxide radical techniques or transfer agents (preferably thiols).

[0033] Particles comprising an oligomer or polymer are preferably dispersed in the aqueous carrier of the inkjet ink, said oligomer or polymer comprising at least three repeating units functionalized with a functional group selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes. The particles are preferably dispersed in the aqueous medium of the inkjet ink by using a dispersant or surfactant.

[0034] The particles preferably have an average particle size of not more than 4 μm, as determined by dynamic light scattering. The nozzle diameter of an inkjet printhead is typically 20 - 35 μm. Therefore, preferably, the average particle size is 0.05 - 2 μm, more preferably 0.10 - 1 μm. Excellent resolution and dispersion stability over time are obtained when the average particle size of the particles is less than 2 μm.

[0035] The particles are preferably present in the aqueous inkjet ink, but can also be present in a primer or overcoat. Based on the total weight of the ink, the amount of particles in the inkjet ink does not exceed 45% by weight, preferably between 5 - 25% by weight. It has been observed that jetting is not always reliable above 30% by weight.

[0036] In a preferred embodiment, the oligomers or polymers according to the invention are preferably encapsulated by polymerization (more preferably by using interfacial polymerization) to form an aqueous dispersion. Encapsulation increases the storage stability of the aqueous inkjet ink due to the formation of a polymer barrier (i.e., the polymer shell of the capsule) between the oligomer or polymer and other compounds in the aqueous inkjet ink.

[0037] The capsules preferably have an average particle size of not more than 4 μm, as determined by dynamic light scattering for the same reasons explained above.

[0038] The capsules are preferably dispersed in the aqueous medium of the inkjet ink using a dispersion group covalently bonded to the polymer shell, or by using a dispersant or surfactant preferably added during or after the formation of the capsules. The dispersion group covalently bonded to the polymer shell is preferably selected from carboxylic acids or their salts, sulfonic acids or their salts, phosphate esters or their salts, phosphonic acids or their salts.

[0039] The dispersing groups can be used in combination with a polymeric dispersant to achieve steric stabilization. For example, the polymeric shell can have covalently bonded carboxylic acid groups that interact with the amine groups of the polymeric dispersant. However, in a more preferred embodiment, no polymeric dispersant is used, and the dispersion stability of the inkjet ink is achieved only by electrostatic stabilization. For example, a slightly basic aqueous medium converts the covalently bonded carboxylic acid groups of the polymeric shell into ionic groups, after which the negatively charged capsules do not have a tendency to coalesce. If a sufficient number of dispersing groups are covalently bonded to the polymeric shell, the capsules become so-called self-dispersing capsules.

[0040] These negatively charged capsule surfaces can also be advantageously used during inkjet printing. For example, a second liquid that is a cationic polymer or a polyvalent salt (such as a pretreatment liquid containing cationic substances) can be used to precipitate the anionic capsules in the inkjet ink printed on top of the second liquid. Due to the immobilization of the capsules, an improvement in image quality can be observed by using this method.

[0041] There is no practical limitation on the type of polymer for the polymeric shell of the capsules. Preferably, the polymer used for the polymeric shell is preferably crosslinked. By crosslinking, more rigidity is built into the capsules, allowing a wider range of temperatures and pressures to be used for processing the capsules in both ink preparation and inkjet printers.

[0042] Preferred examples of the polymeric shell material include polyureas, polyesters, polycarbonates, polyamides, melamine-based polymers, and mixtures thereof, with polyureas being particularly preferred.

[0043] A.1.2. Preparation of the Polymer Particles According to the Invention

[0044] Both chemical and physical methods can be used to prepare oligomers or polymers surrounded by a polymeric shell and containing at least three repeating units functionalized with functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes. Suitable encapsulation methods include complex coacervation, liposome formation, spray drying, and polymerization methods.

[0045] In the present invention, a polymerization method is preferably used because it allows the highest control in the design of the capsules. More preferably, interfacial polymerization is used to prepare the capsules of the present invention. This technique is well known and reviewed by Zhang Y. and Rochefort D. (Journal of Microencapsulation, 29(7), 636 - 649 (2012)) and Salitin (Encapsulation Nanotechnologies, Vikas Mittal (editor), Chapter 5, 137 - 173 (Scrivener Publishing LLC (2013)).

[0046] In interfacial polymerization (e.g., interfacial polycondensation), two reactants meet and react rapidly at the interface of emulsion droplets.

[0047] Typically, interfacial polymerization requires an oil phase to be dispersed in an aqueous continuous phase, or vice versa. Each phase contains at least one dissolved monomer (first shell component) capable of reacting with another monomer (second shell component) dissolved in the other phase. Upon polymerization, a polymer insoluble in both the aqueous and oil phases is formed. As a result, the formed polymer has a tendency to precipitate at the interface of the oil and aqueous phases, where a shell forms around the dispersed phase and grows upon further polymerization. The capsules according to the invention are preferably prepared from an oil dispersion in an aqueous continuous phase.

[0048] Typical polymer shells of capsules formed by interfacial polymerization according to the invention are selected from polyamides, typically prepared from diacyl chlorides or polyacyl chlorides as the first shell component and diamines or oligoamines as the second shell component; polyureas, typically prepared from diisocyanates or oligoisocyanates as the first shell component and diamines or oligoamines as the second shell component; polyurethanes, typically prepared from diisocyanates or oligoisocyanates as the first shell component and diols or oligols as the second shell component; polysulfonamides, typically prepared from disulfonyl chlorides or oligodisulfonyl chlorides as the first shell component and diamines or oligoamines as the second shell component; polyesters, typically prepared from diacyl chlorides or oligodiacyl chlorides as the first shell component and diols or oligols as the second shell component; and polycarbonates, typically prepared from dichloroformates or oligochloroformates as the first shell component and diols or oligols as the second shell component. The shell can be composed of a combination of these polymers.

[0049] In a further embodiment, polymers (such as gelatin, chitosan, albumin, and polyethyleneimine) can be used as the second shell component in combination with diisocyanates or oligoisocyanates, diacyl chlorides or oligodiacyl chlorides, dichloroformates or oligochloroformates, and epoxy resins as the first shell component.

[0050] In a particularly preferred embodiment, the shell is composed of a polyurethane or a combination thereof with a polyurethane. In a further preferred embodiment, a water-immiscible solvent is used for the dispersion step and the water-immiscible solvent is removed by solvent stripping before or after shell formation. In a particularly preferred embodiment, the boiling point of the water-immiscible solvent is below 100 °C at atmospheric pressure. Esters are particularly preferred as the water-immiscible solvent.

[0051] A water-immiscible solvent is an organic solvent that has low miscibility in water. Low miscibility is defined as any water-solvent combination that forms a two-phase system when mixed in a 1:1 volume ratio at 20 °C.

[0052] The core contains an oligomer or polymer having repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes. These are typically incorporated into the capsules by dissolving them in an organic solvent that has low miscibility with water and a boiling point lower than that of water. A preferred organic solvent is ethyl acetate because it also has a low flammability hazard compared to other organic solvents.

[0053] However, in some cases, the organic solvent can be omitted. For example, when the viscosity of the oligomer or polymer having repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes is less than 100 mPa·s, the organic solvent can be omitted.

[0054] The method for preparing the dispersion for the capsules preferably includes the following steps:

[0055] a) Prepare a non-aqueous solution of a first shell component for forming a polymer shell and an oligomer or polymer having repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes in an organic solvent that has low miscibility with water and a boiling point lower than that of water;

[0056] b) Prepare an aqueous solution of a second shell component for forming a polymer shell;

[0057] c) Disperse the non-aqueous solution in the aqueous solution under high shear;

[0058] d) Optionally, strip the organic solvent from the mixture of the aqueous solution and the non-aqueous solution; and

[0059] e) Prepare a polymer shell around the oligomer or polymer having repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes by interfacial polymerization of the first shell component and the second shell component for forming a polymer shell.

[0060] Then, the capsule dispersion can be made into an aqueous inkjet ink by adding, for example, a colorant, water, a wetting agent, a surfactant, etc.

[0061] In a preferred embodiment, the capsules are self-dispersing capsules. To make the capsules self-dispersing, an anionic dispersing group (such as a carboxylic acid or its salt, a sulfonic acid or its salt, a phosphate ester or its salt, or a phosphonic acid or its salt) is coupled to the polymer shell of the capsules to ensure dispersion stability.

[0062] A preferred strategy for incorporating an anionic stabilizing group into the polymer shell of the capsules utilizes a carboxylic acid-functionalized reactive surfactant capable of reacting with isocyanates. This results in an amphoteric type of surfactant that contains at least partially secondary or primary amines. Other reactive surfactants functionalized with a sulfonic acid or its salt, a phosphate ester or its salt, or a phosphonic acid or its salt can be used.

[0063] Several zwitterionic surfactants which are mixtures of surfactants having secondary amines and also containing tertiary amines are commercially available. Foam formation is inhibited in inkjet inks based on capsules prepared by using commercially available zwitterionic surfactants, which is encountered in inkjet printers. Foaming causes problems in ink supply and in degassing which attempts to remove air from the ink, thus leading to unreliable jetting. Therefore, surfactants of formula (I) according to WO2016 / 165970 are preferably used during the encapsulation process of oligomers or polymers comprising at least three repeating units functionalized with functional groups selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes.

[0064] The capsules according to the invention are dispersed in an aqueous medium. The aqueous medium consists of water, but may preferably include one or more water-soluble organic solvents.

[0065] One or more organic solvents may be added for various reasons. For example, it may be advantageous to add a small amount of an organic solvent to improve the solubility of the compounds in the inkjet ink to be prepared, to obtain better penetration in porous substrates or to prevent the ink from drying quickly at the nozzles of the inkjet head. Preferred water-soluble organic solvents are 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, butylene glycol, 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), amines (e.g., ethanolamine and 2-(dimethylamino)ethanol), monohydric alcohols (e.g., methanol, ethanol and butanol), 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 (e.g., N,N-dimethylformamide), heterocycles (e.g., 2-pyrrolidone and N-methyl-2-pyrrolidone) and acetonitrile.

[0066] A.1.3. Colorants

[0067] The colorants in the aqueous inkjet inks according to the invention can be dyes, such as disperse dyes, acid dyes, reactive dyes, and can be pigments, or combinations thereof. Preferably, the colorants in the inkjet inks according to the invention are pigments. The colored inks provide images with extended lightfastness stability and improved water and solvent resistance.

[0068] The pigments of the ink can be black, white, cyan, magenta, yellow, red, orange, purple, blue, green, brown, their mixtures, etc. The colored pigments can be selected from those disclosed by HERBST, Willy et al. in Industrial Organic Pigments, Production, Properties, Applications, 3rd Edition, Wiley-VCH, 2004, ISBN 3527305769.

[0069] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0070] The pigment particles are dispersed in the aqueous medium by a polymeric dispersant or a surfactant. Self-dispersible pigments can also be used. If combined with particles or capsules according to the invention and having anionic dispersing groups, an anionic surfactant is preferably used as the dispersant for the pigments. The latter prevents the interaction of the polymeric dispersant with the dispersing groups of the particles or capsules included in the inkjet ink, since the dispersion stability of the pigments is achieved by the same electrostatic stabilization technique as for the capsules.

[0071] Self-dispersible pigments are pigments having covalently bonded anionic hydrophilic groups (such as salt-forming groups or the same groups used as dispersing groups for the capsules) on their surfaces, which allow the pigments to be dispersed in the aqueous medium without using a surfactant or a resin. Suitable commercially available self-dispersible colored pigments are, for example, CAB-O-JET obtained from CABOT TM Inkjet colorant.

[0072] The pigment particles in the inkjet ink should be small enough to allow the ink to flow freely through the inkjet printing device, especially at the ejection nozzles. It is also desirable to use small particles for maximum color intensity and reduced settling.

[0073] The average pigment particle size is preferably between 0.050 - 1 μm, more preferably between 0.070 - 0.300 μm, and particularly preferably between 0.080 - 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 determined using a Brookhaven Instruments Particle Sizer BI90plus based on the principle of dynamic light scattering. The sample is diluted with water to a pigment concentration of 0.002 wt%. The measurement settings of the BI90plus are: 5 runs at 23 °C, angle 90°, wavelength 635 nm, and graph = correction function.

[0074] Suitable white pigments are given in Table 2 of

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

[0117] and

[0118] of WO 2008 / 074548.

[0075] Special colorants can also be used, such as fluorescent pigments for special effects on clothing, and metallic pigments for printing silver and gold luxury looks on textiles.

[0076] Suitable polymeric dispersants for the pigments are copolymers of two monomers, but they can contain three, four, five or even more monomers. The properties of the polymeric dispersant depend on both the nature of the monomers and their distribution in the polymer. The copolymeric dispersant preferably has the following polymer compositions:

[0077] · Statistically polymerized monomers (e.g., monomers A and B polymerized into ABBAABAB);

[0078] · Alternatingly polymerized monomers (e.g., monomers A and B polymerized into ABABABAB);

[0079] · Gradient (graded) polymerized monomers (e.g., monomers A and B polymerized into AAABAABBABBB);

[0080] · 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 polymeric dispersant;

[0081] · Graft copolymers (graft copolymers consist of a polymer backbone with polymer side chains attached to the backbone); and

[0082] · Mixed forms of these polymers, such as block-gradient copolymers.

[0083] Suitable dispersants are DISPERBYK available from BYK CHEMIE TM dispersant, JONCRYL available from JOHNSON POLYMERS TM dispersant and SOLSPERSE available from Lubrisol TMDispersants. A detailed list of non-polymeric and some polymeric dispersants is disclosed in MCCUTCHEON, Functional Materials, North American Edition, Glen Rock, N.J.: Manufacturing Confectioner Publishing Co., 1990, pages 110 - 129.

[0084] The polymeric dispersant preferably has a number average molecular weight Mn between 500 and 30,000, more preferably between 1,500 and 10,000.

[0085] The polymeric dispersant preferably has a weight average molecular weight Mw less than 100,000, more preferably less than 50,000, and most preferably less than 30,000.

[0086] The pigment is preferably present in the range of 0.01 - 20% by weight, more preferably in the range of 0.05 - 10% by weight, and most preferably in the range of 0.1 - 5% by weight, each based on the total weight of the inkjet ink. For white inkjet inks, the white pigment is preferably present in an amount of 3% - 40% by weight of the inkjet ink, and more preferably 5% - 35%. An amount less than 3% by weight does not achieve sufficient covering ability.

[0087] A.1.4. Additives

[0088] The aqueous inkjet ink according to the present invention contains water, but may include one or more water-soluble organic solvents. Suitable organic solvents are described in §A.1.2.

[0089] The aqueous inkjet ink according to the present invention may also contain a wetting agent. The wetting agent prevents nozzle clogging. This prevention is due to its ability to slow down the evaporation rate of the inkjet ink (especially the water in the liquid). The wetting agent is preferably an organic solvent having a boiling point higher than that of water. Suitable wetting agents include triacetin, N-methyl-2-pyrrolidone, glycerol, urea, thiourea, ethylene urea, alkyl ureas, alkyl thioureas, dialkyl ureas and dialkyl thioureas, diols (including ethylene glycol, propylene glycol, glycerol, butylene glycol, pentylene glycol and hexylene glycol), glycols (including propylene glycol, polypropylene glycol, ethylene glycol, polyethylene glycol, diethylene glycol, tetraethylene glycol) and their mixtures and derivatives. The preferred wetting agent is glycerol.

[0090] Based on the total weight of the liquid, the wetting agent is preferably added to the inkjet ink in an amount of 0.1 - 20% by weight.

[0091] The aqueous inkjet ink according to the present invention may contain a surfactant. Any known surfactant may be used, but glycol surfactants and / or acetylene alcohol surfactants are preferred. The use of acetylene glycol surfactants and / or acetylene alcohol surfactants further reduces bleeding to improve printing quality and also improves the drying properties in printing to allow for high-speed printing.

[0092] The acetylene glycol surfactant and / or acetylene alcohol surfactant is preferably one or more selected from 2,4,7,9-tetramethyl-5-decyn-4,7-diol, an alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 2,4-dimethyl-5-decyn-4-ol, and an alkylene oxide adduct of 2,4-dimethyl-5-decyn-4-ol. These are available, for example, as Olfine (registered trademark) 104 series and E series (e.g., Olfine E 1010) from Air Products (GB), or as Surfynol (registered trademark) 465 and Surfynol 61 from Nissin Chemical Industry.

[0093] The inkjet ink composition according to the present invention may further contain an additional resin. The resin is usually added to the inkjet ink formulation to further 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 polyethylene waxes.

[0094] 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.

[0095] In a preferred embodiment, the inkjet ink according to the present invention is part of an inkjet ink set, more preferably part of a multicolor inkjet ink set including a plurality of inkjet inks according to the present invention. The inkjet ink set preferably includes at least a cyan inkjet ink, a magenta inkjet ink, a yellow inkjet ink, and a black inkjet ink. Such a CMYK-inkjet ink set may also be extended with additional inks (e.g., red, green, blue, purple, and / or orange) to further expand the color gamut of the image. The inkjet ink set may also be extended by a combination of full-density inkjet inks and light-density inkjet inks. The combination of dark and light inks and / or black and gray inks improves the image quality by reduced particle size.

[0096] In a preferred embodiment, the inkjet ink set further includes a white inkjet ink. This allows for obtaining brighter colors, especially on transparent substrates. When observing the image through the transparent substrate, the white inkjet ink may be applied as a primer or on top of the colored inkjet inks.

[0097] The viscosity of the inkjet ink according to the present invention is preferably less than 25 mPa·s at a shear rate of 25 °C and 90 s -1 and more preferably between 2 and 15 mPa·s at a shear rate of 25 °C and 90 s -1 .

[0098] The surface tension of the inkjet ink according to the present invention is preferably in the range of about 18 mN / m to about 70 mN / m at 25 °C, and more preferably in the range of about 20 mN / m to about 40 mN / m at 25 °C.

[0099] A.2. Fluid according to the present invention

[0100] A.2.1. Compounds functionalized with primary or secondary amines

[0101] The fluid according to the present invention comprises a compound functionalized with at least two functional groups selected from primary and secondary amines (more preferably primary amines). The compound functionalized with at least two functional groups selected from primary and secondary amines may be selected from difunctional or polyfunctional low molecular weight compounds and oligomers or polymers.

[0102] In a more preferred embodiment, the amino-functionalized compound is a low molecular weight compound with a functionality of 2-8, more preferably 2-5, and most preferably difunctional or trifunctional. These compounds are more readily available in the market.

[0103] Typical amine-functionalized ink additives are given in Table 2, but are not limited thereto.

[0104] Table 2

[0105]

[0106]

[0107] In a more preferred embodiment, the compound functionalized with at least two functional groups selected from primary and secondary amines is a polymer functionalized with at least 5, more preferably at least 10, and most preferably at least 15 functional groups selected from primary and secondary amines (more preferably primary amines).

[0108] The polymer may be dissolved in the fluid or may be present as dispersed or emulsified polymer particles. Typical polymers useful in formulating the fluid as a primer are selected from poly(allylamine), poly(vinylamine), poly(vinylamine-co-vinylformamide), chitosan, homopolymers or copolymers of 4-aminomethyl-styrene or its salts, 2-aminoethyl-acrylate or its salts, 2-aminoethyl-methacrylate or its salts, 3-aminopropyl-acrylamide or its salts, 3-aminopropyl-methacrylamide or its salts, poly(lysine) or its copolymers, etc.

[0109] In a preferred embodiment, the fluid comprises at least one resin particle functionalized with at least 5, more preferably at least 10, and most preferably at least 15 functional groups selected from primary and secondary amines (more preferably primary amines). Using functionalized resin particles instead of functionalized compounds in the fluid has the advantage of improved rheological behavior, resulting in improved fluid jetting reliability and colloidal stability. This is highly important if the fluid has to be jetted through an inkjet head or a valve jet head in an image forming method, for example if the fluid is an imagewise applied primer (pretreatment liquid), an aqueous inkjet ink or an overcoat.

[0110] The amino-functionalized resin particles can be prepared by derivatization of an amino-functionalized polymer, subsequently dispersing the derivative in an aqueous environment, and optionally subsequently crosslinking the particles. Preferred starting polymers are homopolymers or copolymers of vinylamine or allylamine. Typical examples include poly(allylamine), poly(vinylamine), poly(vinylamine-co-vinylformamide), chitosan, homopolymers or copolymers of 4-aminomethyl-styrene or its salts, 2-aminoethyl-acrylate or its salts, 2-aminoethyl-methacrylate or its salts, 3-aminopropyl-acrylamide or its salts, 3-aminopropyl-methacrylamide or its salts, poly(lysine) or its copolymers, etc. The weight-average molecular weight of the starting polymer is preferably at least 7000, more preferably at least 15000, and most preferably at least 25000.

[0111] Other synthetic strategies include derivatization of a carboxylic acid-functionalized acrylic polymer with azeridine, subsequently emulsifying and optionally crosslinking, emulsion or microemulsion polymerization of an optionally protected amino-functionalized monomer, optionally subsequently deprotecting, post-derivatization of a reactive latex comprising a reactive monomer (e.g. 4-chloromethyl-styrene), and sol-gel based polycondensation based on amino-functionalized alkoxysilanes.

[0112] In a preferred embodiment, the amino-functionalized resin particles are crosslinked. The crosslinked particles provide greater formulation freedom. In fact, due to crosslinking, the resin particles will be more resistant to water-soluble organic solvents present in the ink vehicle. In a further preferred embodiment, at least 5 mol%, more preferably at least 10 mol%, and most preferably at least 20 mol% of the repeating units in the polymeric resin particles are functionalized with functional groups selected from primary and secondary amines.

[0113] The amine can be at least partially neutralized with an acid (e.g. hydrochloric acid, methanesulfonic acid, p-toluenesulfonic acid, phosphoric acid, sulfuric acid) and a carboxylic acid (e.g. acetic acid, citric acid and lactic acid).

[0114] A.2.2. Additives

[0115] The fluid may contain additives specific for the functionalization of the fluid.

[0116] A.2.2.1. Additives for the fluid used as a primer

[0117] If the fluid, which is part of a fluid set according to the invention, is used as a primer, the fluid may further contain a flocculant that reacts with the colorant of the aqueous ink of the fluid set. When the aqueous ink comes into contact with the fluid used as a primer, the flocculant induces an increase in the viscosity of the ink, precipitation, or fixation of the colorant.

[0118] The flocculant is preferably a resin or a polyvalent metal ion. Suitable examples of polyvalent metal ions are water-soluble metal salts formed from divalent or higher-valent metal cations (such as magnesium, calcium, strontium, barium, zirconium, and aluminum) and anions (such as fluoride ion (F - ), chloride ion (Cl - ), bromide ion (Br - ), sulfate ion (SO4 2- ), nitrate ion (NO3 - ), and acetate ion (CH3COO - ).

[0119] These polyvalent metal ions have the function of aggregating the colorant (more specifically, the pigment) by acting on the carboxyl groups on the surface of the pigment in the inkjet ink or on the dispersed polymer of the capsules contained in the ink. As a result, the colorant of the ink is fixed, leading to reduced bleeding and beading. Therefore, it is preferred that the surface of the pigment and / or the dispersed polymer of the capsules (if contained in the ink) in the ink has anionic groups, preferably carboxyl groups.

[0120] The resin used as a flocculant may be selected from starch; cellulosic materials such as carboxymethyl cellulose and hydroxymethyl cellulose; polyurethanes; polysaccharides; proteins such as gelatin and casein; water-soluble naturally occurring polymers such as tannic acid and lignin; and synthetic water-soluble polymers such as polymers containing polyvinyl alcohol, polymers containing polyethylene oxide, polymers formed from acrylic monomers, and polymers formed from maleic anhydride monomers. Other suitable resins are acrylic polymers as described in EP2362014 [0027 - 0030]. The preferred resin is a cationic resin, more preferably a cationically charged polyurethane. The resin content is preferably not more than 20% by weight relative to the total mass (100% by mass) of the fluid used as a primer.

[0121] The fluid used as a primer may also contain a colorant (more specifically, a white colorant) to obtain a vivid colored image when the primer is overprinted with the aqueous inkjet ink of the fluid set according to the present invention on a dark or colored substrate (such as cardboard, black textile... or a transparent substrate). More specifically, the fluid used as a primer preferably contains a white pigment. Suitable white pigments are given in Table 2 of

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

[0117] and

[0118] of WO 2008 / 074548. The titanium dioxide (TiO2) pigments useful in the present invention can be in the rutile or anatase crystal form. The methods for preparing TiO2 are 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 set forth herein.

[0122] The titanium dioxide particles can have a broad average particle size of about 1 micron or less, depending on the desired end-use application of the fluid. For applications requiring high hiding or decorative printing applications, the titanium dioxide particles preferably have an average size of less than about 1 μm. Preferably, the average size of the particles is from about 50 to about 950 nm, more preferably from about 75 to about 750 nm, and still more preferably from about 100 to about 500 nm.

[0123] For applications requiring a white color with a certain degree of transparency, the pigment is preferably “nano” titanium dioxide. The “nano” titanium dioxide particles generally have an average size 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. The fluid containing nano titanium dioxide can provide improved chroma and transparency while still maintaining good lightfastness and proper color angle. An example of a commercially available uncoated nano-scale titanium dioxide is P-25, available from Degussa (Parsippany N.J.).

[0124] In addition, unique advantages such as opacity and UV protection can be achieved with multiple particle sizes. These multiple sizes can be achieved by adding both pigments and nano-scale TiO2.

[0125] Titanium dioxide pigments can also carry one or more metal oxide surface coatings. These coatings can be applied using techniques known to those skilled in the art. Examples of metal oxide coatings include silica, alumina, alumina-silica, boron oxide, and zirconium oxide, among others. These coatings can provide improved properties, including reducing the photoreactivity of titanium dioxide. Metal oxide coatings of alumina, alumina-silica, boron oxide, and zirconium oxide result in a positively charged surface of the TiO2 pigment and are thus particularly suitable for use in combination with compounds functionalized with at least two functional groups selected from primary and secondary amines, which have a positive charge at the typical pH of the primer. Then no additional surface treatment of the pigment is required.

[0126] Commercial examples of such coated titanium dioxides include R700 (alumina-coated, available from E.I. DuPont de Nemours, Wilmington Del.), RDI-S (alumina-coated, available from Kemira Industrial Chemicals, Helsinki, Finland), R706 (available from DuPont, Wilmington Del.), and W-6042 (silica-alumina-treated nanoscale titanium dioxide, obtained from Tayco Corporation, Osaka Japan).

[0127] When a fluid used as a primer is ejected via an inkjet head or a valve jet head, other additives can be added, such as those described in §A.1.4.

[0128] A.2.2.2. Additives for Fluids Used as Aqueous Inkjet Inks

[0129] The fluid that is part of the fluid set according to the invention can also be used as an aqueous inkjet ink in forming an image and is also referred to as a co-reactive inkjet ink due to its ability to react with the first aqueous inkjet ink of the set.

[0130] The fluid used as an inkjet ink preferably contains a colorant as described in §A.1.3. and additives as described in §A.1.4.

[0131] A.2.2.3 Additives for Fluids Used as Outer Coatings

[0132] If the fluid that is part of the fluid set according to the invention is used as an outer coating applied or printed on top of the ejected aqueous inkjet ink according to the invention, the fluid can further contain a resin. Suitable resins can be acrylic-based resins, urethane-modified polyester resins, or polyethylene waxes.

[0133] The polyurethane resin can be incorporated as a dispersion into a fluid formulation used as an outer coating and can be selected, for example, from aliphatic polyurethane dispersions, aromatic polyurethane dispersions, cationic 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 a combination of two or more thereof.

[0134] Some examples of suitable polyurethane dispersions are, for example, NEOREZ R-989, NEOREZ R-2005, and NEOREZ R-4000 (DSM NeoResins); BAYHYDROL UH 2606, BAYHYDROL UH XP 2719, BAYHYDROL UH XP 2648, and BAYHYDROL UA XP 2631 (Bayer Material Science); DAOTAN VTW 1262 / 35WA, DAOTAN VTW 1265 / 36WA, DAOTAN VTW 1267 / 36WA, DAOTAN VTW 6421 / 42WA, DAOTAN VTW 6462 / 36WA (Cytec Engineered Materials Inc., Anaheim CA); and SANCURE 2715, SANCURE 20041, SANCURE 2725 (Lubrizol Corporation), or a combination of two or more thereof.

[0135] The acrylic-based resin includes polymers of acrylic monomers, polymers of methacrylic monomers, and copolymers of the foregoing monomers with other monomers. These resins exist as dispersions of particles having an average diameter of from about 30 nm to about 300 nm. The acrylic latex polymer is formed from acrylic monomer or methacrylic monomer residues. By way of illustration, examples of monomers of the acrylic latex polymer include acrylic monomers (such as acrylates, acrylamides, and acrylic acid), and methacrylic monomers (such as methacrylates, methacrylamides, and methacrylic acid). The acrylic latex polymer can be a homopolymer of an acrylic monomer or a copolymer of an acrylic monomer and additional monomers (such as vinyl aromatic monomers including, but not limited to, styrene, styrene butadiene, p-chloromethylstyrene, divinylbenzene, vinylnaphthalene, and divinylnaphthalene).

[0136] Some examples of suitable acrylic latex polymer suspensions are, for example, JONCRYL 537 and JONCRYL 538 (BASF Corporation, Port Arthur TX); 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 A 2651 (Bayer), or combinations of two or more of the above.

[0137] The concentration of the resin in the fluid used as the outer coating is at least 1% by weight, and preferably less than 30% by weight, more preferably less than 20% by weight.

[0138] The outer coating can be applied to the ejected aqueous inkjet ink by coating techniques or printed using printing techniques (such as: gravure printing, flexographic printing, offset printing or inkjet printing). In a particularly preferred embodiment, inkjet printing is used to print the varnish.

[0139] B. Inkjet printing method

[0140] The fluid set according to the invention is suitable for an inkjet image recording method. The inkjet recording method according to the invention comprises the following steps:

[0141] a) ejecting an aqueous inkjet ink forming part of the fluid set according to the invention onto a substrate (preferably a non-porous substrate), the ink comprising a colorant and a dispersion of particles of an oligomer or polymer containing repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes, more preferably the ink comprises a dispersion of capsules consisting of a polymer shell surrounding a core containing an oligomer or polymer containing repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes; and

[0142] b) When the fluid of the fluid set according to the present invention is applied to a substrate (preferably a non-porous substrate), the fluid serves as a primer, or when applied to a sprayed aqueous inkjet ink, the fluid serves as an overcoat, or when the fluid is sprayed together with an aqueous inkjet ink to form a colored image, the fluid serves as an aqueous inkjet ink, and more particularly as a co-reactive inkjet ink.

[0143] c) The applied fluid set is dried by applying heat, for example to obtain a temperature of at least 60 °C, more preferably at least 80 °C, of the sprayed ink. If the temperature obtained is lower than 60 °C, no crosslinking reaction or an insufficient crosslinking reaction occurs between the particles containing an oligomer or polymer having at least three repeating units functionalized with a functional group selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes and a compound functionalized with at least two functional groups which are primary or secondary amines. Thus, no improvement in the solvent resistance or the adhesion of the sprayed and dried ink occurs.

[0144] In a preferred inkjet recording method, the method comprises the following steps: a) applying the fluid according to the present invention as a primer to a substrate (preferably a non-porous substrate). The fluid contains a compound functionalized with at least two functional groups selected from primary and secondary amines (more preferably primary amines). The fluid can be applied by any suitable coating method or printed using printing techniques (such as: gravure printing, flexographic printing, offset printing or inkjet printing). In a particularly preferred embodiment, inkjet printing is used to spray the fluid, and the compound functionalized with at least two functional groups selected from primary and secondary amines is resin particles. This last way of applying the fluid has the advantage that the amount of fluid required is significantly lower than other application methods for priming the substrate. Optionally, the fluid can be dried by applying heat to dry or semi-dry conditions. b) spraying an aqueous inkjet ink of the fluid set according to the present invention onto the applied fluid, the ink containing a dispersion of particles containing an oligomer or polymer having at least three repeating units functionalized with a functional group selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes, and more preferably the ink contains a dispersion of capsules composed of a polymer shell surrounding a core, the core containing an oligomer or polymer having at least three repeating units functionalized with a functional group selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes; and c) drying the sprayed inkjet ink by applying heat, for example to obtain a temperature of at least 60 °C, more preferably at least 80 °C, of the sprayed ink.

[0145] In another preferred inkjet recording method, the method comprises the following steps: a) forming an image by jetting a fluid set onto a substrate (preferably a non-porous substrate). The fluid of the fluid set contains a compound functionalized with at least two functional groups selected from primary amines and secondary amines (more preferably primary amines) and preferably a colorant. More preferably, the compound is a resin particle. The aqueous inkjet ink of the fluid set according to the present invention contains a dispersion of particles of an oligomer or polymer containing repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes. More preferably, the ink contains a dispersion of capsules composed of a polymer shell surrounding a core containing an oligomer or polymer containing repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes. Jetting the fluid set during image formation can be carried out by sequentially or simultaneously jetting the fluid and the aqueous inkjet ink; and b) drying the jetted fluid set by applying heat, for example to obtain a jetted ink temperature of at least 60 °C, more preferably at least 80 °C.

[0146] In another preferred inkjet recording method, the method comprises the following steps: a) jetting the aqueous inkjet ink of the fluid set according to the present invention onto a substrate (preferably a non-porous substrate). The ink contains a dispersion of particles of an oligomer or polymer containing repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes. More preferably, the ink contains a dispersion of capsules composed of a polymer shell surrounding a core containing an oligomer or polymer containing repeating units functionalized with at least three functional groups selected from 1,3-diketones, β-ketoaldehydes, and 1,3-dialdehydes. Optionally, the inkjet ink can be dried by applying heat to drying or semi-drying conditions; and b) applying the fluid according to the present invention as an overcoat to the jetted aqueous inkjet ink. The fluid contains a compound functionalized with at least two functional groups selected from primary amines and secondary amines (more preferably primary amines). The fluid can be coated by any suitable coating method or printed using printing techniques (e.g., gravure printing, flexographic printing, offset printing, or inkjet printing). In a particularly preferred embodiment, inkjet printing is used to jet the fluid, and the compound functionalized with at least two functional groups selected from primary amines and secondary amines is a resin particle. c) drying the applied fluid set by applying heat, for example to obtain a jetted ink temperature of at least 60 °C, more preferably at least 80 °C.

[0147] In another preferred inkjet recording method, two or three of the above preferred methods can be combined.

[0148] The substrate in the inkjet recording method can be porous, such as textile, paper, leather, and cardboard substrates, but preferably non-absorbent substrates, such as polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polylactide (PLA), or polyimide.

[0149] The substrate can also be a paper substrate, such as plain paper or resin-coated paper, such as polyethylene- or polypropylene-coated paper. There is no practical limitation on the type of paper, and it includes newsprint, blotting paper, office paper, wallpaper, and also includes higher grammage papers, commonly referred to as cardboard, such as white-lined chipboard, corrugated board, and packaging board.

[0150] The substrate can be transparent, translucent, or opaque. Preferred opaque substrates include so-called synthetic papers, such as Synaps from Agfa-Gevaert TM grade, which is an opaque polyethylene terephthalate sheet with a density of 1.10 g / cm 3 or greater.

[0151] Examples of heating methods for drying the fluid set according to the present invention or at least drying the fluid or aqueous inkjet ink include but are not limited to hot pressing, atmospheric steam, high-pressure steam, THERMOFIX. Any heat source can be used for the heating method; for example, an infrared ray source is employed.

[0152] The drying step can be carried out under ambient air, but the heating step to achieve a temperature of at least 60 °C, more preferably 80 °C, for at least one of the applied fluid set or fluid or aqueous inkjet ink must be carried out by using a heat source. Examples of suitable heat sources include devices for forced air heating, radiant heating (e.g., IR-radiation, including NIR radiation and CIR radiation), conduction heating, high-frequency drying, and microwave drying.

[0153] The preferred inkjet head for an inkjet printing system for jetting inkjet ink and optionally a fluid used as a primer and / or overcoat is a piezoelectric inkjet head. Piezoelectric inkjet ejection is based on the movement of a piezoelectric ceramic transducer when a voltage is applied to the piezoelectric ceramic transducer. Applying the voltage changes the shape of the piezoelectric ceramic transducer in the print head, creating a void, which is subsequently filled with ink or liquid. When the voltage is removed again, the ceramic expands to its initial shape, ejecting ink droplets from the inkjet head. However, jetting the aqueous inkjet ink and optionally the fluid according to the present invention is not limited to piezoelectric inkjet printing. Other inkjet print heads can be used and include various types, such as continuous type, thermal print head type, MEM-jet type heads, and valve jet type.

[0154] C. Examples

[0155] C.1. Materials

[0156] Unless otherwise specified, all compounds were supplied by TCI Europe.

[0157] · Desmodur N75 BA is a trifunctional isocyanate supplied by Bayer AG.

[0158] · Lakeland ACP70 is an zwitterionic surfactant supplied by Lakeland Laboratories LTD.

[0159] · Alkanol XC is an anionic surfactant supplied by Dupont.

[0160] · Arquad T-50 is a mixture of cationic surfactants supplied by Akzo Nobel NV.

[0161] · DISP-1 is a PR122 dispersion supplied by Diamond as EXP IJ M03.

[0162] · AminoPOL-1 is an amino-functionalized alkoxysilane homopolymer prepared from aminopropyl-methyl-dimethoxysilane as follows: 35 g of aminopropyl-methyl-dimethoxysilane was dissolved in 65 g of water and the mixture was heated to 70 °C for 24 hours. The evaporated methanol was made up to 100 g of polymer solution with water.

[0163] · KETO-1 is 3-[(4-vinylphenyl)methyl]pentane-2,4-dione and was prepared as follows: 9.8 g of sodium acetylacetonate, 7.15 g of acetylacetone, 0.34 g of sodium iodide and 0.31 g of BHT were dissolved in a mixture of 20 ml of dimethylformamide and 60 ml of acetonitrile. 10.89 g of 4-chloromethyl-styrene was added and the reaction mixture was heated to 80 °C. The reaction was continued at 80 °C for 2 hours. The reaction mixture was cooled to room temperature. 150 ml of water was added and the mixture was extracted twice with 120 ml of toluene. The combined toluene fractions were dried over MgSO4 and evaporated under reduced pressure. 3-[(4-vinylphenyl)methyl]pentane-2,4-dione was purified by preparative column chromatography on a Prochrom LC80 column using Kromasil Si 60A 10 μm as the stationary phase and dichloromethane / hexane 80 / 20 as the eluent. 6.7 g (y: 43.4%) of 3-[(4-vinylphenyl)methyl]pentane-2,4-dione was isolated (TLC analysis on TLC silica gel 60F 254 supplied by Merck, eluent dichloromethane, Rf: 0.55).

[0164] · KETO-4 is N-(2-benzoyl-3-oxo-butyl)prop-2-enamide and is prepared as follows: 175 g of sulfuric acid was cooled to 0 °C. 10.1 g of hydroxymethylacrylamide and 0.66 g of BHT were added, and then 16.2 g of 1-phenylbutane-1,3-dione was added in portions while maintaining the temperature below 5 °C. The reaction was continued at room temperature for 20 hours. The reaction mixture was added to 250 g of ice. The mixture was extracted twice with 250 ml of dichloromethane. The combined dichloromethane fractions were extracted twice with 120 ml of saturated NaHCO3 solution and once with 100 ml of brine. The dichloromethane fraction was dried over MgSO4 and evaporated under reduced pressure. The residue was treated with 120 ml of acetone and 400 ml of n-hexane. The crude N-(2-benzoyl-3-oxo-butyl)prop-2-enamide was separated by filtration. N-(2-benzoyl-3-oxo-butyl)prop-2-enamide was purified by preparative column chromatography on a Graceresolve column, using a gradient elution from dichloromethane to dichloromethane / ethyl acetate 60 / 40. 7.8 g (y: 31%) of N-(2-benzoyl-3-oxo-butyl)prop-2-enamide was isolated (TLC analysis was carried out on TLC silica gel 60F 254 supplied by Merck, eluent dichloromethane / ethyl acetate 70 / 30, Rf: 0.3).

[0165] · Cab-o-Jet 465M is a magenta pigment dispersion supplied by Cabot

[0166] · Cab-O-Jet 450C is a cyan pigment dispersion supplied by Cabot

[0167] · Tego Wet 270 is an ether-modified poly(dimethylsiloxane) supplied by Evonik Industries

[0168] C.2. Measuring methods

[0169] C.2.1. Solvent resistance and water resistance

[0170] The solvent resistance was tested by wiping 40 times on the coating or printed image with isopropyl alcohol and methyl ethyl ketone as solvents or water using a cotton swab (Q-tip).

[0171] A score of 0 means that the coating or image layer is completely dissolved. A score of 1 means that damage is clearly visible when wiped. A score of 2 means that slight damage is visible when wiped. A score of 3 means that there is no or almost no obvious damage to the coating or image.

[0172] Synthesis of the polymer INVPOL-1 of the present invention

[0173] Dissolve 0.94 g of phenoxyethyl acrylate and 3.97 g of 3-[(4-vinylphenyl)methyl]pentane-2,4-dione in 15 ml of ethyl acetate. Add 0.51 g of dodecyl mercaptan and 0.07 g of WAKO V59, and flush the mixture with nitrogen. Allow the polymerization to continue at 75 °C for 20 hours. Then add 0.1 g of WAKO V59, and allow the polymerization to continue at 75 °C for 4 hours. Cool the reaction mixture to room temperature, and add 200 ml of n-hexane. INVPOL-1 precipitates from the medium and is separated by filtration. 3.5 g (yield: 64%) of INVPOL-1 is isolated.

[0174] Synthesis of the polymer INVPOL-2 of the present invention

[0175] Dissolve 1.04 g of phenoxyethyl acrylate and 4.38 g of N-(2-benzoyl-3-oxobutyl)prop-2-enamide in 15 ml of ethyl acetate. Add 0.51 g of dodecyl mercaptan and 0.07 g of WAKO V59, and flush the mixture with nitrogen. Allow the polymerization to continue at 75 °C for 20 hours. Cool the reaction mixture to room temperature, and add 200 ml of n-hexane. INVPOL-2 precipitates from the medium and is separated by filtration. 5.5 g (yield: 92%) of INVPOL-2 is isolated.

[0176] Preparation of the capsule INVCAP-1 of the present invention:

[0177] Add a solution of 1 g of INVPOL-1 and 0.5 g of Desmodur N75 BA in 4 ml of ethyl acetate to a solution of 0.15 g of Lakeland ACP70 and 0.15 g of triethylamine in 10 ml of water, and sonicate for 2 minutes. Add 15 ml of water, and remove the ethyl acetate under reduced pressure. Evaporate the water to obtain a dispersion of 15 g of INVCAP-1 in water. Add 50 mg of N-methylmorpholine, and heat the mixture to 65 °C for 24 hours. Cool the mixture, and use the INVCAP-1 dispersion for the formulation of INVINK-1.

[0178] Measure the average particle size using a ZetasizerTM Nano-S (Malvern Instruments, Goffin Meyvis). The average particle size is 130 nm.

[0179] Preparation of the capsule INVCAP-2 of the present invention:

[0180] A solution of 1 g of INVPOL-1 and 0.5 g of Desmodur N75 BA in 4 ml of ethyl acetate was added to a solution of 0.15 g of Lakeland ACP70 and 0.15 g of triethylamine in 10 ml of water, and the mixture was sonicated for 2 minutes. 15 ml of water was added, and the ethyl acetate was removed under reduced pressure. The water was evaporated to obtain a dispersion of 15 g of INVCAP-1 in water. 50 mg of N-methylmorpholine was added, and the mixture was heated to 65 °C for 24 hours. The mixture was allowed to cool, and the INVCAP-2 dispersion was used for the formulation of INVINK-2.

[0181] The average particle size was measured using a ZetasizerTM Nano-S (Malvern Instruments, Goffin Meyvis). The average particle size was 160 nm.

[0182] Example 1

[0183] This example illustrates the improvement of solvent resistance by using an ink set, which comprises an aqueous ink having a resin based on 1,3-diketone (KETO-1), and an aqueous liquid used as an overprint varnish and containing an amino-functionalized alkoxysilane homopolymer.

[0184] Preparation of the inventive ink INVINK-1 and the comparative ink COMPINK-1

[0185] The inventive ink INVINK-1 and the comparative ink COMPINK-1 were prepared by mixing the components according to Table 3. PU-1 has been prepared as PU-9 and is disclosed in WO2018077624. All weight percentages are based on the total weight of the inkjet ink.

[0186] Table 3

[0187] Mass (wt.%) INVINK-1 COMPINK-1 INVCAP-1 39 PU-1 28.5 DISP-1 11 Cab-O-Jet 450C 20 1,2-propylene glycol 39 2-pyrrolidone 20 1,2-hexanediol 20 Sufynol 104H 0.2 Tego Wet 270 0.6 Water 10.8 10.9

[0188] Preparation of the inventive overcoat INVOV-1.

[0189] The overcoat INVOV-1 was prepared by mixing the components according to Table 4. All weight percentages are based on the total weight of the overcoat.

[0190] Table 4

[0191]

[0192]

[0193] INVINK-1 and COMPINK-1 inks were coated on polypropylene (Priplak, supplied by Antalis) using a 4-micron wire bar and dried in an oven at 80 °C for 5 minutes. The water resistance and solvent resistance of these coatings were evaluated. A 10-micron INVOV-1 coating was applied on top of the INVINK-1 coating and dried in an oven at 80 °C for 15 minutes. The solvent resistance of the coating was measured according to the above method. Before measuring the solvent resistance, the coating was stored at room temperature for 7 days. The ink of the present invention, INVINK-1, was stored at 6 °C for 14 days and coated again as above. The solvent resistance of the coating was measured again according to the above method. Before measuring the solvent resistance, the coating was stored at room temperature for 7 days. The results are summarized in Table 5.

[0194] Table 5

[0195]

[0196] It is apparent from Table 4 that applying the fluid set according to the present invention significantly improves the chemical resistance compared to a poly (urethane)-based resin ink (COMPINK-1), and the set remains stable even after storage at 60 °C for 14 days.

[0197] Example 2

[0198] This example illustrates the improvement of solvent resistance by using an ink set comprising an aqueous ink having a resin based on 1,3-diketone (KETO-4), and an aqueous liquid used as an overprint varnish and comprising an amino-functionalized alkoxysilane homopolymer.

[0199] Preparation of the ink INVINK-2 of the present invention

[0200] The ink INVINK-2 of the present invention was prepared by mixing the ingredients according to Table 6. All weight percentages are based on the total weight of the ink.

[0201] Table 6

[0202] Mass (wt.%) INVINK-2 INVCAP-2 39 DISP-1 11 1,2-propylene glycol 39 Sufynol 104H 0.2 Water 10.8

[0203] INVINK-2 and INVOV-1 were applied and tested in the same manner as in Example 1. The results are summarized in Table 7.

[0204] Table 7

[0205]

[0206] It is apparent from Table 7 that the application of the fluid set according to the present invention significantly improves the chemical resistance compared to the poly (urethane)-based resin ink (COMPINK-1 of Example 1), and the set remains stable even after storage at 60 °C for 14 days.

Claims

1. A fluid set, which comprises a fluid and an aqueous inkjet ink, the fluid comprising a compound functionalized with at least two functional groups selected from primary amines and secondary amines, the aqueous inkjet ink comprising a colorant and polymer particles, the polymer particles comprising a polymer, the polymer comprising at least three repeating units functionalized with functional groups selected from 1,3-diketones, β-ketoaldehydes and 1,3-dialdehydes, provided that the active methylene is functionalized with at least one hydrogen.

2. The fluid set according to claim 1, wherein the polymer particles are capsules, the capsules comprising a polymer shell surrounding a core, the core comprising the polymer.

3. The fluid set according to claim 1, wherein the polymer can be obtained by polymerization of a monomer according to Formula I Formula I wherein R1 - R3 are independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl and substituted or unsubstituted aryl or heteroaryl, provided that one of R1 - R3 is functionalized with a functional group selected from acrylate, methacrylate, acrylamide, methacrylamide, styrene, vinyl ether, vinyl ester, itaconate, fumarate, maleate and maleimide, and the monomer according to Formula I is a monofunctional monomer, either R1 or R3 represents an atom necessary for forming a five - to eight - membered ring.

4. The fluid set according to claim 2, wherein the polymer can be obtained by polymerization of a monomer according to Formula I Formula I wherein R1 - R3 are independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl and substituted or unsubstituted aryl or heteroaryl, provided that one of R1 - R3 is functionalized with a functional group selected from acrylate, methacrylate, acrylamide, methacrylamide, styrene, vinyl ether, vinyl ester, itaconate, fumarate, maleate and maleimide, and the monomer according to Formula I is a monofunctional monomer, either R1 or R3 represents an atom necessary for forming a five - to eight - membered ring.

5. The fluid set according to claim 3, wherein R1 and R3 are selected from substituted or unsubstituted alkyl and substituted or unsubstituted aryl.

6. The fluid set according to claim 4, wherein R1 and R3 are selected from substituted or unsubstituted alkyl and substituted or unsubstituted aryl.

7. The fluid set according to claim 5, wherein R2 is functionalized with a functional group selected from acrylate, methacrylate, acrylamide, methacrylamide, styrene, vinyl ether, vinyl ester, itaconate, fumarate, maleate, maleimide.

8. The fluid set according to claim 2, wherein the polymer shell comprises a polyurea, a polyurethane or a combination thereof.

9. The fluid set according to claim 4, wherein the polymer shell comprises a polyurea, a polyurethane or a combination thereof.

10. The fluid set according to claim 7, wherein the polymer particles are capsules, the capsules comprising a polymer shell surrounding a core, the core comprising the polymer and the polymer shell comprising a polyurea, a polyurethane or a combination thereof.

11. The fluid set according to claim 1, wherein the compound is a resin particle functionalized with at least 5 functional groups selected from primary amines and secondary amines.

12. The fluid set according to claim 1, wherein the compound is a resin particle functionalized with at least 10 functional groups selected from primary amines and secondary amines.

13. The fluid set according to claim 1, wherein the compound is a resin particle functionalized with at least 15 functional groups selected from primary amines and secondary amines.

14. The fluid set according to claim 1, wherein the polymer comprises at least 15 repeating units.

15. The fluid set according to claim 1, wherein the compound is difunctional or trifunctional.

16. The fluid set according to claim 2, wherein the dispersing group is covalently bonded to the polymer shell, the dispersing group selected from carboxylic acids or their salts, sulfonic acids or their salts, phosphoric esters or their salts, and phosphonic acids or their salts.

17. The fluid set according to claim 1, wherein the colorant is a pigment.

18. The fluid set according to claim 1, wherein the fluid comprises a flocculant selected from polyvalent salts and cationic resins.

19. The fluid set according to claim 1, wherein the fluid comprises a resin selected from polyacrylates and polyurethanes.

20. The fluid set according to claim 1, 2, 3, 4 or 14, wherein the polymer is an oligomer.

21. An inkjet recording method using the fluid set defined in claim 1, comprising the steps of: a) ejecting the aqueous inkjet ink of the fluid set onto a substrate; and b) applying the fluid of the fluid set before, after or during the ejection of the inkjet ink; and c) drying the applied fluid set by applying heat.

22. The inkjet recording method according to claim 21, wherein step c) is drying the applied fluid set by applying heat to obtain a temperature of the ejected ink of at least 60 °C.

23. An inkjet recording method using the fluid set defined in claim 4, comprising the steps of: a) ejecting the aqueous inkjet ink of the fluid set onto a substrate; and b) applying the fluid of the fluid set before, after or during the ejection of the inkjet ink; and c) drying the applied fluid set by applying heat.

24. The inkjet recording method according to claim 23, wherein step c) is drying the applied fluid set by applying heat to obtain a temperature of the ejected ink of at least 60 °C.

25. The inkjet recording method according to claim 21, wherein the fluid is applied via a technique selected from inkjet, valve jetting and spraying.

Images