Resin containing water-based inkjet ink and recording method

Abstract

An aqueous dispersion of microcapsules comprising a crosslinked polymer shell surrounding a core, the core comprising a second polymer that is non-polymerizable. The dispersion is useful in aqueous pigmented inkjet inks or pretreatments for inkjet printing on low-absorbency or non-absorbency substrates.

Description

[Technical Field]

[0001] The present invention relates to an aqueous inkjet ink or pretreatment solution containing microcapsules having a resin-containing core for use in inkjet printing on low-absorbency or non-absorbency substrates. [Background technology]

[0002] Images printed on non-absorbent and semi-absorbent substrates must meet a set of requirements, including excellent adhesion, water and solvent resistance, chemical resistance, and abrasion resistance. To meet these requirements, additional resins or polymers acting as binders are incorporated into aqueous inkjet inks. In some applications, the substrates used are temperature-sensitive, limiting the usable drying temperature and optionally the curing temperature. Depending on the requirements of a particular application, different resin technologies suitable for temperature-sensitive substrates are disclosed in the prior art.

[0003] Approaches based on latex that have the ability to bond and meet several requirements regarding physical properties for various applications are disclosed in the patent documents (see Patent Documents 1, 2, and 3). However, latex-based inkjet inks generally do not simultaneously improve the water resistance and abrasion resistance of printed images on low-absorbency substrates such as corrugated cardboard or non-absorbent substrates. Furthermore, latex-based inkjet inks tend to form films in the nozzles and ink supply sections of the print head, leading to reliability problems during printing. In industrial applications, system reliability, especially the reliability of the ink jet, is paramount. Therefore, the need for more optimal resin technology still exists.

[0004] Patent Document 4 describes an aqueous resin-based inkjet ink in which the resin exists as capsules. To achieve good bonding properties and, consequently, durable printed images, reactive chemicals such as blocked isocyanates are incorporated into the core of the capsules. The presence of such reactive substances may pose health and safety problems if they do not react completely in the resulting image. Furthermore, the release of reactive chemicals from the core requires a thermal activation step during or after the drying of the ink. The thermal activation step involves heating the printed image to a temperature exceeding 100°C, which is incompatible with poly(olefin) substrates such as polyethylene or polypropylene film.

[0005] Patent Document 5 discloses an inkjet ink comprising a capsule having a core containing a polymerizable compound such as a polymerizable oligomer or polymer. The polymerizable compound is polymerized only under the application of ultraviolet light or in the presence of a blocked isocyanate. The need for a UV light source or heat source to activate the blocked isocyanate introduces further complexity in the design of a reliable inkjet printing system.

[0006] Polymerizable polymers with reactive functional groups are known to be reactive with typical shell monomers used in interfacial polymerization, such as isocyanates, particularly from moderately alkaline pH upwards. This reactivity with shell monomers limits the acceptable range for encapsulation of these polymers based on interfacial polymerization, which poses a problem for industrialization and scalability. The acceptable range in the industrialization of core-shell particles is crucial to avoid production losses, which can result in significant economic and ecological losses.

[0007] Therefore, there is still a need for resin technologies for inkjet printing applications that combine excellent physical properties in end-use applications with reliable industrialization. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2018 / 114314A Pamphlet [Patent Document 2] U.S. Patent Application Publication No. 2013 / 0245157A1 [Patent Document 3] European Patent No. 3275949A1 [Patent Document 4] International Publication No. 2016 / 165956 Brochure [Patent Document 5] U.S. Patent Application Publication No. 2019 / 0023922 Specification [Overview of the project]

[0009] The object of the present invention is to provide a solution to the above-mentioned problems. This object is achieved by providing an aqueous inkjet ink or other inkjet printing solution, such as a pretreatment solution, which contains the capsule described in claim 1.

[0010] A further object of the present invention is to provide a method for preparing the above-described capsules as defined in claim 9.

[0011] Another aspect of the present invention is to provide a printing method using an inkjet ink comprising the capsule described in claim 1, as defined in claim 10.

[0012] Other features, elements, processes, characteristics, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention. Specific embodiments of the invention are also defined in the dependent claims. [Modes for carrying out the invention]

[0013] Description of the manner A. Aqueous dispersion of microcapsules A.1. Microcapsules The object of the present invention is realized by an aqueous dispersion of microcapsules comprising a core surrounded by a polymer shell, the core comprising a second polymer substantially free of ethylenically unsaturated groups, epoxy groups, isocyanate groups, or active methylene groups.

[0014] A.1.1. Second polymer The second polymer is a polymer that is substantially free of reactive groups selected from the group consisting of ethylenically unsaturated groups, epoxy groups, isocyanate groups, β-keto-esters, β-keto-amides, and 1,3-diketones. Because these groups are absent, the second polymer is nonpolymerizable and therefore cannot react with shell monomers (see § A.1.2 and § A.2).

[0015] Examples of ethylenically unsaturated groups include (meth)acrylic, vinyl, allyl, and styryl groups.

[0016] In principle, any known second polymer can be used in the present invention. Preferably, the second polymer is substantially soluble in water-immiscible organic solvents. In a preferred embodiment, the second polymer is poly(urethane) and its copolymers, acrylic and its copolymers, poly(ester) and its copolymers, poly(styrene) and its copolymers, poly(vinylamide) and its copolymers, poly(olefin) and its copolymers, poly(vinyl alcohol) derivatives and their copolymers, poly(acetal) and its copolymers, poly(ether) and its copolymers, polyamide and its copolymers, poly(imide) and its copolymers, poly(imine) and its copolymers, polycarbonate It is selected from the group consisting of polyurethanes and acrylates. Acrylates are defined as polymer resins obtained by polymerization or copolymerization of acrylates, methacrylates, acrylamides, and methacrylamides. In the present invention, acrylate- and methacrylate-based polymers and copolymers are particularly preferred.

[0017] Polyesters and acrylics are particularly preferred. Acrylics are defined as polymer resins obtained by polymerization or copolymerization of acrylates, methacrylates, acrylamides, and methacrylamides. In the present invention, acrylate- and methacrylate-based polymers and copolymers are particularly preferred.

[0018] In a preferred embodiment, the second polymer and the first shell monomer such as polyisocyanate are mixed before the high-shear treatment of interfacial polymerization. Therefore, the second polymer preferably needs to be soluble in an organic solvent and form a lipophilic phase in interfacial polymerization (see § A.2), or at least have segments that are soluble or swellable in an organic solvent.

[0019] It should be noted that there seems to be some inaccuracies or discontinuities in the original text structure and content, which may affect the overall coherence and comprehensibility. The above translation is carried out based on the existing text as accurately as possible.Segmented second polymers such as graft or block copolymers, in which different segments have different solubilities in organic solvents, can be used. The presence of hydrophilic segments, such as in graft copolymers having polyether chains in the second polymer, appears to be useful for obtaining microcapsules having a particle size of less than 500 nm, and further less than 200 nm.

[0020] When the second polymer is polyurethane, the incorporation of hydrophilic grafts can be achieved by copolymerization of polyether diols. When the second polymer is polyacrylate, the incorporation of hydrophilic grafts can be achieved by graft copolymers of methacryl-terminated polyethylene glycol. Examples thereof are polyethylene glycol-functional polyacrylate copolymers such as Byk LPG21241, or polyethylene glycol-based block copolymers that are sufficiently soluble in the organic phase (ethyl acetate). In that case, such block copolymers contain segments insoluble in water (for example, polyester, polyether) in addition to polyether chains compatible with water.

[0021] Suitable polyether diols in the present invention are Ymer N120, Ymer N90 or Tegomer D 3403, that is, α-[2,2-bis(hydroxymethyl)butyl]-ω-methoxy-poly(oxy-1,2-ethanediyl). These diols can be prepared from trimethylolpropane oxetane (TMPO). Possible synthetic procedures are described by Fock, J.; Moehring, V., Polyether-1,2- and -1,3-diols as macromonomers for the synthesis of graft copolymers, 1. Synthesis and characterization of the macromonomers. Die Makromolekulare Chemie 1990, 191(12), 3045-3057. Generally, other polyether 1,2- or 1,3-diols can also be used.

[0022] It has been observed that the length of the polyether chains incorporated into the second polymer also determines the water resistance of the printed image. Shorter polyether chains, such as Ymer N90, are preferred over longer polyether chains, such as Ymer N180. The second polymer according to the present invention can be prepared according to any polymerization method known in the art, including free radical polymerization, cationic polymerization, anionic polymerization, ring-opening polymerization, metathesis polymerization, and polycondensation. In resins prepared using free radical polymerization, the molecular weight of the resin can be controlled using RAFT agents, ATRP, nitroxyl radical technology, or transfer agents, preferably thiols.

[0023] The second polymer may be a poly(ester). Suitable poly(esters) can be selected from the group consisting of copolymers of dicarboxylic acids such as terephthalic acid, isophalic acid, adipic acid, succinic acid, or their alkyl esters, or copolymers prepared by ring-opening polymerization of cyclic esters such as caprolactone or cyclic diesters such as DL-lactide.

[0024] A suitable poly(ether) as the second polymer can be selected from the group consisting of polyalkylene oxides or copolymers, polyphenylene oxide, polystyrene oxide, and polyTHF.

[0025] Suitable poly(acetal) as the second polymer can be selected from the group consisting of poly(vinyl butyral), polyvinylacetaldehyde, and reaction products of hydroxy-functional polymers with aliphatic or aromatic aldehydes.

[0026] A suitable poly(urethane) as the second polymer can be obtained by polymerization of a diisocyanate or polyisocyanate with a diol. Typical diisocyanates can be selected from the group consisting of isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 2,4,4'-trimethyl-1,6-hexamethylene diisocyanate (TMDI), hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tolylene diisocyanate (TDI), xylene diisocyanate (XDI), and diphenylmethane diisocyanate (MDI).

[0027] Diols can be low molecular weight compounds, but oligomerols are particularly preferred. Typical oligomerols can be selected from the group consisting of polyester polyols, polyether polyols, polyamide polyols, polyacrylate polyols, polycarbonate polyols, and polyolefin polyols.

[0028] Suitable acrylics as the second polymer can be obtained by polymerization of copolymers of acrylic or methacrylic monomers with monomers selected from the group consisting of ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, methyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate, lauryl acrylate, lauryl methacrylate, cetyl acrylate, cetyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isopropyl acrylate, and isopropyl methacrylate, as well as monomers selected from the group consisting of α-methylstyrene, vinyl acetate, vinyl versate, butadiene, isoprene, acrylonitrile, methacrylonitrile, styrene, para-methylstyrene, tert-butylstyrene, butyl vinyl ether, hydroxybutyl vinyl ether, and ethylene.

[0029] The second polymer is preferably 500 g / mol to 400,000 g / mol, more preferably It has a weight-average molecular weight (Mw) of approximately 1,000 g / mol to 100,000 g / mol, most preferably 2,000 g / mol to 50,000 g / mol.

[0030] The second polymer preferably has a number-average molecular weight (Mn) of 300 g / mol to 200,000 g / mol, more preferably 1,000 g / mol to 50,000 g / mol, and most preferably 1,000 to 30,000 g / mol.

[0031] A.1.2. Polymer shell The polymer shell may encapsulate a second polymer and ensure the dispersibility of microcapsules in an aqueous vehicle of inkjet ink or pretreatment solution.

[0032] There are no practical limitations on the type of polymer in the polymer shell of the capsule. Preferably, the polymer is crosslinked. Crosslinking incorporates more rigidity into the capsule and allows for a wider temperature and pressure range for handling the capsule in both ink manufacturing and inkjet printing equipment.

[0033] Preferred examples of polymer shell materials include polyurea, polyurethane, polyester, polycarbonate, polyamide, polysulfonamide, melamine-based polymers, silica-based sol-gel polymers, or mixtures thereof as described in U.S. Patent No. 603149B1, with polyurea and polyurethane being particularly preferred, and polyurea being most preferred.

[0034] The particles are preferably present in the aqueous inkjet ink or pretreatment solution in an amount of 45% by weight or less, preferably 5-25% by weight, based on the total weight of the ink or liquid. It has been observed that when the amount exceeds 30% by weight, the spraying is not always reliable.

[0035] The capsules are preferably dispersed in an aqueous medium such as an inkjet ink or pretreatment solution via dispersing groups covalently bonded to the polymer shell, or preferably dispersed by using a dispersant or surfactant added during or after the formation of the capsules.

[0036] The dispersed group covalently bonded to the polymer shell is preferably selected from the group consisting of carboxylic acids or their salts, sulfonic acids or their salts, phosphate esters or their salts, and phosphonic acids or their salts.

[0037] Dispersion groups can be used in combination with polymer dispersants to achieve stereostabilization. For example, the polymer shell may have covalently bonded carboxylic acid groups that interact with the amine groups of the polymer dispersant. However, in a more preferred embodiment, no polymer dispersant is used, and the dispersion stability of the inkjet ink is achieved solely by electrostatic stabilization. For example, a slightly alkaline aqueous medium converts the covalently bonded carboxylic acid groups on the polymer shell into ionic groups, and the negatively charged capsules then do not tend to aggregate. If there are enough dispersion groups covalently bonded to the polymer shell, the capsules become so-called self-dispersing capsules.

[0038] These negatively charged capsule surfaces can also be advantageously used during inkjet printing. For example, an anionic capsule in the inkjet ink printed on top of the second liquid can be precipitated using a second liquid, such as a pretreatment solution containing a cationic substance, which is a cationic polymer or polyvalent salt. By using this method, an improvement in image quality due to the immobilization of the ink capsules can be observed.

[0039] The dispersed groups covalently bonded to the polymer shell incorporated into the pretreatment solution are preferably proto The compounds are selected from the group consisting of amines, protonated nitrogen-containing heteroaromatic compounds, quaternary tertiary amines, N-quaternary heteroaromatic compounds, sulfonium, and phosphonium.

[0040] The capsules used in sprayable aqueous formulations such as inkjet inks or sprayable pretreatment solutions have an average particle size of 4 μm or less, determined by dynamic laser diffraction. The nozzle diameter of an inkjet print head is typically 20 to 35 μm. When the average particle size of the capsules is one-fifth of the nozzle diameter, reliable inkjet printing is possible. An average particle size of 4 μm or less enables spraying by a spray head having a minimum nozzle diameter of 20 μm. In a more preferred embodiment, the average particle size of the capsules is one-tenth of the nozzle diameter. 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 capsules is less than 2 μm, excellent resolution and dispersion stability over time are obtained.

[0041] A.2. Preparation of microcapsule dispersion The microcapsule dispersion according to the present invention can be prepared using both chemical and physical methods. Suitable encapsulation methodologies include complex droplet formation, liposome formation, spray drying, and polymerization methods.

[0042] In the present invention, polymerization methods are preferably used because polymerization methods allow for the best control in capsule design. More preferably, interfacial polymerization is used to prepare the capsules of the present invention. This technique is well known, as described by Zhang Y. and Rochefort D. (Journal of Microencapsulation, 29(7), 636-649 (2012) and Salitin (in Encapsulation) This is outlined in Nanotechnologies, Vikas Mittal (ed.), chapter 5, 137-173 (Scrivener Publishing LLC (2013)).

[0043] In interfacial polymerization, such as interfacial polycondensation, two reactants meet at the interface of an emulsion droplet and react rapidly.

[0044] Generally, interfacial polymerization requires an emulsion of a lipophilic phase in an aqueous continuous phase, or vice versa. The lipophilic phase is preferably obtained by using a substantially water-immiscible organic solvent. Each phase contains at least one dissolved monomer (first shell monomer) that can react with another monomer (second shell monomer) dissolved in the other phase. Polymerization forms a polymer that is insoluble in both the aqueous and lipophilic phases. As a result, the formed polymer tends to precipitate at the interface between the lipophilic and aqueous phases, thereby forming a shell around the dispersed phase, which grows during further polymerization. The capsules according to the present invention are preferably prepared from a lipophilic emulsion in an aqueous continuous phase.

[0045] A typical polymer shell for a capsule according to the present invention, formed by interfacial polymerization, is typically a polyamide prepared from a di- or polyacid chloride as a first shell monomer and a di- or oligoamine as a second shell monomer; typically a polyurea prepared from a di- or oligoisocyanate as a first shell monomer and a di- or oligoamine as a second shell monomer; typically a polyurethane prepared from a di- or oligoisocyanate as a first shell monomer and a di- or oligoalcohol as a second shell monomer; typically a polysulfonamide prepared from a di- or oligosulfochloride as a first shell monomer and a di- or oligoamine as a second shell monomer; typically a polyester prepared from a di- or oligoacid chloride as a first shell monomer and a di- or oligoalcohol as a second shell monomer; and Typically, the shell monomer is selected from the group consisting of polycarbonates prepared from a di- or oligochloroformate as the first shell monomer and a di- or oligo alcohol as the second shell monomer. The shell can be composed of a combination of these polymers.

[0046] In a preferred embodiment of the present invention, interfacial polymerization is carried out to form a polyurea shell at the interface. Preferably, the first shell monomer is a polyisocyanate present in the lipophilic phase, while a polyamine is present in the aqueous phase as a second shell monomer, acting as a crosslinking agent. Polyamines are preferred, while polyols exhibit a much slower reaction rate. Alternatively, the second shell monomer can be omitted because water can react with the isocyanate moiety to form an amine. The amine formed in situ can then further react with another isocyanate moiety present in the polyisocyanate. Therefore, a crosslinked polyurea shell can be obtained without adding a second shell monomer.

[0047] Different chemicals can be used as suitable polyisocyanates. The structure and reactivity of the polyisocyanate, as well as its molecular weight and viscosity, are important in the process of generating small droplets under high shear.

[0048] When emulsifying a water-immiscible solvent in an aqueous phase, droplet breakdown depends on the viscosity of the solvent and the aqueous phase. Typically, the highest shear force can be applied when the viscosities of the water-immiscible solvent and the aqueous phase are close to each other. Therefore, polyisocyanates with lower molecular weights also yield better results in reducing droplet size by high shear. Smaller droplet sizes in the lipophilic phase (obtained by the water-immiscible solvent, second polymer, and polyisocyanate) result in capsules with smaller particle sizes.

[0049] The ratio of water-immiscible solvent to water is also important. Adding too much water (>65 wt%) during the dispersion process will not only result in lower viscosity and higher shear force, but will also cause some of the water-immiscible solvent to partially enter the aqueous phase. For a second polymer or polyisocyanate with low solubility in water-immiscible solvent, too low a concentration of water-immiscible solvent during the high-shear dispersion process will result in particles with larger particle sizes.

[0050] Furthermore, the concentration of the polyisocyanate and the added second polymer, particularly the water-immiscible solvent phase / aqueous phase ratio, determines the size of the lipophilic droplets during high-shear treatment. The amount of isocyanate groups in the polyisocyanate, their reactivity, and the concentration of the second shell monomer in the aqueous phase, preferably the polyamine, determine the crosslinking density of the polymer shell.

[0051] The type of solvent that forms the lipophilic phase in interfacial polymerization is important for obtaining an industrially scalable process. Preferably, a low-boiling point organic solvent that can be easily removed, such as ethyl acetate or methylene chloride, is used. The organic solvent preferably has a lower boiling point than water.

[0052] The type of polyisocyanate has a significant effect on microcapsule formation. Suitable polyisocyanates may be monomeric isocyanates, biuret structures, urethions, allophanates, isocyanurate trimers, isocyanate adducts, or (partially) modified polyisocyanates.

[0053] Examples of modified polyisocyanates include hydrophilic isocyanates, such as polyether-modified polyisocyanates, such as Bayhudur 3100, Bayhydur 305, and Bayhydur XP2451 / 1.

[0054] The reactivity of isocyanates depends on their structure. Aromatic isocyanates are more reactive than aliphatic isocyanates. Reactivity is further reduced by steric hindrance at the isocyanate group. The structure of polyisocyanates also determines the final mechanical properties of the shell. Many sp groups are present in its structure. 3 Polyisocyanates with hybrid carbon atoms have a low sp 3 This would result in a more flexible shell than polyisocyanates containing carbon atoms.

[0055] Ionic polyisocyanates such as Bayhydur XP2547 or Bayhydur XP2700 can also be used, but they are not preferred due to their low solubility in organic solvents such as ethyl acetate.

[0056] In addition to the second polymer type, the type of isocyanate present in the polyisocyanate also determines the adhesion properties of the inkjet ink or pretreatment solution on the non-absorbent substrate. For example, hexamethylene diisocyanate (HDI) provides greater flexibility in printed images than isophorone diisocyanate (IPDI).

[0057] Optimized properties such as dispersibility in water and reactivity with amines can be obtained using polyisocyanates based on a mixture of monomer isocyanates. The use of a mixture of HDI and IPDI in polyisocyanates is extremely common. Polyisocyanates can be based on the following monomer isocyanates: isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 2,4,4'-trimethyl-1,6-hexamethylene diisocyanate (TMDI), hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tolylene diisocyanate (TDI), xylene diisocyanate (XDI), and diphenylmethane diisocyanate (MDI).

[0058] When a highly reactive second shell monomer is used in an aqueous phase, the lipophilic phase can first be emulsified with high shear to create small droplets, and then the second shell monomer (e.g., polyamine) can be added to the emulsion to prevent premature polymerization. If the second shell monomer has low reactivity, it can be added before the emulsification step.

[0059] Modified polyisocyanates are also suitable for the preparation of microcapsules according to the present invention. Examples include reaction products of diisocyanates or polyisocyanates with alcohols such as TMP (trimethylolpropane) or alcohol-terminated polymers such as monoalkoxy-terminated polyethylene glycol.

[0060] In further embodiments, polymers such as gelatin, chitosan, albumin, and polyethyleneimine can be used as a second shell monomer in combination with di- or oligo-isocyanates, di- or oligo-acid chlorides, di- or oligo-chloroformates, and epoxy resins as the first shell monomer.

[0061] In a particularly preferred embodiment, the shell is composed of polyurea or a combination thereof with polyurethane. In a more preferred embodiment, a substantially water-immiscible solvent is used in the dispersion step, which is removed by solvent stripping before or after shell formation. In a particularly preferred embodiment, the water-immiscible solvent has a boiling point of less than 100°C at atmospheric pressure. Esters and ketones are particularly preferred as water-immiscible solvents.

[0062] A solvent that is practically immiscible with water is an organic solvent that has low miscibility with water. Low miscibility means that when mixed in a 1:1 volume ratio, either combination of water and solvent forms a two-phase system at 20°C. It is defined as a blend.

[0063] The core of the microcapsule contains a second polymer. This is typically incorporated into the capsule by dissolving the second polymer in an organic solvent that has low miscibility with water and a lower boiling point than water. Ethyl acetate is a preferred organic solvent because it also poses a lower risk of flame retardancy compared to other organic solvents.

[0064] A method for preparing a capsule dispersion according to the present invention preferably includes the following steps: a) A step of preparing a non-aqueous solution of a first shell monomer and a second polymer for forming a polymer shell in an organic solvent that is substantially water-immiscible and preferably has a lower boiling point than water. b) A step of preparing an aqueous solution of an emulsifier and a second shell monomer for optionally forming a polymer shell, c) A step of emulsifying a non-aqueous solution in an aqueous solution under high shear conditions. d) A step of optionally stripping an organic solvent from a mixture of an aqueous solution and a non-aqueous solution, and e) A step of optionally adding water removed during evaporation to obtain a desired capsule concentration, and f) A step of forming a polymer shell by initiating interfacial polymerization of a first shell monomer, for example, by raising the temperature, adding a catalyst, or irradiating with UV light.

[0065] A second shell monomer or crosslinking agent can be added to the emulsion prior to or after the high-shear dispersion step. Since the initiation of interfacial polymerization occurs almost spontaneously at room temperature, initiation is not necessary. If the emulsifier is reactive, as in a preferred embodiment of the present invention, the emulsifier can also become part of the polymer shell.

[0066] In some cases, when using a self-dispersing second polymer, polyisocyanate, or highly efficient emulsifier, the high-shear emulsification process can be carried out by normal stirring.

[0067] In a more preferred embodiment, a dispersion of microcapsules according to the present invention is prepared according to a method comprising the following steps: a) For example, a step of preparing a second polymer according to the present invention in a substantially water-immiscible solvent in order to form a non-aqueous solution, b) A step of adding the first shell monomer to a non-aqueous solution of the second polymer. c) A step of preparing an aqueous solution of an emulsifier and a second shell monomer for optionally forming a polymer shell, d) A step of emulsifying a non-aqueous solution in an aqueous solution under high shear, e) Optionally, a step of stripping an organic solvent from a mixture of an aqueous solution and a non-aqueous solution, and f) A step of forming a polymer shell by interfacial polymerization of the first component. This may occur spontaneously or be initiated by increasing the temperature, adding a catalyst, or irradiating with UV light.

[0068] Next, the capsule dispersion can be completed into an aqueous inkjet ink or pretreatment solution by adding, for example, a colorant, water, a humectant, a surfactant, or a solvent.

[0069] A preferred strategy for incorporating anionic stabilizing groups into the polymer shell of a capsule is to utilize carboxylic acid-functionalized reactive surfactants that can react with isocyanates. This results in amphoteric surfactants containing at least partially secondary or primary amines, such as sulfonic acids or their salts, phosphate esters or their salts, or phosphonic acids. Alternatively, other reactive surfactants functionalized with its salt can be used.

[0070] Several amphoteric surfactants are commercially available, which are mixtures of surfactants that partially contain secondary amines but also contain tertiary amines. Unwanted foaming has been encountered in inkjet printers in inkjet inks based on capsules manufactured using commercially available amphoteric surfactants. Foaming causes problems with ink supply and also causes problems with degassing, which attempts to remove air from the ink, resulting in unreliable spraying. Therefore, preferably, a surfactant according to formula (I) of International Publication No. 2016 / 165970 is used in the encapsulation process of the second polymer.

[0071] The capsules according to the present invention are dispersed in an aqueous medium. The aqueous medium consists of water, but preferably may contain one or more water-soluble organic solvents.

[0072] One or more organic solvents may be added for various reasons. For example, adding a small amount of organic solvent may be advantageous to improve the dissolution of compounds in the inkjet ink being prepared, to obtain better penetration into porous substrates, or to prevent the ink from drying out too quickly at the nozzles of the inkjet head. Preferred water-soluble organic solvents include polyols (e.g., ethylene glycol, glycerin, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, tetraethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, 1,6-hexanediol, 1,2-hexanediol, 1,5-pentanediol, 1,2-pentanediol, 2,2-dimethyl-1,3-prapanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 3-methyl-1,3-butanediol, and 2-methyl-1,3-propanediol), N-hydroxyethyl-pyrrolidone, N-butyl-pyrrolidone These include rolidone, 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 monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether), amides such as 2,2'-thiodiethanol and N,N-dimethylformamide, heterocyclic compounds such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and acetonitrile.

[0073] B. Aqueous formulation containing the dispersion of the present invention. B.1. Pretreatment solution The aqueous pretreatment solution is preferably used in inkjet printing using aqueous-based inks on low-absorbent or non-absorbent substrates. The aqueous pretreatment solution according to the present invention comprises microcapsules consisting of a polymer shell surrounding a core, the core comprising a second polymer. The polymer shell preferably further comprises a dispersion group preferably covalently bonded to the shell, more preferably the dispersion group being a group selected from the group consisting of protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternary tertiary amines, N-quaternary heteroaromatic compounds, sulfonium, and phosphonium.

[0074] Cationic dispersive groups will help agglomerate, soft agglomerate, precipitate, or break down anionic stabilizing colorants and / or binders in aqueous inkjet inks, resulting in a reduction of bleeding and beading in the formed image. The capsules are present in an amount of preferably 45% by weight or less, more preferably 5-25% by weight, based on the total weight of the pretreatment solution. It was observed that when the amount exceeds a certain percentage, the injection is not always reliable.

[0075] Polyvalent metal ions can be included in the pretreatment solution as compounds that can precipitate or agglomerate anionic compounds, such as dyes, pigments, and binders, from inkjet inks. Suitable examples include divalent or higher metal cations such as magnesium, calcium, strontium, barium, zirconium, and aluminum, and fluoride ions (F - ), chloride ions (Cl - ), bromide ions (Br - ), sulfate ions (SO4 2- ), nitrate ion (NO3 - ), and acetate ions (CH3COO - It is a water-soluble metal salt formed from anions such as ).

[0076] These polyvalent metal ions have the function of agglomerating the ink by acting on the carboxyl groups on the surface of the pigment in the inkjet ink, or on the dispersion polymer of the capsules contained in the ink. As a result, the colorants of the ink are fixed, resulting in a reduction of bleeding and beading in the printed image. Therefore, it is preferable that the surface of the pigment and / or the dispersion polymer of the capsules in the ink has anionic groups, preferably carboxyl groups, when contained in the ink.

[0077] The pretreatment solution may also contain a pigment. A pretreatment solution containing a white pigment is particularly useful for printing on dark or transparent substrates. A preferred pigment for water-based pretreatment inks is titanium dioxide. The titanium dioxide (TiO2) pigment useful in this invention may be in the rutile or anastase crystalline form. The manufacturing process of TiO2 is described in "The Pigment Handbook," Vol. I, 2nd Ed., John The relevant disclosures are described in detail by Wiley & Sons, NY (1988), and are incorporated herein by reference for all purposes as if they were described in their entirety.

[0078] Titanium dioxide particles can have a wide variety of average particle sizes of about 1 micron or less, depending on the desired final application of the pretreatment solution. For applications requiring high opacity or decorative printing, the titanium dioxide particles preferably have an average particle size of less than about 1 μm. Preferably, the particles have an average particle size of about 50 to about 950 nm, more preferably about 75 to about 750 nm, and even more preferably about 100 to about 500 nm.

[0079] For applications requiring a white color with a certain degree of transparency, a preferred pigment is "nano" titanium dioxide. "Nano" titanium dioxide particles typically have an average particle size in the range of about 10 to about 200 nm, preferably about 20 to about 150 nm, and more preferably about 35 to about 75 nm. Inks containing nano titanium dioxide can provide improved saturation and transparency while still retaining good resistance to photobleaching and appropriate hue angles. A commercially available example of uncoated nanograde titanium dioxide is P-25, available from Degussa (Parsippany NJ).

[0080] Furthermore, using multiple particle sizes can sometimes achieve unique advantages such as opacity and UV protection. These multiple particle sizes can be achieved by adding both pigment-grade and nano-grade TIO2.

[0081] Titanium dioxide is preferably incorporated into the pretreatment formulation via a slurry concentration composition. The amount of titanium dioxide present in the slurry composition is preferably about 15% to about 80% by weight based on the total slurry weight.

[0082] Titanium dioxide pigments may also have one or more metal oxide surface coatings. These coatings can be applied using techniques known to those skilled in the art. Examples of metal oxide coatings include, among others, silica, alumina, alumina-silica, boria, and zirconia. These coatings can provide improved properties, including reduced photoreactivity of titanium dioxide. Metal oxide coatings of alumina, alumina-silica, boria, and zirconia are particularly beneficial in combination with the cation-stabilizing capsules of the present invention because they result in a positively charged surface of the TiO2 pigment, thus eliminating the need for further surface treatment of the pigment.

[0083] Commercially available examples of such coated titanium dioxide include R700 (alumina coated, available from EIDuPont deNemours, 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 nanograde titanium dioxide from Tayco Corporation, Osaka, Japan).

[0084] The pretreatment solution may contain at least one pH adjusting agent. Suitable pH adjusting agents include organic amines, NaOH, KOH, NET3, NH3, HCl, HNO3, and H2SO4. In a preferred embodiment, the pretreatment solution has a pH of less than 7. A pH of 7 or less can favorably affect the electrostatic stabilization of the capsule, especially when the dispersing group of the capsule is an amine.

[0085] B.2. Water-based inkjet ink. The aqueous inkjet ink according to the present invention comprises at least a) an aqueous medium, b) a colorant, and c) a capsule consisting of a polymer shell surrounding a core, the core comprising a second polymer. The polymer shell may further preferably contain a dispersion group covalently bonded to the shell, more preferably a dispersion group selected from the group consisting of carboxylic acids or salts thereof, sulfonic acids or salts thereof, phosphate esters or salts thereof, phosphonic acids or salts thereof. The capsule can also be stabilized in the inkjet ink using a combination of both anionic and nonionic dispersion groups bonded to the polymer shell.

[0086] The resin particles according to the present invention are preferably present in the inkjet ink in an amount of 30% by weight or less, preferably 2 to 25% by weight, based on the total weight of the inkjet ink. It has been observed that spraying at concentrations exceeding 30% by weight is not necessarily reliable.

[0087] 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 containing a plurality of inkjet inks according to the present invention. The inkjet ink set preferably includes at least cyan inkjet ink, magenta inkjet ink, yellow inkjet ink, and black inkjet ink. Such a CMYK-inkjet ink set may also be extended with additional inks such as red, green, blue, violet and / or orange in order to further expand the color gamut of the image. The inkjet ink set may also be extended by a combination of full density inkjet ink and light density inkjet ink. The combination of dark and light inks, and / or black and gray inks improves the image quality by reducing the graininess.

[0088] In a preferred embodiment, the inkjet ink set also includes white inkjet ink. This makes it possible to obtain more vivid colors, especially on transparent substrates, where the white inkjet ink can be applied as a primer on a primer containing a cationic compound or on the color inkjet ink when viewing the image through the transparent substrate.

[0089] The viscosity of the inkjet ink is preferably less than 25 mPa·s at a shear rate of 25 °C and 90 seconds -1 and more preferably 2 - 15 mPa·s at a shear rate of 25 °C and 90 seconds -1 and a shear rate of 90 seconds.

[0090] The surface tension of the inkjet ink 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.

[0091] The inkjet ink may also contain at least one surfactant in order to obtain good spreading properties on the substrate.

[0092] B.2.1. Solvents The aqueous medium of the ink contains water, but may preferably contain one or more water-soluble organic solvents. Suitable solvents that can be incorporated into the ink are described in § A.2.

[0093] B.2.2. Pigments The pigments in water-based inkjet inks may include black, white, cyan, magenta, yellow, red, orange, violet, blue, green, brown, or mixtures thereof. The coloring pigments may be selected from those disclosed in HERBST, Willy, et al. Industrial Organic Pigments, Production, Properties, Applications. 3rd edition. Wiley - VCH, 2004. ISBN 3527305769.

[0094] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of International Publication No. 2008 / 074548.

[0095] Pigment particles are dispersed in an aqueous medium by a polymer dispersant or surfactant. Self-dispersing pigments may also be used. When combined with capsules having anionic dispersing groups, anionic surfactants may be preferably used as pigment dispersants. Self-dispersing pigments are pigments that have covalently bonded anionic hydrophilic groups on their surface, such as salt-forming groups or the same groups used as dispersing groups for capsules, and can disperse the pigment in an aqueous medium without the use of surfactants or resins. A suitable commercially available self-dispersing colored pigment is, for example, CAB--JET® inkjet colorants from CABOT.

[0096] Particularly suitable types of pigments for the inkjet inks of the present invention are encapsulated pigments in which the pigment is at least partially covered with a polymer, preferably a crosslinked polymer. Suitable examples of encapsulated pigments are described in [0070-0076] of U.S. Patent No. 2014 / 092168, which is incorporated herein by reference.

[0097] The pigment particles in inkjet inks must be small enough to allow the ink to flow freely through the inkjet printing device, especially through the spray nozzles. It is also desirable to use small particles for maximum color intensity and to slow down sedimentation.

[0098] The average pigment particle size is preferably 0.050 to 1 μm, more preferably 0.070 to 0.300 μm, and particularly preferably 0.080 to 0.200 μm. Most preferably, the number-average pigment particle size is 0.150 μm or less. The average particle size of the pigment particles is measured using a Brookhaven Instruments Particle Sizer BI90plus based on the principle of dynamic light scattering. The ink is diluted with water to a pigment concentration of 0.002 wt%. The BI90plus measurement settings are 23°C, angle 90°, wavelength 635 nm, and five runs with the graphic correction function.

[0099] However, for white pigment inkjet inks, the number-average particle size of the white pigment is § This is the same as what is described in B.1.

[0100] Suitable white pigments are shown in Table 2 of Section

[0116] of International Publication No. 2008 / 074548. The white pigments are preferably pigments having a refractive index greater than 1.60. The white pigments may be used alone or in combination. Preferably, titanium dioxide is used as a pigment having a refractive index greater than 1.60. Suitable titanium dioxide pigments are disclosed in Sections

[0117] and

[0118] of International Publication No. 2008 / 074548.

[0101] In addition, special colorants may be used, such as fluorescent pigments for special effects in clothing, and metallic pigments for printing a high-quality silver and gold appearance on fabrics.

[0102] Polymer dispersants suitable for pigments are copolymers of two monomers, but may contain three, four, five, or even more monomers. The properties of the polymer dispersant 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 polymerized to ABBAABAB), • Alternating polymerization monomers (for example, monomers A and B polymerized to ABABABAB), • Gradient (tapered) polymerized monomers (for example, monomers A and B polymerized to AAABAABBABBB), • Block copolymers (e.g., monomers A and B polymerized to AAAAABBBBBB), where the block length of each block (2, 3, 4, 5 or more) is important for the dispersing ability of the polymer dispersant, • Graft copolymers (graft copolymers consist of a polymer main chain having polymer side chains bonded to the main chain), and • Mixed forms of these polymers, such as block-shaped gradient copolymers.

[0103] Suitable dispersants include DISPERBYK® dispersant from BYK CHEMIE, JONCRYL® dispersant from JOHNSON POLYMERS, and SOLSPERSE® dispersant from Lubrisol. A detailed list of non-polymeric dispersants and several polymeric dispersants is disclosed in MC CUTCHEON, Functional Materials, North American Edition, Glen Rock, NJ: Manufacturing Confectioner Publishing Co., 1990, pp. 110-129.

[0104] The polymer dispersant preferably has a number-average molecular weight Mn of 500 to 30,000, more preferably 1,500 to 10,000.

[0105] The polymer dispersant preferably has a weight-average molecular weight Mw of less than 100,000, more preferably less than 50,000, and most preferably less than 30,000.

[0106] The pigment is preferably present in an amount ranging from 0.01 to 20% by weight, more preferably from 0.05 to 10% by weight, and most preferably from 0.1 to 5% by weight, based on the total weight of the inkjet ink. In the case of white inkjet ink, the white pigment is preferably present in an amount of 3% to 40% by weight, more preferably from 5% to 35% by weight of the inkjet ink. An amount less than 3% by weight cannot achieve sufficient coverage.

[0107] B.2.3. Resin The inkjet ink composition according to the present invention may further contain additional resins. These resins are often added to the inkjet ink formulation to further achieve good adhesion of the pigment to the substrate or to enhance the water resistance and solvent resistance of the printed image. The resin is preferably a polymer, and suitable resins may be acrylic resins, urethane-modified polyester resins, or waxes. Suitable waxes include polyethylene wax, polypropylene wax, and polytetrafluoroethylene wax. In one example, the wax is selected from the group consisting of polypropylene wax, high-density polyethylene (HDPE) wax, and combinations thereof.

[0108] The concentration of the resin in the inkjet ink according to the present invention is at least 1% by weight, preferably less than 30% by weight, and more preferably less than 20% by weight.

[0109] B.2.4. Additives Inkjet inks may also contain humectants. Humectants are preferably incorporated into the inkjet ink if the liquid must be applied by an inkjet or a jetting technology such as a valve jet. Humectants prevent nozzle clogging. This prevention is due to their ability to slow the evaporation rate of water in the inkjet ink, especially the liquid. Humectants are preferably organic solvents having a higher boiling point than water. Suitable humectants include triacetin, N-methyl-2-pyrrolidone, glycerol, urea, thiourea, ethyleneurea, alkylurea, alkylthiourea, dialkylurea and dialkylthiourea, diols including ethanediol, propanediol, propanetriol, butanediol, pentanediol and hexanediol; glycols including propylene glycol, polypropylene glycol, ethylene glycol, polyethylene glycol, diethylene glycol, tetraethylene glycol, and mixtures and derivatives thereof. A preferred humectant is glycerol.

[0110] The humectant is preferably added to the liquid formulation in an amount of 0.1 to 20% by weight based on the total weight of the liquid.

[0111] Inkjet inks may contain surfactants. Any known surfactant may be used, but glycol surfactants and / or acetylene alcohol surfactants and / or polysiloxane surfactants are preferred. The use of acetylene glycol surfactants and / or acetylene alcohol surfactants and / or polysiloxane surfactants further reduces bleeding and improves print quality, and also improves drying during printing, enabling high-speed printing.

[0112] The acetylene glycol surfactant and / or acetylene alcohol surfactant is preferably one or more selected from 2,4,7,9-tetramethyl-5-decine-4,7-diol, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decine-4,7-diol, 2,4-dimethyl-5-decine-4-ol, and alkylene oxide adducts of 2,4-dimethyl-5-decine-4-ol. These are, for example, Air These include the 104 series and Surfynol® E series, such as Olfine® E1010, 465, and Surfynol® 61, which are available from Products (GB) or Nissin Chemical Industry.

[0113] C. Inkjet printing method In a preferred inkjet recording method, the method is: a) A step of spraying an aqueous inkjet ink onto a substrate, wherein the ink comprises a capsule consisting of a colorant and a polymer shell surrounding a core, and the core comprises a second polymer. b) A step of drying the sprayed inkjet ink by applying heat to obtain a temperature of at least 50°C, more preferably at least 80°C. Includes.

[0114] Before spraying the inkjet ink according to the present invention, an aqueous pretreatment solution or primer can be applied to the substrate. The aqueous pretreatment solution preferably contains components that can agglomerate the components of the aqueous inkjet ink of the present invention. Examples of such components are soft flocculants selected from the group consisting of polyvalent salts, cationic surfactants, and cationic resins.

[0115] In another preferred inkjet recording method, the method comprises: a) applying an aqueous pretreatment solution onto a substrate, wherein the pretreatment solution comprises a dispersion of microcapsules comprising a polymer shell and a core, the core comprising a second resin, and the polymer shell comprising a dispersion group selected from the group consisting of protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternary tertiary amines, N-quaternary heteroaromatic compounds, sulfonium, and phosphonium; b) optionally, at least partially drying the applied aqueous pretreatment solution to obtain a temperature of at least 50°C, more preferably at least 60°C, and most preferably at least 80°C; c) spraying an aqueous inkjet ink onto the applied pretreatment solution, wherein the ink comprises a colorant, preferably a pigment, and more preferably also comprises a dispersion of microcapsules according to the present invention; and d) drying the sprayed inkjet ink. If step b) is not performed, or if the pretreatment solution is not dried, the drying in step d) should be carried out by applying heat such that the temperature of the applied pretreatment solution is at least 50°C, more preferably at least 80°C.

[0116] The aqueous dispersion according to the present invention may be contained in a post-treatment liquid or overprint varnish, which is then preferably sprayed by an inkjet head.

[0117] The substrate used in the inkjet recording method may be porous, such as textiles, paper, and leather, but preferably it is a low-absorbent substrate, such as cardboard, or a non-absorbent substrate, such as polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polyester, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polylactide (PLA), polymethyl methacrylate, or polyimide.

[0118] The base material may also be plain paper or resin-coated paper, such as polyethylene or polypropylene coated paper. There are no practical restrictions on the type of paper, and it includes newsprint, magazine paper, office paper, wallpaper, and even higher-basis-weight papers commonly referred to as boards, such as white-lined chipboard, corrugated board, and packaging board.

[0119] The substrate may be transparent, translucent, or opaque. A preferred opaque substrate is 1.10 g / cm³. 3 This includes so-called synthetic paper, such as Synaps® grade from Agfa-Gevaert, which is an opaque polyester sheet having the above density.

[0120] In another preferred inkjet recording method, the pretreatment solution is applied via a technique selected from the group consisting of inkjet, valve jet, and spray. More specifically, these inkjet and valve jet techniques apply the pretreatment solution according to the present invention, preferably via inkjet. This allows for the image-like application of inkjet ink onto a surface on which an image is obtained. These last-resort methods of applying pretreatment solutions have the advantage that the amount of pretreatment solution required is substantially less than other application methods for priming the substrate.

[0121] Examples of heating processes for drying pretreatment liquids or inkjet inks according to the present invention include, but are not limited to, heating presses, atmospheric steam treatment, high-pressure steam treatment, and THERMOFIX. Any heat source can be used in the heating process, for example, an infrared source.

[0122] The drying process can be carried out in air, but the heating process must be carried out using a heat source, which includes equipment for forced air heating, radiative heating such as IR radiation including NIR-, CIR-, and SWIR radiation, conductive heating, high-frequency drying, and microwave drying. The drying process is such that the temperature of the printed image is preferably below 150°C.

[0123] A preferred inkjet head for an inkjet printing system for ejecting inkjet ink or pretreatment liquid containing resin particles according to the present invention is a piezoelectric inkjet head. Piezoelectric inkjet ejection is based on the movement of a piezoelectric ceramic transducer when a voltage is applied. The application of voltage changes the shape of the piezoelectric ceramic transducer in the print head, creating a void, which 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 aqueous inkjet ink or aqueous pretreatment liquid containing particle dispersion according to the present invention is not limited to piezoelectric inkjet printing. Other inkjet print heads can be used, including various types such as continuous type, thermal print head type, MEM jet type head, and valve jet type. [Examples]

[0124] D. Examples D.1. Materials All materials used in the following examples were readily available from standard sources such as Sigma-Aldrich (Belgium) and Acros (Belgium), unless otherwise specified. Demineralized water was used. Dynacoll 7150 is a polyester polyol containing terephthalate and isophthalate units supplied by Evonik. Ymer N90 is a 1,3-diol polyether supplied by Perstorp. Ymer N120 is a 1,3-diol polyether supplied by Perstorp. Reaxis C708 is a catalyst supplied by Reaxis BV. IPDI is an IPDI monomer supplied by Evonik. Vestanat T1890E IPDI is a 70% IPDI trimer solution in butyl acetate, supplied by Evonik. Desmodur N3200 is an HDI-based polyisocyanurate supplied by Covestro. • Desmodur N75 is an HDI biuret from Covestro. Lakeland ACP70 is a 70% solution of N-cocoalkyl β-alanine derivatives supplied by Espachem. BD is 1,4-butanediol supplied by Acros. • Triethylamine is triethylamine supplied by Acros. PU-3 is an aqueous dispersion of polyurethane resin, and is prepared as resin PU-3 in International Publication No. 2019 / 106089 A. • 2,2'-Azobis(2-methylbutyronitrile) is an initiator obtained from Wako Chemicals. NeoCryl A-1127 is a 44 wt% aqueous polyacrylate dispersion from DSM NeoResins. Mowinyl 6969D is a 42% by weight aqueous polyacrylate dispersion from Japan Coating Resin Co., Ltd. • PD is 1,2-propanediol manufactured by Dow Chemical. • DPM is Dowanol DPM manufactured by Dow Chemical. SolvMIX is a 1:1 mixture of Dowanol DPM and glycol. COL-1 is a commercially available cyanide dispersion supplied by Lubrizol, available under the trade name Diamond D75C. COL-2 is a 15% aqueous dispersion of Pigment Red 122 from Lubrizol, available under the trade name DIAMOND D75M. • HD is 1,2-hexanediol. • SURF-1 is a Tegowet 270 supplied by Evonik. • SUBST-1 is a 180gsm MM-X liner supplied by MM Karton. • SUBST-2 is a clay-coated EB flute supplied by Antalis. • SUBST-3 is a polypropylene film supplied by Antalis as Pripak Classic.

[0125] D.2. Measurement method D.2.1. Sample Preparation An inkjet ink formulation was coated onto each substrate using an automatic bar coater with a 10 μm spiral bar. After drying the coated film in an 80°C oven for 5 minutes, it could be further evaluated.

[0126] Inkjet ink formulations were ejected using a Dimatix® DMP2831 system equipped with a standard Dimatix® 10pl printhead. The ink was ejected at 22°C using a 5kHz ejection frequency, 25V ejection voltage, and a standard waveform. The ink was ejected onto SUBST-3 and dried at 100°C for 5 minutes to obtain a solid color patch.

[0127] D.2.2. Water resistance Water resistance on the dry coating was evaluated by performing double friction five times on the substrate using a water-soaked Q-tip. The level of water resistance was quantified according to the criteria in Table 1 below.

[0128] D.2.3. Water resistance - Solvent resistance The water resistance and i-propanol resistance of sprayed and dried solid patches were evaluated by rubbing a Q-tip 10 times. The levels of water resistance and solvent resistance were quantified according to the criteria in Table 1. [Table 1]

[0129] D.2.4. Scratch resistance Abrasion resistance was evaluated on a dry film by performing 10 double friction cycles using adjacent white fibers, as in ISO 105-X12. The coloration of the white friction cloth was evaluated based on ΔEab (CIE76), as shown in Table 2. [Table 2]

[0130] D.2.5. Ink ejection reliability The inkjet ink formulation was sprayed as described in § D.2.1.

[0131] Waiting time was evaluated based on the number of fully functional nozzles in the inkjet head after restarting the ejection process following a 2-minute idle period with the nozzles uncapped (1 = all nozzles still ejecting, 2 = more than half of the nozzles still ejecting, 3 = less than half of the nozzles ejecting).

[0132] D.3. Preparation of Microcapsules of the Present Invention D.3.1. Second polymer: Preparation of polyurethane resin PU-1 solution First, polyurethane solution PU-1 was prepared according to the following steps: 227.49 g of Dynacol 7150 was dissolved in 402.83 g of ethyl acetate at 45°C in an Erlenmeyer flask. 56.87 g of Ymer N120 was added to the Dynacol solution. The Ymer N120 was initially preheated to 90°C to make it liquid and easier to handle. A clear solution in ethyl acetate was thus obtained. This mixture was cooled to room temperature. The catalyst solution was prepared by diluting 2.14 g of Reaxis C708 with 19.34 g of ethyl acetate. The mixture of Ymer N120 and Dynacol 7150 was transferred to a 1000 mL three-necked round-bottom flask equipped with a coil condenser and an overhead stirrer. The flask was flushed with nitrogen, and a slow nitrogen flow was maintained during stirring and reaction. Subsequently, the catalyst was added dropwise through an addition funnel equipped with a pressure equalizing arm. The oil bath was heated to 75°C. After 1 hour, the reaction mixture reached a constant temperature of 68°C. Subsequently, 31.32 g of IPDI was added over 35 minutes via an addition funnel equipped with a pressure equalization arm. The oil bath was then heated to 70°C, and the reactants were allowed to react overnight for 22 hours. After the overnight reaction, The oil bath was heated again to 75°C for 30 minutes, and then cooled to room temperature. 42.98% of the theoretical solids content of the PU-1 solution was used for further application.

[0133] PU-2 solution Polyurethane solution PU-2 was prepared by the following steps: 260.08 g of Dynacol 7150 was dissolved in 402.90 g of ethyl acetate at 45°C in an Erlenmeyer flask. 28.90 g of Ymer N90 was added to the Dynacol solution. The Ymer N90 was preheated to 90°C to become liquid and easier to handle. A clear solution in ethyl acetate was thus obtained. This mixture was cooled to room temperature. A catalyst solution was prepared by diluting 2.14 g of Reaxis C708 with 19.34 g of ethyl acetate. The polyol solution was transferred to a 1000 mL three-necked round-bottom flask equipped with a coil condenser and an overhead stirrer. The flask was flushed with nitrogen, and a slow nitrogen flow was maintained during stirring and reaction. Subsequently, the catalyst was added dropwise through an addition funnel equipped with a pressure equalizing arm. The oil bath was heated to 75°C. After 1 hour, the reaction mixture reached a constant temperature of 68°C. Next, 26.70 g of IPDI was added over 40 minutes via an addition funnel with a pressure equalizing arm. The oil bath was then heated to 70°C and the reactants were allowed to react overnight for 22 hours. After the overnight reaction, the oil bath was heated again to 75°C for 30 minutes and then cooled to room temperature. 42.98% of the theoretical solids content of the PU-2 solution was used for further use.

[0134] PU-4 solution Polyurethane solution PU-4 was prepared by the following steps: 114.63 g of Dynacol 7150 was dissolved in 201.45 g of ethyl acetate at 45°C in an Erlenmeyer flask. 28.66 g of Ymer N90 was added to the Dynacol solution. The Ymer N90 was preheated to 90°C to make it liquid and easier to handle. A clear solution in ethyl acetate was thus obtained. This mixture was cooled to room temperature. A catalyst solution was prepared by diluting 1.07 g of Reaxis C708 with 9.67 g of ethyl acetate. The polyol solution was transferred to a 500 mL three-necked round-bottom flask equipped with a coil condenser and an overhead stirrer. The flask was flushed with nitrogen, and a slow nitrogen flow was maintained during stirring and reaction. Subsequently, the catalyst was added dropwise through an addition funnel equipped with a pressure equalizing arm. The oil bath was heated to 75°C. After 1 hour, the reaction mixture reached a constant temperature of 68°C. Next, 14.56 g of IPDI was added via an addition funnel with a pressure equalization arm over 35 minutes. The oil bath was then heated to 70°C and the reactants were allowed to react overnight for 22 hours. After the overnight reaction, the oil bath was heated again to 75°C for 30 minutes and then cooled to room temperature. A theoretical solid content of 42.98% of the PU-4 solution was used for further use.

[0135] D.3.2. Second polymer: Preparation of polyacrylic resin PMMA-1 PMMA-1 is a polymethyl methacrylate synthesized as follows: 10 g of methyl methacrylate was dissolved in 30 mL of ethyl acetate in a 100 mL three-necked flask. The clear solution was flushed with nitrogen for 10 minutes, and then 0.506 g of 1-dodecanethiol was added. This mixture was flushed again with nitrogen for 10 minutes. 0.288 g of 2,2'-azobis(2-methylbutyronitrile) was added, and the reaction mixture was refluxed overnight. The reaction was monitored using TLC (NP Merck 90 / 10 heptane / ethyl acetate and I2 staining). After all monomers had been consumed, the solvent was evaporated to obtain a solid product.

[0136] Polyacrylates were analyzed by size exclusion chromatography (3× mixed B column set, THF / HOAc 95 / 5). The measurement results are listed in Table 3. [Table 3]

[0137] D.3.3. Preparation of the Microcapsule Dispersion of the Present Invention The microcapsule dispersion CAP-1 of the present invention was prepared by interfacial polymerization. A lipophilic phase was prepared by mixing 25.73 g of ethyl acetate, 16.5 g of Desmodur N3200, and 38.42 g of PU-1 solution. An aqueous phase was prepared by mixing 7.00 g of Lakeland ACP70, 1.80 g of lysine, 2.0 g of triethylamine, and 102.94 g of water. The organic phase was placed in a plastic bottle with a wide opening and placed in an ice bath. The aqueous phase was added to the lipophilic phase. The lipophilic phase was emulsified in the aqueous phase at 18000 RPM for 5 minutes using an Ultraturrax apparatus. The emulsion was placed in a round-bottom flask. The plastic bottle was rinsed with 80.00 g of water to transfer all of the dispersion. The ethyl acetate was evaporated in a rotary evaporator until it weighed 145 g. The temperature was set to 40°C and the ethyl acetate was removed under reduced pressure. Evaporation was initiated at a pressure of 200 mbar and gradually reduced to 40 mbar. Excess water was evaporated and replaced by adding up to 145 g in total. The round-bottom flask was placed in an oil bath at 40°C and heated to 60°C within 30 minutes. The dispersion was then kept at 60°C overnight for 16 hours and then cooled to room temperature. The resulting microcapsule dispersion CAP-1 had a solid content of 32.09 wt%, a pH of 7.88, and an average particle size of 208.7 nm (measured by a Malvern particle size analyzer).

[0138] The microcapsule dispersion CAP-2 of the present invention was prepared by interfacial polymerization. A lipophilic phase was prepared by mixing 25.73 g of ethyl acetate, 16.5 g of Desmodur N3200, and 38.42 g of PU-4 solution. An aqueous phase was prepared by mixing 7.00 g of Lakeland ACP70, 1.80 g of lysine, 2.0 g of triethylamine, and 103.28 g of water. The lipophilic phase was placed in a plastic bottle with a wide opening and placed in an ice bath. The aqueous phase was added to the lipophilic phase. The lipophilic phase was emulsified in the aqueous phase at 18000 RPM for 5 minutes using an Ultraturrax apparatus. The emulsion was placed in a round-bottom flask. The plastic bottle was rinsed with 80.00 g of water to transfer all of the emulsion. The ethyl acetate was evaporated in a rotary evaporator until it weighed 145 g. The temperature was set to 40°C, and ethyl acetate was removed under reduced pressure. Evaporation was started at a pressure of 200 mbar and gradually reduced to 40 mbar. When excess water evaporated, it was replenished by adding up to 145 g in total. The round-bottom flask was placed in an oil bath at 40°C and heated to 60°C within 30 minutes. The dispersion was then kept at 60°C overnight for 16 hours, and then cooled to room temperature. The resulting microcapsule dispersion CAP-2 had a solid content of 25.44 wt%, a pH of 7.12, and an average particle size of 200.2 nm (measured by a Malvern particle size analyzer).

[0139] The microcapsule dispersion CAP-3 of the present invention was prepared by interfacial polymerization. A lipophilic phase was prepared by mixing 24.56 g of ethyl acetate, 12.19 g of Vestanat T1890E IPDI, and 19.86 g of PU-2 solution. 3.62 g of Lak An aqueous phase was prepared by mixing eland ACP70, 0.93 g of lysine, 1.04 g of triethylamine, and 103.28 g of water. The lipophilic phase was placed in a plastic bottle with a wide opening and placed in an ice bath. The aqueous phase was added to the lipophilic phase. The lipophilic phase was emulsified in the aqueous phase at 18000 RPM for 5 minutes using an Ultraturrax apparatus. The emulsion was placed in a round-bottom flask. The plastic bottle was rinsed with 80.00 g of water to transfer all of the emulsion. Ethyl acetate was evaporated in a rotary evaporator until its weight was 75 g. The temperature was set to 40°C and the ethyl acetate was removed under reduced pressure. Evaporation was started at a pressure of 200 mbar and the pressure was gradually reduced to 40 mbar. If excess water was evaporated, this water was replenished by adding up to a total of 75 g. A round-bottom flask was placed in an oil bath at 40°C and heated to 60°C within 30 minutes. The dispersion was then kept at 60°C overnight for 16 hours, and then cooled to room temperature. The resulting microcapsule dispersion, CAP-3, had a solid content of 26.68% by weight, a pH of 7.43, and an average particle size of 171.1 nm (measured by a Malvern particle size analyzer).

[0140] The microcapsule dispersion CAP-4 of the present invention was prepared by interfacial polymerization. A lipophilic phase was prepared by mixing 24.56 g of ethyl acetate, 12.19 g of IPDI Vestanat T1890E IPDI, and 19.86 g of PU-2 solution. An aqueous phase was prepared by mixing 3.62 g of Lakeland ACP70, 0.93 g of lysine, 0.622 g of 28% NH4OH aqueous solution, and 54.29 g of water. The lipophilic phase was placed in a plastic bottle with a wide opening and placed in an ice bath. The aqueous phase was added to the lipophilic phase. The lipophilic phase was emulsified in the aqueous phase at 18000 RPM for 5 minutes using an Ultraturrax apparatus. The emulsion was placed in a round-bottom flask. The plastic bottle was rinsed with 80.00 g of water to transfer all of the emulsion. The ethyl acetate was evaporated in a rotary evaporator until its weight was 75 g. The temperature was set to 40°C, and ethyl acetate was removed under reduced pressure. Evaporation was started at a pressure of 200 mbar and gradually reduced to 40 mbar. When excess water evaporated, it was replenished by adding up to a total of 75 g. The round-bottom flask was placed in an oil bath at 40°C and heated to 60°C within 30 minutes. The dispersion was then kept at 60°C overnight for 16 hours, and then cooled to room temperature. The resulting microcapsule dispersion CAP-4 had a solid content of 25.52 wt%, a pH of 7.43, and an average particle size of 239.1 nm (measured by a Malvern particle size analyzer).

[0141] A microcapsule dispersion CAP-5 of the present invention, containing a second polymer as a polyacrylate, was prepared as follows:

[0142] In potage A, 3.5 g of PMMA-1 was added to 10 g of ethyl acetate along with 4.657 g of Desmodur N75 and 0.7 g of Lakeland ACP70. In potage B, 1.120 g of Lakeland ACP70, 0.469 g of L-lysine, and 0.400 g of triethanolamine were added to 17.5 g of water. Potage A was added to potage B and stirred under high shear at 15,000 rpm using an Ultra-Turrax for 5 minutes. The solvent was removed under reduced pressure, and the removed water was added afterward. A capsule dispersion containing 27.4% by weight of dry residue was obtained.

[0143] The capsule dispersion was evaluated under a microscope, and the particle size was measured using a nanosizer (Malvern).

[0144] Table 4 shows an overview of the properties of the CAP-5 dispersion. [Table 4]

[0145] The dispersion has good microscopic quality.

[0146] D.4. Preparation of water-based inkjet inks D.4.1. Water-based inkjet ink containing PU polymer. Three types of cyan inkjet inks were prepared by mixing the compounds shown in Table 5. All weight percentages are relative to the total weight of the inkjet ink. When resin or microcapsules were used in the ink formulation, the solid content of the resin / microcapsules was 6.0% by weight of the total weight of the ink. [Table 5]

[0147] D.4.2. Preparation of aqueous inkjet inks containing polyacrylate polymers. Table 6 summarizes the compositions of the ink of the present invention containing encapsulated polyacrylate polymer, and comparative inks containing unencapsulated polyacrylate polymer.

[0148] The INVINK-2 ink of the present invention was formulated as follows: 3.962 g of CAP-5 was mixed with 2.28 g of COL-2 and stirred at room temperature. 3.962 g of SolvMIX was added dropwise, the ink was stirred at room temperature for 5 minutes, and filtered (1.6 μm). All of the resulting inks were stable at room temperature for 2 weeks.

[0149] The comparison inks, COMPINK-3 and COMPINK-4, were compared by having the same solid concentration in the ink. To obtain the desired result, Mowinyl 6969D and NeoCryl A-1127 were first prepared by diluting them with water. Then, 2.28 g of COL-2 was added, and the mixture was stirred at room temperature. 3.962 g of SolvMIX was added dropwise, the ink was stirred at room temperature for 5 minutes, and then filtered (1.6 μm). [Table 6]

[0150] D.5. Evaluation of the physical properties of the coatings obtained using INVINK-1, COMPINK-1, and COMPINK-2. The inks in Table 5 were applied to SUBST-1 and SUBST-2 (see § D.2.1) and evaluated as described in D.2.2 and D.2.4. The evaluation results are summarized in Table 7. [Table 7]

[0151] The results in Table 7 clearly show that the ink according to the present invention scores well in both water resistance and abrasion resistance. When no binder / resin is used in the ink, abrasion resistance remains acceptable, but water resistance is insufficient. Adding a PU binder as latex to the ink improves water resistance, but abrasion resistance remains insufficient.

[0152] D.6. Evaluation of INVINK-2, COMPINK-3, and 4 inks. The water resistance and solvent resistance of the solid patches of the spray inks shown in Table 6 (see § D.2.1) were evaluated according to § D.2.3. The results are summarized in Table 8.

[0153] The ink ejection reliability was evaluated as described in § D.2.5. The results are listed in the "Wait Time" column of Table 8. [Table 8]

[0154] From Table 8, it can be concluded that, in addition to the excellent water resistance and solvent resistance of the ink of the present invention, which contains the microcapsule dispersion of the present invention, sprayed and dried, more reliable re-spraying after restarting is obtained compared to the comparative ink.

Claims

1. An aqueous inkjet ink comprising a pigment and an aqueous dispersion of microcapsules having an average particle size of 0.05 μm to 2 μm, wherein the microcapsules comprise a crosslinked polymer shell surrounding a core, the core comprises a second polymer, the second polymer does not contain an active methylene group, an ethylenically unsaturated group, an epoxy group, an isocyanate group, a β-keto-ester, a β-keto-amide, or a 1,3-diketone, and the crosslinked polymer shell comprises a polymer selected from the group consisting of poly(urea) and poly(urethane).

2. The aqueous inkjet ink according to claim 1, wherein the second polymer is selected from the group consisting of poly(urethane) and its copolymers, acrylic and its copolymers, poly(ester), poly(styrene) and its copolymers, poly(vinylamide) and its copolymers, poly(olefin) and its copolymers, poly(vinyl alcohol) derivatives and their copolymers, poly(acetal) and its copolymers, poly(ether) and its copolymers, poly(vinyl ether) and its copolymers, polyvinyl(ester) and its copolymers, poly(imide) and its copolymers, poly(imine) and its copolymers, polycarbonate and its copolymers, poly(vinyl chloride) and its copolymers, poly(vinylidene chloride) and its copolymers, poly(amidic acid) and its copolymers, polysaccharides and their derivatives, and cellulose and its derivatives.

3. The aqueous inkjet ink according to claim 1 or 2, wherein a dispersion group is covalently bonded to a polymer shell.

4. The aqueous inkjet ink according to claim 3, wherein the dispersing group is selected from the group consisting of carboxylic acid or a salt thereof, sulfonic acid or a salt thereof, phosphate ester or a salt thereof, and phosphonic acid or a salt thereof.

5. The aqueous inkjet ink according to claim 3, wherein the dispersing group is selected from the group consisting of protonated amines, protonated nitrogen-containing heteroaromatic compounds, quaternary tertiary amines, N-quaternary heteroaromatic compounds, sulfonium, and phosphonium.

6. A pretreatment solution comprising a compound capable of precipitating or agglomerating compounds from aqueous inkjet ink, and an aqueous dispersion of microcapsules having an average particle size of 0.05 μm to 2 μm, wherein the microcapsules comprise a crosslinked polymer shell surrounding a core, the core comprises a second polymer, the second polymer does not contain active methylene groups, ethylenically unsaturated groups, epoxy groups, isocyanate groups, β-keto-esters, β-keto-amides, or 1,3-diketones, and the crosslinked polymer shell comprises a polymer selected from the group consisting of poly(urea) and poly(urethane).

7. An inkjet recording method, a) A step of spraying the inkjet ink described in claim 1 onto a substrate, b) A step of drying the sprayed inkjet ink by applying heat to obtain a temperature of at least 50°C of the sprayed ink. Methods that include...

8. An inkjet recording method, a) A step of applying the pretreatment solution described in claim 6 onto a substrate, b) Optionally, a step of at least partially drying the pretreatment solution so that the temperature of the pretreatment solution is at least 50°C, c) A step of spraying an aqueous inkjet ink containing a colorant onto the applied pretreatment solution; d) A step of drying the inkjet ink, and if step b) was not performed, a step of drying the pretreatment solution by applying heat to obtain a temperature of at least 50°C in the pretreatment solution; Methods that include...

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