Aqueous dispersions of polymer capsules

Abstract

The present invention relates to aqueous dispersions of polymer capsules. An aqueous dispersion of capsules comprises a polymeric shell surrounding a core comprising an oligomer or polymer having at least 3 repeating units comprising a functional group according to general formula (I), (II) or (III). The dispersion of capsules may be incorporated into an aqueous pigmented inkjet ink. # imgabs0 #

Description

This application is a divisional application of the parent application No. 202080087606.7. The application date of the parent application is December 14, 2020; the name of the invention is "Aqueous dispersion of polymer capsules". Technical Field

[0001] The present invention relates to aqueous dispersions of capsules having a core comprising an oligomer or polymer for use in printing, and more particularly for inkjet printing on non-absorbent substrates using aqueous resin-based inkjet inks. Background Art

[0002] Industrial applications of inkjet are expanding into more and more technical fields and must meet even more and more demanding physical properties. Industrial printing technology must be compatible with inexpensive substrates, which are usually based on poly(olefins). It is known in the industry that adhesion to poly(olefins) is usually very difficult.

[0003] Until now, inkjet technology on non-absorbent substrates, including poly(olefins), has been UV-based. However, water-based technology is also gradually gaining ground on non-absorbent substrates. Bonding water-based resin-based inks directly on poly(olefins) is still even more difficult than with UV technology.

[0004] Several methods are known in the art to improve the adhesion of aqueous inks, including corona treatment, flame treatment of the substrate, and priming the substrate with a primer containing a resin, such as a polyurethane resin. Pre-treating the substrate with corona and flame treatment complicates the workflow and does not always solve the adhesion problem.

[0005] Aqueous base paints or aqueous inkjet inks containing resins (e.g., polyurethane resins) have been designed to improve image durability (e.g., scratch resistance, wear resistance, and chemical resistance). WO 2018 / 077624 describes aqueous inkjet inks containing polyurethane resins with dispersed groups that provide electronic and spatial colloid stability. WO 2016 / 122569 teaches primer solutions containing polyurethane resins with specific diols. Aqueous inks and primers still suffer from the disadvantage of insufficient adhesion to poly(olefin) substrates. In addition, the use of resins dispersed or dissolved in aqueous inks or primers that must be ejected via, for example, an inkjet head causes problems with jetting reliability. This may be due to the formation of a film of resin at the nozzle plate causing clogging of the nozzle when the inkjet head is not used for a period of time.

[0006] Aqueous resin-based inkjet inks are described in WO 2016 / 165956, in which the resin is present as capsules to improve the jetting reliability of the resin-based ink. However, in order to achieve good adhesion properties and thus obtain a durable image, reactive chemicals (e.g. blocked isocyanates) are incorporated into the core of the capsule. The presence of such reactants may create health and safety issues when not fully reacted. In addition, the release of the reactive chemicals from the core requires a thermal activation step during or after drying the ink. The thermal activation step involves heating the printed image to a temperature above 100°C, which is incompatible with poly(olefin)-based substrates (e.g. polyethylene or polypropylene films).

[0007] US2019 / 0023922 discloses an inkjet ink containing a capsule having a core, wherein the core comprises a polymerizable compound, such as a polymerizable oligomer or polymer. The polymerizable compound is a compound or a blocked isocyanate that polymerizes only when UV light is applied.

[0008] Therefore, there remains a need for resin technology that inherently exhibits good adhesion properties to poly(olefins) and at the same time can be incorporated into inkjet inks or jettable primers, providing reliable jetting performance. Summary of the invention

[0009] The object of the present invention is to provide a solution to the above mentioned problems.

[0010] This object has been achieved by providing an inkjet ink comprising capsules.

[0011] Another embodiment of the present invention is to provide a printing method using the inkjet ink of the capsule.

[0012] Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention. DETAILED DESCRIPTION

[0013] A. Aqueous dispersion according to the invention A.1. Oligomers or polymers according to the invention The objects of the present invention are achieved by an aqueous dispersion comprising capsules comprising a core surrounded by a polymer shell, wherein the core comprises an oligomer or polymer having at least 3 repeating units comprising a functional group according to 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, C(=O)R3 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 C(=O)R3 R1 and R2 may represent atoms necessary to form a 5-8 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 5-8 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 5-8 membered ring.

[0014] In a preferred embodiment, the oligomer or polymer comprising repeating 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 repeating units.

[0015] 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, more preferably unsubstituted, even more preferably lower alkyl, and most preferably methyl.

[0016] 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.

[0017] The polymers according to the invention may be homopolymers or copolymers of different repeating units.

[0018] The oligomers or polymers according to the invention can be prepared by addition polymerization, polycondensation and ring-opening polymerization of ethylenically unsaturated monomers, particularly preferably addition polymerization. In the most preferred embodiment, free radical polymerization of ethylenically unsaturated monomers is used to prepare the resin according to the invention. In another embodiment of the invention, RAFT agents, ATRP, nitroxyl radical technology or transfer agents (preferably thiols) are used to control the molecular weight of the resin according to the invention.

[0019] Typical monomers used to prepare the resin according to the present invention are given below, but are not limited thereto.

[0020] Monomers for addition polymerization: see Table 1 .

[0021] Table 1 Free radical and cationic polymerization conditions are preferred for preparing the addition polymers according to the present invention.

[0022] Monomers used for ring-opening polymerization: see Table 2 .

[0023] Table 2 Poly(ethers), poly(esters), poly(carbonates) and poly(amides) or copolymers thereof can be prepared using ring-opening polymerization environments documented in the scientific literature.

[0024] Monomers used for polycondensation: see Table 3 .

[0025] Table 3 Poly(esters) can be prepared by condensation of 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 condensation of functionalized diols with diisocyanates under conditions known to those skilled in the art.

[0026] A.2. Capsules according to the invention The oligomers or polymers according to the present invention are encapsulated to form an aqueous dispersion, preferably by polymerisation, more preferably by using interfacial polymerisation.

[0027] The capsules are preferably present in the pretreatment liquid (or primer), overprint varnish or printing ink (more preferably inkjet ink) in an amount not exceeding 45 wt %, preferably between 5 and 25 wt %, based on the total weight of the liquid / varnish / ink. It has been observed that above 30 wt %, jetting is not always reliable.

[0028] The average particle size of the capsules to be used for the jettable aqueous formulation (e.g., inkjet ink or jettable pretreatment liquid) is no more than 4 μm, as determined by dynamic laser diffraction. The nozzle diameter of the inkjet print head is typically 20-35 μm. Reliable inkjet printing is possible if the average particle size of the capsules is 1 / 5 of the nozzle diameter. An average particle size of no more than 4 μm allows jetting through a print head with a minimum nozzle diameter of 20 μm. In a more preferred embodiment, the average particle size of the capsules is 1 / 10 of the nozzle diameter. Therefore, the preferred average particle size is 0.05-2 μm, more preferably 0.10-1 μm. When the average particle size of the capsules is less than 2 μm, excellent resolution and dispersion stability are obtained over time.

[0029] The capsules are dispersed in the aqueous medium of the pre-treatment liquid or inkjet ink using dispersing groups covalently bonded to the polymer shell, or by using a dispersant or surfactant which is preferably added during or after the formation of the capsules. 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 polyethylene oxide groups.

[0030] 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 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 alkaline aqueous medium converts the carboxylic acid groups of the covalently bonded polymer shell into ionic groups, after which the negatively charged capsules do not have a tendency to condense. If enough dispersing groups are covalently bonded to the polymer shell, the capsule becomes a so-called self-dispersing capsule.

[0031] These negatively or positively charged capsule surfaces can also be advantageously used during inkjet printing. For example, a second liquid that is a cationic polymer or a multivalent salt (e.g., a pretreatment liquid containing a cationic substance) can be used to precipitate anionically stabilized colorants for aqueous inkjet inks printed on top of the second liquid. Due to the immobilization of the capsules, improvements in image quality can be observed by using this method.

[0032] There is no practical limit to the type of polymer used for the polymer shell of the capsule. Preferably, the polymer used for the polymer shell is cross-linked. By cross-linking, more rigidity is built into the capsule, allowing a wider range of temperatures and pressures for processing the capsule both in ink preparation and in the inkjet printer.

[0033] Preferred examples of polymer shell materials include polyureas, polyesters, polycarbonates, polyamides, melamine-based polymers, and mixtures thereof, with polyureas being particularly preferred.

[0034] A.3. Preparation of capsules according to the invention The oligomer or polymer encapsulating at least 3 repeating units comprising functional groups according to formula I, II or III with a polymer shell can be prepared using both chemical and physical methods. Suitable encapsulation methods include complex coacervation, liposome formation, spray drying and polymerisation methods.

[0035] In the present invention, it is preferred to use a polymerization method because it allows the highest control in designing the capsule. More preferably, interfacial polymerization is used to prepare the capsules of the present invention. This technology 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 (ed.), Chapter 5, 137-173 (Scrivener Publishing LLC (2013)).

[0036] In interfacial polymerization (eg, interfacial condensation), two reactants meet at the interface of an emulsion droplet and react rapidly.

[0037] Typically, 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 (first shell component) that is capable of reacting with another monomer (second shell component) dissolved in the other phase. During polymerization, a polymer is formed that is insoluble in both the aqueous phase and the lipophilic phase. As a result, the polymer formed has a tendency to precipitate at the interface of the lipophilic and aqueous phases, where it forms a shell around the dispersed phase, which grows during further polymerization. The capsules according to the invention are preferably prepared from a lipophilic dispersion in an aqueous continuous phase.

[0038] Typical polymer shells of capsules according to the invention and formed by interfacial polymerization are selected from polyamides, usually prepared from diacyl chlorides or polyacyl chlorides as first shell components and diamines or oligoamines as second shell components; polyureas, usually prepared from diisocyanates or oligoisocyanates as first shell components and diamines or oligoamines as second shell components; polyurethanes, usually prepared from diisocyanates or oligoisocyanates as first shell components and diols or oligoalcohols as second shell components; polysulfonamides, usually prepared from disulfonyl chlorides or oligosulfonyl chlorides as first shell components and diamines or oligoalcohols as second shell components; polyesters, usually prepared from diacyl chlorides or oligoacyl chlorides as first shell components and diols or oligoalcohols as second shell components; and polycarbonates, usually prepared from dichloroformates or oligochloroformates as first shell components and diols or oligoalcohols as second shell components. The shell may consist of a combination of these polymers.

[0039] In further embodiments, 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 oligoacyl chlorides, dichloroformates or oligochloroformates, and epoxy resins as the first shell component.

[0040] 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 for the dispersing step, which is removed by solvent stripping before or after the shell is formed. In a particularly preferred embodiment, the boiling point of the water-immiscible solvent is below 100° C. at normal pressure. Esters are particularly preferred as water-immiscible solvents.

[0041] 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 when mixed in a 1:1 volume ratio at 20°C.

[0042] The core contains an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III. These are usually incorporated into the capsule by dissolving them in an organic solvent with low miscibility with water and a lower boiling point than water. The preferred organic solvent is ethyl acetate as it also has a low flammability hazard compared to other organic solvents.

[0043] However, in some cases, the organic solvent may be omitted. For example, when the viscosity of the oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III is less than 100 mPa.s, the organic solvent may be omitted.

[0044] The method for preparing a dispersion of capsules 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 a low miscibility with water and a lower boiling point than water; b) preparing an aqueous solution of a second shell component for forming the polymer shell; c) dispersing a non-aqueous solution in an 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 functional groups according to formula I, II or III by interfacial polymerization of a first shell component and a second shell component for forming the polymer shell.

[0045] Capsule dispersion can be accomplished in inkjet inks, aqueous pretreatment liquids, or any liquid suitable for the printing process by adding, for example, water, humectants, surfactants, and the like.

[0046] In a preferred embodiment, the capsule is a self-dispersing capsule. In order to make the capsule self-dispersing, anionic dispersing groups (e.g., carboxylic acids or salts thereof, sulfonic acids or salts thereof, phosphates or salts thereof, or phosphonic acids or salts thereof) or cationic dispersing groups (e.g., quaternary ammonium salts, protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfonium and phosphonium) can be covalently bonded to the polymer shell of the capsule to ensure dispersion stability.

[0047] A preferred strategy for incorporating anionic stabilizing groups in the polymer shell of the capsule utilizes carboxylic acid functionalized reactive surfactants capable of reacting with isocyanates. This results in amphoteric type surfactants containing at least in part secondary or primary amines. Other reactive surfactants functionalized with sulfonic acids or salts thereof, phosphates or salts thereof, or phosphonic acids or salts thereof may be used.

[0048] Several amphoteric surfactants, which are mixtures of surfactants partially having secondary amines and also containing tertiary amines, are commercially available. Capsules prepared using commercially available amphoteric surfactants are encountered in inkjet printers to suppress foam formation in inkjet inks. Foaming causes problems in the ink supply and in the exhaust of attempts to remove air from the ink, thus leading to unreliable jetting. Therefore, it is preferred to use a surfactant according to formula (I) of WO2016 / 165970 during the encapsulation process of an oligomer or polymer having at least 3 repeating units containing a functional group according to formula I, II or III.

[0049] Incorporation of cationic dispersing groups in the polymer shell of the capsules for pre-treatment of liquid or cationic based inkjet inks (as disclosed in patent application WO2019 / 105867) utilizes a surfactant with cationic dispersing groups bound to the shell of the capsules according to the present invention. This is achieved 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 an isocyanate monomer of the shell). In an even more preferred embodiment, the surfactant is a surfactant according to formula IV.

[0050] in R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, and substituted or unsubstituted alkynyl, provided that R1 contains at least 8 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 linking group containing no more than 8 carbon atoms; X represents a counter ion that compensates for the positive charge of the ammonium group.

[0051] 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.

[0052] One or more organic solvents can be added for a variety of reasons. For example, it is advantageous to add a small amount of organic solvent to improve the dissolution of the compound in the pre-treatment liquid to be prepared or the inkjet ink. 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-propanediol). alcohols), amines (e.g., ethanolamine and 2-(dimethylamino)ethanol), monohydric alcohols (e.g., methanol, ethanol and butanol), alkyl ethers of polyhydric alcohols (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.

[0053] B. Aqueous Formulations Containing the Dispersion of the Invention .

[0054] B.1. Pretreatment of liquid The aqueous pretreatment liquid is preferably used for printing with aqueous-based ink on non-absorbent substrates. The aqueous pretreatment liquid according to the present invention comprises a dispersion of capsules consisting of a polymer shell around a core. The core contains an oligomer or polymer having at least 3 repeating units containing functional groups according to formula I, II or III. The shell further comprises a dispersing group, preferably covalently bonded to the shell, more preferably, the dispersing group is a group selected from protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfonium and phosphonium. The aqueous medium contains water, but may include one or more water-soluble organic solvents. Suitable organic solvents are described in §A.3. If present in the pretreatment liquid, the amount of the capsule is preferably no more than 45% by weight, more preferably between 5-25% by weight, based on the gross weight of the pretreatment liquid.

[0055] Polyvalent metal ions may be included in the pretreatment liquid as flocculants. Suitable examples are those composed of divalent or higher valent metal cations (e.g. magnesium, calcium, strontium, barium, zirconium and aluminum) and anions (e.g. fluoride ions (F - ), chloride ion (Cl - ), bromide ion (Br - ), sulfate ion (SO4 2- ), nitrate ion (NO3 -) and acetate ions (CH3COO - )) formed water-soluble metal salts.

[0056] These multivalent metal ions have the function of aggregating the ink by acting on the carboxyl groups on the surface of the pigment in the inkjet ink or the dispersed polymer of the capsules contained in the ink. As a result, the colorant of the ink is fixed, resulting in reduced bleeding and beading. Therefore, it is preferred that the surface of the pigment in the ink and / or the dispersed polymer of the capsules (if contained in the ink) has anionic groups, preferably carboxyl groups.

[0057] The pretreatment may also contain an organic acid as a flocculant. Preferred examples of organic acids include, but are not limited to, acetic acid, propionic acid, and lactic acid.

[0058] The pretreatment liquid may further contain a resin as a flocculant. 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 tannic acid and lignin; and synthetic water-soluble polymers such as polymers comprising polyvinyl alcohol, polymers comprising 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 not more than 20% by weight, relative to the total mass of the pretreatment liquid.

[0059] The pre-treatment liquid may also contain a wetting agent. If the pre-treatment liquid must be applied by a jetting technique (e.g., inkjet or valve jetting), the wetting agent is preferably incorporated into the liquid. The wetting agent prevents nozzle clogging. Prevention is due to the evaporation rate of the pre-treatment liquid (particularly the water in the liquid) being slowed down. The wetting agent is preferably an organic solvent with a higher boiling point than water. Suitable wetting agents include triacetin, N-methyl-2-pyrrolidone, glycerine, urea, thiourea, ethylene urea, alkyl urea, alkyl thiourea, dialkyl urea and dialkyl thiourea, diols (including ethylene glycol, propylene glycol, glycerol, butylene glycol, pentanediol and hexylene glycol), glycols (glycol) (including propylene glycol, polypropylene glycol, ethylene glycol, polyethylene glycol, diethylene glycol, tetraethylene glycol) and mixtures and derivatives thereof. A preferred wetting agent is glycerine.

[0060] The wetting agent is preferably added to the liquid preparation in an amount of 0.1 to 20% by weight, based on the total weight of the liquid.

[0061] The pretreatment liquid may contain a surfactant. Any known surfactant may be used, but preferably a glycol surfactant and / or an acetylene alcohol surfactant. The use of an acetylene glycol surfactant and / or an acetylene alcohol surfactant further reduces bleeding to improve print quality, and also improves drying properties in printing to allow high-speed printing.

[0062] The acetylene glycol surfactant and / or acetylene alcohol surfactant is preferably one or more selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol. These are available, for example, as Olfine (registered trademark) 104 series and E series (e.g. Olfine E1010) from Air Products (GB) or as Surfynol (registered trademark) 465 and Surfynol 61 from Nissin Chemical Industry.

[0063] The pretreatment liquid may also contain a pigment. Particularly useful for printing on dark or transparent substrates are pretreatment liquids containing white pigments. 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. Methods for preparing TiO2 are described in more detail in "The Pigment Handbook", Volume 1, 2nd Edition, John Wiley & Sons, NY (1988), the relevant disclosures of which are incorporated herein by reference for all purposes as if fully set forth.

[0064] The titanium dioxide particles can have a wide range of average particle sizes of 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 average size of the particles is from about 50 to about 950 nm, more preferably from about 75 to about 750 nm, and even more preferably from about 100 to about 500 nm.

[0065] For applications requiring white with a certain degree of transparency, the pigment is preferably "nano" titanium dioxide. "Nano" titanium dioxide particles generally have an average size of about 10 to about 200 nm, preferably about 20 to about 150 nm, and more preferably about 35 to about 75 nm. Inks containing nano titanium dioxide can provide improved chroma and transparency while still maintaining good light fading resistance and appropriate color angles. An example of commercially available uncoated nanoscale titanium dioxide is P-25, available from Degussa (Parsippany N.J.).

[0066] In addition, unique advantages such as opacity and UV protection can be achieved with a variety of particle sizes. These various sizes can be achieved by adding both pigments and nano-sized TiO2.

[0067] Titanium dioxide is preferably incorporated into the pretreatment formulation via the slurry concentrate composition.The amount of titanium dioxide present in the slurry composition is preferably from about 15 wt % to about 80 wt %, based on the total slurry weight.

[0068] The titanium dioxide pigment may also carry one or more metal oxide surface coatings. These coatings may be applied using techniques known to those skilled in the art. Examples of metal oxide coatings include silica, alumina, alumina silica, boria, and zirconium oxide, among others. These coatings may provide improved properties, including reduced photoreactivity of the titanium dioxide. Metal oxide coatings of alumina, alumina silica, boria, and zirconium oxide result in a positively charged surface of the TiO2 pigment, and are therefore particularly useful in combination with the cationically stabilized capsules of the present invention, since no additional surface treatment of the pigment is required.

[0069] Commercial examples of such coated titanium dioxide include R700 (alumina coated, available from EI 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 nanosized titanium dioxide, available from Tayco Corporation, Osaka Japan).

[0070] The pretreatment liquid may contain at least one pH regulator. Suitable pH regulators include organic amines, NaOH, KOH, NEt3, NH3, HCl, HNO3 and H2SO4. In a preferred embodiment, the pH of the pretreatment liquid is less than 7. A pH of 7 or less can favorably affect the electrostatic stabilization of the capsules, especially when the dispersing groups of the capsules are amines.

[0071] B.2. Aqueous inkjet ink.

[0072] The aqueous inkjet ink according to the present invention comprises at least a) an aqueous medium; and b) a dispersion of capsules consisting of a polymer shell surrounding a core. The core contains an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III. The shell further comprises a dispersing group, preferably covalently bonded to the shell, more preferably, the dispersing group is a group selected from a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphate or a salt thereof, a phosphonic acid or a salt thereof.

[0073] The capsules are preferably present in the inkjet ink in an amount not exceeding 30 wt%, preferably between 5 and 25 wt%, based on the total weight of the inkjet ink. It has been observed that above 30 wt%, jetting is not always so reliable.

[0074] 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 (e.g. red, green, blue, purple and / or orange) to further expand the color gamut of the image. The inkjet ink set can also be extended by a combination of a full-density inkjet ink with a light-density inkjet ink. The combination of dark and light inks and / or black and grey inks improves the image quality by reducing the granularity.

[0075] In a preferred embodiment, the inkjet ink set further comprises a white inkjet ink. This allows brighter colors to be obtained, especially on transparent substrates, where the white inkjet ink can be applied as a primer or on top of the colored inkjet inks when the image is viewed through the transparent substrate.

[0076] At 25 °C and for 90 s -1 The viscosity of the inkjet ink is preferably less than 25 mPa.s at a shear rate of 25°C and at 90 s -1 At a shear rate of , the viscosity is more preferably between 2 and 15 mPa.s.

[0077] The surface tension of the inkjet ink at 25°C is preferably in the range of about 18 mN / m to about 70 mN / m, more preferably in the range of about 20 mN / m to about 40 mN / m at 25°C.

[0078] The inkjet ink may also contain at least one surfactant for obtaining good spreading characteristics on the substrate.

[0079] B.2.1. Solvents The aqueous medium of the ink contains water, but may preferably include one or more water-soluble organic solvents. Suitable solvents that may be incorporated into the ink are described in §A.3.

[0080] B.2.2. Pigments The pigment of the ink can be black, white, cyan, magenta, yellow, red, orange, purple, blue, green, brown, mixtures thereof, etc. The colored 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.

[0081] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0082] The pigment particles are dispersed in an aqueous medium by a polymeric dispersant or a surfactant. Self-dispersible pigments can also be used. If combined with capsules having anionic dispersing groups, anionic surfactants can be preferably used as dispersants for pigments. If combined with capsules having cationic dispersing groups, cationic surfactants can be preferably used as dispersants for pigments. The latter prevents the interaction of polymeric dispersants with the dispersing groups (see below) of the capsules that may be included in the inkjet ink, because the dispersion stability of the pigment is achieved by the same technology as the electrostatic stabilization for the capsules.

[0083] Self-dispersible pigments are pigments having covalently bonded anionic hydrophilic groups (e.g. salt-forming groups or the same groups used as dispersing groups for capsules) on their surface, 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.

[0084] The pigment particles in inkjet inks should be small enough to allow the ink to flow freely through the inkjet printing device, especially at the jetting nozzles. It is also desirable to use small particles for maximum color strength and to slow down sedimentation.

[0085] The average pigment particle size is preferably between 0.050 and 1 μm, more preferably between 0.070 and 0.300 μm, and particularly preferably between 0.080 and 0.200 μm. Most preferably, the number average pigment particle size is not greater than 0.150 μm. The average particle size of the pigment particles is determined using a Brookhaven Instruments Particle Sizer BI90plus based on the principle of dynamic light scattering. The ink is diluted with ethyl acetate to a pigment concentration of 0.002% by weight. The measurement settings of the BI90plus are: 5 runs at 23°C, angle 90°, wavelength 635 nm, and graph = correction function.

[0086] However, for white pigment inkjet inks, the number average particle size of the white pigment is the same as described in §B.1.

[0087] Suitable white pigments are given in Table 2 in

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

[0117] and

[0118] of WO 2008 / 074548.

[0088] Special colorants can also be used, such as fluorescent pigments for special effects on clothing, and metallic pigments for printing silver and gold luxurious looks on textiles.

[0089] 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 dispersants depend on both the properties 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 polymerize to form ABBAABAB); Alternating monomers (e.g. monomers A and B polymerize to form ABABABAB); Gradient polymerization of monomers (e.g. monomers A and B polymerize into AAABAABBABBB); Block copolymers (e.g. monomers A and B polymerized to AAAAABBBBBB), where the block length of each block (2, 3, 4, 5 or even more) is important for the dispersing ability of the polymeric dispersant; Graft copolymers (graft copolymers consist of a polymer backbone with polymer side chains attached to the backbone); and • Mixed forms of these polymers, such as block gradient copolymers.

[0090] A suitable dispersant is DISPERBYK available from BYK CHEMIE TM Dispersants, 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.

[0091] The polymer dispersant preferably has a number average molecular weight Mn between 500 and 30,000, more preferably between 1,500 and 10,000.

[0092] 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.

[0093] The pigment is preferably present in the range of 0.01-20%, 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% to 40% by weight, and more preferably 5% to 35% by weight of the inkjet ink. An amount less than 3% by weight may not achieve sufficient covering power.

[0094] B.2.3. Resin The inkjet ink composition according to the present invention may further comprise a resin. Resins are generally added to the inkjet ink formulation to further achieve good adhesion of the pigment to the substrate. Resins are polymers, and suitable resins may be acrylic resins, urethane-modified polyester resins or polyethylene waxes.

[0095] The polyurethane resin can be incorporated into the ink formulation as a dispersion and can be, for example, selected from 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.

[0096] Preferred urethane resins to be used as dispersants in the ink of the present invention are polyester resins comprising structural units containing urethane bonds. Among such resins, water-soluble or water-dispersible urethane-modified polyester resins are preferred. Preferred urethane-modified polyester resins include at least one structural unit derived from a hydroxyl-containing polyester resin (polyester polyol) and at least one structural unit derived from an organic polyisocyanate.

[0097] Furthermore, the hydroxyl-containing polyester resin is a resin formed by an esterification reaction or an ester exchange reaction between at least one polyacid component and at least one polyol component.

[0098] Preferred polyurethane resins that can be included in the ink of the present invention are polyurethane resins that can be obtained by reacting polyester polyols, polyether diols, polyols containing anionic groups with polyisocyanates. Particularly preferred polyurethane resins are polyurethane resins that can be obtained by reacting polyester polyols, polyether diols, polyols containing anionic groups with polyisocyanates, and wherein the polyester polyol is obtained by reacting aromatic polycarboxylic acids with polyols. Examples of suitable polyurethane resins and their preparation are disclosed in unpublished patent application EP16196224.6.

[0099] 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 XP2648, and BAYHYDROL UAXP 2631 (Bayer Material Science); DAOTAN VTW 1262 / 35WA, DAOTANVTW 1265 / 36WA, DAOTANVTW 1267 / 36WA, DAOTANVTW 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.

[0100] Acrylic resins include polymers of acrylic acid monomers, polymers of methacrylic acid monomers and copolymers of the aforementioned monomers and other monomers. These resins exist as dispersions of particles with an average diameter of about 30nm to about 300nm. Acrylic latex polymers are formed by acrylic acid monomers or methacrylic acid monomer residues. By way of illustration, examples of monomers of acrylic latex polymers include acrylic acid monomers (e.g., acrylate, acrylamide and acrylic acid) and methacrylic acid monomers (e.g., methacrylate, methacrylamide and methacrylic acid). Acrylic latex polymers can be copolymers of homopolymers or acrylic acid monomers and another monomer (e.g., vinyl aromatic monomers, including but not limited to styrene, styrene butadiene, p-chloromethyl styrene, divinyl benzene, vinyl naphthalene and divinyl naphthalene).

[0101] 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, NEOCRYLA-1131, NEOCRYLA-2091, NEOCRYLA-1127, NEOCRYL XK-96, and NEOCRYL XK-14 (DSM); and BAYHYDROLAH XP 2754, BAYHYDROLAH XP 2741, BAYHYDROLA 2427 and BAYHYDROLA 2651 (Bayer), or a combination of two or more thereof.

[0102] The concentration of resin (if included) in the inkjet ink according to the present invention is at least 1 wt % and preferably below 30 wt %, more preferably below 20 wt %.

[0103] B.2.4. Additives The aqueous inkjet ink may further comprise surfactants, humectants and thickeners as additives. Such suitable additives are described in §B.1.

[0104] C. Inkjet Printing Method In a preferred inkjet recording method, the method comprises the following steps: a) jetting an aqueous inkjet ink comprising a dispersion of capsules consisting of a polymer shell surrounding a core comprising an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III onto a substrate, preferably a non-porous substrate; and b) drying the jetted inkjet ink by applying heat to such an extent that a temperature of the jetted ink of at least 60° C., more preferably at least 80° C. is obtained. Prior to jetting the inkjet ink according to the present invention, a pretreatment or primer may be applied to the substrate.

[0105] In another preferred inkjet recording method, the method comprises the following steps: a) applying an aqueous pretreatment liquid on a substrate, preferably a non-porous substrate, the pretreatment liquid comprising a dispersion of capsules consisting of a polymer shell surrounding a core, the core comprising an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III, the polymer shell preferably comprising a dispersing group selected from protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfonium and phosphonium; b) optionally at least partially drying the applied aqueous pretreatment liquid by applying heat to an extent to obtain a temperature of the applied pretreatment liquid of at least 60° C., preferably 80° C.; c) jetting an aqueous inkjet ink on the applied pretreatment liquid, the ink preferably comprising a colorant (e.g. a pigment) and even more preferably comprising a resin. More preferably, the ink may comprise a dispersion of capsules consisting of a polymer shell surrounding a core comprising an oligomer or polymer having at least 3 repeating units comprising a functional group according to formula I, II or III, d) drying the jetted inkjet. If step b) is not performed, or the drying of the pretreatment liquid is not completed, the drying in step d) should be performed by applying heat so that the temperature of the jetted ink is at least 60°C, more preferably at least 80°C.

[0106] The substrate in the ink jet recording method may be porous, such as textile, paper, leather and paperboard substrates, but is preferably a non-absorbent substrate, such as polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polyester such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polylactide (PLA) or polyimide.

[0107] The substrate may also be a paper substrate, such as plain paper or a resin coated paper, such as polyethylene or polypropylene coated paper. There is no practical limitation on the type of paper, and it includes newsprint, junk paper, office paper, wallpaper, but also higher grammage papers, commonly known as paperboard, such as white liner chipboard, corrugated board and packaging board.

[0108] 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 a density of 1.10g / cm 3 or larger opaque polyethylene terephthalate.

[0109] 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 invention to be applied imagewise, preferably onto a surface on which the inkjet ink will be printed to obtain an image. These last ways of applying the pretreatment liquid have the advantage that the amount of pretreatment liquid required is substantially lower than other application methods for priming the substrate.

[0110] Examples of heating methods for drying the pre-treatment liquid or inkjet ink according to the present invention include, but are not limited to, hot pressing, atmospheric steaming, high pressure steaming, thermal fixing. Any heat source can be used for the heating method; for example, an infrared ray source is used.

[0111] The drying step can be carried out under air, but the heating step must be carried out by using a heat source; examples include equipment for forced air heating, radiation heating (e.g. IR-radiation, including NIR radiation and CIR radiation), conduction heating, high-frequency drying and microwave drying. The drying step is such that a temperature of less than 150° C., more preferably less than 100° C., is preferably obtained to avoid deformation of the substrate.

[0112] The preferred inkjet head for inkjet printing system to eject inkjet ink or pre-treatment liquid is a piezoelectric inkjet head. Piezoelectric inkjet ejection is based on the movement of piezoelectric ceramic transducer when voltage is applied thereto. The applied voltage changes the shape of the piezoelectric ceramic transducer in the print head, produces a gap, and then fills the gap 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, ejecting 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 type, thermal print head type, MEM-jet head and valve jet type. Example

[0113] Material Unless otherwise stated, all compounds were supplied by TCI Europe.

[0114] Desmodur N75 BA is a trifunctional isocyanate supplied by Bayer AG.

[0115] Lakeland ACP70 is a zwitterionic surfactant supplied by Lakeland Laboratories LTD.

[0116] Alkanol XC is an anionic surfactant supplied by Dupont.

[0117] Cab-o-Jet 465M is a magenta pigment dispersion supplied by Cabot Cab-O-Jet 450C is a cyan pigment dispersion supplied by Cabot Surfinol 104H is a surfactant supplied by Nissin Chemical Industry Diamond D75 M is a magenta dispersion supplied by Diamond Dispersions.

[0118] MNDA is methyldiethanolamine, supplied by Aldrich Diamond D75Y is a yellow dispersion supplied by Diamond Dispersions.

[0119] Diamond D75K is a black dispersion supplied by Diamond Dispersions.

[0120] MA-1 is 2-(acetoacetoxy)ethyl methacrylate MA-2 is 2-prop-2-enoyloxyethyl 3-oxobutanoate and was prepared according to Christopherson C. et al., Journal of Polymer Science, Part A: Polymer Chemistry, 56(22), 2539-2546 (2018).

[0121] MA-4 is (4-vinylphenyl)methyl 3-oxobutanoate and is prepared as follows: First, 4-hydroxymethyl-styrene was prepared as follows: 0.4 g of sodium hydroxide, 32.23 g of tetrabutylammonium bromide and 2.2 g of BHT were added to 400 ml of water. The mixture was stirred at room temperature for 10 minutes; 15.62 g of 4-chloromethyl-styrene was added, and the mixture was heated to 90°C for 40 minutes. The reaction mixture was cooled to room temperature and extracted three times with 100 ml of ethyl acetate. The pooled organic fractions were dried over magnesium sulfate, and the solvent was removed under reduced pressure. The crude 4-hydroxymethyl-styrene was purified by preparative column chromatography on a Prochrom LC80 column using Kromasil Si 10 μm as stationary phase, using a gradient elution from dichloromethane to dichloromethane / ethyl acetate 80 / 20 as eluent. 5.76 g (yield: 43%) of 4-hydroxymethyl-styrene were isolated (TLC analysis on TLC silica gel 60 F254 (supplied by Merck): eluent dichloromethane / ethyl acetate 90 / 10: Rf=0.45).

[0122] Next, 3-oxobutyric acid (4-vinylphenyl) methyl ester was prepared as follows: 11 g of 4-hydroxymethyl-styrene, 19.45 g of t-butyl acetoacetate and 25 mg of TEMPO were dissolved in 150 ml of toluene. The reaction mixture was heated to reflux while removing the mixture of t-butyl alcohol and toluene by distillation. The distillation was continued for 90 minutes. The reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure. The crude 3-oxobutyric acid (4-vinylphenyl) methyl ester was purified by preparative column chromatography on a Prochrom LC80 column using Kromasil Si 10 μm as stationary phase and hexane / ethyl acetate 70 / 30 as eluent. 12 g (yield: 67%) of (4-vinylphenyl)methyl 3-oxobutyrate were isolated (TLC analysis on TLC silica gel 60 F254 (supplied by Merck): eluent hexane / ethyl acetate 70 / 30: Rf=0.4).

[0123] MA-5 is 2-[(4-vinylphenyl)methoxy]ethyl 3-oxobutanoate, prepared as follows: First, 2-[(4-vinylphenyl)methoxy]ethanol was prepared as follows: 400 ml of tetrahydrofuran was added to 1.19 kg of ethylene glycol. The mixture was stirred at room temperature, and 3.98 g of 4-tert-butylcatechol was added, followed by 35 g of a 60 wt % dispersion of sodium hydride in mineral oil in batches over one hour. During the addition, the temperature rose to 45°C. The mixture was stirred at room temperature for 2 hours. A solution of 74.19 g of 4-chloromethyl-styrene in 100 ml of tetrahydrofuran was added, and the reaction was continued at 45°C for 48 hours. The mixture was added to 500 ml of water and extracted three times with 300 ml of dichloromethane. The collected organic fractions were dried over sodium sulfate and evaporated under reduced pressure. The crude 2-[(4-vinylphenyl)methoxy]ethanol was purified on a Graceresolve RS80 column by preparative column chromatography, using a gradient elution from dichloromethane to dichloromethane / ethyl acetate 80 / 20. 64 g (yield: 74%) of 2-[(4-vinylphenyl)methoxy]ethanol were separated (on TLC silica gel 60F 254 TLC analysis on 4% paraformaldehyde (supplied by Merck): eluent: dichloromethane / ethyl acetate 90 / 10: R f =0.27).

[0124] Next, 2-[(4-vinylphenyl)methoxy]ethyl 3-oxobutyrate was prepared as follows: 17.8 g of 2-[(4-vinylphenyl)methoxy]ethanol, 15.82 g of t-butyl acetoacetate and 31 mg of TEMPO were dissolved in 150 ml of toluene. The mixture was heated to reflux and the mixture of t-butyl alcohol and toluene was removed by distillation. 20 ml of the mixture was removed within half an hour. Another 7.9 g of t-butyl acetoacetate was added after half an hour and distillation was continued for half an hour. The reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure. The crude 2-[(4-vinylphenyl)methoxy]ethyl 3-oxobutyrate was purified by preparative column chromatography on a Prochrom LC80 column using Kromasil Si 10 μm as stationary phase and dichloromethane / ethyl acetate 70 / 30 as eluent. 19.6 g (yield: 75%) of 2-[(4-vinylphenyl)methoxy]ethyl 3-oxobutanoate (on TLC silica gel 60F 254 TLC analysis on 4% paraformaldehyde (supplied by Merck): eluent hexane / ethyl acetate 70 / 30: R f =0.3).

[0125] MA-6 is 4-prop-2-enoyloxybutyl 3-oxobutyrate and is prepared as follows: 79.1 g of tert-butyl acetoacetate, 86.5 g of 4-hydroxybutyl-acrylate and 5.5 g of BHT are dissolved in 300 ml of toluene. The mixture is heated to reflux. While refluxed, a mixture of toluene and tert-butanol is removed by distillation. 70 g of the toluene / tert-butanol mixture is removed by distillation for 30 minutes. The mixture is cooled to room temperature. The solvent is removed under reduced pressure, and 4-prop-2-enoyloxybutyl 3-oxobutyrate is purified by preparative column chromatography on a Graceresolve RS80 column using n-hexane / dichloromethane as eluent. 46.1 g of 4-prop-2-enoyloxybutyl 3-oxobutyrate (on TLC silica gel 60F 254 TLC analysis on 40 μL PBS (supplied by Merck) using n-hexane / ethyl acetate as eluent: R f =0.3) MA-7 is ethyl 3-oxo-2-[(4-vinylphenyl)methyl]butyrate and is prepared as follows: 3.45 g of sodium and 0.49 g of 4-tert-butylcatechol are added to 250 ml of ethanol while the solution is cooled to 0°C. The mixture is stirred at room temperature for 45 minutes. 22.8 g of 4-chloromethylstyrene is added to the reaction mixture followed by 25 ml of ethanol. 39.04 g of ethyl acetoacetate is added to the reaction mixture followed by 25 ml of ethanol. The reaction mixture is refluxed for 3 hours. The reaction mixture is cooled to room temperature and poured into 800 ml of water. The mixture is extracted three times with 150 ml of methyl tert-butyl ether. The pooled organic fractions are dried over sodium sulfate and the solvent is removed under reduced pressure. The crude ethyl 3-oxo-2-[(4-vinylphenyl)methyl]butyrate is purified by preparative column chromatography on a Prochrom LC80 column using Kromasil Si 10 μm as stationary phase and dichloromethane / hexane 96 / 4 as eluent. 16.6 g (yield: 45%) of ethyl 3-oxo-2-[(4-vinylphenyl)methyl]butanoate (on TLC silica gel 60F 254 TLC analysis on (supplied by Merck): eluent: dichloromethane: R f＝ 0.3).

[0126] MA-14 is N,N-diethyl-3-oxo-2-[(4-vinylphenyl)methyl]butanamide and is prepared as follows: 200 ml of ethanol are cooled to 0° C. 0.33 g of 4-tert-butyl-catechol is added, followed by 9.2 g of a 25 wt% dispersion of sodium in paraffin (0.1 mol) in portions. The mixture is stirred at 25° C. for 30 minutes. 15.2 g of 4-chloromethyl-styrene in 25 ml of ethanol and 31.4 g of N,N-diethyl-3-oxo-butanamide in 25 ml of ethanol are added, and the reaction is continued at reflux for 6 hours. The reaction mixture is cooled to room temperature and the mixture is poured into 400 ml of water. The mixture is extracted with 400 ml of methyl tert-butyl ether. The precipitated residue is removed by filtration and the organic fraction is dried over sodium sulfate. The solvent was evaporated under reduced pressure and N,N-diethyl-3-oxo-2-[(4-vinylphenyl)methyl]butanamide was purified by preparative column chromatography on a Prochrom LC 80 column using a gradient elution from dichloromethane to dichloromethane / ethyl acetate 95 / 5. 2.2 g of N,N-diethyl-3-oxo-2-[(4-vinylphenyl)methyl]butanamide were isolated (yield: 8%) (TLC analysis on TLC silica gel 60 F254 (supplied by Merck) using hexane / ethyl acetate as eluent: Rf: 0.5).

[0127] Embodiment 1: Synthesis of resin INVRES-1 of the present invention: 10 g (46.6 mmol) of 2-(acetoacetoxy)ethyl methacrylate was dissolved in 30 ml of ethyl acetate. 0.472 g (2.33 mmol) of dodecyl mercaptan was added, and the mixture was purged with nitrogen. 134 mg (0.7 mmol) of 2,2′-azobis[2-methylbutyronitrile] was added, and the mixture was refluxed for 6 hours. The mixture was cooled to room temperature. The solution of the resin INVRES-1 of the present invention in ethyl acetate was directly used to synthesize the capsule INVCAP-1 of the present invention.

[0128] The molecular weight of INVRES-1 was determined using GPC relative to poly(styrene) standards. The number average molecular weight, Mn, of INVRES-1 was 10,500 and the weight average molecular weight, Mw, was 15,400.

[0129] Preparation of capsule INVCAP-1 of the present invention: 13.2 g of Desmodur N75 BA was added to a solution of 37 g of the above INVRES-1 in ethyl acetate. 1.2 g of Lakeland ACP 70 was added and the solution was stirred at room temperature for one hour.

[0130] 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 for 5 minutes using an Ultra Turrax at a speed of 16000 rpm. 52 g water was added and the solvent was evaporated at 60 ° C under reduced pressure while vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 88 g by evaporating water at 120 mbar. The dispersion was stirred for 16 hours at 65 ° C. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0131] The average particle size of all capsule dispersions was measured using a Zetasizer™ Nano-S (Malvern Instruments, Goffin Meyvis). The average particle size of INVCAP-1 was 183 nm.

[0132] Ink INV-1 of the present invention By mixing Table 4 The ink INV-1 of the present invention is prepared by mixing the components of the present invention. All weight percentages are based on the total weight of the inkjet ink.

[0133] Table 4 Mass (wt%) INV-1 INVCAP-1 38 Cab-O-Jet465M 22 Surfinol104H 2 DowanolDPM 19 Ethylene glycol 19 Comparative ink COMP-1 Prior art polyurethane-based inks have been disclosed in WO2018077624. Based on WO2018077624, by mixing according to Table 5 The components of the comparative ink COMP-1 have been formulated. All weight percentages are based on the total weight of the inkjet ink.

[0134] Table 5 PU-1 has been prepared as disclosed in WO2018077624.

[0135] The inventive composition INV-1 and the comparative composition COMP-1 were coated on polyethylene using a 10 micron wire wound rod and dried in an oven at 80°C for 15 minutes.

[0136] The adhesion of each sample was evaluated by cross-cut test according to ISO 2409:1992 (E). Paint (International Standard 1992-08-15), using a Braive No. 1536 cross-cut tester from Braive Instruments, with a spacing of 1 mm between the cuts and a weight of 600 g, with Tesatape TM 4104PVC tape combination. Table 6 The evaluation was performed according to the criteria described in , where adhesion was evaluated both in the cross cut and outside the cross cut.

[0137] Table 6 Rating standard 0 Not removed, perfectly bonded 1 Only very minor separation of the cured layers, almost perfect adhesion 2 Small part of the cured layer is removed by the tape, good adhesion 3 Partially cured layer removed by tape, poor adhesion 4 Most of the cured layer was removed by the tape, poor bonding 5 The cured layer is completely removed from the substrate by the tape, without bonding The results are summarized in Table 7.

[0138] Table 7 Adhesion performance Samples of the present invention 0 Comparative samples 5 Depend on Table 7 It is evident that the resin technology according to the present invention is superior to prior art poly(urethane) technology.

[0139] In standard Dimatix TM The jettability of the inventive ink INV-1 was tested on a 10 pl printhead. The ink was jetted at 22°C using a firing frequency of 5 kHz, a firing voltage of 25 V and a standard waveform. All nozzles were jetted without any specific need for purging.

[0140] Embodiment 2: This example illustrates the stability of the resin-based aqueous ink according to the present invention upon storage.

[0141] Preparation of capsule INVCAP-2 of the present invention: 8.8 g of Desmodur N75 BA was added to a solution of 37 g of the above INVRES-1 in ethyl acetate. 1.2 g of Lakeland ACP 70 was added and the solution was stirred at room temperature for one hour.

[0142] 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 for 5 minutes using an Ultra Turrax at a speed of 16000 rpm. 52 g water was added and the solvent was evaporated at 60 ° C under reduced pressure while vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 88 g by evaporating water at 120 mbar. The dispersion was stirred for 16 hours at 65 ° C. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0143] The average particle size is 170 nm.

[0144] Evaluation of ink stability: By mixing Table 8 The inks INV-2 to INV-5 of the present invention were prepared using the components of the present invention. All weight percentages are based on the total weight of the inkjet ink.

[0145] Table 8 Mass (wt%) INV-2 INV-3 INV-4 INV-5 INVCAP-2 38.5 38.5 38.5 38.5 DiamondD75C 24 - - - Cab-O-Jet465M - 24 - - DiamondD75Y - - 24 - DiamondD75K - - - 24 AlkanolXC 0.5 0.5 0.5 0.5 Methyldiethanolamine 1 1 1 1 1,2-Propanediol 18 18 18 18 glycerin 18 18 18 18 The inventive inks INV-2 to INV-5 were aged at 60° C. for 14 days. The viscosity increase of each ink was monitored. The viscosity increase of all ink samples was less than 10% compared to the starting point, demonstrating the excellent storage stability of the inks according to the present invention.

[0146] Example 3 This example illustrates that excellent physical properties can be obtained using a wide range of encapsulated β-keto-ester polymers.

[0147] Synthesis of β-keto-ester polymers according to the invention The β-keto-ester polymers according to the present invention are prepared according to the following reaction scheme: Different polymers were obtained by preparing mixtures as shown in Table 9.

[0148] Table 9. Element INVRES-2 INVRES-3 INVRES-4 INVRES-5 INVRES-6 <![CDATA[C 12 H 25 SH]]> 0.826g 0.413g 0.723g 1.03g 0.826g MA-2 16g - - - - MA-4 - 8.73g - - - MA-5 - - 18.36g - - MA-6 - - - 22.8g - MA-7 - - - - 19.7g WAKOV59 0.346g 0.115g 0.206g 0.288g 0.235g Ethyl acetate 43.3g 23.8g 49.6g 61.34g 53.4g Unless otherwise stated, the mixture described in Table 9 was flushed with nitrogen and heated to reflux for 16 hours. Monomer conversion was followed using TLC analysis until complete conversion. The reaction mixture was cooled to room temperature and the ethyl acetate solution was used for encapsulation without isolating the polymer.

[0149] INVRES-3: The polymerization was continued for 60 hours instead of 16 hours. After 60 hours, another 0.146 g of WAKO V59 in 1 g of ethyl acetate was added, and the mixture was further refluxed for 7 hours. An additional 0.146 g of WAKO V59 in 2 g of ethyl acetate was added, and the polymerization was continued at reflux for another 16 hours. The conversion was almost complete based on TLC analysis.

[0150] INVRES-4: After 16 hours, another 0.396 g of WAKO V59 in 2 g of ethyl acetate was added and the polymerization was continued at reflux for another 24 hours. The conversion was complete based on TLC analysis.

[0151] INVRES-6: After 16 hours, another 0.4 g of WAKO V59 in 2 g of ethyl acetate was added and the polymerization was continued at reflux for another 24 hours. The conversion was complete based on TLC analysis.

[0152] INVRES-7: INVRES-7 was prepared according to the following reaction: 1.63 g of MA-14 was dissolved in 4.47 g of ethyl acetate. The reaction mixture was purged with nitrogen. 62 mg of 1-dodecyl mercaptan was added, followed by 23 mg of WAKO V59 in 0.5 g of ethyl acetate. The mixture was refluxed for 64 hours. After 64 hours, an additional 23 mg of WAKO V59 in 0.5 g of ethyl acetate was added, and the polymerization was continued at reflux for 7 hours. An additional 30 mg of WAKO V59 in 0.5 g of ethyl acetate was added, and the polymerization was continued at reflux for another 16 hours. Complete conversion was confirmed based on TLC analysis.

[0153] The molecular weights of INVRES-2 to INVRES-7 were measured using GPC relative to polystyrene standards and are given in Table 10.

[0154] Table 10 Mn M INVRES-2 10700 14008 INVRES-3 12900 21200 INVRES-4 16800 32300 INVRES-5 10500 13500 INVRES-6 24000 37100 INVRES-7 19400 31900 Preparation of capsules INVCAP-3 to INVCAP-8 of the present invention INVCAP-3: 9.26 g of Desmodur N75 BA were added to a solution of 60.4 g of the above INVRES-2 in ethyl acetate.

[0155] This solution was added to a solution of 3.07 g of Lakeland ACP 70, 0.79 g of lysine and 1.1 g of triethylamine in 80 g of water while stirring for 5 minutes using an Ultra Turrax at 17000 rpm. 80 g of water was added and the solvent was evaporated at 60° C. under reduced pressure while the vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 110 g by evaporating water at 120 mbar. The dispersion was stirred at 60° C. for 24 hours. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0156] The average particle size is 200 nm.

[0157] INVCAP-4: 5.15 g of Desmodur N75 BA was added to a solution of 33.6 g of the above INVRES-3 in ethyl acetate.

[0158] This solution was added to a solution of 1.72 g of Lakeland ACP 70, 0.44 g of lysine and 0.61 g of triethylamine in 39.3 g of water while stirring for 5 minutes using an Ultra Turrax at 17000 rpm. 80 g of water was added and the solvent was evaporated at 60° C. under reduced pressure while the vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 100 g by evaporating water at 120 mbar. The dispersion was stirred at 60° C. for 24 hours. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0159] The average particle size is 195 nm.

[0160] INVCAP-5: 9.55 g of Desmodur N75 BA was added to a solution of 62.28 g of the above INVRES-4 in ethyl acetate.

[0161] This solution was added to a solution of 3.18 g of Lakeland ACP 70, 0.82 g of lysine and 1.14 g of triethylamine in 72.7 g of water while stirring for 5 minutes using an Ultra Turrax at 17000 rpm. 80 g of water was added and the solvent was evaporated at 60° C. under reduced pressure while the vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 100 g by evaporating water at 120 mbar. The dispersion was stirred at 60° C. for 24 hours. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0162] The average particle size is 200 nm.

[0163] INVCAP-6: 10.5 g of Desmodur N75 BA was added to a solution of 68.5 g of the above INVRES-5 in ethyl acetate.

[0164] This solution was added to a solution of 3.5 g Lakeland ACP 70, 0.9 g lysine and 1.25 g triethylamine in 80 g water while stirring for 5 minutes using an Ultra Turrax at 17000 rpm. 80 g water was added and the solvent was evaporated at 60 ° C under reduced pressure while the vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 110 g by evaporating water at 120 mbar. The dispersion was stirred at 60 ° C for 24 hours. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0165] The average particle size is 180 nm.

[0166] INVCAP-7: 9.55 g of Desmodur N75 BA was added to a solution of 62.28 g of the above INVRES-6 in ethyl acetate.

[0167] This solution was added to a solution of 3.18 g Lakeland ACP 70, 0.82 g lysine and 1.14 g triethylamine in 72.73 g water while stirring for 5 minutes using an Ultra Turrax at a speed of 17000 rpm. 80 g water was added and the solvent was evaporated at 60 ° C under reduced pressure while vacuum was gradually increased from 500 mbar to 120 mbar. The weight of the dispersion was adjusted to 100 g by evaporating water at 120 mbar. The dispersion was stirred at 60 ° C for 24 hours. The dispersion was cooled to room temperature and filtered through a 1.6 μm filter.

[0168] The average particle size is 215 nm.

[0169] INVCAP-8: 0.888 g of Desmodur N75 BA was added to a solution of 5.79 g of the above INVRES-7 in ethyl acetate.

[0170] This solution is added to a solution of 0.296g Lakeland ACP 70, 0.076g lysine and 0.106g triethylamine in 6.760g water, then ultrasound (SONICS VIBRACELL) is used to emulsify ethyl acetate solution in aqueous solution for 1 minute at full power, without pulse. 10g water is added, and the solvent is evaporated at 60 ℃ under reduced pressure, while vacuum is progressively increased to 120 mbar from 500 mbar. The weight of the dispersion is adjusted to 9.4g by evaporating water at 120 mbar. The dispersion was stirred for 24 hours at 60 ℃. The dispersion is cooled to room temperature, and filtered through a 1.6 μm filter dispersion.

[0171] The average particle size is 150 nm.

[0172] Ink INV-6 to INV-11 of the present invention: Inventive inks INV-6 to INV-11 were prepared by mixing the components according to Table 11. All weight percentages are based on the total weight of the inkjet ink.

[0173] Table 11 Weight% INV-6 INV-7 INV-8 INV-9 INV-10 INV-11 INVCAP-3 39 - - - - - INVCAP-4 - 39 - - - - INVCAP-5 - - 39 - - - INVCAP-6 - - - 39 - - INVCAP-7 - - - - 39 - INVCAP-8 - - - - - 39 Cab-O-Jet465M 21 21 21 21 21 21 Surfinol104H 2 2 2 2 2 2 Diol 19 19 19 19 19 19 DowanolDPM 19 19 19 19 19 19 The inventive inks INV-6 to INV-11 were evaluated for adhesion on polyethylene sheets as described in Example 1. The results are summarized in Table 12.

[0174] Table 12 Adhesion performance INV-6 0 INV-7 0 INV-8 1 INV-9 0 INV-10 0 INV-11 0 As is apparent from Table 12, a wide range of encapsulated β-keto-ester functionalized polymers yield excellent adhesion to poly(ethylene).

Claims

1. An aqueous inkjet ink comprising a pigment and a dispersion of capsules, the capsules comprising a polymer shell surrounding a core, wherein the polymer shell comprises poly(urea), poly(urethane) or a combination thereof, the core comprising an oligomer or polymer having repeating units consisting of functional groups according to 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, C(=O)R3 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 C(=O)R3 R1 and R2 may represent atoms necessary to form a 5-8 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. R5 and R6 may represent the atoms necessary to form a 5-8 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. An aqueous inkjet ink comprising a pigment and a dispersion of capsules, the capsules comprising a polymer shell surrounding a core, wherein the polymer shell comprises poly(urea), poly(urethane) or a combination thereof, the core comprising an oligomer or polymer having repeating units consisting of functional groups according to formula II in 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 C(=O)R3 R2 may represent atoms necessary to form a 5-8 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. R5 and R6 may represent the atoms necessary to form a 5-8 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.

3. An aqueous inkjet ink comprising a pigment and a dispersion of capsules, the capsules comprising a polymer shell surrounding a core, wherein the polymer shell comprises poly(urea), poly(urethane) or a combination thereof, the core comprising an oligomer or polymer having repeating units consisting of a functional group according to formula III in 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 C(=O)R3 R2 may represent atoms necessary to form a 5-8 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. R5 and R6 may represent the atoms necessary to form a 5-8 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 5-8 membered ring. The aqueous inkjet ink according to claim 1 , wherein dispersing groups are covalently bonded to the polymer shell.

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

6. The aqueous inkjet ink according to claim 3, wherein dispersing groups are covalently bonded to the polymer shell.

7. 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 or salts thereof, and phosphonic acid or salts thereof.

8. 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.

9. The aqueous inkjet ink according to claim 6, 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.

10. An aqueous pretreatment liquid comprising a flocculant and a dispersion of capsules, the capsules comprising a polymer shell surrounding a core, the core comprising an oligomer or polymer having repeating units consisting of functional groups according to 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, C(=O)R3 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 C(=O)R3 R1 and R2 may represent atoms necessary to form a 5-8 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. R5 and R6 may represent the atoms necessary to form a 5-8 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 5-8 membered ring. wherein the dispersing group is covalently bonded to the polymer shell, the dispersing group being selected from the group consisting of protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternized tertiary amines, N-quaternized heteroaromatic compounds, sulfonium, and phosphonium.

11. The aqueous pre-treatment liquid of claim 10, wherein the polymer shell comprises poly(urea), poly(urethane), or a combination thereof.

12. An inkjet recording method comprising the steps of: a) jetting an inkjet ink as defined in claim 1 onto a substrate; and b) drying said jetted inkjet ink by applying heat to such an extent that a temperature of said jetted ink of at least 60°C is obtained.

13. An inkjet recording method, comprising the steps of: a) jetting an inkjet ink as defined in claim 2 onto a substrate; and b) drying said jetted inkjet ink by applying heat to such an extent that a temperature of said jetted ink of at least 60°C is obtained.

14. An inkjet recording method, comprising the steps of: a) jetting an inkjet ink as defined in claim 3 onto a substrate; and b) drying said jetted inkjet ink by applying heat to such an extent that a temperature of said jetted ink of at least 60°C is obtained.

15. An inkjet recording method comprising the steps of: a) applying an aqueous pretreatment liquid as defined in claim 10 to a substrate; and b) optionally at least partially drying said applied aqueous pre-treatment liquid by applying heat to an extent to obtain a temperature of said applied pre-treatment liquid of at least 60°C c) jetting inkjet ink onto the applied pre-treatment liquid; and d) drying said jetted inkjet ink by applying heat to an extent to obtain a temperature of said jetted ink of at least 60°C.

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