Aqueous resin-based inkjet inks

Abstract

The invention relates to aqueous resin-based inkjet inks. An aqueous inkjet ink comprising a compound functionalized with at least two functional groups selected from a primary amine and a secondary amine, a colorant, and polymer particles, the polymer particles being capsules comprising a polymer shell surrounding a core, the polymer shell comprising a polyurea, a polyurethane, or a combination thereof, said core comprising an oligomer or polymer consisting of repeating units comprising a functional group according to general formula I: # imgabs0 #

Description

This application is a divisional application of the following application: Application date: April 26, 2021; Application number: 2021800331074; Invention name: "Water-based resin-based inkjet ink". Technical Field

[0001] The present invention relates to aqueous inkjet inks comprising resin particles comprising an oligomer or polymer and a compound functionalized with at least two functional groups which are primary or secondary amines, for inkjet printing on non-absorbent substrates. Background Art

[0002] The industrial application of inkjet is expanding into more and more technical fields and must meet increasingly demanding physical property requirements.Industrial printing technology must be compatible with a wide range of non-absorbent substrates (such as glass and metal) as well as synthetic resins (including temperature-sensitive resins such as polyolefins).

[0003] Chemical resistance to aggressive solvents is one of the requirements that graphics must meet in durable applications. To date, inkjet technology for durable applications has been UV-based. However, water-based technology is gradually gaining ground in more demanding applications.

[0004] To meet the requirements of industrial inkjet applications, water-based resin-based inks have been designed based on various technologies. Latex-based technologies, such as those disclosed in WO2018077624A, are based on adjusting the film-forming temperature of the latex to be compatible with temperature-sensitive substrates. However, their adhesion properties are not always optimal, and their chemical resistance is particularly limited. Furthermore, latex-based inks tend to form films at the nozzles of inkjet heads, leading to issues with inkjet reliability.

[0005] Encapsulation-based technologies, such as those disclosed in WO2015158654A and EP293337A, avoid film formation at the inkjet nozzles, but often require high activation temperatures, making them unsuitable for printing on temperature-sensitive substrates such as polyolefins. To address issues of chemical resistance and compatibility with temperature-sensitive substrates, several approaches based on water-based UV technology have been disclosed. These methods require both drying and curing, complicating printer design.

[0006] US20190249024 discloses a dual-ink approach, in which the first ink contains an epoxy compound and the second contains a primary amine-based polymer. This combination is said to result in good adhesion properties and alcohol resistance. However, epoxy compounds are known to be susceptible to hydrolysis, posing a risk of loss of activity during storage of water-based inks. The need to separate the two reactive compounds into separate printing liquids makes the inkjet recording method and printing apparatus significantly more complex than integrated liquid methods.

[0007] Therefore, there remains a need for waterborne resin-based technologies that show reliable inkjet behavior, are compatible with temperature-sensitive substrates, yield excellent physical properties such as chemical resistance when dry, do not carry the risk of hydrolysis on storage and do not require two separate printing liquids. Summary of the Invention

[0008] It is an object of the present invention to provide a solution to the above-mentioned problems. This object has been achieved by providing an inkjet ink comprising a compound functionalized with at least two functional groups being primary or secondary amines and a particle dispersion as defined in claim 1 .

[0009] Another embodiment of the present invention is to provide a printing method as defined in claim 10 using the inkjet ink of claim 1 .

[0010] Other features, elements, steps, characteristics and advantages of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention. Specific embodiments of the present invention are also defined in the dependent claims. Specific implementation plan

[0011] A. Aqueous inkjet ink according to the present invention The aqueous inkjet ink according to the present invention comprises a compound functionalized with at least two functional groups selected from primary and secondary amines, a colorant, and polymer particles comprising an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II, or III (see below). Without being bound by any theory, it is believed that a crosslinking reaction occurs between the particles comprising the oligomer or polymer and the compound functionalized with at least two functional groups selected from primary and secondary amines, the oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II, or III. Crosslinking of the oligomer or polymer results in improved solvent resistance of the jetted image.

[0012] A.1. Polymer particles comprising oligomers or polymers having at least three repeating units comprising a functional group according to the general formula I, II or III The objects of the present invention are achieved by polymer particles comprising oligomers or polymers having at least three repeating units comprising a functional group according to the general formula I, II or III in R1 is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aryl or heteroaryl, COR3 and CN R2 is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aryl or heteroaryl and COR3 R1 and R2 may represent atoms necessary to form a five- to eight-membered ring R3 is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aryl or heteroaryl, OR4 and NR5R6R4 are selected from 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 R5 and R6 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. R5 and R6 may represent the atoms necessary to form a five to eight membered ring. X is selected from O and NR7 R7 is 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. R8 and R9 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. R8 and R9 may represent the atoms necessary to form a five- to eight-membered ring.

[0013] In a preferred embodiment, the oligomer or polymer comprising repeat units functionalized with moieties according to formula I comprises at least 7 functionalized, more preferably at least 10 and most preferably at least 15 functionalized repeat units.

[0014] The oligomer or polymer according to the present invention preferably has a weight average molecular weight of at least 2,000, more preferably 4,000 and most preferably between 6,000 and 30,000.

[0015] The polymers according to the invention may be homopolymers or copolymers of different repeating units.

[0016] The oligomers or polymers according to the present invention can be prepared by addition polymerization, polycondensation, and ring-opening polymerization of ethylenically unsaturated monomers, with addition polymerization being particularly preferred. In a most preferred embodiment, the resins according to the present invention are prepared by free radical polymerization of ethylenically unsaturated monomers. In another embodiment of the present invention, the molecular weight of the resins according to the present invention is controlled using RAFT agents, ATRP, nitroxyl free radical technology, or transfer agents (preferably thiols).

[0017] In a further preferred embodiment, X represents oxygen. In an even further preferred embodiment, R1 represents hydrogen. In an even further preferred embodiment, R2 represents substituted or unsubstituted alkyl, unsubstituted being more preferred, lower alkyl being even more preferred and methyl being most preferred.

[0018] Typical monomers used to prepare the resin according to the present invention are given below, but are not limited thereto.

[0019] Monomers used for addition polymerization: see Table 1 Table 1 Free radical and cationic polymerization conditions are preferred for preparing the addition polymers according to the present invention.

[0020] Monomers used for ring-opening polymerization: see Table 2 Table 2 Poly(ethers), poly(esters), poly(carbonates) and poly(amides) or copolymers thereof can be prepared using ring-opening polymerization environments described in the scientific literature.

[0021] Monomers used for polycondensation: see Table 3 Table 3 Poly(esters) can be prepared by condensing functionalized diols with diacids or diacid chlorides under conditions known to those skilled in the art. Functionalized diacids can be converted to poly(esters) by condensation with diols. Poly(urethanes) can be prepared by condensing functionalized diols with diisocyanates under conditions known to those skilled in the art.

[0022] The particles comprising an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II or III are preferably dispersed in the aqueous carrier of the inkjet ink. The particles are preferably dispersed in the aqueous medium of the inkjet ink by using a dispersant or surfactant.

[0023] The particles to be used in a jettable aqueous formulation, such as an inkjet ink, a jettable pretreatment liquid, or a jettable overcoat formulation (overprint varnish), have an average particle size of no greater than 4 μm, as determined by dynamic laser diffraction. The nozzle diameter of an inkjet printhead is typically 20 to 35 μm. Therefore, preferably, the average particle size is 0.05 to 2 μm, more preferably 0.10 to 1 μm. When the average particle size of the particles is less than 2 μm, excellent resolution and dispersion stability over time are achieved.

[0024] The particles are preferably present in aqueous inkjet inks, but may also be present in pre-treatment liquids (or primers) or overprint varnishes. The amount of particles in the inkjet ink is no more than 45 wt.%, preferably between 5 and 25 wt.%, based on the total weight of the liquid / varnish / ink. It has been observed that jetting above 30 wt.% is not always reliable.

[0025] In a preferred embodiment, the oligomer or polymer according to the present invention is encapsulated to form an aqueous dispersion, preferably by polymerization, more preferably by using interfacial polymerization. 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 the compound functionalized with at least two functional groups selected from primary and secondary amines.

[0026] More specifically, partial hydrolysis of the functional groups according to formula I is prevented upon storage of the aqueous inkjet ink. Consequently, the reactivity of the printed image and the resulting improvement in solvent and water resistance do not diminish upon storage of the inkjet ink.

[0027] It has also been observed that encapsulating an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III results in a more reliable jetting behavior of the inkjet ink comprising the resin compared to without encapsulation.

[0028] The capsules are preferably present in the inkjet ink, but may also be present in the pre-treatment liquid (or primer) or overprint varnish. Preferably, the amount of capsules is no more than 45 wt.%, preferably between 5 and 25 wt.%, based on the total weight of the liquid / varnish / ink. It has been observed that jetting above 30 wt.% is not always reliable.

[0029] For the same reasons as explained above, the capsules to be used in a jettable aqueous formulation (such as an inkjet ink, a jettable pretreatment liquid, or a jettable overprint varnish) have an average particle size of no more than 4 μm, as determined by dynamic laser diffraction. Therefore, preferably, the average particle size is from 0.05 to 2 μm, more preferably from 0.10 to 1 μm. When the average particle size of the capsules is less than 2 μm, excellent resolution and dispersion stability over time are achieved.

[0030] The capsules are dispersed in the aqueous medium of the inkjet ink using dispersing groups covalently bonded to the polymer shell, or by using a dispersant or surfactant that is preferably added during or after capsule formation. The dispersing groups covalently bonded to the polymer shell are preferably selected from carboxylic acids or salts thereof, sulfonic acids or salts thereof, phosphates or salts thereof, phosphonic acids or salts thereof, ammonium groups, sulfonium groups, phosphonium groups, and polyoxyethylene groups.

[0031] Dispersing groups can be used in combination with polymeric dispersants to achieve steric stabilization. For example, the polymer shell can have covalently bonded carboxylic acid groups that interact with the amino 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, weakly alkaline aqueous media can convert the carboxylic acid groups of the covalently bonded polymer shell into ionic groups, after which the negatively charged capsules do not tend to aggregate. If enough dispersing groups are covalently bonded to the polymer shell, the capsule becomes a so-called self-dispersing capsule.

[0032] These negatively or positively charged capsule surfaces can also be used to advantage during inkjet printing. For example, a second liquid, such as a pretreatment liquid containing cationic-dispersed capsules, can be used to precipitate anionically stabilized colorants for aqueous inkjet inks printed on top of the second liquid. By using this approach, improvements in image quality can be observed due to the immobilization of the colorant.

[0033] There is no real limitation on the type of polymer used for the polymer shell of the capsule. Preferably, the polymer used in the polymer shell is cross-linked. Through cross-linking, more rigidity is built into the capsule, which allows for a wider range of temperatures and pressures for processing the capsule in both ink making and inkjet printers.

[0034] Preferred examples of polymer shell materials include polyureas, polyesters, polycarbonates, polyamides, melamine-based polymers, and mixtures thereof, with polyureas being particularly preferred.

[0035] A.2. Preparation of capsules according to the invention Both chemical and physical methods can be used to prepare encapsulation of oligomers or polymers containing polymer shells having at least 3 repeating units comprising a functional group according to formula I, II or III. Suitable encapsulation methods include coacervation, liposome formation, spray drying and polymerization methods.

[0036] In the present invention, polymerization methods are preferably used because they allow the highest control in the design of the capsule. More preferably, interfacial polymerization is used to prepare the capsules of the present invention. This technology is well known and has been reviewed by Zhang Y. and Rochefort D. (Journal of Microencapsulation, 29(7), 636-649 (2012)) and by Salitin in Encapsulation Nanotechnologies, Vikas Mittal (ed.), Chapter 5, 137-173 (Scrivener Publishing LLC (2013)).

[0037] In interfacial polymerization, such as interfacial condensation, two reactants meet at the interface of an emulsion droplet and react rapidly.

[0038] In general, interfacial polymerization requires a lipophilic phase to be dispersed in an aqueous continuous phase, or vice versa. Each phase contains at least one dissolved monomer (the first shell component) that is capable of reacting with another monomer (the second shell component) dissolved in the other phase. After polymerization, a polymer is formed that is insoluble in both the aqueous and lipophilic phases. Consequently, the formed polymer has a tendency to precipitate at the interface between the lipophilic and aqueous phases, thereby forming a shell around the dispersed phase that grows upon further polymerization. Capsules according to the present invention are preferably prepared from a lipophilic dispersion in an aqueous continuous phase.

[0039] Typical polymer shells of capsules according to the present invention formed by interfacial polymerization are selected from polyamides, typically prepared from di- or poly-acid chlorides as the first shell component and di- or oligoamines as the second shell component; polyureas, typically prepared from di- or oligoisocyanates as the first shell component and di- or oligoamines as the second shell component; polyurethanes, typically prepared from di- or oligoisocyanates as the first shell component and di- or oligoalcohols as the second shell component; polysulfonamides, typically prepared from di- or oligosulfonyl chlorides as the first shell component and di- or oligoamines as the second shell component; polyesters, typically prepared from di- or oligo-acid chlorides as the first shell component and di- or oligoalcohols as the second shell component; and polycarbonates, typically prepared from di- or oligo-chloroformates as the first shell component and di- or oligoalcohols as the second shell component. The shell may be composed of a combination of these polymers.

[0040] In further embodiments, polymers such as gelatin, chitosan, albumin, and polyethyleneimine may be used as the second shell component in combination with di- or oligo-isocyanates, di- or oligoacid chlorides, di- or oligo-chloroformates, and epoxy resins as the first shell component.

[0041] In a particularly preferred embodiment, the shell consists of polyurea or a combination thereof with polyurethane. In a further preferred embodiment, a water-immiscible solvent is used in the dispersion step, which is removed by solvent stripping before or after the shell is formed. In a particularly preferred embodiment, the water-immiscible solvent has a boiling point of less than 100° C. at normal pressure. Esters are particularly preferred as water-immiscible solvents.

[0042] Water-immiscible solvents are organic solvents with low miscibility in water. Low miscibility is defined as any water-solvent combination that forms a two-phase system at 20°C when mixed in a one to one volume ratio.

[0043] The core contains an oligomer or polymer having at least three repeating units containing a functional group according to Formula I, II, or III. These are typically incorporated into the capsule by dissolving them in an organic solvent that has low miscibility with water and a lower boiling point than water. A preferred organic solvent is ethyl acetate, as it also has a lower flammability hazard compared to other organic solvents.

[0044] However, in some cases the organic solvent may be omitted. For example, when the oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III has a viscosity of less than 100 mPa.s, the organic solvent may be omitted.

[0045] The method for preparing the capsule dispersion preferably comprises the following steps: a) preparing a non-aqueous solution of a first shell component for forming the polymer shell and an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III in an organic solvent having low miscibility with water and having a lower boiling point than water; b) preparing an aqueous solution of a second shell component for forming the polymer shell; c) dispersing the non-aqueous solution in the aqueous solution under high shear; d) optionally stripping the organic solvent from the mixture of the aqueous solution and the non-aqueous solution; and e) preparing a polymer shell around an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III by interfacial polymerization of a first and a second shell component for forming the polymer shell.

[0046] The capsule dispersion can then be completed by adding, for example, colorants, water, humectants, surfactants, etc. to inkjet inks, aqueous pre-treatment liquids, or any liquid suitable for the printing process.

[0047] In a preferred embodiment, the capsule is a self-dispersing capsule. To make the capsule self-dispersible, anionic dispersing groups such as carboxylic acids or salts thereof, sulfonic acids or salts thereof, phosphates or salts thereof, or phosphonic acids or salts thereof, or cationic dispersing groups such as quaternary ammonium salts, protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfoniums, and phosphoniums may be covalently bonded to the polymer shell of the capsule to ensure dispersion stability.

[0048] A preferred strategy for incorporating anionic stabilizing groups into the polymer shell of the capsule utilizes carboxylic acid-functionalized reactive surfactants capable of reacting with isocyanates. This results in amphoteric surfactants containing at least some secondary or primary amines. Other reactive surfactants functionalized with sulfonic acids or salts thereof, phosphates or salts thereof, or phosphonic acids or salts thereof can be used.

[0049] Several amphoteric surfactants are commercially available as mixtures of surfactants partially containing secondary amines but also containing tertiary amines. The formation of prohibitive foam in inkjet inks based on capsules made using commercially available amphoteric surfactants has been encountered in inkjet printers. Foaming causes problems in the ink supply and also in the degassing process in which air is removed from the ink, resulting in unreliable jetting. Therefore, during the oligomer or polymer encapsulation process, it is preferred to use a surfactant according to formula (I) of WO2016 / 165970, wherein the oligomer or polymer has at least three repeating units comprising a functional group according to formula I, II or III.

[0050] Cationic dispersing groups are incorporated into the polymer shell of the capsule for pre-treatment of liquids or cationic inkjet inks (as disclosed in patent application WO2019 / 105867) by bonding a surfactant containing cationic dispersing groups to the capsule shell according to the present invention. This is accomplished by reacting a surfactant comprising at least one primary or secondary amine group and at least one group selected from protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfonium and phosphonium with the first shell component (preferably the isocyanate monomer of the shell). In an even more preferred embodiment, the surfactant is a surfactant according to formula IV.

[0051] in R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, and substituted or unsubstituted alkynyl, provided that R1 contains at least eight carbon atoms; R2, R3 and R4 are independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl and substituted or unsubstituted (hetero)aryl. L1 represents a divalent linked group containing not more than eight carbon atoms; X represents a counterion that compensates for the positive charge of the ammonium group.

[0052] The capsules according to the present invention are dispersed in an aqueous medium. The aqueous medium consists of water, but may preferably include one or more water-soluble organic solvents.

[0053] One or more organic solvents may be added for various reasons. For example, it may be advantageous to add a small amount of organic solvent to improve the dissolution of the compound in the pre-treated liquid to be prepared or the inkjet ink, or to improve the permeability of the ink into the porous substrate, or to reduce the drying rate of the ink at the nozzle 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, 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-propylene glycol), amines (such as ethanolamine and 2-(dimethylamino)ethanol), monohydric alcohols (such as methanol, ethanol and butanol), alkyl ethers of polyhydric alcohols (such as 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), heterocycles (such as 2-pyrrolidone and N-methyl-2-pyrrolidone) and acetonitrile.

[0054] A.3. Compounds functionalized with at least two amine groups The ink according to the present invention further comprises at least one compound functionalized with at least two functional groups selected from primary amines and secondary amines, primary amines being more preferred.

[0055] In a more preferred embodiment, the amino-functional compound has a functionality of 2 to 8, more preferably a functionality of 2 to 5, and most preferably is di- or trifunctional. The lower the functionality, the lower the risk of agglomeration with polymer particles. Di- or trifunctional compounds are more readily available on the market than compounds with higher functionality.

[0056] Typical amine-functionalized ink additives are given in Table 4, but are not limited thereto.

[0057] Table 4 In a preferred embodiment, the aqueous inkjet ink or jettable pre-treatment liquid 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, primary amines being more preferred.

[0058] The polymer may be dissolved in the aqueous inkjet ink or may be present as dispersed or emulsified polymer particles. Typical polymers useful in fluid designs as primers are selected from poly(allylamine), poly(vinylamine), poly(vinylamine-co-vinylformamide), chitosan, 4-aminomethyl-styrene homopolymers or copolymers thereof, 2-aminoethyl-acrylate or salts thereof, 2-aminoethyl-methacrylate or salts thereof, 3-aminopropyl-acrylamide or salts thereof, 3-aminopropyl-methacrylamide or salts thereof, poly(lysine) or copolymers thereof, and the like.

[0059] In a preferred embodiment, the aqueous inkjet ink comprises at least one resin particle that is functionalized with at least 5, more preferably at least 10, and most preferably at least 15 functional groups selected from primary and secondary amines, with primary amines being more preferred. The use of functionalized resin particles rather than functionalized compounds in aqueous inkjet inks has the advantage of improved rheological behavior, resulting in improved jetting reliability and colloidal stability of the inkjet ink.

[0060] Amino-functionalized resin particles can be prepared by derivatizing an amino-functionalized polymer, followed by 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, homo- or copolymers of 4-aminomethyl-styrene or salts thereof, 2-aminoethyl-acrylate or salts thereof, 2-aminoethyl-methacrylate or salts thereof, 3-aminopropyl-acrylamide or salts thereof, 3-aminopropyl-methacrylamide or salts thereof, poly(lysine) or copolymers thereof, and the like. The weight average molecular weight of the starting polymer is preferably at least 7,000, more preferably at least 15,000, and most preferably at least 25,000.

[0061] Other synthetic strategies include derivatization of carboxylic acid-functionalized acrylic polymers with azeridine, followed by emulsification and optional crosslinking of optionally protected amino-functionalized monomers, emulsion or miniemulsion polymerization, optionally followed by deprotection of a reactive latex containing a reactive monomer such as 4-chloromethyl-styrene, post-derivatization and sol-gel-based polycondensation based on amino-functionalized alkoxysilanes.

[0062] In a preferred embodiment, the amino-functionalized resin particles are crosslinked. 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.

[0063] The amines can be at least partially neutralized with acids such as hydrochloric acid, methanesulfonic acid, p-toluenesulfonic acid, phosphoric acid, sulfuric acid, and carboxylic acids such as acetic acid, citric acid, and lactic acid.

[0064] A.4. Colorants The colorant in the aqueous inkjet ink according to the present invention may be a dye such as a disperse dye, an acid dye, a reactive dye, and may be a pigment or a combination thereof. Preferably, the colorant in the inkjet ink according to the present invention is a pigment.

[0065] The pigment of the ink can be black, white, cyan, magenta, yellow, red, orange, violet, blue, green, brown, mixtures thereof, etc. The coloring pigment can be selected from those disclosed in HERBST, Willy et al., Industrial Organic Pigments, Production, Properties, Applications, 3rd edition, Wiley-VCH, 2004. ISBN 3527305769.

[0066] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0067] The pigment particles are dispersed in the aqueous medium with the aid of a polymeric dispersant or surfactant. Self-dispersible pigments can also be used. When combined with particles or capsules according to the present invention and having anionic dispersing groups, anionic surfactants are preferably used as dispersants for the pigment. When combined with particles and capsules according to the present invention having cationic dispersing groups, cationic surfactants are preferably used as dispersants for the pigment. The latter prevent interaction between the polymeric dispersant and the dispersing groups of the particles or capsules included in the inkjet ink, as the dispersion stability of the pigment is achieved through the same electrostatic stabilization technology used for the capsules.

[0068] Self-dispersible pigments are pigments having covalently bonded anionic hydrophilic groups on their surface, such as salt-forming groups or the same groups used as dispersing groups for capsules, which allow the pigment to be dispersed in aqueous media without the use of surfactants or resins. Suitable commercially available self-dispersible colored pigments are, for example, CAB-O-JET from CABOT. TM Inkjet colorants.

[0069] The pigment particles in inkjet inks should be small enough to allow free flow of the ink through the inkjet printing device, especially at the ejection nozzle. Small particles are also desirable to obtain maximum color strength and slow down sedimentation.

[0070] 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 no greater than 0.150 μm. The average pigment particle size is determined using a Brookhaven Instruments Particle Sizer BI90plus based on dynamic light scattering. The ink is diluted with water to a pigment concentration of 0.002 wt%. The BI90plus measurement settings are: 5 runs at 23°C, 90° angle, 635 nm wavelength, and image = correction function.

[0071] Suitable white pigments are given in Table 2 of WO 2008 / 074548

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

[0117] and

[0118] .

[0072] Specialty colorants can also be used, such as fluorescent pigments for special effects on clothing, and metallic pigments for printing silver and gold colors on textiles for a luxurious look.

[0073] Suitable polymer dispersants for pigments are copolymers of two monomers, but they may contain three, four, five, or even more monomers. The properties of the polymer dispersant depend on both the nature of the monomers and their distribution in the polymer. Copolymer dispersants preferably have the following polymer composition: Statistically polymerized monomers (e.g., monomers A and B polymerized as ABBAABAB); Alternating monomers (e.g. monomers A and B polymerized as ABABABAB); Gradient (decreasing) polymerization of monomers (e.g. monomers A and B polymerized as AAABAABBABBB); Block copolymers (e.g., monomers A and B polymerized as AAAAABBBBBB), where the block length of each block (2, 3, 4, 5, or even more) is important to the dispersing ability of the polymeric dispersant; Graft copolymers (graft copolymers consist of a polymer backbone and polymer side chains attached to the backbone); and Mixed forms of these polymers, such as block gradient copolymers.

[0074] Suitable dispersants are DISPERBYK available from BYK CHEMIE. TM Dispersant, JONCRYL available from JOHNSON POLYMERS TM Dispersants and SOLSPERSE available from Lubrisol TM Dispersants. A detailed list of non-polymeric as well as some polymeric dispersants is disclosed by MC CUTCHEON. Functional Materials, North American Edition. Glen Rock, NJ: Manufacturing Confectioner Publishing Co., 1990. pp. 110-129.

[0075] The polymeric dispersants preferably have a number average molecular weight Mn of between 500 and 30,000, more preferably between 1,500 and 10,000.

[0076] The polymeric 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.

[0077] The pigment is preferably present in a range of 0.01 to 20%, more preferably in a range of 0.05 to 10% by weight, and most preferably in a range of 0.1 to 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% to 40% and more preferably 5% to 35% by weight of the inkjet ink. An amount of less than 3% by weight may not achieve sufficient covering power.

[0078] A.5. Additives The aqueous inkjet inks according to the present invention contain water but may include one or more water-soluble organic solvents. Suitable organic solvents are described in §A.2.

[0079] 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 ink). The wetting agent is preferably an organic solvent with a boiling point higher than that of water. Suitable wetting agents include triacetin, N-methyl-2-pyrrolidone, glycerol, urea, thiourea, ethylene urea, alkyl urea, alkyl thiourea, dialkyl urea and dialkyl thiourea, glycols including ethylene glycol, propylene glycol, glycerol, butanediol, pentanediol and hexanediol; glycols including propylene glycol, polypropylene glycol, ethylene glycol, polyethylene glycol, diethylene glycol, tetraethylene glycol; and mixtures and derivatives thereof. The preferred wetting agent is glycerol.

[0080] The humectant is preferably added to the inkjet ink in an amount of 0.1 to 20 wt. %, based on the total weight of the liquid.

[0081] The aqueous inkjet ink according to the present invention may contain a surfactant. Any known surfactant may be used, but preferably an ethylene glycol surfactant and / or an acetylene alcohol surfactant. The use of an acetylene glycol surfactant and / or an acetylene alcohol surfactant further reduces bleeding of the ink to improve print quality and also improves drying characteristics during printing to allow high-speed printing.

[0082] The acetylene glycol surfactant and / or acetylene alcohol surfactant is preferably one or more selected from the group consisting 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, for example, from Air Products (GB) as Olfine (registered trademark) 104 series and E series (such as Olfine E1010) or from Nissin Chemical Industry as Surfynol (registered trademark) 465 and Surfynol 61.

[0083] The inkjet ink composition according to the present invention may further comprise an additional resin. This resin is often added to the inkjet ink formulation to further improve 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.

[0084] The polyurethane resin may 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 a combination of two or more thereof.

[0085] Preferred urethane resins to be used as dispersants in the inks of the present invention are polyester resins comprising structural units containing urethane bonds. Of 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 hydroxyl group-containing polyester resin (polyester polyol) and at least one structural unit derived from an organic polyisocyanate.

[0086] Furthermore, the hydroxyl group-containing polyester resin is a resin formed by an esterification reaction or a transesterification reaction between at least one polyacid component and at least one polyol component.

[0087] Preferred polyurethane resins that may be included in the inks of the present invention are those obtainable by reacting polyester polyols, polyether diols, polyols containing anionic groups, and polyisocyanates. Particularly preferred polyurethane resins are those obtainable by reacting polyester polyols, polyether diols, polyols containing anionic groups, and polyisocyanates, wherein the polyester polyols are obtainable by reacting aromatic polycarboxylic acids and polyols. Suitable polyurethane resins and examples of their preparation are disclosed in unpublished patent application EP16196224.6.

[0088] Examples of some 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 UAXP 2631 (Bayer Material Science); DAOTAN VTW 1262 / 35WA, DAOTAN VTW 1265 / 36WA, DAOTAN VTW 1267 / 36WA, DAOTAN VTW 6421 / 42WA, DAOTAN VTW6462 / 36WA (Cytec Engineered Materials Inc., Anaheim CA); and SANCURE 2715, SANCURE 20041, SANCURE 2725 (Lubrizol Corporation); or a combination of two or more of the above.

[0089] Acrylic-based resins include polymers of acrylic acid monomers, polymers of methacrylic acid monomers, and copolymers of the aforementioned monomers with other monomers. These resins exist as a suspension of particles having an average diameter of about 30 nm to about 300 nm. Acrylic latex polymers are formed from the residues of acrylic acid monomers or methacrylic acid monomers. By way of example, examples of monomers for acrylic latex polymers include acrylic acid monomers such as acrylates, acrylamides, and acrylic acid; and methacrylic acid monomers such as methacrylates, methacrylamides, and methacrylic acid. Acrylic latex polymers can be homopolymers or copolymers of acrylic acid monomers and another monomer, such as a vinyl aromatic monomer, including but not limited to styrene, styrene butadiene, parachloromethylstyrene, divinylbenzene, vinyl naphthalene, and divinylnaphthalene.

[0090] Examples of some 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 A2427, and BAYHYDROL A2651 (Bayer), or a combination of two or more of the above.

[0091] The concentration of the resin in the inkjet ink according to the present invention is at least 1 (wt.) % and preferably less than 30 (wt.), more preferably less than 20 (wt.) %.

[0092] 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 comprising a plurality of inkjet inks according to the present invention. The inkjet ink set preferably comprises 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 can also be extended with additional inks such as red, green, blue, violet, and / or orange to further expand the color gamut of the image. The inkjet ink set can also be extended by combining a full-density inkjet ink with a light-density inkjet ink. Combining dark and light-colored inks and / or black and gray inks improves image quality by reducing granularity.

[0093] In a preferred embodiment, the inkjet ink set further comprises a white inkjet ink. This allows brighter colors to be achieved, especially on transparent substrates, through which the white inkjet ink can be applied as a primer or on top of a pigmented inkjet ink when the image is viewed.

[0094] The viscosity of the inkjet ink according to the present invention is preferably 25 ° C and 90s -1 less than 25 mPa.s at a shear rate of 100 mPa.s, more preferably at 25°C and 90 s -1 The shear rate is between 2 and 15 mPa.s.

[0095] 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, more preferably in the range of about 20 mN / m to about 40 mN / m at 25°C.

[0096] B. Inkjet Printing Method In a preferred inkjet recording method, the method comprises the following steps: a) jetting an aqueous inkjet ink according to the present invention onto a substrate, preferably a non-porous substrate, the ink comprising a colorant, a compound functionalized with at least two functional groups being primary or secondary amines, more preferably primary amines, a dispersion of particles comprising an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II or III, more preferably the ink comprising a dispersion of capsules consisting of a polymer shell surrounding a core comprising an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II or III; and b) drying the jetted inkjet ink by applying heat, such as to obtain a jetted ink temperature of at least 60° C., more preferably at least 80° C. If the temperature obtained is below 60° C., no or insufficient crosslinking reaction occurs between the particles comprising an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II or III and the compound functionalized with at least two functional groups being primary or secondary amines. Therefore, improvement in solvent resistance of the jetted and dried inks does not occur.

[0097] In another preferred inkjet recording method, the method comprises the steps of: a) applying an aqueous pre-treatment liquid to a substrate, preferably a non-porous substrate, b) jetting an aqueous inkjet ink according to the present invention onto a substrate, preferably a non-porous substrate, the ink comprising a colorant, a compound functionalized with at least two functional groups being primary or secondary amines, more preferably primary amines, a dispersion of particles containing an oligomer or polymer having at least 3 repeating units containing a functional group according to formula I, II or III, more preferably the ink comprises a dispersion of capsules consisting of a polymer shell surrounding a core, the core containing an oligomer or polymer having at least 3 repeating units containing a functional group according to formula I, II or III; and c) drying the jetted inkjet ink by applying heat, such as to obtain a temperature of the jetted ink of at least 60°C, more preferably at least 80°C.

[0098] The pretreatment liquid preferably contains a compound capable of aggregating components in the aqueous inkjet ink, such as a flocculant, such as an organic acid, a resin, a polyvalent metal ion, or a cationic surfactant. Suitable examples of polyvalent metal ions are water-soluble metal salts composed of divalent or higher valent metal cations such as magnesium, calcium, strontium, barium, zirconium, and aluminum, and cations such as fluoride (F).- ), chloride ion (Cl - ), bromide ion (Br - ), sulfate ion (SO4 2- ), nitrate ions (NO3 - ) and acetate ions (CH3COO - ) anion is formed.

[0099] These polyvalent metal ions aggregate 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. This immobilizes the colorant in the ink, reducing color bleeding and cross-linking. Therefore, it is preferred that the pigment surface and / or the dispersed polymer of the capsules (if included in the ink) in the ink contain anionic groups, preferably carboxyl groups.

[0100] Preferred examples of the organic acid include, but are not limited to, acetic acid, propionic acid, and lactic acid.

[0101] Preferred examples of resins include, but are not limited to, 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 tannins and lignin; and synthetic water-soluble polymers such as polymers containing polyvinyl alcohol, polymers containing polyethylene oxide, polymers formed from acrylic acid monomers, and polymers formed from maleic anhydride monomers. Other suitable resins are acrylic acid polymers as described in EP2362014 [0027-0030]. Preferably, the resin is a cationic resin, more preferably a cationic charged polyurethane. The resin content is preferably no more than 20 wt.% relative to the total mass of the pretreatment liquid (100 mass%).

[0102] The aqueous pretreatment liquid can also comprise a compound functionalized with at least two functional groups (primary amine is more preferred) of a primary or secondary amine, a particle dispersion comprising an oligomer or polymer with at least 3 repeating units comprising the functional group of general formula I, II or III, or a capsule consisting of a polymer shell surrounding the core. The core contains an oligomer or polymer with at least 3 repeating units comprising the functional group of general formula I, II or III. The shell further comprises a dispersing group, which is preferably covalently bonded to the shell, and more preferably, the dispersing group is a group selected from protonated amine, protonated nitrogenous heteroaromatic compound, quaternized tertiary amine, N-quaternized heteroaromatic compound, sulfonium and phosphonium. The pretreatment liquid can also further comprise a compound functionalized with at least two functional groups of a primary or secondary amine, and primary amine is more preferred.

[0103] In a more preferred embodiment, the amino-functional compound has a functionality of 2 to 8, more preferably a functionality of 2 to 5 and most preferably is di- or trifunctional.

[0104] The aqueous medium of the pretreatment liquid contains water but may include one or more water-soluble organic solvents. Suitable organic solvents are described in §A.2. If present in the pretreatment liquid, the capsules preferably comprise no more than 45 wt.%, more preferably between 5 and 25 wt.%, based on the total weight of the pretreatment liquid.

[0105] The pre-treatment liquid may also contain a wetting agent. If the pre-treatment liquid must be applied by means of a spraying technique such as inkjet or valve jet, the wetting agent is preferably incorporated into the pre-treatment liquid. The wetting agent prevents nozzle clogging.

[0106] The pretreatment liquid may also contain a pigment. Pretreatment liquids containing white pigments are particularly useful for printing on dark or transparent substrates. A preferred pigment for aqueous pretreatment liquid inks is titanium dioxide. Titanium dioxide (TiO₂) pigments useful in the present invention may be in the form of rutile or anatase crystals. The process for producing TiO₂ is described in detail in "The Pigment Handbook," Volume 1, Second Edition, John Wiley & Sons, NY (1988), the relevant disclosure of which is incorporated herein by reference for all purposes as if fully set forth.

[0107] The titanium dioxide particles can have a wide range of average particle sizes, from about 1 micron or less, depending on the desired end-use application of the pretreatment liquid. 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 particles have an average size of 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.

[0108] For applications requiring white with some transparency, the pigment is preferably "nano" titanium dioxide. "Nano" titanium dioxide particles typically have an average size ranging from about 10 to about 200 nm, preferably from about 20 to about 150 nm, and more preferably from about 35 to about 75 nm. Inks comprising nano titanium dioxide can provide improved chroma and transparency while still maintaining good light fading resistance and appropriate hue angle. A commercially available example of uncoated nano-sized titanium dioxide is P-25, available from Degussa (Parsippany NJ).

[0109] Titanium dioxide pigments can also be loaded with 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 silicon dioxide, aluminum oxide, aluminum silicon, boron oxide, and zirconium oxide. These coatings can provide improved properties, including reducing the photoreactivity of titanium dioxide. Metal oxide coatings of aluminum oxide, aluminum silicon, boron oxide, and zirconium oxide result in positively charged TiO2 pigment surfaces and are therefore particularly useful in conjunction with the cationically stable capsules of the present invention because no additional surface treatment is required for the pigment.

[0110] Commercial examples of such coated titanium dioxide include R700 (coated alumina, available from EI DuPont de Nemours, Wilmington Del.), RDI-S (coated alumina, available from Kemira Industrial Chemicals, Helsinki, Finland), R706 (available from DuPont, Wilmington Del.), and W-6042 (silica-alumina treated nanosized titanium dioxide from Tayco Corporation, Osaka Japan).

[0111] In another preferred embodiment of the present invention, the overprint varnish to be applied to the jetted aqueous inkjet ink may also comprise a compound functionalized with at least two functional groups that are primary or secondary amines, with primary amines being more preferred, and a dispersion of particles comprising an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II or III, or a capsule consisting of a polymer shell surrounding a core. The core comprises an oligomer or polymer having at least three repeating units comprising a functional group according to formula I, II or III. The overprint varnish may be applied by any suitable coating method or printed using a printing technique such as gravure printing, flexographic printing, offset printing or inkjet printing.

[0112] The substrate in the inkjet recording method may be porous, such as textile, paper, leather and cardboard substrates, but is preferably a non-absorbent substrate such as polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polyester such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polylactide (PLA) or polyimide.

[0113] The substrate may also be a paper substrate, such as plain paper or resin coated paper, for example polyethylene or polypropylene coated paper. There is no real limitation on the type of paper and it includes newsprint, magazine paper, office paper, wallpaper, but also heavier papers, often referred to as paperboard, such as white pulp lined chipboard, corrugated board and packaging board.

[0114] The substrate may be transparent, translucent or opaque. Preferred opaque substrates include so-called synthetic papers, such as Synaps from Agfa-Gevaert. TM Grade, which is 1.10g / cm 3 or higher density opaque polyethylene terephthalate sheet.

[0115] In another preferred inkjet recording method, the pretreatment liquid is applied via a technique selected from inkjet, valve jet, and spray. More specifically, these inkjet and valve jet techniques allow the pretreatment liquid according to the present invention to be applied image-wise, preferably to the surface on which the inkjet ink will be printed to obtain the image. These latter methods of applying the pretreatment liquid have the advantage that the amount of pretreatment liquid required is significantly lower than with other application methods for priming the substrate.

[0116] Examples of heating processes for drying pretreatment liquids, inkjet inks, or overprint varnishes comprising a compound functionalized with at least two functional groups that are primary or secondary amines and polymer particles comprising an oligomer or polymer having at least three repeating units comprising a functional group according to Formula I, II, or III, more preferably capsules comprising a polymer shell surrounding a core comprising an oligomer or polymer having at least three repeating units comprising a functional group according to Formula I, II, or III, include, but are not limited to, hot pressing, atmospheric steam, high-pressure steam, and THERMOFIX. Any heat source can be used for the heating process; for example, an infrared source can be used.

[0117] The drying step can be carried out in air, but the heating step to achieve a temperature of the jetted ink, pretreatment liquid or overprint varnish of at least 60° C., more preferably 80° C., must be carried out by using a heat source. Suitable examples of heat sources include devices for forced air heating, radiant heating (such as IR-radiation, including NIR- and CIR-radiation), conductive heating, high-frequency drying and microwave drying.

[0118] The preferred inkjet head for ejecting inkjet ink or pre-treatment liquid or overprint varnish in an inkjet printing system is a piezoelectric inkjet head. Piezoelectric inkjet ejection is based on the movement of a piezoelectric ceramic transducer when a voltage is applied to it. The application of voltage changes the shape of the piezoelectric ceramic transducer in the print head, creating a gap that is then filled with ink or liquid. When the voltage is removed again, the ceramic expands to its original shape, ejecting ink droplets from the inkjet head. However, the ejection of ink or pre-treatment liquid 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, thermal print head, MEM-jet head and valve jet type. Example

[0119] Material Unless otherwise specified, all compounds were supplied by TCI Europe.

[0120] Desmodur N75 BA is a trifunctional isocyanate supplied by Bayer AG.

[0121] Lakeland ACP70 is a zwitterionic surfactant supplied by Lakeland Laboratories LTD.

[0122] Alkanol XC is an anionic surfactant supplied by Dupont.

[0123] Cab-o-Jet 465M is a magenta pigment dispersion supplied by Cabot.

[0124] Amino-1 is a difunctional amine supplied by TCI.

[0125] Example 1: Synthesis of the resin INVRES-1 of the present invention Dissolve 10 g of 2-(acetoacetoxy)ethyl methacrylate in 30 ml of ethyl acetate. Add 0.472 g of dodecyl mercaptan and purge the mixture with nitrogen. Add 134 mg of 2,2′-azobis[2-methylbutyronitrile] and reflux the mixture for 6 hours. Allow the mixture to cool to room temperature. This solution of the resin INVRES-1 of the present invention in ethyl acetate is used directly in the synthesis of the capsule INVCAP-1 of the present invention.

[0126] The molecular weight of INVRES-1 was determined using GPC relative to poly(styrene) standards. INVRES-1 had a number average molecular weight, Mn, of 10,500 and a weight average molecular weight, Mw, of 15,400.

[0127] Preparation of capsule INVCAP-1 of the present invention: 13.2 g of Desmodur N75 BA were added to a solution of 37 g of the above INVRES-1 in ethyl acetate. 1.2 g of Lakeland ACP 70 were added and the solution was stirred at room temperature for one hour.

[0128] This solution was added to a solution of 3.36 g Lakeland ACP 70, 1.17 g lysine, and 1.5 g triethanolamine in 44 g water while stirring at 16,000 rpm using an Ultra Turrax for 5 minutes. 52 g of water was added and the solvent was evaporated under reduced pressure at 60°C while gradually increasing the vacuum from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 88 g by evaporating the water at 120 mbar. The dispersion was stirred at 65°C for 16 hours. The dispersion was allowed to cool to room temperature and filtered through a 1.6 μm filter.

[0129] The average particle size was measured using a Zetasizer™ Nano-S (Malvern Instruments, Goffin Meyvis) and was found to be 183 nm.

[0130] Preparation of comparative ink COMP-1 and ink INV-1 of the present invention Inventive ink INV-1 and comparative ink COMP-1 were prepared by mixing the components according to Table 5. All weight percentages are based on the total weight of the inkjet ink.

[0131] Table 5 Mass (wt.%) COMP-1 INV-1 INVCAP-1 5 5 Cab-O-Jet 465M 2 2 water 5 5 Alkanol XC 0.1 0.1 Amino-1 - 0.144 Inventive composition INV-1 and comparative composition COMP-1 were coated on glass and dried for 15 minutes at 80° C. Solvent resistance was tested by rubbing the coatings 40 times with a Q-tip using isopropyl alcohol and methyl ethyl ketone as solvents.

[0132] The coating of the comparative composition COMP-1 was clearly damaged, whereas the coating of the inventive composition INV-1 was completely resistant to both solvents, demonstrating crosslinking of the coating at 80°C.

[0133] Example 2 : Example 2 shows that the storage stability of the ink according to the present invention is sufficient for practical use.

[0134] Inventive ink INV-2 was prepared by mixing the components according to Table 6. All weight percentages are based on the total weight of the inkjet ink.

[0135] Table 6 Ink INV-2 of the present invention was stored at 60°C for 14 days, and the viscosity change was monitored. The initial viscosity was 7.5 mPas. After aging, the viscosity change was less than 10% of the original value, indicating that the combination of a compound functionalized with at least two functional groups selected from primary and secondary amines, a colorant, and polymer particles comprising an oligomer or polymer having at least three repeating units containing a functional group according to Formula I, II, or III is sufficiently stable for practical use.

Claims

1. An aqueous inkjet ink comprising a compound functionalized with at least two functional groups selected from primary and secondary amines, a colorant, and polymer particles, the polymer particles being capsules comprising a polymer shell surrounding a core, the polymer shell comprising polyurea, polyurethane, or a combination thereof, the core comprising an oligomer or polymer consisting of repeating units containing functional groups according to formula I: Formula I in R1 is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aryl or heteroaryl, COR3 and CN, R2 is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aryl or heteroaryl and COR3, R1 and R2 may represent atoms necessary to form a five- to eight-membered ring, R3 is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aryl or heteroaryl, OR4 and NR5R6, R4 is selected from 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, R5 and R6 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, and R5 and R6 may represent the atoms necessary to form a five- to eight-membered ring, X is selected from O and NR7, R7 is 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.

2. Aqueous inkjet ink according to claim 1, wherein the compound is a 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.

3. The aqueous inkjet ink according to claim 1, wherein the compound is di- or trifunctional.

4. The aqueous inkjet ink according to claim 1, wherein the dispersing groups are covalently bonded to the polymer shell.

5. The aqueous inkjet ink according to claim 2, wherein the dispersing groups are covalently bonded to the polymer shell.

6. The aqueous inkjet ink according to claim 4, wherein the dispersing group is selected from carboxylic acid or salts thereof, sulfonic acid or salts thereof, phosphoric acid ester or salts thereof and phosphonic acid or salts thereof.

7. The aqueous inkjet ink according to claim 5, wherein the dispersing group is selected from carboxylic acid or salts thereof, sulfonic acid or salts thereof, phosphoric acid or salts thereof and phosphonic acid or salts thereof.

8. The aqueous inkjet ink according to claim 1, wherein the colorant is a pigment.

9. The aqueous inkjet ink according to claim 4, wherein the colorant is a pigment.

10. The aqueous inkjet ink according to claim 7, wherein the colorant is a pigment.

11. An inkjet recording method comprising the following steps: a) jetting an inkjet ink as defined in claim 1 onto a substrate; and b) drying the jetted inkjet ink by applying heat, such as to obtain a temperature of the jetted ink of at least 60°C.

12. The inkjet recording method according to claim 11, further comprising the step of applying an aqueous pre-treatment liquid onto the substrate before step a), the pre-treatment liquid comprising a compound capable of aggregating components in the aqueous inkjet ink.

13. The inkjet recording method according to claim 12, wherein the pretreatment liquid is applied via a technique selected from the group consisting of inkjet, valve jet and spray.

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