Resin particle, method for producing resin particle, ink and ink production method

Abstract

To provide resin particles which have excellent discharge property when being used in ink, and are excellent in glossiness and washing resistance on a recorded medium.SOLUTION: Resin particles contain a copolymer obtained by polymerizing at least one monomer having a polymerizable unsaturated double bond and a reactive emulsifier, and further contain a non-reactive emulsifier.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to resin particles, a method for producing resin particles, an ink, and a method for producing an ink. [Background technology]

[0002] Inkjet (IJ) recording devices are now used not only for printing on paper but also on a wider variety of printing surfaces, such as fabric and non-absorbent film, and the market is expanding, so there is a demand for improved cost performance. While urethane resins, which have been used as binders in inks, have the advantage of providing high adhesion to a variety of materials, they are expensive due to raw material price constraints. Therefore, there is a demand for inks that can provide excellent adhesion even when using acrylic resin binders.

[0003] As such ink, an inkjet ink containing at least water, a pigment, an organic solvent, and an acrylic resin binder has been proposed (see, for example, Patent Document 1).

[0004] However, although acrylic resins are cheaper than urethane resins, they sometimes fail to provide excellent wash resistance and gloss. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-155246 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide resin particles that, when used in ink, have excellent ejection properties, and also have excellent gloss and washability on a recording medium. [Means for solving the problem]

[0007] The resin particles according to the first aspect of the present disclosure include: a copolymer obtained by polymerizing at least one monomer having a polymerizable unsaturated double bond and a reactive emulsifier; and a non-reactive emulsifier. [Effects of the Invention]

[0008] The resin particles of the present disclosure, when used in ink, have excellent ejection properties, and also have excellent gloss and washability on a recording medium. DETAILED DESCRIPTION OF THE INVENTION

[0009] (resin particles) The resin particles according to one embodiment of the present disclosure comprise a copolymer obtained by polymerizing at least one monomer having a polymerizable unsaturated double bond and a reactive emulsifier; A non-reactive emulsifier may be included, and other ingredients may be included as needed.

[0010] <Monomer> The monomer has a polymerizable unsaturated double bond. The polymerizable unsaturated double bond is not particularly limited as long as it is polymerizable, and can be appropriately selected depending on the purpose. Examples of the polymerizable unsaturated double bond include a vinyl group and an acrylic group.

[0011] Examples of the monomer include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versatate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, and hexyl vinyl ether; (meth)acrylic acid esters such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, and hexyl vinyl ether; Examples of the vinyl nitrile include vinyl nitriles such as styrene, α-methylstyrene, vinyltoluene, vinylanisole, α-halostyrene, vinylnaphthalene, and divinylstyrene; vinyl monomers having an aromatic ring such as styrene, α-methylstyrene, vinyltoluene, vinylanisole, α-halostyrene, vinylnaphthalene, and divinylstyrene; vinyl monomers containing a glycidyl group such as glycidyl (meth)acrylate and allyl glycidyl ether; vinyl monomers containing a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and glycerol mono(meth)acrylate; vinyl monomers containing a methylolamide group or an alkoxylated product thereof such as N-methylol (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and N-isobutoxymethyl (meth)acrylamide; (meth)acrylamide, N-monoalkyl (meth)acrylamide, and N,N-dialkyl (meth)acrylamide. These may be used alone or in combination of two or more.

[0012] The content of the monomer is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 50% by mass or more and 99% by mass or less relative to the total amount of resin particles, and more preferably 70% by mass or more and 97% by mass or less, in order to obtain resin particles that can be used to produce printed materials with better washing resistance.

[0013] <Reactive emulsifier> The reactive emulsifier has a polymerizable unsaturated double bond. The polymerizable unsaturated double bond is not particularly limited as long as it is polymerizable, and can be appropriately selected depending on the purpose. Examples of the polymerizable unsaturated double bond include a vinyl group, an allyl group, and an acryloyl group.

[0014] The reactive emulsifier is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include ether sulfate ammonium salt, polyoxyethylene-1-(allyloxymethyl) alkyl ether ammonium sulfate, polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate, polyoxyethylene styrenated propenyl phenyl ether ammonium sulfate, polyoxyethylene-1-(allyloxymethyl) alkyl ether, and polyoxyethylene nonylpropenyl phenyl ether.

[0015] The reactive emulsifier may be a commercially available product. The commercially available product is not particularly limited and can be appropriately selected depending on the purpose. Examples include ADEKA REASOAP SR-10, SR-20, ER-20, SE-10N, SE-1025A, NE-10, NE-20, and PP-70 (manufactured by ADEKA Corporation), ELEMINOL JS-20 and RS-3000 (manufactured by Sanyo Chemical Industries, Ltd.), and AQUALON HS-10, BC-10, KH-05, and KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). These may be used alone or in combination of two or more.

[0016] The content of the reactive emulsifier is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 1% by mass or more and 15% by mass or less relative to the total amount of resin particles, and more preferably 1% by mass or more and 10% by mass or less, in order to obtain resin particles that can be used to produce printed materials that have both better abrasion resistance and washing resistance.

[0017] The copolymer is obtained by polymerizing at least one of the monomers having a polymerizable unsaturated double bond and the reactive emulsifier.

[0018] The weight average molecular weight of the copolymer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1,000 or more and 2,000,000 or less, and more preferably 3,000 or more and 1,000,000 or less, from the viewpoint of achieving both excellent abrasion resistance and color development properties.

[0019] <Non-reactive emulsifier> The non-reactive emulsifier is an emulsifier that does not have a polymerizable unsaturated double bond.

[0020] The non-reactive emulsifier is not particularly limited as long as it does not have a polymerizable unsaturated double bond, and can be appropriately selected depending on the purpose. Examples of the non-reactive emulsifier include polyoxyethylene alkyl ethers such as polyoxyethylene tridecyl ether, polyoxyalkylene alkyl ethers, polyoxyethylene lauryl ether sodium sulfate, 2-ethylhexyl sodium sulfate, dioctyl sodium sulfosuccinate, and polyoxyethylene polycyclic phenyl ether sulfate.

[0021] The non-reactive emulsifier may be a commercially available product, which is not particularly limited and may be appropriately selected depending on the purpose, and examples thereof include Noigen TDS-30, TDS-50, TDS-100, and TDS-500D (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Newcol 707SF, 2320-SN, and CMP-4-SN (manufactured by Nippon Nyukazai Co., Ltd.), Eleminol CLS-20, NS-5S, Sandet ONA, and Sunmorin OT-70 (manufactured by Sanyo Chemical Industries, Ltd.).

[0022] The content of the non-reactive emulsifier is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 1% by mass or more and 15% by mass or less relative to the total amount of resin particles, and more preferably 1% by mass or more and 10% by mass or less, in order to obtain resin particles that can be used to produce printed materials that have both better abrasion resistance and washing resistance.

[0023] The resin particles have a structure in which a non-reactive emulsifier is attached by physical adsorption onto a copolymer formed by polymerizing at least one monomer having a polymerizable unsaturated double bond and a reactive emulsifier. This ensures ink stability and ejection performance while making the resin particles hydrophobic after printing, thereby improving adhesion to the substrate.

[0024] The particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.01 μm or more and 0.5 μm or less in order to obtain excellent wash resistance.

[0025] The copolymer can be produced, for example, by supplying the mixture of vinyl monomers described above all at once or in portions in the presence of water and, if necessary, a polymerization initiator and a chain transfer agent, and then subjecting the mixture to radical polymerization.

[0026] Examples of the polymerization initiator that can be used include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; peroxides such as benzoyl peroxide, cumene hydroperoxide, and t-butyl hydroperoxide; hydrogen peroxide; redox polymerization initiators that combine the peroxides with a reducing agent; and azo initiators such as 4,4'-azobis(4-cyanovaleric acid) and 2,2'-azobis(2-amidinopropane) dihydrochloride. Examples of the reducing agent that can be used include ascorbic acid, erythorbic acid, sodium erythorbate, metal salts of formaldehyde sulfoxylate, sodium thiosulfate, and sodium bisulfite. Among these, the use of persulfates as the polymerization initiator is preferred in terms of improving copolymer production efficiency.

[0027] The chain transfer agent may be, for example, thiomalic acid, thioglycerin, or the like, which may be used alone or in combination of two or more thereof. The use of thiomalic acid is preferred in order to obtain an ink that has excellent dispersion stability and can be used to produce printed matter with excellent color development.

[0028] The production of the copolymer is preferably carried out, for example, at a temperature in the range of 30° C. to 100° C. for 1 hour to 40 hours. The production of the polymer (A) is preferably carried out in the presence of an inert gas such as nitrogen gas in order to rapidly polymerize the vinyl monomer.

[0029] After polymerization of the monomers, the copolymer may be mixed with a basic compound as a neutralizing agent, if necessary, to form a neutralized base in which the carboxyl group of the copolymer is neutralized by the basic compound.

[0030] Examples of the basic compound include alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; and organic amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, dimethylethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine, which can be used alone or in combination of two or more. The use of ammonia or aqueous ammonia is preferred in order to obtain an ink that can be used to produce printed matter having excellent dispersion stability and color development properties.

[0031] (Method of producing resin particles) A method for producing resin particles according to an embodiment of the present disclosure includes a step of mixing a monomer having at least one polymerizable unsaturated double bond, a reactive emulsifier, and a non-reactive emulsifier, and further includes polymerizing the monomer and the reactive emulsifier to form a copolymer.

[0032] Examples of methods for producing the resin particles include the following methods. First, a non-reactive emulsifier and deionized water are charged into a reaction vessel, and the temperature is raised to 50°C while blowing in nitrogen. Next, a reactive emulsifier, deionized water, at least one monomer, and a polymerization initiator are added dropwise to the reaction vessel over 6 hours, and the reaction mixture is maintained for 1 hour to polymerize the reactive emulsifier and the monomer.

[0033] (ink) The ink according to the first aspect of the present disclosure comprises resin particles according to the first aspect of the present disclosure, A pigment, The solvent may further contain other components as required.

[0034] As the pigment, for example, organic pigments or inorganic pigments can be used alone or in combination of two or more kinds.

[0035] Examples of the organic pigment that can be used include quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, phthalone pigments, isoindolinone pigments, methine-azomethine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, azo lake pigments, insoluble azo pigments, and condensed azo pigments.

[0036] Examples of the inorganic pigment that can be used include titanium dioxide, zinc oxide, iron oxide, chromium oxide, iron black, cobalt blue, alumina white, iron oxide yellow, viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmium red, yellow lead, molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, baryte powder, calcium carbonate, white lead, Prussian blue, manganese violet, carbon black, aluminum powder, and pearl pigments.

[0037] As the pigment, a pigment that is self-dispersible in water can also be used.

[0038] The content of the pigment is not particularly limited and can be selected appropriately depending on the purpose. However, in terms of providing good storage stability and excellent ejection stability when applied to inkjet printing, the content of the pigment is preferably in the range of 0.1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass, and particularly preferably 2% by mass to 10% by mass, relative to the total amount of the ink.

[0039] When the pigment is used as the colorant, it is preferable to use a pigment dispersing resin to stably disperse the pigment in a solvent. Unlike the resin particles, the pigment dispersing resin adsorbs around the pigment particles, thereby imparting dispersion stability to the pigment in the solvent.

[0040] The pigment dispersing resin may be, for example, a pigment dispersing resin having an anionic group, such as a carboxyl group, a sulfonic acid group, or a phosphate group.

[0041] As the pigment dispersing resin having an anionic group, it is particularly preferable to use a resin having a hydrophobic structural unit and a structural unit derived from a hydrophilic anionic group, as this provides a high degree of freedom in designing the structure that maintains the stability of the ink of the present invention and allows for the formation of an ink that can form printed matter with excellent color development when printed on plain paper.

[0042] As the resin having a hydrophobic structural unit and a hydrophilic anionic group-derived structural unit, for example, the pigment dispersing resin can be a resin having a styrene-derived structural unit and an acrylic acid-derived structural unit.

[0043] The resin having a hydrophobic structural unit and a structural unit derived from a hydrophilic anionic group preferably has an acid value in the range of 60 to 300 mgKOH / g, and the use of a resin in the range of 100 to 250 mgKOH / g is suitable from the viewpoint of achieving a balance between pigment dispersibility, ink stability, and high print density.

[0044] As the resin having a hydrophobic structural unit and a structural unit derived from a hydrophilic anionic group, from the viewpoint of balancing the dispersibility of the pigment in water (C), the ink stability, abrasion resistance, high print density, and also the ejection property, it is preferable to use one having a weight average molecular weight in the range of 3,000 to 50,000, more preferably in the range of 4,000 to 40,000, even more preferably in the range of 5,000 to 30,000, and particularly preferably in the range of 5,000 to 20,000.

[0045] As the resin having a hydrophobic structural unit and a structural unit derived from a hydrophilic anionic group, it is preferable to use one having a glass transition temperature in the range of 60°C to 150°C, and more preferably in the range of 70°C to 150°C, so that even when the ink of the present invention is applied to an inkjet printing method using a thermal jet system, the resin is not altered by the heat derived from the thermal jet system and excellent ejection stability is maintained.

[0046] The resin having the hydrophobic structural unit and the structural unit derived from the hydrophilic anionic group is preferably one that can be made water-dispersible by neutralization of the anionic group, and is preferably a resin that has the ability to form stable water-dispersed particles under the action of a basic compound that serves as a neutralizing agent without using a dispersion stabilizer such as an emulsifier.

[0047] When a resin having an anionic group is used as the pigment dispersing resin, the basic compound that can be used to neutralize the anionic group may be an inorganic basic compound or an organic basic compound. In order to obtain an ink having even better storage stability, it is preferable to use an inorganic basic compound as the basic compound.

[0048] The inorganic basic compound may be an alkali metal hydroxide, ammonium hydroxide, or the like, and the use of an alkali metal hydroxide, such as potassium hydroxide or sodium hydroxide, is preferred in order to impart better dispersion stability to the pigment. The inorganic basic compound may be used as an aqueous solution having a concentration of 20% by mass to 50% by mass, which is previously dissolved or dispersed in water, in order to improve mixability.

[0049] As the organic basic compound, for example, amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, diethanolamine, triethanolamine, etc. Since the amines are generally liquid, they can be used in the form as they are.

[0050] The content of the basic compound is adjusted so that the neutralization rate of the resin having an anionic group is preferably 50% or more, more preferably 80% or more, which is suitable for improving the dispersion rate in the solvent and ensuring good dispersion stability and long-term storage stability. The upper limit of the neutralization rate is not particularly limited, but in order to ensure that the ink is stable even during long-term storage and does not gel, it is preferably 200% or less, more preferably 120% or less. The neutralization rate here is a value calculated using the following formula:

[0051] Neutralization rate (%) = [{mass of basic compound (g) × 56.11 × 1000} / {acid value of pigment dispersing resin (mg KOH / g) × equivalent of basic compound × mass of pigment dispersing resin (g)}] × 100

[0052] More specifically, examples of the pigment dispersing resin that can be used include the above-mentioned polyester resin having an anionic group, epoxy resin having an anionic group, urethane resin having an anionic group, acrylic acid-based resin having an anionic group, maleic acid-based resin having an anionic group, styrene-based resin having an anionic group, and vinyl copolymers having an anionic group, such as polyvinyl acetate-based resin having an anionic group.

[0053] Examples of the pigment dispersing resin that can be used include poly(meth)acrylic acid, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, and vinyl acetate-acrylic acid copolymer.

[0054] Examples of the wetting agent include polyhydric alcohols such as ethylene glycol and glycerol, ethers of polyhydric alcohols such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether, polyoxyalkylene adducts of glycerin, nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone and γ-butyrolactone, amides such as N,N-dimethylformamide, organic amines such as triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, propylene carbonate, ethylene carbonate, and the like, which can be used alone or in combination of two or more.

[0055] As the wetting agent, it is preferable to use one having a high boiling point in order to uniformly disperse the pigment and the pigment dispersing resin, and it is more preferable to use polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerin, and polyethylene oxide adducts of glycerin.

[0056] The wetting agent is preferably used in an amount of 10% by mass to 300% by mass, and more preferably 30% by mass to 200% by mass, based on the total amount of the pigment.

[0057] Examples of the other components that can be used include coloring materials such as dyes, pigment dispersing resins, solvents other than the water (C), wetting agents, lubricants, alkali agents, pH adjusters, surfactants, preservatives, chelating agents, plasticizers, antioxidants, waxes, and ultraviolet absorbers.

[0058] The viscosity of the ink is not particularly limited and can be appropriately selected depending on the purpose. For example, the viscosity is preferably from 1 mPa·sec to 10 mPa·sec, and more preferably from 1 mPa·sec to 6 mPa·sec in terms of excellent ejection stability when the ink is ejected by the inkjet printing method described below.

[0059] (Ink manufacturing method) A method for producing an ink according to an embodiment of the present disclosure includes: The method includes a step of mixing the solvent.

[0060] When the ink of the present invention contains the pigment and the pigment dispersion resin, examples of a method for producing the ink of the present invention include a method in which an aqueous pigment dispersion obtained by previously mixing the pigment, the pigment dispersion resin, and a solvent is mixed with the resin particles.

[0061] The aqueous pigment dispersion can be produced, for example, by a step [1] of kneading a composition containing the pigment, a pigment dispersing resin, and, if necessary, a basic compound and a wetting agent, and a step [2] of diluting and dispersing the kneaded mixture obtained in the step [1] in a solvent.

[0062] In steps [1] and [2], by appropriately selecting the pigment dispersion resin, the affinity of the pigment dispersion resin to the pigment becomes extremely good, which improves the dispersion stability of the aqueous pigment dispersion and also improves the gloss, durability, water resistance, etc. of a printed matter formed by printing an ink obtained using the pigment dispersion on plain paper.

[0063] In the step [1], for example, a roll mill, a Henschel mixer, a pressure kneader, a planetary mixer, or the like can be used. The use of a Henschel mixer, a pressure kneader, a planetary mixer, or the like, which has a stirring vessel and stirring blades and whose stirring vessel can be sealed, is preferred because it allows the solids ratio of the composition in the step [1] to be kept constant and a kneaded product with a good dispersion state can be obtained. The use of a planetary mixer is preferred because it allows the kneading treatment over a wide range of viscosity.

[0064] The step [2] is a step of diluting and dispersing the kneaded product obtained in the step [1] in a solvent.

[0065] The aqueous pigment dispersion obtained by the above method is preferably subjected to a centrifugation treatment or a filtration treatment to remove coarse particles and aggregated particles derived from raw materials such as the pigment, in order to prevent clogging of ink ejection nozzles when the ink of the present invention is applied to inkjet printing.

[0066] The ink of the present invention can be used for printing on a recording medium.

[0067] The recording medium is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include plain paper, clothing, etc. Among these, clothing is preferred.

[0068] A typical example of the plain paper is PPC paper used in electrophotographic copiers, etc. The plain paper varies in terms of the percentage of recycled paper pulp used, the degree of bleaching, etc., depending on the brand, and also in paper thickness, but in exchange for being inexpensive, it is not coated with an ink-receiving layer, etc. Therefore, when performing double-sided printing using an inkjet printing method in particular, if a transport roll comes into contact with the printed surface of a single-sided printed item when the single-sided printed item is turned over after being printed on one side (front side) of the plain paper, the printed surface is likely to be scratched, resulting in a deterioration in print quality.

[0069] The ink of the present invention can produce printed matter with little damage and high color development even when double-sided printing is performed on the plain paper.Furthermore, when printing on the clothing, the ink has excellent abrasion resistance and washing resistance.

[0070] The ink of the present invention can be applied to various printing methods, but is preferably used in printing situations using an inkjet printing method.

[0071] Examples of the inkjet printing method include continuous jetting methods (charge control methods, spray methods, etc.) and on-demand methods (piezo methods, thermal methods, electrostatic suction methods, etc.), and the ink of the present invention is suitable for printing using thermal inkjet printing methods. When this water-based ink for inkjet recording is applied to these various inkjet methods, it basically enables extremely stable ink ejection and can also achieve good scratch resistance and abrasion resistance in the formed images.

[0072] Inkjet printers capable of printing on both sides of a recording medium often print a single-sided print on one side (front side) of the recording medium, dry it for a certain period of time, and then flip it over using a transport roll and flipping mechanism inside the printer, and print on the other side (back side) of the single-sided print. When flipping the single-sided print, if the transport roll comes into contact with the printed surface of the single-sided print, there has been concern that the printed surface may be scratched, resulting in a decrease in print quality. However, the ink of the present invention has excellent abrasion resistance, making it less likely to be scratched, even when printing on both sides of plain paper, and can effectively prevent a decrease in color development when printing on plain paper. [Example]

[0073] [Example 1] A reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet pipe was charged with 1 part by mass of Noigen TDS-200D (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 1 part by mass of Newcol 707SF (manufactured by Nippon Nyukazai Co., Ltd.) as non-reactive emulsifiers, and 90 parts by mass of deionized water, and the temperature was raised to 50°C while blowing in nitrogen.

[0074] Next, a mixture of 3 parts by weight of SR-10 (manufactured by ADEKA Corporation) and 1 part by weight of ER-10 (manufactured by ADEKA Corporation) as reactive emulsifiers, and 50 parts by weight of deionized water, a mixture of 40 parts by weight of ethyl acrylate (EA), 40 parts by weight of styrene (St), and 20 parts by weight of 2-hydroxyethyl methacrylate (HEMA) as monomers, and 5 parts by weight of a 10% by weight aqueous solution of ammonium persulfate as a polymerization initiator were added dropwise over 6 hours and maintained for 1 hour to carry out polymerization. The composition of Example 1 is shown in Table 1.

[0075] After the reaction was completed, deionized water was added to adjust the nonvolatile content to 40% by mass, and resin particles 1 were obtained.

[0076] [Examples 2 to 3 and Comparative Examples 1 to 2] Resin particles 1 to 5 were obtained in the same manner as in Example 1, except that the compositions in Example 1 were changed to those shown in Table 1. Note that each composition in Table 1 is shown in parts by mass.

[0077] [Table 1]

[0078] <Ink preparation> (Production of pigment dispersion) 50 parts by mass of CI Pigment Red 122 ("FASTOGEN Super Magenta RY" manufactured by DIC Corporation) and 10 parts by mass of styrene-acrylic acid copolymer (weight average molecular weight 11,000, acid value 180 mgKOH / g) were added in that order to a 0.5 L jacketed tank of a mini planetary mixer (Aikosha mini-PLM Co., Ltd.). After that, the temperature of the jacketed tank was heated to 80°C, and the mixture was stirred for 10 minutes at a rotation speed of 80 rpm and a revolution speed of 25 rpm.

[0079] Next, with the temperature of the jacketed tank maintained at 80°C, 5.29 parts by mass of a 34% by mass aqueous potassium hydroxide solution and 30 parts by mass of triethylene glycol were added to the composition, and the mixture was kneaded for 60 minutes at a rotation speed of 80 rpm and a revolution speed of 25 rpm to obtain a solid kneaded product.

[0080] To the kneaded product, 100 parts by mass of ion-exchanged water and 10 parts by mass of triethylene glycol were added, and the mixture was stirred and mixed for 10 minutes using a juicer mixer. Then, the ion-exchanged water and Proxel-GXL (Lonza Japan Co., Ltd.) were mixed to obtain an aqueous pigment dispersion with a pigment concentration of 15.1% by mass, a triethylene glycol concentration of 12.0% by mass, and a Proxel-GXL concentration of 0.1% by mass.

[0081] (Ink manufacturing) 19.9 parts by mass of the aqueous pigment dispersion, 2.5 parts by mass of each of resin particles 1 to 5 obtained in Examples 1 to 3 and Comparative Examples 1 and 2, 8.0 parts by mass of 2-pyrrolidinone, 8.0 parts by mass of triethylene glycol mono-n-butyl ether, 3.0 parts by mass of glycerin, 0.5 parts by mass of Surfynol 440 (manufactured by Air Products Co., Ltd.), and 58.1 parts by mass of ion-exchanged water were mixed to obtain inks 1 to 5 with a pigment concentration of 3.0% by mass and a resin particle solids concentration of 1.0% by mass.

[0082] The resulting inks 1 to 5 were evaluated for "washing resistance," "jetability," "gloss," and "storage stability." The evaluation results are shown in Table 2.

[0083] <Washing resistance> After dyeing the entire surface of cotton broadcloth with inks 1 to 5, it was dried at 150°C for 5 minutes. Thereafter, a washing solution prepared based on the color fastness test for washing in accordance with JISL0844:2011 was heated to 50°C, and the cotton broadcloth was immersed therein for 30 minutes. The solution was then stirred in a food mixer for 1 minute, and the OD of the cotton broadcloth after stirring in the mixer was measured using an X-Rite integrating sphere spectrophotometer. A washing resistance index was calculated from the measurement results using the following formula 1, and the washing resistance was evaluated based on the following evaluation criteria. Samples with an evaluation result of B or higher were evaluated as having washing resistance sufficient for practical use. The results are shown in Table 2. Washing durability index = (OD of cotton broadcloth after stirring) / (OD of cotton broadcloth before stirring) (Equation 1) [Evaluation criteria] A: Washing resistance index is 0.9 or more B: Washing resistance index is 0.8 or more and less than 0.9 C: Washing resistance index is 0.7 or more and less than 0.8 D: Washing resistance index less than 0.7

[0084] <Dischargeability> Inks 1 to 5 were filled into the black ink cartridge of an inkjet printer ENVY4500 (manufactured by HP), and a solid print was made on a transparent OHP sheet with a print density setting of 100% to obtain a print for evaluation. Next, using an unprinted OHP sheet as a reference, the absorbance (value at the maximum peak near 536 nm) of the printed surface of the OHP sheet was measured using a V-660 manufactured by JASCO Corporation. The absorbance was compared with that of ink containing no resin particles, and a jetting index was calculated using the following formula 2. The jetting performance was evaluated based on the following evaluation criteria. An evaluation result of B or higher was considered to have sufficient jetting performance for practical use. The results are shown in Table 2. Ejection performance index = (absorbance of ink with added resin particles) / (absorbance of ink without added resin particles) (Equation 2) [Evaluation criteria] A: Dischargeability index is 0.80 or more B: Dischargeability index is 0.70 or more and less than 0.80 C: Dischargeability index is 0.60 or more and less than 0.70 D: Dischargeability index is less than 0.60

[0085] <Glossiness> Inks 1 to 5 were filled into the black ink cartridge of an inkjet printer ENVY4500 (manufactured by HP), and a solid print was made on the printing surface of photo printing paper (HP Advanced Photo Paper, manufactured by HP) with a print density setting of 100%. The gloss of the coated product was measured using a gloss meter manufactured by BYK MICRO-HAZE PLUS. The glossiness was evaluated based on the measured glossiness values ​​according to the following evaluation criteria. Samples with an evaluation result of B or higher were evaluated as having sufficient glossiness for practical use. The results are shown in Table 2. [Evaluation criteria] A: Glossiness of 50 or more B: Glossiness is 40 or more but less than 50 C: Glossiness is 30 or more and less than 40 D: Gloss less than 30

[0086] <Storage stability> Inks 1 to 5 were diluted, and the volume particle diameter (MV) was measured by detecting scattered light of laser light using a Nanotrac particle size distribution analyzer (UPA150) manufactured by Microtrac Bell Corporation in an environment of 25°C. The samples were then stored at 60°C for one week, and the MV was measured in the same manner after storage, and the rate of increase in MV before and after storage was calculated. The storage stability was evaluated based on the calculated MV increase rate according to the following evaluation criteria. Those with an evaluation result of A were evaluated as having storage stability sufficient for practical use. The results are shown in Table 2. [Evaluation criteria] A:MV increase rate is less than 10% B:MV increase rate is 10% or more

[0087] [Table 2]

Claims

1. a copolymer obtained by polymerizing at least one monomer having a polymerizable unsaturated double bond and a reactive emulsifier; and a non-reactive emulsifier.

2. The resin particle according to claim 1 , comprising a particle comprising said copolymer and said non-reactive emulsifier on said particle.

3. The resin particles according to claim 1 , wherein the copolymer comprises an acrylic resin.

4. 2. The resin particles according to claim 1, wherein the monomer having a polymerizable unsaturated double bond is at least one of styrene, ethyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate.

5. The resin particles according to claim 1 , wherein the reactive emulsifier has a polymerizable unsaturated double bond.

6. The resin particles according to claim 1 , wherein the non-reactive emulsifier does not have a polymerizable unsaturated double bond.

7. A method for producing resin particles, comprising mixing at least one monomer having a polymerizable unsaturated double bond, a reactive emulsifier, and a non-reactive emulsifier.

8. The method for producing resin particles according to claim 7 , wherein the monomer and the reactive emulsifier are polymerized to form a copolymer.

9. The resin particles according to any one of claims 1 to 6, A pigment, and a solvent.

10. A method for producing an ink, comprising mixing the resin particles according to claim 1 , a pigment, and a solvent.

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