Resin dispersion for aqueous inkjet ink, aqueous inkjet ink, and method for producing the same

Abstract

To provide an aqueous inkjet ink resin dispersion having excellent inkjet dischargeability.SOLUTION: An aqueous inkjet ink resin dispersion according to the present invention contains resin particles and water, and the resin particles contain a radical polymer containing a structural unit derived from a polymerizable monomer represented by formula (1). (In formula (1), R1 represents an alkylene group having 1 to 10 carbon atoms, n represents an integer of 1 to 100, R2 represents an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 30 carbon atoms, and X represents -SO3M (M represents an alkali metal atom or NH4)).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin dispersion for an aqueous inkjet ink and an aqueous inkjet ink. [Background technology]

[0002] As a textile printing method, so-called ink-jet printing, in which an image is formed on a fabric by an ink-jet system, is widely used because it allows dyeing in a short time and has high production efficiency.

[0003] In inkjet textile printing, dye inks or pigment inks are used. Known dye inks include aqueous inks containing reactive dyes. In aqueous inks containing reactive dyes, the reactive dyes dissolve in or react with the fibers of the fabric, resulting in highly fixable images. However, a step of washing away the dye that has not dissolved or reacted is required. From the viewpoint of eliminating such a washing step, the use of pigment inks has been considered.

[0004] Known pigment inks include aqueous inks containing pigment, resin particles (binder resin), a sulfonate-based anionic surfactant, and water (see, for example, Patent Document 1). Because pigment alone is difficult to adhere to fabric, the addition of a binder resin as described above allows the ink to adhere to fabric.

[0005] Known dispersions of resin particles used in aqueous inks include aqueous dispersions of resin particles composed of a polymer containing structural units derived from a polymerizable component having a vinyl group and a polyalkyleneoxy group, and structural units derived from a polymerization-reactive emulsifier component (see, for example, Patent Document 2). The polymerizable component having a vinyl group and a polyalkyleneoxy group functions as a nonionic reactive emulsifier, and the polymerization-reactive emulsifier component is shown to be a nonionic or anionic polymerization-reactive emulsifier. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-163397 [Patent Document 2] Japanese Patent Publication No. 2020-33512 Summary of the Invention [Problem to be solved by the invention]

[0007] The pigment ink containing the resin particles is usually prepared by mixing a pigment-containing ink component (such as a pigment dispersion) with an aqueous dispersion of resin particles. The aqueous dispersion of resin particles is prepared, for example, by emulsion polymerization.

[0008] However, pigment inks containing resin particles obtained by emulsion polymerization may exhibit good dispersibility when stored, but may have poor or insufficient ejection properties from an inkjet head.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a resin dispersion for an aqueous inkjet ink, and an aqueous inkjet ink, which have excellent inkjet ejection properties. [Means for solving the problem]

[0010] The above problem can be solved by the following configuration.

[0011] The resin dispersion for an aqueous inkjet ink of the present invention contains resin particles and water, and the resin particles contain a radical polymer containing a structural unit derived from a polymerizable compound represented by formula (1). [ka] (In formula (1), R 1 is an alkylene group having 1 to 10 carbon atoms, n is an integer from 1 to 100, R 2 is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 30 carbon atoms, X is -SO3M (M is an alkali metal atom or NH4)

[0012] The aqueous inkjet ink of the present invention is an aqueous inkjet ink comprising a colorant, resin particles, and an aqueous medium, wherein the resin particles comprise a radical polymer comprising a structural unit derived from a polymerizable monomer represented by formula (1). [ka] (In formula (1), R 1 is an alkylene group having 1 to 10 carbon atoms, n is an integer from 1 to 100, R 2 is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 30 carbon atoms, X is -SO3M (M is an alkali metal atom or NH4) [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a resin dispersion for an aqueous inkjet ink and an aqueous inkjet ink that are excellent in inkjet ejection properties. DETAILED DESCRIPTION OF THE INVENTION

[0014] As described above, resin particles produced by emulsion polymerization maintain their dispersibility by physically adsorbing the emulsifier to the surface of the resin particles. Aqueous inkjet inks (hereinafter simply referred to as "ink") containing such resin particles may exhibit good dispersibility under normal storage conditions, but may have poor ejection properties from an inkjet head. The reason for this is unclear, but high pressure is likely to be applied to the ink when ejected from an inkjet head. This high pressure is thought to cause some of the emulsifier components adsorbed to the surface of the resin particles to easily detach, making the resin particles more likely to aggregate.

[0015] In contrast, in the present invention, the resin particles used in the ink are emulsion-polymerized using an anionic reactive emulsifier (polymerizable compound represented by formula (1)) having an allyl group and a polyoxyalkylene group as polymerizable groups, thereby improving the ejection properties from an inkjet head.

[0016] The reason for this is not clear, but is speculated as follows. The reactive emulsifier is incorporated into the molecular chains of the polymer that constitutes the resin particles during emulsion polymerization. As a result, even when high pressure is applied to the ink, the reactive emulsifier is unlikely to come off the resin particles, thereby suppressing aggregation of the resin particles. Furthermore, since the reactive emulsifier has an allyl group as a polymerizable group, the polymerization reaction rate is slower than that of a component having a vinyl group as a polymerizable group (e.g., (meth)acrylates). As a result, the polymerizable component having a vinyl group reacts first, and then the reactive emulsifier having an allyl group is more likely to polymerize, and the reactive emulsifier is more likely to be oriented on the surface of the resin particles. Furthermore, the reactive emulsifier oriented on the surface of the resin particles has both an anionic group and a polyalkyleneoxy group, and therefore can exhibit a high emulsifying effect and dispersion stability of the resin particles. These effects can improve the ejection properties from the inkjet head.

[0017] Furthermore, by the resin dispersion further containing unreacted anionic reactive emulsifier in addition to the resin particles, the dispersibility of the resin particles can be further improved. This is because some of the reacted anionic reactive emulsifier penetrates into the interior of the resin particles and is not exposed on the surface of the resin particles. In this way, it is presumed that the unreacted anionic reactive emulsifier present separately can compensate for the part of the surface of the resin particles that is not completely covered with the reacted anionic reactive emulsifier.

[0018] The composition of the resin dispersion used in the ink of the present invention and the composition of the ink using the same will be described in detail below.

[0019] 1. Resin dispersion for water-based inkjet inks The resin dispersion for aqueous inkjet ink of the present invention (hereinafter referred to as "resin dispersion") is obtained by emulsion polymerization of a monomer composition in a medium containing water, and contains resin particles and water.

[0020] 1-1.Resin particles (Polymerizable compound represented by formula (1)) The resin particles contain a radical polymer containing a structural unit derived from the polymerizable compound represented by formula (1). [ka]

[0021] In formula (1), R 1 is an alkylene group having 1 to 10 carbon atoms. The alkylene group having 1 to 10 carbon atoms is preferably an alkylene group having 2 to 5 carbon atoms, and more preferably an ethylene group or a propylene group. Of these, an ethylene group is preferred from the viewpoint of increasing the hydrophilicity of the resin particles and facilitating the improvement of dispersibility.

[0022] n is an integer of 1 to 100. In terms of dispersibility and water resistance, n is preferably an integer of 10 to 60, more preferably 10 to 30, and even more preferably 10 to 15.

[0023] X is -SO3M (M is an alkali metal atom or NH4). X is preferably -SO3NH4.

[0024] R 2 is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 30 carbon atoms. The alkyl group having 1 to 50 carbon atoms is preferably an alkyl group having 5 to 20 carbon atoms, more preferably 10 to 15 carbon atoms. The aryl group having 6 to 30 carbon atoms is preferably a phenyl group. The alkyl group may further have a substituent such as a phenyl group; and the aryl group may further have a substituent such as an alkyl group.

[0025] As described above, the resin dispersion is obtained by emulsion polymerization of a monomer composition containing a polymerizable compound represented by formula (1) in a medium containing water. The polymerizable compound represented by formula (1) is an anionic reactive emulsifier having an allyl group as a polymerizable group. Because the anionic reactive emulsifier has an allyl group as a polymerizable group, it is easily incorporated into the molecular chain of the radical polymer that constitutes the resin particles and is easily oriented on the surface of the resin particles. This facilitates orientation of polyoxyalkylene groups and anionic groups on the surface of the resin particles, and these groups are not easily removed even when high pressure is applied, thereby maintaining high dispersibility.

[0026] Examples of the polymerizable compound represented by formula (1) include ADEKA REASOAP SR-10 and SR-20 (both manufactured by ADEKA Corporation).

[0027] The content of the polymerizable compound represented by formula (1) is preferably 0.5 to 10% by mass relative to all structural units constituting the radical polymer. When the content is 0.5% by mass or more, emulsion polymerization can be easily and stably carried out, and the dispersibility of resin particles can be sufficiently improved. When the content is 10% by mass or less, gelation due to an increase in the solution viscosity of the polymer solution can be sufficiently suppressed. From the same viewpoint, the content of the polymerizable compound represented by formula (1) is more preferably 1 to 5% by mass relative to all structural units constituting the radical polymer.

[0028] (Alkyl (meth)acrylate) The radical polymer constituting the resin particles preferably further contains a structural unit derived from alkyl(meth)acrylate, which means alkyl acrylate or alkyl methacrylate.

[0029] Among these, from the viewpoint of use in aqueous inkjet inks for textile printing, alkyl (meth)acrylates preferably contain alkyl acrylate as a main component, because alkyl acrylate polymers have a lower glass transition temperature (Tg) and are more flexible than alkyl methacrylate polymers, and therefore are less likely to impair the texture of fabrics during inkjet textile printing.

[0030] The number of carbon atoms in the alkyl group of the alkyl acrylate is, for example, 1 to 20, preferably 4 to 12, and more preferably 4 to 8. Examples of such alkyl acrylates include butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, and 2-ethylhexyl acrylate, with butyl acrylate being preferred.

[0031] The number of carbon atoms in the alkyl group of the alkyl methacrylate is, for example, 1 to 20, preferably 1 to 110, and more preferably 1 to 8. Examples of such alkyl methacrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, etc., and preferably methyl methacrylate.

[0032] The content of the structural units derived from alkyl (meth)acrylate is preferably 60 to 99 mass %, more preferably 90 to 99 mass %, based on the total structural units of the radical polymer. Among these, the content ratio of the structural units derived from alkyl acrylate to the structural units derived from alkyl methacrylate is preferably alkyl acrylate: alkyl methacrylate = 50:50 to 90:10 (mass ratio), more preferably 60:40 to 80:20 (mass ratio).

[0033] (Other monomers) The radical polymer constituting the resin particles may further contain structural units derived from other monomers than those mentioned above. The other monomers are not particularly limited and include (meth)acrylamide, hydroxyalkyl (meth)acrylate, and (meth)acrylate having an aromatic ring.

[0034] (Physical Properties) The glass transition temperature (Tg) of the radical polymer constituting the resin particles varies depending on the application, but from the viewpoint of use in an aqueous inkjet ink for textile printing, it is preferably −35° C. or lower, and more preferably −35 to −50° C. This is because a lower Tg of the radical polymer constituting the resin particles results in high flexibility and less loss of the texture of the fabric. The Tg of the radical polymer can be measured by differential scanning calorimetry in accordance with JIS K7121 at a heating rate of 10° C. / min.

[0035] The Tg of the radical polymer constituting the resin particles can be adjusted by the monomer composition of the polymer. For example, increasing the content of alkyl acrylate lowers the Tg of the radical polymer.

[0036] The weight-average molecular weight of the radical polymer constituting the resin particles is, for example, 500,000 or more, more preferably 1,000,000 to 2,000,000. When the weight-average molecular weight is equal to or greater than the lower limit, the fixability of the image to the fabric and the mechanical properties can be improved. The weight-average molecular weight can be measured in styrene equivalent terms using gel permeation chromatography (GPC).

[0037] The average particle size of the resin particles in the resin dispersion is preferably 30 to 200 nm, more preferably 50 to 120 nm, from the viewpoint of ejection properties, for example, by inkjet. The average particle size is the average value of primary particle sizes. The average particle size of the resin particles in the resin dispersion can be measured as the dispersed particle size (Z average) using, for example, a Zataizer Nano S90 manufactured by Melvern.

[0038] The content of the resin particles is not particularly limited, but is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 10 to 35% by mass, based on the resin dispersion.

[0039] 1-2.Other ingredients The resin dispersion may further contain other components in addition to those described above. The other components may be, for example, various additives used when preparing resin particles by emulsion polymerization or unreacted monomer components. In particular, from the viewpoint of further improving the dispersibility of the resin particles, it is preferable that the resin dispersion further contains an emulsifier (surfactant).

[0040] The emulsifier may be anionic, nonionic, amphoteric or cationic, but from the viewpoint of dispersibility, anionic emulsifiers are preferred.

[0041] Examples of anionic emulsifiers include sulfonates such as sodium dodecylbenzenesulfonate, sulfate ester salts, and anionic reactive emulsifiers having a polymerizable group. These may be used alone or in combination. Among these, it is preferable that the resin dispersion contains an anionic reactive emulsifier having an allyl group.

[0042] The anionic reactive emulsifier having an allyl group is preferably an anionic reactive emulsifier having an allyl ether group. The anionic reactive emulsifier having an allyl ether group is not particularly limited, but from the viewpoint of productivity and affinity with resin particles, it is preferable that the anionic reactive emulsifier contains the unreacted anionic reactive emulsifier used in preparing the resin particles, i.e., the unreacted polymerizable compound (free component) represented by the above formula (1).

[0043] The mechanism by which the dispersibility of resin particles is further improved by the inclusion of unreacted anionic reactive emulsifier in the resin dispersion is not clear, but it is thought that this is because the parts of the surface of the resin particles that are not covered with the (reacted) anionic reactive emulsifier are covered with the anionic reactive emulsifier having unreacted free allyl groups.

[0044] That is, the content of the unreacted polymerizable compound represented by formula (1) is preferably 5 to 40 mass %, and more preferably 15 to 40 mass %, of the total amount of the polymerizable compound represented by formula (1) contained in the monomer composition (the total amount of the unreacted polymerizable compound represented by formula (1) and the reacted polymerizable compound represented by formula (1)). When the content of the unreacted polymerizable compound represented by formula (1) is equal to or greater than the lower limit, the dispersibility of the resin particles is likely to be further improved. When the content of the unreacted polymerizable compound represented by formula (1) is equal to or less than the upper limit, the deterioration of the dispersion stability of the resin particles and the resulting deterioration of the ink jetting performance are more likely to be suppressed.

[0045] In the resin dispersion, the content of the unreacted polymerizable compound represented by formula (1) (free component) can be measured by the following method. The resin dispersion is heated to 80°C, and a 10% MgCl2 aqueous solution is added to precipitate the resin particles. Meanwhile, a calibration curve for the polymerizable compound represented by formula (1) is prepared using HPLC. The supernatant is measured using HPLC, and the obtained data is compared with the data from the calibration curve to determine the amount of the released polymerizable compound represented by formula (1).

[0046] 1-3. Manufacturing method As described above, the resin dispersion of the present invention can be prepared by emulsion polymerization of a monomer composition containing a polymerizable compound represented by formula (1) as an anionic reactive emulsifier. That is, the above-mentioned components are mixed and polymerized by emulsion polymerization, and then filtered to obtain a resin dispersion in which resin particles are dispersed in an aqueous medium.

[0047] The emulsion polymerization method is a method for preparing resin particles by polymerizing an emulsion prepared by adding a monomer, a polymerization initiator, an emulsifier, and, if necessary, a chain transfer agent, etc. to an aqueous medium (e.g., water). In the emulsion polymerization method, the reactive emulsifier described above functions as both a monomer and an emulsifier. Therefore, when preparing resin particles, it is not necessary to add any other emulsifiers other than the anionic reactive emulsifier. Note that a known emulsifier may be added separately as long as it does not impair the ejection property or the coagulation property.

[0048] The type of polymerization initiator is not particularly limited, and examples thereof include inorganic persulfates (e.g., potassium persulfate, sodium persulfate, ammonium persulfate, etc.), azo initiators (e.g., 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 4,4'-azobis(4-cyanovaleric acid), etc.), organic peroxides (e.g., t-butyl peroxypivalate, t-butyl hydroperoxide), etc., or salts thereof. Among these, it is preferable to use an azo initiator or an organic peroxide.

[0049] The amount of the polymerization initiator to be added is usually 0.01 to 5 parts by mass, and preferably 0.2 to 2 parts by mass, based on 100 parts by mass of all the monomers.

[0050] 2. Water-based inkjet ink The aqueous inkjet ink of the present invention contains a colorant, resin particles, and an aqueous medium.

[0051] 2-1. Coloring materials The colorant is a disperse dye or a pigment. A disperse dye is a dye that is insoluble or slightly soluble in water. "Insoluble or slightly soluble in water" means that the solubility in water at 25°C is 10 mg / L or less, preferably 5 mg / L or less, and more preferably 1 mg / L or less. Among these, pigments are preferred because of their good light resistance.

[0052] The pigment is not particularly limited, but may be, for example, an organic pigment or an inorganic pigment having the following numbers listed in the Color Index:

[0053] Examples of orange or yellow pigments include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 128, CI Pigment Yellow 138, CI Pigment Yellow 151, CI Pigment Yellow 154, CI Pigment Yellow 155, CI Pigment Yellow 180, CI Pigment Yellow 185, and CI Pigment Yellow 213.

[0054] Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, and Pigment Orange 13, 16, 20, and 36.

[0055] Examples of blue or cyan pigments include Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, 60.

[0056] Examples of green pigments include Pigment Green 7, 26, 36, and 50. Examples of yellow pigments include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193.

[0057] Examples of black pigments include Pigment Black 7, 28, and 26.

[0058] From the viewpoint of improving dispersibility in the ink, the pigment is preferably further dispersed with a pigment dispersant, which will be described later.

[0059] The pigment may also be a self-dispersing pigment. A self-dispersing pigment is a pigment particle whose surface is modified with a group having a hydrophilic group, and has pigment particles and hydrophilic groups bonded to the surface of the pigment particles.

[0060] Examples of hydrophilic groups include carboxyl groups, sulfonic acid groups, and phosphorus-containing groups, and examples of phosphorus-containing groups include phosphoric acid groups, phosphonic acid groups, phosphinic acid groups, phosphite groups, and phosphate groups.

[0061] Examples of commercially available self-dispersing pigments include Cabot Corporation's Cab-0-Jet (registered trademark) 200K, 250C, 260M, and 270V (sulfonic acid group-containing self-dispersing pigments), Cab-0-Jet (registered trademark) 300K (carboxylic acid group-containing self-dispersing pigments), and Cab-0-Jet (registered trademark) 400K, 450C, 465M, 470V, and 480V (phosphate group-containing self-dispersing pigments).

[0062] The content of the coloring material is not particularly limited, but from the viewpoint of easily adjusting the viscosity of the ink within the above range and enabling the formation of a high-density image, it is preferably 0.3 to 10% by mass of the ink, and more preferably 0.5 to 3% by mass. If the content of the coloring material is equal to or greater than the lower limit, the color of the image tends to be vivid, and if it is equal to or less than the upper limit, the viscosity of the ink does not become too high and ejection stability is less likely to be impaired.

[0063] 2-2.Resin particles The resin particles are those of the resin dispersion of the present invention. The content of the resin particles is preferably 1 to 30% by mass relative to the ink. When the content of the resin particles is 1% by mass or more, the fixation of the ink to the fabric is easily improved sufficiently, and when it is 30% by mass or less, the texture is less likely to be impaired. From the same viewpoint, the content of the resin particles is preferably 10 to 25% by mass relative to the ink.

[0064] 2-3.Aqueous medium The aqueous medium contains at least water, and preferably further contains a water-soluble organic solvent.

[0065] Examples of the water-soluble organic solvent include alcohols (e.g., methanol, ethanol, propanol, pentanol, hexanol, cyclohexanol, and benzyl alcohol), polyhydric alcohols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, glycerin, and compounds represented by the following formula (A)), polyhydric alcohol ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether), ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether), amines (e.g., ethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine), amides (e.g., formamide, N,N-dimethylformamide, N,N-dimethylacetamide), heterocycles (e.g., 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidine), sulfoxides (e.g., dimethyl sulfoxide), sulfones (e.g., sulfolane). [ka] (In formula (A), R 11 represents an ethylene glycol group or a propylene glycol group, x, y, and z are all positive integers, and x+y+z=3 to 30.

[0066] In particular, from the viewpoint of facilitating the ink penetration into the interior of the fabric and enhancing ejection properties from an inkjet head, it is preferable that the ink is resistant to thickening due to drying. Therefore, it is preferable that the ink contains a high-boiling-point solvent with a boiling point of 200°C or higher.

[0067] High boiling point solvents having a boiling point of 200°C or higher include polyols and polyalkylene oxides having a boiling point of 200°C or higher, preferably polyols having a boiling point of 200°C or higher, more preferably glycerin.

[0068] The content of the water-soluble organic solvent is not particularly limited, but from the viewpoint of ejection properties from an inkjet head, it is preferably 10 to 40% by mass, and more preferably 20 to 35% by mass, of the ink.

[0069] The content of the aqueous medium is not particularly limited, but is preferably 50 to 90% by mass, and more preferably 60 to 85% by mass, based on the ink.

[0070] 2-4.Other ingredients The ink may further contain other components as necessary, such as pigment dispersants, surfactants, preservatives, antifungal agents, and pH adjusters.

[0071] The pigment dispersant is present in the ink so as to surround the surface of the pigment particle or is adsorbed to the surface of the pigment particle to form a pigment dispersion, thereby dispersing the pigment well. The pigment dispersant is preferably a polymer dispersant, more preferably an anionic polymer dispersant.

[0072] The anionic polymer dispersant is a polymer dispersant having a hydrophilic group such as a carboxylic acid group, a phosphorus-containing group, or a sulfonic acid group, and is preferably a polymer dispersant having a carboxylic acid group.

[0073] The polymer dispersant having a carboxylic acid group may be a polycarboxylic acid or a salt thereof. Examples of polycarboxylic acids include (co)polymers of monomers selected from acrylic acid or its derivatives, maleic acid or its derivatives, itaconic acid or its derivatives, and fumaric acid or its derivatives, and salts thereof. Examples of other monomers that may form the copolymer include styrene and vinylnaphthalene.

[0074] From the viewpoint of sufficiently dispersing pigment particles, the anionic group equivalent of the anionic polymer dispersant is preferably, for example, 1.1 to 3.8 meq / g. When the anionic group equivalent is within the above range, high pigment dispersibility is easily obtained without increasing the molecular weight of the anionic polymer dispersant. The anionic group equivalent of the anionic polymer dispersant can be determined from the acid value. The acid value can be measured in accordance with JIS K0070.

[0075] The weight average molecular weight (Mw) of the polymer dispersant is not particularly limited, but is preferably 5,000 to 30,000. When the Mw of the polymer dispersant is 5,000 or more, the pigment particles can be easily dispersed sufficiently, and when it is 30,000 or less, the ink does not thicken too much, so that the penetration into the fabric is less likely to be impaired. The Mw of the polymer dispersant can be measured by the same method as above.

[0076] The content of the polymer dispersant is not particularly limited as long as it is in a range that sufficiently disperses the pigment particles and has a viscosity that does not impair the permeability into the fabric, but it is preferably 20 to 100% by mass, and more preferably 25 to 60% by mass, relative to the pigment.

[0077] The ink may further contain a surfactant as needed. The surfactant can reduce the surface tension of the ink and increase its wettability to the fabric. The type of surfactant is not particularly limited, but may be, for example, an acetylene glycol surfactant, a silicone surfactant, or a fluorine surfactant.

[0078] Examples of the preservative or antifungal agent include aromatic halogen compounds (eg, Preventol CMK), methylene dithiocyanate, halogen-containing nitrogen-sulfur compounds, 1,2-benzisothiazolin-3-one (eg, PROXEL GXL), and the like.

[0079] Examples of pH adjusters include citric acid, sodium citrate, hydrochloric acid, and sodium hydroxide.

[0080] 2-5.Physical properties The viscosity of the ink at 25°C is not particularly limited as long as it provides good ejection properties using an inkjet system, but is preferably 3 to 20 mPa·s, and more preferably 4 to 12 mPa·s. The viscosity of the ink can be measured at 25°C using an E-type viscometer.

[0081] 2-6. Preparation of ink The ink of the present invention can be produced by any method, for example, by 1) mixing a pigment, a pigment dispersant, and a solvent (such as water) to obtain a pigment dispersion, and 2) further mixing the obtained pigment dispersion with the resin dispersion of the present invention and an aqueous medium or the like.

[0082] 3.Image forming method The image forming method of the present invention includes a step of applying droplets of the ink of the present invention onto a fabric by an ink jet system.

[0083] Specifically, the image forming method of the present invention includes 1) a step of ejecting ink from an inkjet recording head and applying ink droplets onto a fabric (ink application step), and 2) a step of drying and fixing the ink applied to the fabric (drying and fixing step).

[0084] Regarding step 1 (ink application process) Ink is ejected from an inkjet recording head to deposit ink droplets onto the fabric.

[0085] The type of fiber material constituting the fabric is not particularly limited, and preferably includes natural fibers such as cotton (cellulose fiber), hemp, wool, and silk; and chemical fibers such as rayon, vinylon, nylon, acrylic, polyurethane, polyester, and acetate. The fabric may be made from these fibers in any form, such as woven fabric, nonwoven fabric, or knitted fabric. The fabric may also be a blended woven fabric or blended nonwoven fabric of two or more types of fibers.

[0086] For example, when the ink contains an anionic dispersant, the fabric preferably has cationic groups or acid groups at least on its surface, from the viewpoint of increasing the pigment adsorption rate and fixability. The fabric having cationic groups or acid groups at least on its surface may or may not be pretreated.

[0087] Regarding step 2 (drying and fixing process) In the drying step, the ink applied to the fabric is dried to remove the solvent component in the ink, thereby fixing the pigment to the fabric.

[0088] The drying method is not particularly limited, and may be a method using a heater, a hot air dryer, a heated roller, etc. Among these, it is preferable to use a hot air dryer and a heater to heat and dry both sides of the fabric.

[0089] The drying temperature may be set so as to evaporate the solvent component in the ink. Specifically, the drying temperature is preferably equal to or higher than the temperature at which the solvent component evaporates and equal to or lower than (Tg + 170)°C (Tg means the Tg of the resin particles). The drying temperature may be room temperature.

[0090] In the present invention, since the Tg of the resin particles applied to the fabric is low, even if the resin particles fuse together when the ink dries, they are unlikely to form a hard coating, and therefore the texture of the fabric is unlikely to be damaged.

[0091] Furthermore, the image forming method of the present invention may further include 3) a step of pretreating the fabric (pretreatment step), if necessary.

[0092] Regarding step 3 (pre-treatment process) In the pretreatment step, a pretreatment agent is applied to the fabric. The type of pretreatment agent is not particularly limited and can be selected depending on the composition of the ink. For example, when the ink contains an anionic polymer dispersant, the pretreatment agent preferably contains a compound having an acid group or a cationic group.

[0093] The compound having an anionic group is not particularly limited and may be the same as an anionic surfactant, a polymer compound having an anionic group, etc. Examples of the polymer compound having an anionic group include plant peels such as pectinic acid, cellulose derivatives such as carboxymethyl cellulose, modified starches such as carboxymethyl starch and carboxyethyl starch, and synthetic glues such as acrylic polymers containing acrylic acid as a copolymerization component, such as acrylic acid-acrylic acid ester copolymers and styrene-acrylic acid copolymers.

[0094] The method for applying the pretreatment agent is not particularly limited and may be, for example, a pad method, a coating method, a spray method, an inkjet method, etc. The pretreatment agent applied to the fabric can also be heated and dried using hot air, a hot plate, or a heat roller. [Example]

[0095] The present invention will be described below with reference to examples, which should not be construed as limiting the scope of the present invention.

[0096] 1. Preparation of Resin Dispersion <Monomer> Alkyl (meth)acrylate Methyl methacrylate (MMA) Butyl acrylate (BA) A polymerizable compound represented by formula (1) ADEKA ADEKA Rear Soap SR-10 (n=10, X=-SO3NH4, R 1 = ethylene group, R 2 = alkyl group with 6 to 10 carbon atoms) ADEKA ADEKA Rear Soap SR-20 (n=20, X=-SO3NH4, R 1 = ethylene group, R 2 = alkyl group with 6 to 10 carbon atoms) Other monomers 2-Methyladamantyl acrylate (MADA) JS-20 (anionic reactive emulsifier represented by the following formula) [ka] NE-10 (nonionic reactive emulsifier represented by the following formula) [ka] Diethylene glycol monomethacrylate (DEGMA)

[0097] <Preparation of Resin Dispersion 1> A surfactant solution prepared by dissolving 2.52 g of anionic surfactant (sodium dodecylbenzenesulfonate: SDS) and 0.58 g of sodium carbonate in 553 g of ion-exchanged water was placed in a separable flask equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introducing device, and the internal temperature was raised to 80°C while stirring at a stirring speed of 330 rpm under a nitrogen stream. On the other hand, a monomer solution was prepared by dissolving 162 g of n-butyl acrylate (BA), 66 g of methyl methacrylate (MMA), and 12 g of SR-10 manufactured by ADEKA Corporation. Next, a solution was prepared by dissolving 0.07 g of a polymerization initiator (potassium persulfate: KPS) in 2.66 g of ion-exchanged water, and the solution was heated to 80° C. The monomer solution prepared above was added dropwise to this solution over 60 minutes, and the mixture was stirred to prepare a dispersion of resin particles. After the dropwise addition was completed, the mixture was heated and stirred for 120 minutes, and then a solution of 0.07 g of polymerization initiator (potassium persulfate: KPS) dissolved in 2.66 g of ion-exchanged water was added, stirred for 60 minutes, and then cooled to 40°C to obtain resin particle dispersion 1.

[0098] <Preparation of Resin Dispersions 2 and 3> Resin particle dispersions 2 and 3 were obtained in the same manner as resin particle dispersion 1, except that the content of ADEKA SR-10 was changed to the ratio shown in Table 1.

[0099] <Preparation of Resin Dispersion 4> Resin particle dispersion 4 was obtained in the same manner as in resin dispersion 1, except that ADEKA SR-10 was changed to ADEKA SR-20.

[0100] <Preparation of Resin Dispersion 5> Resin Dispersion 5 was obtained in the same manner as Resin Dispersion 1, except that the composition of the monomer solution was changed without adding ADEKA SR-10 and the mass ratio of n-butyl acrylate (BA) to methyl methacrylate (MMA) was changed as shown in Table 1.

[0101] <Preparation of Resin Dispersion 6> A surfactant solution prepared by dissolving 2.52 g of anionic surfactant (sodium dodecylbenzenesulfonate: SDS) and 0.58 g of sodium carbonate in 553 g of ion-exchanged water was placed in a separable flask equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introducing device, and the internal temperature was raised to 80°C while stirring at a stirring speed of 330 rpm under a nitrogen stream. On the other hand, 162 g of n-butyl acrylate (BA) and 66 g of methyl methacrylate (MMA) were dissolved to prepare a monomer solution. Next, a solution was prepared by dissolving 0.7 g of a polymerization initiator (potassium persulfate: KPS) in 26.6 g of ion-exchanged water and heated to 80° C. The monomer solution prepared above was added dropwise to this solution over 60 minutes and stirred to produce resin particles. After the dropwise addition was completed, the mixture was heated and stirred for 120 minutes, and then a solution of 0.7 g of a polymerization initiator (potassium persulfate: KPS) dissolved in 26.6 g of ion-exchanged water was added, followed by stirring for 60 minutes and cooling to 40° C. 12 g of ADEKA SR-10 was added and mixed to obtain a dispersion of resin particles.

[0102] <Preparation of Resin Dispersions 7 to 13> Resin Dispersions 7 to 13 were obtained in the same manner as Resin Dispersion 1, except that the composition of the monomer solution was changed to the quantitative ratio shown in Table 1.

[0103] <Evaluation> The Tg (Tg of the radical polymer) and average particle size of the obtained resin dispersion were measured by the following methods.

[0104] (Tg) The resin particles were collected and dried, and the sample was subjected to differential scanning calorimetry to determine the glass transition temperature, under the same conditions as above.

[0105] (Average particle size) The dispersed particle size (Z average) of the resin particles in the resin dispersion was measured using a Zataizer Nano S90 manufactured by Melvern.

[0106] The compositions and physical properties of Resin Dispersions 1 to 13 are shown in Table 1. The amount of unreacted polymerizable compound represented by formula (1) in the resin dispersion was measured by the following method. Specifically, the resin dispersion was heated to 80°C, and a 10% MgCl2 aqueous solution was added to precipitate the resin particles. Meanwhile, a calibration curve for the polymerizable compound represented by formula (1) was prepared by HPLC; the supernatant was measured by HPLC, and the obtained data was compared with the data on the calibration curve to measure the amount of the free polymerizable compound represented by formula (1).

[0107] [Table 1]

[0108] 2. Ink Preparation and Evaluation <Preparation of pigment dispersion> A neutralized pigment dispersant was prepared by mixing 7 parts of styrene-butyl acrylate-methacrylic acid copolymer (anionic dispersant, weight-average molecular weight 16,000, anionic group equivalent weight 3.5 meq / g) with 78 parts of water and warming and stirring. To this mixture was added 15 parts of CI Pigment Blue 15:3, premixed, and dispersed using a sand grinder filled with 50% 0.5 mm zirconia beads to obtain a cyan pigment dispersion with a pigment concentration of 15% by volume.

[0109] <Preparation of Ink 1> Next, the following components were mixed to a total of 100 parts by mass to obtain ink 1. The pigment dispersion liquid prepared above (pigment concentration 15% by mass): 10 parts by mass (solid content concentration 1.5 parts by mass) Resin dispersion 1 prepared above (solid content concentration 30% by mass): 41 parts by mass (solid content concentration 12.3 parts by mass) Ethylene glycol: 10 parts by mass Propylene glycol: 10 parts by mass Glycerin: 10 parts by mass Olfine E1010 (acetylene glycol surfactant manufactured by Nissin Chemical Industry): 0.10 parts by mass Proxel GXL (manufactured by Lonza Japan): 0.10 parts by mass Ion-exchanged water: Remaining

[0110] <Preparation of Inks 2 to 13> Inks 2 to 13 were prepared in the same manner as Ink 1, except that the resin dispersions shown in Table 2 were used.

[0111] <Evaluation> The resulting inks 1 to 13 were evaluated for filterability, ejection properties and storage stability.

[0112] (1) Filterability The resin dispersion was filtered at a constant pressure of 0.08 MPa using a 1 μm filter (manufactured by Advantec). The mass of the filtrate passing through the filter was measured until the mass of the filtrate stopped changing (until it became impossible to filter). The mass of the filtrate was used to evaluate the filterability of the resin dispersion according to the following evaluation criteria. For 230g of filtrate, A: The mass of the filtrate is 200g or more B: The mass of the filtrate is 130g or more but less than 200g C: Filtrate mass is 80g or more but less than 130g D: The mass of the filtrate is less than 80g

[0113] (2) Dischargeability The magenta ink prepared above was ejected using a fixed Konica Minolta KM1024iMHE in a line method under ejection conditions of a droplet volume of 13 pL. After confirming that the filled ink was being ejected from all 60 nozzles at the start of ejection, the ink was ejected continuously for 60 minutes. After the 60 minutes of continuous ejection was completed, the number of nozzles that had been able to eject to the end (the number of ejecting nozzles after 60 minutes of continuous ejection) was counted. The number of ejecting nozzles after 60 minutes of continuous ejection was applied to the following evaluation criteria to evaluate the ink ejection properties. A: The number of nozzles ejecting after 60 minutes of continuous ejection is 60 or more. B: Number of nozzles after 60 minutes of continuous discharge is 57-59 C: Number of nozzles after 60 minutes of continuous discharge is 54-56 D: The number of nozzles after 60 minutes of continuous discharge is 53 or less

[0114] (3) Storage stability The prepared magenta ink was placed in a polyethylene terephthalate container, sealed, and stored in a thermostatic chamber at 50°C for 14 days. The viscosity and spectral absorption after storage were measured, and the storage stability was evaluated based on the rate of change in the viscosity and spectral absorption after storage compared to the viscosity and spectral absorption before storage. The viscosity was measured using an R100 viscometer (manufactured by Toki Sangyo Co., Ltd.) at 25°C with a cone rotation speed of 20 to 100 rpm. The spectroscopic absorption was measured using a V-570 (manufactured by JASCO Corporation) and a quartz cell. Specifically, the ink was diluted 1500 times with ultrapure water, and ultrapure water was used as a control, and the change in absorbance at 600 nm was compared. The rate of change in viscosity and spectral absorption was calculated using the following formula, and the storage stability was evaluated based on the following evaluation criteria. Rate of change (%) = 100 x {absolute value of [(measured value after saving) - (measured value before saving)]} / (measured value before saving) A: The change rate of both viscosity and spectral absorption is less than 10% B: The rate of change in either viscosity or spectral absorption is 10% or more C: The change rate in both viscosity and spectral absorption is 10% or more.

[0115] The evaluation results are shown in Table 2.

[0116] [Table 2]

[0117] As shown in Table 2, inks 1 to 4 using resin dispersions 1 to 4 in which the polymer constituting the resin particles contains a structural unit derived from the polymerizable compound represented by formula (1) showed good results in terms of filterability, ejection property, and storage stability.

[0118] In contrast, inks 5 and 7 to 9 using resin dispersions 5 and 7 to 9 in which the polymer constituting the resin particles does not contain a structural unit derived from the polymerizable compound represented by formula (1) are found to have poor ejection properties. In particular, in Resin Dispersion 7, the polymer constituting the resin particles does not have repeating units of allyl groups, oxyalkylene groups, or anionic groups; in Resin Dispersion 8, the polymer constituting the resin particles does not have repeating units of oxyalkylene groups; and in Resin Dispersion 9, the polymer constituting the resin particles does not have anionic groups. Therefore, it is presumed that none of these dispersions provided an improvement in dispersibility, and the ejection performance from an inkjet head under high pressure was not improved. Furthermore, in Resin Dispersion 6, the polymerizable compound represented by formula (1) was simply added unreacted without being reacted, and therefore the polymer constituting the resin particles did not have structural units derived from the polymerizable compound represented by formula (1), and thus a sufficient improvement in dispersibility was not obtained.

[0119] 3. Image Formation First, an inkjet head (Konica Minolta head #204) was prepared as an image forming apparatus. Next, the resulting ink 11 or 12 was set in the image forming apparatus. Then, a solid image was formed on the above-mentioned fabric using the ink at 540 dpi in the main scanning direction and 720 dpi in the sub-scanning direction. Note that dpi represents the number of ink droplets (dots) per 2.54 cm. The ejection frequency was 22.4 kHz. The fabric to which the ink had been applied was then dried at 120°C for 5 minutes in a belt-conveying dryer to obtain an image-formed product.

[0120] The texture of the resulting image-printed product and fabric was evaluated sensorily by touch with the fingers, and it was confirmed that the original softness of the fabric was maintained in both inks 11 and 12. In particular, when ink 12 was used, the original softness of the fabric was maintained to a greater extent than when ink 11 was used, and it was confirmed that the texture was even better. [Industrial Applicability]

[0121] According to the present invention, it is possible to provide a resin dispersion for an aqueous inkjet ink and an aqueous inkjet ink that are excellent in inkjet ejection properties.

Claims

1. A resin dispersion for an aqueous inkjet ink, comprising resin particles and water, The resin particles contain a radical polymer containing a structural unit derived from a polymerizable compound represented by formula (1), The radical polymer is obtained by emulsion polymerization of a monomer composition containing a polymerizable compound represented by formula (1), The resin dispersion for an aqueous inkjet ink contains an unreacted polymerizable compound represented by formula (1), In the resin dispersion for an aqueous inkjet ink, the content of the unreacted polymerizable compound represented by formula (1) is 10 to 40 mass % based on the total amount of the reacted polymerizable compound represented by formula (1) and the unreacted polymerizable compound represented by formula (1). Resin dispersion for water-based inkjet inks. 【Chemistry 1】 (In formula (1), R １ is an alkylene group having 1 to 10 carbon atoms, n is an integer from 1 to 100, R ２ is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 30 carbon atoms, X is -SO ３ M (M is an alkali metal atom or NH ４ ) is)

2. R １ is an ethylene group, The resin dispersion for an aqueous inkjet ink according to claim 1.

3. the content of the structural unit derived from the polymerizable compound represented by formula (1) is 1 to 10 mass % based on the total structural units constituting the radical polymer; The resin dispersion for an aqueous inkjet ink according to claim 1 or 2.

4. The radical polymer further contains a structural unit derived from alkyl (meth)acrylate. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 3.

5. The glass transition temperature of the radical polymer is −35° C. or lower. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 4.

6. An aqueous inkjet ink comprising a colorant, resin particles, and an aqueous medium, The resin particles contain a radical polymer containing a structural unit derived from a polymerizable monomer represented by formula (1), The radical polymer is obtained by emulsion polymerization of a monomer composition containing a polymerizable compound represented by formula (1), The aqueous inkjet ink contains an unreacted polymerizable compound represented by formula (1), In the aqueous inkjet ink, the content of the unreacted polymerizable compound represented by formula (1) is 10 to 40% by mass based on the total amount of the reacted polymerizable compound represented by formula (1) and the unreacted polymerizable compound represented by formula (1). Water-based inkjet ink. 【Chemistry 2】 (In formula (1), R １ is an alkylene group having 1 to 10 carbon atoms, n is an integer from 1 to 100, R ２ is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 30 carbon atoms, X is -SO ３ M (M is an alkali metal atom or NH ４ ) is)

7. R １ is an ethylene group, The aqueous inkjet ink according to claim 6.

8. the content of the structural unit derived from the polymerizable compound represented by formula (1) is 1 to 10 mass % based on the total structural units constituting the radical polymer; The aqueous inkjet ink according to claim 6 or 7.

9. The radical polymer further contains a structural unit derived from alkyl (meth)acrylate. The aqueous inkjet ink according to any one of claims 6 to 8.

10. The glass transition temperature of the radical polymer is −35° C. or lower. The aqueous inkjet ink according to any one of claims 6 to 9.

11. the content of the resin particles is 1 to 20% by mass relative to the water-based inkjet ink; The aqueous inkjet ink according to any one of claims 6 to 10.

12. Used in inkjet printing, The aqueous inkjet ink according to any one of claims 6 to 11.

13. A method for producing a resin dispersion for an aqueous inkjet ink according to claim 1, comprising the steps of: a step of preparing an aqueous inkjet ink by mixing the resin dispersion for an aqueous inkjet ink, a pigment dispersion, and an aqueous medium; having A method for producing aqueous inkjet ink.

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